Miracle-dz/UniFAR-FTUs huggingface dataset:
Image segmentation based on rough set theory and neural networks

A new method for image segmentation based on rough set theory and neural networks is proposed. First, the rough set is used to reduce the image attributes, extract rules, draw out the key components of image as the input of the neural networks; then, it ascertains the number of neurons in the hidden layers according to the rules and revises the weight of the neural networks by the attribute essentiality of rough set theory. Experimental results show that the method has a greater ability on resisting noise. At the same time, it solves the problem that happens in image segmentation by only using neural networks, such as "blind spots" of the neurons, the complicated structure of the networks, slower speed of constringency and so on. It greatly shortens the training time of the networks while improving the result of segmentation.
Reflection of the s0 Lamb mode from a flat bottom circular hole

A study of the interaction of the s0 Lamb wave with a flat bottom circular hole in a plate is presented. The majority of the study was performed using a three-dimensional finite element model, representing an area of the plate with a circular flat-bottom hole (33% or 50% of the plate thickness deep). In the first part of the work, the incident s0 wave was specified to be a plane wave. The specular reflection was predicted and showed the importance of several factors: the interference phenomena between reflections from the leading and trailing edges of the hole and secondary reflections, and the decay in amplitude of the reflected wave. Some results of this case are also compared with analytical solutions based on modal superposition. In the second part of the work, the Lamb wave mode is excited by a small circular source. The specular reflection is predicted and compared with experimental results. An assessment is made of the significance of the path lengths, wavelengths, and defect sizes on the reflectio.
Computational Investigation of Three-dimensional Unsteady Flowfield Characteristics around Insects' Flapping Flight

This paper investigates the unsteady flowfield characteristics around three-dimensional insect flapping motion under forward flight conditions. A realistic wing trajectory, called the "figure-of-eight" motion, is extracted from a blowfly's (phormia regina) tethered flight experiment under a freestream velocity of 2.75 m/s. In the authors' preliminary research [Lee, J., Kim, J., and Kim, C. , "Numerical Study on the Unsteady-Force-Generation Mechanism of Insect Flapping Motion," AIAA Journal, Vol. 46, No. 7, 2008, pp. 1835―1848. doi:10.2514/1.35646], the two-dimensional blowfly's wing motion was computationally investigated, and the results revealed very interesting and distinctive vortical flowfields, which provide a decisive clue in understanding the rapid maneuverability of insects' flight. On the line of continuous efforts, the present work investigates the role of three-dimensional vortical structure in unsteady aerodynamic force generation. Detailed numerical simulation and analysis on three-dimensional flapping motion are conducted, and interesting flow features of insects' flapping flight are observed, such as the existence of a spanwise flow component, leading-edge vortex, wing tip vortex, trailing-edge vortex, and various forms of vortex tubes and vortex rings. It turns out that vortical structures play a crucial role in determining unsteady characteristics of lift and thrust generation. In particular, the vortex pairing and vortex staying phenomena, which have been observed in two-dimensional flapping motion, are also observed but with a more complicated pattern. On top of that, distinctive lift and thrust generation is observed owing to three-dimensional wing shape, trajectory, and vortex structure. Consequently, the results of the present work provide an important clue in understanding generation of aerodynamic force for rapid maneuverability in insects' flight.
Radiation by Plasma Waves in a Homogeneous Plasma

Conversion of the energy of a plasma wave into electromagnetic radiation as a result of plasma wave scattering on density fluctuations of a statistical nature in a homogeneous plasma is treated. Boltzmann-Vlasov equations and Maxwell equations are used, and plasma wave scattering within a localized region of the main plasma is handled as a stationary problem. Equations for the scattered fields having both the longitudinal and the transverse mode are given using the Born approximation. A far-distance solution of the fields is also obtained, using a Fourier transform over space and time; and radiation intensities are expressed in terms of mass and charge fluctuations. The results are compared with works on non-uniform models. (D.C.W.)
Extremal problems and harmonic interpolation on open Riemann surfaces

1. The ultimate purpose of the present paper is to study interpolation of harmonic and analytic functions on open Riemann surfaces W. We shall, however, first take a less restricted viewpoint and consider, in general, extremal problems on Riemann surfaces. Extrema of given functionals can often be immediately found in the special case where W is compact and bounded by a finite number of analytic Jordan curves. The difficulties arise when the contours are arbitrary or, as is always the case for an infinite genus, the boundary exists in an ideal sense only. With this in view, we shall start with a theorem for reducing extremal problems from the general case of an open Riemann surface W to the special case just mentioned. The content of the reduction theorem (no. 5) will be, roughly speaking, as follows: If the functional to be minimized increases with the region, and if the minimizing functions on compact subregions Wn with analytic boundaries form a normal family, then the solvability of the extremal problem for Wn implies that for W. 2. The reduction theorem will enable us to establish a rather general theorem on minimizing functionals of harmonic functions on Riemann surfaces. We consider the class of single-valued harmonic functions p with a finite number of prescribed poles or logarithmic singularities f ,• (i = 1, • • • , n) on W. The expansions of p about J"i have the form
The Development of a Volume-Averaged Entropy-Generation Function for Nonequilibrium Heat Transfer in High-Conductivity Porous Foams

The study of entropy-generation characteristics is of great utility in the field of enhanced heat transfer. Previously, entropy-generation studies involving porous media have been restricted to local thermal equilibrium conditions; however, this assumption is not applicable to high-conductivity foams. In this work, a volume-averaged entropy-generation function suitable for use in the analysis of high-conductivity foams is developed for the condition of local thermal nonequilibrium. The constraints imposed in the derivation are reasonable for a wide variety of realistic scenarios. The derived model is employed in the analysis of a simple enhanced heat transfer device.
Effects of thermally induced aberrations on radially and azimuthally polarized beams

We investigate the radial and azimuthal polarization degradation in high-power lasers induced by thermal aberrations. Thermal and propagation simulations, supported by measurements, show that thermally induced wavefront aberrations can strongly affect the polarization. Depolarization induced by primary aberrations and high-order azimuthal aberrations that arise in high-power rod-based lasers was analyzed along the beam propagation axis. Implications for pump-chamber design and amplifier architecture, in order to eliminate the depolarization effect, are discussed.
Supervisory control of nondeterministic systems under partial observation

In this paper we extend our earlier work on supervisory control of nondeterministic discrete event systems (DES) using prioritized synchronization as the control mechanism and trajectory model as the modeling formalism by considering design of supervisors under partial observation. We introduce the notion of observation-compatible systems and show that prioritized synchronous composition of observation-compatible systems can be used as a mechanism of control of nondeterministic systems under partial observation in presence of driven events. Conditions for the existence of a supervisor in the above setting are obtained. Although these conditions are similar to the standard conditions of controllability and observability found in literature, they are significantly different, as they depend on the trajectory model of the plant as opposed to its language model. <<ETX>>
Expressing the decoupled equations of motion for the Green's function as a partial sum of Feynman diagrams

Abstract It is shown that any given decoupling of the equations of motion for the propagators of an interacting Fermi system is equivalent to a particular partial sum of Feynman diagrams. This result is established for many-time propagators in a straightforward way by iterating in the diagrammatic form of the equations of motion. The iteration method does not work for two-time propagators, but we are able to present an alternative argument which makes it plausible that the result holds true in this case as well. The decouplings leading to the Hartree-Fock, ladder, and ring diagram (RPA) partial sums are discussed in detail. It is conjectured that the reverse correspondence is not true, i.e. to any given partial sum there does not necessarily correspond a decoupling.
Development of a personal dust monitor with a piezoelectric quartz crystal sensor

A monitoring system using the collection technique of electrostatic precipitation on to a piezoelectric sensing element is examined. The transduction mechanism is the change in the resonant frequency of the sensing element from its unloaded nominal value of 9 MHz caused by the collected dust. The monitor had the three main design areas (point-to-plane distance, precipitator voltage and electrode-to-dust-inlet distance) optimized at a flow rate of approximately . This led to collection efficiencies greater than 97% with crystal mass sensitivity constants in the range for the aerosol Arizona Road Dust. The total sampling time is limited by overloading of the sensing element by dust. A method of extending the sampling time by using compressed air to clean the sensing element is described.
Comparison of Results from a Meandering-Plume Model with Measured Atmospheric Tracer Concentration Fluctuations

Abstract Measured wind-azimuth data are used in a simple meandering-plume model to predict observed SF6 concentration fluctuations measured downwind of a point source during a range of stability conditions. The meander component of plume diffusion is calculated as the running mean of wind-azimuth signal using travel time as the smoothing time. Instantaneous plume coefficients are derived from measured peak instantaneous concentrations in a subset of the data for distances less than 1 km. These empirical plume coefficients are shown to be a linear function of the standard deviation of the residual azimuth signal after the meander component is removed (σθI = 0.285 σ¯θR). Instantaneous concentration time series predicted with the model using the observed azimuth data are quite similar to observed time series. Sensitivity analyses indicate that the model predictions are strongly dependent upon the averaging period used to filter the azimuth signal but that the instantaneous plume width is only a weak function.
Testing for Independence of Irrelevant Alternatives

In a recent article, Zhang and Hoffman discuss the use of discrete choice logit models in sociological research. In the present article, the authors estimate a multinomial logit model of U.K. Magistrates Courts sentencing using a data set collected by the National Association for the Care and Resettlement of Offenders (NACRO) and test the independence of irrelevant alternatives (IIA) property using six tests. Conducting the tests with the appropriate large sample critical values, the authors find that the acceptance or rejection of IIA depends both on which test and which variant of a given test is used. The authors then use simulation techniques to assess the size and power performance of the tests. The empirical example is revisited with the inferences performed using empirical critical values obtained by simulation, and the resultant inferences are compared. The results show that empirical workers should exercise caution when testing for IIA.
Observation of terahertz absorption signatures in microliter DNA solutions

Strong, repeatable Terahertz (THz) signatures are measured in small samples of DNA solution using a THz photomixing spectrometer with custom conical-horn coupling. The DNA specimen is linear, single-stranded (ss), 13-mer polynucleotide, and is diluted in buffer solution to have a concentration of 0.15 μmol/ml. The strongest signature is centered ∼717 GHz, and has a strength of 2.5 × 1016 cm−1/mol, linewidth 48 GHz, and damping time of 6.6 ps. The origin of the signature is attributed to the hydrogen bond of locally cross-linked ssDNAs.
An omnidirectional broadband mirror design inspired by biological multilayer reflectors

Biological multilayer reflectors are common in nature and some are able to reflect light across a broad range of wavelengths with a low degree of polarization over all angles of incidence. This inspired us to examine theoretically possible mechanisms that would allow stacks of biological materials to produce broadband omnidirectional reflections. Through the application of anisotropic multilayer theory, we establish that the degree of polarization of light reflected from the structure can be neutralized by birefringent layers with variations in the orientation of their optics axis and random variations in their optical thickness. The degree of polarization of reflected light decreases with the number of crystal layers and can be made arbitrarily low to produce true omnidirectional reflection. We also show that systematic variation in orientation and layer thickness can produce the same effect. This reflective structure is distinct from existing omnidirectional mirrors and can produce omnidirectional reflection even if the refractive index of the external environment is same as the low index isotropic layers.
Polygonal products of residually finite groups

A group G is called cyclic subgroup separable for the cyclic subgroup H if for each x ∈ G\H, there exists a normal subgroup N of finite index in G such that x / ∈ HN . Clearly a cyclic subgroup separable group is residually finite. In this note we show that certain polygonal products of cyclic subgroup separable groups amalgamating normal subgroups are again cyclic subgroup separable. We then apply our results to polygonal products of polycyclic-by-finite groups and free-byfinite groups.
Nonlinear programming-based sliding mode control with an application in the stabilization of an Acrobot

A new approach to compute optimal forcing functions for nonlinear dynamic systems expressed by differential equations and stemming from the sliding mode control (SMC) problems is presented. SMC input achieves generation of a desired trajectory in two phases. In the first phase, the input is designed to steer the state of the nonlinear dynamic system towards a stable (hyper) surface (in practice, it is generally a subspace) in the state space. The second phase starts once the state enters a prespecified neighbourhood of the surface. In this phase, the control input is required to drive the system state towards the origin while keeping it in this neighbourhood. It is shown that by appropriate selection of the objective functions and the constraints, it is possible to model both phases of this problem in the form of constrained optimization problems, which provide an optimal solution direction and thus improve the chattering. Generally, these problems are not convex and therefore require a special solution approach. The modified subgradient algorithm, which serves for solving a large class of nonconvex optimization problems, is used here for solving the optimization problems so constructed. This article also proposes a generalized optimization problem with a unified objective function by taking a weighted sum of two objectives representing the two stages. Validity of the approach of this work is illustrated by stabilizing a two-link planar robot manipulator.
Counting on the basics: mathematical skills among tertiary entrants

This study reports on basic, mostly pre-senior mathematical skills, as measured by a multiple choice questionnaire, of 566 students enrolled in a first year introductory data analysis subject within a science or broadly scientific degree programme. Most students had previously undertaken a senior high-school algebra and calculus based mathematics subject. Rasch analysis was used to validate the questionnaire and assist in the description of levels of skill. General linear models demonstrated that a student's skills score depended on the result obtained in senior mathematics, whether or not the student was a mathematics student, gender, whether or not higher level mathematics had been studied, self-efficacy and year. It is concluded that in order to have full and confident use of basic, pre-senior mathematical skills, algebra-based mathematics needs to be studied beyond this level.
Thermal instabilities in rapidly rotating systems

Thermal instabilities of a contained fluid are investigated for a fairly general class of problems in which the dynamics are dominated by the effects of rotation. In systems of constant depth in the direction of the axis of rotation the instability develops when the buoyancy forces suffice to overcome the stabilizing effects of thermal conduction and of viscous dissipation in the Ekman boundary layers. Owing to the Taylor–Proudman theorem, a slight gradient in depth exerts a strongly stabilizing influence. The theory is applied to describe the instability of the ‘lower symmetric régime’ in the rotating annulus experiments at high rotation rates. An example of geophysical relevance is the instability of a self-gravitating, internally heated, rotating fluid sphere. The results of the perturbation theory for this problem agree reasonably well with the results of an extension of the analysis by Roberts (1968).
The Optical Signatures of Magnetospheric Phenomena at the End of the Main Sequence and Beyond

In recent years, very low mass stars and brown dwarfs, togeth er known as ultracool dwarfs, have unexpectedly been detected as a radio transient source , where periodic bursts of radio emission were also discovered. Periodicity has subsequ ently been detected in H α and other photometric data from a number of these objects. It rem ained unclear whether this periodic behavior was related to the presence of the periodi c pulsed radio emission. This thesis investigates this possible connection, and present s multi-epoch periodic photometric variability from a lengthy campaign encompassing six ra dio detected ultracool dwarfs, spanning the∼M8 L3.5 spectral range. These include the M tight binary dwa rf LP 34925AB and L tight binary dwarf 2MASS J0746+2000AB, as well as t he M8.5 dwarf LSR J1835+3259, the M9 dwarf TVLM 513-46546, the M9.5 dwarf BRI 0 021-0214, and the L3.5 dwarf 2MASS J0036+18. Five of these dwarfs exhibit peri odic photometric variability, where three of these are newly discovered. One other sho w persistent variability, with the possibility of periodicity detected in the data. This wo rk was primarily carried out using the GUFI photometer (Galway Ultra Fast Imager), an instrume nt commissioned during this campaign to specifically detect optical signatures from the se objects, currently stationed on the 1.83 m Vatican Advanced Technology Telescope, on Mt. Gra ham, Arizona. We sought to investigate the ubiquity of periodic optical variabilit y n both quiescent and time-variable radio detected ultracool dwarfs. The periodic variability is associated with the rotation of the dwarf in all cases and we consider a number of causal photo spheric phenomena, including magnetic cool spots and atmospheric dust. An exciting al ternative may associate the periodic variability with chromospheric auroral hot spots directly related to the previously discovered periodic radio emission. One dwarf in this study is part of this larger study, and we present the photometric results possibly associated wit h this phenomenon. In addition to the search for optical signatures from these u ltracool dwarfs, and based on the newly discovered rotation periods for the binary dwar fs, we investigate the orbital
Low-cost, high-sensitivity SERS nano-bio-chip for kinase profiling, drug monitoring and environmental detection: a translational platform technology

The interaction of biomolecules and solid-state nanomaterials at the nano-bio interfaces is a long-lasting research topic in nanotechnology. Historically, fundamental problems, such as the electron transfer, energy transfer, and plasmonic interaction at the bio-nano interfaces, have been intensively studied, and revolutionary technologies, such as molecular electronics, peptide chips, nanoplasmonic sensors, have been created. With the combined effort of molecular dynamics simulation and surface-enhanced Raman spectroscopy, we studied the external electric field-induced conformation changes of dodecapeptide probes tethered to a nanostructured metallic surface. Through this study, we demonstrated a reversible manipulation of the biomolecule conformations as well as an in situ eletro-optical detection of the subnanometer conformational changes at the bio-nano interfaces. Based on the proof-of-concept established in this study, we further propose a novel nanophotonic peptide phosphorylation sensor for high-sensitive peptide kinase profiling. We have also demonstrated the same SERS nano-bio-chip can be used for environmental monitoring applications, such as detection of contaminants in drinking water at ultralow concentrates. The fabrication of this nanosensor is based on a single step, lithography-less nanomanufacturing process, which can produce hundreds of these chips in several minutes with nearly 100% yield and uniformity. Therefore, the demonstrated research can be readily translated into industrial mass productions.
Improving charge injection in high-mobility rubrene crystals: From contact-limited to channel-dominated transistors

With progressively improving charge carrier mobility in organic semiconductors and miniaturization of organic field-effect transistors (OFETs), low contact resistances become ever more important. To study the capabilities of metal electrodes in OFETs and to explore the transition from contact-limited to channel-dominated transistor operation, we used flip-crystal FETs with gold electrodes having different contact resistances Rc to high-quality rubrene crystals. 4-terminal transfer and output measurements reveal that Rc decreases from 105–106 Ω cm for 15 min air exposure to 3 × 103 Ωcm for at least 5 h air exposure of the gold electrodes before the flip-crystal FET is assembled. We conclude the reduction of Rc to be caused by a growing contamination layer on the gold electrodes that weakens the electrostatic coupling between rubrene crystal and gold electrode, and lowers the Schottky contact diode parameter V0. In channel-dominated (low Rc) FETs, the mobility is in the range of 10–17 cm2/(Vs); in contrast,.