• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2018.05a
• /
• pp.481-483
• /
• 2018

Recently, as the demand for electronic communication equipment increases, the importance of image and signal processing is increasing. However, noise is generated in digital signal due to various causes during transmission and reception, lowering equipment reliability and causing malfunction. Particularly, since AWGN may be found in most electronic equipments, AWGN removal is mandatorily performed as a preprocessing phase in various fields, such as image recognition, extraction, and segmentation. In the present paper, an AWGN removal algorithm which considers high frequency components is proposed. Conventional methods show relatively inadequate performance in images with high frequency components. To overcome this problem, proposed is a filter algorithm that add or subtract difference images in the local mask. And to verify performance of the proposed algorithm, PSNR and enlarged images are used to compare with the existing methods.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.51 no.3
• /
• pp.120-125
• /
• 2002

The switching-mode power converter has been widely used because of its features of high efficiency and small weight and size. These features are brought by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI(Electromagnetic Interference) which deteriorate the reliability of the converter themselves and entire electronic systems. This problem on the surge and noise is one of the most serious difficulties in AC-to-DC converter. In the switching-mode power converter, the output voltage is generally controlled by varying the duty ratio of main switch. When a converter operates in steady state, duty ratio of the converter is kept constant. So the power of switching noise is concentrated in specific frequencies. Generally, to reduce the EMI and improve the immunity of converter system, the switching frequency of converter needs to be properly modulated during a rectified line period instead of being kept constant. Random Pulse Width Modulation (RPWM) is performed by adding a random perturbation to switching instant while output-voltage regulation of converter is performed. RPWM method for reducing conducted EMI in single switch three phase discontinuous conduction mode boost converter is presented. The more white noise is injected, the more conducted EMI is reduced. But output-voltage is not sufficiently regulated. This is the reason why carrier frequency selection topology is proposed. In the case of carrier frequency selection, output-voltage of steady state and transient state is fully regulated. A RPWM control method was proposed in order to smooth the switching noise spectrum and reduce it's level. Experimental results are verified by converter operating at 300V/1kW with 5%~30% white noise input. Spectrum analysis is performed on the Phase current and the CM noise voltage. The former is measured with Current Probe and the latter is achieved with LISN, which are connected to the spectrum analyzer respectively.

• Geophysics and Geophysical Exploration
• /
• v.17 no.3
• /
• pp.163-170
• /
• 2014

Development of a modeling technique for accurately interpreting electromagnetic (EM) data is increasingly required. We introduce finite difference (FD) and finite-element (FE) methods for three-dimensional (3D) frequency-domain EM modeling. In the controlled-source EM methods, formulating the governing equations into a secondary electric field enables us to avoid a singularity problem at the source point. The secondary electric field is discretized using the FD or FE methods for the model region. We represent iterative and direct methods to solve the system of equations resulting from the FD or FE schemes. By applying the static divergence correction in the iterative method, the rate of convergence is dramatically improved, and it is particularly useful to compute a model including surface topography in the FD method. Finally, as an example of an airborne EM survey, we present 3D modeling using the FD method.

• Safety and Health at Work
• /
• v.11 no.3
• /
• pp.335-346
• /
• 2020

Background: Nursing service is a nonroutine work with an excessive physical load and diverse tasks. This study derived representative common tasks based on the frequently occurring tasks with a high physical load in the nursing workers' daily work and developed indicators to evaluate the work risk by reflecting the characteristics of nonroutine work. Methods: Common tasks were classified through the following stages: literature review, first focus group interview (FGI) with experts, first classification of common tasks, second FGI with hospital health managers, a survey of nursing service workers, and the final classification of common tasks for each task type. To develop an objective risk index for physical load assessment, we investigated the frequency and duration of the derived common tasks via survey. Results: Nursing common tasks were categorized into six task types and 56 subtasks. To evaluate the risks of various tasks in nonroutine works, three frequencies and three working time levels were defined by examining the task frequency and working hours. Exposure time was defined to reflect the characteristics of a nonroutine job. The final risk assessment was the product of the exposure time level and job intensity level. From this, four risk action levels were derived. Conclusion: This study has the advantage of solving the problem of focusing on some tasks in evaluating the physical load. It was meaningful in that a new risk assessment index based on exposure time was proposed based on the development of an evaluation scale for frequency and time by reflecting the characteristics of nonroutine work.

• Korean Parent-Child Health Journal
• /
• v.3 no.2
• /
• pp.41-48
• /
• 2000

The sleep is the most important problem for new parents. However, there were very rare the study about sleep of normal neonates and early infants in Korea. So we attempted pilot survey study of neonates' sleep pattern. The purpose of this study was to investigate the sleep pattern of normal neonates in Seoul and Kyungki area and to provide for basis for nursing intervention for parents of them. The subjects of this study were 37 normal full-term neonates of 2~3weeks of age who were visited by researcher or assistant at postpartum care unit, health care clinic, outpatient clinic located in Seoul and Kyungki area from April 20, 1999 to March 15, 2000. This study was descriptive survey study under the convenient sampling method. The instrument of this study was the NCASA translated by Korean Parent Child Health Academic Association. The collected data were coded as 1/4hour unit, and analyzed by MS Office Excel program. The result of this study were as followed: 1. The mean amount of total sleep was 15.1hours. The mean amount of daytime sleep was 9.5hours. The mean amount of nighttime sleep was 5.7 hours. The mean amount of longest sleep was 2.9hours. The mean amount of shortest sleep was 0.6hour. 2. The mean amount of total activity was 8.9hours. The mean amount of daytime activity was 6.5 hours. The mean amount of nighttime activity was 2.3hours. The frequency of feeding was 10.4 times a day. The frequency of daytime feeding was 7.3 times. The frequency of nighttime feeding was 3.1 times. It is suggested that various subjects and more data according to age, and comparative study among different cultures are needed for further study in the future.

• Research in Community and Public Health Nursing
• /
• v.8 no.2
• /
• pp.178-196
• /
• 1997

The purpose of this study is to identify the kind, the frequency, and the type of Stress Management Program(SMPs) throughout life-span used foreign, recent research. The period of this study was from July 1 to Dec. 10, 1997. The data were collected through Medline using two concepts: stress management programs and life-span. The number of these research were 106 and thirty-one experimental researches that were tested the effectiveness of SMPs throughout life span were selected. The data were analysed by the kind, frequency, and life-span. The results were as follows: 1. The kind and frequency of SMP : The total number of the kind of SMP were twenty-two. The most used SMP was relaxation therapy, 22 out of 31. The second biofeedback was 10, the third, cognitive behavior program was 9, the fourth, nutrition and diet, and education were 7. The others were coping skill(4), cognitive therapy(4), breathing(4), imagery(3), autogenic training(3), sleep and rest(2), meditation(2), information(2), desensitization(2), hypnosis(2), behavior therapy(1), time management (1), visualization(I), yoga(I), diversion(1), and problem solving skill. 2. Throughout life-span: Most SMPs were applied to adolescents, young adults, and middle-adults. Other subjects could not be found under the schooler. 3. The type of SMPs : 28(90.3%) out of 31 research used combined-SMP : two-combined SMP, 5: three-combined SMP, twelve: four-combined SMP, seven: five-combined SMP. 4. Afterward, further study such as meta-analysis are needed in order to identify effective ness of the SMPs.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.46 no.5
• /
• pp.36-47
• /
• 2009

There exists RFID reader-to reader frequency which can not recognize tag in dense reader nude because the interference causes low SIR. To solve this frequency, the many algorithms based on TDM have been proposed. But the most of existing algorithms not obtain the optimal time allocation but propose heuristic scheduling algorithm. In this paper, we apply game theory which deals with interest between players of game to RFID reader-to reader interference and analyze the time allocation problem of reader based on TDM in terms of cooperative game which the players bind agreements using Nash Bargaining Solution(NBS) and non-cooperative game which the players do not bind agreements using Nash Equilibrium(NE). The applied results show that in dense reader mode, NBS of cooperative game is superior to NE of non-cooperative game and present optimal time allocation in dense reader mode.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.42 no.1
• /
• pp.1-8
• /
• 2005

In this paper, peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) with respect to the subchannel coding schemes for interchannel interference (ICI) self-cancellation is analyzed. It is shown theoretically and experimentally that a shaping component is generated in the transmitted sequence in the conventional correlative coding where a pair of antipodal signals is assigned in adjacent subchannels. Due to the shaping component, the signal powers in the mid and edges of a symbol are scaled by different weighting coefficients, resulting in increased PAPR. To overcome this problem a simple adjacent subchannel coding scheme is presented in this paper. In the new scheme, the shaping component caused by partial repetition of signals is eliminated by assigning a pair of signals in which phase difference varies signal-to-signal. As results, the new scheme has 2-3 dB smaller PAPR than the conventional ICI self-cancellation OFDM while maintaining much higher carrier-to-interference ratio than a normal OFDM system.

• Journal of Advanced Marine Engineering and Technology
• /
• v.36 no.6
• /
• pp.780-787
• /
• 2012

In general, the ocean wave vibration power generator consists of buoy, vibration system and linear generation system. It maximized energy efficiency by using resonance phenomenon that turned to the natural frequency of vibration system and frequency of ocean wave energy. But it is difficult to obtain efficiently energy from ocean wave because the frequency of ocean wave changes from moment to moment. In this paper, we study the buoy and vibration system of ocean wave power generator to solve these problem. Firstly, we designed the buoy that gives rise to resonance between ocean wave and buoy. Secondly, we designed vibration system that is occurred to resonance between buoy and vibration system. And then the relative velocity between the buoy and magnetic of ocean wave vibration generator increases and the relative displacement between buoy and ocean wave decreases at the same time. As a result, the method which is proposed in this paper has merits not only securing its stability from harsh ocean wave environment but also obtaining more kinetic energy from ever-changing ocean wave.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.9
• /
• pp.825-829
• /
• 2012

The global warming caused the changes of our environment like an increasing tropical night phenomenon in the middle latitude areas. Especially, in Korea, the habitats of tropical Korean blockish cicada have changed from Jeju island located in Southern part of Korea to the whole of Korea because of the increasingly warming weather. The cicadas crying sound have been social problem because the tropical Korean blockish cicadas cry at middle of the night owing to the various outdoor lights. The cicada is positive phototaxis insect. So, the cicada is not cry at night. But if the outdoor light is very bright, then the cicada confuse the night as a day and start to cry. As a result, the cicadas crying noise has caused the resident living in downtown to an unpleasure and sleeplessness. In this research, we have measured three kinds of cicada singing noise at 16 points of urban area(Incheon, Gwangju, Busan, Gyeonggido Anyang). And then we analyzed the sound quality of the three kinds of cicada singing noise using by CADA-X signal process program. And we analyzed the acoustical characteristics by STFT(short time Fourier transform) which is a time-frequency analysis method. The characteristics of the cicada singing noise in terms of the sound quality and the time-frequency variation will be usefull to discover the relations between the human annoyance about the cicada singing noise and the acoustical characteristics.