A new approximate evaluation method for two-echelon inventory systems with emergency shipments

We consider the control of repairable spare parts in a network consisting of a central warehouse, a central repair facility, and multiple local warehouses. Demands for spare parts occur at the local warehouses. If a local warehouse is out of stock, then an arriving demand is satisfied by an emergency delivery from the central warehouse or the central repair facility. Such emergency shipments are common practice for networks that support technical systems with high downtime costs, and it is important to take them into account when the inventory is optimized. Our main contribution consists of the development of a new approximate evaluation method. This method gives accurate approximations for the key performance measures, as we show via numerical analysis. The method is also fast and thus can easily be incorporated in existing (greedy) heuristic optimization methods. Our method outperforms the approximate evaluation method of Muckstadt and Thomas (1980), as we also show via the numerical analysis. Finally, we show that the performance of the system is rather insensitive to the leadtime distribution of the repairs at the central repair facility, which implies that our method works well for generally distributed repair leadtimes

Kurgu veya Olgu Oluş Bağlamında Benlik Sorunu

Öz: Felsefenin benlik konusundaki geleneksel tutumu töz dualizmine başvurarak açıklanabilir. Çağdaş zihin araştırmalarında benlik ise, daha çok fizik dünyanın gerçekliği dolayımıyla ve genellikle bilinçli zihin durumu olarak olgusallık temelinde araştırılmaktadır. Bu çalışmada ise benliğin olgusallığı, olgu ve kurgu kategorilerinin bilgikuramsal bir çözümlemesi aracılığıyla ve mantığa uyarlık açısından ele incelenecektir. Bu bağlamda “olgu” ve “kurgu”yu bir tür karşıtlık ya da derin farklılıklar içeren iki kavram olarak açıklamanın haklı gerekçelere dayanmadığı öne sürülmektedir. Buna bağlı olarak da herhangi bir zihin araştırmasının benliği olgu saymadan yapılamayacağı savunulmaktadır. Bu çalışmada özellikle deneyime ilişkin yeni bir kavrayışın gerekli olmasının sonucunda benlik tartışmalarının belli türden bir araştırma programı izlendiğinde gündemimize taşıyabileceği olanaklar soruşturulacaktır

Evaluating the Effects of Improving Forest Road Standards on Economic Value of Forest Products

Forest roads are the key infrastructures that provide access to forest areas for sustainable management, protection, and utilization of forest resources. In order to benefit from the important functions of forest roads, they should be built in with adequate technical road standards. The road network with low technical standards require more frequent major repairs to ensure continues access to forest resources. In addition, only small trucks with low load capacity can move on the low standard roads. Furthermore, the low road standards limit the truck speed that increases vehicle travel time. These negative effects increase the transportation costs which are an important part of the timber production costs in Turkey. Thus, improving the road standards and developing forest transportation planning should be evaluated together in the most appropriate way. Large logging trucks with high load capacity are generally preferred for efficient transportation of wood-based forest products. In Turkey, large logging trucks, however, cannot operate on the most of the forest roads because insufficient technical road standards (road width, curve radius, surface materials, road structures) limit the maneuverability of large logging trucks. In this study, the objective is to determine the effects of improving forest road standards on total net profit of forest products by using the NETWORK 2000 program, a heuristic approach for solving forest transportation problems. Three Forest Enterprise Chiefs (FECs) located in Mustafakemalpaşa Forest Enterprise Directorate (FED) in Bursa Forest Regional Directorate were selected as the study area. The digital data layers for forest road network was generated by using ArcGIS 10.4 software. In the solution process, firstly, the optimum routes that minimize the transportation cost and maximize the total net profit of forest products on existing forest road networks were investigated for a truck type (15 ton) currently used in the region. In the second case, forest transportation was planned for the high load capacity truck (29 ton) moving on the forest roads with improved standards. In the first case, the transportation costs and annual major repair costs were considered in the calculation of the net profit of forest products, while one time cost of road improvement activities (i.e. road improvement construction, road structure installation, road surface construction) and annual maintenance costs were considered along with transportation costs in the second case. In both cases, the costs of other forest operations (i.e. felling, logging, etc.) were not considered since it was assumed that they do not vary with the forest transportation alternatives. As a result of the transportation plan developed for high load capacity truck, the annual transportation cost decreased by 46.85% comparing to the local logging trucks with low load capacity. Using improved road standards, the total road costs computed for the time period of 30 years (i.e. the average expected life cycle of forest roads) were reduced by 4.64%. The total net profit of forest products transported by using a high load capacity truck was 473 340 Euro more than that of using low load capacity truck on the existing forest road network. Thus, improving road standards might result in some additional costs in the road construction stage, but total net profit of forest products increase since transportation costs along with maintenance and repair costs considerably decrease in the long term

The problem of self in the context of being fiction or phenomenon

Felsefenin benlik konusundaki geleneksel tutumu töz dualizmine başvurarak açıklanabilir. Çağdaş zihin araştırmalarında benlik ise, daha çok fizik dünyanın gerçekliği dolayımıyla ve genellikle bilinçli zihin durumu olarak olgusallık temelinde araştırılmaktadır. Bu çalışmada ise benliğin olgusallığı, olgu ve kurgu kategorilerinin bilgikuramsal bir çözümlemesi aracılığıyla ve mantığa uyarlık açısından ele incelenecektir. Bu bağlamda “olgu” ve “kurgu”yu bir tür karşıtlık ya da derin farklılıklar içeren iki kavram olarak açıklamanın haklı gerekçelere dayanmadığı öne sürülmektedir. Buna bağlı olarak da herhangi bir zihin araştırmasının benliği olgu saymadan yapılamayacağı savunulmaktadır. Bu çalışmada özellikle deneyime ilişkin yeni bir kavrayışın gerekli olmasının sonucunda benlik tartışmalarının -belli türden bir araştırma programı izlendiğinde- gündemimize taşıyabileceği olanaklar soruşturulacaktır.The traditional attitude of philosophy towards self can be explained by invoking the dualism of substance. In contemporary research of mind, self is mostly investigated through the reality of the physical world and generally on the basis of reality as a conscious state of mind. In this paper, the phenomenality of self will be examined in terms of logic and through an epistemological analysis of the categories of phenomena and fiction. In this context, it is argued that it is not justified to describe "phenomenon" and "fiction" as two concepts that contain a kind of opposition or deep differences. Accordingly, it is argued that any research of mind cannot be done without considering self as a phenomenon. In this study, especially as a result of the necessity of a new understanding of experience, the possibilities that debates on self can bring to our agenda, when a certain type of research program is followed, will be investigated

Experimental application of sum rules for electron energy loss magnetic chiral dichroism

We present a derivation of the orbital and spin sum rules for magnetic circular dichroic spectra measured by electron energy loss spectroscopy in a transmission electron microscope. These sum rules are obtained from the differential cross section calculated for symmetric positions in the diffraction pattern. Orbital and spin magnetic moments are expressed explicitly in terms of experimental spectra and dynamical diffraction coefficients. We estimate the ratio of spin to orbital magnetic moments and discuss first experimental results for the Fe L_{2,3} edge.Comment: 11 pages, 2 figure

Tableaux accessibles dans les documents numériques THEMATIQUE -Informatique -Robotique -Imagerie

National audienceAccessibility of tables on websites for Visually Impaired Persons (VIP) is not optimal with screen readers which are not always effective for the recovery of visual information (2D). Actual Web/Multimedia technologies are not taking in account the difference of the visual perception with respect to the vocal perception which is linear. This paper analyses the difficulties for accessing to spatial information with the existing recommendations for the conception of accessible (for all) websites. Different solutions to facilitate accessible table creation are presented.L'accessibilité des tableaux sur les sites web pour les personnes présentant une incapacité visuelle (PPIV) n'est pas optimale avec les lecteurs d'écran qui ne sont pas toujours performants pour la restitution d'informations visuelles (2D). Les technologies web/multimédia actuelles ne prennent pas en compte le décalage de la perception visuelle par rapport à la perception vocale qui est linéaire. Ce papier analyse les difficultés d'accès à l'information spatiale avec les recommandations existantes pour la conception des sites web accessibles à tous. Différentes solutions pour faciliter la création des tableaux accessibles sont présentées

Using computer-assisted optimum bucking method in producing log

Orman ürünlerinin üretiminde ağaçtan elde edilecek toplam ekonomik değerleri en yüksek miktara çıkarmak için bütün muhtemel boylama kombinasyonları hızla değerlendirilmeli ve bunlar arasından optimum boylama kombinasyonu seçilmelidir. Birçok alternatif çözüm içeren bu tip problemlerin sistematik olarak çözülebilmesi için bilgisayar destekli yöntemlere gereksinim duyulmaktadır. Bu çalışmada, ağ analizi tabanlı NETWORK 2001 yazılımı kullanılarak tek ağaç düzeyinde optimum boylama yöntemi uygulanmıştır. Uygulama, Artvin Orman Bölge Müdürlüğü, Ardanuç Orman İşletme Müdürlüğü, Ovacık Orman İşletme Şefliği sınırlarında yer alan Kafkas Göknarları (Abies nordmanniana) üretim sahasında gerçekleştirilmiştir. Daha sonra, optimum boylama yönteminden elde edilen sonuçlar ile geleneksel boylama yönteminin sonuçları karşılaştırılmıştır. Sonuçlar, optimum boylama yönteminin üretilen ağaçların toplam ekonomik değerlerini %12’ye kadar (ortalama %5,20) arttırabileceğini göstermiştir. Ayrıca, optimum boylama yönteminin uzun ve kalın çaplı tomruklara sahip yüksek hacimli ağaçlarda daha iyi sonuç verdiği bulunmuşturIn order to maximize total economic value of a tree during extraction of forest products, all of the possible bucking combinations should be quickly evaluated and optimum bucking combination should be selected among them. The computer-assisted methods are required to systematically solve such problems with many alternative solutions. In this study, single tree level (stem-level) optimum bucking method was implemented by using network analysis based NETWORK 2001 software. The application was conducted in a harvesting unit of Caucasian Fir (Abies nordmanniana) stand located in Forest Regional Directorate of Artvin, Forest Enterprise Directorate of Ardanuç, Forest Enterprise Chief of Ovacık. Then, the results from optimum bucking method were compared with the results from the traditional bucking method. The results indicted that optimum bucking method increased the total economic values of harvested trees up to 12% (average 5.2%). Besides, it was found that optimum bucking method provided better results for high-volume trees with long and large diameter logs

Experimental study of solubility of elemental sulphur in methane

International audienceThe chemical engineering department of LaTEP has been working for many years on theproblem of sulphur deposition especially in natural gas network [1, 2]. The solid sulphurappears immediately downstream of a pressure reduction facility. One of the hypothesesproposed to explain the solid formation, based on a thermodynamic approach, is thedesublimation of sulphur. During gas expansion, both pressure and temperature decrease.Consequently the gas may become over saturated in sulphur. Because we are below thetemperature of sulphur triple point, part of the gaseous sulphur can be transformed into solidparticles. Thus, it is important to obtain solubility data of sulphur in natural gases. Methane isthe major natural gas component. So, it is of importance to measure solubility of elementalsulphur in CH4. In this paper experimental measurements up to a pressure and temperature of30 MPA and 363.15 K are presented.The principle of the experimental pilot can be resumed following three steps: saturationof the gas with sulphur, trap of all the dissolved gaseous sulphur and finally quantification.Although the principle is simple, experimental difficulties occur at the three steps. A variablevolume equilibrium cell is used to saturate the gas with sulphur. Since sulphur solubility valueis weak in gas transport conditions, the volume of the cell is necessarily big (0.5 Litre). Thepressure of the equilibrium cell is held constant thanks to a piston during the trapping step. Anoriginal gaseous sulphur trapping method was developed. It is based on the reactiveabsorption of the gaseous sulphur with solvent. Indeed, the gas bubbles into a liquid solutionwhich traps gaseous sulphur. Finally, the solution which contains a standard is analysed bygas chromatography and sulphur is quantified. The total volume of the gas withdrawn isdetermined by a position transducer placed on the autoclave. Then, the sulphur solubilityvalue is calculated

The Minimal Supersymmetric Standard Model: Group Summary Report

CONTENTS: 1. Synopsis, 2. The MSSM Spectrum, 3. The Physical Parameters, 4. Higgs Boson Production and Decays, 5. SUSY Particle Production and Decays, 6. Experimental Bounds on SUSY Particle Masses, 7. References.Comment: 121 pages, latex + epsfig, graphicx, axodraw, Report of the MSSM working group for the Workshop "GDR-Supersym\'etrie",France. Rep. PM/98-4