Notes on Inhomogeneous Quantum Walks

We study a class of discrete-time quantum walks with inhomogeneous coins defined in [Y. Shikano and H. Katsura, Phys. Rev. E {\bf 82}, 031122 (2010)]. We establish symmetry properties of the spectrum of the evolution operator, which resembles the Hofstadter butterfly.Comment: 4 pages, 2 figures, as the proceedings of QCMC 201

Electric field induced thermal Hall effect of triplons in the quantum dimer magnets XXCuCl3_{3} (X=X = Tl, K)

We propose the electric field induced thermal Hall effect of triplons in the quantum dimer magnets $X$CuCl$_{3}$ ($X =$ Tl, K), which exhibit spin-driven ferroelectricity in the Bose-Einstein condensation phase of triplons. The interplay between ferroelectricity and magnetism in these materials leads to the magnetoelectric effect, i.e., an electric-field induced Dzyaloshinskii-Moriya (DM) interaction between spins belonging to the same dimer. We argue that this intra-dimer DM interaction breaks the symmetry of the system in the absence of an electric field and gives rise to the thermal Hall effect, which can be detected in experimentally accessible electric and magnetic fields. We also show that the thermal Hall effect can be controlled by changing the strength or direction of the electric field.Comment: 12 pages, 4 figure

Development and verification of control system for heat recovery ground source heat pump system

An operation method and control system for heat recovery ground source heat pump (HR-GSHP) systems have been developed. By applying the operation method and control system, the heating and cooling output from the respective GSHP units can be controlled according to the operational condition. This maximizes the energy saving effect by operating the GSHP units without excess temperature change of the heat carrier fluid. In this paper, the outlines of HR-GSHP system and the importance of control system for the HR-GSHP systems were firstly explained. Next, the control system's configuration and the control methodology were explained. In addition, the operation of a HR-GSHP system with the control system, in which the control methodology had been installed, was verified by using the field test apparatus. As the result, it was confirmed that the above control methodologies were applicable

Design and simulation tool for ground source heat pump systems considering groundwater advection

Calculation of the underground temperature resulting from heat injection/extraction into/from ground heat exchangers (GHEXs) with hourly variation is one of the most noteworthy challenges to address when simulating and designing a ground source heat pump (GSHP) system. Especially in Japan, considering the groundwater flow is desirable because there is the possibility to reduce the installation cost for GSHP system. In order to overcome this challenge, the authors introduce a method to calculate the underground temperature, by considering heat injection/extraction into/from GHEXs with hourly variation. The method applies the superposition of the Moving Infinite Cylindrical Source (MICS) solution and the Moving Infinite Line Source (MILS) solution to calculate the temperature change due to heat injection/extraction into/from the certain GHEX and other neighboring GHEXs, respectively. In this paper, the outlines of the MICS and the method that calculate the MICS solution were firstly introduced. Next, the calculation method of underground temperature and the simulation model for the GSHP system were explained. Finally, the temperature variations of the heat carrier fluid were calculated by changing the conditions the geological layer and groundwater velocity