Ultimate Capability Research Articles

Refreshment of SrTiO3 Substrate for Layer Peeling‐off using Sacrificial Sr3Al2O6

AbstractThe use of water‐soluble sacrificial layer of Sr3Al2O6 has tremendously boosted the research on freestanding functional oxide thin films, especially thanks to its ultimate capability to produce high‐quality epitaxial perovskite thin films. However, the costly single‐crystalline substrates, e.g., SrTiO3, are generally discarded after obtaining the freestanding thin films. Here, it is demonstrated that the SrTiO3 substrates can be recycled to fabricate La0.7Sr0.3MnO3 films with nearly identical structural and electrical properties. After attaining freestanding thin films, the residues on SrTiO3 can be removed by 80 °C hot water soaking and rinsing treatments. Consequently, the surface of SrTiO3 reverted to its original step‐and‐terrace structure.

Theoretical models and reliability assessment of steel-UHPC-steel composite beams in offshore structures

Steel-concrete-steel composite structures (SCS-CS) with ultra-high performance concrete (UHPC) exhibit wide potential applications in civil constructions. This paper aims to revealing the failure mechanism, proposing the theoretical models and conducting the reliability assessment of SCS composite beams with UHPC (SUS-CB). Firstly, several static tests on SUS-CB were summarized to analyze the failure features and failure modes. A nonlinear finite element (FE) model of SUS-CB was developed and validated. Parametric study was carried out to explore the structural behaviors of SUS-CB, including matching relationship between steel plate (SP) and core UHPC, and bond-slip. Subsequently, failure mechanism of SUS-CB was revealed and failure modes were defined systematically. Considering slippage and effects of steel fibers, the novel theoretical model of calculating ultimate capability of SUS-CB was proposed and compared with existing design codes. Based on these theoretical models, uncertainties of statistics variables were calculated, and reliability analysis of SUS-CB was conducted. Results indicate that reliability index of these theoretical models and design codes is lower than target reliability index. Consequently, adjustment factors of ultimate capacity were calculated to confirm reaching the target reliability index in offshore structures. Finally, sensitivity analysis of statistic variables was performed to provide advices for offshore structural design.

Behaviors of photovoltaic cells illuminated by a laser of different operation modes.

The ultimate capability of light-electricity conversion of a laser with different operation modes in a typical photovoltaic (PV) cell was investigated for the technologic concept of laser power transmission (LPT). The quasi-linear correlation between the maximum allowable laser power density and the pulsed laser power percentage (PPP) of the combined dual lasers was found experimentally on a tri-junction GaAs PV cell. At the same time, the patterns of thermomechanical damage in the PV cells were characterized. The physical mechanism on the difference in the light-electricity conversion ability for a multi-pulse (MP) laser and a continuous wave (CW) laser was revealed by the coupled model on thermal diffusion and the carrier transport.

Cutting of Graphite at Atomic and Close-to-Atomic Scale Using Flexible Enhanced Molecular Dynamics

Atomic and close-to-atomic scale manufacturing is the key technology for the production of next-generation devices with atomic precision. As an important approach of mechanical processing, cutting has evolved as a potential candidate to generate an atomically smooth surface; thus, exploring its ultimate capability is significant. In this paper, single-crystal graphite, whose lattice structure and chemical bond property are of representation for demonstration, is selected to study the mechanism of atomic layer removal using molecular dynamics. A localized workpiece, which is dynamically updated on the basis of the tool position, is used to improve the computation efficiency. The principle and bullet points of this modeling method are first introduced, followed by a series of simulations under various undeformed chip thicknesses and tool edge radii. In addition, different potentials for the tool–workpiece interaction are tested, and the effect on the material response is presented. Based on the analysis of deformation, the number of carbon layers removed, and cutting forces, the chip formation mechanism and further understanding of the controllability of cutting at atomic and close-to-atomic scale can be achieved.

Numerical Simulation of Steel Concrete Composite Floor System

This paper explores the ultimate strength of the composite floor system of structural steel concrete. ABAQUS, used to research non-linear competencies and ultimate load-carrying capability of such floor systems, developed the Finite Element Model (FEM) in 3-D. A comparison of computed values with experimental results has validated the proposed finite element model. The measured and experimental findings show a good match with an average variation of 10%. In parametric study effects of different sizes of shear studs on the ultimate strength of the floor system have been explored on full size specimens. Results show that an increase in height of the shear stud with the same diameter increases the ultimate strength of the floor system. An Increase in the diameter of the shear stud also increases the ultimate capacity of the floor system.

Empirical Assessment Method of Ultimate Capability of Steel Stiffened Panel under Longitudinal Compressive Load

The hull block erection network process, which is performed during the master production planning stage of the shipyard, is frequently delayed because of limited resources, workspace, and block preparation ratio. In this study, a study to predict the delay with respect to the block erection schedule is conducted by considering the variability of the block preparation ratio based on the discrete event simulation algorithm. It is confirmed that the variation of the key event observance ratio is confirmed according to the variability caused by the block erection process, which has the minimum lead time in a limited resource environment, and the block preparation ratio. Furthermore, the optimal pitch value for the key event concordance is calculated based on simulation results.

Fiction, Truth and Method

How does fiction help to build a consensual narrative of the time we live? How necessary is this narrative and how close it should resemble the reality? Since its inception, fiction can state and frame ideas and concepts through the refutation of the established aesthetical, ethical, hermeneutical, ontological and political consensus. This inverted logics that Aristotle regarded so dangerous is in fact the ultimate capability of the fictional narrative to capture the reality in vivo and to describe it with its full colours. However, it is undeniable that this intrinsically disruptive strength can be particularly unsettling. The very imagination that turns Gregor Samsa into an insect and transforms David Kepesh into a huge breast can very well distort reality and pretend that a lost election have been rigged and won by a lot. How can one be sure that a culture is mature enough in exercising fact verification and in analysing reality with scientific tolls that it is shielded against ideological, political or religious fictions? How to ensure that society has means to deconstruct distortions and lies engendered by social agents with specific interests? We believe that just a blend of objective means of fact verification, scientific analysis and an uncommitted ethical bond with truth can ensure that society is not misled by lies and misrepresentations of reality.

Safety Evaluation of High Concrete-Faced Rockfill Dam Based on Site-Related Response Spectrum Using Scenario Earthquake

To clarify how to arrive at earthquake ground motion parameters for use in evaluating the high rockfill dams during seismic loading conditions, as well as to evaluate reasonably the seismic response of dams subjected to strong earthquake, the differences of design response spectra determined by scenario earthquake and uniform hazard spectra theory are investigated in detail. Coupled with the safety evaluation of the Houziyan concrete-faced rockfill dam (CFRD) with a height of 200 m located in meizoseismal regions, comprehensive comparisons of key safety evaluation indices are performed using input motions determined from the abovementioned two design response spectra. The key safety evaluation indices include dynamic response acceleration, permanent deformation, safety of the impervious body, safety factor, and sliding displacement of the potential failure sliding body. Additionally, the ultimate seismic capability of the high CFRD is discussed based on the two response spectra. More considerable results can be achieved and offered to the engineers for the seismic design. It is obvious that the uniform hazard spectra, which are used to adopt in the safety evaluation of high CFRD, typically result in conservative evaluations and unnecessary economic cost for seismic design and reinforcements.

Large‐Scale Sub‐1‐nm Random Gaps Approaching the Quantum Upper Limit for Quantitative Chemical Sensing

AbstractMetallic nanostructures with nanogap features can confine electromagnetic fields into extremely small volumes. In particular, as the gap size is scaled down to sub‐nanometer regime, the quantum effects for localized field enhancement reveal the ultimate capability for light–matter interaction. Although the enhancement factor approaching the quantum upper limit has been reported, the grand challenge for surface‐enhanced vibrational spectroscopic sensing remains in the inherent randomness, preventing uniformly distributed localized fields over large areas. Herein, a strategy to fabricate high‐density random metallic nanopatterns with accurately controlled nanogaps, defined by atomic‐layer‐deposition and self‐assembled‐monolayer processes, is reported. As the gap size approaches the quantum regime of ≈0.78 nm, its potential for quantitative sensing, based on a record‐high uniformity with the relative standard deviation of 4.3% over a large area of 22 mm × 60 mm, is demonstrated. This superior feature paves the way towards more affordable and quantitative sensing using quantum‐limit‐approaching nanogap structures.

Effect of Magnetic Field of Elongated Solenoid on Deformation of Metal Shaped-Charge Jets

Inertial stretching of a metal shaped-charge jet in the presence of magnetic field of elongated solenoid is analyzed. Effect of the magnetic field on the shaped-charge jet is aimed at inhibition of the development of plastic instability of the jet with an increase in its ultimate elongation and penetration capability. Several simplifying assumptions are used to obtain analytical description of electromagnetic processes in a fragment of the jet that moves inside and outside the solenoid. Induction heating of a fragment of the jet and the stress state therein are calculated with allowance for electromagnetic forces under the experimental conditions of the earlier experiments on the effect of the magnetic field of solenoid on shaped-charge jets. The results are used to substantiate the hypothesis on the possible reason for a relatively large difference between the experimental data of different authors on an increase in the penetration capability of shaped charges.

Ultimate energy recovery from spent relativistic electron beam in energy recovery linear accelerators

Energy recovery linear accelerators (ERLs) rely upon single-axis superconducting radio frequency (SRF) cavities to be an efficient source of relativistic electrons for high energy and nuclear physics. SRF cavities are also considered relevant for next-generation photon factories and radio-isotope production facilities. The ultimate energy recovery capability for the accelerator would be the ability to operate with a sufficiently spent beam and decrease the energy of the beam before the beam dump to a value lower than the beam injection energy. This is especially important for high current accelerators, where the beam injection energy could be as high as several MeV, and systems where partial beam loss can be expected. The efficient operation of energy recovery in linear accelerators is adversely affected by the typical degradation of the beam quality and current loss. This hinders the application of the ERLs in research and industry, and enabling the use of spent (partially lost current), degraded beams should broaden their application. We suggest that the use of the asymmetric operating mode observed in the dual-axis asymmetric cavities will enable such ultimate capabilities. We discuss the advantages of the application of fields of different amplitude along the cavity accelerating and decelerating axes and demonstrate that the fields can be tuned separately in each axis of the dual-axis cavity. The design of such a cavity and ways to optimize the energy recovery of a spent electron beam by tuning the dual-axis asymmetric SRF cavity are discussed.

What is the ultimate capability of acoustophoretic volumetric displays?

Advances in acoustophoresis have allowed the recent development of a free-space volumetric display called an Acoustophoretic Volumetric Display (AVD) that can render 3D graphics observable without obstructions. The current generation of AVD can render simple vector graphics in real-time, but larger and complex graphics require 10 s or more to render. Here, we present a generalized model of an AVD and use this to understand its performance limits; in particular, we answer the question of how large a display (1:1 raster screen) can be created. We show that AVD performance is affected by the size and properties of the particle, along with the viscosity of the surrounding fluid. Optimal performance is achieved when the viscous drag force and inertial force are minimized relative to the acoustic radiation force. Our model suggests that, for expanded polystyrene particles (ρp=19 kg m−3), a screen size of up to 117 mm by 117 mm can be rendered at 10 Hz with an acoustic frequency of 20 kHz and an acoustic pressure amplitude of 25 kPa.

Principles of functional neural mapping using an intracortical ultra-density microelectrode array (ultra-density MEA)

Objective. Intracortical electrical neural recording using solid-state electrodes is a prevalent approach in addressing neurophysiological queries and implementing brain-computer interfacing systems. As a variety of ultra-density microelectrode arrays (ultra-density MEAs) are being created more recently, this paper answers to the rising demand for a more rigorous theory concerning this new type of neural electrode technology, both to guide the proper design and to inform the proper usage. Approach. This design and use problem of ultra-density MEAs for functional intracortical neuronal circuit mapping is approached from a signal analysis perspective. Starting with quantitative derivations of key basic concepts, the concept of ultra-density MEA is defined in the context for fully resolving the voltage sources within its view volume. Then, the principle of using such an ultra-density MEA for functional neural mapping is elaborated, and a recursive approach to completely resolve all voltage sources from the ultra-density MEA’s recordings is proposed. This approach is further validated using a simulated experiment. Last, the limitations and implications of this work are discussed. Main results. MEAs can only be used to map the extracellular somatic action potential (esAP) sources in a neural microcircuit, and AP propagation along individual axons cannot be detected. The key for the ultra-density MEA design is to make sure that each spatial unit of analysis (SUA) contains no more than one active esAP source. The unique neural resolving capability of ultra-density MEAs comparing to conventional MEAs is to be able to spatiotemporally resolve each esAP source within its view volume. Significance. The ultimate capability and limitation of neural electrode array technology at such an unprecedented fabrication resolution is unraveled. This work strives to further the discussions on this topic into a more quantitative and rational direction, while providing a theoretical guideline for the rational development and neuroscientific application of an ultra-density MEA for intracortical functional mapping.

From Optical to Chemical Hot Spots in Plasmonics.

In recent years, the possibility to induce chemical transformations by using tunable plasmonic modes has opened the question of whether we can control or create chemical hot spots in these systems. This can be rationalized as the reactive analogue of the well-established concept of optical hot spots, which have drawn a great deal of attention to plasmonic nanostructures for their ability to circumvent the far-field diffraction limit of conventional optical elements. Although optical hot spots can be mainly defined by the geometry and permittivity of the nanostructures, the degrees of freedom influencing their photocatalytic properties appear to be much more numerous. In fact, the reactivity of plasmonic systems are deeply influenced by the dynamics and interplay of photons, plasmon-polaritons, carriers, phonons, and molecular states.These degrees of freedom can affect the reaction rates, the product selectivity, or the spatial localization of a chemical reaction. In this Account, we discuss the oportunities to controlchemical hot spotsbytuning the cascade of events that follows theexcitation and decay of plasmonic modes in nanostructures. We discuss a series of techniques to spatially map and image plasmonic nanoscale reactivity at the single photocatalyst level. We show how to optimize the reactivity of carriers by manipulating their excitation and decay mechanisms in plasmonic nanoparticles. In addition, the tailored generation of non-thermal phonons in metallic nanostructures and their dissipation is shown as a promise to understand and exploit thermal photocatalysis at the nanoscale. Understanding and controlling these processes is essential for the rational design of solar nanometric photocatalysts. Nevertheless, the ultimate capability of a plasmonic photocatalyst to trigger a chemical reaction is correlated to its ability to navigate through, or even modify, the potential energy surface of a given chemical reaction. Here we reunite both worlds, the plasmonic photocatalysts and the molecular ones, identifying different energy transfer pathways and their influence on selectivity and efficiency of chemical reactions. We foresee that the migration from optical to chemical hot spots will greatly assist the understanding of ongoing plasmonic chemistry.

(Invited) The Impact of Work By Dr. Gottesfeld and Coworkers on the Commercial Introduction of the Fuel Cell Vehicle -- Calling the Shots in Polymer Electrolyte Fuel Cells

Dr. Gottesfeld’s entire career has been characterized by developing early stage fuel cell technology using fundamental science and practical engineering intuition and analysis. It is unusual to see fundamental electrochemistry expertise coupled with electrochemical engineering intuition and skills in the same person. This combination has enabled him and his coworkers to identify controlling phenomena that have proven to be focal points for development and the critical points that determine the ultimate capability of the technology and its application outcome. Furthermore, his dedication and passion in these areas guide and inspire the next generation of contributors across four distinct fuel cell families. In this talk, I will describe how this pairing of fundamental and device level intuition from the group that he led at Los Alamos National Lab (LANL) from 1987-2000 impacted the development of proton exchange membrane fuel cells from initial development stages to readiness for automotive market introduction. For example, the pathway for the reduction of precious metal loadings to commercially viable levels was initially defined by experiments and fundamental models from the LANL group. The LANL work on membrane water transport was critical to understanding why thinner membranes offered performance benefits beyond their ionic resistance impact. Even the contemporary R&D work to push to high current density (>2 A/cm2) for the sake of reduction of fuel cell area is informed by initial LANL developments as well as Dr. Gottesfeld’s work (published in 2008) on the impact of the Pt-oxides on oxygen reduction kinetics. More broadly, this body of work reminds us that the pathway to push any fuel cell technology to its best possible outcome is to systematically apply coupled experiments and models in order to identify and focus R&D attention on the rate processes that are “calling the shots”.

Multiobjective Optimization Design for Structural Parameters of TBM Disc Cutter Rings Based on FAHP and SAMPGA

As a key component of tunnel boring machines (TBMs), the disc cutter ring and its structural parameters are closely related to the TBM tunneling quality. Literature review shows that investigations on optimization design methods for cutter ring structure are seriously insufficient. Therefore, in this paper, a multiobjective optimization design model of structural parameters for disc cutter rings is developed based on the complex geological conditions and the corresponding cutter ring structure design requirements. The rock breaking capability, energy consumption, load‐bearing capability, wear life, and wear uniformity of disc cutter are selected as the objectives, and the geometric structure of cutter rings, ultimate load‐bearing capability, and cutterhead drive performance are determined as constraints. According to the characteristics of this model, a self‐adaptive multipopulation genetic algorithm (SAMPGA) is utilized to solve the optimization problem, and the Fuzzy analytical hierarchy process (FAHP) is employed to calculate weight coefficients for multiple objectives. Finally, the applicability of the proposed method is demonstrated through a case study in a TBM project. The results indicated that the rock breaking performance and service life of the disc cutter are improved after optimization by using the proposed method. The utilization of SAMPGA effectively solves the premature local convergence problems during optimization. The geological adaptability should be considered in the cutter ring structure design, which can be realized by using the proposed method based on the suitable weight coefficients.

Ultimate capability of variable pitch milling cutters

Variable pitch milling cutters intend to increase performance, but off-the-shelf cutters do not ensure this generally. Depending on the milling process they are selected for, they can perform better or even worse than uniform pitch cutters do. Improved performance can be guaranteed by considering the reflected dynamic behaviour of the machine/tool/workpiece system. This work presents the achievable upper and lower capability bounds by introducing so-called stabilizability diagrams of a hypothetical variable pitch milling cutter that is tuned continuously along the stability boundaries. Robustly tuned milling cutters are designed for selected spindle speed ranges, which are experimentally tested both under laboratory and industrial conditions.

The effects of delamination deficiencies on compressive properties of composite grid-stiffened structures

ABSTRACTThis article provides a systematic approach to accurately predict the effects of delamination deficiencies on compressive properties of composite grid-stiffened structures. The deformation of the stiffener and the skin is investigated during a mechanical test. Cohesive elements in the finite element method were employed to calculate the ultimate load-carrying capacity. The delamination deficiencies in the interface between the skin and the stiffener have a significant effect upon its ultimate load-carrying capability compared with the delamination deficiencies in the skin and in the stiffener.

Experiment and design methods of composite scarf repair for primary-load bearing structures

A relative thick plate of composite being repaired by scarf bonding was substituted as the scarf joints and studied under tensile load in this paper. The experimental investigation told us the ultimate capability of load and failure mechanism of composite scarf joints. In order to explain failure mechanism for scarf bonding repair of composite structures distinctly, FEM based on continuum damage mechanics (CDM) was carried out. CDM equations were derived by adding the delamination mode and 3D Hashin criteria based on strain into the composite constitutive relation. Furthermore, a modified semi-analytical method (MAM) was developed to obtain shear stress distribution in theory. MAM can improve the accuracy of Harman and Wang method, solve the stress asymmetry, obtain secondary peak of shear stress, and increase the highest peak of stress. In the end, the discussions for the methodologies of MAM, CDM and linear FEM were executed to compare the errors of predicting ultimate load. The discussion revealed that MAM has sufficient accuracy as an analytical methodology which could be utilized to design composite scarf repairs in a short cycle simply.

DART: Distributed Particle Filter Algorithm with Resampling Tree for Ultimate Real-Time Capability

A novel Distributed Particle Filter Algorithm with Resampling Tree, called DART, is proposed in this paper, where particles are resampled by Branch Resampling and Root Resampling in a flexible tree-like structure. Though sampling and weight calculation can be executed in parallel on a group of Processing Elements, resampling is the bottleneck for distributed particle filters since it requires the knowledge of the whole particle set. Conventional approaches to accelerate resampling on distributed platforms often introduce extra procedure other than the standard processing flow and achieve acceleration limited by linear speedup. By introducing the proposed algorithm, where Branch Resampling can be executed in parallel with sampling and weight calculation, the number of particles in the final sequential implemented Root Resampling can be reduced in an exponential relationship with the depth of the tree. With the same linear speedup in sampling and weight calculation steps, the overall speedup achieved in DART surpasses linear boundary and outperforms state-of-art approaches. The corresponding implementation architecture, which possesses unique features of hardware efficiency and scalability, is also presented. The prototype of the algorithm with 8 PEs is implemented on a Xilinx Virtex-IV Pro FPGA (XC4VFX100-12FF1152) under BOT system. With 8192 particles, the input observation can achieve 63.3 kHz at a clock speed of 80 MHz.