Modelling cheetah relocation success in southern Africa using an Iterative Bayesian Network Development Cycle

Relocation is one of the strategies used by conservationists to deal with problem cheetahs in southern Africa. The success of a relocation event and the factors that influence it within the broader context of long-term viability of wild cheetah metapopulations was the focus of a Bayesian Network (BN) modelling workshop in South Africa. Using a new heuristics, Iterative Bayesian Network Development Cycle (IBNDC), described in this paper, several networks were formulated to distinguish between the unique relocation experiences and conditions in Botswana and South Africa. There were many common underlying factors, despite the disparate relocation strategies and sites in the two countries. The benefit of relocation BNs goes beyond the identification and quantification of the factors influencing the success of relocations and population viability. They equip conservationists with a powerful communication tool in their negotiations with land and livestock owners, which is key to the long-term survival of cheetahs in southern Africa. Importantly, the IBNDC provides the ecological modeller with a methodological process that combines several BN design frameworks to facilitate the development of a BN in a multi-expert and multi-field domain.     

Dynamic failure probability analysis of urban gas pipeline network

The gas pipeline network is an essential infrastructure for a smart city. It provides a much-needed energy source; however, it poses a significant risk to the community. Effective risk management assists in maintaining the operational safety of the network. The risk management of the network requires reliable dynamic failure probability analysis. This paper proposes a methodology of condition monitoring and dynamic failure probability analysis of urban gas pipeline network. The methodology begins with identifying key design and operational factors responsible for pipeline failure. Subsequently, a causation-based failure model is developed as the Bowtie model. The Bowtie model is transformed into a Bayesian network, which is analyzed using operational data. The key contributory factors of accident causation are monitored. The monitored data is used to analyze the updated failure probability of the network. The gas pipeline network's dynamic failure probability is combined with the potential consequences to assess the risk. The application of the approach is demonstrated in a section of the urban gas pipeline.     

Determination of the critical length of the crack-like flaws and its effect on safety

Methodologies of API 579 have been widely accepted as the de-facto standard guideline for fitness for service assessment on crack-like flaws in pressure equipment. For different purposes and needs, the evaluation is divided into three levels, from critical length estimation in level 1, use of the failure analysis diagram (FAD) in level 2, to performing finite element stress analysis in level 3, that is from simplified to accurate. It is generally considered safe as long as the crack is smaller than the critical crack, but not all of them are actually the case. Therefore, it is very important to study the physical meaning behind the critical crack and understand the conservativeness of it.In this study, numerous examples of critical cracks determined according to API 579 Level 1 were put into Level 2 analysis for comparison. Each case is mapped onto the FAD of level 2 analysis to see its position and distance from the borderline between safe and danger zones. A huge amount of examples covering the majority of possible scenarios, including the geometry, thickness, inner diameter, pressure and half-length of the flaw, depth of the crack, crack tip and crack bottom, as a whole, there are 960 cases to be analyzed.Results show that cracks on the circumferential direction of the cylindrical and spherical vessels are distributed tightly in a small area far from the borderline on the FAD diagram. In these cases, the vessel is actually not as dangerous as the critical crack implies, since most of the points lie quite far from the danger zone. As for the longitudinal cracks of a cylindrical vessel, the results are scattered around, and three data points are located outside the allowable zone. The peculiar results are partly due to a discrepancy of interpolating procedure as the influence coefficient is being computed. Through this study, it is also found that the cumbersome process of estimating the critical crack length can be greatly simplified for longitudinal cracks in a cylindrical vessel.     

Bayesian Decision Analysis for Evaluating Management Options to Promote Recovery of a Depleted Salmon Population

Abstract:  The endangered population of sockeye salmon (Oncorhynchus nerka) in Cultus Lake, British Columbia, Canada, migrates through commercial fishing areas along with other, much more abundant sockeye salmon populations, but it is not feasible to selectively harvest only the latter, abundant populations. This situation creates controversial trade-offs between recovery actions and economic revenue. We conducted a Bayesian decision analysis to evaluate options for recovery of Cultus Lake sockeye salmon. We used a stochastic population model that included 2 sources of uncertainty that are often omitted from such analyses: structural uncertainty in the magnitude of a potential Allee effect and implementation uncertainty (the deviation between targets and actual outcomes of management actions). Numerous state-dependent, time-independent management actions meet recovery objectives. These actions prescribe limitations on commercial harvest rates as a function of abundance of Cultus Lake sockeye salmon. We also quantified how much reduction in economic value of commercial harvests of the more abundant sockeye salmon populations would be expected for a given increase in the probability of recovery of the Cultus population. Such results illustrate how Bayesian decision analysis can rank options for dealing with conservation risks and can help inform trade-off discussions among decision makers and among groups that have competing objectives.     

清代北京地区瘟疫流行的社会影响及政府应对

清代北京地区瘟疫反复流行,不仅导致人口大量死亡,还对政治制度、经济发展、城市建设、民众信仰产生重大影响.瘟疫流行期间,清政府拨付专款,设局施药施棺进行直接救治.同时,还注意安置解决来京流民饥民问题,对控制疫情的蔓延起了重要的作用.此外,基于传统天象示警的观念,统治者还通过重清理刑狱和征求直言的方式挽回天意,达到消除瘟疫...     

基于FLAC3D的盾构隧道施工过程建模影响因素分析

基于FLAC3D对盾构隧道施工过程模拟,研究建模影响因素及其影响程度。首先,综合隧道开挖过程中盾构机前体与岩土层间相互作用的影响因素来模拟隧道开挖过程,确定地表沉降和隧道垂直（Z）方向应力;然后,分别模拟去除其中一种因素后的隧道开挖过程,并求出相应的地表沉降和隧道垂向应力;最后,基于傅里叶变换对各种情况下的地表沉降量和应力应变状况进行比较分析,找出各因素对建模的影响程度,从而为利用FLAC3D进行盾构隧道施工模拟时的影响因子的选择提供参考。研究结果表明：一方面,建模过程中的各种因素对地表沉降的影响大于对隧道Z向压力影响;另一方面,盾构机推进给作业面土体压力、盾尾灌浆延迟于管片拼装造成的暂时对土体支护力不足、盾构机刀盘转动给作业面土体的扭力等因素对模型解算造成的影响最大。     

考虑动态施工超长管棚预支护力学特性及参数影响分析*

为研究复杂地层超长管棚随动态施工的力学特性和管棚合理化参数,依托某下穿高速公路浅埋暗挖隧道工程,采用数值法进行三维动态建模分析。研究结果表明:管棚挠度曲线呈鱼腹形,拱顶部和拱腰管棚最终稳定在10.7,2.9 mm;管棚各测点轴力经历由受拉到受压的变化过程,通过各测点后受压区轴力逐渐减小,拱顶部动态响应更明显;管棚弯矩集中于掌子面前后方区域,随开挖面推进,弯矩作用范围逐渐向前扩张,最大弯矩发生在洞口套拱处;通过参数影响分析,当采用短进尺开挖时,管棚直径取129~159 mm、间距为0.4~0.5 m、注浆区厚度为0.4~0.5 m时可确保上方高速公路安全。研究结果可为类似工程施工和设计提供参考。     

调节风窗对瓦斯爆炸影响的数值分析*

为研究调节风窗的面积、位置对瓦斯爆炸传播特性的影响,通过FLACS软件构建不同面积和不同位置调节风窗的风门-巷道模型,对瓦斯在该模型中的爆炸及其传播进行数值模拟,并分析瓦斯爆炸压力、火焰传播速度。研究结果表明:风门前最大瓦斯爆炸压力值与调节风窗边长呈现指数减小关系,而风门后最大瓦斯爆炸压力值与调节风窗边长呈现指数增加关系;火焰传播速度与调节风窗边长呈现指数增加关系;相同面积情况下,调节风窗中心位置对瓦斯爆炸影响较小。     

Effects of social networks on interventions to change conservation behavior

Social networks are critical to the success of behavioral interventions in conservation because network processes such as information flows and social influence can enable behavior change to spread beyond a targeted group. We investigated these mechanisms in the context of a social marketing campaign to promote a wildlife poisoning hotline in Cambodia. With questionnaire surveys we measured a social network and knowledge and constructs from the theory of planned behavior at 3 points over 6 months. The intervention initially targeted ∼11% (of 365) of the village, but after 6 months ∼40% of the population was knowledgeable about the campaign. The likelihood of being knowledgeable nearly doubled with each additional knowledgeable household member. In the short term, there was also a modest, but widespread improvement in proconservation behavioral intentions, but this did not persist after 6 months. Estimates from stochastic actor-oriented models suggested that the influences of social peers, rather than knowledge, were driving changes in intention and contributed to the failure to change behavioral intention in the long term, despite lasting changes in attitudes and perceived norms. Our results point to the importance of accounting for the interaction between networks and behavior when designing conservation interventions.     

Index System and Influence of Drought in Northwest China

In this paper, the index systems of the agricultural drought and decrease percentage of grain crop are established. The trend and influence of drought in the region is analyzed based on the 50 years （1951-2000） statistical data of precipitation and 52 years （1951 2002） agricultural drought of the region, including tire provinces： Shaanxi, Gansu, Ningxia, Qinghai and Xinjiang. The result shows that the drought disaster is increasing and the most serious were in the 1970s and 1990s, and main agricultural drought is a great disaster incident. The regression prediction equation of drought and flood grades and agricultural drought areas grades are set up by the harmonic wave method, and forecasting the drought will lighten during the first ten years of the 21st century.