• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1B
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• pp.80-85
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• 2011

The mount of network traffic from the Internet is increasing because of the use of Broadband Convergence Networks(BcN). Network traffic is also increasing because of the development of application, especially multimedia traffic from IPTV, VOD, and online games. This multimedia traffic not only has a huge payload but also should be considered a threat in real time. For this reason, this study examines the ways that routers distribute the bandwidth in accordance to traffic properties. To classify the property of the traffic, it is essential to analyze the application layer. However, the general network processor architecture serially processes the L2-4 and L7 layer. We propose a novel parallel network processor architecture with a global cache that processes L2-4 and L7 in parallel. To verify the proposed architecture, we simulated both of the architecture with SystemC. EEMBC and SNORT was used to measure L2-4 and L7 processing time. When multimedia traffic was entered into the network processor in the same flow, the proposed architecture showed about 85% higher performance than general architecture.

• The Journal of the Convergence on Culture Technology
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• v.9 no.4
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• pp.331-335
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• 2023

As the viscosity of the blood increases, the blood becomes more sticky and difficult to flow, so the possibility of thrombosis increases and the probability of ischemic cerebral infarction increases. The importance of measuring blood viscosity has recently been emphasized for the prevention of circulatory system diseases, and the need for a viscometer capable of easily and accurately measuring blood viscosity has emerged. In this study, the measured values of a viscosity standard solution and an artificial blood by a parallel-plate viscometer ARS-Medi were compared with the those by Ares-G2 of TA instrument, which is internationally recognized for its accuracy and reliability. The viscosity of N44 standard solution, which is a Newtonian solution, was almost perfectly matched between the two instruments at all shear rates. In the case of an artificial blood, which is a non-Newtonian solution, the measured values between the two instruments showed a difference of about 10% at the lowest shear rate 1 rad/s; however, at a clinically significant shear rate of 10 rad/s or higher, the measured values between them were consistent within the error range. We expect that ARS-Medi, a newly developed parallel-plate viscometer for blood, using disposable plates, will be very useful in clinical practice as it improves the convenience and hygiene of blood viscosity measurement.

• Journal of the Korean Chemical Society
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• v.23 no.4
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• pp.217-236
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• 1979

The author's theory for plastic deformation was applied to superplastic alloys (Zn-Al eutectoid, Al-Cu, Pb-Sn, Sn-Bi, Mg-Al eutectics). The plastic deformation of the superplastic alloys could be described by two Maxwell models connected in parallel which represent two grain boundary flow units. The flow units are characterized by the two parameters $X_{gj}/{\alpha}_{gj}\;and\;{\beta}_{gj}$ (j=l or 2, g signifies the grain boundary) the values of which were obtained by applying our flow equation [Eq. (5)] to experiment. We confirmed that our flow equation describes the superplasticity very well. The curve of strain rate sensitivity m (=${\partial}\;In\;f/{\partial}\;In\;\dot{s})\;vs.\;-In\dot{s}$, where f and s are stress and strain rate, respectively, showed two peaks corresponding to flow unit gl and g2, the separation of the two peaks is determined by the difference between ${\beta}_{g1}\;and\;{\beta}_{g2}$. The condition of superplasticity is also determined by ${\beta}_{gj}$, which satisfies $\dot{s}_{mj}{\leqslant}1.53}{\beta}_{gj}$ [Eq.(13)], where $\dot{s}_{mj}$ is the s of the jth unit at the peak. The grain size dependence of ${\beta}_{gj}$ is described by $ln({\beta}_{gj})^{-1}$=alnx+b [Eq. (16)], where x is the grain size, and a and b are constants. The activation enthalpy for each flow unit, ${\Delta}H_{gj}^{\neq}$ was also determined from the temperature dependence of ${\beta}_{gj}$ which is proportional to the relaxation time of the j th unit. Since the superplasticity is determined by Eq. (13), and since ${\beta}_{gj}$ and ${\Delta}H_{gj}^{\neq}$ are related, we obtained the conclusion that superplasticity occurs in the system having small ${\Delta}H_{gj}^{\neq}$ values. The Aej values were equal to the activation enthalpies of grain boundary self-diffusion of the component atoms of the alloys, this accords with our proposed flow mechanism. The ${\Delta}H_{gj}^{\neq}$ value increases with grain size as expected from Eq. (16).

• The Korean Journal of Nuclear Medicine
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• v.1 no.2
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• pp.1-25
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• 1967

In 20 normal cases and 39 pulmonary tuberculosis cases, regional pulmonary arterial blood flow measurements and lung perfusion scans by $^{131}I$-Macroaggregated albumin, lung inhalation scans by colloidal $^{198}Au$ and spirometries by respirometer were done at the Radiological Research Institute. The measured lung function tests were compared and the results were as the following: 1. The normal distribution of pulmonary blood flow was found to be $54.5{\pm}2.82%$ to the right lung and $45.5{\pm}2.39%$ to the left lung. The difference between the right and left pulmonary arterial blood flow was significant statistically (p<0.01). In the minimal pulmonary tuberculosis, the average distribution of pulmonary arterial blood flow was found to be $52.5{\pm}5.3%$ to the right lung and $47.5{\pm}1.0%$ to the left lung when the tuberculous lesion was in the right lung, and $56.2{\pm}4.4%$ to the right lung and $43.8{\pm}3.1%$ to the left lung when the tuberculous lesion was in the left lung. The difference of pulmonary arterial blood flow between the right and left lung was statistically not significant compared with the normal distribution. In the moderately advanced pulmonary tuberculosis, the average distripution of pulmonary arterial blood flow was found to be $26.9{\pm}13.9%$ to the right lung and $73.1{\pm}13.9%$ to the left lung when the tuberculous lesion was more severe in the right lung, and $79.6{\pm}12.8%$ to the right lung and $20.4{\pm}13.0%$ to the left lung when the tuberculous lesion was more severe in the left lung. These were found to be highly significant statistically compared with the normal distribution of pulmonary arterial blood flow (p<0.01). When both lungs were evenly involved, the average distribution of pulmonary arterial blood flow was found to be $49.5{\pm}8.01%$ to the right lung and $50.5{\pm}8.01%$ to the left lung. In the far advanced pulmonary tuberculosis, the average distribution of pulmonary arterial blood flow was found to be $18.5{\pm}11.6%$ to the right lung and $81.5{\pm}9.9%$ to the left lung when the tuberculous lesion was more severe in the right lung, and $78.2{\pm}8.9%$ to the right lung and $21.8{\pm}10.5%$ to the left lung when the tuberculous lesion was more severe in the left lung. These were found to be highly significant statistically compared with the normal distribution of pulmonary arterial blood flow (p<0.01). When both lungs were evenly involved the average distribution of pulmonary arterial blood flow was found to be $56.0{\pm}3.6%$ to the right lung and $44.0{\pm}3.2%$ to the left lung. 2. Lung perfusion scan by $^{131}I$-MAA in patients with pulmonary tuberculosis was as follows: a) In the pretreated minimal pulmonary tuberculosis, the decreased area of pulmonary arterial blood flow was corresponding to the chest roentgenogram, but the decrease of pulmonary arterial blood flow was more extensive than had been expected from the chest roentgenogram in the apparently healed minimal pulmonary tuberculosis. b) In the pretreated moderately advanced pulmonary tuberculosis, the decrease of pulmonary arterial blood flow to the diseased area was corresponding to the chest roentgenogram, but the decrease of pulmonary arterial blood flow was more extensive in the treated moderately advanced pulmonary tuberculosis as in the treated minimal pulmonary tuberculosis. c) Pulmonary arterial blood flow in the patients with far advanced pulmonary tuberculosis both before and after chemotherapy were almost similar to the chest roentgenogram. Especially the decrease of pulmonary arterial blood flow to the cavity was usually greater than had been expected from the chest roentgenogram. 3. Lung inhalation scan by colloidal $^{198}Au$ in patients with pulmonary tuberculosis was as follows: a) In the minimal pulmonary tuberculosis, lung inhalation scan showed almost similar decrease of radioactivity corresponding to the chest roentgenogram. b) In the moderately advanced pulmonary tuberculosis the decrease of radioactivity in the diseased area was partly corresponding to the chest roentgenogram in one hand and on the other hand the radioactivity was found to be normally distributed in stead of tuberculous lesion in the chest roentgenogram. c) In the far advanced pulmonary tuberculosis, lung inhalation scan showed almost similar decrease of radioactivity corresponding to the chest roentgenogram as in the minimal pulmonary tuberculosis. 4. From all these results, it was found that the characteristic finding in pulmonary tuberculosis was a decrease in pulmonary arterial blood flow to the diseased area and in general decrease of pulmonary arterial blood flow to the diseased area was more extensive than had been expected from the chest roentgenogram, especially in the treated group. Lung inhalation scan showed almost similar distribution of radioactivity corresponding to the chest roentgenogram in minimal and far advanced pulmonary tuberculosis, but there was a variability in the moderately advanced pulmonary tuberculosis. The measured values obtained from spirometry were parallel to the tuberculous lesion in chest roentgenogram.

• Journal of Aerospace System Engineering
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• v.14 no.5
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• pp.66-72
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• 2020

In this study, a method for increasing the initial water supply was employed to protect the water injection nozzle by the flame when supplying the water to the steam generator. During the initial steam generator test, the flow rate was controlled by using the only venturi, but cooling water was not supplied to the combustion chamber at the beginning of combustion, thereby resulting in damage to the water nozzle. To solve this problem, a venturi and an orifice were configured in parallel to increase the initial supply flow rate to form a differential pressure between the water manifold and the combustion chamber. Venturi and orifice supply sequences were established through the water flow tests, and combustion tests were conducted for final verification. Consequently, a continuous supply of the cooling water at the beginning of combustion was achieved, and the experiment was successfully performed without damaging the cooling water nozzle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.338-348
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• 2004

The present study is conducted to investigate the effect of rib arrangements on an impingement/effusion cooling system with initial crossflow. To simulate the impingement/effusion cooling system, two perforated plates are placed in parallel and staggered arrangements with a gap distance of 2 times of tile hole diameter. Initial crossflow passes between the injection and effusion plates, and the square ribs (3mm) are installed on the effusion plate. Both the injection and effusion hole diameters are 10mmand Reynolds number based on the hole diameter and hole-to-hole pitch are fixed to 10,000 and 6 times of the hole diameter, respectively. To investigate the effects of rib arrangements, various rib arrangements, such as 90$^{\circ}$transverse and 45$^{\circ}$angled rib arrangements, are used. Also, the effects of flow rate ratio of crossflow to impinging jets are investigated. With the initial crossflow, locally low transfer regions are formed because the wall jets are swept away, and level of heat transfer rate get decreased with increasing flow rate of crossflow. When the ribs are installed on the effusion plate, the local distributions of heat/mass transfer coefficients around the effusion holes are changed. The local heat/mass transfer around the stagnation regions and the effusion holes are affected by the rib positions, angle of attack and rib spacing. For low blowing ratio, the ribs have adverse effects on heat/mass transfer, but for higher blowing ratios, higher and more uniform heat transfer coefficient distributions are obtained than the case without ribs because the ribs prevent the wall jets from being swept away by the crossflow and increase local turbulence of the flow near the surface. Average heat transfer coefficients with rib turbulators are approximately 10% higher than that without ribs, and the higher values are obtained with small pitch of ribs. However, the attack angle of the rib has little influence on the average heat/mass transfer.

• Wind and Structures
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• v.30 no.5
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• pp.465-474
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• 2020

Vortex-induced vibrations of a yawed flexible cylinder near a plane boundary are numerically investigated at a Reynolds number Re_n= 500 based on normal component of freestream velocity. Free to oscillate in the in-line and cross-flow directions, the cylinder with an aspect ratio of 25 is pinned-pinned at both ends at a fixed wall-cylinder gap ratio G/D = 0.8, where D is the cylinder diameter. The cylinder yaw angle (α) is varied from 0° to 60° with an increment of 15°. The main focus is given on the influence of α on structural vibrations, flow patterns, hydrodynamic forces, and IP (Independence Principle) validity. The vortex shedding pattern, contingent on α, is parallel at α=0°, negatively-yawed at α ≤ 15° and positively-yawed at α ≥ 30°. In the negatively- and positively-yawed vortex shedding patterns, the inclination direction of the spanwise vortex rows is in the opposite and same directions of α, respectively. Both in-line and cross-flow vibration amplitudes are symmetric to the midspan, regardless of α. The RMS lift coefficient C_L,rms exhibits asymmetry along the span when α ≠ 0°, maximum C_L,rms occurring on the lower and upper halves of the cylinder for negatively- and positively-yawed vortex shedding patterns, respectively. The IP is well followed in predicting the vibration amplitudes and drag forces for α ≤ 45° while invalid in predicting lift forces for α ≥ 30°. The vortex-shedding frequency and the vibration frequency are well predicted for α = 0° - 60° examined.

• Wind and Structures
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• v.30 no.6
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• pp.617-631
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• 2020

Wake-induced aerodynamics of yawed circular cylinders with smooth and grooved surfaces in a tandem arrangement was studied. This pair of cylinders represent sections of stay-cables with smooth surfaces and high-voltage power conductors with grooved surfaces that are vulnerable to flow-induced structural failure. The study provides some insight for a better understanding of wake-induced loads and galloping problem of bundled cables. All experiments in this study were conducted using a pair of stationary section models of circular cylinders in a wind tunnel subjected to uniform and smooth flow. The aerodynamic force coefficients and vortex-shedding frequency of the downstream model were extracted from the surface pressure distribution. For measurement, polished aluminum tubes were used as smooth cables; and hollow tubes with a helically grooved surface were used as power conductors. The aerodynamic properties of the downstream model were captured at wind speeds of about 6-23 m/s (Reynolds number of 5×10⁴ to 2.67×10⁵ for smooth cable and 2×10⁴ to 1.01×10⁵ for grooved cable) and yaw angles ranging from 0° to 45° while the upstream model was fixed at the various spacing between the two model cylinders. The results showed that the Strouhal number of yawed cable is less than the non-yawed case at a given Reynolds number, and its value is smaller than the Strouhal number of a single cable. Additionally, compared to the single smooth cable, it was observed that there was a reduction of drag coefficient of the downstream model, but no change in a drag coefficient of the downstream grooved case in the range of Reynolds number in this study.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.325-333
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• 2001

The present study investigates convective heat/mass transfer and flow characteristics inside the cooling passage of the gas-turbine blades. It is important to increase not only the heat transfer rates but also the uniformity of heat transfer in the cooling passage. The square duct has compound-angled ribs with $60^{\circ},\;70^{\circ}$ and $90^{\circ}$ attack angles, which are installed on the test plate surfaces. a naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients using the heat and mass transfer analogy. The ribs disturb the main flow resulting in the recirculation and secondary flows near the ribbed wall and the vertices near the side-wall. The local heat transfer and the secondary flow in the duct are changed largely according to the rib orientation. Therefore, geometry and arrangement of the ribs are important fur the advantageous cooling performance. The angled ribs increase the heat transfer discrepancy between the wall and center regions because of the interaction of the secondary flows. The average heat/mass transfer coefficient and pressure drop of the ribs with the $60^{\circ}$ $-90^{\circ}$ compound-angle are higher than those with the $60^{\circ}$ attack angle. Also, the thermal efficiency of the compound-angled rib is higher than that with the $60^{\circ}$ attack angle. The uniformity of heat/mass transfer coefficient on the cross ribs may is higher than that on the parallel ribs array.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.1
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• pp.95-104
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• 2007

A new design approach of complex geometries such as wing/body configuration is arranged by using overset mesh techniques under large scale computing environment. For an in-depth study of the flow physics and highly accurate design, several special overlapped structured blocks such as collar grid, tip-cap grid, and etc. which are commonly used in refined drag prediction are adopted to consider the applicability of the present design tools to practical problems. Various pre- and post-processing techniques for overset flow analysis and sensitivity analysis are devised or implemented to resolve overset mesh techniques into the design optimization problem based on Gradient Based Optimization Method (GBOM). In the pre-processing, the convergence characteristics of the flow solver and sensitivity analysis are improved by overlap optimization method. Moreover, a new post-processing method, Spline-Boundary Intersecting Grid (S-BIG) scheme, is proposed by considering the ratio of cell area for more refined prediction of aerodynamic coefficients and efficient evaluation of their sensitivities under parallel computing environment. With respect to the sensitivity analysis, discrete adjoint formulations for overset boundary conditions are derived by a full hand-differentiation. A smooth geometric modification on the overlapped surface boundaries and evaluation of grid sensitivities can be performed by mapping from planform coordinate to the surface meshes with Hicks-Henne function. Careful design works for the drag minimization problems of a transonic wing and a wing/body configuration are performed by using the newly-developed and -applied overset mesh techniques. The results from design applications demonstrate the capability of the present design approach successfully.