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为丰富换能器固有频率的研究理论,以及提供一种新的计算方法供工程人员选择,提出了计算其固有频率的有限差分法。以由径向极化的压电陶瓷圆管与金属预应力管沿径向复合而成的二元压电陶瓷复合换能器为例,建立并推导了其向振动的数学模型及其有限差分形式,给出了换能器径向振动的特征方程。利用MTALAB对计算实例的径向振动的固有频率进行编程计算,理论计算结果与已有实验结果符合很好,验证了有限差分法计算压电陶瓷复合换能器固有频率的可行性及准确性。通过仿真计算,给出了换能器径向振动固有频率与其结构尺寸的影响关系:换能器径向振动的固有频率随压电陶瓷圆管内径的增大而降低,随换能器壁厚比的增大而降低。该文所建立的换能器径向振动固有频率的有限差分法同样适用于结构形式相近的换能器及其他元器件。 相似文献
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基于密度与光谱反射率的关系建立了一种凹版专色梯尺的光谱反射率预测模型。该方法首先依据密度的定义建立实地光谱反射率与其密度的关系,并基于实地光谱反射率建立阶调光谱反射率的计算方法;然后根据密度的叠加原理,假设阶调密度与实地密度比例关系成立建立阶调密度、实地密度和承印物密度的关系;最后结合计算阶调光谱反射率的方法建立凹版专色梯尺光谱反射率预测模型;调配30种专色油墨通过凹印实打样,对预测模型通过决定系数R2和色差进行验证。实验结果表明,不同专色在同一网点面积率下实际阶调密度与实际实地密度的比例系数相同,两者的决定系数R2均大于0.98。在此关系基础上所建立的预测模型在不同网点面积率下都具有较高的决定系数,其均方根误差都小于0.01,最大色差为2.667 NBS。最后另外调配10种专色油墨在相同工艺条件下实打样样张,利用实际阶调密度与实际实地密度的比例系数,通过色差公式进而验证该模型预测专色油墨梯尺光谱反射率的精度。色差结果表明,82.12%的色差小于2.5 NBS,大部分色差在0.5~2 NBS之间,占据了总频率的58.32%,平均色差为1.58... 相似文献
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针对脉冲管制冷机内部交变流动及多孔介质蓄冷机的特点建立了数值计算模型,采用改进的数值模拟方法对脉冲管制冷机内部气流的交变流动、换热以及制冷过程进行了详尽的数值研究,得到了脉冲管制冷机内各参数的动态变化,分析了各动态参数变化对制冷机整机性能的影响,并从提高数值方程的计算精度和收敛性方面给出了改进的数值模拟方法。模拟分析与实验结果符合良好。该模拟方法的特点从基本流动换热微分方程出发,尽可能多的考虑实际制冷机工作过程中的各种不可逆因素,包括实际气体的物性变化,各部件的流动阻力和传热损失。 相似文献
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针对水质多参数监测仪器的低功耗、微型化、集成化和智能化,研制了一种基于顺序注射分析技术(SIA)和连续光谱检测方法融合的微型测定原位水质多参数检测仪,系统设计的核心在于消解池结构设计且消解池作为检测池,以及微控技术顺序注射平台的原理设计和多参数联合消解测定流程设计.对融合SIA和连续光谱水质多参数原位分析的新方法进行实... 相似文献
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为了实时在线监测颗粒物料在装卸和运输过程中所产生粉尘的浓度,提高粉尘浓度测量结果的精确性与可靠性,提出了一种基于图像透光率特征值计算的粉尘浓度测量算法。通过搭建粉尘浓度视觉测量实验平台,采集粉尘图像,再提取粉尘图像的透光率特征,以暗通道理论为基础,结合图像饱和度与亮度信息对粉尘图像透光率值进行计算,并采用多项式拟合的方式建立了粉尘浓度与图像透光率之间的映射关系,实现了粉尘浓度的高效率、高精度测量。研究结果表明:该算法不仅能有效地测量出粉尘浓度,且平均相对误差仅为7.77%,精确度得到有效提高,测量范围更大。 相似文献
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《中国物理C(英文版)》2015,(7)
In this paper, the distribution of radiation field in the CSNS spectrometer hall at Dongguan, China, was simulated by the FLUKA program. The results show that the radiation field of the high energy proton accelerator is dominated by neutron radiation, with a broad range of neutron energies, spanning about eleven orders of magnitude.Simulation and calculation of the response functions of four Bonner spheres with a simplified model is done with FLUKA and MCNPX codes respectively, proving the feasibility of the FLUKA program for this application and the correctness of the calculation method. Using the actual model, we simulate and calculate the energy response functions of Bonner sphere detectors with polyethylene layers of different diameters, including detectors with lead layers, using the FLUKA code. Based on the simulation results, we select eleven detectors as the basic structure for an Extended Range Neutron Multisphere Spectrometer(ERNMS). 相似文献
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提出了一种基于声韵母能量分布和共振峰结构特性的汉语连续语音声韵母边界检测方法。该方法首先将语音经过Seneff听觉感知模型得到听觉谱,然后基于听觉谱,选取全频带能量、低频带能量、谱重心、高低频能量比、中高频能量等特征参数对各声韵母类别能量分布和共振峰结构特性进行描述,最后根据特征参数变化剧烈的点确定出声韵母边界,并采用包络的一阶差分和基于样点的Kullback-Leibler距离对得到的边界进行修正。实验结果表明,对8 kHz采样的语音边界检测准确率可达到93.7%;信噪比10dB的语音边界检测准确率可达到85.3%以上;经过参数编码后语音边界检测准确率可达86 7%以上。 相似文献
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Rongji Wang Xiaoxin Feng Yuejun Xia Junliang Zeng 《Journal of Macromolecular Science: Physics》2013,52(10):1414-1426
This paper presents a back propagation artificial neural network (BP ANN) prediction model of the gate freeze time (tgf) for injection molded polypropylenes. An orthogonal design method was applied to enhance the BP ANN performance. The test results on the performance of the BP ANN prediction model showed that it can predict tgf with reasonable accuracy. Utilizing the BP ANN prediction model, the effects of the process factors, melt temperature (Tme), fill time (tf), gate area (Ain), packing pressure (Pp), and mold temperature (Tmo) on tgf were investigated. The simulation results showed that the most important process factor affecting tgf was Tme, followed by tf, Ain, and Pp, with Tmo having the least effect. The gate freeze time increased with elevated Tme, tf, Ain, and Pp. 相似文献
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《Proceedings of the Combustion Institute》2023,39(3):3539-3549
An improved model of fine particulate matter formation coupling the mechanism of mineral coalescence and char fragmentation under different pulverized coal combustion environments has been constructed. Firstly, based on the theoretical model of char fragmentation and percolation, the included minerals with different types and particle sizes are constructed in the model, and a three-dimensional char particle sub-model is established. And the type, content and particle size distribution of included minerals are introduced as input parameters by using computer controlled scanning electron microscopy (CCSEM) technology. All of the above makes it more in line with the actual distribution of the included minerals. Then a sub-model of char fragmentation is built based on the sub-model of the char particle. And considering the influence of char combustion reaction on the particle formation process and melting characteristics of included minerals, a sub-model of mineral melting coalescence under different combustion environments is established. Finally, based on this improved model, we compared the calculation results with the experimental data and the calculation results of the traditional model. Fully considering the process of mineral coalescence and char fragmentation, which contains the characteristics of different included minerals, the results show that the newly established model has a good fitting effect for the experiment and is closer to the actual process of char particle combustion to generate particles. By the new model, the influence of the factors (mineral content, particle size distribution and porosity) on the formation of particulate matter is preliminarily analyzed. 相似文献
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Atmospheric pressure plasma arc (APPA) cleaning is a newly developed method of metal surface cleaning. In this paper, a mathematical model of reactive kinetics in the metal surface contaminant cleaning using APPA has been developed. Based on the analysis of APPA cleaning mechanism and the feature of cleaning interface, a governing equation was established with heat transfer equation and energy conservation on the moving interface. Using fourth-order Rounge-Kutta method, above equation was solved and removal percentages of the cleaning contaminant at different time were obtained. In virtue of reactive kinetics theory, a reactive kinetics model of metal surface cleaning using APPA was established on the base of above calculation results. Afterwards, reactive kinetics parameters such as activation energy and pre-exponential factor were calculated. Cleaning lubricant was taken as an example, the results indicated that predictive values of lubricant removal percentages gotten from this established reactive kinetics model show good consistent with experimental data at the same time. Furthermore, the ambient temperature on the cleaning lubricant surface affects the removal rate strongly. The removal rate increases with the increase of the ambient temperature. To avoid the damage of metal substrate surface because of higher temperature and ensure the removal rate of the lubricant, the appropriate temperature which lies between the lubricant decomposition temperature and damage temperature of metal substrate under given calculation conditions should be determined. 相似文献
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提出并研究一种利用两板间微缝进行阻尼耦合的双层微穿孔板(DMPP)吸声体。该吸声体在两层微穿孔板(MPP)之间形成一个宽度小于1mm的微缝,因此其阻尼不仅可由板上的微穿孔提供,还可由两板之间形成的微缝提供。采用声电类比法建立了DMPP转移阻抗的理论模型,并进行实验验证,结果表明理论计算结果与实验吻合较好。然后利用建立的理论模型,对单层MPP和DMPP吸声体的吸声性能进行了对比研究,结果表明,相比于单层MPP,DMPP可以利用微缝提供的阻尼显著改善吸声性能,同时减少实际板厚。最后,对DMPP吸声体的吸声性能及其几何参数的关系进行研究,结果表明,当保持其它结构参数不变时,微缝宽度对DMPP吸声系数的提高存在一个最优值,超过或低于此值会导致吸声系数下降。 相似文献
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针对某水下目标的抗水下爆炸实验数据,利用小波包良好的时频局部化性质,对被监测水下目标内部装置的冲击加速度信号进行了能量分析,得到了冲击信号的时频分布和不同频带上的能量分布。冲击信号的频带能量分布与目标毁伤的关系密切,选用冲击信号峰值、冲击信号主振频带能量、水下目标内部装置自振频率所在频带能量作为判别因子,建立距离判别模型,对水下目标毁伤情况进行了预测;利用回代估计法对模型的合理性进行了检验。研究结果表明,预测结果与实际结果相符,证明将频带能量作为水下爆炸毁伤水下目标的特征指标是合理的。 相似文献
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The electronic and lattice structures of poly (phenylene vinylene)
(PPV) are studied theoretically. Both the electron-electron and
electron-phonon interactions are taken into account in the
Pariser-Parr-Pople model. The electronic band and the lattice structure of the ground state and the polaronic state are calculated by means of the unrestricted Hartree-Fock method. In the ground state, there exist eight bands in PPV including four valence bands and four conduction
bands, and the benzenes can be considered to be rigid. The polaron
induces the split of energy bands. There are four localized electronic
states within the energy gap. The defect of the polaron appears to extend
over about 5 units. The benzenes are strongly affected by the
electron-phonon interaction. Our calculation for the energy band
structure of the ground and polaron states are consistent with experimental
absorption spectra. The results of our calculation show that the
electron-phonon and inter-site electron-electron interactions play an
important role in determining the electronic and lattice structures. 相似文献
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The electronic and lattice structures of poly (phenylene vinylene) (PPV) are studied theoretically. Both the electron-electron and electron-phonon interactions are taken into account in the Pariser-Parr-Pople model. The electronic band and the lattice structure of the ground state and the polaronic state are calculated by means of the unrestricted Hartree-Fock method. In the ground state, there exist eight bands in PPV including four valence bands and four conduction bands, and the benzenes can be considered to be rigid. The polaron induces the split of energy bands. There are four localized electronic states within the energy gap. The defect of the polaron appears to extend over about 5 units. The benzenes are strongly affected by the electron-phonon interaction. Our calculation for the energy band structure of the ground and polaron states are consistent with experimental absorption spectra. The results of our calculation show that the electron-phonon and inter-site electron-electron interactions play an important role in determining the electronic and lattice structures. 相似文献