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The concept of cloud computing makes it possible to have a shared pool of reconfigurable computing resources that can be deployed and released with little involvement from administration work or service providers. Cloud computing makes this possible. The communication among the nodes is possible with the help of internet. All users are able to use the services of cloud. The small-scale industries are really happy to use the cloud services. The attackers are degrading the performance of services, and also the users are not receiving the response. This paper presents the imprint of cloud computing. Flooding attacks or the DoS attack is one attack that reserves the communication resources in network, and the rest of the attacks, like Sybil attack, misguide the users, and also it is not easy to identify the exact identification of the sender. The security schemes are able to remove attacker infection, and on the basis of that, it is possible to design better schemes against attackers in the cloud.

In an optical like free space optical communication system, there always exits a focal or focal reflective optical antenna system working as beam expander. As optical antenna can expand and reshape the narrow and highly collimated emitted beam, it efficiently compresses divergence angle and decreases the influence of beam expansion in space optical communication. However, the optical antenna structure will decrease the transmission power for the obscuration loss caused by the secondary reflective mirror. The design of two-mirror reflective optical antenna at Tx affects the transmission efficiency in space uplink optical communication. An improved scheme with two diffractive optical elements (DOEs) can help reduce central obscuration caused by the secondary mirror of optical antenna. In order to further investigate the influence of the DOEs on communication quality, we give a bit error rate (BER) model based on space uplink optical communication system. The effect of the DOEs on the relationship curves of BER versus typical parameters at different obscuration ratios of optical antenna is the research focus. Typical system parameters include transmission power, receiving diameter, Receiver angle, divergence angle and wavelength. With the demand for data volume and data velocity growing, space optical communication has gained extensive attention. It originated in the 1960s and a large number of ground verification experiments have been carried out since 1980. Compared with traditional microwave communication, space optical communication has the advantages of small volume, low power consumption, large optical gain, and small divergence angle, strong anti-jamming and anti-interception ability.

In Optical Time Division Multiplexing (OTDM)-based systems, several optical signals with low bit rate B share the same carrier frequency and are optically multiplexed to form a composite bit stream at the higher bit rate N*B, where N denotes the number of channels multiplexed. In this paper, the analysis and investigation of the performance of OTDM link are carried out with help of simulation. In this paper, OTDM link is designed based on four channels having data rate of each channel which is equal to 10 Gbps with the use of RZ and NRZ schemes being analyzed. The proposed optical link achieved maximum transmission distance of 348 km over single mode fiber. The system operated over a distance of 348 km with bit error rate of 1.39×10−31 and Q-value of 11.60 with RZ, and bit rate of 1.47×10−24 and Q-value of 10.13 with NRZ respectively. The results shows that the proposed link performance is better optimized using RZ modulation scheme in comparison to NRZ scheme. This simulation work is done in optisystem 7.0. Further in this proposed OTDM link the comparison of the link performance is also analyzed using different pulse shapes for RZ and NRZ. The results being presented in this paper are significantly taken at transmitted power of 0 dBm and 2 dBm.

Free Space Optics (FSO) communication technique is a unique method for the communication between optical transmitter and optical receiver using a free space as a medium. The advantages of FSO over other wireless communication techniques is its low power, high security, low cost infrastructure, high data rates and unlicensed spectrum. There are many atmospheric disturbances like rain, fog, water molecules particles which degrade the performance of the FSO Link. In this paper, the FSO Link is optimized at different optical wavelengths of 1550 nm, 850 nm, 650 nm and 532 nm keeping into consideration the various atmospheric challenges and weather conditions. The performance of the proposed FSO link is evaluated in terms of BER and Quality factor. Simulation results for the proposed FSO link achieve maximum link range of 1000 m at 1550 nm. The achieved values of Bit Error Rate (BER) and Quality Factor (Q) for FSO link at 1550 nm are 10e-9 and 5.58 respectively.

A first principle flotation model has been derived from the basic mechanisms involved in flotation. It consists of a set of analytical equations for various sub-processes such as bubble generation, bubble-particle collision, attachment, detachment, bubble coarsening, and froth phase recovery. A computer simulator based on the model can predict flotation from both hydrodynamic and surface chemistry parameters such as bubble size, particle size, energy dissipation rate, ζ-potentials, contact angles, etc . The model predictions are in good agreement with the flotation results obtained in both laboratory and pilot-scale tests. The model-based simulator can be used to design and diagnose flotation circuits. Typical input parameters include the size-by-class mineralogical composition of a feed, flotation cell characteristics, flow rates, and the types and dosages of reagents.

An extended meniscus of a ferrofluid solution on a silicon surface is subjected to axisymmetric, non-uniform magnetic field resulting in significant forward movement of the thin liquid film. Image analyzing interferometry is used for accurate measurement of the film thickness profile, which in turn, is used to determine the instantaneous slope and the curvature of the moving film. The recorded video, depicting the motion of the film in the Lagrangian frame of reference, is analyzed frame by frame, eliciting accurate information about the velocity and acceleration of the film at any instant of time. The application of the magnetic field has resulted in unique changes of the film profile in terms of significant non-uniform increase in the local film curvature. This was further analyzed by developing a model, taking into account the effect of changes in the magnetic and shape-dependent interfacial force fields.

A novel 3 cm × 3 cm × 600 μm-thick Ti-based flat heat pipe is developed for Thermal Ground Plane (TGP) applications. The Ti-based heat pipe architecture is constructed by laser welding two microfabricated titanium substrates to form a hermetically sealed vapor chamber. The scalable heat pipes' flat geometry facilitates contact with planar heat sources, such as microprocessor chip surfaces, thereby reducing thermal contact resistance and improving system packaging. Fluid transport is driven by the wicking structure in the TGP, which consists of an array of Ti pillars that are microfabricated from a titanium substrate using recently developed high-aspect-ratio Ti processing techniques. The hydrophilic nature of the Ti pillars is increased further by growing ~200-nm hairlike nanostructured titania of the pillar surfaces. The resulting super hydrophilic wick offers the potential to generate high wicking velocities of ~27.5 mm/s over distances of 2 mm. The experimental wetting results show a diffusive spreading behavior that is predicted by Washburn dynamics. The maximum effective thermal conductivity of a heat pipe is directly related to the speed of capillary flow of the working fluid through the wick and is measured experimentally in the first-generation device to be k = 350 W/m · K. A dummy TGP with a cavity volume of ~170 μL was used to test the hermiticity level of the laser packaging technique. The device gave a 0.067% of water loss based on ~60 μL of charged water at 100°C in air for over a year.