Miracle-dz/UniFAR-FTUs huggingface dataset:
Raman line profile in polycrystalline silicon

Raman spectroscopy is applied to the study of the structure of polycrystalline silicon films. The analysis of the transversal optical phonon Raman line shows its complex structure consisting of two dominant contributions, centered at about 519 and 517 cm−1 and attributed to two dominant groups of grains with different size. The profile of this Raman line is demonstrated to give deeper information about the film morphology, directly influenced by the deposition temperature in terms of the ratio of amorphous to crystalline phases, as well as the grain-size distribution, and the film stress.
Original pycnometers for volatile liquid density over wide ranges of temperature and pressure: practical example

A novel kind of pycnometer was designed for liquid density measurements suitable to be used over wide ranges of temperature and pressure. Two similar pycnometers have been manufactured and tested with n-nonane 99.7 mol% in the temperature range from 233 K to 313 K at pressure lower than 10 MPa. To validate the procedure, the experimental values of density of an n-nonane sample have been compared with the density values given in the literature by means of the En number. The density uncertainty of n-nonane is found to be 0.16 kg m−3 (0.02%) in the temperature range from 253 K to 313 K and lower than 0.07% between 233 K and 243 K over the whole pressure range tested.
Controllability of McKean–Vlasov Stochastic Integrodifferential Evolution Equation in Hilbert Spaces

Sufficient conditions for controllability of McKean–Vlasov stochastic integrodifferential evolution equation in Hilbert spaces are obtained by using Banach fixed point analysis approach. This paper is motivated primarily by the work of Ahmed and Ding (Stochastic Processes Appl. 1995; 60:65–85), which is extended to a more general class of McKean–Vlasov stochastic integrodifferential equation in Hilbert space for establishing controllability result.
Improved linear shrinkage estimators of large structured covariance matrices (New Advances in Statistical Inference and Its Related Topics)

The problem of estimating large covariance matrices with use of factor models is addressed. In this article, we consider a general class of weighted estimators which includes (i) linear combinations of the sample covariance matrix and the model-based estimator under the factor model and (ii) ridge-type estimators without factors as special cases. The optimal weights in the class are derived, and the plug-in weighted estimators are suggested since the optimal weights depend on unknown parameters. Some asymptotic arguments are given. Numerical results show our methods perform well under both normal and non-normal distributions.
Effects of diffusion and mass flows on C IV and Si IV lines formed in the solar atmosphere

A model for the transition region is derived from an initial interpretation of EUV observations, assuming ionization equilibrium and constant elemental abundance with height. The effects of diffusion and mass flow are then included in the initial model and the emergent profiles of several C IV and Si IV lines are computed. We find that diffusion and mass flows have a strong effect on both the emergent intensity and spectral shape of these lines. Diffusion acts to deplete the transition region of heavy ions to an extent which depends on the detailed temperature and density structure. The net effect is a weighting of the coronal emission relative to that in the transition region. Based on our results, we suggest that the downflows observed in the network in lines of C IV and Si IV could be due to gravitational settling of the ions following their injection, via diffusion, into the corona from spicules. When flows are superposed on our basic diffusion model, the rapid change in elemental abundance characteristic of the model is virtually eliminated and the coronal contribution to the emission in C IV and Si IV lines becomes negligible relative to that in the transition region. Flows havemore » a strong effect on the computed line intensities and introduce large asymmetries into the line shapes. « less
Bulk photoconductive gain in poly(phenylene vinylene) based diodes

We observe large, bulk photoconductive gain (>100) in organic polymer diodes. Photoconductive gain was measured in diode structures employing the soluble polymer poly[2-methoxy,5-(2′-ethyl-hexyloxy)-1, 4-phenylene vinylene] (MEH-PPV) as the active layer. The MEH-PPV layer was either undoped or doped by incorporation of a soluble C60 derivative or PbSe quantum dots. The gain characteristics of the doped and undoped diodes are similar. We present the spectral response, transient response, and bias dependence of the gain. The photoconductive gain is due to the circulation of hole carriers through the diode in response to electrons trapped in the polymer layer. The bulk photoconductive gain reported here is distinct from the previous observations of gain in organic diodes that has been attributed to charge trapping near electrodes which increases the charge injection from that contact. The observed gain is consistent with estimates using previously established charge transport parameters of MEH-PPV.
Stability limits for 'isothermal' cores in globular cluster models - Two-component systems

Stable equilibria of energy truncated models for stellar systems with two masses, m/sub 1/ and m/sub 2/>m/sub 1/, have been calculated. The models used are those that give the best fit to quasi-isothermal cores of one-mass stellar systems in Monte Carlo calculations. A relation is found between stable quasi-isothermal cores and a critical value around 0.16 of S = (M/sub 2//M/sub 1/) x (m/sub 2//m/sub 1/)/sup 3/2/ (with M/sub 2//M/sub 1/ the ratio of total masses) found by Spitzer. Stable quasi-isothermal cores exist for S or =4, they rapidly disappear as S becomes greater than 0.16. It is also found that, in critically stable configurations with S<0.16, massive stars reduce the total binding energy but augment both the escape energy from the core and the degree of equipartition of energy at the center. To the extent that energy-truncated models are mainly good representations of the core, it is concluded that a small number of massive stars (m/sub 2//m/sub 1/< or =10) has a slight stabilizing effect.
Delft Measures Rain Analysing patterns in the rainfall that occurred in the city of Delft during the summer of 2020

Delft Measures Rain is a collaboration project between Smartphones4water(S4W), Delft's technical university and the municipality of Delft. This research aims to elucidate patterns in the rainfall that occurred in the city of Delft during the summer of 2020.Ultimately, this project aims to have a better insight into rain patterns in the municipality of Delft and to communicate back to the citizen scientists what the results of their hard work are. This was achieved by analysing the results of the Citizen Science rain measurements provided by the citizens of Delft via the S4W ODK system, municipality of Delft rain data and the rain data of the KNMI. The measurements taken by the citizen scientists have been compared to the rain data of government institutions to have a better understanding of the differences and similarities between the three datasets collected by different organisations. The three datasets were outlined in an automated Python script. The results show higher spatial resolution that could not be detected by the government gauges. Furthermore, specific precipitation could be detected by the citizen science dataset. Even though there were many inconsistencies with data processing caused by the way in which the data was collected, this citizen science project could prove beneficial in the field of water management.
A Nonmonotone Modified BFGS Algorithm for Nonconvex Unconstrained Optimization Problems

In this paper, a modified BFGS algorithm is proposed to solve unconstrained optimization problems. First, an update formula is recommended to approximate Hessian matrix based on a modified secant condition. Second, thanks to the remarkable nonmonotone line search properties, this work takes advantages of nonmonotone line search strategies. Under some mild conditions, the global convergence properties of the algorithm are established without convexity assumption on the objective function. By the numerical experiments, it is established that the suggested algorithm is promising.
Control of Uncertain Nonlinear Multibody Mechanical Systems

Descriptions of real-life complex multibody mechanical systems are usually uncertain. Two sources of uncertainty are considered in this paper: uncertainties in the knowledge of the physical system and uncertainties in the “given” forces applied to the system. Both types of uncertainty are assumed to be time varying and unknown, yet bounded. In the face of such uncertainties, what is available in hand is therefore just the so-called “nominal system,” which is our best assessment and description of the actual real-life situation. A closed-form equation of motion for a general dynamical system that contains a control force is developed. When applied to a real-life uncertain multibody system, it causes the system to track a desired reference trajectory that is prespecified for the nominal system to follow. Thus, the real-life system’s motion is required to coincide within prespecified error bounds and mimic the motion desired of the nominal system. Uncertainty is handled by a controller based on a generalization of the concept of a sliding surface, which permits the use of a large class of control laws that can be adapted to specific real-life practical limitations on the control force. A set of closed-form equations of motion is obtained for nonlinear, nonautonomous, uncertain, multibody systems that can track a desired reference trajectory that the nominal system is required to follow within prespecified error bounds and thereby satisfy the constraints placed on the nominal system. An example of a simple mechanical system demonstrates the efficacy and ease of implementation of the control methodology. [DOI: 10.1115/1.4025399]
Gravity shear waves atop the cirrus layer of intense convective storms

Recent visual satellite photographs of certain intense convective storms have revealed concentric wave patterns. A model for the generation and growth of these waves is proposed. The proposed initial generating mechanism is similar to the effect noticed when a pebble is dropped into a calm pond. The penetration of the tropopause by overshooting convection is analogous to the pebble's penetration of the water's surface. The model for wave growth involves instability due to the wind shear resulting from the cirrus outflow. This model is based on an equation for the waves' phase speed which is similar to the Helmholtz equation. It, however, does not assume an incompressible atmosphere, but rather assumes density is a logarithmic function of height. Finally, the model is evaluated on the two mid-latitude and three tropical cases. The data indicate that shearing instability may be a significant factor in the appearance of these waves.
Infrared emission and star formation in the central regions of the galaxy IC 342

The face-on Scd galaxy IC 342 has been studied at infrared wavelengths between 1.2 μm and 250 μm and at centimeter radio wavelengths. At 10 μm the nucleus is bright and extended on a scale of 200 pc, with a double structure unlike that of the stars seen at 2 μm. The infrared emission between 8 and 250 μm probably arises from heated dust grains in star formation regions in the disk of the galaxy. The radio emission comes from a region with many of the same spatial features as the 10 μm source; it appears to include both thermal and nonthermal sources. IC 342 is intermediate in luminosity between the Galaxy and NGC 253; the difference can probably be accounted for by a difference in the current rate of star formation at their centers.
Using a Monotonic Density Ratio Model to Find the Asymptotically Optimal Combination of Multiple Diagnostic Tests

ABSTRACT With the advent of new technology, new biomarker studies have become essential in cancer research. To achieve optimal sensitivity and specificity, one needs to combine different diagnostic tests. The celebrated Neyman–Pearson lemma enables us to use the density ratio to optimally combine different diagnostic tests. In this article, we propose a semiparametric model by directly modeling the density ratio between the diseased and nondiseased population as an unspecified monotonic nondecreasing function of a linear or nonlinear combination of multiple diagnostic tests. This method is appealing in that it is not necessary to assume separate models for the diseased and nondiseased populations. Further, the proposed method provides an asymptotically optimal way to combine multiple test results. We use a pool-adjacent-violation-algorithm to find the semiparametric maximum likelihood estimate of the receiver operating characteristic (ROC) curve. Using modern empirical process theory we show cubic root n consistency for the ROC curve and the underlying Euclidean parameter estimation. Extensive simulations show that the proposed method outperforms its competitors. We apply the method to two real-data applications. Supplementary materials for this article are available online.
A model for the formation of optimal vortex rings taking into account viscosity

The evolution of a viscous vortex ring from thin to thick-cored form is considered using an improved asymptotic solution, which is obtained after impressing a spatially uniform drift on the first-order solution of the Navier–Stokes equations. The obtained class of rings can be considered as the viscous analog solution to the Norbury vortices and classified in terms of the ratio of their initial outer radius to the core radius. The model agrees with the reported theoretical and experimental results referring to the post-formation and the formation stages. By using the matching procedure suggested earlier and the obtained properties of the viscous vortex ring, it is found that when the length-to-diameter aspect ratio L∕D reaches the limiting value 4.0 (“formation number”), the appropriate values of the normalized energy and circulation become around 0.3 and 2.0, respectively. An approach that enables to predict the “formation number” is proposed.
Electronic structure of conducting polymers: Limitations of oligomer extrapolation approximations and effects of heteroatoms

Density-functional methods are used to analyze the scaling of discrete oligomeric π-electron conducting molecules towards idealized isolated polymer chains, treated in periodic boundary conditions. The band gaps of a series of conjugated oligomers of incrementally increasing lengths exactly fit a nearly-free-electron molecular-orbital picture and exhibit a smooth deviation from the classical empirical "I/N" trend for long oligomers and infinite polymers. The calculations also show a smooth convergence of bond lengths. The full band structures and densities of states of a polyacetylene, polypyrrole, polyfuran, and polythiophene show that band crossing, localized bands, and other effects cannot be accurately determined from simple extrapolation of oligomer electronic structures. Systematic comparisons of the electronic structure variations of the polymers investigated indicate that the electron affinity, rather than the electronegativity of the heteroatom or the bond-length alternation of the conjugated backbone, significantly affects the band gap of the resulting polymer as indicated by the presence of heteroatom states in the partial density of states of the conduction band, requiring revision of previous semiempirical analyses. Consequences for doping processes are also studied, along with a comparison of valence bandwidths, conduction bandwidths, and carrier effective masses as a function of heteroatom.
Student perception of the impact of mathematics support in higher education

Mathematics support in higher education has become increasingly widespread over the past two decades, particularly in the UK, Ireland and Australia. Despite this, reliable evaluation of mathematics support continues to present challenges for those working in this area. One reason is because ideally, properly structured support should function as an integral part of the overall educational experience of the student, in tandem with lectures and tutorials. When this occurs, it makes it difficult to isolate the impact of mathematics support from these other entities. In this paper, the results of a large-scale nationwide survey conducted with first-year service mathematics students in nine higher education institutes in Ireland are considered, exploring students’ perceptions of the impact of mathematics support upon their retention, mathematical confidence, examination performance and overall ability to cope with the mathematical demands they face. Students were extremely positive about the effectiveness of mathematics support in all of these areas, providing valuable insights into the value of learning support in mathematics.
Thresholds for formant‐frequency discrimination in isolated vowels

The threshold of discrimination (or DL) of a shift in formant frequency is thought to be in the range of 3%‐6%, based on the oft‐replicated results of Flanagan [J. Acoust. Soc. Am. 27, 613‐617 (1955)]. This range may not, however, represent the limits of resolution in the auditory system because, for most experiments, subjects were not trained and several pairs of stimuli were presented within trial blocks. In present experiments, thresholds were obtained from well‐trained subjects listening to vowels under minimal stimulus uncertainty using an adaptive‐tracking paradigm. Thresholds were determined for increments and decrements in F 1 and F 2 for ten synthetic, steady‐state vowels modeling a female talker. Results indicated that the DL for both increments and decrements in frequency of the formants increased linearly as a function of frequency, with the exception of 50% higher thresholds where a harmonic fell exactly on the formant frequency. About 80% of the ΔF/F ratios were below 0.02 for formant freque.
Efficient estimation for case‐cohort studies

The author considers time‐to‐event data from case‐cohort designs. As existing methods are either inefficient or based on restrictive assumptions concerning the censoring mechanism, he proposes a semi‐parametrically efficient estimator under the usual assumptions for Cox regression models. The estimator in question is obtained by a one‐step Newton‐Raphson approximation that solves the efficient score equations with initial value obtained from an existing method. The author proves that the estimator is consistent, asymptotically efficient and normally distributed in the limit. He also resorts to simulations to show that the proposed estimator performs well in finite samples and that it considerably improves the efficiency of existing pseudo‐likelihood estimators when a correlate of the missing covariate is available. Although he focuses on the situation where covariates are discrete, the author also explores how the method can be applied to models with continuous covariates.
Primal-Dual Instrumental Variable Estimators

Abstract This paper gives a primal-dual derivation of the Least Squares Support Vector Machine (LS-SVM) using Instrumental Variables (IVs), denoted simply as the Primal-dual Instrumental Variable Estimator. Then we propose a convex optimization approach for learning the optimal instruments. Besides the traditional argumentation for the use of IVs, the primal-dual derivation gives an interesting other advantage, namely that the complexity of the system to be solved is expressed in the number of instruments, rather than in the number of samples as typically the case for SVM and LS-SVM formulations. This note explores some exciting issues in the design and analysis of such estimator.
EMS-Vision: combining on- and off-road driving

In the past, work at the Universitat der Bundeswehr Muenchen (UBM) has been focused on autonomous road vehicles. During the last four years the Expectation-based Multi-focal Saccadic Vision (EMS-Vision) system has been developed and implemented. EMS-Vision is the 3rd generation dynamic vision system following the 4-D approach. The explicit representation of the own capabilities combined with a complex control and information flow allows the implementation of decision units for goal oriented activation of locomotion and perception. Due to this general approach and in contrast to former UBM systems that were specially designed and optimized for certain limited scenarios and domains, e.g., road following on Autobahnen, the EMS-Vision system can handle complex driving missions spanning multiple domains. It has been realized on a decentralized parallel hardware structure, exclusively built of commercial off-the-shelf components, in both UBM test vehicles VaMoRs and VaMP. Results from an autonomously performed mission on the UBM campus are discussed.
On the dynamics of hurricane‐like vortices in vertical‐shear flows

A simple two‐layer analogue model is used to elucidate aspects of vortex motion in a vertically sheared zonal flow. The model is based on the idea that a vortex can be considered as the sum of a pair of barotropic vortices, one whose vorticity, or potential vorticity, resides in the upper layer and the other whose vorticity resides in the lower layer. Each vortex has an associated tangential velocity distribution in the other layer, which advects the vortex in that layer. The strength of this velocity distribution is characterized by a coupling parameter, which, in the case of quasi‐geostrophic vortices, is related to the Rossby depth scale. Besides their mutual advection, the component vortices are differentially advected by vertical shear. The model leads to a set of coupled ordinary differential equations for the motion of each component vortex, which may be solved analytically in certain circumstances. The calculations indicate two types of flow behaviour according to the strength of the component vortices, the degree of vertical coupling and the strength of the shear. For weak shear and/or strong vortices and strong coupling, the vortices rotate around each other as their mean centre translates with a fraction of the mean zonal flow. For Strong shear and/or weak vortices and weak coupling, the vortices undergo a partial rotation while they are in proximity, but become progressively separated by the shear. The calculations are an aid to understanding the range of behaviour of vortices in shear in numerical calculations by other authors, and it is reasonable to presume that the processes represented by the model are fundamental processes in tropical cyclones also.
Extraneous frequencies generated in air carrying intense sound waves

The exact equation of the propagation of plane sound waves in air is not linear and consequently harmonics and combination tones are generated. The pressure of these extraneous frequencies in terms of the fundamental pressure, frequency, and distance from the source has been mathematically determined by Rayleigh, Lamb and others. These equations have been applied to an exponential horn. Measurements of the second harmonic and combination tones have been made at various points within a long tube, and in front of an exponential horn. Measurements, in general, agree with theory, but the absolute values are lower than the calculated values.