Enhanced strength-ductility synergy in a wire and arc additively manufactured Mg alloy via tuning interlayer dwell time

Strength-ductility trade-off is a common issue in Mg alloys. This work proposed that a synergistic enhancement of strength and ductility could be achieved through tuning interlayer dwell time(IDT) in the wire and arc additive manufacturing(WAAM) process of Mg alloy.The thermal couples were used to monitor the thermal history during the WAAM process. Additionally, the effect of different IDTs on the microstructure characteristics and resultant mechanical properties of WAAM-processed Mg alloy thin-wall were investigated. The results showed that the stable temperature of the thin-wall component could reach 290 ℃ at IDT=0s, indicating that the thermal accumulation effect was remarkable. Consequently, unimodal coarse grains with an average size of 39.6 μm were generated, and the resultant room-temperature tensile property was poor. With the IDT extended to 60s, the thermal input and thermal dissipation reached a balance, and the stable temperature was only 170 ℃, closing to the initial temperature of the substrate. A refined grain structure with bimodal size distribution was obtained. The remelting zone had fine grains with the size of 15.2 μm, while the arc zone owned coarse grains with the size of 24.5 μm.The alternatively distributed coarse and fine grains lead to the elimination of strength-ductility trade-off. The ultimate tensile strength and elongation of the samples at IDT=60s are increased by 20.6 and 75.0% of those samples at IDT=0s, respectively. The findings will facilitate the development of additive manufacturing processes for advanced Mg alloys.

Dynamic train dwell time forecasting:a hybrid approach to address the influence of passenger flow fluctuations

Train timetables and operations are defined by the train running time in sections,dwell time at stations,and headways between trains.Accurate estimation of these factors is essential to decision-making for train delay reduction,train dispatching,and station capacity estimation.In the present study,we aim to propose a train dwell time model based on an averaging mechanism and dynamic updating to address the challenges in the train dwell time prediction problem(e.g.,dynamics over time,heavy-tailed distribution of data,and spatiotemporal relationships of factors)for real-time train dispatching.The averaging mechanism in the present study is based on multiple state-of-the-art base predictors,enabling the proposed model to integrate the advantages of the base predictors in addressing the challenges in terms of data attributes and data distributions.Then,considering the influence of passenger flow on train dwell time,we use a dynamic updating method based on exponential smoothing to improve the performance of the proposed method by considering the real-time passenger amount fluctuations(e.g.,passenger soars in peak hours or passenger plunges during regular periods).We conduct experiments with the train operation data and passenger flow data from the Chinese high-speed railway line.The results show that due to the advantages over the base predictors,the averaging mechanism can more accurately predict the dwell time at stations than its counterparts for different prediction horizons regarding predictive errors and variances.Further,the experimental results show that dynamic smoothing can significantly improve the accuracy of the proposed model during passenger amount changes,i.e.,15.4%and 15.5%corresponding to the mean absolute error and root mean square error,respectively.Based on the proposed predictor,a feature importance analysis shows that the planned dwell time and arrival delay are the two most important factors to dwell time.However,planned time has positive influences,whereas arrival delay has negative influences.

Separating spins by dwell time of electrons across parallel double δ-magnetic-barrier nanostructure applied by bias

The dwell time and spin polarization(SP)of electrons tunneling through a parallel doubleδ-magnetic-barrier nanostructure in the presence of a bias voltage is studied theoretically in this work.This nanostructure can be constructed by patterning two asymmetric ferromagnetic stripes on the top and bottom of InAs/AlxIn1-xAs heterostructure,respectively.An evident SP effect remains after a bias voltage is applied to the nanostructure.Moreover,both magnitude and sign of spin-polarized dwell time can be manipulated by properly changing the bias voltage,which may result in an electrically-tunable temporal spin splitter for spintronics device applications.

Critical dwell time of switched linear systems

In this paper, we consider the relation between the switching dwell time and the stabilization of switched linear control systems. First of all, a concept of critical dwell time is given for switched linear systems without control inputs, and the critical dwell time is taken as an arbitrary given positive constant for a switched linear control systems with controllable switching models. Secondly, when a switched linear system has many stabilizable switching models, the problem of stabilization of the overall system is considered. An on-line feedback control is designed such that the overall system is asymptotically stabilizable under switching laws which depend only on those of uncontrollable subsystems of the switching models. Finally, when a switched system is partially controllable (While some switching models are probably unstabilizable), an on-line feedback control and a cyclic switching strategy are designed such that the overall system is asymptotically stabilizable if all switching models of this uncontrollable subsystems are asymptotically stable. In addition, algorithms for designing switching laws and controls are presented.

Minimum Dwell Time for Global Exponential Stability of a Class of Switched Positive Nonlinear Systems

This paper will investigate global exponential stability analysis for a class of switched positive nonlinear systems under minimum dwell time switching, whose nonlinear functions for each subsystem are constrained in a sector field by two odd symmetric piecewise linear functions and whose system matrices for each subsystem are Metzler. A class of multiple time-varying Lyapunov functions is constructed to obtain the computable sufficient conditions on the stability of such switched nonlinear systems within the framework of minimum dwell time switching.All present conditions can be solved by linear/nonlinear programming techniques. An example is provided to demonstrate the effectiveness of the proposed result.

Transmission and Dwell Time Oscillations Caused by Coexistence of Tunneling and Propagating in a Trapezoidal Barrier

A 精制了我们的确切可解决的 trapezoidal 障碍潜力模型之一[薄固体电影， 414 (2002 ) 136 )] 为 metal-insulator-metal，隧道连接被介绍了。根据精制模型的意见，纵的动能(ExL ) 和在障碍的在左边的电极的电子的有效的团(m *L ) 在右与那区分开来。因为 ExL 比结果的 trapezoidal 障碍潜力的更短的方面大，它被发现那，将有通道的共存并且在障碍宣传。结果证明在宣传障碍分区局部性的抑制震荡的电子波浪在传播系数 DT 和居住时间 D 导致摆动和改进。为障碍高度 1 = 2.6 eV 和 2 = 1.4 eV，宽度 d = 22？并且 ExL = 1.0 eV， DT 和 D 有 0.054 和 0.58 的最大值(

Dwell time estimation models for bus rapid transit stations

Bus rapid transit (BRT) systems have been shown to have many advantages including affordability, high capacity vehicles, and reliable service. Due to these attractive advantages, many cities throughout the world are in the process of planning the construction of BRT systems. To improve the performance of BRT systems, many researchers study BRT operation and control, which include the study of dwell times at bus/BRT stations. To ensure the effectiveness of real-time control which aims to avoid bus/BRT vehicles congestion, accurate dwell time models are needed. We develop our models using data from a BRT vehicle survey conducted in Changzhou, China, where BRT lines are built along passenger corridors, and BRT stations are enclosed like light rails. This means that interactions between passengers traveling on the BRT system are more frequent than those in traditional transit system who use platform stations. We statistically analyze the BRT vehicle survey data, and based on this analysis, we are able to make the following conclusions: (Ⅰ) The delay time per passenger at a BRT station is less than that at a non-BRT station, which implies that BRT stations are efficient in the sense that they are able to move passengers quickly. (Ⅱ) The dwell time follows a logarithmic normal distribution with a mean of 2.56 and a variance of 0.53. (Ⅲ) The greater the number of BRT lines serviced by a station, the longer the dwell time is. (Ⅳ) Daily travel demands are highest during the morning peak interval where the dwell time, the number of passengers boarding and alighting and the number of passengers on vehicles reach their maximum values. (Ⅴ) The dwell time is highly positively correlated with the total number of passengers boarding and alighting. (Ⅵ) The delay per passenger is negatively correlated with the total number of passengers boarding and alighting. We propose two dwell time models for the BRT station. The first proposed model is a linear model while the second is nonlinear. We introduce the conflict between passengers boarding and alighting into our models. Finally, by comparing our models with the models of Rajbhandari and Chien et al., and TCQSM (Transit Capacity and Quality of Service Manual), we conclude that the proposed nonlinear model can better predict the dwell time at BRT stations.

Dwell time and bloodstream infection incidence of umbilical venous catheterization in China

Importance:Central line-associated bloodstream infection(CLABSI)is one of the most serious complications of central venous access devices.Reducing the risk of CLABSI is of utmost significance in efforts to improve neonatal mortality rates and enhance long-term prognosis.Objective:To determine the dwell time and incidence of CLABSI of umbilical venous catheterization(UVC)for preterm infants in China.Methods:Preterm infants with UVC admitted to 44 tertiary neonatal intensive care units in 24 provinces in China were enrolled.Study period was from November 2019 to August 2021.The end point of observations was 48 h after umbilical venous(UV)catheter removal.The primary outcomes were dwell time of UV catheter and UVC-associated CLABSI.Data between infants with UV catheter dwell time≤7 days and>7 days,and with birth weight(BW)≤1000 g and>1000 g were compared.Results:In total,2172 neonates were enrolled(gestational age 30.0±2.4 weeks,BW 1258.5±392.8 g).The median UV catheter dwell time was 7(6–10)days.The incidence of UVC-associated CLABSI was 3.03/1000 UV catheter days.For infants with UV catheter dwell time≤7 days and>7 days,the UVC-associated CLABSI incidence was 3.71 and 2.65 per 1000 UV catheter days,respectively,P=0.23.For infants with UVC dwell times of 3–6,7–12,and 13–15 days,the UVC-associated CLABSI rates were 0.14%,0.68%,and 2.48%(P<0.01).The Kaplan–Meier plot of UV catheter dwell time to CLABSI showed no difference between infants with BW≤1000 g and>1000 g(P=0.60).Interpretation:The median dwell time of UV catheter was 7 days,and the incidence of UVC-associated CLABSI was 3.03/1000 catheter days in China.The daily risk of UVC-associated CLABSI and other complications increased with the dwell time.

A numerical method to calculate dwell time for electron in semiconductor nanostructure

To some extent,the operational quickness of semiconductor devices depends on the transmission time of an electron through semiconductor nanostructures.However,the calculation of transmission time is very difficult,thanks to both the contentious definition of the transmission time in quantum mechanics and the complicated effective potential functions experienced by electrons in semiconductor devices.Here,based on an improved transfer matrix method to numerically solve the Schr?dinger equation and H G Winful’s relationship to calculate the dwell time,we develop a numerical approach to evaluate the transmission time of an electron in semiconductor devices.Compared to the exactly resolvable case of the rectangular potential barrier,the established numerical approach possesses high precision and small error,which may be employed to explore the dynamic response and operating speed of semiconductor devices.This proposed numerical method is successfully applied to the calculation of dwell time for an electron in double rectangular potential barriers and the dependence of transmission time on the number of potential barriers is revealed.

Stability of Switched Positive Descriptor Systems with Average Dwell Time Switching

In this paper, the problems of stability for a class of switched positive descriptor systems(SPDSs)with average dwell time(ADT) switching are investigated. First, based on the equivalent switched system and the properties of the projector matrix, sufficient stabilities are given for the underlying systems in both continuoustime and discrete-time contexts. Then, a sufficient stability condition for the SPDS with both stable and unstable subsystems is obtained. The stability results for the SPDSs are represented in terms of a set of linear programmings(LPs) by the multiple linear co-positive Lyapunov function(MLCLF) approach. Finally, three numerical examples are given to illustrate the effectiveness of the obtained theoretical results.

Stabilization of switched linear systems under asynchronous switching subject to admissible edge-dependent average dwell time

The problem of stabilizing switched linear systems under asynchronous switching is addressed.The admissible edge-dependent average dwell time method is applied to design a switching signal that comprises slow admissible edge-dependent average dwell time and fast admissible edge-dependent average dwell time.Under this switching signal,the restriction that the maximum delay of asynchronous switching is known in advance is removed.The constructed Lyapunov function is associated with both the system mode and controller mode.The stabilization criteria and the corresponding algorithm are presented to obtain the controller gains and to design the switching signal.Finally,two examples are given to demonstrate the effectiveness of the proposed results.

High-Accuracy Polishing Technique Using Dwell Time Adjustment

Two algorithms for dwell time adjustment are evaluated under the same polishing conditions that involve tool and work distributions.Both methods are based on Preston’s hypothesis.The first method is a convolution algorithm based on the Fast Fourier Transform.The second is an iterative method based on a constraint problem,extended from a one-dimensional formulation to address a two-dimensional problem.Both methods are investigated for their computational cost,accuracy,and polishing shapes.The convolution method has high accuracy and high speed.The constraint problem on the other hand is slow even when it requires larger memory and thus is more costly.However,unlike the other case a negative region in the polishing shape is not predicted here.Furthermore,new techniques are devised by combining the two methods.

Energy Cost and Mean Dwell Times for the Activity of Promoter with Complex Structure

Regulatory molecules present on the core promoter of a gene interact often in a dynamic,highly combinatorial and possibly energy-dependent manner, leading to complex promoter structure and even complex global dynamics. The authors analyze dynamics of an arbitrarily complex promoter from the view of thermodynamics combined with statistic physics. First, the authors formulize transcription factors-mediated promoter kinetics in terms of energy. Then, the authors analyze energetic cost in several representative cases of promoter structure, deriving useful analytical results. Third, the authors derive analytical expressions for mean dwell times of the promoter activity states, experimentally measurable quantities related to the energy cost of promoter dynamics. The overall framework lays a theoretical foundation for analysis of complex promoter kinetics and gene expression dynamics.

Pose Synchronization of Multiple Rigid Bodies Under Average Dwell Time Condition

这份报纸在交换在哪儿的拓扑学下面考虑一组动人的僵硬身体的姿势同步问题每拓扑学的居住时间可以没有非零更低的界限。作者介绍一个平均居住时间条件描绘图在被连接的时间间隔的长度。由设计尖速度和线性速度的分布式的控制法律，有交换拓扑学的多重僵硬身体的靠近环的动力学能被变换成一个混合动态系统。作者采用 Lyapunov 稳定性定理，并且证明姿势同步能在平均居住时间条件下面被到达。而且，作者在一个类似的平均居住时间条件下面调查领导人追随者模型的姿势同步问题。模拟例子被给说明结果。

Analytical general results for handoff dwell time distribution in wireless networks

This article presents a general evaluation of handof dwell time distribution based on geometric analysis methods Considering the geometric characteristic of the deployed secto pattern, and the distribution of the users’ position and the moving direction in the given sector, the general formulas of the probability density function of sector handoff dwell time ar derived. Some numerical results are also presented fo illustration.

INFLUENCE OF DWELL TIME ON HIGH TEM-PERATURE LOW CYCLE FATIGUE (HTLCF) BEHAVIOR IN AN Nd-BEARING NEAR-α TITANIUM ALLOY

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Comparison of Dwell-Times of Two Commonly Placed Peripheral Intravenous Catheters: Traditional vs. Ultrasound-Guided

Introduction: Because establishing venous access in patients can be difficult and time consuming, the use of ultrasound to guide the insertion of peripheral intravenous catheters has become more common. Anecdotal evidence indicates ultrasound-guided catheter insertion may result in decreased catheter survival in the vein (dwell-time), but there is little evidence to support this observation. The purpose of this study was to compare dwell-times for peripheral intravenous catheters placed with ultrasound guidance with intravenous catheters placed by means of traditional anatomic insertion in patients in an acute care hospital. Methods: This secondary data analysis examined outcomes of 298 patients who received ultrasound-guided catheter insertion and 299 patients who received traditionally placed intravenous catheters. Multivariable linear regression was used to identify significant predictors of dwell-time for both the traditional and US-guided catheters. Results: The average dwell-times for ultrasound-guided and traditionally placed catheters were significantly different (p 2 = 0.22). Discussion: Dwell-times of catheters placed with ultrasound guidance are shorter than traditionally placed catheters. Ultrasound-guided catheters should be monitored closely for inadvertent removal or infiltration. A plan to place a more permanent type of intravenous access should be considered for patients admitted for patients longer than 24 hours.

基于驻留时间控制的压气机叶片前缘砂带磨削研究

提出了一种面向叶片前缘廓形精准控制的机器人砂带磨削加工方法.以轴流压气机叶片为研究对象,结合半赫兹接触理论和有限元仿真获取了柔性磨具和叶片前缘的接触区域内的应力分布,基于Preston方程求解材料去除函数.遍历刀位点对控制点的磨削深度,建立全局材料去除矩阵,搭建驻留时间求解非线性方程组.采用带有阻尼因子的Tikhonov正则化消除大型稀疏病态矩阵对求解精度波动的影响,将所求驻留时间转换为对应刀位点的进给速度,生成机器人加工代码.磨削试验结果表明,基于驻留时间控制的机器人砂带磨削方法能够实现给定允差范围内叶片前缘廓形的精准加工,型面误差可以控制在0.02mm以内.

变负载机械手轨迹跟踪控制器设计

本文针对具有变负载的不确定刚性机械手系统,提出了一种依赖平均驻留时间的神经网络自适应切换控制策略.本控制方案将夹持不同负载的刚性机械手系统视为切换系统,即根据负载的不同将整个系统分为若干子系统,并基于平均驻留时间原则对每个子系统分别设计控制器.在各子系统中,分别采用径向基函数(RBF)神经网络逼近系统结构参数,以避免控制器对系统精确模型的依赖.同时,基于神经网络设计鲁棒补偿项,以抑制集总扰动对系统的影响.然后,利用多Lyapunov函数方法证明了轨迹跟踪误差的一致最终有界性.最后,通过仿真验证,所提出的控制方案不仅可实现变负载机械手期望轨迹的高精度跟踪,而且可有效削弱输入力矩的抖振.