Preparation of Tripalmitin Micronization by Supercritical Fluids Technique

利用气体饱和溶液微粒形成技术实验装置,分别用超临界n2和超临界CO2制备三棕榈酸甘油酯微粒,探讨压力、温度以及喷嘴大小等工艺参数对微粒(粒径、粒径分布和形貌)的影响。结果表明:n2辅助过程得到的微粒基本为球状;预膨胀压力越高,粒径越小,粒径分布越窄;100μM喷嘴下制得的微粒粒径最小,且分布较均匀。CO2辅助过程得到的微粒部分为球状,部分为针状和片状;预膨胀压力越高,粒径越小,粒径分布越窄;喷嘴直径大小对微粒平均粒径及粒径分布影响不大;预膨胀温度升高,颗粒的粒径稍微增大。CO2辅助过程得到的微粒粒径比n2辅助过程得到的微粒粒径稍大,但两者的粒径分布相差不大。Generation of tripalmitin microparticles from its melts was investigated by using both supercritical CO2 and supercritical N2.The effects of various operating conditions,such as the pre-expansion pressure,pre-expansion temperature,and nozzle size on the particle morphology,particle size and particle size distribution(PSD) were investigated.Results showed that microspheres were obtained from the N2-assisted process,the particle size decreased and PSD narrowed with the increasing of the pre-expansion pressure,nozzle size showed no obvious effect on the microparticles,and pre-expansion temperature should be less than 72 ℃ to obtain solid particles.From the CO2-assited process,spherical,lamellate and needle-like particles were obtained,the particle size decreased,PSD narrowed with the increasing of the pre-expansion pressure,nozzle size showed no obvious effect on the particles and the pre-expansion temperature slightly increased the average size of particles.Particles' PSD from supercritical CO2 was close to that from supercritical N2

中等实验规模下不同营养环境对苦草(Vallisneria natans)生长的影响

本实验分别选用武汉东湖中营养和富营养湖区的湖水和底泥,并在水柱中添加氮或磷以设置高营养、中营养、中营养添加磷、中营养添加氮等四种营养环境.测定这四种营养条件下栽培苦草(Vallisneria natans)的生长和生化指标变化,探讨不同营养环境对苦草生长的影响机制.实验结果表明,苦草的生物量、叶数和新芽数等生长指标在中营养环境最高,中营养环境添加磷次之,中营养环境添加氮较低,在高营养环境最低;苦草可溶性糖和游离氨基酸含量在高营养环境中最高,在中营养环境、中营养环境添加磷和中营养环境添加氮等处理间没有明显

DNA damage in the liver of Boleophthalmus pectinirostris with benzo(a) pyrene exposure

在实验生态条件下 ,采用碱解旋技术检测了暴露于BaP后大弹涂鱼肝脏的DNA单链断裂程度 ,结果发现DNA单链断裂程度同时受到曝污时间和曝污浓度的影响 ,并具有一定的时间—效应和剂量—效应特征 ;污染解除后DNA单链断裂程度未明显减轻 ,表明DNA损伤的修复能力较弱。以上这些结果表明DNA单链断裂适于作为BaP暴露后DNA损伤的检测指标。DNA single strand breaks in the liver of Boleophthalmus pectinirostris with benzo(a) pyrene exposure were detected using DNA alkaline unwinding assay under experimental ecological conditions. It turned out that DNA single strand breaks were effected by exposure time and exposure concentration and were time dependent and dose related. The repair of DNA damage was weak because no significant change was observed after the fishes were transferred to clean sea water. All of the results show that DNA single strand breaks are suitable to be the bioindicator of DNA damage with BaP exposure.国家自然科学基金!资助项目 (49876 0 2 9);; 福建省自然科学基金!资助项目 (C9810 0 0 3

低速大偏心滑动轴承润滑状态转变及特性分析

以动压滑动轴承为研究对象，建立了完全流体润滑模型和混合润滑模型。采用有限差分法进行数值求解，得到摩擦阻力、摩擦因数、承载力和端泄油温升等特性参数；通过膜厚比和摩擦因数判断轴承所处润滑状态，分析润滑状态转变后表面粗糙度对轴承特性的影响；并基于M2000型摩擦磨损实验机进行了混合润滑状态摩擦副跑合实验。结果表明，低转速下增大偏心率，轴承润滑状态从完全流体润滑转变为混合润滑，且综合表面粗糙度越大，润滑状态转变所需偏心率越小；混合润滑状态粗糙峰接触可以提高承载力，但导致轴承摩擦阻力和端泄油温升迅速升高；大偏心下实验结果与混合润滑理论计算结果基本一致

风向对半固定沙垄表面风速影响——以古尔班通古特沙漠为例

利用DETI可移动测风系统对古尔班通古特沙漠半固定沙垄表面风速进行实地观测,获取了主要风季不同风向条件下沙垄表面7个典型部位距离地表20cm、40cm、60cm、100cm和200cm5个高度的风速系列数据,系统研究风向对半固定沙垄表面坡面风速及风速廓线的影响。结果表明,迎风坡的气流加速和背风坡的风速降低现象在实际观测中得到证实,但受风向的影响甚大。垄顶风速放大率随入射角的增大呈指数关系递增,而背风坡风速占垄顶风速的比率则随入射角的增大呈线性关系递减。大角度入射气流速度变化主要受控于沙垄形态,小角度入射气流速度变化主要受控于地表植被状况。无论气流以何种角度入射,距沙垄表面20cm高度气流的加速均较其他高度缓和。沙垄底部和坡中下部的风速廓线变化趋势基本一致,且呈较好的对数拟合关系;两坡中上部和垄顶部的对数拟合方程相关系数偏小;受回旋涡流的影响,风速廓线在背风坡上部有明显偏折,初步断定涡流中心在距地表40cm左右的高度

Integration of Numerical Simulation and Control Scheme for Energy Conservation of Aluminum Melting Furnaces

Aluminum melting process is a semi-continuous process with high-energy consumption. In this paper, a software-based strategy which considers numerical simulation and control scheme simultaneously is employed to improve energy consumption of aluminum melting furnaces without changing the hardware. For numerical simulation, a nonlinear steady-state optimization is performed offline to obtain optimal operating points. Extensively, the optimal operating conditions include not only product exit temperature, but also ratio of combustion air flow and natural gas flow, furnace temperature, flue gas temperature and some important manipulated variables. For control scheme, a two-layer model predictive control which consists of steady state target calculation and dynamic optimization is developed to track the optimal operating conditions. In steady state target calculation layer, a priority strategy is proposed based on the different importance of controlled variables to make the steady state targets more reasonably. In dynamic optimization layer, a quadratic objective function is defined in terms of tracking both the optimal steady-state of controlled variables and manipulated variables. The method is successfully carried out in F aluminum melting furnace of a company in Tianjin. Compared with previous operation, the comprehensive energy consumption and the comprehensive energy consumption for unit output of product decrease 5.99% and 6.56% respectively.</p

春夏季放牧对古尔班通古特沙漠南部土壤种子库和地上植被的影响

位于新疆北部准噶尔盆地腹地的古尔班通古特沙漠,是世界上温带荒漠生物多样性的精华和最为丰富的典型区域。历史上这里就是北疆羊和部分马匹重要的冬牧场,但近年来的放牧活动在春夏季也开始进入沙漠腹地,使地表性质与植被覆盖发生了明显改变。应用野外随机取样与室内萌发实验相结合的方法,对比研究了古尔班通古特沙漠南部春夏季放牧和冬季放牧沙垄土壤种子库差异及其与地上植被的关系。结果表明:冬季放牧沙垄种子库种数为24种,而春夏季放牧沙垄有20种,后者明显减少了植物种数。冬季放牧沙垄种子库密度为(353.2&plusmn;87)粒.m-2,而春夏季放牧沙垄为(189.1&plusmn;23)粒.m-2,比前者减少了88%。两类沙垄土壤种子库的生活型组成都以一年生植物为主,相似性系数为0.711。相同沙垄不同部位的物种相似性系数在0.429~0.600之间,异质性较大,尤其表现在除垄顶之外的其他部位。冬季放牧沙垄和春夏季放牧沙垄地上植被中分别有植物36种和26种,各生活型所有物种均为后者低于前者,其中短命、类短命物种数量减少幅度最大。春夏季放牧沙垄地上植被的物种多样性和均匀度降低,而优势度升高。回归分析显示,冬季放牧沙垄定植群落有21%的变异来源于土壤种子库,而春夏季放牧沙垄有51%的变异来源于土壤种子库,可见不同季节的放牧干扰显著影响土壤种子库及其与地上植被的相关关系

~(265)Bh(Z=107)同位素的首次观测

在兰州的重离子加速器上用 2 6Mg离子束轰击 2 43 Am靶 ,产生了新同位素 2 65Bh .通过观测新同位素 2 65Bh和它的已知子核 2 61Db和 2 57Lr之间的α衰变的关联 ,实现了对新核素的鉴别 .实验中使用了一套新建立的具有数个探测器对的转轮收集探测系统 .将该系统用于特殊的母 -子核搜索模式 ,从而大大减少了本底 .共测得了 8个 2 65Bh的α衰变关联事件 ;同时 4个已知核 2 64Bh的衰变关联事件也被鉴别出来 .实验测得 2 65Bh的α衰变能量为 (9.2 4± 0 .0 5 )MeV ,半衰期为 0 .94 + 0 .70-0 .3 1s