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Temperature rise induced by an annular focused transducer with a wide aperture angle in multi-layer tissue 下载免费PDF全文
In order to improve the operability and accuracy of high-intensity focused ultrasound(HIFU), an annular focused transducer, whereby a B-ultrasound probe is placed in its center, is used to realize the real time monitoring and control of the treatment. In this paper, the spheroidal beam equation(SBE) was used to calculate the sound field by an annular focused transducer with a wide aperture angle to first derive the heat deposition and the Pennes equation was used to calculate the temperature field in multi-layer tissue. We studied the effect of different parameters on the temperature of the tissues. The result shows that the focal length has a significant influence on both maximum liver temperature rise and skin temperature rise, and both increase with the increase in the focal length. When the frequency increases, the temperature rise first undergoes a rapid increase before gradually reaching a maximum, and then finally decreasing. The temperature rise increases while the inner radius decreases or the sound pressure increases. By choosing suitable parameters, the proper temperature rise both on the target tissue and skin via an annular focused transducer with a wide aperture angle can be obtained. 相似文献
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Calculation of the heat deposition and temperature distribution of the target bombarded by high-energy protons using Monte Carlo simulation and finite element method 下载免费PDF全文
The Monte Carlo simulation and the finite element methods have been used to calculate the heat deposition and temperature distribution in tungsten plate target when the target is bombarded by high-energy protons from the accelerator with nuclear power of 100 kW. The results show that the heat deposition in the target, reflector and shield will be 48 kW, 15 kW and 11 kW, respectively, and the highest temperature in the target plates will be lower than 100℃ when the surfaces of plates are cooled by water. 相似文献
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将Fourier-Bessel级数引入KZK方程的求解,用于计算黏滞媒质中零阶Bessel型超声场的二次谐波声场,得到其级数形式的解析解,并由此得出二次谐波声场在近场分布的一个新结论.设声源表面声压分布为J0(α0r),则二次谐波声压在近场的径向分布服从J20(α0r)函数规律.这一结论合理解释了相关的实验结果,表明二次谐波声场在近场和远场有不同的径向分布,从而解决了非线性Bessel型超声场二次谐波的近场分布问题.研究还发现二次谐波声场具有类似基波声场的有限衍射特性.给出了一个数值计算和仿真实例. 相似文献
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可调谐二极管激光吸收光谱技术测量气体浓度时,由于测量氛围温度变化的影响引起解调的二次谐波信号发生变化,最终导致浓度测量的较大误差. 为了修正温度变化对浓度反演结果的影响,适应工业测量、燃烧诊断的需要,采用通过实验所得温度关系的数值拟合修正方法即经验公式修正和根据HITRAN数据库参数的理论关系即理论公式修正两种方法进行分析与讨论. 实验中采用在50 cm长的高温管式炉中通入高温安全的21%浓度的 氧气为目标测定气体,选定760.77 nm的中心吸收波长,测量了温度变化范围为300–900 K,间隔50 K的情况下所得到的谐波信号,并利用一次谐波比值消元法消除光强波动影响后的结果,得出了不同温度下未修正的原始浓度值和通过修正方法后的修正值. 实验结果表明所述的经验公式和理论公式两种修正方法对温度影响都有一定的抑制作用,可以应用到温度变化引起的气体浓度误差修正监测中,为下一步开展燃烧诊断实时在线监测提供了依据.
关键词:
可调谐二极管激光吸收光谱 (TDLAS)
温度修正
经验公式
理论公式 相似文献
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Impact of the firing temperature profile on light induced degradation of multicrystalline silicon 下载免费PDF全文
Rebekka Eberle Wolfram Kwapil Florian Schindler Martin C. Schubert Stefan W. Glunz 《固体物理学:研究快报》2016,10(12):861-865
Light‐ and elevated temperature‐induced degradation in multicrystalline silicon can reduce the efficiency of solar cells significantly. In this work, the influence of the firing process and its temperature profile on the degradation behaviour of neighbouring mc‐Si wafers is analysed. Five profiles with measured high peak temperatures ≥800 °C and varying heating and cooling ramps are examined. With spatially resolved and lifetime calibrated photoluminescence images, normalized defect concentrations N*t are calculated to determine the degradation intensity. Wafers that underwent a fast firing process typical for industrial solar cell production show a significantly stronger degradation than samples that were subjected to the same peak temperature but with slower heating and cooling rates. A spatially resolved analysis of the carrier lifetime in the whole wafer shows that the degradation begins in low lifetime areas around dislocation clusters, spreading into good grains after several hours. By the use of optimized ramp‐up and/or ramp‐down rates during the firing even at very high peak temperatures, light and elevated temperature induced degradation can be suppressed. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
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A simple new model of the spatial distribution of the liquid temperature near a cavitation bubble wall (Tli) is employed to numerically calculate Tli. The result shows that Tli is almost same with the ambient liquid temperature (T0) during the bubble oscillations except at strong collapse. At strong collapse, Tli can increase to about 1510 K, the same order of magnitude with that of the maximum temperature inside the bubble, which means that the chemical reactions occur not only in gas-phase inside the collapsing bubble but also in liquid-phase just outside the collapsing bubble. Four factors (ultrasonic vibration amplitude, ultrasonic frequency, the surface tension and the viscosity) are considered to study their effects for the thin liquid layer. The results show that for the thin layer, the thickness and the temperature increase as the ultrasonic vibration amplitude rise; conversely, the thickness and the temperature decrease with the increase of the ultrasonic frequency, the surface tension or the viscosity. 相似文献
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HIRFL CSR的电子冷却系统是采用强流电子束对重离子束进行冷却。在冷却段漂移管区,由于强流电子束自身的空间电荷场和螺线管磁场的作用,使得电子束的包络发生振荡。通过求解电子束的横向包络方程,研究了强流电子束包络随电子束参数和螺线管聚焦磁场的变化关系。计算结果表明:对于不同的电子束能量和磁场,电子束包络的振荡频率也不相同;在相同的条件下,磁场越强,电子束包络振荡幅度越小,电子束能量越大,其包络的振荡频率也越快。 相似文献
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Investigating the thermal conductivity of materials by analyzing the temperature distribution in diamond anvils cell under high pressure 下载免费PDF全文
Caihong Jia 《中国物理 B》2022,31(4):40701-040701
Investigating the thermal transport properties of materials is of great importance in the field of earth science and for the development of materials under extremely high temperatures and pressures. However, it is an enormous challenge to characterize the thermal and physical properties of materials using the diamond anvil cell (DAC) platform. In the present study, a steady-state method is used with a DAC and a combination of thermocouple temperature measurement and numerical analysis is performed to calculate the thermal conductivity of the material. To this end, temperature distributions in the DAC under high pressure are analyzed. We propose a three-dimensional radiative-conductive coupled heat transfer model to simulate the temperature field in the main components of the DAC and calculate in situ thermal conductivity under high-temperature and high-pressure conditions. The proposed model is based on the finite volume method. The obtained results show that heat radiation has a great impact on the temperature field of the DAC, so that ignoring the radiation effect leads to large errors in calculating the heat transport properties of materials. Furthermore, the feasibility of studying the thermal conductivity of different materials is discussed through a numerical model combined with locally measured temperature in the DAC. This article is expected to become a reference for accurate measurement of in situ thermal conductivity in DACs at high-temperature and high-pressure conditions. 相似文献
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The rigorous electromagnetic theory of the diffraction of vector beams by an aperture is proposed and numerically evaluated by the diffraction of vector Gaussian beams by a circular aperture. The results are compared with those, by using the vector Rayleigh–Sommerfeld diffraction integrals and angular-spectrum expression theory, showing a good consistency. The numerical calculation shows that the result calculated by the rigorous theory is much more precise than those calculated by the integral method in diffraction near field, and a highly consistency reaches by the three methods in diffraction far field. A further extension of the theory is discussed. 相似文献
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根据Sigmund溅射能量沉积理论建立了低能离子入射光学元件引起的能量扰动层厚度模型.理论推导了离子束倾斜入射时光学元件表面的束流密度,并建立了低能离子束对光学元件的热量沉积模型.采用MonteCarlo方法模拟了低能离子与熔石英光学表面的相互作用.分析了离子能量、离子类型、入射角度等参数对光学元件热量沉积和扰动层深度的影响规律.以离子束沉积在工件的能量作为热源,采用有限元分析软件ANSYS模拟了离子束入射工件的温度场分布、温度梯度场分布和温度应力分布.入射表面温度和热梯度呈高斯分布,束斑中心最高并向工件边缘逐渐减小.入射表面束斑区域受热膨胀,其膨胀受到外环区域的制约,从中心区域到大约束斑半峰值半径的区域,所受环向应力为压应力,在大致束斑半峰值半径以外区域为拉应力. 相似文献
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Khalid Masood 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2006,82(7):224-231
We investigate the inverse problem associated with the heat equation involving recovery of initial temperature distribution in a two-layer cylinder with perfect thermal contact at the interface. The heat equation is solved backward in time to obtain a relationship between the final temperature distribution and the initial temperature profile. An integral representation for the problem is found, from which a formula for initial temperature is derived using Picard’s criterion and the singular system of the associated operators. The known final temperature profile can be used to recover the initial temperature distribution from the formula derived in this paper. A robust method to regularize the outcome by introducing a small parameter in the governing equation is also presented. It is demonstrated with the help of a numerical example that the hyperbolic model gives better results as compared to the parabolic heat conduction model. 相似文献
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Nong-Chao Xin 《中国物理 B》2021,30(11):113701-113701
Molecular dynamics simulation of a sympathetically-cooled 113Cd+ ion crystal system is achieved. Moreover, the relationship between ions' axial temperature and different electric parameters, including radio frequency voltage and end-cap voltage is depicted. Under stable trapping condition, optimum radio frequency voltage, corresponding to minimum temperature and the highest cooling efficiency, is obtained. The temperature is positively correlated with end-cap voltage. The relationship is also confirmed by a sympathetically-cooled 113Cd+ microwave clock. The pseudo-potential model is used to illustrate the relationship and influence mechanism. A reasonable index, indicating ions' temperature, is proposed to quickly estimate the relative ions' temperature. The investigation is helpful for ion crystal investigation, such as spatial configuration manipulation, sympathetic cooling efficiency enhancement, and temporal evolution. 相似文献