High-definition Digital Camera Research Articles

PIV Techniques for Velocity Fields of Internal Waves over a Slowly Varying Bottom Topography

This paper reviews transformation processes and nonlinear properties of internal waves over a uniform slope in a two-fluid system, attempting to reveal water particle kinematics by using particle image velocimetry (PIV). Attenuation and setup induced by wave breaking are predicted using an energy-dissipation model including the radiation stress. In the present paper, the radiation stress is associated with the time-averaged momentum flux owing to the interaction between incident and reflected internal waves. These predictions agree with experimental data obtained by an image processing technique with which the boundary plane between the upper and lower layers could be detected as a density interface. A set of halogen lamps and three high-definition digital video cameras are used to illustrate velocity vector fields during one wave period. Instantaneous velocity fields measured by the PIV system are compared with the calculated velocity distribution by the method of characteristics in combination with the first-order Stokes theory. The rundown behavior is then investigated, and its influence upon the undertow in the lower layer is explained with a simple turbulent-jet model. Furthermore, the theoretical approach for examining mass transport and undertow is discussed in relation to the measured mean velocity.

A High-Definition Exoscope System for Neurosurgery and Other Microsurgical Disciplines: Preliminary Report

An 8-mm diameter rigid lens telescope with a focal distance of 20 cm was developed for open microsurgery. The telescope was attached to a 3-chip high-definition digital camera and then to a high-definition monitor. A pneumatic scope holder permitted repositioning. The optical quality of the device was compared with the operating microscope with a step wedge and 1-mm grid paper. Craniotomies and microsurgical dissections with the telescope system (high-definition exoscope system) were performed in a live pig model. The high-definition exoscope system provided image quality that rivaled the operating microscope even at high magnification. The system was easy to manipulate and comfortable during neurosurgical operations. The lack of stereopsis was a relative drawback of the system but was compensated for with repeated procedures. Overall, this prototype telescope-based system rivals the operating microscope optical quality and field of view. With further refinement, this system could have widespread application in many microsurgical disciplines.

Elongated bubbles in microchannels. Part I: Experimental study and modeling of elongated bubble velocity

The velocity of elongated vapor bubbles exiting two horizontal micro-evaporator channels with refrigerant R-134a was studied. Experiments with tube diameters of 509 and 790 μm, mass velocities from 200 to 1500 kg/m 2 s, vapor qualities from 2% to 19% and a nominal saturation temperature of 30 °C were analyzed with a fast, high-definition digital video camera. It was found from image processing of numerous videos that the elongated bubble velocity relative to that of homogeneous flow increased with increasing bubble length until a plateau was reached, and also increased with increasing channel diameter and increasing mass velocity. Furthermore an analytical model developed for a diabatic two-phase flow, has been proposed that is able to predict these trends. In addition, the model shows that the relative elongated bubble velocity should decrease with increasing pressure, which is consistent with the physics of two-phase flow.

Media Reporting, Mobility and Trauma

Media Reporting, Mobility and Trauma

Effects of selected pesticides, metals and organometallics on development of blue crab ( Callinectes sapidus) embryos

Blue crab embryos develop in egg sacs (nine stages) for 14 to 20 days after which they ‘hatch’ from the egg sacs into a swimming zoea stage (stage 10). Until they emerge from the egg sacs, embryos depend on lipids and lipovitellin stored within the eggs. A number of organic and inorganic toxicants were found to inhibit hatching. For example, at a fenvalerate concentration of 3.2 μg l −1 only 50% of embryos hatched, while 90 to 95% of the controls hatched. Pesticides, including chlorphyrifos, cypermethrin, fenvalerate and diflubenzuron, inhibited hatching at concentrations ranging from 1.8 to 5.9 μgl −1 (EC 50s). The most toxic of the metals tested was mercuric chloride and the most toxic of all compounds tested was methyl mercury. The addition of mercuric chloride at concentrations above 4.0 μg l −1 to stage three embryos resulted in stage 7 embryos with no heart beat. Abnormal eye spots were produced by exposure to high concentrations of metals. Time lapse video with a high definition digital camera was used to follow and document both normal and abnormal developments of the eyes, hearts and hatching process. In addition, the time lapse video was used to determine the time of the first appearance of a pulsating heart and eye spots. The advantages of crab embryos as a test for development toxicants include: (1) availability of embryos for most of the year: (2) sensitivity of embryos to toxicants; (3) nutrients for developing embryo are obtained from yolk so no external feeding is necessary; (4) good reproducibility of the assay; (5) use of culture plates allows the testing of many toxicants and concentrations in a small space and at low cost; (6) tests take from 2 to 6 days depending on stage used at the beginning of the assay; (7) obvious end point of the assay, i.e. emergence of zoea from egg sac.