Ranking units in DEA based on efficiency intervals and decision‐maker's preferences

Data Envelopment Analysis (DEA) uses the best favorable weight set for the inputs and outputs of each decision‐making unit (DMU) to obtain its best possible score. Hence, this score can be considered as an upper bound of the real efficiency score. If we also use the least favorable weight set of each DMU, then a lower bound of the efficiency score can also be obtained. So, instead of one score, we can find an interval that gives all possible values of the efficiency score for each DMU. The aim of this paper is to propose an approach for determining efficiency intervals and setting up a full ranking of DMUs based on these intervals. We incorporate explicitly the decision‐maker's preferences in two phases. The first phase is for obtaining efficiency intervals, by introducing some restrictions on the input and output weights. The second one is for ranking the intervals based on the combination of the lower and the upper bounds of the efficiency intervals. The developed formulations will be illustrated through some numerical examples.     

Spatial power amplifier using a passive and active TEM waveguide concept

A new spatial power amplifier is presented in which power is spatially combined within a TEM waveguide using a low-loss transition array of E-plane integrated finlines to microstrip lines. The TEM-mode waveguide is implemented using a periodically patterned surface called a uniplanar compact electromagnetic bandgap (UC-EBG) structure. Our designed Ku-band back-to-back transition array demonstrates a maximum return loss of 17.5 dB and a maximum insertion loss of 0.65 dB. The TEM waveguide is found to have a 1-GHz bandwidth centered at 14.5 GHz. Tuning of the center frequency may be accomplished via an active UC-EBG structure that incorporates varactor diodes. The use of the UC-EBG surface allows more power cards to be inserted within the TEM waveguide since the amplifier cells saturate uniformly. The spatial power combiner is used to combine the output powers of 12 20-mW monolithic-microwave integrated-circuit amplifier chips. The designed power module yields an output power of 23.15 dBm and a combining efficiency of 86%. A comparison between the passive and active UC-EGB surfaces is experimentally demonstrated.     

Adaptive vectorial lifting concept for convolutive blind source separation

This paper describes a new multi-resolution approach for the blind separation of convolutive image mixtures in transform domain. The proposed method uses an Adaptive Vectorial case of Quincunx Lifting Scheme (AVQLS), based on wavelet decomposition, and a geometric unmixing algorithm. It proceeds in three steps: first, the mixed images are decomposed by AVQLS. Then, the unmixing algorithm is applied to the more relevant component to get a transformed estimate of the original images. An inverse transform is, thereafter, applied to obtain an estimate of the original images. Experiments carried out on medical images showed that the proposed method yields better separation results than many widely used blind source separation algorithms.     

Application of Cyclic Spectral Analysis in Diagnosis of Bearing Faults in Complex Machinery

Bearing failure can lead to major damage to rotating components and its diagnosis and prognosis are therefore of paramount importance. Techniques and approaches for detecting bearing faults abound. However, application of these methods is limited for complex systems such as aircraft engines. This stems from the fact that the complex configuration of the system and inaccessibility make it difficult to place the vibration transducers close to the bearings. In most cases, available instrumentation is limited to few vibration transducers on the casing of the machine. In such cases, the vibration due to bearing faults is barely detectable using traditional methods, because it normally makes only a small contribution to the overall energy and this is to some extent dissipated by the transmission path. For bearing fault detection to be effective in such applications, the methodology must be capable of detecting faint bearing signals and also allow consistent trending and tracking. This study examines these requirements in detail and presents an experimental assessment of newly emerging cyclic spectral analysis in this field for such requirements.     

Electrochemical treatment of olive mill wastewaters: Removal of phenolic compounds and decolourization

Olive mill wastewaters (OMW) characterized by their dark brown colour and their very high content of phenolic compounds constitute an environmental concern, particularly in Mediterranean countries where the production of olive oil is important. In this investigation, OMW were electrolyzed at platinized expanded titanium electrodes in a modified Grignard reactor divided into two cylindrical compartments separated by a cation-exchange membrane. Results show better than 90% decolourization and nearly 85% removal of phenols, as established by gas chromatography/mass spectrometry, at high current intensity. This process can easily be monitored by cyclic voltammetry at a boron-doped diamond electrode. A significant reduction of chemical oxygen demand and total organic carbon was observed. The electrodes are not passivated and the ohmic potential drop is very low. Electrochemical oxidation in a modified Grignard reactor is a promising process for the destruction of phenolic compounds present in OMW.     

Nonlinear supersonic flutter of truncated conical shells

A numerical model was developed to investigate the flutter instability of truncated conical shells subjected to supersonic flows. The exact solution of Sanders’ best firstorder approximation was used to develop the finite elements model of the shell. Nonlinear kinematics of Donnell’s, Sanders’ and Nemeth’s theories, in conjunction with the generalized coordinates method, were used to formulate the nonlinear strain energy of the shell. A pressure field was formulated using the piston theory with the correction term for the curvature. Lagrangian equations of motion based on Hamilton’s principle were obtained. A variation of the harmonic balance method was used for developing the amplitude equations of the shell, and a numerical method was used for solving these equations. Results of linear and nonlinear flutter of truncated conical shells were validated against the existing data in the literature. It was observed that geometrical nonlinearities have a softening effect on the stability of the shell in supersonic flows.     

Occurrence and characterization of Escherichia coli O157 and other serotypes in raw meat products in Morocco

In this study, 100 raw meat samples were collected from 15 local Moroccan butcheries in five different areas of the city of Rabat during a period of 4 months. Overall, 7 of 15 butcheries from three areas of the city yielded strains of Escherichia coli O157. Single isolates from 9 (9%) of 100 raw meat samples were biochemically and serologically confirmed as E. coli O157. Using molecular techniques, two strains were positive for the Shiga toxin, with two additional strains containing an attaching-effacing gene. All potentially virulent serotypes isolated from these meat samples showed distinct pulsed-field gel electrophoresis profiles. Based on antibiotic susceptibility testing, more than 70% of the isolates were resistant to ampicillin and clavulanic acid-amoxicillin. Moreover, one strain was resistant to more than three antibiotics. Our study represents the first survey of E. coli O157 and related serotypes in raw meat products in Morocco.     

Resource‐constrained project scheduling through the goal programming model: integration of the manager's preferences

The aim of this paper is to present a multi‐objective project scheduling approach to help project managers when deciding on a baseline schedule. The concepts of satisfaction functions and goal programming are incorporated to generate this baseline schedule that represents the best compromise among a set of conflicting project objectives. An efficient computerized procedure based on the tabu search algorithm is proposed and enables the handling of large planning and scheduling projects.