Development of High Speed Gas Gun with a New Trigger System

This paper reports development of a new trigger system for a high speed gas gun and experimental results on muzzle speed ofa spherical ceramic projectile launched by a gas gun equipped with the new trigger system. A new trigger system was designed carefully using numerical simulation of interaction between a trigger system and a projectile, and deformation of the trigger system. Launching pressure levels are precisely adjustable by changing trigger system parameters. Calculated launching pressure agreed well with experimental result. It was concluded that a gas gun equipped with this new trigger system can work out more powerful as compared with a commercial air rifle

Method for Extracting the Equivalent Admittance from Time-Varying Metasurfaces and Its Application to Self-Tuned Spatiotemporal Wave Manipulation

With their self-tuned time-varying responses, waveform-selective metasurfaces embedded with nonlinear electronics have shown fascinating applications, including distinguishing different electromagnetic waves depending on the pulse width. However, thus far they have only been realized with a spatially homogeneous scattering profile. Here, by modeling a metasurface as time-varying admittance sheets, we provide an analytical calculation method to predict the metasurface time-domain responses. This allows derivation of design specifications in the form of equivalent sheet admittance, which is useful in synthesizing a metasurface with spatiotemporal control, such as to realize a metasurface with prescribed time-dependent diffraction characteristics. As an example, based on the proposed equivalent admittance sheet modeling, we synthesize a waveform-selective Fresnel zone plate with variable focal length depending on the incoming pulse width. The proposed synthesis method of pulse-width-dependent metasurfaces may be extended to designing metasurfaces with more complex spatiotemporal wave manipulation, benefiting applications such as sensing, wireless communications and signal processing

Phototactic and Chemotactic Signal Transduction by Transmembrane Receptors and Transducers in Microorganisms

Microorganisms show attractant and repellent responses to survive in the various environments in which they live. Those phototaxic (to light) and chemotaxic (to chemicals) responses are regulated by membrane-embedded receptors and transducers. This article reviews the following: (1) the signal relay mechanisms by two photoreceptors, Sensory Rhodopsin I (SRI) and Sensory Rhodopsin II (SRII) and their transducers (HtrI and HtrII) responsible for phototaxis in microorganisms; and (2) the signal relay mechanism of a chemoreceptor/transducer protein, Tar, responsible for chemotaxis in E. coli. Based on results mainly obtained by our group together with other findings, the possible molecular mechanisms for phototaxis and chemotaxis are discussed

Effects of Neck Position and Movement on the Tonic Vibration Reflex in the Arms

The present study investigated the tonic vibration reflex (TVR) in humans elicited by vibratory stimulation applied to the muscle of the triceps brachii and examined the effects of rotation of the neck on misperception of movement of the elbow. Fifteen healthy subjects actively flexed their elbows from 0° to 90° for 3 s with their eyes closed. During the time that the elbow was flexed, vibratory stimulation (100 Hz) was applied to the tendon of the right triceps brachii. In the first experiment, only the right elbow was flexed (one-arm experiment), whereas in the second experiment both elbows were flexed simultaneously (two-arm experiment). In the two-arm experiment with vibratory stimulation, the mean ( ± SD) angle of the elbow was 63.2 ± 11.2° with neck rotation at 0°, which decreased significantly to 53.0 ± 15.5° (P< 0.05) when the neck was rotated back to 0° from the position of maximal right rotation. This suggests that there is an asymmetric tonic neck reflex as a result of neck movement, with the pathways involved in the crossed extension reflex enhanced by the simultaneous movement of both elbows. The TVR is an effective tool with which the convergence of various reflexes on α-motor neurons innervating the muscles of the extremity can be examined

Large Reduction in the aa-axis Knight Shift on UTe2_2 with TcT_{\rm c} = 2.1 K

Spin susceptibility in the superconducting (SC) state was measured in the higher-quality sample of uranium-based superconductor UTe$_2$ by using Knight-shift measurements for a magnetic field $H$ along all three crystalline axes. In the higher-quality sample, the SC transition temperature $T_{\rm c}$ is about 2.1 K, and the residual electronic term in the specific heat is almost zero. The NMR linewidth becomes narrower and is almost half of that in the previous sample with $T_{\rm c} \sim 1.6$ K when $H \parallel a$ and $c$. Although the Knight-shift behavior was not so different from the previous results for $H \parallel b$, and $c$, a large reduction in Knight shift along the $a$ axis was observed, in contrast with the previous $a$-axis Knight shift result. We discuss the origin of the difference between the previous and present results, and the possible SC state derived from the present results.Comment: 7 pages, 6 figures, including supplemental material

Pulse-Driven Self-Reconfigurable Meta-Antennas

Wireless communications and sensing have notably advanced thanks to the recent developments in both software and hardware. Although various modulation schemes have been proposed to efficiently use the limited frequency resources by exploiting several degrees of freedom, antenna performance is essentially governed by frequency only. Here, we present a new antenna design concept based on metasurfaces to manipulate antenna performances in response to the time width of electromagnetic pulses. We numerically and experimentally show that by using a proper set of spatially arranged metasurfaces loaded with lumped circuits, ordinary omnidirectional antennas can be reconfigured by the incident pulse width to exhibit directional characteristics varying over hundreds of milliseconds or billions of cycles, far beyond conventional performance. We demonstrate that the proposed concept can be applied for sensing, selective reception under simultaneous incidence and mutual communications as the first step to expand existing frequency resources based on pulse width.Comment: 61 pages, 6 figures, 26 supplementary figure

Multiparametric analysis for pharynx SCC

Purpose : To predict local control / failure by a multiparametric approach using magnetic resonance (MR)-derived tumor morphological and functional parameters in pharynx squamous cell carcinoma (SCC) patients. Materials and Methods : Twenty-eight patients with oropharyngeal and hypopharyngeal SCCs were included in this study. Quantitative morphological parameters and intratumoral characteristics on T2-weighted images, tumor blood flow from pseudo-continuous arterial spin labeling, and tumor diffusion parameters of three diffusion models from multi-b-value diffusion-weighted imaging as well as patients’ characteristics were analyzed. The patients were divided into local control / failure groups. Univariate and multiparametric analysis were performed for the patient group division. Results : The value of morphological parameter of ‘sphericity’ and intratumoral characteristic of ‘homogeneity’ was revealed respectively significant for the prediction of the local control status in univariate analysis. Higher diagnostic performance was obtained with the sensitivity of 0.8, specificity of 0.75, positive predictive value of 0.89, negative predictive value of 0.6 and accuracy of 0.79 by multiparametric diagnostic model compared to results in the univariate analysis. Conclusion : A multiparametric analysis with MR-derived quantitative parameters may be useful to predict local control in pharynx SCC patients

Design guidelines for the SPICE parameters of waveform-selective metasurfaces varying with the incident pulse width at a constant oscillation frequency

In this study, we numerically demonstrate how the response of recently reported circuit-based metasurfaces is characterized by their circuit parameters. These metasurfaces, which include a set of four diodes as a full wave rectifier, are capable of sensing different waves even at the same frequency in response to the incident waveform, or more specifically the pulse width. This study reveals the relationship between the electromagnetic response of such waveform-selective metasurfaces and the SPICE parameters of the diodes used. First, we show that reducing a parasitic capacitive component of the diodes is important for realization of waveform-selective metasurfaces in a higher frequency regime. Second, we report that the operating power level is closely related to the saturation current and the breakdown voltage of the diodes. Moreover, the operating power range is found to be broadened by introducing an additional resistor into the inside of the diode bridge. Our study is expected to provide design guidelines for circuit-based waveform-selective metasurfaces to select/fabricate optimal diodes and enhance the waveform-selective performance at the target frequency and power level.Comment: 9 pages, 9 figure