• Journal of Auto-vehicle Safety Association
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• v.12 no.3
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• pp.43-51
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• 2020

Currently, the second level of the six stages of self-driving technology, as defined by SAE, is commercialized, and the third level is preparing for commercialization. The purpose of ACC is to be evaluated as a system useful for preventing and preventing accidents by minimizing driver fatigue through longitudinal speed control and relative distance control of the vehicle. In this regard, for the study of safety assessment methods in the practical environment of ACC. Distance measurement method using monocular camera and data acquisition equipment such as DGPS are utilized. Based on the evaluation scenario considering the domestic road environment proposed by the preceding study, the relative distance obtained from equipment such as DPGS and the relative distance using a monocular camera in the actual test is verified by comparing and analyzing the safety assessment. The comparison by scenario results showed a minimum error rate of 3.83% in Scenario 1 and a maximum of 14.61% in Scenario 6. The cause of the maximum error is that the lane recognition is not accurate in the camera image and irregular operation conditions such as rushing in or exiting the surrounding area from the walkway. It is expected that safety evaluation using a monocular camera will be possible for other ADAS systems in the future.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.4
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• pp.313-323
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• 2017

As vehicles become more intelligent this is focused on ways to enhance safety and convenience for both drivers and passengers. In particular, x-by-wire systems that replace rigid mechanical components with dynamically configurable electronic elements are being developed to expand intelligent functions, such as adaptive cruise control or lane departure warning system. Because the malfunction of safety-related modules controlling critical functions, such as brakes, throttle, and steering in x-by-wire systems, can cause injury or death, safety and reliability are the most critical issue for automotive vendors and parts manufacturers. In an effort to develop better and effective brake-by-wire system, this paper presents EMB system by using the low speed electric vehicle, which is not required large braking force, with motor controller. In addition, we design performance evaluation system of EMB with 1/4 low speed electric vehicle model and suggested EMB is evaluated through the performance evaluation system.

• Journal of Auto-vehicle Safety Association
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• v.9 no.2
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• pp.6-12
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• 2017

An autonomous driving system based on a precise digital map is developed. The system is implemented to the Hyundai's Tucsan fuel cell car, which has a camera, smart cruise control (SCC) and Blind spot detection (BSD) radars, 4-Layer LiDARs, and a standard GPS module. The precise digital map has various information such as lanes, speed bumps, crosswalks and land marks, etc. They can be distinguished as lane-level. The system fuses sensed data around the vehicle for localization and estimates the vehicle's location in the precise map. Objects around the vehicle are detected by the sensor fusion system. Collision threat assessment is performed by detecting dangerous vehicles on the precise map. When an obstacle is on the driving path, the system estimates time to collision and slow down the speed. The vehicle has driven autonomously in the Hyundai-Kia Namyang Research Center.

• Journal of Technologic Dentistry
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• v.37 no.3
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• pp.169-178
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• 2015

Purpose: This study was to investigate usage satisfaction of multi type handpiece with equipped air-jet function Methods: The subjects of this study through the survey was conducted for fifty-nine dental technicians in Daegu and Gyeongsangbukdo from the May 7 to 19, after the June 23 to July 4 2014. The survey was about the function and quality through user testing environment by cutting zirconia specimens using appliance for zirconia. The collected date was analyzed by the statistical program SPSS Win Ver 19.0 for the satisfaction of handpiece and control system. To test for significance on each item, p<0.05 had been decided a standard. General characteristics and relationship between the handpiece and control system was performed correlation analysis. Results: The results of this study is as follows. 35 dental technicians had 1~2 years career in zirconia part as the highest 59.3%, 95% of subjects expected that the prospects for the zirconia material have bright prospects. The satisfaction of multi type handpiece and control system design and function showed a significant difference. Subjects satisfied with the design and function of the multi type showed negative correlation with those of Standard. The satisfaction of multi type handpiece showed 3.37 points of air jet, 3.05 points of noise level, 2.69 points of water flow rate, and 1.98 points of cruise function. Sample differences in all parameters showed a statistically higher difference. Conclusion: High-speed cutting mechanism of multi-type is recommended working with zirconia materials and the multi-type unit combined handpiece motor, air-turbine and air-gun will be expected the increase of user due to the high satisfaction of air jet.

• Maritime Security
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• v.1 no.1
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• pp.241-271
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• 2020

The military technology currently receiving the most attention is the hypersonic missile. hypersonic is faster than the speed of sound or Mach 5+. The vast majority of the ballistic missiles that it inspired achieved hypersonic speeds as they fell from the sky. Rather than speed, today's renewed attention to hypersonic weapons owes to developments that enable controlled flight. These new systems have two sub-varieties: hypersonic glide vehicles and hypersonic cruise missiles. Hypersonic weapons could challenge detection and defense due to their speed, maneuverability, and low altitude of flight. The fundamental question of this study is: 'What effect will the hypersonic missile have on the maritime strategy?' It is quite prudent to analyze and predict the impact of technology in the development stage on strategy in advance. However, strategy is essential because it affect future force construction. hypersonic missiles act as a limiting factor in securing sea control. The high speed and powerful destructive power of the hypersonic missile are not only difficult to intercept, but it also causes massive ship damage at a single shot. As a result, it is analyzed that the Securing sea control will be as difficult as the capacity of sea denial will be improved geographically and qualitatively. In addition, the concept of Fortress Fleet, which was criticized for its passive strategy in the past, could be reborn in a modern era. There are maritime power projection/defence, SLOC attack/defence in exploiting sea control. The effects of hypersonic missiles on exploiting sea control could be seen as both limiting and opportunity factors.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.1
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• pp.59-66
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• 2022

In order to solve the problem of urban traffic congestion, Urban Air Mobility (UAM) concept using Electric Vertical Take-off and Landing (eVTOL) aircraft has been gaining popularity, and many domestic and international studies are underway. However, since these aircraft inevitably fly over densely populated areas, it is essential to ensure safety, which starts with accurately analyzing the crash risk. In this paper, the locations and impact speeds of crash are computed using six degree-of-freedom simulations of an eVTOL aircraft in a fixed-wing mode. System malfunction was modeled by a sudden loss of thrust with control surfaces being stuck during cruise. Because most of these eVTOL aircraft are still under development, a methodology of constructing a six degree-of-freedom dynamics model from generic specification is also developed. The results show that the crash locations are highly concentrated right under the aircraft within a square that has an edge length similar to the cruise altitude. Speed distribution is more complicated because almost identical crash locations can be achieved by two very different paths resulting in a large variation in the speeds.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.631-640
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• 2016

A dual-mode power management for a hybrid-electric UAV with a cruise power of 200W is proposed and empirically verified. The subject vehicle is a low-speed long-endurance UAV powered by a solar cell, a fuel cell, and a battery pack, which operate in the same voltage bounds. These power sources of different operational characteristics can be managed in two different methods: passive management and active management. This study proposes a new power management system named PMS2, which employs a bypass circuit to control the individual power sources. The PMS2 normally operates in active mode, and the bypass circuit converts the system into passive mode when necessary. The output characteristics of the hybrid system with the PMS2 are investigated under simulated failures in the power sources and the conversion of the power management methods. The investigation also provides quantitative comparisons of efficiencies of the system under the two distinct power management modes. In the case of the solar cell, the efficiency difference between the active and the passive management is shown to be 0.34% when the SOC of the battery is between 25-65%. However, if the SOC is out of this given range, i.e. when the SOC is at 90%, using active management displays an improved efficiency of 6.9%. In the case of the fuel cell, the efficiency of 55% is shown for both active and passive managements, indicating negligible differences.

• The Journal of Korean Institute of Information Technology
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• v.16 no.11
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• pp.133-144
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• 2018

IEC 62278, the Railway System Safety Standard, requires for hazard analysis to prevent or control the hazard that the railway system may have. If hazard analysis is not performed sufficiently, there is a high probability that accidents will occur. For this reason, hazard analysis methods are actively studied. In this paper, we propose the hybrid hazard analysis method to combine two representative hazard analysis methods: reliability-based and system-theoretic. As the proposed method is complementary to existing ones, it covers both the hazard caused by failure of components and the hazard occurred from the unintended control between components. It applies to the development of a safety protection mechanism for multiple cruise control system that automatically control the speed of trains to avoid the collision among trains. As a result, we drive more safety requirements than the existing analysis methods and it turns out that the safety requirements protect the trains with respect to the identified hazards.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.15 no.4
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• pp.9-16
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• 2007

Tilt rotor aircraft can take off and land vertically and cruise faster than any other helicopter. A scaled flight demonstration model of a tilt rotor aircraft has been developed by KARI. Because the flight characteristics of tilt rotor are not well known, the developed scaled model would be helpful to evaluate flight control algorithm of a full scale aircraft. The tethered hover test has been performed in order to improve hover flight characteristics of tilt rotor aircraft prior to flight test of the small scaled model. During the tethered hover test, the performance of rotor speed governor, rate SAS (Stability Augmentation System) and control surface mixers have been evaluated. We expect that the results of real flight hover test would be quite same as tethered hover test. Therefore the tethered hover test results will reduce the risk of flight test properly by fixing some of hidden problems which might occur during the flight test. This paper presents the results of tethered hover test in detail and shows how it could be final ground test before flight test. The control mixer gain and rate SAS feedback gains were modified in order to get higher controllability and stability during the tethered hover flight. The rotor governor showed that it could keep rotor RPM constant with very small deviation even during severe pilot collective input change. The tethered hover test results gave pilot and engineers confirmation and experience about the scheduled flight test.

• Journal of Auto-vehicle Safety Association
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• v.10 no.2
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• pp.20-28
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• 2018

Currently, sharp increase of car is on the rise as a serious social problem due to loss of lives from car accident and environmental pollution. There is a study on ITS (Intelligent Transportation System) to seek coping measures. As for the commercialization of ITS, we aim for occupancy of world market through ASV (Advanced Safety Vehicle) related system development and international standardization. However, the domestic environment is very insufficient. Core factor technologies of ITS are Adaptive Cruise Control, Lane Keeping Assist System, Forward Collision Warning System, AEB (Autonomous Emergency Braking) system etc. These technologies are applied to cars to support driving of a driver. AEB system is stop the car automatically based on the result decided by the relative speed and distance with obstacle detected through sensor attached on car rather than depending on the driver. The purpose of AEB system is to measure the distance and speed of car and to prevent accident. Thus, AEB will be a system useful for prevention of accident by decreasing car accident along with the development of automobile technology. This study suggests a scenario to suggest a test evaluation method that accords with domestic environment and active response of international standard regarding the test evaluation method of AEB. Also, by setting the goal with function for distance, it suggests theoretic model according to the result. And the study aims to verify the theoretic evaluation standard per proposed scenario using car which is installed with AEB device through field car driving test on test road. It will be useful to utilize the suggested scenario and theoretical model when conducting AEB test evaluation.