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11 – 20 of over 16000Yunjuan Liu and Dongsheng Chen
The pressure exerted on the body by clothes is one important factor affecting the comfort of clothing, it is an effective method to evaluate pressure comfort by physiology and…
Abstract
Purpose
The pressure exerted on the body by clothes is one important factor affecting the comfort of clothing, it is an effective method to evaluate pressure comfort by physiology and psychology. The purpose of this paper is to measure, electroencephalography (EEG), an index of brain activity in order to examine the effect on brain activity conditions caused by oppression exerted by clothing on the body.
Design/methodology/approach
EEG power spectrum analysis was conduct to verify the electrophysiological characteristic of brain caused by pressure on the body by girdle.
Findings
Experimental results showed that the intensity of α waves in the pressure condition is decreased compared to the non-pressure condition, and the somatosensory activated by pressure of girdle mainly in occipital, frontal and parietal region of brain.
Originality/value
It was clarified that it is impossible to evaluate the clothes pressure by physiological technique of EEG, this study has enriched methods of evaluation pressure comfort.
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The purpose of this paper is to analyze the effect of pressure fluctuations on the combustion efficiency of the hydrogen fuel injected into the supersonic oxidizing cross flow…
Abstract
Purpose
The purpose of this paper is to analyze the effect of pressure fluctuations on the combustion efficiency of the hydrogen fuel injected into the supersonic oxidizing cross flow. The pressure fluctuations are imposed on inlet air flow and also on the fuel flow stream. Two different situations are considered: the combustion chamber once without and again with the inlet standing oblique shock wave.
Design/methodology/approach
The pressure fluctuations are imposed on inlet air flow and also on the fuel flow stream. Two different situations are considered: the combustion chamber once without and again with the inlet standing oblique shock wave. The unsteady turbulent reacting flow solver is developed to simulate the supersonic flow field in the combustion chamber with detail chemical kinetics, to predict the time-variation of the combustion efficiency due to the imposed pressure fluctuations.
Findings
The results show that the response of the reacting flow field depends on both the frequency of fluctuations and the existence of the inlet shock wave. In addition, the inlet standing shock wave has some attenuating role, but the reacting flow shows an amplifying role on imposed oscillations which is also augmented by imposing anti-phase fluctuations on both inlet and fuel flow streams.
Originality/value
This study is performed to analyze the instabilities in the supersonic combustion which has not been considered before in this manner.
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Zhenzhen Shang, Wendong Zhang, Guojun Zhang, Xiaoyong Zhang, Lansheng Zhang and Renxin Wang
The problem of port and starboard ambiguity will exist when only utilize the vector or scalar parameters. Meanwhile, the amplitude-phase error between the vector and scalar can…
Abstract
Purpose
The problem of port and starboard ambiguity will exist when only utilize the vector or scalar parameters. Meanwhile, the amplitude-phase error between the vector and scalar can also cause this problem. In this paper, a compound MEMS vector hydrophone which contains cilia vector microstructure and piezoelectric ceramic tube has been presented to solve the problem. Compared with traditional MEMS vector hydrophone, the compound MEMS vector hydrophone can realize the measurement of sound pressure and vibration velocity simultaneously.
Design/methodology/approach
A compound MEMS vector hydrophone has been presented. The unipolar directivity of the combined signal which combine the acoustic pressure and vibration velocity is used to achieve the direction of arrival (DOA). This paper introduced the working principle and the target detection mechanism of the compound vector hydrophone. The amplitude and phase error are analyzed and corrected in the standing wave tube. After that, the authors use beam-forming algorithm to estimate the DOA.
Findings
The experimental results in the standing wave tube and the external field verified the vector hydrophone's directional accuracy up to 1 and 5 degrees, respectively.
Practical implications
The research of compound vector hydrophone plays an important role in marine acoustic exploration and engineering applications.
Originality/value
This research provides a basis for MEMS hydrophone directivity theory. The compound vector hydrophone has been applied in the underwater location, with a huge market potential in underwater detection systems.
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The purpose of this paper is to demonstrate the non-destructive methods for detection and localization of interconnection structure discontinuities based on the signal analysis in…
Abstract
Purpose
The purpose of this paper is to demonstrate the non-destructive methods for detection and localization of interconnection structure discontinuities based on the signal analysis in the frequency and time domain.
Design/methodology/approach
The paper deals with the discontinuity characterization of interconnection structures created on substrates used for electronics, and methods for their detection and localization, based on the frequency analysis of transmitted signals. Used analyses are based on the theoretical approach for the solution of discontinuity electrical parameters and are the base for diagnostic methods of discontinuity identification.
Findings
The measurement results of reflection parameters, frequency spectrums of transmitted signals and characteristic impedance values are presented on test samples containing multiple line cracks and their width reduction.
Practical implications
Obtained results can be used practically, not only for the detection of transmission lines discontinuities on printed circuit boards but also in other applications, such as the quality assessment of bonded joints.
Originality/value
Developed methods allow the quick identification and localization of particular discontinuities without the destruction of tested devices.
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Khader Zelani Shaik, Siddaiah P. and K. Satya Prasad
Millimeter wave spectrum represents new opportunities to add capacity and faster speeds for next-generation services as fifth generation (5G) applications. In its Spectrum…
Abstract
Purpose
Millimeter wave spectrum represents new opportunities to add capacity and faster speeds for next-generation services as fifth generation (5G) applications. In its Spectrum Frontiers proceeding, the Federal Communications Commision decided to focus on spectrum bands where the most spectrums are potentially available. A low profile antenna array with new decoupling structure is proposed and expected to resonate at higher frequency bands, i.e. millimeter wave frequencies, which are suitable for 5G applications.
Design/methodology/approach
The presented antenna contains artificial magnetic conductor (AMC) surface as decoupling structure. The proposed antenna array with novel AMC surface is operating at 29.1GHz and proven to be decoupling structure and capable of enhancing the isolation by reducing mutual coupling as 8.7dB between the array elements. It is evident that, and overall gain is improved as 10.1% by incorporating 1x2 Array with AMC Method. Mutual coupling between the elements of 1 × 2 antenna array is decreased by 39.12%.
Findings
The proposed structure is designed and simulated using HFSS software and the results are obtained in terms of return loss, gain, voltage standing wave ratio (VSWR) and mutual coupling. The S-Parameters of each stage of design is tabulated and compared with each other to prove the decoupling capability of AMC surface in antenna arrays.
Originality/value
The proposed structure is designed and simulated using HFSS software, and the results are obtained in terms of return loss, gain, VSWR and mutual coupling. The S-Parameters of each stage of design is tabulated and compared with each other to prove the decoupling capability of AMC surface in antenna arrays.
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Junfeng Sun, Haitao Zhang, Guangyuan Wu, Zuoqiang Liu, Yuping Feng and Minghao Jia
In order to give full play to the function of noise reduction of asphalt pavement, it is necessary to understand its internal sound absorption mechanism. Therefore, the purpose of…
Abstract
Purpose
In order to give full play to the function of noise reduction of asphalt pavement, it is necessary to understand its internal sound absorption mechanism. Therefore, the purpose of this study is to establish a micro model of the pore structure of asphalt mixture with the help of finite element method (FEM), discuss the noise reduction mechanism of asphalt pavement from the micro perspective and analyze and evaluate the noise attenuation law of the pore structure.
Design/methodology/approach
The FEM was used to establish the microscopic model of the pore structure of asphalt mixture. Based on the principle of acoustics, the noise reduction characteristics of asphalt pavement were simulated. The influence of gradation and pore characteristics on the noise reduction performance of asphalt pavement was analyzed.
Findings
The results show that the open graded friction course-13 (OGFC-13) has excellent performance in noise reduction. The resonant sound absorption structure composed of its large porosity can effectively reduce the pavement noise. For asphalt concrete-13 (AC-13) and stone matrix asphalt-13 (SMA-13), the less resonant sound absorption structure makes them have poor sound absorption effect. In addition, the variation rules of noise transmission loss (TL) curve and sound absorption coefficient curve of three graded asphalt mixtures were obtained. At the same time, the peak noise reduction values of OGFC-13, AC-13 and SMA-13 were obtained, which were 650Hz, 1000Hz and 800Hz, respectively.
Originality/value
The results show that the simulation results can well reflect and express the experimental results. This will provide a reference for further exploring the sound absorption mechanism and its variation rule of porous asphalt pavement. It also has some positive significance for the application of low noise asphalt pavement.
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ANTHONY D. LUCEY and PETER W. CARPENTER
A numerical method is developed which can simulate the interaction between a finite compliant panel and an unsteady potential flow. A boundary‐element technique yields the flow…
Abstract
A numerical method is developed which can simulate the interaction between a finite compliant panel and an unsteady potential flow. A boundary‐element technique yields the flow solution whilst finite‐differences are used to solve the wall dynamics; these are then coupled to generate a fully interactive wall/flow system. Thus, the evolution of any wall disturbance can be followed. Parallel computing is appropriately employed and a stability investigation of a realistic compliant panel is carried out. Three‐dimensional flexural waves are found below a critical flow speed whilst beyond this threshold, essentially two‐dimensional unstable divergence waves are found. The form of divergence shows good agreement with that seen in experimental studies. The versatility of this new method will permit the investigation of a wide variety of single‐ and multi‐panel configurations subject to different forms of excitation.
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Afsin Üstündagˇ, Reinhold Ludwig, Peter L. Levin, Joachim Schmidt and Peter Hagedorn
Ultrasonic motors have attractive properties which compare favourably with electromagnetic motors for certain applications. Their operation is based on piezoelectrically exciting…
Abstract
Ultrasonic motors have attractive properties which compare favourably with electromagnetic motors for certain applications. Their operation is based on piezoelectrically exciting bending waves in the stator and transferring energy to the rotor via friction. Prototypes are typically constructed by trial and error; theoretical studies have proved to be difficult. Describes a two‐dimensional model for the stator of a travelling wave ultrasonic motor. The authors have developed a finite element program that is capable of modelling piezoelectric driven systems in the time domain, and their objective is to simulate the excitation of the travelling waves in the stator. They are in fact able to simulate travelling waves. Although the plane strain model cannot account for all excitation modes, they observe the elliptical motion of the material particles on the surface, implying that rotor motion can be mechanically induced.
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Ambrish Maurya and Pradeep Kumar Jha
This investigation aims to analyze the steel-flux interface level fluctuation because of electromagnetic stirring and its process parameters in a continuous casting billet mold.
Abstract
Purpose
This investigation aims to analyze the steel-flux interface level fluctuation because of electromagnetic stirring and its process parameters in a continuous casting billet mold.
Design/methodology/approach
An un-coupled numerical model for electromagnetic field generation and a coupled numerical model of electromagnetic field and two-phase fluid flow have been developed. The two-phase fluid flow has been modeled using volume of fluid method, in which externally generated time-varying electromagnetic field is coupled and analyzed using magnetohydrodynamic method. Top surface standing wave stability criteria are used to study the criticality of interface stability.
Findings
Results show that application electromagnetic field for stirring increases the interface level fluctuation, specifically at the mold corners and near the submerged entry nozzle. The increase in current intensity and stirrer width barely affect the interface level. However, interface level fluctuation increases considerably with increase in frequency. Using stability criteria, it is found that at 20 Hz frequency, the ratio of height to wavelength of interface wave increases much above the critical value. The iso-surface of the interface level shows that at 20 Hz frequency, mold flux gets entrapped into the liquid steel.
Practical implications
The model may be used during optimization of in-mold electromagnetic stirrer to avoid mold flux entrapment and control the cast quality.
Originality/value
The study of mold level fluctuation in the presence of in-mold electromagnetic stirrer has rarely been reported. The criticality of stirrer process parameters on level fluctuation has not been yet reported. This study lacks in experimental validation; however, the findings will be much useful for the steelmakers to reduce the casting defects.
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