• Title/Summary/Keyword: Concave surface

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Study of Stray-light Analysis and Suppression Methods for the Spectroscopic System of a Solar-radiation Observer Instrument

  • Zheng, Ru;Liu, Bo;Wang, Lingyun;Gao, Yue;Li, Guangxi;Li, Changyu
    • Current Optics and Photonics
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    • v.5 no.3
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    • pp.220-228
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    • 2021
  • To improve the measurement accuracy of a solar-radiation observer instrument, aiming at the problem of multiorder-stray-light interference caused by the diffraction of the flat-field concave grating in the spectroscopic system, straylight suppression methods for different forms of optical traps are studied. According to the grating surface-scattering distribution-function model, the bidirectional scattering distribution function (BSDF) of a dust-polluted surface and the flat-field concave grating's transition area of the spectroscopic system is calculated, and a Lyot stop with blade baffle is designed to suppress this kind of stray light. For diffraction multiorder stray light, based on the theory of light-energy transmission, a design for precise positioning of the trench optical trap is proposed. The superiority of the method is verified through simulation and actual measurement. The simulation results show that in a spectroscopic system approximately 160 mm × 140 mm × 80 mm in size, the energy of the stray light is reduced by one order of magnitude by means of the trench optical trap and Lyot stop, and the number of beams is reduced from 5664 to 1040. The actual measurements show that the stray-light-suppression efficiency is about 69.4%, which is effective reduction of the amount of stray light.

Tool Interference Avoidance in compound Surface Using solid Modeling Method (Solid Modeling 기법을 응용한 복합곡면 가공에 있어서 공구간섭 제거)

  • 장동규
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.5 no.2
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    • pp.20-28
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    • 1996
  • Compound surface modeling is widely used for die cavities and punches. A compound surface is defined in 3-D space by specifying the topological relationship of several anlytic surface elements and a sculptured surface. A constructive solid gemonetry scheme is employed to model the analytic compound surface. the desired compound surface can be accomplished by specifying topological reationship in terms of boolean relations between pimitives and the sculptured surfaces. Additionally, a method is presented for checking and avoiding the tool interference occuued in machining the compound surface. Using this method. the interference of concave, convex, and side region can be checked easily and avoided rpapidly.

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Developent of Scanning and Registration Methods Using Tooling Balls (툴링볼을 이용한 측정 및 레지스트레이션 방법 개발)

  • 김용환;윤정호;이관행
    • Korean Journal of Computational Design and Engineering
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    • v.4 no.1
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    • pp.60-68
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    • 1999
  • In reverse engineering (RE) sustems, the quality of the data aquisition process is crucial to the accuracy of the reverse engineered three dimensional computer-aided design (CAD) model. However, these tasks are predominantly done manually, and little work has been done to improve the efficiency of scanning by determining the minimum number of scans and the optimal scanning directions. In this paper, new scanning and registration methods using tooling balls are developed to assist in determining the optimal parameter for these processes. When the object to scanned has no concavity, attaching path of the object and its bounding rectangle are used for optimal scanning and registration. Then minimum number of tooling balls and their positions are calculated automatically. In the case of concave parts, the scanning plan should include a complete scan of the concave area. With the surface normal vector and the scanning direction, the minimum degree of rotating the part can be calculated. But the maximum rotation should be restricted in order to prevent occlusion of the part. Finally tow sample part ar scanned based on the proposed methods and the results are discussed.

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Effect of heat ring in the water cooled kerosene engine (수냉식 등유기관에 있어서 가열링의 효과)

  • 이성열;김홍남
    • Journal of the korean Society of Automotive Engineers
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    • v.6 no.2
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    • pp.64-75
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    • 1984
  • In the engine design, it will be able to higher compression ratio and decreasing the cylinder size, if improve the vaporization of fuel and increasing the mass burned fraction in the kerosene engine. Therefore, concave, convex and straight types of hear ring set up neighborhood intake valve into the combustion chamber. The vaporization effect of fuel satisfied by heat transfer from the heat ring, but have need of selection of the location and surface area of the heat ring. Also, combustion duration of the combustion chamber with concave heat ring shorter than combustion chamber with other two types of heat ring, and about 30percent decreases in combustion duration as compared with combustion chamber without heat ring.

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Taxonomic Implications of Seed Coat in the Subtribe Calthinae (Ranunculaceae) (미나리아재비과 동의나물아족의 종피형태와 분류학적 검토)

  • Heo, Kweon;Suh, Youngbae
    • Korean Journal of Plant Taxonomy
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    • v.38 no.1
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    • pp.1-16
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    • 2008
  • Anatomical features of seed coat were examined on Trollius, Calathodes, and Caltha of Ranunculaceae to evaluate the taxonomic circumscription of Megaleranthis saniculifolia, which is monotypic and endemic in Korea. Megaleranthis saniculifolia showed the exotestal type of seed coat exhibiting a well-developed palisade structure in exotesta and its external surface of exotesta cells was concave. On the other hand, the shape of exotesta cells in Caltha was cuboidal and the outer surface was smooth. The exotesta of Calathodes seeds was formed of the palisade structure like M. saniculifolia, but the outer surface of exotesta cells was smooth. The palisade structure was much better developed in the exotesta of Calathodes as well as Megaleranthis seeds than in the exotesta of Trollius seeds. The outer surface of exotesta cells in Trollius was either convex or concave according to the species examined. Since the genera of the subtribe Calthinae of the family display differences in seed sculpturing and the anaotmy of seed coat, these characteristics are useful to access taxonomic relationships among them. The morphological and anatomical features of seed coat suggest that Megaleranthis be possibly allied with Trollius rather than Caltha or Calathodes. Concave surface of seed coat cells and well-developed palisade structure of exotesta are shared by M. saniculifolia and some species of Trollius in common.

A Study on the Radiation Characteristics of Microstrip Array Antennas on the Nonplanar Surface (곡면에서의 마이크로스트립 어레이 안테나의 복사 특성에 관한 연구)

  • 구연건;이정수;고광태
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.14 no.2
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    • pp.121-136
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    • 1989
  • In this paper, an attempt has been made to analyze the theoretically and verify experimentally the effect of curvature on the radiation characteristics of microstrip array antennas mounted conformally on the concave surface and the convex surface of the cylindrical body. The analysis of single element microstrip antenna is made by using the analysis method of Transmission Line Model. The theory of array antennas is established by application of the method of transformed coordinates, in which the translation and the ratation about each single element arrayed two-demensionally on the nonplanar surface are under consideration, and it is investigated by computation of the synthetic electric field strength in the far zone. In addition, various radiation characteristics, such as return loss, resonant frequency, radiation pattern, half-power, beamwidth, gain, are measrued and compared with the theroetical values according to the variation of curvature, by designing and building 4-element array microstrip antenna operating at 10 GHz, and microstrip feed lines. As predicted in theroy, it is verified that radiation pattern of antennas mounted on the concave and the convex surfaces alike broadens as the radius of curvature decreases. And for the curved surfaces, aggrement between computed values of the total synthetic radiation power pattern by the method of transformed coordinates and measured valuse is good. Besides, it is found that resonant frequency, input impedance and gain are hardly affected by the radius of curvature.

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Surface Ultrastructures of Stictodora fuscatum (Trematoda: Heterophyidae) (자루이형흡충(Stictodora fuscatum)의 표면 미세구조)

  • Sohn, Woon-Mok
    • Applied Microscopy
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    • v.30 no.2
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    • pp.205-212
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    • 2000
  • Present study was performed to observe the surface ultrastructures of Stictadora furcatum (Trematoda: Heterophyidae). Adult worms were recovered from the cat experimentally infected with metacercariae, and were prepared for scanning electron microscopy. The body was leaf-like and ventrally concave. The oral sucker armed with prominent tegumental spines on the inner surface, and it's lips were obscure. Sensory papillae (type I) in single or grouped forms symmetrically arranged around the oral sucker. The ventrogenital opening retained protruding gonotyl spines and sperms discharged from the genital pore . The body surface was covered with scale-like multipointed tegumental spines. The density and digitated point of spines were gradually decreased toward the posterior end of the body. The digitated points of spines on the anterior portion were 9-12, on the middle were 7-8 and 5-6, and on the posterior were 2-3 and peg-like. Although the tegumental ultrastructure of S. fuscatum was generally similar to those of other heterophyid flukes , the oral sucker with tegumental spines on the inner surface and without obvious lips, and the ventrogenital opening with protruding gonotyl spines were suggested to be the characteristic features.

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Dynamic Free-Surface Deformations in Axisymmetric Thermocapillary Convection in Open Cylindrical Annuli (동적인 자유표면을 가진 동심원통에서의 열모세관 대류)

  • Sim, Bok-Cheol;Kim, Woo-Seung
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.1560-1565
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    • 2003
  • Thermocapillary convection in an open cylindrical annulus heated from the inside wall is investigated by two-dimensional numerical simulations. The deformable free surface is obtained as a solution of the coupled transport equations at fixed Prandtl and aspect ratio. Only steady convection can be realized in this axisymmetric computations with either non-deformable or deformable surfaces. Dynamic free-surface deformations do not induce transitions to oscillatory convection even at large Reynolds numbers. Free surfaces are convex near the cold wall due to the stagnation point, and concave near the hot wall. Free surface deformation increases with increasing Ca at a fixed Re. Two peaks appear at the free surface with low Re, while additional ripples, four peaks, occur at larger Re. Thermocapillary convection in the open annulus interior is insensitive to variations in Ca.

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Machined Profile Characteristics for Feedrate Change in Ball End Mill Cutting (볼엔드밀 가공시 이송변화에 따른 가공형상 특성)

  • 왕덕현;김원일;이윤경;임채열;우정윤;박창수
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.11 no.2
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    • pp.95-102
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    • 2002
  • Due to the development of the CNC machine tool and CAM software, sculptured surface machining can be broadly used in die and mold industries and ball end milling process is often used for the sculptured surface machining. It is found out how feedrate affects the precision of the machining and also tried to study the most suitable feedrate in specific cutting condition. Two eddy current sensors were used far measuring tool deflections of X, Y axis, dynamometer for cutting force and roundness tester for roundness. It was found that the tool deflection is getting better as tool path is going to further from the center of convex surface. The reason is that the cutting force is increased as the tool approaches to the center. Examining the roundness, cutting force and tool deflection characteristics, it was found that the most suitable feedrate is 90mm/min in convex surface and 120mm/min in concave surface.

A Study on the Avoidance of Tool Interference in Analytic Compound Surface Machining (해석적 복합 곡면 가공에 있어서의 공구 간섭 방지에 관한 연구)

  • Kang, S.G.;Cho, S.W.;Ko, S.L.
    • Journal of the Korean Society for Precision Engineering
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    • v.13 no.9
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    • pp.156-164
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    • 1996
  • Tool interference is one of the most critical problems in machining die cavities and punches. When machining concave or convex regions of cavities with large radius tool in rough cutting, the tool easily overcuts or undercuts the portions of the surface, which result in machining inaccuracy. So the generation of interference-free tool path must be required for more efficient rough cutting. In this paper, we present a method for modeling die cavities which consist of simple surface or analytic compoyund surfaces and present an algorithm for checking and removing the tool interference occurred in machining the die cavities. Using these algorithms, we can represent a die cavity, and check the interfer- ence regions, and then remove these interferences. Especially we focus on the side interference in the sides of analytic elements and base surface boundary.

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