Multifunctional reconfigurable antennas for cognitive radars

Moving contents proximity to the network edge and proactively caching popular contents at multiple infrastructures are promising directions for solving the backhaul congestion problem. This letter proposes and evaluates a multi-level cache-enabled network, where cache-hit users can fetch their data from the available cache at either small base-stations, unmanned aerial vehicles, or cache-enabled mobile device-to-device users. Cache-miss users, on the other hand, fetch their data from the central cloud via limited capacity backhaul links. This letter considers the problem of maximizing the network weighted-sum rate by jointly determining the users’ mode of operation and their transmit powers, subject to backhaul capacity and transmit power constraints. After showing how the association problem can be formulated as a generalized assignment problem, the letter solves the transmit power problem using an iterative function evaluation apprach. The resulting mode-selection and power-allocation (MSPA) iterative algorithm is then tested through numerical simulations, which suggest that, while being easily implementable, the proposed multi-level caching can substantially relieve the backhaul congestion, especially in dense-networks, and at low-backhaul capacity regimes.

We present a composite suite of technologies for spectral coexistence of existing communication and radar systems using the Xampling framework. For a stand-alone communication system, we consider a cognitive radio (CRo) that receives multiband signals with unknown carrier frequencies and directions of arrival, and demonstrate joint spectrum sensing via CompreSsed CArrier and Direction-ofarrival Estimation (CaSCADE) with an L-shaped configuration of two uniform linear arrays. For radars operating in bands with widespread spectral interference, we present an X-band prototype of cognitive sub-Nyquist multiple input multiple output (MIMO) radar (SUMMeR). The prototype allows sampling in both spatial and spectral domains at sub-Nyquist rates and cognitively transmits over multiple narrow subbands. Finally, we demonstrate Spectral Coexistence via Xampling (SpeCX) technology that shows joint operation of both - cognitive radio and cognitive monostatic radar - over a common spectrum. Our solutions to individual and joint operation of communication and radar systems supersede existing spectrum sharing technologies that require a compromise over performance of one of the systems.

Full-duplex (FD) radio with wireless backhauling, is a key technology for dense small cell deployments in fifth generation (5G) cellular networks. In this paper, the problem of joint user scheduling, operation mode selection and power allocation in a two-tier cellular network with FD-capable small basestations is considered. The objective is to maximize the network sum rate under quality-of-service requirements and backhaul capacity constraints. In order to solve the problem, a distributed algorithm is developed which divides the original problem into two subproblems, viz., (i) user scheduling and mode selection; and (ii) power allocation. For the first subproblem, a low-complexity search method is proposed for opportunistically finding the best user scheduling and operation modes. In the second subproblem, an iterative successive convex approximation method is proposed to transform the nonconvex power allocation problem into a sequence of convex subproblems. The proposed solution provides a hybrid strategy which opportunistically selects FD or half-duplex (HD) operation modes for access and backhaul links. It is observed that the proposed algorithm converges in few iterations and mitigates the interferences by properly adjusting the transmission powers. Numerical results demonstrate the superiority of the proposed scheme over other possible scenarios. In particular, the proposed algorithm can achieve up to 44% gain in overall sum rate compared to a network that solely uses HD.

The theory of characteristic modes is a popular physics-based deterministic approach, which has found several recent applications in the fields of radiator design, electromagnetic interference modeling, and radiated emission analysis. To apply the characteristic mode analysis of a given structure, proper selection of significant modes is an essential requirement for the correct conclusion of the resultant field. This paper reviews the development of the conventional modal significance measure together with other related significance criteria that have been proposed over the last few decades. In particular, the thought process that relates to the development of initial measures to the excitation of the induced current vector will be explained. The common problems with the existing measures will also be identified. Later a suitable modal metric will be suggested and validated with an example. The proposed measure will be further applied for approximating the shielding response of the aperture examples for both the infinite and finite cases.

Daily activities have been increasingly supported by intelligent devices and applications. Smart devices are constantly communicating through the Internet of Things (IoT) networks, either by sending collected data and notifying the actions taken or by receiving instructions for actions to be taken. Most of this communication requires the confidentiality of data through the usage of encryption algorithms, being the Advanced Encryption Standard (AES) algorithm one of the most used. However, how do the operation modes of AES algorithm perform in a resource-constraint device? This paper aims to evaluate the impact on the time to encrypt and decrypt different sized messages in IoT devices when using each one of the five AES modes of operation and the three key sizes defined. The test scenario was implemented using two programming languages, running on a Raspberry Pi device. The results achieved infers that Python was quicker and had a more homogeneous result set than JavaScript implementation in most AES operation modes. These results help to understand the trade-off between IoT devices' security needs and delays in communication caused by the selection of the AES algorithm operation mode.

This study examines GIS-integrated design management practices in Zimbabwean infrastructure development projects through a web-based survey of 198 respondents. Despite development efforts, Bulawayo faces persistent project management challenges, including issues with stakeholder coordination, design quality, and environmental sustainability. These difficulties have led to project failures, wasted resources, and unmet needs, exacerbated by the underutilisation of GIS-integrated design management. The study seeks to identify the root causes of these challenges and propose solutions to improve project success rates in Bulawayo. Firstly, the study aims to examine the current practices of GIS-integrated design management in Zimbabwe's IDPs, providing a comprehensive overview of how these practices are implemented and utilised. Second, it seeks to analyse how the integration of GIS in design management can enhance environmental sustainability in IDPs, exploring the potential for GIS technologies to contribute to more eco-friendly infrastructure projects. Third, the study will evaluate the role of GIS-integrated design management in improving the success of infrastructure development projects through enhanced stakeholder collaboration, highlighting the benefits of improved communication and coordination among project stakeholders. Finally, the study will assess the impact of GIS-integrated design management on cost efficiency in infrastructure development projects, examining how these practices can lead to cost savings and more efficient use of resources. The results indicate that Design Thinking and Agile Design are the most prevalent methodologies, with mean scores of 3.6549 and 3.6429, respectively. These methods are favoured for their iterative, flexible, and user-centric approaches, which align well with the evolving demands of infrastructure projects. The analysis shows a moderate positive correlation (r = 0.265) between integrated design management and environmental sustainability, which is statistically significant (p = 0.000). This suggests that enhanced design management practices are linked to better environmental outcomes. Additionally, there is a significant correlation (r = 0.268, p = 0.01) between integrated design management and stakeholder collaboration, indicating that these practices improve collaboration by providing shared platforms for communication and project information. Conversely, the correlation between integrated design management and cost efficiency is minimal (r = 0.043, p = 0.552), suggesting that these practices do not significantly influence cost efficiency. A positive but modest correlation (r = 0.249) with project success, significant at the 0.01 level, implies that effective design management practices contribute to project success, though the impact is moderate. Based on these findings, it is recommended to continue developing and integrating Design Thinking and Agile Design methodologies to enhance project management effectiveness. Furthermore, to maximise the positive impact on environmental sustainability, it is advisable to deepen the integration of GIS tools that support environmental management and regulatory compliance. Investment in advanced GIS tools that facilitate real-time collaboration and data sharing can also improve stakeholder engagement and project alignment. The study makes significant contributions to the practical use of GIS integration in design management, which is an emerging and developing practice in infrastructure development projects considering the rapid pace and development of technology.

Antidepressant-like activity of venlafaxine and clonidine in mice exposed to single prolonged stress – A model of post-traumatic stress disorder. Pharmacodynamic and molecular docking studies

The construction of a flame detector, the FIDOH, is described. The effects of fuel and carrier gas flow rates and the polarity and magnitude of the polarising voltage on the response of the detector are studied. Three modes of operation are identified, one in which response is based only on carbon content (the molar mode), one based on response to all constituent atoms (the weight mode), and one on the presence of halogen atoms only (the selective mode). For each of these modes, quantitative analysis of mixtures has been undertaken and the results compared with those obtained using a normal flame ionisation detector.

With the advent of battery-powered portable devices and mandatory adoption of power factor correction, noninverting buck-boost converters are garnering lots of attention. Conventional two-switch or four-switch noninverting buck-boost converters choose their operation modes by measuring input and output voltage magnitude. The criterion for the selection of the operation mode can cause higher output voltage transients in the neighborhood, where input and output are close to each other. For the mode selection, due to the voltage drops raised by the parasitic components, it is not enough just to compare the magnitude of input and output voltages. In addition, the difference in the minimum and maximum effective duty cycles between controller output and switching device yields discontinuity at the instant of mode change. Moreover, the different properties of output voltage versus a given duty cycle of buck and boost operating modes contribute to the output voltage transients. In this paper, the effect of the discontinuity due to the effective duty cycle derived from the device switching time at the mode change is analyzed. A technique to compensate the output voltage transient due to this discontinuity is proposed. In order to attain additional mitigation of output transients and a linear input/output voltage characteristic in buck and boost modes, the linearization of DC gain of the large-signal model in boost operation is analyzed as well. Analytical, simulation, and experimental results are presented to validate the proposed theory.

The electromagnetic radiation characteristic of the Koch fractal dipole antenna is analyzed, the logical assumption that the current along the Koch fractal dipole antenna obeys sine distribution is demonstrated, and the approximate expression of the magnetic vector potential of the Koch fractal dipole antenna is obtained. Using the magnetic vector potential, the far electromagnetic field is simulated, and the simulated results are compared with those obtained from the traditional symmetrical dipole antenna. For electrically large or electrically equivalent antennas, the results indicate that the electrical length of the Koch fractal dipole antenna has little influence on the radiation patterns. By using of this conclusion, the size of antennas can be reduced, as well as the least gain of antenna is satisfied. Therefore, it will be good for analytical design of multi-band and multi-functional antennas using fractal geometries. Finally, the rationalities of formulas and computations are validated by CST simulation.

This paper presents a non-monolithic top-down reconfigurable multiplier suitable for embedding in an FPGA structure. It is constructed of four individual partitions that can operate as separate multipliers but also concatenate to form a superior multiplier with increased precision and sign handling ability. The number of possible operation modes is limited in order to keep the reconfiguration overhead low. A small set of control signals determines behavior and mode selection. Inactive partitions are disconnected from the supply to save power. EMMA (Embedded Multi-precision Multiplier Array) can compute signed twopsilas complement numbers at up to 32 times 16-bit precision when all partitions are active and concatenated, or up to four separate 16 times 8-bit multiplications running simultaneously.

This paper presents the design of three-port converters (TPCs) for smooth transitions (i.e., fast settling time, and no obvious overshoot/undershoot) of 7 distinctive operating modes, depending on sources and loads scheduling. Two viable converter configurations have been identified and selected for further analysis and design of PV-battery systems. Conventionally, mode transition is achieved by assigning specific switching patterns through feedback signals and appropriate control algorithms. This incurs a delay in the response and unavoidable noise in the circuit. Additionally, in TPCs, three voltage sensors and three current sensors are generally required for decision making in mode selection, where errors in sensors may lead to an inaccurate response. This paper presents a new control strategy where the number of switching patterns is significantly reduced to 3 patterns instead of minimum 5 patterns for existing reported topologies. Therefore, decisions are simplified so that the transition occurs naturally based on the power availability and load demand but not deliberately as in the conventional method. In addition, instead of six sensors, three voltage sensors and only one current sensor are required to achieve all the necessary operations, namely, MPPT, battery protection, and output regulation. Moreover, these sensors do not participate in mode selection decision, which leads to seamless and fast mode transition. In addition, this work considers two bidirectional ports as compared with only one bidirectional port in most reported topologies. This configuration enables both standalone and DC grid-connected applications. Experimental results are reported to verify the proposed solution.

A low noise and highly linear wideband RF front-end circuit for sub-㎓ Internet of Things (IoT) applications is proposed. The proposed frontend is composed of a broadband single-ended LNA, a wideband differential LNA employing thermal noise cancellation technique, and an in-phase and quadrature (I/Q) linearized harmonic rejection mixer (HRM). Depending on the interference environment, the proposed front-end supports two operation modes having high sensitivity and selectivity performance by enabling or disabling the first building block of the single-ended LNA. At high sensitivity mode, the frontend shows a voltage gain (A<SUB>v</SUB>) of greater than 38 ㏈, a noise figure (NF) of less than 2.1 ㏈, an input-referred third-order intercept point (IIP3) of greater than -23 ㏈m, and an input-referred second-order intercept point (IIP2) of greater than +15 ㏈m in the sub-㎓ frequency band. Concerning for high selectivity mode, it achieves an Av of greater than 22.5 ㏈, a NF of less than 4.7 ㏈, an IIP3 of greater than – 6.8 ㏈m, and an IIP2 of greater than +50 ㏈m over the same operating frequency range.

Infrared isomer-specific fragmentation for the identification of aminobutyric acid isomers separated by differential mobility spectrometry

The coherent signal subspace method (CSSM) enables the direction-of-arrival (DoA) estimation of coherent sources with subspace localization methods. The focusing process that aligns the signal subspaces within a frequency band to its central frequency is central to the CSSM. Within current focusing approaches, a direction-independent focusing approach may be more suitable for reverberant environments since no initial estimation of the sources' DoAs is required. However, these methods use integrals over the steering function, and cannot be directly applied to arrays around complex scattering structures, such as robot heads. In this article, current direction-independent focusing methods are extended to arrays for which the steering function is available only for selected directions, typically in a numerical form. Spherical harmonics decomposition of the steering function is then employed to formulate several aspects of the focusing error. A case of two coherent sources is studied and guidelines for the selection of the frequency smoothing bandwidth are suggested. The performance of the proposed methods is then investigated for an array that is mounted on a robot head. The focusing process is integrated within the direct-path dominance (DPD) test method for speaker localization, originally designed for spherical arrays, extending its application to arrays with arbitrary configurations. Finally, experiments with real data verify the feasibility of the proposed method to successfully estimate the DoAs of multiple speakers under real-world conditions.