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The bulk heterostructure having nanopillar growth on top surface of the proposed photodetector structure is a promising candidate of high detection for high resolution quantum optic and high speed optical communication. Here, we report Si-ZnO-ZnMgO having grown with aligned hexagonal nanopillars for high performance photo detector, due to having its high quantum efficiency. From the proposed structure (electro-optically modified) high responsivity of $2.857\times 10^{2}$ AW $^{-1}$ and detectivity of $1.33\times 10^{15}$ cm Hz $^{1/2}\,\,\text{W}^{-1}$ (3mm $\times$ 3mm) was achieved and also the small performance degradation with increase of temperature shows thermal stability.

The remarkable development and continual proliferation of research in the nanotechnology field have led to improvement in the efficiency of elementary devices. To improve their performance, the parameters of such devices can be scaled down while optimizing their characteristics. However, this simultaneously results in degraded switching characteristics and the appearance of short-channel effects. Multigate-based fin-shaped field-effect transistors (FinFETs) represent a new option to address all these problems. However, thermal failure of FinFET devices under nominal operating conditions is an important issue in the design and implementation of high-speed semiconductor devices. It is also seen that bulk FinFETs exhibit better thermal performance compared with silicon-on-insulator FinFETs. In the work presented herein, various FinFET characteristics including the subthreshold swing, drain-induced barrier lowering, threshold voltage, and drain current were investigated as functions of temperature. The (effective) channel length is larger than the physical gate length (in off-state) due to the undoped underlap regions. This paper also discusses the effects of drain, source, and gate overlap.

The two popular techniques of packet combining based error correction schemes are: Packet Combining (PC) scheme and Aggressive Packet Combining (APC) scheme. PC scheme and APC scheme have their own merits and demerits; PC scheme has better throughput than APC scheme, but suffers from higher packet error rate than APC scheme. The wireless channel state changes all the time. Because of this random and time varying nature of wireless channel, individual application of SR ARQ scheme, PC scheme and APC scheme can’t give desired levels of throughput. Better throughput can be achieved if appropriate transmission scheme is used based on the condition of channel. Based on this approach, adaptive packet combining scheme has been proposed to achieve better throughput. The proposed scheme adapts to the channel condition to carry out transmission using PC scheme, APC scheme and SR ARQ scheme to achieve better throughput. Experimentally, it was observed that the error correction capability and throughput of the proposed scheme was significantly better than that of SR ARQ scheme, PC scheme and APC scheme.

As such various cryptanalytic attacks become stronger day by day, attaining the security over a single key based techniques become a complicated and burning problem among the researchers. Even, in the session key approaches, when session extends for a little bit longer, protecting data in ciphertext only attack also cannot be assured. In this regard, various mechanisms have been proposed to change the key frequently by establishing the session keys in every short interval. But, such schemes may not be suitable and survive for real time applications because of unnecessary increase of network overheads and enhancement of costs exponentially. So, to tackle such problems, we have proposed a true random key variation technique based on piggybacking strategies and one time pad (OTP) under public key environments.

In modern era, ensuring high order security becomes one and only objective of computer networks. From the last few decades, many researchers have given their contributions to achieve the secrecy over the communication channel. In achieving perfect security, Shannon had done the pioneer work on perfect secret theorem and illustrated that secrecy of the shared information can be maintained if the key becomes variable in nature instead of static one. In this regard, a key generation technique has been proposed where the key can be changed every time whenever a new block of data needs to be exchanged. In our scheme, the keys not only vary in bit sequences but also in size. The experimental study is also included in this article to prove the correctness and effectiveness of our proposed technique.

Various limitations, such as gate leakage through hot carrier tunnelling, parasitic resistance and capacitance, Drain Induced Barrier Lowering (DIBL), subthreshold slope (SS), and threshold voltage roll-off are present due to size reduction. Improvements in transistor speed and performance while, reducing the device dimensions is possible using the concept of Multiple-gate Field Effect phenomenon. Temperature dependency in thin fin transistor has been systematically studied with respect to the dependence on the fin width, fin height, and gate length. In this paper the performance of miniaturized Fin-FET structure is optimized. Also, temperature (300K, 400K and 500K) dependent performances on DIBL, SS and threshold voltage are observed and optimized.

A hydrothermal growth technique is introduced to synthesize hexagonal high sensitive zinc oxide (ZnO) with a large surface to volume ratio. Pre and post treatments are carried out to obtain suitable resistive performance, which enhanced sensing performance of the device. The morphological structure of synthesized ZnO under different conditions (such as reaction time solution concentrations) is characterized by scanning electron microscope (SEM). X ray diffraction (XRD) verifies the crystallinity in fabricated ZnO nanorod. X-ray photoelectron spectroscopy (XPS) is performed to measure the elemental composition corresponding to binding energy before and after treatment. Optical properties for as-grown sample and uniform ZnO nanorod are characterized through Photoluminescence (PL). Sensing properties depending on the shape, size, distribution of hexagonal nanorod, position of the IDE and temperature are investigated. The highest sensor response is achieved for the hexagonal nanorod which is uniform in shape, distribution and for the position of IDE below the sensing layer.

In this paper with and without disorder grapheme nanoribbon (GNR) channel is being considered for different electrical parameters (Current, Number of carriers at steady state, Density of states, Quantum Capacitance). Due to increase in drain potential from 0 V to 0.7 V, the carrier concentration changes in channel region. Because of the dependence of channel potential on carrier concentration, the constant value carrier concentration cannot be considered to calculate drain current. Self-consistent field (SCF) method is utilized to calculate channel potential for the proposed model. The change in carrier concentration of channel is related to quantum capacitance. Quantum capacitance has a significant effect when drain to source bias is low. Density of states (DOS), dependent current expression is derived for with and without disorder grapheme nanoribbon (GNR) channel based field effect transistor (FET). Energy broadening due to the contact between grapheme nanoribbon (GNR) and metal leads is also considered to show effective carrier collection. The model also presents the short channel effect of device. The simulation of current-voltage, Density of states (DOS) using MATlab 2014a software is carried out.

In this paper, we proposed an efficient full adder circuit using 16 transistors. The proposed high-speed adder circuit is able to operate at very low voltage and maintain the proper output voltage swing and also balance the power consumption and speed. Proposed design is based on CMOS mixed threshold voltage logic (MTVL) and implemented in 180nm CMOS technology. In the proposed technique the most time-consuming and power consuming XOR gates and multiplexer are designed using MTVL scheme. The maximum average power consumed by the proposed circuit is 6.94μW at 1.8V supply voltage and frequency of 500 MHz, which is less than other conventional methods. Power, delay, and area are optimized by using pass transistor logic and verified using the SPICE simulation tool at desired broad frequency range. It is also observed that the proposed design may be successfully utilized in many cases, especially whenever the lowest power consumption and delay are aimed.

The design, analysis, optimization, and fabrication of layered and nanostructure-based surface acoustic wave (SAW) gas sensors are presented. A lithium niobate and zinc oxide (ZnO) nano multilayer structure is proposed to enhance the sensitivity of the SAW-based gas sensor. Different materials are considered for the intermediate layer in the design for optimization purposes. The sensitivity of the sensor could be improved due to increased active surface area obtained by varying the aspect ratio of the nanorods, the thickness of the intermediate layer, and the gap between the electrodes. The total displacement and frequency shift of the device were significantly improved. Overall, the mechanically engineered surface-based (nanorod) SAW gas sensor offered better sensing response than the layered SAW gas sensor in terms of sensitivity performance.

In this paper, the design and characterization of a tunable patch antenna loaded with complementary split ring resonators (CSRRs) on the patch have been realized. To achieve tunable resonant frequency, bandwidth and radiation pattern, the antenna is further loaded with coplanar waveguide (CPW) on which Microelectromechanical System (MEMS) capacitive switches are placed periodically. The tunable property is achieved, when the switches moves from up state with the capacitive gap 1.5 μm to down state having capacitive gap of 1 μm. A parametric analysis has been presented to check the sensitivity of the antenna in terms of S11 parameter by varying different parameters of the MEMS switches and CSRRs. This work, strives to improve the degree of reconfigurability with increase in the number of switches. The value of actuation voltage to move switch from up to down state is 10.4 V, which is very low over the other design. The switches exhibit fundamental frequency 14.6 kHz, switching time 28.59 μs, and capacitance ratio 15.27. Simulation has been carried out in Ansoft HFSS v. 13 and the distinct characterization property of the tunable antenna is shown through simulation.

In an automatic repeat request (ARQ) scheme, a packet is retransmitted if it gets corrupted due to transmission errors caused by the channel. However, an erroneous packet may contain both erroneous bits and correct bits and hence it may still contain useful information. The receiver may be able to combine this information from multiple erroneous copies to recover the correct packet. Packet combining (PC) is a simple and elegant scheme of error correction in transmitted packet, in which two received copies are XORed to obtain the bit location of erroneous bits. Thereafter, the packet is corrected by bit inversion of bit located as erroneous. Aggressive packet combining (APC) is a logic extension of PC primarily designed for wireless communication with objective of correcting error with low latency. PC offers higher throughput than APC, but PC does not correct double bit errors if occur in same bit location of erroneous copies of the packet. A hybrid technique is proposed to utilize the advantages of both APC and PC while attempting to remove the limitation of both. In the proposed technique, applications of APC-PC on Gilbert two state model has been studied. The simulation results show that the proposed technique offers better throughput than the conventional APC and lesser packet error rate than PC scheme.

To enhance the security level of the cryptosystem in shared encrypted data over the insecure channel; Automatic variable key (AVK) is a perfect mechanism as being experimented by many researchers. In AVK, after establishment of the secret key (through some IKE protocols, like IKEv2 or 2 PAKA or 3 PAKA, etc), the successive keys are generated that are variable in nature from session to session by using time variant key technique. In this work, it is shown that how AVK can provide higher security than fixed key from well-known plaintext attack (for example, brute force attack) and ciphertext only attack (for example, frequency attack etc) due to randomness of keys. In order to improve the level of randomness among the key set, a new method is proposed to generate keys where the randomness are achieved not only in terms of change in bits sequence but also flexible in size as well. Randomness of the key set is also compared with other related time variant key mechanisms to prove superiority.

Theoretical and graphical analysis of pull-in-voltage and figure of merit for a fixed-fixed capacitive Micro Electromechanical Systems (MEMS) switch is presented in this paper. MEMS switch consists of a thin electrode called bridge suspended over a central line and both ends of the bridge are fixed at the ground planes of a coplanar waveguide (CPW) structure. A thin layer of dielectric material is deposited between the bridge and centre conductor to avoid stiction and provide low impedance path between the electrodes. When an actuation voltage is applied between the electrodes, the metal bridge acquires pull in effect as it crosses one third of distance between them. In this study, we describe behavior of pull-in voltage and figure of merit (or capacitance ratio) of capacitive MEMS switch for five different dielectric materials. The effects of dielectric thicknesses are also considered to calculate the values of pull-in-voltage and capacitance ratio. This work shows that a reduced pull-in-voltage with increase in capacitance ratio can be achieved by using dielectric material of high dielectric constant above the central line of CPW.

Aggressive Packet combining scheme is very efficient technique for error correction in wireless data communication. Transmitter transmits three copies of the original packet. Receiver applies bit by bit majority voting on the received erroneous copies and gets the original packet. The major limitation of APC is that, if the bit error occurs in the same bit location of all the received copies then APC fail to correct them which results in reduced correction capability and reduced throughput. In this paper, a new modified APC technique is proposed that can eliminate the major limitation of the APC by using half-byte packet reverse technique and even & odd selection method thus increasing correction capability and throughput. General Terms Correction capability, odd-even selection, packet reverse technique.

One technique, named as AVK, we can create keys from data to data or session to session that is known as dynamic key. Using this type of technique we can overcome the problem that arises with a static key. The same key has been used for the entire data communication in case of static key and if anyhow it has been compromised then the basic requirement of cryptography fails. In these proposed techniques, few dynamic key generation techniques have been generated and the variable keys have been generated based on some existing techniques namely, CSAVK, ASAVK, LSAVK and KVRN by incorporating noise burst bit. From the performance analysis, we have been observed that the auto generated keys are more random in the proposed techniques. The randomness of successive generated keys has been tested with the help of National Institute of Standards and Technology (NIST) which is a statistical tool and proved that the generated keys are truly random. Finally, we have concluded that these techniques can be used in real-time applications as they provide more security as compared to other existing schemes.

Fill factor of the solar cell mainly depends on series resistance and contact resistance, which are the most effective parameters to collect carriers (electrons and holes) from both electrodes of C-Si solar cells. We have used both mathematical and experimental approaches to reduce these resistances for enhancement of power conversion efficiency (PCE) by increasing fill factor. After processing by light-induced plating (LIP) for metal contact, the PCE of solar cell is obtained as 14.43%, which is 8.8% more than that before LIP processing.

As the sharing of information through the communication channels increases, the indispensability of maintaining confidentiality of those shared information also increases proportionally. Providing reasonable security over the insecure channel is a challenging research. Due to the advancement of computational efficiency, confidentiality of the information cannot be assured with the help of a static key. Keeping this in mind, many researchers have proposed several time variant key generation techniques, out of which Automatic Variable Key (AVK) is a novel approach. In conventional AVK and in different variations of AVK; the key varies every time as new data is exchanged between sender and receiver while the key size remains constant throughout the data communication. Therefore, to increase the randomness among the successive keys that is the key for ensuring the greater security, we have proposed a 2-dimensional AVK in which the auto generated keys not only vary in bits sequence (i.e. session by session) but also in size.

Overall series resistance of the contact increases due to unwanted pores created during the time of contact formation in solar cell. Light induced plating is an industrial established process which is used to reduce the series resistance and to improve the contact resistance resulting in increase of fill factor of solar cell through modification of front side contact. In this paper a theoretical modeling is done to show how distributed pores affect the series resistance and solar cell performance. Here we explored several parameters like: series resistance, shunt resistance, fill factor, short circuit current, and external quantum efficiency. Through our experimental setup it is found that the short circuit current improves significantly and also it is observed that during the time of experiment due to unintentional deposition of silver nanoparticles, external quantum efficiency improved by 5.249 % and a reduction of reflectance by 2.03 %. An overall enhancement of solar cell efficiency of 1.65 % is obtained during the process.

As computer networks become an essential part of our daily life, therefore, protecting the resources from unauthorized users come forward with more challenging and complicated task for the researchers. From the last few decades, many number of password-based authentication schemes have been adopted in multi-server environment to protect the resources from any adversary means. Recently, Li et al. has proposed a dynamic-id based remote user authentication scheme and claimed that their scheme can provide more security than existing schemes and is suitable for practical applications. But, in this paper, we have shown that their scheme is not too much secured as they have claimed and it can suffer from stolen smart card attack, user impersonate attack and lack of some important features of smart card as well. To overcome these security flaws, we have further proposed an improved anonymous authentication scheme.

Aggressive Packet Combining (APC) scheme is well established for receiving correct packet in high error prone wireless link. In APC three copies of a packet are transmitted and receiver does bit wise majority decision to get the correct copy. The main research challenge in APC is that if two or more copies of the packet become erroneous at the particular bit location then majority logic fails to correct the error and also as three copies of packet are sent at a time, throughput degradation takes place at higher error rate channel. In this paper we propose a new method of correction in APC which will address the limitation which occurs in conventional APC. General Terms Throughput comparison

Antenna is a significant component of wireless communication system. Radio Frequency Identification (RFID) is one of the activities of Automatic Identification (AUID) system which comes under wireless system. To track any object wirelessly in RFID system, antenna acts as the primary and critical component. Radio Frequency (RF) micromachining technology provides an innovative approach in the development of effective antenna. In this paper, initially we present rectangular patch antenna resonant at 40GHz on silicon substrate. In the consecutive step, in order to improve performance of the antenna silicon micromachining has done by etching the substrate between the ground and the patch. Ansoft High Frequency Structure Simulator (HFSS) provides the simulation result and the different performance parameters like gain, return loss, bandwidths etc. are analyzed.

To protect the resources from unauthorized users, the remote user authentication have become an essential part in the communication network. Currently, smart card-based remote user authentication for multi-server environment is a widely used and researched method. Remote user authentication for multi-server environment has resolved the problem of users to manage the different identities and passwords. Recently, Mishra et al. proposed a multi-server authenticated key agreement scheme using smart cards, where they claim that their scheme is secure enough and could resist the various well known attacks. However, in this paper, we have shown that their scheme is not secure as they have claimed and can suffer from impersonation attacks and stolen smart card attack. Later in the paper, we propose an improved multi-server authentication scheme using smart cards, which not only overcomes the mentioned weaknesses but also can provide more functionality features.

Aggressive packet combining (APC) scheme is well-established in literature. Several modifications were studied earlier for improving throughput. In this paper, three new modifications of APC are proposed. The performance of proposed modified APC is studied by simulation and is reported here. A hybrid scheme is proposed here for getting higher throughput and also the disjoint factor is compared among conventional APC with proposed schemes for getting higher throughput.

In this paper, we reported improvement in crystalline quality by changing structural properties of ZnO thin film into hexagonal shaped nanorods. ZnO thin films were deposited on Si (1 0 0) substrate using dielectric sputter. As-grown film (Sample A) was subjected to chemical etching for forming hexagonal nanorods. The overall electrical & optical performances like photo luminescence performance, X-ray diffraction performance in terms of crystal formation & reflectance performance are improver after rapid thermal & chemical treatments.

For reliable transport of data in wireless network, Aggressive Packet Combining (APC) scheme is one of the protocols, which is well established. APC has several limitations including low throughput. Several modifications were earlier studied elsewhere for achieving higher throughput in APC. In this work, it has been proposed the two new modifications of APC. The performance of proposed modified APC are studied numerically and reported accordingly. The throughput of the proposed new techniques is found higher than that of APC.

In realizing the time variant key or variable key from session to session is the key challenge in achieving perfect security. Automatic variable key (AVK) is a novel approach to realise time variant key. In AVK, key is generated for use between the sender and the receiver by using a simple computation technique. The AVK was widely experimented by other researchers that established the superiority of AVK over a single/fixed key. In this paper we propose two new techniques for generating time variant key. Our techniques ensure better randomness among the successive two keys so generated.