bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigating mechanical properties of purplish-red siltstones and mudstones
Authors: Wen T , Huang L
Published: October 2019

We investigate mechanical properties and energy conversion patterns of special rock types (purplish-red siltstones and mudstones) broadly distributed in the Three Gorges Reservoir (TGR) area, China. The mechanical properties deteriorate under unloading conditions. For loading conditions, the cumulative dissipation energy is slightly lower than elastic strain energy before crack propagation stage, while after crack propagation stage the elastic strain energy converts into cumulative dissipation energy. Similar energy conversion patterns are found for unloading conditions. This work offers a new perspective into the failure mechanism of the two special rock types.
Impact characteristics of gustiness debris flow on check dam
Authors: Jiang X G , Liu F W , Hu K H , Liu T , Wang H J , Li L , Zheng S Y , Chen Y , Song S J , Wang Y D
Published: October 2019

The gustiness is a common motion form of debris flow, especially viscous debris flow. However, few researches have considered the gustiness into the impact characteristics of debris flow, which needs further research. In this study, the check dam was used as the load receptor to study the impact characteristics of gustiness debris flow. The results show that, under the same general flow depth, the dam stress considering the impact of gustiness debris flow is far less than that of disposable continuous debris flow. The impact force increases with the increase of the times of gustiness debris flow, and the impact torque increases linearly. Under the impact of gustiness debris flow, the displacement and stress of the dam vary in the same rule. The safety factors of anti-sliding and anti-overturning of the dam under the effect of gustiness debris flow are larger than those of disposable continuous debris flow, and the decrease rate of the safety factors increases with the increase of the times of gustiness debris flow. And under the condition of the same total flow depth, the increase of the debris flow depth can significantly decrease the stability of dam. The conclusions can provide reference for the design of blocking structures of gustiness and frequent debris flow.
Numerical investigation of plane wave propagation in three soil models and a simple viscoelastic treatment of the boundary considering gravity using MPM
Authors: Zhang R Y , Haider A
Published: October 2019

The importance of plane wave propagation in geotechnical engineering problems considering both small and large deformation is well understood but the theory of wave propagation in the latter is maybe not mature. In this paper, the mechanism of plane wave propagation in constitutive models such as linear elastic model, Mohr Coulomb model (MC) and elastoplastic density-dependent model (DDSM) considering finite deformations is extensively studied using the material point method. The classical laws of wave propagation and reflection in a continuum are found to provide reasonable explanations to the considered problems. The stress propagation mechanism in the three models considered is mainly related to the variation of the material wave impedance. An accurate silent boundary condition is found difficult even impossible to be determined for complicated models, which is verified by a simple deduction. Moreover, a simple viscoelastic silent boundary is proposed to consider the realistic effects of gravity in geotechnical engineering problems and its performance is compared with that of the classical viscous boundary for truncating a 1D linear elastic half-space.
Simulation analysis of liquid sloshing under different working conditions of hazardous materials rescue truck
Authors: Zhou S W , Liu Z H
Published: October 2019

The geometric model is built with SOLIDWORKS, and the VOF(Volume Of Fluid) method in the CFD(Computational Fluid Dynamics) software fluent is used to simulate the sloshing characteristics during the brake and steering of the Hazardous Materials Rescue Truck. The braking acceleration, the liquid filling ratio of the vehicle, lateral acceleration, the effect of the baffle during braking and steering are respectively studied. The results show that the steering and braking of Hazardous Materials Rescue Trucks will cause the liquid in the tank to slosh, and the liquid sloshing will cause the wall slosh force of the tank to change. The driving stability of Hazardous Materials Rescue Trucks can be effectively improved by the reduction of braking force, proper liquid-filling ratio, reduction of lateral acceleration, and increase of baffles.
Composite scattering from complex conductor-medium assembly object above a rough surface
Authors: Li N , Xie S J , Tian G L , Wei S J
Published: October 2019

To solve the scattering from complex object combining conductor and medium, this paper proposes a hybrid iterated method combining single integral equation (SIE) and Kirchhoff approximation (KA). Firstly, SIE is used to calculate the electromagnetic current in the facet of the conductor-medium assembly object. Then, the electric and magnetic currents on the facet of a rough surface are calculated by KA. The electromagnetic current on the facet of object and a rough surface are updated by mutual iteration. Finally, some examples for composite scattering from object above a rough surface are analysed and discussed in detained.
Lattice Boltzmann simulation of the methane backward flow in coal mine tunnels after methane outburst
Authors: Wang Q J , Zhao Y C , Nie Y
Published: October 2019

Numerical study of the methane backward flow in coal mine tunnels after a methane outburst is necessary to the engineering design and emergency rescue. In this paper, we introduce Lattice Boltzmann Method (LBM) coupled with the Large Eddy Simulation (LES) model to simulate the methane backward flow in the air-intake tunnel of twin-tunnel construction in the coal mine after the methane outburst and analyze the effects of the inlet air velocity, the intensity of the methane outburst and the width of the tunnel to the distance that the methane can flow backward. It demonstrates that with the increase of the inlet air velocity, the distance that the methane can flow backward decreases. With the increase of the intensity of the methane outburst, the distance that the methane can flow backward increases. There exist linear relationships between the inlet air velocity, the intensity of the methane outburst and the distance that the methane can flow backward. The change of the tunnel width has almost no influence on the distance that the methane can flow backward.
Study on wind-induced response of a simplified model of transmission tower based on finite particle method
Authors: Huang Z , Liu S , Nie M , Yang Y , Gao Q S , Zhang C
Published: October 2019

A reduced model of a transmission tower was established based on the principle of equivalent stiffness. The finite particle method was used to analyse the wind-induced response of the reduced model. The analysis of the dynamic characteristics of the reduced model shows that the accuracy of the equivalent formula proposed in this paper was very high. Compared with the first five order natural frequencies of the complete model, the maximum calculation error of the reduced model was only 0.87%. Since the first order shear deformation beam theory was used in the reduced model, the interpolation-independent element shape functions were developed to avoid the shear locking phenomenon. Moreover, the formula for calculating the internal force of Timoshenko beam for finite particle method was derived. By using two successive Euler angles, a new method for separating the rigid motion and pure deformation of the element was proposed. The computational efficiency of this method is significantly improved, and the computational time is less than half of that of the traditional finite particle method. The results of wind-induced response analysis of the transmission tower show that the simplified model proposed in this paper can obtain highly accurate displacement response of the structure, and the maximum error of the RMS of the displacements at the top of the tower is less than 3.2%. This model is suitable for studying the dynamic response of transmission tower line system and evaluating the effect of the wind-induced vibration control of damping device.
A damage constitutive model and its characterization parameters identification for elastic-plastic materials
Authors: Wang C H , Jiang W X , Xin K H , Wang J , Ji H J
Published: October 2019

This paper proposes a simple damage constitutive model for elastic-plastic materials on the basis of the classical elastic-plastic constitutive model and damage mechanics theory. Based on the simple damage constitutive model, ABAQUS built-in Python software was used to develop the virtual experimental platform, and the whole process simulation of the specimens stretching until the fracture was carried out. The correspondence between the damage characterization parameters and the performance indexes such as the fracture strain and the percentage reduction of area was studied. According to the comparison of the virtual/real test results of ZL114A, the situation shows that the simple damage constitutive model can realize the high fidelity simulation of the damage behavior of elastic-plastic materials. The relative accuracy of the important material property parameters such as the ultimate strength, the percentage total elongation at fracture and the percentage reduction of area reaches 5%.
Investigation of gas-dynamic processes in a boundary layer on a basis of molecular dynamics simulation
Authors: Kuryashova T A , Podryga V O , Polyakov S V
Published: October 2019

The work is devoted to numerical simulation of the nonlinear gas dynamic processes in technical systems of micron sizes. This problem is relevant for many applications related to the implementation and the use of nanotechnology in various industries. As an example, a gas flow in micro channel with metal walls is considered. Within this problem, we are interested in a calculation of the boundary layer parameters from first principles. The numerical analyses are carried out according to the Newton's equations of classical dynamics. The model under consideration takes into account the molecular composition of the gas, the atomic structure of the metal surfaces, and heat exchange of the gas with the metal. Computer implementation is focused on using high-performance systems with hybrid architecture. The calculations are performed on the example of a nitrogen flow into a nickel micro channel for several micro channel lengths. The flow velocity varied over a wide range. It is considered in the subsonic, transonic, and supersonic ranges. In numerical experiments, macro parameters of gas flow in the boundary layer are obtained and the corresponding near-wall model is formed. It can be used for the calculation of flows in micro channels using continuum mechanics methods.
Forecasting methods in engineering
Authors: Tratar L F , Strmčnik E
Published: October 2019

Forecasting in engineering is one of the most important topics when it comes to optimisation, which is related to energy savings, material savings, increasing efficiency, and appropriate and correct decisions at the level of a company, institution, city, or region. Moreover, forecasting is indirectly related to cost savings and the sustainable development of society and environment. In the energy industry (electricity, natural gas, heat load), there are requirements to balance the supply and demand. Markets are very dynamic, and for this reason forecasting is more challenging. Forecasting errors are usually penalized drastically. However, a well-developed forecasting approach represents a competitive advantage, and so a company may significantly reduce expenditure and increase profits. Many publications on forecasting have been published during recent years. Long-term forecasting methods offer many opportunities for strategic planning and optimal scheduling, whereas a short-term forecasting approach would help attain optimal daily operations and the maximum utilisation of the company’s resources. Although different forecasting techniques can be used, the major conclusions are that exponential smoothing methods are the simplest and the least expensive. Distinguished by their simplicity, their forecasts are comparable to forecasts of more complex statistical time series models. In this paper, the forecasting performance of Additive, Multiplicative, and Extended Holt-Winters methods were analysed. We also analyse whether the data format influences the choice of the forecasting method: is the most accurate method for monthly data also the best method for quarterly data?
Numerical study on flow around vane in a channel using immersed boundary method
Authors: Huang J F , Yang S , Yao J , Zhang L X
Published: October 2019

The immersed boundary method is applied to simulate the flow around a guide vane of hydro-turbine. The complex dynamic boundary effect caused by the moving guide vanes is modelled as the forcing term in the Navier-Stokes equation. Numerical simulation of threedimensional transient turbulence is conducted to flow around one moving guide vane of a benchmark hydro-turbine unit in a channel. The dynamical Smagorinsky-Lilly model of large eddy simulation is also used. The evolution process of the dynamic vortex structure is obtained by the interaction between the guide vane and the flow around vane to reveal the physical mechanism of wake oscillation flow around vane. This method serves as a reference for the fine simulation and study of the flow around the multi-stage cascade flow in hydro-turbine. The research on the transient effects of the coupling upstream pipeline system and hydroturbine has theoretical guiding significance.
Influence of different oil-paper configurations on the electric field distribution simulation of the internal insulation of converter transformer
Authors: Cheng Z D , Cheng L , Wang J H , Wang L
Published: October 2019

Converter transformer is an important equipment in HVDC system and it is the key to the stable operation of the whole power transmission and distribution system. Unlike the traditional AC transformer, the oil-paper insulation of converter transformer will receive both AC and DC voltage. So the requirement for the structure design of oil-paper insulation system will be more stringent. It is of great engineering significance to study the electric field distribution of converter transformer and to study the influence of different oil-paper insulation configuration on the electric field distribution in the internal insulation of converter transformer. In this paper, first, an oil-paper insulation structure of converter transformer is established and electric field distribution under AC/DC composite voltage is studied. Then change the thickness and layers of pressboard, the distance of oil channel and the oil-paper ratio to get different oil-paper configurations. Use the simulation software to calculate the electric field distribution under the different oil-paper configurations. Finally, the influence of different oil-paper configuration on the electric field distribution of internal insulation structure of converter transformer is analysed which will provides significant reference for the internal insulation design of converter transformer.
Numerical modelling and vibration analysis of human middle ear for application in sound conduction reconstruction
Authors: Liu Y , Higashimachi T , Toriya R
Published: October 2019

In this paper, we introduce a new numerical approach for estimating the hearing restoration eect prior to the tympanoplasty operation using the nite element harmonic vibration analysis. This kind of approach makes it possible to propose a new medical treatment for the recovery of conductive or cochlear hearing loss. First of all, precise geometric models of the middle ear, including healthy type model and tympanoplasty type models, are constructed on the basis of the computerized tomography (CT) scanning data. Then, frequency response characteristics of the stapes displacement in sound conduction are claried using the three-dimensional nite element harmonic vibration analysis. Based on the investigation results, we propose that the hearing restoration eect can be estimated by a comparison of the dierences in the stapes displacement between the reconstruction model and the healthy subject.
Weak-form differential quadrature element method for dynamic analysis of fluid-saturated soil
Authors: He G H , Kuang Z H , Li X K
Published: October 2019

It is formulated the weak-form of differential equations that govern the two-dimensional dynamical behavior of fluid-saturated soil, then the weak-form equations are discretized by the differential quadrature technique, and finally solved by the implicit Euler method. The proposed weak-form equations and numerical programs developed are verified through comparisons with benchmark solutions, and the convergence performance of the presented method is investigated. Numerical results show that the proposed weak-form quadrature element method not only possesses significantly higher computational efficiency, for the dynamic analysis of saturated soil, than the conventional finite element method, but it is also significantly alleviated the problem of numerical smoothness in the stress analysis.
Influences of various orifice layouts on the properties of aerostatic journal bearings based on finite element method
Authors: Gao S Y , Shi Y G , Yang S , Sun P , Li T J
Published: October 2019

It is essential to thoroughly investigate influences of orifice layouts on properties of aerostatic journal bearings employed in ultra-high speed spindles. In this paper, four orifice layouts of aerostatic journal bearings which have a large length-diameter ratio are designed and investigated, particularly in light of the nonlinear compressible Reynolds equation and the associated computational analysis and algorithms using the FEM-based Galerkin weighted residual method. A series of pressure distributions as well as the load capacity, attitude angle, volume flow rate and air film stiffness of the aerostatic journal bearings for the cases of four orifice layouts are analysed with respect to different rotational speeds and eccentricity ratios. It can be concluded that increasing orifice sets is not beneficial to enhance the performance of the aerostatic journal bearing. The aerostatic journal bearing divided into two identical independent aerostatic journal bearings has relative optimal performance at rotational speeds from 0 r/min to 160,000 r/min, such as the highest load capacity, the lowest attitude angle and modest air film stiffness, however, with consumption of the largest quantities of pressurized gas. The designers can use the analysis results to optimize the orifice layout for improving the performance of the aerostatic journal bearing.
Optimizing basket transplanting parameters using the mechanical properties of tomato plug seedlings
Authors: Liu Y , He Y C , Li Y X , Mao H P , Li B , Wang T , Wang S G , Li H
Published: October 2019

The collision between tomato plug seedlings and the planting device during basket transplanter function causes the seedlings’ root lump to lose some mass. To resolve this problem, we establish a contact mechanics model using Hertzian contact theoretical and Newtonian methods, enabling us to formally derive the maximum deformation of the root lump. The equation of motion describing the collision between the tomato plug seedling and planting device is constructed using the principles of impulse and momentum. Then, we identify the optimization function of contact angle θ—which consists of the maximum deformation of the root lump, the angular velocity of the tomato plug seedling, and the absolute velocity of the root lump—via multi-objective methods. When the angular velocity of the planting device is 1.05 rad/s or 1.15 rad/s, the optimal contact angle is 67°. Further, we examine the velocity of the tomato plug seedling after collision. A small plant height reduces the root lump’s mass loss; we found that 12-cm-tall tomato plug seedlings lose less root lump mass than taller seedlings. Finally, for angular velocities of 1.05 rad/s and 1.15 rad/s, we carry out of tomato plug seedling crush tests with the optimized parameters, achieving minimum root lump mass losses of 8.76% and 7.43%, respectively.
Experimental investigation on micro-drilling properties of Mg-based MMCs reinforced with HAP nanoparticles
Authors: Sun F Z , Fu G Y , Shen J R
Published: October 2019

Mg-based metal matrix composites (MMCs) reinforced with Hydroxyapatite (Ca10(PO4)6(OH)2, HAP) nanoparticles have been studied as bone substitute materials because of their excellent biocompatibility and biological activity. In this paper, Mg/HAP MMCs with different HAP contents (0.5, 1.0 wt%) were selected and the micro-drilling properties were revealed. Firstly, the chip of MMCs was analyzed. Secondly, the surface roughness of Mg/HAP MMCs under different cutting parameters was studied. The results showed that the surface roughness decreases with the increasing of feedrate and decreases with the increasing of spindle speed, which are contrary to pure Mg. Furthermore, the shapes of burr are all classified as uniform burr, and the burr height increased with the increase of spindle speed and feed. Finally, the size effect of micro-drilling was studied. The minimum cutting thickness per tooth of Mg/HAP MMCs was determined to be 1.0 μm.
Application of resonance demodulation method based on local characteristic-scale decomposition and spectral kurtosis in gearbox fault
Authors: Cong R , Li C H , Wu J Q
Published: October 2019

Resonance demodulation technology has been widely used for its advantages on magnification and selection of fault information. However, the selection of filter parameters is affected by the subjectivity, and the analysis results are easily affected by the noisy signals under actual working conditions. To solve this problem, a method combining relative entropy and correlation coefficient is proposed to analyze and select Intrinsic Scale Components obtained by Local Characteristic-scale Decomposition, remove false components, and to some extent, denoise. Then, after reconstructing the remaining components, we use spectral kurtosis analysis to find out the most easily detected frequency bands of fault features and analyze them by resonance demodulation, aiming to diagnose gearbox failures. Finally, we compare this method with that based on the empirical mode decomposition. The research shows that the method proposed in this paper can effectively diagnose the gearbox fault and is better than the empirical mode decomposition.
Numerical analysis of mini-channel cooling applied in power battery
Authors: Huang F X , Zhao J , Wang C , Zhang H
Published: October 2019

Working in the extreme condition such as high temperature and discharge rate, causes the generated heat shapely increasing and rising of temperature of power battery. Further influence the cell performance. It is important to efficiently dissipate heat. In this paper, a minichannel cooling system can be designed to cope with the problem. Moreover, creating numerical model to study different placement, ambient temperature and coolant inlet properties how to function on the system. The results express the system be placed at vertical direction can obtained a good temperature effect, only sacrificing few of pump energy than placed at horizontal. The results show the variation of ambient temperature has little effect on the temperature contribution of battery module, and the temperature of the battery pack is presented linear with the coolant inlet temperature. The temperature of battery pack is decrease and the uniformity is improved by increasing the inlet velocity of the coolant. In the end, increasing the height of the channel are a better scheme through the process of structure optimization.
Dynamic effects of low-velocity impact on composite plates
Authors: Wang R , Chen D D , Zhu M , Xing S L
Published: October 2019

In low-velocity impact research on composites, quasi-static indentation experiments are typically used to make inner fractures. However, dynamic effects caused by impacts cannot be studied by quasi-static experiments. In this paper, the dynamic effects are discussed using simulation. Low-velocity impact processes were simulated through ABAQUS/Explicit software. Quasi-static processes were also simulated with ABAQUS/Explicit, in which very-low-speed displacement loadings were adopted to ensure that the kinetic energy could be ignored. The results show nearly no dynamic effect in the thickness direction, due to the thin nature of the composite plate and high-stress wave velocity in the through-the-thickness direction. In the radial direction, in contrast, apparent dynamic effects are observed, although the associated stress wave velocity is much higher. This may be attributed to the wave propagation from the impact site to the edge of the plate, reflecting repeatedly between the top and bottom surfaces of the plate.
Estimation of aircraft magnetic field model coefficient under Geomagnetic Gradient Change
Authors: Li C J , Zhang B , Ouyang T H , Gong Y Z , Li B
Published: October 2019

Traditional airplane magnetic field models simplify geomagnetic field values as constants, overlooking changes to the model coefficient brought by gradually variational magnetic field which reduces the model accuracy. This paper puts forward an aircraft magnetic field model under geomagnetic gradient change. The geomagnetic gradient change is adopted the truncated singular value decomposition (TSVD) to solve multicollinearity in the model solving. It is proposed to use the coefficient obtained from the truncated singular value as initial conditions and utilize recursive damped least square (RDLS) to conduct adaptive adjustment to model coefficients aiming at the coefficient variation of induction field and Eddy Current Field caused by the geomagnetic field. The simulation outcome indicates that the method boasts a high magnetic compensation effect.
Investigation on characteristics of arc extinguishing time of a new lighting protection gap for transmission lines
Authors: Yan R B , Wang J F , Li Z J , Huang SS
Published: October 2019

The present research envisages the development of a novel arc extinguishing lightning protection gap in pursuit of reducing the lightning trip-out rate and accident rate. In the developed setup, the jetting stream arc extinction lightning protection gap device was used for transmission line. When this transmission line was struck by lightning and the lightning surge was going to break down the gap, the arc extinguishing lightning protection gap immediately jetted out sufficient electronegative gas flow that quickly cut off the arc and effectively prevented the insulator from being damaged by the arc. Furthermore, when the line was attacked by lightning, the generated overvoltage instantaneously broke the gap that was parallel to the insulator string, so that the lightning current was oriented to the earth from the gap. Simultaneously, it triggered the gas generator and generated a high speed stream, then extinguished the frequency continuous current arc rapidly, thus effectively reducing the rate of line trip to ensure the reliability of power supply. We used a high-speed camera and ordinary camera that automatically captured the process of the jetting stream arc in the extinction lightning protection gap device, while extinguishing the 1kA power frequency arc. The image of the high-speed camera indicated that the power frequency arc of 1kA was quenched in 10 ms before the relay protection action of the test loop, which made that the overhead line lightning flashover but the circuit breaker did not trip. Thus, a reduction in the rate of lightning trip was observed by the developed setup, and it has an immense potential for application at the transmission lines of China.
Simulation on temperature field of initial segment of electromagnetic rail launch
Authors: Tong S Y , Feng G , Lian Z M , Cheng J S
Published: October 2019

The temperature field analysis of electromagnetic rail launcher is an important basis for studying the launching stability and life. Aiming at the rail groove erosion phenomenon, the launching initial segment is selected as the research site. The heat generation mechanism of Joule heat and friction heat is analyzed, the heat source model is established, the three-dimensional finite element simulation model is established and the position, velocity and current waveform of the launching initial section are determined according to the circuit simulation, the finite element simulation results show that the heat in the initial stage of launching mainly concentrates on the contact surface between armature and rail. The friction heat is the main factor affecting the temperature rise of the contact surface, and the uneven distribution of the current density will lead to the uneven temperature distribution of the contact surface.
Numerical simulation of heavy truck’s aerodynamic noise
Authors: Liu J , Zhuang C , Liu S , Zhou H M
Published: October 2019

A 3D numerical simulation is built on heavy truck including cab, frame, and tires. And vehicle exterior flow field in steady state is computed by computational fluid dynamics software. In the computation process, the distribution of sound power levels on the surface of vehicle body as well as the connection between sound power level and vehicle speed are obtained from aerodynamic noise source, which is using broadband noise source models. Taking the steady flow field results as original values, the exterior flow field computations in transient state are performed by large eddy simulation. Based on the transient fluid field, the near field aerodynamic noise from cab accessories is predicted using FW-H model, and the comparison of the simulation results and the test results is carried out. The results show that the aerodynamic noise sources are from the upwind side with a great pressure gradient. Attentions should be paid more on rearview mirror, diversion trench and sun visor for Aerodynamic noise optimization of heavy truck. The maximum sound power level of aerodynamic noise in vehicle body accessories is quadratic to vehicle speed. And the aerodynamic noise of heavy trucks is analysed by numerical simulation, in which noise distribution law is consistent with the test. Therefore, the numerical simulation can be adopted to provide the guidance for the design of vehicle body with low noise.
Numerical simulation of dendritic evolution based on an improved cellular automaton model involving solute field
Authors: Wang J J , Meng H J , Yang J , Xie Z
Published: October 2019

This paper studied the single crystal growth of Fe-0.64C alloy under a fixed cooling rate, proposed an improved cellular automaton model. The influence of solute field on dendrite growth is especially considered into the model. And a new solute distribution scheme based on Fick's first law and solute conservation was proposed from the microscopic scale. In addition, the present work improved the acquisition algorithm, which takes the growth length of the interface cell to the neighbouring cell as the determination condition of the capture. A solid fraction calculation method based on the solidification area of interface cell to total area is also proposed. The results show that this model can not only dynamically display the formation process of secondary dendrites and high-order dendrites, but also simulate the distribution of solute inside the dendrites and at the interface front.
The rolling contact research of three dimensional wheel-rail based on finite element analysis
Authors: Tian J H , Jing G Q , Lu X X , Xiao K , Zhang H R
Published: October 2019

In this paper, wheel-rail contact model was established and analyzed, some useful results were obtained. The results show that In the early stage of wheel-rail contact, the wheel-rail contact pressure increases gradually and the contact point shape changes from regular polygon to irregular polygon in the process of wheel approaching rail joint. The equivalent stress and elastic deformation trend of the rail are basically the same, both of which decrease rapidly and then slowly increase. The plastic deformation of the rail gradually increases and accumulates, and the stress concentration area occurs at the side of the rail joint. When the wheel starts rolling, the equivalent stress of the wheel gradually decreases at first, and then increase. The peak value of the maximum equivalent stress occurs at the joint where the wheel reaches the rail.
Stability of Sn based inorganic perovskite quantum dots
Authors: Pradeep K R , Chakraborty Saptarshi , Viswanatha Ranjani
Published: October 2019

Metal halide perovskite crystal structures have emerged as a class of optoelectronic materials, which combine the ease of solution processability with excellent optical absorption and emission qualities. However, the most promising perovskite structures rely on lead as a cationic species, thereby hindering commercial application. The replacement of lead with non-toxic alternatives such as tin has been studied in bulk but not in nanocrystals. In this work, we synthesize Sn and Pb based alloy perovskite nanocrystals by direct synthesis method, taking mixture of Pb and Sn precursors in the desired ratio leading to quantum dots (QDs) of CsPb1−xSnxBryI3−y with successful Sn incorporation into the host lattice. As colloidal stability of these QDs is a crucial factor for device applications, we have studied the stability of the QDs under different conditions for these Sn based QDs and have found them to degrade faster upon using anti-solvents during washing process. In order to stabilize them, we have devised a purification method that is also discussed. Further, even though the optical and crystal structure stability in some of the inorganic perovskites leaves much room for improvement, so far there have been no studies on the structure property correlation. Here we study their structural purity and their optical stability after understanding the structure property correlation in CsPbI3 and CsPbBr3 perovskite structures. The stability of Sn doped perovskites obtained from a logical understanding of structure property correlation is found to be extremely stable across the series of compounds for upto three months.
Dominant plant speciation types. A commentary on: ‘Plant speciation in the age of climate change’
Authors: Gao Jianguo
Published: October 2019

This article comments on:

Donald A. Levin. 2019. Plant speciation in the age of climate change. Annals of Botany 124(5): 769–775.
Time trends in sudden cardiac death risk in heart failure patients with cardiac resynchronization therapy: a systematic review
Authors: Barra Sérgio , Providência Rui , Narayanan Kumar , Boveda Serge , Duehmke Rudolf , Garcia Rodrigue , Leyva Francisco , Roger Véronique , Jouven Xavier , Agarwal Sharad , Levy Wayne C , Marijon Eloi
Published: October 2019

Aims

While data from randomized trials suggest a declining incidence of sudden cardiac death (SCD) among heart failure patients, the extent to which such a trend is present among patients with cardiac resynchronization therapy (CRT) has not been evaluated. We therefore assessed changes in SCD incidence, and associated factors, in CRT recipients over the last 20 years.

Methods and results

Literature search from inception to 30 April 2018 for observational and randomized studies involving CRT patients, with or without defibrillator, providing specific cause-of-death data. Sudden cardiac death was the primary endpoint. For each study, rate of SCD per 1000 patient-years of follow-up was calculated. Trend line graphs were subsequently constructed to assess change in SCD rates over time, which were further analysed by device type, patient characteristics, and medical therapy. Fifty-three studies, comprising 22 351 patients with 60 879 patient-years of follow-up and a total of 585 SCD, were included. There was a gradual decrease in SCD rates since the early 2000s in both randomized and observational studies, with rates falling more than four-fold. The rate of decline in SCD was steeper than that of all-cause mortality, and accordingly, the proportion of deaths which were due to SCD declined over the years. The magnitude of absolute decline in SCD was more prominent among CRT-pacemaker (CRT-P) patients compared to those receiving CRT-defibrillator (CRT-D), with the difference in SCD rates between CRT-P and CRT-D decreasing considerably over time. There was a progressive increase in age, use of beta-blockers, and left ventricular ejection fraction, and conversely, a decrease in QRS duration and antiarrhythmic drug use.

Conclusion

Sudden cardiac death rates have progressively declined in the CRT heart failure population over time, with the difference between CRT-D vs. CRT-P recipients narrowing considerably.
Molecular signature of cardiogenic shock
Authors: Iborra-Egea Oriol , Rueda Ferran , García-García Cosme , Borràs Eva , Sabidó Eduard , Bayes-Genis Antoni
Published: October 2019

The incidence of cardiogenic shock (CS) has increased remarkably over the past decade and remains a challenging condition with mortality rates of ∼50%. Cardiogenic shock encompasses cardiac contractile dysfunction; however, it is also a multiorgan dysfunction syndrome, often complicated by a systemic inflammatory response with severe cellular and metabolic dysregulations. Here, we review the evidence on the biochemical manifestations of CS, elaborating on current gold standard biomarkers and novel candidates from molecular signatures of CS. Glucose and lactate, both identified over a century ago, remain the only clinically used biomarkers in current predictive risk scores. Novel genomic, transcriptomic, and proteomic data are discussed, and a recently reported molecular score derived from unbiased proteomic discovery, the CS4P, which includes liver fatty acid-binding protein, beta-2-microglobulin, fructose-bisphosphate aldolase B, and SerpinG1 is comprehensively described. Recent advances in -omics technologies provide new insight into a more holistic molecular signature of CS. Thus, we need to open new diagnostic and therapeutic avenues if we aim to improve outcomes.
Pharmacodynamics, pharmacokinetics, and safety of single-dose subcutaneous administration of selatogrel, a novel P2Y12 receptor antagonist, in patients with chronic coronary syndromes
Authors: Storey Robert F , Gurbel Paul A , ten Berg Jurrien , Bernaud Corine , Dangas George D , Frenoux Jean-Marie , Gorog Diana A , Hmissi Abdel , Kunadian Vijay , James Stefan K , Tanguay Jean-Francois , Tran Henry , Trenk Dietmar , Ufer Mike , Van der Harst Pim , Van't Hof Arnoud W J , Angiolillo Dominick J
Published: October 2019

Aims

To study the pharmacodynamics and pharmacokinetics of selatogrel, a novel P2Y12 receptor antagonist for subcutaneous administration, in patients with chronic coronary syndromes (CCS).

Methods and results

In this double-blind, randomized study of 345 patients with CCS on background oral antiplatelet therapy, subcutaneous selatogrel (8 mg, n = 114; or 16 mg, n = 115) was compared with placebo (n = 116) (ClinicalTrials.gov: NCT03384966). Platelet aggregation was assessed over 24 h (VerifyNow assay) and 8 h (light transmittance aggregometry; LTA). Pharmacodynamic responders were defined as patients having P2Y12 reaction units (PRU) <100 at 30 min post-dose and lasting ≥3 h. At 30 min post-dose, 89% of patients were responders to selatogrel 8 mg, 90% to selatogrel 16 mg, and 16% to placebo (P < 0.0001). PRU values (mean ± standard deviation) were 10 ± 25 (8 mg), 4 ± 10 (16 mg), and 163 ± 73 (placebo) at 15 min and remained <100 up to 8 h for both doses, returning to pre-dose or near pre-dose levels by 24 h post-dose. LTA data showed similarly rapid and potent inhibition of platelet aggregation. Selatogrel plasma concentrations peaked ∼30 min post-dose. Selatogrel was safe and well-tolerated with transient dyspnoea occurring overall in 7% (16/229) of patients (95% confidence interval: 4–11%).

Conclusions

Selatogrel was rapidly absorbed following subcutaneous administration in CCS patients, providing prompt, potent, and consistent platelet P2Y12 inhibition sustained for ≥8 h and reversible within 24 h. Further studies of subcutaneous selatogrel are warranted in clinical scenarios where rapid platelet inhibition is desirable.
Effects of Transcranial Direct Current Stimulation on Episodic Memory in Older Adults: A Meta-analysis
Authors: Huo Lijuan , Zhu Xinyi , Zheng Zhiwei , Ma Jialing , Ma Zhuoya , Gui Wenjun , Li Juan
Published: October 2019

Objectives

In the last two decades, the number of intervention studies using transcranial direct current stimulation (tDCS) has grown enormously. Though some studies have shown positive influences on episodic memory among older adults, disagreement exists in the literature. Therefore, the current meta-analysis aimed to provide a quantitative assessment of the efficacy of tDCS in modulating episodic memory functions in older adults.

Method

Eligible studies were sham-controlled trials examining the effects of anodal tDCS on episodic memory in older adults. Twenty-four articles comprising 566 participants aged over 60 qualified for inclusion.

Results

Compared to the sham tDCS group, the active tDCS group showed significant memory improvements at both immediate poststimulation (Hedges’ g = 0.625, p = .001) and long-term follow-up (Hedges’ g = 0.404, p = .002). There were no differences in effect sizes between cognitively healthy and impaired older adults. Moderator analyses suggested that tDCS having a duration of 20 min or less, bilateral stimulation, or a larger stimulation area would produce greater benefits for episodic memory performance in older adults.

Discussion

These findings suggest that tDCS holds great promise to ameliorate memory decline in older individuals. In the future, well-designed randomized controlled trials are expected to verify the optimal stimulation protocols and determine the factors impacting the long-term effects of tDCS in enhancing episodic memory.
Personhood and Dementia Care: A Qualitative Evidence Synthesis of the Perspectives of People With Dementia
Authors: Hennelly Niamh , Cooney Adeline , Houghton Catherine , O’Shea Eamon
Published: October 2019

Background and Objectives

Personhood is considered the cornerstone of person-centered care for people with dementia. However, there is little research on personhood in dementia care from the perspective of the person with dementia themselves. This article presents a qualitative evidence synthesis of the experiences and perceptions of people with dementia on personhood in dementia care.

Research Design and Methods

A systematic search of nine databases was conducted. In addition to initial screening, CART analysis was used to determine the most relevant papers. Thematic synthesis was conducted on 20 papers. The CASP tool was used to examine the quality of the included papers. GRADE CERQual analysis examined confidence in the review findings.

Results

People with dementia experience many changes due to the disease and the experience of being cared for in different settings. Personhood is affirmed through personal interactions with family, friends, other care recipients, and formal caregivers, as well as through continued engagement in social and occupational roles.

Discussion and Implications

The review has important implications for practice, regulation, and policy. The person and their personhood should be protected rather than undermined, and relationships should be enhanced not diminished by the formal care process. The focus should be on creating and amplifying opportunities for people with dementia to affirm the self through interactions with others and engaging in occupational and social roles to ensure continuity of self.
Hidden health IT hazards: a qualitative analysis of clinically meaningful documentation discrepancies at transfer out of the pediatric intensive care unit
Authors: Orenstein Evan W , Ferro Daria F , Bonafide Christopher P , Landrigan Christopher P , Gillespie Scott , Muthu Naveen
Published: October 2019

Objective

The risk of medical errors increases upon transfer out of the intensive care unit (ICU). Discrepancies in the documented care plan between notes at the time of transfer may contribute to communication errors. We sought to determine the frequency of clinically meaningful discrepancies in the documented care plan for patients transferred from the pediatric ICU to the medical wards and identified risk factors.

Materials and Methods

Two physician reviewers independently compared the transfer note and handoff document of 50 randomly selected transfers. Clinically meaningful discrepancies in the care plan between these two documents were identified using a coding procedure adapted from healthcare failure mode and effects analysis. We assessed the influence of risk factors via multivariable regression.

Results

We identified 34 clinically meaningful discrepancies in 50 patient transfers. Fourteen transfers (28%) had ≥1 discrepancy, and ≥2 were present in 7 transfers (14%). The most common discrepancy categories were differences in situational awareness notifications and documented current therapy. Transfers with handoff document length in the top quartile had 10.6 (95% CI: 1.2–90.2) times more predicted discrepancies than transfers with handoff length in the bottom quartile. Patients receiving more medications in the 24 hours prior to transfer had higher discrepancy counts, with each additional medication increasing the predicted number of discrepancies by 17% (95% CI: 6%–29%).

Conclusion

Clinically meaningful discrepancies in the documented care plan pose legitimate safety concerns and are common at the time of transfer out of the ICU among complex patients.
Modelling the photometric variability of magnetic massive stars with the Analytical Dynamical Magnetosphere model
Authors: Munoz M S , Wade G A , Nazé Y , Puls J , Bagnulo S , Szymański M K
Published: October 2019

In this paper, we investigate the photometric variability of magnetic O-type stars. Such stars possess oblique, predominantly dipolar magnetic fields that confine their winds roughly axisymmetrically about the magnetic equator, thus forming a magnetosphere. We interpret their photometric variability as phase-dependent magnetospheric occultations. For massive star winds dominated by electron scattering opacity in the optical and NIR, we can compute synthetic light curves from simply knowing the magnetosphere’s mass density distribution. We exploit the newly-developed Analytical Dynamical Magnetosphere model (ADM) in order to obtain the predicted circumstellar density structures of magnetic O-type stars. The simplicity in our light curve synthesis model allows us to readily conduct a parameter space study. For validation purposes, we first apply our algorithm to HD 191612, the prototypical Of?p star. Next, we attempt to model the photometric variability of the Of?p-type stars identified in the Magellanic Clouds using OGLE photometry. We evaluate the compatibility of the ADM predictions with the observed photometric variations, and discuss the magnetic field properties that are implied by our modelling.