• Structural Engineering and Mechanics
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• 제90권5호
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• pp.447-458
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• 2024

This study investigated the influence of scale ratio and vertical load on the seismic performance of Puzuo joints in traditional Chinese timber structures. Three low-cyclic reversed loading tests were conducted on three scaled specimens of Bujian Puzuo in Yingxian Wooden Pagoda. This study focused on the deformation patterns and analyzed seismic performance under varying scale ratios and vertical loads. The results indicated that the slip and rotational deformations of Bujian Puzuo were the primary deformations. The scale of the specimen did not affect the layer where the maximum interlayer slip occurred, but it did decrease the proportion of slip deformation. Conversely, the reducing vertical load caused the layer with the maximum slippage and the position of the damaged Dou components to shift upward, and the proportion of slip deformation increased. When the vertical load was decreased by 3.7 times, the maximum horizontal bearing capacity under positive and negative loadings, initial stiffness, and energy dissipation of the specimen decreased by approximately 60%, 58.79%, 69.62%, and 57.93%, respectively. The horizontal bearing capacity under positive loading and energy dissipation of the specimen increased by 35.63% and 131.54%, when the specimen scale was doubled and the vertical load was increased by 15 times.

• 한국ITS학회 논문지
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• 제13권1호
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• pp.99-108
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• 2014

최근 들어, 차량 제어 기술의 집약체라 할 수 있는 자율 주행 차량에 관한 관심이 증대되고 있다. 특히, 자율 주행 차량의 안정적인 주행과 직결되는 자기 위치 인식 기술에 관한 연구가 꾸준히 진행되어져 왔으며, GPS가 갖는 한계점을 보완하기 위한 다양한 추측항법 기술이 소개되어져왔다. 하지만 기존의 추측항법들은 추가적으로 센서를 장착해야하는 단점과 차량 거동의 급격한 변화로 인하여 자기 위치 인식 정확도가 떨어진다는 단점을 가진다. 따라서 본 논문에서는 기존의 추측항법의 단점을 보완하기 위하여 대부분의 차량에 장착되어 있는 휠속 센서(Wheel Speed Sensor)를 활용하고, 휠속 센서에서 계측된 값을 토대로 타이어 슬립율(Slip ratio)을 추정하여 차량의 급격한 거동 변화에 대응하기 위한 새로운 개념의 슬립율 기반의 추측항법 알고리즘을 개발하였다. 기존의 추측항법 알고리즘과의 성능을 비교 평가하기 위해서 차량의 거동이 급격하게 변화하는 상황이 포함된 시뮬레이션 환경을 구성하여 그 결과를 비교하였다.

• KSTLE International Journal
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• 제7권2호
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• pp.27-34
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• 2006

Knudsen number is the ratio of molecular mean free path versus mm thickness and the criterion to determine the flow form. When its value is lower than 0.01, the flow can be assumed to has no slip boundary condition. And in the case that the value is between 0.01 and 10, then the flow has slip boundary condition at both the adjacent walls. The condition of the air flow between the rotating journal and top foil in the air foil bearing is determined by the rotating speed and load, and the Knudsen number is also varied by those values. Because the molecular mean free path is variable to the pressure and temperature, more exact formulation is necessary to understand and analyze the flow regime. In this study, the analysis considering Knudsen number formulated with those variables (pressure, temperature and mm thickness) was executed. The approximate value was examined using the equation to confirm whether the flow has the slip or no-slip boundary condition. From the analytic investigation, it was decided to range approximately 0.01 to 1.0 and the flow can be supposed to have the slip boundary condition. Under the condition of the slip flow, the static characteristics of the air foil bearing were examined using modified Reynolds equations. The results were compared with those considering no slip condition. It shows that the slip condition makes the flow decelerates and the load carrying capacity decreases compared with no slip condition. And as the bearing number and eccentricity ratio increase, the load carrying capacity also increased at both the cases. From this result, it can be supposed that the bearing torque also increases. In the analysis of the dynamic characteristics, the perturbed Knudsen number was taken into consideration. Because the Knudsen number is expressed as the terms of each variable, the perturbed equation can be simply derived. The results of both cases considering and not considering Knudsen number were compared each other. In the case of the direct terms of the stiffness and damping coefficients, the difference between both cases was little and increased as the bearing number and eccentricity ratio increased. And the cross terms have less or more differences.

• Steel and Composite Structures
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• 제51권5호
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• pp.529-543
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• 2024

The bonding efficacy of steel I-section embedded in metakaolin-fly ash-based geopolymer concrete (MK-FA-GC) was investigated in this study. Push-out tests were conducted on nine column specimens to evaluate the influence of compressive strength of concrete, embedded length of steel I-section, thickness of concrete cover, and stirrup ratio on the bond performance. Failure patterns, load-slip relationships, bond strength, and distribution of bond stress among the specimens were analyzed. The characteristic bond strength of geopolymer concrete (GC) increased with higher compressive strength, longer embedded steel section length, thicker concrete cover, and larger stirrup ratio. Empirical formulas for bond strength at the loading end were derived based on experimental data and a bond-slip constructive model for steel-reinforced MK-FA-GC was proposed. The calculated bond-slip curves showed good agreement with experimental results. Furthermore, numerical simulations using ABAQUS software were performed on column specimens by incorporating the suggested bond-slip relationship into connector elements to simulate the interface behavior between MK-FA-GC and the steel section. The simulation results showed a good correlation with the experimental findings.

• Steel and Composite Structures
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• 제36권5호
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• pp.493-506
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• 2020

The load-slip relationship of the shear connection is an important parameter in design and analysis of composite structures. In this paper, a load-slip curve prediction method of the shear connection based on the artificial neural networks (ANNs) is proposed. The factors which are significantly related to the structural and deformation performance of the connection are selected, and the shear stiffness of shear connections and the transverse coordinate slip value of the load-slip curve are taken as the input parameters of the network. Load values corresponding to the slip values are used as the output parameter. A twolayer hidden layer network with 15 nodes and 10 nodes is designed. The test data of two different forms of shear connections, the stud shear connection and the perforated shear connection with flange heads, are collected from the previous literatures, and the data of six specimens are selected as the two prediction data sets, while the data of other specimens are used to train the neural networks. Two trained networks are used to predict the load-slip curves of their corresponding prediction data sets, and the ratio method is used to study the proximity between the prediction loads and the test loads. Results show that the load-slip curves predicted by the networks agree well with the test curves.

• 대한기계학회논문집A
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• 제27권4호
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• pp.479-484
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• 2003

In this paper, film thickness and temperature distribution are measured in EHL point contact at high slip ratios. Infrared temperature mapping with two band pass fillers. proposed by Ausherman (1976). is used to measure temperature distribution. And the optical interferornetric method with two filters (red and green filters) is used to measure film thickness. Result of experiment showed that temperature rising at film and ball surface occurred very dramatically in Dimple zone. As slip velocity, slip ratio and load increased, size of Dimple and temperature rising became more large In addition, Position and shape of Dimple we changed by slip ratios, and increasing of Dimple size decreased traction coefficient. In short, it is appointed that the Dimple phenomenon be developed by the effect of viscosity wedge.

• 한국산학기술학회논문지
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• 제13권9호
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• pp.4277-4283
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• 2012

고장력볼트 마찰이음에서 접촉면의 표면상태에 따라 다양한 값을 갖는 미끄러짐계수는 볼트의 축력과 미끄러짐하중에 의해 결정되어진다. 또한 접촉면적은 미끄러짐하중에 영향을 미치게 되므로 볼트구멍에 따라 변하는 접촉면적은 미끄러짐계수와 상관관계를 갖게 된다. 본 연구에서는 부재의 종류, 볼트의 직경 및 볼트구멍의 크기에 따른 미끄러짐계수와 미끄러짐하중의 변화를 파악하기 위하여 32개의 시험편을 제작하여 휨시험 및 인장시험을 실시하였다. 과대볼트구멍으로 제작된 시험편의 미끄러짐하중은 표준볼트구멍으로 제작된 미끄러짐하중의 80%이상의 강도를 발휘하였으며 설계 미끄러짐강도를 상회하였다. 또한 과대볼트구멍으로 제작된 시험편과 표준볼트구멍으로 제작된 시험편의 순단면적비와 미끄러짐비간에는 상당한 상관성을 가지는 것으로 나타났다. 그러나 시험결과가 각 시험체에 따라 다소의 차이를 보이는 것은 미끄러짐계수의 중요한 파라메타인 고장력볼트의 도입축력이 감소하기 때문인 것으로 판단된다. 볼트구멍 크기의 증가는 미끄러짐 계수 뿐 아니라 볼트 축력의 감소를 야기시키므로 설계강도의 감소를 초래하는 것은 자명한 사실이지만 외국의 경우와 같이 구조적 안정을 위협하지 않는 범위 내에서 볼트구멍에 대한 규정에 유연성을 갖는 것도 시공성과 효율성에 긍정적인 요소가 될 것으로 기대된다.

• Steel and Composite Structures
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• 제38권5호
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• pp.563-582
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• 2021

The present study experimentally and analytically investigated the push-out behaviour of H-shaped steel section embedded in ultrahigh-performance fibre-reinforced concrete (UHPFRC). The effect of significant parameters such as the concrete types, fibre content, embedded steel length, transverse reinforcement ratio and concrete cover on the bond stress, development of bond stress along the embedded length and failure mechanism has been reported. The test results show that the bond slip behaviour of steel-UHPFRC is different from the bond slip behaviour of steel-normal concrete and steel-high strength concrete. The bond-slip curves of steel-normal concrete and steel-high strength concrete exhibit brittle behaviour, and the bond strength decreases rapidly after reaching the peak load, with a residual bond strength of approximately one-half of the peak bond strength. The bond-slip curves of steel-UHPFRC show an obvious ductility, which exhibits a unique displacement pseudoplastic effect. The residual bond strength can still reach from 80% to 90% of the peak bond strength. Compared to steel-normal concrete, the transverse confinement of stirrups has a limited effect on the bond strength in the steel-UHPFRC substrate, but a higher stirrup ratio can improve cracking resistance. The experimental campaign quantifies the local bond stress development and finds that the strain distribution in steel follows an exponential rule along the steel embedded length. Based on the theory of mean bond and local bond stress, the present study proposes empirical approaches to predict the ultimate and residual bond resistance with satisfactory precision. The research findings serve to explain the interface bond mechanism between UHPFRC and steel, which is significant for the design of steel-UHPFRC composite structures and verify the feasibility of eliminating longitudinal rebars and stirrups by using UHPFRC in composite columns.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.135-138
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• 1991

In this study, a variety of characteristics is considered when LIM for transit is driven with acceleration and deceleration. From the characteristics of constant voltage, with V/f ratio fixed, slip frequency is derived. With slip frequency of 12[Hz] and objective velocity of 40[km/h], the robust control characteristics which are generated constant thrust and normal force, except for open-loop control interval, are obtained.

• 한국자동차공학회논문집
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• 제18권5호
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• pp.85-90
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• 2010

As the environmental regulation of vehicle emission is strengthened, investigations for $NO_x$ and PM reduction strategies are popularly conducted. Two current available technologies for continuous $NO_x$ reduction onboard diesel vehicles are Selective Catalytic Reduction (SCR) using aqueous urea and lean $NO_x$ trap (LNT) catalysts. The experiments were conducted to investigate the $NO_x$ reduction performance of SCR system which can control the ratio of $NO/NO_2$, temperature and SV(space velocity), and the model gas was used which is similar to a diesel exhaust gas. The maximum reduction efficiency is indicated when the $NO:NO_2$ ratio is 1:1 and the SV is 30,000 $h^{-1}$ in $300^{\circ}C$. Generally, ammonia slip from SCR reactors are rooted to incomplete conversion of $NH_3$ over the SCR. In this research, slip was occurred in 6cases (except low SV and $NO:NO_2$ ratio is 1:1) after SCR. Among 6 case of slip occurrence, the maximum conversion efficiency is observed when SV is 60,000 $h^{-1}$ in $400^{\circ}C$.