Serial Lines Research Articles

Lagrangian Relaxation for Stochastic Disassembly Line Balancing Problem

This study deals with the problem of profit oriented disassembly line balancing considering partial disassembly, presence of hazardous parts and uncertainty of task times. The objective of this paper is to design a serial line that obtains the maximum profit under uncertainty. Tasks of the best selected disassembly alternative are to be assigned to a sequence of workstations while respecting precedence and cycle time constraints. The line profit is computed as the difference between the positive revenue generated by the retrieved parts of the End of Life (EOL) product and the line operation cost. The latter includes the workstation operation costs and additional costs for handling hazardous parts. Task times are assumed to be random variables with known probability distributions. An AND/OR graph is used to model the disassembly alternatives and the precedence relationships among tasks and subassemblies. To cope with uncertainties, a solution method based on Lagrangian relaxation and Monte Carlo sampling technique is developed. To show the relevance and applicability of the proposed method, it is evaluated on a set of problem instances from the literature.

English

Reconfigurable manufacturing systems are recognized as next generation manufacturing systems capable of providing the exact functionality and capacity as and when required. The reconfiguration of the system depends upon the ease with which any machine can be added, removed or re-adjusted for upcoming configuration from any initial or outgoing configuration. The efforts required while changing any existing configuration to a new configuration have serious implications on the cost aspect as well. The complexity and economics involved in changing one configuration to another depend on the existing initial configuration and the new upcoming configuration required for subsequent production of part families. In the present paper, based on the different types of effort associated with the reconfiguration process, a new indicator of performance termed as “Service Level” is proposed. The proposed indicator is modeled for a multipart reconfigurable manufacturing system. The proposed methodology is demonstrated using a numerical example. The values obtained for service levels while switching from one configuration to another were calculated for a serial product flow line. Some of the important implications regarding service level evaluation and implementation are finally discussed.

Fault Tolerant Ethernet Based Network for Time Sensitive Applications in Electrical Power Distribution Systems

The paper analyses and experimentally verifies deployment of Ethernet based network technology to enable fault tolerant and timely exchange of data among a number of high voltage protective relays that use proprietary serial communication line to exchange data in real time on a state of its high voltage circuitry facilitating a fast protection switching in case of critical failures. The digital serial signal is first fetched into PCM multiplexer where it is mapped to the corresponding E1 (2 Mbit/s) time division multiplexed signal. Subsequently, the resulting E1 frames are then packetized and sent through Ethernet control LAN to the opposite PCM demultiplexer where the same but reverse processing is done finally sending a signal into the opposite protective relay. The challenge of this setup is to assure very timely delivery of the control information between protective relays even in the cases of potential failures of Ethernet network itself. The tolerance of Ethernet network to faults is assured using widespread per VLAN Rapid Spanning Tree Protocol potentially extended by 1+1 PCM protection as a valuable option.

Bernoulli serial lines with deteriorating product quality: performance evaluation and system-theoretic properties

Manufacturing systems with perishable products are widely seen in practice (e.g. food, metal processing, etc.). In such systems, the quality of a part is highly dependent on its residence time within the system. However, the behaviour and properties of these systems have not been studied systematically and, therefore, it is carried out in this paper. Specifically, we assume that the probability that each unfinished part is of good quality is a decreasing function of its residence time in the preceding buffer. Then, in the framework of serial production lines with machines having Bernoulli reliability model, we derive closed-form formulas for performance evaluation in the two-machine line case, and develop an aggregation-based procedure to approximate the performance measures in -machine lines. In addition, we study monotonicity properties of these production lines using numerical experiments. A case study in an automotive stamping plant is described to illustrate the theoretical results obtained.

Raw material release rates to ensure desired production lead time in Bernoulli serial lines

Production systems are often managed to maximise their production rate (). In some cases, this leads to excessive work-in-process and, as a result, long production lead time (). This issue is of particular importance in systems with ‘unlimited’ buffer space, where may also become unlimited. The question addressed in this paper is: What should be the release rate of raw materials so that the desired is obtained, while is maximised? We answer this question for serial lines with infinite buffers and machines obeying the Bernoulli reliability model. Specifically, given a serial line, we quantify the set of attainable s (feasible set), and for each point in the feasible set provide the release rate (as a function of machine parameters) that guarantees the desired lead time, while maximising the production rate. In addition, we offer a feedback control law that enforces the desired system behaviour. The development is based on a recursive aggregation procedure that leads to analytical estimates of . The accuracy of these estimates is evaluated by simulations and is shown to be acceptable for practical applications (well within 5%). The results obtained offer small- and mid-size enterprises the possibility of managing their production lead time, when neither limited buffers nor kanban/CONWIP systems are available, by releasing raw materials on, say, an hourly basis.

Transient analysis of Bernoulli serial lines: performance evaluation and system-theoretic properties

Transient behavior of production systems has significant practical and theoretical implications. However, analytical methods for analysis and control of production systems during transients remain largely unexplored. In the framework of serial production lines with Bernoulli machines and finite buffers, this article develops a mathematical model for transient analysis and derives closed-form expressions for evaluating the production rate, consumption rate, work-in-process, and probabilities of machine starvation and blockage during transients. In addition, a computationally efficient procedure based on recursive aggregation is developed to approximate the transient performance measures with high accuracy. Finally, based on the mathematical model derived, system-theoretic properties of several important system transient characteristics are studied.

Abstract 1407: A transgenic mouse model for the Hedgehog pathway effector GLI1 induced mammary gland tumors.

Abstract Increased expression of the Hedgehog (Hh) signaling pathway effector GLI1 in breast cancer patients has been shown to correlate inversely with disease free and overall survival. Activation of the Hh signaling pathway is known to promote proliferation of breast cancer cells and stimulate mammosphere formation. In addition, the Hh signaling pathway has been reported activated in CD44 positive breast cancer stem cells. Despite the evidence supporting a role for Hh signaling in breast cancer development and maintenance, the model systems to study the Hh pathway in breast carcinogenesis are limited. We used a transgenic mouse model to show that GLI1 expression in the mammary gland cause tumor formation. The GLI1 induced primary tumors showed different histological characteristics, suggesting that the GLI1 expression influenced the tumor initiating cells. The GLI1 induced primary tumors were orthotopically transplanted on NOD/SCID mice and we have established serial transplantable tumor lines. The different histological characteristics of the individual primary tumors have been maintained for >10 serial transplantations in NOD/SCID mice. The stem cell marker CD44 is expressed in the mouse mammary gland ducts. The CD44 positive cell population is increased in the GLI1 induced tumors. The G protein coupled receptor (GPCR) like protein Lgr5 has been suggested as a stem cell marker in several tissues, including mammary gland. We show that cells in the basal layer of the adult mammary gland ducts express Lgr5. The Lgr5 positive cell population is increased in the GLI1 induced tumors, suggesting a basal like characteristic of these tumors. Taken together, our data show that expression of GLI1 in the mammary gland result in formation of mammary gland tumors with heterogeneous histological characteristics. The cell populations identified by the stem cell markers CD44 or Lgr5 are increased in the GLI1 induced tumors compared with the normal mammary gland. Furthermore, we have established serial transplantable GLI1 induced mammary gland tumor lines. These serial transplantable tumor lines are novel tools to address the role of GLI1 expression in breast carcinogenesis. Citation Format: Jens H. Norum, Agneta Andersson, Maria Kasper, Therese Sørlie, Rune Toftgård. A transgenic mouse model for the Hedgehog pathway effector GLI1 induced mammary gland tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1407. doi:10.1158/1538-7445.AM2013-1407

Evaluation of production control strategies for negligible‐setup, multi‐product, serial lines with consideration for robustness

PurposeThe aims of this paper is to investigate simulation‐based optimisation and stochastic dominance testing while employing kanban‐like production control strategies (PCS) operating dedicated and, where applicable, shared kanban card allocation policies in a multi‐product system with negligible set‐up times and with consideration for robustness to uncertainty.Design/methodology/approachDiscrete event simulation and a genetic algorithm were utilised to optimise the control parameters for dedicated kanban control strategy (KCS), CONWIP and base stock control strategy (BSCS), extended kanban control strategy (EKCS) and generalised kanban control strategy (GKCS) as well as the shared versions of EKCS and GKCS. All‐pairwise comparisons and a ranking and selection technique were employed to compare the performances of the strategies and select the best strategy without consideration of robustness to uncertainty. A latin hypercube sampling experimental design and stochastic dominance testing were utilised to determine the preferred strategy when robustness to uncertainty is considered.FindingsThe findings of this work show that shared GKCS outperforms other strategies when robustness is not considered. However, when robustness of the strategies to uncertainty in the production environment is considered, the results of our research show that the dedicated EKCS is preferred. The effect of system bottleneck location on the inventory accumulation behaviour of different strategies is reported and this was also observed to have a relationship to the nature of a PCS's kanban information transmission.Practical implicationsThe findings of this study are directly relevant to industry where increasing market pressures for product diversity require operating multi‐product production lines with negligible set‐up times. The optimization and robustness test approaches employed in this work can be extended to the analysis of more complicated system configurations and higher number of product types.Originality/valueThis work involves further investigation into the performance of multi‐product kanban‐like PCS by examining their robustness to common sources of uncertainties after they have been initially optimized for base scenarios. The results of the robustness tests also provide new insights into how dedicated kanban card allocation policies might offer higher flexibility and robustness over shared policies under conditions of uncertainty.

Production Lead Time Problem: Formulation and Solution for Bernoulli Serial Lines

This paper is intended to formulate the so-called production lead time problem as the problem of throughput optimization under a constraint on production lead time. A solution is provided for serial lines with Bernoulli machines and infinite buffers. Specifically, analytical formulas are derived for raw material release rates, which guarantee the desired lead time, while maximizing the throughput. Based on this solution, a method for selecting design parameters of kanban- and CONWIP-controlled systems, which ensure the desired lead time, is provided.

Energy-Efficient Production Systems Through Schedule-Based Operations

Control of production operations is considered as one of the most economical methods to improve energy efficiency in manufacturing systems. This paper investigates energy consumption reduction in production systems through effective scheduling of machine startup and shutdown. Specifically, we consider serial production lines with finite buffers and machines having Bernoulli reliability model. This machine reliability model is applicable in production situations, where the downtime is relatively short and comparable to machine cycle time (e.g., automotive paint shops and general assembly). In this paper, using transient analysis of the systems at hand, an analytical performance evaluation technique is developed for Bernoulli serial lines with time-dependent machine efficiencies. In addition, tradeoff between productivity and energy-efficiency in production systems is discussed and the energy-efficient production problem is formulated as a constrained optimization problem. The effects and practical implications of operations schedule are demonstrated using a numerical study on automotive paint shop operations. Note to Practitioners - This paper develops an effective analytical tool to evaluate the performance of production systems with time-varying parameters of machine reliability. Using this tool, production engineers and managers can predict the performance of the production systems in real-time with high accuracy. In addition, based on this tool, production operators can determine the machine startup and shutdown schedule based on the current status of the line and production requirement. Numerical experiments show that significant energy savings can be obtained by applying effective machine operations schedule.

Machine Reconfigurability Models Using Multi-Attribute Utility Theory and Power Function Approximation

Reconfigurable Machines (RMs) are considered to be one the key elements of modern manufacturing systems like Reconfigurable Manufacturing Systems (RMSs). These machines offered customized flexibility in terms of capacity and functionality. These machines are modular machines assembled using basic/essential modules and auxiliary modules. These RMs can be reconfigured into several other configurations offering variable functionality and capacity by keeping its base modules and just adding/removing or adjusting the auxiliary modules. Measuring machine reconfigurability may be considered as one of the important parameter in assessing the performance of these manufacturing systems. In the present paper, reconfigurability models were developed using Multi Attribute Utility Theory (MAUT) and Power Function Approximation. The developed models are explained and demonstrated using multi stage serial reconfigurable product flow line.

A 5.83pJ/bit/iteration High-Parallel Performance-Aware LDPC Decoder IP Core Design for WiMAX in 65nm CMOS

In this paper, we propose a synthesizable LDPC decoder IP core for the WiMAX system with high parallelism and enhanced error-correcting performance. By taking the advantages of both layered scheduling and fully-parallel architecture, the decoder can fully support multi-mode decoding specified in WiMAX with the parallelism much higher than commonly used partial-parallel layered LDPC decoder architecture. 6-bit quantized messages are split into bit-serial style and 2bit-width serial processing lines work concurrently so that only 3 cycles are required to decode one layer. As a result, 12∼24 cycles are enough to process one iteration for all the code-rates specified in WiMAX. Compared to our previous bit-serial decoder, it doubles the parallelism and solves the message saturation problem of the bit-serial arithmetic, with minor gate count increase. Power synthesis result shows that the proposed decoder achieves 5.83pJ/bit/iteration energy efficiency which is 46.8% improvement compared to state-of-the-art work. Furthermore, an advanced dynamic quantization (ADQ) technique is proposed to enhance the error-correcting performance in layered decoder architecture. With about 2% area overhead, 6-bit ADQ can achieve the error-correcting performance close to 7-bit fixed quantization with improved error floor performance.

Deployment and future prospects of high performance diagnostics featuring serial I/O (SIO) data acquisition (DAQ) at ASDEX Upgrade

The SIO DAQ concept used at the ASDEX Upgrade fusion experiment features data acquisition from a modular front-end (a modular crate-and-interface-cards concept for analog and digital input and output) over standardized serial lines and via a serial input/output computer interface card (the SIO card) in real-time directly into the main memory of a host computer.Deployment of a series of diagnostics using SIO led to various solutions and configurations for the different requirements. Experience has been gained and lessons learned applying the SIO concept at its technical limits. Requirements for a further development of the SIO concept have been identified, and a performance improvement by a factor of 4–8 beyond its current limits seems achievable. An effort has been started to develop a SIO version 2 (SIO II) featuring upgraded serial links and a more powerful FPGA for merging and forwarding data streams to host computer memory. (Compatibility with the existing SIO (SIO I) front-end system has to be maintained.)This paper presents results achieved and experiences gained in the deployment of SIO I, the status of SIO II development (currently in the prototype phase), and projected enhancements and updates to existing implementations.

SPSens: a software package for stochastic parameter sensitivity analysis of biochemical reaction networks

SPSens is a software package for the efficient computation of stochastic parameter sensitivities of biochemical reaction networks. Parameter sensitivity analysis is a valuable tool that can be used to study robustness properties, for drug targeting, and many other purposes. However its application to stochastic models has been limited when Monte Carlo methods are required due to extremely high computational costs. SPSens provides efficient, state of the art sensitivity analysis algorithms in a single software package so that sensitivity analysis can be easily performed on stochastic models of biochemical reaction networks. SPSens implements the algorithms in C and estimates sensitivities with respect to both infinitesimal and finite perturbations to system parameters, in many cases reducing variance by orders of magnitude compared to basic methods. Included among the features of SPSens are serial and parallel command line versions, an interface with Matlab, and several example problems. SPSens is distributed freely under GPL version 3 and can be downloaded from http://sourceforge.net/projects/spsens/. The software can be run on Linux, Mac OS X and Windows platforms.

Fixed task zone chaining: worker coordination and zone design for inexpensive cross-training in serial CONWIP lines

This work introduces a new canonical model of worker cross-training, called a Fixed Task Zone Chain (FTZC), as a special type of zone-based cross-training and develops a methodology to employ it in U-shaped CONstant Work In Process (CONWIP) lines. The FTZC approach is intended to address lines with more stations than workers in environments where extensive cross-training is prohibitive. It incorporates a two-skill chain to cross-train one skill at each end of each zone; however, tasks at the interior of a zone are not cross-trained. A heuristic dynamic control policy is developed that maximizes the line’s throughput given a zone structure. Some useful properties of the optimal policy are provided as a basis for a heuristic control policy that yields high throughput. The performance of an FTZC system is contingent upon the choice of zone structure; therefore, the zone assignment (ZonA) algorithm is created to design the zone structure to achieve high throughput levels. Sufficient conditions which guarantee that the line is balanceable through ZonA are derived. Benchmarking over a test suite supports the effectiveness of the proposed heuristic worker control policy as well as the ZonA algorithm, and its performance is compared with other paradigms.

Sample Path Optimal Policies for Serial Lines with Flexible Workers

We study the dynamic assignment of cross-trained workers in serial production lines characterized by stochastic process times and inventory buffers between stations. Throughput maximization is the objective. Each worker is trained for a subset of tasks, where emphasis is placed on systems with each worker trained for a zone of stations with stations near the zone boundaries being served (shared) by one or more other workers as well. Using sample path comparisons, we identify structural properties of optimal worker allocation policies. We identify when (i) a worker can prioritize the job in the most downstream station (last-buffer-first-served), and (ii) only the downstream (as opposed to upstream) server should serve a single task.

Sample Path Optimal Policies for Serial Lines with Flexible Workers

We study the dynamic assignment of cross-trained workers in serial production lines characterized by stochastic process times and inventory buffers between stations. Throughput maximization is the objective. Each worker is trained for a subset of tasks, where emphasis is placed on systems with each worker trained for a zone of stations with stations near the zone boundaries being served (shared) by one or more other workers as well. Using sample path comparisons, we identify structural properties of optimal worker allocation policies. We identify when (i) a worker can prioritize the job in the most downstream station (last-buffer-first-served), and (ii) only the downstream (as opposed to upstream) server should serve a single task.

The effects of state-dependent human behavior on the design of a serial line

Most research on line design assumes that human operators perform independently from the status of the line. Recent empirical evidence is contradictory. Humans are likely to change their working speed if they might otherwise cause idle time (Schultz et al., Manage Sci 44(12):1595–1607, 1998). This peculiarity of worker behavior is observed in a variety of settings but little is still known about optimal line design that accounts for this more realistic modeling of worker behavior. Therefore, we analyze work allocation in a serial line with limited buffer capacity and adaptive human behavior. An extensive simulation study reveals that optimal work allocation in state-dependent models is different from classical state-independent models. A bowl-shaped work allocation might be suboptimal and design guidelines are more complicated. Depending on the extent of human reactions, a bowl-shaped, balanced, or reversed-bowl work allocation can be preferable.

Abstract 1994: Honokiol reduces drug resistance by down-regulation of survivin expression in multidrug resistant squamous cell carcinoma of the head and neck

Abstract Background: Resistance to chemotherapy is a major obstacle in cancer therapy. The purpose of this study is to evaluate honokiol in combination with paclitaxel in controlling proliferation of multi-drug resistant (MDR) cancer cells. Honokiol is a small molecule purified from Magnolia officinalis. Honokiol has been shown to suppress tumor growth through apoptosis and inhibition of angiogenesis. In this study, we investigated the effects and mechanisms of those effects of honokiol on MDR squamous cell cancers of the head and neck (SCCHN) Methods: Serial MDR SCCHN lines including KB-8-5, KB-C1, and KB-V1 derived from the drug sensitive parental KB-3-1 cells were used in this study. Cytotoxic effects of honokiol alone and in combination with paclitaxel on apoptosis in drug-sensitive and -resistant cells were evaluated in vitro and in a subcutaneous KB-8-5 xenograft model, Results: The cell growth inhibition analysis revealed a wide range of IC50 values of paclitaxel from 1.66±0.09 to 6560.9 ±439.52 ng/ml in the KB serial cell lines, indicating that those cell lines have different levels of resistance to the paclitaxel treatment. In contrast, honokiol effectively inhibited proliferation and induced apoptosis in all four cell lines with IC50 values from 3.35±0.13 to 2.77±0.22 μg/ml. Mechanistic studies revealed that honokiol induced similar mitochondria-dependent apoptosis in drug resistant cell lines regardless of the differential resistance levels to paclitaxel treatment. Moreover these effects were associated with inhibition of STAT3 phosphorylation and down-regulation of STAT3 target gene expression, including survivin and Mcl-1. Combined treatment with honokiol and paclitaxel synergistically increased cytotoxicity as compared to the single drug treatment. This combination also significantly inhibited growth of xenografted tumors in nude mice. Conclusion: These results suggest that honokiol may be a promising drug in overcoming paclitaxel resistence of SCCHN. Targeting MDR SCCHN using honokiol in combination with paclitaxel, may benefit patients with SCCHN. (Supported by grants P50CA128613, GCC Distinguished Cancer Scholar to Dong M. Shin and Jonathan J Beitler) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1994. doi:1538-7445.AM2012-1994

Re-entrant lines with unreliable asynchronous machines and finite buffers: performance approximation and bottleneck identification

In this paper we study a re-entrant line with unreliable asynchronous exponential machines and finite buffers. First, an approximation method is presented to estimate the throughput of the re-entrant line. The idea of the approximation is to transform an M-machine re-entrant line into a 2M-machine serial line. Then, a system approach to identify a c-bottleneck based on blockage and starvation information is proposed, where a c-bottleneck machine is the machine whose improvement in machine capacity leads to the largest improvement in system throughput compared with improving all other machines. It is shown that the approximation method results in acceptable accuracy, and the bottleneck identification method can correctly detect the bottlenecks in most cases.