• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.7
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• pp.1261-1266
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• 2017

A random and systematic jitter suppressed delay locked loop (DLL)-based clock generator with a delay-time voltage variance converter (DVVC) and an averaging circuit (AC) is presented. The DVVC senses the delay variance of each delay stage and generates a voltage. The AC averages the output voltages of two consecutive DVVCs to suppress the systematic and random delay variance of each delay stage in the VCDL. The DVVC and AC averages the delay time of successive delay stages and equalizes the delay time of all delay stages. In addition, a capacitor with a switch working effectively as a negative feedback function is introduced to reduce the variation of the loop filter output voltage. Measurement results of the DLL-based clock generator fabricated in a one-poly six-metal $0.18{\mu}m$ CMOS process shows 13.4-ps rms jitter.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1347-1356
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• 2018

In a three-phase system, three-phase AC signals can be translated into two-phase DC signals through a coordinate transformation. Thus, the PI regulator can realize a zero steady-state error for the DC signals. In the control of a three-phase grid-connected inverter, the phase angle of grid is normally detected by a phase-locked loop (PLL) and takes part in a coordinate transformation. A novel control strategy for a three-phase grid-connected inverter with a frequency-locked loop (FLL) based on coordinate transformation is proposed in this paper. The inverter is controlled as a current supply. The grid angle, which takes part in the coordinate transformation, is replaced by a periodic linear changing angle from $-{\pi}$ to ${\pi}$. The changing angle has the same frequency but a different phase than the grid angle. The frequency of the changing angle tracks the grid frequency by the negative feedback of the reactive power, which forms a FLL. The control strategy applies to non-ideal grids and it is a lot simpler than the control strategies with a PLL that are applied to non-ideal grids. The structure of the FLL is established. The principle and advantages of the proposed control strategy are discussed. The theoretical analysis is confirmed by experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.2
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• pp.73-79
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• 2001

In this paper, the transmitted noise reduction performance of piezoelectric smart panels is experimentally studied. The proposed piezoelectric smart panels are comprised of plate structure on which piezoelectric sensor/actuators are bonded and sound absorbing material is provided. It is a combination of passive and active approaches utilizing a passive effect at high frequencies and an active effect at low frequencies. To prove the concept of piezoelectric smart panels, an acoustic measurement experiment is performed. An acoustic tunnel is designed and its acoustic characteristics are tested. Below 800Hz, the tunnel exhibits a plane wave guide characteristics. When an absorbing material is bonded on a single plate, a remarkable transmitted noise reduction in mid frequency range is observed except the first resonance frequency. By enabling the active control of single smart panel with negative feedback control. about 10dB noise reduction is achieved at the resonance frequencies. The double smart panel got 4dB at the first resonance frequency and has more potential to reduce the transmitted noise in a wide range frequency. Piezoelectric smart panels incorporating passive absorbing material and active piezoelectric devices is a promising technology for noise reduction in a wide range frequency.

• Journal of the Korean Society of Food Culture
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• v.13 no.3
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• pp.215-225
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• 1998

The purpose of this study was to identify the development trends and feasibility of health-oriented convenience foods in Korea for promoting health. Special objectives were to investigate characteristics of health-oriented convenience foods; to determine the factor affecting the sale of health-oriented convenience foods; to examine marketing strategies of the foodservice industry; and to provide feedback for the development plan. Questionnaires were developed in this study and mailed to 10 food companies in Korea and then telephone interviews were carried out. Also, marketing strategies of each industry are analyzed by the visit interview with food processing and marketing chargers. The survey was conducted between September 30 and October 30, 1997. The results of this study were summarized as following : The most popular health-oriented convenience foods were completely precooked type, pouch/PE bag packaging type, diet purpose, 100-300 gram size, and convenience store sales with regard to selling and developing health-oriented convenience foods. About factors affecting selling health-oriented convenience foods, the best contributors among factors were seasonality, convenience, and negative image for instant foods. For health-oriented convenience foods, the most important factor was the improvement of taste and quality. Adults should be the most promising customers for health-oriented convenience foods. Food companies must promote variety, taste, nutrition, convenience, price, and advertising of health-oriented convenience foods for the powerful marketing strategies in the future.

• The Journal of the Korea Contents Association
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• v.11 no.12
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• pp.347-356
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• 2011

The aim of this study was to determine the prevalence of self-assessment halitosis and to offer the basic information that establishes a strategy of effective health promotion and to enhance the quality of life. This study performed a questionnaire survey. The questionnaire was filled out by the 362 adults, who lived in Incheon Metropolitan City from May to July, 2010. The data were analyzed using a Chi-square test in the SPSS version 12.0 program. The prevalence rate of self-assessment halitosis was 24.3%. Hypertension, diabetes, medication and inadequate oral hygiene practice were significantly associated with self-assessment halitosis. Other factors of self-assessment halitosis were older age and occupation. As a result, dental professionals have to investigate a systemic disease history thoroughly. And they have to educate regular checkup of oral health and to perform a continuous feedback. The self-assessment halitosis has a negative influence on mental health and social life, so dental professionals must take into consideration about the halitosis.

• Clinical and Experimental Reproductive Medicine
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• v.28 no.2
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• pp.131-140
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• 2001

Objective: To know the effects of xenoestrogen on spermatogenesis, we investigated the expression of cytochrome P450s enzymes (CYPscc, $CYP_{17{\alpha}}$, CYP19) and $3{\beta}$-HSD genes involved in steroidogenesis. Methods: Mouse testicular cells were prepared from 15-day-old ICR mice which had only pre-meiotic germ cells by enzyme digestion using collagenase and trypsin. Testicular cells were cultured in DMEM supplemented with FSH (0.1 IU/ml) and 10% FBS or medium with estrogen ($E_2$), bisphenol-A (BPA), octylphenol (OP; $10^{-9},\;10^{-7},\;10^{-6},\;10^{-5},\;10^{-4}M$, respectively) and aroclor 1254 (A1254) known as PCBs for 48 hours. The gene expression of cytochrome P450 enzymes were examined by semi-quantitive RT-PCR. The production of estrogen and testosterone was examined by RIA. Results: As results, expression of CYPscc mRNA was not significantly decreased, but $3{\beta}$-HSD and $CYP_{17{\alpha}}$. mRNA were significantly dose-dependent decreased. And production of testosterone and estrogen were not different except BPA and OP group ($10^{-5}M$). Conclusion: BPA, OP and A1254 might inhibit steroidogenesis by decreasing CYPscc, $3{\beta}$-HSD and $CYP_{17{\alpha}}$. mRNA expression in the mouse testis. These results suggest that BPA, OP and PCBs like as an endocrine disruptors inhibit the productions of steroidogenic enzymes and decrease the production of T and E by negative feedback mechanism. Therefore, these might disrupt steroidogenesis in Leydig cells of testis and would disturb testicular function and subsequently impair spermatogenesis.

• Quality Improvement in Health Care
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• v.14 no.1
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• pp.77-91
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• 2008

Objectives : The purpose of this study was to survey the opinion and attitude of hospital managers toward the hospital evaluation program. Method : Managers of 157 hospitals which had participated in the hospital evaluation program were requested to respond to structured self-administered questionnaire. The questionnaire was composed with five categories: the preparation for the hospital evaluation program, the expertise levels of surveyors, the process and contents of the hospital evaluation program, the applying strategies for the result of the hospital evaluation to manager's work at their hospitals, and the main points to improve the hospital evaluation program. Result : 135 out of the 157 subjects completed the questionnaire, and the overall response rate was 86%. The hospital managers answered that they didn't have enough information such as the scoring rule of the standards, the process of the evaluation, and how to ask and get an answer to prepare the hospital evaluation. Furthermore, they estimated that the surveyors weren't specialized enough and didn't give a chance of checking over the result of the evaluation. In addition, they experienced that the result and feedback of the evaluation weren't enough information to be used as a guideline to improve in hospital management. Managers of the hospitals responded that the standards and method of survey in the hospital evaluation system should be reformed. Conclusion : Most of the responded managers seemed to have negative opinion on the hospital evaluation system, even though they were pushed up for interest in quality. Further studies and extensive evaluation of the hospital evaluation program are needed to bring up various information such as receptiveness and effectiveness.

• The Korean Journal of Physiology
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• v.21 no.2
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• pp.291-296
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• 1987

There have been reports on the aberration of the control mechanisms of the blood pressure, hormone secretion, and renal functions in spontaneously hypertensive rats (SHR). However, the contribution of the renin-angiotensin system in the maintenance of high blood pressure in SHR is still controversial. Recently, it has been reported that the negative feedback short loop control mechanism of the renin-angiotensin system may be changed in SHR. In the present experiment, it was attempted to explore the possible alterations in the effect of arginine vasopressin (AVP) on the renal function in SHR. Experiments have been done in anesthetized SHR as well as in normotensive Wistar and Sprague-Dawley rats as control groups. Pharmacologic doses of AVP (10-13 mU/rat/10 min) decreased urine volume, excreted amount of creatinine and para-amino-hippuric acid. No differences in these parameters was observed between normotensive and hypertensive rats. AVP increased sodium and potassium excretion, but the responses in SHR were suppressed as compared with normotensive rats. Intravenous infusion of AVP also increased blood pressure in normotensive and hypertensive rats and a vasopressor effect of AVP was attenuated in SHR. There was a positive correlation between the changes in blood pressure and excreted amount of sodium during AVP infusion. These data suggest that the attenuated natriuretic effect of intravenous infusion of AVP may be due to a difference in renal tubular responsiveness to AVP but not due to a difference in vasopressor responsiveness.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.4
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• pp.819-825
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• 2016

In this paper, a phase locked loop structure with parallel dual loop which have a different bandwidth has been proposed. The bandwidths depending on transfer functions are obtained through dual loops. Two different bandwidths of each loop are used to suppress noise on the operating frequency range. The proposed phase locked loop has two different voltage controlled oscillator gains to control two different wide and narrow loop filters. Furthermore, it has the locking status indicator to achieve an accurate locking condition. The phase margin of $58.2^{\circ}$ for wide loop and $49.4^{\circ}$ for narrow loop is designed for stable operation and the phase margin of $45^{\circ}$ is maintained during both loops work together. It has been designed with a 1.8V 0.18um complementary metal oxide semiconductor (CMOS) process. The simulation results show that the proposed phase locked loop works stably and generates a target frequency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.12
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• pp.2326-2332
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• 2016

In this paper, the proposed small size PLL works stable with the discrete loop filter which is controlled by voltage controlled oscillator's output signal. A switch controlled loop filter is introduced into the proposed PLL instead of a conventional $2^{nd}$-order loop filter. Those three switches are controlled by the very high frequency output signal of voltage controlled oscillator. The switches are also controlled by UP/DN signals and 'on/off' depending the presence of UP/DN signals. A negative feedback functioned capacitor with a switch does make it possible to integrate the PLL into a single chip. The proposed PLL works stably even though a total of small 180pF capacitor used in the discrete loop filter. The proposed PLL has been designed with a 1.8V supply voltage, 0.18um multi - metal and multi - poly layer CMOS process and proved by Hspice simulation.