High Design Flexibility Research Articles

Hybrid-Layers Neural Network Architectures for Modeling the Self-Interference in Full-Duplex Systems

Full-duplex (FD) systems have been introduced to provide high data rates for beyond fifth-generation wireless networks through simultaneous transmission of information over the same frequency resources. However, the operation of FD systems is practically limited by self-interference (SI), and efficient SI cancelers are sought to make the FD systems realizable. Typically, polynomial-based cancelers are employed to mitigate the SI; nevertheless, they suffer from high complexity. This article proposes two novel hybrid-layers neural network (NN) architectures to cancel the SI with low complexity. The first architecture is referred to as hybrid-convolutional recurrent NN (HCRNN), whereas the second is termed as hybrid-convolutional recurrent dense NN (HCRDNN).In the HCRNN, a convolutional layer is employed to extract the input data features using a reduced network scale. Moreover, a recurrent layer is then applied to assist in learning the temporal behavior of the input signal from the localized feature map of the convolutional layer. In the HCRDNN, an additional dense layer is exploited to add another degree of freedom for adapting the NN settings in order to achieve the best compromise between the cancellation performance and computational complexity. The complexity analysis of the proposed NN architectures is provided, and the optimum settings for their training are selected. The simulation results demonstrate that the proposed HCRNN and HCRDNN-based cancelers attain the same cancellation of the polynomial and the state-of-the-art NN-based cancelers with an astounding computational complexity reduction. Furthermore, the proposed cancelers show high design flexibility for hardware implementation, depending on the system demands.

Recent Trends in Advanced Photoinitiators for Vat Photopolymerization 3D Printing.

3D printing has revolutionized the way of manufacturing with a huge impact on various fields, in particular biomedicine. Vat photopolymerization-based 3D printing techniques such as stereolithography (SLA) and digital light processing (DLP) attract considerable attention owing to their superior print resolution, relatively high speed, low cost, and flexibility in resin material design. As one key element of the SLA/DLP resin, photoinitiators or photoinitiating systems have experienced significant development in recent years, in parallel with the exploration of 3D printing (macro)monomers. The design of new photoinitiating systems cannot only offer faster 3D printing speed and enable low-energy visible light fabrication, but also can bring new functions to the 3D printed products and even generate new printing methods in combination with advanced optics. This review evaluates recent trends in the development and application of advanced photoinitiators and photoinitiating systems for vat photopolymerization 3D printing, with a wide range of small molecules, polymers, and nanoassemblies involved. Personal perspectives on the current limitations and future directions are eventually provided.

Development and fabrication of continuous carbon fiber reinforced thermoplastic porous composite structures with different infill patterns by using additive manufacturing

Additive manufacturing is a development of fabricating 3D parts layer by layer with complex geometries and utilized in numerous engineering structural applications. Fused deposition modeling technology provides higher design flexibility with aim of low cost and simplicity of material conversion to generate the composite parts. Previous studies have mainly focused on the manufacturing and characterization of continuous carbon fiber reinforced polymer composites (CCFRPCs) structure for fully dense and solid part structures and no study has been reported for porous CCFRPC parts. In this study, CCFRPCs porous structures were manufactured using FDM technology. The porous structures were fabricated with one perimeter shell by using two different types of infill patterns (grid and triangular) at three different infill densities levels (20%, 40%, and 60%). The reasons for developing such lightweight porous composite structures with continuous carbon fiber are the reduction of mass, efficient material utilization, energy consumption, and less waste generation. This study investigated the effects on tensile and flexural properties of composite specimens under uniaxial tensile loading and flexural loading, respectively. Fracture interface of the printed porous composites were examined and explored using optical microscope after performing mechanical tests. The experimental results demonstrated that infill pattern and density levels greatly affect the mechanical properties. The specimen printed using grid infill pattern with 60% infill density exhibited highest strength level in term of mechanical test and showed maximum tensile and flexural strength of 162.9 MPa and 127.24 MPa, respectively. While triangular infill pattern with 60% infill density level revealed the maximum tensile and flexural strength of 152.62 MPa and 117.53 MPa, respectively. Hence, from the results achieved in this study showed great potential and ability to replace fully dense and solid structure by the porous structure.

High-throughput optimization and fabrication of Bi2Te2.7Se0.3-based artificially tilted multilayer thermoelectric devices

Artificially tilted multilayer thermoelectric devices (ATMTDs) have attracted growing attention due to their ease in miniaturization and high flexibility in device design. However, most of these devices are inefficient due to the lack of effective strategy to optimize their material matching and geometrical configurations. Herein, a high-throughput optimization approach is employed to screen high-performance Bi2Te2.7Se0.3-based ATMTDs from a material genome database covering 230 kinds of candidates. 14 kinds of ATMTDs are found to have ZTzx,max values exceeding 0.3 and tilt angles greater than 15°. Bi0.1Sb1.9Te3/Bi2Te2.7Se0.3 ATMTD is screened out and fabricated because of its excellent transverse figure of merit, large tilt angle, and good interface compatibility. Consequently, transverse figure of merit over 0.3, thermal sensitivity greater than 0.11 mV·K−1, and power density up to 1.1 kW·m−2 are recorded in Bi0.1Sb1.9Te3/Bi2Te2.7Se0.3 ATMTD. This indicates that ATMTDs have great potential for application in the fields of temperature detection and power generation.

Deep learning modeling strategy for material science: from natural materials to metamaterials

Computational modeling is a crucial approach in material-related research for discovering new materials with superior properties. However, the high design flexibility in materials, especially in the realm of metamaterials where the sub-wavelength structure provides an additional degree of freedom in design, poses a formidable computational cost in various real-world applications. With the advent of big data, deep learning (DL) brings revolutionary breakthroughs in many conventional machine learning and pattern recognition tasks such as image classification. The accompanied data-driven modeling paradigm also provides transformative methodology shift in materials science, from trial-and-error routine to intelligent material discovery and analysis. This review systematically summarize the application of DL in material science, based on a model selection perspective for both natural materials and metamaterials. The review aims to uncover the logic behind data-model relation with emphasis on suitable data structures for different scenarios in the material study and the corresponding problem-solving DL model architectures.

Structural topology optimization and path planning for composites manufactured by fiber placement technologies

Fiber reinforced polymers (FRP) suit superbly for lightweight applications. Enormous lightweight potential is launched in combination with fiber placement technologies and topology optimization – both providing high design flexibility and high material efficiency. But FRP show specific material characteristics, such as mechanical anisotropy. Fiber placement processes are also limited to certain designs. Both aspects must be taken into account during topology optimization. Furthermore, a strategy is required to transfer the topology optimization results into fiber placement paths. This paper presents a corresponding workflow that combines existing as well as newly developed methods: The anisotropic material properties are factored by the topology optimization algorithm, which simultaneously optimizes the parts shape and local fiber orientation. Puck’s failure criteria for FRP is evaluated throughout topology optimization for reducing weight while maintaining the parts ability to withstand the specified loads. A dilate sensitivity filter restricts the minimum feature width of the final structure to account for fiber bundle widths, and avoids non-manufacturable undercuts transverse to the placement plane. Finally, a methodology consisting of clustering and a streamline algorithm is utilized to generate manufacturing tolerant fiber placement paths.

RF Rectifiers With Wide Incident Angle of Incoming Waves Based on Rat-Race Couplers

This article presents a radio frequency (RF) rectifier with a wide incident angle of incoming waves, based on a rat-race coupler (RRC). Two identical sub-rectifiers replace the two load circuits of the conventional RRC. When compared with the previous Wilkinson power combiner (WPC)-based rectifier, the proposed topology advances with a smaller variation in power conversion efficiency (PCE) over the incident angle. In addition, it simplifies the matching network (MN) design and enables a lower input return loss due to the fully symmetric circuitry between 0° and 180°. Furthermore, it allows a higher design flexibility on the rectifier topology. For validation, we designed and fabricated two wide-angle rectifiers, one working at single band (2.45 GHz) and the other at dual band (0.9 and 2.4 GHz). The single-band rectifier achieved a 67.3% peak PCE and 7.9% efficiency variation within the 0°–360° incident angle range. For the dual-band rectifier, the peak PCE is 78.4% and 70.2%, while the variation is 4% and 8.8%, for 0.9 and 2.4 GHz, respectively. The PCE variation is the smallest among previous works.

Advances in oral peptide drug nanoparticles for diabetes mellitus treatment.

Peptide drugs play an important role in diabetes mellitus treatment. Oral administration of peptide drugs is a promising strategy for diabetes mellitus because of its convenience and high patient compliance compared to parenteral administration routes. However, there are a series of formidable unfavorable conditions present in the gastrointestinal (GI) tract after oral administration, which result in the low oral bioavailability of these peptide drugs. To overcome these challenges, various nanoparticles (NPs) have been developed to improve the oral absorption of peptide drugs due to their unique in vivo properties and high design flexibility. This review discusses the unfavorable conditions present in the GI tract and provides the corresponding strategies to overcome these challenges. The review provides a comprehensive overview on the NPs that have been constructed for oral peptide drug delivery in diabetes mellitus treatment. Finally, we will discuss the rational application and give some suggestions that can be utilized for the development of oral peptide drug NPs. Our aim is to provide a systemic and comprehensive review of oral peptide drug NPs that can overcome the challenges in GI tract for efficient treatment of diabetes mellitus.

High Frequency Bipolar Electroporator with Double-Crowbar Circuit for Load-Independent Forming of Nanosecond Pulses

In this work, a novel electroporation system (electroporator) is presented, which is capable of forming high frequency pulses in a broad range of parameters (65 ns–100 µs). The electroporator supports voltages up to 3 kV and currents up to 40 A and is based on H-bridge circuit topology. A synchronized double crowbar driving sequence is introduced to generate short nanosecond range pulses independently of the electroporator load. The resultant circuit generates pulses with repetition frequencies up to 5 MHz and supports unipolar, bipolar, and asymmetrical pulse sequences with arbitrary waveforms. The shortest pulse duration step is hardware limited to 33 ns. The electroporator was experimentally tested on the H69AR human lung cancer cell line using 20 kV/cm bipolar and unipolar 100 ns–1 μs pulses. Based on a YO-PRO-1 permeabilization assay, it was determined that the electroporator is suitable for applied research on electroporation. The system offers high flexibility in experimental design to trigger various electroporation-based phenomena.

Differential Polymer Chain Scission Enables Free-Standing Microcavity Laser Arrays.

Control over material architectures is essential to the performance of photonic devices and systems. Optical isolation of the photonic materials from substrates can significantly enhance their performance but suffers from complicated fabrication processes and limited applications. Here a differential polymer chain scission strategy is proposed to fabricate free-standing photonic structures based on one-step electron-beam direct writing on polymer bilayers (EOB). The polymer molecular mass-dependent sensitivity to electron beam enables differential patterning of the two layers of polymers, leading to the direct formation of suspended optical microcavities. The EOB technique features high materials compatibility and design flexibility for the optical microcavities, which significantly expands the application scope of the suspended optical microcavities. As well as providing a versatile strategy for building high-performance photonic materials, the results provide a promising platform for innovative applications of optical microstructures.

The Effects of Core Machining Configurations on the Mechanical Properties of Cores and Sandwich Structures.

Composite sandwich structures are widely used in the fields of aviation, marine, and energy due to their high specific stiffness and design flexibility. Improving the mechanical properties of the cores is significant to the strength, modulus, and stability of composite sandwich structures. Two kinds of core machining configurations were designed by combining thin grooves, perforated holes, and thick contour cuts as well as non-machining plain cores. The cores and sandwich structures with these configurations were fabricated using a vacuum-assistant infusion process. Static tensile, compressive, shear, and peeling tests were conducted on the infused cores and sandwich structures. The results showed that the tensile, compressive, and shear moduli, and compressive strength of the infused cores can be greatly improved. The tensile strength changed negligibly due to stress concentration induced by irregular foam cell and the shear-lag phenomenon of the resin column/foam interface. The shear strength of the infused cores increased slightly. The thick contour cuts and perforated holes can greatly improve the face sheet/core peel capacity of the sandwich structures, whereas the thin grooves can moderately improve the peel capacity. Both infused cores with the designed machining configurations exhibited positive effects on the compressive, tensile, and shear moduli, and compressive strength, considering the material costs. The study provides a comprehensive and quantitative insight into the effects of core machining configurations on mechanical properties of infused cores and composite sandwich structures.

A review of the frictional contact in rock cutting with a PDC bit

Drilling is one of the most expensive processes in the oil and gas exploration and exploitation processes which is commonly performed with polycrystalline diamond compact (PDC) fixed-cutter bits (or PDC bits as they are often referred to) due to their good stability and high flexibility in design. The PDC bit longevity strongly depends on the wear flat surface that changes during progression through rock materials. The wear flat size increases with time and can greatly influences the bit performance and efficiency. The increase in wear causes increasing weight-on-bit (WOB) on the PDC bit to keep the rate of penetration (ROP) constant. Over the past decades, contrary to the pure cutting process, not many investigations have been devoted to studying the friction mechanism at the wear flat–rock interface, resulting in poor understanding of the friction mechanism. The objective of this paper is to provide a detailed review of the state-of-the-art in rock cutting with particular focus on the frictional mechanism of the blunt PDC cutters and issues associated with the contact stress and the friction coefficient at the wear flat–rock interface. Moreover, the contact forces at the wear flat are governed by the wear flat inclination angle. Gaining a better understanding of the frictional contact process can eventually play a significant role in addressing practical issues such as drilling efficiency, optimization, and susceptibility to vibrations. Further, in spite of some obvious differences between the indentation and rock cutting processes, the main similarities between these two processes are also discussed which can provide new insights for the further studies. • A brief review of the cutting forces acting on the sharp PDC cutters. • An extensive review of the contact forces acting on the wear flat of the PDC bits. • Analysis of the factors affecting the contact stress and friction coefficient at the wear flat–rock interface. • A new comparison between the indention test and the rock cutting process. • Review of the factors affecting the development of the wear in the PDC bit/cutters.

Design of Dual-Channel Filter Based on Dual-Mode Dielectric Resonators

In this brief, the design approach of dual-channel filter based on dual-mode dielectric resonator (DR) is proposed. A pair of orthogonal modes in dual-mode DR with the same and different frequencies are analyzed and applied to construct the two channel filtering responses independently. Meanwhile, the isolation between the two channels can be realized due to the orthogonality between the modes. Thus, the design process is simple and efficient. To verify the design approach, two prototypes with the same and different frequencies are designed. Meanwhile, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3^{rd}$ </tex-math></inline-formula> -order dual-channel filter with different frequencies are also implemented and measured. The frequencies of the two designs are 1.54GHz and 1.53/1.68GHz, respectively. In each design, the return losses of the two channels are better than 14dB, the insertion losses are less than 0.68dB, and the band isolation is greater than 20dB. Meanwhile, the results also show that arbitrary filtering order and high design flexibility can be achieved.

Modeling of the mechanical properties of fused deposition modeling (FDM) printed fiber reinforced thermoplastic composites by asymptotic homogenization

Fused deposition modeling (FDM) is a low-cost additive manufacturing method with moderate tolerances and high design flexibility. Ample studies are being undertaken for modeling the mechanical properties of FDM by using the Finite Element Method (FEM). The process technique of FDM results in anisotropic inner structures that are affected by the chosen manufacturing parameters. Moreover, composite filaments, such as fiber-reinforced polymers, have anisotropy even in filament form before FDM printing. These anisotropic effects are needed to be examined and incorporated for an adequate model. In order to speed up the design stage, we aim to prepare a practical method for simulating the mechanical properties of FDM-printed fiber-reinforced polymer composites. In this work, we computed the homogenized material properties for various fiber lengths, fiber volume percentages, and fiber orientations by asymptotic homogenization at the microscale. Then, mesoscale simulations are carried out through FEM simulations by incorporating the influences of process parameters. In this way, we demonstrate the effect of various micro- and mesostructural features on the homogenized properties step by step.

Site-specific Incorporation of Phosphoserine into Recombinant Proteins in Escherichia coli.

This protocol describes the recombinant expression of proteins in E. coli containing phosphoserine (pSer) installed at positions guided by TAG codons. The E. coli strains that can be used here are engineered with a ∆ serB genomic knockout to produce pSer internally at high levels, so no exogenously added pSer is required, and the addition of pSer to the media will not affect expression yields. For "truncation-free" expression and improved yields with high flexibility of construct design, it is preferred to use the Release Factor-1 (RF1) deficient strain B95(DE3) ∆ A ∆ fabR ∆ serB , though use of the standard RF1-containing BL21(DE3) ∆ serB is also described. Both of these strains are serine auxotrophs and will not grow in standard minimal media. This protocol uses rich auto-induction media for streamlined and maximal production of homogeneously modified protein, yielding ~100-200 mg of single pSer-containing sfGFP per liter of culture. Using this genetic code expansion (GCE) approach, in which pSer is installed into proteins during translation, allows researchers to produce milligram quantities of specific phospho-proteins without requiring kinases, which can be purified for downstream in vitro studies relating to phosphorylation-dependent signaling systems, protein regulation by phosphorylation, and protein-protein interactions. Graphical abstract.

Cancellation of unknown multi-harmonic disturbances in multivariable flexible mechanical structures

Active vibration control of flexible mechanical structures is a challenging field of research in control engineering due to typically high state-space dimensions of the plant models and the resulting multi-modal dynamical behavior. This work deals with the cancellation of unknown multi-harmonic disturbances in such flexible mechanical structures with multiple inputs and multiple outputs. The proposed control scheme exploits the passivity property of the closed-loop system to ensure robustness to unknown and slowly varying plant parameters. The controller design follows a decentralized control approach, which features a high flexibility in terms of the number of available actuators. However, the unknown disturbance frequency is estimated in a centralized way. Here, the frequency estimator switches between individual outputs based on the estimated amplitudes of the compensation scheme. This leads to an improved rate of convergence compared to a fixed output frequency estimator while retaining the high flexibility of the controller design regarding the number of available actuators. In this work, the local exponential stability of the respective nonlinear time-varying switched error dynamics is proven. Furthermore, measurements from an experimental test rig for electromagnetic stabilization of thin steel strips demonstrate the effectiveness and robustness of the proposed control scheme.

A Systematic Approach for Developing 3D High-Quality PDMS Microfluidic Chips Based on Micromilling Technology.

In recent years, there has been an increased interest in exploring the potential of micro-and mesoscale milling technologies for developing cost-effective microfluidic systems with high design flexibility and a rapid microfabrication process that does not require a cleanroom. Nevertheless, the number of current studies aiming to fully understand and establish the benefits of this technique in developing high-quality microsystems with simple integrability is still limited. In the first part of this study, we define a systematic and adaptable strategy for developing high-quality poly(methyl methacrylate) (PMMA)-based micromilled structures. A case study of the average surface roughness (Ra) minimization of a cuboid column is presented to better illustrate some of the developed strategies. In this example, the Ra of a cuboid column was reduced from 1.68 μm to 0.223 μm by implementing milling optimization and postprocessing steps. In the second part of this paper, new strategies for developing a 3D microsystem were introduced by using a specifically designed negative PMMA master mold for polydimethylsiloxane (PDMS) double-casting prototyping. The reported results in this study demonstrate the robustness of the proposed approach for developing microfluidic structures with high surface quality and structural integrability in a reasonable amount of time.

Highly efficient patterning technique for silver nanowire electrodes by electrospray deposition and its application to self-powered triboelectric tactile sensor

A patterned transparent electrode is a crucial component of state-of-the-art wearable devices and optoelectronic devices. However, most of the patterning methods using silver nanowires (AgNWs), which is one of the outstanding candidate materials for the transparent electrode, wasted a large amount of unused AgNWs during the patterning process. Here, we report a highly efficient patterning of AgNWs using electrospray deposition with grounded electrolyte solution (EDGE). During electrospray deposition, a patterned electrolyte solution collector attracted AgNWs by strong electrostatic attraction and selectively deposited them only on the patterned collector, minimizing AgNW deposited elsewhere. The enhanced patterning efficiency was verified through a comparison between the EDGE and conventional process by numerical simulation and experimental validation. As a result, despite the same electrospray deposition conditions for both cases except for the existence of the electrolyte solution collector, the coverage ratio of AgNWs fabricated by the EDGE process was at least six times higher than that of AgNWs produced by the conventional process. Furthermore, the EDGE process provided high design flexibility in terms of not only the material of the substrate, including a polymer and a ceramic but also the shape of the substrate, including a 2D flat and 3D curved surface. As an application of the EDGE process, a self-powered touch sensor exploiting the triboelectric effect was demonstrated. Thus, the EDGE process would be utilized in further application in wearable or implantable devices in the field of biomedicine, intelligent robots, and human–machine interface.

Anions mediated amino-type Cd-MOFs catalysts for efficient photocatalytic hydrogen evolution

Photocatalytic water splitting can be used to directly transfer solar energy into chemical energy with highly efficiency. Metal-organic frameworks (MOFs) materials are well known on the advantages of high design flexibility and metal center functionalization. In this study, a series of Cd-centered MOFs were successfully fabricated by a simple solvent evaporation method based on the different anion mediated pyridyl leucine derivatives. Single-crystal X-Ray diffraction showed the isostructural 3D chiral coordination networks of three Cd-MOFs with helical chains connected by the adjacent carboxylate groups. Within the helical coordination chains, the formate (For) and acetate (OAc) anions adopted chelate modes in Cd-LFor and Cd-LOAc, whereas the chloride worked as a monodetate ligand in Cd-LCl. Powder X-ray diffraction (PXRD), Thermogravimetric analysis, UV–vis spectra, Photocurrent-time test (I-t) and Mott-Schottky (MS) curves were carried out to characterize and analysis these Cd-MOFs. All the samples exhibit photocatalytic activity for hydrogen generation in aqueous solution of Na2S/Na2SO3 upon irradiation at full light. The photocurrent time test showed that Cd-LCl showed a higher photocurrent intensity than those of Cd-LFor and Cd-LOAc, which proved the lower electron-hole recombination and correspondingly higher hydrogen production photocatalysis active. The highest H2 production rate reached 17242 ​μmol ​g−1 ​h−1 for Cd-LCl. In the photocatalytic reaction, the hydrogen production rate was stable without significant decrease, indicating that the material had no significant deactivation and had good photocatalytic activity.

SERS Gas Sensors Based on Multiple Polymer Films with High Design Flexibility for Gas Recognition.

The Surface-Enhanced Raman Scattering (SERS) technique is utilized to fabricate sensors for gas detection due to its rapid detection speed and high sensitivity. However, gases with similar molecular structures are difficult to directly discriminate using SERS gas sensors because there are characteristic peak overlaps in the Raman spectra. Here, we proposed a multiple SERS gas sensor matrix via a spin-coating functional polymer to enhance the gas recognition capability. Poly (acrylic acid) (PAA), Poly (methyl methacrylate) (PMMA) and Polydimethylsiloxane (PDMS) were employed to fabricate the polymer film. The high design flexibility of the two-layer film was realized by the layer-by-layer method with 2 one-layer films. The SERS gas sensor coated by different polymer films showed a distinct affinity to target gases. The principle component analysis (PCA) algorithm was used for the further clustering of gas molecules. Three target gases, phenethyl alcohol, acetophenone and anethole, were perfectly discriminated, as the characteristic variables in the response matrix constructed by the combination of gas responses obtained 3 one-layer and 3 two-layer film-coated sensors. This research provides a new SERS sensing approach for recognizing gases with similar molecular structures.