• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.75-82
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• 2021

Low-temperature combustion (LTC) strategies, such as HCCI (Homogeneous Charge Compression Ignition), PCCI (Premixed Charge Compression Ignition), and RCCI (Reactivity Controlled Compression Ignition), have been developed to effectively reduce NOx and PM while increasing the thermal efficiency of diesel engines. Through numerical analysis, this study examined the effects of the injection timing and two-stage injection ratio of diesel fuel, a highly reactive fuel, on the performance and exhaust gas of RCCI engines using gasoline as the low reactive fuel and diesel as the highly reactive fuel. In the case of two-stage injection, combustion slows down if the first injection timing is too advanced. The combustion temperature decreases, resulting in lower combustion performance and an increase in HC and CO. The injection timing of approximately -60°ATDC is considered the optimal injection timing considering the combustion performance, exhaust gas, and maximum pressure rise rate. When the second injection timing was changed during the two-stage injection, considering the combustion performance, exhaust gas, and the maximum pressure increase rate, it was judged to be optimal around -30°ATDC. In the case of two-stage injection, the optimal result was obtained when the first injection amount was set to approximately 60%. Finally, a two-stage injection rather than a single injection was considered more effective on the combustion performance and exhaust gas.

• Journal of Life Science
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• v.33 no.3
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• pp.268-276
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• 2023

This study was conducted to optimize the formulation conditions of the immediate-release layer of carvedilol in the development of a two-layer tablet formulation for carvedilol and ivabradine. Using a 2⁴+3 full-factorial design of experiments, excipients (microcrystalline cellulose, citric acid, and crospovidone) of the carvedilol immediate-release layer (wet granulation part) and process parameters for the tablet compression process (main compression) were optimized, and seven types of each dependent variable (assay, content uniformity, hardness, friability, disintegration, and dissolution [pH 1.2 and 6.8]) were evaluated using design expert software. The analysis of variance results confirmed that the main compression has a significant effect on hardness, friability, and disintegration time and that microcrystalline cellulose has a major effect on friability and dissolution. In addition, it was confirmed that citric acid has a significant effect on friability. Crospovidone affects friability and dissolution. According to the design space from the design of the experiment results, the optimized range is microcrystalline cellulose (~18.0-32.0 mg), citric acid (~0.5-12 mg), and main compression (~615-837 kgf). Consequently, this study confirmed the availability of manufacturing the carvedilol immediate-release layer in which all risk factors evaluated in the initial risk assessment are removed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.2
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• pp.671-686
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• 2020

Due to the long training time and high training cost of traditional surgical training methods, the emerging virtual surgical training method has gradually replaced it as the mainstream. However, the virtual surgical system suffers from poor authenticity and high computational cost problems. For overcoming the deficiency of these problems, we propose an optimized model for the local compression deformation of soft tissue. This model uses a simulated annealing algorithm to optimize the parameters of the soft tissue model to improve the authenticity of the simulation. Meanwhile, although the soft tissue deformation is divided into local deformation region and non-deformation region, our proposed model only needs to calculate and update the deformation region, which can improve the simulation real-time performance. Besides, we define a compensation strategy for the "superelastic" effect which often occurs with the mass-spring model. To verify the validity of the model, we carry out a compression simulation experiment of abdomen and human foot and compare it with other models. The experimental results indicate the proposed model is realistic and effective in soft tissue compression simulation, and it outperforms other models in accuracy and real-time performance.

• The Korean Journal of Pain
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• v.21 no.3
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• pp.197-201
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• 2008

Background: Kyphoplasty is a minimally invasive procedure that can stabilize osteoporotic and neoplastic vertebral fractures. We retrospectively evaluated the clinical outcomes of kyphoplasty for the treatment of vertebral compression fractures in cancer patients. Methods: We reviewed the clinical data of 27 cancer patients who were treated with kyphoplasty (55 vertebral bodies) between May 2003 and Feb 2008. The clinical parameters, using a visual analog 10 point scale (VAS) and the mobility scores, as well as consumption of analgesic, were evaluated preoperatively and at 1 week after kyphoplasty. Results: A total 55 cases of thoracic and lumbar kyphoplasties were performed without complications. The mean age of the patients was 66 years. All the patients experienced a significant improvement in their subjective pain and mobility immediately after the procedures. The pain scores (VAS), mobility scores and other functional evaluations using the Oswestry disability score and the SF-36 showed significant differences between the pre- and postoperational conditions. Conclusions: Kyphoplasty is an effective, minimally invasive procedure that can relieve the pain of patients with vertebral compression fractures and these fractures are the result of metastasis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.197-204
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• 2011

RCM is used to clarify the complex phenomena of engine combustion. In order to describe engine combustion, several significant experimental studies are considered. Prediction of the peak pressure is very important since it has a significant influence on engine combustion. In addition, peak-temperature variation can be calculated from the measured peak pressure by using the fundamental thermodynamic relation. When the RCM is in operation, heat transfer occurs through the cylinder wall. Because of this phenomenon, it is difficult to determine the peak pressure without employing the case by case experimental method. The goal of this study is to evaluate the peak pressure analytically. We conduct an experiment to confirm the relationship between the peak pressure and some parameters. Using the results of the peak pressure variation experiment, we develop a general equation that be used to calculate the peak pressure as a function of operation time and compression ratio.

• Steel and Composite Structures
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• v.35 no.1
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• pp.13-27
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• 2020

To investigate the stress-strain relation of PVC-FRP Confined Concrete (PFCC) column with RC ring beam joint subjected to eccentric compression, the experiment of 13 joint specimens, which were designed with principle of "strong joint and weak column", were presented. Several variable parameters, such as reinforcement ratio, width and height of ring beam, FRP strips spacing and eccentricity, were considered. The specimens were eventually damaged by the crushing of concrete, the fracture of PVC tube and several FRP strips. With the FRP strips spacing or eccentricity increased, the ultimate carrying capacity of specimens declined. The strain of FRP strips and axial strain of PVC tube decreased as FRP strips spacing decreased. The decrease of eccentricity would slow down the development of strain of FRP strips and axial strain of PVC tube. The slope of stress-strain curve of PFCC column decreased as FRP strips spacing or eccentricity increased. The ultimate strain of PFCC column reduced as FRP strips spacing increased, while the effect of eccentricity on the ultimate strain of PFCC was not distinct. Considering the influence of eccentricity on the stress-strain relation, a modified stress-strain model for conveniently predicting the weak PFCC column and strong RC ring beam joint under eccentric compression was proposed and it was in good agreement with the experimental data.

• Science of Emotion and Sensibility
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• v.8 no.4
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• pp.345-354
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• 2005

In this study, the mechanical properties and hand characteristics have been analyze4 according to fabric structural parameters such as the weft density and weave stricture of cotton fabric. KES-FB system was used to measure hand characteristics and mechanical properties of fabric. The weft density made an effect on bending and shear properties but not on tensile , compression, and surface properties. In case of wearing property, B/w, 2HG/G, 2HB/B, 2HB/W, $\sqrt[3]{B/W}$, $\sqrt{2HB/W}$, W/T, WC/W were affected tv the weft density. The crimp was highly correlated with the tightness, hand, wearing an4 mechanical properties, specially tensile linearity, bending, shear, and compression properties. The weft crimp influenced the bending, shear, compression resilience, surface roughness, hand, and wearing properties. The tightness has an effect on tile bending, shear, compression, surface friction, hand, and wearing properties.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.260-266
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• 2018

Cylindrical shells are often used in the construction of ship and land-based structures such as deck plating with a camber, side shell plating for fore and aft part pipes, as well as storage tanks. It has been believed that such curved shells can be modeled fundamentally as a part of the cylinder under axial compression. From the estimations made based on cylindrical models, it is known that in general, curvature increases the buckling strength of a curved shell when subjected to axial compression, and the same curvature is also expected to increase the overall strength. A series of elastic large deflection analyses were conducted in order to clarify the fundamentals observed in the buckling and post-buckling behaviour of circular cylinders under axial compression. In the present paper, an FE-series analysis has been performed based on the elastic large deflection behaviour, and the effect of parameters has been clarified. The ultimate strength behavior of the circular cylinder was found to be significantly influenced by both the initial deflection and the FE-modeling method.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1249-1254
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• 2008

Industrial low temperature waste heat exists sparse in surroundings but its amount is huge. However, large portion of waste heat is discarded due to its poor recovery quality and inferior application technologies. The heat pump system in this research is based on the hybrid combination of compression cycle and absorption cycle in order to recycle various kind of industrial waste heat effectively. The prime objective is to design a compression absorption hybrid heat pump system which can produce high temperature above the level of $90^{\circ}C$ and low temperature of $20^{\circ}C$ at the same time using waste heat water of $50^{\circ}C$. A mathematical simulation was carried out as a basis to design a prototype 3 RT class hybrid heat pump. From the simulation results, fundamental parameters to design the system were obtained.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.2
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• pp.105-113
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• 2017

Recently the direct injection diesel engine is the most efficient one available for road vehicles, so this fundamental advantage suggests the compression injection diesel engine are a wise choice for future development efforts. The compression ignition diesel engine, with its bigger compression ratios if compared to the SI engine, offers a higher thermodynamic efficiency, also additionally the diesel engine with its less pumping losses due to the throttled intake charge as in a SI engine has higher fuel economy. But the largest obstacle to the success of this engine is meeting emission standards for Nitric oxides and particulate matter while maintain fuel consumption advantage over currently available engines. Thus its use should be largely promoted, however, diesel engine emits more Nitric oxides and particulate matter than other competing one. There has been a trade-off between PM and NOx, so efforts to reduce NOx have increased PM and vice versa, but trap change this situation and better possibility emerge for treating NOx emission with engine related means, such as injection timing, equivalence ratio, charge composition, and engine speed. The common rail direct injection system is able to adjust the fuel injection timing in a compression ignition engine, so this electronically controlled injection system can reduce the formation of NOx gas without increase in soot. In this study it is designed and used the engine test bed which is installed with turbocharge and intercooler. In addition to equipped using CRDI by controlling injection timing with mapping modulator, it has been tested and analyzed the engine performance, combustion characteristics, and exhaust emission as operating parameters.