• Steel and Composite Structures
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• 제31권3호
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• pp.303-317
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• 2019

This paper presents a finite element model for predicting the behaviour of high-strength steel bolted beam-to-column joints under monotonic loading. The developed numerical model considers the effects of material nonlinearities and geometric nonlinearities. The accuracy of the developed model is examined by comparing the predicted results with independent experimental results. It is demonstrated that the proposed model accurately predicts the ultimate flexural resistances and moment-rotation curves for high-strength steel bolted beam-to-column joints. Mechanical performance of three joint configurations with various design details is examined. A parametric study is carried out to investigate the effects of key design parameters on the behaviour of bolted beam-to-column joints with double-extended endplates. The plastic flexural capacities of the beam-to-column joints from the experimental programme and numerical analysis are compared with the current codes of practice. It is found that the initial stiffness and plastic flexural resistance of the high-strength steel beam-to-column joints are overestimated. Proper modifications need to be conducted to ensure the current analytical method can be safely used for the bolted beam-to-column joints with high-performance materials.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.484-492
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• 2023

Time-to-digital converters (TDCs) based on the tapped delay line (TDL) architecture have been widely used in various applications requiring a precise time measurement. However, the poor uniformity of the propagation delays in the TDL implemented on FPGA leads to bubble error and large nonlinearity of the TDC. The purpose of this study was to develop an advanced TDC architecture capable of minimizing the bubble errors and improving the linearity. To remove the bubble errors, the decimated delay line (DDL) architecture was implemented on the UltraScale + FPGA; meanwhile, to improve the linearity of the TDC, a histogram uniformization (HU) and multi-chain TDL (MCT) methods were developed and implemented on the FPGA. The integral nonlinearities (INLs) and differential nonlinearities (DNLs) of the plain TDCs with the 'HU method' (HU TDC) and with 'both HU and MCT methods' (HU-MCT TDC) were measured and compared to those of the TDC with 'DDL alone' (plain TDC). The linearity of HU-MCT TDC were superior to those of the plain TDC and HU TDC. The experiment results indicated that HU-MCT TDC developed in this study was useful for improving the linearity of the TDC, which allowed for high timing resolution to be achieved.

• 대한토목학회논문집
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• 제6권2호
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• pp.67-75
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• 1986

본 연구에서는 파랑의 에너지 및 에너지 수송과 관련된 변량들의 계산과 그 비선형효과의 분석을 능률적으로 수행하기 위하여 설계파에 대한 비선형 흐름함수파이론을 도입한다. 흐름함수파이론은 비대칭성 파형을 갖는 실측파와 이론적인 대칭 파형을 갖는 설계파. 두 경우 모두에 사용할 수 있는 이론으로 Dean에 의해 처음 창안되었다. 후에 Dalrymple이 특정한 파고의 조건과 0의 평균해수면 변위의 조건을 만족하도록 하는 두 라그란지 승수를 사용하여 기존의 수치계산 과정을 개량함으로써 수치계산이 좀 더 효율적으로 수행되도록 하였다. 그리고 흐름함수의 계수 (Stream function coeffiicient)들은 본 연구를 위해 개량한 Marquardt algorithm을 사용하여 수치계산된다. 본 연구의 결과로서 평균 위치에너지와 평균 운동에너지, 평균 전에너지의 비선형효과는$L^*/L_O$의 감소와 $H/H_B$의 증가에 한결같이 증가하여 흐름함수이론과 비교하여 선형파이론이 항상 과대평가된다. 군속도와 파장의 비선형효과는 $H/H_B$의 증가에 한결같이 증가하되 선형파이론이 항상 과소평가된다. 마지막으로 평균 전에너지 Flux의 비선형효과는 천해파(shallow-water waves)에 대해서는 선형파이론이 과대평가되고 심해파 (deep-water waves)에 대해서는 선행파이론이 과소평가되는 양면성을 지닌다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.249-252
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• 1997

In this paper the sway-control problem of a container crane is investigated in the perspective of controlling an underactuated mechanical system. For fast loading/unloading of containers from the ship, quick suppression of the remaining swing motion of the container at the end of each trolley stroke is crucial. Known nonlinearities are fully incorporated by feedback linearization. Robustness is enhanced by variable structure control. Compared with the linear LQ control, much better performance can be obtained.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2551-2554
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• 2003

In this paper, we describe the nonlinear character for a friction control. The nonlinear character of friction control is inherent in mechanical system, which has gained more and more interest. The modeling and compensation of nonlinear friction are difficult tasks for precise motion control. This paper is performance evaluation of nonlinearities and mechanical compliance exists together with friction control system.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.17-24
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• 2004

This paper established the dynamic model of a flexible Timoshenko beam with geometrical nonlinearities subject to large overall motions by using the finite element method. The equations of motion are derived by using Hamilton principle based on expressing the kinetic and potential energies of the flexible beam in terms of generalized coordinates. The nonlinear constraint equations are adjoined to the system equations of motion by using Lagrange multipliers.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1611-1616
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• 1991

A high power stewart platform is designed and manufactured to simulate the 6 degrees of freedom motion of moving vehicle. This paper describes the design of such a motion system including kinematic and kinetic analysis, real time servo control mechanical and hydraulic system configuration, and techniques of regeneration of test records. Discussions are also presented for an algorithm called remote parameter control, which has been developed to compensate the dynamic delay of the electro-hydraulic servo actuators and the nonlinearities of stewart platform.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 봄 학술발표회 논문집
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• pp.49-53
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• 1991

The finite element method is applied to analyze the complicated behavior of reinforced concrete beams. The nonlineartiy in concrete and reinforcement steel has been considered. The effects of bond-slip and aggregate interlock have been also taken into account. It is found that realistic analysis requires those major nonlinearities to be included in the analysis.

• 대한수학회논문집
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• 제29권1호
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• pp.37-50
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• 2014

Using variational methods, we prove some results on the nonexistence and multiplicity of weak solutions for a class of semilinear elliptic systems of two equations involving Grushin type operators with sign-changing nonlinearities. We also shows that the similar results can be obtained for systems of m equations, where m is arbitrary.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.189-194
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• 1993

This paper presents an ARW(Anti-Reset Windup) method for discrete-time control systems with saturation nonlinearites. The method is motivated by the concept of the equilibrium point. The design parameters of the ARW scheme is explicitly derived by minimizing a reasonable performance index. The proposed method is closely related with the singular perturbed theory. The proposed method is applicable to any open-loop stable plants with saturation nonlinearities whose controllers are determined a priori by some design technique.