• International Journal of Railway
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• 제6권2호
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• pp.45-52
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• 2013

Railway construction needs vast soil investigation for its infrastructure foundation designs along the planned railway path to identify the design parameters for stability and serviceability checks. The soil investigation data are usually classified and grouped to decide design input parameters per each construction section and budget estimates. Deterministic design method which most civil engineer and practitioner are familiar with has a clear limitation in construction/maintenance budget control, and occasionally produced overdesigned or unsafe design problems. Instead of using a batch type analysis with predetermined input parameters, data population collected from site soil investigation and design load condition can be statistically estimated for the mean and variance to present the feature of data distribution and optimized with a best fitting probability function. Probabilistic approach using entire feature of design input data enables to predict the worst, best and most probable cases based on identified ranges of soil and load data, which will help railway designer select construction method to save the time and cost. This paper introduces two Monte Carlo simulations actually applied on estimation of retaining wall external stability and long term settlement of organic soil in soil investigation area for a recent high speed railway project.

• 한국기계가공학회지
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• 제20권11호
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• pp.92-99
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• 2021

Agricultural tractors drive and operate both off-road and on-road. Tire-road interaction significantly affects the tractive performance of a tractor, which is difficult to predict numerically. Many empirical models have been developed to predict the tractive performance of tractors using the cone index, which can be measured through simple tests. However, a magic formula model that can determine the tractive performance without a cone index can be used instead of traditional empirical models as the cone index cannot be measured on asphalt roads. The aim of this study was to predict the tractive performance of a tractor using the magic formula tire model. The traction force of the tires on an asphalt road was measured using an agricultural tractor. The dynamic wheel load was calculated to derive the coefficients of the traction-slip curve using the measured static wheel load and drawbar pull of the tractor. Curve fitting was performed to fit the experimental data using the magic formula. The parameters of the magic formula tire model were well identified, and the model successfully determined the coefficient of traction of the tractor.

• 한국재난정보학회 논문집
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• 제9권3호
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• pp.324-331
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• 2013

강바닥판 교면포장의 고정하중 감소와 내구성 확보를 위해 사용되는 에폭시 아스팔트 콘크리트는 2액 반응형 재료로서 온도와 시간에 따라 강도가 발현되는 특징을 갖는다. 교통개방과 공정계획 수립을 위해서는 에폭시 아스팔트 콘크리트의 강도를 정확하게 예측할 수 있어야 하며 이를 위해 에폭시 아스팔트 콘크리트의 교통개방 시점 예측 모델을 개발하였다. 현장 시공 사례에 적용 하였을 때 기존 화학반응속도론에 기초한 모델의 R2가 0.806이었으나 비선형 커브피팅을 통해 개발한 예측모델은 R2가 0.943로 보다 높은 예측 정확도를 나타내었다. 포장체의 온도데이터가 보다 많을 경우에는 예측모델과 실측값의 차이를 더 줄일 수 있었다.

• Composites Research
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• 제27권4호
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• pp.135-140
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• 2014

발포 폴리우레탄의 변형거동을 설명하기 위해 제안된 구성방정식을 발포 폴리프로필렌에 적용하였다. 이 방정식은 7개의 매개변수를 갖고 있으며, 그중 5개의 변수는 기준 변형률속도에서 준정적 압축시험을 하여 얻은 결과를 커브 피팅하여 구하고, 나머지 두 변수는 변형률 속도를 다르게 한 준정적 압축시험으로부터 얻은 결과를 커브 피팅하여 구한다. 이렇게 구한 응력-변형률 방정식이 높은 변형률속도에서도 유효한지 알기 위해 충격시험으로부터 얻은 결과와 비교하였으며 30배와 40배로 발포된 폴리프로필렌 폼 시편에 대하여 각각 시행하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제30권6호
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• pp.677-684
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• 2006

An ejector is a fluid transfer device to be used for mixing of fluids, maintaining vacuum, and overcoming a poor suction condition. To date, most ejectors have been made from the casting process. which is time-consuming and high-cost process. Therefore, a new production method of ejectors is desired if any. In this experimental study, we proposed a new type ejector manufactured from the commercial fitting materials and the welding process, which is equipped with an orifice type nozzle. The proposed ejector has a good integrity compared with the conventional ejector because the fittings have manufactured by forging and they have more strength than the casting materials. Furthermore we adopted a multi-opening orifice type nozzle for improving a suction capacity and compared with a single-opening orifice type nozzle. From the experimental results. we confirmed that the multi-opening nozzle had a food suction capacity than the single-opening nozzle and the proposed new type ejector showed higher vacuum than the conventional type ejector in non-load condition. These improved characteristics suggests that a new type ejector by using the commercial fittings opens the feasibility to be adopted in various industry fields and that the increased suction capacity can be achieved by altering the nozzle design of a conventional ejector.

• 한국정밀공학회지
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• 제19권9호
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• pp.118-124
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• 2002

The use of ceramic inserts in hot extrusion dies offers significant technical and economic advantages over other forms of manufacture. In this paper, process simulation and stress analysis are thus combined during the design, and a data exchange program has been developed that enables optimal design of the dies taking into account the elastic deflections generated in shrink fitting the die inserts and that caused by the stresses generated in the process. The shrink fit analysis has been performed that enables optimal design of the dies taking into account the elastic deflections which generated in shrink fitting the die inserts and that caused by the stresses generated in the process and by using DEFORM software for process analysis. This data can be processed as load input data for a finite element die-stress analysis. Process simulation and stress analysis are thus combined during the die design. The stress analysis of the dies is used to determine the stress conditions on the ceramic insert by considering contact and interference effects under both mechanical and thermal loads. The results are compared with the experimental ones for verification.

• 열처리공학회지
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• 제34권1호
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• pp.25-30
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• 2021

The differential gear system is a device designed to distribute the driving force of both vehicle wheels and control the rotational speed when the vehicle turns on a curve. The differential device consists of a differential gear case, a ring gear, and a pressure ring. A differential pinion gear and side gear are mounted on the differential pinion shaft inside the differential gear case. In this study, a pin press-fitting device that mounts the pinier gear and side gear to the differential pinion shaft in the differential gear case was designed, and a jig device for pin press-fitting using servo press was developed. In addition, by precisely measuring the pin press-in load and press-in distance according to the pin hole diameter of the differential gear shaft, the optimization of the pin pressin process was established.

• Earthquakes and Structures
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• 제12권1호
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• pp.23-34
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• 2017

Composite steel plate deep beam (CDB) is proposed as a lateral resisting member, which is constructed by steel plate and reinforced concrete (RC) panel, and it is connected with building frame through high-strength bolts. To investigate the seismic performance of the CDB, tests of two 1/3 scaled specimens with different length-to-height ratio were carried out under cyclic loads. The failure modes, load-carrying capacity, hysteretic behavior, ductility and energy dissipation were obtained and analyzed. In addition, the nonlinear finite element (FE) models of the specimens were established and verified by the test results. Besides, parametric analyses were performed to study the effect of length-to-height ratio, height-to-thickness ratio, material type and arrangement of RC panel. The experimental and numerical results showed that: the CDBs lost their load-carrying capacity because of the large out-of plane deformation and yield of the tension field formed on the steel plate. By increasing the length-to-height ratio of steel plate, the load-carrying capacity, elastic stiffness, ductility and energy dissipation capacity of the specimens were significantly enhanced. The ultimate loading capacity increased with increasing the length-to-height ratio of steel plate and yield strength of steel plate; and such capacity increased with decreasing of height-to-thickness ratio of steel plate and gap. Finally, a unified formula is proposed to calculate their ultimate loading capacity, and fitting formula on such indexes are provided for designation of the CDB.

• Wind and Structures
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• 제38권5호
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• pp.367-379
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• 2024

Compared with traditional transmission towers, T-shaped angle towers have long cross-arms and are specially used for ultrahigh-voltage direct-current (UHVDC) transmission. Nevertheless, the wind loads of T-shaped towers have not received much attention in previous studies. Consequently, a series of wind tunnel tests on the T-shaped towers featuring cross-arms of varying lengths were conducted using the high-frequency force balance (HFFB) technique. The test results reveal that the T-shaped tower's drag coefficients nearly remain constant at different testing velocities, demonstrating that Reynolds number effects are negligible in the test range of 1.26 × 10⁴-2.30 × 10⁴. The maximum values of the longitudinal base shear and torsion of the T-shaped tower are reached at 15° and 25° of wind incidence, respectively. In the yaw angle, the crosswind coefficients of the tower body are quite small, whereas those of the cross-arms are significant, and as a result, the assumption in some load codes (such as ASCE 74-2020, IEC 60826-2017 and EN 50341-1:2012) that the resultant force direction is the same as the wind direction may be inappropriate for the cross-arm situation. The fitting formulas for the wind load-distribution factors of the tower body and cross-arms are developed, respectively, which would greatly facilitate the determination of the wind loads on T-shaped angle towers.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.816-823
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• 2007

As the South Korean rolling stock industry is developing designs for full compliance with the European Standards, it is fitting to take a look at these two core standards. The paper presents an overview of the load cases and structural requirements developed in Europe for the design of safe and compatible rolling stock vehicles. These load cases and structural requirements have been compiled into two standards namely EN12663 and EN15227. Standard EN12663 was developed as a reference design requirements standard. The work was mandated and sponsored by the European Committee for Standardization and Standard issuing National Institutions. EN12663 specifies a series of proof and fatigue load cases for European rolling stock regulations compliant vehicle designs. As EN12663 does not address the crashworthiness issue, a dedicated crashworthiness standard, EN15227, was therefore developed in a similar manner through industry wide consultations managed by a Trans-European working group of experienced engineers and specialists. In both standards, the vehicle and/or trains are grouped into categories reflecting the vehicle types and/or their indented operational function. EN15227, developed to complement EN12663, addresses the "passive" crashworthiness capability of the vehicles and trains. EN15227 specifies reference crash scenarios similar to those found in the Technical Specification for Interoperability (TSI) of high speed trains operating in Europe. The overview also touches on a general comparison with the corresponding British Group Standard (GM/RT2100) and also the UIC leaflet based load cases. The exercise is extended to pertinent design load cases specified by the Federal Railroad Administration (FRA) in the US.