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Effects of the Subgrid-Scale Orography Parameterization and High-Resolution Surface Data on the Simulated Wind Fields in the WRF Model under the Different Synoptic-Scale Environment (종관 환경 변화에 따른 아격자 산악모수화와 고해상도 지면 자료가 WRF 모델의 바람장 모의에 미치는 영향)

  • Lee, Hyeon-Ji;Kim, Ki-Byung;Lee, Junhong;Shin, Hyeyum Hailey;Chang, Eun-Chul;Lim, Jong-Myoung;Lim, Kyo-Sun Sunny
    • Atmosphere
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    • v.32 no.2
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    • pp.103-118
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    • 2022
  • This study evaluates the simulated meteorological fields with a particular focus on the low-level wind, which plays an important role in air pollutants dispersion, under the varying synoptic environment. Additionally, the effects of subgrid-scale orography parameterization and improved topography/land-use data on the simulated low-level wind is investigated. The WRF model version 4.1.3 is utilized to simulate two cases that were affected by different synoptic environments. One case from 2 to 6 April 2012 presents the substantial low-level wind speed over the Korean peninsula where the synoptic environment is characterized by the baroclinic instability. The other case from 14 to 18 April 2012 presents the relatively weak low-level wind speed and distinct diurnal cycle of low-level meteorological fields. The control simulations of both cases represent the systematic overestimation of the low-level wind speed. The positive bias for the case under the baroclinic instability is considerably alleviated by applying the subgrid-scale orography parameterization. However, the improvement of wind speed for the other case showing relatively weak low-level wind speed is not significant. Applying the high-resolution topography and land-use data also improves the simulated wind speed by reducing the positive bias. Our analysis shows that the increased roughness length in the high-resolution topography and land-use data is the key contributor that reduces the simulated wind speed. The simulated wind direction is also improved with the high-resolution data for both cases. Overall, our study indicates that wind forecasts can be improved through the application of the subgrid-scale orography parameterization and high-resolution topography/land-use data.

Run-out Modeling of Debris Flows in Mt. Umyeon using FLO-2D (FLO-2D 모형을 이용한 우면산 토석류 유동 수치모의)

  • Kim, Seungeun;Paik, Joongcheol;Kim, Kyung Suk
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.3
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    • pp.965-974
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    • 2013
  • Multiple debris flows occurred on July 27, 2012 in Mt. Umyeon, which resulted in 16 casualties and severe property demage. Accurate reproducing of the propagation and deposition of debris flow is essential for mitigating these disasters. Through applying FLO-2D model to these debris flows and comparing the results with field observations, we seek to evaluate the performance of the model and to analyse the rheological model parameters. Representative yield stress and dynamic viscosity back-calculated for the debris flows in the northern side of Mt. Umyeon are 1022 Pa and 652 Pas, respectively. Numerical results obtained using these parameters reveal that deposition areas of debris flows in Raemian and Shindong-A regions are well reproduced in 63-85% agreement with the field observations. However, the propagation velocities of the flows are significantly underestimated, which is attributable to the inherent limitations of the model that can't take the entrainment of bed material and surface water into account. The debris flow deposition computed in Hyeongchon region where the entrainment is not significant appears to be in very good agreement with the field observation. The sensitivity study of the numerical results on model parameters shows that both sediment volume concentration and roughness coefficient significantly affect the flow thickness and velocity, which underscores the importance of careful selection of these model parameters in FLO-2D modeling.

Machinability investigation and sustainability assessment in FDHT with coated ceramic tool

  • Panda, Asutosh;Das, Sudhansu Ranjan;Dhupal, Debabrata
    • Steel and Composite Structures
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    • v.34 no.5
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    • pp.681-698
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    • 2020
  • The paper addresses contribution to the modeling and optimization of major machinability parameters (cutting force, surface roughness, and tool wear) in finish dry hard turning (FDHT) for machinability evaluation of hardened AISI grade die steel D3 with PVD-TiN coated (Al2O3-TiCN) mixed ceramic tool insert. The turning trials are performed based on Taguchi's L18 orthogonal array design of experiments for the development of regression model as well as adequate model prediction by considering tool approach angle, nose radius, cutting speed, feed rate, and depth of cut as major machining parameters. The models or correlations are developed by employing multiple regression analysis (MRA). In addition, statistical technique (response surface methodology) followed by computational approaches (genetic algorithm and particle swarm optimization) have been employed for multiple response optimization. Thereafter, the effectiveness of proposed three (RSM, GA, PSO) optimization techniques are evaluated by confirmation test and subsequently the best optimization results have been used for estimation of energy consumption which includes savings of carbon footprint towards green machining and for tool life estimation followed by cost analysis to justify the economic feasibility of PVD-TiN coated Al2O3+TiCN mixed ceramic tool in FDHT operation. Finally, estimation of energy savings, economic analysis, and sustainability assessment are performed by employing carbon footprint analysis, Gilbert approach, and Pugh matrix, respectively. Novelty aspects, the present work: (i) contributes to practical industrial application of finish hard turning for the shaft and die makers to select the optimum cutting conditions in a range of hardness of 45-60 HRC, (ii) demonstrates the replacement of expensive, time-consuming conventional cylindrical grinding process and proposes the alternative of costlier CBN tool by utilizing ceramic tool in hard turning processes considering technological, economical and ecological aspects, which are helpful and efficient from industrial point of view, (iii) provides environment friendliness, cleaner production for machining of hardened steels, (iv) helps to improve the desirable machinability characteristics, and (v) serves as a knowledge for the development of a common language for sustainable manufacturing in both research field and industrial practice.

Converting Ieodo Ocean Research Station Wind Speed Observations to Reference Height Data for Real-Time Operational Use (이어도 해양과학기지 풍속 자료의 실시간 운용을 위한 기준 고도 변환 과정)

  • BYUN, DO-SEONG;KIM, HYOWON;LEE, JOOYOUNG;LEE, EUNIL;PARK, KYUNG-AE;WOO, HYE-JIN
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.23 no.4
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    • pp.153-178
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    • 2018
  • Most operational uses of wind speed data require measurements at, or estimates generated for, the reference height of 10 m above mean sea level (AMSL). On the Ieodo Ocean Research Station (IORS), wind speed is measured by instruments installed on the lighthouse tower of the roof deck at 42.3 m AMSL. This preliminary study indicates how these data can best be converted into synthetic 10 m wind speed data for operational uses via the Korea Hydrographic and Oceanographic Agency (KHOA) website. We tested three well-known conventional empirical neutral wind profile formulas (a power law (PL); a drag coefficient based logarithmic law (DCLL); and a roughness height based logarithmic law (RHLL)), and compared their results to those generated using a well-known, highly tested and validated logarithmic model (LMS) with a stability function (ψν), to assess the potential use of each method for accurately synthesizing reference level wind speeds. From these experiments, we conclude that the reliable LMS technique and the RHLL technique are both useful for generating reference wind speed data from IORS observations, since these methods produced very similar results: comparisons between the RHLL and the LMS results showed relatively small bias values (0.001ms1) and Root Mean Square Deviations (RMSD, 0.122ms1). We also compared the synthetic wind speed data generated using each of the four neutral wind profile formulas under examination with Advanced SCATterometer (ASCAT) data. Comparisons revealed that the 'LMS without ψν produced the best results, with only 0.191ms1 of bias and 1.111ms1 of RMSD. As well as comparing these four different approaches, we also explored potential refinements that could be applied within or through each approach. Firstly, we tested the effect of tidal variations in sea level height on wind speed calculations, through comparison of results generated with and without the adjustment of sea level heights for tidal effects. Tidal adjustment of the sea levels used in reference wind speed calculations resulted in remarkably small bias (<0.0001ms1) and RMSD (<0.012ms1) values when compared to calculations performed without adjustment, indicating that this tidal effect can be ignored for the purposes of IORS reference wind speed estimates. We also estimated surface roughness heights (z0) based on RHLL and LMS calculations in order to explore the best parameterization of this factor, with results leading to our recommendation of a new z0 parameterization derived from observed wind speed data. Lastly, we suggest the necessity of including a suitable, experimentally derived, surface drag coefficient and z0 formulas within conventional wind profile formulas for situations characterized by strong wind (33ms1) conditions, since without this inclusion the wind adjustment approaches used in this study are only optimal for wind speeds 25ms1.

Biphasic Release Characteristics of Dual Drug-loaded Alginate Beads

  • Lee, Beom-Jin;Cui, Jing-Hao;Kim, Tae-Wan;Heo, Min-Young;Kim, Chong-Kook
    • Archives of Pharmacal Research
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    • v.21 no.6
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    • pp.645-650
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    • 1998
  • The dual drug-loaded alginate beads simultaneously containing drug in inner and outer layers were prepared by dropping plain (single-layered) alginate beads into CaCl2 solution. The release characteristics were evaluated in simulated gastric fluid for 2 h followed by intestinal fluids thereafter for 12 h. The surface morphology and cross section of dual drug-loaded alginate beads was also investigated using scanning electron microscope (SEM). The poorlv water-soluble ibuprofen was chosen as a model drug. The surface of single-layered and dual drug-loaded alginate beads showed very crude and roughness, showing aggregated particles, surface cracks and rough crystals. The thickness of dual drug-loaded alginate beads surrounded by outer layer was ranged from about 57 to 329mcm. The distinct chasm between inner and outer layers was also observed. In case of single-layered alginate bead, the drug was not released in gastric fluid but was largely released in intestinal fluid. However, the release rate decreased as the reinforcing Eudragit® polymer contents increased. When the plasticizers were added into polymer, the release rate largely decreased. The release rate of dual drug-loaded alginate beads was stable in gastric fluid for 2 h but largely increased when switched in intestinal fluid. The drug linearly released for 4 h followed by another linear release thereafter, showing a distinct biphasic release characteristics. There was a difference in the release profiles between single-layered and dual drug-loaded alginate beads due to their structural shape. However, this biphasic release profiles were modified by varying formulation compositions of inner and outer layer of alginate beads. The release rate of dual drug-loaded alginate beads slightly decreased when the outer layer was reinforced with Eudragit® RS1OO polymers. In case of dual drug-loaded alginate beads with polymer-reinforced outer layer only, the initial amount of druc released was low but the initial release rate (slope) was higher due to more swellable inner cores when compared to polymer-reinforced inner cores. The current dual drug-loaded alginate beads may be used to deliver the drugs in a time dependent manner.

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Impacts of the High Resolution Land Cover Data on the 1989 East-Asian Summer Monsoon Circulation in a Regional Climate Model (지역기후모델에서 고해상도 지면피복이 1989년 동아시아 여름몬순 순환에 미치는 영향)

  • Suh, Myoung-Seok;Lee, Dong-Kyou
    • Atmosphere
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    • v.15 no.2
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    • pp.75-90
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    • 2005
  • This study examines the impacts of land cover changes on the East Asia summer monsoon with the National Center for Atmospheric Research Regional Climate Model (NCAR RegCM2), coupled with Biosphere Atmosphere Transfer Scheme (BATS). To assess the goals, two types of land cover maps were used in the simulation of summer climate. One type was NCAR land cover map (CTL) and the other was current land cover map derived from satellite data (land cover: LCV). Warm and cold surface temperature biases of 13C occurred over central China and Mongolia in CTL. The model produced excessive precipitation over northern land area but less over southern ocean of the model domain. Changes of biophysical parameters, such as albedo, minimum stomatal resistance and roughness length, due to the land cover changes resulted in the alteration of land-atmosphere interactions. Latent heat flux and wind speed in LCV increased noticeably over central China where deciduous broad leaf trees have been replaced by mixed farm and irrigated crop. As a result, the systematic warm biases over central China were greatly reduced in LCV. Strong cooling of central China decreased pressure gradient between East Asian continent and Pacific Ocean. The decreased pressure gradient suppressed the northward transport of moisture from south China and South China Sea. These changes reduced not only the excessive precipitation over north China and Mongolia but also less precipitation over south China. However, the land cover changes increased the precipitation over the Korean Peninsula and the Japan Islands, especially in July and August.

Distribution of Vertical Earth Pressure due to Surcharge Loads Acting on Cantilever Retaining Wall Near Rigid Slope (강성경사면에 인접한 역T형 옹벽에 작용하는 상재하중에 의한 연직토압분포)

  • 유남재;이명욱;박병수;홍영길
    • Journal of the Korean Geotechnical Society
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    • v.18 no.6
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    • pp.141-152
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    • 2002
  • This paper is the result of the experimental and numerical research on the distribution of vertical earth pressure due to surcharge loads acting on cantilever retaining wall close to a rigid slope with a stiff angle. Centrifuge model experiments were performed with changing the roughness of adjacent slope to the wall, distance between the wall and the slope and gravitational levels. Vertical earth pressures were measured by earth cells embedded in the backfill of the wall. Test results of vertical earth pressures due to surcharge loads were compared with theoretical estimations by using two different methods of limit equilibrium and the numerical analysis. For limit equilibrium methods, the modified silo and the wedge theories, proposed by Chung(1993, 1997), were used to analyze test results. Based on those modified theories, the particular solution with the boundary condition of surcharge loads on the surface of backfill was obtained to find the vertical stress distributions acting on the backfill. FLAC with the hyperbolic constitutive model was also used for the numerical estimation. As a result of comparison of test results with theoretical and numerical estimations, distribution of vertical earth pressures obtained from centrifuge model tests is generally in good agreement with numerical estmated values by using FLAC whereas the wedge theory shows values close to test results in case the distance between the wall and the slope is narrow.

Geometric and mechanical properties evaluation of scaffolds for bone tissue applications designing by a reaction-diffusion models and manufactured with a material jetting system

  • Velasco, Marco A.;Lancheros, Yadira;Garzon-Alvarado, Diego A.
    • Journal of Computational Design and Engineering
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    • v.3 no.4
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    • pp.385-397
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    • 2016
  • Scaffolds are essential in bone tissue engineering, as they provide support to cells and growth factors necessary to regenerate tissue. In addition, they meet the mechanical function of the bone while it regenerates. Currently, the multiple methods for designing and manufacturing scaffolds are based on regular structures from a unit cell that repeats in a given domain. However, these methods do not resemble the actual structure of the trabecular bone which may work against osseous tissue regeneration. To explore the design of porous structures with similar mechanical properties to native bone, a geometric generation scheme from a reaction-diffusion model and its manufacturing via a material jetting system is proposed. This article presents the methodology used, the geometric characteristics and the modulus of elasticity of the scaffolds designed and manufactured. The method proposed shows its potential to generate structures that allow to control the basic scaffold properties for bone tissue engineering such as the width of the channels and porosity. The mechanical properties of our scaffolds are similar to trabecular tissue present in vertebrae and tibia bones. Tests on the manufactured scaffolds show that it is necessary to consider the orientation of the object relative to the printing system because the channel geometry, mechanical properties and roughness are heavily influenced by the position of the surface analyzed with respect to the printing axis. A possible line for future work may be the establishment of a set of guidelines to consider the effects of manufacturing processes in designing stages.

Electrical Properties and Microstructures in Ti Films Deposited by TFT dc Sputtering

  • Han, Chang-Suk;Jeon, Seung-Jin
    • Korean Journal of Materials Research
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    • v.26 no.4
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    • pp.207-211
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    • 2016
  • Ti films were deposited on glass substrates under various preparation conditions in a chamber of two-facing-target type dc sputtering; after deposition, the electric resistivity values were measured using a conventional four-probe method. Crystallographic orientations and microstructures, including the texture and columnar structure, were also investigated for the Ti films. The morphological features, including the columnar structures and surface roughness, are well explained on the basis of Thornton's zone model. The electric resistivity and the thermal coefficient of the resistivity vary with the sputtering gas pressure. The minimum value of resistivity was around 0.4 Pa for both the 0.5μm and 3.0μm thick films; the apparent tendencies are almost the same for the two films, with a small difference in resistivity because of the different film thicknesses. The films deposited at high gas pressures show higher resistivities. The maximum of TCR is also around 0.4 Pa, which is the same as that obtained from the relationship between the resistivity and the gas pressure. The lattice spacing also decreases with increasing sputtering gas pressure for both the 0.5μm and 3.0μm thick films. Because they are strongly related to the sputtering gas pressures for Ti films that have a crystallographic anisotropy that is different from cubic symmetry, these changes are well explained on the basis of the film microstructures. It is shown that resistivity measurement can serve as a promising monitor for microstructures in sputtered Ti films.

Electron Mobility Model in Strained Si Inversion Layer (응력변형을 겪는 Si 반전층에서 전자 이동도 모델)

  • Park Il-Soo;Won Taeyoung
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.42 no.3 s.333
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    • pp.9-16
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    • 2005
  • The mobility in strained Si inversion layer on Si1xGex is calculated considering a quantum effect(subband energy and wavefunction) in inversion layer and relaxation time approximation. The quantum effect in inversion layer is obtained by using self-consistent calculation of Schr¨odinger and Poisson equations. For the relaxation time, intravalley and intervalley scatterings are considered. The result shows that the reason for the enhancement in mobility as Ge mole fraction increases is that the electron mobility in 2-폴드 valleys is about 3 times higher than that of 4-폴드 valleys and most electrons are located in 2-폴드 valleys as Ge mole fraction increases. Meanwhile, for the phonon-limited mobility the fitting to experimental data, Coulomb and surface roughness mobilities are included in total mobility, Deformation potentials are selected for the calculated effective field, temperature, and Ge mole fraction dependent mobilities to be fitted to experimental data, and then upgraded data can be obtained by considering nonparabolicity in Si band structure.