Multi-component diffusion analysis and assessment of GAMMA code and improved RELAP5 code

A loss-of-coolant accident (LOCA) has been considered a critical event for very high temperature gas-cooled reactor (VHTR). Following helium depressurization, it is anticipated that unless countermeasures are taken, air will enter the core through the break by molecular diffusion and ultimately by natural convection leading to oxidation of the in-core graphite structure. Thus, without any mitigating features, a LOCA will lead to an air ingress event, which will lead to exothermic chemical reactions of graphite with oxygen, potentially resulting in significant increases of the core temperature.New and safer nuclear reactors (Generation IV) are now in the early planning stages in many countries throughout the world. One of the reactor concepts being seriously considered is the VHTR. To achieve public acceptance, these reactor concepts must show an increased level of inherent safety over current reactor designs (i.e., a system must be designed to eliminate any concerns of large radiological releases outside the site boundary).A computer code developed from this study, gas multi-component mixture analysis (GAMMA) code, was assessed using a two-bulb experiment and in addition the molecular diffusion behavior in the prismatic-core gas-cooled reactor was investigated following the guillotine break of the main pipe between the reactor vessel and the power conversion unit. The RELAP5 code was improved for the VHTR air ingress analysis and was assessed using inverse U-tube and NACOK natural circulation data.     

Chlorine stable isotopes: a comparison of dual inlet and thermal ionization mass spectrometric measurements

Chlorine stable isotope ratios, 37Cl/35Cl, currently are measured using dual-inlet and thermal-ionization mass spectrometry. These two different analytical techniques, however, have never been cross calibrated. A set of samples with chlorine stable isotope delta values ranging from -4.4 to +0.3 % relative to standard mean ocean water chloride has been analyzed using both of these techniques. Our data show that both techniques can yield similar results within analytical uncertainty. CsCl thermal ionization data are extremely sensitive to the amount of chlorine being measured and cannot be used to determine absolute ratios without an independent means of correcting for machine-induced mass fractionation. As long as standards and samples are of equivalent size, however, the differences between samples measured by thermal ionization remain constant Dual inlet stable isotope mass spectrometry is suited best for samples of > 10 micromol Cl, yielding chlorine stable isotope data with < or =0.1% reproducibilities (2sigma). Thermal ionization mass spectrometry easily accommodates samples of approximately0.1-0.3 micromol Cl, with achievable uncertainties of < or =0.2% (2sigma).     

可互操作的GIS研究

随着“计算机就是网络”的想望成为实现,人们希望独立于数据结构和语义等具体条件,跨平台地获取大量信息,GIS互操作是广大用户跨平台获取地理信息的有效途径,因而它成为目前GIS界的研究热点。按照侧重点的不同,将GIS互操作分为技术互操作,服务互操作和语义互操作三类,并分别说明三者的实现方法,关建技术,研究现状和不足之处,最后对GIS互操作的发展方向进行了展望。     

Rapid recovery of rare earth elements in industrial wastewater by CuFe2O4 synthesized from Cu sludge

This study systematically evaluates the recovery of rare earth elements (REEs) from aqueous solution and industrial wastewater using magnetic nanoparticles CuFe₂O₄. The industrially manufactured CuFe₂O₄ displays a nonlinear isotherm for REEs adsorption, suggesting limiting binding sites on the CuFe₂O₄ surface. The recovery of REEs increases significantly from 0.1% to 99.99% with increasing pH (2.29–8.15). At room temperature, the maxima recovery rates of Nd, La, and Ce are observed to be in a high capacity of 51.02, 42.02, and 40.16 mg/g, respectively. No significant attenuation of REE adsorption is observed with increasing NaCl concentration from 0.001 to 1.0 mol/L, showing high selectivity of REEs even in such high NaCl concentration matrix. In addition, desorption efficiency increases with the increasing concentration of HNO₃ in the range of 0.005–0.05 mol/L. When HNO₃ concentration is over 0.05 mol/L, the desorption efficiency can reach almost 100% in each batch experiment. Importantly, our results show that REEs can be sorbed and recycled from liquid crystal display (LCD) polishing wastewater, suggesting that CuFe₂O₄ may be a good candidate in the efficient and rapid recovery of REEs from industrial wastewater.     

The use of the analytical electron microscope EMMA-4 to study the solute distribution in thin foils: some applications to metals and minerals

Results are reported concerning the application of the analytical electron microscope EMMA-4 to the quantitative analysis of thin foils. A simple procedure by which the observed characteristic X-ray intensities from a thin foil sample can be converted into chemical weight fractions is described. This technique has been applied to study the partitioning of manganese between the carbide and ferrite phases during the isothermal decomposition of a eutectoid steel. The results show that it is possible to analyse the manganese content of the ferrite and carbide phases independently and the partitioning of manganese to the carbide phase has been followed as a function of time at the isothermal transformation temperature. The analysis of a calcium-rich pyroxene which contains calcium-poor precipitate lamellae is described. The results are consistent with the precipitation of a pigeonite, poor in calcium and rich in iron, from an augite host. The third example is the ‘in situ’ analysis of nitride precipitates in a stainless steel. The precipitates are known to contain either titanium or chromium, but it is impossible from morphological or diffraction evidence to differentiate between the two types of nitride. Combined electron microscopy and microprobe analysis is shown to be a rapid and positive means of identifying the precipitates.     

Protective effect of dietary tomatine against dibenzo[a,l]pyrene (DBP)-induced liver and stomach tumors in rainbow trout

The potential anti-carcinogenic effects of tomatine, a mixture of commercial tomato glycoalkaloids alpha-tomatine and dehydrotomatine (10:1), were examined in the rainbow trout chemoprevention model. Prior to the chemoprevention study, a preliminary toxicity study revealed that tomatine in the diet fed daily at doses from 100 to 2000 parts per million (ppm) for 4 weeks was not toxic to trout. For the tumor study, replicate groups of 105 trout were fed diets containing dibenzo[a,l]pyrene (DBP) alone (224 ppm), (N = 3), DBP plus tomatine at 2000 ppm (N = 2), tomatine alone (N = 2), or control diet (N = 2) for 4 weeks. The fish were then returned to control diet for 8 months and necropsied for histopathology. Dietary tomatine was found to reduce DBP-initiated liver tumor incidence from 37.0 to 19.0% and stomach tumor incidence from 46.4 to 29.4%. Tomatine also reduced stomach tumor multiplicity. The tomatine-containing diets did not induce mortality, change in fish weights, or liver weights. No adverse pathological effects in the tissues of the fish on the tomatine diets were observed. Dose-response and chemopreventive mechanisms for tomatine protection remain to be examined. This is the first report on the anticarcinogenic effects of tomatine in vivo.     

Molecules that target beta-amyloid

The devastating effects of Alzheimer's and related amyloidogenic diseases have inspired the synthesis and evaluation of numerous ligands to understand the molecular mechanism of the aggregation of the beta-amyloid peptide. Our review focuses on the current knowledge in this field with respect to molecules that have been demonstrated to interact with either oligomeric or fibrillar forms of the beta-amyloid peptide. We describe natural proteins, peptides, peptidomimetics, and small molecules that have been found to interfere with beta-amyloid aggregation. We also detail recent efforts in selecting molecules that target beta-amyloid isolated from antibody, protein, and peptide libraries. These new molecules will likely aid in deciphering the details of the aggregation pathway for the beta-amyloid peptide and provide reagents that may stabilize relevant oligomeric intermediates which likely have bearing on the pathophysiology of Alzheimer's disease. Moreover, the described anti-amyloid molecular toolbox will also provide an avenue for designing new diagnostic and therapeutic reagents.     

Ionic strength-induced formation of smectite quasicrystals enhances nitroaromatic compound sorption

Sorption of organic contaminants by soils is a determinant controlling their transport and fate in the environment. The influence of ionic strength on nitroaromatic compound sorption by K+- and Ca2+ -saturated smectite was examined. Sorption of 1,3-dinitrobenzene by K-smectite increased as KCl ionic strength increased from 0.01 to 0.30 M. In contrast, sorption by Ca-smectite at CaCl2 ionic strengths of 0.015 and 0.15 M remained essentially the same. The "salting-out" effect on the decrease of 1,3-dinitrobenzene aqueous solubility within this ionic strength range was <1.5% relative to the solubility in pure water. This decrease of solubility is insufficient to account for the observed increase of sorption by K-smectite with increasing KCl ionic strength. X-ray diffraction patterns and light absorbance of K-clay suspensions indicated the aggregation of clay particles and the formation of quasicrystal structures as KCI ionic strength increased. Sorption enhancement is attributed to the formation of better-ordered K-clay quasicrystals with reduced interlayer distances rather than to the salting-out effect. Dehydration of 1,3-dinitrobenzene is apparently a significant driving force for sorption, and we show for the first time that sorption of small, planar, neutral organic molecules, namely, 1,3-dinitrobenzene, causes previously expanded clay interlayers to dehydrate and collapse in aqueous suspension.     

Planning and Planning Education under Conditions of Globalization

The flow of amenity-based migrants to fire-prone areas of the US Rocky Mountain West has brought increasing attention to wildfire hazard mitigation management. This paper attempts to build agent-based models which link natural amenity driven exurban growth to wildfire mitigation regimes to provide a framework for assessing cumulative effects of hazard mitigation policy under alternative policy structures. Three simulations were built to demonstrate how agent-based models (ABM) can be used to examine and compare people's choices of residential location in response to natural amenities and wildfire policies. This paper investigates the ways in which policy effects are incorporated dynamically into the land development decision-making process at an individual level in a case study area. Our results show that individual location choices with respect to wildfire risk are sensitive to wildfire mitigation policies.     

Development and Psychometric Testing of the Rate and Accumulation Concept Inventory

Background

Because a fundamental understanding of rate and accumulation principles is important for engineering students across all subdisciplines, a method is needed to assess their understanding of these principles.

Purpose/Hypothesis

This article discusses the development of the Rate and Accumulation Concept Inventory (RACI) instrument and provides an analysis of its validity and reliability. The RACI is designed to test students’ (1) overall mastery of rate and accumulation concepts and (2) mastery of specific rate and accumulation concepts (e.g., mathematics, mass flow, and heat flow).

Design/Methods

Exploratory findings of students’ conceptual understanding prompted the development of a preliminary RACI instrument. Two pilot studies were conducted, with adjustments made to the instrument between each. Data from the second pilot were used to assess evidence of validity and reliability through classical test theory, item response theory, and structural equation modeling.

Results

Validity and reliability evidence indicates that the RACI can be used to measure students’ overall understanding of the concepts identified, though several items require revision or removal. Issues of potential construct underrepresentation were found in two of the conceptual categories.

Conclusions

The evidence of reliability and validity indicates the appropriateness of the RACI for assessing engineering students’ overall understanding of rate and accumulation principles. Additional research is needed to further enhance the validity and reliability of the RACI as a diagnostic tool, particularly in measuring students’ understanding of rate and accumulation concepts in particular physical contexts.