Multi-element Model Research Articles

Multielement simultaneous quantitative analysis of trace elements in stainless steel via full spectrum laser-induced breakdown spectroscopy

Laser-Induced Breakdown Spectroscopy (LIBS) instruments are increasingly recognized as valuable tools for detecting trace metal elements due to their simplicity, rapid detection, and ability to perform simultaneous multi-element analysis. Traditional LIBS modeling often relies on empirical or machine learning-based feature band selection to establish quantitative models. In this study, we introduce a novel approach—simultaneous multi-element quantitative analysis based on the entire spectrum, which enhances model establishment efficiency and leverages the advantages of LIBS. By logarithmically processing the spectra and quantifying the cognitive uncertainty of the model, we achieved remarkable predictive performance (R2) for trace elements Mn, Mo, Cr, and Cu (0.9876, 0.9879, 0.9891, and 0.9841, respectively) in stainless steel. Our multi-element model shares features and parameters during the learning process, effectively mitigating the impact of matrix effects and self-absorption. Additionally, we introduce a cognitive error term to quantify the cognitive uncertainty of the model. The results suggest that our approach has significant potential in the quantitative analysis of trace elements, providing a reliable data processing method for efficient and accurate multi-task analysis in LIBS. This methodology holds promising applications in the field of LIBS quantitative analysis.

Elevated levels of Zn, Cu and Co are associated with an increased risk of endometriosis: Results from a case[sbnd]control study

BackgroundEndometriosis is a common gynecological disease that affects approximately 5 %∼10 % of reproductive-aged women. Zinc (Zn), selenium (Se), copper (Cu), cobalt (Co) and molybdenum (Mo) are essential trace elements and are very important for human health. However, studies on the relationship between mixtures of essential trace elements and the risk of endometriosis are limited and inconsistent. In particular, studies confirming the association via different sample types are limited. ObjectiveThis study aimed to investigate the associations between Zn, Se, Cu, Co and Mo concentrations in blood and follicular fluid (FF) and endometriosis risk in a Chinese population. MethodsA total of 609 subjects undergoing in vitro fertilization (IVF) were recruited; 836 samples were analyzed, including 451 blood samples (234 controls and 217 cases) and 385 FF samples (203 controls and 182 cases). In addition, 227 subjects provided both blood and FF samples. Zn, Se, Cu, Co and Mo concentrations in blood and FF were quantified via inductively coupled plasma−mass spectrometry (ICP−MS). The associations between the levels of Zn, Se, Cu, Co and Mo and the risk of endometriosis were assessed using single-element models (logistic regression models), and the combined effect of the trace elements on endometriosis risk was assessed using multielement models (Bayesian kernel machine regression (BKMR) and weighted quantile sum (WQS) regression). ResultsBased on the single-element models, significant associations of Zn concentrations in blood (high-level vs. low-level group: aOR = 14.17, 95 % CI: 7.31, 27.50) and FF (first tertile vs. second tertile group: aOR = 0.34, 95 % CI: 0.16, 0.71; third tertile vs. second tertile group: aOR = 2.32, 95 % CI: 1.38, 3.91, respectively) and Co concentrations in blood (first tertile vs. second tertile group, aOR = 0.24, 95 % CI: 0.12, 0.48) and FF (third tertile vs. second tertile group: aOR = 3.87, 95 % CI: 2.19, 6.84) with endometriosis risk were found after adjustment for all confounders. In FF, Cu and Mo levels were significantly greater among the cases than among the controls, with a positive association with endometriosis risk (Cu (first tertile vs. second tertile group: aOR = 0.39, 95 % CI: 0.19, 0.81; third tertile vs. second tertile group: aOR = 2.73, 95 % CI: 1.61, 4.66, respectively) and Mo (high-level vs. low-level group: aOR = 14.93, 95 % CI: 7.16, 31.12)). However, similar associations between blood Cu and Mo levels and endometriosis risk were not found. In addition, the levels of these five essential trace element mixtures in blood and in FF were significantly and positively associated with endometriosis risk according to the BKMR analyses; the levels of Zn and Cu in blood and the levels of Mo in FF were significantly related to the risk of endometriosis, and the posterior inclusion probabilities (PIPs) were 1.00, 0.99 and 1.00 for Zn and Cu levels in blood and Mo levels in FF, respectively. Furthermore, Zn and Mo were the highest weighted elements in blood and FF, respectively, according to WQS analyses. ConclusionThe risk of endometriosis was associated with elevated levels of several essential trace elements (Zn, Cu and Co). Elevated levels of these elements may be involved in the pathomechanism of endometriosis. However, further studies with larger sample sizes will be necessary to confirm these associations.

Multi-element Exposure and Cognitive Function in Rural Elderly Chinese.

To investigate the relationship between selenium (Se) based multi-element combined exposure and cognitive function in rural elderly individuals, a cross-sectional study was conducted. The study involved 416 older adults aged 60 and above, residing in four different areas of Enshi county, China, with varying soil Se levels. Inductively coupled plasma mass spectrometry (ICP-MS) was employed to measure the concentrations of Se, copper (Cu), iron (Fe), zinc (Zn), calcium (Ca), magnesium (Mg), cadmium (Cd), arsenic (As), and lead (Pb) in whole blood. Nine standard cognitive tests were applied to assess cognitive function. Analysis of the least absolute shrinkage and selection operator regression (LASSO), covariance (ANCOVA), and generalized linear model (GLM) were utilized to investigate the relationship between element exposure and cognitive function. The results of LASSO revealed that Se, Cu, Fe, Zn, Ca, and Pb were independently identified to be associated with cognition. Both ANCOVA and GLM demonstrated that Se and Ca were correlated with cognitive function. The multi-element model showed higher composite Z scores of 0.32 (95% CI: 0.09 to 0.55) for log-transformed Se (P = 0.007), 0.75 (95% CI: 0.01 to 1.49) for log-transformed Cu (P = 0.048), and a lower score of - 0.67 (95% CI: - 1.26 to - 0.08) for log-transformed Ca (P = 0.025). Furthermore, there was evidence that Se could counteract the negative impact of Ca on cognitive function (P for interaction = 0.031). Our findings suggested that higher levels of Se and Cu were associated with better cognitive function in the elderly and Se can counteract the cognitive damage caused by Ca.

Prediction of nature of hysteresis and hysteresis based extraction of viscoelastic material model parameters

As almost all materials exhibit viscoelastic behaviour, it is important to understand the material behaviour which would help in its application in different fields. The current research work firstly focuses on understanding the dissipating behaviour of any viscoelastic material through operator-based multi-element model from the experimental hysteresis subject to cyclic or periodic displacement loading. Genetic algorithm-based constrained optimization technique is used as an extraction technique by curve fitting. Further, the technique is used to predict the model parameters of a pig’s lumbar spinal motion segment subjected to periodic displacement loading. Following the derived model parameters, the effect of varying periodic loading on the calculated hysteresis is also compared.

Cognitive enhancement interventions are effective for schizophrenia: why not provide them early?

Cognitive enhancement interventions are effective for schizophrenia: why not provide them early?

Association between Plasma Trace Element Concentrations in Early Pregnancy and Gestational Diabetes Mellitus in Shanghai, China.

(1) Background: Trace elements play important roles in gestational diabetes mellitus (GDM), but the results from reported studies are inconsistent. This study aimed to examine the association between maternal exposure to V, Cr, Mn, Co, Ni, and Se in early pregnancy and GDM. (2) Methods: A nested case-control study with 403 GDM patients and 763 controls was conducted. Trace elements were measured using inductively coupled plasma-mass spectrometry in plasma collected from pregnant women in the first trimester of gestation. We used several statistical methods to explore the association between element exposure and GDM risk. (3) Results: Plasma V and Ni were associated with increased and decreased risk of GDM, respectively, in the single-element model. V and Mn were found to be positively, and Ni was found to be negatively associated with GDM risk in the multi-element model. Mn may be the main contributor to GDM risk and Ni the main protective factor against GDM risk in the quantile g computation (QGC). 6.89 μg/L~30.88 μg/L plasma Ni was identified as a safe window for decreased risk of GDM. (4) Conclusions: V was positively associated with GDM risk, while Ni was negatively associated. Ni has dual effects on GDM risk.

Chemical element concentrations in cord whole blood and the risk of preterm birth for pregnant women in Guangdong, China

Maternal exposure to chemical elements, including essential and non-essential elements, have been found to be associated with preterm births (PTB). However, few studies have measured element concentrations in cord whole blood, which reflects activity at the maternal-fetal interface and may be biologically associated with PTBs. In this study, we determined concentrations of 21 elements in cord whole blood and explored the associations between element concentrations and PTB in a nested case-control study within a birth cohort in Guangdong, China. Finally, 515 preterm infants and 595 full-term infants were included. We performed single-element and multi-element logistic regressions to evaluate linear relationships between element concentrations and PTB. According to the results of single-element models, most essential elements (including K, Ca, Si, Zn, Se, Sr and Fe) were negatively associated with PTB, while Cu, V, Co and Sn were positively associated with PTB. Of the non-essential elements, Sb, Tl, and U were positively associated with PTB, while Pb was negatively associated with PTB. The multi-element model results for most elements were similar, except that the association between Mg and PTB was shown to be significantly positive, and the association for Cu became much larger. A possible explanation is that the effects of Mg and Cu may be influenced by other elements. We performed restricted cubic spline (RCS) regressions and found significantly non-linear exposure-response relationships for Mg, Se, Sr, K and Sb, indicating that the effects of these elements on PTB are not simply detrimental or beneficial. We also examined the joint effect using a Bayesian kernel machine regression (BKMR) model and found the risk of PTB decreased significantly with element mixture concentration when lnC was larger than the median. Bivariate interaction analysis suggested antagonistic effects of Sb on Zn and Sr, which may be attributed to Sb negating the antioxidant capacity of Zn and Sr. This study provides additional evidence for the effect of element exposures on PTB, and will have implications for the prevention of excessive exposures or inappropriate element supplementation during pregnancy.

Associations of exposure to multiple metals with the risk of age-related cataract in Anhui, China: a case-control study.

It's well-known that multiple metal elements can lead to the change of oxidative stress response levels in vivo. However, their relationship with age-related cataract (ARC) had not been well studied. We designed a case-control study including 210 individuals with ARC and 210 matched control group. The metal levels in their urine specimens were measured using graphite furnace atomic absorption spectrometry (GFAAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). Least Absolute Shrinkage and Selection Operator (LASSO) regression was used to select representative metals into the multi-element model and reduce dimension. Multivariate logic analysis and Bayesian kernel machine regression (BKMR) were subsequently used to explore the association of ARC risk with multiple metal elements. We found that magnesium (Mg), chromium (Cr), arsenic (As), manganese (Mn), and selenium (Se) were positively associated with ARC in the single-element model. The multiple exposure model indicated a positive association between Mg and As, in which the OR in their highest quartile were 3.32 (95% CI: 1.24-8.89) and 7.09 (95% CI: 2.56-19.63). The BKMR model also showed the effect of As increased monotonically with its increasing concentration, and high levels of Mg and As had a significant positive effect on ARC risk. In conclusion, we found that exposure to multiple metals was associated with increased ARC risk. Further research is needed to verify these findings in the future.

Neural network surrogate models for absorptivity and emissivity spectra of multiple elements

The emissivity and absorptivity of radiation by matter are fundamental physical parameters required to adequately simulate inertial confinement fusion experiments. We present novel neural network models for predicting these interaction coefficients. This research extends the methods used by Kluth et al. (2020) that made similar predictions for a single chemical element, krypton. Our models are based on fully-connected or convolutional autoencoders coupled with a deep jointly-informed neural network (DJINN) to predict the emissivity and absorptivity of a given element and temperature/radiative field. We show that the previous work could not be directly extended to lower atomic number elements due to a thresholding effect on small values caused by a log10 transformation. Thus, in order to create a multi-element model, or even a single-element model, with low atomic number elements a different transformation is necessary. Utilization of a cube-root transform enables the creation of a multi-element model can achieve mean relative errors between 1% and 2%. Our work demonstrates that a single neural network can predict the results of atomic physics calculations, but additional work is necessary to consider mixtures of elements or a wider range of elements than those used in our study.

Study on influence factors and sources of mineral elements in peanut kernels for authenticity

The objective of this study was to find out the variation mechanism of minerals in peanut for improving the discrimination power of multi-element models of geographical origin. Effects of sub-region, variety, and their interaction on 22 elements in peanut were studied based on field experiments. And the ability of the elements closely related to sub-region to identify the origins of peanuts from the same and different years was examined. In addition, the relationships between geographical markers in peanut and in provenance soil or rainwater were further analyzed. The results showed that sub-region, variety, and their interaction had significant effects on variation of elements in peanut and the elements were classified according to the factor. Na, Mg, Ca, V, Mn, Ni, Zn, Sr, Rh, and Cd were selected as the geographical markers and extremely significantly correlated with soil and rainwater. It was efficient to discriminate peanuts based on ten geographical markers.

Field, textural, geochemical, and isotopic constraints on the origin and evolution of the magmatic microgranular enclaves from the Gharib Granitoid Complex, North Eastern Desert, Egypt

The Neoproterozoic Gharib Granitoid Complex (GGC), in the North Eastern Desert (NED) of Egypt, is characterized by the occurrence of varieties of granitoids. Monzogranite, the most abundant granite variety, contains abundant magmatic microgranular enclaves (MMEs) of mafic to intermediate composition. The MMEs are more mafic than their host and marked by a greater amount of amphibole and biotite. They are finer grained and have porphyritic/poikilitic textures.The sharp, crenulated, and fine-grained quenched contacts of the elongated, rounded, and ellipsoid form of the MMEs with their felsic host indicate rapid cooling during a magma mixing/mingling event. Micro-textural evidence supports the mechanical transfer of minerals that crystallized in felsic magma to the mafic melt (e.g., feldspar phenocrysts cross-cutting the MME-host boundaries, stubby apatite, quartz ocelli, and poikilitic outermost rims of K-feldspar phenocrysts), supercooling/quenching process (e.g., acicular apatite and elongated hornblende and biotite crystals), and disequilibrium growth (e.g., hornblende-biotite clots replaced early crystallized clinopyroxene), which also favour a magma mingling/mixing origin. Linear to curvilinear chemical variations of the MMEs and the host monzogranites on Harker diagrams, highly similar trace element contents, and Sr-Nd isotopic systematics together with mineral-chemical features also support mixing/mingling as the main process in magma genesis and strongly suggest that the MMEs were supercooled hybrid globules within cooler, partially crystallized host felsic magma. The crust-like geochemical signatures (i.e., SiO2 content, metaluminous nature, and lack of upper crustal xenoliths and typical peraluminous minerals), along with low [MMEs: (87Sr/86Sr)initial = 0.70136–0.70373; monzogranites: (87Sr/86Sr)initial = 0.70202–0.70320)] along with zircon and apatite U-Pb age data indicate the possible involvement of juvenile lower continental crust (LCC) of the Arabian-Nubian Shield (ANS) in their genesis. The medium- to high-K calc-alkaline affinity, the LILE enrichment, and the HFSE depletion along with low Nb/La ratios and positive εNd(t) (MMEs = +4.01 - +5.62, monzogranites = +2.29 - +6.03) indicate the contribution of depleted lithospheric mantle in the magma genesis, whereas the low δEu and fairly high δCe values, stable La/Sm, and variable Sr/Th ratios in apatites from the monzogranites and MMEs indicate the contribution of volatile/fluids from the remnants of the oceanic slab in facilitating melting in the source region. The genesis of the monzogranites and MMEs started with asthenosphere upwelling, followed by melting of the remnants of lithospheric mantle, and underplating of mantle magma, which led to partial melting of the LCC. Multi-element modelling postulates that the low degree mixing between partially crystallized mantle magma and LCC-derived felsic melt (Fmix ∼ 0.1) could produce the parent magma for the monzogranites. Further mixing/mingling of the crystal-charged monzogranite parent magma with new pulses of mafic melts (Fmix ∼ 0.25) developed a hybrid zone and formed the hybrid MMEs. Thus, the final episode of the ANS evolution was associated with a complex post-collisional interplay between asthenosphere, lithospheric mantle, and the LCC caused by the removal of delaminated lithospheric root and dense lower crust following the collision between East and West Gondwana in the Neoproterozoic time.

Associations of exposure to multiple trace elements with the risk of goiter: A case-control study

Goiter is one of common endocrine diseases, and its etiology has not been fully elucidated. The changes in trace elements' levels have an important impact on the thyroid. We designed a case-control study, which involved 383 goiter cases and 383 matched controls. We measured these elements in the urine of participants by inductively coupled plasma optical emission spectrometry (ICP-OES), graphite furnace atomic absorption spectrometry (GFAAS) and As3+-Ce4+ catalytic spectrophotometry. Least Absolute Shrinkage and Selection Operator (LASSO) regression was used to select the elements into multi-element models, conditional logistic regression models were applied to analyze the association between elements and goiter risk. Bayesian kernel machine regression (BKMR) model was used to depict elements’ mixtures and evaluate their joint effects. Finally, 7 elements were included in the multi-element model. We found that the concentrations of lithium (Li), strontium (Sr) and barium (Ba) had a negative effect with goiter risk, and lead (Pb) and iodine (I) showed an extreme positive effect. Additionally, compared with the lowest levels, patients with highest quartiles of I and Pb were 6.49 and 1.94 times more likely to have goiter, respectively. On the contrary, in its second and third quartiles, arsenic (As) showed a negative effect (both OR<1). BKMR model showed a certain interaction among Pb, As, Sr and Li on goiter risk. Further large sample studies are needed to confirm these findings in the future.

Multi Elements Simulation of Biaxial Test with Two Different Soil Layers Using Hypoplastic Constitutive Model

Practically, the ground condition usually consists of several layers, which have various properties from each other so it is important to have precise understanding about these layers and their behaviour. For this purpose, two different soil layers in biaxial test was analysed. In the single element simulation, it is impossible to generate the shear strain localization in the porous media but we can get numerous useful results. For strain localization analyse, using multi element models is necessary. The numerical simulation shows that the behaviour of each layer is totally different and the friction angle of both layers changed during simulation.

Controlling flutter of a cable-stayed bridge with output feedback driven winglets

Active control of flutter of a long span cable-stayed bridge is considered in this study. The control action is provided by winglets actuated using constant/variable gain output feedback controllers. Two FE modeling schemes are adopted, namely one element cables, and multi-element cables with each stay-cable discretized into multiple elements to consider the cable vibration effect. Cable discretization results in additional closely spaced modes. Rational function approximation of flat plate flutter derivatives is considered to model aeroelastic forces on deck and winglets. The output feedback controller yields the desired winglet rotation by using vertical and torsional displacements of the deck. Controllability Gramian and response indices are used to obtain the optimal location of winglets, while the best sensor location is obtained based on a combined index. This yields around 40% increase in the stability limit with winglets covering 12% of the central span, and eight measured outputs for feedback. Response indices reduce substantially if a shift from constant to variable gain is performed at a certain wind speed. Controller design based on the one-element model, when applied to the more realistic multi-element model, results in substantially lesser response attenuation. Hence, cable vibration needs to be consider for the controller design. Keywords: Flutter, Cable-stayed bridge, Winglet, Rational function approximation, Variable gain output feedback, Cable vibration.

Modeling a helical fluid inerter system with time‐invariant mem‐models

In this paper, experimental data from tests of a helical fluid inerter are used to model the observed hysteretic behaviour. The novel idea is to test the feasibility of employing mem-models, which are time-invariant herein, to capture the observed phenomena by using physically meaningful state variables. Firstly we use a Masing model concept, identified with a multilayer feedforward neural network to capture the physical characteristics of the hysteresis functions. Following this, a more refined approach based on the concept of a multi-element model including a mem-inerter is developed. This is compared with previous definitions in the literature and shown to be a more general model. Through-out this paper, numerical simulations are used to demonstrate the type of dynamic responses anticipated using the proposed time- invariant mem-models. Corresponding experimental measurements are processed to demonstrate and validate the new mem-modeling concepts. The results show that it is possible to have a unified model constructed using both the damper and inerter from the mem-model family. This model captures many of the more subtle features of the underlying physics, not captured by other forms of existing model.

Interaction between Track and Long-Span Cable-Stayed Bridge: Recommendations for Calculation

Geometric nonlinearity (GN) and initial internal forces (IIFs) are the basic characteristics of cable-stayed bridges, but now there is no effective method for analyzing the effect of them on bridge-track interaction of continuous welded rail (CWR) on cable-stayed bridge. A method for reconstructing the displacement-force curve of ballast longitudinal resistance was put forward according to the deformation of cable-stayed bridges under the completed bridge state. A feasibility study on the method was conducted via two aspects of the force and deformation of CWR on a 5 × 40 m single-line simple-supported beam bridge with initial deformation. With the multi-element modeling method and the updated Lagrangian formulation method, a rail-beam-cable-tower 3D calculation model considering the GN and IIFs of cable-stayed bridge was established. Taking a (140 + 462 + 1092 + 462 + 140 m) twin-tower cable-stayed bridge as an example, the impacts of GN and IIFs on bridge-track interaction were comparatively analyzed. The results show that the method put forward to reconstruct ballast longitudinal resistance can prevent the impact of initial deformation of bridge and makes it possible to consider the effect of IIFs of cable-stayed bridge on bridge-track interaction. The GN and IIFs play important roles in the calculation of rail longitudinal force due to vertical bending of bridge deck under train load and the variance of cable force due to negative temperature changes in bridge decks and rails with rail breaking, and the two factors can reduce rail longitudinal force and variance of cable force by 11.8% and 14.6%, respectively. The cable-stayed bridge can be simplified as a continuous beam bridge with different constraints at different locations, when rail longitudinal force due to positive temperature changes in bridge deck and train braking is calculated.

Self-Assembly of a Metal-Phenolic Sorbent for Broad-Spectrum Metal Sequestration.

Metal contamination of water bodies from industrial effluents presents a global threat to the aquatic ecosystem. To address this challenge, metal sequestration via adsorption onto solid media has been explored extensively. However, existing sorbent systems typically involve energy-intensive syntheses and are applicable to a limited range of metals. Herein, a sorbent system derived from physically cross-linked polyphenolic networks using tannic acid and ZrIV ions has been explored for high-affinity, broad-spectrum metal sequestration. The network formation step (gelation) of the sorbent is complete within 3 min and requires no special apparatus. The key to this system design is the formation of a highly stable coordination network with an optimized metal-ligand ratio (1.2:1), affording access to a major fraction of the chelating sites in tannic acid for capturing diverse metal ions. This system is stable over a pH range of 1-9, thermally stable up to ∼200 °C, and exhibits a negative surface charge (at pH 5). The sorbent system effectively sequesters 28 metals in single- and multielement model wastes, with removal efficiencies exceeding 99%. Furthermore, it is demonstrated that this system can be processed as membrane coatings, thin films, or wet gels to capture metal ions and that both the sorbent and captured metal ions can be regenerated or directly used as composite catalysts.

Multi-element modeling of heavy metals competitive removal from aqueous solution by raw and activated clay from the Aleg formation (Southern Tunisia)

The present study has been carried out for potential use of a raw clay from Gabes district (southern Tunisia) in wastewater treatment. A representative clay sample was collected from the outcropping feature of the Aidoudi area to the west of Gabes city; it followed a simple treatment to enhance its physicochemical properties. Adsorption experiments were performed by using a simple batch technique in single- and multi-element solution (Pb2+, Cd2+, Cu2+ and Zn2+). The obtained results were fitted to different adsorption models, including extended and modified Langmuir, extended Freundlich and modified Redlich–Peterson. Our results indicated that the collected clay sample is mainly a smectite with high amounts of silica, alumina and iron. Adsorptive removal of single elements revealed encouraging efficiencies for most of the studied metals, reaching nearly 100%. Our results also indicated that lead removal reached 26.78 mg/g and 45.94 mg/g for natural and activated clay samples, respectively. Competitive adsorption showed strong dependence on the initial concentration and the metal properties, with preferential removal of lead that reached 41.71 mg/g in binary systems. In most of the mixed systems, metal removal substantially decreased in the presence of competing ions. It showed preferential removal of lead over other metals, regardless of the studied mixture. Further, the use of smectitic clay from southern Tunisia showed a good potential for metal ions removal in single and multi-element systems from aqueous solutions. Thus, it could be turned out to a viable material for the treatment of metal loaded waters.

ANALYSIS OF THE CONDITIONS OF OCCURRENCE AND SUPPRESSION OF LATERAL VIBRATIONS IN MICROWAVE POWER FETS

Lateral instability is inherent in power transistors structures, consisting of several simple transistors connected in parallel. The large number of transistor elements complicates the analysis of such instability. The introduction of suppressing resistors makes it possible to prevent the occurrence of lateral oscillations, however there are no unambiguous criteria for achieving stability this way. The matter is further complicated by the fact that transistor exhibits nonlinear operation in a typical amplifier stage, and the operating conditions in many cases correspond to a relatively wide range of frequencies. In this paper, we present an analysis of lateral instability of a power amplifier stage, created on a basis of modern GaN field-effect transistor (FET). We had designed all dies and circuits for this FET. The main feature of the analysis is that we carried it out in the time domain, which made possible to estimate the stability of the stage not only under the excitation power pulse, but also after the end of the pulse. Our approach makes it possible to assess the stability of the amplifier between the excitation pulses, which is very important from the operational point of view. We calculated the estimates of operational stability and stability factor using a simplified transistor model, with the multi-element model reduced to a two-element model. Nevertheless, the results of the estimates retain their significance in real conditions, when the introduction of suppressing resistors creates a significant margin of stability, including the actual operating frequency band of the stage. To date, the data we have obtained after the manufacture of the samples only partially confirms the calculated estimates, due to the complexity of managing the experimental studies. However, there are no recorded results, which deny our estimates for the model.

Reuse of hazardous electrolytic manganese residue: Detailed leaching characterization and novel application as a cementitious material

Electrolytic manganese residue (EMR) was characterized in detail. A pH-dependent leaching test in combination with geochemical modelling was used to reveal the leaching mechanisms and calculate the solubility-controlling phases of various elements. In addition, a novel EMR-activated cementitious material (EGCH) was developed based on the characteristic of EMR (namely, high gypsum content). The results show that Mn and NH3-N are the most predominant hazardous elements in EMR that pose environmental risks. Mn mainly exists as acid-extractable phases (Mg-bearing jacobsite and szmikite) in EMR, and its solubility is mainly controlled by sorptive phases, rhodochrosite and hausmannite. NH3-N leaching is virtually pH independent in acid regions, but NH3-N reacts with hydroxyl to form NH3 at pH values above 9. The simulated equilibrium concentrations from multi-element modelling match well with the measured results. In addition, hardened EGCH can achieve a 28-day compressive strength of 30 MPa, and its EMR utilization ratio can reach 45 wt.%. The encapsulation effect and strong alkaline buffering capacity provided by EGCH are beneficial for the stabilization of Mn and NH3-N. Overall, the EGCH cementitious material can meet the requirements for green construction.