Evaluating dampening effects of alternative lot-sizing rules to reduce MRP system nervousness

System nervousness in material requirements planning (MRP) has received considerable attention. Although there are different perceptions of system nervousness, it is generally considered as the negative effects of open orders rescheduling. Several methods are suggested to cope with system nervousness. The use of lotsizing rules to cope with MRP system nervousness is investigated here in this paper. Extra inventories need to be carried with most lot-sizing rules, which can be used to accommodate schedule changes. Thus, the nervousness-dampening mechanism is a built-in feature of these lot-sizing rules. The aim of this paper is to focus on the investigation of the effectiveness of using lot-sizing rules to dampen system nervousness in MRP systems by a simulation study. A factorial design was used to examine the dampening effect of various lot-sizing rules considered here. We find that the part-period balancing rule and least total cost rule turn out to be two effective lot-sizing rules to reduce system nervousness.     

Information Systems at Utilities: An Issue of Value

Abstract

Although a variety of IS issues such as containing costs and developing systems that meet users’ needs should be addressed, a recent survey of utility executives reveals that the primary issue of importance for an organization is the overall financial value that the IS function provides. The survey also reveals the specific rankings of several strategic IS issues and the actions these executives would take to address these issues.     

Spectral effects on the transmittance, solar heat gain, and performance rating of glazing systems

This study investigates the potential changes in Solar Heat Gain Coefficient (SHGC) and Visible Transmittance (VT) ratings of vertical or tilted glazing systems that would result from a deliberate change in the reference spectrum used as Spectral Weighting Function (SWF). This SWF is necessary to evaluate broadband-average optical properties from their spectral values, and obtain the desired rating of such bulk properties. The SWFs currently specified by rating institutions in Europe and North America for SHGC and VT are now outdated, and their inadequacies are discussed. Six potential replacements, which have been recently adopted by ASTM are described, including three direct irradiance spectra and three global irradiance spectrum incident on tilted surfaces of various tilts (20°, 37° and 90°). Some of these spectra have been tailored for use in building energy applications, including Building-Integrated Photovoltaics (BIPV). The effect of tilt on the U-factor and hence SHGC of glazing systems used for skylights on roofs is discussed, using a representative dataset of 37 glazing system specimens. The spectral effects on SHGC induced by a change in the current North American SWF are also obtained for this dataset, and show small to moderate deviations from current ratings (−2% to +7% for windows, and −3% to +11% for skylights). The variations in VT are within ±2% for most glazing systems. To remove the current inconsistency in the SWFs used for SHGC and VT, it is recommended that a single SWF be used for both properties. For improved accuracy and reliance on active standards, it is also recommended that the SWF for SHGC and VT be either one of the two recent ASTM G197-08 global irradiance spectra, depending on application (incidence on a vertical surface for window applications, and incidence on a 20°-tilted surface for skylight applications). No change in colorimetric calculations (based on the D65 illuminant) is recommended, however.     

Continuous hydrothermal synthesis of HT-LiCoO2 in supercritical water

A detailed investigation was made into the production of high temperature lithium cobalt oxide (HT-LiCoO₂) particles by continuous hydrothermal synthesis via the reaction of cobalt nitrate, lithium hydroxide, and hydrogen peroxide. The experiments were carried out in both subcritical and supercritical water, at temperatures ranging from 300 to 411 °C, with residence times less than 1 min in all instances. Although Co₃O₄ particles were synthesized in subcritical water at similar reaction conditions designed for comparison, well-ordered particles of HT-LiCoO₂ were obtained in supercritical water. In supercritical conditions, the variations in temperature and residence time did not have significant impacts on the average particle size, particle size distribution, or morphology of obtained HT-LiCoO₂. However, it was important to supply excessive lithium hydroxide and hydrogen peroxide in order to synthesize single-phased HT-LiCoO₂ particles without undesired by-products. The hydrothermal synthetic route for LiCoO₂, CoO, and Co₃O₄ in both subcritical and supercritical conditions was postulated.     

Discrete-event simulation based performance quantification of web-based and traditional bidder inquiry processes

This paper describes an innovative application of discrete-event simulation to model and evaluate differences in business processes following the introduction of new information technologies. Validated models can be used by offices considering the new technology to calibrate existing work loads and then to predict the expected impact of new information technology on measurable business metrics. Following the introduction of the technology, this model may assist in the real-time verification of user paths incorporated in software support tools. This paper will be of interest to those evaluating the impact of information technology and public construction contract administration.