In this article, a low-power and energy-efficient hybrid full adder circuit is proposed, which is implemented based on multi-threshold NAND and NOR gates and transmission gate multiplexers. In order to implement this circuit, carbon nano tube field effect transistors are utilised. For evaluating the proposed design, comprehensive simulations are performed with regard to the most important aspects power, delay and power-delay product. The results are presented and displayed the superiority of the proposed cell in different voltage levels, load conditions, temperatures and robustness against process variations. 相似文献
In this paper a variable gain low noise amplifier (VG-LNA) is designed and analyzed for X band in 0.18 µm CMOS technology. A two-stage structure is utilized in the proposed VG-LNA and its gain, which is controlled by an on-chip voltage (Vcnt), has continuous and almost linear variations. The required range for Vcnt can be initiated from 0.5 V, also the variations of gain doesn’t ruin reflection loss (S11), return loss (S12) and noise figure (NF). The best performance of this VG-LNA is at 10 GHz frequency with 1 GHz bandwidth. In the center frequency, the maximum gain is 20.8 dB that continuously and linearly decreases to 4 dB by increasing Vcnt. Also S11 and S12 in this frequency are lower than ?27 and ?38 dB, respectively. NF is lower than 2 dB in the mentioned frequency range and NFmin is equal to 1.2 dB, while the third-order intercept point (IIP3) equals to 8.27 dBm in the best condition and always stays above ?10 dBm. The main advantage of the proposed structure in compare with the similar structures is not only the key parameters don’t ruin by the gain variations, but also increment of Vcnt operation range (0.5 V to Vdd), leads to expanding gain control range. These results are achieved while the power consumption is 8.4 mW with 1.8 V supply voltage and the chip area is 0.56 mm2. 相似文献
In this paper, two element multiple input–multiple output (MIMO) meander line antenna systems with improved isolation performance and compact size are proposed and fabricated in WLAN frequency band. To increase isolation among antenna elements, a novel metamaterial spiral S-shaped resonator is embedded between two radiating elements. The proposed resonator has planar configuration and miniaturized size and is capable of blocking electromagnetic propagation between antenna elements by exhibiting negative effective permeability in the desired frequency band. To illustrate and evaluate the design process, two design samples are fabricated and tested in WLAN frequency band and the agreement among measurement and simulation results approves the design method. In the frequency range of 2.38–2.48 GHz, some MIMO communication system requirements like total active reflection coefficient, envelope correlation coefficient and capacity loss are tested on design samples which show satisfactory results, so this method can be employed in designing array antennas for small mobile communication systems. The designed MIMO antenna systems separated by 13.8 mm (less than λ/9), has better than ??40 dB isolation coefficient and near zero correlation coefficient and capacity loss at the operating frequency (2.4 GHz).
Due to recent interest in semi-solid metal (SSM) processing, there is a need for fundamental knowledge on the formation and
solidification of primary particles. The primary particle size, distribution, morphology, and percentage are the main concerns
because particle quantity and size affect not only the mechanical properties of as-cast SSM parts but also the flow characteristics
of SSM slurries during die filling. Microstructural characterization is a basic tool for measuring the critical parameters
that influence the resulting properties. This article describes the tools and techniques available for structural analysis
of SSM slurries. It also attempts to elucidate the ambiguities and interpretations of special structural features. 相似文献
Wireless Networks - The main research challenges on developing Wireless Body Area Networks (WBAN) are related to the quality of the communication link and energy consumption. This article combines... 相似文献
This paper presents a method to improve the reliability and fault tolerance of distributed software‐defined networks. This method is called “BIRDSDN (Byzantine‐Resilient Improved Reliable Distributed Software‐Defined Networks).” In BIRDSDN, a group communication is implemented among the controllers of the whole clusters. This method can detect the crash failure and Byzantine failure of any controller and undertakes a fast detection and recovery scheme to select the controllers to take over the orphan switches. BIRDSDN takes into account the reliability of the nodes considering the failure probability of intracluster and intercluster links, topology, load, and latency. The numerical results show that this approach performs better than the other approaches regarding failure detection, recovery, latency, throughput, reliability, and packet loss. 相似文献
Wireless sensor networks (WSNs) have been vastly employed in the collection and transmission of data via wireless networks. This type of network is nowadays used in many applications for surveillance activities in various environments due to its low cost and easy communications. In these networks, the sensors use a limited power source which after its depletion, since it is non‐renewable, network lifetime ends. Due to the weaknesses in sensor nodes, they are vulnerable to many threats. One notable attack threating WSN is Denial of Sleep (DoS). DoS attacks denotes the loss of energy in these sensors by keeping the nodes from going into sleep and energy‐saving mode. In this paper, the Abnormal Sensor Detection Accuracy (ASDA‐RSA) method is utilized to counteract DoS attacks to reducing the amount of energy consumed. The ASDA‐RSA schema in this paper consists of two phases to enhancement security in the WSNs. In the first phase, a clustering approach based on energy and distance is used to select the proper cluster head and in the second phase, the RSA cryptography algorithm and interlock protocol are used here along with an authentication method, to prevent DoS attacks. Moreover, ASDA‐RSA method is evaluated here via extensive simulations carried out in NS‐2. The simulation results indicate that the WSN network performance metrics are improved in terms of average throughput, Packet Delivery Ratio (PDR), network lifetime, detection ratio, and average residual energy. 相似文献
In recent years, hybrid perovskite solar cells (HPSCs) have received considerable research attention due to their impressive photovoltaic performance and low‐temperature solution processing capability. However, there remain challenges related to defect passivation and enhancing the charge carrier dynamics of the perovskites, to further increase the power conversion efficiency of HPSCs. In this work, the use of a novel material, phenylhydrazinium iodide (PHAI), as an additive in MAPbI3 perovskite for defect minimization and enhancement of the charge carrier dynamics of inverted HPSCs is reported. Incorporation of the PHAI in perovskite precursor solution facilitates controlled crystallization, higher carrier lifetime, as well as less recombination. In addition, PHAI additive treated HPSCs exhibit lower density of filled trap states (1010 cm?2) in perovskite grain boundaries, higher charge carrier mobility (≈11 × 10?4 cm2 V?1 s), and enhanced power conversion efficiency (≈18%) that corresponds to a ≈20% improvement in comparison to the pristine devices. 相似文献
In case there is a communication contrary to the system security policies, a covert channel has been created. The attacker can easily disclosure information from the victim’s system with just one public access permission. Covert timing channels, unlike covert storage channels, do not have memory storage and they draw less attention. Different methods have been proposed for their identification, which generally benefit from the shape of traffic and the channel’s regularity. The application nature of HTTP protocol allows the creation of a covert timing channel based on different features of this protocol (or different levels) that has not been addressed in previous researches. This research tries to study the effect of using different features (or levels) of HTTP protocol on identifying the covert channel. The amount of channel’s entropy could be manipulated by changing the channel’s level or adding intentional noise on the channel to protect from the analyzer’s detection. The difference in the placement of the covert channel and the detector causes the amount of channel entropy to be far from the detection threshold. Therefore, we concluded that the analyzer must investigate traffic at all possible levels. Adding noise on the covert channel decrease its capacity, but as entropy increases, it would be harder to detect it.
This paper presents a wide frequency range three-stage voltage-controlled ring oscillator in CNTFET technology. The advantages of CNTFETs are the high speed of charge carriers, high signal to noise ratio, small size and ballistic transport. Therefore in comparison with MOSFETs, they have a higher frequency, and can operate at a wide frequency range with a very low phase noise if forward bulk bias and active inductor techniques are simultaneously used in the oscillators that employ CNTFETs. In this paper, the Stanford CNTFET model is implemented in Verilog-A, and the proposed CNT ring oscillator is simulated using ADS software over the 50–500 GHz frequency range. The phase noise of the oscillator is ? 136 dBc/Hz at 1 MHz offset, which is suitable for PLL applications.