クラスター, 遷移金属錯体, 自己集合系のエネルギー曲面の探索

京都大学新制・課程博士博士(工学)甲第23220号工博第4864号新制||工||1759(附属図書館)京都大学大学院工学研究科分子工学専攻(主査)教授 佐藤 啓文, 教授 佐藤 徹, 教授 田中 勝久学位規則第4条第1項該当Doctor of Philosophy (Engineering)Kyoto UniversityDGA

Technical Efficiency, Regulation, and Heterogeneity in Japanese Airports

In this paper, the random stochastic frontier model is used to estimate the technical efficiency of Japanese airports taking into regulation and heterogeneity in the variables. The airports are ranked according to their productivity for the period 1987 to 2005 and homogenous and heterogeneous variables in the cost function are disentangled. Policy implication is derived.Japan; airports; efficiency; random frontier models; policy implications

Effect of Market Competition on Passengers’ Time Cost by Conventional Rail

Due to heavy deficits, the privatization of Japanese National Railways (JNR) was initiated on April 1, 1987 and was geographically divided into six different railway companies for transporting passengers. This paper investigates the impact of market competition on conventional rail (CR) passengers’ time cost by using a difference-in-differences (DID) approach and directional origin-destination (OD) pair level data in four periods: two years before JNR’s privatization (1976 and 1986) and two years after JNR’s privatization (1996 and 2006). It investigates the effect of market competition on passengers’ time cost in the regions where CR competes with high-speed rail (HSR), when comparing with monopoly region after JNR privatization. The result of this analysis shows that market competition leads to an increment in passengers’ time cost by CR in duopoly regions when comparing with the change of time cost by CR in monopoly region, but it is not statistically significant.The present work was supported through the Hiroshima University TAOYAKA Program for creating a flexible, enduring, peaceful society, funded by the Program for Leading Graduate Schools, Ministry of Education, Culture, Sports, Science and Technology

A quantum chemical model for a series of self-assembled nanocages: the origin of stability behind the coordination-driven formation of transition metal complexes up to [M₁₂L₂₄]²⁴⁺

Herein, we present a systematic computational model to study the electronic states and free energies of a self-assembled multi-metal complex series. By combining the previously developed model Hamiltonian approach for transition-metal complexes and the generalized Born model, the thermodynamics, optimized geometries, and electronic states of the [Pd12L24]24+ nanocage are revealed, together with [PdnLm]2n+ complex series. The effective model Hamiltonian is a theoretical method to obtain the d-electron wavefunction and potential energy including interaction energy between the transition-metal and ligands. In the present improvement, the electronic state on each transition-metal center is focused as a building unit and solved under the whole electronic field of the assembling system. We realize a reliable and systematic treatment of multi-transition-metal complexes with different sizes and charges. Consequently, our model could reproduce binding energies of the [PdnLm]2n+ complex series quantitatively as compared to density functional theory (DFT). Regarding free energy, we revealed that the assembling solute becomes unstable due to the electrostatic interaction, and effects of the solvent and counter anions mainly compensated it. Optimized geometries were also analysed. The local square-planar coordination structures around the palladium centres were characterized in the complex series. The relationships between the entire symmetrical geometries and the local coordination structures are also discussed. Finally, electronic structures of the [Pd12L24]24+ nanocage were well characterized as a single-determinant, where only dx2−y2 is unoccupied due to the ligand-field effect. We also found that the solvent polarized the electronic states of the Pd ions, whereas the counter anion suppressed the polarization. The present method realizes size-independent reliable and rapid computations, and therefore can be expected to further application studies on self-assembly dynamics

Universal Scaling Bounds on a Quantum Heat Current

We derive new bounds on a heat current flowing into a quantum $L$-particle system coupled with a Markovian environment. By assuming that a system Hamiltonian and a system-environment interaction Hamiltonian are extensive in $L$, we show that the absolute value of the heat current scales at most as $\Theta (L^3)$ in a limit of large $L$. Also, we present an example that saturates this bound in terms of scaling: non-interacting particles globally coupled with a thermal bath. However, the construction of such system requires many-body interactions induced by the environment, which may be difficult to realize with the current technology. To consider more feasible cases, we focus on a class of system where any non-diagonal elements of the noise operator (derived from the system-environment interaction Hamiltonian) become zero in the system energy basis, if the energy difference is beyond a certain value $\Delta E$. Then, for $\Delta E = \Theta (L^0)$, we derive another scaling bound $\Theta (L^2)$ on the absolute value of the heat current, and the so-called superradiance belongs to a class to saturate this bound. Our results are useful to evaluate the best achievable performance of quantum-enhanced thermodynamic devices, which contain far-reaching applications for such as quantum heat engines, quantum refrigerators and quantum batteries.Comment: 6+18 pages, 2+2 figure

The Impact of Market Competition on High-Speed Rail Service Quality: Does Monopoly Slow Down a Bullet Train?

When Japan National Railways (JNR) was privatized into six regionally monopolistic railway corporations in 1987, there emerged exceptional areas where the industrial structure of railway transportation happened to be duopolistic due to an operational reason. Leveraging on this natural experimental setting arising from the privatization of JNR, we estimate the impact of market competition on the service quality i.e., speed and scheduling of a high-speed rail (HSR) run by an oligopolistic service provider. The paper shows that the change in time costs is significantly lower in those segments where HSR is competing with a conventional rail, and that such effect is larger for the shorter-distance markets where the competition is presumably more intensive.This work is partly supported by the Ministry of Education of Japan Grant-in-Aid for Scientific Research #24530295, 16K03628, 16H03610, 16H03673