Current-voltage characteristics from an asymptotic analysis of the MOSFET equations

Phenomenological formulae for the current-voltage characteristics of a MOSFET are derived by extending the asymptotic method of Ward. Practical methods for combining the perturbation approximations and numerically implementing the Ward equations are developed. A detailed comparison with real MOSFET data is presented and the model is shown to be effective over a range of device geometries.     

Plastic scintillators with efficient light output and pulse shape discrimination produced via photoinitiated polymerization

Poly(vinyl toluene) (PVT) overdoped with 2,5-diphenyloxazole and using 1,4-bis(5-phenyloxazol-2-yl)benzene as a fluorescent secondary dopant can be used to detect and differentiate neutron and gamma radiation via scintillation. The low cost of PVT makes these plastic scintillators attractive for both portable and larger sized first line detection of special nuclear materials. Current fabrication methods rely on thermally initiated radical polymerization that generally requires an approximately 5-day heating process in order to produce high quality scintillators. In this work, we report a proof-of-concept photopolymerization process to prepare plastic scintillators up to 20 g in size in 1 day. These plastic scintillators were comparable to standard thermally polymerized samples in terms of their physical properties and response to various radiation sources. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47381.     

Ethanol-Modified Supercritical Carbon Dioxide Extraction of the Bioactive Lipid Components of <Emphasis Type="Italic">Camelina sativa</Emphasis> Seed

Camelina sativa seed is an underutilized oil source that attracts a growing interest, but it requires more research on its composition and processing. Its high omega‐3 content and growing demand for clean food processing technologies make conventional oil extraction less attractive. In this study, the effect of extraction methods on the bioactive lipid composition of the camelina seed lipid was investigated, and its bioactive lipid composition was modified at the extraction stage using ethanol‐modified supercritical carbon dioxide (SC‐CO₂). Ethanol‐modified SC‐CO₂ extractions were carried out at varying temperatures (50 and 70 °C), pressures (35 and 45 MPa), and ethanol concentrations (0–10%, w/w), and were compared to SC‐CO₂, cold press, and hexane extraction. The highest total lipid yield (37.6%) was at 45 MPa/70 °C/10% (w/w) ethanol. Phospholipids and phenolic content increased significantly with ethanol‐modified SC‐CO₂ (p < 0.05). SC‐CO₂ with 10% (w/w) ethanol concentration selectively increased phosphatidylcholine (PC) content. Apparent solubility of camelina seed lipids in SC‐CO₂, determined using the Chrastil model, ranged from 0.0065 kg oil/kg CO₂ (35 MPa/50 °C) to 0.0133 kg oil/kg CO₂ (45 MPa/70 °C). Ethanol‐modified SC‐CO₂ extraction allowed modification of the lipid composition that was not possible with the conventional extraction methods. This is a promising green method for extraction and fractionation of camelina seed lipids to separate and enrich its bioactives.     

Screening women for gonorrhea: demographic screening criteria for general clinical use

OBJECTIVES: The purpose of this analysis was to derive potential gonorrhea screening criteria for women. METHODS: Data corresponding to 44,366 gonorrhea cultures from women 15 through 44 years of age in Columbus, Ohio, were analyzed. RESULTS: Characteristics that were associated with gonococcal infection and were suitable for screening decisions included patient's age and marital status and previous prevalence of gonorrhea at provider site. Probabilities of infection ranged from .001 for married women 25 through 44 years of age at low-prevalence provider sites to .078 for unmarried women 15 through 19 years of age at high-prevalence sites. CONCLUSIONS: Patient's age and marital status and prevalence of gonorrhea at provider site can be used as indicators to ensure testing of high-prevalence groups.     

A New Catalytic Route for the Oxidative Halogenation of Cyclic Enol Ethers using Tungstate Exchanged on Takovite

An efficient and benign method for the regio‐ and stereoselective synthesis of halohydrins and β‐halo ethers from dihydropyrans, dihydrofurans and anhydro sugars in the presence of a halide salt and hydrogen peroxide is presented with tungstate‐exchanged takovite as oxidation catalyst.     

Application of High-Power Ultrasound to Improve Adhesion of Honey on Roasted Peanuts to Improve Oxidative Stability

The extent of honey-coating retention on the surface of sonicated peanuts was studied to evaluate the efficacy of sonication to improve adhesion of honey on peanuts. Samples (150 g each) were sonicated in 450 ml petroleum ether for 5, 10, and 15 min. Following sonication, 25 ml of honey was poured and stirred over the peanuts then roasted in an oven at 177 °C for 10 min. Honey adhesion was determined by measuring the weight of 50 g peanuts before and after coating. The effect of honey and sonication on oxidative stability was measured every 7 days by oxidative stability instrument. The results showed that the weight of honey coating was 7, 16, 19, 21, and 21 g on the control, dipped, 5-, 10-, and 15-min sonicated sample, respectively. Sonication improved adhesion of honey on peanuts by 64%, 68%, and 67% after 5, 10, and 15 min of sonication, respectively, relative to the control. Oxidative stability of dipped, 5-, 10-, and 15-min sonicated samples was improved by 22%, 36%, 46%, and 32%, respectively, in relative to the control. Therefore, removing lipids from peanut surface by high-power ultrasound improved adhesion of honey coating and the oxidative stability.     

Spatial variation in biodiversity, soil degradation and productivity in agricultural landscapes in the highlands of Tigray, northern Ethiopia

There is a growing concern about food security and sustainability of agricultural production in developing countries. However, there are limited attempts to quantify agro-biodiversity losses and relate these losses to soil degradation and crop productivity, particularly in Tigray, Ethiopia. In this study, spatial variation in agro-biodiversity and soil degradation was assessed in 2000 and 2005 at 151 farms in relation to farm, productivity, wealth, social, developmental and topographic characteristics in Tigray, northern Ethiopia. A significant decrease in agro-biodiversity was documented between 2000 and 2005, mainly associated with inorganic fertilizer use, number of credit sources and proximity to towns and major roads. Agro-biodiversity was higher at farms with higher soil fertility (available P and total N) and higher productivity (total caloric crop yield). Low soil organic matter, few crop selection criteria and steep slopes contributed to soil erosion. Sparsely and intensively cultivated land use types, as determined from satellite images, were associated with high and low agro-biodiversity classes, respectively, as determined during on-farm surveys in 2005. This study gives insight into the recent changes in and current status of agro-biodiversity and soil degradation at different spatial scales, which can help to improve food security through the maintenance of agro-biodiversity resources.

Principles for wellbore simulator validation and calibration using matching analysis—I. Analytical techniques

Validating a wellbore simulator and calibrating it to a particular well is achieved through matching analysis, the comparison of calculated downhole pressure/temperature profiles with measured data from a discharging well. For matching analysis to be effective, it is shown that any variations or discontinuities in such measurements must be examined, and appropriate matching criteria specified. A procedure for determining the suitability of downhole measurements for application to matching is presented. This procedure, termed the lower bound method, additionally provides lower bounds to the wellbore fluid's CO₂ or NaCl content. The importance of appropriately modelling secondary feed characteristics down the wellbore is also discussed, and an expression is provided for estimating the CO₂ concentration of the fluid entering the wellbore at a two-phase feed zone.     

Coupled reservoir-wellbore simulation of geothermal reservoir behavior

The reservoir simulator TOUGH and the wellbore simulator WFSA have been coupled to model flow of geothermal brine in the reservoir as well as in the wellbore. An outline of the structure of the two computer codes is given, together with the relevant equations. A new module, COUPLE, has been written to serve as an interface between TOUGH and WFSA. Two sample problems are given to illustrate the use of the coupled codes. One of these problems compares the results of the new simulation method to those obtained by using the deliverability option in TOUGH. The coupled computing procedure is shown to simulate more accurately the behavior of a geothermal reservoir under exploitation.     

PRS-XY型混联数控机床设计

介绍了PRS-XY型混联数控机床的基本结构组成,给出了其运动学结构原理。通过运动学分析得出了机床设计中需用的运动学学方程,研究了混联机床定平台、动平台、驱动杆总成三者之间的几何关系。以此为基础,给出了部分零件的具体机械设计过程。