A Model-Based Analysis of Capacitive Flow Metering for Pneumatic Conveying Systems: A Comparison between Calibration-Based and Tomographic Approaches.

Pneumatic conveying is a standard transportation technique for bulk materials in various industrial fields. Flow metering is crucial for the efficient and reliable operation of such systems and for process control. Capacitive measurement systems are often proposed for this application. In this method, electrodes are placed on the conveyor systems transport line and capacitive signals are sensed. The design of the sensor with regard to the arrangement and the number of electrodes as well as the evaluation of the capacitive sensor signals can be divided into two categories. Calibration-based flow meters use regression methods for signal processing, which are parametrized from calibration measurements on test rigs. Their performance is limited by the extend of the calibration measurements. Electrical capacitance tomography based flow meters use model-based signal processing techniques to obtain estimates about the spatial material distribution within the sensor. In contrast to their calibration-based counterparts, this approach requires more effort with respect to modeling and instrumentation, as typically a larger number of measurement signals has to be acquired. In this work we present a comparative analysis of the two approaches, which is based on measurement experiments and a holistic system model for flow metering. For the model-based analysis Monte Carlo simulations are conducted, where randomly generated pneumatic conveying flow patterns are simulated to analyze the sensor and algorithm behavior. The results demonstrate the potential benefit of electrical capacitance tomography based flow meters over a calibration-based instrument design.

Carcinoma and atypical hyperplasia in reduction mammaplasty: increased sampling leads to increased detection. A prospective study.

BACKGROUND: Reduction mammaplasty for symptomatic macromastia or correction of asymmetry is performed more than 100,000 times per year in the United States. The reported incidence of occult breast cancer in reduction mammaplasty ranges from 0.06 to 4.6 percent. No standard pathology assessment for reduction mammaplasty exists. The authors evaluated the incidence of occult carcinoma and atypical hyperplasia in reduction mammaplasty specimens and identified clinical risk factors. Systematic sampling of additional tissue sections was instituted to evaluate the hypothesis that increased sampling would identify more significant pathologic findings. METHODS: All reduction mammaplasty specimens over a 20-month period at a single institution were prospectively examined. All specimens had baseline gross and microscopic evaluations, and then each was subjected to systematic additional sampling. The incidence of significant pathologic findings (carcinoma and atypical hyperplasia) was tabulated. Variables such as age and preoperative mammogram were examined. RESULTS: A total of 202 cases were evaluated. Significant pathologic findings (carcinoma and atypical hyperplasia) were present in 12.4 percent. The rate of carcinoma was 4 percent in all patients (6.2 percent in patients >or=40 years and 7.9 percent in patients >or=50 years). CONCLUSIONS: A significantly higher rate (12.4 percent) of significant pathologic findings was identified in this prospective study compared with published literature. None of the lesions was identified on preoperative mammogram. Age was significantly associated with significant pathologic findings. Increased sampling was associated with significant pathologic findings only in patients 40 years or older, indicating the need for thorough sampling of reduction mammaplasty specimens in patients older than 40.