Computer Simulation Experiments Research Articles

Rhythm-adaptive statistical estimation methods of PROBABILISTIC CHARACTERISTICS OF CYCLIC RANDOM PROCESSES

The paper is devoted to the rhythm-adaptive statistical estimation methods of cyclic random processes probabilistic characteristics. The main goal of the article is development and research of rhythm-adaptive methods of cyclic random processes statistical processing. Based on the fundamental fact of invariance of probabilistic characteristics of a cyclic random process to time shifts determined by its rhythm function, rhythm-adaptive statistical estimations of initial, central and mixed moment functions of cyclic random processes of discrete parameter were obtained. The article analytically proves the unbiasedness and consistency of rhythm-adaptive statistical estimates of the mathematical expectation and the initial moment functions of the higher order of cyclic random process. By conducting a series of computer simulation experiments, it has been demonstrated, that the absolute errors of rhythm-adaptive methods of statistical estimation are significantly smaller than the corresponding errors for classical non-rhythm adaptive methods of statistical estimation of cyclic stochastic signals probabilistic characteristics. The effectiveness of using rhythm-adaptive methods of statistical estimation of probabilistic characteristics of ECG signals has been demonstrated. The results obtained in the work clearly demonstrate the essential advantages of rhythm-adaptive methods of statistical processing of cyclic stochastic signals with a variable (irregular) rhythm in comparison with non-rhythm-adaptive analogues.

The simulation experiment description markup language (SED-ML): language specification for level 1 version 5.

Modern biological research is increasingly informed by computational simulation experiments, which necessitate the development of methods for annotating, archiving, sharing, and reproducing the conducted experiments. These simulations increasingly require extensive collaboration among modelers, experimentalists, and engineers. The Minimum Information About a Simulation Experiment (MIASE) guidelines outline the information needed to share simulation experiments. SED-ML is a computer-readable format for the information outlined by MIASE, created as a community project and supported by many investigators and software tools. Level 1 Version 5 of SED-ML expands the ability of modelers to define simulations in SED-ML using the Kinetic Simulation Algorithm Onotoloy (KiSAO). While it was possible in Version 4 to define a simulation entirely using KiSAO, Version 5 now allows users to define tasks, model changes, ranges, and outputs using the ontology as well. SED-ML is supported by a growing ecosystem of investigators, model languages, and software tools, including various languages for constraint-based, kinetic, qualitative, rule-based, and spatial models, and many simulation tools, visual editors, model repositories, and validators. Additional information about SED-ML is available at https://sed-ml.org/.

Using broadband long-wavelength channel to increase the capture range of segment piston phase retrieval for segmented-aperture systems

Using broadband long-wavelength channel to increase the capture range of segment piston phase retrieval for segmented-aperture systems

A Kalman Filtering Algorithm for Measurement Interruption Based on Polynomial Interpolation and Taylor Expansion.

Combined SINS/GPS navigation systems have been widely used. However, when the traditional combined SINS/GPS navigation system travels between tall buildings, in the shade of trees, or through tunnels, the GPS encounters frequent signal blocking, which leads to the interruption of GPS signals, and as a result, the combined SINS/GPS-based navigation method degenerates into a pure inertial guidance system, which will lead to the accumulation of navigation errors. In this paper, an adaptive Kalman filtering algorithm based on polynomial fitting and a Taylor expansion is proposed. Through the navigation information output from the inertial guidance system, the polynomial interpolation method is used to construct the velocity equation and position equation of the carrier, and then the Taylor expansion is used to construct the virtual measurement at the moment of the GPS signal interruption, which can make up for the impact of the lack of measurement information on the combined SINS/GPS navigation system when the GPS signal is interrupted. The results of computer simulation experiments and road measurement tests based on the loosely combined SINS/GPS navigation system show that when the carrier faces a GPS signal interruption situation, compared with a combined SINS/GPS navigation algorithm that does not take any rescue measures, our proposed combined SINS/GPS navigation algorithm possesses a higher accuracy in the attitude angle estimation, a higher accuracy in the velocity estimation, and a higher accuracy in the positional localization, and the system possesses higher stability.

On energy conservation for fixed-wing UAV assisted practical full-duplex relaying with service requirement and bank angle limit

This paper studies a full-duplex (FD) amplify-and-forward relaying, where a fixed-wing unmanned aerial vehicle (UAV) is dispatched as a mobile relay to serve a source-destination communication pair so as to satisfy their service requirement. Here, the UAV relay flies in a circular path and hence it must continuously change its heading of flight which leads to a bank angle of the aircraft. In order to ensure flight safety, therefore, a bank angle limit is imposed on the UAV relay. By considering a practical FD relaying, namely, there exists both residual loop interference (RLI) and processing time-delay at the relay side, novel signal to interference plus noise ratio (SINR) received at the destination is analyzed, giving a closed-form expression in addition to a concise lower-bound. Armed with the SINR analysis, the size of data received by the destination during a period of flight time of the UAV is calculated, leading to a closed-form lower-bound of the size of data. Taking bank angle limit into consideration and using the calculated lower-bound of the size of data, an optimization problem with the purpose of energy conservation is solved, leading to a novel method for joint adjustment of the UAV's flight parameters. Computer simulation experiments are conducted, and the results demonstrated that the proposed optimization method performs better in terms of energy conservation compared to the benchmark techniques regardless of the value of RLI and/or the service requirement of the source-destination communication pair.

Vision-based collective motion: A locust-inspired reductionist model.

Naturally occurring collective motion is a fascinating phenomenon in which swarming individuals aggregate and coordinate their motion. Many theoretical models of swarming assume idealized, perfect perceptual capabilities, and ignore the underlying perception processes, particularly for agents relying on visual perception. Specifically, biological vision in many swarming animals, such as locusts, utilizes monocular non-stereoscopic vision, which prevents perfect acquisition of distances and velocities. Moreover, swarming peers can visually occlude each other, further introducing estimation errors. In this study, we explore necessary conditions for the emergence of ordered collective motion under restricted conditions, using non-stereoscopic, monocular vision. We present a model of vision-based collective motion for locust-like agents: elongated shape, omni-directional visual sensor parallel to the horizontal plane, and lacking stereoscopic depth perception. The model addresses (i) the non-stereoscopic estimation of distance and velocity, (ii) the presence of occlusions in the visual field. We consider and compare three strategies that an agent may use to interpret partially-occluded visual information at the cost of the computational complexity required for the visual perception processes. Computer-simulated experiments conducted in various geometrical environments (toroidal, corridor, and ring-shaped arenas) demonstrate that the models can result in an ordered or near-ordered state. At the same time, they differ in the rate at which order is achieved. Moreover, the results are sensitive to the elongation of the agents. Experiments in geometrically constrained environments reveal differences between the models and elucidate possible tradeoffs in using them to control swarming agents. These suggest avenues for further study in biology and robotics.

Investigation the feasibility of complex circular motion of implants in magnetic stereotaxis systems

In this paper, we explore the feasibility of controlling the circular motion of the implant in a non-contact manner by controlling the change of the external magnetic field in a magnetic stereotaxic system. The change of the external magnetic field was simulated through computer simulation experiments, so as to control the circular motion of a small permanent magnet in a non-contact manner, and in the actual experiment, the slide rail system was equipped with a large permanent magnet to form an external magnetic field, and the operation of the slide rail system was controlled by an Arduino microcontroller. The results of computer simulation experiments were verified, and the feasibility of non-contact control of the circular motion of the implant was clarified.

A criterion and incremental design construction for simultaneous kriging predictions

In this paper, we further investigate the problem of selecting a set of design points for universal kriging, which is a widely used technique for spatial data analysis. Our goal is to select the design points in order to make simultaneous predictions of the random variable of interest at a finite number of unsampled locations with maximum precision. Specifically, we consider as response a correlated random field given by a linear model with an unknown parameter vector and a spatial error correlation structure. We propose a new design criterion that aims at simultaneously minimizing the variation of the prediction errors at various points. We also present various efficient techniques for incrementally building designs for that criterion scaling well for high dimensions. Thus the method is particularly suitable for big data applications in areas of spatial data analysis such as mining, hydrogeology, natural resource monitoring, and environmental sciences or equivalently for any computer simulation experiments. We have demonstrated the effectiveness of the proposed designs through two illustrative examples: one by simulation and another based on real data from Upper Austria.

Sabretooths, giant hyenas, and hominins: Shifts in the niche of Early Pleistocene scavengers in Iberia at the Epivillafranchian-Galerian transition

The Epivillafranchian and the transition to the Galerian (1.2–0.9 Ma) was a period marked by environmental fluctuations and faunal turnover. Homo arrived into Europe around 1.4 Ma. ago, and was established in Iberia during the Epivillafranchian, as evidenced by the oldest sites with hominin fossils located in the Iberian Peninsula. The Iberian ecosystems offered a variety of trophic resources to hominins, including the opportunity to scavenge carcasses of large ungulates killed by a diverse predatory guild, especially due to the presence of two sabre-toothed cats. It has been claimed that the presence of Pachycrocuta brevirostris, a strong competitor for carrion, prevented hominins from exploiting abandoned carcasses as a reliable meat and fat resource. However, computer simulation experiments suggest that the coexistence of P. brevirostris and hominins competing for carrion was ecologically viable in the Epivillafranchian. Nevertheless, the faunal turnover of the Epivillafranchian-Galerian transition drastically changed the composition of the large carnivore fauna. The changes include the extinction of the sabre-toothed felid Megantereon, frequently considered a key provider of partially consumed carcasses, and the demise of the hyperscavenger P. brevirostris. All these changes modified the ecological scenario and the opportunities for hominins and other facultative scavengers. Computer simulation experiments using the agent-based model SCAVCOMP-ABM are used here to evaluate the viability of the coexistence of hominins and giant hyenas in the Epivillafranchian-Galerian transition. Different ecological scenarios defined by the composition of the predatory guild, ecosystem productivity, and competition pressure from other scavengers are evaluated. Results suggest that hominins and giant hyenas could coexist during the Epivillafranchian with different carnivore guilds, but a disruption of the scavenging niche likely occurred in the transition to the Galerian, coinciding with the extinction of P. brevirostris. A low ecosystem productivity during the cold intervals, maintenance of a high competition for carrion with other facultative scavengers, and a hypothetical social behaviour of the sabre-toothed cat Homotherium latidens appear as key factors to explain the changes in the scavenger guild at the Epivillafranchian-Galerian transition.

Energy Minimization for In-Band Full-Duplex Relaying Using an Amplify-and-Forward UAV Relay

This paper investigates an in-band full-duplex (IBFD) relaying, where a fixed-wing unmanned aerial vehicle (UAV) is dispatched as an amplify-and-forward relay to forward data from a source to a destination. By considering ideal and practical IBFD cases, new received signal-to-noise ratio (SNR) expressions at the destination are derived. Armed with the newly derived SNR expressions and the existing one in literature, three different lower-bounds of the size of data received by the destination are calculated. Using the three lower-bounds of the size of data, an optimization problem corresponding to energy minimization of the IBFD relaying system subject to a total data-bit constraint in addition to a mission completion time (MCT) constraint is solved, leading to three sets of solutions. Computer simulation experiments are conducted and the accuracy of the derived SNR expressions and the three sets of solutions of the optimization problem are compared. The results demonstrated that the newly derived SNR expressions are more accurate than the existing one in literature and are more suitable to be utilized for energy minimization, and the proposed optimization method can complete the relaying task with the minimum energy and MCT. When the residual loop-interference channel power is equal to -100dB, the scheme of ideal IBFD only consumes up to 2.5% of the energy of the compared schemes regardless of the value of the total data-bit constraint.

A STUDY OF IMPROVEMENT OF A TECHNOLOGY FOR OBTAINING RADIATION-PROTECTING MATERIALS FOR SPACECRAFT AND ROCKETRY SYSTEMS


 
 
 Abstract. The use of commercial integrated circuits (ICs) in the electronic equipment of the spacecraft entails a certain risk. This is due to the fact that some commercial ICs are not suitable for operating conditions in space, most have a functional failure rate of about 10 krad per total accumulated dose (ie quite low), durability is not controlled from lot to lot, and reliability in extreme operating conditions is not defined. The object of development and research were the processes of interaction of materials with corpuscular radiation in a wide range of energies, and the subject of research was the shielding of electron and proton flows with energies up to 100 MeV by disperse -filled composite materials with a polymer matrix. A promising way to increase the survivability of the spacecraft by reducing the accumulated radiation dose is the use of protective materials that effectively protect the BEA from the radiation flow. The analysis of the current state of protection of radio- electronic equipment of space technology made it possible to establish that the most effective protection can be achieved by optimally combining the content of light and heavy elements in the composite material (CM). Modern research is aimed at obtaining composite materials that have the ability to weaken and disperse both light and heavy elementary particles. In the State University named after O. Honchar developed fundamentally new composite materials, which are superior in protection efficiency to those used today - metal ones, and are not inferior to the best world analogues. Preliminary results of theoretical and experimental research, including the use of computer modeling and simulation experiments on electron and proton accelerators, made it possible to draw conclusions about the possibility of increasing the complex of protective properties and prospects of the materials being created. The flow of high-energy electrons decreases by 1.4 times, and protons by 1.6 times compared to aluminum alloys. Enterprises of the space industry of Ukraine have shown great interest in the use of new protective materials. Analysis of the available information shows that the created materials are superior in operational parameters to those used today in China, Russia, Ukraine and other space countries. According to theoretical calculations, CM samples were developed, which have a higher stopping power of electrons than aluminum or its alloys, which are currently used in space vehicles in almost the entire range of the spectrum characteristic of GSO. Studies using the ELIAS linear electron accelerator showed that the obtained KM samples are more than 1.3 times more effective in terms of protective properties compared to aluminum at electron energies of the order of 2-3 MeV . There are prerequisites for obtaining an even more effective attenuation of the electron flow in comparison with the "reference" aluminum due to the variation of both the qualitative composition of the CM and its structure.
 
 

Efficient five-axis scanning-inspection path planning for complex freeform surfaces

Freeform surface inspection is vital in manufacturing-related processes, and the newly emerged five-axis continuous sweep scanning technology offers to be a powerful means for accurate inspection of freeform surfaces. However, at present, for an arbitrary freeform surface, it still heavily depends on human intervention in planning an interference-free sweep scanning path, wherein typically the surface is simply partitioned into several subregions and sweep scanning paths are then individually planned for each subregion. In this paper, we present a novel and practical algorithm for automatically planning an efficient five-axis inspection path for an arbitrary freeform surface. The strategy is based on the idea of converting the inspection path planning problem into a set-covering problem, whose solution then gives out a near-minimum set of inspection paths for the freeform surface while subject to necessary constraints such as sampling resolution, collision-free, and others. Both computer simulation and physical inspection experiments of the proposed method have been conducted, and the results give a preliminary confirmation on the effectiveness and advantages of the proposed method.

A Stable Sound Field Control Method for a Personal Audio System

A personal audio system has a wide application prospect in people’s lives, which can be implemented by sound field control technology. However, the current sound field control technology is mainly based on sound pressure or its improvement, ignoring another physical property of sound: particle velocity, which is not conducive to the stability of the entire reconstruction system. To address the problem, a sound field method is constructed in this paper, which minimizes the reconstruction error in the bright zone, minimizes the loudspeaker array effort in the reconstruction system, and at the same time controls the particle velocity and sound pressure of the dark zone. Five unevenly placed loudspeakers were used as the initial setup for the computer simulation experiment. Simulation results suggest that the proposed method is better than the PM (pressure matching) and EDPM (eigen decomposition pseudoinverse method) methods in the bright zone in an acoustic contrast index, the ACC (acoustic contrast control) method in a reconstruction error index, and the ACC, PM, and EDPM methods in the bright zone in a loudspeaker array effort index. The average array effort of the proposed method is the smallest, which is about 9.4790, 8.0712, and 4.8176 dB less than that of the ACC method, the PM method in the bright zone, and the EDPM method in the bright zone, respectively, so the proposed method can produce the most stable reconstruction system when the loudspeaker system is not evenly placed. The results of computer experiments demonstrate the performance of the proposed method, and suggest that compared with traditional methods, the proposed method can achieve more balanced results in the three indexes of acoustic contrast, reconstruction error, and loudspeaker array effort on the whole.

A wide-beam NCS algorithm for multi-receiver SAS based on azimuth spectrum superposition

The existing multi-receiver synthetic aperture sonar (SAS) imaging algorithms are suitable for narrow-beam width, which will lead to a decrease in imaging quality under wide-beam condition and are not in line with the development needs of SAS. We propose a non-linear chirp scaling algorithm (NCSA) for wide beam multi-receiver SAS. Firstly, the point target reference spectrum (PTRS) of each receiver is obtained by the Lagrange inversion theorem (LIT), and then the under-sampled signal in the azimuth frequency domain is obtained through azimuth spectrum extension; Then, considering the cubic term of range frequency in the PTRS and the linear variation of equivalent frequency modulation slope with range, each receiver is imaged using the NCSA, and coherent superposition is performed in the azimuth frequency domain to eliminate spectrum aliasing caused by azimuth spectrum extension; Finally, the azimuth inverse transform is performed on the superimposed signal to obtain the focusing imaging. Computer simulation experiments and field data verify that this method is superior to the existing SAS imaging algorithm, improving the quality of wide-beam imaging, avoiding the interpolation operation of the traditional range-Doppler algorithm, and saving computation cost.

Explore the feasibility study of magnetic stereotaxic system

This paper introduces the magnetic stereotaxis system in detail, and establishes the basic model of the magnetic stereotaxic system in three-dimensional space through the computer simulation software COMSOL, and conducts theoretical analysis and computer simulation experiments on the non-contact control of implants. After that, the slide rail system controlled by Arduino was constructed in actual experiments, and the results of computer simulation experiments were verified. It has also been demonstrated that changing the external magnetic field strength in a magnetic stereotaxic system enables non-contact control of implant movement.

A novel method of interference source direction-finding with an existing single antenna beam in communication satellites

Interference has recently become a critical factor in communication satellite performance, and the interference source location is one of the most important factors in resolving this issue. The article proposes an innovative method of interference source direction-finding suitable for communication satellites with an existing single antenna beam and single radio frequency (RF) channel, which utilizes the symmetry of the antenna pattern to search for interference sources. Compared to traditional position methods with time-frequency-synchronized multi-satellites or a directing antenna array in a single satellite, the method does not require any particular direction-finding payload in communication satellites and shares existing antennas and RF channels with communication systems in satellites. The ability to find the direction of the interference source is a software-defined function in the communication processor. The proposed method provides a novel way to solve the problems of interference source direction-finding with the least engineering complexity, and it has excellent coexistence with other existing systems in communication satellites. The computer simulation and out-field experiment results in this article show that the method has excellent performance with high direction-finding resolution within extensive coverage, offering significant value and bright prospects for resolving the growing interference issues in communication satellites.

Machine learning opens a doorway for microrheology with optical tweezers in living systems

It has been argued that linear microrheology with optical tweezers (MOT) of living systems “is not an option” because of the wide gap between the observation time required to collect statistically valid data and the mutational times of the organisms under study. Here, we have explored modern machine learning (ML) methods to reduce the duration of MOT measurements from tens of minutes down to one second by focusing on the analysis of computer simulated experiments. For the first time in the literature, we explicate the relationship between the required duration of MOT measurements (Tm) and the fluid relative viscosity (ηr) to achieve an uncertainty as low as 1% by means of conventional analytical methods, i.e., Tm≅17ηr3 minutes, thus revealing why conventional MOT measurements commonly underestimate the materials’ viscoelastic properties, especially in the case of high viscous fluids or soft-solids. Finally, by means of real experimental data, we have developed and corroborated an ML algorithm to determine the viscosity of Newtonian fluids from trajectories of only one second in duration, yet capable of returning viscosity values carrying an error as low as ∼0.3% at best, hence opening a doorway for MOT in living systems.

Path following of under-actuated ships based on backstepping and predictive control method.

To deal with the sideslip angle caused by the current disturbances or transverse motion for path following of under-actuated ships, a nonlinear observer established by an exponential function is introduced in the backstepping approach which converts the path following into heading control. Then, the model predictive control (MPC) method is used as a heading controller, addressing the rudder optimization. A linear extended state observer technology was exploited to estimate yaw rate, external disturbances, and internal uncertainties, which could avoid measuring the high-order state used in the MPC controller and promote the accuracy of the MPC internal model. Moreover, an inverse tangent function is applied to develop a new method for switching the reference heading angle to reduce rudder amplitude when the ship is choosing the next waypoint. Finally, the validity and reliability of the design method were verified through comparative computer simulation experiments.

Distributive Justice in Collaborative Outputs: Empowering Minority Viewpoints Through Deliberation

Abstract This article explores how deliberation affects distributive justice for minority view participants in policy decisions made through collaborative governance. It also examines whether the quality of deliberation (i.e., willingness to accept opposing viewpoints) and quantity of deliberation (i.e., length of discussion) can be an effective tool for minority view participants to overcome power imbalances in such collective decision-making processes. I use agent-based modeling, a computer simulation experiment method, to examine interactions among participants in a collaborative governance arrangement. I develop a series of theoretical propositions based on the simulation results, which are robust to various changes in the parameters and assumptions of the model. First, both the quality and quantity of deliberation may enhance the decision acceptability of participants with minority views. Second, the quality of deliberation may be more effective at empowering underrepresented minority view participants than the quantity of deliberation. Third, the quantity of deliberation may better promote minority views than the quality of deliberation when minority view participants are overrepresented. These findings indicate that interpersonal justice in collaborative processes may enhance distributive justice for minority viewpoints in collaborative outputs, even when procedural justice in the design of collaboration is weakened by an underrepresentation of minority view participants. I conclude with suggestions for future research that can further improve the external validity of the theoretical propositions.

Multivariate modular metabolic engineering for enhanced l-methionine biosynthesis in Escherichia coli

Backgroundl-Methionine is the only bulk amino acid that has not been industrially produced by the fermentation method. Due to highly complex and strictly regulated biosynthesis, the development of microbial strains for high-level l-methionine production has remained challenging in recent years.ResultsBy strengthening the l-methionine terminal synthetic module via site-directed mutation of l-homoserine O-succinyltransferase (MetA) and overexpression of metAfbr, metC, and yjeH, l-methionine production was increased to 1.93 g/L in shake flask fermentation. Deletion of the pykA and pykF genes further improved l-methionine production to 2.51 g/L in shake flask fermentation. Computer simulation and auxotrophic experiments verified that during the synthesis of l-methionine, equimolar amounts of l-isoleucine were accumulated via the elimination reaction of cystathionine γ-synthetase MetB due to the insufficient supply of l-cysteine. To increase the supply of l-cysteine, the l-cysteine synthetic module was strengthened by overexpression of cysEfbr, serAfbr, and cysDN, which further increased the production of l-methionine by 52.9% and significantly reduced the accumulation of the byproduct l-isoleucine by 29.1%. After optimizing the addition of ammonium thiosulfate, the final metabolically engineered strain MET17 produced 21.28 g/L l-methionine in 64 h with glucose as the carbon source in a 5 L fermenter, representing the highest l-methionine titer reported to date.ConclusionsIn this study, a high-efficiency strain for l-methionine production was derived from wild-type Escherichia coli W3110 by rational metabolic engineering strategies, providing an efficient platform for the industrial production of l-methionine.