Latest Arrival Time Research Articles

Does Timing Matter? The Effect of Intensive Care Unit Arrival Timing on Elective Cardiac Surgery

BackgroundDue to staffing changes at scheduled intervals and decreases in essential staff in the evenings, late intensive care unit (ICU) arrivals may be at risk for suboptimal outcomes. Utilizing a regional collaborative, we sought to determine the effect of ICU arrival timing on outcomes in elective isolated coronary artery bypass. MethodsAdults undergoing elective, isolated coronary artery bypass from 17 hospitals between 2013 and 2023 were identified. Patients with missing predicted risk of mortality or missing ICU arrival time were excluded. Late ICU arrival time was defined as between 6:00 pm and 6:00 am. Hierarchical logistic regression with appropriate predicted risk scores was utilized for outcome risk adjustment. ResultsWe identified 11,638 patients, with 972 (8.4%) experiencing late ICU arrival. Late ICU arrival patients had higher predicted risk of morbidity or mortality (8.2%; [interquartile range {IQR}, 5.6%, 12.0%] vs 7.7% [IQR, 5.5%, 11.5%], P = .048) compared with early ICU arrival patients with longer median cardiopulmonary bypass times (96 minutes [IQR, 78, 119] vs 93 [IQR, 73, 116], P < .001). Late ICU arrival patients experienced more unadjusted complications including prolonged ventilation (7.7% vs 4.2%, P < .001) and operative mortality (2.0% vs 1.1%, P = .02), although no difference in failure-to-rescue (11.0% vs 10.4%, P = .84). Logistic regression with risk adjustment demonstrated late ICU arrival as a predictor of prolonged ventilation (odds ratio, 1.49 [95% CI, 1.12-1.99], P = .006). ConclusionsAfter adjustment, late ICU arrivals experienced higher rates of prolonged ventilation, although this did not translate to failure-to-rescue.

Characterisation of geological thin layer by borehole radar

To investigate a thin layer, we conducted borehole radar measurements at the GPR facility of Tohoku University, Japan. Both zero-offset profiling and tomography measurements were used to obtain water content distributions. Analyzing first arrival times with amplitudes, we found that a borehole radar can detect velocity changes caused by a high-water content, which acts as an electromagnetic waveguide. We conducted a 3D FDTD simulation and confirmed that the EM wave propagates as a guided wave in a thin layer related to antenna frequency. We determined a thin geological layer compared to an antenna frequency that cannot be detected by reflection measurement due to the poor radar resolution. By comparing the simulated data with measurement data, we could determine the geological boundary between host layers and a thin layer with high water content. In contrast, both the amplitude and the travel time of direct waves are affected by antenna positions and electrical parameters, including permittivity and conductivity. A vertical velocity profile was obtained by combining complementary zero-offset profiling and tomography data, which can be used to investigate water content distribution. The low-velocity thin layer was characterised by amplitude attenuation and late arrival time.

A bidirectional droplet routing in digital microfluidics biochip

Droplet routing in digital microfluidic biochip is very challenging. It involves moving droplets from its source cell to destination cell. The challenge is to maintain fluidic constraints for every droplet movement. In this article, we have proposed a greedy bidirectional droplet routing based on divide and conquerer approach. The biochip is explored using two waves i.e. one from source cell and other from destination cell. Then, the biochip is converted into a bipartite graph by identifying strongly connected components. The route selection is done using our four greedy selection heuristics. The final route is generated by appending multiple sub-routes. The simulation result show an improvement of 7.32% and 18.05% in latest arrival time and number of shared cells respectively in free topology. Similarly we register an enhancement of 8.43% and 19.70% latest arrival time and number of shared cells respectively in virtual topology.

The real-time on-demand bus routing problem: The cost of dynamic requests

The real-time on-demand bus routing problem (ODBRP) supports the online routing of buses in a large-scale ride-sharing system. Given are a set of buses with fixed capacity, a set of bus stations and a set of transportation requests, only part of which are known before the planning horizon. A request consists of a set of possible departure and arrival stations, as well as an earliest departure and latest arrival time. The aim is to (1) assign each passenger to a departure and arrival bus station and (2) develop a set of bus routes to fulfill each request within its time window while minimizing the sum of the total waiting time and the total user ride time.Including the possibility for requests to be issued after the start of the planning horizon, i.e., when buses have already started servicing other requests, requires a dynamic re-optimization of a partially executed solution. Compared to the case in which all requests are known beforehand, the solution quality, expressed as the total waiting and user ride time, is expected to decline. This decline in objective function value can be seen as the “cost” of the dynamic requests. In this paper, we introduce the real-time ODBRP as an extension of its static problem variant and present a heuristic to deal with dynamic requests. In addition, an extensive set of experiments allows us to conclude that dynamic requests indeed lead to higher waiting and user ride times, especially for passengers who submit their request at the last minute. Passengers are therefore encouraged, if possible, to send their request well in advance, as this results in lower and more stable service promises, higher customer satisfaction, and higher revenues for the operating on-demand bus company.

2-1-2 Stroke microsurgical thrombectomy technique as a tertiary/salvage treatment option.

Microsurgical thrombectomy (MST) has been used for many years in few stroke cases without any prospective randomized study, nor detailed systemized technique description. As many centers worldwide are recruited for stroke thrombectomy availability, MST might increase in the near future either as a tertiary or salvage treatment option. A straightforward surgical plan is mandatory empowering a safe, efficient, and rapid neurosurgical operation, so our aim is to describe the 2-1-2 microsurgical technique. Three patients presented at emergency department with large stroke not suitable to venous thrombolysis and/or mechanical thrombectomy due to late arrival time and endovascular suite technical problems. They were referred to 2-1-2 MST after imaging showed brain collaterals on head angio-CT scan and ASPECTS greater than 6 points. The procedure comprised 2 insulin needle punctures in the target artery, 1mm micro-scissor transverse arteriotomy, milk thrombus removal and 2 simple sutures micro stitches. Sixty days clinical follow-up and brain imaging control provided data results. All patients treated with 2-1-2 MST technique had complete thrombus removal by precise surgical maneuvers avoiding surgeons unplanned and insecure movements to reduced operation time. Head angio-CT scan evidenced complete cerebrovascular circulation re-flow with clinical improvements in 60 days follow-up without complications or hospital readmissions. 2-1-2 MST technique can be rapidly and efficaciously performed in a systemized manner offering a tertiary or salvage technique for acute stroke treatment. Specific microsurgical training is mandatory to accomplish this treatment and larger studies are necessary to confirm our hypothesis.

The static on‐demand bus routing problem: large neighborhood search for a dial‐a‐ride problem with bus station assignment

AbstractWe introduce a novel optimization problem to support the planning and routing of on‐demand buses in an urban context. We call this problem the on‐demand bus routing problem (ODBRP). Given are a fleet of buses with fixed capacity, a set of bus stations and travel times between them, and a set of transportation requests. Each transportation request consists of a set of potential departure and a set of potential arrival bus stations, as well as a time window, that is, an earliest departure time and a latest arrival time. The aim of the ODBRP is to (1) assign each passenger to a departure and arrival bus station and (2) develop a set of bus routes to fulfill each request in time while minimizing the total travel time of all users. We present the static version of the ODBRP, as well as a straightforward large neighborhood search heuristic to solve it. The performance of the heuristic is established by comparing it to an off‐the‐shelve heuristic solver (LocalSolver). We also use our heuristic to solve (slightly modified instances of) the well‐known dial‐a‐ride problem. The results found by the heuristic for the on‐demand bus system are compared to those of a simulated traditional public bus system with fixed lines and timetables. A thorough analysis of the comparison demonstrates that total user ride times can be significantly lower in an on‐demand public bus system and shows that an on‐demand bus system works best with a large number of small buses.

Pathways to care: a case study of traffic injury in Vietnam

BackgroundTraffic injuries place a significant burden on mortality, morbidity and health services worldwide. Qualitative factors are important determinants of health but they are often ignored in the study of injury and corresponding development of prehospital Emergency Medical Services (EMS), especially in developing country settings. Here we report our research on sociocultural factors shaping pathways to hospital care for those injured on the roads and streets of Vietnam.MethodsQualitative fieldwork on pathways to emergency care of traffic injury was carried out from March to August 2016 in four hospitals in Vietnam, two in Ho Chi Minh City and two in Hanoi. Forty-eight traffic injured patients and their families were interviewed at length using a semi-structured topic guide regarding their journey to the hospital, help received, personal beliefs and other matters that they thought important. Transcribed interviews were analysed thematically guided by the three-delay model of emergency care.ResultsSeeking care was the first delay and reflected concerns over money and possessions. The family was central for transporting and caring for the patient but their late arrival prolonged time spent at the scene. Reaching care was the second delay and detours to inappropriate primary care services had postponed the eventual trip to the hospital. Ambulance services were misunderstood and believed to be suboptimal, making taxis the preferred form of transport. Receiving care at the hospital was the third delay and both patients and families distrusted service quality. Request to transfer to other hospitals often created more conflict. Overall, sociocultural beliefs of groups of people were very influential.ConclusionsAnalysis using the three-delay model for road traffic injury in Vietnam has revealed important barriers to emergency care. Hospital care needs to improve to enhance patient experiences and trust. Socioculture affects each of the three delays and needs to inform thinking of future developments of the EMS system, especially for countries with limited resources.

Dynamic Carriage Reserving for an Over-crowded Metro Junction Station

ABSTRACT At metro junction stations located in transportation hubs, a great number of passengers need to transfer to the metro system from other transportation modes during peak hours. This paper proposes a new train operation strategy—reserving carriages dynamically on each service train at the departure station for the metro junction station, which aims to relieve the serious passenger accumulation at the target station. We construct a nonlinear integer programming model which determines the number of reserved carriages on each train, and the total risk levels of passenger accumulation and passenger waiting time are both taken into account in the objective function. Furthermore, the latest arrival time of passengers on board is introduced to calculate effective passenger loading times analytically. At last, a set of numerical experiments from Beijing Metro Line 4 are implemented to verify the performance and effectiveness of the proposed approach.

Time-domain diffuse optics with 8.6 mm2 fast-gated SiPM for extreme light harvesting.

Fast time-gated single-photon detectors demonstrated high depth sensitivity in the detection of localized absorption perturbations inside scattering media, but their use for in vivo clinical applications-such as functional imaging of brain activation-was impaired by their small (<0.04mm2) active area. Here, we demonstrate, both on phantoms and in vivo, the performance of a fast-gated digital silicon photomultiplier (SiPM) that features an overall active area of 8.6mm2, overcoming the photon collection capability of established time-gated single-pixel detectors by orders of magnitude, enabling deep investigations within scattering media and high signal-to-noise ratios at late photon arrival times.

Evaluating accessibility of small communities via public transit

Accessibility to and from urban centres allows small communities’ dwellers to participate in primary activities and use essential services that are not available on-site, such as educational, work and medical services. Public transport networks are supposed to enhance accessibility and pursue equity principles, overcoming socio-economical differences among people that can exacerbate during crisis. In this paper a methodology is proposed and implemented to assess small communities’ accessibility via public transit. A metric is defined based on the calculation of total travel time, taken as a proxy of travel impedance, with consideration of in-vehicle time, schedule delay and users’ arrival and departure preference curves (i.e. time-of-day functions). A “rooftops” model is specified and implemented under the assumption that travellers cannot accept (scheduled) late arrival or early departure time penalties before and after the participation in their activities in the main urban centre, as many activities rarely admit time-flexibility. Also, a public transport specific impedance factor (PTSIF) is proposed, in order to account for travel impedance determinants, which are a consequence of service scheduling and routing decisions and not due to inherent geographical and infrastructural disadvantages affecting car users too. An application of the methodology for the city of Cesena, Italy, and 90 surrounding small communities is presented. The city is served by train and bus services. Assessment of small communities' accessibility based on both total travel time and PTSIF is presented and discussed. This practice-ready quantitative method can help transport professionals to evaluate impacts on small communities’ accessibility in light of public transport service changes or reduction. Quantitative approach to support strategic decisions is needed, for example, both to assess public transport strengthening politics against depopulation of rural and marginal mountainous areas and to mitigate the effects of possible increasing concentration of services towards high-demand lines, which may follow as a consequence of budget cuts or contingencies, such as vehicle capacity reductions required by sanitary emergencies.

A Probabilistic Clustering Approach for Identifying Primary Subnetworks of Discrete Fracture Networks with Quantified Uncertainty

Fractures form the main pathways for flow of fluids and transport of constituents carried by these fluids in fractured subsurface media. The majority of flow and transport occurs in the primary subnetwork or backbone, which is a subset of the fracture network. Understanding characteristics of the fracture network flow and transport backbones is thus of great importance towards improving efficiency of subsurface applications, such as aquifer management, hydrocarbon extraction, and long- term storage of spent nuclear fuel. We propose a method for identifying these backbones that also quantifies uncertainty over all possible backbones. Our approach treats the backbone identification problem as a probabilistic clustering problem. We develop a probabilistic generative model to simulate backbones that are induced acyclic flow networks. A user-controlled parameter determines the size of the identified backbones, with small backbones having good agreement with early particle arrival times and larger backbones having good agreement with early and late particle arrival times. We demonstrate our method on a representative fracture network with 264 fractures. Our method discovers flow channelization in backbones roughly 10%--50% the size of the original network, supporting previous experiments and discrete fracture network simulations. To the best of our knowledge, our method is the first backbone identification method to quantify uncertainty over backbones.

A Complete Routing Simulator for Digital Microfluidic Biochip

Microfluidic technology, as well as digital microfluidic biochips (DMFBs), have had a very significant contribution in the field of medical bio-chemistry such as point-of-care diagnostics, environmental monitoring, DNA sequencing, etc. DMFBs are low cost, highly flexible and reconfigurable device that makes it so advantageous in clinical applications. The routing of a nano-liter volume of droplets is very important and is a critical operation in DMFB. Complex heuristic algorithms have been developed for droplet routing. Proper simulation is very essential to measure the effectiveness of these algorithms. In this work, the authors develop a complete routing simulator for both homogeneous and heterogeneous type droplets. The proposed routing simulator graphically represents the routing operation of droplets in DMFB and display the measurement of all parameters of routing algorithms such as latest arrival time, average arrival time, number of cells used, and the total number of contaminations. The proposed simulator was executed on suit I and III benchmark testbenches.

Potential of Taxi-Pooling to Reduce Vehicle Miles Traveled in Washington, D.C.

This paper presents a pilot study of taxi-pooling in Washington, D.C. to demonstrate its potential for city-wide vehicle mileage reduction with real-world taxi trip data. In the taxi-pooling problem, riders specify their origins, destinations, earliest departure times, and latest arrival times. Taking all requests into consideration, the system dispatcher determines which requests can be grouped and thus served by one taxi, without violating any user-specified time windows and taxi capacity. This paper first presents a mathematical programming model whose objective is to minimize the system-wide vehicle miles traveled. Then an efficient solution approach to this problem is proposed. Results from analyzing the case of Washington, D.C. show that the total vehicle miles traveled can be reduced by 18% if the average buffer time in their travel schedule is 25% of their direct travel time.

Disaster relief routing under uncertainty: A robust optimization approach

ABSTRACTThis article addresses the Capacitated Vehicle Routing Problem (CVRP) and the Split Delivery Vehicle Routing Problem (SDVRP) with uncertain travel times and demands when planning vehicle routes for delivering critical supplies to a population in need after a disaster. A robust optimization approach is used for CVRP and SDVRP considering the five objective functions: minimization of the total number of vehicles deployed (minV), the total travel time/travel cost (minT), the summation of arrival times (minS), the summation of demand-weighted arrival times (minD), and the latest arrival time (minL), out of which we claim that minS, minD, and minL are critical for deliveries to be fast and fair for relief efforts whereas minV and minT are common cost-based objective functions in the traditional VRP. A new two-stage heuristic method that combines the extended insertion algorithm and tabu search is proposed to solve the VRP models for large-scale problems. The solutions of CVRP and SDVRP are compared for different examples using five different metrics in which we show that the latter is not only capable of accommodating the demand greater than the vehicle capacity but also is quite effective to mitigate demand and travel time uncertainty, and thereby outperforms CVRP in the disaster relief routing perspective.

An optimized decision-making algorithm for talent supply

The paper draws on the postponement strategy applied in production management of enterprises to optimize the mode of college talent supply. The paper will establish time postponement (TP) and form postponement (FP) model for talent supply under the conditions of M/M/1 and G/G/1, and analyze the impacts of system utilization, variation of the early and late arrival time, training time variation, interest rate, the rate of using general training modules and the number of talent types on the costs and times of TP and FP strategy. The research will provide a scientific basis for colleges to make optimal strategies in talent supply.

Fault Zone Imaging from Correlations of Aftershock Waveforms

We image an active fault zone environment using cross correlations of 154 15 s long 1992 Landers earthquake aftershock seismograms recorded along a line array. A group velocity and phase velocity dispersion analysis of the reconstructed Rayleigh waves and Love waves yields shear wave velocity images of the top 100 m along the 800 m long array that consists of 22 three component stations. Estimates of the position, width, and seismic velocity of a low-velocity zone are in good agreement with the findings of previous fault zone trapped waves studies. Our preferred solution indicates the zone is offset from the surface break to the east, 100–200 m wide, and characterized by a 30% velocity reduction. Imaging in the 2–6 Hz range resolves further a high-velocity body of similar width to the west of the fault break. Symmetry and shape of zero-lag correlation fields or focal spots indicate a frequency and position dependent wavefield composition. At frequencies greater than 4 Hz surface wave propagation dominates, whereas at lower frequencies the correlation field also exhibits signatures of body waves that likely interact with the high-velocity zone. The polarization and late arrival times of coherent wavefronts observed above the low-velocity zone indicate reflections associated with velocity contrasts in the fault zone environment. Our study highlights the utility of the high-frequency correlation wavefield obtained from records of local and regional seismicity. The approach does not depend on knowledge of earthquake source parameters, which suggests the method can return images quickly during aftershock campaigns to guide network updates for optimal coverage of interesting geological features.

Solute transport in aquifers: The comeback of the advection dispersion equation and the First Order Approximation

Abstract Natural gradient steady flow of mean velocity U takes place in heterogeneous aquifers of random logconductivity Y = ln K , characterized by the normal univariate PDF f(Y) and autocorrelation ρY, of variance σ Y 2 and horizontal integral scale I. Solute transport is quantified by the Breakthrough Curve (BTC) M at planes at distance x from the injection plane. The study builds on the extensive 3D numerical simulations of flow and transport of Jankovic et al. (2017) for different conductivity structures. The present study further explores the predictive capabilities of the Advection Dispersion Equation (ADE), with macrodispersivity αL given by the First Order Approximation (FOA), by checking in a quantitative manner its applicability. After a discussion on the suitable boundary conditions for ADE, we find that the ADE-FOA solution is a sufficiently accurate predictor for applications, the many other sources of uncertainty prevailing in practice notwithstanding. We checked by least squares and by comparison of travel time of quantiles of M that indeed the analytical Inverse Gaussian M with α L = σ Y 2 I , is able to fit well the bulk of the simulated BTCs. It tends to underestimate the late arrival time of the thin and persistent tail. The tail is better reproduced by the semi-analytical MIMSCA model, which also allows for a physical explanation of the success of the Inverse Gaussian solution. Examination of the pertinent longitudinal mass distribution shows that it is different from the commonly used Gaussian one in the analysis of field experiments, and it captures the main features of the plume measurements of the MADE experiment. The results strengthen the confidence in the applicability of the ADE and the FOA to predicting longitudinal spreading in solute transport through heterogeneous aquifers of stationary random structure.

Homogeneous droplet routing in DMFB: An enhanced technique for high performance bioassay implementation

Digital Microfluidic Biochip, a new generation of Lab-on-chip device has emerged in the last decade as a viable alternative for conventional biochemical laboratory applications. The major advantages of such devices are its capabilities of automation, reconfigurability, flexibility, low cost, portability and precision analysis. Among other microfluidic operations droplet routing poses a critical challenge specifically due to the blockages caused by microfluidic modules. In this paper we propose a two stage routing technique for simultaneous routing while resolving issues of blockages and conflicts with other nets. Here we considered routing of homogeneous droplets where instead of crossovers, sharing of route paths among multiple nets are mainly under focus. The proposed method is simulated on two different sets of testbenches namely Benchmark suite I and III respectively. The route performance measured in terms of parameters namely latest arrival time and cell utilization shows considerable improvement with respect to some major contemporary contributions.

Uncertainty quantification of environmental performance metrics in heterogeneous aquifers with long-range correlations

We investigate how the uncertainty stemming from disordered porous media that display long-range correlation in the hydraulic conductivity (K) field propagates to predictions of environmental performance metrics (EPMs). In this study, the EPMs are quantities that are of relevance to risk analysis and remediation, such as peak flux-averaged concentration, early and late arrival times among others. By using stochastic simulations, we quantify the uncertainty associated with the EPMs for a given disordered spatial structure of the K-field and identify the probability distribution function (PDF) model that best captures the statistics of the EPMs of interest. Results indicate that the probabilistic distribution of the EPMs considered in this study follows lognormal PDF. Finally, through the use of information theory, we reveal how the persistent/anti-persistent correlation structure of the K-field influences the EPMs and corresponding uncertainties.

Pulse Jitter, Delay Spread, and Doppler Shift in Mode-Stirred Reverberation

A time-domain characterization and stochastic model are developed for analyzing the evolution of the early randomization of fields inside mode-stirred reverberation chambers. The chamber is excited by a pulse amplitude modulated RF signal and stirred mechanically by a rotational stirrer. Phase noise (jitter) in the arrival times of a received pulse train is found to contain a systematic contribution that depends on stir speed and stir sense, as well as a random contribution governed by the rate of field depolarization. For the systematic component, a model of the phase delay for a uniformly orbiting scatterer inside a cavity is derived. For the random component, a nonhomogeneous Poisson model for arrivals of wave fronts in a nonstationary stir process exhibits good agreement with the empirical distribution of the measured jitter. At increasing stir velocities, the rate of field mixing increases less rapidly. The excess delay approaches asymptotically an Erlang distribution, in the limit of a homogeneous Poisson process for uniformly distributed late arrival times.