Force Sensor Characterization Under Sinusoidal Excitations
The aim in the current work is the development of a method to characterize force sensors under sinusoidal excitations using a primary standard as the source of traceability. During this work the influence factors have been studied and a method to minimise their contributions, as well as the corrections to be performed under dynamic conditions have been established. These results will allow the realization of an adequate characterization of force sensors under sinusoidal excitations, which will be essential for its further proper use under dynamic conditions. The traceability of the sensor characterization is based in the direct definition of force as mass multiplied by acceleration. To do so, the sensor is loaded with different calibrated loads and is maintained under different sinusoidal accelerations by means of a vibration shaker system that is able to generate accelerations up to 100 m/s2 with frequencies from 5 Hz up to 2400 Hz. The acceleration is measured by means of a laser vibrometer with traceability to the units of time and length. A multiple channel data acquisition system is also required to simultaneously acquire the electrical output signals of the involved instrument in real time.
A generalised multiple-mass based method for the determination of the live mass of a force transducer
Abstract Many applications in Experimental Modal Analysis (EMA) require that the sensors’ masses are known. This is because the added mass from sensors will affect the structural mode shapes, and in particular its natural frequencies. EMA requires the measurement of the exciting forces at given coordinates, which is often made using piezoelectric force transducers. In such a case, the live mass of the force transducer, i.e. the mass as ‘seen’ by the structure in perpendicular directions must be measured somehow, so that compensation methods like mass cancelation can be performed. This however presents a problem on how to obtain an accurate measurement for the live mass. If the system is perfectly calibrated, then a reasonably accurate estimate can be made using a straightforward method available in most classical textbooks based on Newton’s second law. However, this is often not the case (for example when the transducer’s sensitivity changed over time, when it is unknown or when the connection influences the transmission of the force). In a self-calibrating iterative method, both the live mass and calibration factor are determined, but this paper shows that the problem may be ill-conditioned, producing misleading results if certain conditions are not met. Therefore, a more robust method is presented and discussed in this paper, reducing the ill-conditioning problems and the need to know the calibration factors beforehand. The three methods will be compared and discussed through numerical and experimental examples, showing that classical EMA still is a field of research that deserves the attention from scientists and engineers.
The Role of Daily Measurement of Lower Limb Circumference in Early Diagnosis of Deep Vein Thrombosis in the Presence of Other Risk Factors in Patients Admitted to Infectious Diseases Ward of Imam Reza Hospital, Mashhad, during 2012-2013
Introduction: Considering the high rate of mortality in patients with Deep Vein Thrombosis (DVT) and pulmonary embolism, the aim of this study was to evaluate the role of daily measurement of lower limb circumference in early diagnosis of DVT in patients admitted to Infectious Diseases Ward of Imam Reza Hospital, Mashhad, during 2012-2013. 
Materials and Methods: This cross-sectional study was conducted in Infectious Diseases Ward of Imam Reza Hospital of Mashhad, Iran. Patients were divided into two age- and gender-matched groups. In the first group, the difference between the two legs was greater than 1 cm and in the second group it was 3 cm or more. Circumference of the two legs was assessed on a daily basis at 10 cm above tibial tuberosity. Doppler sonography was performed to rule out DVT. Data were analyzed using SPSS, Version 16.   
Results:A total of 204 patients were enrolled in this study, 18 of whom (8/8%) were diagnosed with DVT through Doppler sonography. In addition, 17 patients (11/3%) had fever as a comorbidity. Mean difference of the two legs was more than 3 cm in 16 DVT patients (14%), and two patients with mean difference of less than 3 cm had DVT. 
Conclusion: Daily measurement of lower limb circumference was an accurate and cost-effective technique for early diagnosis of DVT.