Step Structure Research Articles

Efficiency of Friction Pendulum Bearings in Vertically Irregular Structures Subjected to Various Types of Earthquakes

The attention towards seismic mitigation using passive control systems has increased significantly over the last few decades to reduce earthquake demands and achieve the required performance objectives. Nowadays, friction pendulum bearings have proven efficient in mitigating regular RC structures subjected to a wide range of earthquakes. Nonetheless, limited studies were dedicated to investigating the performance and efficiency of this type of isolation system utilized in RC structures with various types of vertical irregularities. Besides, comprehensive parametric assessments that investigate the behavior of structures supported on friction pendulum bearings subjected to pulse-like and non-pulse-like earthquakes are scarce. Thus, this study aims to assess the behavior of RC frames equipped with friction pendulum isolators under different types of earthquakes. In the context of the paper, three types of vertical irregularities, known as soft-story, heavy-story, and stepped structures, will be modeled and investigated. Moreover, the outcomes of these buildings will be benchmarked to a regular model to illustrate the efficiency of the selected isolation systems. Furthermore, the performance of the base-isolated buildings with friction pendulum isolators subjected to pulse-like and non-pulse-like earthquakes will be reported. In general, the study results have shown that pulse-like earthquakes exhibited higher values than non-pulse-like earthquakes for the different responses of the structures at the periods of 2.5 and 3 and the damping ratios of 15%, 20%, and 25%. Doi: 10.28991/CEJ-2022-08-09-05 Full Text: PDF

Kinetic Modeling of Grain Boundary Cementite Evolution

Prediction of grain boundary cementite growth kinetics in hypereutectoid steels is necessary to control its thickness. It is a question of major industrial importance but has remained unresolved to date. This paper presents and compares two different and new modeling approaches. The first one relies on diffusion-based nucleation and growth of cementite precipitates using a modified SFFK model with short-circuit grain boundary diffusion and accounting for heterogeneous nucleation site energy during isothermal treatments and continuous cooling. It is compared to previously published simulations of diffusion-controlled reaction with moving phase boundaries and a similar simulation using the software Dictra. The second approach implies that cementite thickening is driven by the nucleation of ledges at the stepped austenite/cementite interface, controlled by a structure barrier to ledge formation previously assumed in the literature.[1] We suggest a semi-empirical formulation of this barrier to ledge nucleation during isothermal transformation. Both approaches lead to an excellent match to experimental data for an almost pure Fe–C system. This implies that modeling the stepped structure of the austenite/cementite interface is not imperative for simulation of thickening kinetics, but also that understanding the governing physics of ledge formation allows for a comprehensive description of secondary cementite formation.

A self-powered photoelectrochemical molecular imprinted sensor for chloroquine phosphate with enhanced cathodic photocurrent via stepped energy band alignment engineering

Fabricating a self-powered photoelectrochemical (PEC) sensor with superior performances and cost-effective design is highly desirable but still remains challenges. Herein, we develop a self-powered PEC molecular imprinted (MIP) sensor integrating WO3/TiO2 photoanode and gold nanoparticles modified carbon intercalated MoS2 photocathode for highly sensitive and specific detection of chloroquine phosphate (CQP). By constructing a reasonable stepped energy band structure, the electrons are efficiently transferred driven by the Fermi energy level gap between photoanode and photocathode, which amplifies the cathodic photocurrent. Furthermore, the mechanism of electron transfer driven by the Fermi energy level gap in the self-powered sensor was demonstrated for the first time by density functional theory (DFT). The Molecular imprinted polymer was modified on the photocathode as recognition element, which avoids the interference of reducing substances in the samples and complex biometric reactions. Under optimal conditions, the proposed MIP sensor for CQP presents the detection limit of 0.11 μM with a broad linear range from 10−6 M to 10−3 M. This work presented an innovative design strategy for constructing self-powered sensor.

A Review on Mesophase and Physical Properties of Cyclotriphosphazene Derivatives with Schiff Base Linkage

Over the last decades, liquid crystalline has been of great recent importance due to many unique and different features. The linking unit, terminal group, and core system are the most factors to influence the liquid crystal behaviour. Schiff base linkage with the formula of -C=N- can maintain linearity by providing the stepped core structure with high stability. Incorporation of Schiff base linkage in cyclotriphosphazene system enhances the mesophase characteristic and high thermal stability. This review focussed on the mesophase behaviour and physical properties of cyclotriphosphaze derivatives attached to Schiff base linkages. A basic introduction to liquid crystalline materials, including description and classification, is provided in this review.

The charge transport double-channel structure facilitating Fe5Ni4S8/Ni3S2 nanoarray for efficient and stable overall water splitting

Overall water splitting technology is critical for the future of a clean and sustainable hydrogen energy infrastructure. Ni3S2 (NS) is considered a good performing oxygen evolution reaction (OER) catalyst, but exhibits unsatisfactory hydrogen evolution reaction (HER) activity. In this study, Fe5Ni4S8 (FNS) material was incorporated into an NS nanoarray, generating a low-cost, efficient, and stable bifunctional FNS/NS heterostructure for electrolyzed water catalysts. The hydrophilicity of pretreated FNS was quite high, whereas the stepped rod-shaped NS structure had a large number of radial active sites. Additionally, the high-conductivity of FNS and nickel foam (NF) provided a double-channel structure for rapid internal charge transfer. The interconnecting a network of FNS, rod-shaped NS nanoarray, and NF substrate enabled one to accomplish a synergistic effect of enhanced kinetics and activity of OER, HER, and overall water splitting. To achieve a current density of 10 mA cm−2 in 1.0 M KOH solution, only overpotentials of 248 and 94 mV were required. Moreover, the voltage of the constructed FNS/NS||FNS/NS double-electrode battery system was only 1.64 V@10 mA cm−2, but the battery could have run for at least 120 h at an industrial current density of 500 mA cm−2. Therefore, this study offers a rational design of heterostructures as bifunctional electrocatalysts for overall water splitting.

Replaceable drill bit with compound step and sawtooth structures for damages and drilling-cost reduction of CFRP composite

Frequently-occurred drill-exit damages and short tool life are challenging issues for drilling CFRP in aerospace industries. High-performance and cost-effective drill bits are always desired. This paper proposes a replaceable drill bit with compound step and sawtooth structures for drilling CFRP to reduce damages as well as cost. A multiple-stage damage reduction concept of reducing thrust force and performing upward cutting on the drill-exit materials is proposed and introduced for drill bit design by combining step and sawtooth structures. Compound geometry of step and sawtooth structures is further integrated on a replaceable drill tip with a reusable body for cost-saving improvement. Drilling performance and cost were evaluated among an ordinary step drill bit, a compound drill bit, and a replaceable drill bit with the compound geometry. Results indicated that the compound and replaceable drill bits could produce better drill-exit and hole wall qualities as expected and the hole sizes are also more stable based on Cpk value; in addition, the tool life of both is over two times than the ordinary one. Drilling costs of the compound and replaceable drill bits are formulated with the consideration of manufacturing cost and tool life, and a case study is conducted for cost-saving comparison. In the specific case, it indicated that the replaceable drill bit is preferable in cost if over 58 CFRP holes are required to be drilled, the expected saving of overall cost would reach 9 % under 116 CFRP holes, and the saving ratio will finally reached a fixed level of 20 % for a large amount of drilling. This saving ratio would be affected by the manufacturing costs of drill bits. The cost-saving calculation method would be referenced for replaceable drill bit with compound step and sawtooth structures for industrial partners in mass drilling task for CFRP.

First-Principles Calculation of the Evaporation Field and Roll-up Effect of M (M = Fe, Cu, Si, and Mn) on the Fe (001) and Fe Step Structure.

First-principles calculations were performed on the evaporation field of Fe, Cu, Mn, and Si in Fe (001) and on the evaporation field and roll-up effect of Fe, Cu, and Mn in the Fe (001) step structure. The larger the evaporation barrier energy tendency, at an electric field of 0 V/nm (absorption energy), the larger was the evaporation field. Electric field evaporation calculation results indicate that the order in which the electric field is easily evaporated is Mn > Cu > Fe > Si. The tendency that Mn and Cu evaporate more easily than does Fe and that the evaporation of Si is less probable is consistent with the experiment of a dilute element in steel. In the Fe (001) step structure, when the electric field is low, the roll-up effect where the evaporated atoms move on the step is large, and when the electric field is large, the roll-up effect is small. The roll-up effect of Cu was almost the same as that of Fe, and the roll-up effect of Mn was small because the chemical bond between Mn and Fe was weak.

Effectiveness of Different Base Isolation on Stepped Buildings

Abstract: Seismic isolation devices are commonly employed to protect structures from the impacts of severe ground motions. ETABS2016, a modelling and analysis programme, was used in this work to model and analyse the isolated stepped building. Rubber isolator link components were used as a single joint element to represent the rubber isolators between the ground and the superstructure. El-Centro seismic records were used to analyse the isolated building. The lateral inter-storey drifts, story displacement and peak absolute floor accelerations, of the isolated building were compared to those of the fixed-base structure. The current study aims to evaluate the effectiveness of several types of base isolation systems for seismic protection of 6-story stepped structures using Time history analysis. The isolation systems considered include, i) rubber isolators, ii) rubber isolators with energy dissipation systems, and iii) friction pendulum isolators.

Different decorated ZIF-67 adsorption performance towards methamphetamine revealed by theoretical and experimental investigations

Metal-organic framework (MOF) materials, which have been deemed as effective adsorbents for removing emerging contaminants, suffered from difficult separation that limited their application in water treatment. Two different decorated ZIF-67 multifunctional adsorbents have been successfully fabricated by anchoring ZIF-67 on diverse magnetic substrates. The comparative study combining a series of adsorption experiments and structural characterization analyses was facilitated to explore the adsorption performance of two adsorbents (MrGO/ZIF and MZIF). The better adsorption capacity of MrGO/ZIF for methamphetamine (MAMP) was observed. For the introduction of reduced graphene oxide (rGO), ZIF-67 nanocrystals showed stratified multidimensional distribution on rGO, and formed a stepped pore structure. Relatively large pores of MrGO/ZIF were beneficial for the transport and adsorption of MAMP in aqueous phase. The adsorption of MAMP could be described by the Langmuir isotherm and pseudo-second-order kinetic model, and adsorption process was spontaneous and endothermic. Theoretical investigation in combination with analyses of the XPS characterization illustrated that the H-bonding interaction between the Co−OH and −NH of MAMP, and π-π interaction among the heteroaromatic rings in adsorbent and the benzene ring of MAMP was the mainly contribution of driving MAMP adsorption on MrGO/ZIF. Summarily, the excellent adsorption properties of MrGO/ZIF coupled with facile separation and sustainability make MrGO/ZIF remove MAMP more efficiently from water, which provide an insight for contaminated water treatment, and psychoactive substances monitoring.

Sensitivity Analysis of NEMS Cantilever to Detect Volatile Organic Compounds Using Finite Element Method

Nano Electro Mechanical System (NEMS) based cantilever is the alternate form of Micro Electro Mechanical system (MEMS) with dimensional changes in perspectives like thickness, length, and width. The advantage of the dimensional change leads to great improvement in sensitivity and performance with portable structure. In this paper, a stepped nanocantilever sensor is designed for the detection of volatile organic compounds. The same is compared with the conventional micro cantilevers in order to assess the sensitivity. The advantage of incorporating longitudinal cut at fixed end of the cantilever is investigated for different materials with load analysis and stress distributed results. COMSOL Simulation software is used to perform the analysis of nanocantilever and the result shows sensitivity increased with longitudinal cut and type of material which exhibits good sensitivity. In this research, we suggest a stepped cantilever structure that uses FEM (Finite Element Method) of analysis to calculate the change in deflection owing to various loads in both static and dynamic analyses. Similarly, changes in resonance frequency for changes in beam thickness are examined using parametric study. The experimental results from COMSOL simulation are found that the displacement occurred in proposed cantilever that the deflection sensitivity 2.85 x10-9m under maximum stress of 3.32 x10-9 N/m2. From the dynamic analysis, resonant frequency occurs at 20nm thickness is 2.8x107 Hz, and at 30nm is 3.5 x 107 Hz respectively.

Application of suspension systems with rigid elastic elements in the physical rehabilitation of patients with amputation defects of the lower extremities

BACKGROUND: Exercise on suspension systems (gravitational neuromuscular activation) is a highly effective means of physical rehabilitation for patients with various pathologies. Modernization of these products through the use of rigid elastic slings or equipping standard simulators with elastic elements expands the capabilities of this type of equipment, allows you to master new types of exercises, positively affecting the strength, tone and endurance of muscle groups.
 AIMS: to study the impact of the inclusion of suspension systems with rigid elastic elements (slings) in physical rehabilitation programs for patients with amputation stumps at the hip level.
 MATERIAL AND METHODS: Twelve patients were tested before and after repeated prosthetics in the conditions of the FB MSE Clinic, which, due to the use of suspension systems, including elastic elements, not only increased strength, endurance and coordination relationships of muscles, but also changed the structure of their walking. The active part of the course of physical rehabilitation with the inclusion of suspension systems with elastic elements was less than two weeks. Setting the patient the task of increasing the speed of movement on the prosthesis in the long term, in the near future we focused exclusively on the correctness of the step structure and subjective sensations.
 RESULTS: The technical improvement of suspension systems due to elastic elements increases the convenience of their use, the speed of mastering by patients and the degree of efficiency, determining a high percentage of achieving the planned result. Inclusion in the course of training on the simulator with the use of elastic slings allows the patient to master and confidently perform various complexly coordinated movements, including squats, to participate in new types of game activities, which contributes to an increase in his adaptation and socialization in society. Subjectively, patients note greater strength of muscle groups that have undergone additional stress on these systems, improved coordination of movements and endurance when walking on a prosthesis as a whole, as well as a sense of "correctness" of walking, which is confirmed by clinical examination methods and the results of biomechanical tests (increased pace and speed of walking with a decrease in the duration of the step cycle).
 CONCLUSIONS: Suspension systems are most useful for the prevention and elimination of atrophy of the muscles that support the movement of the pelvic girdle, in comparison with conventional dynamic training and walking on a prosthesis. Modifications of suspension systems by including elastic elements in them allow functional training not only using static, but also dynamic exercises, expanding their application possibilities in medical and complex rehabilitation, adaptive physical culture and adaptive sports.

Numerical analysis of the broadband interferometric sensor in the planar gradient-step index configuration

In the paper the model of an optical sensor based on a two-mode interference in a planar gradient-step index configuration is presented. The analyzed structure consists of a single-mode gradient index waveguide, made by Ag+-Na+ ion exchange, which is partially covered by a step-index SU-8 polymer layer. This step and gradient index structure forms a two-mode waveguide which is excited by a broadband light source from a selected spectral range. The refractive index variation of measured external surrounding affects the modal properties of multimode waveguide and the spectral field distribution at the output of the structure. Full Text: PDF ReferencesM. Błahut, "Numerical analysis of planar multimode optical sensor with active nanolayer", Opt. Appl. 50, 377 (2020). CrossRef M. Nordstrom et al J. Light. Technol. 25, 1284 (2007). CrossRef K. Gut, "Study of a Broadband Difference Interferometer Based on Low-Cost Polymer Slab Waveguides", Nanomaterials, 9, 729 (2019). CrossRef M. Błahut, "Numerical characteristics of the polarimetric interferometer made by K+-Na+ ion exchange", Opt. Appl. 27, 3 (1998). CrossRef https://www.filmetrics.com/refractive-index-database/BK7/Float-Glass DirectLink M. Błahut, "Model of the broadband interferometric optical biosensor in a planar configuration", Phot. Lett. Pol. 12, 28 (2020). CrossRef K. Gut, "Broad-band difference interferometer as a refractive index sensor", Opt. Express, 25, 31111 (2017). CrossRef

A new stepped-channel liquid cooling plate thermal management system combined with composite phase change materials

• A novel stepped structure channel combining parallel and tree channel was proposed. • Effects of structure style, number, structural parameters were analyzed. • Filling CPCM to enhance cooling performance and reduce the weight of cooling plate. • Average temperature and pressure drop were reduced by 2.46 °C and 22.14 Pa. Aiming at the problems of large temperature gradient of traditional parallel channel and high pressure loss of tree fractal channel, a novel stepped liquid cooling plate combining the above two structures was proposed in this paper. Firstly, based on the liquid cooling plate experimental platform, the reliability of computational fluid dynamics method was verified by experiments. Secondly, based on computational fluid dynamics and orthogonal test methods, the effects of the arrangement form of cooling channels, the number of inlets and outlets and structural parameters (number of channels, longitudinal length, width, thickness and width of inlets and outlets) were analyzed. In comparison with the original model, the average temperature and pressure drop were reduced by 1.17 °C and 22.14 Pa, respectively. Finally, in order to further improve the heat dissipation effect of the system, a new hybrid liquid cooling plates formed by filling the liquid cooling plate with composite phase change material were proposed. The results indicated that the cooling performance of the hybrid liquid cooling plate filling with more phase change material was better, meanwhile, the average temperature and pressure drop were reduced by 2.46 °C and 22.14 Pa, respectively, compared with the original model. In addition, the effect of inlet mass flow was discussed. The results revealed that the cooling performance of hybrid liquid cooling plate was better at lower mass flow rate, while the cooling performance of the liquid cooling plate was better at higher mass flow rate.

Orthogonal Optimization Design and Finite Element Analysis of Converging Stepped Magnetic Fluid Seal

In order to better solve the problem of air leakage during compressor operation, based on the converging stepped magnetic fluid seal structure, the LSUB16/SUB (4⁴) orthogonal test design and the numerical simulation of the finite element method are combined to optimize the sealing structure. Four factors, four levels and the corresponding orthogonal table are selected in this paper. The simulation results of each test are calculated and range values are studied. Finally, sealing pressure capability of the structure before and after optimization are calculated and compared. The results show that under the conditions of different axial and radial sealing gaps, the sealing pressure capability of converging stepped magnetic fluid seal structure has been significantly improved after orthogonal optimization, especially when the radial sealing gap is relatively small. The maximum pressure capability can be improved by about 11 %, which fully proves the effectiveness of orthogonal optimization. At the same time, the research results can also provide references for the application of other rotary sealing conditions.

Macrosteps formation on 4H-SiC surfaces via Si melting within a sandwich configuration

With a view to designing a homogeneous and controlled step-bunched morphology on large monocrystalline 4H-SiC(0001) surfaces, a sandwich configuration was investigated. A piece of silicon was melted between two 4H-SiC 4° off wafers, allowing a better spreading of the liquid than with a Si drop approach. Using as low liquid Si thickness as 30 µm, homogeneously highly step-bunched surfaces were obtained, though with irregular step shapes. This was found to be the result of time dependent dissolution of the SiC-bottom wafer under the natural vertical thermal gradient of the setup. The most parallel step and terrace structures were generated using 400 µm thick liquid Si though this led to long range inhomogeneities associated with complex mass transport. The proposed mechanism includes the combined effects of H2 etching at the edges acting as C pump and electromagnetic convection rolls for long range transport of these dissolved C atoms.

Numerical Simulation of Solitary Waves Propagating on Stepped Slopes Beaches

The objective of the current paper is to study the propagating and breaking of solitary waves on stepped slopes beaches, to simulate the shoaling and breaking, specifically the location of breaking point Xb, and solitary wave height at breaking Hb of solitary waves on the different stepped slopes. Ansys Fluent is used to implement the simulation, a two-dimensional volume of fluid (VOF) which is based on the Reynolds-Averaged Navier–Stokes (RANS) equations and the k–ε turbulence closure solver. The obtained results were firstly validated with existing empirical formulas for solitary wave run-up on the slope without stepped structure and are compared with the experimental and numerical results. The numerical computation has been carried out for several, configurations of beach slopes with tan ß= 1:15, 1:20, 1:25, wave height H0= 0.04, 0.06, 0.08m, water depth h0= 0.15, 0.2, 0.25m, and step height Sh= 0.025, 0.05, 0.075m. A set of numerical simulations were implemented to analyze shoaling and breaking of solitary waves, wave reflection, wave transmission, and wave run-up with various parameters wave heights, water depth, beach slopes, and Sh step height.

TECHNOLOGICAL METHODS OF CONSTRUCTION MILITARY ENGINEERING FACILITIES RUBAS FORTIFICATION VI C. (EAST CAUCASUS)

The article reviews building techniques, used for constructing a monumental fortification of the 6th century, erected in the river-valley of Rubas, near the village of Kommuna, Derbent region of the Republic of Dagestan. The site includes six objects different in layout and construction, connected with building junctions into a single object – a construction of arched type, Wall 1, Long wall 2, Stepped structure 6, Wall 3, Platform 5. Analysis of the excavation material shows that the technology of their building was due to the functional purpose of these objects. Moreover, each of the architectural structures was built with the use of unique building techniques, variety of masonry, as well as the sizes of stone blocks and plates. The aim of the research is to conduct the analysis of the technological methods of constructing multi-type military-engineering fortifications; to determine the links of technological methods with the object’s functional purposes; to determine the level of development of construction engineering and architecture in the Peri-Caspian region in the era of the Great Migration of Peoples and the significance of this site as a military-defensive construction. The research methodology includes a detailed analysis of technological methods for the construction of military engineering structures; carrying out the classification of methods for the construction of defensive objects and the system of laying stone structures; analysis of building materials used in the construction of structures. The analysis of the excavation materials of the Rubas fortification shows that, according to the technology of construction, this object is close to the Derbent defensive complex of the middle 6th century (large stone blocks; massiveness of structures; the use of “opus quadratum” masonry; the presence of a bonding lime mortar, etc.). According to the main indicators (monumentality and functional orientation), this structure belongs to a series of barriers in the Western Peri-Caspian, built by Persia with the financial assistance of Byzantium in the era of the Great Migration of Peoples, typologically and chronologically similar to Derbent.

Generalized Peierls substitution for the tight-binding model of twisted graphene systems in a magnetic field

This work aims at addressing an important advanced methodology for twisted graphene in the presence of applied magnetic field, which is the Bloch-basis tight-binding model (TBM) in conjunction with the generalized Peierls substitution. We investigate extensively the band structures, Landau levels (LLs), and quantum Hall conductivity (QHC) of twisted bilayer graphene and twisted double-bilayer graphene, as well as their dependence on the twist angle. Comparison between these crucial properties of monolayer graphene, Bernal bilayer graphene, and the twisted systems is carefully made to highlight the roles played by twisting. The unique selection rules of inter-LL transition, which is crucial for achieving a deep understanding of the step structures of QHC, are identified through the properties of LL wave functions. The effective TBM is combined with the generalized Peierls substitution to investigate the magnetic quantization of twisted graphene systems at magic angle. Our theoretical model opens up an opportunity for comprehension of the interplay between an applied magnetic field and the twisting effect associated with layered graphene. The proposed method is expected to be applicable for the calculation of magnetic quantization problems of other complex systems.

A Study of English Learning Vocabulary Detection Based on Image Semantic Segmentation Fusion Network.

College students learn words always under both teachers' and school administrators' control. Based on multi-modal discourse analysis theory, the analysis of English words under the synergy of different modalities, students improve the motivation and effectiveness of word learning, but there are still some problems, such as the lack of visual modal memory of pictures, incomplete word meanings, little interaction between users, and lack of resource expansion function. To this end, this paper proposes a stepped image semantic segmentation network structure based on multi-scale feature fusion and boundary optimization. The network aims at improving the accuracy of the network model, optimizing the spatial pooling pyramid module in Deeplab V3+ network, using a new activation function Funnel ReLU (FReLU) for vision tasks to replace the original non-linear activation function to obtain accuracy compensation, improving the overall image segmentation accuracy through accurate prediction of the boundaries of each class, reducing the intra-class error in the prediction results. The accuracy compensation is obtained by replacing the original linear activation function with FReLU. Experimental results on the Englishhnd dataset demonstrate that the improved network can achieve 96.35% accuracy for English characters with the same network parameters, training data and test data.

Analysis of the Morphology of the Growth Interface as a Function of the Gas Phase Composition during the PVT Growth of Silicon Carbide

The growth conditions of 75 mm SiC crystals in the PVT process is varied by different methods while the temperature field is kept constant. The addition of graphite into the source material leads to the formation of an ordered step flow with step heights of 0.014 µm, while the addition of graphite into the source together with N2 doping changes the step kinetics on the main facet, leading to very large, bunched steps of 0.17 µm. When elemental Si was added into the source material large macro steps are formed on the whole crystal surface. While the doping induced step bunching is related to the incorporation kinetics, the large steps induced in Si-rich conditions are attributed the reduction of surface energy. With the variation of the inert gas pressure the morphology of the surface is altered, similarly. Under low pressure conditions (0.2 mbar) a fine step structure evolves, while at a high pressure (40mbar) large surface steps are formed on the whole growth interface. Large surface steps are strongly impeded in their lateral motion at defects permeating the growth interface. At these sites the formation of foreign polytypes is facilitated.