Xiangzan Meng

Olivier Herbinet

Tianyou Wang

Frédérique Battin-Leclerc
email: frederique.battin-leclerc@univ-lorraine.fr

Experimental and modeling study of 1-octene jet-stirred reactor oxidation

Keywords: 1-octene, low temperature oxidation, detailed chemical kinetic modeling

Highlights

• Experimental study of the oxidation of 1-octene in a jet-stirred reactor (500-1100 K).

• Detailed speciation of obtained products.

• A new detailed kinetic model developed for 1-octene oxidation.

• Computed kinetic analyses highlighting the specific pathways for large alkene oxidation.

Introduction

Since alkenes are important components of gasoline [START_REF] Guibet | Fuels and engines[END_REF], the oxidation kinetics of linear alkenes including 5 to 6 carbon atoms has been frequently investigated [START_REF] Prabhu | 1-Pentene oxidation and its interaction with nitric oxide in the low and negative temperature coefficient regions[END_REF][START_REF] Ribaucour | Autoignition of n-pentane and 1-pentene: Experimental data and kinetic modeling[END_REF][START_REF] Minetti | The chemistry of pre-ignition of n-pentane and 1-pentene[END_REF][START_REF] Vanhove | On the influence of the position of the double bond on the low-temperature chemistry of hexenes[END_REF][START_REF] Touchard | Modeling of the oxidation of large alkenes at low temperature[END_REF][START_REF] Yahyaoui | Kinetics of 1-hexene oxidation in a JSR and a shock tube: Experimental and modeling study[END_REF][START_REF] Mehl | Detailed chemistry promotes understanding of octane numbers and gasoline sensitivity[END_REF][START_REF] Mehl | Oxidation and combustion of the n-hexene isomers: A wide range kinetic modeling study[END_REF][START_REF] Bounaceur | Influence of the position of the double bond on the autoignition of linear alkenes at low temperature[END_REF][START_REF] Mehl | Autoignition behavior of unsaturated hydrocarbons in the low and high temperature regions[END_REF][START_REF] Battin-Leclerc | Products from the oxidation of linear isomers of hexene[END_REF][START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF][START_REF] Yang | Comparative study on ignition characteristics of 1-hexene and 2-hexene behind reflected shock waves[END_REF][START_REF] Fan | Experimental and kinetic modeling study of 1-hexene combustion at various pressures[END_REF][START_REF] Yang | Experimental and kinetic modeling study on trans-3-hexene ignition behind reflected shock waves[END_REF]. However, there is only very few experimental studies concerning the reactivity of larger linear alkenes. Tanaka et al. [START_REF] Tanaka | Two-stage ignition in HCCI combustion and HCCI control by fuels and additives[END_REF] have measured the pressure profile during the ignition of the 3 linear heptene isomers in a rapid compression machine at 827 K and 4.16 MPa. The ignition of four linear octene isomers, including 1-octene, was investigated by Hellier et al. [START_REF] Hellier | The importance of double bond position and cis-trans isomerisation in diesel combustion and emissions[END_REF] on a diesel engine supplied with a range of single-molecule fuels. Piperel et al. [START_REF] Piperel | Impact of acetaldehyde and NO addition on the 1-octene oxidation under simulated HCCI conditions[END_REF] investigated the impact of acetaldehyde and NO addition on the 1-octene oxidation under simulated HCCI conditions in a jet-stirred reactor at 10 atm, temperatures from 560 to 1160 K, and equivalence ratio of 0.75. In the shock tube study at high pressures (P = 3.8-6.2 MPa) and temperatures (T = 850-1500 K) of the oxidation of methyl trans-2-nonenoate and methyl trans-3-nonenoate by Fridlyand et al. [START_REF] Fridlyand | Chemical kinetic influences of alkyl chain structure on the high pressure and temperature oxidation of a representative unsaturated biodiesel: Methyl nonenoate[END_REF], 1-octene (and trans-2octene) was (were) taken as the reference fuel for comparison. The same shock tube has been used to study the oxidation of linear decene isomers under similar experimental conditions [START_REF] Fridlyand | Influence of the double bond position on the oxidation of decene isomers at high pressures and temperatures[END_REF].

In the case of the studies of 1-octene oxidation by Piperel et al. [START_REF] Piperel | Impact of acetaldehyde and NO addition on the 1-octene oxidation under simulated HCCI conditions[END_REF] and Fridlyand et al. [START_REF] Fridlyand | Chemical kinetic influences of alkyl chain structure on the high pressure and temperature oxidation of a representative unsaturated biodiesel: Methyl nonenoate[END_REF], only a few products, i.e. water, carbon oxides, formaldehyde, and C1-C4 hydrocarbons, were quantified. Notably products including 8 atoms of carbon produced by the primary reactions of the reactant were not measured.

The objective of the present paper is then to describe a new experimental and modeling study of 1-octene oxidation. The experiments were performed in jet-stirred reactor with gas chromatography analyses in order to detect the widest range of reaction products, including C8 compounds, for equivalence ratios from 0.25 to 2. A new detailed kinetic model has been developed. It was built using the same rules as that previously described for 1-hexene [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF].

Experimental method

As in many organic compound oxidation studies [START_REF] Herbinet | Progress in Understanding low-temperature organic compound oxidation using a jet-stirred reactor[END_REF], experiments were carried out in a heated isothermal jet-stirred reactor (JSR). Gas chromatography was used as the analytical method. The reactive gases, with helium as dilutant, entered the spherical JSR made out of quartz through four nozzles, positioned in the center of the reactor, and designed in order to ensure a perfect gas mixing and to avoid concentration gradients inside the reactor [START_REF] Herbinet | Jet-stirred reactor[END_REF]. To also limit thermal gradients inside the reactor, the gaseous mixture was heated to the reactor temperature in a quartz annular pre-heating zone prior to entering the spherical vessel. The residence time in this zone was negligible compared to the residence time in the reactor ( ) which was taken equal to reaction temperature was measured by a type K thermocouple positioned at the center of the reactor. The pressure in the reactor ( ) was controlled using a needle valve positioned at the downstream of the reactor and taken equal to 106.7 kPa.

Helium and oxygen were provided by Messer (purities of 99.99% and 99.999%, respectively) with flows to the reactor controlled using flow rate controllers. 1-Octene was provided by Aldrich (purity of 98%) and used without further purification. The liquid flow was controlled using a liquid-Coriolis-flow-controller, mixed with helium and passed through an evaporator before being mixed with oxygen prior entering to the reactor. The relative uncertainty in gas flow rates was assumed to be around 5%.

The gases leaving the reactors were analyzed using three gas chromatographs (GCs) connected on-line to the exit of the reactor through heated transfer lines kept at 423 K to avoid condensation:

•

The first GC equipped with a thermal conductivity detector and a Carbosphere packed column was used to quantify O2, CO, CO2 and CH4.

• The second GC equipped with a flame-ionization detector and a PlotQ capillary column was used to quantify molecules containing up to five carbon atoms. The flame-ionization detector was preceded by a nickel catalyst for the hydrogenation of carbonyl functions. This technique enables a more accurate quantification of species like CO, CO2 and formaldehyde.

• The third GC was equipped with a flame-ionization detector and a HP-5 capillary column for quantifying molecules containing at least five carbon atoms.

A fourth off-line GC fitted with a Plot Q or a HP-5MS column, and coupled with a mass spectrometer, was used for identification. Response factors were determined by injecting calibration mixtures or using the effective carbon number method [START_REF] Tranchant | Chromatographie en phase gazeuse[END_REF]. Relative uncertainties in mole fractions were estimated to be ±5% for species which were calibrated using standards and ±10% for species which were calibrated using the effective carbon number method. The peak of formaldehyde has a long tail compared to other species, and co-elution occurs with the peaks of three other oxygenates: oxirane, acetaldehyde and methanol. The peak of methanol is usually very small and located in the tail of that of acetaldehyde. In the present work, methanol was identified but not quantified due to a too strong co-elution with acetaldehyde. Nevertheless the accurate quantification of oxirane, acetaldehyde and formaldehyde was possible. The strategy used for the quantification consists in integrating all co-eluted peaks, the peak of oxirane, and the peak of acetaldehyde/methanol. The peak area of formaldehyde is obtained by doing a subtraction. This strategy was successfully tested by comparing formaldehyde mole fractions obtained using it and an independent diagnostic: cavity ting-down spectroscopy. An excellent agreement was obtained as it can be seen in the case of the oxidation of n-pentane (see Figure 1 in ref [START_REF] Rodriguez | Measuring hydroperoxide chain-branching agents during n-pentane low-temperature oxidation[END_REF]).

Detailed kinetic model

Model development

The 1-octene oxidation model presented hereafter, together with a glossary giving the linear notation corresponding to the name of each species used in the model, can be found in the SM under CHEMKIN format. All the related simulations have been performed using CHEMKIN PRO [START_REF]CHEMKIN-PRO 15151[END_REF]. As previously done in the case of 1-hexene [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF], a basis of this new model has been generated thanks to EXGAS software which was used to automatically generate model for the oxidation of many components of fuels and biofuels [START_REF] Blurock | Automatic generation of detailed mechanisms[END_REF], with some reaction pathways and kinetic data updated according to the recent literature. EXGAS software was in the past used to generate detailed kinetic models for hexene and heptene isomers [START_REF] Bounaceur | Influence of the position of the double bond on the autoignition of linear alkenes at low temperature[END_REF].

A reaction mechanism generated by EXGAS contains three parts:

• A C0-C2 reaction base, including all the reactions involving radicals or molecules containing less than three carbon atoms.

• A comprehensive primary mechanism with all the reactions of the initial organic reactants and oxygen, and of the derived free radicals. For 1-octene oxidation, the primary mechanism includes "ene" and "retro-rene" molecular reactions, 1-octene unimolecular initiations, the bimolecular initiations with O2 or between two 1-octene molecules, the additions of H atoms and ȮH, ĊH3, and HȮ2 radicals to the 1-octene double bond, the abstractions of alkylic and allylic Hatoms from the 1-octene molecule, the additions of alkylic, and allylic radicals to oxygen to form peroxy radicals, the alkylic, allylic and peroxy radical isomerisations involving a cyclic transition state including a ring with from 4 to 8 members, radical decompositions by β-scission or to produce cyclic ethers or branching agents, and allylic radical combinations including especially the combination with HȮ2 radicals.

• A lumped secondary mechanism, including reactions consuming the molecular products of the primary mechanism which do not react in the reaction base.

Note that in the primary mechanism, in the case of the peroxy radicals obtained by addition to O2 of alkylic radicals produced by addition of ȮH radicals to the double bond, isomerisations include the Waddington mechanism leading to aldehyde formation [START_REF] Stark | Oxidation of propene in the gas phase[END_REF]. Thermochemical data for molecules or radicals are automatically generated based on group and bond additivity methods proposed by Benson [START_REF] Benson | Thermochemical kinetics[END_REF].

To be consistent with the reactions and rate parameters described in details with the development of our new model in the case of 1-hexene [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF], the following reactions have been up-dated or added:

• The rate coefficients for the thermal dissociation and the reverse recombination of H2O2 have been updated to the values proposed by Troe [START_REF] Troe | The thermal dissociation/recombination reaction of hydrogen peroxide III: Analysis and representation of the temperature and pressure dependence over wide ranges[END_REF].

• The rate constant for the bimolecular initiation of C3-C4 alkenes with O2 has been taken as those proposed by Baulch et al. [START_REF] Baulch | Evaluated kinetic data for combustion modeling. Supplement I[END_REF] in the case of propene.

• The rate constants of the reactions of ȮH radicals with the fuel, including additions with hydroxyl adduct stabilization, additions followed by decomposition, and H-abstractions, have been estimated from the calculations of Zádor et al. [START_REF] Zádor | The reaction between propene and hydroxyl[END_REF] on propene using the same pressure dependence. For 1-hexene modeling, these reaction changes, which were especially important for allylic H-abstractions and additions followed by decomposition, were shown to have a significant effect on fuel consumption and aldehyde production [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF].

• The rate constants for the reactions via the Waddington mechanism, i.e. the reactions of hydroxyperoxyradicals through a cyclic transition state to produce ȮH radicals and aldehydes, have been taken from the calculations of Lizardo-Huerta et al. [START_REF] Lizardo-Huerta | Intramolecular effects on the kinetics of unimolecular reactions of β-HOROO˙ and HOQ˙OOH radicals[END_REF]. During 1-hexene modeling, this up-date resulted mainly in significant changes in the prediction of aldehyde distribution [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF].

• The reactions between of C3-C8 allylic and HȮ2 radicals have been added using the kinetics proposed for allyl radical by Goldsmith et al. [START_REF] Goldsmith | Theoretical rate coefficients for allyl + HO2 and allyloxy decomposition[END_REF][START_REF] Goldsmith | Role of O2 + QOOH in low-temperature ignition of propane. 1. Temperature and pressure dependent rate coefficients[END_REF] (with A-factors of all these pathways divided by two in this 1-octene model). During 1-hexene modeling, the addition of these new reaction pathways notably influenced the fuel reactivity, and was also acted as the main route to unsaturated aldehydes [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF].

• The rate constant for the H-abstraction from 1-octene by CH3Ȯ radicals giving an allylic radical has been taken from the recent work of Zhang et al. [START_REF] Zhang | An up-dated experimental and kinetic modeling study of n-heptane oxidation[END_REF] (40 T 2.9 exp(-8609 cal/RT) s -1 ) instead of the older values (1.8 × 10 12 exp(-1200 cal/RT) s -1 ) proposed by Bounaceur et al. [START_REF] Bounaceur | Influence of the position of the double bond on the autoignition of linear alkenes at low temperature[END_REF].

During 1-hexene modeling [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF], this up-date massively decreased the predicted production of methanol, with only a slight decrease of simulated fuel consumption. In the present work, the use of the older value [START_REF] Bounaceur | Influence of the position of the double bond on the autoignition of linear alkenes at low temperature[END_REF] leads to a slightly better agreement for fuel consumption in lean mixtures, but to a 20% overprediction in stoichiometric conditions, with no notable change for product formation.

• The rate constant of the reaction with α-hydroxyalkyl radicals to yield aldehydes/ketones and HȮ2 radicals has been taken from the work of da Silva et al. [START_REF] Da Silva | Ethanol Oxidation: Kinetics of the αhydroxyethyl radical + O2 reaction[END_REF]. This new theoretically calculated rate constant for this reaction, which is the main route via aldehydes/ketones of the same size as the reactant, is larger by at least three orders of magnitude than the estimated value of Bounaceur et al. [START_REF] Bounaceur | Influence of the position of the double bond on the autoignition of linear alkenes at low temperature[END_REF]. However, a division by a factor of 10 of this value did not have a significant effect on the octanal / 2-octanone prediction, especially below 800 K.

•

The formation and the decomposition of C8 keto-and aldo-hydroperoxides have been detailed and have replaced the reactions automatically generated using the EXGAS lumping method [START_REF] Biet | Experimental and modeling study of the low-temperature oxidation of large alkanes[END_REF]. During 1-hexene modeling [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF], this up-date massively increased the predicted production of propanal, with no effect on simulated fuel consumption.

• The rate constants of the decomposition of large hydroperoxides has been taken as: at 1 atm, the rate expression of 4.0 × 10 15 exp(-42,900 cal/RT) s -1 , as proposed by the review Baulch et al.

[31] for C2H5OOH decomposition, and, at 10 atm, the rate expression of 1.5 × 10 16 exp(-42,000 cal/RT) s -1 as adopted by Curran et al. [START_REF] Curran | A comprehensive modeling study of isooctane oxidation[END_REF] in their iso-octane mechanism.

• The rate constants for the decomposition by C-C bond breaking of C8 alkenyl and allylic radicals were adopted from the recent theoretical work of Bian et al. [START_REF] Bian | Unimolecular reaction properties for the longchain alkenyl radicals[END_REF].

• The 1,6-endo-cycloaddition and 1,7-endo-cycloaddtion of oct-1-en-6-yl and oct-1-en-7-yl radicals, followed by the decomposition by CH bond breaking of the obtained cyclic radicals, have been added with rate constants taken from Wang et al. [START_REF] Wang | Reactivity-structure-based rate estimation rules for alkyl radical h atom shift and alkenyl radical cycloaddition reactions[END_REF] (with the A-factor divided by two in the case of the 1,6-endo-cycloadditions).

The two last updates were not considered in the 1-hexene model [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF], but were found to be important for a larger reactant such as 1-octene.

Simulations of previous literature data

The model was first used to simulate literature data: the results of Piperel et al. [START_REF] Piperel | Impact of acetaldehyde and NO addition on the 1-octene oxidation under simulated HCCI conditions[END_REF] obtained also using a jet-stirred reactor, but at higher pressures than that in the present study, as well as the results of Fridlyand et al. [START_REF] Fridlyand | Chemical kinetic influences of alkyl chain structure on the high pressure and temperature oxidation of a representative unsaturated biodiesel: Methyl nonenoate[END_REF] measured in a shock tube.

Figure 1 displays a comparison between simulations using the current model and experimental results of Piperel et al. [START_REF] Piperel | Impact of acetaldehyde and NO addition on the 1-octene oxidation under simulated HCCI conditions[END_REF]. A reasonable agreement is observed over all the temperature range for fuel, water, carbon oxides and formaldehyde, with nevertheless, an underprediction of the reactivity between 650 and 750 K. Figure 2 shows the same comparison for the results of Fridlyand et al. [START_REF] Fridlyand | Chemical kinetic influences of alkyl chain structure on the high pressure and temperature oxidation of a representative unsaturated biodiesel: Methyl nonenoate[END_REF] who provided the detailed experiment conditions and results. The initial pressures, temperatures and reaction times were set as the same as in the experiments. From the experimental data, it seems the initial fuel mole fraction is 110 ppm, rather than 100 ppm. In their simulation, Fridlyand et al. [20] also used 110 ppm as the initial fuel mole fraction. The initial fuel mole fraction of oxygen is set as stated (1200 ppm). The shock tube experiment was simulated using a constant pressure batch reactor model as did by Fridlyand et al. [START_REF] Fridlyand | Chemical kinetic influences of alkyl chain structure on the high pressure and temperature oxidation of a representative unsaturated biodiesel: Methyl nonenoate[END_REF]. The reactant mole fraction profile indicated that the reactivity with the current model would not be high enough: it is similar to simulation results with the model of methyl 9-decenoate by Herbinet et al. [START_REF] Herbinet | Detailed chemical kinetic mechanism for the oxidation of biodiesel fuels blend surrogate[END_REF] which included a high temperature 1-octene model. Fridlyand et al. [START_REF] Fridlyand | Chemical kinetic influences of alkyl chain structure on the high pressure and temperature oxidation of a representative unsaturated biodiesel: Methyl nonenoate[END_REF] obtained a better agreement but with an adjustment of the rate constant for the fission of the allylic C-C bond by a factor of 2-5. However, it can be also seen in Figure 2 that the current 1-octene model predicts well the evolution with temperature of the product mole fraction, with a good simulation of the temperature at which the maximum mole fraction is observed.

Discussion about JSR experimental results and comparison with simulations using the new model

Figures 34567show experimental results obtained in JSR for temperatures from 500 to 1100 K, at atmospheric pressure, with dilute mixtures at equivalence ratios of 0.25, 0.5, 1.0, and 2.0 in helium, as well as comparison with simulations performed using the previously described model. The mole fractions obtained for all performed measurements can be found in a spreadsheet of the SM.

Reactants, carbon oxides and methane

Figure 3 displays the evolution with temperature of fuel conversion and of the mole fraction of oxygen, carbon oxides, and methane. A negative temperature coefficient (NTC) zone is observed at all equivalence ratios. The temperature range where this NTC zone is observed expands as mixture becomes leaner. When the equivalence ratio decreases, the fuel reactivity is significantly promoted at low temperatures below 800 K. This promoting effect is gradually reduced at higher temperatures. The model reproduced reasonably well the experimental results including the influence of changing temperatures and equivalence ratios. However, the effect of equivalence ratio on the low temperature fuel reactivity is underpredicted. Note that, in a narrow temperature range around 650 K, a sharp peak of the fuel reactivity is predicted for the equivalence ratio of 2.0. This peak was not experimentally observed. This temperature corresponds also to sharp peaks in the mole fraction profiles of several products: ethylcyclohexenes, octanal and 2-octanone, as described further in the text.

Alkenes and dienes

C2-C4 alkenes, C4-C5 dienes and cyclic alkenes, namely cyclohexene and ethylcyclohexenes, were detected and quantified during these experiments. Their mole fraction profiles are displayed in Figure 4. Note that, 1,3-octadiene was also detected, but it was not quantified due to a strong co-elution with another unknown product. The decrease of equivalence ratio promotes the formation of alkenes and dienes below 800 K while it reduces the production of these unsaturated hydrocarbons when temperature continues increasing. Reducing equivalence ratio enhances the formation of cycloalkenes at all temperatures. Concerning simulated results, despite significant discrepancies in absolute values for 1,4-pentadiene and ethylcyclohexenes, the evolution of product mole fractions with temperature and equivalence ratio is correctly predicted by the model. 1,4-pentadiene is mainly produced from the β-scission of the oct-1-en-4yl radical, and it is overpredicted by almost a factor of four. Further consumption reactions of 1,4-pentadiene need to be investigated to improve this prediction.

It is interesting that cyclohexenes bearing an ethyl function were detected during the oxidation of 1-octene. As is shown in Figure 8, the oct-1-en-6-yl radical formed by H-abstractions from 1-octene proceed via an 1,6-endo-cycloadditon to produce the 3-ethylcyclohexyl radical. This radical can subsequently eliminate an H atom either by reaction with O2 or by β-scission to form 3-ethylcyclohexene or 4-ethylcyclohexene. Such formation pathways were investigated in recent theoretical studies [START_REF] Bian | Unimolecular reaction properties for the longchain alkenyl radicals[END_REF][START_REF] Wang | Reactivity-structure-based rate estimation rules for alkyl radical h atom shift and alkenyl radical cycloaddition reactions[END_REF]. However, the current mechanism lacks of low-temperature reactions related to ethyl-cyclohexane and ethyl-cyclohexenes, for which very few papers can be found in the literature. Although recent experimental, theoretical and modeling studies of ethylcyclohexane oxidation were recently published [START_REF] Husson | Detailed product analysis during low-and intermediate-temperature oxidation of ethylcyclohexane[END_REF][START_REF] Ning | Low-and intermediate-temperature oxidation of ethylcyclohexane: A theoretical study[END_REF][START_REF] Wang | Kinetics of ethylcyclohexane pyrolysis and oxidation: An experimental and detailed kinetic modeling study[END_REF] and detailed kinetic models are available for the high-temperature oxidation and pyrolysis of this molecule [START_REF] Wang | Kinetics of ethylcyclohexane pyrolysis and oxidation: An experimental and detailed kinetic modeling study[END_REF], there is still no validated model for its low-temperature oxidation. As a result, the production of ethylcyclohexenes is largely overpredicted at temperatures below 800 K; by contrast, the predictions at high temperatures are close to the experimental data. This incomplete knowledge about the kinetics of the consumption of ethyl-cyclohexenes is certainly one of the major reason explaining that the present 1-octene model consistently underestimates the reactivity in the lowtemperature region, not only in comparison with the present experiments but also with literature ones.

Products with a carbonyl function

Several products with a carbonyl function, such as saturated and unsaturated aldehydes were detected and quantified during the experiments. Figure 5 shows the experimental results for saturated aldehydes and 2-octanone. The decrease of equivalence ratio promotes the production of aldehydes. This is correctly predicted by the model. However, the high temperature productions of formaldehyde, acetaldehyde and propanal is overpredicted, while the low temperature productions of C1 to C5 aldehydes is mostly underpredicted. The large aldehyde underprediction observed at low-temperature especially for lean mixtures is partly related to the reactivity underprediction obtained under these conditions, but also certainly to missing formation pathways which are important for large alkenes while they did not play such a big role during 1-hexene oxidation, since the predictions concerning aldehydes were better with the model of Meng et al. [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF].

Heptanal, the main product of the Waddington mechanism apart from formaldehyde, is shown to be mainly formed in the low-temperature range. The model reasonably predicts its evolution or with temperature and equivalence ratio. Although hexanal is another expected product of the Waddington mechanism (see a scheme of possible pathways through Waddington mechanism in Figure 9), its formation pathway is notably less favored than that of heptanal, and a co-elution with the fuel also makes it hard to be measured quantitatively in our GC experiments. Figure 9. Scheme of the possible reactions pathways through the Waddington mechanism.

Figure 5 also indicates a production of octanal and 2-octanone, which are mainly produced by the oxidation of α-hydroxyalkyl radicals as shown in Figure 10. Our previous 1-hexene modeling study [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF] showed that this type of reaction had an inhibiting effect on the fuel reactivity. The model predicts reasonably well the formation of octanal, while the mole fractions of 2-octanone are overpredicted by a factor around 10. Nevertheless, the shape of the mole fraction evolution with temperature and the influence of equivalence ratio are well predicted. The overprediction of 2-octanone may be attributed to the lack of consuming reactions in the current model. Note that, there is a large peak production of octanal and 2-octanone around 650 K in rich mixtures.

Note that, with the help of the work of Pelucchi et al. [START_REF] Pelucchi | An experimental and kinetic modeling study of the pyrolysis and oxidation of n-C3-C5 aldehydes in shock tubes[END_REF] on aldehydes, the reactions consuming octanal were considered in greater details than for octanone. As only few information was available on the kinetics of reactions consuming ketones [START_REF] Kopp | Ab initio kinetics predictions for H-atom abstraction from 2-butanone by H and CH3 and the subsequent unimolecular reactions[END_REF], the lumped ketone consumption submechanism generated by EXGAS was kept.

+ ȮH + O 2 Heptanal -ȮH O + ȮH + O 2 -ȮH O H O O H O O O O O H OH OH O O O O OH OH + O 2 -ȮH OH O O O O O H Hexanal O O Figure 10
. Oxidations of α-hydroxyalkyl radicals to form octanal and 2-octanone.

As suggested in recent studies of alkenes oxidation [START_REF] Battin-Leclerc | Products from the oxidation of linear isomers of hexene[END_REF][START_REF] Burke | An experimental and modeling study of propene oxidation. Part 1: Speciation measurements in jetstirred and flow reactors[END_REF][START_REF] Li | The oxidation of 2-butene: A high pressure ignition delay, kinetic modeling study and reactivity comparison with isobutene and 1butene[END_REF][START_REF] Zhou | A comprehensive experimental and modeling study of isobutene oxidation[END_REF], reactions of allylic and HȮ2 radicals are important reactivity promoting reactions, and are also the main pathways of producing unsaturated aldehydes. Acrolein, 2-butenal and 2-octenal were detected and quantified during these experiments and their mole fraction evolutions with temperature are depicted in Figure 6. Acrolein and 2-butenal are both produced at low and high temperatures.

The high temperature production of these small unsaturated aldehydes can be attributed to the large formation of propene and 1-butene yielded from the β-scission of fuel radicals. While the simulations for acrolein compare well with experimental data, 2-butenal mole fractions are notably underpredicted. Contrary to the experimental result, the predicted formation of 2butenal occurs only above 800 K. Since the β-scissions of fuel radicals are more favored at high temperatures, the production of 2-octenal, which is mainly due to the reaction of the oct-1-en-3-yl with HȮ2 radicals, is significantly lower at high-temperatures than at low temperatures. The fact that 2-octenal is mainly produced at low temperatures is correctly predicted by the model, but the magnitude of the mole fraction is significantly overpredicted.

Such results may be due to a lack of consuming reactions of 2-octenal, which requires further investigation as relevant studies are scarce in literature.

Cyclic ethers

Cyclic ethers were already found to be produced during the oxidation of alkenes [START_REF] Battin-Leclerc | Products from the oxidation of linear isomers of hexene[END_REF]. The reaction of alkenes with HȮ2 radical forming the oxirane (formed via direct epoxidation) is a major reaction pathway both at low and high temperatures. As is shown in Figure 7, when decreasing equivalence ratio, the production of hexyl-oxirane, which is produced by reaction of 1-octene and HȮ2 radical, is promoted regardless of the temperature.

Some other cyclic ethers were also detected during the oxidation of 1-octene. The formation of hydroxycyclic ethers is a concurrent reaction channel to the Waddington mechanism, which was proposed in alkene models since 2005 [START_REF] Touchard | Modeling of the oxidation of large alkenes at low temperature[END_REF]. Hydroxycyclic ethers were experimentally detected and quantified by Battin-Leclerc et al. in their 2014 study on hexenes [START_REF] Battin-Leclerc | Products from the oxidation of linear isomers of hexene[END_REF]. In this study, 2-propyl,5-hydroxymethyl-tetrahydrofuran was detected and quantified during the oxidation of 1-octene, as is shown in Figure 7. The formation pathways of this species is described in Figure 12: hydroxyl radical adds first to the terminal carbon of the double bond. This is followed by an addition to oxygen, an isomerization and 2-propyl,5-hydroxymethyl-tetrahydrofuran is finally obtained. The adduct formed by the addition of hydroxyl radical to 1-octene can also isomerize to another radical bearing a hydroxyl function, and finally leads to the formation of 2-propyl,5-hydroxymethyltetrahydrofuran via similar reactions. Since the addition of ȮH radicals is favored at low temperatures, 2-propyl,5-hydroxymethyl-tetrahydrofuran is mainly produced below 800 K. The evolution with temperature and equivalence ratio of 2-propyl,5-hydroxymethyl-tetrahydrofuran mole fraction is correctly predicted. The overprediction of the mole fraction values may be largely due to the lumping treatment of cyclic isomers in the model.

Sensitivity and flow rate analyses

Figure 13 presents sensitivity analysis for the oxidation of 1-octene at 650 K, the low temperature around which the highest reactivity is typically observed under all equivalence ratios investigated in this study. In addition, an overview of the 1-octene oxidation reaction flux at 650 K under stoichiometric condition is given in Figure 14. As is shown in Figure 14a, similar to the low temperature oxidation of 1-hexene [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF], the additions of ȮH radical and H-atom to the double bond are important low temperature consumption pathways of 1-octene oxidation. The addition of ȮH radical is the initial reaction that leads to the Waddington mechanism, the formation of hydroxyl cyclic ethers, and hydroxyketohydroperoxides, the decomposition of which is an important low temperature branching step. It is observed that the two adducts of ȮH radical to 1-octene could lead to the production of octanal and 2-octanone, but with different branching ratios. Only 14.7% of the adducts obtained by the terminal addition of ȮH can isomerize in two steps to produce hydroxyalkyl radicals which can be oxidized to form octanal. In contrast, 87.5% of the adducts produced from the central addition of ȮH can isomerize in two steps via R83C8H16OH to the give hydroxyalkyl radicals which can react to form 2-octanone. The isomerization of R83C8H16OH is shown to have a strong inhibiting effect on the low temperature reactivity, while the competing oxygen addition reaction promotes the reactivity as illustrated in Figure 13.

The addition of H-atom to the terminal end of the double bond is shown to have a lager flow rate than that to the central end in Figure 14a. The adducts are octyl radicals, which would typically go through the low temperature oxidation pathways as in the oxidations of long chain alkanes, where the formation of ketohydroperoxides contributes to the low temperature branching step.

Moreover, the terminal addition of H-atom is shown to promote the reactivity in Figure 13.

As illustrated in Figure 14b, H atom abstractions are other important fuel consuming pathways during 1-octene oxidation. As 1-octene has two more carbon atoms than 1-hexene, it produces two more akenyl radicals along with more isomerizations, which makes the low temperature oxidation of 1-octene more complex. As is shown in Figure 13, most H-atom abstraction reactions promote the reactivity except for the reaction that produces the oct-1-en-6-yl radical (R32C8H15Z). This is because the oct-1-en-6-yl radical can proceed via an 1,6-endocycloadditon to produce the 3-ethylcyclohexyl radical, which mostly reacts to form 3ethylcyclohexene or 4-ethylcyclohexene. Note that reactions leading to the formation of ethylcyclohexenes are shown to have a strong inhibiting effect on the reactivity. By contrast, the addition of O2 to the oct-1-en-6-yl radical is a sensitive promoting reaction as shown in Figure 13.

As is shown in Figure 14b, the allylic oct-1-en-3-yl radical (R27C8H15X) can be produced not only from the abstraction of H-atoms from 1-octene, but also from the isomerizations of other octenyl radicals. The reactions of the oct-1-en-3-yl radical play an important role in the low temperature oxidation of 1-octene. Its combination reactions with HȮ2 radical are the main reactions leading to the formation of unsaturated aldehydes, such as 2-octenal and acrolein.

Moreover, a product of the reaction of oct-1-en-3-yl with HȮ2 radical, namely the pentyl radical, could lead to low temperature branching reactions, which is also highlighted by the sensitivity analysis as shown in Figure 13. A certain amount (20.4%) of the oct-1-en-3-yl radical could also go directly through β-scission to produce 1,3-butadiene and a butyl radical. This butyl radical can promote the low temperature reactivity by forming the branching agent via addition to O2, as both shown in Figures 13 and14b.

Conclusion

This paper presents a speciation study of the oxidation of 1-octene in a jet-stirred reactor for temperatures from 500 to 1100 K, at atmospheric pressure, with dilute mixtures of equivalence ratios of 0.25, 0.5, 1.0, and 2.0 in helium. A detailed oxidation mechanism of 1-octene is also developed to reproduce the experimental data obtained herein as well as previous studies in the literature. A broad range of oxidation products, such as 1,4-pentadiene, cyclohexene, ethylcyclohexene, C5-C8 aldehydes, 2-octanone, octenal, hexyl-oxirane, and 2-propyl,5-hydroxytetrahydrofuran have been quantified, most of which are satisfactorily described by the model.

However, even if based on the same kinetic rules as that proposed for 1-hexene [START_REF] Meng | Revisiting 1-hexene lowtemperature oxidation[END_REF], the agreement obtained with the 1-octene model is all together less satisfactory than for the C6 reactant. This is due to an increase in the complexity of the chemistry with increasing the size of the studied 1-alkene. The 1,6-endo-cycloaddition of the oct-1-en-6-yl radical, which finally leads to the formation of ethylcyclohexenes is shown to be important to the low temperature oxidation of 1-octene. However, the low temperature reactions producing aldehydes and the pathways consuming ethylcyclohexenes still require further investigations as well as those decomposing long chain carbonyl species, such as octanal, 2-octanone, and 2-octenal.

Figure 1 .

 1 Figure 1. Comparison between simulated (with the current model) and experimental data for the JSR experiments by Piperel et al. [19] (pressure of 10 atm, equivalence ratio of 0.75).

Figure 2 .

 2 Figure 2. Comparison between simulated (with the current model) and experimental data for the shock tube experiments by Fridlyand et al. [20] (pressure of 5 MPa, equivalence ratio of 1.1).

Figure 3 .

 3 Figure 3. Mole fraction profiles of reactants and C0-C1 reaction products (except formaldehyde) for 1-octene oxidation in a jet-stirred reactor at = 0.25, 0.5, 1.0 and 2.0, = 106.7 kPa, = 2 s. Full symbols are experiments and lines simulations.

Figure 4 .

 4 Figure 4. Mole fraction profiles of alkenes and dienes produced during 1-octene oxidation in a

Figure 5 .

 5 Figure 5. Mole fraction profiles of saturated aldehydes and ketone with a carbonyl function formed during 1-octene oxidation in a jet-stirred reactor at = 0.25, 0.5, 1.0 and 2.0, = 106.7 kPa, = 2 s. Full symbols are experiments and lines simulations.

Figure 6 .

 6 Figure 6. Mole fraction profiles of unsaturated aldehydes with a carbonyl function formed during 1-octene oxidation in a jet-stirred reactor at = 0.25, 0.5, 1.0 and 2.0, = 106.7 kPa, = 2 s. Full symbols are experiments and lines simulations.

Figure 7 .

 7 Figure 7. Mole fraction profiles of cyclic ethers formed during 1-octene oxidation in a jet-stirred reactor at = 0.25, 0.5, 1.0 and 2.0, = 106.7 kPa, = 2 s. Full symbols are experiments and lines simulations.

Figure 8 .

 8 Figure 8. Scheme of formation of ethylcyclohexenes.

Figure 11 .

 11 Figure 11. A chromatogram showing some cyclic ethers detected during the experiments plotted versus retention time.

Figure 12 .

 12 Figure 12. Possible formation pathways of 2-propyl,5-hydroxymethyl-tetrahydrofuran for 1-octene.

Figure 13 .

 13 Figure 13. Sensitivity analysis for fuel conversion at 650 K under the conditions of Figure3.

Figure 14 .

 14 Figure 14. Flow rate analysis at 650 K under the conditions of Figure 3 for stoichiometric mixtures, KHP = ketohydroperoxide, KHP-OH = hydroxyketohydroperoxide, species in boxes were detected during the JSR experiments. Broken arrows correspond to several elementary steps; numbers with arrows corresponds to the flux of intermediate consumption.

Acknowledgement

Xiangzan Meng would like to acknowledge the financial support from the program of China Scholarship Council (NO. 201506250038).

Mechanism

Thermodynamic properties Species glossary.

Supplementary material

Experimental data for the oxidation of 1-octene.


Javier Osorio
email: josorio@dede.ulpgc.es

Jacques Bulchand

Moving Towards 2020: A Tentative Approach to ITEM

Keywords: Learning 2.0, Web 2.0, Education & Training, Information Technology, 2020, ITEM

A decade into the 21st Century, it seems that Humanity has given itself time to ensure that the rest of the century will pass by according to the universally accepted principles of equal opportunities and sustainable economic development. Year 2020 appears as a symbolic moment to attain this desired maturity, though it is, nevertheless, a complex goal to reach. Education is an essential area in any action that intends to accomplish this model of society, an instrument without which all efforts will be in vain. The outline of this paper is to try to glimpse which will probably be the determining factors of the worldwide economic situation and, therefore, what kind of professionals society will be demanding. The reply to this demand will structure future teaching and learning, and a series of needs will subsequently arise in Educational Management. Finally, according to this scenario we will propose improvements in Educational Management supported by Information Technology.

Introduction

Year 2020 has become an especially relevant date in which to accomplish certain indicators regarding climate change prevention and more environmentally aware lifestyles. The Copenhagen Climate Change Summit 2009 has been an important milestone that has contributed to reinforce 2020's iconic symbolism. Also, the United Nations Millennium Goals are another milestone to achieve. But 2020 is not only a key date to check if these internationally shared aspirations concerning the environment and society have been completed, but also a crucial date as regards education. Will we be ready by then to state that citizens are being offered an education that responds to the times? Moreover, we could include this query in the subsequent debate as to whether integrating people into a national education system to provide them with skills and competences, as well as accrediting their achievement, will make sense in 2020.

If we accept that an education system's aim is to train citizens and professional persons to carry out their work in such a way as to allow both individuals and communities to benefit from the knowledge and competences so acquired, then we should firstly establish which could be the future working environment's main characteristics in a hypothetical scenario, setting year 2020 as a time reference.

Starting off from here we could then consider which should be the education system's goals for its different levels. After that the next step could be to deduce possible trends in education. At this point we could centre our attention on our specific interest, that is to say, establishing Information Technologies' role in Educational Management and, subsequently, what actions are required to ensure that Information Technologies effectively contribute to improve Educational Management. Figure 1 shows part of the aspects we have mentioned as well as the outline of this paper. The European Qualification Framework 1

These two basic concepts have become important in the European and international educational picture as a form of agreement on a common language that will allow setting goals and indicators of their achievement, notwithstanding the educational level, whether it be primary, secondary or higher education. Having ascertained these basic concepts, we can now consider aspects that will influence education in our set time reference, such as the labour market. This will allow us to identify the challenges Educational Management will be facing and, more specifically, the challenges to ensure an optimal use of information technologies to support Educational Management.

gives a precise definition for the terms "skills" and "competences" in order to establish a common working language. According to these recommendations, skills means the ability to apply knowledge and use know-how to complete tasks and solve problems. In the context of the European Qualification Framework, skills are described as cognitive (involving the use of logical, intuitive and creative thinking) and practical (involving manual dexterity and the use of methods, materials, tools and instruments). On the other hand, competence means the proven ability to use knowledge, skills and personal, social and/or methodological abilities, in work or study situations and in professional and personal development. In the context of the European Qualification Framework, competence is described in terms of responsibility and autonomy.

Anticipating and adjusting the labour market and necessary skills

It's impossible to say for certain what the future holds in 2020 as regards labour matters, just as impossible as trying to predict our own future in any area of our lives. Nevertheless, it is generally agreed that we must try to anticipate and plan for the future in order to avoid undesirable results and, to the contrary, make the most of any opportunities that may arise. In the socioeconomic field, attempting to predict and plan is a strategic activity, due to the implications it has for the market and labour policies. In a wide sense, education is very sensitive to the labour market needs. Certainly, formal education of children, young people and adults cannot depend exclusively on such demands, as they are of a contextual nature, but it is also true that students are trained to carry out their professional activity under specific socioeconomic conditions and they must be fully qualified to offer their best in a defined professional environment. Therefore, as previously mentioned, and although not a conclusive element, anticipating what the labour environment will be like towards 2020 can give us important clues as to some of the main aspects on which to build educational structures and systems that will provide students with skills and competences that will respond adequately to the labour challenges of the future. Consequently, we should try at an early stage to identify the skills and competences required. Accordingly, we must also discover factors that may condition the future labour market and, as a result, the educational system. Some of these are as follows:

Technological change. Technological change is part of an equation in which the need for skilled workers is directly proportional to the magnitude of change required. In fact, technological change is considered the main reason stated to justify the need for highly skilled workers [START_REF] Machin | Changes in Wage Inequality[END_REF].

Organizational change. Parallel to technological development, ways of organizing work evolve according to such varied criteria as the search for flexible production systems, product and service customization, quality improvement, production chain optimization, humanization of work, etc. All of them are usually associated with a body of knowledge that subsequently demands skilled workers who are capable of adapting to new situations [START_REF] Breshanan | Information Technology, Workplace Organization and the Demand for Skilled Labour: Firm Level Evidence[END_REF].

Globalization and international commerce. Over the past years we have witnessed an increase of international commerce without precedent in the World's economic history. Traditionally developed countries, which are specialized in turning out high added value products and services, have centred the demand for skilled workers, whereas emerging countries, with a less skilled workforce, have concentrated on a low added value production. Nevertheless, similarly to what happened in Japan during the 70's, the current trend is for developing countries to focus increasingly on generating high added value products and services and, therefore, they need to train more highly skilled students. Following the action-reaction mechanism, if developed countries want to continue being competitive, they will have to make a decided bet for innovation and superspecialization, which in turn requires developing more skills and competences.

Climate change and environmental challenges. Over the last few years both governments and citizens have become increasingly aware of the damage economy can suffer due to climate change. This has brought around a general effort to reduce climate change and combat environment degradation, a trend that could favour the surge of a green economy that would employ millions of skilled workers all over the world (UNEP, 2008).

All these factors are currently foremost, but will probably have taken second place as we approach 2020, when new circumstances and concerns will dominate the economic, social and, therefore, educational scenario. This does not mean we should ignore such factors, quite to the contrary it would be convenient to consider them a starting point to begin to plan for the future, though allowing for new variables as they appear.

In short, we can refer to the document published by the European Commission {COM(2008)868}, titled New Skills for New Jobs: Anticipating and matching labour market and skill needs, which explains that socioeconomic changes imply the need for more highly skilled workers with an increased capacity to add value through their work and, therefore, a greater demand of university graduates, the education level that will experiment the greatest growth. In this sense, the REFLEX report (ANECA, 2008) states that university graduates of the future will have to be competent in at least the following five areas: professional expertise, functional flexibility, innovation and knowledge management, mobilisation of human resources, and international orientation.

Although we don't want to study these aspects more in depth, and continuing with this paper's basic argument as put forward in the introduction, we would like to try to perceive the implications of socioeconomic trends for the education system as respects the skills and competences of future professionals, considering all educational levels and not just the university one.

Educational Institutions on the Horizon of 2020

As mentioned above, as a result of a series of circumstances towards 2020 the socioeconomic setting will point towards the need for graduates with highly specialized skills and competences, mainly because that society will no longer be dominated by the industrial era's logic based on mass production and mass consumption. Foreseeably, large scale production will cease to be the main guideline and will give way to the creation of added value, mostly at an individual level. And so, following our reasoning, the next step is how to develop the skills and competences required to suit this change of model. This is where we enter the field of education and learning. It is not excessive to say that the 21 st Century society will be a Learning Intensive Society in which educational models of formal education will undergo a profound transformation and life-long learning will become a regular activity of all professionals, who will find it to be the only reasonable way to permanently update the skills and competences that the socioeconomic situation will generate continuously.

Together with the Learning Intensive Society concept another term has gained popularity after it appeared in a report published in 2006 by the Institute for Prospective Technological Studies, as a way to embrace a different view of future learning [START_REF] Punie | The Future of ICT and Learning in the Knowledge Society[END_REF]. This term is Learning Spaces, which intends to encompass such a multifaceted reality as learning by including both tangible and non tangible aspects, therefore separating itself from the idea that learning spaces can only refer to physical locations (classrooms, research laboratories, one's own home, etc). To the contrary, it shows that ideas, persons and objects are mobile and they come together in 24/7 asynchronous contexts.

It is not unreasonable to say that we are entering a setting in which the limits between educational institutions and people's homes, between formal, non-formal and informal learning and between teachers and students are all becoming blurred. One of the reasons that leads us to this hypothesis is the emergence of combined educational environments, in which the role of transmitting knowledge, that has traditionally been more or less monopolized by educational institutions, is gradually being taken over by other agents, not necessarily educational ones, that exist in the web and whose most relevant example is Web 2.0.

A possible consequence of the changes we have listed above could be a hypothetical scenario in which children's schooling would no longer be compulsory in 2020, whereas different communities would decide how to manage aspects concerning children's education and safety. The challenge for each Ministry of Education would then be how to handle the shift from large educational institutions, the school-factory type with a great number of students and homogeneous teachinglearning methods for them all, allocating resources for the take over of new unique organizations which would offer distinct teaching-learning services to a much more reduced number of students. In such circumstances each Ministry of Education should also provide for mechanisms that can guarantee the development of evaluation, quality and accreditation systems that assure with utmost clarity that results are being achieved according to regional, national o supranational standards.

Significance of Web n.0 on the 2020 Educational Horizon

The uprise of combined learning environments, such as Learning 2.0, can be seen as a sign of the rupture of the highly consolidated notion as to the role institutions play in education and training, which could give way to a new educational culture. At present Web 2.0 tools have changed the rules of the game in the environment of Internet, communication and education. But we cannot exclude that this new environment may encourage novel learning and communication philosophies in Internet, so we will surely witness the rise and development of Web 3.0, 4.0 and so forth. All of which will be accompanied by related developments such as Learning 3.0, 4.0, etc. Therefore, although on the 2020 horizon we will probably be referring to Web n.0, right now we will concentrate on Web 2.0 and its present implications in order to explain the challenges the educational sector will have to face.

Learning 2.0 is a philosophy based on a Web 2.0 platform, as opposed to closed virtual learning environments and content management systems. Learning 2.0 favours creating and expanding interest groups and communities of practice that can remain active even after the lecture/course/module is over [START_REF] Ala-Mutka | Learning 2.0: The Impact of Web 2.0 Innovation on Education and Training in Europe[END_REF], thus promoting collaboration between peers. The key to the development of this collaboration can be found in the way the new available tools on which this teachinglearning philosophy is based motivate and hook people. The student takes control of the learning speed, structure and contents thanks to diverse audiovisual resources.

Probably one of the main challenges that Web 2.0 will bring regarding pedagogic and organizational innovation is the fact that learning seems to be surpassing the limits of formal education and traditional schooling systems. This means questioning matters such as: (a) what kind of learning can be found beyond the limits of formal education; (b) what role do educational methods play in today's society; and (c) which educational methods can best provide the skills and competences that our socio-economic environment is demanding (there is a growing demand to alter these methods towards more active ones that concentrate on the social construction of knowledge, instead of the more passive type, including traditional instructionist theories).

Challenges for ITEM in the 2020 Scenario

If we take a look at current educational institutions we can see that investment in Information Technology (IT) in primary, secondary and higher education is still at an initial stage [START_REF] Miller | School's Over: Learning Spaces in Europe in[END_REF]. Although there is abundant empirical evidence to show that investment in IT has had a positive impact, it is also widely agreed that it has not been developed to its full potential. This is because little attention has been given to the pedagogic opportunities it offers, instead of which it has basically been used to give support to teaching structures and methods of the past and as a vehicle to improve communication while using traditional pedagogic and didactic resources. In this sense, IT investment seems to have had a greater impact on administrative services, such as admissions, registry, payment of fees, purchases, staff and timetable management, etc, rather than on the foundations of teaching and learning [START_REF] Miller | School's Over: Learning Spaces in Europe in[END_REF][START_REF] Balanskat | The Impact of ICT on Education -a Review of Existing Studies Analysing the Impact of ICT[END_REF].

This leads us to a matter of utmost importance: what role shall Information Technology for Educational Management (ITEM) play on the 2020 horizon? As we have mentioned above, there is a risk that is may be used exclusively for administrative support purposes and, though this is a fundamental task which must be carried out as efficiently as possible, ITEM should not be reduced to this merely operative function. A shared strategic vision must be found to give ITEM long term meaning of added value.

At this point we should decide what part of the IT-EM equation should centre our efforts and in what way. In other words, should we concentrate on what technology (IT) can bring to education on the 2020 horizon, especially emerging technology that we have called Web n.0, or, on the other hand, should we focus on the educational side of this equation (EM). Our aim is to try to achieve a reasonable balance between both IT and EM in order to offer a unified vision of ITEM, but we must keep in mind certain aspects that will possibly set the pace of its development.

Firstly we must consider a basically technical matter regarding how to guarantee universal access to IT, the bandwidth, the use of open-software and author's rights in respect of the contents. Certainly, technological infrastructure evolves along its own channels. This way, even though in developed countries cable based nets have become well established, connectivity based on mobile technology is growing strong and is the main way of connecting to the Internet in developing countries. Universal access to the web brings about certain uniformity in educational management practices, thanks to an increased knowledge and replication of successful experiences in points of the globe that are geographically far apart. In such a context, the search for solutions other than owner software will bring an upsurge and prevalence of tools based on open-source software, which, in turn, will allow technological resources to become more democratically available to people all over the world. Lastly, within this democratising trend we will very likely reach a stage in which not only tools will be freely available, but also contents and, therefore, creative commons type formulas will certainly be more thoroughly developed.

Secondly, concerning educational management, it is necessary to support the design and development of new educational applications and also to actively involve teachers in the process of defining requirements and adopting iterative design approaches. In general terms, one of the main aspects of management is generating leadership that will encourage people to work towards corporate goals. In a similar manner, educational management must efficiently guide changes that are already ocurring in the world of education and will continue to do so in coming years. A first class challenge in educational management concerns the fact that there are educators of different age groups and propensity profiles towards the use of information technology and, therefore, towards a cultural change in teaching methods and organization. It will be necessary to establish methods that are recognized as effective to assist this change of attitude and in working ways. In this sense, the existence of communities of practice, as well as making known their results could be powerful ways of involving teachers in the new system.

Finally, if the trends we have mentioned are leading us towards new educational environments which may even place in doubt the figure of schools and other educational institutions, then we must consider how to manage them from the point of view of the institution itself, municipalities, regions and, lastly, countries. Undoubtedly this implies the appearance of new standards and models with which to manage educational activity. On the other hand, due to the foreseeable dispersal of educational institutions and the teaching methods that will be in use, Information Technology's position will be more important than ever in such circumstances, as it will be the only link to coordinate and run this immense network. So the convergence of IT and educational management (EM) reaches its high point because the means to achieve quality, coherence and interchangeability among future education systems must be based on technology, that is, IT as the facilitating element. In such a context, accreditation systems implemented by national and international agencies will be especially relevant. These systems must guarantee that students have, in effect, acquired certain competences, the consistency of goals achieved in different teaching communities and also the transnational validity of resulting certificates.

Conclusions

Present educational models reflect the needs of an industrial society, whose paradigm is progressively giving way to a knowledge based society. Learning in a knowledge based society has different requirements and, therefore, it is still to be defined. As well as this, constant changes in Information Technologies also alter what we consider to be the vision and mission of educational institutions. We don't yet know which will be the prevailing educational philosophy on the 2020 horizon, nor do we know what version of the Web will be supporting it. But we have little doubts that we do not know for sure what the educational model will be like then, even though it will retain many of the characteristics that inspire the present one.

We must be ready for what looks like a possible trend, that is, schools and teachers will lose importance in favour of more flexible structures managed according to business models, which will be much more competitive and transparent due to the inevitable need to gain students as clients. In such a context a new design of ITEM must be developed.

On the 2020 horizon, in order to reach its full development, the ITEM field must support technological infrastructure related standards, as well as the measures to promote cultural change associated to the new educational model. It must also be the means to ensure homogeneity in a highly fragmented environment in which customized education based on knowledge will break with the postindustrial educational model, according to which we have carried out learning processes for decades.

Fig. 1 .

 1 Fig.1. Interrelated Challenges for Educational Management.

Trends Regarding Skills and Competences Required by the Labour Market

	2
	Society and Economy in 2020
	FUTURE WORKING FORCE
		• HOME
	FORMAL	• COMMUNITIES NON-FORMAL
	EDUCATION	OF PRACTICE EDUCATION
	• SCHOOLS	• HOME
	• HIGH SCHOOLS	• COMMUNITIES
	• COLLEGES AND	OF PRACTICE
	UNIVERSITIES
	Web 2.0	Learning 2.0

Recommendation of the European Parliament and the Council (2008) on the establishment of the European Qualifications Framework.


Rita Nankanja
email: ritanankanja@yahoo.com

Ronald Bisaso
email: ronald.bisaso@uta.fi

Emerging issues in the utilization of synchronous ICT in the delivery of distance education at public universities in Uganda

Keywords: Transactional distance, distance education, synchronous ICT

This paper reports on the utilization of synchronous information and communication technologies (ICT) in the delivery of distance education at the two largest public universities in Uganda. This was an exploratory descriptive survey that aimed at establishing the emerging issues in the utilization. Applying Peter's theory of industrialization of distance education and Moore's theory of transactional distance as interpretive frameworks, the findings illuminate variations in ICT usage for communication among the learners, and with their instructors. This nascent use of ICT was mainly supported by telephones as well as text-based chat and projectors, but on a smaller scale. It was concluded that learners and instructors should be given training in basic utilization of the available and accessible synchronous ICT. Besides, more studies on the changing patterns of distance education in Ugandan universities and comparative studies with other African universities concerning their distance education trajectories were needed.

Introduction

Integration of ICT into distance education in Uganda has been on a small scale and distance education has been limited to first generation approaches such as print and face-to-face sessions. But this trend has been changing with the emergence of ICTrelated project initiatives by the WorlDLinks in schools and ConnectED in Teachers' colleges to integrate ICT in teaching and learning through distance education [START_REF] Aguti | Integration of Information Communication Technologies (ICTs) in the distance education Bachelor of Education program[END_REF]. Related developments have shown that Uganda is one of the countries with active markets for the Internet, which is a valuable tool in distance education. Moreover, the two largest Ugandan public universities in terms of enrolment and distance education programmes have enhanced their ICT infrastructure pertinent to distance education [START_REF] Aguti | Integration of Information Communication Technologies (ICTs) in the distance education Bachelor of Education program[END_REF][START_REF] Binns | Quality assurance in open distance education-Towards a culture of quality: A case study of Kyambogo University, Uganda[END_REF][START_REF] Mayende | Mobile Technologies to Support Discussion Groups within in Distance Education in Developing Countries, Software Engineering Group[END_REF][START_REF] Saint | Tertiary distance education and technology in sub-Saharan Africa[END_REF]. Despite these budding developments in ICT for distance education, little systematic inquiry has been done on the interactive processes between the learners, and between the learners and their instructors. Additionally, while this current study builds on available research evidence, unlike some of the earlier studies, it takes a theoretical orientation by applying two theoretical frameworks to interpret the emerging issues in the utilization of synchronous ICT in distance education. In this paper, synchronous ICT denotes the direct exchange or real time communication between teachers and learners and includes text-based chat, videoconferencing, projectors and telephone. Distance education has been defined as an education process in which a significant portion of the teaching is conducted by someone removed in space and/or time from the learner [START_REF] Perraton | Teacher education guidelines: using open and distance learning[END_REF]. Thus, we attempt to answer the question "how does synchronous ICT facilitate distance education in public universities in Uganda?" The rest of the paper is structured as follows. First, the theoretical framework is provided. Second, the methods used in gathering evidence are discussed. Third, the findings from the study are given and fourth, conclusions are made.

Theoretical Framework

Peters' (1994) Theory of Industrialization of Distance Education portrays the role of mechanization in distance education and indicates that distance education cannot take place without the use of machines. Examples such as duplicating machines and transport systems are pre-requisites to distance education and additional facilities of modern means of communication and electronic data-processing installations are later forms of distance teaching. Therefore machines which are in this case ICT are inseparable with distance education. Peters suggests that machines ensure efficient dissemination of knowledge and education becomes accessible to as many people as possible. [START_REF] Moore | Theory of Transactional Distance[END_REF] Theory of Transactional Distance entails dialogue, structure and autonomy of learners in distance education and therefore it is used to explain the relationship between ICT and distance education. It looks at the real teaching and learning process and how it is done in distance education. The transaction which here is the communication between the teachers and the learners is explained in terms of dialogue that is the way in which the communication is carried out; structure, which is how the program is designed to accommodate all learners' needs; and learner autonomy that implies the degree to which learners can learn on their own. In this case, ICT is presumed to be useful in the transactional distance between the learner and fellow learners and between the learner and the teacher. In other words, dialogue, structure and autonomy in the process of all these interactions during distance education can be interpreted as being facilitated by ICT. Recent studies on the use of synchronous ICT in distance education have evaluated ICT in terms of flexibility, improving perceptions about instructional approaches and efficacy in terms of levels of cognitive process and meta-cognition in distance teacher education in Uganda [START_REF] Gudula | Distance education and a realistic teacher education pedagogy in Uganda: impact of an ICT -supported learning environment[END_REF]. Prior to this, [START_REF] Ouma | A national Distance Education (DE) solution for Uganda: Innovative Application of Digital ICT s to Overcome the Barriers of the Existing Digital Divide[END_REF] found out that emphasis was on ICT for enhancing face-to-face delivery and that Makerere and Kyambogo Universities were advancing towards introducing ICT in the management and teaching/learning processes. Building on these earlier studies, we concentrate on the role of the budding synchronous ICT infrastructure and resources in reducing the transactional distance in the teaching and learning process in distance education. In this study, synchronous ICT was conceptualized in terms of telephone, text-based chat, video conferencing and projectors while distance education was conceptualized as the use of print, face to face sessions, student groups and individualized learning. It was hypothesized that the ICT resources enhance dialogue, provide better structure and promote autonomy in distance education.

Methods

This was an exploratory descriptive survey in which self-administered questionnaires and structured interview guides were designed and distributed to the students and lecturers respectively. The instruments were designed in such a way that they had a main title, an introduction to the study which included background information, a section on ICT (independent variable) synchronous ICT and the last section on distance education (dependent variable). The population of students on distance education in Makerere university was approximately 6000 [START_REF] Aguti | Integration of Information Communication Technologies (ICTs) in the distance education Bachelor of Education program[END_REF] and in Kyambogo University there were over 5026 distance education students [START_REF] Binns | Quality assurance in open distance education-Towards a culture of quality: A case study of Kyambogo University, Uganda[END_REF]. According to [START_REF] Krejcie | Determining sample size for research activities[END_REF], with a population of 11,000, the sample should be 370. Out of the 370 targeted respondents, a total of 188 students responded and 10 lecturers were interviewed out of the approximated 20 in both universities. Data was collected from both students and lecturers of distance education. Students are those in Makerere University offering Bachelor of Science, Bachelor of Commerce and Bachelor of Education and those in Kyambogo University offering Diploma in Education-primary (External) and Diploma in Special Needs Education (External). Data obtained using questionnaires was analyzed by use of frequency distributions generated through the use of Epi-data and Statistical Package for Social Scientists (SPSS) software package. Interview data was coded and emerging themes were identified.

Findings

A number of questions were put to both the instructors and the students from Makerere and Kyambogo universities, to find out if they really use these ICT, what they use them for and if they do not, why. Over 63% of the students were from Makerere University and about 37% of the students were from Kyambogo University. The difference was mainly due to the fact that there are more students and at the same time, more courses offered through distance education at Makerere compared to Kyambogo. Male respondents comprised 57% whereas 43% were female. Over 70% of the respondents were below 30 years of age, 24% between the age of 30 and 45, while only one per cent was over the age of 45 years. The modal age of the students is below 30 years which implies that majority of those who are currently upgrading through distance education are quite young. This may also be attributed to the increasing demand for higher education in the recent years by secondary school leavers as seen in the rising enrolments in universities. Out of all the students contacted, about 39% were offering Bachelor of Education followed by those of the Diploma in Education Primary (External). Bachelor of commerce (B COM) and Bachelor of education (BED) are courses offered at Makerere University in the distance education department. Diploma in Education Primary (External) (DEPE) and Diploma in Special Needs Education (DSNEE) are courses offered at Kyambogo University distance education department. Table 1 shows the percentage of students participating in the study enrolled in the different courses. All these courses utilize these ICT. According to the table, majority of the respondents were offering Bachelor of Education, Diploma in Education Primary (External) and Bachelor of Commerce.

Table 1: Respondents in the different Distance Education Courses

Throughout the different courses these respondents were currently offering, they were asked their years of study and 29% of the respondents were in their first year. In second year we had around 18% of the respondents and 41% of the respondents were actually in their third year. A small percentage was in their fourth year and that is about 12% of all the respondents. The respondents were again asked their highest level of education so far and 34% of them had acquired certificates, 53% had a diploma, while those who had attained a degree status were over 12% of the respondents. A small percentage of the students, 0.5% had a post graduate diploma as their highest level of education so far attained.

Synchronous ICT involved here are telephones, text-based chat, video conferencing and projectors. Telephones are highly used in distance education according to both students and instructors. Approximately 76% of the students showed that they use telephones as shown in Figure 1 and about the same percentage of instructors (70%) also showed their use of telephones. These mainly are mobile telephones that are used in the communication between the learners and instructors. This is probably because mobile telephones have got a wider coverage and are convenient for any location. Besides, the information exchanges are synchronous since they involve real time communication between the instructors and the learners and between the learners themselves. Actually only around 30% of the students show its utilization. Over 60% of the instructors on the other hand indicate its usage. However, most of the respondents who say they use text based chat might mean the use of Short Message Service (SMS) because text-based chat technology is not so much in use in Uganda and especially in both Makerere and Kyambogo universities for distance education. Video conferencing involves communication between the learners and instructors using a video but in any case it is easy for the learners to communicate directly to their instructors. This is not common in Uganda and in this case, it is also not used in distance education in our universities. A limited percentage of students (about 20%) show that they use it in their studies. This is not in line with what prevails at the universities or the study centres. This might mean that the respondents use this type of ICT in their other business and not in education. Instructors on the other hand do not show any use of video conferencing in their delivery and development of distance education.

Projectors are mainly used for communication between the instructor and a large group of students. It conveys the message to a big number of students and it is controlled by the instructor. The students get a chance to ask for clarification there and then. There is little utilization of the projectors in distance education in Ugandan universities. Only 20% of the students show their use of projectors though about 40 % of the instructors show that they use them. When asked as to why there is no or low utilization of synchronous ICT especially video conferencing, instructors had reasons to give which include, the lack of video conferencing facilities though these have been found at the Uganda Management Institute in Uganda, ICT not being properly developed in Ugandan universities and computer literacy still being low among others. The utilization of synchronous ICT has been curtailed by the fact that the current nature of distance education has been mainly first-generation that is, print and second-generation, face-to-face and less on the other forms of distance education. Therefore, the synchronous ICT like telephones, projectors, text-based chat and video conferencing that would have been exploited to enhance distance education have been underutilized. Students and instructors were contacted to present their opinions on the purpose of synchronous ICT in distance education in both Kyambogo and Makerere universities. The purposes were access to learning materials, interaction with the instructor, interaction with other students, assessment and research and these were rated accordingly by both students and instructors. Table 2 below shows how instructors rated the purpose of ICT to their delivery and development of distance education. interact with other students and also to access learning materials. Instructors give the main purposes of synchronous ICT as being to access teaching materials, to interact with students and to do research. f. For purposes of accessing learning materials, interaction, assessment and research in distance education, students use synchronous ICT more than instructors. Respondents were also asked on their learning activities in distance education and a lot was gleaned from them. Printed material is used mostly by instructors and students find it easy to follow it. Again, most of the students do not find problems in face to face sessions as they can understand the content delivered and follow the instructors as well as refer to the content given later. Most instructors also find it easy to develop content for face to face sessions, deliver it and refer to it later. Most of the students can again understand the content given on their own, can follow that given by instructors later on their own and find it easy to add on it later on their own. Most instructors (50%) however say that it is not easy for students to refer to content given on their own. However, they say that it is easy for these students to search for content to add on that delivered to them. Most of the students find it easy to understand content given in organized study groups and can always refer to content given in class in their organized study groups and can search for more to add on in these groups.

Instructors also agree with students that it is easy to understand content given in organized study groups and to refer and add to it later in these groups. With reference to audio methods like the use audio cassettes, students indicate that they do not find it easy to understand content provided using audio methods. Even when the instructors use audio methods, content is not easy to understand and thus making it difficult to refer to it. On the other hand, instructors find it easy to deliver content using audio methods. They also think that students learn more with the use of these methods and find them to be good for reference by the students.

The high use of telephones in distance education emphasizes the fact that machines are very important in distance education as suggested by [START_REF] Peters | Otto Peters on Distance Education: The Industrialization of Teaching and Learning[END_REF]. They also create a dialogue between the learners and instructors which is an essential element in distance education [START_REF] Moore | Theory of Transactional Distance[END_REF]. Video conferencing usage is not available hence making it hard to show the relationship between ICT and distance education. However, Projectors are available and are used mostly with face to face sessions. They therefore bring out Peters' (1994) Theory since they are machines and also structure and dialogue (Moore, 1994) are emphasized here. Overall, the available synchronous ICT and as used in Ugandan universities, enhance distance education as predicted.

Conclusion

The opinions from Makerere University and Kyambogo University presented in this paper have various implications on the teaching and learning process in distance education. The discussion presents an overview of the meaning, implication and views of the respondents in both universities. The use of ICT in the enhancement of distance education is very essential if the process of learning and teaching is to be effective and efficient. This means that one cannot disintegrate ICT from distance education if one is to achieve what is advocated for in both [START_REF] Peters | Otto Peters on Distance Education: The Industrialization of Teaching and Learning[END_REF] Industrialization of distance education Theory and [START_REF] Moore | Theory of Transactional Distance[END_REF] Transactional Theory. [START_REF] Peters | Otto Peters on Distance Education: The Industrialization of Teaching and Learning[END_REF] here suggests that ICT are really needed and are part of the industrialization process of distance education. It has also been discovered that to achieve autonomy of the learner, dialogue and a good structure, ICT are very important [START_REF] Moore | Theory of Transactional Distance[END_REF]. From the findings of this study, we can conclude that:

1. The use of the telephone is paramount in distance education more especially the mobile telephone. This is a big step in the incorporation of ICT into distance education and it shows that there is always room for more ICT to be integrated into the program if we are to achieve industrialization and the dialogue advocated for in this kind of education. 2. Some ICT are not being used at all like video conferencing technology in the process of teaching and learning in distance education in Ugandan public universities. This is because they are not available or are inaccessible. Yet, in order to industrialize distance education [START_REF] Peters | Otto Peters on Distance Education: The Industrialization of Teaching and Learning[END_REF] and to develop learner autonomy as per [START_REF] Moore | Theory of Transactional Distance[END_REF] theory, some of these are the best ICT that can be exploited. Dialogue can also be created between the learner and the instructor using technology as video conferencing.

3. Synchronous ICT are used mainly for interaction between students and students, students and instructors and instructors and instructors. This is probably due to their being able to provide a dialogue for real time communication. This direct exchange between and within both parties concerned with distance education make its transaction easy and clear. At the same time, to achieve that needed dialogue, more industrialization through the use of ICT is essential. Putting into consideration the findings of this study, in order to improve on the utilization of ICT in the enhancement of distance education, the following recommendations can be made. To the policy makers, it is recommended that all the available ICT on the market that are expected to improve learning should be made available to institutions of learning for easy exploitation. This means that, all institutions that provide distance education should be equipped with technology that is fully supported for its easy transaction as suggested by [START_REF] Peters | Otto Peters on Distance Education: The Industrialization of Teaching and Learning[END_REF]. In practice, it is recommended that instructors involved in distance education should have knowledge on the use of different technology and should always be ready to learn whenever a need arises. This can be achieved through training programmes on the use of the distance education technologies. All the available technology at the disposal of instructors should be exploited in the delivery and development of distance education to the maximum. This will make it easier for the learners to learn its use and use it as expected. Again, synchronous ICT would be the best to consider since they allow real time communication between the learners and instructors. With respect to research, more empirical research should be done on the extent and strength of the relationship between ICT utilized and distance education. Also research on the trends in distance education and ICT in Uganda is recommended in addition to comparative studies with other African Universities.

Figure 1 :

 1 Figure 1: Utilization of telephones in distance education by students

Table 2 : The purpose of synchronous ICT in distance education as rated by the Instructors

 2 Most instructors agree that synchronous ICT are important in the delivery and development of distance education as shown in Table2.Therefore: a. Students and instructors utilize synchronous ICT on a large scale b. Telephones and text based chat (can be taken to mean SMS) are the most highly utilized synchronous ICT by both students and instructors c. The utilization of synchronous ICT by students does not vary much from the utilization of synchronous ICT by instructors d. The main reason for none or low utilization of synchronous ICT especially video conferencing and projectors is because they are not available and those which are available are inaccessible. e. Most students give the main purposes of synchronous ICT as being to

		Access to	Interaction	Interaction	Assessment	Research
		teaching	with other	with
		materials	instructors	students
	Frequency	8	6	8	6	8
	Missing	1	1	1	2	1