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排序方式: 共有711条查询结果,搜索用时 15 毫秒
51.
采用正交试验法完成了HSS/Co-M35含钴高速钢丝锥加工Ti-6Al-4V钛合金的攻丝试验。利用极差分析法研究了丝锥全生命周期参数即丝锥前角(刀具设计参数)、刃口钝化半径(刀具制造参数)、主轴转速(刀具使用参数)对攻丝性能的影响。利用综合评分法将扭矩max、轴向切削力max和切削温度max等3项攻丝性能指标转化为单一综合切削性能指标y*i,分析结果表明:攻钛合金时丝锥全生命周期参数取刃口钝化半径0.01 mm,丝锥前角10°,主轴转速150 r/min时最优。通过试验与数值模拟获得的扭矩值及趋势、切屑形态及切削刃对比图,验证了在Advant Edge FEM软件中建立的丝锥攻Ti-6Al-4V钛合金模型的可靠性。 相似文献
52.
Novel hybrid films of fluorinated hyperbranched polyimide (HBPI) and zinc oxide (ZnO) were prepared via the in situ sol-gel polymerization technique, in which mono-ethanolamine (MEA) was used as the coupling agent between the termini of HBPI and the precursor of ZnO. The hybrid films were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) absorption, ultraviolet-visible (UV-vis) absorption, and fluorescent excitation/emission spectroscopy. The films, which originated from the colourless fluorinated HBPI structure and homogeneously dispersed ZnO nanoparticles, exhibited good optical transparency. Furthermore, two kinds of model compounds with and without ZnO and a HBPI film blended with ZnO microparticles were prepared to clarify the fluorescence mechanism in the pristine HBPI and in situ hybrid films. Efficient energy transfer from the ZnO nanoparticles to the aromatic HBPI main chains was observed in the in situ hybrid films, whereas energy transfer occurred only from the locally excited (LE) states to the charge-transfer (CT) state in the HBPI film. These facts demonstrate that the peripheral termini of HBPI are covalently bonded to ZnO particles via the MEA function, which operates as an effective pathway for energy transfer to give intense fluorescent emission. 相似文献
53.
Young, gregariously living larvae of the willow leaf beetles Plagiodera versicolora are known to exhibit characteristic aggregation-dispersion-reaggregation behavior and local fidelity to a host tree. In this
study, we investigated whether plant volatiles induced by feeding P. versicolora larvae were involved in the reaggregation behavior. Under laboratory conditions, we conducted dual-choice bioassays and found
that the first and second instars discriminated between volatiles from leaves infested by larvae and volatiles from uninfested
leaves. The discriminative behavior was dependent on both the time leaves were infested and the age of discriminating larvae.
First and second instars preferred odor from 1-d-infested leaves to odor from uninfested leaves, whereas third instars (solitary
stage) did not discriminate between these volatile blends. Odor from 2-d-infested leaves was preferred to odor from 1-d-infested
leaves by first instars, whereas odor from leaves infested for 3 d was not attractive to these very young larvae. Neither
was odor of leaves infested for 1 d and then left uninfested for 1 or 2 d attractive to young larvae. The data suggest that
the first and second instars use volatiles from a leaf newly infested by conspecific larvae as one of the reaggregation cues.
We detected several herbivore-induced compounds in the headspace of the attractive leaves. Among those, a mixture of synthetic
(E)-β-ocimene, (Z)-β-ocimene, allo-ocimene, and linalool was found to attract the larvae. 相似文献
54.
Soichi Kugimiya Takeshi Shimoda Jun Tabata Junji Takabayashi 《Journal of chemical ecology》2010,36(6):620-628
Females of the solitary endoparasitoid Cotesia vestalis respond to a blend of volatile organic compounds (VOCs) released from plants infested with larvae of their host, the diamondback
moth (Plutella xylostella), which is an important pest insect of cruciferous plants. We investigated the flight response of female parasitoids to the
cruciferous plant Brassica rapa, using two-choice tests under laboratory conditions. The parasitoids were more attracted to plants that had been infested
for at least 6 hr by the host larvae compared to intact plants, but they did not distinguish between plants infested for only
3 hr and intact plants. Although parasitoids preferred plants 1 and 2 days after herbivory (formerly infested plants) over
intact plants they also preferred plants that had been infested for 24 hr over formerly infested plants. This suggests that
parasitoids can distinguish between the VOC profiles of currently and formerly infested plants. We screened for differences
in VOC emissions among the treatments and found that levels of benzyl cyanide and dimethyl trisulfide significantly decreased
after removal of the host larvae, whereas terpenoids and their related compounds continued to be released at high levels.
Benzyl cyanide and dimethyl trisulfide attracted parasitoids in a dose-dependent manner, whereas the other compounds were
not attractive. These results suggest that nitrile and sulfide compounds temporarily released from plants under attack by
host larvae are potentially more effective attractants for this parasitoid than other VOCs that are continuously released
by host-damaged plants. 相似文献
55.
Novel transdermal drug delivery system with polyhydroxyalkanoate and starburst polyamidoamine dendrimer 总被引:1,自引:0,他引:1
Wang Z Itoh Y Hosaka Y Kobayashi I Nakano Y Maeda I Umeda F Yamakawa J Kawase M Yag K 《Journal of Bioscience and Bioengineering》2003,95(5):541-543
In search of an efficient transdermal drug delivery system (TDDS), a polyhydroxyalkanoate (PHA)-based system with a polyamidoamine dendrimer was examined. Tamsulosin was used as the model drug. The dendrimer was found to act as the weak enhancer. By adding the dendrimer, the dendrimer-containing PHA matrix achieved the clinically required amount of tamsulosin permeating through the skin model. This is also the first report of the application of PHA and dendrimer to the TDDS. 相似文献
56.
Daisuke Hiramatsu Yoichi Uemura Shinji Uemoto Junji Okumoto Takehiko Imai Mikio Kakiuchi Ken Nagakura Masafumi Fujita Toru Otaka 《Electrical Engineering in Japan》2011,177(3):17-27
Two‐pole large generators are extensively used in power utilities. Growing demand for electric power in recent years has led to substantial increases in the capacity of generators. In line with this trend, our company has manufactured two‐pole turbine generators in the 900,000‐kVA to 1,200,000‐kVA classes. As the capacity of generators becomes larger, equivalent circuits are increasingly expected to improve their precision in estimating operation characteristics. The Park model has been widely used as an equivalent circuit model. The Park model with quadrature axis transient reactance $x_{q}^{\prime}$ is claimed to be useful for accurately estimating the load rejection characteristics of turbine generators. However, it is difficult to measure $x_{q}^{\prime}$, few studies based on measured data have appeared. As one of the few examples, we have conducted a measured data on a 500,000‐kVA‐class generator. Recently, the authors obtained test data on $x_{q}^{\prime}$ of a 900,000‐kVA‐class generator. In this study, based on these data, we studied the effect of $x_{q}^{\prime}$ using the finite element method and a transient analysis program (EMTP‐ATP). © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(3): 17–27, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21099 相似文献
57.
Nobuhisa Ochi Shigetaka Okano Masahito Mochizuki Junji Shimamura Nobuyuki Ishikawa 《Welding International》2013,27(3):174-183
In recent years, in order to reduce the costs of transportation and construction of pipelines, which are often constructed using multiple-electrode submerged arc welding (SAW), higher joint performance is required. Therefore, there has arisen the need to understand theoretically and control appropriately metallurgical and mechanical characteristics in heat-affected zone (HAZ), which has a significant influence on the strength and toughness of welded joints. Commonly, metallurgical phenomena in HAZ are evaluated based on the highest temperature and the cooling rate. Therefore, in order to control metallurgical and mechanical characteristics in HAZ by means of the welding conditions, evaluating the temperature distribution and the temperature history near the melted zone is essential. However, a detailed investigation of the temperature distribution for multiple-electrode SAW has not yet been carried out enough. In this study, in order to investigate the temperature distribution and histories during multiple-electrode SAW, the experimental results are compared with the theoretical results. In the theoretical analysis, the temperature rise equation in multiple heat sources welding is developed using the method of summation. Furthermore, on temperature distribution during welding, the effects of multiple heat sources, such as the number of heat sources and the distance between each electrodes, are considered quantitatively through the thermal conduction theoretical analysis. As the result, the distance between lead heat source and final heat source primally influences the area with the difference between a single heat source welding and multiple heat sources welding. Based on the results, it is expected to control temperature distribution near melted zone by more appropriate heat input characteristics, which is depended on heat source arrangement. 相似文献
58.
59.
Yong-Jin Pu Makoto Yoshizaki Takahiro Akiniwa Ken-ichi Nakayama Junji Kido 《Organic Electronics》2009,10(5):877-882
3,5-Dipyrenylpyridine (PY1) and 2,6-dipyrenylpyridine (PY2) were synthesized to achieve not only efficient electron injection from cathode but also high electron mobility. The both of compounds showed much higher electron mobilities than that of Alq3, and have a similar ionization potential and electron affinity. However, the barrier height of electron injection from cathode to PY1 in an organic light emitting device was much smaller than that to PY2, probably due to the steric hindrance to the central pyridine group. These results suggest that the chemical affinity of electron-transporting materials with cathode is more important than their own electron affinity to improve the electron injection. 相似文献
60.
The purpose of this study is to create a natural fiber-reinforced fully green composite with excellent toughness. By treating
ramie plied yarns in a high concentration alkali solution, the reinforcements were mercerized. Results of tensile tests showed
that unidirectional composites using mercerized ramie yarns exhibited two to three times larger fracture strain, without a
marked decrease in strength, than composites using untreated yarns. In addition, mercerization for the ramie yarns brings
a better interfacial strength to the composites. Laminated composites using mercerized ramie yarns also showed approximately
twice larger impact energy than composites using untreated yarns. Thus, mercerization for natural fibers is expected for application
to mechanical materials requiring a high toughness. 相似文献