Enargite Cu3PS4: A Cu–S‐Based Thermoelectric Material with a Wurtzite‐Derivative Structure

Compound semiconductors derived from ZnS (zincblende and wurtzite) with tetrahedral framework structures have functions for various applications. Examples of such materials include Cu–S‐based materials with zincblende‐derivative structures, which have attracted attention as thermoelectric (TE) materials over the past decade. This study illuminates superior TE performance in polycrystalline samples of enargite Cu₃P_1?xGe_xS₄ with a wurtzite‐derivative structure. The substitution of Ge for P dopes holes into the top of the valence band composed of Cu‐3d and S‐3p, whereby its multiband characteristic leads to a high TE power factor. Furthermore, a reduction in the grain size to 50–300 nm can effectively decrease phonon mean free paths, leading to low thermal conductivity. These features result in a dimensionless TE figure of merit ZT of 0.5 at 673 K for the x = 0.2 sample. Environmentally benign and low‐cost characteristics of the constituent elements of Cu₃PS₄, as well as its high‐performance thermoelectricity, make it a promising candidate for large‐scale TE applications. Furthermore, this finding extends the development field of Cu–S‐based TE materials to those with wurtzite‐derivative structures.     

Understanding the final-state control from the standpoint of the model predictive control and its application to a three-dimensional trajectory control problem

Microsystem Technologies - In many motion control problems of mechatronic equipment, the control performance of the final-state of the control period is strictly important for positioning or...     

Development of 1 kW class solid oxide fuel cell stack using anode-supported planar cells

We have developed a 1 kW class solid oxide fuel cell (SOFC) stack composed of 50 anode-supported planar 120-mm-diameter SOFCs. Intermediate plates, which exhibited negligible deformation under operating conditions, were placed in the stack to cancel out the cumulative error related to the position and angle of the stack parts. The stack provided an electrical conversion efficiency of 54% (based on the lower heating value (LHV) of the methane used as a fuel) and an output of 1120 W when the fuel utilization, current density, and operating temperature were 67%, 0.28 A cm⁻², and 1073 K, respectively. The stack operated stably for almost 700 h.     

Highly efficient and durable anode-supported SOFC stack with internal manifold structure

We have developed a solid oxide fuel cell (SOFC) stack with an internal manifold structure. The stack, which is composed of 25 anode-supported 100-mm-diameter SOFCs, provided an electrical conversion efficiency of 56% (based on the lower heating value of methane, which was used as a fuel) and an output of 350 W when the fuel utilization, current density, and operating temperature were 75%, 0.3 A cm⁻², and 1073 K, respectively. The electrical efficiency and the output were maintained for 1100 h. The cell voltage fluctuation was ±2% for 25 cells. The relationship between average cell voltage and current density in the 25-cell stack was as almost the same as that in the 1- and 10-cell stacks, which suggests that our stack provides almost the same cell performance regardless the number of the cells.     

Strategy/False-name Proof Protocols for Combinatorial Multi-Attribute Procurement Auction

In this paper, we investigate a model of a combinatorial, procurement multi-attribute auction, in which each sales item is defined by several attributes called quality, the buyer is the auctioneer (e.g., a government), and the sellers are the bidders. Furthermore, there exist multiple items and both buyer and sellers can have arbitrary (e.g., substitutable/complementary) preferences on a bundle of items. Our goal is to develop a protocol that is strategy-proof for sellers. We first present a VickreyClarkeGroves (VCG)-type protocol. As in a standard combinatorial auction, a VCG-type protocol is not false-name-proof, i.e., it is vulnerable against manipulations using multiple identifiers. Next, we show that any strategy-proof protocol in this model can be represented as a framework called Price-Oriented Rationing-Free (PORF) protocol, in which for each bidder, for each bundle of items, and for each quality, the payment for the bidder is determined independently of his own declaration, and the bidder can obtain a bundle that maximizes his utility independently of the allocations of other bidders. We develop a false-name-proof protocol in this model.     

Evidence of Electron–Phonon Interaction in Al-Substituted Mg1−x Al x B2

Phonon density of states in Al substituted Mg_1?x Al _x B₂ has been studied by means of inelastic neutron scattering experiments with pulsed neutron time-of-flight technique. Phonon dynamics have a significant role for realizing superconductivity in the recent discovered superconductor MgB₂. We present a systematic investigation on generalized phonon density of states (PDOS) up to E = 120 meV on Al content of x = 0.1, 0.25, and 0.5. We have clearly observed a large effect on the PDOS by Al substitution; a large energy shift occurs around at 70 meV and 89 meV. We have also observed a visible increase of PDOS at a particular energy range below T _c. Those phonon states are related with E _2g mode to be expected to have a strong coupling with the electron states at the Γ–A region.     

Joining of zirconia using zirconium-based alloys

The contact angles of Zr-Ni, Zr-Cu and Zr-Co alloys against PSZ were measured by the sessile drop method. Each alloy wetted PSZ very well. Zr-Co alloys showed a different behaviour. Joints of PSZ plates were obtained using Zr-17Ni alloy. At the joint interface, internal oxidation of zirconium occurred. The fracture shear strength of this joint was 55 MPa.     

An improvement of dynamic Huffman coding with a simple repetitionfinder

A mixed-mode file compression scheme that incorporates interval encoding for finding duplicate occurrences of strings without storing or parsing the past sequence and a one-pass scheme for dynamic Huffman codes is presented. Results from experiments performed on various types of files are discussed. The proposed method runs in linear time, and the memory requirement depends only on the alphabet size. The code efficiency is compared experimentally to that of other schemes     

Evidence of Electron–Phonon Interaction in Al-Substituted Mg1?xAlxB2

Phonon density of states in Al substituted Mg_1–x Al _x B₂ has been studied by means of inelastic neutron scattering experiments with pulsed neutron time-of-flight technique. Phonon dynamics have a significant role for realizing superconductivity in the recent discovered superconductor MgB₂. We present a systematic investigation on generalized phonon density of states (PDOS) up to E = 120 meV on Al content of x = 0.1, 0.25, and 0.5. We have clearly observed a large effect on the PDOS by Al substitution; a large energy shift occurs around at 70 meV and 89 meV. We have also observed a visible increase of PDOS at a particular energy range below T _c. Those phonon states are related with E _2g mode to be expected to have a strong coupling with the electron states at the –A region.