• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2022.06a
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• pp.1343-1345
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• 2022

본 논문에서는 다해상도 피라미드 피처 맵 압축 손상 보상 방법을 제안한다. 본 논문에서 제안하는 방법은 패킹된 C-레이어 피처 맵을 비디오 코덱으로 압축할 때, 저해상도 계층의 원본 피처 맵과 복원된 피처 맵 간의 차분 값을 구해 이를 고해상도 계층의 피처 맵에 더해줌으로써 부호화 과정에서 발생하는 오차를 보상하는 방법이다. 본 논문에서 제안하는 방법의 성능을 평가하기 위하여 OpenImageV6 데이터셋 중 1000 장에 대해 객체 검출 성능을 평가하였다. 본 논문에서 제안하는 피처 맵 압축 방법은 C-레이어 피처 맵 압축 방법 대비 bpp 와 mAP 의 BD-rate 관점에서 35.10%의 성능 향상을 보인다.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.5
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• pp.1-6
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• 2009

A development of a composite solid propellant is carried out for an application to gas generators as an energy source of rocket system. With HTPB as a propellant binder which has 80% of particle loading ratio, a favorable rheology, and moderate curing properties at the range of $-50^{\circ}{\sim}70^{\circ}C$, AN is selected as the first kind of oxidizer having the characteristics of a low flame temperature, minimal particle residual as well as nontoxic products. AP is the second oxidant for ballistic property control. A series of experiments for the improvement of physical properties were conducted and resulted in the propellant formulation having 30% of strain rate at 8 bar of max. stress.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1189-1196
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• 1988

Thermal entrance lengths of turbulent tube flow for viscoelastic polymer solutions are investigated experimentally in the recirculating flow system with tubes of inside diameters 8.5mm(L/D=710) and 10.3mm(L/D=1158), respectively. In the present system, the hydrodynamic and thermal boundary layers develop simultaneously from the beginning of the test section. To provide the boundary condition of constant heat flux at the wall, the test tubes are heated directly by electricity. The polymer solution used in the current study is 1000 wppm aqueous solution of polyacrylamide(Separan AP-273). The apparent viscosity of the polymer solutions circulating in the flow system are measured by the capillary tube viscometer at regular time intervals. Thermal entrance lengths vary due to the rate of degradation. The entrance lengths of degraded polymer solutions are about 500~600 times the diameter. However, the entrance lengths of fresh polymer solutions are greater than the lengths of the test tubes used in this study suggesting that thermal entrance lengths for viscoelastic polymer solutions are greater than 1100 tube times the diameters. Friction factor is almost insensitive to the degradation, but the heat transfer $j_{H}$-factor is affected seriously by degradation. Based on the present experimental data of fresh solutions a correlation for the heat transfer $j_{H}$-factor is presented.ted.

• Journal of Astronomy and Space Sciences
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• v.26 no.1
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• pp.9-24
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• 2009

We compare the relation among the annual distribution of sunspots: coronal mass ejections (CMEs) and geomagnetic storms and North-South asymmetry during solar cycle 23. For this purpose, we calculate correlation coefficients between (i) annual distribution and N-S asymmetry of CMEs - sunspots (ii) distribution of CMEs - occurrence number of geomagnetic storms (iii) distribution of sunspots - occurrence number of geomagnetic storms. We find that (i) the annual distribution of total CMEs has good correlation with distribution of annual average of sunspots but poor correlation with N-S asymmetry of sunspots, N-S asymmetry of CMEs has good correlation with N-S asymmetry of sunspots: (ii) total and N-S asymmetry of CMEs have poor correlation with occurrence number of geomagnetic storms, it's, however, well correlated with the classified groups of CMEs (Ap, Dst and an indices vs. fast CMEs($\upsilon$ > $1000kms^{-1}$), Dst index vs. Halo CMEs), and (iii) sunspot numbers and area are correlated with occurrence number of geomagnetic storms. We conclude that annual distribution of CMEs and sunspots have well correlated with geomagnetic storms, N-S asymmetry of CMEs and sunspots have poor correlated with the geomagnetic storms.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.4
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• pp.342-350
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• 1992

An experimental investigation of the stenosis effects on the pressure drop and flow change in the internal flow is presented. Stainless steel tubes of small diameter(3.175mm, 3.4mm) are used for the test section of the flow loop. Percent contraction ranges from 35% to 83% and the stenosis length ratio (L/d) is varied from 2.8 to 8. Water and aqueous glycerol solutions are used for Newtonian fluids and polymer solutions of Separan AP-273 (500 wppm, 1000 wppm) for non-Newtonian fluids. Pressure loss coefficients of non-Newtonian fluids decrease just as those of Newtonian fluids. The loss coefficients of Newtonian and non-Newtonian fluids increase as the percent contraction increases and the loss coefficients of non-Newtonian fluids are larger than those of Newtonian fluids for the same stenosed tube. The loss coefficient increases as the stenosis length ratio increases.

• Nuclear Engineering and Technology
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• v.51 no.7
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• pp.1842-1852
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• 2019

The AP1000 reactor coolant pump is a vertical shielded-mixed flow pump, is the most important coolant power supply and energy exchange equipment in nuclear reactor primary circuit system, whose steadystate and transient performance affect the safety of the whole nuclear island. Moreover, safety demonstration of reactor coolant pump is the most important step to judge whether it can be practiced, among which software simulation is the first step of theoretical verification. This paper mainly introduces the fluid-solid coupling simulation method applied to reactor coolant pump, studying the feasibility of simulation results based on workbench fluid-solid coupling technology. The study found that: for the unsteady calculations of the pure liquid media, the average head of the reactor coolant pump with bidirectional fluid-solid coupling decreases to a certain extent. And the coupling result is closer to the real experimental value. The large stress and deformation of rotor under different flow conditions are mainly distributed on impeller and idler, and the stress concentration mainly occurs at the junction of front cover plate and blade outlet. Among the factors that affect the dynamic stress change of rotor, the pressure load takes a dominant position.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2736-2747
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• 2022

The operations in the design lifecycle of a nuclear power plant targeted to be decommissioned lead to neutron activation. Operations in the decommissioning process include cutting, decontamination, disposal, and processing. Among these, cutting is done close to the target material, and thus workers are exposed to radiation. As there are only a few studies on pressurizers, there arises the need for further research to assess the radiation exposure dose. This study obtained the specifications of the AP1000 pressurizer of Westinghouse and the distribution of radionuclide inventory of a pressurizer in a pressurised water reactor for evaluation based on literature studies. A cutting scenario was created to develop an optimal method so that the cut pieces fill a radioactive solid waste drum with dimensions 0.571 m × 0.834 m. The estimated exposure dose, estimated using the tool VISIPLAN SW, in terms of the decontamination factor (DF) ranged from DF-0 to DF-100, indicating that DF-90 and DF-100 meet the ICRP recommendation on exposure dose 0.0057 mSv/h. At the end of the study, although flame cutting was considered the most efficient method in terms of cutting speed, laser cutting was the most reasonable one in terms of the financial aspects and secondary waste.

• Journal of the Korean Arthroscopy Society
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• v.10 no.2
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• pp.165-172
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• 2006

Purpose: The purpose of this study is to evaluate the effects of intratunnel fixation in the tibial side on the arthroscopic ACL reconstruction with quadruple hamstring tendon at the second look arthroscopy. Materials and Method: From Dec 1999 to May 2005, we arthroscopically reexamined 32 cases who had been done arthroscopic ACL reconstruction with quadruple hamstring tendons. Hamstring tendons of all cases were fixed at femoral side with RigidfixTM. At the tibial side hamstring tendons were fixed only Post-tie (Group I) or Post-tie combined with IntrafixTM (Group II). At the time of second look arthroscopy mean age of cases was 30 years and mean duration for second look arthroscopy was 21.3 months. We analyzed the results with IKDC score, KT-1000 arthrometer under anesthesia, Telos stress radiography, tibial tunnel widening on the radiography and second look arthroscopic findings. Results: Group II had more superior than group I at side to side differences with KT-1000 and Telos stress radiograph, IKDC score, but the differences were insignificant. At arthroscopic evaluation, Group ll also had more superior than group I at graft tension and graft appearance, graft synovialization, but the differences were insignificant. Tibial tunnel widening in the knee AP radiograph was 2.3 mm in Group I and 1.7 mm in Group II and the difference was significant. (P=0.042) Conclusions: Additional procedure of tibial intratunnel fixation in arthroscopic ACL reconstruction with autogenous hamstring tendon significantly prohibited from tibial tunnel widening but clinical results, radiologic joint stability, findings in second look arthroscopy were insignificantly different. We concluded that Post-tie itself induced satisfactory clinical results, joint stability and graft maturation and that tibial tunnel widening did not affect the results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.1
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• pp.37-48
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• 1990

The drag and heat transfer reduction phenomena and degradation effects of drag reducing polymer solutions which are known as the viscoelastic fluids are investigated experimentally for the turbulent circular tube flows. Two stainless steel tubes are used for the experimental flow loops. Aqueous solutions of Polyacrylamide Separan AP-273 with concentrations from 300 to 1000 wppm are used as working fluids. Flow loops are set up to measure the friction factors and heat transfer coefficients of test tubes in the once-through system and the recirculating flow system. Test tubes are heated by power supply directly to apply constant heat flux boundary conditions on the wall. Capillary tube viscometer and falling ball viscometer are used to measure the viscous characteristics of fluids and the characteristic relaxation time of a fluid is determined by the Powell-Eyring model. The order of magnidude of the thermal entrance length of a drag reducing polymer solution is close to the order of magnitude of the laminar entrance length of Newtonian fluids. Dimensionless heat transfer coefficients of the viscoelastic non-Newtonian fluids may be represented as a function of flow behavior index n and newly defined viscoelastic Graetz number. As degradation continues viscosity and the characteristic relaxation time of the testing fluids decrease and heat transfer coefficients increase. The characteristic relaxation time is used to define the Weissenberg number and variations of friction factors and heat transfer coefficients due to degradation are presented in terms of the Weissenberg number.

• Journal of The Korean Astronomical Society
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• v.28 no.2
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• pp.169-175
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• 1995

Deep V I CCD photometry of the Pegasus dwarf irregular galaxy shows that the tip of the red giant branch (RGB) is located at I = $21.15{\pm}0.10$ mag and (V - I) = $1.58{\pm}0.03$. Using the I magnitude of the tip of the RGB (TRGB), the distance modulus of the Pegasus galaxy is estimated to be $(m\;-\;M)_o\;=\;25.13{\pm}0.11$ mag (corresponding to a distance of d = $1060{\pm}50$ kpc). This result is in a good agreement with the recent distance estimate based on the TRGB method by Aparicio [1994, ApJ, 437, L27],$ (m\;-\;M)_o$ = 24.9 (d = 950 kpc). However, our distance estimate is much smaller than that based on the Cepheid variable candidates by Hoessel et al.[1990, AJ, 100, 1151], $(m\;-\;M)_o\;=\;26.22{\pm}0.20$ (d = $1750{\pm}160$ kpc) mag. The color-magnitude diagram illustrates that the Cepheid candidates used by Hoessel et al.are not located in the Cepheid instability strip, but in the upper part of the giant branch. This result shows that the Cepheid candidates studied by Hoessel et al.are probably not Cepheids, but other types of variable stars. Taking the average of our distance estimate and Aparicio's, the distance to the Pegasus galaxy is d= $1000{\pm}80$ kpc. Considering the distance and velocity of the Pegasus galaxy with respect to the center of the Local Group, we conclude that the Pegasus galaxy is probably a member of the Local Group.