A new approach for layout optimization in maintenance workshops with safety factors: The case of a gas transmission unit

In this study, an Integrated Simulation-Data Envelopment Analysis (DEA) approach is presented for optimum facility layout of maintenance workshop in a gas transmission unit. The process of repair of incoming parts includes various operations on different facilities. The layout problem in this system involves determining the optimum location of all maintenance shop facilities. Layout optimization plays a crucial role in this type of problems in terms of increasing the efficiency of main production line. Standard types of layouts including U, S, W, Z and straight lines are considered. First, the maintenance workshop is modeled with discrete-event-simulation. Time in system, average waiting time, average machine utilization, average availability of facilities, average queue length of facilities (AL) and average operator utilization are obtained from simulation as key performance indicators (KPIs) of DEA. Also, safety index and number of operators are considered as other KPIs. Finally, a unified non-radial Data Envelopment Analysis (DEA) is presented with respect to the stated KPIs to rank all layouts alternatives and to identify the best configuration. Principle Component Analysis (PCA) is used to validate and verify the results. Previous studies do not consider safety factor in layout design problems. This is the first study that presents an integrated approach for identification of optimum layout in a maintenance workshop of gas transmission unit by incorporating safety and conventional factors.     

宏观环境督察信息获取机制研究

本文对信息获取过程中的信息来源分析方法、信息采集方法、信息检索方法、信息加工方法进行了简要介绍,并将上述信息获取方法用于宏观环境督察信息获取过程中,研究了宏观环境督察信息获取机制,并对宏观环境督察信息获取过程进行了详细地分析,为后续的宏观环境督察信息发布提供了基础。     

静电除尘器的粉尘非稳态收集过程

为了全面揭示电除尘器粉尘非稳态收集过程,建立完整的非稳态静电收尘理论,根据静电学基本原理,研究了极板粉尘层电荷导人、积累、释放的过程,推导出随粉尘层厚度增长而改变的动态收尘电场强度计算公式,进而得到荷电粒子动态驱进速度公式,最终形成静电除尘非稳态收集理论.研究结果表明,在静电收尘过程中,粒子驱进速度与粉尘比电阻、工作电压、粉尘层厚度等多种因素有关;随粉尘比电阻的升高,收尘效率下降,当供电电压为最佳工作电压时收尘效率最高.针对不同比电阻粉尘进行了多项实验研究,实验结果与理论研究结果吻合.非稳态静电收尘理论成功地解释了实际静电收尘过程中与传统静电收尘理论相矛盾的地方,为静电除尘器的设计及其运行参数的选取提供了更为科学的理论基础.     

平顶山市区煤烟型大气污染现状及治理措施

分析了平顶山市区燃煤造成大气污染的严重现状及其原因,对实施"蓝天工程",提出了治理措施,政策措施,煤炭燃烧前、燃烧过程以及烟气排放三个阶段的除尘脱硫技术措施。     

The influence of collection facility attributes on household collection rates of electronic waste: The case of televisions and computer monitors

In the US, household electronic waste collected for recycling is primarily by voluntary drop-off at designated collection facilities. This study examines the influence of specific collection facility attributes (recycling fees charged, number of days open, and driving distance) on the household collection rate of e-waste in the US state of Maine. Data were collected for household computer monitor and television collection for 92 municipal waste transfer facilities representing 30% of the state's population for one year. Results suggest that recycling fees are negatively correlated with the number of televisions and computer monitors collected; furthermore, the more frequently facilities were open, the more televisions and computer monitors were collected per capita. The distance from the facility had no correlation, which prompted an analysis of whether the existence of a curbside collection system in the municipality was influential. Results show a negative correlation between computer monitor and television collection and a municipality having recycling (but not e-waste) curbside collection. Based on the results of this study, policymakers may be able to increase the collection rate of household e-waste by eliminating or lowering recycling fees, expanding collection days and hours to increase convenience, and/or considering curbside collection of e-waste.     

An innovative computer design for modeling forest landscape change in very large spatial extents with fine resolutions

Although forest landscape models (FLMs) have benefited greatly from ongoing advances of computer technology and software engineering, computing capacity remains a bottleneck in the design and development of FLMs. Computer memory overhead and run time efficiency are primary limiting factors when applying forest landscape models to simulate large landscapes with fine spatial resolutions and great vegetation detail. We introduce LANDIS PRO 6.0, a landscape model that simulates forest succession and disturbances on a wide range of spatial and temporal scales. LANDIS PRO 6.0 improves on existing forest landscape models with two new data structures and algorithms (hash table and run-length compression). The innovative computer design enables LANDIS PRO 6.0 to simulate very large (>10⁸ ha) landscapes with a 30-m spatial resolution, which to our knowledge no other raster forest landscape models can do. We demonstrate model behavior and performance through application to five nested forest landscapes with varying sizes (from 1 million to 100 million 0.09-ha cells) in the southern Missouri Ozarks. The simulation results showed significant and variable effects of changing spatial extent on simulated forest succession patterns. Results highlighted the utility of a model like LANDIS PRO 6.0 that is capable of efficiently simulating large landscapes and scaling up forest landscape processes to a common regional scale of analysis. The programming methodology presented here may significantly advance the development of next generation of forest landscape models.     

Techno-economic characteristics of wastewater treatment plants retrofitted from the conventional activated sludge process to the membrane bioreactor process

• Retrofitting from CAS to MBR increased effluent quality and environmental benefits. • Retrofitting from CAS to MBR increased energy consumption but not operating cost. • Retrofitting from CAS to MBR increased the net profit and cost efficiency. • The advantage of MBR is related to the adopted effluent standard. • The techno-economy of MBR improves with stricter effluent standards. While a growing number of wastewater treatment plants (WWTPs) are being retrofitted from the conventional activated sludge (CAS) process to the membrane bioreactor (MBR) process, the debate on the techno-economy of MBR vs. CAS has continued and calls for a thorough assessment based on techno-economic valuation. In this study, we analyzed the operating data of 20 large-scale WWTPs (capacity≥10000 m³/d) and compared their techno-economy before and after the retrofitting from CAS to MBR. Through cost-benefit analysis, we evaluated the net profit by subtracting the operating cost from the environmental benefit (estimated by the shadow price of pollutant removal and water reclamation). After the retrofitting, the removal rate of pollutants increased (e.g., from 89.0% to 93.3% on average for NH₃-N), the average energy consumption increased from 0.40 to 0.57 kWh/m³, but the operating cost did not increase significantly. The average marginal environmental benefit increased remarkably (from 0.47 to 0.66 CNY/g for NH₃-N removal), leading to an increase in the average net profit from 19.4 to 24.4 CNY/m³. We further scored the technical efficiencies via data envelopment analysis based on non-radial directional distance functions. After the retrofitting, the relative cost efficiency increased from 0.70 to 0.73 (the theoretical maximum is 1), while the relative energy efficiency did not change significantly. The techno-economy is closely related to the effluent standard adopted, particularly when truncating the extra benefit of pollutant removal beyond the standard in economic modeling. The modeling results suggested that MBR is more profitable than CAS given stricter effluent standards.     

贵溪冶炼厂烟尘布袋收集系统改造

介绍了贵溪冶炼厂烟尘布袋收集系统改造及运行状况。     

Effects of Detectability on Estimates of Geographic Range Size in Bignonieae

Abstract: Extinction risk has not been evaluated for 96% of all described plant species. Given that the Global Strategy for Plant Conservation proposes preliminary conservation assessments of all described plant species by 2010, herbarium specimens (i.e., primary occurrence data) are increasingly being used to infer threat components from estimates of geographic range size. Nevertheless, estimates of range size based on herbarium data may be inaccurate due to collection bias associated with interspecific variation in detectability. We used data on 377 species of Bignonieae to test the hypothesis that there is a positive relationship between detectability and estimates of geographic range size derived from herbarium specimens. This relationship is expected if the proportion of the true geographic range size of a species that is documented by herbarium specimens is given by the product of the true geographic range size and the detectability of the species, assuming no relationship between true geographic range size and detectability. We developed 4 measures of detectability that can be estimated from herbarium data and examined the relationship between detectability and 2 types of estimates of geographic range size: area of occupancy and extent of occurrence. Our results from regressing estimates of extent of occurrence and area of occupancy on detectability across genera provided no support for this hypothesis. The same was true for regressions of estimated extent of occurrence on detectability across species within genera. Nevertheless, regressions of estimated area of occupancy on detectability across species within genera provided partial support for our hypothesis. We considered 3 possible explanations for this mixed outcome: violation of the assumption of no relationship between true geographic range size and detectability; the relationships between estimated geographic range size and detectability may be an artifact of a negative relationship between estimated area of occupancy and the sampling variance of detectability; detectability may have had 2 opposite effects on estimated species range sizes: one determines the proportion of the true range of a species documented by herbarium specimens and the other determines the distribution of true range size for the species actually observed with herbarium data. Our findings should help improve understanding of the potential biases incurred with the use of herbarium data.