双频复合超声强化无水葡萄糖溶液结晶成核研究

溶液结晶技术在许多领域有着广泛的应用,其中结晶成核是溶液结晶的关键环节。以无水α-葡萄糖为研究对象,采用双频复合超声(25 k Hz+40 k Hz)强化糖液结晶成核,研究了溶液浓度、超声功率和作用时间对成核速率的影响,对单频和双频作用的晶核形态进行了对比,并采用碘化钾溶液中碘的释放量研究超声空化产额。研究结果表明:在同等条件下,双频复合超声降低了溶液成核的初始浓度,提高了成核速率,同时得到粒度均匀的晶核;双频复合超声的空化产额远高于单频25 k Hz超声和单频40 k Hz超声的空化产额,双频复合超声具有协同作用。双频复合超声强化溶液成核是一种快速、高效、节能的方法。     

单频超声和双频复合超声的空化效应实验研究

从超声电功率、超声作用时间和溶液温度来研究超声的空化效应,采用碘化钾溶液中碘的释放量来测定超声的空化产额,研究结果表明：在相同的电功率输入情况下,双频复合超声（25kHz/40kHz）释放碘的量远大于单频25kHz超声和单频40kHz超声释放的碘的量,双频复合超声的空化产额高于单频超声。     

LS2F传声器的高频自由场互易校准

为满足空气超声声压量值的溯源需求,利用PULSE分析仪和互易校准仪,采用时间加窗技术对频域信号转换得到的时域信号进行处理,建立了LS2F传声器的高频互易校准装置,实现了实验室标准传声器的20~51 kHz的自由场灵敏度校准。通过对比时间加窗处理前后的实验数据,分析了驻波和墙体发射波对传声器灵敏度的影响。结果表明,高于40 kHz时,时间加窗处理技术能够减小1.0 dB的偏差。     

双频超声空化效应强化提取中药有效成分的实验研究

设计了25kHz和40kHz的双频超声强化提取装置,以碘化钾中碘的释放量研究双频超声的空化效应,并以黄柏为原料研究双频超声对提取小檗碱的强化效果,结果表明:在相同实验条件下,双频超声的空化效应远大于单频超声的空化效应;25kHz与40kHz双频超声时的提取率为64.1%,单频25kHz及40kHz时的提取率分别为36.8%和19.0%,双频超声强化的提取率显著高于单频超声强化的提取率。研究还表明,双频超声强化可以降低提取温度,缩短提取时间,为热敏性药物的提取提供了新的强化方法。     

超声对黑曲霉产菊粉酶的影响

为了探索超声提高黑曲霉产菊粉酶的可能,考察了超声处理时间、超声频率和不同发酵时期超声处理等参数的影响。试验发现在黑曲霉的延滞期和对数增长期的初期阶段（〈30h）,40kHz和59kHz的超声处理均抑制了黑曲霉产菊粉酶的活力,高频超声的抑制效果更明显,菊粉酶活力降低了47.4%。在黑曲霉的对数增长期的后期阶段（〉36h）,这两种频率的超声处理均促进了黑曲霉产菊粉酶的活力,低频超声的促进作用更明显,菊粉酶活力提高了29.3%。结果表明,在一定条件下,超声能够促进微生物的发酵产酶。     

Sonoluminescence generated by the interaction of two ultrasonic fields with strongly different frequencies

The phenomenon of luminescence under the action of ultrasound (sonoluminescence, SL) was studied in a liquid exposed to the field of a high-frequency (HF, 880 kHz) focusing radiator with simultaneous or preliminary action of a low-frequency (LF, 19.9 kHz) ultrasound on the sample. It is shown that a nonadditive increase in the SL intensity takes place for simultaneously operating radiators and is observed for a long time (up to several hours) after switching off the LF source. This is evidence of a long-term aftereffect of the LF ultrasound on the magnitude of SL induced by the HF oscillations. The possible mechanisms of the observed effect are discussed.     

Experimental Study on Distribution Characteristics of Condensate Droplets Under Ultrasonic Vibration

This paper studied the effect of ultrasound on distribution characteristics of condensate droplets on a vertical metal surface. The surface was made of aluminum and coated with PVC film to obtain durable condensate droplets. Visualization of the condensation process was carried out under the action of ultrasonic vibration with a constant frequency of 20 kHz. The effects of ultrasonic power on surface coverage of condensate droplets, first shedding time of condensate droplets, total number of shedding, heat flux and condensation heat transfer coefficient were analyzed. Furthermore, the mechanism of ultrasonic vibration on accelerating the shedding of condensate droplets was discussed. The results indicated that the shedding of condensate droplets was accelerated by ultrasound compared with those without ultrasound. In addition, the shedding period of condensate droplets was decreased with the increase of ultrasonic power. Contrarily, the heat flux and the condensation heat transfer coefficient were increased with the increase of ultrasonic power. The maximum enhancement ratio of heat transfer coefficient reached 2.67 compared with that without applying ultrasound. This study shows that ultrasound has a good application prospect in strengthening condensation heat transfer, particularly for space applications in microgravity environment.     

Ultrasonic Plasma Spray--A New Plasma Spray Process

The method of arc- ultrasonic is introduced into plasma spray process. The process of spray ZrO2-NiCoCr AlY thermal barrier coatings (TBCs) using air plasma spray (APS) process is studied. A exciting source which can be adjusted from audio frequency to several hundred thousand Hertz is designed successfully. The ultrasonic exciting source is coupled with conventional DC spraying power supply. A few ultrasonic frequencies are selected in the testing. Several parts of the coatings with the coupling arc- ultrasonic are compared with the coatings without it. The results show: with 50 kHz and 80 kHz ultrasound, the coating qualities are improved, whereas 30 kHz has an opposite effect.     

Sonochemical disinfection of municipal wastewater

The application of high intensity, low frequency ultrasound for the disinfection of simulated and septic tank wastewaters is evaluated in this work. Laboratory scale experiments were conducted at 24 and 80kHz ultrasound frequency with horn-type sonicators capable of operating in continuous and pulsed irradiation modes at nominal ultrasound intensities up to 450W. For the experiments with simulated wastewaters, Escherichia coli were used as biological indicator of disinfection efficiency, while for the experiments with septic tank wastewaters, the total microbiological load was used. Complete elimination of E. coli could be achieved within 20-30min of irradiation at 24kHz and 450W with the efficiency decreasing with decreasing intensity and frequency. Moreover, continuous irradiation was more effective than intermittent treatment based on a common energy input. Irradiation of the septic tank effluent prior to biological treatment at 24kHz and 450W for 30min resulted in a three-log total microbiological load reduction, and this was nearly equal to the reduction that could be achieved during biological treatment. Bacterial cell elimination upon irradiation was irreversible as no reappearance of the microorganisms occurred after 24h.     

Influence enhancement effect of bi-frequency ultrasonic irradiation by TA fluorescence method

Based on a previous research of cavitation effect under bi-frequency ultrasound irradiation, this paper studies bi-frequency irradiations with similar experimental settings. The additional irradiation sources with frequencies of 1.04MHz, 0.8MHz and 1.7MHz are individually combined with the main ultrasonic irradiation source with frequency of 28kHz to form bi-frequency ultrasonic irradiation. The intensity of 28kHz irradiation was fixed at 12.5W/cm2, while the intensity of the ultrasound at the other three frequencies is varied from1 W/cm2 to 18 W/cm2. It turns out that under the influence of the bi-frequency irradiation, the fluorescence intensity is obviously greater than the sum of those at individual frequencies. So the frequency of the additional sonication strikingly influences the fluorescence enhancement effect. For example, the fluorescence enhancement effect of 1.04MHz is stronger than that of 1.7MHz, and the enhancement effect of 0.8MHz is further stronger than that of 1.04MHz. Under the sonic intensity of 7.9W/cm2, the fluorescence intensity of 1.04MHz is approximately twice that of 1.7MHz while the fluorescence intensity of 0.8MHz is approximately 1.5 times that of 1.04MHz.     

Structure refinement and thermal stability of gibbsite

The crystal structure of gibbsite (aluminum hydroxide) has been refined by Rietveld powder diffraction analysis, and the thermal stability of the crystal structure of the mineral has been studied in detail by high-temperature X-ray diffraction. The X-ray diffraction data obtained in the temperature range from 25 to 300°C indicate that the crystal structure of gibbsite is stable up to 200–250°C. The unit-cell parameters of gibbsite increase with temperature. Above 200°C, the gibbsite to boehmite (AlO(OH)) phase transformation begins.     

Controlled ultrasound tissue erosion

The ability of ultrasound to produce highly controlled tissue erosion was investigated. This study is motivated by the need to develop a noninvasive procedure to perforate the neonatal atrial septum as the first step in treatment of hypoplastic left heart syndrome. A total of 232 holes were generated in 40 pieces of excised porcine atrial wall by a 788 kHz single-element transducer. The effects of various parameters [e.g., pulse repetition frequency (PRF), pulse duration (PD), and gas content of liquid] on the erosion rate and energy efficiency were explored. An Isppa of 9000 W/cm2, PDs of 3, 6, 12, and 24 cycles; PRFs between 1.34 kHz and 66.7 kHz; and gas saturation of 40-55% and 79-85% were used. The results show that very short pulses delivered at certain PRFs could maximize the erosion rate and energy efficiency. We show that well-defined perforations can be precisely located in the atrial wall through the controlled ultrasound tissue erosion (CUTE) process. A preliminary in vivo experiment was conducted on a canine subject, and the atrial septum was perforated using CUTE.     

双频超声破解污泥实验方法

使用20kHz和25kHz双频超声破解污泥装置,根据污泥滤液COD、NH3-N、TP的增量研究复频超声破解污泥的效果,并且详细探讨了影响复频超声破解污泥的影响因素（不同频率组合、不同作用方式、不同功率组合、不同时间组合）。实验结果表明双频超声更有利于污泥破解,为污泥破解方法的应用和今后进一步扩大其研究提供一定的基础。     

Ultrasonic reduction of excess sludge from the activated sludge system

Sludge treatment has long become the most challenging problem in wastewater treatment plants. Previous studies showed that ozone or chlorine effectively liquefies sludge into substrates for bio-degradation in the aeration tank, and thus reduces the excess sludge. This paper employs ultrasound to reduce the excess sludge from the sequential batch reactor (SBR) system. Partial sludge was disintegrated into dissolved substrates by ultrasound in an external sono-tank and was then returned to the SBR for bio-degradation. The results showed that ultrasound (25kHz) effectively liquefied the sludge. The most effective conditions for sludge reduction were as following: sludge sonication ratio of 3/14, ultrasound intensity of 120kW/kgDS, and sonication duration of 15min. The amount of excess sludge was reduced by 91.1% to 17.8mg/(Ld); the organic content and settleability of sludge in the SBR were not impacted. The chemical oxygen demand (COD) removal efficiency was 81.1%, the total nitrogen (TN) removal efficiency was 17-66%, and high phosphorus concentration in the effluent was observed.     

基于声学法测温的声波飞渡时间研究

声波飞渡时间的准确测量是声学法测温中影响温度场测温准确性的主要因素。采用互相关分析法计算单一频率声波信号及宽带频率声波信号的声波飞渡时间,仿真结果表明宽带频率信号由于具有较强的抗噪能力在计算声波飞渡时间时不受声波信号周期、信号延时时间等因素的限制,可用于工程实践。同时采用频率为40kHz的正弦波超声波探测器在均匀温场条件下对超声波信号的衰减程度进行试验研究,试验结果表明40kHz的正弦波超声信号在不经过放大处理条件下,其可测温场的距离仅为160mm。     

The correlation between the SOS in trabecular bone and stiffness and density studied by finite-element analysis

For the clinical assessment of osteoporosis (i.e., a degenerative bone disease associated with increased fracture risk), ultrasound has been proposed as an alternative or supplement to the dual-energy X-ray absorptiometry (DEXA) technique. However, the interaction of ultrasound waves with (trabecular) bone remains relatively poorly understood. The present study aimed to improve this understanding by simulating ultrasound wave propagation in 15 trabecular bone samples from the human lumbar spine, using microcomputed tomography-based finite-element modeling. The model included only the solid bone, without the bone marrow. Two structural parameters were calculated: the bone volume fraction (BV/TV) and the structural (apparent) elastic modulus (E_s), and the ultrasound propagation parameter speed of sound (SOS). Relations between BV/TV and E_s were similar to published experimental relations. At 1 MHz, correlations between SOS and the structural parameters BV/TV and E_s were rather weak, but the results can be explained from the specific features of the trabecular structure and the intrinsic material elastic modulus E_i. In particular, the systematic differences between the three main directions provide information on the trabecular structure. In addition, at 1 MHz the correlation found between the simulated SOS values and those calculated from the simple bar equation was poor when the three directions are considered separately. Hence, under these conditions, the homogenization approach - including the bar equation - is not valid. However, at lower frequencies (50-300 kHz) this correlation significantly improved. It is concluded that detailed analysis of ultrasound wave propagation through the solid structure in various directions and with various frequencies, can yield much information on the structural and mechanical properties of trabecular bone.     

Embedded fiber-optic Fabry-Perot ultrasound sensor

A fiber-optic ultrasound sensor is presented. The sensor consists of a continuous length of single-mode optical fiber with a built-in Fabry-Perot interferometer. The acoustic pressure produces changes in the index of refraction along the interferometer cavity through the strain-optic effect, thus modulating the reflected power of the light propagating in the fiber. The dielectric internal mirrors that form the interferometer are fabricated by joining a fiber coating with a TiO(2) film at one end to an uncoated fiber by electric arc fusion splicing. Experimental results have been obtained for sensors embedded in plastic and graphite composite materials, using ultrasound waves in the range from 100 kHz to 5 MHz. Values for the optical phase shift amplitude as large as 0.5 rad were obtained at an acoustic frequency of 200 kHz for a 1.1-cm-long interferometer embedded in plastic.     

超声波辅助竹片染色工艺优化的研究

探讨了超声波辅助竹片染色在染液质量分数、pH值和染色温度一定的情况下,超声波功率、频率和超声波辅助染色时间等因素对竹片上染率的影响。在单因素实验的基础上,采用响应面法建立了二次回归模型,并对染色工艺进行了优化。研究结果表明:使用超声波辅助竹片染色能够提高上染率,当超声波功率为525 W、频率为30kHz、染色温度为70.0℃、染料质量分数为1.0%、染色时间为52min时,竹片的上染率可达到34.16%,比在相同工艺条件下未使用超声波辅助的提高了8.43%。     

功率超声对小麦面粉可溶性组分形成溶液过冷度的影响

应用自行设计的超声辅助冷冻循环系统,研究了频率为25kHz、不同电功率的超声对小麦面粉可溶性组分形成溶液过冷度的影响.研究结果表明,功率超声能显著地降低小麦面粉可溶性组分形成溶液中冰结晶的过冷度,促进冰晶晶核的形成.随着超声电功率逐渐增加,小麦面粉可溶性组分形成溶液过冷度逐渐减小,即成核温度随着超声电功率的增加而增加.研究结果有助于揭示超声强化食品冷冻过程中,溶解有多种无机与有机化合物的食品复杂溶液的冰结晶机理.     

Preparation of aluminosilicate precursor by mechanochemical method from gibbsite-fumed silica mixtures

Aluminosilicate (mullite) precursor was prepared by mechanochemical treatment of gibbsite and fumed silica mixtures. The effect of grinding on its structure and thermal behaviour was examined by²⁷Al and²⁹Si MAS NMR, XRD, DTA-TG and FTIR. Thermal treatment of this precursor led to the crystallization of mullite at about 1200°C via a spinel-phase.²⁷Al and²⁹Si MAS NMR spectroscopies show lowering of mullitization temperature, which is associated with increased homogeneity of the precursor. Mechanochemical treatment of gibbsite and fumed silica mixtures resulted in the formation of a more homogeneous aluminosilicate precursor.