• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6B
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• pp.1092-1099
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• 2000

An adaptive array system can effectively remove all received interferences by using adaptive algorithms even though the received signal condition is not known. The conventional adaptive array systems, however, cannot remove all interferences adaptively and converge very slowly when the eigenvalue spread of the input covariance matrix is large. In the paper, a new adaptive array system called an automatic gain controller (AGC) Applebaum array and its control algorithm are proposed to overcome the performance degradation of conventional Applebaum array in multiple interference conditions. The performance analysis of the proposed AGC Applebaum array is described under the condition of multiple narrowband interferences. Simulation results show the array output signal-to-noise ratio (SNR) of the AGC Applebaum array increases by 30dB compared to that of the conventional Applebaum array in the simulation condition. The gain of the AGC Applebaum array in the incident direction of a weaker interference is also shown to be lower than that of the conventional Applebaum array.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.11
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• pp.720-728
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• 2000

This paper describes the calculation of the equivalent circuit parameters and the characteristic analysis of a capacitor-run type single-phase induction motor by means of the finite element method in coupled with the conventional equivalent circuit model. The circuit parameters of the stator are calculated form the lumped parameter and the slot leakage reactance of the rotor with the closed slot can be obtained by the use of slot pitch boundary condition. From the analysis result this combined equivalent circuit and finite element method which is used slot pitch boundary condition is compared with the experimental results, the validity of the method is proved.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.735-739
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• 1995

An experiment was carried out to investigate the effect of $Na_{2}O$ additive on the magnetic and physical properties of $SrZn_{2}-W$ type hexagonal ferrite. The specimens were prepared by the conventional manufacturing methods without atmosphere control. It was found that the magnetic properties of SrO.2ZnO.$8Fe_{2}O_{3}$ are considerably improved on adding 1.5wt% $Na_{2}O$. Theoptimum condition of making magnet with suitable properties are as follows : chemical analysis composition : $Sr^{2+}_{0.852}Zn^{2+}_{1.721}Na^{+}_{0.301}Fe^{2+}_{0.723}Fe^{3+}_{15.703}O_{27}$ ; semisintering condition : $1300^{\circ}C\;{\times}\;1h$ in air ; sintering condition : $1250^{\circ}C\;{\times}\;0.5h\;T_{c}=371^{\circ}C,\;H_{A}=1091.5kA/m,\;K_{A}=2.13{\times}10^{5}J/m^{3}\;and\;n_{B}=31.8\mu\textrm{B}$.

• Phonetics and Speech Sciences
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• v.4 no.3
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• pp.25-30
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• 2012

This study investigated whether native Korean listeners could use visual cues for the identification of the English consonants /b/ and /v/. Both auditory and audiovisual tokens of word minimal pairs in which the target phonemes were located in word-initial or word-medial position were used. Participants were instructed to decide which consonant they heard in $2{\times}2$ conditions: cue (audio-only, audiovisual) and location (word-initial, word-medial). Mean identification scores were significantly higher for audiovisual than audio-only condition and for word-initial than word-medial condition. Also, according to signal detection theory, sensitivity, d', and response bias, c were calculated based on both hit rates and false alarm rates. The measures showed that the higher identification rate in the audiovisual condition was related with an increase in sensitivity. There were no significant differences in response bias measures across conditions. This result suggests that native Korean speakers can use visual cues while identifying confusing non-native phonemic contrasts. Visual cues can enhance non-native speech perception.

• Nonlinear Functional Analysis and Applications
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• v.27 no.4
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• pp.709-730
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• 2022

We consider the nonlinear matrix equation (NMEs) of the form 𝓤 = 𝓠 + Σ^k_i=1 𝓐^*_iℏ(𝓤)𝓐_i, where 𝓠 is n × n Hermitian positive definite matrices (HPDS), 𝓐₁, 𝓐₂, . . . , 𝓐_m are n × n matrices, and ~ is a nonlinear self-mappings of the set of all Hermitian matrices which are continuous in the trace norm. We discuss a sufficient condition ensuring the existence of a unique positive definite solution of a given NME and demonstrate this sufficient condition for a NME 𝓤 = 𝓠 + 𝓐^*₁(𝓤²/900)𝓐₁ + 𝓐^*₂(𝓤²/900)𝓐₂ + 𝓐^*₃(𝓤²/900)𝓐₃. In order to do this, we define 𝓕𝓖_w-contractive conditions and derive fixed points results based on aforesaid contractive condition for a mapping in extended Branciari b-metric distance followed by two suitable examples. In addition, we introduce weak well-posed property, weak limit shadowing property and generalized Ulam-Hyers stability in the underlying space and related results.

• Journal of the Korean Mathematical Society
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• v.54 no.1
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• pp.281-302
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• 2017

For a Banach space operator $A{\in}B(\mathcal{X})$, let ${\sigma}(A)$, ${\sigma}_a(A)$, ${\sigma}_w(A)$ and ${\sigma}_{aw}(A)$ denote, respectively, its spectrum, approximate point spectrum, Weyl spectrum and approximate Weyl spectrum. The operator A is polaroid (resp., left polaroid), if the points $iso{\sigma}(A)$ (resp., $iso{\sigma}_a(A)$) are poles (resp., left poles) of the resolvent of A. Perturbation by compact operators preserves neither SVEP, the single-valued extension property, nor the polaroid or left polaroid properties. Given an $A{\in}B(\mathcal{X})$, we prove that a sufficient condition for: (i) A+K to have SVEP on the complement of ${\sigma}_w(A)$ (resp., ${\sigma}_{aw}(A)$) for every compact operator $K{\in}B(\mathcal{X})$ is that ${\sigma}_w(A)$ (resp., ${\sigma}_{aw}(A)$) has no holes; (ii) A + K to be polaroid (resp., left polaroid) for every compact operator $K{\in}B(\mathcal{X})$ is that iso${\sigma}_w(A)$ = ∅ (resp., $iso{\sigma}_{aw}(A)$ = ∅). It is seen that these conditions are also necessary in the case in which the Banach space $\mathcal{X}$ is a Hilbert space.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.4
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• pp.49-55
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• 2006

This study deals with the friction welding of SM25C and SCNCrM-2B; The friction time was variable conditions under the conditions of spindle revolution 2,000rpm, friction pressure of 100MPa, upset pressure of l50MPa, and upset time of 4.0 seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied, and so the results were as follows. 1. When the friction time is 2.0 seconds, the tensile strength of friction welds was 874MPa, which is around as much as 117% of the tensile strength of base metal(SM25C), the bending strength of friction welds was 1,354MPa, which is around as much as 108.9% of the bending strength of base metal(SM25C). 2. At the same condition, the maximum vickers hardness was Hv443 at SCNCrM-2B nearby weld interface, which is higher Hv20 than condition of the friction time 0.5 seconds. 3. The results of microstructure analysis show that the structures of two base materials have fractionated and rearranged along a column due to heating and axial force during friction, which has affected in raising hardness and tensile strength.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.3
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• pp.107-113
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• 1990

A series of cubical triaxial tests with independent control of the three principal stresses were performed on a compressible sand. All specimens which were formed by depositing the fine sand loosely, were used. It was found that slope of the stress-strain curve increased with increased b value, and the major principal strain at failure first remains approximetely constant for b values smaller than about 0.3 for drained condition and 0.6 for undrained condition respectively, and thereafter decreases with increasing value of b. The test results showed that the direction of the strain increments at failure form acute angles with the failure surfaces for both the drained and undrained condition. The results are thus not in agreement with the normality criterion from classic plasticity theory. However, it was found that the projections of the plastic strain increment vectors on the octahedral plane are perpendicular to the faiure surface in that plane.

• Journal of Korea Water Resources Association
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• v.46 no.4
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• pp.327-334
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• 2013

In this study, the optimal slit length of perforated wall with single chamber below the still water level (SWL) is studied through the two dimensional test. The relationship between the reflection coefficient and the shape of structures such as chamber width(B) and slit length(S) are investigated by applying the various wave conditions. The random waves were used for the test by using Bretschneider-Mitsuyasu frequency spectrum. Minimum reflection coefficient is obtained at $B/L_s{\approx}0.15$ condition, this result is different from the regular wave condition. Also the minimum reflection coefficients are measured at $S/H_s{\approx}2.5$. This means that the optimal slit length below the still water level is 2.5 times of the incident wave height.

• The Journal of Internal Korean Medicine
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• v.37 no.2
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• pp.374-380
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• 2016

Objective: Although the incidence of chronic hepatitis B has decreased around the world due to widespread national preventative control measures, mortality from the same condition can increase if the condition leads to liver cancer or liver cirrhosis. In most cases, herbal medicine does not show any statistically significant effects related to liver damage, but preconceptions do exist that herbal medicine can be toxic and cause such liver damage. To investigate this situation, this study therefore investigated a patient with hepatitis B who had combined traditional Korean medicine therapy and the use of analgesic drugs during a hospitalization period.Method: A patient with hepatitis B was given combined traditional Korean medicine therapy and the use of analgesic drugs during a hospitalization period.Results: Within 26 days, the patient was free from liver damage during the hospitalization period. She was followed up with a liver function test and was discharged after her condition improved; she also reported decreased back pain.