Summary A particle tuned mass damper (PTMD), which is a creative integration of a traditional tuned mass damper and an efficient particle damper in the vibration control area, is proposed. This paper presents a comprehensive study that involves experimental, analytical, and computational approaches. The vibration control effects of a PTMD that is attached to a five‐story steel frame under seismic input are investigated by a series of shaking table tests. The influence of some parameters (auxiliary mass ratio, gap clearance, mass ratio of particles to the total auxiliary mass, frequency characteristics, and amplitude level of the input) is explored, and the performance of the PTMD with/without buffered material is compared. The experimental results show that the PTMD can achieve significant damping effects under seismic excitations, and the bandwidth of the suppression frequency is expanded, showing the device's robustness and control efficiency. In addition, an approximately analytical solution that is based on the concept of an equivalent single‐particle damper is presented, and the method to determine the corresponding system parameters is introduced. A comparative study between experimental and numerical results is conducted to verify the feasibility and accuracy of this analytical model. Copyright © 2016 John Wiley & Sons, Ltd.

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Nonlinear energy sinks (NES) are efficient vibration control devices, which have been studied and applied in mechanical, automobile, and aerospace engineering.However, there are few applications in civil engineering. A new type of NES, which is termed as track NES, is proposed in this paper. The optimal mass ratio and track shape expression of NES were determined based on a preliminary optimization design process. To verify its vibration control effects on building structures, a series of shake table tests were conducted on a five-story steel frame. Tracks of the NES were installed at the roof of the frame with rigid connections and the mass of the NES was constrained to slide along the track by using wheels. Five earthquake waves with different frequency spectrums were selected to excite the frame coupled with NES under minor, moderate, and major levels. Accelerations and displacements on each story of the frame were measured, recorded, and evaluated. The experimental results demonstrate that with small mass ratio (2%) of main structure, NES has good performance in reducing the dynamic responses of the frame under seismic excitations. The reduction ratio for peak response is up to 50%, while for root mean square response is up to 80%. NES also exhibits wide-band frequency vibration controlling attributes, and the responses of the frame are reduced in multiple vibration modes. In addition, the vibration reduction capability of the NES with steel wheels and that with rubber wheels are compared, and it is verified that different damping of NES makes a difference to the vibration control effects. The displacement reduction performance is not sensitive to the damping factor of the NES, but acceleration response is highly affected by the damping feature of the NES.

At present, there are various wound dressings that can protect the wound from further injury or isolate the external environment in wound treatment. Whereas, infection and slow self-healing still exist in wound healing process. Therefore, it is urgent to develop an ideal wound dressing with good biocompatibility and strong antibacterial activity to promote wound healing. Bacterial cellulose is a kind of promising biopolymer because it can control wound exudate and provide a moist environment for wound healing. However, the lack of antibacterial activity limits its application. In this paper, the advantages of bacterial cellulose as wound dressings were introduced, and the preparation and research progress of bacterial cellulose-based antibacterial composites in recent years were reviewed, including adding antibiotics, combining with inorganic antibacterial agents or organic antibacterial agents. Finally, the existing problems and future development direction of bacterial cellulose-based antibacterial wound dressings were discussed.

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SummaryThe tuned liquid damper (TLD) and particle damper (PD) have been used as effective passive vibration absorbers to suppress undesirable structural vibrations induced by dynamic loads such as earthquake and strong winds. In this paper, through an integrated use of the TLD and PD, a new damper system named the tuned liquid particle damper (TLPD) was developed. The dynamic characteristics of TLPD in terms of tuning conditions and transfer functions were investigated through a series of shaking table tests. Nonlinear behaviors of TLPD in the frequency domain were discussed, and a preliminary framework was applied in the design of a five‐story steel frame building model using shaking table tests. Testing results confirmed the workability of the preliminary design framework as the primary structure is subjected to earthquake loadings. Performances of different TLPD‐structure systems were summarized from these testing programs. One of observations is that the TLPD system worked as a modified TLD in this study. The testing programs provide proof‐of‐concept results for this proposed vibration absorber.

Abstract:We have developed techniques to map the distribution and composition of clay-rich soils with portable field spectrometers on the ground. Spectral reflectance measurements in the 1800-2400-nm region with 10-nm resolution can distinguish smectites, which cause swelling, from illites and kaolinite that do not swell significantly. Illites and smectites are often mixed in the soil and result in varying swell potential. Standard engineering soil tests are too time consuming and costly to be used in areas where there is highly varying swell potential. Therefore, in many instances in regions of steeply dipping sedimentary layers, beds of swelling clay go undetected. We show that it is possible to determine smectite content with a standard cross-validation error of 10% based on partial least-squares analysis of second-derivative reflectance spectra. Loadings show that the 1800-2000-and 2150-2250-nm regions contain the most relevant information for the detection and quantification of smectite content and these correspond to the bound water in the clay lattice interlayer and the Al-OH combination band, respectively. Correlations as high as 87% were obtained with the Seed swell-potential index. The correlations are higher when the samples were dried rather than measured in their moist condition shortly after collection in the field, as in an earlier study. Correlation with other swell indices shows that reflectance spectroscopy would be a reliable indicator that could divide samples into low, medium, and high swell potential. The effect of sample moisture was studied and the results show that the surface of the field samples must first be dried before measurement, in order to obtain a reliable swell potential value from the model.