Reliable Support System Research Articles

Reliability analysis of idealized tunnel support system using probability-based methods with case studies

In order to determine the overall safety of a tunnel support lining, a reliability-based approach is presented in this paper. Support elements in jointed rock tunnels are provided to control the ground movement caused by stress redistribution during the tunnel drive. Main support elements contribute to stability of the tunnel structure are recognized owing to identify various aspects of reliability and sustainability in the system. The selection of efficient support methods for rock tunneling is a key factor in order to reduce the number of problems during construction and maintain the project cost and time within the limited budget and planned schedule. This paper introduces a smart approach by which decision-makers will be able to find the overall reliability of tunnel support system before selecting the final scheme of the lining system. Due to this research focus, engineering reliability which is a branch of statistics and probability is being appropriately applied to the field and much effort has been made to use it in tunneling while investigating the reliability of the lining support system for the tunnel structure. Therefore, reliability analysis for evaluating the tunnel support performance is the main idea used in this research. Decomposition approaches are used for producing system block diagram and determining the failure probability of the whole system. Effectiveness of the proposed reliability model of tunnel lining together with the recommended approaches is examined using several case studies and the final value of reliability obtained for different designing scenarios. Considering the idea of linear correlation between safety factors and reliability parameters, the values of isolated reliabilities determined for different structural components of tunnel support system. In order to determine individual safety factors, finite element modeling is employed for different structural subsystems and the results of numerical analyses are obtained in different design scenarios. Finally, the reliability index values are obtained for the entire support structure in different design scenarios. The results of the work demonstrates that proposed reliability evaluation method of tunnel support system is effective not only for investigating the reliability of individual elements in the structure, but also for building an overall estimation about reliability performance of the entire tunnel structure.

Study on the Theory and Methods of Bolt-Shotcrete Support for Weak Surrounding Rock Based on Reliability Analysis

The evaluation of stability and reliability of support system for tunnel weak surrounding rock are difficult issues of concern in rock and soil engineering. Aiming at the problem of parameter design and reliability evaluation of tunnel weak surrounding rock and bolt-shotcrete support system, the deformation, failure mechanism and physical mechanical properties of weak surrounding rock are analyzed as well as the mechanism of bolt-shotcrete support in soft rock is studied. And the reliability analysis equation of bolt-shotcrete support in two kinds of weak surrounding rock (nearly horizontal layered mechanics medium and continuum mechanics medium) is established. The quantitative soft rock supporting theory is introduced into the reliability analysis equation. The calculation formula of two important design parameters of anchoring force and bolt spacing in bolt-shotcrete support is established. Finally an engineering example is adopted to prove the rationality of the calculation results. Therefor this paper provides theoretical basis and design method for supporting structure design and reliability evaluation of tunnel weak surrounding rock.

Study on the Theory and Methods of Bolt-Shotcrete Support for Weak Surrounding Rock Based on Reliability Analysis

The evaluation of stability and reliability of support system for tunnel weak surrounding rock are difficult issues of concern in rock and soil engineering. Aiming at the problem of parameter design and reliability evaluation of tunnel weak surrounding rock and bolt-shotcrete support system, the deformation, failure mechanism and physical mechanical properties of weak surrounding rock are analyzed as well as the mechanism of bolt-shotcrete support in soft rock is studied. And the reliability analysis equation of bolt-shotcrete support in two kinds of weak surrounding rock (nearly horizontal layered mechanics medium and continuum mechanics medium) is established. The quantitative soft rock supporting theory is introduced into the reliability analysis equation. The calculation formula of two important design parameters of anchoring force and bolt spacing in bolt-shotcrete support is established. Finally an engineering example is adopted to prove the rationality of the calculation results. Therefor this paper provides theoretical basis and design method for supporting structure design and reliability evaluation of tunnel weak surrounding rock.

Modification of the Psychosocial Assessment of Candidates for Transplantation (PACT) Improves Risk Classification and Prediction of Hospital Readmission of MCS Patients

Purpose We previously demonstrated that the PACT falsely characterized some patients (pts) considered for MCS therapy as high risk. We developed and evaluated a new MCS-specific PACT; thus, the purpose of this study was to examine the sensitivity and specificity of this revised instrument to classify MCS pts. Methods and Materials PACT domains were re-written to reflect psychosocial criteria influencing social success defined as a reliable support system, discharge on schedule, and no social re-admissions. Areas of concern for HT candidates were eliminated and social support was emphasized. A social worker, blinded to outcomes, re-scored previously studied pts with the revised instrument. mPACT and PACT scores were then compared. Team members were surveyed: Was this pt a social success? Answers were assigned a value [no=0, yes=1] to determine a social success score. Success was considered a mean score >.5. Results 48 pts (72% men, 44% AA, 50.4 yrs) supported on MCS for 274 days were evaluated. The sensitivity of a score of 17 to identify a social success was .97 and the specificity was .56. The PPV was .97 and NPV was .56, compared to .86 and .44 respectively, for the PACT. A reclassification table was developed to assess the difference in risk stratification of the mPACT compared to the PACT. Net reclassification showed 19% improvement in risk stratification by the mPACT. Five of the 9 patients falsely categorized as high risk by the original PACT score were appropriately re-categorized as low risk with the mPACT. Patients with an mPACT score Conclusions By eliminating risk factors that do not have the same bearing on MCS outcome as HT and emphasizing areas of social support, we appropriately re-classified patients as acceptable risk who had been incorrectly considered high risk by the PACT. The mPACT score showed improved performance and warrants prospective validation.

Broad‐scale reliability analysis of the flood defence infrastructure within the Taihu Basin, China

AbstractThe Taihu Basin is home to some of the most economically active and populous cities in China, including Shanghai. The Basin lies in the coastal delta of the Yangtze River and is defended from frequent flooding by a complex system of flood control infrastructure (including dikes, numerous large sluice gates and pumping stations). Flood risk in the Basin is closely related to the reliability of the flood defences. The information available to support system reliability analysis is however limited. A simplified defence classification and reliability analysis has therefore been adopted in which the behaviour of defence subsystems (dike rings) are presented through a single representative fragility curve. A combination of expert judgement and available quantified data is used to support the analysis. The approach is found to be informative within the context of (i) a broad scale flood risk analysis, (ii) an exploration of longer term management policies and (iii) targeting more detailed analysis and data collection required to support specific management choices.

Relationship and Changing Analysis of Birnbaum Importance for Different Components with Bayesian Networks

Importance measures are widely used in reliability engineering. To support system reliability optimization, this paper studies the relationship and changing characteristics of the Birnbaum importance measures (BMs) for different components in binary coherent systems. First, the probabilistic meaning of BM and a modeling method for binary coherent system based on Bayesian network (BN) are presented. Then, the relationship of BMs for different components is explored according to the position of corresponding nodes (components) in BN structures. Later, the changing of BMs for different components, which is caused by the reliability improvements of related root or middle nodes (components) in BN structures, is analyzed respectively. Finally, an illustrative example of a helicopter convertor is implemented to demonstrate the calculation and application process of the relationship and changing characteristics in binary coherent systems with BN. The experimental analysis results substantiate the correctness and effectiveness of the proposed relationship and changing characteristics of BMs for different components.

Early breastfeeding experiences of adolescent mothers: a qualitative prospective study

BackgroundTeen mothers face many challenges to successful breastfeeding and are less likely to breastfeed than any other population group in the U.S. Few studies have investigated this population; all prior studies are cross-sectional and collect breastfeeding data retrospectively. The purpose of our qualitative prospective study was to understand the factors that contribute to the breastfeeding decisions and practices of teen mothers.MethodsThis prospective study took place from January through December 2009 in Greensboro, North Carolina in the U.S. We followed the cohort from pregnancy until two weeks after they ceased all breastfeeding and milk expression. We conducted semi-structured interviews at baseline and follow-up, and tracked infant feeding weekly by phone. We analyzed the data to create individual life and breastfeeding journeys and then identified themes that cut across the individual journeys.ResultsFour of the five teenagers breastfed at the breast for nine days: in contrast, one teen breastfed exclusively for five months. Milk expression by pumping was associated with significantly longer provision of human milk. Breastfeeding practices and cessation were closely connected with their experiences as new mothers in the context of ongoing multiple roles, complex living situations, youth and dependency, and poor knowledge of the fundamentals of breastfeeding and infant development. Breastfeeding cessation was influenced by inadequate breastfeeding skill, physically unpleasant and painful early experiences they were unprepared to manage, and inadequate health care response to real problems.ConclusionsContinued breastfeeding depends on a complex interplay of multiple factors, including having made an informed choice and having the skills, support and experiences needed to sustain the belief that breastfeeding is the best choice for them and their baby given their life situation. Teenagers in the US context need to have a positive early breastfeeding experience, be able to identify and claim a reliable support system supportive of breastfeeding, and gain through their experience, a belief in their own agency and competency as mothers.

Based on the Series System Initial Tunnel Lining Supporting System Reliability Analysis

For the initial lining structure of tunnel , constructing an consider integrated safety factor function.Consider the initial shotcrete tunnel support structure as a series system, using the interval estimation of the "wide boundaries of law" system of tunnel lining structure analysis, on this basis to determine the system failure mode. Using the limit displacement under the condition of axial force and bending moment of the corresponding displacement and construction monitoring of displacement are analyzed, considering the material properties, geometry and random effects. Using the Monte Carlo finite element method, combined with a typical project example to tunnel structural system reliability index were calculated. The calculation results show that in the engineering example, tunnel lining structure in some local section of the reliability index is smaller, but the whole support system reliability indexes meet the design requirements, the whole tunnel lining structure in a safe state.

Based on the Series System Initial Tunnel Lining Supporting System Reliability Analysis

For the initial lining structure of tunnel , constructing an consider integrated safety factor function.Consider the initial shotcrete tunnel support structure as a series system, using the interval estimation of the "wide boundaries of law" system of tunnel lining structure analysis, on this basis to determine the system failure mode. Using the limit displacement under the condition of axial force and bending moment of the corresponding displacement and construction monitoring of displacement are analyzed, considering the material properties, geometry and random effects. Using the Monte Carlo finite element method, combined with a typical project example to tunnel structural system reliability index were calculated. The calculation results show that in the engineering example, tunnel lining structure in some local section of the reliability index is smaller, but the whole support system reliability indexes meet the design requirements, the whole tunnel lining structure in a safe state.

Monitoring new oral anticoagulants, managing thrombosis, or both?

Monitoring new oral anticoagulants, managing thrombosis, or both?

Modelling Service Support System Reliability

Functional Products, where the customer pays for the function and availability of a product instead of the product itself, are increasingly popular in capital intensive industries such as aerospace. Such products are integrated systems involving the combination of hardware and service support systems. The reliability prediction and optimisation of the service system that supports the hardware availability is essential to the feasibility of the product. These systems consist of maintenance procedures and resource provisions. Simulation based techniques are presented in this paper to analyse the reliability of support systems and their application is demonstrated through a simple example.

The lived experiences of brokered brides who have attempted suicide in Taiwan

The purpose of this study was to explore the lived experiences of brokered brides who have attempted suicide in Taiwan. There has been a significant rise in number of brokered brides since the 1970s in Western world and since the 1990s in several Asian countries. However, there is a great lack of research on brokered brides' suicide around the world. A descriptive phenomenological study was used to explore the lived experiences of brokered brides who have attempted suicide. Purposive sampling, one-on-one, in-depth with semi-structural interviews were conducted to collect data. Narratives were analysed by Colaizzi's (1978) seven-step method. Data saturation was achieved after interviewing 12 brokered brides. The study group was comprised of females whose average age was 33. Three themes and the sub-themes were: being a chrysalis (loss of support, loneliness, suffering abused experience, loss of self-esteem), death of a chrysalis (loss of hope and seeking salvation) and birth of a chrysalis (regaining hope and sense of self-worth). These brokered brides suffered from numerous pressures and difficulties in life. Their hopelessness led to suicidal behaviours as a way to get out of trouble. Hence, the need to provide brokered brides with substantial assistance and support in their lives is an issue that cannot be neglected. The results of this study could be used as a reference to provide professionals and the public with a deeper understanding of suicide in this vulnerable group, and provide more appropriate help and care. Relevance to clinical practice. The suffering may be alleviated by giving brokered brides a reliable support system that they so obviously need. Several recommendations have been made, including amendments in terms of policy, society and the services offered by healthcare professionals.

Long-Term Mechanical Circulatory Support System Reliability Recommendation by the National Clinical Trial Initiative Subcommittee

The Long-Term Mechanical Circulatory Support (MCS) System Reliability Recommendation was published in the American Society for Artificial Internal Organs (ASAIO) Journal and the Annals of Thoracic Surgery in 1998. At that time, it was stated that the document would be periodically reviewed to assess its timeliness and appropriateness within 5 years. Given the wealth of clinical experience in MCS systems, a new recommendation has been drafted by consensus of a group of representatives from the medical community, academia, industry, and government. The new recommendation describes a reliability test methodology and provides detailed reliability recommendations. In addition, the new recommendation provides additional information and clinical data in appendices that are intended to assist the reliability test engineer in the development of a reliability test that is expected to give improved predictions of clinical reliability compared with past test methods. The appendices are available for download at the ASAIO journal web site at www.asaiojournal.com.

The Genesis mission: unifying science and engineering

Design of the Genesis spacecraft mission was derived from top-down flow of a basic and highly challenging science requirement: obtain samples of solar matter of such high quality and low background that they would sustain investigations of chemical and isotopic composition of the solar system for the coming decades, and well into the 21 st Century. Within the framework of several dozen competing mission concepts for planetary exploration under NASA's Discovery program, Genesis needed to perform extremely high quality science (solar collection and sample return) for an affordable yet realistic level of effort. Key issues included preservation of collector cleanliness, avoidance of spacecraft-generated con-tamination, control of collector temperatures, simplicity of long-term operation, ability to efficiently reach the L1 operations point, reliability of avionics and other support systems, return to a specific landing locale on Earth, and provision for soft capture of the descent capsule via mid-air parachute snatch. Genesis is now in the final stages of spacecraft testing and system validation, the culmination of a highly interwoven effort to meet science objectives with innovative solutions that also satisfy engineering challenges for reliability, affordability, rapid development and a comprehensive test program. Genesis is scheduled for launch in February 2001.

Reliability model from the in vitro durability tests of a left ventricular assist system.

A reliability test of the Novacor N100PC left ventricular assist system (LVAS) with valved conduits, including a pump/drive unit with compact controller and LVAS monitor was performed. The initial test objective was to demonstrate sufficient reliability for clinical use as a long-term circulatory support system. The subsequent objective, a test to failure, was intended to provide an assessment of the durability of the design and to determine the LVAS wearout modes. Testing began in April 1993 and was performed with 12 systems on gravity-feed mock circulatory loops. The pump/ drive units were submersed in body temperature saline for the duration of the test. Each of the LVAS units was operated at nominal afterloads of 75, 90, and 105 mm Hg, with test conditions varied to yield nominal pump outputs of 5.6, 7.1, and 8.3 L/min. Failure was defined as the inability of the LVAS to maintain an average pump output of 4 L/min or an average output pressure of 60 mm Hg. After 3 years, all systems remained on test, with durations of 2.3 to 3.0 years. Analysis of the testing to that date, using a constant hazard rate model, indicated a minimum demonstrated reliability of 94% at a 60% confidence level, or 86% at a 90% confidence level, for a 2 year mission time. This greatly surpasses the reliability level included in the STS-ASAIO Long-Term Mechanical Circulatory Support System Reliability Recommendation (80% reliability, 60% confidence level for a 1 year mission time). In the subsequent test-to-failure protocol, all systems ran failure-free for at least 3 years. System failures occurring at longer durations were caused by a single common cause: wear of the energy converter's armature support bearings and shafts. The wearout mode was gradual and could be diagnosed noninvasively before failure. An analysis using a Weibull model was performed, using the test durations of those devices that failed, those that were electively removed from test for analysis of the wear mode, and those that continued on test. As of April 1998, the test results showed a reliability, at a 60% confidence level, of >99.9% for a 1 year mission time, 99.5% for a 2 year mission, and 92.0% for a 3 year mission (>99.9%, 98.3%, and 85.9% for equivalent mission times, at a 90% confidence level). Systems continue on test after as long as 4.9 years.

Potentialities of theoretical and experimental prediction of Life Support Systems reliability.

To develop and design Life Support Systems it is necessary to evaluate their reliability. However direct experiments take much time, are very expensive, and therefore are practically impossible. Promising way is to use approximate estimates of reliability, which need essentially fewer amounts of experimental data. Two types of estimates of Life Support System reliability--additive and multiplicative ones are considered in the paper. Additive estimate is based on the assumption that total system failure probability is low and therefore it can be considered as the sum of failure probability of separate units. Additive approach allows obtaining near lower-bounded estimate of failure probability. Multiplicative estimate allows evaluating the possibility of system catastrophe due to simultaneous effect of several factors when each of them separately is not dangerous. Evaluation shows that the possible error of reliability forecast increases with the increasing of number of external factors faster than exponential function. An illustration of the ecological similarity approach as promising tool for providing estimation of full-scale system reliability by means the set of small similar experimental models.

Long-term mechanical circulatory support system reliability recommendation: American Society for Artificial Internal Organs and The Society of Thoracic Surgeons: Long-term mechanical circulatory support system reliability recommendation

Jointly developed by members of the American Society for Artificial Internal Organs and the Society of Thoracic Surgeons along with staff from the Food and Drug Administration, the National Heart, Lung and Blood Institute and other experts, this recommendation describes the reliability considerations and goals for Investigational Device Exemption and Premarket Approval submissions for long-term, mechanical circulatory support systems. The recommendation includes a definition of system failure, a discussion of an appropriate reliability model, a suggested in vitro reliability test plan, reliability considerations for animal implantation tests, in vitro and animal in vivo performance goals, the qualification of design changes during the Investigational Device Exemption clinical trial, the development of a Failure Modes Effects and Criticality Analysis, and the reliability information for surgeons and patient candidates. The document will be periodically reviewed to assess its timeliness and appropriateness within five years.

Factors in perception of earthquake hazard.

130 subjects participated in a study of the relationship between selected predictors and responses to potential earthquake hazard. The results of backstep regression analyses indicated that amount of education was the best predictor from those selected of perceived probability of earthquake occurrence, that estimation of potential damage was related to number of damage reduction measures, perceived reliability of official support systems, and expectation of earthquake, and that trait-anxiety and expectation of earthquake accounted for a significant percentage of the variance in acknowledged anxiety in response to prediction of an earthquake.