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91.
以某全地域机动车驾驶室为研究对象,建立驾驶室的有限元模型,验证了有限元模型的有效性。以此有限元模型为基础构建驾驶室谐响应模型,进行谐响应分析,发现驾驶室后壁板的振动是引起驾驶室内部噪声的主要原因。研究驾驶室内部噪声特性,分别进行了声学空腔模态分析和声固耦合模态分析,发现声固耦合系统声压分布比较均匀,大部分呈现局部模态,主要原因可能是驾驶室后壁板的振动。通过驾驶员耳旁声压分析发现增加驾驶室后壁板的厚度,可以在一定程度内降低驾驶室内部噪声对驾驶员的影响,为同类驾驶室通过依靠结构改进来改善声场环境提供了案例依据。 相似文献
92.
基于UWB信号的井下探测成像系统中,根据Nyquist采样定理,提高发射信号的带宽以获取高分辨率,将导致大量的采样数据产生,过大的采样率将会在成像系统的硬件实现上带来很大困难。另一方面,在实际成像过程中,成像数据的完整性决定了最后成像结果的准确性,但由于存在不可避免的误差和噪声影响,以及塌方体阻碍下目标的隐蔽性,这些因素都将使得成像目标的回波数据无法满足成像要求。因此,在对目标回波进行成像处理之前,必须对回波数据进行处理,通过相关算法使回波数据满足理想的成像模型,最后聚焦方位向回波信息得到目标成像结果。为了提高穿透塌方体遮蔽目标成像的分辨率,并解决超宽带信号穿透塌方体成像得到方位向回波数据不足的问题,通过对传统的压缩感知成像算法进行分析介绍,结合井下具体成像环境,提出一种基于相位误差估计的CS成像算法对回波数据进行补偿。该算法的核心思想就是通过对回波数据计算得到相位误差,首先对回波信号的稀疏性进行验证,并构建目标信号的测量矩阵,利用CS成像算法对回波数据重构的同时对数据进行补偿,通过反复迭代误差估计,逐渐提高回波数据量和成像的质量。最后通过不同场景的仿真试验,验证所提算法在回波数据补偿问题上的有效性。 相似文献
93.
94.
《中国有色金属学会会刊》2020,30(3):789-799
To solve the problem that the existing acoustic emission (AE) source location algorithms cannot always obtain accurate results for multilayer cylindrical media, a new acoustic emission source location method considering refraction was proposed. AE source coordinates were solved by the complex method. Pencil-lead-break experiments were used to verify this method. The absolute distance errors of location results are less than 3 mm, much less than those by the traditional method. The numerical experiments were used to further analyze factors that affect location accuracy. The results of numerical experiments show that the location accuracy of the proposed method is not affected by the ratio of wave velocities but affected by the measurement accuracy of wave velocity. These results show that new method can obtain accurate AE source location in the two-layered cylindrical surface media such as the triaxial compression test. 相似文献
95.
Manas M. Mandalahalli Evert C. Wagner Luis M. Portela Robert F. Mudde 《American Institute of Chemical Engineers》2020,66(1):e16696
In this work, the effect of an electrolyte (up to 2 M of NaCl dissolved in water) on a homogeneous dense bubbly flow, in an airlift bubble column, is studied using nonintrusive techniques. X-ray and high-speed imaging are used to investigate the bubble size distribution, the local and the global gas-fraction profiles. The major effect of the electrolyte is the bubble size distribution at the fine-pore sparger, which is a consequence of the bubble coalescence inhibition promoted by the electrolyte. The bubble plume widening, the increase in overall gas fraction, and the onset of bubble recirculation in the column can all be explained by the bubble size reduction at the fine-pore spargers. As a result of the bubble size reduction, the overall role of the electrolyte is in a reduction of the driving force for the liquid recirculation. Furthermore, an accumulation of the small bubbles causes a layer of foam at the free surface, which is dynamic in nature and induces additional bubble recirculation. 相似文献
96.
为研究船用低速柴油机增压器压气机气动噪声,采用计算流体动力学和声学有限元的混合计算方法进行了数值预测。通过试验对压气机计算模型进行了验证。在3个工况下对压气机非定常流场进行了计算,其中压力脉动被用作声学计算中的声源信息;采用声学有限元方法对压气机气动噪声进行了预测。结果表明:计算流体力学和声学有限元的混合计算方法具有较高的计算精度,可以用于压气机气动噪声数值预测;压气机进口气动噪声主要谱成分为离散单音噪声和宽频噪声;离散单音噪声在叶片通过频率处有明显的指向性,存在两个突出峰值。 相似文献
97.
98.
Shabnam Rezaei Barat Ghobadian Mohammad-Taghi Ebadi Farzaneh Jangi Hamid Ghomi 《Color research and application》2020,45(1):29-39
This research was conducted to evaluate the effects of cold atmospheric plasma treatment on the color of Hyssop (Hyssopus officinalis L.) and also to compare the usage of the spectrophotometer vs the color imaging instrumentation for the evaluation of the treatment on the color parameters. The experiments were investigated at different treatment times of 1, 5, and 10 minutes and the voltage values of 17, 20, and 23 kV. Possible changes of color were evaluated by using CIE L*a*b* values obtained with HunterLab colorimeter and CIE L*a*b* values obtained with a digital still camera (DSC) using digital image processing (MATLAB software). The values of L*, a*, and b* of the samples were obtained using both the methods. The results revealed that the L*, a*, and b* values of the treated Hyssop samples changed with increasing the treatment time and the voltage applied. Evaluating the interaction effects revealed that there was a significant difference in the (−a*/b* ) ratio. In addition, the results showed that the effects of all variables on the color parameters were significantly different in the case of the DSC using digital image processing. However, these effects were not significantly different using HunterLab colorimeter except for time variable and interaction effects of a* and (−a*/b* ) ratio. The lightest green color and the maximum chlorophyll content loss were observed for 23 kV applied over 10 minutes. Based on the results, the digital image processing can be used as a practical tool to study the variations at the color of dried Hyssop leaves after cold plasma treatment. 相似文献
99.
100.
Yun Shuai Peng Zhang Xiaoyun Guo Xinyan Wang Zhengliang Huang Yao Yang Jingyuan Sun Meng Li Yan Jiang Jiong Ma Jingdai Wang Yongrong Yang 《American Institute of Chemical Engineers》2020,66(1):e16778
Three gas–liquid dispersion states including flooding, loading, and complete dispersion are observed sequentially in a jet bubbling reactor with an increase of the liquid jet velocity at the nozzle outlet (uj). The gas–liquid dispersion states are identified through the slope (k) of the curve of fluctuation distribution index (FI) versus uj as follows: (a) under the flooding, k = 0; (b) under the loading, k > 0; (c) under the complete dispersion, k < 0. In particular, the uj at the transition points from flooding to loading and from loading to complete dispersion are referred to flooding jet velocity (ujf, the transition point between k = 0 and k > 0) and complete dispersion jet velocity (ujcd, the transition point from k > 0 to k < 0), respectively. The average relative deviations of the uj at the transition points obtained through the acoustic emission measurement and visual observation are less than 5%. 相似文献