• ETRI Journal
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• 제26권6호
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• pp.605-614
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• 2004

In this paper, we investigate array calibration algorithms to derive a further improved version for correcting antenna array errors and RF transceiver errors in CDMA smart antenna systems. The structure of a multi-channel RF transceiver with a digital calibration apparatus and its calibration techniques are presented, where we propose a new RF receiver calibration scheme to minimize interference of the calibration signal on the user signals. The calibration signal is injected into a multi-channel receiver through a calibration signal injector whose array response vector is controlled in order to have a low correlation with the antenna response vector of the receive signals. We suggest a model-based antenna array calibration to remove the antenna array errors including mutual coupling errors or to predict the element patterns from the array manifold measured at a small number of angles. Computer simulations and experiment results are shown to verify the calibration algorithms.

• Structural Engineering and Mechanics
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• 제55권3호
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• pp.605-638
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• 2015

It is intended to perform buckling analysis of steel gabled frames with tapered members and flexible connections. The method is based on the exact solutions of the governing differential equations for stability of a gabled frame with I-section elements. Corresponding buckling load and subsequently effective length factor are obtained for practical use. For several popular frames, the influences of the shape factor, taper ratio, span ratio, flexibility of connections and elastic rotational and translational restraints on the critical load, and corresponding equivalent effective length coefficient are studied. Some of the outcomes are compared against available solutions, demonstrating the accuracy, efficiency and capabilities of the presented approach.

• Structural Engineering and Mechanics
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• 제56권4호
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• pp.605-623
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• 2015

A formulation of the boundary element method (BEM) based on Kirchhoff's hypothesis to analyse stiffened plates composed by beams and slabs with different materials is proposed. The stiffened plate is modelled by a zoned plate, where different values of thickness, Poisson ration and Young's modulus can be defined for each sub-region. The proposed integral representations can be used to analyze the coupled stretching-bending problem, where the membrane effects are taken into account, or to analyze the bending and stretching problems separately. To solve the domain integrals of the integral representation of in-plane displacements, the beams and slabs domains are discretized into cells where the displacements have to be approximated. As the beams cells nodes are adopted coincident to the elements nodes, new independent values arise only in the slabs domain. Some numerical examples are presented and compared to a wellknown finite element code to show the accuracy of the proposed model.

• Journal of Navigation and Port Research
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• 제27권6호
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• pp.605-610
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• 2003

According to SOLAS Convention, a voyage data recorder(VDR) is to be fitted onboard ships to assist in the marine casualty investigation However, a review of Korean Maritime Safety tribunal(KMST), shows that the current VDR systems is inconvenient in practical because the storage format of VDR and the casualty reproduction method are different from one manufacturer to another making it economically and timely difficult for the maritime casualty investigation bodies to carry out investigation in a proper manner. To solve this problem, this paper proposed a newly designed VDR Analysis System(VDRAS), which decodes the voyage data of VDR producea by different manufacturers, reproduces the condition at the time of casualty in an accurate, and performs necessary checks.

• Advances in nano research
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• 제3권1호
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• pp.13-27
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• 2015

Size dependent emission properties and the interband optical transition energies in group-III nitride based quantum dots are investigated taking into account the geometrical confinement. Exciton binding energy and the optical transition energy in $Ga_{0.9}In_{0.1}N$/GaN and $Al_{0.395}In_{0.605}N$/AlN quantum dots are studied. The largest intersubband transition energies of electron and heavy hole with the consideration of geometrical confinement are brought out. The interband optical transition energies in the quantum dots are studied. The exciton oscillator strength as a function of dot radius in the quantum dots is computed. The interband optical absorption coefficients in GaInN/GaN and AlInN/AlN quantum dots, for the constant radius, are investigated. The result shows that the largest intersubband energy of 41% (10%) enhancement has been observed when the size of the dot radius is reduced from $50{\AA}$ to $25{\AA}$ of $Ga_{0.9}In_{0.1}N$/GaN ($Al_{0.395}In_{0.605}N$/AlN) quantum dot.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제20권2호
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• pp.605-615
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• 1996

Laminar flows in which mixing and chemical reactions take place between parallel streams of reactive species are studied numerically. The governing equations for laminar flows are from two-dimensional compressible boundary-layer equations. The chemistry is a finite rate single step irreversible reaction with Arrhenius kinetics. Ignition, premixed flame, and diffusion flame regimes are found to exist in the laminar reacting mixing layer at high activation energy. At high Mach numbers, ignition occurs earlier due to the higher temperatures in the unburnt gas. In diffusion regimes, property variations affect the laminar profiles considerably and need to be included when there are large temperature differences. The maximum temperature of a laminar reacting mixing layer is almost linear with the adiabatic flame temperature at low heat release, but only weakly at high heat release.

• Communications for Statistical Applications and Methods
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• 제25권6호
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• pp.605-618
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• 2018

Risk management has been a crucial part of the daily operations of the financial industry over the past two decades. Value at Risk (VaR), a quantitative measure introduced by JP Morgan in 1995, is the most popular and simplest quantitative measure of risk. VaR has been widely applied to the risk evaluation over all types of financial activities, including portfolio management and asset allocation. This paper uses the implementations of multivariate GARCH models and copula methods to illustrate the performance of a one-day-ahead VaR prediction modeling process for high-dimensional portfolios. Many factors, such as the interaction among included assets, are included in the modeling process. Additionally, empirical data analyses and backtesting results are demonstrated through a rolling analysis, which help capture the instability of parameter estimates. We find that our way of modeling is relatively robust and flexible.

• Childhood Kidney Diseases
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• 제2권1호
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• pp.1-8
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• 1998

Purpose : To evaluate the diagnostic value of dipstick urinalysis($Multistix^{(R)}$) as a screening test for urinary tract infection(UTI) in acute febrile children. Methods : We compared dipstick uinalysis (leukocyte estease(LE) and nitrite) with microscopic urinalysis (WBC and bacteria) and urine culture in 80 children with UTI and 605 children without UTI, who were admitted due to acute fever at EWHA Womans University Hospital between Oct. 1994 and Feb. 1996. Results : 1) In dipstick urinalysis, LE and nitrite were positive in 38.7%, and 13.8% of 80 children with UTI and in 2.1%. and 1.2% of 605 children without UTI. 2) In microscopic urinalysis, WBC and bacteria were positive in 31.2%, and 17.5% of 80 children with UTI and in 4.1%, and 0.6% of 605 children without UTI. 3) Positive rate of LE on dipstick urinalysis was 38.7%, which was significantly higher than 31.5% of WBC on microscopic urinalysis (P<0.05). Positive rate of nitrite was not significantly different to that of bacteria. 4) Sensitivity, specificity, positive predictive value, negative predictive value of dipstick urinalysis were 43.7%, 98.3%, 63.6%, 92.9% which were not significant different to 40.0%, 99.0%, 54.0%, 92.3% of microscopic urinalysis. The sensitivity of combined dipstick and microscopic urinalysis were still low(50%). 5) Additional positive rate of microscopic urinalysis to negative dipstick urinalysis was 6.3%(5/80) in 80 children with UTI. Conclusion : The sensitivity of dipstick urinalysis was low and additional value of microscopic urinalysis was minimal in febrile UTI. So urine culture is mandatory in acute febrile children even though dipstick and microscopic urinalysis are negative.

• Korean Journal of Plant Resources
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• 제23권4호
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• pp.327-349
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• 2010

This study was carried out to investigate the distribution of vascular plants and their use from 2007 to 2009 in Mt. Unmum(Cheongdo-gun, Gyeongsangbuk-Do). The vascular plants were summarized as 605 taxa including 98 families, 304 genus, 514 species, 3 subspecies, 68 varieties, and 20 forma. Among the investigated 605 taxa, 21 rare and endangered plants, 29 Korean endemic plants were included. Based on the list of specially designated plants by Ministry of Environment, 70 taxa included Iris odaesanensis and Gastrodia elata were recorded in the investigated area. The naturalized plants were identified as 23 taxa and the percent of naturalized index(NI) was 3.8% of total 605 taxa vascular plants. Usage of 605 taxa were consists of 225 taxa(37.2%) of edible plants, 191 taxa(31.6%) of medicinal plants, 64 taxa(10.6%) of ornamental plants, 46 taxa(7.6%) of pasture plants, 18 taxa(3.0%) of timber plants, 14 taxa(2.3%) of fiber plants, and 3 taxa(0.5%) of industrial plants. To management of natural resource, we suppose that it is required to establish an ecological learning area to minimize human disturbance and an effective managemet strategy by continuous monitoring for ecosystem change.

• East Asian mathematical journal
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• 제28권5호
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• pp.605-615
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• 2012

In this paper, we show that any definite lattice over $\mathbb{F}_q[x]$ is universal if and only if it is quaternary and its discriminant is of degree 2, where $ch(\mathbb{F}_q){\neq}2$. The Four Conjecture follows as an immediate consequence.