Fast microwave detection system for coherent synchrotron radiation study at KEK: Accelerator test facility

A fast room temperature microwave detection system based on the Schottky Barrier-diode detector was created at the KEK ATF (Accelerator Test Facility). It was tested using Coherent Synchrotron Radiation (CSR) generated by the 1.28 GeV electron beam in the damping ring. The speed performance of the detection system was checked by observing the CSR from a multi-bunch (2.8 ns bunch separation time) beam. The theoretical estimations of CSR power yield from an edge of bending magnet as well as new injection tuning method are presented. A very high sensitivity of CSR power yield to the longitudinal electron distribution in a bunch is discussed.     

Piezoresistive Behavior Study on Finger‐Sensing Silicone Rubber/Graphite Nanosheet Nanocomposites

A novel finger‐sensing nanocomposite with remarkable and reversible piezoresistivity is successfully fabricated by dispersing homogeneously conductive graphite nanosheets (GNs) in a silicone rubber (SR) matrix. Because of the high aspect ratio of the graphite nanosheets, the nanocomposite displays a very low percolation threshold. The SR/GN nanocomposite with a volume fraction of conductive nanosheets closest to that for the percolation threshold presents a sharp positive‐pressure coefficient effect of the resistivity under very low pressure, namely, in the finger‐pressure range (0.3–0.7 MPa), whereby the abrupt transition could be attributed to compressive‐stress‐induced deformation of the conducting network. The super‐sensitive piezoresistive behavior of the nanocomposite is accounted for by an extension of the tunneling conduction theory which provides a good approximation to the piezoresistive effect.     

A threshold temperature effect for a carbon particle heated in plasma

Numerical simulations of the heating of a carbon dust particle (pellet) in hydrogen plasma showed that the character of heating depends in a threshold manner on the initial temperature of the pellet. The heating proceeds at a high rate if the initial temperature is above a certain threshold (“hot” regime), and at a much lower rate for an initial temperature below this threshold (“cold” regime). An important factor in this process is thermionic emission, which leads to positive charging of a pellet in hydrogen plasma due to electron emission from the surface in the hot regime. In the cold regime, the pellet acquires a negative charge that retards the electron flux from plasma to the particle. A method for the experimental observation of this effect is proposed.     

The Influence of Ir and Pt Addition on the Synthesis of Fullerenes at Atmospheric Pressure

The addition of metallic Ir and Pt to a fullerene-forming, atmospheric-pressure plasma reactor was found to influence the generation of carbonaceous products. It was observed that the added metals were efficiently dispersed into the plasma and that their presence increased the yield of fullerenes. The addition of Ir led to a noticeable shift in the fullerene distribution towards C₆₀, whereas the addition of Pt increased the proportion of C₆₀ oxides and decreased the proportion of higher fullerenes. Addition of Ir also caused a reduction of the soot particle size and the formation of a considerable quantity of carbon nanotubes.     

Results of benchmark calculations based on OLHF-1 test

The subject of this paper is to compare the results of the different calculations performed by the benchmark participants in the framework of the OECD Lower Head Failure (OLHF) program. The benchmark consists in the finite element (FE) calculation or in analytical calculations of the mechanical behavior of the OLHF-1 experiment. Seven participants from six countries and seven companies or organizations (AVN, VTT, GRS, UJV, SNL, IPSN and CEA) have performed the benchmark.The OLHF experiment program extends the NRC-sponsored SNL LHF program (NUREG/CR-5582) completed in 1998: these experiments where intended to simulate the thermal/mechanical loads to a 1/4.85-scale model of a reactor pressure vessel. The pressure vessel material (SA533B1 steel) used in these experiments is prototypic of reactor PWR vessel material and has been well characterized by material property testing as part of this program. The OLHF tests advance the results of the previous testing program by examining the effects of large temperature differences across the vessel wall. Large temperature differences in excess of 150–400 K are more prototypic of accident conditions.Most of the participants performed 2-D axisymmetric analyses and doesn’t study the crack opening. The global mechanical behaviour of OLHF-1 experiment is well represented but prediction of the maximum vertical displacement is not in good agreement with the experimental value. Failure time and location are in quite good agreement with experimental results but large discrepancies are observed on the mode of failure: creep or plasticity. To improve predictions, more investigation and work is needed on the choice of the failure criteria and failure mode.     

Parallel path consistency

Filtering algorithms are well accepted as a means of speeding up the solution of the consistent labeling problem (CLP). Despite the fact that path consistency does a better job of filtering than arc consistency, AC is still the preferred technique because it has a much lower time complexity. We are implementing parallel path consistency algorithms on multiprocessors and comparing their performance to the best sequential and parallel arc consistency algorithms.^(1,2) (See also work by Kerethoet al. ⁽³⁾ and Kasif⁽⁴⁾) Preliminary work has shown linear performance increases for parallelized path consistency and also shown that in many cases performance is significantly better than the theoretical worst case. These two results lead us to believe that parallel path consistency may be a superior filtering technique. Finally, we have implemented path consistency as an outer product computation and have obtained good results (e.g., linear speedup on a 64K-node Connection Machine 2).     

A VLSI architecture for a half-edge-based corner detector

Corner detection is a low-level feature detection operator that is of great use in image processing applications, for example, optical flow and structure from motion by image correspondence. The detection of corners is a computationally intensive operation. Past implementations of corner detection techniques have been restricted to software. In this paper we propose an efficient very large-scale integration (VLSI) architecture for detection of corners in images. The corner detection technique is based on the half-edge concept and the first directional derivative of Gaussian. Apart from the location of the corner points, the algorithm also computes the corner orientation and the corner angle and outputs the edge map of the image. The symmetrical properties of the masks are utilized to reduce the number of convolutions effectively, from eight to two. Therefore, the number of multiplications required per pixel is reduced from 1800 to 392. Thus, the proposed architecture yields a speed-up factor of 4.6 over conventional convolution architectures. The architecture uses the principles of pipelining and parallelism and can be implemented in VLSI.