Effect of the Fins Length for the Passive Cooling of the Photovoltaic Panels

A two-dimensional (2D) numerical model was used to simulate the use of a phase change material linked to a PV system to control the temperature rise of the PV cells. The predicted temperatures using the 2D model have been compared with experimental and numerical data of the literature and a good agreement was obtained for both the isotherm contours and time evolution of the temperature.An extended surface (fins) has been used in order to improve conductive heat transfer and to reinforce the thermal homogeneity. Concerning the inner fins included on the PV panel (Front), the obtained results show that these fins reduce significantly the temperature. Furthermore, the configurations of L = 25, 30 and 35 mm allow better cooling of the PV panel. On the other hand, the back inner fin used reduces dramatically the performance of the PV/PCM system for cooling the panel

Numerical analysis of the influence of maximum residual thermal stresses on the intensity factor between the matrix and particle interfaces in metal matrix composite

A critical problem in the application of metal matrix composites is the presence of high residual thermal stresses induced during the development process. These thermally induced stresses are generally detrimental to the service life of this type of composite. This article discusses the influence of maximum residual stresses on the intensity factor. The results interpreted in terms of damage, allowed us to identify the risk zones; characterized by a significant level of maximum residual stresses (S11Max, S22Max, S33Max), namely the particle/Matrix interface. The results also show that the loading conditions and the inter-distance between matrix and particle with two interfacial cracks have an important effect on max residual stresses and stress intensity factors. &nbsp

Eigenvalue estimates for non-normal matrices and the zeros of random orthogonal polynomials on the unit circle

We prove that for any $n\times n$ matrix, $A$, and $z$ with $|z|\geq \|A\|$, we have that \|(z-A)^{-1}\|\leq\cot (\frac{\pi}{4n}) \dist (z, \spec(A))^{-1}. We apply this result to the study of random orthogonal polynomials on the unit circle.Comment: 27 page

Univalence criterion for meromorphic functions and Loewner chains

The object of the present paper is to obtain a more general condition for univalence of meromorphic functions in the U*. The significant relationships and relevance with other results are also given. A number of known univalent conditions would follow upon specializing the parameters involved in our main results

Plus-minus construction leads to perfect invisibility

Recent theoretical advances applied to metamaterials have opened new avenues to design a coating that hides objects from electromagnetic radiation and even the sight. Here, we propose a new design of cloaking devices that creates perfect invisibility in isotropic media. A combination of positive and negative refractive indices, called plus-minus construction, is essential to achieve perfect invisibility (i.e., no time delay and total absence of reflection). Contrary to the common understanding that between two isotropic materials having different refractive indices the electromagnetic reflection is unavoidable, our method shows that surprisingly the reflection phenomena can be completely eliminated. The invented method, different from the classical impedance matching, may also find electromagnetic applications outside of cloaking devices, wherever distortions are present arising from reflections.Comment: 24 pages, 10 figure

A lower bound in Nehari's theorem on the polydisc

By theorems of Ferguson and Lacey (d=2) and Lacey and Terwilleger (d>2), Nehari's theorem is known to hold on the polydisc D^d for d>1, i.e., if H_\psi is a bounded Hankel form on H^2(D^d) with analytic symbol \psi, then there is a function \phi in L^\infty(\T^d) such that \psi is the Riesz projection of \phi. A method proposed in Helson's last paper is used to show that the constant C_d in the estimate \|\phi\|_\infty\le C_d \|H_\psi\| grows at least exponentially with d; it follows that there is no analogue of Nehari's theorem on the infinite-dimensional polydisc

Palestinian Children in the Hemato-Oncology Ward of an Israeli Hospital

Purpose An encounter between Palestinian parents of children with cancer and Israeli medical staff is a very special situation where “potential enemies” interact in a caring, trusting and intimate relationship for long periods of time. Our aim was to study the psychological and cultural encounter in order to understand the dynamics involved. Method The study is a qualitative one. Data was collected by way of structured in-depth interviews. Participants were physicians and nurses employed in the department, and Palestinian parents accompanying their children who were hospitalized during the research period. Results Six main themes emerged from the analysis of the interviews: (1) The decision to come to Israel for treatment. (2) The “meeting points” of the two peoples: the Israeli check points and the Palestinian Authority permits. (3) Encounter with the Israeli hospital. (4) Relationship between medical staff and parents. (5) Language and cultural barriers. (6) Emotions, thoughts and behaviors during high security tension. Conclusion The interviews depict a poignant picture of the unique encounter between Israeli Doctors and nurses and Palestinian parents. The psychological mechanism used by parents and doctors is “splitting”-having a dichotomized, simple emotional-perceptual picture of a situation with no conflicts. Nurses use another psychological mechanism in addition which enables them to contain the paradox and the conflict

The Investigation of the Mixed Convection from a Confined Rotating Circular Cylinder

In this paper, a numerical study on the two-dimensional laminar mixed convective flow and heat transfer from an rotating circular horizontal and isothermal cylinder confined in a horizontal channel. The blockage ratio and the Prandtl number are fixed at 0.05 and 0.7 respectively. The continuity, momentum and energy equations are solved via the finite-volume method. Our results are in very good agreement with those resulting from preceding studies to Ri=0 and a=0, which makes it possible to validate on important extension of present work. The mixed convective flow and heat transfer is simulated by the Reynolds number is studied in the range 1 <Re <40, the Richardson number (Ri) demonstrating the influence of thermal buoyancy ranges from 0 to 1 and for rotational rate from α=0 to α=4. Major emphasis is given to the effect of rotating a circular cylinder on the mixed convection and also on the measurements of the local and average Nusselt numbers are also obtained. Furthermore, the representative streamlines and isotherm patterns are presented and discussed

Conformal mapping of ultrasonic crystals: confining ultrasound and cochlear-like wave guiding

Conformal mapping of a slab of a two-dimensional ultrasonic crystal generate a closed geometrical arrangement of ultrasonic scatterers with appealing acoustic properties. This acoustic shell is able to confine ultrasonic modes. Some of these internal resonances can be induced from an external wave source. The mapping of a linear defect produces a wave-guide that exhibits a spatial-frequency selection analogous to that characteristic of a synthetic "cochlea". Both, experimental and theoretical results are reported here.Comment: 4 pages, 4 figure