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排序方式: 共有7248条查询结果,搜索用时 15 毫秒
991.
Katrin Ortstein Sebastian Hutsch Alexander Hinderhofer Jrn Vahland Martin Schwarze Sebastian Schellhammer Martin Hodas Thomas Geiger Hans Kleemann Holger F. Bettinger Frank Schreiber Frank Ortmann Karl Leo 《Advanced functional materials》2020,30(32)
In modern electronics, it is essential to adapt band structures by adjusting energy levels and band gaps. At first sight, this “band structure engineering” seems impossible in organic semiconductors, which usually exhibit localized electronic states instead of Bloch bands. However, the strong Coulomb interaction in organic semiconductors allows for a continuous shift of the ionization energy (IE) over a wide range by mixing molecules with halogenated derivatives that exhibit different quadrupole moments. Here, this effect of energy level engineering on blends of pentacene and two fluorinated derivatives, in which the position but not the number of fluorine atoms differ, is studied. Structural investigations confirm that pentacene forms intermixed phases in blends with the fluorinated species. The investigation of electronic properties and simulations reveals a much larger shift of the ionization energy (1.5 eV) than in previous studies, allowing to test this model in a range not investigated so far, and emphasizing the role of the position of the halogen atoms. The tuning effect is preserved in electronic devices such as field‐effect transistors and significantly influences device characteristics. 相似文献
992.
为定量分析压力传感器的测量量程及其过载能力,提出一种微型光纤光栅土压力传感器并构建其气压标定系统。对微型光纤光栅土压力传感器进行理论分析得其灵敏度为7.5 nm/MPa,测量量程可达1.06 MPa。而分析光纤光栅土压力传感器性能测试数据得:该传感器压力灵敏度为5.9 nm/MP,线性度为99.93%,可测量实际量程为225 kPa,过载能力上限值为300 kPa。研究结果可用于指导设计规定量程的光纤光栅土压力传感器,具备一定应用价值。 相似文献
993.
The paper investigates the observer‐based H∞ synchronization for coronary artery time‐delay system under the state immeasurement and external uncertainty. A Luenberger‐like state observer, the observation system, is designed to realize the state reconstruction of the master system. Based on the Lyapunov stability theory and Lyapunov‐Krasovskii functional (LKF), the observer‐based synchronization control condition is derived for a coronary artery system subjected to the external uncertainty bounded by L2 norm. By introducing the delay‐interval bounds and delay‐derivative limits in LKF, the time‐delays are handled by the delay‐range‐dependent strategy. The tighter upper bound of inequality can be obtained to reduce the conservation by employing further improved result of Jensen inequality and reciprocally convex approach. Furthermore, a decoupling technique is utilized to render the separate and simple controller and observer synthesis condition, which can be further solved by applying the cone complementary linearization approach respectively. Numerical simulations are listed to exhibit the effectiveness of the presented methodology. 相似文献
994.
995.
The traditional Range Doppler (RD) algorithm is unable to meet practical
needs owing to the limit of resolution. The order of fractional Fourier Transform (FrFT)
and the length of sampling signals affect SAR imaging performance when FrFT is
applied to RD algorithm. To overcome the above shortcomings, the purpose of this paper
is to propose a high-resolution SAR image algorithm by using the optimal order of FrFT
and the sample length constraints for the range direction. The expression of the optimal
order of SAR range signals via FrFT is deduced in detail. The initial sample length and
its constraints are proposed to obtain the best sample length of SAR range signals.
Experimental results demonstrate that, when the range sampling-length changes in a
certain interval, the best sampling-length will be obtained, which the best values of the
range resolution, PSLR and ISLR, will be derived respectively. Compared with
traditional RD algorithm, the main-lobe width of the peak-point target of the proposed
algorithm is narrow in the range direction. While the peak amplitude of the first side-lobe
is reduced significantly, those of other side-lobes also drop in various degrees. 相似文献
996.
To address the low-resolution imaging problem in relation to traditional Range
Doppler (RD) algorithm, this paper intends to propose a new algorithm based on
Fractional Fourier Transform (FrFT), which proves highly advantageous in the
acquisition of high-resolution Synthetic Aperture Radar (SAR) images. The expression of
the optimal order of SAR range signals using FrFT is deduced in detail, and the
corresponding expression of the azimuth signal is also given. Theoretical analysis shows
that, the optimal order in range (azimuth) direction, which turns out to be very unique,
depends on the known imaging parameters of SAR, therefore the engineering
practicability of FrFT-RD algorithm can be greatly improved without the need of order
iteration. The FrFT-RD algorithm is established after an analysis of the optimal timefrequency transform. Experimental results demonstrate that, compared with traditional
RD algorithm, the main-lobe width of the peak-point target of FrFT-RD algorithm is
narrow in both range and azimuth directions. While the peak amplitude of the first sidelobe is reduced significantly, those of other side-lobes also drop in various degrees. In
this way, the imaging resolution of range and azimuth can be increased considerably. 相似文献
997.
Y. F. Liu Y. S. Zhao C. G. Liu Y. Y. Guo J. Zhang Y. S. Luo 《Materials Science & Technology》2018,34(10):1188-1196
Tensile tests within a temperature range from room temperature (RT) to 1100°C were performed on a novel second-generation single-crystal superalloy DD11. The experimental results indicated that the yield strength (YS) remained constant up to 760°C, while a maximum was reached at 850°C. The elongation and area reduction decreased gradually from RT to 760°C and then they increased rapidly at temperatures above 760°C. As for the deformation mechanism, when the temperature was below 850°C, the γ′ precipitates were sheared by isolated faults, faulted loops and dislocation pairs. The formation of dislocation networks and dislocation climb mechanism were confirmed at temperatures above 980°C. Finally, the relationship between the YS of the DD11 alloy and the operative deformation mechanism was discussed. 相似文献
998.
999.
针对高准确度超宽量程力值测量的需求,本文提出了一种基于组合式力传感器的力值测量方法,通过对小量程和大量程力传感器的转换,在保证测量准确度的前提下,有效扩展了力传感器的力值测量范围,并进行了实验验证,实验结果表明:采用该组合式力传感器的力值测量方法可以有效扩展单只力传感器测量范围,使传统力传感器的测量范围从额定力值的(10~100)%测量范围扩展到(1~100)%测量范围,该组合式力传感器的准确度高,可以达到0. 01级标准测量仪的技术指标要求,可以作为参考力传感器应用在超宽量程力标准机或材料试验机上。 相似文献
1000.
Jun Li Daniel R. Jeske Yangmei Zhou Xin Zhang 《Quality and Reliability Engineering International》2019,35(2):644-658
Statistical process control (SPC) has natural applications in data network surveillance. However, network data are commonly autocorrelated, which presents challenges to the basic SPC methods. Most existing SPC methods for correlated data assume parametric models to account for the correlation structure within the data. Those model assumptions can be difficult to justify in practice. In this paper, we propose a nonparametric cumulative sum (CUSUM) control chart for autocorrelated processes. In our proposed approach, we incorporate a wavelet decomposition and a nonparametric multivariate CUSUM control chart to obtain a robust procedure for autocorrelated processes without distribution assumptions. Extensive simulations show that the procedure appropriately controls the in‐control average run length and also has good sensitivity for detecting location shifts. 相似文献