Low temperature cracking behavior of asphalt binders and mixtures: A review

Low temperature cracking(LTC)distress on pavement seriously affects road life.This paper finished a literature review of the research on the mechanism of LTC of asphalt composites(asphalt composites refers to asphalt binder and asphalt mixture in this article),test methods,factors contributing to LTC,measures to prevent and control the distress,and prediction of LTC in asphalt pavements.The following conclusions were obtained:the cracking mechanism of asphalt mixtures needs to be further revealed by means of simulation at the micro level,the BBR and 4 mm plate test(by DSR)methods are currently optimal,and a correlation between asphalt and asphalt mixture evaluation indexes needs to be established.Sensitivity analyses are needed for the factors affecting LTC of asphalt mixtures.It is necessary to calculate the contribution of each factor to the LTC of asphalt mixtures.The aim is to propose targeted improvement measures for the most unfavourable factors,as well as to carry out research and development of key materials for anti-cracking.Measures for the prevention and control of LTC of asphalt pavement are analyzed and discussed.Existing researches on the prediction of LTC of asphalt pavements is discussed.It is necessary to analyse the mechanical response of asphalt pavement,the damage process and the sensitivity of anti-cracking parameters on the basis of considering the complex geometrical characteristics and material properties of asphalt pavement materials.Finally,the mechanism of LTC,evaluation methods,factors influencing LTC,and remedial measures for asphalt composites were summarized,and future research prospects were suggested.This paper provides theoretical support for the further solution of LTC distress of asphalt pavement,which is effective on the improvement of pavement life.

Influence of preparation methods on the physicochemical properties and catalytic performance of MnO_x-CeO_2 catalysts for NH_3-SCR at low temperature

This work examines the influence of preparation methods on the physicochemical properties and catalytic performance of MnOx‐CeO2 catalysts for selective catalytic reduction of NO by NH3 (NH3‐SCR) at low temperature. Five different methods, namely, mechanical mixing, impregnation,hydrothermal treatment, co‐precipitation, and a sol‐gel technique, were used to synthesizeMnOx‐CeO2 catalysts. The catalysts were characterized in detail, and an NH3‐SCR model reaction waschosen to evaluate the catalytic performance. The results showed that the preparation methodsaffected the catalytic performance in the order: hydrothermal treatment > sol‐gel > co‐precipitation> impregnation > mechanical mixing. This order correlated with the surface Ce3+ and Mn4+ content,oxygen vacancies and surface adsorbed oxygen species concentration, and the amount of acidic sitesand acidic strength. This trend is related to redox interactions between MnOx and CeO2. The catalystformed by a hydrothermal treatment exhibited excellent physicochemical properties, optimal catalyticperformance, and good H2O resistance in NH3‐SCR reaction. This was attributed to incorporationof Mnn+ into the CeO2 lattice to form a uniform ceria‐based solid solution (containing Mn‐O‐Cestructures). Strengthening of the electronic interactions between MnOx and CeO2, driven by thehigh‐temperature and high‐pressure conditions during the hydrothermal treatment also improved the catalyst characteristics. Thus, the hydrothermal treatment method is an efficient and environment‐friendly route to synthesizing low‐temperature denitrification (deNOx) catalysts.

Low Temperature Chlorination of Nd₂O₃by Mechanochemical Method with CCl₄

For a chlorinating method at low temperature, the possibility of chlorination of Nd2O3 by a mechanochemical reaction with CCl4 was studied using a planetary ball mill. The mechanochemical experiments were conducted by changing the pot materials, milling time, molar ratio of CCl4/Nd2O3, and revolution speed. As the results of obtained products by X-ray diffractometry and Raman spectroscopy, it was confirmed that the chlorination to NdOCl from Nd2O3 with CCl4 was advanced at room temperature in a zirconia or tungsten pot with balls. We found that an extension of the milling time and an increase of the number of ball were effective to the chlorination to NdOCl and that tensile stress remained in the milled powder by using a planetary ball mill.

Preparation of YAG:Ce^(3+) phosphor by sol-gel low temperature combustion method and its luminescent properties

YAG:Ce3+ phosphor was prepared by sol-gel low-temperature combustion method. The effects of the precursor properties and calcining temperature on the crystallization process, microscopic morphology and luminescent properties of phosphor were studied. The results indicate that the pure phase of YAG can be obtained at 800 ℃ by sol-gel low temperature combustion method, using citric acid as complexing agent. When the molar ratio of metal ion to citric acid is 2.0 and pH value is 2, the crystallinity increases and the phosphor particle size grows up gradually with the increase of the calcining temperature. The powders were characterized through thermal analysis, X-ray diffraction analysis and scanning electron microscope analysis. The excitation spectra of YAG:Ce3+ phosphor take on a double peak structure, and the peak value of the main excitation spectra occurs at 460 nm and that of the emission spectra is near 530 nm. With the gradual increase of the calcining temperature, the peak position of excitation and emission spectra remains basically unchanged, but its relative intensity increases gradually.

Study on Free Surface and Channel Flow Induced by Low Temperature Plasma via Lattice Boltzmann Method

Active boundary layer flow control and boundary layer manipulation in the channel flow that was based on low temperature plasma were studied by means of a lattice Boltzmann method. Two plasma actuators were placed in a row to obtain the influence rule of their separation distance on the velocity profile at three locations and maximum velocity in the flow field. Two plasma actuators were placed symmetrically inside a channel to examine the effect of channel height and voltage on the velocity profile and flow rate. It was found that the channel height controls the distribution of flow velocity, which affected the flow rate and its direction. Increasing plasma voltage had a negative effect on the flow rate due to the generation of a larger and stronger flow vortex.

A Novel Low Temperature Synthesis of KNN Nanoparticles by Facile Wet Chemical Method

Sodium potassium niobate (KNN) (K0.5Na0.5NbO3) nanopowder with a mean particle size of about 20 - 30 nm was synthesized by wet chemical route using Nb2O5 as Nb source. A solution of K, Na and Nb cations was prepared, which resulted in a clear gel after the thermal treatment. Phase analysis, microstructure and morphology of the powder were determined by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Field Emission Scanning Electron Microscopy (FESEM). The obtained gel was first analyzed by Thermo Gravimetric Analyzer (TGA) and Differential Scanning Calorimetry (DSC), and then calcined at different temperatures of 400℃, 500℃, 600℃ and 700℃. The X-Ray Diffraction (XRD) patterns of the synthesized samples confirmed the formation of the orthorhombic crystal phase of K0.5Na0.5NbO3 at 500?C, a temperature significantly lower than that typically used in the conventional mixed oxide route. The process developed in this work is convenient to realize the mass production of KNN nanopowders at low cost and suitable for various industrial applications.

Low Temperature Synthesis of Nano Porous 12CaO?7Al_2O_3 Powder by Hydrothermal Method

Single-phase insulating 12CaO？7Al_2O_3（C12A7） powder was synthesized using an optimized hydrothermal method. Pure phase of C12A7 was got at a comparatively lower temperature（c.a. 300 ℃） than that has been previously reported. The crystallite size of the synthesized C12A7 powder was 7±2 nm. The surface area values calculated for all the samples at a synthesis temperature range of 250-800 ℃ for 5 h were in the range of about 19-24 m^2/g, with pore sizes of 12-20 nm. This low-temperature-based synthetic strategy along with nano porous structures and a high surface area value can facilitate catalyst application.

Overwhelming low ammonia escape and low temperature denitration efficiency via MnOx-decorated two-dimensional MgAl layered double oxides

Low temperature catalysts are attracting increasing attention in the selective catalytic reduction(SCR)of NO with NH3.Mn Ox-decorated Mg Al layered double oxide(Mn/Mg Al-LDO)was synthesized via a facile fast pour assisted co-precipitation(FP-CP)process.Compared to the Mn/Mg Al-LDO obtained via slow drop assisted coprecipitation(SD-CP)method,the Mn/Mg Al-LDO(FP-CP)has excellent activity.The Mn/Mg Al-LDO(FP-CP)catalyst was shown to possess a high NO conversion rate of 76%-100%from 25 to 150℃,which is much better than the control Mn/Mg Al-LDO(SD-CP)(29.4%-75.8%).In addition,the Mn/Mg Al-LDO(FP-CP)offered an enhanced NO conversion rate of 97%and a N2selectivity of 97.3%at 100℃;the NO conversion rate was 100%and the N2selectivity was 90%at 150℃with a GHSV of 60,000 h^-1.The Mn/Mg Al-LDO(FP-CP)catalyst exhibited a smaller fragment nano-sheet structure(sheet thickness of 7.23 nm).An apparent lattice disorder was observed in the HRTEM image confirming the presence of many defects.The H2-TPR curves show that the Mn/Mg Al-LDO(FP-CP)catalyst has abundant reducing substances.Furthermore,the enhanced surface acidity makes the NH3concentration of the Mn/Mg Al-LDO(FP-CP)catalyst lower than 100 ml·m^-3after the reaction from 25 to 400℃.This can effectively reduce the ammonia escape rate in the SCR reaction.Thus,the Mn/Mg Al-LDO(FP-CP)catalyst has potential applications in stationary industrial installations for environmentally friendly ultra-low temperature SCR.

Remove of Phenolic Compounds in Water by Low-Temperature Plasma: A Review of Current Research

Phenolic compounds have very strong toxicity, so it has been paid sharply attention to find an effective way of controlling the wastewater containing phenolic compounds. The work on this subject done by domestic and overseas scholars is studied in this paper, and the progress of researches on low-temperature plasma treatment is summarized through the electrical discharge types, mechanism, kinetics of phenolic compounds decomposition and combination of several methods with low-temperature plasma treatment. In addition, the crucial problem and the developing tendency on low-temperature plasma treatment for phenol-bearing wastewater are briefly discussed.

复合助剂对低温喷雾干燥蓝靛果粉理化性质的影响

为保证低温喷雾干燥后蓝靛果粉品质,采用黄金分割法研究复合助剂(麦芽糊精、β-环糊精和乳清蛋白)对喷雾干燥蓝靛果粉理化性质的影响,分析低温进风温度(50~90℃)对蓝靛果粉花青素保留率、集粉率和含水率的影响规律。结果表明,在麦芽糊精、β-环糊精的质量比例为85.4%、14.6%时,集粉率高达37.96%;随进料溶液中麦芽糊精质量比例增加,蓝靛果粉玻璃化转变温度、水溶性指数、堆积密度、亮度L^(*)值、红度a^(*)值和色差值ΔE呈增加趋势,含水率、花青素含量和黄度b^(*)值呈下降趋势;在麦芽糊精、β-环糊精和乳清蛋白质量比例为72.9%、12.5%、14.6%时,集粉率达到最高(40.11%);随料液中乳清蛋白质量比例增加,蓝靛果粉含水率、花青素含量呈上升趋势,其玻璃化转变温度、水溶性指数、亮度L^(*)值、红度a^(*)值、黄度b^(*)值和色差值ΔE等指标呈下降趋势;复合助剂显著提高蓝靛果粉集粉率(P<0.05),对其中的花青素起到较强保护作用,其含水率、水溶性指数、堆积密度等理化指标均接近于最优水平。低温喷雾干燥研究发现,随进风温度上升,集粉率和含水率呈负相关,在进风温度90℃时,集粉率最高的配方中可实现较高花青素保留率(89.94%)。低频核磁共振波谱以及质子密度图像信息分析表明,加入的助剂与蓝靛果果汁中水分通过氢键、静电结合力和疏水作用等分子间作用力,形成稳定性高水合物、增强液滴聚结抵抗力,提高料液玻璃态转换温度,从而实现高集粉率和高花青素保留率的蓝靛果果粉低温喷雾干燥;红外光谱分析表明,复合助剂可在蓝靛果果粉中形成分子间氢键,并对花青素等活性物质进行固定包埋保护。研究结果可为蓝靛果粉喷雾干燥加工生产提供理论支撑和参考依据。

3种灭菌方式对磁外科器件磁通量的影响及灭菌成本分析

目的 分析压力蒸汽、低温等离子及环氧乙烷3种灭菌方式对磁外科器件磁通量的影响及其灭菌成本。方法234件不同规格型号磁外科器件-磁环,配对编号标记后随机分为A组、B组和C组,每组78件(39对),其中A组使用压力蒸汽灭菌,B组使用低温等离子灭菌,C组使用环氧乙烷灭菌,每对器件按灭菌规范进行包装;测量3组磁环灭菌前后磁通量,对单包灭菌成本和灭菌时间比较分析。结果 3种灭菌方式对磁外科器件磁通量的影响差异无统计学意义(P>0.05),每种灭菌方式灭菌前后的磁通量有统计学差异(P<0.001);灭菌成本:A组为(1.96±0.16)元,B组(23.17±0.32)元、C组(8.16±0.18)元,差异有统计学意义(P<0.01);灭菌时间:A组为(65.21±3.36)min, B组(45.46±1.39)min, C组(1 020.38±12.21)min,差异具有统计学意义(P<0.01)。结论 3种灭菌方式对磁外科器件的磁通量没有影响。压力蒸汽灭菌法单包成本最低,低温等离子单包灭菌成本最高,环氧乙烷灭菌时间最长。压力蒸汽应为磁外科手术器件的首选灭菌方法。

医院过氧化氢低温等离子体灭菌质量评价指标体系构建

目的构建系统、规范的过氧化氢低温等离子体灭菌质量评价指标体系,为科学评价其灭菌效果提供参考。方法以三维质量评价模型为理论框架,通过文献回顾、理论分析、小组讨论法制订过氧化氢低温等离子体灭菌质量评价指标体系初稿,采用德尔菲法对全国15名消毒供应、感染防控、设备管理等相关领域专家进行2轮函询,并运用层次分析法确定指标权重。结果2轮函询问卷有效回收率分别为88%、100%,专家权威系数分别为0.940、0.960,肯德尔和谐系数分别为0.166、0.236(均P<0.001)。最终确定的医院过氧化氢低温等离子体灭菌质量评价指标体系包括3项一级指标、11项二级指标、52项三级指标。结论构建的过氧化氢低温等离子体灭菌质量评价指标内容科学、全面、实用,具有针对性,可为过氧化氢低温等离子体灭菌质量评价提供理论参考。

不同葡萄砧木抗寒抗抽干能力比较研究

[目的]气候变化新形势下,进一步筛选适宜西北地区抗寒、抗抽干葡萄砧木品种,可为葡萄免埋土栽培推广提供理论依据和技术支撑。[方法]本文以41Bmgt、Riparia、420Bmgt、101-14、196-17、44-53ma、110R、Rupestris du Lot、SO4、161-490、1103P、5BB、3309、Leon Millt共14种13年生葡萄砧木为试材,通过测定离体一年生枝条累计失水速率,结合田间调查葡萄砧木存活率和离体一年生枝条抽干率,以此来评价不同葡萄砧木品种抗抽干能力;结合前人研究及砧木品种特性,采用高低温交变试验箱模拟低温的方法,设置4(对照)、-15、-20、-25和-30℃一系列温度梯度水平,测定不同葡萄砧木一年生枝条相对电导率、丙二醛、游离脯氨酸、可溶性糖及可溶性蛋白5个生理生化指标,利用隶属函数法进行综合评价不同葡萄砧木的抗寒性。[结果]不同葡萄砧木的抗抽干能力由强到弱依次为:3309>161-490>196-17>Leon Millt>420Bmgt>44-53ma>Riparia>110R>1103P>SO4>101-14>41Bmgt>5BB>Rupestris du Lot;随着处理温度的降低,不同葡萄砧木枝条的抗寒指标总体呈现上升趋势,但不同品种之间存在差异。根据隶属函数的综合分析,结果显示各葡萄砧木的抗寒性由强到弱依次为:SO4>196-17>Leon Millt>5BB>Riparia>44-53ma>420Bmgt>1103P>3309>110R>Rupestris du Lot>101-14>41Bmgt>161-490。[结论]Riparia、196-17、44-53ma和Leon Millt具有较强的抗抽干能力和抗寒性,可作为我国西北地区免埋土葡萄砧木使用。

低温加氢催化剂CT6-13在硫磺尾气处理系统的应用

中国石油四川石化有限责任公司硫磺回收装置采用加氢还原吸收工艺及专用加氢催化剂进行尾气处理。将低温加氢催化剂CT6-13与常规加氢催化剂CT6-5B从物性、装填方法及预硫化、技术性能等方面进行了对比。深入对比分析CT6-5B和CT6-13在尾气加氢反应器的应用情况,发现采用CT6-13催化剂,节能降耗效果明显,尾气排放满足总硫不大于50μL/L、SO_(2)排放浓度不大于100 mg/m^(3)的设计要求。配套高效脱硫剂CT8-26及烟气洗涤技术,可实现开工过程尾气达标排放及日常运行过程尾气SO_(2)排放浓度不大于5 mg/m^(3)的超低排放。在节能降耗的同时解决了开停工及异常工况下的绿色生产及制约硫磺回收装置尾气焚烧炉长周期运行瓶颈问题。

基于响应面法的半柔性路面材料低温性能研究

为提高半柔性路面材料(SFPM)低温抗裂性能,采用橡胶粉与硅烷偶联剂对水泥砂浆进行改性,制备复合半柔性路面材料(R&S-SFPM)。基于响应面分析法以劈裂抗拉强度、抗弯拉强度、最大弯拉应变、弯曲蠕变速率以及平均线收缩系数作为评价指标分析胶粉目数、掺量及硅烷偶联剂用量对SFPM低温性能的影响,并确定了可获得最优低温性能表现的R&S-SFPM掺配比例。结果表明:橡胶粉可提高SFPM的应力松弛能力,使其具有更好的柔韧性;硅烷偶联剂可提高SFPM力学强度。此外,橡胶粉及硅烷偶联剂掺量、胶粉目数均对SFPM低温性能改善效果有较大影响。当胶粉目数为60目、掺量为14%,硅烷偶联剂用量为0.72%时,R&S-SFPM综合低温效果最佳;与普通半柔性路面材料(O-SFPM)相比,R&S-SFPM的劈裂抗拉强度、抗弯拉强度、最大弯拉应变以及弯曲蠕变速率分别提高23.7%、7.6%、29.9%和15.2%。

低温液相法从脱硫废渣中制备不溶性硫磺

HPF脱硫废渣是煤气脱硫工序的副产物,含有焦油、铵盐、酚、萘等多种杂质,是煤化工企业难以处理的固体废弃物。通过萃取-结晶技术,得到了纯度高于99.97%的高纯度硫磺。在较低的温度条件下,用提纯的硫磺制备了不溶性硫磺,通过三因素三水平正交试验,得到了低温液相法的最佳工艺条件。采用化学分析、差热、热重分析和X射线衍射分析技术,对产品的结构和性质进行了分析定性。试验结果表明,不溶性硫磺晶体结构和普通硫磺存在显著差异,具有较好的热稳定性。

基于流场换热的阀壳瞬态温度场分析及强度评估

文章基于浸入边界法,对汽轮机阀壳进行了流场分析,得到了阀壳在不同开度下的换热系数场和温度场,根据机组启停曲线分析了阀壳瞬态温度场,并在循环热载荷和压力载荷下的得到了阀壳在启停过程的低周疲劳和长时运行时的高温蠕变,为研制更加安全、高效的汽轮机阀壳提供了重要理论依据。

基于压汞-低温液氮联孔与核磁共振分析的煤中孔径分布对比研究

煤中孔隙结构测量常用压汞法、低温液氮法和核磁共振法,因不同方法的原理和测试范围不同,导致结果无法统一使用,且压汞法中基质压缩效应会造成较大误差;为解决该问题,以沁水盆地晋城和长治矿区的3个高阶煤样为例,利用压汞、低温液氮吸附及核磁共振驰豫法分别测试煤样的孔隙结构,通过对压汞数据进行压缩性校正,与低温液氮数据在衔接孔径处拼接,对煤的孔隙结构进行了联合表征,并结合核磁共振对比分析了煤的孔径分布特征。结果表明:压汞数据校正后孔体积与低温液氮的结果更接近,偏差值在22.40%~38.51%;不同煤样采用联孔法进行孔隙结构分析的联孔位置在75~89 nm之间;联孔法煤样孔容积为0.00136~0.00458 cm^(3)/g,不同孔径孔容比例表现为过渡孔>大孔>中孔>微孔;与单一测试方法相比,联孔法与核磁共振法孔径分布更为接近,但同时也存在差异,联孔法表征的微孔、过渡孔、中孔和大孔平均分布比例分别为8.68%、45.58%、20.54%和25.20%,核磁法微孔、过渡孔、中孔和大孔平均分布比例分别为10.64%、64.21%、14.23%和10.92%,结果差异原因可能主要与压汞法、低温液氮法加压改变了煤的孔隙结构有关;通过核磁共振结果对比,联合校正后的压汞与低温液氮数据可提高煤中孔径分布测试结果的准确性。

不同包装方式对龙滩珍珠李低温贮藏品质的影响

【目的】探讨3种包装方式对龙滩珍珠李果实采后低温贮藏品质的影响,筛选适合龙滩珍珠李果实低温冷藏的最佳包装方式,以期为龙滩珍珠李果实采后贮藏保鲜提供新途径。【方法】以龙滩珍珠李果实为材料,采用保鲜袋、硅窗袋和保鲜盒分别包装后置于(4±1)℃低温贮藏49 d,贮藏过程中每隔7 d检测1次果实品质指标。【结果】随着贮藏时间的延长,3种包装的龙滩珍珠李果实失重率、腐烂率、固酸比(TSS/TA)和果皮红绿色度(a^(*)值)均不断升高,硬度、咀嚼性、可溶性糖(SSC)含量、可滴定酸(TA)含量、糖酸比(SSC/TA)和维生素C(Vc)含量不断下降;果皮亮度(L^(*)值)及果实弹性、内聚性和可溶性固形物(TSS)含量在贮藏前7 d先略有升高,之后整体不断下降;果实呼吸速率先升高后降低再升高,贮藏28 d时均达呼吸高峰。贮藏至第49 d,保鲜袋、硅窗袋和保鲜盒包装的果实失重率分别为2.39%、5.14%和13.18%;与贮藏0 d相比,a^(*)值分别提高76.15%、91.23%和104.43%,硬度分别下降62.58%、62.79%和69.04%,TSS含量分别下降9.94%、12.18%和13.01%,Vc含量分别下降71.68%、73.81%和77.70%;贮藏至第28 d的呼吸峰值分别为28.18、28.85和30.85 mg CO_(2)/(kg·h)。保鲜袋包装可有效抑制果实低温贮藏期失重率、果皮a^(*)值和TSS/TA的升高,延缓果皮L^(*)值及果实硬度、咀嚼性、TSS含量、SSC含量、TA含量和Vc含量的下降,抑制果实呼吸强度,降低呼吸峰值。【结论】保鲜袋包装结合低温贮藏对龙滩珍珠李果实的贮藏保鲜效果最佳,能更好地保持果实贮藏品质,延缓果实衰老进程。

4个葡萄品种在内蒙古高寒地区的抗寒性研究

对内蒙古地区主栽的4个葡萄品种的枝条及根系进行抗寒性分析,旨在为葡萄抗寒育种、优良品种推广提供理论依据。以北玫、双庆、玫瑰香和芳堤娜为试验材料,模拟自然冷冻降温过程,枝条模拟温度设置为-5、-15、-20、-25、-30、-35、-40℃;根系模拟温度设置为0、-3、-6、-9、-12、-15、-18℃,分别测定丙二醛含量、可溶性糖含量、可溶性蛋白含量、脯氨酸含量。结果表明,随着温度逐渐降低,4个葡萄品种的渗透调节物质均呈现显著差异。其中,根系可溶性蛋白含量均呈上升趋势,枝条可溶性蛋白含量均呈先上升后下降的趋势,枝条和根系的丙二醛含量和脯氨酸含量均呈上升趋势,而可溶性糖含量均呈先上升后下降的趋势。通过隶属函数法分析,4个葡萄品种的抗寒性强弱顺序为双庆>北玫>芳堤娜>玫瑰香。