• Structural Engineering and Mechanics
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• 제42권3호
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• pp.425-448
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• 2012

In this paper, a new damage detection and quantification method has been presented to perform detection and quantification of structural damage under ambient vibration loadings. To extract modal properties of the structural system under ambient excitation, natural excitation technique (NExT) and eigensystem realization algorithm (ERA) are employed. Sensitivity matrices of the dynamic residual force vector have been derived and used in the parameter subset selection method to identify multiple damaged locations. In the sequel, the steady state genetic algorithm (SSGA) is used to determine quantified levels of the identified damage by minimizing errors in the modal flexibility matrix. In this study, performance of the proposed damage detection and quantification methodology is evaluated using a finite element model of a truss structure with considerations of possible experimental errors and noises. A series of numerical examples with five different damage scenarios including a challengingly small damage level demonstrates that the proposed methodology can efficaciously detect and quantify damage under noisy ambient vibrations.

• 대한수학회지
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• 제59권2호
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• pp.337-352
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• 2022

We consider the set of points with historic behavior (which is also called the irregular set) for continuous flows and suspension flows. In this paper under the hypothesis that (X_t)_t is a continuous flow on a d-dimensional Riemaniann closed manifold M (d ≥ 2) with gluing orbit property, we prove that the set of points with historic behavior in a compact and invariant subset ∆ of M is either empty or is a Baire residual subset on ∆. We also prove that the set of points with historic behavior of a suspension flows over a homeomorphism satisfyng the gluing orbit property is either empty or Baire residual and carries full topological entropy.

• ETRI Journal
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• 제44권1호
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• pp.117-124
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• 2022

In this paper, the performance of precoding-aided differential spatial modulation (PDSM) systems with optimal transmit antenna subset (TAS) selection is examined analytically. The average bit error rate (ABER) performance of the optimal TAS selection-based PDSM systems using a zero-forcing (ZF) precoder is evaluated using theoretical upper bound and Monte Carlo simulations. Simulation results validate the analysis and demonstrate a performance penalty < 2.6 dB compared with precoding-aided spatial modulation (PSM) with optimal TAS selection. The performance analysis reveals a transmit diversity gain of (N_T-N_R+1) for the ZF-based PDSM (ZF-PDSM) systems that employ TAS selection with N_T transmit antennas, N_S selected transmit antennas, and N_R receive antennas. It is also shown that reducing the number of activated transmit antennas via optimal TAS selection in the ZF-PDSM systems degrades ABER performance. In addition, the impacts of channel estimation errors on the performance of the ZF-PDSM system with TAS selection are evaluated, and the performance of this system is compared with that of ZF-based PSM with TAS selection.

• Childhood Kidney Diseases
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• 제27권1호
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• pp.1-10
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• 2023

Pediatric nephrotic syndrome (NS) is a clinical syndrome characterized by massive proteinuria, hypoalbuminemia, and generalized edema. Most childhood NS cases are idiopathic (with an unknown etiology). Traditional therapeutic approaches based on immunosuppressive agents largely support the key role of the immune system in idiopathic NS (INS), especially in the steroid-sensitive form. Although most previous studies have suggested the main role of T cell dysfunction and/or the abnormal secretion of certain glomerular permeability factors, recent studies have emphasized the role of B cells since the therapeutic efficacy of B cell depletion therapy in inducing and/or maintaining prolonged remission in patients with INS was confirmed. Furthermore, several studies have detected circulating autoantibodies that target podocyte proteins in a subset of patients with INS, suggesting an autoimmune-mediated etiology of INS. Accordingly, a new therapeutic modality using B cell-depleting drugs has been attempted, with significant effects in a subset of patients with INS. Currently, INS is considered an immune-mediated disorder caused by a complex interplay between T cells, B cells, soluble factors, and podocytes, which may vary among patients. More in-depth investigations of the pathogenic pathways of INS are required for an effective personalized therapeutic approach and to define precise targets for therapeutic intervention.

• 대한수학회보
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• 제26권2호
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• pp.119-126
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• 1989

Throughout this paper, X will always denote a Banach space over the complex numbers C, and L(X) will denote the Banach algebra of all continuous linear operators on X. Operator will always mean continuous linear operator. An n-tuple of operators T$_{1}$,..,T$_{n}$ on X will be denoted by over ^ T=(T$_{1}$,..,T$_{n}$ ). Let L$^{n}$ (X) be the set of all n-tuples of operators on X. X' will denote the dual space of X, S(X) its unit sphere and .PI.(X) the subset of X*X' defined by .PI.(X)={(x,f).mem.X*X': ∥x∥=∥f∥=f(x)=1}.

• 대한수학회논문집
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• 제9권4호
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• pp.819-823
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• 1994

If H is a Hilbert space, then an operator $T : D(T) \subset H \to H$ is said to be monotone if $$ (x-y, Tx-Ty) \geq 0$$ for any x, y in D(T). Many authors [1], [4] obtained the existence theorem for the equation $y = x + Tx$ for x, given an element y in H and a monotone operator T. On the other hand some iterative methods were applied to the approximations for the solution of the above equation [6], [8]. For example Bruck [2] obtained the iterative solution of the above equation with an explicit error estimate as follows.

• 대한수학회보
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• 제43권2호
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• pp.245-252
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• 2006

In this paper we study the uniform decay estimates of the energy for the nonlinear wave equation of Kirchhoff type $$y'(t)-M({\mid}{\nabla}y(t){\mid}^2){\triangle}y(t)\;+\;{\delta}y'(t)=f(t)$$ with the damping constant ${\delta} > 0$ in a bounded domain ${\Omega}\;{\subset}\;\mathbb{R}^n$.

• 대한수학회보
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• 제57권6호
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• pp.1491-1499
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• 2020

We give a strong fundamental domain for the quotient of PGL₂(𝔽_q((t^-1))) by PGL₂(𝔽_q[t]) as a subset of distinct ordered triple points of ℙ¹(𝔽_q((t^-1))).

• 핵의학기술
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• 제15권1호
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• pp.17-24
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• 2011

현재 핵의학 분야에서는 디지털 컴퓨터의 급속한 발전 및 응용으로 인해 FBP 법의 대용으로 OSEM 알고리즘과 같은 고속 영상 재구성 알고리즘이 널리 이용되고 있다. 그 동안 여러 연구에서 파라미터 변경에 따른 OSEM 재구성 영상 질 변화에 대한 평가가 이루어져 왔으나, 어떠한 파라미터를 적용할 지에 관해서는 명확하게 정해진 것은 없다. 본 연구에서는 3D beam modeling을 적용한 3D OSEM 재구성 법에서 iteration 횟수와 subset 개수 변경에 따른 영상의 질 변화를 팬텀 실험과 환자 데이터을 통해 확인하고자 한다. 환자 데이터는 2010년 8월부터 9월까지 본원 핵의학과에서 Brain SPECT를 시행한 환자 5명을 대상으로 연구 분석하였다. 영상은 물과 $^{99m}Tc$ (500 MBq)을 균등하게 혼합한 Jaszczak 팬텀을 이용하여 Siemens사의 이중 헤드 감마 카메라 Symbia T2에서 획득하였다. 환자 데이터는 영상 재구성 시 환자 데이터와 팬텀 데이터 모두 iteration 횟수는 1, 4, 8, 12, 24, 48회, subset 개수는 2, 4, 8, 16, 32개로 변화를 주며 각각의 영상을 재구성하였다. 재구성된 각각의 영상에서 대조도와 영상의 잡음 정도를 가늠하기 위한 변이계수, FWHM을 산출하여 비교하였다. 팬텀 데이터와 환자 데이터에서 영상의 대조도와 공간해상력은 iteration 횟수와 subset 개수의 증가에 따라 모두 선형적으로 증가하는 경향을 나타냈으나 변이계수는 두 파라미터의 증가에 따라 향상되는 경향을 보이지 않았다. Projection 시간에 따른 비교에서도 Projection 당 10초, 20초, 30초 영상에서 모두 영상 대조도와 FWHM은 iteration 횟수와 subset 개수 증가에 따라 선형적으로 향상되는 결과를 나타냈으나 변이계수는 향상되는 경향을 보이지 않았다. 본 실험을 통해 3D beam modeling을 적용한 3D OSEM 재구성 법 영상에서도 기존의 1D와 2D OSEM 재구성 법과 같이 iteration 횟수와 부분집합 개수 증가에 따라 향상하는 영상 대조도의 선형적 관계를 확인할 수 있었다. 하지만 이는 단순한 팬텀 실험과 일부 환자 데이터 만으로 얻은 결과이고, 실제 임상에서는 보다 구조적으로 복잡한 대상과 다양한 변수들이 존재 가능하기 때문에 본 실험의 데이터만을 바탕으로 이를 일반화하기에는 무리가 있으며 차후 실험들을 통해 3D OSEM 재구성 법에 대한 평가가 추가로 이루어져야 할 것이다.

• Journal of Nutrition and Health
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• 제32권7호
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• pp.781-786
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• 1999

This study was designed to investigate the effects of vitamin E supplementation on radical scavenger activity and immune responses in female judo athletes(n=18). The age and sex matched sedentary students were used as controls(n=15). The initial plasma vitamin E concentration, lipid peroxide level and radical scavenger activity (RSA) were not different between two groups. The supplementation of $\alpha$-tocopheryl acetate(400IU/d) for 4 weeks significantly increased plasma vitamin E concentration of the subjects in both groups. In addition, the decrease in thiobarbituric acid reactive substance(TBARS)(p<0.05) and enhancement of RSA(p<0.05) were observed in both groups. Percentages of total T-cells in the athletic group was lower than that in the control group(p<0.05). However, the ratio of CD4 / CD8(helper T-cal $l^pressor T-cell) was higher in the sports group, due to more decrease in CD8 subset than in CD4 subset. The concentrations of IgG and IgM in the sports group were significantly lower than those in the control group(p<0.05). Therefore, severe training of the athletic group seems to be associated with the changes of supplementation. In conclusion, vitamin E supplementation (400IU/d, 4 weeks) of the female university students improved antioxidative activities of the blood, by decreasing lipid peroxide and enhancing radical scavenger activity. Percentages of T lymphocytes and IgG and IgM concentrations in the athletic group were lower than those in the control group. Meanwhile, vitamin E supplementation had no effects on immune status in both groups.ps.