Beijing Institute Of Technology Research Articles

Graphene fiber: a new material platform for unique applications

Graphene fiber (GF) is of practical importance because it integrates the remarkable properties of individual graphene sheets into useful, macroscopic ensembles that possess the common characteristics of fibers, such as mechanical flexibility for textiles, while maintaining the unique advantages over conventional carbon fibers, such as low cost, light weight, shapeability and ease of functionalization in an in situ or post-synthetic manner for various applications. In this review, we judiciously summarize the significant advances in GFs achieved by our group and others in recent years, including the tunable and controllable preparation of GFs with functionality and their remarkable applications for unconventional devices, such as flexible fiber-type actuators, robots, motors, photovoltaic cells and supercapacitors. In this review, the significant advances of the new type of graphene fibers (GFs) achieved during the recent few years have been systematically summarized, including the tunable and controllable preparation of GFs with functionalizations and their remarkable applications for unconventional devices such as flexible fiber-type of actuators, robots, motors, photovoltaic cells and supercapacitors. Graphene has set records for both its mechanical strength and electrical conductivity. Exploiting these properties for use in practical devices, however, requires techniques that transform this atom-thin substance into large-scale objects. Liangti Qu and colleagues from the Beijing Institute of Technology in China review an innovative approach to achieving this goal that uses ‘graphene fibers’ — long, thin and robust materials that can be synthesized by extruding liquid-crystal-like graphene oxide suspensions into filaments or through spontaneous reactions inside dimensionally confined glass pipelines. These stretchable fibers can be woven inside textiles for wearable electronics applications, combined with photovoltaic elements to make solar wires or used as shape-shifting actuators for robotic devices. The researchers caution, however, that more effort is needed to reduce defects inside graphene fibers that currently hinder their performance.

Large Eddy Simulation of turbulent vortex-cavitation interactions in transient sheet/cloud cavitating flows

The objectives of this study are to: (1) quantify the influence of sheet/cloud cavitation on the hydrodynamic coefficients and surrounding flow turbulent structures, (2) provide a better insight in the physical mechanisms that govern the dynamics and structure of a sheet/cloud cavity, (3) improve the understanding of the interaction between unsteady cavitating flow, vortex dynamics and hydrodynamic performance. Results are presented for a 3D Clark-Y hydrofoil fixed at an angle of attack of α=8 degrees at a moderate Reynolds number, Re=7×105, for both subcavitating (σ=2.00) and sheet/cloud cavitating conditions (σ=0.80). The experimental studies were conducted in a cavitation tunnel at Beijing Institute of Technology, China. The numerical simulations are performed via the commercial code CFX using a transport equation-based cavitation model, the turbulence model utilizes the Large Eddy Simulation (LES) approach with the Wall-Adapting Local Eddy-viscosity model. The results show that numerical predictions are capable of capturing the initiation of the cavity, growth toward the trailing edge, and subsequent shedding, in accordance with the quantitative features observed in the experiment. The detailed analysis of the vorticity transport equation shows strong correlation between the cavity and vorticity structure, the transient development of sheet/cloud cavitation has significantly changed the interaction between the leading edge and trailing edge vortices, and hence the magnitude as well as the frequency of the hydrodynamic load fluctuations. Compared to the subcavitating case, the sheet/cloud cavitation leads to much higher turbulent boundary layer thickness and substantial increase in velocity fluctuation.

Design and Development of the Humanoid Robot BHR-5

This paper presents the mechanical and control system design of the latest humanoid robot platform, BHR-5, from Beijing Institute of Technology. The robot was developed as a comprehensive platform to investigate the planning and control for the fast responsive motion under unforeseen circumstances, for example, playing table-tennis. It has improvement on mechanical structure, stiffness, and reliability. An open control architecture based on concurrent multichannel communication mode of CAN bus is proposed to upgrade the real-time communication performance and the expansibility of the control system. Experiments on walking and playing table-tennis validate the effectiveness of the design.

Stochastic methods in reliability and risk management

This volume focuses on stochastic methods developed for reliability modeling and risk analysis. Reliability theory and risk analysis have been closely related, and stochastic methods that are commonly used in both fields serve as a natural conduit through which useful concepts and best practices can migrate from one field to the other. This special volume highlights this convergence of reliability modeling and risk analysis, that forms the core of the science of analyzing hazards and its applications to various fields. Most of papers appearing in this volume were selected from the presentations given at the 7th International Conference on Mathematical Methods in Reliability (MMR2011), held in Beijing, China, June 20–24, 2011. The conference was co-chaired by Yiming Wei (Beijing Institute of Technology, China), N. Balakrishnan (McMaster, Canada), and N. Limnios (UTC, France). The papers have been significantly extended from the conference presentations and all papers have been refereed according to the standards of Annals of Operations Research. The MMR2011 is the seventh in a series of international conferences on Mathematical Methods in Reliability. Since 1997, when the first of MMR conferences was held in Bucharest, Romania, the MMR has become a major international gathering of researchers from the international reliability community. The MMR conferences intend to serve as a forum for discussing fundamental issues and recent advances in reliability theory and risk analysis methods, as well as their applications, and have attracted an increasing number of participants from every continent in the world. The Beijing conference focused on all aspects

Physical and numerical investigation on transient cavitating flows

The objective of this paper is to investigate transient cavitating flows around a hydrofoil via combined physical and numerical studies. The aims are to 1) investigate the periodic formation, breakup, shedding, and collapse of the sheet/cloud cavities, 2) provide a better insight in the physical mechanism that governs the dynamics and structures of the sheet/cloud cavitation, 3) quantify the influence of cavitation on the surrounding flow structures. Results are presented for a Clark-Y hydrofoil fixed at an angle of attack of α=8° at a moderate Reynolds number, Re=7×105, for sheet/cloud cavitating conditions. The experimental studies were conducted in a cavitation tunnel at Beijing Institute of Technology, China. The numerical simulations are performed by solving the incompressible, multiphase unsteady Reynolds-averaged Navier-Stokes (URANS) equations via the commercial code CFX using a transport equation-based cavitation model; a filter-based density corrected model (FBDCM) is used to regulate the turbulent eddy viscosity in both the cavitation regions near the foil and in the wake. The results show that numerical predictions are capable of capturing the initiation of the cavity, growth toward the trailing edge, and subsequent shedding in accordance with the quantitative features observed in the experiment. Regarding vapor shedding in the cavitating flow around the three-dimensional foil, it is primarily attributed to the effect of the re-entrant flow, which is formed due to the strong adverse pressure gradient. The results show strong correlation between the cavity and vorticity structures, demonstrating that the inception, growth, shedding, and collapse of sheet/cloud cavities are important mechanisms for vorticity production and modification.

Controlled Synthesis of Polyoxopalladates, and Their Gas‐Phase Fragmentation Study by Electrospray Ionization Tandem Mass Spectrometry

Invited for the cover of this issue is the group of Changwen Hu at the Beijing Institute of Technology, China. The cover image shows the most recent developments in the synthesis and study of the gas-phase fragmentation of new polyoxopalladates.

Preliminary study of CT in combination with MRI perfusion imaging to assess hemodynamic changes during angiogenesis in a rabbit model of lung cancer

BackgroundThis study used CT (computed tomography) and magnetic resonance imaging (MRI) to identify correlations between perfusion parameters for squamous cell lung carcinoma and tumor angiogenesis in a rabbit model of VX2 lung cancer.MethodsVX2 tumors were implanted in the lungs of 35 New Zealand White rabbits. CT and MRI perfusion scanning were performed on days 14, 17, 21, 25, and 28 after tumor implantation. CT perfusion parameters were perfusion, peak enhanced increment, transit time peak, and blood volume, and MRI perfusion parameters were wash in rate, wash out rate, maximum enhancement rate, and transit time peak. CT and MRI perfusion parameters were obtained at the tumor rim, in the tumor tissue, and in the muscle tissue surrounding the tumor.ResultsOn CT perfusion imaging, t values for perfusion, peak enhanced increment, and blood volume (tumor rim versus muscle) were 16.31, 11.79, and 5.21, respectively (P < 0.01); t values for perfusion, peak enhanced increment, and blood volume (tumor versus muscle) were 9.87, 4.09, and 5.35, respectively (P < 0.01); and t values for transit time peak were 1.52 (tumor rim versus muscle) and 1.29 (tumor versus muscle), respectively (P > 0.05). On MRI perfusion imaging, t values for wash in rate, wash out rate, and maximum enhancement rate (tumor rim versus muscle) were 18.14, 8.79, and 6.02, respectively (P < 0.01); t values for muscle wash in rate, wash out rate, and maximum enhancement rate (tumor versus muscle) were 9.45, 8.23, and 4.21, respectively (P < 0.01); and t values for transit time peak were 1.21 (tumor rim versus muscle) and 1.05 (tumor versus muscle), respectively (P > 0.05).ConclusionA combination of CT and MRI perfusion imaging demonstrated hemodynamic changes in a rabbit model of VX2 lung cancer, and provides a theoretical foundation for treatment of human squamous cell lung carcinoma.

1D Nanomaterials: Synthesis, Properties, and Applications

1 School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing 100081, China 2Department of Materials and Metallurgical Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA 3Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China 4College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, Jiangsu 225009, China

MIMO Antenna Design and Channel Modeling 2013

1 Department of Electronic Engineering, Tsinghua University, Beijing 100084, China 2The School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0250, USA 3 School of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China 4 Beijing Institute of Technology, Beijing 100081, China 5 Texas Instruments, Dallas, TX 75266-0199, USA

A Novel Spatial Clustering Analysis Method Using Bat Algorithm

Guanghui LIU , Heyan HUANG , Shumei WANG , Zhaoxiong CHEN *1 School of Computer Science and Technology, Nanjing University of Science & Technology, Nanjing, 210094, China, lgh025@163.com 2 School of Computer Science and Technology, Beijing Institute of Technology, Beijing, 100081, China, hhy63@bit.edu.cn 3 school of Information Engineering, Nanjing University of Finance & Economics, Nanjing, 210046, China

Computational explosion mechanics and related progress

Explosion mechanics is the theoretical basis for the design of highly efficient arms and ammunition and industrial explosion safety. Because it involves the complex physical and mechanical behaviors of multi-materials under extreme conditions, such as high speed, high temperature and high pressure, it is almost impossible to give exact solutions for explosion problems. As explosion occurs in a very short time and has a strong destructive effect, there will be limited amounts of experimental data obtained during the explosion process. With the continuous development of numerical methods and computer performance, computational explosion mechanics has become a new interdisciplinary branch of explosion mechanics, material dynamics, computational mathematics and computer technology, and greatly promoted the development of explosion mechanics and weapons equipment. Since the late 1960s, US-led western developed countries have developed more than one hundred calculation codes of explosion mechanics. Based on the simulation software for explosion mechanics, calculations about three-dimensional physical processes on a system scale during the course of weapon system development have been performed, which resulted in the development of a number of high efficiency arms and ammunition. Such research institutions as the Beijing Institute of Technology, the Chinese Academy of Engineering Physics, the Institute of Applied Physics and Computational Mathematics, the Institute of Mechanics of the Chinese Academy of Sciences, Peking University, the University of Science and Technology of China and other research institutions have developed different numerical methods for explosion mechanics, dynamic constitutive models and software development. Finite Difference Method and Finite Element Method are the most common methods of the discrete methods adopted in computational explosion mechanics. The former is a representative method by which time and space are covered with cells to gain approximate numerical solutions after partial differential equations (governing equations) are established. The latter is a representative method by which continuous space is decomposed into finite elements. Classed by coordinates, Eulerian method and Lagrangrian Method are two common methods utilized in computational explosion mechanics. On the base of these two methods, two hybrid methods, ALE (Arbitrary Lagrange Euler) and CLE (Coupled Lagrange Euler), are developed. Eulerian method has an advantage in treating the large deformation of materials, which always occurs in explosion mechanics. However, it is difficult to handle mixed cells using this method if the studied system includes multi-materials because a transition region forms along the interface which becomes fuzzy between materials. How to determine the position of interfaces and how to calculate the physical quantities in the mixed cells have been difficult problems in Eulerian codes. PIC (Particle in Cell) method and VOF (Volume of Fluid) method are the traditional methods to solve the interface problems in Eulerian codes. Youngs method can determine the interface clearly by transporting fluid of cells around the interface, becoming the mainstream of VOF methods. The original Youngs method just determines the interface in a mixed cell, and cannot determine the transport order and quantity of material. That is a problem of Eulerian methods. A modified Youngs method is adopted in [1], in which the material’s fractions are adopted to determine the transport order of material. Ref. [2] proposes an interface treatment method, in which the interface curve of material is traced by a series of straight-line segments which connect head and tails, and the material interface is determined by marker line located on the grid lines. Ref. [3] proposed a hybrid VOF and PIC multi-material interface treatment method, in which PIC method is utilized in the important regions, and continuous method is used in the other, resulting in high precision and high efficiency of algorithm by which the deformation of material is tracked successfully during penetration. Another method, Level Set, has been proposed and widely used in recent years. In [4], Level Set method combined with Ghost Fluid method is employed to track the

Single‐Side Organically Functionalized Anderson‐Type Polyoxometalates

Polyoxometalate (POM)-based organic–inorganic hybrid materials have attracted extensive attention in the last ten years due to their potential applications in catalysis, nonlinear optics, photovoltaic, and self-assembly research. Currently, trisalkoxo tripodal ligand (Tris)-functionalized Lindqvist-, Anderson-, and Dawson-type POMs show high stability and varied functionalities. Zubieta et al. used Tris ligands to stabilize macro-POM clusters and to functionalize hexavanadate. The functionalized hexavanadate was further developed by Hill and co-workers for the construction of metal–organic frameworks, which can function as highly efficient heterogeneous catalytic materials. Due to the high reactivity of vanadate, vanadium-containing Dawsontype POMs were observed to be capped by only one Tris ligand. In particular, after Hasenknopf et al. had established the synthesis of Tris derivatives of Anderson-type POMs in 2002, the groups of Cronin and Hasenknopf introduced different kinds of functional groups to the system through further organic reactions. The resulting materials show interesting functions including high biological activity against cells, photocatalytic properties, and interesting selfassembly behavior. Due to their high symmetry (D3d), both sides of Anderson-type POMs are easily functionalized simultaneously by Tris ligands during their synthesis, which seems to be an unquestionable fact (Figure 1), and there has never been any report on a single-sided functionalized Anderson-type POM with Tris. Herein, we report the synthesis and characterization of Anderson-type POMs with only one side functionalized by a Tris ligand, which not only afforded asymmetric POM-based hybrid materials for further research, but also uncovered more structural and reactive properties of Anderson-type POMs, and the reaction mechanism for the functionalization of POMs with Tris. In the previous protocol, to synthesize the double-sided functionalized Anderson-type POMs, octamolybdate, a salt of the central heteroatom, and organic ligands (Tris) were mixed in an organic solvent, such as acetonitrile, and the final products were obtained after heating to reflux for approximately 16 hours, which is a classical one-pot reaction. However, our new protocol to synthesize the single-side organically functionalized Anderson-type POM, [(C4H9)4N]5{H7ACHTUNGTRENNUNG[HOCH2C ACHTUNGTRENNUNG(CH2)3 ACHTUNGTRENNUNG(CrO6)Mo6O18]2} (1), is a two-step aqueous reaction with high yield through the direct functionalization of the parent Anderson-type POM, [CrMo6O18(OH)6] 3 . Compound [CrMo6O18(OH)6] 3 was first synthesized according to Perloff s method reported in 1970. Pentaerythritol was then added to the resulting aqueous solution of [CrMo6O18(OH)6] 3 , and the mixture was refluxed at once for a prolonged time to finish the esterification. Interestingly, the reaction is of high yield and high selectivity for the mono Tris-functionalized product 1, probably due to the hierarchical synthesis protocol and aqueous reaction media (see the Experimental Section). In the preparation reaction, a single-side-functionalized Anderson-type POM is obtained in high yield (based on Mo), even when the ratio of Tris to the parent Anderson-type POM is two or much higher than two. Therefore, the selectivity for producing such single-sided species might be related to the aqueous environment. [a] P. Wu, P. Yin, Dr. J. Zhang, Dr. J. Hao, Dr. Z. Xiao, Prof. Dr. Y. Wei Department of Chemistry, Tsinghua University Beijing, 100084 (P.R. China) Fax: (+86)10-6277-1149 E-mail : yinpanchao@tsinghua.org.cn yonggewei@tsinghua.edu.cn [b] P. Wu Institute of POM-based Materials Key Laboratory of Fermentation Engineering (Ministry of Education) Hubei University of Technology Wuhan, 430068 (P.R. China) [c] Prof. Dr. Y. Wei Key Laboratory of Cluster Science (Beijing Institute of Technology) Ministry of Education of China Beijing, 100081 (P.R. China) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201101552. Figure 1. Molecular structures of: a) unfunctionalized and b) bifunctionalized Anderson-type POMs. Color code: Mo: large black sphere; Cr: central gray sphere; O: small black sphere; C: large gray sphere; H: small gray sphere; X= functional group: -CH2OH, -NH2, -CH3, or -NO2.

10 scientific problems in virtual reality

Virtual Reality was one of the 14 Grand Challenges identified as awaiting engineering solutions for the 21st century announced in 2008 by the U.S. National Academy of Engineering (NAE http://www.nae.edu/). Here, I explore 10 related open VR challenges, with hoped-for potential breakthroughs promising to advance VR techniques and applications. VR is today being applied in multiple contexts, including training, exercise, engineering design, and entertainment, while also serving as a research tool in such fields as neuroscience and psychology, as explored in Michael Heim's pioneering 1993 book Metaphysics of Virtual Reality (http://www.mheim.com/books.html). More recently, scholars have described the Internet itself as representing a virtual world modeling its real-world counterpart. The relationship between VR and its application fields is, in terms of expression and validation, like the relationship between mathematics and physics, while VR is attracting attention from a growing number of governments and science/engineering communities. Along with the NAE Committee on Engineering 14 Grand Challenges (http://www.engineeringchallenges.org/), the Chinese government's 2006 report Development Plan Outline for Medium- and Long-Term Science and Technology Development (2006--2020) (http://www.gov.cn/jrzg/2006-02/09/content_183787.htm) and the Japanese government's 2007 report Innovation 2025 (http://www.cao.go.jp/innovation/index.html) both included VR as a priority technology worthy of development. VR has likewise emerged as an important research area for many Chinese universities and research institutes, ranging from theoretical foundations to technology innovation, system development, and practical applications. For example, Zhejiang University in Hangzhou and Tsinghua University in Beijing are known for realistic modeling and rendering; Peking University in Beijing focuses on computer vision and human-machine interaction; the Beijing Institute of Technology in Beijing emphasizes head-mounted displays; and the Institute of Computing Technology of Chinese Academy of Sciences in Beijing has made significant progress in crowd simulation. Since 1995, I have directed the State Key Laboratory of Virtual Reality Technology and Systems of China (http://www.skvrlab.net) in Beijing, focusing on VR. Over that time, we have proposed many new methods and technologies in distributed virtual environments, realistic modeling and rendering, and augmented reality, including two major VR software infrastructures: BH_RTI for distributed virtual environments (http://www.hlarti.com) and BH_GRAPH for real-time 3D rendering (http://www.skvrlab.net:8080/soft). This work has produced several influential VR application systems, including the 2008 Beijing Olympic Games Opening Ceremony Simulation Platform and the Beijing 08 Digital Museum. We also designed a training-and-scenario-simulation system for a military review of China's 2009 60th anniversary celebration, with more than 8,000 soldiers, based on visualized immersion technologies to deliver scenario preview, modification, and decision-making functions. Meanwhile, our work advancing theory in related fundamental disciplines may help produce further breakthroughs in VR; for example, electrorheological fluids could change the existing method of haptic rendering.

Terahertz crystals

An electromagnetic crystal terahertz horn antenna, fabricated on a silicon substrate, has been developed by collaborating researchers from the University of Arizona and the Beijing Institute of Technology. As was shown in their Letter in the previous issue of Electronics Letters, low attenuation and simple integrability confirm the suitability of such crystals for the successful implementation of terahertz technology.

Advances in medicine and biology via engineering approaches: Highlights from the 3rd International Conference on Bioinformatics and Biomedical Engineering

The 3rd International Conference on Bioinformatics and Biomedical Engineering (iCBBE2009, http://www.icbbe.org/2009) was held from June 11th to 13th, 2009, in Beijing, China. The iCBBE was initially launched by the Advanced Research Center for Science and Technology at Wuhan University in 2006, and technically sponsored by the Engineering in Medicine and Biology Society (EMBS) of the Institute of Electrical and Electronics Engineers (IEEE). The first conference, iCBBE2007 was held in Wuhan University, Wuhan, China. The second one, iCBBE2008, was held in Shanghai Jiaotong University, co-sponsored by EMBS, Gordon Life Science Institute (USA), Fudan University (China), Beijing University of Posts and Telecommunications (China), Beijing Institute of Technology (China), Wuhan University (China), and Journal of Biomedical Science and Engineering (USA). Dr. Kuo-Chen Chou of Gordon Life Science Institute (USA) chaired the third conference, iCBBE2009, which included 10 keynote speeches, 12 oral sessions and 4 poster sessions. More than 600 distinguished scholars around the world attended the conference to exchange their new discoveries in the related areas. The conference proceedings have been published by IEEE; all accepted papers by the conference are archived in IEEE Xplore database and will be indexed by EI Compendex soon.

Erratum to: Elastic Fields for the Ellipsoidal Cavity Problem

The online version of the original article can be found under doi:10.1007/s10659-009-9210-8.B.-X. Xu ·M.-Z. WangState Key Laboratory for Turbulence and Complex Systems and Department of Mechanics andAerospace Engineering, College of Engineering, Peking University, 100871 Beijing, People’s Republicof ChinaY.-T. Zhao ( )Department of Applied Mechanics, Beijing Institute of Technology, 100081 Beijing, People’s Republicof Chinae-mail: ytzhao623@bit.edu.cn

Selected Papers from the 3rd International Symposium on Computational Intelligence and Industrial Applications (ISCIIA2008)

The biennial International Symposium on Computational Intelligence and Industrial Applications (ISCIIA2008) focuses on advanced technologies for soft computing, computational intelligence, and real-world applications. The first ISCIIA was held in 2004 in Haikou, China, the second in Guangzhou, China, and the third, hosted by Dali University, held Nov. 21-Nov. 26 in Dali, Yunnan Province, China. From the 58 papers published in ISCIIA2008 proceedings, 5 have been selected and reviewed for publication in JACIII. This special issue covers learning systems, signal and image processing, human-computer interfacing, intelligent control, and robotics. These selected papers should prove to be interesting and informative for many researchers. ISCIIA2008 was cochaired by Professor Yaping Dai of Beijing Institute of Technology and professor Lihua Duan of Dali University. The local organizing committee member included Prof. Yilong Gu and Dr. Chen, who worked hard from CFP preparation to local arrangement. The founding chairs – Prof. Kaoru Hirota of Tokyo Institute of Technology, Prof. Shibin Zhao of Guangdong Polytechnical Normal University, and Mr. Raymond Tay of Mycom Inc., Singapore – contributed much to the success of ISCIIA2008. The fourth ISCIIA will be held in August in Harbin, China, and we look forward to the advances in computational intelligence technologies and industrial applications the occasion will bring.

Linkages between research, scholarship and teaching in universities in China

Linkages between research, scholarship and teaching are a topic of contemporary interest in UK universities, driven by pressures such as traditional views of the nature and purpose of universities, reputation, student expectations of their teachers, educational enhancement through up‐to‐date research and scholarly input, and personal ambitions and satisfaction. The paper describes a study of these linkages at the Beijing Institute of Technology (BIT) during 2006 within the Sino‐UK Higher Education Leadership Development Programme, which allows for senior academics from China and the UK to study a particular management issue to identify good practice which they can apply in their institution. The activities included a preliminary workshop in the UK, a two‐week visit to BIT in and a workshop in Beijing. My study was conducted through a semi‐structured interview programme with a wide range of academics and administrators. It was enlightening to find that a leading Chinese university, which operates within quite different systems and cultures from the UK, nevertheless has similar issues, imperatives and problems. My overall conclusion is that there is international agreement that research and scholarly performance underpins the credibility of academic staff to teach at a university, which in turn attracts good students and research staff.

A Highly Efficient Parallel Approach of Multi-level Fast Multipole Algorithm

Based on the different characteristics of memory requirement and CPU time at different levels in the Multi-Level Fast Multipole Algorithm (MLFMA), a new highly efficient parallel approach is proposed, which employs different techniques to parallelize the plane waves and translation matrices at different levels. The formulae for efficiently implementing this proposed approach are presented by theoretical analysis and numerical experiments. Several techniques have also been employed to reduce memory requirement. The proposed parallel approach is implemented and investigated numerically, showing that the proposed approach is very accurate and efficient. The radar cross-section (RCS) of a conducting sphere with a diameter of 144λ (wavelength), simulated by over 10 millions unknowns, is successfully computed in the Center for Electromagnetic Simulation (CEMS) in the Beijing Institute of Technology (BIT), demonstrating the strong computation power of this proposed approach. The comparison of numerical performance between Center for Computation Electromagnetics (CCEM) in University of Illinois at Urbana-Champaign (UIUC) and our CEMS is also presented in this paper.

Error Evaluation of Aspheric Surfaces and Calibration of the Test Instrument

As aspheric surfaces are more often used in optical systems, suitable error evaluation methods and suitable accuracy calibration methods for related test instruments are urgently required. The two unsolved but important issues are addressed. For evaluation of aspheric surfaces, a scheme is proposed to separate the surface errors into radius error and local error. The effects of the two errors on image quality are discussed. For test instrument calibration, a practical method using a defocused spherical surface is described and verified with an absolute testing instrument based on laser deflectometry, which was developed at Beijing Institute of Technology. The feasibility of the schemes is shown and experimental results are presented.