• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.109-112
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• 2004

Of late, the thrust vectoring control, using fluidic co-flow and counter-flow concepts, has been received much attention since it not only improves the maneuverability of propulsive engine but also reduces an additional material load due to the trailing control wings, which in turn reduce the aerodynamic drag. However, the control effects are not understood well since the flow field involves very complicated non: physics such as shock wave/boundary layer interaction, separation and significant unsteadiness. Existing data are not enough to achieve the effectiveness and usefulness of the thrust vectoring control, and systematic work is required for the purpose of practical applications In the present study, computational study has been performed to investigate the effects of the thrust vector control using the fluidic co-and counter-flow concepts. The results obtained show that, for a given pressure ratio, the thrust deflection angle has a maximum value at a certain suction flow rate, which is at less than $5\%$ of the mass flow rate of the primary jet. With a longer collar, the same vector angle is achievable with smaller mass flow rate.

• Journal of the Korea Fashion and Costume Design Association
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• v.24 no.2
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• pp.11-26
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• 2022

The Hallyu wave based on K-pop and K-culture has increased the global interest in Korean culture. Therefore, to satisfy consumer demand, there is an attempt to develop a variable fashion design using traditional Korean culture. Transformable fashion design causes changes in form and meaning according to various situations and needs and can induce active participation of consumers. Therefore, we intend to propose a transformable fashion design that is based on traditional Korean culture but appears in a new form and meets the needs of consumers of fashion design. Among Korean traditional culture, wrapping cloths, bojagi are practically used by ordinary people until now, and their shape and use change according to the user's needs. This study intends to derive expression characteristics by examining the expression tendencies of bojagi and to develop transformable fashion designs through the derived data. The purpose of this study is to make and propose transformable fashion designs in real life using the expression characteristics of Korean bojagi. As the method of this study, we first conducted a literature review. Through this, a case study of empirical production was conducted in parallel with the development and production of transformable fashion designs using bojagi. A total of three illustrations and six variable fashion designs were developed. Two of the six works are transformable fashion design that change through movement and expansion of the square shape, the prototype of the bojagi, and two works are modular, bringing changes in function through combination and separation. The work was produced as a multi-purpose transformable fashion design that can be used as clothes or a bag.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.715-726
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• 2023

This study suggested that protective panels should be installed as sacrificial members as a safety design method for structures with potential explosions such as hydrogen charging stations to minimize direct damage to the structure and have resilience. To this end, the focus of the experiment is on quantitatively evaluating the impact of the structure when the protection panel is installed closely or spaced apart from the structure in a high-speed collision situation of the projectile. The experimental design used steel plates instead of concrete structural members mainly used in the past for excellent reproducibility, and the impact of structural members was compared and analyzed through deformation differences on the back of the steel plate. In addition, the impact of changes in the physical properties of the elastic body used as a separation material for the protective member and the difference in shock wave transmission time according to the protective member and the elastic body on the structural member was investigated.

• Korean Journal of Radiology
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• v.1 no.1
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• pp.11-18
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• 2000

Objective: To evaluate the hydrodynamic changes occurring in cerebrospinal fluid (CSF) flow in cervical spinal stenosis using the spatial modulation of magnetization (SPAMM) technique. Materials and Methods: Using the SPAMM technique, 44 patients with cervical spinal stenosis and ten healthy volunteers were investigated. The degree of cervical spinal stenosis was rated as low-, intermediate-, or high-grade. Low-grade stenosis was defined as involving no effacement of the subarachnoid space, intermediate-grade as involving effacement of this space, and high-grade as involving effacement of this space, together with compressive myelopathy. The patterns of SPAMM stripes and CSF velocity were evaluated and compared between each type of spinal stenosis and normal spine. Results: Low-grade stenosis (n = 23) revealed displacement or discontinuity of stripes, while intermediate- (n = 10) and high-grade (n = 11) showed a continuous straight band at the stenotic segment. Among low-grade cases, 12 showed wave separation during the systolic phase. Peak systolic CSF velocity at C4-5 level in these cases was lower than in volunteers (p < .05), but jet-like CSF propulsion was maintained. Among intermediate-grade cases, peak systolic velocity at C1-2 level was lower than in the volunteer group, but the difference was not significant (p > .05). In high-grade stenosis, both diastolic and systolic velocities were significantly lower (p < .05). Conclusion: Various hydrodynamic changes occurring in CSF flow in cervical spinal stenosis were demonstrated by the SPAMM technique, and this may be a useful method for evaluating CSF hydrodynamic change in cervical spinal stenosis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.23-23
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• 2009

GaN-based nitride semiconductors have attracted considerable attention in high-brightness light-emitting-diodes (LEDs) and laser diodes (LDs) covering from green to ultraviolet spectral range. LED and LD heterostructures are usually grown on (0001)-$Al_2O_3$. The large lattice mismatch between $Al_2O_3$ substrates and the GaN layers leads to a high density of defects(dislocations and stacking faults). Moreover, Ga and N atoms are arranged along the polar [0001] crystallographic direction, which leads to spontaneous polarization. In addition, in the InGaN/GaN MQWs heterostructures, stress applied along the same axis can also give rise to piezoelectric polarization. The total polarization, which is the sum of spontaneous and piezoelectric polarizations, is aligned along the [0001] direction of the wurtzite heterostructures. The change in the total polarization across the heterolayers results in high interface charge densities and spatial separation of the electron and hole wave functions, redshifting the photoluminescence peak and decreasing the peak intensity. The effect of polarization charges in the GaN-based heterostructures can be eliminated by growing along the non-polar [$11\bar{2}0$] (a-axis) or [$1\bar{1}00$] (m-axis) orientation instead of thecommonly used polar [0001] (c-axis). For non-polar GaN growth on non-polar substrates, the GaN films have high density of planar defects (basal stacking fault BSFs, prismatic stacking fault PSFs), because the SFs are formed on the basal plane (c-plane) due to their low formation energy. A significant reduction in defect density was recently achieved by applying blocking layer such as SiN, AlN, and AlGaN in non-polar GaN. In this work, we were performed systematic studies of the defects in the nonpolar GaN by conventional and high-resolution transmission electron microscopy.

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.2
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• pp.45-49
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• 1999

The second harmonic, wavelength is 397nm, of the continuous wave diode laser, whose maximum power is 35mW, was generated in $LiIO_3$ crystals in a ring enhancement cavity. 5mm- and 10mm-long crystals cut $43.21^{\circ}$ for optic axis were used in this experiment. Both surfaces of those were anti-reflection coated for 794nm. In case the crystal was inserted into the cavity, the condition of separation between two concave mirrors for the optimum mode matching was found. The conversion efficiency of second harmonic generation was increased by the resonant enhancement of pumping power in the ring enhancement cavity, and the frequency of diode laser was locked to that of the counter-propagation mode generated from the surface of crystal. When the pumping power was 28 mW, the infrared buildup factor was about 45 without the crystal, and 14 with the crystal due to the transmission loss of crystal. The maximum second harmonic powers of $1.5{\mu}W$ and $6.6{\mu}W$ were obtained, and corresponding conversion efficiencies were $(6.584{\pm}0.56){\times}10^{-3}$%, $2.6{\pm}0.21){\times}10%{-2}$% in 5mm- and 10mm-long $LiIO_3$, respectively.

• Journal of Korean Society of Transportation
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• v.21 no.5
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• pp.61-71
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• 2003

Existent DDHV draws and is calculating K coefficient. D coefficient from sum of traffic volume two-directions time. There is difference of design order and actuality order, error of DDHV estimation value, problem of irregular change etc. of DDHV thereby. In this study, among traffic volume of each other independent two direction(going up, going down), decide design target order in the directional traffic volume, presented way(way) applying without separating K coefficient and D coefficient at the same time. The result were analysis about national highway permanent count point 360 points 30 orders by existing DDHV estimation value method(separation plan) analysis wave and following variation appear. - design order and actuality order are collision at 357 agencies(99.2%) - actuality order special quality : Measuring efficiency of average 80 orders, maximum 1,027 order, minimum 2 orders - error distribution of design order and actuality order : inside 10 hours is(30$\pm$10hour) 106 points(29.4%), 254 points(70.6%) more than 30 orders and $\pm$10 orders error occurrence be - DDHV estimation value : Average 8.4%, maximum 46.7% The other side, average 50 orders. error improvement effect of DDHV 8.4% was analysed that is at design hourly volume computation by inseparability method in case of AADT premises correct thing because inseparability plan agrees actuality order at whole agency with design order and measuring efficiency of DDHV estimation value is "0".t;0".uot;.

• Journal of the Korean Electrochemical Society
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• v.12 no.3
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• pp.276-281
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• 2009

Electrochemical behaviors of $U^{3+}$ and $Gd^{3+}$ were investigated in LiCl-KCl eutectic molten salt by using various electrochemical techniques. The electrodeposition and dissolution currents for uranium show the maximum at -1.51V and -1.35V, respectively while, for gadolinium,at -2.15V and -1.9V, respectively. In case of LiCl-KCl molten salt containing both of $U^{3+}$ and $Gd^{3+}$, the peak potential of electrodeposition of gadolinium shifts to more positive potential than in the solution without $U^{3+}$. The potentials in chronopotentiometric data suddenly dropped to negative value as soon as the reduction currents were applied and became constant at the potential around which the $U^{3+}$ and $Gd^{3+}$ are electrodeposited. The results of normal pulse voltammetry (NPV) and square wave voltammetry show that those methods can be used to qualitatively analyze the elements in the melts. Especially, the differentiation of NPV result was found to be useful for the separation of the peaks of which potentials are close each other.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.4
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• pp.23-32
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• 1988

The rates of infiltration contributed to the flow fo water in an unconfined aquifer under the partially penetrated stream at an ungaged station and the corresponding base flow in channel are coupled by using the hydraulic and/or hydrologic characteristics obtained from the geomorphologic and soil maps. For the determination of groundwater flow, the linearized model which is originally Boussinesq's nonlinear equation is applied in this study. Also, a stream flow routing model for base flow in channel is based on a simplification of the Saint-venant. The distributed runoff model with piecewise spatial uniformity is presented for obtaining its solution based on a finite difference technique of the kinematic wave equations. The method developed in this study was tested to the Bocheong watershed(area : $475.5km^2$) of the natural stream basin which is one of tributaries in Geum River basin in Korea. As a result, it is suggested that the rationality of hydro-graph separation according to a wide variability in hydrogeologic properties be worked out as developing the physically based subsurface model. The results of the present model are shown to be possible to simulate a base flow due to an arbitrary rate of infiltration for ungaged basins.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.9
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• pp.1248-1256
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• 1993

The propagation and delay properties in opical fiber are particularly attractive because digital signal processing and conventional analog signal processing techniques such as those using surface acoustic wave devices are limited In their usefulness for signal bandwidth exceeding one or two GHz, although they are very effective at lower frequencies. Since an accurate, low loss and short time delay elements can be obtained by using such an optical fiber, optical signal precessing has attracted much attention for high speed and broad-band signal precessing in particular channel separation filtering for optical FDM signals. In this paper, we consider a coherent optical lattice filter, which uses coherent light sources and consists of directional couplers and optical fiber delay elemnts. The optical fiber fitters are more restricted than the usual digital filters. The reasons are as follows. 1) the coupling coefficients of directional couplers are restricted to the number between 0 and 1. 2) optical signal E(complex amplitude) is divided into J If-$\boxUl$ and J L/7$\div$$\boxUl$ at the directional coupler. Considering these restrictions and in this case all the coupling coefficients of summing and branching elements are set to be equal, we have given design formulae for optical lattice filter, which make the best use of optical signal energy.