Fixed and random effect models were applied to a pseudo-panel data built of soil analysis reports from tobacco farms to analyze relationships between soil characteristics like soil organic matter (SOM) and soil nitrog...Fixed and random effect models were applied to a pseudo-panel data built of soil analysis reports from tobacco farms to analyze relationships between soil characteristics like soil organic matter (SOM) and soil nitrogen (N), phosphorous (P) and potassium (K) and to explore the potential for improving nutrients availability by increasing SOM content. These econometric models may account for unobserved specific characteristics such as location-specific characteristics, management strategies, farmers’ skills and preferences and environmental heterogeneity. Positive relationships were found between N, P and K availability and SOM. The random effect model reports a highly significant elasticity of N with respect to SOM of 0.75, meaning that an increase of 1% of SOM will increase soil N by 0.75%. Using this elasticity, the required SOM improvement of green manure was calculated at which costs of green manure would exactly equal benefits in terms of reduced N fertilizer use. Costs and benefits are equal if the SOM increases from 1.55% to 3.61%, which is barely achieved according to the literature. Hence, growing green manure crops to increase SOM and thereby N availability is not economically attractive. However, additional benefits may arise from SOM improvement and growing green manure crops.展开更多
Productivity improvement of an operation without increasing operation risk and operation fatigue that increase the needed relaxation allowance is an important subject in process design. This research subject stimulate...Productivity improvement of an operation without increasing operation risk and operation fatigue that increase the needed relaxation allowance is an important subject in process design. This research subject stimulates researchers to focus on improving the productivity of the whole production process by changing the technique of performing significant operations in the process. However, two important issues that affect the implementation of any new technique were not considered in the pervious research works. These are the risk magnitude of the new technique on the workplace environment and the fatigue level that affect human's health. In this paper, a model was developed that maximize the productivity of the production process by selecting the best technique to perform significant process operations among proper candidate techniques that improve these operations productivity while minimizing these operations risk and fatigue.展开更多
In modern society, a plastic part has its own important position. To the managers and decision makers in the field of plastic component, how to decide the manufacturing cost of the injection part or injection mold as...In modern society, a plastic part has its own important position. To the managers and decision makers in the field of plastic component, how to decide the manufacturing cost of the injection part or injection mold as quickly as possible is most valuable. Cost estimation formulae (CEF) are the most common method to evaluate the cost of injection part/mold, which is similar to our ordinary thinking. In this paper, a CEF method used by Dr. Weiyi Hu in Massachusetts University is first discussed. To the problems existed in the formulae, we propose an improved algorithm. This algorithm can be used to estimate the manufacturing cost of injection part/mold accurately in the early design stage.展开更多
文摘Fixed and random effect models were applied to a pseudo-panel data built of soil analysis reports from tobacco farms to analyze relationships between soil characteristics like soil organic matter (SOM) and soil nitrogen (N), phosphorous (P) and potassium (K) and to explore the potential for improving nutrients availability by increasing SOM content. These econometric models may account for unobserved specific characteristics such as location-specific characteristics, management strategies, farmers’ skills and preferences and environmental heterogeneity. Positive relationships were found between N, P and K availability and SOM. The random effect model reports a highly significant elasticity of N with respect to SOM of 0.75, meaning that an increase of 1% of SOM will increase soil N by 0.75%. Using this elasticity, the required SOM improvement of green manure was calculated at which costs of green manure would exactly equal benefits in terms of reduced N fertilizer use. Costs and benefits are equal if the SOM increases from 1.55% to 3.61%, which is barely achieved according to the literature. Hence, growing green manure crops to increase SOM and thereby N availability is not economically attractive. However, additional benefits may arise from SOM improvement and growing green manure crops.
文摘Productivity improvement of an operation without increasing operation risk and operation fatigue that increase the needed relaxation allowance is an important subject in process design. This research subject stimulates researchers to focus on improving the productivity of the whole production process by changing the technique of performing significant operations in the process. However, two important issues that affect the implementation of any new technique were not considered in the pervious research works. These are the risk magnitude of the new technique on the workplace environment and the fatigue level that affect human's health. In this paper, a model was developed that maximize the productivity of the production process by selecting the best technique to perform significant process operations among proper candidate techniques that improve these operations productivity while minimizing these operations risk and fatigue.
文摘In modern society, a plastic part has its own important position. To the managers and decision makers in the field of plastic component, how to decide the manufacturing cost of the injection part or injection mold as quickly as possible is most valuable. Cost estimation formulae (CEF) are the most common method to evaluate the cost of injection part/mold, which is similar to our ordinary thinking. In this paper, a CEF method used by Dr. Weiyi Hu in Massachusetts University is first discussed. To the problems existed in the formulae, we propose an improved algorithm. This algorithm can be used to estimate the manufacturing cost of injection part/mold accurately in the early design stage.
