Matching Characteristics Research Articles

Broadband and strong microwave absorption combining excellent EMI shielding of VGCF/carbonyl iron composites derived from synergistic magnetic and dielectric losses

As one of the most effective approaches to reduce microwave radiation in electromagnetic stealth and compatibility, broadband microwave absorbers have attracted widespread attention. However, it is challenging to maintain broadband absorption performance and maintain thin thickness simultaneously. Herein, by cooperating electromagnetic characteristics of vapor-grown carbon fiber (VGCF) and flaky carbonyl iron particles (CIP) to manipulate complex permittivity and complex permeability, a broadband metastructure absorber is proposed. The local conducting network composed of VGCF enriches the transmission path and greatly boosts dielectric loss capability of VGCF/CIP composites. The constructed VGCF/CIP reinforced metastructure absorber covered the 95% (−13 dB) absorption bandwidth in the full frequency band of 2–18 GHz at 8.4 mm thickness. The outstanding microwave absorption performance is benefit from the synergistic effect of magnetic-dielectric characteristics of the VGCF/CIP composite. The result provides a multi-resonant coupling mode to improve the overall impedance matching characteristics, which opens up a broad prospect for the development of ultra-wideband microwave absorbing materials. Moreover, VGCF/CIP composite shows a high electromagnetic interference (EMI) shielding effectiveness, and the excellent green shielding index (gs) of more than 10 indicates its potential application as an EMI shielding material.

Improving Law Enforcement and Emergency Response to Disabled Vehicle Crashes Using Waze Crowdsourced Data

Disabled and abandoned vehicles (DAVs) on limited access freeways are exposure risks that can result in congestion and crashes. Improving law enforcement response to DAVs can reduce their impact and potentially prevent some crashes from occurring. Crowdsourced data, such as Waze user alerts, can provide near real-time information on highway conditions, including the presence of DAVs. The challenge is effectively filtering the data so law enforcement can more efficiently respond to actual DAV incidents. In this paper, over 3.8 million Waze alerts and 329 DAV crashes on Florida limited access roadways from July 1, 2019, to December 31, 2020, were analyzed to determine appropriate matching parameters, characteristics, and potential benefits that could be provided by the Waze alerts. Evaluation of various spatiotemporal buffers to match Waze and crash data showed that buffers of 0.5 km (0.31 mi) and 30 min would provide the best matching. Using these buffers, 41 crashes were found to have matched Waze alerts. Analyses of these matched data showed that DAV Waze alerts would likely provide the most benefits during morning peak hours and on urban interstates. The earlier detection because of Waze alerts could have potentially allowed responders to reach 12 DAVs before a crash occurred. This earlier response could have potentially prevented over US$23 million in comprehensive crash costs. The results from this paper can be used to develop more efficient DAV response strategies using crowdsourced data, allowing law enforcement to better detect DAVs while keeping the number of alerts at a manageable level.

Research on a short-sleeper type ballastless-track that can adapt to large foundation deformation

Settlement and arch deformation on the ballastless-track foundation during rail transit operations pose challenges to the existing track structure, which can only accommodate up to 30 mm of foundation deformation through the replacement of fastener adjusting pads. These limitations result in prolonged remediation cycles, increased expenses, and disruptions to train runs. To address these issues, a height-adjustable short-sleeper ballastless-track structure is proposed. Using the vehicle-track coupled dynamics theory and FEM, this study investigates the geometric matching characteristics, modal behavior of the track structure and their impact on the dynamics performance of the vehicle and track system when the HSBS structure is adjusted to 200 mm. Findings demonstrate that the ballastless-track can easily adjust the height by modifying the thickness of pads or replacing the short sleepers, enabling effective adaptation to substantial track foundation deformation with an adjustment capacity exceeding 200 mm. Importantly, the vibration mode and natural frequency of the short sleeper remain unchanged before and after lifting the track structure. Under the condition of unchanged support stiffness, the stability of the track structure, as well as the safety and smooth performance of the vehicle, are maintained at the same level as before the height adjustment.

Influence of Variable-Geometry Adjustment on the Matching Characteristics of a Medium Variable Bypass Ratio Compression System

The research is based on a full 3D model of a medium variable bypass ratio compression system. The effects of core-driven fan stage (CDFS) VIGV adjustment and forward variable area bypass injector (FVABI) adjustment on the internal flow and component matching characteristics of the compression system during the mode transition process are investigated. The findings of the study reveal that during the mode transition period, the adjustment of variable-geometry components has a negligible impact on the aerodynamic performance of the fan. The closure of the CDFS VIGV has a significant effect on reducing the pressure ratio of the CDFS but only a minor effect on its efficiency. Additionally, the efficiency and pressure ratio of the high-pressure compressor (HPC) increase with the closure of the CDFS VIGV, particularly the second stage of the HPC. When the CDFS VIGV is closed by 30°, the efficiency of the second stage of the HPC increases by 3.4%, while that of the first stage only increases by 3.1%. Under the high bypass mode, increasing the FVABI opening will move the matching point of the CDFS towards the choke boundary. When the FVABI opening increases from 0.30 to 0.58, the efficiency of the CDFS decreases by 3.6%, while the efficiency of the HPC only increases by 0.4%. In summary, closing the CDFS VIGV and increasing the opening of the FVABI will increase the bypass ratio of the compression system, and the former has a more significant impact. When the compression system transitions from the low bypass mode to the high bypass mode, opening of the FVABI should be appropriately reduced to prevent CDFS matching in the operating condition too closely to the choke boundary, thereby maintaining the efficiency of each component of the compression system at a relatively high level.

Unpacking the Racial Gap: Helicobacter pylori Infection Clearance Among Different Racial Groups.

Introduction Helicobacter pylori (H. pylori) is a bacteria causing chronic stomach infections, influenced by various factors, including host traits and bacterial virulence. It uses both urease-dependent and independent mechanisms to survive acidic gastric environments. Management entails diagnosis, treatment, and eradication verification. Combining drugs is key to overcoming resistance and ensuring bacteria elimination, thus preventing recurrence and complications. H. Pylori eradication mitigates gastric cancer risk and alleviates symptoms. Racial disparities persist despite declining H. pylori and gastric cancer incidence in the United States (US). African Americans (AA) have higher gastric cancer risks than non-Hispanic Whites. Addressing these disparities is crucial to protect high-risk populations. Methods This study retrospectively compiled H. pylori infection data from 2009 to 2022, categorized by race. Propensity score matching balanced initial group characteristics before analysis. Chi-squared and odds ratio tests were used on the cohort, with Kaplan Meier and Log Rank methods evaluating disease clearance in ethnic groups. Data were extracted from the Sunrise Electronic Medical Record software, including patient demographics, health details, and treatment specifics. Patients aged 18-65 with H. pylori infection at Nassau University Medical Center, who followed their treatment, were selected. Data were processed using Statistical Package for the Social Sciences (SPSS) and RStudio software. Results The study initially included 10,040 H. pylori-diagnosed patients, with 9,288 meeting the study's criteria after attrition. Predominantly female (64.7%), the cohort was racially diverse. A longer disease clearance time was noted among Hispanics (p=0.044). Binomial logistic regression analysis identified influential factors like high school graduation rates, poverty level income, and language proficiency on disease clearance. An odds ratio analysis further emphasized language barriers (HR 0.346, p=0.043) and education status (HR 0.756, p=0.025) as primary covariates impacting disease clearance, underlining the role of socio-economic factors and language proficiency in health outcomes. Conclusion The study highlights racial disparities in H. pylori clearance rates, particularly among Hispanics, necessitating culturally sensitive interventions. It advocates for improved diagnostics, increased healthcare access, and social determinants of health-focused initiatives. It identifies socio-economic status and language proficiency as key factors impacting health outcomes, calling for actions to bridge these disparities. Addressing these differences can decrease healthcare inequalities and economic burden, improving overall health outcomes and reducing costs associated with H. pylori clearance.

Performance comparison of semi‐conductive shielding layer for high‐voltage cable based on polypropylene and low density polyethylene resin

AbstractWith the concept of environmental protection is deeply popular, the power cables change from traditional thermosetting cross‐linked polyethylene (XLPE) cables to low‐carbon, environmentally friendly, recyclable polypropylene (PP) cables and the semi‐conductive shielding layer that matches the insulation layer for PP cables is highly valued. In this paper, LDPE is replaced with PP in the formulation of shielding layer of commercial XLPE cables. The physicochemical and electrical properties of PP/EVA/CB (PP‐based) and LDPE/EVA/CB (LDPE‐based) shielding layers were compared. The effect of interface matching characteristics on the electric field distortion was analyzed by finite element simulation software. The experimental results show that the volume resistivity of the shielding layers all tend to rise with the increasing temperature, but the resistivity of the PP‐based shielding layer has a smaller fluctuation. The PP‐based shielding layer has a smoother surface, while the space charge injected into the PP insulation layer is the lowest, about 0.433 × 10−7 C. Compared to the LDPE‐based shielding layer/insulation layer, the PP‐based shielding layer/insulation layer has a 50% reduction in interfacial electric field distortion rate. This work is an essential reference for the development for PP cables and their shielding layer selection.

Amorphism SiBON interface anchored rGO nanoplatelets composites with tunable electromagnetic properties for microwave absorption

Benefiting from a particular ceramic/graphene interface anchored structure, SiBON/reduced graphene oxide nanoplatelets (RGNPs) composite was successfully designed. The electromagnetic wave is smoothly introduced into the composite from the outer layer composed of wave transmission ceramics and attenuated from the inner RGNPs layer, which solves the high impedance matching characteristic of RGNPs. With high-performance electromagnetic absorption, the composites are synthesized by an innovative chemical grafting method, and its absorbing mechanism is discussed. The SiO2 (110) lattice plane is oriented to the edge of RGNPs using the preferred orientation when forming SiBON ceramic. A composite structure is formed with SiBON as external antenna poles and RGNPs as internal signal processors. The interaction between different dielectric loss mechanism balances is achieved by adjusting the content of the ceramic. Results prove that the composite has the best electromagnetic wave absorption performance, when the mass ratio of SiBON ceramics to RGNPs is 1:10, and the filling amount is 20 wt%, forming a broad absorption band (4.80 GHz, 12.88 GHz–17.68 GHz). When the mass ratio of SiBON ceramics to RGNPs is 1:40, the maximum reflection loss is −50.43 dB (13.44 GHz) at a small thickness (1.7 mm).

Improved microwave absorption properties of ferrite-rGO composites by covalent bond

In this work, to investigate the effect of electron motion mode on the microwave absorption performance, ferrite Fe3O4 and graphene oxide (GO) were united by covalent bonding and subsequent reduction to fabricate microwave absorbing material (MAM) with excellent impedance matching characteristics and superb attenuation ability. Under the synergistic effect of the magnetic and dielectric properties, the Fe3O4-rGO hybrid nanocomposites present high absorption performance. Its minimum reflection loss (RLmin) reached –47.46 dB when the thickness was 3.5 mm. The effective absorption bandwidth (EAB) was 5.86 GHz when the thickness was only 2.0 mm. XPS and FT-IR spectroscopy indicate the formation of amide bonds between the modified Fe3O4 and functional GO. SEM, EDS, TEM and Raman spectroscopy were used to analyze the morphology and structure of the hybrid nanocomposites. The effects of bonding modes and component fractions on the electron motion and the resulting impedance matching of the hybrid nanocomposites were discussed.

Summary of Turbocharging as a Waste Heat Recovery System for a Variable Altitude Internal Combustion Engine.

The increase in altitude causes the decrease in internal combustion engine power and the increase in pollutant emission. Converting waste heat into more useful forms of energy through the recovery of waste heat from internal combustion engines is the most promising mechanism for improving both of these goals. This paper comprehensively reviews the development and research of waste heat recovery technology of an internal combustion engine in a variable altitude environment. It is found that exhaust gas turbocharging is the most promising waste heat recovery technology to restore high-altitude internal combustion engine power. Turbochargers are affected by low temperature and low pressure at high altitudes, resulting in poor environmental adaptability, inadequate supercharging ratios, and decreased supercharging efficiency. Therefore, it is very important to select the high pressurization system facing the plateau area and its reasonable matching characteristics. The quality of exhaust energy determines how much waste heat a turbine can recover, and only the exergy part of exhaust energy can realize heat/work conversion. The main disadvantage of turbocharging technology applied in the plateau area is that the speed ratio deviates from the design value, leading to the increase of flow loss inside the supercharger. Therefore, optimizing the internal flow field of a high-altitude supercharger is a key problem to improve the efficiency of energy recovery. The conclusion drawn from this Review is that a two-stage turbocharging system will be a key technology to improve the thermal efficiency and reduce the fuel consumption of high-altitude internal combustion engines in the coming decades. In addition, the efficient utilization of the exhaust energy of the two-stage turbine and the influence of the variable compression process of the two-stage compressor on the working medium in the cylinder will be the focus of future research.

Design of Flexible Multi-Band Miniature Antenna Based on Minkowski Fractal Structure and Folding Technique for Miniature Wireless Transmission System

In light of the predicament concerning the small gain and narrow frequency range of miniature antennas, this paper employs the implementation of a fractal repeating array structure and a double-layer folding antenna structure. Through these measures, the miniature antenna is endowed with a high gain and an expansive frequency range, all within its diminutive size. The paper presents an exquisite and high-gain flexible multi-band antenna, utilizing a dielectric substrate composed of the flexible material polyimide, with a thickness of merely 0.1 mm. The implementation of this flexible material bestows a feathery mass of merely 4 mg upon the antenna, enabling it to seamlessly conform to various shapes. This makes it particularly well-suited for employment within miniature wireless transmission systems and compact mobile communication devices. In an endeavor to enhance impedance matching and radiation characteristics, the Minkowski fractal structure is ingeniously incorporated as the repeating array element. This repeating array structure assumes a pivotal role and, when combined with the double-layer folding antenna structure, achieves the objective of miniaturization. Remarkably, the antenna’s dimensions measure a mere 0.04 λ0 × 0.026 λ0 (λ0 @ 2.4 GHz). The proposed antenna boasts a remarkably diminutive volume of merely 5 × 3 × 0.1 mm3, with the measured and simulated results exhibiting a striking concurrence. Both sets of results demonstrate resonance across multiple frequencies, namely, 2.4 GHz, 5.2 GHz and 5.8 GHz. Furthermore, within the effective frequency range, the antenna attains a maximum gain of 1.65 dBi and 4.37 dBi, respectively.

Sub-axillary cosmetic incision versus single-incision thoracoscopic surgery for primary spontaneous pneumothorax

BackgroundIn recent years, single-incision thoracoscopic surgery (SITS) has been increasingly applied as an optimal treatment option for primary spontaneous pneumothorax (PSP). However, most SITS techniques are used in the fourth to sixth intercostal space between the anterior axillary and mid axillary lines. To find out more concealed incisions, this study performed PSP surgery via the sub-axillary cosmetic incision (SACI) technique.MethodsA total of 128 PSP patients were subjected to video-assisted thoracoscopic surgery (VATS) between January 2017 and January 2019 at our institution. These patients were evaluated and assigned into SACI (n = 21) and SITS (n = 57) groups. Propensity score matching (PSM) was performed based on patients’ backgrounds, and the enrolled cohort was divided into 21 pairs. The incision satisfaction was assessed at 2 weeks and 6 months post-surgery.ResultsThe 21 pairs with matching baseline characteristics in the two groups did not exhibit significant differences in their backgrounds and surgical results. However, compared with the SITS group, the operation time was longer in the SACI group (p = 0.013). There were no post-operative complications in both groups. At 2 weeks and 6 months, incision satisfaction scores in the SACI group were significantly lower than those in the SITS group (p = 0.022 and p = 0.039, respectively). There were no recurrences of ipsilateral pneumothorax in both groups.ConclusionsSACI is a safe and feasible surgical method for PSP treatment. In addition, incision concealment can be used for patients with incision needs.

Energy saving and carbon emission reduction potential for cold store with new dynamic linkage control strategy

Management optimization is economical and effective to reduce energy consumption and carbon emission for cold stores in service, needing more appropriate control strategy. The state of different components of refrigeration system affects each other, which indicates control strategies based on matching characteristics are essential. This study compared the operating data before and after control upgrade for an actual cold store that had the ability to adjust capacity stage. To better evaluate the input-output ability of air coolers, a new parameter, cooling efficiency, was calculated to represent their refrigeration per power consumption. New control strategy based on the matching operation of compressors and air coolers was put forward as dynamic linkage control strategy (DICS) with real-time flow rate and refrigeration capacity calculation to improve system efficiency. Through system control optimization, the coefficient of performance (COP) of the refrigeration system was increased by 29%, and the cooling efficiency of the air coolers (CEAC) was increased by 37%. The average power consumption decreased by 21.15%, and carbon emission was reduced by 320.840 tonnes at a decreasing rate of 19.95% per year for the whole cold store.

Interspecies comparison of temporomandibular joint condylar cartilage extracellular matrix from macro to microscopy

Interspecies comparisons of the extracellular matrix of temporomandibular joint (TMJ) condylar cartilage are necessary to elucidate the mechanisms underlying its superior mechanical properties, to guide the construction of animal models of TMJ-related diseases, and to establish standards for the engineering of TMJ condylar cartilage. Here we characterize and compare TMJ condylar cartilage from six different species from a materials science perspective, including structure, composition and mechanical properties from the macroscopic to the microscopic level. The gross morphology showed obvious interspecies differences in size and shape, which may be related to the different joint motion patterns. Although the condylar cartilage of all species can be divided histologically into a superficial fibrous layer and a deep hyaline layer, there are significant interspecies differences in the microstructure of the fibrils in the two layers, mainly in the diameter of the fibrils. Compositionally, there were no significant differences in collagen composition between species, but the content of glycosaminoglycans (GAGs) decreased progressively with increasing body size, with the same results obtained by Safranin O staining and biochemical analysis. Mechanically, the elastic modulus of mouse condylar cartilage was significantly higher than that of the other species and tended to decrease with increasing body size. This study shows that the TMJ condylar cartilage of different species has its own specific structure-composition-mechanics matching characteristics for their unique masticatory stress dissipation, and differences in fibril diameter and GAGs content may be the two ultimate factors influencing the differences in cartilage mechanical properties between species, while the condylar cartilage of pigs is most similar to that of humans, suggesting that pigs may be a suitable animal model for TMJ studies.

Enhanced electromagnetic wave absorption performance of multiphase (TiC/TiO2/C)/SiOC composites with unique microstructures

Incorporating multiphases can not only increase the attenuation capacity but also partially alleviate impedance mismatch. In this work, (TiC/TiO2/C)/SiOC composites were prepared from polymer-derived ceramics (PDCs) using a TiC nanoparticle modified polysiloxane (PSO) precursor at 900 °C under an Ar flow. The addition of TiC serves a dual purpose of enhancing conductivity loss and acting as a source of Ti for the generation of TiO2 particles. The combination of these particles with the carbon layer in amorphous SiOC creates a multiphase loss medium that significantly improves not only conductive loss and dipole polarization loss but also interface polarization loss, resulting in excellent impedance matching characteristics and EM wave absorption. Accordingly, the (TiC/TiO2/C)/SiOC with a TiC fraction of 20 wt% indicated a significant minimum reflection loss (RLmin) of −54.2 dB (over 99.999% absorption), and the effective absorption bandwidth (EAB) covered 4.2 GHz with a thickness ranging from 2.5 to 3.3 mm in the X band. A maximum radar cross section (RCS) reduction of 24.6 dBm2 was achieved at a scattering angle of 75°. Thus, the (TiC/TiO2/C)/SiOC composites have the potential to be utilized in radar stealth technology and reduce EM pollution, offering a novel approach to address these challenges.

Rock recognition and identification for selective mechanical mining: a self-adaptive artificial neural network approach

In situ characterisation of rock is crucial for mine planning and design. Recent developments in machine learning (ML) have enabled the whole learning, reasoning, and decision-making process to be more efficient and accurate. Despite these developments, the application of ML in rock-cutting is at an early stage due to the lack of mining applications of mechanised excavation leading to limited availability of data sets and the lack of the expert knowledge required when fine-tuning models. This study presents a novel approach for rock identification during mechanical mining by applying a self-adaptive artificial neural network (ANN) model to classify the rock types for selective cutting, in which datasets from two novel cutting operations (actuated disc cutting (ADC) and oscillating disc cutting (ODC)) were employed to test and train a model. The model was also configured with the Bayesian optimization algorithm to determine optimal hyperparameters in an automated manner. By comparing the performance of each evaluation, the model was trained to identify the best set of hypermeters at which uncertainty is minimal. Further testing indicated the model is very accurate in classifying rock types for ADC as the accuracy, recall, and precision all equal unity. Some misclassifications occurred for ODC with the accuracy, recall, and precision ranging from 0.68 to 0.99. The promising results proved the model is a robust and scalable tool for classifying the rock types for selective cutting operations enabling the interpretation to be performed more precisely, selectively, and efficiently. Since mechanical cutting requires significant energy, any improvement in matching machine characteristics to the rock mass will increase productivity, and energy efficiency and reduce cost.

Hydrangea-like N-doped Carbon/MoO2@SnS2 microspheres with Schottky contact: A multi-interface heterostructure for high-performance microwave absorption

Heterointerface engineering is now recognized as a powerful strategy to optimize the microwave absorption performance of dielectric materials through composition adjustment and structural design. Herein, a hydrangea-like N-doped Carbon/MoO2@SnS2 (NC/MoO2@SnS2) composite was successfully prepared by high-temperature pyrolysis and oil bath treatment. The surface of each NC/MoO2 microsphere was vertically covered with interconnected SnS2 nanosheets, forming a porous core-shell morphology. We found that the number of heterojunctions and the proportion of high-lossy phases played a decisive role in optimizing the electromagnetic parameters. By regulating the content of dielectric phases, the optimized NC/MoO2@SnS2 (S3 sample) displayed a minimum reflection loss (RLmin) of −75.0 dB at an ultrathin thickness of 1.41 mm and a wide EAB of 4.2 GHz at 1.53 mm. The enhanced microwave absorption was mainly ascribed to multiple polarization relaxation, multi-interface reflection and good impedance matching characteristics produced by this semiconductor/carbon heterostructure with dual Schottky barriers. Therefore, this work provided a feasible strategy for making full use of heterointerface engineering to design ternary semiconductor/carbon heterostructures as high-performance dielectric MAMs.

Polarization-insensitive composite gradient-index metasurface array for microwave power reception

A composite gradient-index metasurface (C-GM) array for microwave power reception (MPR) operating at 5.8 GHz center frequency was introduced. The array is insensitive to the polarization of incident plane waves and possesses cosine gradient modulation characteristics, which can convert the incident plane waves into surface waves focused at the center of the array. The focused surface wave energy is then collected by an omnidirectional antenna and fed back to a single rectifier for radio frequency (RF) to direct current (DC) conversion, resulting in DC output. Simulation results show that the array can fully excite surface waves under different polarized plane wave excitations, and the omnidirectional antenna has good matching characteristics with the array, achieving an energy collection efficiency of 66.52%. The array was fabricated and measured, achieving an energy reception efficiency of 59.91% and an RF-DC conversion efficiency of 34.83%, which is consistent with the simulation results. The proposed C-GM array can capture higher electromagnetic power by simply increasing its size, without the need for additional rectifiers or complex matching networks, making it a flexible and efficient MPR solution for different application scenarios.

Thermal matching characteristics in an autothermal methanol reforming microchannel reactor for hydrogen production

To ensure efficient operation of an onboard hydrogen production reactor, it is essential to synchronize heat generation and consumption in the channels. A computational fluid dynamics study is conducted to simulate a base case of the microchannel reactor that couples hydrogen catalytic combustion with methanol steam reforming in response to this problem. Our results show poor thermal matching of the reactor under the base case, with hydrogen combustion concentrated in the first half of the channel, creating a hot spot (796.09 K) and incomplete catalyst utilization (89% and 60% for reforming and combustion, respectively). Compared to the base case, when reducing the combustion side’s pre-exponential factors to 1.5×106, the local hot spots are eliminated, and the catalysts in the reforming and combustion channels are fully utilized. Furthermore, the maximum temperature of the reactor decreases to 691 K, producing more hydrogen while less hazardous carbon monoxide.

Dataset dependency of low-density lipoprotein-cholesterol estimation by machine learning.

We evaluated the applicability of a machine learning-based low-density lipoprotein-cholesterol (LDL-C) estimation method and the influence of the characteristics of the training datasets. Three training datasets were chosen from training datasets: health check-up participants at the Resource Center for Health Science (N = 2664), clinical patients at Gifu University Hospital (N = 7409), and clinical patients at Fujita Health University Hospital (N = 14,842). Nine different machine learning models were constructed through hyperparameter tuning and 10-fold cross-validation. Another test dataset of another 3711 clinical patients at Fujita Health University Hospital was selected as the test set used for comparing and validating the model against the Friedewald formula and the Martin method. The coefficients of determination of the models trained on the health check-up dataset produced coefficients of determination that were equal to or inferior to those of the Martin method. In contrast, the coefficients of determination of several models trained on clinical patients exceeded those of the Martin method. The means of the differences and the convergences to the direct method were higher for the models trained on the clinical patients' dataset than for those trained on the health check-up participants' dataset. The models trained on the latter dataset tended to overestimate the 2019 ESC/EAS Guideline for LDL-cholesterol classification. Although machine learning models provide valuable method for LDL-C estimates, they should be trained on datasets with matched characteristics. The versatility of machine learning methods is another important consideration.

Robust and thermostable C/SiOC composite aerogel for efficient microwave absorption, thermal insulation and flame retardancy

Carbon aerogel (CA) has been generally regarded as a potential electromagnetic wave (EMW) absorber, but unsatisfactory microwave absorption, mechanical and anti-oxidation properties are still the primary challenges for its application. Herein, a novel C/SiOC composite aerogel (CSA) was successfully synthesized by a simple copolymerization of dual sols, ambient pressure drying and thermal treatment process for the first time. The morphology and performance of the as-prepared CSA could be tailored just by controlling the initial ratio of silane and phenolic resin (PR) to adjust the content of SiOC in CSA, whose density was in the range of 0.252 to 0.294 g·cm−3 with a low thermal conductivity from 0.061 to 0.067 W·m−1·K−1. Notably, the EMW absorption capacity of CSA was greatly enhanced with the increase of SiOC content, with the optimal reflection loss (RL) value of −67.85 dB and effective absorption bandwidth (EAB) of 6.88 GHz, which was dramatically improved than CA (–22.89 dB, 5.34 GHz) and mainly ascribed to the optimized impedance matching characteristics and strong attenuation capacity. Meanwhile, compared with CA (2.63 MPa) with a density of 0.248 g·cm−3, the mechanical properties of CSA (3.30–5.12 MPa) were also remarkably improved, and the maximum compression strength was nearly doubled. Furthermore, CSA obtained superior oxidation resistance than CA and exhibited excellent flame-retardant properties. All the results indicated that CSA could be considered as a highly promising candidate for applications in extreme environments due to its lightweight, high strength and outstanding microwave absorption capacity along with good oxidation resistance, superior thermal insulation performance and high flame retardancy.