Regular Field Research Articles

Numerical investigation of wave-cylinder interaction based on a momentum source wave generation method

A momentum source function is constructed for wave generation based on linear wave theory. Based on Navier-Stokes equation and volume of fluid (VOF) method, a three-dimensional numerical wave tank (NWT) is established. Regular and irregular waves can be simulated by applying the momentum source function to NWT, and the expected wave characteristic parameters and wave spectrum are obtained. Furthermore, the load characteristics of two types of cylinders, fully piercing cylinder (FPC) and truncated cylinder (TC), are studied under regular wave field combined with boundary data immersed method (BDIM). Results show that the transverse force exerted on cylinders is dominated by inertial force. And because of the effects of the cylinder on wave profile and drag force, the maximum transverse force occurs soon after the wave node passes through the centerline of the cylinder. Compared with the FPC, the drag force has a greater influence on TC.

Large-scale turbulence cascade in the spiral galaxy NGC 6946

ABSTRACT The generation mechanism of compressible fluid turbulence at kiloparsec scales in the interstellar medium is a long-lasting puzzle. In this work, we explore the nature of large-scale turbulence in the external spiral galaxy NGC 6946. We use the visibility moment estimator to measure the H i column density and line-of-sight turbulent velocity power spectra combining the new observations of A array configuration of Karl G. Jansky Very Large Array (VLA) with the VLA B, C, D array observations from The H i Nearby Galaxy Survey. The estimated power spectra are obeying a power law with a slope of −0.96 ± 0.05 in column density and −1.81 ± 0.07 in line-of-sight velocity in length-scales ranging from 6 kpc to 170 pc. This points towards a forward energy cascade in the plane of the disc with a driving scale at least as large as 6 kpc. The values of the power-law indices indicate a combination of solenoidal and compressive force responsible for driving the measured turbulence. The presence of strong regular magnetic fields from the magnetic spiral arms in the galaxy is possibly contributing to the solenoidal part, while self-gravity or gravitational instability can mostly be the input for the compressive part of the forcing in the driving mechanism.

Analytic study of the Maxwell electromagnetic invariant in spinning and charged Kerr-Newman black-hole spacetimes

The Maxwell invariant plays a fundamental role in the mathematical description of electromagnetic fields in charged spacetimes. In particular, it has recently been proved that spatially regular scalar fields which are non-minimally coupled to the Maxwell electromagnetic invariant can be supported by spinning and charged Kerr-Newman black holes. Motivated by this physically intriguing property of asymptotically flat black holes in composed Einstein-Maxwell-scalar field theories, we present a detailed analytical study of the physical and mathematical properties of the Maxwell electromagnetic invariant FKNrθMaQ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\mathcal{F}}_{\ extrm{KN}}\\left(r,\ heta; M,a,Q\\right) $$\\end{document} which characterizes the Kerr-Newman black-hole spacetime [here {r, θ} are respectively the radial and polar coordinates of the curved spacetime and {M, J = M a, Q} are respectively the mass, angular momentum, and electric charge parameters of the black hole]. It is proved that, for all Kerr-Newman black-hole spacetimes, the spin and charge dependent minimum value of the Maxwell electromagnetic invariant is attained on the equator of the black-hole surface. Interestingly, we reveal the physically important fact that Kerr-Newman spacetimes are characterized by two critical values of the dimensionless rotation parameter â≡a/r+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\hat{a}\\equiv a/{r}_{+} $$\\end{document} [here r+ (M, a, Q) is the black-hole horizon radius], âcrit−=3−22\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\hat{a}}_{\ extrm{crit}}^{-}=\\sqrt{3-2\\sqrt{2}} $$\\end{document} and âcrit+=5−25\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\hat{a}}_{\ extrm{crit}}^{+}=\\sqrt{5-2\\sqrt{5}} $$\\end{document}, which mark the boundaries between three qualitatively different spatial functional behaviors of the Maxwell electromagnetic invariant: (i) Kerr-Newman black holes in the slow-rotation â<âcrit−\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\hat{a}<{\\hat{a}}_{\ extrm{crit}}^{-} $$\\end{document} regime are characterized by negative definite Maxwell electromagnetic invariants that increase monotonically towards spatial infinity, (ii) for black holes in the intermediate spin regime âcrit−≤â≤âcrit+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\hat{a}}_{\ extrm{crit}}^{-}\\le \\hat{a}\\le {\\hat{a}}_{\ extrm{crit}}^{+} $$\\end{document}, the positive global maximum of the Kerr-Newman Maxwell electromagnetic invariant is located at the black-hole poles, and (iii) Kerr-Newman black holes in the super-critical regime â<âcrit+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\hat{a}<{\\hat{a}}_{\ extrm{crit}}^{+} $$\\end{document} are characterized by a non-monotonic spatial behavior of the Maxwell electromagnetic invariant FKNr=r+θMaQ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\mathcal{F}}_{\ extrm{KN}}\\left(r={r}_{+},\ heta; M,a,Q\\right) $$\\end{document} along the black-hole horizon with a spin and charge dependent global maximum whose polar angular location is characterized by the dimensionless functional relation â2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\hat{a}}^2 $$\\end{document} · (cos2θ)max = 5 – 25\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ 2\\sqrt{5} $$\\end{document}.

Retention Schemes for Cross-Cultural Missionaries: Enhancing Long-Term Commitment and Effectiveness

This paper aims to provide a comprehensive review and analysis of academic journal publications relevant to retention schemes for cross-cultural missionaries. Retention refers to the ability to sustain missionaries' commitment and engagement in the field. It encompasses strategies aimed at reducing attrition rates and fostering missionaries' long-term effectiveness. Several studies have delved into this topic and provided valuable insights regarding strategies that can positively influence retention. However, this paper seeks to uncover the retention schemes that might serve as a panacea for cross-cultural missionary attrition. The study investigates and identifies effective strategies and interventions that can contribute to the long-term engagement and effectiveness of cross-cultural missionaries in their various places of assignment. By examining a range of scholarly articles, this paper has provided an overview of various retention schemes, including pre-deployment training and cultural orientation; continuous learning and professional development opportunities; personal, spiritual, emotional, and psychological support; adequate financial support and benefits; family care and support; mentorship and supervision; and regular field evaluations and feedback. This paper sheds light on key retention schemes for cross-cultural missionaries and offers evidence-based approaches to address them. Thereafter, it states the importance of the retention of cross-cultural missionaries.

First Record and Range Extension of &lt;i&gt;Burmattus pococki&lt;/i&gt; Thorell (Arachnida: Araneae: Salticidae)

The first record of the jumping spider Burmattus pococki Thorell from Assam, Northeast India is reported. During regular field surveys inside Moran College campus from March-May 2022, one male individual of B. pococki was found resting underneath the leaves of Ageratum conyzoides. The earlier Indian records of B. pococki are from Karnataka, Maharashtra and Manipur. This study updates distribution of B. pococki in India, showing a range extension of about 452 km from the last nearest location.

Climatology of quiet time geomagnetic field variations at two locations in Antarctica

During geomagnetic quiet conditions, Indian Antarctic stations are considered to be located outside the auroral oval: Maitri (CGM coordinates: 63.3°S, 54.2°E) is equatorward and Bharati (CGM coordinates: 74.8°S, 98.4°E) is poleward of the auroral oval. Simultaneous observations of magnetic field variations at these two locations for 10-years (2013–2022) provide an opportunity to study quiet-time magnetic field patterns, if any. Geomagnetic quiet days with ΣKp ≤ 3 are selected, during which the lower values of solar wind and interplanetary parameters are also confirmed. Maitri station exhibits clear southern hemispheric solar quiet (Sq) type of magnetic field variation on geomagnetic quiet days in all seasons, indicating the influence of ionospheric dynamo due to thermospheric winds. Interestingly, Bharati station also displays regular and systematic magnetic field variations in all three components. The D-component at Bharati exhibits very strong variation at early morning hours (7–8 MLT), which is ∼2–4 times stronger than that of H-component, driving strong equatorward/northward currents during all seasons. Both stations show annual type of seasonal variation with peak amplitude during summer and least during winter. The schematic illustration of global and polar Sqs proposed here explains the results obtained through 10-years’ statistical study.

Avifaunal diversity of Tsirang District with a new country record for Bhutan

Birds play a vital role in ecosystems. Studying avifaunal diversity therefore has a noteworthy role in indicating nature’s ecological balance in the environment. A total of 749 bird species have so far been recorded in Bhutan. We present a comprehensive checklist of birds of Tsirang, District which largely lies outside Bhutan’s protected area system. The data was collected through opportunistic encounters and with regular field visits to a range of locations in different seasons. One-fourth of the country’s total avifauna and a new species recorded for Bhutan, The Plum-headed Parakeet Psittacula cyanocephala was recorded as part of this study. In all, 285 avian species belonging to 18 orders and 65 families including one globally ‘Critically Endangered’, three ‘Vulnerable’, and a ‘Near Threatened’ species were recorded during the survey. The high species richness of birds in the study area reveals that it includes good habitats for birds in Bhutan. Similar studies are suggested in other areas contiguous to the protected areas in Bhutan including the current study area. This should aid in understanding of the factors driving the differences in bird diversity within and outside the protected areas so as to facilitate informed conservation actions in future.

Efficiency of satellite data in the agro-ecological monitoring system

The article discusses the ecological value of the normalized vegetation index (NDVI). Generalization of scientific data on the possibility of use in forestry, agriculture, ecological research, modeling of ecosystems and monitoring of the earth’s surface has been carried out. It was found that, unlike the surveyor, the operational/satellite monitoring of crops makes it possible to automatically generate reports, control the condition of crops, forecast yields and plan agricultural operations taking into account the real ecological state and weather conditions. In particular, you can create electronic vegetation maps; develop images and field relief for a specific region. It has been established that the use of data from remote sensing of the Earth (RSE) ensures the determination of the objective state of crops (density, quantitative and qualitative changes in crops, obtaining information on chemical treatments) on large areas. The factors that influence the calculation of NDVI are given, and the necessity of using an approach focused on climatic conditions is indicated. It was found that the transformation of multispectral NDVI data into one image layer allows estimating the amount of available vegetation and the development of crops on a field scale. Regular field NDVI mapping helps identify and mitigate any crop problems, increase yields, and make agribusiness more profitable. NDVI has become one of the most important and frequently used indicators in precision agriculture, so it deserves further practical research. This is a numerical indicator of the quality and quantity of plants in the field. It is emphasized that NDVI has become one of the most important and frequently used indicators in precision agriculture. Therefore, deserves further practical investigation. Ecosystem service is a means of identifying threats to ecosystems in order to develop socially acceptable and effective solutions to environmental problems. The ecosystem approach allows predicting changes, which is extremely important for spatial planning and land use management. This approach is especially important when assessing and resolving conflict situations in nature management, when the economic benefit from the use of one or another natural resource becomes a strong argument. From the point of view of human benefit, operational monitoring becomes an ecosystem service. The use of spectral indices contributes to the production of high-quality «environmentally friendly» products, the preservation of environmental components, the reproduction of soil fertility, obtaining the maximum profit, along with the transition from a linear economy to a circular one (economic effect), saving resources, optimizing and diversifying agricultural production.

Nested invariant tori foliating a vector field and its curl: Toward MHD equilibria and steady Euler flows in toroidal domains without continuous Euclidean isometries

This paper studies the problem of finding a three-dimensional solenoidal vector field such that both the vector field and its curl are tangential to a given family of toroidal surfaces. We show that this question can be translated into the problem of determining a periodic solution with periodic derivatives of a two-dimensional linear elliptic second-order partial differential equation on each toroidal surface and prove the existence of smooth solutions. Examples of smooth solutions foliated by toroidal surfaces that are not invariant under continuous Euclidean isometries are also constructed explicitly, and they are identified as equilibria of anisotropic magnetohydrodynamics. The problem examined here represents a weaker version of a fundamental mathematical problem that arises in the context of magnetohydrodynamics and fluid mechanics concerning the existence of regular equilibrium magnetic fields and steady Euler flows in bounded domains without continuous Euclidean isometries. The existence of such configurations represents a key theoretical issue for the design of the confining magnetic field in nuclear fusion reactors known as stellarators.

Fine asymptotic expansion of the ODE's flow

We study the dynamics of the flow X solution to the ODE: X′(t,x)=b(X(t,x)) with X(0,x)=x∈Rd, where b is a regular Zd-periodic vector field in Rd. We provide conditions on b to get the fine asymptotic expansion: |X(t,x)−x−tζ(x)|≤M<∞. To this end, we try to express X(t,x)−x−tζ(x) as Φ(X(t,x))−Φ(x), which yields the desired expansion when Φ is bounded. Then, assuming that the 2D Kolmogorov theorem and some extension for d>2 hold, we establish several regimes depending on the commensurability of the rotation vectors ζ(x) for which the expansion of X is valid. Moreover, we prove that for any 2D flow with a non vanishing smooth b inducing a unique incommensurable rotation vector ξ, the fine expansion holds in R2 if, and only if, ξ1/ξ2 is a Diophantine number. The case where ξ is commensurable is also investigated. Finally, several examples illustrate the different results, including the case of a vanishing b which blows up the asymptotic expansion in some direction. In particular, the case of some Euler flows is investigated.

FAST Polarization Mapping of the Supernova Remnant VRO 42.05.01

We have obtained the polarization data cube of the supernova remnant (SNR) VRO 42.05.01 at 1240 MHz using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST). Three-dimensional Faraday synthesis is applied to the FAST data to derive the Faraday depth spectrum. The peak Faraday depth map shows a large area of enhanced foreground rotation measure (RM) of ∼60 rad m−2 extending along the remnant’s “wing” section, which coincides with a large-scale H i shell at −20 km s−1. The two depolarization patches within the “wing” region with RMs of 97 rad m−2 and 55 rad m−2 coincide with two H i structures in the H i shell. Faraday screen model fitting on the Canadian Galactic Plane Survey 1420 MHz full-scale polarization data reveals a distance of (0.7–0.8)d SNR in front of the SNR with enhanced regular magnetic field there. The highly piled-up magnetic field indicates that the H i shell at −20 km s−1 could originate from an old evolved SNR.

CactiViT: Image-based smartphone application and transformer network for diagnosis of cactus cochineal

The cactus is a plant that grows in many rural areas, widely used as a hedge, and has multiple benefits through the manufacture of various cosmetics and other products. However, this crop has been suffering for some time from the attack of the carmine scale Dactylopius opuntia (Hemiptera: Dactylopiidae). The infestation can spread rapidly if not treated in the early stage. Current solutions consist of regular field checks by the naked eyes carried out by experts. The major difficulty is the lack of experts to check all fields, especially in remote areas. In addition, this requires time and resources. Hence the need for a system that can categorize the health level of cacti remotely. To date, deep learning models used to categorize plant diseases from images have not addressed the mealy bug infestation of cacti because computer vision has not sufficiently addressed this disease. Since there is no public dataset and smartphones are commonly used as tools to take pictures, it might then be conceivable for farmers to use them to categorize the infection level of their crops. In this work, we developed a system called CactiVIT that instantly determines the health status of cacti using the Visual image Transformer (ViT) model. We also provided a new image dataset of cochineal infested cacti.11The dataset is open-source and available at: https://github.com/AnasBerka/CactiViT-materials.git Finally, we developed a mobile application that delivers the classification results directly to farmers about the infestation in their fields by showing the probabilities related to each class. This study compares the existing models on the new dataset and presents the results obtained. The VIT-B-16 model reveals an approved performance in the literature and in our experiments, in which it achieved 88.73% overall accuracy with an average of +2.61% compared to other convolutional neural network (CNN) models that we evaluated under similar conditions.

Ethnomedicinal plants used by the paniya tribes in Gurusimalai hills, Pandalur, Niligiri district

In the present report an attempt has been made to document the available ethno-medicinal plants and their application among Paniya tribes in Gurusimalai Hills, Pandalur, Niligiri district. Regular field trips were conducted during the months of July-November 2022. The information about the plants was recorded by means of discussion using standard questionnaire with the informers along with the field visits during the collection hours. According to the report of study, a total about 70 plant species belonging to 62 genera and 35 families for treating various kinds of ailments such as Fever, bronchitis, piles, ulcer, abdominal disorders, skin diseases, urinary discharges, snake bite, asthma, diabetes, heart diseases and weight loss. Among the parts, Root, leaves, fruits and Seeds were mainly utilized by the informants. A detailed analysis concluded that, Leaves (46 species) were the most frequently used part of a plant followed by the Fruit (15 species), Root (10 species), Seed (9 species), Whole plant parts, Flower and Bark (each 4 species), Stem (2 species) and Tuber (1 species). The most commonly used medicinal plants fell under shrub forms (25 species) followed by Herb (19 species), tree (13 species), Climber (12 species) and succulent herb (1 species). The mode of formulation preparation or administration was observed to be in the form of juice (27 species) followed by past (15 species), decoction (14 species), Powder (11 species), and vapour (3 species). The present study concluded that the native people in the study area have their unique way of utilizing medicinal plants to treat different kinds of ailments. This might pave the path for developing a scientifically validated botanical or lead to semi-synthetic derivatives intended for modern medicine.

Peculiarities of medium parameter dynamics and cosmic ray density in strong Forbush decreases associated with magnetic clouds

Diffusion and electromagnetic mechanisms determine the formation of sporadic Forbush decreases. The diffusion mechanism affects the Forbush decrease amplitude in the turbulent layer, and the part of the coronal mass ejection preceding the magnetic cloud, and its efficiency depends on the level of magnetic field turbulence. The electromagnetic mechanism works in a magnetic cloud, and its efficiency depends on the intensity of regular magnetic and electric fields. We analyze solar wind parameters and cosmic ray density, using the superposed epoch analysis. In 1996–2006, 23 strong Forbush decreases (amplitude &gt;5 %) were detected. The average amplitude of 7 % is equally formed by both mechanisms. The events can be divided into 2 groups depending on the contribution of the mechanisms to Forbush decrease amplitude. Group 1 includes the strongest Forbush decreases (amplitude=8.5 %), formed by both diffusion and electromagnetic mechanisms. The diffusion mechanism forms 0.26 amplitude, and the electromagnetic mechanism is responsible for 0.74 one. In group 2, the averege amplitude Forbush decrease =5.7 %, the diffusion mechanism forms 0.79 of amplitude; and the electromagnetic one, 0.21. The spatial distributions of the mean values of the medium parameters in the region of disturbances in the groups differ. This difference can be explained by the fact that Forbush decrease amplitude in groups 1 and 2 are formed in the central and peripheral parts of coronal mass ejection respectively.

Особенности динамики параметров среды и плотности космических лучей в сильных форбуш-понижениях, связанных с магнитными облаками

Diffusion and electromagnetic mechanisms determine the formation of sporadic Forbush decreases. The diffusion mechanism affects the Forbush decrease amplitude in the turbulent layer, and the part of the coronal mass ejection preceding the magnetic cloud, and its efficiency depends on the level of magnetic field turbulence. The electromagnetic mechanism works in a magnetic cloud, and its efficiency depends on the intensity of regular magnetic and electric fields. We analyze solar wind parameters and cosmic ray density, using the superposed epoch analysis. In 1996–2006, 23 strong Forbush decreases (amplitude &gt;5 %) were detected. The average amplitude of 7 % is equally formed by both mechanisms. The events can be divided into 2 groups depending on the contribution of the mechanisms to Forbush decrease amplitude. Group 1 includes the strongest Forbush decreases (amplitude=8.5 %), formed by both diffusion and electromagnetic mechanisms. The diffusion mechanism forms 0.26 amplitude, and the electromagnetic mechanism is responsible for 0.74 one. In group 2, the averege amplitude Forbush decrease =5.7 %, the diffusion mechanism forms 0.79 of amplitude; and the electromagnetic one, 0.21. The spatial distributions of the mean values of the medium parameters in the region of disturbances in the groups differ. This difference can be explained by the fact that Forbush decrease amplitude in groups 1 and 2 are formed in the central and peripheral parts of coronal mass ejection respectively.

Interstellar Polarization Survey. III. Relation between Optical Polarization and Reddening in the General Interstellar Medium

Optical starlight can be partially polarized while propagating through the dusty, magnetized interstellar medium (ISM). The polarization efficiency describes the polarization intensity fraction per reddening unit, P V /E(B − V), related to the interstellar dust grains and magnetic field properties. The maximum value observed, [P V /E(B − V)]max, is thus achieved under optimal polarizing conditions of the ISM. Therefore, the analysis of polarization efficiency observations across the Galaxy contributes to the study of magnetic field topology, small-scale magnetic fluctuations, grain-alignment efficiency, and composition. Infrared observations from Planck satellite have set [P V /E(B − V)]max to 13% mag−1. However, recent optical polarization observations in Planck's highly polarized regions showed polarization efficiency values between 13.6% mag−1 and 18.2% mag−1 (depending on the extinction map used), indicating that [P V /E(B − V)]max is not well constrained yet. We used V-band polarimetry of the Interstellar Polarization Survey (consisting of ∼10,500 high-quality observations distributed in 34 fields of 0.°3 × 0.°3) to accurately estimate the polarization efficiency in the ISM. We estimated the upper limit of P V /E(B − V) with the weighted 99th percentile of the field. In five regions, the polarization efficiency upper limit is above 13% mag−1. Furthermore, we found [P V /E(B − V)]% mag−1 using diffuse intermediate-latitude (∣b∣ > 7.°5) regions with apparently strong regular Galactic magnetic field in the plane-of-sky. We studied the variations of P V /E(B − V) across the sky and tested toy models of polarization efficiency with Galactic longitude that showed some correspondence with a uniform spiral magnetic field.

О единственности потока, порождаемого нерегулярным векторным полем

The flow in time of an initial state ensemble in a multidimensional phase space, as a rule, models some dynamic process. Under what conditions is such a flow generated by a vector field in such a way that the given flow corresponds to the vector field in a unique way? A positive answer to this question is given by the classical uniqueness theorems for the solution of the initial value problem in the case of a regular vector field with the required properties of the modulus of continuity in space variables. In mathematical models of stochastic differential equations, in models of irregular hydrodynamic flows, and in a number of other cases when the flow is generated by a “bad” vector field that has a modulus of continuity in space variables that does not meet the conditions of the uniqueness theorem for solving the initial problem for a vector field, generating this flow, we cannot speak about the correctness of the initial problem for the vector field and, thus, about the correctness of finding the trajectories connecting the initial and actual states of the ensemble of particles in the phase space. In this case, the uniqueness of the flow generated by the vector field remains to be judged only by the properties of the flow itself. The only known result of this type is van Kampen's theorem, which states that the uniqueness of a flow generated by a vector field continuous in space variables is guaranteed by the properties of homeomorphism and the Lipschitz property of the flow in space variables. If the vector velocity field loses the property of continuity in space variables, then van Kampen's theorem does not work and some other properties of the flow are required to guarantee its uniqueness. In this paper, we establish such properties of a flow that guarantee its uniqueness even in the case of a violation of the continuity of the vector field that generates this flow. The conditions of van Kampen's theorem in a certain sense are a special case of the properties of the flow established in this paper, which guarantee its uniqueness as a solution to the initial problem for an irregular vector field. The general construction constructed here makes it possible to establish such properties of flows in various mathematical models that guarantee its uniqueness for a generating vector field.

Field Complete Coverage Path Planning Based on Improved Genetic Algorithm for Transplanting Robot

The Complete Coverage Path Planning (CCPP) is a key technology in the field of agricultural robots, and has great significance for improving the efficiency and quality of tillage, fertilization, harvesting, and other agricultural robot operations, as well as reducing the operation energy consumption. The traditional boustrophedon- or heuristic-search-algorithm-based CCPP methods, when coping with the field with irregular boundaries, obstacles, and other complex environments, still face many problems and challenges, such as large repeated work areas, multiple turns or U-turns, low operation efficiency, and prone to local optimum. In order to solve the above problems, an improved-genetic-algorithm-based CCPP method was proposed in this paper, the proposed method innovatively extends the traditional genetic algorithm’s chromosomes and single-point mutation into chromosome pairs and multi-point mutation, and proposed a multi-objective equilibrium fitness function. The simulation and experimental results on simple regular fields showed that the proposed improved-genetic-algorithm-based CCPP method achieved the comparable performance with the traditional boustrophedon-based CCPP method. However, on the complex irregular fields, the proposed CCPP method reduces 38.54% of repeated operation area and 35.00% of number of U-turns, and can save 7.82% of energy consumption on average. This proved that the proposed CCPP method has a strong adaptive capacity to the environment, and has practical application value in improving the efficiency and quality of agricultural machinery operations, and reducing the energy consumption.

Novel exact ultracompact and ultrasparse hairy black holes emanating from regular and phantom scalar fields

In the framework of a simple gravitational theory that contains a scalar field minimally coupled to gravity, we investigate the emergence of analytic black-hole solutions with nontrivial scalar hair of secondary type. Although it is possible for one to obtain asymptotically (anti)de Sitter solutions using our setup, in the context of the present work, we are solely interested in asymptotically flat solutions. At first, we study the properties of static and spherically symmetric black-hole solutions emanating from both regular and phantom scalar fields. We find that the regular-scalar-field-induced solutions are solutions describing ultracompact black holes, while the phantom scalar fields generate ultrasparse black-hole solutions. The latter are black holes that can be potentially of very low density since, contrary to ultracompact ones, their horizon radius is always greater than the horizon radius of the corresponding Schwarzschild black hole of the same mass. Then, we generalize the above static solutions to slowly rotating ones and compute their angular velocities explicitly. Finally, the study of the axial perturbations of the derived solutions takes place, in which we show that there is always a region in the parameter space of the free parameters of our theory that allows the existence of both ultracompact and ultrasparse black holes.

Numerical study for nonlinear hydrodynamic coefficients of an asymmetric wave energy converter

In this study, the nonlinear dynamic behavior of an asymmetric Wave Energy Converter (WEC) was studied on a 1/11-scale model based on a numerical and experimental method in a regular wave field. The numerical analysis involved both frequency-domain and time-domain solutions. The frequency-domain solution was based on linear potential flow theory using the WAMIT® model whereas the time-domain solution was based on the Reynolds-Averaged Navier-Stokes (RANS) equation using the OpenFOAM® model. The pitch response amplitude operators obtained from the numerical results were compared with experimental data. Additionally, the nonlinear dynamic behavior of the asymmetric WEC due to various wave heights and periods obtained through the experiments were compared with the OpenFOAM results. Wave excitation moments and hydrodynamic coefficients based on the linear solution approach were separately obtained for the fixed asymmetric WEC induced by waves and the forced oscillating motion with OpenFOAM. Moreover, frequency-domain solutions based on linear potential flow theory were obtained in order to ascertain the nonlinear effects observed in the OpenFOAM results. It was found that a higher motion amplitude could be attributed to nonlinear hydrodynamic coefficients on the asymmetric WEC calculated by the forced oscillation motion of the RANS-based solution.