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RISS 인기검색어
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- 저자 : 최정일 ( Choe Jeong Il ) (검색결과 5 건)
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최정일,성형진,Choe, Jeong-Il,Xu, C.X.,Seong, Hyeong-Jin 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.2
A suboptimal control law in turbulent pipe flow is derived and tested. Two sensing variables ∂p/∂$\theta$│$\_$w/ and ∂v$\_$$\theta$/∂γ│$\_$w/ are applied with two actuations ø$\_$$\theta$/ and ø$\_$γ/. To test the suboptimal control law, direct numerical simulations of turbulent pipe flow at Re$\_$$\tau$/=150 are performed. When the control law is applied, a 13∼23% drag reduction is achieved. The most effective drag reduction is made at the pair of ∂v$\_$$\theta$/∂γ│$\_$w/ and ø$\_$γ/. An impenetrable virtual wall concept is useful for analyzing the near-wall suction and blowing. The virtual wall concept is useful for analyzing the near-wall behavior of the controlled flow. Comparison of the present suboptimal control with that of turbulent channel flow reveals that the curvature effect is insignificant.
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최정일,성형진,Choe, Jeong-Il,Seong, Hyeong-Jin 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.9
A direct numerical simulation in turbulent curved channel flow is performed. The drifting Taylor-Gortler vortices are identified by applying a conditional averaging. A new algorithm is proposed based on the wavelet transform of the wall information. A continuous wavelet transform with Marr wavelets is employed to decompose the flow signals at a chosen length scale. An active cancellation is applied to attenuate the Taylor-Gortler vortices and to reduce the wall skin friction.
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최정일,성형진,Choe, Jeong-Il,Seong, Hyeong-Jin 대한기계학회 1996 大韓機械學會論文集B Vol.20 No.7
A numerical study was made of the control of transient oscillatory flow modes in Czochralski convection. The reduction of temperature oscillation was achieved by changing the rotation rate of crystal rod, .OMEGA.$_{S}$=.OMEG $A_{S0}$(1+ $A_{S}$sin(2.pi. $f_{S}$/ $t_{p}$t)). The temporal behavior of oscillation flow was scrutinized over broad ranges of two parameters, i.e., the rotation amplitude( $A_{S}$.leq.0.5) and the nondimensional frequency (0.9.leq. $f_{S}$.leq.1.5). The mixed convection parameter was ranged 0.225.leq.Ra/PrR $e^{2}$.leq.0.929, which encompassed the buoyancy-and forced-dominant convection regimes. Computational results revealed that the temperature oscillations could be reduced effectively by a proper adjustment of the control parameters. The uniformity of temperature distribution near the crystal rod was examined. The control of oscillatory flow modes was also made for a realistic, low value of Pr.
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당뇨병 환자에서 방사성핵종 요류역학 검사를 이용한 배뇨기능의 평가
정병천 ( Jeong Byeong Cheon ),최정일 ( Choe Jeong Il ),김광원 ( Kim Gwang Won ),이재태 ( Lee Jae Tae ),이규보 ( Lee Gyu Bo ),김성국 ( Kim Seong Gug ),김보완 ( Kim Bo Wan ),이인규 ( Lee In Gyu ) 대한내과학회 1992 대한내과학회지 Vol.42 No.3
연구배경 : 신경인성 방광의 경우 당뇨병의 말초 및 중추 신경계 침습과 관련지어 설명되어지고 있으며 요류의 역동학적 검사가 방광기능의 침습정도를 평가하는데 이용되고 있으나, 이방법은 비교적 침습적이어서 검사에 따르는 합병증과 불편함으로 순응도가 문제가 되며 주기적인 추적관찰에는 이용하기 어렵다. 저자들은 당뇨병 환자에서 방광기능을 평가하고, 다른 합병증과의 관련성을 알아보기위해 ^(99m)Tc-DTPA를 이용한 방사성 핵종 요류역학 검사를 시행하여 배뇨량, 잔뇨량, 배뇨시의 방광용적, 배뇨 시간, 50% 배뇨 시간, 평균 요류속도, 최고 요류속도, 보정 최고요류속도 및 박출계수등을 구하여 신경계 및 망막의 침습정도와 비교하였다. 결과 : 당뇨병 환자 62명과 31명의 대조군에 ^(99m)Tc-DTPA를 이용하여 배뇨능과 잔뇨량을 살펴본 결과, 환자군은 배뇨량을 제외한 모든 계측치가 유의한 변화를 보였으며 이는 감각 및 자율 신경계 합병증 유무와 관련이 있었다. 특히 잔뇨량과 50% 배뇨시간은 자율 신경계 합병증과 평균, 최고 및 보정 최고요류속도와 박출 계수는 감각 신경계 합병증과 유의한 관계가 있었다. 또한 잔뇨량, 50% 배뇨 시간, 평균 및 최고 요류속도와 박출 계수는 망막의 합병증 정도와도 유의한 관계가 있음을 관찰 할 수 있었다. 결론 : 저자들은 이번 연구를 통하여 방사성 핵종 요류역학검사는 근전도나 배뇨시 방광내의 압력 변화등은 기록할 수 없지만 당뇨병 환자에 있어서 신장 스캔과 동시 에 방광 기능을 평가할 수 있는 간편하며 부작용이 없는 유용한 검사로 생각할 수 있었다. 그리고 자각 증상이 없이 요로나 전신 감염이 동반된 경우 본 검사법을 실시한다면 요도삽관술등의 침습적인 처치없이 배뇨기능을 추적 관찰 할 수 있어 치료 방침의 설정이나 치료 효과의 평가의 도움이 되리라 판단할 수 있었다. Background: Patients suffering from diabetes mellitus for long duration are known to have serious complications involving various organs. Diabetic cystopathy occurs in 43% to 87% of all diabetic patients and is closely related with development of the diabetic neuropathy Cystometry, sphincter electromyography, uroflowmetry, urethral pressure profilometry and electro physiologic test are applied in assessing diabetic cystopathy. But these methods are invasive and inadequate procedures for repetitive usage. Methods: The radionuclide urodynamic study using a gamma camera and ^(99m)Tc-DTPA) is more convenient and a non-invasive test than the above mentioned tests and it allows the measuremnt of residual urine without urinary catheterization. We have performed 93 radionuclide urodynamic examinations in 62 diabetic men and 31 healthy men for diagnosis of urinary bladder dysfunction. Results: The results obtained were as follows. 1) Urinary bladder function of the diabetic was shown to be remarkably deteriorated when compared to normal men. Voiding time (VT), 50% voiding time (50% VT), average flow rate (AFR), peak flow rate (PFR), corrected peak flow rate (C.PFR) and ejection fraction (EF) of patients developed neuropathy were significantly different when compared to healthy men, but it was well preserved in those without neuropathy. Futhermore, residual urine volume (RV) and 50% VT seemed to be the most sensitive parameters for diagnosis of urodynamic deragments of diabetes. 2) In patients with proliferative diabetic retinopathy, RV and 50% VT were higher, and AFR, C-PFR and EF were lower than those with no retinopathy. 3) 50% VT had positive correlation with diabetic duration, and AFT, PFR, C-PFR, negative correlatons. Conclusion: Urinary bladder dysfunction was noted in patients with diabetes and it was more severe in patients with neuropathy, retinopathy and a long histroy of diabetes. The radionuclide urodynamic study can be used for diagnosis of diabetic cystopathy and for gollowup evaluations after treatment.
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김진구 ( Kim Jin Gu ),최정일 ( Choe Jeong Il ),장대수 ( Jang Dae Su ),나종태 ( Na Jong Tae ),김용억 ( Kim Yong Eog ) 한국수산과학회 2003 한국수산과학회지 Vol.36 No.5
N/A Distribution of ichthyoplanktons and its relation to environmental factors (temperature, salinity, chlorophyll a ) around the Youngsan River Estuary of Mokpo, southwest coast of Korea were investigated based on the samples collected bimonthly from February to December, 2001. Unidentified fish eggs were most abundant 1,345 eggs/100㎥ in August, while eggs of Erzgraulis juponicus were most abundant 63 eggs/ 100㎥ in June. A total of forty species of fish larvae and juveniles belonging to the twenty families under six orders were caught, with six gobiids, four icefishes, four croakers and three herrings being represented. Fish larvae and juveniles peaked 17,757 inds./100 ㎥ in August, which consisted of 91.02% of gobiids, 3.69% of gunncls and 3.67% of icefishes, and they were most abundant 7,467 inds./100 ㎥ at St. 7. Cluster analysis based on the individuals of fish larvae and juveniles showed that six months were classified into two groups at the dissimilarity 70, the first was composed of June and August and the second was February and December and April and October were not clustered with any other months. In August when species diversity index was the highest, eight stations were classified into two groups at the dissimilarity 70, the first was composed of St. 1, 3, 4, 5 and 8 and the second was St. 6, 7 and 2. As a result from correspondence analysis, there is no effect of the environmental factors with a density of fish eggs and larvae, but correlation could be found between a density of fish eggs and chlorophyll α.
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