Near-optimal stochastic MIMO signal detection with a mixture of t-distribution prior

Multiple-input multiple-output (MIMO) systems will play a crucial role in future wireless communication, but improving their signal detection performance to increase transmission efficiency remains a challenge. To address this issue, we propose extending the discrete signal detection problem in MIMO systems to a continuous one and applying the Hamiltonian Monte Carlo method, an efficient Markov chain Monte Carlo algorithm. In our previous studies, we have used a mixture of normal distributions for the prior distribution. In this study, we propose using a mixture of t-distributions, which further improves detection performance. Based on our theoretical analysis and computer simulations, the proposed method can achieve near-optimal signal detection with polynomial computational complexity. This high-performance and practical MIMO signal detection could contribute to the development of the 6th-generation mobile network.Comment: to be published in the 2023 IEEE Global Communications Conference (GLOBECOM

SERENADE II: An ALMA Multi-Band Dust-Continuum Analysis of 28 Galaxies at 5<z<85<z<8 and the Physical Origin of the Dust Temperature Evolution

We present an analysis of ALMA multi-band dust-continuum observations for 28 spectroscopically-confirmed bright Lyman-break galaxies at $5<z<8$. Our sample consists of 11 galaxies at $z\sim6$ newly observed in our ALMA program, which substantially increases the number of $5<z<8$ galaxies with both rest-frame 88 and 158 $\mu{\rm m}$ continuum observations, allowing us to simultaneously measure the IR luminosity and dust temperature for a statistical sample of $z\gtrsim5$ galaxies for the first time. We derive the relationship between the UV slope ($\beta_{\rm UV}$) and infrared excess (IRX) for the $z\sim6$ galaxies, and find a shallower IRX-$\beta_{\rm UV}$ relation compared to the previous results at $z\sim2$--4. Based on the IRX-$\beta_{\rm UV}$ relation consistent with our results and the $\beta_{\rm UV}$-$M_{\rm UV}$ relation including fainter galaxies in the literature, we find a limited contribution of the dust-obscured star formation to the total SFR density, $\sim30\%$ at $z\sim6$. Our measurements of the dust temperature at $z\sim6-7$, $T_{\rm dust}=40.9_{-9.1}^{+10.0}\,{\rm K}$ on average, supports a gentle increase of $T_{\rm dust}$ from $z=0$ to $z\sim6$--7. Using an analytic model with parameters consistent with recent {\it{JWST}} results, we discuss that the observed redshift evolution of the dust temperature can be reproduced by an $\sim0.6\,{\rm dex}$ increase in the gas depletion timescale and $\sim0.4\,{\rm dex}$ decrease of the metallicity. The variety of $T_{\rm dust}$ observed at high redshifts can also be naturally explained by scatters around the star-formation main sequence and average mass-metallicity relation, including an extremely high dust temperature of $T_{\rm dust}>80\,{\rm K}$ observed in a galaxy at $z=8.3$.Comment: Submitted to Ap

Energizing Star Formation: The Cosmic Ray Ionization Rate in NGC 253 Derived From ALCHEMI Measurements of H3_3O+^+ and SO

The cosmic ray ionization rate (CRIR) is a key parameter in understanding the physical and chemical processes in the interstellar medium. Cosmic rays are a significant source of energy in star formation regions, which impacts the physical and chemical processes which drive the formation of stars. Previous studies of the circum-molecular zone (CMZ) of the starburst galaxy NGC 253 have found evidence for a high CRIR value; $10^3-10^6$ times the average cosmic ray ionization rate within the Milky Way. This is a broad constraint and one goal of this study is to determine this value with much higher precision. We exploit ALMA observations towards the central molecular zone of NGC 253 to measure the CRIR. We first demonstrate that the abundance ratio of H$_3$O$^+$ and SO is strongly sensitive to the CRIR. We then combine chemical and radiative transfer models with nested sampling to infer the gas properties and CRIR of several star-forming regions in NGC 253 due to emission from their transitions. We find that each of the four regions modelled has a CRIR in the range $(1-80)\times10^{-14}$ s$^{-1}$ and that this result adequately fits the abundances of other species that are believed to be sensitive to cosmic rays including C$_2$H, HCO$^+$, HOC$^+$, and CO. From shock and PDR/XDR models, we further find that neither UV/X-ray driven nor shock dominated chemistry are a viable single alternative as none of these processes can adequately fit the abundances of all of these species.Comment: 24 pages, 15 figures, accepted for publication in Ap

Starburst Energy Feedback Seen through HCO+/HOC+Emission in NGC 253 from ALCHEMI

Molecular abundances are sensitive to the UV photon flux and cosmic-ray ionization rate. In starburst environments, the effects of high-energy photons and particles are expected to be stronger. We examine these astrochemical signatures through multiple transitions of HCO+ and its metastable isomer HOC+ in the center of the starburst galaxy NGC 253 using data from the Atacama Large Millimeter/submillimeter Array large program ALMA Comprehensive High-resolution Extragalactic Molecular inventory. The distribution of the HOC+(1-0) integrated intensity shows its association with "superbubbles,"cavities created either by supernovae or expanding H ii regions. The observed HCO+/HOC+ abundance ratios are ∼10-150, and the fractional abundance of HOC+ relative to H2 is ∼1.5 × 10-11-6 × 10-10, which implies that the HOC+ abundance in the center of NGC 253 is significantly higher than in quiescent spiral arm dark clouds in the Galaxy and the Galactic center clouds. Comparison with chemical models implies either an interstellar radiation field of G 0 ⪆ 103 if the maximum visual extinction is ⪆5, or a cosmic-ray ionization rate of ζ ⪆ 10-14 s-1 (3-4 orders of magnitude higher than that within clouds in the Galactic spiral arms) to reproduce the observed results. From the difference in formation routes of HOC+, we propose that a low-excitation line of HOC+ traces cosmic-ray dominated regions, while high-excitation lines trace photodissociation regions. Our results suggest that the interstellar medium in the center of NGC 253 is significantly affected by energy input from UV photons and cosmic rays, sources of energy feedback.N.H. acknowledges support from JSPS KAKENHI grant No. JP21K03634. K.S. has been supported by grants MOST 108-2112-M-001-015 and 109- 2112-M-001-020 from the Ministry of Science and Technology, Taiwan. Y.N. is supported by the NAOJ ALMA Scientific Research grant No. 2017-06B. V.M.R. and L.C. are funded by the Comunidad de Madrid through the Atracción de Talento Investigador (Doctores con experiencia) Grant (COOL: Cosmic Origins Of Life; 2019-T1/TIC-15379)

豊橋技術科学大学における学生と教員の英語学習に対する意識

This is a report based on a general survey given to undergraduate students and professors at Toyohashi University of Technology (TUT) about English education at TUT. Regarding students, the main purposes of the survey, conducted in the fall of 2005, were to find how students had studied English before enrolling in TUT, what the students thought of English teaching and learning at TUT, and how important they thought English was for their majors. As for the survey to professors, the main purposes were finding out instructor attitudes toward the teaching and learning of English at TUT and how necessary they felt the acquisition of English was for their students. In this study, attention is paid to the differences of awareness and attitudes between the professors and students toward English teaching and learning. Based on the results of this study, discussions on and refinements to the current English curriculum will be made in the near future at TUT with the aim of raising student English fluency, particularly in the areas of written and oral communication ability

Second nationwide surveillance of bacterial pathogens in patients with acute uncomplicated cystitis conducted by Japanese Surveillance Committee from 2015 to 2016: antimicrobial susceptibility of Escherichia coli, Klebsiella pneumoniae, and Staphylococcus saprophyticus

The Japanese Surveillance Committee conducted a second nationwide surveillance of antimicrobial susceptibility patterns of uropathogens responsible for acute uncomplicated cystitis (AUC) in premenopausal patients aged 16–40 years old at 31 hospitals throughout Japan from March 2015 to February 2016. In this study, the susceptibility of causative bacteria (Escherichia coli, Klebsiella pneumoniae, Staphylococcus saprophyticus) for various antimicrobial agents was investigated by isolation and culturing of organisms obtained from urine samples. In total, 324 strains were isolated from 361 patients, including E. coli (n = 220, 67.9%), S. saprophyticus (n = 36, 11.1%), and K. pneumoniae (n = 7, 2.2%). The minimum inhibitory concentrations (MICs) of 20 antibacterial agents for these strains were determined according to the Clinical and Laboratory Standards Institute (CLSI) manual. At least 93% of the E. coli isolates showed susceptibility to fluoroquinolones and cephalosporins, whereas 100% of the S. saprophyticus isolates showed susceptibility to fluoroquinolones and aminoglycosides. The proportions of fluoroquinolone-resistant and extended-spectrum β-lactamase (ESBL)-producing E. coli strains were 6.4% (13/220) and 4.1% (9/220), respectively. The antimicrobial susceptibility of K. pneumoniae was retained during the surveillance period, while no multidrug-resistant strains were identified. In summary, antimicrobial susceptibility results of our second nationwide surveillance did not differ significantly from those of the first surveillance. Especially the numbers of fluoroquinolone-resistant and ESBL-producing E. coli strains were not increased in premenopausal patients with AUC in Japan