Pure Exchange Research Articles

Elliptical skyrmions: Theory and nucleation by a magnetic tip in an antiskyrmion-hosting material

Motivated by experimental findings in Jena et al. [1] and Peng et al. [2], we find an elliptical skyrmion can be nucleated in a material with a Dzyaloshinskii–Moriya interaction (DMI) that supports antiskyrmions. The DMI favors the elongation of the skyrmion along a given direction so that it is characterized by two size parameters. We derive analytical properties of the elliptical skyrmion using the Belavin–Polyakov (BP) pure exchange model. We show that the DMI which typically favors isotropic skyrmions or antiskyrmions, respectively, can also support elliptical antiskyrmions or skyrmions, respectively. Using the real material parameters extracted from Jena et al. [1] and including all relevant interactions, numerical computations indicate that the elliptical skyrmion can be nucleated from the stripe or labyrinth domain state by a magnetic force microscope tip in a thin film with a DMI favoring antiskyrmions that consists of at least a few atomic layers.

Efficient simulation of resonance Raman spectra with tight-binding approximations to density functional theory.

Resonance Raman spectroscopy has long been established as one of the most sensitive techniques for detection, structure characterization, and probing the excited-state dynamics of biochemical systems. However, the analysis of resonance Raman spectra is much facilitated when measurements are accompanied by Density Functional Theory (DFT) calculations that are expensive for large biomolecules. In this work, resonance Raman spectra are therefore computed with the Density Functional Tight-Binding (DFTB) method in the time-dependent excited-state gradient approximation. To test the accuracy of the tight-binding approximations, this method is first applied to typical resonance Raman benchmark molecules, such as β-carotene, and compared to results obtained with pure and range-separated exchange-correlation functionals. We then demonstrate the efficiency of the approach by considering a computationally challenging heme variation. Overall, we find that the vibrational frequencies and excited-state properties (energies and gradients) that are needed to simulate the spectra are reasonably accurate and suitable for interpretation of experiments. We can therefore recommend DFTB as a fast computational method to interpret resonance Raman spectra.

Relations of Debt and Credit Networks in Post-Soviet Uzbekistan, Russia and Kazakhstan

Any relations and practices of debt within credit networks include not only pure economic exchange, such as barter or non-monetary exchange, but diverse kinds of social relations of debt. In this article, we consider case studies embedded in the particular context of early and late post-Soviet economic and political crisis, in which economic informalization was characterised by ‘wild capitalism’ or the absence of cash and livelihoods. We observe the coping strategies and mechanisms of economic survival adopted by ordinary people in response to these crises and to the absence of state social and economic institutions. We portray people’s concrete experiences of debt, solidary social relations, and economic exchange based on debt relationships in post-Soviet economies. The case studies are drawn from ethnographic material from Uzbekistan, Russia and Kazakhstan. Our case studies reveal that debt relations are not about two individuals who owe money but serve as the basis for debt-based trade, survival, and socializing networks, as well as part of moral economies. The article builds on scholarly works related to informal economies and survival mechanisms in post-Soviet space, to anthropology of debt, as well as discussion of (dis)trust.

General Equilibrium with Price Adjustments—A Dynamic Programming Approach

This research article develops a dynamic framework for the Walrasian pure exchange economy and thus extends the static Walrasian general equilibrium theory into a dynamic one with price adjustments. An evolution equation for the price vector is derived from dynamic programming considerations. The economy tries to move from disequilibrium to general equilibrium by minimizing certain cost functional. The cost functional measures transactions costs and the total expenditure of agents when they optimize individually. Price determination is directly related to a gradient search. The general equilibrium is shown to be stable in the sense of Lyapunov if price adjustments can be large, when needed. The conditional stability could be one reason for volatility clustering in financial time series.

The proportional ordinal Shapley solution for pure exchange economies

We define the proportional ordinal Shapley (the POSh) solution, an ordinal concept for pure exchange economies in the spirit of the Shapley value. Our construction is inspired by Hart and Mas-Colell's (1989) characterization of the Shapley value with the aid of a potential function. The POSh exists and is unique and essentially single-valued for a fairly general class of economies. It satisfies individual rationality, anonymity, and properties similar to the null-player and null-player out properties in transferable utility games. The POSh is immune to agents' manipulation of their initial endowments: It is not D-manipulable and does not suffer from the transfer paradox. Moreover, we characterize the POSh through a Harsanyi's (1959) system of dividends and, when agents' preferences are homothetic, through a weighted balanced contributions property à la Myerson (1980).

Particle swarm exchange algorithms with applications in generating optimal model-discrimination designs

Exchange-type algorithms have been commonly used to construct optimal designs. As these algorithms may converge to a local optimum, the typical procedure requires the use of several randomly chosen initial designs. Thus, the search for the optimal design can be conducted by performing several independent optimizations. We propose a general framework that combines exchange algorithms with particle swarm intelligence techniques. The main strategy is to represent each initial design as a particle and make the algorithm share information from various converging paths from those initial designs. This amounts to conducting one coordinated optimization instead of several independent optimizations. The proposed general algorithm is called the particle swarm exchange (PSE) algorithm. We compare the performance of PSE with those of two commonly used exchange algorithms – the columnwise-pairwise (CP) exchange algorithm of Li and Wu (1997) for designs with structural requirements and the coordinate exchange algorithm of Meyer and Nachtsheim (1995) for designs without such requirements. In the context of model-robust discriminating designs, we demonstrate that PSE typically performs as well as or, very often, better than the corresponding pure exchange algorithms.

The equilibrium of the bargaining game and core convergence theorem on an exchange economy with limited traders

AbstractDebreu and Scarf (1963), Hildenbrand (1974), Aumann (1964), Dierker (1975), Bewley (1973), and others have shown that the core of an exchange economy with infinitely many or finitely many traders converges. However, an exchange economy does not always consist of infinitely many or finitely many traders. This note provides proof of the core convergence theorem on an exchange economy with limited traders by a bargaining game methodology. The main contribution of this note is to innovate the equilibrium solution to the bargaining game in the exchange economy. In this note, the concept of common payoff is introduced; in the bargaining game of a coalition on its common payoff, all coalition members will get the same distribution, thus the distribution scheme of the cooperation surplus of the exchange economy is determined.This note shows that the bargaining game among the traders on the distribution of the cooperation surplus will make the pure exchange economy with limited traders converge to the Walrasian equilibrium, all the allocations other than the Walrasian equilibrium will be eliminated from the core of this economy.

Optical force spectroscopy for measurement of nonlinear optical coefficient of single nanoparticles through optical manipulation.

Compared with manipulation of microparticles with optical tweezers and control of atomic motion with atom cooling, the manipulation of nanoscale objects is challenging because light exerts a significantly weaker force on nanoparticles than on microparticles. The complex interaction of nanoparticles with the environmental solvent media adds to this challenge. In recent years, optical manipulation using electronic resonance effects has garnered interest because it has enabled researchers to enhance the force as well as sort nanoparticles by their quantum mechanical properties. Especially, a precise observation of the motion of nanoparticles irradiated by resonant light enables the precise measurement of the material parameters of single nanoparticles. Conventional spectroscopic methods of measurement are based on indirect processes involving energy dissipation, such as thermal dissipation and light scattering. This study proposes a theoretical method to measure the nonlinear optical constant based on the optical force. The nonlinear susceptibility of single nanoparticles can be directly measured by evaluating the transportation distance of particles through pure momentum exchange. We extrapolate an experimentally verified method of measuring the linear absorption coefficient of single nanoparticles by the optical force to determine the nonlinear absorption coefficient. To this end, we simulate the third-order nonlinear susceptibility of the target particles with the kinetic analysis of nanoparticles at the solid-liquid interface incorporating the Brownian motion. The results show that optical manipulation can be used as nonlinear optical spectroscopy utilizing direct exchange of momentum. To the best of our knowledge, this is currently the only way to measure the nonlinear coefficient of individual single nanoparticles.

How much does regional bias affect China's regional agricultural trade?

PurposeMarket integration in China is still progressing, while the border effects of trade among regions still exist. The question of whether eliminating or weakening regional bias can promote of China's agricultural trade still remains an important issue. This paper analyzes the impact of regional bias on China's agricultural trade.Design/methodology/approachThis paper constructs a pure exchange computable general equilibrium model of nine regions and three sectors, and analyzes the impact of regional bias on China's regional agricultural trade; Comparing the differences of regional bias on China's inter-regional and external agricultural trade, the paper especially analyzes the impact of the agricultural imports and exports in eight regions of China.FindingsThe results show that regional bias has had substantial impacts on China's agricultural trade. Elimination of regional bias would therefore increase China's agricultural exports and imports by factors of 1.32 and 1.63, respectively while its agricultural trade deficit would increase by 84%. Inter-regional agricultural trade in China would increase by 3.53 times. With the elimination of regional bias, the Northern coastal, Central and Northwestern regions would have the largest increase in inter-regional agricultural trade. Unlike the Northern coastal region, inter-regional agricultural import in the Central and Northwestern regions tends to be greater than inter-regional agricultural exports.Originality/valueThis paper thus aims to fill existing gap in investigating the impacts of regional bias on China's agricultural trade. Firstly, the model proposed in this paper does not only consider the linkage between the agricultural and non-agricultural sectors, but also the inter-regional agricultural trade linkages of the different regions in China. Secondly, the authors decompose home bias into national and regional biases and assess how regional bias affects agricultural trade of the various regions of China.

Remarks on criticality and crisis in pure exchange economies

Remarks on criticality and crisis in pure exchange economies

Cosmological direct detection of dark energy: Non-linear structure formation signatures of dark energy scattering with visible matter

Abstract We consider the recently proposed possibility that dark energy (DE) and baryons may scatter through a pure momentum exchange process, leaving the background evolution unaffected. Earlier work has shown that, even for barn-scale cross-sections, the imprints of this scattering process on linear cosmological observables is too tiny to be observed. We therefore turn our attention to non-linear scales, and for the first time investigate the signatures of DE-baryon scattering on the non-linear formation of cosmic structures, by running a suite of large N-body simulations. The observables we extract include the non-linear matter power spectrum, halo mass function, and density and baryon fraction profiles of haloes. We find that in the non-linear regime the signatures of DE-baryon scattering are significantly larger than their linear counterparts, due to the important role of angular momentum in collapsing structures, and potentially observable. The most promising observables in this sense are the baryon density and baryon fraction profiles of haloes, which can potentially be constrained by a combination of kinetic Sunyaev–Zeldovich (SZ), thermal SZ, and weak lensing measurements. Overall, our results indicate that future prospects for cosmological and astrophysical direct detection of non-gravitational signatures of dark energy are extremely bright.

Theoretical Modeling of Absorption and Fluorescent Characteristics of Cyanine Dyes

The rational design of cyanine dyes for the fine-tuning of their photophysical properties undoubtedly requires theoretical considerations for understanding and predicting their absorption and fluorescence characteristics. The present study aims to assess the applicability and accuracy of several DFT functionals for calculating the absorption and fluorescence maxima of monomethine cyanine dyes. Ten DFT functionals and different basis sets were examined to select the proper theoretical model for calculating the electronic transitions of eight representative molecules from this class of compounds. The self-aggregation of the dyes was also considered. The pure exchange functionals (M06L, HFS, HFB, B97D) combined with the triple-zeta basis set 6-311+G(2d,p) showed the best performance during the theoretical estimation of the absorption and fluorescent characteristics of cyanine dyes.

KiDS-1000 cosmology: machine learning – accelerated constraints on interacting dark energy with CosmoPower

ABSTRACT We derive constraints on a coupled quintessence model with pure momentum exchange from the public ∼1000 deg2 cosmic shear measurements from the Kilo-Degree Survey and the Planck 2018 cosmic microwave background data. We compare this model with Lambda cold dark matter and find similar χ2 and log-evidence values. We accelerate parameter estimation by sourcing cosmological power spectra from the neural network emulator CosmoPower. We highlight the necessity of such emulator-based approaches to reduce the computational runtime of future similar analyses, particularly from Stage IV surveys. As an example, we present Markov Chain Monte Carlo forecasts on the same coupled quintessence model for a Euclid-like survey, revealing degeneracies between the coupled quintessence parameters and the baryonic feedback and intrinsic alignment parameters, but also highlighting the large increase in constraining power Stage IV surveys will achieve. The contours are obtained in a few hours with CosmoPower, as opposed to the few months required with a Boltzmann code.

REMINISCING ON THE USE AND ABUSE OF 14C AND 13C IN ATMOSPHERIC CO2

ABSTRACTWe are observing a dramatic increase of CO2 in the atmosphere, unprecedented in the last several million years. Carbon isotopic ratios have been very useful in helping to untangle the respective roles of anthropogenic emissions and sources/sinks of CO2 in the oceans or terrestrial biosphere. However, this untangling has not been as simple as was often hoped. The isotope ratio signatures produced by emissions and removals that are present in atmospheric CO2 are always vigorously being erased by isotopic exchange with the oceans and terrestrial ecosystems, without there necessarily being any effect on total CO2. Especially in the last decades this pure isotopic exchange effect has led to gross errors that have clouded the public debate on climate change, obscuring mankind’s role. This paper traces my own struggle with the scientific and public sides of this issue, which I ran into from the start of my career in Groningen and throughout my years at NOAA. It is still relevant today.

Fixed price equilibria on peer‐to‐peer platforms: Lessons from time‐based currencies

There are many online platforms for peer-to-peer exchange that introduce a platform-specific currency and fix prices to some extent. We model such platforms as pure exchange economies and characterize all fixed price equilibria. We demonstrate the inherent inefficiency following from the combination of fixed prices and voluntary trade and show that simple additional Pareto improving trades exist. While our theoretical analysis predicts that fixed prices lead to less trade than competitive prices, we also discuss some potential advantages of price restrictions, in particular, with respect to simplicity and fairness considerations. Strikingly, it is not those agents with the most attractive goods who have the highest willingness to participate in a fixed price platform. In an empirical illustration, we explore how these theoretical insights unfold in reality by describing patterns of several platforms covering around 100k transactions. This work is informative for the market design of peer-to-peer platforms and for markets with price restrictions more generally.

A Process Intensification synthesis framework for the design of dividing wall column systems

In this work, we present a process intensification synthesis approach for the design of dividing wall columns based on the Generalized Modular Representation Framework. A superstructure-based representation is developed to represent chemical process alternatives leveraging modular phenomenological building blocks (i.e., pure heat exchange module, mass/heat exchange module). Novel process structures, including but not limited to dividing wall columns, can be systematically generated to enhance process cost and/or energy performance without pre-postulation of equipment design. To describe the possible liquid-vapor and liquid-liquid phase behaviors of the multi-component mixture, rigorous physical property calculations (e.g., UNIQUAC) are explicitly incorporated. The synthesis model is formulated as a single mixed-integer nonlinear optimization problem. The applicability and versatility of the proposed framework is showcased via an industrial case study on methyl methacrylate purification by Dow Global Technologies. Two new dividing wall column designs are obtained, both of which can achieve equipment size reduction and substantial energy savings compared to the original patent design.

Transfer paradox in a general equilibrium economy: An experimental investigation

The transfer paradox, whereby a transfer of resources that influences the equilibrium price benefits the donor while harming the recipient, is a classic paradox in general equilibrium theory. This paper pursues an experimental investigation of the transfer paradox using a three-agent pure exchange economy that is predicted to have such a paradox. The results indicate that an endowment adjustment among agents influences the market price, and consequently the donors benefit from the transfer, consistent with the competitive equilibrium theory. When given an option to make a transfer, half of donor agents voluntarily decide to adjust the endowment distribution.

Decentralized Pure Exchange Processes on Networks

We define a class of pure exchange Edgeworth trading processes that under minimal assumptions converge to a stable set in the space of allocations, and characterise the Pareto set of these processes. Choosing a specific process belonging to this class, that we define fair trading, we analyse the trade dynamics between agents located on a weighted network. We determine the conditions under which there always exists a one-to-one map between the set of networks and the set of stable equilibria. This result is used to understand what is the effect of the network topology on the trade dynamics and on the final allocation. We find that the positions in the network affect the distribution of the utility gains, given the initial allocations

Gainers and losers from market integration

We compare integration of economic, matching and networking markets. There can be losers from integration in all three cases, but their relative numbers depend on the type of market. There can be many losers from integration of pure exchange economies. There are relatively few losers from integration of networking markets. In the matching case, the relative numbers tend to lie between those of the other two cases. In particular, in the grand economy of matching markets, there are weakly more non-losers than losers, and with strict preferences there are weakly more gainers than losers.

Experimental research on the cooling performance of a new regenerative dew point indirect evaporative cooler

This paper presents an experimental investigation of a new regenerative dew point indirect evaporative cooler that uses a polymer plant fibre composite material and a pure counter-flow heat exchange structure. The wet bulb efficiency, dew point efficiency and cooling capacity of the cooler were tested and analysed under various working conditions, such as a dry area, moderate humidity area and high humidity area conditions in an enthalpy laboratory. The experimental results show that the wet bulb efficiency reaches 105.6% and the dew point efficiency reaches 76% under standard drying conditions (dry-bulb temperature of 38 °C and wet-bulb temperature of 23 °C) and when the secondary air/primary air volume ratio is equal to 1.1, the cooling capacity is 2.83 kW, the dry-bulb temperature drop can reach 15.2 °C. Simulating the experimental results of the working conditions of Urumqi and a standard dry environment shows that the application of dew point indirect evaporative cooling technology in hot and dry areas has great advantages and broad application prospects. • The cooler is made of polymer plant fiber composite material, which has high-efficiency hydrophilicity. • The cooler is a pure countercurrent heat exchange structure to improve the heat and mass transfer efficiency. • The performance of the cooler under different environmental parameters was studied experimentally. • The experimental results show that the wet bulb efficiency reaches 105.6% and the dew point efficiency reaches 76% under standard drying conditions.