The Largest Laplacian and Signless Laplacian H-Eigenvalues of a Uniform Hypergraph

In this paper, we show that the largest Laplacian H-eigenvalue of a $k$-uniform nontrivial hypergraph is strictly larger than the maximum degree when $k$ is even. A tight lower bound for this eigenvalue is given. For a connected even-uniform hypergraph, this lower bound is achieved if and only if it is a hyperstar. However, when $k$ is odd, it happens that the largest Laplacian H-eigenvalue is equal to the maximum degree, which is a tight lower bound. On the other hand, tight upper and lower bounds for the largest signless Laplacian H-eigenvalue of a $k$-uniform connected hypergraph are given. For a connected $k$-uniform hypergraph, the upper (respectively lower) bound of the largest signless Laplacian H-eigenvalue is achieved if and only if it is a complete hypergraph (respectively a hyperstar). The largest Laplacian H-eigenvalue is always less than or equal to the largest signless Laplacian H-eigenvalue. When the hypergraph is connected, the equality holds here if and only if $k$ is even and the hypergraph is odd-bipartite.Comment: 26 pages, 3 figure

Solid polymer electrolytes: Ion conduction mechanisms and enhancement strategies

Solid polymer electrolytes (SPEs) possess comprehensive advantages such as high flexibility, low interfacial resistance with the electrodes, excellent film-forming ability, and low price, however, their applications in solid-state batteries are mainly hindered by the insufficient ionic conductivity especially below the melting temperatures, etc. To improve the ion conduction capability and other properties, a variety of modification strategies have been exploited. In this review article, we scrutinize the structure characteristics and the ion transfer behaviors of the SPEs (and their composites) and then disclose the ion conduction mechanisms. The ion transport involves the ion hopping and the polymer segmental motion, and the improvement in the ionic conductivity is mainly attributed to the increase of the concentration and mobility of the charge carriers and the construction of fast-ion pathways. Furthermore, the recent advances on the modification strategies of the SPEs to enhance the ion conduction from copolymer structure design to lithium salt exploitation, additive engineering, and electrolyte micromorphology adjustion are summarized. This article intends to give a comprehensive, systemic, and profound understanding of the ion conduction and enhancement mechanisms of the SPEs for their viable applications in solid-state batteries with high safety and energy density

Clinical application of Kirschner wires combined with 5-Ethibond fixation for patella fractures

BackgroundPatella fractures that require surgery are conventionally treated using Kirschner wires (K-wires) and stainless steel wires. In recent years, the nonabsorbable polyester has been reported to have excellent outcomes clinically. Therefore, the goal of our study was to evaluate the effects of Kirschner wires combined with 5-Ethibond on treating patellar fractures.MethodsFrom July 2018 to January 2022, 22 patella fracture patients were treated with Kirschner wires combined with 5-Ethibond. Radiographs of the knees were used to evaluate fracture healing and hardware complications. The clinical results were evaluated through the functional score, knee joint range of motion (ROM), and Bostman patella fracture functional score.ResultsThe average age of patients was 57.4 ± 11.9 (range 33–74) years. The mean follow-up time was 15.2 ± 7.6 (range 4–36) months. The mean operation time was 56.8 ± 8.7 (range 45–80) min. The entire patients had bony union at an average of 10.5 ± 1.9 (range 8–14) weeks. At the final follow-up, the mean range of postoperative ROM was 123.4° ± 14.6° (range 95°–140°), and the functional score was 28.7 ± 1.2 (range 26–30) points. No patient exhibited internal fixation failure, and no symptomatic implants or skin complications were recorded.ConclusionsThe fixation approach using K-wires combined with 5-Ethibond has a lower complication rate and delivers superior clinical results. This research reveals that such technology is a safe and prospective substitute for conventional metal fixation approaches

Heat transfer and fluid flow characteristics in various micro devices for the development of micro absorption heat pump systems

This thesis presents a series of studies on heat transfer and fluid flow characteristics in various micro devices for the development of micro absorption heat pump systems. The study covered a feasibility analysis of an absorption micro heat pump system, convective condensation in micro condensers, electroosmotic (EO) micro pump, flow friction in microchannels and the performance of a laboratory scale micro absorption heat pump system. Mass, energy density, efficiency and the orientation issues of a micro absorption heat pump system were analyzed. It showed that the micro absorption heat pump system can have a quite high energy density and its efficiency can be comparable with that of macro absorption heat pump systems. Micro absorption heat pump systems are worth developing for many potential applications. Five condensation flow regimes were identified in micro silicon condensers, i.e., pure droplet flow, droplet/liquid slug flow, stratified flow, injection flow and slug-bubbly flow. A correlation was obtained to predict the transition of the flow pattern from slug-bubbly flow to the mixed flow patterns. Heat transfer property of the five flow regimes was analyzed. Slug-bubbly flow, pure droplet flow and droplet/liquid slug flow were identified to be the dominant flows. Heat transfer coefficients and pressure drops of slug-bubbly flow were studied with the effect of channel dimension, mass flux and heat flux. Heat transfer property of pure droplet flow and droplet/liquid slug flow was also studied via experiments and theoretical analysis. Size of droplets with the effects of steam mass flux, steam-surface temperature difference and channel dimension was investigated. Classical dropwise condensation theory was modified for the prediction of the dropwise condensation heat flux in microchannels. Condensation heat flux in microchannels was studied experimentally at various steam mass fluxes, steam-surface temperature differences and channel dimensions. The predicted heat fluxes and those from the experiments agreed with each other well. In the study of the EO micro pump, issues including fabrication, theoretical model and performance of the EO micro pump were investigated. A revised mathematical model was established in which Boltzmann equation, Debye-Huckle approximation and symmetric condition were avoided. A fabrication process was designed and EO micro pumps were fabricated successfully. Distribution of the potential and the ions in EO micro pumps were investigated via numerical simulation. It showed that when the EO pump was very thin, the error of traditionally used Poisson Boltzmann equation could be quite large while the error of the developed model remained to be acceptable. Performance of EO micro pumps with the effects of pump depth, temperature, electric field strength and bulk ionic concentration was investigated via experiments and numerical simulations. Experiments were also carried out to study the flow friction characteristic in microchannels for the development of expansion devices. The results showed that pressure drops in microchannels exhibit a linear behavior with the Reynolds number, which was in agreement with that in macro tubes. Friction factor was found to be proportional to Re-1 in microchannels as was observed in macro tubes. Friction factors in microchannels were found to be lower than those predicted by the classical laminar flow theory. The deviation of the friction factor from the theoretical value was dependant on the channel dimension. Based on the experimental data, a correlation was developed to predict the friction factors in smooth microchannels with hydraulic diameters from about 118 to 175 μm. We established a laboratory scale micro absorption heat pump system. Cooling was successfully generated by this micro absorption heat pump system. Performance of the micro absorption heat pump system was studied via experiments. It showed that the COP of the system was comparable to some macro absorption heat pump systems. Key Words: Micro Absorption Heat Pump System, Convective Condensation in Microchannels, Slug-bubbly Flow, Pure Droplet Flow, Droplet/ Liquid Slug Flow, Electroosmotic Micro Pump, Pumping Performance, Flow Friction in Microchannel

Cluster driven anisotropic diffusion for speckle reduction in ultrasound images

© 2016 IEEE. In this paper, we propose a cluster-driven anisotropic diffusion (CDAD) filter for speckle reduction in ultrasound images. The proposed filter is based on the multiplicative noise model and is driven by K-means clustering algorithm. Instead of choosing homogeneous sample region with manual selection, the proposed algorithm is able to do it automatically (based on the clustering results). In addition, clustering result is used as a global characteristics descriptor to further improve the performance of noise removal as well as edge enhancement. The proposed filter was implemented and evaluated with real ultrasound images. Experimental results show that the proposed CDAD filter shows improved performance compared with Speckle Reducing Anisotropic Diffusion (SRAD)

A hybrid algorithm for the segmentation of books in libraries

This paper proposes an algorithm for book segmentation based on bookshelves images. The algorithm can be separated into three parts. The first part is pre-processing, aiming at eliminating or decreasing the effect of image noise and illumination conditions. The second part is near-horizontal line detection based on Canny edge detector, and separating a bookshelves image into multiple sub-images so that each sub-image contains an individual shelf. The last part is book segmentation. In each shelf image, near-vertical line is detected, and obtained lines are used for book segmentation. The proposed algorithm was tested with the bookshelf images taken from OPIE library in MTU, and the experimental results demonstrate good performance