Expansion Problem Research Articles

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

Service expansion for chained business facilities under congestion and market competition

We study a service expansion problem for chained business facilities under endogenic facility congestion and exogenous market competition. More specifically, we consider a company that operates a chain of facilities and plans to expand service capacities with the objective of maximizing its profit, accounting for revenue and expansion costs. To estimate revenue, the company needs to anticipate customer behaviors. Due to the co-existence of competition and congestion, customer behaviors are explained as a two-stage process. In the first stage, customers make “channel” choices, i.e., they decide whether to seek services from the company. Such a choice reflects the market competition and is predicted by a discrete choice model. Subsequently, customers who select the company will choose one facility to patronize. Owing to congestion, the facility choice will induce “user equilibrium”, which in return affects the outcome of market competition. To facilitate the company’s decision-making in this complex business environment, we develop a generic modeling framework. Unfortunately, the proposed model is nonconvex. To solve it, we first design an approximate mixed-integer linear programming approach subject to adjustable approximation errors. We then propose a surrogate optimization framework for large-scale instances, which explores the hidden bilevel structure of the model and leverages a “learning-to-optimize” problem and a customer behavior estimation subroutine. Using extensive computational experiments, we demonstrate the effectiveness of the proposed approaches. Finally, we conduct sensitivity analysis and draw practical implications.

The SnO2 nanotube with CNT core structure (SnO2@void@CNT) and graphene composite electrode for Li-ion batteries

In this study, the problem of volume expansion and agglomeration of SnO2-based electrode materials has been solved with a unique and multifaced approach. Nanosized SnO2 is coated around CNT with a void and this structure is decorated between graphene sheets. The problem of aggregation and volume expansion has been solved with nanostructure and voided structure. Besides, conductivity and buffering contributions have been provided by the production composite with graphene and CNT. Herein graphene layers were decorated SnO2 nanotube with CNT core structure (SnO2@void@CNT) and used as an anode for Li-ion battery. The electrodes were produced by vacuum filtration technique as flexible and free-standing with no any binder. To compare, pure SnO2 and SnO2 decorated graphene/CNT skeleton anodes were prepared and characterized. The SnO2@void@CNT/graphene anode exhibited excellent cycling performance and rate capability properties.

ІНДУСТРІАЛЬНІ ПАРКИ ЯК МЕХАНІЗМ ПОСТКОНФЛІКТНОГО ВІДНОВЛЕННЯ УКРАЇНИ

The article examines the essence of the concepts of special economic zones such as "industrial parks". The world experience of creation of industrial parks in the Czech Republic, Poland, South Korea and Turkey is studied. The conditions and the list of benefits that facilitated the attraction of foreign investment in the creation of new industrial parks are determined. The value and impact on the economic situation of the countries where special economic zones have been implemented are determined. Industrial parks have brought significant economic success, which has become a major factor in accelerated economic development, in particular, the growth of real gross domestic product and exports. The article analyses the state of development of industrial parks in Ukraine after the beginning of the full-scale armed aggression of the Russian Federation. The problems of creation, operation and expansion of industrial parks during the martial law in Ukraine are identified. In order to avoid the complete destruction of enterprises and industry, the Cabinet of Ministers of Ukraine approved the Action Plan for the relocation of production facilities from the areas of active hostilities to safer central and western regions of the country. The largest share of relocated enterprises is made up of wholesale and retail trade, processing industry, motor vehicle repair, professional, scientific, technical activities, and construction enterprises. This article identifies the institutional problems of creating a favourable investment climate in Ukraine before the war, including political, economic and legal instability. The war and attacks on the energy system have had a negative impact on the investment climate in Ukraine since the start of Russia's full-scale armed aggression. The activity of industrial parks in Ukraine remains insufficient due to a number of systemic shortcomings in the preparation and implementation of initiatives to create industrial parks. Insufficient experience of the initiators and imperfect legislative regulation of certain aspects have a negative impact on the investment climate, as potential participants in special economic zones do not receive offers to locate production facilities.

Хирургическое лечение клапанного аортального стеноза в сочетании с узким корнем аорты. Место задней аортопластики у взрослых. Обзор потребности в этой операции, техник ее выполнения и нашего опыта

Aim: to describe the current state of the problem of surgical expansion of the aortic root during aortic valve replacement. Aortic valve replacement is a radical operation aimed at reducing the symptoms of chronic heart failure, reducing left ventricular overload, regressing its hypertrophy, and thereby increasing the quality and life expectancy of the patient. For the greatest success of the operation, the replacement should be made with the appropriate valve size suitable for the particular patient. Materials and methods. The latest literature data on the place of surgical expansion of the aortic root in the problem of treating aortic stenosis were studied. The own experience of these operations during the implantation of mechanical and biological prostheses in the aortic position in the practice of the cardiosurgical department of the Belgorod Regional Clinical Hospital is presented. Results. The study is devoted to the actual problem of choosing the right size of the prosthesis, the frequency of additional surgical procedures for its placement. Many studies have established an association between prosthesis-patient mismatch (PPM) and surgical outcome. The association of prosthesis-patient mismatch with long-term survival is inverse, although sometimes reported as ambiguous. We reviewed the literature and our experience with the surgical management of narrow aortic root situations to determine the incidence of PPM and the need for an additional surgical procedure of posterior aortoplasty to accommodate the appropriate size of the prosthesis. The results of modern meta-analyses, multicenter studies and limited series of operations presented in the literature are reviewed. The experience of the cardiosurgical department of the Belgorod Regional Clinical Hospital for the period 01.01.2015-30.04.2023 in aortic valve replacement with a small size of the aortic ring (17-20 mm) is presented. The study material consisted of 303 patients. As prosthesis-patient mismatch, we defined all cases of posterior aortoplasty with implantation of an appropriately sized aortic prosthesis. According to modern studies, the incidence of prosthesis-patient mismatch in aortic valve replacement without aortic root plasty is 11-33%. The frequency of posterior aortoplasty in adults is, according to different authors, 5-40%. Our experience has shown that the situation of PPM, which required aortic plasty, occurred in 14.8% of cases of implantation of stented biological prostheses, in 17.3% of cases of implantation of mechanical bicuspid prostheses. In general, on average, aortic plasty was performed in 15.8% of cases. Prosthetic-patient mismatch in aortic valve replacement occurs at a relatively constant rate. Posterior aortoplasty allows implanting the calculated size of the prosthesis and avoiding this problem. Conclusion. Surgery to patch the aortic root to accommodate an adequately sized prosthesis in the aortic position is required in 15-30% of patients with narrow aortic annulus. It allows you to get good hemodynamic results. The surgical risk of the operation is low.

Mean-square Approximation of Iterated Ito and Stratonovich Stochastic Integrals: Method of Generalized Multiple Fourier Series. Application to Numerical Integration of Ito Sdes and Semilinear Spdes (third Edition)

This is the third edition of the monograph (first edition 2020, second edition 2021) devoted to the problem of mean-square approximation of iterated Ito and Stratonovich stochastic integrals with respect to components of the multidimensional Wiener process. The mentioned problem is considered in the book as applied to the numerical integration of non-commutative Ito stochastic differential equations and semilinear stochastic partial differential equations with nonlinear non-commutative trace class noise. The book opens up a new direction in researching of iterated stochastic integrals. For the first time we use the generalized multiple Fourier series converging in the sense of norm in Hilbert space for the expansion of iterated Ito stochastic integrals of arbitrary multiplicity k with respect to components of the multidimensional Wiener process (Chapter 1). Sections 1.11-1.13 (Chapter 1) are new and generalize the results of Chapter 1 obtained earlier by the author and are also closely related to the multiple Wiener stochastic integral introduced by Ito in 1951. The convergence with probability 1 as well as the convergence in the sense of n-th (n=2, 3,...) moment for the expansion of iterated Ito stochastic integrals have been proved (Chapter 1). Moreover, the rate of both types of convergence has been established. The main difference between the third and second editions of the book is that the third edition includes original material (Chapter 2, Sections 2.10-2.19) on a new approach to the series expansion of iterated Stratonovich stochastic integrals of arbitrary multiplicity k with respect to components of the multidimensional Wiener process. The above approach allowed us to generalize some of the author's earlier results and also to make significant progress in solving the problem of series expansion of iterated Stratonovich stochastic integrals. In particular, for iterated Stratonovich stochastic integrals of the fifth and sixth multiplicity, series expansions based on multiple Fourier-Legendre series and multiple trigonometric Fourier series are obtained. In addition, expansions of iterated Stratonovich stochastic integrals of multiplicities 2 to 4 were generalized. These results (Chapter 2) adapt the results of Chapter 1 for iterated Stratonovich stochastic integrals. Two theorems on expansion of iterated Stratonovich stochastic integrals of arbitrary multiplicity k based on generalized iterated Fourier series with pointwise convergence are formulated and proved (Chapter 2). The results of Chapters 1 and 2 can be considered from the point of view of the Wong-Zakai approximation for the case of a multidimensional Wiener process and the Wiener process approximation based on its series expansion using Legendre polynomials and trigonometric functions. The integration order replacement technique for iterated Ito stochastic integrals has been introduced (Chapter 3). Exact expressions are obtained for the mean-square approximation error of iterated Ito stochastic integrals of arbitrary multiplicity k (Chapter 1) and iterated Stratonovich stochastic integrals of multiplicities 1 to 4 (Chapter 5). Furthermore, we provided a significant practical material (Chapter 5) devoted to the expansions and mean-square approximations of specific iterated Ito and Stratonovich stochastic integrals of multiplicities 1 to 6 from the unified Taylor-Ito and Taylor-Stratonovich expansions (Chapter 4). These approximations were obtained using Legendre polynomials and trigonometric functions. The methods constructed in the book have been compared with some existing methods (Chapter 6). The results of Chapter 1 were applied (Chapter 7) to the approximation of iterated stochastic integrals with respect to the finite-dimensional approximation of the Q-Wiener process (for integrals of multiplicity k) and with respect to the infinite-dimensional Q-Wiener process (for integrals of multiplicities 1 to 3).

Implementation of the CST complex Sadik transform to treat population expansion and decay problems

Now with the increasing problems of expansion of the population and decay in the world, researchers are making great efforts to find new ideas and proposals to find successful solutions to solve these problems through the utilization of different integrated transformations. In our paper, the complex Sadik transform is applied to resolve the issues of population expansion and decay.

Contrast Optimization for Size Invariant Visual Cryptography Scheme.

Visual cryptography scheme (VCS) serves as an effective tool in image security. Size-invariant VCS (SI-VCS) can solve the pixel expansion problem in traditional VCS. On the other hand, it is anticipated that the contrast of the recovered image in SI-VCS should be as high as possible. The investigation of contrast optimization for SI-VCS is carried out in this article. We develop an approach to optimize the contrast by stacking t ( k ≤ t ≤ n ) shadows in (k, n) -SI-VCS. Generally, a contrast-maximizing problem is linked with a (k, n) -SI-VCS, where the contrast by t shadows is considered as an objective function. An ideal contrast by t shadows can be produced by addressing this problem using linear programming. However, there exist (n-k+1) different contrasts in a (k, n) scheme. An optimization-based design is further introduced to provide multiple optimal contrasts. These (n-k+1) different contrasts are regarded as objective functions and it is transformed into a multi-contrast-maximizing problem. The ideal point method and lexicographic method are adopted to address this problem. Additionally, if the Boolean XOR operation is used for secret recovery, a technique is also provided to offer multiple maximum contrasts. The effectiveness of the proposed schemes is verified by extensive experiments. Comparisons illustrate significant advancement on contrast is provided.