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1.
利用太阳能对水加热并通入相变墙进行蓄热,对减少严寒地区单体建筑供热能耗有重要意义。以大庆市某单体建筑为例,结合该地区太阳能分布特点及建筑热负荷大小,对适用于该地区的太阳能-相变墙系统进行集热与储热能力计算,并采用CFD方法研究单一工况下该系统的热工变化规律及不同热水参数、换热管规格对相变墙蓄热特性的影响。结果表明:该相变墙热稳定性良好,但受自然对流影响,底部相变材料熔化较慢;管径DN25、入口流速0.3m/s、供水温度310.15K、回水温度309.15K、管间距107mm可使相变材料在4小时内完成蓄热,平均节能率为31.8%。研究结果可望为降低严寒地区建筑供热能耗提供新思路。 相似文献
2.
To evaluate the fill of internal resorption cavities obturated with thermoplasticized gutta‐percha and GuttaFlow2 using CT scan. Twenty human maxillary anterior teeth were selected and root canals were prepared using ProTaper system to size F3. Irrigation was performed with 5 ml of 2.5% sodium hypochlorite (NaOCl) and 5 ml of 17% ethylenediaminetetraacetic acid (EDTA). Each root was then sectioned horizontally into two halves and semicircular cavities were prepared around the periphery of the root canal opening of each root half, using a round bur. Both the root halves were then fixed using cyanoacrylate glue. All the specimens were subjected to preoperative CT scan analysis to determine the volume of internal cavities. The samples were then randomly divided into two groups. In Group 1, the specimens were obturated with thermoplasticized gutta‐percha (E&Q system) and specimens in Group 2 were obturated using GuttaFlow2. All specimens were then subjected to postoperative CT scan analysis. The volume of voids in internal resorptive cavities were calculated, which was then used to estimate the amount of gutta‐percha filled. There was no significant difference in volume of internal resorptive cavities between thermoplasticized gutta‐percha and GuttaFlow2 groups before obturation (p = 0.466). However, after obturation there was a significant difference between both the groups, in which GuttaFlow2 demonstrated better fill (p = .014). Thermoplasticized gutta‐percha filled 81% of internal resorptive cavity while GuttaFlow2 filled 91%, respectively. GuttaFlow2 showed better fill than thermoplasticized gutta‐percha in the filling of internal resorptive cavities. 相似文献
3.
5种浆果果酒抗氧化活性差异及综合评价 总被引:2,自引:0,他引:2
该研究测定了5种浆果(蓝莓(野生和北陆)、蓝靛果(野生和蓓蕾)、不老莓)果酒的理化指标、单体酚类物质含量和抗氧化活性,探究5种浆果果酒抗氧化活性差异,并通过主成分分析(PCA)对其进行综合评价。结果表明,野生蓝靛果果酒中的总糖、总酸、多酚、黄酮、花色苷含量最高,分别为3.82%、9.69 mg/g、12.58 mg/g、1.55%、1.21 mg/g,单体酚类物质中咖啡酸、儿茶素、表儿茶素、绿原酸、对香豆酸、芦丁含量最高,分别为66.19 mg/g、878.09 mg/g、13.28 mg/g、735.50 mg/g、275.32 mg/g、23.86 mg/g,其DPPH·清除率(92.29%)、 ·OH清除率(96.28%)和还原力(1.744)最强;野生蓝莓果酒的ABTS+·清除率(96.77%)和O2-·的清除率(50.54%)最强;浆果果酒综合得分表明,5种浆果果酒的抗氧化活性排序为野生蓝莓果酒>野生蓝靛果果酒>蓓蕾蓝靛果果酒>不老莓果酒>北陆蓝莓果酒。 相似文献
4.
Global decrease in crude oil resources and frequent crude oil leaks cause the energy crisis and ecological pollution. The absorption and release of leaked crude oil through absorption materials are a necessary process for environmental protection and recycling. In this article, a CO2-responsive olefin copolymer was obtained by copolymerization of styrene and an amine-containing olefin monomer. The structure of resultant copolymer was characterized by FTIR; thermal properties and CO2-responsive morphology changes were determined by DSC/TGA and SEM, respectively. Copolymers had certain absorption capacity for toluene with absorption rate up to 180.0%. The absorbed toluene could be released upon CO2 stimulation with desorption rate up to 84.6%. The CO2-responsive copolymer could be regenerated through a simple heating process and showed stable absorption–desorption performance even after being recycled for 4 times. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47439. 相似文献
5.
以牦牛坪西部矿区的氟碳铈矿为研究对象,利用 X 射线衍射分析、扫描电镜、光学显微镜、MLA矿物自动测量系统等分析手段对其进行了较为系统的工艺矿物学分析。结果表明,该矿石中稀土元素以镧、铈、钕及镨四种元素为主,总稀土氧化物(TREO)品位为 6.9%。该矿样中稀土矿物种类主要为氟碳铈镧矿,稀土矿物品位较高,属高价值稀土矿。其他矿物主要为重晶石、萤石、长石和石英等,其次是云母、角闪石及褐铁矿、赤铁矿等。矿石中氟碳铈镧矿、重晶石、萤石具不均匀中细粒嵌布的特征,需要细磨至 -0.019mm 才能达到单体解离。 相似文献
6.
为促进我国化纤行业转型升级与持续发展,对以生物基聚对苯二甲酸乙二醇酯纤维、聚对苯二甲酸-1,3-丙二醇酯纤维、聚乳酸纤维、聚呋喃二甲酸乙二醇酯纤维、聚呋喃二甲酸丙二醇酯纤维,以及生物基聚酰胺56纤维为代表的生物基聚酯、聚酰胺纤维的国内外生产现状,市场需求、技术发展及趋势进行了综述,对全球生物基纤维专利的分布、各主要开发机构的专利战略及技术情况进行了梳理及剖析。在此基础上结合国内高分子材料产业实际,对我国生物基聚酯、聚酰胺纤维的发展建言应重点攻关生物基乙二醇、对苯二甲酸、己二胺等战略性生物基单体制备的核心技术,同时就重点任务和发展路径提出了建议。 相似文献
7.
非线性电导材料的应用是解决高压直流电缆附件内部电场集中问题的一种有效方案。因此,通过掺杂钛酸铜钙(calcium copper titanate,CCTO)纳米填料对三元乙丙橡胶(ethylene-propylene-diene monomer,EPDM)进行改性,在较低的掺杂体积分数(2%CCTO)下,复合介质展现出较好的非线性电导率;当掺杂10%CCTO时,非线性系数可达到5.40。但同时发现,高掺杂含量复合介质的击穿场强劣化严重。基于此,选择具有良好绝缘及导热特性的六方氮化硼(boronnitride,BN)与CCTO共同掺杂至EPDM中,研究发现,共掺杂复合介质的击穿场强有明显改善,φ=10%CCTO/ω=9%BN/EPDM的特征击穿场强为90.1 kV/mm(φ为体积分数,ω为质量分数),相比10%CCTO/EPDM(66.3 kV/mm)提高了35.9%,此时,共掺杂复合介质仍然表现出明显的非线性电导特征。此外,探讨了温度对复合介质非线性电导和击穿特性的影响,并对掺杂复合介质的力学性能进行测试分析,研究发现,2种无机填料的掺杂对EPDM力学性能的改善效果较为显著,随着CCTO掺杂含量增加,复合介质的拉伸强度以及断裂伸长率逐渐增加。 相似文献
8.
In order to endow feather keratin with good sizing properties for all-polyester or high-polyester yarns, methyl acrylate (MA) and acrylic acid (AA) monomers with a variation in feed molar ratio from 10/90 to 30/70 were grafted onto the molecular chains of native feather keratin under equal monomer concentration. Effects of monomer compatibility of MA/AA on sizing properties of the feather keratin-g-P(AA-co-MA) were studied in terms of apparent viscosity, contact angle of sizing paste on polyester fibers, mechanical properties of sizing film, and adhesion to polyester fibers. It was found that grafting MA & AA monomers with rational compatibility onto the molecular chains of feather keratin was an effective method to improve sizing properties of grafted feather keratin, such as adhesion to polyester fibers and toughness of sizing film. In view of overall performance of the grafted feather keratin sizes, the appropriate feed molar ratio of MA/AA should be 20/80. 相似文献
9.
10.