煤粉锅炉点火技术研究与应用

煤粉锅炉广泛应用于国内大型电厂和化工企业,实际运行过程中煤粉锅炉点火系统存在诸多问题。通过广泛调研和深入研究,对比分析微(少)油点火、等离子点火以及清洁能源(天然气、弛放气、甲醇)点火技术之工作原理、特点及其应用情况,并对某煤化工企业采用甲醇点火技术并配置掺烧杂醇油对煤粉锅炉原有大油枪点火系统的改造升级实例进行详细介绍。实际应用情况表明,甲醇点火技术节能环保,配置掺烧杂醇油更是具有变废为宝的作用,可在大型煤化工企业中推广应用。并指出,企业可根据自产产品和生产中的副产物进行煤粉锅炉点火燃料的选用,从而实现锅炉系统点火技术的改造升级。

超声引导下腰方肌阻滞在全髋关节置换患者中的应用效果分析

目的 分析超声引导下腰方肌阻滞在全髋关节置换患者中的应用效果。方法 选取2019年1月至2021年3月河南省洛阳正骨医院收治的100例拟行全髋关节置换术的髋关节疾病患者作为研究对象,按照随机数表法将其随机分为观察组(50例)和对照组(50例),观察组患者术中采用超声引导下腰方肌阻滞联合全身麻醉、术后行腰方肌阻滞外导管连接自控镇痛泵自控镇痛,对照组患者术中单纯采用全身麻醉、术后行静脉留置针连接自控镇痛泵自控镇痛,对比观察两组患者手术时间、术中出血量、麻醉起效时间、麻醉维持时间以及术后静息和活动时的疼痛程度。结果 观察组患者手术时间及术中出血量与对照组无明显差异(t=0.377、0.375,P=0.707、0.709),麻醉起效时间明显短于对照组(t=17.320,P<0.001),麻醉维持时间明显长于对照组(t=10.080,P<0.001)。术后4、8、12、24 h,观察组患者静息和活动时数字分级评分法(NRS)评分均明显低于对照组(静息时:t=2.116、4.698、2.418、2.296,P=0.037、P<0.001、P=0.017、P=0.024;活动时:t=2.590、2.500、4.892、2.346,P=0.011、P<0.001、P<0.001、P=0.021)。结论 超声引导下腰方肌阻滞可有效缩短麻醉起效时间,延长麻醉维持时间,降低全髋关节置换术后疼痛程度。

Gas sensing properties of Y-doped ZnO nanosheets synthesized via combustion method

ZnO nanosheets doped with yttrium（Y） were synthesized via a solution combustion method using zinc nitrate and tartaric acid as raw materials.The scanning electron microscopy and X-ray powder diffraction were used to characterize ZnO nanosheets and the gas sensing properties of them were investigated.The results show that the as-synthesized ZnO nanosheets with diameters of20-100 nm have a wurtzite structure with rough surface.The sensor made from the 2%Y-doped ZnO nanosheets exhibits a stronger response toward 100x10-6（volume fraction） ethanol,its sensitivity at 300℃ is 17.50,and its optimal operating temperature（300℃）is lower than that of the pure ZnO（330℃）.The obvious sensitivity（about 2.5） can be observed at the volume fraction of ethanol as low as 5×10-（-6）,while its the response time is only 2s at 300℃.Moreover,the Y-doped ZnO sensor has a better selectivity to ethanol than other gases.

Synthesis of K-doped three-dimensionally ordered macroporous Mn_(0.5)Ce_(0.5)O_δ catalysts and their catalytic performance for soot oxidation

A series of K-doped Mn0.5Ce0.5Oδ （K-MCO） catalysts with three-dimensionally ordered macroporous （3DOM） structure and different K loadings were successfully synthesized using simple methods. These catalysts exhibited well-defined 3DOM nanostructure, which consisted of extensive interconnecting networks of spherical voids. The effects of the calcination temperature and calcination time on the morphological characteristics and crystalline forms of the catalysts were systematically studied. The catalysts showed high catalytic activity for the combustion of soot. 3DOM 20% K-MCO-4h catalyst, in particular, showed the highest catalytic activity of all of the catalysts studied （e.g., Ts0 = 331 ~C and Smco2 = 95.3%）. The occurrence of structural and synergistic effects among the K, Mn, and Ce atoms in the catalysts was favorable for enhancing their catalytic activity towards the combustion of diesel soot. Furthermore, the temperatures required for the complete combustion of the soot （〈400 ℃） were well within the exhaust temperature range （175-400 ℃）, which means that the accumulated soot can be removed under the conditions of the diesel exhaust gas. These catalysts could therefore be used in numerous practical applications because they are easy to synthesize, exhibit high catalytic activity, and can be made from low cost materials.

Formation mechanism and crystal simulation of Na_2O-doped calcium aluminate compounds

Calcium aluminate clinkers doped with Na2O were synthesized using analytically pure reagents CaCO3, Al2O3, SiO2 and Na2CO3. The effects of Na2O-doping on the formation mechanism of calcium aluminate compounds and the crystal property of 12CaO·7Al2O3 (C12A7) cell were studied. The results show that the minerals containing Na2O mainly include 2Na2O·3CaO·5Al2O3 and Na2O·Al2O3, when the Na2O content in clinkers is less than 4.26% (mass fraction). The rest of Na2O is mainly doped in 12CaO·7Al2O3, which results in the decrease of the crystallinity of 12CaO·7Al2O3. The crystallinity of 2Na2O·3CaO·5Al2O3 is also inversely proportional to the Na2O content in clinkers. The formation processes of 2Na2O·3CaO·5Al2O3 and 12CaO·7Al2O3 can be divided into two ways, which are the direct reactions of raw materials and the transformation of CaO·Al2O3, respectively. The simulation shows that the covalency of O-Na bond in Na2O-doped 12CaO·7Al2O3 cell is weaker than those of O-Ca and O-Al bonds. The free energy of the unit cell increases because of Na2O doping, which results in the improvement of chemical activity of 12CaO·7Al2O3. The leaching efficiency of Al2O3 in clinker is improved from 34.81% to 88.17% when the Na2O content in clinkers increases from 0 to 4.26%.

Effect of Pd doping on CH_4 reactivity over Co_3O_4 catalysts from density-functional theory calculations

Palladium oxide(PdOx)and cobalt oxide(Co3O4)are efficient catalysts for methane(CH4)combustion,and Pd‐doped Co3O4catalysts have been found to exhibit better catalytic activities,which suggest synergism between the two components.We carried out first‐principles calculations at the PBE+U level to investigate the Pd‐doping effect on CH4reactivity over the Co3O4catalyst.Because of the structural complexity of the Pd‐doped Co3O4catalyst,we built Pd‐doped catalyst models using Co3O4(001)slabs with two different terminations and examined CH4reactivity over the possible Pd?O active sites.A low energy barrier of0.68eV was predicted for CH4dissociation over the more reactive Pd‐doped Co3O4(001)surface,which was much lower than the0.98and0.89eV that was predicted previously over the more reactive pure Co3O4(001)and(011)surfaces,respectively.Using a simple model,we predicted CH4reaction rates over the pure Co3O4(001)and(011)surfaces,and Co3O4(001)surfaces with different amounts of Pd dopant.Our theoretical results agree well with the available experimental data,which suggests a strong synergy between the Pd dopant and the Co3O4catalyst,and leads to a significant increase in CH4reaction rate.

Effects of doping route on microstructure and mechanical properties of W−1.0wt.%La2O3 alloys

A comparative study was conducted by using solution combustion synthesis with three different doping routes(liquid-liquid(WL10), liquid-solid(WLNO) and solid-solid(WLO)) to produce nanoscale powders and further fabricate the ultrafine-grained W-1.0 wt.%La2O3 alloys by pressureless sintering. Compared with pure tungsten, W-1.0 wt.%La2O3 alloys exhibit ultrafine grains and excellent mechanical properties. After sintering, the average grain size of the WLO sample is larger than that of WL10 and WLNO samples;the microhardness values of WL10 and WLNO samples are similar but larger than the value of WLO sample. The optimized La2O3 particles are obtained in the WL10 sample after sintering at 1500 ℃ with the minimum mean size by comparing with WLNO and WLO samples, which are uniformly distributed either at grain boundaries or in the grain interior with the sizes of(57±29.7) and(27±13.1) nm, respectively. This study exhibits ultrafine microstructure and outperforming mechanical properties of the W-1.0 wt.%La2O3 alloy via the liquid-liquid doping route, as compared with conventionally-manufactured tungsten materials.

Synthesis and Conductivity of Oxyapatite Ionic Conductor La10-xVx（SiO4）6O3＋x

Apatite-lanthanum silicate has attracted considerable interest in recent years due to its high oxide ion conductivity.In this paper,V-doped samples La10-xVx(SiO4) 6O3+x(0≤x≤1.5) were prepared by sol-gel method and the influences of V-dopant content on calcining temperature and conductivity were reported.The samples were characterized by thermal analysis(TG-DSC) ,X-ray diffraction(XRD) and scanning electron micrograph(SEM) . The apatite was obtained at 800°C,a relatively low temperature in comparison to 1500°C with the conventional solid-state method.The ceramic pellets sintered at 1200°C for 5 h showed a higher relative density than La9.33Si6O26 pellets sintered at 1400°C for 20 h.The conductivities of samples were measured by electrochemical impedance spectroscopy.The conductivity was improved with the increase of V-dopant content on La site.

Low-temperature sintering and microwave dielectric properties of Li_2MgTi_3O_8 ceramics doped with BaCu(B_2O_5)

The influences of BaCu（B2O5） （BCB） addition on sintering, microstructure and microwave dielectric properties of Li2MgTi308 ceramics were investigated using X-ray diffractometry, scanning electron microscopy and microwave dielectric measurements. The experimental results show that a small amount of BaCu（B2O5） addition can effectively reduce the sintering temperature to 900℃, and induce only a limited degradation of the microwave dielectric properties. Typically, the best microwave dielectric properties of er24.5, Q×f =24 622 GHz, rf=4.2×10-6℃ -1 are obtained for 1.0% BCB-doped Li2MgTi3O8 ceramics sintered at 900℃ for 3 h. The BCB-doped Li2MgTi3O8 ceramics can be compatible with Ag electrode, which may be a strong candidate for low temperature co-fired ceramics applications.

Three-dimensionally ordered macroporous SnO_2-based solid solution catalysts for effective soot oxidation

A series of three‐dimensionally ordered macroporous(3DOM)SnO2‐based catalysts modified by the cations Ce4+,Mn3+,and Cu2+have been prepared by using a colloidal crystal templating method and tested for soot combustion under loose contact condition.XRD and STEM mapping results confirm that all the secondary metal cations have entered the lattice matrix of tetragonal rutile SnO2 to form non‐continuous solid solutions,thus impeding crystallization and improving the surface areas and pore volumes of the modified catalysts.In comparison with regular SnO2 nanoparticles,the 3DOM SnO2 displays evidently improved activity,testifying that the formation of the 3DOM structure can anchor the soot particulates in the macro‐pores,which ensures that the contact of the soot particles with the active sites on the 3DOM skeleton is more easily formed,thus benefiting the target reaction.With the incorporation of the secondary metal cations,the activity of the catalyst can be further improved due to the formation of more abundant mobile oxygen species.In summary,these effects are believed to be the major factors responsible for the activity of the catalyst.

Structural and Magnetic Properties of Bi（Fe1-xMnx）O3

Bi（Fe1-xMnx）O3 bulk ceramics with Mn concentration x up to 0.3 were prepared by rapid sintering using sol-gel derived fine powders. Structure transformation is found to depend on the Mn doping concentration by X-ray diffraction and Raman spectroscopy. Bi（Fe1-xMnx）O3 maintains the rhombohedral structure of BiFeO3 with x=0.05 and 0.1, but changes to the orthorhombic structure with x=0.3. Weak ferromagnetism is observed for Bi（Fe1-xMnx）O3 with x=0.05 and 0.1, but stronger paramagnetism is observed for Bi（Fe1-xMnx）O3 with x=0.3 indicating a magnetic phase change from antiferromagnetic to paramagnetic with the structure changing from R3c to C222. Two anomalies at 30 and 140 K are observed for Bi（Fe1-xMnx）O3 with x=0.05 and 0.1. The anomaly at 30 K is concluded to be related to the freezing of cluster spin glass from dc magnetic memory and relaxation measurements.

Infrared emissivity of transition elements doped ZnO

Infrared emissivity was studied in Zno.99Mo.olO （M is Mn, Fe or Ni） and Znl_xCoxO （x=0.01, 0.02, 0.03 and 0.04） powders synthesized by solid-state reaction at various temperatures. XRD patterns confirm the wurtzite structure of the prepared samples. No peaks of other phases arising from impurities are detected in Mn- and Co-doped ZnO, hut the peaks of ZnFe204 and NiO are observed in Zno.99Feo.010 and Zno.99Nio.o10. The SEM observations indicate that with larger grain sizes than those of Zn0.99Feo.010 and Zno.99Ni0.010, Co-doped ZnO exhibits smooth grain surfaces. The infrared absorption spectra show that infrared absorptions related to oxygen in Zn0.99M0.010 are much stronger than those in Co-doped ZnO. Co ions are dissolved into the ZnO lattice with Co2＋ state from XPS spectra analysis. The infrared emissivity results imply that the emissivity of Zno.99Ni0.010 is the highest （0.829） and that of Zno.99C00.010 is the lowest （0.784） at 1 200 ℃. The emissivity of Zno.99Co0.010 decreases to the minimum （0.752） at 1 150 ℃ and then increases with growing calcination temperature. As the Co doping content grows, the emissivity of Co-doped ZnO calcined at 1 200 ℃ falls to 0.758 in the molar fraction of 3% and then ascends.

论秦始皇文化专制政策对占卜文化发展的促进作用

一秦始皇'不烧之书'中所指卜筮的范畴据《史记》载秦始皇三十四年(前213)焚书时,'史官非秦记皆烧之。非博士官所职,天下敢有藏诗、书、百家语者,悉诣守、尉杂烧之。有敢偶语诗书者弃市。以古非今者族。吏见知不举者与同罪。令下三十日不烧,黥为城旦。所不去者。

Optimization of the Doped Ablator Layers for the Plastic Ignition Capsule

The paper investigates theoretically the optimization of the doped ablator layers for the plastic ignition capsule. The high-resolved one-dimensional implosion simulations show that the inner pure CFI layer of the Si-doped design is excessively preheated by the hard x-ray, leading to the unstable ablator-fuel interface compared to the Ge-doped capsule. This is because that the Si K-shell absorption edge （1.8 keV） is higher than the Ge L-edge （1.3 keV）, and Si dopant makes more hard x-ray penetrate through the doped ablator layers to preheat the inner pure CH layer. So an optimization of the doped ablator layers （called ＂Si/Ge capsule＂） is performed： an Si-doped CH layer is placed next to the outer pure CH layer to keep the high implosion velocity; next to the Si-doped layer is a thin Ge-doped layer, in order to absorb the hard x-ray and protect the inner undoped CH-layer from excessively preheating. The simulations show that the Si/Ge capsule can effectively improve hydrodynamic stability at the ablator-fuel interface while keeping the high implosion velocity.

Excellent thermoelectric performance of boron-doped n-type Mg_(3)Sb_(2)-based materials via the manipulation of grain boundary scattering and control of Mg content

Thermoelectric devices require thermoelectric materials with high figure-of-merit(ZT)values in the operating temperature range.In recent years,the Zintl phase compound,n-Mg_(3)Sb_(2),has received much attention owing to its rich chemistry and structural complexity.However,it hardly achieves high ZT values throughout the medium temperature range.Herein,by increasing the sintering temperature as much as possible,we successfully increased the average grain size of the compound by 15 times,and the grain boundary scattering was manipulated to obtain high carrier mobility of up to 180 cm^(2)V^(-1)s^(-1).Simultaneously,we optimized the Mg content for ultralow lattice thermal conductivity.We first doped the Mg_(3)Sb_(2)-based materials with boron for higher sintering temperature,good thermal stability,and higher hardness.The synergistic optimization of electrical and thermal transport resulted in excellent ZT values(0.62 at 300 K,1.81 at 773 K)and an average ZT of 1.4(from300 to 773 K),which are higher than the state-of-the-art values for n-type thermoelectric materials,demonstrating a high potential in device applications.