• Journal of the Korean Society for Precision Engineering
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• v.12 no.7
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• pp.82-91
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• 1995

Many kind of springs are used in the suspension of automotive vehicles and among these the leaf spring and the air spring are included. These two springs have not been generally used together in one suspension, but recently the automotive models which use these two springs together increase. This reason is due to the merit of the combination of two type springs. The merits are two. One is the character of air spring, that is, the natural frequen- cy of system is constant in spite of variable weight. The other is the character of leaf spring, that is, the suspension mechanism is simple. The combination spring is used in medium size and special purpose bus. In this paper, we formulate the condition which the leaf spring must satisfy to be optimal design in the combination spring. And experiment is performed to prove the theory. The results are that the combination spring is better than leaf spring in the ride, and that the purposed theory is good for the combination spring design.

• Smart Structures and Systems
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• v.34 no.2
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• pp.87-96
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• 2024

Smart materials, such as magnetorheological (MR) fluid, have received considerable research attention in recent years due to their unique capabilities. MR fluid, which possesses a magnetic field controllable viscosity, has been extensively studied for vehicular applications with the aim of synthesizing optimal MR fluids, designing optimal MR dampers, and developing control strategies. However, a comprehensive study that primarily focuses on developing a cost-effective semi-active suspension system for a commercial vehicle in a developing nation is still lacking. This study addresses this gap by synthesizing an in-house MR fluid and studying its rheological properties. Subsequently, a novel single-sensor-based controller is developed and closed-loop simulations are conducted on a quarter-car semi-active model. Finally, the overall semi-active quarter-car suspension system is experimentally tested using a suspension test rig. The performance of the proposed system in terms of ride comfort and road holding is evaluated and is compared with simple control strategies. The dynamic range of the developed semi-active MR damper is found to be around 2.3, indicating a significant MR effect. The results suggest an intermediate response using the proposed acceleration-driven controller (ADV) at lower frequencies and similar performance to that of the skyhook controller at higher frequencies. The cost-effective methodology proposed in this study is effective and can be adapted for other semi-active engineering applications.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.656-662
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• 2011

Recently, rolling stock technology has rapidly developed. Nevertheless, ride quality and vibration vibration on vehicle still need more study. EMU to be operated on SMRT Line 7(SR001) extension section is applied to oil-free reciprocating air compressor considering maintainability and convenience of inspection. But reciprocating air compressor compresses the air by back-and-forth motion of piston, and spreads the vibration to surrounding structures by its force of inertia. Optimum design of mounting bracket is able to reduce the vibration. As a result, we analyzed the frequency spectrum on vibration upon value by measuring vibration during operation of air compressor. On this study, we comprehend the vibration transmission process of reciprocating air compressor and consider the measure for reducing vibration by minimizing propagation of vibration.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2090-2100
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• 2011

Railway rail fastening system is the critical device which gives big influences to not only the vehicle driving stability and the orbit's structural stability against the impulsive load, but also the noise vibration and the ride comfort. As a part of the low-carbon green growth, the importance of the railroad industry is getting highlights on its excellent energy-efficiency and eco-friendliness. However, so far the Korea's domestic rail fastening system technology is not so good and the technical reliance to abroad is very heavy. In this study, we conducted comparative analysis on the rail fastening system with new and used one of the same type. And those systems are imported by Seoul Metro and are being used by it. With this basis, we developed the components and the materials and then, established the durability assessment methods appropriate to the Korean domestic circumstances. And through the reliability qualification test on the 7 parts of the rail fastening system, we've improved the reliability and guaranteed the 15 years of service lifetime. ($B_{10}Life15$) Establishment and standardization of Reliability Standard on the parts of the rail fastening system such as anti-vibration pads, guide-plate, screw spike made it possible to perform the internationally fair assessment. And it is thought that we can satisfy the manufactures' and consumers' needs of cost-cutting and qualification security by shortening of assessment period on rail fastening system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.8
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• pp.1015-1019
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• 2013

To improve the energy efficiency and ride quality of an electric vehicle, it is highly desirable to develop a lightweight suspension system with high travel ratio. Air suspension systems with a rubber tube are often considered optimal for such requirements. In this study, a new lightweight air suspension system with high travel ratio was developed for use in electric vehicles. Furthermore, an FE-based multi-flexible-body dynamics (MFBD) model of the suspension system was developed as a tool for improving the design of an actual suspension system. The MFBD model includes the FE modeling of the rubber tube module as well as other essential parts of the air suspension system. The system parameters for the model were obtained from various experiments. The validity of the developed MFBD model was shown through a comparison between the experimental results and the simulation results.

• Journal of Power System Engineering
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• v.17 no.3
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• pp.72-81
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• 2013

Many articles have been published about a 2-degree of freedom model that includes the lateral and yaw motions for controller synthesis in intelligent transport system applications. In this paper, a 3-degree of freedom linear model that includes the roll motion is developed to design a robust steering controller for lane following maneuvers using ${\mu}$-synthesis. This linear perturbed system includes a set of parametric uncertainties in cornering stiffness and unmodelled dynamics in steering actuators. The state-space model with parametric uncertainties is represented in linear fractional transformation form. Design purpose can be obtained by properly choosing the frequency dependent weighting functions. The objective of this study is to keep the tracking error and steering input energy small in the presence of variations of the cornering stiffness coefficients. Furthermore, good ride quality has to be achieved against these uncertainties. Frequency-domain analyses and time-domain numerical simulations are carried out in order to evaluate these performance specifications of a given vehicle system. Finally, the simulation results indicate that the proposed robust controller achieves good performance over a wide range of uncertainty for the given maneuvers.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.605-616
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• 2014

The purpose of this study is to analyze transport efficiency of each of the 17 urban railway lines being operated by national public agencies using Data Envelopment Analysis (DEA) and to seek strategies for improving efficiency of the urban railway system. The study identified the economies of scale derived from these values of efficiency and examined the effects on cost for free ride loss and profit of transport by the fare system as the external factor. At the time, Transport profits are estimated by two production factors such as the number of vehicles and service frequency derived from multiple regression. Finally, the measures to improve the efficiency were presented in terms of profitability in the national urban railway line by applying the values of efficiency derived from DEA to multidimensional scaling (MDS).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.760-771
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• 2012

In this paper, a blind spot of motor car, and the put case that is driven the miniature model motor system, when make practical application of the permanent magnet synchronous motors(PMSM) braking and having had the ability that can all absorb regenerative power by means of electric brake which is occurred. a tow system of a miniature model motor traction system is established by 1C1M methods to control individually permanent magnet synchronous motors (PMSM) of each motor. vector control method is applied in order to improve ride quality of motor car and the efficient use of energy. it was obtained excellent experiment results from the simulations as a function of momentum load and miniature model. Also, this study is investigated the regenerative braking power securities of permanent magnet synchronous motors, speed detection to stop electric brake at extremely very low speed and motor control method of algorithm.

• Fashion & Textile Research Journal
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• v.17 no.5
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• pp.800-814
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• 2015

This study develops baseball uniforms for amateur baseball players with excellent appearance and functional movement. This study selected a conventional baseball uniform and developed a new one for amateur baseball players with improved function and appearance based on previous research results. In case of developed baseball uniform materials, this study used polyurethane mixed fabric for the top to improve flexibility. A mesh material was used at the armpit, back, and bottom of the top, side line of pants and pockets to improve breathability. In addition, quilted material was added to the knee to improve durability and protection. For the patterns and design, this study used a gusset under the arm to assist in comfortable movement as well as reduced the length of the top and circumference of the hem to decrease unnecessary parts. For the pants, this study used a waistband gripper to avoid the top riding up, added darts behind the knees to bend comfortably, and added additional fabric inside the hem to prevent dirt. In addition, we reduced the width and length of the pants. Wearing evaluation was divided into appearance evaluation by experts and on-site-wearing test by baseball players. The wearing evaluation results for the developed baseball uniform indicated higher evaluations than a conventional baseball uniform in all sections as well as showed significant differences in all sections. The result of movement adaptability evaluation showed the highest satisfaction for 'the top does not ride up' and 'dirt do not get in'.

• Journal of Korea Multimedia Society
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• v.23 no.8
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• pp.1099-1107
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• 2020

The need for customized services providing real-time subway information through mobile devices for the blind using subway as their primary transportation method is becoming more essential. Therefore, this study is aimed at developing a mobile service to provide real-time subway information by displaying with braille and utilizing Dot Watch. The process of real-time subway information guidance mobile service is as follows: the route confirmation stage, the ride waiting & judgment stage, the on-the-go stage, and lastly, the off-road phase & wrong path state. The service provides real-time appropriate information to the visually impaired people for each situation. It receives subway information through API provided by Seoul Metropolitan Government and ODSay API. The service is developed and coded with in Java using Android Studio, and the communicating method with Dot Watch was done using Bluetooth. The usability evaluation was conducted in terms of efficiency, effectiveness, and satisfaction. The evaluation methods mentioned above were carried out by testees, and feedback was given. They assessed that the information provided was useful but still unstable to use the system. It is expected that actual usability will increase if our study is supplemented using voice output function.