• The KSFM Journal of Fluid Machinery
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• v.10 no.2 s.41
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• pp.16-21
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• 2007

Potential advantages of using vapor injection in a two stage rotary compressor for a $CO_2$ heat pump water heater system were addressed in this paper by numerical simulation. Vapor separated from a flash tank in the middle of the expansion process can be used for injection into the second stage suction plenum of the compressor to improve the system performance. Vapor injection increases the intermediate pressure between the two stages, thus increasing the first stage compressor work and reducing that of the second stage. As a whole, however, the compressor input power increases due to injected mass flow rate for the second stage. Computer simulation showed that increment of the cooling capacity by vapor injection exceeded that of the compressor work, thus improving the system performance. COP improvement by vapor injection was calculated to be about 5-14% for normal operating conditions. With vapor injection, a maximum COP was found when the displacement volume of the second stage becomes 90-95% of that of the first stage of the compressor.

• Journal of Korean Foot and Ankle Society
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• v.26 no.2
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• pp.71-77
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• 2022

Purpose: This study sought to investigate the appropriate indications for intra-articular injection of hyaluronic acid in ankle osteoarthritis, its efficacy at each stage of osteoarthritis and to compare the efficacy related differences at each stage. Materials and Methods: A retrospective study was conducted from January 2016 to September 2019 on 43 patients (50 cases) diagnosed with ankle arthritis and given intra-articular injection of hyaluronic acid. Patients were classified according to the modified Takakura ankle osteoarthritis stages. Stage 2 comprised 24 cases; stage 3A, 15 cases; stage 3B, 8 cases; and stage 4, 3 cases. The clinical evaluation was carried out using the visual analogue scale (VAS), American Orthopaedic Foot and Ankle Society (AOFAS) score, and the Foot and Ankle Outcome Score (FAOS). The patients' satisfaction with the injection was evaluated at 1 year after injection. A radiographic evaluation was performed to gauge the progression of osteoarthritis before and after the injection. Results: The VAS, AOFAS score, and FAOS at 3 months and 1 year after injection showed statistically significant improvements compared to those before the injection. There was a significant difference in the VAS for each stage over time; however, this was not the case with the AOFAS score and the FAOS. A significant improvement of the VAS after injection was seen only in stage 3A when compared with the other stages. The overall satisfaction rate with the injection was 90%. There were no ankle osteoarthritic stage changes in the serial follow-up radiograph. Conclusion: Intra-articular injection of hyaluronic acid resulted in a significant clinical improvement up to 1 year after the injection. Therefore, the intra-articular injection of hyaluronic acid could be a treatment option for ankle osteoarthritis.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.66-73
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• 2004

In this study, combustion characteristics and various performances of a Diesel fuel DI-HCCI engine using 2-stage injection method were investigated. From these researches, application ability of 2-stage injection strategy to a DI-HCCI engine was confirmed and improvement methods of performances were considered. As the results, Using 2-stage injection method, without change of engine specifications and loss of IMEP, exhaust of NOx and Smoke emissions could be reduced to about 1/3 (at 1400rpm, IMEP 6bar) compared to conventional Diesel combustion.

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.3
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• pp.77-82
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• 2008

For heat pumps used in a cold region, it is very important to obtain appropriate heating capacity. Several studies using a variable speed compressor and an additional heater have been performed to enhance heating capacity at low ambient temperatures. However, for outdoor temperature conditions below $-15^{\circ}C$, it is still difficult to obtain enough heating capacity above the rated value. In recent studies, the application of gas injection technique into a two-stage heat pump yielded noticeable heating performance improvement at low temperature conditions. In this study, the heating performance of a two-stage gas injection heat pump with a rated capacity of 3.5 kW was measured and analyzed by varying refrigerant charge amount and EEV opening at the standard heating condition. The heating performance of the two-stage gas injection heat pump was compared with that of a two-stage non-injection heat pump. The heating capacity and COP of the two-stage gas injection heat pump were improved by 2-10% at the optimal charging condition over those of the two-stage non-injection heat pump.

• Journal of ILASS-Korea
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• v.17 no.2
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• pp.57-63
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• 2012

For reduction of CO, NOx and soot emission emitted by diesel diffusion combustion, the authors focused on injection actuator to improve fuel availability inside combustion chamber. In this study, it was investigated the internal dynamic characteristics of two-stage injection with diesel injectors with different driving type for the common rail direct injection by using the AMESim simulation code. The analysis parameter defined such as fuel pressure, injection hole's diameter and driven voltage. As the results, it was shown that the piezo-driven injector had a faster response and had better control capability than the solenoid-driven injector. It was found the piezo-driven injector can be utilized effectively as multiple injector than solenoid-driven injector.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.692-698
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• 2020

This paper examines the effects of a multi-stage pilot split injection strategy on combustion and exhaust emission factors in a single-cylinder diesel engine. One analysis noted that in the single-injection condition, the maximum in-cylinder pressure and rate of heat release were highest. The pilot injection quantity was evenly divided, showing a tendency to decrease as the number of injections increased. In another injection condition, when the multi-stage pilot split injection strategy was applied, IMEP, engine torque, and combustion increased. The COV_IMEP was greatest with the lowest combustion efficiency. The combustion ability was poor. In a single injection condition, the O₂ concentration in the exhaust gas was the lowest and the CO₂ was the highest. When the multi-stage split injection strategy was applied, the low temperature combustion process proceeded, and the oxidation rate of CO₂ decreased while the emission level increased. In a single injection condition in which a locally rich mixture was formed, the HC emission level showed the highest results. A 55.6% reduction of NOx emission occurred under a three-stage pilot injection condition while conducting a multi-stage pilot split injection strategy.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.3
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• pp.45-51
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• 2012

This work was investigated 2-stage injection strategy on combustion and emissions in a direct injection compression-ignition engine fueled with DME. Single cylinder engine was equipped with common rail. Injection pressure was 700bar, dSOI between the main injection and the pilot injection was varied. Diesel was used as compared fuel of DME in all cases. The results was shown that maximum pressure was higher than all cases and its amount of DME and diesel was similar. Regardless the pilot injection, the main fuel injection timing was same. The heat release rate of the main injection for diesel was high while that of pilot injection for DME was high. The THC was very low regardless of the fuel type and injection strategy. In the single injection, NOx was increased to retard of main injection timing regardless of the fuel type. NOx emissions was decreased with the retardation of the main injection timing regardless of the fuel type in the case of 2-stage injection strategy.

• The Journal of the Convergence on Culture Technology
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• v.9 no.5
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• pp.557-562
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• 2023

This study reviewed the use of soil injection materials using circulating resources as injection materials for the steel pipe multi-stage construction method. The tests performed were homogel time and homogel compressive strength. The steel pipe multi-stage construction method is an auxiliary construction method for tunnels, and the expression of initial strength after construction is an important factor. The better the strength development in the initial stage, the more it can be used as an injection material suitable for the multi-stage steel pipe construction method. As a result of laboratory test, it was found that the homogel time of the injection material using circulating resources required more time than the mixing ratio using cement as the injection material. In addition, it was found that the initial strength curing time satisfying 2MPa was required for more than 24 hours. Therefore, it was confirmed that the injection material using recycled resources required a longer initial curing time than cement of the same mixing ratio.

• Journal of Korean Foot and Ankle Society
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• v.15 no.1
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• pp.27-31
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• 2011

Purpose: This study evaluated the efficacy of an intra-articular injection of sodium hyaluronate in the treatment of early stage osteoarthritis of the ankle. Materials and Methods: Early stage ankle osteoarthritis (Takakura stage I and II) patients who received hyaluronic acid injection therapy were retrospectively reviewed. Patients underwent intra-articular injections of 2 mL of sodium hyaluronate for 3 consecutive weeks. Clinical evaluation and Visual Analogue Scale (VAS) scoring were performed at every three months after treatment. Results: Total 27 patients were involved and mean age was 55 year old (range 33 to 77 years). There were 13 male and 14 female patients. Mean follow up duration was 13 month and. Pre-intra-articular VAS score was $8.9{\pm}0.7$ and three month follow up score was $3.8{\pm}2.8$. VAS score of last follow up was $3.2{\pm}3.4$. The effect of hyaluronic acid continued about one year when analyzed the VAS score change of the patients followed for more than one year. Patients' satisfaction was "very satisfied" in nine, "satisfied" in 12, "fair" in one, and "not satisfied" in five patients. Overall satisfaction rate was 82%. There were no ankle osteoarthritis stage changes in serial follow up radiograph. Conclusion: Symptomatic relief of signs and symptoms of osteoarthritis of the ankle was achieved by injection of an intra-articular hyaluronate injection. Efficacy of Hyaluronate acid injection persisted more than 1 year in our study. Intra-articular hyaluronate injection to ankle osteoarthritis is safe and effective as knee joint and should be considered as a valid conservative treatment for ankle osteoarthritis.

• Journal of the Korean Ceramic Society
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• v.29 no.9
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• pp.681-688
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• 1992

Ultrafine Si3N4 and Si3N4+SiC mixed powders were synthesized through thermal plasma chemical vapor deposition(CVD) using a hybrid plasma, which was characterized by the supersposition of a radio-frequency plasma and arc jet. The reactant SiCl4 was injected into an arc jet and completely decomposed in a hybrid plasma, and the second reactant CH4 and/or NH3 mixed with H2 were injected into the tail flame through double stage ring slits. In the case of ultrafine Si3N4 powder synthesis, reaction efficiency increased significantly by double stage injection compared to single stage one, although crystallizing behaviors depended upon injection speed of reactive quenching gas (NH3+N2) and injection method. For the preparation of Si2N4+SiC mixed powders, N/C composition ratio could be controlled by regulating the injection speed of NH3 and/or CH4 reactant and H2 quenching gas mixtures as well as by adjusting the reaction space.