Fully 3D refraction correction dosimetry system

The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched medium is 71.8%, an increase of 6.4% compared to that achieved using conventional ART algorithm. Smaller diameter dosimeters are scanned with dry air scanning by using a wide-angle lens that collects refracted light. The images reconstructed using cone beam geometry is seen to deteriorate in some planes as those regions are not scanned. Refraction correction is important and needs to be taken in to consideration to achieve quantitatively accurate dose reconstructions. Refraction modeling is crucial in array based scanners as it is not possible to identify refracted rays in the sinogram space.

Tunability of 1/f Noise at Multiple Dirac Cones in hBN Encapsulated Graphene Devices

The emergence of multiple Dirac cones in hexagonal boron nitride (hBN)-graphene heterostructures is particularly attractive because it offers potentially better landscape for higher and versatile transport properties than the primary Dirac cone. However, the transport coefficients of the cloned Dirac cones is yet not fully characterized and many open questions, including the evolution of charge dynamics and impurity scattering responsible for them, have remained unexplored. Noise measurements, having the potential to address these questions, have not been performed to date in dual-gated hBN graphene hBN devices. Here, we present the low frequency 1/f noise measurements at multiple Dirac cones in hBN encapsulated single and bilayer graphene in dual-gated geometry. Our results reveal that the low-frequency noise in graphene can be tuned by more than two-orders of magnitude by changing carrier concentration as well as by modifying the band structure in bilayer graphene. We find that the noise is surprisingly suppressed at the cloned Dirac cone compared to the primary Dirac cone in single layer graphene device, while it is strongly enhanced for the bilayer graphene with band gap opening. The results are explained with the calculation of dielectric function using tight-binding model. Our results also indicate that the 1/f noise indeed follows the Hooge's empirical formula in hBN-protected devices in dual-gated geometry. We also present for the first time the noise data in bipolar regime of a graphene device.

A Numerical Study of Indentation Using Indenters of Different Geometry

Finite element simulation of the Berkovich, Vickers, Knoop, and cone indenters was carried out for the indentation of elastic-plastic material. To fix the semiapex angle of the cone, several rules of equivalence were used and examined. Despite the asymmetry and differences in the stress and strain fields, it was established that for the Berkovich and Vickers indenters, the load-displacement relation can closely be simulated by a single cone indenter having a semiapex angle equal to 70.3degrees in accordance with the rule of the volume equivalence. On the other hand, none of the rules is applicable to the Knoop indenter owing to its great asymmetry. The finite element method developed here is also applicable to layered or gradient materials with slight modifications.

Lattice Boltzmann method for compressible flows with high Mach numbers

In this paper we present a lattice Boltzmann model to simulate compressible flows by introducing an attractive force. This scheme has two main advantages: one is to soften sound speed effectively, which greatly raises the Mach number (up to 5); another is its relative simple procedure. Simulations of the March cone and the comparison between theoretical expectations and simulations demonstrate that the scheme is effective in the simulation of compressible flows with high Mach numbers, which would create many new applications.

锥形流乘波体优化设计研究

随着马赫数的升高,波阻和摩阻增加,形成升阻比“屏障”,而乘波构型飞行器是克服这一屏障的有效途径.本文在Ma∞=4.0～20.0、高度H=24.0～52.0 km、圆锥角Ac=5°～10°的条件下,以升阻比为目标函数,进行了乘波体的优化设计,讨论了对乘波体优化外形的影响因素,并给出全马赫数范围的优化乘波体外形及其气动力结果.

3D simulation of the micro indentation process and relative problems research

In this paper the finite element method was used to simulate micro-scale indentation process. The several standard indenters were simulated with 3D finite element model. The emphasis of this paper was the differences between 2D axisymmetric cone model and

飞行高度及设计长度对锥形流乘波体优化的影响

高超声速条件下,乘波体布局具有高升阻比特性,本文应用单纯形加速法,以最大升阻比为目标,开展了锥形流乘波体布局优化设计研究.特别是,研究了在高层大气飞行时雷诺数效应与气动特性的关系,从乘波体飞行高度与设计长度两方面探讨雷诺数对乘波体优化的影响,结果表明:给定设计马赫数和圆锥角情况下,对于最大升阻比优化乘波体,其雷诺数越小,摩擦阻力越大,而升阻比越低.

A constitutive model for transversely isotropic foams, and its application to the indentation of balsa wood

An elastic-plastic constitutive model for transversely isotropic compressible solids (foams) has been developed. A quadratic yield surface with four parameters and one hardening function is proposed. Associated plastic flow is assumed and the yield surface evolves in a self-similar manner calibrated by the uniaxial compressive (or tensile) response of the cellular solid in the axial direction. All material constants in the model (elastic and plastic) can be determined from a combination of a total of four uniaxial and shear tests. The model is used to predict the indentation response of balsa wood to a conical indenter. For the three cone angles considered in this study, very good agreement is found between the experimental measurements and the finite element (FE) predictions of the transversely isotropic cellular solid model. On the other hand, an isotropic foam model is shown to be inadequate to capture the indentation response. © 2005 Elsevier Ltd. All rights reserved.

Los dilemas de la acción colectiva global. Un estudio de caso : el movimiento sindical en el MERCOSUR (1991-2012)

Resumen: Este trabajo analiza la acción colectiva sindical postnacional en el MERCOSUR en un período histórico signado por profundas mutaciones políticas, económicas, y productivas sociales (1991-2012) a partir de los relatos y representaciones de sus protagonistas. El trabajo cualitativo intentará explicar la configuración del sindicalismo internacional en la globalización, y describir las estrategias del movimiento obrero mercosureño. La metodología cualitativa ilustra un trabajo de campo a partir de entrevistas en profundidad a 34 sindicalistas del Mercosur, y entrevistas adicionales a tres representantes de la Confederación Sindical de las Américas, dos empresarios del Mercosur, un especialista académico en la dimensión sociolaboral de la integración regional y un representante de la OIT en la región. La metodología de análisis e interpretación de dichas entrevistas ha sido la teoría fundamentada, entendida como la técnica más idónea de aprehender los procesos sociales a través de las voces de los líderes obreros, comprender su realidad, sus representaciones y sistema de valores, sus ideas y su acción colectiva. La literatura de los movimientos sociales en la globalización capitalista ha puesto el énfasis en la emergencia de nuevos colectivos cuyos reclamos se concentran en el reconocimiento (Fraser y Honneth, 2006) de sus identidades que el modelo fordista de producción pareció invisibilizar y soslayar ante la primacía de las prácticas económicas y demandas distributivas. Esta tesis conjuga una perspectiva dualista y demuestra que las estrategias de reconocimiento y las reivindicaciones de redistribución de tipo clasista se resignificaron en el escenario postnacional a través de la Coordinadora de Centrales Sindicales del Cono Sur –CCSCS- (subregional) y, con un desarrollo menor: los Sindicatos Globales (FSI, GUFs) en la acción sectorial [1991-2012]. Para arribar al núcleo configurativo de sus representaciones y su sistema de valores, la investigación transitó por los sentidos y significados del trabajo, las mutaciones productivas y de las condiciones del trabajo, las teorías del fin del trabajo, la precarización y la representación de los trabajadores más frágiles: mujeres, jóvenes y migrantes. En un segundo orden se interpeló sobre la gobernanza mundial, los organismos internacionales, el régimen normativo internacional, la civilización capitalista, para luego abordar el estudio específico del Mercosur y la acción obrera en dicho proceso. El núcleo determinó que para los representantes obreros la acción colectiva sindical debe ser postnacional y su objetivo es limitar la globalización capitalista neoliberal. La CCSCS conformó desde sus inicios un movimiento capaz de elevarse al rango supranacional para representar la voz de los trabajadores del MERCOSUR. La pluralidad configuró su mayor virtud durante sus primeros 20 años, reconociendo una experiencia de aprendizaje de tolerancia y respeto, que ellos definen como la unidad en la diversidad. Esta entidad constituye un patrimonio único como paradigma del sindicalismo postnacional. Los sindicatos del Cono Sur adoptaron diversas modalidades de acción colectiva: a) reactiva (con repertorios de insubordinación, de lucha y resistencia al modelo neoliberal), b) proactiva (con repertorios de incidencia normativa en el MERCOSUR) y c) participativa (con repertorios de producción propositiva de incidencia en la dimensión social del MERCOSUR). Su acción colectiva reactiva, normativa y propositiva fue eficaz a mediano plazo para participar e incidir en el MERCOSUR, crear una dimensión social del bloque y dotar de derechos normativos a los ciudadanos de la región. Su acción tuvo un sentido político de gran poder instituyente, con capacidad movilización y alta exposición pública. Sin embargo, en la segunda década su lógica de construcción quedó subordinada a los procesos nacionales y a los partidos gobernantes, dejó de ser performativa y de creación política, dirimiéndose en la esfera social junto a otros movimientos sociales emergentes, y provocó un ciclo de desmovilización. Simultáneamente, emergió con fuerza otra modalidad de sindicalismo postnacional con la fusión y refundación de los Sindicatos Globales. Su acción sectorial contribuye a restaurar las demandas de distribución que habían quedado soslayadas, pero esta tesis manifiesta que los protagonistas afirman que sus marcos de acción colectiva deberán ser conjuntos para ser exitosa. El sindicalismo postnacional en el MERCOSUR se define a sí mismos como agente de desarrollo, protagonista del modelo socioproductivo, pero también como vehículo partícipe de la democracia y de una matriz sustentable de desarrollo

Computer generated hologram with geometric occlusion using GPU-accelerated depth buffer rasterization for three-dimensional display

We present a method of rapidly producing computer-generated holograms that exhibit geometric occlusion in the reconstructed image. Conceptually, a bundle of rays is shot from every hologram sample into the object volume.We use z buffering to find the nearest intersecting object point for every ray and add its complex field contribution to the corresponding hologram sample. Each hologram sample belongs to an independent operation, allowing us to exploit the parallel computing capability of modern programmable graphics processing units (GPUs). Unlike algorithms that use points or planar segments as the basis for constructing the hologram, our algorithm's complexity is dependent on fixed system parameters, such as the number of ray-casting operations, and can therefore handle complicated models more efficiently. The finite number of hologram pixels is, in effect, a windowing function, and from analyzing the Wigner distribution function of windowed free-space transfer function we find an upper limit on the cone angle of the ray bundle. Experimentally, we found that an angular sampling distance of 0:01' for a 2:66' cone angle produces acceptable reconstruction quality. © 2009 Optical Society of America.

高超声速钝锥流场红外辐射实验研究

报道了在JF-10氢氧爆轰驱动高焓激波风洞中开展的再入流场红外辐射实验研究，风洞的试验状态为：驻室总压19．6MPa，总焓15．5MJ／kg，自由流速度约5km／s，实验以锑化铟多元红外成像系统为测量手段，以球头钝锥体为试验模型，测量激波层与近尾流中红外辐射功率的横向分布剖面，试验数据呈现明显的规律性，试验结果表明，激波层内壁面附近的红外辐射功率较小，中间有一区域辐射较大且相对均匀，激波层外缘辐射单调减小；尾流中红外辐射功率在轴线附近的核心区最大，随着离轴线距离的增大而单调减小。

静力触探锥头阻力的近似理论与实验研究进展

锥头阻力在静力触探试验中扮演着十分重要的角色．从不同角度，对触探中锥头阻力的研究进行简要阐述，对承载力理论、空洞膨胀理论、应变路径法及运动点位错法等几种理论分析方法进行了回顾．另外，对数值分析和实验研究的进展情况进行了叙述．并对各种方法的适用性进行了比较．承载力理论虽然简单，但忽略了土的压缩性和探杆周围初始应力的增加，所以不能精确地模拟锥头的深层贯入．空洞膨胀理论提供了一个分析锥头阻力的简单而较精确的方法，它考虑了土的压缩性(或膨胀性)和锥头贯入过程中锥杆周围应力增加的影响．但这种方法是将锥头贯入与空洞膨胀之间做了一个等效模拟，所以不同的模拟方法，得到的结果差别较大．应变路径法能够有效解决饱和粘土中的不排水贯入，但不适用于砂土．运动点位错法因为考虑了部分排水，所以能较好地预测固结系数，但采用了线弹性分析，故位错法在其他方面的应用还需要大量的试验验证．有限元法在处理锥头贯入这类慢侵彻问题时缺乏一种很好的处理技术，导致它在进行破坏荷载计算时有显著的误差和数值计算困难．标定槽试验将在验证和建立锥头阻力与土的性能关系方面继续起到一个重要作用，但其结果需经过校正后才可应用到现场．最后对该领域的研究趋势进行了讨论．

锥形轴对称微管道内流动特性实验研究

介绍了生物转基因显微注射的应用和存在的问题.针对显微注射所用的锥形轴对称微管道,进行了流动过程理论分析,并在微流动实验平台上对这种管道内流动进行了流量与压力特性参数的连续观测实验,详尽介绍了实验装置和实验过程,并给出了尖端直径为4～15μm的锥形管道流动实验结果.

Artemio Zeno y la conformación de un nuevo espacio del conocimiento quirúrgico en Latinoamérica : la dinámica local en la formación de innovadores: Rosario 1910-1940

Resumen: Este artículo se inscribe en investigaciones realizadas para Conicet sobre la incidencia del surgimiento de las facultades rosarinas de la Universidad Nacional del Litoral en la conformación de un sistema regional de innovación científica, y su relación con la dinámica local y la expansión de las redes profesionales. Centra su enfoque en uno de los articuladores del mencionado proceso, el doctor Artemio Zeno, quién fuera fundador de una nueva escuela en la práctica quirúrgica, catedrático titular de la Facultad de Ciencias Médicas de Rosario, empresario de la salud, promotor de publicaciones científicas y de vinculaciones con los principales institutos de investigación internacional, al punto de publicar y dirigir la Revista de Cirugía, del Sanatorio Británico, y crear la primera Fundación médica de Latinoamérica dedicada exclusivamente a becar investigadores de los países del cono sur que quisieran especializarse en la especialidad quirúrgica.

Two-Dimensional Kinetics Of Beta(2)-Integrin And Icam-1 Bindings Between Neutrophils And Melanoma Cells In A Shear Flow

Cell adhesion, mediated by specific receptor-ligand interactions, plays an important role in biological processes such as tumor metastasis and inflammatory cascade. For example, interactions between beta(2)-integrin ( lymphocyte function-associated antigen-1 and/or Mac-1) on polymorphonuclear neutrophils (PMNs) and ICAM-1 on melanoma cells initiate the bindings of melanoma cells to PMNs within the tumor microenvironment in blood flow, which in turn activate PMN-melanoma cell aggregation in a near-wall region of the vascular endothelium, therefore enhancing subsequent extravasation of melanoma cells in the microcirculations. Kinetics of integrin-ligand bindings in a shear flow is the determinant of such a process, which has not been well understood. In the present study, interactions of PMNs with WM9 melanoma cells were investigated to quantify the kinetics of beta(2)-integrin and ICAM-1 bindings using a cone-plate viscometer that generates a linear shear flow combined with a two-color flow cytometry technique. Aggregation fractions exhibited a transition phase where it first increased before 60 s and then decreased with shear durations. Melanoma-PMN aggregation was also found to be inversely correlated with the shear rate. A previously developed probabilistic model was modified to predict the time dependence of aggregation fractions at different shear rates and medium viscosities. Kinetic parameters of beta(2)-integrin and ICAM-1 bindings were obtained by individual or global fittings, which were comparable to respectively published values. These findings provide new quantitative understanding of the biophysical basis of leukocyte-tumor cell interactions mediated by specific receptor-ligand interactions under shear flow conditions.