Poly(2‐hydroxyethyl methacrylate‐co‐ethylene dimethacrylate) as a mouse embryonic stem cells support

A series of swellable ethylene dimethacrylate‐crosslinked poly(2‐hydroxyethyl methacrylate) (PHEMA) sheets of homogeneous (nonporous) structure or with different degrees of swelling and porosities was produced by bulk polymerization in either the absence or the presence of various diluents (porogens). Calculations performed by use of the solubility parameter δ of the reaction components indicate that the solvation conditions of the polymerization system change, depending on the solvating power of the diluent, which thus controls the porosity. Pore volume also seemed to be sensitive to the presence of the linear polymer diluent. Polystyrene (PS) showed, compared with poly(methyl methacrylate) (PMMA), a higher precipitating ability to form porous PHEMA sheets with an increased pore size because of its higher noncompatibility with newly formed crosslinked PHEMA. Given that PHEMA hydrogel is well known for its biocompatibility, it was used here as a potential carrier of cells in transplantation therapies. Attachment and growth of mouse embryonic stem (ES) cells on gelatin‐coated transparent PHEMA hydrogel substrates were examined. Two days after plating, survival and morphology of ES cells were largely similar on both PHEMA hydrogel sheets and in petri dishes as controls. This suggests that PHEMA hydrogels are likely candidates for application in transplantation therapies involving ES cells. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 425–432, 2003     

Micro-computed tomography scanning approaches to quantify,parameterize and visualize bioturbation activity in clogged streambeds: A proof of concept

Fine particle clogging and faunal bioturbation are two key processes co-occurring in the hyporheic zone that potentially affect hyporheic exchange through modifications in the sediment structure of streambeds. Clogging results from excessive fine sediment infiltration and deposition in rivers, and it is known to decrease matrix porosity and potentially reduce permeability. Faunal bioturbation activity may compensate for the negative effect of clogging by reworking the sediment, increasing porosity, and preventing further infiltration of fines. Although both processes of clogging and bioturbation have received significant attention in the literature separately, their combined effects on streambed sediment structure are not well understood, mostly due to the lack of a standard methodology for their assessment. Here, we illustrate a novel methodology using X-ray computed tomography (CT), as proof of concept, to investigate how, together, clogging and bioturbation affect streambed porosity in a controlled flow-through flume. By visualising gallery formations of an upward conveyor macroinvertebrate; Lumbriculus variegatus as a model species, we quantified bioturbation activity in a clogged streambed, focusing on orientation, depth, and volume at downwelling and upwelling areas of the flume. Gallery creation increased the porosity of the streambed sediment, suggesting a potential improvement in permeability and a possible offset of clogging effects. We illustrate the promising use of X-ray CT as a tool to assess bioturbation in clogged streambeds, and the potential role of bioturbation activity supporting hyporheic exchange processes in streambeds, warranting further studies to understand the extent of bioturbation impacts in natural systems.     

高温气候下沥青混凝土心墙连续碾压施工结合面温控试验研究

在夏季高温气候沥青混凝土心墙连续多层施工时,为减少等待结合面温度降至规范要求上限值90℃的时间,通过室内试验模拟结合面温度提高后心墙连续两层铺筑的情况,分别研究了结合面温度在90℃、100℃、110℃情况下沥青混凝土的压实性和变形情况,并进行了现场试验论证。室内试验结果表明:心墙沥青混凝土结合面温度降至100℃时,上层沥青混凝土的孔隙率为2.88%,下层沥青混凝土的最大侧向应变值为2.78%;结合面温度为110℃时,上层沥青混凝土的孔隙率为3.85%,下层沥青混凝土的最大侧向应变值为4.00%。现场试验结果表明:结合面温度为100℃时的上层沥青混凝土孔隙率和渗透系数均满足规范要求。因此,沥青混凝土心墙连续多层碾压时,结合面温度提高至100℃的施工质量可以得到保证。     

贵州地区粉煤灰种类对长龄期砂浆力学性能与孔隙率的影响

为了区别不同电厂Ⅱ级粉煤灰对长龄期砂浆性能的影响作用,采用贵州地区常见的4种粉煤灰（鸭溪、大方、六盘水和都匀Ⅱ级粉煤灰）,探索各粉煤灰对长龄期砂浆力学性能、孔隙率、吸水率和微观形貌的影响。结果表明：粉煤灰等质量替代水泥后,有利于提高长龄期砂浆的抗折强度和抗压强度,最大分别增大了94.6%和52.1%（鸭溪）、71.6%和49.5%（大方）,100.0%和92.0%（六盘水）以及51.8%和47.6%（都匀）;粉煤灰的掺量越大,砂浆的抗折强度和抗压强度的增加速率越大,孔隙率的降低幅度越大,分别为29.7%（六盘水）、40.0%(鸭溪)、28.7%（都匀）和34.9%（大方）,同时,4种粉煤灰砂浆的最大吸水率分别降低了21.6%（六盘水）、44.0%(都匀)、39.8%（鸭溪）和38.9%（大方）;综合分析发现,养护1 000 d后,粉煤灰仍主要发挥填充作用和火山灰效应,其中活性较低的粉煤灰仍以填充作用为主。     

Thermal properties of open-celled aluminum foams prepared by two infiltration casting methods

Contrastive research was carried out to study the thermal properties of open-celled aluminum foams prepared by counter-gravity infiltration casting system and the traditional process respectively.The experimental results show that the thermal conductivity coefficients of aluminum foams prepared by two different infiltration methods have similar increasing trend with the increase of particle size; along with the reducing porosity,the thermal conductivity coefficients will be enhanced oppositely.However,with the same particle size,the open-celled aluminum foam prepared by the former method has a higher thermal conductivity coefficient obviously.It is largely because that the sample prepared by counter-gravity infiltration casting has a lower void content and better dense crystallization of metal-matrix after the constant pressure process.     

铁矿含碳球团还原后性能的实验研究

通过恒温还原实验,研究C,O摩尔比（C/O）、还原温度、还原时间和煤粉粒度4个因素对铁矿含碳球团还原后金属化率、孔隙率和抗压强度等性能的影响,观察球团断面的显微结构,分析球团还原过程和强度形成机理。结果表明：随还原温度的升高和还原时间的延长,球团的孔隙率降低,铁连晶的致密度增加,抗压强度提高;在C/O为0.67,还原温度1 200℃,还原时间35 min,煤粉粒度45μm以下质量分数为98.4%的实验条件下,含碳球团还原后的金属化率88.15%,孔隙率22.05%,抗压强度2 870 N。     

AVO流体反演技术在低孔渗砂岩气藏预测中的应用

西湖凹陷A构造的砂岩气藏,主要埋藏于3000m以下的深层,且发育于浅水沉积环境,储层物性较致密,厚度横向变化大,导致储层的AVO响应复杂,常规AVO分析难以对储层流体进行有效识别。研究了AVO流体反演技术在该构造含气储层预测中的应用。该技术在对储层以及非储层速度、密度、厚度等关键参数的统计分析的基础上,利用Monte－Carlo随机模型建立、地震正演模拟、流体替换等技术,获得储层在不同流体下AVO响应的验前概率;然后利用Bayes理论,估算实际地震数据AVO响应指示储层含某种流体的可能性一验后概率,从而实现储层流体的预测。实际钻探结果证实了该方法的有效性。     

摩托车箱体压铸件失效分析及预防

为了提高压铸件的质量，优化模具结构，解决JY110摩托发动机箱体压铸件的气孔和缩松缺陷．对这些缺陷作了详细分析。在压铸模具设计上，提出了防止措施，主要是对内浇口的设置和型芯提出了修改方案。结果表明正确地设置内浇口对减少箱体的缺陷有很大的作用。     

A201铝合金针孔形成机制的探讨

本研究的目的为藉由完整的试验,找出铝合金中针孔与铝合金凝固期间热参数之间的关系,进而于铸造实际处理时,可为铸造方案设计及金属凝固提供参考。A201铝合金有127℃的凝固范围,适合作为研究对象;经由有系统的改变冒口大小,及平板铸件的长度及厚度,并浇注于两种不同的砂型中,通过变化铝合金凝固时的各种热参数,例如:局部凝固时间、冷却速率、液相前进速度及热梯度等,经计算针孔量,可得出热参数与针孔量间的关系。试验结果显示,A201铝合金的针孔量减少与补充参数值G/VSt1.10增大有一定的关系。     

填料粒子成型对泡沫铝合金孔结构的影响

在实验的基础上 ,绘制出填料粒子成型时的体积与泡沫铝合金的孔隙率相对应的变化曲线 ,并应用力学的基本原理对泡沫铝合金孔结构的成形机理进行了研究。确定填料粒子成型时的体积变化应在 0 %～ 12 %之间 (此时泡沫铝合金的孔隙率应在 41.6 %～ 47.6 %之间 ) ,才能稳定填料粒子尺寸 ,从而更好地控制泡沫铝合金的孔径尺寸 ,提高成型质量 ,稳定泡沫铝合金的使用性能。