• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.40-46
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• 2001

An experimental investigation is proceeded to study on the relationship between spark ignition characteristics and the performances of an S. I. engine. The ignition parameters examined in this study are the ignition energy and discharging duration. The combustion pressure and exhaust gas are measured during the experiment. From the measured data of cylinder pressure, the heat release rate, the mass fraction burned, and the COV of IMEP are calculated. The dwell time and the injection time are varied. A single cylinder engine and a 30kW dynamometer are employed. Four different kinds of ignition systems are assembled, and one commercial ignition system is adopted. The experimental results show that the ignition energy is increased as the dwell time extended until the ignition energy is saturated. The higher ignition energy is effective in achieving the laster burning velocity and less producing HC emission. However, when the amount of ignition energy is similar, while the discharge duration becomes longer, the burning velocity is reduced but the engine operation becomes stable in terms of the COV of IMEP.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.617-621
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• 2017

The performance characteristics of aluminized high explosive are considered by varying the aluminum(Al) concentration in a two-phase model. Since the time scales of the characteristic combustion process of high explosives and Al particles differ, the process of energy release behind the leading detonation wave front occurs over an extended period of time. Two cardinal observations are reported: a decrease in detonation velocity with an increase in Al concentration and a double front detonation (DFD) feature when anaerobic Al reaction occurs behind the front. In the current study, a series of confined rate sticks are considered for characterizing the performance of aluminized HMX with a maximum Al concentration of 50%. The simulated results are compared with the experimental data for 5%-25% concentrations.

• Textile Coloration and Finishing
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• v.32 no.3
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• pp.150-157
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• 2020

Hexachloro-cyclophosphazene(HCCP), a formaldehyde-free flame retardant (FR), was steam-cured with triethanol amine(TEA) to impart durable flame-retardancy to cotton fabrics. While the HCCP treatment alone showed very limited resistance to repeated laundering cycles, the addition of TEA substantially improved the laundering durability of the FR cotton up to twenty laundering cycles. The extended washing resistance was accomplished by the increased nucleophilic substitution of unreacted P-Cl groups in HCCP by the TEA resulting in the more densely crosslinked FR networks. With increasing molar ratio of TEA to the HCCP up to 2, the flame retarding effectivity and the synergistic effectiveness improved to 2.8 and 1.8 respectively. TGA and microscale combustion calorimetry verified the pyrolysis and combustion behaviors of the FR-cotton, which showed lower maximum pyrolysis and combustion temperatures together with substantially decreased peak pyrolysis and heat release rate, synergistically yielding larger amounts of carbonaceous chars. The formaldehyde-free HCCP and TEA can be a durable FR finishing agents for cotton fabrics acting through a solid-phase flame-retarding mechanism.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.465-471
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• 2006

Controlled auto-ignition(CAI) combustion, offers the potential to improve fuel economy and reduce emission simultaneously. In this study, CAI-combustion was achieved in a single cylinder gasoline DI engine with modified camshafts in order to restrict the gas exchange process. We investigated the effects of air-fuel ratio, residual EGR rate and injection timing such as early injection and late injection on the attainable CAI combustion region. The effect of injection timings on combustion characteristic such as start of combustion, combustion duration and heat release rate was also investigated. From the result early injection causes the mixture to ignite earlier and burn more quickly due to the exothermic reaction during the recompression and gives rise to good mixing of the fuel/air. On the other hand, late injection extended the operation region more than early injection but the emissions of HC and NOx were more or less increased than early injection.

• Journal of The Korean Dental Society of Anesthesiology
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• v.13 no.4
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• pp.167-178
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• 2013

Oxycodone is a semi-synthetic opioid synthesized from poppy-derived thebaine. It is a narcotic analgesic generally indicated for relief of moderate to severe pain. Although developed in an attempt to improve on the existing opioids, the adverse effects of oxycodone are those that are typically found in opioids. In recent years, the use of the opioid oxycodone has increased markedly and replacing morphine as the first line choice of opioid in several countries. There are formulations for oral immediate, oral extended release and intravenous use. In 2013, intravenous oxycodone was approved for marketing by Ministry of Food and Drug Safety (MFDS), with the indication of postoperative intravenous patient-controlled analgesia (IV PAC). Simulation study of oxycodone demonstrated that minimum effective analgesic concentration (MEAC) of oxycodone was most quickly reached with higher loading dose and IV PCA with background infusion, which may reduce the necessity of rescue analgesics during immediate postoperative period. Previous studies for postoperative pain management with intravenous oxycodone are limited in sample size, mostly less than 100 patients, which may not be large enough to assess safety of intravenous oxycodone. The effectiveness and tolerability of IV PCA with oxycodone should, therefore, be evaluated in large scale clinical trials in Korean populations.

• Structural Engineering and Mechanics
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• v.81 no.3
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• pp.267-280
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• 2022

Multiscale structure has attracted significant interest due to its high stiffness/strength to weight ratios and multifunctional performance. However, most of the existing concurrent topology optimization works are carried out under deterministic load conditions. Hence, this paper proposes a robust concurrent topology optimization method based on the bidirectional evolutionary structural optimization (BESO) method for the design of structures composed of periodic microstructures subjected to uncertain dynamic loads. The robust objective function is defined as the weighted sum of the mean and standard deviation of the module of dynamic structural compliance with constraints are imposed to both macro- and microscale structure volume fractions. The polynomial chaos expansion (PCE) method is used to quantify and propagate load uncertainty to evaluate the objective function. The effective properties of microstructure is evaluated by the numerical homogenization method. To release the computation burden, the decoupled sensitivity analysis method is proposed for microscale design variables. The proposed method is a non-intrusive method, and it can be conveniently extended to many topology optimization problems with other distributions. Several numerical examples are used to validate the effectiveness of the proposed robust concurrent topology optimization method.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.36.1-37
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• 2021

Six images of IRC+10216 taken by the Hubble Space Telescope at three epochs in 2001, 2011, and 2016 are compared in the rest frame of the central carbon star. An accurate astrometry has been achieved with the help of Gaia Data Release 2. The positions of the carbon star in the individual epochs are determined using its known proper motion, defining the rest frame of the star. In 2016, a local brightness peak with compact and red nature is detected at the stellar position. A comparison of the color maps between 2016 and 2011 epochs reveals that the reddest spot moved along with the star, suggesting a possibility of its being the dusty material surrounding the carbon star. Relatively red, ambient region is distributed in an Ω shape and well corresponds to the dusty disk previously suggested based on near-infrared polarization observations. In a larger scale, differential proper motion of multiple ring-like pattern in the rest frame of the star is used to derive the average expansion velocity of transverse wind components, resulting in ~12.5 km s-1 (d/123 pc), where d is the distance to IRC+10216. Three dimensional geometry is implied from its comparison with the line-of-sight wind velocity determined from half-widths of submillimeter emission line profiles of abundant molecules. Uneven temporal variations in brightness for different searchlight beams and anisotropic distribution of extended halo are revisited in the context of the stellar light illumination through a porous envelope with postulated longer-term variations for a period of 10 years.

• Tuberculosis and Respiratory Diseases
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• v.86 no.2
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• pp.94-101
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• 2023

A recent understanding of the dynamic continuous spectrum of Mycobacterium tuberculosis infection has led to the recognition of incipient tuberculosis, which refers to the latent infection state that has begun to progress to active tuberculosis. The importance of early detection of these individuals with a high-risk of progression to active tuberculosis is emphasized to efficiently implement targeted tuberculosis preventive therapy. However, the tuberculin skin test or interferon-γ release assay, which is currently used for the diagnosis of latent tuberculosis infection, does not aid in the prediction of the risk of progression to active tuberculosis. Thus, a novel test is urgently needed. Recently, simultaneous and systematic analysis of differentially expressed genes using a high-throughput platform has enabled the discovery of key genes that may serve potential biomarkers for the diagnosis or prognosis of diseases. This host transcriptional investigation has been extended to the field of tuberculosis, providing promising results. The present review focuses on recent progress and challenges in the field of blood transcriptional signatures to predict progression to active tuberculosis.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.873-879
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• 2024

A sodium-cooled fast reactor (SFR) core has a potential of prompt criticality due to a change of core material distribution during a severe accident, and the resultant energy release has been one of the safety issues of SFRs. In this study, the safety assessment of an unprotected loss-of-flow (ULOF) in a small SFR (SSFR) has been performed using the SIMMER-IV computer code, which couples the models of space- and time-dependent neutronics and multi-component, multi-field thermal hydraulics in three dimensions. The code, therefore, is applicable to the simulations of transient behaviors of extended disrupted core material motion and its reactivity effects during the transition phase (TP) of ULOF, including a potential of prompt-criticality power excursions driven by fuel compaction. Several conservative assumptions are used in the TP analysis by SIMMER-IV. It was found out that one of the important mechanisms that drives the reactivity-inserting fuel motion was sodium vapor pressure resulted from a fuel-coolant interaction (FCI), which itself was non-energetic local phenomenon. The uncertainties relating to FCI is also evaluated in much conservative way in the sensitivity analysis. From this study, the ULOF characteristics in an SSFR have been understood. Occurrence of recriticality events under conservative assumptions are plausible, but their energy releases are limited.

• Journal of the Korea Computer Graphics Society
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• v.30 no.3
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• pp.43-49
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• 2024

Hand tracking is currently one of the most promising technologies in XR with the release of extended reality (XR) devices, in which hand tracking is used as the main manipulation. Hand tracking offers advantages in terms of immersion and realism, and as a result, it is being employed in a range of fields, including education, business, and medical care. The archery movement requires using both hands at the same time, but requires sophistication to hit the target and is a movement that has cultural and sports significance in the past. This study aimed to implement this archery movement. Therefore, this paper used the XR Hands package provided by Unity to recognize hand movements, explored the underlying OpenXR, and finally implemented the archery movement and tested it in Meta Quest 2.