scholarly journals A new dynamic model to optimize the reliability of the series-parallel systems under warm standby components

2021 ◽  
Vol 0 (0) ◽  
pp. 0
Author(s):  
Amir Mohammad Fakoor Saghih ◽  
Azam Modares
Keyword(s):  
Dynamic Models ◽  
Failure Time ◽  
Recursive Formula ◽  
Reliability Function ◽  
Mode Analysis ◽  
Redundancy Allocation ◽  
Failure Time Distribution ◽  
Before And After ◽  
Common Technique ◽  
Warm Standby

<p style='text-indent:20px;'>Redundancy allocation problem (RAP) is a common technique for increasing the reliability of systems. In this paper, a new model for the RAP is introduced that takes into account the warm standby and mixed strategy, the model dynamics, and the type of the strategy in redundancy allocation problems. A recursive formula is first obtained for the reliability function in the dynamic warm standby and mixed redundancy strategies that leverages the success mode analysis and works for any arbitrary failure-time distribution. Failure rates for warm standby units change before and after their replacement with a damaged unit, and, therefore, the reliability function in warm standby varies with time (i.e., the model is dynamic). Although dynamic models are commonplace in practice, they are more challenging to assess than static models, which have been mainly considered in the literature. An optimization problem is then formulated to select the best redundancy strategy and redundancy levels. Genetic algorithm and particle swarm optimization are leveraged to solve the problem. Finally, the efficiency of the presented method is verified through a numerical example. The experimental results verify that the proposed model for RAP significantly improves the system reliability, which can be of vital importance for system designers.</p>

Bayesian Nonparametric Estimation of Failure Rates with Censored Data

1983 ◽  
Vol 32 (1-2) ◽  
pp. 79-90 ◽  
Author(s):  
J. S. Rao ◽  
R. C. Tiwari
Keyword(s):  
Failure Time ◽  
Dirichlet Distribution ◽  
Survival Function ◽  
Fixed Time ◽  
Bayes Estimation ◽  
Time Interval ◽  
Failure Rates ◽  
Failure Time Distribution ◽  
Accelerated Life ◽  
Bayesian Nonparametric Estimation

The failure time distribution is estimated in the nonparametric context when some of tbe observations arc censored. The time interval is partitioned into fixed class intervals, and number of failures and number censored in each of these intervals are observed. Using a Dirichlet distribution as the prior, the resulting estimates of the survival function and the failure rate have a nice and simple form. If instead of the fixed time intervals, one uses the “natural” intervals formed by the observed failure times, this gives essentially the same results as in Ferauson IUld Phadia (1977), Susarla and Van Ryzin (1976), but in a much simpler way. Bayes estimation under the increasins and decreasing failure rates is also considered, and applications to accelerated life testing are discussed.

A Detailed Study of a Novel Wafer Separation Method for Surface Sensitive MEMS Wafers

2012 ◽  
Vol 1415 ◽  
Author(s):  
K. Malachowski ◽  
S. Severi ◽  
R. Van Hoof ◽  
S. Sangameswaran ◽  
S. Genda ◽  
...  
Keyword(s):  
Process Integration ◽  
Separation Method ◽  
Work Design ◽  
Back Side ◽  
Design Rules ◽  
Micro Electro Mechanical Systems ◽  
Particle Contamination ◽  
Before And After ◽  
Common Technique ◽  
Process Speed

ABSTRACTAbrasive blade dicing is the most common technique for die separation. In this work an alternative dry and non-abrasive die separation method, which is known as "Stealth dicing", is assessed for surface-sensitive MEMS (Micro Electro Mechanical Systems) wafers. The dicing performance and capability of the system is investigated on 200mm full thickness wafers with and without MEMS structures. The diced wafers are analyzed with respect to the silicon cutting quality, possible particle contamination, the condition of functional structures and their mechanical and electrical functionality. In addition the performance and limitations of two different Stealth Dicing Engine (SDE) types, SDE01 and SDE03, are compared to each other with respect to their performance on MEMS wafer dicing.From this work design rules and proper dimensions of the scribe line can be determined. Process integration solutions, describing steps before and after the Stealth dicing process, including the contact-less dicing tape application to the wafer back side and the final die separation method by tape stretching, are presented. It was also found that the SDE03 laser with its outstanding performance in terms of process speed and separation quality can bring a breakthrough for applying this technology for MEMS wafers.

scholarly journals Truck Handling Stability Simulation and Comparison of Taper-Leaf and Multi-Leaf Spring Suspensions with the Same Vertical Stiffness

2020 ◽  
Vol 10 (4) ◽  
pp. 1293 ◽  
Author(s):  
Leilei Zhao ◽  
Yunshan Zhang ◽  
Yuewei Yu ◽  
Changcheng Zhou ◽  
Xiaohan Li ◽  
...  
Keyword(s):  
Dynamic Models ◽  
Load Capacity ◽  
Lightweight Design ◽  
Steering Wheel ◽  
Leaf Spring ◽  
Slip Angle ◽  
Vertical Stiffness ◽  
Spring Suspension ◽  
Before And After ◽  
Stability Indexes

The lightweight design of trucks is of great importance to enhance the load capacity and reduce the production cost. As a result, the taper-leaf spring will gradually replace the multi-leaf spring to become the main elastic element of the suspension for trucks. To reveal the changes of the handling stability after the replacement, the simulations and comparison of the taper-leaf and the multi-leaf spring suspensions with the same vertical stiffness for trucks were conducted. Firstly, to ensure the same comfort of the truck before and after the replacement, an analytical method of replacing the multi-leaf spring with the taper-leaf spring was proposed. Secondly, the effectiveness of the method was verified by the stiffness tests based on a case study. Thirdly, the dynamic models of the taper-leaf spring and the multi-leaf spring with the same vertical stiffness are established and validated, respectively. Based on this, the dynamic models of the truck before and after the replacement were established and verified by the steady static circular test, respectively. Lastly, the handling stability indexes for the truck were compared by the simulations of the drift test, the ramp steer test, and the step steer test. The results show that the yaw rate of the truck almost does not change, the steering wheel moment decreases, the vehicle roll angle obviously increases, and the vehicle side slip angle slightly increases after the replacement. Thus, the truck with the taper-leaf spring suspension has better steering portability, however, its handling stability performs worse.

Template Calibration Parameter Optimization of Fuzzy Vault Method

2019 ◽  
Vol 34 (07) ◽  
pp. 2059020
Author(s):  
Yifan Liao
Keyword(s):  
Hash Table ◽  
Rejection Rate ◽  
Base Point ◽  
Matching Accuracy ◽  
Fuzzy Vault ◽  
Fuzzy Point ◽  
Before And After ◽  
Common Technique ◽  
Point Distance ◽  
Fingerprint Database

In the concrete implementation of the fuzzy vault algorithm, the geometric hash method is a common technique for automatic calibration of biometric templates. For the fuzzy problem of parameter acquisition, the matching accuracy of fuzzy vault template is affected in the three parameters: the pixel size, hash table and hash table quantization parameters ([Formula: see text] and [Formula: see text]). The single factor experiment method obtains the optimal range of these three parameters, and the extraction range of the fuzzy point and the selection rule of the base point distance are improved for the fuzzy vault algorithm. Finally, based on the FVC fingerprint database, their matching precision is compared for the algorithm before and after optimization. The experimental results show that the false rejection rate (FRR) of the optimized algorithm is reduced by at least 9.84%, and the false acceptance rate (FAR) is reduced by at least 7.12%, indicating that the optimization scheme improves the matching accuracy of the algorithm. The algorithm has certain robustness and practicability.

Approximations for the repairman problem with two repair facilities, I: No spares

1973 ◽  
Vol 5 (3) ◽  
pp. 595-613 ◽  
Author(s):  
Donald L. Iglehart ◽  
Austin J. Lemoine
Keyword(s):  
Markov Chain ◽  
Limit Theorems ◽  
Failure Time ◽  
Failure Time Distribution ◽  
Continuous Parameter ◽  
Server Queue ◽  
Finite State ◽  
Repairman Problem ◽  
Repair Facility

The model considered here consists of n operating units which are subject to stochastic failure according to an exponential failure time distribution. Failures can be of two types. With probability p(q) a failure is of type 1(2) and is sent to repair facility 1(2) for repair. Repair facility 1(2) operates as a -server queue with exponential repair times having parameter μ1 (μ2). The number of units waiting for or undergoing repair at each of the two facilities is a continuous-parameter Markov chain with finite state space. This paper derives limit theorems for the stationary distribution of this Markov chain as n becomes large under the assumption that both and grow linearly with n. These limit theorems give very useful approximations, in terms of the six parameters characterizing the model, to a distribution that would be difficult to use in practice.

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