• 한국물환경학회지
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• 제26권2호
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• pp.343-348
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• 2010

The objective of this study was to investigate the effects of starvation periods with aerobic or non-aerobic conditions on the organic removal efficiencies and physical characteristics of activated sludge for treating saline and non-saline wastewater. During the experiment, MLSS, MLVSS, sludge volume index (SVI), floc size and fractal dimension, $COD_{Mn}$ removal efficiencies were monitored. The reductions of MLSS, MLVSS and SVI with maintaining the sludge under a non-aerobic condition during starvation periods were smaller than those under a aerobic condition. Floc size, fractal dimension and $COD_{Mn}$ removal efficiencies were less decreased under non-aerobic condition than under aerobic condition. And SVI were strongly correlated with floc size and fractal dimension. Consequently, the result showed that maintaining the activated sludge under non-aerobic starvation conditions was better strategy than that under aerobic starvation conditions as it adapted and resisted to starvation.

• 대한방사선기술학회지:방사선기술과학
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• 제19권1호
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• pp.81-87
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• 1996

When high energy photon beam is incident upon an air cavity interface the effect of ionization build-up observed. This phenomenon is resulting from the surface layers of the lesions are significant deficiency of electrons reaching the layers because of the replacement of solid scattering material by the air cavity, that is lack of electronic equilibrium. Measurement have been made in an acrylic phantom with a parallel plate chamber and high energy Photon beams, CO-60, 4MV, 6MV and 10MV X-rays have been investigated. The result of our study show that a significant effect was measured and was determined to be very dependent on field size, air cavity dimension and photon energy. The reductions were much larger for 10MV beam, underdosage at the interface was 12, 12.2, 16.9 and 20.6% for the CO-60, 4 MV, 6MV and 10MV, respectively. It was found that this non-equilibrium effect at the interface is more severe for the higher energy beams than that of lower energy beams and the larger cavity dimensions it is, the larger beam reductions we have. This problem is of clinical concern when lesions such as carcinoma beyond air cavities are irradiated, such as larynx, glottic and the patients with maxillectomy and ethmoidectomy and so forth.

• 대한수학회논문집
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• 제9권4호
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• pp.905-915
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• 1994

Let $M_g$ be the moduli space of isomorphism classes of genus g smooth curves. It is a quasi-projective variety of dimension 3g - 3, when $g > 2$. It is known that a complete subvariety of $M_g$ has dimension $< g-1 [D]$. In general it is not known whether this bound is rigid. For example, it is not known whether $M_4$ has a complete surface in it. But one knows that there is a complete curve through any given finite points [H]. Recently, an explicit example of a complete curve in moduli space is given in [G-H]. In [G-H] they constructed a complete curve of $M_3$ as an intersection of five hypersurfaces of the Satake compactification of $M_3$. One way to get a complete curve of $M_3$ is to find a complete one dimensional family $p : X \to B$ of plane quartics which gives a nontrivial morphism from the base space B to the moduli space $M_3$. This is because every non-hyperelliptic smooth curve of genus three can be realized as a nonsingular plane quartic and vice versa. This paper has come out from the effort to find such a complete family of plane quartics. Since nonsingular quartics form an affine space some fibers of p must be singular ones. In this paper, due to the semistable reduction theorem [M], we search singular plane quartics which can occur as singular fibers of the family above. We first list all distinct plane quartics in terms of singularities.

• 대한방사선치료학회지
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• 제8권1호
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• pp.75-81
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• 1996

When high energy photon beam is incident upon an air cavity interface the effect of ionization build-up observed . This phenomenon is resulting from the surface layers of the lesions are significant deficiency of electrons reaching the layers because of the replacement, of solid scattering material by the air cavity, that is lack of electronic equilibrium. Measurement have been made in an acrylic phantom with a parallel plate chamber and high energy photon beams, CO-60, 4MV, 6MV and 10MV X-rays have been investigated. The result of our study show that a significant effect was measured and was determined to be very dependent on field size, air cavity dimension and photon energy. The reductions were much larger for 10MV beam, underdosage at the interface was 12, 12.2, 16.9 and $20.6\%$ for the CO-60, 4MV, 6MV and 10MV, respectively. It was found that this non-equilibrium effect at the interface is more severe for the higher energy beams than that of lower energy beams and the larger cavity dimensions the larger beam reductions occur. This problem is of clinical concern when lesions such as carcinoma beyond air cavities are irradiated, such as larynx, glottic and the patients with maxillectomy and ethmoidectomy and so forth.

• 센서학회지
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• 제23권2호
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• pp.99-104
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• 2014

Sensor arrays based on chemical sensors produce multidimensional patterns of data that may be used discriminate between different chemicals. For the human observer, visualization of multidimensional data is difficult, since the eye and brain process visual information in two or three dimensions. To devise a simple means of data inspection from the response of sensor arrays, PCA (Principal Component Analysis) or Sammon's nonlinear mapping technique can be applied. The PCA, which is a well-known statistical method and widely used in data analysis, has disadvantages including data distortion and the axes for plotting the dimensionally reduced data have no physical meaning in terms of how different one cluster is from another. In this paper, we have investigated two techniques and proposed a combination technique of PCA and nonlinear Sammom mapping for visualization of multidimensional patterns to two dimensions using data sets from odor sensing system. We conclude the combination technique has shown more advantages comparing with the PCA and Sammon nonlinear technique individually.

• 대한조선학회지
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• 제25권2호
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• pp.19-30
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• 1988

Sectional added masses of an elastic beam vibrating vertically on the free surface in higher harmonic modes are evaluated. Hydrodynamic interactions between neighboring sections, which strip theory ignores, are considered for modal wave lengths of the order of magnitude of cross-sectional dimensions of the body. An approximate solution of modified Helmholtz equation which becomes a singular perturbation problem at small wave lengths is secured to get an analytic expression for added masses attending higher harmonic modes. As a bound of the present theory, the modified Helmholtz equation is solved for the long flat plate vibrating at high frequency on the water surface without any limitations on modal frequency. Finally, extensive series of numerical calculations are carried out for ship-like forms. It is found that when modal wave length is comparable to or shorter than a typical cross-sectional dimension of a body, sectional interaction effects are large which result in considerable reductions in added masses. For a fuller section, the ratio of added mass reduction is greater. In the limit of vanishing sectional area, the added masses approach to that of flat plate of equal beam. It is shown that the added mass distribution for a Legendre modal from can be determined form the present theory and that the results agree with the extensive three-dimensional determination of Vorus and Hilarides.

• 대한수학회지
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• 제59권6호
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• pp.1047-1065
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• 2022

For two dimensional lattices, a Gaussian basis achieves all two successive minima. For dimension larger than two, constructing a pairwise Gaussian basis is useful to compute short vectors of the lattice. For three dimensional lattices, Semaev showed that one can convert a pairwise Gaussian basis to a basis achieving all three successive minima by one simple reduction. A pairwise Gaussian basis can be obtained from a given basis by executing Gauss algorithm for each pair of basis vectors repeatedly until it returns a pairwise Gaussian basis. In this article, we prove a necessary and sufficient condition for a pairwise Gaussian basis to achieve the first k successive minima for three dimensional lattices for each k ∈ {1, 2, 3} by modifying Semaev's condition. Our condition directly checks whether a pairwise Gaussian basis contains the first k shortest independent vectors for three dimensional lattices. LLL is the most basic lattice basis reduction algorithm and we study how to use LLL to compute a pairwise Gaussian basis. For δ ≥ 0.9, we prove that LLL(δ) with an additional simple reduction turns any basis for a three dimensional lattice into a pairwise SV-reduced basis. By using this, we convert an LLL reduced basis to a pairwise Gaussian basis in a few simple reductions. Our result suggests that the LLL algorithm is quite effective to compute a basis with all three successive minima for three dimensional lattices.

• 방송공학회논문지
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• 제14권6호
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• pp.733-741
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• 2009

디지털 통신 시스템에서는 대역폭과 전력을 효율적으로 사용하면서 신뢰성 높은 데이터 전송을 요구한다. 본 논문에서는 다중 반송파 방식을 사용하는 시스템에서 반송파의 직교성을 이용하여 다차원 성상도를 구현하고 전력 소비가 큰 성상 포인트의 위치를 재배치하여 평균 소비 전력을 감소시킬 수 있는 기술을 제안한다. 기존의 2차원 QAM 변조 방식을 N개의 부반송파를 사용하여 다차원 QAM 형태로 단순하게 변환하면 2 N차원 큐브 형태의 성상 포인트가 구성되는데, 전력 소비가 많은 최외각 성상 포인트들을 효율적으로 재배치하면 전력 소비를 최소화할 수 있는 2 N차원 구 형태의 성상도를 구성할 수 있다. 이와 같은 방식으로 16-QAM부터 2,048-QAM까지의 2차원 성상도를 다차원으로 변환하여 구성하고 전산모의실험을 통해 얻을 수 있는 평균 소비 전력 이득 값을 비교 분석하였다. 차원을 높일수록 재배치 성상 포인트들이 증가하므로 평균 소비 전력 이득 값이 커지는 것을 알 수 있다. 하지만 차원 증가에 따른 이득의 증가비율은 로그 형태를 가지고 있기 때문에 QAM의 성상 포인트 개수에 따라 일정한 이득값에 수렴하게 되고 수렴 값을 바탕으로 적정 다차원 성상도를 유도할 수 있다. 본 논문에서 제안한 방법으로 데이터를 전송하는 것은 하드웨어 복잡도 증가가 거의 없이 소비 전력의 효율성을 높이는데 효과적이다.