Desired Configuration Research Articles

Method based on graph theory to extract the best switch set for reconfiguration of photovoltaic panels

This study presents a novel method based on graph theory (GT) to find the best switch set (SWS) topology for reconfiguration of PV panels. In the proposed method, the minimum number of switches and maximum capability for realising different desired configurations for the best topology are taken into account. In spite of the published PSO-based optimisation approach by the authors, the proposed graph-based method is able to derive the best SWS for any expansion of the problem. Mathematic representation of the problem based on GT and the proposed algorithm for finding the best topology of SWS are discussed in details. Different results of the SWS assessment confirm that the optimised SWS is able to implement various desirable configurations with minimum number of switches.

Effect of Doping Temperatures and Nitrogen Precursors on the Physicochemical, Optical, and Electrical Conductivity Properties of Nitrogen-Doped Reduced Graphene Oxide.

The greatest challenge in graphene-based material synthesis is achieving large surface area of high conductivity. Thus, tuning physico-electrochemical properties of these materials is of paramount importance. An even greater problem is to obtain a desired dopant configuration which allows control over device sensitivity and enhanced reproducibility. In this work, substitutional doping of graphene oxide (GO) with nitrogen atoms to induce lattice–structural modification of GO resulted in nitrogen-doped reduced graphene oxide (N-rGO). The effect of doping temperatures and various nitrogen precursors on the physicochemical, optical, and conductivity properties of N-rGO is hereby reported. This was achieved by thermal treating GO with different nitrogen precursors at various doping temperatures. The lowest doping temperature (600 °C) resulted in less thermally stable N-rGO, yet with higher porosity, while the highest doping temperature (800 °C) produced the opposite results. The choice of nitrogen precursors had a significant impact on the atomic percentage of nitrogen in N-rGO. Nitrogen-rich precursor, 4-nitro-ο-phenylenediamine, provided N-rGO with favorable physicochemical properties (larger surface area of 154.02 m2 g−1) with an enhanced electrical conductivity (0.133 S cm−1) property, making it more useful in energy storage devices. Thus, by adjusting the doping temperatures and nitrogen precursors, one can tailor various properties of N-rGO.

Magnetically-actuated micromechanical nickel patches for a monolithically integrated reconfigurable antenna on printed circuit board

In this paper, we present magnetically-actuated micromechanical Ni patches that have been monolithically integrated on a printed circuit board to demonstrate a reconfigurable pixelated antenna operating within the 5–8 GHz frequency bands. The proposed antenna is based on a monolithically integrated grid structure of movable nickel (Ni) and fixed copper (Cu) patches. The Ni patches are magnetically actuated by means of an array of switchable magnets (SMs) placed behind the ground plane of the antenna. This approach eliminates the need for bias lines, which are generally used in reconfigurable antennas and induce losses. Most importantly, the very low mechanical contact resistance (as low as 200 mΩ) between the Ni and Cu patch ensures the insertion of these devices on the antenna plane without introducing significant losses. The use of a SM for the actuation of the patch makes it such that the antenna can hold the desired configurations without consuming active power. Power is consumed only during the switching operation. To demonstrate the feasibility of the proposed idea, the four most relevant operating modes of this small antenna prototype, centered around 5.55 GHz, 6.44 GHz, and 7.89 GHz, are presented.

Algorithms for quantum control without discontinuities: Application to the simultaneous control of two qubits

We propose a technique to design control algorithms for a class of finite dimensional quantum systems so that the control law does not present discontinuities. The class of models considered admits a group of symmetries, which allows us to reduce the problem of control to a quotient space where the control system is “fully actuated.” As a result, we can prescribe a desired trajectory, which is, to some extent, arbitrary, and derive the corresponding control. We illustrate this technique with examples and focus on the application to the simultaneous control of two non-interacting spin 12 particles with different gyromagnetic ratios in zero field nuclear magnetic resonance (NMR). Our method provides a flexible toolbox for the design of control algorithms to drive the state of finite dimensional quantum systems to any desired final configuration, with smooth controls.

Motion Capability Analysis for Multiple Fixed-Wing UAV Formations With Speed and Heading Rate Constraints

This paper analyzes the motion capability of multiple fixed-wing unmanned aerial vehicle (UAV) formations by taking speed and heading rate constraints of individual UAVs into account. Unlike most of the existing literature investigating multi-UAV formation flying problems, which mainly focus on planner/controller design in order to achieve desired configurations, this paper aims at providing a quantitative description of the UAV formation maneuverability, which can serve as a metric for evaluating formation trajectory plans. Three common formations, namely perfect rigid formation, semiperfect rigid formation, and flexible formation are considered in this paper. Motion capabilities of these formations are analyzed in terms of turning performance. In particular, the feasible set of the formation heading rate is employed as the evaluation metric, based on which the relationships among these three formations are discussed. It has been proven that perfect rigid formation suffers from a rather limited mobility, while flexible formation has the largest feasible set of the formation heading rate in some situations. An interesting finding of this paper is that flexible formation is not necessarily more agile than semiperfect rigid formation with the same formation width, due to the special stall speed constraint of fixed-wing UAVs. Besides rigorous mathematical derivations, simulations have also been performed to further support the theoretical analyses.

Cooperative Aerial Load Transportation via Sampled Communication

In this work, we propose a feedback-based motion planner for a class of multi-agent manipulation systems with a sparse kinematics structure. In other words, the agents are coupled together only by the transported object. The goal is to steer the load into a desired configuration. We suppose that a global motion planner generates a sequence of desired configurations that satisfy constraints as obstacles and singularities avoidance. Then, a local planner receives these references and generates the desired agents velocities, which are converted into force inputs for the vehicles. We focus on the local planner design both in the case of continuously available measurements and when they are transmitted to the agents via sampled communication. For the latter problem, we propose two strategies. The first is the discretization of the continuous-time strategy that preserves stability and guarantees exponential convergence regardless of the sampling period. In this case, the planner gain is static and computed off-line. The second strategy requires to collect the measurements from all sensors and to solve online a set of differential equations at each sampling period. However, it has the advantage to provide doubly exponential convergence. Numerical simulations of these strategies are provided for the cooperative aerial manipulation of a cable-suspended load.

Fabricating Mechanically Robust Binder-Free Structured Zeolites by 3D Printing Coupled with Zeolite Soldering: A Superior Configuration for CO2 Capture.

3D‐printing technology is a promising approach for rapidly and precisely manufacturing zeolite adsorbents with desirable configurations. However, the trade‐off among mechanical stability, adsorption capacity, and diffusion kinetics remains an elusive challenge for the practical application of 3D‐printed zeolites. Herein, a facile “3D printing and zeolite soldering” strategy is developed to construct mechanically robust binder‐free zeolite monoliths (ZM‐BF) with hierarchical structures, which can act as a superior configuration for CO2 capture. Halloysite nanotubes are employed as printing ink additives, which serve as both reinforcing materials and precursor materials for integrating ZM‐BF by ultrastrong interfacial “zeolite‐bonds” subjected to hydrothermal treatment. ZM‐BF exhibits outstanding mechanical properties with robust compressive strength up to 5.24 MPa, higher than most of the reported structured zeolites with binders. The equilibrium CO2 uptake of ZM‐BF reaches up to 5.58 mmol g−1 (298 K, 1 bar), which is the highest among all reported 3D‐printed CO2 adsorbents. Strikingly, the dynamic adsorption breakthrough tests demonstrate the superiority of ZM‐BF over commercial benchmark zeolites for flue gas purification and natural gas and biogas upgrading. This work introduces a facile strategy for designing and fabricating high‐performance hierarchically structured zeolite adsorbents and even catalysts for practical applications.

Лист у мережі інтернет як новий тип документа: морально-етичний та діловий аспект

Людство завжди було в комунікативному процесі, який можна розділити на глобальні категорії — вербальну, невербальну, віртуальну. Кожна із них має свою історію і складову.Листування можна розглядати як спілкування у вербально-віртуальному прос­торі. Ця приналежність обумовлена різними засобами: зовнішнє оформлення листа (малюнки, обрамлення, каліграфія та інші естетичні інструменти); культура подання тексту (мовна грамотність, дотримання морально-етичних норм у викладі тексту); матеріал, на якому написані листи; його технічні та інші засоби, за допомогою яких відбувається передавання листів.Тексти листів практично не відрізняються від вербального спілкування. Адже йому так само властиві практично всі ті ж особливості, які притаманні культурі говоріння. Лише варто відзначити ту різницю, що одномоментно не «присутня» й культура (чи її відсутність) слухання.Інтернет-листуванню притаманні ті ж властивості, що й традиційному, лише з новітніми особливостями: замість паперу — екран, на якому формується відповідного формату сторінка/файл, її оздоблення бажаною конфігураціє шрифта, іншими можливостями інтернет-ресурсів і особистих. Все інше — технічно-технологічні можливості: відправка, доставка, зберігання.Оперативність, зручність та інтенсивність листування у значній мірі відсторонює на другий план або й зовсім нівелює морально-етичні норми й традиції спілкування, культуру спілкування в цілому, виокремлюючи тільки обмін інформацією у вигляді листа чи просто прикріпленого листа, документа, що стає вже нормою для активних користувачів Інтернету.Інтернет-листування є невід’ємною складовою як ділового, приватного листування, так і культурної компетентності в цілому, яке на сьогодні майже повністю витіснило традиційне листування.У статті автор робить порівняльну характеристику між традиційним (паперовим) листуванням і листуванням у мережі Інтернет. Описує усталені й відмінні їх компоненти. Однак у своїй основі звертає увагу насамперед на морально-етичну складову, а потім уже й на діловий аспект будь-якого листування, особливо на вплив стосунків у комунікаційних процесах.

PicoTesla absolute field readings with a hybrid 3He/87Rb magnetometer

We demonstrate the use of a hybrid 3He/87 magnetometer to measure absolute magnetic fields in the pT range. The measurements were undertaken by probing time-dependent 3He magnetisation using 87Rb zero-field magnetometers. Measurements were taken to demonstrate the use of the magnetometer in cancelling residual fields within a magnetic shield. It was shown that the absolute field could be reduced to the 10 pT level by using field readings from the magnetometer. Furthermore, the hybrid magnetometer was shown to be applicable for the reduction of gradient fields by optimising the effective 3He T2 time. This procedure represents a convenient and consistent way to provide a near zero magnetic field environment which can be potentially used as a base for generating desired magnetic field configurations for use in precision measurements.Graphical abstract

New method for the evaluation of residual compressive strengths of sandwich panels via four-point bending

There is presently no standard test method for evaluating compression-after-impact (CAI) strengths of sandwich panels. A direct adaption of existing end-loaded CAI method for monolithic laminates by up-scaling the dimensions of a standard specimen shows little usefulness and could lead to such large sandwich panel sizes so that generating CAI design data in such approach would increase material costs significantly and hence be prohibitively expensive. This work develops a low-cost alternative via four-point bending, using a drilled hole of a selected diameter to represent impact damage. A challenge of this development for as-received sandwich beams with a core of a single constant density is to gain a deeper physical insight into desirable construction configurations, in which the compressive skin could fail in flexure consistently for given support span-to-thickness ratio. Sandwich construction encompasses a wide range of combinations of intrinsic parameters and hence some parametric study was essential, including varying skin thickness, lay-up, core density, skin material and sandwich symmetry in addition to the diameter of a hole. It was found that core density and compressive skin thickness were the major factors of significantly influencing the failure modes of the sandwich beams.

Arbitrary point-to-point stabilization control in specified finite time for wheeled mobile robots based on dynamic model

This paper investigates the arbitrary point-to-point stabilization control problem for wheeled mobile robots based on the second-order dynamics. The arbitrary point-to-point stabilization means the robot can be stabilized from any initial configuration to any other desired configurations. In this paper, at first, a global and asymptotical stabilization control law is presented directly based on the dynamic model, which can drive the robot to the identity configuration from any initial condition. Then, assisted by a new converted system, an arbitrary point-to-point stabilization control strategy is proposed, in which the initial and desired configurations are both arbitrarily chosen. Next, by means of a time-rescaling approach, a specified finite-time stabilization control law is derived from the asymptotical controller. In particular, the finite-time moment can be specified in advance. Finally, numerical simulations are presented to demonstrate the effectiveness of the control law.

Hybrid solar and heat-driven district cooling system: Optimal integration and control strategy

An optimal design and well-scheduled district cooling system is crucial for the success of the implementation of such systems especially when the cooling plant(s) are intended to be connected to a group of newly-built consumers. In order to supply such customers the required cooling load, a huge capital and operation investment in district cooling network is a necessity if the cooling network is separated from the heating production units. One solution scheme is to take advantage of the heating generation units, which are off during summer to drive the cooling equipment. However, among various design parameters, the most important one is the desirable configuration of the district of interest: best selection and combination of the heating and cooling generation equipment. A least-annualized-cost mathematical approach based on the mixed integer linear programming (MILP) is described in this paper to determine the optimal integration as well as the optimal control of the flow and the storage. The test case study showed that the methodology was effective to give a huge savings in both total annual cost and emission for a wide range of designs. More than 67% of CO2 emission reduction is achieved through the hybrid heat and solar-driven arrangement.

Photo-induced Bending and Buckling of Polymer Sheets

Shape-shifting has widespread applications in soft robots and self-assembly structures. To achieve their functionalities, these architectures rely on the spatially bending and buckling to transform the polymer sheets into desired configurations. The goal of this work is to demonstrate that it is possible to tune the shape-shifting behavior through the photo-induced mismatch strain. For the mechanistic understanding, Finite element modeling of thin sheets with different geometry are performed to understand the fundamental mechanics behind the shape transformation behavior. Our experiments with cross-linked polymer samples that change shapes through variation in illumination dose and photo patterns confirm the proposed model predictions. Finally, self-folding structures include flowers, claws, pyramid and saddle are duplicated based on the computational models, indicating the guidelines reported here would be applicable to a diverse array of self-assembly devices.

Extending Battery System Operation via Adaptive Reconfiguration

Large-scale battery packs are commonly used in applications such as electric vehicles (EVs) and smart grids. Traditionally, to provide stable voltage to the loads, voltage regulators are used to convert battery packs’ output voltage to those of the loads’ required levels, causing power loss especially when the difference between the supplied and required voltages is large or when the load is light. In this article, we address this issue via a reconfiguration framework for the battery system. By abstracting the battery system as a cell graph, we develop an adaptive reconfiguration algorithm to identify the desired system configurations based on real-time load requirements. Our design is evaluated via both prototype-based experiments, EV driving trace-based emulations, and large-scale simulations. The results demonstrate an extended system operation time of up to 5×, especially when facing severe cell imbalance.

Pea-like Fe/Fe3C Nanoparticles Embedded in Nitrogen-Doped Carbon Nanotubes with Tunable Dielectric/Magnetic Loss and Efficient Electromagnetic Absorption.

One-dimensional microstructure has been regarded as one of the most desirable configurations for magnetic carbon-based microwave absorbing materials (MAMs). Herein, pea-like Fe/Fe3C nanoparticles embedded in nitrogen-doped carbon nanotubes (Fe/Fe3C@NCNTs) are successfully prepared through a direct pyrolysis of the mixture of FeCl3·6H2O and melamine under inert atmosphere. The chemical composition and microstructural feature of these Fe/Fe3C@NCNTs composites are highly dependent on the pyrolysis temperature. As a result, their electromagnetic properties can be also manipulated, where dielectric loss gradually decreases with the increasing pyrolysis temperature and magnetic loss presents a reverse variation trend. When the pyrolysis temperature reaches 600 °C, the as-obtained composite, Fe/Fe3C@NCNTs-600 can perform a maximum reflection loss of -46.0 dB at 3.6 GHz with a thickness of 4.97 mm and a qualified bandwidth of 14.8 GHz with the integrated thickness from 1.00 to 5.00 mm. It is very interesting that the microwave absorption performance of this new kind of composites is not so susceptible to the pyrolysis temperature as those common magnetic carbon-based MAMs because there is an effective balance between dielectric loss and magnetic loss, which accounts for a very stable attenuation ability when the pyrolysis temperature range changes from 600 to 700 °C. These favorable characteristics, including low-cost raw materials, easy preparation, and stable performance, may render Fe/Fe3C@NCNTs composites as a novel kind of MAMs in the future.

Circular Formation Control of Multiple Unicycle-Type Agents With Nonidentical Constant Speeds

This paper discusses the problem of controlling formation shapes for a group of nonholonomic unicycle-type agents with constant speeds. The control input is designed to steer their orientations and the aim is to achieve a desired formation configuration for all the agents subject to constant-speed constraints. The circular motion center is adopted as a virtual position for each agent to define the desired formation shape. We consider several different formation design approaches based on different formation specifications under different interaction graphs. In particular, two different formation design approaches, namely, a displacement-based approach and a distance-based approach, are discussed in detail to coordinate constant-speed agents in achieving a desired formation shape with stable circular motions via limited interactions. The communication and measurement requirements for each approach are also discussed. Furthermore, we propose a combined controller to stabilize a formation shape and synchronize the heading of each agent simultaneously. The effectiveness of the proposed formation control schemes is validated by both numerical simulations and real experiments with actual unmanned fixed-wing aircraft.

Bi-level optimization approach for configuring population and employment distributions with minimized vehicle travel demand

Compact development aims to lead to dense and mixed distributions of population and employment in land use planning which may result in reduced vehicle miles traveled (VMT). However, determining an optimum or desirable configuration of population and employment distribution to achieve the compact development goal remains challenging due to numerous competitive development alternatives or possible exacerbated traffic congestion as a result of over-intensification of urban land use. To address this challenge, a systematic approach is proposed with a bi-level optimization model aiming to find out an efficient population and employment map for vehicle travel reduction. The upper level of the model is formulated to minimize VMT and vehicle hours traveled (VHT) varying with possible changes in population and employment densities. The lower level is based on a tour-based travel demand model to mechanistically represent the response of travel choices to those changes. The programming is solved by a Genetic Algorithm. The proposed method is demonstrated through a case study of Hamilton County, Ohio, U.S. The results indicate that a more compact urban form reduces VMT; however, it may cause longer VHT depending upon the density. To avoid urban overconcentration and reduce both VMT and VHT simultaneously, a compact urban development configuration with a population density < 5289 persons/mi2 and the employment density < 3282 jobs/mi2 is recommended for the area. As a negative relationship demonstrated between transit headway reduction and vehicle travel demand, strategies for improving transit provision are helpful to reducing vehicle travels in compact development scenarios.

Co-Fe-P nanotubes electrocatalysts derived from metal-organic frameworks for efficient hydrogen evolution reaction under wide pH range

The development of high-performance and cost-effective electrocatalysts is of great significance for hydrogen production by water splitting but remains challenge. Herein, a metal organic frameworks (MOFs) templating approach is proposed to synthesize Co incorporating FeP nanotubes (Co-Fe-P nanotubes) for efficient for hydrogen evolution reaction (HER). The MOFs-derived tubular structure with in situ Co substitution lead to abundant catalytic sites, fast mass and charge transport pathways, and desirable electronic configuration. These beneficial effects enable Co-Fe-P nanotubes efficient HER catalytic activity in a wide pH range, achieving small overpotentials of 86, 138, and 66 mV at a current density of 10 mA cm−2 in 1 M KOH, 1 M phosphate buffer solution (PBS), and 0.5 M H2SO4, respectively. The catalytic activity of Co-Fe-P nanotubes outperforms most of the reported FeP-based electrocatalysts. Density functional theory calculations further reveal that Co substitution results in increased density of states near Fermi level, boosting the intrinsic electrocatalytic activity of Co-Fe-P nanotubes. This work affords a feasible way to the synthesis of cheap and efficient FeP-based electrocatalysts for HER.

Variability-Aware Static Analysis at Scale

The advent of variability management and generator technology enables users to derive individual system variants from a configurable code base by selecting desired configuration options. This approach gives rise to the generation of possibly billions of variants, which, however, cannot be efficiently analyzed for bugs and other properties with classic analysis techniques. To address this issue, researchers and practitioners have developed sampling heuristics and, recently, variability-aware analysis techniques. While sampling reduces the analysis effort significantly, the information obtained is necessarily incomplete, and it is unknown whether state-of-the-art sampling techniques scale to billions of variants. Variability-aware analysis techniques process the configurable code base directly, exploiting similarities among individual variants with the goal of reducing analysis effort. However, while being promising, so far, variability-aware analysis techniques have been applied mostly only to small academic examples. To learn about the mutual strengths and weaknesses of variability-aware and sample-based static-analysis techniques, we compared the two by means of seven concrete control-flow and data-flow analyses, applied to five real-world subject systems: B usybox , O pen SSL, SQL ite , the x86 L inux kernel, and u C libc . In particular, we compare the efficiency (analysis execution time) of the static analyses and their effectiveness (potential bugs found). Overall, we found that variability-aware analysis outperforms most sample-based static-analysis techniques with respect to efficiency and effectiveness. For example, checking all variants of O pen SSL with a variability-aware static analysis is faster than checking even only two variants with an analysis that does not exploit similarities among variants.

3D non-linear MHD simulation of the MHD response and density increase as a result of shattered pellet injection

The MHD response and the penetration of a deuterium shattered pellet into a JET plasma is investigated via the non-linear reduced MHD code JOREK with the neutral gas shielding (NGS) ablation model. The dominant MHD destabilizing mechanism by the injection is identified as the local helical cooling at each rational surface, as opposed to the global current profile contraction. Thus the injected fragments destabilize each rational surface as they pass through them. The injection penetration is found to be much better compared to MGI, with the convective transport caused by core MHD instabilities (e.g. 1/1 kink) contributing significantly to the core penetration. Moreover, the injection with realistic JET SPI system configurations is simulated in order to provide some insights into future operations, and the impact on the total assimilation and penetration depth of varying injection parameters such as the injection velocity or fineness of shattering is assessed. Further, the effect of changing the target equilibrium temperature or q profile on the assimilation and penetration is also investigated. Such analysis will form the basis of further investigation into a desirable configuration for the future SPI system in ITER.