In order to avoid the interference to the primary user(PU), in this paper Cognitive Radio (CR) periodically senses the presence of PU, and during one period, CR can sense all the sub-channels based on weighed data fus...In order to avoid the interference to the primary user(PU), in this paper Cognitive Radio (CR) periodically senses the presence of PU, and during one period, CR can sense all the sub-channels based on weighed data fusion and then use all the idle channels decided by the coordinator. The local sensing time of CR is divided into multi-slots in which CR can sense any sub-channel. Through reasonably allocating the sensing slots and users by mathematic optimization, the proposed algorithm can improve the total throughput of CR. The optimization problem of the proposed scheme which seeks to maximize the throughput subject to the constraint of the detected performance of each sub-channel is proposed in order to choose the optimum local sense time and the number of the cooperative CRs. The simulation results indicate that the proposed scheme can obtain higher throughput than the conventional single-channel sense, and there are the optimum local sense time and the number of cooperative CRs to make the throughput reach maximum.展开更多
The centroid coordinate serves as a critical control parameter in motion systems,including aircraft,missiles,rockets,and drones,directly influencing their motion dynamics and control performance.Traditional methods fo...The centroid coordinate serves as a critical control parameter in motion systems,including aircraft,missiles,rockets,and drones,directly influencing their motion dynamics and control performance.Traditional methods for centroid measurement often necessitate custom equipment and specialized positioning devices,leading to high costs and limited accuracy.Here,we present a centroid measurement method that integrates 3D scanning technology,enabling accurate measurement of centroid across various types of objects without the need for specialized positioning fixtures.A theoretical framework for centroid measurement was established,which combined the principle of the multi-point weighing method with 3D scanning technology.The measurement accuracy was evaluated using a designed standard component.Experimental results demonstrate that the discrepancies between the theoretical and the measured centroid of a standard component with various materials and complex shapes in the X,Y,and Z directions are 0.003 mm,0.009 mm,and 0.105 mm,respectively,yielding a spatial deviation of 0.106 mm.Qualitative verification was conducted through experimental validation of three distinct types.They confirmed the reliability of the proposed method,which allowed for accurate centroid measurements of various products without requiring positioning fixtures.This advancement significantly broadened the applicability and scope of centroid measurement devices,offering new theoretical insights and methodologies for the measurement of complex parts and systems.展开更多
The precise acquisition of the quality characteristic parameters of large aircraft directly affects its performance characteristics.For large aircrafts such as missiles and rockets with internal fillings,traditional m...The precise acquisition of the quality characteristic parameters of large aircraft directly affects its performance characteristics.For large aircrafts such as missiles and rockets with internal fillings,traditional measurement methods involving large-angle tilting or rotation may pose safety risks.In light of the characteristics of large aircraft and in combination with existing measurement methods,we design a mass and centroid measurement method based on four-point support and small-angle tilting,and develop a set of mass and centroid testing system.This method obtains the intersection point of the gravity action line in the product coordinate system through coordinate transformation in two postures,thereby obtaining the three-dimensional centroid of the aircraft.We first elaborate on the principle of this method in detail,then introduce the composition of the equipment,and analyze the structural stress of key components.Finally,experimental verification and uncertainty analysis are carried out.Experimental verification shows that the maximum deviation of the mass measurement accuracy is less than 0.02%,the centroid measurement accuracy in the X direction is±0.15 mm,in the Y direction it is±0.21 mm,and in the Z direction it is±0.19 mm.展开更多
This paper deals with the dynamics and control of a novel 3-degrees-of-freedom （DOF） parallel manipulator with actuation redundancy. According to the kinematics of the redundant manipulator, the inverse dynamic equa...This paper deals with the dynamics and control of a novel 3-degrees-of-freedom （DOF） parallel manipulator with actuation redundancy. According to the kinematics of the redundant manipulator, the inverse dynamic equation is formulated in the task space by using the Lagrangian formalism, and the driving force is optimized by utilizing the minimal 2-norm method. Based on the dynamic model, a synchronized sliding mode control scheme based on contour error is proposed to implement accurate motion tracking control. Additionally, an adaptive method is introduced to approximate the lumped uncertainty of the system and provide a chattering-free control. The simulation results indicate the effectiveness of the proposed approaches and demonstrate the satisfactory tracking performance compared to the conventional controller in the presence of the parameter uncertainties and un-modelled dynamics for the motion control of manipulators.展开更多
Molecular microbiological methods, such as competetive PCR, real-time PCR, denaturing gradient gel electrophoresis (DGGE) and large-scale parallel-pyrosequencing, require the extraction of sufficient quantity of high ...Molecular microbiological methods, such as competetive PCR, real-time PCR, denaturing gradient gel electrophoresis (DGGE) and large-scale parallel-pyrosequencing, require the extraction of sufficient quantity of high quality DNA from microbiologically and chemically complex matrices. Due to difficulties in the field to standardize/select the optimum DNA preservation-extraction methods in view of laboratories differences, this article attempts to present a straight-forward mathematical framework for comparing some of the most commonly used methods. To this end, as a case study, the problem of selecting an optimum sample preservation-DNA extraction strategy for obtaining total bacterial DNA from swine feces was considered. Two sample preservation methods (liquid nitrogen and RNAlater?) and seven extraction techniques were paired and compared under six quantitative DNA analysis criteria: yield of extraction, purity of extracted DNA (A260/280 and A 260/230 ratios), duration of extraction, degradation degree of DNA, and cost. From a practical point of view, it is unlikely that a single sample preservation-DNA extraction strategy can be optimum for all selected criteria. Hence, a systematic multi-criteria decision-making (MCDM) approach was used to compare the methods. As a result, the ZR Fecal DNA MiniPrepTM DNA extraction kit for samples preserved either with liquid nitrogen or RNAlater? were identified as potential optimum solutions for obtaining total bacterial DNA from swine feces. Considering the need for practicality for in situ applications, we would recommend liquid nitrogen as sample preservation method, along with the ZR Fecal DNA MiniPrepTM kit. Total bacterial DNA obtained by this strategy can be suitable for downstream PCR-based DNA analyses of swine feces.展开更多
AIM:This paper aims to develop a data-based semi-quantitative food frequency questionnaire (SQFFQ) covering both urban and rural areas in the Chaoshan region of Guangdong Province, China, for the investigation of rela...AIM:This paper aims to develop a data-based semi-quantitative food frequency questionnaire (SQFFQ) covering both urban and rural areas in the Chaoshan region of Guangdong Province, China, for the investigation of relationships between food intake and lifestyle-related diseases among middle-aged Chinese. METHODS: We recruited 417 subjects from the general population and performed an assessment of the diet, using a 3-d weighed dietary record survey. We employed contribution analysis (CA) and multiple regression analysis (MRA) to select food items covering up to a 90% contribution and a 0.90 R2, respectively. The total number of food items consumed was 523 (443 in the urban and 417 in the rural population) and the intake of 29 nutrients was calculated according to the actual consumption by foods/ recipes. RESULTS: The CA selected 233,194, and 183 foods/recipes for the combined, the urban and the rural areas, respectively, and then 196,157, and 160 were chosen by the MRA. Finally, 125 foods/recipes were selected for the final questionnaire. The frequencies were classified into eight categories and standard portion sizes were also calculated. CONCLUSION: For adoption of the area-specific SQFFQ, validity and reproducibility tests are now planned tc determine how the combined SQFFQ performs in actual assessment of disease risk and benefit.展开更多
The control scheme of multifunctional refrigerant recovery and filling control system for air conditioning system is presented in this paper.The scheme of hardware circuit based on micro controller unit （MCU） MSP430...The control scheme of multifunctional refrigerant recovery and filling control system for air conditioning system is presented in this paper.The scheme of hardware circuit based on micro controller unit （MCU） MSP430 uses high-precision weighing sensor and high performance amplifier.The software program uses median average filtering algorithm.The device can recycle discarded refrigerant after purification and quantitative filling refrigerant.Meanwhile,the apparatus has the functions of recovery,filling,pressing,vaccumizing,refueling,etc.The system is proved to be of low cost,good stability and high practical value.展开更多
A general weighted second order elliptic equation involving critical growth is considered on bounded smooth. domain in n-dimension space. There is the singular point for the weighted coefficients in the domain. With g...A general weighted second order elliptic equation involving critical growth is considered on bounded smooth. domain in n-dimension space. There is the singular point for the weighted coefficients in the domain. With generalized blow up method, some results are obtained for asymptotic behavior of positive solutions. This problem includes Laplacian operators as special cases.展开更多
[Objectives]This study aimed to optimize the extraction process of longan(Dimocarpus longan Lour.)leaves by multi-indicator comprehensive evaluation method.[Methods]The contents of gallic acid ethyl ester,astragalin,q...[Objectives]This study aimed to optimize the extraction process of longan(Dimocarpus longan Lour.)leaves by multi-indicator comprehensive evaluation method.[Methods]The contents of gallic acid ethyl ester,astragalin,quercetin,luteolin and kaempferol in longan leaves were determined simultaneously by HPLC.Using the multi-indicator comprehensive evaluation method,the methanol concentration,solid to liquid ratio and extraction time for extraction of longan leaves were optimized by orthogonal test.[Results]The optimal extraction process of longan leaves are as follows:methanol concentration of 100%,solid to liquid ratio of 1∶5,and extraction time of 50 min.[Conclusions]The optimized process is simple and feasible,and it can be used to determine the contents of different ingredients in longan leaves.展开更多
Identification of groundwater potential areas(GPA)is important in regions facing surface water scarcity,as it assists in effective planning and utilization of groundwater for various purposes.This study employs the me...Identification of groundwater potential areas(GPA)is important in regions facing surface water scarcity,as it assists in effective planning and utilization of groundwater for various purposes.This study employs the methods of remote sensing(RS),geographic information system(GIS)model,and analytical hierarchy process(AHP),multi-criteria decision analysis(MCDA)to locate and map the prospective groundwater areas in the Kulfo-Hare watershed.Seven significant groundwater influencing factors were selected for the determination of groundwater potential in the area:Geology,land use/land cover(LULC),soil,rainfall,slope,drainage density,and lineament density.By applying a five-class classification scheme(very low,low,moderate,high,and very high),the GIS models were used to define the distribution of groundwater potential areas in terms of area coverage(km^(2)),percentage and mapping.The results show that the groundwater potential(GWP)distribution in the research region is as follows:9.7%(6035.9 ha)classified as very high GWP,29.6%(18606 ha)classified as high,24.5%(15245 ha)classified as moderate,18.1%(11431 ha)as low and 18.1%(11492 ha)very low GWP,on the basis of the weighted overlay evaluation.Although a few regions are identifies as extremely low GWP,most of the study area is characterized by very high to moderate GWP.These findings provide valuable insight for sustainable groundwater planning by the government bodies,decision-makers,and private sectors.展开更多
Medical research data are often skewed and heteroscedastic. It has therefore become practice to log-transform data in regression analysis, in order to stabilize the variance. Regression analysis on log-transformed dat...Medical research data are often skewed and heteroscedastic. It has therefore become practice to log-transform data in regression analysis, in order to stabilize the variance. Regression analysis on log-transformed data estimates the relative effect, whereas it is often the absolute effect of a predictor that is of interest. We propose a maximum likelihood (ML)-based approach to estimate a linear regression model on log-normal, heteroscedastic data. The new method was evaluated with a large simulation study. Log-normal observations were generated according to the simulation models and parameters were estimated using the new ML method, ordinary least-squares regression (LS) and weighed least-squares regression (WLS). All three methods produced unbiased estimates of parameters and expected response, and ML and WLS yielded smaller standard errors than LS. The approximate normality of the Wald statistic, used for tests of the ML estimates, in most situations produced correct type I error risk. Only ML and WLS produced correct confidence intervals for the estimated expected value. ML had the highest power for tests regarding β1.展开更多
The daily soil water budgets in the red soil areas of central Jiangxi Province,southern China,were investigated with a large-scale weighing lysimeter and runoff plots. From 1998 to 2000,peanuts (Arachis hypogaea L.) a...The daily soil water budgets in the red soil areas of central Jiangxi Province,southern China,were investigated with a large-scale weighing lysimeter and runoff plots. From 1998 to 2000,peanuts (Arachis hypogaea L.) and rape (Brassica napus L.) were planted in the lysimeter and in 1999,peanuts were planted in the runoff plots. The soil water budget components including rainfall,runoff,percolation and evapotranspiration were measured directly or calculated by Richards' equation and water balance equation. The results showed that most rainfall,including rainstorms,occurred from March to July,and induced the greatest soil water percolation during the year. The evapotranspiration was still large from July to September when rainfall was minimal. Thus,the lack of synchronization in soil water inputs and losses was disadvantageous to crops growing in this region. Among the soil water losses,percolation was the largest,followed by evapotranspiration,and then soil runoff. Runoff was very small on farmland with crops. It was significantly different from the uncultivated uplands where large-scale runoff was usually reported. The soil water storage fluctuated sinusoidally,with a large amplitude in the rainy season and a small amplitude in the dry season.展开更多
In our study, entropy weight coefficients, based on Shannon entropy, were determined for an attribute recognition model to model the quality of groundwater sources. The model follows the theory previously proposed by ...In our study, entropy weight coefficients, based on Shannon entropy, were determined for an attribute recognition model to model the quality of groundwater sources. The model follows the theory previously proposed by Chen Q S. In the model, firstly, the author establishes the attribute space matrix and determines the weight based on Shannon entropy theory; secondly, calculates attribute measure; thirdly, evaluates that with confidence criterion and score criterion; finally, an application example is given. The results show that the water quality of the groundwater sources for the city comes up to the grade II or III standard. There is no pollution that obviously exceeds the standard and the water can meet people’s needs .The results from an evaluation of this model are in basic agreement with the observed situation and with a set pair analysis (SPA) model.展开更多
基金Sponored by the National Natural Science Foundation of China ( Grant No. 61071104)the Fundamental Research Funds for the Central Universities( Grant No. HIT. NSRIF. 201149)
文摘In order to avoid the interference to the primary user(PU), in this paper Cognitive Radio (CR) periodically senses the presence of PU, and during one period, CR can sense all the sub-channels based on weighed data fusion and then use all the idle channels decided by the coordinator. The local sensing time of CR is divided into multi-slots in which CR can sense any sub-channel. Through reasonably allocating the sensing slots and users by mathematic optimization, the proposed algorithm can improve the total throughput of CR. The optimization problem of the proposed scheme which seeks to maximize the throughput subject to the constraint of the detected performance of each sub-channel is proposed in order to choose the optimum local sense time and the number of the cooperative CRs. The simulation results indicate that the proposed scheme can obtain higher throughput than the conventional single-channel sense, and there are the optimum local sense time and the number of cooperative CRs to make the throughput reach maximum.
基金supported by National Natural Science Foundation of China(No.52176122).
文摘The centroid coordinate serves as a critical control parameter in motion systems,including aircraft,missiles,rockets,and drones,directly influencing their motion dynamics and control performance.Traditional methods for centroid measurement often necessitate custom equipment and specialized positioning devices,leading to high costs and limited accuracy.Here,we present a centroid measurement method that integrates 3D scanning technology,enabling accurate measurement of centroid across various types of objects without the need for specialized positioning fixtures.A theoretical framework for centroid measurement was established,which combined the principle of the multi-point weighing method with 3D scanning technology.The measurement accuracy was evaluated using a designed standard component.Experimental results demonstrate that the discrepancies between the theoretical and the measured centroid of a standard component with various materials and complex shapes in the X,Y,and Z directions are 0.003 mm,0.009 mm,and 0.105 mm,respectively,yielding a spatial deviation of 0.106 mm.Qualitative verification was conducted through experimental validation of three distinct types.They confirmed the reliability of the proposed method,which allowed for accurate centroid measurements of various products without requiring positioning fixtures.This advancement significantly broadened the applicability and scope of centroid measurement devices,offering new theoretical insights and methodologies for the measurement of complex parts and systems.
基金supported by National Natural Science Foundation of China-Youth Program(No.62303420)。
文摘The precise acquisition of the quality characteristic parameters of large aircraft directly affects its performance characteristics.For large aircrafts such as missiles and rockets with internal fillings,traditional measurement methods involving large-angle tilting or rotation may pose safety risks.In light of the characteristics of large aircraft and in combination with existing measurement methods,we design a mass and centroid measurement method based on four-point support and small-angle tilting,and develop a set of mass and centroid testing system.This method obtains the intersection point of the gravity action line in the product coordinate system through coordinate transformation in two postures,thereby obtaining the three-dimensional centroid of the aircraft.We first elaborate on the principle of this method in detail,then introduce the composition of the equipment,and analyze the structural stress of key components.Finally,experimental verification and uncertainty analysis are carried out.Experimental verification shows that the maximum deviation of the mass measurement accuracy is less than 0.02%,the centroid measurement accuracy in the X direction is±0.15 mm,in the Y direction it is±0.21 mm,and in the Z direction it is±0.19 mm.
基金supported by National Natural Science Foundation of China(Nos.51075222 and E050101)Priority Academic Program Development of Jiangsu Higher Education Institutions(No.6,2011)+1 种基金Zhenjiang Municipal Key Technology R&D Program(No.NY2011013)Postgraduate Research and Innovation Program of Jiangsu Higher Education Institutions(No.1221140046)
文摘This paper deals with the dynamics and control of a novel 3-degrees-of-freedom （DOF） parallel manipulator with actuation redundancy. According to the kinematics of the redundant manipulator, the inverse dynamic equation is formulated in the task space by using the Lagrangian formalism, and the driving force is optimized by utilizing the minimal 2-norm method. Based on the dynamic model, a synchronized sliding mode control scheme based on contour error is proposed to implement accurate motion tracking control. Additionally, an adaptive method is introduced to approximate the lumped uncertainty of the system and provide a chattering-free control. The simulation results indicate the effectiveness of the proposed approaches and demonstrate the satisfactory tracking performance compared to the conventional controller in the presence of the parameter uncertainties and un-modelled dynamics for the motion control of manipulators.
文摘Molecular microbiological methods, such as competetive PCR, real-time PCR, denaturing gradient gel electrophoresis (DGGE) and large-scale parallel-pyrosequencing, require the extraction of sufficient quantity of high quality DNA from microbiologically and chemically complex matrices. Due to difficulties in the field to standardize/select the optimum DNA preservation-extraction methods in view of laboratories differences, this article attempts to present a straight-forward mathematical framework for comparing some of the most commonly used methods. To this end, as a case study, the problem of selecting an optimum sample preservation-DNA extraction strategy for obtaining total bacterial DNA from swine feces was considered. Two sample preservation methods (liquid nitrogen and RNAlater?) and seven extraction techniques were paired and compared under six quantitative DNA analysis criteria: yield of extraction, purity of extracted DNA (A260/280 and A 260/230 ratios), duration of extraction, degradation degree of DNA, and cost. From a practical point of view, it is unlikely that a single sample preservation-DNA extraction strategy can be optimum for all selected criteria. Hence, a systematic multi-criteria decision-making (MCDM) approach was used to compare the methods. As a result, the ZR Fecal DNA MiniPrepTM DNA extraction kit for samples preserved either with liquid nitrogen or RNAlater? were identified as potential optimum solutions for obtaining total bacterial DNA from swine feces. Considering the need for practicality for in situ applications, we would recommend liquid nitrogen as sample preservation method, along with the ZR Fecal DNA MiniPrepTM kit. Total bacterial DNA obtained by this strategy can be suitable for downstream PCR-based DNA analyses of swine feces.
基金Supported by the Science and Technology Project Foundation of Guangdong Province, No. 2003C33706Grant-in-Aid for Scientific Research on Priority Areas (C) from the Ministry of Education, Science, Sports, Culture and Technology, Japan
文摘AIM:This paper aims to develop a data-based semi-quantitative food frequency questionnaire (SQFFQ) covering both urban and rural areas in the Chaoshan region of Guangdong Province, China, for the investigation of relationships between food intake and lifestyle-related diseases among middle-aged Chinese. METHODS: We recruited 417 subjects from the general population and performed an assessment of the diet, using a 3-d weighed dietary record survey. We employed contribution analysis (CA) and multiple regression analysis (MRA) to select food items covering up to a 90% contribution and a 0.90 R2, respectively. The total number of food items consumed was 523 (443 in the urban and 417 in the rural population) and the intake of 29 nutrients was calculated according to the actual consumption by foods/ recipes. RESULTS: The CA selected 233,194, and 183 foods/recipes for the combined, the urban and the rural areas, respectively, and then 196,157, and 160 were chosen by the MRA. Finally, 125 foods/recipes were selected for the final questionnaire. The frequencies were classified into eight categories and standard portion sizes were also calculated. CONCLUSION: For adoption of the area-specific SQFFQ, validity and reproducibility tests are now planned tc determine how the combined SQFFQ performs in actual assessment of disease risk and benefit.
文摘The control scheme of multifunctional refrigerant recovery and filling control system for air conditioning system is presented in this paper.The scheme of hardware circuit based on micro controller unit （MCU） MSP430 uses high-precision weighing sensor and high performance amplifier.The software program uses median average filtering algorithm.The device can recycle discarded refrigerant after purification and quantitative filling refrigerant.Meanwhile,the apparatus has the functions of recovery,filling,pressing,vaccumizing,refueling,etc.The system is proved to be of low cost,good stability and high practical value.
文摘A general weighted second order elliptic equation involving critical growth is considered on bounded smooth. domain in n-dimension space. There is the singular point for the weighted coefficients in the domain. With generalized blow up method, some results are obtained for asymptotic behavior of positive solutions. This problem includes Laplacian operators as special cases.
基金National Natural Science Foundation of China(81560691)Special Fund Project for Innovation Driven Development of Guangxi(Gui Ke AA17202046)+7 种基金Open Program for Construction of TCM Pharmacy Doctor Station in Guangxi University of Chinese Medicine(201410-06)The First-Class Subject of Traditional Chinese Medicine(Ethnic Pharmacy)in Guangxi(Gui Jiao Ke Yan[2018]No.12)Program of Collaborative Innovation Center of Zhuang and Yao Medicine(Gui Jiao Ke Yan[2013]No.20)Program of Key Laboratory of Zhuang and Yao Medicine[Gui Ke Ji Zi[2014]No.32]The Eighth Batch of Special Experts Project of Guangxi Zhuang Autonomous Region(Study on Quality Standard of Zhuang&Yao Medicine,[2019]No.13)High-level Talent Team Cultivation Program of"Qihuang Project"of Guangxi University of Chinese Medicine(2018002)High Level Innovation Team and Excellent Scholar Program of Guangxi Universities(Gui Jiao Shi Fan[2019]No.52)Guangxi One Thousand Young and Middle-aged College and University Backbone Teachers Cultivation Program(Gui Jiao Ren[2019]No.5).
文摘[Objectives]This study aimed to optimize the extraction process of longan(Dimocarpus longan Lour.)leaves by multi-indicator comprehensive evaluation method.[Methods]The contents of gallic acid ethyl ester,astragalin,quercetin,luteolin and kaempferol in longan leaves were determined simultaneously by HPLC.Using the multi-indicator comprehensive evaluation method,the methanol concentration,solid to liquid ratio and extraction time for extraction of longan leaves were optimized by orthogonal test.[Results]The optimal extraction process of longan leaves are as follows:methanol concentration of 100%,solid to liquid ratio of 1∶5,and extraction time of 50 min.[Conclusions]The optimized process is simple and feasible,and it can be used to determine the contents of different ingredients in longan leaves.
文摘Identification of groundwater potential areas(GPA)is important in regions facing surface water scarcity,as it assists in effective planning and utilization of groundwater for various purposes.This study employs the methods of remote sensing(RS),geographic information system(GIS)model,and analytical hierarchy process(AHP),multi-criteria decision analysis(MCDA)to locate and map the prospective groundwater areas in the Kulfo-Hare watershed.Seven significant groundwater influencing factors were selected for the determination of groundwater potential in the area:Geology,land use/land cover(LULC),soil,rainfall,slope,drainage density,and lineament density.By applying a five-class classification scheme(very low,low,moderate,high,and very high),the GIS models were used to define the distribution of groundwater potential areas in terms of area coverage(km^(2)),percentage and mapping.The results show that the groundwater potential(GWP)distribution in the research region is as follows:9.7%(6035.9 ha)classified as very high GWP,29.6%(18606 ha)classified as high,24.5%(15245 ha)classified as moderate,18.1%(11431 ha)as low and 18.1%(11492 ha)very low GWP,on the basis of the weighted overlay evaluation.Although a few regions are identifies as extremely low GWP,most of the study area is characterized by very high to moderate GWP.These findings provide valuable insight for sustainable groundwater planning by the government bodies,decision-makers,and private sectors.
文摘Medical research data are often skewed and heteroscedastic. It has therefore become practice to log-transform data in regression analysis, in order to stabilize the variance. Regression analysis on log-transformed data estimates the relative effect, whereas it is often the absolute effect of a predictor that is of interest. We propose a maximum likelihood (ML)-based approach to estimate a linear regression model on log-normal, heteroscedastic data. The new method was evaluated with a large simulation study. Log-normal observations were generated according to the simulation models and parameters were estimated using the new ML method, ordinary least-squares regression (LS) and weighed least-squares regression (WLS). All three methods produced unbiased estimates of parameters and expected response, and ML and WLS yielded smaller standard errors than LS. The approximate normality of the Wald statistic, used for tests of the ML estimates, in most situations produced correct type I error risk. Only ML and WLS produced correct confidence intervals for the estimated expected value. ML had the highest power for tests regarding β1.
基金Project supported by the Knowledge Innovation Project of the Chinese Academy of Sciences (No. KZCX2-407).
文摘The daily soil water budgets in the red soil areas of central Jiangxi Province,southern China,were investigated with a large-scale weighing lysimeter and runoff plots. From 1998 to 2000,peanuts (Arachis hypogaea L.) and rape (Brassica napus L.) were planted in the lysimeter and in 1999,peanuts were planted in the runoff plots. The soil water budget components including rainfall,runoff,percolation and evapotranspiration were measured directly or calculated by Richards' equation and water balance equation. The results showed that most rainfall,including rainstorms,occurred from March to July,and induced the greatest soil water percolation during the year. The evapotranspiration was still large from July to September when rainfall was minimal. Thus,the lack of synchronization in soil water inputs and losses was disadvantageous to crops growing in this region. Among the soil water losses,percolation was the largest,followed by evapotranspiration,and then soil runoff. Runoff was very small on farmland with crops. It was significantly different from the uncultivated uplands where large-scale runoff was usually reported. The soil water storage fluctuated sinusoidally,with a large amplitude in the rainy season and a small amplitude in the dry season.
文摘In our study, entropy weight coefficients, based on Shannon entropy, were determined for an attribute recognition model to model the quality of groundwater sources. The model follows the theory previously proposed by Chen Q S. In the model, firstly, the author establishes the attribute space matrix and determines the weight based on Shannon entropy theory; secondly, calculates attribute measure; thirdly, evaluates that with confidence criterion and score criterion; finally, an application example is given. The results show that the water quality of the groundwater sources for the city comes up to the grade II or III standard. There is no pollution that obviously exceeds the standard and the water can meet people’s needs .The results from an evaluation of this model are in basic agreement with the observed situation and with a set pair analysis (SPA) model.
