• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.564-573
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• 2001

The mechanical properties of short carbon/glass fiber reinforced polypropylene are experimentally measured as functions of fiber content and nozzle diameter. Also, these properties are compared with the survival rate of reinforced fibers and fiber volume fraction using image analysis after pyrolytic decomposition. The survival rate of fiber aspect ratio as well as fiber volume fraction is influenced by injection processing condition, the used materials and mold conditions such as diameter of nozzle, etc. In this study, the survival rate of fiber aspect ratio is investigated by nozzle size variations in injection/mold sides. It is found that the survival rate of glass fiber is higher that the survival rate of glass fiber is higher than that of carbon fiber. Both tensile modulus and strength of short-fiber reinforced polypropylene are improved s the fiber volume fraction and nozzle diameter are increased.

• Journal of ILASS-Korea
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• v.9 no.4
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• pp.31-37
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• 2004

This paper presents spray and combustion characteristics of hydrocarbon fuel injected from pressure-swirl nozzles. Three commercial nozzles with orifice diameters of 0.256, 0.308 and 0.333mm and injection pressures ranging from 0.7 to 1.3 MPa were selected f9r the experiments. Spray characteristics such as breakup length. spray angle and drop size (SMD) were analyzed using photo image analyses and Malvern Panicle Size Analyzer. The drop size was measured with and without a blower at the same measuring locations. The flame length and width were measured using photo image analyses. The temperature distribution along the axial distance and the gas emission such as CO, $CO_2\;and\;NO_x$ were studied. The breakup length decreased with an increase in injection pressure for each nozzle but increased with an increase in nozzle orifice diameter. The spray angle increased and SMD decreased with an increase in injection pressure. The flame with an increased linearly with an increase in injection pressure and in nozzle orifice diameter. The flame temperature increased with an increase in injection pressure but decreased along the axial distance. The maximum temperatures occurred closer to the burner exit and flame at axial distance of 242mm from the diffuser tip. The experimental results showed that the level of CO decreased while that of $CO_2\;and\;NO_x$ increased with an increase in injection pressure and nozzle orifice diameter.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1089-1092
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• 2001

In the stereolithography process, build parameters are laser power, scan velocity, scan width, bean diameter, layer thickness and so on. These values are determined according to product accuracy and build time. Build time can be reduced by improving of scan velocity, laser power, layer thickness, hatching space and so on. But variation of these parameters influence part accuracy, surface roughness, strength. This paper observed cure properties in various beam diameter. In order to examine these, relationships of scan velocity and cure depth, scan velocity and cure width according to various beam diameter in one scan line are measured. And cure thickness is measured according to beam diameter and scan velocity in scan surface of one layer. For reduction of build time, beam diameter and scan velocity is proposed in stereolithography process.

• Journal of Soil and Groundwater Environment
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• v.8 no.3
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• pp.13-22
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• 2003

Laboratory scale study for an air injection and flowing aspect of groundwater saturated zone was conducted for three sediment grains (AMG 0.34, 1.38, 3.89 mm diameter). Air flow for AMG (Average Modal diameter Grains) 0.34 mm diameter grain size provides indication of pattern of channelized air flow in saturated zone and expansion state in above saturated zone. Maximum area of influence is approximately l5.2%/$\textrm{m}^2$for AMG of 0.34 mm diameter. For AMG of 1.38 mm and 3.89 mm modal diameter grains, air flow are pervasive air flow, forming a symmetrical cone of influence around the injection point. Maximum areas affected are 37%/$\textrm{m}^2$for AMG 1.38 mm diameter and 30%/$\textrm{m}^2$for AMG 3.89 mm diameter. AMG 1.38 mm and 3.89 mm diameter grains show onset of collapse and approach to steady state in above saturated zone, respectively. In this study, optimal sites for in situ air sparging, may be grain diameters between about AMG 1.5-2.5 mm diameter.

• KSBB Journal
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• v.29 no.5
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• pp.385-391
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• 2014

In this study, the emulsion dispersion stability of optimizing storage temperature was investigated. The system was based on oil/water (O/W) emulsions. In order to evaluate the stability, mean diameter of droplet was measured as a function of temperature with various mixed hydrophilic lipophilic balance (HLB). In addition, the correlations between phase inversion temperature (PIT) and the optimum storage temperature were probed. In this system, majority of the smallest droplet was shown at temperature of $20^{\circ}C$ below PIT. Whether the temperature was increased or decreased from the optimum, size of the droplet increased. According to the mixed HLB, the particle size and optimum storage temperature were also affected. As the concentrations of surfactant were increased, the size of particle decreased with lower optimum temperature for storage. If the surfactant (4 wt%) were mixed with HLB, the optimum storage temperature was $21^{\circ}C$ for maintaining the size of smallest droplet at 108.3 nm in diameter. At above optimum condition, increased size of particle was observed approximately 4 % increases from 108.2 nm to 112.3 nm after 600 hours. The size of particle in emulsion was maintained stably without any considerable effect of Ostwald ripening phenomena at the optimum storage temperature with low polydispersity index.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.445-452
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• 2018

In this paper the effects of particle size and model scale of concrete have been investigated on point load index, tensile strength, and the failure processes using a PFC2D numerical modeling study. Circular and semi-circular specimens of concrete were numerically modeled using the same particle size, 0.27 mm, but with different model diameters of 75 mm, 54 mm, 25 mm, and 12.5 mm. In addition, circular and semi-circular models with the diameter of 27 mm and particle sizes of 0.27 mm, 0.47 mm, 0.67 mm, 0.87 mm, 1.07 mm, and 1.27 mm were simulated to determine whether they can match the experimental observations from point load and Brazilian tests. The numerical modeling results show that the failure patterns are influenced by the model scale and particle size, as expected. Both Is(50) and Brazilian tensile strength values increased as the model diameter and particle sizes increased. The ratio of Brazilian tensile strength to Is(50) showed a reduction as the particle size increased but did not change with the increase in the model scale.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.5
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• pp.11-22
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• 1994

The pupose of this study is to measure droplet size and velocity simultaneously for a transient diesel fuel spray in a quiescent chamber at atmospheric temperature and pressure. Generally, diesel combustion phenomena is mainly governed by characteristics of injection system and fuel spray. Therefore we need to clarify these characteristics for developing more economical diesel systems. In this study, correlation between droplet size and velocity was measured at downstream distance from nozzle. Governing parameters are pump speed and fuel quantity for the detailed nature in this transient diesel fuel spray. It is observed effect to the droplet size and velocity distribution. Velocity(peak, mean, rms), number density and droplet size were investigated simulaneously using PDA in the spray. Various results are presented to illustrate the effects of operation factors and correlation between the droplet diameter and velocity.

• Journal of the Korean Society of Hazard Mitigation
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• v.3 no.2 s.9
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• pp.139-145
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• 2003

This study is to propose reduction effect of scour depth and a optimum size of circular collar through experimental analyses with various collar sizes. To do so, we carried out hydraulic model experiments. In the case of with considering the collar, the effect of reduction of scour depth increased according to the increase of collar size. When size of collar is 2 as the ratio of collar diameter(W) to pier diameter(D), scour depth is decreased about 67% and deposition height is increased about 70%. The optimal size of collar proposed in this study is W/D=2 by analyzing reduction effect of scour depth, size of scour hole, and deposition height.

• Journal of the Korean Home Economics Association
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• v.40 no.12
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• pp.119-129
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• 2002

This research aims at finding out situation on purchasing clothes for kids, size recognition and fitting to provide basic data in order to establish standard sizes for kids' clothes. A survey was conducted to 360 mothers who have children ranging from first to third grade in elementary school on clothes purchasing method, wearing situation, criteria in deciding size and fitting preference. In terms of data analysis, frequency, percentage, mean, $X^2$-test, ANOVA and Duncan-test were used via SPSS PC program. The result is as follows; 1. While the recognition on brand was high, the recognition on body size was low: as a result, it is believed that it would be effective to mark the weight along with the brand. 2. Many times, they would select one or two size bigger on all items and they would go for a regular or one that fits as far as filling is concerned showing that it is different from adult clothes. 3. As far as obese kids, they would choose based on the diameter, so the diameter item is right but they are too long in general. The length question should be given special attention when manufacturing clothes for obese kids.

• Food Science and Preservation
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• v.2 no.1
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• pp.195-202
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• 1995

An experiment was conducted to develop the simple methods of ginger storage which decrease the weight reduction and maintain good quality of ginger during the cellar storage. The stored boxes with volume of 0.03㎥ and ventilator diameter of 3, 4, 5cm was hurried under the ground(60, 80, 100cm) in the green house. During the cellar storage at the 100cm depth the average temperature and relative humidity in the stored box were remained in 11.7~16.3$^{\circ}C$ and 73%, respect. The higher storage amount and smaller size of ventilator size increased the CO2 concentration in the stored box, and the concentration in the stored box with 50% storage quantity rate and 3cm ventilator diameter size was more than 10% for about 2 months from early Feburary. The decay rate of ginger during the cellar storage increased with higher amount of storage quantity and smaller size of ventilator. The CO2 concentration was low and remained relatively constant with the deeper location of stored box under the ground, and the decay rate was lower in the deeper stored box. Germination rate increased with the deeper location of stored box, and with the lower storage quantity and larger ventilator size. The germination rate was low in the higher decay rate box. Weight loss, total sugar and moisture contents of ginger were decreased, while crude fiber and ash were increased during the storage.