基于特征和知识的精密注塑模设计和制造系统

采用先进的CAD/CAM技术对传统模具设计制造方法进行改造,是提高模具设计制造质量和效率的关键.此文提出基于特征和知识的才法构造精密注塑模设计和制造系统,并介绍了系统的总体方案和系统包含的各模块功能.这一系统是浙江省科委八五攻关项目“精密注塑模设计和制造(CAD/CAM)技术”的核心.     

Effects of temperature on the acute toxicity of cadmium to Corophium Insidiosum

This study aimed to optimise the methodology for the use of Corophium insidiosum in a bioassay. Taking into account that it would be suitable to execute the bioassay with organisms having a good sensitivity during the year and low mortality in control sediment, the influence of different temperatures (10–15–20 and 25°C) has been examined. C. insidiosum was collected during August, November 2005 and January 2006, in Mar Piccolo basin (Ionian sea). The results obtained show that this species mortality in the negative control sediment, ranged from 2.6 ± 0.6% at 10°C in August to 17 ± 2.2% at 20°C in November, at different temperatures tested. At 20°C there were significant differences in mortality among different months examined. Indeed no relationship among months was found at 15°C. Significant differences between August and November at 25°C, between November and January were not found at 10°C. The 96-h LC50 values found for cadmium at all temperature experimental conditions ranged from 2.11 mg/l (1.57–2.82) to 0.70 mg/l (0.54–0.93). The highest values were found at 10°C in November and January. The results showed that the optimal temperature for the bioassay seems to be between 15°C and 20°C. Even if, at 20°C the mortality differs significantly among organisms sampled.     

Evaluating and managing wildlife impacts of climate change under uncertainty

Wildlife managers face the daunting task of managing wildlife in light of uncertainty about the nature and extent of future climate change and variability and its potential adverse impacts on wildlife. A conceptual framework is developed for managing wildlife under such uncertainty. The framework uses fuzzy logic to test hypotheses about the extent of the wildlife impacts of past climate change and variability, and fuzzy multiple attribute evaluation to determine best compensatory management actions for adaptively managing the potential adverse impacts of future climate change and variability on wildlife. A compensatory management action is one that can offset some of the potential adverse impacts of climate change and variability on wildlife. Implementation of the proposed framework requires wildlife managers to: (1) select climate impact states, hypotheses about climate impact states, possible management actions for alleviating adverse wildlife impacts of climate change and variability, and future climate change scenarios; (2) choose biological attributes or indicators of species integrity; (3) adjust those attributes for changes in non-climatic variables; (4) define linguistic variables and associated triangular fuzzy numbers for rating both the acceptability of biological conditions under alternative management actions and the relative importance of biological attributes; (5) select minimum or maximum acceptable levels of the attributes and reliability levels for chance constraints on the biological attributes; and (6) define fuzzy sets on the extent of species integrity and biological conditions and select a fuzzy relation between species integrity and biological conditions. A constructed example is used to illustrate a hypothetical application of the framework by a wildlife management team. An overall best compensatory management action across all climate change scenarios is determined using the minimax regret criterion, which is appropriate when the management team cannot assign or is unwilling to assign probabilities to the future climate change scenarios. Application of the framework can be simplified and expedited by incorporating it in a web-based, interactive, decision support tool.     

Risk factors associated with bus accident severity in the United States: A generalized ordered logit model

IntroductionRecent years have witnessed a growing interest in improving bus safety operations worldwide. While in the United States buses are considered relatively safe, the number of bus accidents is far from being negligible, triggering the introduction of the Motor-coach Enhanced Safety Act of 2011.MethodThe current study investigates the underlying risk factors of bus accident severity in the United States by estimating a generalized ordered logit model. Data for the analysis are retrieved from the General Estimates System (GES) database for the years 2005–2009.ResultsResults show that accident severity increases: (i) for young bus drivers under the age of 25; (ii) for drivers beyond the age of 55, and most prominently for drivers over 65 years old; (iii) for female drivers; (iv) for very high (over 65 mph) and very low (under 20 mph) speed limits; (v) at intersections; (vi) because of inattentive and risky driving.     

Economic feasibility of adapting crop enterprises to future climate change: a case study of flexible scheduling and irrigation for representative farms in Flathead Valley,Montana, USA

Future climate change directly impacts crop agriculture by altering temperature and precipitation regimes, crop yields, crop enterprise net returns, and net farm income. Most previous studies assess the potential impacts of agricultural adaptation to climate change on crop yields. This study attempts to evaluate the potential impacts of crop producers’ adaptation to future climate change on crop yield, crop enterprise net returns, and net farm income in Flathead Valley, Montana, USA. Crop enterprises refer to the combinations of inputs (e.g., land, labor, and capital) and field operations used to produce a crop. Two crop enterprise adaptations are evaluated: flexible scheduling of field operations; and crop irrigation. All crop yields are simulated using the Environmental Policy Integrated Climate (EPIC) model. Net farm income is assessed for small and large representative farms and two soils in the study area. Results show that average crop yields in the future period (2006–2050) without adaptation are between 7% and 48% lower than in the historical period (1960–2005). Flexible scheduling of the operations used in crop enterprises does not appear to be an economically efficient form of crop enterprise adaptation because it does not improve crop yields and crop enterprise net returns in the future period. With irrigation, crop yields are generally higher for all crop enterprises and crop enterprise net returns increase for the canola and alfalfa enterprises but decrease for all other assessed crop enterprises relative to no adaptation. Overall, average crop enterprise net return in the future period is 45% lower with than without irrigation. Net farm income decreases for both the large and small representative farms with both flexible scheduling and irrigation. Results indicate that flexible scheduling and irrigation adaptation are unlikely to reduce the potential adverse economic impacts of climate change on crop producers in Montana’s Flathead Valley.     

Accounting for risk and uncertainty in determining preferred strategies for adapting to future climate change

Individuals, businesses, and policymakers face the problem of selecting a preferred strategy for adapting a managed ecosystem to future climate change when there is risk and/or uncertainty about future climate change and its ecosystem impacts, and the conditional outcomes of adaptive strategies (i.e., performance of an adaptive strategy given a particular future climate change scenario occurs). Evaluation methods for this purpose are described for two cases; one in which the decision-maker can (climate risk case) and cannot (climate uncertainty case) assign probabilities to future climate change scenarios. Fuzzy sets are used to characterize uncertainty regarding both future climate change, and the conditional outcomes of adaptive strategies. The preferred conditional adaptive strategy for a future climate change scenario is determined by ordering the adaptive strategies for that scenario using a fuzzy set operation. Two methods are described for determining the adaptive strategy that is preferred across all climate change scenarios. The preferred overall adaptive strategy for the climate risk case is determined by maximizing a performance index for strategies. The preferred overall adaptive strategy for the climate uncertainty case is determined using the minimax regret criterion, which selects the strategy that minimizes the maximum loss in performance that can occur across all strategies and climate change scenarios. Ways for making the evaluation methods dynamic are considered.     

The arbuscular mycorrhizal fungus Glomus mosseae induces growth and metal accumulation changes in Cannabis sativa L

The effect of arbuscular mycorrhiza on heavy metal uptake and translocation was investigated in Cannabis sativa. Hemp was grown in the presence and absence of 100 microg g-1 Cd and Ni and 300 microg g-1 Cr(VI), and inoculated or not with the arbuscular mycorrhizal fungus Glomus mosseae. In our experimental condition, hemp growth was reduced in inoculated plants and the reduction was related to the degree of mycorrhization. The percentage of mycorrhizal colonisation was 42% and 9% in plants grown in non-contaminated and contaminated soil, suggesting a significant negative effect of high metal concentrations on plant infection by G. mosseae. Soil pH, metal bioavailability and plant metal uptake were not influenced by mycorrhization. The organ metal concentrations were not statistically different between inoculated and non-inoculated plants, apart from Ni which concentration was significantly higher in stem and leaf of inoculated plants grown in contaminated soil. The distribution of absorbed metals inside plant was related to the soil heavy metal concentrations: in plant grown in non-contaminated soil the greater part of absorbed Cr and Ni was found in shoots and no significant difference was determined between inoculated and non-inoculated plants. On the contrary, plants grown in artificially contaminated soil accumulated most metal in root organ. In this soil, mycorrhization significantly enhanced the translocation of all the three metals from root to shoot. The possibility to increase metal accumulation in shoot is very interesting for phytoextraction purpose, since most high producing biomass plants, such as non-mycorrhized hemp, retain most heavy metals in roots, limiting their application.     

Multiple attribute evaluation of landscape management

Economic approaches to the valuation of ecological services have several limitations. Some of these limitations can be overcome using the multiple attribute decision-making model developed in this paper. The model postulates that a private or public decision-maker selects a site/landscape management plan based on the biophysical and economic attributes of alternative management plans, the decision-maker’s preferences for attributes, and constraints on the selection of a management plan.Two cases are examined. Case A is a watershed consisting of publicly owned land that is managed at the site, management unit and landscape scales. Management is based on the philosophy of ecosystem management. Case B is a watershed composed of several privately owned units that are managed at the site scale by decision-makers whose primary motivation is economic profit. The preferred management plan in both cases is determined using a two-stage procedure. The first stage uses a stochastic programming model to identify the most efficient management plans for a site/landscape. The second stage determines which efficient management plan for a site/landscape is preferred by maximizing an expected utility function that is additive in the attributes and assumes that the decision-maker is risk neutral.Whether a land-management plan results in strongly or weakly sustainable resource conditions is evaluated. Strong sustainability requires the probability of exceeding the minimum acceptable value of an attribute to be greater than or equal to a pre-determined reliability level for each attribute. Weak sustainability requires the same condition except that it applies to a composite index of the attributes rather than each attribute. Bayes theorem is used to evaluate uncertainty about whether the state of a landscape is sustainable.     

Considering built environment and spatial correlation in modeling pedestrian injury severity

Objective: This study looks at mitigating and aggravating factors that are associated with the injury severity of pedestrians when they have crashes with another road user and overcomes existing limitations in the literature by focusing attention on the built environment and considering spatial correlation across crashes.

Method: Reports for 6,539 pedestrian crashes occurred in Denmark between 2006 and 2015 were merged with geographic information system resources containing detailed information about the built environment and exposure at the crash locations. A linearized spatial logit model estimated the probability of pedestrians sustaining a severe or fatal injury conditional on the occurrence of a crash with another road user.

Results: This study confirms previous findings about older pedestrians and intoxicated pedestrians being the most vulnerable road users and crashes with heavy vehicles and in roads with higher speed limits being related to the most severe outcomes. This study provides novel perspectives by showing positive spatial correlations of crashes with the same severity outcomes and emphasizing the role of the built environment in the proximity of the crash.

Conclusions: This study emphasizes the need for thinking about traffic calming measures, illumination solutions, road maintenance programs, and speed limit reductions. Moreover, this study emphasizes the role of the built environment, because shopping areas, residential areas, and walking traffic density are positively related to a reduction in pedestrian injury severity. Often, these areas have in common a larger pedestrian mass that is more likely to make other road users more aware and attentive, whereas the same does not seem to apply to areas with lower pedestrian density.