Peak Value Research Articles

Research on abutment stress distribution of roof-cutting coalface: numerical simulation and field measurement

During the processing of deep mining, revealing the distribution of abutment pressure is significant for controlling stability of the entry. In this study, the abutment pressure distribution of roof-cutting coalface was investigated by FLAC3D and self-developed flexible detection unit (FDU). In the numerical simulation, the double-yield model was built to analyze the goaf abutment pressure under the fracturing roofs to maintain entry (FRME). Compared with the non-fracturing side, the peak value of the advanced abutment pressure on the fracturing side is reduced by 19.29% on average, the influence range (span) increases by 30.78% and the distance between the peak value and the working face increases by 66.7%. The goaf abutment pressure within 23m near the cutting side is significantly higher than other areas along the dip. The FDU was employed in the coalface to record the change of advanced abutment stress. And the field measured results are in well agreement with the numerical results.

Study on Radiation Damage of Silicon Solar Cell Electrical Parameters by Nanosecond Pulse Laser

This experimental study investigates the damage effects of nanosecond pulse laser irradiation on silicon solar cells. It encompasses the analysis of transient pulse signal waveform characteristics at the cells’ output and changes in electrical parameters, such as I–V curves before and after laser irradiation under varying laser fluence and background light intensities, and explores the underlying action mechanisms of laser irradiation. The study reveals that as the laser fluence increases up to 4.0 J/cm2, the peak value of the transient pulse signal increases by 47.5%, while the pulse width augments by 88.2% compared to the initial transient pulse signal. Furthermore, certain parameters, such as open-circuit voltage, short-circuit current, and peak power obtained, from the measured I–V curve indicate a threshold laser fluence for functional degradation of the solar cell at approximately 1.18 ± 0.42 J/cm2. Results obtained from laser irradiation under different background light intensities underscore the significant influence of background light on laser irradiation of silicon cells, with the most severe damage occurring in the absence of light. Moreover, findings from laser irradiation at multiple locations on the silicon cell demonstrate a linear decrease in the output voltage of the silicon cell with an increase in the number of irradiation points.

A novel quantitative method to evaluate lumbar disc degeneration: MRI histogram analysis.

This study aimed to use MRI histogram analysis to routine MRI sequences to evaluate lumbar disc degeneration (LDD), illustrate the correlation between this novel method and the traditional Pfirrmann classification method, and more importantly, perform comprehensive agreement analysis of MRI histogram analysis in various situations to evaluate its objectivity and stability. Lumbar MRI images from 133 subjects were included in this study. LDD was classified into grades by Pfirrmann classification and was measured as peak separation value by MRI histogram analysis. Correlation analysis between the two methods was performed and cutoff values were determined. In addition, the agreement analysis of peak separation value was performed by intraclass correlation coefficient (ICC) in four scenarios, including inter-resolution, inter-observer, inter-regions of interest (ROI) and inter-slice. Peak separation values were strongly correlated with Pfirrmann grades (r = - 0.847). The inter-resolution agreements of peak separation value between original image resolution of 2304 × 2304 and compressed image resolutions (1152 × 1152, 576 × 576, 288 × 288) were good to excellent (ICCs were 0.916, 0.876 and 0.822), except 144 × 144 was moderate (ICC = 533). The agreements of inter-observer (ICC = 0.982) and inter-ROI (ICC = 0.915) were excellent. Compared with the mid-sagittal slice, the inter-slice agreements were good for the first adjacent slices (ICCs were 0.826 and 0.844), and moderate to good for the second adjacent slices (ICC = 0.733 and 0.753). MRI histogram analysis, used in routine MRI sequences, demonstrated a strong correlation with Pfirrmann classification and good agreements in various scenarios, expanding the range of application and providing an effective, objective and quantitative tool to evaluate LDD.

Numerical Simulation on the Spray Angle of the Dual-layer Hole Nozzle in a Partition Combustion System of the Diesel Engine

To study the effect of the spray angles of the dual-layer hole nozzle on the combustion and emissions performance in the partition combustion system, the in-cylinder spray, mixture formation and combustion processes of the new combustion system were simulated and investigated using AVL FIRE software. The results show that, compared with the variation of the lower-layer spray angles, the change of the upper-layer spray angles has a great influence on the instantaneous heat release rate. The increasing spray angles of the lower-layer holes lead to reduced peak values of the heat release rate in the cylinder. In all the spray angle cases, the first fire area of the cylinder is in the B zone of the combustion chamber. Compared with lower-layer spray angle, the upper-layer spray angle has a greater impact on the airflow disturbance in the combustion chamber. Appropriately increasing the upper-layer spray angle facilitates the mixing of fuel and air in the combustion chamber and reduces the unburnt fuel equivalence ratio. When the spray angles of the upper- and lower-layer holes are 157° and 112°, respectively, the combustion indicates power has the largest value of 12.18 kW. At the same time, the Soot emission is also the smallest, with a value of 0.52 g/kW·h.

Simultaneous realization of high power factor and low thermal conductivity in medium-entropy La-doped (Sr1/3Ba1/3Ca1/3)1-xLaxTiO3 oxides with porous structure

Some studies have proven the effectiveness of high-entropy alloying in reducing lattice thermal conductivity; however, the synchronous degradation in carrier mobility limits the thermoelectric properties of high-entropy materials. Herein, we present a series of medium-entropy oxides (Sr1/3Ba1/3Ca1/3)1-xLaxTiO3 (x = 0.05, 0.1, 0.15) with different levels of La doping, breaking the trade-off between carrier and phonon transport. The medium-entropy design helps keep the carrier mobility at a moderate level while modulating the carrier concentration through La3+ doping, thereby yielding a peak power factor value of 1842 μW/(m⋅K2) at 773 K. Meanwhile, the incorporation of nano-micro-porous structure and medium entropy effect leads to a significant reduction in lattice thermal conductivity, reaching 2.3 W/(m⋅K) at 1073 K. Consequently, a ZTmax value of 0.67 is obtained for the MEP-10La sample at 1073 K, which is one of the state-of-the-art ZT values reported for the SrTiO3-based materials. The present work provides a viable approach for the development of thermoelectric materials with enhanced performance.

Experimental study on the effect of circulating liquid velocity on bubble size distribution and turbulence characteristic in an external loop airlift reactor

AbstractThe influence of circulating liquid velocity on bubble size distribution (BSD) and turbulence characteristics of an external loop airlift reactor was studied in this paper. The instantaneous and time‐averaged velocity in the riser were studied using particle image velocimetry (PIV), and BSDs were measured by digital image analysis technique based on machine learning. Then turbulence kinetic energy (TKE) and energy dissipation rate (EDR) were calculated through the velocity field. The results indicate that as the circulating liquid velocity increased, the peak value of BSD rapidly decreased from nearly 6 mm to approximately 2 mm. The radial velocity of the liquid gradually decreased and changed direction, eventually increasing again. TKE first decreased and then increased. Compared with bubble flow with a BSD peak of 2–6 mm, bubble flow with a BSD peak of 2 mm had larger TKE. The radial movement of bubbles had great influence on the turbulence characteristics. This study demonstrates that selecting an appropriate circulating liquid velocity can reduce the diameter of bubbles while obtaining greater TKE, thereby improving the mass transfer and reaction efficiency in external loop airlift reactors (EL‐ALR).

Efficacy and safety of levosalbutamol in patients with mild to moderate asthma compared with racemic salbutamol: results of a crossover placebo-controlled study

Aim. Effectiveness and safety of levosalbutamol metered dose inhaler (MDI) in comparison with placebo and salbutamol. Materials and methods. In this multicenter, randomized, placebo-controlled, 3-period crossover study, all asthma patients (n=91) received levosalbutamol (90 mcg), salbutamol (180 mcg), and placebo using standard MDI. Pulmonary function testing – forced expiratory volume in the first second (FEV1) and forced vital capacity (FVC) – was performed 45 and 15 minutes before and 5, 10, 15, 30, 60, 90, 120, 180, 240, 300 and 360 minutes after dosing. The primary efficacy endpoint was the baseline-corrected area under FEV1 curve from 0 to 6 hours (AUC(0–6h)). Secondary endpoints were the baseline adjusted FEV1 and FVC peak values, as well as the onset of drug action. Results. The FEV1 AUC0–6 hours analysis confirmed similar bronchodilatory levosalbutamol and salbutamol effect (p=0.595), significantly improved compared with placebo (p0.001). The peak values of FEV1 and FVC after levosalbutamol or salbutamol dosing were similar (p=0.643) and significantly higher compared with placebo group (p0.001). The active therapy effect was observed 5 minutes after dosing and throughout the entire observation period up to 6 hours, however, there was some tendency towards a longer duration of action of levosalbutamol compared to salbutamol. Levosalbutamol was well tolerated by patients; after levosalbutamol dosing twiсе fewer adverse reactions were observed compared to salbutamol. Conclusion. Levosalbutamol at a 90-mcg dose showed efficacy similar to that of salbutamol at a dose of 180 mcg, assosiated with a good safety profile.

Constraining Trifluoromethane (HFC‐23) Emission in Eastern China Based on Two‐Year Online Measurements

AbstractTrifluoromethane (CHF3, HFC‐23) is one of the most potent greenhouse gases (GHGs), and eastern China has been recognized as a major source region, yet highly inconsistent emission estimates warrant more extensive studies. In this study, we conducted 2‐year online measurements of halocarbons during 2021–2023 at an urban site in the Pearl River Delta region. The observed average HFC‐23 mixing ratios of 43.6 ± 7.8 ppt were ∼20% enhanced compared to observations at the Mace Head global baseline station. Unlike other halocarbons with significant local emissions, HFC‐23 mixing ratios showed distinct seasonal variations with peak values in winter and bottom values in summer. Similar seasonal patterns and highly significant correlation were observed between HFC‐23 and perfluorocyclobutane (c‐C4F8, PFC‐318), a co‐product from manufacturing PTFE using chlorodifluoromethane (CHClF2, HCFC‐22) as feedstock. The weighted potential source contribution function analysis also demonstrated eastern China was the major source area for both HFC‐23 and PFC‐318. Tracer‐based estimation revealed HFC‐23 emissions of 6.7 ± 3.1 Gg yr−1 (equivalent to 98 Tg‐CO2 yr−1 or 0.7% China's annual GHG emissions in 2021) in eastern China. Our results highlight the importance of HFC‐23 emission control in eastern China for China's GHG and F‐gases emission reductions, and suggest that greater attention should be given to HFC‐23 emissions from PTFE production, which is emerging as a more substantial source than previously anticipated.

The development of high‐strength, anticorrosive, and strongly adhesive polyaspartate polyurea coating suitable for pipeline spray repairs

AbstractThis study synthesized polydimethylsiloxane (PDMS)‐modified polyaspartate polyurea (PPPU) with different ratios, considering the practical performance requirements of underground water supply pipeline spray repair materials. The successful synthesis of PPPU was confirmed using Fourier transform infrared spectrometer (FTIR) spectroscopy. The influence of the ratio of the two components and the content of ‐aminopropyl terminated polydimethylsiloxane (APT‐PDMS) on the drying time and tensile performance of PPPU coatings was evaluated. Based on this evaluation, a superior ratio for PPPU coatings was proposed. Subsequently, the bonding performance, hydrophobicity, and corrosion resistance of PPPU coatings at the superior ratio were tested. The results indicate that as the mass ratio of polyaspartic acid ester to hexamethylene diisocyanate trimer increases, both the drying time and tensile strength of the coating decrease. The addition of APT‐PDMS results in a decrease in the tensile strength of PPPU, but an increase in its elongation at break. The peak value of elongation at break is achieved when the APT‐PDMS content is 5%, making the PPPU2‐1‐5 coating the superior ratio for spray application on water supply pipelines. Through experiments, it was determined that the bonding strength of the PPPU2‐1‐5 coating with cement mortar under dry and humid conditions, static water contact angle (93.4°), and corrosion resistance performance are superior to those of the unmodified polyurea coating, demonstrating its application advantages. The conclusions drawn in this study provide a theoretical foundation for the practical engineering application of PPPU.

Pore structure development of cementitious materials with manufactured sand from various lithologies and differential effect of CaO–MgO blend expansion agent

With intensifying the contradiction between the demand and supply of nature sand (NS), the extensive utilization of manufactured sand (MS) as a substitute has become prevalent in various projects. The pore structure development plays a crucial role in early-age shrinkage of concrete, but research on pore structure development of cementitious materials incorporating diverse lithologic MS is still lacking. This study examined the effects of MS powders and particles from diverse lithologies on pore structure, along with the differential impacts of CaO–MgO blend expansion agent (CMEA) on the pore structure of mortar containing MS from different lithologies. The results demonstrated a significant reduction in the peak value of pore size distribution and porosity in cement paste after incorporating MS powder, particularly with the most pronounced effect observed in tuff powder. In mortar, the incorporation of tuff manufactured sand (TMS) also led to a substantial decrease in both the peak value and peak area. However, the pore size distribution peak value and areas of limestone manufactured sand (LMS) mortar were slightly higher than those of NS mortar at 3 and 7 days. In comparison to cement pastes, the secondary peak proportion in mortars increased by approximately 4–5 percentage points at 28 days. Furthermore, the harmful pores and severely harmful exhibited varying degrees of increase in diverse lithologic MS mortar after incorporating CMEA, with the highest increase observed in NS mortar and the smallest increase observed in TMS mortar.

A COMPARISON OF PEAK WORK RATES DURING SUPER SHOT AND NON-SUPER SHOT PERIODS IN PROFESSIONAL NETBALL PLAYERS

BACKGROUND Since its introduction, the super shot has been a critical period of play in the Australian domestic netball competition. Depending on their shot selection strategy, teams can increase their odds of outscoring oppositions during super shot periods. As a result, players are likely to complete more attacking and defensive actions, possibly increasing their workload. The purpose of this study was to quantify workload and make comparisons between i) super shot and non-supershot periods and ii) different player positions. METHODS Raw acceleration data (VX sport Log units Visuellex New Zealand) from 11 players across 14 matches was collected and used to calculate PlayerLoadTM. Quarters were split into three five-minute periods and player position for each period was reported. Data was only included if a player competed for a full five-minute period (n=1110). A rolling average was applied over 60 seconds to compare peak PlayerLoadTM values between periods and positions. A linear mixed effects model was used to determine the effect of the period and position on peak 60s PlayerLoadTM. Random intercepts were included for player and game, quarter was included as a random effect within game. RESULTS During super shot periods, peak values were significantly lower for GS compared to regular periods (model coefficient = 0.8, 95%CI = 0.02 to 1.59, P = 0.04). During super shot periods, GD and GK positions showed slightly higher peak values compared to regular periods, with model coefficients of -0.05 (95%CI = -1.20 to 0.327) and -0.21 (95%CI = -1.00 to 0.57) respectively. On the other hand, GA, WA, WD, and C positions exhibited lower peak values for super shot periods compared to regular periods. Results indicate that there are differences in peak workloads between positions during super shot periods. CONCLUSION Workload demands may be different between positions during super shot periods, this has implications for player conditioning.

Shear behavior of basalt fiber modified compacted red mudstone as subgrade fill material

This study experimentally investigated the shear behavior of basalt fiber-modified compacted red mudstone as a subgrade of a high-speed railway. We examined the effects of different vertical stresses, initial water contents, and fiber contents on brittleness and dilatancy. Several direct shear tests were conducted under the aforementioned conditions. The stress displacement curve tended to vary from softening to hardening with an increase in vertical stress. In the Mohr–Coulomb mode, except for the saturated state, the residual internal friction angle was greater than the peak value, whereas the residual cohesion was lesser than the peak value. The maximum cohesion occurred at the optimal water and fiber content, whereas the friction angle exhibited a downward trend with an increase in the contents discussed above. The brittleness index (I b ) was defined as the ratio of the peak to residual shear strengths. The magnitude of the brittleness index reduced with increase in the vertical stress. Moreover, the maximum value occurred at the optimal water and fiber content. Furthermore, the deformation mechanism was discussed based on the dilatancy angle(ψ). Based on the data, three different stages were proposed: Softening–Dilatancy (S1), the Hardening–Dilatancy (S2), and Hardening–Shrinkage (S3).

Changes in postural stability after cerebrospinal fluid tap test in patients with idiopathic normal pressure hydrocephalus.

In patients with idiopathic normal pressure hydrocephalus (iNPH), the characteristics of balance disturbance are not as well understood as those related to gait. This study examined changes in postural stability in quiet standing after the cerebrospinal fluid tap test (CSFTT) in these patients. Furthermore, the study explored the relationship between the amount of spontaneous body sway and both gait and executive function. All patients diagnosed with iNPH underwent CSFTT. We evaluated their center of pressure (COP) measurements on a force plate during quiet standing, both pre- and post-CSFTT. Following the COP measurements, we calculated COP parameters using time and frequency domain analysis and assessed changes in these parameters after CSFTT. At pre-CSFTT, we assessed the Timed Up and Go (TUG) and the Frontal Assessment Battery (FAB). We investigated the relationship between COP parameters and the TUG and FAB scores at pre-CSFTT. A total of 72 patients with iNPH were initially enrolled, and 56 patients who responded positively to CSFTT were finally included. Post-CSFTT, significant improvements were observed in COP parameters through time domain analysis. These included the velocity of COP (vCOP), root-mean-square of COP (rmsCOP), turn index, torque, and base of support (BOS), compared to the pre-CSFTT values (p < 0.05). In the frequency domain analysis of COP parameters post-CSFTT, there was a decrease in both the peak and average of power spectral density (PSD) values in both the anteroposterior (AP) and mediolateral (ML) directions below 0.5 Hz (p < 0.05). In addition, the TUG scores showed a positive correlation with vCOP, rmsCOP, turn index, torque, BOS, and both the peak and average PSD values in the AP and ML directions below 0.5 Hz (p < 0.05). The FAB scores demonstrated a negative correlation with vCOP, rmsCOP, turns index, BOS, and both peak and average PSD values in the AP direction below 0.5 Hz (p < 0.05). In patients with iNPH who responded to CSFTT, there was an improvement in spontaneous body sway during quiet standing after CSFTT. Increased spontaneous sway is associated with impaired gait and frontal lobe function. This may be linked to impaired cortico-cortical and cortico-subcortical circuits in patients with iNPH.

Mortality predictors in earthquake victims admitted to intensive care unit in Kahramanmaraş earthquakes

BackgroundThe purpose of this study is to report the data for patients followed-up in our intensive care unit due to the 6th February 2023, earthquake in Kahramanmaraş, Türkiye, and to investigate parameters affecting mortality. MethodsThe demographic characteristics of patients followed-up in intensive care due to trauma following the earthquake, the treatments administered, developing complications, lengths of stay in the hospital and intensive care, and laboratory data were scanned retrospectively and recorded. These data were then compared between the surviving and non-surviving patients. ResultsTwenty-six patients, 13 (50 %) male, were followed-up in our intensive care, 24 (92 %) due to being buried under earthquake debris, and 2 (8 %) due to falling from heights. Increased Sequential Organ Failure Assessment (SOFA) (p = 0.027), higher initial serum potassium (p = 0.043), higher initial serum phosphorus (p = 0.035), higher initial and peak serum magnesium (p = 0.004 and p = 0.001), lower initial and peak bicarbonate (p = 0.021 and p = 0.012) and higher initial and peak serum base deficit values (p = 0.012 and p = 0.009) were associated with mortality. In the subgroup with crush injuries, higher initial and peak serum potassium (p = 0.001 and p = 0.025), higher initial and peak serum magnesium (p = 0.005 and p = 0.004), lower initial and peak bicarbonate (p = 0.019 and p = 0.021) and higher initial and peak serum base deficit values (p = 0.017 and p = 0.025) were associated with mortality. Multiorgan dysfunction failure developed in nine patients, sepsis in seven, dissemine intravascular coagulation in four, and acute respiratory distress syndrome in two. Fasciotomy was performed on 2 (8 %) patients and amputation on 8 (31 %). Extremity injuries were most frequently observed. 10 (38.5 %) of the 12 (46 %) patients developing acute kidney injury required renal replacement therapy. 7 (27 %) patients died during follow-up. In logistic regression analysis, higher SOFA scores, lower initial bicarbonate and BE levels, higher serum initial potassium and magnesium levels were a risk factor for mortality. Higher SOFA scores, lower initial bicarbonate and base deficit and higher initial phosphorus values affected mortality in patients with crush syndrome. ConclusionNot only increased SOFA, serum potassium, serum phosphorus, and serum magnesium, but also decreased bicarbonate, and base deficit were associated with mortality in earthquake victims with crush syndrome in ICU.

Prediction method of regional carbon dioxide emissions in China under the target of peaking carbon dioxide emissions: A case study of Zhejiang

AbstractAll provinces of China respond to the central government, predict future carbon dioxide emissions, and formulate action plans detailing how the province intends to fulfill its target of carbon emission peaking before 2030. Based on the bottom‐up energy consumption prediction and top‐down goal verification, this paper constructs a set of regional carbon dioxide emission prediction methods. Compared to the traditional bottom‐up prediction method, this method could simplify the parameters while improving the prediction accuracy. This model is used to predict and analyze the process of carbon dioxide emission peaking in Zhejiang. The results show that the mean absolute percentage error of the retrospective prediction value is only 1.56%. Zhejiang will reach carbon dioxide emission peaking around 2029–2030, and the peak value will be 569.7 million tons. Different factors have different effects on the process of carbon dioxide emission peaking. There is a strong correlation between the peak time of carbon dioxide emission and the production time of major energy‐consuming projects in Zhejiang. Meanwhile, if the 16 nuclear reactors are not put into operation, Zhejiang will not be able to achieve the goal of carbon dioxide emission peaking. Besides, the basic data used in this model is mainly from the local statistical departments of the region. Thus, it can be applied to other provinces and regions conveniently.

MHD double diffusive mixed convection and heat generation / absorption in a lid-driven inclined wavy enclosure filled with a ferrofluid

The magneto-hydrodynamics (MHD) double-diffusive mixed convection and heat generation/absorption in a lid-driven inclined wavy enclosure filled with (Fe3O4/ water) ferrofluid is quantitatively investigated in this paper. The present study focuses on improving the efficiency of mass and thermal performance of a system. Both the left and right sidewalls of the cavity are allowed to move with a constant velocity in the upward and downward directions, respectively. The finite difference approach was applied to discretize the subsequent governing equations followed by the Bi-Conjugate Gradient Stabilized (Bi-CGStab) method to solve them. The numerical simulation was performed for a variety of parameters, including the Hartmann number varied as 0 ≤ Ha ≤ 45, the inclination angle of the enclosure varied as 0° ≤ δ ≤ 180°, the buoyancy ratio varied as -2 ≤ N ≤ 2, heat generation or absorption parameter varied as −10 ≤ Qo ≤ 10, Richardson number varied as 0.01 ≤ Ri ≤ 10, and solid volume fraction varied as 0 ≤ ϕ ≤ 0.06. The numerical simulation results were presented in terms of streamlines, isotherms, isoconcentrations, average Nusselt number, and average Sherwood number. The heat and mass transfer rates were found to decrease with the increase in Ha but increase with N, Ri, and Φ. Also, both of them reach their peak values at Ri = 10. In addition, the heat generation parameter enhances both thermal and mass performance as they reach their maximum values at Qo = 10. Increasing the heat generation factor from Qo = 5 to Qo = 10 increases the Nusselt number by 3.5 times. The outcomes of the study have significant importance for modern industrial applications specifically in the discipline of electronic device cooling.

Effect of temperature on the tensile deformation mechanisms of a fourth nickel-based single crystal superalloys

This work conducted tensile experiments from room temperature to 1100 °C on a new fourth-generation single crystal superalloys along [001]. The effect of temperature on the tensile properties and deformation mechanism of the alloy were investigated. Results showed that the yield strength of the alloy reached its peak value (1017 MPa) at 850 °C. From room temperature to 760 °C, the occurrence of stacking faults (SFs) was observed in the γ matrix channel. From the room temperature to 850 °C, the occurrence of stacking faults was observed in the γʹ phase. The interface dislocation networks appeared at 980 °C and above. At room temperature, stacking faults sheared γʹ phase, in which three types of stacking faults occurred, which controlled deformation process. The main deformation mechanism from 650 °C to 850 °C was the shearing of γʹ phase by stacking faults and super dislocations, and at 850 °C, stacking faults in different directions of propagation corresponded to the formation of Lomer-Cottrell locks (L-C locks), which greatly increased the yield strength. At 980 °C and 1100 °C, dislocation climbing and bypassing and anti-phase boundary (APB) coupled dislocation pair shear γʹ phase became the main deformation mechanism.

Trends of surface ozone based on hourly concentrations in the Beijing–Tianjin–Hebei region during 2017–2021

As a typical secondary air pollutant, surface ozone has been monitored routinely since 2013 in China. Most studies on the spatiotemporal variation of ozone have been centered around the daily maximum 8-h average, with little attention paid to the trends of hourly ozone, especially hourly ozone exceedances. Focusing on hourly ozone exceedances and peak values, the spatiotemporal trends of hourly ozone at 77 sites in 13 cities of the Beijing–Tianjin–Hebei (BTH) region during 2017–2021 were analyzed in this study. The number of hours with exceedances (NH200) in 2019 was nearly three times that of 2021. On a five-year average, the percentage of cumulative NH200 in June accounted for up to 40.5 % of all hourly exceedances. Cities in central Hebei Province had the highest cumulative annual NH200. June had the highest average hourly ozone exceeded multiples of 0.158. The top two cities with the highest average exceeded multiple were Tangshan (0.166) and Beijing (0.158). Tangshan and Xingtai ranked as the top two in terms of the mean of the 10 highest daily maximum ozone concentrations (MTDM), with 286.74 and 285.37 µg m−3, respectively. The gap between the MTDM and the daily maximum of hourly ozone averaged over all sites had narrowed to 97.88 µg m−3 in 2021, much lower than that in other years, which indicated that the stability and convergence of ozone pollution in BTH region had been enhanced in 2021 to some extent.摘要本文以京津冀地区为研究对象, 采用国际常用的评价指标, 在分析2017–2021年臭氧小时浓度变化趋势的基础上, 重点讨论了小时浓度超标情况及其峰值水平. 结果显示, 2019年臭氧小时浓度超标数约为2021年的3倍, 6月份小时浓度超标数占比高达40.5%, 河北中部城市小时浓度超标情况突出; 2017年和2019年臭氧小时浓度超标倍数在高位区间的占比相对最高, 唐山和邢台的小时浓度峰值水平相对较高. 本文可为后续进一步研究局地臭氧污染特征和异常污染事件提供基础参考.

Ultrahigh average zT realized in polycrystalline SnSe0.95 materials through Sn stabilizing and carrier modulation

The average zT determines the conversion efficiency, and the power factor plays an important role in average zT value. However, the inadequate electrical conductivity of SnSe materials seriously limits its application. Herein, the TaCl5-doped in polycrystalline SnSe0.95 materials synthesized using the melting method and combined with spark plasma sintering technology achieves a zT value of 1.64 at 773 K and a record zTave of 0.62 from 323 K to 773 K. The electrical conductivity increases due to the released electron carrier induced by effective TaCl5 doping. According to the DFT calculation, the energy band of TaCl5-doped samples is narrowed, which can enhance the electron transport. Besides, the Seebeck coefficient is maintained at an elevated level as a result of the incorporation of the heavy element Ta. Due to the significantly enhanced electrical conductivity and maintained high Seebeck coefficient, the power factor reaches to 622 μW·m–1·K–2 at 773 K for the SnSe0.95 + 1.75% (in mass) TaCl5 sample, which is almost 21 times higher than that of the pristine sample. Simultaneously, a high average power factor value of 334 μW·m–1·K–2 for the SnSe0.95 + 1.75% (in mass) TaCl5 sample from 323 to 773 K was obtained. It is surprisingly found that the Ta element plays another important role to improve the stability of SnSe0.95 by forming Ta2Sn3 and removing the low melting point Sn, which usually existed in n-type SnSe samples, resulting in the decreased lattice thermal conductivity. A low lattice thermal conductivity value of 0.24 W·m–1·K–1 was also obtained for the SnSe0.95 + 2.0% (in mass) TaCl5 sample at 773 K due to the multiscale defects. Consequently, the SnSe0.95 + 2.0% (in mass) TaCl5 sample obtains a peak zT value of 1.64 at 773 K and a record zTave of 0.62 from 323 to 773 K, and the theoretically calculated conversion efficiency reaches 11.2%, it can be utilized for power generation and/or cooling at a broad temperature range. This strategy of introducing high-valence halides with heavy element can optimize the thermoelectric performance for other material systems.

Effects of Neurodynamics Along With Conventional Exercises on Sciatica Patients: A Single-Blinded Randomized Clinical Trial.

Introduction Sciatica refers to a pain that travels along the course of the sciatic nerve. Patients also often experience paresthesia along with the pain in thighs, which may further radiate to the legs. Most commonly, compression of the lumbosacral nerve root is the cause of this syndrome. Neurodynamics and conventional exercises are considered effective treatment procedures for sciatica. This study aims to find out the efficacy of neurodynamics along with conventional exercises and conventional exercises alone. Methods A total of 58 patients with sciatica aged between 30 and 60 years of both genders were included in the study and randomly divided into a neurodynamic group (n=29) and a conventional group (n=29). Pre-test data were collected before the interventions, and post-test data were collected on the 14th day. The 101 numeric pain rating scale (NPRS) was used to measure data of sciatic pain, the patient-specific functional scale (PSFS) was used to measure the health-related quality of life (HRQL), and a surface electromyography (EMG) biofeedback instrument was used to measure the peak and average muscle activation of the biceps femoris muscle. Results The pre-post data analysis of the neurodynamics and conventional group showed significant (p<0.05) improvement in 101 NPRS, PSFS, and peak EMG values. Insignificant (p>0.05) improvements were seen in average EMG values in the conventional group, and significant (p<0.05) improvement were seen in the neurodynamic group. Between-group analysis showed insignificant (p>0.05) differences in 101 NPRS as well as peak and average EMG values and showed significant (p<0.05) differences in PSFS values. Conclusion Neurodynamics with conventional exercises can help in reducing pain, improving muscle activation of the biceps femoris, and elevating the HRQL of the patient.