• ETRI Journal
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• v.29 no.6
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• pp.838-840
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• 2007

The relation between the allowed range of variation of polarization controller wave-plates angles and the respective polarization scattering properties is investigated. It is demonstrated that a nearly uniform polarization scattering over the Poincare sphere is obtained using a concatenation of three polarization controllers with angles randomly changed between $-{\pi}$/4 and ${\pi}$/4. It is also shown that an improvement of the scattering properties is obtained if the configuration angles are allowed to change between $-{\pi}$/2 and ${\pi}$/2.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.859-864
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• 2015

This paper analyzes the impact of Plug-in Electric vehicles(PEVs) on power demand and voltage change when PEVs are connected to the domestic distribution system. Specifically, it assesses PEVs charging load by charging method in accordance with PEVs penetration scenarios, its percentage of total load, and voltage range under load conditions. Concretely, we develop EMTDC modelling to perform a voltage distribution analysis when the PEVs charging system by their charging scenario was connected to the distribution system under the load condition. Furthermore we present evaluation algorithm to determine whether it is possible to adjust it such that it is in the allowed range by applying ULTC when the voltage change rate by PEVs charging scenario exceed its allowed range. Also, detailed analysis of the impact of PEVs on power distribution system was carried out by calculating existing electric power load and additional PEVs charge load by each scenario on new-town in Korea to estimate total load increases, and also by interpreting the subsequent voltage range for system circuits and demonstrating conditions for countermeasures. It was concluded that total loads including PEVs charging load on new-town distribution system in Korea by PEVs penetration scenario increase significantly, and the voltage range when considering ULTC, is allowable in terms of voltage tolerance range up to a PEVs penetration of 20% by scenario. Finally, we propose the charging capacity of PEVs that can delay the reinforcement of power distribution system while satisfying the permitted voltage change rate conditions when PEVs charging load is connected to the power distribution system by their charging penetration scenario.

• Asian-Australasian Journal of Animal Sciences
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• v.8 no.2
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• pp.145-149
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• 1995

Validity of use of a Y-maze for determining a foraging strategy of cattle was investigated with the object of establishing a procedure of testing foraging strategies of large herbivores. Cattle were placed in a start box of a Y-maze, forced into either goal arm and allowed to consume half of the feed at the end of the arm. Then, cattle were returned to the start box and allowed to choose either arm in the second half of a trial. This time animals were allowed to deplete the feed in the goal arm they chose. A return to the previous arm was recorded a "stay" Choice of the other arm was recorded as a "shift". Shift strategy was not observed. Rather, their behavior appeared either random or stay. However, it might have been caused by inappropriateness of the application of the apparatus and/or the procedure used in the study of foraging behavior of rats. Although the existence of lateral preference was suggested, further study with an elaborated procedure will be necessary to investigate foraging strategies of cattle.

• Advances in nano research
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• v.5 no.3
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• pp.261-279
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• 2017

Spectroscopic investigation of Si quantum dots (Si-QDs) embedded in silicon nitride was performed over a broad stoichiometry range to optimize light emission. Plasma-enhanced chemical vapor deposition was used to grow the $SiN_x$ films on Si (001) substrates. The film composition was controlled via the flow ratio of silane ($SiH_4$) and ammonia ($NH_3$) in the range of R = 0.45-1.0 allowed to vary the Si excess in the range of 21-62 at.%. The films were submitted to annealing at $1100^{\circ}C$ for 30 min in nitrogen to form the Si-QDs. The properties of as-deposited and annealed films were investigated using spectroscopic ellipsometry, Fourier transform infrared spectroscopy, Raman scattering and photoluminescence (PL) methods. Si-QDs were detected in $SiN_x$ films demonstrating the increase of sizes with Si excess. The residual amorphous Si clusters were found to be present in the films grown with Si excess higher than 50 at.%. Multi-component PL spectra at 300 K in the range of 1.5-3.5 eV were detected and nonmonotonous varying total PL peak versus Si excess was revealed. To identify the different PL components, the temperature dependence of PL spectra was investigated in the range of 20-300 K. The analysis allowed concluding that the "blue-orange" emission is due to the radiative defects in a $SiN_x$ matrix, whereas the "red" and "infrared" PL bands are caused by the exciton recombination in crystalline Si-QDs and amorphous Si clusters. The nature of radiative and no radiative defects in $SiN_x$ films is discussed. The ways to control the dominant PL emission mechanisms are proposed.

• Bulletin of the Korean Chemical Society
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• v.10 no.1
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• pp.60-66
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• 1989

Semiempirical computations using the AM1 and MNDO methods were carried out in order to elucidate allowed mechanisms for 1,3-group(X) rearrangement processes with X = $BH_2$, $CH_3$, CN, F, $NH_2$, OH, Cl and SH. The reactivity of the group migration was largely controlled by the steric effect in the 4-membered ring transition state, an antarafacial process having a greater energy barrier due to a greater steric repulsion. For the groups with lone pair electrons, the participation of the lone pair orbital is found to ease the steric effect by enabling the FMO interation with highly polarizable, high lying, lone pair electrons at relatively distant range; the involvement of lone pairs in the transition state causes an alteration of the symmetry selection rule to that of a 6-electron system with an allowed 1,3-suprafacial migration in contrast to an allowed 1,3-antarafacial migration for a 4-electron system. Various stereoelectronic aspects were analysed in some detail.

• Wind and Structures
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• v.6 no.6
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• pp.471-484
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• 2003

The rain-wind induced vibration of stays is a phenomenon discovered recently and not well explained yet. As it is influenced by a wide range of physical parameters (cable size and shape, wind speed, direction and turbulence, rain intensity, material repellency and roughness, cable weight, damping and pre-strain), this peculiar phenomenon is difficult to reproduce in laboratory controlled conditions. A successful wind tunnel experimental campaign, in which some basic physical quantities were measured, allowed an extensive analysis as to identify the parameters of the rain-wind induced excitation. The unsteady pressure field and water thickness around a cable model were measured under rainy-excited conditions. The knowledge of those parameters provided helpful information about the air-flow around the cable and allowed to clarify the physical phenomenon which produces the excitation.

• Journal of Korean Institute of Industrial Engineers
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• v.33 no.2
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• pp.237-245
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• 2007

In this paper, a modified PCF (Point Coordination Function) MAC (Medium Access Control) Protocol is proposed to support the multiple direct link communication between STAs (STAtions) in infrastructure mode IEEE 802.11 wireless LANs. By the proposed MAC protocol, the direct link communication between STAs, which are located within the communication range of each other, is allowed without the use of AP (Access Point) as a relay. Moreover, when multiple direct data communication between STAs can be simultaneously performed with a sufficiently small interference, multiple simultaneous direct link communication is allowed for the efficient use of radio bandwidth. AP polls STAs to grant the transmission opportunities using the direct link communication by transmitting the polling frames to STAs. An efficient polling method for granting the transmission opportunities to STAs is proposed to reduce the number of the polling frame transmissions and enhance the PCF MAC performance.

• Structural Engineering and Mechanics
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• v.55 no.6
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• pp.1099-1120
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• 2015

External prestressing has been applied to both new construction and retrofitting of existing reinforced and prestressed concrete structures. Continuous beams are preferred to simply supported beams because of economy, fewer movement joints and possible benefits from moment redistribution. However, this paper argues that continuous prestressed concrete beams with external unbonded tendons demonstrate different full-range behaviour compared to reinforced concrete (RC) beams. Applying the same design approach for RC to external prestressing may lead to design with a lower safety margin. To better understand the behaviour of continuous prestressed concrete beams with unbonded tendons, an experimental investigation is performed in which nine such specimens are tested to failure. The full-range behaviour is investigated with reference to moment-curvature relationship and moment redistribution. The amounts of moment redistribution measured in the experiments are compared with those allowed by BS 8110, EC2 and ACI 318. Design equations are also proposed to estimate the curvature ductility index of unbonded prestressed concrete beams.

• Journal of Environmental Health Sciences
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• v.27 no.3
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• pp.87-98
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• 2001

There has been increased interest in the health effects of the Environmental Tobacco Smoke(ETS) as a confirmed human carcinogen. It has been known to be extremely difficult to make an accurate assessment of exposure to ETS since it is consisted of a variety of components and there are a number of labile chemicals. Therefore, it is necessary to obtain, to interpretate and to provide the data of quantitative exposure assessment to ETS in the field of environmental health. The purpose of this research is to evaluate the concentration of ETS using VOC in indoor office environments. The correlations and concentrations of benzene, RSP, 3-EP, nicotine that are indicators for ETS were investigate with smoking density, air change per hour(ventilation rate). Air samples were taken in smoking room(7 sites), smoking allowed office (3 sites), corridor outside smoking room(7 sites), non-smoking office (9 sites). The concentrations of benzene showed significant difference according to category of indoor office environments. The geometric mean concentration of benzene were 23.56 ${\mu}{\textrm}{m}$/㎥(range 4.80~192.90 ${\mu}{\textrm}{m}$/㎥) in smoking rooms. 6.16 ${\mu}{\textrm}{m}$/㎥ in smoking allowed offices, 1.32 ${\mu}{\textrm}{m}$/㎥ in the non-smoking offices respectively. The ratios of the concentration of benzene between outdoor air and smoking room, smoking allowed office, and non-smoking indicators concentrations, SD, and SI were 0.82(benzene and nicotine). 0.76(benzene and RSP), 0.60(benzene and SD), 0.76(benzene and SI). It is proposed that benzene is a good indicator for ETS.

• Journal of Biomedical Engineering Research
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• v.29 no.2
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• pp.139-145
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• 2008

Many recent studies suggest that the posterior dynamic stabilization(PDS) can be a more physiologically-relevant alternative to the rigid fixation for the patients suffering from low back pain. However, its biomechanical effects or clinically proven efficacies still remain unknown. In this study, we evaluated kinematic behaviors of the lower lumbar spine with the PDS system and then compared to those of the rigid fixation system using finite element (FE) analysis. A validated FE model of intact lumbar spine(L2-L5) was developed. The implanted model was then constructed after modification from the intact to simulate two kinds of pedicle screw systems (PDS and the rigid fixation). Hybrid protocol was used to flex, extend, laterally bend and axially rotate the FE model. Results showed that the PDS systems are more flexible than rigid fixation systems, yet not flexible enough to preserve motion. PDS system allowed $16.2{\sim}42.2%$ more intersegmental rotation than the rigid fixation at the implanted level. One the other hand, at the adjacent level it allowed more range of motion ($2.0%{\sim}8.3%$) than the rigid fixation. The center of rotation of the PDS model remained closer to that of the intact spine. These results suggest that the PDS system could be able to prevent excessive motion at the adjacent levels and restore the spinal kinematics.