Rotating wheel filter design and optimization for a uniform depth dose distribution in heavy ion therapy

Treatment planning of heavy-ion radiotherapy involves predictive calculation of not only the physical dose but also the biological dose in a patient body. The goal in designing beam-modulating devices for heavy ion therapy is to achieve uniform biological effects across the spread-out Bragg peak (SOBP). To achieve this, a mathematical model of Bragg peak movement is presented. The parameters of this model have been resolved with Monte Carlo method. And a rotating wheel filter is designed basing on the velocity of the Bragg peak movement.

添加剂Li_8SiN_4对cBN晶体形貌的影响

在４．５～５．０ＧＰａ，１５００～１８００℃范围内，在Ｌｉ基复合氮硼化物的催化体系中添加Ｌｉ８ＳｉＮ４后，得到了具有光泽的棕色透明的ｃＢＮ单晶。研究了ｃＢＮ晶体的形貌，结果表明，添加Ｌｉ８ＳｉＮ４后得到的等积形ｃＢＮ晶体的百分比明显增多，除部分截角四面体外，多为截角八面体晶体，且棱角尖锐，晶面致密光滑

硅在cBN单晶合成中的行为

实验制备了复合氮化物Ｌｉ＿８ＳｉＮ＿４，并对合成温度、合成时间、气流量等因素的影响以及产物的稳定性进行了讨论。研究了Ｌｉ＿８ＳｉＮ＿４作为触媒添加剂时硅在ｃＢＮ单晶合成中的作用。结果表明：ｃＢＮ晶体多为截角八面体，晶面致密光滑；硅参与ｃＢＮ的合成反应，并以ＳｉＯ＿２的形式沉积在ｃＢＮ表面。

Crystallographic and electrochemical characteristics of melt-spun Ti–Zr–Ni–Y alloys

Ti45Zr30Ni25Yx (x = 1, 3, 5 and 7) alloys were prepared by melt-spinning at wheel velocity of 20 m s(-1). The effect of additive Y on phase structure and electrochemical performance of melt-spun alloys was investigated. Ti45Zr30Ni25Yx melt-spun alloys were composed of I-phase and amorphous phase. T

A {Co-32} Nanosphere Supported by p-tert-Butylthiacalix[4]arene

Calixarene-capped Co-32 clusters are constructed by a sodalite Co-24(II) cage and an encapsulated Co-8(III) cube. The spherical units are arranged into three isomeric structures, two of which are stacked by the bcc lattices and the third of which is assembled by the cubic closest packing of the spherical units.

Synthesis and characterization of the nanoporous ultrathin multilayer films based on molybdenum polyoxometalate (Mo-36)(n)

Ultrathin multilayer films of the wheel-shaped molybdenum polyoxometalate cluster (Mo-36)(n) and poly(allylamine hydrochloride) (PAH) have been prepared by the layer-by-layer (LbL) self-assembly method. The ((Mo-36)(n)/PAH)(m) multilayer films have been characterized by Xray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). UV-VIS measurements reveal regular film growth with each (Mo-36)(n) adsorption. The electrochemical behavior of the film at room temperature was investigated.

Lanthanide coordination polymers with dicarboxylate-like ligands: crystal structures of polymeric lanthanum(III) and terbium(III) complexes with flexible double betaines

Four novel polymeric lanthanide(III) complexes of two new double betaine derivatives have been synthesized and structurally determined. In [{La-2(L-1)(2)(H2O)(9)}(n)]Cl-6n. 2nH(2)O (1) and [{Tb(L-1)(H2O)(4)}(n)]Cl-3n. nH(2)O (2) (L-1 =4,4'-trimethylenedipyridinio-N,N'-diacetate), the lanthanide(III) ions form a two-dimensional layer in which each pair of lanthanide(III) ions is bridged by two syn-anti mu-carboxylato-O,O' groups. Adjacent layers are cross-linked through hydrogen bonds among aqua ligands, lattice water molecules and chloride ions, to form a three-dimensional network. Isomorphous [{Ln(L-1)(H2O)(4)}(n)]Cl-3n. 5nH(2)O (Ln=La, 3; Ln=Tb, 4; L-2=1,3 bis(pyridinio-4-carboxylato)-propane) each contain a centrosymmetric paddle-wheel-like dimeric unit in which each pair of adjacent metal atoms is bridged by four syn-syn mu-carboxylato-O,O' groups that are oriented nearly perpendicular to each other about the metal-metal axis. Neighboring dimeric subunits are bridged by a pair of flexible LL ligands into a polymeric chain. Adjacent chains are inter-linked by hydrogen bonds among aqua ligands, lattice water molecules and chloride ions into a three-dimensional network. (C) 1999 Elsevier Science Ltd. All rights reserved.

Li_8SiN_4-Li_3N-BN体系中立方BN转化行为的研究

研究了高温高压下x·Li_8SiN_4-0.1(1-x)·Li_3N-0.9(1-x)·BN体系中立方氮化硼(cBN)的转化行为。Li_8SiN_4的存在可显著改善cBN晶体的发育,提高晶体质量。在4.2～5.5GPa,1340～1750℃范围内确定了x=4.8％时体系的cBN转化区,并对转化区内cBN转化率、平均生长速度、成核速度及破碎强度与转化温度和压力的关系进行了研究。

高温高压下立方氮化硼晶体的生长机制

在４．５～５．０ＧＰａ，１５００～１８００℃范围内，对在Ｌｉ基复合氮化物或氮硼化物的催化体系中以及其中添加Ｌｉ８ＳｉＮ４后合成ｃＢＮ进行了研究，探讨了ｃＢＮ晶体的表面构造和生长机制，研究了由六方氨化硼向立方氮化硼转变过程中硅的存在行为．本实验中合成的立方氮化硼为具有光泽的棕色透明单晶．

立方氮化硼的振动光谱及反射光谱的研究

将黑色、黄色、棕色三种小于50μm立方氮化硼粉末为样品,研究了其红外光谱、拉曼光谱、反射光谱,结果表明: (1)样品的红外光谱中,1818cm~(-1)和1548cm~(-1)属于cBN的晶格本征振动,而立方氮化硼的晶格本征振动外的晶体缺陷吸收则发生在～800cm~(-3),1580cm~(-1)～1740cm~(-1)和大于2400cm~(-1)处。 (2)拉曼光谱测试表明,在1052cm~(-1)和1304cm~(-1)附近出现的散射与cBN不具有反演中心及cBN具有立方结构这样的事实相一致,并且这种散射伴随着布里渊区中心声子的横向和纵向发射。144cm~(-1)附近出现的散射,被认为是由于局部振荡模式的出现,在反斯托克斯区造成的信号,这与晶格中杂质缺陷有关。 (3)依据得到的反射光谱,计算了cBN单晶禁带宽度,发现这三种cBN都具有大于金刚石的禁带宽度值,分别为:E_s(黑)=6.21eV,E_s(黄)=5.73eV,E_s(棕)=5.71eV。

Amphi-Eomes/Tbr1: An amphioxus cognate of vertebrate Eomesodermin and T-Brain1 genes whose expression reveals evolutionarily distinct domain in amphioxus development

A cDNA for a novel T-box containing gene was isolated from the amphioxus Branchiostoma belcheri. A molecular phylogenetic tree constructed from the deduced amino acid sequence of the isolated cDNA indicates that this gene belongs to the T-Brain subfamily. In situ hybridization reveals that the expression is first detected in the invaginating archenteron at the early gastrula stage and this expression is down-regulated at the neurula stage. In early larvae, the expression appears again and transcripts are detected exclusively in the pre-oral pit (wheel organ-Hatschek's pit of the adult). In contrast to the vertebrate counterparts, no transcripts are detected in the brain vesicle or nerve cord throughout the development. These results are interpreted to mean that a role of T-Brain products in vertebrate forebrain development was acquired after the amphioxus was split from the lineage leading to the vertebrates. On the other hand, comparison of the tissue-specific expression domain of T-Brain genes and other genes between amphioxus and vertebrates revealed that the pre-oral pit of amphioxus has several molecular features which are comparable to those of the vertebrate olfactory and hypophyseal placode. (C) 2002 Wiley-Liss, Inc.

轮式仿人机器人的ZMP建模及动态稳定判据

介绍了ZMP的概念,比较常见的几种ZMP建模方法,提出将高效牛顿-欧拉算法(RENA)与ZMP的概念相结合的迭代ZMP建模方法,并利用该方法完成轮式仿人机器人的ZMP建模.通过模型分析,得出该轮式仿人机器人的ZMP简化计算公式.最后得出此类轮式仿人机器人的稳定性判据及稳定度的定义.

轮-腿复合移动机器人构型控制及越障策略

本文构型和越障控制研究的是如何控制机器人的姿态和如何控制机器人以一系列的构型翻越障碍物,构型及越障控制是轮-腿复合移动机器人技术领域的研究重点,针对轮-腿复合移动机器人的结构特点以及早期方法存在的不足,本文提出了在不平整地面上的构型控制方法和针对沟、坎典型地形环境的越障控制策略,并利用六轮-腿复合移动机器人试验平台开展了验证实验。

轮腿复合移动机器人自主越障姿态设定及轮腿运动协调算法实现

轮腿复合移动机器人具有很好的地面适应能力和越障能力。本文通过对机器人系统结构的分析和其越障高度的静态分析,计算出机器人能够越障的最大高度,并提出了针对典型地形环境(沟、坎、台)越障问题的机器人构型优化以及轮腿运动协调控制算法,而且通过实验验证了算法的有效性。