Investigation of Heat Transfer and Flow Using Ribs Within Gas Turbine Blade Cooling Passage: Experimental and Hybrid Les/rans Modeling

Gas turbines are extensively used for aircraft propulsion, land based power generation and various industrial applications. Developments in innovative gas turbine cooling technology enhance the efficiency and power output, with an increase in turbine rotor inlet temperatures. These advancements of turbine cooling have allowed engine design to exceed normal material temperature limits. For internal cooling design, techniques for heat extraction from the surfaces exposed to hot stream are based on the increase of heat transfer areas and on promotion of turbulence of the cooling flow. In this study, it is obtained by casting repeated continuous V and broken V shaped ribs on one side of the two pass square channel into the core of blade. Despite extensive research on ribs, only few papers have validated the numerical data with experimental results in two pass channel. In the present study, detailed experimental investigation is carried out for two pass square channels with 180° turn. Detailed heat transfer distribution occurring in the ribbed passage is reported for steady state experiment. Four different combinations of 60° and Broken 60° V ribs in channel are considered. Thermocouples are used to obtain the temperature on the channel surface and local heat transfer coefficients are obtained for various Reynolds numbers, within the turbulent flow regime. Area averaged data are calculated in order to compare the overall performance of the tested ribbed surface and to evaluate the degree of heat transfer enhancement induced by the ribs with. Flow within the channels is characterized by heat transfer enhancing ribs, bends, rotation and buoyancy effects. Computational Fluid Dynamics (CFD) simulations were carried out for the same geometries using different turbulence models such as k-&omega Shear stress transport (SST) and Reynolds stress model (RSM). These CFD simulations were based on advanced computing in order to improve the accuracy of three dimensional metal temperature prediction which can be applied routinely in the design stage of turbine cooled vanes and blades. This study presents an attempt to collect information about Nusselt number inside the ribbed duct and a series of measurement is performed in steady state eliminating the error sources inherently connected with transient method. A Large Eddy Simulation (LES) is carried out on the best V and Broken V rib arrangements to analyze the flow pattern inside the channel. A novel method is devised to analyze the results obtained from CFD simulation. Hybrid LES/Reynolds Averaged Navier Strokes (RANS) modeling is used to modify Reynolds stresses using Algebraic Stress Model (ASM)

Are there optical communication channels in the brain?

Despite great progress in neuroscience, there are still fundamental unanswered questions about the brain, including the origin of subjective experience and consciousness. Some answers might rely on new physical mechanisms. Given that biophotons have been discovered in the brain, it is interesting to explore if neurons use photonic communication in addition to the well-studied electro-chemical signals. Such photonic communication in the brain would require waveguides. Here we review recent work [S. Kumar, K. Boone, J. Tuszynski, P. Barclay, and C. Simon, Scientific Reports 6, 36508 (2016)] suggesting that myelinated axons could serve as photonic waveguides. The light transmission in the myelinated axon was modeled, taking into account its realistic imperfections, and experiments were proposed both in-vivo and in-vitro to test this hypothesis. Potential implications for quantum biology are discussed.Comment: 13 pages, 5 figures, review of arXiv:1607.02969 for Frontiers in Bioscience, updated figures, new references on existence of opsins in the brain and experimental effects of light on neuron

A Security Solution for Wireless Local Area Network (WLAN) Using Firewall and VPN

In the era of internet millions of users share resource for different purpose. The chances of security risks are more when a user connected with internet. Internet technology plays an important role in every aspect of human life. We can create virtual connectivity with-in seconds with anyone in the world and can exchange or share the information through internet. Sometimes these information is very useful for Defense, and personal use. Sometimes this information is stolen on the internet or we can say destroyed so that receiver cannot receive that information, so for successful communication on internet our connection should be protected. For this protection we can use Firewall protection, VPN Network. These Networks is much more protected than normal Network. Network with VPN and Firewall is faster and efficient rather than normal connection. In normal Network user may faces unexpected delay due to malware and virus. In this paper we have described and analyze impact of Virtual Private Network technology and firewall with normal network. We have simulated three scenarios without firewall, with firewall and Firewall_VPN. The simulation results of three scenarios are compared over WLAN and analyze the impact of Firewall and VPN on network performance. OPNET 14.5 is used for simulator work. Keywords: VPN, Firewall, Security, WLAN, OPNET 14.5

GFDM FOR NEXT GENERATION WIRELESS COMMUNICATION SYSTEM

In modern scenarios, there are several applications of OFDM, but it also has some demerits like sensitive to Carrier Frequency Offset (CFO), high Peak to Average Power Ratio (PAPR), and timing offset large. Out Of Band (OOB) and low spectral efficiency due to cyclic prefix per symbol insertion. To diminish and discard above problems, new multiplexing technique is required for next generation wireless communication i.e. GFDM. GFDM is becoming popular day by day due to flexibility in pulse shape as well as single cyclic prefix in a multipath channel and which makes it eligible for the 5th generation technology. This paper deals with an overview of a GFDM and presents a comparative study between OFDM and GFDM

Thermodynamics of one and two-qubit quantum refrigerators interacting with squeezed baths: a comparative study

We investigate the nonequilibrium refrigeration of one and two-qubit systems in a squeezed thermal bath. We characterize the performance of one and two-qubit refrigerators in the presence of squeezed heat baths, in terms of their coefficients of performance, cooling rates, and figures of merit. Our results show that the performance of the refrigerators is strongly influenced by the squeezing parameter and the number of qubits. The performance of the two-qubit refrigerator is found to be better than that of the one-qubit refrigerator under the same operating conditions. Our findings suggest that a squeezed thermal bath can be a promising resource for the design of efficient quantum refrigerators in the non-equilibrium regime.Comment: 17 pages, 10 figure

Design of a Compact Biaxial Tensile Stage for Fabrication and Tuning of Complex Micro- and Nano-scale Wrinkle Patterns

Wrinkling of thin films is a strain-driven process that enables scalable and low-cost fabrication of periodic micro- and nano-scale patterns. In the past, single-period sinusoidal wrinkles have been applied for thin-film metrology and microfluidics applications. However, real-world adoption of this process beyond these specific applications is limited by the inability to predictively fabricate a variety of complex functional patterns. This is primarily due to the inability of current tools and techniques to provide the means for applying large, accurate, and nonequal biaxial strains. For example, the existing biaxial tensile stages are inappropriate because they are too large to fit within the vacuum chambers that are required for thin-film deposition/growth during wrinkling. Herein, we have designed a compact biaxial tensile stage that enables (i) applying large and accurate strains to elastomeric films and (ii) in situ visualization of wrinkle formation. This stage enables one to stretch a 37.5 mm long film by 33.5% with a strain resolution of 0.027% and maintains a registration accuracy of 7 μm over repeated registrations of the stage to a custom-assembled vision system. Herein, we also demonstrate the utility of the stage in (i) studying the wrinkling process and (ii) fabricating complex wrinkled patterns that are inaccessible via other techniques. Specifically, we demonstrate that (i) spatial nonuniformity in the patterns is limited to 6.5%, (ii) one-dimensional (1D) single-period wrinkles of nominal period 2.3 μm transition into the period-doubled mode when the compressive strain due to prestretch release of plasma-oxidized polydimethylsiloxane (PDMS) film exceeds ∼18%, and (iii) asymmetric two-dimensional (2D) wrinkles can be fabricated by tuning the strain state and/or the actuation path, i.e., the strain history. Thus, this tensile stage opens up the design space for fabricating and tuning complex wrinkled patterns and enables extracting empirical process knowledge via in situ visualization of wrinkle formation