Turn-of-the-Month Anomaly in Stock Returns: Revisited

FRM Project-Simon Fraser Universit

Natural Convection Heat Transfer in Enclosure with Uniformly Heated Inner Elliptic Cylinder and Outer square Cylinder

Experimental and numerical simulation study for natural convection heat transfer formed by uniformly heated inclined elliptical cylinder concentrically located in an enclosed square cylinder subjected to the ambient have been investigated. Experiments have been carried out for Rayliegh number ranges from 0.9×106 to 3.3×106. The enclosure angles of inclination are f =0o (horizontal), 45o (inclined), and 90o (vertical), and for axis ratio of elliptic cylinder (minor/major=b/c) of 1:2, while the dimensions of outer square cylinder was 0.5×0.5×2 m. A numerical simulation was conducted by using commercial Fluent CFD code to investigate the steady laminar natural convective heat transfer for air between a heated elliptic cylinder and its square enclosure. It covered a range of hydraulic radius ratios (HRR) of 1.97, 2.62, and 3.93 and for orientation angles j = 0o (the major axis is vertical), 30o, 45o. Two values of Rayligh number were taken: 0.9×106 and 3.3×106. The experimental results showed that the heat transfer process improves as Rayliegh number increases and is better in f =0o than other angles of inclination at the same heat input. Theoretical results showed that the HRR, Rayligh number, and angle of orientation have significant effect on the physical behavior of stremlines and isotherms inside the equivalent annular gap

NATURAL CONVECTION HEAT TRANSFER IN A VERTICAL CONCENTRIC ANNULUS

Experiments were carried out to study the local and average heat transfer by natural convection in a vertical concentric cylindrical annulus. The experimental setup consists of an annulus has a radius ratio of 0.555 and inner cylinder with a heated length 1.2m subjected to the constant heat flux while the outer cylinder is subjected to the ambient temperature. The investigation covers heat flux range from 58.2 W/m2 to 274.31 W/m2. Results show an increase in the natural convection as heat flux increases leads to an improve in the heat transfer process. An empirical equation of average Nusselt number as a function of Raylieh number was deduce

NATURAL CONVECTION HEAT TRANSFER IN A VERTICAL CONCENTRIC ANNULUS

Experiments were carried out to study the local and average heat transfer by natural convection in a vertical concentric cylindrical annulus. The experimental setup consists of an annulus has a radius ratio of 0.555 and inner cylinder with a heated length 1.2m subjected to the constant heat flux while the outer cylinder is subjected to the ambient temperature. The investigation covers heat flux range from 58.2 W/m2 to 274.31 W/m2 . Results show an increase in the natural convection as heat flux increases leads to an improve in the heat transfer process. An empirical equation of average Nusselt number as a function of Raylieh number was deduced

Heat Transfer and Pressure Drop Characteristics of Turbulent Flow In a Tube Fitted With Conical Ring and Twisted Tape Inserts

The present work shows the results obtained from experimental investigations of the augmentation of turbulent flow heat transfer in a horizontal tube fitted with combined conical-ring turbulators and a twisted-tape swirl generator. The air is the working fluid for Reynolds number range of 5000-23000 under constant wall heat flux thermal boundary condition. In this study, two enhancement heat transfer devices are used. One is the conical-ring used as a turbulator and placed in the tested tube with constant diameter ratio (d/D=0.538) and the other is the twistedtape swirl generator placed at the core of the conical-rings. Three twisted-tapes of different twist ratios, Y=2, 3, and 6, are introduced in each run. The experimental data obtained are compared with those obtained from the plain tube and from the literature to ensure the validation of experimental results. Correlations for Nusselt number, friction factor, and enhancement efficiency are developed. It is observed that the heat transfer process enhances by using combined conical-ring and twisted-tape inserts or each one alone when compared to plain tube at the same mass flow rate, and this enhancement increases as twist ratio decreases for the case of combined insertion

INTERACTION EFFECTS OF HYDRODYNAMICALLY FULLY DEVELOPED PRIMARY FLOW AND SECONDARY FLOW IN THE THERMAL ENTRANCE REGION OF ANNULAR DUCT

Experiments have been conducted to study the local and average heat transfer by mixed convection for hydrodynamically fully developed, thermally developing and fully developed laminar upward air flow in an inclined annulus with adiabatic inner cast iron tube and uniform heated outer aluminum tube with an aspect ratio ( Ω = 0.72) and (L/Dh≈40) for both calming and test sections). A wide range of Reynolds number from 859 to 2024 has been covered, and heat flux has been varied from 159 W/m2 to 812 W/m2 (these values of heat flux and Reynolds number gave Richardson number range from 0.03 to 0.٣٨), with angles of annulus inclination φ =0o (horizontal position), φ =60o (inclined position), and φ =90o (vertical position). The hydrodynamically fully developed condition has been achieved by using aluminum annulus (calming section) has the same dimensions as test section and has connected with it by Teflon piece. The average Nusselt numbers have been correlated with the product of (Richardson number and Reynolds number) and compared with available literature and showed satisfactory agreement. The temperature and local Nusselt number profiles results have revealed that the secondary flows created by natural convection have a significant effect on the heat transfer process

A Comparison of Tubular Minimal Invasive Surgery and Conventional Surgery in The Treatment of Patients Suffering from Single Level Lumber Disc Herniation (Short Term Follow Up)

Background:  Lumbar disc herniation is frequently-occurring and the most common spine-related disease in orthopedic surgery. However, nearly more than 50% of affected persons usually respond to conservative treatment. Furthermore, there is another group of patients who are suffering from incapacitating low back pain and sciatica although they have been treated for more than 6 weeks or who are suffering from early or progressive neurological impairment that required another approach far from the conservative treatments. Aim of the Study: The present study is designed to unveil the most reliable procedure which should be most adopted for single level lumbar disc herniation in Iraqi patients. Patients and Methods: A total of 40 patients who were suffering from back pain radiated to the lower limb were included in the present investigation.  Out of them, 20 patients underwent open discectomy and the other 20 patients underwent tubular discectomy. Results: 1- At the 10th day of postoperatively assessment, an obvious statistically significant decrease in the mean total Oswestry low back pain disability score was recorded in micro-tubular discectomy compared with the open discectomy ( P<0.001). 2-  At the 6th month of postoperatively, the mean total Oswestry low back pain disability score was increased in both groups; nonetheless, there has still been a decrease in the micro-tubular discectomy group in comparison with that of open discectomy group (P<0.001)

IMPROVED IMAGE COMPRESSION BASED WAVELET TRANSFORM AND THRESHOLD ENTROPY

In this paper, a method is proposed to increase the compression ratio for the color images by dividing the image into non-overlapping blocks and applying different compression ratio for these blocks depending on the importance information of the block. In the region that contain important information the compression ratio is reduced to prevent loss of the information, while in the smoothness region which has not important information, high compression ratio is used .The proposed method shows better results when compared with classical methods(wavelet and DCT)