• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.694-699
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• 2002

As the demand for slim laptops requires ion'-height optical disc drives, vibration problems of optical disc drives are of great concern. Additionally, with the decrease of a track width and a depth of focus in high density drives, studies on vibration resonance between mechanical parts become more important. From the vibration point of view, the performance of optical disc drives is closely related with the relative displacement between a disc and an objective lens which is controlled by servo mechanism. In other words, to read and write data properly, the relative displacement between an optical disc and an objective lens should be within a certain limit. The relative displacement is dependent on not only an anti-vibration mechanism design but also servo control capability. Good servo controls can make compensation for poor mechanisms, and vice versa. In a usual development process, robustness of the anti-vibration mechanism is always verified with the servo control of an objective lens. Engineers partially modify servo gain margin in case of a data reading error. This modification cannot correct the data reading error occasionally and the mechanism should be redesigned more robustly. Therefore it is necessary to verify a mechanism with respect to the possible servo gain plot. In this study we propose the experimental verification method far anti-vibration mechanism with respect to the existing servo gain plot. This method verifies axial vibration characteristics of optical disc drives on the basis of transmissibility. Using this method, we verified our mechanism and modified the mechanism for better anti-vibration characteristics.

• 패션비즈니스
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• 제19권4호
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• pp.37-56
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• 2015

This thesis aimed to determine the effecting factors(eating pattern, working condition, stress, health care) that help maintain the health of the cosmetologists' digestive system and the diseases involved (acid reflux, indigestion, gastritis, constipation & diarrhea). The research methods included survey and statistical analysis. The survey was conducted on 242 cosmetologists from August 30 to October 30 2014. The data analysis included frequency, cross table, ${\chi}^2$-test, and regression with SPSS(V. 14). The results were as follows ; (1) The cosmetologists' health of digestive system and eating pattern are related. Regular and enough meal times cause less digestive disease. Acid reflux, indigestion, gastritis, constipation and diarrhea are differently related with the type of usual eating pattern, especially, instant food is not good for digestive health. (2) The cosmetologists' health of digestive system and working condition are related. Longer daily working hours and exposure time to chemical odors are more likely to be associated with digestive diseases; whereas, longer time of standing and talking with colleagues are less likely to be associated with digestive diseases. (3) The cosmetologists' health of digestive system and stress are related. Headache, boredom, conflict of pay and compensation, and insomnia are not good for digestive health. (4) The cosmetologists' health of digestive system and health care are related. Periodical medical examination and usual body stretching are correlated with digestive diseases; whereas, people who do regular exercise and bowel movement are less likely to have digestive diseases.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권9호
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• pp.4334-4356
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• 2017

In orthogonal frequency-division multiplexing (OFDM) systems, phase noise introduced by the local oscillators can cause bit error rate (BER) performance degradation. To solve the phase noise problem, a novel orthogonal-polarization-based phase noise self-cancellation (OP-PNSC) scheme is proposed. First, the efficiency of canceling the phase noise of the OP-PNSC scheme in the AWGN channel is investigated. Then, the OP-PNSC scheme in the polarization-dependent loss (PDL) channel is investigated due to power imbalance caused by PDL, and a PDL pre-compensated OP-PNSC (PPC -OP-PNSC) scheme is proposed to mitigate the power imbalance caused by PDL. In addition, the performance of the PPC-OP-PNSC scheme is investigated, where the signal-to-interference-plus-noise ratio (SINR) and spectral efficiency (SE) performances are analyzed. Finally, a comparison between the OP-PNSC and polarization diversity scheme is discussed. The numerical results show that the BER and SINR performances of the OP-PNSC scheme outperform the case with the phase noise compensation and phase noise self-cancellation scheme.

• 한국전자파학회논문지
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• 제26권8호
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• pp.740-747
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• 2015

최근 밀리미터파 대역을 활용하는 이동통신시스템이 제안되고 있으며, 60 GHz 대역 전력증폭기로 인해 발생하는 비선형성을 효율적으로 보상하기 위한 방법의 중요성이 증가하고 있다. 본 논문에서는 전력증폭기의 비선형성이 상대적으로 작은 구간과 큰 구간으로 구분하여 계수를 사용하는 다중계수 사전왜곡기 구조를 제안하고, 이를 60 GHz 대역 고출력 전력증폭기 FMM5715X에 적용하여 LTE 신호의 선형성 보상 성능을 평가하였다. 하드웨어 테스트베드를 활용한 성능평가를 통해, 기존 방식 대비 제안 방식은 ACLR(Adjacent Channel Leakage Ratio) 측면에서 최대 6 dB 개선됨을 보인다.

• 대한전자공학회논문지TC
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• 제40권6호
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• pp.247-252
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• 2003

본 논문에서는 ETRI의 0.5 ㎛ MESFET 공정을 이용하여 광대역 MMIC 2단 증폭기를 설계 및 제작하였다. 정합회로에 의한 보상 방법(Compensated matching network)을 응용하여 2단 증폭기에서 첫 번째 단과 두 번째 단의 이득 특성이 서로 보상되도록 설계하여 광대역 특성을 얻을 수 있었으며, 일반적인 광대역 증폭기가 넓은 대역폭과 낮은 이득 및 출력 전력을 갖지만 본 논문에서는 compensated matching network를 이용하여 넓은 대역폭뿐만 아니라 높은 이득 특성을 얻었다. 제작된 광대역 증폭기의 측정결과, 1.1∼2.8 ㎓의 대역폭을 가졌으며 S/sub 21/ 이득은 11.1±0.3 ㏈를 얻었다. 전력 특성의 경우 2.4 ㎓에서 입력전력이 4 ㏈m일 때 P1㏈는 12.6 ㏈m을 얻었다.

• 대한전자공학회논문지TC
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• 제37권5호
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• pp.25-32
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• 2000

본 논문에서는 주파수에 따른 인버터의 위상특성 변화가 대역통과 여파기의 특성에 미치는 영향을 고려하고, 이러한 인버터의 위상특성 변화로 인한 대역통과 여파기의 특성 변화를 보정하기 위한 새로운 인버터 구조를 제안한다. 그리고 본 논문에서 제안된 새로운 인버터 구조에 대하여 위상변화 특성을 고려한 새로운 인버터 식을 유도한다. 제안된 인버터 구조와 설계 식을 이용하여 대역통과 여파기를 설계하고, 설계된 여파기의 특성을 시뮬레이션을 통하여 주파수에 따른 인버터의 위상특성 변화로 인한 대역통과 여파기의 특성 왜곡이 최적화 설계 기법이나 반복 설계 과정 없이 보정됨을 나타낸다.

• 고려인삼학회:학술대회논문집
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• 고려인삼학회 1980년도 학술대회지
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• pp.151-170
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• 1980

Physiological response of Panax ginseng var. atropurpureacaulo (purple stem variety, Pg) to light was reviewed through old literatures and recent experiments. Canopy structure, growth, pigment, leaf anatomy, disease occurence, transpiration, photosynthesis (PS), leaf saponin, photoperiodism and nutrient uptake were concerned. P. ginseng var. xanthocarpus (yellow berry variety, Px) and Panax quinquefolius(Pq) were compared with Pg if possible. Compensation point(Cp) increased with increase of light and ranged from 110 to 150 at $20^{\circ}C$ but from 140 to 220 at $30^{\circ}C$ with 4 to 15 Klux indicating occurence of light and temperature-dependent high photorespiration. Characteristics of Korea ginseng to hate high temperature was well accordance with an observation 2000 years ago. Korea ginseng showed lower Cp and appeared to be more tolerant to high light intensity and temperature than American sheng although the latter showed greater PS, stomata frequency and conductance, chlorophyll and carotenoids. Px showed lower PS than Pg probably due to higher Cp. Total leaf saponin was higher in leaves grown under high light. Ratio or diol saponin and triol saponin(PT/PD) decreased with increase of light intensity during growing mainly due to decrease of ginsenoside $Rg_1$ but increase of ginsenoside Rd. Leaves of Pg and Px had $Rg_1$ but no $Rb_3$ which was only found as much as $20\%$ of total in Pq leaves, and decreased with increase of light intensity. Re increased in Pg and Px but decreased in Pq with increase of light. PT/PD in leaf ranged 1.0-1.5 in Pg and Px but around 0.5 in Pq. Korea ginseng has Yang characteristics(tolerant to high light and temperature), cultured under Eum(shade) condition and long been used for Yang efficacy (to build up energy) while Pq was quite contrary. Traditional low light $intensity(3-8\%)$ for Korea ginseng culture appeared to be strongly related to historical unique quality. Effect of light quality and photoperiodism was not well known. Experiences are long but scientific knowledge is short for production and quality assessment of ginseng. Recent scientific knowledge of ginseng should learn wisdom from old experiences.

• 대한전자공학회논문지SD
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• 제47권2호
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• pp.60-67
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• 2010

본 논문에서는 입력 전류를 정현파가 되도록 제어하기 위하여 boost 인덕터 전류의 평균값이 정현파 모양을 따라가도록 하는 평균전류 제어 방식의 PFC IC를 설계하였다. 설계된 IC는 EMI 규격에 적합하도록 75kHz의 고정주파수를 가지고 고속 제어를 위해 넓은 대역폭을 갖도록 오차 증폭기 및 전류 증폭기에 RC 보상 루프를 구성하였다. 또한 시스템 내부의 오실레이터를 이용해 구형파와 삼각파를 발생시켜 역률제어에 적합한 신호를 생성하고, UVLO, OVP, OCP, TSD의 회로를 추가하여 시스템이 안정적으로 동작이 되도록 하였다. 설계된 IC는 $1{\mu}m$ High Voltage(20V) CMOS 공정을 이용하였고, 역률보정기능과 각종 보호 회로를 검증하기 위해 Cadence의 Spectre simulator를 이용하였다.

• 대한전자공학회논문지SD
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• 제48권2호
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• pp.35-43
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• 2011

본 논문에서는 Quadrature LC VCO(Voltage controlled oscillator)의 I/Q 오차를 분석하고, 그 분석된 결과를 이용하여 I/Q 오차 보정 회로를 제안한다. 제안된 I/Q 오차 보정 회로는 높은 주파수 대역폭을 요구하는 위상 오차 검출기를 사용하는 대신에 낮은 주파수 대역폭으로도 동작이 가능한 진폭 오차 검출기를 사용한다. 제안된 I/Q 오차 보정 회로의 검증을 위하여 2.5GHz Quadrature LC VCO가 $0.18{\mu}m$ CMOS 공정으로 제작 및 측정되었다. 측정결과 제안된 진폭 오차 검출기를 사용해도 기존의 위상 오차 검출기는 사용하는 경우들과 유사한 I/Q 오차 보정 성능을 얻을 수 있음을 확인하였다. 본 I/Q 오차 보정 회로는 1.8V 전원 전압에서 0.4mA 전류를 소모하며, 차지하는 칩 면적은 $0.04mm^2$이다.

• Safety and Health at Work
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• 제1권2호
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• pp.149-157
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• 2010

Objectives: To quantify disability level in salespeople with concurrent low back pain (LBP) and to determine the relative associations between demographic, occupational, psychosocial and clinical factors and back disability. LBP is the most common cause of work-related disability in people under 45 years of age and the most expensive cause of work-related disability, in terms of workers' compensation and medical expenses. Evidence suggests high prevalence of LBP in salespeople. Methods: A cross-sectional survey was conducted in which 184 saleswomen with a current episode of self-reported LBP working in a large up-scale department store filled out a battery of 6 self-administered questionnaires and received a standardised physical examination. Results: Saleswomen with concurrent LBP had low disability levels. Factors significantly associated with disability were pain intensity, measured by a visual analogue scale, in the past week (p < 0.001), physical and mental health status (p < 0.001, p = 0.003, respectively), fear avoidance scores for both work and physical activities (p = 0.031, p = 0.014, respectively), past history of LBP (p = 0.019), and self-reported frequency of pushing or pulling objects placed in high positions during work (p = 0.047). A significant level (45%) of the variance in disability status was explained by these variables. Conclusion: In clinical management of LBP workers who required prolonged standing, such as salespeople, clinicians should look for modifiable risk factors associated with disability. Specific measures need to be taken to prevent disability due to LBP among salespeople.