Several medical procedures involve the use of needles. The advent of robotic and robot assisted procedures requires dynamic estimation of the needle tip location during insertion for use in both assistive systems as well as for automatic control. Most prior studies have focused on the maneuvering of solid flexible needles using external force measurements at the base of the needle holder. However, hollow needles are used in several procedures and measurements of forces in proximity of such needles can eliminate the need for estimating frictional forces that have high variations. These measurements are also significant for endoscopic procedures in which measurement of forces at the needle holder base is difficult. Fiber Bragg grating sensors, due to their small size, inert nature, and multiplexing capability, provide a good option for this purpose. Force measurements have been undertaken during needle insertion into tissue mimicking phantoms made of polydimethylsiloxane as well as chicken tissue using an 18-G needle instrumented with FBG sensors. The results obtained show that it is possible to estimate the different stages of needle penetration including partial rupture, which is significant for procedures in which precise estimation of needle tip position inside the organ or tissue is required.
Real time monitoring of the mass of an evaporating liquid drop from a real surface by optical methods cannot account for the volume of the drop that gets trapped between asperities. Mass measurement methods do not have high resolution, necessary to account for the small volume of the drop trapped in the pores. This work uses a non resonant mass sensor with a goniometer to simultaneously measure the mass and contact angle of the evaporating drop. Evaporative flux is used as the quantity of comparison across all surfaces. For a pinned sessile drop, the evaporative flux remains almost a constant for any kind of surface. For inkjet printing paper, the negative slope of the flux rate means evaporation is dominant. The drop breaches the hydrophobic coating on the paper to indicate a positive slope of this flux rate. In short, evaporation is strictly controlled by relative humidity and not the nature of the substrate.
Resonant sensors and crystal oscillators for mass detection need to be excited at very high natural frequencies (MHz). Use of such systems to measure mass of biological materials affects the accuracy of mass measurement due to their viscous and/or viscoelastic properties. The measurement limitation of such sensor system is the difficulty in accounting for the "missing mass" of the biological specimen in question. A sensor system has been developed in this work, to be operated in the stiffness controlled region at very low frequencies as compared to its fundamental natural frequency. The resulting reduction in the sensitivity due to non-resonant mode of operation of this sensor is compensated by the high resolution of the sensor. The mass of different aged drosophila melanogaster (fruit fly) is measured. The difference in its mass measurement during resonant mode of operation is also presented. That, viscosity effects do not affect the working of this non-resonant mass sensor is clearly established by direct comparison.
Acute shortage of drinking water has been on the rise owing to increasing population as well as shortage of drinkable water. Generation of potable water using passive solar stills is among the simplest and easier devices which make use of solar heat energy. However, the output of solar still is generally low owing to greater heat loss and needs improvement. In this paper, an experimental analysis is carried out to determine the performance of passive solar still with glass cover cooling using cold water generated using passive evaporative cooling process. The cold water required for cooling the glass cover is obtained using evaporative cooling process in the water tank which is wound with wet cotton cloth wick. The cold water thus obtained is sprayed onto the top surface of glass cover. The experiment is carried out in the outdoor conditions of Dubai from 10:00h to 14:00h and the temperature recordings of basin plate, glass cover, basin water, ambient air and cooling water are noted for every 30 minutes. The results reveal that the average increase in condensation heat transfer coefficient is found to be about 20.8% higher in the presence of glass cover cooling and the distillate output is found to increase by about 3.32 times. The average still efficiency is found to be relatively higher in the presence of cooling which is about 7.3% higher in the presence of cooling. The cold water temperature generated through evaporative cooling process is about 20.4% lower as compared to ambient temperature. Thus, the cooling of glass cover using cold water obtained through evaporative cooling process is found to be effective in enhancing the thermal performance of single basin solar still system.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.