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基于有限元法与超胞法的结构声表面波缺陷态分析
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作者 谢素君 欧阳仕粮 +1 位作者 邓科 赵鹤平 《人工晶体学报》 EI CAS CSCD 北大核心 2017年第2期381-384,共4页
简要介绍了有限元法与超胞法相结合计算结构声表面波缺陷能带结构的方法,理论上分析了缺陷型表面声子晶体的声限制和声波导。表面声子晶体由刻有周期性凹槽的刚性板构成,通过改变晶体中某一格点或某一排格点的几何参数可以构建点缺陷和... 简要介绍了有限元法与超胞法相结合计算结构声表面波缺陷能带结构的方法,理论上分析了缺陷型表面声子晶体的声限制和声波导。表面声子晶体由刻有周期性凹槽的刚性板构成,通过改变晶体中某一格点或某一排格点的几何参数可以构建点缺陷和线缺陷。利用有限元法与超胞法能够十分方便地计算出表面声子晶体的点缺陷和线缺陷对应的缺陷带结构以及特定频率声波局域在点缺陷与线缺陷的本征压力场。通过分析缺陷能带结构与本征压力场,可以直观地了解缺陷型表面声子晶体中的声限制和声波导。 展开更多
关键词 声表面波 声限制 声波导 有限元 超胞法
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GaN/AlN半导体异质结带阶超原胞法计算
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作者 宋佳明 陈光德 +2 位作者 耶红刚 竹有章 伍叶龙 《光子学报》 EI CAS CSCD 北大核心 2009年第12期3097-3099,共3页
为了对GaN/AlN异质结电子结构有更为深入的认识,采用超原胞模型,对其进行了基于密度泛函理论的第一性原理计算.结果发现GaN/AlN为突变同型异质结,价带顶带阶为0.62eV,与实验值很接近.通过使用常用的平均键能法、平均势法和芯态法三种近... 为了对GaN/AlN异质结电子结构有更为深入的认识,采用超原胞模型,对其进行了基于密度泛函理论的第一性原理计算.结果发现GaN/AlN为突变同型异质结,价带顶带阶为0.62eV,与实验值很接近.通过使用常用的平均键能法、平均势法和芯态法三种近似方法对GaN/AlN带阶的计算,比较得出,超原胞法虽然计算量较大,但能够给出异质结界面附近更为详细的信息,这一点其他三种近似方法无法得到,但他们也能够得出与实验值基本一致的带阶参量. 展开更多
关键词 第一性原理 GaN/AlN 异质结带阶
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LMTO-ASA超原胞法计算空位有序的稳定性
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作者 沈耀文 李俊达 黄美纯 《厦门大学学报(自然科学版)》 CAS CSCD 北大核心 1994年第2期163-167,共5页
用LDF-LMTO-ASA超原胞法,以Nb(C_(1-x)□_x)为例直接计算Nb_4C_4□_0、Nb_4C_3□_1、Nb_4C_2□_2、Nb_4C_1□3和Nb_4C_□_4五种“样本”在不同晶格常数下的总能... 用LDF-LMTO-ASA超原胞法,以Nb(C_(1-x)□_x)为例直接计算Nb_4C_4□_0、Nb_4C_3□_1、Nb_4C_2□_2、Nb_4C_1□3和Nb_4C_□_4五种“样本”在不同晶格常数下的总能的变化,结合统计分布直接计算碳空位在非金属元素的f,c,c子晶格上分布有序的稳定性,计算结果表明NaCl型Nb(C_(1-x)□_x)的有序相和无序相仅在0<x<0.5组分范围内存在,其中有序相更稳定。x>0.5时不存在上述结构的有序或无序相。这与实验结果一致。 展开更多
关键词 过剩能 空位 稳定性
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基于COMSOL Multiphysics的光子晶体线缺陷波导设计
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作者 曹江勇 谢素君 +2 位作者 尹洁威 欧阳仕粮 孙晶 《科技创新与应用》 2017年第1期21-22,共2页
文章利用COMSOL Multiphysics有限元物理仿真软件构建二维光子晶体,并计算其光子能带,简要介绍了超胞法计算线缺陷带结构,以及计算了线缺陷光子晶体的透射率和线缺线光波导传输效果。
关键词 有限元软模拟 超胞法 光子晶体 线缺陷 光波导
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Au1-xPtxSn2(x=0,0.125,0.25,0.50,0.75,0.875,1)体系相结构稳定性、电子结构与弹性性质的第一性原理研究 被引量:2
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作者 胡洁琼 谢明 +3 位作者 陈永泰 陈松 李爱坤 王塞北 《功能材料》 EI CAS CSCD 北大核心 2018年第5期5208-5215,共8页
通过基于密度泛函理论的第一性原理计算方法,研究了Au_(1-x)Pt_xSn_2(x=0,0.125,0.25,0.50,0.75,0.875,1)体系各合金相的结构、形成能、电子结构和弹性性质。首先分别采用虚拟晶体近似法(VCA)和超胞法(SC)搭建晶体结构模型,再由形成能... 通过基于密度泛函理论的第一性原理计算方法,研究了Au_(1-x)Pt_xSn_2(x=0,0.125,0.25,0.50,0.75,0.875,1)体系各合金相的结构、形成能、电子结构和弹性性质。首先分别采用虚拟晶体近似法(VCA)和超胞法(SC)搭建晶体结构模型,再由形成能的计算结果判断出稳定的结构模型,然后对其能带结构、总态密度、分态密度、键合特征和弹性性质等进行研究。结果表明,SC法搭建的晶体结构模型较稳定,且随着Pt元素摩尔含量的增大,Au_(1-x)Pt_xSn_2合金相的形成能随之减小,说明该体系更倾向于形成C1型结构。同时发现Au_(0.125)Pt_(0.875)Sn_2稳定性较好。而Au_(0.5)Pt_(0.5)Sn_2成键强度较其他合金相强,这与该合金中同时存在两种类型的d-p杂化有关。对Au_(1-x)Pt_xSn_2体系弹性性质的研究表明,Au_(0.75)Pt_(0.25)Sn_2和Au_(0.5)Pt_(0.5)Sn_2为脆性相,而AuSn_2、Au_(0.875)Pt_(0.125)Sn_2、Au_(0.25)Pt_(0.75)Sn_2、Au_(0.125)Pt_(0.875)Sn_2和PtSn_2为延性相,其中Au_(0.5)Pt_(0.5)Sn_2合金相的原子间结合力较强,材料强度较大。 展开更多
关键词 第一性原理 虚拟晶体近似 超胞法 电子结构 弹性性质
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准一维声子晶体中兰姆波低频禁带特性研究
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作者 丁红星 戴丽莉 +2 位作者 沈中华 陆建 倪晓武 《南京理工大学学报》 EI CAS CSCD 北大核心 2013年第6期869-874,共6页
为了优化一维声子晶体薄板中的兰姆波禁带结构,在薄板侧面基体组元中嵌入空气圆孔,构建了准一维声子晶体系统。运用超原胞平面波展开法和有限元法计算了空气圆孔半径对禁带结构的影响,分析了空气圆孔对特征模式位移场的扰动效应,研究了... 为了优化一维声子晶体薄板中的兰姆波禁带结构,在薄板侧面基体组元中嵌入空气圆孔,构建了准一维声子晶体系统。运用超原胞平面波展开法和有限元法计算了空气圆孔半径对禁带结构的影响,分析了空气圆孔对特征模式位移场的扰动效应,研究了空气柱散射体对该声子晶体兰姆波带隙结构的优化作用。结果表明:随着空气圆孔半径的增加,同模式兰姆波间的耦合作用显著增强,完全禁带数量和宽度因此明显增加,其在0~4 MHz低频范围内的占有比例可以提高至70%左右。 展开更多
关键词 兰姆波 声子晶体 低频 禁带 平面波展开 有限元
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二维复式晶格磁振子晶体的带隙结构 被引量:5
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作者 刘艳玲 刘文静 +1 位作者 包佳美 曹永军 《物理学报》 SCIE EI CAS CSCD 北大核心 2016年第15期218-224,共7页
提出了一种复式晶格磁振子晶体的模型,该模型由两种铁磁材料散射体周期排列在另一种铁磁材料基底中构成.应用超原胞的思想拓展了平面波展开法,用于数值计算研究自旋波在复式晶格磁振子晶体中的本征性质本文数值计算了由两种大小不同的铁... 提出了一种复式晶格磁振子晶体的模型,该模型由两种铁磁材料散射体周期排列在另一种铁磁材料基底中构成.应用超原胞的思想拓展了平面波展开法,用于数值计算研究自旋波在复式晶格磁振子晶体中的本征性质本文数值计算了由两种大小不同的铁(Fe)-铁(Fe)圆柱体交替正方排列在氧化铕(EuO)基底材料中构成的二维复式晶格磁振子晶体的带结构,研究了带隙宽度随体积填充率的变化行为,并与同一铁(Fe)圆柱正方排列在氧化铕(EuO)基底材料中构成的简单晶格磁振子晶体的带隙结构随体积填充率的变化行为进行了比较.结果表明,利用复式晶格可以优化或调节自旋波带隙的宽度和频率位置. 展开更多
关键词 磁振子晶体 复式晶格 带隙 平面波展开
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Current role of ultrasound for the management of hepatocellular carcinoma 被引量:24
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作者 Hitoshi Maruyama Masaharu Yoshikawa Osamu Yokosuka 《World Journal of Gastroenterology》 SCIE CAS CSCD 2008年第11期1710-1719,共10页
Hepatocellular carcinoma (HCC) has a decisive influence on the prognosis of cirrhotic patients. Although α-fetoprotein (AFP) is a known and specific tumor maker for HCC, it is not suitable for the screening and s... Hepatocellular carcinoma (HCC) has a decisive influence on the prognosis of cirrhotic patients. Although α-fetoprotein (AFP) is a known and specific tumor maker for HCC, it is not suitable for the screening and surveillance of HCC because of its poor predictive value and low sensitivity. The use of imaging modalities is essential for the screening, diagnosis and treatment of HCC. Ultrasound (US) plays a major role among them, because it provides real-time and non-invasive observation by a simple and easy technique. In addition, US-guided needle puncture methods are frequently required for the diagnosis and/or treatment process of HCC. The development of digital technology has led to the detection of blood flow by color Doppler US, and the sensitivity for detecting tumor vascularity has shown remarkable improvement with the introduction of microbubble contrast agents. Moreover, near realtime 3-dimensional US images are now available. As for the treatment of HCC, high intensity focused ultrasound (HIFU) was developed as a novel technology that provides transcutaneous ablation effect without needle puncture. These advancements in the US field have led to rapid progress in HCC management, and continuing advances are expected. This article reviews the current application of US for HCC in clinical practice. 展开更多
关键词 ULTRASOUND Contrast agent Hepatocellular carcinoma LIVER SURVEILLANCE TREATMENTS
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Overexpression of Slug is associated with malignant progression of esophageal adenocarcinoma 被引量:24
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作者 Paras Jethwa Mushal Naqvi +4 位作者 Robert G Hardy Neil A Hotchin Sally Roberts Robert Spychal Chris Tselepis 《World Journal of Gastroenterology》 SCIE CAS CSCD 2008年第7期1044-1052,共9页
AIM: To characterise expression of known E-cadherin repressors; Snail, Slug and Twist in the development of esophageal adenocarcinoma. METHODS: E-cadherin, Slug, Snail and Twist mRNA expression in Barrett's metapl... AIM: To characterise expression of known E-cadherin repressors; Snail, Slug and Twist in the development of esophageal adenocarcinoma. METHODS: E-cadherin, Slug, Snail and Twist mRNA expression in Barrett's metaplasia and esophageal adenocarcinoma specimens was examined by real-time reverse transcription-polymerase chain reaction (RT-PCR). Semi-quantitative immunohistochemistry was used to examine cellular localisation and protein levels. The effect of Slug on epithelial mesenchymal transition (EMT) markers was examined by transfection of Slug into an adenocarcinoma line OE33.RESULTS: Cellular localisation of Slug in Barrett's metaplasia was largely cytoplasmic whilst in adenocarcinoma it was nuclear. Semi-quantitative analysis indicated that Slug was more abundant in adenocarcinoma compared to matched Barrett's metaplastic specimens. Snail and Twist were expressed in adenocarcinoma but were cytoplasmic in location and not induced compared to Barrett's mucosa. These observations were supported by mRNA studies where only Slug mRNA was shown to be over-expressed in adenocarcinoma and inversely correlated to E-cadherin expression. Overexpression of Slug in OE33 mediated E-cadherin repression and induced the mesenchymal markers vimentin and fibronectin.CONCLUSION: Progression to adenocarcinoma is associated with increased Slug expression and this may represent a mechanism of E-cadherin silencing. 展开更多
关键词 SLUG OESOPHAGUS CANCER Barrett's metaplasia Epithelial-mesenchymal transition
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Comparative study of helical CT with contrast-enhanced ultrasound of renal carcinoma 被引量:1
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作者 Yan Guo Guangsheng Wan +3 位作者 Yaqing Chen Mingjuan Liu Qian Peng Zhaomin Huang 《The Chinese-German Journal of Clinical Oncology》 CAS 2008年第2期93-97,共5页
Objective: To investigate the efficiency of helical CT comparing with contrast-enhanced ultrasound, and to im- prove the diagnosis efficiency of renal cell carcinoma (RCC). Methods: Thirty RCCs confirmed pathologicall... Objective: To investigate the efficiency of helical CT comparing with contrast-enhanced ultrasound, and to im- prove the diagnosis efficiency of renal cell carcinoma (RCC). Methods: Thirty RCCs confirmed pathologically were studied retrospectively. The un-enhanced CT scan and the triphasic enhanced helical CT scan were performed in all cases, the gray-scale US and angiosonography with SonoVue were performed in all cases meantime. Results: 22 cases (73.3%) were diagnosed correctly by helical CT alone before operation. 7 cases (23.3%) were suspected as RCC with helical CT. One case (3.3%) was misdiagnosed with helical CT. 25 cases (83.3%) were diagnosed correctly with contrast-enhanced ultrasound alone pre-operation. One case (3.3%) was suspected as RCC with angiosonography. Four cases (13.3%) were misdiagnosed with angiosonography alone. 29 cases (96.7%) were diagnosed correctly by helical CT combining with angiosonography before operation, one case (3.3%) was diagnosed as renal mass with both helical CT and angiosonography. Conclusion: Contrast-enhanced ultrasound is sensitive in detecting blood flow, it can detect the enhancement of the tumor which cannot be detected by helical CT. CT and angiosonography have strong complement each other in the diagnosis of RCC. 展开更多
关键词 carcinoma renal cell tomography x-ray computed contrast-enhanced ultrasound
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Diagnostic laparoscopy and laparoscopic ultrasonography withlocal anesthesia in hepatocellular carcinoma 被引量:2
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作者 Mariano Gómez-Rubio Mercedes Moya-Valdés Jesús García 《World Journal of Gastroenterology》 SCIE CAS CSCD 2005年第26期4120-4123,共4页
Diagnosis of hepatocellular carcinoma (HCC), a common digestive malignancy, remains a challenge. The aim of this study was to evaluate the feasibility of performing laparoscopy and laparoscopic ultrasound with local a... Diagnosis of hepatocellular carcinoma (HCC), a common digestive malignancy, remains a challenge. The aim of this study was to evaluate the feasibility of performing laparoscopy and laparoscopic ultrasound with local anesthesia as a diagnostic procedure in HCC. Laparoscopy and laparoscopic ultrasound with local anesthesia was performed in the gastrointestinal endoscopy unit in three patients diagnosed of HCC. Endoscopy staged diffuse liver disease. Laparoscopic ultrasonography identified all liver tumors not visible during endoscopy and guided needle biopsy in one case. No complications happened. In conclusion, laparoscopy and laparoscopic ultrasound,performed as a minimally invasive diagnostic procedure can be a safe and very promising tool in planning therapy of HCC. 展开更多
关键词 LAPAROSCOPY Laparoscopic ultrasonography Hepatocellular carcinoma
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