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1.
多频超声辐照的声化学产额研究进展   总被引:5,自引:0,他引:5       下载免费PDF全文
声化学是一门新兴的交叉学科,具有很多用途,广泛地应用于医药,生物,海洋,航空,轻工,食品,化学,化工等诸多领域,打基础这年来对声化学的研究十分活跃,多频超声对声化学产额的影响是其中研究的热点之一。声化学反应的主动力是声空化,声化学产额与超声辐照频率有一定的关系。双频,三频正交超声辐照能显著地提高声化学产额,具有明显的增强效应。文章综述了这方面的研究进展情况,阐述了声化学产额的影响因素。提出了目前所存在的问题并进行展望。  相似文献   

2.
用碘释放法研究低频超声的声化学产额   总被引:19,自引:3,他引:16       下载免费PDF全文
陈兆华  朱昌平  赵逸云  王惠  冯若 《声学技术》1997,16(4):192-193,197
本文用碘释放法研究了28kHz超声的声化学产额随扬强和辐照时间的变化。表明声化学产额随声强呈非线性变化,而随辐照时间近似呈线性变化。进而研究了由28kHz与1.06MHz组成的正交辐照系统的声化学产额。  相似文献   

3.
卢群  丘泰球  罗登林 《声学技术》2005,24(4):215-218
针对多频超声促进声化学产额的研究热点问题,简述了单频、双频、三频超声辐照的声化学反映规律及其研究进展,分析了多频辐射能显著提高声化学产额的原因。指出了多频超声在医药方面的应用,尤其是在中药复方提取中更显示出其优越性,可以达到很好的提取率,多频辐射有很好的开发前景。  相似文献   

4.
C2 用于声化学研究的大功率超声系统的研制   总被引:1,自引:1,他引:0       下载免费PDF全文
根据声化学反应的特殊要求,我们研制了上前用于声化学研究的大功率超声系统,由参数可调节的超声发生器配合不同频率的换能器工作,并用它组合成杯式幅杆结构声化学反应器,解决了有关声化学设备的一些技术问题。为声化学技术从实验室规模向工业应用过渡做了必要的准备。  相似文献   

5.
朱昌平  冯若  杨勇  徐勇 《声学技术》2000,19(3):125-126
本文首次采用碘释放法发现双束脉冲超声辐照的空化产率增强效应。这一发现无疑对声空化效应的基础研究和声化学技术发展具有重要的意义。  相似文献   

6.
根据声化学反应的特殊要求,我们研制了用于声化学研究的大功率超声系统,由参数可调节的超声发生器配合不同频率的换能器工作,并用它组合成杯式变幅杆结构声化学反应器。解决了有关声化学设备的一些技术问题,为声化学技术从实验室规模向工业应用过渡做了必要的准备  相似文献   

7.
徐峥  陈皓  程茜  周红生  钱梦騄 《声学技术》2014,33(3):218-221
通过数值模拟和实验分别研究了点聚焦超声换能器在液体中直接辐照和间接辐照时产生的声场和声化学场分布。研究结果表明,在直接辐照时,数值模拟得到的液体中声压较大位置与声化学反应场位置相一致:在聚焦超声焦点处及液体表面附近。当使用间接辐照时,焦点处声压减小,在试管底与超声换能器之间形成驻波。为了增加间接辐照时容器内的声压,实验使用底端贴有薄膜的双通试管,通过计算机模拟和实验证明在该情况下,容器内声压,特别是容器焦点处声压和声化学反应场有所增强。  相似文献   

8.
超声辐照乳液聚合研究进展   总被引:11,自引:0,他引:11  
综述了超声辐照乳液聚合的特点,聚合成核机理,影响因素及反应动力学特点,简要介绍了超声辐照无皂乳液聚合,超声辐照微乳液聚合,超声辐照乳液共聚和纳米粒子存在下的超声辐照乳液聚合。  相似文献   

9.
超声声化学激活血卟啉效应的研究   总被引:1,自引:0,他引:1       下载免费PDF全文
本文用1,3-二苯基异苯并呋喃(DPBF)检测了超声激活血卟淋的效率,并寻找了声参量与激活效率之间的关系。结果表明,在一定条件下,DPBF的相对消耗量随着辐照时间、声强度的增大而增大,超声频率及血卟淋浓度对DPBF相对消耗量也有影响。这一结果为声动力学疗法应用于临床具有重要的意义。  相似文献   

10.
阎杰  丘泰球  任庆功 《声学技术》2008,27(5):690-695
对声化学技术在强碱催化制备生物柴油方面的研究与应用进行了评述。介绍了催化剂种类及用量、温度、反应时间、醇种类及用量、频率与功率、原料种类等因素对超声场中酯交换反应的影响,同时也对超声促进连续酯交换,水力空化促进酯交换,以及超声辅助萃取酯交换法等声化学新技术进行了分析、评述,指出采用声化学方法具有环境友好、反应快速等优点,但在工程放大、设备设计等方面尚需进一步研究。  相似文献   

11.
长江口和杭州湾浮泥声参数测量   总被引:3,自引:1,他引:2       下载免费PDF全文
凌鸿烈  孙耀秋  杨挺 《声学技术》1997,16(4):194-197
本文报导了用4种频率的超声波,对长江口和杭州湾的水底浮泥在不同重度下测得的声速和重度之间,声衰减与重度之间以及在一定重度下频率与声衰减之间的变化关系曲线。实验结果表明;在相同条件下,杭州湾浮泥的声衰减比长江口浮泥的声衰减大一点。  相似文献   

12.
The effect of high-energy (50 MeV) Li3+ ion beam irradiation on polypropylene (PP) film has been studied in the fluence range 2.4 × 1012−l.5 × 1014 ions/cm2. The a.c. electrical properties of PP films were measured in the frequency range from 0.05– 100 kHz, and at temperature range between 30 and 140°C. This study indicates two peaks at 60°C and 120°C with comparatively high magnitudes. There is an exponential increase in conductivity with log of frequency and the effect is significant at higher fluences. The loss factor (tan δ) vs frequency plot suggests that PP film based capacitors may be useful below 10 kHz. The capacitance is constant over a wide temperature range up to 130°C. FTIR spectra of the PP films before and after irradiation indicate that intensity of C-H stretching vibration at 2900 cm−1 is modified. The presence of many new peaks with the increase of fluence suggests the formation of alkanes and alkynes which might be responsible for the observed changes in the dielectric and electrical properties of PP films.  相似文献   

13.
The electrical and dielectric behaviour of a gadolinium-based zirconium fluoride glass have been studied over a wide temperature (23–275 °C) and frequency (100 Hz–1 MHz) range. The conductivity at 200 °C was of the order of 10–6 (ohm-cm)–1 and the activation energy was 0.75 eV. The dielectric constant measured at 1 kHz was 14 and was independent of frequency at low temperatures. The observed dielectric dispersion has been attributed to the conduction mechanism.  相似文献   

14.
In this work, we have studied the frequency effect on the metal/polysilicon/oxide/silicon (MSPOS) structure. We present the capacitance–voltage (CV) characteristics at four frequencies (10 kHz, 100 kHz, 400 kHz and 1 MHz). The results show that the CV curves have dispersion when the frequency decreases. The increase of the frequencies translates the CT(V) curve towards negative voltages and causes the decrease of the minimum value of capacitance. The variation of the capacitance for low frequencies is less important compared to that of the high frequencies.  相似文献   

15.
We report on experimental investigations of acoustic emission by quartz tuning forks resonating at frequencies 32 kHz, 38 kHz, 77 kHz and 100 kHz immersed in cold gaseous 4He and its normal and superfluid liquid phases. Frequency dependence of the observed low-drive-linewidth at 350 mK together with the temperature and pressure dependences (1.3 K < T < 4.2 K, 0 < p < 25 bar) of the observed damping of the high frequency (77 and 100 kHz) resonators measured in normal liquid 4He and its superfluid phase provide strong and direct evidence of the importance of sound emission by these tuning forks. Three analytical models of acoustic emission by vibrating tuning forks are developed and compared with the experimental results. We also discuss the importance of sound emission for experiments with the commonly used 32 kHz tuning forks as well as other oscillating structures??spheres, wires, grids and various micromachined sensors. We compare the relative importance of dissipative losses due to laminar viscous/ballistic drag and acoustic emission in liquid and superfluid 4He.  相似文献   

16.
Our ultimate objective is to design a combined frequency standard for optical as well as radio frequencies. A mode-locked laser provides frequency components that can be used as a ruler to measure any unknown optical source through direct beating. The frequency spacing of a pair of teeth of this comb is in itself a radio frequency reference. Fast control and correction for both the average frequency and the repetition rate of a mode-locked Ti : sapphire laser are achieved by locking the laser to a reference cavity of ultra-low expansion quartz with equal mode spacing. We measure an optical frequency with a mean square deviation of 700 Hz, instability limited by the radio-frequency sources used to count the repetition rate. As a reference standard to achieve absolute accuracy, we use the Λ transition 5S1/2 (F = 1) → 5D5/2 (F = 3) → 5S1/2 (F = 2) of rubidium. The theory for this coherent interaction shows that, with one mode resonant with the two-photon 5S1/2 (F = 1) → 5D5/2 (F = 3) transition, the fluorescence goes through a resonance for a change in repetition rate of less than 10 kHz. These results suggest that, by locking to the peak of that resonant feature, optical stability and absolute accuracy better than 1 kHz can easily be achieved.  相似文献   

17.
This article describes the magnetic and hyperthermic investigation of a concentrated magnetic fluid on the basis of a transformer mineral oil with magnetite particles. The structure of a ferrofluid and general magnetic parameters of a medium were determined from vibrating sample magnetometer measurements. The hyperthermic experiments were carried out at a frequency f = 1500 kHz for various magnetic field amplitudes. The analysis of calorimetric results allowed an estimate of the contribution of relaxational and hysteresis loss mechanisms in total energy losses in the hyperthermic effect under the influence of an alternating magnetic field. Additional calorimetric measurements were also performed (at H C = 1500 A · m−1) versus frequency in the range from 50 kHz to 2 MHz which indicated that for f o =  653 kHz the heating process is the most effective.  相似文献   

18.
This paper presents the structural, ferroelectric, ferromagnetic, resonance and magnetoelectric (ME) properties of multilayered ME composites fabricated using tape casting method. The compositions corresponding to CoFe2O4 (CFO) with particle size of ~150?nm and BaTiO3 (BTO) with particle size of ~100?nm were chosen as ferromagnetic and ferroelectric phases, respectively. Delamination was found at the interface between CFO and BTO layers, which was related to the residual stress due to the difference in thermal expansion coefficient between the two layers. The largest direct magnetoelectric and converse magnetoelectric coefficients of the multilayered ME composite were, respectively, 36?μV/cm?Oe at a bias magnetic field of 2,800?Oe and 1.16?×?10?3?G/V at a frequency of 30?kHz. In addition, the corresponding interfacial coupling coefficient was calculated to be 3.2?×?10?5. For the multilayered ME composite, a resonance frequency of 4.96?MHz and a bandwidth of 40?kHz were obtained using capacitance-frequency spectrum method.  相似文献   

19.
Pulsed NMR measurements have been performed on 3He films adsorbed on an exfoliated graphite sample of area 2 m2. The spectrometer is constructed using a DC SQUID with additional positive feedback, operating in flux locked loop mode with a bandwidth of 3.4 MHz. The input circuit, is a superconducting flux transformer, and so is intrinsically broadband. This spectrometer can therefore operate from typical frequencies used in conventional NMR down to otherwise inaccessible low kHz frequencies. With this system studies at the “ferromagnetic anomaly” have been undertaken at frequencies from 2 kHz to 100 kHz (0.06 to 3.09 mT), with the static magnetic field oriented normal to the nominal direction of the graphite platelets. At 50 and 100 kHz, measurements of the susceptibility are fit by high temperature series expansions between 100 mK and 5 mK, to determine an exchange constant J=1.86 mK. Below 1.3 mK the dipolar frequency shift increases linearly with temperature down to 0.3 mK, extrapolating to 10 kHz, close to our calculated value of 9.6 kHz, for fully polarised spins with an assumed lattice spacing of 0.392 nm for the second layer solid. Below 1.5 mK, a significant field dependence to the magnetisation and dipolar frequency shift appears at fields comparable to the characteristic dipolar field, below which the equilibrium alignment of the magnetization is field dependent. Assuming the frequency shift, in applied fields of 1.54 and 3.09 mT, to be proportional to the sample polarisation we find that it is not possible to fit the observed temperature dependence by 2D ferromagnetic spin-wave theory, with a consistent set of parameters for both fields. The theory is applied in the range 0.15>T/J>0.5, takes into account the Zeeman gap and finite system size, and includes the k=0 spin wave term. At present, the data provide no unambiguous evidence for a finite ordering temperature induced by the anisotropic dipolar interaction.  相似文献   

20.
A high-temperature superconducting magnetometer with double modulation at frequencies of 50 kHz and 5 MHz, which uses the nonlinear properties of a ceramic superconductor, is described. The magnetometer has a noise level of 2.3 nA/(m·Hz1/2) in the 0–14.5 kHz frequency band.  相似文献   

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