Papers by Keyword: Frequency

Abstract: Ag/AgCl electrodes as an important sensor are used in modern clinical detection and biomedical measurement, which have been widely applied in electrocardiograph (ECG), electroencephalogram (EEG), electromyography (EMG), electricity impedance technology (EIT) and so on. In this study, the electrode pairs were gel-to-gel connected. After a stimulating current, the alternating current (AC) or the direct current (DC), was injected through the electrode pair, the electrical potential was recorded, then impedance data of Ag/AgCl electrode was obtained. The results showed that the AC impedance of electrode increased, and then gradually decreased with the increase of current size. It was found that the DC impedance data of Ag/AgCl electrode was changed greatly after the electrode pair was injected into the alternating current. With the long time continuous measurement, the AC impedance of electrode pair gradually increased within the 12 hours. However, the significant fluctuations of AC impedance were observed after 12 hours. Comparing with the AC impedance, the DC impedance of electrode pair exhibited a great increase with the increase of measurement time.

Abstract: Presented paper offers simplified equations for evaluation of residual stresses. Residual stresses are very important for evaluation of properties of steel thin-walled structures. They play a crucial role in definition of ultimate load and stiffness properties. Generally the residual stresses must be in equilibrium. In the case of statically determinate beam structures residual stresses do not have influence for natural frequency. But in case of plate structures situation is different. Relationship between residual stresses and natural frequency can be used as the base for preparation of non-destructive method for the investigation of residual stresses in thin-walled structures.

Abstract: Surface acoustic wave can be generated at the free surface of an elastic solid. Interdigital transducers (IDTs) are fabricated on the piezoelectric substrate surface that will act as electrical input and output port. When appropriate AC voltage stimulus is applied to the input transducer, surface acoustic wave will be produced. The output or receiving port will detect the incident surface acoustic wave and convert it back to a suitably filtered electrical once. For this property, surface acoustic based devices were initially developed for the telecommunication purpose such as signal filters and resonators. SAW based devices have been modified to be sensors later on from for gas detections and have been moving towards biological detections recently for its ultra-sensitivity to surface perturbation. The main component of this device is the IDTs. Recently, there are several methods to produce IDTs; Ultra-Violet (UV), deep UV lithography, Electron beam (e-beam) lithography and X-ray lithography. Although, these methods can produce very fine and accurate electrodes in term of submicron size but the costs are extremely expensive. Thus, this paper will discuss the conventional CMOS method which is much more economical to produce the applicable IDTs for the bacterial pathogens sensing purpose. Shear horizontal surface acoustic wave (SHSAW), one of the SAW based types is used in this paper as it is most suitable for the liquid based application as it has the advantage of acoustic energy is not being radiated into liquid.

Abstract: With the development of MEMS, more attention has been paid to the uniformity between the performance of the products in practical processing and the expected performance. A case study is conducted here with fixed-fixed beam and comb-drive resonator as the pattern to explore how geometry size deviation and geometry shape error influence the devices. It is discovered that the length, inclining profile and undercutting of the anchor is the key factor which influences the vibration mode of the fixed beam, and the geometry size and corrugating profile mainly affect the comb-drive resonator.

Abstract: This paper presents the study of the influence of cutting parameters on surface quality in laser cutting of metallic materials. In this paper, it is shown which of the cutting parameters have the greatest influence on the quality of the processed surfaces by measuring various roughness parameters. After the experimental research was carried out a ranking of the factors of influence on the response functions was made, also graphs of dependency to various parameters of roughness were made.

Abstract: A testing circuit of probe is designed to research the electrical properties of the probe under different loading frequencies. Sinusoidal signals of different frequencies are produced by Tektronix AFG3102 signal generator, and DSOX2022A Oscilloscope is used to measure the probe voltage,constant resistance voltage and the source voltage, so the phase between the probe voltage and constant resistance voltage can be calculated. Assumed the constant resistance is a pure resistance. Since the circuit is connected in series, so the phase between the probe voltage and the probe current can be calculated. The result reveals that the probe shows resistive when the phase between the probe voltage and the probe current is 0 ° within 200 KHz frequency. Beyond 200 KHz the phase between the probe voltage and the probe current increases to 60 ° and then declines to a steady value 40°, which shows that the probe is inductive.

Abstract: Considering the characteristics of light-weight and small-size liquid-filled pipes, the method of utilizing the fiber Bragg grating (FBG) sensor to explore the natural frequency of the pipe has been proposed. Meanwhile the natural frequencies of the tested pipe were obtained through the theoretical calculation and simulation analysis. The calculation results show that the mathematical model and computing method are reliable to calculate the natural frequencies of the tested pipe. The experiments show that the measurement results of the FBG sensor are closer to theoretical calculation results. Because of added mass of the sensor, the natural frequencies of the tested pipe are lowered by the accelerometer. However, the measurement results of the FBG sensor can better reflect the actual characteristics with a negligible mass. The FBG sensor can be applied to frequency measurement, especially to those structures affected by added mass of the sensor.

Abstract: The basic principle of sequential quadratic programming method and the concrete implementation steps in MATLAB are expounded. Sequential quadratic programming method is used for the cabin structure optimization. In the optimization, the minimal sizes of components stipulated by the rules are used as size constraints, the frequencies required by the rules are used as performance constraints and the minimum lightness of the ship are used as objective. Finite element analysis of the ship structure optimized is done and the results obtained show that both the maximum equivalent stress and the maximum shear stress meet the requirements and first three order frequencies of the cabin structure are also far away from the working frequency of propeller and host. The optimization reduces the weight of the cabin under the condition of meet the static characteristic and dynamic characteristic.

Abstract: The selection, fitting and evaluation methods of response surface functions are expounded. The parameter sensitivity analysis of the cabin is carried out. The response surface functions of the stress and the vibration frequencies are constructed through the Box-Behnken experimental design method. Fitting inspection on the response surface functions is done with correlation coefficient, correction coefficient, etc. The results show that the response surface models are very similar to the real models. Four design variables are extracted randomly as the test sample of each response surface function. The data gotten by the response surface function are compared with the data gotten by the finite element analysis. The results show that the response surface models are with high accuracy and can reflect the real test values well. These response surface models can be used for further optimization design. They are helpful in reducing the ship mass without exceeding the allowable stress and resonance.

Abstract: The problem is solved that it is hard to provide analysis formulas about the maximum equivalent stress, the maximum shear stress and the structural geometric parameters for a ship. The finite element calculation is done with orthogonal experimental design under the most dangerous case. The data obtained are used as the training and test samples to establish BP neural network models of ship’s maximum equivalent stress and maximum shear stress. With the aid of Neural network toolbox in MATLAB, the topological structure of BP neural network mapping relationship between the whole ship performance indexes and design variables is established. The training and testing are completed with the data tested by the shipyard and the correctness of this network is verified. The neural network required for further optimization design is obtained. The neural network is helpful in reducing the ship mass without exceeding the allowable stress.