• Title/Summary/Keyword: Cylindrical Surfaces

Search Result 112, Processing Time 0.028 seconds

SAXS and AFM Study on Porous Silicon Prepared by Anodic Etching in HF-based Solution (SAXS와 AFM에 의한 HF-용액내 양극 에칭에 의해 제조된 기공성 실리콘의 구조연구)

  • Kim, Eu-gene;Kim, Hwa-Joong
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.17 no.11
    • /
    • pp.1218-1223
    • /
    • 2004
  • Porous silicon materials have been shown to have bright prospects for applications in light emitting, solar cell, as well as light- and chemical-sensing devices. In this report, structures of porous silicon prepared by anodic etching in HF-based solution with various etching times were studied in detail by Atomic Force Microscopy and Small Angle X -ray Scattering technique using the high energy beam line at Pohang Light Source in Korea. The results showed the coexistence of the various pores with nanometer and submicrometer scales. For nanameter size pores, the mixed ones with two different shapes were identified: the larger ones in cylindrical shape and the smaller ones in spherical shape. Volume fractions of the cylindrical and the spherical pores were about equal and remained unchanged at all etching times investigated. On the whole uniform values of the specific surface area and of the size parameters of the pores were observed except for the larger specific surface area for the sample with the short etching time. The results implies that etching process causes the inner surfaces to become smoother while new pores are being generated. In all SAXS data at large Q vectors, Porod slope of -4 was observed, which supports the fact that the pores have smooth surfaces.

Design and Impact Testing of Cylindrical Composite Antenna Structures (원통형 복합재료 안테나의 설계 및 충격 실험에 관한 연구)

  • Lee, Sang-Min;Cho, Sang-Hyun;Lee, Chang-Woo;Hwang, Woon-Bong
    • Composites Research
    • /
    • v.22 no.3
    • /
    • pp.55-59
    • /
    • 2009
  • Microstrip antennas are low profile, are conformable to planar and nonplanar surfaces, are simple and inexpensive to manufacture, mechanically robust when mounted on rigid surfaces and are compatible with MMIC(Monolithic microwave integrated circuit) designs; they have been used in diverse communication systems. The rectangular microstrip patch antenna is designed for a central frequency of 12.5 GHz, and the final product is a $4{\times}1$ array antenna with curvature radius of 200 mm. The microstrip antenna is embedded in a sandwich structure which consists of skin and core material. After impact, the performance of damaged antenna is estimated by measuring the return loss and radiation pattern. The antenna performance was not affected by this impact damage.

Study of Acoustic Holography using Equivalent Source Method with Continuation of Acoustic Near-field (근접음장 연속법과 등가 음원법을 이용한 음향홀로그래피 연구)

  • Kim, Sung-Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2011.10a
    • /
    • pp.643-648
    • /
    • 2011
  • This paper deals with the ESM(equivalent source method) with the continuation of acoustic near-field for NAH(near-field acoustic holography) to overcome the finite measurement aperture effect and reconstruct the normal velocity on an arbitrarily shaped structure surface. The continuation method is an extension of the measured sound field into a region outside and is based on the Green's function relating acoustic quantities on the two conformal surfaces. This algorithm is not limited to planar surfaces and can be applied to arbitrarily shaped surfaces. The ESM is an alternative approach of BEM-based NAH for the reconstruction on a general structure. In ESM the acoustic field is represented by a set of point sources located over a surface that is close to the structure surface. The simulation results of this study shows that the reconstruction error of particle velocity on the source surface is 11% and 16% for planar and cylindrical sources separately.

  • PDF

Determination of Contact Area of Cylindrical Nanowire using MD Simulation (MD 시뮬레이션을 이용한 실린더 형태 나노와이어의 접촉면적에 관한 연구)

  • Kim, Hyun-Joon
    • Tribology and Lubricants
    • /
    • v.32 no.1
    • /
    • pp.9-17
    • /
    • 2016
  • Contact between solid surfaces is one of the most important factors that influence dynamic behavior in micro/nanoscale. Although numerous theories and experimental results on contact behavior have been proposed, a thorough investigation for nanomaterials is still not available owing to technical difficulties. Therefore, molecular dynamics simulation was performed to investigate the contact behavior of nanomaterials, and the application of conventional contact theories to nanoscale was assessed in this work. Particularly, the contact characteristics of cylindrical nanowires were examined via simulation and contact theories. For theoretical analysis, various contact models were utilized and work of adhesion, Hamaker constant and elastic modulus those are required for calculation of the models were obtained from both indentation simulation and tensile simulation. The contact area of the cylindrical nanowire was assessed directly through molecular dynamics simulation and compared with the results obtained from the theories. Determination of the contact area of the nanowires was carried out via simulation by counting each atom, which is within the equilibrium length. The results of the simulation and theoretical calculations were compared, and it was estimated that the discrepancy in the results calculated between the simulation and the theories was less than 10 except in the case of the smallest nanowires. As the result, it was revealed that contact models can be effectively utilized to assess the contact area of nanomaterials.

Development of an Analytic Nodal Expansion Method of Neutron Diffusion Equation in Cylindrical Geometry

  • Kim, Jae-Shik;Kim, Jong-Kyung;Kim, Hyun-Dae
    • Proceedings of the Korean Nuclear Society Conference
    • /
    • 1996.05a
    • /
    • pp.131-136
    • /
    • 1996
  • An analytic nodal expansion method has been derived for the multigroup neutron diffusion equation in 2-D cylindrical(R-Z) coordinate. In this method we used the second order Legendre polynomials for source, and transverse leakage, and then the diffusion eqaution was solved analytically. This formalism has been applied to 2-D LWR model. $textsc{k}$$_{eff}$, power distribution, and computing time have been compared with those of ADEP code(finite difference method). The benchmark showed that the analytic nodal expansion method in R-Z coordinate has good accuracy and quite faster than the finite difference method. This is another merit of using R-Z coordinate in that the transverse integration over surfaces is better than the linear integration over length. This makes the discontinuity factor useless.s.

  • PDF

The Thermal Stress Analysis of Axisymmetric Hollow Long Cylinder by Finite Element Method (유한요소법에 의한 축대칭 실린더의 열응력 해석)

  • Park, Jong-Gwon
    • 한국기계연구소 소보
    • /
    • s.14
    • /
    • pp.33-43
    • /
    • 1985
  • Thick cylindrical structures, such as assemblies with electrical induction heaters or nuclear fuel element, are sometimes subjected to thermal stresses from internal heating. Such stresses are produced by temperature gradients between the inside and outside surfaces. These problems possess symmetry about either a point or an axis. the objective of this paper is to present the determination of the temperature distribution and thermal stress-strain within a conducting body by finite element method.

  • PDF

Centrifugal Induction Coating of Metallic Powders

  • Natanovich, Gafo Yuri;Pavlovich, Kashitsyn Leonid;Aleksandrovich, Sosnovsky Igor
    • Proceedings of the Korean Powder Metallurgy Institute Conference
    • /
    • 2006.09b
    • /
    • pp.985-986
    • /
    • 2006
  • Principal peculiarities of technology for applying coatings of metallic powders on internal surfaces of hollow cylindrical parts by centrifugal method with induction heating from internal surface of part are examined. It is shown that most effective checking and regulating method of sintered powder layer is monitoring the high-frequency current generator power upon contactless pickup indications of external surface temperature of rotating part.

  • PDF

A Experimental Study on Efficient Applicable Combination of Super Finishing Films for Mirror Surface Machining (경면가공을 위한 수퍼피니싱필름의 효율적인 적용조합에 관한 실험적 연구)

  • Cho, Kang-Su;Kim, Sang-Kyu;Cho, Young-Tae;Jung, Yoon-Gyo
    • Journal of the Korean Society of Manufacturing Process Engineers
    • /
    • v.13 no.1
    • /
    • pp.121-128
    • /
    • 2014
  • Superfinishing is essential for mirror surfaces, because among mechanical components cylindrical workpieces such as spindles must maintain precision and reliability with respect to functional characteristics. However, research on standardization of polishing film application combination to obtain mirror surfaces is insufficient. Consequently, this has been a factor in rising costs of mechanical components. Therefore, in this study, experiments have been conducted to determine efficient polishing film application combination for mirror surfaces ranging from ductile materials such as SM45C, brass, aluminium 7075, and titanium to brittle materials such as $Al_20_3$, SiC, $Si_3N_4$, and $ZrO_2$. From the experimental results, efficient polishing film application combination for metallic materials and ceramic materials is confirmed.

S-CODE: A Subdivision Based Coding System for CAD Models

  • Takarada, Yosuke;Takeuchi, Shingo;Kawano, Isao;Hotta, Jun;Suzuki, Hiromasa
    • International Journal of CAD/CAM
    • /
    • v.3 no.1_2
    • /
    • pp.97-109
    • /
    • 2003
  • A large scale polygon models are often used to approximately represent 3D CAD models in Digital Engineering environment such as DMU (Digital Mockups) and network based collaborative design. However, they are not suitable for distribution on the network and for interactive rendering. We introduce a new coding system based on subdivision schemes called S-CODE system. In this system, it is possible to highly compress the model with sufficient accuracy and to view the model efficiently in a level of detail (LOD) fashion. The method is based on subdivision surface fitting by which a subdivision surface and curves which approximate a face of a CAD model are generated. We also apply a subdivision method to analytic surfaces such as conical and cylindrical surfaces. A prototype system is developed and used for evaluation with reasonably complicated data. The results show that the method is useful as a CAD data coding system.

Kinematics of Grasping and Manipulation of Curved Surface Object with Robotic Hand (로봇 손에 의한 자유곡면 물체의 파지 및 조작에 관한 운동학)

  • Hwang Chang-Soon
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.29 no.1 s.232
    • /
    • pp.1-13
    • /
    • 2005
  • Kinematics of grasping and manipulation by a multi-fingered robotic hand where multi-fingertip surfaces are in contact with an object is solved. The surface of the object was represented by B-spline surfaces in order to model the objects of various shapes. The fingers were modeled by cylindrical links and a half ellipsoid fingertip. Geometric equations of contact locations have been solved for all possible contact combinations between the fingertip surface and the object. The simulation system calculated joint displacements and contact locations for a given trajectory of the object. Since there are no closed form solutions for contact or intersection between these surfaces, kinematics of grasping was solved by recursive numerical calculation. The initial estimate of the contact point was obtained by approximating the B-spline surface to a polyhedron. As for the simulation of manipulation, exact contact locations were updated by solving the contact equations according to the given contact states such as pure rolling, twist-rolling or slide-twist-rolling. Several simulation examples of grasping and manipulation are presented.