• Nuclear Engineering and Technology
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• v.56 no.7
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• pp.2458-2473
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• 2024

The turbulent flow in reactor pressure vessel (RPV) of pressurized water reactor (PWR) is important for the flow rate distribution at core inlet. Thus, it is vital to study the turbulent flow phenomena in RPV. However, the complicated fluid channel consisted of inner structures of RPV will block or refract the laser sheet of particle image velocimetry (PIV). In this work, the matched index of refraction (MIR) of sodium iodide (NaI) solution and acrylic was applied to support optical path for flow field measurements by PIV in the 1/10th scaled-down RPV model. The experimental results show detailed velocity field at different locations inside the scaled-down RPV model. Some interesting phenomena are obtained, including the non-negligible counterflow at the corner of nozzle edge, the high downward flowing stream in downcomer, large vortices above vortex suppression plate in lower plenum. And the intensity of counterflow and the strength of vortices increase as inlet flow rate increasing. Finally, the case of asymmetry flow was also studied. The turbulent flow has different pattern compared with the case of symmetrical inlet flow rate, which may affect the uniformity of flow distribution at the core inlet.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.349-362
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• 1999

To understand the role of protozoa in the early formation of microbial fouling community, the studies on the formation of microbial film, the succession of microbial fouling communities, and the grazing pressure on bacteria population in microbial film were carried out in the laboratory, Inchon outer port and Inchon inner harbour. Bacteria and heterotrophic flagellates formed primary microbial film on the aluminum surface within 6 hours and oligotrich ciliates were observed 2 cells $mm^{-2}$ on the same surface at 9 hours in Inchon inner harbour which had physically stagnant condition. The larvaes of Balanus albicostatus which were dominant meiobenthos in Inchon coastal area attached on the glass surface at the first day of experiment. Heterotrophic flagellates showed maximum abundance of 465 cells $mm^{-2}$ at the 13rd day and ciliates showed maximum abundance of 63 cells $mm^{-2}$ at the 11st day in the Inchon inner harbour. In the Inchon outer port which opens to the outer sea, the maximum abundance of protozoa occurred at early phase, but not so many. The dominant heterotrophic flagellates were Metrornonas simplex and Bodonids. Dominant ciliates were small tintinnids and oligotrich ciliate Strombidium sp., Large Strombidium (oligotrich ciliate) and sessile Acineta turberosa (suctorian ciliate) occurred after 10 days. The attached larvae of Balanus occurred as biofouling organism on the early surface and showed maximum abundance of 18 indiv. $cm^{-2}$ at 7th day. At that time, adult barnacles were observed on the surface and dead barnacles were observed after two days. Except barnacles, the larvaes of Anthozoa sp., Oysters (Crassostrea gigas) and Polychaeta were observed on the surface from 3rd day. 3 benthic copepods including Harpacticus sp., I isopod, 1 polychaeta and 1 gastropoda were observed as predators of the microbial film on the surface after 7 days when microbial film developed very well. Although the ingestion rates of protozoa on the bactctia of the rnicrobi31 film were relatively low, the average grazing rate of protozoa on bacteria was high of 0.058 $h^{-1}$. This implied that the grazing pressure of protozoa influences the mortality of bacteria populations on the microbial film. but protozoa cannot get enough energy from only bacteria on the microbial film.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.3
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• pp.215-221
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• 1976

In this study, noise arresting effect of the noise control room from the transmission of surrounding noise was tested when the packing noise control rooms were set up in the test room in which the prerecorded noise from an engine room was reradiated at the same level as the original pressure. The inner space of control room A is $3.389m^3(1.19\times1.19\times2.14m)$ having walls furnished with plywood board 9mm in thickness and noise control room door$(60\times45cm) $ and illumination lamp are placed. In case of the control room B, noise absorption board(10mm fiber board which holds the corntype concavity with diameter of 5mm, depth 5mm, space 15mm) is adhered to the internal ceiling and styrol foam boards(20mm) to the walls. The other struction is same as the control room A. Type C is the same as B except wool board(Glass Fiber, 33mm) on the walls. Type D is same as type A except that the thickness of wall is 12mm and wood pyramid type cone$(5\times5\times13cm)$ is adhered to the ceiling ana walls(Fig. 1). When the recorded noise and vibrated noise were controlled in various levels. The noise pressure which passed through the control rooms was measured by sound level meter(Bruel & Kjar 2205, measuring range 37-140dB). In order to calculate the absorption rate in the control rooms the noise pressure was measured at different distances when the recorded noise pressure was radiated. The followings are the results obtained from the experiment. 1. When the noise pressure of the test room was 60dB, transmission rate of type A was $69.7\%$ and increased $3.3\%$ per 10dB. At the same condition, the rate was $53.9\%$ and increased $4.5\%$ per 10dB in type D. Type D was the most effective in noise arresting of the four and the effect was D,C,B and A in order(Fig.2). 2. When the oscillator sound and vessels noise were radiated in 1,000Hz, at one meter distance to the type A and D, the oscillator sound pressure were 77dB and 73dB, while the vessels noise pressure were 73.3dB and 66.2dB respectivley(Fig.3). 3. Refering to the influence of the frequency to the lower oscillator sound(1,000Hz) pressure, both type C and D were almost same at 140cm but type C was 0.3dB lower than type D at 20cm distance(Fig.4).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.8
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• pp.991-998
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• 2013

The fuel injection pipe of a common rail system used in a clean diesel vehicle plays a role in supplying fuel from a rail to the injector of each cylinder connecting the engine under a repeated internal pressure. The fuel injection pressure is increased to over 200 MPa for satisfying EU emission standards and improving fuel efficiency, and a heading process and an autofrettage process are required for preventing folding defects and improving fatigue life. In this study, the flow stress and SN data of the material of the pipe are obtained through a tensile test and a fatigue test. The heading process for checking the folding defects of pipe ends is performed by using FEA. Furthermore, the optimal design of the autofrettage process for improving fatigue life considering not only the compressive residual stresses of the inner surface but also the tensile residual stresses of the outer surfaces of the pipe under the repeated internal pressure is performed by using FEA. To verify the process design, fatigue analysis for the autofrettaged pipe is performed.

• Journal of Acupuncture Research
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• v.26 no.6
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• pp.101-110
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• 2009

Objectives : We developed and proposed a guideline for safety and performance assessment of electric cupping apparatus(Class 2 medical device). Methods : We drafted the guideline for safety and performance assessment of electric cupping apparatus by referring the existing standards and guideline, based on online questionnaire for Korean medical doctors and measurement data from commercially available products. Physical dimension of cups and inner vacuum pressure were acquired for the measurement in order to achieve the purposes. Results : This guideline only can be applied to electric cupping apparatus for enhancing blood circulation by employing negative pressure generated by electricity. Seven items of appearance and label, operation test of pump, variation test of input electricity, vacuum level test, vacuum sustain test, cup-size dependent test, noise level test are suggested for evaluation subjects and methods required for electric cupping devices. Requirements for the design and development of electric cupping devices are suggested: vacuum level indicator, vacuum generation rate, pressure control, valve detachment stability, cup comparability, safety measure, surge protection, user friendliness, instruction for use (IFU). Conclusions : We proposed a guideline for safety and performance assessment of electric cupping apparatus to improve the quality of relating products and aid the commercialization of them, by aiming higher industrial competitiveness of the medical device sectors in Korea. Discussion with related institutes such as industry, academy and government is further required. Public hearings also need to be held prior to the establishment of a final guideline and standard.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.87-94
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• 2017

In the nuclear power plant, the steel or polymer liner plates are adopted to prohibit the inner concrete surface from contacting with gas or liquid materials. If there is an accident, the plate may be damaged, and, in this case, concrete shall have the final responsibility to safety requirements. In this paper, an experimental research was carried out to investigate the effects of construction joint and wet and loading conditions on the permeability of concrete. The test results showed that, under a construction joint in the wet condition, leakage of gas pressure has been started from $1kg/cm^2$. However, when there are no construction joints, it is initiated from $2kg/cm^2$. In addition, under the air dried and unloading condition, regardless of with or without the presence of the construction joint, since the gas passage that exist in concrete is constant, leakage has a constant tendency to increase. Finally, under the loading condition, as described in Reference 1, since leakage is inversely proportional to the thickness of the wall, and, considering the wall thickness of the actual plant, it is found that there will not be no problem in the sealing of the gas.

• Applied Chemistry for Engineering
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• v.19 no.1
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• pp.80-85
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• 2008

Catalytic filter is capable of performing shallow bed dust filtration plus a catalytic reaction, promoted by a catalyst deposited in its inner structure. Such a feature may allow potential cost and space reduction in several environmental applications. Dust filtration and halogenated volatile organic compound (1,2-dichlorobenzene) destruction were carried out in a lab-scale reactor. $WO_3-V_2O_5/TiO_2$ supplied by MaGreen, which showed high catalytic acitivity at low temperature, was used as a catalyst. P-84 that can be operated under $250^{\circ}C$ was used as a felt. The catalytic activity and filtration efficiency of catalytic filters were investigated under the operating conditions, including temperature, face velocity, and dust concentration. The catalytic activity of catalytic filter increased with increasing temperature and the amount of catalyst loaded. The test results showed that the filtration efficiency was primarily affected by the face velocity. Pressure drop variations as a function of time were investigated for a variety of conditions. In case of virgin filter, a dramatic decrease in the pulse interval and a slightly increase in the base line pressure drop were observed. A relatively slow pressure drop build-up was recorded for the catalytic filter due to smooth and slippery surface characteristics of nanofiber. The catalytic filter indicated that high filtration efficiency over 99.98% and high catalytic activity over 90% at 1 m/min and $210^{\circ}C$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.566-573
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• 2004

A variable optical attenuator with a bending-sensitive fiber (BSF) that can be used in optical networks is developed. The proposed BSF consists of inner core, outer core, center dip and cladding. The proposed BSF is also very sensitive to mechanical perturbation, such as bending and pressure, making the light propagating in the BSF easily controlled and attenuated. The fabricated fiber-type variable optical attenuator using the proposed BSF (VOAFB) consisted of the BSF in a rectangular rubber ring with a fixed bend radius (BR) in a steady state. The variable optical attenuator using the proposed BSF (VOAFB) was able to attenuate the optical power by more than about -38㏈ with the gradient -88.4［㏈$.$$cm^{-1}$ /］ at (1540∼1560nm) based m adjusting the mechanical pressure applied to the upper surface of the rectangular rubber ring with the bent BSF. According to the experimental results when using the proposed VOAFB, the optical power was easily controlled by adjusting mechanical pressure and produced an insertion loss of 0.68㏈, polarization loss of 0.5㏈, and return loss of less than -60㏈.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.18-23
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• 2003

Composite powder of$B_4C-A1_2O_3$was prepared from a mixed powder of$B_2O_3/A1/C$by SHS under argon pressure instead of using a chemical furnace. A mixture of$B_2O_3,$Al and C powder (equivalent amounts to the reaction,$2B_2O_3+4A1+C=B_4C+2A1_2O_3)$was ball milled for 2 h. The mixed powder was placed in a SHS reactor and filled with 10 atm of argon gas and ignited. The inner and outer products were the same by XRD analysis. It was consisted of a composite powder of$B_4C-A1_2O_3$without $AlB_{12}/C_2$which was always produced using a chemical furnace. The composite powder was about$60~100{mu}m$size which was composed of crystalline particles of about 0.3~l${mu}m$size. But when 15 atm of argon was employed, partial sintering took place to give rise hard composite powder of$15~25{mu}m$$B_4C$with $0.1~0.2{mu}m$$A1_2O_3.$

• The Journal of Engineering Geology
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• v.24 no.1
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• pp.23-38
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• 2014

The composition of carbonate sands from a sabkha at Ruwais in the UAE differs from that of silica sand, and these sands are crushed easily under low compression pressures. Accordingly, particle crushing of carbonate sand occurs under high pressure, which results in additional settlement and reduces the shear strength. In this study, consolidation and triaxial tests were conducted to analyze the characteristics of carbonate sands following particle crushing. The unusual shear strength graphs of the carbonate sands result from the degree of particle pre-crushing. For the range at p' > p in the p (p')-q diagram, negative (-) excess porewater pressures occur if the axial pressure causes particle crushing that induces exposure of the inner voids. In addition, the q value decreased after particle crushing. In conclusion, the unusual characteristics of the carbonate sands were induced by particle crushing. The triaxial tests revealed that the degree of particle pre-crushing influenced the excess porewater pressure.