Effect of Residual Charge Carrier on the Performance of a Graphene Field Effect Transistor

The temperature-dependent effect of residual charge carrier （no）, at the Dirac point, on mobility is studied. We fabricate and characterize a graphene field effect transistor （GFET） using 7nm TiO2 as the top-gate dielectric. The temperature-dependent gate voltage-drain current and room temperature gate capacitance are measured to extract the carrier mobility and to estimate the quantum capacitance of the GFET. The device shows the mobility value of gOO cm^2 /V.s at room temperature and it decreases to 45 cm^2 /V.s for 20 K due to the increase of n0. These results indicate that the phonon scattering is not the dominant process for the unevenness dielectric layer while the coulomb scattering by charged impurities degrades the device characteristically at low temperature.

Additively manufactured Ti–Ta–Cu alloys for the next-generation load-bearing implants

Bacterial colonization of orthopedic implants is one of the leading causes of failure and clinical complexities for load-bearing metallic implants. Topical or systemic administration of antibiotics may not offer the most efficient defense against colonization, especially in the case of secondary infection, leading to surgical removal of implants and in some cases even limbs. In this study, laser powder bed fusion was implemented to fabricate Ti3Al2V alloy by a 1:1 weight mixture of CpTi and Ti6Al4V powders. Ti-Tantalum(Ta)–Copper(Cu) alloys were further analyzed by the addition of Ta and Cu into the Ti3Al2V custom alloy. The biological,mechanical, and tribo-biocorrosion properties of Ti3Al2V alloy were evaluated. A 10 wt.% Ta(10Ta) and 3 wt.% Cu(3Cu) were added to the Ti3Al2V alloy to enhance biocompatibility and impart inherent bacterial resistance. Additively manufactured implants were investigated for resistance against Pseudomonas aeruginosa and Staphylococcus aureus strains of bacteria for up to 48 h. A 3 wt.% Cu addition to Ti3Al2V displayed improved antibacterial efficacy, i.e.78%–86% with respect to CpTi. Mechanical properties for Ti3Al2V–10Ta–3Cu alloy were evaluated, demonstrating excellent fatigue resistance, exceptional shear strength, and improved tribological and tribo-biocorrosion characteristics when compared to Ti6Al4V. In vivo studies using a rat distal femur model revealed improved early-stage osseointegration for alloys with10 wt.% Ta addition compared to CpTi and Ti6Al4V. The 3 wt.% Cu-added compositions displayed biocompatibility and no adverse infammatory response in vivo. Our results establish the Ti3Al2V–10Ta–3Cu alloy’s synergistic effect on improving both in vivo biocompatibility and microbial resistance for the next generation of load-bearing metallic implants.

Leaching behavior of zinc and copper from zinc refinery residue and filtration performance of pulp under the hydrothermal process

This study aims to investigate the leaching behavior and filtration performance of zinc refinery residue under hydrothermal conditions. The relationships between the structure and morphology of silicon in the leaching residue and the pulp filtration performance were explored by determining the pulp filtration speed, analyzing quantitatively the silicon content in the leachate, and characterizing the leaching residue structure. The results show that hydrothermal leaching induces the coagulation–hydrolysis of the silicon in solution, consequently altering the microstructure of the leaching residue, and that silicon oxygen tetrahedra([SiO_4]^(4-)) form the main skeleton structure of the residue. The results obtained also show that the leaching rates of zinc and copper are 98.1% and 98.7%, respectively, and that the filtration speed is 526.32 L/(m^2·h) under the conditions of sulfuric acid concentration of 140 g/L, leaching temperature of 160°C, leaching time of 3.0 h, oxygen partial pressure of 0.75 MPa, stirring speed of 600 r/min, and a liquid-to-solid ratio of 10 mL/g.

Impacts of support properties on the vacuum residue slurry-phase hydrocracking performance of Mo catalysts

To deeply understand the effects of support properties on the performance of Mo-based slurry-phase hydrocracking catalysts,four Mo-based catalysts supported on amorphous silica alumina(ASA),γ-Al_(2)O_(3),ultra-stable Y(USY)zeolite and SiO_(2) were prepared by the incipient wetness impregnation method,respectively,and their catalytic performances were compared in the vacuum residue(VR)hydrocracking process.It is found that the Mo/ASA catalyst exhibits the highest VR conversion among the different catalysts,indicating that both the appropriate amount of acid sites,especially B acid sites and larger mesoporous volume of ASA can enhance the VR hydrocracking into light distillates.Furthermore,Mo catalysts supported on the different supports show quite different product distributions in VR hydrocracking.The Mo/ASA catalyst provides higher yields of naphtha and middle distillates and lower yields of gas and coke compared with other catalysts,it is attributed to the highest MoS_(2) slab dispersion,the highest sulfuration degree of Mo species,and the most Mo atoms located at the edge sites for the Mo/ASA catalyst,as observed by HRTEM and XPS analyses.These features of Mo/ASA are beneficial for the hydrogenation of intermediate products and polycyclic aromatic hydrocarbons to restrict the gas and coke formation.

Effects of Guar (<i>Cyamopsis tetragonoloba</i>) Residues on the Performance and Nutrients Digestibility in Finishing Awassi Lambs

The nutritive quality of guar (Cyamopsis tetragonoloba) residues (GR) was investigated and the effects of partial replacement of wheat straw by GR on nutrients intake, digestibility, and growth performance. Twenty four male lambs, with average body weight (BW) of 40.3 ± 2.5 kg were divided into three groups. Lambs were fed individually for 104 days with concentrate mixture (18% crude protein) and wheat straw as a total mixed ration. Wheat straw was replaced with 0, 100 and 145 g/kg dry matter guar residues. All rations were isonitrogenous and isocaloric. The fattening trial lasted 104 days. At the end of week 10 of the trail, a digestion trial was performed using six lambs from each group. The composition of nutrients in the GR was 87%, 8.5%, 56.4% and 40.1% for DM, CP, NDF and ADF, respectively. DM and crude protein (CP) intake were not affected by the inclusion of GR. However, neutral detergent fibre (NDF) and acid detergent fibre (ADF) intake were lower in lambs fed GR compared to control lambs. At the end of the experiment, lambs fed 100 and 145 g GR/kg DM diets gained more weight (P < 0.05) than those fed the control diet. The same trend was found for feed conversion (CR). Results from this work suggested that GR had advantages compared to regular roughage (wheat straw) in regard to parameters investigated as well as the significant reduction in fattening diets cost.

Simultaneous Determination of 14 β-Receptor Agonists Residues in Mutton by High Performance Liquid Chromatography-Tandem Mass Spectrometry (HPLC-MS/MS)

[Objectives]A high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS)method was established for the determination of 14β-receptor agonist residues in mutton.[Methods]Samples were hydrolyzed byβ-glucuronidase and extracted with 5%acetic acid-acetonitrile(1:99,V/V)solution.An Eclipse plus C 18 column was used for separation,and the MRM mode was used for qualitative analysis,and the external standard method was used for quantitative analysis of matrix standard solutions.[Results]Under the optimal conditions,the retention time of the 14 kinds ofβ-receptor agonists ranged from 1.0 to 9.5 min.When the mass concentration was in the range of 0.05-0.50μg/ml,the linear relationship ofβ-receptor agonists was good,with correlation coefficients(r)≥0.9992.The detection limits of the method were in the range of 0.04-0.87μg/kg,and the quantitative limits were in the range of 0.35-1.86μg/kg.The average recovery values were in the range of 82.8%-108.9%,with RSDs(n=6)in the range of 1.9%-6.7%.[Conclusions]The method is simple,sensitive,reproducible,accurate,and can be used for simultaneous determination of the 14 kinds ofβ-receptor agonist residues in mutton.

Preparation of Flax Residue Activated Carbon by KOH Method and Its Electrode Performance

In this study, activated carbon was prepared by the potassium hydroxide activation method with flax residues as raw materials. High-quality activated carbon was prepared by single factor and orthogonal experiments. Iodine adsorption and methylene blue adsorption were used as performance indicators. As prepared activated carbon was characterized by XRD, XPS and SEM. The results showed that the optimized electrode material was prepared under an impregnation ratio of 1:2, activation temperature of 800°C and activation time of 100 min. The yield of activated carbon was 49.48%, the iodine value was 1667.13 mg/g and the methylene blue value was 429 mg/g. The specific surface area measured by the automatic porosity analyzer is 1221 m2/g, and the mass-specific capacitance is 215.7 F/g under current density of 0.1 A/g.

Residual life estimation based on bivariate Wiener degradation process with measurement errors

An adaptive method of residual life estimation for deteriorated products with two performance characteristics (PCs) was proposed, which was sharply different from existing work that only utilized one-dimensional degradation data. Once new degradation information was available, the residual life of the product being monitored could be estimated in an adaptive manner. Here, it was assumed that the degradation of each PC over time was governed by a Wiener degradation process and the dependency between them was characterized by the Frank copula function. A bivariate Wiener process model with measurement errors was used to model the degradation measurements. A two-stage method and the Markov chain Monte Carlo (MCMC) method were combined to estimate the unknown parameters in sequence. Results from a numerical example about fatigue cracks show that the proposed method is valid as the relative error is small.

Effect of Optimum Plastic Depth on Stresses and Load-bearing Capacity of Autofrettaged Cylinder

Autofrettage is an effective measure to even distribution of stresses and raise load-bearing capacity for （ultra-）high pressure apparatus. Currently, the research on autofrettage has focused mostly on specific engineering problems, while general theoretical study is rarely done. To discover the general law contained in autofrettage theory, by the aid of the authors’ previous work and according to the third strength theory, theoretical problems about autofrettage are studied including residual stresses and their equivalent stress, total stresses and their equivalent stress, etc. Because of the equation of optimum depth of plastic zone which is presented in the authors’ previous work, the equations for the residual stresses and their equivalent stress as well as the total stress and their equivalent stress are simplified greatly. Thus the law of distribution of the residual stresses and their equivalent stress as well as the total stress and their equivalent stress and the varying tendency of these stresses are discovered. The relation among various parameters are revealed. The safe and optimum load-bearing conditions for cylinders are obtained. According to the results obtained by theoretical analysis, it is shown that if the two parameters, namely ratio of outside to inside radius, k, and depth of plastic zone, kj, meet the equation of optimum depth of plastic zone, when the pressure contained in an autofrettaged cylinder is lower than two times the initial yield pressure of the unautofrettaged cylinder, the equivalent residual stress and the equivalent total stress at the inside surface as well as the elastic-plastic juncture of a cylinder are lower than yield strength. When an autofrettaged cylinder is subjected to just two times the initial yield pressure of the unautofrettaged cylinder, the equivalent total stress within the whole plastic zone is just identically equal to the yield strength, or it is a constant. The proposed research theoretically depicts the stress state of ultra-）high pressure autofrettaged cylinder more accurately and more reasonably and provides the reference for design of （ultra-）high pressure apparatus.

Effect of Si content on laser welding performance of Al-Mn-Mg alloy

The correlation between Si content （0.1%-0.5%, mass fraction） and pulse laser welding performance of AI-Mn-Mg aluminum alloy sheets was studied. The sheets were fabricated in the laboratory, with gauge of 0.45 mm, H16 temper by pulse laser welding. It was found that no cracking existed in the welding pool as Si content was below 0.34%. However, when the Si content increased to 0.47%, cracking formed in the welding pool. Microstructure observations indicated that residual eutectic phases distributed at the grain boundaries were discontinuous and appeared to be small particles in lower Si content alloys; the residual eutectic phases distributed at the grain boundaries were partially continuous and appeared to be films in higher Si content alloys. These phenomena could explain why Si content adversely affected the laser welding performance.

Effect of dynamic loading conditions on the dynamic performance of MP1 energy-absorbing rockbolts:Insight from laboratory drop test

Energy-absorbing rockbolts have been widely adopted in burst-prone excavation support, and their serviceability is closely related to the frequency and magnitude of seismic events. In this research, the splittube drop test with varying impact energy was conducted to reproduce the dynamic performance of MP1rockbolts under a wide range of seismic event magnitudes. The test results showed that the impact process could be subdivided into four distinct stages, i.e. mobilization, strain hardening, plastic flow(ductile), and rebound stage, of which strain hardening and plastic flow are the primary energy absorbing stages. As the impact energy per drop increases from 8.1 to 46.7 k J, the strain rate of the shank varies between 1.20 and 2.70 s^(-1), and the average impact load is between 240 and 270kN, which may be considered as constant. The MP1 rockbolt has a cumulative maximum energy absorption(CMEA) of 31.9–40.0 k J/m, with an average of 35.0 k J/m, and the elongation rate is 11.4%–14.7%, with an average of 12.7%, both of which are negatively correlated with the impact energy per drop. Regression analysis shows that energy absorption and shank elongation, as well as momentum input and impact duration,conform to the linear relationship. The complete dynamic capacity envelope of MP1 rockbolts is proposed, which reflects the dynamic bearing capacity, elongation, and distinct stages. This study is helpful to better understand the dynamic characteristics of energy-absorbing rockbolts and assist design engineers in robust reinforcement systems design to mitigate rockburst damage in seismically active underground excavations.

Improving the fatigue performance of longitudinal welded joints by low transformation temperature electrodes

For a longitudinal welded joint, the tensile residual stresses are as high as the yield stress of the metal, so that the weld toes are sensitive to fatigue load. In this case a low transformation temperature electrode (LTTE) is one of the most useful methods used to improve the fatigue strength of the longitudinal welded joint, because the tensile residual stress is reduced or changed into compressive stress. Three kinds of longitudinal welded joints were selected to conduct fatigue tests. The tests results show that the fatigue strengths at 2×10 6 cycles of the joints welded with LTTE were improved by 41%, 47% and 59% respectively compared with those of the joints welded with E5015, and the fatigue lives at 162 MPa were improved by 9.9 times, 9.6 times and 46.8 times respectively. Furthermore, the LTTE method is not necessary to add process after welding and so that it can be valuable method to improve the fatigue performance of longitudinal welded joints.

Post-fire residual service performance of magnesium alloys reinforced by rare earths

The flammability of magnesium alloys continues to be a significant barrier to their extensive application,and alloying with rare earth elements(REs)is an effective way to enhance the ignition and fire resistance of Mg alloys.Three commercial as-extruded Mg alloys(AZ80 and two Mg-RE alloys:EZ30K and WE43)were directly exposed to flame heating for revealing the evolutions of microstructure and mechanical properties,which is valuable in assessing the post-fire residual service performance of Mg alloy components.Results show that secondary phase dissolution,grain growth,grain boundary melting,alloy melting,and defects generation successively occur during the heating process.After short-term heating for 30 s,the elongation of AZ80 alloy increases significantly by 214%,from 3.82%to 12.01%,with minimal change in strength compared to the initial unheated state.This transformation is attributed to the recovery,grain growth,Mg17Al12 dissolution and dislocation density reduction.Conversely,EZ30K and WE43 alloys exhibit minimal changes in mechanical properties after short-term heating for 60 s,attributed to the pinning effect of REs.However,in subsequent heating states,resolidified microstructure and the presence of defects lead to a noteworthy decrease in both strength and elongation.Among these three alloys,the fire resistance follows this ranking:EZ30K>WE43>AZ80,primarily due to the high thermal conductivity of EZ30K alloy and the thermal stability improved by the addition of REs.

Supplementation of Lycium barbarum residue increases the growth rate of Tan sheep by enhancing their feed intake and regulating their rumen microbiome and metabolome

Lycium barbarum residue(LBR),a by-product of L.barbarum processing,is packed with bioactive components and can be potentially utilized as a feed additive in animal husbandry.However,the fundamental understanding of its effectiveness on livestock animals is still lacking,particularly in ruminants.To explore the effects of LBR on the growth performance,rumen fermentation parameters,ruminal microbes and metabolites of Tan sheep,sixteen fattening rams(aged 4 mon)were fed a basal diet(CON,n=8)or a basal diet supplemented with 5%LBR(LBR,n=8).The experiment lasted for 70 d,with 10 d adaptation period and 60 d treatment period.The results showed that the LBR enhanced the average daily feed intake,average daily gain(P<0.05),and ruminal total volatile fatty acids(P<0.01)while decreasing ammonia-nitrogen concentration and rumen pH value(P<0.05).Additionally,the LBR improved the relative abundances of Prevotella,Succiniclasticum,Ruminococcus,Coprococcus,Selenomonas,and Butyrivibrio(P<0.05)and reduced the relative abundances of Oscillospira and Succinivibrio(P<0.05).The LBR altered the ruminal metabolome(P<0.01)by increasing the abundances of ruminal metabolites involved in amino acids(e.g.,L-proline,L-phenylalanine,L-lysine,and L-tyrosine),pyrimidine metabolism(e.g.,uridine,uracil,and thymidine),and microbial protein synthesis(e.g.,xanthine and hypoxanthine).In conclusion,LBR had positive effects on the growth rate of Tan sheep as well as on rumen fermentation parameters,rumen microbiome and rumen metabolome.

铝盐混凝剂对地表水的混凝性能及残留铝形态研究

为深入解析残留铝形态与混凝剂种类和水质的关系,研究了氯化铝(AlCl_(3))、硫酸铝[Al_(2)(SO_(4))_(3)]和聚氯化铝(PAC)对夏秋季及冬春季苏州市阳澄湖水的混凝性能及其残留铝形态的影响。相同投加量下,对夏秋季地表水的除浊性能由大到小的顺序依次为AlCl_(3)、Al_(2)(SO_(4))_(3)、PAC,冬春季由大到小的顺序依次为PAC、AlCl_(3)、Al_(2)(SO_(4))_(3)。残留铝形态分析结果表明,夏秋季和冬春季3种混凝剂残留铝主要形态为总溶解性铝,夏秋季出水残留溶解性铝约占总铝的40%~80%、冬春季约占30%~90%。溶解性有机铝在总溶解性铝中所占比例较大(夏秋季约占80%~90%、冬春季约占50%~70%),而溶解性有机单体铝的含量低于10µg/L,可忽略不计。通过相关性分析得出,残留铝组分中总溶解性铝受铝盐种类影响较大(相关性系数为+0.996),其与水质中浊度、温度及有机物的相关性较强。结合混凝性能、残留铝形态分析结果,对不同季节地表水混凝处理条件的建议是:阳澄湖水夏秋季建议使用AlCl_(3),剂量为1.50~2.00mg/L;冬春季建议使用PAC,剂量为1.00~1.50mg/L,其最佳pH均为7。相关结果为不同水质地表水铝盐的适配性提供技术支持。

六层自复位钢筋混凝土框架结构振动台试验研究

为研究多层自复位框架结构整体抗震性能,进行一个1/4缩尺比六层自复位框架结构模型的模拟地震振动台试验,研究该结构的动力特性及其在7度多遇至7度极罕遇4个水准地震作用下的动力反应和破坏情况。试验结果表明:在多遇以及设计基本地震作用下,结构构件无可见裂缝和损伤;随着输入地震动峰值的增加,结构损伤增加,但损伤主要集中在梁、柱端的表面混凝土,构件自身几乎没有损伤,表明自复位混凝土框架结构的抗震性能良好;在7度罕遇地震作用下,主体结构最大层间位移角为1/62,自复位框架的节点开始张开;在7度极罕遇地震作用下,模型节点张开更加明显,角钢进入屈服阶段,而主体结构的最大残余位移角仅为1/2533,证明结构具有很强的自复位能力。

弱阳离子交换固相萃取-超高效液相色谱-串联质谱法测定牛奶中13种氨基糖苷类药物残留

本研究建立弱阳离子交换固相萃取-超高效液相色谱-串联质谱测定牛奶中13种氨基糖苷类药物(安普霉素、阿米卡星、巴龙霉素、潮霉素B、核糖霉素、卡那霉素、链霉素、庆大霉素C1、双氢链霉素、妥布霉素、壮观霉素、新霉素和小诺霉素)的检测方法。牛奶样品经乙酸铵缓冲溶液和乙腈提取,弱阳离子交换固相萃取柱净化,SILICA SG80液相色谱柱分离。采用0.1%甲酸溶液和乙腈作为流动相进行梯度洗脱,在电喷雾电离源、正离子模式下进行超高效液相色谱-串联质谱检测,采用基质匹配标准外标法定量。在5.0~500.0 ng/mL范围内,13种氨基糖苷类药物呈现良好的线性关系(R^(2)≥0.998 3)。潮霉素B、核糖霉素、链霉素、妥布霉素和双氢链霉素的检出限均为3μg/kg,定量限均为10μg/kg;安普霉素、阿米卡星、巴龙霉素、卡那霉素、庆大霉素C_(1)、小诺霉素、新霉素和壮观霉素的检出限均为15μg/kg,定量限均为50μg/kg。在1、2倍和5倍的定量限加标水平下,回收率为73.8%~107.4%,相对标准偏差为1.0%~9.8%。该方法灵敏度高、操作简单、稳定性好,可用于检测牛奶中13种氨基糖苷类药物。

镍电极MLCC排胶后残碳量及其电性能研究

多层陶瓷电容(MLCC)固有的坯体有机物残留导致产品可靠性低,其主要原因是排胶不充分。通过改变排胶工序的不同工艺条件,使用硫碳分析仪对排胶后坯体残碳量进行量化,结合破坏性物理分析、扫描电镜对烧成后的产品进行结构分析,并对成品进行电性能测试,探索残碳量与成品的电极连续性、电性能及可靠性之间的联系。结果表明通过增大气体交换、降低排胶升温速率、延长保温时间等手段可有效降低排胶后的残碳量,烧成MLCC的内电极连续性变得更好,容量和击穿电压等电性能数据得到提升,介质层变得更致密,使用寿命延长。所探讨的测定排胶充分性以及增加排胶充分性的方法可为MLCC工业生产中的排胶作业提供参考。

多壁碳纳米管改进QuEChERS净化结合高效液相色谱串联质谱法快速测定水产品中四唑虫酰胺残留

该文建立了一种多壁碳纳米管(multi-walled carbon nanotube,MWCNTs)改进QuEChERS净化结合高效液相色谱串联质谱法快速测定水产品四唑虫酰胺残留的分析方法。样品经乙腈提取,无水硫酸钠4 g,无水硫酸镁4 g分离水相和有机相,MWCNTs改进QuEChERS(每毫升提取液加入3 mg MWCNTs,60 mg C18,50 mg PSA)净化包净化,在Agilent Venusil MP C18(100 mm×2.1 mm,3μm)上分离,以甲醇和水为流动相,电喷雾离子化,负离子扫描,多反应监测模式检测,基质匹配外标法定量。结果显示,四唑虫酰胺在不同水产品基质下0.1~20μg/L线性范围内相关系数(R^(2))均大于0.999。方法定量限(S/N≥10)为0.80μg/kg。以草鱼、带鱼、小龙虾、基围虾、大闸蟹、梭子蟹、花甲为基质,四唑虫酰胺在2.0、4.0、20μg/kg 3个水平加标回收率为82%~97%,批内相对标准偏差(relative standard deviation,RSD,n=6)为0.66%~4.02%,批间RSD(n=6)为0.88%~2.95%。本方法便捷高效,可满足水产品中四唑虫酰胺残留的检测工作要求。

QuEChERS-超高效液相色谱-串联质谱法同时测定柚花中317种农药残留量

目的建立QuEChERS前处理法结合超高效液相色谱-串联质谱(ultra performance liquid chromatography-tandem mass spectrometry,UPLC-MS/MS)同时测定柚花中317种农药残留量的方法。方法柚花样品采用乙腈作为提取剂,经萃取盐盐析处理,采用乙二胺-N-丙基硅烷化硅胶(ethylenediamine-N-propylsilane silica gel,PSA)和石墨化炭黑(graphitized carbon black,GCB)作为净化剂,选用ACQUITY UPLC HSS T3色谱柱,采用梯度洗脱方式在30 min完成317种目标物质的分析。电喷雾源正离子和负离子同时扫描,采用多重反应监测(multiple reaction monitoring,MRM)模式、基质匹配标准曲线外标法定量。结果317种农药在该条件下在2.0~200.0μg/L质量浓度范围内均线性良好,相关系数r>0.995,方法定量限为0.002~0.010 mg/kg,在低、中、高3个添加水平下的平均回收率为74.3%~120.3%,相对标准偏差在0.36%~10.00%。结论该方法具有简单、快速、准确、灵敏等特点,为柚花中多种农药残留的测定和柚花研制的食品安全地方标准提供了可靠的技术支持。