Doping Effects on Thermoelectric Properties in the Mg2Sn System

A weak point of Mg₂X thermoelectrics is the absence of a p-type composition, which motivates research into the Mg₂Sn system. Mg₂Sn thermoelectrics were fabricated by a vacuum melting method and a spark plasma sintering process. As a result, Mg₂Sn single phases were acquired in a wide range of Mg-to-Sn atomic ratios (67:33 to 71:29), showing slightly different thermoelectric characteristics. However, the thermoelectric properties of the undoped system were not sufficient for application in commercial production. To maximize the p-type characteristics, many atoms [Ni (VIIIA), Cu (IB), Ag (IB), Zn (IIB), and In (IIIB)] were doped into the Mg₂Sn phase. Among them, the power factor values increased only in the Ag-doped case. Ag-doping resulted in a power factor that was more than 10 times larger than the value in the undoped case. This result could be important for developing p-type polycrystalline thermoelectrics in the Mg₂X (X?=?Si, Sn) system. However, other atoms [Ni (VIIIA), Cu (IB), Zn (IIB), and In (IIIB)] were not determined to act as acceptor atoms. The maximum ZT value for the Ag-doped Mg₂Sn thermoelectric was more than 0.18, which is comparable to the value for the n-type Mg₂Si system.     

Selective Wavelength Enhanced Photochemical and Photothermal H2 Generation of Classical Oxide Supported Metal Catalyst

Conventional views of constructing simply broadband catalysts for photothermal-enhanced catalysis do not realize that without designating photochemical and photothermal conversion to their optimal working spectra can lead to a performance trade-off. Here, spectrally selective designed photoredox and photothermal heating functions of a classical oxide supported metal catalyst are demonstrated, which exhibits markedly improved hydrogen reactivity. While photothermal hydrogen producing catalysis is previously demonstrated, distinctive wavelength dominant redox and thermal phenomena are not studied due to the complex interdependent behavior they exhibit. The exceptionally high H₂ evolution rate of 30.2 mmol g⁻¹ h⁻¹ (≈74 times that of the control sample) is attributed to the nonoverlapped light absorption and undisrupted charge transfer rationales. This study presents a proof-by-existence that spectrally tailored solar utilization strategy is broadly impactful for the hybrid photothermal–photochemical catalysis. Moreover, the spatially decoupled structural configuration may open up discrete parametric control over photoredox and photoheating functionalities.     

Development of Metallic Hermetic Sealing for MEMS Packaging for Harsh Environment Applications

Hermetic sealing of microelectromechanical system sensors is indispensable to ensure their reliable operation and also to provide protection during fabrication. This work proposes two prospective candidates for hermetic sealing for rugged environment applications, i.e., Al-Ge and Pt-In. Al-Ge was chosen due to its compatibility with complementary metal–oxide–semiconductor technology. Pt-In possesses the highest remelting temperature among all the solder systems, which is desired for high-temperature applications in both the energy and aerospace industries. The various bonding parameters for Al-Ge eutectic bonding and Pt-In transient liquid-phase (TLP) bonding have been optimized, and their influence on the bond quality is reported. Optimization of bonding parameters has been carried out with the objective of ensuring void-free bonds. A new configuration for stacking Al-Ge thin films has been demonstrated to tackle the issue of loss of Ge prior to bonding, since native Ge oxides are soluble in deionized water. The impact of solid-state aging prior to Al-Ge eutectic bonding has been investigated. The method of tailoring the phases in the Pt-In joint is also discussed. The prospects and constraints of eutectic and TLP bonding from the hermeticity perspective are discussed in detail. Furthermore, changes in the microstructure under aging at 300°C up to 500 h and the resulting influence on the mechanical properties are presented. The overall finding of this work is that Al-Ge can achieve better mechanical and hermetic performance for high-temperature applications.     

Fast mode decision algorithm for H.264 inter-prediction

A fast mode decision algorithm for H.264/AVC inter-prediction to reduce computational complexity of the H.264 encoder is presented. Experimental results show that the algorithm can save the entire encoding time by 77% on average while introducing only negligible loss in PSNR value and small increment of bit rate.     

Signaling and Control Procedures Using Generalized MPLS Protocol for IP over an Optical Network

This paper reviews the existing research activities on signaling and control procedures for IP over optical networks. We focus on the IP‐centric signaling and control architecture based on the generalized multi‐protocol label switching (GMPLS) protocol and analyze various scenarios and technical issues for deploying the IP over an optical network. We analyze the signaling and operations and administration and maintenance requirements for integrating an IP network and an optical network in order to cope with the high bandwidth and poor resource granularity of the optical network, including the optical cross‐connect system. On the basis of network architecture and a reference configuration model, we investigate the GMPLS‐based control architecture and interconnection model appropriate for controlling IP bandwidth and optical lambda resources. The signaling and control procedure based on GMPLS on optical user‐network interface and network‐network interface are comparatively investigated to provide the optical lightpath. We also study protection and restoration procedures to protect link failure when it applies to GMPLS signaling.     

Broadband access using subcarrier multiplexing and asymmetric digital subscriber lines

A broadband access system using subcarrier multiplexing on optical fibre and asymmetric digital subscriber lines (ADSL) or very high‐speed digital subscriber lines (VDSL) on unshielded twisted‐pair is proposed to provide broadband access. In this hybrid‐fibre/twisted‐pair (HFTP) system, the digital multiplexing/demultiplexing process is moved back to the central office by using subcarrier multiplexing for fibre transmission. Instead of installing in remote node, ADSL/VDSL transceivers are installed at the central office to greatly reduce the remote node complexity. The local node simply down‐converts the subcarrier multiplexed ADSL/VDSL signal to the baseband, suitable to send directly into the twisted‐pair. The reduction of complexity could result in a lower initial installation cost, especially for a low service penetration rate. Copyright © 2000 John Wiley & Sons, Ltd.     

Inverted Staggered Poly-Si Thin-Film Transistor With Planarized SOG Gate Insulator

In this letter, we have studied the inverted staggered thin-film transistor (TFT) using a spin-on-glass (SOG) gate insulator and a low-temperature polycrystalline silicon (poly-Si) by Ni-mediated crystallization of amorphous silicon. The p-channel poly-Si TFT exhibited a field-effect mobility of 48.2 cm²/V ldr s, a threshold voltage of -4.2 V, a gate-voltage swing of 1.2 V/dec, and a minimum off-current of < 4 times 10^-13A/ mum at V_ds = -0.1 V. Therefore, the gate planarization technology by SOG can be applicable to low-cost large-area poly-Si active-matrix displays.     

Thermal buffer materials for enhancement of device performance of organic light emitting diodes fabricated by laser imaging process

Laser Induced Thermal Imaging (LITI) is a laser addressed thermal patterning technology with unique advantages such as an excellent uniformity of transfer film thickness, a capability of multilayer stack transfer and a possibility to fabricate high resolution as well as large-area display. Nevertheless, it has been an obstacle to use such a laser imaging process as a commercial technology so far because of serious deterioration of the device performances plausibly due to a re-orientation of the molecular stacking especially in the emitting layer during thermal transfer process. To improve device performances, we devised a new concept to suppress the thermal degradation during such kind of thermal imaging process by using a high molecular weight small molecular species with large steric hindrance as well as high thermostability as a thermal buffer layer to realize highly efficient LITI devices. As a result, we obtained very high relative efficiency (by EQE) up to 91.5% at 1000 cd/m² from the LITI devices when we utilize 10-(naphthalene-2-yl)-3-(phenanthren-9-yl)spiro[benzo[ij]tetraphene-7,9′-fluorene] as a thermal buffer material.     

Phase-matched four-wave mixing between pumps and signals in a copumped Raman amplifier

We observe four-wave mixing (FWM) between copropagating pumps and signals in a Raman amplifier when the zero-dispersion wavelength of the transmission fiber lies symmetrically between the pump and the signal wavelengths. The resultant FWM products, which grow as they experience Raman gain along the fiber, can degrade the signal's optical signal-to-noise ratio by as much as 10 dB for a Raman ON-OFF gain of 15 dB.