Expansion Problem Research Articles

Tibial Press-Fit Fixation Technique in Anterior Cruciate Ligament Reconstruction

Implant-free press-fit tibial fixation technique has gained popularity recently due to the problems in bone tunnel expansion, defect, and revision surgery due to the tibial fixation material preferred in anterior cruciate ligament surgery. Patellar tendon-tibial bone autograft offers several advantages in anterior cruciate ligament reconstruction. We describe a tibial tunnel preparation method and the use of patellar tendon-bone graft in the implant-free tibial press-fit technique. We call this the Kocabey press-fit technique.

Inspired by nature: Self-fractal cobalt sulfate composite electrode for sodium ion storage

Generally, the metal sulfide itself has poor conductivity, and the volume expansion occurs when it is converted with sodium, which will destroy the integrity of the electrode structure, resulting in poor cycle performance and rate performance. To solve the problems of low initial coulombic efficiency (ICE) and volume expansion of metal compounds used as anodes in sodium-ion batteries (SIBs). Inspired by nature, the CoSO4/hard carbon/graphene (CHG) fractal structure electrode was designed. Self-fractal structures with electron/ion transport channels and high strain tolerance proved to be an effective strategy to overcome these challenges. The fractal dimension (D) is measured by synchronous Small Angle X-ray scattering, and the D remains stable during charging and discharging. The fractal CHG also showed excellent electrochemical performance, especially 97.4% ICE. Theoretical calculation shows that self-fractal CHG can promote the formation of a thin solid electrolyte interface (SEI). Synchrotron radiation absorption spectrum proved the reaction mechanism of CHG. This study not only proves that cobalt sulfate is a feasible strategy for developing high-performance SIBs anodes but also provides an advanced method for measuring the fractal dimension of energy storage electrode materials.

One−Step Synthesis of Fe−Based Metal–Organic Framework (MOF) Nanosheet Array as Efficient Cathode for Hybrid Supercapacitors

With the flourishing development of the new energy automobile industry, developing novel electrode materials to balance the capacity between cathode and anode is a challenge for hybrid supercapacitors. In comparison to conventional inorganic materials, metal–organic frameworks materials offer higher porosity and greater surface area for use in supercapacitors. Herein, we proposed a facile one–pot solvothermal technique to synthesize an Fe(BPDC) nanosheet array on Ni foam, which we then applied as a binder–free cathode for a supercapacitor. The solvothermal time was adjusted to ensure a desirable morphology of the final product. Benefitting from the impressive nanosheet morphology, to a great extent, Fe(BPDC) has solved the problem of volume expansion of Fe–based electrode materials during cycling, and exhibits brilliant electrochemical performances, i.e., high specific capacitance (17.54 F/cm2 at 1 mV/s) and satisfactory cycle performance (129% retention after 10,000 cycles). Furthermore, Fe(BPDC) and activated carbon (AC) have been chosen to assemble a hybrid supercapacitor (namely Fe(BPDC)//AC), delivering an energy density of 45.64 Wh/kg at the power density of 4919.6 W/kg with 87.05% capacitance retention after 10,000 cycles. These brilliant results prove that Fe(BPDC) material has great potential as the cathode of supercapacitors.

Correction to: Decision rule-based method in solving adjustable robust capacity expansion problem

Correction to: Decision rule-based method in solving adjustable robust capacity expansion problem

Decision rule-based method in solving adjustable robust capacity expansion problem

Decision rule-based method in solving adjustable robust capacity expansion problem

Cavity expansions in partially drained soils and a comparison to CPT results

Cylindrical and spherical cavity expansions in soils are of interest, especially when interpreting cone penetration tests (CPTs) and pressuremeter tests (PMTs). Here the cavity expansion problem is solved semi-analytically, considering partial drainage of the soil, when the cavity wall velocity is constant. The solutions may assist with the interpretation of CPTs and PMTs when partially drained conditions prevail in the surrounding soils. The solution procedure involves writing the governing partial differential equations in dimensionless form. The modified Cam-clay constitutive model is adopted for the soil to demonstrate the solution procedure, due to its wide familiarity, although other models could be used by making simple modifications. The variables in the partial differential equations are functions of a dimensionless time, T, and a dimensionless radial coordinate, H. T depends on cavity radius, the time after expansion began and a coefficient of consolidation. The equations are solved for when T is fixed, simultaneously as an initial value problem, as the partial differential equations become ordinary differential equations. Important features captured by the analyses include pore water pressure variations with soil volume changes, as well as the differential of the pore water pressure satisfying the no-flow cavity wall boundary condition. Results for a cavity expansion reveal that initially, when T and the cavity are small, drained conditions prevail. As T and the cavity become larger the soil becomes partially drained and eventually undrained. T is analogous to the dimensionless cone penetration velocity used in CPT studies. Normalised cavity wall pressures vary with T similar to that of normalised cone penetration resistances, demonstrated using experimental data. Plots of the normalised cavity wall pressures against the state parameter show that the two key fitting constants are heavily influenced by partial drainage. A similar dependence must exist when plotting a normalised cone penetration resistance against the state parameter when partially drained conditions prevail. The practical ramifications of not dealing with this partial drainage may be huge, especially when assessing liquefaction susceptibility through estimations of the state parameter using correlations developed for when drained conditions prevail. Significant underestimations of state parameter, liquefaction susceptibility and post-liquefaction strengths may result.

Existence of solutions to gas expansion problem through a sharp corner for 2‐D Euler equations with general equation of state

AbstractIn this article, we study the gas expansion problem by turning a sharp corner into a vacuum for the two‐dimensional (2‐D) pseudosteady compressible Euler equations with a convex equation of state. This problem can be considered as the interaction of a centered simple wave with a planar rarefaction wave. To obtain the global existence of a solution up to the vacuum boundary of the corresponding 2‐D Riemann problem, we consider several Goursat‐type boundary value problems for 2‐D self‐similar Euler equations and use the ideas of characteristic decomposition and bootstrap method. Further, we formulate 2‐D‐modified shallow water equations newly and solve a dam‐break‐type problem for them as an application of this work. Moreover, we also recover the results from the available literature for certain equations of states that provide a check that the results obtained in this article are actually correct.

Seismic design and performance study of self‐centering moment‐resisting frames with sliding rocking beams and preloaded disc springs

AbstractThis paper focuses on the seismic analysis and performance assessment of the self‐centering moment‐resisting frames with sliding rocking beams (SCMRF‐SRB) through a nonlinear numerical simulation study. In the SCMRF‐SRB systems, the beam is comprised of three segments with the rocking beam placed in the middle segment. The beam growth (expansion) problem due to the gap‐opening in the rocking joint is counteracted by the sliding movement of the rocking beam inside the beam brackets. The restoring force of such SCMRF‐SRBs is generated by two sets of preloaded disc springs mounted on each side of the web of the beam and the energy dissipation is provided by replaceable hysteretic dampers (RHD). The relative movement of the rocking beam inside the brackets generates a friction force that contributes to the energy dissipation capacity and strength of the system based on prior experimental observations. Load vs. displacement relationships of an SCMRF‐SRB modular structure were formulated and verified with nonlinear finite element analysis results. A three‐story building located in downtown Seattle was designed and its seismic performance was studied through nonlinear static and dynamic analyses. According to the results of the nonlinear dynamic analyses, the prototype structure met the expected performance criteria in terms of inter‐story drift ratio (IDR), re‐centering behavior, and responses of the frame member at design basis earthquake (DBE). In different parametric studies, the effect of the length and location of the rocking beam on the seismic performance of the prototype structure was investigated. Moreover, the effects of the energy dissipation capacity and post‐yielding stiffness on the structural responses of the prototype buildings were studied. It was also shown that an SCMRF‐SRB structure with a large energy dissipation ratio of up to 90% can be utilized without adversely affecting the self‐centering performance of the system.

How can the sustainable goal of cultivated land use in the Qinghai-Tibet Plateau be realized?—based on a research framework of cultivated land use patterns

The study of cultivated land use models is an important means to improve the benefit of cultivated land use and promote the sustainable use of cultivated land. The rational optimization of regional cultivated land use models based on the consideration of regional background conditions and development goals can provide a scientific basis for ensuring the sustainable use of cultivated land. This study constructed a three-dimensional research framework of "natural quality-utilization intensity-spatial layout" of cultivated land utilization pattern. Taking the county as a unit, the natural quality, spatial distribution and utilization intensity of cultivated land in the Qinghai-Tibet Plateau were evaluated, and the types of cultivated land utilization models were determined. Based on the ecological protection and the regulation and control of agriculture and animal husbandry in the Qinghai-Tibet Plateau, the optimization direction of cultivated land use patterns was discussed. The results show that the cultivated land use pattern divided by the “NUS” three-dimensional model can accurately reflect the characteristics of cultivated land use in the Qinghai-Tibet Plateau. The existing cultivated land use pattern in the Qinghai-Tibet Plateau is basically consistent with its ecological protection and development direction zoning, but the problems of unreasonable expansion and excessive use intensity of cultivated land exist in the ecotone between some development areas and restricted areas. Therefore, the utilization and optimization of cultivated land in the Qinghai-Tibet Plateau should be based on the premise of protecting ecological security and striving to solve the contradiction between agricultural development and ecological protection to realize the sustainable utilization of cultivated land.

A Selective Oxidation Strategy towards the Yolk-Shell Structured ZnS@C Material for Ultra-Stable Li-Ion Storage.

Metal chalcogenides are attractive anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacities. With the advantages of low cost and abundance reserves, ZnS is regarded as the prime candidate anode material for future generations, but its practical application is hindered by the large volume expansion during repeated cycling processes and inherent poor conductivity. Rational design of the microstructure with large pore volume and high specific surface area is of great significance to solve these problems. Here, a carbon-coated ZnS yolk-shell structure (YS-ZnS@C) has been prepared by selective partial oxidation of a core-shell structured ZnS@C precursor in air and subsequent acid etching. Studies show that the carbon wrapping and proper etching to bring cavities can not only improve the material's electrical conductivity, but can also effectively alleviate the volume expansion problem of ZnS during its cycles. As a LIB anode material, the YS-ZnS@C exhibits an obvious superiority in capacity and cycle life compared to ZnS@C. The YS-ZnS@C composite shows a discharge capacity of 910 mA h g-1 at the current density of 100 mA g-1 after 65 cycles, compared to only 604 mA h g-1 for ZnS@C after 65 cycles. Notably, at a large current density of 3000 mA g-1, a capacity of 206 mA h g-1 can still be maintained after 1000 cycles (over three times of the capacity for ZnS@C). It is expected that the synthetic strategy developed here is applicable to designing various high-performance metal chalcogenide-based anode materials for LIBs.

Technologies and Applications of Pipeline-type Oil-gas-water Separation

The separation of oil, gas, and water mixture is an important process in the production of crude oil. Traditional separation tanks are large, heavy, long in separation time, and high cost to manufacture. This paper introduces a separation technology with the main characteristics of the pipeline structure. This technology uses the principles of centrifugation, expansion, air flotation, and gravity separation. Pipes and other equipment are the core equipment, which has the advantages of flexible process composition, small footprint, and high separation efficiency. This technology can be used for rapid oil, gas, and water separation, solving the problems of expansion, upgrading old oilfield stations, realizing the purpose of re-injection of water in-situ, energy saving, and reducing emissions.

Using Lagrangian relaxation to locate hydrogen production facilities under uncertain demand: a case study from Norway

Hydrogen is considered a solution to decarbonize the transportation sector, an important step to meet the requirements of the Paris agreement. Even though hydrogen demand is expected to increase over the next years, the exact demand level over time remains a main source of uncertainty. We study the problem of where and when to locate hydrogen production plants to satisfy uncertain future customer demand. We formulate our problem as a two-stage stochastic multi-period facility location and capacity expansion problem. The first-stage decisions are related to the location and initial capacity of the production plants and have to be taken before customer demand is known. They involve selecting a modular capacity with a piecewise linear, convex short-term cost function for the chosen capacity level. In the second stage, decisions regarding capacity expansion and demand allocation are taken. Given the complexity of the formulation, we solve the problem using a Lagrangian decomposition heuristic. Our method is capable of finding solutions of sufficiently high quality within a few hours, even for instances too large for commercial solvers. We apply our model to a case from Norway and design the corresponding hydrogen infrastructure for the transportation sector.

Enhanced electrochemical performance of silicon anode materials with titanium hydride treatment

As a promising anode material for the next generation of lithium-ion batteries, silicon (Si) suffers from the main problems of severe volume expansion and poor electrical conductivity. Compounding Si-based materials with metal hydrides is one of the ways to overcome these problems. Herein, we proposed TiH2 decorated Si composites prepared by ball milling and subsequent high-temperature calcination to restrain the volume expansion of Si and enhance the electrical conductivity. The resulting Si-0.05TiH2 anode delivered a reversible discharge capacity of 766.1 mAh/g after 100 cycles at a current density of 100 mA/g and better rate capability than the Si anode. Additionally, the impedance measurements and the density functional theory (DFT) calculation demonstrated that the insertion of Ti after dehydrogenation of TiH2 enhanced the conductivity of the composite anode. The charge transfer resistance (Rct) of Si-0.05TiH2 and Si anodes were 43.03 Ω and 609.6 Ω, respectively, indicated that the charge transfer process of Si/TiH2 electrodes was faster. This study provides a new strategy for compounding metal hydrides with Si, and a further attempt to enhance the electrochemical properties of Si.

Two-dimensional pseudo-steady supersonic isothermal flow around a sharp corner

The problem of the two-dimensional pseudo-steady supersonic isothermal flow around a sharp corner expanding into vacuum is studied in this article. It is worth noting that the gas will diffuse to infinity, that is, there is no vacuum boundary in this work. The essence of this problem is the interaction of the centered simple wave with the planar rarefaction wave, which can be solved by the Goursat problem for the two-dimensional self-similar Euler equations. Through the methods of characteristic decompositions and invariant regions, we establish a priori C1 estimates and the hyperbolicity of the solution in the wave interaction domain. The global existence of solution to the gas expansion problem is obtained constructively.

A robust stress update algorithm for elastoplastic models without analytical derivation of the consistent tangent operator and loading/unloading estimation

AbstractA robust and concise implicit stress integration algorithm of elastoplastic models is presented. It does not require the loading/unloading estimation and analytical derivation operation for the stress update. First, the elastoplastic stress update problem is recast into an unconstrained minimization problem by utilizing the smooth function to bypass the loading/unloading estimation. Then, the object problem is solved by the line search method instead of the Newton method for better convergence. The consistent tangent operator is evaluated by the complex step derivative approximation without the subtraction cancellation error, which provides the quadratic convergence rate of global iteration. The rationality of the numerical consistent tangent operator is validated by the one obtained by the analytical derivation. A recently developed non‐orthogonal elastoplastic (NEP) clay model is implemented using the new algorithm. The algorithm is confirmed through comparing the numerical solution and the analytical one for a cavity expansion problem. The algorithm performance is assessed based on a series of geotechnical boundary value problems. It is found that the new algorithm is more robust than the one employed by ABAQUS. The source code of the model implementation can be downloaded from https://github.com/zhouxin615.

An improved RRT-Connect path planning algorithm of robotic arm for automatic sampling of exhaust emission detection in Industry 4.0

In the time of industrial 4.0 era represented by intelligent manufacturing, as the most widely used equipment in the industrial robots filed, robotic arms can replace people for a large number of exhaustive, repetitive and harmful work. In the process of vehicle exhaust emission detection, manual exhaust gas sampling is required, which is inefficient and easily harmful to the human body. Using a robotic arm in the detection scene can improve the detection efficiency and prevent the exhaust gas from affecting the human body. In this paper, an improved RRT-Connect path planning algorithm is proposed to realize a reliable path design required for automatic sampling control of exhaust emission detection. For the problems of blind expansion, low efficiency in the RRT and its improved algorithm, an improved RRT-Connect algorithm through setting the adaptive step strategy and using the fixed sampling function to construct four random trees from the starting point, the end point and the fixed point for search is proposed in this paper, which can solve the problem of slow expansion and speed up convergence. Experimental results show that compared with the unimproved RRT-Connect algorithm, the improved algorithm decreases the number of iterations by 18.11% and reduces the number of path nodes by 23.02%, which meets the path planning requirements of automatic sampling control of the robotic arm.

Development of Approaches and Organizational Models for the Mass Implementation of Information Modeling Technologies in the Investment and Construction Sphere

The rapidly increasing use of building information modeling (BIM) technologies in the world is highly relevant to the search for new approaches and managerial models for enterprises in the construction sphere. As shown in the study of several developing countries, there is a certain lag in this area compared with highly industrialized countries. A comparative analysis of countries in terms of the level of spread of BIM technologies was made using open data from job search Internet sites. In this regard, the urgency of the research is due to the need to develop appropriate approaches to intensify the implementation of BIM technologies in the construction and operation of buildings. The purpose of the study is the development of methodological foundations and applied models of functional interaction between participants of construction projects based on BIM. As a working hypothesis, the authors assume that the mass application of BIM technologies is possible in providing a set of measures of different nature: market, non-market, legal, economic, and organizational. The main results of the study provided a solution to the problem of a significant expansion of the scope of BIM technologies in the construction sector through the formation of an information eco-environment for interaction of participants in the project management system.

Applications of Nanotechnology: lithium-ion based batteries in electric vehicles

With the benefit of zero emissions, free noise and stable operation, the electrical vehicle market has grown dramatically. More expectations are raised for electric vehicles to achieve a better user experience of long-range, long-lifespan and time-saving charging. Thus the capacity, cycling ability and rate capability of electric vehicle batteries are aimed to be improved. Since the advent of nanotechnology, it has made great contributions to various industries and is also believed to be a breakthrough in battery performance. This article introduced nanotechnologies, summarised and discussed its application that could improve lithium-ion-based electric vehicle battery performance. Three typical commercialised cathode materials (Lithium Manganese Oxide (LMO), Lithium Nickel Manganese Cobalt Oxide (NMC), and Lithium Nickel Cobalt Aluminium Oxide (NCA)) suffer capacity fading due to lattice distortion, ion dissolution, and electrolyte decomposition, which can be mitigated by nano-doping, nanocoating, and special nanostructure to certain extents. Two promising anode materials (Lithium titanate (LTO) and silicon) face problems of poor electrical conductivity and volumetric expansion during cycling. Nanotechnologies provide solutions that greatly accelerate their commercialisation. In the future, quantitative composition manipulation is the key point to further promoting cathode material performance. And anode materials still need to be improved to be genuinely used in life. This article combines nanotechnology with the electric vehicle industry and provides innovative ideas for their development.

Basic Characterization and Sputtering Processing of Diatom‐Based Anode Materials

AbstractSilicon‐based anode materials are advantageous because of its high specific capacity, rich resources and appropriate lithium deintercalation potential. However, it is also limited by some disadvantages including large volume expension, poor electronic conductivity and low Initial Coulomb Efficiency(ICE). Benefitting from the original hierarchical porous structure of diatom and amorphous framework of SiO2, we explore the diatoms cultured on a large scale as the anode materials of lithium batteries. Herein, we obtain a suitable diatom‐based anode material with particle diameter D50 4.065 μm, BET specific surface area 228.28 m2/g and biomass of carbon approximately 25 %, while it successfully solves the problems of volume expansion and electronic conductivity. Furthermore, after facile sputtering processing, we successfully introduced metallic elements into the diatom‐based anode. The elements include 3.40 % of Al, 0.75 % of Ti, 10.40 % of Ni, etc. The charge‐dischare results show that the introduction of both Al and Ti lead to performance improvement in some extend.

Half-Tone Visual Cryptography Scheme For RGB Color Images

Objectives: Currently used visual-cryptography methods which use binary and gray-level images have some shortcomings such as large pixel expansion, poor visual quality of the reconstructed image, etc. Further modifications in visualcryptography methods are required to provide error-free and better results. It has been observed that the use of color images is more convenient and accurate in approach. Method: This research study presents a new and optimal scheme for the visual-cryptography which is centered on RGB color images. Jarvis halftoning is applied on each decomposed color channel that is used in share generation. A special code matrix is defined for the generation of color shares and the optimal reconstruction of the original image. The method is tested with color images of different sizes, no specific dataset is required. Pixel Expansion, The Aspect Ratio, and Contrast of the method is compared with the existing method, and found more enhanced result. Findings: The scheme projected eliminates the problems of large pixel expansion and poor visual quality in the reconstructed images. The performance of the method is tested with the different statistical measures and values obtained as Mean Square Error (MSE):0, Peak- Signal-to-Noise-Ratio (PSNR): ¥, Universal Index Quality (UIQ):1, etc. This means that the original image is completely recovered with good contrast. Novelty: Color images of varied sizes and channels can be processed by applying the Jarvis half-toning technique through the codebook calculated to abolish the problems of pixel expansion and to improve the superiority of the renovated image. Keywords: Color HalfTone Images; Error Diffusion; Optimal Contrast; Secret and Secure Sharing Scheme; Expansion of Pixels