• Journal of Korean Society for Atmospheric Environment
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• v.32 no.2
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• pp.158-166
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• 2016

To characterize the features of particle apparent density, continuous measurements of particle number size distributions from optical particle sizer (OPS) and 24 hr integrated particle mass concentrations from filter based sampler were conducted at the National institute of environmental research NamBu Supersite (NNBS, $35.22^{\circ}N$, $126.84^{\circ}E$) in Gwangju for 16 days from Nov. 4 in 2014. Source apportionment model was carried out by applying Positive Matrix Factorization (PMF) to particle size distribution data. Three different distributions related to primary and secondary sources were investigated by the diurnal patterns of identified factors. Density estimated by gaussian model has been calculated as $1.69g/cm^3$ with 95% confidence bounds ($1.57{\sim}1.81g/cm^3$).

• Journal of the Korean Society of Food Culture
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• v.22 no.5
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• pp.609-614
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• 2007

Quality characteristics of dasik were studied with varied the levels of rice grain particle size and green tea powder and compared them with commercially sold dasik. Among the samples with the same number of grinding times, the sample groups with the higher amount of green tea showed significantly the less mosture content(p<0.05). Hardness was higher in the samples containing higher amount of green tea among the ones with the same grain size (p<0.05). The M13G0.5 was evaluated to have the highest savory aroma with significance (p<0.05), and C1 to have the highest sweetness by sensory analysis. The developed dasik samples with lower rice grain particle size had significantly lower adhesiveness, chewiness, gumminess, and cohesiveness compared to those of commercial sample groups. In sensory tests, the compared groups showed significantly the higher savory aroma and flavor and very lower hardness when compared to those of commercial sample groups. With the results above, dasik with with varied the levels of rice grain particle size and green tea powder were developed with improved qualities compared to those of commercially sold dasik.

• Industrial Engineering and Management Systems
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• v.6 no.2
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• pp.136-145
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• 2007

The selection of suppliers and the determination of order quantities to be placed with those suppliers are important decisions in a supply chain. In this research, a non-linear mixed integer programming model is presented to select suppliers and determine the order quantities. The model considers the purchasing cost which takes into account quantity discount, the cost of transportation, the fixed cost for establishing suppliers, the cost for holding inventory, and the cost of receiving poor quality parts. The capacity constraints for suppliers, quality and lead-time requirements for the parts are also taken into account in the model. Since the purchasing cost, which is a decreasing step function of order quantities, introduces discontinuities to the non-linear objective function, it is not easy to employ traditional optimization methods. Thus, a heuristic algorithm, called particle swarm optimization (PSO), is used to find the (near) optimal solution. However, PSO usually generates initial solutions randomly. To improve the PSO solution quality, a heuristic procedure is proposed to find an initial solution based on the average unit cost including transportation, purchasing, inventory, and poor quality part cost. The results show that PSO with the proposed initial solution heuristic provides better solutions than those with PSO algorithm only.

• Korean journal of food and cookery science
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• v.8 no.3
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• pp.233-239
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• 1992

The characteristics of Packsulgi were investigated with different cooking methods of conventional and pressure cookers and variation in panicle size of rice flour. The water contents of rice f1ours and Packsulgis were greater as the particle became coarser. The water contents of Packsulgis cooked with pressure cooker (P) were greater than those of conventional cooker (C). Degree of gelatinization in P was higher than that of C. There were no significant differences among the samples of P, whereas coarser f1ours tended to show higher degree of gelatinization than finer ones in C. The results of textural properties measured by rheometer showed that hardness, cohesiveness and gumminess of P was higher than that of C. The textural parameter of P increased as the particle became finer, whereas mat of C increased as the particle became coarser. L value of C was higher than that of P in me same particle size, whereas a and b value of P was higher than that of C. L and a value of both P and C increased as the particle became finer. b value in P increased as the particle became coarser, whereas mat in C increased as the particle became finer. According to me sensory evaluation, the appearance of C was more acceptable man that of P, whereas the texture of P was more acceptable than mat of C. There were no significant differences in overall quality among P and c and Packsulgis made by 60, 100 mesh rice f1our had higher acceptability than others.

• Journal of Korean Society for Atmospheric Environment
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• v.33 no.2
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• pp.124-138
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• 2017

Physico-chemical measurement of non-refractory submicron particles($NR-PM_1$) was conducted in Baengnyeong Island, Korea using Aerodyne High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) from 2012 to 2014. Organics and ammoniated sulfate were dominant species in $NR-PM_1$. The organics was found to have similar fractions(approximate 40%) of $NR-PM_1$ during the summer and winter, while the sulfate fractions of $NR-PM_1$ were calculated to be approximately 47% and 31% for the summer and winter, respectively, suggesting the possibility that particles provide non-acidic surfaces for condensation of nitric acid in the winter. The nitrate fractions of approximate 4% and 20% of $NR-PM_1$ were observed in August (summer) and November (winter), respectively, resulting that the relatively low concentration of sulfate in $NR-PM_1$ provided a non-acidic surface for nitric acid condensation and formation of particulate ammoniated nitrate is favored thermodynamically in winter. The new particle formation (NPF) event and particle growth rate were analyzed for each month in 2014 using Scanning Mobility Particle Sizer(SMPS). The Percent of NPF events was the highest in winter, but NPF event was not observed during summer due to relatively high temperature and frequent rainfall. The average particle growth rate was 3.5 nm/h and the highest particle growth rate was 5.5 nm/h in May. We observed the long-range transport of the anthropogenic sulfate from the East Asia during the intensive monitoring period of November between Qingdao and Baengnyeong Island in 2013. The relatively high concentrations of m/z 60 measured in HR-ToF-AMS was observed in May and June at Baengnyeong Island, suggesting the possibility of the influence of biomass burning from the East Asia to the Korean Peninsula.

• Journal of Industrial Technology
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• v.26 no.B
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• pp.173-181
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• 2006

We analyzed systematically particle growth in the pulsed $SiH_4$ plasmas by a numerical method and investigated the effects of pulse modulations (pulse frequencies, duty ratios) on the particle growth. We considered effects of particle charging on the particle growth by coagulation during plasma-on. During plasma-on ($t_{on}$), the particle size distribution in plasma reactor becomes bimodal (small sized and large sized particles groups). During plasma-off ($t_{off}$), there is a single mode of large sized particles which is widely dispersed in the particle size distribution. During plasma on, the large sized particles grows more quickly by fast coagulation between small and large sized particles than during plasma-off. As the pulse frequency decreases, or as the duty ratio increases, $t_{on}$ increases and the large sized particles grow faster. On the basis of these results, the pulsed plasma process can be a good method to suppress efficiently the generation and growth of particles in $SiH_4$ PCVD process. This systematical analysis can be applied to design a pulsed plasma process for the preparation of high quality thin films.

• Particle and aerosol research
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• v.8 no.4
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• pp.143-150
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• 2012

Fungal particles have been known to aggravate indoor air quality. To develop fungal particle cleaning devices requires a well-controlled generator of fungal aerosol particles. In this study, a novel fungal aerosol generator was designed and tested for anti-fungal experiment. Cladosporium cladosporioides was selected as test fungal particle. After aerosolization, the number concentration and the size of particles were measured by aerodynamic particle sizer. The number concentration depended on the vibration strength and vibration period of the designed fungal aerosol generator. For the vibration strength of 10volt and the period of 10 sec (5 sec on and 5 sec off), the stable particle generation with concentration of 10#/cm3 was maintained during 35 minutes.

• Journal of ILASS-Korea
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• v.15 no.2
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• pp.53-60
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• 2010

This study presents development of digital particle holographic system and its application to spray field to measure three-dimensional velocities and sizes of spray droplets. A double exposure hologram recording system with synchronization system for time control was established and digital holograms can be recorded in a short time interval. To process recorded holograms, the correlation coefficient method was used for focal plane determination of particles. To remove noises and improve the quality of holograms and reconstructed images, the Wiener filter was adopted. The two-threshold and image segmentation methods were used in binary image transformation. For particle pairing, the match probability method was adopted. The developed system was applied to spray field and three-dimensional velocities and sizes of spray droplets were measured. The measurement results of digital holographic system were compared with those made by laser instruments, PDPA(Phase Doppler Particle Analyzer), which proved the feasibility of in-line digital particle holographic system as a good measurement tool for spray droplets.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.3
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• pp.136-143
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• 2001

A micro particle manipulator, which is devised for trapping particles at fixed positions by negative dielectrophoretic force (DEP force), has been fabricated and experimented. It is composed of square type electrode arrays fabricated by nickel electroplating with the height of 28 ${\mu}m$. To improve the quality of electroplated nickel electrodes, plating conditions have been optimized. Micro particles used in this study are polystyrene spheres and their to the specific position and trapped. The DEP force along the moving path of the particles has been estimated by the motion equation of a single particle. The displacement of a particle with an elapsed time was measured using a high-speed camera (1000 frames/sec). The velocity and acceleration of the particle were calculated from the measured data. The DEP force acting on the particle was estimated.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.2
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• pp.214-220
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• 2005

Errors may occur due to analysis methods and water quality during the application of the on-line particle counter In water treatment process. Errors caused by analysis methods include particle destruction by shear force due to inflow speed and tube friction, as well as interruption by screening, bubbles and contaminants. Since errors happen frequently because of these factors, it is necessary to examine and evaluate such errors during the application of a particle counter. Errors can be large due to screening and bubbles. Measurement values are effective for water analysis after filtration process. However, because of screening, only measurement values for particles above $7{\mu}m$ are valid for water with a turbidity between 3-10NTU. As particle numbers around $10{\mu}m$ increase a lot after ozone treatment, sufficient pretreatment process is necessary. Physical conditions should keep stable for inflow to decrease errors caused by shear force.