• Proceedings of the Korea Concrete Institute Conference
• /
• 2010.05a
• /
• pp.89-90
• /
• 2010

Three post-tensioned lightweight concrete beams were tested to examine the effect of the reinforcement index on the unbonded tendon stress at ultimate strength of the beams. The reinforcement index selected for main variables were 0.06, 0.15, 0.30. Test results showed that the stress of the unbonded tendons in the ultimate strength of the post-tensioned lightweight concrete beams can be conservatively evaluated using the empirical equations specified in ACI 318-08.

• 제어로봇시스템학회:학술대회논문집
• /
• 1992.10b
• /
• pp.229-234
• /
• 1992

This paper presents a compensator design method for multivariable feedback control systems with saturating actuators based on the concept of the equilibrium point. Am explicit expression for the compensation matrix of the general anti-reset windup(ARW) scheme is derived by minimizing the distances between the equilibrium points. The resulting dynamics of the compensated controller exhibits the reduced model form of the unsaturated system which can be obtained by the singular perturbational method. The proposed method is applicable to any open-loop stable plants with saturating actuators whose controllers are determined by some design technique. An example is given to show the effectiveness of the proposed method.

• Proceedings of the IEEK Conference
• /
• 2003.07a
• /
• pp.414-417
• /
• 2003

In this paper, a performance of Bluetooth piconet is analyzed. Average cycle time, average waiting time, average transfer delay and average queue length are used for measure of performance (MOP). Simple round robin (RR) scheduling policy with exhaustive service is used for the analysis. Packet loss is considered because of noise environments of wireless communication. Numerical results have been presented. Simulation is performed to validate the correctness of analysis.y and its maximum operating frequency is 800MHz.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.457-462
• /
• 2003

It studies the non-structural crack factors that are produced in Steel Box Girder Bridge concrete floor plate using analytical method. It mainly studies humidity and design standard of concrete strength. It used MIDAS CIVIL Ver 5.4.0, a general structure analysis program that applies drying shrinkage rate of domestic road bridge design standard and standard value of creep coefficient, CEF-FIP standard equation and ACI standard equation from the aspect of creep, drying shrinkage and hydration heat to see the effect of the two factors on concrete crack and found the following result. The analytical results of this study showed that the initial stress, which was obtained by ACI standard, exceeds the allowable tensile stress between 5 to 18 days. This result means that even if a bridge is designed and constructed according to design standard, the bridge can have cracks due to various variables such as drying shrinkage, hydration heat and creep that produce stress in slab.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.878-883
• /
• 2003

To modify some problems of ACI shear provisions, ultimate shear strength equation considering size effect and arch action to compute shear strength in high-strength concrete beams without stirrups is presented in this research. Three basic equations, namely size reduction factor, rho factor, and arch action factor, are derived from crack band model of fracture mechanics, analysis of previous some shear equations for longitudinal reinforcement ratio, and concrete strut described as linear function in deep beams. Constants of basic equations are determined using statistical analysis of previous shear testing data. To verify proposed shear equation for each variable, namely d, , ρ, f/sub c/' and aid, about 250 experimental data are used and proposed shear equation is compared with ACI 318-99 code, CEB-FIP Model code, Kim & Park's equation and Zsutty's equation. While proposed shear equation is simpler than other shear equations, it is shown to be economical predictions and reasonable safety margin. Hence proposed shear strength equation is expected to be applied to practice shear design.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.481-486
• /
• 2003

This paper presents experimental study on long-term behavior of RC and SRC columns. Shrinkage and creep tests were performed for two types of concrete used in manufacturing RC and SRC column specimens. Also, long-term tests under sustained load were carried out for RC and SRC column specimens. Shrinkage functions and creep coefficients to optimally fit the corresponding data were obtained from regression analysis and the regression results, ACI and CEB- FIP 90 model were applied to analyse long-term behvavior of RC and SRC column specimens. Creep coefficients calculated from test data were lower than those predicted by ACI and CEB-FIP 90 models. Long-term analysis results for RC and SRC column specimens using the regression results were relatively more accurate than those obtained using the existing models.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.925-930
• /
• 2003

Provisions for ACI 318-02 and NZS 3101 pertaining to shear design of shear walls evaluated the applicability of high-strength, concrete shear walls subjected to lateral loads. Results of 73 tests of reinforced concrete shear walls were reviewed. Evaluation of test results conducted in Korea, England, America, Japan, and Australia for low-aspect ratio walls indicates that the nominal unit shear strength($\phi$=1.0) calculated using the provisions of ACI and NZS does not represent the observed shear strength well. Based on the limited database considered in this study, a reasonable lower bound to the shear strength of high-strength concrete shear walls is found to be $\sqrt[0.4]{f_{cu}}$ MPa. Similar to that of normal strength concrete walls, the rate of increase of the measured shear strength with $$\rho$_n/ㆍf_y$ is less than 1.0. Therefore, the rate of increase of shear strength attributable to the web reinforcement in shear walls appears to be overestimated by the modified truss analogy.

• Proceedings of the KIEE Conference
• /
• 1997.11a
• /
• pp.675-678
• /
• 1997

In this research we continue the study of nuclear power plant steam generator's intelligent modeling. This model represents the input-output behavior and is a preliminary stage for intelligent control. Among many intelligent models available, we study neural network models that have been proven as universal function approximators. We select multilayer perceptrons, circular backpropagation networks, piecewise linearly trained networks and recurrent neural networks as the candidates for the steam generator's intelligent models. We take the input-output pairs from steam generator's reference model and train the neural network models. We validate trained neural network models as intelligent models of steam generator.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.428-429
• /
• 2008

In a previous paper, the distance relay algorithm for protecting of the underground power cable system was introduced. It effectively advance the errors using ACI(Advanced Computing Intelligence) technique. In this algorithm, the optimization was performed by fuzzy inference system and genetic algorithm. In this paper, hardware system based on ACI technique is introduced and tested by hardware test.

• Journal of the Korean Graphic Arts Communication Society
• /
• v.24 no.1
• /
• pp.35-44
• /
• 2006

본 연구에서는 PCB에 진공인쇄 방식이 적용된 스크린 인쇄방법을 이용하여 Pattern 및 Hole충전의 신뢰성을 향상시킬 수 있는 기술을 적용하였다. 새로운 dry process 기술인 직접회로 인쇄 기술은 일반적으로 사용되고 있는 wet process 중 도금, 에칭, 박리 등의 공정을 줄일 수 있어 제조원가, 공정 리드타임 감소, 폐기물 감소로 환경 친화적 공정이라고 할 수 있다. 직접회로 인쇄는 진공도 100 Pa, 인쇄압력 0.45 MPa, 인쇄 속도 30 mm/sec, 인쇄각도 85도, 스크린 마스크와 기판 사이의 Gap 2 mm에서 인쇄될 때 가장 좋은 결과를 보였다. 직접회로 인쇄에 사용된 인쇄기는 일반 PCB공정에서 사용되는 동일한 형태에 진공조건을 유지시킬 수 있도록 개선하여 사용하였다.