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61.
The finite element method for the dynamic problem of cracked linear viscoelastic solids is developed using the singular element where the displacement function is taken from the analytical solution near the crack-tip. The time variation of the dynamic stress intensity factors is determined for a center crack and an oblique crack in standard linear viscoelastic rectangular plates subjected to dynamic loading.
Résumé La méthode par éléments finis permettant d'aborder le problème dynamique des solides linéaires viscoélastiques fissurés est développée en recourant à un élément singulier pour lequel la fonction de déplacement est prise dans une solution analytique au voisinage del'extrémité de la fissure. La variation dans le temps des facteurs d'intensité de contrainte dynamique est déterminée pour une fissure centrale et pour une fissure oblique dans des plaques rectangulaires standard en matériau linéaire viscoélastique soumises à une sollicitation dynamique.相似文献
62.
Efficient construction of cDNA microarrays utilizing normalized cDNA libraries of Arabidopsis thaliana 总被引:1,自引:0,他引:1
Ando K Yamakawa S Miyashita K Yoshida K Yokota A Shinmyo A Kohchi T 《Journal of Bioscience and Bioengineering》2004,97(1):85-88
We have demonstrated the utility of normalization for efficient cDNA microarray preparation using Arabidopsis as a model. Nonredundant cDNAs including 5722 species were efficiently collected from random 7914 expressed sequence tags (ESTs) in four normalized cDNA libraries. The prepared microarrays were successfully used to monitor gene expression. These methodologies should be applicable to the study of other species in plant biotechnology. 相似文献
63.
Takemitsu Kunio Tatsuya Yamazaki Eiji Ohta Makoto Sakata 《Solid-state electronics》1983,26(2):155-160
The transient capacitance technique has been used to study the chromium-related levels in the silicon band gap. Chromium was diffused at temperature of 1100 and 1150°C for 0.5 and 3 hr. Five different levels at Ec?0.11 eV, Ec?0.21 eV, Ec?0.28 eV, Ec?0.36 eV and Ec?0.45 eV were obtained from the Arrheniu plots of the electron thermal-emission rates. The number of levels in the upper half of the band gap decreased from five to two with an increase of Cr-diffusion period. Two levels were located at Ec?0.20 eV (donor) and Ec?0.43 eV (acceptor). A donor level was also observed at Ev + 0.25 eV. The donor level was not affected by the diffusion condition. The majority carrier capture cross sections of the three dominant levels have been measured by the transient capacitance technique modified by the pulse transformer. The values were σn = 4.1 × 10?15 cm2 for the upper donor at Ec?0.20 eV, σn = 2.0 × 10?16 cm2 for the acceptor at Ec ?0.43 eV and σp = 9.1 × 10?18 cm2 for the lower donor at Ev + 0.25 eV, and were independent of temperature. The three dominant levels are due to distinct chromium centers. 相似文献
64.
The photovoltaic and dark electrical properties of hydrogenated amorphous silicon diodes were changed by forward bias carrier injection for several hours. These changes were similar to photoinduced (PI) changes previously reported, and this result supports previous explanations for PI changes. The differences between these two types of change are also discussed. 相似文献
65.
Mitsuhiro Horade Sommawan Khumpuang Kazuya Fujioka Susumu Sugiyama 《Microsystem Technologies》2007,13(3-4):215-219
We have investigated and report in this paper the factors influencing the deformation caused by the dependence between the
absorbed X-ray energy on the resist and the shape of the absorber on the X-ray mask. Based on the measurement of errors that
occurred during the transferring process between the 2-D shape of mask pattern and the resulting wall of the fabricated 3-D
structure, we have developed newly useful graphical data on the absorbed X-ray energy, dosage, and shape of a microstructure.
As a result, it is being reported as a method for compensation for the deformed shape after the fabrication of a quadruplets-microneedle.
We have considered a number of factors affecting the deformation and finally realized that the effect of a dose–depth nonlinear
curve is the most possible cause. Without the compensation of the mask design, we could observe the deformed shapes of the
sloped sidewall on the exposed structures. Polymethylmethacrylate microneedle structures fabricated by X-ray lithography with
an additional plane-pattern to cross-section transfers technique are directly influenced by the absorber on the X-ray mask
pattern. The sidewall of the microneedle was improved by changing the mask pattern from a double right-triangular pattern
to a double semi-circular pattern, modeled by comparing the results from a mask-pattern and the actual structure. 相似文献
66.
Isaku Nagai Genki Yamauchi Keiji Nagatani Keigo Watanabe Kazuya Yoshida 《Advanced Robotics》2013,27(15):1147-1160
We propose a novel method for positioning a mobile robot in an outdoor environment using lasers and optical sensors. Position estimation via a noncontact optical method is useful because the information from the wheel odometer and the global positioning system in a mobile robot is unreliable in some situations. Contact optical sensors such as computer mouse are designed to be in contact with a surface and do not function well in strong ambient light conditions. To mitigate the challenges of an outdoor environment, we developed an optical device with a bandpass filter and a pipe to restrict solar light and to detect translation. The use of two devices enables sensing of the mobile robot’s position, including posture. Furthermore, employing a collimated laser beam allows measurements against a surface to be invariable with the distance to the surface. In this paper, we describe motion estimation, device configurations, and several tests for performance evaluation. We also present the experimental positioning results from a vehicle equipped with our optical device on an outdoor path. Finally, we discuss an improvement in postural accuracy by combining an optical device with precise gyroscopes. 相似文献
67.
68.
This paper describes an approximate microstructural optimization using the ns-kriging (noise-resistant smoothed kriging) method
for minimizing the maximum stochastic variation of homogenized elastic properties of a composite material caused by microscopic
uncertainties of component materials. Since evaluation of a stochastic characteristic of a homogenized material property such
as expectation or variance will involve a high computational cost and its results include inaccuracy in using the Monte Carlo
simulation, an approximation-based optimization technique is useful for solving the optimization problem considering the multiscale
stochastic problem. Especially, the ns-kriging will work well in case of using inaccurate data for an unknown objective function.
In order to investigate applicability and effectiveness of the proposed ns-kriging based approach to the optimization problem,
it is applied to the cross-sectional shape optimization of fiber in a unidirectional FRP. From the numerical results, validity
and effectiveness of the proposed approach are confirmed. 相似文献
69.
Friction and frictional tracks on 2 µm thick SiO2 films evaporated on polymethylmethacrylate (PMMA) substrate were investigated. Diamond spherical sliders of radius 30 and 100 µm, respectively, were slid on these coatings under a load of 50 to 200g at a sliding speed of 15 cm min–1. The static and dynamic friction coefficients for SiO2 films were found to be 0.1 and 0.06, respectively, depending on the load and radius of the slider. For lower load and small slider radius the tracks on SiO2 film were groove-like, and whisker-like cracks regularly grew from the edges of the tracks. For higher loads and larger slider radius, semicircular cracks in the film were regularly found behind the slider, but in thicker film (6 µm thick), circular cracks occurred. The origin of these cracks is discussed in terms of a tension zone produced around the contact area between the slider and the substrate under frictional force. 相似文献
70.
Yugo Tadano Shota Urushibata Kazuya Ogura Akira Shigaki Masakatsu Nomura 《Electrical Engineering in Japan》2008,165(2):77-88
Recently, high‐voltage motor direct drive systems have been put to practical use, and various multilevel PWM strategies have also been proposed. This paper describes a multilevel PWM strategy [our group calls it the Carrier Phase Selection Method (CPS)] that has the lowest line voltage harmonic distortion in order to prevent the degradation of high‐voltage motor winding insulations. This method takes the adverse effect of dead time into consideration, and it controls the shift direction of a carrier phase. Therefore, a favorable output waveform without instantaneous voltage surges is achieved even if the line voltage level changes. Moreover, the switching transitions across all switching devices are well‐balanced, so the utilization of inverter unit cells is equalized. This is an important factor when designing the entire system. Based on simulation and experimental results, it is shown that this CPS method is particularly effective in high‐voltage motor direct drive systems. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(2): 77–88, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20474 相似文献