Likelihood Ratio Test and Non-parametric Test for Load Sharing

In present article, we propose a likelihood ratio test and a non-parametric test for testing the load sharing effect observed in the two component parallel load sharing system. We have modeled the load sharing phenomenon observed in such system by the exponentiated conditional distribution function based load sharing model proposed by Sutar and Naik-Nimbalkar (2016). We have taken component baseline distribution as Weibull distribution and linear failure rate distribution. The simulation study to see the performance of proposed test procedures is reported. We analyze two data sets for illustrative purpose.

Estimation of R for geometric distribution under lower record values

In this paper, the estimation of the stress-strength model R=P(Y<X), based on lower record values is derived when both X and Y are independent and identical random variables with geometric distribution. Estimating R with maximum likelihood estimator and Bayes estimator with non-informative prior information based on mean square errors and LINIX loss functions for geometric distribution are obtained. The confidence intervals of R are constructed by using exact, bootstrap and Bayesian methods. Finally, different methods have been used for illustrative purpose by using simulation. The main results are obtained and introduced through a set of tables and figures with discussions.

The Topp-Leone Generalized Inverted Exponential Distribution with Real Data Applications

In this article, a new three parameters lifetime model called the Topp-Leone Generalized Inverted Exponential (TLGIE) Distribution is introduced. Various properties of the model are derived, including moments, quantile function, survival function, hazard rate function, mean deviation and mode. The method of maximum likelihood is used to estimate the unknown parameters. The properties of the maximum likelihood estimators using Fisher information matrix are studied. Three real data sets are applied for illustrative purpose of this study.

A Dual-Vector Method to Derive the Equivalent Screw of Two Successive Finite Screw Displacements for Line Segments

For finite rigid body motion, every two successive screw displacements can be represented by one equivalent screw displacement. However, such phenomenon should not be considered naturally to be valid for incompletely specified displacements (ISDs). There is neither a precise statement for such phenomenon nor an understanding of its range of validity within ISD, such as line segment displacements. As one of the main contributions in this paper, based on dual vector algebra and screw theory, an algorithm is provided to prove the existence of the subset within the scope of the line segment motion, which expresses the similar relation as shown in finite rigid body motion. A numerical example is presented for illustrative purpose.

Simultaneously Testing for Location and Scale Parameters of Two Multivariate Distributions

In this article, we propose nonparametric tests for simultaneously testing equality of location and scale parameters of two multivariate distributions by using nonparametric combination theory. Our approach is to combine the data depth based location and scale tests using combining function to construct a new data depth based test for testing both location and scale parameters. Based on this approach, we have proposed several tests. Fisher's permutation principle is used to obtain p-values of the proposed tests. Performance of proposed tests has been evaluated in terms of empirical power for symmetric and skewed multivariate distributions and compared to the existing test based on data depth. The proposed tests are also applied to a real-life data set for illustrative purpose.

Conditional direction dependence analysis in linear models with SPSS macros and custom dialogue implementation

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] In nonexperimental data, the causal ordering of variables can be examined with Direction dependence analysis (DDA), a statistical method that utilizes various asymmetry properties of the linear regression model to validate a postulated explanatory model against plausible causally reversed alternative models. However, standard DDA assumes that the observed causal effect is constant for all subjects and does not consider the conditional effect of a third variable on direction dependence, which may lead to biases and/or compromised power. The present work relaxes this assumption by proposing conditional direction dependence analysis (CDDA). CDDA examines the direction of effect when a moderator is present and extends standard DDA by combining the pick-a-point approach and variable purification technique, which enables researchers to examine the direction of effect at a certain moderator value. The results of two Monte-Carlo simulation studies are reported which evaluate the performance of CDDA. The first simulation study shows that the observed power of DDA tests vary across moderator values when a t hird variable moderators the main effect. The second study shows that, under certain conditions, CDDA is able to identify the true data-generating mechanism when a third variable determines the direction of causal flow. SPSS macros and auxiliary custom dialogues are provided for easy implementation of CDDA procedures, which is illustrated with a worked example. A real-world example is given for illustrative purpose.

Hypergraphia: Illustrating clinical pictures

IntroductionHypergraphia is an extensive writing tendency sometimes coupled with hyperreliogiosity and atypical sexuality, completing a syndrome described by Waxman and Geschwind in 1975 during interictal phases of patients with temporal lobe epilepsy. Nevertheless, it may arise from any temporolimbic lesion, usually in the right hemisphere, in contrast to the schizophreniform psychosis more often seen in left-sided lesions.ObjectiveA review on the lateralizing significance of temporolimbic lesions, highlighting the (un)specificity of hypergraphia, after a case report concerning a patient with both hypergraphia and schizophreniform psychosis.MethodsAnalyse patient's clinical records and PubMed review, using hypergraphia, epilepsy and psychosis as keywords.ResultsWe report a 74-year-old male admitted due to aggressiveness. The patient had a traumatic brain injury in his 20s with secondary left temporal epilepsy. He lived in a psychiatric asylum, for almost 40 years, with the diagnosis of schizophrenia, showing fluctuant atypical sexual behavior. After being transinstitutionalized to community nursing-home he developed meningoencephalitis, leading to medication change and behavior relapse. He showed viscosity, circumstantiality, soliloquy, euthymic mood and normal cognition. He wrote profusely, e.g. lists of various categories and letters to eminent clerics and politics. His diary was scanned for illustrative purpose.ConclusionsHypergraphia is an uncommon but easy to find symptom that deserves the full attention of the clinician, especially in the differential diagnosis between schizophreniform psychosis and temporal epilepsy.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Testing a simple method for computing directly the bulk modulus by NPT simulation: The case of polydisperse hard sphere solids

The bulk modulus of hard sphere solids has been computed directly by constant pressure Monte-Carlo simulations, using the histogram of the volume fluctuations. In considering first the one-component system, we show that the method is accurate in a large range of pressures, including high-pressure regime. The method is then applied to a polydisperse solid with relatively low polydispersity index. For illustrative purpose, we took a three-component mixture with symmetric size-distribution, and we studied the solid phase (fcc crystal) of this system. Our results show that the equation of state is very sensitive to the polydispersity. Furthermore, in the high-pressure region, where no (accurate) analytical fit for the equation of state exists, our simulations are able to predict the bulk modulus of such systems.

Seeking rigor in South African business research: Aspirational principles in contrast to a recent publication

Studies of organizational success and other aspects of management are critical in understanding and improving critical areas of African economic stability. This article seeks to urge high levels of rigor in South African research in this area, notably empirical research, proposing several aspirational research principles. First, the article considers claims of uniqueness versus the practical value of embedding research as a replication in a well-considered wider body of knowledge. Second is the desirability of conforming to sufficiently high norms of model fit and effect size and accuracy. Third is empirical comparison of South African studies with previous findings, with attendant possibilities for new theory development. Fourth is proper tests for and treatment of common method bias. Fifth is specification of appropriate sets of constructs. Finally, this article proposes specification of alternate models that will add substantial rigor to such research. In advocating these possibilities, the current article contrasts these aspirational principles to a recent SAJEMS article. This critique serves an exclusively illustrative purpose, showing some pitfalls of not conforming to the aspirational principles, the benefits of explicitly including certain easy to achieve solutions, and the ease with which greater rigor can sometimes be achieved. Ultimately, this article seeks to constructively advance African business research standards.

Optimization Problems of Costs in a MultiState System with Imperfect Maintenance

We consider optimal replacement policies with periodic imperfect maintenance actions and minimal repairs. The multistate system is minimally repaired at failure and imperfect maintenance actions are regularly carried out for preventive maintenance. The discrete modified Weibull distribution is introduced and some cost functions applied to this distribution are defined in order to be minimized. Moreover, we assume that the costs of preventive maintenance depend on the degree of repair via a Kijima type 2 model. For illustrative purpose, the obtained results are applied on sets of simulated data.