Capacity allocation problem in flexible manufacturing systems: branch and bound based approaches

This study considers an operation assignment and capacity allocation problem that arises in flexible manufacturing systems. The machines have limited time and tool magazine capacities and the available tools are limited. Our objective is to maximise total weight of assigned operations. We develop a branch and bound algorithm that finds the optimal solutions and a beam search algorithm that finds high quality solutions in polynomial time.     

Artificial neural network and regression models for performance prediction of abrasive waterjet in rock cutting

An experimental study is carried out for modeling the rock cutting performance of abrasive waterjet. Kerf angle (KA) is considered as a performance criteria and modeled using artificial neural network (ANN) and regression analysis based on operating variables. Three operating variables, including traverse speed, standoff distance, and abrasive mass flow rate, are studied for obtaining different results for the KA. Data belonging to the trials are used for construction of ANN and regression models. The developed models are then tested using a test data set which is not utilized during construction of models. Additionally, the regression model is validated using various statistical approaches. The results of regression analysis are also used to determine the significant operating variables affecting the KA. Furthermore, the performances of derived models are compared for showing the accuracy levels in prediction of the KA. As a result, it is concluded that both ANN and regression models can give adequate prediction for the KA with an acceptable accuracy level. The compared results reveal also that the corresponding ANN model is more reliable than the regression model. On the other hand, the standoff distance and traverse speed are statistically determined as dominant operating variables on the KA, respectively.     

A simulation study of performance evaluation of single-stage absorption refrigeration system using conventional working fluids and alternatives

This study presents a literature review, especially in recent years, on the absorption refrigeration systems (ARSs), the currently used refrigerant–absorbent pairs and their alternatives. Additionally, in this study, the thermodynamic analysis of ARS using commonly encountered solution pairs in the literature was carried out, and a user-friendly software package including visual components was developed. The effects of operating temperatures, the effectivenesses of solution, refrigerant and solution–refrigerant heat exchangers (SHE, RHE, SRHE), and selection of working fluid pair on the system performance were examined by using the developed package. It was concluded that performances of the cycles improve with increasing generator and evaporator temperatures, but reduce with increasing condenser and absorber temperatures. The performance of system was affected from the SHE more than the RHE and SRHE. While the use of SHE improves the system COP up to 66%, RHE and SRHE have an effect of only 14% and 6%, respectively. For that reason, the SRHE may not be considered practically significant. Suitable solutions depending on operating conditions showed variations with respect to generator and evaporator temperatures.     

Exploring the dynamics of the Turkish construction industry using input–output analysis

Construction is commonly regarded as an important industry in economic policy making owing to its strong interactions with other sectors in the economy. Using six national input–output (IO) tables compiled to date and economic data for the period between 1969 and 2006, the behaviour of the Turkish construction sector and its relationships to investment, income and to other sectors in the economy are examined. Analysis reveals that the construction industry is losing its propulsive role and that it tends to exaggerate the fluctuations of the economy. The examination of lead and lag times between changes in GNP, construction activity and investments show that public sector spending cuts, in particular, have significant effects on the amplitude and the timing of slumps of the industry. The analysis of linkage indicators indicates that for the whole period under consideration the construction industry has high linkages with only one other industry. Thus the ‘leading’ role it plays in the economy is questioned.     

Allochthonous blocks misidentified as the basement: Implication for petroleum exploration in the SW Thrace Basin (Turkey)

The sedimentary sequence of the SW Thrace Basin (NW Turkey) comprises of three major sedimentary packages: a) Cretaceous (Meastrichtien)–Early Eocene package formed as pelagic carbonate, turbidite, shelf and nearshore-fluvial deposits, b) Middle Eocene–Early Oligocene package formed as shallow marine, slope apron and turbidite sediments, c) Middle Miocene–Early Pliocene package formed as alluvial fan-fluvial and nearshore deposits. This basin is structurally complex and its southern margin is represented by a fold-thrust zone. The Westward Propagation of the North Anatolian Fault (WPNAF) intersects the Thrace Basin along its southwestern flank. In the SW Thrace Basin, there are ophiolite and limestone blocks in the sedimentary succession, which previously were interpreted as suture of the Intra-Pontide Ocean, Cretaceous aged Yeniköy Mélange or Olistostromal Unit in the Eocene sediments. In this study these rocks have been defined as allochthonous blocks facies of the Gaziköy Formation aged Middle–Late Eocene.In previous studies the Karaağaç Formation (Early Eocene) was considered to be within oil window and have an average potential for oil and gas generation. According to our data the Karaağaç Formation has a moderate TOC content, is mature and overmature. In the study area, there are potential stratigraphic traps (submarine fans and channels of the Karaağaç and Keşan Formations, fluvial channels of the Fıçıtepe Formation and reefs of the Soğucak Formation), potential fractured tuffs (the Gaziköy Formation) and, potential structural traps related to the folds, thrusts and the WPNAF. Although 17 exploration wells have been drilled in the study area and vicinity, no discovery has yet been made. The cause of this may be that the wells were terminated at depths shallower than potential targets or possibly drilling may have been terminated at the allochthonous block facies of the Gaziköy Formation, which is especially derived from ophiolite mélange and was misidentified as basement.     

A three-way clusterwise multidimensional unfolding procedure for the spatial representation of context dependent preferences

Various deterministic and latent structure approaches for combining forms of multidimensional scaling and cluster analysis have been previously discussed. A new clusterwise three-way unfolding methodology for the analysis of two-way or three-way metric dominance/preference data is proposed. The purpose of this proposed methodology is to simultaneously estimate a joint space of stimuli and cluster ideal point representations, as well as the clusters themselves, such that the geometry underlying the clusterwise model renders some indication of the underlying structure in the data. In the three-way case, it is shown how multiple ideal points can represent preference change over contexts or situations. Partitions, overlapping clusters, stationary and context dependent preference representations are allowed. After a literature review of related methodological research, the technical details of the proposed three-way clusterwise spatial unfolding model are presented in terms of modeling context/situational dependent preferences (i.e., preferences for various stimuli collected over the same set of subjects over time, situation, etc.). The psychological basis for the models is provided in terms of the extensive behavioral decision theory and consumer psychology literature on contextual preferences and situational effects. An application to a data set exploring preferences for breakfast/snack food data over a number of different usage situations is then presented, followed by a discussion on future potential research directions.     

Multilayer Graphene Broadband Terahertz Modulators with Flexible Substrate

Fabrication of terahertz modulators as simple devices with high modulation depth across a broad bandwidth is still very challenging. In this study, four different chemical vapor deposition grown multilayer graphene (MLG) modulators based on MLG/ionic liquid/gold sandwich structures have been investigated. Flexible substrates (PVC and PE) were chosen as host materials, and devices were fabricated with three different thicknesses. The resultant MLG devices can be operated at low voltages between 0 and 3.4 V providing nearly complete modulation between 0.2 and 1.5 THz with low insertion losses. Even with such low gate voltages, the devices have been doped significantly inducing 7–11-fold improvement in their sheet conductivities depending on device thickness. In addition, sheet conductivity has been improved more than three times as the graphene layer number increased from 30 to 100. With the demonstration of promising device performances, the proposed modulators can be potential candidates for applications in terahertz and related optoelectronic technologies.     

Projection based method for segmentation of human face and its evaluation

We detect facial features and then circumscribe each facial feature with the smallest rectangle possible by using vertical and horizontal gray value projections of pixels. The result is evaluated with respect to the manually located enclosing rectangle on the images of a publicly available database.