Search results

There is limited discussion in the literature of the problems associated with constructing stress tests. The Credit Crunch has revealed that attention simply to haircuts to asset values and resulting margin calls is insufficient. The purpose of this paper is to explore additional avenues for stress testing.

The paper is largely discursive.

Stress tests must look into the debt position of the firm, as well as its position and credit exposures. Not only the volume of debt but its maturity structure, callability and the indentures attached to it are extremely important.

The paper is geared more toward management and practitioners than to academic researchers. Implications for the analysis of corporate strategy are significant.

Stress testing is essential to the confident continuance of firms.

So much of the work in this area is proprietary and so little has been published on it.

Focuses on the development and capabilities of interconnect stress testing (IST), a stress testing method for printed circuit boards (PCBs) that is fast, repeatable and reproducible. IST technology was originally developed in the mid 1980s. Notes that using IST as an electrical test delivers a capability to remove the human factor from the decision making process of product acceptance or rejection and that the technology is emerging as an important test methodology for the assessment of PCB interconnects. IST has the capability to effectively and rapidly quantify the integrity of plated through holes and the unique ability to identify the presence and levels of post separations within a multilayer board.

To obtain an optimal simple time‐step stress accelerated life test for the case involving pre‐specified censoring time. Such a test saves time and expenses over tests at normal conditions.

Most of the available literature on step‐stress accelerated life testing deals with the exponential and weibull distribution. The log‐logistic life distribution has been found appropriate for high reliability components.

The method developed has been illustrated using the data simulated from cumulative exposure log‐logistic step‐stress model with censoring time specified.

The model suggested is appropriate in the field of high reliability components such as insulation system.

The increased capital requirements and the implementation of new liquidity standards under Basel III sparked various concerns among researchers, academics and other stakeholders. The question is whether Basel III regulation is ideal, that is, adequate to deal with a crisis, such as the 2007–2009 global financial crisis? The purpose of this paper is threefold: First, perform a stress testing exercise on the US banking sector, while examining liquidity and solvency risk indicators jointly under the Basel III regulatory framework. Second, allow the study to cover the post-crisis period, while referring to key Basel III regulatory requirements. And third, focus on the resilience of domestic systemically important banks (D-SIBs), which are supposed to support the US financial system in times of stress and therefore whose failure causes the entire financial system to fail.

The authors used a sample of the 24 largest US banks observed over the period Q1-2015 to Q1-2021 and a scenario-based vector autoregressive conditional forecasting approach.

The authors found that the model successfully produces accurate forecasts and simulates the responses of the solvency and liquidity indicators to different real and historical macroeconomic shocks. The authors also found that the US banking sector is resilient and can withstand both historical and hypothetical macroeconomic shocks because of its compliance with the Basel III capital and liquidity regulations, which consist of encouraging banks to hold high-quality liquid assets and stable funding resources and to strengthen their capital, which absorbs the losses incurred in a crisis.

The authors developed a framework for testing the resilience of the US banking sector under macroeconomic shocks, while examining liquidity and solvency risk indicators jointly under Basel III regulatory framework, a point not yet well studied elsewhere, and most studies on this subject are based on precrisis data. The authors also focused on the resilience of D-SIBs, whose failure causes the failure of the entire financial system, which previous studies have failed to examine.

SEVENTEEN papers were presented during the three days of the conference on a variety of topics affecting fatigue in aircraft structures. The conference was organized under the joint auspices of the Department of Civil Engineering and Engineering Mechanics, Columbia University, and the Air Research and Development Centre, U.S.A.F., Baltimore.

The purpose of this paper is to consider the general k level step-stress accelerated life test with the Rayleigh lifetime distribution for units subjected to stress under progressive Type-I censoring.

The parameter of this distribution is assumed to be a log-linear function of the stress, and a tampered failure rate model holds. The progressive Type-I censoring reduces the cost of testing. Due to constrained resources in practice, the test design must be optimized carefully. A numerical study is conducted to illustrate the optimum test design based on several four optimality criteria under the constraint that the total experimental cost does not exceed a pre-specified budget.

This paper compares unconstrained and constrained optimal k level step-stress test. Based on the results of the simulation study, the cost constraint reduces cost and time of the test and it also, in the most cases, increases the efficiency of the test. Also, the T-optimal design is lowest cost and time for testing and it is found more optimal in both conditions.

In this paper, various optimization criteria for selecting the stress durations have been used, and these criteria are compared together. Also, because of affecting the stress durations on the experimental cost, the author optimize under the constraint that the total experimental cost does not exceed a pre-specified budget. The efficiency of the unconstrained test in comparison with constrained test is discussed.

Three main subjects are presented in this paper: (i) A description of tests made for the purpose of determining design data; (ii) a discussion of the problems arising in the establishment of the approval procedures necessary to ensure safety and reliability; and (iii) a discussion of proposals for cyclic reliability tests. In the first section, tests to provide design data for glazing materials are described with particular emphasis placed on glasses. Types of specimen and apparatus for obtaining data at room temperature are mentioned and illustrations given of apparatus and specimens used in long term elevated temperature tests. In the second section, the overall level of reliability of complete components is discussed both in terms of structural safety and satisfactory service. While the current requirements have proved satisfactory for the past generation of aircraft, proposals are now put forward for patterns of testing that are more closely linked to the various design conditions now in use with both high‐speed and low‐speed aircraft, in order to place equal importance on the effects of temperature. In the third section, proposals are put forward for cyclic testing to overcome what appears to be an increasingly unsatisfactory record of reliability. The purpose of the tests is not to establish a safe life for any particular design but to reveal design deficiencies occurring from repeated applications of flight and thermal loadings.

This article comprises Chapter 6 from the recently published book ‘An Engineer’s Guide to Flexible Circuit Technology by J. Fjelstad

The circuit elements of every printed circuit board have the potential for failure during test and/or use. These failures can occur by forming short‐circuits between adjacent circuit elements, or by forming open‐circuits in the conductors. The risk sites can be identified by type, and the total number enumerated by manual inspection of the photolithographic masks used to fabricate the printed circuit layers. However, the circuit density of high performance printed circuit boards has become so great that meaningful manual analysis has become impractical. A more effective method is to use special graphics programs to analyse the computer‐aided design (CAD) data. The methodology developed to perform the CAD analysis of high performance printed circuit boards for short‐circuits utilises two powerful computer graphic tools: the Interactive Graphics System and the Unified Shapes Checking system. Test data for open‐circuits are generated using specially written alphanumeric routines. The data can be used for stress testing the printed circuit boards by wiring up special test modules that are plugged into the boards and then placing the boards into environmental test chambers. The printed circuits are checked for short‐circuits by putting them into groups that have no risk of shorting to each other (zero risk), and placing the groups in parallel under an electrical potential. The flow of current between the groups would indicate a short‐circuit. Similarly, the printed circuits can be checked for open‐circuits, by stringing them together into groups in series, and measuring the changes in resistance under thermal stress. Both types of test data can also be used for in‐process testing.

This article outlines the procedures being used at Westland Helicopters Limited to establish the fatigue lives of the dynamic and structural components of the Lynx and to demonstrate how an adequate safety level is achieved under the loading sustained by the aircraft. For the newcomer to the fatigue problem a brief introduction to the phenomenon of fatigue will be provided and it will be shown how it is applicable to a helicopter. A philosophical outline of the fatigue procedures in current use at Westlands follows and then a description of the Lynx is given. The article will then describe the fatigue testing, flight testing and substantiation procedures used with the Lynx and it will be shown how the eventual fatigue lives are estimated. Finally some thoughts are put forward about the future of fatigue substantiation.