Design Solutions for Slender Bars with Variable Cross-Sections to Increase the Critical Buckling Force

In large metal civil constructions (stadium roofs, bridges), slender bars can lose their stability under compression loading. There is a lack in the literature regarding design solutions and methods for increasing the critical buckling force of bars with variable cross-sections. The aim of this research is to present a numerical model with finite elements used for a comparative analysis of increasing the critical force of stability loss in cases of (i) bars with stepwise variation in the cross-sections and (ii) bars with continuous variation in the moment of inertia along the bar axis (parabolic, sinusoidal, triangular, and trapezoidal variation). Considering the large-scale applications in civil engineering, bars that were pin-connected at one end and simple-supported at the other end were analyzed. Firstly, the analytical model was described to compute the critical buckling force for bars with stepwise variation in the cross-sections. Then, a finite element model for a slender bar and the assumptions considered were presented. The results were computed using the MATLAB program based on the numerical model proposed and were validated with the analytical model for stepwise variable cross-sections of the bars. The numerical model was adapted for bars with continuous variation in the moment of inertia along the bar axis. It was shown that, by trapezoidal variation in the second moment of inertia along the axis of a bar, i.e., as buckling occurred in the elastic field, the critical buckling force could be increased by 3.556 times compared to a bar with a constant section. It was shown that there was certain bar with stepwise variation in the cross-section for which the critical buckling force was approximately equal to the one obtained for the bar with sinusoidal variation in the moment of inertia (increased by 3.427 times compared to a bar with a constant section).

Numerical analysis of Atangana-Baleanu fractional model to understand the propagation of a novel corona virus pandemic

In this manuscript, we formulated a new nonlinear SEIQR fractional order pandemic model for the Corona virus disease (COVID-19) with Atangana-Baleanu derivative. Two main equilibrium points F0∗,F1∗ of the proposed model are stated. Threshold parameter R0 for the model using next generation technique is computed to investigate the future dynamics of the disease. The existence and uniqueness of solution is proved using a fixed point theorem. For the numerical solution of fractional model, we implemented a newly proposed Toufik-Atangana numerical scheme to validate the importance of arbitrary order derivative ρ and our obtained theoretical results. It is worth mentioning that fractional order derivative provides much deeper information about the complex dynamics of Corona model. Results obtained through the proposed scheme are dynamically consistent and good in agreement with the analytical results. To draw our conclusions, we explore a complete quantitative analysis of the given model for different quarantine levels. It is claimed through numerical simulations that pandemic could be eradicated faster if a human community selfishly adopts mandatory quarantine measures at various coverage levels with proper awareness. Finally, we have executed the joint variability of all classes to understand the effectiveness of quarantine policy on human population.

Flexural Response of Axially Restricted RC Beams: Numerical and Theoretical Study

Reinforced concrete (RC) frame beams are subject to axial restriction at the ends, which plays an important role in the nonlinear behavior of these beams. This paper presents a numerical and theoretical investigation into the flexural behavior of RC beams axially restricted with external steel or fiber reinforced polymer (FRP) reinforcement. A numerical procedure for RC beams axially restricted with external reinforcement has been developed and it is verified against available experimental results. A numerical parametric study is then performed on axially restricted RC beams, focusing on the effect of type, area, and depth of external reinforcement. The results show that axial restriction increases the post-cracking stiffness and ultimate load-carrying capacity but reduces the flexural ductility. The ultimate stress in external reinforcement is substantially impacted by reinforcement type, area, and depth. A simplified model is developed to predict the ultimate load of RC beams axially restricted with external steel/FRP reinforcement. The predictions of the proposed simplified model agree favorably with the numerical results. The correlation coefficient for the ultimate load is 0.984, and the mean difference is -2.11% with a standard deviation of 3.62%.

Investigation of the Surface Coating, Humidity Degradation, and Recovery of Perovskite Film Phase for Solar-Cell Applications

Presently, we inquire about the organic/inorganic cation effect on different properties based on structure, morphology, and steadiness in preparing a one-step solution of APbI₃ thin films, where A = MA, FA, Cs, using spin coating. This study was conducted to understand those properties well by incorporating device modeling using SCAPS-1D software and to upgrade their chemical composition. X-ray diffraction (XRD) was used to analyze the crystal structures. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were conducted to characterize the surface morphology; photoluminescence, Transmission Electron Microscopy (TEM), and a UV-Visible spectrometer helped us to study the optical properties. The (110) plane is where we found the perovskite's crystalline structure. According to the XRD results and by changing the type of cation, we influence stabilization and the growth of the APbI3 absorber layer. Hither, a homogenous, smooth-surfaced, pinhole-free perovskite film and large grain size are results from the cesium cation. For the different cations, the band gap's range, revealed by the optical analysis, is from 1.4 to 1.8 eV. Moreover, the stability of CsPbI3 remains excellent for two weeks and in a ~60% humid environment. Based on the UV-Visible spectrometer and photoluminescence characterization, a numerical analysis for fabricated samples was also performed for stability analysis by modeling standard solar-cell structures HTL/APbI3/ETL. Modeling findings are in good agreement with experimental results that CsPbI3 is more stable, showing a loss % in PCE of 14.28%, which is smaller in comparison to FAPbI3 (44.46%) and MAPbI3 (20.24%).

Analysis of Energy Loss Characteristics of Vertical Axial Flow Pump Based on Entropy Production Method under Partial Conditions

The energy loss of the vertical axial flow pump device increases due to the unstable internal flow, which reduces the efficiency of the pump device and increases its energy consumption of the pump device. The research results of the flow loss characteristics of the total internal conduit are still unclear. Therefore, to show the internal energy loss mechanism of the axial flow pump, this paper used the entropy production method to calculate the energy loss of the total conduit of the pump device to clarify the internal energy loss mechanism of the pump device. The results show that the energy loss of the impeller is the largest under various flow conditions, accounting for more than 40% of the total energy loss of the pump device. The variation trend of the volume average entropy production and the energy loss is similar under various flow coefficients (K_Q). The volume average entropy production rate (EPR) and the energy loss decrease first and then increase with the increase of flow, the minimum volume average entropy production is 378,000 W/m³ at K_Q = 0.52, and the area average EPR of the impeller increases gradually with the increase of flow. Under various flow coefficient K_Q, the energy loss of campaniform inlet conduit is the smallest, accounting for less than 1% of the total energy loss. Its maximum value is 63.58 W. The energy loss of the guide vane and elbow increases with the increase of flow coefficient K_Q, and the maximum ratio of energy loss to the total energy loss of the pump device is 29% and 21%, respectively, at small flow condition K_Q = 0.38. The energy loss of straight outlet conduit reduces first and then increases with the increase of flow coefficient K_Q. When flow coefficient K_Q = 0.62, it accounts for 27% of the total energy loss of the pump device, but its area average entropy production rate (EPR) and volume average entropy production rate (EPR) are small. The main entropy production loss in the pump device is dominated by entropy production by turbulent dissipation (EPTD), and the proportion of entropy production by direct dissipation (EPDD) is the smallest.

Analysis of Statistically Predicted Rate Constants for Pyrolysis of High-Density Plastic Using R Software

The surge in plastic waste production has forced researchers to work on practically feasible recovery processes. Pyrolysis is a promising and intriguing option for the recycling of plastic waste. Developing a model that simulates the pyrolysis of high-density polyethylene (HDPE) as the most common polymer is important in determining the impact of operational parameters on system behavior. The type and amount of primary products of pyrolysis, such as oil, gas, and waxes, can be predicted statistically using a multiple linear regression model (MLRM) in R software. To the best of our knowledge, the statistical estimation of kinetic rate constants for pyrolysis of high-density plastic through MLRM analysis using R software has never been reported in the literature. In this study, the temperature-dependent rate constants were fixed experimentally at 420 °C. The rate constants with differences of 0.02, 0.03, and 0.04 from empirically set values were analyzed for pyrolysis of HDPE using MLRM in R software. The added variable plots, scatter plots, and 3D plots demonstrated a good correlation between the dependent and predictor variables. The possible changes in the final products were also analyzed by applying a second-order differential equation solver (SODES) in MATLAB version R2020a. The outcomes of experimentally fixed-rate constants revealed an oil yield of 73% to 74%. The oil yield increased to 78% with a difference of 0.03 from the experimentally fixed rate constants, but light wax, heavy wax, and carbon black decreased. The increased oil and gas yield with reduced byproducts verifies the high significance of the conducted statistical analysis. The statistically predicted kinetic rate constants can be used to enhance the oil yield at an industrial scale.

Tensile Experiments and Numerical Analysis of Textile-Reinforced Lightweight Engineered Cementitious Composites

Despite many cases of textile-reinforced engineered cementitious composites (TR-ECCs) for repairing and strengthening concrete structures in the literature, research on lightweight engineered cementitious composites (LECC) combined with large rupture strain (LRS) textile and the effect of textile arrangement on tensile properties is still lacking. Therefore, this paper develops textile-reinforced lightweight engineered cementitious composites (TR-LECCs) with high strain characteristics through reinforcement ratio, arrangement form, and textile type. The study revealed that, by combining an LRS polypropylene (PP) textile and LECC, TR-LECCs with an ultimate strain of more than 8.0% (3-4 times that of traditional TR-ECCs) could be developed, and the PP textile's utilization rate seemed insensitive to the enhancement rate. The basalt fiber-reinforced polymer (BFRP) textile without epoxy resin coating had no noticeable reinforcement effect because of bond slip; in contrast, the BFRP grid with epoxy resin coating had an apparent improvement in bond performance with the matrix and a better reinforcement effect. The finite element method (FEM) verified that a concentrated arrangement increased the stress concentration in the TR-LECC, as well as the stress value. In contrast, a multilayer arrangement enabled uniform distribution of the stress value and revealed that the weft yarn could help the warp yarn to bear additional tensile loads.

Numerical analysis and animal study of noninvasive handheld electroporation delivery device for skin superficial lesion treatment

INTRODUCTION

This study aims to investigate the feasibility of a noninvasive handheld electroporation pulses delivery device (EPDD) for electroporation-based treatment (EBT) of skin superficial lesions through numerical analysis and animal study.

METHODS

Finite element analysis was performed to investigate the performance of the EPDD. The electric field, temperature, EI and TI were calculated under pulse voltages of 600, 800, and 1000 V. A mouse subcutaneous tumor model was established to evaluate the performance of the EPDD through histopathology and survival analyses.

RESULTS

The electrical field strength increased from 151 (600 V) to 252 V/cm (1000 V) in the skin and from 1302 (600 V) to 2171 V/cm (1000 V) in the tumor. The volume of EI grew and reached a plateau at the 165th pulse, whereas the maximum volume of EI increased with higher voltage. The growth tendency of TI differed between groups, and it was higher in the high-voltage group (HVG) than in the low-voltage group. Histopathological analysis showed that the depth and range of the ablation area could be controlled by adjusting pulse voltage. Survival analysis showed that the survival of the HVG was better than that of the low-voltage and the control group (p < 0.01).

CONCLUSIONS

The results demonstrate that the EPDD is feasible, safe, and effective for skin EBT. The volume of EP tissue injury can be controlled by adjusting the pulse voltage, pulse number, and other parameters. The proposed noninvasive handheld EPDD can be a potential therapeutic tool for EBT of superficial skin lesions in the future.

The intra-arterial selective cooling infusion system: A mathematical temperature analysis and in vitro experiments for acute ischemic stroke therapy

Introduction

The neuroprotection of acute ischemic stroke patients can be achieved by intra‐arterial selective cooling infusion using cold saline, which can decrease brain temperature without influencing the body core temperature. This approach can lead to high burdens on the heart and decreased hematocrit in the scenario of loading a high amount of liquid for longtime usage. Therefore, autologous blood is utilized as perfusate to circumvent those side effects.

Methods

In this study, a prototype instrument with an autologous blood cooling system was developed and further evaluated by a mathematical model for brain temperature estimation.

Results

Hypothermia could be achieved due to the adequate cooling capacity of the prototype system, which could provide the lowest cooling temperature into the blood vessel of 10.5°C at 25 rpm (209.7 ± 0.8 ml/min). And, the core body temperature did not alter significantly (−0.7 ~ −0.2°C) after 1‐h perfusion. The cooling rate and temperature distributions of the brain were analyzed, which showed a 2°C decrease within the initial 5 min infusion by 44 ml/min and 13.7°C perfusate.

Conclusion

This prototype instrument system could safely cool simulated blood in vitro and reperfuse it to the target cerebral blood vessel. This technique could promote the clinical application of an autologous blood perfusion system for stroke therapy.

Numerical Analysis of Physical Characteristics and Heat Transfer Decoupling Behavior in Bypass Coupling Variable Polarity Plasma Arc

A novel bypass coupling variable polarity plasma arc was proposed to achieve the accurate adjusting of heat and mass transfer in the welding and additive manufacturing of aluminum alloy. However, the physical characteristics and decoupled transfer behavior remain unclear, restricting its application and development. A three-dimensional model of the bypass coupling variable polarity plasma arc was built based on Kirchhoff's law, the main arc and the bypass arc are coupled by an electromagnetic field. The model of current attachment on the tungsten electrode surface is included for simulating different heating processes of the EP and EN phases in the coupling arc. The distribution of temperature field, flow field, and current density of the bypass coupling variable polarity plasma arc was studied by the three-dimensional numerical model. The heat input on the base metal under different current conditions is quantified. To verify the model, the arc voltages are compared and the results in simulation and experiment agree with each other well. The results show that the radius of the bypass coupling arc with or without bypass current action on the base metal is different, and the flow vector of the bypass coupling arc plasma with bypass current is larger than the arc without bypass current. By comparing the heat transfer on the electrodes' boundary under different current conditions, it is found that increasing the bypass current results in the rise in heat input on the base metal. Therefore, it is concluded that using bypass current is unable to completely decouple the wire melting and the heat input of the base metal. The decoupled degree of heat transfer is one of the important factors for accurate control in the manufacturing process with this coupling arc.

Flexural Behavior on Damaged Steel Beams Strengthened with CFRP Sheets Subjected to Overloading

This paper presents results of testing and numerical analyses of damaged steel beams strengthened with carbon-fiber reinforced polymer (CFRP) sheet and subjected to overloading. The test results showed that as cyclic times increase, the yield load and stiffness increase, but the ultimate bearing capacity decreases to a certain extent. Applying prestress could improve the ductility of the girder. The damage level greatly influenced the girders with overloading, and the increase in damage degree reduced the stiffness, yield load and ultimate load. The numerical calculation showed that the yield load would decrease by 0.4–0.8 kN when the cyclic times increase by 100 times. The yield load would increase by 1–2 kN and the ultimate bearing capacity would decrease by 0.6–1.2 kN when the overloading amplitude increased by 0.02 Pu. The increase in damage degree would obviously reduce the yield load and ultimate bearing capacity of the steel beam after overloading. The yield load and ultimate bearing capacity could be increased by approximately 3 kN when the CFRP sheet thickness increases by 0.05 mm.

Computation of the Electrical Resistance of a Low Current Multi-Spot Contact

In high complexity electrical systems such as those used in the automotive industries, electric connectors play an important role. The automotive industry is gradually shifting its attention to electric cars, which means more electrical connectors for sensors and data collection. A fault in connectors for sensors used in a vehicle can cause drastic damage to capital equipment and, in the worst case, the loss of life. The studies of faults or degradation of electrical contacts are essential for safety in vehicles and various industries. Although such faults can be due to numerous factors (such as dust, humidity, mechanical vibration, etc.) and some yet to be discovered, high contact resistance is the main factor causing erratic behavior of electrical contacts. This paper presents a study on the computation of electrical contact resistance of two metal conductors (in the form of a disk) with analytical relations and a numerical computation model based on the finite element method (FEM) in COMSOL Multiphysics. The contact spots were considered to have a higher electrical resistivity value (ρ_cs) than those of the two metal conductors (ρ_Cu). Studies such as the one in view that is carried out on a microscopic level are often difficult to investigate experimentally. Therefore, with the help of a simplified numerical model, the consequences of the degradation of electrical contacts are investigated. To validate the FEM model, the numerical results were compared to those obtained from analytical models.

Numerical Study on Death of Squamous Cell Carcinoma Based on Various Shapes of Gold Nanoparticles Using Photothermal Therapy

Due to increased exposure to ultraviolet radiation caused by increased outdoor activities, the incidence of skin cancer is increasing. Incision is the most typical method for treating skin cancer, and various treatments that can minimize the risks of incision surgery are being investigated. Among them, photothermal therapy is garnering attention because it does not cause bleeding and affords rapid recovery. In photothermal therapy, tumor death is induced via temperature increase. In this study, a numerical study based on heat transfer theory was conducted to investigate the death of squamous cell carcinoma located in the skin layer based on various shapes of gold nanoparticles (AuNPs) used in photothermal therapy. The quantitative correlation between the conditions of various AuNPs and the laser intensity that yields the optimal photothermal treatment effect was derived using the effective apoptosis ratio. It was confirmed that optimal conditions exist for maximizing apoptosis within a tumor tissue and minimizing the thermal damage to surrounding normal tissues when using AuNPs under various conditions. Furthermore, it is envisioned that research result will be utilized as a standard for photothermal treatment in the future.

Experimental Assessment and Numerical Modeling of the Bond-Slip Correlation for Steel Rebars in r.c. Members

Refined non-linear static or dynamic analyses are increasingly used to assess the behavior of new and existing reinforced concrete structures. To perform these analyses, an adequate knowledge of the force–displacement, bending moment–curvature, and bending moment–rotation curves of relevant parts of structural members is needed, and modeling the bond–slip correlation for steel rebars becomes fundamental. The paper presents the results of an experimental campaign on r.c. specimens under tension, aiming, differently from previous studies, to better reproduce the bond–slip relationship accounting for the local confinement and anchorage conditions of real structural members. Resorting to an original numerical procedure allowing us to predict the relative displacement between steel reinforcement and the surrounding concrete in a reinforced concrete element, once assigned the stress in the naked steel bar and the bond–slip law, the experimental results are compared with the numerical outcomes obtained by adopting codified bond–slip laws. The comparison highlights that experimental values of sliding are well below those that are commonly given in existing bond slip laws, such as that adopted by the CEB-FIP Model Code. A new bond–slip model, which is able to satisfactorily predict actual strain fields and slips along the investigated r.c. elements, is thus proposed with the final aim of extending its implementation into non-linear analyses of r.c. structures.

Cyclic Behavior of Masonry Shear Walls Retrofitted with Engineered Cementitious Composite and Pseudoelastic Shape Memory Alloy

The behavior of masonry shear walls reinforced with pseudoelastic Ni-Ti shape memory alloy (SMA) strips and engineered cementitious composite (ECC) sheets is the main focus of this paper. The walls were subjected to quasi-static cyclic in-plane loads and evaluated by using Abaqus. Eight cases of strengthening of masonry walls were investigated. Three masonry walls were strengthened with different thicknesses of ECC sheets using epoxy as adhesion, three walls were reinforced with different thicknesses of Ni-Ti strips in a cross form bonded to both the surfaces of the wall, and one was utilized as a reference wall without any reinforcing element. The final concept was a hybrid of strengthening methods in which the Ni-Ti strips were embedded in ECC sheets. The effect of mesh density on analytical outcomes is also discussed. A parameterized analysis was conducted to examine the influence of various variables such as the thickness of the Ni-Ti strips and that of ECC sheets. The results show that using the ECC sheet in combination with pseudoelastic Ni-Ti SMA strips enhances the energy absorption capacity and stiffness of masonry walls, demonstrating its efficacy as a reinforcing method.

FEM Analysis as a Tool to Study the Behavior of Methacrylate Adhesive in a Full-Scale Steel-Steel Shear Joint

The use of adhesive to joint structural elements, despite many advantages of this technology, is not a method commonly used in engineering practice, especially in construction. This is mainly due to the poor recognition of the behavior, both in terms of testing and analysis, of joints made on a scale similar to the actual elements of building structures. Therefore, this paper presents the results of model tests and then numerical analyses of adhesively bonded joints made of high-strength steel elements in a full-scale (double-lap joint). In order to properly model the adhesive connection, material tests of the methacrylate adhesive were performed in the field of tensile, shear (in two versions: single lap joint test and thick adherent shear test) and bond properties. Comparison of the results of the model and numerical tests showed very good agreement in terms of the measurable values, which makes it possible to consider the results obtained in the adhesive layer as reliable (not directly measurable in model tests). In particular, the distribution of stresses inside the adhesive layer, the range of plastic zones and areas of loss of adhesion are presented and discussed. The results indicate the possibility of a reliable representation of the behavior of adhesively bonded joints of high-strength steel, thus providing a tool for the analysis of semirigid adhesive in large-size joints.

Yield Load Solutions for SE(B) Fracture Toughness Specimen with I-Shaped Heterogeneous Weld

The objective of this work was to investigate the fracture behavior of a heterogeneous I-shaped welded joint in the context of yield load solutions. The weld was divided into two equal parts, using the metal with the higher yield strength and the metal with the lower yield strength compared to base metal. For both configurations of the I-shaped weld, one with a crack in strength in the over-matched part of the weld and one for a crack in the under-matched part of the weld, a systematic study of fracture toughness SE(B) specimen was carried out in which the crack length, the width of the weld and the strength mismatch factor for both weld metals were varied, and the yield loads were determined. As a result of the study, two mathematical models for determination of yield loads are proposed. Both models were experimentally tested with one strength mismatch configuration, and the results showed good agreement and sufficiently conservative results compared to the experimental results.

Coupled Finite Element-Finite Volume Multi-Physics Analysis of MEMS Electrothermal Actuators

Microelectromechanical systems (MEMS) are the instruments of choice for high-precision manipulation and sensing processes at the microscale. They are, therefore, a subject of interest in many leading industrial and academic research sectors owing to their superior potential in applications requiring extreme precision, as well as in their use as a scalable device. Certain applications tend to require a MEMS device to function with low operational temperatures, as well as within fully immersed conditions in various media and with different flow parameters. This study made use of a V-shaped electrothermal actuator to demonstrate a novel, state-of-the-art numerical methodology with a two-way coupled analysis. This methodology included the effects of fluid-structure interaction between the MEMS device and its surrounding fluid and may be used by MEMS design engineers and analysts at the design stages of their devices for a more robust product. Throughout this study, a thermal-electric finite element model was strongly coupled to a finite volume model to incorporate the spatially varying cooling effects of the surrounding fluid (still air) onto the V-shaped electrothermal device during steady-state operation. The methodology was compared to already established and accepted analysis methods for MEMS electrothermal actuators in still air. The maximum device temperatures for input voltages ranging from 0 V to 10 V were assessed. During the postprocessing routine of the two-way electrothermal actuator coupled analysis, a spatially-varying heat transfer coefficient was evident, the magnitude of which was orders of magnitude larger than what is typically applied to macro-objects operating in similar environmental conditions. The latter phenomenon was correlated with similar findings in the literature.

A Methodology to Evaluate Long Term Durability of Dam Concrete Due to Calcium Leaching through Microscopic Tests and Numerical Analysis

Hydropower dams are subjected to soft water penetration during their service lives. Concrete deterioration due to calcium leaching will decrease the durability of concrete and affect dam safety. The long-term performance of concrete dams due to calcium leaching should be evaluated and predicted accurately to complete reinforcement work in a timely manner. In this paper, a methodology that combined microscopic tests and numerical analysis to evaluate the long-term performance of dam concrete due to calcium leaching is proposed. The current state of concrete is evaluated by analyzing the components of sediments and seepage water through microscopic and spectroscopic tests, such as X-ray photoelectron spectroscopy, scanning electron microscopy, and inductively coupled plasma mass spectrometry. The long-term degradation of concrete was predicted by utilizing a multi-scale model of calcium leaching, which considered the micro-pore structure of cement hydrates flux with time. The simulated results using this calcium leaching model showed a good agreement with other experiments. Finally, a real case study including field inspection was performed and the long-term durability of dam concrete was predicted through microscopic tests and finite element analysis method. It implies that the proposed method could provide calculation and theoretical basis for the durability analysis of concrete dams due to calcium leaching.

The Processivity of Telomerase: Insights from Kinetic Simulations and Analyses

Telomerases are moderately processive reverse transcriptases that use an integral RNA template to extend the 3' end of linear chromosomes. Processivity values, defined as the probability of extension rather than dissociation, range from about 0.7 to 0.99 at each step. Consequently, an average of tens to hundreds of nucleotides are incorporated before the single-stranded sDNA product dissociates. The RNA template includes a six nucleotide repeat, which must be reset in the active site via a series of translocation steps. Nucleotide addition associated with a translocation event shows a lower processivity (repeat addition processivity, RAP) than that at other positions (nucleotide addition processivity, NAP), giving rise to a characteristic strong band every 6th position when the product DNA is analyzed by gel electrophoresis. Here, we simulate basic reaction mechanisms and analyze the product concentrations using several standard procedures to show how the latter can give rise to systematic errors in the processivity estimate. Complete kinetic analysis of the time course of DNA product concentrations following a chase with excess unlabeled DNA primer (i.e., a pulse-chase experiment) provides the most rigorous approach. This analysis reveals that the higher product concentrations associated with RAP arise from a stalling of nucleotide incorporation reaction during translocation rather than an increased rate constant for the dissociation of DNA from the telomerase.

Improvement of Automatic Measurement Evaluation System for Subway Structures by Adjacent Excavation

This study evaluated the structural stability of subway structures based on adjacent excavations by comparing automatically measured and numerically analyzed data. The reliability of the automated measurement methodology was evaluated by first applying probability statistical analysis to the measured results and then comparing these results with the numerically analyzed results. An improvement in the calculation method evaluation system, including the method of processing and analysis of the automatically measured data of subway structures through the average value of probability density, was proposed. As a result of the field measurement and numerical analysis, the measured results of tunnel displacement and track deformation exhibited some differences. However, it was determined that the construction stage and location where the maximum values of the tunnel displacement and track deformation occurred had similarities.

Description of Limit States in the Subsurface Layer of Loosened Subsoil in View of Critical State Soil Mechanics

The article aims to present an effective numerical method for the behaviour analysis and safety assessment of a subsurface layer of subsoil in the existing or predicted states of mining and post-mining deformations. Based on our own analytical record, using the equations of the Modified Cam-Clay model, the description of limit states in the subsurface layer of subsoil was validated, making it consistent with in situ observations. The said effect was demonstrated by comparing numerical analyses of the subsoil layer subjected to the limit state, using the Modified Cam-Clay (MCC) model and the Coulomb-Mohr model (C-M). The article also presents the applicability potential of the numerical analysis of the loosened subsoil layer for the assessment of protection elements (e.g., geo-matresses) used under linear structures in the areas subjected to mining and post-mining impacts.

Material Model Effect for Simulating a Single-Lap Joint with a Blind Rivet

This paper concerns the influence of the material modeling method on the results of strength analyses. The research object was a single lap joint with a blind rivet (ISO 12996). The results of numerical strength analysis for various configurations of material models with material and contact nonlinearity were compared not only with the experimental results of such a connection but also with the values estimated using classical analytical tools (pressure stress and Hertz stress). The research aimed to determine how the results of numerical analyses (FEMs) were influenced by the method of modeling the material model and how it relates to the experimental results. As part of the analyses, a discrete riveted model and material models were constructed. The analyses took into account various load cases (from 10 to 90% of the connection capacity) to better illustrate the relationship between the numerical and experimental results. As a result of the conducted analyses, it was determined that the linear-elastic model was an acceptable and suggested solution (with a load of up to 90% of the load capacity of the joint connection) for further tests. The work was summarized with general and specific conclusions relating to all cases of numerical modeling. In addition, the summary includes suggestions for future works.

Flexural Behavior of Two-Span Continuous CFRP RC Beams

This paper investigates the feasibility of replacing steel bars with carbon-fiber-reinforced polymer (CFRP) bars in continuous reinforced concrete (RC) beams. A numerical model is introduced. Model predictions are compared with the experimental results that are available in the literature. A comprehensive numerical investigation is then performed on two-span CFRP/steel RC beams with ρ_b2 = 0.61-3.03% and ρ_b1/ρ_b2 = 1.5, where ρ_b1 and ρ_b2 are tensile bar ratios (ratios of tensile bar area to effective cross-sectional area of beams) over positive and negative moment regions, respectively. The study shows that replacing steel bars with CFRP bars greatly improves the crack mode at a low bar ratio. The ultimate load of CFRP RC beams is 89% higher at ρ_b2 = 0.61% but 7.2% lower at ρ_b2 = 3.03% than that of steel RC beams. In addition, CFRP RC beams exhibit around 13% greater ultimate deflection compared to steel RC beams. The difference of moment redistribution between CFRP and steel RC beams diminishes as ρ_b2 increases. ACI 318-19 appears to be conservative, and it leads to more accurate predictions of moment redistribution in CFRP RC beams than that in steel RC beams.

Chloride Transport Behaviour and Service Performance of Cracked Concrete Linings in Coastal Subway Tunnels

The concrete lining in subway tunnels often undergoes cracking damage in coastal cities. The combination of cracked tunnel lining structures and high concentrations of corrosive ions in the groundwater (e.g., chlorine) can accelerate concrete erosion, reduce the mechanical performance of the lining structures and shorten the tunnel service life. This paper investigates the chloride ion concentration in the groundwater of several subway tunnels in the coastal city of Qingdao, China. Indoor experiments and numerical simulations are conducted to investigate the chloride ion transport behaviour and service performance of cracked concrete linings. The results are applied to predict the service life of lining structures. The crack depth in concrete linings is found to have the most significant effect on the transport rate of chloride ions, followed by the crack width. The numerical simulations are carried out using COMSOL software to study the chloride transport behaviour in cracked specimens and predict the service lifetimes of lining structures of different thicknesses, and the results correspond well with the experimental data. The durability of a concrete lining can be enhanced by increasing the thickness of the protective concrete layer. Additional measures are proposed for treating cracked concrete linings to resist chloride ion attack in subway tunnels.