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[en] This experimental study concerns the characteristics of vortex flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one is rotating. Pressure losses and skin friction coefficients have been measured for fully developed flows of water and of 0.4% aqueous solution of sodium CarboxyMethyl Cellulose (CMC), respectively, when the inner cylinder rotates at the speed of 0∼600rpm. Also, the visualization of vortex flows has been performed to observe the unstable waves. The results of present study reveal the relation of the bulk flow Reynolds number Re and Rossby number Ro with respect to the skin friction coefficients. In somehow, they show the existence of flow instability mechanism. The effect of rotation on the skin friction coefficient is significantly dependent on the flow regime. The change of skin friction coefficient corresponding to the variation of rotating speed is large for the laminar flow regime, whereas it becomes smaller as Re increases for the transitional flow regime and, then, it gradually approach to zero for the turbulent flow regime. Consequently, the critical (bulk flow) Reynolds number Rec decreases as the rotational speed increases. Thus, the rotation of the inner cylinder promotes the onset of transition due to the excitation of Taylor vortices
[en] This experimental study concerns the characteristics of a transitional flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one rotating. The pressure losses and skin-friction coefficients have been measured for the fully developed flow of a 0.2% aqueous solution of sodium CarboMethyl Cellulose(CMC) at a inner cylinder rotational speed of 0∼600 rpm. The transitional flow has been examined by the measurement of pressure losses, to reveal the relation of the Reynolds numbers with the skin-friction coefficients, in the laminar and transitional flow regimes. The occurrence of transition has been checked by the gradient change of pressure losses and skin-friction coefficient with respect to the Reynolds numbers. The increasing rate of skin-friction coefficient due to the rotation is uniform for laminar flow regime, whereas it is suddenly reduced for transitional flow regime and, then, it is gradually declined for turbulent flow regime. Consequently, the critical(axial-flow) Reynolds number decrease as the rotational speed increases. Thus, the rotation of inner cylinder promotes the early occurrence of transition due to the onset of taylor vortices
[en] Metamaterials (MMs), which are not existing in nature, but artificially-engineered materials for controlling electromagnetic wave. MMs have attracted more and more research attentions, since they have shown greatly novel properties such as left-handed behavior, negative refractive index, classical analog of electromagnetically-induced transparency, and extraordinary transmission. Among MMs, MM perfect absorbers (MMPAs), which are useful to enhance the efficiency in capturing solar energy and applied to various application areas, have been rapidly developed. In general, the structure of MMPAs is very simple, which consist of three layers: patterned conductor layer, which is used for minimizing the reflection by impedance matching, dielectric layer and continuous conductor layer for blocking the transmission. In addition, the unit-cell size of general MM absorbers is only 1/3−1/5 of the working wavelength of incident electromagnetic wave. Nevertheless, the properties of general MMPAs are in problems of the absorption only at specific frequency, the narrow absorption band, the polarization sensitivity and so on. In this review paper, the introduction of recent researches in the field of MMPAs operating in different frequency ranges is presented. Moreover, the researches on the improved electromagnetic properties are discussed, which comprise multi-band, broadband, tunable, polarization-insensitive, and wide-incident-angle MMPAs. The perspectives and the future works for the further investigations and the various real applications of MMPAs are also presented.
[en] Possibilities of recycling of waste bread as culture media for efficient biological treatment of wastewater were investigated. In order to get the highest growth of microorganism for increased contaminants' removal efficiency of the system, different compositions of waste bread and skim milk with and without adding Powdered Activated Carbon (PAC) were tested. Mixed waste bread compositions with added PAC showed relatively higher number of microorganisms than the compositions without added PAC. A composition of 40% mixed waste bread and 60% skim milk produced highest number of microorganisms with subsequent increased contaminants' removal efficiency of the system. 'Contrast' alone showed lower contaminants' removal efficiency than mixed bread compositions. Use of waste bread in the composition of skim milk reduced cost of using foreign source of nutrients in biological treatment of wastewater and also facilitated waste bread management through recycling. (author)
[en] When a cyclotron produces 18F-, accelerated protons interact with metal parts of the cyclotron machine and induces radioactivity. Especially, the target window and chamber of the target assembly are the main parts where long-lived radionuclides are generated as they are incident by direct beams. It is of great importance to identify radionuclides induced in the target assembly for the safe operation and maintenance of a cyclotron facility. In this study, we analyzed major radionuclides generated in the target assembly by an operation of the Cyclotron 18/9 machine and measured dose rates after the operation to establish the radiation safety guideline for operators and maintenance personnel of the machine. Gamma spectroscopy with HPGe was performed on samples from the target chamber and Havar foil target window to identify the radionuclides generated during the operation for production of 18F-- isotope and their specific activity. Also, the dose rates from the target were measured as a function of time after an operation. These data will help improve radiological safety of operating the cyclotron facilities
[en] The author analysed tomograms and submento-vertex radiograms of 90 temporomandibular joints from 45 asymptomatic young adults. 15 had Angle class I malocclusion, 15 class II and 15 class III. Corrected lateral tomograms were obtained in three condylar positions; centric occlusion, centric relation and 1 inch mouth opening. The condylar angulation, depth of cut, joint spaces were analysed in each radiogram. The obtained results were as follow; 1. The mean condylar angulation in Angle class I, II, III group was 17.55 ± 5.51 degree,13.33 ± 8.85 degree,16.25 ± 6.60 degree, respectively, and there was no significant difference in each group. The mean condylar angulation of right side (16.62 ± 7.23 degree) was larger than left side (14.80 ± 7.33 degree). 2. The mean depth of cut in Angle class I, II, III group was 8.13 ± 1.61 cm, 3.05 ± 3.80 cm, 7.75 ± 2.19 cm, respectively. Angle class I and class II group revealed significant difference in measurement (p<0.01). 3. The mean height of articular fossa in Angle class I, II, III group was 8.67 ± 3.06 mm, 9.61 ± 2.57 mm, 8.93 ± 2.83 mm, respectively. And the mean width of articular fossa was 19.90 ± 2.80 mm, 19.48 ± 3.83 mm, 20.36 ± 4.82 mm, respectively. 4. The mean height and width of condylar head was 5.11± 1.16 mm, 11.20 ± 2.26 mm, respectively. 5. In centric occlusion, the superior joint space was the largest (3.42 ± 1.42 mm), followed by anterior joint space (2.94 ± 1.95 mm) and the posterior joint space (2.64 ± 1.19 mm). In centric relation, the anterior joint space was the largest (3.86 ± 2.17 mm), followed by the superior joint space (3.64 ± 3.68 mm) and the posterior joint space (1.18 ± 0.77 mm). 6. The displaced measurement from centric relation to centric occlusion was 1.10 ± 1.04 mm anteriorly and 0.24 ± 0.97 mm inferiorly. In 1 inch mouth opening state, the condylar head displaced posteroinferiorly (2.49 ± 2.49 mm posteriorly, 1.17 ± 1.34 mm inferiorly) from the apex of articular eminence. And Angle class I and II group, Angle class II and III group revealed significant difference in posterior measurement, respectively (p<0.01).
[en] The purpose of this study was to determine whether any difference existed in craniofacial morphology between cleft children and normal subjects. Thirty three measurements of the various regions of cranium and face were obtained from lateral cephalometric radiograms in 40 cleft children (27 males, 13 females) and 40 normal subjects (23 males, 17 females) in our dental hospital from Jan. 1988 to Dec. 1995. The measurements were compared with those in control subjects who had no history of craniofacial abnormalities.. The obtained results were as follows; l. In the cranium, the cleft children had significantly shorter posterior cranial base length (S-Ba) and total antero-posterior cranial base length (N-Ba) (P<0.05). 2. In the upper face, the cleft children had significantly shorter upper anterior facial height (N-ANS) and upper posterior facial height (Ptm'-SNL) (P<0.05). 3. In the lower face, the cleft children had significantly shorter antero-posterior mandibular length (Pog-Ar) and antero-posterior mandibular body length (Pog-Go) (P<0.05). 4. In the facial profile, the cleft children had significantly shorter total facial height (N-Me) and posterior facial height (S-Go) (P<0.05).
[en] An investigation is conducted to understand hydraulic transport characteristics of a solid-liquid mixture flowing vertically upward. Namely, this is the instance that solid particles are carried by non-Newtonian fluids in a slim hole concentric annulus with rotating inner cylinder. In this study a clear acrylic pipe was used in order to observe the movement of solid particles. The bulk axial velocities varied from 0.4 m/s to 1.2 m/s. The mud systems which were utilized included aqueous solution of sodium carboxymethyl cellulose (0.2∼0.4%CMC) and 5% bentonite solutions. Solid volumetric concentration and pressure drops were measured for the various parameters such as inclined annulus, flow rate, and rotational speed of inner cylinder. For both CMC and bentonite solutions, the higher the concentration of the solid particles are, the larger the pressure drops become
[en] The purpose of this study was to compare the results of different agents for bronchial artery embolization of hemoptysis. From March 1992 to December 2006, a bronchial artery embolization was performed on 430 patients with hemoptysis. The patients were divided into three groups. Group 1 included 74 patients treated with a gelfoam particle (1Χ1Χ1 mm), while group 2 comprised of 205 patients treated with polyvinyl alcohol (PVA) at 355-500 μm, and group 3 included 151 patients treated with PVA at 500-710 μm. We categorized the results as technical and clinical successes, and also included the mid-term results. Retrospectively, the technical success was compared immediately after the procedure. The clinical success and mid-term results (percentage of patients who were free of hemoptysis) were compared at 1 and 12 months after the procedure, respectively. Neither the technical successes (group 1; 85%, 2; 85%, 3; 90%) nor the clinical successes (group 1; 72%, 2; 74%, 3; 71%) showed a significant difference among the 3 groups (p > 0.05). However, the mid-term results (group 1; 45%, 2; 63%, 3; 62%) and mid-term results excluding the recurrence from collateral vessels in each of the groups (group 1; 1 patient, 2; 4 patients, 3; 2 patients) showed that group 1 was lower than the other two groups (p < 0.05). No significant difference was discovered for the mid-term results between groups 2 and 3. Moreover, the same results not including incidences of recurrence from collateral vessels also showed no statistical significance between the two groups (p > 0.05). Polyvinyl alcohol appears to be the more optimal modality compared to gelfoam particle for bronchial artery embolization in order to improve the mid-term results. The material size of PVA needs to be selected to match with the vascular diameter
[en] Grating interferometry based imaging technology is a kind of radiation imaging system, which can acquire not only absorption image but also phase difference and dark field image using the Talbot pattern. However, because of the technological difficulties and high cost of fabricating the gratings that make up the system, much efforts are being made to look for ways to replace them. The is a preliminary study to see how the Talbot pattern transfer through various kinds of scintillators and if the optical grating can be a way to replace the conventional absorption gratings. The geometry of the interferometer, the scintillator model, and the scintillator thickness are the main inputs for our simulation. We have used the concept of modulation for quantitative analysis of the contrast ratio of the Talbot pattern. This research is expected to provide very useful information on the design of optical gratings, which is an alternative way to analyze the Talbot pattern, which we have filed a patent on