Application Of Temperature Gradient Research Articles

A design of fully soft robot actuated by gas–liquid phase change

This study aims to investigate the application of temperature gradient between the ground and the air to the locomotion of soft robot. Soft robots attract attention due to its flexible adaptability and safety to the real environment in recent years. Although many soft robots are soft themselves, they require hard material as an external device such as air compressors and external power supplies for driving. To solve the problem, some authors reported an autonomous driving robot composed of a completely flexible material using gas generation by a chemical change of hydrogen peroxide solution. However, as the driving system utilizes a chemical reaction, its driving time is relatively short. On the contrary, the proposed robot moves without electricity and any external devices such as air compressors and an electrical power supplies. It can move just on the ground using the temperature gradient between the ground and the air. In experiments, we developed some prototypes and confirmed that continuous movement could be achieved with the proposed model.

On the Possibility of Two-Dimensional Focusing of Reflected X-Rays from Quartz Single Crystal in the Presence of External Temperature Gradient

The Laue reflection from a quartz single crystal was experimentally studied in the presence of temperature gradient applied perpendicularly to reflecting atomic planes ( $$10\bar 11$$ ), so that a two-dimensional bending of these planes occurs. It is shown that as a result of such an application of temperature gradient to a crystal, the two-dimensional focusing of reflected X-rays is obtained. With increasing temperature gradient the focus of X-rays approaches the crystal more rapidly in the plane of reflection than in the perpendicular one.

Influence of temperature gradients on mono- and divalent ion transport in electrodialysis at limiting currents

Temperature gradients in electrodialysis (ED) stacks can potentially enhance the efficiency of charge separation and the selective transport of ions. We have previously investigated temperature gradients in the Ohmic regime but not in the limiting current regime, where diffusion of ions towards the membrane determines the transport rate and temperature gradients potentially have the largest influence. In this research, commercial ion exchange membranes (FAS and FKS, FUMATECH, Germany) are used for the investigation of temperature gradients in the limiting current regime. In contrast to the Ohmic regime, we find that heating the diluted stream increases the current obtained (at a constant applied potential) when compared to heating the concentrate stream in systems containing monovalent KCl and NaCl solutions. For mixtures of mono- and divalent ions, the temperature gradient has a larger influence on the selectivity of the separation. If the desalinated stream is heated, divalent Mg2+ ions show a higher transport than the monovalent K+ and Na+ ions. This is due to the enhanced competitive transport of the mono- and divalent ions under the application of a temperature gradient. These results show the potential application and relevance of temperature gradients to enhance the selective separation of mono- and divalent ions.

Analysis of Stresses Due to Traffic and Thermal Loads in Two-Lift Bonded Concrete Pavements by Finite Element Method

Abstract The current practice in the construction of jointed plain concrete pavements in India is to lay paving quality concrete (PQC) over roller-compacted concrete designated as dry lean concrete (DLC). A 125-µm plastic sheet is placed as a bond-breaking layer at the interface of the DLC and PQC. By placing the PQC layer directly over fresh lean concrete (LC), the two layers will bond without any extra bond-breaking layers, and there may be a considerable reduction in PQC thickness. Reducing the PQC layer thickness decreases the amount of aggregates used, which helps preserve quality aggregates that are rapidly depleting. Pavements in which the PQC is laid directly over LC can be designated as a two-lift concrete pavement (TLCP). Joints must be provided with deep saw cuts to avoid random cracking. The LC can be made up of recycled concrete or marginal aggregates to obtain a sustainable pavement. However, readymade analytical solutions are not available for the computation of stresses in two-lift bonded concrete layers for pavement design. This article presents a three-dimensional finite element solution for stresses in bonded concrete pavements. Stresses in both layers are presented in order to arrive at an optimum thickness combination so that both layers are safe during the design life. Stress computation is done for the conditions of simultaneous application of temperature gradients and axle loads. The cracking of the LC layer because of high flexural stresses at the bottom is found to be the critical factor in the design of TLCP.

Orienting cylindrical microdomains in polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene triblock copolymer/diluent sheet by application of temperature gradient

Orienting cylindrical microdomains in polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene triblock copolymer/diluent sheet by application of temperature gradient

Dynamics of a spreading thin film with gravitational counterflow using slip model

Thin liquid films can be made to spread along a solid surface by application of temperature gradients at the liquid–gas interface. The surface tension of usual liquids decreases linearly with temperature thus producing the driving thermocapillary stresses due to the applied temperature gradient. These spreading films are susceptible to a fingering instability at the advancing solid–liquid–vapor contact line, which is linked to the development of a capillary ridge near the advancing front. A thin film climbing up on a vertical substrate against gravity shows interesting dynamics due to strong opposing gravitational counterflow. At the contact-line of the spreading film, slip-model is used to alleviate the stress-singularity due to more usual no-slip boundary condition. It is shown that depending upon the magnitude of a gravitational drainage parameter the steady-profiles of the spreading films show qualitatively different dynamics. The dynamics is in agreement with the experimentally observed profiles in the literature as well as computed profiles using precursor-film model at the contact-line in some earlier theoretical studies. Briefly, their stability behavior is also discussed.

STRUCTURAL AND OPTICAL PROPERTIES OF ZnO SYNTHESIZED BY TEMPERATURE GRADIENT THERMAL OXIDATION

In this work, a series of polycrystalline ZnO samples have been synthesized from Zn thin films deposited on Si (100) substrates by using thermal oxidation technique. The ZnO thin film samples grown by this technique were then characterized by a variety of structural and optical characterization tools. The results revealed that the use of novel annealing process i.e. the application of temperature gradient in the thermal treatment could enhance the structural and optical quality of the ZnO thin films significantly as compared to the normal annealing process, i.e. a fixed temperature under different durations. Apart from the improvement of structural and optical properties of ZnO thin films, another striking feature of this novel annealing process was the promotion of the growth of ZnO nanostructures.

Surface indentation arrays for high-throughput analysis of viscoelastic material properties

Viscoelastic relaxation processes factor into polymer performance and stability throughout an application lifetime, controlled by the polymer network structure and dynamics which occur over a wide spectrum of time scales. In this work, we detail the design and operation of an independent array of surface indenters which can measure the creep response at multiple points on a polymer substrate. Samples with composition and temperature gradients are used to exhibit the ability to measure viscoelastic properties under unique conditions for each indentation. Methacrylate photopolymer systems are measured at different compositions and crosslink densities simultaneously within an indenter array to increase the measurement throughput, with a measured creep compliance ranging from 10(-9) Pa(-1) to 10(-5) Pa(-1). The application of temperature gradients allows for the viscoelastic measurements to be assembled onto a master curve using time-temperature superposition.

Microfludic Device for Creating Ionic Strength Gradients over DNA Microarrays for Efficient DNA Melting Studies and Assay Development

The development of DNA microarray assays is hampered by two important aspects: processing of the microarrays is done under a single stringency condition, and characteristics such as melting temperature are difficult to predict for immobilized probes. A technical solution to these limitations is to use a thermal gradient and information from melting curves, for instance to score genotypes. However, application of temperature gradients normally requires complicated equipment, and the size of the arrays that can be investigated is restricted due to heat dissipation. Here we present a simple microfluidic device that creates a gradient comprising zones of defined ionic strength over a glass slide, in which each zone corresponds to a subarray. Using this device, we demonstrated that ionic strength gradients function in a similar fashion as corresponding thermal gradients in assay development. More specifically, we noted that (i) the two stringency modulators generated melting curves that could be compared, (ii) both led to increased assay robustness, and (iii) both were associated with difficulties in genotyping the same mutation. These findings demonstrate that ionic strength stringency buffers can be used instead of thermal gradients. Given the flexibility of design of ionic gradients, these can be created over all types of arrays, and encompass an attractive alternative to temperature gradients, avoiding curtailment of the size or spacing of subarrays on slides associated with temperature gradients.

Effect of Temperature in micro‐HPLC Separation of PAHs under Isocratic Conditions Using Octadecyl and Alkylamide Phases

AbstractThe main difficulty in micro‐HPLC separation is the manipulation with the composition of the mobile phase (degassing of solvents and a slow establishment of equilibrium) but the problem of elution can be solved by temperature optimalization. The effect of temperature in micro‐HPLC separation of the 16 polycyclic aromatic hydrocarbons (PAHs) (mixture SRM 1647 of the US EPA) has been studied using conventional C18 and new developed AP phase (an amide group localized in the hydrophobic ligands). All the investigations have been performed under isocratic conditions (binary hydroorganic mobile phase: acetonitrile/water). The results have shown that, in the case of AP phase, application of temperature gradient (from 298 to 303 K), enabled the attainment of complete 16 PAHs separation (especially of the first 4 solutes).