Further results on discrete mean past lifetime

Abstract

The present paper aims at studying the mean past lifetime of a discrete random variable. The notion of discrete mean past lifetime is studied in relation to the concepts of reversed hazard rate, reversed lack of memory property, and cumulative past entropy. New classes of distributions characterized by particular forms of discrete mean past life are also investigated. Implications of an increasing mean past lifetime on other reliability notions are studied and finally some bivariate generalizations are discussed.     

Negotiating Accessibility for Electronic Resources

Abstract

Accessibility of library electronic resources is a must. Its importance derives from professional ethics of librarianship, rising total costs of acquisition, and mounting legal challenges to colleges and universities that fail to provide resources accessible to users with disabilities. Library staff are responsible for ensuring the accessibility of vendor-licensed eresources. This column reviews the accessibility clauses of nine model license agreements for electronic resources. It describes terms that should go into an optimal accessibility clause and creates a composite model clause. It also provides guidance for library staff seeking to negotiate stronger accessibility language into vendor license agreements. Finally, it addresses the impact of accommodation requests on the total cost of acquiring library eresources, concluding with a call to redouble efforts to advocate for greater accessibility and educate both vendors and library staff about its importance.     

Two graphical displays for the detection of potentially influential subsets in regression

In the context of the general linear model Y=Xβ+ε, the matrix P_z =Z(Z^TZ)^?1 Z^T , where Z=(X: Y), plays an important role in determining least squares results. In this article we propose two graphical displays for the off-diagonal as well as the diagonal elements of P_Z . The two graphs are based on simple ideas and are useful in the detection of potentially influential subsets of observations in regression. Since P_Z is invariant with respect to permutations of the columns of Z, an added advantage of these graphs is that they can be used to detect outliers in multivariate data where the rows of Z are usually regarded as a random sample from a multivariate population. We also suggest two calibration points, one for the diagonal elements of P_Z and the other for the off-diagonal elements. The advantage of these calibration points is that they take into consideration the variability of the off-diagonal as well as the diagonal elements of P_Z . They also do not suffer from masking.     

Digital Accessibility as a Core Competency for E-Resources Librarians

Abstract

This article will outline the electronic resources life cycle and identify key elements involved in e-resource management that exhibit potential for growth in terms of accessibility remediation. The aim of the article is to convey an understanding of the importance of digital accessibility to electronic resources librarians and the role they may play in making digital collections more available to users with impairments.     

Effectively Evaluating the Accessibility of Electronic Monographs Using VPATs and Other Resources at the College of Staten Island Library- CUNY

Abstract

This study, building upon previous research work at the College of Staten Island (CSI) library, attempts to evaluate the accessibility of select digital monograph platforms and file formats utilized at the City University of New York (CUNY). The usability of CSI library’s locally developed ER-ACT tool to assist librarians with limited technical knowledge to review VPATs and to perform simple testing was also evaluated with challenges and successes reported. It was determined that the use of color-coded results in this study can help identify serious accessibility issues within ebooks and to communicate the results within libraries to assist with collection development decision-making. The study also includes a review of new court rulings related to accessibility issues in higher education and discusses where accessibility staffing reports in terms of job roles and duties held by university professionals. The testing of the accessibility of library ebooks, with various accessibility tools, are reviewed within the context of Section 508 revisions and new VPAT standards.     

The Role of an Electronic Resources Librarian in Procuring Accessible Online Resources

Abstract

Per the 2019 NASIG Core Competencies for electronic resources librarians (ERL), ERLs “work with concepts and methods that are very much in flux … [they are] knowledgeable about the legal framework within which libraries and information agencies operate… [including] laws relating to… equal rights (e.g., the Americans with Disabilities Act)”. However, the Core Competencies do not define the level to which an ERL is responsible for determining the accessibility of an electronic resource. This article aims to create a better understanding of the steps an ERL can take to develop an accessibility statement pertaining to procuring accessible content. This article synthesizes key laws and policies that ERLs should be aware of in order to draft an accessibility procurement statement for their institution. It will also discuss licensing strategies, documentation collection, and conducting potential audits of electronic purchases.     

Numerical solution to stochastic partial differential equation with variable repair rate

ABSTRACT

In this paper, a numerical solution technique to stochastic partial differential equations in reliability engineering is presented. The method is based upon finite difference discretization of the governing equations for the Markovian reliability model. In realistic situations, the repair rates and failure rates of engineering system are variable. Such variable repair and failure rates are difficult to account in reliability modeling. The novelty in this work is to present a numerical method to easily take into consideration such variables and give an accurate prediction of reliability measures of engineering systems.     

Exploring Accessibility in DOAJ: A Case Study

Abstract

This study explores the accessibility of HTML articles indexed in the Directory of Open Access Journals (DOAJ). The researchers tested a random sample of journals that possessed the DOAJ seal of approval, added content in 2019, were published in English and had 50 or more indexed articles. From this sample, HTML full-text articles were randomly selected for accessibility testing, using the W3C Easy Checks. 131 journals on 22 platforms were reviewed. All content reviewed provided unique web page titles. The majority of articles reviewed allowed for increases in text size and had meaningful heading structure. The application of alternative text tags for images and form labels was inconsistent, as was the ability to use keyboard controls for page navigation. Further, most content did not clearly indicate cursor location. The most egregious accessibility issues came from design choices, which generated a variety of contrast errors. More in-depth studies of DOAJ and other OA indexes and content providers are recommended, as is requiring adherence to WCAG 2.0 accessibility criteria as a condition of article submission.     

On estimating the reliability in a multicomponent stress-strength model based on Chen distribution

Abstract

In this article, we obtain point and interval estimates of multicomponent stress-strength reliability model of an s-out-of-j system using classical and Bayesian approaches by assuming both stress and strength variables follow a Chen distribution with a common shape parameter which may be known or unknown. The uniformly minimum variance unbiased estimator of reliability is obtained analytically when the common parameter is known. The behavior of proposed reliability estimates is studied using the estimated risks through Monte Carlo simulations and comments are obtained. Finally, a data set is analyzed for illustrative purposes.     

An improved algorithm for reliability bounds of multistate networks

Abstract

Indirect approaches based on minimal path vectors (d-MPs) and/or minimal cut vectors (d-MCs) are reported to be efficient for the reliability evaluation of multistate networks. Given the need to find more efficient evaluation methods for exact reliability, such techniques may still be cumbersome when the size of the network and the states of component are relatively large. Alternatively, computing reliability bounds can provide approximated reliability with less computational effort. Based on Bai’s exact and indirect reliability evaluation algorithm, an improved algorithm is proposed in this study, which provides sequences of upper and lower reliability bounds of multistate networks. Novel heuristic rules with a pre-specified value to filter less important sets of unspecified states are then developed and incorporated into the algorithm. Computational experiments comparing the proposed methods with an existing direct bounding algorithm show that the new algorithms can provide tight reliability bounds with less computational effort, especially for the proposed algorithm with heuristic L1.     

Statistical Analysis of General Degradation Path Model and Failure Time Data with Multiple Failure Modes

ABSTRACT

This article considers degradation and failure time models with multiple failure modes which used to study the problem of longevity and aging in survival analysis and reliability. Degradation process is modeled using general nonparametric, nonlinear path models. Semi-parametric models for the intensities of the traumatic failures are used supposing that these intensities depend on degradation level. Semi-parametric estimators of various reliability characteristics are proposed and asymptotic properties of the estimators are obtained. The theoretical results are illustrated using simulated data.     

Robust designs for multinomial models

Abstract

Model misspecification in generalized linear models (GLMs) occurs usually when the linear predictor and/or the link function assumed are incorrect. This article discusses the effect of such misspecification on design selection for multinomial GLMs and proposes the use of quantile dispersion graphs to select robust designs. Due to misspecification in the model, parameter estimates are usually biased and the designs are compared on the basis of their mean squared error of prediction. Several numerical examples including a real data set are presented to illustrate the proposed methodology.     

Working Together to Improve Accessibility: Consortial E-Resource Accessibility and Advocacy

Abstract

In 2015, the Big Ten Academic Alliance (BTAA) Libraries formed the BTAA Library E-Resource Accessibility Group. This group, which consists of members from each Big Ten library and the BTAA Library Initiatives staff, was charged with creating boilerplate accessibility license language for vendor contracts, as well as collectively funding high level accessibility testing of e-resources and posting these publicly for all libraries and users. Since the creation of the group, about 50 databases have been tested and accessibility license language has been created that can be used and adapted by anyone. In 2019, the group welcomed another consortia, the Association of Southeastern Research Libraries (ASERL), to be partners in this work, renaming themselves the Library Accessibility Alliance. This paper examines the mission, accomplishments, and new partnership in more depth while also discussing the need for focused efforts to help ensure accessible e-resources.     

Role of weights in improving the efficiency of Kim and Warde's mixed randomized response model

ABSTARCT

In this paper we have suggested a class of unbiased estimators of π_S, the proportion of respondents possessing a sensitive attribute A using mixed randomized response model. The variance of the proposed class of estimators has been obtained. In addition to Kim and Warde's (2005) estimator, several other acceptable estimators of π_S have been identified from the proposed class for suitable weights. It has been shown that the newly identified estimators are more efficient than the Kim and Warde's (2005) estimator. Numerical illustrations and graphs are also given in support of the present study.     

ASYMPTOTIC PROPERTIES FOR MAXIMUM LIKELIHOOD ESTIMATORS FOR RELIABILITY AND FAILURE RATES OF MARKOV CHAINS

ABSTRACT

In this paper, we shall study a homogeneous ergodic, finite state, Markov chain with unknown transition probability matrix. Starting from the well known maximum likelihood estimator of transition probability matrix, we define estimators of reliability and its measurements. Our aim is to show that these estimators are uniformly strongly consistent and converge in distribution to normal random variables. The construction of the confidence intervals for availability, reliability, and failure rates are also given. Finally we shall give a numerical example for illustration and comparing our results with the usual empirical estimator results.     

Reliability design for a MANET with cluster-head gateway routing protocol

ABSTRACT

A MANET is a self-configuring network connected by wireless links. In order to facilitate communication within the network, a routing protocol is used to control the traffic. One of the prominent routing protocols for MANET is CGSR. Network reliability related problems have resulted in the construction of many algorithms. The UGFT has an enterprise approach to analyze the reliability of the MANET. The emphasis in this paper has been on executing the MANET reliability using UGFT. An efficient algorithm has been proposed to guarantee the reliability of MANET using UGFT with CGSR and is validated with a case study in a military test bed.     

A New Direction for Library Technical Services: Using Metadata Skills to Improve User Accessibility

Abstract

An increased awareness about the importance of resource accessibility for all library users has set the stage for transforming traditional cataloger roles into a new realm of possibility. The Acquisitions & Discovery (A&D) and the User Experience (UX) departments of North Carolina State University Libraries have formed a partnership to explore the benefits of working together amidst this climate of innovation and change. A pilot project was created to develop a workflow through which technical services staff can use their metadata skills to help resolve accessibility issues found on the Libraries’ main website. By performing this work, staff can grow in technical expertise, enhance the quality of metadata in web content, and build mutually beneficial partnerships within the library community.     

A Poisson Limit Theorem for Reliability Models Based on Markov Chains

Abstract

In this article, we deal with a class of discrete-time reliability models. The failures are assumed to be generated by an underlying time inhomogeneous Markov chain. The multivariate point process of failures is proved to converge to a Poisson-type process when the failures are rare. As a result, we obtain a Compound Poisson approximation of the cumulative number of failures. A rate of convergence is provided.     

A class of distributions with the quadratic mean residual quantile function

Abstract

The present paper introduces a new family of distributions with quadratic mean residual quantile function. Various distributional properties as well as reliability characteristics are discussed. Some characterizations of the class of distributions are presented. The estimation of parameters of the model using method of L-moments is studied. The practical application of the class of models is illustrated with a real life data set.