• Journal of Mechanical Science and Technology
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• 제19권8호
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• pp.1632-1648
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• 2005

The effects of Reynolds number on the non-nulling calibration of a typical cone-type five-hole probe have been investigated for the representative Reynolds numbers in turbomachinery. The pitch and yaw angles are changed from - 35 degrees to 35 degrees with an angle interval of 5 degrees at six probe Reynolds numbers in range between $6.60{\times}10^3\;and\;3.17{\times}10^4$. The result shows that not only each calibration coefficient itself but also its Reynolds number dependency is affected significantly by the pitch and yaw angles. The Reynolds-number effects on the pitch- and yaw-angle coefficients are noticeable when the absolute values of the pitch and yaw angles are smaller than 20 degrees. The static-pressure coefficient is sensitive to the Reynolds number nearly all over the pitch- and yaw-angle range. The Reynolds-number effect on the total-pressure coefficient is found remarkable when the absolute values of the pitch and yaw angles are larger than 20 degrees. Through a typical non-nulling reduction procedure, actual reduced values of the pitch and yaw angles, static and total pressures, and velocity magnitude at each Reynolds number are obtained by employing the calibration coefficients at the highest Reynolds number ($Re=3.17{\times}10^4$) as input reference calibration data. As a result, it is found that each reduced value has its own unique trend depending on the pitch and yaw angles. Its general tendency is related closely to the variation of the corresponding calibration coefficient with the Reynolds number. Among the reduced values, the reduced total pressure suffers the most considerable deviation from the measured one and its dependency upon the pitch and yaw angles is most noticeable. In this study, the root-mean-square data as well as the upper and lower bounds of the reduced values are reported as a function of the Reynolds number. These data would be very useful in the estimation of the Reynolds-number effects on the non-nulling calibration.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3467-3472
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• 2007

The effects of the wall geometry on the spray-wall impingement process of a hollow-cone fuel spray emerging from a high-pressure swirl injector of the Gasoline Direct Injection (GDI) engine were investigated by means of a numerical method. The ized Instability Sheet Atomization (LISA) & Aerodynamically Progressed Taylor Analogy Breakup (APTAB) model for spray atomization process and the Gosman model were applied to model the atomization and wall impingement process of the spray. The calculation results of spray characteristics, such as a spray development process and a radial distance after wall impingement, compared with the experimental ones by the Laser Induced Exciplex Fluorescence (LIEF) technique. It was found that the radial distance of the cavity angle of 90$^{circ]$ after wall impingement was the shortest and the ring shaped vortex was generated near the wall after spray-wall impingement process.

• Journal of Korean Neurosurgical Society
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• 제50권6호
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• pp.517-519
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• 2011

Stent assisted coiling on intracranial broad neck aneurysm has been considered as an effective technique and has made the complex aneurysms amenable to coiling. However, stent navigation and application themselves often have the problems especially when the parent vessel angle (entrance between afferent and efferent vessel) is over 90 degrees. We report here a case of a ruptured broad neck basilar top aneurysm that was successfully coiled using two self-expandable stents (Enterprise and Neuroform) placed in a fashion of modified Y-configured stents with waffle cone technique.

• 대한치과의사협회지
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• 제48권10호
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• pp.724-728
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• 2010

Accurate analysis of facial asymmetry prior to any orthognathic or orthodontic treatment plan is essential in ensuring good treatment result. Dental CBCT (Cone-beam Computed Tomography) provides as actual three-dimensional measurements of distance and angle without any radiographic magnification as medical CT provides, while its field of view is limited to the oral and maxillofacial area. CBCT is a useful tool for the diagnosis of facial asymmetry. The coordinates of facial landmarks are obtained from the 3D reconstruction software which enables the establishment of perpendicular planes and the identification of the landmarks. Then, the bilateral discrepancies of the landmarks are obtained as spherical polar coordinates which can show the amount of asymmetry and its direction. A method of 3D analysis of facial asymmetry using CBCT is introduced in this report.

• Journal of applied mathematics & informatics
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• 제6권3호
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• pp.859-866
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• 1999

In Eucliden k-space the cone of vectors x=($\chi$1, $\chi$2, ...,$\chi$k) satisfying $\chi$1$\leq$$\chi$ 2, $\leq$...$\leq$$\chi$k and {{{{ SUM { }`_{j } ^{k } }}= 1 $\chi$j=0 is generated by the vectors vj=(j-k,...j-k...j) having j-k's in its first j coordinates and j's for the remaining k-j coordinates for 1$\leq$j$\leq$i

• 한국분무공학회지
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• 제4권3호
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• pp.15-23
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• 1999

The use of LPG as clean fuel for Diesel engine is very attractive way to reduce soot and NOx emission. In this study, a numerical study has been done to know the transient behavior of LPG fuel in chamber pressures which is held at a pressure above (0.37MPa)and below(0.15MPa)the fuel vapor pressure. Results show that the vortex formed within the start of injection at the leading edge of the spray cone and was most apparent for 0.15MPa chamber pressure case. The high speed photographs and model results showed a narrower cone angle during the quasi-steady spray period at the 0.37MPa chamber pressure compared to the 0.15MPa case. And it can be shown that more realistic vaporization process is necessary to predict the spray length well.

• 한국가시화정보학회지
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• 제6권1호
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• pp.59-65
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• 2008

Distribution of spray was measured. Optical Line Patternator (OLP) was used to measure the planar distribution of the spray from a swirl-coaxial type injector. Ambient pressure was varied and injection pressure was fixed in experiment. As ambient pressure increased, spray distribution was changed from hallow cone to solid cone shape, and spray angle was decreased. Limitation in measuring dense spray was found at high ambient pressure condition.

• Journal of Forest and Environmental Science
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• 제9권1호
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• pp.1-9
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• 1993

잣송이 수확기계의 개발을 위한 기초자료를 얻기 위하여 강원대학교 임과대학 부속연습림에서 7영급 및 4영급의 착과한 잣나무의 정단부위 성장특성과 착과특성을 1992년 8월 말부터 9월 중순까지 조사하였다. 1. 당년 성장한 가지의 길이는 4영급에서 주지는 27~56cm이고 측지는 18~47cm로 7영급보다 훨씬 왕성하였다. 2. 측지의 분지각은 $24{\sim}89^{\circ}$이었고, 2년 성장한 주지의 직경은 10~30mm로서 두 특징에 있어 영급간 유의적인 차이가 없었으나, 1년생 주지의 직청은 4영급에서 9~18mm로서 7영급보다 생장량이 더 높았다. 3. 착과수는 평균 5개, 구과 생중량은 평균 272g으로 영급간 유의적인 차가 없었다. 4. 2년 자란 주지의 착과위치는 그 마디 아랫 쪽으로부터 7영급에서는 9.7~33.0cm, 4영급에서는 18.0~51.0cm의 범위인 곳으로 평균위치는 각 마디의 1/2과 4/5되는 위치였다. 5. 착과한 나무에 있어서 구과, 1년생지 및 2년생지를 합한 총생중량의 범위는 1.0~7.4kg이었다.

• 천문학회보
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• 제37권1호
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• pp.95.2-95.2
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• 2012

We have compared the geoeffective parameters of halo coronal mass ejections (CMEs) to predict geomagnetic storms. For this we consider 50 front-side full halo CMEs whose asymmetric cone model parameters and earthward direction parameter were available. For each CME we use its projected velocity (Vp), radial velocity (Vr), angle between cone axis and sky plane (${\gamma}$) from the cone model, earthward direction parameter (D), source longitude (L), and magnetic field orientation (M) of the CME source region. We make a simple and multiple linear regression analysis to find out the relationship between CME parameters and Dst index. Major results are as follows. (1) $Vr{\times}{\gamma}$ has a higher correlation coefficient (cc = 0.70) with the Dst index than the others. When we make a multiple regression of Dst and two parameters ($Vr{\times}{\gamma}$, D), the correlation coefficient increases from 0.70 to 0.77. (2) Correlation coefficients between Dst index and $Vr{\times}{\gamma}$ have different values depending on M and L. (3) Super geomagnetic storms (Dst ${\leq}$ -200 nT) only appear in the western and southward events. Our results demonstrate that not only the cone model parameters together with the earthward direction parameter improve the relationship between CME parameters and Dst index but also the source longitude and its magnetic field orientation play a significant role in predicting geomagnetic storms.

• Structural Engineering and Mechanics
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• 제53권2호
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• pp.227-248
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• 2015

A CFPBS (Cone-type Friction Pendulum Bearing System) was developed to control the acceleration delivered to a structure to prevent the damage and degradation of critical communication equipment during earthquakes. This study evaluated the isolation performance of the CFPBS by numerical analysis. The CFPBS was manufactured in the shape of a cone differenced with the existing FPS (Friction Pendulum System), and a pattern was engraved on the friction surface. The natural frequencies of the CFPBS were evaluated from a free-vibration test with a seismic isolator system consisting of 4 CFPBS. To confirm the earthquake-resistant performance, a numerical analysis program was prepared using the equation of the CFPBS induced from the equations of motion. The equation reported by Tsai for the rolling-type seismic isolation bearings was proposed to design the equation of the CFPBS. Artificial seismic waves that satisfy the maximum earthquake scale of the Korean Building Code-Structural (KBC-2005) were created and verified to review the earthquake-resistant performance of the CFPBS by numerical analysis. The superstructural mass of the CFPBS and the skew angle of friction surface were considered for numerical analysis with El Centro NS, Kobe NS and artificial seismic waves. The CFPBS isolation performance evaluation was based on the numerical analysis results, and comparative analysis was performed between the results from numerical analysis and simplified theoretical equation under the same conditions. The validity of numerical analysis was verified from the shaking table test.