•We propose a parallel policy for autonomous tier-captive storage/retrieval systems.•A fork-join queueing network is formulated to analyze the system performance.•The parallel policy has advantages ...in small size systems.•The parallel policy has advantages below a critical transaction arrival rate.
This paper models and analyzes tier-captive autonomous vehicle storage and retrieval systems. While previous models assume sequential commissioning of the lift and vehicles, we propose a parallel processing policy for the system, under which an arrival transaction can request the lift and the vehicle simultaneously. To investigate the performance of this policy, we formulate a fork-join queueing network in which an arrival transaction will be split into a horizontal movement task served by the vehicle and a vertical movement task served by the lift. We develop an approximation method based on decomposition of the fork-join queueing network to estimate the system performance. We build simulation models to validate the effectiveness of analytical models. The results show that the fork-join queueing network is accurate in estimating the system performance under the parallel processing policy. Numerical experiments and a real case are carried out to compare the system response time of retrieval transactions under parallel and sequential processing policies. The results show that, in systems with less than 10 tiers, the parallel processing policy outperforms the sequential processing policy by at least 5.51 percent. The advantage of parallel processing policy is decreasing with the rack height and the aisle length. In systems with more than 10 tiers and a length to height ratio larger than 7, we can find a critical retrieval transaction arrival rate, below which the parallel processing policy outperforms the sequential processing policy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The nucleoside antibiotic toyocamycin (TM), which was produced by
Streptomyces diastatochromogenes
1628, was found to be highly efficient against a broad range of plant pathogenic fungi. Despite its ...importance, little is known about the regulation TM biosynthesis. In this study,
toyA
, located in the TM biosynthetic gene cluster, was identified as a regulatory gene encoding a large ATP-binding regulator of the LuxR family (LAL-family). The role of
toyA
in TM biosynthesis in
S. diastatochromogenes
1628 was investigated by gene deletion, complementation, and over-expression. Gene disruption of
toyA
resulted in almost loss of TM production. TM production in complemented strain was restored to the level comparable to that in the wild-type strain
S. diastatochromogenes
1628. Over-expression of
toyA
separately controlled by promoter SPL57, SPL21, and p
erm
E
*
in wild-type strain
S. diastatochromogenes
1628 led to a 2-fold, 1-fold, and 80% increase in TM production compared with wild-type strain
S. diastatochromogenes
1628, respectively. Quantitative RT-PCR analysis revealed that the transcriptional level of
toy
structural genes was downregulated in the ΔtoyA mutant but restored in complemented strain and further upregulated in the
toyA
over-expression strain. The detection results from GFP reporter system in
Escherichia coli
and GUS reporter system and GUS activities in
S. albus
J1074 and
S. diastatochromogenes
1628 showed that ToyA activated the expression of
toyB
and
toyE
operon directly and activated the expression of other
toy
structural genes indirectly. These results indicate that ToyA is essential for TM biosynthesis controlling the expression of structural genes.
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CEKLJ, DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We study an entrepreneur's joint inventory and rationing decision if the required capital for a venture is raised in a reward-based crowdfunding campaign. The entrepreneur sets a financing target ...first, and then decides the rationing policy and inventory if the campaign succeeds. We investigate the whole event with a backward induction. Maximizing the profit in our inventory model, we first obtain the optimal order quantities under each rationing policy and find that surplus funding is critical for the inventory decision. Under both policies, we find that additional borrowing yields a suboptimal order quantity, that the optimal order quantity can be reached without borrowing on a working capital line, and that the entrepreneur will expense all available funds for ordering products without borrowing. Then, we compare rationing policies and analyse the optimal financing target. The results show that, compared to the "funders first" policy, the "regular consumers first" policy is more profitable and yields lower inventory. Meanwhile, we find the optimal financing target is the lower bound in the feasible zone of the funding amount, and the "funders first" policy is more likely to yield a greater financing target. Finally, we conduct numerical examples to verify these results.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
•We prove the lower bound on penalty for decentralization.•We propose a revised revenue-sharing (RRS) contract to coordinate the developed system.•The RRS contract always yields a higher profit than ...the revenue-sharing (RS) contract.•Under these two contracts, the optimal conditions of attaining a win-win outcome are derived.
This study considers a one-manufacturer and one-retailer supply chain for deteriorating items over a finite planning horizon. In the case with multi-factor-dependent demand, we analyze the coordination of the system within a contract mechanism. First, we formulate and then compare a decentralized model and a centralized model. Next, we propose a revenue-sharing contract and a revised revenue-sharing contract to coordinate the decentralized supply chain. We illustrate the proposed models with a numerical example and we perform sensitivity analysis of the coordination results based on several key parameters. The results show that the supply chain’s profit in the centralized system increases by at least 13, where both contracts can coordinate the system and the fraction parameter of the revenue exists when each contract is acceptable to both members of the supply chain, and the revised revenue-sharing contract always yields a higher profit than the revenue-sharing contract. Furthermore, the supply chain’s profit under the revised revenue-sharing contract is shown to be equivalent to that with the centralized system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract Menaquinone‐7 (MK‐7), a form of vitamin K2, supports bone health and prevents arterial calcification. Microbial fermentation for MK‐7 production has attracted widespread attention because of ...its low cost and short production cycles. However, insufficient substrate supply, unbalanced precursor synthesis, and low catalytic efficiency of key enzymes severely limited the efficiency of MK‐7 synthesis. In this study, utilizing Bacillus subtilis BSAT01 (with an initial MK‐7 titer of 231.0 mg/L) obtained in our previous study, the glycerol metabolism pathway was first enhanced to increase the 3‐deoxy‐arabino‐heptulonate 7‐phosphate (DHAP) supply, which led to an increase in MK‐7 titer to 259.7 mg/L. Subsequently, a combination of knockout strategies predicted by the genome‐scale metabolic model etiBsu1209 was employed to optimize the central carbon metabolism pathway, and the resulting strain showed an increase in MK‐7 production from 259.7 to 318.3 mg/L. Finally, model predictions revealed the methylerythritol phosphate pathway as the major restriction pathway, and the pathway flux was increased by heterologous introduction (Introduction of Dxs derived from Escherichia coli ) and fusion expression (End‐to‐end fusion of two enzymes by a linker peptide), resulting in a strain with a titer of 451.0 mg/L in a shake flask and 474.0 mg/L in a 50‐L bioreactor. This study achieved efficient MK‐7 synthesis in B. subtilis , laying the foundation for large‐scale MK‐7 bioproduction.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Retailers have treated the buy-online-and-return-in-store (BORS) policy as an important initiative to reduce return losses and provide a better customer experience. Studies on BORS policy have ...primarily focused on the retailer's strategic value, but not on how such a seamlessly integrated omnichannel operation affects customer behavior. Using Chinese customer data and the structural equation model (SEM), we investigate how BORS channel integration impacts customer behavioral intentions, with the consideration of the mediating effect of customer satisfaction and the moderating effect of offline store characteristics. Based on the stimulus-organism-response framework, our research found that two dimensions of BORS channel integration (integrated return fulfillment and integrated customer service) positively impact customer satisfaction and subsequently impact behavioral intentions in different channels. Furthermore, offline store convenience moderates the relationship between integrated customer service and customer satisfaction. Product variety in the offline store moderates the relationship between customer satisfaction and offline behavioral intentions, while it is not statistically significant in the relationship between customer satisfaction and online behavioral intentions. Compared to the younger group, the older group who is satisfied with BORS service is more likely to purchase offline. These findings generate important theoretical and practical implications for omnichannel return operations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Robotic compact storage and retrieval systems (RCSRS) have seen many implementations over the last few years. In such a system, the inventory items are stored in bins, organized in a grid. In each ...cell of the grid, a certain number of bins are stored on top of each other. Robots with transport and lifting capabilities move on the grid roof to transport bins between manual workstations and storage stacks. We estimate performance and evaluate storage policies of RCSRS, considering both dedicated and shared storage policies coupled with random and zoned storage stacks. Semi-open queuing networks (SOQNs) are built to estimate the system performance, which can handle both immediate and delayed reshuffling processes. We approximate the models by reduced SOQNs with two load-dependent service nodes and use the matrix-geometric method to solve them. Both simulations and a real case are used to validate the analytical models. Assuming a given number of stored products, our models can be used to optimize not only the length-to-width ratio of the system but also the stack height, depending on the storage strategy used. For a given inventory and optimal system configuration, we demonstrate that the dedicated storage policy outperforms the shared storage policy when the objective is to minimize dual command throughput time. However, from a cost perspective, with a maximum dual command throughput time as a constraint, we show that shared storage substantially outperforms dedicated storage. The annualized costs of dedicated storage are up to twice as large as those of shared storage, as a result of the larger number of storage positions required by dedicated storage and the relatively lower filling degree of storage stacks.
The online appendix is available at
https://doi.org/10.1287/trsc.2017.0786
.
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BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Triacylglycerols (TGs) are important components of human diet. The positional distribution of fatty acids (FAs) on the glycerol backbone affects the chemistry and physical properties of fats. ...Especially for infants, the structure of TGs plays an important role in the growth and development. However, limited by detecting technology, accurately identifying regioisomers of ABA/AAB and BAC/ABC/ACB type TGs is a significant challenge for human milk utilization and the development of infant formula. For this, we exploit a novel method for identifying the regioisomers of ABA/AAB and BAC/ABC/ACB type TGs within complex lipid mixtures, via used electron activated dissociation (EAD) tandem mass spectrometry. The distribution information of acyl chains at the sn-2 and sn-1/3 positions of glycerol backbone and double bonds in unsaturated FAs can be easily obtained by fragmenting TG ions with energetic electrons (15 eV). Then, the standard curve was established by correlating the peak area intensity of sn-2 characteristic product ion with the content of TG regioisomers standard. These analytical methods successfully enabled the identification and quantification of TG regioisomers in human milk, cow milk, infant formula, palm oil, and sunflower oil. Additionally, the distribution of the double-bond positions of unsaturated FAs in these samples was also identified. Compared to traditional methods, this approach eliminates the need for complex processing and analysis procedures, enabling rapid structural characterization of ABA/AAB and BAC/ABC/ACB type TGs within 17 min. Hence, we provide a rapid and convenient methodology for detecting and analyzing ABA/AAB and BAC/ABC/ACB type TG regioisomers, thereby offering valuable assistance in the development of specialized formulations and facilitating effective process control for ensuring the quality of edible oils and fats.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A new logistics mode has emerged in online retailing, which ships products before customers place orders online to reduce the waiting time for customers to receive them. The existing research on this ...logistics mode mainly focuses on the shipping quantity (i.e., the quantity of products to be shipped in advance from the order fulfillment center to the distribution center nearby customers before the order is placed online), while the product pricing problem and carbon emissions have not been studied comprehensively. Moreover, the risk attitudes of decision-makers have been ignored in the studies related to this new logistics mode. This paper builds an extended newsvendor model to explore the optimal joint decision problem of shipping quantity and product pricing under this new logistics mode and analyzes the carbon emissions of this new logistics mode compared with the traditional logistics mode. We consider decision-makers to be risk averse and take Conditional Value-at-Risk (CVaR) as the risk measure criterion. For both multiplicative and additive demand models, we obtain the closed-form solution of the optimal strategy. The differences between the optimal strategies of risk-averse and risk-neutral decision-makers and between the optimal strategies of this logistics mode and the traditional one have also been explored. Based on the optimal shipping quantity and product pricing strategies, we analyze the carbon emission variation of this logistics mode compared with the traditional one and provide sufficient conditions for reducing carbon emissions. Numerical experiments verify the theoretical conclusions and analyze the effect of some parameters on the optimal strategy, profit and carbon emission variation. The results show that online retailers should reduce product price in this new logistics mode compared with the traditional one. The risk-aversion degree slightly affects the optimal price but significantly affects the shipping quantity. Moreover, implementing this new logistics mode contributes to reducing carbon emissions compared with the traditional logistics mode in most cases. This study helps support online retailers in developing shipping quantity and product pricing strategies under this new logistics mode and helps the Environmental Protection Association to understand the carbon emissions under this new logistics mode so that relevant strategies can be developed.
•We explore the shipping quantity, pricing and carbon emission in a new logistics mode.•We have considered the risk attitude, which has been ignored in the relevant studies.•We find the price should be reduced in the new mode compared with the traditional one.•We find the risk aversion degree significantly affects the optimal shipping quantity.•We find that implementing the new mode helps to reduce carbon emissions in most cases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract Autonomous mobile robots are increasingly used for order picking, order delivery, and parcel sorting. This article studies a robotic sorting system that uses robots to transport parcels from ...loading stations to drop‐off points. While this system provides more flexible throughput capacity than conventional sorting systems, its performance is significantly affected by the robot travel distance and robot congestion. We study the problem of assigning parcel destinations to drop‐off points to minimize the throughput time, trading off travel distance and congestion. First, an open queuing network (OQN) with finite capacity queues is constructed to estimate the congested throughput time. A decomposition method based on the analysis of the tandem queuing network of each aisle is developed to solve the OQN. Second, using the obtained throughput time as an objective and the destination assignments as decisions, we formulate an optimization model and solve the problem using an adaptive large neighborhood search (ALNS) algorithm. We validate the accuracy of the OQN by simulation and verify the efficiency of the ALNS algorithm by comparing it with Gurobi, a tabu search algorithm, several heuristic assignment rules, and the rule used by our case company, that assigns high demands close to loading stations. The results show that the ALNS solution provides a relatively low throughput time by dispersing destinations with high demands over drop‐off points. In addition, we investigate the effects of different system layouts and travel path topologies. We also show that the ALNS assignment rule produces substantially lower operational costs than the heuristic assignment rules for a given required throughput capacity.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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