High-performance Design Research Articles

Negative temperature coefficient of ZnO microwires for cryogenic temperature sensing

Negative temperature coefficient (NTC) thermistors are expected to be developed at cryogenic temperature sensing. In this paper, a kind of cryogenic thermistor was developed based on NTC response of single crystal ZnO microwires (MWs). The current–voltage (I–V) characterization demonstrated a NTC response, which was temperature dependence of resistance that decreased with increasing temperature. A sensitive NTC response, especially at the cryogenic temperature range, was observed. The defects in ZnO MWs play an important role in NTC response; therefore, we studied the origin of NTC effect associated with defects to improve the recognition of relationship between defects and the NTC effect and further optimize the temperature sensor design for high performance. Annealing at 800 °C in air was undertaken to make a significant influence on the concentration of defects in as-grown sample, and a series of temperature-dependent features were investigated by photoluminescence, Raman, XPS, and EPR measurements. The results indicated the zinc interstitials to be effective donors for sensitive NTC effect at the cryogenic region. This study provides insight into the ZnO NTC effect and sensitive cryogenic sensing technology.

Computational discovery of ultra-strong, stable, and lightweight refractory multi-principal element alloys. Part II: comprehensive ternary design and validation

Here the discovery of refractory multi-principal element alloys (MPEAs) with high-temperature strength and stability is pursued within a constrained and application-relevant design space. A comprehensive approach is developed and applied to explore all 165 ternary systems in the Al-Ce-Fe-Hf-Mo-Nb-Ta-Ti-V-W-Zr family. A subset of ternary systems that contain large areas in composition–temperature space with high strength and robust BCC phase stability is found. Twelve sets of high-performing alloys are identified, each set optimized for one combination of phase constraint, optimization target, and temperature range. Preliminary mechanical tests support the viability of the method. This work highlights the importance of considering phase stability, exploring non-equiatomic regions of composition space, and applying application-relevant constraints. Parts I and II provide three down-selection techniques for identifying high-performing BCC refractory MPEAs, design guidelines, and many candidates predicted to have BCC phase stability and strengths 2–3 times higher than any reported to date.

Accelerated Fe(II) regeneration on Fe-doped oxidized carbon nanotube enabling highly-efficient electro-Fenton process for pollutants removal

Heterogeneous electro-Fenton (e-Fenton) is considered a prospective technology for persistent organic contaminants removal that relies on the strongly oxidizing •OH. However, the efficiency of e-Fenton is still low as the sluggish Fe(II) regeneration caused by the difficulty modulating the electronic structure of Fe(III) center. Herein, the Fe-doped oxidized carbon nanotube catalysts (OCNT-Fe) is prepared to accelerate Fe(II) regeneration by introducing electronegative oxygen-containing groups and inducing local charge distribution of Fe(III) center. The OCNT-1Fe exhibits an excellent e-Fenton performance for phenol degradation with a kinetic rate of 0.11 min−1 at pH 6.5, which is the highest among reported state-of-the-art e-Fenton catalysts. Moreover, OCNT-1Fe catalyst is demonstrated to be more energy efficient in coking wastewater treatment with an energy consumption of 6.5 kW h kgCOD−1 than other e-Fenton systems of 9.2–29.7 kW h kgCOD−1. This work offers a new perspective on the high-performance e-Fenton catalysts design by rationally modulating the electronic structure for organic pollutants removal.

Cracking behavior of newly-developed high strength eutectic high entropy alloy matrix composites manufactured by laser powder bed fusion

A novel AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) composite doped with SiC particles was designed and fabricated by laser powder bed fusion (LPBF). Its microstructure characteristic, tensile properties, and metallurgical defects, with an emphasis on cracking behavior, have been investigated. The results showed that the addition of SiC particles into the AlCoCrFeNi2.1 matrix enabled the development of a {100} texture and highly elongated columnar grains, which were the main contributors to mechanical behavior anisotropy. The ultimate tensile strength of 1466 ± 26 MPa and elongation of 9% ± 3% achieved in the as-deposited EHEA composite surpassed those of advanced metal alloys subjected to additive manufacturing processes. Unfortunately, severe horizontal and longitudinal cracks, as well as a few micro-cracks were observed in the as-deposited bulk samples. Micro-cracks were verified to be associated with the aggregation of carbon and oxide particles. They formed in the final stage of solidification owing to insufficient liquid feeding ability and solidification contraction. The formation of macroscopic cracking was induced by the tensile stress accumulations at sample edges, and the stress concentration areas where microcracks and pores were located were the predominant propagation location. This work provides guidelines for defect control in SiC-reinforced EHEA, assisting in the high-performance design and integrated manufacturing of EHEA composite components.

Improved compressive and flexural performances of functionally graded graphene nanoplatelet reinforced cement composites: Experiments and modelling

Graphene reinforced cement composites (GRCCs) have demonstrated competitive mechanical and physical properties. Instead of uniform distribution, functionally graded distribution of the graphene fillers can effectively utilize the advantages of each constituents with improved performances and reduced cost. This paper conducts experiments and modelling on mechanical properties of functionally graded graphene nanoplatelet reinforced cement composites (FG-GNPRCCs). Samples with three functionally graded distributions (X, A and O types) together with uniform distribution (H-type) are prepared and tested. Compared to uniform distribution, the flexural strength and maximum compressive load of functionally graded distributions are significantly increased. For example, the flexural strength of X-5 pattern is increased by 24.36% and the maximum compressive load of O-3 pattern is increased by 13.42%. Based on effective medium theory (EMT) and Mori-Tanaka (MT) model, a parallel triple-inclusion model is developed to predict the Young’s modulus of GNPRCCs. The effects of GNP dispersion, agglomeration and pores on the mechanical properties of the composites are comprehensively studied. Moreover, the cracking load for FG-GNPRCCs is evaluated by combining experiments and modelling, which can provide reference for the design and optimization of high-performance of cement composites and structures.

Design and analysis of compact flower-shaped wideband slotted monopole antenna for RFID reader applications

This article introduces the design and analysis of a compact, high gain, and wide bandwidth flower-shaped slotted monopole antenna for RFID reader antenna applications. The proposed antenna comprises a flower-shaped radiator with six arc-shaped slots and a partial ground plane. The measurement results indicate a wide operating band in the frequency range of 2.4 GHz–7.6 GHz. The proposed antenna is designed to operate at 5.8 GHz ISM band for RFID reader applications with a peak measured gain of 3.9 dBi. The structure has an overall dimension of 0.78λ× 0.58λ× 0.03λ at an operating frequency of 5.8 GHz and is found compact in comparison to some related designs. The monopole antenna shows an omnidirectional radiation pattern in the operating band and indicates a maximum realized gain value of 4.2 dBi. The study provides a detailed mathematical analysis of the operating principle with surface current distribution plots. The design indicates a reading range of 2.56 cm at 5.8 GHz and the satisfaction of the propagation-test makes the compact, wideband, and high-performance design suitable for different short-range RFID reader applications.

High-Performance Surface Electromyography Armband Design for Gesture Recognition.

Wearable surface electromyography (sEMG) signal-acquisition devices have considerable potential for medical applications. Signals obtained from sEMG armbands can be used to identify a person's intentions using machine learning. However, the performance and recognition capabilities of commercially available sEMG armbands are generally limited. This paper presents the design of a wireless high-performance sEMG armband (hereinafter referred to as the α Armband), which has 16 channels and a 16-bit analog-to-digital converter and can reach 2000 samples per second per channel (adjustable) with a bandwidth of 0.1-20 kHz (adjustable). The α Armband can configure parameters and interact with sEMG data through low-power Bluetooth. We collected sEMG data from the forearms of 30 subjects using the α Armband and extracted three different image samples from the time-frequency domain for training and testing convolutional neural networks. The average recognition accuracy for 10 hand gestures was as high as 98.6%, indicating that the α Armband is highly practical and robust, with excellent development potential.

On the photoresponse regulations by deep-level traps in CsPbBr3 single crystal photodetectors

The all-inorganic halide perovskite CsPbBr3 has attracted significant attention owing to its excellent opto-electronic properties. However, deep-level traps within the material are significant for the properties of CsPbBr3 based opto-electronic devices. In this study, the effects of deep-level traps on the photoresponse characteristics of CsPbBr3 photodetectors were thoroughly studied. By tailoring the illumination combinations where 532 nm light emitting diode (LED) illumination corresponds to the band-to-band excitation of photo-carriers and 648 nm LED illumination corresponds to sub-band excitation by the deep-level traps, it is proven that the device photoresponse performance is improved by the existence of deep-level traps. The photoresponsivity was enhanced by ∼63.64% (from 0.44 to 0.72 A W−1) under 3.18 μW cm−2 532 nm LED illumination. The rise/fall time was reduced by 21.95% (from 20.5 to 16.0 ms)/25.47% (from 21.2 to 15.8 ms). The underlying physical mechanisms of deep level trap-induced modulations on the photoresponse performance of the CsPbBr3 photodetector were revealed and discussed. By further systematic simulation of the effects of material properties on the photoresponse regulation, it was concluded that a shorter carrier lifetime, higher carrier mobility, higher trap concentration, and deeper trap level could improve the photoresponse of the CsPbBr3 photodetector. This study aims to clarify the physical relation between material properties and device performance and provide guidance for high-performance CsPbBr3 photodetector design.

On the strain stiffening and nanofiber orientation of physically crosslinked nanocellulose hydrogels

Nanocellulose hydrogels that consist of physically crosslinked nanofibrous networks with large amounts of interstitial water have many potential applications as structural materials in biomedical engineering. Quantifying the relationship between micro/nanostructures and their mechanical responses can provide some guidelines for the high-performance mechanical design of counterparts. To this end, we develop a modified physically based constitutive model for examining the effects of the micro/nanostructures of a nanofibrous network on the strain stiffening behaviors of nanocellulose hydrogels under stretching. In addition to the configurational entropy of cellulose nanofiber and mixing energy of water molecule, this theoretical model is particularly concerned with the contribution of the potential energy of hydrogen bond in a thermodynamics framework. Increasing the physical crosslinks between cellulose nanofibers or decreasing the content of water molecules in a certain range can enhance the strain stiffening behaviors of nanocellulose hydrogels. Relatively long and thin cellulose nanofibers have increased tensile strengths. The theoretical predictions are in good agreement with the relevant experimental results. We propose a fiber orientation model for quantifying the relationship between the nanofiber orientation degree and mechanical stretching. This model provides a theoretical foundation for fabricating anisotropic nanofibrous hydrogels via cold drawing.

Highly enhanced direct catalytic oxidation of cyclohexane to adipic acid with molecular oxygen: Dynamic collaboration between zeolite channel micro-environment and Au clusters

Adipic acid is a valuable chemical used to product Nylon-66, and one of the greenest ways to synthesize it is catalyzing the oxidation of cyclohexane by molecular oxygen in the absence of any other chemicals. However, it is challenging to convert cyclohexane effectively with high selectivity to adipic acid using the available catalysts. In response to the dilemma of achieving satisfactory conversion and selectivity at the same time, a remarkable Au@NaX catalyst is proposed using an improved in-situ crystallization method that exhibits Au clusters surrounded by X-zeolite channels. A 29.5% conversion of cyclohexane and an 85.6% selectivity to adipic acid can be obtained in a one-pot oxidation of cyclohexane at 140 °C, 20 bar O2, far exceeding most published results. Since determined by detailed characterizations and DFT calculations, the effective dynamic collaboration between Au clusters and zeolite inner micro-environment is the decisive role for superior catalytic performance. Specifically, the surrounding zeolite channel encourages the adsorption and activation of cyclohexane over the confined Au clusters, resulting in an unprecedented activity. The continuous oxidation of cyclohexanol and cyclohexanone to adipic acid is also vulnerable on the enclosed Au clusters, and the subsequent adipic acid can be further stabilized as a result of the strong interaction of –COOH with Na± in zeolite channels surrounding enclosed Au clusters. It prevents AA from poisoning active sites and generates a higher selectivity for the desired adipic acid. Our study highlighted the critical significance of the dynamic interaction between metal clusters and the zeolite channel microenvironment. It would shed light on the further high-performance catalysts designs for selective oxidation.

Deciphering the role of A-site ions of AZrO3-type dopants in (K, Na)NbO3 ceramics

As one of the most important lead-free piezoelectric candidates, potassium sodium niobate [(K, Na)NbO3, KNN] has gained popularity due to its attractive functional properties, which are much improved by chemical modifications. However, there still remains an insufficient understanding of how these dopants influence the structure and performance of KNN ceramics. Herein, we comparatively studied a series of changes triggered by introducing (Bi0.5Na0.5)ZrO3, BaZrO3, and PbZrO3 into the KNN matrix. The analysis highlights their different roles in modulating the orthorhombic-tetragonal phase transition temperature (TO-T) by considering discrepancies in the electronegativity and radius among Bi3+, Ba2+, and Pb2+ ions. The synergistic effects of the large electronegativity and the small radius of the Bi3+ ion are the key to regulating TO-T, which is relatively unaffected by Pb2+ and Ba2+ ions. Based on experimental results and first-principles calculations, a multi-scale model is proposed to summary the general law of how the electronegativity and radius of the A-site ion in AZrO3-type dopants synergistically affect the phase structure, ferroelectric domains, and electrical properties of KNN ceramics. Therefore, this work helps understand the role of chemical dopants in the structure and performance of KNN ceramics and promote the future composition design for high performance.

Triggering High Capacity and Superior Reversibility of Manganese Oxides Cathode via Magnesium Modulation for Zn//MnO2 Batteries.

Aqueous zinc-ion batteries (ZIBs) have attracted extensive attention in recent years because of its high volumetric energy density, the abundance of zinc resources, and safety. However, ZIBs still suffer from poor reversibility and sluggish kinetics derived from the unstable cathodic structure and the strong electrostatic interactions between bivalent Zn2+ and cathodes. Herein, magnesium doping into layered manganese dioxide (Mg-MnO2 ) via a simple hydrothermal method as cathode materials for ZIBs is proposed. The interconnected nanoflakes of Mg-MnO2 possess a larger specific surface area compared to pristine δ-MnO2 , providing more electroactive sites and boosting the capacity of batteries. The ion diffusion coefficients of Mg-MnO2 can be enhanced due to the improved electrical conductivity by doped cations and oxygen vacancies in MnO2 lattices. The assembled Zn//Mg-MnO2 battery delivers a high specific capacity of 370mAhg-1 at a current density of 0.6Ag-1 . Furthermore, the reaction mechanism confirms that Zn2+ insertion occurred after a few cycles of activation reactions. Most important, the reversible redox reaction between Zn2+ and MnOOH is found after several charge-discharge processes, promoting capacity and stability. It believes that this systematic research enlightens the design of high-performance of ZIBs and facilitates the practical application of Zn//MnO2 batteries.

Design of outdoor LED ground display system in major scenes

AbstractLED ground display system, as an important outdoor display system in major scenes such as some international performance events or interactive display system, has brought spectacular and gorgeous artistic effect to the audience. According to the customized design and the effort we made, this world class super large‐scale outdoor display system has realized successfully at the beginning of the year 2022 in Beijing. This LED ground display system has many innovation in product design, control system design, and field implementation especially for the need of super high reliability, high environmental suitability, convenient installability, 4,500 m2 super large display area, very complex system integration, and long service time. This paper indicates the detail introduction of the ground display system, specially focuses on the high reliability product design, high display performance design, system reliability design, field implementation, and actual verification results of the semi‐circular display area on both sides of the stage. Meanwhile, some simulation technologies are used in this design related to optics, mechanics, and so on. Furthermore, under the special application environment, to ensure the reliability of the outdoor display system, a dynamic screen preheating method according to temperature change is proposed and proved effectively by practice.

Origami-inspired sandwich structures under low-to-high velocity impacts: A numerical simulation approach

In this study, the ballistic impact performance of sandwich structures with Miura-origami pattern inspired core (MPIC) panels subjected to low-to-high velocity impacts is studied. Sandwich panels with MPIC structure were modeled and finite element analysis was performed using commercially available software LS-DYNA to evaluate their specific energy absorption (SEA) and load-bearing capabilities. A cylindrical indenter (diameter = 10 mm and height = 15 mm) with material property of mild Steel (ρ = 7800 kg/m3) was impacted at three different velocities, i.e., 10 m/s (0.46 J), 50 m/s (11.49 J), 100 m/s (45.95 J) under predefined impact conditions. The obtained results were compared with that of a monolithic solid plate under identical loading conditions and geometrical dimensions. The proposed MPIC design was 93% lighter in weight than the monolithic solid plate. On comparison of stress contours, the monolithic solid plate exhibited regions of high-stress concentration at the impact zone. However, for the MPIC sandwich panel, the stress contour was found to be uniform. For an impact velocity of 100 m/s, the SEA of the MPIC sandwich panel was found to be 1142.6 J/kg, while for the monolithic solid plate, it was obtained as 57.17 J/kg. Eventhough complete penetration of the MPIC sandwich panel occurred for an impact velocity of 100 m/s, the SEA of the MPIC sandwich panels were found to be significantly higher than that of the monolithic solid plate. Since MPIC sandwich panels exhibit enhanced energy dissipation characteristics, they can be an alternative to the conventional monolithic solid plate as light-weight high performance designs for specific applications.

Hole processing in parts made of titanium alloys

The features of machining of titanium alloys by cutting are considered. Measures are developed to improve the machinability of these alloys. It is shown that a decrease in the vibration amplitudes of the machine—fixture—tool—part (MFTP) technological system during cutting can significantly increase the machinability of such materials. Methods are given to increase the vibration resistance of the MFTP system, the accuracy of processing and tool life when threading with taps and drilling, namely: reducing the contact area of the tool with the workpiece in the cutting zone; increasing the strength and stiffness of the tool itself. It is indicated that the first method is the main one for increasing the tool life and the quality of hole processing. Taking this into account, patented high-performance designs of taps and attachments, drills are developed. The results of their tests are presented. Keywords: titanium alloys, machinability of titanium alloys, processing of holes, taps, drills for titanium machining. ragus05@mail.ru

AI 공격용 드론 개발 방향 및 시사점

The role of attack drones in the ongoing war between Ukraine and Russia is drawing worldwide attention. In order to prepare for changes in the defense security environment and rapid decline in military resources, the Ministry of National Defense announced the National Defense Innovation 4.0 Basic Plan in March 2023, and established the concept of joint operation by reflecting the operation of AI-based manned and unmanned complex systems and new concept weapon systems. did Drones are the most important force in building manned and unmanned complex systems, and the dronebot combat system will be the basis for promoting Defense Innovation 4.0. Drones are a system that can be operated for multiple purposes that change their use according to mission equipment, and it is key to have advanced technology that is suitable for the future battlefield environment and efficient. If the existing attack drone is an operating system in which combatants remotely control the ground control device while watching the ground control device, the future direction of the development of attack drones for the Korean military to apply to dronebots is an AI attack drone in which the drone detects the target by itself and directly strikes and self-destructs. will develop into In order to develop AI attack drones, not only the performance of the drone system, but also AI-based cutting-edge technology for object tracking technology, object identification technology and shape recognition technology of reconnaissance equipment (EO/IR), which is mission equipment, as well as attack ammunition or Small, high-performance warhead design technology, ultra-small fuze design technology, shock absorption and launch control device technology, etc. must be developed to mount the projectile. In addition, as the amount of image information acquired through mission equipment increases, high-speed data transmission technology development to improve the transmission rate between the aircraft and the ground control equipment in real time must be simultaneously developed. It is necessary to quickly overcome drone and AI technologies, which are currently very poor compared to advanced countries, and take the lead in developing intelligent AI attack drones with excellent autonomy based on Korea's excellent ICT technology. Therefore, this study aims to find out the technological trends of domestic and foreign attack drones and to consider the development plans and tasks of AI attack drones.

Modelling and Multi-Objective Optimisation of Finger Joints: Improving Flexural Performance and Minimising Wood Waste

The wood industry faces the dual requirements of improving the quality of timber products and minimising waste during the manufacturing process. The finger joint, which is an end-to-end joining method for timber boards, is one of the most important aspects of engineering wood products. This study presents a numerical and optimisation investigation of the effects of finger-joint design parameters on the flexural behaviour of finger-jointed timber beams. A numerical model based on advanced three-dimensional finite element analysis was developed to model the behaviour of finger-jointed beams. Using the validated finite element (FE) model and automated parameterisation, a parametric study was conducted to assess the impact of each design parameter of the finger joint, including finger length, tip thickness, and the number of finger joints. The results indicate that the number of fingers and finger length significantly influence the maximum load capacity, while the tip thickness has a marginal effect on performance. This study identifies a design threshold of five fingers and a 14 mm finger length for achieving efficient, high-performance finger-joint designs. In addition, the multi-objective modified firefly algorithm (MOMFA) was proposed to maximise the finger joint resistance while simultaneously minimising the material waste. The optimisation shows that there will be a significant amount of wood waste when using traditional single-objective optimisation that only focuses on structural performance. In contrast, the proposed method achieves comparable load capacity while significantly reducing waste (up to 53.31%) during the joining process. The automated finite element modelling framework and holistic optimisation developed in this study can be used to design and optimise engineering wood products for construction applications.

Optimizing FPGA-Based Convolutional Neural Network Performance

In deep learning, convolutional neural networks (CNNs) are a class of artificial neural networks (ANNs), most commonly applied to analyze visual imagery. They are also known as Shift-Invariant or Space-Invariant Artificial Neural Networks (SIANNs), based on the shared-weight architecture of the convolution kernels or filters that slide along input features and provide translation-equivariant responses known as feature maps. Recently, various architectures for CNN based on FPGA platform have been proposed because it has the advantages of high performance and fast development cycle. However, some key issues including how to optimize the performance of CNN layers with different structures, high-performance heterogeneous accelerator design, and how to reduce the neural network framework integration overhead need to be improved. To overcome and improve these problems, we propose dynamic cycle pipeline tiling, data layout optimization, and a pipelined software and hardware (SW–HW)-integrated architecture with flexibility and integration. Some benchmarks have been tested and implemented on the FPGA board for the proposed architecture. The proposed dynamic tiling and data layout transformation improved by 2.3 times in the performance. Moreover, with two-level pipelining, we achieve up to five times speedup and the proposed system is 3.8 times more energy-efficient than the GPU.

High-performance designs for fiber-pigtailed quantum-light sources based on quantum dots in electrically-controlled circular Bragg gratings.

We present a numerical investigation of directly fiber-coupled hybrid circular Bragg gratings (CBGs) featuring electrical control for operation in the application relevant wavelength regimes around 930 nm as well as the telecom O- and C-band. We use a surrogate model combined with a Bayesian optimization approach to perform numerical optimization of the device performance which takes into account robustness with respect to fabrication tolerances. The proposed high-performance designs combine hybrid CBGs with a dielectric planarization and a transparent contact material, enabling > 86% direct fiber coupling efficiency (> 93% efficiency into NA 0.8) while exhibiting Purcell factors > 20. Especially the proposed designs for the telecom range prove robust and can sustain expected fiber efficiencies of more than (82.2±4.1)-5.5+2.2% and expected average Purcell factors of up to (23.2±2.3)-3.0+3.2 assuming conservative fabrication accuracies. The wavelength of maximum Purcell enhancement proves to be the most affected performance parameter by the deviations. Finally, we show that electrical field strengths suitable for Stark-tuning of an embedded quantum dot can be reached in the identified designs. Our work provides blueprints for high-performance quantum light sources based on fiber-pigtailed and electrically-controlled quantum dot CBG devices for quantum information applications.

Design and In Situ Additive Manufacturing of Multifunctional Structures

Multifunctional structures (MFSs) integrate diverse functions to achieve superior properties. However, conventional design and manufacturing methods—which generally lack quality control and largely depend on complex equipment with multiple stations to achieve the integration of distinct materials and devices—are unable to satisfy the requirements of MFS applications in emerging industries such as aerospace engineering. Motivated by the concept of design for manufacturing, we adopt a layer regulation method with an established optimization model to design typical MFSs with load-bearing, electric, heat-conduction, and radiation-shielding functions. A high-temperature in situ additive manufacturing (AM) technology is developed to print various metallic wires or carbon fiber-reinforced high-melting-point polyetheretherketone (PEEK) composites. It is found that the MFS, despite its low mass, exceeds the stiffness of the PEEK substrate by 21.5%. The embedded electrics remain functional after the elastic deformation stage. Compared with those of the PEEK substrate, the equivalent thermal conductivity of the MFS beneath the central heat source area is enhanced by 568.0%, and the radiation shielding is improved by 27.9%. Moreover, a satellite prototype with diverse MFSs is rapidly constructed as an illustration. This work provides a systematic approach for high-performance design and advanced manufacturing, which exhibits considerable prospects for both the function expansion and performance enhancement of industrial equipment.