Performance Evaluation of Tree-based Mobility Management in Infrastructure Incorporated Mobile Ad Hoc Networks

Khalil Ur Rahman,Trung-Dinh Han,Hoon Oh 한국통신학회 2009 한국통신학회 학술대회논문집 Vol.2009 No.6

Mobility management of mobile nodes in the integrated network of infrastructure networks and wireless ad hoc networks is required to provide them with Internet connectivity. Tree topology has been proven to be highly dependable for mobility management where a mobile node registers with a gateway along tree paths. In this paper, we present an efficient tree-based mobility management method by building trees. The approach is evaluated against the other traditional methods - proactive, reactive, and hybrid by resorting to simulation. The results show that the new approach outperforms the other ones and also is very robust against the rapid change of topology.

Risk Informed Design of I&C Architecture for Research Reactors

Khalil Ur, Rahman,Gyunyoung Heo IEEE 2015 IEEE transactions on nuclear science Vol.62 No.1

<P>A deterministic design philosophy for systems, structures, and components of nuclear facilities, accepted by all stakeholders, has been adopted to address safety concerns. However, over-conservatism makes the design of nuclear facilities, especially research reactors, expensive; therefore, the industry needs to reevaluate its level of over-conservatism to obtain an optimized design. This paper proposes a probabilistic design and optimization approach for instrumentation & control (I&C) systems of research reactors based on sensitivity, availability criteria, and cost. Compared to commercial nuclear power plants, research reactors are sensitive to the cost competitiveness of I&C systems, so optimization of I&C system design is needed. As a case study, we formulated four architecture configurations for a reactor protection system and performed the reliability feature analysis, assessed cost, and computed reliability index. In addition to International Electrotechnical Commission (IEC) and American Society of Mechanical Engineers (ASME) criteria, we introduce the reliability index, a novel parameter describing the correlation between cost and reliability used to determine the point at which an I&C architecture has been optimized. To observe the significance of this study, we compared our results with a benchmark architecture. Our novel probabilistic design and optimization approach produced two optimized I&C architectures with design cost reductions of 30-40% compared to the benchmark architecture, while maintaining safety and availability.</P>

Sensitivity Analysis of Digital I&C Modules in Protection and Safety Systems

Khalil Ur, Rahman,Zubair, M,Heo, G IOP Publishing 2013 IOP conference series. Materials science and engin Vol.51 No.-

Risk-Informed Design of Hybrid I&C Architectures for Research Reactors

Rahman, Khalil Ur,Kyungho Jin,Gyunyoung Heo IEEE 2016 IEEE transactions on nuclear science Vol.63 No.1

<P>The risk-informed probabilistic design approach toward the hybridized instrumentation and control (I&C) systems of research reactors based on sensitivity and availability criteria has been applied in this paper. An optimized hybrid I&C architecture is worthwhile and emphasized because of low budget for I&C and simple functionality of research reactors. Hybridization in input/output modules using analog and digital components has been introduced to enhance diversity and provide resistance to common mode failures. Based on the approach, two hybrid (named I and II) architecture configurations of reactor protection systems have been formulated from a reference architecture with an analysis performed on their reliability features; availability and sensitivity assessments were performed using Bayesian network models. International Electrotechnical Commission and American Society of Mechanical Engineers criteria have been applied for an evaluation of the architecture reliability features. A novel concept for assessing the sensitivity and risk impact of components based on single and multiple component risk reduction indices have been introduced and used for sensitivity evaluations. It was determined that hybrid-II architectures yielded good reliability features compared to hybrid-I and the reference architecture because the unavailability of hybrid-II architecture decreases by one or two orders of magnitude by just adding one more bi-stable processor based on the risk feedback of hybrid-I architecture. It was concluded that architecture designs based on hybrid and risk-informed design approaches have the ability to maintain high levels of safety and availability through cost-savings.</P>

Identifying the Annual and Seasonal Trends of Hydrological and Climatic Variables in the Indus Basin Pakistan

Muhammad Shahid,Khalil Ur Rahman 한국기상학회 2021 Asia-Pacific Journal of Atmospheric Sciences Vol.57 No.2

The uneven hydro-climatic changes and droughts have significantly affected the socioeconomic condition of people dependent on the Indus basin, Pakistan. This study aims to examine the annual and seasonal hydro-climatic trends for the Upper Indus Basin (UIB), Middle Indus Basin (MIB) and Lower Indus Basin (LIB). The mean monthly data from 44 meteorological and 30 hydrological stations have been analyzed. The Mann Kendall test, Spearman’s rho test, linear trend estimation method and Van Belle and Hughes test have been used to perform analysis of hydro-climatic trends. The Standardized Precipitation Index (SPI), Sequential Mann Kendall test and rescaled range analysis have been introduced to detect the seasonal and annual drought. The results showed that significant warming has been observed throughout the Indus basin. The spring precipitation decreased significantly in the UIB with the maximum decrease of 5.3 mm/year. The streamflow of UIB has presented significant increasing trends on annual basis and spring season due to significant warming and glacier melt. The streamflow of MIB presented a significant increase in spring, and it decreased in summer, which can be related to significant warming. The annual precipitation of LIB presented significant increasing trends, and a similar trend has been observed in autumn. However, the LIB showed decreasing streamflow trends on an annual and seasonal basis which is possible due to significant warming trends and water regulation in upstream. The Hurst index value indicates that the Indus basin is expected to maintain current trends and the degree of drought is expected to increase in the future.

Problems and Benefits of the China-Pakistan Economic Corridor (CPEC) for Local People in Pakistan: A Critical Review

Shakir Ullah,Usman Khan,Khalil Ur Rahman,Aman Ullah 경남대학교 극동문제연구소 2021 ASIAN PERSPECTIVE Vol.45 No.4

This study provides a critical literature review of the benefits and problems associated with one of the largest Chinese- funded development projects, the China-Pakistan Economic Corridor (CPEC), with particular focus on the implications of this project for local people in Pakistan. CPEC is one of the most significant development projects in Pakistan, covering infrastructure, agriculture, and energy cooperation. Although some studies have examined challenges and problems brought about by CPEC, the majority of them fail to examine specific localities and the Pakistani communities that have been impacted by the project. Hence, most of the investigations have reported general development impacts rather than indicating whether and how CPEC has brought either benefits or problems to local people. In examining previously published studies on CPEC, this essay highlights gaps in research, especially from anthropological and sociological perspectives, with the goal of encouraging further studies from the vantage point of the local communities regarding development projects in Pakistan.

Study on Nuclear Accident Precursors Using AHP and BBN

Park, Sujin,Yang, Huichang,Heo, Gyunyoung,Zubair, Muhammad,Khalil Ur, Rahman Hindawi Limited 2014 Science and technology of nuclear installations Vol.2014 No.-

<P>Most of the nuclear accident reports used to indicate the implicit precursors which are not easily quantified as underlying factors. The current Probabilistic Safety Assessment (PSA) is capable of quantifying the importance of accident causes in limited scope. It was, therefore, difficult to achieve quantifiable decision-making for resource allocation. In this study, the methodology which facilitates quantifying these precursors and a case study were presented. First, four implicit precursors have been obtained by evaluating the causality and hierarchy structure of various accident factors. Eventually, it turned out that they represent the lack of knowledge. After four precursors are selected, subprecursors were investigated and their cause-consequence relationship was implemented by Bayesian Belief Network (BBN). To prioritize the precursors, the prior probability is initially estimated by expert judgment and updated upon observations. The pair-wise importance between precursors is calculated by Analytic Hierarchy Process (AHP) and the results are converted into node probability tables of the BBN model. Using this method, the sensitivity and the posterior probability of each precursor can be analyzed so that it enables making prioritization for the factors. We tried to prioritize the lessons learned from Fukushima accident to demonstrate the feasibility of the proposed methodology.</P>