Batch Transfers Research Articles

Microalgae adaptation as a strategy to recycle the aqueous phase from hydrothermal liquefaction

Hydrothermal liquefaction (HTL) produces bio-crude oil from wet algae along with an aqueous phase (AP). This effluent contains minerals that can be reused for cultivating new microalgae but whose utility remains limited due to the presence of inhibitors. Reduced photosynthetic performance, growth, and null lipid accumulation were observed in wild-type Chlorella vulgaris NIES 227 cultivated in AP (1/200). Adaptive laboratory evolution was studied by batch transfers and turbidostat mode. Both methods effectively counterbalanced AP toxicity and restored the fitness of the microalgae. After adaptation, a higher AP addition was achieved, from 1/600 to 1/200, without inhibition. As compared with the wild typein control medium (0.261 g/L/d), both adapted-strains maintained competitive productivity (0.310 and 0.258 g/L/d) of lipid-rich biomass (37 %–56 %). The improved tolerance of the adapted strains persisted after the removal of AP and under axenic conditions. Adaptive laboratory evolution is suggested for AP reutilization in the algae production process.

Sustainable Interoperability among Biological Collections and their Computing Platforms

Integration and interoperability have been persistent drivers of biocollections software innovation for over 40 years—both within the biodiversity community and to the outside with external linkages to broader computing initiatives. Currently, global-scale "real-time" data integration is an aspirational dream, mostly constrained by cost and by being technically much more demanding than can generally be supported with current levels of investment and expertise. Today the collections community shuffles along relying on web portals for data discovery, and multi-step, batch transfers of species occurrence data for aggregation. With sufficient resources and collaboration, much more seamless integration and data fluidity are possible. The digital specimen architecture being planned by DiSSCo (The Distributed System of Scientific Collections) promises to re-invent the ways in which institutions curate, improve, and share their collections' data, by transforming the pipelines and methods with which specimen and related information will frictionlessly course among them. With robust integration of applications running on local systems (desktops, laptops, phones), that architecture will ultimately greatly advance the ease of rapidly assembling and updating custom distributed databases for research, education, and outreach. This presentation will touch on the future of collections community data integration and interoperability from the perspective of sustainability with allusions to the experience we have had with Specify Collections Consortium. Long-term revenue support models, actual financial stakeholders, widespread implementation of robust services behind Application Programming Interfaces (APIs), co-dependent collaborations on open source software infrastructure, unprecedented levels of technical coordination, and last but not least, quickly-evolving data standards will all be key resources needed to trek out of our current data landscape to reach the next plateau of biocollections computing.

Benefits of a Recombination-Proficient Escherichia coli System for Adaptive Laboratory Evolution.

Over 80 years ago Fisher and Muller began a debate on the origins of sexual recombination. Although many aspects of sexual recombination have been examined at length, experimental evidence behind the behaviors of recombination in many systems and the means to harness it remain elusive. In this study, we sought to experimentally validate some advantages of recombination in typically asexual Escherichia coli and determine if a sexual strain of E. coli can become an effective tool for strain development.

Conditions for a product-form stationary distribution of one queueing system with batch transfers and a disaster flow

We consider an open exponential network with two types of arrival flows at the network nodes: a message flow and a disaster flow. Messages arriving at the nodes form batches of customers of a random size. A disaster arrival at a node completely empties the queue at the node if it is nonempty and has no effect otherwise. Customers are served in batches of a random size. After a batch is served at a node, the batch quits the network and, according to a routing matrix, either sends a message or a disaster to another node or does not send anything. We find conditions for the stationary distribution of the network state probabilities to be represented as a product of shifted geometric distributions.

Tritium Assay and Dispensing in TriMARS

The tritium metering, assay, recovery and storage (TriMARS) facility of KEPCO Research Institute has been installed to develop expertise in the tritium handling technology and to support the tritium control system in Korea. The major systems and equipment of the facility consisted of a tritium assaying and dispensing system, a tritium recovery system, a purge gas recombiner system, a tritium calorimeter, a gas chromatograph, tritium monitors, a high integrity glove box and air purged enclosures. The annual tritium usage is restricted below 11.5 PBq of tritium. The tritium dispensing and loading would be carried out by batch transfers. Tritium metering is based on accurate pressure-volume-temperature measurements and GC analysis. Three metering tanks were provided to measure 0.37 TBq to 185 TBq of T2 gas at sub-atmospheric pressure. Three uranium beds were installed to store tritium from outside and to recover the tritium residual of process equipment in the facility. Tritium recovery systems, secondary enclosures and tritium monitors were provided to protect workers from tritium exposure. For tritium accountancy for all shipments in and out at the facility, a dedicated twin cell tritium calorimeter was installed and demonstrated.

Integrated Process Gas Modeling for Tritium Systems at the Savannah River Site

Significant savings are being realized from the consolidated tritium gas-processing operations at the Savannah River Site. However, the trade-off is some reduction of operational flexibility due to decreased storage capacity for process and waste gases. Savannah River National Laboratory researchers are developing an integrated process gas model for tritium processing using Aspen Custom ModelerTM (ACM) software. The modeling involves fully characterizing process flow streams (gas composition, quantity), frequency of batch transfers, and availability of equipment in the flow stream. The model provides a valuable engineering tool to identify flow bottlenecks, thereby enabling adjustments to be made to improve process operations.

Decentralized multi-product multi-stage systems with backorders

A multi-stage production/inventory system with decentralized two-card kanban control policies producing multiple product types is considered. The system involves one-at-a-time processing at each stage, finite target levels in the buffers and batch transfers between production stages. The demand process for each product is assumed to be Poisson and excess demand is backordered. Products have a priority structure and the processor at each stage is shared according to a switching rule. Our objective is to obtain steady-state performance measures such as the average inventory and service levels for each product type. We propose an approximation algorithm based on: (i) characterization of the delay by a product type before receiving the processor's attention at each stage; and (ii) creation of subsystems for all the storage activity and phase-type modeling of the remaining system's behavior. Numerical examples are presented to show the accuracy of the method and its potential use in system design.

Analysis of decentralized multi‐product pull systems with lost sales

AbstractWe study a pull‐type, flexible, multi‐product, and multi‐stage production/inventory system with decentralized two‐card kanban control policies. Each stage involves a processor and two buffers with finite target levels. Production stages, arranged in series, can process several product types one at a time. Transportation of semi‐finished parts from one stage to another is performed in fixed lot sizes. The exact analysis is mathematically intractable even for smaller systems. We present a robust approximation algorithm to model two‐card kanban systems with batch transfers under arbitrary complexity. The algorithm uses phase‐type modeling to find effective processing times and busy period analysis to identify delays among product types in resource contention. Our algorithm reduces the effort required for estimating performance measures by a considerable margin and resolves the state–space explosion problem of analytical approaches.Using this analytical tool, we present new findings for a better understanding of some tactical and operational issues. We show that flow of material in small procurement sizes smoothes flow of information within the system, but also necessitates more frequent shipments between stages, raising the risk of late delivery. Balancing the risk of information delays vis‐à‐vis shipment delays is critical for the success of two‐card kanban systems. Although product variety causes time wasted in setup operations, it also facilitates relatively short production cycles enabling processors to switch from one product type to another more rapidly. The latter point is crucial especially in high‐demand environments. Increasing production line size prevents quick response to customer demand, but it may improve system performance if the vendor lead‐time is long or subject to high variation. Finally, variability in transportation and processing times causes the most damage if it arises at stages closer to the customer. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007

Approximate Analysis of Decentralized, Multi-Stage, Pull-Type Production/Inventory Systems

We consider a decentralized, pull-type manufacturing system with each stage having its own input and output stock keeping activities. Material handling between stages is carried out according to a fixed quantity, non-constant withdrawal cycle. We approximate the system behavior using a two-node decomposition approach, which decomposes the system into smaller subsystems. The analysis of two-node subsystems is achieved using a matrix-recursive approach due to phase-type modeling of certain random variables. Our solution algorithm resolved a major difficulty (due to batch transfers) in the analytical approach to study multi-stage manufacturing systems. We also discuss system behavior and suggest several rules-of-thumb to improve system performance.

Predicting Mixing Volumes in Serial Transport in Pipelines

This paper presents a model for predicting the contaminated mixing volume arising in pipeline batch transfers without physical separators. The proposed technique represents an improvement over the existing methods since it takes into account time-dependent flow rates and accurate concentration-varying axial dispersion coefficients. The governing equation of the model forms a nonlinear boundary-value problem that is solved by a finite element method coupled to the Newton’s method. A comparison among the theoretical predictions of this method, a field test, and other classical procedures show that the proposed method exhibits the best estimate over the whole range of admissible concentrations investigated.

Optimal Policies for Multi-Echelon Inventory Problems with Batch Ordering

In many production/distribution systems, materials flow from one stage to another in fixed lot sizes. For example, a retailer orders a full truckload from a manufacturer to qualify for a quantity discount; a factory has a material handling system that moves full containers of parts from one production stage to the next. In this paper, we derive optimal policies for multi-stage serial and assembly systems where materials flow in fixed batches. The optimal policies have a simple structure, and their parameters can be easily determined. This research extends the multi-echelon inventory theory in several ways. It generalizes the Clark-Scarf model by allowing batch transfers of inventories. Rosling (1989) shows that assembly systems can be interpreted as serial systems under the assumption that there are no setup costs. We show that the series interpretation still holds when materials flow in fixed batches which satisfy a certain regularity condition. Finally, Veinott (1965) identifies an optimal policy for a single-location inventory system with batch ordering. This paper generalizes his result to multi-echelon settings.

Partial balances in batch arrival batch service and assemble-transfer queueing networks

Recently Miyazawa and Taylor (1997) proposed a new class of queueing networks with batch arrival batch service and assemble-transfer features. In such networks customers arrive and are served in batches, and may change size when a batch transfers from one node to another. With the assumption of an additional arrival process at each node when it is empty, they obtain a simple product-form steady-state probability distribution, which is a (stochastic) upper bound for the original network. This paper shows that this class of network possesses a set of non-standard partial balance equations, and it is demonstrated that the condition of the additional arrival process introduced by Miyazawa and Taylor is there precisely to satisfy the partial balance equations, i.e. it is necessary and sufficient not only for having a product form solution, but also for the partial balance equations to hold.

Partial balances in batch arrival batch service and assemble-transfer queueing networks

Recently Miyazawa and Taylor (1997) proposed a new class of queueing networks with batch arrival batch service and assemble-transfer features. In such networks customers arrive and are served in batches, and may change size when a batch transfers from one node to another. With the assumption of an additional arrival process at each node when it is empty, they obtain a simple product-form steady-state probability distribution, which is a (stochastic) upper bound for the original network. This paper shows that this class of network possesses a set of non-standard partial balance equations, and it is demonstrated that the condition of the additional arrival process introduced by Miyazawa and Taylor is there precisely to satisfy the partial balance equations, i.e. it is necessary and sufficient not only for having a product form solution, but also for the partial balance equations to hold.

A Geometric Product-Form Distribution for a Queueing Network by Non-Standard Batch Arrivals and Batch Transfers

We introduce a batch service discipline, called assemble-transfer batch service, for continuous-time open queueing networks with batch movements. Under this service discipline a requested number of customers is simultaneously served at a node, and transferred to another node as, possibly, a batch of different size, if there are sufficient customers there; the node is emptied otherwise. We assume a Markovian setting for the arrival process, service times and routing, where batch sizes are generally distributed. Under the assumption that extra batches arrive while nodes are empty, and under a stability condition, it is shown that the stationary distribution of the queue length has a geometric product form over the nodes if and only if certain conditions are satisfied for the extra arrivals. This gives a new class of queueing networks which have tractable stationary distributions, and simultaneously shows that the product form provides a stochastic upper bound for the stationary distribution of the corresponding queueing network without the extra arrivals.

A Geometric Product-Form Distribution for a Queueing Network by Non-Standard Batch Arrivals and Batch Transfers

We introduce a batch service discipline, called assemble-transfer batch service, for continuous-time open queueing networks with batch movements. Under this service discipline a requested number of customers is simultaneously served at a node, and transferred to another node as, possibly, a batch of different size, if there are sufficient customers there; the node is emptied otherwise. We assume a Markovian setting for the arrival process, service times and routing, where batch sizes are generally distributed.Under the assumption that extra batches arrive while nodes are empty, and under a stability condition, it is shown that the stationary distribution of the queue length has a geometric product form over the nodes if and only if certain conditions are satisfied for the extra arrivals. This gives a new class of queueing networks which have tractable stationary distributions, and simultaneously shows that the product form provides a stochastic upper bound for the stationary distribution of the corresponding queueing network without the extra arrivals.