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The final chapter explores the relationship between the work of art and its diverse spectators by developing the idea of the ‘multi-layered interface’. I argue that this work engages spectators in ways that move beyond previous theory and practice examining images of the body. I focus on performance in photography and video, exhibited in galleries or disseminated online. This art negotiates a way between a complex web of icons, from Samuel Aranda’s photograph of a fully veiled Yemeni woman holding her injured son, to the controversial naked selfies posted on social media by certain women from Tunisia and Egypt in 2011. Lalla Essaydi and Majida Khattari develop a complex interface through Arabic writing, photography and a range of French, other European, or Arabic and Persian imagery, in interaction with the performing body. New means of concealing and revealing the body evoke the revolutions in Tunisia, Libya or Syria in photographic work by Mouna Karray and videos by Naziha Arebi and Philip Horani. Online videos of street art and dance (by Ahl Al Kahf, El Seed, JR and Art Solution) at public sites in Tunisia interpolate their diverse audience in comparable ways, while extending the work in time and space.
Chapter 3 argues that while globalised liberal citizenship norms—including universalised notions of citizenship as a human right—generated a politics of inclusion thus boosting dual citizenship advocacy for Liberia, the transmission in Africa of transnational belonging—dual citizenship diffusion in the continent—has had varied outcomes for the country. It also reveals that the bundle of visceral responses to dual citizenship as a proposed development intervention in Liberia signifies an interface wherein actors negotiate the discontinuities and continuities in their lived experiences of being Liberian, with homeland actors particularly resistant. Viewed as both promise and peril for diasporic and domestic actors, respectively, dual citizenship represents an instrumental tug-of-war in which homelanders prefer to protect their privileges while transnationals wish to expand their rights.
Divided into three parts, Chapter 1 outlines the rationale for selecting respondents—homeland Liberians, permanent and circular returnees, diasporas—with an overview of their demographic profiles; the conceptual framework, actor-oriented analysis, which considers myriad responses to development interventions based on actors’ disparate life-worlds (lived experiences), social locations (socio-economic positions), and levels of agency (capacity to act); as well as deep thinking about the author’s positionality. The methodological, theoretical, and biographical reflections in this chapter are intended to contextualise how the author came to understand Liberia’s political economy of belonging and its relationship to contestations over dual citizenship.
Chapter 1 demonstrates why it was essential to converse with Liberian actors inhabiting different locales in three continents. It shows, for example, that diasporas disclose through their identities, practices, and relationships that citizenship can be simultaneously passive, active, and interactive. They also both challenge and substantiate certain theoretical approaches including conceptualisations of diasporic influences on homeland foreign policy and, by the author’s extension, homeland domestic policy. Reflecting on her positionality as a Liberian researcher who has occupied multiple spaces and places, the author evaluates her own biases as someone who made a conscious choice not to naturalise abroad and how this decision influences her analysis of Liberian citizenship construction and practice.
Intermetallic γ-TiAl-based alloys are commonly used as structural materials for components in high-temperature applications, although they generally suffer from a lack of ductility and crack resistance at ambient temperatures. Within this study, the process-adapted 4th generation TNM+ alloy, exhibiting a fully lamellar microstructure, was examined using notched micro-cantilevers with defined orientations of lamellar interfaces. These configurations were tested in situ using superimposed continuous stiffness measurement methods during loading with simultaneous scanning electron microscopy observations. Subsequently, the video signal was used for visual crack length determination by computer vision and compared to values calculated from in situ changes in stiffness data. Applying this combinatorial approach enabled to determine the J-integral as a measure of the fracture toughness for microstructurally different local crack propagation paths. Thus, distinct differences in conditional fracture toughness could be determined from 3.7 MPa m1/2 for γ/γ-interface to 4.4 MPa m1/2 for α2/γ-interface.
Nanocrystalline metals possess high strength and outstanding resistance to irradiation damage. However, the high-density grain boundaries in nanocrystalline metals lead to low plasticity and poor thermal stability. In recent years, interface engineering has gradually become an important way to improve the comprehensive properties of nanocrystalline metals. In this paper, the interface structure, deformation mechanism, and physical properties of Cu–Nb nanolayered composites fabricated by physical vapor deposition and accumulative roll bonding are reviewed. Both Cu–Nb nanolayered composites possess semi-coherent interfaces. The nanolayered composites could achieve excellent resistance to irradiation damage since the interfaces are good sinks for the irradiation point defects. In addition, nanolayered metallic composites with abundant heterogeneous interfaces have better thermal stability compared to nanocrystalline metallic materials. Moreover, the interactions between dislocations and interfaces can be adjusted effectively through controlling the atomistic interface structure and alignment of slip systems across the interface, so as to achieve high strength and high plastic deformation ability simultaneously.
Lead-free perovskite layers may provide a good alternative to the commonly used lead-halide-based perovskite absorber layers in photovoltaics. Energy level alignment of the active semiconductor with contact layers is a key factor in device performance. Kelvin probe force microscopy was used during vapor deposition of C60 onto formamidinium tin iodide to investigate contact formation with detailed local resolution of these materials that are significant for photovoltaic cells. Significant differences dependent on the growth rate of C60 were detected. Sufficiently high deposition rates were essential to reach compact C60 films needed for good contact. A space charge layer larger than 90 nm within the C60 layer was established without indication of interfacial dipoles. The present analysis gives a clear indication of a well-functioning contact of fullerenes to formamidinium tin iodide that is suitable for the use in photovoltaic devices provided that thin compact fullerene films are formed.
A novel g-C3N4 nanoparticle@porous g-C3N4 (CNNP@PCN) composite has been successfully fabricated by loading g-C3N4 nanoparticles on the porous g-C3N4 matrix via a simply electrostatic self-assembly method. The composition, morphological structure, optical property, and photocatalytic performance of the composite were evaluated by various measurements, including XRD, SEM, TEM, Zeta potential, DRS, PL, FTIR, and XPS. The results prove that the nanolization of g-C3N4 leads to an apparent blueshift of the absorption edge, and the energy band gap is increased from 2.84 eV of porous g-C3N4 to 3.40 eV of g-C3N4 nanoparticle (Fig. 6). Moreover, the valence band position of the g-C3N4 nanoparticle is about 0.7 eV lower than that of porous g-C3N4. Therefore, the photo-generated holes and electrons in porous g-C3N4 can transfer to the conduction band of g-C3N4 nanoparticle, thereby obtaining higher separation efficiency of photo-generated carriers as well as longer carrier lifetime. Under visible-light irradiation, 6CNNP@PCN exhibits the highest photocatalytic performance (Fig. 8) on MB, which is approximately 3.4 times as that of bulk g-C3N4.
The effect of the combined chemical treatment of sisal fibres through the subsequent processes of mercerisation (alkali-treatment), then silane treatment and eventually acid hydrolysis, on sisal fibre were investigated. The effect of the treated fibres on the tensile strength and stiffness, flexural strength and stiffness, compression strength and shear strength of their composites with epoxy resin were also studied. Scanning electron microscopy studies of the surfaces of the treated and untreated fibres showed that the chemical treatment processes enhanced the removal of surface extractives and therefore increased the roughness of the surfaces of the fibres in the range of 20 % - 70 %. This avails an increased reinforcement surface area for interlocking with matrix and is, therefore, expected to enhance adhesion of the two. The treated fibre reinforced composites were observed to have higher values of tensile strength and stiffness, flexural strength and stiffness, compression strength and shear strength than the un-treated fibre reinforced composites. These higher values were attributed to better interfacial bonding due to better mechanical interlocking between the treated fibres and epoxy resin arising from the increased roughness of the treated fibres.
We report a novel strategy to render stainless steel (SS) a more versatile material that is suitable to be used as the substrate for preparing electrodes for efficient hydrogen evolution by interface engineering. Our strategy involves the growth of carbon nanotubes (CNTs) by atmospheric pressure chemical vapor deposition (APCVD) as the interface material on the surface of SS. We optimized the procedure to prepare CNTs/SS and demonstrate a higher activity of the CNTs/SS prepared at 700 °C for the hydrogen evolution reaction (HER) when compared to samples prepared at other temperatures. This can be attributed to the higher number of defects and the higher content of pyrrolic N obtained at this temperature. Our strategy offers a new approach to employ SS as a substrate for the preparation of highly efficient electrodes and has the potential to be widely used in electrochemistry.
Residual stress can considerably weaken systems with ceramics-to-metal joints. Herein, we investigate the dependence of bonding strength and residual stress variation of a ceramics-to-metal joint system on the interface wedge angle and bonding temperature condition. First, disparity between large-scale displacement models with varying work-hardening parameters was confirmed using thermal elastoplastic Finite Element Method (FEM) analysis. Each interface wedge shape was set to a plane surface to compare FEM results to experimental results related to the effect of the interface wedge angle on the practical bonding strength. The experimental results were specifically for a system consisting of Si3N4-WC/TiC/TaC bonded to Ni plate. The effects of the wedge angle of the metal side on residual stress near the interface edge were numerically predicted using FEM models. The interface wedge angles for this model, φ1 and φ2, were defined using the configuration angle between the interface and free surfaces of both materials. The numerical results showed that the stress σr on the free surface of the ceramic side was concentrated near the interface edge at which discontinuity in the stress state is generated. Dependence of the residual stress variation on both the wedge angle and temperature conditions can be predicted. It was confirmed that the bonding strength improves with decreasing residual stress in geometrical conditions. Therefore, residual stress appears to be a predominant factor affecting bonding strength. The observed fracture pattern showed that the fracture originated near the interface edges, after which small cracks propagated on the ceramic side. The residual stress is presumed to dominate bonding strength as the fracture occurred near the interface edge of the ceramic side. Results showed that the maximum bonding strength appears at the geometrical condition where the fracture pattern changes to φ2 lower than 90° of joint bonded at 980 °C. Therefore, the optimum interface wedge angle depends on a combination of materials and bonding temperature conditions, because the weak point of the bonded joint system will affect the stiffness balance of both materials and the adhesion power of the bonded interface.
Light Detection and Ranging (LiDAR) is a primary sensor for autonomous vehicles to recognize surroundings. It detects near-infrared (NIR) light pulses, typically at 905nm, which is emitted and reflected by surrounding objects. Here, the fact of the matter is that conventional black or dark-tone cars with extremely low NIR reflection are hard to be detected by LiDAR and endanger the future highway. In this work, we propose to use platelet-shaped effect pigments with visible absorption and NIR reflectivity. Copper(Ⅱ) oxide and Silicon dioxide multilayer are theoretically investigated with different numbers of layers and thicknesses. The optimized structures appear various dark-tone colors with high NIR-reflectivity over 90%.
Chitosan has attracted significant attention in the past decade because of its potential applications in water engineering, the food and nutrition technology, the textile and paper industries, and drug delivery. Recently, a particularly interesting application of chitosan has been proposed in transparent flexible electronic devices, including memristors and transistors. In this work, the resistive switching (RS) effect of chitosan thin films in a capacitor-like structure with Ag and Al as alternative top electrodes was studied. Both the devices showed a bistable RS effect under an external electric field with a high endurance of 102. The electrical conduction and RS mechanisms of chitosan-based devices were investigated. The trap-controlled space charge–limited current was responsible for electrical transport at the low-resistance state of both devices, while direct tunneling and Schottky emission at the high-resistance state were related to Ag/chitosan/fluorine-doped tin oxide (FTO) and Al/chitosan/FTO, respectively. The RS mechanism of the Ag/chitosan/FTO device was attributed to the formation and dissociation of Ag filaments through the dielectric layer, whereas the change in the barrier height at the Al and chitosan interface under an external electric field could control the RS mechanism of the Al/chitosan/FTO device.
Polyhydroxyalkanoates (PHAs) are degradable (co)polyesters synthesized by microorganisms with a variety of side-chains and co-monomer ratios. PHAs can be efficiently hydrolyzed under alkaline conditions and by PHA depolymerase enzymes, altering their physicochemical properties. Using 2D Langmuir monolayers as model system to study the degradation behavior of macromolecules, we aim to describe the the interdependency between the degradation of two PHAs and the surface potential, which influences material-proteins interaction and cell response. We hypothesize that the mechanism of hydrolysis of the labile ester bonds in (co)polyesters defines the evolution of the surface potential, owing to the rate of accumulation of charged insoluble degradation products. The alkaline hydrolysis and the enzymatically catalyzed hydrolysis of PHAs were previously defined as chain-end scission and random-scission mechanisms, respectively. In this study, these two distinct scenarios are used to validate our model. The surface potential change during the chain-end scission of poly(3-R-hydroxybutyrate) (PHB) under alkaline conditions was compared to that of the enzymatically catalyzed hydrolysis (random-scission) of poly[(3-R-hydroxyoctanoate)-co-(3-R-hydroxyhexanoate)] (PHOHHx), using the Langmuir monolayer technique. In the random-scission mechanism the dissolution of degradation products, measured as a decrease in the area per molecule, was preceded by a substantial change of the surface potential, provoked by the negative charge of the broken ester bonds accumulated in the air-water interface. In contrast, when chains degraded via the chain-ends, the surface potential changed in line with the dissolution of the material, presenting a kinetic dependent on the surface area of the monolayers. These results provide a basis for understanding PHAs degradation mechanism. Future research on (co)polymers with different main-chain lengths might extend the elucidation of the surface potential development of (co)polyesters as Langmuir monolayer.
Na–Se batteries are promising energy storage systems for grid and transportation applications, due to the high volumetric energy density and relatively low cost. However, the development of Na–Se batteries has been hindered by the shuttle effect originating from polyselenide dissolution from the Se cathode. Herein, we reported the utilization of nanoscale Al2O3 surface coating by atomic layer deposition (ALD) to protect a microporous carbon/Se (MPC/Se) cathode and reduce polyselenide dissolution. Compared with the pristine MPC/Se, Al2O3-coated MPC/Se cathode exhibited improved discharge capacity, cycling stability, and rate capability in Na–Se batteries. Post-cycling analysis disclosed that Al2O3 coating on MPC/Se cathode effectively suppressed the polyselenide dissolution, facilitated the formation of thin and stable solid electrolyte interphase (SEI) layers, and reduced charge transfer resistance, thus improving the overall performance of Na–Se batteries. This work suggests the effectiveness of interface control by ALD in enabling high-performance Na–Se batteries and might shed light on the development of new-generation Li/Na/K-chalcogenide batteries.
In this study, cast tungsten carbide particle/steel matrix surface composites were fabricated using a vacuum evaporative pattern casting (V-EPC) infiltration process. Through thermal shock tests at 500 °C, the initiation and propagation of cracks at the interface of the composites were investigated. Owing to the mismatch in the coefficients of thermal expansion (CTE), cracks tended to appear at the interface reaction zone (IRZ) between the particles and the matrix. Because there was also a difference in the CTE between the composite and the substrate, the cracks propagated rapidly along the transition layer (TL) between the composite and the substrate, and finally connected to form macro-cracks. Based on the stress analysis and calculation, the maximum thermal stress at the TL was 63.4 MPa, while the maximum thermal stress at the IRZ was 38 MPa. It could thus be inferred that the TL is the weak link under thermal fatigue. In addition, the experimental results were verified and found to be in good agreement with the calculations.
Conventional tests with written information used for the evaluation of sign language (SL) comprehension introduce distortions due to the translation process. This fact affects the results and conclusions drawn and, for that reason, it is necessary to design and implement the same language interpreter-independent evaluation tools. Novel web technologies facilitate the design of web interfaces that support online, multiple-choice questionnaires, while exploiting the storage of tracking data as a source of information about user interaction. This paper proposes an online, multiple-choice sign language questionnaire based on an intuitive methodology. It helps users to complete tests and automatically generates accurate, statistical results using the information and data obtained in the process. The proposed system presents SL videos and enables user interaction, fulfilling the requirements that SL interpretation is not able to cover. The questionnaire feeds a remote database with the user answers and powers the automatic creation of data for analytics. Several metrics, including time elapsed, are used to assess the usability of the SL questionnaire, defining the goals of the predictive models. These predictions are based on machine learning models, with the demographic data of the user as features for estimating the usability of the system. This questionnaire reduces costs and time in terms of interpreter dedication, as well as widening the amount of data collected while employing user native language. The validity of this tool was demonstrated in two different use cases.
There is an emerging body of legal thought directed at contemporary profiling and data science. Some of this focuses on limiting ‘human computability’, some addresses questions of ‘manipulation’ and ‘behavioural optimisation’, and some suggests ways to introduce friction into the information environment to interrupt the translation of data into meaning. This chapter looks at how some of these ideas might be implemented as computational legal applications. It argues that the legal subject of algorithmic accountability can be expanded into a rights-bearing entity that can actively contest how it is computationally interpreted, through mechanisms of ‘contestation by design’. The chapter also describes the utility of concepts like ‘context’ for building boundaries and friction into information architectures, not simply in terms of information flow but also for constraining how the design of those architectures influences and structures behaviour. Finally, it suggests the shape of a new ‘composite’ legal person as a mechanism to constrain profiling behavior by producing an identity as an interface to the ‘world state’ it inhabits.
This chapter considers the application of computers to data gathering. Computers play a key role in data gathering as well as the analysis and presentation of data derived from experiments. An appreciation of the power and limitations of computers used in this context requires some familiarity with the performance and characteristics of transducers, signal conditioning circuits, and DAQ software. Several options for data gathering are explored, including plug and play systems, the Arduino microcontroller, and smartphones that utilise their on-board sensors.
Nonuniform dispersion and weak interfacial bonding between carbon nanotubes (CNTs) and Cu matrix are two critical issues for achieving high strength and good ductility of CNT/Cu composites. Here, acid-treated CNTs precoated with Ni coatings were used to enhance the dispersion uniformity of CNTs and interfacial bonding between CNTs and Cu matrix in the CNT/Cu composites fabricated through spark plasma sintering and subsequently cold rolling. Scanning electron microscopy analysis revealed the homogeneous dispersion of Ni-coated CNTs (Ni-CNTs) in the composite compared with uncoated CNTs. Transmission electron microscope observation indicated that Cu2O nanoparticles were in situ formed at the interface in Ni-CNT/Cu composite, where CNTs were uncovered by Ni coatings. After rolling, the distribution of Ni-CNTs transformed into ribbons aligning along the rolling direction. The ultimate tensile strength (UTS) of 261 MPa was achieved in rolled 1 vol% Ni-CNT/Cu composite, which was 24.3% higher than that before rolling. The UTS of 2 vol% Ni-CNT/Cu composite obviously decreased, which could be attributed to the agglomeration of Ni-CNTs in the Cu matrix due to the increased volume content.