The Japanese Repo Market: Theory and Evidence

Repurchase agreement (repo) transactions are widely used as a risk-free means of borrowing or lending funds and securities. Repo transactions can be categorized into (1) general collateral (GC) repos that borrow or lend funds, and (2) special collateral (SC) repos that borrow or lend specific securities. GC repo rates are priced at a level close to the risk-free interest rate, while SC repo rates are often priced far below the GC repo rates. This paper aims to examine the pricing mechanism of the Japanese repo market from both theoretical and empirical perspectives. First, Duffie (1996) and Krishnamurthy (2001) show that (1) equilibrium in the repo market requires no-arbitrage profits from combining repo and cash bond transactions, (2) the equilibrium level of repo spreads between GC and SC repo rates is determined at the point where the supply and demand curves of the underlying bond issues intersect in the repo market, and (3) expected returns from future matched book trading are reflected in the cash prices of SC bond issues. Second, the paper empirically examines the above theoretical implications using the data of repo rates and government bond prices in Japan. Our empirical results show that, regarding the on-the- run and the cheapest-to-deliver (CTD) issues, the above no-arbitrage condition is significantly satisfied.

Spatial Concept Acquisition for a Mobile Robot that Integrates Self-Localization and Unsupervised Word Discovery from Spoken Sentences

In this paper, we propose a novel unsupervised learning method for the lexical acquisition of words related to places visited by robots, from human continuous speech signals. We address the problem of learning novel words by a robot that has no prior knowledge of these words except for a primitive acoustic model. Further, we propose a method that allows a robot to effectively use the learned words and their meanings for self-localization tasks. The proposed method is nonparametric Bayesian spatial concept acquisition method (SpCoA) that integrates the generative model for self-localization and the unsupervised word segmentation in uttered sentences via latent variables related to the spatial concept. We implemented the proposed method SpCoA on SIGVerse, which is a simulation environment, and TurtleBot2, which is a mobile robot in a real environment. Further, we conducted experiments for evaluating the performance of SpCoA. The experimental results showed that SpCoA enabled the robot to acquire the names of places from speech sentences. They also revealed that the robot could effectively utilize the acquired spatial concepts and reduce the uncertainty in self-localization.Comment: This paper was accepted in the IEEE Transactions on Cognitive and Developmental Systems. (04-May-2016

Online Spatial Concept and Lexical Acquisition with Simultaneous Localization and Mapping

In this paper, we propose an online learning algorithm based on a Rao-Blackwellized particle filter for spatial concept acquisition and mapping. We have proposed a nonparametric Bayesian spatial concept acquisition model (SpCoA). We propose a novel method (SpCoSLAM) integrating SpCoA and FastSLAM in the theoretical framework of the Bayesian generative model. The proposed method can simultaneously learn place categories and lexicons while incrementally generating an environmental map. Furthermore, the proposed method has scene image features and a language model added to SpCoA. In the experiments, we tested online learning of spatial concepts and environmental maps in a novel environment of which the robot did not have a map. Then, we evaluated the results of online learning of spatial concepts and lexical acquisition. The experimental results demonstrated that the robot was able to more accurately learn the relationships between words and the place in the environmental map incrementally by using the proposed method.Comment: This paper was accepted in the 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2017

Role of structural relaxations and vibrational excitations in the high-frequency dynamics of liquids and glasses

We present theoretical investigation on the high-frequency collective dynamics in liquids and glasses at microscopic length scales and terahertz frequency region based on the mode-coupling theory for ideal liquid-glass transition. We focus on recently investigated issues from inelastic-X-ray-scattering and computer-simulation studies for dynamic structure factors and longitudinal and transversal current spectra: the anomalous dispersion of the high-frequency sound velocity and the nature of the low-frequency excitation called the boson peak. It will be discussed how the sound mode interferes with other low-lying modes present in the system. Thereby, we provide a systematic explanation of the anomalous sound-velocity dispersion in systems -- ranging from high temperature liquid down to deep inside the glass state -- in terms of the contributions from the structural-relaxation processes and from vibrational excitations called the anomalous-oscillation peak (AOP). A possibility of observing negative dispersion -- the {\em decrease} of the sound velocity upon increase of the wave number -- is argued when the sound-velocity dispersion is dominated by the contribution from the vibrational dynamics. We also show that the low-frequency excitation, observable in both of the glass-state longitudinal and transversal current spectra at the same resonance frequency, is the manifestation of the AOP. As a consequence of the presence of the AOP in the transversal current spectra, it is predicted that the transversal sound velocity also exhibits the anomalous dispersion. These results of the theory are demonstrated for a model of the Lennard-Jones system.Comment: 25 pages, 22 figure

A Mathematical Model for Estimating Biological Damage Caused by Radiation

We propose a mathematical model for estimating biological damage caused by low-dose irradiation. We understand that the Linear Non Threshold (LNT) hypothesis is realized only in the case of no recovery effects. In order to treat the realistic living objects, our model takes into account various types of recovery as well as proliferation mechanism, which may change the resultant damage, especially for the case of lower dose rate irradiation. It turns out that the lower the radiation dose rate, the safer the irradiated system of living object (which is called symbolically "tissue" hereafter) can have chances to survive, which can reproduce the so-called dose and dose-rate effectiveness factor (DDREF).Comment: 22 pages, 6 Figs, accepted in Journal of the Physical Society of Japa

Instrumental Resolution of the Chopper Spectrometer 4SEASONS Evaluated by Monte Carlo Simulation

We performed simulations of the resolution function of the 4SEASONS spectrometer at J-PARC by using the Monte Carlo simulation package McStas. The simulations showed reasonably good agreement with analytical calculations of energy and momentum resolutions by using a simplified description. We implemented new functionalities in Utsusemi, the standard data analysis tool used in 4SEASONS, to enable visualization of the simulated resolution function and predict its shape for specific experimental configurations.Comment: 8 pages, 5 figure

<Articles>"Other World" as a Ideology : The Funeral Oration of Hani People in Honhe Pref., Yunnan Prov., China

儀礼においてそのテキストを翻訳し、それに内在化された意味を考えることは、儀礼におけるイデオロギーとプラクティスという問題形式[田部1989]からすると、そのイデオロギー側の一端を明らかにするに過ぎない。他界観という言葉で括られるものはある民族的論理形式をとった一連の観念的構築物であって、モビ(司祭)の持っているイデオロギーである。・・