Miracle-dz/UniFAR-FTUs huggingface dataset:
The impact of open-loop vehicle stability on closed-loop control system performance: an analysis of four AUV concepts

The hull shape and tail appendage design of underwater vehicles is frequently driven by the require- ment to achieve a specified degree of controls-fixed stability, often referred to as its open-loop stability. In an Autonomous IJnderwater Vehicle (AUV), which cannot operate without its automatic control system functioning, this requirement may more appropriately be replaced by requirements for stability and controllability during automatic control system operation. These are often called closed-loop characteristics. In some cases, achiev- ing good open-loop stability requires either compromising closed-loop clharacteristics or demanding increased performance from elements of the automatic control system. Here, an analysis is performed comparing four similar AUVs with varying open-loop stability. Some key requirements for their automatic control systems and their closed-loop performance are compared. Specifically, the impact of the open-loop stability requirement is illustrated in terms of vehicle controllability during maneuvering in turns and horizontal overshoots. Automatic control America's Cup competition, one of the finalists tested over fifty configurations in the towing tank. In the second approach, hydrodynamic coefficients are computationally estimated prior to in-water testing. Using this second approach, many design options can be examined prior to confirming the design with an in-water test (6) (7). In the first approach, model experiments are used to explore design options, while in the second approach, model tests are used to confirm the design while using the computational tool to guide the test program. Prediction techniques that currently represent the state of the art rely on semi-empirical methods, consisting of theoretical models and data correlations of systematic data bases (8) (9). The heart of the semi-empirical method is the body build-up technique in which hydrodyna- mic coefficients for isolated components are determined, interference effects between various components are predicted, and contributions are totaled to give the coefficients for the complete vehicle. These methods have been used in the design and analysis of over 130 undersea vehicles by the authors (lo) through (15).
Laser and vision sensing for road detection and reconstruction

In most urban roads, and similar environments such as in theme parks, campus sites, industrial estates, science parks and the like, the painted lane markings that exist may not be easily discernible by CCD cameras due to poor lighting, bad weather conditions, and inadequate maintenance. An important feature of roads in such environments is the existence of pavements or curbs on either side defining the road boundaries. These curbs, which are mostly parallel to the road, can be harnessed to extract useful features of the road for implementing autonomous navigation or driver assistance systems. However, extraction of the curb or road edge feature using vision image data is a very formidable task as the curb is not conspicuous in the vision image. To extract the curb using vision data requires extensive image processing, heuristics and very favorable ambient lighting. In our approach, the curb data is extracted speedily rising range data provided by a 2D laser range measuring device. This information is then used to extract the mid-line(s) in the vision image using an extended Kalman filtering approach. Subsequently, midline data is used for the prediction of the road boundaries. Experimental results are presented to demonstrate the viability and effectiveness of the proposed methodology.
Multifeed tri‐band circularly polarized antenna for UHF/MW‐RFID application

A compact three‐port tri‐band circularly polarized (CP) antenna for radio‐frequency identification (RFID) technique is introduced. Four inverted‐F radiating elements fed with a 90° phase delay feeding network realize the CP radiation at the FCC UHF‐RFID band (0.902–0.928 GHz). With the slot‐coupled feeding technique, Corner‐truncated slot and patch have been employed to achieve CP radiation at MW‐RFID bands (2.4–2.485/5.725–5.875 GHz). Decoupling structures are implemented to obtain excellent 20 dB port isolations during all operating bands. The relative impedance bandwidths in the three bands are 6.6%, 5.3%, and 5.1%, respectively, with peak gains of 2, 5.1, and 5.7 dBic.
On the Potential of 3D Transdimensional Surface Wave Tomography for Geothermal Prospecting of the Reykjanes Peninsula

Seismic travel time tomography using surface waves is an effective tool for three-dimensional crustal imaging. Historically, these surface waves are the result of active seismic sources or earthquakes. More recently, however, also surface waves retrieved through the application of seismic interferometry are exploited. Conventionally, two-step inversion algorithms are employed to solve the tomographic inverse problem. That is, a first inversion results in frequency-dependent, two-dimensional maps of phase velocity, which then serve as input for a series of independent, one-dimensional frequency-to-depth inversions. As such, a two-dimensional grid of localized depth-dependent velocity profiles are obtained. Stitching these separate profiles together subsequently yields a three-dimensional velocity model. Relatively recently, a one-step three-dimensional non-linear tomographic algorithm has been proposed. The algorithm is rooted in a Bayesian framework using Markov chains with reversible jumps, and is referred to as transdimensional tomography. Specifically, the three-dimensional velocity field is parameterized by means of a polyhedral Voronoi tessellation. In this study, we investigate the potential of this algorithm for the purpose of recovering the three-dimensional surface-wave-velocity structure from ambient noise recorded on and around the Reykjanes Peninsula, southwest Iceland. To that end, we design a number of synthetic tests that take into account the station configuration of the Reykjanes seismic network. We find that the algorithm is able to recover the 3D velocity structure at various scales in areas where station density is high. In addition, we find that the standard deviation on the recovered velocities is low in those regions. At the same time, the velocity structure is less well recovered in parts of the peninsula sampled by fewer stations. This implies that the algorithm successfully adapts model resolution to the density of rays. Also, it adapts model resolution to the amount of noise on the travel times. Because the algorithm is computationally demanding, we modify the algorithm such that computational costs are reduced while sufficiently preserving non-linearity. We conclude that the algorithm can now be applied adequately to travel times extracted from (time-averaged) station-station cross correlations by the Reykjanes seismic network.
The impact of pre‐sale and post‐sale factors on online purchasing satisfaction: a survey

Purpose – This work seeks to contribute a series of reflections and conclusions in response to the following questions: what variables determine satisfaction in the pre‐sale phase and post‐sale phase of B2C electronic commerce? How are the variables of the pre‐sale phase related to those of the post‐sale phase of B2C electronic commerce? Design/methodology/approach – The authors develop a theoretical scale that includes the important variables of quality in the pre‐sale and post‐sale phases of B2C electronic commerce. After the empirical validation of the theoretical scale, we measure the impact of the pre‐sale dimensions on the post‐sale dimensions.Findings – The results confirm the principal hypotheses of the study, that is to say, the dimensions of the pre‐sale phase have a significant impact on the dimensions of the post‐sale phase of B2C electronic commerce.Research limitations/implications – This research shows that, in B2C electronic commerce, the organisation's actions in the pre‐sale phase will, t.
Robust Optimality of Secure TIN

In order to discover larger networks and parameter regimes where sharp Generalized Degrees of Freedom (GDoF) characterizations may be found based on the optimality of robust schemes for interference and broadcast networks with channel state information at the transmitters (CSIT) limited to finite precision, we explore the impact of secrecy constraints. In the absence of secrecy constraints, the largest such parameter regime for <inline-formula> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> user interference networks is the CTIN regime (so named for the <underline>C</underline>onvexity of the GDoF region achieved by Treating Interference as Noise (TIN)) originally discovered by Yi and Caire, whose optimality was established by Chan <italic>et al.</italic> For the corresponding broadcast networks the largest regime is the SLS (Simple Layered Superposition) regime discovered by Davoodi and Jafar, but only for small networks with <inline-formula> <tex-math notation="LaTeX">$K\leq 3$ </tex-math></inline-formula> users. By including secrecy constraints, we identify much larger regimes, the STIN regime and the SLS regime, where GDoF are fully characterized for arbitrary number of users under finite precision CSIT, for interference networks and broadcast networks, respectively. The optimal achievable scheme in both cases is based on TIN along with power control and jamming. Proofs of optimality rely on a combination of secrecy constraints and Aligned Images sum-set inequalities.
Genetic algorithm design for nonperiodic planar graphene leaky‐wave antennas in THz

The aim of this paper is proposing a new fast designing method for planar graphene leaky‐wave antennas without periodical changes. Thus, Floquet theory cannot be used for designing, an optimization in numerical EM solver is needed. Since leaky‐wave antennas are electrically long, their simulation using commercial EM simulators needs a large number of meshes, also the optimization of the large number of parameters (slot lengths and their distances) needs huge amount of memory and computation time. To resolve this problem, the method of Moments, implemented in MATLAB, which has been accelerated by applying some techniques, has been used in the design procedure. The antenna comprises a slotted graphene micro ribbon with a specific pattern, which is placed on two dielectric substrates and a PEC reflector. Graphene is used in the proposed LWA, instead of the electric conductor, because of its wonderful properties. The suitable pattern of slots on the graphene microstrip, is obtained using optimization by MATLAB Genetic algorithm tool. The usefulness and performance of the proposed designing approach, is verified in one example. It has been shown that the presented antenna, compared with one of the new successful similar antennas, has a better gain, radiation efficiency, and a wider range of beam scanning.
Computer-Based Simulation as an Adjunct to Ab Initio Flight Training

Two groups of ab initio student pilots were given training on a flight simulation package running on a desk-top computer prior to performing some basic flight maneuvers in the air. One group interacted with the computer using a representative set of flight controls. The other group used only the computer's cursor and function keys. Both groups exhibited superior performance compared to a control group who had no computer-based training. Students with prior training who used representative flight controls also experienced lower in-flight workload. The results suggest that PC-based flight simulators do not aid in the psychomotor skills required to fly a light aircraft. Their benefits lie elsewhere. However, even very low levels of simulator fidelity can be beneficial in the initial stages of pilot training.
Time domain modeling in the thickness mode of a piezoelectric transducer and its electrical circuit including time-varying components

Existing models for piezoelectric transducers are generally frequency domain-based. A limitation of these models is that they do not consider the fact that some components of the exciting or receiving electrical circuit can be time-dependent. This can happen when transducers are excited by capacitance discharge via a switch or when the circuit integrates active components such that diodes. In particular, in the case of capacitance discharge excitation, it is well known that the switch output impedance varies according to time. Indeed, its value is high when the switch is off and low when the switch is on. A temporal-based method is presented for the analysis of piezoelectric transducers in the thickness mode and their excitation circuit. A backing material and a matching layer are also considered. This model takes into account time-varying components by means of a step-by-step calculation process. The method has been successfully tested by comparison with measurements of transducer responses using an electrical circuit based on capacitance discharge via a transistor switch.
Numerical Investigation on Mixed Convection in Triangular Cross-Section Ducts with Nanofluids

Convective heat transfer can be enhanced passively by changing flow geometry and boundary conditions or by improving the thermal conductivity of the working fluid, for example, introducing suspended small solid nanoparticles. In this paper, a numerical investigation on laminar mixed convection in a water-Al2O3-based nanofluid, flowing in a triangular cross-sectioned duct, is presented. The duct walls are assumed at uniform temperature, and the single-phase model has been employed in order to analyze the nanofluid behaviour. The hydraulic diameter is equal to 0.01 m. A fluid flow with different values of Richardson number and nanoparticle volume fractions has been considered. Results show the increase of average convective heat transfer coefficient and Nusselt number for increasing values of Richardson number and particle concentration. However, also wall shear stress and required pumping power profiles grow significantly.
Robust speed identification for speed sensorless vector control of induction motors

An approach to estimating induction motor speed from measured terminal voltages and currents for speed-sensorless vector control is described. The proposed technique is very simple and robust to variations of motor parameters. This approach is not dependent upon the knowledge of the value of the stator resistance, nor is it affected by stator-resistance thermal variations. Pure integration of sensed variables, in principle, is not required. Therefore, this method can achieve much wider bandwidth speed control than previous tacholess drives. The effectiveness of the technique is verified by simulation and experiment. <<ETX>>
Acquiring enterprise systems as a portfolio of real options

Abstract : The Department of Defense (DoD) has an enterprise architectural vision and an accompanying transformation plan. The enterprise transformation plan describes multiple individual projects and systems that collectively deliver the desired capabilities and enterprise architecture. These projects are performed over planning horizons that span several years or more. Deciding on what projects to invest in, when to invest in them, and whether to continue the investment as time progresses is a difficult problem because of the uncertainty involved in the operational environment, the technology, and the associated project risks. This paper argues that enterprise systems acquisition can be modeled using real options to obtain project valuations that consider the environmental uncertainty and guide acquisition decisions. Moreover, because the enterprise architecture involves many projects that are interdependent, a portfolio investment approach is called for. We present a real options framework to plan a portfolio of projects as a collection of compound real options. We illustrate how the model can be applied in a case study derived from the DoD's transformation plan. The model and method contribute an approach to value a portfolio of projects that intentionally creates options to preserve decision flexibility and acquire the target architecture's capabilities at lower cost and risk.
Rural-Urban Migration and Unemployment Tendency

The study examined the effect of rural-urban migration on unemployment tendency, while controlling for other variables. We make use of the instrumental variable approach and probit controlling for endogeneity to determine the relationship between rural-urban migration and unemployment. Cameroon labour force survey is used to estimate our results. Results shows that the likelihood of unemployment decreases among rural-urban migrates compared to their rural counterparts who do not migrate. By the same token, holders of primary, secondary and tertiary levels of are less likely to be unemployed relative to their counterparts with no education, respectively. These findings have a number of policy implementations: the government could create an enabling environment for labour markets to work better for the youths seeking employment and could invest rationally on education to enable the youth become self-reliant instead of job seekers through skill development and training.
Community Help for Inclusive Learning and Development (CHILD): A Study of How Mobile Phones Were Used to Recruit and Equip Community Volunteers to Support Children's Learning During Covid-19 School Closures in Zimbabwe

By mid-March 2020, 107 governments around the world had instructed schools to close their doors to learners, still more closed clusters of schools in particular areas. Record numbers of children found themselves ‘out of school’. UNESCO predicts ‘devastating’ impacts from long-term disruption to education. While many technology-centred initiatives were launched in response to Covid school closures, an equitable educational response must recognise that in low and middle-income countries most of these ‘out of school’ children are offline. In Sub-Saharan Africa, most disadvantaged children will not have access to TV or radio to continue their learning. How then to design alternative arrangements for girls’ learning and to maintain children’s identity as learners? In this paper, we explore how a collective sense of responsibility for education was activated and supported in remote communities in Zimbabwe, and how this re-shaped local understanding of educational practices. We examine the experiences of those involved to address the overarching research question: ‘In the context of pandemic disease and widespread school closures across Sub-Saharan Africa, how can young people in disadvantaged rural communities be supported, locally and from a distance, to maintain engagement in educational activities? ’.
Probabilistic Load Flow

The paper describes a method for evaluation of power flow which takes into consideration uncertainty of node data. The essence of the method is that the net loads are given as a set of values together with additional information on the frequency of its accuracy. The described mathematical model and the practtical application are discussed and an example given.
Cone-beam computed tomography assessment of upper airway dimensions in patients at risk of obstructive sleep apnea identified using STOP-Bang scores

Purpose The aim of this study was to identify correlations between the STOP-Bang score and upper airway dimensions using cone-beam computed tomography (CBCT) scans. Materials and Methods This study included 101 subjects (46 men, 55 women) from dental patients who received CBCT scans from 2014 to 2020. The patients were divided into those with a low obstructive sleep apnoea (OSA) risk (STOP-Bang score<3) and those with an intermediate to high OSA risk (STOP-Bang score≥3), and their upper airway dimensions were then analysed on CBCT scans. Comparisons between the low-risk and intermediate/high-risk groups were conducted using the t-test and the Mann-Whitney test. Correlations between the total STOP-Bang score and upper airway dimension parameters were established using Spearman correlation coefficients. P values≤0.05 were considered to indicate statistical significance. Results Intermediate/high-risk subjects were predominantly male and over 50 years of age, with a higher body mass index. They had significantly longer upper airways, smaller average airway volumes, and smaller widths and antero-posterior dimensions of the narrowest upper airway segment. The total upper airway length was positively correlated with the STOP-Bang score (rs= 0.278). The average volume (rs= −0.203) and width of the narrowest upper airway segment (rs= −0.305) were both negatively correlated with STOP-Bang scores. Conclusion Subjects with higher STOP-Bang scores had upper airways that were longer, narrower, and smaller in terms of average volume. CBCT scans taken for dental patients as part of investigative procedures could be correlated with STOP-Bang scores to screen for patients at risk of OSA.
Parameter Identification for Piezoelectric Material in a Piezoelectric Laminated Composite Beam Model

A fit-to-data technique was proposed to identify the mechanical and piezoelectric parameters of a model involving a piezoelectric laminated composite beam. Analytical solutions for displacement of the model were derived for parameter identification. The parameter identification problem was formulated as the problem of minimizing the objective function defined as a square sum of differences between the measured displacement and the computed displacement by the analytical solutions. Levenberg-Marquardt method was used to solve the minimization problem. The sensitivities of displacements with respect to the parameters were based on the finite difference approximation method. Numerical example shows that the proposed technique for parameter identification is effective.
Web Squared: Web 2.0 Five Years On

At the first web 2.0 conference in 2004, Tim O'Reilly and John Battelle argued that "the network as platform" means building applications that literally get better the more people use them. Five years on they survey the changes and make some predictions for the future. The Web is no longer a collection of static pages of HTML that describe something in the world. Increasingly, the Web is the world -- everything and everyone in the world casts an "information shadow," an aura of data which, when captured and processed intelligently, offers extraordinary opportunity and mindbending implications. Web Squared is our way of exploring this phenomenon and giving it a name.
Exact solution for dynamic response of size dependent torsional vibration of CNT subjected to linear and harmonic loadings

Rotating systems concern with torsional vibration, and it should be considered in vibration analysis. To do this, the time-dependent torsional vibrations in a single-walled carbon nanotube (SWCNT) under the linear and harmonic external torque, are investigated in this paper. Eringen's nonlocal elasticity theory is considered to demonstrate the nonlocality and constitutive relations. Hamilton's principle is established to derive the governing equation of motion and consequently related boundary conditions. An analytical method, called the Galerkin method, is utilized to discretize the driven differential equations. Linear and harmonic torsional loads, along with determined amplitude, are applied to the SWCNT as the external torques. SWCNT is considered under the clamped-clamped end supports. In free vibration, analysis of small scale effect reveals the capability of natural frequencies in different modes, and this results desirably are in coincidence with another study. The forced torsional vibration in the time domain, especially for carbon nanotubes, has not been done before in the previous works. The previous forced studies were devoted to the transverse vibrations. It should be emphasized that the dynamical analysis of torsion is novel, workable, and at the beginning of the path. The variations of nonlocal parameter, CNT's thickness, and the influence of excitation frequency on timedependent angular displacement and nondimensional angular displacement are investigated in the context.