Chong Huang

Haiguang Wang
email: wanghaiguang@cau.edu.cn

Development of a Web-based Information Service Platform for Protected Crop Pests

Keywords: Information service platform, protected crop, pest, aided diagnosis

With the rapid development of internet technology and protected cultivation in China, it is impending to implement a web-based information service system to spread professional agricultural knowledge. In this study, a 3-layer architecture web-based information service platform (ISP) for protected crop pests was developed using HTML, JavaScript and active server page (ASP). The platform included the information management module, the aided diagnosis module, the module of instructions for pest control, the technology BBS module, the system management module and the relative references module. Two logical algorithms, namely, identification key method and fuzzy diagnostic method, were designed for aided diagnosis of protected crop pests. The ISP could provide a technological platform for decision makers, agricultural technique extension workers and farmers. It is favorable to the effective management of protected crop pests.

Introduction

In recent years, protected cultivation has been developing rapidly in China. Protected agriculture could provide off-season vegetable, fruit and fresh flowers to meet people's increasingly living demand. Meanwhile, protected agriculture has enhanced the related farmers' income, which makes contributions to solving the question of "three agriculture", namely the question of agriculture, countryside and farmers. However, high-level technique and management are indispensable in protected agriculture. Therefore, it is very important to spread the professional knowledge of protected agricultural production.

Protected cultivation has important influence on the occurrence and epidemics of protected crop pests. It provides favorable conditions for the outbreak of the pests. It makes the pests occur during the off-season or in the areas where they could not occur before. Especially, the pest problems are very severe in the fields where protected cultivation has been applying for many years. Protected crop pests could reduce the crop yield or affect the quality of agricultural products, and then reduce the income of the farmers. In addition, some pests occurring severely in protected environment could provide initial inoculums for the crops growing in the open fields. Therefore, the issue of the pests is a main obstacle for the healthy development of protected agriculture. To solve this issue, it is important to identify or diagnose the pests in a timely and accurate manner, and take suitable control measures consequently. However, the lack of agricultural technique extension workers in China makes farmer training technical guidance facing many difficulties. Although the farmers could get some knowledge through watching TV, listening to broadcast or reading the technological books, they could not timely get related professional knowledge or communicate with related agricultural technique workers, so in most cases they could not solve the problems in the agricultural production that they have never met before. With the construction of agricultural informatization in China, internet construction in rural areas is developing rapidly. Some agricultural technique extension workers in the rural areas and some farmers can get access to internet conveniently and easily. Especially in the areas where protected agriculture has been developing well, the economic conditions are also good so that the extension workers and the farmers could obtain the agricultural knowledge and solve the problems that they meet in the agricultural production via internet. With the development and popularization of computer technology, the computers have been widely applied in the researches on plant protection [START_REF] Wang | Application of Computer Technology in Plant Pathology (in Chinese)[END_REF][START_REF] Ren | Research Progress on Expert System Technology and its Application in Plant Protection (in Chinese)[END_REF]. Some web-based plant pests information management systems have been developed [START_REF] Liu | The Wheat Diseases Expert System Based on the Web and the Implementation Using the Java Technology (in Chinese)[END_REF][START_REF] Wu | Expert Consulting System for the Diagnosis, Prevention and Control of Important Forest Diseases and Insect Pests (in Chinese)[END_REF][START_REF] Shao | Study on Vegetable Pests Remote Diagnosis Expert System (VPRDES) (in Chinese)[END_REF][START_REF] Ying | Analysis and Research on Web-based Grape Diseases Intelligent Decision Support System (in Chinese)[END_REF][START_REF] Jin | Grape Diseases Diagnose Expert System Based on Artificial Neural Network (in Chinese)[END_REF][START_REF] Tan | Realization of Long-distance Diagnosis of Forest Disease and Pest (in Chinese)[END_REF][START_REF] Li | Study and Development on the Information Query System of Tobacco Pests & Diseases (in Chinese)[END_REF].These systems made the spread of agricultural knowledge and the solution of some practical agricultural problems more convenient and faster.

Using Delphi, we developed Information Retrieval and Aided Diagnosis System for Protected Crop Pests (IRADS-PCP) on the Windows operation system platform [START_REF] Huang | Development of Information Retrieval and Aided Diagnosis System for Protected Crop Pests (in Chinese)[END_REF]. IRADS-PCP provided an opening and tree-shaped knowledge database for the information management of protected crop pests and for the retrieval of this kind of information in different ways. It is intelligent and useful for the diagnosis and the control of protected crop pests. However, IRADS-PCP is a software system and could only be run on personal computer so that it is not very easy and convenient for the users. In this study, we developed a web-based information service platform (ISP) for protected crop pests on the base of IRADS-PCP. The use of the internet enables the users to get information more efficiently and rapidly. The platform can provide the latest information of protected crop pests and pest control measures to the users so that they could identify or diagnose the crop pests and take suitable control measures timely and efficiently.

The structure of the information service platform

The web-based information service platform

The web-based information service platform (ISP) has been designed as a 3-layer architecture as shown in Fig. 1. The ISP consists of three layers: the user interface layer, the application layer and the database layer. The user interface layer running on an internet environment such as the Internet Explorer has been developed by HTML (Hypertext Markup Language), CSS (Cascading Style Sheets) and JavaScript with Microsoft FrontPage. This layer transfers the user's action to the application layer, and then the result from the application layer could be displayed on the Internet Explorer. The application layer uses the internet information server (IIS) and active server page (ASP). The IIS can response the requests from the users and send the corresponding results back to the users. All users connect the IIS through the internet and obtain information by submitting queries. The application layer includes some services applications and database applications programmed based on ASP. ASP is a widely-used scripting language that is suited to web development and can be embedded into HTML running on the internet information server. Actions services applications analyze the user's request from the IIS and the results are provided to the IPS DB algorithm and programs according to the requests. Then the ISP DB applications return the necessary data to the action services logic and programs. The database layer has been built on a SQL server which is a relational database management system, and provides data for information service including the pests' information data, research advance data and diagnosis characteristic values data, etc.

The main logical algorithm of the web-based ISP

Two logical algorithms were adopted in the web-based ISP for the aided diagnosis: diagnose through binary tree structural taxonomic key (TK) and fuzzy diagnosis (FD). Some taxonomic keys were designed in the system, in which each item including three components, namely id1 (serial number of the retrieval item), diagnostic characteristic and id2 (serial number of the retrieval item related to id1) or result. When diagnosing the pests, the items will be provided to the user for selection and then be located to the next item according to the user's selection until the result is given (Fig. 2A).

When fuzzy diagnosis style is used by the user, a characteristic table should be submitted on the Internet Explorer to make the algorithm on the application layer partly or completely. The structure of the tables was designed by the experts with considerations of some diagnostic characteristics that are crucial to the pest diagnosis. The weight coefficient of each characteristic would be evaluated along to their importance. And then a specific table will be produced for a crop or a type of pest for diagnosis. The characteristic values of each kind of pest should be added to the database as many as possible by the experts before diagnosing. When diagnosing, the users select one crop or one type of pests, and then fill a table partly or completely, the result or the result list will be given with accurate probability (Fig. 2B).

The construction of the information service platform

The modules of the web-based ISP

The web-based ISP is composed of six modules as shown in Fig. 3: information of the pests (pest name, symptoms, incidence, control method, and so on, were included in this module), search and diagnosis (the main module of the system, by which the users can search a pest or make diagnosis of an unknown pest), instruction for pest control (some control methods or some management advice for pests was given in this module), technology BBS (this module provides a open platform for the users and the experts to exchange their ideas or ask for help), system management (a module specific to the web manager), and relative references (some research references about the protected crop pests were collected in this module).

The functions of the web-based ISP

Information service. In the web-based ISP, it is easy for the users to search some useful information such as pest information, pest control advice, and relative research papers through our own search engine or by the Google engine. When searching the information of a specific pest, the pest name is needed. The users can also search the information of a specific pest by inputting some information such as infested host, symptom, infesting period, and so on (Fig. 4A), a pest list satisfying the search conditions will be provided to the users by the platform, and then the users can choose what they need from the list. Pest control methods and lots of research advances are also available in the web-based ISP.

Pest diagnosis.

Pest diagnosis is the key function of the web-based ISP. It can not only help the users to determine what the pest is, but provide some advices for them. When running the algorithms of taxonomic key (Fig. 4B), some pests are given and some pests are excluded when the diagnosis going on. When some selections and decisions have been done by the users on the Internet Explorer according to the items or the figures to run the logical algorithms of diagnosis in the internet information services, the result will appear on the computer screen (Fig. 4D).

Technology communication. BBS was designed in the web-based ISP enabling the experts and the users to exchange their ideas about protected crop pests. In the BBS, the users can ask questions, and the experts can answer the users' questions.

System and database management. System management module was designed for the web administrator. In the registration interface, the administrator inputs the user name and the corresponding password, and then log in the system management interface. The administrator can manage the columns of the system and conduct the data maintenance including adding data, modifying data, deleting data and so on.

Conclusion and discussion

A web-based information service system has been developed for protected crop pests to provide information service and aided diagnosis for the users including decision makers, agricultural technique extension workers and farmers. Through this system, the users can get pests' information and control methods. When an unknown pest occurring, the users can also use the function of aided diagnosis to determine what it is and how to control it. In the web-based ISP, two logical algorithms were designed for pest diagnosis. One was based on the identification key that was widely used in the taxonomic. The accuracy of the method mostly depends on the identification key. And another was a probabilistic diagnosis.

With the development of information technology and the improvement of living standard, more and more Chinese farmers who are eager to obtain the technology to instruct their production, can get access to the internet and obtain the agricultural knowledge and the technology guidance from web-based information service platform. The platform we developed could promote the spread and the popularization of the knowledge about protected crop pest and could efficiently relieve the shortage of agricultural experts and agricultural technique extension workers.

In further studies, more pest information would be added into the platform. And the platform could provide video information in addition to the texts and the images. The function of image assistant diagnosis could also be added into the platform so that the users could get diagnosis result when they upload one image of an unknown pest. The platform could combine with Geographic Information System (GIS) to provide pest information in certain area [START_REF] Yang | Research on Fruit Tree Plant Diseases and Insect Pests Publication System Based on WebGIS (in Chinese)[END_REF][START_REF] Wang | Study of Web-based Expert System for Control Diseases and Insects in Forest (in Chinese)[END_REF][START_REF] Gong | Construction of a WebGIS-based Forecast System of Crop Diseases and Pests (in Chinese)[END_REF][START_REF] Li | Study on WebGIS and Knowledge Model Based Decision Support System for Disease-pest-weed Management in Wheat (in Chinese)[END_REF][START_REF] Liu | The Study and Construction of Winter-Jujube Pest and Disease Information Forum Based on WebGIS (in Chinese)[END_REF]. With more understanding of protected crop pests, the function of pest forecast may be added to the platform. Using pest forecast, occurrence information of protected crop pests could be provided to the farmers earlier, so they could make enough preparation as early as possible.

Pest management is a part of protected crop production management. Some crop production management systems have been developed [START_REF] Qiu | Cotton Production Management System Based on the CottonPlus Model for Xinjiang and Huang-Huai-Hai Region in China[END_REF][START_REF] Li | Expert System of Wheat and Corn Production Management Based on WEB (in Chinese)[END_REF]. Most of them contain the pest management module or subsystem. On the whole, the crop production management systems make important contribution to crop production management and improve the level of agricultural production management. In order to drive the development of protected crop industry, it is necessary to develop the production management system for protected crops on the base of this platform in further researches.

Fig. 1 .

 1 Fig.1. The 3-layer architecture adopted in the web-based ISP.

Fig. 2 .

 2 Fig.2. Logical algorithms of binary tree structural taxonomic key (A) and fuzzy diagnosis (B) for the aided diagnosis.

Fig. 3 .

 3 Fig.3. The structure of the web-based information service platform.

Fig. 4 .

 4 Fig.4. The diagnostic functions of the web-based ISP.

Acknowledgements

. This research was supported by Project in the National Science & Technology Pillar Program during the Eleventh Five-year Plan Period of China (Grant No: 2007BAD57B02).


Xingang Xu

Xiaohe Gu

Xiaoyu Song
email: songxy@nercita.org.cn

Cunjun Li

Wenjiang Huang
email: huangwj@nercita.org.cn

Assessing Rice Chlorophyll Content With Vegetation Indices From Hyperspectral Data

Keywords: Chlorophyll Content, Vegetation Indices, Weight Optimization Combination, Hyperspectral Remote Sensing

Leaf chlorophyll content is not only an important biochemical parameter for determinating the capacity of rice photosynthesis, but also a good indicator of crop stress, nutritional state. Due to the reliable, operational and non-destructive advantages, hyperspectral remote sensing plays a significant role for assessing and monitoring chlorophyll content. In the study, a few of typical vegetation indices (VI) with the combination of 670nm and 800nm band reflectance, Normalized Difference Vegetation Index (NDVI), Modified Simple Ratio index (MSR), Modified Chlorophyll Absorption Ratio Index (MCARI), Transformed Chlorophyll Absorption Ratio Index (TCARI), and Optimized Soil-Adjusted Vegetation Index (OSAVI) are modified by using 705nm and 750nm band reflectance so as to reduce the effect of spectral saturation in 660-680nm absorptive band region, and then used to assess the rice chlorophyll content. The result shows that the five mentioned VIs have better correlation with rice chlorophyll content while using 705nm and 750nm. In addition, in the study the Weight optimization combination (WOC) principle is utilized to further assess the capacity of the five modified VIs for estimating rice chlorophyll content, it is proved that OSAVI and MSR display the better performance.

Introduction

Chlorophyll is one of most important matters for crop photosynthesis, and the amount of chlorophyll in crops can reflect whether the growth state of crop is in health or not. Healthy and stressed crops often display changes in pigment levels [START_REF] Niinemets | A model separating leaf structural and physiological effects on carbon gain along light gradients for the shade-tolerant species Acer saccharum[END_REF]; Penuelas, J., Filella , 1998; [START_REF] Rasmus | Utility of an image-based canopy reflectance modeling tool for remote estimation of LAI and leaf chlorophyll content at the field scale[END_REF]. In addition, chlorophyll content is firmly related with nitrogen level. Consequently, accurately assessing the chlorophyll content is very useful for obtaining crop productivity, probing crop stresses and nutritional state [START_REF] Zarco-Tejada | Hyperspectral indices and model simulation for chlorophyll estimation in open-canopy tree crops[END_REF]. Hyperspectral remote sensing plays a unique role in detecting crop biochemical parameters, such as dry matter, pigments and so on. In the visible regions, crops present the different changes of spectrographic curve, and leaf chlorophyll content is the most important factor leading to the leaf spectral variation (Zhang et al., 2008), which provides the base for remote detection of crop growth state through monitoring chlorophyll content. Vegetation indices (VIs) with the combination of different bands can reduce some noise caused by external factors such as the atmosphere and the soil background to some extent [START_REF] Demarez | A modeling approach for studying forest chlorophyll content[END_REF][START_REF] Rasmus | Mapping leaf chlorophyll and leaf area index using inverse and forward canopy reflectance modeling and SPOT reflectance data[END_REF], and are widely used to monitor and assess the leaf chlorophyll content.

The typical VIs based on hyperspectral remote sensing, such as NDVI [START_REF] Rouse | Monitoring the vernal advancements and retrogradation of natural vegetation[END_REF][START_REF] Gitelson | Spectral reflectance changes associated with autumn senescence of Aesculus hippocastanum L and Acer platanoides L leaves-spectral features and relation to chlorophyll estimation[END_REF], MSR [START_REF] Chen | Evaluation of vegetation indices and modified simple ratio for boreal applications[END_REF], MCARI, TCARI [START_REF] Daughtry | Estimating corn leaf chlorophyll concentration from leaf and canopy reflectance[END_REF], and OSAVI [START_REF] Rondeaux | Optimization of soiladjusted vegetation indices[END_REF], commonly use 670nm to estimate leaf chlorophyll content. However, in 660-680nm red spectral region, the chlorophyll absorptions begin to show the saturated tendency at lower chlorophyll content, which would weaken the sensitivity of VIs to higher chlorophyll content. By contrast, the absorptions in the region around 550nm or 700nm show the same phenomena at higher chlorophyll content [START_REF] Sims | Relationships between leaf pigment content and spectral reflectance across a wide range of species, leaf structures and developmental stages[END_REF]. So the spectral indices with these bands in the latter regions would have better precision for assessing chlorophyll content.

The objective of the study is to compare the performance of the above five VIs for assessing chlorophyll content by using different bands combination of reflectance to modify these indices. In addition, the Weight optimization combination (WOC) principle is utilized to further analyze the capacity of the five modified VIs for estimating rice chlorophyll content.

2

Material And Method

Study Area

The study site is located in Qianjin and Youyi Farm, Heilongjiang Nongken, China.

In the two farms, rice is main crop. Specially in Qianjin Farm, rice accounts for about 95% of total crop planting areas. In the study, there are thirty-eight paddy fields to be selected to obtain the spectral and chlorophyll content data, and these selected paddy fields are homogeneous for rice breed and field management. The collections of data are carried out on August 6, 2009.

Field Data Acquisition

In the paper, canopy spectral data in every selected paddy field are collected at 380-2500 nm by a portable spectroradiometer (FS-FR2500, ASD, USA) with field of view of 25° and a distance of about 150 cm above the ground surface. Reflectance spectra are derived through calibration with the 99% white reference board (Labsphere, Inc., North Sutton, New Hampshire, USA).The measured spectra data for ten times are averaged as the final spectral data in every paddy field. Chlorophyll content is obtained by using the portable Chlorophyll Meter SPAD-502 (Minolta Corporation, New Jersey, USA). In every measured paddy field, twenty rice samples are randomly selected, and then the averaged SPAD value of all leaves of each rice samples is viewed as chlorophyll content of the measured rice samples. Finally, the SPAD values of the twenty rice samples are further averaged as the rice chlorophyll content for the measured paddy field.

Vegetation Indices Used in the Study

In the study, the five vegetation indices, NDVI, MSR, MCARI, TCARI, and OSAVI are comparatively applied to assess the rice chlorophyll content.

NDVI (Normalized Difference Vegetation Index) should be the most extensively used VI which couples the maximum reflection in the infrared with the maximum absorption in the red, and is formulated with the following equation when using hyperspectral wavebands, where is R the reflectance at the given waveband (nm):

800 670 800 670 [670,800] R R NDVI R R - = +
MSR (Modified Simple Ratio index) is the improvement on SR (Simple Ratio index). In hyperspectral remote sensing applications, SR is directly formulated with the reflection extremum in the infrared and that of the absorption in the red, and can enhance the contrast between soil and vegetation while minimizing the effect of the illumination conditions (Barnet and Guyot, 1991), but their effectiveness is reduced by the soil reflectance underneath the canopy. So MSR is proposed to further decrease the soil noise, and its quantified equation is as the following:

800 670 800 670 1 [670,800] 1 R R MSR R R - = +
Based on CARI (Chlorophyll Absorption Ratio Index) which measures the depth of chlorophyll absorption at 670 nm relative to the green reflectance peak at 550 nm and the reflectance at 700 nm in order to reduce the effect of some non-photosynthetic materials, MCARI (Modified Chlorophyll Absorption Ratio Index) is developed to further weaken the noise due to non-photosynthetic materials, as the following equation:

( ) ( ) ( ) 700 670 700 550 700 670 [670,700] 0.2 MCARI R R R R R R = - - - ⎡ ⎤ ⎣ ⎦
TCARI (Transformed Chlorophyll Absorption Ratio Index) is proposed to eliminate reflectance effect of background matters (soil and non-photosynthetic components) and to increase the sensitivity at low chlorophyll content, and is formulated with the following equation:

( ) ( )( ) 700 670 700 550 700 670 [670,700] 3 0.2 TCARI R R R R R R = - - - ⎡ ⎤ ⎣ ⎦
OSAVI (Optimized Soil-Adjusted Vegetation Index) belongs to SAVI family [START_REF] Huete | A soil-adjusted vegetation index (SAVI)[END_REF], and is developed to further reduce background soils, and defined as the following:

( )( ) (
)

800 670 800 670 1 0.16 [670, 800] 0.16 R R OSAVI R R + - = + +
Vegetation spectrum from 400 nm to 700 nm region is primarily determined by chlorophyll and other pigments. The bands in the above five VIs is commonly selected to assess the chlorophyll content. In recent years, it is proved that besides the combination of the above bands, the new combinations of the other bands is possibly more sensitive and effective to leaf chlorophyll. For example, [START_REF] Sims | Relationships between leaf pigment content and spectral reflectance across a wide range of species, leaf structures and developmental stages[END_REF] found that the band of 705 nm has better correlation with leaf total chlorophylls besides 680 nm, and they also found a strong correlation between different combinations of reflectance at 700 nm, 705 nm, and 750 nm, and leaf chlorophyll content. Wu et al (2008) utilized the reflectance at 750 nm and 705 nm to form the revised VIs to estimate the chlorophyll of wheat and corn. Therefore, the reflectance of these bands may have potentials in assessing chlorophyll content. In this study, the above five VIs are modified to assess the rice chlorophyll content with the new combination of the reflectance at 750 nm and 705 nm replacing that of 800 nm and 670 nm. The formulas of the five modified VIs are as Table 1.

Weight Optimization Combination Method

Weight optimization combination (WOC) is a method which calculates optimal weights of different models solving the same problem to form the combination model with the aim of the least errors (Xu et al., 2009). The principle of WOC is as the following:

There are different N models constructed with n samples for settling the same problem, where both N and n are the same as the following mentioned, respectively. The estimated value of the combination model formed by N models for j sample is defined as the following:

1 N j i ij i f k f = ∑ = (1)
Here, i k are weights of N single models, and k is constrained by the following conditions: 0

1 i i k k ∑ ≥ ⎧ ⎨ = ⎩ (2)
The error of the combination model for j sample is formulated with the following:

1 N j j j i j i i e y f e k = ∑ = -= (3)
For determining k i , e j is usually looked on as independent variable of the objective function, and the mathematic framework of WOC is commonly expressed as the following:

1 2 min ( , , , ) 1
0 i i i E E k k k k k ∑ = … ⎧ ⎪ = ⎨ ⎪ ≥ ⎩ (4)
Where minE is the objective function that can be the minimum error square sum, or minimum absolute error sum, or the other cost function. The process solving the formula (4) for the acquisition of k i is a little complicated, and there are various solving algorithms for the formula (4) with different effectiveness. In the study, the iterative optimization algorithm based on dual optimal combination is selected to calculate the optimal weights, whose detailed description can be found in Tang et al (Tang et al., 1994).

Result and Discussion

To analyze the performance of the five modified VIs for assessing chlorophyll content, the five VIs, respectively using the combination of 670 nm & 800 nm, 705 nm & 750 nm, are correlated with the measured rice chlorophyll in 38 paddy fields from the two farms. Their correlation coefficients are as shown in Table 2. From Table 2, we can see that after using the combination of 705nm and 750nm, the correlations between the modified VIs and rice chlorophyll have more obvious increase in comparison with those of the initial VIs with 670nm and 800nm. Although the correlation coefficient of TCARI with rice chlorophyll improves unconspicuously, the correlations of the other four VIs, NDVI, MSR, MCARI and OSAVI have been greatly raised.

In order to further compare the ability of the five modified VIs assessing rice chlorophyll, WOC is adopted by using the following steps: Firstly, the five models which correlate the five revised VIs with rice chlorophyll respectively are set up, the LLST(Linear Least Squares Fit) is the main modeling method in the study; Secondly, the five models viewed separately as the single model are input into WOC; Finally, the iterative optimization algorithm above mentioned is applied to calculate the weights.

In the process of using WOC with the iterative optimization algorithm, the more useful information the single model contributes to, the bigger weight it is given, and vice versa. That is to say, WOC has the function of judging redundant information (Tang, 1992). As far as the single model providing little or useless information is concerned, WOC would give the model less or zero weight. Therefore, in the study, we can determine which of the VIs are more probably sensitive to rice chlorophyll according to the weight when the five models constructed separately by the five modified VIs are input into WOC. Table 3 shows the weights of the five models with the modified VIs based on WOC. From Table 3, the VIs MSR and OSAVI acquire non-zero weight, 0.33 and 0.67 respectively, and the other three are given zero weight, which illustrates that it would be enough to use the two VIs MSR and OSAVI when preparing to adopt the modified VIs at the same time to assess the rice chlorophyll. Moreover, Table 3 also tells us that the combination model has higher precision than each of the single models due to the minimum least Sum of Square Error.

Conclusion

In the study, the five typical vegetation indices, NDVI, MSR, MCARI, TCARI and OSAVI with usually using the combination of 670nm and 800nm are modified by replacing the two bands with 705nm and 750nm to assess rice chlorophyll content, and there are conclusions as the followings:

(1) The five modified vegetation indices with the combination of 705nm and 750nm have better correlation with rice chlorophyll content in comparison in the five VIs with 670nm and 800nm, which shows that the former has the potentials in assessing chlorophyll content. (2) When using WOC to further compare the performance of the five modified vegetation indices for assessing rice chlorophyll, the two vegetation indices MSR and OSAVI show better performance than the other three VIs The study only explores the ability of the five modified vegetation indices assessing rice chlorophyll for one rice growth period, and the following research work would focus on multi-periods.

  estimated result for j sample with i model( 1the error for j sample with i model;

Table 1 .

 1 The formulas of the five modified Vis in the study.

	Vegetation indices								Formula
	NDVI	NDVI	[705, 750]	=	R R	750 750	-+	R R	705 705
	MSR	MSR	[705, 750]	=		750 750 R R	705 705 R R -+ 1 1
	MCARI	[705,750] M CARI	=	( ⎡ ⎣	750 R R 705 -	) ( 0.2 -	750 R R 550 -	) ( ⎤ ⎦	750 R R 705	)
	TCARI OSAVI	( ⎡ ⎣ [7 705, 750] 750 [705,750] 3 TCARI R R 705 = -( ( ) ( 0.2 -750 1 0.16 R R R R )( 750 550 750 705 -)( ) ) 750 705 705 0.16 R R OSAVI R R + -= = + +	)	⎤ ⎦

Table 2 .

 2 The correlation coefficients between the five VIs and SAPD chlorophyll content.

	Vegetation index	R[670,800]	R [705,750]
	NDVI	0.351	0.478
	MSR	0.365	0.485
	MCARI	-0.345	0.453
	TCARI	-0.457	-0.474
	OSAVI	0.342	0.470

Table 3 .

 3 Weights of the single model in the combining model based on WOC.

	Model with different VI [705,750]	Weight	Least Sum of Square Error
	NDVI	0	272.08
	MSR	0.33	262.43
	MCARI	0	273.65
	TCARI	0	266.88
	OSAVI	0.67	261.79
	Combination Model	--	261.60

Acknowledgments

. Funding for this research is supported by 863 National High Technology R&D Program (code: 2006AA210108, 2006AA10A302 & 2006AA10A307) (P. R. China).


Hui Li

Ningning Ge

Lingwang Gao
email: lwgao@cau.edu.cn.

Zuorui Shen

Guoliang Zhang

Zhiyuan Zang

Yi Li3

Development of the Information Management System for Monitoring Alien Invasive Species

Keywords: The alien invasive species, the epidemic situation, multipath report, integrated technology

One of the effective methods to prevent the excessive extending of alien invasive species is to really master their epidemic trends and to take appropriate measures to control them. So, the information management system for monitoring alien invasive species based on the integrated technology was developed to provide the information services for the governments, experts and farmers. The main modules of the system are the sub-system of investigation data management and the sub-system of real-time epidemic reporting in new extending area. In the investigation data management sub-system, the dynamic data of the invasive species in invaded areas can be input into the system. And in the sub-system of real-time epidemic reporting in new extending area, the epidemic information can be reported in E-mail, telephone-voice, short message, voice mail, videoconference or other format with users' telephone, cell phone, personal computer, and personal digital assistant(PDA) based on the integrated technology. The system built the information exchanging bridges among the governments, experts and farmers, letting them to make more effective decisions.

Introduction

At present, the situation of alien invasive species is very serious in China. The whole country except Tibetan plateau in remote areas has been threaten or been effected by the alien invasive species in variant degrees [START_REF] Cai | Control Alien Invasive Species to Conserve Biodiversity[END_REF].

Cattau's study highlights the implications of conservation of native species and also describes the importance of effects that invading species have on the native species, especially those that are endangered, because the subtle influences on behavior may have an important significance on population density [START_REF] Cattau | Effects of an exotic prey species on a native specialist: example of the snail kite[END_REF]. Pine wood nematode had extended into Jiangsu, Zhejiang, Anhui, Shandong and Guangdong in 1999, making 15 million trees cumulatively die [START_REF] Zhang | Research Progress and Prospects of Invasive Alien Species[END_REF].

Till present a lot of research has been done. Darren's research on the interactions between a biological control agent (Cleopus japonicas) and its plant host (Buddleja davidii). It is based on a mess of data, which are precise and reliable and successive three years' data from 2007 to 2009 [START_REF] Kriticos | Watson: A process-based population dynamics model to explore target and non-target impacts of a biological control agent[END_REF]. And some risk assessment models are introduced for preventing alien invasive species. But the reliability of the total risk score clearly depends on the quality of the available data and the experience of the assessor.

The key principle of international environment law is to prevent the risks and harms before the insertion of the alien invasive species [START_REF] Kriticos | Watson: A process-based population dynamics model to explore target and non-target impacts of a biological control agent[END_REF]. The exact investigation data will help people put the theoretical principle into the factual effect. And they directly influence the macro decision of the harmful biological control [START_REF] Xing | Principle of International Law and Its Implementing to Prevent Alien Invasive Species[END_REF].

With the rapid development of the computer and information technology, the agriculture in China gets an opportunity of rapid progress. On the fields of agricultural production and management, computers, as a resource, take a prominent role by its high speed and large storage, retrieval convenience and quick transmission of information [START_REF] Qiang | The application prospect of computer-centered information technology on agriculture[END_REF]. From a Japanese report about the computer's application on the alien invasive species, because of their potentially wide spatial coverage, an integrated information system that presents their epidemic situation needs to be developed [START_REF] Kitamoto | Information visualization and organization for participatory monitoring of invasive alien species[END_REF]. In addition, the integrated technology mixes sensors, computers, and communication devices and unceasingly change the ways of precision agriculture [START_REF] Newell | Emerging technologies for real-time and integrated agriculture decisions[END_REF].

In this paper, the development of the information management system for monitoring alien invasive species based on the integrated technology was reported. The system can provide information services for the governments, experts and farmers with the data of occurrence and dissemination of the alien species and set an entire set of information interaction in them.

Designing of the system

Environment for the system development

The system was developed with PHP5.0 based on the Microsoft Windows XP Professional Service Pack 2 on PC with Intel(R) Pentium(R) 4 CPU3.00GHz, 1.25G EMS, and 120G HD. MySQL DBMS was employed to provide the support of the data management in the system. The system can be run on Microsoft Windows 2000/XP/2003 and Linux, etc.

Structure of the system

The platform consists of six main parts by now: (1) The sub-system of investigation data management; (2) The sub-system of real-time epidemic reporting in new extending area; (3) The sub-system of monitoring data acquisition and management; (4) The sub-system of expert response based on the internet and telecommunications networks; (5) The sub-system of management system of literature; (6) The sub-system of administration of experts.

This passage mainly introduces the first two parts.

The Sun-system of Investigation Data Management

In order to meet the need of scientific research and preventive practice, a lot of epidemic data will be put into the multifunctional platform by professional workers in this field. The epidemic data are mainly divided into three parts.

The first part includes the natural information (for example, the area in which the alien invasive species has occurred.); the second part are about the agricultural information, including crops and their details; and the last one is the fugacious data-the epidemic information, that is, the occurrence and hazard information of the alien species (Fig. 1). The system provides investigators the access to inputting the data and record the information of them. So, each datum can cast back to a single recorder insuring the reliability and veracity of the data in the system.

In addition, the environmental data (including the air temperature, air humidity, soil temperature, soil humidity, etc.) is recorded with automation recorder and transmitted to database in the system.

The Sub-system of Real-time Epidemic Reporting in New Extending Area

When new extending area of the alien invasive species is found, the information can be easily concentrated on the platform by sending short messages, calling phone or using Internet and stored to a stable database in the system.

After the reporting information into the platform, the system would send the information to the related departments and experts automatically, and the information would be verified by professionals. If it is confirmed as a piece of valid new epidemic information, the administrative departments, experts, and local departments would hold a consultation meeting to discuss the emergency and develop specific implementation plans. Emergency measures would be started up. The detailed process is as fig2. So this sub-system saves more reporting time from finder to decision maker than paper file reporting. It is quite significant that any person can access to the platform in time no matter who are you and where are you.

Fig. 1 The last part-the epidemic information Fig. 2 The flow chart of epidemic information reporting

Discussion

3.1The Superiority of the Platform

Till now a lot of researches have largely been referred to plant physiology, plant ecology, biology and some prediction modules including the dynamic population of alien invasive species [START_REF] Bartomeus | Combined effects of Impatiens glandulifera invasion and landscape structure on native plant pollination[END_REF][START_REF] Smolik | Integrating species distribution models and interacting particle systems to predict the spread of an invasive alien plant[END_REF][START_REF] Stanisci | Leaf and root trait variability of alien and native species along Adriatic coastal dunes (Italy)[END_REF]. But all researches will be based on abundant reliable data. This is also the fetter of promoting recent research. And any ecological systems are often very complicated involving non-linear responses to environmental factors and involving density-dependent processes. And every of the alien invasive species might have wide potential suitable areas in China. For example Flaveria bidentis, a new exotic invasive plant originating from South America [START_REF] Powell | Systematics of Flaveria (F1averimae, Asteraceae)[END_REF]. The potential extended areas of it in China, which are estimated by using the CLIMEX software, would contain Guangdong, Guangxi, Yunnan, Hainan, Fujian, Taiwan, Jiangxi, Hunan, Guizhou, Sichuan, Chongqing, Hubei, Anhui, Jiangsu, and Shanghai provinces. Among these, Guangdong, Guangxi, Taiwan, Hainan, Fujian, Yunnan, Sichuan, Guizhou, Chongqing and part of Xizang are at the high risk [START_REF] Bai | Potential distribution areas of alien invasive plant[END_REF]. But it is obvious that getting dynamic data of the alien invasive species is an enormous, intricate and lengthy project. So the superiority of the platform lies in inputting and saving dynamic information by computer and web.

In addition, the multipath information report in the platform, which integrates the internet, mobile and fixed-line telephone, is very convenient especially for farmers in rural regions to report the extending situation. No matter which is chosen, the extending information can be stored in a database and be timely transmitted to related government departments and experts. This would change the situation that most efficiency information in the rural and remote regions cannot be timely transmitted to related departments. And it also resolves this problem that the alien invasive species, in broad china area, could be hard timely discovered [14] by widening channels of information (mobile, fix-phone and internet) to the related departments and by arousing the broad masses.

And by means of these interactive methods the government departments are able to give some instructive and legal advice to the farmers and experts in this region. Simultaneously experts also can provide some actual preventative measures through their decision-making according to the physiological property of alien species and the natural conditions of this region. This platform becomes an orderly high-speed information cyclic system, which breaks the limitation of geographical space and which simplifies the procedure of the information report.

The Development of the Platform

Remote Sensing, Geographical Information System and Global Positioning System (3S) would be introduced into the platform which can make epidemic data richer and more precise. 3S technology has been broadly applied in agricultural data inquiry. For example, the inquiry of slop soil distribution in indifferent slop grades [START_REF] Su | the Inquiry of Slop Soil Distribution in Indifferent Slop Grade Based on '3S[END_REF].

And even if farmers' and researchers' hard drives have filled up with images, maps and data-filled spreadsheets, we are drowning in information. So we need to accelerate the process from collecting information into making reliable decisions [START_REF] Newell | Emerging technologies for real-time and integrated agriculture decisions[END_REF]. It is necessary to add a forecasting support system, an identification system and an expert decision-making system to the integrated platform, such as a forecasting decision support system [START_REF] Wu | Design and Implementation of a Forecasting Decision Support System[END_REF], the expert system platform for forecast and prediction of agricultural pests [START_REF] Gao | Research and development of the expert system platform for forecast and prediction of agricultural pests[END_REF], and a management system for rice leaf roller [START_REF] Hu | A Management System for Rice Leaf Roller[END_REF].

If this platform can be associated with the related webs, for example, the national quarantine web and the national agricultural web, it would be more advantageous to government departments, experts, investigators, and formers.

More full information, more sagacious decisions.

Acknowledgments.

This research was supported by Public Welfare Project from Ministry of Agriculture of the People's Republic of China (Grant No: 200803022 and 200803006).


Xiaojun Liu

Yuou Zhang

Weixing Cao

Yan Zhu
email: yanzhu@njau.edu.cn

Design and Realization of a VRGIS-Based Digital Agricultural Region Management System

Keywords: VRGIS, agro-region, knowledge model for crop management, information management, virtual simulation

In order to realize the digitalization and visualization of information management in agricultural-region, a VRGIS-based digital agricultural region management system (VDARMS) was developed with SuperMap 2008 as the platform of spatial information management, VRMap 3.0 as the driver of scene, and integrating with the existing knowledge model for crop management. This system realized the functions as file management, spatial handling, information query, data analysis, cultural management plan design, virtual simulation, and system maintenance, etc. Case studies of the system were carried out in Heheng village of Jiangyan city and Qinglong village of Nanjing city, Jiangsu province, China, the application results indicated that VDARMS accorded with the development of modern agricultural spatial information management, realized standard, digital management and visual display of agricultural information, and greatly promoted the development of digital agriculture technology.

Introduction

Along with the development of information and computer technologies, digital agriculture has been an effective method for many countries to promote the skills of agricultural production and improve the capacity of agricultural competition [START_REF] Liu | The Origin and the Initial Practice of the Digital Agriculture (in Chinese)[END_REF][START_REF] Song | Study Progress and Development Trend of Digital Agriculture (in Chinese)[END_REF][START_REF] Zhou | 3S Technique and Digital Agriculture (in Chinese)[END_REF]. Agricultural information management system is one of the core technologies in the technological system of digital agriculture. Up to now, correlative researches were reported at home and abroad, for example, [START_REF] Shane | Development of a Field-Level Geographic Information System[END_REF] in Kansas State University developed a field-level geographic information system based on object-oriented programming concept. [START_REF] Ma | Developing and Studying of Spatial Information Management System of Digital Agriculture Based on COM GIS (in Chinese)[END_REF] established a spatial information management system of digital agriculture by using ComGIS technology. Liu et al. (2006) designed and realized a WebGIS-based system for agricultural spatial information management and aided decision-making with Brower/Server mode as distributing network structure and WebGIS as spatial information management platform. These systems were mostly developed based on GIS, had the functions as information query, spatial analysis and aided decisionmaking. However, geometrical and topological information in the third dimension (vertical direction) were disappeared for using 2D showing mode in expressing spatial information, so the realistic world cannot be exhibited perfectly.

Virtual reality geographic information system (VRGIS) is one of the pop research domains in geographic information system (GIS) and virtual reality (VR). As the integrating combination of GIS and VR, VRGIS has the functions as spatial information management of GIS and virtual visualization of VR, user can observe, immerge and communicate in the virtual environment [START_REF] Deng | Virtual Reality Geographic Information System (VRGIS)-a New Field of the Research of GIS (in Chinese)[END_REF]. Recently, several correlative researches based on VRGIS were reported in the domains of urban layout, forest resource management and tour resources management, moreover, a series of virtual simulation systems were developed [START_REF] Jiang | Research and Application of VRGIS in Forest Resources Management (in Chinese)[END_REF][START_REF] Zou | Study on Large-Scale City VR Simulation System and its Realization (in Chinese)[END_REF]Liu et al, 2006;[START_REF] Wu | Realization of the Dynamic Interactive 3D Virtual Wandering System in the Rural Community Based on VRML (in Chinese)[END_REF]. Although these systems realized the functions as 3D wandering, data management and information query, but couldn't realize the spatial information analysis and decision support. Therefore, the object of this paper is to develop a VRGIS-based digital agricultual region management system by integrating the technologies of VRGIS, crop management knowledge model, database and decision support system [START_REF] Cao | Digital Farming Technology[END_REF]. The system aims to realize the functions such as digitalization management for agro-region information, aided decision-making for crop cultivation and visualization simulation display, furthermore improve the efficiency and effect of information management and display in agro-region.

2

Design of system

Design of system structure

Based on the theory of system engineering, software technology, research target and technology characteristic, the system was composed of three parts: user layer, operational logic layer and basal data layer (Fig. 1). Elementary data: included spatial and attributive data. The spatial data included the data as road, watershed, building and field in agro-region. The attributive data was composed of elementary attributive data and geographic attributive data. The first one consisted of agricultural resource data that driving model run and scene constructing parameters, such as meteorological data, soil data, variety parameter data and terrain creating parameters, etc; the second one was the data that described spatial characters, such as position, area, aspiration information of building, crop type, yield and variaty information, etc, these data were connected with spatial data by correlative code.

3D model data: included digital elevation model (DEM), digital orthograph model (DOM) and digital model (DM). DEM was used to simulate the variable status of terrain by digital vector and grid formats [START_REF] Huang | An Introduction to Geographic Information System[END_REF]. DOM was the digital image to express the 3D model's textures [START_REF] Hu | Implementation of Shenzhen Private House 3D Demonstration System (in Chinese)[END_REF], DM was the 3D model of ground object with complicated structure by 3D modeling software (such as 3DS Max), moreover it was the foundation of 3D virtual scene.

2.1.2

Operational logic layer. The operational logic layer consisted of spatial information management module, plan design module for crop cultivation and virtual simulation module of agricultural-region, three modules were integrated based on data level and COM components. The first module could realize information query, data analysis, display of thematic map and maintenance by GIS platform. The second module could realize the decision support for agricultural production management based on existing crop management knowledge model, result data were transferred to GIS platform and 3D virtual platform to fulfill the display of thematic map and virtual scene. The third module could realize the display and alternation of 3D virtual scene, alternation between 2D digital map and 3D scene on the 3D virtual platform.

2.1.3

User layer. Taking Windows as system interface, the system could communicate with user by menu, toolbar, list table, map and 3D virtual scene, etc. By clicking the mouse or keyboard, user could operate the functions such as file management, spatial handling, information query, data analysis, crop cultural plan design, virtual simulation and system maintenance, etc.

Design of system function

In order to realize the digitalization and visualization of information management in agricultural region, and supply the convenient alternation, the functions of file management, spatial handling, information query, data analysis, cultural plan design, virtual simulation and system maintenance were designed in this system (Fig. 2). The original spatial data of agricultural region were acquired from RS images and GPS coordinates by manual vectorization, disposed data were stored into spatial database by spatial data engine of GIS. SuperMap 2008 software can easily realize the operations as data browse, data edit, information query, result output, spatial analysis and 3D modeling for its good alternating interfaces and convenient handling. Furthermore, all kinds of spatial objects and RS image data can store into database or file by spatial data engine of SuperMap SDX+. Based on all these virtues, we selected SuperMap Deskpro 2008 software to design and develop the spatial database of system.

Map management

The attributive data of agricultural region were gathered by collecting historical data and field survey, in which the geographic attributive data were stored into the spatial database, and the elementary attributive data were stored into the attributive database via Microsoft Access 2007.

3.1.2

DEM disposal. DEM were the models used to simulate change status of terrain wave by digital vector and grid formats. These data were disposed by grid simplified algorithm to control the level of detail (LOD) process, and form the different detail level of terrain data.

3.1.3

DOM disposal. DOM was composed of disposed digital navigation photo and satellite RS image, these data could be used to optimize the texture of 3D models and control background status of terrain by geometrical rectification and inlay.

3.1.4

DM making. DM were the 3D models with complicated structural characteristic, which were made by 3DS Max software, such as the models of building, road and field, etc. In order to make VDARMS have a better performance, models must be developed based on little triangle faces by polygon modeling function of 3DS Max software, additionally, vivid texture picture would be stuck onto the surface of models.

Construction of 3D virtual scene

The main work in the virtual simulation module of agricultural region was concentrated on setting up 3D virtual scene, so the constructing procedure and fidelity of 3D virtual scene would directly affect the quality of system. Recently, there are many good 3D virtual simulation platforms at home and abroad, by comparing the platforms and considering the actual condition of agricultural region, VRMap 3.0 was selected as the scene driver of VRGIS which supplied key technologies as management of mass data, display of advanced simulation, communication among different platforms and database driver. In the procedure of constructing scene, the program could automatically create 3D virtual scene by using correlative parameters inputted by user in the attributive database (Table .1), and showed high reusability and flexibility.

Alternation between digital map and virtual scene

Each object from agricultural region was distributed a code to be distinguished each other and make for managing and querying spatial information. These were stored into spatial and attributive databases via conjunct code, and used to realize the alternation between digital map and virtual scene. This function was designed under the query menu of virtual simulation module. The acting procedure was: (1) stored the code into the scene as the name of correlative 3D model; (2) acquired the name of 3D model by VRMap 3.0 SDK engine; (3) queried the information of correlative spatial object by SuperMap SDX+ engine, realized the function of real-time alternation.

Change of crop landscape

The landscapes of crops show different forms at different growth stages and varieties.

Considering the characters of crops in different growth stages, changing large-scale crop landscapes was realized by selecting the main growth stages to carry out the replacement for 3D models of fields. The acting procedure was: (1) first of all, added all the fields into the VRMapSelectionSet. (2) secondly, got the name, coordinate, rotation, zoom-adaption and remotion of one field object by IVRMapPMObjectDisp.

(3) finally, replaced the 3D model of field with the obtained information by CreatePMObjectFrom3DS, and then transferred to another field until all the fields were changed.

3.5

System development

The VRGIS-based digital agricultural region management system was developed on the computer with Intel(R) Core (TM) 2 Duo CPU, 1G memory and Windows XP Professional operating system(Version: Chinese). By applying Visual Basic 6.0 to design the interface of system, SuperMap Deskpro 2008 to design spatial database, Microsoft Access 2007 to disign attributive database. The 3D models were set up on the platform of 3DS Max 2009 software, the modules of spatial information management and crop management plan design were developed by using the components of SuperMap Objects 2008 and existing crop management knowledge model, while the 3D virtual scene and the module of virtual simulation of agricultural region were established by VRMap 3.0 software.

System application

Case studies of the system were carried out in Heheng village of Jiangyan city and Qinglong village of Nanjing city, Jiangsu province, China. The executing procedure was: Firstly, the spatial and attributive databases were constructed with Google Earth images, digital photos and data resources via vectorization and tabulation. Secondly, the 3D models of building, road and field in the agro-region were made by 3D modeling software. Finally, all the data were imported into system. The application results indicated that the structure framework and design idea of VDARMS accorded with the development demand of modern agricultural information technology, realized the standard management and convenient query of information in agro-region, prescription design for crop management, and alternation between map and scene. At the same time, the function of virtual simulation also realized the automatic constructing and wandering of 3D virtual scene for rice and wheat in different growth stages (Fig. 3-Fig. 6).

Discussion

In order to realize the digitalization and visualization of information management in agricultural-region, a VRGIS-based digital agricultural region management system was developed with SuperMap 2008 as the platform of spatial information management and VRMap 3.0 as the driver of scene, and integrating with the existing crop model resources. The system had the functions as file management, spatial handling, information query, data analysis, prescription design for crop cultural management, virtual simulation and system maintenance, etc. Case studies of the system were carried out in Heheng village of Jiangyan city and Qinglong village of Nanjing city, Jiangsu province, the application result indicated that it accorded with the development of modern agricultural spatial information management, realized the standardization, digital management and visual display of agricultural information.

The results provided a digital and visual platform for the construction and management of new countryside, exceedingly promoted the development of digital agriculture.

Comparing with the existing agricultural spatial information management systems and virtual simulation systems [START_REF] Shane | Development of a Field-Level Geographic Information System[END_REF][START_REF] Ma | Developing and Studying of Spatial Information Management System of Digital Agriculture Based on COM GIS (in Chinese)[END_REF]Liu et al., 2006;[START_REF] Jiang | Research and Application of VRGIS in Forest Resources Management (in Chinese)[END_REF][START_REF] Zou | Study on Large-Scale City VR Simulation System and its Realization (in Chinese)[END_REF]Liu et al., 2006;[START_REF] Wu | Realization of the Dynamic Interactive 3D Virtual Wandering System in the Rural Community Based on VRML (in Chinese)[END_REF], the system has the following characters: (1) the display of spatial information is not only in the nonfigurative 2D space, but also in the dynamic and communicated 3D space, user can apperceive the real world by a intuitionistic manner; (2) by setting the parameters for the construction of scene and using the function of plug, the system can automatically and quickly construct the 3D virtual scene of agro-region. The weakness of costing much time in establishing 3D virtual scene and fixed applied object was overcame, and exceedingly promoted the reusability of virtual simulation technology. (3) the alternation of digital map and virtual scene eliminated the wildering sense in wandering 3D virtual scene, effectively showed the integrity of 2D digital map and the visualization of 3D virtual scene, and perfectly annotated the spatial information of agro-region.

However, on account of the integration between GIS and VR based on data level, additional studies should be undertaken on the same data structure to realize the absolute integration; Further, considering the limitations of 3D GIS and computer technologies, the system should be updated by VRMap 4.0 or higher version of 3DGIS software to improve the efficiency of system running.

Fig. 2 .

 2 Fig. 2. Functional chart of systemVRGIS-based digital agricultural region management system

Fig. 3 .Fig. 4 .Fig. 5 .Fig. 6 .

 3456 Fig. 3. Main interface of VDARMS

Fig. 1. Framework of system 2.1.1 Basal data layer. The

  basal data layer managed elementary data and 3D model data.

	User layer
		Information query
	File management			Virtual simulation
		Data analysis
	Spatial handling			System maintenance
		Cultural plan design
	Operational logic layer
		Crop management
	GIS platform	knowledge model	3D virtual platform
	Spatial information	Design for crop		Virtual simulation of
	management	management plan	agro-region
	Basal data layer
	Elementary data	DEM	DOM	DM

Table 1 .

 1 Parameters of scene creation

	Parameter type	Parameter name	Plug name
	Terrain creating	Scene name, terrain texture name,	Terrain creating plug
	parameters	maximum and minimum longitude,
		maximum and minimum latitude
	Object importing	Coordinate, object name and rotation,	Standard	importing
	parameters	agro-region name, model name, conjunct	and exporting plug
		code, numbers of transverse and
		longitudinal models, degrees of transverse
		and longitudinal excursions
	Background creating	Sky radius, bottom color of sky, top color	Standard creating plug
	parameters	of sky, texture picture name of sky,
		texture picture name of ground
	Light creating	Type, coordinate, angle	Standard creating plug
	parameters
	Camera adding	Type, name, coordinate, angle	Standard creating plug
	parameters

1 Project supported by the National High-Technology Research and Development Program of China (No. 2006AA10A303)


Ding-Feng Wu

Jian Wang

Guo-Min Zhou

Li-Bo Liu

A Method to calibrate the electromagnetic tracking instrument when measuring branches of fruit trees

Keywords: Fastrak, Instrument error, Calibration

To reduce the effect from instrument error when getting characteristic parameters of branches of fruit trees by the electromagnetic tracking instrument, a calibration method was sounded based on a discussion of the instrument error of electromagnetic tracking instrument. Finally, the method was tested in an experiment. By comparing the data of the experiment and the standard data which was got by slide caliper, we proved that the method is effective in increasing the accuracy of measurement.

Introduction

China is the biggest producer of fruits in the world. In many parts of this country, the fruit industry has become the pillar industry. based on the measurement of fruit tree structure, the research of the connection between the structure and the output, the utility rate of luminous energy and the anti-disease ability of a fruit tree is an important impetus of developing of punning skill and breeding technique of fruit trees [START_REF] Thanisawanyangkura | Leaf orientation and sunlit leaf area distribution in cotton[END_REF] .

Electromagnetic tracking instrument is a kind of digital measuring tools based on electromagnetism [START_REF] Danjon | Characterisation of structural tree root architecture using 3D digitising and AMAP mod software[END_REF] . It is an effective tool of getting structure data of fruit trees because it is not only an easy-to-use, extremely accurate and broad action sphere device but also a powerful survey tool which can track the space track and calculate the inclination angle of stylus [START_REF] Ivanov | Estimation of the Height and Angles of Orientation of the Upper Leaves in the Maize Canopy Using Sterovision[END_REF] .

The electromagnetic tracking instrument is vulnerable to external magnetic effects.

It will fall in complicated electromagnetic environment [START_REF] Polhemus | 3Space Fastrak Users Manual[END_REF] . Besides, after a long time working, the status of equipment will be different from the initial status and the accuracy of the device will reduce. When measuring branches of fruit trees, a high degree of accuracy is required, so the electromagnetic tracking instrument must be calibrated before working [START_REF] Thanisawanyangkura | Leaf orientation and sunlit leaf area distribution in cotton[END_REF] . In this paper, a calibration method is put forward.

Materials and methods

Device

Fastrak is an advanced electromagnetic tracking instrument [START_REF] Polhemus | 3Space Fastrak Users Manual[END_REF] . It was used as the measuring device in the experiment.

Assume the error of the measuring instrument to be calibrated is μ and the error of the standard measuring device is μ'. Then in the course of the instrument calibration, we must ensure thatμ' is at a lower order of magnitude than μ, otherwise the calibration may increase the error because the error of standard device affects the result. As we known, the Fastrak electromagnetic tracking device can working with accuracy of 0.8mm [START_REF] Polhemus | 3Space Fastrak Users Manual[END_REF] , which means the normal rulers can not provide a standard Reference Data, so we use a slide caliper with the precision of 0.05mm as the standard measuring device in the experiment.

Analysis of error

Because of the effects of devices and experiment environment, the measurement result of physical amount is definitely different with the real value, the difference is called measurement error, the part which caused by the imperfect instrument structure and the external environment is named instrument error.

When Fastrak is working, following causes may bring instrument error:

1. External magnetic effects 2. Deviation of origin of coordinate 3. Instrument mechanical wear and decline of circuit state

Error under the magnetic effects

In the electromagnetic environment, eight space points were measured by Fastrak electromagnetic tracking instrument, every point was measured ten times. The result was compared with the standard data got by slide caliper. Error of one point's ten times measurement is shown in Figure 1. As shown in Figure 1, in electromagnetic environment, Fastrak's error is random and irregular. So the error brought by external magnetic effects is hard to reduce by calibration, the calibration should be conducted without the effect of external magnetic.

Calibration method

Assume the initial space coordinates of origin are (x, y, z), after the deviation, the coordinates are changed to (x', y', z'), the amounts of deviation are Δx, Δy and Δ z, so Δx= x' -x,Δy= y' -y,Δz= z' -z. When a space point is measured by the measuring device, assume the coordinates of the point got by measuring device are (X, Y, Z), then the real coordinates are (X'-Δx, Y'-Δy, Z'-Δz). As we known, Δx, Δ y and Δz are constants, so we just need to use the above method to n space points to get their Δx i , Δy i , Δz i (i∈[1,n]), Δx, Δy and Δz can be calculated by following formulas:

Δx= n n i ∑ =1 i x Δ (1)
Δy=

n n i ∑ =1 i y Δ (2) Δz= n z n i i ∑ =1 Δ (3)
The other part of instrument error can be parted into two parts: one has the relationship with the distance between the space point and the transmitter of Fastrak, the other one is a constant. Assume they areμ1 and μ2. μ2 is a constant, so it can be reduced by the same method as the method reducing the error brought by origin deviation. Assume the distance between the space point and the transmitter of Fastrak is L, then μ1=f (L). In theory, when L is 0, f(L) is going to be 0, but in actual use of Fastrak, as shown in Figure 2, when L was enough small, the time of signal transmitting was too short to be accurately measured by the device, as a result, it brought in an un-negligible error, so the calibration can only reduce the constant error.

Fig. 2. Relationship between error and distance between space point and transmitter

The calibration method is shown in Figure 3.

Experiment

We got one space point in each quadrant of the eight quadrants conformed by the Spatial three dimensional coordinate axis and one space point on each axis, so we had eleven points which were measured in the experiment. Those points were measured by Fastrak electromagnetic tracking instrument. The result of the measurement was processed by the above calibration method. At the end of the experiment, we compared the result with the standard data got by slide caliper.

Result and analysis

The experiment result is shown in Figure 4, Figure 5 and Figure 6. It is clear that the errors after the calibration were less than the errors before the calibration. It proved that the method does work.

Conclusion and discussion

Based on the analysis of causes and characters of the error of the electromagnetic tracking instrument, a calibration method was given, and then an experiment proved the availability of the method. The method can improve the accuracy when measuring branches of fruit trees by the electromagnetic tracking instrument.

Fig. 1 .

 1 Fig. 1. Randomness of electromagnetic tracking instrument's error in electromagnetic environment

Fig. 3 .

 3 Fig. 3. Flow chart of Calibration method

Fig. 4 .Fig. 5 .Fig. 6 .

 456 Fig. 4. The compare of the error before and after the calibration (the X axis)


Xia Sun

Xiangyou Wang

Wenping Zhao

Shuyuan Du

Qingqing Li

Xiangbo Han

A Comparative Study of Modified Materials of Acetylcholinesterase Biosensor

Keywords: Biosensor, Acetylcholinesterase, Pesticide residue, Modified electrode

In this study, multi-walled carbon nanotubes (MWCNTs), gold nanoparticles (GNPs) and Prussian Blue (PB) were used for modifying glassy carbon working electrode (GCE) to construct acetylcholinesterase (AChE) biosensor respectively. Chitosan membrane was used for immobilizing AChE through glutaraldehyde cross-linking attachment to recognize pesticides selectively. Before the detection, the enzyme membrane was quickly fixed on the surfaces of modified electrode with O-ring to prepare an amperometric acetylcholinesterase biosensor for organophosphate pesticides. The fabrication procedures were characterized by cyclic voltammetry and amperometric i-t curve. The electrochemical behaviours of three modified sensors were compared, and the results showed that AChE-PB/GCE possessed higher oxidation peak current at a lower potential. Based on the inhibition of organophosphorus pesticides to the enzymatic activity of AChE, using dichlorvos as model compound, the sensitivity of three modified biosensors were compared, the results showed that the detection limit of AChE-PB/ GCE was lowest.

Introduction

Organophosphorus (OP) pesticides are widely used in agricultural production which leads to the most important environmental pollutants. Moreover, OP compounds inhibit acetylcholinasterase (AChE) that hydrolyses the neurotransmitter acetylcholine (ACh), often causing severe impairment of nerve functions of human or even death. [1][2][3] For these reasons, the development of rapid and efficient monitoring methods is very important. In the past years, many studies have focused on biosensors based on the enzymatic inhibition by the OP pesticides. They have the additional advantage of simplicity, rapidity, reliability, low cost devices and on site monitoring. 4 Generally speaking, the concentration of pesticides is monitored by measuring the change of oxidation current of thiocholine before and after exporsured to pesticides. [5][6][7] However, the oxidation generally requires high potential value on a suitable electrode. 8 In order to enhance the test sensitivity, decrease potential values and the electrochemical interference of other oxidable compounds, the use of some modified materials and methods have gained enormous attention in biosensor technology in recent years, such as multi-walled carbon nanotubes(MWNTs), [9][10][11] prussian blue (PB) 7,[12][13] and gold nanoparticles(GNPs). [14][15][16] Most of these methods rely on enzyme immobilization directly onto the electrode surface, which cannot overcome the biofouling of the electrode surface, and would eventually lead to the deactivation of the biosensor or at least to worsening of the electrochemical response. Our previous investigation results have shown that using a replaceable membrane as support for the enzyme immobilization has many advantages, for example, enzyme membrane can be easily replaced when enzyme's activity is lost. 9,17 Moreover, there are multiple options for analyte detection based on enzyme immobilization on the membrane (one electrode-multiple membranes-multiple enzymes). 18 This present work is a continuation of our previous investigations and focused on the comparative study of three modified (MWCNTs, GNPs and PB) materials to obtain higher sensitivity and stability biosensor for OP pesticides. The fabrication procedure was characterized by cyclic voltammograms and amperometric i-t curve, respectively. The electrochemical behaviours of three modified sensors and no modified AChE/GCE sensor were compared, and the results showed that the AChE-PB/GCE obtained higher oxidation peak current at a lower work potential. Using dichlorvos as model compound, the sensitivity of three modified biosensors were compared, the results showed that the detection limit of AChE-PB/GCE was lowest. The AChE-PB/GCE biosensor exhibited good reproducibi-lity, stability and it was suitable for trace detection of OP pesticide residue.

Experimental

Apparatus

Cyclic voltammograms and amperometric i-t curve were performed with CHI660D electrochemical workstation (Shanghai Chenhua Co., China). 10ml of electrochemical cell was made in our laboratory. The working electrode was glassy carbon electrode (d = 3mm) or modified glassy carbon electrode. A saturated calomel electrode (SCE) and platinum electrode were used as referenceand auxiliary electrodes, respectively.

2.2

Reagents

Acetylcholinesterase was purchased from Nuoyawei Biology Tech.Co. (Shanghai, China). Acetylthiocholine iodide (ATChI), glutaraldehyde (25%) and bovine serum albumin (BSA) were provided by Sigma. Cellulose nitrate microporous membrane was purchased from Hangzhou Rikang purification equipment co.,ltd (Hangzhou, China). Chitosan (95% deacetylation), phosphate buffer (PBS, pH 8.0) and other reagents were of analytical grade. Dichlorvos was standard product. All the other chemicals were of analytical grade. Distilled water was used throughout for the preparation of solutions.

Preparation of AChE Biosensors

Preparation of chitosan membrane

A solution was prepared with 0.1 g chitosan added to 10 ml of acetate solution (1%, mass ratio), and the mixture was centrifuged for 5min in high-speed centrifuge at 3000rpm to remove insoluble particles. Finally, the pretreated cellulose nitrate microporous membrane was immersed in this sol for 12 h, and then immersed in phosphate buffer (PBS, 0.1 mol/l, pH 8.0) for 12 h, dried and stored for use. 19

The AChE immobilization

A solution of 100µl of AChE liquid (100U/ml), 30.0µl of BSA (1.0%), 10µl of glutaraldehyde (5.0%), and 360µl of PBS (0.1mol/l, pH8.0) were mixed in a 1 ml of centrifuge tube. A chitosan membrane was immersed in it for 8h at 4 o C. Finally, enzyme membranes was washed with PBS (0.1mol/l, pH8.0), immersed in PBS (0.1mol/l, pH8.0), and stored at 4 o C before use. 17

Electrode modification

(1) The preparation of MWCNTs/GCE 20µL of mixture of MWNTs, chitosan and glutaraldehyde were covered on a pretreated GCE with final contents of 0.12% (w/v), 0.48% (w/v) and 0.47% (v/v) respectively, and allowed for reaction at room temperature for 4 h. After being washed thoroughly with double distilled water, the obtained modified electrode was stored at 4 o C before use. 20 (2) The preparation of AuNPs /GCE 0.01% HAuCl4 solution was heated to boiling, and quickly added 1 ml 1% sodium citrate. After 1min, the color of solution changed from yellowish to light rose red. Then the AuNPs solutions were stored in dark glass bottles at 4°C. After the working electrode was immersed in 10 ml of AuNPs solutions for 24 h at 4°C, the surface of working electrode was rinsed in double-distilled water for use. 21 (3) The preparation of PB/GCE A solution was a mixture of 2 mM K3[Fe (CN)6], 2 mM FeCl3, 0.1 M KCl, and 10 mM HCl, and the B solution was a mixture of 0.1 M KCl and 10 mM HCl. First, a potential of +0.4V was applied to the electrode in solution A for 60 s and then the electrode was transferred to solution B, and scanned by cyclic voltammetry from -0.05 and 0.35V at a rate of 50mV/s for 12 times. The electrode surface was rinsed with double-distilled water. Finally, the electrode was stored at room temperature. 22

Electrochemical detection of pesticide

The biosensor was tested with amperometric i-t curve (i-t) at a potential of 600 mV versus saturated calomel electrode (SCE). After 100µL of ATChI (15mg/ml) solution was injected into the cell, and the peak current was recorded as I 0 . The cell was washed with distilled water between measurements.

For OP pesticide detection, the pretreated biosensor was first incubated in a given concentration of dichlorvos for 10 min, then it was transferred to the electrochemical cell of 10mL PBS (0.1mol/L, pH8.0), and 100µL of ATChI (15 mg/mL) was injected after the current stabilized. The peak current was recorded as I 1 . The inhibition of pesticides was calculated as follows:

( )

0 1 0 % / 100% I I I I = - ×
Where I% was the degree of inhibition related to the inhibitor concentration. I 0 was the initial current of the biosensor which was measured without inhibitor in PBS (0.1mol/L, pH8.0). I 1 was the current after the incubation in the PBS (0.1mol/L, pH8.0) with different concentrations of inhibitor.

Result and Discussion

Electrochemical Behavior of AChE-MWCNTs/GCE, AChE-AuNPs/GCE and AChE-PB/GCE

Fig. 1 showed the cyclic voltammograms of AChE-MWCNTs/GCE, AChE-AuNPs/GCE and AChE-PB /GCE in the presence of ATChI (15mg/ml) in PBS (pH 8.0) at a scan rate of 100mV/s. After 100µl of ATChI (15mg/ml) was injected into PBS, AChE-GNPs/GCE identified an oxidation peak current of 45µA at 510mV, and the AChE-MWCNTs/GCE obtained an oxidation peak current of 22µA at 600mV, and the AChE-PB/GCE was an oxidation peak current of 90µA at 570mV respectively. The oxidation peak (curve a, b and c) came from the oxidation of thiocholine, hydrolysis product of ATChI, catalyzed by immobilized AChE. Fig. 1 also showed that this peak current of AChE-PB/GCE (curve c) was much higher compared with AChE-MWCNTs /GCE and AChE-AuNPs/GCE. The phenomena was due to PB possess better electrocatalytic ability on the AChE. Whereas, the potential of AChE-AuNPs/GCE shifted negatively compared with AChE-MWCNTs/GCE (curve a) and AChE-PB/GCE (curve c). It was likely because that AuNPs possessed inherent high electricity conducting ability, thus can provide a conductive pathway for electron transfer and promote electrocatalysis reactions at a lower potential. At the same time, these three modified biosensor obtained oxidation peak current were comparable with that reported electrochemical biosensor at the same potential. [23][24] For this main reason were the use of chitosan membrane, which provided a biocompatible micro-environment around the enzyme molecule to stabilize its biological activity and prevented the enzyme leaking out from chitosan membrane effectively. Dual-layer membranes had synergistic effects towards enzymatic catalysis, thus, the oxidation peak current increased, which can improve detection sensitivity. The current produced by AChE-MWCNTs/GCE, AChE-AuNPs/GCE and AChE-PB/GCE catalyzing ATChI achieved to 22µA, 35µA and 80µA at 600mV repectively (Fig. 1), which were according with the result tested by ampomeretric i-t (Fig. 2), which indicated that we can also detect electrochemical behavior of enzyme biosensor with ampomeretric i-t.

Effect of Phosphate Buffer pH on AChE-MWCNTs/GCE, AChE-AuNPs/GCE and AChE-PB/GCE

The effect of phosphate buffer pH value on the peak currents was shown in Fig. 3. The current response of three modified biosensors increased with an increase of pH value up to 7.5, and then the AChE-MWCNTs /GCE current decreased at higher pH value, whereas, the current of AChE-AuNPs/GCE and AChE-PB/GCE continue increase until pH value arrive to 8.0. It could be concluded that the values of the peak current of biosensors changed with the different pH in the range of 5.0 to 8.5. Obviously, the maximum response of peak current appeared at pH 7.5 about AChE-MWCNTs/GCE, and the others at pH 8.0. The phenomena was due to the pH value of electrolyte, which had great influence on the activity of enzyme, which led to the change of the anodic peak current at these biosensors.

Effect of ATChI Concentration on AChE-MWCNTs /GCE, AChE-AuNPs /GCE and AChE-PB/GCE

Fig. 4. showed the effect of different ATChI concentration on anodic peak current of AChE-MWCNTs/GCE, AChE-AuNPs/GCE and AChE-PB/ GCE. The peak current all increase when the ATChI concentration was less than 15mg/l, whereas the peak current have no change with further the increasing of the concentration of ATChI. It was likely because that the velocity of enzyme catalyzing substrate reaches to the equilibrium when the substrate added to some concentration, so subsequent increased the substrate concentration, the velocity of enzyme catalyzing substrate did not increase. In this work, the ATChI concentration of 15mg/l was selected. As shown in Fig. 5, OP pesticides displayed increasing inhibition to AChE with incubated time. When the incubated time was longer than 10 min the three curves all trended to maintain a stable value, which indicated that the binding interaction with active target groups in enzyme could reach saturation. This change tendency of the peak current value showed the alteration of enzymatic activity, which resulted in the change of the interactions with its substrate. In this work, the three biosensors optimum incubation time of 10 min was selected.

3.5

Determination of Pesticides

After AChE-MWCNTs/GCE, AChE-AuNPs/GCE and AChE-PB/GCE were incubated in the standard solution of dichlorvos at a certain concentration for 10 min respectively, the inhibition rate (calculated by the change of peak current) of these three modified biosensors and the logarithm of dichlorvos concentration all had a certain linear relationship in some range. The detection limit and linear range of AChE-MWCNTs/GCE and AChE-AuNPs/GCE were shown in Tab.1. The results showed that the detection limit of AChE-PB/GCE was lowest. The phenomena were indicated that the electrode modified materials played an important role on the sensitivity of enzyme biosensor. Table 1. The detection limit of three modified biosensors of dichlorvos pesticides

Precision of Measurements and Stability of Biosensor

The precision intra-assay of the three biosensors was evaluated by assaying three enzyme membranes on the same electrode for ten replicate determinations after exposure to a certain concentration pesticides respectively. Similarly, the inter-assay precision was estimated by assaying three enzyme membranes on six different electrodes. The average relative standard deviation (R.S.D.) of intra-assay and interassay were found to be 5.1 and 4.27% of AChE-MWCNTs/GCE, 5.2 and 3.1% of AChE-AuNPs/GCE and 4.8 and 3.5% of AChE-PB/GCE respectively, which indicated these three modified biosensors are all acceptable re-producibility.

Conclusion

In this paper, three materials modified have been used for the fabrication of amperometric AChE biosensors. These AChE biosensors all introduce the chitosan membrane to immobilize AChE, the results have shown that chitosan membrane prevent leakage of the enzmye, improve the activity of immobilization enzyme, and can immobilize sufficient amount of AChE. The fabrication procedures have been characterized by cyclic voltammetry and amperometric i-t curve. The electrochemical behaviours of three modified sensor have been compared, and the results showed that AChE-PB/GCE possess higher oxidation peak current at a lower potential. Using dichlorvos as model compound, the sensitivity of three modified biosensors have been compared, the detection limit of AChE-PB/GCE is lowest. This study indicates we

Fig. 1 .

 1 Fig.1. Cyclic voltammograms of enzyme biosensor modified. MWCNTs modified (a); GNPs modified (b); PB modified (c) in pH 8.0 PBS containing 100µL of ATChI(15mg/mL). Scan rate: 100mV/s.

Fig. 2 .

 2 Fig.2. Amperometric i-t curve of enzyme biosensor modified. MWCNTs modified (a); GNPs modified (b); PB modified (c) in PBS (0.1mol/L, pH8.0) after injected 100µL of ATChI (15mg/mL).

Fig. 3 .

 3 Fig.3.The influence of pH on the peak current of enzyme biosensor modified with MWCNTs, GNPs and PB respectively.

Fig. 4 .

 4 Fig.4. The influence of ATChI concentration on the peak current of enzyme biosensor modified with MWCNTs, GNPs and PB respectively.

Fig. 5 .

 5 Fig.5. The influence of Pesticide inhibition time on the peak current of enzyme biosensor modified with MWCNTs, GNPs and PB respectively.

  can improve the sensitivity of enzyme biosensor by the selection of the modified materials of electrode and realize the trace detection of OP pesticide residue.

	modified biosensor	linear range	equation of linear	equation	of	detection
			regression	linear regression	limit
	AChE-PB/GCE	10ng/l~10µg/l	I=32.3lgc-10.9	0.9968		2.5ng/l
	AChE-GNPs/GCE	50ng/l~10µg/l	I=22.804lgc-6.3489	0.9928		30ng/l
	AChE-MWCNTs/GCE	5µg/l~50µg/l	I=48.853lgc+10.927	0.9921		1ug/l

Corresponding author; E-mail: wxy@sdut.edu.cn

Acknowledgments

. This work was supported by the National Natural Science Foundation of China (No.30972055), Scientific and Technological Project of Shandong Province (No.2008GG10009027), and the Natural Science Foundation of Shandong Province (No. Q2008D03).