• Restorative Dentistry and Endodontics
• /
• 제37권4호
• /
• pp.201-206
• /
• 2012

Objectives: The purpose was to investigate the preference and usage technique of NiTi rotary instruments and to retrieve data on the frequency of re-use and the estimated incidence of file separation in the clinical practice among general dentists. Materials and Methods: A survey was disseminated via e-mail and on-site to 673 general dentists. The correlation between the operator's experience or preferred technique and frequency of re-use or incidence of file fracture was assessed. Results: A total of 348 dentists (51.7%) responded. The most frequently used NiTi instruments was ProFile (39.8%) followed by ProTaper. The most preferred preparation technique was crown-down (44.6%). 54.3% of the respondents re-used NiTi files more than 10 times. There was a significant correlation between experience with NiTi files and the number of re-uses (p = 0.0025). 54.6% of the respondents estimated experiencing file separation less than 5 times per year. The frequency of separation was significantly correlated with the instrumentation technique (p = 0.0003). Conclusions: A large number of general dentists in Korea prefer to re-use NiTi rotary files. As their experience with NiTi files increased, the number of re-uses increased, while the frequency of breakage decreased. Operators who adopt the hybrid technique showed less tendency of separation even with the increased number of re-use.

• 보건의료생명과학 논문지
• /
• 제8권2호
• /
• pp.135-142
• /
• 2020

본 연구는 강원도 영북지역에 주소를 둔 환자의 입원/외래 진료의 이용빈도를 분석하여 영북지역의 의료수요 및 의료이용 현황 파악을 하고자 국민건강보험공단 공공데이터포털(www.data.go.kr) 2003년 부터 2017년까지 건강보험 및 의료급여(입원/외래) 진료비 청구자료를 분석하였다. 다빈도 순위는 '진료건 및 %'에 따라 최빈도의 상병순으로 1-60순위까지의 순위를 선정하였다. 또한, 영북권 유일의 속초의료원 환자의 이용 추이를 병행 분석하였다. 분석결과 강원도 영북지역은 과거 급성기 질환에서 점차 만성인 비감염성 질환의 형태로 상병에 따른 외래 진료 이용과 입원환자의 이용이 증가하고 있다. 특히 조현병과 산과진료의 기능을 확충하고 지역사회의 건강관리에 필요한 구체적인 보건사업을 수행할 필요가 있으며 이를 통해 강원도 영북지역 주민의 삶의 질적 향상을 높여야 한다.

• 한국생활과학회지
• /
• 제15권3호
• /
• pp.373-384
• /
• 2006

This study analysed the effect of mothers' work status on time use in child care and use of market child care services. There were two major questions: Do self-employed (and family worker without being paid) mothers have a flexible work schedule and so can they care her child(ren) well? If it is true, is the work status as self-employee related to non-market child care services? To answer these questions, 1,196 samples were selected from the Time Use Data of 1999, which had been administered by Korea National Statistical Office. Major results were as follows: First, a mother who is family workers without being paid made time to care children frequently more than wage earners. Second, according to regression analysis, mothers' work status was one of the important variables to explain child care activity frequency. Third, among categories of child caring ('physical caring', 'non-physical caring', and 'caring of the others'), mothers spent more frequently in 'caring of the others', and had higher probability to use market child care services. But the more frequently a mother made time in 'non-physical caring' for her child, the lower probability to choose market child care services. In conclusion, it was certain that self-employed mothers benefit from a flexible time schedule at work places. But the relationship of child care activity frequency with use of market child care services was inconsistent.

• 한국조경학회지
• /
• 제34권5호
• /
• pp.52-58
• /
• 2006

Wildlife roadkill is a serious problem for road planners and biologists concerned with traffic safety, species conservation, and animal welfare. The objective of this paper was to analyze the effect of land use on the frequency of mammal roadkills. This study took part in three steps. First, data for 1,279 road kills of nine species were collected by survey over 26 months on 107km of roads near the Mt. Jirisan area. Second, the type of land use near the roadkill points was analyzed, and the area of each land use within loom of the road was calculated using GIS. Finally, the question of whether the land use affects the Sequency of mammal roadkills was analyzed by determining the density of roadkill occurrences for each land-use type. The results of the study were as follows. First, the roadkill density of all species was highest near grasslands, especially natural grasslands. Second, when comparing forests and rice fields, roadkill densities of the Eurasian red squirrel, Siberian chipmunk and Korean hare were higher near the forests, while the densities of the raccoon dog, water deer and leopard cat were higher near rice fields. The results of this study could be an essential information source for mitigating the roadkill problem in Korea.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• 제5B권2호
• /
• pp.181-188
• /
• 2005

In this paper, a DC smoothing filterless soft switching pulse modulated high frequency AC power conversion circuit connected to utility. frequency AC power source is proposed for consumer induction heating hot water producer, steamer and super heated steamer. The operating principle of DC link filterless utility frequency AC-high frequency AC (HF AC) power conversion circuit defined as high frequency cycloinverter is described, which can operate under a principle of ZVS/AVT and power regulation based on alternate asymmetrical PWM in synchronization with the utility frequency single phase AC positive or negative half wave voltage. The dual mode modulation control scheme based on high frequency PWM and commercial frequency AC voltage PDM for the proposed high frequency cycloinverter are discussed to enlarge its soft switching commutation operating range for wide HF AC power regulation. This high frequency cycloinverter is developed for high frequency IH Dual Packs Heater (DPH) type boiler used in consumer and industrial fluid pipeline systems. Based on the experiment and simulation results, this high frequency cycloinverter is proved to be suitable for the consumer use IH-DPH boiler and hot water producers. The cycloinverter power regulation and power conversion efficiency characteristics are evaluated and discussed.

• 한국정보통신학회논문지
• /
• 제9권2호
• /
• pp.402-407
• /
• 2005

주파수 합성기로서 통신시스템에 많이 사용되어온 PLL 방식은 여러 장점을 갖고 있지만, 위상잡음 특성이 나쁘고 주파수 도약 시간이 긴 단점을 갖기 때문에 최근의 고속(l$mu$s이하)으로 주파수 호핑(Frequency Hopping)을 요구하는 차세대 이동 통신 시스템에서는 사용이 불가능하다. 본 연구는 차세대 이동통신 시스템에서 1600 hops/s 속도로 600개 이상의 랜덤한 주파수를 발생하는 주파수합성기를 CPLD를 사용하여 DDS (Direct Digital Synthesis) 방식으로 설계하였다.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
• /
• pp.682-688
• /
• 1994

LSM(Least-Squares Method) has inherent limitation that precise system identification over wide frequency band is difficult especially at low frequency hand. In this paper we propose to use decimation, a spectrum analysis method widely used in signal processing. The merits of decimation are the flexibility of selection of the frequency hand concerned and the function of LPF(Low Pass Filter). In this paper, frequency-domain is divided into separate frequency bands which will be combined into full frequency-domain by using MDM(Multiple Decimation Method). In this way, free selection of sampling frequency for each hand is possible and the low frequency oscillation modes of LSM are avoided.

• 말소리와 음성과학
• /
• 제6권3호
• /
• pp.149-153
• /
• 2014

In frequency domain ICA, the frequency bin permutation problem falls off the quality of separated signals. In this paper, we propose a new algorithm to solve the frequency bin permutation problem using the covariance of power ratio of separated signals in multi-channel FD-ICA. It makes use of the continuity of the spectrum of speech signals to check if frequency bin permutation occurs in the separated signal using the power ratio of adjacent frequency bins. Experimental results have shown that the proposed method could fix the frequency bin permutation problem in the multi-channel FD-ICA.

• Journal of Communications and Networks
• /
• 제9권1호
• /
• pp.34-42
• /
• 2007

Orthogonal frequency division multiplexing (OFDM) combined with time division multiplexing (TDM), in this paper called OFDM/TDM, can overcome the high peak-to-average-power ratio (PAPR) problem of the conventional OFDM and improve the robustness against long time delays. In this paper, the bit error rate (BER) performance of OFDM/FDM in a frequency-selective Rayleigh fading. channel is evaluated by computer simulation. It is shown that the use of frequency-domain equalization based on minimum mean square error criterion (MMSE-FDE) can significantly improve the BER performance, compared to the conventional OFDM, by exploiting the channel frequency-selectivity while reducing the PAPR or improving the robustness against long time delays. It is also shown that the performance of OFDM/FDM designed to reduce the PAPR can bridge the conventional OFDM and single-carrier (SC) transmission by changing the design parameter.

• 대한전기학회논문지:전력기술부문A
• /
• 제55권12호
• /
• pp.544-548
• /
• 2006

The instantaneous frequency gives a frequency value at a time instance. Thus, it is natural to use the instantaneous frequency for detecting disturbances of voltage signal in power line. Various instantaneous frequency estimators are introduced. By applying to different types of disturbed signals, we show the estimators' ability to classify flickers. Also, the computational costs are compared between different instantaneous frequency estimators. The Prony's method (PRONY) and the modified covariance method (MCOV) need relatively smaller amount of calculation than the Teaser-Kaiser energy operator based estimator (DESA II). For an AM-FM modulated signal, the tracking performance of different instantaneous frequency estimators is also compared. Through simulation, it is shown that MCOV produces less variant frequency estimation values than DESA II and PRONY method.