Delay Variation Research Articles

Reliability and sensitivity to altered hemodynamics measured with resting-state fMRI metrics: Comparison with 123I-IMP SPECT

Blood oxygenation level-dependent (BOLD) contrast is sensitive to local hemodynamic changes and thus is applicable to imaging perfusion or vascular reactivity. However, knowledge about its measurement characteristics compared to reference standard perfusion imaging is limited. This study longitudinally evaluated perfusion in patients with steno-occlusive disease using resting-state functional MRI (rsfMRI) acquired before and within nine days of anterior circulation revascularization in patients with large cerebral artery steno-occlusive diseases. The reliability and sensitivity to longitudinal changes of rsfMRI temporal correlation (Rc) and time delay (TDc) relative to the cerebellar signal were examined voxel-wise in comparison with single-photon emission CT (SPECT) cerebral blood flow (CBF) using the within-subject standard deviation (Sw) and intraclass correlation coefficients (ICCs). For statistical comparisons, the standard deviation (SD) of longitudinal changes within the cerebellum, the number of voxels with significant changes in the left middle cerebral artery territory ipsilateral to surgery, and their average changes relative to the cerebellar SD were evaluated. The test-retest reliability of the fMRI metrics was also similarly evaluated using the human connectome project (HCP) healthy young adult dataset. The test-retest time interval was 31 ± 18 days. Test-retest reliability was significantly higher for SPECT (cerebellar SD: −2.59 ± 0.20) than for fMRI metrics (cerebellar SD: Rc, −2.34 ± 0.24, p = 0.04; TDc, −2.19 ± 0.21, p = 0.003). Sensitivity to postoperative changes, which was evaluated as the number of voxels, was significantly higher for fMRI TDc (8.78 ± 0.72) than for Rc (7.42 ± 1.48, p = 0.03) or SPECT CBF (6.88 ± 0.67, p < 0.001). The ratio between the average Rc, TDc, and SPECT CBF changes within the left MCA target region and cerebellar SD was also significantly higher for fMRI TDc (1.21 ± 0.79) than Rc (0.48 ± 0.94, p = 0.006) or SPECT CBF (0.23 ± 0.57, p = 0.001). The measurement variability of time delay was also larger than that of temporal correlation in HCP data within the cerebellum (t = −8.7, p < 0.001) or in the whole-brain (t = −27.4, p < 0.001) gray matter. These data suggest that fMRI time delay is more sensitive to the hemodynamic changes than SPECT CBF, although the reliability is lower. The implication for fMRI connectivity studies is that temporal correlation can be significantly decreased due to altered hemodynamics, even in cases with normal CBF.

On the Design and Performance Analysis of Flexible Planar Monopole Ultra-Wideband Antennas for Wearable Wireless Applications

With the promising developments in wearable communication technology, attention towards flexible electronics is increasing day-by-day. This study presents flexible low-profile ultra-wideband (UWB) antennas for wearable applications. The antenna comprised of a modified dewdrop-inspired radiator and a defected ground plane and has an impedance bandwidth of 3.1–10.6 GHz. The antenna flexibility is investigated using four different substrates (polyester, polyamide, denim, and Teslin) and tested on a cotton shirt and a high-end Res-Q jacket to evaluate their performance stability for body-worn applications. The fabricated planar dewdrop-shaped radiator (PDSR) antennas have a radiation efficiency of &gt;90%, a gain of &gt;4 dBi, and a group delay variation of fewer than 0.5 ns. The antenna conformability is measured by placing the fabricated antennas on various curved and nonplanar parts of the human body. The aforementioned antennas offer better flexibility for different bent conditions. The specific absorption rate (SAR) of the designed antennas is investigated to determine their wearability, and values are found to be less than 0.2 W/Kg. Also, the received signal strength (RSS) is discussed in order to analyze signal attenuation, and the performance analysis of the antennas is compared.

Paradigm analysis of performance and exhaust emissions in CRDI engine powered with hydrogen and Hydrogen/CNG fuels: A green fuel approach under different injection strategies

An engine with common-rail direct injection diesel uses Hydrogen and hydrogen-enriched CNG to investigate their possible usage. The engine's air intake manifold delivers hydrogen/CNG and hydrogen mixes. Different injection pressures (three) and at higher load are used to test out the different engine output parameters. In dual and single-fuel operations with diesel, dual-fuel operations produce higher in-cylinder pressure (73.39 bar) and shown better combustion. Due to induction of dual fuel, there is large variability in ignition delay and combustion duration compared to pure diesel. Enriching hydrogen reduces specific fuel usage. Significant reduction in engine pollutants is observed in dual fuel mode compared to diesel fuel. Hydrogen substitutes reduce THC and CO2 emissions by 30–35% and 3–4% respectively. Dual-fuel operations emit less smoke (5–10%) in different injection pressure than diesel. At all injection pressure the different combustion parameters, performances (37.2% better than D100) and emissions like NOx, CO2, and smoke are better for all dual-fuel than diesel at rated load for the different fuel approach type two (DFA2).

Turing–Hopf bifurcation co-induced by cross-diffusion and delay in Schnakenberg system

The dynamics of Schnakenberg model subjected to gene expression time delay and cross-diffusion is investigated. It is shown that the presence of cross-diffusion allows the enlarged Turing instability region compared with self-diffusion and the variation of time delay can either lead to destabilization of the positive equilibrium or fail Turing instability through Turing–Hopf bifurcation. A bifurcation analysis of the Schnakenberg model in question has been provided to derive the stable regime, Turing instability regime and also the condition for delay-induced Turing–Hopf bifurcation. With the aid of normal form of Turing–Hopf bifurcation, the spatiotemporal dynamics near this bifurcation point can be divided into six categories where various solutions including stable spatially homogeneous or inhomogeneous periodic solutions, stable steady states and the transition from one type of spatiotemporal patterns to another would exhibit. These spatiotemporal solutions have also been illustrated through some numerical simulations, confirming the theoretical predictions.

Prediction of delay discounting in intertemporal decisions by future thinking: Accounting for fluency, contents, and functions of future thoughts.

PurposeTo study the variations of delay discounting rates as a function of fluency, contents, and functions of future thoughts in healthy subjects.BackgroundDelay discounting (DD) is a concept that can measure a frequent tendency toward smaller, yet immediate rewards, while a delayed reward is greater in value. DD describes people's choices in intertemporal decisions and is associated with self‐control. Future thinking (FT) and having a vivid imagination of the future can reduce individuals’ DD rates. However, constructing a specific episodic future representation was merely studied in relation to DD. Although fluency and contents of future thoughts have been reported related to various disorders and behaviors, their association with DD has not been previously addressed.MethodsThe present study applies a verbal fluency task named the personal future task (PFT), the functions of future thinking scale (FoFTS), and the 27‐item delay discounting questionnaire (DDQ) in order to assess fluency, contents, and functions of future thoughts, and delay discounting in healthy subjects (N = 114, Female = 64%, Male = 36%, Mage = 34.22, SDage = 7.15).ResultsFindings indicate that fluency of future thoughts is associated with DD. Among the contents of FT categories, financial contents (future thoughts about money and real estate matters), and regarding functions of FT, engaging in FT for planning are related to DD. Due to the final model, the above‐mentioned correlated variables can be considered as significant predictors of intertemporal choices when controlling for education and gender (R 2 = 0.4, Adjusted R 2 = 0.33, F = 5.186, p‐value = 0.001).ConclusionThe frequency of future thoughts one can generate, specifically future thoughts about financial contents, is associated with less short‐sighted intertemporal decisions. The former relationship is enhanced for longer delays (e.g., 5–10 years). Besides, individuals who frequently engage in FT for planning (planning out sequences of actions) discount future rewards to a lesser extent.

Energy-Efficient Power and Subcarrier Allocation in Downlink OFDMA Systems with Channel Estimation Errors

In this paper, we investigate the joint optimization of power and subcarrier allocation for maximizing the energy efficiency (EE) in downlink OFDMA systems. The problem of EE maximization is formulated as a stochastic optimization to determine the optimal power and subcarrier allocation, in which many practical factors including channel estimation errors, delay requirements, and time-varying channel are considered. We first propose a dynamic power and subcarrier allocation (DPSA) algorithm to solve the formulated problem. Then, we derive the two bounds of EE and delay and reveal the tradeoff between them. The theoretical analysis and simulation results demonstrate the variations of EE and delay with channel estimation errors.

A machine learning-based optimization for end-to-end latency in TSN networks

Ultra-low latency (ULL) is a challenging but nonetheless essential network requirement to achieve in many contexts. Industrial automation (IEC/IEEE 60802), in-vehicle communications (IEEE P802.1DG), audio and video bridging (IEEE Std 802.1BA), aerospace, and 5G fronthaul (IEEE 802.1CM) applications demand a low network latency in the order of few milliseconds or even microseconds. ULL services target a more controlled latency for end-to-end device communication and, in critical environments, near real-time connections. Time-Sensitive Networks (TSN) aim at providing deterministic connectivity over IEEE 802 networks guaranteeing packet transport with bounded latency, low packet delay variation, and low packet loss. This work analyzes TSN latency mechanisms and examines how they influence E2E latency. Moreover, it builds a regression-based surrogate model that enables the creation of optimization models to find optimal configurations for a given TSN network. Our findings span the discussion of the characteristics of each individual TSN latency mechanism to the benefits achieved by the proposed optimization models and using these to achieve optimal E2E latency.

Analysis of a Delayed Reaction-Diffusion Predator–Prey System with Fear Effect and Anti-Predator Behaviour

This paper is devoted to studying the dynamics of a delayed reaction-diffusion predator–prey system incorporating the effects of fear and anti-predator behaviour. First, based on its mathematical model, the global attractor is analyzed and the local stability of its positive equilibria is derived. Moreover, the Hopf bifurcation induced by the time delay variable is also investigated. Furthermore, the existence and non-existence of non-constant positive solutions are analyzed. Finally, numerical simulations are presented to validate the theoretical analysis.

Evaluation of Seasonal Variability of First-Order Ionospheric Delay Correction at L5 and S1 Frequencies Using Dual-Frequency NavIC System

For the precise positioning applications it is important to determine and eliminate the positioning error introduced by various sources such as the ionosphere. To develop a standalone precise navigation system, India has launched the seven satellite constellations for NavIC (Navigation with Indian Constellation) system which can provide precision positioning over India and surrounded landmass. Since the ionospheric delay depends on the frequency of the satellite signal and NavIC systems work at different frequencies L5 and S1 than Global Positioning System (GPS) at L1 and L2, it is not possible to use the GPS data-driven study for NavIC based location calculations directly. Thus there is a need for a specialized ionospheric study for NavIC systems. In addition, the ionospheric delay is directly proportional to Slant Total Electron Content (STEC) which is dependent upon diurnal and seasonal solar activity. To achieve accurate positioning facilities, there is also a need for evaluation for seasonal variability of ionospheric delay correction for NavIC receivers. This paper deals with the STEC estimation; it's smoothing, and removal of instrumental biases from STEC. The determined true STEC has been used to determine first-order ionospheric delay correction at L5 and S1 frequencies. The delay correction at S1 has been found less (2–7 m) as compared to L5 (10–30 m). Furthermore, the seasonal variability of ionospheric delay has been analyzed using about 19 months of data (from June 2017 to December 2018) and found that the ionospheric delay follows unique seasonal characteristics which can be utilized for delay modeling. It has been also observed that the geostationary satellites of the NavIC system are more appropriate than geosynchronous satellites for ionospheric related studies.

Delay Distributions in Discrete Time Multiclass Tandem Communication Network Models

An exact computational algorithm for the solution of a discrete time multiclass tandem network with a primary class and cross-traffic at each queue is developed. A sequence of truncated Lindley recursions is defined at each queue relating the delays experienced by the first packet from consecutive batches of a class at that queue. Using this sequence of recursions, a convolve-and-sweep algorithm is developed to compute the stationary distributions of the delay and inter-departure processes of each class at a queue, delays experienced by a typical packet from the primary class along its path as well as the mean end-to-end delay of such a packet. The proposed approach is designed to handle the non-renewal arrival processes arising in the network. The algorithmic solution is implemented as an abstract class which permits its easy adaptation to analyze different network configurations and sizes. The delays of a packet at different queues are shown to be associated random variables from which it follows that the variance of total delay is lower bounded by the sum of variances of delays at the queues along the path. The developed algorithm and the proposed lower bound on the variance of total delay are validated against simulation for a tandem network of two queues with three classes under different batch size distributions.

Microfluidic-Based Bacterial Molecular Computing on a Chip

Biocomputing systems based on engineered bacteria can lead to novel tools for environmental monitoring and detection of metabolic diseases. In this paper, we propose a Bacterial Molecular Computing on a Chip (BMCoC) using microfluidic and electrochemical sensing technologies. The computing can be flexibly integrated into the chip, but we focus on engineered bacterial AND Boolean logic gate and ON-OFF switch sensors that produces secondary signals to change the pH and dissolved oxygen concentrations. We present a prototype with experimental results that shows the electrochemical sensors can detect small pH and dissolved oxygen concentration changes created by the engineered bacterial populations’ molecular signals. Additionally, we present a theoretical model analysis of the BMCoC computation reliability when subjected to unwanted effects, i.e., molecular signal delays and noise, and electrochemical sensors threshold settings that are based on either standard or blind detectors. Our numerical analysis found that the variations in the production delay and the molecular output signal concentration can impact on the computation reliability for the AND logic gate and ON-OFF switch. The molecular communications of synthetic engineered cells for logic gates integrated with sensing systems can lead to a new breed of biochips that can be used for numerous diagnostic applications.

Inserting of heuristic techniques into the stability regions for multiarea load frequency control systems with time delays

The design and optimization of robust controller parameters are required to improve the controller performances and to keep the stability of load frequency control (LFC) system. In addition, reducing the number of iterations and computational time is very important for swiftly tuning of the controller parameters and the system to reach stability rapidly. For this purpose, this study presents the inserting of heuristic optimization techniques into stability regions method identified in proportional-integral (PI) controllers space for multiarea LFC systems with communication time delays (CTDs). This method consists of two steps: determination of stability region for the system and application of heuristics. Stability region for the system is found via stability boundary locus (SBL) and moth-flame optimization (MFO), particle swarm optimization (PSO), sine cosine algorithm (SCA), slime mould algorithm (SMA) and whale optimization algorithm (WOA) are inserted and applied to this region. In addition, a cost function having time domain specifications is developed for improving the performances of LFC and it is compared with the well-known integral error functions. Also, the robust stability region, which tolerates any system parameter and any time delay variation, is identified and the significance of this region is given for robustness analysis. It is observed from the analyses that better system outputs have been obtained with developed cost function. Steady state errors are minimized and transient state performances are improved with the proposed method. Moreover, desired system performances have been achieved with lower computational time and iteration number (approximately more than about 89% reduced according to classical approach) without deteriorating the stable structure of the system by the proposed method.

Influence of Intermittent Fasting During Ramadan on Circadian Variation of Symptom-Onset and Prehospital Time Delay in Acute ST-Segment Elevation Myocardial Infarction.

Ramadan interferes with circadian rhythms mainly by disturbing the routine patterns of feeding and smoking. The objective of this study was to investigate the circadian pattern of ST elevation acute myocardial infarction (STEMI) during the month of Ramadan. We studied consecutive STEMI patients 1 month before and after Ramadan (non-Ramadan group-NRG) and during Ramadan (Ramadan group-RG). The RG group was also divided into two groups, based on whether they chose to fast: fasting (FG) and non-fasting group (NFG). The time of STEMI onset was compared. A total of 742 consecutive STEMI patients were classified into 4 groups by 6h intervals according to time-of-day at symptom onset. No consistent circadian variation in the onset of STEMI was observed both between the RG (P = .938) and NRG (P = .766) or between the FG (P = .232) and NFG (P = .523). When analyzed for subgroups of the study sample, neither smoking nor diabetes showed circadian rhythm. There was a trend towards a delay from symptom onset to hospital presentation, particularly at evening hours in the RG compared with the control group. In conclusion, there was no significant difference in STEMI onset time, but the time from symptom onset to hospital admission was significantly delayed during Ramadan.

AN ANALYSIS OF WIRELESS NETWORKS

Wireless networks have a unique capability of maintaining same contact even if one moves from one location to another. It provides the flexibility and versatility for wireless communications. The wireless and mobile communications have found usefulness in the area of commerce, education, defense, home-based and industrial applications, and military environment. Wireless networks have had a significant impact on the world through the use of wireless networks; information could be sent overseas or behind the enemy lines easily, efficiently and more reliably. Wireless networking is an essential productivity tool for today's mobile workforce. With wireless networking, we can stay connected to companies and others information resources virtually anytime, anywhere. Wireless networks are becoming more and more ubiquitous in recent years, ranging from mobile analog and digital cellular telephony up to satellite broadcasting. Therefore, supporting a high Quality of Service (QoS) in delivering voice, video and data in this context has emerged as one of the most important challenge of the new century. In this research article we present a survey on introduction to wireless networks, classification of wireless networks, quality of service(QOS) parameters like bandwidth, Delay, Delay Variation (Jitter), Throughput, Energy, and finally to provide the Security to information about different parameters for end-to-end communication over wireless networks.

On the SIR Meta Distribution for Cache-Enabled Wireless Networks With Random Discontinuous Transmission: Analysis and Optimization

A fine-grained analysis of the cache-enabled networks is crucial for system design. In this paper, we focus on the meta distribution of the signal-to-interference ratio for the cache-enabled networks where the locations of the base stations are modeled as a Poisson point process. With the application of the random caching and the random discontinuous transmission schemes, we derive the moments of the conditional successful transmission probability, the exact meta distribution and its beta approximation by utilizing stochastic geometry. The closed-form expressions of the mean and variance of the local delay (i.e., the jitter) are also derived. We then consider the maximization of the mean successful transmission probability and the minimization of the average system transmission delay by jointly optimizing the caching probability and the BS active probability. Finally, the numerical results demonstrate the superiority of the proposed optimization schemes over the existing caching strategies and reveal the impacts of the key network parameters on the cache-enabled networks in terms of successful transmission probability, successful transmission probability variance, meta distribution, mean local delay and jitter.

Effect of data aggregation on the delay of demand-response communications within a Wi-Fi home area network with and without other traffic

Home area networks play an important role in the demand-response function of smart grids. It is responsible for responding to requests received from the grid by controlling the devices in the home in a predefined manner. Communication within a Home Area Network should be efficient in terms of both delay and energy. Delay matters since the devices need to respond to the request within the stipulated delay. Energy matters since thousands of Home Area Networks are likely to create a significant energy footprint on the global level. In order to reduce energy consumption, the number of communications needs to be reduced and data aggregation can achieve this goal. However, data aggregation introduces a prolonged delay and may thus render the system unfit for its purpose. Therefore, it is required to determine the variation of delay when data aggregation is performed at different levels. This paper presents algorithms for data aggregation and device clustering optimization. Finally, the delay distribution was studied in a simulation environment with one level of data aggregation. The results show that an existing Wi-Fi network can be used for Smart Grid communications with in-network data aggregation provided that there is a spare (unused) bandwidth of 3 Mbit/s in the network.

A new compact ultra-wideband frequency selective surface with angular stability and polarization independence for antenna radiation enhancement in microwave imaging application

A new compact, rudimental, uni layered frequency selective surface (FSS) is proposed to work in the commercial ultra-wideband (UWB) spectrum with its application in enhancing broadside radiation of an UWB antenna. The overall unit cell dimension (length × width × thickness) of the proposed UWB FSS is 0.15λL × 0.15λL × 0.016λL only where λL represents the wavelength corresponding to lowest band edge in the 3.04 to 10.88 GHz (∼112.6 %) spectrum with transmission coefficient less than −10 dB. Moreover, the proposed FSS provides certain degree of angular stability of 45° in both TE and TM planes of polarization. The proposed FSS is well suited for antenna gain augmentation as it offers linearly decreasing reflection phase profile. A compact ultra-wideband U-shaped CPW fed antenna with the dimension of 32 × 26 × 0.8 mm3 is designed that covers a bandwidth from 2.7 to 12.76 GHz (130 %). The proposed FSS is integrated with the U-shaped antenna to exhibit an improved and steady gain profile of 5.1–6.8dBi in the 2.82–12.92 GHz (128.34 %) impedance band. Maximum gain augmentation of 3.62 dBi is achieved at 9.5 GHz along with steady gain profile in the entire operating band of “antenna-FSS”, linear S21 response and flat group delay variations which implies the applicability of proposed antenna-FSS in various UWB communication purposes that comprise impulse radar, through wall imaging, microwave imaging, short range indoor communication etc. The applicability of UWB ‘antenna-FSS’ is established by ground coupling microwave imaging test in proximity of soil test bed where the fundamental characteristics of ‘antenna-FSS’ is found to be unaltered.

Development of a Theoretical Delay Model for Heterogeneous and Less Lane-Disciplined Traffic Conditions

In developing countries with limited or no availability of traffic sensors, theoretical delay models are the most commonly used tool to estimate control delay at intersections. The traffic conditions in such countries are characterised by a large mix of vehicle types and limited or no lane discipline (Heterogeneous, Less Lane-Disciplined (HLLD) traffic conditions), resulting in significantly different traffic dynamics. This research develops a queueing theory-based theoretical delay model that explicitly incorporates HLLD traffic conditions’ characteristic features like lack of lane discipline, violation of the First-In-First-Out rule, and a large mix of vehicle types. A new saturation flow-based Passenger Car Equivalent (PCE) estimation methodology to address heterogeneity and a virtual lane estimation approach to address lack of lane-discipline are proposed. The developed model shows 64% lesser error in average control delay estimation compared to the in-practice delay estimation models under HLLD traffic conditions. The developed model is used for signal optimisation under HLLD traffic conditions and reductions of up to 24% in control delay in comparison to the in-practice signal timing approach are observed. The study also highlights the significance of knowing the variation of delay in addition to average delay and presents a simple approach to capture the variation in delay.

A Super‐Formula‐based compact ultra‐wideband antenna and its application to indoor real‐time positioning systems

AbstractA Super‐Formula‐based compact ultra‐wideband (UWB) printed monopole antenna is proposed in this paper. The presented design is implemented by using inexpensive FR‐4 laminates, and is optimized so as to enable excellent radio frequency performance in terms of impedance matching, realized gain, total efficiency, radiation pattern characteristics, maximal group delay variation, and system fidelity factor (SFF), while covering the Federal Communications Commission UWB channel 5, from 6.24 to 6.74 GHz, and channel 9, from 7.74 to 8.24 GHz. The proposed antenna solution has been characterized both passively and actively using a commercially available indoor real‐time positioning system, which relies on the phase‐difference‐of‐arrival algorithm. The collected measurement results demonstrate the high accuracy in real‐time positioning achieved with the developed antenna both in terms of distance and angle.

Identifying the Adaptability of Different Control Types Based on Delay and Capacity for Isolated Intersection

In urban road networks, intersections are the main bottlenecks. Selecting an appropriate intersection control type can significantly improve the performance of an isolated intersection. Therefore, this paper offers recommendations for selecting the most efficient control type among two-way stop control, signalized intersection (SIG), roundabout (RB), and signalized roundabout (SIGRB) based on capacity and delay. The procedure to calculate delay and capacity is taken from the Highway Capacity Manual 6th edition (2016), or developed separately if needed. Two flow patterns are assumed: fixed and time-varying demand. For fixed demand, the results show that SIGRB outperforms other control types both in capacity and delay at higher demand levels. It was also observed that increase in left-turn ratio increases the delay and decreases the capacity of all control types while its impact on SIGRB was the least. Considering time-varying demand, traffic volume fluctuates over the 5-h period of the analysis. It was found that using both RB and SIGRB together creates significantly less delay compared with the other options. Additionally, using RB provides less variability in delay when there is fluctuation in demand. The major finding of this research is that RB and SIGRB have potential benefits for delay in conditions of (i) high traffic volume, (ii) high left-turn ratio, and (iii) demand fluctuation. Furthermore, it is suggested that SIG should be used if the left-turn ratio is relatively low. The results of this study could help decision-makers to choose the best control type for an isolated intersection under various traffic conditions.