System dynamics modeling of engineering change management in a collaborative environment

Engineering changes to products aim to correct design faults, exploit new market opportunities, improve overall product performance, or reduce production costs. These changes are thus considered as opportunities to stay competitive in the market place and companies strive to implement them in their products at the lowest possible costs. Such engineering changes in a collaborative environment require the original equipment manufacturer to work together with suppliers for designing, manufacturing, and marketing a product profitably. Simulation of an engineering change management process provides an understanding of important factors affecting the engineering change management process and helps in identifying any critical components of the entire process. In this research, system dynamics models have been developed to study the complex interrelationships among various members in a collaborative supply chain to achieve effective and efficient engineering change management processes. To address the complexity of the models, several standard templates have been developed and used.     

Synthesis of Bisindolylmethanes and Their Cytotoxicity Properties

Polymer supported dichlorophosphate (PEG-OPOCl₂) is an efficient green catalyst for the electrophilic substitution reaction of indole with aromatic aldehydes, in neat condition, to afford an excellent yield of bis(indolyl) methanes with short reaction time, at room temperature. The synthesized compounds and their anti-cancer activity are evaluated.     

Hydrogen refueling station compression and storage optimization with tube-trailer deliveries

Hydrogen refueling stations require high capital investment, with compression and storage comprising more than half of the installed cost of refueling equipment. Refueling station configurations and operation strategies can reduce capital investment while improving equipment utilization. Argonne National Laboratory developed a refueling model to evaluate the impact of various refueling compression and storage configurations and tube trailer operating strategies on the cost of hydrogen refueling. The modeling results revealed that a number of strategies can be employed to reduce fueling costs. Proper sizing of the high-pressure buffer storage reduces the compression requirement considerably, thus reducing refueling costs. Employing a tube trailer to initially fill the vehicle's tank also reduces the compression and storage requirements, further reducing refueling costs. Reducing the cut-off pressure of the tube trailer for initial vehicle fills can also significantly reduce the refueling costs. Finally, increasing the trailer's return pressure can cut refueling costs, especially for delivery distances less than 100 km, and in early markets, when refueling stations will be grossly underutilized.     

Analytical Modeling of Threshold Voltage for Dual-Metal Double-Gate Gate-All-Around (DM-DG-GAA) MOSFET

Silicon - This paper presents, analytical modeling of surface potential,threshold voltage and DIBL for a Dual-Metal Double-Gate Gate-All-Around (DM-DG-GAA) MOSFET considering the parabolic...     

Platelet monoamine oxidase activity in subgroups of alcoholics and controls: results from the Collaborative Study on the Genetics of Alcoholism

OBJECTIVE: Platelet monoamine oxidase (MAO) B activity levels were evaluated to determine whether low platelet MAO activity is a marker for alcoholism, correlates of alcoholism (e.g., cigarette smoking), or a subtype of alcoholism. METHODS: Adult women (n = 788) and men (n = 685) participating in the Collaborative Study on the Genetics of Alcoholism study were evaluated with a semistructured interview, and blood samples were obtained for determination of platelet MAO activity using tryptamine (0.1 mM) as substrate. DSM-III-R alcohol-dependent individuals were subgrouped using four currently available methods (e.g., two variations of the type 1/type 2 scheme, primary versus secondary typology, type A/type B dichotomy). RESULTS: In the overall sample, subjects' gender, cigarette smoking status, and the Collaborative Study on the Genetics of Alcoholism site at which their platelets were prepared explained 22% of the variance in platelet MAO activity levels, and multivariate analysis showed that carrying a broad diagnosis of alcohol dependence did not uniquely explain any additional variance in platelet MAO activity levels. Furthermore, within each of the alcoholic subgrouping methods tested, there were no significant differences in platelet MAO activity for type 1 versus type 2, type A versus type B, or primary versus secondary alcoholics. CONCLUSIONS: Cigarette smoking and male gender are associated with decreased platelet MAO activity levels. After considering these factors, a diagnosis of alcohol dependence does not predict any additional variance in MAO-B activity. Phenotypes of alcoholics (e.g., type 1 versus type 2, type A versus type B, primary versus secondary) do not differ in platelet MAO activity. The results suggest that decreased platelet MAO activity is not a trait marker of alcoholism or one of its subtypes; but, rather, is a state marker of cigarette smoking.     

Permeability Reduction of Soil Filters due to Physical Clogging

Soil filters, which are commonly used to provide stability to the base soils in subsurface infrastructure, are prone to long-term accumulation of fine micron-sized particles. This causes reduction in the permeability, which in turn may lead to intolerable decreases in their drainage capacity. In this paper, the extent of this reduction is addressed using results from both experimental and theoretical investigations. In the experimental phase, a sandy soil commonly used as a filter or drainage layer was subjected to pore fluids containing polystyrene or kaolinite particles, and their permeability reductions were determined in terms of the pore fluid suspension parameters. In the theoretical phase of the investigation, a representative elemental volume of the soil filter was modeled as an ensemble of capillary tubes and the permeability reduction due to physical clogging was simulated using basic principles of flow in cylindrical tubes. The results from the experimental and theoretical investigations were in good agreement. In general, the permeability reduced by more than one order of magnitude, even when the migrating particles were smaller than the majority of the soil filter pores. The concentration of particles in the pore stream affected the rate at which the permeability reduced. Self-filtration of particles, which is prominent at higher flow rates, may itself lead to a 20% reduction in the permeability for these sands.     

Animal Waste Containment in Anaerobic Lagoons Lined with Compacted Clays

The practice of animal waste containment has recently drawn much interest from public and regulatory agencies in agriculture-oriented states such as Kansas and North Carolina. In this paper, the debate surrounding the practice is outlined, and results from a research investigation pertinent to the state of Kansas are presented. The research investigation involved two phases. In the first phase, compacted specimens of Kansas soils were tested with animal waste as the influent. The key objective of this phase of research was to assess the range of seepage quantities and the transport characteristics of nitrogen in the ammonium form (NH4-N) through the compacted soils. Results from this phase indicated a steady increase of microbial counts in the liquid effluent. However, biological clogging did not appear to be prominent during the NH4-N breakthrough time period. The results indicate significant differences in microbial uptake of NH4-N among samples of the same soil type. In the second phase, analytical and numerical solutions were used to simulate ammonium transport in the field-scale liners and to estimate upper-bound travel times and final concentrations of NH4-N in the underlying soils. Results from this phase showed drastic differences in travel times and end concentrations of NH4-N among liners prepared from the same soil type. The potential for significant retardation, decay, and saturation levels of NH4-N in clay liners suggests that liner thickness is an important parameter. It is concluded that mass transfer characteristics of liner material, cation exchange capacity and microbial uptake in particular, should be important considerations in the design of animal waste lagoon liners.