Joint order batching and picker routing in single and multiple-cross-aisle warehouses using cluster-based tabu search algorithms

The organization of order picking operations is one of the most critical issues in warehouse management. In this paper, novel tabu search (TS) algorithms integrated with a novel clustering algorithm are proposed to solve the order batching and picker routing problems jointly for multiple-cross-aisle warehouse systems. A clustering algorithm that generates an initial solution for the TS algorithms is developed to provide fast and effective solutions to the order-batching problem. Unlike most common picker routing heuristics, we model the routing problem of pickers as a classical TSP and propose efficient Nearest Neighbor+Or-opt and Savings+2-Opt heuristics to meet the specific features for the problem. Various problem instances including the number of orders, weight of items, and picking coordinates are generated randomly, and detailed numerical experiments are carried out to evaluate the performances of the proposed methods. In conclusion, the TS algorithms come out to be the most efficient methods in terms of solution quality and computational efficiency.     

A heuristic based batching and assigning method for online customer orders

In an online order picking system, customer orders arrive in real time and the picking information is updated dynamically. One challenging problem is how to process customer orders in a timely manner. In this paper, a nonparametric heuristic method, Green Area, is presented to address the real-time online order batching problems. By nonparametric, we mean that our method is independent of the parameters of a warehouse layout and the characteristics of customer orders; these parameters facilitates the implementation in real life. The advantages of this method are verified under different scenarios by simulations. Specifically, the influences of the arrival rate, the number of order pickers and the number of orders in the order service time are discussed. The results demonstrate that the Green Area method leads to shorter order service times than traditional methods for optimal batch sizes. Finally, we demonstrate that the Green Area method can be applied to online order picking systems with variable arrival rates.     

ASOCEM: Automatic Segmentation Of Contaminations in cryo-EM

Particle picking is currently a critical step in the cryo-electron microscopy single particle reconstruction pipeline. Contaminations in the acquired micrographs severely degrade the performance of particle pickers, resulting in many “non-particles” in the collected stack of particles. In this paper, we present ASOCEM (Automatic Segmentation Of Contaminations in cryo-EM), an automatic method to detect and segment contaminations, which requires as an input only the approximate particle size. In particular, it does not require any parameter tuning nor manual intervention. Our method is based on the observation that the statistical distribution of contaminated regions is different from that of the rest of the micrograph. This nonrestrictive assumption allows to automatically detect various types of contaminations, from the carbon edges of the supporting grid to high contrast blobs of different sizes. We demonstrate the efficiency of our algorithm using various experimental data sets containing various types of contaminations. ASOCEM is integrated as part of the KLT picker (Eldar et al., 2020) and is available at https://github.com/ShkolniskyLab/kltpicker2.     

Comparison of a batch, fed-batch and continuously operated stirred-tank reactor for the enzymatic synthesis of (R)-mandelonitrile by using a process model

The suitability of a batch, fed-batch and continuously operated stirred-tank reactor for the enzymatic production of (R)-mandelonitrile in an aqueous-organic biphasic system was investigated by using a process model. The considered biphasic system is 10-50% (v/v) 100 mM sodium citrate buffer of pH 5.5 dispersed in methyl tert-butyl ether. The constraints were that 750 moles of benzaldehyde per cubic meter should react towards (R)-mandelonitrile with an enantiomeric excess of 99% and a conversion of 98%. A continuously operated stirred-tank reactor could not meet the constraints, but the production in a batch or fed-batch reactor was feasible. The choice for a batch or fed-batch reactor is dependent on the influence of the costs for reactor operation and for the enzyme on the product costs. The choice for operating at a small or large aqueous-phase volume fraction is dependent on the costs and reusability of the enzyme. The volumetric productivity is maximal when operating as batch. The enzymatic productivity and turnover are maximal when operating as fed batch. In the fed-batch mode, the enzymatic productivity increased by 24-37%, the turnover increased by 50-60% and the volumetric productivity decreased by 33-71% as compared to a batch reactor. By enhancement of mass transfer both the volumetric and enzymatic productivity can be increased considerably, while the turnover is only slightly decreased.     

Methyl eugenol and cue-lure traps for suppression of male oriental fruit flies and melon flies (Diptera: Tephritidae) in Hawaii: effects of lure mixtures and weathering

Methyl eugenol (4-allyl-1,2-dimethoxybenzene-carboxylate) and cue-lure [4-(p-acetoxyphenyl)-2-butanone] are highly attractive kairomone lures to oriental fruit fly, Bactrocera dorsalis (Hendel), and melon fly, B. cucurbitae (Coquillett), respectively. Plastic bucket traps were evaluated as dispensers for methyl eugenol and cue-lure for suppression of the 2 fruit flies in Hawaii. Methyl eugenol and cue-lure mixtures were compared with pure methyl eugenol or cue-lure over 4 seasons. B. dorsalis captures differed significantly with treatment and season. B. dorsalis captures with 100% methyl-eugenol were significantly greater than all other treatments (25, 50, and 75%). B. cucurbitae captures also differed significantly with treatment but not with season. Captures with 100, 75, and 50% cue-lure were not significantly different. Bucket traps baited with cue-lure (+ malathion) and weathered under Hawaiian climatic conditions were attractive to B. cucurbitae up to 8 wk. Two methyl eugenol dispensers (canec disks and Min-U-Gel) were compared with bucket traps. Dispensers (methyl eugenol + malathion) were weathered for 2-16 wk under Hawaiian climatic conditions and bioassayed during summer and winter. Initially, captures of B. dorsalis were not significantly different for the 3 dispensers. Bucket traps and canec disks were most resistant to weather, remaining attractive to B. dorsalis flies up to 16 wk. Min-U-Gel was least resistant, losing attractiveness to B. dorsalis flies within 2 wk. On the basis of performance, bucket traps and canec disks were equally long-lived up to 14 wk; thereafter, bucket traps were slightly more attractive during winter. Canec disks were cheapest, but on the basis of possible environmental concerns, bucket traps may be the best all-around choice for areawide suppression of fruit flies.     

Linking cranial morphology to prey capture kinematics in three cleaner wrasses: Labroides dimidiatus,Larabicus quadrilineatus,and Thalassoma lutescens

Cleaner fishes are well known for removing and consuming ectoparasites off other taxa. Observers have noted that cleaners continuously “pick” ectoparasites from the bodies of their respective client organisms, but little is known about the kinematics of cleaning. While a recent study described the jaw morphology of cleaners as having small jaw‐closing muscles and weak bite forces, it is unknown how these traits translate into jaw movements during feeding to capture and remove ectoparasites embedded in their clients. Here, we describe cranial morphology and kinematic patterns of feeding for three species of cleaner wrasses. Through high‐speed videography of cleaner fishes feeding in two experimental treatments, we document prey capture kinematic profiles for Labroides dimidiatus, Larabicus quadrilineatus, and Thalassoma lutescens. Our results indicate that cleaning in labrids may be associated with the ability to perform low‐displacement, fast jaw movements that allow for rapid and multiple gape cycles on individually targeted items. Finally, while the feeding kinematics of cleaners show notable similarities to those of “picker” cyprinodontiforms, we find key differences in the timing of events. In fact, cleaners generally seem to be able to capture prey twice as fast as cyprinodontiforms. We thus suggest that the kinematic patterns exhibited by cleaners are indicative of picking behavior, but that “pickers” may be more kinematically diverse than previously thought. J. Morphol. 276:1377–1391, 2015. © 2015 Wiley Periodicals, Inc.     

Batch sizes and lead-time performance in flexible manufacturing systems

Production lead-time performance in flexible manufacturing systems is influenced by several factors which include: machine groupings, demand rates, machine processing rates, product batching, material handling system capacity, and so on. Hence, control of lead-time performance can be affected through the manipulation of one or more of these variables. In this article, we investigate the potential of batch sizing as a control variable for lead-time performance through the use of a queueing network model. We establish a functional relationship between the two variables, and incorporate the relationship in an optimization model to determine the optimal batch size(s) which minimizes the sum of annual work-in-process inventory and final inventory costs. The nonlinear batch sizing problem which results is solved by discrete optimization via marginal analysis. Results show that batch sizing can be a cheap and effective variable for controlling flexible manufacturing system throughput.     

Precultures Grown under Fed‐Batch Conditions Increase the Reliability and Reproducibility of High‐Throughput Screening Results

One essential task in bioprocess development is strain selection. A common screening procedure consists of three steps: first, the picking of colonies; second, the execution of a batch preculture and main culture, e.g., in microtiter plates (MTPs); and third, the evaluation of product formation. Especially during the picking step, unintended variations occur due to undefined amounts and varying viability of transferred cells. The aim of this study is to demonstrate that the application of polymer‐based controlled‐release fed‐batch MTPs during preculture eliminates these variations. The concept of equalizing growth through fed‐batch conditions during preculture is theoretically discussed and then tested in a model system, namely, a cellulase‐producing Escherichia coli clone bank containing 32 strains. Preculture is conducted once in the batch mode and once in the fed‐batch mode. By applying the fed‐batch mode, equalized growth is observed in the subsequent main culture. Furthermore, the standard deviation of cellulase activity is reduced compared to that observed in the conventional approach. Compared with the strains in the batch preculture process, the first‐ranked strain in the fed‐batch preculture process is the superior cellulase producer. These findings recommend the application of the fed‐batch MTPs during preculture in high‐throughput screening processes to achieve accurate and reliable results.     

Unstructured model for L-lysine fermentation under controlled dissolved oxygen

An unstructured model was developed for batch cultivation of Corynebacterium lactofermentum (ATCC 21799) under controlled dissolved oxygen. The model is capable of predicting batch experiments performed at various initial substrate concentrations. By extending the batch culture model to a fed-batch model and using a heuristic approach to optimize the fed-batch cultivation, it is shown that fed-batch cultivation is superior to batch operation due to increased productivity at high substrate concentrations.     

Modeling retrovirus production for gene therapy. 1. Determination Of optimal bioreaction mode and harvest strategy

Although retroviruses are a promising tool for gene therapy, there are two major problems limiting the establishment of viable industrial processes: retrovirus stability and low final yield in the supernatant. This fact emphasizes the need for an effective process optimization, not only at a genetic level but also at a bioprocess engineering level. In part 1 of this paper a mathematical model was developed to optimize the bioreaction yield by determining the best retrovirus harvest strategy in perfusion cultures. PA317 cells producing recombinant retroviruses were used to develop and test this model. Cell culture was performed in stirred tanks using porous supports. The parameters of the proposed model were experimentally determined for batch and perfusion cultures at 32 and 37 degrees C both with and without additives to enhance production; the model was then validated. This model allowed the determination of the optimal values of all operational variables included: batch and perfusion duration and perfusion rate. The highest productivity (2682 virus cm(-)(3) h(-)(1)) was obtained under the following conditions: batch at 37 degrees C for 53 h followed by perfusion at 32 degrees C for 23 h with a perfusion rate of 0.107 h(-)(1). This value was 3.5-fold higher than the best result obtained in batch cultures for the same conditions of titer and quality. A sensitivity analysis of the parameters showed that the parameters that affect most the final productivity depend on the bioreaction phase: cell growth in batch culture and production and product degradation in perfusion culture. In part 2 of this paper, this model is extended to the first step of downstream processing, and the addition of further steps to the process is discussed in order to achieve global process optimization.     

Order Release and Product Mix Coordination in a Complex PCB Manufacturing Line with Batch Processors

In this paper, we study the role of order releases and product mix coordination in a complex manufacturing line with batch processors. We develop a planning methodology for synchronizing production in such manufacturing lines and discuss the decision-making process in the context of a PCB production environment at Northern Telecom's Fiberworld Division. The planning methodology includes developing mathematical programming models for determining a configuration of batch processors, order releases to the shop floor, and daily loading decisions at the batch processors. The optimization models are linked to a simulation model of the shop, which provides key statistics like lead time, work in process, and utilization rates. The objective is to reduce lead time for manufacturing different products in this environment while meeting the demand. We analyze the performance of such a line, study the efficacy of various types of shop floor synchronization policies, and establish the role of batch processors in managing such complex lines effectively. We exhibit how batch processors (which are bottleneck operations) could be scheduled effectively to incorporate the logical constraints that govern their operations and react to variabilities in the manufacturing line.     

Maximizing interferon-gamma production by Chinese hamster ovary cells through temperature shift optimization: experimental and modeling

The Chinese hamster ovary (CHO) cell line producing interferon-gamma (IFN-gamma) exhibits a 2-fold increase in specific productivity when grown at 32 degrees C compared to 37 degrees C. Low temperature also causes growth arrest, meaning that the cell density is significantly lower at 32 degrees C, nutrients are consumed at a slower rate and the batch culture can be run for a longer period of time prior to the onset of cell death. At the end of the batch, product concentration is doubled at the low temperature. However, the batch time is nearly doubled as well, and this causes volumetric productivity to only marginally improve by using low temperature. One approach to alleviate the problem of slow growth at low temperature is to utilize a biphasic process, wherein cells are cultured at 37 degrees C for a period of time in order to obtain reasonably high cell density and then the temperature is shifted to 32 degrees C to achieve high specific productivity. Using this approach, it is hypothesized that IFN-gamma volumetric productivity would be maximized. We developed and validated a model for predicting the optimal point in time at which to shift the culture temperature from 37 degrees C to 32 degrees C. It was found that by shifting the temperature after 3 days of growth, the IFN-gamma volumetric productivity is increased by 40% compared to growth and production at 32 degrees C and by 90% compared to 37 degrees C, without any decrease in total production relative to culturing at 32 degrees C alone. The modeling framework presented here is applicable for optimizing controlled proliferation processes in general.     

Multi-stage high cell continuous fermentation for high productivity and titer

We carried out the first simulation on multi-stage continuous high cell density culture (MSC-HCDC) to show that the MSC-HCDC can achieve batch/fed-batch product titer with much higher productivity to the fed-batch productivity using published fermentation kinetics of lactic acid, penicillin and ethanol. The system under consideration consists of n-serially connected continuous stirred-tank reactors (CSTRs) with either hollow fiber cell recycling or cell immobilization for high cell-density culture. In each CSTR substrate supply and product removal are possible. Penicillin production is severely limited by glucose metabolite repression that requires multi-CSTR glucose feeding. An 8-stage C-HCDC lactic acid fermentation resulted in 212.9 g/L of titer and 10.6 g/L/h of productivity, corresponding to 101 and 429% of the comparable lactic acid fed-batch, respectively. The penicillin production model predicted 149% (0.085 g/L/h) of productivity in 8-stage C-HCDC with 40 g/L of cell density and 289% of productivity (0.165 g/L/h) in 7-stage C-HCDC with 60 g/L of cell density compared with referring batch cultivations. A 2-stage C-HCDC ethanol experimental run showed 107% titer and 257% productivity of the batch system having 88.8 g/L of titer and 3.7 g/L/h of productivity. MSC-HCDC can give much higher productivity than batch/fed-batch system, and yield a several percentage higher titer as well. The productivity ratio of MSC-HCDC over batch/fed-batch system is given as a multiplication of system dilution rate of MSC-HCDC and cycle time of batch/fed-batch system. We suggest MSC-HCDC as a new production platform for various fermentation products including monoclonal antibody.     

The effect of degree and timing of nitrogen limitation on lipid productivity in Chlorella vulgaris

Improvements in lipid productivity would enhance the economic feasibility of microalgal biodiesel. In order to optimise lipid productivity, both the growth rate and lipid content of algal cells must be maximised. The lipid content of many microalgae can be enhanced through nitrogen limitation, but at the expense of biomass productivity. This suggests that a two-stage nitrogen supply strategy might improve lipid productivity. Two different nitrogen supply strategies were investigated for their effect on lipid productivity in Chlorella vulgaris. The first was an initial nitrogen-replete stage, designed to optimise biomass productivity, followed by nitrogen limitation to enhance lipid content (two-stage batch) and the second was an initial nitrogen-limited stage, designed to maximise lipid content, followed by addition of nitrogen to enhance biomass concentration (fed-batch). Volumetric lipid yield in nitrogen-limited two-stage batch and fed-batch was compared with that achieved in nitrogen-replete and nitrogen-limited batch culture. In a previous work, maximum lipid productivity in batch culture was found at an intermediate level of nitrogen limitation (starting nitrate concentration of 170 mg L^?1). Overall lipid productivity was not improved by using fed-batch or two-stage culture strategies, although these strategies showed higher volumetric lipid concentrations than nitrogen-replete batch culture. The dilution of cultures prior to nitrogen deprivation led to increased lipid accumulation, indicating that the availability of light influenced the rate of lipid accumulation. However, dilution did not lead to increased lipid productivity due to the resulting lower biomass concentration.     

Peak picking multidimensional NMR spectra with the contour geometry based algorithm CYPICK

The automated identification of signals in multidimensional NMR spectra is a challenging task, complicated by signal overlap, noise, and spectral artifacts, for which no universally accepted method is available. Here, we present a new peak picking algorithm, CYPICK, that follows, as far as possible, the manual approach taken by a spectroscopist who analyzes peak patterns in contour plots of the spectrum, but is fully automated. Human visual inspection is replaced by the evaluation of geometric criteria applied to contour lines, such as local extremality, approximate circularity (after appropriate scaling of the spectrum axes), and convexity. The performance of CYPICK was evaluated for a variety of spectra from different proteins by systematic comparison with peak lists obtained by other, manual or automated, peak picking methods, as well as by analyzing the results of automated chemical shift assignment and structure calculation based on input peak lists from CYPICK. The results show that CYPICK yielded peak lists that compare in most cases favorably to those obtained by other automated peak pickers with respect to the criteria of finding a maximal number of real signals, a minimal number of artifact peaks, and maximal correctness of the chemical shift assignments and the three-dimensional structure obtained by fully automated assignment and structure calculation.     

Lactic acid production from lactose in batch culture: analysis of the data with the help of a mathematical model; relevance for nitrogen source and preculture assessment

Batch fermentation performances are usually optimized on the basis of an overall criterion, the mean volumetric productivity. For lack of more suitable criteria, a great number of experiments have to be carried out under various conditions, in order to identify the factors acting on product formation rate. With the help of a mathematical model, every batch fermentation is quantitatively described by a set of parameters, so the reason of every improvement observed for the fermentation productivity is easy to recognize. Therefore, such a model appears to be an invaluable tool for finding quickly and at lower expense the optimal conditions. Nitrogen supplementation and inoculum preparation for lactobacilli growing on whey and whey permeate have been assessed with the help of a new mathematical model. Correspondence to: Y. Prigent     

Enhanced continuous production of lovastatin using pellets and siran supported growth of Aspergillus terreus in an airlift reactor

Lovastatin, a hypocholesterolemic agent, is a secondary metabolite produced by filamentous microorganism Aspergillus terreus in submerged batch cultivation. Lovastatin production by pellets and immobilized siran cells was investigated in an airlift reactor. The process was carried out by submerged cultivation in continuous mode with the objective of increasing productivity using pellet and siran supported growth of A terreus. The continuous mode of fermentation improves the rate of lovastatin production. The effect of dilution rate and aeration rate were studied in continuous culture. The optimum dilution rate for pellet was 0.02 h⁻¹ and for siran carrier was 0.025 h⁻¹. Lovastatin productivity using immobilized siran carrier (0.0255 g/L/h) was found to be greater than pellets (0.022 g/L/h). The productivity by both modes of fermentation was found higher than that of batch process which suggests that continuous cultivation is a promising strategy for lovastatin production.     

Run-to-run fed-batch optimization for protein production using recombinant Escherichia coli

A two-phase design approach is introduced to determine the optimal feed rate, fed glucose concentration and fermentation time to maximize protein productivity using recombinant Escherichia coli BL21 (pBAW2) strain. The first phase is applied to determine a primary S-system kinetic model using batch time-series data. Two runs were carried out in the second phase to achieve the maximum protein productivity for the fed-batch fermentation process. The computational results using the S-system kinetic model obtained from the second run are in better agreement with the experiments than those using the kinetic model obtained from batch time-series data. For cross-validation, two extra fed-batch experiments with different feed strategies were carried out for comparison with the optimal fed-batch result. From the experimental results, this approach could improve productivity by at least 3%.     

The effect of nitrogen limitation on lipid productivity and cell composition in Chlorella vulgaris

Chlorella vulgaris accumulates lipid under nitrogen limitation, but at the expense of biomass productivity. Due to this tradeoff, improved lipid productivity may be compromised, despite higher lipid content. To determine the optimal degree of nitrogen limitation for lipid productivity, batch cultures of C. vulgaris were grown at different nitrate concentrations. The growth rate, lipid content, lipid productivity and biochemical and elemental composition of the cultures were monitored for 20 days. A starting nitrate concentration of 170 mg L^?1 provided the optimal tradeoff between biomass and lipid production under the experimental conditions. Volumetric lipid yield (in milligram lipid per liter algal culture) was more than double that under nitrogen-replete conditions. Interpolation of the data indicated that the highest volumetric lipid concentration and lipid productivity would occur at nitrate concentrations of 305 and 241 mg L^?1, respectively. There was a strong correlation between the nitrogen content of the cells and the pigment, protein and lipid content, as well as biomass and lipid productivity. Knowledge of the relationships between cell nitrogen content, growth, and cell composition assists in the prediction of the nitrogen regime required for optimal productivity in batch or continuous culture. In addition to enhancing lipid productivity, nitrogen limitation improves the lipid profile for biodiesel production and reduces the requirement for nitrogen fertilizers, resulting in cost and energy savings and a reduction in the environmental burden of the process.     

The Impacts of Climate and Social Changes on Cloudberry (Bakeapple) Picking: a Case Study from Southeastern Labrador

The traditional subsistence activities of Indigenous communities in Canada’s subarctic are being affected by the impacts of climate change, compounding the effects of social, economic and political changes. Most research has focused on hunting and fishing activities, overlooking berry picking as an important socio-cultural activity and contributor to the diversity of food systems. We examined the vulnerability of cloudberry (referred to as ‘bakeapple’ consistent with local terminology) picking to environmental changes in the community of Cartwright, Labrador using semi-structured interviews (n =?18), field surveys, and satellite imagery. We identified the components of vulnerability including: the environmental changes affecting the abundance, quality, and ripening time of bakeapples (i.e., exposure), the characteristics of the community that affect how these changes have local impacts (i.e., sensitivity), and the ways in which the community is responding to environmental changes (i.e., adaptive capacity). Our results confirm that environmental changes related to permafrost, vegetation, and water have occurred at the bakeapple picking grounds with observed impacts on bakeapples. It is becoming increasingly difficult for bakeapple pickers to respond to variable growth as in the past because of changes in summer settlement patterns that place families farther from their bakeapple patches. We conclude that harvesters in Cartwright have high adaptive capacity to respond to environmental changes due to their knowledge of their bakeapple patches, and at present, socioeconomic changes have had a greater impact than environmental changes on their harvesting capacity.