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The security of Internet of Things (IoT) systems has consistently been a challenge, particularly in the context of critical infrastructure. One particular approach not yet employed in this domain is the unidirectional communication paradigm. This survey presents an analysis of the most prevalent unidirectional communication solutions, namely, data diodes, network pumps, unidirectional gateways, and unidirectional protocols. The objective of the survey is to present an analysis of the unidirectional communication methods that meet the requirements of IoT security. These methods are classified according to their implementation and operational mode. The survey analyzes the unidirectional communication solutions based on their performance, the level of security offered, the cost-effectiveness, and their cost of implementation. Additionally, it includes an analysis of the existing off-the-shelf unidirectional communication implementations found in the industry. Furthermore, it identifies some of the most important current issues and development directions.

Solar vapor generation technology is promising in seawater desalination, sewage purification, and other fields. However, wide application of this technology is still largely confined due to its high cost and difficulties for scalable production. In this study, an ever‐floating solar evaporator is fabricated by coating multiwall carbon nanotubes on a bicomponent nonwoven composed of polypropylene/polyethylene core–sheath fibers. This all‐fiber structure is highly porous and ultralight, with large specific area (for efficient water evaporation), interconnected channels (for easy vapor escape), and low thermal conductivity (to avoid heat loss). The unique unidirectional water‐transfer behavior of the nonwoven enables it to spontaneously pump an adjustable amount of water for interfacial solar heating and a delicate balance between water supply and loss may accelerate the evaporation speed of water. These distinct benefits endow the solar evaporator with excellent evaporation rates of 1.44 kg m–2 h–1 under the simulated irradiation of 1 sun and 12.81 kg m–2 d–1 under natural sunlight. Moreover, the evaporator can be fabricated by using low‐cost materials and industrialized methods (overall cost ≈2.4 USD m−2), making one believe its practical significance for commercial solar steam evaporation. An ever‐floating and durable solar evaporator is fabricated by coating multiwall carbon nanotubes on an unidirectional water‐transfer nonwoven composed of low‐cost poly(propylene)/polyethylene core–sheath fibers. The evaporator is capable of self‐pumping water. The balance between water supply and evaporation and the using of industrialized method help promote the applization of interfacial solar water evaporation.

The article describes the measurement of unidirectional pose accuracy and repeatability of a collaborative robot. The objective of the measurements is to investigate and evaluate unidirectional accuracy of the six-axis collaborative robot UR5 of the company Universal Robots. The measurement methodology was based on outlining an imaginary ISO cube placed in the robot’s workspace, in which the robot’s tool centre point (TCP) attained five measurement points in thirty measurement cycles. A video camera and six linear incremental sensors with six evaluation units were used for the measurement. The measured values are presented and applied according to the ISO 9283 standard. On the basis of the measurement, we verified technical specifications of unidirectional pose accuracy and repeatability of the robotic arm UR5 specified by its producer.

Carbon fiber-reinforced polymer (CFRP) composites have excellent mechanical properties and electromagnetic interference (EMI) shielding performance. Recently, their EMI shielding performance has also attracted great attention in many industrial fields to resolve electromagnetic pollution. The present paper mainly investigated the EMI shielding anisotropy of CFRP materials using a specified set-up of free-space measurement. The electrical conductivity of unidirectional CFRP composites was identified to vary with the fiber orientation angles, and the formula was proposed to predict the results consistent with the experimental. The obvious EMI shielding anisotropy of unidirectional CFRP composites was clarified by free-space measurement. The theoretical formula can predict the EMI shielding value at different carbon fiber orientation angles, and the predicted results were highly consistent with the experimental results. A comparison of the free-space measurement and the coaxial transmission line method was also conducted, which indicated that special attention should be paid to the influence of the anisotropy of CFRP composites on the shielding results. With those results, the mechanism of EMI shielding anisotropy of CFRP composites is clarified, which will provide an effective design of EMI shielding products with a designable shielding direction and frequency.

The objective of this research was to examine the bamboo fiber preforming procedures and the effects of preforming on the mechanical properties. The bamboo fibers were bent to an angular shape by using mold compression. Different moisture contents were applied to the bamboo fibers before bending. Next, tensile tests were conducted on the preformed bent fibers to investigate the strength degradation caused by fiber damage during the forming process. Additionally, the vacuum preforming method, limited to a pressure of 1 atm, was used for bamboo fiber bending preforming. Different fillet radii of the angled shapes were used in the experiments to investigate the impact of the angle curvature at the bending points on the strength of the bent bamboo fibers. Unidirectional bamboo fiber mats were manually woven using polyester fiber lines and preformed with a closed mold. The fabrication of the unidirectional bamboo fiber/epoxy resin composites was conducted by vacuum-assisted resin transfer molding (VARTM). In this study, valuable insights into the design of the bamboo fiber preforming and composite manufacturing processes are provided, and our results can be used to contribute to the progress and utilization of the bamboo fibers in composite materials.

Time-reversal symmetry for elastic wave propagation breaks down in a resonant mass-in-mass lattice whose inner-stiffness is weakly modulated in space and in time in a wave-like fashion. Specifically, one-way wave transmission, conversion and amplification as well as unidirectional wave blocking are demonstrated analytically through an asymptotic analysis based on coupled mode theory and numerically thanks to a series of simulations in harmonic and transient regimes. High-amplitude modulations are then explored in the homogenization limit where a non-standard effective mass operator is recovered and shown to take negative values over unusually large frequency bands. These modulated metamaterials, which exhibit either non-reciprocal behaviours or non-standard effective mass operators, offer promise for applications in the field of elastic wave control in general and in one-way conversion/amplification in particular.

This paper focuses on the transverse tensile and compressive mechanical properties of T800-grade unidirectional (UD) carbon fiber-reinforced polymers (CFRPs). Firstly, transverse tensile and compressive tests were conducted on UD composite laminates, yielding corresponding stress–strain curves. The results indicated that, for tension, the transverse tensile modulus, strength, and failure strain were 8.7 GPa, 64 MPa, and 0.74%, respectively, whereas for compression, these values were 8.4 GPa, 197.1 MPa, and 3.43%, respectively. The experimental curves indicated brittle failure under tensile loadings and significant plastic failure characteristics under compressive loading for the T800-grade composite. Subsequently, fractography experiments were performed to observe the fracture morphologies, revealing that tensile fractures were through-thickness cracks perpendicular to the loading direction, while compressive fractures were at a 52° angle to the loading direction. Finally, a micromechanical finite element method (FEM) was employed to simulate the tensile and compressive failure processes of the unidirectional composite, and the tensile and compressive properties were predicted. The simulation results showed that under both tensile and compressive loadings, interfacial elements failed first, causing stress concentration and damage to nearby resin elements. The damaged resin and interfacial elements expanded and connected, leading to ultimate failure. The predicted tensile stress–strain curve exhibited linear characteristics consistent with the experimental results in most regions but showed more pronounced nonlinearity before ultimate failure. The predicted compressive stress–strain curve aligned well with the experimental results in terms of nonlinearity. The predicted elastic modulus, failure strengths, and failure strains were in good agreement with the experimental results, with differences of 1.1% (tension modulus), 3.2% (tension strength), and 13.5% (tension failure strain), and 3.6% (compression modulus), −8.5% (compression strength), and −3.8% (compression failure strain). The final failure morphologies were in good accordance with the fractography experimental observations.

Recently, the demand for reinforced plastics from natural, sustainable, biodegradable, and environmentally friendly fibers has been rising worldwide. However, the main shortcoming of natural fibers reinforced plastics is the poor compatibility between reinforcing fibers and the matrix. Hence, it is necessary to form a strong attachment of the fibers to the matrix to obtain the optimum performance. In this work, chemical treatments (acid pretreatment, alkali pretreatment, and scouring) were employed on jute fibers to modify them. The mechanical properties, surface morphology, and Fourier transform infrared spectra of treated and untreated jute fibers were analyzed to understand the influence of chemical modifications on the fiber. Then, jute fiber/epoxy composites with a unidirectional jute fiber organization were prepared. Basic properties of the composites such as the void fraction, tensile strength, initial modulus, and elongation at break were studied. The better interfacial adhesion of treated fibers was shown by scanning electron microscope (SEM) images of fractured coupons. Hence, the chemical treatment of jute fiber has a significant impact on the formation of voids in the composites as well as the mechanical properties of jute fiber composites.

In this paper, we propose a new approach for numerically simulating the growth of cracks in unidirectional composite materials, termed extended isogeometric analysis, evaluating the maximum stress intensity factor and T-stress. To validate our approach, we used a small anisotropic plate with two edge cracks, beginning with formulating the governing equations based on the energy integral method, Stroh’s Formula, and the Elastic Law describing the behaviour of anisotropic materials, while considering boundary conditions and initial states. A MATLAB code was developed to solve these equations numerically and to post-process the tensile stress and the stress intensity factor (SIF) in the first mode. The results for the SIF closely match those obtained using the extended finite element method (X-FEM), with a discrepancy of only 0.0021 Pa·m0.5. This finding underscores the credibility of our approach. The extended finite element method has demonstrated robustness in predicting crack propagation in composite materials in recent years, leading to its adoption by several widely used software packages in various industries.

Ultrasonic welding of fibre-reinforced thermoplastics is a joining technology with high potential for short welding times and low energy consumption. While the majority of the current studies on continuous ultrasonic welding have so far focused on woven reinforcements, unidirectional materials are preferred for highly loaded aerospace components due to their better mechanical performance. Therefore, this paper investigates the influence and interdependence of the welding speed, amplitude, and energy director thickness on the weld quality of adherends made of unidirectional composites. The quality of the welded joints is assessed by a single-lap shear strength and fracture surface analysis complemented by the microscopic analysis of cross-sections and comparison to a co-consolidated reference. The results showed that the welding process is highly affected by changing welding speeds for a given amplitude. Furthermore, while lower amplitudes lead to significant scatter in the welding quality, higher amplitudes result in increased heating rates and a fully molten energy director even for high welding speeds. Nevertheless, insufficient consolidation at high welding speeds results in porosity in the weld line. Finally, it was observed that thicker, and therefore more compliant, energy directors lead to more uniform melting of the energy director and less deviation in the weld quality for a wider range of welding speeds.