Sequential Supply Research Articles

Replenishment behaviour in sequential supply chains

Inventory managers do not predominantly follow normative optimisation models. At best, they introduce a level of bounded rationality in their inventory replenishment decisions. This paper examines the behaviour of inventory decision-makers under continuous review in a decentralised supply chain, using an experimental approach with unknown market demand and local information availability. The analysis reveals that not only the magnitude and the variability of order quantity tend to be larger, but also that the order-time intervals is lengthen and highly variable while moving upstream along the supply chain. The role of the inventory managers' replenishment decisions on the echelon holding, backorder, and total costs, is also investigated. Finally, a normative model is designed and its solutions are compared to the experimental results. It is observed that humans do not operate in a perfectly optimal way, but are generally reluctant to risk increasing backorder costs and reducing inventory carrying cost, even if this would lead to lower total cost.

Replenishment behaviour in sequential supply chains

Inventory managers do not predominantly follow normative optimisation models. At best, they introduce a level of bounded rationality in their inventory replenishment decisions. This paper examines the behaviour of inventory decision-makers under continuous review in a decentralised supply chain, using an experimental approach with unknown market demand and local information availability. The analysis reveals that not only the magnitude and the variability of order quantity tend to be larger, but also that the order-time intervals is lengthen and highly variable while moving upstream along the supply chain. The role of the inventory managers' replenishment decisions on the echelon holding, backorder, and total costs, is also investigated. Finally, a normative model is designed and its solutions are compared to the experimental results. It is observed that humans do not operate in a perfectly optimal way, but are generally reluctant to risk increasing backorder costs and reducing inventory carrying cost, even if this would lead to lower total cost.

Optimal Organizational Choice in a Sequential Supply Chain

We study the optimal organizational structure of a firm in a sequential supply chain when investments are relationship specific and contracts are incomplete. The market structure for the final product is monopolistic competition. Production follows a preordered sequence and exhibits high complementarity between stages. There are three types of actors: upstream suppliers, downstream suppliers and final-good producers (firms). In designing their organizational structure, firms in each stage choose not only the ownership structure, i.e., vertical integration versus outsourcing, but also the input-procurement strategy, i.e., delegation versus control. The separation of asset ownership and input-procurement rights leads to a novel organizational mode, which we call `outsourcing with delegation.' We determine the conditions under which this new organizational mode emerges as an equilibrium outcome.

A one-warehouse/multi-retailer inventory system with lost sales, Erlangian lead times, and emergency shipments

We consider a two-echelon inventory system with one central warehouse and a number of retailers. In case of a stock-out at the warehouse, the external supplier replenishes retailers' stocks by emergency shipments. The warehouse and retailers apply a base-stock ordering policy and unsatisfied demands at retailers will be lost. We assume that lead times of retailers are Erlangian distributed. Under the realistic assumption that the replenishment orders do not cross in time, the Erlangian lead times become stochastically dependent. This dependency will affect the optimal base-stock levels at retailers and, consequently, the optimal base-stock level at the warehouse. In this paper, we estimate the demand rate at the warehouse, and calculate the total cost function of the inventory system. We also present an algorithm to compute the optimal base-stock levels at the warehouse and retailers. Our numerical study illustrates that the sequential supply system cannot be ignored.

Effect of Ga droplet deposition rate on morphology of concentric quantum double rings

For the fabrication of particular nanostructures, Stranski-Krastanov (SK) growth mode driven by strain is most widely used. Meanwhile, another technique that is used to form the complex nanostructures is the droplet epitaxy technique, which is based on the deposition of group III element nanoscale droplets onto substrate and followed by the reaction with group V element for crystallization into III-V compound nanostructures. Droplet epitaxy technique is simple and flexible, and it does not require additional complicated processing and has potential to develop various quantum nanostructures. It, unlike standard MBE growth, exploits the sequential supply of group-III and group-V elements to form quantum nanostructures. Quantum rings are a special class of quantum-confinement structure that can be fabricated by the droplet epitaxy technique and have attracted wide attention due to the Aharonov-Bohm effect, which is specific to the topology of a ring. In this paper, GaAs/GaAs (001) concentric quantum double rings (CQDRs) are prepared by droplet epitaxy technique at different Ga droplet deposition rates in monolayer per second (ML/S). The 2 μm × 2 μm atomic force microscope images are obtained to show the morphologies of CQDRs. We study the effects of Ga droplet deposition rates (0.09 ML/s, 0.154 ML/s, 0.25 ML/s, 0.43 ML/s) on CQDRs. The results show that with the increase of Ga droplet deposition rate, the density of CQDRs increases and the radius of inner ring and the radius of outer ring decrease. According to the nucleation theory, through the relationship between the maximum cluster density and the Ga droplet deposition rate, the critical number of atom nucleations is found to be 5, which suggests that the stable Ga atom crystal nucleus should contain at least 5 Ga atoms in the process of forming Ga droplet, and a nucleation state transformation diagram is drawn in order to obtain an insight into the process of forming Ga droplet according to the nucleation theory and fitting results. The research results could be instructive for preparing the GaAs concentric quantum double rings that the density can be controlled by droplet epitaxy.

Analysis of the impact of changes in the stator magnetic circuit on static properties of the electromagnetic linear motor model

In this paper, the static characteristics as a function of changes in geometric dimensions of the stator magnetic circuit of the linear stepper actuator with permanent magnets is presented. The stator is built from a series of cylindrical coils encapsulated with ferromagnetic case. The runner is made of permanent magnet rings connected with ferromagnetic spacers. The electromagnetic interac-tion between the stator and the runner for the sequential supply of coils was analyzed. The electro-magnetic force as a function of the geometry of the coils and the ferromagnetic housing for the con-stant graduation of the runner was determined. The maximum, minimum, and average values of the electromagnetic force as a function of the geometric independent variable were determined. The ratio of the mean force to the maximum, and mechanical work calculated as the integral of the force on the path of the runner was adopted as the evaluation criteria. A comparison between the maximum, average and relative values of forces as a function of the geometric dimensions of the stator was made. Keywords: modelling and simulation, linear actuator, finite element method, field calculations, cogging force, magnetic force.

PARÂMETROS LIMNOLÓGICOS EM VIVEIROS DE PISCICULTURA SEMI-INTENSIVA DE TAMBAQUI COM ABASTECIMENTO EM DISPOSIÇÃO SEQUENCIAL

A piscicultura é um dos segmentos da produção animal que mais cresce no cenário mundial; neste ramo a qualidade da água é preocupação constante, pois quando esta apresenta má qualidade causa problemas na produção e pouca lucratividade. Objetivou-se avaliar a qualidade da água com base em algumas variáveis limnológicas em viveiros de piscicultura de engorda de tambaqui (Colossoma macropomum) com abastecimento em disposição sequencial. Os resultados indicaram que o regime de chuvas e o manejo durante o ciclo de produção influenciaram os parâmetros avaliados. No universo temporal da pesquisa (ago./2013 a jul./2014), os valores de pH, amônia e nitrito estiveram de acordo com a resolução Conama 357/2005; a alcalinidade e temperatura estiveram dentro dos padrões indicados para piscicultura, o contrário para a maioria dos valores amostrados para o oxigênio dissolvido e fósforo total. Em ago./2013, mês dos menores índices pluviométricos na região, os viveiros apresentaram condutividade elétrica acima do estabelecido pela resolução Conama 357/2005; em out./2013 houve aumento expressivo da densidade da comunidade fitoplanctônica com florações pontuais, acarretando a menor transparência e oxigênio dissolvido em todos os viveiros. Os resultados indicam a necessidade de adoção sistemática de boas práticas de manejo a fim de melhorar a qualidade ambiental das criações, como também contribuir para a sustentabilidade da atividade aquícola.

Filters and limits in filtered spaces

In this lecture notes, we study filters and limits in a feasible sufficiently general way for many applications to Physics, Economics and Social Science. In particular we analyze:
 
 Filters;
 
 
 Filter bases;
 
 
 Basic example in topological spaces;
 
 
 Basic examples in preordered spaces;
 
 
 Filtered spaces;
 
 
 Induced filter bases;
 
 
 Examples in topological spaces;
 
 
 Examples on the real line;
 
 
 Limits;
 
 
 Limits with respect to filter bases;
 
 
 Limits with respect to filter bases on subspaces;
 
 
 Limits and topology;
 
 
 Limits of functions on topological spaces;
 
 
 Limits of functions on a topological subspace;
 
 
 Some basic theorems for topology;
 
 
 Unicity of the limit in Hausdor spaces;
 
 
 Limits and functionals;
 
 
 Limits for real functional;
 
 
 Limits and operations;
 
 
 Local boundness;
 
 
 Complements;
 
 
 Limits and convergence of filtered bases;
 
 
 Limit of composition.
 

AGGREGATION WITH SEQUENTIAL INDIVISIBLE AND CONTINUOUS LABOR SUPPLY DECISIONS AND AN INFORMAL SECTOR

The purpose of this paper is to explore the problem of non-convex labor supply decision in an economy with both discrete and continuous labor decisions. In contrast to the setup in Vasilev (2016a), here each household faces a sequential labor market choice - an indivisible labor supply choice in the market sector, and conditional on non-working in the official sector, a divisible hours choice in the informal sector. We show how lotteries as in Rogerson (1988) can again be used to convexify consumption sets, and aggregate over individual preferences. With a mix of sequential discrete and continuous labor supply decisions, aggregate disutility of non-market work becomes separable from market work, and the elasticity of the latter increases from unity to infinity.

Eco-design practices towards sustainable supply chain management: interpretive structural modelling (ISM) approach

Due to increasing emphasis on sustainable practices, many organisations have attempted to leverage their supply chain performance towards balancing triple bottom line dimensions (economic, environmental and social perspectives). This paper, therefore, determines the priorities of sustainable supply chain management focusing on eco-design. Interpretive structural modelling (ISM) and Matriced’ Impacts Croise’s Multiplication Appliquée a UN Classement (MIMAC) are used to identify the hierarchical structure of the relationships among eco-design dimensions, and to analyse characteristics power of each dimension on supporting eco-design practices. The relationships and characteristics power of each dimension are used to determine indicators that are effective in enhancement of eco-design practice, evaluated through sustainable supply chain performance. Results indicate that product deployment is an important approach for improving eco-design practice towards sustainable supply chain management. This emphasises the purpose and impact of eco-design on sequential supply chain activities at deployment phase. Further research is required to make an overall assessment of eco-design practices across range of manufacturing industries, given the current research is based on inputs from a limited number of experts of selected organisations.

Experimental Study of the Conditions for Quenching Forest Combustible Materials

To confirm the possibility of quenching forest combustible materials by small volumes of water, experimental studies have been made of the processes of interaction of droplets, films, and aerosol flows of water with small sources of combustion of typical forest combustible materials — birch leaves, pine needles, birch and asp twigs. Model combustion sources in the form of cylinders of diameter 20–60 mm and height 40–100 mm were constructed. With the use of high-speed video recording, the characteristic times of thermal decomposition of forest combustibles and the times of suppressing combustion of these materials under various conditions of their interaction with water (pulsed supply of aerosol, injection of water ″mist″ with droplets of radius up to 100 μm, sequential supply of large drops of radius about 1.5 mm) have been determined. Volumes of water sufficient for suppressing combustion depending on the method of supplying it onto the surface of the reacting forest combustible have been determined. Estimates have been made of the nonreacted portion of the material by comparing the initial mass of the sample of the forest combustible with its final mass (upon quenching the material).

Sequential Supply Decision and Market Efficiency: Theory and Evidence

In a homogeneous goods market, due to the lack of the preemption effect, each firm's demand is likely to be proportional to its share of total output. Firms are inclined to supply more to increase their market shares, but should also consider the potential cost from excess supply. Thus, firms should make strategic decisions on how much to supply. We study this topic by considering an oligopoly market in which firms make decisions sequentially under a fixed price. We first provide a theoretical model and find the conditions under which either an efficient supply or oversupply occurs. Our model proposes two practical ways to evaluate the efficiency of a market, specifically regarding excess supply, that do not require information about market demand. Using these, we evaluate the efficiency of the Korean movie theater industry. Our empirical findings indicate oversupply of seating capacity in that industry.

Intangible Assets and the Organization of Global Supply Chains

This paper introduces the concept of intangible assets in sequential supply chains and the importance of their appropriability in the organizational decision of firms. We focus on the quality of intellectual property rights (IPR) institutions, which on top of the hold-up problem between a supplier and the final producer entails an additional risk of imitation as technology may leak to competing producers in the market. The level of IPR enforcement in the location of a supplier can therefore play a crucial role in determining the decision of a final good producer whether to outsource or integrate a particular stage of production. The analysis is performed with Antras and Chor (2013) in the background, where the position of the input along the supply chain, i.e. its upstreamness, and the degree of sequential complementarity of stage-specific inputs influence the organizational strategy of firms through the incentive structure of supplier investments. Our findings show that introducing intangible assets in sequential supply chain may have the opposite effect of contractibility on outsourcing decision, where only tangible property rights are considered. We argue therefore that the risk of imitation is a relevant feature that needs to be accounted for in the incomplete contract literature. Our theoretical predictions are validated on Slovenian firm-level data.

Complex structure of cytochrome c–cytochrome c oxidase reveals a novel protein–protein interaction mode

Mitochondrial cytochrome c oxidase (CcO) transfers electrons from cytochrome c (Cyt.c) to O2 to generate H2O, a process coupled to proton pumping. To elucidate the mechanism of electron transfer, we determined the structure of the mammalian Cyt.c–CcO complex at 2.0‐Å resolution and identified an electron transfer pathway from Cyt.c to CcO. The specific interaction between Cyt.c and CcO is stabilized by a few electrostatic interactions between side chains within a small contact surface area. Between the two proteins are three water layers with a long inter‐molecular span, one of which lies between the other two layers without significant direct interaction with either protein. Cyt.c undergoes large structural fluctuations, using the interacting regions with CcO as a fulcrum. These features of the protein–protein interaction at the docking interface represent the first known example of a new class of protein–protein interaction, which we term “soft and specific”. This interaction is likely to contribute to the rapid association/dissociation of the Cyt.c–CcO complex, which facilitates the sequential supply of four electrons for the O2 reduction reaction.

Coordinated process of polarized growth in filamentous fungi.

Filamentous fungi are extremely polarized organisms, exhibiting continuous growth at their hyphal tips. The hyphal form is related to their pathogenicity in animals and plants, and their high secretion ability for biotechnology. Polarized growth requires a sequential supply of proteins and lipids to the hyphal tip. This transport is managed by vesicle trafficking via the actin and microtubule cytoskeleton. Therefore, the arrangement of the cytoskeleton is a crucial step to establish and maintain the cell polarity. This review summarizes recent findings unraveling the mechanism of polarized growth with special emphasis on the role of actin and microtubule cytoskeleton and polarity marker proteins. Rapid insertions of membranes via highly active exocytosis at hyphal tips could quickly dilute the accumulated polarity marker proteins. Recent findings by a super-resolution microscopy indicate that filamentous fungal cells maintain their polarity at the tips by repeating transient assembly and disassembly of polarity sites.

Characterisation of plasma synthetic jet actuators in quiescent flow

An experimental characterisation study of a large-volume three-electrode plasma synthetic jet actuator (PSJA) is presented. A sequential discharge power supply system is used to activate the PSJA. Phase-locked planar particle image velocimetry (PIV) and time-resolved Schlieren imaging are used to characterise the evolution of the induced flow field in quiescent flow conditions. The effect of orifice diameter is investigated. Results indicate three distinct features of the actuator-induced flow field. These are the initial shock waves, the high speed jet and vortex rings. Two types of shock waves with varied intensities, namely a strong shock wave and a weak shock wave, are issued from the orifice shortly after the ignition of the discharge. Subsequently, the emission of a high speed jet is observed, reaching velocities up to 130 m s−1. Pronounced oscillation of the exit velocity is caused by the periodical behaviour of capacitive discharge, which also led to the formation of vortex ring trains. Orifice diameter has no influence on the jet acceleration stage and the peak exit velocity. However, a large orifice diameter results in a rapid decline of the exit velocity and thus a short jet duration time. Vortex ring propagation velocities are measured at peak values ranging from 55 m s−1–70 m s−1. In the case of 3 mm orifice diameter, trajectory of the vortex ring severely deviates from the actuator axis of symmetry. The development of this asymmetry in the flow field is attributed to asymmetry in the electrode configuration.

Atomic layer deposited self-forming Ru-Mn diffusion barrier for seedless Cu interconnects

Ru-based alloy thin films were prepared by atomic layer deposition (ALD) at a deposition temperature of 225 °C for use as a diffusion barrier for seedless Cu interconnects. Ru-Mn alloy thin films were grown by a repetition of super-cycles consisting of multiple Ru and Mn ALD sub-cycles. Ru and Mn ALD was performed using a sequential supply of a Ru precursor [1-Isopropyl-4-methylbenzene (cyclohexa-1, 3-diene) Ru (0)] and NH3 plasma, and a Mn precursor [bis(1,4-di-isopropyl-1,3-diazabutadienyl)Mn(II)] and H2 plasma, respectively. Secondary ion mass spectrometry (SIMS) indicated that Mn had been incorporated successfully into the Ru film by the periodic addition of Mn ALD sub-cycles during the ALD-Ru process. Plan-view transmission electron microscopy (TEM) showed that the grain size was reduced obviously from ∼15 nm (pristine Ru) to ∼8 nm (Ru-Mn alloy) and continuous columnar grain growth of the ALD-Ru film was prevented by the addition of the periodic Mn ALD sub-cycles. After annealing at 500 °C, the formation of a MnSiOx diffusion barrier was observed between the Ru-Mn film and underlying SiO2 surface by both cross-sectional view TEM and energy dispersive spectroscopy analysis and confirmed by SIMS depth profile. X-ray diffraction showed that the ultrathin ALD Ru-Mn thin film (∼5 nm) prevented Cu diffusion up to an annealing temperature of 600 °C, whereas the ALD-Ru thin film with the same thickness failed to prevent Cu diffusion only after annealing at 500 °C. Finally, the capability of the direct plating of Cu was demonstrated on the annealed ALD Ru-Mn film.

Effects of annealing on the properties of atomic layer deposited Ru thin films deposited by NH3 and H2 as reactants

Atomic layer deposition (ALD) of Ru using a non-oxidizing reactant is indispensable considering its application as a seed layer for Cu electroplating and a bottom electrode for dynamic random access memory capacitors. In this study, ALD-Ru films were deposited using a sequential supply of dicarbonyl-bis(5-methyl-2,4-hexanediketonato) Ru(II) (C16H22O6Ru) and potential non-oxidizing reducing agents, NH3 or H2, as the reactants at a substrate temperature of 250°C, and the effects of post-annealing in a H2 ambient on the film properties were investigated. The highly conformal deposition of Ru films was possible using the present reaction scheme but its resistivity was as high as ~750μΩ-cm due to carbon incorporation into the film and the formation of an amorphous structure. Low temperature annealing at 300°C at H2 ambient after deposition was found to improve the properties significantly in terms of the resistivity, impurities contents and crystallinity. For example, the film resistivity was decreased drastically to ~40μΩ-cm with both the release of C in the film and crystallization after annealing based on secondary ion mass spectrometry and transmission electron microscopy, whereas perfect step coverage at a very small-sized dual trench (aspect ratio: ~3, the top opening size of 45nm and bottom size of 20nm) was maintained after annealing.

Plasma-free atomic layer deposition of Ru thin films using H2 molecules as a nonoxidizing reactant

The ruthenium (Ru) thin films were grown by atomic layer deposition (ALD) using a sequential supply of dicarbonyl-bis(5-methyl-2,4-hexanediketonato) Ru(II) (C16H22O6Ru) and H2 as a reactant at a substrate temperature of 250 °C. Deposition was possible using H2 molecules without a plasma by increasing the chamber pressure to above 10 Torr. Specifically, high-quality Ru films with a low resistivity of ∼40 μΩ cm and few amount of oxygen (∼1.2 at. %) were obtained under a chamber pressure of 300 Torr though the oxygen was contained in the precursor. Under the optimized conditions, self-limited film growth with regard to the precursor and reactant pulsing times was confirmed under elevated chamber pressures. The ALD-Ru process proposed in this study showed one of the highest growth rates of 0.12 nm/cycle on a thermally grown SiO2 substrate, as well as a very low number of incubation cycles (approximately 12 cycles). Cross-sectional view transmission electron microscopy showed that no interfacial oxide had formed during the deposition of the ALD-Ru films on a W surface using H2 molecules, whereas ∼7 nm thick interfacial oxide was formed when O2 molecules were used as a reactant. The step coverage of the ALD-Ru film onto very small-sized trenches (aspect ratio: ∼4.5 and the top opening size of 25 nm) and holes (aspect ratio: ∼40 and top opening size of 40 nm) was excellent (∼100%).

Highly-conformal nanocrystalline molybdenum nitride thin films by atomic layer deposition as a diffusion barrier against Cu

Molybdenum nitride (Mo2N) thin films were grown by atomic layer deposition (ALD) using a sequential supply of a newly synthesized Mo metalorgranic precursor, Mo(NtBu)2(StBu)2, and H2 plasma at a substrate temperature of 300 °C. A newly proposed ALD system exhibited typical ALD characteristics, such as a self-limited film growth and a linear dependency of the film thickness on the number of ALD cycles, and showed a growth rate of 0.028 nm/cycle on a thermally grown SiO2 substrate. Such the ideal ALD growth characteristics enabled excellent step coverage of ∼80% for the ALD-grown Mo2N film onto nano-trenches with a width of 25 nm and an aspect ratio ∼4.5. The optimized film had a resistivity as low as ∼350 μΩ-cm. X-ray diffraction, Rutherford backscattering spectrometry, and X-ray photoelectron spectroscopy analyses confirmed that formation of N-rich cubic Mo2N (N/Mo = ∼0.7) phase with carbon and sulfur impurities of 2.6 and 7.4 at.%, respectively. Plan-view transmission electron microscopy analysis showed that the film formed a nanocrystalline microstructure with 5–8-nm-sized grains embedded in an amorphous matrix. An ultrathin (only ∼4 nm-thick) ALD-grown Mo2N film effectively prevented diffusion of Cu into Si after annealing at a temperature even up to 650 °C.