基于系统动力学的县域土地利用变化模型——以浙江省缙云县为例

土地利用变化与区域社会经济的可持续发展、全球环境效应密切相关。根据系统动力学的基本原理,在分析县域土地利用与社会系统、经济系统、环境系统以及城市化政策之间相互关系的基础上,借助系统动力学ithink软件,构建了以粮食供给安全、经济增长、环境容量等为动力机制的土地利用变化系统动力学模型。最后,通过案例的模型仿真表明模型的有效性。     

集约农作条件下土壤有机碳动态模拟及其在黄淮海平原区的应用

 集约农田土壤有机碳动态对作物可持续生产有重要意义。本研究基于碳固持CQESTR模型，在国内短期、中长期物料填埋试验资料基础上进行修正，将CQESTR模型按照物料降解与累积积温关系划分4个阶段，确定了不同降解阶段的物料类型因子。通过对黄淮海平原集约化农区7个独立肥料长期定位点1 151组耕层土壤有机质观测值与模拟值进行验证，模型模拟95％置信区间为1.91 g·kg-1，r2＝0.91。修正的CQESTR模型可以预测不同种植和管理措施下作物残体、外源有机物料及土壤有机质的矿化，从而对集约耕作条件下土壤有机碳矿化和固持进行评价。     

Cotton responses to ultraviolet-B radiation: experimentation and algorithm development

The potential impact of an increase in solar ultraviolet-B (UV-B) radiation due to human activity on higher plants has been the subject of many studies. Little work has been carried out so far on cotton responses to enhanced UV-B radiation. The objective of this study was to determine whether or not the current and projected increases in UV-B levels affect cotton growth and development, and to quantify and develop UV-B radiation functional algorithms that can be used in simulation models. Two experiments were conducted during the summer of 2001 using sunlit plant growth chambers in a wide range of UV-B radiations under optimal growing conditions. Leaves exposed to UV-B radiation developed chlorotic and necrotic patches depending on the intensity and length of exposure. Along with changes in visible morphology, cotton canopy photosynthesis declined with increased UV-B radiation. The decline in canopy photosynthesis was partly due to loss of photosynthetic pigments and UV-B-induced decay of leaf-level photosynthetic efficiency (maximum photosynthesis) and capacity (quantum yield) as the leaves aged. The total leaf area was less due to smaller leaves and fewer leaves per plant. Less plant height was closely related to a shorter average internode length rather than a fewer mainstem nodes. The UV-B did not affect cotton major developmental events such as time taken to square, time to flower, and leaf addition rates on the mainstem. Lower biomass was closely related to both smaller leaf area and lower photosynthesis. The critical limit, defined as 90% of optimum or the control, for stem elongation was lower (8.7 kJ m⁻² per day UV-B) than the critical limit for leaf expansion (11.2 kJ m⁻² per day UV-B), indicating that stem elongation was more sensitive to UV-B than leaf expansion. The critical limits for canopy photosynthesis and total dry weight were 7 and 7.3 kJ m⁻² per day, respectively. The identified UV-B-specific indices for stem and leaf growth and photosynthesis parameters may be incorporated into cotton simulation models such as GOSSYM to predict yields under present and future climatic conditions.     

黑龙江省发展低碳经济的动力因素体系构成

依据黑龙江省175家典型工业企业的调查数据,运用结构方程模型(SEM)方法实证分析了促进黑龙江省发展低碳经济的动力因素、各因素的驱动效应及作用机理。结果表明:产业转型、技术创新、政策扶持,构成了促进黑龙江省发展低碳经济的动力因素体系,产业转型、技术创新、政策扶持对黑龙江省发展低碳经济的驱动效应分别为0.93、0.82、0.76;产业转型具有中介变量特征,是推动发展低碳经济的核心载体;政策扶持、技术创新,是促进发展低碳经济的最佳组合,可实现"1+12"的实践成效;产业转型、技术创新、政策扶持,对黑龙江省发展低碳经济的推动作用各有侧重。基于实证分析结果,提出促进黑龙江省发展低碳经济的几点建议。     

Analysis of sediment transport modeling using computational fluid dynamics (CFD) for aquaculture raceways

A simulation model to analyze the water flow and sediment transport in aquaculture raceways was developed using a computational fluid dynamics (CFD) software package. The simulation was used to evaluate the efficiency of solids settling in the quiescent zone of existing trout raceways. This efficiency was based on the percentage of solids removed, which corresponds to the percentage of solids introduced into the raceway that settle in it, with settling taking place primarily in the quiescent zone.

The raceway selected for model validation was a rectangular concrete raceway 30.0 m long, 3.0 m wide, 0.9 m deep, with a slope of 0.01. The raceway included a quiescent zone of approximately 5.3 m in length, which was separated from the rearing area by a screen. The water flow rate through the raceway was approximately 0.058 m³/s. Velocity measurements were recorded at 230 stations along the raceway using an acoustic Doppler velocimeter, for comparison with the results obtained from the simulations.

For the purpose of simulating sediment transport, six groups of particles were used to account for the total suspended solids. The sizes of the particles selected were based on an experimentally determined distribution for solids from a similar raceway, and were 692, 532, 350, 204, 61, and 35 μm for Groups 1–6, respectively. The particle density for each size was assumed to be 1150 kg/m³. Values of the percentage of solids removed for the different particle sizes were 100.0% for the largest particles, and 54.7, 0.9, and 0.1% for the three smallest particles, respectively. This methodology of analyzing the raceway sediment transport in terms of its percentage of solids removed based on CFD simulations can also be used to examine raceway design alternatives for improving the particle removal efficiency.     

Adaptive implementation of information technology for real-time, basin-scale salinity management in the San Joaquin Basin, USA and Hunter River Basin, Australia

Pollutant trading schemes are market-based strategies that can provide cost-effective and flexible environmental compliance in large river basins. The aim of this paper is to contrast two innovative adaptive strategies for salinity management have been developed in the Hunter River Basin, New South Wales, Australia and in the San Joaquin River Basin, California, USA, respectively. In both instances web-based stakeholder information dissemination has been a key to achieving a high level of stakeholder involvement and the formulation of effective decision support tools for salinity management. A common element to implementation of salinity management strategies in both the Hunter River and San Joaquin River basins has been the concept of river assimilative capacity as a guide for controlling export salt loading and the establishment of a framework for trading of the right to discharge salt load to the Hunter River and San Joaquin River respectively. Both rivers provide basin drainage and the means of exporting salt load to the ocean. The paper compares the opportunities and constraints governing salinity management in the two basins as well as the use of monitoring, modeling and information technology to achieve environmental compliance and sustain irrigated agriculture in an equitable, socially and politically acceptable manner. The paper concludes by placing into broader context some of the issues raised by the comparison of the two approaches to basin salinity management.     

Effect of temperature on metabolic activity of intact microbial communities: Evidence for altered metabolic pathway activity but not for increased maintenance respiration and reduced carbon use efficiency

We used metabolic tracers and modeling to analyze the response of soil metabolism to a sudden change in temperature from 4 to 20 °C. We hypothesized that intact soil microbial communities would exhibit shifts in pentose phosphate pathway and glycolysis activity in the same way as is regularly observed for individual microorganisms in pure culture. We also hypothesized that increased maintenance respiration at higher temperature would result in greater energy production and reduced carbon use efficiency (CUE). Two hours after temperature increase, respiration increased almost 10-fold. Although all metabolic processes were increased, the relative activity of metabolic processes, biosynthesis, and energy production changed. Pentose phosphate pathway was reduced (17-20%), while activities of specific steps in glycolysis (51%) and Krebs cycle (7-13%) were increased. In contrast, only small but significant changes in biosynthesis (+2%), ATP production (−3%) and CUE (+2%) were observed. In a second experiment, we compared the metabolic responses to temperature increases in soils from high and low elevation. The shift in activity from pentose phosphate pathway to glycolysis with higher temperature was confirmed in both soils, but the responses of Krebs cycle, biosynthesis, ATP production, and CUE were site dependent. Our results indicate that 1) in response to temperature, communities behave biochemically similarly to single species and, 2) our understanding of temperature effects on CUE, energy production and use for maintenance and growth processes is still incomplete.     

基于PID模糊控制的汽车电动助力转向系统助力特性研究

概述了电动助力转向系统(EPS)的结构和工作原理,在分析电动助力转向系统数学模型的基础上,构建了基于MATLAB/Simulink的电动助力转向系统仿真模型。采用PID模糊控制策略对电动机目标电流进行闭环跟踪控制。仿真结果表明:与未加EPS系统的车辆相比,采取基于PID模糊控制的EPS系统使车辆具有良好的助力转向性能,验证了控制策略的有效性。     

GM(1,1)建模机理与应用条件分析及其改进方法

GM(1,1)拟合的原始序列为非负齐次指数函数,对任何呈指数变化的序列x(k),可采用x~(0)(k)=x(k)—M或x~(0)(k)=M—x(k)将其转换为非负齐次指数函数变化。GM(1,1)建模的背景值生成Z~(1)=xx~(1)(k)+(1—α)x~(1)(k+1),应满足α=1/α—1/(e~0—1)。当|α|较小时,α非常接近0.5,但当|α|较大时,α偏离0.5值较大,这是在|α|较大时GM(1,1)传统建模方法失效的原因。文中基于建模机理与应用条件的分析,提出了改进的计算方法。     

浅析丝绸服装造型设计的工艺技法

本文在对丝绸服装面料和款式等特征阐述的基础上,通过其平面与立体结构设计以及制作工艺中的准备、裁剪、缝制、整理、装饰等方面对丝绸服装造型设计中的工艺技法进行了浅析,以期对丝绸服装设计提供相关工艺理论参考。