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"Tanaka, M"
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Development of a new methodology for site distribution determination by powder diffraction with anomalous scattering using focused beam and flat shape sample geometry
A new methodology of synchrotron powder diffraction with anomalous scattering for site occupancy determination has been examined. We have been developing a new Synchrotron powder diffraction geometry with focused X-ray beam, flat shape sample and area detectors. As an application of the geometry, a new methodology for site occupancy determination has been tried. The diffraction intensity ratio change against X-ray energy near an absorption edge was observed and was compared with the calculation obtained from various site distribution crystal structure models. The methodology has been successfully applied for site distribution determination of In atom in β -(Ga,In) 2 O 3 crystal. The new methodology can obtain diffraction intensity without approximation in absorption correction and can eliminate preferred orientation effect. By the combination of these features the new methodology can be a new application of synchrotron powder diffraction with anomalous scattering.
Journal Article
Cosmic time synchronizer (CTS) for wireless and precise time synchronization using extended air showers
Precise time synchronization is an essential technique required for financial transaction systems, industrial automation and control systems, as well as land and ocean observation networks. However, the time synchronization signals based on the global-positioning-system (GPS), or global-navigation-satellite-system, are sometimes unavailable or only partially available in indoor, underground and underwater environments. In this work, the simultaneous and penetrative natures of the muon component of the extended air shower (EAS) were used as signals for time synchronization in environments with little or no GPS coverage. CTS was modeled by combining the results of previous EAS experiments with OCXO holdover precision measurements. The results have shown the capability of CTS to reach perpetual local time synchronization levels of less than 100 ns with a hypothetical detector areal coverage of larger than 2 × 10
−4
. We anticipate this level of areal coverage is attainable and cost-effective for use in consumer smartphone networks and dense underwater sensor networks.
Journal Article
Wireless muometric navigation system
While satellite-based global navigation systems have become essential tools in our daily lives, their effectiveness is often hampered by the fact that the signals cannot be accessed in underground, indoor, or underwater environments. Recently, a novel navigation system has been invented to address this issue by utilizing the characteristics of the ubiquitous and highly penetrative cosmic-ray muons. This technique, muometric navigation, does not require active signal generation and enables positioning in the aforementioned environments within a reference coordinate defined by the three-dimensional positions of multiple detectors. In its first phase of development, these reference detectors had to be connected to the receivers via a wired configuration to guarantee precise time synchronization. This work describes more versatile, wireless muometric navigation system (MuWNS), which was designed in conjunction with a cost-effective, crystal-oscillator-based grandmaster clock and a performance evaluation is reported for shallow underground/indoor, deep underground and undersea environments. It was confirmed that MuWNS offers a navigation quality almost equivalent to aboveground GPS-based handheld navigation by determining the distance between the reference frame and the receivers within a precision range between 1 and 10 m.
Journal Article
Cosmic time calibrator for wireless sensor network
Time synchronization of sensor nodes is critical for optimal operation of wireless sensor networks (WSNs). Since clocks incorporated into each node tend to drift, recurrent corrections are required. Most of these correction schemes involve clients periodically receive RF timing signals from a time server. However, an RF-based scheme is prone to glitches or failure unless operating in a region with almost entirely unobstructed space; hence it only operates well in a limited range of environments. For example, GPS requires open-sky environments. Moreover, the precision of land-based RF schemes is limited to a few micro seconds. In this work, we report on a more versatile and new type of recurrent clock resynchronization scheme called cosmic time calibrator (CTC) and its development and testing. CTC utilizes cosmic-ray muon signals instead of RF signals. Muons are penetrative and continuously precipitating onto the Earth’s surface, and they tend to travel linearly through encountered matter at approximately the speed of light in vacuum. Therefore, muons themselves can periodically transfer the precise timing information from node to node; hence, the performance of the inter-nodal communication device such as Wi-Fi or Bluetooth is minimized/unnecessary for an online/offline WSN analysis. The experimental results have indicated that a resynchronization frequency and precision of 60 Hz and ± 4.3 ns (S.D.) can be achieved. Modelling work of the WSN-based structural health monitoring of aerospace structures has shown that CTC can contribute to the development of new critical and useful applications of WSN in a wider range of environments.
Journal Article
Muometric positioning system (muPS) utilizing direction vectors of cosmic-ray muons for wireless indoor navigation at a centimeter-level accuracy
Since the development of many future technologies are becoming more and more dependent on indoor navigation, various alternative navigation techniques have been proposed with radio waves, acoustic, and laser beam signals. In 2020, muometric positioning system (muPS) was proposed as a new indoor navigation technique; in 2022, the first prototype of wireless muPS was demonstrated in underground environments. However, in this first physical demonstration, its navigation accuracy was limited to 2–14 m which is far from the level required for the practical indoor navigation applications. This positioning error was an intrinsic problem associated with the clock that was used for determining the time of flight (ToF) of the muons, and it was practically impossible to attain cm-level accuracy with this initial approach. This paper introduces the completely new positioning concept for muPS, Vector muPS, which works by determining direction vectors of incoming muons instead of utilizing ToF. It is relatively easier to attain a 10-mrad level angular resolution with muon trackers that have been used for muographic imagery. Therefore, Vector muPS retains the unique capacity to operate wirelessly in indoor environments and also has the capacity to achieve a cm-level accuracy. By utilizing an essentially different concept from what is used in other navigation techniques, (measuring the distance between the reference and the receiver), Vector muPS enables more flexible, and longer-term stable positioning. Anticipated applications and the future outlook of Vector muPS is also discussed.
Journal Article
Cosmic coding and transfer storage (COSMOCATS) for invincible key storage
Thus far, a perfectly secure encryption key storage system doesn’t exist. As long as key storage is connected to a network system, there is always a chance that it can be cracked. Even if storage is not continually connected to a network system; it is repeatedly necessary for an individual to access storage to upload and download the data; hence there is always a loophole with every conventional encryption key storage system. By utilizing the penetrative nature of cosmic-ray muons, the COSMOCAT (Cosmic coding and transfer) technique may tackle this problem by eliminating the requirement for any network connection to data storage. COSMOCAT was invented as a post quantum key generation and distribution technique for wireless near field communication. However, in its first stage of development, COSMOCAT relied on standard comparators and Global Positioning System (GPS) or other Global Navigation Satellite Systems (GNSS) for key generation. Temporal jitters of the signals outputted from comparators and frequency fluctuations in GPS-disciplined oscillators degraded the key strength and the efficiency of both the key generation and distribution. New strategies are tested in this paper to improve these factors. As a result, the key strength and the key authenticating rate limit are respectively improved by 4 orders of magnitude and more than 5 orders of magnitude. As a consequence, it has become possible to propose a practical methodology for a new key storage and authentication strategy which has the potential to be an impregnable defense against any kind of cyber/physical attack to data storage. Practical applications of COSMOCATS-based symmetric-key cryptosystems to an electronic digital signing system, communication, and cloud storage are also discussed.
Journal Article
Sex in the Time of COVID-19: Results of an Online Survey of Gay, Bisexual and Other Men Who Have Sex with Men’s Experience of Sex and HIV Prevention During the US COVID-19 Epidemic
This paper presents data from a recent cross-sectional survey of gay, bisexual and other men who have sex with men (GBMSM) in the US, to understand changes in sexual behavior and access to HIV prevention options (i.e. condoms and pre-exposure prophylaxis (PrEP)) during the COVID-19 lockdown period. The Love and Sex in the Time of COVID-19 survey was conducted online from April to May, 2020. GBMSM were recruited through advertisements featured on social networking platforms, recruiting a sample size of 518 GBMSM. Analysis considers changes three in self-reported measures of sexual behavior: number of sex partners, number of anal sex partners and number of anal sex partners not protected by pre-exposure prophylaxis (PrEP) or condoms. Approximately two-thirds of the sample reported that they believed it was possible to contract COVID-19 through sex, with anal sex reported as the least risky sex act. Men did not generally feel it was important to reduce their number of sex partners during COVID-19, but reported a moderate willingness to have sex during COVID-19. For the period between February and April–May 20,202, participants reported a mean increase of 2.3 sex partners during COVID-19, a mean increase of 2.1 anal sex partners (range − 40 to 70), but a very small increase in the number of unprotected anal sex partners. Increases in sexual behavior during COVID-19 were associated with increases in substance use during the same period. High levels of sexual activity continue to be reported during the COVID-19 lockdown period and these high levels of sexual activity are often paralleled by increases in substance use and binge drinking. There is a clear need to continue to provide comprehensive HIV prevention and care services during COVID-19, and telehealth and other eHealth platforms provide a safe, flexible mechanism for providing services.
Journal Article
Muopause sounder to derive vertically averaged atmospheric temperature underneath the muopause with the distance of flight muography technique
A number of papers have focused on monitoring surface temperature to evaluate the greenhouse effect. However, it is well known that measuring the net radiation from the entire troposphere using vertically averaged temperature would be preferable as an index to evaluate the greenhouse effect. Thus far, upper-air weather balloon systems, satellite-mounted hyperspectral infrared sounders, and microwave sounders have been used for acquiring vertically averaged tropospheric temperature. It would be advantageous to have another independent method to derive variations in vertically averaged tropospheric temperature (separate from balloon, infrared/microwave sounder measurements) to diversify the options that allow researchers to compare tropospheric temperature datasets with more variety. This paper presents the first demonstration result from a muopause sounder prototype that applies the distance of flight muography technique to measure the vertically averaged tropospheric temperature (surface = 70 hPa). The resultant relative temperature gauging accuracies of the muopause sounder prototype were respectively 1.2 K and 0.2 K for daily-averaged and monthly-averaged data. These muopause sounder’s accuracies were evaluated by comparing with measurement data acquired from a reference weather balloon station. Muopause sounders can be cheaply produced and installed into drifting buoys. The concept and design of a future large-scale muopause sounder array, suitable for enhancing spatial coverage of measurements to the global scale, is proposed.
Journal Article