The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

Topology optimization has undergone a tremendous development since its introduction in the seminal paper by Bendsoe and Kikuchi in 1988. By now, the concept is developing in many different directions, including “density”, “level set”, “topological derivative”, “phase field”, “evolutionary” and several others. The paper gives an overview, comparison and critical review of the different approaches, their strengths, weaknesses, similarities and dissimilarities and suggests guidelines for future research.

Topology optimization approaches: A comparative review

Notably, many significant breakthroughs for a new generation of supercapacitors have been reported in recent years, related to theoretical understanding, material synthesis and device designs. Herein, we summarize the state-of-the-art progress toward mechanisms, new materials, and novel device designs for supercapacitors. Firstly, fundamental understanding of the mechanism is mainly focused on the relationship between the structural properties of electrode materials and their electrochemical performances based on some in situ characterization techniques and simulations. Secondly, some emerging electrode materials are discussed, including metal–organic frameworks (MOFs), covalent organic frameworks (COFs), MXenes, metal nitrides, black phosphorus, LaMnO3, and RbAg4I5/graphite. Thirdly, the device innovations for the next generation of supercapacitors are provided successively, mainly emphasizing flow supercapacitors, alternating current (AC) line-filtering supercapacitors, redox electrolyte enhanced supercapacitors, metal ion hybrid supercapacitors, micro-supercapacitors (fiber, plane and three-dimensional) and multifunctional supercapacitors including electrochromic supercapacitors, self-healing supercapacitors, piezoelectric supercapacitors, shape-memory supercapacitors, thermal self-protective supercapacitors, thermal self-charging supercapacitors, and photo self-charging supercapacitors. Finally, the future developments and key technical challenges are highlighted regarding further research in this thriving field.

Latest advances in supercapacitors: from new electrode materials to novel device designs.

The Arithmetic Optimization Algorithm

Topology optimization is the process of determining the optimal layout of material and connectivity inside a design domain. This paper surveys topology optimization of continuum structures from the year 2000 to 2012. It focuses on new developments, improvements, and applications of finite element-based topology optimization, which include a maturation of classical methods, a broadening in the scope of the field, and the introduction of new methods for multiphysics problems. Four different types of topology optimization are reviewed: (1) density-based methods, which include the popular Solid Isotropic Material with Penalization (SIMP) technique, (2) hard-kill methods, including Evolutionary Structural Optimization (ESO), (3) boundary variation methods (level set and phase field), and (4) a new biologically inspired method based on cellular division rules. We hope that this survey will provide an update of the recent advances and novel applications of popular methods, provide exposure to lesser known, yet promising, techniques, and serve as a resource for those new to the field. The presentation of each method's focuses on new developments and novel applications.

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A survey of structural and multidisciplinary continuum topology optimization: post 2000

This paper presents a stress constrained topology optimization problem and its level set based solution. The volume of material is minimized, and stress constraints at all the points in a structure are efficiently aggregated into a single equivalent global constraint. Using the material derivative and adjoint method we derived the shape sensitivity. The steepest descent optimization algorithm is implemented. Several numerical examples in two dimensions are provided and discussed.

A level set based method for topology optimization of continuum structures with stress constraint

For simultaneously measuring specimen’s surface morphology and material properties, multifrequency atomic force microscopy is often employed. In this kind of atomic force microscopy, if the probe’s...

https://journals.sagepub.com/doi/pdf/10.1177/1687814018811200

An optimized harmonic probe with tailored resonant mode for multifrequency atomic force microscopy

To enhance the measurement performance of tapping-mode atomic force microscopy (TM-AFM), it is highly desirable that the TM-AFM probe has high resonant frequency and large effective slope at its free end However, the two design objectives may lead to conflict requirements on the geometry of probe Conventional design approaches that involve a lot of trials and errors are not so effective to solve such a complex design problem Therefore, in order to address this difficulty, a structural optimization problem is formulated The objective of optimization is to ensure the mode shape of probe match a user-specified target shape and the corresponding resonant frequency is maximized Similarity between the actual mode shape and the target is characterized by modal assurance criterion Users can freely select which vibration mode is to be optimized A three-layer geometry model is used to represent cantilever probes The middle layer is not subject to optimization The top and bottom layers have the same width profile, and it is iteratively changed during the optimization The optimization problem is solved through a gradient based method Examples of design optimization show that the proposed method is effective

Design optimization of high performance tapping mode AFM probe

Nano-structures on the wing of Morpho butterflies generate bright blue color, and this color is sensitive to ambient gas, or more specifically, the refractive index of ambient gas. It was found that even slight change of the refractive index can lead to obvious change of the color. Such phenomenon has caught much attention and was employed as a sensing principle for detecting gas. In the present study, a typical nano-structure on the wing of Morpho butterflies is mimicked and simplified for constructing a refractive index based gas sensor. Moreover, partial derivative of the optical reflection efficiency with respect to the refractive index of ambient gas, i.e., sensitivity of the sensor, is utilized based on the rigorous coupled-wave analysis (RCWA) method. Finally, the effects of the nano-structure’s shape on the partial derivative are analyzed. The results can be applied to the design of the bioinspired refractive index based gas sensor.

Sensitivity Analysis of a Bioinspired Refractive Index Based Gas Sensor

We present an image registration method based on geometric pattern matching. The method is applicable to the situation
that there is a similarity transformation between two images. First of all, the edges of the images were detected and the
edge points were described with subpixel position and direction of gradient vector of intensities. The geometric denoising
method was proposed to smooth the position and direction of the edge points. And then a coarse registration was
performed to compute the similarity transformation parameters with pixel accuracy. In the end, a high accuracy
registration based on iterative closest point (ICP) algorithm is used to obtain the final result.

Qi Xia

Papers

A level set based method for topology optimization of continuum structures with stress constraint

An optimized harmonic probe with tailored resonant mode for multifrequency atomic force microscopy

Design optimization of high performance tapping mode AFM probe

Sensitivity Analysis of a Bioinspired Refractive Index Based Gas Sensor

Image registration based on geometric pattern matching