Propagation of single flux quantum pulse of superconducting transmission line

Josephson tunnel junction switching by single flux quantum (SFQ) pulses generated by a two-junction interferometer and propagated on a superconducting transmission line have been investigated experimentally and by numerical simulation. High current density tunnel junctions have been used to enhance voltage SFQ pulse amplitudes and reduce junction damping parameters. The measured effective amplitudes of SFQ pulses allow an evaluation of the applicability of transmission lines to SFQ logic circuits and Josephson samplers.     

Novel single-electron logic circuits using charge-induced signal transmission (CIST) structures

In this paper, on the basis of the Monte Carlo simulation, we demonstrate a method to realize logical operations by the use of the single-electron charge-induced signal transmission (CIST) circuit which we have proposed previously. First, we propose three new-type signal transmission circuits. Then, we demonstrate through construction of a NAND circuit and a full-adder circuit on the basis of the Monte Carlo simulation that we can construct any logic circuit by the use of these circuits. Since the CIST circuit can perform any logical operation and can transmit the state of the presence or absence of an electron and a hole as a binary signal over long distance during one clock cycle bidirectionally, these CIST circuits are expected to be applied to integrated circuit devices as a new circuit construction method.     

Current measurement system utilizing cryogenic techniques for theabsolute measurement of the magnetic flux quantum

A series of systems composed of cryogenic devices such as a Josephson potentiometer and a cryogenic current comparator, developed to precisely measure a current with any value up to 1 A, is proposed. These systems will be used to measure the injected electrical energy with an uncertainty of the order of 0.01 p.p.m. or less in the absolute measurement of the magnetic flux quantum by superconducting magnetic levitation. Some preliminary experiments are described     

Active circuits for flux waveform compensation in ferromagnetic cores

Some new schemes using active circuits are proposed for realization of sinusoidal flux in a ferromagnetic core during loss testing. One of the suggested configurations facilitates the loss measurements to be made from the primary side itself. A few filter circuits enable the tests to be carried out on normal supply mains without the need for a calibration generator. Experimental results are reported to confirm the acceptability of the proposed schemes.     

Bloch's oscillations in quantum circuits with charge discreteness

We consider the effect of charge discreteness in a quantum circuit with inductance L. The inductance is pierced by a time-depending external magnetic field, which creates a time-dependent magnetic flux /spl phi//sub ext/(t). When the external magnetic flux varies linearly with time, the induced current in the inductance oscillates with a frequency proportional to the flux variation and charge discreteness. This phenomenon is equivalent to well-known Bloch's oscillation in crystal or periodic superlattices heterostructures. In fact, formally, the charge discreteness plays the role of a lattice constant. The same phenomenon occurs when the flux variations are replaced by a (constant) electromotive force. We expect this phenomena to be realized in micrometer sized solid-state systems.     

Nonlinear coupling and squeezing in solid-state quantum circuits

We propose an attractive realization of nonlinear coupling of superconducting charge qubit coupled to a transmission-line resonator. Our scheme provides a new approach to produce the strong squeezing effect via a flexible design of the superconducting qubit and mature experimental setup of circuit QED. By properly tuning the external magnetic flux, considerable squeezing can be generated. Strong coupling strength, immunity to noises and suppression of spontaneous emission make our scheme more robust and may be realized with conservative experimental parameters.     

Quantum-confined ion superfluid in nerve signal transmission

We propose a process of quantum-confined ion superfluid (QISF), which is enthalpy-driven confined ordered fluid, to explain the transmission of nerve signals. The ultrafast Na⁺ and K⁺ ions transportation through all sodium-potassium pump nanochannels simultaneously in the membrane is without energy loss, and leads to QISF wave along the neuronal axon, which acts as an information medium in the ultrafast nerve signal transmission. The QISF process will not only provide a new view point for a reasonable explanation of ultrafast signal transmission in the nerves and brain, but also challenge the theory of matter wave for ions, molecules and particles.

     

Dependence of signal on depth in transmission Raman spectroscopy

Recently, transmission Raman spectroscopy has been shown to be a valuable tool in the volumetric quantification of pharmaceutical formulations. In this work a Monte Carlo simulation and experimental study are performed to elucidate the dependence of the Raman signal on depth from the viewpoint of probing pharmaceutical tablets and powders in this experimental configuration. The transmission Raman signal is shown to exhibit a moderate bias toward the center of the tablets and this can be considerably reduced by using a recently developed Raman signal-enhancing concept, the "photon diode." The enhancing element not only reduces the bias but also increases the overall Raman signal intensity and consequently improves the signal-to-noise ratio of the measured spectrum. Overall, its implementation with appropriately chosen reflectivity results in a more uniform volumetric sampling across the half of the tablet where the photon diode is used (or across the tablet's entire depth if two photon diodes are used on each side of tablet) and enhanced overall sensitivity. These findings are substantiated experimentally on a segmented tablet by inserting a poly(ethelyne terephthalate) (PET) film doped with TiO(2) at different depths and monitoring its contribution to the overall transmission Raman signal from the segmented tablet. The numerical simulations also indicate considerable sensitivity of the overall Raman signal to the absorption of the sample, which is in line with large migration distances traversed by photons in these measurements. The presence of sample absorption was shown numerically to reduce the signal enhancement effect while the overall depth-dependence profile remained broadly unchanged. The absorption was also shown to produce a depth profile with the photon diode similar to that without it, although with a reduced absolute intensity of Raman signals and diminished enhancement effect.     

Symmetry tests using the half-integer flux quantum effect in cuprate superconducting rings

The presence or absence of the half-integer flux quantum effect in controlled orientation tricrystal grain boundary rings is a general test of the phase of the superconducting order parameter. One such test proves that this effect is symmetry dependent, and that the order parameter in YBa₂Cu₃O₇- has lobes and nodes consistent with d-wave symmetry. Our measurements show that the flux in the 1/2 integer ground state is quantized to ₀/2 within ± 3%. This puts limits on the imaginary component of the superconducting order parameter in YBa₂Cu₃O₇-.     

Statistical modelling of building transmission in a cellular urban environment

Channel sounding measurements have been reported which show that transmission through buildings can be important for microcellular coverage planning. A theoretical-statistical model for propagation through a building, or row of buildings, is proposed in the paper. Expressions for the mean and covariance of the channel transfer function are obtained and compared with measurements. The model exhibits good prediction accuracy for residential homes, while similar trends with the measurements for office blocks were obtained also     

自由空间量子密钥分发中的信号同步解决方案

针对目前自由空间量子密钥分发（QKD）中的信号同步这一难点问题,提出一种采用外置光信号来解决信号同步问题的方案——光同步方案。在发送端利用声光调制器将外置激光器的连续激光分割成周期光脉冲序列,并作为同步光信号发送给接收端。接收端采用光电倍增管接收同步光脉冲信号,生成一个与发送端严格同步的信号,以此作为接收端的时基标准来进行单光子计数。采用高频的内部时钟信号来“监视”接收到的同步信号,从而提高计数准确性。该方案具有长距离性、无线性、低复杂度等特点,已成功应用于一个基于B92协议的自由空间QKD系统中。     

Complex building element monitoring – interior insulation in practical test

Germany has set ambitious targets at a national level for the reduction of emissions with the Energiekonzept 2010: by 2020, emissions should be reduced by at least 40 % compared to 1990. By 2050, a reduction of emissions by 80 to 95 % (compared to 1990) is intended [1]. In order to even come near to these targets, the energy‐related refurbishment of existing buildings has been gaining significance for some years. Facades that are worth preserving or under listed building protection limit the upgrading options on the outside, but interior insulation solutions are as ever regarded with suspicion by some protagonists. The following article reports on the building physics support for a particularly challenging refurbishment project.     

Single excitons in InGaN quantum dots on GaN pyramid arrays

Fabrication of single InGaN quantum dots (QDs) on top of GaN micropyramids is reported. The formation of single QDs is evidenced by showing single sub-millielectronvolt emission lines in microphotoluminescence (μPL) spectra. Tunable QD emission energy by varying the growth temperature of the InGaN layers is also demonstrated. From μPL, it is evident that the QDs are located in the apexes of the pyramids. The fact that the emission lines of the QDs are linear polarized in a preferred direction implies that the apexes induce unidirected anisotropic fields to the QDs. The single emission lines remain unchanged with increasing the excitation power and/or crystal temperature. An in-plane elongated QD forming a shallow potential with an equal number of trapped electrons and holes is proposed to explain the absence of other exciton complexes.     

编码发射技术在医学高频超声成像中的研究进展

高频超声成像以其高分辨和实时性好等优势成为近年来医学超声成像领域研究的热点。但由于超声的衰减随频率增加呈指数级升高,导致高频超声信号幅值小,图像信噪比低。为了增强高频超声成像的信噪比,近年来编码发射（又称编码激励）技术得到了越来越多的研究和应用。文章对近几年国内外编码发射技术在医学高频超声成像方面的应用和研究进展进行了综述,重点分析了Chirp码、巴克（Barker）码和格雷（Golay）码3种主要编码发射技术在高频超声成像方面应用的优缺点,并综合对比了各种编码发射技术在高频成像方面的应用前景。     

Determination of moisture distributions in porous building materials by neutron transmission analysis

The movement of moisture inside building structures can affect them in important ways, causing physical and chemical damage. Therefore the study of moisture transport in porous building materials is highly relevant to a better understanding of the durability of building structures made of porous materials. The moisture transport can be described phenomenologically by a diffusion equation using a moisture content dependent moisture transfer coefficient. To determine the transfer coefficient in a given material, the experimental quantitative measurement of the time and space dependent moisture distribution in the material is necessary. Neutron radiography provides a highly sensitive non-destructive method for the detection of the presence of water and provides high spatial resolution. A new neutron transmission analysis technique has been developed and optimized for the study of moisture in building materials to extract the quantitative information from the experimental data. Typically, moisture contents down to a few mg/cm³ can be detected at a spatial resolution of 1 mm. As an application example, the determination of the time and space dependent moisture distribution in a brick sample and the subsequent determination of the moisture transfer coefficient are presented.     

Implementation of digital signal processing techniques in thedesign of thermal pulse flowmeters

Various digital signal processing methods, which could be applicable to the design of a microcomputer-based thermal pulse flowmeter, are examined. Two excitation methods are investigated: a single thermal pulse, and a pseudorandom binary sequence signal (PRBS). The signal recovered downstream is processed by two alternative numerical algorithms to recover the time of flight (i.e. by peak detection of the signal itself and the peak of the differentiated signal). The recovered thermal pulse and the time of flight are then used to test the validity of two models: a diffusion-advection model and a simple time-delay model. The delay model is found to be compatible with the data, especially when the peak of the output signal derivative is used as a marker for determining the time of flight. The single-pulse injection method is found, in general, to be superior to the PRBS cross-correlation technique, except for the ability of the latter to provide early indication of flow-rate variations