Search

This article proposes a toolkit for developing a culturally critical—resistant—reading method building on cognitive cultural studies and feminist hermeneutics. It illustrates the potential for resistant literacy fostered by a cognitively challenging text, De duik (The Plunge). A postcolonial, anti-imperialist text, The Plunge foregrounds a resistant way of dealing with issues of displacement, slavery, and cultural rifts. As the analysis demonstrates, this text intermingles the past and the present, the personal and the communal, while questioning the boundaries of "us" and "them." The analysis proffers cognitive strategies geared toward resistant reading that are generally applicable, such as challenging stereotypes, undermining cultural hegemony, and stimulating Theory of Mind. [ABSTRACT FROM AUTHOR]

In this paper, an analysis is applied to a hybrid airship considering the added mass. First, based on the dynamic mesh technology, a computational fluid dynamics (CFD) method is employed to obtain the added mass coefficient matrix. Through a validation process using the 6:1 prolate spheroid, the 6×6 added mass matrix of hybrid airship is obtained. After a dynamic modeling, the equations of motion with added mass are developed. Through the linearization based on small perturbation, the linearized longitude model is used to simulate the dynamic response of a trim condition. The take-off and landing performance has been analyzed and affected by the added mass. The result shows an obvious vertical destabilizing trend on the hybrid airship dynamics due to the added mass and the inertial effect has little influence on the vehicle during the take-off and landing. [ABSTRACT FROM AUTHOR]

Abstract Topographic site effects in anti-plane problems have been studied for four decades cause of the obtained analytical solutions. The authors have developed proposed hybrid methods combining Lamb's series with finite element method (FEM) to resolve the problem of anti-plane scattering; however, it has been difficult to account for site effects in in-plane problems due to mode conversion. In this study, we sought to resolve this issue by developing a novel hybrid method to investigate the site effects of a canyon subjected to longitudinal waves (P waves) as well as horizontal and vertical displacement amplitudes (| u x | and | u z |) near and along canyons of various shapes. A transfinite interpolation function (TFI) was used to obtain the coordinates of nodes and conduct node numbering in the inner finite region within the canyon. Combining hybrid method with TFI function, similar procedures can be used to resolve the scattering problems in both anti-plane and in-plane problems. Canyons are divided into three groups according to shape: 1) smooth shallow, 2) non-smooth, and 3) smooth deep. We also examine the incident angle of P waves (θ), the dimensionless frequencies (η), and the shape of a canyon in terms of their effect on | u x | and | u z |. These factors were shown to generate site effects, including canyon-decay-effect, oblique-effect, shield effect, and SDCP (slope discontinuous points) effect. The site effects induce variations in | u x | and | u z | with constructive interference in the illuminated zone, destructive interference in the shadow zone, and attenuation along the surface of the canyon. Graphical abstract The hybrid method, comprising FEM and a Lamb series, was applied in conjunction with transfinite interpolation to study the effects of canyons of various shapes, incident angle of P waves (θ), and dimensionless frequency (η) on the displacement amplitude (| u x | and | u z |) near and along the canyon. fx1 Highlights • In-plane scattered problem of canyons of various shapes was studied. • FEM and a Lamb series were applied in conjunction with TFI to study displacement u x and u z. • We detailed canyon-decay-effect, oblique-effect, shield effect and SDCP effect of canyons. [ABSTRACT FROM AUTHOR]

The increasing application of hybrid airships which have been recently proposed as high altitude platforms, makes it necessary for research into the thermal performance of such airships that possess a photovoltaic module array(PVMA). In this study, a simplified thermal model of a high-altitude hybrid airship with a PVMA, was proposed that included direct solar, infrared, reflected, and scattered radiation and convective heat transfer. Based on computational fluid dynamics(CFD), a simulation methodology, using a user defined function(UDF) program, was introduced to investigate the PVMA's thermal effects on the hybrid airship. A ground experiment was also performed to validate this numerical method's effectiveness. Further simulations and discussion of temperature and velocity distributions of the hybrid airship's internal helium were conducted. The results showed that the PVMA atop the hull had large effects on the hybrid airship's thermal performance. The temperature distribution of the envelope varied greatly during the day and night because of the PVMA's influence as well as the internal helium flow. In addition, forced convection had little influence on the PVMA's output performance, which was analyzed in detail. [ABSTRACT FROM AUTHOR]

An increasing focus on hybrid airships and the developments in renewable energies has allowed a methodology for conceptual design and analysis to be described. After a model presented and its aerodynamic characteristics obtained through a computational fluid dynamics method, two types of hybrid airships, solar powered at high altitudes and hydrogen powered for cargo, are demonstrated using a wing loading as their independent variable. Then the constraints determining the design point are presented. Parametric estimates of two types for component mass are then illustrated on distribution diagrams. And the sensitivity of wing loading and its effects on hybrid airships are discussed. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study on the kinematics of buoyant round jets in a wave environment. A buoyant round jet was horizontally discharged at the mid-depth in regular waves using three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations with the standard κ − ε turbulence model. Three kinds of effluent with various densities were used for the jets. The numerical results were compared with the experimental data, with reasonable agreement observed. The mechanism of the jet oscillation under different wave-to-jet momentum ratios was presented. The effects of relative water depth, the ratio of the wave height to the water depth, and buoyancy on jet diffusion were considered. Among them, the ratio of the wave height to the water depth appears to be the most important factor on jet diffusion processes under the conditions being considered. Finally, the variations of the jet cross-sectional profiles in the potential core region and the near field region were studied. [ABSTRACT FROM AUTHOR]

Abstract: Aquatic–aerial unmanned vehicles recently became the focus of many researchers due to their various possible applications. Achieving a fully operational vehicle that is capable of aerial, water‐surface, and underwater operations is a significant challenge considering the vehicle's air–water–air transition, propulsion system, and stability underwater. We present in this paper an unconventional unmanned hybrid aquatic–aerial quadcopter with active buoyancy control that is capable of aerial flight and water‐surface operation, as well as subaquatic diving. We report on the first successful prototype of the vehicle, named the Loon Copter, to provide initial evaluation results of its performance in both mediums. The Loon Copter uses a single set of motors and propellers for both air and underwater maneuvering. It utilizes a ballast system to control vehicle buoyancy and depth underwater, as well as to perform seamless air‐to‐water and water‐to‐air transitions. A closed loop control algorithm is utilized for the vehicle's aerial and water‐surface stability and maneuver, whereas an open loop control algorithm is used for underwater maneuver. The experimental results show a fully operational prototype with six degrees of freedom underwater, stable flight, operation capabilities on water surface, and agile maneuvering underwater. [ABSTRACT FROM AUTHOR]

Since the high altitude airship provides an economical platform for earth observation, telecommunication and space exploration, its structural envelope materials attracted wide research interests. Although the uniaxial strength was studied extensively, it cannot properly characterize the real strength of the envelope due to the normal biaxial tensile state in operation service. The biaxial strength determination, which is the key parameter related to the airship structural strength, remained unsolved due to the stress concentration and unsatisfactory failure location. This paper presents a new specimen design and test method for biaxial strength ascertaining. A high-speed camera was employed to capture the biaxial failure process of specimens. According to photographs, single slit or crossed slits failure may occur when materials reached their load bearing limits. The authentic biaxial failure stress was obtained utilizing numerical software. Other than the previous perspective, the biaxial strength equals the lower uniaxial strength multiplied by an amplification factor of 1.1–1.3 under a 1:1 stress ratio. The further work may focus on expanding the test range with various load ratios, which could complete a precise failure envelope in biaxial plane stress space. [ABSTRACT FROM AUTHOR]

The goal of this study was to investigate the influence of aerodynamic factors on the static behavior of a tethered high-altitude lighter-than-air platform. The system design comprised a lighter-than-air vehicle and a tether cable, and the conceptual platform configuration of such a system is studied herein. Governing equations were derived to model the static behavior of the system, and the effects of aerodynamic lift and buoyancy were parametrically analyzed based on the advection distance of the platform under storm conditions. The aerodynamic lift and buoyancy of the hull were shown to have nonlinear effects. We further analyzed the influence of the aerodynamic drag created by the tether. Since this was shown to have a significant influence, we concluded that the cable should ideally have a cross-sectional shape resembling the airfoil of a heavier-than-air aircraft. However, it is sufficient to ensure that the drag coefficient is of the order of 10 − 1 . [ABSTRACT FROM AUTHOR]

The aerodynamic lift and drag performance is one of the important considerations for hybrid airship configuration design. In conjunction with this, simulation study of aerodynamic characteristics can certainly benefit the process of deriving the best possible configuration for hybrid airship design. The aim of this study is to investigate the trend of aerodynamic lift and drag performance for an airship design in different velocities, altitudes and design fineness ratio using the Star CCM+ analysis tool. The airship model applied in this case study is an approximate model of the Atlant-100 airship. It is found that the airship model with low design fineness ratio typically generates much better aerodynamic lifting force in comparison to those with high design fineness ratio. On the other hand, while the range of estimated drag coefficient values is found to be rather insignificantly different, the presence of effects from the design fineness ratio is still evident. Generally, high design fineness ratio for the airship model seems to produce much lower drag force. [ABSTRACT FROM AUTHOR]

This paper aims to develop a high-altitude solar-powered hybrid airship, which combines aerodynamic lift and buoyancy with buoyancy force and cruises continuously. A multi-lobed configuration is employed and the solar irradiance and photovoltaic array model are proposed. After introducing all the parts mass of the hybrid airship and design procedure, an optimal problem with the constraint of energy and the equilibrium between buoyancy and weight are proposed. Through a hybrid optimization search method, the solution is obtained and the sensitivities of geographical location and seasons are discussed. The results show a comprehensive influence of the constraint both in latitude and wind field environment. [ABSTRACT FROM AUTHOR]

Development and implementation of alternative solutions in vehicles propelled by internal combustion engines are made by creators of technology and environmental planners only through technical information and rigorous technical calculations applied from the design stage. In this context, Hybrid-Air vehicles are gaining ground being supported by environmental policies for reducing emissions and the fuel consumption, addressing at the same time issues of global warming and global dependence on oil. This paper describes the procedure to graphically represent a vehicle using Hybrid-Air technology with the help of Catia V5 software. The way in which this system can be graphically represented is presented step by step; its solid foundation is represented by engine and transmission calculations performed in Mathcad and Mathconnex. [ABSTRACT FROM AUTHOR]

In this research, an experimental investigation was carried out at the International Islamic University Malaysia - Low Speed Wind Tunnel facility on a generic model of a hybrid lifting hull. Based on the historical trends of non-rigid airships, the fineness ratio of the said hull has been selected equal to 4. Free stream velocity was kept at 20 m·s-1 and, along with the estimation of aerodynamic parameters, longitudinal and lateral stability characteristics were determined over a range of angles of attack from -8° to +12° and angles of sideslip from -10° to +10°. Zero lift coefficient was obtained at -4.2°, and the corresponding value was found to be greater than that at zero angle of attack. The comparison of the experimental results with the existing analytical relationships of wing has revealed that such an airfoil shaped hull cannot be considered as a wing due to 37% less analytical value of lift coefficient than that obtained by CFD simulations of the said hull. Existing equation of form factor of hull for conventional airships was also revisited, and a correction factor equal to 1.16 in the fundamental drag equation of aircraft's fuselage was also proposed for fineness ratio equal to 4. Trends of the experimental data and comparison of the same with the theoretical calculations and computational results posed some interesting findings. The longitudinal and directional stabilities of a hybrid lifting hull were found to be statically unstable. [ABSTRACT FROM AUTHOR]

A hybrid variational-ensemble data assimilation scheme to estimate the vertical and horizontal parts of the background error covariance matrix for an ocean variational data assimilation system is presented and tested in a limited-area ocean model implemented in the western Mediterranean Sea. An extensive data set collected during the Recognized Environmental Picture Experiments conducted in June 2014 by the Centre for Maritime Research and Experimentation has been used for assimilation and validation. The hybrid scheme is used to both correct the systematic error introduced in the system from the external forcing (initialisation, lateral and surface open boundary conditions) and model parameterisation, and improve the representation of small-scale errors in the background error covariance matrix. An ensemble system is run offline for further use in the hybrid scheme, generated through perturbation of assimilated observations. Results of four different experiments have been compared. The reference experiment uses the classical stationary formulation of the background error covariance matrix and has no systematic error correction. The other three experiments account for, or not, systematic error correction and hybrid background error covariance matrix combining the static and the ensemble-derived errors of the day. Results show that the hybrid scheme when used in conjunction with the systematic error correction reduces the mean absolute error of temperature and salinity misfit by 55 and 42% respectively, versus statistics arising from standard climatological covariances without systematic error correction. [ABSTRACT FROM AUTHOR]

Controlled boiling will occur on Enceladus whenever a long, narrow conduit connects liquid water to the vacuum of space. In a companion paper we focus on the upward flow of the vapor and show how it controls the evaporation rate through backpressure, which arises from friction on the walls. In this paper we focus on the liquid and show how it flows through the conduit up to its level of neutral buoyancy. For an ice shell 20 km thick, the liquid water interface could be 2 km below the surface. We find that the evaporating surface can be narrow. There is no need for a large vapor chamber that acts as a plume source. Freezing on the icy walls and the evaporating surface is avoided if the crack width averaged over the length of the tiger stripes is greater than 1 m and the salinity of the liquid is greater than 20 g kg −1 . Controlled boiling plays a crucial role in our model, which makes it different from earlier published models. The liquids on Enceladus are boiling because there is no overburden pressure—the saturation vapor pressure is equal to the total pressure. Salinity plays a crucial role in preventing freezing, and we argue that the subsurface oceans of icy satellites can have water vapor plumes only if their salinities are greater than about 20 g kg −1 . [ABSTRACT FROM AUTHOR]

The high altitude platform such as a buoyancy-driven airship has been receiving much attraction recently. However, to control the airship is challenging because of its complicated model. This paper applies model predictive control with Laguerre functions to the airship. The simulation results are given in this paper and show satisfaction regarding the proposed control method. [ABSTRACT FROM AUTHOR]

This study focuses on the confined upward flow and heat transfer around a square cylinder under the effect of aiding buoyancy (Richardson number,Ri=0–1) in the vertical channel for Reynolds number (Re)=1–40 and blockage ratio (BR)=25–50% for the air as working fluid. Flow is found to be steady and symmetric for the range of settings. ForRe≤2, no separation zone occurs for BR=25% and 30%. However, for BR=50%, no wakes are observed forRe≤3. The onset of flow separation takes place betweenRe=2 and 3 for BR=25% and 30%; whereas, for BR=50%, it exists betweenRe=3 and 4, irrespective of the value ofRi. Heat transfer correlations have also been obtained at different values ofRe, BR andRi. [ABSTRACT FROM PUBLISHER]

A comprehensive laboratory study of negatively buoyant discharges is presented. Unlike previous studies, here the focus is on generating data sets where influences of the bottom boundary have been eliminated. There are significant discrepancies in the published dilution data for these flows and a contributing factor is the large variation in the bottom boundary condition. A Laser-induced Fluorescence system is employed to gather flow spread, peak concentration (minimum dilution) and trajectory data for a wide range of densimetric Froude numbers and initial discharge angles. Data from these experiments are compared with previously published data, along with predictions from integral models and a revised form of the previously published semi-analytical solutions. The new data sets are not distorted by mixing processes associated with the bottom boundary and therefore provide the basis for more meaningful assessments of the predictive capabilities of existing models, given that the influences of the bottom boundary on contaminant mixing are not incorporated into these models. In general the models assessed are able to predict key geometric quantities with reasonable accuracy, but their minimum dilution predictions are conservative. Importantly dilution at the return point shows a strong dependence on the initial discharge angle and this could have important implications for the design of discharge systems. [ABSTRACT FROM AUTHOR]

Hybrid Airships (HAs) are being touted as an efficient aerial platform for various applications involving heavy cargo transportation, communications, scientific exploration, observation, and surveillance in the stratosphere. Hybrid airship technologies have developed significantly from mid-20th century onwards, and promise to offer unique operational advantages over conventional airships. The purpose of this review paper is to explore the concepts of hybrid airship designs that have been proposed in the recent past, and highlight the current state-of-the-art in this field. Major milestones in the development of hybrid airships are presented followed by the description of types of hybrid airships and their distinct features. This review paper focuses on dynastat type of hybrid airships, since they seem to be the most promising version of hybrid airships owing to the simplicity in their designs, and suitability for various civil and military applications. The characteristics of two types of dynastat, viz., winged-hull and multiple-hull are discussed in detail. The different aspects of the conceptual design and key disciplines including aerodynamics, dynamics, performance, thermal characteristics, structure, and optimization involved in the design of hybrid airships are reviewed in detail. [ABSTRACT FROM AUTHOR]

This section offers world news briefs on engineering and technology as of May 2016 including the Airlander 10 hybrid aircraft assembled in Great Britain, the sustainable office block built in Haelen, Netherlands, and the ice wall in Fukushima, Japan that has been activated to prevent contaminated water from the Fukushima Daiichi nuclear power plant from leaking into the sea.