Experimental investigation of time-dependent cavitation in an oscillatory squeeze film

The occurrence of time-dependent cavitation and tensile stress in an oscillatory oil squeeze film were investigated experimentally. The test apparatus was a simple thrust bearing consisting of two parallel circular plates separated by a thin viscous oil film. During the test, one plate was at rest while the other (transparent) oscillated in a direction normal to its surface. This test configuration was chosen to avoid the rotational motion and complicated geometry of a squeeze film journal bearing. The frequency of oscillation was in the range of 5 to 50 Hz and was controlled by an electro-magnetic exciter. The process of cavity formation and its subsequent development was recorded by a high-speed video camera. Concomitant pressure in the oil film was measured both within and without the cavitation region. It was found that both tensile stress and cavities existed in a squeeze film under certain working conditions.     

In situ conversion electron Mössbauer spectrometry applied to the study of the corrosion products formed in solution

The new gas-flow type detector chamber was designed for thein situ CEM spectrometric study of solid-liquid interface. The chamber has both a proportional counter and a solution cell. A sample was immersed in the solution of the lower part of the chamber and a CEM spectrum was collected in the upper after emersion of the sample by continuous rotation of it. It was found that a control of a revolution rate of a sample and the counting gas flow rate was important for good performance. Thein situ CEMS was applied to the analysis of corrosion products formed on a steel in various solutions and its usefulness was demonstrated.     

Experimental study of a quasi-optical cavity with slotted output mirror

This paper describes an experimental study of a quasi-optical cavity to be used in qyrotrons. The cavity configuration was designed so that its output wave could pass into a quasi-optical transmission line. The test cavity was coaxially composed of a pair of annular mirrors, one of which was a curved conical mirror and the other was a plane mirror having a radial slot array for wave output. A mode excited in the cavity at 56.4 GHz was observed by detecting the radiation wave that leaked out through the slotted mirror. It was shown that the present slotted mirror served as a partially and uniformly transparent mirror to radiate the output wave with the same mode as in the cavity.     

高温非平衡条件下氟原子亲电动力学的激波管研究

用激波管方法研究了氟原子亲电动力学.利用反射激波加热获得离子化气体,随后经冷却速度达106K/s的强稀疏波冷却,离化气体将经历以电子复合为主的非平衡过程.用Langmuir静电探针监测反射激波后离子浓度随时间的演变,分析了探针工作状态,引入了探针鞘层内的弹性散射修正.测定了温度在1200～2200K以氩气为碰撞第三体的F原子与电子复合速率系数,讨论了温度依赖关系.     

Application of a non-thermal surface plasma discharge in wet condition for gas exhaust treatment: NOx removal

This paper deals with the NOx removal with the help of a non-thermal surface plasma discharge in wet conditions. The gas treatment device consisting of a surface discharge and a wet-type reactor, was characterized through FTIR and electrical measurements. The ability of the proposed system for the cleaning of gas exhaust was studied. NOx as gaseous pollutant was decomposed effectively. To improve the chemical conversion, a coil was inserted in the electric circuit then a catalyst was placed in the plasma area. Results showed an improvement of NOx removal by an increase in radical species produced and synergistic effect, respectively.     

Surface aided replica exchange algorithm applied to the prewetting transition

A novel algorithm, termed surface aided replica exchange (SARE), was introduced in which the fluid–surface interaction was varied in order to generate different replicas in a particular ensemble. Exchange between replicas was allowed with a probability of acceptance obtained by imposing detailed balance. The method was implemented in a modified isothermal-isobaric ensemble that permitted precise characterization of the prewetting line of a simple adsorbed fluid. The prewetting line for each surface was characterized by computing the adsorption of the fluid as a function of pressure, and the wetting temperature estimated for each surface.     

Evaluation of an oral carrier system in rats: bioavailability and gastrointestinal absorption properties of curcumin encapsulated PBCA nanoparticles

A new oral delivery system, polybutylcyanoacrylate nanoparticles (PBCNs), was introduced to improve the oral bioavailability of curcumin (CUR), a poorly soluble drug. The formulation was optimized by orthogonal design and the optimal PBCNs loading CUR exhibited a spherical shape under transmission electron microscopy with a range of 40?C400?nm. Physicochemical state of CUR in PBCN was investigated by X-ray diffraction and the possible structure changes occurring in CUR after conjugating with polybutylcyanoacrylate were studied with FTIR. The results indicated that CUR in PBCN was in a non-crystalline state and CUR was encapsulated in PBCN without chemical reaction. The oral pharmacokinetic study was conducted in rats and the relative bioavailability of CUR encapsulated PBCNs to the crude CUR was more than 800%. The in situ absorption experiment in rat intestine indicated the absorption was first order with passive diffusion mechanism. The absorption results in various segments of intestine showed that the main absorption sites were ileum and colon. It can be concluded that PBCNs as an oral carrier can significantly improve the oral absorption of a poorly soluble drug.     

新型准光腔同轴虚阴极振荡器的研究

 集合准光腔型虚阴极振荡器和同轴虚阴极振荡器的优点,设计了一种新型的准光腔同轴虚阴极振荡器。采用自由电磁振荡理论分析了3反射镜准光学谐振腔中的场分布,并用2.5维全电磁PIC程序对该器件进行了粒子模拟。在输入电压为600 kV,二极管电流为50 kA的条件下,得到主频为7.0 GHz,峰值功率超过6 GW的功率输出,其平均功率达2.5 GW,平均束波转换效率为8.3%。     

一种电流引线的热力学计算方法

从超导磁体气冷电流引线的热平衡方程出发,对电流引线进行分段,提出了一种较为精确计算电流引线长横比及由电流引线末端流入低温容器热量的计算方法;电流引线中氦气流阻是设计电流引线时一个很重要的参数,由于电流引线片形状很复杂,计算其中氦气流阻比较好的方法是采用CFD软件Fluent。氦气模型单元数很庞大,因此对氦气模型进行了简化和分段,相邻两段模型间采用流量和压力边界条件进行耦合。     

Experimental investigation of time-dependent cavitation in an oscillatory squeeze film

The occurrence of time-dependent cavitation and tensile stress in an oscillatory oil squeeze film were investigated experimentally. The test apparatus was a simple thrust bearing consisting of two parallel circular plates separated by a thin viscous oil film. During the test, one plate was at rest while the other (transparent) oscillated in a direction normal to its surface. This test configuration was chosen to avoid the rotational motion and complicated geometry of a squeeze film journal bearing. The frequency of oscillation was in the range of 5 to 50 Hz and was controlled by an electro-magnetic exciter. The process of cavity formation and its subsequent development was recorded by a high-speed video camera. Concomitant pressure in the oil film was measured both within and without the cavitation region. It was found that both tensile stress and cavities existed in a squeeze film under certain working conditions.     

Application of pressure sensitive paint measurement to a low-solidity cascade diffuser of a transonic centrifugal compressor

A pressure sensitive paint (PSP) measurement has been known as a pressure field measurement technique based on the oxygen quenching phenomenon of luminescence of specific luminophores. A PSP measurement was applied for pressure field measurement in a low-solidity circular cascade diffuser of a single-stage transonic centrifugal compressor with 5 in pressure ratio for HFC134a gas. The oxygen concentration was about 500 ppm. Ru (bath-phen) was adsorbed on a silica-gel thinlayer chromatography sheet, and the sheet was pasted onto the side-wall between the cascade vanes. A drastic change in luminescent intensity was recognized during a surge condition. Also the pressure variations based on luminescent intensity agreed well with the pressure fluctuations measured using a semiconductor pressure sensor with high-frequency-response. It was shown that a PSP measurement worked well to investigate the unsteady pressure fields in a circular cascade diffuser of a transonic centrifugal compressor. Moreover, the time response of PSP becomes clear as a problem to be overcome for the present.     

Comodulation masking release for speech stimuli.

This study sought to determine whether speech recognition in a modulating noise background can be facilitated by a process attributable to comodulation masking release (CMR). Experiment 1 examined the masked identification of six filtered vowels as a function of the number of comodulated noisebands present. A benefit of increased number was observed, consistent with an interpretation in terms of CMR, although it could not be certain that the basis of the discrimination was word recognition in the semantic sense. Experiment 2 made use of a forced-choice rhyming test in which the response foils differed only in a single filtered consonant; again, the measure of interest was performance as a function of the number of comodulated noisebands present. No evidence for a suprathreshold CMR was observed. Experiment 3 made use of open-set sentence material and employed a different paradigm, which allowed a measure of CMR in terms of the difference between thresholds in correlated and uncorrelated noise to be determined. While a CMR for speech detection was observed, no CMR for speech recognition was found. It was concluded that CMR is most evident in masked detection tasks and that diminishing returns are encountered as the signal-to-masker ratio is raised.     

Design of optimal configuration for generating A0 Lamb mode in a composite plate using piezoceramic transducers

This work concerned a technique for a health monitoring system based on the generation and sensing of Lamb waves in composite structures by thin surface-bonded piezoceramic transducers. The objective was to develop transducers that are adapted for the damage detection in orthotropic composites. The key problem with the investigated Lamb waves was to select a mode to be sensitive to the damage. A hybrid modeling technique was therefore used to conceive transducers that were adapted to achieve such a feature. This modeling technique enabled studying the influence of the transducer characteristics on the Lamb waves propagating in orthotropic plates. It was demonstrated that a Lamb mode could be generated dominantly to other modes by using a multi-element transducer. The effectiveness of this technique was successfully verified experimentally on composite plates. It was shown that the dominant Lamb mode, obtained by use of dual-element transducers, was an appropriate mode for successfully detecting a damage in composites.     

Consistency of the preoperative and intraoperative diagnosis of benign vocal fold lesions

The purpose of this retrospective study was to compare the preoperative and intraoperative diagnosis of benign vocal fold lesions for consistency. The diagnosis was made in 221 consecutive patients with benign vocal fold lesions for which a microlaryngoscopy was carried out in a general ENT-clinic. The preoperative diagnosis was obtained by both white halogen and stroboscopic light. The intraoperative diagnosis was obtained by direct microscopic visualization and palpation of the vocal folds. In 36% of the patients, the preoperative diagnosis was changed intraoperatively. In 31% of the patients, a lesion was missed at the preoperative examination and a lesion was diagnosed only during microlaryngoscopy. Bilateral lesions were found in 53% of the patients preoperatively, and in 82% of the patients intraoperatively. Specially intracordal lesions constituted a diagnostic pitfall. Because the preoperative and intraoperative diagnosis often differed, both the patients and the ENT-surgeon must keep an open mind about what may need to be done at surgery.     

Effect of hardness and composition gradients on Barkhausen emission in case hardened steel

The effect of gradients in hardness, structure and composition in the surface layers on magnetic Barkhausen noise (MBN) was investigated in two widely used low alloy steels. One material was case hardened by induction hardening. The other was case carburised. Similar hardness profiles were produced by the two treatments. It was found that the variation in structure and hardness through the case in the induction-hardened steel had a minor effect on the MBN profile. In contrast, the inhomogeneity in the case-carburised material showed up clearly. This took the form of a broadened or two-peak MBN profile. When the surface layer containing the case was removed by etching, the broadened profile was replaced by a profile with a single peak. It is concluded that the shape and position of the MBN profile is significantly affected when a gradient in microstructure is induced by a gradient in carbon content. On the other hand, a gradient in microstructure induced by heat treatment with a constant carbon level has much less affect on the MBN profile for the induction-hardened steel.     

Effect of ultrasound on leaching of lead from landfilled metallurgical residues

The potential of ultrasound as a process intensification technique in the extraction of lead from a landfilled metallurgical residues is explored. The silent or non-sonicated process makes use of acidic sodium chloride as the leachate with lead leaching in the range of 45% if a three-stage process is followed. The mixture was sonicated in a batch setup manufactured in-house. The yield obtained in silent conditions at the end of 240 min was already obtained within 30 min with ultrasound, which by itself was an improvement of 8 times. The yield of the process as a whole was improved by 19–26%. The reason for this improvement was investigated with respect to the reaction kinetics. The physical effect of ultrasound on the particle size was also studied by laser diffraction analysis. Finally, the improvement when using ultrasound in a multi-stage process was studied and it was shown that yields being obtained at the end of the 3rd stage in silent conditions is already obtained in the second stage when using ultrasound with 20% more selectivity.     

One-dimensional modelling of TEA CO2 lasers

One-dimensional modelling was applied to a TEA CO₂ laser whose discharge volume was divided into multiple narrow channels. Each of these channels was regarded as a separate laser channel in which a circuit-coupled kinetic model was employed to compute its discharge formation, and a rate-equation model was used to predict its laser output. Such a one-dimensional model could be employed to study the spatial variation in the transverse discharge—due mainly to a one-sided ultraviolet-preionization and the electrode contour—and its effects on the laser output. Reasonably good agreement was obtained between the one-dimensional model and the experiment, which employed a pair of Ernst profile electrodes.     

钛宝石飞秒激光器用色散补偿Gires-Tournois镜的研究

根据钛宝石飞秒激光器的色散补偿要求设计了单次反射平均补偿量为-60 fs²的GT(Gires-Tournois)镜,采用离子束辅助沉积技术结合光学监控技术制作了器件.用分光光度计对650—950 nm波段薄膜反射率进行测试,结果表明反射率测试曲线与设计曲线十分符合,同时利用白光干涉系统对群延迟色散进行了测试,测试结果与设计符合得很好,实际的色散曲线振荡基本控制在±20 fs²以内.应用该GT镜进行钛宝石飞秒激光系统的色散补偿,取得了很好的锁模效果,得到了29 fs的超短脉冲. 关键词： 色散补偿 钛宝石飞秒激光器 GT镜 离子束辅助沉积     

Nonlinear resonance induced by the higher spatial coherence harmonics

The spectrum of a test field in a three-level ArII Λ scheme in the presence of a strong standing wave on the adjacent transition was measured. The known light-induced transparency peak was observed; the peak shifted as the detuning of the strong field was varied. In addition, a new resonance in the line center arose whose position was independent of the strong-field frequency. The resonance was caused by the higher spatial coherence harmonics on the test transition. Perturbation theory for a low and numerical calculations for a high standing wave intensity give qualitative agreement with experiment and substantiate the nature of the central transition.     

W波段回旋管宽带低损耗输入耦合系统

给出了一种十字交叉型TE□10-TE○01宽带模式转换器的设计原理,同时完成了一套W波段低损耗输入耦合系统的设计方案。根据该设计方案在电磁模拟软件HFSS中建立三维模型进行优化仿真。得到了衰减为0.14dB、最大驻波比为1.388、带宽为10GHz的高性能TE□10-TE○01宽带模式转换器。同时计算得到整套传输系统的衰减小于1dB,远小于采用矩形波导TE10模式的衰减(约15dB),大大提高了传输效率,降低了能量损耗。实际加工得到了一对模式转换器,经测试可得其衰减为1dB左右,整套系统的衰减约为3dB,与矩形波导(衰减约为15dB)相比,有了很大的提高。