Buffer Level Research Articles

The performance of unpaced production lines with unbalanced mean operation times and unreliability patterns

This paper reports on the performance of unbalanced non-automated production lines, whose workstations differ in terms of their mean operation times and their degree of unreliability (failure and repair rates). Simulations are done of 5- and 8-station lines with 1, 2 and 6 buffer units. Statistical analysis shows that breakdown patterns have a significant effect in terms of throughput and average buffer level, leading to the conclusion that the study of unreliable unbalanced lines needs not only take into account overall line breakdown, but should consider where in the line failure occurs.

Simulation platform for anticipative plant-level maintenance decision support system

Global competition and increasing customer expectations are forcing automobile manufacturers to improve their operations. Maintenance, being one of the most critical components in many industries, has a direct impact on the improvement of the overall production performance. In this paper, we introduce an anticipative plant-level maintenance decision support system (APMDSS) that provides guidance on corrective and preventive maintenance priorities based on the equipment bottleneck ranks with the objective of improving daily plant throughput. APMDSS anticipates the plant dynamics (i.e. bottlenecks, hourly buffer levels and likelihood of machine breakdowns) for upcoming shifts using starting state information of the production shift (e.g. equipment maintenance history, operational status of machines, buffer levels and scheduled production model mix). We also evaluate the performance of APMDSS using real data from an automotive body shop experiencing routine throughput difficulties due to frequent machine breakdowns. The results are compared with other methods from the literature and found to be superior in many settings.

An RFID-based inventory management framework for emergency relief operations

In the aftermath of super storm Sandy, a large region from North Carolina to Maine endured food shortages, power outages, and long lines at gas stations forced to ration fuel due to low supply and high demand. These issues were largely the result of the affected transportation network’s inability to effectively cope with random and highly dynamic changes, and a lack of available resources and suppliers who were capable of enacting adequate emergency response measures. These problems experienced during super storm Sandy further underscored the need for a robust emergency inventory management system, where planning policies can be integrated with real-time on-line inventory management strategies to keep track of fluctuations of vital commodities such as food, water, medicine, fuel and power supplies. Motivated by this important problem, this paper investigates a comprehensive feedback-based emergency management framework for disasters such as super storm Sandy that provides integration with an emerging intelligent transportation systems technology, namely Radio Frequency Identification Devices (RFID). Within this framework, the offline-planning problem is solved by the stochastic humanitarian inventory management approach; and the online modeling strategy includes the application of a continuous time model predictive control technique. After introducing the mathematical background, the proposed framework is discussed using case studies built based on super storm Sandy in order to understand the efficiency and practicality of this RFID-based methodology. Results suggest that the methodology can properly account for and react to the rapidly changing needs for vital supplies that occur during the emergency relief operations. Based on this approach, planners and decision makers can be aware of the time delay that can happen due to disaster-related disruptions and thus maintain a safe level of buffer for vital supplies.

A Fluid EOQ Model of Perishable Items with Intermittent High and Low Demand Rates

We consider a stochastic fluid EOQ-type model with demand rates operating in a two-state random environment. This environment alternates between exponentially distributed periods of high demand and generally distributed periods of low demand. The inventory level starts at some level q, and decreases linearly at rate βH during the periods of high demand, and at rate βL < βH at periods of low demand. Refilling of the inventory level to level q is required when the first of two events takes place: Either the buffer level reaches zero, or the buffer content becomes outdated. If such an event occurs during a high demand period, an order is instantaneously placed; otherwise, ordering is postponed until the beginning of the next high demand period. We determine the steady-state distribution of the inventory level, as well as other quantities of interest such as the distribution of the time until a refill is required. Finally, for a given cost/revenue structure, we determine the long-run average profit, and we consider the problem of choosing q such that the profit is optimized.

InP/InGaAs double heterojunction bipolar transistors with BV CEO = 12 V and f max = 470 GHz

0.25 μm emitter InP/InGaAs double heterojunction bipolar transistors (DHBTs) are presented that simultaneously exhibit a high collector current density (J c) of more than 3 mA/μm2 and high breakdown voltage (BVCEO) of 12 V. The DHBTs consist of a 30 nm-thick InGaAs base, 250 nm-thick InGaAs/InAlGaAs/InP collector and 150 nm-thick n-doped InP field buffer. Since the doping level of the InP field buffer is relatively high, only the InGaAs/InAlGaAs/InP collector is depleted at low V CE. Thus, the DHBTs can provide f t = 173 GHz and f max = 470 GHz at J c = 3.5 mA/μm2. On the other hand, at a high V CE, both the InGaAs/InAlGaAs/InP collector and InP field buffer are depleted. Therefore, the effective depletion thickness increases, which results in a BVCEO of 12 V. These results indicate that the use of the InP field buffer provides both high-speed performance and high BVCEO.

Identification of geochemical processes controlling the neutralization of abandoned coal mine drainage using integration of geochemical modelling, geochemical analysis, and batch test: an example from the south of Bochum, Germany

Geochemical modelling, geochemical analysis, and batch extraction test were used to determine the geochemical processes controlling neutralization of the abandoned coal mine drainage of a Ruhr hard coal coalfield, presented in the south of Bochum. The geochemical modelling was performed on the surface water and the groundwater samples collected from the vicinity of the abandoned coal mines, while the geochemical analysis and the batch extraction test were performed on man-made materials, untreated soil samples, treated fertilized soil samples, and rock samples collected from the study area. The geochemical analysis, represented by pH and carbonate test, and the batch test aimed to classify the buffering systems existing in the study area, to identify the buffering level of each system, and to determine the potential sources and reactions controlling the buffering levels. Conversely, the geochemical modelling aimed to determine the source of the carbonate alkalinity. The results of experiments and methods used in this study showed that the neutralization of the abandoned coal mine drainage in this area is controlled by dissolution of carbonate minerals (calcite, aragonite, and dolomite), weathering of silicate and clay minerals, and redissolution of secondary minerals (hydroxides). Furthermore, the buffering systems in this area were divided into geogenic and anthropogenic. The anthropogenic buffering system includes the man-made materials and the treated fertilized soil covers, while the geogenic buffering system consists of the untreated soil cover, the hydroxides and the rock formations. The anthropogenic system has a buffering level of 5.6–11.71 identifying a highly effective short-lived buffer system, while the geogenic system has a buffer level of 4.01–7.17 identifying a moderately effective long-lived buffer system. The importance of this research is related to being a foundation that must be taken into account when making plans for the management of water in the coal mines that will be closed in the near future all over Germany.

Demographic buffering: titrating the effects of birth rate and imperfect immunity on epidemic dynamics.

Host demography can alter the dynamics of infectious disease. In the case of perfectly immunizing infections, observations of strong sensitivity to demographic variation have been mechanistically explained through analysis of the susceptible–infected–recovered (SIR) model that assumes lifelong immunity following recovery from infection. When imperfect immunity is incorporated into this framework via the susceptible–infected–recovered–susceptible (SIRS) model, with individuals regaining full susceptibility following recovery, we show that rapid loss of immunity is predicted to buffer populations against the effects of demographic change. However, this buffering is contrary to the dependence on demography recently observed for partially immunizing infections such as rotavirus and respiratory syncytial virus. We show that this discrepancy arises from a key simplification embedded in the SIR(S) framework, namely that the potential for differential immune responses to repeat exposures is ignored. We explore the minimum additional immunological information that must be included to reflect the range of observed dependencies on demography. We show that including partial protection and lower transmission following primary infection is sufficient to capture more realistic reduced levels of buffering, in addition to changes in epidemic timing, across a range of partially and fully immunizing infections. Furthermore, our results identify key variables in this relationship, including R0.

The contribution of mitochondria to sensory processing and pain.

Mitochondria have a variety of essential functions within neurons including oxygen consumption, ATP generation, calcium buffering, and reactive oxygen species (ROS) generation. Despite extensive research into the contribution of mitochondrial function in other neurological disorders such as Parkinson's disease, the role of mitochondrial function in sensory processing and pain has been relatively unexplored until recent years. As this area of pain research is in its infancy, this review will be a descriptive summary-rather than a critical review-of data that suggests mitochondrial function/dysfunction as a causal or contributory mechanism of normal sensory processing and chronic pain. Evidence for mitochondrial dysfunction from both chronic pain patients and animal models of chronic pain will be described. Such evidence involves different aspects of mitochondria and their function including mitochondrial ultrastructure, distribution, oxygen consumption, oxidative phosphorylation, calcium buffering, ROS, and ATP levels. Most recently, substantial amounts of data have demonstrated mitochondrial involvement in painful peripheral neuropathies evoked by chemotherapy, diabetes, and HIV and these topics will be particularly highlighted in this review.

The impact of failure, repair and joint imbalance of processing time means and buffer sizes on the performance of unpaced production lines

This article studies the performance of unpaced serial production lines that are subject to breakdown and are imbalanced in terms of both of their processing time means (MTs) and buffer storage capacities (BCs). Simulation results show that the best pattern in terms of throughput is a balanced line With respect to average buffer level; the best configuration is a monotone decreasing MT order, together with an ascending BC arrangement. Statistical analysis shows that BC, combined patterns of MT and BC imbalance, line length and degree of imbalance all contribute significantly to performance. [...] Sabry Shaaban, Tom McNamara and Sarah Hudson

Real-time Bottleneck Detection and Prediction to Prioritize Fault Repair in Interlinked Production Lines

To identify the momentary bottleneck of serial production lines with finite buffers is still a challenge in the automobile industry. In literature there are already some detection methods. However, these methods lack the applicability for a real-time fault repair prioritization. A new method is being developed because of this disadvantage to detect the bottlenecks by analyzing the increase and decrease of buffer levels. This method has the benefit of detecting the real-time bottlenecks as well as giving a forecast bottleneck emerging in the near future by indicating the remaining time until a machine becomes one. The new fault repair prioritization method was validated in a material flow simulation of a production line. This simulation indicates a significant output increase. In the following steps, the new method is going to be implemented in a case study.

Capital buffers based on banks’ domestic systemic importance: selected issues

Purpose– The purpose of this paper is to assist the numerous regulators around the globe who are currently considering ways to impose domestic systemic importance-based capital requirements on banks.Design/methodology/approach– The article discusses in some detail a number of issues from the viewpoint of regulatory practice, mentioning relevant literature where available. Comments partly reflect the experience that the Czech National Bank gathered over the past two years while preparing its own regime of domestic systemic importance-based capital requirements on banks.Findings– The authors stress, among other points, one weakness of the (otherwise well-designed) method suggested by the Basel Committee for Banking Supervision (BCBS) for assessment of banks’ systemic importance: the method is “relative” in that it does not reflect the absolute importance of the banking sector for the economy. The paper also explains that in some cases, use of individual-level rather than consolidated-level data may be preferable, in contrast to what the BCBS guidance suggests. Further, implications of the buffers over a longer term are pointed out.Originality/value– As far as the authors are aware, this article is the first to comprehensively discuss the main issues surrounding both key steps (systemic importance assessment and determination of buffer level) in the process of introducing buffers based on domestic systemic importance. A number of questions related to these two steps are raised which regulators may appreciate to be reminded of, even if some of the questions are such that it is not possible to give a generally applicable answer to them.

Single pyruvate intake induces blood alkalization and modification of resting metabolism in humans

ObjectivesThree separate studies were performed with the aim to 1) determine the effect of a single sodium pyruvate intake on the blood acid-base status in males and females; 2) compare the effect of sodium and calcium pyruvate salts and establish their role in the lipolysis rate; and 3) quantify the effect of single pyruvate intake on the resting energy metabolism. MethodsIn all, 48 individuals completed three separate studies. In all the studies, participants consumed a single dose of pyruvate 0.1 g/kg 60 min before commencing the measurements. The whole blood pH, bicarbonate concentration, base excess or plasma glycerol, free fatty acids, glucose concentrations, or resting energy expenditure and calculated respiratory exchange ratio were determined. The analysis of variance for repeated measurements was performed to examine the interaction between treatment and time. ResultsThe single dose of sodium pyruvate induced blood alkalization, which was more marked in the male than in the female participants. Following the ingestion of sodium or calcium pyruvate, the blood acid-base parameters were higher than in the placebo trial. Furthermore, 3-h postingestion glycerol was lower in both pyruvate trials than in placebo. Resting energy expenditure did not differ between the trials; however, carbohydrate oxidation was increased after sodium pyruvate ingestion. ConclusionPyruvate intake induced mild alkalization in a sex-dependent fashion. Moreover, it accelerated carbohydrate metabolism and delayed the rate of glycerol appearance in the blood, but had no effect on the resting energy expenditure. Furthermore, sodium salt seems to have had a greater effect on the blood buffering level than calcium salt.

PENGARUH PENAMBAHAN NATRIUM KLORIDA (NaCl) DAN WAKTU PERENDAMAN BUFFER FOSFAT TERHADAP PEROLEHAN CRUDE PAPAIN DARI DAUN PEPAYA (CARICA PAPAYA, L.)

Papaya (Carica papaya L.) is one of the fruits of commodities internationally, either in the form of fresh fruit or as processed products. The leaves are green still not fully utilized. Papaya leaves contains papain enzyme which is a protease enzyme that very helpful for the industry. Papain is a protease enzyme contained in papaya latex, whether in fruit, stems and leaves, as an enzyme capable of solving the protein molecules, current papain into products that are beneficial to human life, either at home or industrial ladder. This study aims to determine the effect of the degree of saturation of sodium chloride and phosphate buffer to yield soaking rough papaya protease. This study varying the time of immersion phosphate buffer and saturation levels of sodium chloride. Analysis of protease activity was performed using UV-Vis spectrophotometer to measure the wavelength and absorbance values​​. The best research results obtained at 12 h immersion phosphate buffer with a concentration of sodium chloride 60% is 272.8222 unit / ml. In the analysis of the rendemen obtained by the best condition at the time of immersion phosphate buffer for 36 hours at a concentration of 90% is 43,5152%. In the analysis of moisture content obtained the best condition at the time of immersion of 36 hours at a concentration of 90% is 37.4266%.

MiRNA-based buffering of the cobblestone-lissencephaly-associated extracellular matrix receptor dystroglycan via its alternative 3'-UTR.

Many proteins are expressed dynamically during different stages of cellular life and the accuracy of protein amounts is critical for cell endurance. Therefore, cells should have a perceptive system that notifies about fluctuations in the amounts of certain components and an executive system that efficiently restores their precise levels. At least one mechanism that evolution has employed for this task is regulation of 3′-UTR length for microRNA targeting. Here we show that in Drosophila the microRNA complex miR-310s acts as an executive mechanism to buffer levels of the muscular dystrophy-associated extracellular matrix receptor dystroglycan via its alternative 3′-UTR. miR-310s gene expression fluctuates depending on dystroglycan amounts and nitric oxide signalling, which perceives dystroglycan levels and regulates microRNA gene expression. Aberrant levels of dystroglycan or deficiencies in miR-310s and nitric oxide signalling result in cobblestone brain appearance, resembling human lissencephaly type II phenotype.

Buffer allocation and preventive maintenance optimization in unreliable production lines

In this paper, we consider a serial production line consisting of $$n$$n unreliable machines with $$n-1$$n-1 buffers. The objective is to determine the optimal preventive maintenance policy and the optimal buffer allocation that will minimize the total system cost subject to a given system throughput level. We assume that the mean time between failure of all machines will be increased after performing periodic preventive maintenance. An analytical decomposition-type approximation is used to estimate the production line throughput. The optimal design problem is formulated as a combinatorial optimization one where the decision variables are buffer levels and times between preventive maintenance. To solve this problem, the extended great deluge algorithm is proposed. Illustrative numerical examples are presented to illustrate the model.

Do Higher Levels of Resilience Buffer the Deleterious Impact of Chronic Illness on Disability in Later Life?

In examining the ability of resilience, or the ability to navigate adversity in a manner that protects well-being, to buffer the impact of chronic disease onset on disability in later life, the authors tested 2 hypotheses: (a) People with greater levels of resilience will have lower levels of disability and (b) resilience will moderate the association between the onset of a new chronic condition and subsequent disability. This study used a sample of 10,753 Americans between the ages of 51 and 98, derived from 3 waves of the Health and Retirement Study (2006-2010). Ordinary least squares regression was used to estimate the impact of resilience on changes in disability (measured as difficulty with activities of daily living [ADLs] and instrumental activities of daily living [IADLs]) over a 2-year period using a simplified resilience score. Resilience protects against increases in ADL and IADL limitations that are often associated with aging. Resilience mitigates a considerable amount of the deleterious consequences related to the onset of chronic illness and subsequent disability. Our results support our hypotheses and are consistent with claims that high levels of resilience can protect against the negative impact of disability in later life.

Economic Capital Modeling Closed Form Approximation for Real-Time Applications

Economic capital (ECap) modeling is a fundamental part of Pillar II of the Basel framework. Indeed, 'sophisticated' financial institutions need to have in place internal models for the assessment of the level of the overall capital buffer which is deemed sufficient to cover the risk of their business activities. On top, ECap models are also frequently used for pricing purposes on an ex-ante basis: financial institutions need to know the incremental economic capital (IECap), i.e. the size by which the overall capital buffer needs to be increased after addition of e.g. a single new loan to the existing portfolio. This is important in order to be able to price such additional loan accordingly. Finally, ECap contributions (ECapC) are also required ex-post in order to break down the overall capital buffer to the individual obligors, products etc. within the portfolio. Simulation of IECap and ECapC can be computationally expensive and unstable, but it appears that closed form approximations provide accurate, consistent and quick solutions in many cases. The formula introduced here is based on the multi-factor approximation from [Pykhtin, 2004] applicable to a default-mode Merton type model. As such, default correlations between obligors (stemming from a multi-factor-model) are taken into account, but the formula also captures specific amortization schedules and loss given default (LGD) values for each individual position -- a feature which is of practical relevance, but often neglected in standard default-mode models. For the time being, credit-risk mitigants such as the existence of guarantors on individual loans, are not captured by the formula, neither are credit migrations or correlations between default probabilities and LGDs. Our formula allows for approximation of all ECap contributions without extra computational cost. After calculation of the ECap of the original portfolio, IECap can be computed within few seconds and more accurately than in standard linear approximations based on ECap contributions.

Genetic strategies for probing conscientiousness and its relationship to aging.

Conscientiousness is an important trait for understanding healthy aging. The present article addresses how behavioral and molecular genetics methodologies can aid in furthering explicating the link between conscientiousness and aspects of health and well-being in later life. We review the etiology of conscientiousness documented by both quantitative and molecular genetics methods. We also discuss the ways behavior genetics can be used to continue to help refine the concept of conscientiousness and to help identify points of etiological overlap between conscientiousness and healthy aging outcomes. Phenotypic research has established nontrivial associations between conscientiousness and important outcomes, but behavior genetic methods can determine what the causal (genetic and environmental) mechanisms are behind these relationships. An empirical example of one of these techniques is provided using twin data from the Midlife in the United States (MIDUS) study. We demonstrate that conscientiousness moderates genetic and environmental influences on problem alcohol use, such that greater levels of conscientiousness buffer against the random effects of the environment. Finally, suggestions for future work in this area are discussed.

Mean time imbalance effects on unreliable unpaced serial flow lines

This paper investigates the benefits of deliberately unbalancing operation time means for unreliable non-automated production lines. The lines were simulated with various line lengths, buffer capacities, degrees of imbalance and patterns of imbalance. Data on two performance measures, namely throughput and average buffer level were gathered, analyzed and compared to a balanced line counterpart. A number of conclusions were made with respect to the ranking of configurations, as well as to the relationships among the independent design parameters and the dependent variables. It was found that the best configurations are a balanced line arrangement and a monotone decreasing order, with the first generally resulting in lower throughput and the second leading to lower average buffer levels than those of a balanced line. Preliminary results show that unbalanced lines cope well with unreliability.

Positive Affect Protects Against Deficient Safety Learning During Extinction of Fear of Movement-Related Pain in Healthy Individuals Scoring Relatively High on Trait Anxiety

From a treatment perspective, it is highly relevant to pinpoint individual vulnerability factors for resistance to exposure treatment in highly fearful chronic pain patients. Previous fear conditioning research showed that healthy individuals scoring relatively high on trait anxiety display sustained fear to safety cues during extinction. In the context of fear of movement-related pain, this intriguing question has been largely neglected so far. Even more importantly, positive psychological traits such as trait positive affect may function as protective factors against the spreading of fear to safe movements and improve exposure treatment outcomes. In this study, healthy participants completed a trait anxiety and trait positive affect questionnaire and underwent acquisition and extinction of fear of movement-related pain using an experimental voluntary movement paradigm. During acquisition, one movement (CS+) was paired with a painful stimulus and another movement was not (CS−). During extinction, the CS+ was no longer reinforced. Results show failure of fear inhibition to the CS− during extinction in healthy individuals scoring relatively high on trait anxiety or relatively low on positive affect. These findings seem to suggest that safety learning is more vulnerable in healthy people with a high anxious disposition and/or relatively lower levels of positive affect. In addition, this is the first study to show that the negative impact of high trait anxiety on fear inhibition to safety cues during extinction can be countered by high levels of positive affect. These findings may have important clinical implications. PerspectiveBoth low positive affect and high trait anxiety are associated with impaired fear inhibition to nonpainful movements during fear extinction. Interestingly, high levels of positive affect buffer against the negative impact of trait anxiety. Increasing positive affect during exposure may counter the effects of trait vulnerabilities and improve treatment outcomes.