scholarly journals Maintenance Optimization of a 2-Component Swappable Series System Using the Delay-Time Concept

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Liying wang ◽  
Wenhua Zhang
Keyword(s):  
Delay Time ◽  
Failure Process ◽  
Inspection Time ◽  
Maintenance Optimization ◽  
Series System ◽  
Two Stage ◽  
Long Run ◽  
Operating Process ◽  
Two Stages ◽  
Normal Stage

In the 2-component swappable series system, the two components undertake tasks with different loads and degrade at different speeds. To prolong the lifetime of the series system, these two components are swapped in the operating process of the system in practice. This is common in the maintenance of duplexing steelmaking systems, tires of vehicles, and steel rails in curves. The failure process of each component in the system is modeled based on a two-stage delay-time concept and divided into two stages: normal and defective. Inspections are carried out periodically on the system. Two components may be swapped once at an inspection time that the two components are both in the normal stage. Due to the increase or decrease of loads, normal and defective time distributions after the swap are assumed to be different from those prior to the swap. The system is subjected to failure, inspection, and age-based renewals. The number of inspections over the maximum usage time of the system and the swap time are optimized jointly by minimizing the expected cost per unit time in a long run. A numerical example is presented to demonstrate the model.

scholarly journals Multicomponent Maintenance Optimization: A Stochastic Programming Approach

2020 ◽  
Author(s):  
Zhicheng Zhu ◽  
Yisha Xiang ◽  
Bo Zeng
Keyword(s):  
Structural Properties ◽  
Failure Process ◽  
Cost Savings ◽  
Planning Horizon ◽  
Combinatorial Problems ◽  
Programming Approach ◽  
Maintenance Optimization ◽  
Stage Model ◽  
Two Stage ◽  
Decision Dependent Uncertainty

Maintenance optimization has been extensively studied in the past decades. However, most of the existing maintenance models focus on single-component systems and are not applicable to complex systems consisting of multiple components, due to various interactions among the components. The multicomponent maintenance optimization problem, which joins the stochastic processes regarding the failures of components with the combinatorial problems regarding the grouping of maintenance activities, is challenging in both modeling and solution techniques, and has remained an open issue in the literature. In this paper, we study the multicomponent maintenance problem over a finite planning horizon and formulate the problem as a multistage stochastic integer program with decision-dependent uncertainty. There is a lack of general efficient methods to solve this type of problem. To address this challenge, we use an alternative approach to model the underlying failure process and develop a novel two-stage model without decision-dependent uncertainty. Structural properties of the two-stage problem are investigated, and a progressive-hedging-based heuristic is developed based on the structural properties. Our heuristic algorithm demonstrates a significantly improved capacity to handle large-size two-stage problems comparing to three conventional methods for stochastic integer programming, and solving the two-stage model by our heuristic in a rolling horizon provides a good approximation of the multistage problem. The heuristic is further benchmarked with a dynamic programming approach and a structural policy, which are two commonly adopted approaches in the literature. Numerical results show that our heuristic can lead to significant cost savings compared with the benchmark approaches.

A novel two-stage method of plant seedlings classification based on deep learning

2021 ◽  
pp. 1-11
Author(s):  
Tianhong Dai ◽  
Shijie Cong ◽  
Jianping Huang ◽  
Yanwen Zhang ◽  
Xinwang Huang ◽  
...  
Keyword(s):  
Deep Learning ◽  
Learning Technology ◽  
Two Stage ◽  
Second Stage ◽  
Stage Classification ◽  
Different Types ◽  
Two Stages ◽  
Plant Seedlings

In agricultural production, weed removal is an important part of crop cultivation, but inevitably, other plants compete with crops for nutrients. Only by identifying and removing weeds can the quality of the harvest be guaranteed. Therefore, the distinction between weeds and crops is particularly important. Recently, deep learning technology has also been applied to the field of botany, and achieved good results. Convolutional neural networks are widely used in deep learning because of their excellent classification effects. The purpose of this article is to find a new method of plant seedling classification. This method includes two stages: image segmentation and image classification. The first stage is to use the improved U-Net to segment the dataset, and the second stage is to use six classification networks to classify the seedlings of the segmented dataset. The dataset used for the experiment contained 12 different types of plants, namely, 3 crops and 9 weeds. The model was evaluated by the multi-class statistical analysis of accuracy, recall, precision, and F1-score. The results show that the two-stage classification method combining the improved U-Net segmentation network and the classification network was more conducive to the classification of plant seedlings, and the classification accuracy reaches 97.7%.

scholarly journals Simple Method of Approximate Calculation of Statically Indeterminate Trusses

2019 ◽  
Vol 16 (06) ◽  
pp. 1840026 ◽  
Author(s):  
Janusz Rębielak
Keyword(s):  
Approximate Calculation ◽  
Computer Software ◽  
Two Stage ◽  
Simple Method ◽  
Two Stages

The paper presents principles of the simple method which makes possible approximate calculations of statically indeterminate truss systems in two stages. The two-stage method applies rules of other methods used for calculations of statically determinate trusses. In each of the two stages, there are considered statically determinate trusses, patterns of which are obtained as results of suitable withdrawing of appropriate members from the pattern of the basic statically indeterminate truss. There are presented results of calculations carried out for two cases of load for selected type of plane truss together with comparison of outcomes obtained by means of using appropriate computer software.

The Occurrence of Meniscal and Chondral Injury in Two-Stage Revision Anterior Cruciate Ligament Reconstruction: A Consecutive Case Series

2019 ◽  
Vol 33 (03) ◽  
pp. 223-227
Author(s):  
Floris R. van Tol ◽  
Willem A. Kernkamp ◽  
Robert J. P. van der Wal ◽  
Jan-Willem A. Swen ◽  
Samuel K. Van de Velde ◽  
...  
Keyword(s):  
Anterior Cruciate Ligament ◽  
Acl Reconstruction ◽  
Cruciate Ligament ◽  
Meniscal Tear ◽  
Partial Meniscectomy ◽  
Two Stage ◽  
Revision Acl Reconstruction ◽  
Chondral Injury ◽  
Anterior Cruciate ◽  
Two Stages

AbstractTwo-stage revision anterior cruciate ligament (ACL) reconstruction is an effective way to revise suboptimal tunnel-placement allowing for proper graft fixation. However, prolonged increased laxity of the knee may increase the risk of meniscal or chondral injury. It was hypothesized that no additional meniscal or chondral lesions occur in between the two stages of the two-stage revision ACL reconstruction. In this retrospective study, 42 patients undergoing a two-stage revision ACL reconstruction were included. Surgical notes for both stages were screened for meniscal and chondral status, interventions to any concurrent injury, surgery dates, along with basic patient characteristics. In 4 of the 42 patients, a new meniscal tear occurred in between the two stages, of which three required partial meniscectomy during the second stage of the ACL revision. One patient experienced a new small degenerative tear that did not require intervention. Two out of the four menisci that were repaired during the first stage had failed and required partial meniscectomy. No significant difference was found in the time between the two stages with respect to the occurrence of meniscal tears. No significant differences in chondral status were found. In conclusion, approximately 10% of patients developed a new meniscal tear and no difference in macroscopic chondral injury was observed between the first and second stages.

scholarly journals Two-Stage Late Jurassic to Early Cretaceous Hydrothermal Activity in the Sakar Unit of Southeastern Bulgaria

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 266
Author(s):  
Krzysztof Szopa ◽  
Anna Sałacińska ◽  
Ashley P. Gumsley ◽  
David Chew ◽  
Petko Petrov ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Hydrothermal Activity ◽  
Two Stage ◽  
Accessory Minerals ◽  
Icp Ms ◽  
Two Stages ◽  
Age Constraints ◽  
Hydrothermal Veins

Southeastern Bulgaria is composed of a variety of rocks from pre-Variscan (ca. 0.3 Ga) to pre-Alpine sensu lato (ca. 0.15 Ga) time. The Sakar Unit in this region comprises a series of granitoids and gneisses formed or metamorphosed during these events. It is cut by a series of post-Variscan hydrothermal veins, yet lacks pervasive Alpine deformation. It thus represents a key unit for detecting potential tectonism associated with the enigmatic Cimmerian Orogenic episode, but limited geochronology has been undertaken on this unit. Here we report age constraints on hydrothermal activity in the Sakar Pluton. The investigated veins contain mainly albite–actinolite–chlorite–apatite–titanite–quartz–tourmaline–epidote and accessory minerals. The most common accessory minerals are rutile and molybdenite. Apatite and titanite from the same vein were dated by U–Pb LA–ICP-MS geochronology. These dates are interpreted as crystallization ages and are 149 ± 7 Ma on apatite and 114 ± 1 Ma on titanite, respectively. These crystallization ages are the first to document two stages of hydrothermal activity during the late Jurassic to early Cretaceous, using U–Pb geochronology, and its association with the Cimmerian orogenesis. The Cimmerian tectono-thermal episode is well-documented further to the east in the Eastern Strandja Massif granitoids. However, these are the first documented ages from the western parts of the Strandja Massif, in the Sakar Unit. These ages also temporally overlap with previously published Ar–Ar and K–Ar cooling ages, and firmly establish that the Cimmerian orogeny in the studied area included both tectonic and hydrothermal activity. Such hydrothermal activity likely accounted for the intense albitization found in the Sakar Unit.

scholarly journals Performance Analysis and Working Fluid Selection for Single and Two Stages Vapor Compression Refrigeration Cycles

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1017
Author(s):  
Bahaa Saleh ◽  
Ayman A. Aly ◽  
Mishal Alsehli ◽  
Ashraf Elfasakhany ◽  
Mohamed M. Bassuoni
Keyword(s):  
Energy Efficiency ◽  
Environmental Impacts ◽  
High Energy ◽  
Working Fluid ◽  
Vapor Compression ◽  
Alternative Refrigerants ◽  
Two Stage ◽  
Azeotropic Mixtures ◽  
Vapor Compression Refrigeration ◽  
Two Stages

Screening for alternative refrigerants with high energy efficiency and low environmental impacts is one of the highest challenges of the refrigeration sector. This paper investigates the performance and refrigerant screening for single and two stages vapor compression refrigeration cycles. Several pure hydrocarbons, hydrofluorocarbons, hydrofluoroolefins, fluorinated ethers, and binary azeotropic mixtures are proposed as alternative refrigerants to substitute R22 and R134a due to their environmental impacts. The BACKONE equation of state is used to compute the thermodynamic properties of the candidates. The results show that the maximum coefficients of performance (COP) for single and two stage cycles using pure substances are achieved using cyclopentane with values of 4.14 and 4.35, respectively. On the other side, the maximum COP for the two cycles using azeotropic mixtures is accomplished using R134a + RE170 with values of 3.96 and 4.27, respectively. The two-stage cycle presents gain in COP between 5.1% and 19.6% compared with the single-stage cycle based on the used refrigerant. From the obtained results, among all investigated refrigerants, cyclopentane is the most suitable refrigerant for the two cycles from the viewpoint of energy efficiency. However, extra cautions should be taken due to its flammability.

scholarly journals High-Performance Parallel Simulation of Airflow for Complex Terrain Surface

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Kenji Ono ◽  
Takanori Uchida
Keyword(s):  
Mesh Generation ◽  
High Performance ◽  
Power Plants ◽  
Domain Decomposition Method ◽  
Simulation Method ◽  
Two Stage ◽  
Hybrid Parallelization ◽  
Strong Scaling ◽  
Computing Performance ◽  
Two Stages

It is important to develop a reliable and high-throughput simulation method for predicting airflows in the installation planning phase of windmill power plants. This study proposes a two-stage mesh generation approach to reduce the meshing cost and introduces a hybrid parallelization scheme for atmospheric fluid simulations. The meshing approach splits mesh generation into two stages: in the first stage, the meshing parameters that uniquely determine the mesh distribution are extracted, and in the second stage, a mesh system is generated in parallel via an in situ approach using the parameters obtained in the initialization phase of the simulation. The proposed two-stage approach is flexible since an arbitrary number of processes can be selected at run time. An efficient OpenMP-MPI hybrid parallelization scheme using a middleware that provides a framework of parallel codes based on the domain decomposition method is also developed. The preliminary results of the meshing and computing performance show excellent scalability in the strong scaling test.

scholarly journals Three-Dimensional Modeling and Structured Vibration Modes of Two-Stage Helical Planetary Gears Used in Cranes

2017 ◽  
Vol 2017 ◽  
pp. 1-18 ◽  
Author(s):  
Lina Zhang ◽  
Yong Wang ◽  
Kai Wu ◽  
Ruoyu Sheng
Keyword(s):  
Three Dimensional ◽  
Structure Design ◽  
Parameter Method ◽  
Vibration Modes ◽  
Two Stage ◽  
Planetary Gears ◽  
Three Dimensional Modeling ◽  
Translational Mode ◽  
Gyroscopic Effects ◽  
Two Stages

The dynamic investigation of helical planetary gears plays an important role in structure design as the vibration and noise are perceived negatively to the transmission quality. With consideration of the axial deformations of members, the gyroscopic effects, the time-variant meshing stiffness, and the coupling amongst stages, a three-dimensional dynamic model of the two-stage helical planetary gears is established by using of the lumped-parameter method in this paper. The model is applicable to variant number of planets in two stages, different planet phasing, and spacing configurations. Numerical simulation is conducted to detect the structured vibration modes of the equally spaced systems. Furthermore, the unique properties of these vibration modes are mathematically proved. Results show that the vibration modes of the two-stage helical planetary gears can be categorized as five classes: the rigid body mode, the axial translational-rotational mode, the radical translational mode, and the 1st-stage and the 2nd-stage planet mode.

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