A STRUCTURED RELIABILITY AND MAINTAINABILITY ASSESSMENT MODEL: AN APPLICATION TO HIGH VOLTAGE MOTORS

Motors are one of the vital equipment and generally the higher in numbers in oil and gas processing facilities. The primary function is to drive the process equipment such as compressors, fans, pumps etc. Unreliability of the motors is a threat to safety but also to production loss and high operating expenditure. Motors experience higher failure rates and maintenance costs with age due to lower focus during useful life periods. In order to properly address the long-term reliability and maintainability of the motors and associated subsystems, this paper aims to propose a structured methodology and set of tools to ensure effective assessment. The proposed model mainly consists of data collection, analysis, assessment, financial analysis and later developed actions to properly address the concerns. Equipment failure and repair data is a challenge to any reliability assessment; hence, proposed methodology was introduced to collect, verify and validate the data. Later, multiple tools such as Pareto Analysis, Failure Mode and Effect Analysis and Root Cause Analysis were used to perform a detailed assessment. Weibull analysis was also explored to understand the failure modes, which ultimately helped in improving the availability of the motors. The proposed methodology has been applied to high-voltage motors to observe the effectiveness of the tools and proposed model in addressing reliability and maintainability. The results show significant reliability improvements of 12% (from 58% to 70%) and prove that the structured method can be effectively used in complex process facilities with significant benefits

Reactive metal/graphene oxide doping to fabricate porous geopolymers for arsenic removal

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Impact of magnetic resonance imaging on arthroscopic surgeries of knee joint

Background: Though magnetic resonance imaging (MRI) is popular as a diagnostic tool, questions arise regarding imaging when clinical diagnosis of most internal derangements of knee can be done. Treatment of meniscal and anterior cruciate ligament (ACL) injuries usually involves arthroscopic surgery after MRI. But accurately performed examination with positive signs alone will be justified for arthroscopy directly without MRI. The aims and objectives of this study are to assess the impact of MRI in selecting or excluding cases which genuinely require an arthroscopic surgery. To know whether routine MRI is required pre-operatively in all cases with positive clinical findings.Methods: 60 cases underwent clinical examination of affected knee and a preliminary diagnosis was made. Further they were subjected to MRI. Results of arthroscopy were considered as definitive diagnosis and results of clinical examination and MRI were judged accordingly.Results: Of 60 patients, examination revealed 85% accuracy, 82% sensitivity, 89% specificity for ACL injuries. For medial meniscus 58% accuracy, 66% sensitivity, 48% specificity. For lateral meniscus 55% accuracy, 58% sensitivity, 50% specificity. MRI revealed 73% accuracy, 82% sensitivity, 63% specificity for ACL injuries. For medial meniscus 63% accuracy, 90% sensitivity, 39% specificity. For lateral meniscus 62% accuracy, 79% sensitivity, 50% specificity.Conclusions: Clinical examination is more sensitive, specific and accurate in diagnosis of ACL. MRI is more sensitive but less specific for meniscal injuries. Clinical examination for cruciate injuries can surpass the MRI findings. Arthroscopy can be performed without MRI in single lesion injuries. However, MRI will play a role in meniscal injuries or doubtful cases

Uncovering Bugs in Distributed Storage Systems during Testing (not in Production!)

Testing distributed systems is challenging due to multiple sources of nondeterminism. Conventional testing techniques, such as unit, integration and stress testing, are ineffective in preventing serious but subtle bugs from reaching production. Formal techniques, such as TLA+, can only verify high-level specifications of systems at the level of logic-based models, and fall short of checking the actual executable code. In this paper, we present a new methodology for testing distributed systems. Our approach applies advanced systematic testing techniques to thoroughly check that the executable code adheres to its high-level specifications, which significantly improves coverage of important system behaviors. Our methodology has been applied to three distributed storage systems in the Microsoft Azure cloud computing platform. In the process, numerous bugs were identified, reproduced, confirmed and fixed. These bugs required a subtle combination of concurrency and failures, making them extremely difficult to find with conventional testing techniques. An important advantage of our approach is that a bug is uncovered in a small setting and witnessed by a full system trace, which dramatically increases the productivity of debugging

The Experience of International Students and Institutional Recommendations: A Comparison Between the Students From the Developing and Developed Regions

Prior studies on the experiences of international students in China have mostly focused on their academic, sociocultural, and accommodation experiences. Hence, student health and safety, discrimination, and the services by the International Student Office (ISO) have remained unexplored. Moreover, due to the motivational differences between the students from developing and developed regions, a study that samples students from both regions may depict an exact picture of the experience of international students. Therefore, the objective of this study is to examine the influence of the dimensions (including those dimensions that have been ignored) of the experience of international students on their satisfaction. In addition, we make recommendations regarding Chinese institutes for future students based on a comparison between the students from developing and developed regions. Using hierarchical regression analysis, this study reveals that educational and non-educational experiences vary among students from different regions. Therefore, based on developing (e.g., Asia and Africa) and developed (e.g., America, Europe, and Australia) regions, important recommendations are discussed regarding how educational institutions and the Chinese government could best allocate resources and introduce policies to improve the experience of international students

Cortical suspensory endobutton versus aperture interference screw fixation for arthroscopic anterior cruciate ligament reconstruction using hamstring graft: a prospective study

Background: Anterior cruciate ligament injury is a common injury which occurs in sports with an annual incidence of 68.6% per 100,000 population. Anatomic arthroscopic reconstruction remains the main stay treatment of ACL injury. Fixation of graft is classified as direct and indirect. To compare the stability of knee joint, complications in arthroscopic anterior cruciate ligament reconstruction by aperture interference screw fixation versus suspensory device fixation in femur. Methods: The randomized control study was conducted in department of orthopedics, The Oxford Medical College Hospital and RC from 2020-2021. 30 knees were operated, Ethical clearance taken and patient is followed up for six months. Results: The preoperative Tegner Lysholm knee score was poor in both groups. Post-op in interference screw group, 12 patients 80% had excellent functional outcome, 3 patients 20% had good outcome. In the Endbutton group, 11 patients (73%) had excellent outcome while 4 patients (27%) had good outcome. Conclusions: Suspensory device fixation gives equivalent results when compared to aperture screw fixation. complications of screw fixation were graft rupture cyst formation; complications of suspensory devices were loosening of graft and bungee cord effect. Hence, Both the techniques showed no statistical difference in post operative outcome

Event Stream Processing with Multiple Threads

Current runtime verification tools seldom make use of multi-threading to speed up the evaluation of a property on a large event trace. In this paper, we present an extension to the BeepBeep 3 event stream engine that allows the use of multiple threads during the evaluation of a query. Various parallelization strategies are presented and described on simple examples. The implementation of these strategies is then evaluated empirically on a sample of problems. Compared to the previous, single-threaded version of the BeepBeep engine, the allocation of just a few threads to specific portions of a query provides dramatic improvement in terms of running time

GPUVerify: A Verifier for GPU Kernels

We present a technique for verifying race- and divergence-freedom of GPU kernels that are written in mainstream ker-nel programming languages such as OpenCL and CUDA. Our approach is founded on a novel formal operational se-mantics for GPU programming termed synchronous, delayed visibility (SDV) semantics. The SDV semantics provides a precise definition of barrier divergence in GPU kernels and allows kernel verification to be reduced to analysis of a sequential program, thereby completely avoiding the need to reason about thread interleavings, and allowing existing modular techniques for program verification to be leveraged. We describe an efficient encoding for data race detection and propose a method for automatically inferring loop invari-ants required for verification. We have implemented these techniques as a practical verification tool, GPUVerify, which can be applied directly to OpenCL and CUDA source code. We evaluate GPUVerify with respect to a set of 163 kernels drawn from public and commercial sources. Our evaluation demonstrates that GPUVerify is capable of efficient, auto-matic verification of a large number of real-world kernels

Stemness of the CT-2A Immunocompetent Mouse Brain Tumor Model: Characterization In Vitro

Evidence has pointed to brain tumor stem cells (BTSC) as culprits behind human high-grade glioma (hHGG) resistance to standard therapy. Pre-clinical rodent models are the mainstay for testing of new therapeutic strategies. The typical model involves the intracranial injection of human glioma cells into immunocompromised hosts, hindering the evaluation of tumor-host responses and resulting in non-infiltrative tumors. The CT-2A model is an immunocompetent mouse model with potential to overcome these disadvantages. In this study, we confirmed the highly infiltrative nature of intracranial CT-2A tumors and optimized reproducible injection parameters. We then generated neurospheres and established, for the first time, the stemness of this model. CT-2A expression of the BTSC marker, CD133, increased from 2% in monolayer cells to 31% in fully-formed neurospheres. Investigation of three stem cell markers (Oct4, Nanog and Nestin) revealed a distinct stemness signature with monolayer cells expressing Oct4 and Nestin (no Nanog), and neurospheres expressing all three. Additionally, CT-2A cells were more proliferative and invasive than U87 cells, while CT-2A neurospheres were significantly more proliferative and invasive than either monolayer cells in vitro. Taken together, our results show that this model is a valuable tool for pre-clinical testing of novel therapeutics against hHGG and also affords the opportunity for investigation of BTSC in an immunocompetent setting