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Search Results: 1 - 10 of 445 matches for " Kazuki Kikkawa "
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Measurement Reliability for Evaluating Lumbopelvic Curvature during Active Knee Extension in Sitting Using a Flexible Ruler in Individuals with Clinically Tight Hamstring Muscles: A Secondary Analysis  [PDF]
Hiroshi Takasaki, Kazuki Kikkawa, Toby Hall
Open Journal of Therapy and Rehabilitation (OJTR) , 2018, DOI: 10.4236/ojtr.2018.61001
Abstract: In a previous study, we established reliability of a method for determining the angle of lumbopelvic sagittal alignment during active knee extension in sitting (AKEiS) using a flexible ruler and image analysis software (2-point-Method). In addition to this method, a flexible ruler can also be used to measure lumbopelvic sagittal alignment without image analysis software. This study primarily aimed to investigate the minimum number of repetitions, inter-session reliability and inter-examiner reliability of two alternative methods of measurement in a secondary analysis of our previous study. A flexible ruler was used to measure lumbopelvic curvature during AKEiS when the knee reached 10° flexion from 27 individuals with clinically tight hamstring muscles and subsequently analyzed. Lumbopelvic sagittal alignment was evaluated for the region between T12 and S2 using the maximum depth to the curvature (Max-Method) or depth to the curvature at the middle point between T12 and S2 vertebral levels (Mid-Method). It was determined that four repetitions for the Max-Method and 11 repetitions for the Mid-Method were required for the minimum number of repetitions, respectively. Inter-session reliability and inter-examiner reliability were assessed using Intraclass Correlation Coefficients and were 0.91 and 0.91 for the Max-Method and 0.90 and 0.91 for the Mid-Method, respectively. The current study suggests that the Mid-Method would not be recommended for use in the clinical setting as 11 repetitions of data sampling is required. The 2-point-Method or Max-Method may be promising but the ideal measurement method will be identified when the validity of these methods has been established.
Simple Calculus of Resolving the Fiscal Policy Puzzle: The Role of Human Capital  [PDF]
Kazuki Hiraga
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.49093
Abstract: This paper investigates how much externality of human capital a la on-the-job training resolves the fiscal policy puzzle that is consistent with the empirical evidences which obtain the positive response of consumption and wage to increase of fiscal spending in general equilibrium model.
Simple Analysis of Dynamic Efficiency in Endogenous Fertility  [PDF]
Kazuki Hiraga
Theoretical Economics Letters (TEL) , 2015, DOI: 10.4236/tel.2015.54063
Abstract: This paper compares with two conditions of dynamic (in)efficiency, which is “traditional” and “modified” in overlapped generations (OLG) model with endogenous fertility. We show that both two conditions of dynamic efficiency have a bliss point which maximizes the utility at steady state in endogenous fertility.
The Construction of Pairwise Additive Minimal BIB Designs with Asymptotic Results  [PDF]
Kazuki Matsubara, Sanpei Kageyama
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.514207
Abstract: An asymptotic existence of balanced incomplete block (BIB) designs and pairwise balanced designs (PBD) has been discussed in [1]-[3]. On the other hand, the existence of additive BIB designs and pairwise additive BIB designs with k = 2 and λ = 1 has been discussed with direct and recursive constructions in [4]-[8]. In this paper, an asymptotic existence of pairwise additive BIB designs is proved by use of Wilson’s theorem on PBD, and also for some and k the exact existence of l pairwise additive BIB designs with block size k and λ = 1 is discussed.
Fiscal Sustainability of Japanese Prefectural Government Debt  [PDF]
Rena Akamatsu, Kazuki Hiraga
Open Journal of Social Sciences (JSS) , 2015, DOI: 10.4236/jss.2015.38009
Abstract: This paper investigates whether the Japanese local government debt is sustainable. We apply the fiscal stabilization rule that each local government improves their primary balance in the current year when they issue additional debt the previous year. We check it using panel data of the Japanese prefectural governments. We find that Japanese prefectural governments were not sustainable across 1956-2007, though were sustainable across 1956-1989.
Preparation of PDOT:PSS Transparent Conductive Film Using Ink-Jet Printing  [PDF]
Atsushi Nitta, Kazuki Shimono
Advances in Materials Physics and Chemistry (AMPC) , 2015, DOI: 10.4236/ampc.2015.512047
Abstract: Flexible devices produced using organic materials have attracted the attention of many researchers. Important components of these flexible devices include transparent electrodes, which transmit visible light and possess conductivity. The present study improved the characteristics of a transparent conductive film that was made of poly(3, 4 ethylenedioxythiophene):poly(styrenesul-fonate) (PEDOT:PSS), an organic conductive material, and that had been prepared using ink-jet printing. To improve the resistance value and visible light transmittance of the film, the film substrate was first cleaned with ultraviolet/ozone treatment, and then the film was annealed after it was deposited on the substrate and dipped into a polar solvent. Consequently, the resistance value of the thin film decreased. However, the surface state of the film changed according to the treatment method and affected its visible light transmittance. Thus, the surface state of the film substrate, the annealing temperature after film deposition, and the dipping treatment with a polar solvent influenced the characteristics of a thin film.
Effect of Signal Filtering on Image Quality of Projection-Based Magnetic Particle Imaging  [PDF]
Kazuki Shimada, Kenya Murase
Open Journal of Medical Imaging (OJMI) , 2017, DOI: 10.4236/ojmi.2017.72005
Abstract: Purpose: Magnetic particle imaging (MPI) allows for imaging of the spatial distribution of magnetic nanoparticles (MNPs) in positive contrast, with high sensitivity, high spatial resolution, and high imaging speed. It is necessary to increase the signal-to-noise ratio to enhance the reliability of MPI. The purpose of this study was to investigate the effect of signal filtering on the image quality and quantitativity in projection-based MPI using phantoms. Materials and Methods: We fabricated two kinds of phantom (cylindrical tube phantom with a diameter of 6 mm and A-shaped phantom) and evaluated the effect of signal filtering in terms of root-mean-square (RMS) granularity and the correlation coefficient between iron concentrations of MNPs and average MPI values for four filter modes (THRU, BPF, BEF, and LPF). In the THRU mode, the signal input was output without passing through the filter. In the BPF mode, only the third-harmonic signal was passed using a band-pass filter (central frequency: 1200 Hz, band width: 1/3 octave). In the BEF mode, the first-harmonic signal was eliminated using a band-elimination filter (central frequency: 400 Hz, band width: 1/3 octave). In the LPF mode, only the signal with a frequency less than the third-harmonic frequency was passed using a low-pass filter (cut-off frequency: 1200 Hz, -24 ± 2 dB/octave). The RMS granularity was obtained by calculating standard deviations of the pixel values in the MPI image without MNPs, whereas average MPI values were obtained by drawing a circular region of interest with a diameter of 6 mm on the MPI image of the cylindrical tube phantom. Results: When using the filtered back-projection (FBP) method with a ramp filter for image reconstruction, the RMS granularity and correlation coefficient decreased in the order of THRU, BPF, BEF, and LPF. In the BPF mode, however, some artifacts were observed. When using the maximum likelihood-expectation maximization (ML-EM) algorithm with an iteration number of 15, the correlation coefficient decreased in the order of THRU, BPF, BEF, and LPF, whereas the RMS granularity did not largely depend on the filter mode and was significantly (p < 0.05) lower than that for the FBP method for all the filter modes. Conclusion: The BEF mode is adequate for the FBP method in projection-based MPI, whereas THRU is a best option in use of the ML-EM algorithm.
Study of an Omnidirectional Guide Wave Sensor Using an EMAT  [PDF]
Riichi Murayama, Kazuki Iwaya
Journal of Sensor Technology (JST) , 2017, DOI: 10.4236/jst.2017.72002
Abstract: Nondestructive inspection of structures is important for ensuring the safety of the social infrastructure. Among them, the ultrasonic inspection method plays a role as a major technology. However, when examining a huge structure, the inspection time tends to be very long. Therefore, a system for transmitting and receiving ultrasonic waves in all directions from the ultrasonic sensor has been constructed. Several types of ultrasonic sensors using this concept have already been devised, but since the ultrasonic energy is dispersed in all directions, there is a problem that a sufficient detection performance cannot be ensured, especially when the thickness of the material to be inspected becomes thick. Therefore, we developed a highly sensitive omnidirectional ultrasonic sensor utilizing the resonance phenomenon of the ultrasonic wave propa-gating in the thickness direction. The omnidirectional ultrasonic system also consists of an electromagnetic ultrasonic transducer (EMAT) using a circular magnet. It is possible to inspect the plate thickness from 0.3 mm to 10 mm and the inspection range of the diameter of 300 mm around the sensor by the developed system. It is indicated that the developed system allows the high-speed inspection of huge structures.
The Sustainability of Japan’s Government Debt: A Review  [PDF]
Tomomi Miyazaki, Kazuki Onji
Theoretical Economics Letters (TEL) , 2017, DOI: 10.4236/tel.2017.76110
Abstract: This paper reviews the literature on the sustainability of Japanese government debt/deficit. First, we offer an overview of the approaches and the key findings on the sustainability analysis. Second, we introduce the arguments of Hoshi and Ito [1], which they predict that foreign investors’ share of JGBs could exceed beyond domestic ownership. Finally, we discuss the coordination problem in the JGB market based on the findings of Onji et al. [2] that examine how government withdrawal from the JGBs could roil the market.
Lock-in-Amplifier Model for Analyzing the Behavior of Signal Harmonics in Magnetic Particle Imaging  [PDF]
Kenya Murase, Kazuki Shimada
Open Journal of Applied Sciences (OJAppS) , 2018, DOI: 10.4236/ojapps.2018.85014
Abstract: The purpose of this study was to present a lock-in-amplifier model for analyzing the behavior of signal harmonics in magnetic particle imaging (MPI) and some simulation results based on this model. In the lock-in-amplifier model, the signal induced by magnetic nanoparticles (MNPs) in a receiving coil was multiplied with a reference signal, and was then fed through a low-pass filter to extract the DC component of the signal (output signal). The MPI signal was defined as the mean of the absolute value of the output signal. The magnetization and particle size distribution of MNPs were assumed to obey the Langevin theory of paramagnetism and a log-normal distribution, respectively, and the strength of the selection magnetic field (SMF) in MPI was assumed to be given by the product of the gradient strength of the SMF and the distance from the field-free region (x). In addition, Gaussian noise was added to the signal induced by MNPs using normally-distributed random numbers. The relationships between the MPI signal and x were calculated for the odd- and even-numbered harmonics and were investigated for various time constants of the low-pass filter used in the lock-in amplifier and particle sizes and their distributions of MNPs. We found that the behavior of the MPI signal largely depended on the time constant of the low-pass filter and the particle size of MNPs. This lock-in-amplifier model will be useful for better understanding, optimizing, and developing MPI, and for designing MNPs appropriate for MPI.
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