EOQ Model: The Case in Which the Placing of Orders Is Rewarded

The first models of optimization of inventory management costs have undergone few changes since they were developed at the beginning of the last century. It is only with the passage of time that new scenarios have appeared with the introduction of new systems of production, and consequently of new strategies in the logistics chain. In this article, we analyze and propose a revision of the basic inventory model of economic order quantity first defined by Harris in 1913 for a scenario in which the owner of the stock receives a bonus or reward each time he replenishes his stock. This situation arises when the supplier receives a benefit (which he then shares with the customer) when managing his stock replenishment. An array of nested models is shown to illustrate this scenario, from which the constraints of previous scenarios have been removed. The model provides insights into the negotiation of batch size between supplier and buyer in a win‐win environment in the specific situation in which the supplier gives a bonus to the buyer at each stock replenishment. © 2011 Wiley Periodicals, Inc.     

Analyzing locality over a P2P computing architecture

A characteristic of Peer-to-Peer (P2P) computing networks is their huge number of different computational resources scattered across the Internet. Gathering peers into markets according to their multi-attribute computational resources makes it easier to manage these environments. This solution is known as market overlay. In this context, the closeness of the markets with similar resources, known as locality, is a key feature for ensuring good P2P resource management. Thus, the locality feature over a market overlay allows a lack of resources in a given market to be compensated quickly by any other market with similar resources, whenever these are close to each other. Consequently, locality becomes an essential challenge.This paper addresses the analysis of the locality of P2P market over-lays. According to this, a new procedure for measuring locality is applied together with an extensive analysis of some well-known structured P2P overlays. Based on this analysis, a new P2P computing architecture, named DisCoP, oriented towards optimizing locality is proposed. Our proposal gathers the peers into markets according to their computational resources. A Hilbert function is used to arrange multi-attribute markets in an ordered and mono-dimensional space and the markets are linked by means of a Bruijn graph. In order to maintain the DisCoP locality whenever the overlay is not completed, a solution based on the virtualization of markets is also proposed. Finally, the DisCoP locality is tested together with the proposed virtualization method for approximate searches over uncompleted overlays. The simulation results show that approximate searches exploit the DisCoP locality efficiently.     

Relationships between memory models

There have been many proposals of shared memory systems, each one providing different types of memory coherence for interprocess communication. However, they have usually been defined using different formalisms. This makes it difficult to compare among them the different proposals put forward. In this paper we present a formal framework for specifying memory models with different coherency properties. We specify most of the known shared memory models using our framework, showing some of the relationships that hold among them.     

A Task Model to Reduce Control Delays

Industrial control applications are usually developed in two phases: control design and real-time system implementation. In the control design stage a regulator is obtained and later it is translated into an algorithm in the implementation phase. Traditionally, these two phases have been developed in separate ways. Recently, some works have pointed out the necessity of the integration of the control design and its implementation. One of these works reduce the delay variance of control tasks (defined as the control action interval (CAI) and data acquisition interval (DAI) parameters) splitting every task into three parts. The CAI reduction method highly reduces the delay variance and improves the control performance. This work shows how to evaluate these delays under static and dynamic scheduling policies. A new task model is proposed in order to reduce the CAI and DAI parameters, which implies an improvement in the control performance. The new task model will be implemented in a real process, and the experimental measurements will show how, effectively, the control performance is highly improved with the methods presented in this paper.     

Simulatable certificateless two-party authenticated key agreement protocol

Key agreement (KA) allows two or more users to negotiate a secret session key among them over an open network. Authenticated key agreement (AKA) is a KA protocol enhanced to prevent active attacks. AKA can be achieved using a public-key infrastructure (PKI) or identity-based cryptography. However, the former suffers from a heavy certificate management burden while the latter is subject to the so-called key escrow problem. Recently, certificateless cryptography was introduced to mitigate these limitations. In this paper, we first propose a security model for AKA protocols using certificateless cryptography. Following this model, we then propose a simulatable certificateless two-party AKA protocol. Security is proven under the standard computational Diffie-Hellman (CDH) and bilinear Diffie-Hellman (BDH) assumptions. Our protocol is efficient and practical, because it requires only one pairing operation and five multiplications by each party.     

The necessity of sample quality assessment in 14C AMS dating: The case of Cova des Pas (Menorca – Spain)

The Cova des Pas cave is a karstic cave in the cliffs of the Barranc (canyon) de Trebalúger. It is a small cave only 6.5 m deep, 4.5 m wide and 1.7 m high. Yet more than 70 burials, in foetal position, from the Early Iron Age were found in this small cave. The conservation of the archaeological remains was very unusual. Not only wood, ropes and other plant material was found, but also remains of body tissue, hair and leather. In spite of the remarkable preservation of the bodies and artefacts, the state of conservation of the bone material was very bad. The bones contained little and heavily deteriorated collagen and the organic plant material was very fragile. The special environmental conditions of the cave are the cause of these unusual preservation conditions. Although the cave is situated in a limestone cliff, the soil of the cave is very acid. Unexpectedly bad sample quality seemed to be the major drawback for AMS radiocarbon dating on hair, wood, ropes and bone collagen, as well as on bio-apatite.     

Detecting vegetable oil adulteration in hazelnut paste (Corylus avellana L.)

The possibilities of detecting hazelnut paste adulterated with refined and non-refined vegetable oils have been studied. Research was focussed mainly on peanut, high oleic-acid sunflower, corn and soybean oils which have a similar composition to hazelnut oil. The analytical procedures to detect fatty acid (FA), triacylglycerol (TAG) and tocopherol profiles as indicators of adulteration were determined. The better indicators experimentally determined were seven FA (palmitic, stearic, linoleic, linolenic, arachidonic, behenic and lignoceric acids) and different TAG with three unsaturated FA (the code letters used for FA are: P = C_16:0; S = C_18:0; O = C_18:1; L = C_18:2;; L_n = C_18:3) (LLL_n, LLL and OOO), two unsaturated FA (POL, PLL and SOO), and one unsaturated FA (PPL). As expected, when refined vegetable oils were added to hazelnut paste, the increment of stigmasta-3,5-diene allowed detection at levels of 2% oil added. Limits of detection were measured using standard and adulterated hazelnut with different amounts of non-refined vegetable oils added (5%, 10%, 20% and 30%). The distribution of tocopherols and tocotrienols is highly useful, except in the case of added sunflower oil. The differences between the experimental and theoretical values of the TAG with equivalent carbon number (ΔECN) of 42 does not improve the detection limit of hazelnut paste adulterated with peanut or sunflower oils. Similarly, tocopherols usually added to refined vegetable oils as an antioxidant were also determined.     

High level communication functionalities for wireless sensor networks

In this paper we show how to establish a reliable and efficient high level communication system in a randomly deployed network of sensors equipped with directional antennas. This high level communication system enables the programming of the sensor network using high level communication functionalities without the burden of taking care of their physical capacities (low range, unidirectional links, single frequency, presence of collisions, etc.). The high level communication functionalities we offer include point-to-point communication, point-to-area communication, and one-to-all communication. The basic idea to implement this system is to simulate a virtual network that emerges from the ad-hoc network using self-organization, self-discovery and collaborative methods. We also analyse the efficiency, scalability and robustness of the proposed protocols.     

Dynamical modeling of transport in MOS structures containing silicon nanocrystals for memory applications

A compact model that can be used to reproduce both quasi-static and dynamic characteristics of basic MOS cells with embedded Si-nc is presented. The structure is modeled through a device-like complex matrix of tunnel junctions, resulting in a time-dependent non-linear system of differential equations that is numerically solved, including calculation of the capacitance matrix, analytical tunneling expressions (direct and Fowler-Nordheim) for electrons/holes, and derivation of the effective tunneling area. The threshold evolution is calculated by monitoring the charge at each Si-nc as a function of time. The model is successfully validated against experimental data, showing its applicability to predict program/erase characteristics of nanocrystal memories as well as threshold voltage bit-to-bit dispersion as a consequence of geometrical non-uniformities in the nanocrystal layer position and/or gate areal coverage.     

HS-SPME coupled to GC/MS for quality control of Juniperus communis L. berries used for gin aromatization

HS-SPME coupled to GC/MS was applied to the analysis of the volatile fraction of Juniperus communis L. berries, which are the principal ingredient used for gin aromatization. Seventy seven compounds were identified by comparison with reference compounds or tentatively identified by comparing their mass spectra and retention index with those reported in mass spectra libraries and literature, respectively. Seventy four were detected by SPME and sixty eight were detected by solvent distillation extraction (SDE). These were mainly mono- and sesquiterpenic compounds that represented more than the 80% of the gin’s volatile composition. A high percent content was due to monoterpenoids, whose analysis could be important for the assessment of sensory quality control of juniper due to their impact on gin aroma. The main monoterpenoids detected in the headspace of the juniper berries from two periods of collection were terpinen-4-ol, p-cymene, β-myrcene, γ-terpinene, α-pinene and limonene. These represented more than the 70% of the sample’s volatile fraction. The proposed SPME method required short times and the low cost of analysis and enabled to detect a number of compounds comparable with SDE or much higher than the number of compounds reported by other extraction techniques. The results suggested the suitability of this technique for the assessment of the volatile composition of juniper berries intended for gin flavouring.