Effects of the Domain Size on Local d33 in Tetragonal (Na0.53 K0.45Li0.02)(Nb0.8Ta0.2)O3 Ceramics

Lead‐free (Na_0.53K_0.45Li_0.02)(Nb_0.8Ta_0.2)O₃ (NKLNT) was prepared using a conventional cold‐pressing method. A commercial piezoresponse force microscope (PFM) was applied to observe the domain structures of NKLNT ceramics. The typical configuration of the ferroelectric domain was analyzed in abnormal grains with grain sizes that exceeded 40 μm, where tetragonal 90° domains are predominant. The local piezoresponse hysteresis loops were characterized and studied as a function of the domain width (dw) in the range 300–1000 nm. It was found that the amplitude signals increased and the coercive field reduced significantly with a decrease in the domain size. Finally, the local longitudinal piezoelectric coefficient (d₃₃) increased as the domain size decreased.     

Effect of Interfacial Adhesion on the Mechanical Properties of Organic/Inorganic Hybrid Nanolaminates

Two different kinds of organic polyelectrolyte (PE)/inorganic silicate nanolaminates carrying dissimilar interfacial adhesion between the organic and the inorganic layers were prepared using the layer-by-layer self-assembly. To investigate the mechanical behavior of the prepared hybrid films, apparent modulus (E′), hardness (H), and crack length were measured by depth-sensing nanoindentation as well as a microVickers experiment. The fracture toughness of the hybrid films was then calculated based on the measured mechanical values. In the case of forming strong interfacial adhesion between the organic and the inorganic layers (A series), the fracture toughness and the crack resistance of hybrid multilayer films were significantly improved as a result of the redistribution of stress concentration and the dissipation of fracture energy by the plasticity of organic PE layers. On the other hand, samples with relatively low interfacial adhesion between the organic and the inorganic layers (T series) had little effect on the improvement of fracture toughness of the hybrid films.     

Storing continuous media objects to multizone recording disks using multirate smoothing technique

Since multizone recording disks have different bandwidths and capacities depending on the zone in use, data placement schemes for traditional constant angular density disks are not suitable for multizone recording disks. In this paper, we propose a new block placement algorithm for multizone recording disks used for continuous media servers. The proposed scheme exploits the bandwidth-saving effect of smoothing variable bit rate data before storing them. The diversity of zone bandwidths in multizone recording disks enables it possible to achieve large smoothing effect using relatively small buffer space. Variable bit rate data blocks of an object are smoothed using multiple smoothing rates which are bandwidths of zones multiplied by the service time assigned to the object and are stored into the corresponding zones. This multirate smoothing technique decreases the buffer space required to provide deterministic service to clients. Simulation results show that a proper restructuring of blocks according to the smoothing algorithm results in dramatic performance enhancement in continuous media servers.     

Piezoelectric translational agitation for enhancing forced-convection channel-flow heat transfer

Piezoelectric translational agitator (PTA) is proposed and its heat transfer performance is demonstrated by experiments in a narrow channel. For the present study, this channel simulates a portion of an air-cooled heat sink. An oval loop shell structure successfully generates millimeter-range translational displacement to a blade attached to the shell. A PTA operating at 961 Hz as its second resonance mode with a 1.4 mm displacement under 60 Liters Per Minute (LPM) of cross flow achieved about 55% improvement in heat transfer coefficient compared to the non-agitated state. Pressure drop in the test section and the corresponding power required to drive the flow through the channel against the oscillating blade were measured. In addition, the PTAs were tested in the open channel without through-flow to examine the sole effect of agitation and to investigate the possibility of using it as a stand-alone cooling device. A total Reynolds number was defined to characterize the combined effects of cross flow and agitation. The Stanton number developed from the relationship between the total Reynolds number and heat transfer coefficients enables predicting operating performance.     

Optimization of a one-step direct process for biodiesel production from blended sewage sludge

Biodiesel production from blended sewage sludge (BSS) by a one-step direct process was investigated, and optimal conditions for this process were determined. The one-step direct process comprises extraction of lipids from BSS and simultaneous transesterification of these lipids with methanol. Among the organic solvents evaluated, pure methanol showed higher biodiesel yields compared with other solvents or solvent mixtures. The optimum conditions determined included 10 mL of methanol/g-BSS, 0.7% (g/g-BSS) of H₂SO₄, 60 °C, 4 h of reaction time and 300 rpm of agitation speed. Under these conditions, biodiesel yield was 3.1% (g-biodiesel/g-BSS), which was 63.2% higher than that obtained under initial conditions, and 24.0%-63.2% higher than those obtained in previous studies.     

The use of partitioning bioreactors for the treatment of high‐concentration benzene solutions

Aqueous solutions containing high concentrations (circa 1000 mg/L) of benzene can be treated biologically through the intervention of organic 'sponges'. In reality these sponges are immiscible and biocompatible organic solvents that can be added in very low volumes, and act to draw benzene out of the aqueous phase, reducing levels appropriate for biological treatment. As the organisms consume benzene, the sponges release additional substrate to maintain an equilibrium relationship between the two phases, and this rate is determined by the metabolic activity of the cells. We have used 1‐actadsene as the organic sponge, and Klebsiella sp. as the degradative organism to consume 1000 mg/L of benzene in 12 h. By draining the aqueous phase to 10% of its original volume (and letting it serve as an inoculum), additional benzene solutions, at 1000 mg/L, can be reintroduced to the system, and the action of the sponge used a second, and subsequent times, to control benzene levels and benzene delivery to the organisms.     

Study on functional microcapsules containing catalysts for controlling the curing time and temperature of epoxy resin

In this study, functional microcapsules (FMs) were designed for controlling the curing time and temperature of epoxy through modifications to thermally expandable microcapsules. The FMs were prepared with a mixture of liquid hydrocarbons and N,N-dimethylbenzylamine in the core, and acrylonitrile (AN)—methyl methacrylate copolymer or AN–methacrylate copolymer were used for the shell. Since the FMs were intentionally designed to have thermally vulnerable polymeric shells, the catalyst in the core could be released at the designated temperature. Therefore, FMs do not activate in epoxy at room temperature; rather, the FMs only become functional when the epoxy is cured under a heated atmosphere. Released catalyst at the higher temperature was confirmed by pyrolysis gas chromatography–mass spectrometry and optical microscopy. This study shows that the results will depend on the different compositions of liquid hydrocarbons and catalyst. Particle size of the capsules was changed with different ratio of catalyst and liquid hydrocarbon at the core and type of polymeric shell. Differential scanning calorimetry and rheometer results showed that higher catalyst loading resulted lower in crystalline and shear thickening temperature, respectively. Adhesion strength of epoxy containing FMs was analyzed by lap shear strength in order to detect the void effect due to released gas from the FM. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47499.     

Intelligent unmanned anti-theft system using network camera

In this paper, we propose the intelligent unmanned anti-theft system using network cameras. To do this, we use two Internet Protocol (IP) cameras, which are installed at the inside and the outside of the restricted area. First of all, the external camera is used to monitor a potential intruder entering the restricted area in real time. To detect the potential intruder from sequential images obtained by external IP camera, we propose the robust algorithm combining the background modeling, the hybrid silhouette, the convex summation, the morphology and the smoothing. Once the intruder is detected by the external camera, the internal camera with pan-tilt mechanism is then activated and starts tracking the intruder and monitoring the prescribed valuables registered with some feature points in the database. To track the intruder, we propose the tracking algorithm using the background elimination and the histogram. And then, we completes the proposed anti-theft system by using the Scale Invariant Feature Transform (SIFT) algorithm in order to monitor whether the intruder steals the prescribed valuables or not. Finally, we have shown the effectiveness and the applicability of the proposed method through experiments.     

Characterization of deformation behavior for waspaloy under creep-fatigue interaction

Hysteresis loops of strain controlled LCF tests for Waspaloy were characterized within the temperature range of 350°C and 600°C. Materials deformation behaviors under symmetric and asymmetric loading conditions were assessed using Chaboche’s viscoplasticity model. The strain hardening and stress relaxation occurring in the loading cycles were estimated. Hardening plays an important role at an early stage of loading, but the stress relaxation becomes dominant at a later stage. The observed change in the slope of hysteresis loops between the first cycle and the second cycle and mean stress relaxation under asymmetric loading conditions may be explained by the evolution of the kinematic hardening variable which depends on the inelastic strain range. The effect of creep on the cyclic shake down is expected to be limited.     

A Metal-Like Conductive Elastomer with a Hierarchical Wrinkled Structure

For the development of wearable electronics, the replacement of rigid, metallic components with fully elastomeric materials is crucial. However, current elastomeric electrodes suffer from low electrical conductivity and poor electrical stability. Herein, a metal-like conductive elastomer with exceptional electrical performance and stability is presented, which is used to fabricate fully elastomeric electronics. The key feature of this material is its wrinkled structure, which is induced by in situ cooperation of solvent swelling and densely packed nanoparticle assembly. Specifically, layer-by-layer assembly of metal nanoparticles and small-molecule linkers on elastomers generates the hierarchical wrinkled elastomer. The elastomer demonstrates remarkable electrical conductivity (170 000 and 11 000 S cm⁻¹ at 0% and 100% strain, respectively), outperforming previously reported elastomeric electrodes based on nanomaterials. Furthermore, a fully elastomeric triboelectric nanogenerator based on wrinkled elastomeric electrode exhibits excellent electric power generation performance due to the compressible, large contact area of the wrinkled surface during periodic contact and separation.