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Control Factors (control + factor)
Selected AbstractsRobust design of communication systems: The case of expedited forwarding of voice traffic in differentiated services networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 10 2007Hyoup-Sang Yoon Abstract Design of experiments (DOE) is gaining acceptance in the community of telecommunication researchers, especially during the past several years. In this paper, a state-of-the-art review on the use of DOE in the field of communication networks is presented, and the need for introducing a systematic robust design methodology to network simulations or testbed experiments is identified in ensuring robust behaviours of a network against uncontrollable sources of variation. Then, the Taguchi robust design methodology is applied for optimizing the expedited forwarding (EF) of voice traffic in a differentiated services network, and its step-by-step procedures are described in detail. The experimental data are collected using the ns-2 simulator, and the SN ratio, a robustness measure, is analysed to determine an optimal design condition for each performance characteristic. The analysis results show that ,type of queue scheduling schemes' is a major control factor for ensuring robust behaviours of one-way delay and jitter while ,EF queue size' is for throughput and loss rate. Finally, a compromised optimal design condition is identified using a desirability function approach adapted to multi-characteristic robust design problems. Copyright © 2007 John Wiley & Sons, Ltd. [source] Optimal Design of the Online Auction Channel: Analytical, Empirical, and Computational Insights,DECISION SCIENCES, Issue 4 2002Ravi Bapna ABSTRACT The focus of this study is on business-to-consumer (B2C) online auctions made possible by the advent of electronic commerce over an open-source, ubiquitous Internet Protocol (IP) computer network. This work presents an analytical model that characterizes the revenue generation process for a popular B2C online auction, namely, Yankee auctions. Such auctions sell multiple identical units of a good to multiple buyers using an ascending and open auction mechanism. The methodologies used to validate the analytical model range from empirical analysis to simulation. A key contribution of this study is the design of a partitioning scheme of the discrete valuation space of the bidders such that equilibrium points with higher revenue structures become identifiable and feasible. Our analysis indicates that the auctioneers are, most of the time, far away from the optimal choice of key control factors such as the bid increment, resulting in substantial losses in a market with already tight margins. With this in mind, we put forward a portfolio of tools, varying in their level of abstraction and information intensity requirements, which help auctioneers maximize their revenues. [source] A National Study of Efficiency for Dialysis Centers: An Examination of Market Competition and Facility Characteristics for Production of Multiple Dialysis OutputsHEALTH SERVICES RESEARCH, Issue 3 2002Hacer Ozgen Objective. To examine market competition and facility characteristics that can be related to technical efficiency in the production of multiple dialysis outputs from the perspective of the industrial organization model. Study Setting. Freestanding dialysis facilities that operated in 1997 submitted cost report forms to the Health Care Financing Administration (HCFA), and offered all three outputs,outpatient dialysis, dialysis training, and home program dialysis. Data Sources. The Independent Renal Facility Cost Report Data file (IRFCRD) from HCFA was utilized to obtain information on output and input variables and market and facility features for 791 multiple-output facilities. Information regarding population characteristics was obtained from the Area Resources File. Study Design. Cross-sectional data for the year 1997 were utilized to obtain facility-specific technical efficiency scores estimated through Data Envelopment Analysis (DEA). A binary variable of efficiency status was then regressed against its market and facility characteristics and control factors in a multivariate logistic regression analysis. Principal Findings. The majority of the facilities in the sample are functioning technically inefficiently. Neither the intensity of market competition nor a policy of dialyzer reuse has a significant effect on the facilities' efficiency. Technical efficiency is significantly associated, however, with type of ownership, with the interaction between the market concentration of for-profits and ownership type, and with affiliations with chains of different sizes. Nonprofit and government-owned facilities are more likely than their for-profit counterparts to become inefficient producers of renal dialysis outputs. On the other hand, that relationship between ownership form and efficiency is reversed as the market concentration of for-profits in a given market increases. Facilities that are members of large chains are more likely to be technically inefficient. Conclusions. Facilities do not appear to benefit from joint production of a variety of dialysis outputs, which may explain the ongoing tendency toward single-output production. Ownership form does make a positive difference in production efficiency, but only in local markets where competition exists between nonprofit and for-profit facilities. The increasing inefficiency associated with membership in large chains suggests that the growing consolidation in the dialysis industry may not, in fact, be the strategy for attaining more technical efficiency in the production of multiple dialysis outputs. [source] The Taxonomy, Model and Message Strategies of Social BehaviorJOURNAL FOR THE THEORY OF SOCIAL BEHAVIOUR, Issue 3 2007TSUEN-HO HSU ABSTRACT In an era of rising social awareness, both academics and practitioners have been concerned about the effectiveness of pro-social consumer influence strategies. The main assumption here is that for social marketing to succeed one must first understand the factors underlying pro-social consumer behavior. Firstly, drawing on two dimensions (i.e. the welfare receiver and restitution intention) the authors first identify four types of social behavior (altruism, compensation, reciprocity, and egoism). Next, the model describes social behavior as a result of preceding social behavior motivation and actual social behavior intention. Norms and economic evaluation have an impact on social behavior motivation, which in turn influences social behavior intention, eventually leading to actual social behavior. Actual control factors, such as the availability of resources and opportunities, decide whether social behavior intention can really translate into actual social behavior. Finally, authors propose message strategies (incorporating message appeal, message frame and central/peripheral processing) for each type of social behavior. [source] The Mediterranean bryozoan Myriapora truncata (Pallas, 1766): a potential indicator of (palaeo-) environmental conditionsLETHAIA, Issue 3 2007BJÖRN BERNING Fossil and Recent specimens of the Mediterranean bryozoan Myriapora truncata show considerable intra- and intercolonial differences in branch diameter and zooid size. Statistically significant variability occurs within colonies, between colonies within sites, and between sampled sites, while the presence of intracolonial variability clearly shows that branch diameter is largely controlled by environmental parameters. The three structural traits measured (branch diameter, zooid size and zooid depth) do not correlate, thus indicating a disconnection between the controls on overall zooid size and branch diameter. Possible environmental parameters that may have an influence on morphology are temperature, food supply or current energy. Whereas current energy has an effect on the colony branching pattern (branch spacing), there are indications that temperature may be the main, but not the only, parameter controlling zooid size, and it is suggested that food supply largely determines the branch diameter in M. truncata. However, the identification of the decisive factors and quantification of the relationships between environmental and morphological change is beyond the scope of this study. The results nevertheless show that, if the control factors of morphological variability can be ascertained in Recent M. truncata, this species may prove to be an indicator of environmental conditions and their change at different spatial and temporal scales in Cenozoic to Recent Mediterranean habitats. [source] Project portfolio control and portfolio management performance in different contextsPROJECT MANAGEMENT JOURNAL, Issue 3 2008Ralf Müller Abstract This article investigates the nature and relationship of project portfolio control techniques and portfolio management performance, and how this relationship is moderated by situational idiosyncrasies of internal and external dynamics, industries, governance types, and geographic location. A worldwide questionnaire with 242 responses was used, of which 136 high-performing responses were filtered out for quantitative analysis of best practices. Three portfolio control factors were identified: portfolio selection, portfolio reporting, and decision-making style. Two measures for portfolio management performance were identified: achievement of desired portfolio results and achievement of project and program purpose. The results indicate that different portfolio control mechanisms are associated with different performance measures. A contingency model was developed, including moderating effects by contextual variables. [source] | ||||||||||