Tunable Performance Research Articles

Hybrid Modular Redundancy: Exploring Modular Redundancy Approaches in RISC-V Multi-Core Computing Clusters for Reliable Processing in Space

Space Cyber-Physical Systems (S-CPS) such as spacecraft and satellites strongly rely on the reliability of onboard computers to guarantee the success of their missions. Relying solely on radiation-hardened technologies is extremely expensive, and developing inflexible architectural and microarchitectural modifications to introduce modular redundancy within a system leads to significant area increase and performance degradation. To mitigate the overheads of traditional radiation hardening and modular redundancy approaches, we present a novel Hybrid Modular Redundancy (HMR) approach, a redundancy scheme that features a cluster of RISC-V processors with a flexible on-demand dual-core and triple-core lockstep grouping of computing cores with runtime split-lock capabilities. Further, we propose two recovery approaches, software-based and hardware-based, trading off performance and area overhead. Running at 430MHz, our fault-tolerant cluster achieves up to 1160MOPS on a matrix multiplication benchmark when configured in non-redundant mode and 617 and 414 MOPS in dual and triple mode, respectively. A software-based recovery in triple mode requires 363 clock cycles and occupies 0.612 mm 2 , representing a 1.3% area overhead over a non-redundant 12-core RISC-V cluster. As a high-performance alternative, a new hardware-based method provides rapid fault recovery in just 24 clock cycles and occupies 0.660 mm 2 , namely ∼ 9.4% area overhead over the baseline non-redundant RISC-V cluster. The cluster is also enhanced with split-lock capabilities to enter one of the available redundant modes with minimum performance loss, allowing execution of a mission-critical portion of code when in independent mode, or a performance section when in a reliability mode, with <400 clock cycles overhead for entry and exit. The proposed system is the first to integrate these functionalities on an open-source RISC-V-based compute device, enabling finely tunable reliability vs. performance trade-offs.

Tunable Thermoelectric Performance of the Nanocomposites Formed by Diketopyrrolopyrrole/Isoindigo-Based Donor-Acceptor Random Conjugated Copolymers and Carbon Nanotubes.

This paper presents the development of thermoelectric properties in nanocomposites comprising donor-acceptor random conjugated copolymers and single-walled carbon nanotubes (SWCNTs). The composition of the conjugated polymers, specifically the ratio of diketopyrrolopyrrole (DPP) to isoindigo (IID), is manipulated to design a series of random conjugated copolymers (DPP0, DPP5, DPP10, DPP30, DPP50, DPP90, DPP95, and DPP100). The objective is to improve the dispersion of SWCNTs into smaller bundles, leading to enhanced thermoelectric properties of the polymer/SWCNT nanocomposite. This dispersion strategy promotes an interconnected conducting network, which plays a critical role in optimizing the thermoelectric performance. Accordingly, the effects of morphologies on the thermoelectric properties of the nanocomposites are systematically investigated. The DPP95/SWCNT nanocomposite exhibits the strongest interaction, resulting in the highest power factor (PF) of 711.1 μW m-1 K-2, derived from the high electrical conductivity of 1690 S cm-1 and Seebeck coefficient of 64.8 μV K-1. The prototype flexible thermoelectric generators assembled with a DPP95/SWCNT film achieve a maximum power output of 20.4 μW m-2 at a temperature difference of 29.3 K. These findings highlight the potential of manipulating the composition of random conjugated copolymers and incorporating SWCNTs to efficiently harvest low-grade waste heat in wearable thermoelectric devices.

A confined self-assembly approach towards chiral photonic materials with circularly polarized structural colors for information storage and encryption

Chiroptical materials with tunable circular polarization performances have gained wide interest because of promising applications in optical devices and information communication. However, limited by their intrinsic chirality, such materials suffer from serious deficiencies in dynamical manipulation on circularly polarized light (CPL). Here, we demonstrate a kinetic trapping approach to capture multi-domain cholesteric mesophases for polarization-dependent structural coloration. The resultant photonic structures depicted by limited solvent evaporation display light control from selective left-handed circularly polarized light reflection to dual reflection, as a result of forming highly tilted and distorted domains with a phase-retardation effect. Notably, a positive linear correlation is established between the circular polarization behavior and structural orientation regulated by the solvent evaporation. The tunable circular polarization structural colors enable the application of the photonic materials for complex encryption in terms of polychromatic coding arrays. The confined-anisotropic-fabrication method of photonic structures paves a foundation toward advanced functional materials with promising applications in light science and technology.

Multi-layer carbon fiber paper @reduced graphene oxide/Co/C composite with adjustable electromagnetic interference shielding properties

Paper-based composite materials exhibit a marked tendency towards thinner and lighter profiles in the context of electromagnetic interference (EMI) shielding. Carbon fiber paper (CFP) has excellent electrical conductivity and Lightweight base characteristics. However, its single electrical loss characteristic and uncontrollable EMI shielding performance are limited in application. Therefore, we prepared CFP@ graphene oxide (GO)/ZIF-67 composites by chemical bonding and in-situ polymerization, and then prepared CFP@rGO/Co/C composites with integrated structure and function by heat treatment. Layer-by-layer assembly technology was employed to develop composite materials with tunable EMI shielding performance. The composite material has excellent high conductivity (2475.86 S/m) and excellent EMI shielding performance (average X-band EMI efficiency (SE)38.46 dB, absolute shielding effectiveness (SSE/t) = 14388.56 dB cm2 g−1). Through the layer-by-layer assembly technology, the EMI SE performance of the 7-layer assembled material reached 85.83 dB, and the EMI SSE/t reached 32110.51 dB cm2 g−1. Through simulation verification, the EMI shielding performance of the materials is compared, and ideas for EMI material design are provided. In addition, the material also has excellent Joule heating performance, fast electrothermal response and good temperature controllability. The material exhibits remarkable resilience against harsh environmental conditions, including strong acids, bases, organic reagents, ultrasonic waves, combustive processes, and extremely low temperatures. Despite these severe treatments, its performance remains above 90 % intact. This study proposes a magnetic-dielectric synergistic, performance-adjustable CFP-based shielding material, which has great application potential in the future wearable, defense, and aerospace fields.

Controlled caging, flat band and thermoelectric response in a quasi-one dimensional kagomé ribbon

A quasi-one dimensional kagomé ribbon geometry is studied in respect of its band spectrum, electronic transport as well as the thermopower within the tight-binding formalism. Analytic proposition of Bloch bands along with the dispersionless flat band states is seen to be consistent with the numerical evaluation of density of states, transmission and band dispersion. A uniform magnetic flux can act as an external agency to tune the spectral landscape and the transport at will. Flux sensitive band engineering leads to an interesting proposal of tunable thermoelectric performance of an identical model device. The tunable behavior can be explored by the calculation of Seebeck co-efficient. The external magnetic perturbation plays the key role in this demonstration and it is an easily adjustable parameter. We have critically investigated all the characteristic features using the Sommerfeld expansion within a tight-binding framework based on Green’s function formalism. The present analysis may provide useful directive for constructing efficient thermoelectric devices at the nanoscale level.

Chlorinated benzothiadiazole-based donor-acceptor polymers with tunable optoelectronic performances

Chlorinated benzo[c][1,2,5]thiadiazole, a new analogue of benzo[c][1,2,5]thiadiazole (BT), exhibits strong electron-withdrawing ability nature, while also offering advantages of lower cost and easier accessibility compared to its fluorinated analogues. This inspires us to investigate donor-acceptor-type (D-A) conjugated polymers based on chlorinated BT. Therefore, in this work, three D-A-D type monomers (0Cl, 1Cl, and 2Cl) were successfully synthesized with BT and chlorinated BT as acceptor units and EDOT as donor units by Stille coupling reaction. Subsequently, the corresponding D-A polymers (P0Cl, P1Cl, and P2Cl) were obtained via electrochemical polymerization. The results show that the two chlorinated monomers have higher initial oxidation potentials of 1.08 V (1Cl) and 1.09 V (2Cl), which are significantly higher than their non-chlorinated analogue (0.72 V). The two chlorinated polymers demonstrate good redox activity but with relatively poor stability (only 65.7 % and 20.7 % electroactivity are preserved after 100 cycles). Due to the decreased effective conjugation length caused by the deviations from planarity, both absorption spectra of the chlorinated polymers were blue-shifted when compared with P0Cl, leading to an increase in the optical band gap (1.64–1.68 eV). Introducing the Cl atom substitution on the BT unit resulted in the improvement of both the switching time and coloration efficiency. Specifically, the monochlorinated polymer (P1Cl) showed light gray in the neutral state and obvious electrochromic properties in the near-infrared region (optical contrast: 24 %, coloration efficiency: 195.6 cm2 C−1, and quick response time: 0.4 s). This study further expands the selection of chlorinated BT-based acceptor units and the application prospect of D-A electrochromic polymers.

Ferroelectric Layer‐Assisted Asymmetric Heterojunction Boosts Power Output in Silicon Hydrovoltaic Device

AbstractHydrovoltaic devices (HDs) that convert ubiquitous environmental energy via water evaporation serves as a prospective technology for renewable power schemes. However, it remains a grand challenge to perform controllable and stable modulation of hydrovoltaic power generation for multi‐scenario practical applications. Here, a ferroelectric‐field assisted silicon HD is proposed, which sandwiches an ultrathin polarizable polymer between nanostructured silicon and the top electrode, constituting an asymmetric heterojunction designed to clinch well‐regulated and robust electrical signal output. Tunable modulation of the internal electric field at the silicon/top electrode interface can be realized by facilely aligning the polarization orientation of the ferroelectric domains, thus dominating the silicon energy band bending and controlling the ultimate electrical signal. Upon effective forward polarization, the interfacial dipoles can build a stronger asymmetric electric field, which allows an efficient sweep of the charges out of the heterojunction. Accordingly, the resulting device clinches to yield a considerably modulated voltage of 1.04 V, nearly three‐fold modulation over the reverse polarization one. As prospective applications, multifunctional sensing platforms including the self‐sufficient environmental temperature detector, intelligent water‐level alarm system, and automatic‐manual dual‐mode irrigation control system are demonstrated. This work exhibits the unique characteristics of ferroelectric HDs with tunable electrical performance.

Oriented bacterial cellulose microfibers with tunable mechanical performance fabricated via green reassembly avenue

Bacterial cellulose has garnered remarkable interest from researchers, particularly those working in the biomedical field. In this work, BC microfibers were fabricated via green dissolution (ZnCl2) and regeneration (ethanol). The orientation of cellulose chains was investigated during extrusion and simple post-processing via polarized optical microscopy and small-angle X-ray scattering. The results implied that the mechanical properties of BC microfibers can be tuned by rational pre-stretching. The BC microfibers can be programmable, and be used to suture hard or soft tissues. The as-designed paralleled BC microfibers have good biocompatibility and can regulate the directional growth of cells on their surface. The as-obtained BC microfiber with a high tensile strength of up to ∼115 MPa is suitable for surgical sutures. The tunable BC microfibers may be utilized as an adequate fiber-derived biomedical material product.

O-band tunable multiwavelength Brillouin-Raman fiber laser based on a wavelength-agile Raman pump.

Multiwavelength Brillouin-Raman fiber laser (MBRFL) features broadband multiwavelength generation with flat-amplitude and high optical signal to noise ratio (OSNR), which has great potential in optical fiber communication applications. Till now, the spectral regions of MBRFLs are mostly concentrated at conventional C- and L-band and the tunability of MBRFL is limited by using the Raman pump with fixed wavelength. Here, by utilizing wavelength-agile random fiber laser which can emit tunable lasing at 1.2 µm band as the Raman pump, we experimentally demonstrate the tunable MBRFL in the O-band for the first time, to the best of our knowledge. At Raman and Brillouin pump powers of 920 mW and -3 dBm, respectively, up to 90 Stokes lines with 0.13 nm wavelength spacing and >13 dB OSNR can be obtained when the Raman and Brillouin pump wavelength are set at 1231 nm and 1300 nm, respectively. Moreover, by tuning the wavelength of Brillouin pump from 1295 nm to 1330 nm, tunable MBRFL can be achieved with similar multiwavelength generation bandwidth by simultaneously tuning the Raman pump wavelength, and the number of Stokes lines are beyond 85 across the tuning range. The bandwidth of the demonstrated O-band MBRFL is also the widest wavelength span ever reported for multiwavelength Brillouin fiber lasers at 1.3 µm band. Our work indicates that the use of wavelength-agile random fiber laser as Raman pump in MBRFL can provide an effective way to extend the spectral regions of MBRFL and also improve the tunability performance of MBRFL.

Photocontrollable DNA Walker-Based Molecular Circuit for the Tunable Detection of MicroRNA-21 Using Metal-Organic Frameworks as Label-Free Fluorescence Tags.

Tunable detection of microRNA is crucial to meet the desired demand for sample species with varying concentrations in clinical settings. Herein, we present a DNA walker-based molecular circuit for the detection of miRNA-21 (miR-21) with tunable dynamic ranges and sensitivity levels ranging from fM to pM. The phosphate-activated fluorescence of UiO-66-NH2 metal-organic framework nanoparticles was used as label-free fluorescence tags due to their competitive coordination effect with the Zr atom, which significantly inhibited the ligand-to-metal charge transfer. To achieve a tunable detection performance for miR-21, the ultraviolet sensitive o-nitrobenzyl was induced as a photocleavable linker, which was inserted at various sites between the loop and the stem of the hairpin probe to regulate the DNA strand displacement reaction. The dynamic range can be precisely regulated from 700- to 67,000-fold with tunable limits of detection ranging from 2.5 fM to 36.7 pM. Impressively, a Boolean logic tree and complex molecular circuit were constructed for logic computation and cancer diagnosis in clinical blood samples. This intelligent biosensing method presents a powerful solution for converting complex biosensing systems into actionable healthcare decisions and will facilitate early disease diagnosis.

Tunable thermoelectric performance in metal–organic framework Ni(BDC) studied by first principles

Metal–organic frameworks (MOFs) have unique advantages in thermoelectric applications due to their low lattice thermal conductivity. However, the low electrical conductivity limits their thermoelectric performance. In this work, we report a strategy to improve the electrical conductivity of MOFs by infiltrating pillar molecules into the layered MOFs. First principles studies indicate that after the Ni(BDC) (BDC = terephthalic) is infiltrated with DABCO (1,4-diazabicyclo[2,2,2]octane), the electrical conductivity of Ni(BDC) demonstrates a significant increase, and the power factor finally reaches 1.5 × 10−3 W m−1 K−2 at 300 K. The high electrical conductivity arises from the interaction between 3dz2 orbital of Ni and the 2pz orbital of N in DABCO. The p–d orbital coupling leads to the electron delocalization on HOMO and also the decrease in carriers effective mass. Our results provide a useful strategy for increasing the conductivity of MOFs and suggest that MOFs can be a promising class of thermoelectric materials.

Shape-memory performance of electrospun thermoplastic polyurethane/polyethylene oxide blend fibrous membranes with diverse morphological structures

The present study aimed at exploring the effect of morphological structure design on shape-memory effect (SME) of thermoplastic polyurethane/polyethylene oxide (TPU/PEO) blend electrospun fibrous membranes (EFMs), that were fabricated by co-spinning, dual-jet spinning, and layer-by-layer spinning, respectively. Tunable shape-memory performances of co-spun EFMs were realized by simply varying the blend ratio of TPU and PEO in individual fiber. By comparison, the sample containing 50 wt% PEO showed the best SME due to the rich blend interface in individual fiber and the sufficient fusion points between fibers, both of which promoted the synergistic effect between two components in optimizing SME. As turning the TPU/PEO co-spun fibers into well-separated TPU and PEO fibers by dual-jet electrospinning, the interaction channels were reduced to only the fusion points between fibers, leading to the simultaneous decrease of shape-fixity and -recovery ratios. After assembling the TPU and PEO fibers into a sandwich-structured structured EFM, the SME was further degraded due to the few diffusion points between fibers located at the layer interface. This work provides a good guidance for developing high-performance shape-memory EFMs.

MXene-Based Functional Platforms for Tumor Therapy.

Recently, 2D transition metal carbide, nitride, and carbonitrides (MXenes) materials stand out in the field of tumor therapy, particularly in the construction of functional platforms for optimal antitumor therapy due to their high specific surface area, tunable performance, strong absorption of near-infrared light as well as preferable surface plasmon resonance effect. In this review, the progress of MXene-mediated antitumor therapy is summarized after appropriate modifications or integration procedures. The enhanced antitumor treatments directly performed by MXenes, the significant improving effect of MXenes on different antitumor therapies, as well as the MXene-mediated imaging-guided antitumor strategies are discussed in detail. Moreover, the existing challenges and future development directions of MXenes in tumor therapy are presented.

Tunable polarization-drived high energy storage performances in flexible PbZrO 3 films by growing Al 2O 3 nanolayers

Tunable polarization-drived high energy storage performances in flexible PbZrO ₃ films by growing Al ₂O ₃ nanolayers

Magnetorheological shear thickening gel reinforced iron-nickel foam composites with tunable energy absorption performance

Magnetorheological shear thickening gel reinforced iron-nickel foam composites with tunable energy absorption performance

Semitransparent Perovskite Solar Cells with an Evaporated Ultra‐Thin Perovskite Absorber

AbstractMetal halide perovskites are of great interest for application in semitransparent solar cells due to their tunable bandgap and high performance. However, fabricating high‐efficiency perovskite semitransparent devices with high average visible transmittance (AVT) is challenging because of their high absorption coefficient. Here, a co‐evaporation process is adopted to fabricate ultra‐thin CsPbI3 perovskite films. The smooth surface and orientated crystal growth of the evaporated perovskite films make it possible to achieve 10 nm thin films with compact and continuous morphology without pinholes. When integrated into a p‐i‐n device structure of glass/ITO/PTAA/perovskite/PCBM/BCP/Al/Ag with an optimized transparent electrode, these ultra‐thin layers result in an impressive open‐circuit voltage (VOC) of 1.08 V and a fill factor (FF) of 80%. Consequently, a power conversion efficiency (PCE) of 3.6% with an AVT above 50% is demonstrated, which is the first report for a perovskite device of a 10 nm active layer thickness with high VOC, FF and AVT. These findings demonstrate that deposition by thermal evaporation makes it possible to form compact ultra‐thin perovskite films, which are of great interest for future smart windows, light‐emitting diodes, and tandem device applications.

A Review of Sodium-Metal Chloride Batteries: Materials and Cell Design

The widespread electrification of various sectors is triggering a strong demand for new energy storage systems with low environmental impact and using abundant raw materials. Batteries employing elemental sodium could offer significant advantages, as the use of a naturally abundant element such as sodium is strategic to satisfy the increasing demand. Currently, lithium-ion batteries represent the most popular energy storage technology, owing to their tunable performance for various applications. However, where large energy storage systems are required, the use of expensive lithium-ion batteries could result disadvantageous. On the other hand, high-temperature sodium batteries represent a promising technology due to their theoretical high specific energies, high energy efficiency, long life and safety. Therefore, driven by the current market demand and the awareness of the potential that still needs to be exploited, research interest in high-temperature sodium batteries has regained great attention. This review aims to highlight the most recent developments on this topic, focusing on actual and prospective active materials used in sodium-metal chloride batteries. In particular, alternative formulations to conventional nickel cathodes and advanced ceramic electrolytes are discussed, referring to the current research challenges centered on cost reduction, lowering of the operating temperature and performance improvement. Moreover, a comprehensive overview on commercial tubular cell design and prototypal planar design is presented, highlighting advantages and limitations based on the analysis of research papers, patents and technical documents.

Bright Transparent Scintillators with High Fraction BaCl2 : Eu2+ Nanocrystals Precipitation: An Ionic-Covalent Hybrid Network Strategy toward Superior X-Ray Imaging Glass-Ceramics.

Metal halide crystals are bright but hygroscopic scintillator materials that are widely used in X-ray imaging and detectors. Precipitating them in situ in glass to form glass ceramics (GCs) scintillator offers an efficient avenue for large-scale preparation, high spatial resolution, and excellent stability. However, precipitating a high fraction of metal halide nanocrystals in glass to maintain high light yield remains a challenge. Herein, an ionic-covalent hybrid network strategy for constructing GCs scintillator with high crystallinity (up to ≈37%) of BaCl2 : Eu2+ nanocrystals is presented. Experimental data and simulations of glass structure reveal that the Ba2+ -Cl- clustering promotes the high crystallization of BaCl2 nanocrystals. The ultralow phonon energy (≈200 cm-1 ) of BaCl2 nanocrystals and good Eu reduction effect enable high photoluminescence inter quantum efficiency (≈80.41%) in GC. GCs with varied crystallinity of BaCl2 : Eu2+ nanocrystals demonstrate efficient radioluminescence and tunable scintillator performance. They either outperform Bi4 Ge3 O14 single crystal by over 132% steady-state light yield or provide impressive X-ray imaging resolutions of 20 lp mm-1 . These findings provide a new design strategy for developing bright transparent GCs scintillators with a high fraction of metal halide nanocrystals for X-ray high-resolution imaging applications.

Design of a wideband and tunable radar absorber

To effectively address the challenges posed by intricate and dynamic electromagnetic environments, we propose a wideband and tunable radar absorber in this paper. The proposed absorber, composed of graphene capacitor, plasma enclosed within a sealed glass cavity, radar absorbing material (RAM), FR-4 and copper plate, allows for tunable radar absorbing performance through the manipulation of the electromagnetic properties of the graphene capacitor and plasma. Based on the equivalent circuit model, the reflectivity of the radar absorber is analyzed using transmission line theory (TLT). Good agreement is observed between the full-wave simulations and the TLT. The study thoroughly investigates the influence of graphene, plasma, and RAM components, as well as their sequential arrangement within the radar absorber, on its reflectivity, expounding the fundamental mechanism of these materials’ synergistic integration. Additionally, the effects of key factors, including the surface resistance R g of graphene, plasma frequency collision frequency and plasma thickness on the radar absorbing performance are examined. Our findings reveal that adjusting surface resistance R g controls the absorbing amplitude, and manipulation of the plasma frequency and collision frequency tunes the absorbing frequency and effective absorbing band. By appropriately adjusting the surface resistance R g of graphene, plasma frequency and collision frequency the proposed radar absorber exhibits superior performance in the frequency range of 1 GHz to 10 GHz. The radar absorber we propose serves as a significant reference for the application of tunable radar absorbers and adaptive radar stealth techniques.

The Structure Design of a Microstrip Tunable Attenuator Based on Few-Layer Graphene

There are innovative applications for graphene materials in microwave Radio Frequency (RF) due to their unique optoelectronic properties. In this paper, a series of existing tunable microstrip attenuators based on few-layer graphene are compared and studied, and a new microstrip tunable attenuator based on few-layer graphene is proposed on this basis. Firstly, the relationship between the performance of different pair spacing attenuators with 4 pairs of graphene structures is analyzed based on the existing pair spacing studies with 1-3 pairs of structures; after that, the performance characteristics of the existing 1-4 pairs of graphene structures on different substrates are tested and analyzed; finally, a new tunable attenuator structure is proposed based on the above research results. The new attenuator consists of four parts, including a dielectric substrate, a microstrip line, a total of five pairs of graphene flakes on both sides and corresponding metal vias. The resistivity of the graphene flake can be changed by changing the access bias voltage, thus regulating the insertion loss of the attenuator. The experimental results show that the proposed attenuator can operate in the frequency range from 3 GHz to 10 GHz, and the insertion loss can be adjusted from -2 dB to -63 dB, with a high tunable performance of 61 dB.