Impact of retention on trans‐column velocity biases in packed columns

The heights equivalent to a theoretical plate of a weakly and strongly retained compounds were measured on two packed columns having different average mesopore sizes. The measurements were carried out in two different cases, with access to the mesopores by the sample molecules blocked (filled with n‐nonane) or not. The experimental results demonstrate that the eddy dispersion terms of both columns are significantly smaller for porous than for nonporous particles. Two simultaneous phenomena explain this observation. First, packed columns are radially heterogeneous which causes significant trans‐column velocity biases warping the bands. Second, radial dispersion contributes to mass transfer across the column, relaxing the radial concentration gradients that are caused by these velocity biases. The impact of these biases is minimized when the pores of the particles are not blocked; it decreases with increasing residence time and radial dispersion coefficient of the solutes. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

正弦扫描试验中分段扫描方法探讨

从试验的角度出发,对正弦扫描振动试验的有关技术做了初步的探讨。以一个实际的例子为例,介绍了正弦扫描振动试验中的重要参数并给出了计算方法。对一次扫描和分段扫描的方法进行了对比,并说明了在何种情况下两者是否等效的问题,而且给出了明确的结论。     

A molecular-structure hypothesis

The self-similar symmetry that occurs between atomic nuclei, biological growth structures, the solar system, globular clusters and spiral galaxies suggests that a similar pattern should characterize atomic and molecular structures. This possibility is explored in terms of the current molecular structure-hypothesis and its extension into four-dimensional space-time. It is concluded that a quantum molecule only has structure in four dimensions and that classical (Newtonian) structure, which occurs in three dimensions, cannot be simulated by quantum-chemical computation.     

基于LM/SVM方法的二次反应清洁汽油辛烷值预测

提出了一种莱文伯格—马夸特(LM)算法和支持向量机(SVM)有机结合的LM/SVM新算法,并将其应用于基于集总模型的二次反应清洁汽油研究法辛烷值的预测。借鉴复杂反应动力学研究中的集总方法,将汽油研究法辛烷值看成汽油饱和烃集总、烯烃集总、芳烃集总的函数,并采用支持向量机表达该函数。针对支持向量机参数及核函数参数难以选择的问题,通过莱文伯格-马夸特算法搜索支持向量机中的参数,并采取把训练集分割成工作样本和检验样本的策略,从而解决了过拟合的问题。利用经典测试函数对LM/SVM算法的性能测试结果表明:LM/SVM算法不但精度优于文献报道的遗传算法与支持向量机相结合的GA/SVM方法,而且其效率也远高于GA/SVM方法。LM/SVM方法对二次反应清洁汽油研究法辛烷值预测的相对误差绝对值的平均值为0.71%。     

双卧轴搅拌机返回叶片数的试验研究

利用正交试验,对双卧轴搅拌机返回叶片数进行试验研究。极差分析结果表明:在相同的搅拌时间和搅拌臂围流布置的前提下,搅拌线速度是影响混凝土搅拌质量的首要参数;返回叶片数对搅拌质量有一定影响,在满足搅拌线速度为1.2m/s,返回叶片数为2个,双轴交错布置,双轴正正排列的条件时,混凝土搅拌质量较好。     

我国号码携带业务访问数据库技术方案的研究

主要对我国在试验期间网间移动号码携带访问数据库的技术方案进行了研究和分析,包括不同业务如何确定访问数据库的运营商网络,以及运营商网内访问数据库的方式。但任何一种方案都不是完美的,不可能同时满足所有运营商的要求。目前只能站在整个行业的角度,暂时确定了一个试验阶段的技术方案。将来再根据实际情况,考虑未来开展号码携带时的技术方案。     

脉冲激光沉积制备TiN/AlN多层薄膜及其工艺研究

本文采用脉冲激光沉积（PLD）法,在单晶硅试样表面上沉积制备了TiN/AlN多层硬质薄膜;研究了激光能量、靶衬距离和基体温度等工艺参数对薄膜性能的影响。采用X射线衍射（XRD）、扫描电子显微镜（SEM）和显微硬度仪方法研究了薄膜的性能。结果表明：薄膜由TiN和立方AlN细晶和无定型的非晶TiN、AlN组成,薄膜的调制周期尺寸均在λ=（50-200）nm范围内,多层结构界面清晰;当多层薄膜调制周期在100nm以下时,薄膜的显微硬度明显高于TiN和AlN的混合硬度值。     

Fully redundant decimal addition and subtraction using stored-unibit encoding

Decimal computer arithmetic is experiencing a revived popularity, and there is quest for high-performance decimal hardware units. Successful experiences on binary computer arithmetic may find grounds in decimal arithmetic. For example, the traditional fully redundant (i.e., the result and both of the operands are represented in a redundant format) and semi-redundant (i.e., the result and only one of the operands are redundant) binary addition schemes have influenced the design and implementation of similar decimal arithmetic units. However, special comparison and correction steps are required when decimal arithmetic algorithms are implemented on binary hardware. To circumvent these difficulties, alternative encodings of decimal digits and a variety of decimal arithmetic algorithms have been examined by many researchers over decades. In this paper we offer a new redundant decimal digit set [−8, 9] and a fully redundant addition/subtraction scheme. The proposed digit set, faithfully encoded as a mix of posibits, negabits, and unibits, is shown to obviate the need for any compare-to-9 operations and leads to minimal penalty subtraction using the addition circuitry. Moreover, conversion from the standard BCD encoding to the proposed stored-unibit encoding is possible with the latency of one logic level. However, the reverse conversion, like any other redundant to nonredundant conversion, involves carry propagation.     

紫外-可见光双通道拉曼光谱仪光学设计

紫外拉曼光谱技术具有高强度拉曼散射、无荧光干扰的特点;可见光拉曼光谱技术可实现低波数、高分辨率探测。为兼具两种激发波长的优势,设计了一款对称分布的双Czerny-Turner光路聚焦于一个探测器的双通道拉曼光谱仪。通过元器件的选型和初始结构的计算,在不增加多余元器件的情况下,对弧矢方向像散进行补偿,避免了像面上的能量损失。配合Zemax软件对双通道光谱分别进行建模优化,最终实现了对400~5000 cm^-1（266 nm激发）和50~3500 cm^-1（633 nm激发）两段光谱的同时探测。均方根半径、点列图和调制传递函数等评价指标有效验证了设计的合理性和可行性。结果表明,两套拉曼光谱仪分别可达8 cm^-1和5 cm^-1分辨率,本设计具有高分辨率、低波数、多波长激发、集成化等优势。     

Bent函数的一种迭代构造

对于不小于4的偶数n,建立了由4个n-元Bent函数构造(n+2)-元Bent函数的一个充要条件.提出了由n-元Bent函数构造(n+2)-元Bent函数的一种迭代构造方法,也对所构造的Bent函数的代数次数进行了分析.这种迭代方法统一并推广了以前的两种Bent函数的构造.