Implementation of a real-time frequency-selective RF channelsimulator using a hybrid DSP-FPGA architecture

A low cost frequency-selective RF channel simulator architecture is explored in this paper. The technique of quadrature amplitude modulation (QAM) by independent low-pass filtered white Gaussian noise sources forms a rational function approximation (RFA) to the desired Doppler spectrum for flat Rayleigh fading. To simulate frequency-selective fading, this QAM/RFA architecture may be extended by combining delayed outputs from multiple flat fading generators. In this paper, the noise shaping filter considered is in the form of an infinite-impulse-response digital filter followed by an interpolator (upsampler) using linear interpolation. The performance requirements are those in the standard channel simulator section of TIA IS-55-A. The system is implemented almost entirely in the digital domain by use of IF sampling, with the signal processing performed in a high-end floating-point digital signal processor and a field-programmable gate array. The theoretical performance of the simulator is studied with respect to the TIA standard, and limitations of the hardware prototype are identified. A system capable of simulating 12 delay taps, with a processing bandwidth of 5 MHz, can be built at about one-tenth the cost of commercially available channel simulators of comparable performance     

A wrinkle in flight: the role of elastin fibres in the mechanical behaviour of bat wing membranes

Bats fly using a thin wing membrane composed of compliant, anisotropic skin. Wing membrane skin deforms dramatically as bats fly, and its three-dimensional configurations depend, in large part, on the mechanical behaviour of the tissue. Large, macroscopic elastin fibres are an unusual mechanical element found in the skin of bat wings. We characterize the fibre orientation and demonstrate that elastin fibres are responsible for the distinctive wrinkles in the surrounding membrane matrix. Uniaxial mechanical testing of the wing membrane, both parallel and perpendicular to elastin fibres, is used to distinguish the contribution of elastin and the surrounding matrix to the overall membrane mechanical behaviour. We find that the matrix is isotropic within the plane of the membrane and responsible for bearing load at high stress; elastin fibres are responsible for membrane anisotropy and only contribute substantially to load bearing at very low stress. The architecture of elastin fibres provides the extreme extensibility and self-folding/self-packing of the wing membrane skin. We relate these findings to flight with membrane wings and discuss the aeromechanical significance of elastin fibre pre-stress, membrane excess length, and how these parameters may aid bats in resisting gusts and preventing membrane flutter.     

Spatially resolved protein hydrogen exchange measured by matrix-assisted laser desorption ionization in-source decay

Mass spectrometry has become a powerful tool for measuring protein hydrogen exchange and thereby reveal the structural dynamics of proteins in solution. Here we describe the successful application of a matrix-assisted laser desorption ionization (MALDI) mass spectrometry approach based on in-source decay (ISD) to measure spatially resolved amide backbone hydrogen exchange. By irradiating deuterated protein molecules in a crystalline matrix with a high laser fluence, they undergo prompt fragmentation. Spatially resolved deuteration levels are readily obtained by mass analysis of consecutive fragment ions. MALDI ISD analysis of deuterated cytochrome c yielded an extensive series of c-fragment ions which originate from cleavage of nearly all N-C(α) bonds (Cys17 to Glu104) allowing for a detailed analysis of the deuterium content of the backbone amides. While hydrogen scrambling can be major concern when using mass spectrometric fragmentation to obtain detailed information on protein hydrogen exchange, we show that the level of hydrogen scrambling in our MALDI ISD measurements is negligible and that the known dynamic behavior of cytochrome c in solution is accurately reflected in the deuterium contents of the fragment ions. The developed method combines several attractive features from a practical point of view as it is simple to perform and it readily provides a detailed mapping of the dynamic structure of a protein in solution.     

The Reactions of N,N′-Diphenyldithiomalondiamide with Arylmethylidene Meldrum’s Acids

The Michael addition reaction between dithiomalondianilide (N,N′-diphenyldithiomalondiamide) and arylmethylidene Meldrum’s acids, accompanied by subsequent heterocyclization, was investigated along with factors affecting the mixture composition of the obtained products. The plausible mechanism includes the formation of stable Michael adducts which, under the studied conditions, undergo further transformations to yield corresponding N-methylmorpholinium 4-aryl-6-oxo-3-(N-phenylthio-carbamoyl)-1,4,5,6-tetrahydropyridin-2-thiolates and their oxidation derivatives, 4,5-dihydro-3H-[1,2]dithiolo[3,4-b]pyridin-6(7H)-ones. The structure of one such product, N-methylmorpholinium 2,2-dimethyl-5-(1-(2-nitrophenyl)-3-(phenylamino)-2-(N-phenylthiocarbamoyl)-3-thioxopropyl)-4-oxo-4H-1,3-dioxin-6-olate, was confirmed via X-ray crystallography.     

Development of the bus joint for the ITER Central Solenoid

The terminations of the Central Solenoid (CS) modules are connected to the bus extensions by joints located outside the CS in the gap between the CS and torodial field (TF) assemblies. These joints have very strict space limitations. Low resistance is a common requirement for all ITER joints. In addition, the CS bus joints will experience and must be designed to withstand significant variation in the magnetic field of several tenths of a Tesla per second during initiation of plasma. The joint resistance is specified to be less than 4 nΩ.The joints also have to be soldered in the field and designed with the possibility to be installed and dismantled in order to allow cold testing in the cold test facility. We have developed coaxial joints that meet these requirements and have demonstrated the feasibility to fabricate and assemble them in the vertical configuration. We introduced a coupling cylinder with superconducting strands soldered to the surface of the cable that can be installed in the ITER assembly hall and at the cold test facility. This cylinder serves as a transition area between the CS module and the bus extension.We made two racetrack samples and tested four bus joints in our Joint Test Apparatus. Resistance of the bus joints was measured by a decay method and by a microvoltmeter; the value of the current was measured by the Hall probes. This measurement method was verified in the previous tests. The resistance of the joints varied insignificantly from 1.5 to 2 nΩ.One of the challenges associated with a soldered joint is the inability to use corrosive chemicals that are difficult to clean. This paper describes our development work on cable preparation, chrome removal, compaction, soldering, and final assembly and presents the test results.     

Fermilab Fast Parallel Readout System for Data Acquisition

Three modules have recently been developed at Fermilab to provide high speed parallel readout of data for high energy physics experiments. This paper describes how these modules provide a fast and efficient method for transferring CAMAC event data into VME-based or FASTBUS-based memories, thus enhancing and extending the usefulness of experiments' large investments in CAMAC hardware. Using these modules can decrease the dead time of an experiment by up to a factor of 10. This paper includes a discussion of the experiment topologies In which these modules are being used.     

络合剂在优化纺织品湿加工整理中的应用

新型络合剂在多种工序中的应用,可以为单道工序甚至整个生产过程节约大量成本,加速生产循环,省去部分加工步骤,同时还提高了不稳定配方的生产可靠性.极简化的操作水平也可以节约大量能源.现代技术和设计应将络合剂作为重要的过程控制参数,因为这关系到整个工艺的成败.