Intersubband absorption properties of high Al content AlxGa1?xN/GaN multiple quantum wells grown with different interlayers by metal organic chemical vapor deposition

High Al content Al_xGa_1−xN/GaN multiple quantum well (MQW) films with different interlayers were grown by metal organic chemical vapor deposition. These MQWs were designed to achieve intersubband (ISB) absorption in the mid-infrared spectral range. We have considered two growth conditions, with AlGaN interlayer and GaN/AlN superlattice (SL) interlayer, both deposited on GaN-on-sapphire templates. Atomic force microscopy images show a relatively rough surface with atomic-step terraces and surface depression, mainly dominated by dislocations. High-resolution X-ray diffraction and transmission electron microscopy analyses indicate that good crystalline quality of the AlGaN/GaN MQW layer could be achieved when the AlGaN interlayer is inserted. The ISB absorption with a peak at 3.7 μm was demonstrated in MQW films with AlGaN interlayer. However, we have not observed the infrared absorption in MQW films with GaN/AlN SL interlayer. It is believed that the high dislocation density and weaker polarization that resulted from the rough interface are determinant factors of vanished ISB absorption for MQW films with the GaN/AlN SL interlayer.     

独立院校“仪器分析”课程教学组织与设计探讨

仪器分析课是面向化工类相关专业开设的重要专业课程。为提高教学效果,培养学生对综合知识的运用能力,结合课程学时相对较少的实际情况,对教学内容进行了优化处理;对教学中的组织与设计进行了改革和探索,提高了教学水平和质量。     

应用型本科院校仪器分析设计性实验的探索与实践——以食品中亚硝酸盐含量的测定为例

文章分析了"食品中亚硝酸盐含量的测定"的实验过程,阐述了开设仪器分析计性实验对于拓大学生知识面、提高学生的查阅文献和获取信息的能力、加深学生对仪器分析各原理的理解、培养学生分析和解决问题的能力、强化学生的实验技能等各方面的积极意义。     

Comparison of different methods to prepare MgO whiskers

Magnesia whiskers have been made by hydrolysis of MgCl₂–KCl melt and conversion of magnesium hydroxide whiskers. The morphology of MgO whiskers was examined by SEM and TEM. Composition of products was identified by XRD. Comparisons have been made on the morphology and quality of the products by different methods. Discussions have been made on the efficiency, product quality control and scale-up feasibility of these methods. Whiskers prepared by hydrolysis have uniform diameter but other shapes of magnesia are often found. Conversion of Mg(OH)₂ whiskers to MgO whiskers is simple and easy to scale-up, but the product often has many defects caused by decomposition. Nevertheless, the single crystal structure can be reserved as revealed by electron diffraction. XRD results show that the purity of products by hydrolysis is better than that by conversion. The conversion method is more hopeful for industrial production.     

热处理过程中牡蛎闭壳肌肌原纤维蛋白部分理化特性的变化

通过对牡蛎闭壳肌肌原纤维蛋白加热过程中浊度、溶解度、表面疏水性、α螺旋含量和总巯基含量的测定,研究了热处理过程中牡蛎闭壳肌肌原纤维蛋白理化特性的变化,结果表明,在20～40℃,牡蛎闭壳肌肌原纤维蛋白溶液的浊度、溶解度、表面疏水性、α螺旋含量和总巯基含量均无明显变化。在温度高于40℃时,随着温度的升高,牡蛎闭壳肌肌原纤维蛋白的浊度整体呈增大趋势,46℃下变化最为明显;溶解度在40～50℃变化最大,结合浊度的变化规律推测其变性温度为46℃;表面疏水性总体上逐渐增加,在40～50℃变化最大;α螺旋含量总体上逐渐降低,60℃变化最大,当温度达到70℃时约有80%的α螺旋结构被破坏;总巯基含量逐渐降低,50℃时下降最快。     

番木瓜籽油的提取工艺优化及其理化特性

以番木瓜籽为原料,通过单因素试验和响应面优化试验研究了浸提溶剂、料液比、浸提温度、浸提时间等因素对番木瓜籽油提取率的影响,确定了溶剂浸提番木瓜籽油的最佳工艺条件,并分析了番木瓜籽油的理化性质和脂肪酸组成。结果表明:正己烷浸提法提取番木瓜籽油的浸提温度为61℃、浸提时间为2.5 h和液料比为3.18∶1(mL∶g)。在该条件下油脂提取率为21.27%;番木瓜籽油的酸值、过氧化值等指标达到了食用油脂的标准,但是其杂质含量较高,还需进一步精炼;番木瓜籽油中含有5种脂肪酸,主要是棕榈酸(18.90%)、油酸(71.06%)和亚油酸(4.28%)。     

赛络纺Parster粘胶混纺纱的开发

为了顺利开发Parster粘胶赛络纺针织用纱,针对Parster和粘胶两种纤维的特性,采取一预并三混并混和工艺和赛络纺纺纱方法,重点解决了Parster纤维黏卷、梳棉棉网飘浮断头、并条易绕罗拉及胶辊等问题;优选前纺工序各部速度与隔距、梳棉机针布型号、粗纱定量、粗纱捻系数、细纱双孔喇叭口间距、细纱捻系数、络筒清纱参数,同时加强各工序温湿度管理,最终确保了赛络纺Parster粘胶混纺纱的顺利生产,成纱质量满足了使用要求。     

橘子果糕的研制

以橘子为原料,用卡拉胶、软糖粉复配型胶凝剂生产橘子果糕,所得产品色泽透明,风味优良,有较好的咬劲。     

专家系统在磨削工艺过程仿真预报中的应用

磨削模型中的参数值大多可依赖专家的知识和经验加以确定,本文提出了一种关于磨削领域的知识的表达方法,针对磨削工艺过程仿真预报的应用场合提出了一种可以根据已知输入条件自动确定相关参数值的专家系统,并对专家系统实现的技术作了详细的介绍,同时还对该专家系统作了实际运行测试和验证。     

聚晶金刚石复合片磨削试验研究

本文采用金刚石砂轮对聚晶金刚石(PCD)复合片材料进行了精密平面磨削试验,研究了磨削工艺参数和砂轮特性对磨削力的影响规律,分析了磨削PCD材料去除机理.研究发现:随着砂轮速度的增大,切向磨削力和法向磨削力不断减小;随着磨削深度的增加,切向磨削力和法向磨削力都增加,相同粒度的陶瓷结合剂砂轮的磨削力大于树脂结合剂砂轮的磨削力;切向磨削力和法向磨削力都随着工件进给速度的增加而增大;粒度号越大,切向磨削力和法向磨削力越大.PCD材料去除主要是通过磨粒的机械磨耗、破碎作用和热物理、热化学作用等方式.