Asymmetric Trajectories Research Articles

Terahertz single/dual beam scanning with tunable field of view by cascaded metasurfaces

Dynamic beam scanning with a dynamically tunable beam number, beam direction, and beam polarization remains a challenge in the terahertz gap, which is urgently needed for terahertz radar, next-generation wireless communication, and imaging applications. Different from programmable metasurfaces with element-level phase control, the beam direction is dynamically controlled by two cascaded all-dielectric metasurfaces during in-plane rotation. For a pair of circularly polarized beams with opposite handedness, the scanning field of view (FOV) can be the same or different according to the independent phase modulation in both layers and for both polarization states. Switchable single-beam and dual-beam scanning is achieved by controlling the incident polarization, which covers the ±60° FOV at 0.291 THz with an angular step of 1° and an average gain of 16.2 dBi. The output beam is quasi-circular polarized with an average ellipticity of 0.83. Single beam scanning along a Fibonacci spiral trajectory and dual beam scanning along symmetric and asymmetric trajectories are experimentally validated. Different beam scanning processes are recorded using a terahertz camera, which show good agreement with the theoretical prediction. The wide field-of-view continuous beam scanning with a switchable number of beams and a flexible FOV may have a significant impact on the development of terahertz radar and terahertz intelligent antennas.

DESTINOS TURÍSTICOS COM DESENVOLVIMENTO LOCAL ASSIMÉTRICO: OS “CENTROS TURÍSTICOS PLANEJADOS INTEGRALMENTE” DE LOS CABOS E LORETO, BAJA CALIFORNIA SUR (MÉXICO)

Objective: This paper examines the effects of tourism on local development in two IPCs, Los Cabos and Loreto, located in the state of Baja California Sur (BCS), in northwestern Mexico. Theoretical Framework: The Integrally Planned Centers (IPC) are tourism development poles established in Mexico during the 1960s and 1970s to promote economic growth in peripheral coastal regions (then) underdeveloped but rich in natural resources and landscapes. Method: An analytical-descriptive methodology is used, specifically the analysis of principal components, which allows contextualizing the evolution of tourism and development trajectories. Results and Discussion: The results indicate the presence of asymmetric development trajectories, despite the fact that both regions started from the same development initiative, with FONATUR (the Mexican government's tourism board) in charge in both cases. Forty years after its creation, the government's tourism policy yields differentiated results. Los Cabos has become a world-renowned destination, associated with sport fishing, golf, and residential tourism. In contrast, the Loreto-Nopoló-Puerto Escondido tourist corridor has stagnated and is still waiting for its take-off towards sustained development. Research implications: The IPCs of Los Cabos and Loreto, Mexico, are the result of a public tourism policy based on an exogenous development model, fundamentally oriented to "sun and beach" tourism, where economic variables are prioritized, to the detriment of social and environmental variables, which are important elements of sustainable tourism. A markedly uneven growth process is observed between the two IPCs, Los Cabos points out, which, to date, is successful in macroeconomic variables, while in terms of development it is very limited and lower than planned. Originality/Value: In the research, inferential statistical methods are applied, through the analysis of Principal Components, from which the impact of public tourism policies on regional development is measured. This instrument is applied to two tourist destinations that show an asymmetrical development, one of which was constituted as the second international tourist destination in Mexico.

An asymmetric S-curve trajectory planning based on an improved jerk profile

AbstractIn this paper, a method of planning the expanded S-curve trajectory of robotic manipulators is proposed to minimize the execution time as well as to achieve the smoother trajectory generation in the deceleration stage for point-to-point motions. An asymmetric parameter is added to the piecewise sigmoid function for an improved jerk profile. This asymmetric profile is continuous and infinitely differentiable. Based on this profile, two analytical algorithms are presented. One is applied to determine the suitable time intervals of trajectory satisfying the time optimality under the kinematic constraints, and the other is to determine the asymmetric parameter generating the minimum execution time. Also, the calculation procedure for the time-scaled synchronization for all joints is given to decrease unnecessary loads onto the actuators. The velocity, acceleration, jerk and snap (the derivative of jerk) of the joints and the end-effector are equal to zero at two end points of motion. The simulation results through 3 DOF and 6 DOF robotic manipulators show that our approach reduces the jerk and snap of the deceleration stage effectively while decreasing the total execution time. Also, the analysis for a single DOF mass-spring-damper system indicates that the residual vibration could be reduced to 10% more than the benchmark techniques in case velocity, acceleration and jerk are limited to 1.24 m/s, 6 m/s2 and 80 m/s3, respectively and displacement is set to 0.8m. These results manifest that the performance of reducing residual vibrations is good and demonstrate an important characteristic of the proposed profile suitable for point-to-point motion.

Speed-dependent modulations of asymmetric center of body mass trajectory in the gait of above-knee amputee subjects.

How to achieve stable locomotion while overcoming various instabilities is an ongoing research topic. One essential factor for achieving a stable gait is controlling the center of body mass (CoM). The CoM yields more instability in the mediolateral direction. Examining speed-dependent modulations of the CoM trajectories in the frontal plane can provide insight into control policies for achieving stable locomotion. Although these modulations have been studied while assuming symmetric CoM trajectories, this assumption is generally incorrect. For example, amputee subjects demonstrate asymmetric CoM trajectories. Here, we investigated speed-dependent modulations of asymmetric CoM trajectories in above-knee amputee subjects using Fourier series expansion. Despite the asymmetric CoM trajectories in amputee subjects, the framework of Fourier series expansion clarified that amputee subjects showed the same speed-dependent modulations as non-amputee subjects whose CoM trajectories were symmetric. Specifically, CoM trajectories became narrower in the mediolateral direction and broader in the superoinferior direction as walking speed increased. The speed-dependent modulations of CoM trajectories had a functional role in improving dynamic stability, and faster walking speeds provided greater dynamic stability on both prosthetic and non-prosthetic sides. Although the asymmetry of foot contact duration and CoM trajectory decreased as walking speed increased, step width and the asymmetry of dynamic stability between prosthetic and non-prosthetic sides remained constant across the walking speed, which corresponded to the predictions by our framework. These findings could offer a better strategy for achieving stable walking for amputee subjects.

Thz four-beam steering using metagrating pair with angle insensitivity and tailored geometric symmetry

Dynamic multi-beam steering is highly desired in target tracking and networking, with faster speed and larger flexibility as compared to single-beam steering. Here, instead of actively controlling meta-atoms in phased array metasurfaces, four beams are simultaneously scanned by cascaded diffraction of a pair of rotating metagratings. By tailoring the rotation symmetry and azimuth-angle-insensitive diffraction of the metagratings, multiple tangential wave vectors in the two layers are one-to-one added vectorially in order to govern the output four-beam direction. By combining a four-beam splitter metagrating with a beam deflector, we experimentally demonstrate THz four-beam steering with symmetric or asymmetric trajectories. The asymmetric steering shows ± 60° field of view with average efficiency of 41 % by tuning the relative orientation of the two metagratings, and the symmetric steering shows ± 22° field of view with the potential for further increasing the coverage. The efficiency fluctuation of the four beams is less than 4 %. This dynamic multi-beam steering strategy shows great potential for flexible signal transmission and processing in the THz band.

Asymmetric Drifter Trajectories in an Anticyclonic Mesoscale Eddy

The influences of sea surface wind on the oceanic mesoscale eddy are complex. By integrating our self-developed surface drifters with satellite observations, we examined the influence of sea surface wind on the distribution of water masses and biomass within the interior of an anticyclonic eddy. Ten drifters were deployed in the northern South China Sea in the spring of 2021. Eventually, six were trapped in an anticyclonic mesoscale eddy for an extended period. Interestingly, the drifters’ trajectories were not symmetric around the eddy center, displaying a significant offset of the distance from the wind turns to the southerly wind. Particle tracking experiments demonstrated that this departure could mainly be attributed to wind-driven ageostrophic currents. This is due to the strength of wind-driven ageostrophic currents being more comparable to geostrophic currents when accompanied by a deflection between the directions of the wind-driven current and the eddy’s translation. The drifters’ derived data indicated that sub-mesoscale ageostrophic currents within the eddy contributed to this asymmetric trajectory, with Ekman and non-Ekman components playing a role. Furthermore, the evolution of ocean color data provided corroborating evidence of these dynamic processes, highlighting the importance of ageostrophic processes within mesoscale eddies.

Fabrication of n-shaped micro copper structures through localized electrochemical deposition

Localized electrochemical deposition is a cost-effective technique for fabricating 3D microstructures. In this study, to fabricate a complete n-shaped micro copper structure, multi-layer deposition was adopted, and the v-groove was removed by an asymmetric trajectory. Thereafter, the merging mechanism of the n-shaped structure was analyzed using COMSOL simulations. The results demonstrated that multilayer deposition was suitable for connecting the copper column in different directions; the optimized layer was 15 layers with a height of 15 μm. The simulation showed that the v-groove was caused by the speed difference between the column and bumps, and an asymmetric trajectory with a height difference of 55 μm could suppress vertical deposition and remove the v-groove.

Time-Optimal Asymmetric S-Curve Trajectory Planning of Redundant Manipulators under Kinematic Constraints

This paper proposes a novel trajectory planning algorithm to design an end-effector motion profile along a specified path. An optimization model based on the whale optimization algorithm (WOA) is established for time-optimal asymmetrical S-curve velocity scheduling. Trajectories designed by end-effector limits may violate kinematic constraints due to the non-linear relationship between the operation and joint space of redundant manipulators. A constraints conversion approach is proposed to update end-effector limits. The path can be divided into segments at the minimum of the updated limitations. On each path segment, the jerk-limited S-shaped velocity profile is generated within the updated limitations. The proposed method aims to generate end-effector trajectory by kinematic constraints which are imposed on joints, resulting in efficient robot motion performance. The WOA-based asymmetrical S-curve velocity scheduling algorithm can be automatically adjusted for different path lengths and start/end velocities, allowing flexibility in finding the time-optimal solution under complex constraints. Simulations and experiments on a redundant manipulator prove the effect and superiority of the proposed method.

DEM-AIA: Asymmetric inclination-aware trajectory planner for off-road vehicles with digital elevation models

Planning safe and effective trajectories for off-road unmanned ground vehicles (UGV) is a critical Artificial Intelligence (AI) challenge that can benefit from recent advances in digital elevation models (DEM) for readily capturing accurate terrain geometry. Considering path slopes is crucial to preserve stability and assess terrain traversability at feasible speeds to optimize travel time, which is highly dependent on direction (i.e., pitch and roll). In this article, we propose a new DEM-based asymmetric inclination-aware (DEM-AIA) trajectory planner for ground vehicles. The planner is an any-angle variant of the A⋆ algorithm that computes pitch and roll estimations for each segment crossing cell triangles in the line-of-sight. Furthermore, we define a non-linear velocity constraints function that integrates information about tip-over safety limitations, maximum uphill and downhill slopes for the vehicle, and asymmetric modulation of nominal flat-ground velocity for all pitch and roll combinations. The planner produces a time sub-optimal trajectory with feasible speed references for each segment crossing a cell triangle. Moreover, we provide an extensive experimental analysis of inclination-aware performance on simulated and real-world DEMs as well as a comparison with state-of-the-art path planners adapted to travel-time optimization. An executable version of the planner with parameterizable variations is publicly available.

Numerical analysis of ammonia HCCI combustion in a free piston engine through trajectory-based combustion control

Ammonia is a promising carbon–neutral fuel, able to power heavy-duty vehicles, non-road machineries and ocean ships with zero CO2 emission. However, practical challenges still exist when applying ammonia in traditional internal combustion engines (ICEs) due to its high ignition energy, slow flame propagation and significant NOx emissions. Free piston engine (FPE) is a flexible alternative to ICE whose piston can move freely without the constraints of crankshaft. Therefore, its piston trajectory can be leveraged as a new control means to facilitate ammonia combustion. In this paper, a numerical analysis investigating ammonia HCCI combustion in FPE was presented. A physical-based model was developed at first, including a unique trajectory synthesizing mechanism and a detailed reaction mechanism of ammonia oxidation. Various asymmetric piston trajectories were then employed into the model and the simulated HCCI combustion were analyzed through six characteristics, namely indicated thermal efficiency, location of peak pressure, exhaust gas temperature, combustion duration, ignition delay, and NOx emissions. This investigation not only determines the best compression ratio (CR = 25) for ammonia ignition, but also shape the optimal piston trajectory (symmetric trajectory with Ω = 0.5) for ammonia HCCI combustion to enhance thermal efficiency and reduce NOx emission simultaneously.

Asymmetrical forward and reverse developmental trajectories determine molecular programs of B cell antigen receptor editing.

During B lymphopoiesis, B cell progenitors progress through alternating and mutually exclusive stages of clonal expansion and immunoglobulin (Ig) gene rearrangements. Great diversity is generated through the stochastic recombination of Ig gene segments encoding heavy and light chain variable domains. However, this commonly generates autoreactivity. Receptor editing is the predominant tolerance mechanism for self-reactive B cells in the bone marrow (BM). B cell receptor editing rescues autoreactive B cells from negative selection through renewed light chain recombination first at Igκ then Igλ loci. Receptor editing depends on BM microenvironment cues and key transcription factors such as NF-κB, FOXO, and E2A. The specific BM factor required for receptor editing is unknown. Furthermore, how transcription factors coordinate these developmental programs to promote usage of the λ chain remains poorly defined. Therefore, we used two mouse models that recapitulate pathways by which Igλ light chain-positive B cells develop. The first has deleted J kappa (Jκ) genes and hence models Igλ expression resulting from failed Igκ recombination (Igκdel). The second models autoreactivity by ubiquitous expression of a single-chain chimeric anti-Igκ antibody (κ-mac). Here, we demonstrated that autoreactive B cells transit asymmetric forward and reverse developmental trajectories. This imparted a unique epigenetic landscape on small pre-B cells, which opened chromatin to transcription factors essential for Igλ recombination. The consequences of this asymmetric developmental path were both amplified and complemented by CXCR4 signaling. These findings reveal how intrinsic molecular programs integrate with extrinsic signals to drive receptor editing.

Effect of pipe orientation on erosion of π-shaped pipelines

Erosion of particles in elbows mounted in series is a detriment in the course of natural gas transmission. The flow and erosion characteristics of π-shaped pipelines were investigated via coupling the computational fluid dynamics (CFD) and the discrete phase model (DPM) method. The effect of pipe orientation on particle erosion was mainly studied. Spiral and asymmetrical trajectories of particles were observed from the second elbow to the downstream straight pipe of the fourth elbow in the non-coplanar π-shaped pipelines. The integral erosion rate of the first elbow increased by 0.35%, and it grew by 72.49% and 87.48% in the second and fourth elbows in non-coplanar structures, respectively, while the integral erosion rate of the third elbow reduced by 32.94%. In the actual transportation of natural gas, it is necessary to make local thickening treatment of the second and fourth elbow of the non-coplanar π-shaped pipelines. • A swirling effect was discovered in non-coplanar structures. • Spiral and asymmetrical particle trajectories were generated. • Integral erosion degree of fourth elbow increased by 87.48% due to swirling effect. • The erosion rate increased exponentially with the increase of velocity.

Biogeography and diversification of the freshwater planarian Crenobia alpina sensu lato (Platyhelminthes, Tricladida): A synthetic review

Through an in-depth study of the literature, as well as some other sources of information, geographical distribution maps of the various taxa of the European freshwater planarian genus Crenobia (Platyhelminthes, Tricladida) are provided, which document their records and distributional ranges in a detail that was previously unavailable. The genus Crenobia ranges across Northern, Western, Southern, and Eastern Europe, including several islands in the Mediterranean region, but is absent from a major part of the Iberian Peninsula; it is distributed also in Turkey. The chromosome portrait of Crenobia is complex, as it exhibits chromosome numbers that are multiples of 7, such as 28, 35, 42, 56, and 63. Sexually reproducing populations are tetraploid or hexaploid, while asexually reproducing populations exhibit high chromosome numbers. All taxa of Crenobia are stenothermic, cold-loving species. Although historical biogeographic scenarios interpreting the taxonomic diversification of the genus as being the result of the vicissitudes of the Last Ice Age are still captivating, it may be the case that the genus already diversified 6-20 million years ago. The paper sketches in some detail the anatomy of the copulatory complex of the various taxa. Previously, it went unnoticed that in two of the taxa (Crenobia alpina and C. anophthalma) the two sperm ducts have different, asymmetrical trajectories. Further, it was largely undocumented that in several taxa the sperm ducts exhibit a pronounced recurvature, as well as a dorsal loop before entering the penis papilla. Neither did previous studies document that in C. montenigrina the mouth opening is not located at the most posterior end of the pharyngeal pocket, but has shifted anteriad for some distance. Polypharyngy is a stable, species-specific character, with C. montenigrina usually exhibiting 11-17 pharynges, while C. anophthalma has never more than three pharynges. Different views have been expressed on the taxonomic status of several geographic and anatomical forms of Crenobia. It is shown here that Crenobia comprises five, well-defined full species, viz., C. alpina, C. corsica, C. montenigrina, C. anophthalma, and C. bathycola.

Time-Optimal Asymmetric S-Curve Trajectory Planning of Redundant Manipulators Under Kinematic Constraints

Time-Optimal Asymmetric S-Curve Trajectory Planning of Redundant Manipulators Under Kinematic Constraints

Polarization and tipping points

Research has documented increasing partisan division and extremist positions that are more pronounced among political elites than among voters. Attention has now begun to focus on how polarization might be attenuated. We use a general model of opinion change to see if the self-reinforcing dynamics of influence and homophily may be characterized by tipping points that make reversibility problematic. The model applies to a legislative body or other small, densely connected organization, but does not assume country-specific institutional arrangements that would obscure the identification of fundamental regularities in the phase transitions. Agents in the model have initially random locations in a multidimensional issue space consisting of membership in one of two equal-sized parties and positions on 10 issues. Agents then update their issue positions by moving closer to nearby neighbors and farther from those with whom they disagree, depending on the agents' tolerance of disagreement and strength of party identification compared to their ideological commitment to the issues. We conducted computational experiments in which we manipulated agents' tolerance for disagreement and strength of party identification. Importantly, we also introduced exogenous shocks corresponding to events that create a shared interest against a common threat (e.g., a global pandemic). Phase diagrams of political polarization reveal difficult-to-predict transitions that can be irreversible due to asymmetric hysteresis trajectories. We conclude that future empirical research needs to pay much closer attention to the identification of tipping points and the effectiveness of possible countermeasures.

The trajectory of cortical GABA across the lifespan, an individual participant data meta-analysis of edited MRS studies.

γ-Aminobutyric acid (GABA) is the principal inhibitory neurotransmitter in the human brain and can be measured with magnetic resonance spectroscopy (MRS). Conflicting accounts report decreases and increases in cortical GABA levels across the lifespan. This incompatibility may be an artifact of the size and age range of the samples utilized in these studies. No single study to date has included the entire lifespan. In this study, eight suitable datasets were integrated to generate a model of the trajectory of frontal GABA estimates (as reported through edited MRS; both expressed as ratios and in institutional units) across the lifespan. Data were fit using both a log-normal curve and a nonparametric spline as regression models using a multi-level Bayesian model utilizing the Stan language. Integrated data show that an asymmetric lifespan trajectory of frontal GABA measures involves an early period of increase, followed by a period of stability during early adulthood, with a gradual decrease during adulthood and aging that is described well by both spline and log-normal models. The information gained will provide a general framework to inform expectations of future studies based on the age of the population being studied.

Investigation of Response Dynamics in the Simon Task with Mouse Tracking Methodology.

Introduction:Despite their popularity in Neuropsychology, reaction time analysis based on the subtraction and additive factors methods is critiqued for not paying adequate attention to the dynamical nature of cognition. Mouse-tracking methods aim to cater to this need by allowing researchers to explore response dynamics during cognitive tasks by recording mouse trajectories.Methods:A mouse-tracking adaptation of the Simon task is developed to explore decision-making dynamics in different stimulus-response compatibility conditions. The study focuses on the effects of stimulus design decisions on mouse trajectories, including relocation of the choice buttons from the top corners to the bottom and the mid-session reversal of stimulus-response mapping on mouse responses.Results:Consistent with previous studies, significant stimulus-response compatibility effects were observed, where contrasts over mouse-tracking measures had larger effect sizes than simple reaction time contrasts. Moreover, in the conflict trials, asymmetric response trajectories towards the left and right corners were observed. Moving the response buttons from top to bottom increased the degree of asymmetry between the mouse trajectories towards the bottom-left and bottom-right corners during the conflict condition. Finally, in the reverse Simon task, the switch to a new color-response mapping inflicted the largest effect on the average number of y-flips.Conclusion:Mouse tracking provides measures suitable for exploring decision-making dynamics beyond classical reaction time analysis, provided asymmetries due to the starting position and response layout are considered during experiment design.

Enantioselective retention mechanisms of dipeptides on antibiotic-based chiral stationary phases. II. Effect of the methanol content in the mobile phase.

Effect of mobile phase (water-methanol) composition on the enantioseparation of dipeptides on the chiral stationary phase Chirobiotic R was investigated using Ala-Ala, Leu-Leu, Gly-Leu, and Leu-Gly as case studies. The lipophilicity of dipeptides was found to be an essential factor in the dependence of their retention on the methanol percentage, the retention factor of lipophobic dipeptides increasing monotonously and that of lipophilic dipeptides changing according to an asymmetric U-shaped trajectory as methanol concentration increases. The behavior of enantioselectivity as a function of the methanol content also depends on the lipophilicity of dipeptide. For lipophilic Leu-Leu, the dependence has a dome-like shape, and for more lipophobic dipeptides, Ala-Ala and Gly-Leu, it is an increasing function of the methanol concentration. The importance of solvation equilibria in the bulk liquid and on the surface of the stationary phase for the total retention is discussed from the thermodynamic point of view. Special consideration is given to the adsorption of the water-methanol mixture on the surface of the Chirobiotic R stationary phase.

Gait analysis of patients with distal radius fracture by using a novel laser Timed Up-and-Go system

BackgroundPostmenopausal women are at risk of fall and fracture with the physical decline. Distal radius fracture (DRF) is considered as the primary fragility fracture, and women with this fracture showed poor results in the usual Timed Up-and-Go (TUG) test, indicating a decline in balance and physical ability. The detailed physical characteristics of female DRF patients have not been extensively examined. Research questionIs the novel laser TUG system able to detect and analyze the detailed gait characteristics in patients with DRF whose physical ability has tended to decline? MethodsIn this cross-sectional case control study, the gait characteristics of 32 female patients with DRF who had undergone surgery were evaluated at 2 weeks postoperatively with a laser TUG system to analyze the detailed leg motion during normal TUG test. Forty-three age- and sex-matched non-fractured women were evaluated by the laser TUG system as controls. Lifestyle and present illness were corrected at the time of TUG measurement. Detailed data during laser TUG in both groups were compared statistically, and odds ratio and thread shod of the fracture was elucidated through a logistic regression analysis. ResultsDRF patients showed slower speed and had to do more steps to complete the TUG test. Furthermore, asymmetric trajectory and significantly further distance from the marker were observed. Thirteen steps to complete the TUG test was the thread shod of DRF. SignificanceDetailed gait characteristics of patients with DRF were detected by the laser TUG system. The gait decline and abnormality could be one of the reasons of consecutive fragility fracture. To prevent secondary fragility fractures, this system can be useful for screening.

Propagations of Airy beams with quadratic phase modulation, and their interaction in paraxial optical systems

We, both theoretically and numerically, investigate dynamic evolutions of Airy beams with quadratic phase modulation (QPM) and their interaction in paraxial optical systems, including free space, dynamic linear potential, and parabolic potential. In free space case, the beam with negative QPM will undergo deceleration and then acceleration, while positive QPM beam only accelerates. The presence of dynamic linear index potentials leads to single beam propagating along predefined trajectory and counterpropagating beams following asymmetric trajectories. The intersection points and their range are only dependent on QPM parameter. For parabolic index potentials, the beam exhibits periodic inversion of profile and periodic self-Fourier transformation. QPM causes the trajectory modulated and the energy distribution distorted, and considerably influences the intersection points. We extend our results to circular Airy beams with QPM. Beside the shape and trajectory modified, the autofocusing effect can be strengthened or weakened in negative or positive QPM case.