• 제목/요약/키워드: Minimal surface system

검색결과 72건 처리시간 0.022초

MINIMAL SURFACE SYSTEM IN EUCLIDEAN FOUR-SPACE

  • Hojoo Lee
    • 대한수학회지
    • /
    • 제60권1호
    • /
    • pp.71-90
    • /
    • 2023
  • We construct generalized Cauchy-Riemann equations of the first order for a pair of two ℝ-valued functions to deform a minimal graph in ℝ3 to the one parameter family of the two dimensional minimal graphs in ℝ4. We construct the two parameter family of minimal graphs in ℝ4, which include catenoids, helicoids, planes in ℝ3, and complex logarithmic graphs in ℂ2. We present higher codimensional generalizations of Scherk's periodic minimal surfaces.

ON MINIMAL SURFACES WITH GAUSSIAN CURVATURE OF BIANCHI SURFACE TYPE

  • Min, Sung-Hong
    • 충청수학회지
    • /
    • 제34권4호
    • /
    • pp.379-385
    • /
    • 2021
  • We consider the local uniqueness of a catenoid under the condition for the Gaussian curvature analogous to Bianchi surfaces. More precisely, if a nonplanar minimal surface in ℝ3 has the Gaussian curvature $K={\frac{1}{(U(u)+V(v))^2}}$ for any functions U(u) and V (v) with respect to a line of curvature coordinate system (u, v), then it is part of a catenoid. To do this, we use the relation between a conformal line of curvature coordinate system and a Chebyshev coordinate system.

$37^{\circ}C$에서 incubate 한 가토(家兎) 폐포표면활성물질(肺胞表面活性物質)의 활성도(活性度)의 변화(變化)와 in vitro X 선조사(線照射)의 영향(影響) (Changes of Activities of Rabbit Pulmonary Surfactant Incubated at $37^{\circ}C$, and effect of X-Irradiation in Vitro)

  • 김형규;주영은
    • The Korean Journal of Physiology
    • /
    • 제5권2호
    • /
    • pp.63-70
    • /
    • 1971
  • In an attempt to understand the possible effects of temperature and X-irradiation on the activities of surfactant in rabbits, the pulmonary surfactant from the rabbit was subjected to the incubation at $37^{\circ}C$ and X-irradiation with 900r in vitro, and activities of surfactant were measured at 10, 30, 60, and 90 minutes. Tension-area diagram of the lung extract was recorded automatically by the modified Langmuir-wilhelmy balance with a synchronized recording system designed in this Department. A comparison was made with the normal and the following results were obtained. 1) The maximal surface tension, minimal surface tension, width of the tension area diagram at the surface area of 40% and stability index of the normal rabbit lung extract were $31.6{\pm}3.11\;dynes/cm,\;8.2{\pm}0.56\;dynes/cm,\;21.4{\pm}4.40\;dynes/cm\;and\;1.12{\pm}0.22$,respectively. 2) In the $37^{\circ}C$ incubation group, maximal surface tension was similar to the normal value, while minimal surface tension was significantly lower and stability infer was markedly higher than the normal. 3) In the group where X-irradiation of 900r in vitro was applied, maximal surface tension did not differ greatly with the normal or the $37^{\circ}C$ incubation group. The minimal surface tension was significantly lower than the normal but comparing with the $37^{\circ}C$ incubation group, some decrease in minimal surface tension was noted. The width of the tension·area diagram at 40% and stability index in the irradiated group were significantly higher than the normal but a tendency of increase was noted comparing with the $37^{\circ}C$ incubation group.

  • PDF

Effectiveness of Minimal Quantity Lubrication in Machining Processes

  • Suda, S.;Yokota, H.;Inasaki, I.;Wakabayashi, T.
    • 한국윤활학회:학술대회논문집
    • /
    • 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
    • /
    • pp.309-310
    • /
    • 2002
  • A minimal quantity lubrication (MQL) machining is able to achieve both functions of cooling and lubrication with an extremely low quantity of a cutting fluid and a large amount of air blow. Using a biodegradable ester oil, turning tests were carried out to evaluate the effectiveness of the MQL system. It was found that the performance of MQL cutting was equivalent to, or better than, that of conventional cutting, because the MQL system tends to prevent the heat damage of the tool tip and, if an effective lubricant such as a particular polyol ester is applied to the system, it can avoid the extensive transfer of workpiece materials on to the tool surface.

  • PDF

In Vitro X선조사(線照射)가 가토폐포표면(家兎肺胞表面) 활성물질(活性物質)에 미치는 영향(影響) (Effect of X-Irradiation in Vitro on the Pulmonary Surfactant in Rabbits)

  • 조중환;주영은
    • The Korean Journal of Physiology
    • /
    • 제5권1호
    • /
    • pp.51-58
    • /
    • 1971
  • In an attempt to further clarify the effect of X·irradiation on the activity of surfactant in rabbits, X-ray in dose of 900r was irradiated to the lung tissues of rabbits in vitro. Tension-area diagram of the lung extract was recorded automatically by a modified Langmuir-Wilhelmy balance with a synchronized recording system designed in this department. The surface tension of the lung extract was measured at 1,3,5,24 and 48 hours post-irradiation, and the results were compared with the non·irradiated normal group. The result$ thus obtained are summarized as follows: I The maximal surface tension, minimal surface tension, width of the tension·area diagram at the surface area of 40% in the lung extract and stability index of the normal rabbit long extract were 40.73 dynes/cm, 8.96 dynes/cm, 20.71 dynes/cm and 1.28, respectively. II. When 900r of X-ray was irradiated to the lung in vitro, 1) The maximal and minimal surface tensions did not differ noticeably from the normal at 1,3, and 5 post-irradiation hours, but the minimal surface tension increased significantly at 24 and 48 hours Post-irradiation. 2) The width of the tension area at the surface area of 40% showed a tendency of decrease throughout the experiment. 3) The stability index showed no significant change at 1,3 and 5 post-irradiation hours,but at 24 and 48 hours post-irradiation a significant decrease was observed comparing with the control. III. Activity of surfactant was significantly depressed by X·irradiation in vitro especially at 24 and 48 hours post-irradiation.

  • PDF

Constructing Nonlinear Sliding Surface for Spacecraft Attitude Control Problems

  • Cheon, Yee-Jin
    • 제어로봇시스템학회:학술대회논문집
    • /
    • 제어로봇시스템학회 1999년도 제14차 학술회의논문집
    • /
    • pp.41-44
    • /
    • 1999
  • Nonlinear sliding surface design in variable structure systems for spacecraft attitude control problems is studied. A robustness analysis is performed for regular form of system, and calculation of actuator bandwidth is presented by reviewing sliding surface dynamics. To achieve non-singular attitude description and minimal parameterization, spacecraft attitude control problems are considered based on modified Rodrigues parameters(MRP). It is shown that the derived controller ensures the sliding motion in pre-determined region irrespective of unmodeled effects and disturbances.

  • PDF

단회(單回) 및 분획(分劃) X선(線) 흉부(胸部) 조사(照射)가 가토(家兎) 폐포(肺胞) 표면활성(表面活性) 물질(物質)에 미치는 영향(影響) (Effect of Single or Fractionated X-Irradiation on the Pulmonary Surfactant in Rabbits)

  • 김준;주영은
    • The Korean Journal of Physiology
    • /
    • 제4권2호
    • /
    • pp.53-60
    • /
    • 1970
  • In an attempt to clarity the effect of X-irradiation on the activity of surfactant in rabbits, and also to observe the possible difference when the irradiation was made in single or fractionated dose, X-ray in dose of 900 r was irradiated to rabbits either in single or fractionated dose of 300 r each day for three day, Tension-area diagram of lung extract was recorded automatically by a modified Langmuir-Wilhelmy balance with a synchronized recording system designed in this department. The surface tension of lung extract was measured at 1,3,5,24, and 48 hours post-irradiation, and the results were compared with the non-irradiated normal group. The result obtained are summerized as follows: 1) The maximal surface tension, minimal surface tension, width of the tension-area diagram at the surface area of 40% in lung extract, and stability index of the normal rabbit lung extracts were 40.73 dynes/cm, 8.96 dynes/cm. 20.71 dynes/cm, and 1.28 respectively. 2) Activity of surfactant was significantly depressed by X-irradiation, and the pattern of depression was more prominent in the single irradiation group than in the fractionated group. 3) It was found that the changes of the width of the tension-area diagram at the surface area of 40% in lung extract and stability indices corresponded well with that of the maximal or minimal surface tension.

  • PDF

레이저클래딩 공정 모니터링 시스템 개발 (I) - 최적공정변수 추출 (Development of A Laser Cladding Process Monitoring System (I) -Extraction of optimal process variables)

  • 오기석;윤길상;조명우;김문기
    • 한국정밀공학회:학술대회논문집
    • /
    • 한국정밀공학회 2000년도 추계학술대회 논문집
    • /
    • pp.89-92
    • /
    • 2000
  • Laser claddmg 1s thc deposition of material on the surface of a part or workpiece. Cladding of metals produces a 100% dense metallurgically-bonded coating with minimal dilution for enhanced corrosion, abrasion and wear resistance. Despite of minimal heat Input and reduced processing time, cladding quality 1s affected by various process condition such as laser power and feed rate. Therefore, it is necessary to develop the momtoring and control methods of laser cladding process for the best cladding quality. In this paper, laser cladding monitoring system using CCD camera for measuring cladding pool shape, and photo-diode sensor for detecting optical signal emitted from the cladding front is introduced The variables extracted using this system can be apphed to control the laser cladding system to achieve the best claddmg results..

  • PDF

공간 가상 디자인을 위한 다해상도 곡면트리밍을 이용한 넙스곡면 조각효과 렌더링 (NURBS Surface Rendering of Sculpting Effect Using Multiresolution Surface Trimming for Spatial Virtual Design)

  • 권정훈;김희준;채영호
    • 한국CDE학회논문집
    • /
    • 제11권6호
    • /
    • pp.403-411
    • /
    • 2006
  • NURBS surfaces have been widely used in engineering design since it can create a smooth surface using minimal numbers of data. But deformation of the surfaces is quite difficult especially for the detailed modification. Also, NURBS surface deformation processes need many inputs, and it is not easy to be implemented in 3D virtual system. In this paper, both the surface trimming and multi-resolution surface are used for the detailed sculpting including sharp edges of NURBS surface. QuadTree is used to separate cleanly the target surface with the surface for sculpting effect. Simple user strokes are also used for the sculpting target curves and GOMS(Goals, Operators, Methods, Selection Rules) model is applied to verify the efficiency of the proposed sculpting process.

고체 내부의 구조적 변화를 위한 Laser Pulse의 설계 (Designing Laser Pulses for Manipulating the Interior Structure of Solids)

  • 김영식
    • 대한화학회지
    • /
    • 제39권1호
    • /
    • pp.14-22
    • /
    • 1995
  • 주어진 시간에 금속 고체 내부의 목표 부위에 탄성에너지를 집중시킬 수 있도록 표면에 가해주는 최적의 레이저 pulse의 형태를 디자인 하는 문제에 관하여 연구하였다. 금속고체 표면에 레이저를 쪼여주면 흡수된 광에너지가 열로 바뀌어 열팽창에 의하여 종파와 횡파가 고체 내부로 전파된다. 최소의 레이저의 세기를 사용하고 다른 부위에 영향을 최소화하면서 목표 부위에 원하는 에너지를 집중시킬 수 있는 최적의 레이저 펄스의 형태를 공액 변화 방법과 반 공간 Green 함수를 이용한 유한 요소법으로 조사하였다. 최적의 레이저 펄스로부터 원하는 시간에 목표 부위에 탄성에너지를 집중시키는 것을 보여주었고 또한 대부분의 에너지가 방향성이 큰 횡파로부터 온다는 것을 알았다.

  • PDF