Speed-up Mechanisms Research Articles

Numerical Simulation of Rock Breaking by Resonance Coring Based on Laboratory Experiments

Summary Efficiency and quality have always been the focus of coring operations. This paper proposes a new method of resonance coring to solve the problems of slow penetration rate, poor quality, and low efficiency when coring in deep formations. First, a stress field distribution model of rock under resonance coring conditions is developed in the paper, which specifies the magnitude of the force at any location inside the rock. Then, a 3D numerical simulation for resonance coring with the full-size drill bit is conducted based on indoor resonance coring experiments. Subsequently, a 2D numerical simulation on a single-tooth resonantly cutting rock is carried out by embedding a zero-thickness cohesive element globally. Finally, the resonance coring speedup mechanism is investigated from the perspectives of lithology, load form, and dynamic load characteristics, respectively. Based on the analysis undertaken, it can be concluded that the resonance coring method is feasible in principle. The harmonic dynamic load can aggravate the damage and the fracture degree of rock under the coring bit as well as the stress field on the surface of the core. The particle size of cuttings is larger and the proportion of tensile fracture of rock is increased by the combination of static and dynamic loads. The increase in frequency and amplitude of dynamic load is beneficial to promote the penetration rate of resonance coring. It is possible to improve coring efficiency without compromising core quality and wellbore integrity by optimizing the combination of static and dynamic loads. The study provides a new solution for efficient coring in deep and complex formations.

Cross-sectional analysis of speed-up mechanism in normal gait among healthy older adults with and without falls – Results from the Baltimore Longitudinal Study of Aging

BackgroundFalls in older adults increase the risk of mobility loss. Proper understanding of gait mechanisms related to falls may provide novel solutions for maintaining mobility in older adults. Research questionIdentify fall-related gait patterns through analyzing alterations in gait parameters to walk faster than usual pace in older adults. MethodsA Total of 519 participants (mean age = 73.12 years; 51.05 % female), including non-fallers (n = 396) and fallers (n = 123), aged 60–96 years were assessed in the Baltimore Longitudinal Study of Aging. Participants completed gait assessments at both usual and fast paces. Range of motions (ROM) for the hip, knee, and ankle joint in the sagittal plane and hip abductor ROM during normal and fast pace gait were measured by 3D motion capture system (Vicon 612). For all gait variables, percentage-changes (PC; (((fast-walking_parameter – usual-walking_parameter) /usual-walking_parameter)*100)) was calculated. Associations of PC for gait speed and PC for other gait parameters were compared between fallers and non-fallers. ResultsCompared to non-fallers, fallers walked with shorter stride, elongated double support time and shorter knee ROM in the faster pace walk (p = 0.044, p = 0.019, and p = 0.036, respectively). PCs of all gait related variables were significantly associated with PC of gait speed in non-fallers (ps < 0.005), while in the fallers, only PC for stride length, cadence, and hip ROM were associated with PC for gait speed (ps < 0.001). SignificanceAmong non-fallers related PC for gait speed was associated with PC across gait parameters suggesting the use of similar biomechanical approaches in usual and fast gait. Compared to non-fallers, fallers demonstrated different mechanisms of transition from usual to fast gait. Evaluating speed-up strategies could provide insight into subtle yet important gait modifications in apparently well-functioning older adults that would help identify individuals at high risk of falling.

A novel pendulum kinetic energy harvester based on magnetic coupling bistable buckling beam for low-power appliances in new energy buses

The rapid development of internet of things technology has created an urgent demand for wireless sensors. Although wireless sensors have the advantage of widespread use, their applications are limited by power supply. This manuscript proposes a novel magnetically coupled piezoelectric kinetic energy harvester (MPKEH) system to address this issue and enable wireless sensors to be self-powered. The proposed system included four parts: motion capture module, motion transformation module, energy transformation module, and power storage module. The motion capture module, a single-pendulum, is selected to convert the vehicle’s inertial energy into the mass ball kinetic energy. The motion transformation module, which includes a double-directional rectification mechanism and a mechanical speed-up mechanism, converts two-way rotations into one-way rotations and increases rotation speed. Piezoelectric material is frequently bent in the energy transformation module to generate alternating current (AC). The power storage module rectifies AC into direct current and stores the power in the super-capacitor, which supplies power to the electrical equipment. The velocity of the mass ball under five realistic bus driving cycles is obtained using multi-body dynamics software and Simulink. Experiments revealed that the average output power of the system could be as high as 2.4 W. Charging capacitors of 100 µF, 220 µF, 470 µF, and 1000 µF to 2 V using the MPKEH system takes 25 s, 49 s, 70 s, and 238 s, respectively. In the conducted experiments using the Liaocheng University campus bus, the maximum average power output reached 1.97 W. These results suggest that the MPKEH system can effectively self-supply energy for low-power appliances in new energy buses.

AutoOC: Automated multi-objective design of deep autoencoders and one-class classifiers using grammatical evolution

One-Class Classification (OCC) corresponds to a subclass of unsupervised Machine Learning (ML) that is valuable when labeled data is non-existent. In this paper, we present AutoOC, a computationally efficient Grammatical Evolution (GE) approach that automatically searches for OCC models. AutoOC assumes a multi-objective optimization, aiming to increase the OCC predictive performance while reducing the ML training time. AutoOC also includes two execution speedup mechanisms, a periodic training sampling, and a multi-core fitness evaluation. In particular, we study two AutoOC variants: a pure Neuroevolution (NE) setup that optimizes two types of deep learning models, namely dense Autoencoder (AE) and Variational Autoencoder (VAE); and a general Automated Machine Learning (AutoML) ALL setup that considers five distinct OCC base learners, specifically Isolation Forest (IF), Local Outlier Factor (LOF), One-Class SVM (OC-SVM), AE and VAE. Several experiments were conducted, using eight public OpenML datasets and two validation scenarios (unsupervised and supervised). The results show that AutoOC requires a reasonable amount of execution time and tends to obtain lightweight OCC models. Moreover, AutoOC provides quality predictive results, outperforming a baseline IF for all analyzed datasets and surpassing the best supervised OpenML human modeling for two datasets.

Erratum: Mechanism for quantum speedup in open quantum systems [Phys. Rev. A 93 , 020105(R) (2016)

Received 30 July 2021DOI:https://doi.org/10.1103/PhysRevA.104.029907©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasOpen quantum systems & decoherenceTechniquesNon-Markovian processesGeneral Physics

The bilevel optimisation of a multi-agent project scheduling and staffing problem

In this paper, we study a multi-agent project staffing problem involving a single project, which has to be scheduled under resource constraints. We consider a functional organisational structure where a team leader and a project manager are together responsible for the operational execution of a project. The team leader, which has the formal authority over the resources, is standing at the top of the hierarchy and determines the number and mix of (additional) employees and tries to level the workload over the planning period in order to avoid idle resource times. The project manager is responsible for the scheduling of the project activities and his/her objective is to minimise the project duration. The interaction between both agents in the decision-making process is, on the one hand, hierarchical, i.e. the team leader imposes his/her decision on the project manager. On the other hand, the decision taken by the team leader should comply to the objective of the project manager such that the staffing plan and project schedule is agreed by both parties. We propose a bilevel optimisation model that embeds a nested inner optimisation problem, i.e. the project manager decision problem, as a constraint in the outer optimisation problem, i.e. the decision problem of the team leader. The algorithm is a mathematical programming method thriving on the generation of additional lazy constraints via feasibility callbacks so that the team leader problem has to respect the requirements formulated in the project manager problem. In the computational experiments, we compare this solution approach to alternative classical optimisation approaches and we validate the design choices related to the proposed speed-up mechanisms and parameter settings.

Investigation of the Cross-Cutting Polycrystalline Diamond Compact Bit Drilling Efficiency

The parallel track scraping principle of conventional PDC bits largely limits the cutting efficiency and working life in deep formations. Cross-cutting polycrystalline diamond compact (PDC) bit may be an efficient drilling tool that increases the rock-breaking efficiency through both cross-cutting and alternate-cutting modes of the PDC cutter. The motion track equation of the cross-cutting PDC bit was derived by using the compound coordinate system, and the motion track was analyzed. Meanwhile, through the unit experiment and discrete element simulation, the cutting force, volume-specific load, and crack propagation were analyzed under different cutting modes. Through establishing a nonlinear dynamic model of the bit-rock system, the speed-up mechanism of the novel bit was analyzed based on rock damage, rock stress state, and motion characteristic of the bit during the rock-breaking process. Compared with unidirectional cutting, cross-cutting produces less cutting force, more brittle fracture, and a greater decrease of formation strength. The novel PDC bit can put more rock elements into a tensile stress condition than a conventional PDC bit, and the plastic energy dissipation ratio of the cross-cutting PDC bit is lower while the damage energy consumption ratio is higher than they are for conventional bits, which is beneficial to increasing the ratio of fracture failure and improving rock-breaking efficiency. Laboratory drilling tests show that the cross-cutting PDC bit can create mesh-like bottom-hole features. Drilling contrast experiments show that a mesh-like bottom-hole pattern can be obtained by using the cross-cutting PDC bit, of which the ROP is obviously higher than that of the conventional bit when drilling in sandstone or limestone formation. Meanwhile, the influence of deviation angle, weight on bit, and rock properties on cutting efficiency of the cross-cutting PDC bit are studied.

A column generation-based diving heuristic to solve the multi-project personnel staffing problem with calendar constraints and resource sharing

Project managers are often responsible for the management of multiple projects and associated personnel budgeting decisions. In order to determine the workforce size and mix accurately, we integrate the multi-project scheduling problem and personnel staffing problem. We construct a baseline personnel roster that takes the personnel scheduling constraints into account and model the workload stemming from the project activities as an endogenous variable in the model. In order to decrease the overall staffing budget, we consider the sharing of resources, i.e. personnel resources can be transferred between projects. In the problem under study, we consider unproductive resource transfer times and different restrictions related to the sharing of resources imposed on the schedule of individual workers, which is often neglected in the literature. We propose a multi-stage solution procedure that exploits the optimal linear programming solution, obtained via column generation, to find a high-quality integer solution based on a diving heuristic. In order to improve the computational performance, different speed-up mechanisms are included relying on a state space reduction. Detailed computational experiments are presented to evaluate and benchmark different alternative optimisation strategies. Managerial insights are provided which give insight in the benefits of resource sharing.

Working mechanism and experimental study of dual-diameter and bi-speed composite drilling tool

ABSTRACTAs oil and gas production gradually shifts to deep and ultra-deep formations, the pressure and complexity of stratum is increased and drilling efficiency is decreased. Based on this, a Dual-diameter and bi-speed composite drilling method that can realize the different depth, diameter, and rotate speed coupling using only hole-bottom power is proposed in this paper. And a Dual-diameter and bi-speed composite drilling tool is designed, processed, and carried out to complete the field experiment. The tool is connected by a two-stage screw to make the rotate speed of a pilot bit higher than that of the reaming bit to increase the rate of penetration. And a concave bottom hole is formed so that the ground stress is released and the drillability of rock is lifted. Based on the introduction of the speed-up mechanism of the tool, the numerical analysis of the drilling performance of the tool with different diameter ratios and rotate-velocity combinations is completed. The experimental data showed that the Dual-diameter and bi-speed composite drilling method can obviously increase the rate of penetration and drilling efficiency, and also help to reduce the risk of stick-slip and prolong the service life of the drill bit.

A multi-objective discrete invasive weed optimization for multi-objective blocking flow-shop scheduling problem

The flow-shop scheduling problem with blocking constraints has received an increasing concern recently. However, multiple scheduling criteria are rarely considered simultaneously in most research. Therefore, in this paper, a multi-objective blocking flow-shop scheduling problem (MOBFSP) that minimizes the makespan and total tardiness simultaneously is investigated. To address this problem, a multi-objective discrete invasive weed optimization (MODIWO) algorithm is proposed. In the proposed MODIWO, a high-quality and diversified initial population is firstly constructed via two heuristics and varying weighed values. Then, a reference line-based reproduction and a sliding insertion-based spatial dispersal are developed to guide the global exploration and local exploitation of algorithm. Meanwhile, to enhance intensification search in local region, a self-adaption phase is introduced, which is implemented by a Pareto-based two stage local search with speedup mechanism. Furthermore, a new competitive exclusion strategy is also embedded to construct a superior population for the next generation. Finally, extensive computational experiments and comparisons with several recent state-of-the-art algorithms are carried out based on the well-known benchmark instances. Experimental results demonstrate the efficiency and effectiveness of the proposed MODIWO in solving the considered MOBFSP.

Self-adaptive discrete invasive weed optimization for the blocking flow-shop scheduling problem to minimize total tardiness

This paper proposes a self-adaptive discrete invasive weed optimization (SaDIWO) to solve the blocking flow-shop scheduling problem (BFSP) with the objective of minimizing total tardiness which has important applications in a variety of industrial systems. In the proposed SaDIWO, an improved NEH-based heuristic is firstly presented to generate an initial solution with high quality. Then, to guide the global exploration and local exploitation, a self-adaptive insertion-based spatial dispersal is presented. A distance-based competitive exclusion is developed to strike a compromise between the quality and diversity of offspring population. A variable neighborhood search with a speed-up mechanism is embedded to further enhance exploitation in the promising region around the individuals. Afterward, the parameters setting and the effectiveness of each component of the proposed algorithm are investigated through numerical experiments. The performance of the proposed algorithm is evaluated by comparisons with the existing state-of-the-art algorithms in the literature. Experimental results show that the proposed algorithm outperforms the existing state-of-the-art algorithms. Furthermore, the proposed SaDIWO also improves the best known solutions for 132 out of 480 problem instances.

Quantum speed limit of the evolution of the qubits in a finite XY spin chain

We study the quantum speed limit (QSL) time of qubits in a finite XY spin chain with the influence of external transvers magnetic field. When the magnetic field is first at a given value and then suddenly turns off, the evolution of the system occurs. It is a novel discovery for us that there is different mechanism for speed-up of the three kinds of qubits in the same spin chain. For the QSL time of single-site qubit, we find that the transverse magnetization is a potential influence factor for the evolution of single qubit. As for the nearest-neighbor qubits’ QSL time, it is found that the entanglement between two nearest spins is an important resource for speeding up the system evolution. Finally, we analyze the QSL time of next-nearest-neighbor qubits and show that when the effect of entanglement is limit, quenched magnetic field and anisotropy parameter show the effectiveness on accelerating quantum evolution.

The Constant Speedup Mechanism on Adiabatic Quantum Computation

In the adiabatic quantum computation model, a computational procedure is described by the continuous time evolution of a time dependent Hamiltonian. Classically, the unstructured search problem can be solved only in a running time of order O(G). However, by modifying the structure of local Hamiltonian or using specific interpolating functions, it is possible to do the calculation in constant time for a quantum computer. This paper reveals the cause that lead to the speedup. We analyze two kinds of specific adiabatic quantum models, and conclude that the value of relevant elements in back-diagonal of the local Hamiltonian is the main factors affecting the time complexity of adiabatic quantum algorithms. According to the speedup mechanism, we have proposed two kinds of adiabatic quantum algorithms to make a constant time complexity.

Mechanism for quantum speedup in open quantum systems

The quantum speed limit (QSL) time for open system characterizes the most efficient response of the system to the environmental influences. Previous results showed that the non-Markovianity governs the quantum speedup. Via studying the dynamics of a dissipative two-level system, we reveal that the non-Markovian effect is only the dynamical way of the quantum speedup, while the formation of the system-environment bound states is the essential reason for the quantum speedup. Our attribution of the quantum speedup to the energy-spectrum character can supply another vital path for experiments when the quantum speedup shows up without any dynamical calculations. The potential experimental observation of our quantum speedup mechanism in the circuit QED system is discussed. Our results may be of both theoretical and experimental interests in exploring the ultimate QSL in realistic environments, and may open new perspectives for devising active quantum speedup devices.

Research and Development of Multi Section Floating Mechanical Wave Energy Power Generation Device

In order to study the principle of wave power generation, a multi section floating mechanical wave energy power generation device and a rectifier voltage regulator circuit are designed. The device consists of multi cylinder buoys, direction changing and speed-up mechanism, generator, rectifier voltage regulator circuit and other components. According to the certain regulation of wave movement, the structure and parameters of the wave energy capture device are designed; based on the movement characteristics of wave energy capture device, the direction changing and speed-up mechanism is designed, including crank-rocker mechanism and gear mechanism. The rectifier voltage regulator circuit is designed by the law of generator output. The experiment research shows that the efficiency of wave energy power generation device is up to 45.8% under the condition of prescribed test wave.

A Generic Branch-and-Cut Algorithm for Multiobjective Optimization Problems: Application to the Multilabel Traveling Salesman Problem

This paper describes a generic branch-and-cut algorithm applicable to the solution of multiobjective optimization problems for which a lower bound can be defined as a polynomially solvable multiobjective problem. The algorithm closely follows standard branch and cut except for the definition of the lower and upper bounds and some optional speed-up mechanisms. It is applied to a routing problem called the multilabel traveling salesman problem, a variant of the traveling salesman problem in which labels are attributed to the edges. The goal is to find a Hamiltonian cycle that minimizes the tour length and the number of labels in the tour. Implementations of the generic multiobjective branch-and-cut algorithm and speed-up mechanisms are described. Computational experiments are conducted, and the method is compared to the classical ϵ-constraint method.

New developments of the MCNP/CTF/NEM/NJOY code system – Monte Carlo based coupled code for high accuracy modeling

High accuracy code systems are necessary to model core environments with considerable geometry complexity and great material heterogeneity. These features are typical of current and innovative nuclear reactor core designs. Advanced methodologies and state-of-the art coupled code systems must be put into practice in order to model with high accuracy these challenging core designs. The presented research comprises the development and implementation of the thermal–hydraulic feedback to the Monte Carlo method and of speed-up mechanisms to accelerate the Monte Carlo criticality calculation. Coupled Monte-Carlo calculations can serve as reference solutions for verifying high-fidelity coupled deterministic neutron transport methods with detailed and accurate thermal–hydraulic models. The development and verification of such reference high-fidelity coupled multi-physics scheme is performed at the Pennsylvania State University (PSU) in cooperation with AREVA, AREVA NP GmbH in Erlangen, Germany, on the basis of MCNP5, NEM, NJOY and COBRA-TF (CTF) computer codes. This paper presents the latest studies and ameliorations developed to this coupled hybrid system, which includes a new methodology for generation and interpolation of Temperature-Dependent Thermal Scattering Cross Section Libraries for MCNP5, a comparison between sub-channel approaches, and acceleration schemes.

Narrative Speed in Contemporary Fiction

Many contemporary novels subject their readers to a breathless sense that the events are hurtling past too quickly for real understanding. Scenes and focal figures change rapidly, and helpful transitions are missing. The resultant feeling of excessive rapidity is what I mean by narrative speed. Why has speed become a commonplace in fiction? What effects do authors seek by using it? How does such a frantic pace af- fect audiences and their attitudes towards the texts? (Quite differently, one assumes, since some readers glory in the effect while others fight it or dislike the discomfort it causes them.) These questions confront readers of numerous recent novels, and they invite us to ask how one might best understand speed as a narrative technique. Nar- rative theory to date seems to offer relatively little insight into these problems. Crit- ics have so far theorized pace (fast or slow) in just four basic fashions: (1) prose portrayal of physical speed; (2) narrative retardation; (3) the amount of story time covered per page; and (4) fictional reflections of cultural speed. Critical concern with portraying physical speed focuses on the modernist fasci- nation with physical speed and how to represent it in painting, sculpture, and writing. This is only marginally relevant to the kind of frantic narrative I am trying to ana- lyze, because narrative speed does not necessarily increase as one describes physical speed, though the two sometimes coincide. DeQuincey's prose, for example, actu- ally slows down as he attempts to catalog the sensations of fear provoked by a speed- ing mail coach. One significant connection between mechanical speed and prose speed has been helpfully analyzed by Stephen Kern. In exploring the speed-up mechanisms of the modernist era—bicycle, telegraph, telephone, car, and film—he notes that reporters wired stories to their newspapers. Kern attributes to this practice

Asymptotic and numerical study of the stabilization of diffusion flames by hot gas

Recirculating hot combustion products play an essential role in the stabilization of diffusion flames in a combustor. An idealized one-dimensional configuration is utilized to elucidate this process. It consists of three parallel streams: to the left, a layer of fuel at subignition temperature; an intermediate finite thickness layer of oxidizer at the same low temperature; and to the right, a layer of hot combustion products. Using numerical simulations, three distinct ignition regimes are identified as the thickness of the intermediate layer is decreased, with corresponding ignition time variations spanning several orders of magnitude. The main speed-up mechanism is attributed to the abrupt transition from ignition via a classical triple flame at the fuel-oxidizer boundary, to ignition at a competing site located at the boundary between the cold oxidizer and the hot products. High activation energy asymptotics leads to a practical procedure to relate the intermediate layer thickness and the ignition time.

Complete worst-case execution time analysis of straight-line hard real-time programs

In this article, the problem of finding a tight estimate on the worst-case execution time (WCET) of a hard real-time program is addressed. The analysis is focused on straight-line code (without loops and recursive function calls) which is quite commonly found in synthesised code for embedded systems. A comprehensive timing analysis system covering both low-level (assembler instruction level) as well as high-level aspects (programming language level) is presented. The low-level analysis covers all speed-up mechanisms used for modern superscalar processors: pipelining, instruction-level parallelism and caching. The high-level analysis uses the results from the low-level to compute the final estimate on the WCET. This is done by a heuristic for searching the longest really executable path in the control flow, based on the functional dependencies between various program parts.