Probabilistic Failure Analysis of Complex Systems with Case Studies in Nuclear and Hydropower Industries

Detailed Monte-Carlo simulation of a complex system is the benchmark method used in probabilistic analysis of engineering systems under multiple uncertain sources of failure modes; such simulations typically involve a large amount of CPU time. This makes the probabilistic failure analysis of complex systems, having a large number of components and highly nonlinear interrelationships, computationally intractable and challenging. The objective of this thesis is to synthesize existing methods to analyze multifactorial failure of complex systems which includes predicting the probability of the systems failure and finding its main causes under different situations/scenarios. Bayesian Networks (BNs) have potentials in probabilistically representing complex systems, which is beneficial to predicting the systems failure probability and diagnosing its causes using limited data, logic inference, expert knowledge or simulation of system operations. Compared to other graphical representation techniques such as Event Tree Analysis (ETA) and Fault Tree Analysis (FTA), BNs can deal with complex networks that have multiple initiating events and different types of variables in one graphical representation with the ability to predict the effects, or diagnose the causes leading to a certain effect. This thesis proposes a multifactor failure analysis of complex systems using a number of BN-based approaches. In order to overcome limitations of traditional BNs in dealing with computationally intensive systems simulation and the systems having cyclic interrelationships (or feedbacks) among components, Simulation Supported Bayesian Networks (SSBNs) and Markov Chain Simulation Supported Bayesian Networks (MCSSBNs) are respectively proposed. In the latter, Markov Chains and BNs are integrated to acquire analysis for systems with cyclic behavior when needed. Both SSBNs and MCSSBNs have the distinction of decomposing a complex system to many sub-systems, which makes the system easier to understand and faster to be simulated. The efficiency of these techniques is demonstrated first through their application to a pilot system of two dam reservoirs, where the results of SSBNs and MCSSBNs are compared with those of the entire system operations simulation. Subsequently, two real-world problems including failure analysis of hydropower dams and nuclear waste systems are studied. For such complex networks, a bag of tools that depend on logically inferred data and expert knowledge and judgement are proposed for efficiently predicting failure probabilities in cases where limited operational and historical data are available. Results demonstrate that using the proposed SSBN method for estimating the failure probability of a two dam reservoir system of different connections/topologies results in probability estimates in the range of 3%, which are close to those coming from detailed simulation for the same system. Increasing the number of states per BN variables in the states’ discretization stage makes the SSBN results converge to the simulation results. When Markov chains are integrated with SSBN (i.e. MCSSBN), the results depend on the MCSSBN approach that is used according to the scenarios of interest that need to be included in the BN representation. Evidence of system failure can be used to diagnose the main contributors to the failure (i.e. inflow, reservoir level, or defected gates). This posterior diagnostic capability of the BN is distinctive for the real world case studies presented in this thesis. In Mountain Chute Dam that is operated by Ontario Power Generation, the main contributors to system failure, according to the logically inferred data and expert knowledge, are inadequate discharge capacity of the sluiceway, electromechanical equipment failure, head gates failure, non-safe ice loading, high inflow, high rain/precipitation, sluice gate failure, and high water pressure. While for the Nuclear Waste Management system, the main contributors to system failure according to the known and assumed data are due to high pressures and bentonite failures. In summary, modelling, validating, and developing appropriate modifications of the BN method for applications in complex systems failure analysis is the major contribution of this thesis

A MILP model for an integrated project scheduling and multi-skilled workforce allocation with flexible working hours

In this paper, we integrate two decision problems arising in various applications such as production planning and project management: the project scheduling problem, which consists in scheduling a set of precedence-constrained tasks, where each task requires executing a set of skills to be performed, and the workforce allocation problem which includes assigning workers as scarce resources to the skills of each task. These two problems are interrelated as the tasks durations are not predefined, but depend on the number of workers assigned to that task as well as their skill levels. We here present a mixed integer linear programming model that considers important real life aspects related to the flexibility in the use of human resources, such as multi-skilled workers whose skill levels are different and measured by their efficiencies. Hence, execution times of the same workload by different workers vary according to these efficiencies. Moreover, the model considers the flexible working time of employees; i.e. the daily and weekly workload of a given worker may vary from one period to another according to the work required. Furthermore, efficient team building is incorporated in this model; i.e. assigning an expert worker and one or more apprentice worker(s) together with the purpose of skill development thanks to knowledge transfer. A numerical example is provided to check the performance of the model

Enhancement of Blast Resistance of R.C Beams Using Micro/Nano Silica in Presence of Steel Fibers

An analytical investigation using ABAQUS/Explicit dynamic analysis was carried out to investigate the effect of using Micro/Nano silica in the presence of steel fibers on improving the dynamic response of reinforced concrete beams. According to the results of Magnusson and Hallgren's experimental investigation, the FE model has been well verified and calibrated. The finite element test program was extended further to study the effect of tensile reinforcement ratio by (0.5%, 0.78%, and 1.13%) comparing with the enhancement of concrete’s material on the behavior of tested R.C beams under blast loading. The results where compared in terms of changes in the max deflection at mid-span and flexural toughness values. The results showed that the combination between the compressive and flexural characteristic of concrete is necessary in case of high steel reinforcement ratio to reduce the brittle behavior of the R.C structure element, especially when the R.C elements exposed to a high strain rate loading due to the addition value of (DIF) for steel reinforcement properties which make the element stiffer than usual, compared with quasi-static loading condition.           &nbsp

A reproducible protocol for regeneration and transformation in canola (Brassica napus L.)

The objective of the present study is to develop an efficient protocol for shoot and plant regeneration using five commercial canola cultivars grown under the Egyptian agricultural conditions. The regeneration efficiency from hypocotyl explants was examined. The data indicated that embryonic calli were formed within two weeks in the presence of 1 mgl-1 2,4-D. Adventitious shoots emerged from the embryonic callus in the presence of 4.5 mgl-1 BA. The cultivars showed a varied response to shoot regeneration. Regeneration frequency was high in the cultivar Sarow-4 (68%) followed by Masrri L-16 (64%) compared with the other cultivars tested. Hypocotyl explants from the cultivars Sarow-4 and Semu-249 were inoculated and co-cultivated with Agrobacterium tumefaciens strain LBA4404 harboring a binary vector pBI-121 containing the neomycin phosphotransferase-II gene (NPT-II). The resulted putative transgenic plantlets were able to grow under knanamycin containing medium. The stable integration of the NPT-II gene into the plant genomes was tested by PCR using NPT-II -specific primers. The GUS gene expression can be detected only in the transgenic plants. The reported protocol in the present study is repeatable and can be used to regenerate transgenic canola plants expressing the genes present in A. tumifaciens binary vectors.Keywords: Agrobacterium, canola, GUS assay, regeneration, fransformation, NPT II gen

Učinak zamjene obroka od pšeničnih mekinja obrokom sa sjemenkama kima na nesenje, kvalitetu jaja i masnokiselinski profil u kokoši nesilica

The objective of the present study was to investigate the effect of substituting wheat bran (WB) with cumin seed meal (CSM) on laying performance, egg quality characteristics and egg-yolk fatty acids profile in laying hens. A total of 180 Bovans hens at 55 weeks of age were divided randomly into three treatments. The CSM was incorporated into a standard corn- and soybean meal-based diet by replacing 0, 50, and 100% of WB [i.e., 100% WB (control), 50% WB+50% CSM and 100% CSM] from 55 to 61 weeks of age. Body weight was measured at the beginning and end of the experiment. Feed intake, hen-day egg production and egg weight were recorded daily. At 61 weeks of age, 30 eggs were taken at random from each treatment group to determine the egg quality characteristics. Replacing 100% of WB by CSM did not affect body weight, however, hen-day egg production, egg weight and egg mass significantly increased, while feed conversion ratio significantly decreased (P<0.05). Haugh unit, shell thickness and yolk color significantly increased by CSM substitution in comparison with 100% WB. Plasma concentrations of total cholesterol, triglycerides, LDL-cholesterol and glutamic oxalacetic transaminase (GOT) significantly decreased by replacing WB with CSM, while, plasma HDL-cholesterol significantly increased. Furthermore, the liver malondialdehyde (MDA) concentration significantly decreased, while vitamin E, linoleic acid and alpha-linolenic acid significantly increased (P<0.05) due to CSM inclusion. Therefore, it could be concluded that substitution of WB with CSM could improve laying performance and egg quality characteristics, and reduce lipid peroxidation in laying hens.Cilj ovoga rada bio je istražiti učinak zamjene obroka s pšeničnim mekinjama (WB) obrokom sa sjemenkama kima (CSM) na nesenje, kvalitetu jaja te profil masnih kiselina u žumanjku jajeta kokoši nesilica. Ukupno je 180 Bovans kokoši u dobi od 55 tjedana slučajnim odabirom podijeljeno u tri pokusne skupine, u kojima su sjemenke kima dodane u standardni obrok s kukuruzom i sojom zamjenjujući 0, 50 i 100 % pšeničnih mekinja. Tako je kontrolna skupina hranjena obrocima sa 100 % pšeničnih mekinja, druga skupina s 50 % obroka s pšeničnim mekinjama i 50 % obroka sa sjemenkama kima, a treća skupina obrokom koji je sadržavao 100 % sjemenki kima. Pokusno razdoblje je trajalo od 55. do 61. tjedna starosti nesilica. Tjelesna je masa mjerena na početku i na kraju pokusa. Unos hrane, dnevna proizvodnja jaja i njihova masa bilježili su se svaki dan. U dobi od 61 tjedna iz svake je skupine slučajnim odabirom uzeto 30 jaja kako bi se odredila njihova kvaliteta. zamjenjujući 100 % obrok od pšeničnih mekinja sjemenke kima nisu utjecale na tjelesnu masu, no ipak su dnevna proizvodnja, težina i masa jaja znakovito porasle, dok se stopa konverzije hrane znakovito smanjila (P<0,05). Haugh-ova jedinica, debljina ljuske i boja žumanjka znakovito su porasle u skupinama u kojima su pšenične mekinje zamijenjene sjemenkama kima u odnosu na kontrolnu skupinu. Ukupni kolesterol, trigliceridi, LDL-kolesterol i glutaminska oksalooctena transaminaza (GOT) znakovito su sniženi u skupinama u kojima su pšenične mekinje zamijenjene sjemenkama kima, dok je HDL-kolesterol znakovito povišen. nadalje, koncentracija malondialdehida (MDA) u jetri znakovito je snižena, dok su vitamin E, linolna i alfa-linolna kiselina znakovito porasli (P<0,05) uslijed dodanih sjemenki kima. Može se zaključiti da zamjena obroka s pšeničnim mekinjama obrokom sa sjemenkama kima može poboljšati nesenje i kvalitetu jaja te smanjiti lipidnu peroksidaciju u kokoši nesilica

Aggregate production planning considering organizational learning with case based analysis

Responding rapidly to customer needs is one of the main targets of industrial organizations that want to survive in the current market competition. This objective can be attained through robust planning. Workforce productivity is considered one of the important entities in production planning. However, it has a dynamic nature, i.e. the productivity growths thanks to on-job training or learning phenomenon. Considering this fact in manufacturing planning enhances the robustness of the developed plans. The present paper presents a mathematical model for medium-range production planning that is used to find the optimal aggregate production plan. The model aims to optimize the total production costs while respecting most of the operational constraints and considering the process of organizational learning. The presented model is constructed relying on the real industrial practices; the outcome is a mixed-integer linear program. The model was validated and checked using real data collected from an Egyptian factory that produces electric motors for home appliances. The proposed mathematical model was optimally solved using “ILOG-CPLEX 12.6”. By comparing the results obtained versus that of the method adopted in the factory, a cost reduction of 6.3% is achieved for the presented data set. A set of managerial aspects are concluded after the model analysis. Moreover, the impact of using detailed learning rates on the production cost is discussed

Clinical, biochemical and inflammatory predictors of mortality in patients with spontaneous bacterial peritonitis

Background: Spontaneous bacterial peritonitis (SBP) is a serious complication of liver cirrhosis. It contributes to high morbidity and mortality in this population. In-hospital mortality of SBP ranges between 20% and 40%, suggesting that further refinements are essential in managing SBP. Early recognition of high-risk patients would enable us to reduce the short-term mortality.Objective: The current study aimed to evaluate the value of clinical, biochemical and inflammatory markers in the prediction of 1-month and 3-month cumulative mortality in patients with SBP.Patients and methods: Two hundred patients with a confirmed diagnosis of SBP were enrolled. They were admitted and received the proper treatment at the National Liver Institute Hospital-Menoufia University, Egypt. Patients were prospectively followed up for mortality over a period of three months. Predictors of mortality were assessed and analyzed.Results: Mortality rates were 20% and 41% at 1 month and 3 month respectively. Our findings showed that low blood pressure, abdominal pain, fever, higher Child-Pugh score, MELD score, serum bilirubin, INR, serum creatinine, C-reactive protein to albumin (CRP/Albumin) ratio, neutrophil–lymphocyte ratio (NLR), massive splenomegaly and large ascites have been demonstrated as risk factors associated with short-term mortality.Conclusion: SBP carries a high risk of mortality among cirrhotic patients. Clinical parameters (low blood pressure, abdominal pain, fever, massive splenomegaly and large ascites), prognostic scores (Child-Pugh and MELD) and inflammatory markers (CRP, CRP/albumin ratio, and NLR) seem to be accurate and reliable tools that could independently predict short-term mortality in patients with SBP

Phenotypic and Genotypic Characterization of ESBL-Producing Escherichia coli and Klebsiella pneumonia isolates from Patient’s Urine specimens

Introduction: Extended-spectrum β-lactamases (ESBL)-producing Enterobacteriaceae are a clinical threat that may cause nosocomial as well as community-acquired infections. E.coli and Klebsiella are among the most common Gram-negative bacilli causing urinary tract infections. Aim of the study: Molecular confirmation of ESBL production among phenotypically proved ESBL-producing E.coli and Klebsiella. Materials and Methods: A total of 64 community and hospital-acquired Enterobacteriaceae suspected to produce ESBLs by routine antimicrobial susceptibility test. Identification of species of Enterobacteriacea was done by the API 20E identification system. ESBL production was detected by double disc synergy test (DDST) followed by detection of the encoding genes by PCR using primers for bla-TEM, bla-CTX-M1, bla-CTX-M2, bla-SHV and bla-PER genes. Results: E.coli (n=40) and Klebsiella pneumonie (n=24) were identified by API 20E. Fourty nine isolates were positive for ESBL-production by DDST. Fifty seven isolates proved to produce ESBLs by PCR. The bla-TEM, bla-CTX-M1 and bla-PER were the most prevalent ESBL genes detected by PCR. Conclusion: The double disc synergy test showed sensitivity of 82.5% in relation to PCR. The study showed high prevalence of ESBLs in E.coli and Klebsiella pneumonie with bla-TEM, bla-CTX-M1 and bla-PER as the predominant ESBL genes. Key words: E.coli, Klebsiella pneumonie, ESBL, DDST, PCR