Discrete Positions Research Articles

On the theory and methodology of systematic analysis of positions, singular configurations, branches and circuits, and ranges of motion for planar complex linkages

Complex linkages refer to the linkages composed of 4-bar or more than 4-bar Assur Groups (AG). This paper presents a hybrid position analysis method for complex AG. Firstly, position solutions of an external link in AG are obtained by solving the position analysis polynomial, then all configurations of the AG corresponding to the solutions can be determined through solving 2-bar AG. Above is the position analysis process at a single input condition. With the increasement of the input angle, a series of discrete position solutions can be obtained. How to connect these solutions to form different branches and circuits, and determine the movement range of the linkage are the other problems to be solved. This paper presents an effective methodology to determine the branches and circuits as well as the movement range of the linkage and gives a novel discriminant for identifying singular configurations of complex AG. Finally, several numerical examples are presented to demonstrate the correctness, effectiveness and universality of the proposed methods and the practicability of the program compiled based on the formulations and methodology.

A DPS-PLL based rotor position estimation method for permanent magnet wind turbine

Aiming at the problem of slow response and low tracking accuracy in the synchronous reference frame phase-locked loop (SRF-PLL) estimation of the permanent magnet synchronous generator (PMSG) rotor position when the wind speed changes suddenly, a rotor position estimation method based on the discrete position set phase-locked loop(DPS-PLL) is proposed. The estimated position in certain moment is selected from a discretized alternative position set. Then, combined with sliding mode observer, rotor position is obtained by calculating back-EMF cost function. The experimental results demonstrate the rotor position and speed can be detected accurately under sudden change of wind speed. The convergence time of estimation is within 42 ms. The estimated error of rotor position is less than 0.03 rad. The results show that the proposed method provides a satisfactory dynamic performance and strong disturbance rejection ability.

A review of last interglacial sea-level proxies in the western Atlantic and southwestern Caribbean, from Brazil to Honduras

Abstract. We use a standardized template for Pleistocene sea-level data to review last interglacial (Marine Isotope Stage 5 – MIS 5) sea-level indicators along the coasts of the western Atlantic and southwestern Caribbean, on a transect spanning from Brazil to Honduras and including the islands of Aruba, Bonaire, and Curaçao. We identified six main types of sea-level indicators (beach deposits, coral reef terraces, lagoonal deposits, marine terraces, Ophiomorpha burrows, and tidal notches) and produced 55 standardized data points, each constrained by one or more geochronological methods. Sea-level indicators are well preserved along the Brazilian coasts, providing an almost continuous north-to-south transect. However, this continuity disappears north of the Rio Grande do Norte Brazilian state. According to the sea-level index points (discrete past position of relative sea level in space and time) the paleo sea-level values range from ∼ 5.6 to 20 m above sea level (a.s.l.) in the continental sector and from ∼ 2 to 10 m a.s.l. in the Caribbean islands. In this paper, we address the uncertainties surrounding these values. From our review, we identify that the coasts of northern Brazil, French Guiana, Suriname, Guyana, and Venezuela would benefit from a renewed study of Pleistocene sea-level indicators, as it was not possible to identify sea-level index points for the last interglacial coastal outcrops of these countries. Future research must also be directed at improving the chronological control at several locations, and several sites would benefit from the re-measurement of sea-level index points using more accurate elevation measurement techniques. The database compiled in this study is available in spreadsheet format at the following link: https://doi.org/10.5281/zenodo.5516444 (Version 1.02; Rubio-Sandoval et al., 2021).

A DOI-PET detector inserting glass plates to provide multiple spatial resolutions

A DOI-PET detector with multiple spatial resolutions to provide high versatility for both clinical and research applications using a single camera was proposed and examined. Two layers of pixelated LYSO crystal arrays with different pixel pitches were stacked in the depth direction. The top layer was a 6 × 6 array of 2.1 × 2.1 × 10 mm3 crystals, arranged with a 2.2-mm fine pitch. The bottom layer was a 4 × 4 array of 3.2 × 3.2 × 10 mm3 crystals, arranged with a coarse 3.3-mm pitch. A Monte-Carlo simulation was conducted to estimate the glass plate thickness which allows the discrimination of each crystal position from the 2D flood histogram. In experimental measurement, we inserted 4-mm, 5-mm, and 6-mm thick glass plates between the crystal layers. These generated a unique light response for each discrete scintillator position. Light was shared more relatively when the top layer interacted with the gamma rays, whereas light sharing was reduced when the bottom layer interacted with the gamma rays. These light spreading methods allow us to extract 3D information from a 2D flood histogram. Sixteen output signals from a 4 × 4 GAPD array were multiplexed by resistive charge division networks. These were fed into the preamplifiers. The four amplified signals were digitized and were recorded into the DAQ system. By inserting the glass plates into the detectors, we acquired 2D flood histograms without the overlapping of each crystal position. The average peak-to-valley ratios of selected line profiles of a DOI-PET detector with 4-mm thick glass plate were 12.5 for the top layer and 30.8 for bottom layer. The mean energy resolution of the top layer providing high spatial resolution (the bottom layer providing moderate spatial resolution) were 14.4 ± 1.0% (13.4 ± 1.4%), 13.3 ± 1.7% (13.8 ± 0.8%), and 13.7 ± 1.6% (13.8 ± 0.9%) for the DOI-PET detector using 4-mm-, 5-mm-, and 6-mm-thick glass plates, respectively. Our results demonstrated that it is feasible to provide multiple spatial resolutions and 2-layer depth positions for the proposed DOI-PET detector using fine- and coarse-pitch crystals and inserting a glass plate between the crystal layers.

Computing and Assessment of Discrete Angle Positions for Optimizing the Solar Energy Harvesting for Urban Sustainable Development

This paper proposes the computation and assessment of optimal tilt and azimuth angles for a receiving surface, using a mathematical model developed at the University of Tomsk, Russia. The model was validated and analyzed for the Nuevo León State, Northeast Mexico, utilizing a set of metrics, comparing against satellite data from NASA. A point of interest in the city of Monterrey was analyzed to identify orientation patterns throughout the year for an optimal solar energy gathering. The aim is providing the best orientation tilt angles for photovoltaic or solar thermal panels without tracking systems. In addition, this analysis is proposed as a tool to achieve optimal performance in sustainable urban development in the region. Based on the findings, a set of optimal tilt and azimuth surface angles are proposed for the analyzed coordinates. The aim is to identify the optimal performance to obtain the maximum solar irradiation possible over the year for solar projects in the region. The results show that the model can be used as a tool to accelerate decision making in the design of solar harvesting surfaces and allows the design of discrete tracking systems with an increase in solar energy harvesting above 5% annually.

Influence of the PFNA screw position on the risk of cut-out in an unstable intertrochanteric fracture: a computational analysis

The position of the lag screw in the femoral head is a key factor to cut-out, the most reported complication in the internal fixation of intertrochanteric fractures. Considering that the best position for the lag screw remains controversial, the aim of this study was to evaluate the influence of different lag screw positions on the risk of cut-out of an unstable intertrochanteric fracture fixed with a Proximal Femoral Nail Anti-Rotation (PFNA) implant. The relationship between cut-out and the tip-apex distance (TAD) or the calcar referenced tip-apex distance (CalTAD) was also investigated.Finite element models of one male and one female femur treated with a PFNA implant were developed considering the lag screw positioned centrally and inferiorly on the anteroposterior view, and for each of these, the screw tip at 4 discrete positions along its longitudinal axis. All 8 positions simulated for each femur considered the lag screw in a centre position on the lateral view. The risk of cut-out was evaluated for two loading conditions assuming it is related with high compressive strains.The bone region at the fracture line, near the tip of the missing medial fragment, was always the most concerning regarding high compressive strains. The inferior positioning of the lag screw reduced the volume of bone susceptible to yielding compared to the centre positioning. The deep placement of the screw tip improved the outcome for both centre and inferior positions.The results suggested the inferior and deep placement of the screw to be the best position to reduce the risk of cut-out. The volume of bone susceptible to yielding was found not to be correlated to TAD or CalTAD, suggesting that further investigation is necessary to identify other, more reliable, predictors of cut-out.

Isolation and characterization of a lytic bacteriophage against Pseudomonas aeruginosa

In recent years, the use of bacteriophages (or 'phages') against multidrug-resistant (MDR) bacteria including Pseudomonas aeruginosa has drawn considerable attention, globally. In this work, we report the isolation and detailed characterization of a highly lytic Pseudomonasphage DRL-P1 isolated from wastewater. Under TEM, DRL-P1 appeared as a member of the phage family Myoviridae. DRL-P1 featured rapid adsorption (~ 5 min), short-latency (~ 30 min), and large burst size (~ 100 PFU per infected cell). DRL-P1 can withstand a wide temperature range (4 °C to 40 °C) and pH (5.0 to 10.0) conditions. The 66,243 bp DRL-P1 genome (MN564818) encodes at least 93 ORFs, of which 36 were functionally annotated based on homology with similar phage proteins available in the databases. Comparative analyses of related genomes suggest an independent evolutionary history and discrete taxonomic position of DRL-P1 within genus Pbunavirus. No toxin or antibiotic resistance genes was identified. DRL-P1 is tolerant to lyophilization and encapsulation techniques and retained lytic activity even after 18 months of storage. We also demonstrated decontaminating potentials of DRL-P1 in vitro, on an artificially contaminated cover-slip model. To the best of our knowledge, this is the first Pbunavirus to be reported from India. Our study suggests DRL-P1 as a potential candidate for various applications.

Non-Uniform B-Spline Curve Interpolation Method for Feature Points Selection under Curvature Adaptive Condition

<p indent=0mm>Aiming at the massive discrete tool position data generated in the computer numerically controlled programming stage, a non-uniform B-spline curve interpolation method based on curvature adaptive selecting feature point is proposed under the condition of satisfying the preset interpolation accuracy. Firstly, the curvature of each discrete data point is calculated by the method of forming an approximate arc from three adjacent points, and the feature data points such as the segment point of the curvature segment and the maximum point of curvature are used as the initial interpolation data points to construct and generate the initial non-uniform B-spline interpolation curve. Secondly, the interpolation error calculation model is established and used to calculate the interpolation errors between all the data points not participating in the interpolation and the non-uniform B-spline interpolation curve, and the new feature points that are beyond the preset interpolation error in the curve segments are added to generate a new non-uniform B-spline interpolation curve. Repeat the above processes until all data points that are not on the non-uniform B-spline interpolation curve can meet the interpolation accuracy condition. The simulation calculation results of the actual tool position data show that the method can better retain the characteristics of the original data curve in terms of shape and accuracy even when a large amount of the original tool position data is removed, and it has advantages of fewer iteration calculations and larger removing the data points. The method will have high application value to the spline computer numerically controlled programming of massive discrete tool position data.

A single-cell atlas reveals unanticipated cell type complexity in Drosophila ovaries.

Organ function relies on the spatial organization and functional coordination of numerous cell types. The Drosophila ovary is a widely used model system to study the cellular activities underlying organ function, including stem cell regulation, cell signaling and epithelial morphogenesis. However, the relative paucity of cell type–specific reagents hinders investigation of molecular functions at the appropriate cellular resolution. Here, we used single-cell RNA sequencing to characterize all cell types of the stem cell compartment and early follicles of the Drosophila ovary. We computed transcriptional signatures and identified specific markers for nine states of germ cell differentiation and 23 somatic cell types and subtypes. We uncovered an unanticipated diversity of escort cells, the somatic cells that directly interact with differentiating germline cysts. Three escort cell subtypes reside in discrete anatomical positions and express distinct sets of secreted and transmembrane proteins, suggesting that diverse micro-environments support the progressive differentiation of germ cells. Finally, we identified 17 follicle cell subtypes and characterized their transcriptional profiles. Altogether, we provide a comprehensive resource of gene expression, cell type–specific markers, spatial coordinates, and functional predictions for 34 ovarian cell types and subtypes.

Evaluation of the force applied by the adductor muscles in a healthy student population performing an adduction task

Abstract Background The adduction and abduction movement (closing and open the legs) are important tasks in daily activities. The evaluation and monitor of the force exerted by the adductor muscles can be used as a rehabilitation progress indicator, particularly in people with injuries in the central nervous system or motor neurons. The development of biomechanical devices to quantify and identify patterns in this type of force with healthy people can be a contribution in this domain. This work, approved by the Ethical Committee of IPC, aims to evaluate the force applied by the adductor muscles from a healthy group of students, performing the closing legs task. Methods The study was carried out at Applied Biomechanics Laboratory of IPC, with a group of 32 healthy volunteers from the student community (19-26 yo), half men - half women, without lower limb injuries, 59,38% with a prevalence of sedentary lifestyle. Volunteers, sitting in a comfortable position, press a biomechanical device placed between the legs. The time-force was registered for four discrete open-leg positions. Results The maximum mean forces were 199N in women and 257N in men, both in the shorter range of the open-leg position. The peak of force decreases with open leg distance for both genders and was achieved between 34%–54% of the performance time ([3, 28] seconds). Moderate correlations were identified between forces applied and skeletal muscles and resting metabolism. Conclusion The time-force applied was identified and registered with a developed biomechanical device. Obtained values are reliable and can be a support for future investigations.

Antiderivative of gradient data by spline model integration

Numerous optical techniques describe the local slope of the functions at their discrete positions but do not report the actual functions. However, many applications require the description of the functions, which must be retrieved from the gradients by an integration process. This study shows a spline model function-based integration technique that can construct original functions from irregularly measured gradient data over general shape domains with high accuracy and speed.

Charting galactic accelerations: when and how to extract a unique potential from the distribution function

ABSTRACT The advent of data sets of stars in the Milky Way with 6D phase-space information makes it possible to construct empirically the distribution function (DF). Here, we show that the accelerations can be uniquely determined from the DF using the collisionless Boltzmann equation, providing the Hessian determinant of the DF with respect to the velocities is non-vanishing. We illustrate this procedure and requirement with some analytic examples. Methods to extract the potential from data sets of discrete positions and velocities of stars are then discussed. Following Green &amp; Ting, we advocate the use of normalizing flows on a sample of observed phase-space positions to obtain a differentiable approximation of the DF. To then derive gravitational accelerations, we outline a semi-analytic method involving direct solutions of the overconstrained linear equations provided by the collisionless Boltzmann equation. Testing our algorithm on mock data sets derived from isotropic and anisotropic Hernquist models, we obtain excellent accuracies even with added noise. Our method represents a new, flexible, and robust means of extracting the underlying gravitational accelerations from snapshots of 6D stellar kinematics of an equilibrium system.

Auralization of a car pass-by inside an urban canyon using measured impulse responses

Development of methodologies for the auralization of moving cars can be of great value for a virtual acoustic experience of urban areas. In this paper11Parts of this study were presented at the conference: Euronoise 2018, Crete, Greece a methodology for the auralization of car pass-by based on measured binaural impulse responses (BIRs) is presented. Measured BIRs for different locations in a street canyon were convolved with dry synthesized car signals in which cross-fade windows were applied in order to create a smooth transition between the source positions. Next, the convolved signals are summed in order to create the final car pass-by auralizations. A same/different listening test was carried out in order to investigate if increasing the angular spacing between the discrete source positions affects the perception of the auralizations. The experiments revealed that the auralizations with a larger angular increment (up to 16∘) are perceptually different to the reference auralizations (2∘ spacing), even in the case where the increment increased by only 2∘ compared to the reference. Compared to previous listening experiments of a car pass-by in the scenario without buildings it was shown that the discrimination performance of the subjects was significantly better compared to the test conditions where buildings are absent, where subjects found it very difficult to distinguish differences between auralizations of larger and smaller increment.

The Korean discourse particle kulssey across discrete positions and contexts in talk-in-interaction

The Korean discourse particle kulssey has been examined primarily as a response to a question in turn initial position, indicating the speaker's uncertainty or hesitation (e.g., ‘well’). A detailed examination of 183 instances of kulssey in ordinary conversation shows that its usage and function are much more complex. Kulssey occurs in multiple positions (in the beginning, middle, or final position of a turn-constructional unit) and carries out various functions (indexing a prior turn or proposition, serving as a filler or prospective indexical, or retroactively adding the speaker's stance to a matter just reported) across discrete or sometimes even opposite contexts (i.e., claiming or disclaiming epistemic rights, displaying agreements or disagreements). By examining its interactional usage and developmental path, the study shows how kulssey's origin as a deictic expression (kuleha-ta ‘to be like that’) is linked to its current ability to anaphorically and cataphorically index matters discussed in prior turns or about to be discussed in unfolding turns, and how this indexical function explains its mobility and versatility in talk-in-interaction. The findings are supported by diachronic and synchronic empirical examinations.

Food Web Trophic Structure at Marine Ranch Sites off the East Coast of Korea

Understanding the trophic ecology of the giant Pacific octopus Enteroctopus dofleini is challenging in developing marine ranches and in reestablishing its regional stocks against the severe stress of fishing. We adopted carbon and nitrogen stable isotope techniques (termed δ13C and δ15N, respectively) to identify the trophic niche (i.e., pathways and positions) of this species systematically in the entire food webs of two marine ranches off the east coast of the Korean peninsula. While a slight spatial shift in the isotopic nestedness of faunal communities was observed, the δ13C and δ15N values of consumers were distinct and separate among functional groups at both ranches. The consumer δ13C values spanned a broad range between pelagic and benthic sources of organic matter, and their δ15N values recorded a stepwise trophic-level enrichment, indicating that suspension feeders and herbivore-deposit feeders served as baselines of pelagic- and benthic-based trophic pathways, respectively. The δ13C values of predators, including E. dofleini, were arrayed between the two primary consumer groups. Neither δ13C nor δ15N values showed any remarkable variations with increasing octopus weight. Dietary mixing-model calculations indicated that E. dofleini is a generalist predator relying on both benthic- and pelagic-affinity prey, similar to some teleost species that consume a diverse spectrum of prey. In contrast, other teleost groups showed prevalent trophic links with either pelagic- or benthic-based pathways. The trophic-level estimations revealed that E. dofleini occupies an intermediate position slightly below the teleosts. A lack of discrete trophic positions between E. dofleini and teleosts seemed to be indicative of the released teleost predation but instead reflects the imposed food competition. Overall, the results demonstrated that despite compositional changes in the taxa constituting individual trophic groups, E. dofleini occupied a very similar trophic niche in both ranching systems. Finally, as extracted from information based on octopus marine ranches launched on natural rocky bottoms, our isotopic evidence provides a greater understanding of the trophic ecology of this octopus species in nearshore natural habitats along the southwestern margin of its distribution range.

Task-Aware Waypoint Sampling for Robotic Planning

To achieve a complex task, a robot often needs to navigate in a physical space in order to complete activities in different locations. For example, it may need to inspect several structures, making multiple observations of each structure from different perspectives. Typically, the positions from which these activities can be performed are represented as waypoints – discrete positions that are sampled from the continuous physical space and used to find a task plan. Existing approaches to waypoint selection either iteratively consider the entire space or use domain knowledge to consider each activity separately. This can lead to task planning problems that are more complex than is necessary or to plans of compromised quality. Moreover, all previous approaches only consider geometric constraints that can be imposed on the waypoint selection process. We present Task-Aware Waypoint Sampling (TAWS), which offers two key novelties. First, it is an anytime approach that combines the benefits of random sampling with the use of domain knowledge in waypoint selection by performing a one-time computation of the connectivity graph from which waypoints are sampled. In addition, TAWS is the first approach that accounts for performance preferences, which are preferences a system operator may have about the generated task plan. These can account, for example, for areas near doorways where it is preferable that the robot does not stop to perform activities. We demonstrate the performance benefits of our approach on simulated automated manufacturing tasks.

Proline codon pair selection determines ribosome pausing strength and translation efficiency in bacteria

The speed of mRNA translation depends in part on the amino acid to be incorporated into the nascent chain. Peptide bond formation is especially slow with proline and two adjacent prolines can even cause ribosome stalling. While previous studies focused on how the amino acid context of a Pro-Pro motif determines the stalling strength, we extend this question to the mRNA level. Bioinformatics analysis of the Escherichia coli genome revealed significantly differing codon usage between single and consecutive prolines. We therefore developed a luminescence reporter to detect ribosome pausing in living cells, enabling us to dissect the roles of codon choice and tRNA selection as well as to explain the genome scale observations. Specifically, we found a strong selective pressure against CCC/U-C, a sequon causing ribosomal frameshifting even under wild-type conditions. On the other hand, translation efficiency as positive evolutionary driving force led to an overrepresentation of CCG. This codon is not only translated the fastest, but the corresponding prolyl-tRNA reaches almost saturating levels. By contrast, CCA, for which the cognate prolyl-tRNA amounts are limiting, is used to regulate pausing strength. Thus, codon selection both in discrete positions but especially in proline codon pairs can tune protein copy numbers.

Perception of Static Position and Kinesthesia of the Finger using Vibratory Stimulation.

Proprioception provides information regarding the state of an individual's limb in terms of static position and kinesthesia (dynamic movement). When such feedback is lost or impaired, the performance of dexterous control of our biological limbs or assistive devices tends to deteriorate. In this study, we determined if external vibratory stimulation patterns could allow for the perception of a finger's static position and kinesthesia. Using four tactors and two stimulus levels, eight vibratory settings corresponded to eight discrete finger positions. The transition patterns between these eight settings corresponded to kinesthesia. Three experimental blocks assessed the perception of a finger's static position, speed, and movement (amplitude and direction). Our results demonstrated that both position and kinesthesia could be recognized with over 93% accuracy. The outcomes suggest that vibratory stimulus can inform subjects of static and dynamic aspects of finger proprioception. This sensory stimulation approach can be implemented to improve outcomes in clinical populations with sensory deficits, and to enhance user experience when users interact with assistive devices.

Context-aware positional representation for self-attention networks

In self-attention networks (SANs), positional embeddings are used to model order dependencies between words in the input sentence and are added with word embeddings to gain an input representation, which enables the SAN-based neural model to perform (multi-head) and to stack (multi-layer) self-attentive functions in parallel to learn the representation of the input sentence. However, this input representation only involves static order dependencies based on discrete position indexes of words, that is, is independent of context information, which may be weak in modeling the input sentence. To address this issue, we proposed a novel positional representation method to model order dependencies based on n-gram context or sentence context in the input sentence, which allows SANs to learn a more effective sentence representation. To validate the effectiveness of the proposed method, it is applied to the neural machine translation model, which adopts a typical SAN-based neural model. Experimental results on two widely used translation tasks, i.e., WMT14 English-to-German and WMT17 Chinese-to-English, showed that the proposed approach can significantly improve the translation performance over the strong Transformer baseline.

Vehicle Trajectory Prediction Method based on Deep Learning under the background of Internet of Vehicles

With the expansion of the Internet, big data and other industries, mobile devices are almost used in all aspects of life. The location-based service platform provides convenient services for users, but also obtains a large number of user history tracks. Through the trajectory data mining, we can extract valuable user behavior information, help user’s better plan routes, and can be applied in urban traffic management and commercial advertising layout and other scenarios. In this paper, a trajectory prediction algorithm based on deep learning is proposed to solve the problem of vehicle trajectory prediction. In this paper, the vehicle passing records are preprocessed and the vehicle trajectory is generated. The trajectory is transformed into the discrete position sequence of the vehicle as the input of the algorithm. Then the space-time multi-dimensional features of vehicle trajectory are extracted. Finally, a trajectory prediction algorithm based on deep learning is constructed. The batch size is 256 and the average track length of training set is 46.45. The convolution neural network and deep bidirectional long-term memory network are fused to learn the local and global information of vehicle trajectory. The research shows that compared with traditional machine learning, deep learning has achieved better results in various fields of computer vision because of its powerful representation ability. The visual perception algorithm based on deep learning can accurately analyze the regularity of vehicle movement and make accurate prediction of vehicle moving trajectory in the future.