• Wind and Structures
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• v.29 no.2
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• pp.111-127
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• 2019

The tapered and set-back type of unconventional designs have been used earlier in many buildings. These shapes are aerodynamically efficient and offer a significant amount of damping against wind-induced forces and excitations. Various studies have been conducted on these shapes earlier. The present study adopts a hybrid approach of turbulence modelling i.e., Detached-eddy Simulation (DES) to investigate the effect of height modified tapered and set-back buildings on aerodynamic forces and their sensitivity towards pressure. The modifications in the flow field around the building models are also investigated and discussed. Three tapering ratios (T.R.=(Bottom width- Top width)/Height) i.e., 5%, 10%, 15% are considered for tapered and set-back buildings. The results show that, mean and RMS along-wind and across-wind forces are reduced significantly for the aerodynamically modified buildings. The extent of reduction in the forces increases as the taper ratio is increased, however, the set-back modifications are more worthwhile than tapered showing greater reduction in the forces. The pressure distribution on the surfaces of the buildings are analyzed and in the last section, the influence of the flow field on the forces is discussed.

• Wind and Structures
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• v.13 no.1
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• pp.21-36
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• 2010

A new full scale testing apparatus generically named the Wall of Wind (WoW) has been built by the researchers at the International Hurricane Research Center (IHRC) at Florida International University (FIU). WoW is capable of testing single story building models subjected up to category 3 hurricane wind speeds. Depending on the relative model and WoW wind field sizes, testing may entail blockage issues. In addition, the proximity of the test building to the wind simulator may also affect the aerodynamic data. This study focuses on the Computational Fluid Dynamics (CFD) assessment of the effects on the quality of the aerodynamic data of (i) blockage due to model buildings of various sizes and (ii) wind simulator proximity for various distances between the wind simulator and the test building. The test buildings were assumed to have simple parallelepiped shapes. The computer simulations were performed under both finite WoW wind-field conditions and in an extended Atmospheric Boundary Layer (ABL) wind flow. Mean pressure coefficients for the roof and the windward and leeward walls served as measures of the blockage and wind simulator proximity effects. The study uses the commercial software FLUENT with Reynolds Averaged Navier Stokes equations and a Renormalization Group (RNG) k-${\varepsilon}$ turbulence model. The results indicated that for larger size test specimens (i.e. for cases where the height of test specimen is larger than one third of the wind field height) blockage correction may become necessary. The test specimen should also be placed at a distance greater than twice the height of the test specimen from the fans to reduce proximity effect.

• JSTS:Journal of Semiconductor Technology and Science
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• v.10 no.3
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• pp.203-212
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• 2010

In this paper, we present an analytical model for the first eigen energy level ($E_0$) of the carriers in the inversion layer in present generation MOSFETs, having ultrathin gate oxides and high substrate doping concentrations. Commonly used approaches to evaluate $E_0$ make either or both of the following two assumptions: one is that the barrier height at the oxide-semiconductor interface is infinite (with the consequence that the wave function at this interface is forced to zero), while the other is the triangular potential well approximation within the semiconductor (resulting in a constant electric field throughout the semiconductor, equal to the surface electric field). Obviously, both these assumptions are wrong, however, in order to correctly account for these two effects, one needs to solve Schrodinger and Poisson equations simultaneously, with the approach turning numerical and computationally intensive. In this work, we have derived a closed-form analytical expression for $E_0$, with due considerations for both the assumptions mentioned above. In order to account for the finite barrier height at the oxide-semiconductor interface, we have used the asymptotic approximations of the Airy function integrals to find the wave functions at the oxide and the semiconductor. Then, by applying the boundary condition at the oxide-semiconductor interface, we developed the model for $E_0$. With regard to the second assumption, we proposed the inclusion of a fitting parameter in the wellknown effective electric field model. The results matched very well with those obtained from Li's model. Another unique contribution of this work is to explicitly account for the finite oxide-semiconductor barrier height, which none of the reported works considered.

• Korean Journal of Soil Science and Fertilizer
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• v.8 no.1
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• pp.37-43
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• 1975

Effect of inoculation trial on plant height and dry matter yield of seven alfalfa varieties (Medicago sativa L. var. Washoe, Ranger, Lahontan, Narragensett, Atlantic, Vernal, and Moapa 69) which are considered to be well adapted in these areas were conducted during 1973-1974 in a relatively poor soil at the field station in Kyung Hee University. Root nodule bacteria: Rhizobium meliloti (Noculator Northrup Kings Co. Ltd) was applied at a rate to provide 6 oz/30l of alfalfa seeds. Seven varieties were seeded in pots on May 31, 1973 and in second year, they were transplanted in field. 1. Dry matter yield and plant height of all inoculation plots were significantly greater than those of the no inoculation plots in all varieties. 2. In the 1973, dry matter yield of inoculation plot a in pot experiment was in the order of Moapa 69> Vernal> Lahontan> Washoe> Atlantic> Narragensett> Ranger. 3. There was no difference in dry matter yield between with and without-inoculation after transplanted in a field in the second year (1974). Total dry matter yield of varieties was in the order of Washoe> Lahontan> Moapa 69> Ranger> Narragensett> Vernal> Atlantic.

• Wind and Structures
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• v.19 no.3
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• pp.249-270
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• 2014

Through comparing the mean wind profiles observed overland during the passages of four typhoons, and the gradient wind speeds calculated based on the sea level pressure data provided by a numerical model, the present paper discusses, (a) whether the gradient balance is a valid assumption to estimate the wind speed in the height range of 1250 m ~ 1750 m, which is defined as the upper-level mean wind speed, in a tropical cyclone over land, and (b) if the super-gradient feature is systematically observed below the height of 1500 m in the tropical cyclone wind field over land. It has been found that, (i) the gradient balance is a valid assumption to estimate the mean upper-level wind speed in tropical cyclones in the radial range from the radius to the maximum wind (RMW) to three times the RMW, (ii) the super-gradient flow dominates the wind field in the tropical cyclone boundary layer inside the RMW and is frequently observed in the radial range from the RMW to twice the RMW, (iii) the gradient wind speed calculated based on the post-landfall sea level pressure data underestimates the overall wind strength at an island site inside the RMW, and (iv) the unsynchronized decay of the pressure and wind fields in the tropical cyclone might be the reason for the underestimation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2260-2266
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• 2009

In this paper, the problem of electromagnetic coupling between a slit fed by a flanged parallel-plate waveguide (FPPW) and a nearby conducting strip parallel to the slit is studied as a simplified problem for a near-field scanning microscopy (NSM). The characteristics of the FPPW are investigated from the results for the variations of the equivalent slit admittance, the reactive powers near the slit inside and outside the FPPW, the magnitude and phase of the voltage reflection coefficient of the TEM wave. The performance of the proposed apparatus as an NSM is tested by examining the effects of various geometrical parameters such as guide height, slit width, strip width, distance between slit and strip, and the ratio of slit width to guide height on the magnitude and phase of the voltage reflection coefficient of the TEM wave. From the results for the voltage reflection coefficient against the strip offset from the slit, it is found that a slit in the FPPW with smaller guide height gives higher scanning resolution and the phase variation is more sensitive than the magnitude variation.

• Journal of the Korean Society of Combustion
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• v.22 no.3
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• pp.17-22
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• 2017

An experimental study has been conducted to elucidate the effect of AC electric field on behaviors of laminar lifted flame in nitrogen-diluted methane coflow-jets. Our concerns are focued on the regime to show a decrease in liftoff height, $H_L$ with increasing nozzle exit velocity, $U_O$ (hereafter, $decreasing-H_L$). The $H_L$ with $U_O$ near flame extinction were measured by varying the applied AC voltage, $V_{AC}$ and frequency, $f_{AC}$ in a single electrode configuration. The behavior of $H_L$ with a functional dependency of $V_{AC}$ and $f_{AC}$ was categorized into two regime : (I) $H_L$ decreased for nozzle diameter, D = 1.0 mm, and (II) $H_L$ increased in the increase of $f_{AC}$ for a fixed $V_{AC}$ in a D = 4.0, 8.4 mm. The lifted flames in $decreasing-H_L$ region was unstable in high voltage regimes while the $H_L$ showed a decreasing tendency with $U_O$ except them. Such behaviors in $H_L$ were also characterized by functional dependencies of related physical parameters such as $V_{AC}$, $f_{AC}$, $U_O$, fuel mole fraction ($X_{F.O}$) and D.

• Journal of The Korean Society of Grassland and Forage Science
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• v.9 no.2
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• pp.88-95
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• 1989

This experiment 'was conducted to investigate the grazing cattle's palatability by the method of grazing time on the pasture dominated orchardgrass and on the pasture dominated perennial ryegrass from June to October, 1987. The experiment was carried out on the experimental field at Livestock Ex- Experiment Station. The results are summarized as follows: 1. In summer, the grazing time on the pasture dominated orchardgrass increased in 49.7 min, 57.4 min, 102 min, 118.7 min, respectively as sward height decreased in 50 cm, 45 cm, 35 cm, 23 cm, respectively and their correlation coefficiet was -0.9722*(P <0.05). 2. In autumn, the grazing time on the pasture dominated perennial ryegrass decreased in 182 min, 98.5 min, 49.4 min, 31.9 min, respectively as sward height decreased in 43 cm, 34 cm, 25 cm, 18 cm, respectively and their correlation coefficient was 0.9684*. (P <0.05). 3. Grazing time increased as sward height increased on the pasture dominated perennial ryegrass because the composition rate of orchardgrass and red clover which were palatability on the plot of the high sward height.was many. It was suggested that the factor that could be first related to palatability on mixture pasture was the factor of species than the factor of sward height. 4. When the eating rate on the plot of the low sward height was over 55% as the grazing day went by, it gradually decreased because the eating rate on it was high but the fresh yield was low. After all it seemed that it affected palatability because forage availability on the plot of the low sward height was degenerating.

• Bulletin of the Korean Chemical Society
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• v.27 no.9
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• pp.1433-1438
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• 2006

An AsFlFFF channel was designed and built, and then tested for analysis of pullulans and proteins. Pullulans and proteins having various nominal molecular weights were injected at various conditions of the cross-flow rate ($F_c$) and the channel-out flow rate ($F_{out}$). The retention (measured by the retention ratio R) and the zone broadening (measured by the plate height H) were measured, and then compared with theory. When the incoming flow rate, $f_{in}$ (and thus $F_{out}$) was varied with $F_c$ fixed at 2.5 mL/min, the plate height measured for the pullulan with nominal molecular weight (M) of about 100,000 showed the trend expected by the longitudinal diffusion theory (H decreases with increasing flow rate). In contrast, when $F_{out}$ was varied with the flow rate ratio, $F_c/F_{out}$, fixed constant at 5, the plate height measured for the same sample showed the trend expected from the non-equilibrium theory (H increases with increasing flow rate). Calibration plots (log D vs. log M) obtained with pullulans and proteins were not coincide, probably due to the difference in molecular conformation, suggesting the analysis of pullulans and proteins using AsFlFFF requires independent calibration. It was found that the linearity of the protein-calibration plot was improved by using a buffer solution as the carrier.

• Journal of the Korean Institute of Landscape Architecture
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• v.19 no.2
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• pp.65-74
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• 1991

The purpose of this study was to find the basic application of Disporum genus in landscape-arc-hitectual space. Environment of native site (Daeducksan, Piseulsan) and growth characteristics of experiment plot were investigated and analyzed in this study. The results of this study were as follows; 1. In the case of environment of native site, the relative light intensity was about 10% and distribution of species were primarily north slope. Gradient of Daeducksan and Piseulsan were 10$^{\circ}$, 18$^{\circ}$ Soil textures was Lic both and field capacity of Daeducksan and Piseulsan were 69%, 73.5%. The soil pH of Daeducksan and Piseulsan were 6.1 and 5.8. The both content of organic matter and C.E.C. were high markedly. The P2O5 content of Daeducksan showed high but total nitrogen showed nearly the same level when comparing with the common dry field condition. 2. In tree layer, Daeducksan composed of broadleaved forest of 80% involving Quercus variabilis, and Piseulsan composed of coniferous forest of 80% involving Pinus densiflora on the other hand. Daeducksan, therefore, was more appearance species than Piseulsan in herbaceous layer. 3. Result in ANOVA Test, significance followed with light intensity was recognized in plant height, leaf width, leaf length, leaf thick and No. of leaf, while in the case of soil was not. Plant height was longest in 1% and leaf width, leaf length was largest in 25%. Therefore ornamental value of leaf was the very best in 25%. 4. Result in correlation coefficient analysis, plant height was correlated leaf width, leaf length. The longer plant height, the smaller leaf width, leaf length. In relative light intensity of 1%, flower was hardly expected because of the more shade, the less flower. Disporum smilacinum is expected great use as ground covers in the shades of tall-building or hdavy woods.