Specificity Values Research Articles

Real-time FPGA Integration for ECG Monitoring: Bidirectional Recurrent Chimp Search Model

The primary diagnostic tool for monitoring problems with the heart or related diseases is the electrocardiogram (ECG). The rising mortality rate caused by cardiac abnormalities leads to the development of more advanced techniques to detect heart anomalies are is of paramount importance. An electrocardiogram (ECG) is used for multiple diagnostic purposes since it produces continuous tracings of the electrophysiological activity generated from the heart. This paper developed a Bidirectional recurrent chimp search (Bi-RCS) method for diagnosing abnormalities by collecting ECG signals via various phases such as the data acquisition phase, signal processing phase, feature extraction phase, abnormality detection phase, real-time FPGA integration phase, monitoring and reporting phase as well as feedback phase. Signal pre-processing removes contaminants like noise using the Adaptive filtering methodology which severely limits the utility of the recorded ECG for better clinical evaluation. Bi-RNN is utilized for extracting related features and detecting abnormalities and the Chimp search optimization is employed to tune the parameters of Bi-RNN. After detecting the abnormalities, the reports of patients are monitored and recorded to provide an alert signal to healthcare providers. Finally, the potency of the methodology is analyzed with the ECG signal dataset and metrics like precision, F1-score accuracy, sensitivity, and specificity values. The obtained outputs equalized with the existing methods like KNN, EBT, and SVM. The analysis showed convincing performance with an accuracy of 99% and less error rate of 0.05.

Fuzzy cognitive maps for municipal governance improvement.

This paper applies Fuzzy Cognitive Maps (FCMs) to understand the diverse behavior of municipal governments in Ecuador to find common elements that influence the well-being of citizens in the short and long term. Information gathering was conducted in two stages: in the first one, a group of 16 national experts was consulted to develop the initial FCM; in the second stage, local experts from 220 municipalities were interviewed to collect information on the general validity of initial FCMs and specific values given to concepts and relationships in their municipalities. Results show the importance of certain concepts for long-term municipal performance, such as the need for a competitive entrepreneurial sector, improving human resources in the municipality, and, particularly, having a competent mayor with leadership skills and a forward-looking vision that enables the development of municipal projects required to reach an efficient and equitable coverage of goods and services throughout the city. Through the application of genetic algorithms, the FCM was calibrated to ascertain the long-term dynamics of municipal development and the optimal values of the concepts that would optimize the attainment of the set objectives. The derived outcomes suggest the desirability of the maintenance of, in principle, unwanted structures like financial transfers from the central government and the need to exploit natural resources to attain urban development.

Evaluation of CLINITEST® Rapid Covid-19 + Influenza antigen test in a cohort of symptomatic patients in an emergency department.

Rapid management of patients with respiratory tract infections in hospital emergency departments is one of the main objectives since the concurrent circulation of respiratory viruses following the SARS-CoV-2 pandemic. The use of new combined point-of-care antigen tests for detecting influenza A/B and SARS-CoV-2 represents an advantage in response time over the molecular tests. The objective was to evaluate the suitability of the CLINITEST® Rapid Covid-19 + Influenza Antigen test (Siemens Healthineers, Germany) (RCIA test) by measuring the sensitivity, specificity, Cohen's kappa, and cut-off values. Nasopharyngeal samples were collected from a randomised group of symptomatic patients of all ages at emergency department during January-February 2023. In parallel, these patients were screened for influenza A/B, and SARS-CoV-2 using RT-PCR. The Ct (cycle threshold) values were collected for positive [RT-PCR (+) /RCIA test (+)] and false negative [(RT-PCR (+) /RCIA test (-)] samples. A subanalysis was performed in the paediatric population (< 16 years-old). We included 545 patients (55.8% females) with a median age of 7 years-old (IQR: 1-66.5). The RCIA test showed a sensitivity of 59.7% [95%CI: 46.9-67.33] for influenza A, 65.6% [95%CI: 49.5-80.3] for influenza B, and 76.9% [95%CI: 45.8-84.8] for SARS-CoV-2. The specificity was between 90.7%-99.7% with a moderate/high level of agreement with RT-PCR (kappa score: 0.6-0.8) for the three respiratory viruses included in the RCIA test. The sensitivity of the RCIA test is insufficient for screening of patients, including patients with low Ct values (Ct > 20). Despite its good specificity and Cohen's kappa value, its use as a screening test is not comparable to RT-PCR systems in the ED environment with a high number of false negative results.

Phytochemical profiling of Striga asiatica; characterisation and anti-microbial assessment of the isolates

One undescribed compound, striasinol (1), and twelve previously described compounds were isolated from the aerial parts of Striga asiatica. Structure elucidation of isolated compounds was achieved by the interpretation of 1D and 2D NMR and HRESIMS data. The absolute configuration (1S,5S) of 1 was ascertained based on GIAO NMR calculations, DP4+ probability analysis, and a comparison of the experimental and calculated specific rotation values. The isolated compounds were evaluated for their antimalarial action, and none was found to be effective against the chloroquine-sensitive (D6) or chloroquine-resistant (W2) strains of Plasmodium falciparum. The isolates were found non-toxic to the Vero cell line as well. Subsequent testing of these metabolites for antimicrobial activities against various bacterial and fungal strains (up to 20 µg/mL), revealed that compounds 6 (chryseriol) and 7 (apigenin) showed a reasonable activity towards methicillin-resistant Staphylococcus aureus ATCC 1708 (MRSA), with IC50 values of 5.81 and 3.60 μg/mL, respectively.

Switching in quantum networks: an optimization investigation

Quantum key distribution (QKD) promises information theoretic security. However, the distances over which complete security can be achieved are fundamentally limited in the absence of quantum repeaters. Thus, a key question is how to build a quantum network (QN) given this restriction. One paradigm that has been considered is trusted node (TN) quantum networks where intermediate trusted nodes are used as relays of quantum keys. Another paradigm is to route key channels through intermediate nodes optically, either through wavelength or fiber switching, thus avoiding the use of TNs. In both of these paradigms, a QKD receiver or transmitter at a specific node can be shared between multiple QKD transmitters or receivers at different nodes in order to reduce the overall costs; this sharing can be enabled via an optical switch. In this paper, we investigate the two paradigms for designing QNs. In the TN model we assume the Decoy BB84 protocol, whereas in the non-TN model, we employ twin-field QKD (TF-QKD) due to the increased single hop distances. We present mixed integer linear program models to optimize network design in both of these paradigms and use these to investigate the viability of switching in the network models as a method of sharing devices. We show that sharing of devices can provide cost reduction in QNs up to a certain transmission requirement rate between users in the TN model, while also providing benefits even at significantly higher transmission requirements in the TF-QKD model. The specific value of this rate is dependent on the network graph; however, for mesh topology TN networks this is expected to occur at average key transmission requirements of ∼1000−5000bits/s. We further use the models to investigate the effects of different network parameters, such as cooling costs, switch frequency, and device costs. We show that cooled detectors are useful in large TF-QKD networks, despite higher costs, but are only useful in TN networks when transmission requirements are very high or cooling is cheap. We also investigate how network costs vary with switching frequency and switch loss, showing that compromising for slightly faster switching times and higher loss switches does not significantly increase network costs; thus a significant effort in improving switch loss may not be necessary. Finally, we look at how the benefits of sharing devices change as the cost of devices changes, showing that for any non-negligible device cost, device sharing is always beneficial at low transmission requirements.

Overview of the catalytic properties of bulk unsupported and supported group 4–5-6 oxides

The number of active sites (Ns), surface chemistry (redox, acid, base) and TOF values were compared for bulk one component oxides, bulk mixed metal oxides and supported metal oxides. The number of active sites was based on CH3OH chemisorption. The surface chemistry was based on CH3OH-TPSR and steady state CH3OH oxidation. The specific TOF values were based on the steady state methanol oxidation activity values and Ns values. The Ns values were found to depend on the catalyst morphology (isotropic > anisotropic). The surface chemistry was found to dramatically depend on the specific metal oxide element. For supported bulk mixed metal molybdates, the surfaces were found to be dominated by segregation of MoOx and, consequently, the surface chemistry and TOFredox values were dominated by the characteristics of the bulk one component MoO3. Similarly, for the supported molybdenum oxide catalysts, the surface is dominated by the surface MoOx sites that dictate the surface chemistry and TOFredox values that reflect the surface chemistry and TOFredox of the bulk one component MoO3. Thus, it is possible to predict the surface chemistry and TOF values from knowledge of the surface composition of mixed oxides and the surface chemistry and TOF values of the bulk one component oxides. This conclusion should also hold for other types of mixed oxides such as polyoxometalates (POMs) and supported MOx/silicates and MOx/zeolite catalyst systems.

Estimation of Infiltration Parameters: The Role of Pedotransfer Functions and Initial Moisture Conditions

Infiltration is one of the key components of rainfall-runoff processes at small catchment scale and is therefore a vital component of hydrological models. However, small catchments typically lack direct infiltration measurements and associated soil hydraulic characteristics, which are being substituted with soil databases and pedotransfer functions built upon these databases. We utilized two sets of pedotransfer functions Rosetta 3 and EUPTFv2 derived from two well known soil databases: UNSODA, based on US and global soil data, and EU-HYDI, based on EU soil data. Our study evaluates the impact of choosing one of these pedotransfer functions on modeled infiltration in relation to variable initial moisture content- It investigates the behavior of the simplified infiltration models of Green-Ampt and Philip under different initial conditions, in comparison with Richards’ complex solution, which is used as a benchmark. Our evaluation was conducted using soil property data available in the Czech Republic, covering ten USDA soil textures that are prevalent within the European Union. The applied initial moisture conditions were derived for specific suction pressure values that correspond to hydrological initial conditions ranging from near saturation to near the permanent wilting point. Variation in the derived parameters for the Green-Ampt and Philip models across the pedotransfer function sources results in considerable variation in the modeled infiltration. Our results imply different sensitivities of the simplified infiltration models to the initial moisture for different pedotransfer functions. The Green-Ampt and Philip infiltration models demonstrate better alignment with Richards’ complex solution with a low and consistent RMSE when using the Rosetta 3 pedotransfer function. By contrast, the EUPTFv2 model scenarios, show a clear trend of increasing RMSE towards dry initial conditions. As the European soil database is not an open data source, we only hypothesize that the distributions of soil characteristics in the European soil database differ systematically from those in UNSODA, and that this would cause different results of pedotransfer functions for different initial moisture conditions. The findings of this study are important for selecting appropriate infiltration models and, appropriate pedotransfer functions for estimating model parameters, and for assessing uncertainties connected with varying initial conditions.

Characteristics physical and chemical properties of fuel from plastic waste for mineral water glasses

This research aims to convert plastic waste, especially plastic cups for packaging mineral water, into fuel oil through a pyrolysis process. The experimental method used is with the following stages: first, 1kg of plastic raw material is chopped before being put into a pyrolysis tube. Next, the tube is heated to change the plastic into a liquid form which then evaporates. The hot steam from this plastic is channeled to a heat exchanger to be condensed. Cooling is carried out using water flowing in the opposite direction to the direction of the steam. The results of plastic vapor condensation are collected to analyze their physical and chemical properties. Testing of physical and chemical properties includes specific gravity, heating value, kinematic viscosity, flash point, ash, lead and sulfur content. The result is that fuel from plastic bottle waste has a density value of 742 kg/m3, kinematic viscosity of 1.76 cSt, lower heating value of 43.28 MJ/kg, flash point of 1OC, ash, lead and sulfur content respectively of 0.003905%, 0.0000231%, and 0.000462%.

A novel deep learning-based perspective for tooth numbering and caries detection.

The aim of this study was automatically detecting and numbering teeth in digital bitewing radiographs obtained from patients, and evaluating the diagnostic efficiency of decayed teeth in real time, using deep learning algorithms. The dataset consisted of 1170 anonymized digital bitewing radiographs randomly obtained from faculty archives. After image evaluation and labeling process, the dataset was split into training and test datasets. This study proposed an end-to-end pipeline architecture consisting of three stages for matching tooth numbers and caries lesions to enhance treatment outcomes and prevent potential issues. Initially, a pre-trained convolutional neural network (CNN) utilized to determine the side of the bitewing images. Then, an improved CNN model YOLOv7 was proposed for tooth numbering and caries detection. In the final stage, our developed algorithm assessed which teeth have caries by comparing the numbered teeth with the detected caries, using the intersection over union value for the matching process. According to test results, the recall, precision, and F1-score values were 0.994, 0.987 and 0.99 for teeth detection, 0.974, 0.985 and 0.979 for teeth numbering, and 0.833, 0.866 and 0.822 for caries detection, respectively. For teeth numbering and caries detection matching performance; the accuracy, recall, specificity, precision and F1-Score values were 0.934, 0.834, 0.961, 0.851 and 0.842, respectively. The proposed model exhibited good achievement, highlighting the potential use of CNNs for tooth detection, numbering, and caries detection, concurrently. CNNs can provide valuable support to clinicians by automating the detection and numbering of teeth, as well as the detection of caries on bitewing radiographs. By enhancing overall performance, these algorithms have the capacity to efficiently save time and play a significant role in the assessment process.

Establishing a Gold Standard for Noninvasive Identification of Painful Lumbar Discs: Prospective Comparison of Magnetic Resonance Spectroscopy vs Low-Pressure Provocation Discography.

Verifying lumbar disc pain can present a clinical challenge. Low-pressure provocative discography (PD) has served as the gold standard, although it is invasive and often a challenge to interpret. We reported that magnetic resonance spectroscopy (MRS) biomarkers accurately predict PD results in lumbar discs and improved outcomes for patients with surgery at positive MRS levels versus nonsurgery. To further substantiate MRS for diagnosing painful discs, we report a prospective comparison of 2 MRS-derived measures: NOCISCORE (pain) and SI-SCORE (degeneration severity). Lumbar MRS and software-based postprocessing (NOCISCAN-LS, Aclarion Inc.) was performed in 44 discs in 14 patients (prospective cohort [PC]). PC data were compared to prior data used to establish the NOCISCORE (training cohort [TC]). The NOCISCORE was converted to an ordinal value (high/intermediate/low; NOCI+/mild/-) and compared against painful (P) versus nonpainful (NP) control diagnosis (PD) for 19 discs where PD was performed in the PC (12 NP; 7 P). Sensitivity, specificity, and positive and negative predictive values were calculated. The SI-SCORE was compared against MRI Pfirrmann Grades for 465 discs in 126 patients (PC plus TC). For the PC, MRS (NOCI+/-) compared to PD (P/NP) with an accuracy of 87% and sensitivity and specificity of 100%. The positive and negative predictive values of MRS were 100%. NOCISCOREs were significantly higher for PD+ versus PD- discs for PC and TC (P < 0.05), and the NOCISCORE distributions for PD+/- group were not statistically different between the PC and TC (P > 0.05). SI-SCORES differed between Pfirrmann Grades 1 and 2 (less degenerated) versus Grades 3 and 4 (more degenerated; P < 0.05), with a progressively decreasing trend with Pfirrmann Grades 1-5. These current data provide prospective confirmation of the predictive value of disc MRS for distinguishing painful discs and for assessing the disc structural integrity. NOCISCAN is an adoptable, noninvasive, and objectively quantitative test to improve management of low back pain patients.

Highly stable, self-powered UV-Vis-NIR broadband isotype photodetector based on Ti-doped amorphous MoO3

Ti-doped MoO3 thin film was sputtered onto a n-Si substrate and the MoO3:Ti/n-Si heterojunction photodetector fabricated. The elemental composition and the morphological analyses of the MoO3 film have been carried out by EDX and SEM studies, respectively. The band gap of sputtered MoO3:Ti film was found to be 3.26 eV from UV-Vis spectra. The optical performance of the constructed device under visible light between 10 and 150 mW, under 365 nm and 395 nm UV light and 850 nm NIR light was examined in detail with the help of current-voltage (I-V) characteristics. From the analysis of the experimental I-V characteristics of the MoO3:Ti/n-Si heterojunction photodetector, the largest responsivity values were determined as 0.41 A/W in visible light of 10 mW/cm2, 2.03 A/W under UV light of 365 nm and 0.67 A/W for 850 nm NIR light, respectively. Furthermore, the largest specific detectivity values were calculated as 3.21×109 Jones in visible light (10 mW/cm2), 1.61×1010 Jones, under UV light of 365 nm, and 3.21×109 Jones, respectively. Repeated measurements after 30 days showed that the device was quite stable both in the dark and in a broadband.

A dual‐band dual‐polarized omnidirectional patch antenna for on‐body application

AbstractAiming at the 3.5 GHz world interoperability for microwave access band and 5.8 GHz industrial scientific medical band, a dual‐band antenna operating in omnidirectional mode is proposed. The antenna uses a single‐layer dielectric substrate made of FR‐4, which is cheap and easy to process. It uses circular patches and metal branches to generate orthogonal electric fields to achieve circular polarization. At the same time, the upper patch is symmetrically slotted in a T shape, so that the patch produces two resonance frequencies. The measured impedance bandwidth of the antenna in circular polarization on‐body mode and linear polarization on‐body mode is 110 MHz (3.41–3.52 GHz) and 460 MHz (5.42–5.88 GHz), respectively. In addition, the antenna shows good performance under bending conditions and close to human tissue. At the same time, the low specific absorption rate value proves that the antenna is safe to wear on the human body.

Synthesis of flower-type nanorods with Zn-doped manganese vanadate (Mn(VO3)2) and carbon nanofibers (CNFs) for enhanced performance in battery-type supercapacitors

Among the various novel electrode materials prepared to enhance the electrochemical performance of supercapacitors, ordered nanoarray structures stand out as highly promising candidates for use as binder-free electrodes. In this study, flower type nanorods of zinc manganese vanadate (MnZn3(VO4)2) grown on 3-D nickel foam, with additional incorporation of Carbon nanofibers (CNFs)(MZVC) by using a one-step hydrothermal method. The nanostructured MZVC electrode exhibited a specific capacitance of 469 Fg−1 at a current density of 0.5 Ag−1, surpassing the specific capacitance values of the pristine electrodes (ZV-304 Fg−1, MV-263 Fg−1) and MZV − 333 Fg−1) at the same current density. Remarkably, the MZVC composite electrode exhibited an exceptional retention rate of approximately 82.6 % even after 5000 charge–discharge cycles. All of the fabricated electrodes underwent comprehensive characterization utilizing different analytical techniques to assess their structural, and surface morphological attributes. Further, Electrochemical behavior was assessed for ZV, MV, MZV, and MZVC nanostructures through cyclic voltammetry (CV), galvanostatic charge /discharge (GCD), and electrochemical impedance spectroscopy (EIS). This 3D porous flower-type electrode structure offers an abundance of active sites for electrochemical reactions, enables efficient electron and ion transport, and mitigates the aggregation of MZVC flower structures throughout prolonged cycling.

Correlation between serum markers and transjugular intrahepatic portosystemic shunt prognosis in patients with cirrhotic ascites.

Individuals with refractory ascites in the context of liver cirrhosis typically face an adverse prognosis. The transjugular intrahepatic portosystemic shunt (TIPS) is an efficacious intervention, but there is a lack of reliable tools for postoperative prognosis assessment. Previously utilized clinical biochemical markers, such as the serum albumin concentration (Alb), sodium (Na+) concentration, and serum creatinine (Scr), have limited predictive value. Therefore, the quest for novel, specific biomarkers to evaluate the post-TIPS prognosis in patients with liver cirrhosis and refractory ascites holds significant practical importance. To investigate the associations between the Child-Pugh score, model for end-stage liver disease (MELD) score, and serum cystatin C (Cys C) level and post-TIPS prognosis in patients with liver cirrhosis and refractory ascites. A retrospective analysis was conducted on 75 patients with liver cirrhosis and refractory ascites who underwent TIPS at our institution from August 2019 to August 2021. These patients were followed up regularly for two years, and the death toll was meticulously documented. The patients were allocated into a survival group (n = 45 patients) or a deceased group (n = 30 patients) based on their prognosis status. The clinical data of the two groups were collected, and Child-Pugh scores and MELD scores were calculated for analysis. Spearman correlation analysis was carried out to evaluate the correlation of prognosis with Child-Pugh grade, MELD score, and Cys C level. Additionally, a multiple-factor analysis utilizing the Cox proportional hazard model was used to identify independent risk factors affecting the post-TIPS prognosis of patients with liver cirrhosis and refractory ascites. The receiver operating characteristic curve (ROC) ascertained the predictive value of the Cys C concentration, Child-Pugh grade, and MELD score for the prognosis of liver cirrhosis with refractory ascites in post-TIPS patients. During a 2-year follow-up period, among 75 patients with liver cirrhosis and refractory ascites who underwent TIPS treatment, 30 patients (40.00%) passed away. The deceased cohort exhibited heightened aspartate aminotransferase, alanine aminotransferase, total bilirubin, Scr, prothrombin time, Cys C, international normalized ratio, Child-Pugh, and MELD scores compared to those of the survival cohort, while Alb and Na+ levels were attenuated in the deceased group (P < 0.05). Spearman analysis revealed moderate to high positive correlations between prognosis and Child-Pugh score, MELD score, and Cys C level (r = 0.709, 0.749, 0.671, P < 0.05). Multivariate analysis using the Cox proportional hazard model demonstrated that the independent risk factors for post-TIPS prognosis in patients with liver cirrhosis and refractory ascites were Cys C (HR = 3.802; 95%CI: 1.313-11.015), Child-Pugh (HR = 3.030; 95%CI: 1.858-4.943), and MELD (HR = 1.222; 95%CI: 1.073-1.393) scores. ROC analysis confirmed that, compared to those of the classic prognostic models for Child-Pugh and MELD scores, the predictive accuracy of Cys C for post-TIPS prognosis in patients with liver cirrhosis and refractory ascites was slightly lower. This analysis yielded sensitivity and specificity values of 83.33% and 82.22%, respectively. The area under the curve value at this juncture was 0.883, with an optimal cutoff value set at 1.95 mg/L. Monitoring the serum Cys C concentration is valuable for assessing the post-TIPS prognosis in patients with liver cirrhosis and refractory ascites. Predictive models based on serum Cys C levels, as opposed to Scr levels, are more beneficial for evaluating the condition and prognosis of patients with ascites due to cirrhosis.

Intestinal metabolomics in premature infants with late-onset sepsis

We aimed to investigate the characteristics of intestinal metabolomics and non-invasive biomarkers for early diagnosis of late-onset sepsis (LOS) by analyzing gut metabolites in preterm infants with LOS. We collected stool samples from septic and healthy preterm infants for analysis by liquid chromatography–mass spectrometry. 123 different metabolites were identified and 13 pathways were mainly involved. Glycine, serine, and threonine metabolism; glyoxylate and dicarboxylic acid metabolism; glutathione metabolism; primary bile acid biosynthesis; steroid synthesis; pentose and glucuronic acid interconversion may be involved in the pathogenesis of LOS in preterm infants. The significant changes of N-Methyldopamine, cellulose, glycine, gamma-Glutamyltryptophan, N-Ribosylnicotinamide and 1alpha, 25-dihydroxycholecalciferol showed specific diagnostic values and as non-invasive biomarkers for LOS.

Enhanced Donor Antigen Presentation by B Cells Predicts Acute Cellular Rejection and Late Outcomes After Transplantation.

Enhanced B-cell presentation of donor alloantigen relative to presentation of HLA-mismatched reference alloantigen is associated with acute cellular rejection (ACR), when expressed as a ratio called the antigen presenting index (API) in an exploratory cohort of liver and intestine transplant (LT and IT) recipients. To test clinical performance, we measured the API using the previously described 6-h assay in 84 LT and 54 IT recipients with median age 3.3 y (0.05-23.96). Recipients experiencing ACR within 60 d after testing were termed rejectors. We first confirmed that B-cell uptake and presentation of alloantigen induced and thus reflected the alloresponse of T-helper cells, which were incubated without and with cytochalasin and primaquine to inhibit antigen uptake and presentation, respectively. Transplant recipients included 76 males and 62 females. Rejectors were tested at median 3.6 d before diagnosis. The API was higher among rejectors compared with nonrejectors (2.2 ± 0.2 versus 0.6 ± 0.04, P value = 1.7E-09). In logistic regression and receiver-operating-characteristic analysis, API ≥1.1 achieved sensitivity, specificity, and positive and negative predictive values for predicting ACR in 99 training set samples. Corresponding metrics ranged from 80% to 88% in 32 independent posttransplant samples, and 73% to 100% in 20 independent pretransplant samples. In time-to-event analysis, API ≥1.1 predicted higher incidence of late donor-specific anti-HLA antibodies after API measurements in LT recipients (P = 0.011) and graft loss in IT recipients (P = 0.008), compared with recipients with API <1.1, respectively. Enhanced donor antigen presentation by circulating B cells predicts rejection after liver or intestine transplantation as well as higher incidence of DSA and graft loss late after transplantation.

Mechanical properties of Q355 hot-rolled steel during the entire fire process

This study conducts steady-state tests to comprehensively examines the mechanical properties of Q355 hot-rolled steel throughout the entire fire process, including the cooling stage. Results show that the mechanical properties at the fire-cooling stage are influenced by both the peak heating temperature (Tp) and the tensile test temperature (Tt). Within a specific threshold value of Tp, the mechanical properties at the cooling stage of fire resemble those observed in the heating stage. However, when Tp surpasses this threshold value, notable disparities emerge between the mechanical properties of steel at the cooling and heating stages. The threshold temperatures for elastic modulus, ultimate strength, and ultimate strain are all 600 °C, while that for the yield strength f0.2 is 400 °C. A cooling stage influence coefficient is used to quantitatively portray the variance in mechanical properties between the cooling and heating stages of fire. Calculation formulas for the fire cooling stage influence coefficients were provided for the elastic modulus, yield strength f0.2, ultimate strength, and ultimate strain, respectively. Finally, a constitutive model for the entire fire process of Q355 steel was established.

MaglevMotor: Design and optimisation of a novel hybrid linear actuator for 6 degrees of freedom rail‐passive Maglev carrier

AbstractA novel levitating hybrid linear actuator is proposed for magnetically levitated carrier systems. This hybrid linear actuator, “MaglevMotor”, is capable to levitate itself under the passive rail and thrusts itself in a single longitudinal direction. The proposed structure aims to reduce complexity by minimising the necessary number of components, resulting in simplified geometry, improved assembly convenience, and decreased manufacturing tolerances. The MaglevMotor is optimised in multi‐physics aspect. Optimisation objectives are maximising thrust force, minimising total mass and minimising mechanical deformation of yoke with constraints of a user defined magnetic flux density (B) in yoke and zero power condition for specific air gap value. The authors present pre‐optimisation studies, optimisation results and final MaglevMotor designs step by step. By utilising three of the MaglevMotors units, the carrier is able to achieve motion in six degrees of freedom. The carrier's performance targets, including a 0.2 G acceleration, a total mass of less than 10 kg, and a 5 mm levitation air gap, have been both attained and validated through corresponding experiments.

Impact of ZnFe2O4 nanoparticles parameters on magnetic and electrochemical performance

Nanostructured ZnFe2O4 powder with crystallite size from 4 to 55 nm was synthesized via coprecipitation method followed by calcination process carried out at different temperatures. The obtained samples were characterized by XRD, SEM, XPS and ICP-AES methods; magnetic properties at 298 and 77 K were measured and analyzed, the electrochemical behavior of anode materials was tested. The Fe – Zn ratio and oxygen vacancies amount were established. It was found that the magnetization values depend on the crystallite size, and the Fe – Zn ratio determine magnetic performance of the samples in the case of field cooling curves. The sample calcined at 500 °С showed the highest Coulombic efficiency of 76.2 % (at the first cycle) and initial discharge and charge specific capacity of 1400 and 1067 mAh·g−1 at current densities of 0.2 A·g−1. Also, it was demonstrated that the initial capacity depends on oxygen vacancies amount, the highest specific capacity value was for sample with crystallite size 46.9 nm and with a smallest oxygen vacancies amount.

Effect of Heat Treatment on Color Change and The Physical Properties of Sembilang Bamboo (Dendrocalamus giganteus Munro)

Timber as a raw material for making furniture is still lacking. One alternative to overcome this problem is bamboo. The potential for bamboo in Indonesia is quite large. Sembilang bamboo is a species of bamboo that has not been widely used. Research related to the effect of heat treatment on color change and the physical properties of bamboo needs to be carried out to determine color change and the dimensional stability of bamboo. This research was carried out by giving heat at 180°C for various durations (control, 3 hours, and 6 hours). The color change, moisture content, absorption, and specific gravity of heat-treated sembilang bamboo were researched. The results showed that the color of sembilang bamboo after heat treatment became darker than the control. The moisture content and absorption values of sembilang bamboo with heat treatment at 180°C for 6 hours were higher than the control and 3 hours. The specific gravity value of the bamboo control was higher than 3 hours and 6 hours for sembilang bamboo. Heat treatment at 180°C for 6 hours had an adverse effect on the physical properties of sembilang bamboo. Heat-treated sembilang bamboo at 180°C for 3 hours was recommended in this research