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Search Results: 1 - 10 of 248 matches for " Keigo; "
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The Effects of Income Inequality on Education Policy and Economic Growth  [PDF]
Katsuyuki Naito, Keigo Nishida
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.21020
Abstract: This paper presents a simple model to investigate the relationship among initial income inequality, education and eco- nomic growth. Public expenditure on education is determined through majority voting. Although preferences of individuals are not single-peaked, the individual with the median income becomes the decisive voter. Our model predicts that high initial inequality has a negative impact on education expenditure and therefore retards economic growth.
TLRs, Alcohol, HCV, and Tumorigenesis
Keigo Machida
Gastroenterology Research and Practice , 2010, DOI: 10.1155/2010/518674
Abstract: Chronic liver damage caused by viral infection, alcohol, or obesity can result in increased risk for hepatocellular carcinoma (HCC). Ample epidemiological evidence suggests that there is a strong synergism between hepatitis C virus (HCV) and alcoholic liver diseases (ALD). The Toll-like receptor (TLR) signaling pathway is upregulated in chronic liver diseases. Alcoholism is associated with endotoxemia that stimulates expression of proinflammatory cytokine expression and inflammation in the liver and fat tissues. Recent studies of HCC have centered on cancer-initiating stem cell (CSC), including detection of CSC in cancer, identification of CSC markers, and isolation of CSC from human HCC cell lines. Synergism between alcohol and HCV may lead to liver tumorigenesis through TLR signaling. 1. HCV, Alcohol, and HCC Chronic liver damage caused by viral infection, alcohol, or metabolic syndrome can result in increased risk for HCC which is the third most common cancer in the world [1]. This virus is a major cause of HCC, which is the fifth most common cancer in the world. HCC has a low five-year survival rate due to the lack of therapeutic options and is highly prevalent in the world, especially in Africa and Asia [1]. Clearly, understanding the molecular mechanisms of HCV-induced hepatocarcinogenesis is required for the eventual development of improved therapeutic modalities for this disease [2]. In particular, chronic infection with HBV or HCV represents a major risk factor for HCC [1]. HCV affects more than 170 million people worldwide [1, 3, 4]. Ample epidemiological evidence suggests that there is a strong connection between hepatitis C virus (HCV) and ALD. First, the prevalence of HCV is significantly higher among alcoholics than in the general population; for example, while the HCV positive rate in the general population of the U.S. is roughly 1%, it is 16% for alcoholics and nearly 30% for alcoholics with liver diseases [5]. Second, the presence of HCV infection correlates with the severity of the disease in alcoholic subjects, that is, HCV-infected patients with ALD develop liver cirrhosis and HCC at a significantly younger age than uninfected ALD patients, suggesting that alcohol and HCV work synergistically to cause liver damage [6]. Many studies also support synergistic interactions between HCV and alcoholism in hepatocarcinogenesis [7–11]. Heavy alcohol consumption and viral hepatitis synergistically increase the risk for HCC among blacks and whites in the U.S. [10]. HCC odds ratio increases to 48.3-fold and 47.8 from 8.1 and 8.6 by having
Wideband Infrared Spectrometer for Characterization of Transiting Exoplanets with Space Telescopes
Keigo Enya
Physics , 2012, DOI: 10.1117/12.925597
Abstract: This paper presents a conceptual design for a spectrometer designed specifically for characterizing transiting exoplanets with space-borne infrared telescopes. The design adopting cross-dispersion is intended to be simple, compact, highly stable, and has capability of simultaneous coverage over a wide wavelength region with high throughput. Typical wavelength coverage and spectral resolving power is 1-13 micron with a spectral resolving power of ~ a few hundred, respectively. The baseline design consists of two detectors, two prisms with a dichroic coating and microstructured grating surfaces, and three mirrors. Moving parts are not adopted. The effect of defocusing is evaluated for the case of a simple shift of the detector, and anisotropic defocusing to maintain the spectral resolving power. Variations in the design and its application to planned missions are also discussed.
Particle mesh multipole method: An efficient solver for gravitational/electrostatic forces based on multipole method and fast convolution over a uniform mesh
Keigo Nitadori
Physics , 2014,
Abstract: We propose an efficient algorithm for the evaluation of the potential and its gradient of gravitational/electrostatic $N$-body systems, which we call particle mesh multipole method (PMMM or PM$^3$). PMMM can be understood both as an extension of the particle mesh (PM) method and as an optimization of the fast multipole method (FMM).In the former viewpoint, the scalar density and potential held by a grid point are extended to multipole moments and local expansions in $(p+1)^2$ real numbers, where $p$ is the order of expansion. In the latter viewpoint, a hierarchical octree structure which brings its $\mathcal O(N)$ nature, is replaced with a uniform mesh structure, and we exploit the convolution theorem with fast Fourier transform (FFT) to speed up the calculations. Hence, independent $(p+1)^2$ FFTs with the size equal to the number of grid points are performed. The fundamental idea is common to PPPM/MPE by Shimada et al. (1993) and FFTM by Ong et al. (2003). PMMM differs from them in supporting both the open and periodic boundary conditions, and employing an irreducible form where both the multipole moments and local expansions are expressed in $(p+1)^2$ real numbers and the transformation matrices in $(2p+1)^2$ real numbers. The computational complexity is the larger of $\mathcal O(p^2 N)$ and $\mathcal O(N \log (N/p^2))$, and the memory demand is $\mathcal O(N)$ when the number of grid points is $\propto N/p^2$.
Accelerating Iterative Detection for Spatially Coupled Systems by Collaborative Training
Keigo Takeuchi
Mathematics , 2012,
Abstract: This letter proposes a novel method for accelerating iterative detection for spatially coupled (SC) systems. An SC system is constructed by one-dimensional coupling of many subsystems, which are classified into training and propagation parts. An irregular structure is introduced into the subsystems in the training part so that information in that part can be detected successfully. The obtained reliable information may spread over the whole system via the subsystems in the propagation part. In order to allow the subsystems in the training part to collaborate, shortcuts between them are created to accelerate iterative detection for that part. As an example of SC systems, SC code-division multiple-access (CDMA) systems are considered. Density Evolution for the SC CDMA systems shows that the proposed method can provide a significant reduction in the number of iterations for highly loaded systems.
Iterative LMMSE Channel Estimation, Multiuser Detection, and Decoding via Spatial Coupling
Keigo Takeuchi
Mathematics , 2014,
Abstract: Spatial coupling is utilized to improve the performance of iterative channel estimation, multiuser detection, and decoding for multiple-input multiple-input (MIMO) bit-interleaved coded modulation (BICM). Coupling is applied to both coding and BICM---the encoder uses a protograph-based spatially-coupled low-density parity-check (SC LDPC) code. Spatially and temporally coupled (STC) BICM is proposed to enable iterative channel estimation via coupling. Linear minimum mean-squared error (LMMSE) estimation is applied for both channel estimation and detection to reduce the complexity. Tractable density evolution (DE) equations are derived to analyze the convergence property of iterative receivers in the large-system limit, via a tool developed in statistical physics---replica method. The DE analysis implies that the STC BICM can improve the performance of iterative channel estimation especially for higher-order modulation. Numerical simulations show that the STC BICM can provide a significant gain of the performance at high signal-to-noise ratios for 64 quadrature amplitude modulation (QAM), as well as an improvement in the decoding threshold, compared to conventional BICM.
A Generalization of Threshold Saturation: Application to Spatially Coupled BICM-ID
Keigo Takeuchi
Computer Science , 2014,
Abstract: Spatial coupling was proved to improve the belief-propagation (BP) performance up to the maximum-a-posteriori (MAP) performance. This paper addresses an extended class of spatially coupled (SC) systems. A potential function is derived for characterizing a lower bound on the BP performance of the extended SC systems, and shown to be different from the potential for the conventional SC systems. This may imply that the BP performance for the extended SC systems does not coincide with the MAP performance for the corresponding uncoupled system. SC bit-interleaved coded modulation with iterative decoding (BICM-ID) is also investigated as an application of the extended SC systems.
Land-Use and Land-Cover Mapping Using a Gradable Classification Method
Keigo Kitada,Kaoru Fukuyama
Remote Sensing , 2012, DOI: 10.3390/rs4061544
Abstract: Conventional spectral-based classification methods have significant limitations in the digital classification of urban land-use and land-cover classes from high-resolution remotely sensed data because of the lack of consideration given to the spatial properties of images. To recognize the complex distribution of urban features in high-resolution image data, texture information consisting of a group of pixels should be considered. Lacunarity is an index used to characterize different texture appearances. It is often reported that the land-use and land-cover in urban areas can be effectively classified using the lacunarity index with high-resolution images. However, the applicability of the maximum-likelihood approach for hybrid analysis has not been reported. A more effective approach that employs the original spectral data and lacunarity index can be expected to improve the accuracy of the classification. A new classification procedure referred to as “gradable classification method” is proposed in this study. This method improves the classification accuracy in incremental steps. The proposed classification approach integrates several classification maps created from original images and lacunarity maps, which consist of lacnarity values, to create a new classification map. The results of this study confirm the suitability of the gradable classification approach, which produced a higher overall accuracy (68%) and kappa coefficient (0.64) than those (65% and 0.60, respectively) obtained with the maximum-likelihood approach.
MEASURING DEGREE OF DEPARTURE FROM EXTENDED QUASI-SYMMETRY FOR SQUARE CONTINGENCY TABLES MEDICIóN DEL GRADO ALEJAMIENTO DEL MODELO EXTENDIDO CUASI SIMéTRICO PARA TABLAS DE CONTINGENCIA CUADRADAS
Tahata Kouji,Kozai Keigo
Revista Colombiana de Estadística , 2012,
Abstract: For square contingency tables with ordered categories, the present paper proposes a measure to represent the degree of departure from the extended quasi-symmetry (EQS) model. It is expressed by using the Cressie-Read power-divergence or Patil-Taillie diversity index. The present paper also defines the maximum departure from EQS which indicates the maximum departure from the uniformity of ratios of symmetric odds-ratios. The measure lies between 0 and 1, and it is useful for not only seeing the degree of departure from EQS in a table but also comparing it in several tables. El presente artículo propone una medida para representar el grado de alejamiento del modelo extendido cuasisimétrico (EQS, por su sigla en inglés) para tablas de contingencia con categorías ordenadas. Esta medida se expresa mediante el uso de la divergencia de potencia de Cressie-Read o el índice de diversidad Patil-Taillie. Nuestro trabajo también define el máximo alejamiento de EQS, el cual indica el alejamiento máximo de la uniformidad de razones de odds-ratios simétricos. La medida cae entre 0 y 1 y es útil no solo para determinar el grado de alejamiento de EQS en una tabla, sino también para comparar este grado de alejamiento en varias tablas.
Structure of energy level degeneracy of a single-spin model from a view point of symmetry of the spin anisotropy and its nontrivial spin($S$)-dependence on the higher order anisotropy
Keigo Hijii,Seiji Miyashita
Physics , 2009,
Abstract: We study structure of the gapless points (diabolical points) at zero magnetic field ($H_z=0$) of single-spin models with spin anisotropies. Nontrivial appearance of diabolical points at finite transverse field $H_x$ has been studied from the view point of interference of the Berry phase, and related phenomena have been experimentally found in the single molecular magnet Fe$_8$. We study effects of the orthorhombic single-ion anisotropy $E(S_+^2+S_-^2)$ and find a symmetry associated with the degeneracy, which provides a clear picture of the global structure of energy level diagram including the excited states. Moreover, we study effects of the higher order anisotropy $C(S_+^4+S_-^4)$, and find that, in contrast to the semiclassical limit $(S\to\infty)$, location of a pair annihilation of the diabolical point does not coincides with a point at which a pair of diabolical points appears in nonzero $H_y$ space(bifurcation points). Distance between the annihilation and bifurcation points vanishes when $S\to\infty$, which restores the semiclassical result. We obtain a complete structure of the diabolical points in the $(C,H_x)$ plane.
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