Frame Field Research Articles

Hybrid Trefftz polygonal elements for heat conduction problems with inclusions/voids

Hybrid Trefftz Voronoi finite elements on polygon meshes are developed to capture thermal response of heterogeneous materials with randomly dispersed inclusions/voids. In this approach, the temperature intra-element field within the polygon is approximated by the homogeneous solutions to the heat conduction governing equation which are also called the T-complete functions. Whereas an auxiliary temperature frame field is independently defined on the polygonal boundary. The continuity at the matrix–inclusion interface is guaranteed by exterior and interior T-complete functions and that across element boundaries is enforced by incorporating the known hybrid functional at the element level. Thus, only the hybrid functional should be established for the matrix region. In conjunction with the divergence theorem, the domain integral involved in the functional vanishes, which leads to the element stiffness equation including boundary integrals only. It is reported that there exists a linear relationship between the maximum number of T-complete functions and the number of Gauss points sampled on each element side. Numerical results demonstrate that the proposed methodology is remarkably more efficient than the conventional finite element method (ABAQUS) and consequently becomes popular in micromechanical and microthermal modeling of composite and porous materials.

The importance of selecting the right messenger: A framed field experiment on recycled water products

This study tests how different messengers—scientists, government agencies, non-profit organizations, and newspapers—influence individual behavior. We conducted framed field experiments to compare the effects of these messengers on consumers' monetary bids on different items produced with recycled and conventional irrigation water. Using recycled wastewater for agricultural irrigation has the potential to conserve substantial amounts of fresh water. Although using recycled water for irrigating of both edible and inedible crops can be safe for human consumption, people may stigmatize these products since the origin of the waste water is still too apparent. Providing consumers with information about recycled water can help ameliorate their negative perceptions, and the effectiveness of such information can depend on the origin, i.e. the messenger. Our results suggest that participants respond least favourably when the message is attributed to a scientist and most favourably when the message is attributed to a newspaper. Further analysis shows that consumer responses to the scientist messenger fall into two general categories: (1) individuals who place zero bids and (2) individuals who place relatively larger bids in response to information from scientists.

The impact of uncertainty on cooperation intent in a conservation conflict

Abstract Stakeholder cooperation can be vital in managing conservation conflicts. Laboratory experiments show cooperation is less likely in the presence of uncertainty. Much less is known about how stakeholders in real‐life conservation conflicts respond to different types of uncertainty. We tested the effects of different sources of uncertainty on cooperative behaviour using a framed field experiment and interviews. The experiment compared a baseline scenario of perfect certainty with scenarios including either: (a) scientific uncertainty about the effectiveness of a conflict‐reduction intervention; (b) administrative uncertainty about intervention funding; or (c) political uncertainty about the extent of community support. We applied these scenarios to a conservation conflict in the Outer Hebrides, Scotland, involving the management of geese to simultaneously meet both conservation and farming objectives. We asked 149 crofters (small‐scale farmers) if they would commit to cooperate with others by helping fund a goose management plan given the three sources of uncertainty. On average, intention to cooperate was highest (99%) in scenarios without uncertainty, and lowest under administrative uncertainty (77%). Scientific uncertainty and political uncertainty both had less of an effect, with over 95% of crofters predicted to be willing to cooperate in these scenarios. Crofters who indicated concern for other crofters suffering the impact of geese were more likely to cooperate. The longer an individual had been a crofter, the less likely they were to cooperate. Synthesis and applications. Crofters’ intention to cooperate is high but lessened by uncertainty, especially over the commitment from other stakeholders such as government, to cooperate on goose management. Existing cooperation on goose management may be at risk if uncertainty is not reduced outright or commitments between parties are not strengthened. This has wide applicability, supporting the need for researchers and government advisers to: (a) determine how uncertainty will impact intention of stakeholders to cooperate; and (b) take steps (such as uncertainty reduction, communication or acceptance) to reduce the negative impact of uncertainty on cooperation.

The Spectrum of Teleparallel Gravity

The observer’s frame is the more elementary description of the gravitational field than the metric. The most general covariant, even-parity quadratic form for the frame field in arbitrary dimension generalises the New General Relativity by nine functions of the d’Alembertian operator. The degrees of freedom are clarified by a covariant derivation of the propagator. The consistent and viable models can incorporate an ultra-violet completion of the gravity theory, an additional polarisation of the gravitational wave, and the dynamics of a magnetic scalar potential.

Tied Labour, Savings and Rural Labour Market Wages: Evidence from a Framed Field Experiment

Abstract How does the introduction of tied labour or a saving product affect labour market decisions and wages in rural agricultural labour markets? We develop a theoretical model of labour tying that incorporates diminishing marginal returns to consumption and inequality (behindness) aversion in the context of a rural agricultural labour market with seasonally fluctuating demand for labour, and test model predictions using a framed field experiment (modified ultimatum game) in rural Uganda. Our main findings are that (1) wages fluctuate with productivity, (2) access to tied contracts decreases wages for casual labour and (3) access to a saving technology does not improve wages for tied labour. Consistent with model predictions and earlier theory, we empirically find that income for workers goes down (and income for landlords goes up) if an institutional innovation enables consumption smoothing by workers (tied contracts or a saving technology).

Performance of Agglomeration Bonuses in Conservation Auctions: Lessons from a Framed Field Experiment

The incorporation of an agglomeration bonus payment to encourage spatial coordination in auction mechanisms to allocate payments for ecosystem services (PES) contracts has been explored as a promising innovation that could enhance the effectiveness of PES schemes. Empirical evidence on the performance of this particular design feature is scant, and almost exclusively derived from laboratory experiments using student subjects. This study reports results from a framed field experimental auction allocating PES contracts with and without agglomeration bonus payments using actual forest land owners in rural China as subjects. We find tentative evidence that, in a PES auction that provides agglomeration bonuses, subjects tend to bid less in anticipation of receiving bonus payments when their neighbours are also successful in the auction. In addition, we have mixed findings as to whether the agglomeration bonus is able to induce a bidding pattern in favour of contiguous conservation. The two sets of results convey some encouraging signals of the theoretically postulated cost-effectiveness and conservation efficacy of the agglomeration bonus. Further research from the actual field is warranted in light of the policy significance of this innovative incentive mechanism.

Microclimatic Conditions in Office Spaces - Case Study

A modern man stays in closed rooms for most of the day. That is why, the indoor environment should have a beneficial effect on people’s health and well-being. The conditions in the room are called the microclimate of the interior. It is the set of all physical and chemical parameters of rooms affecting the human body and building. The values of these parameters are influenced by the structure of the building and installations such as heating, ventilation and lighting. Since the introduction of installation systems into the construction industry, shaping the internal microclimate of the building has become on the one hand an easier task, but on the other hand it requires due diligence and professional knowledge of the design of the internal conditions. The office space is located in a building that will be thermo-modernized. Currently, spaces have various technical solutions in the field of window frames, installed radiators and installed lighting fittings. The Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD) indicators were determined in an analytical way for selected office spaces and the analysis of factors affecting conditions in particular rooms was carried out. The article contains the comparison of the results obtained from the observation analytically for selected office spaces in different seasons. The article also presents the comparison of the results obtained from the observations with the recommendations contained in the legal regulations together with the analysis of the applied technical solutions of the central heating installation.

Observational signatures of magnetic field structure in relativistic AGN jets

Context. Active galactic nuclei (AGN) launch highly energetic jets sometimes outshining their host galaxy. These jets are collimated outflows that have been accelerated near a supermassive black hole located at the centre of the galaxy. Their, virtually indispensable, energy reservoir is either due to gravitational energy released from accretion or due to the extraction of kinetic energy from the rotating supermassive black hole itself. In order to channel part of this energy to the jet, though, the presence of magnetic fields is necessary. The extent to which these magnetic fields survive in the jet further from the launching region is under debate. Nevertheless, observations of polarised emission and Faraday rotation measure confirm the existence of large scale magnetic fields in jets.Aims. Various models describing the origin of the magnetic fields in AGN jets lead to different predictions about the large scale structure of the magnetic field. In this paper we study the observational signatures of different magnetic field configurations that may exist in AGN jets in order to asses what kind of information regarding the field structure can be obtained from radio emission, and what would be missed.Methods. We explore three families of magnetic field configurations. First, a force-free helical magnetic field corresponding to a dynamically relaxed field in the rest frame of the jet. Second, a magnetic field with a co-axial cable structure arising from the Biermann-battery effect at the accretion disk. Third, a braided magnetic field that could be generated by turbulent motion at the accretion disk. We evaluate the intensity of synchrotron emission, the intrinsic polarization profile and the Faraday rotation measure arising from these fields. We assume that the jet consists of a relativistic spine where the radiation originates from and a sheath containing thermalised electrons responsible for the Faraday screening. We evaluate these values for a range of viewing angles and Lorentz factors. We account for Gaussian beaming that smooths the observed profile.Results. Radio emission distributions from the jets with dominant large-scale helical fields show asymmetry across their width. The Faraday rotation asymmetry is the same for fields with opposing chirality (handedness). For jets which are tilted towards the observer the synchrotron emission and fractional polarization can distinguish the field’s chirality. When viewed either side-on or at a Blazar type angle only the fractional polarization can make this distinction. Further this distinction can only be made if the direction of the jet propagation velocity is known, along with the location of the jet’s origin. The complex structure of the braided field is found not to be observable due to a combination of line of sight integration and limited resolution of observation. This raises the possibility that, even if asymmetric radio emission signatures are present, the true structure of the field may still be obscure.

Doubled aspects of generalised dualities and integrable deformations

The worldsheet theories that describe Poisson-Lie T-dualisable σ-models on group manifolds as well as integrable η, λ and β-deformations provide examples of ℰ-models. Here we show how such ℰ-models can be given an elegant target space description within Double Field Theory by specifying explicitly generalised frame fields forming an algebra under the generalised Lie derivative. With this framework we can extract simple criteria for the R/R fields and the dilaton that extend the ℰ-model conditions to type II backgrounds. In particular this gives conditions for a type II background to be Poisson-Lie T-dualisable. Our approach gives rise to algebraic field equations for Poisson-Lie symmetric spacetimes and provides an effective tool for their study.

Protests as Strategic Games: Experimental Evidence from Hong Kong's Antiauthoritarian Movement*

Social scientists have long viewed the decision to protest as strategic, with an individual’s participation a function of their beliefs about others’ turnout. We conduct a framed field experiment that recalibrates individuals’ beliefs about others’ protest participation, in the context of Hong Kong’s ongoing antiauthoritarian movement. We elicit subjects’ planned participation in an upcoming protest and their prior beliefs about others’ participation, in an incentivized manner. One day before the protest, we randomly provide a subset of subjects with truthful information about others’ protest plans and elicit posterior beliefs about protest turnout, again in an incentivized manner. After the protest, we elicit subjects’ actual participation. This allows us to identify the causal effects of positively and negatively updated beliefs about others’ protest participation on subjects’ own turnout. In contrast with the assumptions of many recent models of protest participation, we consistently find evidence of strategic substitutability. We provide guidance regarding plausible sources of strategic substitutability that can be incorporated into theoretical models of protests.

Vectorization of Line Drawings via Polyvector Fields

Image tracing is a foundational component of the workflow in graphic design, engineering, and computer animation, linking hand-drawn concept images to collections of smooth curves needed for geometry processing and editing. Even for clean line drawings, modern algorithms often fail to faithfully vectorize junctions, or points at which curves meet; this produces vector drawings with incorrect connectivity. This subtle issue undermines the practical application of vectorization tools and accounts for hesitance among artists and engineers to use automatic vectorization software. To address this issue, we propose a novel image vectorization method based on state-of-the-art mathematical algorithms for frame field processing. Our algorithm is tailored specifically to disambiguate junctions without sacrificing quality.

A Wireless Radio Frequency Triggered Acquisition Device (WRAD) for Self-Synchronised Measurements of the Rate of Change of the MRI Gradient Vector Field for Motion Tracking.

In this paper, we present a device that is capable of wireless synchronization to the MRI pulse sequence time frame with sub-microsecond precision. This is achieved by detecting radio frequency pulses in the parent pulse sequence using a small resonant circuit. The device incorporates a 3-axis pickup coil, constructed using conventional printed circuit board (PCB) manufacturing techniques, to measure the rate of change of the gradient waveforms with respect to time. Using Maxwell's equations, assuming negligible rates of change of curl and divergence, a model of the expected gradient derivative (slew) vector field is presented. A 3-axis Hall effect magnetometer allows for the measurement of the direction of the static magnetic field in the device co-ordinate frame. By combining the magnetometer measurement with the pickup coil voltages and slew vector field model, the orientation and position can be determined to within a precision of 0.1 degrees and 0.1 mm, respectively, using a pulse series lasting 880 μs . The gradient pulses are designed to be sinusoidal, enabling the detection of a phase shift between the time frame of the pickup coil digitization circuit and the gradient amplifiers. The signal processing is performed by a low power micro-controller on the device and the results are transmitted out of the scanner bore using a low latency 2.4 GHz radio link. The device identified an unexpected 40 kHz oscillation relating to the pulse width modulation frequency of the gradient amplifiers that is predominantly in the direction of the static magnetic field. The proposed wireless radio frequency triggered acquisition device enables users to probe the scanner gradient slew vector field with minimal hardware set-up and shows promise for the future developments in the prospective motion correction.

The Efficient BackFi Transmission Design in Ambient Backscatter Communication Systems for IoT

According to the limited communication distance and the low transmission efficiency for massive electronic tags/sensors of traditional or bistatic backscatter technology, the BackFi transmission protocol design with energy harvesting of massive smart multi-hop electronic tags/sensors was investigated in the ambient backscatter communication systems. This paper proposed the large-scale tags/sensors multi-hop communication protocols with energy harvesting under Wi-Fi architecture, where the “CTS-to-self” frame can be used to set the traditional AP/STA to the sensing status without sending, and then, the new defined frame “Multi-RTS” may send the trigger signal to massive tags or sensors with its frame field as “M-RTS” strategy, compressed bitmap, tags/sensors number, and other messages. The tags/sensors shall respond to the sounding signal and give the backscatter signal to AP using energy harvesting. It can be mentioned that the Wi-Fi standard in this paper is based on the IEEE 802.11ah. Finally, AP can collect and modulate the backscatter signal after massive tags/sensors response to the reader. It was worth noting that the multi-hop relay adopts the power splitting way to implement the communication process, where the object function was energy efficiency maximization with the parameters optimization of transmitting power and relay scaling factor. In order to solve the non-convex problem, this paper derived the approximate expression in the high SNR case and achieved the optimal solution via the Lambert $W$ function. The simulation and analysis verified the effectiveness of the proposed schemes and the correctness of the derivations.

Sunda and Sumatra Block Motion in ITRF2008

The Southeast Asia region is mostly surrounded by active subduction zones in which the Australian plate, the Indian plate, and the Philippine Sea plate submerges beneath the continental plates and blocks. The Sunda block covers the large part of the Southeast Asia region, which comprises of Indochina, the South China Sea, the northeastern part of Sumatra, Borneo, the northern part of Java, and the shallow seas in between. We collect the GPS data in the whole Southeast Asia region for the period from 1994 to 2016, and process the original carrier phase data of GPS using GAMIT/GLOBK 10.6 to obtain the velocity field in the International Terrestrial Reference Frame, ITRF2008. The velocity field thus obtained is utilized to update the Euler rotation parameters of the Sunda block in ITRF2008, and model the long-term slip rates between the adjacent plate and blocks. In this study, we model the Sunda block and the Sumatra block together with the Australian plate by using TDEFNODE. The estimated Euler pole parameters of the Sumatra and Sunda blocks are estimated as their locations at (37.4°S, 106.8°E) and (46.2°N, 89.4°W), respectively, and their angular velocities of 0.371°/Myr clockwise, and 0.327°/Myr counter clockwise, respectively. These parameters result in the slip rate of the Sumatra fault with magnitude of ~9 mm/yr.

Video Super Resolution via Deep Global-Aware Network

Video super-resolution aims to increase the resolution of videos by exploiting the intra-frame and inter-frame dependencies of the low-resolution video sequences. There are usually two dependent steps in the video super-resolution: the motion compensation and the super-resolution reconstruction. In this paper, we propose a new deep learning framework without the explicit motion estimation by utilizing the self-attention model to exploit the full receptive field of the input video frames. In other words, the proposed deep neural network extracts the local features at all spatial–temporal locations for combining into global features using the self-attention networks in order to reconstruct the high-resolution video frame. The proposed global-aware network outperforms the state-of-the-art deep learning-based image and video super-resolution algorithms in terms of subjective and objective quality with less computational operations, as verified by extensive experiments on public image and video datasets, including Set5, Set14, B100, Urban100, and Vid4.

Image Deblocking Detection Based on a Convolutional Neural Network

With the development of multimedia processing technology, it is becoming much easier to manipulate and tamper with digital video without leaving any visual clues. Because video compression is very common in digital videos, the tamper might employ powerful multimedia deblocking methods to cover up the video tampering traces. Motion JPEG (MJPEG) is one of the most popular video formats, in which each video frame or interlaced field of a digital video sequence is compressed separately as a JPEG image. By splitting the MJPEG video into JPEG image frames, the tamper might employ powerful multimedia deblocking methods to cover up the video tampering traces. To the best our knowledge, there is no existing method for the forensics of deblocking. In this paper, we propose a novel method to detect deblocking, which can automatically learn feature representations based on a deep learning framework. We first train a supervised convolutional neural network (CNN) to learn the hierarchical features of deblocking operations with labeled patches from the training datasets. The first convolutional layer of the CNN serves as the preprocessing module to efficiently obtain the tampering artifacts. Then, we extract the features for an image with the CNN on the basis of a patch by applying a patch-sized sliding-window to scan the whole image. The generated image representation is then condensed by a simple feature fusion technique, i.e., regional pooling, to obtain the final discriminative feature. The experimental results on several public datasets demonstrate the superiority of the proposed scheme.

Self-Governance and the Effects of Rules in Irrigation Systems: Evidence from Laboratory and Framed Field Experiments in China, India and Vietnam

This paper employs laboratory and framed field experiments to investigate factors influencing the behavior of irrigation users, with an emphasis on the effects of exogenously and endogenously designed allocation rules. The experiments were conducted with 36 groups of farmers and students from China, India and Vietnam. The results show that physically asymmetric access to water as a resource creates an asymmetric distribution of investments, harvests and revenues that favors upstream users. Exogenously designed allocation rules appear able to equalize the distribution of revenue between upstream and downstream users, but are also likely to reduce the volume of investment and generated revenue. Meanwhile, communication between irrigation users with the possibility of endogenously designed rules appears to have a stronger equalizing effect on asymmetric resource access but also increases overall investment, which then increases water availability in a hypothetical irrigation channel. This suggests that promoting participation of irrigation users in designing rules for water distribution, water use monitoring and sanctioning might improve the performance of irrigation systems.

Entanglement measures of a new type pseudo-pure state in accelerated frames

In this work we analyze the characteristics of quantum entanglement of the Dirac field in noninertial reference frames in the context of a new type pseudo-pure state, which is composed of the Bell states. This will help us to understand the relationship between the relativity and quantum information theory. Some states will be changed from entangled states into separable ones around the critical value F = 1/4, but there is no such a critical value for the variable y related to acceleration a. We find that the negativity \({N_{A{B_I}}}\left( {\rho _{A{B_I}}^{{T_A}}} \right)\) increases with F but decreases with the variable y, while the variation of the negativity \({N_{{B_I}{B_{II}}}}\left( {\rho _{{B_I}{B_{II}}}^{{T_{{B_I}}}}} \right)\) is opposite to that of the negativity \({N_{A{B_I}}}\left( {\rho _{A{B_I}}^{{T_A}}} \right)\). We also study the von Neumann entropies S(ρABI) and S(ρBIBII). We find that the S(ρABI) increases with variable y but S(ρBIBII ) is independent of it. However, both S(ρABI) and S(ρBIBII ) first decreases with F and then increases with it. The concurrences C(ρABI) and C(ρBIBII) are also discussed. We find that the former decreases with y while the latter increases with y but both of them first increase with F and then decrease with it.

Bubble networks: framed discrete geometry for quantum gravity

In the context of canonical quantum gravity in 3+1 dimensions, we introduce a new notion of bubble network that represents discrete 3d space geometries. These are natural extensions of twisted geometries, which represent the geometrical data underlying loop quantum geometry and are defined as networks of SU(2) holonomies. In addition to the SU(2) representations encoding the geometrical flux, the bubble network links carry a compatible SL(2,R) representation encoding the discretized frame field which composes the flux. In contrast with twisted geometries, this extra data allows to reconstruct the frame compatible with the flux unambiguously. At the classical level this data represents a network of 3d geometrical cells glued together. The SL(2,R) data contains information about the discretized 2d metrics of the interfaces between 3d cells and SL(2,R) local transformations are understood as the group of area-preserving diffeomorphisms. We further show that the natural gluing condition with respect to this extended group structure ensures that the intrinsic 2d geometry of a boundary surface is the same from the viewpoint of the two cells sharing it. At the quantum level this gluing corresponds to a maximal entanglement along the network edges. We emphasize that the nature of this extension of twisted geometries is compatible with the general analysis of gauge theories that predicts edge mode degrees of freedom at the interface of subsystems.

Natives, immigrants and social cohesion: intra-city analysis combining the hedonic approach and a framed field experiment

ABSTRACTThe literature on the hedonic price approach applied to housing highlights the existence of natives’ preferences against living in urban areas with high foreign-born population. At the same time, empirical and experimental evidence show that ethnic fragmentation reduces social cohesion in society. Mainly because of the difficulty to measure social cohesion at the neighborhood level, the correlation between these two phenomena is still largely unexplored. In this paper, we investigate natives’ preferences for immigrants following an original approach that combines the hedonic price approach and a framed field experiment. The latter allows us to collect a measure of cooperation at the neighborhood level. We apply this methodology to the city of Milan. Our findings show that natives prefer to not live in dense immigrants neighborhoods. However, this preference is not attributable to an erosion of social cohesion in those areas.