Utilizing swelling force to decrease the ice adhesion strength

The phase transformation that occurs during water freezing process is accompanied by volume expansion and the release of latent heat. The swelling force generated by this phase transformation can have a harmful impact on structural safety and integrity, as it can lead to bursting in roads, water pipes and reservoir dams. So, why not effectively adopt the swelling force as the active de-icing power to diminish the stability of the contact interface. This paper proposes a new method to remove this accumulated ice by using polymethyl methacrylate (pmma) and 6061 aluminum alloy with pits as substrate materials. Pits were filled with solutions of different freezing points; owing to the different freezing point between the pit solution and water, their phase transformations occurred at different time, where the solutions in the pit would freeze more slowly than the surface water. The generated phase swelling force directly acted on the contact interface and decreased the stability of the interface to decrease the ice adhesion strength. The experimental results showed that the ice adhesion strength was obviously affected and reduced by the swelling force in contrast to the ice adhesion strength on the smooth sample, and the reduction in ice adhesion strength changed depending on the filling solution. Compared to the ice adhesion strength of the specimen without pits, the frozen ice was completely separated from the ice-pmma interface owing to the water filling the pit. The ice adhesion strength on the surface of the aluminum alloy sample filled with 10% ethanol solution was reduced by 81.42%. Utilizing the phase swelling force to reduce the adhesion strength enhances the active de-icing ability of the material, providing a novel method for developing new anti-icing methods

Influence of substrate initial temperature on adhesion strength of ice on aluminum alloy

The present work investigates the influence of the initial temperature of a substrate on the ice adhesion strength by analyzing the freezing characteristics of water droplets adhered to the substrate. The ice adhesion strength on 6061 aluminum alloy was measured using a dedicated strength testing apparatus, and the freezing process of water droplets at different initial temperatures of the alloy surface was examined with a microscope. The results of the experiments show that the ice adhesion strength on the aluminum alloy surface at ambient temperature was twice as large as that measured on a colder surface (e.g., −5 °C). Combining the experimental results with the microscopic observation of the freezing process revealed that at high initial surface temperature (i.e. equal to 18 °C), the water droplets thoroughly spread on the aluminum alloy surface at high temperature, formed a larger contact area. In addition, the initial surface temperature would influence the type of crystallization. Moreover, the advantages and disadvantages of thermal de-icing approaches, widely used in engineering (especially in the high-speed rail and aerospace fields), were discussed

Changes of Water/Ice Morphological, Thermodynamic, and Mechanical Parameters During the Freezing Process

To reduce ice adhesion hazards, optimize or develop the anti/de-icing methods, it is necessary to understand the change of freezing parameters during the freezing process, such as thermodynamic, morphological, and mechanical parameters. The present study investigates the freezing characteristics by purpose-built devices to describe the freezing process quantitatively. Morphological parameters were calculated the reverse engineering. The results showed that the inner temperature and morphology of water droplet were obviously changed, and the freezing process could be mainly divided into three stages: initial and spreading, freezing, and steady-state. Moreover, an experimental apparatus that measured the phase swelling force was built on investigating the freezing process of water from the mechanical aspect. It was found that the swelling force generated from the freezing process of 2473 mm3 water could reach 46.38 N. The generation process of swelling force could also be separated into three stages: non-expansive stage, increasing stage, and stable stage. The formation stage of swelling force was similar to that of ice. Combining the measured expansion force with the calculated freezing parameters based on the observed test, the freezing process of water could be better understood. The study would help researchers and engineers understand the freezing process and provide some freezing characteristics parameters for the anti/de-icing research

Ultra-Wideband Robust RCS Reduction with Triangle-type AMC Structure

A novel planar artificial magnetic conductor (AMC) structure is presented for ultra-wideband radar cross section reduction (RCSR). The structure consists of three different AMC tiles in a quadruple triangle-type chessboard configuration. By precise design, a 180°±30° reflection phase difference between every two of the three units nearly covers from 3.98GHz to 18.84GHz to broaden the RCSR bandwidth. By this means, the scattered energy is redirected into several lobes and the measured RCSR for over -6dB is achieved nearly from 3.62GHz to 18GHz with a relative bandwidth of 133.02% for both polarizations. Both full-wave simulation and measurement results verify the capability and potentiality of the proposed design for ultra-wideband RCSR

A Uniform Description of the States Recently Observed at B-factories

The newly found states Y(4260), Y(4361), Y(4664) and Z$^\pm$(4430) stir broad interest in the study of spectroscopy in a typical charmonium scale. The Y(4260) which was observed earlier has been interpreted as hybrid, molecular state, and baryonium, etc. In this note we show for the first time that these new structures, which are hard to be interpreted as charmonium states, can be systematically embedded into an extended baryonium picture. According to this assignment, the so far known characters of these states are understandable. And, in the same framework, we make some predictions for experimenters to measure in the future.Comment: 6 pages in Latex. to appear in J.Phys.

Distinct magnetic regimes through site-selective atom substitution in the frustrated quantum antiferromagnet Cs2_2CuCl4−x_{4-x}Brx_x

We report on a systematic study of the magnetic properties on single crystals of the solid solution Cs$_2$CuCl$_{4-x}$Br$_x$ (0 $\leq$ x $\leq$ 4), which include the two known end-member compounds Cs$_2$CuCl$_4$ and Cs$_2$CuBr$_4$, classified as quasi-two-dimensional quantum antiferromagnets with different degrees of magnetic frustration. By comparative measurements of the magnetic susceptibility $\chi$($T$) on as many as eighteen different Br concentrations, we found that the inplane and out-of-plane magnetic correlations, probed by the position and height of a maximum in the magnetic susceptibility, respectively, do not show a smooth variation with x. Instead three distinct concentration regimes can be identified, which are separated by critical concentrations x$_{c1}$ = 1 and x$_{c2}$ = 2. This unusual magnetic behavior can be explained by considering the structural peculiarities of the materials, especially the distorted Cu-halide tetrahedra, which support a site-selective replacement of Cl- by Br- ions. Consequently, the critical concentrations x$_{c1}$ (x$_{c2}$) mark particularly interesting systems, where one (two) halidesublattice positions are fully occupied.Comment: 15 pages, 4 figure

An inverse problem by boundary element method

Boundary Element Methods (BEM) have been established as useful and powerful tools in a wide range of engineering applications, e.g. Brebbia et al. In this paper, we report a particular three dimensional implementation of a direct boundary integral equation (BIE) formulation and its application to numerical simulations of practical polymer processing operations. In particular, we will focus on the application of the present boundary element technology to simulate an inverse problem in plastics processing.by extrusion. The task is to design profile extrusion dies for plastics. The problem is highly non-linear due to material viscoelastic behaviours as well as unknown free surface conditions. As an example, the technique is shown to be effective in obtaining the die profiles corresponding to a square viscoelastic extrudate under different processing conditions. To further illustrate the capability of the method, examples of other non-trivial extrudate profiles and processing conditions are also given

Review of Person Re-identification Techniques

Person re-identification across different surveillance cameras with disjoint fields of view has become one of the most interesting and challenging subjects in the area of intelligent video surveillance. Although several methods have been developed and proposed, certain limitations and unresolved issues remain. In all of the existing re-identification approaches, feature vectors are extracted from segmented still images or video frames. Different similarity or dissimilarity measures have been applied to these vectors. Some methods have used simple constant metrics, whereas others have utilised models to obtain optimised metrics. Some have created models based on local colour or texture information, and others have built models based on the gait of people. In general, the main objective of all these approaches is to achieve a higher-accuracy rate and lowercomputational costs. This study summarises several developments in recent literature and discusses the various available methods used in person re-identification. Specifically, their advantages and disadvantages are mentioned and compared.Comment: Published 201

A Crucial Test for Color-Octet Production Mechanism in Z^0 Decays

The direct production rates of $D$-wave charmonia in the decays of $Z^0$ is evaluated. The color-octet production processes $Z^0\rightarrow ^3D_J(c\bar c) q\bar q$ are shown to have distinctively large branching ratios, the same order of magnitude as that of $J/\psi$ prodution, as compared with other $D$-wave charmonium production mechanisms. This may suggest a crucial channel to test the color-octet mechanism as well as to observe the $D$-wave charmonium states in $Z^0$ decays. In addition, a signal for the $^3D_J$ charmonium as strong as $J/\psi$ or $\psi^\prime$ with large transverse momentum at the Tevatron should also be observed.Comment: 14 pages in LaTex (3 figures in PS-file