• 한국분무공학회지
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• 제6권1호
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• pp.25-34
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• 2001

Several efforts to meet the exhaust gas regulation have been undertaken by many researchers in recent years. Main researches are on development of design techniques of intake port and combustion chamber, atomisation of fuel and precise control of air-fuel ratio, post-treatment of exhaust gas and so on. Engine technology is changed from PFI to GDI to correspond with exhaust gas regulation. GDI technique makes it possible to preserve lean air-fuel ratio and control accurate air-fuel ratio. Nevertheless, It is not cleared that information of spray characteristics and atomization process are very dependent on fluctuation of pressure and change of temperature in intake stroke. In this study, a constant volume combustion chamber is manufactured to investigate various fluctuations of in-cylinder pressure for injection duration. It is taken photographs of injection process of conventional GDI injector using PMAS. Then, it was verified experimently that ambient conditions as temperature and pressure of combustion chamber have effects on process of spray growth and atomization of fuel.

• 한국생산제조학회지
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• 제20권1호
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• pp.34-39
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• 2011

Temperature control of a rubber injection mold is important for the dimensional accuracy of product. The main objective of this paper is to optimize the arrangement of heaters by FEM and optimal design method. Firstly, 3-dimensional transient heat transfer analysis was carried out for a square specimen mold. Results of FE analysis are a good agreement with the experimental results, showing about 1.22~7.22% error in temperature distribution. Secondly, we suggested the optimal method about an arrangement of heaters of rubber injection mold by using the optimal design technique. Distances between heater's center and the contact surface of mold, distances between heater's center and symmetric surface were considered as design variables. And the variances between the temperatures of cavity surfaces and their average temperature were used as the objective functions. Applying the optimal solution, the temperature variation was improved about 52.9~88.1 % compared to the existing mold. As a result of sensitivity analysis for design variables, design variables parallel to the direction of the split plane in mold affect the largest on the surface temperature variation in mold cavity.

• Nuclear Engineering and Technology
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• 제44권7호
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• pp.709-718
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• 2012

The pressurized water reactor APR1400 adopts DVI (Direct Vessel Injection) for the emergency cooling water in the upper downcomer annulus. The International Standard Problem number 50 (ISP-50) was launched with the aim to investigate thermal hydraulic phenomena during a 50% DVI line break scenario with best estimate codes making use of the experimental data available from the ATLAS facility located at KAERI. The present work describes the calculation results obtained for the ISP-50 using the RELAP5/MOD3.3 system code. The work aims at validation and assessment of the code to reproduce the observed phenomena and investigate about its limitations to predict complicated mixing phenomena between the subcooled emergency cooling water and the two-phase flow in the downcomer. The obtained results show that the overall trends of the main test variables are well reproduced by the calculations. In particular, the pressure in the primary system show excellent agreement with the experiment. The loop seal clearance phenomenon was observed in the calculation and it was found to have an important influence on the transient progression. Moreover, the collapsed water levels in the core are accurately reproduced in the simulations. However, the drop in the downcomer level before the activation of the DVI from safety injection tanks was underestimated due to multi-dimensional phenomena in the downcomer that are not properly captured by one-dimensional simulations.

• Fisheries and Aquatic Sciences
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• 제18권2호
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• pp.229-233
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• 2015

We developed a new softening technology applicable to the main body of the jumbo squid Dosidicus gigas; this will aid in squid consumption by elderly individuals and those who have masticatory and dysphagia problems. Protease solutions were injected into jumbo squid and hardness was measured using a texture analyzer. Seven enzymes were tested. Jumbo squid became progressively softer during bromelain and collupulin treatment; the hardness attained $5.6{\times}10^3N/m^2$ at bromelain concentrations of 1.00% (w/v) and $6.7{\times}10^3N/m^2$ at collupullin concentrations of 1.00% (w/v). The extents of tissue softening after bromelain and collupulin injection to 0.1%, 0.25%, 0.50%, and 1.00% (all w/v) were evaluated; the squid retained its shape after steaming for 10 min at $100^{\circ}C$ to inactivate the enzymes. Thus, the results of this research indicate that enzyme injection softens the texture of jumbo squid.

• 천문학회보
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• 제36권1호
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• pp.36.1-36.1
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• 2011

It is generally believed that eruptive phenomena in the solar atmosphere such as solar flares and coronal mass ejections (CMEs) occur in the solar active regions with complex magnetic structures. Magnetic helicity has been recognized as a useful parameter to measure the complexity such as twists, kinks, and inter-linkages of magnetic field lines. The objective of this study is to understand a long-term (a few days) variation of magnetic helicity in active regions and its relationship with the energy buildup and instability leading to flares and CMEs. Statistical studies of flare productivity and magnetic helicity injection in about 400 active regions were carried out. The temporal variation of magnetic helicity injected through the photosphere of active regions was also examined related to 46 CMEs. The main findings in this study are as follows: (1) the study of magnetic helicity for active regions producing major flares and CMEs indicates that there is always a significant helicity injection through the active-region photosphere over a long period of 0.5 - a few days before the flares and CMEs; (2) for the 30 CMEs under investigation, it is found that there is a fairly good correlation (linear correlation coefficient of 0.71) between the average helicity injection in the CME-productive active regions and the CME speed. Beside the scientific contribution, a major impact of this study is the observational discovery of a characteristic variation pattern of magnetic helicity injection in flare/CME-productive active regions which can be used for the improvement of solar eruption forecasting.

• International Journal of Automotive Technology
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• 제8권5호
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• pp.543-553
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• 2007

It is becoming increasingly difficult for engines using conventional fuels and combustion techniques to meet stringent emission norms. The homogeneous charge compression ignition(HCCI) concept is being evaluated on account of its potential to control both smoke and NOx emissions. However, HCCI engines face problems of combustion control. In this work, a single cylinder water-cooled diesel engine was operated in the HCCI mode. Diesel was injected during the suction stroke($0^{\circ}$ to $20^{\circ}$ degrees aTDC) using a special injection system in order to prepare a nearly homogeneous charge. The engine was able to develop a BMEP(brake mean effective pressure) in the range of 2.15 to 4.32 bar. Extremely low levels of NOx emissions were observed. Though the engine operation was steady, poor brake thermal efficiency(30% lower) and high HC, CO and smoke were problems. The heat release showed two distinct portions: cool flame followed by the main heat release. The low heat release rates were found to result in poor brake thermal efficiency at light loads. At high brake power outputs, improper combustion phasing was the problem. Fuel deposited on the walls was responsible for increased HC and smoke emissions. On the whole, proper combustion phasing and a need for a well- matched injection system were identified as the important needs.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.622-627
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• 2008

Experiment of active noise control on supersonic jet noise was conducted by use of microjet injection. The microjets were injected to the shear layer of the main jet through 22 small holes at the lip of a rectangular nozzle. Based on the measurement of farfield sound pressure, it was found that the jet noise was effectively reduced by several dB(in some cases up to 10 dB). The power levels of all measurement points were also reduced by use of microjet injection. The microjet affected not only the broadband noise but also the screech tone noise. The sound pressure level, the frequency of the screech tone, and the structure of the jet could be changed by the microjet. Flow visualization with schlieren technique was also made to observe the effect of microjet on the flow field.

• Clinical Pain
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• 제19권1호
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• pp.49-53
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• 2020

Piriformis muscle syndrome is a condition that causes direct muscle pain around piriformis muscle or sciatica from irritated sciatic nerve and the diagnosis remains debatable. The main treatment is symptomatic relief from conservative therapy such as medication and piriformis stretching exercise, and various therapeutic injections including local anesthetic, corticosteroid, botulinum toxin can be considered for diagnostic and therapeutic purposes. In this case, a 54-year-old male who had sciatica and gait disturbance showed piriformis muscle hypertrophy in the pelvis MRI. From imaging studies, electrodiagnostic study and physical examination, he was diagnosed with piriformis muscle syndrome. He underwent trigger point injection and botulinum toxin injection into the piriformis muscle, and pain and gait disturbance significantly improved. This case reports a case of piriformis muscle syndrome with clinical symptom of gait disturbance, which was improved by botulinum toxin injection.

• Nuclear Engineering and Technology
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• 제55권1호
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• pp.248-253
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• 2023

Directly, it is not possible to measure the absorbed dose of radiopharmaceuticals in the organs of the human body. Therefore, simulation methods are utilized to estimate the dose in distinct organs. In this study, individual organs were separately considered as the source organ or target organ to calculate the mean absorption dose, which SAF and S factors were then calculated according to the target uptake via MIRD method. Here, ^99mTc activity distribution within the target was analyzed using the definition and simulation of ideal organs by summing the fraction of cumulative activities of the heart as source organ. Thus, GATE code was utilized to simulate the Zubal humanoid phantom. To validate the outcomes in comparison to the similar results reported, the accumulation of activity in the main organs of the body was calculated at the moment of injection and cardiac rest condition after 60 min of injection. The results showed the highest dose absorbed into pancreas was about 21%, then gallbladder 18%, kidney 16%, spleen 15%, heart 8%, liver 8%, thyroid 7%, lungs 5% and brain 2%, respectively, after 1 h of injection. This distinct simulation model may also be used for different periods after injection and modifying the prescribed dose.

• 한국정밀공학회지
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• 제14권11호
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• pp.58-68
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• 1997

The residual stresses in injection-molded plastic parts can be divided into two, i.e., the flow-induced residual stress produced in flowing stage and the thermally-induced residual stress produced in cooling stage. Especially, the main source for the defect in the final parts, such as warpage, is known to be the thermally-induced stresses. For the freely quenched samples the structures of residual stresses and bire-fringence have been investigated by many researchers extensively. However, the boundary condition for free quenching was found to be improper to study actual injection molding process. In the present study a datailed structure of the residual stresses and birefringence produced under constrained quenching has been investigated experimentally. In constrained quenched samples a similar pattern but much less stress values than that for the freely quenched samples has been found in the case of the thickness of 1.0 mm. Howvere, in the case of the thickness of 4.0mm, totally different stress profile has been found experimentally. Suprisingly uniform birefringence throughout whole thickness has been found for all the cases of constrained quenching. Finally, to explain the mechanism to produce the final residual stresses and bire-fringence some preliminary numerical results including free volume theory have been introduced briefly.