Parameter estimation in a highly non-linear model using simultaneous perturbation stochastic approximation

Often it is necessary to estimate the parameters of a model or unknown system. Various techniques exist to accomplish this task, including Kalman and Wiener filtering, least-mean-square (LMS) algorithms, and the Levenberg-Marquardt(L-M) algorithm. These techniques require an analytic form of the gradient of the function of the parameters to be estimated. A key feature of the simultaneous perturbation stochastic approximation (SPSA) method is that it is a gradient-free optimization technique (Spall; 1992,1998a,b, 1999). In the current problem, the function of parameters to be identified is highly non-linear and of sufficient difficulty that obtaining an analytic form of the gradient is impractical. Therefore, in this paper the

performance of the SPSA algorithm will be examined in terms of parameter selection, data requirements, and convergence performance on this non-linear problem. Results will be reported on both a first-order "standard" implementation of SPSA and on a second-order version of SPSA that tends to enhance convergence.     

Additive Risk Model Using Piecewise Constant Hazard Function

We study a weighted least squares estimator for Aalen's additive risk model with right-censored survival data which allows for a very flexible handling of covariates. We divide the follow-up period into intervals and assume a constant hazard rate in each interval. The model is motivated as a piecewise approximation of a hazard function composed of three parts: arbitrary nonparametric functions for some covariate effects, smoothly varying functions for others, and known (or constant) functions for yet others. The proposed estimator is an extension of the grouped data version of the Huffer and McKeague (1991 Huffer , F. W. , McKeague , I. W. ( 1991 ). Weighted least squares estimation for Aalen's additive risk model . Journal of the American Statistical Association 86 : 114 – 129 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) estimator. For our model, since the number of parameters is finite (although large), conventional approaches (such as maximum likelihood) are easy to formulate and implement. The approach is illustrated by simulations, and is compared to the previous studies. The method is also applied to the Framingham study data.     

ENGAGING COMMUNITY IN A CYCLE OF PRAXIS

This study employed an action research model known as the community wellness cycle of praxis in research with culturally diverse community members from the St Albans region (Melbourne, Australia). The major aim of the study was to gain a theoretical and pragmatic understanding of well-being from a multicultural perspective. In order to meet this aim, a qualitative study was designed to find out (1) What are the community ideals; needs; and strengths of residents of St Albans, and (2) What actions can be undertaken to improve the well-being of the community? The research involved focus groups with a total of 29 Anglo, Maltese, Vietnamese and Italian community members. The first research question was addressed by asking community members systematically about positive and negative aspects of personal, relational and collective well-being. The second research question was addressed by asking community members to generate ideas on what could be done to improve well-being and by identifying issues of concern that emerged throughout the research. The issues identified by participants offer a rich picture of community ideals, strengths and needs, as well as possible actions that could improve personal, relational and collective wellness in St Albans.

Cette étude utilise un approche de recherche action connu sous le nom du cycle de bien-être de praxis de recherche avec des membres culturellement varies dans un banlieue de Melbourne (Australie). Le but principal de l’étude était de comprendre théoriquement et pragmatiquement bien-être dans d'une perspective multiculturelle. Dans ce perspective étude qualitative a été conçue pour identifier (1) ce que sont les opinions des groupes diverses; leurs besoins et leurs atouts, et (2) de quelles actions peuvent être entreprises affin d améliorer le bien-être de ces groupes? La recherche a utilisé 29 Anglo-Australiens, Maltais, Vietnamiens et Italiens. Les premières questions ce sont posées a propos des aspects positifs et négatifs de bien-être individuel et collectif. Ensuite des questions ont été demandé à propos des idées sur ce qui on pourrait être fait pour améliorer le bien-être et en identifiant leurs soucis. Les soucis identifiées par les participants offrent une image riche des images et des représentations leurs atouts leurs, aussi bien que les actions qui pourraient améliorer le bien-être individuel et collective.     

Domestic violence in veterans with posttraumatic stress disorder who seek couples therapy

Domestic violence rates among veterans with posttraumatic stress disorder (PTSD) are higher than those of the general population. Individuals who have been diagnosed with PTSD who seek couples therapy with their partners constitute an understudied population. Self-report measures of domestic violence, relationship satisfaction, and intimacy were administered at intake to 179 couples seeking relationship therapy at a Veterans Affairs clinic. Couples in which the veteran was diagnosed with combat-related PTSD were compared with two other groups based on the veteran's primary diagnosis (depression, adjustment disorder/V-code). Both the PTSD- and depression-diagnosed veterans perpetrated more violence than did those with adjustment/V-code diagnoses. Domestic violence rates among depressed and PTSD-diagnosed veterans were much higher than those found in previous research. Implications for assessment and treatment are discussed.     

The Institutional Grammar: A Method for Coding Institutions and its Potential for Advancing Third Sector Research

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - Institutions—defined as strategies, norms and rules (Ostrom Understanding institutional diversity, Princeton...     

Optimizing Service Attributes: The Seller's Utility Problem*

Service designers predict market share and sales for their new designs by estimating consumer utilities. The service's technical features (for example, overnight parcel delivery), its price, and the nature of consumer interactions with the service delivery system influence those utilities. Price and the service's technical features are usually quite objective and readily ascertained by the consumer. However, consumer perceptions about their interactions with the service delivery system are usually far more subjective. Furthermore, service designers can only hope to influence those perceptions indirectly through their decisions about nonlinear processes such as employee recruiting, training, and scheduling policies. Like the service's technical features, these process choices affect quality perceptions, market share, revenues, costs, and profits. We propose a heuristic for the NP‐hard service design problem that integrates realistic service delivery cost models with conjoint analysis. The resulting seller's utility function links expected profits to the intensity of a service's influential attributes and also reveals an ideal setting or level for each service attribute. In tests with simulated service design problems, our proposed configurations compare quite favorably with the designs suggested by other normative service design heuristics.     

What makes a developmental network state durable?

As dynamic collaborations between networks of specialists have become more central to developing cutting-edge innovations, designing and sustaining innovation policies that foster them has become an increasingly central concern. This article reviews the characteristics of the “developmental network” or “neo-developmental” states that have been shown to foster innovations at the technological horizon. It then analyzes the US case to suggest why some developmental network approaches to governance have proven relatively durable, while others have not. We conclude with a discussion of what can – and cannot – be learned from the US case, and suggest the importance of comparative work on the sustainability of effective innovation-centered approaches to governance.     

Trajectories of loneliness during COVID-19 pandemic and associations with mental health and substance use

We examined patterns of longitudinal trajectories of loneliness during the COVID-19 pandemic using six time points (January 2020 [pre-pandemic] to March/April 2021) and whether trajectories were associated with psychological distress (depression/anxiety) and substance use (alcohol/cannabis) outcomes in Spring 2021. Participants were 644 young adults who completed online assessments. Outcomes were regressed on most-likely loneliness trajectory adjusting for pre-pandemic measures. Three loneliness trajectories varied from consistently lower to consistently higher. Pre-pandemic social support was associated with lower odds of a higher loneliness trajectory. Higher loneliness trajectories were associated with greater odds of past-month cannabis use compared to Low trajectories, but not significantly associated with depression, anxiety, or alcohol use in Spring 2021. Interventions addressing co-occurring loneliness and cannabis use are needed.     

Organizations and the structure of culture

Recent work emphasizes how organizations and organizing are suffused by culture. Ignored, however, is the question of how organizations and organizing shape cultural understandings. In this paper, we draw attention to how organizations impact the creation, maintenance, and matching of cultural associations: The “structure of culture.” Cultural associations are distributed understandings of “what goes with what,” diffused via their co-adoption by individual and corporate actors. We argue that the process of associative diffusion is heavily influenced by organizational forms, routines, and operations. While organizations shape culture production, they likewise shape resulting associations between cultural items, actively modifying the structure of culture. We conclude that the role of organizations in shaping the structure and dynamics of culture should be a central topic of study moving forward.