• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.12 s.255
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• pp.1203-1210
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• 2006

The filmwise condensation heat transfer coefficients of R-134a on the horizontal copper and stainless steel tubes were measured and analyzed. The outside diameter of the tubes was 15.88 mm, and the tube thickness ranged from 0.89 to 1.65 mm. The polished stainless steel tube had an RMS surface roughness($R_q$) of 0.37 $\mu$m, and commercial stainless steel tubes had an surface roughness($R_q$) of 1.855 $\mu$m. The tests were conducted at the saturation temperatures of 20 and $30^{\circ}C$, and the liquid wall subcoolings from 0.4 to $2.1^{\circ}C$. The measured condensation heat transfer coefficients were significantly lower than the predicted data by the Nusselt analysis. This trend in the stainless steel tube was explained by the effects of thermal resistance of tube material and surface roughness. Based on the experimental data with respect to wall thickness and surface roughness, it was suggested that the existing correlation on external condensation should be modified by considering material and surface roughness factors. The revised correlation was developed by introducing the effects of wall thickness and surface roughness into the Nusselt equation. The average deviation of the revised correlation was 13.0 %.

• KIEAE Journal
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• v.3 no.2
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• pp.37-44
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• 2003

The aim of this study was to analyze the thermal performance through Test-Cell of TI-wall in domestic climate. This study was carried out as follows: 1) The TI-wall was studied for ability to reduce heat loss through the building envelope and analyzed to TIM properties. 2) Test models of TI-wall were designed through the investigation of previous paper and work, measured for winter and spring, and the thermal effects were analyzed. The type of the TIM used in test model is small-celled(diameter 4mm and thickness 50mm) capillary and cement brick(density $1500kg/m^3$) was used by thermal mass. 3) Test-cell of TI-wall was calibrated from measured data and the dynamic simulation program ESP-r 9.0. In these simulations, the measured climate conditions of TaeJon were used as outdoor conditions, and the simulation model of Test-cell was developed. 4) The sensitivity analysis is executed in various aspects with standard weather files and ESP-r 9.0, and then most suitable system of TI-wall are predicted. Finally, The suitable system of TI-wall was analysed according to sizes of air gap, kinds, thickness, and the surface absorption of therm wall. The result is following. In TI-wall, Concrete is better than cement brick, at that time the surface absorption is 95%, and the most efficient thickness is 250mm. As smaller of a air gap, as reducer of convection heat loss, it is efficient for heating energy. However, ensuring of a air gap at least more than 50mm is desirable for natural ventilation in Summer.

• Journal of the Korean Institute of Gas
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• v.21 no.1
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• pp.18-26
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• 2017

This work proposes an alternative pipe wall-thinning inspection method based on change of eigenfrequencies of shell vibration modes in wall-thinned pipes. It takes much time to detect wall-thinning of pipes using ultrasonic thickness gauge and only a limited number of pipes are under regular inspection. In a pipe with locally decreased thickness, stiffness varies along circumferential direction and natural frequencies of shell vibration modes of the pipe change or frequencies of same modes bifurcate into two different values. Therefore, one can monitor pipe wall-thinning by measuring change of natural frequencies or estimate wall-thinning shape qualitatively. The feasibility of the proposed method was studied by FE vibration analysis for wall-thinned pipes. Modal testing was also carried out for the pipes with artificial wall-thinned section to verify the working performance of the suggested technique.

• Journal of Radiation Protection and Research
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• v.26 no.3
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• pp.299-303
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• 2001

Using ultrasound techniques, the Korea Atomic Energy Research Institute has measured chest wall thicknesses of a group of male workers at the Korea Atomic Energy Research Institute. A site-specific biometric equation has been developed for these workers. Chest wall thickness is an important modifier on lung counting efficiency. These data have been put into the perspective of the ICRP recommended dose limits for occupationally exposed workers: 100 mSv in a 5-year period with a maximum of 50 mSv in anyone year. For measured chest wall thicknesses of 1.9 cm to 4.1 cm and a 30 min counting time, the achievable MDAs for natural uranium in the KAERI lung counter vary from 5.75 mg to 11.28 mg. These values are close to, or even exceed, the predicted amounts of natural uranium that will remain in the lung (absorption type M and S) after an intake equal to the Annual Limit on Intake corresponding to a committed dose of 20 mSv. This paper shows that the KAERI lung counter probably cannot detect an intake of Type S natural uranium in a worker with a chest wall thickness equal to the average value (2.7 cm) under routine counting conditions.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.1
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• pp.46-51
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• 1999

The most important effect of refining is believed as the internal fibrillation. The internal fibrillation is the separation of the fiber wall into several lamellae. The internal fibrillation results in fiber swelling as water penetrates the fiber wall. The increase in paper strength as a result of refining was due to delamination which made the fiber more flexible. Pulp fibers are refined to 20, 40, and 70$^{\circ}$SR freeness at Valley beater. Changes of Physical paper properties are analyzed depending on fiber wall thickness and fiber's collapse index at 2.5 and 5.6kg$_f$ refining load. At same $^[\circ}$SR freeness with 2.5kg$_f$ refining load, fiber wall thickness is increased further than at high 5.6kg$_f$ refining load. With higher fiber wall thickness by lower intensity refining load, higher internal fibrillation, flexibility, collapsability of fibers are achieved. Those effects improve WRV, tensile strength, and burst strength. Tear strength shows opposite trend to tensile and burst strength as usual.

• Journal of Magnetics
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• v.15 no.4
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• pp.204-208
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• 2010

Local wall thinning in pipelines affects the structural integrity of industries like nuclear power plants (NPPs). In the present study, a pulsed eddy current (PEC) differential probe with two excitation coils and two Hall-sensors was fabricated to measure the wall thinning in insulated pipelines. A stainless steel test sample was prepared with a thickness that varied from 1 mm to 5 mm and was laminated by plastic insulation to simulate the pipelines in NPPs. The excitation coils in the probe were driven by a rectangular current pulse, the difference of signals from two Hall-sensors was measured as the resultant PEC signal. The peak value of the detected signal is used to describe the wall thinning. The peak value increased as the thickness of the test sample increased. The results were measured at different insulation thicknesses on the sample. Results show that the differential PEC probe has the potential to detect wall thinning in an insulated NPP pipelines.

• Journal of the Korea Society for Simulation
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• v.14 no.2
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• pp.35-43
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• 2005

Feedwater heaters of many nuclear power plants have recently experienced wall thinning damage, which will increase as operating time progresses. As it is judged that the wall thinning damages have generated due to local fluid behavior around the impingement baffle installed in downstream of the high pressure turbine extraction steam line to avoid colliding directly with the tubes, numerical analyses using PHOENICS code were performed for two models with original clogged impingement baffle and modified multi-hole impingement baffle. To identify the relation between wall thinning and fluid behavior, the local velocity components in x-, y-, and z-directions based on the numerical analysis for the model with the clogged impingement baffle were compared with the wall thickness data by ultrasonic test. From the comparison of the numerical analysis results and the wall thickness data, the local velocity component only in the y-direction, and not in the x- and z-direction, was analogous to the wall thinning configuration. From the result of the numerical analysis for the modified impingement baffle to mitigate the shell wall thinning, it was identified that the shell wall thinning may be controlled by the reduction of the local velocity in the y-direction.

• Journal of Chest Surgery
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• v.32 no.10
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• pp.883-890
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• 1999

Long term patency of arterial graft has been better than venous graft and redo coronary artery bypass grafting has been increasing, therefore, there has been an increasing need for alternative arterial grafts except internal thoracic artery(ITA). Material and Method: Right gastroepiploic arteries(RGEA) were harvested from 100 patients who had received gastrectomy for gastric cancer or ulcer. ITAs were obtained from 10 patients undergoing coronary artery bypass grafting. The length of RGEA was measured from the pyloric ring. Items of the morphometric and histologic study at the pyloric ring and sites of the 10cm and 20cm RGEA from the pyloric ring were luminal diameter, intimal thickness, medial thickness, wall thickness, degree of intimal hyperplasia, intimal thickness, medial thickness, wall thickness, degree of intimal hyperplasia, intimal thickness index, medial thickness index, and the number of discontinuities of the internal elastic lamina. Similar items were applied to the proximal site of ITAs. Result: The length of RGEA was 23${\pm}$2.7cm(range 17∼31cm). Comparing the 20cm RGEA with ITA, intimal thickness, medial thickness, wall thickness, and degree of intimal hyperplasia did not show any difference(p>0.05). However, 20cm RGEA was greater than ITA at the luminal diameter, intimal thickness index, and the number thickness and wall thickness in each site of the RGEA(pyloric ring, 10cm, 20cm) decreased from the pyloric ring to the distal sites(p<0.05). The degree of intimal hyperplasia and the number of discontinuities of the internal elastic lamina did not show any difference between the pyloric ring and 10cm, however, those of 20cm were smaller than these sites(p<0.05). RGEA had more number of discontinuities of the internal elastic lamina and rich smooth muscle cells in the media than ITA. Conclusion: The length and diameter of RGEA is good enough to reach most of the coronary arteries. Moreover, long term patency of RGEA may be improved, if anastomosed in the distal site.

• Steel and Composite Structures
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• v.21 no.2
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• pp.323-342
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• 2016

To study the effect of collar-plate reinforcement on the static strength of tubular T-joints under axial loading, fundamental research work is carried out from both experimental test and finite element (FE) simulation. Through experimental tests on 7 collar-plate reinforced and 7 corresponding un-reinforced tubular T-joints under axial loading, the reinforcing efficiency is investigated. Thereafter, the static strengths of the above 14 models are analyzed by using FE method, and it is found that the numerical results agree reasonably well with the experimental data to prove the accuracy of the presented FE model. Additionally, a parametric study is conducted to analyze the effect of some geometrical parameters, i.e., the brace-to-chord diameter ratio ${\beta}$, the chord diameter-to-chord wall thickness ratio $2{\gamma}$, collar-plate thickness to chord wall thickness ratio ${\tau}_c$, and collar-plate length to brace diameter ratio $l_c/d_1$, on the static strength of a tubular T-joint. The parametric study shows that the static strength can be greatly improved by increasing the collar-plate thickness to chord wall thickness ratio ${\tau}_c$ and the collar-plate length to brace diameter ratio $l_c/d_1$. Based on the numerical results, parametric equations are obtained from curving fitting technique to estimate the static strength of a tubular T-joint with collar-plate reinforcement under axial loading, and the accuracy of these equations is also evaluated from error analysis.

• The Journal of Korean Physical Therapy
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• v.22 no.6
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• pp.7-12
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• 2010

Purpose: This study investigated changes in the thickness of the transversus abdominis (TrA), internal abdominal oblique (IO), and external abdominal oblique (EO) muscles between crook lying and wall support standing positions during abdominal hollowing (AH), using ultrasound imaging. Methods: Experiments were conducted on 20 healthy male adults (mean age=$22.45{\pm}4.08$ years) who voluntarily agreed to participate in the experiments. The changes in the thickness of the subjects' abdominal muscles were measured during AH in crook lying and wall support standing positions. Results: The difference in the thickness of TrA between the two positions during AH was statistically significant, but the differences in the thicknesses of IO and EO were not significant. Conclusion: Activity of the TrA, which is a deep muscle, was stimulated in the standing position, which is, therefore, more functional than the crook position, but the activities of IO and EO muscles did not decrease. Therefore, various methods to induce the activity of TrA while decreasing the activities of IO and EO, in the functional standing position that can stimulate deep muscles, need to be designed.