Data relaying with constraints in hierarchical sensor networks

In this paper we present and discuss several optimisation problems that arise in the management of data flow in wireless sensor networks (WSNets). We consider a hierarchical architecture for WSNets composed of sensors, relays, and relay gateways. Sensors send data they generate at a known average bit rate to relays in one hop. The relay nodes use a multi-hop mechanism to reach a set of assigned gateways which then forward the data directly to the base station. We are concerned with finding an assignment of relay gateways to relays so that certain constraints are satisfied. We define a unified model in which constraints such as lifetime, data delay, and data flow splitting are formulated in terms of four optimisation problem in graphs.     

Three explanations of marital status differences in suicide rates: social integration, marital status integration, and the culture of suicide

Our first goal is to link empirical measures of three theoretical explanations of marital status differences to the variation in male and female standardized suicide difference coefficients SSDCs in 12 developed countries, circa 1960. We include predictors of Durkheim's social integration hypothesis, Gibbs and Martin's concept of marital status integration, and norms on suicide acceptability. All three are significantly related to variation in male and female SSDCs. The second goal is to examine how our empirical indicators impact age-specific differences in the male minus female SSDC--differences that vary by age in all 12 of our study populations. The strongest predictor of these differences is the male minus female difference in the percent married.     

Life cycles of growing organizations: A review with implications for knowledge and learning

Conceptualizing growth trajectories of organizations in organismic terms describing transitions through a series of stages, from birth to maturity, has considerable intuitive appeal. Recently, the assumptions underpinning the life‐cycle perspective (growth is linear, sequential, deterministic and invariant) have been argued not to pertain to organizations. This paper reviews the literature on life‐cycle growth models, traces the development of a growing sophistication of conceptualizing growth and highlights some of the limitations of the literature. The authors make a contribution by proposing an alternative conceptual framework for thinking about growing businesses. The framework consists of two dimensions. First, a typology of key issues that are likely to be faced by all growing firms, and the discussion is shaped by M. Gladwell's (The Tipping Point: How Little Things Can Make a Big Difference. Boston: Little Brown, 2000) notion of ‘tipping points’. The second dimension is developed by drawing on the knowledge management literature and the concept of absorptive capacity ( Cohen, W.M. and Levinthal, D.A. (1990 ). Absorptive capacity: a new perspective on learning and innovation. Administrative Science Quarterly, 35 , 128–152). This concept is applied to a discussion of the state of an organization regarding its ability to absorb and use new knowledge. Further, it is suggested that the framework has value for both policy and practice and can be used for the design and specification of interventional support and, to identify and evaluate their impact. If interventions are to help firms to grow, they must provide the right knowledge or support in forms that the firm can utilize. Together, these two dimensions provide a framework to examine firm growth issues and to analyse the effectiveness of different interventions on firms in different states within this framework.     

Intensity of Interaction in Supply of Business Advice and Client Impact: A Comparison of Consultancy,Business Associations and Government Support Initiatives for SMEs

This paper assesses the supply of business advice using new empirical evidence from a large-scale survey of SMEs. The chief focus of the paper is on a comparison of suppliers that operate in different environments of regulation, contract and reputation. The paper argues that interaction intensity varies with the level of information asymmetry of these different environments, between different types of service supplier and their clients. Interaction intensity between suppliers also varies as a result of the level of trust they enjoy: for example, the low trust enjoyed by consultants appears to encourage higher intensity of interaction which improves the tailoring of the service to the client's needs and enhances impact. The paper assesses interaction intensity using the existence of site visits and/or a written brief/contract as indicators. Although these measures have limitations, the paper demonstrates clear and significant differences between suppliers in terms of interaction intensity, use of contracts and impact in three broad categories: private-sector consultancy (low trust, high intensity, high impact), business associations (high trust, low intensity, moderate impact) and government support agencies (moderate trust, moderate to high intensity, moderate or low impact). Multivariate estimation methods demonstrate that significant differences in interaction intensity, use of contracts and impact by client type are much less important than differences in supplier type. This indicates that suppliers generally develop more into niche service fields or groups of services rather than niches related to types of firm.     

Replanning the Master Production Schedule for a Capacity-Constrained Job Shop

This research examines the use of both frozen and replanning intervals for planning the master production schedule (MPS) for a capacity-constrained job shop. The results show that forecast error, demand lumpiness, setup time, planned lead time, and order size have a greater impact on the mean total backlog, total inventory, and number of setups than the frozen and replanning intervals. The study also shows that a repetitive lot dispatching rule reduces the importance of lot sizing, and a combination of repetitive lot dispatching rule and single-period order size consistently produces the lowest mean total backlog and total inventory. The results also indicate that rescheduling the open orders every period produces a lower mean total backlog and total inventory when the forecast errors are large relative to the order sizes. This result suggests that the due date of an open order should be updated only when a significant portion of the order is actually needed on the new due date.     

Distribution of Exposure Concentrations and Doses for Constituents of Environmental Tobacco Smoke

The ultimate goal of the research reported in this series of three articles is to derive distributions of doses of selected environmental tobacco smoke (ETS)-related chemicals for nonsmoking workers. This analysis uses data from the 16-City Study collected with personal monitors over the course of one workday in workplaces where smoking occurred. In this article, we describe distributions of ETS chemical concentrations and the characteristics of those distributions (e.g., whether the distribution was log normal for a given constituent) for the workplace exposure. Next, we present population parameters relevant for estimating dose distributions and the methods used for estimating those dose distributions. Finally, we derive distributions of doses of selected ETS-related constituents obtained in the workplace for people in smoking work environments. Estimating dose distributions provided information beyond the usual point estimate of dose and showed that the preponderance of individuals exposed to ETS in the workplace were exposed at the low end of the dose distribution curve. The results of this analysis include estimations of hourly maxima and time-weighted average (TWA) doses of nicotine from workplace exposures to ETS (extrapolated from 1 day to 1 week) and doses derived from modeled lung burdens of ultraviolet-absorbing particulate matter (UVPM) and solanesol resulting from workplace exposures to ETS (extrapolated from 1 day to 1 year).     

Reliability Analysis for Hazardous Waste Treatment Processes

The reliability of a treatment process is addressed in terms of achieving a regulatory effluent concentration standard and the design safety factors associated with the treatment process. This methodology was then applied to two aqueous hazardous waste treatment processes: packed tower aeration and activated sludge (aerobic) biological treatment. The designs achieving 95 percent reliability were compared with those designs based on conventional practice to determine their patterns of conservatism. Scoping-level treatment costs were also related to reliability levels for these treatment processes. The results indicate that the reliability levels for the physical/chemical treatment process (packed tower aeration) based on the deterministic safety factors range from 80 percent to over 99 percent, whereas those for the biological treatment process range from near 0 percent to over 99 percent, depending on the compound evaluated. Increases in reliability per unit increase in treatment costs are most pronounced at lower reliability levels (less than about 80 percent) than at the higher reliability levels (greater than 90 percent, indicating a point of diminishing returns. Additional research focused on process parameters that presently contain large uncertainties may reduce those uncertainties, with attending increases in the reliability levels of the treatment processes.