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41.
Shunji Umetani Mutsunori Yagiura Shinji Imahori Takashi Imamichi Koji Nonobe Toshihide Ibaraki 《International Transactions in Operational Research》2009,16(6):661-683
The irregular strip-packing problem (ISP) requires a given set of non-convex polygons to be placed without overlap within a rectangular container having a fixed width and a variable length, which is to be minimized. As a core sub-problem to solve ISP, we consider an overlap minimization problem (OMP) whose objective is to place all polygons into a container with given width and length so that the total amount of overlap between polygons is made as small as possible. We propose to use directional penetration depths to measure the amount of overlap between a pair of polygons, and present an efficient algorithm to find a position with the minimum overlap for each polygon when it is translated in a specified direction. Based on this, we develop a local search algorithm for OMP that translates a polygon in horizontal and vertical directions alternately. Then we incorporate it in our algorithm for OMP, which is a variant of the guided local search algorithm. Computational results show that our algorithm improves the best-known values of some well-known benchmark instances. 相似文献
42.
There are two major ways of calculating ray and parametric surface intersections in rendering. The first is through the use of tessellated triangles, and the second is to use parametric surfaces together with numerical methods such as Newton's method. Both methods are computationally expensive and complicated to implement. In this paper, we focus on Phong Tessellation and introduce a simple direct ray tracing method for Phong Tessellation. Our method enables rendering smooth surfaces in a computationally inexpensive yet robust way. 相似文献
43.
Masaki T Ishikawa T Paradis PF Yoda S Okada JT Watanabe Y Nanao S Ishikura A Higuchi K Mizuno A Watanabe M Kohara S 《The Review of scientific instruments》2007,78(2):026102
A compact electrostatic levitator was developed for the structural analysis of high-temperature liquids by x-ray diffraction methods. The size of the levitator was 200 mm in diameter and 200 mm in height and can be set up on a two axis diffractometer with a laboratory x-ray source, which is very convenient in performing structural measurements of high-temperature liquids. In particular, since the laboratory x-ray source allows a great amount of user time, preliminary or challenging experiments can be performed with trial and error, which prepares and complements synchrotron x-ray experiments. The present small apparatus also provides the advantage of portability and facility of setting. To demonstrate the capability of this electrostatic levitator, the static structure factors of alumina and silicon samples in their liquid phases were successfully measured. 相似文献
44.
Haijme Yamamoto Shinji Okamoto Satoe Mitsumine 《Journal of the Society for Information Display》2000,8(3):241-245
Abstract— A red‐emitting phosphor, SrTiO3:Pr3+, for low‐voltage‐type FEDs and VFDs was developed by Futaba Corporation in 1996. The addition of Al or Ga is essential in the preparation of this phosphor because it improves the luminescence efficiency dramatically. For this impurity effect, Futaba Corporation proposed a charge‐compensation mechanism, which was supported by a recent observation of emission lines due to Al3+‐Pr3+ pairs. In addition, it was found that Al also works as a scavenger of planar defects, presumably SrO thin layers interleaved in the SrTiO3 lattice, by forming strontium aluminates. The latter mechanism suggests the possibility that a similar impurity effect can be found in materials with crystal structures, including alkaline‐earth oxide layers (Ruddlesden‐Popper phases). 相似文献
45.
The flux flow viscosity coefficient b
–1 (in units of 0
H
c
n
–1
c
–2) of vacuum-deposited indium thin films with low values (1.0–2.8) is measured at temperatures between 0.5T
cand 0.98T
cin the weak magnetic field region. At each temperature, b
–1 decreases as increases for larger than 1.7. The decrease of b
–1 with increasing is more rapid as the temperature increases. From an analysis of the present results as well as the existing data on intermediate- and high- superconducting alloys, the relation between b
–1 and is established over a wide range of . The dependence of b
–1 on is qualitatively explained by taking into account the contribution of the normal electron dissipation to the viscosity coefficient in the Bardeen-Stephen model.Financial support provided by the Fonds National Suisse de la Recherche Scientifique.On leave from the Department of Electronic Engineering, Faculty of Engineering, Kyushu Industrial University, Fukuoka, Japan. 相似文献
46.
S. Takayama 《Journal of Materials Science》1981,16(9):2411-2418
Fe-Ni-base metallic glass ribbons were rolled directly and indirectly by changing the rolling direction with respect to the ribbon axis. In the case of direct rolling, no visible deformation bands appeared on the rolling surfaces (except at the edges) but wavy deformation markings appeared on the side surfaces. In the case of indirect rolling, however, the deformation markings developed on the entire surface; they were wavy and straight in appearance on the rolling and side surfaces, respectively. Tensile tests, performed on the samples rolled directly and indirectly show little and much change in fracture stresses, respectively. As a result of the intersecting of plastic flow systems, fracture shear stresses increase by 7% compared with those of as-quenched samples. Fracture shear stresses on a predeformed area were, however, found to be 3% lower than those for an undeformed area. These results are discussed in terms of both work-hardening and work-softening in metallic glasses. 相似文献
47.
Akira Nakayama Shinji Nambu Masahiro Inagaki Masahiko Miyauchi Nobuyuki Itoh 《Journal of the American Ceramic Society》1996,79(6):1453-1456
Complex permittivity of polycrystalline AlN was measured over the frequency range 100 MHz to 13 GHz using reflection coefficient and cavity resonator methods. Dielectric relaxation peaks of loss tangent were observed in the frequency range 200 MHz to 3 GHz. The maximum value of loss tangent was ∼200 × 10−4 . Relative permittivities decreased by ∼4% with increased frequency at the region of relaxation peaks. It was shown that these dispersion frequencies were inversely proportional to the grain sizes of AlN and independent of purities and processes. Model calculations for elastic vibration of a single-crystal grain of AlN were performed to investigate the origin of the dielectric dispersion due to piezoelectric effect. The calculated results of elastic sphere and 14-faced-polyhedron models showed a good quantitative agreement with the observed dispersion frequencies, which suggested that the dispersion was due to a piezoelectric vibration of a single grain of AlN ceramics at microwave frequencies. 相似文献
48.
Considerations of metropolitan commuting have often related to urban space as a continuum, and to commuting itself as a process. This approach has led to escalating complexity in the measurement, modeling and analysis of commuting, often with no commensurate results. The present study extends an alternative approach that considers commuter space of a metropolis as a discrete set of small areas. Each small area throughout the metropolis is a nighttime location of some households and, as a possible discrete destination choice of individuals within households, each subarea is also a daytime location of some persons. Each subarea, therefore, may be thought of as attaining two values, corresponding to its daytime (e.g., noontime) and nighttime (e.g., midnight) populations. The diurnal demographic shift of subareas, as a set of binary events, or toggles, between daytime and nighttime populations, is associated with commuter access throughout the metropolis. Diurnal shift offers structural simplicity aimed at estimating small-area daytime populations across a metropolitan region that might suitably precede and complement conventional continuum considerations of commuting. Using data for the Tokyo Metropolitan Region, we identify average household size as the nighttime indicator of small-areas, and daytime population density as their daytime indicator. The potential for the estimation of daytime populations across metropolitan regions where daytime population data are unavailable, is underscored by the clear tendency towards inverse relation of these two indicators of diurnal shift. 相似文献
49.
K. Ohtani D. Numata T. Kikuchi M. Sun K. Takayama K. Togami 《International Journal of Impact Engineering》2006,33(1-12):555-565
This paper reports a result of hypervelocity impact experiments on cryogenically cooled aluminum alloys and a composite material. Experiments are carried out on a target palate at 122 K. Aluminum spheres at 1.95 km/s in 50 kPa air were impinged against the target plate at cryogenic temperature and the result was compared with room temperature target plates. Hypervelocity impact (HVI) processes were visualized with shadowgraph arrangement and recorded with high-speed video camera and to ensure the temperature dependence we compared HVI tests with metal target plates with AUTODYN 2D and SPH numerical simulations. We found that cryogenic impacts created slight differences of impact damage from room temperature ones, i.e., the shape and averaged diameters of HVI crater holes were less at cryogenic impacts. 相似文献
50.
NO reduction experiment was performed by injecting ammonia radicals, which were externally generated by flowing the NH3 gas diluted with Ar gas through a dielectric barrier discharge with a one-cycle sinusoidal-wave power source. The discharge was intermittently formed between coaxial cylindrical electrodes with a space of 1.5 mm at an applied peak-to-peak voltage of 3-25 kV. The generated radicals were injected into simulation gas (NO/O2/N2). The simulation gas contained 0-5.6% O2, and the effect of O2 on NOx removal was discussed. The minimum reaction temperature for NO reduction was low when simulation gas contained O2. High O2 concentration (O2=5.6%) in simulation gas, high repetition rate to NH3, and high applied power to NH3 decreased NO removal efficiency. 相似文献