多目标投资组合模型的理想点解法

对多目标证券组合投资模型进行了研究,该模型用于解决多目标线性优化问题,模型以绝对偏差和代替方差、以换手率刻画流动性。研究考虑到了投资者的效用函数,采用理想点法对模型进行了求解,便于实际操作;通过实例分析了该模型的应用价值。     

上海股市收益与流动性风险动态关系实证

应用Engle(2002)提出的动态条件相关多元GARCH模型(DCC-MVGARCH)和向量自回归(VAR)方法,研究了上海股票市场收益与Acharya and Pedersen(2005)提出的三种流动性风险以及系统风险变量的动态关系.研究结果表明,上海股市存在系统风险溢价和流动性风险溢价,但风险变量对收益率的影响较小,股市的风险传递机制尚未真正形成.     

Reducing the startup time of aerobic granular sludge reactors through seeding floccular sludge with crushed aerobic granules

One of the main challenging issues for the aerobic granular sludge technology is the long startup time when dealing with real wastewaters. This study presents a novel strategy to reduce the time required for granulation while ensuring a high level of nutrient removal. This new approach consists of seeding the reactor with a mixture of crushed aerobic granules and floccular sludge. The effectiveness of the strategy was demonstrated using abattoir wastewater, containing nitrogen and phosphorus at approximately 250 mgN/L and 30 mgP/L, respectively. Seven different mixtures of crushed granules and floccular sludge at granular sludge fractions (w/w in dry mass) of 0%, 5%, 10%, 15%, 25%, 30% and 50% were used to start eight granulation processes. The granulation time (defined as the time when the 10th percentile bacterial aggregate size is larger than 200 μm) displayed a strong dependency on the fraction of granular sludge. The shortest granulation time of 18 days was obtained with 50% crushed granules, in comparison with 133 days with 5% crushed granules. Full granulation was not achieved in the two trials without seeding with crushed granules. In contrast to the 100% floccular sludge cases, where a substantial loss of biomass occurred during granulation, the biomass concentration in all other trails did not decrease during granulation. This allowed that good nitrogen removal was maintained in all the reactors during the granulation process. However, enhanced biological phosphorus removal was achieved in only one of the eight trials. This was likely due to the temporary accumulation of nitrite, a strong inhibitor of polyphosphate accumulating organisms.     

某缸内直喷发动机进气歧管CFD模拟分析

进气歧管控制着发动机各缸的进气,尤其对于多缸发动机,进气控制对发动机各循环变动的影响非常大。对于四缸以下发动机的进气歧管采用稳态CFD分析完全满足优化设计要求,但对于四缸以上发动机需要采用瞬态CFD分析方法更为合适。进气歧管是发动机最关键进气系统部件之一,其核心功能是为发动机各缸提供充足均匀的混合气,是影响发动机动力性和经济性的关键因素;除此之外,电喷系统主要传感器和执行器均安装在进气歧管上,导致进气歧管结构复杂和高成本。计算机模拟可以降低开发成本,文中用三维CFD软件对某缸内直喷发动机进气歧管进行了稳态流动分析,通过CFD分析基本可以确定进气歧管结构要求,指导实际产品设计。     

Pharmaceutical production of tableting granules in an ultra-small-scale high-shear granulator as a pre-formulation study

Objective: In some of drug developments, the amount of bulk drug powder to use in early stages is limited and it is not easy to supply a sufficient drug amount for conventional preparation methods. Therefore, an ultra-small-scale high-shear granulator (less than 5?g) (USG) was developed and applied to small-scale granulation as a pre-formulation.

Method: The sample powder consisted of 66.5% lactose, 28.5% microcrystalline cellulose and 5.0% hydroxypropylcellulose. The granules were obtained to agitate 5?g of the sample powder with 1.0?mL of water at 300?rpm for 5?min after pre-powder mixing for 3?min by the USG and the manual hand (HM) methods.

Results: The granules were evaluated by the 10% and 90% accumulated particle size and the recoveries of the granules and the powder solid. Median particle size for the USG and the HM methods was 159.2?±?2.3 and 270.9?±?14.9 µm, respectively. The USG method had a narrower particle size distribution than those by the HM method. The recovery of the granules by USG was significantly larger than that by the HM method.

Conclusion: Characteristics of all of the granules indicated that the USG method could produce higher quality granules within a shorter time than the HM methods.     

真空干燥法制备甘薯全粉

选用真空干燥方法制备甘薯熟制全粉,研究了真空干燥温度、浸钙浓度、蒸制时间和乳化剂添加量对甘薯熟制全粉游离淀粉含量的影响。利用正交试验优化了工艺参数,当干燥温度为40℃,浸钙浓度为25 mg/L,乳化剂添加量为0.2%,蒸煮时间为12 min时生产出的甘薯熟制全粉品质最好,游离淀粉含量为21.89%。     

Automatic image acquisition, calibration and montage assembly for biological X-ray microscopy

We describe a system for the automatic acquisition and processing of digital images in a high-resolution X-ray microscope, including the formation of large-field high-resolution image montages. A computer-controlled sample positioning stage provides approximate coordinates for each high-resolution subimage. Individual subimages are corrected to compensate for time-varying, non-uniform illumination and CCD-related artefacts. They are then automatically assembled into a montage. The montage assembly algorithm is designed to use the overlap between each subimage and multiple neighbours to improve the performance of the registration step and the fidelity of the result. This is accomplished by explicit use of recorded stage positions, optimized ordering of subimage insertion, and registration of subimages to the developing montage. Using this procedure registration errors are below the resolution limit of the microscope (43 nm). The image produced is a seamless, large-field montage at full resolution, assembled automatically without human intervention. Beyond this, it is also an accurate X-ray transmission map that allows the quantitative measurement of anatomical and chemical features of the sample. Applying these tools to a biological problem, we have conducted the largest X-ray microscopical study to date.     

Starch Granules in Arabidopsis thaliana Mesophyll and Guard Cells Show Similar Morphology but Differences in Size and Number

Transitory starch granules result from complex carbon turnover and display specific situations during starch synthesis and degradation. The fundamental mechanisms that specify starch granule characteristics, such as granule size, morphology, and the number per chloroplast, are largely unknown. However, transitory starch is found in the various cells of the leaves of Arabidopsis thaliana, but comparative analyses are lacking. Here, we adopted a fast method of laser confocal scanning microscopy to analyze the starch granules in a series of Arabidopsis mutants with altered starch metabolism. This allowed us to separately analyze the starch particles in the mesophyll and in guard cells. In all mutants, the guard cells were always found to contain more but smaller plastidial starch granules than mesophyll cells. The morphological properties of the starch granules, however, were indiscernible or identical in both types of leaf cells.     

一种简单长期保藏乳酸菌菌种方法的研究

为了适应发酵蔬菜生产企业菌种保藏,本试验探讨乳酸菌培养基质的灭菌时间,并在单因素试验基础上,采用响应面法优化改良MRS培养基配方。结果表明,乳酸菌培养基质白菜帮颗粒灭菌时间为9 min,改良MRS培养基最佳配方为：白菜帮颗粒25 g/L、蛋白胨9 g/L、牛肉膏8 g/L、葡萄糖14 g/L、柠檬酸三铵2 g/L、酵母膏5 g/L、乙酸钠2 g/L、K2HPO4 2 g/L、MgSO4·7H2O 0.58 g/L、MnSO4·4H2O 0.25 g/L。在优化培养基条件下,副干酪乳杆菌的菌数为1.19×1010 CFU/mL。1～4 ℃冷藏可保藏3～4年,-16～-20 ℃冷冻可保藏4～5年。此保藏方法操作简单、成本低,菌种质量稳定可靠,适合蔬菜发酵企业保藏生产用乳酸菌菌种。     

桑椹汁保健泡腾冲剂的研制

以桑椹汁和桑叶为主要原料,添加白砂糖、柠檬酸、香精、L-赖氨酸盐酸盐等辅料,经调配、过滤、浓缩、干燥、灭菌、包装等工序加工而成的桑椹汁保健泡腾冲剂,其色泽美观、口感较好、风味独特、溶解和泡腾性好,是具有较强保健作用的产品。