Re-entrant System Research Articles

Bottleneck identification and transfer prediction for automated production lines based on FNN

Abstract In a re-entrant production system, the throughput of the whole system depends on the capacity of the bottleneck machine. In this study, a new definition of bottleneck is proposed for a precision forging blade shop. The reinforcement learning algorithm is used to optimize the production scheduling to determine the most suitable scheduling scheme, which lays the foundation for bottleneck identification. Subsequently, the bottleneck identification index system was established according to the optimization objective, and the bottleneck identification problem was transformed into a multi-attribute decision-making problem. Finally, a fuzzy neural network is used for training, and the basic scheduling examples of each flow shop are utilized for bottleneck identification and prediction to verify their effectiveness.

Measurement of complex permittivity of liquids in the frequency range 100-1000MHz by using a re-entrant cavity.

For many liquid materials and biological media, their complex permittivity varies with frequency in the P-band (100-1000MHz). In this paper, a re-entrant coaxial cavity resonance test system with intensive multi-frequency points testing capability is designed for the P-band to realize the test of the complex permittivity of P-band materials. For this system, a test algorithm has been written, and on the basis of this system, a perturbation block has been designed, using stepper motors to control the up and down movement of the perturbation block to achieve frequency tunability of the cavity, enabling more P-band frequency test data to be obtained. The experimental results show that the system is suitable for testing the electrical parameters of P-band biological media and liquid materials and for testing solid materials in aerospace, electromagnetic shielding, and other fields where there is a great demand for P-band testing.

Simulation-Based Analysis on Operational Control of Batch Processors in Wafer Fabrication

In semiconductor wafer fabrication (wafer fab), wafers go through hundreds of process steps on a variety of processing machines for electrical circuit building operations. One of the special features in the wafer fabs is that there exist batch processors (BPs) where several wafer lots are processed at the same time as a batch. The batch processors have a significant influence on system performance because the repetitive batching and de-batching activities in a reentrant product flow system lead to non-smooth product flows with high variability. Existing research on the BP control problems has mostly focused on the local performance, such as waiting time at the BP stations. This paper attempts to examine how much BP control policies affect the system-wide behavior of the wafer fabs. A simulation model is constructed with which experiments are performed to analyze the performance of BP control rules under various production environments. Some meaningful insights on BP control decisions are identified through simulation results.

Axion detection with negatively coupled cavity arrays

Using eigenmode analysis and full 3D FEM modelling, we demonstrate that a closed cavity built of an array of elementary harmonic oscillators with negative mutual couplings exhibits a dispersion curve with lower order modes corresponding to higher frequencies. Such cavity arrays may help to achieve large mode volumes for boosting sensitivity of the axion searches, where the mode volume for the composed array scales proportional to the number of elements, but the frequency remains constant. The negatively coupled cavity array is demonstrated with magnetically coupling coils, where the sign of next-neighbour coupling (controlled with their chirality) sets the dispersion curve properties of the resonator array medium. Furthermore, we show that similar effects can be achieved using only positively coupled cavities of different frequencies assembled in periodic cells. This principle is demonstrated for the multi-post re-entrant system, which can be realised with an array of straight metallic rods organised in chiral structures.

Magnetism of a sigma-phase Fe60V40 alloy: Magnetic susceptibilities and magnetocaloric effect studies

Magnetic properties of a sigma-phase Fe60V40 intermetallic compound were studied by means of ac and dc magnetic susceptibility and magnetocaloric effect measurements. The compound is a soft magnet yet it was found to behave like a re-entrant spin-glass system. The magnetic ordering temperature was found to be TC≈170K, while the spin-freezing temperature was ∼164K. Its relative shift per decade of ac frequency was 0.002, a value smaller than that typical of canonical spin-glasses. Magnetic entropy change, ΔS, in the vicinity of TC was determined for magnetic field, H, ranging between 5 and 50kOe. Analysis of ΔS in terms of the power law yielded the critical exponent, n, vs. temperature with the minimum value of 0.75 at TC, while from the analysis of a relative shift of the maximum value of ΔS with the field a critical exponent Δ=1.7 was obtained. Based on scaling laws relationships values of other two exponents viz. β=0.6 and γ=1 were determined.

Re-entrant spin glass behaviour and large magnetocaloric effect in Er2PtSi3

We present the magnetic properties and magnetocaloric effect of ternary intermetallic compound Er2PtSi3 with the orthorhombic Ba2LiSi3-type structure. Dc magnetization, ac susceptibilit, magnetic relaxation, electrical resistivity and specific heat measurements indicate that this system undergoes two magnetic phase transitions from a paramagnetic state sequentially to an antifwerromagnetic state at TN=5.4 K and then to a random spin freezing state at Tf=2.4 K. In addition, the large magnetocaloric effect is also observed for the Er2PtSi3 alloy. Near its Néel temperature TN, the maximum magnetic entropy change, relative cooling power and maximum adiabatic temperature change are estimated to be 16.1 Jkg-1K-1, 290 Jkg-1 and 7.7 K, respectively, for a field change of 5 T. These results suggest that Er2PtSi3 should be classified as a re-entrant spin-glass system and can be considered as a potential low-temperature magnetic refrigeration material.

Global Feedback Stabilization for a Class of Nonlocal Transport Equations: The Continuous and Discrete Case

In this paper, we prove the global output feedback stabilization for a class of nonlinear transport equations with nonlocal velocity. It models a highly re-entrant system which is widely encountered in semiconductor manufacturing. The exponential stability of the solution to a constant equilibrium is proved by a Lyapunov function method under a natural feedback law. The smallness restriction on the initial data in [J.-M. Coron and Z. Wang, SIAM J. Math. Anal., 45 (2013), pp. 2646--2665] is removed by using the special feature of the velocity function. The exponential stabilization results for the related discretized system with an upwind scheme are obtained by the eigenvalue decomposition method and by a Lyapunov function method. Numerical simulations are provided to supplement the theoretical results.

On optimization of a highly re-entrant production system

We discuss the optimal control problem stated as the minimization in the $L^2$-sense of the mismatch between the actual out-flux and a demand forecast for a hyperbolic conservation law that models a highly re-entrant production system. The output of the factory is described as a function of the work in progress and the position of the switch dispatch point (SDP) where we separate the beginning of the factory employing a push policy from the end of the factory, which uses a quasi-pull policy. The main question we discuss in this paper is about the optimal choice of the input in-flux, push and quasi-pull constituents, and the position of SDP.

Про існування слабких розв'язків задачі Коші для одного класу гіперболічних законів збереження

We discuss the existence of weak solutions to the Cauchy problem for one class of hyperbolic conservation laws that models a highly re-entrant production system. The output of the factory is described as a function of the work in progress and the position of the so-called push-pull point (PPP) where we separate the beginning of the factory employing a push policy from the end of the factory, which uses a pull policy. The main question we discuss in this paper is about the optimal choice of the input in-ux, push and pull constituents, and the position of PPP.

Brachytherapy source calibration, reviews, and consistency of192Ir high-dose rate afterloading sources supplied over the period of 10 years: A retrospective analysis

Measurement and verification of strength of monomodal high-dose rate (mHDR)192 Ir source supplied by the vendor is a major part of quality assurance program. Reference air kerma rate (RAKR) or air kerma strength (AKS) is the recommended quantity to specify the strength of gamma emitting brachytherapy sources. Physicist in our institution performed the source calibration as soon as each 192 Ir new source was loaded on the mHDR afterloading machine. The AKS accurately measured using a physikalisch technische werkstatten (PTW) re-entrant chamber-electrometer system in a scatter-free geometry was used to compute the air kerma rate (AKR) at one-meter distance in the air. To ensure accurate dose delivery to brachytherapy patients, measured AKS or RAKR should be entered correctly in both HDR treatment console station (TCS) as well as treatment planning system (TPS) associated with it. The clinical outcome mainly depends not only on the accuracy of the source strength measurement in the hospital but also on the correct source strength entered into both TCS and TPS software. A retrospective study on 22 mHDR V2 sources supplied by the vendor for the period of 10 years was taken up to access the accuracy of source strength supplied to the Radiotherapy department. The results are analyzed and reported. The accuracy in measured RAKR of all 22 sources supplied by vendor was well within the tolerance limits set by the national regulatory body and international recommendations. The deviations observed between measured RAKR versus manufacturer's quoted RAKR were in the range from −1.71% to +1.15%. In conclusion, the measured RAKR have good agreement with vendor quoted RAKR values.

Analysis of a system of nonlocal conservation laws for multi-commodity flow on networks

We consider a system of scalar nonlocal conservation laws on networks that model a highly re-entrant multi-commodity manufacturing system as encountered in semi-conductor production.Every single commodity is modeled by a nonlocal conservation law, and the corresponding PDEs are coupled via a collective load, the work in progress. We illustrate the dynamics for two commodities. In the applications, directed acyclic networks naturally occur, therefore this type of networks is considered. On every edge of the network we have a system of coupled conservation laws with nonlocal velocity. At the junctions the right hand side boundary data of the foregoing edges is passed as left hand side boundary data to the following edges and PDEs. For distributing junctions, where we have more than one outgoing edge, we impose time dependent distribution functions that guarantee conservation of mass. We provide results of regularity, existence and well-posedness of the multi-commodity network model for $L^{p}$-, $BV$- and $W^{1,p}$-data. Moreover, we define an $L^{2}$-tracking type objective and show the existence of minimizers that solve the corresponding optimal control problem.

Efficient methods to schedule reentrant flowshop system

In order to apply a continuous improvement of their production systems, all managers are always trying to improve their production systems by optimizing their scheduling method. This involves the search for efficient methods for obtaining the best results according to the costs and the delay criteria for example. This paper aims to solve a specific hybrid reentrant flow shop scheduling problem. This one contains some stages with some identical parallel machines. The orders sequenced are splited in batches. Each batch is processed one or more time on the system. For the resolution, various methods have been developed. An exact method which lists all the solutions and selects the best one and approximated methods such as the genetic algorithm GA, the genetic algorithm under fuzzy controller FLCGA, the particle swarm optimization PSO and the particle swarm optimization under fuzzy controller FLCPSO. The results discussed in the paper are very interesting.

An Experimental Comparison of Production Planning Using Clearing Functions and Iterative Linear Programming-Simulation Algorithms

We compare the performance of three algorithms for production planning with workload-dependent lead times. These include a clearing function model using two different methods for estimating the clearing functions, and two iterative algorithms that combine linear programming and simulation models. Our experimental comparison uses a simulation model of a re-entrant bottleneck system built with attributes of a real-world semiconductor fabrication environment. We vary the bottleneck utilization, demand patterns, the mean time to failure, and the mean time to repair. Results indicate that the clearing function model performs better than the iterative algorithms on the scaled-down system considered, giving less variable production plans and higher profit values.

Microwave-Plasma-Coupled Re-Ignition of Methane-and-Oxygen Mixture Under Auto-Ignition Temperature

The re-ignition phenomenon is observed when fuel/oxidizer is re-introduced into an atmospheric-pressure plasma discharge generated by cutting off the gas flow in a re-entrant microwave-plasma applicator system used for plasma-assisted ignition and combustion research works. Results indicate that, for re-ignition to occur, the electric field must be strong enough to fully establish a weakly ionized and self-sustained plasma discharge, and with elevated radical concentrations. The re-ignition was possible at gas flow speeds higher than typical flame propagation rates, and temperature measurements (thermocouple and N2 emission) reveal that re-ignition occurs under auto-ignition temperatures. The high-speed imaging of the flame propagation shows that it is a two step process of initiating a fast pyrolysis flame, which, in turn, stabilizes and starts the direct coupling process of the plasma energy into the flame for full re-ignition to occur.

Synchronization for fast and reentrant operating system kernel tracing

AbstractTo effectively trace an operating system, a performance monitoring and debugging infrastructure needs the ability to trace various execution contexts. These contexts range from kernel running as a thread to Non‐Maskable Interrupt (NMI) contexts. Given that any part of the kernel infrastructure used by a kernel tracer could lead to infinite recursion if traced, and because most kernel primitives require synchronization unsuitable for some execution contexts, all interactions of the tracing code with the existing kernel infrastructure must be considered in order to correctly inter‐operate with the existing operating system kernel. This paper presents a new low overhead tracing mechanism and motivates the choice of synchronization sequences suitable for operating system kernel tracing, namely local atomic instructions as main buffer synchronization primitive and the Read–Copy Update (RCU) mechanism to control tracing. It also proposes a wait‐free algorithm extending the time‐base needed by the tracer to 64‐bit on architectures that lack hardware 64‐bit time‐base support. Copyright © 2010 John Wiley & Sons, Ltd.

F211 3次元人体頭部モデルによる空胴共振器アプリケータの加温特性解析(OS-6:バイオ・メディカルテクノロジーと関連した熱・物質移動現象(IV))

We proposed a non-invasive heating method using the re-entrant resonant cavity applicator system for deep-seated brain tumors. We have already confirmed the effectiveness of this heating system by experimental results and computer simulations with an agar phantom. This paper describes the specific absorption rate (SAR) analysis of this heating system with 3-D human head model for non-invasive brain tumor hyperthermia treatments. First, we described a method of reconstructing a 3-D anatomical human head model from 2-D MRI and X-ray CT images using 3D-CAD software. Second, we presented the results of the SAR distributions of this heating system with developed 3-D anatomical human head model. From these results, we found that the possibility of clinical heating using this system was confirmed by estimating SAR distributions with developed model.

20916 人体頭部形状モデルを用いたTMモードアプリケータの加温特性(OS9 バイオエンジニアリング(3),オーガナイズドセッション)

We have proposed the re-entrant resonant cavity applicator system for non-invasive brain tumor hyperthermia treatments. This paper discusses the heating properties of this system with human models for hyperthermia treatments. First, we present the heating properties of this system with human head agar phantoms and with computer simulations. Second, the brain tumors were seated in various locations within the human brain. Then, by changing the position of the human head agar phantom, we present the effectiveness of the heating properties for heating different locations in the agar phantoms. From these results, the possibility of clinical heating using our heating system was confirmed. Effective heating was possible in human head models with various types of deep-seated tumors by changing the position of the human head.

Photoinduced phase transitions

Employing actinic light to alter/stabilise a particular thermodynamic phase via the photo-isomerisation of the constituent molecules is an interesting tool to investigate soft matter from a new dimension. This article focuses on our recent results on several aspects of these non-equilibrium phase transitions, which are isothermal in nature. We specifically discuss (i) the influence of different parameters, such as confinement, applied electric field, pressure etc., on the dynamics associated with both the photochemical transition driving the equilibrium nematic to the non-equilibrium isotropic phase and the thermal back relaxation recovering the nematic phase, (ii) unique light-driven disorder–order transition in a reentrant system, (iii) dynamic self-assembly of the smectic A phase, which is stabilised only in the presence of actinic light, (iv) novel temperature-intensity phase diagrams and an example of primary and secondary photo-ferroelectric effects in an antiferroelectric smectic C system. These results highlight the fact that the actinic light can be used as a new tool to study phase transitions and the associated critical phenomena that could also bring about effects that are not seen in equilibrium situations.

High-resolution x-ray study of nematic–smectic-Aand smectic-A–reentrant-nematic transitions in liquid-crystal–aerosil gels

We have studied the effects of quenched random disorder created by dispersed aerosil nanoparticle gels on the nematic to smectic- A (N- SmA ) and smectic- A to reentrant nematic ( SmA -RN) phase transitions of thermotropic liquid-crystal mixtures of hexyloxycyanobiphenyl (6OCB) and octyloxycyanobiphenyl (8OCB). These effects are probed using high-resolution synchrotron x-ray diffraction techniques. We find that the reentrant characteristics of the system are largely unchanged by the presence of the aerosil gel network. By comparing measurements of the smectic static structure amplitude for this 8OCB- 6OCB+aerosil system with those for butyloxybenzilidene-octylaniline (4O.8)+aerosil gels, we find that the short-range smectic order in the smectic- A phase is significantly weaker in the reentrant system. This result is consistent with the behavior seen in pure 8OCB-6OCB mixtures. The strength of the smectic ordering decreases progressively as the 6OCB concentration is increased. Detailed line shape analysis shows that the high- and low-temperature nematic phases (N and RN) are similar to each other.

Return map structure and entrainment in a time-state-scale re-entrant system

From the perspective of a heterarchy, endo-physics, or internal measurement, a time-state-scale re-entrant system has been proposed [Y.-P. Gunji, K. Sasai, S. Wakisaka, BioSystems (submitted for publication)]. However, the dynamical structure of this system has yet to be estimated. Because the return map of the time-space re-entrant system results from the twisted coupling between the temporal and state-scale states, it is analytically determined. The attractors of entrainment in the interactive re-entrant system are also determined by a particular recursive rule, and it is also shown that a resulting return map can control the attractors of the interactive systems.