A 12-bit 300 MHz CMOS DAC for high-speed system applications

This paper describes a 12-bit 300 MHz CMOS DAC for high-speed system applications. The proposed DAC consists of a unit current-cell matrix for 8 MSBs and a binary-weighted array for 4 LSBs. In order to ensure the linearity of DAC, a double Centro symmetric current matrix is designed by using the Q(2) random walk strategy. To minimize the feedthrough and improve the dynamic performance, the drain of the switching transistors is isolated from the output lines by adding two cascoded transistors.

Transfer property of electron pulse in a femto-second electron diffraction system

An ultra-fast electron diffraction system has been designed. The static and dynamic characters of an electron pulse with 150 fs temporal dispersion are studied during its transmission in the whole ultra-fast electron diffraction system, including the size of the electron spot, temporal dispersion, distribution of azimuths and elevation angles. The initial status of the photoelectrons are put down by Monte Carlo method, both the two dimensional and three dimensional electric fields are calculated by finite difference method and the magnetic flux are. calculated by finite element method.

Real-time far distance micro-vibration measurement using an external cavity semiconductor laser interferometer with a feedback control system

An external cavity semiconductor laser interferometer used to measure far distance micro-vibration in real time is proposed. In the interferometer, a single longitudinal mode and excellent coherent characteristic grating external cavity semiconductor laser is constructed and acted as a light source and a phase compensator. Its coherent length exceeds 200 meters. The angle between normal and incidence beam of the far object is allowed to change in definite range during the measurement with this interferometer, and this makes the far distance interference measurement easier and more convenient. Also, it is not required to keep the amplitudes of the first and second harmonic components equal, and then the dynamic range is increased. A feedback control system is used to compensate the phase disturbance between the two interference beams introduced by environmental vibration.

Simulations to design an online motion compensation system for scanned particle beams

Respiration-induced target motion is a major problem in intensity-modulated radiation therapy. Beam segments are delivered serially to form the total dose distribution. In the presence of motion, the spatial relation between dose deposition from different segments will be lost. Usually, this results in over-and underdosage. Besides such interplay effects between target motion and dynamic beam delivery as known from photon therapy, changes in internal density have an impact on delivered dose for intensity-modulated charged particle therapy. In this study, we have analysed interplay effects between raster scanned carbon ion beams and target motion. Furthermore, the potential of an online motion strategy was assessed in several simulations. An extended version of the clinical treatment planning software was used to calculate dose distributions to moving targets with and without motion compensation. For motion compensation, each individual ion pencil beam tracked the planned target position in the lateral aswell as longitudinal direction. Target translations and rotations, including changes in internal density, were simulated. Target motion simulating breathing resulted in severe degradation of delivered dose distributions. For example, for motion amplitudes of +/- 15 mm, only 47% of the target volume received 80% of the planned dose. Unpredictability of resulting dose distributions was demonstrated by varying motion parameters. On the other hand, motion compensation allowed for dose distributions for moving targets comparable to those for static targets. Even limited compensation precision (standard deviation similar to 2 mm), introduced to simulate possible limitations of real-time target tracking, resulted in less than 3% loss in dose homogeneity.

System size dependence of associated yields in hadron-triggered jets STAR Collaboration

We present results on the system size dependence of high transverse momentum di-hadron correlations at root s(NN) = 200 GeV as measured by STAR at RHIC. Measurements in d + Au, Cu + Cu and Au + Au collisions reveal similar jet-like near-side correlation yields (correlations at small angular separation Delta phi similar to 0, Delta eta similar to 0) for all systems and centralities. Previous measurements have shown Chat the away-side (Delta phi similar to pi) yield is suppressed in heavy-ion collisions. We present measurements of the away-side Suppression as a function of transverse momentum and centrality in Cu + Cu and Au + Au collisions. The suppression is found to be similar in Cu + Cu and An + An collisions at a similar number of participants. The results are compared to theoretical calculations based on the patron quenching model and the modified fragmentation model. The observed differences between data and theory indicate that the correlated yields presented here will further constrain dynamic energy loss models and provide information about the dynamic density profile in heavy-ion collisions. (C) 2009 Elsevier B.V. All rights reserved.

a dynamic model to handle defect-oriented processes

Tongji Univ, Inst Dev Study, Syst Engn Soc China, Comm Syst Dynam, Syst Dynam Soc, China Chapter, Shanghai Inst Foreign Trade, Syst Dynam Soc, Chapters Asia Pacific Area

Emergy Assessment of a Wheat-Maize Rotation System with Different Water Assignments in the North China Plain

Sustainable water use is seriously compromised in the North China Plain (NCP) due to the huge water requirements of agriculture, the largest use of water resources. An integrated approach which combines the ecosystem model with emergy analysis is presented to determine the optimum quantity of irrigation for sustainable development in irrigated cropping systems. Since the traditional emergy method pays little attention to the dynamic interaction among components of the ecological system and dynamic emergy accounting is in its infancy, it is hard to evaluate the cropping system in hypothetical situations or in response to specific changes. In order to solve this problem, an ecosystem model (Vegetation Interface Processes (VIP) model) is introduced for emergy analysis to describe the production processes. Some raw data, collected by investigating or observing in conventional emergy analysis, may be calculated by the VIP model in the new approach. To demonstrate the advantage of this new approach, we use it to assess the wheat-maize rotation cropping system at different irrigation levels and derive the optimum quantity of irrigation according to the index of ecosystem sustainable development in NCP. The results show, the optimum quantity of irrigation in this region should be 240-330 mm per year in the wheat system and no irrigation in the maize system, because with this quantity of irrigation the rotation crop system reveals: best efficiency in energy transformation (transformity = 6.05E + 4 sej/J); highest sustainability (renewability = 25%); lowest environmental impact (environmental loading ratio = 3.5) and the greatest sustainability index (Emergy Sustainability Index = 0.47) compared with the system in other irrigation amounts. This study demonstrates that application of the new approach is broader than the conventional emergy analysis and the new approach is helpful in optimizing resources allocation, resource-savings and maintaining agricultural sustainability.

Electrooxidative polymerization of phenothiazine derivatives on screen-printed carbon electrode and its application to determine NADH in flow injection analysis system

The electrooxidation polymerization of phenothiazine derivatives, including azure A and toluidine blue 0, has been studied at screen-printed carbon electrodes in neutral phosphate buffer. Both compounds yield strongly adsorbed electroactive polymer with reversible behavior and formal potentials closed to 0.04 V at pH 6.9. The modified electrodes exhibited good stability and electrocatalysis for NADH oxidation in phosphate buffer (pH 6.9), with an overpotential of more than 500 mV lower than that of the bare electrodes. Further, the modified screen-printed carbon electrodes were found to be promising as an amperometric detector for the flow injection analysis (FIA) of NADH, typically with a dynamic range of 0.5-100 muM.

Electropolymerization of azure B on a screen-printed carbon electrode and its application to the determination of NADH in a flow injection analysis system

The electrooxidation polymerization of azure B on screen-printed carbon electrodes in neutral phosphate buffer was studied. The poly(azure B) modified electrodes exhibited excellent electrocatalysis and stability for dihydronicotinamide adenine dinucleotide (NADH) oxidation in phosphate buffer (pH 6.9), with an overpotential of more than 400 mV lower than that at the bare electrodes. Different techniques, including cyclic voltammetry, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy have been employed to characterize the poly (azure B) film. Furthermore, the modified screen-printed carbon electrodes were found to be promising as an amperometric detector for the flow injection analysis (FIA) of NADH, typically with a dynamic range of 0.5 muM to 100 muM.

Investigation of the effect of branched structure on the performances of the copolymers synthesized from ethylene and alpha-olefin with rac-Et(Ind)(2)ZrCl2/MMAO catalyst system

The branched copolymers prepared from ethylene and alpha-olefins using rac-Et(Ind)(2)ZrCl2/MMAO catalyst system were studied. Both the absolute molecular weight ((M) over bar (W)) and the molecular size (radius of glyration, R-g) of the polymers eluting from gel permeation chromatography (GPC) columns were obtained simultaneously via a high temperature GPC coupled with a two-angle laser light scattering (TALLS) detector. The branched structures and performances of the copolymers display approximate molecular weight and molecular sizes were investigated. Wide angle X-ray diffraction analyses indicate that 16-carbon side branch could co-crystallize effectively with backbone chain at low alpha-olefin incorporation. The melt behaviors of the copolymers were studied by dynamic rheological measurements. Both branch length and comonomer content affect considerably the loss modulus, storage modulus and complex viscosity of the copolymers. The relationship between the dynamic-mechanical behavior and the comonomer content of the copolymers was also examined by dynamic-mechanical experiments.

Preparation of poly(thionine) modified screen-printed carbon electrode and its application to determine NADH in flow injection analysis system

A poly(thionine) modified screen-printed carbon electrode has been prepared by an electrooxidative polymerization of thionine in neutral phosphate buffer. The modified electrodes are found to give stable and reproducible electrocatlytic responses to NADH and exhibit good stability. Several techniques, including cyclic voltammetry, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), have been employed to characterize the poly(thionine) film. Further, the modified screen-printed carbon electrode was found to be promising as an amperometric detector for the flow injection analysis (FIA) of NADH, typically with a dynamic range of 5-100 muM.

Dynamic mechanical properties of interpenetrating polymer networks based on polyacrylates and epoxy

Interpenetrating polymer networks (IPNs) based on polyacrylate (poly(polyethylene glycol diacrylate), PEGDA) and epoxy(diglycidyl ether of bisphenol A, DGEBA) were prepared simultaneously Dynamic mechanical properties of the SINs (simultaneous interpenetrating networks) with various compositions were studied. Enhanced mechanical properties were found in this case. From the point of view of pre-swollen networks, all of the PEGDA/DGEBA IPNs were composed of the individual pre-swollen networks. A micro-phase segregation system was produced in the SIN. Glass transition temperatures shifted inward, which was attributed to molecular packing effects or mutual-entanglements of molecular segments among the individual pre-swollen networks. In accordance with the additivity of properties, namely the parallel model, the entanglement density between the two polymer networks reached its maximum at 50/50 PEGDA/DGEBA IPN.

Modern sedimentary environments and dynamic depositional systems in the southern Yellow Sea

Based on analyses of more than 600 surface sediment samples together with large amounts of previous sedimentologic and hydrologic data, the characteristics of modern sedimentary environments and dynamic depositional systems in the southern Yellow Sea (SYS) are expounded, and the controversial formation mechanism of muddy sediments is also discussed. The southern Yellow Sea shelf can be divided into low-energy sedimentary environment and high-energy sedimentary environment; the low-energy sedimentary environment can be further divided into cyclonic and anticyclonic ones, and the high-energy environment is subdivided into high-energy depositional and eroded environments. In the shelf low-energy environments, there developed muddy depositional system. In the central part of the southern Yellow Sea, there deposited the cold eddy sediments under the actions of a meso-scale cyclonic eddy (cold eddy), and in the southeast of the southern Yellow Sea, an anticyclonic eddy muddy depositional system (warm eddy sediment) was formed. These two types of sediments showed evident differences in grain size, sedimentation rate, sediment thickness and mineralogical characteristics. The high-energy environments were covered with sandy sediments on seabed; they appeared mainly in the west, south and northeast of the southern Yellow Sea. In the high-energy eroded environment, large amounts of sandstone gravels were distributed on seabed. In the high-energy depositional environment, the originally deposited fine materials (including clay and fine silt) were gradually re-suspended and then transported to a low-energy area to deposit again. In this paper, the sedimentation model of cyclonic and anticyclonic types of muddy sediments is established, and a systematic interpretation for the formation cause of muddy depositional systems in the southern Yellow Sea is given.

Influence of the earth rotation on the interfacial wave solutions and wave-induced tangential stress in a two-layer fluid system

Interfacial waves and wave-induced tangential stress are studied for geostrophic small amplitude waves of two-layer fluid with a top free surface and a flat bottom. The solutions were deduced from the general form of linear fluid dynamic equations of two-layer fluid under the f-plane approximation, and wave-induced tangential stress were estimated based on the solutions obtained. As expected; the solutions derived from the present work include as special cases those obtained by Sun et al. (2004. Science in China, Set. D, 47(12): 1147-1154) for geostrophic small amplitude surface wave solutions and wave-induced tangential stress if tire density of the upper layer is much smaller than that of the lower layer. The results show that the interface and the surface will oscillate synchronously, and the influence of the earth's rotation both on the surface wave solutions and the interfacial wave solutions should be considered.