Capacity and Modulations with Peak Power Constraint

A practical communication channel often suffers from constraints on input other than the average power, such as the peak power constraint. In order to compare achievable rates with different constellations as well as the channel capacity under such constraints, it is crucial to take these constraints into consideration properly. In this paper, we propose a direct approach to compare the achievable rates of practical input constellations and the capacity under such constraints. As an example, we study the discrete-time complex-valued additive white Gaussian noise (AWGN) channel and compare the capacity under the peak power constraint with the achievable rates of phase shift keying (PSK) and quadrature amplitude modulation (QAM) input constellations.Comment: 9 pages with 12 figures. Preparing for submissio

Icosahedral quasicrystal and 1/1 cubic approximant in Au-Al-Yb alloys

A P-type icosahedral quasicrystal is formed in Au-Al-Yb alloy of which 6-dimensional lattice parameter a6D = 7.448 {\AA}. The composition of the quasicrystal was analyzed to be Au51Al34Yb15. This quasicrystal is formed in as-cast alloys, and is regarded as metastable because of decomposition into other crystalline phases by annealing at 700 \degree C. Among Tsai-type quasicrystals, this quasicrystal is situated just between Zn-Sc group with smaller a6D and larger Cd-Yb group. Intermediate valence of Yb recently observed in this quasicrystal may be due to this unique situation, namely smaller major component Au-Al than in Cd-Yb. The predominant phase in the annealed specimen is a 1/1 cubic approximant with lattice parameter a = 14.500 {\AA} belonging to the space group Im-3 . This phase is stable at the composition Au51Al35Yb14 at 700 \degree C. Rietveld structural analysis indicated that the crystal structure is understood as periodic arrangement of Tsai-type clusters each including four Au-Al atoms at their centers. Chemical ordering of Au and Al is characteristics of this approximant.Comment: 20 pages including 1 table and 7 figure

Quasiparticle Dissipation in d-wave Superconductor Phase Qubit

Recent phase sensitive experiments on high Tc superconductors, e.g., YBa_2Cu_3O_7 single crystals, have established the d-wave nature of the cuprate materials. Here we discuss how to make use of d-wave Josephson junctions in the construction of a phase qubit. We especially focus on the effect of quasiparticle dissipation on the macroscopic quantum tunneling which corresponds to the measurement process for the d-wave phase qubit.Comment: 3 pages, 1 figure, The Seventh International Conference on Quantum Communication, Measurement and Computing, Glasgow, UK, from 25th to 29th July 2004. To appear in the AIP Conference Proceeding

Macroscopic quantum dynamics of pi-junctions with ferromagnetic insulators

We theoretically investigate the macroscopic quantum dynamics of a pi junction with a superconductor (S) and a multiferroic material or a ferromagnetic insulator (FI). By deriving the effective action from a microscopic Hamiltonian, a pi-junction qubit (a S-FI-S superconducting quantum interference device ring) is proposed. In this qubit, a quantum two-level system is spontaneously generated and the effect of the quasiparticle dissipation is found to be very weak. These features make it possible to realize a quiet qubit with high coherency. We also investigate macroscopic quantum tunneling (MQT) in current-biased S-FI-S pi junctions and show that the influence of the quasiparticle dissipation on MQT is negligibly small.Comment: 4 pages, 2 figure

Über das Koagulationsband von Weltmann bei Lungentuberkulose

Es ist ein altes Bestreben, eine Methode auszuarbeiten, die über die Gualität und Quantität der tuberkulosen Prozesse genauere Auskunft gibt. Diesbezüglich sind zahlreiche Reaktionen angegeben worden. Im Jahre 1930 berichtete Weltmann über eine sogenannte Serumkoagulationsreaktion, mit welcher nach ihm die exsudative oder produktive Art tuberkuloser Prozesse zu unterscheiden ware. Verfasser hat die Weltmannsche Reaktion bei 76 Lungentuberkulosen und 10 Gesunden angewandt. Gleichzeitig hat er auch die Senkungsreaktion der roten Blutkorperchen, das Gesamteiweiss und den Albumin-Globulin-Quotient des Serums bestimmt. Die Resultate konnen folgendermassen zusammengefasst werden: 1) Für die Sera von Gesunden trat die komplette Gerinnung bei 0,4-0,45‰, die inkomplette Gerinnung bei 0,3‰ Konzentration ein. 2) Bei exsudativer Lungentuberkulose (26 Fälle) fand beim Koagulationsband fast immer eine Linksverschiebung statt. 3) Bei gemischter Form von Lungentuberkulose (20 Fälle) war das Koagulationsband wie beim normalen Menschen oder neigte zu einer leichten Linksverschiebung. 4) Bei fibrös-produktiver Lungentuberkulose (30 Fälle) zeigte sich ein normales Koagulationsband oder es verlängerte sich uber 0,35‰. 5) Das Koagulationsband, die Senkungsreaktion, das Gosamteiweiss und der Albumin-Globulin-Quotient gehen nicht durchweg parallel. 6) Die Serienuntersuchung des Koagulationsbandes bei Lungentuberkulose ist gut verwertbar für die Diagnose des Krankheitszustande und die Prognosestellung. 7) Die Methode, welehe teehnisch einfach und billig ist, kann dem Praktiker daher wärmstens empfohlen werden

ガス拡散層を持たない新規構造による固体高分子形燃料電池の耐フラッディング性向上に関する研究

The gas diffusion layer (GDL)-less fuel cell that is composed of a corrugated-mesh shows less flooding performance even in the high current density region, because gases are supplied more uniformly to the catalyst layer in comparison with the conventional fuel cell utilizing GDL. On the other hand, its internal electrical resistance is higher than that of conventional fuel cell, because corrugate mesh and underneath microporous layer (MPL) makes less contact area with points-contact. This can increase the resistance at the interface between corrugated-mesh and MPL as well as MPL and catalyst layer (CL) greatly from the conventional fuel cell where GDL can make good contact with MPL. In this study the conductivities and contact resistances of each material are measured under various mechanical compression pressures, and coupled mechanical-electric-electrochemical simulation is developed to investigate the effect of these electrical resistance. As a result, it is found that our model can simulate well for the GDL-less fuel cell and the effect of the electric resistance in the GDL-less fuel cell has a big contribution on the polarization performance.固体高分子形燃料電池は次世代の自動車用動力源として期待されるが，その本格的利用のためには発電出力密度の更なる向上が求められる．燃料電池の発電出力向上のためには，反応物供給の均一化，内部抵抗の低減，触媒活性の向上などが求められるが，とくに高電流密度条件においては，発電と同時に生成する水が反応物流路を閉塞して反応物の均一な供給を妨げるフラッディングと呼ばれる現象が問題となる．このため，フラッディングの問題の解決は固体高分子形燃料電池の発電出力密度を向上させる上で極めて重要な課題である．以上の背景から，本研究では，金属製のマイクロコイルおよびコルゲートメッシュを用いた新たな構造の反応物流路を提案し，これらの流路を固体高分子形燃料電池に用いることによる発電性能向上を試みた．その際，とくに耐フラッディング性の向上および内部抵抗の低減に着目した検討を行い，流路構造がそれらに与える影響について解析を行った．首都大学東