• Journal of the Korean Chemical Society
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• v.64 no.6
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• pp.327-333
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• 2020

Performance of a portable GC that can be utilized for the real time determination of volatile organic compounds in air was evaluated. It employs purified/compressed ambient air as the carrier gas eliminating the need for high pressure gas tanks. The compact system with dimensions of 35 × 26 × 15 ㎤ and weight of 5 kg is powered by either a 24 V DC external adapter or battery pack. Chromatograms of the mixture sample including benzene, toluene, ethylbenzene, and oxylene at concentrations of 1 ppmv and 20 ppmv represent a good reproducibility: 3.79% and 0.48% relative standard deviations (RSDs) for peak area variations; 0.40% and 0.08% RSDs for retention times. The method detection limit was 0.09 ppmv. A 30 m long, 0.28 mm I.D. column operated at an optimal condition yielded a peak capacity of 61 with good resolution for a 10 min isothermal analysis. The relative standard deviations (RSD) of the peak area variations and retention times during consecutive measurements over 27 h were less than 2.4%RSD and 0.5%RSD, respectively. Thus, this instrument makes it suitable for continuous and field analysis of low-concentration VOC mixtures in the indoor/outdoor environment as well as the spillage accident of hazardous chemicals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.460-468
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• 2021

This study investigated the enhanced combustion efficiency of an "air-cooled combustion system" with single F.D. fan, and performed a numerical analysis for the operation and design conditions to increase the combustion efficiency. The combustion efficiency in an actual combustor was compared before and after the structure modification. Numerical analysis for application of a single fan revealed the difficulty of forming a turbulence for circular combustion conditions. This is because the supply ratio of combustion air supplied into 2 flow paths becomes irregular in the combustion furnace due to a change in friction force and pressure in each flow path. Subsequently, two methods of supplying air into the combustion furnace were analyzed numerically to obtain the optimal combustion conditions of an air-cooled combustion system. The first method involved injecting the preheated combustion air after a 180~360 degree rotation from the outer wall, whereas in the second method, the combustion air was injected into the combustion furnace in a tangential direction after primary heat exchange outside the combustion furnace, by applying a rotatable vane structure in the combustion furnace. Results reveal that application of a single F.D. fan to the air injection into a rotatable combustion furnace is desirable for optimization of the combustion conditions for applying a duct structure having a dual cooling wall for the cooling of the outer wall of the combustion furnace, and for maintaining perfect mixing in the combustion furnace. We therefore confirmed enhanced combustion efficiency by comparing the actual combustion efficiency before and after structure modification.

• The Journal of the Korea Contents Association
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• v.21 no.4
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• pp.520-532
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• 2021

The purpose of this study is to provide basic data for the development of the anger provoking situation scale using the mixed research method. For this purpose, three research methods were used: content analysis of domestic and international anger-inducing situation scale, NAS-PI factor and reliability analysis of youth anger-provoking scale, and FGI with youth expert. In the results of NAS-PI, there were four categories of 'unrespectful treatment', 'unfairness', 'annoying traits of others', and 'irritation' except 'frustration' among five categories. The results of the FGI consisted of seven categories: 'rejection', 'physical and verbal violence', 'ignorance', 'frustration', 'control and restraint', 'rumination', and 'interpersonal relationship'. As a result of integrating these contents, it is finally possible to reconstruction in to seven categories such as 'unfairness', 'injustice', 'ignorance', 'control and restraint', 'ignorance', 'frustration' 'interpersonal relationship'. The meaning of this study is to provide the basic data for the development of the anger provoking situation scale for domestic adolescents by integrating the contents analysis and quantitative and qualitative researches of domestic and international anger provoking situation scale. The results of this study are as follows. First, it is necessary to study the anger provoking situations reflecting sociocultural context, and to develop the reliability and validity of the anger provoking situation scale.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.300-307
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• 2022

Time-resolved serial femtosecond crystallography (TR-SFX) is a powerful technique for determining temporal variations in the structural properties of biomacromolecules on ultra-short time scales without causing structure damage by employing femtosecond X-ray laser pulses generated by an X-ray free electron laser (XFEL). The mixing rate of reactants and biomolecule samples, as well as the hit rate between crystal samples and x-ray pulses, are critical factors determining TR-SFX performance, such as accurate image acquisition and efficient sample consumption. We here develop two distinct sample delivery systems that enable ultra-fast mixing and on-demand droplet injecting via pneumatic application with a square pulse signal. The first strategy relies on inertial mixing, which is caused by the high-speed collision and subsequent coalescence of droplets ejected through a double nozzle, while the second relies on on-demand pneumatic jetting embedded with a 3D-printed micromixer. First, the colliding behaviors of the droplets ejected through the double nozzle, as well as the inertial mixing within the coalesced droplets, are investigated experimentally and numerically. The mixing performance of the pneumatic jetting system with an integrated micromixer is then evaluated by using similar approaches. The sample delivery system devised in this work is very valuable for three-dimensional biomolecular structure analysis, which is critical for elucidating the mechanisms by which certain proteins cause disease, as well as searching for antibody drugs and new drug candidates.

• Land and Housing Review
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• v.14 no.3
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• pp.93-106
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• 2023

This study attempted to simulate changes in the thermal environment according to the type of apartment complex in Korea using CFD techniques and evaluate the thermal environment by type of apartment. First, apartment complex types in the 2000s and 2010s were referred from previous studies and four types of apartment complex were extracted from. Second, the layout of the apartment complex and temperature changes were analyzed by the direction of wind inflow. Third, a standardized model was created from each type using tower type, plate type, and mixed driving. Last, CFD simulations were performed by setting up the inflow of wind from a total of eight directions. The temperature was relatively low in the type consisting of only the tower type and the type of placing the tower type in the center of the complex, regardless of the direction of the wind. It was due to the good inflow of wind from these types to the inside of the complex. It can be interpreted because wind flows easily into the complex in these types. The findings showed that wind flow and resulting temperature distribution patterns differed depending on the building type and complex layout type, confirming the need for careful consideration of the complex layout in the early design stage. The results are expected to be used as basic data for creating a sustainable residential environment in the early design stage of apartment complexes in the future.

• Journal of Aerospace System Engineering
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• v.18 no.1
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• pp.53-63
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• 2024

Adopting an engine igniter with high efficiency and ignition performance is essential for reliable operation of liquid rocket engines. In this study, we developed a spark torch igniter for a 450 N-scale methane-oxygen liquid rocket engine by conducting numerical analyses, igniter manufacturing and validation. Specifically, we conducted a parametric study for maximizing the enthalpy at the igniter exit, specifically by adjusting the mass flow rate, nozzle area ratio, fuel-oxidizer mixture ratio, and the igniter length-to-diameter. The heat transferred via the igniter nozzle exit was computed using 3-dimensional numerical simulations. We also manufactured and tested the igniter based on a deduced design to confirm ignition performance of the designed spark torch igniter. The igniter developed through this study could contribute to the development of practical propulsion systems such as upper-stage engines of small launch vehicles.

• Journal of the Korean Society of Food Science and Nutrition
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• v.25 no.6
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• pp.907-914
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• 1996

To enhance the shelf-life and quality of baechu kimchi, the effects of CSP(crab shell powder) addition to kimchi was investigated. Overall qualities were deteriorated by fish odor, chewiness of particles, sharp pH increase at the early fermentation stage; therefore in order to solve these problems kimchi fermentation was carried out with kimchi containing 1, 3, 5% CSPB for salted baech weight at $10^{\circ}C$ for 300ays. Quality of kimchi was evalutated by the measurement of pH, acidity, colour L, a, and b value, the number of microbe and lactic acid bacteria, texture. Ten highly trained panelists were involved in the sensory evaluation. During the entire fermentation periods, pH, hardness, colour L, a and b value, the number of lactic acid bacteria of kimchi with CSPB were higher than those of control, but acidity was lower. Sensory quality showed that sour taste of control at 15-day fermentation was already strong. However, sour taste, crispness taste, and overall taste of kimchi with CSPB untill 20-day fermentation were good. Especially, overall taste of kimchi containing 3% CSPB at 30-day fermentation was good, but that of kimchi containing 5% showed fish odor from the early periods of fermentation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.1
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• pp.98-104
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• 1999

To investigate the relationships between ocean environmental characteristics, the time-series data of temperature and salinity observed at a station near at Hanlim set net in 1995 and 1996 are analyzed, and the results are as follow ; 1. In hanlim set net, the diurnal range of temperature and salinity variation in summer is very large and the amplitude of short-period fluctuation of temperature and salinity is very large. That is, not only the water of the middle and bottom layers (low temperature and high salinity) but also the coalstal water (high temperature and low salinity) appears alternatively depending on the current direction 2. from the result of mooring for 22 days in Hanlim set net, the mean speed and direction of tidal current in neap tide were 9.1 cm/sec and south westward in ebb time, and 11.6 cm/sec and north or northeastward in flood time, respectively. The highest speed of the current was 15cm/sec in ebb time, and 22.6 cm/sec in flood time. The mean speed and direction of tidal current in spring tide were 10.4 cm/sec, and southwestward in ebb time, and 12.3 cm/sec, and north or northestward in flood time, respectively. The highest speed of the current was 19.4 cm/sec in ebb time, and 20 cm/sec in flood time respectively. The mean speed of the current in flood time was larger than that in ebb time. The velocity vector along the major axis of semidiurnal tide ($M_2$) component was 1.5 times larger than that of diurnal tide ($K_1$), The major directions of two compornants were northwestward and east-southeastward and residiual current were 3.25 cm/sec and northwestward-directed. Result of TGPS Buoy tracer for 3 days between Biyang-Do and Chgui-Do showed that the mean speed was 1.6 knot in ebb time and 1.3 knot in flood time. Direction of tidal was southwestward in ebb time and northeastward in flood time respectively. The maximum current speed was 4.8 knot in ebb time and 3.7 knot in flood time respectively. The mean speed and direction of tidal in of offshore were 1.7 knot and northwestward in flood time. The residual current appeared 0.3 knot northeastward.

• Korean Chemical Engineering Research
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• v.55 no.6
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• pp.837-845
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• 2017

A recirculating integrated system composed of a fluidized biofilter filled with waste-tire crumb media fixed with return sludge from wastewater treatment facility of D dyeing industrial center, and a UV/photocatalytic reactor packed with calcined $TiO_2$ coated-glass beads as photocatalyst-support, was constructed and was run to treat authentic textile-dyeing wastewater from D-dyeing industrial center, which was mixed with an alkaline polyester-weight-reducing wastewater and a wastewater from sizing process. As a result, its total removal efficiency(RE(tot)) of $COD_{cr}$ and colors were ca. 81% and 55%, respectively. The synergy effect of the recirculating integrated system to enhance total removal efficiency(RE(tot)) of $COD_{cr}$ and colors were evaluated at most ca. 7% and 3%, respectively. The fluidized biofilter and the UV/photocatalytic reactor were responsible for ca. 94% and 6% of the total $COD_{cr}$ removal efficiency, respectively, and were also responsible for ca. 86% and 14% of the total color-removal efficiency, respectively. Thus, the degree of the UV/photocatalytic reactor-unit process's contribution to RE(tot) of color, was about 2.4 times of that to RE(tot) of $COD_{cr}$. Therefore, the UV/photocatalytic reactor facilitated the more effective elimination of colors by breaking down the chemical bonds oriented from colors of dyes such as azo-bond, than $COD_{cr}$. In addition, the effect of the removal efficiency of each unit process(i.e., the fluidized biofilter or the UV/photocatalytic reactor) of the recirculating integrated system on RE(tot) of $COD_{cr}$ and colors, was analysed by establishing its model equation with an analytic correlation.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.3
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• pp.231-238
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• 2022

Purpose. This study aimed to investigate the effect of different veneering methods on the tensile bond strength between polyetherketoneketone (PEKK) and denture base resins. Materials and methods. A total of 80 PEKK T-shaped specimens were fabricated and the primer (Visio.link) was applied after airborne-particle abrasion with 110 ㎛ alumina oxide powder. According to the veneering method, the specimens were divided into four groups (n = 20) to be veneered with the gingival colored packable photopolymerized composite resin (SR Adoro); flowable photopolymerized composite resin, (Crea.lign); heat-polymerized resin (Vertex); and self-polymerized resin (ProBase Cold). Each group was divided into two subgroups (n = 10) according to the artificial thermal aging. After the tensile bond strength measurement via universal testing machine, the fracture sections of all specimens were observed. Two-way ANOVA and Tukey's HSD post hoc test were used for the statistical analysis (α = .05). Results. The results of the two-way ANOVA showed statistically significant differences in the tensile bond strength according to the veneering method and artificial thermal aging of denture base resins (P<.001). The highest tensile bond strength showed in the packable photopolymerized resin group before and after the artificial thermal aging. The lowest tensile bond strength showed in the heat-polymerized resin group. The mixed and adhesive fracture showed in all groups. Conclusion. The veneering method and artificial thermal aging can influence in the tensile bond strength between the resin and PEKK. The artificial thermal aging can reduce the tensile bond strength.