Parallel Set Research Articles

Mean Lipschitz–Killing curvatures for homogeneous random fractals

Homogeneous random fractals form a probabilistic extension of self-similar sets with more dependencies than in random recursive constructions. For such random fractals we consider mean values of the Lipschitz–Killing curvatures of their parallel sets for small parallel radii. Under the uniform strong open set condition and some further geometric assumptions, we show that rescaled limits of these mean values exist as the parallel radius tends to 0 . Moreover, integral representations are derived for these limits which extend those known in the deterministic case.

Improved radial basis functions mesh deformation based on parallel point selection strategy and incremental LDLT decomposition

Mesh deformation based on radial basis functions (RBF) is widely used in CFD simulations with moving boundaries due to its simplicity, generality, and robustness, among which selecting an optimum reduced set from all boundary nodes is a crucial data reduction step for fewer support points. However, there remains a great need to reduce the computation costs for large-scale mesh. To solve this issue, a parallel point selection strategy and incremental LDLT decomposition method are proposed. With all boundary nodes distributed to all processors on average, the displacements of boundary nodes are calculated at local ones, and the nodes with local maximum error in divergent processors are added to the support point set in parallel. Besides, the matrix decomposition and solution of weight coefficients are conducted with full uses of corresponding results in the last iteration in incremental LDLT decomposition method. The calculation costs of conventional methods and proposed approaches are theoretically analyzed and compared. Three typical test cases of different mesh scales and motion modes are carried out for validation, including the rigid motion of a NACA0012 airfoil, the bending of an ONERA M6 wing, and the pitch of a missile. The results demonstrate that the proposed approaches greatly improve the efficiency of the data reduction procedure compared with the conventional methods, with similar deformation effect represented by support point distribution and deformed mesh quality.

Mechanical stratigraphy controls fracture pattern and karst epigenic dissolution in folded Cretaceous carbonates in semiarid Brazil

Carbonate reservoirs are often affected by fractures and karst that increase rock's permeability. An accurate characterization of reservoir architecture, fracture attributes and distribution of karst features are critical to modeling carbonate reservoirs, predicting flow behavior and estimating geofluids recoveries. In this contribution, we describe a case study of epigenic karst dissolution concentrated in a fold hinge zone and controlled by stratigraphic and structural processes in Cretaceous layered carbonates in the Potiguar Basin, Brazil. The stratigraphic setting and petrographic/petrophysical properties of host rocks were defined before fracture analysis. Two main joint sets were recognized: master joints (persistent fold hinge parallel set) and cross-joints (orthogonal to fold hinge and confined within master joints). The quantitative mesoscale fracture analysis was performed on a hinge-parallel joint set in 10 field sites distributed across the fold using scanlines to determine two parameters: Fracture Spacing Ratio in individual beds and the Fracture Spacing Index of bed packages. Fracture density and intensity of cross-joints were analyzed in one site using digital scanlines and scanareas on drone images. Results indicate that (i) systematic fractures consist of strata-bound joints, mostly oriented parallel to fold hinge, (ii) fracture intensity does not depend on intrinsic petrophysical properties of individual beds, and (iii) fracture intensity increases within a ∼2.5 km-wide fold hinge zone, consistent with previous studies performed via remote sensing analysis. By integrating our new results with published data, we provide a conceptual model that considers the role of regional-scale tectonic process and local-scale mechanical stratigraphy in controlling the size, shape and distribution of epigenic karst dissolution. Our findings indicate that facture permeability anisotropy, inferred from the karst pattern, is imparted by the combination of bed's attributes (mechanical stratigraphy) and fold-related fracturing. These results are an effective tool to predict the meso- and macro-scale porosity systems in fractured and karstified hydrocarbon reservoirs.

Kinetic modeling and experiments on removal of COD/nutrients from dairy effluent using chlorella and co-culture.

A sustainable and cost-effective approach of waste water management is biological treatment for reducing organic carbon, nitrate, and phosphate content. Co-culturing of algae with bacteria in wastewater leads to higher biomass yield and improvement in COD/nutrients removal compared to the single strain counterparts. In this study, a mathematical modeling framework is proposed to predict the dynamic behavior of microbial co-culture in dairy waste water. Initially, the model has been developed to predict the biomass growth and COD/nutrients removal with discrete cultures (algae and bacteria). As an extension of the single strain kinetic model, Lotka-Volterra model was formulated to explore the symbiotic relationship between algae and bacteria in a co-culture and the impact of the interactions on the COD/nutrients removal efficiency and growth dynamics. Supporting experiments were carried out in 6 parallel sets (3 sets with triplicates) with standalone algae (Chlorella vulgaris, CV), bacteria (activated sludge), and co-culture in real-time dairy liquid effluent in lab flasks and predicted values from modeling were validated against experimental findings. Statistical analysis confirms reasonably good agreement between the model predictions and experimental findings indicating a positive synergistic effect of the algae-bacterial co-culture on COD removal.

Algorithm 1036: ATC, An Advanced Tucker Compression Library for Multidimensional Data

We present ATC, a C++ library for advanced Tucker-based lossy compression of dense multidimensional numerical data in a shared-memory parallel setting, based on the sequentially truncated higher-order singular value decomposition (ST-HOSVD) and bit plane truncation. Several techniques are proposed to improve speed, memory usage, error control and compression rate. First, a hybrid truncation scheme is described which combines Tucker rank truncation and TTHRESH quantization. We derive a novel expression to approximate the error of truncated Tucker decompositions in the case of core and factor perturbations. We parallelize the quantization and encoding scheme and adjust this phase to improve error control. Implementation aspects are described, such as an ST-HOSVD procedure using only a single transposition. We also discuss several usability features of ATC, including the presence of multiple interfaces, extensive data type support, and integrated downsampling of the decompressed data. Numerical results show that ATC maintains state-of-the-art Tucker compression rates while providing average speed-up factors of 2.2 to 3.5 and halving memory usage. Our compressor provides precise error control, deviating only 1.4% from the requested error on average. Finally, ATC often achieves higher compression than non-Tucker-based compressors in the high-error domain.

Parallel Strong Connectivity Based on Faster Reachability

Computing strongly connected components (SCC) is among the most fundamental problems in graph analytics. Given the large size of today's real-world graphs, parallel SCC implementation is increasingly important. SCC is challenging in the parallel setting and is particularly hard on large-diameter graphs. Many existing parallel SCC implementations can be even slower than Tarjan's sequential algorithm on large-diameter graphs. To tackle this challenge, we propose an efficient parallel SCC implementation using a new parallel reachability approach. Our solution is based on a novel idea referred to as vertical granularity control (VGC). It breaks the synchronization barriers to increase parallelism and hide scheduling overhead. To use VGC in our SCC algorithm, we also design an efficient data structure called the parallel hash bag. It uses parallel dynamic resizing to avoid redundant work in maintaining frontiers (vertices processed in a round). We implement the parallel SCC algorithm by Blelloch et al. (J. ACM, 2020) using our new parallel reachability approach. We compare our implementation to the state-of-the-art systems, including GBBS, iSpan, Multi-step, and our highly optimized Tarjan's (sequential) algorithm, on 18 graphs, including social, web, k-NN, and lattice graphs. On a machine with 96 cores, our implementation is the fastest on 16 out of 18 graphs. On average (geometric means) over all graphs, our SCC is 6.0× faster than the best previous parallel code (GBBS), 12.8× faster than Tarjan's sequential algorithms, and 2.7× faster than the best existing implementation on each graph. We believe that our techniques are of independent interest. We also apply our parallel hash bag and VGC scheme to other graph problems, including connectivity and least-element lists (LE-lists). Our implementations improve the performance of the state-of-the-art parallel implementations for these two problems.

Adaptive Damping Control to Enhance Small-Signal Stability of DC Microgrids

This paper proposes an adaptive active control approach for damping the low-frequency oscillations in a DC microgrid (DC-MG). The DC-MG is comprised of hybrid power sources (HPSs) formed by a parallel set of supercapacitor modules and photovoltaic systems. The HPS controller includes a multi-loop voltage controller for adjusting the DC-MG voltage and a virtual impedance loop for damping current oscillations. The virtual impedance loop is augmented to the inner loop of the voltage controller. An adaptive tuning strategy is developed to adjust the damping coefficient of the virtual impedance loop optimally. In the tuning process, small-signal analysis is used to determine an initial adjustment for the damping coefficient. Subsequently, an approach based on intelligent neural network is intended to provide accurate online correction of the damping coefficient, which passes the dependency of the converter control system on the operating point conditions and accommodates different operation conditions. A sensitivity analysis is also conducted to investigate the effects of the system parameters on the HPS stability. Moreover, a mesh analysis is carried out to examine the stability of low-frequency modes of the whole DC-MG using the proposed control scheme. Case studies are conducted to demonstrate the performance of the proposed control strategy, and the analysis results are verified by Hardware-in-the-Loop (HIL) setup using OPAL-RT (OP5600) and dSPACE (DS1202) simulators.

GNNLens: A Visual Analytics Approach for Prediction Error Diagnosis of Graph Neural Networks.

Graph Neural Networks (GNNs) aim to extend deep learning techniques to graph data and have achieved significant progress in graph analysis tasks (e.g., node classification) in recent years. However, similar to other deep neural networks like Convolutional Neural Networks (CNNs) and Recurrent Neural Networks (RNNs), GNNs behave like a black box with their details hidden from model developers and users. It is therefore difficult to diagnose possible errors of GNNs. Despite many visual analytics studies being done on CNNs and RNNs, little research has addressed the challenges for GNNs. This paper fills the research gap with an interactive visual analysis tool, GNNLens, to assist model developers and users in understanding and analyzing GNNs. Specifically, Parallel Sets View and Projection View enable users to quickly identify and validate error patterns in the set of wrong predictions; Graph View and Feature Matrix View offer a detailed analysis of individual nodes to assist users in forming hypotheses about the error patterns. Since GNNs jointly model the graph structure and the node features, we reveal the relative influences of the two types of information by comparing the predictions of three models: GNN, Multi-Layer Perceptron (MLP), and GNN Without Using Features (GNNWUF). Two case studies and interviews with domain experts demonstrate the effectiveness of GNNLens in facilitating the understanding of GNN models and their errors.

Cosmopolitanism and Decolonization: Contradictory Perspectives on School Reform to Advance Reconciliation with Indigenous Peoples

Canadian school jurisdictions have taken steps to accommodate objectives to advance cosmopolitan education reflecting principles such as global citizenship, compassion, tolerance, responsibility, and respect within school curricula and educational practice. At the same time, a parallel set of reconciliation-related educational reforms, aligned with the Calls to Action that accompanied the 2015 Truth and Reconciliation Commission final report, have also gained urgency. Elements of reconciliation processes complement visions of cosmopolitanism, including objectives to foster dialogue and understanding between groups and advancements towards more holistic orientations to pedagogy and knowledge. However, conceptually and in practice, several tensions emerge, especially in a context in which educational priorities are contested. In this paper, we explore these connections and tensions with reference to findings from our research examining public perspectives on educational reforms to support reconciliation.

Evaluating the validity of depression-related stigma measurement among diabetes and hypertension patients receiving depression care in Malawi: A mixed-methods analysis.

Mental illness stigma research is sparse in Malawi. Our team previously analyzed the reliability and statistical validity of a quantitative tool to measure depression-related stigma among participants with depressive symptoms using quantitative psychometric methods. This analysis aims to further evaluate the content validity of the stigma tool by comparing participants' quantitative responses with qualitative data. The SHARP project conducted depression screening and treatment at 10 noncommunicable disease clinics across Malawi from April 2019 through December 2021. Eligible participants were 18-65 years with depressive symptoms indicated by a PHQ-9 score ≥5. Questionnaires at each study timepoint included a vignette-based quantitative stigma instrument with three thematic domains: disclosure carryover (i.e., concerns about disclosure), treatment carryover (i.e., concerns about external stigma because of receiving depression treatment), and negative affect (i.e., negative attitudes about people having depression). Sub-scores were aggregated for each domain, with higher scores indicating greater stigma. To better understand participants' interpretation of this quantitative stigma questionnaire, we asked a subset of six participants a parallel set of questions in semi-structured qualitative interviews in a method similar to cognitive interviewing. Qualitative responses were linked with participants' most recent quantitative follow-up interviews using Stata 16 and NVivo software. Participants with lower quantitative stigma disclosure sub-scores had qualitative responses that indicated less stigma around disclosure, while participants with higher quantitative stigma sub-scores had qualitative responses indicating greater stigma. Similarly, in the negative affect and treatment carryover domains, participants had parallel quantitative and qualitative responses. Further, participants identified with the vignette character in their qualitative interviews, and participants spoke about the character's projected feelings and experiences based on their own lived experiences. The stigma tool was interpreted appropriately by participants, providing strong evidence for the content validity of the quantitative tool to measure these stigma domains.

Reverse Faber-Krahn inequality for the p-Laplacian in hyperbolic space

In this paper, we study the shape optimization problem for the first eigenvalue of the p-Laplace operator with the mixed Neumann-Dirichlet boundary conditions on multiply-connected domains in hyperbolic space. Precisely, we establish that among all multiply-connected domains of a given volume and prescribed (n−1)-th quermassintegral of the convex Dirichlet boundary (inner boundary), the concentric annular region produces the largest first eigenvalue. We also derive Nagy's type inequality for outer parallel sets of a convex domain in the hyperbolic space.

Quasilattices and complex concept analysis

Quasilattices are algebraic structures that comprise a semilattice-ordered system of lattices. In this paper, certain quasilattices (that are characterized abstractly by a local completeness property) provide an extension of Wille's concept analysis to the study of complex systems that function on a number of distinct levels. In an important special case, a chain semilattice serves to represent a time series governing the evolution of a single system. Natural set representations of locally complete quasilattices have opposed set inclusions describing order relations within a complete lattice, and parallel set inclusions tracking homomorphisms that connect distinct lattice fibers. In the time series model, the sets that appear within the set representation accumulate successive layers at each time point, establishing a mathematical model for historical phenomena.

Integer codes correcting single errors and detecting burst errors within two bytes

AbstractThe need for fast communication has led to the introduction of 100 Gbps optics in local area networks (LANs). To avoid retransmission of corrupted packets, in some LANs, the CRC codes were replaced by Reed‐Solomon (RS) codes. Although this solution has met its primary goal, it has two drawbacks: first, the payload size was significantly reduced, and second, each network node had to be equipped with much more complex hardware, which increased the cost of the network. Starting from the fact that the vast majority of corrupted packets contain only single errors, in this paper, a simple strategy for error control in 100 Gbps optical LANs is presented. More precisely, instead of protecting the data with the CRC or RS codes, using integer codes is suggested that can correct single errors and detect two types of burst errors: l‐bit burst errors within one b‐bit byte and h‐bit burst errors within two b‐bit bytes (1 ≤ h < l < b). Unlike the CRC or RS codes, the proposed ones use integer and lookup table operations, which are supported by all processors. In addition, the proposed codes can be interleaved without delay and without using any additional hardware. This feature allows the decoder not only to process larger data sets in parallel, but also to detect all double burst errors.

A Comprehensive Review on Distributed Feeder Protection Problems in the Gaza Strip 22/0.4 kV Overhead Power Distribution System – A Case Study

This paper provides a perspective on protective system at 22kV overhead feeders in Gaza distribution network using symmetrical components method and ETAP software. Electrical disturbances from high rate of outage feeders at the 22 kV overhead power lines frequently cause disruptions on the generating plant and customer loads. One sub-transmission feeder from a parallel set of ten 22 KV feeders (140 MW) in the Gaza west substation is selected as a case study in this research. Because the protection system lacks a data fault recorder (DFR), the paper calculates the fault currents at both the nearest substation bus and the last bus in the distributed feeder using the symmetrical components method and verifies the results by using ETAP software simulation. The results from calculating the minimum fault at the last bus indicated that the current protective parameters are reasonable and satisfied for detecting and interrupting the occurring faults. This author paper proposes increasing the fault clearing time at farthest feeder bus to make protective functions less sensitive by adjusting TMS to 0.08 for time overcurrent and earth fault and setting pickup level to 3.8 for instantaneously overcurrent. The design model is run on the selected feeder, and simulation results guarantee the proposed model's accurate performance for both overcurrent and earth faults after changing the fault clearing time. There will be no miscoordination of protective devices or operational risks while running the design model for the selected feeder with new settings. Gaza's distribution feeder network requires structural improvements to become more reliable and to reduce the high rate of feeder trip, and practical recommendations to improve current installation distribution grid are included in this paper.

Research on dynamic characteristics of a multi-motor electric driving system caused by parasitic power

To reduce greenhouse gas emissions in dealing with climate change, raplacing fule vehicles with electric vehicles (EVs) is one of the most effective measures. The multi-motor electric drive system (MMEDS), which is widely used in EVs, is driven by two or more permanent magnet synchronous motors (PMSM) by parallel shaft gear set (PSGS). Due to the action of forced synchronization of PSGS, once there is a rotational speed difference (∆V) between PMSMs, this will break the balance of output power between PMSMs and cause the increase in output power of some PMSMs while others decrease or even become negative, and eventually generate parasitic power. Parasitic power in MMEDS is bound to cause an autoexcitation vibration and a variation in dynamic characteristics of MMEDS. Therefore, in this paper, an electro-mechanical coupled dynamic model of MMEDS is set up, including a dynaimc model of PSGS and a dynaimc model of PMSM. Then, the affect of the forced synchronization action of PSGS on the dynamic characteristic of MMEDS is investigated under different ∆V. The results show that under the action of the forced synchronization of PSGS, the output power of the PMSM with a fast speed (or a slow speed) increase (or decreases) with the increasing of ∆V, and when ∆V ≤5 rpm, the increment rate or decrement rate of the output power of PMSM is obviously greater than that when ∆V>5 rpm. Meanwhile, ∆V has a singnificant effect on the nonlinearity of the vibration of the wheel, which increases first and then decreases with ∆V increases. The dominated frequencies of dynamic meshing force (DMF) of gear pair do not change with ∆V, but their contributions to the amplitude of the DMF change with ∆V. Moreover, the modulation frequencies also appear in the spectrum of the DMF, but their contributions to the amplitude of the DMF are singnificantly less than that of the dominated frequencies

ACCELERATED PARALLEL MRI USING MEMORY EFFICIENT AND ROBUST MONOTONE OPERATOR LEARNING (MOL).

Model-based deep learning methods that combine imaging physics with learned regularization priors have been emerging as powerful tools for parallel MRI acceleration. The main focus of this paper is to determine the utility of the monotone operator learning (MOL) framework in the parallel MRI setting. The MOL algorithm alternates between a gradient descent step using a monotone convolutional neural network (CNN) and a conjugate gradient algorithm to encourage data consistency. The benefits of this approach include similar guarantees as compressive sensing algorithms including uniqueness, convergence, and stability, while being significantly more memory efficient than unrolled methods. We validate the proposed scheme by comparing it with different unrolled algorithms in the context of accelerated parallel MRI for static and dynamic settings.

Effective elastic properties and S-wave anisotropy for rocks containing any oriented penny-shaped cracks in transversely isotropic background

Fractures have a significant influence on rock elastic properties. The existing elastic models for cracked medium mainly consider the crack dip angle. In this work, based on the previous transversely isotropic (TI) background and arbitrary dip crack model, a theoretical model is derived using the Bond transform matrix to quantify the effects of any oriented penny-shaped cracks on the elastic properties of rocks with a TI background. Based on this model, the effects of crack orientation on rock elastic properties are studied. Particularly, a special case with random crack orientation is investigated by using the spherical averaging of the crack compliance matrix with any orientations. Furthermore, the S-wave anisotropy for rocks containing multiple crack sets also is analyzed. The results indicate that the crack orientation has a great influence on rock elastic properties. Especially, the rock elastic properties indicate nonlinear changes with crack azimuth angles when cracks are inclined with respect to the TI background isotropic plane. The randomly oriented cracks decrease the overall rock elastic moduli but have little effect on rock anisotropy. For rocks containing multiple crack sets, parallel crack sets have great effects on the S-wave anisotropy, whereas the effects of orthogonal crack sets are negligible. Using this model, a complete workflow for the inversion of fracture properties using field data measured by acoustic logging is introduced. To explain the effect of crack azimuth angle, the crack density is inverted without considering crack orientation, only considering crack dip angle, and considering both crack dip and azimuth angles. The results indicate that the inversion results considering the crack dip and azimuth angles are in good agreement with the resistivity imaging results. This work provides the theoretical basis for fracture properties inversion for rocks with a TI background.

Barium isotope fractionation in barite–fluid systems at chemical equilibrium

The barium isotope composition of sedimentary barite (BaSO4, barium sulfate) is emerging as a powerful tracer of the sources and cycling of Ba in modern and ancient marine environments. To reliably use Ba isotopes to interrogate the marine Ba cycle, it is important to identify and constrain processes that fractionate the isotope composition of Ba in BaSO4. Of particular interest is ion exchange: micro-scale dissolution and precipitation that occurs in mineral–fluid systems at chemical equilibrium. This process is often important in systems where minerals, such as BaSO4, and a fluid remain in contact for prolonged periods of time; however, the impact of ion exchange on Ba isotope compositions in BaSO4 is unknown. To constrain the rate and isotopic effect associated with ion exchange in BaSO4–fluid systems, we conducted a series of experiments under marine-relevant conditions and interpreted the results using a multi-phase time-dependent numerical reactor model. From a series of isotope-tracer experiments, we find that BaSO4–fluid ion exchange progresses at a rate between 5 and 53 pmol m−2 s−1. In a parallel set of experiments used to assess mass-dependent isotope fractionation of Ba, the combined effect of BaSO4 dissolution and precipitation while at chemical equilibrium was found to result in the continued evolution of Ba isotopes and produced a modeled offset of Δ138Babarite–dBa = −0.10 ± 0.05 ‰ at isotopic equilibrium. We then constrained the magnitude of isotopic fractionation during BaSO4 dissolution by fitting our data in the numerical reactor model and using previous estimates of Ba isotope fractionation during BaSO4 precipitation (⍺precipitation = 0.99968 ± 0.00002). At chemical equilibrium, we find our data are best explained by an ⍺dissolution = 0.99978 ± 0.00006, implying that BaSO4 dissolution releases isotopically ‘light’ Ba to solution. Since the magnitude of the isotope effects associated with BaSO4 precipitation and dissolution are imbalanced, ion exchange will tend to alter the isotope composition of co-located BaSO4 and fluids until the two phases are offset by ≈0.10 ‰. The importance of this effect on sedimentary BaSO4 likely depends on several factors and we suggest multiple site-screening criteria to maximize the utility of this emerging proxy.

On resistance: As evinced in Iranian political affairs

AbstractAlong with fundamental rights such as liberty and property, the Declaration of the Rights of Man and of the Citizen in 1789 also envisions a right to resist oppression. Irrespective of one's place on the political spectrum, resistance has been employed as an alternative both to submission and to revolt. After briefly sketching a historical and theoretical account of resistance I propose two parallel sets of criteria to further characterize good resistance. I submit that the first set is normative (I call it emancipatory) and the second set is critical (meaning it can be empirically assessed). I further break this typology down as follows: (1) Resistance is emancipatory when it is (a) nonviolent, (b) progressive, and (c) civil; and (2) it is critical when it seeks to (a) change policies and practices that are unjust, and (b) empower citizens to enjoy their full rights. I show the usefulness of this scheme by applying it to the political situation in Iran and by evincing these criteria in three instances of resistance there. Thus, in this context, I argue, resistance is a preferable alternative to both revolution and reform.

Troubled waters : reviewing legal pluralism at the interface of caste and the access to water in India

This essay argues that access to water, and the right to water in India is subject to legal pluralism in India: the plurality of state law and the normative order of the caste system in India. While the Constitution of India prohibits discrimination against or exploitation of the Scheduled Castes, society is also subject to a parallel set of social rules set forth by caste hierarchies. The Dalit community has been historically subject to exploitation and limited access to resources, with the use of religious and social sanction, this essay focuses particularly on the right to water, which is an essential part of the constitutional right to the environment is subject to plural legal systems, of state law and caste-based normative orders. Ethnographic social science research, particularly in anthropology and sociology has produced extensive findings on how the caste system limits access to natural resources and particularly water, owing to ideas of purity and impurity associated with water use, and the status of water as a common public good. This essay explores how lawyers must consider legal pluralities when understanding access and management of natural resources. The essay analyses John Griffiths’ idea of legal pluralism which describes a scenario in which not all law is administered by the State or its institutions, and there exists de facto law, beyond the boundaries of the State. This paper expands Griffiths’ model of pluralism to explain how the right to water is subject to both caste order and state law and how the lived reality of Dalits when accessing water is subject to a constant pluralism.