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991.
The sound field in front of, and close to a building facade is relevant to the measurement and prediction of environmental noise and sound insulation. For simplicity it is often assumed that the facade can be treated as a semi-infinite reflector, however in the low-frequency range (50-200 Hz) this is no longer appropriate as the wavelengths are similar or larger than the facade dimensions. Scale model measurements and predictions using integral equation methods have been used to investigate the effect of diffraction on the sound field in front of finite size reflectors. For the situation that is commonly encountered in front of building facades, the results indicate that diffraction effects are only likely to be significant in the low-frequency range (50-200 Hz) when the façade dimensions are less than 5 m. This assumes that there is a point source close to the ground and microphones at a height of 1.2 or 1.5 m, at a distance between 1 and 2 m in front of the façade. 相似文献
992.
To comply with the EU Noise Directive 2002/49/EC, Member States are required to produce strategic noise maps for designated areas, including mapping road traffic noise from major roads. These maps must be presented using the EU indicators Lden and Lnight. However, the most common noise indicator used in Ireland at present is the LA10,18h indicator arising from the use of the Calculation of Road Traffic Noise (CRTN) prediction method. Therefore, a relationship needs to be established between LA10,18h and Lden and Lnight, separately. In addition to noise mapping these indicators are used for noise abatement purposes, so the proposed relationship must be accurate and robust. In 2002, the UK’s Transport Research Laboratory (TRL) published a paper describing mathematical procedures that could be used to convert values of LA10 to Lden and Lnight. These procedures were then adopted for use in Ireland. This paper examines the suitability of the TRL conversion methods 1 and 3 for use under Irish road conditions. Method 2 was not considered in this study, as it was a methodology not applicable in an Irish scenario. Studies concluded that where hourly traffic data are available, the conversion methodology outlined in TRL Method 1 is robust and reproducible. However, in the absence of hourly traffic data where daily traffic counts are used, the relevant conversion procedures produce variable results for both Lden and Lnight when applied to Irish road conditions. To reduce the variability, new conversion procedures were developed, specifically for Irish road conditions. 相似文献
993.
The Pixium 4700 detector represents a significant step forward in detector technology for high‐energy X‐ray diffraction. The detector design is based on digital flat‐panel technology, combining an amorphous Si panel with a CsI scintillator. The detector has a useful pixel array of 1910 × 2480 pixels with a pixel size of 154 µm × 154 µm, and thus it covers an effective area of 294 mm × 379 mm. Designed for medical imaging, the detector has good efficiency at high X‐ray energies. Furthermore, it is capable of acquiring sequences of images at 7.5 frames per second in full image mode, and up to 60 frames per second in binned region of interest modes. Here, the basic properties of this detector applied to high‐energy X‐ray diffraction are presented. Quantitative comparisons with a widespread high‐energy detector, the MAR345 image plate scanner, are shown. Other properties of the Pixium 4700 detector, including a narrow point‐spread function and distortion‐free image, allows for the acquisition of high‐quality diffraction data at high X‐ray energies. In addition, high frame rates and shutterless operation open new experimental possibilities. Also provided are the necessary data for the correction of images collected using the Pixium 4700 for diffraction purposes. 相似文献
994.
利用Lang-Firsov正则变换和Keldysh非平衡格林函数方法研究了低温下具有电子-声子相互作用的量子点系统的噪声。我们特别注意了电-声子耦合强度的变化对量子点系统噪声的影响。数值结果表明:随着电-声子耦合强度的增大,系统的噪声增大,同时微分噪声谱中会出现一系列的声子伴带峰,峰的高度和数目对电-声子耦合强度的变化非常敏感。我们也研究了系统的Fano因子,它显示系统噪声对肖特基(Schottky)公式的偏离。在高偏压区,Fano因子随着电-声子耦合强度的增大而增大。 相似文献
995.
从量子力学诞生以来,关于宏观物体的运动是否遵循量子力学的辩论就一直没有停止过.上世纪八十年代初期以来,一系列在约瑟夫森结和超导最子干涉器件(SQUID)中观测到的实验结果,包括相位和磁通的宏观量子隧穿,能级量子化,宏观共振隧穿,和在微波驱动下的相干动力学过程对认为宏观物体的运动在满足一定条件下同样遵循量子力学规律的观点提供了强有力的实验证据.在众多已观察到的宏观量子现象中,宏观共振隧穿结合了能级分立和隧穿这两个最具特征的量子现象.由于宏观共振隧穿的观测无需使用高频电磁波激发,这就避免了实验结果也可以用经典物理解释的可能,所以在一个系统中观测到宏观共振隧穿可以说是展示该系统的量子属性的最有力证据.本文讨论近年来从理论和实验两方面理解耗散和磁通噪声对类似SQUID的双势阱系统宏观共振隧穿率和谱线形状的影响.评述宏观共振隧穿谱的测量在探寻、理解、克服超导磁通量子比特中的退相干机制并最终实现规模化量子计算方面的应用. 相似文献
996.
Jaël Pauwels Guy Van der Sande Guy Verschaffelt Serge Massar 《Entropy (Basel, Switzerland)》2021,23(8)
We present a method to improve the performance of a reservoir computer by keeping the reservoir fixed and increasing the number of output neurons. The additional neurons are nonlinear functions, typically chosen randomly, of the reservoir neurons. We demonstrate the interest of this expanded output layer on an experimental opto-electronic system subject to slow parameter drift which results in loss of performance. We can partially recover the lost performance by using the output layer expansion. The proposed scheme allows for a trade-off between performance gains and system complexity. 相似文献
997.
基于流形学习的人脸图像超分辨率技术研究 总被引:1,自引:0,他引:1
超分辨率技术是由低分辨率图像复原出高分辨率图像的技术。针对人脸图像进行基于学习的超分辨率技术研究,将流形学习算法融入到超分辨率算法中,并且将其用于人脸图像的超分辨率复原。对流形学习应用于基于学习的超分辨率原理进行了介绍。为了使得人脸图像取得更好的复原效果,对特征提取模板进行改进,使得新的特征提取模板考虑更多的像素之间的相关性,并更好地抑制噪声的影响,保留了更多的特征信息。加入了新的特征(即拉普拉斯特征)。该特征突出的边缘细节,保持了人脸图像鲜明的轮廓和清晰的边缘信息。实验结果表明,算法复原出的人脸图像更接近于真实图像,具有更高的峰值信噪比。 相似文献
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