The influence of air content in water on ultrasonic cavitation field

Cavitation is a complex physical phenomenon affected by many factors, one of which is the gas dissolved in the medium. Researchers have given some efforts to the influence of gas content on sonoluminescence or some specific chemical reactions in and around the bubble, but limited work has been reported about the influence on the ultrasonic cavitation field distribution. In this work, the intensity distribution of the ultrasound field in a cleaning tank has been measured with the hydrophone. After analysed and visualised by MATLAB software, it was found that the cavitation intensity distribution in degassed water was much better than that in tap water. And further study proved that degassing process can improve the cavitation effect dramatically both in intensity and scope. Finally, the cavitation fields in mediums with different gas content were measured and the specific influence of air content on cavitation field was discussed.     

Construction and calibration of a multipurpose instrument to simultaneously measure dose,voltage and half-value layer in X-ray emission equipment

This work reports on the development of a multipurpose instrument that simultaneously measures delivered dose (air kerma), peak voltage (kVp) and half value layer (HVL) in X-ray machines. The device will help control quality of X-ray equipment routinely used in diagnostic and interventional radiological procedures. The measuring device is equipped with several attenuating filters of different materials and thicknesses, and Gafchromic^® XR-QA2 radiochromic films are used as sensitive elements. The films are scanned after being irradiated and the resulting color intensities indicate a relationship between the degree of film darkening under each individual filter and the quantities of interest, i.e. air kerma, kVp and HVL. Comparing HVL values measured using the proposed multipurpose instrument with those of a reference standard ionization chamber, discrepancy reached 8.4%. As for the kVp evaluation, anomalous results were observed for low atomic number materials and small thicknesses, especially for peak voltages higher than 70 kVp. However, for materials with higher Z and reasonable thickness, the calibration curve R × kVp was quite satisfactory, being R the ratio between the color intensities obtained with two distinct filters. We have also observed a decrease in the influence of Tungsten characteristic radiation on the calibration curve. These results suggest that the proposed instrument may be satisfactorily used to routinely control quality of X-ray equipment, estimating the radiation dose resulting from the direct beam, the applied voltage across the electrodes and the half value layer.     

The effects of air temperature and humidity on the acoustic design of voice alarm systems on underground stations

Sound attenuation of air due to climatic conditions is often assumed to be constant and/or negligible in the electro acoustic design of voice alarm (VA) systems. However, air attenuation variations can be significant in large underground spaces and particularly as the frequency increases to the mid to high frequencies which are the most relevant to speech intelligibility. This investigation evaluates and quantifies the impact of the variability of the most influential climatic parameters, air temperature and relative humidity, on the performance of VA systems in underground stations. Computer simulations were employed to predict the effect of varying these climatic parameters on key performance metrics. Results demonstrated a significant increase in the values of reverberation time parameters with both temperature and humidity, at frequencies critical for speech intelligibility. Consequently the values of speech intelligibility related metrics decreased with rising temperatures and humidity. Hence, the study shows how ignoring temperature and humidity effects can lead to calculation errors in the design of VA systems. These errors could cause over-specification of the absorption required of surface materials, and the inaccurate prediction of acoustic and speech intelligibility related parameters.     

Determination of ppt levels of atmospheric volatile organic compounds in Yakushima, a remote south-west island of Japan

An analytical method was utilized to detect ppt levels of VOCs in air. The method was based on the US-EPA method TO-14, consisting of canister sampling, three module enrichment and GC/MS analysis. Target compounds included chlorofluorocarbons (four kinds), benzene and its derivatives (14), halogenated hydrocarbons (20), and others (three). The minimum detection limits of the method for the target compounds ranged from 0.016 to 0.040 ppb (0.06–0.23 μg/m³). The recoveries of the target compounds ranged from 77 to 113% and relative coefficients of variation (n=4) were 3.0–9.0%. The sampled air was stable for at least 14 days after pressurizing with humidified nitrogen gas at 200 kPa (absolute pressure). The method was applied to analyze the VOCs in the air of Yakushima, a remote island of south-west Japan where no distinct local pollution source is considered.     

Orthogonal-polarization compensation method for measuring unsteady vertical force of a bumblebee in a wind tunnel

It is important to measure the unsteady vertical force of an insect in a wind tunnel for studying the flight performance of insects. Optical method can measure it with high accuracy, but it is affected by air turbulence. An orthogonal-polarization compensation (OPC) method is developed for measuring the beating force of a bumblebee in a wind tunnel and compensating the error due to beam fluctuations induced by air turbulence. The applicability of the OPC method was confirmed by using a piezo translator to generate the tilt angle variation. The results show that by using the OPC method, the error in tilt angle measurement due to air turbulence can be decreased by about 80% compared with that using the conventional angle measurement method. The OPC method was then applied to measure the tilt angle variation caused by the beating motion of a bumblebee attached to one end of a sensor block in a wind tunnel for a wind velocity of 1.1 ms⁻¹. The results confirmed the effectiveness of this new method.     

Tailor-made derivatizing agents for carbonyl compounds using liquid chromatography

A new approach for the synthesis and application of tailor-made derivatizing agents for liquid chromatography is presented. The s-triazine ring serves as the backbone for these substances. Synthesis is performed in three steps based on substitution reactions of cyanuric chloride. A chromophor or fluorophor, a reactive group and a third moiety intended to modify the polarity of the derivatizing agent are coupled to cyanuric chloride. The three groups may be selected freely from molecules which carry functional groups which might be linked to cyanuric chloride. As an example, the synthesis and application of a respective reagent for the determination of aldehydes and ketones using HPLC with fluorescence detection is carried out. Baseline separation of the derivatives and low limits of detection (1.5×10⁻⁹ mol/l for formaldehyde, 2.0×10⁻⁹ mol/l for acetaldehyde and 3.0×10⁻⁹ mol/l for p-tolualdehyde) are obtained with the new versatile reagent.     

A 4D-sequencing approach for air traffic management

The current air traffic system is forecasted to face strong challenges due to the continuous increase in air traffic demand. Hence, there is a need for new types of organization permitting a more efficient air traffic management, with both a high capacity and a high level of safety, and possibly with a reduced environmental impact. In this article, we study a holistic approach, consisting in designing across Europe a very organized air traffic system, as opposed to free flight, to reduce costs while maintaining safety.     

Performance characteristics between horizontally and vertically oriented electrodes EHD ESP for collection of low-resistive diesel particulates

The novel electrohydrodynamically-assisted electrostatic precipitator (EHD ESP) was developed to suppress particle reentrainment for collection of low resistive diesel particulates. The collection efficiency was compared between vertically and horizontally oriented electrodes of the EHD ESP using 400 cc diesel engine. The particle size dependent collection efficiency was evaluated for the particle size ranging in 20 to 5000 nm using a scanning mobility particle sizer (SMPS) and a particle counter (PC). Both horizontally and vertically oriented EHD ESP showed an excellent suppression of particle reentrainment. However, the horizontally oriented electrode EHD ESP showed significantly improved for the particle size of 300–500 nm in comparison with vertically oriented electrode EHD ESP, resulting in more than 90% collection efficiency for all particle size range. The EHD ESP has high potential especially for highly concentrated marine diesel engine emission control.     

A novel evacuation passageway formed by a breathing air supply zone combined with upward ventilation

With the development of transportation, the tunnel has become one of the important facilities of railway, highway and subway transportation. However, fire hazards occurring inside the tunnel may incur huge numbers of casualties and property losses. In this paper, a breathing air supply zone combined with an upward ventilation assisted tunnel evacuation system (BTES) is introduced. It can be used to create a safe, smoke-free evacuation passageway out of the tunnel. The BTES is optimized to achieve high-performance. The impacts of heat release rates, fire source locations and fire detection times are also discussed.     

Laccase initiated oxidative domino reactions for the efficient synthesis of 3,4-dihydro-7,8-dihydroxy-2H-dibenzofuran-1-ones

Laccase initiated domino reactions of cyclohexane-1,3-diones with catechols using air as an oxidant afford 3,4-dihydro-7,8-dihydroxy-2H-dibenzofuran-1-ones with yields ranging from 70% to 97%.