Initial Mode Research Articles

Mechanical behavior of a novel steel–concrete joint in concrete-composited hybrid continuous bridges

The steel–concrete joint is of great importance to the hybrid girder, while its mechanical behavior has not been understood enough due to the diversity of structural forms and application areas. This paper presented a mechanical performance investigation on a novel steel–concrete joint applied in a hybrid continuous bridge. A static flexural test and numerical simulation were conducted on a 16.6-m-long full-scale segmental joint. Parametric analysis via finite element models with the material damage plasticity on the joint performance was also carried out, in which structural dimensions and pre-stress extent were analyzed. The test results revealed that the border between the concrete girder and steel–concrete joint was the most cracking-prone position, while the joint remained comparatively intact at the ultimate state. The structural safety and internal force transfer mechanism were discussed with the presented strain distributions and deflection along the test girder. The simulation results showed that the effect of joint length on the bending performance of hybrid girder was more significant than back bearing plate thickness and pre-stress extent. The calculated ultimate capacity and bending stiffness increased by 8.3% and 4.0%, respectively, as the joint length increased from 3.6 m to 4.4 m. In addition, the initial cracking mode of the hybrid girder was exhibited to be correlated with the joint length because of changing structural stiffness. The research outcomes could provide the fundamental basis for a rational design of the joint component applied in hybrid continuous bridges.

Study on the Influence of Initiation Model on the Forming Characteristics of MEFP Warhead

To study the influence of different initiation modes on the forming characteristics of the MEFP warhead, numerical simulations were carried out on three types of initiation modes. The numerical simulation results showed that the number of EFPs was the least by double-column multipoint synchronous initiation, the number of EFPs was the largest by the central single-point (multipoint) initiation, and single-column single-point (multipoint synchronous) detonation forms the number of EFPs between central single-point (multipoint synchronous) detonation and double-column multipoint synchronous detonation. For the MEFP warhead of a small-caliber grenade, whether it is center detonation or eccentric detonation, the EFP velocity of multipoint detonation is higher than that of the single-point detonation, the velocity of double-column multipoint eccentric synchronous detonation is 2%–9% higher than that of the single-column single-point (multipoint eccentric synchronous) detonation, the velocity of double-column multipoint eccentric synchronous detonation is 10%–17% higher than that of the central single-point (multipoint synchronous) detonation, and the velocity of single-column single-point (multipoint eccentric synchronous) detonation is 5%–17% higher than that of the central single-point (multipoint synchronous) detonation. Research results show that although the number of EFPs is reduced during eccentric single-point (multipoint simultaneous) detonation of MEFP warheads, a higher velocity can be obtained.

Revealing the role of micron-sized in situ TiC particles on tensile properties and fracture mechanism of martensitic wear-resistant steel at elevated temperature

In order to improve the performance of the TiC ceramic reinforced wear-resistant steel at medium and high temperatures, such as slag transportation and cement production, its high-temperature tensile properties need to be well understood. In this paper, an in situ micron-sized TiC ceramic particle reinforced wear-resistant steel with 1 vol% TiC particles was fabricated. The tensile behavior and fracture mechanism of the TiC ceramic reinforced steel at 25–600 °C were investigated. The role of micron-sized TiC particles on tensile properties and fracture mechanism at elevated temperature was studied. Results indicated that the high temperature strength of TiC ceramic reinforced wear-resistant steel was enhanced by improving the thermal stability of the matrix. In the low and medium temperature range (25–500 °C), micron-sized TiC ceramic particles played a role in improving the strength, but had little effect on the elongation to failure. However, the micron-sized TiC ceramic particles greatly reduced the elongation to failure of the experimental steel when the temperature exceeded 500 °C. In the range of 25–600 °C, the fracture mechanism matched the typical ductile fracture. However, the mechanism of cavity formation varied at 500 °C. At 25–500 °C, the micro-cavities mainly formed due to fracture of the micron-sized TiC particles with sizes in the range of 1–9 μm and defects of the matrix. Above 500 °C, the interfacial debonding between the micron-sized TiC and the matrix was the main mode of crack initiation.

Cavity mode dephasing via the optomechanical interaction with an acoustic environment

We consider an optomechanical system comprising a single cavity mode and a dense spectrum of acoustic modes and solve for the quantum dynamics of initial cavity mode Fock (i.e., photon number) superposition states and thermal acoustic states. The optomechanical interaction results in dephasing without damping and bears some analogy to gravitational decoherence. For a cavity mode locally coupled to a one-dimensional (1D) elastic string-like environment or two-dimensional (2D) elastic membrane-like environment, we find that the dephasing dynamics depends respectively on the string length and membrane area--a consequence of an infrared divergence in the limit of an infinite-sized string or membrane. On the other hand, for a cavity mode locally coupled to a three-dimensional (3D) bulk elastic solid, the dephasing dynamics is independent of the solid volume (i.e., is infrared finite), but dependent on the local geometry of the coupled cavity--a consequence of an ultraviolet divergence in the limit of a "pointlike" coupled cavity. We consider as possible respective realizations for the cavity-coupled-1D and 2D acoustic environments, an LC oscillator capacitively coupled to a partially metallized strip and a cavity light mode interacting via light pressure with a membrane.

Markov Perfect Equilibria in Multi-Mode Differential Games with Endogenous Timing of Mode Transitions

We study Markov perfect equilibria (MPE) of two-player multi-mode differential games with controlled state dynamics, where one player controls the transition between modes. Different types of MPE are characterized distinguishing between delay equilibria, inducing for some initial conditions mode switches after a positive finite delay, and now or never equilibria, under which, depending on the initial condition, a mode switch occurs immediately or never. These results are applied to analyze the MPE of a game capturing the dynamic interaction between two incumbent firms among which one has to decide when to extend its product range by introducing a new product. The market appeal of the new product can be influenced over time by both firms through costly investments. Under a wide range of market introduction costs a now or never equilibrium coexists with a continuum of delay equilibria, each of them inducing a different time of product introduction.

Multi-Scale Object-Based Probabilistic Forecast Evaluation of WRF-Based CAM Ensemble Configurations

Convection-allowing model (CAM) ensembles contain a distinctive ability to predict convective initiation location, mode, and morphology. Previous studies on CAM ensemble verification have primarily used neighborhood-based methods. A recently introduced object-based probabilistic (OBPROB) framework provides an alternative and novel framework in which to re-evaluate aspects of optimal CAM ensemble design with an emphasis on ensemble storm mode and morphology prediction. Herein, we adopt and extend the OBPROB method in conjunction with a traditional neighborhood-based method to evaluate forecasts of four differently configured 10-member CAM ensembles. The configurations include two single-model/single-physics, a single-model/multi-physics, and a multi-model/multi-physics configuration. Both OBPROB and neighborhood frameworks show that ensembles with more diverse member-to-member designs improve probabilistic forecasts over single-model/single-physics designs through greater sampling of different aspects of forecast uncertainties. Individual case studies are evaluated to reveal the distinct forecast features responsible for the systematic results identified from the different frameworks. Neighborhood verification, even at high reflectivity thresholds, is primarily impacted by mesoscale locations of convective and stratiform precipitation across scales. In contrast, the OBPROB verification explicitly focuses on convective precipitation only and is sensitive to the morphology of similarly located storms.

Kidney Recovery and Death in Critically Ill Patients With COVID-19–Associated Acute Kidney Injury Treated With Dialysis: The STOP-COVID Cohort Study

Rationale & ObjectiveAcute kidney injury treated with kidney replacement therapy (AKI-KRT) occurs frequently in critically ill patients with coronavirus disease 2019 (COVID-19). We examined the clinical factors that determine kidney recovery in this population.Study DesignMulticenter cohort study.Setting & Participants4,221 adults not receiving KRT who were admitted to intensive care units at 68 US hospitals with COVID-19 from March 1 to June 22, 2020 (the “ICU cohort”). Among these, 876 developed AKI-KRT after admission to the ICU (the “AKI-KRT subcohort”).ExposureThe ICU cohort was analyzed using AKI severity as the exposure. For the AKI-KRT subcohort, exposures included demographics, comorbidities, initial mode of KRT, and markers of illness severity at the time of KRT initiation.OutcomeThe outcome for the ICU cohort was estimated glomerular filtration rate (eGFR) at hospital discharge. A 3-level outcome (death, kidney nonrecovery, and kidney recovery at discharge) was analyzed for the AKI-KRT subcohort.Analytical ApproachThe ICU cohort was characterized using descriptive analyses. The AKI-KRT subcohort was characterized with both descriptive analyses and multinomial logistic regression to assess factors associated with kidney nonrecovery while accounting for death.ResultsAmong a total of 4,221 patients in the ICU cohort, 2,361 (56%) developed AKI, including 876 (21%) who received KRT. More severe AKI was associated with higher mortality. Among survivors, more severe AKI was associated with an increased rate of kidney nonrecovery and lower kidney function at discharge. Among the 876 patients with AKI-KRT, 588 (67%) died, 95 (11%) had kidney nonrecovery, and 193 (22%) had kidney recovery by the time of discharge. The odds of kidney nonrecovery was greater for lower baseline eGFR, with ORs of 2.09 (95% CI, 1.09-4.04), 4.27 (95% CI, 1.99-9.17), and 8.69 (95% CI, 3.07-24.55) for baseline eGFR 31-60, 16-30, ≤15 mL/min/1.73 m2, respectively, compared with eGFR > 60 mL/min/1.73 m2. Oliguria at the time of KRT initiation was also associated with nonrecovery (ORs of 2.10 [95% CI, 1.14-3.88] and 4.02 [95% CI, 1.72-9.39] for patients with 50-499 and <50 mL/d of urine, respectively, compared to ≥500 mL/d of urine).LimitationsLater recovery events may not have been captured due to lack of postdischarge follow-up.ConclusionsLower baseline eGFR and reduced urine output at the time of KRT initiation are each strongly and independently associated with kidney nonrecovery among critically ill patients with COVID-19.

Observation of spatial nonlinear self-cleaning in a few-mode step-index fiber for special distributions of initial excited modes

In this paper, we experimentally demonstrate that a nonlinear Kerr effect in suitable coupling conditions can introduce a spatially self-cleaned output beam for a few-mode step-index fiber. The impact of the distribution of the initial excited modes on spatial beam self-cleaning has been demonstrated. It is also shown experimentally that for specific initial conditions, the output spatial pattern of the pulsed laser can be reshaped into the LP11 mode due to nonlinear coupling among the propagating modes. Self-cleaning into LP11 mode required higher input powers with respect to the power threshold for LP01 mode self-cleaning. Our experimental results are in agreement with the results of numerical calculations.

Divergence features of laser beams with angular momentum

The physical features of the divergence of laser beams with angular momentum are investigated. The beams are presented in the form of a coherent superposition of two modes without angular momentum. Analytical formulas are used that satisfy Maxwell’s equations for all components of the electric and magnetic fields of the initial modes. This allows one to describe the superposition of modes in terms of the components of the Umov–Poynting vector. The relationship between the beam divergence and its angular momentum, caused by the dependence of the radial and azimuthal components of the Umov–Poynting vector on the longitudinal components of the fields, is demonstrated. The components of this vector are analysed for an annular beam obtained using the superposition of azimuthally and radially polarised modes at various phase shifts between them. According to the analysis, beams with angular momentum can propagate without divergence. A method for generating such beams is discussed.

Dynamics of an autonomous spacecraft control system at initial transition to a tracking mode

The problems of autonomous digital control of the information satellites and space robots during their initial transition to a tracking mode, namely in the initial orientation modes, are considered. Autonomous angular guidance and modularly limited vector digital control using a vector of the modified Rodrigues parameters are applying to bring the spacecraft’s orientation from completely arbitrary to the required one. The developed methods, algorithms and simulation results for a mini-satellite in a sun-synchronous orbit are presented.

Analyzing Possible Applications for Multilevel Inverters Designed for Energy-Saving Electrical Machines Utilized in the Non-Ferrous Metals Industry

This paper uses multilevel inverter diagrams to describe some optional applications for such inverters in order to enhance the efficiency, electromagnetic compatibility and service life of electric motors utilized in the non-ferrous metals industry. The authors consider using active rectifiers with a five-level structure that serve as variable reactivity units and reactive power compensators. They also consider using a five-level independent voltage source inverter as a part of the variable frequency drive system. An option is described that can help optimize the control algorithm and voltage rectification in the DC link capacitor in the five-level active rectifier circuit. For the variable frequency drive with a five-level independent voltage source inverter, it is proposed to change the circuit topology to introduce a transformerless power circuit. The proposed solutions were analyzed for efficiency with the help of MatLab simulation package. The paper considers the problem of voltage accuracy as maintained by each DC link capacitor. Each DC link capacitor has its features typical of both studied circuits in both transient and steady-state conditions. In the circuit involving a multilevel active rectifier, the authors simulated conditions when the variable reactivity drastically changes from the initial steady-state equivalent capacitance mode to equivalent inductance. A soft start was simulated in the circuit involving a multilevel independent voltage source inverter. A feasibility study was conducted that proved the feasibility of the proposed solutions when adopted by concentrator plants and non-ferrous metals producers.This research was carried out as part of a governmental assignment, Project&nbsp;No. FSWF-2020-0019.This research was carried out at the facilities of the Shared Knowledge Centre&nbsp;High-Voltage Research &amp; Development Complex, a part of Moscow Power&nbsp;Engineering Institute.

Case for quarkyoniclike matter from a constituent quark model

Based on the fact that the constituent quark model reproduces the recent lattice result on baryon-baryon repulsion at short distance and that it includes the quark dynamics with confinement, we analyze to what extent the quarkyonic modes appear in the phase space of baryons as one increases the density before only quark dynamics and hence deconfinement occurs. We find that as one increases the baryon density, the initial quark mode that appears will involve the $d(u)$-quark from a neutron (proton), which will leave the most attractive ($ud$) diquark intact.

Abstract 11780: Longitudinal Echocardiographic Parameters Before and After Pacemaker Placement in Congenital Complete Heart Block

Introduction: Congenital complete heart block (CCHB) is rare, 1:15,000 - 1:20,000 live births, with left ventricular (LV) dysfunction developing in 7-14% of subjects. We investigate longitudinal trajectories of echo parameters in CCHB and the effect of pacemaker implantation on those parameters. Methods: This is a retrospective cohort study of identifiable CCHB subjects at the Children’s Hospital of Philadelphia from 1970-2018, excluding those with structural, genetic, or acquired cardiac conditions. Subjects with echo data available before and after pacemaker implantation are included. LV end diastolic diameter (LVEDD) z-score and LV ejection fraction (EF) are modeled with least-squares regression models, with slopes compared before and after pacemaker placement. Results: Of 114 subjects with CCHB, 52 (40% male, 73% white) have echo data available before and after pacemaker placement. Median age of diagnosis is 0.6 years, age at pacemaker placement 3.4 years, and duration of pacing 10.8 years. Figure 1 displays modeled trajectories of LVEDD z-score and EF over 20 years. Mean LVEDD z-score at pacemaker placement is less than 2 and decreases significantly over time, especially 10 years post placement. Participants have mean LV ejection fraction of 54% at pacemaker placement, rising significantly prior to placement and in the first 10 years post-placement, after which significant decreases are observed. Older age at pacemaker placement is associated with a higher EF at placement but an earlier and steeper decline in EF beginning at 8 years post-placement. LVEDD and EF trajectories do not vary significantly by sex, race, maternal antibody status, age at diagnosis, or initial pacemaker mode. Conclusions: In a cohort of 52 subjects with CCHB, LVEDD z-score steadily decreases over time whereas EF rises for 10 years post-pacemaker placement and subsequently decreases. Pacemaker placement has no apparent immediate effect on trajectories of these echo parameters.

Failure analysis of brazed sandwich structures with square honeycomb-corrugation hybrid cores under three-point bending

In this work, the bending stiffness, initial failure load, initial failure modes and minimum mass design of square honeycomb-corrugation hybrid core sandwich structures (SHCH) subjected to bending were explored by a combined theoretical analysis, experimental testing, and numerical prediction method. Samples were fabricated by brazing process and measured under three-point bending. To theoretically obtain the initial failure mechanism map, six different initial failure modes were taken into account, which agree well with associated experimental data and numerical results. It is found that honeycomb filler not only changed the failure mode of corrugated core sandwiches but also enhanced dramatically its bending resistance. Then the minimum weight design is achieved as a function of load index, and the effect of key factors, including honeycomb relative density, loading platen width, material parameters, and inclination angle are quantified. Furthermore, the mechanical performances of SHCHs are compared with the competing structures.

Lateral behavior of monopiles considering the effects of sand subsidence and densification under lateral cyclic loading

The deformation characteristics (namely, subsidence and densification) of sandy soil surrounding piles under lateral cyclic loading has become a major research topic. The behavior of soil subsidence reduces the embedded depth of monopiles and increases the bending moment of the pile head, which causes reduction of the piles’ lateral capacity. In contrast, soil densification results in stiffening effect, which can increase the lateral capacity of monopiles. In this study, first, the changes of pile-soil system parameters caused by subsidence and densification are quantified based on the mass conservation principle of the subsidence zone and densification region. Then, lateral responses of monopiles before and after cycling are investigated by American Petroleum Institute (API) p-y curve model. The effects of the subsidence dimensions, initial relative densities and densification region modes (Mode 1 and Mode 2) on the pile lateral responses are analyzed. Lastly, a simple framework is proposed to evaluate the pile lateral capacity after cycling. Salient findings of this study are: (i) The lateral capacity of monopiles increases with the increment of subsidence dimension; (ii) The effect of cyclic loading on the lateral capacity of monopiles gradually decreased with the increase of initial relative densities; (iii) The significant nonlinear relationship between improvement ratio of pile lateral capacity and subsidence dimension revealed that Mode 2 agreed better with the actual conditions compared with Mode 1.

Spectral self-imaging of optical orbital angular momentum modes

The Talbot self-imaging effect is mostly present in the forms of space or time, or in the frequency domain by the Fourier duality. Here, we disclose a new spectral Talbot effect arising in optical orbital angular momentum (OAM) modes. The effect occurs in the context of petal-like beams, which are typically constructed from a number of in-phase equidistant OAM modes with at least one void mode in between. When illuminating such beams on phase masks that are azimuthally modulated with Talbot phases, the initial OAM modes are self-imaged to create new OAM modes, meanwhile preserving the initial OAM spectral profile. Such a phenomenon is theoretically predicted, and a close analogy is drawn with the spectral Talbot effect of frequency combs. The prediction is also experimentally confirmed by observing versatile spectral self-imaging on various optical petal-like beams.

Analytical Models to Determine In-Plane Damage Initiation and Force Capacity of Masonry Walls with Openings

Masonry panels consisting of piers and spandrels in buildings are vulnerable to in-plane actions caused by seismicity and soil subsidence. Tectonic seismicity is a safety hazard for masonry structures, whereas low-magnitude induced seismicity can be detrimental to their durability due to the accumulation of light damage. This is particularly true in the case of unreinforced masonry. Therefore, the development of models for the accurate prediction of both damage initiation and force capacity for masonry elements and structures is necessary. In this study, a method was developed based on analytical modeling for the prediction of the damage initiation mode and capacity of stand-alone masonry piers; the model was then expanded through a modular approach to masonry walls with asymmetric openings. The models account for all potential damage and failure modes for in-plane loaded walls. The stand-alone piers model is applicable to all types of masonry construction. The model for walls with openings can be applied as is to simple buildings but can also be extended to more complex structures with simple modifications. Model results were compared with numerous experimental cases and exhibited very good accuracy.

Behaviour of castellated beam-to-column end-plate connection under monotonic load

The development of plastic hinges in a steel frame structure with steel beam-to-column end-plate connection joints by strengthening the end-plate area is a widely used design concept. This study explores the realization of this design concept with a beam web opening and without end-plate stiffening. The factors that impact the mechanical properties and failure modes of these joints are the end-plate thickness, opening diameter, opening position, and opening type. These parameters are tested for monotonic loading of six beam-column joints, and 220 finite element models are parametrically analysed. Additionally, the development of plastic hinge of the beam based on the development trend of maximum strain of each component section is studied. The initial rotational stiffness, ductility, bearing capacity, deformation capacity, and failure mode are used as the evaluation criteria to assess the behaviour of this joint. The research indicates that a castellated steel beam-to-column end-plate connection can realize the occurrence of plastic hinge and exhibit good ductility and load-bearing performance. This study highlights the premise that the beam web opening and end-plate thickness parameters must be within a specific range to achieve accurate results; additionally, the division method of the interval of parameters is described. The influence of end-plate thickness on the working mechanism of the connection is clarified, and the mechanical properties and failure modes of connections under different parameter intervals are studied. This study proposes a method for calculating the initial rotational stiffness of the connection to achieve good accuracy by considering the participation of the components on the beam in the rotation of the connection.

Two elastically equivalent compound truss lattice materials with controllable anisotropic mechanical properties

Compound lattice structures are novel lattice structures with high stiffness and strength and their anisotropy can be easily controlled. In this study, two elastically equivalent compound truss lattice materials, BCS-I and BCS-II, are designed, and their anisotropic elastic properties and strength, such as the initial yield strength and elastic buckling strength, are analyzed and compared. The results show that the anisotropy of the elastic properties and strength as well as the initial deformation mode of the two compound truss lattice materials can be controlled by adjusting the relative thicknesses of their elementary trusses and relative densities. Combined with theoretical analysis, the mechanism of the influence of the relative thickness on the anisotropic mechanical properties of the two truss lattice materials is elucidated. In addition, comparing the mechanical properties of the two compound truss lattice materials reveals that they have the same elastic properties and initial yield strength. And the BCS-I truss lattice material shows better buckling resistance, its elastic buckling strength is never less than that of the BCS-II truss lattice material. By both numerical simulations and experiments, the analytical elastic modulus, initial yield strength, and deformation characteristics are verified. The analysis in this study indicates that by rationally designing and selecting the BCS-I and BCS-II truss lattice materials, the most suitable truss lattice materials can be found according to the loading direction without the need to add more material, which has implications for improving the performance of a wide range of truss systems.

Experimental Study on Vibration Reduction Technology of Hole-by-Hole Presplitting Blasting

In order to effectively reduce the disturbance of the precrack blasting vibration on slope rock mass, except paying attention to the damping effect of the precrack, it is also necessary to optimize the blasting parameters and initiation mode of the precrack itself. Based on the blasting theory and empirical formula, the parameters of presplitting blasting such as the hole diameter, hole spacing, charge decoupling coefficient, and line charge density were determined, and field tests of conventional pre-splitting blasting and presplitting blasting with precise delay and hole-by-hole initiation were carried out on the west slope of Buzhaoba. Regression analysis was carried out on the vibration monitoring data, and the blasting vibration attenuation regularity of slope particles was obtained. By comparing the monitored vibration velocity of the two presplitting blasting tests and the forecast results of theoretical calculation, the average reduction rate of the conventional same row blasting vibration is 26.40%, while that of the hole-by-hole blasting vibration can reach 41.45% with a half hole rate of 80.7% and an irregularity of about 130 mm. Results show that the effect of precise delay initiation between preholes based on the digital electronic detonator is better than that of the simultaneous initiation of preholes. Therefore, it is suggested that the hole-by-hole presplitting blasting technology should be applied in the excavation of boundary slope and the treatment of high and steep slope.