On electro-acoustic characteristics of a marine broadband sparker for seismic exploration

The construction of major marine infrastructure projects and the exploration and development of deep-sea mineral resources require fine imaging of seabed strata and structures.The highresolution marine seismic exploration based on a high broadband sparker source is an important approach to reveal seabed stratum and reservoir structure,and identify geohazard.To optimize the performance of sparker seismic source,we investigated the electro-acoustic characteristics of spark discharge under conditions of different charging voltages and electrode numbers.Results show that the sound source level increased with the increase of the charging voltage,whereas the main frequency decreased when the charging voltage increases.In addition,it was found that the charging capacitance had more obvious influence on the main frequency than the sound source level did.Although the load energy decreased with increasing electrode number,the sound source level still increased but the main frequency decreased.Meanwhile,the primary to bubble(P/B)ratio increased with the increase of the electrode number.To gain a deeper insight into the electro-acoustic characteristics,we investigate the relationship between sound source level and power peak,from which a good correlation was observed.A more practical statistical analysis on the rise rate of current was processed,and a perfect logarithmic function was derived.Furthermore,we found that the main frequency was most possibly subjected to the electrical energy,especially the charging energy per electrode.The results indicate that the charging energy per electrode less than 10 J could increase the main frequency to above 300 Hz.At last,the main frequency could be reduced to 20 Hz when the charging energy of a single-electrode discharge was enhanced to over 4 kJ.This study shall be helpful in developing a sparker seismic source and improving the performance for marine engineering exploration and geohazard assessment.

Study on the fast elimination of smoke particle based on electro-acoustic coupling agglomeration technology

Fire smoke,which consists large amounts of fine particles,is considered as the fatal factor in fires.In this study,a fast smoke particle elimination method based on electro-acoustic coupling agglomeration technology is proposed.First,the experimental results show that the electro-acoustic coupling agglomeration has higher smoke elimination efficiency compared to single-field.The smoke transmission is much less than 80%after 30s of single acoustic or electric field action,while the coupled field reaches 90%.Then,the effects of acoustic frequency,sound pressure level and voltage on the smoke elimination characteristics are discussed.It is found that the optimal acoustic frequency is 1.5kHz.While as the sound pressure level and voltage increase,the elimination efficiency first increases and then tends to stabilize,the critical values of the sound pressure level and voltage are 135 dB and 7kV.This indicates that there is an optimal combination of the three variables.Finally,through the theoretical analysis of particle movement and the micro-morphology of agglomerates,the particle agglomeration mechanism under the electro-acoustic coupling is analyzed.This study provides a new idea for the fast elimination of fire smoke particle.

A micro-machined thin film electro-acoustic biosensor for detection of pesticide residuals

Increasing awareness concerning food safety problems has been driving the search for simple and efficient biochemical analytical methods.In this paper,we develop a portable electro-acoustic biosensor based on a film bulk acoustic resonator for the detection of pesticide residues in agricultural products.A shear mode ZnO film bulk acoustic resonator with a micro-machining structure was fabricated as a mass-sensitive transducer for the real-time detection of antibody-antigen reactions in liquids.In order to obtain an ultra-low detection level,the artificial antigens were immobilized on the sensing surface of the resonator to employ a competitive format for the immunoassays.The competitive immunoreactions can be observed clearly through monitoring the frequency changes.The presence of pesticides was detected through the diminution of the frequency shift compared with the level without pesticides.The limit of detection for carbaryl(a widely used pesticide for vegetables and crops)is2?10-10 M.The proposed device represents a potential alternative to the complex optical systems and electrochemical methods that are currently being used,and represents a significant opportunity in terms of simplicity of use and portability for on-site food safety testing.

The effect of the configuration of a single electrode corona discharge on its acoustic characteristics

A new sparker system based on pulsed spark discharge with a single electrode has already been utilized for oceanic seismic exploration. However, the electro-acoustic energy efficiency of this system is lower than that of arc discharge based systems. A simple electrode structure was investigated in order to improve the electro-acoustic energy efficiency of the spark discharge. Experiments were carried out on an experimental setup with discharge in water driven by a pulsed power source. The voltage-current waveform, acoustic signal and bubble oscillation were recorded when the relative position of the electrode varied. The electro-acoustic energy , efficiency was also calculated. The load voltage had a saltation for the invaginated electrode tip, namely an obvious voltage remnant. The more the electrode tip was invaginated, the larger the pressure peaks and first period became. The results show that electrode recessing into the insulating layer is a simple and effective way to improve the electro-acoustic energy efficiency from 2% to about 4%.

Molecular mechanisms and roles of inflammatory responses on low-frequency residual hearing after cochlear implantation

Preservation of low-frequency residual hearing is very important for combined electro-acoustic stimulation after cochlear implantation.However,in clinical practice,loss of low-frequency residual hearing often occurs after cochlear implantation and its mechanisms remain unclear.Factors affecting lowfrequency residual hearing after cochlear implantation are one of the hot spots in current research.Inflammation induced by injury associated with cochlear implantation is deemed to be significant,as it may give rise to low-frequency residual hearing loss by interfering with the blood labyrinth barrier and neural synapses.Pathological changes along the pathway for low-frequency auditory signals transmission may include latent factors such as damage to neuroepithelial structures,synapses,stria vascularis and other ultrastructures.In this review,current research on mechanisms of low-frequency residual hearing loss after cochlear implantation and possible roles of inflammatory responses are summarized.

An Acoustic Modem Featuring a Multi-Receiver and Ultra-Low Power

Wireless technology for underwater communication possesses a wide range of potential application, but it is still a relatively unexplored area in many aspects concerning modems physical design. A step towards future deployment of underwater networks is the reduction of power consumption. Therefore, asynchronous wakeup systems need to be integrated within the physical layer design while avoiding the use of additional transducers. This paper offers a practical and generic solution to adapt data reception and transmission together with asynchronous wakeup sub-systems in acoustic underwater modem architectures using a low power and low cost solution. The proposal has been implemented in a real prototype with success.

Space Charge Characteristics of Oil-paper Insulation in the Electro-thermal Aging Process

High electric field and temperatures can result in electrical property degradation of oil-paper insulation and accelerate its aging process.This paper describes the regulation of space charge in the process of electro-thermal aging.Electric field distortion and differences in characteristic parameters during electro-thermal aging are analyzed,along with the effects of electro-thermal aging on space charge from the perspective of trap energy.High temperature and an electric field are used to accelerate the aging of oil-paper,and space charge characteristics are measured using the pulsed electro-acoustic(PEA)method throughout the electro-thermal aging.Based on results obtained,it can be concluded that homo-charge injection occurs at the anode and the type of the charge injection at the cathode varies throughout the electro-thermal aging;the decrease of permittivity during aging allows for space charge injection to take place;growth of trap depth makes the space charge accumulate in the middle of the sample;and space charge accumulation after electro-thermal aging results in inner electric field distortion,which leads to large current and decreased breakdown in voltages.