A multiobjective maximal covering location problem incorporating inter-city traffic network

Location-allocation models provide a valuable tool for operationalizing the central place theory. This paper attempts to integrate the marketing principle and the traffic principle in Christaller\u27s central place theory using multiobjective model. The model is formulated with two objectives: (a) minimize the total population uncovered by each service, and (b) minimize the total cost of constructing arcs between centers. Some computational results indicate that the model is possible to derive the flexible system of central place hierarchy

Generalization of Central Place Theory Using Mathematical Programming

首都大学東京, 2015-03-25, 博士（理学）, 乙第101号首都大学東

Self-evolving photonic crystals for ultrafast photonics

高速自己変化可能なフォトニック結晶による高ピーク出力・短パルス光の発生 --超スマート社会を支える高精度光センシングやレーザー微細加工応用に向けて--. 京都大学プレスリリース. 2023-01-27.Ultrafast dynamics in nanophotonic materials is attracting increasing attention from the perspective of exploring new physics in fundamental science and expanding functionalities in various photonic devices. In general, such dynamics is induced by external stimuli such as optical pumping or voltage application, which becomes more difficult as the optical power to be controlled becomes larger owing to the increase in the energy required for the external control. Here, we demonstrate a concept of the self-evolving photonic crystal, where the spatial profile of the photonic band is dynamically changed through carrier-photon interactions only by injecting continuous uniform current. Based on this concept, we experimentally demonstrate short-pulse generation with a high peak power of 80 W and a pulse width of <30 ps in a 1-mm-diameter GaAs-based photonic crystal. Our findings on self-evolving carrier-photon dynamics will greatly expand the potential of nanophotonic materials and will open up various scientific and industrial applications

Public Status and Prevalence of Acupuncture in Japan

Acupuncture originated in China and is widespread throughout Asia. It is expected that a higher utilization of this remedy exists in these countries compared to Western countries. We conducted annual nationwide surveys from 2003 through 2006 on the utilization of acupuncture in Japan. Face-to-face interviews were conducted with 2000 individuals randomly chosen from the resident database. Annual utilization percentages, based on the number of respondents, from 2003 to 2006 were 6.5%, 4.8%, 6.4%, and 6.7%, respectively, while lifetime experiences determined in each surveys were estimated as 26.7, 19.4, 24.4 and 25.4, respectively. Respondents who had utilized acupuncture and/or moxibustion tended to be older than those who had no experience. Acupuncture was mainly used for musculoskeletal symptoms, and a detailed breakdown of the musculoskeletal symptoms identified in the 2005 survey showed 50.9% for low back pain, 35.9% for shoulder stiffness and 12.0% for knee pain. Reasons given for continuing therapy included the effective amelioration of symptoms, comfort of the procedure and low number of side-effects, while those who decided against continuing cited no improvement of symptoms, cost and lack of time for treatment. In conclusion, annual utilization of acupuncture and/or moxibustion was estimated at more than 6%, and the percentage of those with a lifetime experience was ∼25%, thus demonstrating the relatively higher utilization of the remedy in Japan over utilization in western countries. Application of the treatment for musculoskeletal problems and utilization by the older population were specific standouts of the use of acupuncture and/or moxibustion in Japan

High-brightness scalable continuous-wave single-mode photonic-crystal laser

フォトニック結晶レーザーの高輝度単一モード連続動作の実現 --スマート製造を始めとする各種分野のゲームチェンジに向けて--. 京都大学プレスリリース. 2023-06-15.Realizing large-scale single-mode, high-power, high-beam-quality semiconductor lasers, which rival (or even replace) bulky gas and solid-state lasers, is one of the ultimate goals of photonics and laser physics. Conventional high-power semiconductor lasers, however, inevitably suffer from poor beam quality owing to the onset of many-mode oscillation, and, moreover, the oscillation is destabilized by disruptive thermal effects under continuous-wave (CW) operation. Here, we surmount these challenges by developing large-scale photonic-crystal surface-emitting lasers with controlled Hermitian and non-Hermitian couplings inside the photonic crystal and a pre-installed spatial distribution of the lattice constant, which maintains these couplings even under CW conditions. A CW output power exceeding 50 W with purely single-mode oscillation and an exceptionally narrow beam divergence of 0.05° has been achieved for photonic-crystal surface-emitting lasers with a large resonant diameter of 3 mm, corresponding to over 10, 000 wavelengths in the material. The brightness, a figure of merit encapsulating both output power and beam quality, reaches 1 GW cm⁻² sr⁻¹, which rivals those of existing bulky lasers. Our work is an important milestone toward the advent of single-mode 1-kW-class semiconductor lasers, which are expected to replace conventional, bulkier lasers in the near future

Photonic-crystal lasers with high-quality narrow-divergence symmetric beams and their application to LiDAR

Light detection and ranging (LiDAR) is a key technology for smart mobility of robots, agricultural and construction machines, and autonomous vehicles. However, current LiDAR systems often rely on semiconductor lasers with low-quality, large-divergence, and asymmetric beams, requiring high-precision integration of complicated lens systems to reshape the beam. Also, due to the broad linewidth and the large temperature dependence of their lasing spectrum, a bandpass filter with broad bandwidth must be used in front of the detector, so the detected signal is affected by noise from background light such as sunlight. These critical issues limit the performance, compactness, affordability, and reliability of the LiDAR systems. Photonic-crystal surface-emitting lasers (PCSELs) have attracted much attention as novel semiconductor lasers that can solve the issues of conventional semiconductor lasers owing to their capability of high-quality, very-narrow-divergence, and symmetric beam operation supported by broad-area band-edge resonance in their two-dimensional photonic crystal. In this paper, we show the progress and the state of the art of broad-area coherent PCSELs and their application to a time-of-flight (ToF) LiDAR system. We first review the progress of PCSELs made so far. Next, we show recent progress based on PCSELs with a double-lattice structure that enables higher-power and narrower-divergence operation while keeping a symmetric beam shape. By optimizing the double-lattice photonic crystal and the reflective properties of a backside distributed Bragg reflector (DBR), we achieve a high peak power of 10 W while maintaining a nearly diffraction-limited beam divergence of ∼0.1° (FWHM) from a 500 µm diameter resonator. Using this PCSEL, we construct a LiDAR system that uses no external lens system in its light source and demonstrate highly spatially resolved ToF sensing (measurement range of ∼20 m), which is appropriate for autonomous robots and factory automation

Wide-bandgap GaN-based watt-class photonic-crystal lasers

青色GaN系フォトニック結晶レーザーの高出力・高ビーム品質動作に成功 --次世代の高品位レーザー加工、高輝度照明、水中LiDAR等の実現に向けて--. 京都大学プレスリリース. 2022-11-04.Short-wavelength (blue-violet-to-green) lasers with high power and high beam quality are required for various applications including the machining of difficult-to-process materials and high-brightness illuminations and displays. Promising light sources for such applications are wide-bandgap GaN-based photonic-crystal surface-emitting lasers (PCSELs), which are based on two-dimensional resonance in the photonic crystal. Developments of these devices have lagged behind those of longer-wavelength GaAs-based PCSELs, because device designs for achieving robust two-dimensional resonance and a nanofabrication process that avoids introducing disorders have remained elusive for wide-bandgap GaN-based materials. Here, we address these issues and successfully realize GaN-based PCSELs with high, watt-class (>1 W) output power and a circular, single-lobed beam with a very narrow (~0.2°) divergence angle at blue wavelengths. In addition, we demonstrate continuous-wave operation with a high output power (~320 mW) and a high beam quality (M²~1). Our results will enable the use of GaN-based PCSELs in the above-mentioned applications

Proposal and Demonstration of Free-Space Optical Communication Using Photonic Crystal Surface-Emitting Lasers

We propose and demonstrate free-space optical (FSO) communication using photonic crystal surface-emitting lasers (PCSELs). Unlike other types of conventional semiconductor lasers, such as edge-emitting lasers (EELs) and vertical-cavity surface-emitting lasers (VCSELs), PCSELs achieve much larger area single-mode coherent lasing, and this unique feature enables high-power (>watt) and lens-free operations at the same time. To date, these advantages have been recognized to be game changing, especially in light detection and ranging (LiDAR) and laser processing applications. In this work, we show that FSO communication can also benefit from these advantages of PCSELs; more specifically, conventional transmitters that include low-power semiconductor lasers, optical lenses, and fiber-based amplifiers could be replaced with a single PCSEL. Since fiber amplifiers usually consist of bulky components and have low conversion efficiencies, PCSELs can offer more space- and power-saving solutions. Moreover, the narrow beam divergence angles directly obtained from large-area single-mode PCSELs can also eliminate the need for lens systems on the transmitter side. To experimentally verify these potential advantages, we performed FSO transmission experiments based on PCSELs and successfully transmitted 480-MHz and 864-MHz orthogonal frequency division multiplexed (OFDM) signals over 1.1 m using a 500-μm PCSEL in a lens-free transmitter configuration. We believe that PCSELs open new possibilities and choices in FSO communication

Human NINEIN polymorphism at codon 1111 is associated with the risk of colorectal cancer

NINEIN serves an essential role in centrosome function as a microtubule organizing center, and in the reformation of the interphase centrosome architecture following mitosis. In the present study, the association between NINEIN Pro1111Ala (rs2236316), a missense single nucleotide polymorphism, and the risk of colorectal cancer (CRC), related to smoking and alcohol consumption habits in 200 patients with CRC and 1,141 cancer‑free control participants were assessed in a case‑control study performed in Japan. The results showed that the NINEIN Ala/Ala genotype compared with the Pro/Pro genotype was significantly more associated with an increased risk of CRC, and the males with the Ala/Ala genotype exhibited a significantly increased risk of CRC compared with those with Pro/Pro and Pro/Ala genotypes. Stratified analyses of the Ala/Ala genotype with CRC risk further showed an increased association in never/light drinkers (<23 g of ethanol/day), in male never/light drinkers and in male patients with rectal cancer. These findings suggest that the genetic variant of the NINEIN Pro1111Ala polymorphism has a significant effect on CRC susceptibility in the Japanese population