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关键词： isotopic water   heavy water   graphene oxide   membrane   filtration   pressurized system  

摘要： There is an increasing demand for nuclear reactors, driven by the global need for low CO2 producing energy sources. The use of light (H2O) or heavy water (D2O) in a nuclear reactor environment produces radioactive tritiated heavy (HTO, DTO) water as an inevitable contaminant. Considering the need for tritiated water removal and also the high commercial value of purified water isotopes, technologies that can efficiently separate isotopic mixtures of water in nuclear reactors are highly desirable. This study presents an experimental approach for producing graphene oxide (GO) membranes and assessing their performance in the filtration of isotopic water mixtures. Specifically, using D2O/H2O mixtures as model systems, we investigate the effect of physicochemical properties of GO, as well as membrane preparation conditions on membrane filtration efficiency. We find that membranes assembled using larger GO platelets of lower oxidation level generally exhibit higher deuterated water (HDO, D2O) rejection and filtrate flux. Moreover, membrane preparation conditions have a strong impact on the interlayer space between stacked GO nanoplatelets in the membrane, hence as a direct effect on filtration performance. Our experimental results also show a strong, nonmonotonic dependence of separation performance on operating temperature, as well as the existence of local temperature optima. Our work provides guidelines for simple and scalable preparation of GO membranes with very good mechanical stability, capable of achieving efficient separation of isotopic water.

关键词： Chloromethane to olefin (CMTO)   Light olefin production   CoAPSO-34   Co/Al molar ratio   Deactivation behavior  

摘要： In this work, a series of CoAPSO-34(cobaltsilicoaluminophosphate, X = Co/Al, X = 0, 0.02, 0.05, 0.07, and 0.10) catalysts with different Co/Al molar ratio(X) were prepared for use in the chloromethane to olefin (CMTO) reaction to produce light olefins, such as ethylene and propylene. The CMTO reaction at 450 degrees C showed that CoAPSO-34(0.05) catalyst had the highest chloromethane conversion among the catalysts with a conversion of 78.75 % at the reaction time of 250 min. The catalytic lifetime increased with increasing Co/Al molar ratio up to 0.05 and then decreased with increasing Co/Al molar ratio up to 0.10. The deposition of coke originating from polymethylbenzene species is thought to be the main reason for deactivation of the catalysts. As the molar ratio of Co/Al increased from 0 to 0.05, the amount of acid site increased, although the textural property did not change. However, as the molar ratio of Co/Al increased from 0.05 to 0.10, the BET surface area and pore volume of the catalysts decreased sharply, in addition to the amount of acid sites. Hence, it is concluded that both the acidic properties and textural properties of the catalysts play a crucial role in determining the catalytic activities in the chloromethane to olefin reaction, resulting in the highest chloromethane conversion and light olefin selectivity over CoAPSO-34(0.05).

关键词： Natural macromolecules   Chondroitin sulfate   Biomaterials  

摘要： In the present work, the potential of the Prionace glauca jaw as a source of both chondroitin sulfate and bioapatite is explored. The sandwich-type structure in cross section of the jaw based on alternate layers with prevalence in organic tissue or mineralized is shown and these bands respectively confirmed as CS or hydroxyapatite -enriched zones. As result of this, an optimized process in sequential steps for the recovery of both biomaterials and their purification process is proposed, by combining enzymatic proteolysis, chemical precipitation and separation using ultrafiltration membrane for CS production together with controlled thermal treatment for hydroxyapatite obtaining. The purified CS was characterized by Gel Permeation Chromatography, Nuclear Magnetic Resonance and Strong Anion Exchange Chromatography, revealing a polymeric material with a molecular weight of 67 kDa, and prevalent 6S-GalNAc sulfation (68%), followed by 4S-GalNAc (13%), a significant proportion of disulfated disaccharides (12%) and only 7% of non-sulfated units. In the case of the bioapatite a purified biphasic 60:40 porous calcium phosphate of hydroxyapatite: whitlockite/beta-TCP was confirmed. Hydroxyapatite as major component (85%) was also obtained for jaws directly subjected to the thermal treatment. This proved the influence of the enzymatic hydrolysis and centrifugation on the composition of the mineral fraction. (C) 2020 Elsevier B.V. All rights reserved.

关键词： 物理化学   爆热   恒温式量热计   故障前数据   稳健辨识  

摘要： 针对恒温法爆热经典测量方法存在测量时间长、出现系统故障易导致测量失败等问题,提出一种基于故障前数据辨识爆热的解决方案。首先建立了基于炸药瞬态反应假设的量热计传热学方程,解算得到内桶水温的变化规律;然后基于系统辨识的思想,给出了先辨识中间参数kNW/(cNmN)、u1、λ1、λ2,然后辨识目标参数TE(τM)、kNZ/cNmN、kNZ/cZmZ,再辨识修正温升与爆热的系统辨识方法,误差分析表明爆热的辨识值可稳健地收敛于经典值,氧化、燃烧等非瞬态反应对辨识精度的影响可忽略;最后,针对8个典型炸药样本爆热测量数据进行模拟分析并提出收敛时刻的试验判据。模拟结果表明,爆热的辨识值可在不超过3%的相对误差、1/2主末期时间的条件下快速、可靠地收敛于经典值,试验判据能可靠地判断爆热辨识值的收敛时刻,有效降低了系统故障导致测量失败的风险。

关键词： 物理化学   固体推进剂   动态燃速测试   质量流率法   冲量法   自增压燃烧  

摘要： 为了实现单次发动机试验测得多个压强条件下推进剂的燃速,提出了一种固体推进剂动态燃速测试方法——质量流率法。该法以质量流率计算公式为依据,通过处理推进剂燃烧过程中随时间递增的压强曲线,计算得到发动机工作全过程中不同时刻对应压强下的燃速值;对比了通过质量流率法与冲量法处理得到的双铅-2(SQ-2)推进剂燃速结果;分析了特征速度和喷管喉径变化对质量流率法燃速测试结果的影响。结果表明,两种方法得到的燃速结果随压强变化趋势完全一致;当压强为9.945MPa时,两种方法的误差为1.06%;当压强为22MPa时,误差为3.87%。造成质量流率法与冲量法燃速结果之间差异的主要原因为喷管喉径实际尺寸的变化。

关键词： Gelatin   Techno-functional properties   Physico-chemical characterization  

摘要： Gelatin from saithe (Pollachius virens) skin, with high mineral content, was characterized and compared to marine gelatin from the market. As expected, gelatin extracted from the saithe skin had a high mineral content (>= 20%), compared to commercial gelatin (<0.2%). SDS-PAGE analysis revealed the presence of alpha-chains, beta-chains and other high molecular weight aggregates. The absorption bands of gelatin in FTIR spectra were mainly situated in the amide band region (amide A. amide B, amide I,amide II and amide III), whereas DSC thermograms showed typical gelatin behavior. Interesting viscoelastic and higher foaming properties were observed for the saithe gelatins, compared to the market gelatins, probably due to the presence of high sea mineral content. The potential applications in food and cosmetic area of gelatin with high mineral content are presented and discussed in the conclusions. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Ball milling   Botanical sources   Heat-moisture treatment  

摘要： The morphology, structure and physicochemical properties of ball milling (BM) damaged starches from mung bean, potato, corn and waxy corn were investigated before and after heat-moisture treatment (HMT) (100 degrees C, for 12 hat a moisture content of 25%). The results showed that the damaged starch (DS) content of BM modified starches was decreased by 4.49%, 10.68%, 17.11% and 22.98% after HMT for mung bean, potato, corn and waxy corn starch, respectively. The solubility and swelling power were significantly decreased, and the modified effect was depended on the type of starch, among which waxy corn starch exhibited the maximum reduction. Different degrees of aggregation and fusion of granules were found in starches modified with BM-HMT, and the extent of fusion was related to amylose content and crystalline pattern. The crystallinity of BM modified starches was increased by 6.3%, 5.9%, 17.9% and 22.4% alter HMT for mung bean, potato, corn and waxy corn starch, respectively. The dual physical modification had various effects on the starches from different botanical sources, the increase in crystallinity and peak temperature (T-p) were related to the DS and amylose content, and the changes in gelatinization temperature range (T-c-T-o) were related to the crystalline pattern of starches. (C) 2020 Elsevier B.V. All rights reserved.

关键词： 光催化分解水   金属氧化物   物理化学   核量子效应   分子尺度   氢键   模型体系   基本相互作用  

摘要： 水/固界面在自然界中无处不在,而氢键是水/固界面最为重要的基本相互作用。在单分子尺度上表征水/固界面的氢键结构与动力学过程对深入理解光合作用、光催化分解水、核量子效应等具有重要的意义,成为物理化学与生命科学中广为关注的科学问题之一1–3。二氧化钛(TiO2)是研究金属氧化物光催化分解水制氢气的模型体系4–6。

关键词： Contamination factors   Overburden material   Phytostabilization   Pollution load index   Tailings dam  

摘要： Soil characterization is a vital activity to develop appropriate and effective restoration protocols for mine wastelands while insights into the total content of heavy metals in the soil is an important step in estimating the hazards that the metals may pose to the vital roles of soil in the *** study addressed the following research questions:(1)To what extent do the physico-chemical characteristics vary between mine waste sediments and the nearby forest soil?(2)Are the concentrations of heavy metals high enough to be considered as toxic?and(3)Are heavy metals present in mine waste sediments potential sources of pollution?We hypothesized that the physicochemical characteristics of mine waste sediments are less favorably for plant establishment and growth while the concentrations of heavy metals are very high,thus restricting the success of revegetation of mine waste *** waste sediments were sampled following a diagonal transect across tailings dams,overburden dump sites and the local forest soil from the top layer(0-20 cm)using a closed *** were analyzed for arsenic,barium,lead,cadmium,cobalt,copper,chromium,nickel,vanadium,and zinc as well as for soil physico-chemical *** mine waste sediments were dominated by silt whilst the forest soil by sand particles,with significantly high bulk density in the *** the forest soil and overburden sediments were acidic than the alkaline tailings dam *** organic carbon and nitrogen contents were significantly low in mine wasteland substrates but the concentration of Ca and Mg were significantly higher in tailings dam substrate than the forest *** concentrations of available P,K and Na were similar across *** mean concentrations of heavy metals were significantly(p<0.01)higher in mine waste sediments than the forest soil;except for cadmium(p=0.213).The order of contamination by heavy metals on the tailings was Cu>Co>Ba>Ni>As>Zn>Pb>Cr>V>Cd,and that on the overburd

关键词： 思维导图   大学物理化学   教学  

摘要： 大学物理化学课程是一项有关食品工程专业的基础课程,是学生参与科研实践工作之前的理论基础课程,引导学生学好这门课程非常重要,是给学生以后进行实践课程的一个重要的坚实的基础。而思维导图在学习的过程中也是对知识点梳理的一个非常好用的防守,思维导图对于学生来说可以培养学生的学习兴趣以及创新意识和思维能力。