Successful fabrication of bicrystal Si substrates for YBa2Cu3O7 − y Josephson junctions

Bicrystal Si(BiSi) substrates for grain boundary (GB) Josephson junctions (GBJJs) have been fabricated by a direct bonding technique using a hot press method. The fracture strength and structure of the bonding interfaces were investigated to obtain substrates suitable for the junctions. It was found that an increase in the pressure of the hot press improves the reproducibility of the GBJJs. YBa₂Cu₃O_{7 − y} GBJJs were successfully fabricated on Bi-Si substrates with a misorientation angle of 15 ° bonded under a pressure of 90 kgf cm⁻² at 1200 °C in a vacuum of ≈10⁻³ Pa. These junctions showed typical I-V curves described by the RSJ model. The Shapiro steps induced by millimetre wave irradiation of 101 GHz were clearly observed in the I-V curves up to 3 mV, corresponding to at least 1.5 THz (, where e is the unit charge, V the voltage and h Planck's constant).     

Characterization of the Advanced Satellite for Cosmology and Astrophysics x-ray telescope: preflight calibration and ray tracing

The x-ray properties of multinested thin-foil mirror x-ray telescopes (XRT's) on board ASCA, the Advanced Satellite for Cosmology and Astrophysics, were fully evaluated with an x-ray pencil beam.Scanning over the telescope aperture of 35 cm in diameter with an x-ray pencil beam, we found the effective area of a set of XRT's to be 325, 200, and 113 cm(2) at energies of 1.5, 4.5, and 8.0 keV, respectively. We derive the point-spread functions (PSF's) of the XRT's by measuring the image profile at the focal plane with an x-ray CCD. The PSF is found to exhibit a sharp core concentrated within 30 arcsec and a broad wing extended to 3 arcmin in half-power diameter. We also evaluate the contribution of stray light, which is caused by the single reflection of x rays by primary or secondary mirrors and by the backside reflection of the mirrors. To obtain the characteristics of the XRT in the energy region of 0.5-10.0 keV, incorporated with the measurements at discrete energies, we develop a ray-tracing method with the telescope design parameter, the PSF, and optical constants. In particular, we obtain the optical constants around the gold-atom M shell (Au-M) absorption-edge energies by measuring the reflectivity of our mirror sample, with monochromatized x-rays in the energy range of 2.0-3.5 keV from synchrotron radiation. Taking into account the PSF's and optical constants, we find that our ray-tracing program can reproduce all these XRT performances.     

The cluster of arachnoid diverticula in the occipital bone: report of two cases with literature review

The authors report two cases of multicentric osteolytic lesions in the occipital bone without any history of head trauma. The excisional biopsy of the first case revealed that the lesion was multicentric but a continuous cavity with the subarachnoid space through various sizes of dural defect, and the cavities were covered by arachnoid lining. Together with the previously reported similar 5 cases, the characteristic common feature is multicentric osteolytic lesions in the occipital bone at advanced age without marginal sclerosis. "The cluster of arachnoid diverticula in the occipital bone (CADOB)" is probably the most appropriate term for these non-traumatic lesions with the following characteristics: elderly patients, occipital bone, midline, multiple, intact outer table, nonsclerotic margin and without history of trauma. Operation may not be indicated because of its non-progressive and benign nature.     

Fabrication of X-rays mask with carbon membrane for diffraction gratings

We have produced diffraction gratings for obtaining high resolution X-ray phase imaging, such as X-ray Talbot interferometer. These diffraction gratings were required to have a fine, high accuracy, high aspect ratio structure. Therefore, we decided to use the X-rays lithography technique that used synchrotron radiation of the directivity for a manufacture process. The accuracy of the completed structure depends largely on the accuracy of the X-ray mask. In our group, a resin material is conventionally used for the membrane of large X-ray masks. However, X-ray masks comprising a resin membrane have the disadvantage that, after several cycles of X-ray exposure, they crease and sag due to X-ray-derived heat. As a substitute for the conventional resin membrane, we experimentally fabricated a new X-ray mask using a carbon wafer membrane. The newly fabricated X-ray mask was subjected to X-ray exposure experiment. We succeeded in making the structure body which was almost shape. And the experimental results verified that the new mask did not deteriorate even when used repeatedly, demonstrating that it was highly durable.     

Fabrication of high hardness Ni mold with electroless nickel–boron thin layer

The nickel electroforming method using a high-concentration nickel sulfamate bath is commonly used to fabricate micro metal molds in the LIGA process; however, this method does not produce micro metal molds of sufficient hardness. One means of improving the hardness of micro metal molds made using the nickel electroforming method is to include additives in the nickel plating solution. Another method is nickel alloy plating or a similar technique. In this research, we used a nickel–boron (Ni–B) electroless alloy plating method to obtain a hard nickel plated film having hardness of 832 Hv. It was also ascertained that Ni–B electroless alloy plated film retains its high hardness even during heat treatment in conditions of 250°C for 1 h. To deal with the high stresses developed in high-hardness plated films, we proposed double-layer nickel electroforming. This method is covered and used on conventional nickel electroforming layer by high hardness micro mold. High hardness micro metal mold using double-layer was fabricated by nickel electroforming and Ni–B electroless alloy plating method.     

Deformation characteristics of ultra-thin liquid film considering temperature and film thickness dependence of surface tension

Thermocapillary deformations of an ultra-thin liquid film caused by temperature distribution were three-dimensionally analyzed using the unsteady and linearized long wave equation considering the temperature and film thickness dependence of surface tension. The temperature and film thickness dependence equation for the surface tension of a liquid was firstly established. The temperature dependence of the surface tension was obtained experimentally using a surface tensiometer and the film thickness dependence was obtained theoretically from the corrected van der Waals pressure equation for a symmetric multilayer system. Time evolutions of depression and groove of the ultra-thin liquid film caused by local heating were obtained quantitatively.     

A simple method for testing the electromigration resistance of solders

Recently, the size of solder bump interconnects have been significantly reduced with the advent of high-density packaging, and thus the evaluation of electromigration in solder bumps has become necessary. The present paper proposes a simple method to test the electromigration resistance of Pb-free solders. One of the key points of the present method is the fabrication of a simple solder sample that can produce sufficient current density to cause electromigration. Moreover, the actual local temperature of a small area subjected to electromigration in the sample was measured by a direct method. A right-angled diamond-shaped hole was introduced in a thin film of solder using a focused-ion-beam system. A direct current was supplied to the film far from the hole, perpendicular to the diagonal of the hole. In this way, the current density was concentrated near to the corner of the hole, and the value of this was obtained through a theoretical analysis. It was noted that the steady temperature in the film along a line extending from the diagonal, remained constant, although the current density decreased gradually far from the corner. Therefore, the temperature at a position near the corner, where electromigration takes place, can easily be found by measuring the temperature far from the corner. The temperature was measured directly under current flow conditions by utilizing the chemical reagents with known melting points. Finally, by measuring the ratio of hillock volume to the time for the current supply as a measure of the atomic flux divergence due to electromigration, the corresponding resistances of some Pb-free solders to electromigration were evaluated.     

Tabu search for scheduling on identical parallel machines to minimize mean tardiness

This paper presents a tabu search approach for scheduling jobs on identical parallel machines with the objective of minimizing the mean tardiness. Initially, we consider a basic tabu search that uses short term memory only. Local search is performed on a neighborhood defined by two types of moves. Insert moves consist of transferring each job from one machine to another and swap moves are those obtained by exchanging each pair of jobs between two machines. Next, we analyze the incorporation of two diversification strategies with the aim of exploring unvisited regions of the solution space. The first strategy uses long term memory to store the frequency of the moves executed throughout the search and the second makes use of influential moves. Computational tests are performed on problems with up to 10 machines and 150 jobs. The heuristic performance is evaluated through a lower bound given by Lagrangean relaxation. A comparison is also made with respect to the best constructive heuristic reported in the literature.