Bidirectional Modes Research Articles

Unveiling intrusions: explainable SVM approaches for addressing encrypted Wi-Fi traffic in UAV networks

AbstractUnmanned aerial vehicles (UAVs), also known as drones, have become instrumental in various domains, including agriculture, geographic information systems, media, logistics, security, and defense. These UAVs often rely on wireless communication networks for data transmission, making them vulnerable to cyberattacks. To address these challenges, it is necessary to detect potential threats by analyzing the encrypted Wi-Fi traffic data generated by UAVs. This study aimed to develop a linear SVM model that is enhanced with explainable artificial intelligence (XAI) techniques and fine-tuned using Bayesian optimization for intrusion detection systems (IDSs); the model is specifically designed to identify malware threats targeting UAVs. This research utilized encrypted Wi-Fi traffic data derived from three different UAV networks, namely, Parrot Bebop 1, DBPower UDI, and DJI Spark, while considering unidirectional and bidirectional communication flow modes. SVM-based intrusion detection models have been modeled on these datasets, identified their key features using the local interpretable model-agnostic explanations (LIME) technique, and conducted a cost analysis of the proposed modeling approach. The incorporation of the LIME method enabled to highlight the features that are highly indicative of cyberattacks and provided valuable insights into the importance of each feature in the context of intrusion detection. In conclusion, this interpretable IDS model, fine-tuned with Bayesian optimization, demonstrated its superiority over the state-of-the-art methods, proving its efficacy in detecting and mitigating threats to UAVs while offering a cost-effective solution.

A comparative study on the multidirectional piezo-resistive scenario of conventional and auxetic silicone-based sensors coated with graphite powder

The (comparative) study on the multidirectional piezo-resistive scenario of conventional and auxetic sensors is presented using silicone RTV2 as a base material coated with graphite powder as a sensing element. The key parameter of this comparison is the added area that appeared by applying the strain. The larger this parameter is, the larger the area for the sensing elements separation, and subsequently, the greater the sensitivity. To do the sensing performance test in a three-directional mode, a low-cost idea is to use a chuck lathe and an electric motor to open and close the chuck lath cyclically. The available commercial software ABAQUS2021 is used for numerical study. The sensitivity test on conventional and auxetic sensors in different loading modes shows that the performance of the auxetic sensor in unidirectional and bidirectional loading modes is 272% and 130% better than the conventional sensor, respectively. It means that if the added area for the two sensors is closer to each other, the sensory performance of the two sensors will be more similar. Although the sensing performance of the two sensors in the three-directional loading mode is almost equal, the consumed strain energy required to deform the conventional sensor is 30 times more than that of the auxetic one.

Investigation of the precipitation behavior and its role on creep deformation and failure mechanisms at high temperatures for a turbine disk alloy

The creep deformation behavior of a turbine disk alloy at high temperatures was studied, and the role of the multi-scale precipitates on the creep deformation and failure mechanisms was revealed. The turbine disk alloy shows a typical microstructure with the micron-scale MC carbides, submicron delta phase, together with nanoscale γ″ and γ' precipitates distributed in the matrix after hot working and aging treatment. The MC carbides are mostly formed from the solidification process due to enrichment of Nb in the inter-dendritic areas. The creep life decreases from 763.5 h to 5.7 h when the creep temperature increases from 953 K to 1023 K at 500 MPa. The fracture surfaces exhibit a transgranular fracture pattern accompanied with the formation of substantial microvoids. Slipping occurs in both unidirectional and bidirectional modes during deformation. The microvoids along the grain boundaries are generated through decohesion of δ precipitates from the matrix or the interaction between slip traces and grain boundaries. When the intragranular MC carbides interact with the slip traces, microcracks can be formed by particle fracturing. The dense distribution of particles along the grain boundaries will result in a significantly higher critical stress required for microvoid nucleation, whereas the non-coherent particles inside the grains, particularly the large size MC carbides, can decrease the critical shear stress for microcrack formation to as low as 88.9 MPa, thereby contributing to alloy rupture. For the coherent precipitates, a comprehensive strengthening effect of 389.12 MPa is achievable by the synergistic precipitation of γ″ and γ', which primarily serve to enhance and coordinate intragranular deformation during creep.

Transmission and reflection bidirectional terahertz coding metasurface based on thermally switchable materials

Metasurface, with its powerful and flexible terahertz(THz) wave manipulation capability, has become a key component of beamforming and imaging systems in the THz band. However, its practical application is limited by fixed properties and propagation mode on a single metasurface. In this paper, we propose a coding metasurface with tunable characteristics and bidirectional working modes. The complete 2π phase compensation can be realized by rotating the InSb unit according to the Pancharatnam-Berry phase concept, and eight meta-atoms are selected to regulate the wavefront of terahertz waves using phase compensation. By increasing the temperature of the InSb from 290 K to 370 K, the working frequency permits wideband coverage from 1.7 to 4.5 THz. As the temperature reaches 341.15 K, which is required for vanadium dioxide's(VO2) phase transition, the metasurface's propagation direction mode will switch from transmission to reflection. The proposed metasurface can perform beam deflecting, splitting, and focusing functions when VO2 is in a dielectric state. Meanwhile, beam deflecting, splitting, and radar scattering surface (RCS) reduction can also be achieved when VO2 is in a metallic state. Furthermore, a near-field image of the letter P is presented as verification. Numerous potential applications for the reconfigurable metasurfaces include polarization beam splitters, imaging, and terahertz switching.

Caterpillar-inspired soft crawling robot with distributed programmable thermal actuation.

Many inspirations for soft robotics are from the natural world, such as octopuses, snakes, and caterpillars. Here, we report a caterpillar-inspired, energy-efficient crawling robot with multiple crawling modes, enabled by joule heating of a patterned soft heater consisting of silver nanowire networks in a liquid crystal elastomer (LCE)-based thermal bimorph actuator. With patterned and distributed heaters and programmable heating, different temperature and hence curvature distribution along the body of the robot are achieved, enabling bidirectional locomotion as a result of the friction competition between the front and rear end with the ground. The thermal bimorph behavior is studied to predict and optimize the local curvature of the robot under thermal stimuli. The bidirectional actuation modes with the crawling speeds are investigated. The capability of passing through obstacles with limited spacing are demonstrated. The strategy of distributed and programmable heating and actuation with thermal responsive materials offers unprecedented capabilities for smart and multifunctional soft robots.

Optimal Cooperative Power Management Framework for Smart Buildings Using Bidirectional Electric Vehicle Modes

The high potential for implementing demand management approaches across multiple objectives has been significantly enhanced. This study proposes a cooperative energy management strategy based on the end-user sharing of energy. The proposed method promotes the intelligent charging and discharging of EVs to achieve vehicle-to-anything (V2X) and anything-to-vehicle (X2V) operating modes for both integrated and nonrenewable residential applications. These sharing modes have already been discussed, but resolution approaches are applicable to a specific use case. Other application cases may require additional metrics to plan the fleet of electric vehicles. To avoid that problem, this study proposes the MIP method using a robust Gurobi optimiser based on a generic framework for cooperative power management (CPM). Moreover, the CPM ensures an overall target state of charge (SoC) at leaving time for all the vehicles without generating a rebound peak in total grid power, even without introducing photovoltaic power. Two different methods are proposed based on the flow direction of the EV power. The first method only includes the one-way power flow, while the second increases the two-way power flow between vehicles, operating in vehicle-to-vehicle or vehicle-to-loads modes. A thorough analysis of the findings of the proposed model was conducted to demonstrate the robustness and efficiency of the charging and discharging schedule of several EVs, favouring a sharing economy concept, reducing peak power, and increasing user comfort.

Aluminum Scrap to Hydrogen: Complex Effects of Oxidation Medium, Ball Milling Parameters, and Copper Additive Dispersity

An effective combination of oxidation medium, ball milling parameters, and copper additive disperstiy ensuring fast aluminum scrap reaction with high hydrogen yield, was suggested. Different milling parameters (5, 10, and 15 mm steel balls; 1 and 2 h; unidirectional and bidirectional rotation modes) were tested for Al-10 wt.% Cu (50–70 μm) composition. The samples milled with 5 (2 h) and 10 mm (1 and 2 h) balls contained undesirable intermetallic phases Al2Cu and Cu9Al4, while those activated with 15 mm balls (1 h) provided the second-finest powder and best preservation of the original Cu and Al phases. Among the tested (at 60 °C) 2 M solutions NaCl, LiCl, KCl, MgCl2, ZnCl2, BaCl2, CaCl2, NiCl2, CoCl2, FeCl2, and AlCl3, the first six appeared to be almost useless (below 4% hydrogen yield), the following four provided better results, and the ultimate 91.5% corresponded to AlCl3. Samples with Cu dispersity of 50–100 nm, 1–19, 50–70, and 150–250 μm, and with no additive, were milled under the optimal parameters and tested in AlCl3. Their total yields were similar (~90–94%), while reaction rates differed. The highest rate was obtained for the sample modified with 50–70 μm powder.

Experimental and simulation studies on the mechanical performance of concrete T-Girder bridge strengthened with K-Brace composite trusses

In this paper, a new transverse strengthening method was proposed for T-girder bridges with K-brace composite trusses. A series of experiments and simulations were conducted to study the strengthening effects under four different loading conditions, including non-eccentric loading, transverse eccentric loading, longitudinal eccentric loading, and bidirectional eccentric loading modes. Altogether four groups of specimens were fabricated and studied. Each group consisted of a control specimen and a strengthened one. Furthermore, the concrete plastic damage model was used to simulate the mechanical behaviors of the specimens. The results showed that such a strengthening method could significantly upgrade the mechanical behaviors of the T-girder bridge specimens, especially the local deformation and crack propagation manner of the T-girder. Compared with the control specimen, the deflection of concrete T-girder bridge specimen strengthened with the K-brace composite trusses was significantly decreased, with a maximum reduction of 38.6% under the prescribed load. Moreover, the K-brace composite trusses can markedly better the load distribution and improve the failure modes of the specimens, where the crack widths decreased even by 44.0%. They distributed along the beam more evenly. So, it provides a new method to strengthen and upgrade the mechanical properties of T-girder bridges.

Bidirectional, unlike unidirectional transport, allows transporting axonal cargos against their concentration gradient

Even though most axonal cargos are synthesized in the soma, the concentration of many of these cargos is larger at the presynaptic terminal than in the soma. This requires transport of these cargos from the soma to the presynaptic terminal or other active sites in the axon. Axons utilize both bidirectional (for example, slow axonal transport) and unidirectional (for example, fast anterograde axonal transport) modes of cargo transport. Bidirectional transport seems to be less efficient because it requires more time and takes more energy to deliver cargos. In this paper, we studied a family of models which differ by the modes of axonal cargo transport (such as anterograde and retrograde motor-driven transport and passive diffusion) as well as by the presence or absence of pausing states. The models are studied to investigate their ability to describe axonal transport against the cargo concentration gradient. We argue that bidirectional axonal transport is described by a higher-order mathematical model, which allows imposing cargo concentration not only at the axon hillock but also at the axon terminal. The unidirectional transport model allows only for the imposition of cargo concentration at the axon hillock. Due to the great lengths of the axons, anterograde transport mostly relies on molecular motors, such as kinesins, to deliver cargos synthesized in the soma to the terminal and other active sites in the axon. Retrograde transport can be also motor-driven, in which case cargos are transported by dynein motors. If cargo concentration at the axon tip is higher than at the axon hillock, retrograde transport can also occur by cargo diffusion. However, because many axonal cargos are large or they assemble in multiprotein complexes for axonal transport, the diffusivity of such cargos is very small. We investigated the case of a small cargo diffusivity using a perturbation technique and found that for this case the effect of diffusion is limited to a very thin diffusion boundary layer near the axon tip. If cargo diffusivity is decreased in the model, we show that without motor-driven retrograde transport the model is unable to describe a high cargo concentration at the axon tip. To the best of our knowledge, our paper presents the first explanation for the utilization of seemingly inefficient bidirectional transport in neurons.

An efficient simulation model for layout and mode performance evaluation of robotic mobile fulfillment systems

The robotic mobile fulfillment system (RMFS) is a “goods to man” picking system that employs numerous automatic guided vehicles (AGVs) instead of workers to transport goods from the storage station to the picking station. Using smarter AGVs enhances the performance but also leads to layout problems and the challenge of efficiently estimating the system performance with various layouts. With the same capability of storage, the different row and column of storage position area can lead to different system performance. The number of combinations of rows and columns is huge which makes it time-consuming to compare all the combinations to find the best one, and different path modes (unidirectional path mode and bidirectional path mode) and different number of AGVs further complicate the problem. Quickly modeling and performance estimating of RMFS become the biggest challenge for logistics enterprise. In this paper, according to the modular simulation theory, an efficient model based on discrete-event system simulation is proposed for quickly constructing different RMFS layouts and estimating their performance. The model contains two independent components: a physical component and a control component. The nuclear module for physical component is the track module that forms all tracks and can be temporarily or permanently blocked to satisfy the requirements of both unidirectional and bidirectional path mode models. The main functions of the control component are routing, collision prediction, and collision avoidance. The physical and control components are independent but work together to construct and run a certain model according to the input parameters; thus, an RMFS model can be efficiently built by simply entering parameters. A series of experiments were conducted to evaluate the performance of the RMFS in different layouts with various numbers of AGVs in both the unidirectional and bidirectional path modes. The results indicated that in the same layout, the bidirectional path mode can reach the summit output with fewer AGVs. The experimental results also indicated that in a large-scale RMFS, vertically arranging the storage station on the block island and then horizontally positioning the block island can result in a higher output than other layouts. In addition, the experimental results indicated that the proposed model can quickly construct different RMFS layouts and efficiently determine the best scheme.

Experimental study on the influence of seismic subsidence of loess under bidirectional loading modes

Water content, dry density, void ratio, depth of soil layer, and seismic loading may all exert influence on the seismic subsidence of loess. Many scholars have carried out seismic subsidence tests of loess to simulate the stress on soil using unidirectional (axial) vibration instead of bidirectional vibration. We conduct seismic subsidence tests of loess using two different dynamic stress loading methods, unidirectional and bidirectional dynamic stress. In addition, the effects of different dynamic stress loading modes on the development of seismic subsidence of loess are compared for a case-study in northwestern China. The results show that (1) the increasing ratio of radial stress to axial stress has exerted significant influence on the seismic subsidence coefficient of loess under the loading mode of bidirectional dynamic stress (2) there is a critical ratio of radial stress to axial stress for seismic subsidence of loess, ranging from 0.6 to 0.8; when the ratio of radial load to axial load is greater than the critical value, the effect of bidirectional load on the development of seismic subsidence is more remarkable (3) when the ratio of radial load to axial load is smaller, the seismic subsidence of loess calculated by the existing unidirectional stress loading method is safe for engineering projects. However, if the value exceeds the safety ratio range it is dangerous to conduct safety evaluations using the seismic loess subsidence. The prediction value of seismic subsidence at engineering sites directly affects the later foundation treatment and the safety of the overlying structures. The seismic subsidence calculation and evaluation method in this study may provide a scientific basis for safety evaluations of loess sites in northwestern China.

A low‐complexity FS‐MPDPC with extended voltage set for grid‐connected converters

The conventional finite control set model predictive control (FS-MPC) for converter control is a well-studied area, but performance degradation due to the finite candidate vector set is still limiting its practical applications. Extending the voltage vector set using discrete space vector modulation has been proposed as a solution to overcome the limitations, but the brute-force search inherent to FS-MPC increases the computational complexity for a larger voltage set. This paper proposes a technique to alleviate the above issue by avoiding the brute-force search that is being executed in FS-MPC. The technique utilises the basics of direct-power-control theory to cut down the number of candidate voltage vectors applied in each cycle in the optimization problem. In this work, a design example having a voltage vector set of 37 elements is considered, and the proposed technique narrows down the search to eight optimal vectors. The proposed controller is specifically designed for active–reactive power control of a grid-connected converter that interlinks an energy storage system to the grid. The system is modelled in MATLAB Simulink environment and simulations are carried out to analyse the performance in all four active–reactive bidirectional power flow modes. Results validate the performance of the controller, both in steady-state and transient conditions. Further, the reduction in computational complexity due to the proposed algorithm is evaluated. It is observed that the number of computations was reduced approximately by 75% after applying the proposed algorithm for a system with a 37 voltage vector set.

Rediscovering Geula Cave: A Middle Paleolithic cave site in northern Mt. Carmel, Israel

This paper focuses on new findings from Middle Paleolithic Geula Cave, Israel, located in the northern part of Mt. Carmel. The cave, consists of several small chambers that are remnants of a larger cave system, initially excavated between 1958 and 1964. The occupation at the cave was ascribed to Middle Paleolithic modern humans.In 2016, a salvage excavation was conducted in areas of the cave that were not previously explored. Analyses of the new excavation revealed a consistency in lithic technology throughout the new excavation areas, with an emphasis on Levallois production using mainly bidirectional and centripetal core preparation modes. The faunal study identified intensive hyena and porcupine activities in small chambers, probably at the back part of the cave, while fractured bones in association with flint artifacts were found at what appears as the living area in the cave. Luminescence ages indicated that Geula Cave was occupied as early as 175 ka, but that the major occupation was from 120 to 100 ka.The major occupation at Geula chronologically overlaps with the Skhul and Qafzeh Caves thus reinforcing the notion that Homo sapiens dominated the southern Levant during early MIS 5. This study demonstrates the importance of reinvestigating and reevaluating past excavated prehistoric sites and their contents to enhance our understanding of the regional, cultural and biological history.

Deep Predictive Video Compression Using Mode-Selective Uni- and Bi-Directional Predictions Based on Multi-Frame Hypothesis

Recently, deep learning-based image compression has shown significant performance improvement in terms of coding efficiency and subjective quality. However, there has been relatively less effort on video compression based on deep neural networks. In this paper, we propose an end-to-end deep predictive video compression network, called DeepPVCnet, using mode-selective uni- and bi-directional predictions based on multi-frame hypothesis with a multi-scale structure and a temporal-context-adaptive entropy model. Our DeepPVCnet jointly compresses motion information and residual data that are generated from the multi-scale structure via the feature transformation layers. Recent deep learning-based video compression methods were proposed in a limited compression environment using only P-frame or B-frame. Learned from the lesson of the conventional video codecs, we firstly incorporate a mode-selective framework into our DeepPVCnet with uni- and bi-directional predictive modes in a rate-distortion minimization sense. Also, we propose a temporal-context-adaptive entropy model that utilizes the temporal context information of the reference frames for the current frame coding. The autoregressive entropy models for CNN-based image and video compression is difficult to compute with parallel processing. On the other hand, our temporal-context-adaptive entropy model utilizes temporally coherent context from the reference frames, so that the context information can be computed in parallel, which is computationally and architecturally advantageous. Extensive experiments show that our DeepPVCnet outperforms AVC/H.264, HEVC/H.265 and state-of-the-art methods in an MS-SSIM perspective.

Bidirectional Operation Scheme of Grid-Tied Zeta Inverter for Energy Storage Systems

The zeta inverter has been used for single-phase grid-tied applications. For its use of energy storage systems, this paper proposes the bidirectional operation scheme of the grid-tied zeta inverter. A shoot-through switching state is introduced, providing reliable bidirectional operation modes. A shoot-through duty cycle is utilized for the bidirectional grid current control of the inverter. The grid current is bidirectionally controlled by the shoot-through duty cycle, which enables the inverter to operate with seamless change of operation modes. Over the state-of-the art techniques using flyback and Cuk inverter topologies, the grid-tied zeta inverter using the proposed operation scheme provides advantages of high efficiency, low cost, and high reliability. The operation principle is presented by describing the operation mode and control method for the grid-tied zeta inverter. A 500 W prototype has been built and tested to verify its operation principle.

Bidirectional LCLL Resonant Converter With Wide Output Voltage Range

A new bidirectional LCLL-type resonant dc-dc converter (LCLL-BDC) is proposed in this article, which features a wide output voltage range for both ports, thus achieving zero-voltage switching (ZVS) at the input side and zero-current switching (ZCS) at the output side. The snubberless converter is similar to the type-11 LLC-type resonant converter, with the exception of an additional inductor. The auxiliary inductor allows for the converter to achieve a wide voltage range power transfer, thus addressing the inability of the LLC-type converter to be boosted in the reverse mode. The equivalent model and the steady-state operation are presented in this article. Moreover, the design methodology for the resonant network was derived for the LCLL-BDC. A 1-kW prototype, which interfaces two batteries of different energy systems, was developed to verify the validity and applicability of the proposed converter. The input and output voltage range was found to be 80-120 V, and the highest efficiencies for the bidirectional operational modes exceeded 96%.

Unidirectional and Bidirectional Optimistic Modes IP Header Compression for Real-Time Video Streaming

Communication over Internet Protocol (IP) networks, has become crucial component of day everyday activities. They are utilized over the Internet to support a wide range of services. The flexibility of this kind of transmission relies on the IP User Datagram Protocol (UDP), IP/UDP/Real-time Transport Protocol (RTP) and IP/Transmission Control Protocol (TCP). Unfortunately, the weight of encapsulated protocol headers affects the transmission efficiency. This research aims at improving a technique that reduce the packets header size by compression. Performance analysis of the enhanced efficient techniques in both unidirectional and bidirectional optimistic modes applied to real-time video streaming traffic for UDP/IP and HTTP/TCP flows over free error channel has been conducted. The finding shows that the header compression ratio in each case is good and better than the previous studies. The technique achieved a reduction up to 90% for RTP/UDP/IP, 89% for UDP /IP and 77.5 to 86.5 % for TCP/IP profile. This research contribution is restricted to compression gain and saving for 0 × 0000, 0 × 0001, 0 × 0002 and 0 × 0006 profiles in the unidirectional and bidirectional optimistic modes.

Anomalous Dynamics of in Vivo Cargo Delivery by Motor Protein Multiplexes.

Vesicle transport conducted by motor protein multiplexes (MPMs), which is ubiquitous among eukaryotes, shows anomalous and stochastic dynamics qualitatively different from the dynamics of thermal motion and artificial active matter; the relationship between in vivo vesicle-delivery dynamics and the underlying physicochemical processes is not yet quantitatively understood. Addressing this issue, we perform accurate tracking of individual vesicles, containing upconverting nanoparticles, transported by kinesin-dynein-multiplexes along axonal microtubules. The mean-square-displacement of vesicles along the microtubule exhibits unusual dynamic phase transitions that are seemingly inconsistent with the scaling behavior of the mean-first-passage time over the travel length. These paradoxical results and the vesicle displacement distribution are quantitatively explained and predicted by a multimode MPM model, developed in the current work, where ATP-hydrolysis-coupled motion of MPM has both unidirectional and bidirectional modes.

A Bidirectional CDT-LC Resonant DC–DC Converter With a Wide Voltage Range

A novel high conversion ratio bidirectional C-dual transformers-LC (CDT-LC) resonant dc–dc converter is proposed in this paper. Based on the traditional LLC, an auxiliary transformer and an extra resonant capacitance are employed in the CDT-LC structure. It not only harvests high efficiency, but exhibits a good voltage gain feature. Especially for the case of light load, CDT-LC still harvests a high efficiency, compared with traditional converters. Also, it can achieve a fast gain reduction when the switching frequency is higher than resonant frequency. In this paper, the operating principles of the converter are analyzed in both bidirectional operation modes. In addition, its dual-transformers structure feature and voltage gain characteristics are discussed in details. Furthermore, the parameter design method is provided. Moreover, the loss breakdown for the converter is given in details. Finally, a 2.5-kW prototype is established to verify the performance of the CDT-LC converter, and its maximum efficiency reaches 97%.

Topological insulators in longitudinally driven waveguides: Lieb and kagome lattices

Topological insulators are studied via tight-binding approximations of longitudinally driven photonic lattices with three lattice sites per unit cell. Two cases are considered in detail: Lieb and Kagome lattices. The lattice is decomposed into three sublattices each of which are allowed move independently of one another. Emphasis is placed on periodic driving induced by laser-etched helical coils along the direction of propagation. The linear Floquet bands are constructed for various inter-sublattice rotation patterns such as: different radii, different frequency, phase offset and quasi one-dimensional motion. Depending on the nature of the band structure, bulk spectral bands with nonzero Chern number are found to support topologically protected edge states which can move unidirectionally. In this case, the modes move scatter-free around defects due to underlying topological protection. Intriguing mode dynamics are found including bi-directional topological modes and bulk-edge leakage i.e. excitation of bulk modes at a defect for edge modes with dispersion frequencies nearby the bulk bands. Finally, certain nonlinear edge modes are also found to propagate unidirectionally and scatter-free around lattice defects.