• 대한기계학회논문집B
• /
• 제28권10호
• /
• pp.1231-1237
• /
• 2004

Determination of geometric design parameters of a second-throat type annual supersonic ejector is described. Tested geometric parameters were primary nozzle area ratio, cross-sectional area of second-throat, L/D ratio of second-throat and primary flow injection angle. Varying these four geometric parameters, we build a test matrix made of 81 test conditions, and experimental apparatus was fabricated to accommodate them. For each test condition, the stagnation pressure of primary flow and the static pressure of the secondary flow were measured simultaneously along with their transition to steady operation and finally to unstarting condition. Comparing the performance curve of every case focused on starting pressure, the unstarting pressure and the minimum secondary pressure, we could derive correlations that the parameters have on the performance of the ejector and presented the optimal design method of the ejector. Additional experiments were carried out to find effects of temperature and mass flow rate of the secondary flow.

• 한국강구조학회 논문집
• /
• 제13권2호
• /
• pp.153-162
• /
• 2001

본 논문에서는 실용적인 고등해석을 이용한 3차원 강뼈대구조물의 직접설계방법을 제시하였다. 고등해석을 이용한 직접설계법에서는 해석시에 구조시스템과 그에 속한 부재의 강도와 인정을 직접 고려함으로서, 해석후 개별부재의 강도검토가 필요없는 설계방법이다. 고등해석은 기하학적 비선형과 재료적 비선형을 고려한다. 기하학적 비선형은 안정함수를 사용함으로서 고려하였다. 재료적 비선형은 CRC 접선 탄성계수와 포물선 함수를 사용함으로서 고려하였다. 제안한 해석방법에 의하여 예측된 하중-변위는 다른 해석기법의 결과들과 잘 일치하였다. 또한, 22층 강뼈대구조물에 대하여 설계예제를 수행하였다. 본 설계예제를 통하여 제안한 방법이 매우 실용적인 방법임을 알 수 있었다.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제7권1호
• /
• pp.142-156
• /
• 2015

A new method for ship Inner Shell optimization, which is called Parametric Inner Shell Optimization Method (PISOM), is presented in this paper in order to improve both hull performance and design efficiency of transport ship. The foundation of PISOM is the parametric Inner Shell Plate (ISP) model, which is a fully-associative model driven by dimensions. A method to create parametric ISP model is proposed, including geometric primitives, geometric constraints, geometric constraint solving etc. The standard optimization procedure of ship ISP optimization based on parametric ISP model is put forward, and an efficient optimization approach for typical transport ship is developed based on this procedure. This approach takes the section area of ISP and the other dominant parameters as variables, while all the design requirements such as propeller immersion, fore bottom wave slap, bridge visibility, longitudinal strength etc, are made constraints. The optimization objective is maximum volume of cargo oil tanker/cargo hold, and the genetic algorithm is used to solve this optimization model. This method is applied to the optimization of a product oil tanker and a bulk carrier, and it is proved to be effective, highly efficient, and engineering practical.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 춘계학술대회 논문집
• /
• pp.1583-1586
• /
• 2005

Grinding process is different from other machining processes such as turning, milling and drilling because the cutting edges in a grinding wheel doesn't have uniformity and acts differently on the workpiece at each grinding. This study focus on predicting the geometric error produced during surface grinding and selecting an optimal grinding condition to reduce the geometric error. To achieve the aim, the Taguchi design of experiments was applied and the S/N ratios of each grinding was used for evaluating the results. The predicted quantities by the S/N ratios were compared with the experimental results.

• 대한기계학회논문집
• /
• 제17권10호
• /
• pp.2634-2645
• /
• 1993

Dome structures of pressure vessels subjected to internal pressure are usually analyzed by linear elastic theory assuming small deformation. Geometric and material nonlinear behaviors appear in actual dome structures because of large deformation and loads exceeding yield strength. In this paper, linear and nonlinear analyses were performed for various hemispherical and torispherical domes to check the effects of geometric and material nonliearity on the stress and displacement by the finite element method. The effect of the geometric nonlinearity decreased the stress levels a lot for very thin general torispherical domes, which enables more realistic and effective design. The material nonlinear effects are negligible for hemispherical and optimum torispherical domes, and those are large for most of the general torispherical domes.

• 대한조선학회논문집
• /
• 제43권4호
• /
• pp.521-528
• /
• 2006

In this study, we developed a new systematic approach to assess the influence of geometric parameter change on the horizontal and vertical stability indices. To do this, three phases of sensitivity analyses were carried out. First, typical geometric parameters were defined and their effects on hydrodynamic coefficients were assessed by the Sensitivity Analysis (SA) of the indirect method. Second, the effects of hydrodynamic coefficients on the stability indices were calculated. Finally, the sensitivities of geometric parameters on the stability indices were obtained by merging the outputs of two phases using chain rule. The developed approach cau contribute to a submarine designer to determine geometric parameters satisfying pre-requirements about stability systematically.

• Structural Engineering and Mechanics
• /
• 제24권1호
• /
• pp.63-89
• /
• 2006

Geometric imperfections have an important influence on the buckling response of structural components. This paper describes an experimental technique for determining imperfections in long (5.7 m) structural members using a series of overlapping measurements. Measurements were performed on 31 austenitic stainless steel sections formed from three different production routes: hot-rolling, cold-rolling and press-braking. Spectral analysis was carried out on the imperfections to obtain information on the periodic nature of the profiles. Two series were used to model the profile firstly the orthogonal cosine and sine functions in a classic Fourier transform and secondly a half sine series. Results were compared to the relevant tolerance standards. Simple predictive tools for both local and global imperfections have been developed to enable representative geometric imperfections to be incorporated into numerical models and design methods.

• 건축역사연구
• /
• 제3권2호
• /
• pp.125-141
• /
• 1994

Alois Riegl's aesthetic theory of visual perception provided one of important conceptual backgrounds for Vienna Art Nouveau architecture. Riegls theory of visual perception consists of geometric style and two-dimensional transformation. Riegl's theory of geometric style is based on the modern aesthetic theory of abstraction, which says that the artistic perfection can be obtained not from a direct imitation of natural objects, but from an abstract transformation of them. Riegl's theory of two-dimensional transformation, on the other hand, aims at obtaining artistic perfection by disintegrating volumetric conditions of natural things into planes and combining the planes thus obtained into another new world of art. These two theories of Alois Rigl's provided an important aesthetical background for the design strategy of 'abstract ornamentaion of two-dimension' in Vienna Art Nouveau architecture. This paper is to review the basic concept of Alois Rigl's theory of geometric style and two-dimensional transformation.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2001년도 ICCAS
• /
• pp.125.5-125
• /
• 2001

Until now, many guidance laws have been developed. They mainly used the classical tail-pursuit guidance method based on geometric angle information, the proportional navigation method based on the line of sight(LOS) rate, and the optimal guidance law based on optimal control theorem. In the augmented guidance law, target acceleration information and autopilot characteristics are added the guidance command. In this study, new guidance laws considering geometric angle are proposed. Two guidance laws are developed for the midcourse guidance law, and a guidance law is developed for the terminal guidance respectively. The proposed guidance laws utilize the LOS rate and the geometric angle information simultaneously. In the midcourse guidance, the guidance command is ...

• 대한기계학회논문집A
• /
• 제24권10호
• /
• pp.2451-2460
• /
• 2000

In order to minimize straightness error of deflected shaft, a geometric adaptive straightness controller system is studied. A multi-step straightening and a three-point bending process have been developed for the geometric adaptive straightness controller. Load-deflection relationship, on-line identification of variations of material properties, on-line springback prediction, and real-time hydraulic control methodology are studied for the three-point bending process. By deflection pattern analysis and fuzzy self-learning method in the multi-step straightening process, a straightening point and direction, desired permanent deflection and supporting condition are determined. An automatic straightening machine has been fabricated for rack bars by using the developed ideas. Validity of the proposed system is verified through experiments.