Miracle-dz/UniFAR-FTUs huggingface dataset:
Entropy Generation Through Heat and Fluid Flow

The first textbook to bridge the gap between three cornerstones of engineering education: fluid mechanics, thermodynamics and heat transfer. It provides an effective method to teach the thermodynamic (second law) aspects of heat and fluid flow processes, and shows how to use such processes in the design of energy-efficient devices. The text offers a wide range of original research to support the entropy generation minimazation'' philosophy and includes 250 references in the field of thermodynamic optimization and the thermodynamics of heat and fluid flow.
Studying turbulence using direct numerical simulation: 1987 Center for Turbulence Research NASA Ames/Stanford Summer Programme

This paper is an account of a summer programme for the study of the ideas and models of turbulent flows, using the results of direct numerical stimulations of the Navier-Stokes equations. These results had been obtained on the computers and stored as accessible databases at the Center for Turbulence Research (CTR) of NASA Ames Research Center and Stanford University. At this first summer programme, some 32 visiting researchers joined those at the CTR to test hypotheses and models in five aspects of turbulence research: turbulence decomposition, bifurcation and chaos; two-point closure (or k-space) modelling; structure of turbulent boundary layers; Reynolds-stress modelling; scalar transport and reacting flows. A number of new results emerged including: computation of space and space-time correlations in isotropic turbulence can be related to each other and modelled in terms of the advection of small scales by large-scale motion; the wall layer in turbulent boundary layers is dominated by shear layers which protrude into the outer layers, and have long lifetimes; some aspects of the ejection mechanism for these layers can be described in terms of the two-dimensional finite-amplitude Navier-Stokes solutions; a self-similar form of the two-point, cross-correlation data of the turbulence in boundary layers (when normalized by the r.m.s. value at the furthest point from the wall) shows how both the blocking of eddies by the wall and straining by the mean shear control the lengthscales; the intercomponent transfer (pressure-strain) is highly localized in space, usually in regions of concentrated vorticity; conditioned pressure gradients are linear in the conditioning of velocity and independent of vorticity in homogeneous shear flow; some features of coherent structures in the boundary layer are similar to experimental measurements of structures in mixing-layers, jets and wakes. The availability of comprehensive velocity and pressure data certainly helps the investigation of concepts and models. But a striking feature of the summer programme was the diversity of interpretation of the same computed velocity fields. There are few signs of any convergence in turbulence research! But with new computational facilities the divergent approaches can at least be related to each other.
On the identification of elastoviscoplastic constitutive laws from indentation tests

This paper addresses the identification of the parameters of a nonlinear constitutive law from indentation tests. The identification problem is considered as a constrained minimization problem and the gradient is computed using the adjoint state method, in spite of the difficulties of the underlying contact problem. This provides a general framework to perform optimization in some problems involving contact conditions and nonlinear material behaviour. The case of a Maxwell viscoelastic and a Norton-Hoff elastoviscoplastic constitutive law are treated extensively and a series of numerical identification examples are shown.
The Abundance of Interstellar Oxygen toward Orion: Evidence for Recent Infall?

We present high S/N (greater than 800) Goddard High-Resolution Spectrograph (GHRS) observations of the weak interstellar O I lambda 1356 absorption in the low-density sight lines toward iota Ori and kappa Ori. By comparing these data with observations toward more reddened stars, we find no evidence of density-dependent depletion from the gas phase for oxygen. The derived total oxygen abundance (gas plus grains) towards iota Ori and kappa Ori is consistent with stellar and nebular determinations in Orion at a level that is one-half the solar value. We speculate that the O/H abundance ratio is lower in Orion compared to the Sun because the local Milky Way has suffered a recent infall of metal-poor material, perhaps from the Magellanic Stream.
Inhomogeneous Dependence Modeling with Time-Varying Copulae

Measuring dependence in multivariate time series is tantamount to modeling its dynamic structure in space and time. In risk management, the nonnormal behavior of most financial time series calls for non-Gaussian dependences. The correct modeling of non-Gaussian dependences is, therefore, a key issue in the analysis of multivariate time series. In this article we use copula functions with adaptively estimated time-varying parameters for modeling the distribution of returns. Furthermore, we apply copulae to the estimation of Value-at-Risk of portfolios and show their better performance over the RiskMetrics approach.
Flow induced vibration of two rigidly coupled circular cylinders in tandem and side-by-side arrangements at a low Reynolds number of 150

Flow induced vibration of two rigidly coupled identical circular cylinders in tandem and side-by-side arrangements at a low Reynolds number of 150 is studied numerically. The two cylinders vibrate in the cross-flow direction and have the same displacement. The Navier-Stokes equations are solved by the finite element method and the equation of motion of the cylinders is solved by the fourth-order Runge-Kutta algorithm. Simulations are conducted for a constant mass ratio of 2 and the gap ratios (defined as the ratio of the centre-to-centre distance between the two cylinders L to the cylinder diameter D) of 1.5, 2, 4, and 6. The reduced velocities range from 0.5 to 15 with an increment of 0.5 for the tandem arrangement and from 0.5 to 30 with an increment of 0.5 for the side-by-side arrangement. It is found that the gap between the two cylinders has significant effect on the response. For a tandem arrangement, the lock-in regime of the reduced velocity is narrower than that of a single cylinder for L/D = 1.5.
The state of molecular gas in the Small Magellanic Cloud

Abstract We compare the resolved properties of giant molecular clouds (GMCs) in the Small Magellanic Cloud (SMC) and other low mass galaxies to those in more massive spirals. When measured using CO line emission, differences among the various populations of GMCs are fairly small. We contrast this result with the view afforded by dust emission in the Small Magellanic Cloud. Comparing temperature-corrected dust opacity to the distribution of H i suggests extended envelopes of CO-free H2, implying that CO traces only the highest density H2 in the SMC. Including this CO-free H2, the gas depletion time, H2-to-H i ratio, and H2-to-stellar mass/light ratio in the SMC are all typical of those found in more massive irregular galaxies.
Experimental Study on Structure of Gas Flow in Tube Banks with Tube Axes Normal to Flow : Part 1, Karman Vortex Flow from Two Tubes at Various Spacings

A gas flow in and behind tube banks with tuber axes normal to the gas flow is highly turbulent containing numerous vortices of different sizes and intensities. Each vortex in this complicated wake is the result of a periodic generation, and the periodicity sometimes induces serious vibration problems in steam generators and heat exchangers. The structure of the flow may be treated ass a complex synthesized result of Karman vortex flow. This paper is the first report of a series of studies carried out form the above mentioned viewpoint, and presents the experimental results about a Karman vortex flow from two tubes at various spacings. The vortex formation region was visualized by means of the Schlieren method and was recorded by a 16mm movie camera. The vortex shedding frequency was systematically studied. The frequency for two tubes is entirely different from that for a single tube. It was found that the size of the vortex formation domain has a dominant effect on the frequency.
Gaussian tricritical behavior of heat capacity at the smectic-A-smectic-C liquid crystal transition.

High resolution ac calorimetric measurements have been carried out near the smectic-$A$\char22{}smectic-$C$ phase transition in a racemic mixture of 4-(1-methylheptyloxycarbonyl)phenyl 4\ensuremath{'}-octyloxybiphenyl-4-carboxylate (MHPOBC). The heat capacity data show a distinct pretransitional excess above the transition temperature as well as below it. Analysis of the data reveals Gaussian tricritical behavior of this transition. It is also found that the anomaly is described well with the renormalization-group expression with corrections-to-scaling terms.
The effects of surfactants on drop deformation and breakup

The effects of surface-active agents on drop deformation and breakup in extensional flows at low Reynolds numbers are described. In this free-boundary problem, determination of the interfacial velocity requires knowledge of the distribution of surfactant, which, in turn, requires knowledge of the interfacial velocity field. We account for this explicit coupling of the unknown drop shape and the evolving surfactant distribution. An analytical result valid for nearly spherical distortions is presented first. Finite drop deformation is studied numerically using the boundary-integral method in conjunction with the time-dependent convective–diffusion equation for surfactant transport. This procedure accurately follows interfacial tension variations, produced by non-uniform surfactant distribution, on the evolving interface. The numerical method allows for an arbitrary equation of state relating interfacial tension to the local concentration of surfactant, although calculations are presented only for the common linear equation of state. Also, only the case of insoluble surfactant is studied. The analytical and numerical results indicate that at low capillary numbers the presence of surfactant causes larger deformation than would occur for a drop with a constant interfacial tension equal to the initial equilibrium value. The increased deformation occurs owing to surfactant being swept to the end of the drop where it acts to locally lower the interfacial tension, which therefore requires increased deformation to satisfy the normal stress balance. However, at larger capillary numbers and finite deformations, this convective effect competes with ‘dilution’ of the surfactant due to interfacial area increases. These two different effects of surface-active material are illustrated and discussed and their influence on the critical capillary number for breakup is presented.
Bragg diffraction of an atom laser by an optical standing wave

We derive the exact explicit analytical expressions of incident and diffracted atom lasers and their difference in phase from the Bragg diffraction of an atom laser from an optical standing wave in the presence of two-body atomic interactions. These expressions demonstrate that two-body atomic interactions may significantly affect the Bragg diffraction of an atom laser from an optical standing wave, and they provide a convenient basis for discussing and designing the future Bragg devices of strong atom lasers.
Active Control of a Stalled Airfoil Through Steady or Unsteady Actuation Jets

The active control of the leading-edge (LE) separation on the suction surface of a stalled airfoil (NACA 0012) at a Reynolds number of 106 based on the chord length is investigated through a computational study. The actuator is a steady or unsteady jet located on the suction surface of the airfoil. Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations are solved on hybrid meshes with the Spalart–Allmaras turbulence model. Simulations are used to characterize the effects of the steady and unsteady actuation on the separated flows for a large range of angle of attack (0<a<28 deg). Parametric studies are carried out in the actuator design-space to investigate the control effectiveness and robustness. An optimal actuator position, angle, and frequency for the stalled angle of attack a¼19 deg are found. A significant increase of the lift coefficient is obtained (+84% with respect to the uncontrolled reference flow), and the stall is delayed from angle of attack of 18 deg to more than 25 deg. The physical nonlinear coupling between the actuator position, velocity angle, and frequency is investigated. The critical influence of the actuator location relative to the separation location is emphasized.
Improvement of a Film-Cooled Blade by Application of the Conjugate Calculation Technique

The conjugate calculation technique has been used for the three-dimensional thermal load prediction of a film-cooled test blade of a modern gas turbine. Thus, it becomes possible to take into account the interaction of internal flows, external flow, and heat transfer without the prescription of heat transfer coefficients. The numerical models consist of all internal flow passages and cooling hole rows, including shaped holes. Based on the results, deficiencies of the test configuration close to the leading edge region and in the blade tip region have been detected, which lead to hot spots and surface areas of high thermal load. These regions of high thermal load have been confirmed by thermal index paint measurements in good agreement to the conjugate calculation results. Based on the experimental and numerical results, recommendations for the improvement of the blade cooling were derived and an improved blade-cooling configuration has been designed. The conjugate calculation results, as well as new measurement data, show that the changes in the cooling design have been successful with respect to cooling performance. Regions of high thermal load have vanished, and effective cooling is reached for all critical parts of the test blade.
Lasso regression in sparse linear model with ' -mixing errors

This paper investigates the Lasso method for sparse linear models with exponential ϕ - mixing errors under a ﬁxed design, where the number of covariates p is large, or even much larger than the sample size n . The non-asymptotic concentration inequalities for the estimation and prediction errors of the Lasso estimators are given when the errors follow the Gaussian distribution and the sub-exponential distribution, respectively. The prediction and variable selection performance of Lasso estimators are further illustrated through numerical simulations. Finally, the results of the empirical application show that the Index Tracking Fund based on the sparse selection of Lasso can closely track the trend of the target index, and thus provide some useful guidance for the investors.
H/sub infinity /-optimal control with state-feedback

A H/sub infinity /-optimal control problem in which the measured outputs are the states of the plant is considered. The main result shows that the infimum of the norm of the closed-loop transfer function using linear static state-feedback equals the infimum of the norm of the closed-loop transfer function over all stabilizing dynamic (even, nonlinear time-varying) state-feedback controllers. >
Dilations and Operator Models of W -Hypercontractions

We revisit the study of ω -hypercontractions corresponding to a single weight sequence ω = { ω k } k ≥ 0 introduced by Olofsson ([22] J Oper Theory 74:249–280, 2015) and ﬁnd an analogue of Nagy-Foias characteristic function in this setting. Explicit construction of characteristic functions is obtained and it is shown to be a complete unitary invariant. By considering a multi-weight sequence W and W -hypercontractions we extend Olofsson’s work ([22] J Oper Theory 74:249–280, 2015) in the multi-variable setting. Model for W -hypercontractions is obtained by ﬁnding their dilations on certain weighted Bergman spaces over the polydisc corresponding to the multi-weight sequence W . This recovers and provides a different proof of the earlier work of Curto and Vasilescu ([13] Indiana Univ Math J 42:791–810, 1993 and [14] Indiana Univ 12 Math J 44:727–746, 1995) for y -contractive multi-operators through a particular choice of multi-weight sequence.
Phases of N = 2 Sachdev-Ye-Kitaev models

We study N = 2 supersymmetric Sachdev-Ye-Kitaev (SYK) models with complex fermions at non-zero background charge. Motivated by multi-charge supersymmetric black holes, we propose a new N = 2 SYK model with multiple U(1) symmetries, integer charges, and a non-vanishing supersymmetric index, realizing features not present in known SYK models. In both models, a conformal solution with a super-Schwarzian mode emerges at low temperatures, signalling the appearance of nearly AdS2/BPS physics. However, in contrast to complex SYK, the fermion scaling dimension depends on the background charge in the conformal limit. For a critical charge, we find a high to low entropy phase transition in which the conformal solution ceases to be valid. This transition has a simple interpretation– the fermion scaling dimension violates the unitarity bound. We offer some comments on a holographic interpretation for supersymmetric black holes.
Compton scattering opacities in a partially degenerate electron plasma at high temperatures

We solve the integral equation for the Compton scattering mean free path, in a partially degenerate electron gas at high temperature, where this process dominates the photon transport. We avoid two approximations which were made in previous calculations and correct an error in the literature. Finally we give an expression for the Rosseland mean opacity. (AIP)
Nonlinear SEM numerical analyses of dry dense sand specimens under rapid and dynamic loading

The paper mainly concerns the mechanical response of 2D dry dense sand specimens under shock loading. The problem is numerically analysed by means of a SEM dynamic code, within which an already conceived non‐local viscoplastic constitutive model characterized by a non‐associated flow rule and by an anisotropic strain hardening has been implemented. In particular the strain localization and time dependency of the material mechanical response are taken into consideration.
Analysis of an M / ( G 1 G 2 ) / 1 Queue with Bernoulli Vacation and Server Breakdown

In this article, an M/ ( G1 G2 ) /1 queue with service interruption consisting of a definite repairability is analyzed in the steady-state regime. Here, the server, after completion of a service, is allowed to take in a single vacation under the Bernoulli schedule. For this model, probability generating function (PGF) for queue length distribution at arbitrary and service completion epoch are derived. Laplace Stieltjes Transform (LST) of a busy period distribution and waiting time distribution are obtained. In addition to these, some important performance measures such as the mean queue size and the mean waiting time of a customer are achieved. The reliability indices for this model are carried out and are included in the study. An optimal operation policy of the model in terms of total expected cost is developed at a lower cost. Finally, various numerical examples are presented in support of the theory.
A Convenient Method for Generating Normal Variables

A normal random variable X may be generated in terms of uniform random variables $u_1 $, $u_2 $, in the following simple way: 86 percent of the time, put $X = 2(u_1 + u_2 + u_3 - 1.5)$,11 percent of the time, put $X = 1.5(u_1 + u_2 - 1)$, and the remaining 3 percent of the time, use a more complicated procedure so that the resulting mixture is correct. This method takes only half again as long as the very fastest methods, is much simpler, and requires very little storage space.
Performance of the LHD magnet system

The Large Helical Device (LHD) is a plasma physics experimental device with a magnetic stored energy of 960 MJ, consisting of two superconducting (SC) helical coils and six SC poloidal coils. The trial operation and the first plasma discharge of the 8-yr Phase I project for LHD were completed on March 31, 1998 as initially planned. The second experimental campaign was conducted by additional heating using two neutral beam injection (NBI) devices. The third campaign started in June 1999 and was completed in January 2000. The fourth campaign started in August 2000 and was completed in March 2001. The fifth campaign is carried on since August 2001. Many plasma heating tests up to a plasma field of 2.90 T were carried out. Major test results on the SC magnet system for LHD are as follows: 1) The LHD cryogenic system succeeded in 17 900-h operation as of September 21, 2001 and proved its high reliability. 2) A central field of 2.993 T at a radius of 3.50 m was achieved at a helical coil inner block (H-I) current of 10.97 kA, a helical coil middle block (H-M) current of 11.87 kA and a helical coil outer block (H-O) current of 12.07 kA. 3) All six poloidal coils were excited stably. 4) Nine flexible SC bus-lines with a total length of 497 m were operated stably and safely.
On the stabilization of the ball and beam system using a direct Lyapunov method

I presents the stabilization of the ball on the actuated beam, whether the damping force acts or not in the non-actuated coordinate. The control law is based on the application of the traditional Lyapunov method. The balance strategy consists of shaping a convenient energy function that allow us to derive the required asymptotic stabilizing controller. To this end, we subtle introduce an auxiliary control variable in order to algebraically obtain the kinetic metric and the potential energy of the whole system. The formed positive energy function in conjunction with the proposed feedback controller assures that the whole system be a dissipative one.
Fluorinated Carbon Films with Low Dielectric Constant Made from Novel Fluorocarbon Source Materials by RF Plasma Enhanced Chemical Vapor Deposition

An attempt to fabricate fluorinated carbon (fluoropolymer) films by rf (13.56 MHz) plasma enhanced chemical vapor deposition was made using novel fluorocarbon source materials of C7F16, (C3F7)3N/(C4F9)3N and C8F18/C8F16O. The deposited films were transparent and displayed excellent electrical properties as interlayer dielectrics for LSI using deep-submicron technology, namely, a dielectric constant as low as 2.0 and a dielectric strength higher than 2 MV/cm. The refractive index of these films was 1.38.
On the Integral Representation and Applications of the Generalized Function of Two Variables

In this paper, the author defines the Aleph function of two variables, which is a generalization of the I-function of two variables due to Sharma et al.(9). In this regard the integral representation and applications of new function has been discussed. Similar results obtained by other authors follows as special cases of our findings.
Some coincidence theorems and applications

In this paper, we establish a new coincidence theorem for a Browder type set-valued mapping and an upper semi-continuous set-valued mapping with compact acyclic values in an H-space which generalises some recent results in the literature. As applications we obtain two H a type coincidence theorems and existence theorems of maximal elements for preference correspondences.