This study was an effort to objectify and test empirically Tillich's theory. Its purpose was to investigate certain traditional aspects of religion to see whether their presence was associated with purposefulness in life. The variables used in this study were measures of participation in a faith, belief in an afterlife, belief in God, past and current doubts, religious experiences, commitment implied in the consideration of a church related vocation, and of purpose in life. Tillich would say that participation in a faith, a belief in God, and a commitment of some kind are essential elements of one's ultimate concern. The belief in an after life is a common way of avoiding the anxiety of death, which is an element of the anxiety of meaninglessness of today. Doubt concerning the Ultimate undermines ones meaning or purpose in life.

A Ce:YAG-doped glass phosphor layer instead of conventional Ce:YAG-doped silicone phosphor layer as phosphor-converted white-light emitting diodes (PC-WLEDs) is demonstrated. The advantage of employing doped glass encapsulation in high power PC-WLEDs could be explained the material property of glass transition temperature of 750¢J was higher than silicone of 150¢J. The lumen degradation, chromaticity shift, color temperature change, transmittance, and fluorescence spectrum in glass and silicone based high-power PC-WLEDs under thermal aging at 150¢J, 200¢J, and 250¢J is compared and presented. Under highest temperature of 250¢J, the glass and silicone encapsulation base d PC-WLEDs exhibited 8.15% and 38.85% in lumen loss, 1.07 and 7.32 in chromaticity shift, 856 K and 3666 K in color temperature change, 4.21% and 28.1% in transmittance loss, respectively. However, the excitation spectrum altered as slight as emission spectrum before and after experiments. After aging test, the mean-time-to-failure (MTTF) evaluation of glass and silicone encapsulation materials for PC-WLEDs in accelerated thermal tests is also compared and presented by the using of Weibull distribution and Arrhenius equation. The MTTF of PC-WLEDs is defined the lumen decayed to 90%. The results showed that the glass as encapsulation material of PC-WLEDs exhibited higher MTTF than the silicone encapsulation by about 4.81, 5.92, and 7.53 times in lumen loss at 150¢J, 200¢J, and 250¢J, respectively. The results of the lumen loss, chromaticity shift, and MTTF investigations demonstrated that the thermal-stability performance of the glass based PC-WLEDs were better than silicone based PC-WLEDs at 150¢J, 200¢J, and 250¢J. A better thermal stability phosphor layer of glass as encapsulation material may be beneficial to the many applications where the LED modules with high power and high reliability are demanded.

abstract: Accelerated life testing (ALT) is the process of subjecting a product to stress conditions (temperatures, voltage, pressure etc.) in excess of its normal operating levels to accelerate failures. Product failure typically results from multiple stresses acting on it simultaneously. Multi-stress factor ALTs are challenging as they increase the number of experiments due to the stress factor-level combinations resulting from the increased number of factors. Chapter 2 provides an approach for designing ALT plans with multiple stresses utilizing Latin hypercube designs that reduces the simulation cost without loss of statistical efficiency. A comparison to full grid and large-sample approximation methods illustrates the approach computational cost gain and flexibility in determining optimal stress settings with less assumptions and more intuitive unit allocations. Implicit in the design criteria of current ALT designs is the assumption that the form of the acceleration model is correct. This is unrealistic assumption in many real-world problems. Chapter 3 provides an approach for ALT optimum design for model discrimination. We utilize the Hellinger distance measure between predictive distributions. The optimal ALT plan at three stress levels was determined and its performance was compared to good compromise plan, best traditional plan and well-known 4:2:1 compromise test plans. In the case of linear versus quadratic ALT models, the proposed method increased the test plan's ability to distinguish among competing models and provided better guidance as to which model is appropriate for the experiment. Chapter 4 extends the approach of Chapter 3 to ALT sequential model discrimination. An initial experiment is conducted to provide maximum possible information with respect to model discrimination. The follow-on experiment is planned by leveraging the most current information to allow for Bayesian model comparison through posterior model probability ratios. Results showed that performance of plan is adversely impacted by the amount of censoring in the data, in the case of linear vs. quadratic model form at three levels of constant stress, sequential testing can improve model recovery rate by approximately 8% when data is complete, but no apparent advantage in adopting sequential testing was found in the case of right-censored data when censoring is in excess of a certain amount. / Dissertation/Thesis / Doctoral Dissertation Industrial Engineering 2014

Accelerated life tests (ALT) are appealing to practitioners seeking to maximize information gleaned from reliability studies, while navigating resource constraints due to time and specimen costs. A popular approach to accelerated life testing is to design test regimes such that experimental specimens are exposed to variable stress levels across time. Such ALT experiments allow the practitioner to observe lifetime behavior across various stress levels and infer product life at use conditions using a greater number of failures than would otherwise be observed with a constant stress experiment. The downside to accelerated life tests, however, particularly for those that utilize non-constant stress levels across time on test, is that the corresponding lifetime models are largely dependent upon assumptions pertaining to variant stress. Although these assumptions drive inference at product use conditions, little to no statistical methods exist for assessing their validity. One popular assumption that is prevalent in both literature and practice is the cumulative exposure model which assumes that, at a given time on test, specimen life is solely driven by the integrated stress history and that current lifetime behavior is path independent of the stress trajectory. This dissertation challenges such black box ALT modeling procedures and focuses on the cumulative exposure model in particular. For a simple strep-stress accelerated life test, using two constant stress levels across time on test, we propose a four-parameter Weibull lifetime model that utilizes a threshold parameter to account for the stress transition. To circumvent regularity conditions imposed by maximum likelihood procedures, we use median rank regression to fit and assess our lifetime model. We improve the model fit using a novel incorporation of desirability functions and ultimately evaluate our proposed methods using an extensive simulation study. Finally, we provide an illustrative example to highlight the implementation of our method, comparing it to a corresponding Bayesian analysis. / Ph. D. / Have you ever wondered how manufacturers determine the guaranteed lifetime warranty for the products they produce? From automotive showrooms to store shelves, consumer goods often have a unique story to tell, one involving meticulous research, engineered design, and statistically driven testing. This is the realm of accelerated life testing (ALT) where reliability engineers, in their e↵orts to estimate overall product life, subject test specimens to harsher conditions than what are expected under normal operating conditions. Ideally, ALT experiments will induce multiple failures in a short amount of time and provide a basis for statistical modeling to predict failure in the field. The problem with this, however, is that such experiments require many mathematical assumptions which describe the physics of failure. This dissertation challenges one of the most common assumptions used for ALT experiments when specimens are exposed to multiple stress levels. We develop an alternative approach to the analysis of ALT data which drops this assumption (referred to as cumulative exposure) and explore the statistical properties of our method. We find that our approach has many features which will appeal to practitioners who may wish to use our procedures as they seek to understand the data gleaned from ALT experiments. Overall, this work represents an important addition to the reliability practitioner’s toolbox and will allow researchers to avoid potentially dubious assumptions concerning real world behavior.

The service life and electrocatalytic activity of tantalum oxide/iridium oxide coated titanium plate and mesh anodes used in the electrolytic production of chromic acid were investigated by performing accelerated life tests, voltammetric and chronoamperometric measurements in chrome (VI) solutions. Experimental results showed that the service life for the coated mesh anode was 1059 hours, compared to 828 hours for the plate anode at a current density of 1.2 A cm-2. In addition, the coating failed earlier in higher chromic acid concentration. Physical analysis by SEM and EDS before and after accelerated life test confirmed that the deactivation was a result of corrosion of IrO2 followed by titanium substrate passivation. A simple and rapid method for assessing the electrocatalytic activity of iridium–tantalum oxide coating based on a chronoamperometric technique was developed.

Accelerated life testing (ALT) has been widely used in collecting failure time data of highly reliable products. Most parametric ALT models assume that the ALT data follows a specific probability distribution. However, the assumed distribution may not be adequate in describing the underlying failure time distribution. In this dissertation, a more generic method based on a phase-type distribution is presented to model ALT data. To estimate the parameters of such Erlang Coxian-based ALT models, both a mathematical programming approach and a maximum likelihood method are developed. To the best of our knowledge, this dissertation demonstrates, for the first time, the potential of using PH distributions for ALT data analysis. To shorten the test time of ALT, degradation tests have been studied as a useful alternative. Among many degradation tests, destructive degradation tests (DDT) have attracted much attention in reliability engineering. Moreover, some materials/products start degrading only after a random degradation initiation time that is often not even observable. In this dissertation, two-stage delayed-degradation models are developed to evaluate the reliability of a product with random initiation time. For homogeneous and heterogeneous populations, fixed-effects and random-effects Gamma processes are considered, respectively. An expectation-maximization algorithm and a bootstrap method are developed to facilitate the maximum likelihood estimation of model parameters and to construct the confidence intervals of the interested reliability index, respectively. With an Accelerated DDT model, an optimal test plan is presented to improve the statistical efficiency. In designing the ADDT experiment, decision variables related to the experiment must be determined under the constraints on limited resources, such as the number of test units and the total testing time. In this dissertation, the number of test units and stress level are pre-determined in planning an ADDT experiment. The goal is to improve the statistical efficiency by selecting appropriately allocate the test units to different stress levels to minimize the asymptotic variance of the estimator of the p-quantile of failure time. In particular, considering the random degradation initiation time, a three-level constant-stress destructive degradation test is studied. A mathematical programming problem is formulated to minimize the asymptotic variance of reliability estimate.

This thesis describes theway of BPM motors control and its use in life testing. Firstly it describes the properties of motors and their differences. Secondly it describes possibilities of motor control and their need for life testing. Finally it describes proposal of the universal control unit, types of controling, programming part and technical documentations.

This master’s thesis deals with construction design of cylindrical roller bearing for traction motor and design of life test tool for designed bearing. At the thesis beginning there is an overview of new trends in design of cylindrical roller bearing, according to new trends is designed a new construction design of cylindrical roller bearing. Other part of thesis is strain stress analysis, which assesses an optimal inclination of collar faces and optimal raceway modification of hybrid bearing rings. At the end life test will be analyzed.

The subject of this diploma thesis is the design and the development of accelerated Life test of Ball-joint in cooperation with company TRW-DAS a. s. The diploma thesis includes a review about accelerated life tests on specialized tests made by the company. In the thesis are analyzed the preparations of accelerated life tests, the implementation and verification by experiment. The thesis also includes the computer strain simulation of Ball-Joint by FEM software.

<p>  </p> <p>Environmental challenges, increasing energy costs and demand, and upcoming regulations (e.g., new equipment performance ratings, phase-down of HFCs) are a few of the main drivers behind the research on advanced HVAC&R equipment. The HVAC&R systems are one of the largest energy consumers in both commercial and residential buildings and their operation is essential to ensure thermal comfort as well as other industrial needs. Within this context, large chillers provide chilled water to condition commercial buildings and the new generation of smart chillers feature variable speed compressors that enable active capacity modulation. In turn, variable speed operation along with other factors can contribute to performance degradation. Understanding mechanisms of degradation and developing models that enable predicting the decrease in performance with respect to the rated values are still open topics in the literature. </p> <p>The overarching goal of this research is to investigate the performance degradation of a water-cooled variable-speed screw chiller under long term operation and to gain insights on the behavior of the chiller under accelerated life testing. In particular, this thesis covers the initial task of designing an experimental test setup that enables performance testing according to the AHRI 550/590 standard. Once the experimental setup was commissioned, a set of four standard-conform baseline tests was conducted to map the rated performance of the chiller at both full and part-load conditions. After completing the baseline tests, an accelerated life test cycle procedure was developed and implemented in order to conduct 24/7 automated testing on the chiller. To this end, two test modes were established to simulate a real-life use of the chiller and induce high level of thermo-mechanical stresses on the compressor. Furthermore, eight recurring baseline tests were conducted to determine the performance behavior after 1000 operating hours. Finally, a preliminary system model was set up. This thesis describes the design of the system, the commissioning and control and provides insights on the performance testing as well as long-term testing methodology and the modeling work that was done so far. </p>