Effects of wall temperature on boundary layer stability over a blunt cone at Mach 7.99

Effects of wall temperature on stabilities of hypersonic boundary layer over a 7-degree half-cone-angle blunt cone are studied by using both direct numerical simulation (DNS) and linear stability theory (LST) analysis. Four isothermal wall cases with Tw/T0= 0.5, 0.7, 0.8 and 0.9, as well as an adiabatic wall case are considered. Results of both DNS and LST indicate that wall temperature has significant effects on the growth of disturbance waves. Cooling the surface accelerates unstable Mack II mode waves and decelerates the first mode (Tollmien–Schlichting mode) waves. LST results show that growth rate of the most unstable Mack II mode waves for the cases of cold wall Tw/T0=0.5 and 0.7 are about 45% and 25% larger than that for the adiabatic wall, respectively. Numerical results show that surface cooling modifies the profiles of rdut/dyn and temperature in the boundary layers, and thus changes the stability haracteristic of the boundary layers, and then effects on the growth of unstable waves. The results of DNS indicate that the disturbances with the frequency range from about 119.4 to 179.1 kHz, including the most unstable Mack modes, produce strong mode competition in the downstream region from about 11 to 100 nose radii. And adiabatic wall enhances the amplitudes of disturbance according to the results of DNS, although the LST indicates that the growth rate of the disturbance of cold wall is larger. That because the growth of the disturbance does not only depend on the development of the second unstable mode

Direct numerical simulation of hypersonic boundary layer transition over a blunt cone with a small angle of attack

The direct numerical simulation of boundary layer transition over a 5° half-cone-angle blunt cone is performed. The free-stream Mach number is 6 and the angle of attack is 1°. Random wall blow-and-suction perturbations are used to trigger the transition. Different from the authors’ previous work [Li et al., AIAA J. 46, 2899(2008)], the whole boundary layer flow over the cone is simulated (while in the author’s previous work, only two 45° regions around the leeward and the windward sections are simulated). The transition location on the cone surface is determined through the rapid increase in skin fraction coefficient (Cf). The transition line on the cone surface shows a nonmonotonic curve and the transition is delayed in the range of 0° ≤ θ ≤ 30° (θ = 0° is the leeward section). The mechanism of the delayed transition is studied by using joint frequency spectrum analysis and linear stability theory (LST). It is shown that the growth rates of unstable waves of the second mode are suppressed in the range of 20° ≤ θ ≤ 30°, which leads to the delayed transition location. Very low frequency waves VLFWs� are found in the time series recorded just before the transition location, and the periodic times of VLFWs are about one order larger than those of ordinary Mack second mode waves. Band-pass filter is used to analyze the low frequency waves, and they are deemed as the effect of large scale nonlinear perturbations triggered by LST waves when they are strong enough.The direct numerical simulation of boundary layer transition over a 5° half-cone-angle blunt cone is performed. The free-stream Mach number is 6 and the angle of attack is 1°. Random wall blow-and-suction perturbations are used to trigger the transition. Different from the authors’ previous work [ Li et al., AIAA J. 46, 2899 (2008) ], the whole boundary layer flow over the cone is simulated (while in the author’s previous work, only two 45° regions around the leeward and the windward sections are simulated). The transition location on the cone surface is determined through the rapid increase in skin fraction coefficient (Cf). The transition line on the cone surface shows a nonmonotonic curve and the transition is delayed in the range of 20° ≤ θ ≤ 30° (θ = 0° is the leeward section). The mechanism of the delayed transition is studied by using joint frequency spectrum analysis and linear stability theory (LST). It is shown that the growth rates of unstable waves of the second mode are suppressed in the range of 20° ≤ θ ≤ 30°, which leads to the delayed transition location. Very low frequency waves (VLFWs) are found in the time series recorded just before the transition location, and the periodic times of VLFWs are about one order larger than those of ordinary Mack second mode waves. Band-pass filter is used to analyze the low frequency waves, and they are deemed as the effect of large scale nonlinear perturbations triggered by LST waves when they are strong enough

非离子态氨对转“全鱼”生长激素基因鲤鱼的急性毒性和慢性毒性

在自然水体和人工水体中氨氮对鱼类是有毒的.利用静水更新式生物测试研究了非离子态氨对转基因鲤鱼和对照鱼的96h急性毒性实验和21d慢性毒性实验.通过96h非离子态氨急性毒性实验发现,转基因鲤鱼的非离子态氨氮24,48,72和96h半数致死浓度(LC50)(2.64,2.44,2.28和2.16mg/L)分别比对照鲤鱼相应的24,48,72和96h半数致死浓度(LC50)(2.70,2.64,2.52和2.33mg/L)略低,没有显著性差异;但在不同非离子态氨氮(3.86,3.29和2.09mg/L)胁迫下

A New High Order Accurate Shock Capture Method with Wave Booster

A new kind of shock capturing method is developed. Before applying the high order accurate traditional scheme which is called as base scheme in this paper the fluid parameters are preconditioned in order to control the group velocity. The newly constructed scheme is high order accurate, simple, has high resolution of the shock, and less computer time consumed

Development of a quantitative ELISA detection method for Coxsackievirus A group 16 strain(CA16) antigen

目的:建立柯萨奇病毒A组16型(CA16)抗原的双抗体夹心ElISA定量检测方法,用于CA16灭活疫苗的研发和生产过程的抗原定量检测。方法:以CA16中和单抗T26H12为包被抗体、nA14b9为标酶抗体,构建定量检测CA16抗原的双抗体夹心ElISA方法,并对方法的特异性、灵敏度、精密度、准确性、线性和稳定性进行分析。结果:建立了双抗体夹心定量检测CA16抗原的ElISA方法。方法的线性相关系数r2=0.998,线性范围为8~128 ng/Ml,定量限度为8 ng/Ml;变异系数CV80%;与CA16以外的其他样本没有交叉反应。结论:构建的CA16抗原ElISA定量检测方法的各项性能符合定量检测需要,可用于CA16疫苗的研发和生产过程的抗原活性的定量检测。Objective:To develop an a quantitative enzyme linked immunosorbent assay(Q-ELISA) to determine the concentration of Coxsackievirus A Group 16 Strain(CA16) antigen.This method was used to determine CA16 antigen content at each stage of CA16 vaccine developing and manufacturing process.Methods:A double antibody sandwich Q-ELISA was developed to determine concentration of CA16 antigen,which was based on the high-affinity neutralizing monoclonal antibodies T26H12 as capture antibodies,and NA14B9 as HRP-labeled antibody.The performance of reagent were evaluated.Results:The Q-ELISA for CA16 antigen content was successfully developed.The reagent had good performance.The quantitation scope was 8-128 ng/ml,the coefficient correlation was 0.998,the limit of detection was 8 ng/ml,the recovery was between 87% and 113.8%.The stability was up to 80% after reagent was heated for 6 days at 37℃.The variation coefficient was lower than 15%,and thereagent was no reaction with other sample except CA16 antigen.Conclusion:The Q-ELISA for CA16 antigen was developed with good specificity,accuracy,precision and stability.The method can be used to determine CA16 antigen content during development and production of CA16 vaccine

Primary studies on the biology of ‘all-fish’ growth hormone transgenic common carp (Cyprinus carpio L.)

世界首例转基因鱼的诞生开辟了鱼类遗传育种的新纪元。转基因鱼由于具有生长速度快、饵料转化效率高、抗病和抗逆等优良养殖性状而显示出强大的应用潜力。转基因鱼被认为将在转基因动物中率先实现商业化。然而，由于政府和民众对转基因鱼潜在的生态风险的关注，致使迄今仍然无任何一例具有优良养殖性状的转基因鱼成功的实现商业化。因此，全面衡量和评估转基因鱼的生态风险是其商业化进程中的重要一环。 本研究围绕转基因鱼的生态风险这一重要科学问题，有针对性地对影响转“全鱼”生长激素基因黄河鲤种群适合度的重要生物学特征进行了初步的研究。与此同时，本研究也以快速生长转基因黄河鲤为模型，探讨鱼类生长速率与其存活率、繁殖特征以及游泳能力之间的权衡关系。主要研究结果如下： 1. 建立了快速生长转“全鱼”生长激素基因黄河鲤家系。通过测交的方式证实，转植基因在该家系 F2、 F3、 F4 和 F5 代中的分离比均为 50％。F2 代转基因鱼的平均体重是对照鱼的 1.8-2.5 倍，体重的特定生长率比对照鱼高出 10-20%。结果表明：“全鱼”生长激素转植基因有效整合在转基因黄河鲤基因组中，并能够在所建立的转基因鱼家系的各个世代间以孟德尔方式稳定遗传，且表现出明显的促生长效应。 2. 在 22.4 ± 0.09℃ 的水温环境下，转基因黄河鲤仔胚的孵化速率比对照仔胚快大约 2 个小时。与同一尾对照雌鱼杂交，转基因雄鱼与对照雄鱼后代的孵化率之间没有显著差异。内源性营养阶段的转基因仔鱼标准长、标准长特定生长率与对照鱼相似。外源摄食阶段，转基因仔鱼的体重、体重特定生长率、标准长、标准长特定生长率均显著的大于对照鱼。在人工养殖模式下，转基因黄河鲤在其仔、幼鱼阶段的死亡率显著的高于对照鱼。该结果进一步证实硬骨鱼类的快速生长与死亡率之间存在权衡关系。 3. 转基因鱼的体重和标准长分别是同龄对照鱼的 1.3-2.2 倍和 1.1-1.4 倍。实验期间，转基因雌鱼的性腺指数均显著的低于对照鱼，转基因雄鱼在不进行繁殖活动时的性腺指数也均显著的低于对照鱼，但在自然繁殖后的前两个月内，则与对照鱼没有显著差异。转基因鱼性腺的绝对重量显著的低于或等于对照鱼。转基因鱼性腺发育的速率慢于对照鱼。结果表明，具有快速生长效应的转基因黄河鲤首次性成熟年龄推迟，其快速生长效应以降低繁殖投资 (性腺指数) 为代价。 4. 转基因黄河鲤的绝对临界游泳速度和相对临界游泳速度的平均值分别比对照鱼低 22% 和 24%。这暗示着具有快速生长效应的转基因黄河鲤表现出低劣的游泳能力，同时也证实了鱼类生长速率和游泳能力之间存在权衡，即同一物种的个体生长率越高，临界游泳速度则越低。 5. 转基因黄河鲤与对照鲤的体型之间存在显著的差异。较对照鱼而言，转基因鱼具有较大的头部深度、较大的尾柄长度，但其体高和尾柄深度却较小。形态特征对实验鱼的临界游泳速度具有显著的影响。临界游泳速度比较高的鱼类通常具有较大的体高和尾柄深度，较小的尾柄长度。这些结果说明，形态特征的变化或许是造成转基因鱼临界游泳速度较低的因素之一。 6. 转基因黄河鲤的红细胞长度、宽度、表面积和体积均显著的小于对照鱼，其红细胞表面积与体积比显著的高于对照鱼，但其红细胞长度与宽度比与对照鱼之间没有显著差异。转基因鱼的日常代谢率显著的高于对照鱼，最大代谢率与对照鱼相似。正常状态下，转基因鱼的血细胞比容、血红蛋白浓度、血浆葡萄糖浓度、血浆乳酸浓度、血浆胆固醇浓度、血浆蛋白浓度均与对照鱼没有显著差异，但其平均血细胞血红蛋白浓度和血浆甘油三酯浓度则分别显著的低于和高于对照鱼。疲劳运动对两种鱼的血细胞比容、血浆蛋白浓度以及平均红细胞血红蛋白浓度没有造成显著的影响。疲劳运动后转基因鱼和对照鱼的血浆葡萄糖浓度和乳酸浓度均显著的增加，并分别经过 4h 恢复到了正常状态，表现出典型的次级应激反应。转基因鱼与对照鱼的血浆葡萄糖浓度应对疲劳运动的方式相似，但转基因鱼的血浆乳酸浓度应对疲劳运动刺激的反应强度较弱。疲劳运动后，转基因鱼的血浆胆固醇浓度和甘油三酯浓度均显著的升高，2h 后恢复到正常状态，而对照鱼的上述两种指标没有表现出明显的应答。转基因鱼血浆蛋白浓度对疲劳运动没有明显应答，但是对照鱼的血浆蛋白浓度从运动后 2h 后开始显著的低于对照鱼。结果表明：转基因鱼较对照鱼具有较小的红细胞形态、较高的日常代谢率、相似的最大活动代谢率和血液载氧能力，但是其血液生理指标 (血浆乳酸、胆固醇、甘油三酯和蛋白) 在应对疲劳运动的方式上较对照鱼发生了明显的变化

可压缩衰减湍流的直接数值模拟

构造了八阶精度的群速度控制型差分格式并根据激波捕捉能力及对小尺度分辨能力对格式系数进行了优化。采用该格式对可压缩均匀各向同性湍流进行了直接数值模拟,所计算的最大湍流马赫数达到0.95。相同计算条件下的结果与他人结果吻合较好,说明了格式在捕捉激波的同时对湍流小尺度有较好的分辨能力。对特定流场进行了标度律分析,发现即使在较高的湍流马赫数下,扩展自相似性仍然成立,而且压缩性效应对标度指数影响很小,说明了标度指数的普适性

可压槽道湍流的直接数值模拟及标度律分析

采用基于非等距网格的紧致差分方法对Mach数为0.8，Reynolds数为3300的可压缩槽道湍流进行了直接数值模拟。建立了充分发展的可压缩槽道湍流数据库。该流场的统计特征(如等效平均速度分布，半局部尺度无量纲化的脉动均方根分布)与他人的数值结果吻合较好。在此DNS结果的基础上，作者对该流场进行了统计分析和机理研究。得到了可压缩槽道湍流场的高阶统计矩。同时分析了压缩性效应对近壁相干结构的影响机理，认为在可压壁湍流的近壁区，压力在压缩-膨胀上的做功部分吸收了脉动速度的动能，使得可压湍流的近壁速度条带结构更加平整。还对可压缩槽道湍流进行了标度律分析，指出可压槽道湍流中心线附近较宽的区域内存在标度律及扩展的自相似性。认为当Mach数不是很高时压缩性效应对标度指数影响不大。通过数值计算得到可压缩槽道湍流的标度指数