Review and comparison of methods to study the contribution of variables in artificial neural network models

Convinced by the predictive quality of artificial neural network (ANN) models in ecology, we have turned our interests to their explanatory capacities. Seven methods which can give the relative contribution and/or the contribution profile of the input factors were compared: (i) the ‘PaD’ (for Partial Derivatives) method consists in a calculation of the partial derivatives of the output according to the input variables; (ii) the ‘Weights’ method is a computation using the connection weights; (iii) the ‘Perturb’ method corresponds to a perturbation of the input variables; (iv) the ‘Profile’ method is a successive variation of one input variable while the others are kept constant at a fixed value; (v) the ‘classical stepwise’ method is an observation of the change in the error value when an adding (forward) or an elimination (backward) step of the input variables is operated; (vi) ‘Improved stepwise a’ uses the same principle as the classical stepwise, but the elimination of the input occurs when the network is trained, the connection weights corresponding to the input variable studied is also eliminated; (vii) ‘Improved stepwise b’ involves the network being trained and fixed step by step, one input variable at its mean value to note the consequences on the error. The data tested in this study concerns the prediction of the density of brown trout spawning redds using habitat characteristics. The PaD method was found to be the most useful as it gave the most complete results, followed by the Profile method that gave the contribution profile of the input variables. The Perturb method allowed a good classification of the input parameters as well as the Weights method that has been simplified but these two methods lack stability. Next came the two improved stepwise methods (a and b) that both gave exactly the same result but the contributions were not sufficiently expressed. Finally, the classical stepwise methods gave the poorest results.     

Trophic relationships in the recently impounded Bagré reservoir in Burkina Faso

The trophic dynamics of Bagré reservoir which has been recently impounded in Burkina Faso was based on the data collected during 1997–1998 period using the Ecopath model and software. Total fish biomass is 22.63 t km⁻² and mainly represents trophic levels (TLs) 2 and 3. The trophic food chain is relatively long and the overall transfer efficiency is quite low. Grazing foodweb based on primary producers is prominent in the reservoir ecosystem and detritus plays a less significant role. Seasonal and long-term variations in water quality have significant influences on the lower TLs clearly showing a bottom-up functioning of the ecosystem. Environmental degradations, such as siltation occurring in the lake, suggest possible risks in limiting ecosystem productivity.     

阴极射线管中低熔点玻璃的溶解规律研究

阴极射线管是电子显示系统的主要部件,含有大量铅,其废弃物的浸出毒性超过我国危险废物鉴别标准.废阴极射线管资源化的关键是锥-屏的分离,分离后的锥-屏玻璃可用于显像管的再制造、铅的提炼和玻璃的再生产等.采用超声波辅助酸-热冲击法对低熔点玻璃的溶解规律进行研究的结果表明,同乙酸相比硝酸溶解低熔点玻璃的速率更大,硝酸浓度对低熔点玻璃的溶解速率有影响;低熔点玻璃中存在的金属离子与硝酸反应后生成的物质,如硝酸铅、硝酸钡、硝酸锌及硼酸等的存在会使低熔点玻璃的溶解速率降低.     

自组织神经网络在有害赤潮预警研究中的应用

根据非线性理论及有害赤潮的特点，探讨应用人工神经网络原理进行赤潮预警预报的方法，提出网络可塑性较强，无监督的ART－KOHONEN网络模型，阐述了其基本原理和算法。将该模型应用于辽宁省营口市鲅鱼圈海域，结果表明：该方法能较理想地解决无训练样本的分类识别问题，具有较高的精度，可用于有害赤潮的预警预报工作。     

An environmental approach for used oil management in Asian cities: a Bangkok' s experience

This paper addresses increasing concern about the pollution threat of used oil being illegally dumped and the impact of oil on air pollution and freshwater ecosystems in Asian countries. Used oil is a very serious waste management problem. These results call for management action such as maximising the collection and recovery of used oil. The Thai government recognizes the need to recycle used oil and has been active in encouraging programs to accomplish this goal. Thus unless new approaches and incentives are developed, used oil generation may become an increasing serious problem to our environment. The purpose of this study is to examine the technical and economic feasibility, of recycling used oils. In addition, this paper briefly discusses the problems to be overcome and outlines potential mechanisms for providing the necessary disposal controls in order to maximize the protection to public health and environmental quality from potential hazards posed by used lube oil disposal.     

旧工业建筑再生利用项目施工安全的评价及改进

针对旧工业建筑再生利用项目施工过程中存在诸多安全隐患的问题,首先,结合此类项目遗留工业垃圾冗杂、施工场地狭窄、部分构件拆换、大型机械使用受限的施工特点从4MTE角度构建施工安全评价指标体系。然后,在考虑指标赋权的主客观综合性与评价工作的未确知性后,建立了基于结构熵权法与未确知测度理论的旧工业建筑再生利用项目施工安全评价模型,并通过工程实例验证该模型,得出的评价结果与实际情况相符。最后,结合未确知测度单因素指标测度函数的特点,提出了施工安全管理改进策略的制定方法。     

A practical dialogue protocol for sustainability science to contribute to regional resources management: its implementation in Réunion

Over the last decade, adaptive co‐management has been recommended as a policy framework to address complex and uncertain resources management issues. Implementing this theoretical management concept requires the integration of multidisciplinary research and local knowledge. Yet practical protocols to link science, policymaking and societies have yet to be developed. We designed a protocol to produce legitimate, credible and relevant solutions to a regional resources management issue. This is a two‐component protocol. A stakeholder grid categorizes stakeholder representatives in three distinct specialized dialogue arenas: institution representatives, technical experts and local end‐users. An iterative co‐design process then builds on these arenas to assess the institutional legitimacy, technical credibility and empirical relevance dimensions of a common solution initiated by an initial plausible promise. We tested this framework in Réunion to address organic waste management issues at the regional level. The plausible solution explored was the introduction of a recycling industry involved in collecting organic waste and producing and selling organic fertilizers tailored for local crop systems. The protocol application outcomes were consolidated and documented scenarios accepted by all, with knowledge exchange and the broad spread of a stabilized expectation contributing to private initiatives and public policy change.     

More time in the kitchen,less time on the streets: the micropolitics of cultivating an ethic of care in alternative food networks

There is increased attention to alternative food efforts as individuals and groups seek to build stronger local food infrastructures to increase accessibility, transparency, and fairness with how food is grown, produced, and distributed. In considering individuals and families contending with food injustices and insecurities; concerns and questions have surfaced about what it means to privilege the leadership and participation of these communities in alternative food efforts. While there are no linear answers to these questions, this paper explores how one statewide food network in the United States seeks to involve youth contending with the juvenile justice system in a job readiness programme, Youth Kitchen, that interfaces the youth with farmers, chef educators, community organisations, and farmers markets. This paper contends that integrating alternative food and juvenile justice work is a complex terrain that both advances social justice and reproduces existing power asymmetries within alternative food networks. The inclusion of accounts from multiple stakeholders in the local food and juvenile justice system generates a multilayered view that moves away from an either sustainability or social justice rubric to a more process-oriented lens that reveals the strategic dilemmas that alternative food networks encounter. On the one hand, the social landscape of this programme promotes an ethic of care and shared ownership between the staff and participating youth. At the same time, akin to many alternative food networks, neoliberal interests bump against this ethic of care and white privilege seeps into staffing patterns and everyday programmes in ways that reproduce the status quo.     

成渝城市群碳排放空间关联结构演化及影响因素

本文基于社会网络分析法（SNA）以及二次分配程序（QAP）方法,利用成渝城市群2005~2016年面板数据,对成渝城市群碳排放空间关联性及影响因素进行研究.结果表明：①成渝城市群碳排放空间关联性显著,呈现出复杂的网络结构形态,样本期内,网络密度由0.16增长至0.68,关联关系数从38个增长为162个.②重庆、成都、绵阳和南充等城市位于网络的中心地位,发出了较多的关联关系,同时发挥着中介作用.③碳排放空间关联网络被划分成为5个层级,层级结构整体较为稳定,然而第一层级与第二层级存在较为严重的断层现象.④空间距离、人口数量差异以及经济水平差异是碳排放关联性的主要驱动因素.城市间空间距离越近、人口数量与经济水平差异越大,越容易产生碳排放关联关系.     

黑水虻转化厨余垃圾过程中病原菌灭活规律的研究与综合评价

黑水虻能够有效取食厨余垃圾等有机固体废弃物,其自身转化为昆虫蛋白和脂肪等生物质,将厨余垃圾转化为虫沙有机肥,处理过程是一种有机固体废弃物的资源化新方法.为评估黑水虻处理厨余垃圾的效率与安全性,本课题研究黑水虻在厨余垃圾处理过程中,对大肠杆菌O157：H7（EC）、鼠伤寒沙门氏菌（ST）及金黄色葡萄球（SA）的灭活能力,评价黑水虻体内的抑菌因子,分析3种病原菌对黑水虻生长增重及厨余转化效率的影响.经过18 d的黑水虻处理,研究发现：①第0和第6 d两次以6.4~7.1 log₁₀ CFU·g^-1的浓度向厨余垃圾中分别接种EC、ST和SA以后,EC经4~6 d处理被全部灭活、ST经3~4 d处理被全部灭活,SA经6 d处理,浓度下降到1.9~2.6 log₁₀ CFU·g^-1,但不能被全部灭活,病原菌的灭活效率呈现EC=ST>SA的趋势（p < 0.001）,且黑水虻体内无EC、ST或SA残留;②厨余垃圾降解过程中,初期和中期pH值主要呈现酸性（4.0~5.3）,对抑制EC、ST和SA起到了促进作用,后期pH值呈中性至弱碱性;③黑水虻对于EC和ST能够产生自身免疫抑制因子,且抑制活性ST>EC,但对SA无明显的免疫抑制能力,SA的灭活主要依赖于黑水虻肠道菌群的竞争性抑制作用;④黑水虻的体长、体重、预蛹率、产率,以及厨余垃圾的生物转化率和减量化率未受病原菌存在的影响,18 d后EC组、ST组和SA组的预蛹率均达到在80%以上,厨余减量化率分别达到74.0%、79.1%和78.5%,生物转化率分别达到13.0%、13.2%、19.4%.综上,黑水虻能够在彻底灭活EC、ST,99%灭活SA的同时,高效降解厨余垃圾（减量化率>74%）,并转化为虫体有机质（虫产率>10%）,是一种高效卫生的厨余垃圾资源化方法.今后的研究中,还需要加强以金葡菌为代表的抗逆性病原菌的灭活机制的探讨.