基于约束熵的复杂系统重要节点崩溃控制研究

为有效控制复杂系统崩溃,提出一种基于约束熵的复杂系统重要节点崩溃控制方法。通过概述现有事故致因理论及模型,建立分析复杂系统安全事故致因的"认知-约束"模型。针对复杂系统节点众多,关联复杂的本质,指出为预防安全事故,必须在强化安全认知能力的基础上对重要节点进行约束控制。在提取节点重要度评估参数后,设计一种改进的复杂系统节点重要度评估算法。最后,引入约束熵概念,构建抑制复杂系统重要节点崩溃的约束熵度量模型。研究结果表明,存在可量化的用于控制复杂系统崩溃的手段;预防安全事故的关键是将适量的约束熵"引入"重要节点。     

水资源管理“三条红线”约束下的城镇化水平阈值分析——以张掖市为例

水资源与城镇化的关系问题是水科学研究的热点,二者之间存在着复杂的交织关系。论文选取典型干旱区城市张掖市为研究对象,以最严格水资源管理制度为约束条件,基于水资源约束下的城镇化水平阈值计算思路,引入节水量和灰水足迹测算方法改进了传统水量水质双要素水资源承载力计算模型,并在此基础上统筹可供水量、可节水量及水功能区纳污能力构建了水资源管理“三条红线”约束下的城镇化水平阈值计算模型;通过分析张掖市城镇化水平与水资源开发利用的历史数据并进行情景模拟,对2020年和2030年张掖市城镇化水平阈值做出了预测。结果表明：1）在水资源开发利用红线约束下,到2030年张掖市可利用水资源量为23.02×10⁸ m³,与现状基本一致,且以当前的水资源开发利用水平,水量承载能力难以支撑政府未来规划中的城镇化进程与经济增长的用水需求;2）严格遵照用水效率控制红线中所规定的用水定额标准时,张掖市将有望改善水量承载能力不足问题,且到2030年时,水量承载城镇人口能力可达331.91×10⁴人,其中水量承载能力提升主要得益于农业部门节水;3）在水功能区限制纳污红线的约束下,2030年张掖市水质可承载能力上限为62.47×10⁴人,仅为规划城镇人口数量的78%,水质可承载能力对城镇化进程形成了强烈的约束作用,约束力主要来自于城镇区域氨氮排放;4）在水资源管理“三条红线”约束下,到2030年时张掖市城镇化水平阈值上限为48.05%。     

The puzzle of North America's Late Pleistocene megafaunal extinction patterns: Test of new explanation yields unexpected results

Although Late Pleistocene extinctions disproportionately affected larger mammalian species, numerous smaller species were also lost. To date, no satisfactory explanation has been presented to account for this pattern. Beginning with the assumption that human predation caused the extinctions, we offer and test the first such explanatory hypothesis, which is predicated on considering more realistic functional response forms (i.e., those that allow for predator interference or prey sharing). We then test the hypothesis via a one-predator, six-prey ecological model that maintains transparency, minimalism of design, and maximal constraint of parameters. Results indicate that altering assumptions about one cornerstone of ecological modeling (i.e., functional response) fails to produce qualitative differences in survival–extinction outcomes—even in conjunction with a wide range of capture efficiency permutations. This unexpected finding suggests that no reasonable form of predation alone is capable of producing the survival–extinction pattern observed. We conclude that the matter of causation and the conclusions of previous Late Pleistocene extinction models remain far less certain than many have assumed.     

Impact of product heterogeneity and soft budget constraint on excess capacity in Chinese energy industry based on the duopoly model

Chinese energy industries are facing serious problems such as excess capacity, homogeneous product, and soft budget constraint. This paper provides a duopoly model to investigate the influence of heterogeneity and soft budget constraint on production capacity decision and internal action mechanism, respectively, under Cournot and Bertrand competitions, which reveals the formation mechanism of excess capacity. We conclude that excess capacity would exist when the products are not wholly heterogeneous under Cournot competition, and the higher level of the soft budget constraint or the more homogeneous the products are, the worse the excess capacity will be. The insufficient capacity would exist provided that products are not wholly heterogeneous under Bertrand competition, and the higher level of soft budget constraint or the more homogeneous the products are, the more insufficient capacity will be. Both soft budget constraint and product heterogeneity mutually affect to decision-making of capacity and output.     

基于潜变量回归模型的城市火灾风险评估

为评估城市火灾风险等级,针对城市火灾发生的可能性与严重性2个基本问题,建立评估指标体系,提出一种基于潜变量回归的评估模型,并给出无须迭代的确定性算法。该模型和算法无需事先指定风险等级评估分数的训练样本,不必事先指定指标汇总的加权系数,利用合理的配方约束,完成潜变量回归,实现城市火灾风险按地区或者按行业的等级评估,利用现成的软件计算,同样适用于其他具有类似数据结构的评估问题。     

基于系统动力学的安全生产监管有效性研究

为改善我国安全生产监管的效果,研究引入激励性监管措施后的安全生产监管效果。运用系统动力学(SD)建模方法,对比单用约束性监管措施的效果与综合运用约束性监管措施和激励性监管措施的效果。研究结果表明:单独使用约束性监管措施时,提高检查罚金和事故赔偿额,会使企业净收益、政府与企业的净收益总和增加。然而,综合使用约束性监管措施和激励性监管措施时,企业的净收益额增加,政府的净收益额减少,而企业与政府的净收益总额变化不大,但结合对事故负外部性的考虑,通常会使社会福利额外提高。     

长三角地区城市建设用地扩展的水资源约束

基于资源约束理论,构建城市建设用地扩展的水资源约束模型,并测算2002-2013年期间长三角地区地级及以上城市建设用地扩展中的水资源约束强度。结果显示,研究时段内长三角地区城市建设用地扩展受到水资源的明显约束,区域建设用地扩展速度比没有水资源约束时年均下降0.35%;水资源约束强度具有空间分异规律,形成了以"苏州—杭州—宁波"、"南京—苏州"为中心地区向江苏北部和浙江南部区域逐步衰减的空间变化特征;水资源约束与城市经济总量和城市规模等级紧密相关,总体上城市经济总量大,规模等级高,建设用地扩展受水资源的约束越大。依据水资源约束强度大小将长三角地区城市归为强约束、中约束、低约束和无约束四类,发现不同类型城市在劳动力增长率、水资源供给增长率、经济产出对建设用地扩展的弹性上存在明显差异。研究还表明,即使在河网密布的长三角地区,城市用地扩展也受到水资源的约束,其他地区务必重视水资源重要性,严格遵循"以水定产、以水定城"的管理政策,提高水土资源利用效率,促进城市可持续发展。     

志绿隔声产品构建高性能隔声室

为了提高居民居住和工作环境质量,降低噪声对人们的干扰,创造社会一片安宁和谐的氛围,志绿隔声产品将复合高性能新材料形成阻尼约束结构放置在两块板中间,将透过墙板的噪音能量降低85%以上。本文结合项目工程案例,来展现志绿隔声产品的高性能,解决噪声对人们的危害。     

Safety rules: procedural freedom or action constraint?

The paper presents a partial classification of safety rules as constraints imposed from outside on the freedom of choice of individuals or companies. The classification is linked to the Reason model of skill-, rule-, and knowledge-based behaviour. The imposition of constraints is related to a number of criteria concerning the context and use of the rules to arrive at proposals for when and where to apply what type of rule. To illustrate the principles discussed an example is given of the rule from the Dutch Working Environment legislation concerning the requirement to use “current state of the art in prevention” in companies. The paper proposes providing procedural rule support to companies on how to meet the rule, in the form of a data bank of practicable solutions to health and safety problems.     

Pyrrolizidine alkaloid content in <Emphasis Type="Italic">Senecio</Emphasis>: ontogeny and developmental constraints

Summary. The ontogeny of pyrrolizidine alkaloid (PA) synthesis and constraints on defence level during the seedling stage were examined in the annual Senecio vulgaris and the monocarpic perennial Senecio jacobaea. In both species, PAs were actively synthesized from the onset of seedling growth so that juvenile stages did not go through an undefended stage. Roots are known to be the exclusive sites where PAs are produced. Root biomass was the single most important biomass parameter explaining variation in total PAs per seedling. All correlation coefficients between—relative growth rate and PA concentration were negative, but none was significant. However, a significant negative—correlation was found between shoot to root ratio and PA concentration in S. jacobaeaseedlings, suggesting a dilution effect of the PAs. Earlier studies have shown that the shoot to root ratio is positively correlated with relative growth—rate of established S. jacobaea plants. It is therefore suggested that young S. jacobaea plants with a high shoot to root ratio and hence a high growth capacity necessarily have lower PA defence levels than plants with a low shoot to root ratio. Received 10 July 2002; accepted 16 November 2002.