• The Journal of Engineering Geology
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• v.18 no.4
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• pp.405-414
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• 2008

When we evaluate slope stability, we regard the slope homogeneous and evaluate slope stability at the most dangerous portion of slope. However, since conditions and properties of rock mass/soil are different from one location to another within a single slope, slope stability evaluated by current concept can not represent slope correctly. This also result in over-reinforcement at the portion where reinforcement is not necessary. In order to solve these problems, we suggest a cell unit evaluation method in which we apply small rectangular cells in a slope and regard each cell as a single slope. In this method, slopes are classified into soil slope and rock slope depending on materials. Strength of rock, volumetric joint count, spacing of joints, condition of joints, ground water condition and so on are examined and SMR and condition index values are calculated. Finally, all data and results are presented as contour maps. We apply the cell unit evaluation method into 3 cut slopes. SMR values estimated by the new method are larger than those by current concept at most portions of slope, indicating that the new method suggested by this research represent slope stability more correctly than methods which were used. This method will prevent over-reinforcement at the portion of slope where reinforcement is not necessary.

• Journal of Korea Water Resources Association
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• v.52 no.1
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• pp.51-60
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• 2019

The major purpose of this study is to construct an in-situ soil moisture verification network employing Frequency Domain Reflectometry (FDR) sensors for Cosmic-ray soil moisture observation system operation as well as long-term field-scale soil moisture monitoring. The test bed of Cosmic-ray and FDR verification network system was established at the Sulma Catchment, in connection with the existing instrumentations for integrated data provision of various hydrologic variables. This test bed includes one Cosmic-ray Neutron Probe (CRNP) and ten FDR stations with four different measurement depths (10 cm, 20 cm, 30 cm, and 40 cm) at each station, and has been operating since July 2018. Furthermore, to assess the reliability of the in-situ verification network, the volumetric water content data measured by FDR sensors were compared to those calculated through the core sampling method. The evaluation results of FDR sensors- measured soil moisture against sampling method during the study period indicated a reasonable agreement, with average values of $bias=-0.03m^3/m^3$ and RMSE $0.03m^3/m^3$, revealing that this FDR network is adequate to provide long-term reliable field-scale soil moisture monitoring at Sulmacheon basin. In addition, soil moisture time series observed at all FDR stations during the study period generally respond well to the rainfall events; and at some locations, the characteristics of rainfall water intercepted by canopy were also identified. The Temporal Stability Analysis (TSA) was performed for all FDR stations located within the CRNP footprint at each measurement depth to determine the representative locations for field-average soil moisture at different soil profiles of the verification network. The TSA results showed that superior performances were obtained at FDR 5 for 10 cm depth, FDR 8 for 20 cm depth, FDR2 for 30 cm depth, and FDR1 for 40 cm depth, respectively; demonstrating that those aforementioned stations can be regarded as temporal stable locations to represent field mean soil moisture measurements at their corresponding measurement depths. Although the limit on study duration has been presented, the analysis results of this study can provide useful knowledge on soil moisture variability and stability at the test bed, as well as supporting the utilization of the Cosmic-ray observation system for long-term field-scale soil moisture monitoring.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.740-745
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• 2015

This study investigated the effect of different collection methods on physical properties of pectin hydrogels in microfluidic synthetic approach. The pectin hydrogels were simply produced by the incorporation of calcium ions dissolved in continuous mineral oil. Then, different collection methods, pipetting, tubing, and settling, for harvesting pectin hydrogels were applied. The settling method showed most uniform and monodispersed hydrogels. In the case of settling, a coefficient of variation was 3.46 which was lower than pipetting method (18.60) and tubing method (14.76). Under the settling method, we could control the size of hydrogels, ranging from $30{\mu}m$ to $180{\mu}m$, by simple manipulation of the viscosity of pectin and volumetric flow rate of dispersed and continuous phase. Finally, according to the characteristics of simple encapsulation of biological materials, we envision that the pectin hydrogels can be applied to drug delivery, food, and biocompatible materials.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.953-960
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• 2019

The Miller cycle is a diesel engine that has been developed in recent years that it can reduce NOx and improve fuel consumption by reducing the compression ratio through intake valve closing (IVC) time control. The Miller cycle can be divided into the early Miller method of closing the intake valve before the bottom dead center (BDC) and the late Miller method of closing the intake valve after the BDC. At low speeds, the late Miller method is advantageous as it can increase the volumetric efficiency; while at medium and high speeds, the early Miller method is advantageous because of the high internal temperature reduction effect due to the expansion of the intake air during the piston lowering from IVC to BDC. Therefore, in consideration of the ef ects of the early and late Miller methods, it is necessary to adopt the most suitable Miller method for the operating conditions. In this study, a two-stage turbo charge system was applied to four-stroke engines and the process of enhancing the Miller effect through a reduction of the intake and exhaust valve overlap as well as the valve change adjustment mechanism were considered. As a result, the ef ects of fuel consumption and Tmax reduction were confirmed by adopting the Miller cycle with a two-stage supercharge, a reduction of valve overlap, and an increase of suction valve lift.

• International Journal of Highway Engineering
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• v.8 no.1 s.27
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• pp.15-23
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• 2006

Criteria of the current asphalt mix design, Marshall method, includes the stability and flow which are not related with field performance of HMA mixture, together with the air void, Void filled with asphalt (VFA) and/or Void of mineral Aggregate(VMA). In addition, the limits of stability and flow are satisfied in most cases, the Optimum asphalt content (OAC) is determined based on volumetric properties, such as the air void and/or VFA and/of VMA. Therefore, many researchers have sought mechanistic properties which can replace the stability and flow, making the designed mixture having potential for better field performance. This study initiated to develope a mix design by introducing two performance-related mechanistic properties, the deformation strengh and fracture energy, in place of the stability and flow of the Marshall method. The deformation strength $(S_D)$ from the Kim Test has a high correlation with rutting property and the fracture energy(FE) from the indirect tensile test represents the fatigue cracking property of asphalt mixture. Four types of asphalt mixture were prepared for examining possibility of using the suggested mix design method in comparison with current methods. The results showed that mechanical properties were reflected in determination of OAC with this suggested mix design, unlike the existing Marshall method.

• Journal of Biomedical Engineering Research
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• v.23 no.5
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• pp.351-364
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• 2002

Conventional 3D ultrasound imaging using mechanical ID arrays suffers from poor elevation resolution due to the limited depth-of-focus (DOF). On the other hand, 3D imaging systems using 2D phased arrays have a large number of active channels and hence require a very expensive and bulky beamforming hardware. To overcome these limitations, a new real-time volumetric imaging method using curved 2-D arrays is presented, in which a small subaperture, consisting of 256 elements, moves across the array surface to scan a volume of interest. For this purpose, a 2-D curved array is designed which consists of 90$\times$46 elements with 1.5λ inter-element spacing and has the same view angles along both the lateral and elevation directions as those of a commercial mechanical 1-D array. In the proposed method, transmit and receive subapertures are constructed by cutting the four corners of a rectangular aperture to obtain a required image qualify with a small number of active channels. In addition the receive subaperture size is increased by using a sparse array scheme that uses every other elements in both directions. To suppress the grating lobes elevated due to the increase in clement spacing, fold-over array scheme is adopted in transmit, which doubles the effective size of a transmit aperture in each direction. Computer simulation results show that the proposed method can provide almost the same and greatly improved resolutions in the lateral and elevation directions, respectively compared with the conventional 3D imaging with a mechanical 1-D array.

• Journal of Korea Multimedia Society
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• v.10 no.7
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• pp.846-855
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• 2007

Significant feature extraction in cancer cell image analysis is an important process for grading cell carcinoma. In this study, we propose a method for 3D quantitative analysis of cell nuclei based upon digital image cytometry. First, we acquired volumetric renal cell carcinoma data for each grade using confocal laser scanning microscopy and segmented cell nuclei employing color features based upon a supervised teaming scheme. For 3D visualization, we used a contour-based method for surface rendering and a 3D texture mapping method for volume rendering. We then defined and extracted the 3D morphological features of cell nuclei. To evaluate what quantitative features of 3D analysis could contribute to diagnostic information, we analyzed the statistical significance of the extracted 3D features in each grade using an analysis of variance (ANOVA). Finally, we compared the 2D with the 3D features of cell nuclei and analyzed the correlations between them. We found statistically significant correlations between nuclear grade and 3D morphological features. The proposed method has potential for use as fundamental research in developing a new nuclear grading system for accurate diagnosis and prediction of prognosis.

• Journal of the Korean Geotechnical Society
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• v.20 no.1
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• pp.109-120
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• 2004

There has been outstanding research on the soil-water characteristic curves of unsaturated soils over the past several decades. Unfortunately, unsaturated soil mechanics has not been considered as an important factor in Korea. In this paper, laboratory test and numerical analysis(SoilVision Professional ver 3.04) were performed to investigate the prediction method of soil-water characteristic curve and unsaturated permeability coefficient in reclaimed ground. The pressure cell, desiccator, and tensiometor tests were conducted on three types of reclaimed soils(dredged soil, sand, weathered granite soil). Numerical analysis was executed to compare the results with the laboratory test results and also compared with the results of each prediction method. Based on the laboratory test, three different types of soils have shown different soil-water characteristic curves. The hysteresis fir these soils is clearly defined. As a result of numerical analysis, Fredlund & Xing's method and Fredlund & Wilson's model proved to worke out well for reclaimed ground soils in Korea. Also, predicting method based on the soil-water characteristic curves from the particle-size distributions is flirty reliable for estimating unsaturated permeability coefficient.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.12
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• pp.777-784
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• 2016

All-vanadium redox flow batteries (VRFBs) are used as energy storage systems for multiple intermittent power sources. The performance of the VRFBs depends on the materials and operating conditions. Hence, performance characterization is of great importance in the development of the VRFBs. This paper proposes a method for determining the maximum current density based on stoichiometric ratios. A laboratory-scaled VRFB with a projected electrode area of $25cm^2$ is electrically charged when the state of the charge has begun from 0.6. The operating conditions, such as current density and volumetric flow rate are important in the test, and the maximum current density is influenced by the mass transfer coefficient. The results show that increasing the electrolyte flow rate from 5 mL/min to 60 mL/min enhances the maximum current density up to $520mA/cm^2$.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.317-321
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• 1998

X-type Zeolite for the gas separation was prepared by hydrothermal methods and the zeolite was ion-exchanged with KCl, $CaCl_2$, $YCl_3$ and $InCl_3$ in order to investigate the effect of ions on the properties of molecular sieves. Adsorption isotherms of $CO_2$ on ion exchanged X-type zeolites and those of $O_2$ and $N_2$ on the synthesized zeolite were measured at $25^{\circ}C$ using a volumetric method and the adsorption characteristics were compared with each other. Model parameters for the Langmuir, Freundlich and Toth equations were regressed for the measured adsorption isotherms. In order to confirm the applicability of the zeolite on $CO_2-PSA$ processes, breakthrough tests and process simulation were undertaken. It was found that the X-type zeolite could be a potential adsorbent in recovering $CO_2$ from flue gas.