Min Zhang
email: zhangm@shou.edu.cn

Feixia Liang

Yue Xie

Ruguo Huang

Haitao Yuan

Jiahua Lu

Measurement System of Reducing Temperature Fluctuation of Thermostat Bath for Calibrating Thermocouple

Keywords: Temperature fluctuation, Thermostat bath, Thermocouple, Calibrate

Based on the periodic unsteady state heat conduction theory, a new measurement system of reducing temperature fluctuation of thermostat bath was developed in order to obtain a liquid environment with uniform and constant temperature controlled for the measurement requirements of calibrating thermocouple. The experimental results show that the temperature stability in this measurement system is superior to that in traditional system. The measurement system had the advantage of calibrating multipoint thermocouple at the same time and completing the data acquisition and control automatically.

Introduction

Low-temperature thermostat bath is essential laboratory equipment in food, biological, chemical scientific research and industrial applications [START_REF] Merlone | A liquid bath for accurate temperature measurements[END_REF]. It is mainly used to provide liquid controlled environment with uniform and constant temperature. It can be used as heating or cooling source or secondary heating or cooling source [START_REF] Jiangtao | A new research of the high-precision thermostatic bath at low temperature for fluid thermal physical measurement[END_REF][START_REF] Merlone | A liquid bath for accurate platinum resistance thermometers calibrationat IMGC, the 9thInternational Symposium on Temperature and Thermal Measurements in Industry and Science[END_REF]. It is often used as thermocouple calibration equipment in the measurement of food thermal properties. So the performance of low-temperature thermostat bath have a directly impact on the reliability and accuracy of thermocouple calibrating [START_REF] Zhang | Fractal study of the fluctuation characteristic in the calibration of the cryogenic thermocouples[END_REF]. However, there is a defect of bigger temperature fluctuations and consistent unsteady temperature in moderate low-temperature thermostat bath because the temperature of liquid in thermostat bath is affected by compression engine running and fluid convection heat transfer. As a result, it is difficult to get high precision of temperature calibration of thermocouple which is put in the liquid [START_REF] Hu | A research of the precise low-temperature thermostat bath for refrigerants PVT Development for experiment[END_REF][START_REF] Abdelaziz | Stability and calibration of platinum/palladium thermocouples following heat treatment[END_REF][START_REF] Villafañe | Aero-thermal analysis of shielded fine wire thermocouple probes[END_REF][START_REF] Sarma | Design and development of a high precision thermocouple based smart industrial thermometer with on line linearisation and data logging feature[END_REF]. Especially in the process of calibrating multiple thermocouples at the same time, multipoint stable temperature environment is essential. To solve these problems, on the basis of the traditional thermostat bath, a new measurement system of reducing temperature fluctuation of thermostat bath was developed and T-type thermocouple temperature calibration value had been analyzed.

Principle

Based on the Seebeck effect, temperature was measured by thermocouples [START_REF] Danisman | Design of a high precision temperature measurement system based on artificial neural network for different thermocouple types[END_REF]. To reduce errors of temperature measurement system, the temperature dividing should be calibrated due to different thermocouples materials which would cause difference of thermoelectric properties and allowable deviation [START_REF] Villafañe | Aero-thermal analysis of shielded fine wire thermocouple probes[END_REF]. The temperature deviation would be revised according to the measured temperature value of standard thermometer and thermocouple in the same liquid environment with uniform and constant temperature controlled which is provided by low-temperature thermostat bath. The thermocouples and standard thermometer are directly put into a lowtemperature thermostat bath. But the inner liquid would produce cyclical fluctuations of heating and cooling and then it would pass to measured surface. The reason is that temperature control is achieved by means of hot and cold offset. According to the theory of heat transfer [START_REF] Holman | Heat Transfer[END_REF] , the measured object can be considered as a homogeneous semi-infinite body. The temperature field in boundary conditions of periodic change for semi-infinite homogeneous object, can be descripted by nonsteady-state heat conduction differential equation [START_REF] Shiming | Heat transfer [M]. The Fourth Edition. Beijing: higher education press[END_REF]

: 2 2 x t t        ( 1 )
The boundary conditions can be considered to be a harmonic. Then the temperature changes in the surface of object can be obtained as cosine function:

   T A w 2 cos  ( 2 )
By separation of variables method, equation ( 1 )( 2 ) can be integrated and the internal temperature distribution of object is as follow:

) 2 cos( ) exp( ) , ( T x T T x A x w            ( 3
)
Where

t is object temperature (K),  is heating time (s),  is thermal diffusion coefficient (m 2 /s),
x is distance from the surface(m),  is instantaneous surplus temperature on the surface of the object(K),

) , (   x is instantaneous surplus temperature inside the object(K), w A is temperature fluctuation on the surface(K), T is the cycle of wave period (s).

By equation ( 2) and ( 3 ),the surface temperature and the internal temperature will be periodic changes over time. But the fluctuation amplitudes of internal temperature is less than that of surface temperature. Meanwhile, the amplitude decreases greatly with increase of x. The extent of the amplitude attenuation can be expressed:

) exp( T x      ( 4 )
It shows that internal wave amplitude decreases with the deepening of the temperature wave. It is one of the important characteristics of periodic heat conduction. That is to say, the temperature wave amplitude increases gradually as the surface distance attenuation. From the theory, reducing the test ambient temperature fluctuation degree can ensure a liquid environment with uniform and constant temperature controlled.

3

Test System and Method

Test System

As shown in Figure 1,thermocouple calibration measurement system is based on the above principles. The test device includes low-temperature thermostat bath, temperature balance outer pipe, temperature balance inner pipe, blender, insulation cover, insulated container, standard platinum resistance, thermocouple, data acquisition device and computer. The outer pipe and inner pipe of temperature balance are located in the thermostat bath. Flowing medium level within thermostat bath is above temperature balance outer pipe. Flowing medium level within temperature balance outer pipe is higher than temperature balance inner pipe. An anti-mutual contact device is set between two pipes and make inner pipe fix in the middle of outer pipe. The anti-mutual contact device is not touched the bottom and sides wall of temperature balance outside tube.

A supporting insulation cover is used on the outer pipe and inner pipe of temperature balance. A calibrated standard platinum resistance thermometer and several groups of non-touching thermocouples were put in the temperature balance inner pipe at the same time. Platinum resistance thermometer and thermocouples fixed by stents located in the inner pipe nozzle, and not touched bottom and sides wall of temperature balance pipe. Then temperature data of standard platinum resistance thermometer and thermocouples were collected and transferred to computer by FLUKE data acquisition instrument.

Standard Test Method

DC2006 low-temperature thermostat bath was used for this work. The flume dimension was length 250mm, width 200 and depth 200mm. The temperature range was 20-95℃. With water as a working fluid, the heating system is made of L Type stainless steel heating pipe. The heating end was at the bottom of thermostat bath. The evaporator in refrigeration system was made of copper pipe, which was placed directly in the sink in order to increase the cooling rate. T copper-constantan thermocouples with diameter 0.5mm were selected. The reference terminals were immersed in transformer oil surrounded by ice-water mixture. The temperature balance pipes were made of high borosilicate glass material. The outer pipe was external diameter 100mm, depth 100mm and wall thickness 3mm, while the inner pipe external diameter 75mm, depth 100mm and wall thickness 3mm. Due to the presence of glass containers, the distance between thermocouple and fluid walls was increased in the process of calibrating the thermocouple, which could effectively prevent temperature fluctuation caused by heat convection [START_REF] Nouanegue | Conjugate heat transfer by natural convection, conduction and radiation in open cavities[END_REF] . First, water was poured into the thermostat bath with the outer pipe and inner pipe of temperature balance. The water level of the thermostat bath was above the water level of the temperature balance outer pipe, and the water level in the outer pipe was higher than in inner pipe. Secondly, T type thermocouples and calibrated standard platinum resistance thermometer were fixed in the centre of the temperature balance inner pipe by support and kept isolated and out of contact each other. Thirdly, insulated cover was sealed. Finally, the other ends of T type thermocouples and platinum resistor were connected to FLUKE Data collecting instrument into a computer. Temperature data were collected every 30 seconds during testing. The changes of temperature were observed in real-time detection. The temperature stability data could be collected when adjusting to the required temperature [START_REF] Wenfang | The computer measurement and control system based on agilent34970A Data acquisition instrument[END_REF]. T type thermocouple and calibrated standard platinum resistance thermometer could be compared and corrected at the same temperature. Every degree of temperature value of T type thermocouple was calibrated in turn and was contrasted directly place the thermocouple in water and only place the thermocouple in temperature balance inner tube.

Results and Discussion

Temperature Fluctuations

Fig. 2, Fig. 3 and Fig. 4 showed T type thermocouple temperature test case when liquid temperature in the thermostat bath was set to 20℃, respectively. As can be seen from the diagram, temperature wave amplitude of T Thermocouple in contact with fluid directly was greater than other two conditions. Calibration temperature wave amplitude of the T type thermocouple in contact with fluid directly was ±0.075℃. Calibration temperature wave amplitude of only increasing outer pipe is ±0.03℃, Calibration temperature wave amplitude of simultaneously increasing outer pipe and inner pipe was ±0.02℃. The temperature stability raised 73.3% and 33.3% than the previous two conditions, respectively.

It was shown that the thermal resistance of the glass could prevent temperature fluctuation causing by convection. Test results were in accord with the analytical solutions for natural convection boundary layer equations by Pohlhausen and research results of Magyari and Myers [START_REF] Magyari | Backward boundary layer heat transfer in a converging channel[END_REF][START_REF] Myers | An approximate solution method for boundary layer flow of a power law fluid over a flat plate[END_REF] .

Thermocouple Calibration

As shown in Table 1, test results of multipoint T type thermocouple under the conditions of 5-50 ℃, which happened in test device with the temperature balance outer pipe and inner pipe. As can be seen from the Table 1, average temperature fluctuation was ±0.02℃ and ±0.03℃ in the range of 5 -30℃and 40-50℃, respectively. What is more, the experiments were shown no uniform temperature field only occurred in closing to the wall surface of heat transfer in convection heat transfer. The temperature balance inner pipe fixed in outer pipe and outer pipe fixed in insulated cabinet. The presence of glass container increased distance between thermocouple and wall surface in calibration process, attenuated temperature wave amplitude, effectively prevented temperature fluctuations caused by convection heat transfer. The purpose of precise calibration was achieved.

Conclusions

The designed measurement system device included low-temperature thermostat bath, temperature balance outer pipe, temperature balance inner pipe, blender, insulation cover, insulated container, standard platinum resistance, thermocouple, data acquisition device, computer and so on. T type thermocouple under the conditions of 5-50 ℃ was calibration with average temperature fluctuation ±0.02℃ and± 0.03℃ in the range of 5-30℃and 40-50℃, respectively. It is simple, convenient and reliable. There will be a bright prospect for determining temperature in scientific research and engineering application.

Fig. 1 .

 1 Fig. 1. Schematic diagram of measurement system 1. Heating tuber 2. Thermostat bath 3. Insulation layer 4. insulation cover 5.Outer pipe insulation cover 6. Thermocouple 7.Standard platinum resistance 8. Data acquisition device 9. Computer 10. Blender 11. Balance outer pipe 12 balance inner pipe 13.Insulated container 14. Ice-water mixture 15. Heat transfer oil

Fig. 2 .Fig. 3 .Fig. 4 .

 234 Fig. 2. Temperature test curve of thermocouple put in water

Table 1 .

 1 Calibration result of multipoint thermocouple

	Thermosta t setting	Temperature fluctuations of thermocouple test point (℃)	Temperature
	temperatur						fluctuations in
	e (℃)	1	2	3	4	5	average (℃)
	5	±0.02	±0.01	±0.02	±0.01	±0.02	±0.02
	10	±0.02	±0.02	±0.02	±0.02	±0.02	±0.02
	20	±0.02	±0.02	±0.02	±0.02	±0.02	±0.02
	30	±0.02	±0.02	±0.03	±0.02	±0.03	±0.02
	40	±0.03	±0.03	±0.03	±0.03	±0.03	±0.03
	50	±0.03	±0.03	±0.03	±0.03	±0.03	±0.03

Acknowledgment

Funds for this research was provided by the Natural Science Foundation of China, Grant No 31371526.


Yang Liu
email: liuyang@bucea.edu.cn

Mingyi Du
email: bdumingyi@bucea.edu.cn

Changfeng Jing

Guoyin Cai

Design and Implementation of Monitoring and Early Warning System for Urban Roads Waterlogging

Keywords:

Waterlogging happens almost in every rainstorm in city roads and the concave type of overpasses in Beijing. It causes to serious effect for the security of people's daily travel. For resolving this kind of problem, this paper designed a monitoring network by water level sensors and other technologies of internet of things, and developed a monitoring and early warning system for detecting the real-time information of waterlogging conditions in urban roads. This system can capture the real time information of waterlogging depth, make a fast query statistics for certain road or area, and also provide the short message service for the public. It is very convenient for the managers working in department of flood control and command center to collect the real-time information of waterlogging status around urban roads. This is helpful for the local government to perform the correspondingly emergency plan and issue waterlogging information for the public, so as to reduce the impact on the security of people's travel caused by the suddenly bad weather.

Introduction

The speed of city construction has become more and more quickly with the rapid development of urbanization in recent years. As side consequences, the disaster of regional flood in urban areas has increased significantly, and some other weaknesses in city planning, construction and management have been also emerged at the same time [START_REF] Xia | Design of monitoring and alarm system for city stagnant water[END_REF]. A large number of concave type of overpasses and tunnels have been constructed to alleviate traffic pressure and to ensure travel unimpeded in some megacities such as Beijing and Shanghai [START_REF] Wan | The design of urban road in Laixi water monitoring system[END_REF][START_REF] Pan | The design of city overpass water automatic monitoring system in Shanghai [J[END_REF][START_REF] Xu | Application of electronic gauge in the city road water monitoring system[END_REF]. A big challenge should be faced by the people working in the department of city flood control because some sudden extreme rainfall weather happens now and then in recent years. For example, the 7 roads were in traffic disruption, the 27 bridges were covered with water, and the traffic was resumed until 6 hours later during the severe natural disaster happened at July, 21, 2012 in Beijing. The main reason for this phenomenon is due to the unreasonable planning of the city drainage system, additionally, there was no systematic monitoring for the status of the road waterlogging which caused the delay of the early warning and forecasting because of no real time monitoring and transmission of the data with real time water condition [START_REF] Zhou | Urban waterlogging remote monitoring system based on embedded[END_REF][START_REF] Ramos | Form point to areal rainfall: linking the different approaches for the frequency characterisation of rainfalls in urban areas[END_REF].

For resolving the above mentioned problems, this paper designed a road waterlogging monitoring network covering the whole Beijing urban areas by means of sensor technology and wireless transmission technology. Based on this network, a road waterlogging monitoring and early warning system was developed. The system can provide real-time information for managers performing decision-making strategy, and offer technical support for the organization of municipal drainage management. This system can be also used to release water monitoring information to the public through the micro-blog and other rapidly updated media, so as to guide the public travel. The monitoring method, system design and implementation were discussed in this paper.

Methods

As shown in Fig. 1, sensors were installed near the concave type of overpass or lowlying courtyard road where often suffer from waterlogging. Sensors in the whole study areas constitute a waterlogging monitoring network. The mobile GMS/GPRS communication network was used to transmit water information to the monitoring center at certain preset intervals. The road waterlogging monitoring system was developed through the information collected by sensors. The waterlogging locations are displayed in this system. It can be used to query the real-time water information and make an early warning for urban flood. This monitoring system software is installed on the WEB server, which can provide service of real time water information to the public. The workers in department of flood control only needs a computer with internet access to operate the software, realizing the real-time query of road waterlogging, water retention, reminding of early warning, water site inquiries with exceed the standard water, and 12 hours of water values etc.. This system includes two parts, that is, road waterlogging monitoring stations and monitoring center, as shown in Fig. 2. Monitoring center is responsible for data reception, data processing and data display [START_REF] Caudle | Flood waring[J][END_REF]. It is consists of hardware such as the database server, web server and software such as data receiving software and application software. As shown in Fig. 3, the data receiving terminal is responsible for receiving, decoding, checking and storing of the receipted road waterlogging data transmitted by the monitoring network.

Core Functions

This system is an integrated flood control synthetic application system for digital urban which assembles electronic map, real-time water monitoring, early warning analysis. As shown in Fig. 4, the core functions of this system can be divided into 3 major parts, also known as a subsystem. They are water information receiving module, water monitoring and early warning module, and a warning short message service module, each module has its own corresponding function. The core functions of monitoring and early warning system for urban roads waterlogging

Road Waterlogging Alert Levels

There are four alert levels designed in this system. They are blue, yellow, orange and red alert in an ascending order level. The alert level in a single monitoring station is determined by the waterlogging time and water depth. The alert standard for different warning levels is shown in table 1. The synthetic alert in the whole urban region is based on the comprehensive analysis of all the monitoring sites. The alert standard is shown in table 2.

System implementation

City Road Waterlogging Monitoring and warning system is designed as a browser / server (B / S) software system architecture. Flex framework and C# were used as the programming language, and SQL Server 2008 as the database server. ArcSDE is adopted to store the spatial data, and ArcServer is employed to provide the map service. The interface is shown below, as shown in Fig. 5. With the rapid development of social economy in urban region, the disaster of waterlogging or lost caused by sudden rainstorm or other bad weather might become more and more serious. It makes the managers in department of flood control and command center to collect the correct and real time information of waterlogging much more convenient that the establishment of the monitoring and early warning system [START_REF] Zhao | Safety evaluation of Urban Flood Control System Based on Variable fuzzy pattern recognition[END_REF][START_REF] Taufka Akter | An investigation on maintenance problems of some flood embankments in and around Dhaka city[J][END_REF]. This system built by means of sensors not only provide reliable information for the local government to perform some decision-making in flood control and command, but make the working be more of efficiency and the decisionmaking policy be more of scientificalness, so as to guarantee the security of people's daily travel much more better.

Fig. 1 .

 1 Fig. 1. Schematic diagram of monitoring method for urban roads waterlogging

Fig. 2 .

 2 Fig. 2. The system structure diagram Fig. 3. Data receiving Service Road waterlogging monitoring station is consists of electronic gauge and wireless terminal, which are responsible for data acquisition and data transmission of real time road waterlogging. Electronic gauge and wireless client machine are the important components of road waterlogging monitoring station. Ectronic gauge is used to collect data of water level. It is equipped with advanced microprocessor chips for digital water level controller, and built-in communication circuit of sensor. It has the characteristics of high reliability and anti-interference performance with measurement accuracy of 1cm.The wireless client machine: it is used to data transmission. It is a whole new generation of intelligent telemetering terminal through assembling RTU, GPRS/GSM communication module, protection module and the charge controller. It can directly access the 5-10W solar panels or other accords with the power supply voltage requirements.Monitoring center is responsible for data reception, data processing and data display[START_REF] Caudle | Flood waring[J][END_REF]. It is consists of hardware such as the database server, web server and software such as data receiving software and application software. As shown in Fig.3, the data receiving terminal is responsible for receiving, decoding, checking and storing of the receipted road waterlogging data transmitted by the monitoring network.

Fig. 4 .

 4 Fig. 4. The core functions of monitoring and early warning system for urban roads waterlogging

Fig. 5 .

 5 Fig. 5. The Interface of Monitoring and Early Warning System for Urban Roads Waterlogging.

Table 1 .

 1 The alert level of real-time monitoring data for urban roads waterloggin(single

			monitoring site)
	The Depth Duration	5 cm -10cm(Ex)	10 cm -15cm(Ex)	15 cm -20cm(Ex)	>= 20cm
	0-15 min(In)	Yellow alert	Orange alert	Red alert	Red alert
	15-30 min(In)	Yellow alert	Orange alert	Red alert	Red alert
	30-60 min(In)	Blue alert	Yellow alert	Orange alert	Red alert
	> 60 min	Blue alert	Blue alert	Yellow alert	Red alert

Table 2 .

 2 The alert Level of real-time monitoring data for urban roads waterlogging(taking all the monitoring sites into account)Water retention alert only relates to the early warning in an individual site. The alert level is issued based on the water level decline rate. The alert standard is shown in table3.

	The Comprehensive Alert Level	The Specific Standards

Table 3 .

 3 The alert Level of water retention in urban roads

	Withdrawal Rates (unit: cm /	2.0(In) -5.0	2.0(In) -3.0	1.0(In) -2.0	< 1.0
	hour)
	Alert Level	Blue alert	Yellow Alert	Orange Alert	Red Alert

Acknowledgment

The research performed is supported by the National Natural Science Foundation of China (No. 41101444), Beijing Nova Program (No. Z121106002512025), and is partially funded by Beijing Municipal Organization Department talents project(No.2012D005017000001). The work was performed under the Key Laboratory for Urban Geomatics of National Administration of Surveying, Mapping and Geoinformation (No. 20111210N). We wish to thank Guoyin Cai for his careful proofreading of the manuscript.


Weiming Liu
email: 15157622288@139.com

Path analysis on effects of main economic traits on the yield of YU6, a japonica x indica hybrid rice line

Keywords: japonica x indica hybrid rice, economic trait, yield, path analysis, technical approach

To further explore the effect of major factors on the yield of a line of japonica x indica hybrid rice, to clarify technical approaches to high efficient high yield production, the author analyzed 237 groups of data from 9 years in 6 counties of Taizhou. With correlation, regression, and path analyses, effects of major economic traits on the yield were determined. An effective approach to high efficient high yield production is to increase a seed setting rate and to produce large panicles while ensuring the number of productive panicles.

Introduction

Hybridization of japonica rice with indica rice can potentially produce superior hybrids. YU6 is a hybrid that was created by mating between Yg2a and K6001. This 11.4% greater than that of the control, Xiushui 63. It takes 156.4 days to mature, which is 4.7 days longer than that of the control. YU6 has 13.4 thousand productive panicles per 667 m2 and 210.1 spikes per panicle on average. Its seed setting rate is 72.9% and the 1000-seed weight is 24.7 g. It is medium in resistance to rice blast disease and bacterial leaf blight, but susceptible to brown planthopper. Its grain quality is very good, with a head rice rate 66.9%, kernel chalkiness rate 16.4%, chalky 1.9%, and transparent 2.5, gel consistency 69.5 mm, the length to width ratio 2.3, and amylose 14.0%. YU6 inherited both the loose aromatic quality of indica rice and the elastic, sweet and glutinous character of japonica rice. YU6 has high hills, strong stems, straight leaves, large panicles, well developed primary branches, thick leaf sheath and excellent maturity looking. It is resistant to cold and lodging.

In recent years, along with the successful creation and application of YU6 hybrid rice, studies on the cultivation of this type of rice started to erupt [START_REF] Zhang Zujian | Characteristics of matter production of intersubspecific hybrid rice combinations[END_REF][START_REF] Shuguang | Performance of New Japonica Hybrid Rice Combination Yongyou 6 and Its High-yielding Cultural Techniques at Wenzhou, Zhejiang[END_REF][START_REF] Jia-Cheng | Main characters and cultural techniques of the new hybrid rice combination[END_REF][START_REF] Guo-Feng, | Studies on the relationship between grain sink activity of Japonica/Indica hybrid rice and its grain filling[END_REF][START_REF] Bo | Changes of Root Exudate of Indica-Japonica Hybrid Rice and Its Relation to Leaf Physiological Traits[END_REF][START_REF] Wei-Ming | Study on Transplanting Technology and N-application Technology of Yongyou 6 as Single Cropping Late Hybrid Rice[END_REF][START_REF] Li-Ying | Research on seed production of water-saving and drought-resistant japonica hybrid rice Hanyou 8' by machine' transplanting[END_REF][START_REF] Pu | High-efficient Ecological Cultivation Techniques of New Indica-japonica Hybrid Rice Yongyou 9[END_REF][START_REF] Wei-Ming | tudy on the High Yield and High Efficiency Cultivation Technique of Indica-japonica Intersubspecific Hybrid Rice as Single-cropping Late Rice[END_REF]. In order to explore the effect of its main economic traits on the yield, clarify the technical approach for high efficiency, high yield production, the author has analyzed data from the past on economic trait and yield, conducted regression, and path analysis before [START_REF] Weiming | Correlation, Multiple Regression and Path Analysis between Yield Traits and Yield on Intersubspecific Hybrid Rice[END_REF]. Now, the author has collected more data from additional years and sites, conducted further analysis on the influences of major economic traits on the yield of japonica x indica hybrids, using YU6 as a representative.

Materials and Methods

Data for panicle, grain weights

Table 1 shows the data for panicles and grains of YU6 cultivated in 6 counties, districts or cities.

Analysis Method

Using YU6 as a representative, the author performed correlation and regression analyses, and finally, path analysis to determine the relationship between each of the major economic traits and yield, the relationship among these traits in the japonica x indica rice line, to clarify the approaches for high yield and high efficiency.

3 Results and Analysis

Correlation analysis

As shown in Table 2, among the 5 traits, 4 traits showed a very significant positive correlation with the yield, except that the 1000-seed weight displayed a slight negative correlation. Further analysis on relationships among the five traits indicates that there were very significant negative relationship between the number of productive panicles and the number of gains per panicle as well as the number of filled grains per panicle. There was a significant negative relationship between the number of productive panicles and the seed setting rate. The number of grains per panicle was negatively correlated with the number of filled grains per panicle. The number of filled grains per panicle was very significantly correlated with the seed setting rate. The 1000-seed weight was weakly negatively correlated with the other four traits. Thus, among the five main economic traits, although there were very significant correlations among four traits, the 1000-seed weight was weakly correlated with the yield. The relationships among the five traits were also complex. To explore and formulate a standard for high efficient cultivation of the hybrid rice, it is therefore important to pay attention to the compatibility among these economic traits, so that the positive contribution of each trait can be maximized.

Stepwise regression analysis

A regression equation was obtained from a stepwise regression analysis on 237 groups of data, based on the principle of maximizing the correlation coefficient:  y ˆ-13011.07+44.65 1

x +7.70 2 x +18.37 3 x +35.47 4 x +201.54 5 x ±721.04

where, 1

x is the number of productive panicles, 2

x the number of grains per panicle, 3

x the number of filled grains, 4

x seed setting rate, 5

x the 1000-seed weight. Their ranges were, respectively, 1108.5~2161.5 thousand/hm 2 , 214.10~453.18 grains/panicle, 168.70~407.00 grains/panicle, 65.82%~96.60% and 21.42~25.2 g. The range of y (yield) was 6495.00~12540.00 kg/hm 2 。

The F value of the above equation was 73.52, which is very significant. An analysis of the partial regression coefficients indicates that the number of productive panicles per hm had the greatest effect ( r ( y , 1 x ) = 0.6768), followed by sequentially the number of grains per panicle ( r ( y , 2 x ) = 0.0937), the number of filled grains per panicle ( r ( y , 3 x ) = 0.1871) and the seed setting rate ( r ( y , 4 x ) = 0.1101). However, these traits were interdependent to a certain extent. Because multivariate regression analysis has multiple co-linearity, it is not easy to judge contribution of each trait. The path analysis has effectively determined the direct effect of each variable on the result, allowed estimating the indirect effect of an independent variable, thus enabled the direct comparison of the importance of each trait on the yield [START_REF] Pu | High-efficient Ecological Cultivation Techniques of New Indica-japonica Hybrid Rice Yongyou 9[END_REF][START_REF] Wei-Ming | tudy on the High Yield and High Efficiency Cultivation Technique of Indica-japonica Intersubspecific Hybrid Rice as Single-cropping Late Rice[END_REF][START_REF] Weiming | Correlation, Multiple Regression and Path Analysis between Yield Traits and Yield on Intersubspecific Hybrid Rice[END_REF]. Therefore, the author also performed a path analysis to determine effects of the major economic traits on yield in japonica x indica rice.

Path analysis

A path analysis on five major economic traits selected from the stepwise regression analysis was conducted. Results indicates that the number of productive panicles had the greatest contribution, followed by the number of filled grains per panicle, the number of grains per panicle, the seed setting rate and the 1000-seed weight (Table 3). The number of productive panicles had the greatest direct effect, with a direct path coefficient 0.8171. But it had negative effects through the other four traits, especially through the number of filled grains per panicle, with the path coefficient -0.4041. Thus, an increase in the number of productive panicles affected not only the number of grains per year, seed setting rate and the 1000-seed weight, but largely the number of filled grains. The overall effect of the number of productive panicles on the yield was r = 0.1948.

The number of grains per panicle had little effect on the yield, with a direct path coefficient 0.2531. It had a large indirect effect through the number of productive panicles negatively and through the number of filled grains per panicle positively, with coefficients -0.5598 and 0.5252. Its positive indirect effect through seed setting rate and negative indirect effect through the weight of ones thousand grains were small, being 0.0134 and -0.0023. The overall effect on yield from the number of grains per panicle was r = 0.2295.

The number of filled grains had a large direct effect on the yield, with a direct path coefficient 0.6447. Its negative indirect effect was large through the number of productive panicles, with a coefficient -0.5122. Its indirect positive effects through the number of grains per panicle and through the seed setting rate were smaller, with coefficients 0.2062 and 0.1291. Its negative effect through the 1000-seed weight was weak. The number of filled grains per panicle had not only a large direct effect, but also a large overall effect on the yield, being 0.4584. Therefore, while considering other traits especially the number of productive panicles, attention should be paid to increase the number of grains per panicle, especially the number of filled grains per panicle.

The seed setting rate had a direct path coefficient 0.2157, a large positive indirect effect coefficient 0.3859 through the number of filled grains per panicle. Its negative indirect effects through the number productive panicles and the 1000-seed weight, positive indirect effect through the number of grains per panicle were small. The overall effect of the seed setting rate on the yield was 0.4973.

The 1000-seed weight had the smallest direct effect on the yield, with a direct path coefficient 0.1240. It had not only small negative values for indirect effects through other traits, but also a negative overall effect on the yield. Thus, it is not advisable to increase the 1000-seed weight towards the goal of high efficient production.

Discussion and Conclusion

Economic traits affect not only directly the yield, but also indirectly through their influence on other traits. Through the above analysis on YU6, a representative of japonica x indica hybrid rice lines, it can be seen that the technical road to high efficient high yield production is to increase seed setting rate and produce large panicles while ensuring the number of productive panicles.

The stepwise regression analysis retained 5 factors that affect the yield. Path analysis results indicate that the number of productive panicles has the greatest influence on the yield, followed by the number of filled grains per panicle, the number of grains per panicle, seed setting rate and the 1000-seed weight. The previous stepwise regression analysis [START_REF] Li-Ying | Research on seed production of water-saving and drought-resistant japonica hybrid rice Hanyou 8' by machine' transplanting[END_REF] removed the number of grains per panicle due to its insignificant effect. It indicates that the number of filled grains per panicle contributed the greatest influence, followed by the number of productive panicles, the 1000-seed weight and the seed setting rate. Although the first two most import factors are the same between the current analysis and the previous analysis, the order of these two factors has changed. This is due to the retention of the number of grains per panicle in the stepwise analysis in the current analysis. It is clear that the number of filled grains per panicle is highly dependent on the number of grains per panicle, and they were collinear. The current identified technical approach to high efficient, high yield production is the same as previously reported. The current study is more reliable since it had more data and these data covered a longer period.

  line has been evaluated by Zhejiang Science and Technology Department in June 2005. YU6 is the first japonica x indica hybrid rice variety that passed the provincial evaluation (Zhe Ke Jian Zi [2005]#235). It has also passed the examination of experts organized by the Department of Agriculture of China in August, 2006, which confirmed that YU6 is the first recommended japonica x indica hybrid line (Nong Ke Ban [2006] #36). YU6 participated in the single cropping rice regional test of Zhejiang Province in 2002 and 2003. Its average yield was 563.3 kg/mu,which was

Table 1 .

 1 Panicle and grain characteristics of YU6 based on the yield category

	Yield level (㎏/hm 2 ) /	Paddy	Average productive panicles /(million/ hm 2 )	Average grains /panicle	Average filled grains /panicle	Averag e seed setting /%	1000-seed weigh t/g	Average yield /(㎏/ hm 2 )
	>11250	16	1.7795	322.48	290.98	89.75	23.28 11616.13
	≤11250->10500	28	1.7758	310.28	275.75	88.75	23.50 10782.43
	≤10500->9750	55	1.6255	321.31	284.67	88.36	23.66 10064.32
	≤9750->9000	48	1.5552	324.97	285.31	86.70	23.70	9385.09
	≤9000->8250	50	1.6347	304.51	251.45	82.52	23.71	8657.76
	≤8250->7500	30	1.5678	299.65	238.75	79.58	23.60	7958.60
	≤7500->6495	10	1.6979	288.30	219.21	76.64	23.20	7093.35

Table 2 .

 2 Correlation

			coefficients among traits
		grains per panicle	filled grains per panicle	seed setting rate	1000-seed weight	actual yield
	productive panicles	-0.6852 **	-0.6268 **	-0.1355 *	-0.1254	0.1948 **
	grains per panicle		0.8146 **	0.0620	-0.0183	0.2295 **
	filled grains per panicle			0.5985 **	-0.0760	0.4584 **
	seed setting rate				-0.0749	0.4973 **
	1000-seed weight					-0.0482
	Note: * P < 0.05, ** P < 0.01

Table 3 .

 3 Path analysis

	Factor	Direct effect	via x 1	via x 2	via x 3	via x 4	via x 5
	1 x	0.8171		-0.1734	-0.4041	-0.0292	-0.0155
	x	2	0.2531	-0.5598		0.5252	0.0134	-0.0023
	x	3	0.6447	-0.5122	0.2062		0.1291	-0.0094
	x	4	0.2157	-0.1107	0.0157	0.3859		-0.0093
	x	5	0.1240	-0.1024	-0.0046	-0.0490	-0.0161


Liguo Wei

Xiaochao Zhang

Quan Jia

Yangchun Liu

Automatic Navigation System Research For PZ60 Rice Planter

Keywords: rice transplanter, global navigation satellite system, automatic navigation

In order to satisfy the agricultural demond of rice transplanting, the transplanter work should guarantee the escapement even in straight line transplanting that is convenient for field management and harvest later. Because of variable soil conditions and hard work environment, the driver driving level and the long boring driving to follow line is a big influence to the accuracy of the rice transplant. It is easy to produce overline, leak line and cause losses in yield. Aimed at above problem, this text introduces an automatic navigation system developed on PZ60 rice transplanter based on global navigation satellite system (GNSS). The steering, transmission and transplanting control system of the rice transplanter were modified from manual control system to electrohydraulic control system using electro-hydraulic proportional valve. According to the position information of the rice transplanter acquired from GNSS receiver and vehicle sensors, the close-loop feedback control system of steering was builded. The system can accurately control rice transplanter to follow row navigating and turn around at the end of field by the self-adaptive fuzzy control method. The road and field experiment results indicated that the lateral tracking error could be kept within 100 mm when the speed of the rice transplant is not greater than 1.0m/s. The control system can satisfy the requirment of rice transplanting.

Introduction

Rice is one of the most important food crop in China, the national rice planting area accounts for about 30% of the grain crop area, close to half of the total output of grain yield. Rice suitable transplanting operation time is usually 7-10 days, the rural labor resources are insufficient, the labor cost is increasing year by year. Paddy field working environment is poor, and transplanting machine take the personnel, not only energy consumption, there are also operating personnel safety hidden danger. Automatic navigation technology is widly applied in modern agriculture and gradually becoming an important part of the agriculture engineering. At present, GNSS, machine vision and multi-sensors data fusion are the most widely applied automatic navigation technologies in the agricultural project. The technology of machine vision has the price advantage, but its application on the rice planter is restricted in the weak light intensity. As GNSS accuracy is continually rising and GNSS cost is continually falling, GNSS technology has a wide application on precision irrigation, fertilizer and farm robots automatic navigation [START_REF] F.reid | Noboru Noguchi,et a1.Agricultural automatic guidance research inNorth America[END_REF][START_REF] Jianping | Research progress of antomatic guidance technologies applied in agricultural engineering[END_REF][START_REF] Zhigang | Design of GPS Navigation control system for rice transplanter[END_REF] . The implementation of GNSS automatic navigation on the rice transplanter can relieve the labour intensity of the driver, extend the operating time and be conducive to the improvement of productivity and the yield of rice. The objective of this study is to develop an automatic navigation system that was developed on PZ60 rice transplanter based on RTK-GNSS navigation technology in the paper. The steering, transmission and transplanting control system of the rice transplanter were modified from manual control system to electronic control system [START_REF] Nagasaka | Autonomous guidance for rice transplanting using global positioning and gyroscopes[END_REF][START_REF] Q.zhang | T.Hwang,et a1.Use of adaptive control algorithms for automatic calibration of electrohydraulic actuator control[END_REF][START_REF] Hu Lian | Design of electronic control device and control algorithm for rice transplanter[END_REF][START_REF] Zhang | A generic fuzzy electrohydraulic steering controller for off-road vehicles[END_REF] . The automatic navigation system integrating GNSS technology and fuzzy control strategies can control the rice transplanter trace the presetted path and achieve automatic navigation transplanting.

Experiments and Methods

It is key that the manual driving mode of farm machinery is modified to electronic control mode in order to achieve mechanical automatic navigation control and variable assignments. The PZ60 high-speed rice transplanter has four-wheel-drive,six rows,engine power 8.3 kilowatt, the escapement 300 mm, the maximum speed of over 1.6 m/s. In order to realize automatic navigation working of the rice transplanter, the steering, HST no level shift system, braking system of the PZ60 rice transplanter were modified as shown in figure 1.

HST No Level Shift System

The rice transplanter is carried out going forward and backward infinitely variable speeds through adjusting HST hydrovalve flux and flow direction. The manual operation of HST action bar was modified to driving by electric handspike. The distance of the electric handspike is 80 mm, rating torque 75Nm  , the range of work voltage 12~24V. The electric handspike control the hydrovalve through driving connecting plate rotation. The shift sensor fixed at the connecting plate feeds back the control position of the hydrovalve. According to testing, the electric control mechanism costs 2.3 s to complete HST shift system from stop to most gear forward and costs 2.1 s to complete HST shift system from stop to most high gear backward. It can satify the demand of the field working.

Steering Mechanism

The steering mechanism of PZ60 rice transplanter is composed of steering wheel, hydraulic booster and clutch gear box. The manual steering wheel was modified to driving by turning motor. Turning motor is SGMJV-04AAA61 AC servo motor made in Japan, rating power 400 W, rating torque

m N M   27 . 1 0 , rating speed min / r 3000 n 0 
. The motor decelerated by speed reducer pass drive to hydraulic booster by clutch gear box and then turn the steering wheel by the main transmission case. The angle sensor fixed at the end of steering axle gathers steering angle. The clutch gear box was designed for automatic and manual operation switch. as shown figure2. The ininative gear joggles the tooth inlay gear. The tooth inlay can be shifted up and down through the control stick drives shifting fork. When the tooth inlay links the tooth inlay gear together, the steering mechanism is in automatic mode through motor driving. Whereas, the steering mechanism is in manual mode through the steering wheel. 1 . When the motor driving is by way of the clutch gear box, the output torque is:

z 1 0 0 1 M m N 1 . 38 i i M M       (1)
The retardment rate of the main gear box 2

i is 1 : 5 . 10 2  i
. The rating speed of the steering output axis is:

min / r 5 . 9 i i i n n 2 1 0 0 1     (2)
The limit steering angle of the inside wheel is 45 degree. When the steering wheel turns from the left limit angle to the right limit angle, the turning angle  of the steering output axis is 72 degree. It costs time:

s 3 . 1 60 360 n t 1     (3)
Therefore, The power and performing time of the automatic steering mechanism satisfy the need of operation.

Automatic Navigation System

The navigation system of the rice transplanter is composed of GNSS, onboard computer, steering controller, sensors and actuators as shown in figure3. GNSS adopts RTK locate mode that takes FlexPak6 TM receiver as base station, ProPak-V3 TM receiver as remotion station. Accuracy of static positioning is less than 20 mm. The output frequency of positioning information is set for 10Hz. The transplanter navigation control center is a high-powered on-board computer which can receive the informations acquired by GNSS receiver and angle sensors, make intelligent behavioral decision making and output navigation information instructions. The steering controller(SC) used the AD module to acquire the attitude information of transplanter in the navigation control process which measured by angle sensor and velocity sensor, and received the navigation information instructions from on-board cumputer at the same time. SC controlled the steering motor to move accurately, adjusted the HST speed control system to make the vehicle speed within limit, made the transplanting mechanism up or down and controlled the ground-contour-following device. Data transmission between SC and on-board computer was through the serial port. Steering motor thansmitted the driving force to make the steering wheel deflexion and then change the direction timely and accurately. Steering control is the major part of automatic navigation control to the rice transplanter. The steering motor controller used PID position control mode. Figure 4 is its control block diagram. Microcontroller used angle sensor to gather the current angle information of steering axis and send it to on-board computer as feedback information. According the horizonal deviation, yaw angle, the current angle information of steering axis and the preestablished fuzzy control rules, on-board computer made the steering control strategy and ordered microcontroller to output control signal which drove the steering motor. All of these constitute a steering closed-loop control system [START_REF] Heng | Machines and mechanisms theory(Sixth Edition)[END_REF][START_REF] Shousong | Automatic control theory(Fourth Edition)[END_REF][START_REF] Gao | The Study of the MEMS Gyro Zero Drift Signal Based on the Adaptive Kalman Filter[END_REF] . In order to measure the presion of rice transplanter automatic navigation sysytem, the experimentations were done at a blank blacktop nearby beijing xiao wang village experiment station of chinese academy of agricultural mechanization sciences. First, Two points A and B was fixed on blacktop groud, and the distance between point A and point B was longer than 80 m. The latitude and longitude information of two points A and B was achieved using GNSS receivers, and through on-board computer path planning software to prearrange a straight path of AB. A dropping style scriber fixed on rice transplanter was used to record the tracking of the rice transplanter on the ground. The scriber and GNSS receiver were fixed on the same centre axis of rice transplanter. After starting up the navigation control system, the rice transplanter begined automatic navigation in a definite velocity, and the scriber recorded the tracking on the ground at the same time.

Smooth

After the rice transplanter completed the process of automatic navigation, a white fishing line as the navigation datum line was fixed between point A and point B on the ground. Tracking route of the rice transplanter recorded by scriber compared with the navigation datum line, and used meter ruler to measure the deviation as shown in figure 5. The experiment data is shown in table 1. According to the experiment testing, the rice transplanter automatic navigation error is not greater than 100 mm when the rice transplanter is not greater than 3.6 km/h.

Paddy field experimentation

The paddy field experimentations were promoted in MiYun agricultural mechanization demonstration centre. The range of mud depth in the paddy field was 200~300 mm. The paddy field expermentations were as shown in figure 6. The velocity of the rice transplanter was 0.7 m/s. The tracking of the rice transplanter was recorded by GNSS receiver as shown in figure 7, real line for prearranged route, dashed line for following route. It can be seen from figure 5, following route essentially coincides with prearranged route in addition to following error at the end of the field. A large tracking errors appears in the joint of line following and turning at the end of the field, except with the maxiam mechanism steering angle correlation and control strategy also needs to be further improved.

According to measurement, the following line error of the rice transplanter is not greater than 100 mm and the automatic navigation system has good controlling precision and stability. It can satisfy the agricultural demand of rice transplanting

Conclusions

(1) In order to study agricultural machinery navigation and variable working, the steering, transmission and transplanting control system of the rice transplanter were modified from manual control system to electronic control system drived by servo motors. The navigation controller designed based on GPS technology realizes the rice transplanter automatic navigation working.

(2)The tracking error of automatic navigation system is not greater than 10 cm when the rice transplanter velocity is not greater than 1m/s in paddy field experimentations. It can satisfy the precision demand of rice transplanter automatic following line.

(3)Rice transplanter structure is complex, more joysticks need operation, the full realization of the unmanned is difficult. The autopilot system is transformation on the basis of the original, the steering system reform is relatively easy, and the transformation of the shift, clutch, throttle lever is more difficult. Paddy field working environment is poor, odds mud depth and wheel slipping impact on the effect of automatic navigation control. So, how to advance the performance of automatic navigation system from mechanical and control strategies that need more experimentation research.

Fig. 1

 1 Fig.1 Diagram of rice transplanter operating mechanism transformation

Fig. 2

 2 Fig.2 Structure of clutch gear box 1.Fork rotor 2.Control stick rotor 3.Ininative gear 4.Tooth inlay 5.Fork 6.Tooth inlay gear 7.Clutch control stick

Fig. 3

 3 Fig.3 Automatic Navigation system

Fig. 4 of steering control 3 . 1

 431 Fig.4 Diagram of steering control

Fig. 6 Fig. 5

 65 Fig.6 Paddy field experimentations

Fig. 7

 7 Fig.7 Line tracking result

Table 1 .

 1 Experiment data

	Segment number	Sampling point number	Sampling point (mm) deviation	Speed (km/h)
		1	42
		2	28
	S1	3	20	2.0
		4	4
		5	45
		6	51
		7	64
	S2	8	60	2.5
		9	82
		10	80
		11	75
		12	87
	S3	13	13	3.2
		14	40
		15	21

Acknowledgment

Funds for this research was provided by the National Science and Technology Plan Projects (2013BAD28Q01). This study is based on work supported by the key laboratory modern agricultural equipment ministry of agriculture, P.R. China.