Position Assignment Research Articles

Multiple targets enclosure by robotic swarm

Target enclosure by autonomous robots is useful for many practical applications, for example, surveillance of disaster sites. Scalability is important for autonomous robots because a larger group is more robust against breakdown, accidents, and failure. However, since the traditional models have discussed only the cases in which minimum number of robots enclose a single target, there has been no study on the utilization of the redundant number of robots. In this paper, to achieve a highly scalable target enclosure model about the number of target to enclose, we introduce swarm based task assignment capability to Takayama’s enclosure model. The original model discussed only single target environment but it is well suited for applying to the environments with multiple targets. We show the robots can enclose the targets without predefined position assignment by analytic discussion based on switched systems and a series of computer simulations. As a consequence of this property, the proposed robots can change their target according to the criterion about robot density while they enclose multiple targets.

An Approach for Optimal Goal Position Assignment in Vehicle Formations

In this paper one methodology to solve the goal position assignment (GPA) problem is developed, this is, to assign the corresponding goal position (desired position) for a group of vehicles, knowing the initial positions and the established formation shape. By using this GPA methodology, it can be guaranteed that the formation will be reached in a minimum period of time and with lower collision risk compared with the other possible combinations of pairs "vehicles-goal position". Hungarian algorithm was used as combinatorial optimization algorithm, which requires a cost matrix, therefore it is shown the way to compute the cost matrix to obtain the best GPA. In order to show the optimal behavior of the proposed cost matrix, three approaches of cost matrix were evaluated in simulations of quad-rotor formations. Also, the optimal behavior of the proposed GPA is proved with numerical values of some defined parameters to determine optimal performance. The formation control was based on potential functions, while the control law for each vehicle was based on nested saturation.

ERP correlates of letter identity and letter position are modulated by lexical frequency

The encoding of letter position is a key aspect in all recently proposed models of visual-word recognition. We analyzed the impact of lexical frequency on letter position assignment by examining the temporal dynamics of lexical activation induced by pseudowords extracted from words of different frequencies. For each word (e.g., BRIDGE), we created two pseudowords: A transposed-letter (TL: BRIGDE) and a replaced-letter pseudoword (RL: BRITGE). ERPs were recorded while participants read words and pseudowords in two tasks: Semantic categorization (Experiment 1) and lexical decision (Experiment 2). For high-frequency stimuli, similar ERPs were obtained for words and TL-pseudowords, but the N400 component to words was reduced relative to RL-pseudowords, indicating less lexical/semantic activation. In contrast, TL- and RL-pseudowords created from low-frequency stimuli elicited similar ERPs. Behavioral responses in the lexical decision task paralleled this asymmetry. The present findings impose constraints on computational and neural models of visual-word recognition.

The role of orthographic syllable structure in assigning letters to their position in visual word recognition

The way in which letters are assigned their position when recognizing a visually presented word was examined in three experiments using nonwords created by transposing the two medial consonants of a bisyllabic baseword (e.g., nakpin, semron). The difficulty in responding to such “TL” nonwords in a lexical decision task was shown to be lower when the medial consonants of the baseword formed a complex coda (e.g., the rm of sermon) than when they comprised a separate coda and onset (e.g., the p and k of napkin). The same result was shown in false positive responses to nonwords when their visibility was degraded through masking. In addition, these TL effects were just as strong for nonwords like nakpin as they were for nonwords whose medial consonants formed a complex coda like warlus, but whose baseword was syllabified between those consonants (e.g., the l and r of walrus). Such findings are a challenge for most current models of letter position assignment. Instead, they can be explained by an account where bisyllabic words are stored in lexical memory with a structure that maximizes the coda of the first syllable and where medial consonants are tried out in all viable subsyllabic slots.

Optimizing the Operation Sequence of Chip Shooter Machine Based on the Particle Swarm Optimization Algorithm

The mounting process is the key factor of the placement efficiency, it is also important for the improvement of the efficiency of whole production line and decrease of the cost. This paper analyzed the mounting process of the Chip Shooter machine, applied the PSO algorithm, constructed the corresponding coding system, proposed the corresponding particle update mechanism, introduced the partially matched crossover idea of the genetic algorithm into the PSO algorithm, and designed the new re-scheduling method of feeder position assignment to optimize the position assignment of feeders and the pickup and placement sequence of components, thus improved the placement efficiency. After comparing the results before and after the simulation test for selected 8 pieces of PCB, the average efficiency of this algorithm is 7.09% higher than genetic algorithm method that is based on sort encoding. The experimental result shows that, this algorithm is more efficiency on the improvement placement efficiency and decrease of the placement time for the chip shooter machine.

It's Complicated: The Human Side of Medical Complications

It's Complicated: The Human Side of Medical Complications

New dental remains of Hispanopithecus laietanus (Primates: Hominidae) from Can Llobateres 1 and the taxonomy of Late Miocene hominoids from the Vallès-Penedès Basin (NE Iberian Peninsula)

Here we report 12 teeth of the fossil great ape Hispanopithecus (Hominidae: Dryopithecinae: Hispanopithecini), recovered in 2011 from the locality of Can Llobateres 1 (MN9, early Vallesian, Late Miocene, ca. 9.7 Ma [millions of years ago]) in the Vallès-Penedès Basin (Catalonia, Spain). Besides an isolated dP3 from layer CLL1.1b in the eastern (classical) sector of the site, all of the remaining teeth come from facies CLL1.0 (roughly equivalent to CLL1.2 and CLL1.1b), located in the newly excavated western sector, and representing at least two different individuals. Based on facet congruence and degree of wear, all of the upper cheek teeth, a central incisor and a lateral incisor most likely correspond to a single young adult individual of unknown sex, whereas a very worn I2 and a female C1 represent one or two additional individual(s). Morphological and metrical comparisons allow us to attribute these remains to Hispanopithecus laietanus, which is the single hominoid species recognized at CLL1. The newly described teeth represent a significant addition to the hypodigm of this taxon, enabling us to more completely assess the degree of variation displayed by several teeth. In light of the new specimens, the previous tooth position assignment of several upper molars from Can Llobateres and Can Poncic is revised, and the criteria employed to distinguish Hispanopithecus crusafonti from H. laietanus are critically evaluated. On the basis of the available upper cheek teeth from these localities, a distinction at the species level between both samples is tentatively favored, mainly on the basis of P3, M1 and M2 proportions as well as I1 lingual morphology and proportions. The results of the 2011 field season unambiguously confirm that hominoid-bearing fossiliferous layers from CLL1 are not exhausted. Additional excavations at this site are promising for the discovery of additional remains of H. laietanus in the near future.

The processing of consonants and vowels during letter identity and letter position assignment in visual-word recognition: An ERP study

Recent research suggests that there is a processing distinction between consonants and vowels in visual-word recognition. Here we conjointly examine the time course of consonants and vowels in processes of letter identity and letter position assignment. Event related potentials (ERPs) were recorded while participants read words and pseudowords in a lexical decision task. The stimuli were displayed under different conditions in a masked priming paradigm with a 50-ms SOA: (i) identity/baseline condition e.g., chocolate-CHOCOLATE); (ii) vowels-delayed condition (e.g., choc ▪l ▪te-CHOCOLATE); (iii) consonants-delayed condition (cho ▪o ▪ate-CHOCOLATE); (iv) consonants-transposed condition (cholocate-CHOCOLATE); (v) vowels-transposed condition (chocalote-CHOCOLATE), and (vi) unrelated condition (editorial-CHOCOLATE). Results showed earlier ERP effects and longer reaction times for the delayed-letter compared to the transposed-letter conditions. Furthermore, at early stages of processing, consonants may play a greater role during letter identity processing. Differences between vowels and consonants regarding letter position assignment are discussed in terms of a later phonological level involved in lexical retrieval.

Motion-induced position shifts occur after motion integration

Low-level motion processing in the primate visual system involves two stages. The first stage (in V1) contains specialised motion sensors which respond to local retinal motion, and the second stage (in MT) pools local signals to encode rigid surface motion. Recent psychophysical research shows that motion signals influence the perceived position of an object (motion-induced position shift, MIPS). In the present paper we investigate the role played by the two processing stages in generating MIPS. We compared MIPS induced by single grating components (Gabor patches) to MIPS induced by plaids created by combining pairs of components. If motion signals at the lowest level of motion analysis (V1) influence position assignment, MIPS from plaids should reflect the position shift induced by each component when presented separately. On the other hand, if signals generated in MT (or later) influence perceived position, then MIPS from plaids should be consistent with a motion integration computation on the components. Results showed that MIPS from plaids is larger than the MIPS obtained from individual components, and can be explained by the output of an integration process that combines intersection-of-constraints and vector-sum computations.

A fair assignment algorithm for multiple preference queries

Consider an internship assignment system, where at the end of each academic year, interested university students search and apply for available positions, based on their preferences (e.g., nature of the job, salary, office location, etc). In a variety of facility, task or position assignment contexts, users have personal preferences expressed by different weights on the attributes of the searched objects. Although individual preference queries can be evaluated by selecting the object in the database with the highest aggregate score, in the case of multiple simultaneous requests, a single object cannot be assigned to more than one users. The challenge is to compute a fair 1--1 matching between the queries and the objects. We model this as a stable-marriage problem and propose an efficient method for its processing. Our algorithm iteratively finds stable query-object pairs and removes them from the problem. At its core lies a novel skyline maintenance technique, which we prove to be I/O optimal. We conduct an extensive experimental evaluation using real and synthetic data, which demonstrates that our approach outperforms adaptations of previous methods by several orders of magnitude.

Consonants and Vowels Contribute Differently to Visual Word Recognition: ERPs of Relative Position Priming

This paper shows that the nature of letters--consonant versus vowel--modulates the process of letter position assignment during visual word recognition. We recorded Event Related Potentials while participants read words in a masked priming semantic categorization task. Half of the words included a vowel as initial, third, and fifth letters (e.g., acero [steel]). The other half included a consonant as initial, third, and fifth (e.g., farol [lantern]). Targets could be preceded 1) by the initial, third, and fifth letters (relative position; e.g., aeo-acero and frl-farol), 2) by 3 consonants or vowels that did not appear in the target word (control; e.g., iui-acero and tsb-farol), or 3) by the same words (identity: acero-acero, farol-farol). The results showed modulation in 2 time windows (175-250 and 350-450 ms). Relative position primes composed of consonants produced similar effects to the identity condition. These 2 differed from the unrelated control condition, which showed a larger negativity. In contrast, relative position primes composed of vowels produced similar effects to the unrelated control condition, and these 2 showed larger negativities as compared with the identity condition. This finding has important consequences for cracking the orthographic code and developing computational models of visual word recognition.

Distinct position assignment mechanisms revealed by cross-order motion

Motion perception influences perceived position. It has been shown that first-order (luminance defined) motion shifts perceived position across a wide range of spatial and temporal frequencies. On the other hand, second-order (contrast defined) motion shifts perceived position over a narrow range of temporal frequencies, regardless of spatial frequency [Bressler, D. W., & Whitney, D. (2006). Second-order motion shifts perceived position. Vision Research, 46(6–7), 1120–1128]. These results suggest the presence of distinct position assignment mechanisms for first- and second-order motion. We investigated whether the first- and second-order systems independently encode and assign the position of a moving stimulus. To measure motion induced position shift we presented two horizontally offset Gabors placed above and below a central fixation point, with sine wave carriers drifting in opposite directions. Subjects judged the position of the top Gabor relative to the bottom one. We used both first-order Gabors (sinusoidal luminance modulation of a dynamic noise carrier enveloped by a static Gaussian) and second-order Gabors (sinusoidal contrast modulation of a dynamic noise carrier enveloped by a static Gaussian). Results showed a strong position shift in the direction of the carrier motion when both Gabors were first-order, a weak position shift when both Gabors were second-order, and no appreciable position shift when one Gabor was first-order and the other was second-order (cross-order motion). The absence of a position shift using cross-order motion supports the hypothesis that the two motion systems independently encode and assign the position of a moving object. These results are consistent with those of experiments investigating global spatial interactions between static first-order and second-order Gabor patches, indicating a commonality in the underlying spatial integration processes.

Second-order motion shifts perceived position

Many studies have documented that first-order motion influences perceived position. Here, we show that second-order (contrast defined) motion influences the perceived positions of stationary objects as well. We used a Gabor pattern as our second-order stimulus, which consisted of a drifting sinusoidal contrast modulation of a dynamic random-dot background; this second-order carrier was enveloped by a static Gaussian contrast modulation. Two vertically aligned Gabors had carrier motion in opposite directions. Subjects judged the relative positions of the Gabors’ static envelopes. The positions of the Gabors appeared shifted in the direction of the carrier motion, but the effect was narrowly tuned to low temporal frequencies across all tested spatial frequencies. In contrast, first-order (luminance defined) motion shifted perceived positions across a wide range of temporal frequencies, and this differential tuning could not be explained by differences in the visibility of the patterns. The results show that second-order motion detection mechanisms contribute to perceived position. Further, the differential spatial and temporal tuning of the illusion supports the idea that there are distinct position assignment mechanisms for first and second-order motion.

THE EFFECT OF BODY POSITION ON GASTRIC RESIDUAL IN HEALTHY LOW BIRTH WEIGHT(LBW) INFANTS. † 887

To study the effect of body position on GR and to determine the best time after feeding to place LBW infants in Supine (S) position for prevention of SIDS, 45 studies were performed in 15 infants who were randomized into 6 sequences. Each infant had 3 studies performed on the same day; 5 were randomized to start in the Right Lateral Decubitus (RLD), 5 in Prone (P) and 5 in S position. BW was 1158±382g (Mean±SD), GA 30±3wks and age at time of study, 28±17d (range 6-45d); 60% were male, Apgar scores were >3 at 5 min in all infants. Infants were included if they were off the ventilator and were taking at least 25% of fluid requirement via enteral route. Undiluted 20 cal/oz Special Care Formula (Ross) at the same volume as the previous feeding (17±5 cc/kg/feed) was given by nasogastric tube which was kept in place during the entire study. To obtain the maximum amount of GR possible, the infant was rotated in all 3 positions at the time of measurement. GR, expressed as% of volume given, is shown according to primary position assignment. Table

Ejection chains, reference structures and alternating path methods for traveling salesman problems

Ejection chain procedures are based on the notion of generating compound sequences of moves, leading from one solution to another, by linked steps in which changes in selected elements cause other elements to be “ejected from” their current state, position or value assignment. This paper introduces new ejection chain strategies designed to generate neighborhoods of compound moves with attractive properties for traveling salesman problems. These procedures derive from the principle of creating a reference structure that coordinates the options for the moves generated. We focus on ejection chain processes related to alternating paths, and introduce three reference structures, of progressively greater scope, that produce both classical and non-standard alternating path trajectories. Theorems and examples show that various rules for exploiting these structures can generate moves not available to customary neighborhood search approaches. We also provide a reference structure that makes it possible to generate a collection of alternating paths that precisely expresses the symmetric difference between two tours. In addition to providing new results related to generalized alternating paths, in directed and undirected graphs, we lay a foundation for achieving a combinatorial leverage effect, where an investment of polynomial effort yields solutions dominating exponential numbers of alternatives. These consequences are explored in a sequel.

I/O pad assignment for force-directed placement algorithms

Abstract A new method for I/O pad position assignment for force-directed placement algorithms is presented. The pre-placed I/O pads are used as boundary conditions and pulling-out forces in several placement algorithms which would otherwise have collapsed all the modules to the centre of the layout. The objective is to assign the I/O pads of the design to the available pad positions on the chip, based on connectivity information, such that the resulting module arrangement will minimize the total wire length. The results of the I/O pad assignment algorithm, used as a pre-processor to the placement package PROUD, have revealed improvement in minimizing the total wire length.

Race and Position Assignment in English Soccer: A Preliminary Analysis of Ethnicity and Sport in Britain

The belief that soccer offers black Britons an avenue of social mobility is challenged in this study. Examination of their involvement reveals that blacks have suffered both overt and tacit discrimination. Subject to racial abuse from spectators, black Britons also appear to experience a process of “stacking” apparently related to the concept of centrality. In conducting this study, research data and methodologies from North America and Britain were combined, and the concept of centrality was refined in order to apply it to soccer. The evidence supports the contention that blacks are assigned to positions by white managers on the basis of racial stereotypes of abilities. Future research needs to examine this dimension more closely.

Image processing algorithm for automatic detection and position assignment of monodispersed polystyrene spheres from microscope images

Monodispersed polystyrene spheres have recently been introduced as a two-dimensional model system for studying phase transition phenomena. For quantitative studies coordinates must be assigned to each sphere in a microscope sample containing hundreds or thousands of spheres. This paper describes a digital image processing technique for automatically determining the sphere positions from an image of the microscope sample. Results are given for some sample images.

A one-dimensionally position-sensitive scintillation detector

A NaI(Tl) detector has been designed to measure the position, along its midline, of a scintillation caused by the absorption of a 137Cs γ photon. The 1.3 cm thick, 40 cm long scintillator is viewed by twenty-seven photomultipliers, placed closely together on a zig-zag line along the detector. This geometry is shown to be superior to a side-by side linear photomultiplier configuration. The detector utilizes a delay-line readout technique for position assignment, in combination with pulse-height discrimination. The spatial resolution is characterized by 5.8 mm full width at half maximum. The influence of photomultiplier characteristics and geometry, including light guide thickness, has been studied experimentally and by calculations.

A robust attribution error in the personality domain

The error of inferring dispositional causes for constrained behavior was investigated in the domain of personality. Subjects were randomly assigned to write essays presenting themselves as strongly introverted or extraverted. Within groups, subjects exchanged essays and estimated the actual (self-rated) introversion/extraversion of the writer. The procedure minimized the likelihood of certain factors conducive to correspondent inference, e.g., the low salience of constraint or nonrepresentative sample of dispositions among essay writers. The experiment included an instructional set variable which involved accentuating the situational constraint or reinforcing the subjects' inclination to individuate the writer. In all conditions, a significant pattern of correspondent inference occurred, with attributions aligned to the directionality of the essays. The results, consistent with findings from attitude attribution research, suggest that the direction of the essay provides an initial hypothesis of correspondent inference. Subjects may then use their impression of the essay's extremity as a basis upon which to adjust their attribution in accord with the constraint of the position assignment.