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Experimental Splash Studies of Monodisperse Sprays Impacting Variously Shaped Surfaces
Yoon, Sam S.,Kim, Ho Y.,Lee, Dongjo,Kim, Namsoo,Jepsen, Richard A.,James, Scott C. Taylor Francis 2009 Drying technology Vol.27 No.2
<P> Despite numerous studies of the drop impact phenomena, studies of the fundamental mechanisms of how the splash corona and subsequent necking yield splashed droplets, not to mention characteristics of these splashed droplets, remain a subject of great interest. Here, we consider a simple question: After impact, what are the characteristics of splashed droplets? Spatial variations in the fraction of splashed liquid, Sauter mean diameter, and drop-size distribution for water and diesel impacting onto variously shaped rods are reported. Liquid drops of nearly uniform size are continuously injected onto a 2-mm-diameter aluminum cylindrical rod at velocities of up to 17 m/s. The impact face of the rod is flat with angles from &thgr; = 0 to 60° or it has a concave, convex, or conical shape. The experimental results indicate that diesel breaks up more easily than water due to its low surface tension. However, due to increased energy loss through viscous dissipation during drop collapse and spreading, dispersion of diesel drops upon and after impact is less energetic than that of water since diesel droplets do not travel as fast or as far as water droplets. During corona formation, stretching and necking of diesel drops before their snap-off are particularly evident due to diesel's high viscosity. Size distribution of splashed diesel droplets is more uniform than that of water near the impact region and water is more uniform further away.</P>
Are Drop-Impact Phenomena Described by Rayleigh-Taylor or Kelvin-Helmholtz Theory?
Yoon, Sam S.,Jepsen, Richard A.,James, Scott C.,Liu, Jie,Aguilar, Guillermo Taylor Francis 2009 Drying technology Vol.27 No.3
<P> Drop impact, spreading, fingering, and snap-off are important inmany engineering applications such as spray drying, industrial painting, environmentally friendly combustion, inkjet printing, materials processing, fire suppression, and pharmaceutical coating. Controlling drop-impact instability is crucial to designing optimized systems for the aforementioned applications. Classical Rayleigh-Taylor (RT) theory has been widely used to analyze fingering where instabilities at the leading edge of the toroidal ring form fingers that may ultimately snap off to form small droplets. In this study, we demonstrate the inapplicability of RT theory, in particular because it fails to explain the stable regimes observed under conditions of low air density and the instabilities observed when a drop impacts a pool of equal-density fluid. Specifically, finger instability decreases with decreasing air density, whereas the RT theory suggests that instability should remain unchanged. Moreover, experiments show that fingers form upon impact of a dyed water drop with a water pool, whereas the RT theory predicts noinstability when the densities of the two interacting fluids are equal. Experimental evidence is instead consistent with instability predictions made using the shear-driven Kelvin-Helmholtz theory.</P>
Richard A. Pizzo,Jay N. Patel,Anthony Viola,David M. Keller,Richard S. Yoon,Frank A. Liporace 대한고관절학회 2020 Hip and Pelvis Vol.32 No.4
Purpose: Infection following total hip arthroplasty is a challenging and devastating complication. In two-stage revision arthroplasty, antibiotic spacers, although efficacious, can be associated with an unacceptable rate of mechanical complications (e.g., fracture, dislocation). This series describes 15 patients with infected total hip prostheses treated with hybrid cement-screw fixation constrained liner antibiotic spacers to enhance stability and minimize mechanical complications. Materials and Methods: All patients with an infected hip prosthesis undergoing two-stage revision arthroplasty at a single academic medical center were identified and screened for inclusion. Clinical and radiographic data including patient demographics and outcome measures were collected and retrospectively analyzed. Results: Two patients died of unrelated causes at an average of 6-week postoperatively. Infections in the remaining thirteen patients (100%) were successfully eradicated; all underwent uncomplicated revision arthroplasty at a mean duration of 99.5 days after the placement of the antibiotic spacer. No dislocations, fractures, or other mechanical failures of any spacer were observed in this series. Conclusion: The hybrid cement-screw fixation technique for constrained liner antibiotic spacers is a reliable and effective treatment method for eradicating prosthetic joint infections without mechanical complications.
Kim, Dong S.,Ahn, Seung K.,Yoon, Jeong H.,Hong, Seung H.,Kim, Kyoon E.,Maurer, Richard A,Park, Sang D. 충남대학교 생물공학연구소 1996 생물공학연구지 Vol.4 No.-
TRH is known to stimulate the transcription of the TSH gene in pituitary cells. To examine TRH-responsive elements of the human TSH α-subunit gene, we have used transient transfection of GH_3 rat pituitary tumor cells. Using this system, TRH treatment stimulated expression of a reporter gene containing 846 base pairs from the 5'-flanking region of the human glycoprotein hormone α-subunit gene linked to luciferase. Analysis of 5'-deletions of the α-subunit sequence revealed that at least two DNA regions with upstream limits between positions -223 to -190 and positions -151 to -135 are important for regulation by TRH. The more proximal region includes a previously defined cAMP-response element (CRE) while the more upstream region contains an element with sequence similarity to the binding site for the pituitary transcription factor, Pit-1. The TRH responsiveness of each individual region was tested by inserting fragments upstream of a thymidine kinaseluciferase reporter gene. The -151 to -100 region had basal enhancer activity and permitted a 3.4-fold response to TRH. The -223 to -168 region did not permit a TRH response, but possessed basal enhancer activity. The combination of both regions resulted in a 5-fold stimulation by TRH. To assess the contributions of different signal transduction pathways, various combinations of treatments were examined. Combined treatment with TRH and forskolin led to an additive activity. Treatment with TRH plus phorbol 12-myristate-13-acetate resulted in the same level of reporter gene activity as with either agent alone. The calcium channel blocker, verapamil, and the calcium chelator, EGTA, completely blocked induction by TRH of the α-subunit reporter gene. The -151 to -100 region of the α-subunit gene contains two copies of a consensus CRE. Deletion of one copy of the CREs resulted in a loss of TRH and calcium responsivenss. Overall, these results indicate that the TRH responsive element of the α-subunit gene likely involves a previously characterized CRE. At least a portion of the mechanism of TRH effects on the α-subunit gene likely involves changes in intracellular calcium levels leading to activation of calcium-responsive protein kinases and phosphorylation of CRE-binding proteins. (Molecular Endocrinology 8:528-536, 1994)
Park, Hong-Bok,Yoon, Sam S.,Jepsen Richard A.,Heister Stephen D. The Institute for Liquid Atomization and Spray Sys 2006 한국액체미립화학회지 Vol.11 No.2
An inviscid axisymmetric model capable of predicting droplet bouncing and the detailed pre-impact motion, influenced by the ambient pressure, has been developed using boundary element method (BEM). Because most droplet impact simulations of previous studies assumed that a droplet was already in contact with the impacting substrate at the simulation start, the previous simulations could not accurately describe the effect of the gas compressed between a failing droplet and the impacting substrate. To properly account for the surrounding gas effect, an effect is made to release a droplet from a certain height. High gas pressures are computationally observed in the region between the droplet and the impact surface at instances just prior to impact. The current simulation shows that the droplet retains its spherical shape when the surface tension energy is dominant over the dissipative energy. When increasing the Weber number, the droplet surface structure is highly deformed due to the appearance of the capillary waves and, consequently, a pyramidal surface structure is formed; this phenomenon was verified with our experiment. Parametric studies using our model include the pre-impact behavior which varies as a function of the Weber number and the surrounding gas pressure.
John W. Yurek,Nikki A. Doerr,Alex Tang,Adam S. Kohring,Frank A. Liporace,Richard S. Yoon 대한고관절학회 2023 Hip and Pelvis Vol.35 No.3
Purpose: This study aims to determine which intertrochanteric (IT) hip fracture and patient characteristics predict the necessity for adjunct reduction aides prior to prep and drape aiming for a more efficient surgery. Materials and Methods: Institutional fracture registries from two academic medical centers from 2017-2022 were analyzed. Data on patient demographics, comorbidities, fracture patterns identified on radiographs including displacement of the lesser trochanter (LT), thin lateral wall (LW), reverse obliquity (RO), subtrochanteric extension (STE), and number of fracture parts were collected, and the need for additional aides following traction on fracture table were collected. Fractures were classified using the AO/OTA classification. Regression analyses identified significant risk factors for needing extra reduction aides. Results: Of the 166 patients included, the average age was 80.84±12.7 years and BMI was 24.37±5.3 kg/m2. Univariate regression revealed increased irreducibility risk associated with RO (odds ratio [OR] 27.917, P≤0.001), LW (OR 24.882, P<0.001), and STE (OR 5.255, P=0.005). Multivariate analysis significantly correlated RO (OR 120.74, P<0.001) and thin LW (OR 131.14, P<0.001) with increased risk. However, STE (P=0.36) and LT displacement (P=0.77) weren’t significant. Fracture types 2.2, 3.2, and 3.3 displayed elevated risk (P<0.001), while no other factors increased risk. Conclusion: Elderly patients with IT fractures with RO and/or thin LW are at higher risk of irreducibility, necessitating adjunct reduction aides. Other parameters showed no significant association, suggesting most fracture patterns can be achieved with traction manipulation alone.