Self-Consistent Quantum Mechanical Monte Carlo MOSFET Device Simulation

We have developed a self-consistent quantum mechanical Monte Carlo device simulator that takes electron transport in quantized states into consideration. Two-dimensional quantized states in MOSFET channels are constructed from one-dimensional solutions of the Schrödinger equation at different positions along the channel, and the Schrödinger and Poisson equations are solved self-consistently in terms of electron concentration and electrostatic potential distribution. The channel electron concentration, velocity and drain currents are calculated with the one particle Monte Carlo approach incorporating the intra-valley acoustic phonon and inter-valley phonon scattering mechanisms. This simulator was applied to a 70 nm n-MOSFET transistor, and we found that current mostly flows through the lowest subband and transport is quasi-ballistic near the source junction. To quantitatively estimate the performance of advanced devices, we have developed an inversion carrier transport simulator based on a full-band model. Our simulation method enables us to evaluate device characteristics and analyze the transport properties of ultra-small MOSFETs.     

Stochastic security testing of chaos‐based communication systems against error function attack

This paper proposes two stochastic testing methods for the security analysis of a secure communication scheme based on continuous‐time chaotic systems. First, we define an instantaneous EFA (error function attack) function that does not include the average operation. Second, we propose a statistical testing for cryptanalysis, which calculates a standard deviation of the EFA function obtained by random trial keys. As another stochastic testing, moreover, we propose a stochastic evolutional attack to find a secret key. Finally, simulation results for the proposed security testing are presented. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Polarity Effect and Electromagnetic Radiation of Partial Discharge Accompanying Growth of Electrical Tree

We have investigated the characteristics of radiated electromagnetic (EM) waves from positive and negative partial discharges (PD) in epoxy resin and cross‐linked polyethylene. We found that there is a correlation among the EM level from PD, the positive PD current, and electrical trees. Therefore, the growth of an electrical tree produces a lot of positive PD. We have also investigated the characteristics of the frequency region of EM waves from PD in air, insulating oil, and liquid epoxy in addition to the above insulators. EM waves were detected in the frequency region of 40 MHz to 300 MHz from positive and negative PD in epoxy resin and cross‐linked polyethylene. EM waves were also detected in the frequency region of 40 MHz to 150 MHz from positive and negative PD in air. In the case of insulating oil and liquid epoxy, EM waves were detected in the frequency regions of 40 MHz to 150 MHz from positive PD, and 40 MHz to 250 MHz from negative PD. The frequency region differed depending on the material and the discharge polarity. Our investigation indicates that the cause is differences in electric field strength at the time of PD occurrence.     

Formation energies and site preference of substitutional divalent cations in carbonated apatite

First-principles calculations were performed to examine defect formation energies and site preference of substitutional divalent cations M²⁺ (M = Mg, Cu, Zn, Cd, Sr, Pb, and Ba) in hydroxyapatite (HAp, Ca₁₀(PO₄)₆(OH)₂) and carbonated apatite (CAp). All inequivalent substitutional sites of and M²⁺ were investigated to determine their most preferential sites. For all M²⁺ studied, their defect formation energies for the most stable substitutional sites were lower in CAp than in hydroxyapatite (HAp), demonstrating that M²⁺ are preferentially substituted into CAp over HAp. For Ca sites in CAp, correlations between the defect formation energies and Ca-O bond lengths showed that bigger and smaller M²⁺ than Ca²⁺ are preferentially substituted for Ca sites with longer and shorter bond lengths than those in HAp, respectively. In addition, Ca sites with lower coordination numbers than 6 are preferentially substituted by Zn²⁺ and Cu²⁺ that originally tend to form 4- or 5-fold coordination in their phosphate crystals. substitution is therefore likely to effectively stabilize substitutional foreign ions by modifying bond lengths and coordination numbers of Ca sites from those in pure HAp. These effects may play an important role in enhancing the M²⁺ solubility into CAp.     

Chain stiffness and chain conformation of poly(α-methylene-γ-butyrolactone) in dilute solutions

The chain stiffness and local chain conformation of atactic poly(α-methylene-γ-butyrolactone) (PMBL), which is a side chain cyclic structural analog of poly(methyl methacrylate) (PMMA), with a weight-average molecular weight (M_w) ranging from 2.8 × 10³ to 2.6 × 10⁶ in N,N-dimethylformamide (DMF) and γ-butyrolactone (GBL) were characterized by size exclusion chromatography with a multi-angle light-scattering detector (SEC-MALS) and synchrotron radiation small-angle X-ray scattering (SAXS). Based on the Kratky-Porod worm-like chain model, the scattering functions and the M_w dependence of z-average root-mean-square radius of gyration <S²>_z^1/2 yielded the Kuhn segment lengths λ⁻¹, the diameter of the PMBL chains d, and the excluded-volume strengths in DMF and GBL. The local conformation of atactic PMBL in DMF and GBL were slightly larger than those of atactic PMMA, due to the presence of the conformationally rigid lactone ring structure.     

Using Turmeric Oil as a Solvent Improves the Distribution of Sesamin-Sesamolin in the Serum and Brain of Mice

Accumulation of amyloid-β peptide is associated with Alzheimer's dementia. Previously, we reported that sesamin and sesamolin inhibited β-secretase activity in vitro, and each was transported to the serum and brain in mice after oral administration. However, the bioavailability of sesamin and sesamolin was poor in mice. In this study, we aimed to improve the bioavailability of sesamin and sesamolin. We found that the levels of sesamin and sesamolin in mouse serum and brain were higher after the administration of a mixture of sesame extract and turmeric oil (MST) than those after administering sesame extract alone. Serum sesamin and sesamolin contents in the MST-treated group were 23-fold and 15-fold higher, respectively, than those in the sesame extract-treated group. Brain sesamin and sesamolin contents in the MST-treated group were 14-fold and 11-fold higher, respectively, than those in the sesame extract-treated group. These results suggest that turmeric oil is an effective solvent to enhance the bioavailability of sesamin and sesamolin.     

Frequency symbol spreading based adaptive subcarrier block selection for OFDMA system

In a wireless network, the signals transmitted from one sender to different users have independent channel fluctuation characteristics. The diversity that exists between users is called multiuser diversity and can be exploited by the sender to enhance the capacity of wireless network. In multiuser diversity OFDMA system, exploiting channel fluctuation diversity is in essence done by selecting the user with the strong subcarrier channels. The individual subcarrier selection for each user can achieve the best system performance but high signaling overhead and high system complexity are required. On the other hand, the adaptive subcarrier block method achieves worse BER than that of individual subcarrier selection. This is because the selected block contains the poor channel subcarriers. To overcome this problem, in this paper, we propose an adaptive subcarrier block selection with frequency symbol spreading for an OFDMA system.     

Fault tolerant approach for biosignal-based robot control

This paper proposes a fault tolerant framework for biosignal-based robot control with multiple sensor electrodes. In this approach, to cope with sensor faults, a reliable joint torque estimation model is selected from a group of estimation models based on sensor failure classifiers. The correlation among the electromyography (EMG) signal streams is used as input feature vectors for fault detection. To validate our proposed method, we artificially disconnect an EMG electrode or detach one side of an EMG probe from the skin surface during elbow-joint torque estimation experiments with five participants. When one EMG sensor electrode experiences one of the problems, the experimental results show that the joint torque can be estimated with significantly fewer errors using our proposed approach than a joint torque estimation method without sensor fault detection or than a method with a conventional sensor fault detection algorithm. Furthermore, we controlled a mannequin-arm-attached one-DOF exoskeleton based on the estimated torque profiles by generating movements with the estimated torque derived from the selected model.     

Flexible microelectronics: New application for thin‐film transistors in fingerprint sensors

Abstract— Thin‐film transistors (TFTs) are field‐effect transistors that can be used to create large‐scale‐integrated (LSI) circuits. The combination of high‐performance TFTs and transfer technology of the TFTs has the potential to foster the rise of a new flexible microelectronics industry. This paper discusses the current status of flexible microelectronics, using a TFT fingerprint sensor (FPS) as an example. Technology used in active‐matrix displays can easily be applied to the TFT FPS. TFT technology should not be confined to the display industry; its use should be expanded into the semiconductor industry. With the result presented in this paper, we declare a new era of flexible microelectronics open.     

Performance analysis of a greedy algorithm for inferring Boolean functions

We analyzed average case performance of a known greedy algorithm for inference of a Boolean function from positive and negative examples, and gave a proof to an experimental conjecture that the greedy algorithm works optimally with high probability if both input data and the underlying function are generated uniformly at random.