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61.
Low- and high-density polyethylene (PE) films were grafted with acrylonitrile (AN) by electron beam prior to irradiation. The distribution of graft chains over the cross section of the sample film was analyzed in terms of the distribution of nitrogen atoms contained in the AN by means of an electron probe microanalyzer (EPMA), and graft sites were studied in relation to the effect of grafting temperature on the percent graft and the oxygen permeability of the sample films. It was found that diffusion of AN into the film was the rate-limiting step in the grafting process, thus restricting the grafting to the surface of the film in the initial grafting stages. However, the grafting shifted to the center of film as the graft process proceeded, until a uniform distribution of graft chains was observed across the entire film thickness. High-density polyethylene (HDPE) was found to display a higher percent graft than did low-density polyethylene (LDPE), and percent graft tended to increase with increasing grafting temperature. On the other hand, film oxygen permeability decreased with increasing percent graft, but this decreasing trend decreased with increasing percent graft. These findings suggest that the grafting is initiated by radicals trapped in the amorphous phase near the crystalline regions and at the surface of crystallites and that graft chains grow toward the amorphous regions. As for the radicals contributing to graft polymerization, it appears that AN permeates deeper near the crystalline surface and that graft chains grow from these sites. 相似文献
62.
Adaptive interpolation scheme for NURBS curves with the integration of machining dynamics 总被引:13,自引:4,他引:13
Xianbing Liu Fahad Ahmad Kazuo Yamazaki Masahiko Mori 《International Journal of Machine Tools and Manufacture》2005,45(4-5):433-444
This paper develops a comprehensive interpolation scheme for non-uniform rational B-spline (NURBS) curves, which does not only simultaneously meet the requirements of both constant feedrate and chord accuracy, but also real-time integrates machining dynamics in the interpolation stage. Although the existing work in this regard has realized the importance to simultaneously consider chord error and machining dynamics, none has really incorporated these in one complete interpolation scheme. In this paper, machining dynamics is considered for three aspects: sharp corners or feedrate sensitive corners on the curves, components with high frequencies or frequencies matching machine natural ones and high jerks. A look-ahead module was developed for detecting and adaptively adjusting the feedrate at the sharp corners. By Fast Fourier Transform (FFT) analysis with a moving window in the interpolation stage identified were some special frequency components such as those containing high frequencies or with frequencies matching machine natural ones. Then, the notch filtering or time spacing method was used to eliminate these components. To more completely reduce feedrate and acceleration fluctuations, the jerk-limited algorithm was also developed. Finally, the interpolated feedrate was further smoothened with B-spline fitting method and the NURBS curves were re-interpolated with the smoothened feedrate. During the interpolation, the chord error was repeatedly checked and confined in the prescribed tolerance. Two NURBS curves were used as examples to test the feasibility of the developed interpolation scheme. 相似文献
63.
A new history of internal pressure in the hydroforming processes of tubes is developed to attain high formability. The effect of improvement of formability by the oscillation of internal pressure in a pulsating hydroforming process of tubes is examined using both finite element simulation and experiment. The deformation behaviour during the hydroforming is greatly affected by the oscillation of internal pressure. For a monotonic history of small internal pressure, the wrinkling was caused by insufficient bulging, whereas the necking and bursting occurred for a monotonic history of large internal pressure. The occurrence of these defects can be avoided by oscillating the internal pressure in the pulsating hydroforming. The improvement of formability in the pulsating hydroforming is due to both low pressure and oscillation of pressure. The effects of the amplitude and cycle number of pressure in the pulsating hydroforming on the deformation behaviour are investigated. It is found the oscillation of internal pressure is effective in preventing the occurrence of defects. 相似文献
64.
A DC (data center) demands air-conditioning power as large as the 1/3-1/2 of total electricity consumption. Thus, energy saving of cooling power of DC yields considerable effect on both economic and environmental views. PV (Photovoltaic) and absorption refrigerator with CGS (cogeneration systems) or gas boiler are possible power saving options. The waste warm air from DC would be utilized for greenhouse heating when DC and greenhouse locate near in the suburbs. In this study, the authors develop an energy network model to assess the potential contribution of DC as a major electric power and chilled air consumer as well as the warm air supplier in a district to the energy efficiency improvement. The evaporation heat of LNG (liquefied natural gas) utilization is also considered as well as PV, CGS. This model is applied to the cases of the urban area in Tokyo which involves athletic center, shops and hospital and the suburbs including greenhouse and then compared. 相似文献
65.
Ryoichi Kawahara Tetsuya Takine Tatsuya Mori Noriaki Kamiyama Keisuke Ishibashi 《Computer Networks》2013,57(6):1560-1576
We consider the mean–variance relationship of the number of flows in traffic aggregation, where flows are divided into several groups randomly, based on a predefined flow aggregation index, such as source IP address. We first derive a quadratic relationship between the mean and the variance of the number of flows belonging to a randomly chosen traffic aggregation group. Note here that the result is applicable to sampled flows obtained through packet sampling. We then show that our analytically derived mean–variance relationship fits well those in actual packet trace data sets. Next, we present two applications of the mean–variance relationship to traffic management. One is an application to detecting network anomalies through monitoring a time series of traffic. Using the mean–variance relationship, we determine the traffic aggregation level in traffic monitoring so that it meets two predefined requirements on false positive and false negative ratios simultaneously. The other is an application to load balancing among network equipments that require per-flow management. We utilize the mean–variance relationship for estimating the processing capability required in each network equipment. 相似文献
66.
In monitoring flows at routers for flow analysis or deep packet inspection, the monitor calculates hash values from the flow ID of each packet arriving at the input port of the router. Therefore, the monitors must update the flow table at the transmission line rate, so high-speed and high-cost memory, such as SRAM, is used for the flow table. This requires the monitors to limit the monitoring target to just some of the flows. However, if the monitors randomly select the monitoring targets, multiple routers on the route will sometimes monitor the same flow, or no monitors will monitor a flow. To maximize the number of monitored flows in the entire network, the monitors must select the monitoring targets while maintaining a balanced load among them. We propose an autonomous load-balancing method where monitors exchange information on monitor load only with adjacent monitors. Numerical evaluations using the actual traffic matrix of Internet2 show that the proposed method improves the total monitored flow count by about 50% compared with that of independent sampling. Moreover, we evaluate the load-balancing effect on 36 backbone networks of commercial ISPs. 相似文献
67.
Kenichi Mori Michiaki Sakamoto Jin Matsushima Daisuke Inoue Kenichirou Naka Ken Sumiyoshi 《Journal of the Society for Information Display》2009,17(6):513-518
Abstract— In order to improve the reflective contrast ratio of transflective IPS‐LCDs, a novel pixel design for a normally white reflective IPS has been proposed. In this design, the large‐inter‐electrode‐spacing layout using a novel driving method and a double‐layered electrode have effectively reduced the light leakage. By applying these two technologies, a transflective IPS‐LCD has been successfully demonstrated with a high contrast ratio (15:1) in the reflective mode and a wide‐viewing‐angle characteristic in the transmissive mode. 相似文献
68.
This paper aims to assess quantitatively the actual visual environment of uncontrolled urban downtown intersections in Japan in relation to frequently occurring crossing collisions and to discuss the safety countermeasures for them. In Field Study 1 dealing with direct visibility, our ultra-wide-angle photograph analysis revealed that most of the right/left-ward visible range at 11 intersections were insufficient to check safety, and the quality of direct visibility was closely associated with causing crossing collisions. The countermeasures to reduce a blind area were determined to be a top priority. In Field Study 2 dealing with indirect visibility, more than half of the 25 traffic convex mirrors had marked shortcomings for preventive safety, and ergonomics guidelines ensuring indirect visibility were proposed for installing traffic convex mirrors. Low-cost/low-technology-oriented countermeasures are highly recommended to obtain clear/sufficient images of crucial information satisfying drivers' requirements on traffic convex mirrors in accordance with those ergonomics guidelines was highly recommended. Crossing collisions could be prevented by improvement of poor direct and indirect visibility. 相似文献
69.
C. Bäuerle N. Mori G. Kurata Hiroshi Fukuyama 《Journal of Low Temperature Physics》1998,113(5-6):927-932
Scanning tunneling microscopy (STM) studies of two-dimensional (2D) cryocrystals
4
He, Kr, Xe) physisorbed on graphite surfaces are presented. Individual helium atoms, usually thought to be invisible with STM, were recently observed on graphite surfaces at a density corresponding to the
commensurate solid. Here we show that a local elastic deformation seems to be the principal mechanism responsible to render the atoms visible. Recent tight-binding calculations of the local density of states (LDOS) of graphite which predict the appearance of an energy gap support this picture. I-z curve measurements for the case of
4
He show a sharp drop (increase) of the tunneling current I at a certain tip-surface distance z during retraction (approach) of the tip. This drop (increase) may be associated with the tunneling of a single He adatom, opening new possibilities to study the quantum tunneling of atoms via STM. 相似文献
70.
We analyze the linearity and modulation depth of ac magnetic-field sensors or current sensors, using a ferrimagnetic or ferromagnetic film as the Faraday rotator and employing the detection of only the zeroth-order optical diffraction component from the rotator. It is theoretically shown that for this class of sensor the condition of a constant modulation depth and that of a constant ratio error give an identical series of curves for the relationship between Faraday rotation angle Θ and polarizer/analyzer relative angle Φ. We give some numerical examples to demonstrate the usefulness of the result with reference to a rare-earth iron garnet film as the rotator. 相似文献