Frequency response of the axisymmetrically finite pre-stretched slab from incompressible functionally graded material on a rigid foundation

Within the framework of the three-dimensional linearized theory of elastic waves in the initially stressed bodies (TLTEWISB) the axisymmetric frequency response problem of the pre-stretched slab from the incompressible functionally graded material (FGM) resting on the rigid foundation is studied. The elasticity relations of the slab material are given through the Treloar potential. It is assumed that the time-harmonic point located normal force acts on a free face plane of the slab. The approach for the investigation of the problem is developed. According to this approach, the problem for the slab from the continuously inhomogeneous material (FGM) is reduced to the corresponding problem for the slab from the multi-layered, i.e. from the piecewise-homogeneous material. The number of the layers in the reduced problem is determined by the convergence requirement of the numerical results. This replacement allows us to use so-called discrete-analytical approach. By employing this approach the concrete numerical results are presented for the case where the properties of the slab’s material change continuously along the thickness of the slab. In particular, it is established that the “resonance” values of the amplitude increase (decrease), but the “resonance” values of the frequency decrease (increase) with an increase in the slab’s material stiffness and density along the thickness of that.     

Dielectric properties of bismuth doped Ba1−xCaxTiO3 ceramics

The dielectric properties of (Ba_1−xCa_x)_1−1.5yBi_yTiO₃ (x = 0.10, 0.20 and 0.30, y = 0.05) ceramics were investigated. XRD analysis shows that 5 at.% of Bi doping can be fully incorporated into the perovskite lattice of (Ba_1−xCa_x)TiO₃. The maximal dielectric constant K_m of (Ba_1−xCa_x)_1−1.5yBi_yTiO₃ ceramics decreases significantly with increasing x for all the compositions. Compared with undoped Ba_1−xCa_xTiO₃ ceramics [Mater. Chem. Phys. 77 (2002)], Bi doping remarkably shifts the temperature of the peak dielectric constants T_m to lower temperature and a broad dielectric peak exhibits strong frequency dispersion. With increasing frequency, K_m decreases and T_m shifts to higher temperatures in (Ba_1−xCa_x)_1−1.5yBi_yTiO₃ ceramics. A typical behavior to well-known relaxor ferroelectric is observed. The relaxation behavior observation is suggested due to a random electric field induced domain state.     

Interface Characteristics and Laboratory Constructability Tests of Novel Fiber-Reinforced Polymer/Concrete Piles

Conventional pile materials such as steel, concrete, and timber are prone to deterioration for many reasons. Fiber-reinforced polymer (FRP) concrete composites represent an alternative construction material for deep foundations that can eliminate many of the performance disadvantages of traditional piling materials. However, FRP composites present several difficulties related to constructability, and the lack of design tools for their implementation as a foundation element. This paper describes the results of an experimental study on frictional FRP/dense sand interface characteristics and the constructability of FRP–concrete composite piles. An innovative toe driving technique is developed to install the empty FRP shells in the soil and self-consolidating concrete is subsequently cast in them. The experimental program involves interface shear tests on small FRP samples and uplift load tests on large-scale model piles. Two different FRP pile materials with different roughness and a reference steel pile are examined. Static uplift load tests are conducted on different piles installed in soil samples subjected to different confining pressures in the pressure chamber. The results showed that the interface friction for FRP materials compared favorably with conventional steel material. It was shown that toe driving is suitable for installation of FRP piles in dense soils.     

A simplified UTV hand tool featuring 2.25 MHz transducers to measure the BMD of calcaneus—tested on acrylic blocks padded with fresh porcine tissue

The quantitative use of UTV (Ultrasound Transmission Velocity) on the calcaneus (i.e., the heel bone) to assess osteoporosis has been widely used in clinical practice and investigation. However, most existing commercial instruments are bulky and the measurement is largely under the assumption that the thickness of the heel bone is fixed. Moreover, present measuring techniques are unable to cope with the effects of covering soft tissue, thus are incapable of producing accurate results. This study proposes a simplified UTV hand tool. We mount two 2.25 MHz ultrasonic transducers on an industrial vernier caliper and test it on some acrylic testing blocks padded with fresh porcine tissue to simulate the human heel. From the responses obtained, we develop a way to eliminate the influences made by the accompanying soft tissue. Thus, more accurate UTV hand tool for the acrylic block, or the heel bone, can be derived. In our final tests, the error of UTV measurement drops to 1.98%.     

Multi-scale analysis of alkali–silica reaction (ASR): Impact of alkali leaching on scale effects affecting expansion tests

Alkali–silica reaction expansions are disturbed by a variety of mechanisms (alkali leaching, ASR-gel permeation through cracks, chemical conditions in pore solution water and its dependence on temperature). An important consequence is the difficulty of using the expansion test on specimens to analyse the behaviour of ASR-damaged structures. The paper focuses on the influence of leaching: alkali transport and consumption are modelled using a multi-scale approach (aggregate and concrete scales). The evaluation of the alkali concentration below which expansion stops is needed to perform relevant analysis in various alkali conditions and this alkali threshold is quantified according to calcium concentration and temperature. The impact of the coupling between alkali transport in aggregate and silica reactivity is also studied. Lastly, the consequences of leaching on ASR-expansion are analysed in two case studies drawn from the literature.     

Choosing small sets of policy-relevant scenarios by combining vulnerability and diversity approaches

Computer simulation models can generate large numbers of scenarios, far more than can be effectively utilized in most decision support applications. How can one best select a small number of scenarios to consider? One approach calls for choosing scenarios that illuminate vulnerabilities of proposed policies. Another calls for choosing scenarios that span a diverse range of futures. This paper joins these two approaches for the first time, proposing an optimization-based method for choosing a small number of relevant scenarios that combine both vulnerability and diversity. The paper applies the method to a real case involving climate resilient infrastructure for three African river basins (Volta, Orange and Zambezi). Introducing selection criteria in a stepwise manner helps examine how different criteria influence the choice of scenarios. The results suggest that combining vulnerability- and diversity-based criteria can provide a systematic and transparent method for scenario selection.     

Redox active Double Wall Carbon Nanotubes show intrinsic anti-proliferative effects and modulate autophagy in cancer cells

In Double-Walled-Carbon-Nanotubes (DWCNTs) the outer shell screens the inner one from the external environment. As a consequence, the electronic properties of the smaller tube are enhanced and DWCNTs have therefore been advocated for a number of uses. In their raw form they may contain small metallic clusters, left over from the catalytic process, that can give them a redox activity characterized by redox potentials in the range of one hundred millivolts and able to affect biological systems. Indeed, we find that redox active raw-DWCNTs inhibit rat colorectal cancer cell proliferation by blocking cells in the G2 phase through ROS generation by tumor cells. We show that raw-DWCNTs could also modulate autophagy in tumor cells through induction of intracellular acidification. To the best of our knowledge, this is the first time that DWCNTs have been found to inhibit proliferation and modulate autophagy in cancer cells. Our work further supports previous studies that provided promising results on the possibility of future applications of Carbon Nanotubes (CNTs) in nanomedicine.     

Adsorption Behavior of Halogenated Anesthetic and Water Vapor on Cr‐Based MOF (MIL‐101) Adsorbent. Part I. Equilibrium and Breakthrough Characterizations

A synthesized chromium‐based metal organic framework (Cr‐MOF) was used for the adsorption of halogenated anesthetics, i.e., sevoflurane (SF). Adsorption isotherm and breakthrough experiments involving SF (reference sorbate) and water vapor were measured at 298 K and atmospheric pressure on both Cr‐MOF and a commercially used reference adsorbent. The Cr‐MOF MIL‐101 showed a significantly higher SF adsorption capacity and much higher selectivity relative to water vapor compared to the reference adsorbent. Binary‐mixture breakthrough tests demonstrated a “roll‐up effect” for SF on the reference adsorbent while no such effect was observed on MIL‐101.     

On control of transport in Brownian ratchet mechanisms

Engineered transport of material at the nano/micro scale is essential for the manufacturing platforms of the future. Unlike conventional transport systems, at the nano/micro scale, transport has to be achieved in the presence of fundamental sources of uncertainty such as thermal noise. Remarkably, it is possible to extract useful work by rectifying noise using an asymmetric potential; a principle used by Brownian ratchets. In this article a systematic methodology for designing open-loop Brownian ratchet mechanisms that optimize velocity and efficiency is developed. In the case where the particle position is available as a measured variable, closed loop methodologies are studied. Here, it is shown that methods that strive to optimize velocity of transport may compromise efficiency. A dynamic programming based approach is presented which yields up to three times improvement in efficiency over optimized open loop designs and 35% better efficiency over reported closed loop strategies that focus on optimizing velocities.     

Modular product platform configuration and co-planning of assembly lines using assembly and disassembly

Formation of products platforms is carried out during the planning stage and very often separately from the planning of corresponding assembly lines. There is a dearth of literature which considers the different aspects of fully integrating platform design, product family formation, assembly line design, delayed product differentiation, and new concepts of mass customization. A Modular Product Platform Configuration model which uses assembly and disassembly for configuring product variants and Co-Planning of products platforms (MPCC) and their assembly Lines is presented. It is used to co-plan the common platform components and the associated product families simultaneously with the planning of its corresponding mixed-model assembly line. Using both assembly and disassembly to customize the product family platform in order to generate product variants is not commonly discussed in literature. It is defined as the formation of platforms for use to derive multiple products by including many components not shared by every product. The platform is then customized by assembling or disassembling components to form different product variants. The model is formulated using mixed integer mathematical programming to minimize the number of assembly stations and cycle time. Two case studies are used for verification and demonstration. They illustrated the ability of the MPCC model to integrate the planning of product platform, product families and the number of assembly stations required to assemble and disassemble components from mass-assembled product platforms to derive new product variants.