Search

The motivation of this study is to present a numerical simulation for identification of the loss of prestress force in prestressed concrete structures using electro-mechanical impedance responses. In order to achieve the objective, the following approaches are implemented. Firstly, the theories of electro-mechanical impedance responses using PZT (Lead Zirconate Titanate) sensor and four damage indices based on the change in the impedance responses are outlined. Secondly, a finite element model of prestressed concrete beam’s cable anchorage system is simulated by using ANSYS software. The loss of prestress force is investigated with different levels. The reliability of the numerical results is verified by comparison to pre-published experimental results. Finally, the damage indices are determined to identify the loss of prestress force in beam. The results from this study show that the impedance-based damage detection method is high effectiveness for monitoring the loss of prestress force in prestressed concrete structures.

The study aimed to investigate the effects of postoperative position of knee on blood loss and functional recovery after total knee arthroplasty (TKA). We enrolled patients who underwent TKA from 2017 to 2019 in our department with osteoarthritis of the knee in this prospective and randomized study. The patients were randomly allocated to flexion or extension group. In the flexion group, the affected leg was elevated by 30 degrees at the hip and the knee was flexed by 30-degree, postoperatively, while in the extension group, the affected knee was fully extended postoperatively. Patients' data related to postoperative blood loss, Hospital for Special Surgery scores, pain intensity, usage of analgesic drugs, circumference of knee, and range of motion (ROM) of knee were recorded to assess the influence of postoperative leg position on clinical outcomes. Although the transfusion rate was similar between the two groups (p > 0.05), other parameters related to blood loss (including total blood loss, hidden blood loss, usage of analgesic drugs, and postoperative circumference of knee) were significantly lower in the flexion group than those in the extension group (p 0.05). The length of hospital stay and medical expenses were similar in both groups. Incidence of wound infection and other complications was also similar in both groups (p > 0.05). Elevation of the hip by knee flexion of 30 degrees is an effective and simple method to reduce blood loss after TKA, and contributes to reduction of the dosage of analgesic drugs in the early postoperative period. The routine application of the present protocol also did not increase medical costs and length of hospital stay after TKA.

Interdigital transducer and signal transmission in surface acoustic wave pressure sensor design is one of the difficulties in sensor design. The transmission antenna is an important design indicator to determine the wireless function of the sensor. In this paper, we simulated the design of the interdigital transducer of surface acoustic wave pressure sensor through COMSOL and analyzed the relationship between the eigenfrequency of the single-pair interdigital model and the interdigital electrode. Then, we obtained the design of the interdigital electrode with error of 0.01 MHz. We also simulated the size, bandwidth, impedance matching, and other parameters of antenna through high frequency structure simulator, and a matching dipole transmission antenna was designed and miniaturized. When the bandwidth is satisfied, the control matching impedance error is within [Formula: see text], and it is verified that the antenna satisfies the signal transmission requirement of the surface acoustic wave pressure sensor. This design provides a more comprehensive approach to the design of interdigital transducers and signal transmission for the field of surface acoustic wave measurement pressure.

Purpose Being the key sensitive elements of the micro-electromechanical systems (MEMS) resonant sensors, performance of the double-ended tuning fork (DETF) will affect precision of the whole sensor greatly. Currently, most of the research on DETF is concentrated on ideal theory or simply mentioned as part of the sensor. But, in most engineering occasions, there exists many factors such as the additional mass, air damping and fabrication process, etc. However, few references are individually aimed at the mechanical characters of DETF. To choose the suitable DETF, it is important to solely research and measure the performance of this element. Design/methodology/approach In this paper, the authors combine the practical engineering applications and deduce the calculation method of sensitive element’s resonant frequency under various circumstances. The authors also design a force-generating system to make the loading simulation and verify the correctness of theory. Findings On the basis of Euler–Bernoulli theory and Rayleigh’s equation, frequency theories of DETF under four different situations have been deduced. A force-generating device is designed and fabricated to measure the mechanical characters of the DETF. The experiments using force-generating system, DETF, the high performance laser vibrometer and oscillograph are carried out. It verifies the correctness of theory. Originality/value Currently, most of the research on DETF is concentrated on ideal theory or simply mentioned as part of the sensor, and few references are individually aimed at the mechanical characters of DETF. Combining the practical engineering applications, the authors deduced the frequency theories of DETF. A force-generating system is designed and fabricated to measure the mechanical characters of the DETF, and the experiment results match the theoretical results very well.

This paper presents the outputs of a Ministry of Science and Technology-funded national research project on fisheries value chain entitled “Developing Feasible and Comprehensive Policies for Sustainable Fisheries Development in Vietnam” completed in 2019. It was carried out to map the Vietnamese tuna value chain in terms of value chain description, including actors, material flows, volume, knowledge and information, relationships, linkages and trust, and values at different levels of the chain. The point of entry for undertaking this analysis was to identify specific income increasing interventions for fishers to achieve the project objective of better management of tuna fisheries and to improve socio-economic conditions of tuna fishing communities in Vietnam. Three South Central provinces of Binh Dinh, Phu Yen, Khanh Hoa were chosen for the investigation of the tuna value chain. This study was completed in four main phases, which consist of interview surveys, focus group discussions, individual key informant interviews, and a validation workshop. Four hundreds fishers, nineteen middlemen and traders, five processors, three wholesalers, and eight retailers were interviewed in the three investigated provinces during 2018. Several policy recommendations to increase the income and improve the position of fishers in the tuna value chain were proposed, which include (i) the collaboration among fishers to take advantage of purchasing input materials; (ii) the improvements on the handling and maintenance of tuna quality to increase fishers’ income; (iii) the establishment of tuna auction center to decrease financial detriment to fishers, increase their access to public and transparent market information, and strengthen their position in the chain; (iv) the formulation of savings, credit, and microfinance schemes to diversify forms of capital access for fishers; (v) the suggestion on a fair share of profits among shipowners, captains and cruise workers to reduce the vulnerability of the poor and increase the incentive for properly managing the tuna fisheries in Vietnam.

Micro-electromechenical Systems (MEMS) gyroscope is widely used in many occasions to measure the angular speed of the moving objects and attracts the attentions of many research institutions all over the world. This kind of sensor possesses the advantages of high degree of integration, low cost and consumption of power. This paper first introduces the research development of silicon MEMS gyroscope since eighties of last century; the researches of many institutions such as Draper Laboratory and UC Berkeley are mentioned and different design principles, control methods and structures are presented. This review then presents the key theories and technologies of the sensor and some research results of them. In additional, some recent new applications of MEMS gyroscope are also been introduced in this paper such as wearable motion capture system and micro inertial measurement unit. Finally, according to the review, some views of silicon MEMS gyroscope and its future prospects are put forwarded.

Dynamic characteristics of resonators for MEMS resonant vibratory gyroscopes are studied in this paper. Firstly, a small parameter method is introduced to analyze the dynamic characteristic stability of the resonator. It is proved that geometrical parameters of the resonator have to be regulated to match corresponding stability analysis. In order to verify the rationality of the theoretical parameters design, static calibration experiment is built using a resonator sample. It is concluded from the calibrated result that the error between theory design and experiment is 0.03 %, which shows they have a good match, and the design of resonator is reasonable. Moreover, the method of small parameter perturbation is considered to analyze the input–output dynamic characteristic. Under some transformations, which make input angular velocity and output resonant frequency shift possess a good linear relationship. In order to verify the correctness of the theory analysis method, dynamic frequency output characteristic experiment is built using the resonant vibratory gyroscope sample. It is concluded from the dynamic measurement result that the correlation coefficient of output fitted curve is 99.95 %, the measured algorithm scale factor of the gyroscope sample is 0.2116, which prove theoretical analyzing approach is feasible.

A method is introduced to measure the micro-capacitance for MEMS comb actuators whose value is in pF even fF magnitude. This method uses so called peak detection measuring technology to realize this purpose. It is mainly composed of the signal generating circuits, C/V (Capacitance/Voltage) converting part, peak detector circuits and the digital solution element. In order to verify the correctness of the design, detailed theory analysis and simulation are made for every composed portion and corresponding mathematical model is built. It is concluded from the analyzed result that precision of the system can reach 237 aF for 0.98–2 pF measuring range. When corresponding measuring electric circuits is fabricated and debugged, high precision calibration device named Agilent E4980A is used to calibrate it. It is concluded from the calibrated result that the output voltage of the measurement circuit and the micro capacitance have good linear relationship, which verifies the correctness of the pertinent theory. Finally, in order to verify the correctness of the design, dynamic characters of a resonant MEMS gyroscope, which is fabricated with bulk technology and bonding process, is tested with this device. It is concluded from the measured result that relative error of the resonant frequency between the ideal value and the measured result is just 0.02%. Quality factor of this sensor is 312.5. Experimental results indicate this scheme is feasible to measure the static and dynamic characters of micro capacitors.

This paper introduces a new theoretical model of plate capacitor for MEMS comb actuator. In this model, bulk fabrication process and edge effect are both considered using integration method and conformal transformation theory. In order to verify the correctness of the model, FEM software is used to calculate the value of the capacitance of the MEMS comb actuator. The simulated result is 1.441 pF. Relative errors to the model calculated result 1.401 pF and ideal model calculated result 1.267 pF are 2.78 and 12.07% respectively. Then, high precision capacitance measuring device is used to measure the micro-fabricated comb actuator. The tested result is 1.517 pF. Its relative error to the rectified value is 7.65%, much less than the relative error to ideal result 16.48%. This further indicates the correctness of the rectified model.

The far field formulation of an arbitrarily oriented electric dipole located at the interface of layered anisotropic half space is deduced based on the reciprocity theorem. Then, considering the optical path difference of the directed wave and reflected wave, the formulation of the electric dipole located above the interface of layered anisotropic half space is discussed. The General Transmitting Matrix (GTM) method is used to compute the reflection coefficients of anisotropic layered half space. Finally, numerical example of the electric dipole located at the interface of anisotropic half space is given. The numerical results show that this method can be used in the fast computation of far radiation field of an arbitrarily oriented dipole above layered anisotropic half space.

Aiming at the disadvantages of commonly used RFID (Radio Frequency Identification devices) and two-dimensional bar code system, we design the cigarette counterfeiting system that based on RFID and two-dimensional barcode technology. The core center of this system is the fact or fiction confirmation for the cigarette. This article will clearly describe the system operation principle based on the technology of RFID and two-dimensional bar code, counterfeiting system design and software design. Moreover, analyze the system security. From the result, it is easily be concluded that this method is effectively and is adapt to cigarette counterfeiting, and fully protect the rights and interests of sellers and consumers.

In this paper, the transient far radiation field of an arbitrarily electric dipole located above the lossy half-space is computed. The directed wave is obtained by analytic method and the reflected wave can be obtained by using the Fourier transform and the inverse Fourier transform with the consideration of time delay and the reflection of the lossy halfspace. Then the far radiation field of the complex antenna can be obtained by using the superposition principle. At last, the transient far radiation field of a helical antenna located above lossy half-space is computed.

Based on the reciprocity theorem, the far field formulation in the frequency domain of an arbitrarily oriented electric dipole located above the interface of the half space is deduced. Then the radiation patterns of an arbitrarily oriented helical antenna over half-space are given. The results show that this formulation can be applied to fast calculation the far radiation field of an antenna located above the interface of the half space.

We have proposed the concept of inline network measurement, which involves the concept of "plugging'' unactive bandwidth measurement into an active TCP connection. Mechanisms using this method have the advantage of requiring no extra traffic for measuring available bandwidth, whereas other active measurement tools cannot fundamentally avoid adding probing traffic onto the network. However, when the inline network measurement algorithms are implemented in general-purpose computers, some problems arise, such as the clock resolution of the kernel system, interrupt coalescence (IC) deployed in network interface cards, and the behavior of TCP receiver. In the present paper, we explain these difficulties and describe our current solutions. Furthermore, we implement the measurement algorithms and the solutions against those problems in a Free BSD 4.10 kernel system, and present some results on experimental networks. The experimentally obtained results are used to verify the solutions and to confirm the effectiveness of our concept, inline network measurement, on actual networks. We also compare the performance of the packet interval-based approaches and packet-burst interval-based approaches, and demonstrate that using packet-burst for the measurement in high-speed networks is quite effective.

We introduce a new measurement algorithm for the available bandwidth in a network path between two endhosts. This algorithm is an adaptation from existing active measurement methods for the purpose of being applied in inline network measurement. Inline network measurement method measures the available bandwidth by using packets which an active TCP connection transmits, instead of using probe packets, as in the existing methods. The measurement is performed by inferring network characteristics information from transmitting and receiving intervals of TCP data and ACKnowledgement packets. Inline network measurement is useful in service overlay networks, in which up-to-date information on the available bandwidth in the underlying IP network should be known as early as possible. In this paper, we first introduce the measurement algorithm and then discuss the problems with applying the proposed measurement algorithm to an active TCP connection. We evaluate the proposed measurement algorithm using simulation experiments and show that it can provide an estimation of available bandwidth every 2-4 RTTs. Moreover, the accuracy of measurement results can be maintained considerably well while the number of packets in a measurement is reduced by approximately 90% in comparison with existing methods.