Miracle-dz/UniFAR-FTUs huggingface dataset:
Elastic stars in general relativity: II. Radial perturbations

We study radial perturbations of general relativistic stars with elastic matter sources. We find that these perturbations are governed by a second-order differential equation which, along with the boundary conditions, defines a Sturm–Liouville-type problem that determines the eigenfrequencies. Although some complications arise compared to the perfect fluid case, leading us to consider a generalization of the standard form of the Sturm–Liouville equation, the main results of Sturm–Liouville theory remain unaltered. As an important consequence we conclude that the mass–radius curve for a one-parameter sequence of regular equilibrium models belonging to some particular equation of state can be used in the same well-known way as in the perfect fluid case, at least if the energy density and the tangential pressure of the background solutions are continuous. In particular, we find that the fundamental mode frequency has a zero for the maximum mass stars of the models with solid crusts considered in paper I of this series.
Estimation and Compensation of Ionospheric Propagation Delay in Synthetic Aperture Radar (SAR) Signals

Synthetic aperture radar (SAR) and interferometric SAR (InSAR) measurements are disturbed by the propagation velocity changes of microwaves that are caused by the high density of free electrons in the ionosphere. As the ionosphere is an obstacle to increasing the precision of SAR systems needed to remotely measure the Earth's dynamic processes, this thesis aims to develop methods to estimate and compensate ionospheric propagation delays in SAR signals.
Structural performance of AAC hybrid floor system

Current floor systems of Australian low‐rise steel residential houses and buildings consist of cold‐formed light‐gauge steel floor joists and mainly sheet flooring (particleboard). There are potentially some issues including uncomfortable floor vibration and noise, which could annoy the occupants. In Australia, there are several different types of steel floor systems as well as timber systems. Few research on structural performance of Australian floor systems including flooring materials in terms of vibration has been carried out and reported. This paper describes present Australian common steel and timber floor systems and their structural characteristics obtained by static and dynamic loading tests with regard to human comfort. Additionally, a new hybrid AAC flooring system with steel frames is proposed and tested compared with common sheet flooring. It is found that AAC panels connected to the particleboards can greatly improve human comfort but not fundamental frequency.
Phase Diagram for Ashkin–Teller Model on Bethe Lattice

Using the recursion method, we study the phase transitions of the Ashkin–Teller model on the Bethe lattice, restricting ourselves to the case of ferromagnetic interactions. The isotropic Ashkin–Teller model and the anisotropic one are respectively investigated, and exact expressions for the free energy and the magnetization are obtained. It can be found that each of the three varieties of phase diagrams, for the anisotropic Ashkin–Teller model, consists of four phases, i.e., the fully disordered paramagnetic phase Para, the fully ordered ferromagnetic phase Ferro, and two partially ordered ferromagnetic phases ⟨σ⟩ and ⟨σs⟩, while the phase diagram, for the isotropic Ashkin–Teller model, contains three phases, i.e., the fully disordered paramagnetic phase Para, the fully ordered ferromagnetic phase Baxter Phase, and the partially ordered ferromagnetic phase ⟨σs⟩.
The target space geometry of N = (2,1) string theory

We describe the constraints on the target space geometry of the N = (2,1) heterotic superstring due to the left-moving N = 1 supersymmetry and U(1) currents. In the fermionic description of the internal sector supersymmetry is realized quantum mechanically, so that both tree-level and one-loop effects contribute to the order constraints. We also discuss the physical interpretation of the resulting target space geometry in terms of configurations of a (2 + 2)-dimensional object propagating in a (10 + 2)-dimensional spacetime with a null isometry, which has recently been suggested as a unified description of string and M-theory.
Robust Energy and Reserve Scheduling Under Wind Uncertainty Considering Fast-Acting Generators

The large-scale integration of wind power generation has significantly boosted the role played by conventional fast-acting generating units in power system operation. Due to their short response time, these relatively expensive devices are particularly suited to cope with the intermittency and volatility featured by uncertain wind-based generation. Within the context of network-constrained generation scheduling under wind-related uncertainty, this paper presents a new robust approach wherein the operation of both slow- and fast-acting generating units is precisely characterized in a day-ahead co-optimized energy and reserve market. As salient modeling features, the ramping-related effect of dispatch nonanticipativity and nonspinning reserve offers are both accounted for. The resulting robust counterpart is formulated as a challenging trilevel program with lower-level binary variables that is effectively solved by an exact nested column-and-constraint generation algorithm. Numerical results including a practical out-of-sample validation procedure demonstrate the operational advantages and the computational effectiveness of the proposed approach.
Metallization of silicon in a shock wave: the metallization threshold and ultrahigh defect densities

Time-resolved electrical conductivity measurements on monocrystalline doped silicon are performed under shock compression up to 23 GPa followed by release. With increasing normal stress, the electrical conductivity of silicon increases monotonically by five orders of magnitude and reaches that of ‘poor’ metals. The stress dependence of the conductivity comprises two parts: a steep rise and a ‘plateau’. The ‘plateau’ conductivity corresponds to the metallic state of silicon; it does not depend on the compression regime or the doping type or amount of impurity. The onset of the metallic phase corresponds to a shock stress of about 10 GPa; most of the specimen is metallic at 12 GPa. The state of shock-compressed silicon proves to be extremely defective. The defect concentration in shocked silicon exceeds the equilibrium concentration by five orders of magnitude and exceeds the defect concentration in classic metals by an order of magnitude. This indicates distinctive features of brittle solid deformation. Experimentally, the metallic phase proves to be metastable. Releasing stress causes a temporary delay of the reverse transition.
On the adoption of additive manufacturing in healthcare: a literature review

PurposeThe purpose of this paper is to discuss different 3D printing techniques and also illustrate the issues related to 3D printing and cost-effectiveness in the near future.Design/methodology/approachA systematic literature review methodology is adopted for this review paper. 3D printing is in the initial phase of implementation in healthcare; therefore, a study of 70 research papers is done, which discusses the research trends of 3D printing in healthcare sector from 2007 to mid-2018.FindingsThough additive manufacturing has a vast application, it has not been used to its full potential. Therefore, more research is required in that direction. It is revealed from the review that only a few researchers have explored issues related to cost, which can clearly show cost-effectiveness of adopting 3D printing.Originality/valueThis paper helps in understanding the different 3D printing techniques and their application in the healthcare. It also proposed some methods which can be applied in delivering customized pharmaceuticals to the customer and to improve surgery.
Multiple Feature Extraction in CBIR with Relevance Feedback

Rapid expansion of image data on internet opens the way to image retrieval systems. Most commercial image retrieval systems include text based approach which is incompetent as some features are nearly impossible to describe with text. In an effort to overcome these problems and to improve image retrieval performance researchers are focusing on Content Based Image Retrieval (CBIR). CBIR system uses the contents of image such as color, shape and texture features. This paper presents superior feature extraction technique in CBIR using multiple features like color and texture than the single feature. The performance of CBIR systems is further enhanced by relevance feedback (RF) mechanism that incorporates human perception subjectivity into the query process and provides users with opportunity to evaluate retrieval results. Keywords—CBIR; color; texture; feature extraction; relevance feedback
Real-Time Multiplexing of Mixed-Criticality Data Streams for Automotive Multi-Core Test Systems

Historically, automotive test systems were designed for single core architectures on both the Electronic Control Unit (ECU) and the Verification and Validation (V&V). This, however, limited the utilization of shared resources, such as memory management or network interfaces. In this paper we present a redesign of an automotive test system that is based on a multi-core architecture and capable of managing mixed-criticality data that is exchanged between the ECU and V&V system. As part of the redesign, we implemented a Connectivity Manager (CM) that is in charge of multiplexing several data streams from multiple cores across a shared network. Due to the increased complexity of our system, a more flexible communication scheduling approach is required. Our solution to this problem is a novel dynamic prioritization approach that adapts to bandwidth changes on the shared communication network. Through simulations with realistic workloads on the CAN bus, we demonstrate the proper functioning of our algorithm with the result that higher critical data streams are favoured over less critical data streams in case of bus overloads or temporary bottlenecks.
Applications of a new plane stress yield function to orthotropic steel and aluminium sheet metals

Many metallic sheets exhibit a certain initially plastic anisotropy that influences considerably the mechanical behaviour of the sheet material in forming operations. Nowadays, computer modelling based on the finite element method (FEM) in conjunction with the concept of anisotropic yield functions is successfully utilized to design sheet forming processes. The yield function applied in the FEM analysis affects very strongly the computed results such as material flow, springback, wrinkling and limiting strains. Consequently, in order to increase the accuracy of the FEM simulations the yield function used should be as accurate as possible in order to capture all the important anisotropy effects. In this paper, the new plane stress yield function for orthotropic sheet metals recently introduced by the author (Aretz H 2003 J. Mater. Process. Technol. submitted) is applied to orthotropic steel and aluminium sheet metals. The yield function contains eight anisotropy parameters that may be fitted by means of a Newton solver or a least square solver to selected experimental input data. The main attractiveness of the new yield function lies in its very simple mathematical form, which makes it very effective and thus quite interesting for implementation in finite element codes. The capabilities of the new yield function are demonstrated by applications to selected orthotropic sheet materials.
Les multilucarnes : nouveaux contre-exemples à la conjecture de Ragsdale

Une fameuse conjecture attribuee a Ragsdale [1] affirme que le nombre d'ovales pairs et le nombre d'ovales impairs d'une courbe algebrique non-singuliere de degre 2k k sur le plan projectif RP 2 sont chacun majores par R (k) = (3 k(k - 1)/2) + 1. Dans une Note recente [2] I. Itenberg a construit des courbes ayant R (k) + [((k-3) 2 + 4)/8] ovales pairs, [a] designant ici la partie entiere de a. Dans la presente Note sont donnes des contre-exemples ou la borne R(k) est depassee d'un terme de l'ordre de k 2 /6.
Scale-free network of earthquakes

The district of Southern California and Japan are divided into small cubic cells, each of which is regarded as a vertex of a graph if earthquakes occur therein. Two successive earthquakes define an edge or a loop, which may replace the complex fault-fault interaction. In this way, the seismic data are mapped to a random graph. It is discovered that an evolving random graph associated with earthquakes behaves as a scale-free network of the Barabási-Albert type. The distributions of connectivities in the graphs thus constructed are found to decay as a power law, showing a novel feature of earthquake as a complex critical phenomenon. This result can be interpreted in view of the facts that the frequency of earthquakes with large values of moment also decays as a power law (the Gutenberg-Richter law) and aftershocks associated with a mainshock tend to return to the locus of the mainshock, contributing to the large degree of connectivity of the vertex of the mainshock. Thus, a mainshock plays the role of a “hub”. It is also found that the exponent of the distribution of connectivities is characteristic for the plate under investigation.
A Hands-on Project for Avionics Systems Course in Aviation Engineering Technology Program

There are electrical and electronic systems courses that are compulsory for students majoring in Aeronautical Engineering Technology (AET), an undergraduate program accredited by the Engineering Technology Accreditation Commission of ABET (ABET-ETAC). In order to prepare students for the FAA Airframe and Powerplant Certification exams, and future success in their careers, students in the AET program are expected to develop an integrated ability of understanding theoretical knowledge and proficient hands-on skills. This paper introduces a hands-on project for an upper level electrical and electronic systems course to better develop project-oriented, problem-solving experiences. This hands-on project requires assembling an Automatic Dependent Surveillance – Broadcast (ADS-B) flight tracking system that is a realworld aeronautical system. ADS-B is one of the major components of the Next Generation air transportation system. In this project, students are asked to apply relevant electrical and electronic knowledge and skills to build a light-weight ADS-B receiver, and deploy the receiving system to collect and decode flight data broadcast by aircraft. This project is expected to help students develop the ability of integrating skills from different electrical and electronics courses to solve real aviation problems. This course project, based on current avionic technology, allows students to have better understanding of their theoretical knowledge, as well as a good practice of hands-on skills.
The influence of platelet disorientation on the barrier properties of composites: a numerical study

Direct finite element calculations are carried out to study the relationship between the platelet orientational distribution and the overall effective barrier properties (gas permeability) of mineral filled composites. We consider multi-inclusion computer models with microstructures representative of the dilute, semi-dilute and concentration regimes. In the dilute regime, our numerical predictions validate the results of multiple scattering expansion theory. For the semi-dilute and concentration regimes representative of most real composites, we present numerical estimates quantifying the difference between the barrier properties of composites with fully aligned and randomly oriented platelets. Our numerical results can also be used to quantify the effect of the geometric factor on the gas barrier properties of polymer–mineral hybrid nanocomposites.
Corrigendum: Dynamics and energy landscape in a tetrahedral network glass-former: direct comparison with models of fragile liquids

We have recently uncovered two typographical errors in our paper. First, equation (1) should read u αα ( r ) = (cid:15) αα ( σ αα r ) 12 and not u αα ( r ) = 4 (cid:15) αα ( σ αα r ) 12 . Second, in ﬁgure 7 the wavevectors at which τ 1 and τ 2 are evaluated are k = 4 . 7 (ﬁlled squares) and k = 8 . 4 (asterisks), and not 5.0 and 8.0 as indicated in the ﬁgure caption and in the text. None of the results or conclusions of the paper are affected. We thank Kang Kim for bringing these errors to our attention. Abstract We report molecular dynamics simulations for a new model of tetrahedral network glass-former, based on short-range spherical potentials. Despite the simplicity of the forceﬁeld employed, our model reproduces some essential physical properties of silica, an archetypal network-forming material. Structural and dynamical properties, including dynamic heterogeneities and the nature of local rearrangements, are investigated in detail and a direct comparison with models of close-packed, fragile glass-formers is performed. The outcome of this comparison is rationalized in terms of the properties of the potential energy surface, focusing on the unstable modes of the stationary points. Our results indicate that the weak degree of dynamic heterogeneity observed in network glass-formers may be attributed to an excess of localized unstable modes, associated with elementary dynamical events such as bond breaking and reformation. In contrast, the more fragile Lennard-Jones mixtures are characterized by a larger fraction of extended unstable modes, which lead to a more cooperative and heterogeneous dynamics. article features online multimedia enhancements (Some ﬁgures in this article are in colour only in the electronic version)
A photolithographic process for fabrication of devices with isolated single-walled carbon nanotubes

We have successfully fabricated devices with isolated single-walled carbon nanotubes (SWNTs) using exclusively standard i-line (365 nm) photolithography. Catalyst islands were patterned with an SU-8-photoresist-based process. This method provides well-defined islands, down to 1 µm in size. The islands are clearly visible with an optical microscope and are used as alignment marks for optical alignment of subsequent layers. SWNTs were grown by chemical vapour deposition (CVD). Contacts to the nanotubes were fabricated by standard photolithography.
Quality assurance of remanufactured components of end-of-life vehicle: A literature review

This objective of this work is to investigate the quality assurance of remanufactured ELV components by distinguished with other sustainable manufacturing stakeholders, 6Rs. The study is focused on developing countries such as China, India, Malaysia, and Brazil as the authors determine whether remanufactured ELV components are significant to the respective countries. Implications of this study are the three remanufacturing research areas classified and discussed: Remanufacturing Process, Remanufacturing Supply Chain, and Sustainable Remanufacturing Industry. The most significant findings in this study classified quality of remanufactured ELV components in terms of quality assurance and quality after business.
Robust bidding strategies and scheduling of a price‐maker microgrid aggregator participating in a pool‐based electricity market

This study presents a model for the activities of the price-maker microgrid aggregator (MGA). In this model, an MGA is considered to aggregate several microgrids (MGs) and be in charge of obtaining an optimal bidding strategy for MGs as well as scheduling their resources and demand. Two price-maker strategies (the marginal and non-marginal strategies for players) are proposed and the robust scheduling and optimal transactions of a price-taker MGA are also obtained in order to analyse different bidding behaviour of MGA. A robust optimisation is used in this model in order to capture uncertainties associated with renewable generation in the worst-case situation. Accordingly, the robust solution is obtained for the optimal scheduling of an MGA participating in the pool-based day-ahead electricity market. The proposed robust bidding strategies and scheduling of a price-maker MGA are obtained considering a hypothetical test system and the results are compared with the bidding strategy and robust scheduling of a price-taker MGA. The results show that the robust scheduling and also the market prices are completely changed for different strategies of the MGA. Also, using the proposed model for the price-maker MGA increases the profits of MGs.
Nucleon Resonances in the π−p → K0Γ Reaction near Threshold

We investigate the two-body reaction π−p → K0Γ within the effective Lagrangian approach and the isobar model. In addition to the “background” contributions from t-channel K* exchange, u-channel Σ(1192) and Σ*(1385) exchanges, and s-channel nucleon pole terms, the contributions from the nucleon resonances N* (1535), N* (1650), and N* (1720) are investigated. It is shown that the inclusion of these nucleon resonances contributions leads to a good description of the experimental total and differential cross sections data at low energy region. The s-channel N* (1535), N* (1650), and N* (1720) resonances and the t-channel K* exchange give the dominant contributions below W = 1.76 GeV, while the s-channel nucleon pole, u-channel Σ(1192) and Σ*(1385) exchanges give the minor contributions.
Experimental Evaluation of the Performance of a Three-Phase Five-Level Cascaded H-Bridge Inverter by Means FPGA-Based Control Board for Grid Connected Applications

Over the last decades, plants devoted to the generation of green energy significantly increased their number, together with the demand of same electrical energy, also stored in battery systems. This fact produced the growth of energy conversion systems with advanced performances with respect to the traditional ones. In this circumstance, multilevel converters play a significant role for their great advantages in performances, flexibility, fault-tolerability, employment of renewable energy sources and storage systems and finally yet importantly reduced filter requirements. In this context, this paper faces the performance of a cascaded H-bridge 5 level inverter in terms of harmonic distortion generated and injected into the grid. Through an accurate analysis that takes into account the pulse width modulation (PWM) multicarrier modulation techniques (phase disposition PD, phase opposition disposition POD, alternative phase opposition disposition APOD, phase shifted PS) and related reference signals (sinusoidal reference; third harmonic injection THI reference, switching frequency optimal SFO reference), a framework of distorting harmonics is presented by comparing twelve cases. The results obtained from the simulations are reproduced and validated in a prototype system of five level cascaded H-bridge multilevel inverter. A deep discussion of control and filtering system is provided to justify the choice of the best modulation technique to adopt.
Some considerations on the accuracy and frequency response of some derivative filters applied to particle image velocimetry vector fields

This paper concerns the computation of derivatives from particle image velocimetry (PIV) velocity fields with the goal of obtaining the vorticity component normal to the plane. A variety of derivative schemes are characterized by their transfer function, taking into account the truncation and noise amplification. The PIV measurement noise is supposed to be a white one in the Fourier space. A spectral approach is used in order to choose the best filter for turbulent flows. The derivative spectra are discussed. An application is presented on a real turbulent flow with two interrogation window sizes and different derivative schemes. The most significant schemes are also applied to a velocity field containing a single vortex. A comparison of the maximum of vorticity obtained with each scheme and through a least-square fit with an Oseen vortex, allows us to quantify the effect of the band pass filter and to select the best scheme.