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This special section on field methods in authoritarian states and places aims to move beyond the normative language of the liberal/illiberal binary by foregrounding the ways in which closure can be an authoritarian act. Illustrating the variety of scales and places at which these practices unfold, the contributors are concerned with what implications they have for conducting geographic fieldwork. The main questions raised by this set of papers are: how is research in 'closed contexts' different from (or similar to) more 'open' settings? Does it raise unique ethical and methodological dilemmas? In what ways are field methods themselves informed by particular notions of power, agency, and freedom, and how might these differ between more- or less-closed settings? This article first provides some theoretical contextualization, before then introducing how each author variably highlights these themes through a critical reflection on their own experiences of conducting fieldwork in closed contexts, ranging from Vietnam to Kazakhstan, Mozambique, and the United States.

Rice is a staple food and known to accumulate inorganic arsenic (iAs), which is a class 1 carcinogen to humans. Arsenic field-deployable method kits, designed for water testing, are able to screen iAs in rice, to assure food safety and quick decision-making without the need for laboratory analysis. For the arsenic extraction within the field method, nitric acid is used. To make the field method on-site safer, cost-effective and easier to handle, the method was adapted using a Cola in the extraction process. The adapted field-deployable method was tested by screening a total of 30 rice and rice products from the Austrian market. To verify the results obtained by the Cola extraction field-deployable method, the obtained iAs concentration was compared to HPLC-ICP-MS results. The Cola extraction field method obtained an LOD of 39 µg iAs kg−1 rice, and with an average reproducibility of 14% RSD, the method was capable of recording no false-negative but 7% false-positive values at the 2023 updated European Commission (EC) limits for rice. All, but one, screened rice samples were within the EU limits for iAs in rice and rice products.

This dictionary provides a synthesis of information currently available but only in a diverse array of sources.Through judicious choice and careful scrutiny, the author has gathered together a very handy ready-reference in the same style as his companion volumes, Dictionary of Energy and Fuels and Dictionary of Fire Protection.

Wire arc additive manufacturing achieves high efficiency and low costs by using a melting wire for directional depositions. Thermal analyses and the finite element method have been applied to predict residual stress and the deformation of fabricated parts. For Ni-based alloy production, a method for predicting solidification microstructure evolution with segregation is needed in order to design precise heat treatment procedures. In this study, a multi-phase field method coupled with a CALPHAD database is developed to simulate the solidification microstructure evolution of a practical Ni-based alloy. Thermal analyses of a wire arc additive manufacturing model were performed by the process modeling of multi-pass depositions with a running cyclic arc. Solidification microstructure evolution was obtained using the temperature profile in each deposited layer by the multi-phase field method. These predicted microstructures are compared with experimental measurements. It is confirmed that the multi-phase field method coupled with the CALPHAD database is effective for predicting solidification microstructure and segregation in the engineering of Ni-based alloys.

Using the density functional theory and finite field method, nonlinear optical properties of nine triarylamine-α-cyanocinnamic acid derivatives were investigated at the M06-2X/6–311++ G(d,p) and ωB97X-D/6–311++ G(d,p) levels of theory. Except for ( E )-2-cyano-3-(4-(di([1,1′-biphenyl]-4-yl)amino)phenyl)acrylic acid ( a ), which had a D-π-A electronic structure, all the other eight derivatives had an A-π-D-π-A structure. The results suggest that the lowest energy transition of the nine triarylamine derivatives was the π–π* transition from the HOMO to LUMO. The absorption maxima of the derivatives in their ethanol solution were redshifted with respect to those in the gas phase. The introduction of conjugated C = C or C≡C bonds between the biphenyl unit of molecule a had a minor effect on the second-order nonlinear optical properties of the molecule. However, the introduction of C = C bond into the parent molecule improved the third-order nonlinear optical properties. The introduction of a heterocyclic ring (furan ring or thiophene ring) between the triarylamine moiety and the branched chain containing the cyanocinnamic acid group enhanced the second- and third-order nonlinear optical properties; especially, the second- and third-order polarisabilities of molecules b3 and c3 , which were obtained by introducing a thiophene ring, were the highest. The second- and third-order polarisabilities of b3 were 0.13 × 10 5 and 27.13 × 10 5 a.u., respectively, while those of c3 were 0.14 × 10 5 and 28.10 × 10 5 a.u., respectively. This suggests that b3 and c3 have desirable second- and third-order nonlinear optical properties and can be used for designing efficient second- and third-order nonlinear optical materials. Graphical abstract

In an effort to simulate the involved thermal physical effects that occur in Directed Energy Deposition (DED) a thermodynamically consistent phase-field method is developed. Two state parameters, characterizing phase change and consolidation, are used to allocate the proper material properties to each phase. The numerical transient solution is obtained via a finite element analysis. A set of experiments for single-track scanning were carried out to provide dimensional data of the deposited cladding lines. By relying on a regression analytical formulation to establish the link between process parameters and geometries of deposited layers from experiments, an activation of passive elements in the finite element discretization is considered. The single-track cladding of Inconel 625 powder on tempered steel 42CrMo4 was printed with different power, scanning speed, and feed rate to assess their effect on the morphology of the melt pool and the solidification cooling rate. The forecast capability of the developed model is assessed by comparison of the predicted dimensions of melt pools with experiments reported in the literature. In addition, this research correlated the used process parameter in the modeling of localized transient thermal with solidification parameters, namely, the thermal gradient ( G ) and the solidification rate ( R ). The numerical results report an inverse relationship between R with G , and microstructure transition from the planar to dendrite by moving from the boundary to the interior of melt pool, which agree well with experimental measurements.

Topology optimization has undergone a tremendous development since its introduction in the seminal paper by Bendsøe and Kikuchi in 1988. By now, the concept is developing in many different directions, including “density”, “level set”, “topological derivative”, “phase field”, “evolutionary” and several others. The paper gives an overview, comparison and critical review of the different approaches, their strengths, weaknesses, similarities and dissimilarities and suggests guidelines for future research.

Fractional non-relativistic field equations with the derivatives of non-integer order are considered. A connection of these equations with microscopic (lattice) models is discussed. The considered equations contain non-linear terms and fractional Laplacian in the Riesz form. Using the background field method and the mean field method, we obtain corrections to linear solution and equilibrium solution caused by the weak non-linearity.

Ultra pure metals have various applications, e. g. as electrical conductors. Crystallization from the melt, e. g. via zone melting, using the segregation of impurities at the solidification front is the basic mechanism behind different technical processes for the refining of metals and semi-metals. In this paper, we focus on a crystallization methodology with a gas cooled tube (“cooled finger”) dipped into a metallic melt in a rotating crucible. The necessary requirement for purification in a solidification process is a morphologically stable solidification front. This is the only way to enable macroscopic separation of the impurities, e. g. by convection. For cellular or dendritic solidification morphologies, the segregated impurities are trapped into the interdendritic melt and remain as microsegregations in the solidified metal. Morphological stability depends on the temperature gradient G at the solidification front, the solidification front velocity V front and thermodynamic alloy properties like the segregation coefficients of the impurity elements. To quantify the impact of these parameters on the morphological evolution, especially on the planar/cellular transition and thus on microsegregation profiles, phase field simulations coupled to a thermodynamic database are performed for an aluminium melt with three impurities, Si, Mn and Fe. In particular, we have investigated the morphology evolution from the start of solidification at the cooled finger towards a stationary growth regime, because in the technical process a significant fraction of the melt solidifies along the initial transient. To solve the transient long range temperature evolution on an experimental length scale, the temperature field has been calculated using the homoenthalpic approach together with a 1D temperature field approximation. The simulations provide the process window for an energy efficient purification process, i. e. low thermal gradients, and elucidate the benefit of melt convection.

In the phase-field simulation of dendrite growth during the solidification of an alloy, the computational cost becomes extremely high when the diffusion length is significantly larger than the curvature radius of a dendrite tip. In such cases, the adaptive mesh refinement (AMR) method is effective for improving the computational performance. In this study, we perform a three-dimensional dendrite growth phase-field simulation in which AMR is implemented via parallel computing using multiple graphics processing units (GPUs), which provide high parallel computation performance. In the parallel GPU computation, we apply dynamic load balancing to parallel computing to equalize the computational cost per GPU. The accuracy of an AMR refinement condition is confirmed through the single-GPU computations of columnar dendrite growth during the directional solidification of a binary alloy. Next, we evaluate the efficiency of dynamic load balancing by performing multiple-GPU parallel computations for three different directional solidification simulations using a moving frame algorithm. Finally, weak scaling tests are performed to confirm the parallel efficiency of the developed code.