• Journal of Welding and Joining
• /
• 제12권1호
• /
• pp.59-72
• /
• 1994

This paper presents an on-line quality monitoring and control method to obtain a uniform weld quality in gas metal arc welding (GMAW) processes. The geometrical parameters of the weld pool such as the top bead width and the penetration depth plus half back width are utilized to assess the integrity of the weld quality. Since a good quality weld is characterized by a relatively high depth-to-width ratio in its dimensions, the second geometrical parameter is regulated to a desired one. The monitoring variables are the surface temperatures measured at various points on the top surface of the weldment which are strongly related to the formation of the weld pool The relationship between the measured temperatures and the weld pool size is implemented on the multilayer perceptrons which are powerful for realization of complex mapping characteristics through training by samples. For on-line quality monitoring and control, it is prerequisite to estimate the weld pool sizes in the region of transient states. For this purpose, the time history of the surface temperatures is used as the input to the neural estimator. The control purpose is to obtain a uniform weld quality. In this research, the weld pool size is directly regulated to a desired one. The proposed controller is composed of a neural pool size estimator, a neural feedforward controller and a conventional feedback controller. The pool size estimator predicts the weld pool size under growing. The feedforward controller compensates for the nonlinear characteristics of the welding process. A series of simulation studies shows that the proposed control method improves the overall system response in the presence of changes in torch travel speed during GMA welding and guarantees the uniform weld quality.

• 토지주택연구
• /
• 제2권4호
• /
• pp.471-477
• /
• 2011

This paper will describe the experimental results on the shear behaviors of reinforced concrete (RC) beam with recycled coarse aggregate (RCA). The primary objective of this research is to evaluate the influences of different RCA replacement percentage (i.e, 0%, 30%, 60%, and 100%) on the shear performance of reinforced concrete beams without shear reinforcement. Eight large-scale RC beams without shear reinforcement were manufactured and tested to shear failure. All had a rectangular cross-section with 400mm width ${\times}$ 600mm depth and 6000mm length, and were tested with a shear span-to-depth of 5.1. The results showed that the deflection and shear strength were little affected by the different RCA replacement percentage. Actual shear strength of each RCA beam was compared with the shear strength predicted using the provisions of ACI 318 code and Zsutty'e equation for shear design of RC beams. ACI 318 code predicted the shear strength of RCA reinforced concrete beams well.

• 콘크리트학회논문집
• /
• 제15권5호
• /
• pp.697-704
• /
• 2003

본 연구의 목적은 장방형 개구부를 갖는 철근콘크리트 깊은 보에서 개구부 폭, 깊이 및 위치변화와 부재의 전단거동의 관계를 파악하고, 최대내력을 예측하기 위한 모델을 제시하는데 있다. 주요 변수로는 콘크리트 강도, 전단경간비, 개구부 폭, 깊이 및 위치 등이다. 시험체는 모두 25개이며 2점 대칭가력하였다. 실험결과로부터 개구부를 갖는 깊은 보의 전단거동은 개구부 크기와 전단경간비에 의해 가장 큰 영향을 받았으며, 이들이 증가할수록 이들이 증가 할 수록 콘크리트 설계기준은 불안전측에 있었다. 따라서 개구부 상$.$하 스트럿 작용과 주철근의 타이작용을 고려하여 개구부 효과를 반영한 깊은 보의 전단내력을 적절히 평가할 수 있는 모델을 제시하였다.

• Geomechanics and Engineering
• /
• 제13권5호
• /
• pp.825-844
• /
• 2017

This study aimed to find out the pullout capacity of inclined strip anchor plate embedded in anisotropic and nonhomogeneous fully saturated cohesive soil in undrained condition. The ultimate pullout load has been found out by using numerical lower bound finite element analysis with linear programming. The undrained pullout capacity of anchor plate of width B is determined for different embedment ratios (H/B) varying from 3 to 7 and various inclination of anchor plates ranging from $0^{\circ}$ to $90^{\circ}$ with an interval of $15^{\circ}$. In case of anisotropic fully saturated clay the variation of cohesion with direction has been considered by varying the ratio of the cohesion along vertical direction ($c_v$) to the cohesion along horizontal direction ($c_h$). In case of nonhomogeneous clay the cohesion of the undrained clay has been considered to be increased with depth below ground surface keeping $c_v/c_h=1$. The results are presented in terms of pullout capacity factor ($F_{c0}=p_u/c_H$) where $p_u$ is the ultimate pullout stress along the anchor plate at failure and $c_H$ is the cohesion in horizontal direction at the level of the middle point of the anchor plate. It is observed that the pullout capacity factor increases with an increase in anisotropic cohesion ratio ($c_v/c_h$) whereas the pullout capacity factor decreases with an increase in undrained cohesion of the soil with depth.

• Ecology and Resilient Infrastructure
• /
• 제6권4호
• /
• pp.314-327
• /
• 2019

본 연구에서는 본 연구에서는 2차원 수치모형을 적용하여 수제설치에 의한 흐름특성을 분석하고, 하도의 안정성을 평가할 수 있는 평가방법을 개발하였다. 2차원 수치모형의 결과는 관측자료와 1차원 모형의 결과와 비교하여, 그 적용성을 검토하였다. 평가 지표는 대상구간의 수리 및 지형학적 특성을 고려하여 하폭 대 수심의 비, 사행도, 하상경사, 하안 부근에서 유속, Shields number 등 5가지 항목으로 구성하였다. 낙동강의 달성보~강정고령보 구간의 수제 설치 전·후에 대해 평가지표를 적용하여 하도 안정성을 평가하였다. 평가 항목 중에서 하폭 대 수심의 비, 사행도, 하상경사는 하도의 안정성에 영향을 크게 주지 않는 것으로 평가되었다. 양안 부근에서 유속과 유사의 이동 특성을 결정하는 무차원 소류력인 Shields Number는 수제에 의하여 영향을 받으며, 수제의 수가 증가할수록 평가 값은 감소하고, 하안의 안정성은 증가하였다.

• Journal of Animal Science and Technology
• /
• 제60권6호
• /
• pp.10.1-10.6
• /
• 2018

Background: Stress causes inflammation that impairs intestinal barrier function. Dietary spray-dried plasma (SDP) has recognized anti-inflammatory effects and improvement of gut barrier function. Therefore, the purpose of this study was to investigate the effects of dietary SDP on intestinal morphology of mated female mice under stress condition. Results: Villus height, width, and area of small intestines were low on gestation day (GD) 3 or 4 under stress conditions, and higher later (Time, P < 0.05). Crypt depth of colon was low on GD 4 and higher later (Time, P < 0.05). Meanwhile, the SDP treatments improved (P < 0.05) intestinal morphology, indicated by increased villus height, villus width, villus area, and ratio between villus height and crypt depth of small intestines and crypt depth of colon, and by decreased crypt depth of small intestines, compared with the control diet. The SDP treatments also increased (P < 0.05) the number of goblet cells in intestines compared with the control diet. There were no differences between different levels of SDP. Conclusion: Dietary SDP improves intestinal morphology of mated female mice under stress condition.

• 지질공학
• /
• 제17권4호
• /
• pp.601-613
• /
• 2007

연약지반에 보강토옹벽을 시공 시 거동에 영향을 주는 인자로 기본적인 물성뿐만 아니라 보강토옹벽에 의한 하중증가와 압밀기간, 간극수압 등의 영향을 받는 것으로 보고되고 있다. 본 연구에서는 보강토옹벽과 연약지반의 거동해석에 지반해석 프로그램인 SAGE CRISP를 이용하여 수행하였다. 첫 번째로 보강토옹벽의 과도변위를 개선하기 위한 치환공법의 거동 개선 효과를 검토하였으며, 두 번째로 치환공법을 적용 후 보강토옹벽의 배면에 보강재 수직설치간격이 지반의 거동에 미치는 영향을 비교 분석하였다. 마지막으로 치환공법을 적용 시 적정 치환 폭과 깊이를 제안하고자 하였다. 치환공법이 보강토옹벽의 거동 개선에 상당한 효과가 있음을 알 수 있었으며, 보강재 수직설치간격은 옹벽상단의 수평변위 개선효과가 있는 것으로 나타났으나 하단의 수평변위와 옹벽배면의 수직변위 개선효과는 미소한 것으로 나타났다. 또한 치환폭의 증가에 따른 수평 수직변 개선효과는 크지 않은 것으로 나타나 치환폭의 증가는 불필요함을 알 수 있었으며, 적정 치환깊이는 연약층의 두께에 대한 옹벽높이의 비(H/T)에 따라 옹벽높이에 대한 치환깊이의 비(D/H)로 제안하였다.

• 한국기계가공학회지
• /
• 제12권4호
• /
• pp.40-46
• /
• 2013

When impeller machining needs to be machined over a length in order to avoid interference with neighboring surfaces between material and tool, there are no databases about cutting condition according to tool slenderness ratio. So selection and machining of cutting condition depends on expert's experience. Therefore, the purpose of this paper is deciding cutting condition in roughing and finishing process of impeller according to slenderness ratio of AL7075's end-mill that is the most commonly used for impeller. We have tested for about relation between Slenderness ration and fluctuation width of the cutting force, surface roughness and depth of cut ratio to observe cutting characteristics according to slenderness ratio. The experiments of cutting characteristics and processing criteria are compared with AL5052 which is existing information.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
• /
• pp.353-362
• /
• 2000

Herringbone groove journal bearing (HGJB) is developed to improve the static and dynamic performances of hydrodynamic journal bearing. In this study, static and dynamic compressible isothermal lubrication problems are analyzed by the finite element method together with the Newton-Raphson iterative procedure. This analysis is introduced for prediction of the static and dynamic characteristics of air lubricated HGJB for various bearing configurations. The bearing load characteristics and dynamic characteristics are dependent on geometric parameters such as asymmetric ratio, groove depth ratio, groove width ratio and groove angle.

• Journal of Welding and Joining
• /
• 제14권6호
• /
• pp.81-92
• /
• 1996

This study is to compare the weldability of Zircaloy-4 end cap of nuclear fuel pin using by GTA and Nd :YAG LB. The welding parameters which affect bead width and penetration depth have been investigated. The effect of joint geometry of end cap for GTAW and LBW has been studied and optimum conditions of Zircaloy-4 endcap welding have been found. Microstructures and microhardness of GTA and LB welded zones have been also compared.