Interaction Distance Research Articles

Electrical detection of spin-microwave coupling in a cavity

Via exploring the spin dynamics and transport properties at interfaces of magnetic material/non-magnetic metal bilayers, spintronics advanced many techniques on generation, detection, and manipulation of spin currents, which laid down a foundation for designing spintronic devices. New ideas and methods for manipulating spin are required in the spintronics community. Merging with cavity quantum electrodynamics, magnetic resonance in ferromagnets inside of a microwave cavity, realizes a strong magnon-microwave coupling at room temperature, opening an avenue to manipulate spin and spin current for the spintronics community. Spin-microwave coupling strength was significantly improved by replacing a few spins in a paramagnetic spin system with magnetization in ferromagnetic materials. Thus, a strongly coupled magnon-microwave system offers a hybrid quantum platform with many measures to tune the coupled system, such as an exchange magnetic field, an anisotropy field, controlled coupling strength, controlled damping parameters, and so on. Many devices were proposed and demonstrated with potential applications. In this review, we briefly introduce the concept and mechanism of magnon-microwave coupling, a classical electrodynamical coupling model for the coupling, spin currents produced by the coupled magnon, and manipulation of the spin current via the strong coupling. In ferromagnets, magnons can couple to a microwave mode as a magnon-polariton propagating in the materials. The strongly coupled magnon-microwave system is a magnon-polariton in a cavity where the microwave was confined as a resonance mode with a high quality factor. Using the Landau-Lifshitz-Gilbert equation and Maxwell equations, we introduce the classical electrodynamical coupling model and reveal that the magnon is driven by a torque produced by the microwave magnetic field on the magnetization and the microwave is feedback via Faraday’s law. Therefore, the coupling strength of the magnon-microwave system can be controlled by changing the torque. Magnon-microwave coupling is experimentally studied using many techniques, such as microwave transmission, Brillouin light scattering, Faraday rotation measurement, and spin pumping electrical detection. Spin pumping is well explored in the spintronics community as a spin current produced by magnon and detected as a voltage via inverse spin Hall effect in a novel metal. Combining with microwave transmission of the coupled microwave subsystem, spin pumping electrical detection by directly detecting the spin current produced by the magnon subsystem in the coupled system, illustrates a more complete profile of the coupled magnon-microwave system. In addition, the strongly coupled magnon-microwave system offers a new technique to manipulate spin currents. We experimentally demonstrate that spin currents produced by the strongly coupled system are correlated with each other mediated by the microwave cavity, and can be manipulated remotely. Two almost identical magnet samples are used to couple to a cavity and the coupling strengths between each magnet and the cavity are tunable individually. By using electrical detection to locally detect each magnet sample respectively, we find that the spin currents produced by two magnet samples are coherently correlated. By tuning the coupling strength of one magnet sample to the cavity, the spin current produced by the second magnet sample is manipulated distantly over a few centimeters, which is far longer than the distance of spin-orbit interaction or exchange interaction. This distant control is only limited by the coherence length of the microwave and the dimension of the cavity. This flexibility opens the door to improve spin current generation and manipulation for cavity spintronic devices.

Selective gas sensor based on bilayer armchair graphene nanoribbon

Abstract Detection and sensing of toxic gases are vital in many areas such as in environmental and safety monitoring, industrial applications and etc. Fundamental requirements for modern gas sensors typically are small size, low power consumption, high sensitivity and good selectivity towards various gases. Recently, graphene-based gas sensors have attracted significant attention due to their potential applications. Based on published works, the energy band gap of monolayer graphene nanoribbon (GNR) varies by changing its ribbon width. However, in the case of bilayer GNR, the energy band gap varies via three ways: the ribbon width, the layers separation and the symmetry between the layers. Therefore, it is interesting to investigate the characteristics of bilayer armchair graphene nanoribbon (B-AGNR) as gas nanosensor in presence of CO, O2 and CO2 gas molecules. In this study, we report a theoretical investigation and numerical simulation of the electronic properties of monolayer and bilayer AGNR (with 10 atoms in width) and study their sensitivities in presence of CO, O2 and CO2 gas molecules. Using Quantum espresso-5.3.0 package, the structure optimizations are done based on density functional theory (DFT). Moreover, we have evaluated the current-voltage (I-V) characteristics of the aforementioned structures using the open source package TRAN SIESTA which is based on non-equilibrium Green's function (NEGF) method. The obtained results show that the adsorption of CO, O2 and CO2 gas molecules onto AGNR can be modified significantly in bilayer AGNR with respect to the monolayer. These gas molecules show weak interaction with the AGNR atomic structure due to large interaction distances. Thus, it is deduced that the graphene nanoribbon (AGNR) shows weak gas sensing in presence of CO, O2 and CO2 molecules. Meanwhile, bilayer AGNR shows different electronic properties compared to monolayer AGNR which makes it highly sensitive and selective to the presence of O2 and CO gases.

An Unmanned Smart Parcel Locker System with a Parcel Sterilizer

Parcel loss and personal information leakage involved thereof is a critical issue. Existing parcel lockers involve the need to share the password between two. This study suggests a double-security smart parcel locker to keep parcel safe from the risk of loss and personal information leakage by using parcel invoice bar-codes as well as the near field communication (NFC) module for smart-phones. In addition, the suggested method sterilizes a parcel box by means of the ultraviolet-c radiation light emitting diode (UV-C LED) in consideration of the fact that it may be exposed to insanitary conditions for a long time. To verify the suggested smart parcel locker, tests were conducted on the invoice bar-code mechanism for password security, the near field communication (NFC) module for user authentication reliability, and the Bluetooth interaction distance between a smart-phone app and the system. Test results show that the accuracy of the near field communication (NFC)-based user authentication was 97%, bar-code and that of the parcel locker opening mechanism was 95%. Thus, the sufficient level of security was verified. The max. transmission distance for smooth communication between a smart-phone and the parcel locker upon bluetooth pairing turned out to be 5 m. Test results show that as the near field communication (NFC) and invoice bar-codes are used instead of a password, the parcel locker can be utilized as a highly secure instrument.

A consideration of total energetics for close-packed polytypes from viewpoint of atomistic interaction distance

Predicting polytype phase stability for a material has still been a long-standing issue in condensed matter physics and/or materials science. This situation stems from the fact that the atomistic interactions on polytype energetics might be surprisingly quite complex and delicate despite the simplicity of their geometrical structure. In this paper, a theoretical consideration of total energetics for the close-packed (CP) polytypes is presented based on the interlayer partial energy model where the total energy constructed from the two-body interatomic interactions is projected onto the interlayer interactions in CP polytype structures. The present study suggests that it is possible to infer the effective distance of interatomic interactions, which is important property of each element for producing new polytype-based materials, from the distribution of polytype structural energetics.

The Dynamics of Urban Public Space Perception in the New Normal Era

The coronavirus pandemic or Covid-19 has happened in several countries, including Indonesia. This condition has an impact not only on public health but also on all sectors. Yogyakarta, a province in Indonesia, receives the impact of this pandemic, especially the Malioboro as a famous public area in the city. The Malioboro area, as an urban public space, becomes quieter due to the coronavirus pandemic. The new normal policy, which the government implemented through the adaptation of new habits, gradually bringing back the activities in the Malioboro area. Health protocols to maintain social distancing keep on encouraged with direct and written persuasive methods. The purpose of this study is to explore people's perceptions of urban public spaces in the new normal era in Malioboro. The method used was conducting a direct survey in Malioboro and giving a closed questionnaire online to the public. The discussion was performed by examining the results of a closed questionnaire with the current situation in Malioboro. The conclusions obtained that the community has received information to maintain social distancing. However, many people ignore the health protocols so that no difference with the situation before the pandemic. This condition does not change the spatial patterns and layouts related to space at the public scale and the distance of social interactions. Keywords: Covid-19; public spaces; social distancing; social interaction

Hydropathicity-based prediction of pain-causing NaV1.7 variants

BackgroundMutation-induced variations in the functional architecture of the NaV1.7 channel protein are causally related to a broad spectrum of human pain disorders. Predicting in silico the phenotype of NaV1.7 variant is of major clinical importance; it can aid in reducing costs of in vitro pathophysiological characterization of NaV1.7 variants, as well as, in the design of drug agents for counteracting pain-disease symptoms.ResultsIn this work, we utilize spatial complexity of hydropathic effects toward predicting which NaV1.7 variants cause pain (and which are neutral) based on the location of corresponding mutation sites within the NaV1.7 structure. For that, we analyze topological and scaling hydropathic characteristics of the atomic environment around NaV1.7’s pore and probe their spatial correlation with mutation sites. We show that pain-related mutation sites occupy structural locations in proximity to a hydrophobic patch lining the pore while clustering at a critical hydropathic-interactions distance from the selectivity filter (SF). Taken together, these observations can differentiate pain-related NaV1.7 variants from neutral ones, i.e., NaV1.7 variants not causing pain disease, with 80.5% sensitivity and 93.7% specificity [area under the receiver operating characteristics curve = 0.872].ConclusionsOur findings suggest that maintaining hydrophobic NaV1.7 interior intact, as well as, a finely-tuned (dictated by hydropathic interactions) distance from the SF might be necessary molecular conditions for physiological NaV1.7 functioning. The main advantage for using the presented predictive scheme is its negligible computational cost, as well as, hydropathicity-based biophysical rationalization.

The Correlation Between Spatial Configuration and User Satisfaction: A Case Study of an Activity-based vs a Conventional Office

Very few studies have discussed the quantitative correlation between office space configuration and user satisfaction. This research aims to provide more concrete results comparing the spatial configuration of Activity Based Office (ABO) and Conventional Offices (CO) to its users' satisfaction. Data collection is taken with sixty respondents who are ABO and CO. User satisfaction will be measured by the comfort aspect. Satisfaction assessment includes the comfort of social interaction distance and the uniformity of the workspace between colleagues, distance to office facilities, distance to the resting place, and distance to the office's informal socialize area. Metric measurements on physical distances and workspace areas between colleagues are compared to the user's subjective comfort. Objective data measurement using the calculation of metric line, and the workspace area differences, while subjective data collection of users using questionnaires. The statistical analysis that will be used is the cross-tabulation method. Cross tabulation will give an overview of the comparison between comfort level to the objective distance and workspace area differences. The study results show that the physical distance comfort of an activity point will vary according to the needs of its user preference. Comparison of spatial to the activity-based and conventional offices will also influence the perception of the uniformity of the user's workspace, and the behavior of users in the elections performs several activities within the office.

Mother-Infant Interaction Kinect Analysis (MIIKA): An automatic kinematic-based methodology for the investigation of interpersonal distance during early exchanges

Interpersonal distance is a core aspect of mother-child interaction. While conventional measures based on human coders do not fully capture the dynamics of this feature, computational methods provide automatic measures which can detect even small changes and more accurate estimates both spatially and temporally. Using RGB-D sensors (Microsoft Kinect V2), the present study describes a setup to automatically examine interpersonal distance during mother-child interactions, termed Mother-Infant Interaction Kinect Analysis (MIIKA). First, the laboratory setting and the data extraction method are described. By using an ad-hoc algorithm for kinematic data extraction, MIIKA returns three metrics: barycenter position (distance and velocity of approach and separation), movements (number of small, medium and large approaches and separations) and contributions (proportional contributions of mother and child to approaches and separations). Secondly, preliminary MIIKA metrics are described for a non-clinical mother-child dyad as an exemplification of the protocol. As interpersonal distance can be affected by contingent situations, we detected mother-infant full skeleton during three interactional contexts characterized by different kinds of dyadic exchanges: a free play session, a task-oriented activity and an emotionally arousing condition. Results highlighted similarities and differences between the three interactional contexts. MIIKA appears to be a promising setup to automatically examine interpersonal distance in early mother-child interactions.

The Effect of Distance Learning Practicum based on PhET Interactive Simulations on Science Process Skills of Secondary School Students

The condition of the covid-19 pandemic makes face-to-face learning become distance learning, learning activities from home are no exception to practicum learning. Alternative solutions using PhET Interactive Simulations. The research aims to describe the influence and great influence of PhET Interactive Simulations-based distance practicum learning on the science process skills of junior high school students. The research method uses quasi-experimentation with matching pre-test post-test control group design. The research population is grade VIII students of SMP Sepuluh Nopember Sidoarjo with a sample of 2 grade VIII, namely VIII H as an experimental class and VIII F as a control class of 40 students each. Research instruments use science process skills tests with 7 indicators namely formulating problems, formulating hypotheses, identifying variables and operational definitions of variables, assembling tools and materials, presenting data, conducting data analysis, and concluding. The results showed there is a huge influence between distance learning practicum based on PhET interactive simulations on the science process skills of secondary school students in natural science subjects. Further research increases the number of research variables, in addition to science process skills as well as understanding of student concepts to science, and so on.

Serious Games and the COVID-19 Pandemic in Dental Education: An Integrative Review of the Literature

The COVID-19 pandemic has forced faculties including dental schools into a ‘new normal’, where the adoption of remote or distance learning is required to minimise the risk of infection. Synchronous learning historically was favoured due to the perceived advantage of ‘real time’ interactions between instructors and learners; these interactions are not always possible in asynchronous settings. However, serious games can overcome this limitation of asynchronous learning. This integrative review explores the literature on serious games in dental education, to construct a conceptual framework of their strengths in this pandemic. Following consideration of inclusion and exclusion criteria, 15 articles on 11 serious games designed for dental education were included in this review. Our investigation points to an increase in the use of serious games since 2018. The findings of the review support the use of serious games in dental education during the recent crisis. Key strengths include positive educational outcomes, enhanced engagement and motivation, interactive asynchronous distance learning, a safe learning environment, and the advantage of stealth assessment. Consequently, the ‘new normal’ in education appears to support a very promising future for serious games, particularly in dental education. A conceptual framework is proposed to inform further research across all education settings and timeframes.

Escape the EM Boards: Interactive Virtual Escape Room for GI Board Review.

This interactive and entirely virtual escape room based on high yield gastrointestinal/abdominal board review material is a didactic activity for emergency medicine residents of all postgraduate years and third- or fourth-year medical students. This escape room can be completed in small teams or as individuals in a remote, in-person, or mixed location setting. 2020 is a year that will forever change medical education. The novel coronavirus 2019 pandemic caused many national, state, local, or hospital specific recommendations for transition of meetings to be completely virtual or to only allow for limited in-person meetings. In order to abide by these recommendations, the majority of medical education transitioned to online platforms. Now more than ever, creative and engaging methods for expanding clinical knowledge and teaching teamwork as well as unique integrations of technology for medical education delivery are needed. By the end of this didactic activity, learners will be able to:Identify causes of upper gastrointestinal bleeding.Recall test-taking buzzwords for infectious causes of diarrhea.Acknowledge the correct hepatitis B titers that correspond with various clinical scenarios.Describe the management for alkali caustic ingestions.Determine the components of Maddrey Discriminant Function Score, Charcot's triad, Ranson's Criteria for Pancreatitis, and Glasgow-Blatchford Score.Diagnose specific gastrointestinal diseases from a clinical description.Choose the correct gastrointestinal diagnosis based on clinical image findings.Demonstrate teamwork in solving problems. "Gamification" is the use of game elements in a nongame context.1 Gamification creates active, engaged learning opportunities and so it is a highly favored educational method for millennial learners.1 An Escape Room is a team-based game where a small group is locked in a room and they pick up objects at random in this room to solve a series of clues that will play a role in solving the final clue to "escape" the locked room. This didactic learning activity utilizes technology to deliver a fun and interactive distance learning activity that resembles a live escape room.The interactive virtual escape room provided is a no cost, unique alternative educational activity that can be done either entirely or partly remotely. In order to replicate this team-based didactic exercise, the instructor needs to simply divide residents and students into small groups and then share with each group the link provided. A five-point Likert scale survey was distributed to participating learners after completing this activity to assess relevance and satisfaction of the high yield gastrointestinal/abdominal board review escape room. Thirty-two of forty-two participating residents/medical students completed this seven-question survey. All participating resident/medical students who completed the survey enjoyed this activity and that this was a unique learning experience, and the majority of participating residents/medical students thought this interactive virtual escape room was easy to use, learned something, thought this was a helpful way to review for emergency medicine boards or in-training exams, and preferred a game like this to a standard lecture. Additionally, over half of survey respondents said they are going to try to come up with a game for their assigned board review presentations. Escape room gamification of high yield gastrointestinal/abdominal board review material was an engaging, fun, and effective distance learning activity for residents and medical students. This didactic activity not only promoted interactive learning but also encouraged virtual teamwork among small groups. Gastroenterology, GI, abdominal, board review, in-training exam review, escape room, virtual didactics, distance learning, high yield, upper GI bleeding, esophageal varices, diarrhea, alkali ingestion, volvulus, foreign body, intussusception.

Application of adaptive resource allocation algorithm and communication network security in improving educational video transmission quality

With the rapid development of network multimedia technology, video communication technology has made great progress and has been applied in many fields. Educational video communication is an intuitive, timely, efficient, and remote communication tool. Video communication technology extends to educational and management. It includes interactive distance learning, distance course observation, distance conference, and training, which has caused a profound revolution in the education model and actively promoted the development of the education industry. This paper proposes the application of adaptive resource allocation algorithm and communication network security in improving the quality of educational video transmission. This article takes “Internet +” as the background and features media integration as the society enters the era of all-media. The development of education video dissemination in the era of all-media is of great significance. The content and expression of education video dissemination as a new media is mainly for youth. The audience's thinking will have a profound impact, and mainstream values will play a positive role in the physical and mental growth of young people. Therefore, we should correctly understand the application of video communication in the education industry, so that the technology can have fully applied, and a new era of education mode is opened.

Mesoscopic model framework for liquid slip in a confined parallel-plate flow channel

We investigated the liquid slip in a planar confined flow channel by proposing an exponentially decaying interaction force between fluid particles and two flat walls in the mesoscopic lattice Boltzmann model framework. In this way, we can explicitly link density profile, velocity profile, and apparent slip length with the mesoscale interaction parameters (force strength and decay length), and formulate the permeability-enhancement ratio as a function of two dimensionless numbers that indicate the role of interaction strength and interaction distance (relative to gap size of flow channel) in the slip-flow system.

Enhancing the stability of Geobacillus zalihae T1 lipase in organic solvents and insights into the structural stability of its variants

Critical to the applications of proteins in non-aqueous enzymatic processes is their structural dynamics in relation to solvent polarity. A pool of mutants derived from Geobacillus zalihae T1 lipase was screened in organic solvents (methanol, ethanol, propanol, butanol and pentanol) resulting in the selection of six mutants at initial screening (A83D/K251E, R21C, G35D/S195 N, K84R/R103C/M121I/T272 M and R106H/G327S). Site-directed mutagenesis further yielded quadruple mutants A83D/M121I/K251E/G327S and A83D/M121I/S195 N/T272 M, both of which had improved activity after incubation in methanol. The km and kcat values of these mutants vary marginally with the wild-type enzyme in the methanol/substrate mixture. Thermally induced unfolding of mutants was accompanied with some loss of secondary structure content. The root mean square deviations (RMSD) and B-factors revealed that changes in the structural organization are intertwined with an interplay of the protein backbone with organic solvents. Spatially exposed charged residues showed correlations between the solvation dynamics of the methanol solvent and the hydrophobicity of the residues. The short distances of the radial distribution function provided the required distances for hydrogen bond formation and hydrophobic interactions. These dynamic changes demonstrate newly formed structural interactions could be targeted and incorporated experimentally on the basis of solvent mobility and mutant residues.

The problem of art teaching based on interactive multimedia assisted instruction platform

When digital technology reproduces and simulates real scenes, it can realistically multi-dimensionally present and simulate real-life situations. This solves the problem that the design methods that are difficult to avoid in art design teaching are out of touch with the real space environment, and the design concept and function are out of touch. The openness of the teaching knowledge of art design in interactive teaching platform is reflected in the informationization of resources and the development of diverse knowledge. This paper proposes an architecture scheme of multimedia remote interactive teaching system composed of network multimedia teaching platform, general network teaching platform, digital resource management platform, streaming media resource recording platform and interactive distance learning platform. The system architecture has the characteristics that the underlying data are mutually integrated and the platforms complement each other. The essential characteristics of e-Learning are provided in the interaction characteristics, the dynamic resource scheduling function is enabled, and the multimedia-assisted remote interactive teaching in the future m-Learning and u-learning eras The system proposes a vision.

Collective steady-state patterns of swarmalators with finite-cutoff interaction distance.

We study the steady-state patterns of population of the coupled oscillators that sync and swarm, where the interaction distances among the oscillators have a finite-cutoff in the interaction distance. We examine how the static patterns known in the infinite-cutoff are reproduced or deformed and explore a new static pattern that does not appear until a finite-cutoff is considered. All steady-state patterns of the infinite-cutoff, static sync, static async, and static phase wave are repeated in space for proper finite-cutoff ranges. Their deformation in shape and density takes place for the other finite-cutoff ranges. Bar-like phase wave states are observed, which has not been the case for the infinite-cutoff. All the patterns are investigated via numerical and theoretical analyses.

Enhancing the Photovoltaic Performance of Ladder‐Type Heteroheptacene‐based Nonfullerene Acceptors by Incorporating Halogen Atoms on Their Ending Groups

AbstractEnding group halogenation is an effective strategy for modulating the energy levels, bandgaps, and intermolecular interactions of nonfullerene acceptors. Understanding the influence of different halogen atoms on the acceptor properties is of great importance for designing high‐performance nonfullerene acceptors. Here, three acceptor–donor–acceptor (A‐D‐A) type nonfullerene acceptors (M5, M6, and M7), which are constructed by using a ladder‐type heteroheptacene core without the traditional sp3 carbon‐bonded side chains as the electron‐rich core, and 2‐(3‐oxo‐2,3‐dihydro‐1H‐inden‐1‐ylidene)malononitrile without or with halogen atoms as the ending groups. The nonfullerene acceptors with chlorinated (M6) and brominated (M7) ending groups exhibit broadened absorption spectra, down‐shifted energy levels, and enhanced molecular ordering compared to the counterpart without any halogenated ending groups (M5). Among the nonfullerene acceptors, M6 has the strongest intermolecular ππ interaction with its shortest ππ interaction distance and the longest coherent length which are beneficial for enhancing the charge transport and therefore boosting the photovoltaic performance. An excellent power conversion efficiency of 15.45% is achieved for the best‐performing polymer solar cell based on M6. These results suggest that the halogenated ending groups are essential for high‐performance heteroheptacene‐based nonfullerene acceptors considering their simultaneous enhancements in both the light‐harvesting and the charge transport.

Multipoint connection by long-range density interaction and short-range distance rule

The performance of a system is influenced by the way its elements are connected. Networks of cells with high clustering and short paths communicate more efficiently than random or periodic networks of the same size. While many algorithms exist for generating networks from distributions of points in a plane, most of them are based on the oversimplification that a system’s components form connections in proportion to the inverse of their distance. The Waxman algorithm, which is based on a similar assumption, represents the gold standard for those who want to model biological networks from the spatial layout of cells. This assumption, however, does not allow to reproduce accurately the complexity of physical or biological systems, where elements establish both short and long-range connections, the combination of the two resulting in non-trivial topological features, including small-world characteristics. Here, we present a wiring algorithm that connects elements of a system using the logical connective between two disjoint probabilities, one correlated to the inverse of their distance, as in Waxman, and one associated to the density of points in the neighborhood of the system’s element. The first probability regulates the development of links or edges among adjacent nodes, while the latter governs interactions between cluster centers, where the density of points is often higher. We demonstrate that, by varying the parameters of the model, one can obtain networks with wanted values of small-world-ness, ranging from ∼1 (random graphs) to ∼14 (small world networks).

An Approach to Scene Recognition Based on the Local Interaction of a Group of Robots

The paper considers a group of animates (bio-inspired abstract models or technical devices) that use the visual analyzer described by the authors earlier. The visual analyzer recognizes the scene observed by the animat, determines the class of the situation and selects the corresponding behavior. The analyzer is based on the" language of poses" , borrowed from some species of ants, which allows them to visually inform other individuals of their condition. The first proposed algorithm describes a visual memory mechanism that allows an animat to remember seen objects for some time and select its behavior in a more stable way compared to a basic visual analyzer. The second algorithm describes a group recognition approach. Robots are able to exchange information about the scene they are observing presented in the form of a graph using local communication. The robot, receiving such information from its neighbors, is able to expand its picture of the world and more correctly choose its behavior based on the recognized situation than if it only had its own data. A demonstration task was set to test the efficiency, approximately simulating a colony of ants that gather food in a certain area. Colony, nest, food, and enemy individuals are modeled in the developed simulation environment. Group efficiency was defined as the amount of food collected over the allotted time period. Animates using the visual memory algorithm showed an increase in efficiency for all the studied memory parameters. Moreover, the dependence is not monotonic, and there is a certain value at which maximum efficiency is achieved. The use of the group recognition algorithm also showed an increase in efficiency compared to the basic visual analyzer. The experiments were carried out for different distances of local interaction. As with memory, there is a value of interaction distance at which the maximum efficiency is achieved. The combination of both algorithms also has interesting results. The experiments showed that the smaller the memory of the robot, the greater the increase in efficiency from using the collective recognition algorithm.

A Cuda Fast Multipole Method with Highly Efficient M2L Far Field Evaluation

Solving an N-body problem is a computationally quite demanding task in many scientific fields ranging from astrophysics to biomolecular simulations. However, the direct solution scales with O(N2); hence, even on modern hardware, the direct calculation becomes impractical even for moderate numbers of particles, and thus, efficient yet accurate approximations are key. For biomolecular simulations, a widely used such method is Particle Mesh Ewald (PME), which scales with O(N log N). Although extremely fast on a single node, PME runs into communication bottlenecks when parallelized for large simulation systems on many nodes. The fast multipole method (FMM) offers an attractive alternative: It requires less communication and reduces the complexity to optimal O(N). The method approximates long-range interactions by grouping the particles into clusters represented as multipoles. The cluster size grows with the interaction distance according to the underlying octree structure. Hence, further separated particles require fewer interaction computations, hence less communication. Here, we present our full NVIDIA CUDA FMM implementation, which has been optimized for the electrostatic interactions described by Coulomb's law relevant to molecular dynamics simulations. We compare different parallelization approaches to the computationally limiting part of the algorithm, the Multipole-to-Local (M2L) operator, and discuss their performance bottlenecks. The first approach can be implemented with only minimal modifications to the sequential CPU implementation. It features the Unified Memory concept, which allows for a simple utilization of the existing CPU data structures. The second approach enhances the achieved performance by exploiting CUDA Dynamic Parallelism. It introduces a significant speedup, especially for a high accuracy requirement. The third parallelization approach abstracts the underlying octree with precomputed interaction lists and it exploits operator symmetries to achieve nearly optimal performance in the whole tested accuracy range.