• 한국항공우주학회지
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• 제44권2호
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• pp.116-122
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• 2016

터보제트 엔진에서 램제트 엔진으로의 작동 천이를 고려한 TBCC엔진의 성능 특성을 연구하였다. 터보제트 엔진과 램제트 엔진의 성능모델을 제시하고 터보제트와 램제트의 작동 비율을 조절하여 성능 변화가 연속적으로 발생하도록 엔진 작동의 천이 모드를 고려하였다. 이를 통해 다양한 마하수와 고도에서의 완만한 엔진 성능 변화를 나타냈음을 확인하였다. 일정고도(11km)와 가상의 비행 궤적에 대하여 천이 모드를 적용하여 TBCC 엔진의 추력과 비추력의 변화를 분석하였으며, 이를 통해 예상 비행 조건과 엔진의 천이 모드를 고려한 성능 변화와 복합 사이클 엔진 작동 천이 모드의 필요성을 제안하였다.

• 한국산학기술학회논문지
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• 제16권5호
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• pp.3573-3578
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• 2015

완화곡선구간은 직선과 곡선사이에 설치되는 구간이며, 곡선반경 및 캔트 등의 선형변화에 따라 차량의 횡방향 가속도, 횡방향 저크 및 롤속도의 변화가 발생하여 차량주행안전성 및 승차감 측면에서 취약구간이 된다. 본 논문에서는 철도차량의 차체횡가속도와 롤속도의 계측결과를 이용하여 완화곡선 구간의 승차감을 정량적으로 산정하였으며, 승차감 평가기법은 EN규격에서 제시하는 완화곡선 구간의 승차감 평가방법을 사용하였다. 평가결과로 부터 통하여 국내 일반철도 노선의 완화곡선구간 승차감의 분포특성을 조사하였으며, 곡선반경 크기와 차량 속도가 완화곡선 구간의 승차감에 미치는 영향을 분석하였다. 마지막으로, 캔트 시간변화율과 완화곡선 승차감의 관계를 분석하였다.

• 한국콘텐츠학회논문지
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• 제5권3호
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• pp.167-173
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• 2005

유성음원과 무성음원을 사용하는 음성부호화 방식에 있어서, 같은 프레임 안에 모음과 무성자음이 있는 경우에 음질저하현상이 나타난다. 본 논문에서는 같은 프레임 안에 유성음과 무정자음이 같이 존재하지 않도록 Zero Crossing Rate과 개별피치 펄스를 사용하여 무성자음을 포함한 천이구간을 추출하는 방법과 주파수대역을 분할하여 TSIUVC를 근사합성하는 방법을 제안한다. 실험결과, 0.547kHz 이하 2.813kHz 이상의 주파수 정보를 사용하여 TSIUVC 음성파형을 양호하게 근사합성 할 수 있었으며, TSIUVC의 추출율은 여자와 남자음성에서 각각 $91\%$와 $96.2\%$를 얻었다. 이 방법은 음성합성, 음성분석, 새로운 Voiced/Silence/TSIUVC의 음성부호화 방식에 활용할 수 있을 것으로 기대된다.

• Asian Pacific Journal of Cancer Prevention
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• 제16권8호
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• pp.3429-3434
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• 2015

Background: This study analyzed predictors of regular mammography performance in Korea. In addition, we determined factors affecting regular mammography performance in life-transition aged women by applying an attitude, social influence, and self-efficacy (ASE) model. Materials and Methods: Data were collected from women aged over 40 years residing in province J in Korea. The 178 enrolled subjects provided informed voluntary consent prior to completing a structural questionnaire. Results: The overall regular mammography performance rate of the subjects was 41.6%. Older age, city residency, high income and part-time job were associated with a high regular mammography performance. Among women who had undergone more breast self-examinations (BSE) or more doctors' physical examinations (PE), there were higher regular mammography performance rates. All three ASE model factors were significantly associated with regular mammography performance. Women with a high level of positive ASE values had a significantly high regular mammography performance rate. Within the ASE model, self-efficacy and social influence were particularly important. Logistic regression analysis explained 34.7% of regular mammography performance and PE experience (${\beta}=4.645$, p=.003), part-time job (${\beta}=4.010$, p=.050), self-efficacy (${\beta}=1.820$, p=.026) and social influence (${\beta}=1.509$, p=.038) were significant factors. Conclusions: Promotional strategies that could improve self-efficacy, reinforce social influence and reduce geographical, time and financial barriers are needed to increase the regular mammography performance rate in life-transition aged.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.355-359
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• 2003

In this paper, we investigated the wear lift, wear rate, and its transition on the Hertz pressure. In the experiment, we used TiAlCrN coating deposited by the sputtering technique and ball diameter of 10mm, 7.94mm and 4.76mm for the various Hertz pressure. Ball-on-disk sliding tests wire performed under the unlubricated condition. As the diameter of a ball decreased, the failure load of TiAlCrN coating decreased. However, a good correlation was observed between the wear life and Hertz pressure, and all ball specimens showed the infinite wear life at about 450MPa. In measurement of wear rate, as the diameter of the ball inclosed, the wear transition appeared in bigger load. However, a good correlation was observed between the wear rate and Hertz pressure. The transition appeared in the range from 550MPa to 600MPa at all ball speimens.

• 대한금속재료학회지
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• 제50권2호
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• pp.146-151
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• 2012

The present article shows how the fracture strength of single crystal silicon chips, which are generally used as semiconductor devices, is influenced by loading rate variation during a 3-point bending test. It was found that the fracture strength of the silicon chips slightly increases up to 4% with increasing loading rate for loading rates lower than 20 mm/min. Meanwhile, the fracture strength of the chips hardly increases with increase of loading rate to levels higher than 40 mm/min. However, there was an abrupt transition in the fracture strength within a loading rate range of 20 mm/min to 40 mm/min. This work explains through microscopic examination of the fracture surface of all test chips that such a big transition is related to the deflection of crack propagation direction from the (011) [${\bar{1}}00$] system to the (111) [${\bar{2}}11$] system in a particular loading rate (i.e. from 20 mm/min to 40 mm/min).

• 농촌의학ㆍ지역보건
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• 제8권1호
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• pp.66-80
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• 1983

As a part of the epidemiological studies of clonorchiasis in Korea, this study was conducted to evaluate the current endemicity and the natural transition of the Clonorchis infection in Goyang Gun a low endemic area in recent years, prior to the introduction of praziquantel which will eventually influence to the status of the prevalence. The data obtained in this study in 1983 were evaluated for natural transition of the infection in comparison with those obtained 16 years ago in 1967 by the author (Kim, 1974). The areas of investigation, villages and schools surveyed, methods and techniques used in this study were the same as in 1967, except for the contents of the questionnaire for raw freshwater fish consumption by the local inhabitants. 1) The current prevalence rate of Clonorchis infection among the inhabitants was 7.5% on the average out of a total of 479 persons examined. The prevalence rate was 9.0% in the riverside area and 4.2% in the inland area. Among the schoolchildren, the prevalence rate was 1.1% out of a total of 1 319 examined. By area, it was 1.4% in the riverside area and 0.7% in the inland area. By sex, the prevalence rate was 13.3% in the male and 1.3% in the female in the inhabitants and no difference was seen in the schoolchildren. 2) In the natural transition of the infection, the prevalence rate in the inhabitants has decreased from 22.5% in 1967 to 7.5% in 1983, and in the schoolchildren, from 9.5% in 1967 to 1.1% in 1983. The reduction rate was higher in the riverside area than in the inland area. 3) In the prevalence rate by age, 1.2% was seen in the 10-14 age group and gradually increased to 8.1% in the 30-39 age group and reached peak 18.1% in the 40-49 age group. By sex, in the male, the prevalence rates have increased to 31.9% and 33.3% in the 40-49 and 50-59 age groups, respectively and decreased thereafter. In the female, the prevalence rate less than 5% was seen only in between the 10-14 and 30-39 age groups. 4) In the natural transition of the prevalence rate by age, sharp decrease was seen in the male from around 50% in 1967 between 15-19 and 30-39 age groups. The generation over 40s showed less decrease. In the female, the prevalence rate has decreased from 13% in 1967 to 5% in 1983 in the middle age groups and dropped to 0% in the rest of the age groups. 5) The intensity of the infection among clonorchiasis cases by mean EPmg (number of eggs per mg feces) value was 1.4. In the inhabitants, the value was 2.0 in the riverside area and 0.4 in the inland area. While in the schoolchildren, the value was 0.2 in both riverside and inland areas. 6) In the transition of the intensity of the infection, EPmg among the inhabitants has decreased from 3.9 in 1967 to 2.0 in 1983 in the riverside area, and from 2.9 to 0.4 in the inland area. In the schoolchildren, the reduction was similar in both riverside and inland areas resulting from 1.0-1.1 in 1967 to 0.2 in 1983. 7) In the intensity of the infection by age, EPmg 3.4 was peak at the 40-49 age group and 0.2-1.0 was seen in the rest of the age groups. The mean value was 1.5 in the male and 0.6 in the female. 8) In the natural transition of the intensity of the infection, the EPmg has decreased from 2.7 in 1967 to 1.4 in 1983. By age, reduction was seen in all of the age groups, particularly in the young and the old age groups of 50s and over, except in the 40-49 age group in which reverse phenomenon was seen. By sex, it has decreased from 3.5 in 1967 to 1.5 in 1983 in the male and from 1.0 to 0.6 in the female. 9) In the distribution of the clonorchiasis cases by the range of EPmg value, 70.3% of the cases were placed in the range of 0.1-0.9 as the most and 16.2% in 1.0-4.9 as the next. With such figures, those included in the range less than 0.9 as light infection were 78.4% and under 5.0-9.9 up to moderate infection 99.3% of the cases were covered. The cases were distributed up to 20.0-39.9 in the male and to 1.0-4.9 in the female. 10) In the transition of the distribution of the clonorchiasis cases by EPmg, the highest intensity reached up to 60.0-79.9 in 1967 and to 20.0-39.9 in 1983. In the range of light infection, under 0.1-0.9, the distribution in rate was 64.5% in 1967 and 78.4% in 1983. Up to the range of moderate infection, under 5.0-9.9, 91.7% in 1967 and 97.3% in 1983 were seen respectively. 11) In a survey for raw freshwater fish consumption among the local inhabitants,78.3 of the clonorchiasis cases interviewed admitted their experience of the raw consumption. However, those who practised in the past two years were 34.8% 55.6% of those who have such experience in the past professed that they did not practise raw freshwater fish consumption in the past two years. 12) The major cause of the reduction of the raw freshwater fish consumption among the inhabitants were the wide spread water pollution in the locality. The most common reason professed for stopping raw freshwater fish consumption among the inhabitants was the risk of the fluke infection. 13) In animal survey, 3.1% of dogs were found infected with Clonorchis, decreasing from 21.6% in 1967. 14) The distribution of the first intermediate host, Parafossarulus manchouricus has greatly diminished in this locality and found only in two localized ponds. No Clonorchis infection was found from the snails examined. 15) The second intermediate freshwater fish host has been further limited by extended water pollution. No susceptible fish host could be examined. 16) In conclusion, the endemicity of Clonorchis infection in Croyang Gun, low endemic area, has significantly decreased during the past 16 years. The major cause of the regressive transition of the infection was the water pollution of the freshwater system of this locality. This has upset the ecosystems of the intermediate host of Clonorchis sinensis in many areas of waterbodies and further discouraged to a significant extent the local inhabitants from raw freshwater fish consumption.

• 대한기계학회논문집B
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• 제26권5호
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• pp.695-702
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• 2002

Nonlinear dynamics of striped diffusion flames, by the diffusional-thermal instability with Lewis numbers sufficiently less than unity, is numerically investigated by examining various two-dimensional flame-structure solutions. The Lewis numbers for fuel and oxidizer are assumed to be identical and an overall single-step Arrhenius-type chemical reaction rate is employed in the model. Particular attention is focused on identifying the flame-stripe solution branches corresponding to each distinct stripe pattern and hysteresis encountered during the transition. At a Damkohler number slightly greater than the extinction Damkohler number, eight-stripe solution first emerges from one dimensional solution. The eight-stripe solution survives Damkohler numbers much smaller than the extinction Damkohler number until the transition to four-stripe solution occurs at the first forward transition Damkohler number. At the second forward transition Damkohler number, somewhat smaller than the first transition Damkohler number, the transition to two-stripe solution occurs. However, anu further transition from two-stripe solution to one-stripe solution is not always possible even if one-stripe solution can be independently accessed for particular initial conditions. The Damkohler number ranges for two-stripe and one-stripe solutions are found to be virtually identical because each stripe is an independent structure if distance between stripes is sufficiently large. By increasing the Damkohler number, the backward transition can be observed. In comparison with the forward transition Damkohler numbers, the corresponding backward transition Damkohler numbers are always much greater, thereby indicating significant hysteresis between the stripe patterns of strained diffusion flames.

• 전력전자학회논문지
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• 제21권3호
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• pp.238-248
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• 2016

In this study, an automatic command mode transition strategy of direct power control (DPC) is proposed for permanent magnet synchronous generators (PMSGs) medium-voltage (MV) offshore wind turbines (WTs). Benchmarking against the control methods are performed based on a three-level neutral-point-clamped (NPC) back-to-back type voltage source converter (VSC). The ramping rate criterion of complex power is utilized to select the switching vector in DPC for a three-level NPC converter. With a grid command and an MPPT mode transition strategy, the proposed control method automatically controls the generated output power to satisfy a grid requirement from the hierarchical wind farm controller. The automatic command mode transition strategy of DPC is confirmed through PLECS simulations based on Matlab. The simulation result of the automatic mode transition strategy shows that the proposed control method of VOC and DPC achieves a much shorter transient time of generated output power than the conventional control methods of MPPT and VOC under a step response. The proposed control method helps provide a good dynamic performance for PMSGs MV offshore WTs, thereby generating high quality output power.

• 한국분말재료학회지
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• 제21권2호
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• pp.131-136
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• 2014

Cathode materials and their precursors are prepared with transition metal solutions recycled from the the waste lithium-ion batteries containing NCM (nickel-cobalt-manganese) cathodes by a $H_2$ and C-reduction process. The recycled transition metal sulfate solutions are used in a co-precipitation process in a CSTR reactor to obtain the transition metal hydroxide. The NCM cathode materials (Ni:Mn:Co=5:3:2) are prepared from the transition metal hydroxide by calcining with lithium carbonate. X-ray diffraction and scanning electron microscopy analyses show that the cathode material has a layered structure and particle size of about 10 ${\mu}m$. The cathode materials also exhibited a capacity of about 160 mAh/g with a retention rate of 93~96% after 100 cycles.