• Journal of Sensor Science and Technology
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• v.26 no.4
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• pp.286-291
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• 2017

With regards to heading estimation using gyroscope and magnetometer signals, magnetic disturbance added in the magnetometer signals is a main degradation factor in the estimation accuracy. Although there are a number of existing mechanisms that may properly compensate for the magnetic disturbances, they are designed to react only to the magnetic disturbances, but not to the time derivative of disturbances. Note that the sensors may experience abrupt changes in the magnetic disturbances, particularly for ambulatory applications. This paper proposes a magnetic disturbance model-embedded heading estimation filter for time-varying magnetic environments. The proposed magnetic disturbance model is based on a first-order Markov chain with a conditional switching technique depending on the time derivative of disturbances. Once a high amount of derivative is detected, the corrupted magnetometer signals are discarded to protect the filter from them. In our experimental results, the averaged heading error of tests was $1.46^{\circ}$, while that of the original approach without switching was $5.75^{\circ}$.

• The Korean Journal of Emergency Medical Services
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• v.16 no.3
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• pp.103-115
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• 2012

Purpose : Inadequate chest compression during cardiopulmonary resuscitation(CPR) may result in the insufficient blood flow to preserve critical organ function. The study evaluated changes of quality of cardiopulmonary resuscitation over time in 30:2 CPR by laypersons and analyzed rescuer factors affecting the quality of chest compressions over time. Methods : This study was designed to know quality of CPR changes during 5 minutes. 47 students completed CPR training courses. They were performed 30:2 CPR using a manikin with Skill-Reporter for 5 minutes continuously to get data of depth, rate of chest compression, volume and correct rate of ventilation. Results : Time dependent analysis showed significant ineffective compression depth in females and under weight rescuers. In case of female, we found effective compression depth has maintained up to 2 minutes, but it decreased significantly after 2 minutes. However, underweight rescuers maintained effective compression depth up to a minute but it decreased after 1 minute. Conclusion : Although compression rate maintained over time, chest compression quality declined significantly. It suggested switching compression at an interval of 2 minutes is reasonable for 30:2 CPR by layperson but underweight rescuers may provide effective chest compression by switching shift every one minute.

• Journal of IKEEE
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• v.20 no.4
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• pp.432-434
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• 2016

In conventional SIDO(Single Inductor Dual Output) boost converter, charging time is changed by load power consumption. In this case, if the power consumption of one load is changed to such a degree that switching frequency of the boost converter must be changed, another load charge time is also changed, which this causes cross regulation. In this paper, the charge copy technique is proposed to reduce cross regulation. When the switching frequency is changed to an integer ratio, another load charge time is also changed to integer ratio. Simulation result shows that proposed method reduces the 10.24mV cross regulation and 39.118us recover-time compared with conventional method.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.11
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• pp.611-621
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• 2002

For real-time systems, multiprocessor support is indispensable to handle the large number of requests. Existing real-time on-line scheduling algorithms such as Earliest Deadline First Algorithm (EDF) and Least Laxity Algorithm (LLA) may not be suitable for scheduling real-time tasks in multiprocessor systems. Although EDF has low context switching overhead, it suffers from "multiple processor anomalies." LLA has been shown as suboptimal, but has the potential for higher context switching overhead. Earliest Deadline Zero Laxity (EDZL) solved somewhat the problems of those algorithms, however is suboptimal for only two processors. Another algorithm EDA2 shows very good performance in overload phase, however, is not suboptimal for muitiprocessors. We propose two on-line scheduling algorithms, Earliest Deadline/Least Laxity (ED/LL) and ED2/LL. ED/LL is suboptimal for multiprocessors, and has low context switching overhead and low deadline miss rate in normal load phase. However, ED/LL is ineffective when the system is overloaded. To solve this problem, ED2/LL uses ED/LL or EDZL in normal load phase and uses EDA2 in overload phase. Experimental results show that ED2/LL achieves good performance in overload phase as wet] as in normal load phase.oad phase.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1298-1307
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• 2017

The constant on-time current-mode controlled (COT-CMC) switching dc-dc converter is stable, with no subharmonic oscillation in its current loop when a voltage ripple in its outer voltage loop is ignored. However, when its output capacitance is small or its feedback gain is high, subharmonic oscillation may occur in a COT-CMC buck converter with a proportional-integral (PI) compensator. To investigate the subharmonic instability of COT-CMC buck converters with a PI compensator, an accurate reduced-order asynchronous-switching map model of a COT-CMC buck converter with a PI compensator is established. Based on this, the instability behaviors caused by output capacitance and feedback gain are investigated. Furthermore, an approximate instability condition is obtained and design-oriented stability boundaries in different circuit parameter spaces are yielded. The analysis results show that the instability of COT-CMC buck converters with a PI compensator is mainly affected by the output capacitance, output capacitor equivalent series resistance (ESR), feedback gain, current-sensing gain and constant on-time. The study results of this paper are helpful for the circuit parameter design of COT-CMC switching dc-dc converters. Experimental results are provided to verify the analysis results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.12C
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• pp.1197-1206
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• 2002

Recently, the research on the construction of optical Internet backbone networks using WDM has been actively progressed. In this paper, we propose the offset based service-differentiation scheme in optical burst switching (OBS) networks. We classify the services into two classes; high class and low class. The proposed scheme decides the offset time of high class so as to satisfy the required burst loss rate (BLR) of services according to the service-differentiation ratio (SDR). The SDR may be set depending on the environment of OBS network and user's requirements, our scheme decides the BLR of high class by using the required SDR and conservation law. Finally, we use the offset time decision (OTD) algorithm to determine the offset time of high class. The proposed scheme is evaluated through simulation. The result of simulation is compared with that of analysis to verify the proposed scheme.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.4
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• pp.312-321
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• 2013

In this paper, high efficiency control method for flyback inverter with synchronous rectifier(SR) based on photovoltaic AC modules is proposed. In this control method, the operation of SR is classified according to the voltage spike across main switch SP. When the voltage spike across SP is lower than the rating voltage of SP, the operation of active clamp circuit is interrupted for reducing the switching loss of auxiliary switch. In this time, the SR is operated for soft-switching of SP. When the voltage spike across Sp is higher than the rating voltage of SP, the operation of active circuit is activated for reducing the voltage spike. The SR is operated for reducing the conduction loss of secondary output diode. Thus, a switching loss of the main switch can be reduced in low power region, and weighted-efficiency can be improved. A theoretical analysis and the design principle of the proposed method are provided. And validity is confirmed through simulation and experimental results.

• Journal of KIISE
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• v.43 no.5
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• pp.606-612
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• 2016

The multi-view video service based on the DASH(Dynamic Adaptive Streaming over HTTP) switches the viewpoint or object which is selected by the user among the multiple video streams captured by multiple cameras. However, the problem is that the conventional DASH-based multi-view video service takes a long time to switch the viewpoint. The reason is that the conventional scheme switches to the new video stream after consuming all buffered segments of the previous video stream. In this paper, we propose a video streaming scheme for minimizing the viewpoint switching delay in the DASH-based multi-view video service. In order to minimize the viewpoint switching delay, the proposed scheme configures the video streams by controlling the GoP (Group of Pictures) size and controls the client buffer based on bandwidth estimation and playback buffer occupancy. Through the experimental results, we prove that the proposed scheme reduces the viewpoint switching delay.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.5
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• pp.11-116
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• 2000

A topology decreased switching loss and voltage stress by zero voltage switching is presented in this paper. Generally, Switching mode converting productes voltage stress and power losses due to excessive voltage and current. which affect to performance of power supply and reduce overall efficiency of equipments. Virtually, In flyback converter, transient peak voltage and current at switcher are generated by parasitic elements. To solve these problems, present ZVS flyback converter topology applied a auxiliary circuit. Incorporation of auxiliary circuit into a conventional flyback topology serves to reduce power losses and to minimize switching voltage stress. Snubber capacitor in auxiliary circuit serves ZVS state by control voltage variable time at turn on and off of main switch, then reduces voltage stress and power losses. The proposed converter has lossless switching in variable load condition with wide range. A detailed analysis of the circuit is presented and the operation procedure is illustrated. A (50W 100kHz prototype) ZVS flyback converter using a auxiliary circuit is built which shows an efficiency improvement as compared to a conventional hard switching flyback converter.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.433-434
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• 2015

Dictionary meaning of circuit-breaker is a mechanical switching device, capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal circuit conditions such as those of short circuit. and it had been recognized as being operated simultaneously. Controlled Switching System(CSS), which is technology for individual pole operation, are widely used to reduce transient phenomenon, for example switching surges, inrush current, for a all switching cases and nowadays it have become and economical solution for a switching place. The conventional solution to these problem is the use of pre-insertion resistors of $520{\Omega}$. However, it is recognised that the cost for products and maintenance are expensive and this apparatus makes more complex the circuit-breaker mechanism. Korea Electric Power Cooperation (KEPCO) has been study for relevant CCS technology since pilot application in substation in 2003 and plan to apply the actual power grid in 2017. This paper deals with the investigation of international CCS operation status and preview for application in KEPCO power grid.