A Stochastic Approach for Blind Estimation of Multiple Co-Channel Signals Received at an Antenna Array

A stochastic maximum likelihood approach for blind estimation of co-channel signals received at an antenna array is proposed in this letter. A hidden Markov model formulation of the problem is introduced and the Baum-Welch algorithm for the associated stochastic maximum likelihood estimation procedure is modified. The performance of the proposed algorithm based on the evaluation of approximate Cramer-Rao bounds is studied. Finally, some simulation results are presented.     

Semiempirical thermodynamic modeling of a direct methanol fuel cell system

In this study, a thermodynamic model of an active direct methanol fuel cell (DMFC) system, which couples in‐house experimental data for the DMFC with the mass and energy balances for the system components (condenser, mixing vessel, blower, and pumps), is formed. The modeling equations are solved using the Engineering Equation Solver (EES) program. This model gives the mass fluxes and thermodynamic properties of fluids for each state, heat and work transfer between the components and their surroundings, and electrical efficiency of the system. The effect of the methanol concentration (between 0.5 and 1.25 M) and air flow rate (between 20 and 30 mL cm^?2 min^?1) on the net power output and electrical efficiency of the system and the condenser outlet temperature is investigated. The results essentially showed that the highest value for the electrical efficiency of the system is 23.6% when the current density, methanol concentration, and air flow rate are taken as 0.2 A cm^?2, 0.75 M, and 20 mL cm^?2 min^?1, respectively. In addition, the air flow rate was found to be the most significant parameter affecting the condenser outlet temperature.     

Iliac artery stenosis measurements: comparison of two-dimensional time-of-flight and three-dimensional dynamic gadolinium-enhanced MR angiography

OBJECTIVE: We compared our ability to make iliac artery measurements on two-dimensional (2D) time-of-flight (TOF) and three-dimensional dynamic gadolinium-enhanced MR angiography with conventional angiography. SUBJECTS AND METHODS: Fifteen patients with lower extremity vascular disease underwent pelvic MR angiography. Parameters of the cardiac-gated axial 2D TOF sequence included a TR/TE of 24/7 msec and a 50 degrees flip angle. Parameters for the three-dimensional MR angiography sequence, in which we obtained 32 coronal 3-mm slices with fat suppression, included a TR/TE of 32/5 msec and a 40 degrees flip angle during infusion of 40 ml of gadolinium-chelated contrast material. Patients then underwent conventional angiography of the iliac arteries. Maximum stenosis in the common iliac, external iliac, and common femoral arteries was then measured. Measurements of stenosis were compared by repeated measures of analysis of variance. Sensitivity and specificity were calculated for identification of greater than or equal to 50% stenosis and less than 50% stenosis. RESULTS: For all vessels studied, we found no significant difference in measurements obtained from the gadolinium-enhanced MR angiography technique and those obtained from conventional angiography (p > .05). However, significantly different stenotic measurements were obtained from the 2D TOF MR angiography sequence and conventional angiography. In the external iliac arteries, 2D TOF MR angiography exaggerated stenoses most substantially. Gadolinium-enhanced MR angiography achieved 100% sensitivity and specificity. CONCLUSION: Dynamic gadolinium-enhanced MR angiography was more accurate than 2D TOF MR angiography when measuring degree of stenosis in the iliac arteries.     

Topography based design of the T-DAB SFN for a mountainous area

A method for designing a terrestrial digital audio broadcasting single frequency network (T-DAB SFN) for a mountainous region is proposed. A computer database and the digital terrain elevation data are used in designing the network. Two fundamental approaches are compared; first, utilization of the existing transmitter sites is maximized by applying the initial cost constraint; then, the coverage percent of the service is forced to approach to 100% by applying the coverage efficiency constraint. Finally, a T-DAB SFN hybrid design procedure optimizing both constraints is proposed. The three design approaches are illustrated on the coverage of the mountainous Istanbul-Ankara highway. The results are compared using a reference cost look up table. The hybrid approach is shown to optimize the initial cost and the coverage efficiency, and can be applied to similar networking problems     

Elimination of Yersinia enterocolitica on carrots (Daucus carota L.) by using household sanitisers

In this study, the effects of lemon juice, the mixture of lemon juice–vinegar (1:1) and lemon dressing against Yersinia enterocolitica on carrot were investigated. Carrots inoculated with Y. enterocolitica cells (approximately 10⁶ cfu/ml) were treated with 100%, 75% and 50% lemon juice, a mixture of lemon juice–vinegar, and lemon dressing for 0, 15, 30 and 60 min. Enumeration of Y. enterocolitica populations on CIN agar beside TSA agar by using two methods as then performed. One hundred percent lemon juice was the most effective agent used, completely inhibiting viable cells of Y. enterocolitica on carrot after 15 min exposure. Although no growth was observed on carrots treated with 100% lemon juice for 15 min, there was no statistical difference between the antibacterial effects of 100% lemon juice, 75% lemon juice, the mixture of lemon juice–vinegar and lemon dressing whilst the effect of 50% lemon juice was statistically different from those solutions (P < 0.05) and its definite inhibitive activity was seen after 60 min treatment.     

Effect of femtosecond laser beam angle and formed shape on surface roughness and shear bond strength between zirconia and resin cement

Achieving adhesion between resin cement and zirconia requires pretreatment of the surface. This in vitro study aimed to evaluate the effect of femtosecond laser beam angle and the shape of the formed surfaces, on the roughness and shear bond strength (SBS) of resin cement to zirconia ceramic. Seventy Y-TZP ceramic specimens were divided into seven groups (n = 10). A femtosecond laser irradiation was performed on the ceramic surface of three shapes (spiral (SP), square (SQ) and circular (CI) and at two angles (30 and 90°) to give SP-30, SQ-30 and CI-30 and SP-90, SQ-90 and CI-90, respectively. After treatment, the surface roughness of all specimens was evaluated using a profilometer. One specimen from each group was analysed using a scanning electron microscope. The bonded specimens were thermocycled 5000 times and then an SBS test was performed. Kruskal-Wallis and Mann-Whitney U tests were used to analyse surface roughness and SBS values. The control group had statistically lower surface roughness (R_a) values than the treated groups (p < 0.05). SP-30 and SQ-30 laser treated specimens showed higher R_a values than the other specimens. Statistically significant SBS values (p = 0.000) were observed between the groups. All laser treated samples showed greater SBS compared to the control group. SP-30, SQ-30 and SQ-90 groups showed the highest SBS values. Within the limitations of this experimental study, the highest mean values for R_a and SBS were achieved with SP and SQ surfaces using a 30° angle laser beam.     

MR imaging in squamous cell carcinoma of the head and neck with no palpable lymph nodes

PURPOSE: To assess the efficacy of MR imaging in the detection of lymph node metastasis in patients with no palpable lymph nodes ("N0 neck") who have squamous cell carcinoma of the head and neck region. MATERIAL AND METHODS: MR neck imagings in 18 patients who underwent neck dissection (bilaterally in 2) for squamous cell carcinoma of the head and neck region were examined preoperatively for the purpose of detecting lymph node metastases. The imaging features taken into consideration were: size (cutoff point 10 mm), grouping, presence of central necrosis, and appearance of extracapsular spread. The MR examinations comprised spin-echo T1- and T2-weighted sequences. The MR findings were compared with those of surgery and histopathological examination. RESULTS: MR suggested metastatic lymph node involvement in 5 necks. In 2 of these, central necrosis was seen in the enlarged lymph nodes. In a third, a grouping of the lymph nodes was noted. Extracapsular spread was not present. Histopathological examination revealed metastatic lymph nodes in 7 of the 20 necks, the rate of clinically occult disease being 35%, and 4 of them had been accurately graded by MR. There was one false-positive MR examination. The MR sensitivity was 57.1% and specificity 92.3%. CONCLUSION: MR may reveal metastatic lymph nodes in patients with no clinical evidence of metastasis. However, conventional MR techniques are not always sufficient for decision-making on surgery in cases of "N0 neck".     

A comparative study on mechanical properties of carbon fiber/PEEK composites

The aim of this work was to improve mechanical properties such as flexural strength and interlaminar shear strength (ILSS) of polyetheretherketone (PEEK) thermoplastic polymer which has very high processing temperature due to its high melting temperature. Carbon fiber (CF) surface was modified by two different methods: oxidative and non-oxidative. Piranha solution and chromate solution were used for chemical treatment (oxidative treatment), and silicone based polymers were used for polymer coating (non-oxidative). The changes on the surface structure and surface chemistry were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR), respectively. FTIR results indicate that coating fibers decreases carbon element content, whereas increases the oxygen and silicone content as well as their functional groups on the surface. Flexural strength and ILSS properties of CF/PEEK composites were measured according to ASTM D-790 and ASTM D2344, respectively.     

Evaluating Bar Coding‐Aided Medication Administration through Identification of Nursing Work Deficiencies

Health care information technology (IT) systems manage administrative and clinical processes more accurately and efficiently. However, their effects on clinical work flow are still not fully understood. In this article, we investigate the bar‐coded medication administration (BCMA) system for its effect on nurses working in inpatient departments. Evaluation is applied by examining work deficiencies before and after the IT system implementation based on a proposed nursing work model. A list of nurse‐perceived risks of work deficiencies related to the current BCMA system has been identified. Results show five main deficiencies that are mainly related to aspects of the IT environment and work schedule/process, including increased workload, IT systems downtime, unclear orders/task schedules, reduced time for patient‐care tasks, and redundant documentation. This study emphasizes the importance of understanding the reciprocal relationship between IT implementation and health care work system. © 2012 Wiley Periodicals, Inc.     

Construction of a choline biosensor through enzyme immobilization on a poly(2‐hydroxyethyl methacrylate)‐grafted Teflon film

An amperometric choline biosensor was constructed by immobilizing choline oxidase (ChO) on poly(2‐hydroxyethyl methacrylate) (PHEMA)‐grafted Teflon (polytetrafluoroethylene, PTFE) film. Grafting was achieved by γ irradiation. PHEMA‐grafted Teflon films were activated with epichlorohydrin or glutaraldehyde to achieve covalent immobilization of enzyme onto the film. To decrease the diffusional barrier caused by the enzyme‐immobilized film, the film was stretched directly on the electrode. The PHEMA‐grafted Teflon film, therefore, had to have appropriate mechanical properties. Glucose oxidase (GOD) was used in the determination of optimum immobilization conditions, then these were applied to ChO. With GOD, the effect of activation type and film position in electrode on enzyme activity was studied and the highest catalytic activity was obtained when the enzyme was immobilized using glutaraldehyde and the film was stretched over the electrode surface. Further studies revealed that the films activated with glutaraldehyde, immobilized in 2 mg/mL ChO concentration, and stretched directly on the electrode were suitable (specific activity, 0.427 ± 0.068 U mg^?1) for use in the choline biosensor. The linear working range of this biosensor was found to be 52–348 μM, with a 40 ± 5 μM minimum detection limit. The response of the sensor, however, decreased linearly upon repeated use. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007