• Earthquakes and Structures
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• 제11권6호
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• pp.1027-1041
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• 2016

Different incident angles of ground motions have been considered to evaluate the relationship between floor rotation and torsional irregularity coefficient. The issues specifically addressed are (1) variability in torsional irregularity coefficient and floor rotations with varying incident angles of ground motion (2) contradictory relationship between floor rotation and torsional irregularity coefficient. To explore the stated issues, an evaluation based on relative variation in seismic response quantities of linear asymmetric structure under the influence of horizontal bi-directional excitation with varying seismic orientations has been carried out using response history analysis. Several typical earthquake records are applied to the structure to demonstrate the relative variations of floor rotation and torsional irregularity coefficient for different seismic orientations. It is demonstrated that (1) Torsional irregularity coefficient (TIC) increases as the story number decreases when the ground motion is considered along reference axes of the structure. For incident angles other than structure's reference axes, TIC either decreases as the story number decreases or there is no specific trend for TIC. Floor rotation increases in proportion to the story number when the ground motion is considered along reference axes of structure. For incident angles other than structure's reference axes, floor rotation either decreases as the story number increases or there is no specific trend for floor rotation and (2) TIC and floor rotation seems to be approximately inversely proportional to each other when the ground motion is considered along reference axes of the structure. For incident angles other than structure's reference axes, the relationship can even become directly proportional instead of inversely proportional.

• Wind and Structures
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• 제34권2호
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• pp.173-183
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• 2022

The galloping of iced conductors has long been a severe threat to the safety of overhead transmission lines. Compared with normal transmission lines, the ultra-high-voltage (UHV) transmission lines are more prone to galloping, and the damage caused is more severe. To control the galloping of UHV lines, it is necessary to conduct a comprehensive analysis of galloping characteristics. In this paper, a large-span 1000-kV UHV transmission line in China is taken as a practical example where an 8-bundled conductor with D-shaped icing is adopted. Galerkin method is employed for the time history calculation. For the wind attack angle range of 0°~180°, the galloping amplitudes in vertical, horizontal, and torsional directions are calculated. Furthermore, the vibration frequencies and galloping shapes are analyzed for the most severe conditions. The results show that the wind at 0°~10° attack angles can induce large torsional displacement, and this range of attack angles is also most likely to occur in reality. The galloping with largest amplitudes in all three directions occurs at the attack angle of 170° where the incoming flow is at the non-iced side, due to the strong aerodynamic instability. In addition, with wind speed increasing, galloping modes with higher frequencies appear and make the galloping shape more complex, indicating strong nonlinear behavior. Based on the galloping amplitudes of three directions, the full range of wind attack angles are divided into five galloping regions of different severity levels. The results obtained can promote the understanding of galloping and provide a reference for the anti-galloping design of UHV transmission lines.

• Imaging Science in Dentistry
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• 제31권4호
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• pp.205-207
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• 2001

Purpose : The aim of present study is to estimate the relationship among reference lines used for taking the extraoral radiography and panoramic radiography. Materials and Methods: Lateral cephalographs of 40 adults, aged 22 to 30 years were taken. Angles between reference lines (Frankfort line, canthomeatal line, infraorbitomeatal line, and occlusal plane) were measured. Results: Angles between Frankfort line and canthomeatal line, Frankfort line and infraorbitomeatal line, Frankfort line and occlusal plane, canthomeatal line and infraorbitomeatal line, canthomeatal line and occlusal plane, and infraorbitomeatal line and occlusal plane were 16.1° (±2.2), 5.8° (±2.4), 8.7° (±3.5), 10.3° (±1.3), 24.8° (±4.0), and 14.5° (±4.4),respectively. Conclusion: Angle between frankfort and canthomeatal line is very different with commonly known angle. Frankfort horizontal reference lines used for panoramic radiography need an exact definition and more accurate standard is needed for the taking of panoramic radiograph.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1832-1835
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• 1997

Off-line programming systems are widely spread in assembly lines of minute electronic products to huge offshore structures. Any OLP system has to be calibrated before the on-line robot tasks are performed because there are inherent differences between the CAD model on OLP and the real robot workspace. This paper uses simple geometric expressions to propose a calibration method applicable to an OLP for SCARA robots. A positioning task on the two-dimensional horizontal surface was used in the error analysis of a SCARA robot and the anaysis shows that the inaccuracy results from the two error sources non-zero offset angles of two rotational joints at the zero return and differences in link lengths. Pen marks on a sheet of plotting paper are used to determine the accurate data on the joint centers and link dimensions. The calculated offset angles and link lengths are fed back to the OLP for the calibration of the CAD model of the robot and task environments.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.944-947
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• 2004

The purpose of this study was to identify the characteristics of muscular power by COP(center of pressure) training according to the angle variation of tilting bed. We changed the angles of tilting bed(up-down direction 0$^{\circ}$, 15$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$ and right-left direction -15$^{\circ}$, 0$^{\circ}$, +15$^{\circ}$) for the correlation between angles and muscular power. And we measured EMG(electormyography) of lower limbs muscle(rectus femoris, biceps femoris, and gastrocnemius, tibialisa anterior) during COP training. COP training was divided by the COP trace training(in all direction) and sine wave trace training(vertical and horizontal direction). As the result, we obtained the improvement effect of COP training and we showed that electromyography(EMG) variations of lower limbs muscle on the angle variations of tilting bed were investigated.

• 대한기계학회논문집B
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• 제26권1호
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• pp.116-124
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• 2002

An experimental parametric study of a tubular heat exchanger has been carried out far the saturated water at atmospheric pressure to determine effects of tube inclination on pool boiling heat transfer. For the analysis, seven inclination angles(0°, 15°, 30°, 45°, 60°, 75°, and 90°) and two tube diameters(12.7 and 19.1 mm) were tested. According to the results, inclination angles result in very much change on pool boiling heat transfer. As the inclination angle is around horizontal or vertical, maximum or minimum heat transfer is expected, respectively. For the same wall superheat(about 5.5K) the ratio between two heat fluxes fur $\theta$ =15° and 75° has the value of more than five when the tube diameter is 12.7 mm and heat flux is increasing.

• 한국측량학회지
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• 제9권1호
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• pp.27-35
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• 1991

각과 거리를 동시관측할 수 있는 Total station과 3차원 위성 측량 시스템인 GPS는 대형 측지망의 재조정 및 설정을 위해 최근 이의 활용이 크게 기대되고 있다. 본 연구는 동시에 관측한 각과 거리의 과대오차를 검출하고 측지망 간의 다양한 결합조정에 따른 오차의 특성을 고찰함으로서 대형 측지망 조합에의 적용 가능성을 제시한 것이다. 연구 결과, 본 기법은 단기간내 높은 정확도로 측지망을 조합 조정할 수 있었으므로 크고 작은 건설공사는 물론 범 국가적인 측지망의 구성에 이용될 수 있을 것으로 기대된다.

• 한국정보전자통신기술학회논문지
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• 제3권4호
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• pp.76-82
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• 2010

기지국 섹터 배열안테나의 하향 빔틸트 각도를 조절하기 위해 전압제어 이상기를 사용하였다. 틸트 각도에 따른 각 안테나의 위상각을 도출하였으며 이때 생성되는 패턴의 수직과 수평 방향 성능을 분석 평가하였다. 이러한 분석을 통해 이동통신 기지국안테나의 셀커버리지 확보와 통화율 증대, 간섭 저감을 이룰 수 있어 최적의 기지국안테나 설계에 적용 가능할 것이다.

• 대한설비공학회지:설비저널
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• 제15권4호
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• pp.388-395
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• 1986

Numerical solutions of two-dimensional, steady, and natural are investigated in a confined rectangular cavity with porous media. The saturated fluid is bounded by two isothermal vertical walls at different temperatures and two adiabatic horizontal walls. Governing equations are numerically solved by finite difference method with the up wind scheme. Distributions of streamline and temperature we. predicted for aspect ratios ranging from 0.1 to 1.0, Rayleigh numbers 50 to $10^4$, and tilt angles $0^{\circ}\;to\;60^{\circ}$. Representative plots of temperature and velocity field according to tilt angle are presented. The effects of aspect ratio, Rayleigh number, and tilt angle on local and average Nusselt numbers are obtained. The optimum conditions for maximum Nusselt number are also presented with tilt angles.

• 치과방사선
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• 제22권1호
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• pp.109-116
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• 1992

저자는 경북대학교 치과대학 학생중 악관절의 기능장애의 병력 및 현증이 없고 안모가 단정한 정상인 56명을 대상으로 시상정중면에서 양측의 하악우각부사이의 각도와 하악과두장축의 수평경사도를 계측하여 통계학적으로 분석한 바 다음과 같은 결과를 얻었다. 1. 시상정중면에서 하악우각부 사이의 각도는 우측이 18.50±1.48°, 좌측이 19.30±1.55°였다. 2. 하악과두장축의 수평경사도는 우측이 19.25±7.56°, 좌측이 20.27±7.05°였다. 3. 두 각도간의 관계는 우측의 경우 y=20. 31-0.0094×(r=-0 482, p<0.01), 좌측의 경우 y=20.64-0.066×(r=-0.301, p<0.05)인 것으로 나타났다(y : 하악과두장축의 수평경사도, x : 시상정중면에서 하악우각부 사이의 각도).