Linking discrete event simulation models using HLA

The increasing usage of discrete event simulation packages for modeling and analyzing manufacturing and logistics has led to a need for connecting simulation models together at runtime. One such methodology for linking discrete event simulation models together has been developed for this research and this paper demonstrates the usage of this linking method. A unified simulation model is developed from two submodels developed using different simulation packages.

SAS macros for point and interval estimation of area under the receiver operating characteristic curve for non-proportional and proportional hazards Weibull models

Aims and objectives  For prediction of risk of cardiovascular end points using survival models the proportional hazards assumption is often not met. Thus, non-proportional hazards models are more appropriate for developing risk prediction equations in such situations. However, computer program for evaluating the prediction performance of such models has been rarely addressed. We therefore developed SAS macro programs for evaluating the discriminative ability of a non-proportional hazards Weibull model developed by Anderson (1991) and that of a proportional hazards Weibull model using the area under receiver operating characteristic (ROC) curve.

Method  Two SAS macro programs for non-proportional hazards Weibull model using Proc NLIN and Proc NLP respectively and model validation using area under ROC curve (with its confidence limits) were written with SAS IML language. A similar SAS macro for proportional hazards Weibull model was also written.

Results  The computer program was applied to data on coronary heart disease incidence for a Framingham population cohort. The five risk factors considered were current smoking, age, blood pressure, cholesterol and obesity. The predictive ability of the non-proportional hazard Weibull model was slightly higher than that of its proportional hazard counterpart. An advantage of SAS Proc NLP in terms of the example provided here is that it provides significance level for the parameter estimates whereas Proc NLIN does not.

Conclusion  The program is very useful for evaluating the predictive performance of non-proportional and proportional hazards Weibull models.

Alternative service delivery models for families with a new speech generating device: perspectives of parents and therapists

Purpose: Research has revealed limitations in the provision of in-person services to families with a new speech generating device (SGD), both in Australia and overseas. Alternative service models such as parent training, peer support and telepractice may offer a solution, but their use with this population has not been researched to date.

Method: Using interviews and focus groups, this study explored the experiences and opinions of 13 speech-language pathologists and seven parents regarding alternatives to in-person support and training for families with a new SGD. Data were analysed using grounded theory. Themes explored in this paper include the benefits and drawbacks of alternative service models as well as participants’ suggestions for the optimal implementation of these approaches.

Result: Participants confirmed the utility of alternative service models, particularly for rural/remote and underserviced clients. Benefits of these models included reduced travel time for families and therapists, as well as enhanced information access, support and advocacy for parents.

Conclusion: Participants viewed the provision of ongoing professional support to families as critical, regardless of service modality. Additional issues arising from this study include the need for development of organizational policies, resources and training infrastructure to support the implementation of these alternative service models.

Online distance education models and research implications

As a form of education, distance education is influenced by educationaltheories and ideologies. Hence, over time its various theoretical modelshave reflected varying emphases on students, both individually and ingroups, on content and process, and on administration and costs, and itsguiding philosophies have ranged from knowledge replication to knowledge creation, and from teacher direction to learner engagement. Its founding purpose was the provision of education to populations who were not able to access available residential education. The reasons were not only based on the individual situation, such as, geographic location, family commitments,work commitments, or cost factors, but also included state issues such as insufficient institutions or a lack of enrolment places, full-time funding, or sufficient staff. These factors have contributed in various ways to the growth of distance education, both historically as when distance education was a major focus in many European countries after WWII, and as a current imperative in many countries where the need and desire for education outstrips the supply through residential institutions, regardless of their fiscal capacities. Education is seen by both individuals and states as essential for the development of a better socio-economic environment, hence, distance education has become the cost-affordable means of provision for millions worldwide.Distance education, then, is framed within larger socio-economic andpolitical contexts. These are not only reflective of societal characteristics like those identified by Keegan (2000): immediacy, globalization, privatization, and industrialization, to which we added professional learning, but also reflective of current social, political, and economic circumstances, such as the sequence of global economic crises this century.Within these contexts then, the provision of distance education seldomarises from the desire of an institution alone; rather there are likely to becomplex national, local, and individual aspirations where distance education is seen as the best solution. The realization of this provision depends on the issues being addressed and the various influences on the particular configuration of design and provision. It may be publicly or privately funded; it may seek to emulate or extend educational provision in residential institutions; its focus may be on increasing access or openness or convenience.Models or designs for distance education, then, have generally arisen from consideration of these instances, in part to provide a framework for researchers and in part to provide a means to reflect on issues that the models themselves have tried to resolve and sometimes inadvertently create.