Spare parts provisioning for multiple k-out-of-n:G systems

In this paper, we consider a repair shop that fixes failed components from different k-out-of-n:G systems. We assume that each system consists of the same type of component; to increase availability, a certain number of components are stocked as spare parts. We permit a shared inventory serving all systems and/or reserved inventories for each system; we call this a hybrid model. Additionally, we consider two alternative dispatching rules for the repaired component. The destination for a repaired component can be chosen either on a first-come-first-served basis or by following a static priority rule. Our analysis gives the steady-state system size distribution of the two alternative models at the repair shop. We conduct numerical examples minimizing the spare parts held while subjecting the availability of each system to exceed a targeted value. Our findings show that unless the availabilities of systems are close, the HP policy is better than the HF policy

The Impacts of Inward and Outward FDI on Income Inequality in Turkey and Selected Turkic Republics

This study investigates the effects of inward and outward FDI on income inequality in Turkey, Azerbaijan, Georgia, Kazakhstan, Kyrgyzstan, Turkmenistan and Uzbekistan. The methodology covers panel cointegration techniques and balanced panel regressions. The conclusion is that inward and outward FDI have averagely a negative impact on income inequality in the long-run period but on the other hand the short-run effect of inward and outward FDI on income inequality is positive. The conclusion is robust to using different methods for estimation, sample selection and controlling for potential outliers

ROLE OF PUBLIC PRIVATE PARTNERSHIP (PPP) MODEL IN ENERGY INVESTMENTS

The public-private partnership model (PPP) has been met with concern by the community because the privatization model can be confused with itself. PPP models have been used in many sectors around the world and the disadvantages that have emerged with their advantages have been examined. In the energy sector, the contributions of the relevant models were assessed along with the new developments and the results were tried to be found together with the sub-results

Analysis of the finite-source multiclass priority queue with an unreliable server and setup time

In this article, we study a queueing system serving multiple classes of customers. Each class has a finite-calling population. The customers are served according to the preemptive-resume priority policy. We assume general distributions for the service times. For each priority class, we derive the steady-state system size distributions at departure/arrival and arbitrary time epochs. We introduce the residual augmented process completion times conditioned on the number of customers in the system to obtain the system time distribution. We then extend the model by assuming that the server is subject to operation-independent failures upon which a repair process with random duration starts immediately. We also demonstrate how setup times, which may be required before resuming interrupted service or picking up a new customer, can be incorporated in the model

Strategies for a centralized single product multiclass M/G/1 make-to-stock queue

Make-to-stock queues are typically investigated in the M/M/1 settings. For centralized single-item systems with backlogs, the multilevel rationing (MR) policy is established as optimal and the strict priority (SP) policy is a practical compromise, balancing cost and ease of implementation. However, the optimal policy is unknown when service time is general, i.e., for M/G/1 queues. Dynamic programming, the tool commonly used to investigate the MR policy in make-to-stock queues, is less practical when service time is general. In this paper we focus on customer composition: the proportion of customers of each class to the total number of customers in the queue. We do so because the number of customers in M/G/1 queues is invariant for any nonidling and nonanticipating policy. To characterize customer composition, we consider a series of two-priority M/G/1 queues where the first service time in each busy period is different from standard service times, i.e., this first service time is exceptional. We characterize the required exceptional first service times and the exact solution of such queues. From our results, we derive the optimal cost and control for the MR and SP policies for M/G/1 make-to-stock queues

World in Motion: Films from the Collection of the Museum of Ordure

World in Motion (2014) Museum of Ordure proposes a programme of films entitled: WORLD IN MOTION Films from the Collection of the Museum of Ordure Taking the framework of the Aarhus Rapport 1961-1969 as a springboard to examine the modernist avantgarde, the Museum of Ordure’s contribution to the exhibition Systemics #4. Aarhus Rapport 1969-2017: Avantgarde as Network (or, the Politics of the Ultralocal) is a series of films chosen from its collection of World Cinema which is expanded in time and narrative. The Collection emphasises shared content rather than authorship or nationality. The Aarhus Rapport was designed as an event which implies a transitional condition. Did it have a beginning and an end for example, or did it happen as a disclosure of converging interests without a conclusion? Was the event autonomous, did it have a political identity? Was there a grand design or did it appear as a set of independent speculations and in the process ‘naturalised’ itself? Provincialism is generally understood as a state of mind which is narrow in scope and is often seen in contrast to the universalism of the avant-garde. Political principle which applies to provincialism is localism which stands in opposition to great schemes and opposes centralisation. Does this contradict the revolutionary universalism of the avant-garde? These opposing philosophical and political questions have occupied generations and continue to do so which lie at the core of the debates surrounding the modernist avant-garde which see a community, group or nation as an ‘imagined community’ (Benedict Anderson). Imagined communities can be interpreted as a social construction, as in Edward Said’s ‘imagined geographies’. Drawing from films through time and narrative the Museum of Ordure is setting in motion these questions via the twin natural impulses of subject and content. All films are held in our distributed collection across peer-to-peer networks (the commons). In this way the Museum is also promoting commonism by questioning ownership, copyright and acts of piracy. Working on the edges of legality and transgressing the framework of capitalism has urgency as never before. The Museum is further posing the question of inertia – how is a human being to be lifted from an infused condition of helplessness prevailing our times. What kind of a ‘rhizomatic’ system (Gilles Deleuze & Felix Guattari) is possible with common principles of action, justice and equality? Here, the Museum of Ordure is proposing collectivity rather than individualism as a forward mechanism which enhances the inner life of a human being rather than oppressing it. Our bodies and consciousness have been subjugated since time immemorial, human beings have been dishonoured and wasted throughout time and history has been rendered incomprehensible. Can a network of the willing act as agents of unforgetting towards a new reality

On the use of phase-type distributions for inventory management with supply disruptions

Cataloged from PDF version of article.Maintaining the continuity of operations becomes increasingly important for systems that are subject to disruptions due to various reasons. In this paper, we study an inventory system operating under a (q, r) policy, where the supply can become inaccessible for random durations. The availability of the supply is modeled by assuming a single supplier that goes through ON and OFF periods of stochastic duration, both of which are modeled by phase-type distributions (PTD). We provide two alternative representations of the state transition probabilities of the system, one with integral and the other employing Kolmogorov differential equations. We then use an efficient formulation for the analytical model that gives the optimal policy parameters and the long-run average cost. An extensive numerical study is conducted, which shows that OFF time characteristics have a bigger impact on optimal policy parameters. The ON time characteristics are also important for critical goods if disasters can happen. Copyright (C) 2011 John Wiley & Sons, Ltd

Istraživanje savijanja čistih i hibridnih kompozitnih drvnih ploča uz pomoć Weibullove analize

The production of inexpensive wood products compared to their strength is important both in terms of economy and meeting the expectations of users. For this purpose, the use of hybrid wood products is increasing in the furniture industry. With the hybridization process, relatively cheap and flimsy material is combined with a material that has a stronger structure. Thus, stronger bonded material is manufactured cheaper. In this study, the flexural behavior of pure and hybrid wood composite panels, which were prepared by applying longitudinal jointing techniques from different wood materials, was investigated. In this context, pure chipboard, pure medium density fiberboard (MDF), chipboard-east beech and MDF-east beech hybrid wood composite panels were produced. During the hybridization process, oriental beech was combined by using the self-grooving technique in three different numbers as one row, two rows, and three rows. Flexural test results were analyzed according to the Weibull distribution method. The results of the analyses showed that the hybridization process increased the flexural strength and flexural modulus of pure wood panels by up to 214 %, and 95 %, respectively.Proizvodnja jeftinijih proizvoda od drva uz očuvanje njihove čvrstoće ima veliku važnost u ekonomskom smislu i u smislu ispunjavanja korisničkih očekivanja. Rezultat tog nastojanja jest sve veća uporaba hibridnih proizvoda od drva u industriji namještaja. Postupkom hibridizacije relativno jeftin i krhak materijal kombinira se s materijalom jače strukture te se na taj način postiže čvršći a jeftiniji materijal. U ovom je radu istraženo ponašanje čistih i hibridnih kompozitnih drvnih ploča pri savijanju, proizvedenih uzdužnim lijepljenjem različitoga drvnog materijala. Za potrebe istraživanja izrađene su čista ploča vlaknatica srednje gustoće (MDF) i hibridne kompozitne ploče od iverice i bukovine te od MDF ploče i bukovine. Tijekom postupka hibridizacije bukovi su elementi povezivani uz pomoć utora, a izrađeni su uzorci imali jedan, dva ili tri bukova elementa. Rezultati ispitivanja svojstava ploča pri savijanju analizirani su uz pomoć Weibullove distribucije. Pokazalo se da je postupak hibridizacije pridonio povećanju čvrstoće ploča na savijanje za 214 %, a modula elastičnosti za 95 %

The Fracture Behavior of Pure and Hybrid Intraply Knitted Fabric-Reinforced Polymer Composites

Due to the high synergistic effects of the components, hybrid composite materials are more advantageous than nonhybrid composite materials for advanced engineering applications. Additionally, knitted fabrics may have a different behavior than woven ones. Although the nonhybrid composites have only one reinforcing fiber type, the hybrid composites have multiple reinforcing fibers. In this chapter, fracture characterizations of laminated composites reinforced with intraply pure and hybrid knitted fabrics are experimentally and numerically investigated under different loading conditions. For this purpose, pure (100%) and hybrid fabrics (50–50%), which have 1 × 1 rib-knitted structure, were knitted by using glass and carbon fibers. Also, hybrid fabrics were knitted in three different widths in order to investigate the effect of knitting pattern width on the fracture toughness. Fracture toughness and energy strain release rates of pure and hybrid Arcan test specimens were determined under mode I (0o), mixed-mode I/II (30o, 45o, and 60o), and mode II (90o) loading conditions. Also, the J-integral method was used to determine the fracture toughness. Experimental and numerical results were found to be consistent. When the results obtained from pure and hybrid fabrics are compared, it is seen that hybridization had positive effects on the fracture strength of composite material compared to pure glass/epoxy material. Additionally, as the width of the pattern decreased, the fracture strength of the hybrid composites increased. In this respect, the hybridization processing should be done in the narrowest pattern width for higher resistance to fracture