• Journal of the HCI Society of Korea
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• v.1 no.1
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• pp.29-36
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• 2006

Tactile displays can provide useful information without disturbing others and are particularly useful for people with visual or auditory impairments. They can also complement other displays. In this paper, we present a new vibrotactile display device for wearable, mobile, and ubiquitous computing environments. The proposed vibrotactile device has a $5{\times}5$ array configuration for displaying complex information such as letters, numbers, and haptic patterns as well as simple directional ques and situation awareness alarms. Commercially available coin-type vibration motors are embedded vertically in flexible mounting pads in order to best localize vibrations on the skin. An embedded microprocessor controls the motors sequentially with an advanced tracing mode to increase recognition rate. User studies with the vibrotactile device on the top of the foot show 86.7% recognition rate for alphabet characters after some training. In addition, applying vibrotactile device to driving situation shows 83.9% recognition rate. We also propose some potentially useful application scenarios including Caller Identification for mobile phones and Navigation Aids for GPS systems while driving.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.862-868
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• 2013

The mechanics of woven fabric-based laminated composites is complex. Then, many researchers have studied woven fabric CFRP materials but fracture resistance behaviors for composites have not been still standardized. It also shows the different behavior according to load and fiber direction. Therefore, there is a need to consider fracture resistance behavior in conformity with load and fiber direction at designing structure using woven CFRP materials. In this study, therefore, the tensile strength and resistance for plain-weave CFRP composite materials were investigated under various different angle condition(load to fiber angle: $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$). Tensile strength and fracture toughness tests were carried out under mode I transverse crack opening load by using compact tension specimens.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.2
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• pp.132-140
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• 2001

A universal motor is a small dc series machine motor that is designed to operate from an ac machine. The characteristics of universal motors are high no-load and staring torque. Because of the high operating speed, the size of these motors for a given hp rating is typically smaller that other fractional hp ac machine, making it ideal for hand-held tools and appliances where weight, compactness, and speed are importance factors. A phase-angle control with AC drive system gains a high popularity due to their simple implementation, but contains the disadvantage of their poor input power factor, subharmonic current. Pulse width modulation control with DC drive systems increase the power factor as without delay phase angle. This paper analyzed the subharmonic characteristics of the phase angle control system that is controlled by zero voltage crossing similar to traditional method, and the dc chopper system that is used PWM.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.6
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• pp.255-261
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• 2002

Recently, traction motors in trains are supplied with single phase a.c. power. After this power is converted to d.c. power, it is inverted to three phase power to operate traction motors. As going through the process of the conversion, harmonic current is generated in train. The method of conventional analysis on harmonics, studied by RTRI, is modeled with equivalent circuit of ac AT-fed electric railroad system using by the distributed constant circuit. However, this circuit as two-port network model has some difference in comparison with real system. The reason why the conventional method is different from the real system is that the conventional method dose not include three conductor groups, that is catenary, rail, and feeder, and admittance between the conductors for line capacitance. Therefore, this method has a little error. This paper proposes new method to more effectively estimate Harmonic current. In this method, numerous components in electric railway are categorized and each component is defined as a four- port network model. The equivalent circuit for the entire power supply system is also described into a four-port network model with connections of these components. In order to evaluate the efficiency and the accuracy of a proposed method, it is compared with values measured in Kyung-Bu high speed line and ones calculated by the conventional method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.51-56
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• 2020

This study examines the strategies employed by GM, who experienced bankruptcy in 2008. Specifically, we explore the autonomous driving-related technologies and execution, which GM began developing later than other car manufacturing companies. This study found that GM implemented aggressive M&A in search of vertical industrial integration for the development and production of autonomous vehicles. GM selected candidate firms to complement its technological gaps for the development and implementation of the autonomous vehicle. Secondly, GM achieved executive capacity by attempting to build a vertical integration in the wider scope of components, solution, service, and sales. Thirdly, the consistent governmental support and policies, such as the connected car project, M-City, and NCHRP Program expedited the development process. This study provides practical and policy implications for Korean companies and policymakers related to the automotive industry.

• Journal of Korean Physical Therapy Science
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• v.16 no.1
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• pp.11-20
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• 2009

Background: The purpose of this study was to investigate the effect of stretching and strengthening exercise on the static flexibility and pain intensity for the iliopsoas muscle, which is one of the main reasons for the chronic low back pain. Methods: The subjects of this study were 15 male adult patients with showed 6 score or higher in the visual analogue scale(VAS) and complained of low back pain over three months who visited department of the physical therapy, KIA motors Industrial Health Center, from October, 2008 through December, 2008. Fifteen subjects were trained stretching, mat exercises and sling exercises for iliopsoas muscle at 4-5 times a week for 4 weeks. I measured the changes on the extensibility of iliopsoas muscle, static flexibility of low back and VAS between pre- and post exercise treatment. Date were analyzed using the Wilcoxon's signed rank test considering the size of the samples. Results: 1. The angle of the hip joint that showed the extensibility of iliopsoas muscle was relieved, which was significant statistically (p<.05). 2. The static flexibility was statistically significantly improved in the trunk flexion test, trunk extension test and Schober-Test (p<.05). 3. The VAS showed decrease, which is significant statistically (p<.05). Conclusion: It is believed that the exercise treatment of iliopsoas muscle has the significant effects on the improvement of static flexibility and decrease of pain intensity for the chronic low back pain patients.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.1
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• pp.123-133
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• 1998

In this paper, an algorithm of fault detection and diagnosis during operation of induction motors under the condition of various loads and rates is investigated. For this purpose, the spectrum pattern of input currents is used in monitoring the state of induction motors, and by clustering the spectrum pattern of input currents, the newly occurrence of spectrum patterns caused by faults are detected. For the diagnosis of the fault detected, a fuzzy fault tree is designed, and the fuzzy relation equation representing the relation between an induction motor fault and each fault type, is solved. The solution of the fuzzy relation equation shows the possibility of occurence of each fault. The results obtained are summarized as follows : (1) Using clustering algorithm by unsupervised learning, an on-line fault detection method unaffected by the characteristics of loads and rates is implemented, and the degree of dependency for experts during fault detection is reduced. (2) With the fuzzy fault tree, the fault diagnosis process become systematic and expandable to the whole system, and the diagnosis for sub-systems can be made as an object-oriented module.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.520-525
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• 2011

As worldwide concern stands on global warming and greenhouse gases from internal combustion engine, the interests in technologies for a highly efficient powertrain has been increased. Concurrently the investigation to improve the deteriorated NVH, a by-product of energy efficient powertrain, is conducted seriously. The NVH performance of a new type of active engine mount that offers increased advantages over a passive hydraulic mount is examined using a newly developed 6-DOF simulator. The simulator is in the shape of Hexapod Stewart Platform adopting LEMA, a new type of actuator which is patented and commercialized by ACT Inc,, the world wide leader in the design, development, and manufacture of high performance linear electro-magnetic actuators for active vibration control. The target vibration signals of an aimed vehicle at four engine mounts are measured and simulated by 6-DOF simulator at the laboratory. The resulting NVH performances of the new active mounting system at a vehicle and on a simulator are examined and compared. Even though the active mount performance of lab test demonstrates less effective than the result of a real vehicle test, vibration reduction is identified through the simulator.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.118-126
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• 2003

In the present study, the residual stresses can have a significant on the life of structural engineering components. Residual stresses are created by the surface treatment such as shot peening or deep rolling. The objective of this experimental investigation is to study the influence of friction and wear characteristics due to residual stress under dry sliding condition. Friction and wear data were obtained with a specially designed tribometer. Test specimens were made of SUP9(leaf spring material) after they were created residual stress by shot peening treatment. Residual stress profiles were measured at surface by means of the X-ray diffraction. Sliding tests were carried out different contact pressure and same sliding velocity 0.035m/s(50rpm). Leaf spring assembly test used to strain gauge sticked on leaf spring specimen in order to measure interleaf friction of leaf spring. Therefore, we were obtained hysteresis curve. As the residual stresses of surfaces increased, coefficient of friction and wear volume are decreased, but the residual stresses of surfaces are high, and consequently wear volume do not decreased. Coefficient of friction obtained from leaf spring assembly test is lower than that obtained from sliding test. From the results, structural engineering components reduce coefficient of friction and resistant wear in order to have residual stresses themselves.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.6
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• pp.469-475
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• 2017

Workers in industrial fields are highly exposed to accidents or injuries caused by long working hours. An exoskeleton that is able to support the arm muscles of the worker and thereby reduce the probability of an accident and enhance working efficiency could be a solution to this problem. However, existing exoskeletons demand the use of high-priced sensors and motors, which makes them difficult to use in industrial fields. To solve this problem, we developed an arm assisting exoskeleton that consists only of mechanical components without any electronic sensors or motors. The exoskeleton follows the movement of the human arm by shoulder joint and ankle joint. In addition, counterbalance mechanisms are installed on the exoskeleton to support arm strength. The experimental validation of the exoskeleton was conducted using an EMG sensor, confirming the performance of the exoskeleton.