Chunwei Zhang

Determination of oxytetracycline, tetracycline and chloramphenicol antibiotics in animal feeds using subcritical water extraction and high performance liquid chromatography

A rapid analytical method for the determination of oxytetracycline (OTC), tetracycline (TC) and chloramphenicol (CAP) antibiotics in animal feeds has been developed based on subcritical water extraction (SWE) without further sample clean-up followed by high performance liquid chromatography (HPLC) with ultraviolet (UV) detection. On extracting target antibiotics from spiked samples, the efficiency of the water extraction device was evaluated in terms of pH and volume of the extractant, temperature and time of the static extraction. The best extraction conditions were obtained by using 5.5 mL of water adjusted to pH 2 with hydrochloric acid as the extractant at 100 degrees C with 5-min static extraction. After filtration, 20 microL of the aqueous extract was directly injected into the HPLC column. Recoveries between 82.1% and 90.0% with relative standard deviations ranging between 1.6% and 4.8% were achieved from spiked animal feed samples by using this method. Compared with the traditional ultrasonic extraction, this procedure was remarkably more efficient in extracting OTC, TC and CAP, simpler to perform, and there was no use of toxic organic solvents.

Development of Wireless MEMS Inclination Sensor System for Swing Monitoring of Large-Scale Hook Structures

A modular wireless microelectromechanical system (MEMS) inclination sensor system (WMISS) is developed and tested for providing structural health monitoring of large-scale hook structures. The operating principle of a 3-D-MEMS-based dual-axis inclinometer is analyzed. A wireless MEMS sensor is integrated using sensing disposal, wireless communication, and power units. The WMISS is calibrated by using a laser displacement sensor in a pendular structure. The maximal error of the wireless MEMS inclination sensor is about 1%. The resolution is plusmn0.0025deg. With the new-type tuned mass damper control module, an experiment on a WMISS for the swing monitoring of a Lanjiang hook model is developed. Experimental results indicate that the developed WMISS is highly precise, convenient, stable, and low cost and has long range, and thus, a WMISS can accurately and conveniently monitor the swing of a Lanjiang hook model.

Thermoelastic behavior of a thermoelectric thin-film attached to an infinite elastic substrate

Abstract This paper examines the thermoelectric behaviour of a thermoelectric thin film bonded to an elastic substrate. A calculation model for thermoelectric thin films is developed based on the singular integral equation method. The interface shear stress is found to exhibit singular behaviour at the ends of the films. Numerical results for the thermal stress distribution in the film and the film/substrate interface are obtained. Effects of film thickness and the substrate to film stiffness ratio on the stress of the film and the stress intensity factor of the interface are identified. The effects of interface electricity conductivity and the elastic–plastic deformation of the film are discussed.

Control Performance and Robustness of Pounding Tuned Mass Damper for Vibration Reduction in SDOF Structure

This paper investigates the control performance of pounding tuned mass damper (PTMD) in reducing the dynamic responses of SDOF (Single Degree of Freedom) structure. Taking an offshore jacket-type platform as an example, the optimal damping ratio and the gap between mass block and viscoelastic material are presented depending on a parametric study. Control efficiency influenced by material properties and contact geometries for PTMD is analyzed here, as well as robustness of the device. The results of numerical simulations indicated that satisfactory vibration mitigation and robustness can be achieved by an optimally designed PTMD. Comparisons between PTMD and traditional TMD demonstrate the advantages of PTMD, not only in vibration suppression and costs but also in effective frequency bandwidth.

An Updated Analytical Structural Pounding Force Model Based on Viscoelasticity of Materials

Based on the summary of existing pounding force analytical models, an updated pounding force analysis method is proposed by introducing viscoelastic constitutive model and contact mechanics method. Traditional Kelvin viscoelastic pounding force model can be expanded to 3-parameter linear viscoelastic model by separating classic pounding model parameters into geometry parameters and viscoelastic material parameters. Two existing pounding examples, the poundings of steel-to-steel and concrete-to-concrete, are recalculated by utilizing the proposed method. Afterwards, the calculation results are compared with other pounding force models. The results show certain accuracy in proposed model. The relative normalized errors of steel-to-steel and concrete-to-concrete experiments are 19.8% and 12.5%, respectively. Furthermore, a steel-to-polymer pounding example is calculated, and the application of the proposed method in vibration control analysis for pounding tuned mass damper (TMD) is simulated consequently. However, due to insufficient experiment details, the proposed model can only give a rough trend for both single pounding process and vibration control process. Regardless of the cheerful prospect, the study in this paper is only the first step of pounding force calculation. It still needs a more careful assessment of the model performance, especially in the presence of inelastic response.

Design and Experimental Investigations of a Vibration Based Wireless Measurement System for Bridge Cable Tension Monitoring

Cables are important components of a cable-stayed bridge, and the cable tension is a crucial factor in determining the overall condition assessment of a cable-stayed bridge structure. Based on the vibration frequency method, a wireless monitoring system for bridge cable tension force monitoring has been investigated and experimentally validated through laboratory and field tests in this paper. The vibration frequency-based method for cable tension measurement, the design method of the wireless measurement system with embedded identification algorithm, the test procedures, and relevant results are discussed, respectively. The developed wireless monitoring system is verified by a bridge model test in the laboratory and full-scale bridge tests in the field. Field experimental results show that the relative error between this wireless monitoring system and the reference wired system values is within 0.5%. Therefore, the developed wireless measurement system can provide an estimation of cable tension with sufficient accuracy. Moreover, the developed system is highly integrated and convenient in terms of installation and dismantling, and it has potential applicability prospects in emergency for the quick detection of cable tension.

Computer-Aided Analysis of Flow in Water Pipe Networks after a Seismic Event

This paper proposes a framework for a reliability-based flow analysis for a water pipe network after an earthquake. For the first part of the framework, we propose to use a modeling procedure for multiple leaks and breaks in the water pipe segments of a network that has been damaged by an earthquake. For the second part, we propose an efficient system-level probabilistic flow analysis process that integrates the matrix-based system reliability (MSR) formulation and the branch-and-bound method. This process probabilistically predicts flow quantities by considering system-level damage scenarios consisting of combinations of leaks and breaks in network pipes and significantly reduces the computational cost by sequentially prioritizing the system states according to their likelihoods and by using the branch-and-bound method to select their partial sets. The proposed framework is illustrated and demonstrated by examining two example water pipe networks that have been subjected to a seismic event. These two examples consist of 11 and 20 pipe segments, respectively, and are computationally modeled considering their available topological, material, and mechanical properties. Considering different earthquake scenarios and the resulting multiple leaks and breaks in the water pipe segments, the water flows in the segments are estimated in a computationally efficient manner.

Control Force Characteristics of Different Control Strategies for the Wind-Excited 76-Story Benchmark Building Structure

In accordance with the International Association of Structural Control and Monitoring (IASCM) third generation Vibration Control Benchmark problem, two new control strategies: structural adjacent reaction wall control (STA) and mass-semi-active-damper (AMD-2), are proposed and systematically evaluated and compared with the Benchmark standard-extended active control solutions as well as with the structural interbedded (STI) control strategy. A set of innovative evaluation indices, denoting the direction and energy relations between control forces and its velocity and/or displacement, is proposed to study the phenomena behavior as well as intrinsic mechanism of active control force of each control strategy. Throughout the comparisons among different control strategies, the function of inertia mass of Active Mass Driver/Damper (AMD) system is discussed. The AMD-2 control strategy has been developed based on a comprehensive analysis of STA control strategy, and both strategies are thoroughly evaluated against relevant Benchmark results. Based on a force mechanism and inertia mass ratio impact analysis, the AMD-2 control is shown to be capable of achieving comparable performance at a lower cost but with additional attractive advantages. Furthermore, an improved understanding phenomena behavior as well as the intrinsic mechanism of active control force corresponding to each control strategy realized by different control systems may contribute to selection of suitable control systems for application considerations.

Wireless inclinometer acquisition system for reducing swing movement control module experiment of hook model

Large Scale Heavy Derrick Lay Barge is very important for sea work. Under intense wind and wave load, the hook on the Barge will vibrate so large that in some cases it can not work. Through installing the Tuned Mass Damper(TMD) on the hook, the vibration will be reduced to a certain range to meet the demand on sea work, which is also important for increasing the efficiency of sea work. To design the suitable TMD for the hook, the dynamical parameters should be specified beforehand. Generally, the related dynamical parameters such as inclinometer and acceleration are measured by wire sensors. But due to the restriction of the actual condition, the wire sensors are very hard to implement. Recently, the wireless sensors have been presented to overcome the shortcomings of wire ones. It is more suitable and also convenient to utilize wireless sensors to acquire the useful data of large scale heavy derrick lay barge. In this paper, the hook reducing swing movement control module is designed for large scale heavy derrick lay barge. Secondly, wireless inclinometer sensor system is integrated using the technique of MEMS, sensing and wireless communication. Finally, the hook reducing swing movement control module is validated by the developed wireless inclinometer data acquisition system. The wireless inclinometer sensor can be used not only in swing monitoring for large scale heavy derrick lay barges Hook, but also in vibration monitoring for TV tower, large crane. In general, it has great application foreground.

Mass Inertia Effect Based Vibration Control Systems for Civil Engineering Structure and Infrastructure

In 1972, J.T.P. Yao introduced the modern control theory into vibration control of civil structures (Yao, 1972), which started the new era of research on structural active control in civil engineering field. During the development of nearly 40 years, Active Mass Driver/Damper (AMD) control, with the better control effect and cheaper control cost, has taken the lead in various active control occasions, becoming the most extensively used and researched control systems in lots of practical applications (Soong, 1990; Housner etal., 1997; Spencer etal., 1997; Ou, 2003). Several important journals in civil engineering field, such as ASCE Journal of Engineering Mechanics (issue 4th, in 2004), ASCE Journal of Structural Engineering (issue 7th, in 2003), Earthquake Engineering and Structural Dynamics (issue 11th, in 2001 and issue 11th, in 1998), reviewed the-state-of-the-art in research and engineering applications of semi-active control and active control, especially AMD control. In addition, Spencer and Nagarajaiah (2003) systematically overviewed the applications of active control in civil engineering. Up to date, more than 50 high-rising buildings, television towers and about 15 large-scale bridge towers have been equipped with AMD control systems for reducing wind-induced vibration or earthquake-induced vibration of the structures. Besides, there are quite a number of successful applications with passive Tuned Mass Damper (TMD) control system, from wind induced vibration control of long-span bridge towers and building structures, to chimneys and mast structures; from the first applications of the collapsed World Trade Center towers and coetaneous John Hancock building etc., which were built in 1960s, to recently built highest structures in the world, e.g. Twin towers in KuluaLumpur in Malaysia, 101 skyscraper in Taipei city and Guangzhou New TV tower in China etc. It can be seen from these applications, the implementation of incorporating Mass Driver/Damper based vibration control systems for protection of Civil Engineering structures and infrastructures against wind and earthquake excitations, have already been widely accepted by the field researchers as well as engineer societies.