Comparative effectiveness of certain queueing systems with adaptive demand and service mechanisms

This paper sets out to evaluate simple queueing models embodying the concept of adaptation of service to demand and vice versa, systems which hold out the promise of improved operational characteristics by comparison with conventional non-adaptive systems. Over the many years during which research in queueing theory has been in progress there has been little concern with models of this kind, yet it is in the direction of environmental adaptation that one must look for operational improvements. The models studied are mainly of birth and death type. Some consideration is given to renewal models which, in a certain sense, are the equivalents of birth and death types. The emphasis in the paper is placed on the requirements of an operational assessment and on its realization. The use of digital computers in research of this kind is underlined. For illustration extracts from [9] are used to describe the performance of three fundamental adaptive systems.     

Who shall be hired: A biasing effect of the Buckley Amendment on employment practices?

Hypothesized that prospective employers would favor the job candidate whose credentials appeared in a placement file that was confidential as opposed to open. This "file bias" was believed attributable to the greater credibility or perceived accuracy of confidential letters of recommendation. 72 male and 72 female undergraduates examined the credentials of stimulus persons (SPs) who varied in competence, the enthusiasm of their letters of recommendation, and their choice of placement file. Results confirm the primary hypothesis. SPs with confidential placement files were judged more attractive as prospective employees, preferable as job supervisors, and somewhat more socially attractive than SPs with open files. There was no evidence, however, that the favoritism afforded SPs with confidential files was mediated by the greater credibility of confidential letters of recommendation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceived social support for help-seeking behaviors of Black heterosexual and homosexually active women alcoholics.

Seventy African American women in alcoholism treatment centers completed a self-administered questionnaire assessing their perceived emotional and tangible support for entry into treatment for alcoholism and alcohol abuse. Heterosexual women perceived more sources of family, casual, male, and overall support than did lesbian or bisexual women. Quality of perceived emotional support did not differ significantly for heterosexual and lesbian or bisexual women. Findings of differences in sources of perceived support particularly from family of origin as a function of sexual orientation suggest that the same social network may provide different levels and types of support to lesbian and bisexual versus heterosexual Black women alcoholics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determining liver retention of transuranium elements in living beagles

A method has been developed whereby the liver content of photon-emitting transuranium elements can be determined in living beagles by a combination of total-body and partial-body counting. Calibration of the system was accomplished through the photon counting of intact dogs and also of the parts of the same animals following autopsy. A determination of the calibration factors for 252Cf, 247Cf, 243Cm, 237Pu, and 241Am has been made. The special case of 252Cf was treated in which a significant fraction of the high energy fission gamma-ray spectrum penetrates the Pb shield employed in partial-body counting, and methods were developed which allow for this effect in the calculation of liver content. Some uniformity of response in the system was evident for all of the emitters which were considered. It is proposed that similar techniques could be applied in the determination of selected organ radioactivity in other species including man.     

Lactate-mediated enzymatic reduction of metmyoglobin in vitro

This study examined the lactate-mediated enzymatic reduction of equine metmyoglobin (MMb) by using various lactate salts (sodium, potassium and calcium) and bovine m. triceps brachi extracts in vitro. The equine MMb was reduced by the assay mixture containing lactate, NAD⁺, and the muscle extract at pH 5.7. In the absence of the bovine muscle extract, NAD⁺ or l-lactate in the assay mixture, MMb reduction was not observed. Replacing l-lactate with d-lactate or adding oxalate (lactate dehydrogenase inhibitor) to the assay mixture resulted in no MMb reduction, suggesting that lactate dehydrogenase is involved in the MMb reduction, interacting with l-lactate and NAD⁺. An increase (P < 0.05) in the rate of MMb reduction was also observed with an increase of the amount of bovine muscle extract, NAD⁺ or lactate concentration in the assay mixture. There was no difference (P > 0.05) in the rate of MMb reduction when potassium lactate was added to the assay mixture instead of sodium lactate. The MMb reduction through the lactate–NAD⁺-muscle extract system was increased (P < 0.05) with an elevation in pH from 5.1 to 6.1. The results of this research confirm that the inclusion of l-lactate can induce the MMb reduction through the lactate– NAD⁺-enzyme coupling interaction.     

Development of a viability assessment model for hydrogen production from dedicated offshore wind farms

Dedicated offshore wind farms for hydrogen production are a promising option to unlock the full potential of offshore wind energy, attain decarbonisation and energy security targets in electricity and other sectors, and cope with grid expansion constraints. Current knowledge on these systems is limited, particularly the economic aspects. Therefore, a new, integrated and analytical model for viability assessment of hydrogen production from dedicated offshore wind farms is developed in this paper. This includes the formulae for calculating wind power output, electrolysis plant size, and hydrogen production from time-varying wind speed. All the costs are projected to a specified time using both Discounted Payback (DPB) and Net Present Value (NPV) to consider the value of capital over time. A case study considers a hypothetical wind farm of 101.3 MW situated in a potential offshore wind development pipeline off the East Coast of Ireland. All the costs of the wind farm and the electrolysis plant are for 2030, based on reference costs in the literature. Proton exchange membrane electrolysers and underground storage of hydrogen are used. The analysis shows that the DPB and NPV flows for several scenarios of storage are in good agreement and that the viability model performs well. The offshore wind farm – hydrogen production system is found to be profitable in 2030 at a hydrogen price of €5/kg and underground storage capacities ranging from 2 days to 45 days of hydrogen production. The model is helpful for rapid assessment or optimisation of both economics and feasibility of dedicated offshore wind farm – hydrogen production systems.