Multi-State System Reliability: A New and Systematic Review

AbstractReliability analysis considering multiple possible states is known as multi-state (MS) reliability analysis. Multi-state system reliability models allow both the system and its components to assume more than two levels of performance. Through multi-state reliability models provide more realistic and more precise representations of engineering systems, they are much more complex and present major difficulties in system definition and performance evaluation. MSS reliability has received a substantial amount of attention in the past four decades. This article presents a new and systematic review about multi-state system reliability. A timely review is an effective work related to improving the development of MSS theory. The review about the latest studies and advances about multi-state system reliability evaluation, multi-state systems optimization and multi-state systems maintenance is summarized in this paper

Classical Keggin intercalated into layered double hydroxides: facile preparation and catalytic efficiency in Knoevenagel condensation reaction

The family of polyoxometalate (POM) intercalated layered double hydroxides (LDHs) composite materials has shown great promise for the design of functional materials with numerous applications. It is known that intercalation of the classical Keggin polyoxometalate (POM) of [PW12O40]3- (PW12) into layered double hydroxides (LDHs) is very unlikely to take place by conventional ion exchange methods due to spatial and geometrical restrictions. In this paper, such intercalated compound of Mg0.73Al0.22(OH)2 [PW12O40]0.04•0.98H2O (Mg3Al-PW12) has been successfully obtained by adopting a spontaneous flocculation method. The Mg3Al-PW12 has been fully characterized using a wide range of methods (XRD, SEM, TEM, XPS, EDX, XPS, FT-IR, NMR, BET). XRD patterns of Mg3Al-PW12 exhibit no impurity phase usually observed next to the (003) diffraction peak. Subsequent application of the Mg3Al-PW12 as catalyst in Knoevenagel condensation reactions of various aldehydes and ketones with Z–CH2-Z‘ type substrates (ethyl-cyanoacetate and malononitrile) at 60 oC in mixed solvents (Vi-propanol:Vwater = 2 : 1) demonstrated highly efficient catalytic activity. The synergistic effect between the acidic and basic sites of the Mg3Al-PW12 composite proved to be crucial for the efficiency of the condensation reactions. Additionally, the Mg3Al-PW12 catalysed Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate demonstrated the highest turnover number (TON) of 47980 reported so far

A Review on the Little Ice Age and Factors to Glacier Changes in the Tian Shan, Central Asia

Mountain glaciers are a reliable and unequivocal indicator of climate change due to their sensitive response to changes in temperature and precipitation. The importance of mountain glaciers is best reflected in regions with limited precipitation, such as arid and semi-arid central Asia. High concentration of glaciers and meltwater from the Tian Shan contribute considerably to the freshwater resource in Xinjiang (China), Kyrgyzstan and nearby countries. Documenting glacier distribution and research on glacier changes can provide insights and scientific support for water management in central Asia. As the most recent glacial event, the Little Ice Age (LIA, approximately AD 1300–1850) signifies the cold periods prior to the warming trend in the twentieth century. Here we present an overview of topics recently studied on the modern and LIA glaciers in the Tian Shan of the central Asia. With data sets of the Glacier Inventory of China and the presumed LIA glacial extents, we applied statistical models in a case study of the eastern Tian Shan to examine the impact of local topographic and geometric factors on glacier area changes. The findings of glacier size and elevation as key local factors are representative and consistent with other studies

Collaborative Environmental Management: A Case Study Research of Stakeholders' Collaboration in the Nigerian Oil-producing Region

A myriad of environmental issues face the Nigerian industrial region, resulting from; oil and gas production, mining, manufacturing and domestic wastes. Amidst these, much effort has been directed by stakeholders in the Nigerian oil producing regions, because of the impacts of the region on the wider Nigerian economy. Although collaborative environmental management has been noted as an effective approach in managing environmental issues, little attention has been given to the roles and practices of stakeholders in effecting a collaborative environmental management framework for the Nigerian oil-producing region. This paper produces a framework to expand and deepen knowledge relating to stakeholders aspects of collaborative roles in managing environmental issues in the Nigeria oil-producing region. The knowledge is derived from analysis of stakeholders’ practices – studied through multiple case studies using document analysis. Selected documents of key stakeholders – Nigerian government agencies, multi-national oil companies and host communities, were analyzed. Open and selective coding was employed manually during document analysis of data collected from the offices and websites of the stakeholders. The findings showed that the stakeholders have a range of roles, practices, interests, drivers and barriers regarding their collaborative roles in managing environmental issues. While they have interests for efficient resource use, compliance to standards, sharing of responsibilities, generating of new solutions, and shared objectives; there is evidence of major barriers and these include resource allocation, disjointed policy, ineffective monitoring, diverse socio- economic interests, lack of stakeholders’ commitment and limited knowledge sharing. However, host communities hold deep concerns over the collaborative roles of stakeholders for economic interests, particularly, where government agencies and multi-national oil companies are involved. With these barriers and concerns, a genuine stakeholders’ collaboration is found to be limited, and as a result, optimal environmental management practices and policies have not been successfully implemented in the Nigeria oil-producing region. A framework is produced that describes practices that characterize collaborative environmental management might be employed to satisfy the stakeholders’ interests. The framework recommends critical factors, based on the findings, which may guide a collaborative environmental management in the oil producing regions. The recommendations are designed to re-define the practices of stakeholders in managing environmental issues in the oil producing regions, not as something wholly new, but as an approach essential for implementing a sustainable environmental policy. This research outcome may clarify areas for future research as well as to contribute to industry guidance in the area of collaborative environmental management

Key Audit Matters, Audit Quality and Audit Fees: Evidence from China

This paper examines the economic consequences of the implementation of the new auditing reporting standards from the standpoints of audit quality and audit fees in the context of the new auditing standards' exogenous event. Much of the existing research has focused on the empirical study of key audit matters on audit quality, but there is a lack of research on the relationship between key audit matters, audit quality and audit fees. Therefore, this paper selects China listed companies in 2015-2016 as the research sample and empirically tests the three hypotheses on key audit matters, audit quality and audit fees based on theoretical analysis. In the specific design of the empirical study, the absolute value of manipulative accrued profits was selected as an indicator of audit quality, and the results of the logarithm of audit fees and the disclosure of key audit matters were taken as the main explanatory and explanatory variables, together with control variables, as the empirical model of the paper. The Propensity Score Matching PSM method and Difference in Differences DID regression were used to analyse and regression test the model, and finally the empirical results were tested for robustness. The main findings of this paper are as follows: Firstly, A-share companies saw a significant decrease in accrual of earning management following the implementation of the key audit matter standard when compared to control group companies that did not implement the key audit matter standard. Secondly, audit fees have risen significantly since the key audit matter standard was implemented. Thirdly, an increase in audit fees leads to higher audit quality, implying that higher audit fees lead to greater care and dedication in the auditor's practice, which leads to higher audit quality

LiDAR-based Sinkhole Detection and Mapping in Knox County, Tennessee

Sinkholes are one of the major causes of damage to roads, buildings, and other infrastructure throughout the US. Sinkholes near or on roads are especially costly and occasionally deadly. Knox County and much of East Tennessee are located within karst areas (comprised of porous and soluble limestone and dolomite), deeming it at risk for sinkholes. Currently, Knox County uses contour maps to manually identify sinkholes. Supported by a geographic information system (GIS), we developed a streamlined model to identify the locations and extents of potential sinkholes using 1.3-ft resolution LiDAR (Light Detection and Ranging) data and applied it to the Dutchtown area of Knox County. This model consists of creating a Digital Elevation Model (DEM), filling the depressions in the DEM, extracting the depressions with a DEM difference, converting the depressions to a polygon shapefile, and analyzing the shape characteristics of the depressions. This work provides a pilot study for Knox County Stormwater Management in identifying potential sinkholes and has the potential to be used in other similar regions

Assessing the Impact of a Geospatial Data Collection App on Student Engagement in Environmental Education

A critical component of environmental education is to ensure student understanding and use of available technologies to better experience and analyze spatially distributed features of the environment. Combining mobile technologies with geographic information systems in field data collection may provide a unique opportunity for students to feel engaged in what they are learning and take ownership of their learning process. We customized an open access data collection application using Collector for ArcGIS and investigated its impacts on student engagement and perception of the incorporation of technology within an environmental science curriculum. Analyses of pre- and post-surveys indicate that the inclusion of geospatial technologies as a part of environmental curricula allows students to take the lead on their own research, view field data interactively as opposed to looking at a database in hindsight and analyze multiscale data as it is presented during field data collection. The findings of this study are consistent with previous studies, suggesting a strong association between the inclusion of geospatial technologies as a part of curricula and student engagement