Short Flow Times Research Articles

Distributed Real-Time Scheduling in Cloud Manufacturing by Deep Reinforcement Learning

With the extensive application of automated guided vehicles, real-time production scheduling considering logistics services in cloud manufacturing (CM) becomes an urgent problem. Thus, this study focuses on the distributed real-time scheduling (DRTS) of multiple services to respond to dynamic and customized orders. First, a DRTS framework with cloud–edge collaboration is proposed to improve performance and satisfy responsiveness, where distributed actors and one centralized learner are deployed in the edge and cloud layer, respectively. And, the DRTS problem is modeled as a semi-Markov decision process, where the processing services sequencing and logistics services assignment are considered simultaneously. Then, we developed a distributed dueling deep Q network (D3QN) with cloud–edge collaboration to optimize the weighted tardiness of jobs. The experimental results show that the proposed D3QN obtains lower weighted tardiness and shorter flow-time than other state-of-the-art algorithms. It indicates the proposed DRTS method has significant potential to provide efficient real-time decision-making in CM.

Spatially resolved qualified sewage spot sampling to track SARS-CoV-2 dynamics in Munich - One year of experience

Wastewater-based epidemiology (WBE) is a tool now increasingly proposed to monitor the SARS-CoV-2 burden in populations without the need for individual mass testing. It is especially interesting in metropolitan areas where spread can be very fast, and proper sewage systems are available for sampling with short flow times and thus little decay of the virus. We started in March 2020 to set up a once-a-week qualified spot sampling protocol in six different locations in Munich carefully chosen to contain primarily wastewater of permanent residential areas, rather than industry or hospitals. We used RT-PCR and sequencing to track the spread of SARS-CoV-2 in the Munich population with temporo-spatial resolution.The study became fully operational in mid-April 2020 and has been tracking SARS-CoV-2 RNA load weekly for one year. Sequencing of the isolated viral RNA was performed to obtain information about the presence and abundance of variants of concern in the Munich area over time.We demonstrate that the evolution of SARS-CoV-2 RNA loads (between <7.5 and 3874/ml) in these different areas within Munich correlates well with official seven day incidence notification data (between 0.0 and 327 per 100,000) obtained from the authorities within the respective region. Wastewater viral loads predicted the dynamic of SARS-CoV-2 local incidence about 3 weeks in advance of data based on respiratory swab analyses. Aligning with multiple different point-mutations characteristic for certain variants of concern, we could demonstrate the gradual increase of variant of concern B.1.1.7 in the Munich population beginning in January 2021, weeks before it became apparent in sequencing results of swabs samples taken from patients living in Munich.Overall, the study highlights the potential of WBE to monitor the SARS-CoV-2 pandemic, including the introduction of variants of concern in a local population.

Flow-Induced Crystallization in Polyethylene: Effect of Flow Time on Development of Shish-Kebab.

The flow-induced formation and relaxation of the representative oriented shish-kebab structure were studied with synchrotron small-angle X-ray scattering (SAXS) method. The flow duration was varied from 2 to 6 s at an identical strain rate to reveal the effect of flow time on stability and dimension of formed shish. It was found that the short flow time of 2 s was able to generate shish during flow, which, however, relaxed during the isothermal process after cessation of flow. An increase in flow time can improve the shish stability and the long flow time of 6 s can generate the stable shish that nucleate the growth of kebab lamellae. In addition, the quantitative analysis of SAXS results showed that with increasing flow time from 2 to 6 s, the shish length increased from 242 to 574 nm, while the shish diameter remained around 34 nm. This detailed information of the formed shish-kebab structure can be used to shed light on their evolution that occurred during flow from 2 to 6 s, where shish grew at a longitudinal speed of around 80 nm/s, and there was an improvement in the stability and nucleation capability for kebab lamellae.

Short flow-time coefficients of CP -violating operators

Measurements of a permanent neutron electric dipole moment (EDM) potentially probe Beyond-the-Standard Model (BSM) sources of CP-violation. At low energy the CP-violating BSM interactions are parametrized by flavor-conserving CP-violating operators of dimension higher than four. QCD calculations of the nucleon matrix elements of these operators are required to fully reconstruct the sources and magnitudes of the different CP-violating contributions to the nucleon EDM. Herein we study the quark-chromo electric dipole moment (qCEDM) operator and the three-gluon Weinberg operator. The non-perturbative determination, using lattice QCD, of the nucleon matrix elements of these CP-violating operators is hampered by their short-distance behavior. Under renormalization these operators mix with lower dimensional operators, which induces power divergences in the lattice spacing, as the continuum limit is approached. We study the short-distance behavior of the qCEDM and the Weinberg operators using the gradient flow. We perform a short flow time expansion and determine, in perturbation theory, the expansion coefficients of the linearly-divergent terms stemming from the mixing with the pseudoscalar density and the topological charge, confirming the expectations of the operator product expansion. We introduce a new method to perform calculations at non-zero flow-time for arbitrary values of the external momenta. This method allows us to work in four dimensions for most of the calculations described in this paper, avoiding the complications associated with defining $\gamma_5$ in generic d dimensions. We show that leading contributions in the external momenta can be reproduced by defining $\gamma_5$ using the 't Hooft-Veltman-Breitenlohner-Maison scheme.

Comparison of two optimization based order release models with fixed and variable lead times.

Manufacturing planning and control systems ideally seek to simultaneously achieve short and predictable flow times as well as high output and due-date performance. One approach to address this problem is the workload control concept. It is based on the idea to control lead times by controlling order releases and thus the level of work-in-process and output. The focus of this paper is on multi-period optimization models for order release planning. We use a simulation study of a make to order manufacturer in a rolling horizon setting and compare the performance of an order release model that assumes fixed lead times and a model that allows for variable lead times: An input output control and a clearing function model, respectively. We analyze two different approaches to cope with the varying and tight due date slack and find that including more foreknowledge of demand is preferable. Finally, we show that the clearing function model outperforms the input output control model in all scenarios by yielding lower inventory levels with shorter shop floor throughput times. This advantage seems not to be affected by the predictability of the demand, but the IOC model narrows the gap when using near optimal parameters especially for a scenario with deterministic demand.

Molecular outflows in local galaxies: Method comparison and a role of intermittent AGN driving

We report new detections and limits from a NOEMA and ALMA CO(1-0) search for molecular outflows in 13 local galaxies with high far-infrared surface brightness, and combine these with local universe CO outflow results from the literature. The CO line ratios and spatial outflow structure of our targets provide some constraints on the conversion steps from observables to physical quantities such as molecular mass outflow rates. Where available, ratios between outflow emission in higher J CO transitions and in CO(1-0) are typically consistent with excitationRi1 ≲ 1. However, for IRAS 13120−5453,R31 = 2.10 ± 0.29 indicates optically thin CO in the outflow. Like much of the outflow literature, we useαCO(1 − 0)= 0.8, and we present arguments for usingC = 1 in deriving molecular mass outflow ratesṀout=CMoutvout/Rout. We compare the two main methods for molecular outflow detection: CO millimeter interferometry andHerschelOH-based spectroscopic outflow searches. For 26 sources studied with both methods, we find an 80% agreement in detectingvout≳ 150 km s−1outflows, and non-matches can be plausibly ascribed to outflow geometry and signal-to-noise ratio. For a published sample of 12 bright ultraluminous infrared galaxies with detailed OH-based outflow modeling, CO outflows are detected in all but one. Outflow masses, velocities, and sizes for these 11 sources agree well between the two methods, and modest remaining differences may relate to the different but overlapping regions sampled by CO emission and OH absorption. Outflow properties correlate better with active galactic nucleus (AGN) luminosity and with bolometric luminosity than with far-infrared surface brightness. The most massive outflows are found for systems with current AGN activity, but significant outflows in nonAGN systems must relate to star formation or to AGN activity in the recent past. We report scaling relations for the increase of outflow mass, rate, momentum rate, and kinetic power with bolometric luminosity. Short flow times of ∼106yr and some sources with resolved multiple outflow episodes support a role of intermittent driving, likely by AGNs.

Comparison between rule- and optimization-based workload control concepts: a simulation optimization approach

An important goal of Production Planning and Control systems is to achieve short and predictable flow times, especially where high flexibility in meeting customer demand is required, while maintaining high output and due-date performance. One approach to this problem is the workload control (WLC) concept. Within WLC research two directions have been developed, largely separately, over time: Rule based and optimisation-based models. If a company intends to introduce an order release concept based on WLC it first has to decide which of these two approaches should be applied. Therefore, this paper compares two of the most widely used and considered best performing periodic order release models out of both streams: the LUMS (rule based) and the clearing function model (optimisation based). The parameters of both approaches are set using simulation optimisation. The performance is compared using a simulation study of a hypothetical job shop in a rolling horizon setting. The results show that the optimisation model outperforms the rule-based mechanism in all instances with stochastic demand (exponential inter-arrival times), but is outperformed in aggregate cost of backorders and inventory holding and balancing measures by the LUMS approach for scenarios with high utilisation and seasonal demand.

Computational fluid dynamics simulation of full breathing cycle for aerosol deposition in trachea: Effect of breathing frequency

Abstract Aerosols have been widely used in the treatment of certain airway diseases. With different breathing conditions of patients, the flow pattern might not cause the aerosol to transport and deposit on the desired bronchial section. In this study, computational fluid dynamics simulations based on the Euler–Euler method were successfully used to evaluate the airflow behavior when an electrostatic charge was present. The three-dimensional domain was acquired and derived from the computed tomography scan of the patient. Three breathing frequencies were investigated. The instantaneous contour plot revealed that the particles migrated to the wall since charged particles will move from the high to the low potentials. It was found that the variation of the breathing frequency plays a significant role on designated particle deposition region. At a short flow time, the particles only traveled and deposited on the upper part of the airway, whereas as the time flow increased the particles tended to increasingly accumulate on the lower parts of the airway. The electrostatic charge model for aerosol deposition has shown that the further design of aerosol transport must take an average breathing frequency into consideration. The wall shear stress, oscillatory flow velocity index, granular temperature, granular pressure and skin friction coefficient were able to imply the amount of solid particles deposited within the system. All the purposed indices can be used as preliminary indicators for indicating a potential deposition location of the aerosol.

How Lean transformation affects scheduling

The Lean paradigm transforms a production company from utilisation-centric planning into a system in which other operating conditions such as short flow times, local control, reduction in variation, and first-in-first-out control are weighted as well. This paper studies how the scheduling of production changes when the above four conditions are implemented. Their effects are studied by constructing an optimisation model for the scheduling of a flow shop. The optimisation model is based on the following ideas. First, when the flow time is emphasised, the objective of the scheduling changes from utilisation to a short flow time. Second, if local control is used, it means that the optimisation is performed locally, i.e. individually at each station, and it concerns the makespan at the station. Third, if the variation is reduced, the processing times and arrival times have less variation and, fourth, the scheduling can force the flow times to have less variation by using first-in-first-out (FIFO) sequencing. The experimental results achieved using the model describe how and in which order the operating conditions under study should be implemented in the scheduling. For example, if utilisation is important, local control and FIFO should not be used before variation is reduced. Lean focuses on short flow time, local control, variation reduction and FIFO control.Paper studies on how these conditions should be taken into account in scheduling..An optimisation model is constructed to study the effects of conditions.Experiments give insights about the order in which conditions should be used.

How well-connected is the surface of the global ocean?

The Ekman dynamics of the ocean surface circulation is known to contain attracting regions such as the great oceanic gyres and the associated garbage patches. Less well-known are the extents of the basins of attractions of these regions and how strongly attracting they are. Understanding the shape and extent of the basins of attraction sheds light on the question of the strength of connectivity of different regions of the ocean, which helps in understanding the flow of buoyant material like plastic litter. Using short flow time trajectory data from a global ocean model, we create a Markov chain model of the surface ocean dynamics. The surface ocean is not a conservative dynamical system as water in the ocean follows three-dimensional pathways, with upwelling and downwelling in certain regions. Using our Markov chain model, we easily compute net surface upwelling and downwelling, and verify that it matches observed patterns of upwelling and downwelling in the real ocean. We analyze the Markov chain to determine multiple attracting regions. Finally, using an eigenvector approach, we (i) identify the five major ocean garbage patches, (ii) partition the ocean into basins of attraction for each of the garbage patches, and (iii) partition the ocean into regions that demonstrate transient dynamics modulo the attracting garbage patches.

Multicontextual dispatching rules for job shops with dynamic job arrival

The dynamic job shop problem is more challenging than the static job shop problem because dynamic job shops are disrupted by unforeseen events such as job arrivals and machine breakdowns. Each phase of a dynamic job shop problem presents a unique set of circumstances; multicontextual functions can describe the unique characteristics of a dynamic job shop at a specific time. The present work examines 11 basic dispatching rules and 33 composite rules made with multicontextual functions (MCFs) that describe machine idle time (MIT) and job waiting time (JWT). Simple procedures are presented that allow one or both of MIT and JWT to be combined with a single basic dispatching rule. This procedure produced 33 composite dispatching rules; the schedules from all 44 rules for a job shop with dynamic job arrival were compared with regard to make span and mean flow time. One composite rule, most work remaining with MCF2, produced schedules with the shortest make spans in 21 out of 27 cases; another composite rule, most remaining operations (MRO) with MCF3, produced schedules with the shortest mean flow times in 27 out of 27 cases. It was possible to combine JWT and MIT usefully only when the relevant dispatching rule did not depend on operation processing time; because MRO did not consider processing time, it benefitted from both JWT and MIT. Clients who demand short mean flow times might benefit from an implementation of MRO with MCF3.

Determination of interfacial tension between two immiscible polymers with and without surfactants at the interface

A second-order drop deformation method for inferring interfacial tension between two immiscible polymers is proposed and shown to improve the accuracy of tension estimate appreciably. A small step-strain method, which uses a strong flow (capillary number >1) and short flow time ∼ O ( 0.1 s ) , is successfully developed to avoid complications caused by the surfactants for surfactant-laden drops. This method is demonstrated to give good tension estimates for a range of viscosity ratios and surface coverage.

Distributed production planning using a graph-based negotiation protocol

A distributed model for allocating a single job to be processed through multiple machines and alternative routings so that the job flow time is experimentally shown to reach its minimum is presented. Issues are addressed pertaining to dynamic and fully distributed decision-making for determining the job flow time in a cooperative manner between system agents (i.e. machines and a job), and for selecting a good routing (i.e. a short flow time) for a job when alternative routings are available. Two cases with confirmed jobs and without confirmed jobs are examined. The proposed protocols can deal with job shop scheduling with multiple product types in a sequential manner. The model is developed on the basis of a distributed shortest path algorithm using asynchronous job-initiated protocols. These protocols are examined using object-oriented simulation models and it is shown how the agents converge to the optimal path in a finite time.

HST ultraviolet observations of rapid variability in the accretion-disc wind of BZ Cam

We present results from time-resolved Hubble Space Telescope(HST) GHRS ultraviolet spectroscopy of the nova-like cataclysmic variable BZ Cam. Extensive changes are recorded in the extended absorption troughs of the UV resonance line profiles, which betray a highly unsteady and continuously variable supersonic outflow. The large-scale line-profile changes are almost exclusively confined to blueshifted velocities, although the Si iv and C iv emission components reveal orbital phase-linked velocity shifts. The character of the accretion-disc wind of BZ Cam can alter radically on time-scales down to 100 s or less. Correlated behaviour is noted in lines of low and high ionization stages, which may reflect localized density changes. Aside from the incidence of enormous line-profile changes on remarkably short time-scales, BZ Cam provides an important benchmark for the simultaneous presence of very strong absorption and well-developed emission components in Si iv, C iii and C iv, for an estimated low-inclination (i<40°) or possibly even face-on system. We illustrate the problems posed for pure-scattering line-synthesis models in matching the UV line profiles of BZ Cam, and set constraints for alternative thermal emission sources. A phenomenological interpretation is that the high-speed wind of BZ Cam is highly irregular in nature, and the outflow is riddled with structure arising from localized density enhancements. It is tempting to link our empirical results to recent hydrodynamic simulations of unsteady radiatively driven accretion-disc winds, such as those of Proga, Drew & Stone. Ultimately, line profiles synthesized from the hydrodynamic codes would have to match the substantial absorption equivalent width changes in the UV lines of BZ Cam, over the very short flow times across the line formation regions, i.e. the overall contribution of the, structured, disc-projected wind has to be substantially variable.

Multiple-machine scheduling with earliness, tardiness and completion time penalties

We consider the problem of scheduling n jobs on m parallel and identical machines. The goal is to find an optimal permutation of the jobs and an optimal due date which jointly minimize an objective function consisting of earliness tardiness and completion time penalties. We show that the problem is NP-hard and present a polynomially solvable case. Furthermore a heuristic is developed and computationally demonstrated to be efficient in obtaining near-optimal solutions. Scope and purpose This study deals with the problem of scheduling a number of jobs on parallel machines. We assume that companies are mainly interested in two objectives, namely achieving small deviations from a common due date and short flowtimes. Therefore earliness tardiness and completion time penalties for the jobs are introduced. We are able to show that the problem is intractable and consequently develop an efficient heuristic to obtain near-optimal solutions.

A Diode-Laser Based Automated Timing Interface for Rapid Measurement of Liquid Viscosity

We describe an exercise in experimental design suitable for the undergraduate laboratory, involving the construction of an automated timing interface for laminar liquid flow in glass. In many instructional physical chemistry laboratories, viscometry is introduced through measurements on polymer solutions using the principle of laminar flow. The design and construction of the interface are both part of the exercise. The digital timing scheme allows high relative precision even with very short (1s) flow times, making the use of smaller sample volumes feasible.

Quantitative assessment of uroflow: is there a orcadian rhythm?

Objectives To investigate if the circadian rhythm of urinary flow values varies within groups of patients with varying degrees of bladder outlet obstruction. Methods A total of 170 patients with lower urinary tract symptoms suggestive of bladder outlet obstruction used a home-based uroflowmeter and produced a total of 1670 correctly measured flows at home. These patients also underwent a screening program with free urinary flowmetry in the hospital and a urodynamic pressure and flow study. Results There is a circadian variability in urinary flow values in men with higher grades of obstruction. These men have a higher peak urinary flow with a smaller voided volume and thus a shorter flow time in the early afternoon when compared with late evening, early morning, and the midnight to morning periods. Conclusions This significantly greater maximum flow in the afternoon in men with higher grades of obstruction can be an important bias in studies where the primary end point is to assess a small improvement in maximum flow. Therefore, the circadian rhythm of uroflow has to be taken into account in the evaluation of the efficacy of treatment. Patients participating in clinical research studies should produce their urinary flow in the clinic always during the same time period, either in the morning or in the afternoon, and should not switch their appointment time.

Efficient network folding techniques for routing permutations in VLSI : Hussein M. Alnuweiri and Sadiq M. Sait. IEEE Transactions on Very Large Scale Integration (VLSI) Systems, 3 (2), 254 (June 1995).

The Lean paradigm transforms a production company from utilisation-centric planning into a system in which other operating conditions such as short flow times, local control, reduction in variation, and first-in-first-out control are weighted as well. This paper studies how the scheduling of production changes when the above four conditions are implemented. Their effects are studied by constructing an optimisation model for the scheduling of a flow shop. The optimisation model is based on the following ideas. First, when the flow time is emphasised, the objective of the scheduling changes from utilisation to a short flow time. Second, if local control is used, it means that the optimisation is performed locally, i.e. individually at each station, and it concerns the makespan at the station. Third, if the variation is reduced, the processing times and arrival times have less variation and, fourth, the scheduling can force the flow times to have less variation by using first-in-first-out (FIFO) sequencing. The experimental results achieved using the model describe how and in which order the operating conditions under study should be implemented in the scheduling. For example, if utilisation is important, local control and FIFO should not be used before variation is reduced.

Preliminary bounds on the expected postclosure performance of the Yucca Mountain Repository Site, southern Nevada

On the basis of current data and understanding of site characteristics at Yucca Mountain, the likely performance range of a mined repository for spent nuclear fuel can be calculated. Low flux through the unsaturated zone results in groundwater travel times to the water table that probably exceed 10,000 years and may exceed 100,000 years, far longer than required by the Nuclear Regulatory Commission (NRC). The low flux will also limit releases of waste from the waste packages, probably to annual amounts less than one millionth of the mass of the waste inventory remaining 1000 years after repository closure; the corresponding releases of curies would be well within the allowable releases set by the NRC. Geochemical retardation by sorption and diffusion will slow radionuclide movement relative to groundwater flow by factors of hundreds to thousands for many waste species. In combination, these site conditions provide a high degree of confidence that no releases to the accessible environment will occur during the first 10,000 years after repository closure, the time period for which the Environmental Protection Agency (EPA) has set release limits. Carbon 14, technetium 99, iodine 129, and various nuclides of uranium sorb poorly on the tuffs along the flow paths and, together with uranium daughter products, will be the first radionuclides to arrive at the water table. The total radioactivity produced by these and later arriving contaminants will remain far below the allowable releases, even for periods of millions of years, if expected flux conditions prevail. If the flux is currently greater than the values inferred from the measured in situ moisture contents of the volcanic rocks or if it were to increase in the future, fracture flow and attendant short flow times to the water table could occur. Even if rapid fracture flow were to occur, release of wastes to the accessible environment would probably remain low with respect to the EPA's limits because diffusion of radionuclides from the fractures into the rock matrix would ensure slow migration of most of the wastes through the sorbing matrix.

A New Method of Controlling Job Due Dates for Early Due Dates and Short Flow Times

A New Method of Controlling Job Due Dates for Early Due Dates and Short Flow Times