Fixed-interval Length Research Articles

Visual tracking in complex scenes: A location fusion mechanism based on the combination of multiple visual cognition flows

In recent years, deep learning has revolutionized computer vision and has been widely used for monitoring in diverse visual scenes. However, in terms of some aspects such as complexity and explainability, deep learning is not always preferable over traditional machine-learning methods. Traditional visual tracking approaches have shown certain advantages in terms of data collection efficiency, computing requirements, and power consumption and are generally easier to understand and explain than deep neural networks. At present, traditional feature-based techniques relying on correlation filtering (CF) have become common for understanding complex visual scenes. However, current CF algorithms use a single feature to describe the information of the target and locate it accordingly. They cannot fully express changeable target appearances in a complex scene, which can easily lead to inaccurate target locations in time-varying visual scenes. Moreover, owing to the complexity of surveillance scenes, monitoring algorithms can lose their target. The original template update strategy uses each frame with a fixed interval length as a new template, which may lead to unreliable feature extraction and low tracking accuracy. To overcome these issues, in this work, we introduce an original location fusion mechanism based on multiple visual cognition processing streams to achieve real-time and efficient visual monitoring in complex scenes. First, we propose a process for extracting multiple forms of visual cognitive information, and it is periodically used to extract multiple feature information flows of a target of interest. Subsequently, a cognitive information fusion process is employed to fuse the positioning results of different visual cognitive information flows to achieve high-quality visual monitoring and positioning. Finally, a novel feature template memory storage and retrieval strategy is adopted. When the location result is unreliable, the target is retrieved from memory to ensure robust and accurate tracking. In addition, we provide an extensive set of performance results showing that our proposed approach exhibits more robust performance at a lower computational cost compared with 36 state-of-the-art algorithms for visual tracking in complex scenes.

TEDAR: Temporal dynamic signal detection of adverse reactions

Computational approaches to detect the signals of adverse drug reactions are powerful tools to monitor the unattended effects that users experience and report, also preventing death and serious injury. They apply statistical indices to affirm the validity of adverse reactions reported by users. The methodologies that scan fixed duration intervals in the lifetime of drugs are among the most used. Here we present a method, called TEDAR, in which ranges of varying length are taken into account. TEDAR has the advantage to detect a greater number of true signals without significantly increasing the number of false positives, which are a major concern for this type of tools. Furthermore, early detection of signals is a key feature of methods to prevent the safety of the population. The results show that TEDAR detects adverse reactions many months earlier than methodologies based on a fixed interval length.

Real-Time Control System Based on the Values of Derivative of the Redox Potential Aiming Nitrogen Removal in a Sequencing Batch Reactor Applied in Treating Dairy Wastewater

This paper presents a real-time control strategy based on the derivative of the oxi-reduction potential (ORP) values for nitrogen removal via nitrite in a sequencing batch reactor (SBR) fed with effluent from an anaerobic sequencing batch reactor (ASBR) treating dairy wastewater. The developed control strategy optimized the length of aerobic and anoxic phases without external carbon source addition. Firstly, a fixed interval length for aeration period was used in the SBR cycle to promote the nitrogen removal; however, this strategy did not allow the proper alternation of anoxic and aerobic conditions, and thus effective removal of nitrogen was not verified. After that, the real-time control strategy was implemented, and the end of nitrification and denitrification processes was determined when the derivative of the oxi-reduction potential (ORP) was close to zero. This strategy provided a removal of 92.2 ± 9.7 and 63.9 ± 19.0% for concentrations of TKN-N and Nt-N, respectively, which were well above those found for the open-loop system—43.8 ± 21.6 and 26.5 ± 26.2% for the removal of TKN-N and Nt-N, respectively.

Mean Direct-Transit and Looping Times as Functions of the Potential Shape

Any trajectory of a diffusing particle making a transition between two end points of an interval can be divided into two segments, which we call direct-transit and looping parts. The former is the final segment of the trajectory, when the particle goes from one end point of the interval to the opposite end point, without retouching the starting point. The rest of the trajectory is the looping part. We study mean durations of the two parts in the presence of a symmetric linear cusp potential which, depending on the parameter values, forms either a barrier or a well between the end points. For the cusp barrier, we find that the mean direct-transit time decreases as the barrier height increases at a fixed interval length. This happens because the increase in the barrier height results in the increase of the magnitude of the force acting on the particle on both sides of the barrier. Interestingly, though the mean looping and direct-transit times are different in the case of the barrier and well potentials with equal height and depth, respectively, the mean first-passage times for the two cases are identical.

Designing efficient nitrous oxide sampling strategies in agroecosystems using simulation models

Annual cumulative soil nitrous oxide (N2O) emissions calculated from discrete chamber-based flux measurements have unknown uncertainty. We used outputs from simulations obtained with an agroecosystem model to design sampling strategies that yield accurate cumulative N2O flux estimates with a known uncertainty level. Daily soil N2O fluxes were simulated for Ames, IA (corn-soybean rotation), College Station, TX (corn-vetch rotation), Fort Collins, CO (irrigated corn), and Pullman, WA (winter wheat), representing diverse agro-ecoregions of the United States. Fertilization source, rate, and timing were site-specific. These simulated fluxes surrogated daily measurements in the analysis. We “sampled” the fluxes using a fixed interval (1–32 days) or a rule-based (decision tree-based) sampling method. Two types of decision trees were built: a high-input tree (HI) that included soil inorganic nitrogen (SIN) as a predictor variable, and a low-input tree (LI) that excluded SIN. Other predictor variables were identified with Random Forest. The decision trees were inverted to be used as rules for sampling a representative number of members from each terminal node. The uncertainty of the annual N2O flux estimation increased along with the fixed interval length. A 4- and 8-day fixed sampling interval was required at College Station and Ames, respectively, to yield ±20% accuracy in the flux estimate; a 12-day interval rendered the same accuracy at Fort Collins and Pullman. Both the HI and the LI rule-based methods provided the same accuracy as that of fixed interval method with up to a 60% reduction in sampling events, particularly at locations with greater temporal flux variability. For instance, at Ames, the HI rule-based and the fixed interval methods required 16 and 91 sampling events, respectively, to achieve the same absolute bias of 0.2 kg N ha−1 yr−1 in estimating cumulative N2O flux. These results suggest that using simulation models along with decision trees can reduce the cost and improve the accuracy of the estimations of cumulative N2O fluxes using the discrete chamber-based method.

Temporal control in chained fixed-ratio, fixed-interval schedules.

Four rats were subjected to chained fixed-ratio (FR), fixed-interval (FI) schedules of reinforcement (chain FR 5 FI). A FR schedule at one lever produced a discriminative stimulus (i.e., light) associated with an FI schedule of primary reinforcement (water) at the second response lever. The FR schedule was kept constant, whereas the FI length was changed from 10 to 60 s under five different experimental conditions. Increases in the FI length resulted in increases in pre-ratio pauses, but pauses in the FI tended to be a constant percentage of FI length. Data from this experiment indicate that pre-ratio pauses are also a function of the interreinforcement interval (IRI). Data from three experiments with chained FR 5 FI 60-s schedules indicate that pausing in the FI component of chained FR FI schedules with the FI as the second component of the chain may tend to disappear as the IRI duration increases.

Agile diagnostic tool based on electrical signature analysis

AbstractToday, time based maintenance is the most common strategy, to assure a certain level of productivity and reliability in the industrial plants, with a fixed interval length between two maintenance actions. However, given the stochastic nature of the faults, plant equipments and machines usually fail unexpectedly, before the scheduled maintenance action. Therefore, condition based maintenance (CBM) has been introduced, without any fixed interval length between the maintenance actions, as a more efficient maintenance policy. A technique developed for condition based maintenance of electro-mechanical systems is electrical signature analysis. The basic idea behind electrical signature analysis is that, time-dependent load and speed variations in an electro-mechanical system generally induce correlated small variations in the system's electrical response. Electrical signature analysis analyzes these small variations providing diagnostic information. A tool based on this technique is agile in its adoption since no specific sensors must be installed on the machine, but only power signal must be measured and thus the implementation of such tool can be considered simple and flexible. This paper presents a tool that has such kind of characteristics. The tool processes power signals acquired by transducers installed on the electrical lines of electro-mechanical systems, for machine fault diagnosis. The data acquired are processed through some steps, using some signal indicators developed to understand the machine behaviour.

A maximum likelihood estimator for bedrock fracture transmissivities and its application to the analysis and design of borehole hydraulic tests

We propose a new method to estimate the transmissivities of bedrock fractures from transmissivities measured in intervals of fixed length along a borehole. We define the scale of a fracture set by the inverse of the density of the Poisson point process assumed to represent their locations along the borehole wall, and we assume a lognormal distribution for their transmissivities. The parameters of the latter distribution are estimated by maximizing the likelihood of a left‐censored subset of the data where the degree of censorship depends on the scale of the considered fracture set. We applied the method to sets of interval transmissivities simulated by summing random fracture transmissivities drawn from a specified population. We found the estimated distributions compared well to the transmissivity distributions of similarly scaled subsets of the most transmissive fractures from among the specified population. Estimation accuracy was most sensitive to the variance in the transmissivities of the fracture population. Using the proposed method, we estimated the transmissivities of fractures at increasing scale from hydraulic test data collected at a fixed scale in Smithville, Ontario, Canada. This is an important advancement since the resultant curves of transmissivity parameters versus fracture set scale would only previously have been obtainable from hydraulic tests conducted with increasing test interval length and with degrading equipment precision. Finally, on the basis of the properties of the proposed method, we propose guidelines for the design of fixed interval length hydraulic testing programs that require minimal prior knowledge of the rock.

Characterisation of a fractured rock mass for a grouting field test

An investigation was performed to find and describe a rock volume suitable for a grouting field test at the Äspö Hard Rock Laboratory, Sweden. Fixed interval length transmissivities and the corresponding number of fractures from geological mapping of a probe hole were used to calculate a probability of conductive fractures for analyses of data from individual boreholes. Furthermore, the transmissivity and specific capacity of the boreholes were compared to examine the robustness of the specific capacity. From the findings of the study, the probability of conductive fractures from probe hole data, the specific capacity and fracture frequency of individual boreholes were sufficient to construct a simplified model of the fracture and the rock volume. Moreover, the median specific capacity of the boreholes was a good description of the effective cross-fracture transmissivity. The field test was also carried out to demonstrate the usefulness of the methodology for improving the analyses of data from the hydraulic tests and geological mapping for a grouting fan.

ELICITED RESPONDING IN CHAIN SCHEDULES

An omission procedure was employed to study elicited pecking in the first component of a two-component chain schedule. Both components were fixed-interval schedules correlated with colored keylights. The first response following the initial-link schedule produced a second fixed-interval schedule. We studied several fixed-interval lengths in two conditions: a standard response-dependent condition and an omission-contingent condition. The omission-contingent condition differed from the response-dependent condition in that responses during the initial fixed interval terminated the trial (omitting the terminal component and grain). If the terminal component was not omitted, a response following the terminal link's requirement produced 4-s access to grain. Pigeons responded during more than 70% of the initial links in the omission-contingent condition and responded during more than 90% of the initial links in the response-dependent condition. In general, rates of responding were consistent with the percentage data. The responding in the omission condition suggests that there may be elicited pecking, in chain schedules using pigeons, that is not the result of contingent conditioned reinforcement.

THE EFFECTS OF REINFORCEMENT FREQUENCY AND RESPONSE REQUIREMENTS ON THE MAINTENANCE OF BEHAVIOR

Six rats responded under fixed-interval and tandem fixed-interval fixed-ratio schedules of food reinforcement. Basic fixed-interval schedules alternated over experimental conditions with tandem fixed-interval fixed-ratio schedules with the same fixed-interval value. Fixed-interval length was varied within subjects over pairs of experimental conditions; the ratio requirement of the tandem schedules was varied across subjects. For both subjects with a ratio requirement of 10, overall response rates and running response rates typically were higher under the tandem schedules than under the corresponding basic fixed-interval schedules. For all subjects with ratio requirements of 30 or 60, overall response rates and running response rates were higher under the tandem schedules than under the corresponding basic fixed-interval schedules only with relatively short fixed intervals. At longer fixed intervals, higher overall response rates and running rates were maintained by the basic fixed-interval schedules than by the tandem schedules. These findings support Zeiler and Buchman's (1979) reinforcement-theory account of response strength as an increasing monotonic function of both the response requirement and reinforcement frequency. Small response requirements added in tandem to fixed-interval schedules have little effect on reinforcement frequency and so their net effect is to enhance responding. Larger response requirements reduce reinforcement frequency more substantially; therefore their net effect depends on the length of the fixed interval, which limits overall reinforcement frequency. At the longest fixed intervals studied in the present experiment, reinforcement frequency under the tandem schedules was sufficiently low that responding weakened or ceased altogether.

Effects of nicotine on schedule-controlled behaviour: Role of fixed-interval length and modification by mecamylamine and chlorpromazine

The effects of nicotine, alone and in combination with mecamylamine and chlorpromazine, were studied in one group of rats exposed to a fixed-interval 30 sec schedule of food reinforcement, and a second group exposed to a fixed-interval 120 sec schedule. For both groups nicotine increased overall response rates in a dose-related fashion up to a maximum at 0.3 mg/kg. Examination of the within-interval response patterns showed that nicotine tended to increase the low level response rates in the early and middle parts of the interval and decrease, or increase to a proportionally smaller extent, the higher level response rates at the end of the interval. The response rate and pattern of the animal, rather than the schedule to which it was exposed, was found to be the main determinant of the effects of nicotine. Mecamylamine (1.0 mg/kg) blocked most of the changes in rate produced by nicotine, although in the group exposed to the fixed-interval 30 sec schedule, the increases in response rate tended to predominate after combined administration of mecamylamine and nicotine. Chlorpromazine (1.0 mg/kg) failed to block the effects of nicotine in either group. Instead, the effects of combined administration of nicotine and chlorpromazine were similar to the added effects of the two compounds given alone. It appears that the behavioural effects of nicotine are not mediated through catecholaminergic systems.

Schedule-induced water and ethanol consumption as a function of interreinforcement interval in the squirrel monkey

Lever pressing of two squirrel monkeys ( Saimiri sciureus) was maintained under fixed-interval schedules of food delivery that were varied systematically from 1–10 min. First water and then 2% (V/V) ethanol solutions were available during the experimental sessions at each fixed-interval value. Drinking occurred immediately following the delivery of each pellet. The amount of water consumed increased markedly with increases in the length of the fixed-interval value from 1–9 min; drinking was decreased with one monkey at the 10 min fixed-interval, whereas with the second, drinking continued to increase. The amount of ethanol solution ingested was generally lower than that of water. With one animal ethanol consumption increased when the interval length was increased from 1–6 min, and then decreased beyond this point. With the second animal, ethanol drinking typically increased with increases in the fixed-interval length from 1–10 min. The amount of water consumed in the home cage generally decreased when the interval was lengthened from 1 to approximately 3 min and did not change substantially with further increases in the fixed-interval value.

SCHEDULE‐INDUCED POLYDIPSIA IN RATS LIVING IN AN OPERANT ENVIRONMENT

The effect of variations in interreinforcement interval on the temporal and distributional relation between feeding and drinking was continuously monitored. Rats were housed continuously in an operant chamber in which water was freely available, but lever pressing was required to obtain food (45-mg pellets). Initially, pellets were delivered on a fixed-ratio 1 schedule of reinforcement, which was followed by testing on response-initiated fixed-interval 15-, 30-, and 60-second schedules. The total number of discrete, daily meals (a period in which several pellets were earned in succession) was slightly higher during the fixed-interval schedules than during the fixed-ratio 1, but there was no systematic effect of fixed-interval length on meal frequency. Total water consumption, in contrast, increased dramatically as the interval was lengthened: both subjects consumed two to three times as much water on the fixed-interval 60-second schedule as on the fixed-ratio 1. The increased water consumption was the result of an alteration in the distribution of drinking relative to eating. During the fixed-ratio 1 condition, drinking occurred infrequently following individual food pellets and represented the smallest percentage of total drinking; drinking occurred predominantly just before or after a meal. As the fixed interval was lengthened, however, the frequency of postpellet drinking gradually increased and eventually comprised the largest proportion of daily drinking.

EFFECTS ON CHOICE OF REINFORCEMENT DELAY AND CONDITIONED REINFORCEMENT1

Pigeons chose between fixed-interval schedules of different durations presented in the terminal links of concurrent-chains schedules. The pair of schedules was always in the ratio of 2:1, but the absolute duration of the fixed intervals varied. In one set of conditions, the different terminal-link schedules were associated with different keylight stimuli (cued conditions). In a second set of conditions, the different terminal-link schedules were associated with the same stimulus (uncued conditions). Results from the cued conditions replicated previous findings that preference for the shorter fixed-interval schedule increased with fixed-interval duration. Preferences in the uncued conditions were lower than in the corresponding cued conditions but also increased with fixed-interval length. In addition, the degree of control under the uncued conditions was correlated with the extent to which the schedule during the terminal link was discriminated immediately upon entry into the terminal link. The pattern of results in both conditions was inconsistent with the notion that choice behavior matches relative immediacy of reinforcement. Reanalysis of previous evidence for matching (Chung and Herrnstein, 1967) showed that matching in fact did not occur, as the preferences of their subjects for the shorter of two delays also increased with the absolute size of the delays.

LATENCY AND FREQUENCY OF RESPONDING UNDER DISCRETE‐TRIAL FIXED‐INTERVAL SCHEDULES OF REINFORCEMENT1

Pigeons' key pecking was studied under a number of discrete-trial fixed-interval schedules of food reinforcement. Discrete trials were presented by briefly illuminating the keylight repetitively throughout the interreinforcement interval. A response latency counterpart to the fixed-interval scallop was found, latency showing a gradual, negatively accelerated decrease across the interval. This latency pattern was largely invariant across changes in fixed-interval length, number of trials per interval, and maximum trial duration. Frequency of responding during early trials in the intervals varied, however, with different schedule parameters, being directly related to fixed-interval length, inversely related to number of trials, and complexly affected by conjoint variations of fixed-interval length and number of trials. Response latency thus was found to be simply related to elapsed time during the interval while response frequency was complexly determined by other factors as well.

EFFECTS OF CYCLE LENGTH ON PERFORMANCE ON A TEMPORALLY DEFINED AVOIDANCE SCHEDULE1

Three rats were trained on a temporally defined avoidance schedule logically similar to a fixed-interval, limited-hold positive reinforcement schedule. This avoidance schedule was composed of time periods during which responses had no scheduled consequences alternating with time periods during which a response precluded shock. As with fixed-interval length and response rate on positive reinforcement schedules, an inverse relationship was obtained between the length of the no-consequence interval and response rate during the no-consequence interval. An inverse relationship was also obtained between the length of the no-consequence interval and the per cent of shocks avoided. A rate increase within the no-consequence interval, similar to that typically produced by fixed-interval positive reinforcement procedures, was displayed by one of the rats where the no-consequence interval was at intermediate values and frequency of shock was relatively high. The introduction of a discriminative stimulus correlated with the avoidance interval produced typical discriminated avoidance behavior as well as alterations in temporal patterning of responses during the no-consequence interval in the two rats exposed to this procedure. These alterations in temporal patterning disappeared when the discriminative stimulus was removed. The results were consonant with those reported in the literature involving food reinforcement and fixed-interval, limited-hold schedules.

The control of schedule-induced polydipsia: Frequency and magnitude of reinforcement

Rats bar-pressing for 180 45-mg food pellets per experimental session became polydipsic at fixed-interval 5 sec. As the length of the fixed-interval food schedule was increased from 2 to 120 sec with one food pellet delivered per reinforcement, the degree of polydipsia for all rats increased monotonically to a maximum. With increases in the fixed-interval length beyond 120 sec, all animals showed a decrease in the level of water intake. When two pellets were delivered per reinforcement with total number of pellets per session remaining constant, the function relating water intake per session and fixed-interval length was, for all rats, similar in shape to the one-pellet function, but below it. Water intake per reinforcement interval, however, was greater for the two-pellet reinforcement magnitude than for the one-pellet magnitude over most of the fixed-interval lengths investigated. The decrease in total session water intake in the two-pellet condition was attributable to the decreased number of reinforcement intervals and the consequent decreased number of drinking occasions per session.

AVOIDANCE OF A RETURN TO THE FIRST COMPONENT OF A CHAIN FROM THE TERMINAL COMPONENT1

Three pigeons were trained on a chained fixed interval-fixed ratio schedule. Avoidance behavior which postponed a return to the first chain component from the second component was maintained on a second response key concurrently with the second component. When the fixed interval length was increased, avoidance rates first increased and then decreased as a function of fixed interval length. As the fixed ratio requirement was increased for one subject, avoidance rates first declined and then increased at larger fixed ratio values. Avoidance behavior maintained by postponing the first chain component was similar to avoidance behavior maintained by postponing a time out period.