183 research outputs found
Experimental Study of Pulse Tube Refrigerators
The working fluid for the pulse tube refrigerator is Helium, which is non-toxic to humans and harmless to the environment. The Pulse Tube Refrigeration unit offers a viable alternative to units that currently require CFC and HCFC working fluids. Pulse Tube Refrigerators can be operated over wide range of temperatures. These units can be used in numerous space and commercial applications, including food freezers freeze dryers. It can also be used to cool detectors and electronic devices.
The design of Pulse Tube Refrigeration Unit was based on Orifice Pulse Tube Concept. First the gas is compressed in a compressor. Next it floes through the compressor after cooler, where heat is rejected to the water cooled loop. Then the gas enters the regenerator and cold end heat exchanger where heat is added to the gas from surroundings. The gas finally enters the Pulse Tube, orifice and reservoir. These three components produce the phase shift of mass flow and pressure, which is necessary for cooling. The gas shuttles forth between hot and cold ends. Heat is lifted against the temperature gradient and rejected at hot end heat exchanger, which is water cooled
175 Years of linear programming: 2. Pivots in column space
The simplex method has been the veritable workhorse of linear programming for five decades now. An elegant geometric interpretation of the simplex method can be visualised by viewing the animation of the algorithm in acolumn space representation. In fact, it is this interpretation that explains why it is called the simplex method. The extreme points of the feasible region (polyhedron) of the linear programme can be shown to correspond to an arrangement of simplices in this geometry and the pivoting operation to a physical pivot from one simplex to an adjacent one in the arrangement. This paper introduces this vivid description of the simplex method as a tutored dance of simplices performing 'pivots in column space'
Uncertainties inherent in the decomposition of a Transformation
This contribution adds to the points on the <indeterminacy of special
relativity> made by De Abreu and Guerra. We show that the Lorentz
Transformation can be composed by the physical observations made in a frame K
of events in a frame K-prime viz i) objects in K-prime are moving at a speed v
relative to K, ii) distances and time intervals measured by K-prime are at
variance with those measured by K and iii) the concept of simultaneity is
different in K-prime compared to K. The order in which the composition is
executed determines the nature of the middle aspect (ii). This essential
uncertainty of the theory can be resolved only by a universal synchronicity as
discussed in [1] based on the unique frame in which the one way speed of light
is constant in all directions.Comment: 10 pages including an appendix. Published in the European Journal of
Physics as a Comment. Eur. J. Phys. 29 (2008) L13-L1
A Comparative study of Dynamic MRI with Drug induced Sleep Endoscopy in Obstructive Sleep Apnea Patients
BACKGROUND:
OSAS is a disease of modern ages and it is found to predispose to hypertension, myocardial infarction and sudden death .It is imperative to identify the level of obstruction to decide the treatment protocol. Level of obstruction can be identified by Dynamic MRI and DISE.
AIM OF THE STUDY:
To identify and compare the level of obstruction in Dynamic MRI with DISE in OSAS patients.
MATERIALS AND METHODS:
Based on inclusion and exclusion criteria 35 patients were enrolled in our study. These patients were subjected to Sleep MRI to identify the level of obstruction. Then patients were subjected to Drug Induced Sleep Endoscopy to identify the level of obstruction.
RESULTS;
82.8% correlation was seen between dynamic MRI and DISE in identifying the level of obstruction.3 patients had no obstruction in MRI but had obstruction at velum in DISE. ONE patient who had tongue base obstruction in Dynamic MRI had tongue base and epiglottis level obstruction in DISE .ONE patient had obstruction in velum and epiglottis in Dynamic MRI but had obstruction only in velum level in DISE. ONE patient had obstruction at oropharynx in Dynamic MRI was found to have obstruction in oropharynx and epiglottis in DISE.
CONCLUSION:
Both Dynamic MRI and DISE are equally good in identifying the level of obstruction. Dynamic MRI is non-invasive and gives accurate measurements of upper airway while in DISE patient is subjected to an anaesthetic procedure. In all cases planned for surgery after identifying level of obstruction with dynamic MRI, DISE can be done on table before the planned surgery to confirm the level of obstruction so that separate anesthesia for DISE can be avoided
An unusual presentation of primary renal lymphoma: A case report
Lymphomatous involvement of the kidney is often seen as a part of the disseminated disease but primary renal lymphoma is very rare. It is essential to differentiate between renal cell carcinoma and renal lymphoma in patients presenting with renal masses. The prognosis is usually poor with a median survival less than a year. We present the case of a 81-year-old male who presented with type B symptoms and was diagnosed to have primary lymphoma of the kidney and discuss briefly about the primary renal lymphoma
Urologic surgery and COVID-19: How the pandemic is changing the way we operate
The coronavirus disease 2019 (COVID-19) pandemic has had a global impact on all aspects of healthcare, including surgical procedures. For urologists, it has affected and will continue to influence how we approach the care of patients pre-operatively, intra-operatively, and post-operatively. A risk-benefit assessment of each patient undergoing surgery should be performed during the COVID-19 pandemic based on the urgency of the surgery and the risk of viral illness and transmission. Patients with advanced age and comorbidities have a higher incidence of mortality. Routine preoperative testing and symptom screening is recommended to identify those with COVID-19. Adequate personal protective equipment (PPE) for the surgical team is essential to protect healthcare workers and ensure an adequate workforce. For COVID-19 positive or suspected patients, the use of N95 respirators is recommended if available. The anesthesia method chosen should attempt to minimize aerosolization of the virus. Negative pressure rooms are strongly preferred for intubation/extubation and other aerosolizing procedures. Although transmission has not yet been shown during laparoscopic and robotic procedures, efforts should be made to minimize the risk of aerosolization. Ultra low particulate air filters are recommended for use during minimally invasive procedures to decrease the risk of viral transmission. Thorough cleaning and sterilization should be performed post-operatively with adequate time allowed for the operating room air to be cycled after procedures. COVID-19 patients should be separated from non-infected patients at all levels of care including recovery to decrease the risk of infection. Future directions will be guided by outcomes and infection rates as social distancing guidelines are relaxed and more surgical procedures are reintroduced. Recommendations should be adapted to the local environment and will continue to evolve as more data becomes available, the shortage of testing and PPE is resolved, and a vaccine and therapeutics for COVID-19 are developed
Design and Manufacturing of Smart Braking System
Now a days, vehicles have been developed a lot and reach its new margin; but yet accidents are mostly occurred by retard of the driver to stomp the brake or by the sloppiness of the driver or over speed or due to unpleasant weather. So our project points to emerge a system which can actuate the braking system automatically with the aid of high profile sensors with relay circuit and some more changes in conventional braking system which can actuate the brake automatically in emergency state. The brain of this entire set-up is Arduino microcontroller. The ultrasonic sensors are the vision of this system and stepper motor utilised for actuation. This system has been composed to depict the technological improvement in further. In future the actual model may be evolved based on its viability
Reversal in time order of interactive events: Collision of inclined rods
In the rod and hole paradox as described by Rindler (1961 Am. J. Phys. 29
365-6), a rigid rod moves at high speed over a table towards a hole of the same
size. Observations from the inertial frames of the rod and slot are widely
different. Rindler explains these differences by the concept of differing
perceptions in rigidity. Gron and Johannesen (1993 Eur. J. Phys. 14 97-100)
confirmed this aspect by computer simulation where the shapes of the rods are
different as observed from the co-moving frames of the rod and slot. Lintel and
Gruber (2005 Eur. J. Phys. 26 19-23) presented an approach based on retardation
due to speed of stress propagation. In this paper we consider the situation
when two parallel rods collide while approaching each other along a line at an
inclination with their axis. The collisions of the top and bottom ends are
reversed in time order as observed from the two co-moving frames. This result
is explained by the concept of extended present derived from the principle of
relativity of simultaneity
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