Finite element analysis of heat conduction in lasagna during thermal processing

Conductive heat transfer in lasagna during heating was computed by means of the finite element method. the thermophysical properties of the pasta and tomato sauce layers were derived from their chemical composition. Simulation results obtained with an axisymmetric 2D finite element mesh without the typical layer structure differed only slightly from results obtained with a 1D mesh in which the typical layer structure was incorporated. the predicted temperatures at various locations in the lasagna agreed well with experimentally determined temperatures during heating in a commercial medium scale oven under various operating conditions. It is shown that the temperature dependency of the thermophysical parameters has only a minor influence on the temperature near the centre of the lasagna. However, when the lasagna surface is subjected to temperatures above its boiling temperature, incorporation of the water/vapour phase change in the specific heat capacity can avoid over-estimation of the volume averaged temperature and process value.     

丙酮/氯气的氯化反应过程传质系数

利用短的湿壁管并结合双膜模型研究了氯气与丙酮并流氯化反应过程的传质系数，考察了丙酮流量VL、氯气流量QG及湿壁管长／对该气液反传质的影响。表明该传质过程可视为受气膜控制，统计回归分析得气相传质系关联式，当Re≤200，有Nu =kGGDL/D＝29．34ReL^0.185Re^-0.1Pr0.5(l/DtL)^-0/735。当Re＞200，有Nu＝kGDtL/D=1.606ReL^0.08Re^0.524Pr0.5(l/DtL)^-0.735。     

System order and structure indices of linear systems in polynomial form

Linear time-invariant, finite-dimensional discrete time systems are very often specified in a polynomial form representation in either a forward or backward shift operator (sometimes called MFD and ARMA form). In this paper it is shown that there exists a unifying theory for the determination of McMillan degree and Kronecker observability indices of systems represented by polynomial matrices in the two shift operators, considering the MFD and ARMA forms as special cases. Treating dynamical systems in terms of their behaviour, i.e. the set of admissible signal trajectories, the notions of McMillan degree and observability indices can be generalized to non-controllable as well as to non-causal systems.     

Modeling and countermeasures of a social network-based botnet with strong destroy-resistance

To defeat botnets and ensure cyberspace security,a novel social network-based botnet with strong destroy-resistance (DR-SNbot),as well as its corresponding countermeasure,was proposed.DR-SNbot constructed command and control servers (C＆C-Servers) based on social network.Each C＆C-Server corresponded to a unique pseudo-random nickname.The botmaster issues commanded by hiding them in diaries using information hiding techniques,and then a novel C＆C channel was established.When different proportions of C＆C-Servers were invalid,DR-SNbot would send out different levels of alarms to inform attackers to construct new C＆C-Servers.Then,DR-SNbot could automatically repair C＆C communication to ensure its strong destroy-resistance.Under the experimental settings,DR-SNbot could resume the C＆C communication in a short period of time to keep 100% of the control rate even if all the current C＆C-Servers were invalid.Finally,a botnet nickname detecting method was proposed based on the difference of lexical features of legal nicknames and pseudo-random nicknames.Experimental results show that the proposed method can effectively (precision:96.88%,recall:93%) detect pseudo-random nicknames generated by social network-based botnets with customized algorithms.     

内消旋1,2-环丙烷二羧酸衍生物的合成

比较了3种合成内消旋3,3-二甲基-1,2-环丙烷二酰氯的方法,确定了最佳的酰氯化方法为SOCl2法;并研究了反应时间对环丙烷二羧酸与乙醇的酯化反应的影响,当反应时间为65h时,二羧酸的转化率为92.2%。其中内消旋3,3-二甲基-1,2-环丙烷二羧酸由蒈醛酸内酯经高锰酸钾氧化得到。     

二维水库浊流控制模型开发

提出预测水库水温和浊度的二维水质模型.利用日本下小鸟水库和下小鸟电站尾水渠道的实测数据确定模型参数,计算结果与实测数据吻合较好.应用控制模型对快速泄流、分层取水、栏栅以及栏栅和分层取水联合应用模式进行计算.结果表明,分层取水是减少浊流排放较为有效的方式.     

超细SiO2负载型两亲性铑膦络合物催化性能研究

针对均相催化反应后催化剂与产物分离困难和高碳烯烃在水-有机两相中反应速率较低的问题,采用水-有机两亲膦铑络合物负载到超细SiO2载体上催化1-己烯氢甲酰化反应,并与超细SiO2制备负载水相催化剂比较,超细SiO2负载型两亲铑膦络合物催化剂表现出较高的1-己烯氢甲酰化反应活性和选择性,且含水质量分数范围较宽,反应后产物与催化剂容易分离。两亲膦铑络合物超细SiO2负载液相催化剂可避免超细SiO2负载水相催化剂循环使用时水分被提取到有机相的缺点,同时获得较高的氢甲酰化反应活性和选择性。     

一种实用的花键压力角测量方法

利用数学的方法,对理论公式进行推导,得到计算压力角的公式,它比传统测量压力角的方法,快捷和准确。     

A highly reliable and budget-friendly Peltier-cooled camera for biological fluorescence imaging microscopy

The SAC8.5, a low-cost Peltier-cooled black and white 8-bit CCD camera for astronomy, was evaluated for its use in imaging microscopy. Two camera–microscope configurations were used: an epifluorescence microscope (Nikon Eclipse TE2000-U) and a bottom port laser scanning confocal microscope system (Zeiss LSCM 510 META). Main advantages of the CCD camera over the currently used photomultiplier detection in the scanning setup are fast image capturing, stable background, an improved signal-to-noise ratio and good linearity. Based on DAPI-labelled Chinese Hamster Ovarian cells, the signal-to-noise ratio was estimated to be 4 times higher with respect to the currently used confocal photomultiplier detector. A linear relationship between the fluorescence signal and the FITC-inulin concentrations ranging from 0.05 to 1.8 mg mL⁻¹ could be established. With the SAC8.5 CCD camera and using DAPI, calcein-AM and propidium iodide we could also distinguish between viable, apoptotic and necrotic cells: exposure to CdCl₂ caused necrosis in A6 cells. Additional examples include the observation of wire-like mitochondrial networks in Mito Tracker Green-loaded Madin–Darby canine kidney cells. Furthermore, it is straightforward to interface the SAC8.5 with automated shutters to prevent rapid fluorophore photobleaching via easy to use astrovideo software. In this study, we demonstrate that the SAC8.5 black and white CCD camera is an easy-to-implement and cost-conscious addition to quantitative fluorescence microfluorimetry on living tissues and is suitable for teaching laboratories.     

复杂薄壁镁合金筒体件砂型铸造工艺

根据复杂薄壁镁合金筒体铸件的特点和工艺要求,采用底注、封闭-开放式浇注系统,配合垂直缝隙式补缩系统和设置冒口工艺,成功地试制生产出该类复杂薄壁零件.同时,也确定了合理实用的镁合金砂型铸造工艺.