Cycle Time Distribution Research Articles

Comparing growth of titania and carbonaceous dusty nanoparticles in weakly magnetised capacitively coupled plasmas

Abstract This study compares the growth cycles and spatial distribution of dust cloud for titania and carbonaceous dusty nanoparticles in capacitively coupled radiofrequency plasmas, with and without the presence of a weak magnetic field of approximately 500 Gauss. Findings on cycle time, growth rate, and spatial distribution of dust cloud are discussed. The growth of nanoparticles in these plasmas is cyclic, with particles reaching their maximum size and subsequently moving out of the plasma, followed by the generation of a new particle growth cycle. The presence of the magnetic field speeds up the growth cycle in both plasma. The magnetic field also makes the spatial distribution of the two dust cloud different from each other. Langmuir probe measurement of the background plasma parameters such as electron temperature and floating potential reveal radial variations in floating potential but not electron temperature. Furthermore, the magnetic field changes the radial variation of floating potential. These measurements, however, are not sufficient to explain why the two dust clouds appear differently. It is possible that the differences occur due to a gradient in the radial distribution of the magnetic field.

Business process simulation: Probabilistic modeling of intermittent resource availability and multitasking behavior

In business process simulation, resource availability is typically modeled by assigning a calendar to each resource, e.g., Monday–Friday, 9:00–18:00. Resources are assumed to be always available during each time slot in their availability calendar. This assumption often becomes invalid due to interruptions, breaks, or time-sharing across processes. In other words, existing approaches fail to capture intermittent availability. Another limitation of existing approaches is that they either do not consider multitasking behavior, or if they do, they assume that resources always multitask (up to a maximum capacity) whenever available. However, studies have shown that the multitasking patterns vary across days. This paper introduces a probabilistic approach to model resource availability and multitasking behavior for business process simulation. In this approach, each time slot in a resource calendar has an associated availability probability and a multitasking probability per multitasking level. For example, a resource may be available on Fridays between 14:00–15:00 with 90% probability, and given that they are performing one task during this slot, they may take on a second concurrent task with 60% probability. We propose algorithms to discover probabilistic calendars and probabilistic multitasking capacities from event logs. An evaluation shows that, with these enhancements, simulation models discovered from event logs better replicate the distribution of activities and cycle times, relative to approaches with crisp calendars and monotasking assumptions.

Research on the method of predicting the trend of criminal activities based on time series analysis from the perspective of criminal procedure law

Abstract Criminal activity has always been a problem that seriously affects people’s sense of security and well-being in life, and it is also the focus of public security departments in terms of security prevention and control. This study aims to use scientific methods to analyze the time series of existing historical data related to criminal activities and to advance inference or determination of the future trend of criminal activities. In this paper, after mining the spatiotemporal pattern of criminal activities using the centered moving average method, the spatiotemporal cycle characteristics and time distribution characteristics of criminal activities are analyzed. Based on the conclusions drawn, an improved LSTNet algorithm is proposed by combining deep learning spatio-temporal network, convolutional neural network CNN, recurrent neural network RNN, autoregressive AR, and specially designed Skip-RNN, and a GRU-gated recurrent unit structure is used to realize the optimization of the prediction accuracy of the criminal activities, to solve the problems related to the spatio-temporal dependencies, and to establish an improved ST- Res Net crime prediction model. Finally, the prediction performance of the model is examined. The RMSE, MSE, and MAPE values of this paper’s prediction model are 0.88, 5.12, and 5.12%, respectively, which are better than other models. The experiments demonstrate that the prediction model presented in this paper can enhance the accuracy of criminal activity prediction to a certain extent and can be employed in the prevention and management of criminal activities.

Particle circulation and coating in a Wurster fluidized bed under different geometries

The performance of particle coating is essentially determined by the morphology and uniformity of coating shells, which significantly depend on particle circulation. In this study, the geometry of a Wurster fluidized bed is changed by regulating particle circulation port size and nozzle position, and their effects on particle circulation and coating properties are investigated by combining coating experiments and CFD – Discrete Element Model (DEM). By increasing the circulation port size, the particle circulation rate first increases then decreases slightly, accordingly, the uniformity of particle circulation increases then decreases, while the shell porosity decreases. By increasing the nozzle height, the particle circulation rate decreases slightly, accordingly, the uniformity of particle circulation increases then decreases, while the shell porosity decreases. At extremes with a too small circulation port size or too high nozzle position, particle residence and cycle time distribution are broader, and an obvious nonuniformity of particle growth is observed.

Solid-fluid mixing behavior of conical spouted beds with internal devices

The effect of draft tubes and fountain confiner on the gas and solids mixing behavior is studied in conical spouted beds. Accordingly, the bed porosity has been determined in different hydrodynamic regimes of 1.1,1.25 and 1.5u/ums, with beds equipped with draft tubes of 0%,56% and 100% opening ratio. These devices significantly affect the gas residence time and particle cycle time distributions, which are further improved by using a fountain confiner, specially when high inlet gas flow rates are desired. The addition of this device was found to remove stagnant gas pockets over the annular zone, while reducing the particle cycle time by 15% with the OSDT configuration at 1.5u/ums. This reduction heavily depends on the distance between the bed surface and the fountain confiner. By including draft tubes, the expected particle cycle time can be more than doubled due to the reduced annular-spot solids circulation. Therefore, it was found that a combination of internal devices and operating flow rate present a promising strategy to control the gas flow pattern, while keeping the distribution of particles cycle times required for each application.

Data-driven aggregate modeling of a semiconductor wafer fab to predict WIP levels and cycle time distributions

In complex manufacturing systems, such as a semiconductor wafer fabrication facility (wafer fab), it is important to accurately predict cycle times and work-in-progress (WIP) levels. These key performance indicators are commonly predicted using detailed simulation models; however, the detailed simulation models are computationally expensive and have high development and maintenance costs. In this paper, we propose an aggregate modeling approach, where each work area, i.e., a group of functionally similar workstations, in the wafer fab is aggregated into a single-server queueing system. The parameters of the queueing system can be derived directly from arrival and departure data of that work area. To obtain fab-level predictions, our proposed methodology builds a network of aggregate models, where the network represents the entire fab consisting of different work areas. The viability of this method in practice is demonstrated by applying it to a real-world wafer fab. Experiments show that the proposed model can make accurate predictions, but also provide insights into the limitations of aggregate modeling.

GRAIN SIZE OF ELECTROCORUNDUM SINTERED FROM DISPERSED WASTE ALUMINUM GRADE AD0E

To develop technologies for obtaining electrocorundum by spark plasma sintering of aluminum waste dispersed by electroerosion and to evaluate the effectiveness of their practical application, comprehensive the oretical and experimental studies are required. The purpose of this work was the grain size of electrocorundum sintered from dispersed aluminum waste of the AD0E brand. Electrodispersion of aluminum waste of the AD0E brand was carried out in distilled water at the original installation with a capacity of 65.5 UF discharge capacitors, a voltage at the electrodes of 200 V, a pulse repetition frequency of 200 Hz. As a result of exposure to short-term electrical discharges, particles of electroerosive powder of various sizes were formed in the water. Further, the fusion of the electroerosion charge was carried out in the spark plasma fusion system SPS 25-10 "Thermal Technology" (USA) at a pressure of 30 MPa, a temperature of 560 °C and a holding time of 3 minutes. Analysis of the microstructure of sintered electrocorundum showed that it has a fine-grained structure, without inclusions, uniform phase distribution and the absence of significant pores, cracks and discontinuities. The grain size of the studied alloys, determined using the SIMAGIS Photolab automated image analysis system and the OLYMPUS GX51 optical inverted microscope, was about 0.45 microns. The small grain size of the resulting electrocorundum is associated with the high dispersion of the initial electroerosion charge and the effect of "grain growth suppression" during spark plasma fusion due to the short working cycle time, high pressure and uniform heat distribution over the sample when exposed to pulsed electric current and the so-called "spark discharge plasma effect". The conducted studies will allow to perform resource conservation and import substitution in the production of electrocorundum from aluminum waste of the AD0E brand.

Orchiectomy exacerbates sleep-disordered breathing induced by intermittent hypoxia in mice

We tested the hypothesis that low testosterone levels alter the regulation of breathing in mice exposed to intermittent hypoxia (IH). We used orchiectomized (ORX) or control (Sham-operated) mice exposed to normoxia or IH (12 h/day, 10 cycles/h, 6% O2) for 14 days. Breathing was measured by whole-body plethysmography to asses the stability of the breathing pattern (frequency distribution of total cycle time - Ttot) and the frequency and duration of spontaneous and post-sigh apneas (PSA). We characterized sighs as inducing one (S1) or more (S2) apnea and determined the sigh parameters (volume, peak inspiratory and expiratory flows, cycle times) associated with PSA. IH increased the frequency and duration of PSA and the proportion of S1 and S2 sighs. The PSA frequency was mostly related to the sigh expiratory time. The effects of IH on PSA frequency were amplified in ORX-IH mice. Our experiments using ORX support the hypothesis that testosterone is involved in the regulation of breathing in mice following IH.

Influence of cycle time distribution on coating uniformity of particles in a spray fluidized bed by using CFD-DEM simulations

Cycle Time Distribution (CTD) plays a critical role for determining uniformity of particle coating in spray fluidized beds. However, the CTD is influenced by both geometrical structure and operating conditions of fluidized bed. In this study, a spray fluidized bed of coating process is simulated by a comprehensive Computational Fluid Dynamics-Discrete Element Model (CFD-DEM). To achieve different behaviors of CTD, some modifications are designed on a pseudo-2D internally circulating fluidized bed, which traditionally composes of a high-velocity upward bed and low-velocity downward bed. These modifications include making the air distributor slope and/or laying a baffle in the downward bed. First, the CTD and evolution of particle size distribution under different bed structures are compared. The CTD directly influences the coating uniformity. By making the particles flowing along a parallel direction in the downward bed through the geometrical modifications, the CTD becomes narrower and the coating uniformity is significantly improved. Second, under the optimized bed structure, the influence of operating conditions on the coating uniformity is studied. Properly increasing the fluidization gas velocity and the fluidization gas temperature and reducing the liquid spray rate can improve the coating uniformity.

Equivalence framework for an age-structured multistage representation of the cell cycle.

We develop theoretical equivalences between stochastic and deterministic models for populations of individual cells stratified by age. Specifically, we develop a hierarchical system of equationsdescribing the full dynamics of an age-structured multistage Markov process for approximating cell cycle time distributions. We further demonstrate that the resulting mean behavior is equivalent, over large timescales, to the classical McKendrick-von Foerster integropartial differential equation. We conclude by extending this framework to a spatial context, facilitating the modeling of traveling wave phenomena and cell-mediated pattern formation. More generally, this methodology may be extended to myriad reaction-diffusion processes for which the age of individuals is relevant to the dynamics.

Single-Cell Analysis of Human B Lymphoid and Neutrophil/Monocyte Lineage Restriction

Lifelong production of most types of mature blood cells is sustained by a small population of cells with extensive regenerative potential. However, the detailed steps that restrict multipotent or even bipotent human hematopoietic cells to any single lineage remain poorly understood. Those that segregate the human B-lymphoid and neutrophil/monocyte (NM) lineages are of particular interest as these appear to identify a stage that might control the different properties of human leukemias that display perturbed NM and/or B-cell programs. To undertake a refined analysis of this normal lineage restriction process in human cells, we first devised a culture system that permits it to be tracked clonally and efficiently (50%). Initial experiments showed this could be achieved using a combination of multiple stromal cell types and human growth factor-supplemented medium. To elucidate the intervening transitional steps we then used multiplexed flow cytometry to compare the progeny generated in this culture system over a 2-week time course from previously defined lymphoid progenitor-enriched (P-L), NM progenitor-enriched (P-NM) and less restricted P-mix cord blood (CB) subsets. The results suggested that gain of CD45RA (RA) expression and loss of CLEC12A (C) expression appeared to accompany the sequential restriction of early CD34+ progenitors first to cells with dual NM+B-lineage potential and then just to B-lineage potential.Subsequent tracking of the lineage outputs of CD34+ RA-C- cells initially produced in larger numbers from unfractionated CD34+ CB cells either in vitro or in xenografted immunodeficient mice, confirmed the CD34+ RA-C- subset to be highly enriched in cells with dual NM+B potential. In contrast, co-generated CD45RA+ (RA+C-) and RA+CLEC12A+ (RA+C+) phenotypes displayed separate B- and NM lineage-restricted activity, respectively, as indicated by their largely exclusive clonal outputs of CD19+ pre-B and CD14+/CD15+ NM precursors. In agreement with these phenotypically established separate NM and B-lineage outputs, RA+C- cells were found to contain higher levels of B-lineage-associated gene transcripts (e.g., DNTT, CD79A, and EBF1), whereas RA+C+ cells contained higher levels of the NM transcription factor mRNAs encoded by SPI1 and CEBPA. In a further optimized stroma-free liquid culture system, the RA-C- cells could be shown to produce continuously RA+C- and RA+C+ progeny after another 3-4 days, and also RA-C- progeny which are not produced from more restricted RA+C- and RA+C+ cells, suggesting that the acquired expression of RA precedes the separation of NM and B-lineage potential that is then marked by the differential activation of C expression in RA+ cells.To examine more precisely how the process of B+NM restriction to a single lineage might be related to successive cell cycles, we labeled RA-C- cells with carboxyfluorescein diacetate succinimidyl ester (CFSE) to enable the phenotypes and growth potential of the the progeny obtained after 6 days to be directly related to their prior division histories. This revealed extensive heterogeneity in the overall distribution of the initial progeny cell cycle times but with a clear segregation in the outputs of the faster and slower dividing cells. Notably, the faster dividers produced ultimately small M+B or uni-lineage clones whereas the initially slow dividers subsequently produced larger clones, 25% of which still contained CD34+ cells or N+M+B progeny.Taken together, these findings identify new hallmark phenotypic changes that identify a critical step in the lineage restriction of primitive human hematopoietic cells with dual NM+B-lineage potential and a previously unknown association of this process with a shortening of their cell cycle transit time. DisclosuresNo relevant conflicts of interest to declare.

Draft tube design based on a borescopic technique in conical spouted beds

Draft tubes have emerged as promising internal devices to overcome the scale up limitations of the spouted bed. Although only a few parameters define draft tubes, the design of these devices is complex and remains a challenging task, as knowledge concerning the gas–solid flow pattern in the spouted bed is required for a proper implementation. Therefore, this study aims to propose a new criterion for the design of draft tubes (nonporous and open-sided) based on the average spout diameter measured by a borescopic technique in conical spouted beds without draft tube. Based on the radial and axial particle velocity profiles, hydrodynamic analysis, and cycle time distributions, the new configurations are compared with those without tube and with conventional draft tubes. The new open-sided tube provides maximum particle velocities of 480.90 ± 14.60 mm/s in the spout and 90.10 ± 4.40 mm/s in the annulus. These values are lower and higher than the particle velocities obtained without draft tube in the spout and annulus regions, respectively, which means it modifies particle residence time in these regions. The new open-sided tube provides a more efficient gas–solid contact than any conventional one, with spouting behaviour being very similar to the configuration without tube (differences in the minimum spouting velocity being in the 2–6% range), which is a key aspect for scale up purposes.

Forward cycle time distributions for returnable transport items

Forward cycle time distributions for returnable transport items

Supervised-learning-based approximation method for multi-server queueing networks under different service disciplines with correlated interarrival and service times

ABSTRACT Developing efficient performance evaluation methods is important to design and control complex production systems effectively. We present an approximation method (SLQNA) to predict the performance measures of queueing networks composed of multi-server stations operating under different service disciplines with correlated interarrival and service times with merge, split, and batching blocks separated with infinite capacity buffers. SLQNA yields the mean, coefficient of variation, and first-lag autocorrelation of the inter-departure times and the distribution of the time spent in the block, referred as the cycle time at each block. The method generates the training data by simulating different blocks for different parameters and uses Gaussian Process Regression to predict the inter-departure time and the cycle time distribution characteristics of each block in isolation. The predictions obtained for one block are fed into the next block in the network. The cycle time distributions of the blocks are used to approximate the distribution of the total time spent in the network (total cycle time). This approach eliminates the need to generate new data and train new models for each given network. We present SLQNA as a versatile, accurate, and efficient method to evaluate the cycle time distribution and other performance measures in queueing networks.

Stress-Strength Reliability Estimation of Time-Dependent Models with Fixed Stress and Phase Type Strength Distribution

The time-dependent stress-strength reliability models deal with systems whose strength or the stress imposed on it or both are time-dependent. In this paper, we consider time-dependent stress-strength reliability model which is subjected to constant stress and it causes a change in the strength of the system over each run of the system. Assuming a continuous phase- type distribution for the initial strength and exponential distribution for the duration of each run of the system called cycle time we derived the expression for the stress-strength reliability of the system at time t. The model is further extended to the cases where cycle time distribution is Gamma and Weibull. Simulation studies are conducted to assess the variations in stress-strength reliability, R(t) at different time points, corresponding to the changes in the initial strength distribution and cycle time distribution.

Analysis of production cycle-time distribution with a big-data approach

In production planning, one of the most crucial issues involves cycle time forecasting and distribution. Particularly, the parameter aids in realizing high delivery reliability. In the production planning process that involves computer component manufacturing, an estimation of the tasks’ cycle time offers an important basis for dispatching control, material purchase, and due date assignment. In this study, a big-data approach was proposed and examined to determine how it could be used to predict cycle time distribution. Also, the research context involved computer components manufacturing systems. Indeed, the motivation was to determine how the proposed mechanism could improve delivery reliability in manufacturing systems.Regarding the implementation and design of the CT forecasting system, with the proposed DP-RBFN framework being a model to be implemented in computer components manufacturing, components of the system constituted three major parts. The first part, being the basic platform, played the role of Hadoop series software installation. This installation had its role lie in enabling the parallel computing of big data. Another part of the framework design and implementation involved data preprocessing. In this case, the role of the data preprocessing procedure lay in the extraction, transformation, and loading of data to CTF. The third part that followed the basic platform design and data preprocessing procedure involved CT forecasting. Results demonstrated that the proposed model performs superiorly than the contrast or other comparative methods on both the computer components manufacturing system dataset and benchmark datasets. From the findings, the proposed framework (DP-RBFN) exhibited superior performance compared to previous performance outcomes that had been reported relative to the use of the RBFN algorithm. These findings held for both MAD and SD—relative to the selected datasets.

Modeling of inter- and intra-particle coating uniformity in a Wurster fluidized bed by a coupled CFD-DEM-Monte Carlo approach

A coupled CFD-DEM and Monte Carlo approach was developed to investigate coating properties in a Wurster fluidized bed by considering gas flow, particle motion, droplet deposition, and the drying and solidifying of droplets on particle surfaces. Based on the spherical centroidal Voronoi tessellation (CVT), the Monte Carlo approach can model the deposition and splashing of spray droplets on the surface of individual particles. The capillary force induced by liquid bridges between particles was accounted in the DEM to investigate its influence on the coating and agglomeration behavior. The new model can provide information about the cycle time distribution, residence time distribution, coating coverage, uniformity of porosity (influenced by splashing) and layer thickness distributions on each individual particle (intra-particle) and in the particle population (inter-particle). The simulation results are compared with experimental data on residence time and intra-particle layer thickness distributions. Good agreement is observed between the simulation and the measurements.

Modelling the set of earthworks machinery with the use of computer simulation

The paper presents the comparison of deterministic and stochastic approach for modeling the set of earthworks machinery. Simulation takes into account the normal distribution of cycle time and efficiency of machines and points out its influence for total construction works time. Results of the simulation indicate the need of identification time and efficiency deviation as a risk factor, which can cause delay whenever earthworks cycle includes the serial work of several machines.

A decomposition method for assembly/disassembly systems with blocking and general distributions

A modelling methodology is presented for assembly/disassembly systems with general processing time distributions and finite buffers. The approach combines the distributions discretization and a decomposition technique to analyze large manufacturing systems in a reasonable computational time and with good accuracy. In the decomposition technique, the system is decomposed into two station subsystems and the processing time distributions of the virtual stations are iteratively modified to approximate the impact of the rest of the network, adding estimations of the blocking and starving distributions. To analyze each subsystem, the general processing time distributions are discretized by aggregation of the probability masses, and the subsystem is then analytically modeled using a discrete Markov chain. We first show that this approach allows an accurate estimation of the subsystems cycle time distributions, which is crucial in the decomposition technique. Using computational experiments, we show that our decomposition method leads to accurate performance evaluation for large manufacturing systems (relative error on the order of 1%) and that the fine distribution estimation indeed seems to bring an improvement. Furthermore, we show on examples that, using decomposition, the cycle time distributions can be approximated reliably for large systems.

Distribution of Cycle Times in Sawdust Conical Spouted Bed Equipped with Fountain Confiner and Draft Tube

A study has been conducted on the joint influence of the fountain confiner and draft tube on the solid circulation in a conical spouted bed made up of sawdust. Knowledge of the performance of these...