明代麻葛纺织服饰探析

明代是棉织物崛起,麻葛服饰走向回落的节点。文章基于文献与文物的视角,追溯明代麻葛服饰演变的历程,考证其服饰形制特征。研究认为:明代初期,朝廷政令大力推广棉植业,加之棉织物功能性和经济价值同麻葛织物具有比较优势,使其在棉与麻的产业博弈中胜出。明代中晚期,市民阶层僭越逾矩,竞尚奢华之风盛行,在放弃麻葛布衣作为平民视觉符号的同时,加速了麻葛业的衰落。仅从有限的明代麻葛服饰实物考证来看,明代初期麻葛服饰品类广泛,明中晚期其仅局限于单衣夏服或赐服的范畴。     

顶管进出洞设计与施工技术探讨

结合工程实践,阐述顶管施工中工具头进出洞口的技术难点,对顶管施工测量控制、洞口土体加固方法及洞口止水装置的设计提出了看法,并对复杂土层的顶管技术措施进行了探讨。     

Novel Mg-Zr-A-H (A = Li, Na) hydrides synthesized by a high pressure technique and their hydrogen storage properties

It is important to develop the hydrogen storage technology by creating novel metal hydrides. In the present study, the powder mixtures of 6MgH₂ + ZrH₂ + nAH (A = Li, Na; n = 0, 0.3, 0.7, 1.0) were reacted to synthesize quaternary hydrides by use of a high pressure technique. The crystal structures of the new hydrides were refined by the Rietveld method based on the synchrotron XRD data. By reacting 6MgH₂ + ZrH₂ + nLiH, the quaternary hydrides with simple FCC-type structure were formed. In the case of 6MgH₂ + ZrH₂ + nNaH, novel quaternary hydrides with Ca₇Ge type structure were formed as well as the hydrides with simple FCC structure. The hydrogen storage capacities were around 6 wt.% according to the pressure-composition isotherm measurements. The formation enthalpies of the quaternary hydrides with simple FCC structure were proved to be lower while the enthalpies of the Mg-Zr-Na-H hydrides with Ca₇Ge type structure were higher, than that of the ternary Mg-Zr-H hydride obtained by reacting the basic system 6MgH₂ + ZrH₂. The hydrogen releasing temperatures of the quaternary Mg-Zr-A-H hydrides were slightly lower than that of the ternary Mg-Zr-H hydride.     

The effect of quaternary ammonium on discharge characteristic of a non-aqueous electrolyte Li/O2 battery

The effect of quaternary ammonium on discharge characteristic of Li/O₂ cells was studied by using Super-P carbon as air cathode, a 0.2 mol kg⁻¹ LiSO₃CF₃ 1:3 (wt.) PC/DME solution as baseline electrolyte, and tetrabutylammonium triflate (NBu₄SO₃CF₃) as an electrolyte additive or a co-salt. Results show that Li/O₂ cells can run normally in an electrolyte with NBu₄SO₃CF₃ as the sole conductive salt. However, such cells suffer lower voltage and capacity as compared with those using the lithium ionic baseline electrolyte. This is due to the larger molar volume of quaternary ammonium cation, which results in less deposition of oxygen reduction products on the surface of carbon. When used as an electrolyte additive or a co-salt, the ammonium is shown to increase capacity of Li/O₂ cells. The plot of differential capacity versus cell voltage shows that the Li/O₂ cell with ammonium added has broad and scatted differential capacity peaks between the voltages of two reactions of “2Li + O₂ → Li₂O₂” and “2Li + Li₂O₂ → 2Li₂O”. This phenomenon can be attributed to the phase transfer catalysis (PTC) property of quaternary ammonium on the second reaction. Due to inverse effects of the cation geometric volume and the PTC property of ammonium ions on the discharge capacity, there is an optimum range for the concentration of ammonium. It is shown that the addition of NBu₄SO₃CF₃ increases discharge capacity of Li/O₂ cell only when its concentration is in a range from 5 mol% to 50 mol% vs. the total of Li/ammonium mixed salt, and that the optimum concentration is about 5 mol%. In this work we show that the addition of 5 mol% NBu₄SO₃CF₃ into the baseline electrolyte can increase discharge capacity of a Li/O₂ cell from 732 mAh g⁻¹ to 1068 mAh g⁻¹ (in reference to the weight of Super-P carbon) when the cell is discharged at 0.2 mA cm⁻².     

富水砂层土压平衡盾构关键施工技术

沈阳地铁二号线会展中心站一世纪广场站隧道盾构区间穿越中粗砂、砾砂层,砂性土层内摩擦角大,碴土流动性差,排土困难,地下水量丰富、水压高,因此盾构掘进控制困难,容易造成地表沉降.从土压平衡盾构的适应性、刀盘和螺旋输送机的结构、刀具的配置和加固、碴土改良措施、沉降控制方法等方面介绍土压平衡盾构穿越砂层的施工技术.在施工过程中,通过采取同步注浆、二次注浆、加强施工监测等措施保证了既有线行车安全.     

精细化管理在盾构施工中的应用

以广州地铁复合地层土压平衡盾构施工的实践为基础,结合盾构穿越敏感建筑物的正反两方面的经验和教训,分析和强调了精细化管理在盾构施工中的应用,对类似施工环境中盾构机施工具有重要的借鉴意义和指导作用。     

桩基优化设计经济效益分析

分析岩土工程勘察报告中所揭示的地基土层特性,根据所掌握的大量桩基工程检测试验数据、沉降观测实测数据,对桩周(端)地基土的受荷性能以及基桩工作性状进行研究,通过静载荷试验的实际桩基承载能力,分析推导出优化地基土桩基设计参数。据此优化带来了一定的经济效益。     

覆岩结构对松散承压含水层下采煤压架突水的影响研究

针对松散承压含水层下采煤压架突水灾害问题,采用数值模拟和相似材料模拟手段,就松散承压含水层下采煤基岩厚度、硬岩层层位及硬岩层的不同组合特征等覆岩结构因素对压架突水灾害的影响进行了研究。结果表明:在松散承压含水层载荷传递作用较大的情况下,压架突水灾害的发生主要与覆岩结构有关,当基岩越薄、距离煤层10倍采高以内的顶板中存在巨厚硬岩层且距离煤层最近的硬岩层厚度越大时,覆岩越易发生整体破断,引发工作面压架突水灾害。上述影响规律得到了祁东煤矿7114和7112工作面开采实践的验证。根据压架突水灾害发生的覆岩结构条件,可以在采前对压架突水危险区域进行预测,从而为采场压架突水灾害的防治提供依据。     

浅埋特大采高综采工作面关键层“悬臂梁”结构运动对端面漏冒的影响

通过对神东矿区大柳塔煤矿52304综采工作面7.0 m支架开采时端面漏冒的现场实测、模拟实验与理论分析,从特大采高综采工作面覆岩关键层"悬臂梁"结构运动对直接顶作用的角度,阐述了端面漏冒的发生机理,并提出了相应的控制对策。结果表明:综采工作面的端面漏冒不仅与顶板岩性、构造和裂隙发育以及支护工况有关,还与关键层破断块体的回转运动密切相关。特大采高综采工作面覆岩第1层关键层易破断进入垮落带而形成"悬臂梁"结构,不同于低采高综采工作面关键层稳定铰接的"砌体梁"结构,由于其破断块体后方无水平的侧向约束力,它将无法形成自稳的承载结构;当支架初撑力不足以平衡该"悬臂梁"破断块体及其上覆垮落带岩层的载荷时,易造成该块体发生失稳错动而切割直接顶,从而导致贯穿式的端面漏冒的发生。这是造成52304特大采高综采工作面在顶板完整、煤壁片帮并不突出的条件下,仍发生严重端面漏冒的主要原因。由此提出了以提高支架初撑力来防止关键层"悬臂梁"破断块体发生失稳错动为思路的端面漏冒控制对策,并依此确定了52304综采工作面7.0 m支架的合理初撑力为12 405 kN,现有支架的初撑力仍显不足。