• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.8
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• pp.1101-1110
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• 1998

Computational investigation was conducted to examine the performance of a high pressure common-rail fuel injection system which is used to power a passenger car direct injection (Dl) diesel engine. The pipe flows were modeled by one dimensional wave equation and solved by implicit FDM Each volume of injector was considered as chambers with orifice nozzle in connections. These simulation results were compared with the experimental data of Ganser Hydromag. The comparison of needle life and rate of injection between simulation data and experimental data showed quite a good agreement Different shape of injection rate can be made by adjusting the size of inlet orifice and exit orifice in the piston chamber The pilot injection was accomplished by adjusting command signal.

• ETRI Journal
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• v.16 no.2
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• pp.27-41
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• 1994

A new mathematical model to predict the beam pointing instability of a nonconservative two-body satellite system in spinning injection mode has been developed by using Newton-Euler and projection methods. Since the on-axis and null axis of the omni antenna with toroidal pattern beam form a right angle, wobbling of the antenna on-axis is measured by determining the Euler angles which represent the orientation of the satellite's spin axis. Because of the complexity of the system which is a time varying, nonstationary, nonlinear dynamical system, a numerical method is used for the analysis. Computer simulation results present the effects of the mass distribution and internal mass motion on the antenna beam pointing.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.2
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• pp.76-86
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• 2016

SQL Injection attacks are the most widely used and also they are considered one of the oldest traditional hacking techniques. SQL Injection attacks are getting quite complicated and they perform a high portion among web hacking. The big data environments in the future will be widely used resulting in many devices and sensors will be connected to the internet and the amount of data that flows among devices will be highly increased. The scale of damage caused by SQL Injection attacks would be even greater in the future. Besides, creating security solutions against SQL Injection attacks are high costs and time-consuming. In order to prevent SQL Injection attacks, we have to operate quickly and accurately according to this data analysis techniques. We utilized data analytics and machine learning techniques to defend against SQL Injection attacks and analyzed the execution plan of the SQL command input if there are abnormal patterns through checking the web log files. Herein, we propose a way to distinguish between normal and abnormal SQL commands. We have analyzed the value entered by the user in real time using the automated SQL Injection attacks tools. We have proved that it is possible to ensure an effective defense through analyzing the execution plan of the SQL command.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.9
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• pp.1025-1031
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• 2011

Take-out robots used for handling of the plastic parts manufactured with the injection mold are usually the gantry type that consists of long and thin links, The performance of the take-out robot is determined by the speed of the motion and the positioning accuracy to grab the part out of the mold, As the speed of the robot increases the flexure in the links of the take-out robot becomes more significant and it results in more residual vibration, The residual vibration deteriorates the positioning accuracy and compels the operator to slow down the motion of the robot. The typical method to reduce the vibration in the robot requires stiffening the links and/or slowing down the robot, Vibration control could achieve the desired performance without increasing the manufacturing cost or the operation cost that would be incurred otherwise, Considering the point-to-point nature of the task to be performed by the take-out robot the time-delay command (or input) shaping filter approach would be the most effective control method to be adopted among a few available control schemes. In this paper a direct adaptive command shaping filter (ACSF) algorithm has been modified and applied to design the optimal command shaping filters for various configuration of the take-out robot. Optimal filters designed by ACSF algorithm have been implemented on a take-out robot and the effectiveness of the designed filters in terms of vibration suppression has been verified for multiple positions of the robot.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.2
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• pp.163-169
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• 1998

In this paper, we design an optimal model following ${\mu}-$synthesis control system for fuel-injection of diesel engine which has robust performance and satisfactory command tracking performance in spite of uncertainties of the system. To do this, we give gain and dynamics parameters to the weighting functions and apply genetic algorithm with reference model to the optimal determination of the weighting functions that are given by the D-K iteration method which can design ${\mu}-$synthesis controller in the state space. These weighting functions are optimized simultaneously in the search domain which guarantees the robust performance of the system. The ${\mu}-$synthesis control system for fuel-injection designed by the above method has not only the robust performance but also a better command tracking performance than those of the ${\mu}-$synthesis control system designed by trial-and-error method. The effectiveness of this ${\mu}-$synthesis control system for fuel-injection is verified by computer simulation.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1515-1527
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• 2018

This paper presents a sensorless speed control of IPMSM (Interior Permanent Magnet Synchronous Motor) using the high-frequency (HF) square wave injection method. In the proposed HF pulsating square wave injection method, injection voltage is applied into the estimated d-axis of rotor and high-frequency induced q-axis current is considered to estimate the rotor position. Conventional square wave injection methods may need complex demodulation process to find rotor position, while in the proposed method, an easy demodulation process based on the rising-falling edge of the injected voltage and carrier induced q-axis current is implemented, which needs less processing time and improves control bandwidth. Unlike some saliency-based sensorless methods, the proposed method uses maximum torque per ampere (MTPA) strategy, instead of zero d-axis command current strategy, to improve control performance. Furthermore, this paper directly uses resultant d-axis current to detect the magnet polarity and eliminates the need to add an extra pulse injection for magnet polarity detection. As experimental results show, the proposed method can quickly find initial rotor position and MTPA strategy helps to improve the control performance. The effectiveness of the proposed method and all theoretical concepts are verified by mathematical equations, simulation, and experimental tests.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.2
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• pp.309-320
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• 2019

Blockchain has been developed as a key technology for many cryptocurrency systems such as Bitcoin. These days, blockchain technology attracts many people to adopt it to various fields beyond cryptocurrency systems for their information sharing and processing. However, with the development and increasing adoption of the blockchain, security incidents frequently happen in the blockchain systems due to their implementation flaws. In order to solve this problem, in this paper, we analyze the software vulnerabilities of Bitcoin and Ethereum, which are the most widely used blockchain applications in real world. For that purpose, we conduct an in-depth analysis of source code of them to detect software vulnerabilities, and examine an OS command injection attack exploiting the detected ones.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.3
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• pp.288-294
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• 2013

This paper introduces a novel method of on-line identifying the stator resistance and leakage inductance of dual three phase induction motor (DTPIM). According to the machine mathematical model, the stator resistance and leakage inductance can be estimated using the voltage and current values in harmonic subspace. Thus a method of voltage vector injection in harmonic subspace (VVIHS) is proposed, which causes currents in harmonic space. Then the errors between command and actual harmonic currents are utilized to regulate the machine parameters, including stator resistance and leakage inductance. The principle is presented and analyzed in detail. Experimental results prove the feasibility and validity of proposed method.

• The Journal of the Korean dental association
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• v.58 no.7
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• pp.404-411
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• 2020

This study reports the unusual complications of 22-year-old male who presented with sudden hearing loss after the right mandibular third molar extraction under local anesthesia with 3.6 ml of 2 % lidocaine. Total 8.75 mg of oral dexamethasone for 1 week immediately after extraction was prescribed in department of oral and maxillofacial surgery but hearing did not improve after 1 week. As referral to otolaryngology, total 600 mg of oral methylon and hyperbaric oxygen therapies were operated for 2 weeks. The hearing of patient was improved at 6 weeks after extraction but tinnitus was persisted even after 12 months. The reason and treatment were discussed with literature review, searching with the keywords ['hearing loss' AND ('dental' OR 'tooth extraction'OR'teeth extraction')] in PubMed and Google scholar at October 2019. Total five cases were reported after tooth extraction with local anesthesia. The sudden hearing loss could be associated with local anesthesia containing vasoconstrictors. Early steroid (extensive medication and intra-tympanic injection) and hyperbaric oxygen therapies were recommended within 2 weeks. As a proper treatment, hearing could be improved but other additional symptoms, such as tinnitus, dizziness, might be remained.

• ETRI Journal
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• v.25 no.5
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• pp.387-400
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• 2003

Since its launching on 21 December 1999, the Korea Multi-Purpose Satellite-I (KOMPSAT-I) has been successfully operated by the Mission Control Element (MCE), which was developed by the ETRI. Most of the major functions of the MCE have been successfully demonstrated and verified during the three years of the mission life of the satellite. This paper presents the operational performances of the various functions in MAPS. We show the performance and analysis of orbit determinations using ground-based tracking data and GPS navigation solutions. We present four instances of the orbit maneuvers that guided the spacecraft form injection orbit into the nominal on-orbit. We include the ground-based attitude determination using telemetry data and the attitude maneuvers for imaging mission. The event prediction, mission scheduling, and command planning functions in MAPS subsequently generate the spacecraft mission operations and command plan. The fuel accounting and the realtime ground track display also support the spacecraft mission operations.