热力耦合作用对桩及桩间土拱效应的影响研究*

为研究负温对桩侧应力及桩间土拱效应的影响,通过FLAC3D软件模拟热力耦合作用下新型排桩冻结法中桩间土拱效应的变化及温度效应下的桩间距,并根据巴霍尔金单排管冻结稳态温度场解析解,建立冻结壁平均温度区域解。研究结果表明:桩土接触面的应力分量τxy近似线性变化,应力分量σx近似均匀分布,温度降低对应力分量τxy的分布影响较小,但对应力分量σx的影响较大;负温使桩间距发生变化,且整体平均应力的分布也更加均匀化;通过与巴霍尔金解析解对比,证明单排管冻结温度场模型的可行性,在此基础上建立的单排管冻结壁平均温度区域解,其与数值模拟结果相差不超过1 ℃,计算误差满足工程要求;随着冻结时间的增加,单排管冻结壁温度场呈抛物线形式降低。     

Optimization of capture–recapture monitoring of elusive species illustrated with a threatened grasshopper

Information on population sizes and trends of threatened species is essential for their conservation, but obtaining reliable estimates can be challenging. We devised a method to improve the precision of estimates of population size obtained from capture–recapture studies for species with low capture and recapture probabilities and short seasonal activity, illustrated with population data of an elusive grasshopper (Prionotropis rhodanica). We used data from 5 capture–recapture studies to identify methodological and environmental factors affecting capture and recapture probabilities and estimates of population size. In a simulation, we used the population size and capture and recapture probability estimates obtained from the field studies to identify the minimum number of sampling occasions needed to obtain unbiased and robust estimates of population size. Based on these results we optimized the capture–recapture design, implemented it in 2 additional studies, and compared their precision with those of the nonoptimized studies. Additionally, we simulated scenarios based on thresholds of population size in criteria C and D of the International Union for Conservation of Nature (IUCN) Red List to investigate whether estimates of population size for elusive species can reliably inform red-list assessments. Identifying parameters that affect capture and recapture probabilities (for the grasshopper time since emergence of first adults) and optimizing field protocols based on this information reduced study effort (−6% to −27% sampling occasions) and provided more precise estimates of population size (reduced coefficient of variation) compared with nonoptimized studies. Estimates of population size from the scenarios based on the IUCN thresholds were mostly unbiased and robust (only the combination of very small populations and little study effort produced unreliable estimates), suggesting capture–recapture can be considered reliable for informing red-list assessments. Although capture–recapture remains difficult and costly for elusive species, our optimization procedure can help determine efficient protocols to increase data quality and minimize monitoring effort.     

海洋碳汇渔业绿色发展空间外溢效应评价研究

海洋碳汇渔业绿色发展空间关联性及其外溢效应对于海水养殖业的有效协调和区域海洋环境的有效保护具有重要意义,科学估算沿海各省(自治区)海水养殖渔业碳汇量并探讨其空间相关性特征是制定差异化渔业碳汇发展政策的重要基础。根据2006—2016年中国大陆沿海9个省(自治区)的碳汇渔业资源清查数据,在检验和比较省域空间渔业碳汇总量相关性特征的基础上,运用空间计量模型分析了渔业碳汇的外溢效应及其影响因素。结果表明:①中国海水养殖渔业碳汇量整体上呈现上升趋势,但各省渔业碳汇量也存在明显差异。②研究期内的Moran's I指数整体呈现为"V"型的波动变化特征,渔业碳汇在省域空间分布上的差异性并不是随机的,而是具备显著的空间相关性。③海水养殖渔业碳汇存在明显的空间外溢效应,通过随机效应的杜宾模型分解后得出渔业产值、劳动力投入的直接效应为正,而渔业受灾面积和科研项目经费投入的直接效应为负;从间接效应来看,渔业产值在各省域间存在竞争与依存关系,海水养殖业劳动力投入和渔业技术推广的项目经费投入在各省域间存在互补关系。因此,中国沿海各省份在发挥海洋水产养殖业生态功能时,应当考虑省域区位因素,合理制定兼具差异化和协调性的海洋碳汇渔业发展政策。     

Failure mode and effect analysis using regret theory and PROMETHEE under linguistic neutrosophic context

Failure mode and effect analysis (FMEA), which aims to identify and assess potential failure modes in a system, has been widely utilized in diverse areas for improving and enhancing the performance of systems due to it is a powerful and useful risk and reliability assessment instrument. However, the conventional FMEA approach has been suffered several criticisms for it has some shortcomings, such as unable to handle ambiguous and uncertain information, neglect the relative weights of risk criteria, and without considering the psychological behaviors of decision-makers. To ameliorate these limitations, this paper aims at establishing a hybrid risk ranking model of FMEA via combing linguistic neutrosophic numbers, regret theory, and PROMETHEE (Preference ranking organization method for enrichment evaluation) approach. In the presented model, linguistic neutrosophic numbers are adopted to capture decision-makers’ evaluation regarding the failure modes on each risk criterion. A modified PROMETHEE approach based on regret theory is presented to obtain the risk priority of failure modes considering the psychological behaviors of decision-makers. Moreover, a maximizing deviation model and TOPSIS (Technique for order preference similar to ideal solution) are separately applied to derive the weights of risk criteria and decision-makers. Finally, a numerical example relating to the supercritical water gasification system is employed to implement the presented method, and the effectiveness and feasibility of the proposed model are validated by the results derived from a sensitivity and comparison analysis.     

呼吸效应对矿井封闭火区氧浓度的影响分析

为避免因火区封闭导致重大安全事故发生,通过采集某矿井1 d内3个不同监测点的大气压力变化情况,建立大气压力波动模型并分析计算,同时建立火区内外压差100,750 Pa情形下的氧浓度模型进而获得火区内侧氧气浓度因呼吸效应,在不同压差、体积大小火区、风阻、瓦斯涌出量、封闭时刻等多因素耦合影响下随时间的变化规律,以评估火区危险性。研究结果表明:井下大气随地面大气周期波动,封闭火区内、外侧之间的气压差因外界大气波动呈现16 h的余弦波动和8 h的线性波动周期变化;密闭质量好的火区具有更好地抗干扰性,内侧氧浓度的降低主要依靠瓦斯稀释;密闭质量差的火区,内侧氧浓度易受到火区涌出瓦斯、外界涌入大气双重影响;火区氧浓度在2%~12%之间波动,以至火区存在发生瓦斯爆炸的可能性;火区内外压差较大时,氧浓度波动变化幅度更大,危险作用持续时间更长。结合火区氧浓度波动模型,可有效地对矿井火区采取安全的防范措施,避免瓦斯爆炸事故发生。     

深部煤层钻屑粒度随钻进深度分布规律

为了研究煤层钻屑粒度随钻进深度分布规律,选取具有冲击危险性的平煤八矿己15煤作为研究对象,采取钻屑量测试和孔口瓦斯浓度监测,通过筛分实验煤样并应用Rosin Rammler分布模型,探究了钻屑粒度和钻屑量大小随孔深变化关系,分析不同点钻屑粒度分布特征。结果表明:小于0.075 mm钻屑粒度分布随孔深变化与钻屑量变化规律相吻合;不同钻孔随深度变化分别对应不同Rosin Rammler分布函数,随着应力过渡越平缓,粒径分布宽度系数n值越小,煤体应力越大粒径相关系数D越大;不同范围钻屑粒度占比大小也会影响钻屑量大小;在钻屑量较大时,孔口瓦斯体积分数会出现增高现象。通过对钻屑粒度分布规律分析,更好地了解深部煤体应力分布,有助于冲击危险的预警。     

The inhibitory combustion reaction performance and tail gas analysis of composite ultra-fine dry powder extinguishing agent containing different additives

For lack of an extinguishing agent with high-efficiency, non-toxic and environmentally friendly, a new type of extinguishing agent was fabricated to solve such an urgent problem. In this study, the zinc borate (ZB) and ferrocene (Fe(Cp)₂) were utilized as two additives for extinguishants to suppress combustion reaction and the toxicity of the tail gas was detected. The mass fraction of ZB corresponding to the optimal inhibitory effect was determined to be 0.5–1.5%, by contrast, the optimum interval of Fe(Cp)₂ was detected as 0.5–1.0%. Similarly, with the increasing proportion of the two additives, the homologous inhibitory action was gradually weakened. From the perspective of thermogravimetric analysis (TGA), it was indicated that the ZB accelerated the pyrolysis process of the extinguishant, making its thermal decomposition process more thoroughly. Meanwhile, the differential scanning calorimetry (DSC) demonstrated that the decomposition efficiency was markedly improved when the amount of ZB was maintained at 0.5–1.5%. Besides, the tail gas tests were implemented to assess the extent of toxic and harmful properties. In terms of the carbon monoxide (CO) and carbon dioxide (CO₂) generated, once the mass fraction of ZB and Fe(Cp)₂ was less than 1.5% and 1.0% respectively, the concentration of CO and CO₂ was distinctly lower than that without additives. Moreover, the inhibitory ability on nitrogen oxides (NOx) was enhanced when the mass fraction of the two additives was kept below 1.0%. The results confirmed that a more practical extinguishant was proposed and it can provide guidance for the application and development of extinguishants.     

An LC-MS/MS method for creatine and creatinine analysis in paraquat-intoxicated patients

Abstract

A sudden increase in serum creatinine after paraquat intoxication has been reported in several clinical studies. However, this dramatic change of creatinine may be possibly due to an interconversion of creatine-creatinine in relation to paraquat toxicity. In order to investigate the creatine-creatinine relationship, a liquid chromatography tandem mass spectrometry in combination with electrospray ionization was developed and validated for simultaneous determination of creatine and creatinine in the serum. The chromatographic separation was achieved on a Gemini® C₆-Phenyl column with a gradient elution consisting of 0.1% formic acid in ultrapure water and methanol as the mobile phase. The method yielded suitable levels of specificity and selectivity, and calibration curves of creatine and creatinine in serum were linear over the concentration range of 0.5–200?µg mL^?1. The limit of quantification of both compounds was 0.5?µg mL^?1, and the method was accurate within the recovery range of 96.23–102.75%, indicating the robustness of the method. The method was successfully applied to toxicological samples from paraquat-intoxicated patients, and the concentrations of creatine and creatinine were quantified. High creatine concentrations in serum samples were observed which may lead to high serum creatinine despite normal kidney function as creatine is converted to creatinine in proportion to its concentration.     

粗枝云杉不同径级根系分解过程中4种养分元素的释放特征

植物根系分解是养分元素进入土壤的重要途径之一.为了解径级对根系分解过程中养分元素释放的潜在影响,以川西亚高山针叶林中的粗枝云杉(Picea asperata)为对象,采用原位分解试验,研究云杉3个径级(0-2 mm,2-5 mm和5-10 mm)根系分解过程中钾(K)、钠(Na)、钙(Ca)和镁(Mg)元素的浓度、残留...     

Can we gain precision by sampling with probabilities proportional to size in surveying recent landscape changes in the Netherlands?

Seventy-two squares of 100 ha were selected by stratified random sampling with probabilities proportional to size (pps) to survey landscape changes in the period 1996–2003. The area of the plots times the urbanization pressure was used as a size measure. The central question of this study is whether the sampling with probabilities proportional to size leads to gain in precision compared to equal probability sampling. On average 1.03 isolated buildings per 100 ha have been built, while 0.90 buildings per 100 ha have been removed, leading to a net change of 0.13 building per 100 ha. The area with unspoiled natural relief has been reduced by 2.3 ha per 100 ha, and the length of linear relicts by 137 m per 100 ha. On average 74 m of linear green elements have been planted per 100 ha, while 106 m have been removed, leading to a net change of −31 m per 100 ha. For the state variables ‘unspoiled natural relief', ‘ linear relicts', ‘removed linear green elements', and ‘new – removed linear green elements' there is a gain in precision due to the pps-sampling. For the remaining state variables there is no gain or even a loss of precision (`new buildings', ‘removed buildings', ‘new – removed buildings', ‘new linear green elements'). Therefore, if many state variables must be monitored or when interest is not only in the change but also in the current totals, we recommend to keep things simple, and to select plots with equal probability.