• KCI Concrete Journal
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• v.11 no.3
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• pp.79-88
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• 1999

Most difficulties of inducing high fluidity on the concrete mixing design with a strength range of 210 to 240kg/$\textrm{cm}^2$ result from the segregation of aggregates due to the shortage of cementitious binders. To solve the problem, this study concentrated on finding the optimized amount of binder material which does not affect the concrete strength and is also economical. Also there were studies on the use of intermediate sized aggregates to avoid the gap-grading between coarse and fine aggregates so that the material segregation in high flowing concrete was and minimalized the fluidity and penetration capacity of the reinforcing bars was enhanced. Throughout the parametric study with respect to water/binder ratio. superplasticizer. replaceable mineral admixture, the size of coarse aggregate and mixing methods, the effect of each constituent on the characteristics of high flowing concrete could be observed. As a result or partially using stone powder or an intermediate class of aggregate (max. diameter 13mm) . it was fund that the fluidity of concrete significantly increased without material segregation and any change of compressive strengths. It was also proved in this study that proper mixing time and speed are significant factors influence the performence of high flowing concrete.

• Journal of Biomedical Engineering Research
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• v.17 no.4
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• pp.499-506
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• 1996

Blood flow velocimeter is an essential device to measure the blood flow in skin tissue. In this study, we developed a high-speed LDV(laser Doppler Velocimeter) that has real time processing capability using a DSP(digital signal processing) chip and is able to continuously measure information about blood-flow based on a noninvasive method using self-mixing type laser diode. This LDV system has a simpler structure than any other typical blood flow velocimeter and is composed of new self-mixing probe, stabilizer circuits DSP board, and interf'ace boule We measured velocity of speaker-unit by operational frequencies to identify Doppler effect of this system, performed clinical experiment on bare finger tip and compared it with a commercial euipment BPM403A(USA).

• The KSFM Journal of Fluid Machinery
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• v.15 no.5
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• pp.32-36
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• 2012

The positive displacement pump and the regenerative pump are widely used in the range of low specific speed, $n_s{\leq}100$[rpm, m3/min, m]. The positive displacement pump is not suitable for miniaturization and operation in high rotational speed. The regenerative pump has a problem with large leakage flow and low efficiency. While the centrifugal pump has advantages of high efficiency, miniaturization and high rotational speed, efficiency drops sharply with decrease in specific speed. Therefore the purpose of this study is to design a new type of centrifugal pump that has advantages of centrifugal pumps in operation in low specific speed. The name of this new type of pump was called 'Pipe type centrifugal pump', since the flow path through the impeller is simple circular pipe. Due to the simple shape of impeller, the manufacturing process is simple and cost is low. There is strong jet flow at the outlet of the impeller. This jet induces flow path loss, meridional dynamic pressure loss and mixing loss. Large disk friction makes the efficiency be limitted in the range of low specific speed. Even though the loss and the low efficiency, 'Pipe type centrifugal pump' represents stable performance, affordable pressure ratio and efficiency better than that of other low specific speed pumps.

• KSBB Journal
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• v.30 no.6
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• pp.307-312
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• 2015

Transgenic rice cells using RAmy3D promoter can provide high productivity, and the production of recombinant protein is induced by sugar starvation. In this system, productivity was reduced during the scale-up processes. To ensure the influences of shear stress and oxygen transfer rate, working volume and mixing performances were investigated under various agitation speeds and working volumes. In addition, inoculation methods including suspended cells and filtered cells were compared. Working volumes and shaking speeds were 300, 450 mL and 80, 120 rpm, respectively. Hydrodynamic environment of each condition was measured numerically like mixing time and $k_La$. Good mixing performance and high shear stress were measured at high agitation speed and low volume. The highest level of hCTLA4Ig was 30.7 mg/L at 120 rpm, 300 mL. When conditioned medium was used for inoculation, increased cell growth was noticed during the day 0~4 and decreased slower than filtered cells. Compared with filtered cells, the maximum hCTLA4Ig level reached 37.8 mg/L at 120 rpm, 300 mL and lower protease activity level was observed. In conclusion mixing performance is critical factor for productivity and conditioned medium can have a positive effect on damaged cells caused by hydrodynamic shear stress.

• Composites Research
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• v.29 no.4
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• pp.223-229
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• 2016

SiC nanoparticles were used to increase flexural properties of polymer matrix. This study was to manufacture huge concentration SiC nanoparticle/epoxy composites and to evaluate the dispersion. During mixing SiC nanoparticle and epoxy, 20 wt% SiC nanoparticle in total composites was used with both stirrer and sonication equipment together. Mixing speed and dispersion were improved with the method by using both stirrer and sonication equipment at the same time via mechanical test and FE-SEM. Based on the results, modeling of SiC nanoparticle dispersion could be established. Ultimately, unidirectional carbon fiber reinforced composites was manufactured using 20 wt% SiC nanoparticle/epoxy. Mechanical property of CFRP using dual stirrer and sonication mixing method was better than composites by single sonication mixing method.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.171-184
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• 2007

Chemical admixture stabilization has been extensively used in both shallow and deep stabilization in order to improve inherent properties of the soil such as strength and deformation behavior. An increment in strength, a reduction in compressibility, an improvement of the swelling or squeezing characteristics and increasing the durability of soil are the main aims of the admixtures for soil stabilization. Recently, the various advanced cement stabilizer mixing technique was developed. Advanced cement stabilizer mixing technique is environmentally-friendly and has an excellent mixing property and outstanding mixing speed. In this study, to develop the rural road pavement technology using cement stabilizer, compaction and unconfined compression test were performed with various mixing ratio and two types of soil(clay and silty soil). And the freezing/thaw test and bending strength test performed to develop suitable cement stabilizer material for stabilization of rural road. Based on the test results, the liquid types of cement stabilizer material and silty soil mixture are most suitable for rural road construction and although the mixing ratio is low, cement stabilizer mixture is effective for durability of rural road surface layer.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.287-292
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• 2001

Under the condition of variable density and specific heat, maximum pressure, maximum temperature, bearing load, friction and side leakage in high-speed journal bearing operation are examined. The results are compared with the calculation results under the conditions of constant density and specific heat, and variable density and constant specific heat. It is found that the condition of variable density and specific heat play important roles in determining friction and load of journal bearing at high speed operation.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.484-487
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• 1995

An interacting multiple model (IMM) approach which merges two hypotheses for the situations of constant speed and constant acceleration model is considered for the tracking of maneuvering target. The inflexibility of uncertainty which lies in the kinematic constraint (KC) represented by pseudomeasurement noise variance is compensated by the mixing of estimates from two model Kalman tracker: one with KC and one without KC. The numerically simulated tracking performance is compared for the "great circular like turning" trajectory maneuver by the single model tracker with constant speed KC and two model tracker which is developed in this paper.his paper.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.244-250
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• 2023

In this paper, mortar mixed with tapioca starch was manufactured to evaluate the effect of tapioca starch on mortar, through evaluating the quality characteristics of mortar, the impact of tapioca starch on improving the performance and basic quality of mortar was examined. Tapioca starch tended to decrease flow by increasing the viscosity of the dough consistency of fresh mortar, which tended to reduce flow, and decreased by about 10 % as the tapioca starch mixing ratio increased by 0.025 %. In addition, the effect of tapioca starch on the compressive strength of mortar was at the same level regardless of the tapioca starch mixture at 28 days of age. However, at an early age of 3 days, the speed of compressive strength development was accelerated by mix ing tapioca starch. In addition, the effect of tapioca starch on the compressive strength of mortar was at the same level regardless of the tapioca starch mixture at 28 days of age. However, at an early age of 3 days, the speed of compressive strength development was accelerated by mixing tapioca starch. The speed of strength development improved by about 20 % when mixing 0.050 % tapioca starch. The adhesion strength improved by about 60 % when mixing 0.050 % tapioca starch, and the final shrinkage in length change decreased by 5 %.

• Tribology and Lubricants
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• v.23 no.5
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• pp.207-218
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• 2007

Turbocharger bearings are under the circumstance of high temperature, moreover rotated at high speed. It is necessary to be designed overcoming the high temperature. So the type of oil inlet port, the inlet oil temperature and the sort of engine oil should be designed, controlled and selected carefully in order to reduce the bearing inside temperature. In this study, the influence of aerated oil on a high-speed journal bearing is also examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil inlet port's type, oil aeration level and shaft speed. It is found that the type of oil inlet ports and shaft speed play important roles in determining the temperature and pressure distribution, then the friction in a journal bearing at high speed operation. Also, the results show that, under extremely high shaft speed, the high shear effects on aerated oil and the high temperature effects are canceled out each other. So, the bearing load and friction show almost no difference between the aerated oil and pure oil.