• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.115-119
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• 2007

In this paper, a flow visualization analysis has been carried out on an oscillating square section cylinder, numerically, using a commercially available code CFD-ACE. In this study, the square cylinder is forced to oscillate at different frequencies of excitation, viz., fe/fo=0.5, 1.0 and 2.0 (where, fe is the excitation frequency provided to the cylinder and fo is the natural vortex shedding frequency from the stationary cylinder at a particular Reynolds number (=5200). In all the cases, the peak-to-peak amplitude of oscillation is kept at 32% of the side dimension of the square cylinder. These studies are conducted to understand the influence of frequency of oscillation on the flow field features around the cylinder, particularly the mode of vortex shedding. Results indicate that, the flow field around a square cylinder is very much influenced by the excitation frequency, in particular the vortex shedding mode. It is also found that, the vortex street parameters are significantly influence by the oscillation frequency. Comparison with earlier reported experimental studies has also been attempted in this paper. In appears that, such a numerical exercise (as performed in this paper) is first of its kind. It is believed that, these studies would enable one to understand the mechanisms underlying the flow-induced vibrations of a square section cylinder.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2089-2094
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• 2003

The flow around a circular cylinder was controlled by attaching O-rings to reduce drag force acting on the cylinder. Four experimental models were tested in this study; one smooth cylinder of diameter D (D=60mm) and three cylinders fitted with O-rings of diameters d=0.0167D, 0.05D and 0.067D with pitches of PPD=1D, 0.5D and 0.25D. The drag force, mean velocity and turbulent intensity profiles in the near wake behind the cylinders were measured for Reynolds numbers based on the cylinder diameter in the range of $Re_D=7.8{\times}10^3{\sim}1.2{\times}10^5$. At $Re_D=1.2{\times}10^5$, the cylinder fitted with O-rings of d=0.0167D in a pitch interval of 0.25D shows the maximum drag reduction of about 5.4%, compared with the smooth cylinder. The drag reduction effect of O-rings of d=0.067D is not so high. For O-ring circulars, as the Reynolds number increases, the peak location of turbulence intensity shifts downstream and the peak magnitude is decreased. Flow field around the cylinders was visualized using a smoke-wire technique to see the flow structure qualitatively. The size of vortices and vortex formation region formed behind the O-ring cylinders are smaller, compared with the smooth cylinder.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1281-1292
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• 2001

Experiments were done for the comparison of performance and flow characteristics between a two -stage axial flow fan and a counter-rotating axial flow fan. Each stage of the two -stage axial flow fan used fur the present study has an eight bladed rotor and thirteen slater blades. The front and the rear rotor of the counter - rotating axial flow fan have eight blades each and are driven by coaxial counter ro latins shafts through a gearbox located between the rear rotor and the electric motor. Both of the two axial fan configurations have identical rotor blades and the same operating condition fur the one -to-one comparison of the two. Performance curves of the two configurations were obtained and compared by varying the blade pitch angles and axial gaps between the blade rows. The fan characteristic curves were obtained following the Korean Standard Testing Methods for Turbo Fans and Blowers (KS B 6311). The fa n flow characteristics were measured using a five-hole probe by a non-nulling method. The velocity profiles between the hub and tip of the fans were measured and analyzed at the particular operating condition s of peak efficiency, minimum and maximum pressure coefficients. The peak efficiency of the counter-rotating axial fan was improved about 2% respectively, compared with the two stage axial fan. At the minimum pressure coefficient point of the two stage axial fan, the fan inlet flow patterns show that axial velocity highly decreased in the vicinity of the blade tip region. Also, the reverse flow took place at the blade tip.

• Journal of Animal Science and Technology
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• v.48 no.4
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• pp.487-492
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• 2006

This study estimated characteristics and genetic parameters for milking traits in Holstein dairy cattle. Daily records (12,561) were available from a hundred fifty four lactating cows with sixty six sires at National Livestock Research Institute from November, 2005 to April, 2006. The cows were fed same rations, and were milked twice daily using milking parlour equipped with Alpro-system?? to collect milking records automatically. The experimental cows have averaged 1.9 parities, 139.7 days in milk, and 13kg milk yield per milking. Average milk flow was 64% of peak milk flow. Milking duration, peak milk flow, average milk flow, and milk yield per milking were 5.57±1.67 minutes, 3.58±0.79kg/minute, 2.28±0.51kg/minute, and 13.02±4.09kg, respectively. All traits in the morning milking were higher than those of in the evening milking, and were also increased with parity. Heritabilities for milking duration, peak and average milk flow, and milk yield per time were 0.49, 0.70 0.58 and 0.36, respectively. The genetic correlations of milking duration with peak milk flow, average milk flow, and milk yield per time were 0.48, 0.54, and 0.41, respectively. The correlations of milk yield per milking with peak milk flow and average milk flow were 0.23 and 0.30, respectively. In conclusion, milk flow was increased with milk yield; however milk flow was opposite relationship with milk duration. Further studies are not only necessary to warranty genetic parameters, but pre-installation of automatic recording system to collect daily milking record is also necessary.

• Korean Journal of Materials Research
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• v.15 no.8
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• pp.518-520
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• 2005

Effects of the $O_2/Ar$ flow ratio in the sputtering process on the crystallinity, surface roughness, carrier concentration, carrier mobility, and optical properties of Al-doped ZnO thin films deposited on sapphire (001) substrates by RF magnetron sputtering were investigated. XRD spectra showed a preferred orientation along the c-axis and a minimum FWHM of the (002) XRD intensity peak for the $O_2/Ar$ flow ratio of 0.5. The (101)peak also appeared and the degree of preferred orientation decreased as the $O_2/Ar$ flow ratio increased from 0.5 to 1.0. AFM analysis results showed that the surface roughness was lowest at the $O_2/Ar$ flow ratio of 0.5 and tended to increase owing to the increase of the grain size as the $O_2/Ar$ flow ratio increased further. According to the Hall measurement results the carrier concentration and carrier mobility of the fan decreased and thus the resistivity increased as the $O_2/Ar$ flow ratio increased. The transmittance of the ZnO:Al film deposited on the glass substrate was characteristic of a standing wave. The transmittance increased as the $O_2/Ar$ flow ratio in-RF magnetron sputtering increased up to 0.5. Considering the effects of the $O_2/Ar$ flow ratio on the surface roughness, electrical resistivity and transmittance properties of the ZnO:Al film the optimum $O_2/Ar$ flow ratio was 0.5 in the RF magnetron sputter deposition of the ZnO:Al film.

• Clinics in Shoulder and Elbow
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• v.27 no.1
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• pp.11-17
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• 2024

Background: Rotator cuff tears are often associated with synovitis, but the ability of noninvasive ultrasonography to predict the severity of synovitis remains unclear. We investigated whether ultrasound parameters, namely peak systolic velocity in the anterior humeral circumflex artery and Doppler activity in the glenohumeral joint and subacromial space, reflect synovitis severity. Methods: A total of 54 patients undergoing arthroscopic rotator cuff repair were selected. Doppler ultrasound was used to measure peak systolic velocity in the anterior humeral circumflex artery and Doppler activity in the glenohumeral joint and subacromial space, and these values were compared with the intraoperative synovitis score in univariate and multivariate analyses. Results: Univariate analyses revealed that tear size, peak systolic velocity in the anterior humeral circumflex artery, and Doppler activity in the glenohumeral joint were associated with synovitis in the glenohumeral joint (P=0.02, P<0.001, P=0.02, respectively). In the subacromial space, tear size, peak systolic velocity in the anterior humeral circumflex artery, and Doppler activity in the subacromial space were associated with synovitis severity (P=0.02, P<0.001, P=0.02, respectively). Multivariate analyses indicated that tear size and peak systolic velocity in the anterior humeral circumflex artery were independently associated with synovitis scores in both the glenohumeral joint and the subacromial space (all P<0.05). Conclusions: These findings demonstrate that tear size and peak systolic velocity in the anterior humeral circumflex artery, which can both be measured noninvasively, are useful indicators of synovitis severity.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.1 no.1
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• pp.69-76
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• 1994

This study was designed and undertaken to find out the effectiveness of VAS for evaluation of general anesthetic postoperative pulmonary-function. We compared the degree of perceived pulmonary function recovery with peak expiratory flow at postoperative 72 hours of subjects. The subjects of this study were collected 38 patients who had received upper abdominal operation in St. Paul Hospital, Catholic University Medical College, and Kangnam Scared Heart Hospital and Kangdong Scared Heart Hospital, Hallym University. Data collection period was from June 15th, to August 7th, 1992. The degree of pulmonary recovery function was measured with peak expiratory at 72 hours postoperatively. The degree of perceived pulmonary function of the patient was measured with ten points visual analog scale at 72 hours postoperatively. Peak expiratory flow and visual analog score was analyzed with Pearson correlation. Peak expiratory flow was expressed as a ratio of preoperative value. The result was as follows : The recovery of pulmonary function and the degree of perceived pulmonary function of the patient at 72hours postoperatively was revealed high correlation (r=.84). The above result suggested that patients with general anesthetic upper abdominal surgery should evaluate recovery of pulmonary function making use of VAS. We know that VAS is very useful in postoperative patients. We perceived that VAS is to take up a positive attitude of patients. Nurse should furnish the nursing care objectively and scientifically to patients. As VAS was economic and simple, VAS should be adviced for wider application.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.173-173
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• 2015

The flood water level in tidal river is determined by the joint effects of flood discharge and tidal water levels at downstream boundary. Due to the variable tidal boundary conditions, the evaluated design water levels associated with a certain flood event can be significantly different. To avoid determining of design water levels just by a certain tidal boundary condition and remove the influence of variability in boundary condition from the evaluation of design water levels, a probabilistic approach is considered in this study. This study focuses on the development of a method to evaluate the realistic design water levels in tidal river with taking into account the combined effects of river discharge and tidal level. The flood water levels are described by the joint probability of two driving forces, river discharge and tidal water levels. The developed method is applied to determine design water levels for the tidal reach of the Han River. An unsteady flow model is used to simulate the flow in the reach. To determine design water levels associated with a certain flood event, first, possible boundary conditions are obtained by sampling starting times of tidal level time series; then for each tidal boundary condition, corresponding peak water levels along the channel are computed; and finally, design water levels are determined by computing the expectations of the peak water levels. Two types of tides which are composed by different constituents are assumed (one is composed by $M_2$, and the other one is composed by $M_2$ and $M_2$) at downstream boundary, and two flood events with different maximum flood discharges are considered in this study. It is found that (a) the computed design water levels with two assumed tides have no significant difference for a certain flood event, though variability of peak water levels due to the tidal effect is considerably different; (b) tidal effect can reach to the Jamsil submerged weir and the effect is obvious in the downstream reach of the Singok submerged weir; (c) in the tidally affected reach, the variability of peak water levels due to the tidal effect is greater if the maximum flood discharge is smaller.

• Analytical Science and Technology
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• v.21 no.6
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• pp.495-501
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• 2008

Agilent 5973 GC-MS instrument was modified so that the capillary direct interface was removed and that a silicone membrane was installed between GC and MS. Feasibility study of the membrane interface GC-MS has been carried out. Vacuum of the mass spectrometer was not affected by the carrier gas flow rate up to $4.7m{\ell}/min$. As the carrier flow rate was increased, peak tailing was reduced and chromatogram peaks appeared earlier. Chromatogram peaks showed better separation and higher sensitivity as the membrane thickness was reduced from $127{\mu}m$ to $75{\mu}m$, and also as the interface temperature was increased. However, the membrane interface GC-MS had drawbacks such as background ions at 73 and 147 m/z and poor peak separation due to peak tailing.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.1
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• pp.29-36
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• 2009

Power supply noise is fundamentally caused by large current peaks. Since large current peaks are induced by simultaneous switching of many circuit elements, power supply noise can be minimized by deliberate clock scheduling which utilizes nonzero clock skew. In this paper, nonzero skew clock scheduling is used to avoid the large peak current and consequently reduce power supply noise. While previous approaches require extra characterization efforts to acquire current waveform of a circuit, we approximate it only with existing cell library information to be easily adapted to conventional design flow. A simulated annealing based algorithm is performed, and the peak current values are estimated for feasible clock schedules found by the algorithm. The clock schedule with the minimum peak current is selected for a solution. Experimental results on ISCAS89 benchmark circuits show that the proposed method can effectively reduce the peak current.