High-performance Systems Research Articles

In-situ formed Ni2Si into lightweight SiC(rGO) nanocomposite PDCs to boost load bearing-microwave absorption integration for complex environments

As contemporary aerospace and radar-detecting technologies evolve, load bearing-microwave absorption integration of thermal protection materials for complex environment requirements are urgent. Well known for low density, good high-temperature resistance and superior tunable dielectric properties, polymer-derived ceramics (PDCs) promisingly meet most needs of high-performance aircraft thermal protection system (TPS). Aimed at promoting practical application, we integrate in-situ formed Ni2Si into lightweight SiC(rGO) nanocomposite PDCs via re-pyrolyzing coassembled nano-Ni/SiC(rGO)p/polycarbosilane-vinyltriethoxysilane-graphene oxide (PVG) blends to enhance their mechanical and electromagnetic wave (EMW) absorbing performances. Size effect on phase transition of Ni into Ni2Si (as brazing bonding agents) accompanied by volumetric expansion, ingeniously eliminates stretching stress from PVG precursor inward shrinkage for compact framework during re-pyrolysis. In-situ generated Ni/Ni2Si/C core-shell nanostructure (similar to nodular cast iron) has good chemical compatibility with β-SiC/SiOxCy/Cfree(rGO), thereby enables composites improved compactness and toughness. More interestingly, heterogeneous interfaces/defects among Ni, Ni2Si, carbon shell, β-SiC and SiOxCy/Cfree(rGO) matrix, effectively facilitate interfacial/dipole polarization for robust EMW absorption, and lightweight SiC(rGO, Ni2Si)Ni=4% nanocomposite PDCs exhibit outstanding fracture toughness of 6.56 MPa·m1/2 and high compressive strength of 119.25 MPa. Such composite with structure-function integration maintain stable under butane blowtorch at ∼1300 °C, shedding light on a new route to mass-manufacture aerospace vehicle components.

The effects of acoustic disturbances and mechanical vibration on laminar premixed flames: A comparative study

The energy conversion between the combustion process and acoustic waves is very complex in high-performance propulsion systems, which may trigger large-amplitude combustion instabilities, potentially leading to severe vibration or structural damage. Both acoustic disturbances and mechanical vibration are found to be able to cause the combustion instability, but their differences on the influence of laminar premixed flames are still unknown. In this paper, a premixed methane flame burner was disturbed by either a loudspeaker or an electromagnetic vibration exciter, and the effects of their forcing frequencies and amplitudes on the dynamic responses of the premixed methane flame were evaluated. Specifically, the unsteady heat release rate was measured by a photomultiplier tube, and the flame dynamic behaviors were captured by a high-speed camera with image intensifier. Furthermore, the acoustic disturbances upstream of the flame was measured by the two-microphone method, and the structure vibration was measured by an accelerometer. Then, the flame transfer functions were obtained at various equivalence ratios and mean flow velocities. The results demonstrated that the premixed flame exhibited obvious band-pass filtering characteristics when subjected to external forcing, whether through a loudspeaker or an electromagnetic vibration exciter. In addition, increasing either acoustic or structure excitation amplitude to a large extent can make the flame respond in a nonlinear manner. However, when the flame was subjected to mechanical vibration, the peak frequency corresponding to the maximum gain of the flame transfer function had minimal sensitivity to variations in equivalence ratios and mean flow velocities. In contrast, the acoustic disturbances were more likely to induce the nonlinear flame responses and flame front wrinkling.

HerbMet: Enhancing metabolomics data analysis for accurate identification of Chinese herbal medicines using deep learning.

Chinese herbal medicines have been utilized for thousands of years to prevent and treat diseases. Accurate identification is crucial since their medicinal effects vary between species and varieties. Metabolomics is a promising approach to distinguish herbs. However, current metabolomics data analysis and modeling in Chinese herbal medicines are limited by small sample sizes, high dimensionality, and overfitting. This study aims to use metabolomics data to develop HerbMet, a high-performance artificial intelligence system for accurately identifying Chinese herbal medicines, particularly those from different species of the same genus. We propose HerbMet, an AI-based system for accurately identifying Chinese herbal medicines. HerbMet employs a 1D-ResNet architecture to extract discriminative features from input samples and uses a multilayer perceptron for classification. Additionally, we design the double dropout regularization module to alleviate overfitting and improve model's performance. Compared to 10 commonly used machine learning and deep learning methods, HerbMet achieves superior accuracy and robustness, with an accuracy of 0.9571 and an F1-score of 0.9542 for distinguishing seven similar Panax ginseng species. After feature selection by 25 different feature ranking techniques in combination with prior knowledge, we obtained 100% accuracy and an F1-score for discriminating P. ginseng species. Furthermore, HerbMet exhibits acceptable inference speed and computational costs compared to existing approaches on both CPU and GPU. HerbMet surpasses existing solutions for identifying Chinese herbal medicines species. It is simple to use in real-world scenarios, eliminating the need for feature ranking and selection in classical machine learning-based methods.

Primary care quality and provider disparities in China: a standardized-patient-based study

BackgroundPrimary health care is the foundation of high-performing health systems. Achieving an improved primary care system requires a thorough understanding of the current quality of care among various providers within the system. As the world’s largest developing country, China has made significant investments in primary care over the past decade. This study evaluates the quality of primary care across different provider types in China, offering in- sights for enhancing China’s primary care system. MethodsWe merged data from four standardized patient (SP) research projects to compare the quality of five major primary care providers in China: rural clinics, county hospitals, migrant clinics, urban community health cen- ters (CHCs), and online platforms. We evaluated quality of care across process quality (e.g., checklist completion), diagnosis quality (e.g., diagnostic accuracy), and case management (e.g., correct medication), employing multiple regression analyses to explore quality differences by provider type, and their associations with physician characteristics. FindingsWe document a poor quality of primary care in China, with no- table disparities across different providers. CHCs emerge as relatively reliable primary care providers in terms of process quality, diagnostic accuracy, and cor- rect medication prescriptions. Online platforms outpace rural clinics, county hospitals, and migrant clinics in many areas, showcasing their potential to en- hance access to quality healthcare resources in under-resourced rural regions. We observe a positive association between the qualifications of physicians and the quality of primary care, underscoring the necessity for a greater presence of more highly qualified practitioners. InterpretationPrimary care quality in China varies greatly among providers, reflecting inequalities in healthcare access. While online platforms indicate po- tential for improving care in under-resourced areas, their high referral rates suggest they cannot completely substitute traditional care. The findings em- phasize the need for more qualified practitioners and stringent regulation to enhance care quality and reduce unnecessary treatments. FundingNo founders had a role in the study design, data collection, data analysis, data interpretation, or writing of the report. We have acknowledged this in the revised manuscript.

Optical investigation on lubricant combustion characteristics under the ammonia-methane premixed environment

The combustion process is an indispensable energy conversion step in modern industry and energy production. Especially in high-performance engines and energy conversion systems, understanding and controlling the combustion process is critical to improving efficiency and reducing environmental pollution. As a key component of mechanical systems, the combustion characteristics of lubricants at high temperatures and pressures have a direct impact on system performance and emissions. This study investigated the combustion characteristics of lubricant films in an ammonia-methane premixed environment using Planar Laser-Induced Fluorescence (PLIF) and Planar Laser-Induced Incandescence (PLII). It focused on the effects of varying ammonia concentrations on the emission of soot and polycyclic aromatic hydrocarbons (PAHs) in the constant volume combustion vessel. Experiments varied the ammonia-to-methane molar ratios, initial oil film thickness, and base oil type to study their influence on the lubricant combustion characteristics. Results indicated that ammonia significantly reduced soot formation by altering the dynamics of NH* and OH* and impacting PAH distribution. For the lubricating oil soot formation factors, the increase of the initial mean oil film thickness was more obvious for the promotion of soot formation, the increase of the unsaturated hydrocarbon content in the oil film also promoted the generation of carbon soot to a certain extent, and the initial flame energy ratio had the least influence on the promotion of soot formation. Overall, the study contributed to the understanding of the formation mechanism of soot caused by lubricating oil in zero-carbon and low-carbon blended atmospheres and provided a new insight into the interaction between nitrogen-containing zero-carbon fuels and large-carbon-number hydrocarbons, which is of great significance for controlling soot emissions from engines under zero-carbon fuel blending.

Family business culture: a strategic resource and driver of firm performance

PurposeThrough a resource-based theoretical lens, we elucidate conditions under which family business culture (FBC) amplifies the positive effects of high-performance work systems (HPWS) intensity and exacerbates the negative effects of low human capital uniqueness (HCU) on firm performance. By doing so, we answer the call for more research on the conditions under which FBC influences firm outcomes.Design/methodology/approachThe present study sampled 226 small business owners across the USA, who provided their responses to online survey questions. Hypotheses were assessed via path analysis in MPlus 8.8, using maximum likelihood estimation.FindingsFBC, HPWS intensity and HCU were positively associated with firm performance. Further, the HPWS intensity – firm performance and HCU – firm performance links were moderated by FBC. Specifically, increased levels of HPWS intensity were associated with greater firm performance when FBC was high, and firms with low levels of HCU tended to have particularly decreased levels of firm performance when FBC was low.Research limitations/implicationsConsistent with the resource-based view, firms' unique resources and competitive advantage may be tied to the extent to which they have an established FBC. High levels of FBC, which are characterized by shared values, loyalty, proud involvement and care toward the organization, can play a significant role in enhancing organizational performance. Family business leaders should prioritize cultivating an enhanced FBC alongside investments in HPWS and unique human capital.Originality/valueThis study contributes to understanding the theoretical underpinnings of FBC and its relationship with firm performance by examining FBC’s interaction with HPWS intensity and HCU. We highlight FBC as a valuable intangible resource that can enhance or diminish the effectiveness of other strategic resources in family firms, further extending the application of resource-based view theory in family business research.

Developing a roadmap to reach and sustain 90% full immunization coverage through a cross-sectoral system strengthening strategy in Bihar, India

IntroductionReducing childhood mortality by curtailing the incidence of vaccine preventable diseases is contingent upon a robust and high-performing routine immunization system. According to the available data, the full immunization coverage (FIC) in the state of Bihar (India) has reached ~ 71%. While the government aspires to reach 90% FIC, a systematic evidence-based investigation of the reasons behind underimmunization as well as the identification of drivers and enablers to reach and sustain 90% FIC is critical. This study aimed to review the factors leading to underimmunized children in the state of Bihar and develop a forward-looking roadmap to reach and sustain 90% FIC by adopting a system strengthening approach.MethodWe conducted a desk review, followed by extensive stakeholder interviews and field visits to document and analyze the data and evidence relevant to routine immunization system performance in the state of Bihar. The stakeholders included the State Immunization Officer, District Immunization Officers, Block-level health officials, representatives from development agencies, healthcare workers, and caregivers. A total of eighty-six structured interviews were conducted, which included qualitative and quantitative parameters.ResultWhile positive results were observed from the assessment of Bihar’s immunization system, the implementation of targeted strategies for supply, service delivery and demand can provide a means to achieve FIC of 90%. The roadmap developed by the Government of Bihar enlists 40 + interventions across key thematic areas and has been prioritized over a 5-year time horizon as short, medium, and long-term milestones to achieve 90% FIC. These interventions include strengthening the data availability and quality, improving the governance and review mechanism, augmenting the capacity of health workers involve with immunization programme, and initiatives to increase demand for immunization services.ConclusionThe Bihar’s Immunization Roadmap development project work follows a methodical approach to assess and identify intervention to improve immunization coverage and can provide information and reference to other states and countries that are aiming to formulate similar action plans.

Unpacking the dynamics of workplace innovation among nurses: The synergistic relationship between psychological ownership and high-performance work systems

ABSTRACT The study investigated the influence of high-performance work systems on the relationship between psychological ownership and workplace innovation among nurses in the health sector of Ghana. A sample of 327 nurses was selected using convenience sampling technique. The data obtained from self-reported questionnaires were evaluated using partial least squares structural equation modelling. The results indicate that psychological ownership and high-performance work systems positively influence workplace innovation, and high-performance work systems enhance the nexus between psychological ownership and workplace innovation. The findings suggest that the management of health care entities should focus on creating a workplace culture that cultivates psychological ownership among employees and implements high-performance work systems to foster workplace innovation.

Ternary Bi2WO6/TiO2-Pt Heterojunction Sonosensitizers for Boosting Sonodynamic Therapy.

Engineering Z-scheme heterojunctions represents a promising strategy for optimizing the separation and migration of charge carriers in semiconductor sonosensitizers for enhanced reactive oxygen species (ROS) generation. Nevertheless, establishing a continuous and directional pathway for ultrasonic-induced charge flow in Z-scheme heterojunctions remains a significant challenge. In this study, we present a ternary Bi2WO6/TiO2-Pt heterojunction sonosensitizer achieved through the precise growth of Pt nanocrystals on a directionally assembled Bi2WO6/TiO2 Z-scheme structure. The construction of the Bi2WO6/TiO2-Pt heterojunction involves directional growth of Bi2WO6 in situ on the highly exposed (001) crystal facet of TiO2 nanosheets, followed by the precise deposition of nano Pt on the edge (101) crystal facet. The Z-scheme Bi2WO6/TiO2 in the ternary heterojunction ensures effective electron separation, while the Schottky TiO2-Pt interface establishes a well-defined charge flow path and robust redox capabilities. Moreover, nano Pt confers the Bi2WO6/TiO2-Pt heterojunction with excellent peroxidase-mimic and catalase-mimic activities, facilitating interactions with endogenous H2O2 to produce the hydroxyl radicals and O2. It effectively alleviates tumor hypoxia and enhances ROS production. This results in significantly higher efficiency in sonodynamically induced ROS generation compared to pure TiO2 or binary Bi2WO6/TiO2 heterojunctions, as confirmed by DFT theoretical calculation and experiments with both in vitro and in vivo anticancer performance. This study offers valuable insights for designing high-performance Z-scheme sonosensitizer systems.

Monoclinic Silver Vanadate (Ag0.33V2O5) as a High-Capacity Stable Cathode Material for Aqueous Manganese Batteries.

Aqueous rechargeable metal batteries have recently garnered considerable attention owing to their low cost, sufficient capacity, and the use of non-flammable water-based electrolytes. Among them, manganese batteries are particularly favored because of their stability, abundance, affordability, and high energy density. Despite their advantages, Mn storage host structures remain underexplored. Therefore, developing innovative host materials is crucial for advancing this field. In this paper, the study reports for the first time, the use of Ag0.33V2O5 as a cathode material in aqueous manganese batteries. The study explains the displacement/intercalation behavior of manganese and silver using electrochemical, structural, and spectroscopic analyses. Additionally, it is shown that cation (Ag+, Mn2+, H+) diffusion pathways can be simulated using diffusion-barrier calculations. Finally, the study demonstrates high-performance manganese batteries that exhibit a remarkable reversible capacity of ≈261.9 mAhg-1 at a current of 0.1 Ag-1 and an excellent cycle retention of 69.1% after 2000 cycles at a current density of 1.5 A/g. The findings of this study contribute to the advancement of aqueous manganese battery technology, offering a promising pathway for developing safer, more cost-effective, and high-performance energy storage systems.

Revolutionizing Teacher Productivity: Unravelling the Secret of High-Performance Work System in Strategic Human Resource Management

High-performance work systems (HPWS) have been a topic of interest in various industries, but their impact on teachers’ productivity in Nigeria is a crucial area of study. The education sector in Nigeria faces numerous challenges, including inadequate resources, large class sizes, and limited professional development opportunities. In addressing the challenges, this research was conducted to seek their perception of the role of HPWS on teacher’s productivity. Data were collected from the six educational districts of public schools, among 492 teachers in Lagos, Nigeria. The data was analyzed using Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA). The findings provide new insights into the value of HPWS in SHRM in the education sector. The result showed that implementing high-performance work systems in this context could potentially lead to improved teacher productivity, benefiting both educators and students alike.

Enhancing water transportation capacity by asymmetrical patterned surface with super-wettability

Spontaneous and directional water droplet transportation based on patterned surface with super-wettability is crucial for the development of frontier science technology. However, water droplet transportation cannot meet both long distance and fast transportation simultaneously. Here, we overcame this limitation by proposing an asymmetric serial brachistochrone-shaped pattern (ASBP). Water droplet could be transported on the ASBP with a transportation distance of 72.52 mm and a transportation velocity of 158 mm/s after a series of single-factor experiments, orthogonal design optimization, and junction transition optimization. In addition, the water droplet could be transported on a curved ASBP, a super-long ASBP for multi-droplet scenarios, and an ASBP at an inclination angle. Moreover, acidic and alkaline aqueous solution droplet showed similar transportation distance and transportation velocity on the ASBP. Based on the aforementioned superb water transportation capacity, this ASBP can be applied in the fields of fog collection, solution mixing and reaction, and reagent detection. This work has strong implications for promoting the application of patterned surface with super-wettability in the field of high-performance fluid transportation systems.

Highly efficient and stable binary and ternary organic solar cells using polymerized nonfused ring electron acceptors.

This study reports the successful design and synthesis of two novel polymerized nonfused ring electron acceptors, P-2BTh and P-2BTh-F, derived from the high-performance nonfused ring electron acceptor, 2BTh-2F. Prepared via Stille polymerization, these polymers feature thiophene and fluorinated thiophene as π-bridge units. Notably, P-2BTh-F, with difluorothiophene as the π-bridge, exhibits a more planar backbone and red-shifted absorption spectrum compared with P-2BTh. When employed in organic solar cells (OSCs) with PBDB-T as the donor material, P-2BTh-F-based devices demonstrate an outstanding power conversion efficiency (PCE) of over 11%, exceeding the 8.7% achieved by P-2BTh-based devices. Furthermore, all-polymer solar cells utilizing PBDB-T:P-2BTh-F exhibit superior storage stability. Additionally, P-2BTh-F was explored as a functional additive in a high-performance binary system, enhancing stability while maintaining comparable PCE (19.45%). This strategy offers a cost-effective approach for fabricating highly efficient and stable binary and ternary organic solar cells, opening new horizons for cost-effective and durable solar cell development.

A Novel Solid State Polymer Electrolyte for All Solid State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) have gained enormous interest due to their potential high energy density, high performance, and inherent safety characteristics for advanced energy storage systems.1 Currently, solid-state ceramic (inorganic) electrolytes (SSCEs), solid-state polymer electrolytes (SSPEs), and a combination of the two (e.g., SSCE fillers in SSPEs) are being developed for ASSLBs.2 Although SSCEs have high ionic conductivity and high electrochemical stability,3 they experience some significant drawbacks, such as poor electrolyte/electrode interfacial properties and poor mechanical characteristics (brittle, fragile),4 which can hinder their adoption to commercialization. Typically, SSCE-based ASSLBs require high cell stack pressures exerted by heavy fixtures for regular operations, which can reduce the energy density of the overall battery packages.5 One promising solution to circumvent the aforementioned issues of SSCE-based ASSLBs is to develop SSPE-based AASLBs, since SSPEs can provide inherently good interfacial contacts with the electrodes that do not require high cell stack pressures. In addition, SSPEs are advantageous in making flexible batteries due to their elastic nature.6 In this study, a novel method was developed to prepare a high-performance SSPE-based ASSLB, where a π-conjugated polymer was incorporated into a baseline polymer backbone, resulting in an improvement in ionic conductivity, thermal stability, and electrochemical stability. The novel SSPE demonstrated a superior electrochemical performance than the baseline when used in ASSLBs. The strategy developed in this study may lead to a new direction for the research and development of next-generation SSPE-based ASSLBs.

High-Performance Optimised Porosity Iron Electrode for Hybrid Battery Electrolyzer

The growing demand for efficient, cost-effective and sustainable energy systems has prompted significant research into the development of advanced electrochemical devices. Hybrid battery electrolyzer, integrating the capabilities of both battery and electrolyzer, is a groundbreaking technology aiming to enhance both energy conversion efficiency and storage capacity. [1] Iron with large earth-abundance, low-cost, robustness, and high capacity is a promising electrode material for such hybrid energy systems. [2-4]This study focuses on the design, fabrication, and performance evaluation of a novel porous iron electrode tailored for use in a hybrid battery electrolyzer system. The proposed electrode exhibits superior electrocatalytic activity, enhanced mass transport properties, and increased surface area, contributing to improved overall performance. The electrode's porosity and pore structure are tuned to facilitate efficient mass transport and electrolyte penetration, addressing common challenges associated with conventional electrodes. The electrochemical performance of the optimised porosity iron electrode is investigated through comprehensive characterization techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and charge-discharge cycling tests. Results indicate superior electrochemical properties, showcasing enhanced specific capacity, faster charge/discharge kinetics, and prolonged cycle life compared to conventional electrodes. The incorporation of conducting nanocarbon and sintering at optimized temperature of 800 ℃ led to the achievement of a stable and elevated capacity exceeding 500 mAh/g for these advanced iron electrodes. The iron electrodes exhibit outstanding porosity (65 - 70%), along with a pore size of 5-10 µm. This configuration results in exceptional current rate performance, achieving a discharge capacity of 350 mAh/cm2 at a current density of 35 mA/cm2 and 245 mAh/cm2 at 50 mA/cm2. Furthermore, the iron electrodes exhibit superior performance in high-current electrolysis, showcasing an HER potential of -1.25, -1.34, and -1.50 V (vs Hg/HgO) at a current density of 200, 500 and 1000 mA/cm2 respectively.These findings highlight the potential of optimised porosity iron electrodes as a key component in the development of high-performance and cost-effective hybrid battery electrolyzer systems. The integration of such advanced materials holds promise for unlocking new frontiers in energy storage and green hydrogen technology, contributing to the realization of efficient and sustainable energy systems.

Phase Engineering of Two-Dimensional WS2 Nanostructures for Superior Hybrid Supercapacitors

Two-dimensional (2D) tungsten sulfide (WS2) has recently emerged as a nontrivial material for electrochemical applications; however, the boundaries associated with its 1T (instability) and 2H (low electrical conductivity) phases limit its electrochemical parameters. In this work, this issue is addressed using an exclusive chemical approach to evolve a dual-phase 1T-2H WS2 heterostructure that combines two different 1T (trigonal) and 2H (hexagonal) phases directly on the current collector which demonstrated 2D transformable phase structure, large interlayer distance, and highly exposed edge active sites. A simple inert-atmosphere annealing approach under phosphorus vapors is designed to elicit a fractional phase conversion of WS2 from conventional 2H to the 1T phase, where phosphorus is accommodated in the WS2 interspace and lattice, resulting in interlayer expansion. Theoretical calculations confirmed that the 1T WS2 structure formed after phosphorus doping exhibits semimetallic feature with no band gap, thereby elucidating the high electrical conductivity. The presence of edge-enriched metallic phase and interlayer engineering of 1T-2H WS2 heterostructure validates the exceptional sodium (Na+) ion intercalation when tested in hybrid supercapacitor (HSCs) against Prussian blue analog (PBA) cathodes. As a result, the assembled HSC cell with a 1T-2H WS2 heterostructured anode and a CuFe-PBA cathode shows superior specific energy of 65.5 Wh kg-1 at a specific power of 784 W kg-1, and maintains 75% rate capability and 95.7%cycling stability over 10,000 cycles. This work paves a technique for engineering a simple phase transition of 2D materials and sheds light on the expansion of high-performance next-generation energy storage systems.

RS-DFID Africa capacity-building initiative programme grant: harnessing unsteady phase-change heat exchange in high-performance concentrated solar power systems.

The Royal Society and UK Department for International Development supported a consortium of three universities across sub-Saharan Africa and Imperial College London with the aim of developing new knowledge on direct-steam-generation concentrated solar power (CSP) plants and supporting relevant capacity building across the Universities of Lagos, Mauritius and Pretoria. Key research findings from the programme include an improved flow-classification scheme for two-phase, liquid-liquid flows; testing of advanced surfaces with much-improved steady-state heat transfer performance-the commercial nanoFLUX surface showed up to 200% higher heat-transfer coefficients (HTCs) in pool boiling compared with other surfaces with R-134a/R-245fa; first-of-a-kind measurements of transient flow boiling HTCs, which were up to 30% lower in step perturbations than quasi-steady-state expectations in horizontal pipes with R-245fa; error estimation and corrections for laser-induced fluorescence (LIF) measurements, leading to the development of an adapted planar LIF technique with uncertainty <10% for local, instantaneous film thickness measurements in annular flows, and the application of such diagnostic methods to pool, falling-film and flow boiling in pipes; and predictions of an ~80% increase in the net present value of a case-study CSP plant when integrated with solid storage media.

(Invited) Influence of Y6 Aggregation on Energetics and Charge Generation in High Performance OPV Blends

We investigated the origin of the high ratio of open circuit voltage to charge transfer state energy (eVOC/ECT) of OPV polymer blends consisting of the electron donating polymer PM6 and the non-fullerene electron acceptor Y6. PM6-Y6 and related donor-acceptor OPV blends exhibit remarkable optoelectronic properties and record power conversion efficiencies in part because of their unusually high eVOC/ECT ratios, which is believed to be related to the small energetic offset of the HOMO levels of PM6 and Y6. In this study, we varied the amount of Y6 in PM6 blends as a means to control the aggregation of Y6 molecules. We examined the corresponding influence that Y6 aggregation has on the energetic offsets and the charge generation efficiency of the materials by probing the appearance of polaron absorption signals in the mid-infrared using time-resolved infrared spectroscopy. Furthermore, we examined the optical absorption and emission spectra of the PM6-Y6 blends over the range of compositions to correlate the efficiency of charge generation with the signatures of Y6 aggregation in the optical spectra. We observed an abrupt transition around 30 mass% Y6 content at which polarons were efficiently generated by charge separation from PM6 to Y6. Comparison to composition dependent GIWAXS studies of PM6-Y6 blends revealed the formation of Y6 aggregates around the same 30 mass% threshold. These observations demonstrate that aggregation of Y6 molecules is required for charge separation to occur from PM6 to Y6 as measured through the mid-infrared absorption of polarons in the TRIR spectra. Although charges were efficiently generated in blends with only 30 mass% Y6 content, OPV device studies revealed that 50-60 mass% Y6 was needed to reach optimized short-circuit current and OPV device efficiency because these measurements convolve charge generation with charge transport. These findings clarify the optoelectronic properties of the novel class of Y6 acceptors and emphasize the importance of molecular aggregation for tuning the energetics of high performance systems that minimize energy offsets for maximum OPV power conversion efficiencies.

High Performance and Predictable Shared Last-level Cache for Safety-Critical Systems

High Performance and Predictable Shared Last-level Cache for Safety-Critical Systems

Cold SegDiffusion: A novel diffusion model for medical image segmentation

Medical image segmentation is crucial in accurately identifying and delineating regions of interest in medical images, which can inform the diagnosis and treatment of various diseases. Therefore, developing high-performance computer-aided diagnosis systems for medical image segmentation has become a prominent focus within computer vision. With the development of deep learning, diffusion models have exhibited remarkable performance in medical image segmentation tasks. However, traditional segmentation diffusion models typically employ random Gaussian noise to generate segmentation masks, resulting in non-unique segmentation masks that fail to guarantee the reproducibility of segmentation results. To tackle this issue, this paper introduces a novel method, Cold SegDiffusion, for general medical image segmentation based on the diffusion model. In this method, medical image segmentation is conceptualized as a denoising problem. The segmentation masks covering medical images serve as input for the segmentation encoder, addressing the challenge of generating non-unique masks due to noise randomness. Additionally, the contrast enhancement module is designed to translate features into the frequency domain, addressing the issues of low contrast and boundary disappearance in medical images. Furthermore, the suggested conditional cross-attention module utilizes the conditional encoder and cross-attention weights to enhance important features of the segmentation encoder output, improving the network’s capacity to focus on target regions. The proposed method is validated across three medical image segmentation datasets with different modalities. Experimental results demonstrate that Cold SegDiffusion outperforms mainstream segmentation methods. The code is available at https://github.com/TimesXY/Cold-SegDiffusion.