• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.358-367
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• 2013

In the present paper, we apply a porous modelling technique to accurately predict the pressure drop through the strainer by replacing all or some of the filter composed of perforated plates with porous media and there imposing the streamwise and transverse loss coefficients required according to the Forchheimer law and then confirm its effectiveness. At first, the streamwise coefficient is obtained by performing a simple simulation on the pipe flow mimicking the hole flow. Subsequently, the transverse coefficient is obtained by setting a unit pattern to have common flow loss characteristics with the repeated shape patterns in the filter, then performing numerical simulations on the prototype and porous model of the unit shape pattern, and finally comparing their results of pressure drop. To validate the applied modeling technique, we perform the numerical simulation with the two specified loss coefficients on a whole shape of strainer and compare the modeling results with those of the corresponding prototype numerical simulation. Comparison indicates that the modeling technique can predict the pressure drop and flow characteristics comparatively accurately and save the number of nodes closely related to the computational cost (CPU and memory) by about 3~4 times compared with the prototype simulation.

• Journal of Broadcast Engineering
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• v.17 no.3
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• pp.519-528
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• 2012

Voice activity detection (VAD) is generally conducted by extracting features from the acoustic signal and a decision rule. The performance of such VAD algorithms driven by the input acoustic signal highly depends on the acoustic noise. When video signals are available as well, the performance of VAD can be enhanced by using the visual information which is not affected by the acoustic noise. Previous visual VAD algorithms usually use single visual feature to detect the lip activity, such as active appearance models, optical flow or intensity variation. Based on the analysis of the weakness of each feature, we propose to combine intensity change measure and the optical flow in the mouth region, which can compensate for each other's weakness. In order to minimize the computational complexity, we develop simple measures that avoid statistical estimation or modeling. Specifically, the optical flow is the averaged motion vector of some grid regions and the intensity variation is detected by simple thresholding. To extract the mouth region, we propose a simple algorithm which first detects two eyes and uses the profile of intensity to detect the center of mouth. Experiments show that the proposed combination of two simple measures show higher detection rates for the given false positive rate than the methods that use a single feature.

• Journal of Korean Society on Water Environment
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• v.33 no.6
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• pp.715-721
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• 2017

Tree box filters, an example of bioretention systems, were compacted and versatile urban stormwater low impact development technique which allowed volume and water quality treatment performance to be adjusted based on the hydrologic, runoff quality and catchment characteristics. In this study, the overall performance of a 6 year-old tree box filter receiving parking lot stormwater runoff was evaluated. Hydrologic and hydraulic factors affecting the treatment performance of the tree box filter were also identified and investigated. Based on the results, the increase in rainfall depth caused a decrease in hydrologic and hydraulic performance of the tree box filter including volume, average flow, and peak flow reduction (r = -0.53 to -0.59; p<0.01). TSS, organics, nutrients, and total and soluble heavy metals constituents were significantly reduced by the system through media filtration, adsorption, infiltration, and evapotranspiration mechanisms employed in the tree box filter (p<0.001). This significant pollutant reduction by the tree box filter was also found to have been caused by hydrologic and hydraulic factors including volume, average flow, peak flow, hydraulic retention time (HRT) and runoff duration. These findings were especially useful in applying similarly designed tree box filter by considering tree box filter surface area to catchment area of less than 1 %.

• Analytical Science and Technology
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• v.28 no.1
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• pp.33-39
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• 2015

CdS-QD particles are a nano-sized semiconducting crystal that emits light. Their optical properties show great potential in many areas of applications such as disease-diagnostic reagents, optical technologies, media industries and solar cells. The wavelength of emitting light depends on the particle size and thus the quality control of CdS-QD particle requires accurate determination of the size distribution. In this study, CdS-QD particles were synthesized by a simple ${\gamma}$-ray irradiation method. As a particle stabilizer polyvinyl pyrrolidone (PVP) were added. In order to determine the size and size distribution of the CdS-QD particles, sedimentation field-flow fractionation (SdFFF) was employed. Effects of carious parameters including the the flow rate, external field strength, and field programming conditions were investigated to optimize SdFFF for analysis of CdS-QD particles. The Transmission electron microscopy (TEM) analysis show the primary single particle size was ~4 nm, TEM images indicate that the primarty particles were aggregated to form secondary particles having the mean size of about 159 nm. As the concentration of the stabilizer increases, the particle size tends to decrease. Mean size determined by SdFFF, TEM, and dynamic light scattering (DLS) were 126, 159, and 152 nm, respectively. Results showed SdFFF may become a useful tool for determination of the size and its distribution of various types of inorganic particles.

• Geophysics and Geophysical Exploration
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• v.18 no.4
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• pp.223-231
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• 2015

Self-potential (SP) is sensitive to groundwater flow and there are many causes to generate SP. Among many mechanisms of SP, pore-fluid flow in porous media can generate potential without any external current source, which is referred to as electrokinetic potential or streaming potential. When calculating SP responses on the surface due to geothermal fluid within an engineered geothermal system (EGS) reservoir, SP anomaly is usually considered to be generated by fluid injection or production within the reservoir. However, SP anomaly can also result from geothermal water fluid within EGS reservoirs experiencing temperature changes between injection and production wells. For more precise simulation of SP responses, we developed an algorithm being able to take account of SP anomalies produced by not only water injection and production but also the fluid of geothermal water, based on three-dimensional finite-element-method employing tetrahedron elements; the developed algorithm can simulate electrical potential responses by both point source and volume source. After verifying the developed algorithm, we assumed a simple geothermal reservoir model and analyzed SP responses caused by geothermal water injection and production. We are going to further analyze SP responses for geothermal water in the presence of water production and injection, considering temperature distribution and geothermal water flow in the following research.

• Journal of Digital Convergence
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• v.19 no.11
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• pp.315-325
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• 2021

This study conducted a questionnaire survey on 280 people who had experience of using mobile augmented reality-based online concerts. Using the SPSS 21.0 and AMOS 21.0 programs, the factors affecting the intention to reuse were investigated through statistical analysis(correlation analysis, path analysis, etc.). The main results are as follows. First of all, Presence and interactivity had a positive effect on flow, perceived ease of use and perceived usefulness. Flow had a positive effect on perceived ease of use and perceived usefulness. Perceived ease of use had a positive effect on perceived usefulness, and perceived usefulness had a direct positive effect on intention to reuse whereas perceived ease of use had an indirect effect on intention to reuse through perceived usefulness. In order to increase the intention to reuse of the mobile augmented reality-based online concert, it is necessary to prepare a plan to increase the level of presence, interactivity, and flow experienced by users. This study identified factors that affect the intention to reuse online concerts based on mobile augmented reality in an untact society. Therefore, it will be meaningful in that it presents the implications necessary to prepare a plan that can be efficiently accepted by consumers for the rapidly growing mobile augmented reality-based online concert.

• Journal of the Korean Chemical Society
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• v.44 no.4
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• pp.322-327
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• 2000

A new absorption spectrometric method for the determination of the Cr$_2O_7^{2-}$ ionin acidic media has been developed. The new method is based on the oxidation-reduction reaction of the HCr$O_4^-$ ion with H$_2$O$_2$forming a deep blue CrO(O$_2$) $_2$ andis coupled with a technique of flow injection analysis(FIA). The new method provides a linear calibration curve which accurately follows the Beer's law over a wide range of the analytical concentrations(2.0 ${\times}$ $10^{-6}$M~8.0 ${\times}$ $10^{-3}$M) of K$_2$Cr$_2$O$_2$. The sensitivity of the new method is approximately two times greater than the current method and the effects of the interfering substances such as V, Co, Ni, Fe, and Mn are almost negligible except Cu.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2121-2130
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• 2013

Based on the case study methods, the study analyzes that the countless UCC Cloud cloud is the niche creation by the lead users make process. This research show as follows. First, The Drama lovers and fan fiction writers are not only drama consumers but UCC creators/producers. By the process that the UCC and fan fiction is tailored to meet the needs of their users create fan fiction in fandom community, they create an entirely different niche from original drama. Second, the flow(drama consumption/evaluation, viewers needs/adaption, the user's creation/production) which community's creative users make sequentially coevolutes with the flow(drama information offer, intentionally supply/diffusion, derivatives production) of media companies. Third, the drama fandom community activities which is non-commercial activities form the drama ecosystem with a new paradigm, as well as form a virtuous cycle inked to the market continuously beyond fun, play, empathy.

• Environmental Engineering Research
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• v.14 no.1
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• pp.41-47
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• 2009

Column experiments were performed in this study to investigate humic acid adhesion to iron oxide-coated sand (ICS) under different experimental conditions including influent humic acid concentration, flow rate, solution pH, and ionic strength/composition. Breakthrough curves of humic acid were obtained by monitoring effluents, and then column capacity for humic acid adsorption ($C_cap$), total adsorption percent (R), and mass of humic acid adsorbed per unit mass of filter media ($q_a$) were quantified from these curves. Results showed that humic acid adhesion was about seven times higher in ICS than in quartz sand at given experimental conditions. This indicates that humic acid removal can be enhanced through the surface charge modification of quartz sand with iron oxide coating. The adhesion of humic acid in ICS was influenced by influent humic acid concentration. $C_cap$ and $q_a$ increased while R decreased with increasing influent humic acid concentration in ICS column. However, the influence of flow rate was not eminent in our experimental conditions. The humic acid adhesion was enhanced with increasing salt concentration of solution. $C_cap$, $q_a$ and R increased in ICS column with increasing salt concentration. On the adhesion of humic acid, the impact of CaCl2 was greater than that of NaCl. Also, the humic acid adhesion to ICS decreased with increasing solution pH. $C_cap$, $q_a$ and R decreased with increasing solution pH. This study demonstrates that humic acid concentration, salt concentration/composition, and solution pH should be controlled carefully in order to improve the ICS column performance for humic acid removal from water.

• Journal of Korean Neurosurgical Society
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• v.42 no.2
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• pp.118-124
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• 2007

Objective : Adipose tissue is derived from the embryonic mesoderm and contains a heterogenous stromal cell population. Authors have tried to verify the characteristics of stem cell of adipose derived stromal cells (ADSCs) and to investigate immunohistochemical findings after transplantation of ADSC into rat brain to evaluate survival, migration and differentiation of transplanted stromal cells. Methods : First ADSCs were isolated from human adipose tissue and induced adipose, osseous and neuronal differentiation under appropriate culture condition in vitro and examined phenotypes profile of human ADSCs in undifferentiated states using flow cytometry and immunohistochemical study. Human ADSCs were transplanted into the healthy rat brain to investigate survival, migration and differentiation after 4 weeks. Results : From human adipose tissue, adipose stem cells were harvested and subcultured for several times. The cultured ADSCs were differentiated into adipocytes, osteoctye and neuron-like cell under conditioned media. Flow cytometric analysis of undifferentiated ADSCs revealed that ADSCs were positive for CD29, CD44 and negative for CD34, CD45, CD117 and HLA-DR. Transplanted human ADSCs were found mainly in cortex adjacent to injection site and migrated from injection site at a distance of at least 1 mm along the cortex and corpus callosum. A few transplanted cells have differentiated into neuron and astrocyte. Conclusion : ADSCs were differentiated into multilineage cell lines through transdifferentiation. ADSCs were survived and migrated in xenograft without immunosuppression. Based on this data, ADSCs may be potential source of stem cells for many human disease including neurologic disorder.