• 대한수학회지
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• 제44권6호
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• pp.1479-1503
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• 2007

In this paper, we study a strong k-deformation retract derived from a relative k-homotopy and investigate its properties in relation to both a k-homotopic thinning and the k-fundamental group. Moreover, we show that the k-fundamental group of a wedge product of closed k-curves not k-contractible is a free group by the use of some properties of both a strong k-deformation retract and a digital covering. Finally, we write an algorithm for calculating the k-fundamental group of a dosed k-curve by the use of a k-homotopic thinning.

• 대한전자공학회논문지
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• 제18권3호
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• pp.21-24
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• 1981

Micro-torch를 사용하여 두 개와 taper를 동시에 제작하고, fusion splicing에 외해 광섬유 t-branch률 제작하였다. Y-branch의 insertion loss는 2.6dB, branching율은 0.98까지 얻을 수 있었다. 또 Y-branch를 OTDR의 제작에 응용하여 광학계를 대폭 간소화 하였으며, 길 이 측정오차 ±5m, 손실 측정오차 ±0.5bB/km로 광섬유의 특성을 측정할 수 있었다.

• Journal of applied mathematics & informatics
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• 제28권3_4호
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• pp.697-710
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• 2010

In this paper, we prove existence of infinitely many positive and concave solutions, by means of a simple approach, to $3^{th}$ order three-point singular boundary value problem {$x^{\prime\prime\prime}(t)=\alpha(t)f(t,x(t))$, 0 < t < 1, $x(0)=x'(\eta)=x^{\prime\prime}(1)=0$, (1/2 < $\eta$ < 1). Moreover with respect to multiplicity of solutions, we don't assume any monotonicity on the nonlinearity. We rely on a combination of the analysis of the corresponding vector field on the phase-space along with Knesser's type properties of the solutions funnel and the well-known Krasnosel'ski$\breve{i}$'s fixed point theorem. The later is applied on a new very simple cone K, just on the plane $R^2$. These extensions justify the efficiency of our new approach compared to the commonly used one, where the cone $K\;{\subset}\;C$ ([0, 1], $\mathbb{R}$) and the existence of a positive Green's function is a necessity.

• 대한방사선기술학회지:방사선기술과학
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• 제21권1호
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• pp.29-34
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• 1998

The purpose of simple abdomen erect projection is to see the fluid level which indicates gastrointestinal ileus or free air due to perforation. we do not have to insist on low kVp technique in simple abdomen erect position as long as we can detect the fluid level and free air shadow. Therefore, the author tried to decrease patient dose by high kVp technique and to improve the image quality due to motion artifact by reduction of exposure time. [Methods] Experiment 1. * screen/film SRO1000/HRH * exposure factor : $140\;kvp{\pm}5\;kv$ with added filters, 200 mA, 0.01 sec * phantom : Acryles : 15.0 cm(equivalent to 17 cm body thickness) 17.5 cm(equivalent to 21 cm body thickness) 20.0 cm (equivalent to 25 cm body thickness) With the exposure factor for same film density($D=0.8{\pm}0.1$) and with the materials above, we tried to find out entrance skin dose and gonad dose for both male and female. Experiment 2. Burger's phantom radiography were checked to see whether there was any change of image quality according to the kVp and the added filters. Experiment 3. Using rotating meter(self made), we examined the motion artifact and the exposure time limitation. [Results and conculution] 1. Using high voltage technique of 140 kVp with added filter, Skin dose, testicle dose and ovary dose decrease to 89.3%, 47% and 71.4% respectively compare to 70 kVp technique, 2. No great changes of Burger's phantom image has detected as from 70 kVp to 140 kVp and the air hole size of Burger's phantom over 0.028 cc(Diameter 3 mm, hight 4 mm) can be distinghished. 3. 0.01 sec(1 pulse) exposure time is possible in the single phase full wave rectification that why we can quitely reduce the unsharness caused by patient's movement.

• 한국수정란이식학회지
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• 제10권3호
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• pp.229-236
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• 1995

The experiments reported here take advantage of the large number of in vitro matured and in vitro fertilized(IVM /IVF) bovine oocytes which can be produced, permitting the design of controlled experiments to establish a simple defined medium for the study of early embryo requirements. A total of 1,386 IVM /IVF oocytes were used to compare a simple defined medium(KSOM) with more complex culture conditions used successfully for culture of bovine embryos but do not permit study of specific requirements. All experiments were extensively replicated factorials. In Experiment 1, KSOM was superior to Menezo B$_2$ medium in producing morulae plus blastocysts from IVM /IVF oocytes(33 vs 20%, P<0.()5). The yield of morulae plus blastocysts with KSOM was 22% and with BRLC added was 30%. In Experiment 2, (a 2x2 factorial of KSOM with or without BRLC and 0, 1 ng /ml of platelet derived growth factor, PDGF) more morulae plus blastocysts (40%) were produced in KSOM-BRLC co-culture containing 1 ng /ml PDGF than in the control KSOM(12%). In Experiment 3, there was no dose response when 0, 1 and 5 ng /ml of PDGF were added. The results with simple defined KSOM medium are sufficiently promising to indicate that specific requirements of the embryo may be examined in future studies with KSOM as a base.

• Journal of Advanced Marine Engineering and Technology
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• 제39권9호
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• pp.881-889
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• 2015

해양온도차발전은 해양의 표층수와 심층수의 온도차를 이용하여 발전하는 유기랭킨사이클이다. 작동유체와 사이클 구성은 유기랭킨사이클의 열역학적 효율에 큰 영향을 미치는 요소이다. 본 연구에서는 작동유체와 사이클에 따른 해양온도차발전시스템의 성능분석을 수행하였다. 고전적인 단순 랭킨사이클과 단순 랭킨사이클의 대안으로 제시되고 있는 개방형 및 통합형 재생 랭킨사이클 그리고 칼리나 사이클이 본 연구에서 고려되었으며, 작동유체로는 9종의 단일냉매와 3종의 혼합냉매를 본 연구에 적용하였다. 사이클의 성능분석에는 핀치포인트온도차를 일정하게 유지하는 핀치포인트분석이 적용되었다. 성능분석결과를 살펴보면, 단순 랭킨사이클과 개방형 및 통합형 재생 랭킨사이클의 경우 RE245fa2를 작동유체로 사용하며, 칼리나 사이클의 경우 $NH_3/H_2O$의 질량비가 0.9:0.1일 때 열역학적 효율이 가장 높았다. 한편, 개방형 및 통합형 재생 랭킨사이클과 칼리나 사이클을 해양온도차발전시스템에 적용할 경우 단순 랭킨사이클과 비교하여 각각 약 2.0 %, 1.0%, 10.0%의 효율 향상을 기대할 수 있었다.

• Ocean Science Journal
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• 제41권4호
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• pp.235-244
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• 2006

Determining 'photosynthetically active radiation' (PAR) is a key part of calculating phytoplankton productivity in a biogeochemical model. We explore the daily and seasonal variability in the ratio of PAR irradiance to total irradiance that occurred at Ieodo Ocean Research Station (IORS) in the East China Sea under clear-sky conditions in 2004 using a simple radiative transfer model (RTM). Meteorological data observed at IORS and aerosol optical properties derived from Aerosol Robotic Network observations at Gosan are used for the RTM. Preliminary results suggest that the use of simple PAR irradiance-ratio values is appropriate in calculating phytoplankton productivity as follows: an average of $0.44\;({\pm}0.01)$ in January to an average of $0.48\;({\pm}0.01)$ in July, with average daily variabilities over these periods of about $0.016\;({\pm}0.008)$ and $0.025\;({\pm}0.008)$, respectively. The model experiments demonstrate that variations in the major controlling input parameters (i.e. solar zenith angle, precipitable water vapor and aerosol optical thickness) cause PAR irradiance ratio variation at daily and seasonal timescales. Further, increases (>0.012) in the PAR irradiance ratio just below the sea-surface are positively correlated with high solar zenith angles and strong wind stresses relative to those just above the sea-surface.

• Journal of Nutrition and Health
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• 제35권2호
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• pp.250-262
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• 2002

This study was conducted to develop a simple flood frequency questionnaire (FFQ) based on the results of contributions of specific floods to absolute intake and between-person variance in nutrients using semi-quantitative FFQ with 93 flood items. The subjects were 554 healthy adults for development of a simple FFQ, and 37 students for a validation test of a developed simple FFQ. The contribution of specific floods to 80% absolute nutrient intake was measured by assessing their percentage in total consumption of a nutrient. To assess the contributions of floods to the between-person variance in the intake of each specific nutrient, stepwise multiple regressions were performed. The number of floods necessary to account for the respective 80% of absolute intake was 11-36, depending on the nutrient, while flower floods (5-16 floods) were required for the corresponding percentage of between-person variation for all nutrients. Important floods for between-person variance include Tangsuyuk (pork) and snacks for energy and fat, fish for protein and polyunsaturated fatty acids (PUFA) and snacks for carbohydrates. Spearman correlation coefficients between 93-itemed FFQ and 63-itemed FFQ ranged from 0.91 for vitamin A to 0.99 for fat in the population data used in developing a simple FFQ. Also, the correlation coefficients between the two FFQs were 0.82-7.92 in the population for the validation test. This study suggests that useful information on dietary intake could be obtained using a simple semi-quantitative FFQ in a large-scale dietary survey in Korea.

• Clinics in Shoulder and Elbow
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• 제16권1호
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• pp.1-9
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• 2013

목적: 단순 방사선 사진상에서 견봉 및 상완골 대결절의 퇴행성 변화의 정도와 회전근 개 파열의 크기 사이의 연관성을 알아보고자 하였다. 대상 및 방법: 견관절의 자기 공명 영상을 시행한 퇴행성 회전근 개 파열 실험군 234예와 회전근 개 파열이 없는 대조군 284예 등 총 518예를 대상으로 하였다. 견관절 방사선 단순 촬영에서 퇴행성 변화의 정도를 관절와-상완 관절의 퇴행성 변화를 제외한 견봉과 대결절에서 골극의 길이와 형태의 변형에 따라 분류하였고, 자기 공명 영상에서 회전근 개의 파열의 정도 및 전층 파열의 크기를 분류하였다. 회전근 개의 파열의 정도와 크기에 따른 견봉 및 상완골 대결절의 퇴행성 변화 정도와의 연관성에 대해 알아 보았다. 결과: 견관절 단순 방사선 사진에서 보이는 견봉 및 상완골 대결절의 퇴행성 변화에 따른 MRI상 회전근 개 파열의 정도는 유의한 차이를 보였고(p<0.001), 견봉 및 상완골 대결절의 단순 방사선상 퇴행성 변화가 증가할수록 회전근 개 파열의 크기가 커지는 경향이 있었으며(p<0.001), 부분층 파열 보다 전층 파열 가능성이 높은 것으로 나타났다(p<0.001). 또한 고령 및 여자에서 회전근 개의 파열이 더 심하다는 결과를 얻었다(p<0.001, p<0.001). 결론: 퇴행성 회전근 개 파열 환자에서 견관절의 단순 방사선 사진상 견봉 및 상완골 대결절의 퇴행성 변화가 심할수록 회전근 개 파열의 크기가 더 크고, 나이와 성별도 관련 인자 중 하나로 사료된다.

• 한국안광학회지
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• 제4권1호
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• pp.77-82
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• 1999

한국성인 남성의 굴절이상안의 정밀한 이해를 위해서 본연구는 타각적 검사와 자각적 검사법으로 시력검사를 조사하였다. 결과는 다음과 같다. 1. 눈의 종류는 각각 근시가 92.9%, 정시가 4.9%, 원시가 1.7%이다. 2. 굴절이상안은 복합성 근시성 난시가 62.6%, 단순근시가 32.4%, 단순 근시성 난시가 1.6%,단순원시가 1.4%, 단순원시성 난시가 0.5%, 그리고 혼합난시가 1.6%이다. 3. 난시의 축은 각각 직난시가 59.7%, 사난시가 25.3%, 그리고 도난시가 15%이다. 4. 전체 근시성 구면도수는 -2.0 diopter 이하가 41.8%, -2.00에서 -6.00 diopter 이하가 51.6% 그리고 -6.00diopter이상이 6.6%이다. 5. 전체 원시성 구면굴절력은 2diopter 이하가 75%이며, 2diopter이상은 25%이다. 6. 난시굴절력에서 0.5에서 1.0 diopter 미만이 79.3%, 1.0에서 2.0 diopter 미만이 17.4%, 그리고 2.00 diopter 이상이 3.3%이다.