Search

【Objective】 The study on the change characteristics of cultivated land area and its influence on grain production pattern in key watersheds aims to provide reference for promoting the sustainable use of cultivated land and coordinating the relationship between food security and economic development. 【Method】 Taking 82 counties in key watersheds of Sichuan Province as the research unit, using mathematical quantization model and GIS spatial analysis method, this paper explores the spatiotemporal evolution characteristics of cultivated land area and its influence on the change of grain production pattern in the study area in recent 20 years. 【Result】 (1) From 2001 to 2020, the cultivated land area in the key watersheds of Sichuan Province increased by 915,700 hm², with an increase rate of 37.39%, but showed a changing trend of “increase→ basically unchanged→ decrease→ basically unchanged” in different economic development periods. (2) The change of cultivated land area showed a spatial agglomeration state of “high-value cluster area” and “low-value cluster area” in the key watersheds of Sichuan Province, and the changes in quantity of these areas showed an inverted “N” type fluctuation trend in different economic development periods. (3) The spatial transfer types of grain production (grain production transfer out area, grain production transfer into area and grain production stability area) in the key watersheds of Sichuan Province showed a fluctuating trend of increase and decrease in quantity. In general, the area of grain production transferred out and transferred into increased by 13.42% and 13.41%, respectively, and the change trend was basically unchanged. However, the grain production stability area decreased significantly, down by 26.83%, and there was regional degradation in grain production. (4) The change of cultivated land area is an important cause of the spatial transfer of grain production in the key watersheds of Sichuan Province, and the counties that are sensitive to the change of cultivated land area show the characteristics of centralized and multi-point distribution. 【Conclusion】 The change of cultivated land area and its impact on grain production pattern in the key watersheds of Sichuan Province from 2001 to 2020 fluctuated significantly in different periods of economic development. Therefore, countermeasures and suggestions are put forward to strictly implement the cultivated land use control system, strengthen the cooperative management of regional competent departments, establish the long-term benefit compensation mechanism of cultivated land conservation, and construct the cultivated land security early warning and control mechanism. [ABSTRACT FROM AUTHOR]

Cleaning performance is the most important index to evaluate the detergency performance of washing machines and detergents. With the continuous development of the washing industry, the corresponding evaluation methods are also evolving. The stained cloth is adopted as the test object for the detergency performance of washing machines and detergents. At present, China’s washing industry mainly adopts three kinds of standard stained cloths (carbon black, sebum and protein) specified in GB/ T 4288 - 2018 for the testing of detergency performance. In the corresponding international standard EN 60456, the combined stained cloth is used to test the detergency performance. Swissatest Testmaterialien AG and wfk, Testgewebe GmbH have developed dozens of stained cloths, including starch stained cloth, lipstick stained cloth, and cosmetic stained cloth. However, the stain components of these stained cloths greatly differ from the real life. Firstly, in order to ensure the stability and fouling absorption effect of stained cloth, it is a common practice to add a certain amount of stabilizers and adhesives. Secondly, the standard stained cloth is made by immersing the whole base cloth in the stained solution with a large amount of stains, leading to the maximization of washing time, detergent dosage and other indicators in optimizing the washing performance. However, as the stain amount is relatively small in domestic life, the testing and optimization of washing performance with standard stained cloth would easily lead to excessive washing of clothes, damage to clothes, and waste of energy. In order to address the above problems, this paper intends to develop a new type of stained cloth in domestic life. 15 common household stains are selected, including soy sauce, red wine, coffee, grass stains, blood stains, carbon black, ketchup, cocoa milk, mud stains, peanut butter, peanut oil, chili oil, mechanical lubricant, lard, and lipstick. Taking knitted 100% cotton cloth and knitted 100% polyester cloth as the base cloth, the stained cloth is made using spot dyeing method, scraping method, and filling method. The quality of the stained cloth is tested through the evaluation experiment of the detergency performance by the washing machine. First, the standard deviation of the pre-washing Y value for 25 stained cloths of the same stain is tested. Secondly, the stained cloths are washed under the procedures of 7A, 5A and 2A specified in GB/ T 8629 - 2017, respectively to investigate whether the difference in cleaning rate under different washing conditions is significant. Thirdly, the stained cloths are washed three times under the same washing procedure, and the standard deviation and relative standard deviation of the cleaning rate of the 15 fabrics are investigated. Finally, the stained cloths are washed after being stored for one month to investigate the difference in the cleaning rate with the non,storage stained cloths. The stained cloth is made by locally staining, which is closer to the way and the amount of stains for the base cloth in real life. In terms of stain components, no additional ingredients are added, aiming to be close to real life. In terms of types of stains, 15 practical stains that are common in life are selected, covering most of the common types of stains in life. The results show that the best aging conditions for the prepared stained cloth through this method are: at the temperature of 60, and time of 2 hours. The pre-washing reflectance difference of the stained cloth is small, meeting the requirements of dyeing uniformity. The difference in the cleaning rate of the stained cloth under the washing procedures with different strengths is significant, meeting the requirements of washing sensitivity. The cleaning rate of stained cloth under the same washing procedure is stable, meeting the requirements of washing stability. The cleaning rate of stained cloth changes slightly after being stored for 30 days under low temperature and sealing conditions, exhibiting good storage stability. The actual household,use stained cloth prepared in this paper supplements the existing standard cloth and enriches the existing kinds of stained cloth used in the washing evaluation experiments. The research results can provide experimental samples and theoretical basis for household electrical appliance enterprises to design washing machine parameter and develop new products. [ABSTRACT FROM AUTHOR]

Wheatstone bridges are widely used in modern measurement technology as well as in the field of automatic control.This paper theoretically analyzes the relationship between the voltage sensitivity of the Wheatstone bridge and the parameters of the components in the composed circuit, discuss several key factors affecting the voltage sensitivity of bridges, and derive the parameter conditions for obtaining the maximum voltage sensitivity. The analysis results show that the voltage sensitivity of the Wheatstone bridge is mainly determined by the ratio of the resistances on the adjacent sides of the bridge,and the equalarm bridge has the maximum sensitivity.At the same time,considering the nonlinearity of the bridge output voltage and the relative rate of change of the resistance,this paper build an experimental test device using resistive strain gauges in a half-bridge differential way to eliminate the influence of the bridge voltage nonlinearity. Finally, in this paper,the half-bridge differential bridge was built independently to measure the voltage sensitivity under different strain states. The experimental results show that the bridge voltage is linear with the degree of strain in the bending strain condition through the half-bridge differential connection method. [ABSTRACT FROM AUTHOR]

Body temperature is an important indicator of human health detection which can reflect the key information of human life activities. The real-time and accurate monitoring of skin temperature can reflect the health status of the human body for timely intervention and treatment which plays an important role in daily protection and clinical medicine. Conventional contact thermometers are easily to be misplaced during measurement due to poor fit with skin which affects normal human activities. The infrared thermometers without directly contacting the skin can measure the temperature fast but due to the easy shift of the infrared head in the measurement process the skin radiation level and the environmental factors will affect its measurement accuracy. The paper or film-based temperature sensors are flexible and lowly breathable so they are not suitable for dynamic measurement of human body temperature or real-time monitoring of single point skin temperature. Temperature sensing yarns combine a hybrid electronic yarn with microscopic sensing elements and flexible textile fibers which endow them with good feel and comfort to measure single point skin temperature and dynamic human body temperature. In order to know well the development status and trend of temperature sensing yarns and promote their industrial application we firstly analyzed the sensing characteristics of typical temperature sensing yarns i. e. thermoelectric temperature sensing yarns optical fiber temperature sensing yarns and thermal resistance temperature sensing yarns. Among them four methods for preparing thermistor sensing yarns were mainly introduced hybrid spinning filament dipping coating of textiles flexible printing electronics and flexible hybrid electronics. Then we summarized the characterization parameters and influencing factors of these temperature sensing yarns in terms of sensing properties and working performance. In the end we presented the technical challenges and shortcomings of temperature sensing yarns in industrialization and application. It is found that thermoelectric temperature sensing yarns can generate electricity according to the temperature difference between human body and cold environment but the compensation problem of cold end needs to be solved. Optical fiber temperature sensors with high measurement accuracy and anti-electromagnetic interference are settable. Thus they can be used as yarns to manufacture smart textiles. However they are easily broken under mechanical stress in service. Thermal resistance sensing yarns are difficult to locate and their accuracy is easily affected by the surrounding humidity or sweat so further improvement is needed for long-term local temperature measurement on human body. Thermistor sensing yarns are suitable for the medical field because of high sensitivity but they have poor durability and washing ability. At present there is no in-depth study on the mode and mechanism of yarn function failure and no systematic design principle to guide large-scale production. Temperature sensing yarns which boast the advantages of softness comfort and invisibility are suitable for smart textiles to measure human temperature such as socks for predicting early diabetic foot ulcers clothing and bedding for continuous temperature measurement of infants bandage for monitoring wound infection and so on. The summarized characteristics of various temperature sensing yarns provide suggestions for the evaluation criteria structure optimization and functional failure theories of sensing yarns as well as the future application and selection of smart textiles. [ABSTRACT FROM AUTHOR]

When large-scale photovoltaic is connected to the interconnected power grid, the problem of voltage and frequency stability is prominent due to the shortage of photovoltaic active power output during low voltage fault. Firstly, this paper established the frequency response model of the combination of hydropower and photovoltaic, and theoretically analyzed the correlation between the system frequency and the key parameters of photovoltaic active power of LVRT. Then, through the normalized sensitivity index of photovoltaic parameters, it quantitatively analyzed the impact of key parameters of photovoltaic LVRT active power on transient frequency. Thirdly, based on the above normalized sensitivity, the optimization model of photovoltaic active power parameters meeting multi-scenario transient stability constraints was established with the objective of minimizing frequency deviation. Finally, the adaptability of the optimized parameters was verified through an example. With the AC line N-2 fault as an example, the minimum transient frequency is 49.5 Hz in forward mode, which increases by 1.5 Hz. Meanwhile, the maximum transient frequency is 50.4 Hz in outgoing mode. Both scenarios meet the requirements of frequency stability, which verifies that the proposed method can improve the stability of system frequency. [ABSTRACT FROM AUTHOR]

The purpose is to deal with the problems of excessive pruning of important convolutional layers caused by equalscale pruning, retain many redundant parameters and large loss of accuracy. This paper integrated sensitivity analysis on the basis of FPGM pruning strategy for network pruning. The algorithm used precision feedback to analyze the importance of each convolutional layer, control the single-layer pruning ratio, analyze the impact of different pruning ratios in each layer on accuracy loss, and obtained the sensitivity of each convolutional layer. It could be combined with FPGM to analyze the importance of the convolution kernel and cut the unimportant convolution kernel according to the pruning ratio of the sensitivity to complete the neural network pruning. The experimental results show that the accuracy of this method only drops by l. 56% and 0. 11 % when the pruning rate on MobileNet-v 1 and ResNet50 is 50%. This method has a higher pruning rate and lower calculation amount on ResNet50 under the same accuracy loss. [ABSTRACT FROM AUTHOR]