Quadratic Correlation Research Articles

Optimization studies and compositional analysis of subcritical water extraction of essential oil from Citrus hystrix DC. leaves

Subcritical water extraction (SWE) of essential oil (EO) from Citrus hystrix DC. leaves was optimized using response surface methodology (RSM), involving factors of particle size (0.5–1) mm, sample-to-solvent ratio (0.025–0.175) g/mL, extraction temperature (140−180) °C, and extraction time (20−40) minutes. Thus, an optimal EO yield of (2.14 ± 0.03) % (w/w) was obtained at 0.75 mm, 0.025 g/mL, 174 °C, and 29 min. SWE was found to yield significantly higher EO than the conventional hydrodistillation, within a shorter time. The regression model was established, presenting a significant quadratic correlation (R2 = 0.97) and adequate for predictions. SWE at 160 °C and 180 °C yielded 36 compounds, with isopulegol-dominant, exceeding SWE at 140 °C (21 compounds) and hydrodistillation (25 compounds). SWE with tunable temperatures not only improved the quantity of EO but was also capable of enhancing the quality because more EO compounds were extracted, offering diverse functionalities to nutraceutical sectors.

Hf thickness dependence of perpendicular magnetic anisotropy, damping and interfacial Dzyaloshinskii-Moriya interaction in Pt/CoFe/Hf/HfO2

Vibrating sample magnetometery (VSM) combined with Brillouin light scattering (BLS) were used to investigate the Dzyaloshinskii-Moriya interaction (iDMI), the perpendicular magnetic anisotropy (PMA) and the damping in ${\mathrm{Co}}_{0.5}{\mathrm{Fe}}_{0.5}$-based systems grown by sputtering on $\mathrm{Si}/{\mathrm{SiO}}_{2}$ substrates, using Pt or Cu buffer layers and Hf capping layer of variable thickness $(0\ensuremath{\le}{t}_{\mathrm{Hf}}\ensuremath{\le}2\phantom{\rule{0.28em}{0ex}}\mathrm{nm})$. VSM measurements revealed a significant decrease of the areal magnetic moment at saturation as ${t}_{\mathrm{Hf}}$ increases, most likely due to the increase of the magnetic dead layer thickness at CoFe/Hf interface up to $0.73\ifmmode\pm\else\textpm\fi{}0.06\phantom{\rule{0.28em}{0ex}}\mathrm{nm}$ for ${t}_{\mathrm{Hf}}=2\phantom{\rule{0.28em}{0ex}}\mathrm{nm}$. Damping measurements allowed concluding to the weaker spin pumping contribution by the CoFe/Hf interface compared to Pt/CoFe. The analysis of the ${t}_{\mathrm{Hf}}$ dependence of damping within a model considering the contribution of each interface allowed us to determine the spin diffusion length of Hf, found to be 1.7 nm. The Hf thickness dependence of iDMI and PMA constants revealed significant (weak) contribution of the CoFe/Hf interface to PMA (iDMI). The surface iDMI constant of CoFe/Hf interface was estimated to be $(\ensuremath{-}0.37\ifmmode\pm\else\textpm\fi{}0.12)\ifmmode\times\else\texttimes\fi{}{10}^{--7}\phantom{\rule{0.28em}{0ex}}\mathrm{erg}/\mathrm{cm}$. This suggests that the iDMI sign of Hf and Pt are opposite, and an additive behavior can be obtained when they are placed in opposite sides of the CoFe layer, allowing thus to strengthen the iDMI, needed for some applications. Quadratic correlations between PMA and iDMI constants and linear dependence of damping versus PMA constant were obtained confirming their relationship with the spin-orbit coupling.

Release flux of heavy metals from river sediments at different flow rates

Abstract This paper simulates sediment motion under different hydrodynamic conditions, aiming to investigate the release flux of heavy metals in river sediments. During the lab experiments, carried out in a circular rectangular flume device, water velocity in the flume was altered by controlling the gate switch, and the flow rate was controlled from 0 to 1 m/s. Sediment from the Le'an River and chlorine-removed tap water were used as experimental sediment and water, respectively. Through analyses of Cu, Zn, Cd, and Pb concentration in water at different flow rates, the relationship between the release flux (y) of Cu, Zn, Cd, and Pb and the flow rate (x) was established with a fitting error of less than 15%. In order to judge the reliability of the conclusions, experimental results were verified outdoors. The results showed when the sediment particle size is between 0 and 250 μm, within 1 hour, a quadratic polynomial correlation between the release flux of Cu, Cd, and Pb from river sediments and water velocity when the water pH is 5–9 and the flow rate is 0–65 cm/s; when the water pH is 5–9, the flow rate is 0–35 cm/s, the release flux of Zn from river sediments was shown to have a quadratic polynomial relationship with water velocity. The error between the calculated and measured values of heavy metals released from sediment in the Le'an River were within 5–30%. Our results can provide a theoretical reference for the control and treatment of heavy metal pollution in rivers and further improve corresponding water quality models.

Effects of post-washing on pretreated biomass and hydrolysis of the mixture of acetic acid and sodium hydroxide pretreated biomass and their mixed filtrate

Effects of post-washing [one-volume water (I-VW) or double-volume water (Ⅱ-VW)] on pretreated hemp and poplar biomass and enzymatic hydrolysis of the mixture of HOAc and NaOH pretreated biomass and their mixed filtrate were investigated. Compared to I-VW, Ⅱ-VW increased 3.76–6.80% of glucan content in NaOH pretreated biomass, diminished lignin recondensation, and heightened cellulose-related FTIR peak intensities, crystallinity index, and lignin removal. The pH of mixed filtrate was around 4.80, precipitating the NaOH soluble lignin partially. Although Ⅱ-VW showed lower lignin recoveries than I-VW, their FTIR characteristics were equivalent to the commercial alkali lignin. Enzymatic hydrolysis at solid loadings of 2.5–10% (w/v) demonstrated that I-VW and Ⅱ-VW had marginal variations in sugar concentration and conversion efficiency, indicating that I-VW is sufficient for post-washing pretreated biomass. Glucose concentration exhibited a quadratic correlation with solid loading and hemp biomass reached the maximum glucose (43.88 g/L) and total sugar (57.08 g/L) concentrations with I-VW.

The use of ultrasonographic measurement of the heart size and fetal heart rate variation for gestational age determination in local Bulgarian goats.

BackgroundDetermination of gestational age in goats was performed using ultrasound measurements of different fetal biometric parameters. There are no data showing quadratic and exponential dependence between fetal heart parameters and gestational age.ObjectivesThe objective of the present study was to test the significance of the defined indicators (fetal heart rate, longitudinal and transverse fetal heart axes) for determining gestational age in local Bulgarian goats.MethodsA total of 24 pregnant local Bulgarian goats, aged between 2 and 5 years, body weight 42–50 kg were included in the study. Ultrasonographic examinations were performed weekly on gestational days 21, 28, 35, 42 and 49. After gestational day 49 until parturition, scans were performed biweekly. The data from the measurements were subjected to linear (y = a + bx), quadratic (y = aх 2 + bх + c) and exponential (y = ax n) correlation. Results: Average fetal heart rate values decreased with pregnancy progression. The coefficient of determination (R2) and standard error of estimate (SEE) of the heart rate indicator were 0.72, 0.75, 0.58 and 15.1, 14.4, 19.2 days, respectively, for the three correlations. Longitudinal diameter (long axis) had the following values for R2 = 0.94, 0.96, 0.96 and for SEE = 7.0, 5.5, 5.5 days, for the linear, quadratic and exponential correlations, respectively, while the values of the fetal heart transverse diameter (short axis) were higher than those of the external one (R2 = 0.95, 0.97, 0.97). Simultaneously, SEE is lower (SEE = 6.1, 4.9, 5.0 days) compared to that found for the long heart fetal axis.ConclusionsFor precise estimation of gestational age, use of longitudinal (long) and transverse (short) axes is recommended. Fetal heart rate is not an exact indicator but can be used as a reference for gestational age along with changes in the heart size and echogenicity.

Explosion behaviors of hydrogen-nitrous oxide mixtures at reduced initial pressures

In this study, we report the explosion characteristics of H2/N2O mixtures at fuel-lean side and stoichiometric condition in a 113 L cylindrical vessel. Experiments were performed at different sub-atmospherical pressures (P0 =10 kPa–40 kPa). Explosion pressure traces were obtained by a pressure transducer mounted on the wall. Meanwhile, the flame morphology was recorded using schlieren visualization. The maximum explosion pressure (Pmax) and maximum pressure rise rate ((dp/dt)max) were derived and discussed. Results show that two competitive effects (i.e., the adiabatic flame temperature and the molecular number) make the maximum Pmax occurring at φ =0.5—0.6. Linear correlations were found between Pmax and P0. Except the adiabatic flame temperature and flame propagation speed, the flame instability was found to participate in dominating the maximum pressure rise rate. For increased initial pressure, the equivalence ratio of the maximum (dp/dt)max switches to the lean side due to the enhanced flame instability. Depending on different equivalence ratios, both linear and quadratic correlations were found between (dp/dt)max and P0.

Multiphysics coupling study on the effect of blood flow pulsation in patients with pulsatile tinnitus

This work aimed to investigate the effect of blood flow pulsation in patients with pulsatile tinnitus (PT). Nine blood flow patterns with different pulsations were designed on the basis of the blood flow data of a patient with PT (control group; cases with blood flow pulsation indexes that had decreased by 20%, 40%, 60%, and 80%; and cases with blood flow pulsation indexes that had increased by 20%, 40%, 60%, and 80%). The transient-state multiphysics coupling method was used to clarify the biomechanical and acoustic changes that had occurred under different blood flow pulsations. Results showed that blood flow impacted directly the vessel wall in the sigmoid sinus wall dehiscence (SSWD) area. The impact velocity of the blood flow slowed with the decrement in blood flow pulsation index but increased with the increase in blood flow pulsation index. With the reduction in blood flow pulsation index, the average pressure of the SSWD area decreased by 1.84, 3.93, 6.23, and 8.31 Pa; the average displacement of the vessel wall in the SSWD area decreased by 0.11, 0.23, 0.36, and 0.48 µm; and the average sound pressure level at the tympanum decreased by 2.2, 4.16, 7.14, and 12.97 dB. By contrast, with the increase in blood flow pulsation index, the average pressure increased by 2.46, 4.21, 6.28, and 8.56; the average displacement increased by 0.14, 0.2, 0.36, and 0.49 µm; and the average sound pressure level increased by 1.32, 2.87, 4.15, and 5.19 dB. Statistical analysis revealed that the pathological induction of PT had a strong quadratic correlation with the pulsation of blood flow. The degree of PT could be attenuated by reducing blood flow pulsation. Such an approach would aid clinical treatment. The conclusion obtained in this work would present a theoretical basis for the treatment of patients with PT.

Dynamics of physiological characteristics and dry matter accumulation under rain-water storage irrigation

Photosynthesis is related to dry matter accumulation in aboveground part of rice plant, which is the direct factor of production. This study carried out research on physiological indicators and the relationship between photosynthesis and dry matter accumulation under different water management in paddy field. In general, the photosynthetic and physiological indicators showed the trend of increasing and then decreasing with the growth stage of rice. Experimental results showed that, chlorophyll content and leaf area index of rice leaves showed a quadratic curve positive correlation. Canopy light transmission reached the maximum at heading-flowering stage, and it had quadratic relationship with leaf area index, while it showed extremely positive correlation under rain-water storage irrigation mode. Photosynthetic rate (Pn) and transpiration rate (Tr) had quadratic curve positive correlation with chlorophyll content. The water condition under rain-water storage was favorable for dry matter accumulation in panicle. After multiple regression and main factor analysis, canopy light transmission, light transmission coefficient and Pn were main factors related to dry matter accumulation. The conclusions in this article were helpful for promoting rice yield in practice. Keywords: physiological index, dry matter accumulation, canopy light transmission, regression analysis DOI: 10.25165/j.ijabe.20211403.5771 Citation: Li Y Y, Shao X H, Li Y B, Xiao M H. Dynamics of physiological characteristics and dry matter accumulation under rain-water storage irrigation. Int J Agric & Biol Eng, 2021; 14(3): 148–155.

Fluctuations and correlations of net baryon number, electric charge and strangeness in a background magnetic field

We present results on the second-order fluctuations of and correlations among net baryon number, electric charge and strangeness in (2+1)-flavor lattice QCD in the presence of a background magnetic field. Simulations are performed using the tree-level improved gauge action and the highly improved staggered quark (HISQ) action with a fixed scale approach ($a\simeq$ 0.117 fm). The light quark mass is set to be 1/10 of the physical strange quark mass and the corresponding pion mass is about 220 MeV at vanishing magnetic field. Simulations are performed on $32^3\times N_\tau$ lattices with 9 values of $N_\tau$ varying from 96 to 6 corresponding to temperatures ranging from zero up to 281 MeV. The magnetic field strength $eB$ is simulated with 15 different values up to $\sim$2.5 GeV$^2$ at each nonzero temperature. We find that quadratic fluctuations and correlations do not show any singular behavior at zero temperature in the current window of $eB$ while they develop peaked structures at nonzero temperatures as $eB$ grows. By comparing the electric charge-related fluctuations and correlations with hadron resonance gas model calculations and ideal gas limits we find that the changes in degrees of freedom start at lower temperatures in stronger magnetic fields. Significant effects induced by magnetic fields on the isospin symmetry and ratios of net baryon number and baryon-strangeness correlation to strangeness fluctuation are observed, which could be useful for probing the existence of a magnetic field in heavy-ion collision experiments.

Sensitivity analysis of design parameters and power gain correlations of bi-facial solar PV system using response surface methodology

Sensitivity analysis of design parameters and power gain correlations of bi-facial solar PV system is presented in this paper. The main objectives are to study the effects of albedo, tilt angle and height from the ground on the performance of the system; determine the optimum operating conditions; and the development of new correlations for the annual energy yield and bifacial gain of bPV solar system. Three primarily significant installation parameters, albedo [10%, 50%, 90%], tilt angle [15°, 25°, 35°] and height [0.5 m, 1 m, 1.5 m] are investigated with PVSYST for bifacial and mono-facial PV modules. The response surface methodology (RSM) based optimization method is used to determine the optimum conditions and the interaction of these three parameters on the performance of bPV solar system. New quadratic equations or correlations are introduced to estimate the annual energy yield and bifacial gain of bPV. The results show that the albedo is the most significant parameter between tilt angle and height. The increase in albedo factor and height of bPV modules from ground increase the energy yield. In this study, the optimum tilt angle of bPV is found to be 35°for higher albedo and elevation of bPV from the ground as compared to 25° of mPV. An average daily bifacial gain of 35.68% can be achieved in clear sunny day with 90% albedo, tilt angle of 35° and at height of 1.5 m. The maximum specific productions of 192.4 kWh/kWp and 160.6 kWh/kWp are observed in May for bPV and mPV, respectively while the maximum bifacial gain of 21.93% is found in July.

Helicopter parenting and alcohol use in adolescence: A quadratic relation.

Aims: Research has underscored that an excessively intrusive parental style, defined as helicopter parenting, could be a risk factor for maladaptive behaviours in youth, including alcohol use and drug consumption. However, such at-risk behaviours have also been associated with low levels of parental involvement and warmth. Thus, the relationship between parental involvement and at-risk behaviours in adolescents is not clear. The purpose of the current study was to identify the relation between helicopter parenting and alcohol use in a sample of Italian youth. Design: The participants were 402 adolescents (233 female) between the ages of 14 and 19 years (M age= 17.20, SD = 1.66). Hierarchical multiple regression analyses were conducted to examine linear, quadratic, and exponential models and to verify which model best described the correlation. Results: The results showed a quadratic correlation between mothers’ helicopter parenting and alcohol use, whereby higher and lower levels of mothers’ helicopter parenting were associated with adolescents’ alcohol use. Conclusions: The empirical data are essential for improving our understanding of the implications and potential outcomes of helicopter parenting during adolescence.

Permeability variation analysis using the superficial diameter correlation with porosity change

Permeability characterization is a major factor for ensuring more environment-friendly operations and economically viable industrial applications related to carbon capture sequestration, hydrocarbon recovery, nuclear waste disposal, and remediation in groundwater. Regardless, the permeability variation caused by changes in formation stress is simply defined as the power-law function of porosity. An alternative formula can be presented using the Kozeny–Carman equation based on hydraulic diameter and tortuosity. However, the hydraulic tortuosity and the Kozeny constant cannot be precisely measured because of the extremely complex and microscale pores. Accordingly, this study considers the Kozeny–Carman equation for presenting the other definable variables and more general correlations for performing permeability variation analyses. Herein, the effective tortuosity and effective and superficial diameters of porous media are deduced adopting the conventional viscous flow theory. Subsequently, the Kozeny–Carman equation is improved by replacing the immeasurable variables with the effective variables. The correlations of all the key geometric variables with permeability variation are investigated via pore-scale simulations based on two types of 20-series porous medium models with a wide range of porosity (13.4%–47.4%) and permeability (0.0073 –18.3 Darcy). Herein, several impressive functional aspects of the superficial diameter were discovered with porosity changes, such as quadratic functional correlations, parallel shifts for each flow path, and less sensitive variations in low porosity ranges. Consequently, this study proved that permeability variations can be more precisely and generally estimated using the quadratic correlations of the superficial diameter with porosity changes.

Visualizing, quantifying, and controlling local hydrodynamic effects on biofilm accumulation in complex flow paths

Complex flow paths (CFPs) are commonly applied in precision equipment to accurately supply controllable fluids with designed structures. However, the presence of biofilms in CFPs causes quite a few unwanted issues, such as bio-erosion, clogging, or even health risks. To date, visualizing and quantifying the interaction between biofilm distribution and local hydrodynamics remains difficult, and the mechanism during the process is unclear. In this paper, the remodeling simulation method (3D industrial computed tomography scanning-inverse modeling-numerical simulation) and 16S rRNA high-throughput sequencing were integrated. The results indicated that local hydrodynamic characteristics significantly affected biofilm thicknesses on CFP surfaces (relative differences of 41.3–71.2%), which inversely influenced the local turbulence intensity. The average biofilm thicknesses exhibited a significant quadratic correlation with the near-wall hydraulic shear forces (r > 0.72, p < 0.05), and the biofilm reached a maximum thickness at 0.36–0.45 Pa. On the other hand, the near-wall hydraulic shear forces not only affected microbial community characteristics of biofilms, but they also influenced the number of microorganisms involved, which determined the biofilm accumulation thereafter. The PHYLUM Firmicutes and Proteobacteria were the dominant bacteria during the process. The results obtained in this paper could provide practical conceptions for the targeted control of biofilms and put forward more efficient controlling methods in commonly applied CFP systems.

Urinary N-terminal pro\u2013B-type natriuretic peptide as a biomarker for cardiovascular events in a general Japanese population: the Hisayama Study

BackgroundEpidemiological evidence has shown that serum N-terminal pro-brain natriuretic peptide (NT-proBNP) concentrations, a diagnostic biomarker for heart failure, are positively associated with cardiovascular risk. Since NT-proBNP in serum is excreted in urine, it is hypothesized that urinary NT-proBNP concentrations are correlated with serum concentrations and linked with cardiovascular risk in the general population.MethodsA total of 3060 community-dwelling residents aged ≥ 40 years without history of cardiovascular disease (CVD) were followed up for a median of 8.3 years (2007–2015). Serum and urinary concentrations of NT-proBNP at baseline were compared. The hazard ratios (HRs) and their 95% confidence intervals (CIs) for the association between NT-proBNP concentrations and the risk of developing CVD were computed using the Cox proportional hazards model.ResultsThe median values (interquartile ranges) of serum and urinary NT-proBNP concentrations at baseline were 56 (32–104) pg/mL and 20 (18–25) pg/mL, respectively. There was a strong quadratic correlation between the serum and urinary concentrations of NT-proBNP (coefficient of determination [R2] = 0.72): urinary concentrations of 20, 27, and 43 pg/mL were equivalent to serum concentrations of 55, 125, and 300 pg/mL, respectively. During the follow-up period, 170 subjects developed CVD. The age- and sex-adjusted risk of CVD increased significantly with higher urinary NT-proBNP levels (P for trend < 0.001). This association remained significant after adjustment for traditional cardiovascular risk factors (P for trend = 0.009). The multivariable-adjusted risk of developing CVD almost doubled in subjects with urinary NT-proBNP of ≥ 43 pg/mL as compared to those with urinary NT-proBNP of ≤ 19 pg/mL (HR 2.07, 95% CI 1.20–3.56).ConclusionsThe present study demonstrated that urinary NT-proBNP concentrations were well-correlated with serum concentrations and were positively associated with cardiovascular risk. Given that urine sampling is noninvasive and does not require specially trained personnel, urinary NT-proBNP concentrations have the potential to be an easy and useful biomarker for detecting people at higher cardiovascular risk.

Modeling and Optimization of Biochar Based Adsorbent Derived from Kenaf Using Response Surface Methodology on Adsorption of Cd2+

Cadmium is one of the most hazardous metals in the environment, even when present at very low concentrations. This study reports the systematic development of Kenaf fiber biochar as an adsorbent for the removal of cadmium (Cd) (II) ions from water. The adsorbent development was aided by an optimization tool. Activated biochar was prepared using the physicochemical activation method, consisting of pre-impregnation with NaOH and nitrogen (N2) pyrolysis. The influence of the preparation parameters—namely, chemical impregnation (NaOH: KF), pyrolysis temperature, and pyrolysis time on biochar yield, removal rate, and the adsorption capacity of Cd (II) ions—was investigated. From the experimental data, some quadratic correlation models were developed according to the central composite design. All models demonstrated a good fit with the experimental data. The experimental results revealed that the pyrolysis temperature and heating time were the main factors that affected the yield of biochar and had a positive effect on the Cd (II) ions’ removal rate and adsorption capacity. The impregnation ratio also showed a positive effect on the specific surface area of the biochar, removal rate, and adsorption capacity of cadmium, with a negligible effect on the biochar yield. The optimal biochar-based adsorbent was obtained under the following conditions: 550 °C of pyrolysis temperature, 180 min of heating time, and a 1:1 NaOH impregnation ratio. The optimum adsorbent showed 28.60% biochar yield, 69.82% Cd (II) ions removal, 23.48 mg/g of adsorption capacity, and 160.44 m2/g of biochar-specific area.

Assessment of metabolic control and use of flash glucose monitoring systems in a cohort of pediatric, adolescents, and adults patients with Type 1 diabetes.

Flash glucose monitoring (FGM) in patients with type 1 diabetes (DM1) provides glucometric data that allow assessing glycemic control beyond HbA1c. The objective of this study was to evaluate metabolic control and use of FGM in a cohort of the pediatric and adult population with DM1. A cross-sectional study of patients with DM1 and FGM. Data on the use of the system and metabolic control were evaluated, carrying out a comparative study between different age ranges, ≤12 years; 13-19 years, 20-25 years, and ≥26 years. One hundred and ninety-five patients have included: 35.9% children and adolescents (≤19 years), 42.6% female, 26.2% in treatment with an insulin pump. Mean age was 28.5 ± 15.9 years, mean duration of diabetes 13.7 ± 11.0 years, and mean HbA1c 7.1 ± 0.9% (54 ± 6 mmol/l). Average daily FGM scans were 11.1 ± 6.7. Mean glucose was 162 ± 35 mg/dl, mean standard deviation (SD) 66.1 ± 20.4 mg/dl, mean coefficient of variation 41.4 ± 7.9%, mean time in range (TIR) 58.8 ± 17.0%, mean time above range 33.7 ± 17.6% and mean time below range 7.5 ± 5.8%. The pediatric group showed higher TIR, lower HbA1c, lower glycemic variability, lower mean glucose, and higher use of the device than the adult population. In the entire cohort, the device scans showed a negative quadratic correlation with HbA1c, mean glucose, SD, and age and a positive quadratic correlation with TIR. Children under 12 years showed the best metabolic control and the most frequent use of the device. Metabolic control deteriorates with age. The greater number of device scans was in correlation with better metabolic control in all age groups.

Utilization and regeneration of waste sugarcane bagasse as a novel robust aerogel as an effective thermal, acoustic insulator, and oil adsorbent

To deal with the frequent oil-spillage, various sorbents were developed, however, the poor oil/water selectivity and expensive hydrophobic coatings limit widespread. Further, the rise in the earth’s temperature and noise pollution enforce the scientific community to develop economic thermal and acoustic insulators. To explore this, the waste sugarcane bagasse was utilized to synthesize an ultra-light, porous, and flexible macroscopic aerogel through a simple and easily scalable two-step process. Through the surface modification with novel Silicon Ceramic coating, it exhibits super-hydrophobicity as revealed from the water contact angle of 140.1°. The synthesized aerogel exhibits low density (0.012–0.108 g/cc), high porosity (92.8–99.2%), high surface area (309.8–368.3 m2/g), low thermal conductivity (0.026–0.044 W/mK), and an excellent sound absorption coefficient of 0.83 (20% superior to the commercial acoustic insulators). Moreover, the oil adsorption investigations revealed that it could uptake 23 times of crude oil of its weight. Furthermore, the adsorbed oil can be effortlessly recovered by acetone treatment for its further usage as an oil sorbent. Besides, it could retain oil uptake capacity up to ten regeneration cycles. Simultaneously, a quadratic correlation for the oil adsorption capacity was developed to optimize the amount of crosslinkers. Again, the high compressive strength (20–41 kPa) of the aerogel couples its usage as an effective material for thermal, acoustic insulation, and oil spill cleaning.

Geography and climate regime affect needle stoichiometry character of Pinus bungeana across China

Leaf stoichiometric pattern and its potential determinants are of great significance in the modeling nutrient cycling, detecting ecosystem stability and predicting the response of ecosystem to global changes. To reveal the stoichiometric characteristic of Pinus bungeana, we analyzed the needle nitrogen (N) and phosphorous (P) concentrations of 76 needle samples from 15 sampling sites throughout the country, and took the local geographical and climatic variables into consideration. The generalized linear mixed model (GLMM) and principal component analysis (PCA) were used to explore the effects of environmental factors on needle stoichiometry. This study revealed that both the concentrations and ratio of N, P content showed significant differences in needles of P. bungeana among different sampling sites. The needle N, P concentrations and N: P ratio showed quadratic curve correlation with climatic factors. The PCA indicated that all variables can be explained by three principal components, namely, temperature, N and P, which were very important factors affecting the geographical distribution of P. bungeana. Among the three components, N is most crucial factor limiting the growth and metabolism of P. bungeana. In summary, our study will help to elucidate the patterns of needle N and P concentrations in needles of P. bungeana, thus revealing the causes and driving forces for its natural region.

A study on the transient heat generation rate of lithium-ion battery based on full matrix orthogonal experimental design with mixed levels

Determination of the heat generation rate of the lithium-ion battery is crucial in both the design of battery thermal management system (BTMS) and prediction of the transient temperature rise during dynamic operation. In this work, the commercial cylindrical 18,650 lithium-ion battery with Ni-Co-Mn ternary positive materials was exemplified by the full matrix orthogonal experimental design to obtain the heat generation rate. The experiment with 176 over-potential tests and 66 entropy coefficient tests was conducted by taking into account the influencing parameters including the depth of discharge (DOD), discharge rate (DR) and ambient temperature. It was found that the heat generation rate exhibited minor variation for DOD=0~0.8 with slight decrease in the segment of DOD=0.3~0.6, and increased rapidly near the end of discharge (DOD=0.8~1). The average heat generation rate showed the approximate quadratic nonlinear correlation with discharge rate. In addition, the third-order transient heat generation rate model of the lithium-ion battery was correlated with all the influencing parameters by the response surface methodology (RSM). This work provides a detailed method for determining the heat generation rate of the lithium-ion battery, which lays foundation for predicting the temperature field of the battery and designing battery thermal management system.

Temperature control of a low-temperature district heating network with Model Predictive Control and Mixed-Integer Quadratically Constrained Programming

District heating networks transport thermal energy from one or more sources to a plurality of consumers. Lowering the operating temperatures of district heating networks is a key research topic to reduce energy losses and unlock the potential of low-temperature heat sources, such as waste heat. With an increasing share of uncontrolled heat sources in district heating networks, control strategies to coordinate energy supply and network operation become more important. This paper focuses on the modeling, control, and optimization of a low-temperature district heating network, presenting a case study with a high share of waste heat from high-performance computers. The network consists of heat pumps with temperature-dependent characteristics. In this paper, quadratic correlations are used to model temperature characteristics. Thus, a mixed-integer quadratically-constrained program is presented that optimizes the operation of heat pumps in combination with thermal energy storages and the operating temperatures of a pipe network. The network operation is optimized for three sample days. The presented optimization model uses the flexibility of the thermal energy storages and thermal inertia of the network by controlling its flow and return temperatures. The results show savings of electrical energy consumption of 1.55%–5.49%, depending on heat and cool demand.