Uniform Delay Research Articles

Demonstrative comparison of two traffic signal optimization programs: Synchro-6 and PASSER II

To effectively examine and properly response to the traffic congestion on the urban arterial, numerous traffic signal timing optimization programs have been introduced such as Synchro-6 and PASSER II-02. This study is aimed to provide the better insight into the basic difference between these two programs to traffic engineers or transportation practitioners by demonstratively comparing vehicle delay and bandwidth efficiency computed by two programs on the hypothetical arterial having five calibrated intersections spaced by 430-meter each other with varying traffic volume. This study concluded that difference in vehicle delay and bandwidth efficiency results from the characteristic of each program to optimize the traffic signal timing plan and to calculat ethe uniform delay, not from the used parameters (traffic volume). Further studies are requested to present more comprehensive characteristics of two programs to the traffic engineering group by comparing and evaluating them with the other factors that a ffect vehicle delay and bandwidth efficiency, such as intersection spacing, vehicle speeds, intersection capacity, and so on.

Arrival-Based Uniform Delay Model for Oversaturated Signalized Intersections with Poor Progression

For oversaturated traffic conditions, the Highway Capacity Manual (HCM) does not apply a progression adjustment factor to the delay model for signalized intersections when there is an initial queue. This causes counterintuitive results in the calculation of delay; for some cases, delay for a nonzero initial queue condition ends up being less than the delay with zero initial queue conditions. Also, for oversaturated traffic conditions, the delay model in the 2000 edition of HCM yields the same uniform delay values for all arrival types when there is an initial queue. This does not seem reasonable because it ignores the effect of platooning on delay. This paper introduces a new approach for computing uniform delay for oversaturated traffic conditions when progression is poor. This approach directly considers the platooning effects in delay and thus eliminates the need to apply a progression adjustment factor. The proposed model is applicable whether there is an initial queue or not. The approach was validated by a comparison of the control delays obtained from a CORSIM simulation to the delays from the proposed model. Validation procedures were conducted on the basis of zero and nonzero initial queue conditions. The proposed approach resulted in more accurate delay values than the HCM model.

Arrival-Based Uniform Delay Model for Oversaturated Signalized Intersections with Poor Progression

For oversaturated traffic conditions, the Highway Capacity Manual (HCM) does not apply a progression adjustment factor to the delay model for signalized intersections when there is an initial queue. This causes counterintuitive results in the calculation of delay; for some cases, delay for a nonzero initial queue condition ends up being less than the delay with zero initial queue conditions. Also, for oversaturated traffic conditions, the delay model in the 2000 edition of HCM yields the same uniform delay values for all arrival types when there is an initial queue. This does not seem reasonable because it ignores the effect of platooning on delay. This paper introduces a new approach for computing uniform delay for oversaturated traffic conditions when progression is poor. This approach directly considers the platooning effects in delay and thus eliminates the need to apply a progression adjustment factor. The proposed model is applicable whether there is an initial queue or not. The approach was validat...

A stability criterion for HNFDE with non-uniform delays

Abstract Stability of functional differential equations (FDE) is an increasingly important problem in both science and engineering. Delays, whether uniform or non-uniform, play an important role in the dynamics of a system. Since non-uniform delay is more general and less focused than uniform delay, this paper concentrates on the stability of high-order neutral functional differential equations (HNFDE) with non-uniform delay, and proposes a sufficient condition for it. This result may be widely helpful, thanks to the frequent emergence of a HNFDE with non-uniform delay in various fields. Its effectiveness is illustrated by some examples.

Analysis of queueing policies in QoS switches

It is widely accepted that next-generation networks will provide guaranteed services, in contrast to the “best effort” approach today. We study and analyze queueing policies for network switches that support the QoS (Quality of Service) feature. One realization of the QoS feature is that packets are not necessarily all equal, with some having higher priorities than the others. We model this situation by assigning an intrinsic value to each packet. In this paper we are concerned with three different queueing policies: the nonpreemptive model, the FIFO preemptive model, and the bounded delay model. We concentrate on the situation where the incoming traffic overloads the queue, resulting in packet loss. The objective is to maximize the total value of packets transmitted by the queueing policy. The difficulty lies in the unpredictable nature of the future packet arrivals. We analyze the performance of the online queueing policies via competitive analysis, providing upper and lower bounds for the competitive ratios. We develop practical yet sophisticated online algorithms (queueing policies) for the three queueing models. The algorithms in many cases have provably optimal worst-case bounds. For the nonpreemptive model, we devise an optimal online algorithm for the common 2-value model. We provide a tight logarithmic bound for the general nonpreemptive model. For the FIFO preemptive model, we improve the general lower bound to 1.414, while showing a tight bound of 1.434 for the special case of queue size 2. We prove that the bounded delay model with uniform delay 2 is equivalent to a modified FIFO preemptive model with queue size 2. We then give improved upper and lower bounds on the 2-uniform bounded delay model. We also show an improved lower bound of 1.618 for the 2-variable bounded delay model, matching the previously known upper bound.

Properties of Space-Time Codes for Frequency-Selective Channels

Some important properties are derived for the diversity gain and the coding gain of space-time codes (STCs) for frequency-selective channels. It is proven that the diversity gain of a STC that provides maximum diversity gain for channels with a given number of taps is robust to a decrease in the number of taps. For coding gain analysis, we categorize the possible types of correlation matrices into several classes based on the type of power delay profile, spatial correlation, and tap correlation. It is proven that optimum STCs found for spatially independent and frequency-selective channels with uncorrelated taps and uniform power delay profile have coding gains that are robust against a mismatch in correlation structure if the number of taps is fixed. Thereafter, a systematic design procedure is applied to search for the best space-time trellis codes (STTCs) for frequency-selective channels. At a frame error rate (FER) of 0.01, our example 16-state binary phase-shift keying (BPSK) STTC outperforms the delay diversity code by 3.4 dB for a channel with three uncorrelated uniform taps. Further, the example STC designed for a channel with a given number of taps is shown to provide good performance for channels with fewer taps.

Local stability of random exponential marking

Random exponential marking (REM) is an attractive adaptive queue management algorithm. It uses the quantity known as ‘price’ to measure the congestion in a network. REM can achieve high utilisation, small queue length, and low buffer overflow probability. Many works have used control theory to provide the stable condition of REM without considering the feedback delay. Recently, sufficient conditions for local stability of REM have been provided when the sources have a uniform one- or two-step feedback delay. Nevertheless, no work has been done for the case of arbitrary uniform delay. The authors propose a continuous time model to generalise the local stable condition for REM in a multilink and multisource network with arbitrary uniform feedback delay.

Age‐dependent variations in the directional sensitivity of balance corrections and compensatory arm movements in man

We investigated the effects of ageing on balance corrections induced by sudden stance perturbations in different directions. Effects were examined in biomechanical and electromyographic (EMG) recordings from a total of 36 healthy subjects divided equally into three age groups (20-34, 35-55 and 60-75 years old). Perturbations consisted of six combinations of support-surface roll (laterally) and pitch (forward-backward) each with 7.5 deg amplitude (2 pure pitch, and 4 roll and pitch) delivered randomly. To reduce stimulus predictability further and to investigate scaling effects, perturbations were at either 30 or 60 deg s(-1). In the legs, trunk and arms we observed age-related changes in balance corrections. The changes that appeared in the lower leg responses included smaller stretch reflexes in soleus and larger reflexes in tibialis anterior of the elderly compared with the young. For all perturbation directions, onsets of balance correcting responses in these ankle muscles were delayed by 20-30 ms and initially had smaller amplitudes (between 120-220 ms) in the elderly. This reduced early activity was compensated by increased lower leg activity after 240 ms. These EMG changes were paralleled by comparable differences in ankle torque responses, which were initially (after 160 ms) smaller in the elderly, but subsequently greater (after 280 ms). Findings in the middle-aged group were generally intermediate between the young and the elderly groups. Comparable results were obtained for the two different stimulus velocities. Stimulus-induced trunk roll, but not trunk pitch, changed dramatically with increasing age. Young subjects responded with early large roll movements of the trunk in the opposite direction to platform roll. A similarly directed but reduced amplitude of trunk roll was observed in the middle-aged. The elderly had very little initial roll modulation and also had smaller stretch reflexes in paraspinals. Balance-correcting responses (over 120-220 ms) in gluteus medius and paraspinals were equally well tuned to roll in the elderly, as in the young, but were reduced in amplitude. Onset latencies were delayed with age in gluteus medius muscles. Following the onset of trunk and hip balance corrections, trunk roll was in the same direction as support-surface motion for all age groups and resulted in overall trunk roll towards the fall side in the elderly, but not in the young. Protective arm movements also changed with age. Initial arm roll movements were largest in the young, smaller in the middle aged, and smallest in the elderly. Initial arm roll movements were in the same direction as initial trunk motion in the young and middle aged. Thus initial roll arm movements in the elderly were directed oppositely to those in the young. Initial pitch motion of the arms was similar across age groups. Subsequent arm movements were related to the amplitude of deltoid muscle responses which commenced at 100 ms in the young and 20-30 ms later in the elderly. These deltoid muscle responses preceded additional arm roll motion which left the arms directed 'downhill' (in the direction of the fall) in the elderly, but 'uphill' (to counterbalance motion of the pelvis) in the young. We conclude that increased trunk roll stiffness is a key biomechanical change with age. This interferes with early compensatory trunk movements and leads to trunk displacements in the direction of the impending fall. The reversal of protective arm movements in the elderly may reflect an adaptive strategy to cushion the fall. The uniform delay and amplitude reduction of balance-correcting responses across many segments (legs, hips and arms) suggests a neurally based alteration in processing times and response modulation with age. Interestingly, the elderly compensated for these 'early abnormalities' with enlarged later responses in the legs, but no similar adaptation was noted in the arms and trunk. These changes with age provide an insight into possible mechanisms underlying falls in the elderly.

Strategies of text retrieval: a criterion shift account.

This study scrutinized people's ability to apply different strategies to randomly intermixed immediate and delayed test items. In three experiments, participants first read one set of stories. Later, they read more stories, and after each one, answered intermixed questions about that story and one of the earlier ones. The experiments cumulatively manipulated amount of delay, test probe plausibility, probe relation (explicit, paraphrase, inference), and testing procedure (mixed versus uniform delay). Using signal detection response criterion as the index of strategy, we contrasted the single criterion hypothesis, according to which one text retrieval criterion is applied to all test items, and a multiple-criterion hypothesis. The results consistently favoured the multiple-criterion hypothesis. The results also indicated that the presence of immediate and delayed probes mutually influence one another: Less extreme signal detection criteria were adopted under mixed than uniform testing. It was concluded that text retrieval strategy is continually calibrated with reference to the quality of the test probes.

Multi-regime arrival rate uniform delay models for signalized intersections

This paper presents the development and validation of uniform delay models for coordinated signalized intersections. The Highway Capacity Manual (HCM) identifies one uniform and five non-uniform (platoon) arrival types. Delays for non-uniform arrival cases are computed by applying progression adjustment factors (PFs) to the delay for uniform arrival case. The range of PF is from 0% to 256%. We found that the PF approach produced accurate results for only one-half of cases. This paper presents an Arrival-Based approach that eliminates the needs for applying PF. The AB approach directly considers the effects of quality of progression in formulating delay models. It uses different flow rates for vehicles within and outside platoons. A total of 11 different delay models were derived to cover all arrival cases. Data from three different states were used for validation of AB delay models. The results indicate that AB models provided accurate results for all arrival types. However, HCM uniform delay model was not accurate for Arrival Types 1, 4 and 6. Furthermore, the results of cycle-by-cycle delay analyses showed that the difference between field delays and AB models were not significant, but that was not the case for the HCM model. The AB models can be simplified to yield the HCM uniform delay model, if a single regime arrival rate is assumed. Single regime arrival rate implies that the flow rate for vehicles in platoon is the same as those arriving randomly. For only the uniform arrival case, the AB delay model is identical to the HCM delay model; thus making the HCM uniform delay model a special case of AB models.

Theoretical analysis of reverse link capacity for an SIR-based power-controlled cellular CDMA system in a multipath fading environment

Capacity estimation in a code-division multiple-access system is closely related to power control schemes, which complicates the analysis due to the interaction between the signal power and the interference from other users and from other paths. For a signal-to-interference ratio (SIR)-based power control scheme, most previous work has been restricted to a single-cell system or to a multiple-cell system neglecting the effect of multipath fading. This paper is to give a theoretical foundation to the possible reverse link capacity of a multiple-cell system with perfect SIR-based power control, assuming two different multipath Rayleigh fading channel models: uniform and exponential power delay profiles. The effects of the numbers of resolvable propagation paths and RAKE fingers, and other system parameters such as the required E/sub b//I/sub 0/, the processing gain, and the maximum allowable transmit power of a mobile station, are investigated. The results are compared between single- and multiple-cell systems. When the number of resolvable paths is one or the number of Rake fingers is one, the link capacity becomes zero in a multiple-cell environment. This can be avoided by the use of antenna diversity. Antenna diversity reception is found to linearly increase the link capacity as the number of antennas increases.

Delay Model for Right-Turn Lanes at Signalized Intersections with Uniform Arrivals and Right Turns on Red

A framework for the future incorporation of proper right-turn-on-red (RTOR) delay estimation procedures into the Highway Capacity Manual signalized intersection chapters is provided. Models of uniform delay that are based on queuing theory and that incorporate RTORs are developed. Queuing accumulation polygons (QAPs) were used to analyze the effects of RTOR operations. A classification system for placement of any signal phasing scheme into one of four classes based on a sequence of three red regimes and one green regime is showcased. The three red regimes are characterized by the traffic stream that is given priority over the RTOR traffic during the red regime. One red regime gives priority to the intersecting and conflicting traffic. The second red regime gives priority to the intersecting but nonconflicting traffic. The third red regime prioritizes the opposing and conflicting traffic. It is further demonstrated that the four classes of signal phasing schemes result in one of two general QAP patterns. The first pattern consists of two conflicting regimes, followed by two nonconflicting regimes. The second consists of alternating conflicting and nonconflicting regimes. Models used to calculate delay for each basic pattern are presented. The parameters needed to calculate delays based on the models that were developed are discussed. Furthermore, models from related research that may be used to develop any necessary parameter estimates are also presented.

Estimation of coherent detection performance for spread scattering in reverberation-noise mixtures

Narrow-band matched filter processing gain is estimated for medium- and high-frequency active sonars for which the random backscattering processes are assumed to be wide sense stationary in time frequency and uncorrelated in delay-Doppler wide sense stationary and uncorrelated scattering [WSSUS conditions]. Echo and reverberation processes that are WSSUS are described by two-dimensional scattering functions defined in the delay-Doppler plane. The average receiver responses are estimated from the convolution of the appropriate scattering function with the waveform ambiguity function. Estimates of matched filter processing gain are derived for continuous wave (CW) linear frequency modulation (LFM), and discrete frequency shift keyed (FSK) (hop code) waveforms reflected from point and uniform delay spread scatterers masked by reverberation. These bound matched filter performance for a particular waveform and interference distribution since most delay spread scattering falls somewhere between these extremes. The scattering and ambiguity functions are modeled by bounded constant amplitude functions in delay-Doppler that permit the convolutions to be approximated by overlapping area calculations. The results are presented in tabular form as simple formulas that are functions of the reverberation, noise, and waveform parameters. The estimates are shown to be consistent with processing gain measurements made from multiple realizations of synthesized and in-water data.

Analysis of intersection delay under real-time adaptive signal control

The United States Department of Transportation has recently begun implementation of the national demonstration project for suburban Advanced Traffic Management Systems (ATMS) utilizing the Sydney Coordinated Adaptive Traffic System (SCATS). SCATS is an automated, real time, traffic responsive signal control strategy. The expected benefit from the system comes from its ability to constantly modify signal timing patterns to most effectively accommodate changing traffic conditions. The objectives of this research study were to analyze the differences in certain delay parameters which would occur as a result of implementing SCATS signal control. The study employed a macroscopic simulation procedure to compute intersection delay under both a strategy that changed signal timings once per hour and SCATS signal control. A comparison of delay under both forms of control is presented. The study findings demonstrated mixed results regarding the benefit of SCATS control. A general conclusion of the study was that SCATS distributed the delay across competing approaches more evenly. However, in some cases this resulted in an increase in the total intersection delay. The observed delay change was attributed primarily to the saturation equalization objective of the SCATS control program. SCATS attempts to allocate green time to the intersection approaches based on the degree of saturation. Under this philosophy the system is able to balance the percentage of green time between all approaches, resulting in more uniform delay.

Clinical characteristics of children with mental retardation of unknown etiology in Korea.

The purpose of this study was to investigate the clinical characteristics of children with mental retardation (MR) of unknown etiology for early recognition and intervention. In this study, we defined children with MR of unknown etiology as those without clear etiologies for MR despite extensive evaluation and were not associated with pathological behavioral problems such as pervasive developmental disorders and attention-deficit/hyperactivity disorder. The clinical characteristics of children with MR of unknown etiology were as follows. 1) MR of unknown etiology was 48.8% of all MR. 2) MR of unknown etiology was more common in males. 3) Delayed language development was a leading factor that made the parents of children with MR of unknown etiology seek help from physicians. However, most of the children with MR of unknown etiology showed a relatively uniform delay in several areas of development. 4) Most children with MR of unknown etiology were delayed walkers. 5) Most children with MR of unknown etiology were mild cases.

Progression Adjustment Factors for Uniform Delay at Signalized Intersections

Signal progression plays an important role in controlling arrival pattern and delay at coordinated signalized intersections. In the Highway Capacity Manual (HCM), one random and five nonrandom arrival types are identified. The delays for nonrandom arrival cases (platoon arrivals) are computed by applying progression adjustment factors (PFs) to the delay for the random arrival case. However, HCM-estimated delays are found to be significantly different from field-measured delays for Arrival Types 1, 4, and 6. For Arrival Type 2 the HCM estimations are acceptable, although the deviations are still relatively high. For Arrival Types 3 and 5 the HCM estimates the delays accurately. These findings suggest that the HCM PFs need to be revised. A new set of PFs was developed using the arrival-based delay models. A relationship between the effective green ratio, g/C, and the new PFs was established for each arrival type. With the proposed PF values, the HCM approach would be more accurate than it is with the current PF values. For Arrival Type 1, the new PF values are higher than the current HCM values for g/C ⩽ 0.50 and lower for g/C > 0.50. For Arrival Types 2 and 4, the new PF values are lower than those of HCM, as expected, because the HCM overestimates the delays for both Arrival Types 2 and 4. For Arrival Type 6 the new PF values are lower for g/C ⩽ 0.40; otherwise they are higher. A new progression adjustment table similar to Table 9-13 of the HCM is created. It is recommended that the new PF values be adopted by the HCM since they enhance the accuracy of delay estimation.

Bcl-2 Accelerates the Maturation of Early Sensory Neurons

Bcl-2 is a cytoplasmic protein that blocks apoptosis in a wide variety of cell types. Here we report a novel role for Bcl-2 in the early stages of neuronal development. Shortly after differentiating from progenitor cells, sensory neurons undergo a distinct morphological change; initially they have small, spindle-shaped, phase-dark cell bodies that become large, spherical, and phase-bright. Early sensory neurons cultured from the trigeminal ganglia of bcl-2-/- embryos at embryonic day 11 (E11) and E12 underwent this change more slowly than trigeminal neurons of wild-type embryos of the same ages. The delay was not attributable to the well documented role of Bcl-2 in preventing apoptosis, because Bcl-2-deficient early sensory neurons survived as well as wild-type neurons. Accordingly, there was a significantly smaller number of the more mature type of neuron in the early trigeminal ganglia of bcl-2-/- embryos, yet the number of neurons in the trigeminal ganglia of bcl-2-/- and wild-type embryos was similar. The absence of Bcl-2 did not cause a uniform delay in the developmental program of sensory neurons, because the time course of nerve growth factor receptor expression (both trkA and p75) was unaffected in the trigeminal neurons of bcl-2-/- embryos. These findings indicate that Bcl-2 expression is required for the normal progression of a particular early maturational change in embryonic sensory neurons.

Chaos in Neural Networks Composed of Coincidence Detector Neurons

Chaotic behaviour is observed in neural network models composed of coincidence detector neurons. We use a continuous time and deterministic point process model with uniform synaptic strength and random delay, and apply periodical external inputs to a few neurons in the network. We show that the network dynamics becomes chaotic when the length of “chain firing” starting from an external input becomes practically infinite. © 1997 Elsevier Science Ltd.

Estimating Intersection Approach Delay Using 1985 and 1994Highway Capacity ManualProcedures

The current methods for determining average stopped delay at signalized intersections were studied. Field measurements of average stopped delay were obtained and compared with values computed using both the 1985 and 1994 editions of the Highway Capacity Manual (HCM). The 1994 HCM uses an equation to predict the progression adjustment factor (PF), a new technique for determining the left-turn adjustment factor for saturation flow rates, and a new set of equations for determining the uniform delay parameter for left-turn lane groups with primary and secondary phasing. Overall, the 1994 HCM produces better estimates of intersection stopped delay than the 1985 HCM.

Estimating Intersection Approach Delay Using 1985 and 1994 Highway Capacity Manual Procedures

The current methods for determining average stopped delay at signalized intersections were studied. Field measurements of average stopped delay were obtained and compared with values computed using both the 1985 and 1994 editions of the Highway Capacity Manual (HCM). The 1994 HCM uses an equation to predict the progression adjustment factor (PF), a new technique for determining the left-turn adjustment factor for saturation flow rates, and a new set of equations for determining the uniform delay parameter for left-turn lane groups with primary and secondary phasing. Overall, the 1994 HCM produces better estimates of intersection stopped delay than the 1985 HCM.