• 조명전기설비학회논문지
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• 제20권9호
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• pp.70-77
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• 2006

We have fabricated an integrated three-phase flux-lock type SFCL, which consists of an YBCO($YB_a2Cu_3O_7$) thin film and a flux-lock reactor wound around an iron core of each phase. In order to apply the SFCL in a real power system, fault analyses for the three-phase system are essential. The short-circuit currents were effectively limited by adjusting the numbers of winding of each secondary coil and their winding directions. The flux flow generated in the iron core cancelled out under the normal operation due to the parallel connection between primary and secondary windings. However, the flux-lock type SFCL with same iron core was operated just after the fault due to the flux generating in the iron core. To analyze the current limiting characteristics, the additive polarity winding was compared with the subtractive one in the flux lock reactor. Whenever a single line-to-ground fault occurred in any phase, the peak value of the line current of the fault phase in the additive polarity winding increased up to about 12.87 times during the first-half cycle. On the other hand, the peak value in the subtractive polarity winding increased up to about 34.07 times under the same conditions. This is because the current flow between the primary and the secondary windings changed to additive or subtractive status according to the winding direction. We confirmed that the current limiting behavior in the additive polarity winding was more effective for a single-line-to-ground fault

• Geomechanics and Engineering
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• 제7권3호
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• pp.233-246
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• 2014

Estimation of fracture initiation pressure is one of the most difficult technical challenges in hydraulic fracturing treatment of vertical or horizontal oil wells. In this study, the influence of in-situ stresses and pore pressure values on fracture initiation pressure and its profile in vertical and horizontal oil wells in a normal stress regime have been investigated. Cohesive elements with traction-separation law (XFEM-based cohesive law) are used for simulating the fracturing process in a fluid-solid coupling finite element model. The maximum nominal stress criterion is selected for initiation of damage in the cohesive elements. The stress intensity factors are verified for both XFEM-based cohesive law and analytical solution to show the validation of the cohesive law in fracture modeling where the compared results are in a very good agreement with less than 1% error. The results showed that, generally by increasing the difference between the maximum and minimum horizontal stress, the fracture pressure and its profile has been strongly changed in the vertical wells. Also, it's been clearly observed that in a horizontal well drilled in the direction of minimum horizontal stress, the values of fracture pressure have been significantly affected by the difference between overburden pressure and maximum horizontal stress. Additionally, increasing pore pressure from under-pressure regime to over-pressure state has made a considerable fall on fracture pressure in both vertical and horizontal oil wells.

• Wind and Structures
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• 제30권5호
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• pp.465-474
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• 2020

Vortex-induced vibrations of a yawed flexible cylinder near a plane boundary are numerically investigated at a Reynolds number Re_n= 500 based on normal component of freestream velocity. Free to oscillate in the in-line and cross-flow directions, the cylinder with an aspect ratio of 25 is pinned-pinned at both ends at a fixed wall-cylinder gap ratio G/D = 0.8, where D is the cylinder diameter. The cylinder yaw angle (α) is varied from 0° to 60° with an increment of 15°. The main focus is given on the influence of α on structural vibrations, flow patterns, hydrodynamic forces, and IP (Independence Principle) validity. The vortex shedding pattern, contingent on α, is parallel at α=0°, negatively-yawed at α ≤ 15° and positively-yawed at α ≥ 30°. In the negatively- and positively-yawed vortex shedding patterns, the inclination direction of the spanwise vortex rows is in the opposite and same directions of α, respectively. Both in-line and cross-flow vibration amplitudes are symmetric to the midspan, regardless of α. The RMS lift coefficient C_L,rms exhibits asymmetry along the span when α ≠ 0°, maximum C_L,rms occurring on the lower and upper halves of the cylinder for negatively- and positively-yawed vortex shedding patterns, respectively. The IP is well followed in predicting the vibration amplitudes and drag forces for α ≤ 45° while invalid in predicting lift forces for α ≥ 30°. The vortex-shedding frequency and the vibration frequency are well predicted for α = 0° - 60° examined.

• 한국가축번식학회지
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• 제13권1호
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• pp.40-48
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• 1989

Guppy fry were treated for the first 40 days of life with 0, 20, 40, 60 & 100$\mu\textrm{g}$ of estradiol per gram of food in order to change the sex of normal males to functional females(genetic male). The present investigation deals with the effects of steroid hormones, such as $\beta$-estradiol and testosterone, on the sex differentiation in guppy and tilapia. The results obtained were summarized as follows. 1. In B (20$\mu\textrm{g}$/g diet) group 17$\beta$-estradiol-treated, 67.8% of male offsprings were produced. 2. In D (60$\mu\textrm{g}$/g diet) group 17$\beta$-treated, 67% of female offsprings were produced. 3. B, D groups of genetic male brooders had significantly different effects (P<0.01) upon sex ratios of their progeny. 4. This strongly indicates that sex direction has been achieved and that the male is the heterogametic sex. 5. The group that produced the highest percentage of male offspring(male percentage of observed number to expected number was 91%) contained only full-sibling male brooders to the sex-reversed female brooders. 6. After 7 months following treatment, the sex-reversed males had ovarian portion in the anterior region and a testicular portion in the posterior region of the same intersexual gonad, respectively. 7. At 7 months after treatment, the ovareis revealed a complete arrest of the ovarian formation, and appearances of spermatogenetic cell cysts among surviving auxocytes. 8. In most of sex-reversed fish, anterior portion of test is was devoid of sperm ducts including the seminal vesicle and vas deferens. 9. The male transferrin showed two strong bands, while the female transferrin showed a single weak band. 10. One of the two bands of male transferrin showed the same mobility with band of female transferrin.

• 한국항공우주학회지
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• 제31권9호
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• pp.1-8
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• 2003

연장된 앞전을 갖는 삼각날개 위에서 시위방향의 여러 위치에서 3축 hot 필름 풍속계를 사용하여 속도장 데이터를 획득하였다. 속도장 데이터는 받음각 24도와 32도에 대하여 중심 시위선을 기준으로 한 레이놀즈수 $1.76{\times}10^6$에서 날개면에 수직한 유동단면에서 측정하였다. 3축 hot 필름 프로브에 의한 세 가지 속도 성분을 측정함으로써 연장된 앞전을 갖는 삼각날개에서의 와류장을 정량적으로 분석할 수 있었다. 날개 와류와 LEX 와류는 평균 축방향 속도가 국소 최고 속도를 갖는 영역에 존재하였다. 아울러, 앞전 근처의 날개면 위에서 주와류와 반대 방향으로 회전하는 이차와류의 생성을 관찰할 수 있었다. 측정 프로브의 유동장에의 삽입은 와류 중심 위치에 크게 영향을 주지 않음을 알 수 있었다.

• 한국항공우주학회지
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• 제31권6호
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• pp.17-22
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• 2003

비행선은 주익이 없고 미익에 비해 동체 효과가 큰 형상으로 인해 정적으로 불안정한 특성을 지닌다. 따라서 동안정 특성 예측이 매우 중요하다. 본 연구에서는 강제진동 풍동시험을 통한 비행선의 동안정 특성 자료를 확보하였다. 풍동시험은 미국 BAR사의 독일소재 시설인 BAR LAMP 시설을 사용하였으며, 16회의 정적시험과 26회의 강제진동시험을 수행하였다. 시험결과, 비행선의 동안정 특성은 받음각 뿐만 아니라 옆미끄럼각, 각속도의 크기와 방향에 비선형적으로 변한다. 전반적으로 세 방향의 모멘트는 댐핑이 있는 것으로 나타났으며, 수직력과 측력, 교차성분은 불안정하게 나타났다. 조종면의 영향은 작은 것으로 나타났으나 옆미끄럼각의 영향은 완전히 비선형적으로 나타났다.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제16권5호
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• pp.621-625
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• 2010

본 논문에서는 스마트 폰, PDA와 같은 모바일 장치에 있는 카메라 기기를 이용한 손동작 제스처 인터페이스를 위한 손 움직임 추적 방법을 제안하고 이를 바탕으로 한 손 제스처 인식 시스템을 개발한다. 사용자의 손동작에 따라 카메라가 움직임으로써, 전역 optical flow가 발생하며, 이에 대한 우세한 방향 성분에 대한 움직임만 고려함으로써, 노이즈에 강인한 손움직임 추정이 가능하다. 또한 추정된 손 움직임을 바탕으로 속도 및 가속도 성분을 계산하여 동작위상을 구분하고, 동작상태를 인식하여 연속적인 제스처를 개별제스처로 구분한다. 제스처 인식을 위하여, 움직임 상태에서의 특징들을 추출하여, 동작이 끝나는 시점에서 특징들에 대한 분석을 통하여 동작을 인식한다. 추출된 특징점을 바탕으로 제스처를 인식하기 위하여 SVM(Support vector machine), k-NN(k-nearest neighborhood classifier), 베이시안 인식기를 사용했으며, 14개 제스처에 대한 인식률은 82%에 이른다.

• 대한한의학원전학회지
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• 제30권3호
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• pp.77-93
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• 2017

Objectives : Clear and detailed analysis on Pulse-taking on both Carotid and Wrist Pulses is an absolute prerequisite if it is to be applied in real practice or its practical value proven. Methods : The original notes found in Suwen and Lingshu, their translations, and conventional studies regarding Suwen LiuJieCangXiangLun's Pulse-taking are compared and analyzed to find cases within medical texts where this method was used and to get an idea of the direction taken by the conventional study. Results : The ilsung, esung, samsung, and sasung of Carotid (or wrist pulses) refers that the pulse is one-, two-, three-, four-fold in differences. Refrainment should be practiced while comparing carotid and wrist pulses. Rather, they need to be compared with their normal states. Used by Luo Tianyi in Ming Dunasty, this method of pulse-taking was used for (radial artery) when diagnosing and treating the degree of seriousness of food injury. The measurement of maximum blood flow velocity using TCD done recently proved the validity of this pulse-taking, and it's been used for alleviating hypertension or tinnitus through acupuncture, or abating intractable diseases (around carotid). Conclusions : The obscurity of the measuring method of this pulse-taking can be resolved, and the problem which occurs while comparing carotid and wrist pulses can be solved. Even though there are differences in opinion regarding the positions when comparing the two pulses, their practical values are acknowledged since their usages in diagnosis, treatments, experiments, and researches have yielded positive results to a degree. They may not be used that often, but they are nonetheless under utilization.

• Journal of Korean Neurosurgical Society
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• 제55권5호
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• pp.284-288
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• 2014

A rare case of atlantoaxial rotatory subluxation occurred after pediatric cervical spine surgery performed to remove a dumbbell-shaped meningioma at the level of the C1/C2 vertebrae. This case is classified as a post-surgical atlantoaxial rotatory subluxation, but has a very rare morphology that has not previously been reported. Although there are several reports about post-surgical atlantoaxial rotatory subluxation, an important point of this case is that it might be directly related to the spinal cord surgery in C1/C2 level. On day 6 after surgery, the patient presented with the Cock Robin position, and a computed tomography scan revealed a normal type of atlantoaxial rotatory subluxation. Manual reduction was performed followed by external fixation with a neck collar. About 7 months after the first surgery, the subluxation became severe, irreducible, and assumed an atypical form where the anterior tubercle of C1 migrated to a cranial position, and the posterior tubercle of C1 and the occipital bone leaned in a caudal direction. The pathogenic process suggested deformity of the occipital condyle and bilateral C2 superior facets with atlantooccipital subluxation. A second operation for reduction and fixation was performed, and the subluxation was stabilized by posterior fixation. We encountered an unusual case of a refractory subluxation that was associated with an atypical deformity of the upper spine. The case was successfully managed by posterior fixation.

• 한국정보통신학회논문지
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• 제21권12호
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• pp.2387-2393
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• 2017

2017년 5월 출범한 문재인 정부는 통신을 복지의 일환으로 간주하고 통신비 절감을 위하여 노력하고 있다. 그런데 문재인 정부가 제시하고 있는 정책방향도 과거정부와 별 차이가 없는 대증요법적 접근으로 평가된다. 이는 이동통신업계의 현상을 대체로 인정하면서 그 틀안에서 부분적인 개선책을 모색하기 때문으로 풀이된다. 그런데 문제를 근본적으로 접근한다면 결과는 크게 달라질 것으로 보인다. 우리나라의 이동통신비용이 적절한 수준을 유지하고 있지 못한 주요 원인은 정부의 역할이 부실하였기 때문이다. 결과적으로 크게 보면 단말기 수급체계, 보조금 지급 행태와 요금체계에 문제가 있다고 할 수 있다. 이와 같은 복합적인 문제를 해결하자면 자급제 정착을 통한 단말기 유통 시장의 형성, 보조금의 차별적 지급금지 그리고 종량요금제 도입이 필요하다. 불합리한 시장을 정상화하기 위해서는 기업에 대한 요금인가를 규정한 전기통신법도 유용할 수 있으나 공정거래법의 정상적인 적용이 더 중요하다.