Dynamic failure of dry and fully saturated limestone samples based on incubation time concept

This paper outlines the results of experimental study of the dynamic rock failure based on the comparison of dry and saturated limestone samples obtained during the dynamic compression and split tests. The tests were performed using the Kolsky method and its modifications for dynamic splitting. The mechanical data(e.g. strength, time and energy characteristics) of this material at high strain rates are obtained. It is shown that these characteristics are sensitive to the strain rate. A unified interpretation of these rate effects, based on the structuraletemporal approach, is hereby presented. It is demonstrated that the temporal dependence of the dynamic compressive and split tensile strengths of dry and saturated limestone samples can be predicted by the incubation time criterion. Previously discovered possibilities to optimize(minimize) the energy input for the failure process is discussed in connection with industrial rock failure processes. It is shown that the optimal energy input value associated with critical load, which is required to initialize failure in the rock media, strongly depends on the incubation time and the impact duration. The optimal load shapes, which minimize the momentum for a single failure impact, are demonstrated. Through this investigation, a possible approach to reduce the specific energy required for rock cutting by means of high-frequency vibrations is also discussed.

Microscopic phase-field simulation for nucleation incubation time of Ni_(75)Al_xV_(25-x)alloy

With the microscopic phase-field dynamic model, the effects of temperature and concentration on the nucleation incubation time of Ni75AlxV25-x alloy were studied and the relation between the incubation time and precipitation mechanism was investigated by using the atomic occupation probability picture and average order parameter curve. The simulation results demonstrate that there exists the incubation time for different precipitation mechanisms~ such as non-classical nucleation, the mixed style of non-classical nucleation and spinodal decomposition, and spinodal ordering; and the incubation time shortens in turn for the three kinds of mechanisms. With the increase of Al content of Ni75AlxV25-x alloy, the incubation time of Llz phases shortens continuously and that of DOzz phases is prolonged. The effects of temperature on the incubation time of Llz and DOzz phases are accordant, i.e. the incuba- tion time is greatly prolonged with the temperature rising.

Incubation time fracture criterion for FEM simulations

The paper is discussing problems connected with embedment of the incubation time criterion for brittle fracture into finite element computational schemes. Incubation time fracture criterion is reviewed; practical questions of its numerical implementation are extensively discussed. Several examples of how the incubation time fracture criterion can be used as fracture condition in finite element computations are given. The examples include simulations of dynamic crack propagation and arrest, impact crater formation （i.e. fracture in initially intact media）, spall fracture in plates, propagation of cracks in pipelines. Applicability of the approach to model initiation, development and arrest of dynamic fracture is claimed.

EFFECT OF AUSTENITE DEFORMATION ON ISOTHERMAL INCUBATION TIME OF PROEUTECTOID FERRITE NUCLEATION

A calculation method for the isothermal nucleation incubation time of pro-eutectoid ferrite formed from deformed austenite has been developed by introducing Feder's incubation time expression into the decomposition of deformed austenite.The effects of austenite deformation stored energy and austenite grain boundary energy change on the incubation time have been theoretically calculated and the rule of calculated results is consistent with that of experiments,this confirms that austenite deformation stored energy and the change of austenite grain boundary energy are the natural effect of austenite deformation on ferrite nucleation.

Modeling of Incubation Time for Austenite to Ferrite Phase Transformation

On the basis of the classical nucleation theory, a new model of incubation time for austenite to ferrite transformation has been developed, in which the effect of deformation on austenite has been taken into consideration. To prove the precision of modeling, ferrite transformation starting temperature （Ar3） has been calculated using the Scheil＇s additivity rule, and the Ar3 values were measured using a Gleeble 1500 thermomechanical simulator. The Ar3 values provided by the modeling method coincide with the measured ones, indicating that the model is precise in oredicting the incubation time for austenite to ferrite transformation in hot deformed steels.

Evaluation of Energy Saving Operational Modes for Industrial Fracture Connected Processes on the Basis of Incubation Time Fracture Criterion

A problem for a central crack in a plate subjected to plane strain conditions is investigated. Mode I crack loading is created by a dynamic pressure pulse applied at a large distance from the crack. It was found that for a certain combination of amplitude and duration of the pulse applied, the energy transmitted to the sample has a strongly marked minimum, meaning that with the pulse amplitude or duration moving away from the optimal values, minimum energy required for initiation of crack growth increases rapidly. The results obtained indicate a possibility to optimise energy consumption of different industrial processes connected with fracture. Much could be gained in, for example, drilling or rock pounding where energy input accounts for the largest part of the process cost. Presumably further investigation of the effect observed can make it possible to predict optimal energy saving parameters, i.e. frequency and amplitude of impacts, for industrial devices, e.g. bores, grinding machines, and hence significantly reduce the process cost. The pre- diction can be given based on the parameters of the media fractured （material parameters, prevalent crack length and orientation, etc.）.

Optimization of Bacterial Doses and Incubation Time on Bio-Ehanol Fermentation of Nipah （Nypa fruticans） for Biofuel Energy

Nipah （Nypafruticans） is a species of palm trees that grows in mangroves environment near the sea shore. Nipah is potential to produce biofuel energy. The purposes of this research were 1） to determine the optimum bacterial concentration for fermentation to produce high concentration of bio-ethanol, and 2） to determine the optimum incubation time for fermentation to produce high concentration of bio-ethanol. The research had been conducted from June until November 2009 using nipah sap as the substrate and Saceharomyces cerevisiae as a fermentation starter. The experimental design used was a randomized block design （RBD）. Factors tested were starter concentration （5%, 7.5%, 10%） and incubation time （2, 4, 6 days）. The variables observed were concentration of reducing sugar, total microorganism （CFU/mL）, and bio-ethanol production. The results showed that the highest yield of bio-ethanol （8.98%） was produced with 7.5% of starter concentration and 6 days of incubation time.

Time-lapse培养与桌面台式培养箱胚胎培养对胚胎发育的影响

目的探讨Time-lapse培养与桌面台式培养箱胚胎培养对胚胎发育的影响。方法选取2021年3月—2023年3月在本院生殖中心行IVF-ET/ICSI-ET治疗的613个周期的胚胎发育数据,随机分配胚胎培养方式。分为对照组与研究组,其中对照组为桌面台式培养箱方式(360个周期),研究组为Time-lapse培养与桌面台式培养箱方式(253个周期),统计两组胚胎发育质量。结果研究组中正常受精数、可移植胚胎数、形成囊胚数、优质胚胎数、高评分囊胚数、受精率、冷冻胚胎率、胚囊形成率、优质胚胎率、高评分囊胚率高于对照组,组间差异有统计学意义(P<0.05)。结论Time-lapse培养与桌面台式培养箱胚胎培养方式优于桌面台式培养箱方式,可为胚胎培养提供适宜的环境、温度、湿度等,有助于胚胎发育,具有较强的实用性和推广性,值得推广应用。

ESP工艺下DP600热轧双相钢铁素体相变模型

为了建立ESP工艺条件下DP600热轧双相钢的铁素体相变动力学数学模型,采用动态相变膨胀仪对实验钢分别进行等温相变和连续冷却相变实验.基于实测的铁素体相变孕育期和铁素体体积分数,在变形温度以上结合经典形核理论计算铁素体相变孕育期,变形温度以下通过实验数据拟合△GV计算铁素体相变孕育期.考虑冷却速度的影响对可加性法则进行修正并基于此计算了连续冷却条件下的铁素体相变开始温度和体积分数.结果表明:修正后的相变模型计算的铁素体相变开始温度和体积分数与实测值吻合良好,可用于预测ESP工艺下DP600钢的铁素体相变行为.

环形热管蓄冷保温箱空载均温性能研究

针对传统蓄冷箱箱内温度均匀性差的问题,提出环形热管结构蓄冷保温箱的设计,建立了空载均温性能的三维数值仿真模型,并进行了试验验证,对比分析了环形热管保温箱与常规结构蓄冷保温箱蓄冷板不同布置方式(四周布置、侧面+顶部+底部布置、中间布置)保温时间和温度均匀性的差异。结果发现,与常规结构蓄冷箱相比,环形热管结构的蓄冷保温箱的温度场、速度场均表现出较好的均匀性,其温度不均匀度为1.13,保冷时间为23 h。内部的环形热管在箱内形成环形流场,加强了对流换热,使整体温度均匀性更好。

实验教学用植物活体荧光影像系统的研制

通过植物培养及拍摄系统的开发,研制低成本的植物活体荧光影像系统。该系统采用双层箱体结构设计,分为恒温光照培养系统和荧光记录系统两部分,可以为植物生长发育提供所需的生命支撑功能,还能实时获取植物生长发育过程中的关键图像,包括监控转基因植物发育过程中荧光信号的时空模式。利用该系统成功地对EGFP转基因烟草和拟南芥进行培养和实时观察。低廉的成本极大地扩展了该系统在实验教学中的运用,也为生命活动的观察和检测研究奠定基础。

辣椒早疫病潜育期的光谱特性判别方法

辣椒早疫病是影响辣椒安全生长的常见生物灾害,具有突发性和易感性等特点,容易引发大的经济损失。在辣椒生长过程中,针对病害潜育期侵染情况进行科学监测预警是保证作物健康生长的重要前提。利用400~1000 nm波段的高光谱图像结合光谱相似性测度方法建立作物病害潜育期的光谱特性判别方法。针对接种早疫病病菌的辣椒叶片和健康叶片,用高光谱成像仪连续动态监测其不同感染期的高光谱图像。对试验采集的一系列高光谱图像提取感兴趣区的平均光谱,通过卷积平滑、多元散射校正以及最大最小归一化方法(SG-MSC-MMN)预处理,进而提出以光谱角余弦-相关系数和切比雪夫距离两种测度作为早疫病潜育期的光谱特性评价参数。最后利用主成分分析(PCA)验证潜育期的光谱特性判别方法效果,实现样本潜育期的可视化分布。试验结果显示:利用光谱角余弦-相关系数与切比雪夫距离作为辣椒早疫病潜育期的光谱特性评价参数并分别建立相应的判别方法是可行的,且根据这两种判别方法得到的辣椒早疫病潜育期最早可识别时间均为接种后24 h。根据PCA绘制得到接种24 h时的健康-接种样本空间分布情况,分别验证所提出的两种基于光谱特性的潜育期最早可识别时间判别方法。建立的辣椒早疫病潜育期最早可识别时间判别方法可推广应用于其他作物病害潜育期的监测识别,为作物病害潜育期的科学防治提供理论参考与方法借鉴。

兔脂肪干细胞MR示踪前的超顺磁性氧化铁最佳标记条件筛选

目的 采用多聚赖氨酸修饰的超顺磁性氧化铁(Polylysine coated superparamagnetic iron oxide,PLL-SPIO)纳米颗粒标记兔脂肪间充质干细胞(Adipose derived stem cell,ADSCs),探讨不同SPIO浓度及孵育时间对ADSCs标记率、存活率及细胞增殖率的影响,筛选SPIO标记ADSCs的最优标记条件。方法 用含不同浓度的SPIO(12、25、50μg/mL)培养基培养第3代兔ADSCs,分别孵育不同时间(6、12、24、48 h),孵育完成后,普鲁士蓝染色计算细胞标记率;细胞毒性实验检测细胞存活率;根据细胞毒性实验结果筛选细胞存活率较大的6组细胞进行细胞增殖能力检测,检测细胞增殖率。结果 普鲁士蓝染色结果显示,各组细胞标记率及细胞内蓝染颗粒数量,随着SPIO浓度增大及孵育时间的延长而增多。细胞毒性实验结果显示,在较低SPIO浓度和较短孵育时间下,细胞存活率不受影响,且各组之间细胞存活率无明显差异,随着SPIO浓度增大及孵育时间延长,细胞存活率呈下降趋势,48 h时细胞存活率下降最明显。细胞增殖实验结果显示,实验组各组细胞增殖率,随SPIO浓度增大及孵育时间延长而降低;且细胞进入快速增长期后,实验组细胞增殖率与阴性对照组相比,均存在明显差异,其中12μg/mL SPIO-6 h组和25μg/mL SPIO-6 h组细胞增殖率与阴性对照组差异较其他各组小。结论 从细胞内SPIO颗粒含量及细胞标记率、存活率及增殖率几方面综合评价,25μg/mL SPIO孵育6 h,是本研究所选出的PLL-SPIO标记ADSCs的最优标记条件。

Threshold characteristics of short-pulsed loads combined with the ultrasound field causing dynamic delamination of adhesive joints

In the present work, we analyse the delamination problem under the combined dynamic load. We show the effect of background harmonic vibrations on critical amplitudes of the principal force pulse. The effect is demonstrated on the simple model of a string on an elastic foundation and the fracture phenomenon is predicted by the incubation time criterion. The results state the possibility of considerable decrease in threshold amplitude by a proper choice of the frequency of a background excitation.

溶解氧与亚硝酸盐对锈斑蟳卵孵育时间的影响

研究溶解氧与亚硝酸盐对锈斑蟳(Charybdis feriatus)卵孵育时间的影响。结果表明,溶解氧与亚硝酸盐浓度变化均对锈斑蟳的卵孵育时间产生显著影响;海水溶解氧在2~12 mg/L时,锈斑蟳均可正常孵育,随着海水内溶解氧含量的提升,锈斑蟳卵孵育时间逐渐下降;亚硝酸盐浓度对锈斑蟳卵孵育持续时间产生显著影响,其浓度低于50 mg/L的条件适合锈斑蟳卵孵育,在亚硝酸盐浓度低于25 mg/L时,锈斑蟳卵孵育各阶段的持续时间较短。

磷酸奥司他韦不同时序干预对A型H1N1流感病毒感染小鼠模型药效及炎症因子调控作用研究

目的针对目前抗病毒体内实验给药时间点偏早的现状,本研究以磷酸奥司他韦(达菲)作为“工具药”,比较不同时序干预对病毒感染小鼠的影响,为抗病毒药物研究选择合理的模型干预时间点提供依据。方法将Balb/c小鼠随机分成6组,滴鼻感染流感病毒(0.25 TCID_(50))建立病毒感染小鼠模型,达菲-1组、达菲-2组分别在染毒后d 1和d 4灌胃给药。测定体质量,计算生存率、脏器指数,测定病毒载量及炎症因子含量。结果与空白对照组比较,模型组小鼠的体质量降低,肺指数均明显升高(P<0.05);模型-2组13个炎症因子表达水平差异有显著性(P<0.05)。与模型-1组相比,达菲-1组肺指数、脾指数明显降低(P<0.05),病毒载量为模型-1组的0.54倍;与模型-2组相比,达菲-2组肺指数明显降低(P<0.05)、胸腺指数明显升高(P<0.05),病毒载量为模型-2组的0.03倍,13个炎症因子表达水平差异具有显著性(P<0.05)。结论方案2的小鼠染毒后症状更明显、稳定、给药后减轻了肺部炎症损伤,考虑了潜伏期,待模型动物出现症状开始进行药物干预符合临床用药指征,无论是在模型评估还是药物评价将更合理和准确。

温度、时间对不同方法检测地下水中总大肠菌群的影响

分别以温度和时间为变量,比较了滤膜法、酶底物法检测地下水中总大肠菌群的数量。研究表明,2种方法的检测结果随温度变化趋势基本一致,在35、36、37℃时,大肠菌群生长最快,3个温度下的检测结果基本无差异(P<0.05),而与28、32、40℃下的检测结果相比差异明显。滤膜法和酶底物法的培养时间在22、24、28 h时总大肠菌群基本无差异(P<0.05),而16、18、20、32 h的总大肠菌群数差异明显。因此为保证实验数据真实准确,2种检测方法都应严格控制培养温度和时间。培养温度为36±1℃,培养时间为22~28 h。

酶底物法检测水中菌落总数培养24h和48h的比较试验

酶底物法于2023年作为新型水中菌落总数检测方法被纳入《生活饮用水标准检验方法第12部分:微生物指标》(GB/T5750.12—2023)中。为便于更加科学规范地使用酶底物法检测生活饮用水中的菌落总数,文章采用酶底物法对80组生活饮用水及水源水的实际样品进行检测,并分析24h及48 h两个不同培养时间的检测结果。检测结果表明:酶底物法24 h培养结果和48 h培养结果差异较大,通过配对t检验分析可知酶底物法24 h培养结果与48 h培养结果P=0.000(<0.05),具有显著的统计学差异,对差异样品进行菌种鉴定发现,部分致病菌使用酶底物法培养24 h无法检出。故酶底物法检测生活饮用水及水源水菌落总数时,培养时间至少为48 h方可满足实验室对生活饮用水及水源水菌落总数的检测要求。

大环内酯类药物对木糖葡萄球菌敏感菌株及其耐药菌株生物被膜形成的影响

为了探究大环内酯类药物泰乐菌素和阿奇霉素对木糖葡萄球菌敏感菌株及其耐药菌株生物被膜形成的影响,试验首先通过倍比稀释法测定两种药物对木糖葡萄球菌敏感菌株及其耐药菌株的最小抑菌浓度(MIC),然后利用结晶紫染色法考察木糖葡萄球菌敏感菌株及其耐药菌株生物被膜的形成能力,并测定细菌生长情况,最后考察两种药物浓度及药物孵育时间对生物被膜形成的影响。结果表明:木糖葡萄球菌耐药菌株生物被膜的形成能力弱于敏感菌株,木糖葡萄球菌敏感菌株与其耐药菌株的生长存在差异。0.3125μg/mL的泰乐菌素和阿奇霉素对木糖葡萄球菌敏感菌株生物被膜的形成具有极显著抑制作用(P<0.01),对耐药菌株生物被膜形成的抑制作用不显著(P>0.05);25μg/mL的泰乐菌素和阿奇霉素对耐药菌株生物被膜的形成具有显著或极显著抑制作用(P<0.05或P<0.01)。随着药物孵育时间的延长,对生物被膜形成的抑制效果逐渐增强。说明大环内酯类药物泰乐菌素和阿奇霉素在一定程度上能抑制木糖葡萄球菌敏感菌株及其耐药菌株生物被膜的形成且具有时间依赖性。

Incubation time approach in rock fracture dynamics

The paper is summarizing latest results connected with application of the incubation time approach to problems of dynamic fracture of rock materials. Incubation time based fracture criteria for intact media and media with cracks are discussed. Available experimental data on high rate fracture of different rock materials and incubation time based fracture criteria are used in order to evaluate critical parameters of causing fracture in these materials. Previously discovered possibility to optimize (minimize) energy input for fracture is discussed in connection to industrial rock fracture processes. It is shown that optimal value of momentum associated with critical load in order to initialize fracture in rock media does strongly depend on the incubation time and the impact duration. Existence of optimal load shapes minimizing momentum for a single fracturing impact or a sequence of periodic fracturing impacts is demonstrated.