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51.
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针对甘油介质在形成线中的应用,总结了甘油作为储能介质已开展的相关研究工作,并在缩比的同轴电极试件中进行了电极表面、磁场、耐压极性、含气量等条件对甘油介质击穿特性影响的实验研究。搭建了基于晶闸管控制的空心脉冲变压器升压实验平台,设计了浸没于脉冲磁场中的同轴电极击穿试件,实验平台最大输出电压500 kV,上升时间26 s,最大磁场1 T,可通过控制晶闸管的先后触发使击穿过程发生于准稳衡磁场中,并制作了外形一致、表面不同的砂纸打磨、羊毛抛光、金属电镀和非金属电镀四种电极。实验结果表明:甘油的击穿是没有极性的;1 T量级磁场对甘油介质的击穿特性无影响;不同电极表面微观形貌差异较大,使甘油介质具有不同的击穿特性,说明甘油击穿在电极表面的过程具有较大影响;充分的排气能减少甘油中直径较大的气泡,减少概率性的低击穿场强,击穿后产生的大量微小气泡会整体降低甘油的击穿阈值,使甘油的平均击穿场强降低。 相似文献
53.
Thachapan Atchimarungsri Xinhua Gao Kangzhou Wang Qingxiang Ma Jianli Zhang Subing Fan Fugui He Jumei Tian Prasert Reubroycharoen Tiansheng Zhao 《Molecules (Basel, Switzerland)》2022,27(21)
Biodiesel is generally produced from vegetable oils and methanol, which also generates glycerol as byproduct. To improve the overall economic performance of the process, the selective formation of methanol from glycerol is important in biodiesel production. In the present study, a CaO modified HZSM-5 zeolite was prepared by an impregnation method and used for the conversion of glycerol to methanol. We found that the 10%CaO/HZSM-5 with Si/Al ratio of 38 exhibited highest selectivity to methanol of 70%, with a glycerol conversion of 100% under 340 ℃ and atmospheric pressure. The characterization results showed that the introduction of a small amount of CaO into the HZSM-5 did not affect the structure of zeolite. The incorporation of HZSM-5 as an acidic catalyst and CaO as a basic catalyst in a synergistic catalysis system led to higher conversion of glycerol and selectivity of methanol. 相似文献
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聚甲基丙烯酸甲酯/聚甲基丙烯酸-2-羟乙酯复合微球的合成及药物吸放性能 总被引:1,自引:0,他引:1
采用在甲基丙烯酸甲酯(MMA)悬浮聚合过程中滴加甲基丙烯酸-2-羟乙酯(HEMA)乳液聚合组分的悬浮-乳液耦合聚合方法,制备了大粒径聚甲基丙烯酸甲酯/聚甲基丙烯酸-2-羟乙酯(PMMA/PHEMA)复合微球。PMMA/PHEMA复合微球表面以HEMA乳液聚合物为主,且具有微孔结构。PMMA/PHEMA复合微球在水和苄醇中的平衡溶胀率大于PMMA微球。PMMA/PHEMA复合微球48h异丁苯丙酸负载百分比为35.6%,PMMA为27.6%。在磷酸盐缓冲液中释放时间达到360h,释放量占负载总量的82%;而PMMA微球的释放时间为216h,释放量仅占负载总量的60%。 相似文献
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A. Kyritsis P. Pissis J. Grammatikakis 《Journal of Polymer Science.Polymer Physics》1995,33(12):1737-1750
The electrical and dielectric properties of poly(hydroxyethyl acrylate), PHEA, hydrogels were studied by means of dielectric relaxation spectroscopy in wide ranges of frequencies (5–2 × 109 Hz), temperatures (173–363 K) and water contents (0.065–0.46, g of water per gram of dry material). The secondary dipolar mechanisms (γ and βsw) and the dc conductivity mechanism were studied in detail by analyzing the dielectric susceptibility data within the complex permittivity formalism, the modulus formalism, and the complex impedance formalism. For both mechanisms molecular mobility was found to increase with increasing temperature or increasing water content (T-f-h superposition principle). The energy parameters and the shape parameters of the response were determined for both mechanisms at several water contents and temperatures. The temperature dependence of dc conductivity was found to change from Vogel-Tamman-Fulcher (VTF) type to Arrhenius type at water contents of ca. 0.30. At water contents lower than about 0.30 the hydrogels are homogeneous whereas at higher water contents a separate water phase appears. In terms of the strong/fragile classification scheme our results suggest that the PHEA hydrogels are fragile systems. ©1995 John Wiley & Sons, Inc. 相似文献
57.
Non-aqueous birefringent microemulsions were found in a system ofp-xylene, glycerol, triethanolammonium oleate and oleic acid. The microemulsions showed long term stability once formed, but failed to form spontaneously when the components were contacted. After partial separation by centrifugation, no signs of spontaneous reformation were found. 相似文献
58.
合成了孔道平行于短轴方向的W原位掺杂的介孔SBA-15分子筛(W-s-SBA-15), 以其为载体制备了Pt/W-s-SBA-15催化剂, 考察了催化剂中Pt、W负载量变化对甘油氢解制1,3-丙二醇(1,3-PDO)性能的影响. 采用多种手段对催化剂的形貌、活性组分Pt和W的存在状态、催化剂的酸性等性质进行了系统的表征. 催化剂评价结果表明, 随着Pt、W负载量的增加, 甘油的总转化率和液相转化率(CTL)提高, 而1,3-PDO选择性呈先升高后降低的火山型变化趋势. 在Pt负载量为4.0 wt%、W/Si物质的量比为1/480的4Pt/W-s-SBA-15(1/480)催化剂上, 在433 K、H2压力4.0 MPa、反应时间24 h的条件下, 甘油氢解制1,3-PDO的得率可达49.0%. 根据表征结果, 我们发现在Pt/W-s-SBA-15催化剂上的甘油转化率与Pt活性比表面积直接相关, 而小的Pt粒径、Pt与单分散WO4之间密切的协同作用, 则有助于提高1,3-PDO的选择性. 相似文献
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RGDS‐ and SIKVAVS‐Modified Superporous Poly(2‐hydroxyethyl methacrylate) Scaffolds for Tissue Engineering Applications 下载免费PDF全文
Hana Macková Zdeněk Plichta Vladimír Proks Ilya Kotelnikov Jan Kučka Helena Hlídková Daniel Horák Šárka Kubinová Klára Jiráková 《Macromolecular bioscience》2016,16(11):1621-1631
Three‐dimensional hydrogel supports for mesenchymal and neural stem cells (NSCs) are promising materials for tissue engineering applications such as spinal cord repair. This study involves the preparation and characterization of superporous scaffolds based on a copolymer of 2‐hydroxyethyl and 2‐aminoethyl methacrylate (HEMA and AEMA) crosslinked with ethylene dimethacrylate. Ammonium oxalate is chosen as a suitable porogen because it consists of needle‐like crystals, allowing their parallel arrangement in the polymerization mold. The amino group of AEMA is used to immobilize RGDS and SIKVAVS peptide sequences with an N‐γ‐maleimidobutyryloxy succinimide ester linker. The amount of the peptide on the scaffold is determined using 125I radiolabeled SIKVAVS. Both RGDS‐ and SIKVAVS‐modified poly(2‐hydroxyethyl methacrylate) scaffolds serve as supports for culturing human mesenchymal stem cells (MSCs) and human fetal NSCs. The RGDS sequence is found to be better for MSC and NSC proliferation and growth than SIKVAVS.