• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.2
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• pp.12-20
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• 1998

Exter ballistics of a typical high-speed projectile is studied through a flow-visualization experiment and an unstructured grid Navier-Srokes computation. Experiment produced a schlieren photograph that adequately shows the characteristic features of this complex flow, namely two kinds of oblique cone shocks and turbulent wake developing into the downstream. A hybrid scheme of finite volume-element method is used to simulate the compressible Reynolds-Averaged Navier-Stok- es solution on unstructured grids. Osher's approximate Riemann solver is used to discretize the cinvection term. Higher-order spatial accuracy is obtained by MUSCL extension and van Albada ty- pe flux limiter is used to stabilize the numerical oscillation near the solution discontinuity. Accurate Gakerkin method is used to discretize the viscous term. Explict fourth-order Runge-Kutta method is used for the time-stepping, which simplifies the application of MUSCL extension. A two-layer k-$\varepsilon$ turbulence model is used to simulate the turbulent wakes accurately. Axisymmetric folw and two-dimensional flow with an angle of attack have been computed. Grid-dependency is also checked by carrying out the computation with doubled meshes. 2-D calculation shows that effect of angle of attack on the flow field is negligible. Axi-symmetric results of the computation agrees well with the flow visualization. Primary oblique shock is represented within 2-3 meshes in numerical results, and the varicose mode of the vortex shedding is clearly captured in the turbulent wake region.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.1
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• pp.18-24
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• 2015

Train positioning detection information is fundamental for high-speed railroad inspection, making it possible to simultaneously determine the status and evaluate the integrity of railroad equipment. This paper presents the results of measurements and an analysis of an inertial measurement unit (IMU) used as a positioning detection sensors. Acceleration and angular rate measurements from the IMU were analyzed in the amplitude and frequency domains, with a discussion on vibration and train motions. Using these results and GPS information, the positioning detection of a Korean tilting train express was performed from Naju station to Illo station on the Honam-line. The results of a synchronized analysis of sensor measurements and train motion can help in the design of a train location detection system and improve the positioning detection performance.

• Journal of the Korean Society for Railway
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• v.13 no.2
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• pp.131-138
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• 2010

Recently, extruded aluminium-alloy panels have been used in the car bodies in order to meet the needs for the speed-up and light-weight of the railway vehicles. Most of the car bodies were jointed by arc weldings, like GMAW (GasMetal Arc Welding) and GTAW (Gas Tungsten Arc Welding), but these weldings became fairly worse the mechanical properties of the junction than the base metal. Nowadays, FSW (Friction Stir Welding), which is superior to the arc weldings, has been applied in the railway vehicles. In this study, the mechanical properties of the joints in both FSW and GMAW for A6005 extruded aluminium-alloy sheets have discussed. In addition, the relationships between the welding conditions and the mechanical properties for the joint of FSW have analyzed through the sensitivity analysis. It can be concluded that the mechanical properties for the joint of FSW are better than those of GMAW and the welding speed is the most sensible welding condition in the process of FSW.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4171-4176
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• 2012

The conventional block systems for railway signaling currently in operation in Korea have not been electrified or integrated and therefore there have been difficulties in terms of construction and maintenance. Two independent systems have been installed for ABS and LEU of ATP system (for speeded-up lines), although they deal with the same signaling information at the same location in order to control the trains. In these conventional ABS and LEU, a number of duplicate modules are installed in each device including lamp detection units and power supply units and it results increased manufacturing costs and maintenance efforts. This paper deals with the prototype development of integrated electronic block system with CPU-based digital control methods in order to overcome the limitations of the conventional ABS. The suggested system is the integration of the conventional ABS with LEU of ATP and it is also applicable for the non-ATP sections as well.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.817-822
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• 2014

Since the opening of the double-track railway for the Gyeongchun local electric train and the semi-high speed train ITX, floating population between Seoul and Chuncheon has rapidly increased. This is attributable to the competitiveness of the railway service in terms of punctuality and safety of operation, mass transportation and low fare. However, many passengers have expressed strong dissatisfaction and displeasure towards the interior noise and its high rate of increase, particularly in tunnel sections. In this study, the interior noise characteristics of Gyeongchun local electric train and ITX were analyzed and compared. Noise levels, frequency spectrum and sound quality indices were compared for the open land, tunnel and bridge. Finally, from the noise levels depending on the location in the vehicle compartment, the noise transmission path was determined and a basic strategy for reducing the interior noise was developed.

• Korean Journal of Veterinary Service
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• v.40 no.4
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• pp.253-258
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• 2017

The aim of this study is to develop an optimal analytical method for gonadorelin, progesterone, oxytocin and estradiol, the major components of hormones. A relatively simple and reproducible method using high performance liquid chromatography was developed and as a result of the measurement of specificity, linearity, repeatability, accuracy and intermediated precision, the validity of the developed method was verified with the result of meeting the verification criteria of analytical method validation. Using this newly developed method, 12 post-market veterinary products were tested and the ingredient content were 91.9~116.4%, which satisfied the 90~120% condition of the administrative measure standard. Therefore, if the newly developed method is used for the collection examination of hormone in veterinary medicine, it can be useful as an approved test method.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.1
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• pp.68-75
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• 2009

In this paper, an efficient proposed CDR(Clock and Data Recovery Circuits) using 1/4-rate clock based on dual-interpolator is proposed. The CDR is aimed to overcome problems that using multi-phase clock to decrease the clock generator frequency causes side effects such as the increased power dissipation and hardware complexity, especially when the number of channels is high. To solve these problems, each recovery part generates needed additional clocks using only inverters, but not flip-flops while maintaining the number of clocks supplied from a clock generator the same as 1/2-rate clock method. Thus, the reduction of a clock generator frequency using 1/4-rate clocking helps relax the speed limitation and power dissipation when higher data rate transfer is demanded.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.21-34
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• 2014

This paper studies the time-dependent behaviors of tunnel and surrounding ground due to tunnel deterioration. In the first part, the literature on deterioration characteristics of tunnels was reviewed. In the second part, a numerical analysis was performed to investigate the behavior of concrete lining on the typical section of Korean high-speed rail tunnel (weathered rock) after determination of input variables related to deterioration impact. The result shows that the settlement at the crown of tunnel and surface ground increased up to 7.0% and 30.2% of the total settlements during construction stage, respectively, and the internal convergence reduction of 9.0 mm for concrete linings was generated within 30 years after completion of tunnel construction. Also the loosening height increased up to 2.55 times of tunnel height within 50 years, which is higher than that of Terzaghi's recommendation on ultimate state. Due to this process of extending zones, it is found that additional loads were applied to concrete lining with the axial stress about 3.20~3.66 MPa, which accelerates tunnel deterioration. Finally the quantitative design approach to evaluate time-dependent behavior of lining and surrounding ground due to tunnel deterioration was proposed.

• Journal of the Korean GEO-environmental Society
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• v.18 no.12
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• pp.13-23
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• 2017

This paper discusses about the reinforcement materials and construction method in order to cope with roadbed settlement in operating railway. In Korea, concrete tracks have been introduced to urban railways, high-speed railways, and general railways, but some recently constructed concrete tracks have experienced roadbed settlements. Reinforcement of the railway roadbed is urgent task for safe operation of railway, but it is difficult to reinforce the roadbed and there are no case history of reinforcing railway roadbed under an operating railroad track. Therefore, in this study, the target performance level for roadbed reinforcement was determined, and infiltration and solidity injection efficiency were investigated for selected reinforcement materials. As a result of the study, it was found that the generally used reinforcement materials and methods for geotechnical works need to be improved for applying in railway roadbed reinforcement.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.4
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• pp.645-651
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• 2009

In this paper, we present bit error rate(BER) performance of an adaptive decision feedback equalizer(DFE) using experimental data. The experiment was performed at the shore of Geoje in November 2007. The BER of the adaptive DFE whose tap weight is updated by RLS is described with change of feedforward filter length, feedback filter length, training sequence length, and delay, which shows that the uncoded average BER is $4{\times}10^2\;and\;1.5{\times}10^{-2}$ with transmission range of 9.7km and 4km, respectively. The BER of the adaptive DFE can be lower than 10-3 by a forward error correction code and therefore the adaptive DFE may be a good candidate for a high speed AUV communications since the volume and weight of the underwater acoustic modem should be small because of the restricted space and power in the battery-operated AUV.