Performance evaluation of linear and non-linear multi-product multi-stage lines with unreliable machines and finite homogeneous buffers

More and more machines are increasing their flexibility so as to be able to produce different products with the same tooling. In this context, it is necessary to have fast and accurate methods to evaluate the system performance. This paper presents an approximate analytical method for the performance evaluation of production systems in which Z different types of products are produced. The proposed method is based on the decomposition of the complex system into a set of simpler building blocks, each one formed by two machines and Z homogeneous buffers. The set of building blocks models the whole behavior of the original system. The performance of each building block is evaluated by using the aggregation technique applied to two-machine lines in which the behavior of several products is modeled by an aggregate product, thus simplifying the complexity of the analysis. The numerical results reported in this paper prove the method provides accurate results.     

Facile synthesis of 2-methyl-[4,6-di-O-acetyl-1,2-dideoxy-3-O-(2,3,4,6-tetra-O-acetyl-D-glycopyranosyl)-alpha-D-glucopyrano-[2',1':4,5]-2-oxazolines, key intermediates for the synthesis of oligosaccharides

A simple synthesis of disaccharide oxazolines has been developed. Condensation of methyl 2-acetamido-4,6-O-benzylidene-2-deoxy-alpha-D-glucopyranoside with 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide, followed by removal of the 4,6-O-benzylidene group from the resulting disaccharide derivative, gave crystalline methyl 2-acetamido-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-alpha-D-glucpyranoside which, on acetolysis with acetic anhydride-acetic acid-sulfuric acid, provided 2-methyl-[4,6-di-O-acetyl-1,2-dideoxy-3-O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-alpha-D-glucopyrano]-[2',1':4,5]-2-oxazoline (7). Synthesis of the related alpha-D-mannopyranosyl compound was similarly accomplished. The glycosylating capability of 7 was employed for the synthesis of 6-(benzyloxycarbonylamino)hexyl-2-acetamido-4,6-di-O-acetyl-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-beta-D-glucopyranoside (18). An alternative synthesis of compound 18 is also described.     

Differential DNA Methylation in Prostate Tumors from Puerto Rican Men

In 2020, approximately 191,930 new prostate cancer (PCa) cases are estimated in the United States (US). Hispanic/Latinos (H/L) are the second largest racial/ethnic group in the US. This study aims to assess methylation patterns between aggressive and indolent PCa including DNA repair genes along with ancestry proportions. Prostate tumors classified as aggressive (n = 11) and indolent (n = 13) on the basis of the Gleason score were collected. Tumor and adjacent normal tissue were annotated on H&E (Haemotoxylin and Eosin) slides and extracted by macro-dissection. Methylation patterns were assessed using the Illumina 850K DNA methylation platform. Raw data were processed using the Bioconductor package. Global ancestry proportions were estimated using ADMIXTURE (k = 3). One hundred eight genes including AOX1 were differentially methylated in tumor samples. Regarding the PCa aggressiveness, six hypermethylated genes (RREB1, FAM71F2, JMJD1C, COL5A3, RAE1, and GABRQ) and 11 hypomethylated genes (COL9A2, FAM179A, SLC17A2, PDE10A, PLEKHS1, TNNI2, OR51A4, RNF169, SPNS2, ADAMTSL5, and CYP4F12) were identified. Two significant differentially methylated DNA repair genes, JMJD1C and RNF169, were found. Ancestry proportion results for African, European, and Indigenous American were 24.1%, 64.2%, and 11.7%, respectively. The identification of DNA methylation patterns related to PCa in H/L men along with specific patterns related to aggressiveness and DNA repair constitutes a pivotal effort for the understanding of PCa in this population.     

Analysis of two-machine lines with finite buffer,operation-dependent and time-dependent failure modes

An analytical model for evaluating the throughput of two-machine lines, characterised by intermediate buffer with finite capacity, deterministic processing times and multiple failure modes for each machine is presented in this paper. Both operation-dependent failure and time-dependent failure are captured in a unique model as extension of the existing literature that was dealing with either one of them. Each machine has two failure modes, one is operation-dependent and the other is time-dependent. Time to failure and time to repair are assumed to be geometrically distributed. The presented method calculates the steady-state probabilities of the manufacturing system with a computational effort that depends only on the number of failure modes and not on the buffer capacity. A performance comparison of the proposed model with existing techniques is also reported, the aim is to show the error introduced by an analytical model that considers the operation-dependent failure mode as approximation of the time-dependent one.     

A novel approach to analyse adhesive layer strain field in a stepped lap repaired carbon fiber reinforced polymer panel using digital image correlation

Abstract

The present work focuses on the critical strain analysis of thin adhesive layer present in single-sided stepped lap-repaired carbon fibre-reinforced polymer panels subjected to tensile loading. Digital image correlation technique is used for acquiring both the global and local whole field strain, to obtain the longitudinal, peel, and shear strain distribution over the adhesive layer. The evolution of strain field with increasing load is captured to predict its mechanical behaviour. Magnified optics is used to capture the localized strain field at critical zones. Step corners are identified as critical zones of damage. Debonding is observed as the primary source of damage in the adhesive layer. Overall, the load displacement behaviour and damage mechanism are captured from the experiment. A numerical study based on finite-element analysis is carried out for validating the experimental results. In the numerical study, the adhesive layer is modelled using zero thickness contact element with cohesive behaviour to mimic disbonding. The cohesive zone properties for mode-I and mode-II loading are experimentally obtained from DCBt to ENF test respectively. Microscopic load vs. displacement curve obtained from an experiment is found to be in good correlation with FE estimates.     

Mathematical programming representation of pull controlled single-product serial manufacturing systems

Pull policies may perform quite differently depending on the particular manufacturing system they must control. Hence, it is clear the necessity of having efficient performance evaluation models to select the best control policy in a specific context. This paper proposes a mathematical programming representation of the main pull control policies applied to single-product serial manufacturing systems. The proposed models simulate the pull controlled system in the sense that, if instantiated with the same parameter values as in a simulation model, their solution gives the same event sequence of the simulation. The proposed mathematical representation is also used for a formal comparison of the considered pull control policies. The new models presented in this paper can represent a base to build new efficient optimization algorithms for the design of pull controlled production systems.     

A Likelihood-Based Multiple Access for Estimation in Sensor Networks

In a wireless sensor network (WSN), the nodes collect independent observations about a nonrandom parameter thetas to be estimated, and deliver informations to a fusion center (FC) by transmitting suitable waveforms through a common multiple access channel (MAC). The FC implements some appropriate fusion rule and outputs the final estimate of thetas. In this paper, we introduce a new access/estimation scheme, here referred to as likelihood-based multiple access (LBMA), and prove it to be asymptotically efficient in the limit of increasingly large number of sensors , when the used bandwidth is allowed to scale as W ~cap^alpha,O.5 < alpha < 1 . The proposed approach is easy to implement, and simply relies upon the very basic property that the log likelihood is additive for independent observations, and upon the fact that the (noiseless) output of the MAC is just the sum of its inputs. Thus, the optimal fusion rule is automatically implemented by the MAC itself.     

Person recognition using facial video information: A state of the art

In this article we propose a detailed state of the art on person recognition using facial video information. We classify the existing approaches present in the scientific literature between those that neglect the temporal information, and those that exploit it even partially. Concerning the first category, we detail the extensions to video data of: eigenfaces, fisherfaces, active appearance models (AAMs), radial basis function neural networks (RBFNNs), elastic graph matching (EGM), hierarchical discriminative regression trees (HDRTs) and pairwise clustering methods. After that, we focus on the strategies exploiting the temporal information, in particular those analysing: the facial motion with optical flow, the evolution of facial appearance over time with hidden Markov models (HMMs) or with various probabilistic tracking and recognition approaches, and the head motion with Gaussian mixture models.     

Performance evaluation of production lines with finite buffer capacity producing two different products

This paper presents an approximate analytical method for the performance evaluation of a production line with finite buffer capacity, multiple failure modes and multiple part types. This paper presents a solution to a class of problems where flexible machines take different parts to process from distinct dedicated input buffers and deposit produced parts into distinct dedicated output buffers with finite capacity. This paper considers the case of two part types processed on the line, but the method can be extended to the case of n part types. Also, the solution is developed for deterministic processing times of the machines which are all identical and are assumed to be scaled to unity. The approach however is amenable of extension to the case of inhomogeneous deterministic processing times. The proposed method is based on the approximate evaluation of the performance of the k-machine line by the evaluation of 2(k-1) two-machine lines. An algorithm inspired by the DDX algorithm has been developed and the validation of the method has been carried out by means of testing and comparison with simulation. Correspondence to: T. Tolio     

Performance evaluation of multiple access techniques in land mobilesatellite networks

The performances of four different multiple-access techniques for land-mobile satellite networks are compared. These multiple-access techniques are: slotted ALOHA, slow frequency-hopping and two reservation schemes. A hybrid automatic-repeat-request (ARQ) scheme based on Reed-Solomon codes is used to combat the error bursts resulting from multipath fading and shadowing. The advantages of using symbol interleaving and erasure decoding are demonstrated. The effect of such parameters as the rate of the forward error correction code, the guard time, and the error rate on the acknowledgment channel is evaluated