An improved light attenuation technique for measuring large interfacial areas

A laser-based light attenuation technique was successfully used to measure interfacial areas as high as 5832 m²/m³ and Sauter mean bubble diameter varying between 50 and 5600 μm. Good agreement between this approach and the photographic technique was obtained particularly at low gas holdups.     

用直接纺丝法制芳纶短纤维

研究了直接纺丝制取芳纶短纤维的新方法。讨论了纤维长度、直径及力学性能与纺丝条件的关系。发现影响纤维长度的主要因素是空气层高度和喷丝速度,影响纤维直径的主要因素为喷口直径及喷丝速度。此外,还用PPTA短纤维制成了均匀的PPTA"浆粕"纤维。     

Crystallographic Texture Development in Bismuth Sodium Titanate Prepared by Reactive-Templated Grain Growth Method

Bi_0.5Na_0.5TiO₃ (BNT) and 0.94Bi_0.5Na_0.5TiO₃·0.06BaTiO₃ (BNT–BT) bulk ceramics with extensive 〈100〉 texture were prepared by the reactive-templated grain growth method, using platelike Bi₄Ti₃O₁₂ (BIT) particles as templates for BNT. Calcined compacts were composed of matrix grains with random orientation and 〈100〉-oriented grains transformed from aligned BIT particles, and the texture developed by the growth of oriented grains during sintering. Ceramics with extensive texture were obtained by using the starting mixture containing the maximum concentration of platelike BIT to form the maximum volume fraction of oriented grains.     

连云港海域悬沙和表层沉积物交换研究

采用粒度谱计算方法分析连云港及邻近海域悬沙和表层沉积物交换特征,为徐圩防波堤口门布置和连云港港航道回淤研究提供理论支撑。连云港港主航道和徐圩航道5 m等深线以外的区域悬沙和表层沉积物交换率为0.1~0.2,表明航道回淤强度将处于较低水平,对今后航道维护有利;5 m等深线以内区域的交换率为0.3~0.4,悬沙落淤对航道回淤有一定贡献,表明该航道段回淤量相对较大,计算结果与实测航道回淤强度分布特征基本一致。灌河口沙嘴正常天气条件下交换率小于0.2,说明悬沙落淤对沙嘴的影响较小;5 m等深线以内破波带水域交换率大于0.5,表明悬沙和表层沉积物交换频繁。连云港港及邻近海域悬沙和表层沉积物交换主要为粒径小于62 μm的细颗粒组分。分析结果表明,为减少泥沙回淤对徐圩港区港池正常运行的影响,兴建防浪挡沙堤并将堤头布置在破波带之外十分必要。     

Grain-Boundary Wetting-Dewetting in z= 1 SiAlON Ceramic

The grain-boundary structure of a model SiAlON polycrystal with nominal composition Si₅AlON₇ was characterized by transmission electron microscopy (TEM) both in an equilibrium (as-processed) state at room temperature and after quenching from elevated temperature. In addition, low-frequency (1–13 Hz) internal friction data were recorded as a function of temperature, showing a pronounced grain-boundary sliding peak positioned at 1030°C. High-resolution transmission electron microscopy (HRTEM) of the equilibrated low-temperature microstructure revealed residual glass only at multigrain junctions, but no amorphous intergranular films were observed. The detection of clean interfaces in the as-processed sample contradicts the internal friction data, which instead suggests the presence of a low-viscosity grain boundary phase, sliding at elevated temperatures. Therefore, a thin section of the as-sintered material was heated to 1380°C and rapidly quenched. HRTEM analysis of this sample showed, apart from residual glass pockets, wetted grain boundaries, which is in line with the internal friction experiment. This wetting-dewetting phenomenon observed in z = 1 SiAlON is expected to have a strong impact not only on high-temperature engineering ceramics but also on geological, temperature-activated processes such as volcanic eruptions.     

水辅助注塑大直径介质导管制品的冷却分析

采用数学分析方法，通过假设、简化分析模型，用数学模型来表述物理模型，确定了水辅助注塑(VAIM)大直径介质导臂制品的冷却时间，并运用算例和国外试验的结果进行验证。结果发现：水辅助注射成型新工艺可以更加显著地缩短注塑周期，降低制件壁厚，允许制件有更大的实际直径。因此，VAIM技术可用来高效率地生产大直径、高质量、薄壁的介质导臂。     

Admittance—Frequency Response in Zinc Oxide Varistor Ceramics

The lumped parameter/complex plane analysis technique revealed several contributions to the terminal admittance of the ZnO—Bi₂O₃ based varistor grain-boundary ac response. The terminal capacitance has been elucidated via the multiple trapping phenomena, a barrier layer polarization, and a resonance effect in the frequency range 10⁻²≤ f ≤ 10⁹ Hz. The characterization of the trapping relaxation behavior near ∼ 10⁵ Hz (∼ 10⁻⁶ s) provided a better understanding of a previously reported loss-peak. The possible nonuniformity in this trapping activity associated with its conductance term observed via the depression angle of a semicircular relaxation in the complex capacitance ( C *) plane has been postulated.     

Effect of Mode of Drying on Microstructure of Potato

Potato v. Irga was subjected to blanching, and thereafter was dried by convection, puff-drying, and freeze-drying. Microstructure of raw, blanched, and dried tissue was analyzed under the light microscope using computer image analysis. It was found that the tissue of the investigated variety is built up from cells much smaller than those described in literature for other cultivars. Blanching caused starch gelatinization and increase of cross-sectional area of cells. There was no evidence of broken cell walls. Convective drying resulted in cell shrinkage and some breaking of cell walls. It was estimated that some 12% of cells lost integrity during drying. Limited disintegration of the tissue caused by convective drying is attributed to small size of cells, large contact area, and high cohesive forces between cells. Puff-drying damaged the tissue much more than the convective drying. The most devastating to tissue microstructure was freeze-drying, probably freezing per se.     

工艺因素影响焦炭颗粒耐压强度的试验研究

焦炭颗粒的耐压强度一直是焦炭颗粒最重要的性质之一。利用最近提出的表征焦炭颗粒耐压强度的新方法，就模压压力、加压方式、粒度组成范围、粒度大小、粒度配比等因素对单粒度或多粒度组成焦炭颗粒耐压 强度的影响进行了较为详细的试验研究。结果表明：（1）焦炭颗粒的粒度大小和粒度范围均可用其原始平均细度来表征。焦炭颗粒的原始平均细度越大，其耐压强度系数也就越高；（2）多粒度组成焦炭颗粒混合料的耐压能力比单粒度组成混合料的耐压能力要高得多。对多粒度组成焦炭颗粒而言，模压压力及粒度组成配比对其耐压强度系数的影响不甚明显；（3）分阶段缓慢加压到位比一次快速加压到位有利于提高焦炭颗粒的耐压强度系数。     

过量TiO2助烧剂对Ba0.998La0.002TiO3陶瓷晶粒生长的影响

采用电性能测定和微观结构分析等方法研究了过量TiO2助烧剂对Ba0.998La0.002TiO3陶瓷晶粒生长的影响.结果表明:对于Ba0.998La0.002TiO3陶瓷在有液相参与烧结的晶粒溶解-淀析过程中,晶粒生长的必要条件是不仅要有液相的形成,而且BaTiO3晶粒必须在液相中有一定的溶解度.由于BaTiO3晶粒在Ba6Ti17O40和Ba2TiSi2O8液相中有足够的溶解度,促进了晶粒的生长,同时旌主掺杂离子进入晶格而释放氧,形成半导性的陶瓷,而BaTiO3晶粒不能溶解于Ba2Ti2SiP2O13液相中,抑制了晶粒的生长.