Performance analysis of large-scale MIMO system for wireless backhaul network

In this paper, we present a performance analysis of large-scale multi-input multi-output (MIMO) systems for wireless backhaul networks. We focus on fully connected N nodes in a wireless meshed and multi-hop network topology. We also consider a large number of antennas at both the receiver and transmitter. We investigate the transmission schemes to support fully connected N nodes for half-duplex and full-duplex transmission, analyze the achievable ergodic sum rate among N nodes, and propose a closed-form expression of the achievable ergodic sum rate for each scheme. Furthermore, we present numerical evaluation results and compare the resuts with closed-form expressions.     

Highly Bendable and Rotational Textile Structure with Prestrained Conductive Sewing Pattern for Human Joint Monitoring

Human joints have respective ranges of motion and joint forces corresponding to each kind of joint; this necessitates considerations of the characteristics of human joints to fabricate wearable strain sensors conformable to the human body, and capable of precisely monitoring complex motions of the human body. In the present study, the “all textile‐based highly stretchable structure” that is capable of precisely sensing motions (folding and rotation) of the human joints (finger, wrist, elbow, spine, and knee) is fabricated by optimizing patterns (straight, blind, and zigzag) of conductive yarns employed as the conductive part of the strain sensor, and several textile substrates (braided elastic fabric, knit fabric, and woven fabric), having preferable elasticity and conformability employed for the fabrication of strain sensors suitable for human joints. In particular, the technology, enabling the prestraining of textile substrate, is exploited to fabricate a strain sensor that is capable of outputting selective signals corresponding to the folding motion of the spinal joint over a predetermined angle of motion, and the gait pattern of the wearer of the sensor, attached to his or her knee joint doing folding and rotational motions, is analyzed.     

Environmental Enrichment Enhances Cav 2.1 Channel-Mediated Presynaptic Plasticity in Hypoxic–Ischemic Encephalopathy

Hypoxic–ischemic encephalopathy (HIE) is a devastating neonatal brain condition caused by lack of oxygen and limited blood flow. Environmental enrichment (EE) is a classic paradigm with a complex stimulation of physical, cognitive, and social components. EE can exert neuroplasticity and neuroprotective effects in immature brains. However, the exact mechanism of EE on the chronic condition of HIE remains unclear. HIE was induced by a permanent ligation of the right carotid artery, followed by an 8% O₂ hypoxic condition for 1 h. At 6 weeks of age, HIE mice were randomly assigned to either standard cages or EE cages. In the behavioral assessments, EE mice showed significantly improved motor performances in rotarod tests, ladder walking tests, and hanging wire tests, compared with HIE control mice. EE mice also significantly enhanced cognitive performances in Y-maze tests. Particularly, EE mice showed a significant increase in Ca_v 2.1 (P/Q type) and presynaptic proteins by molecular assessments, and a significant increase of Ca_v 2.1 in histological assessments of the cerebral cortex and hippocampus. These results indicate that EE can upregulate the expression of the Ca_v 2.1 channel and presynaptic proteins related to the synaptic vesicle cycle and neurotransmitter release, which may be responsible for motor and cognitive improvements in HIE.     

ZerNet: Convolutional Neural Networks on Arbitrary Surfaces Via Zernike Local Tangent Space Estimation

In this paper, we propose a novel formulation extending convolutional neural networks (CNN) to arbitrary two-dimensional manifolds using orthogonal basis functions called Zernike polynomials. In many areas, geometric features play a key role in understanding scientific trends and phenomena, where accurate numerical quantification of geometric features is critical. Recently, CNNs have demonstrated a substantial improvement in extracting and codifying geometric features. However, the progress is mostly centred around computer vision and its applications where an inherent grid-like data representation is naturally present. In contrast, many geometry processing problems deal with curved surfaces and the application of CNNs is not trivial due to the lack of canonical grid-like representation, the absence of globally consistent orientation and the incompatible local discretizations. In this paper, we show that the Zernike polynomials allow rigourous yet practical mathematical generalization of CNNs to arbitrary surfaces. We prove that the convolution of two functions can be represented as a simple dot product between Zernike coefficients and the rotation of a convolution kernel is essentially a set of 2 × 2 rotation matrices applied to the coefficients. The key contribution of this work is in such a computationally efficient but rigorous generalization of the major CNN building blocks.     

A study on an equivalent model of the threaded fasteners in complex structures through tightening and loosening analysis

Journal of Mechanical Science and Technology - The threaded fasteners are typical machine components in tightening of the machine parts and structures. In addition, as threaded fasteners are easy...     

Numerical simulation of gas-assisted polymer-melt electrospinning: Parametric study of a multinozzle system for mass production

In this study, we developed a multiphysics model for simulation of a gas-assisted melt-electrospinning (GAME) process, focusing on jet formation and propagation behavior. By numerically calculating the stresses acting on the jet during a single-nozzle GAME process, the shear viscous stress was identified as the main factor with respect to jet stretch; thus, the relationship between shear viscous stress and jet thickness was investigated. The jet stretch ratio increased sharply when shear viscous stress reached the level at which jet sharpening occurred, leading to stable jet formation. We defined this stress as the critical shear viscous stress to determine stable spinnability. By imposing an electric field distribution calculated for a multi-nozzle array (number of nozzles, tip-to-tip distance, and applied voltage) on the boundary condition of the single-nozzle GAME simulation model, multinozzle GAME was simulated; this enabled proposal of a spinnability diagram for stable spinning.     

A cost effective on-site fault diagnosis method for home appliance rotor failures

Microsystem Technologies - Rotating components are one of the most important machine parts used in many industrial applications. Rotating machine commonly used in homes has a washing machine, which...     

Origin of Surface Irregularities on Ti–10V–2Fe–3Al Beta Titanium Alloy

We studied the origin of different characteristics and properties of a Ti–10V–2Fe–3Al beta (β) titanium alloy with surface height irregularities that occurred during machining. The height differences were observed in two different regions, labeled as “soft region” and “hard region.” The present study showed a higher Fe and a lower Al content in the hard region, which resulted in higher β-phase stability to resist primary alpha (α_p) phase precipitation caused by a failure of the solution treatment process. In contrast, the soft region contained a higher volume fraction of α_p phase and a lower volume fraction of the matrix, which consisted of a combination of β and secondary alpha (α_s) phase. A high number of α_s/β interface in the matrix with a predicted hardness of 520 HV generated an improvement of hardness in the hard region. Therefore, the hard and the soft regions had different abilities to resist wear during machining process, resulting in surface height irregularities.     

Low-bandgap copolymers consisting of 2,1,3-benzoselenadiazole and carbazole derivatives with thiophene or selenophene π-bridges

Two donor–acceptor-type alternating copolymers consisting of 2,1,3-benzoselenadiazole and carbazole derivatives with thiophene or selenophene π-bridges were synthesized by Suzuki cross-coupling polymerization, and their optical, electrochemical, and photovoltaic properties were compared. The selenophene π-bridged copolymer (PCz-DSeBSe) exhibited a smaller band-gap (1.82 eV) than the thiophene-bridged polymer (PCz-DTBSe; 1.89 eV). PCz-DSeBSe also showed a deeper highest occupied molecular orbital energy level (−5.36 eV) than PCz-DTBSe (−5.20 eV). Moreover, the PCz-DSeBSe thin film showed higher crystallinity and hole mobility than the PCz-DTBSe thin film. Organic photovoltaic devices were fabricated using the polymers as the donors and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) as the acceptor. The device using PCz-DSeBSe showed a higher open circuit voltage (V_oc), short circuit current density (J_sc), and power conversion efficiency (PCE) than that using PCz-DTBSe. The fabricated indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/PCz-DSeBSe:PC₇₁BM/LiF/Al device showed the maximum PCE of 2.88% with a J_sc of 7.87 mA/cm², an V_oc of 0.80 V, and a fill factor of 0.50 under AM 1.5G irradiation (100 mW/cm²).