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1.
兔主动脉冻结膨胀行为及其影响因素的研究   总被引:2,自引:0,他引:2  
文采用热机械分析仪(TMA)分别研究了低温保护剂(CPA)和冻结速率对兔主动脉冻结相变过程中膨胀的影响。研究结果表明:在兔主动脉的冻结过程中,先是逐渐膨胀到某一峰值,然后突然有收缩的发生;降温速率越大,其相应的热膨胀系数也越大;添加二甲亚砜(DMSO)大大增加了主动脉冻结过程的未冻水含量,从而对其冻结膨胀有明显影响,而且,DMSO浓度越大,其冻结膨胀系数越小。  相似文献   

2.
采用动态力学分析仪(DMA)研究了温度、降温速率、低温保护剂对冻结状态下兔胸主动脉的裂纹扩展和断裂模式的影响.研究结果表明:随着温度的降低,主动脉轴向由典型的韧性断裂转变为典型的脆性断裂,并且其裂纹扩展也越困难;降温速率对冻结状态下主动脉的裂纹扩展和断裂模式影响不大;DMSO对主动脉的冻结过程有明显的"软化"作用,裂纹更容易扩展,而且呈现出典型的韧断;均以5℃/min降温到-50℃后,血管周向比轴向易于扩展,但其与轴向试样表现出截然相反的典型韧断,这充分说明冻结状态下主动脉仍然体现出各向异性的特点.  相似文献   

3.
兔主动脉比热容测量   总被引:2,自引:0,他引:2  
本文用差示扫描量热技术的分步扫描方法,测量了未加抗冻剂和加抗冻剂的兔主动脉在30-140℃温度范围内的比热容。实验发现相变过程中,未加抗冻剂的兔主动脉的最大表观比热容大于加抗冻剂的相应值;冻结状态相同温度下未加抗冻剂的兔主动脉的比热容小于的加抗冻剂的兔主动脉的比热容;溶解后的未加抗冻剂和加抗冻剂的兔主动脉的比热容随着温度的升高而减小。并将测量结果与其它方法获得的比热容数值进行了比较,发现实际测量的比热容值与估算之间还是有区别的。  相似文献   

4.
兔主动脉冻结过程中未冻水份额的研究   总被引:4,自引:0,他引:4  
利用差示扫描量热仪(DSC)技术中的分步扫描(Stepwise scanning)法,研究了不同浓度的低温保护剂对主动脉血管冻结过程中未冻水份额的影响。研究结果表明:分步扫描量热技术可以用于血管材料冻结过程中未冻水份额的定量研究,而且具有较高楠度;随着低温保护剂二甲亚砜(DMSO)浓度的增大,血管的初始冻结点温度呈线性降低,但其冻结过程的未冻水份额显著增大,这是由于高浓度DMSO具有很强水合能力所致。  相似文献   

5.
本文实验研究了低温受迫对流条件下空气参数对水平冷表面上液滴冻结的影响。冷表面温度分别为-15.5℃和-19.5℃,空气温度变化范围为-6~8.5℃,相对湿度变化范围为50%~80%,空气流速变化范围为1.0~9.0 m/s。结果表明,冷表面上液滴冻结的时间随冷面温度的升高而增加,随空气相对湿度的升高而减小。另外,空气温度和流速对冷表面液滴冻结也有较大的影响,随着空气温度和流速的增加,液滴冻结时间先减小后增大。  相似文献   

6.
在以前工作的基础上,利用在频率平面上进行空间滤波的方法,研究了α-LiIO_3单晶在静电场作用下,空间电荷分布引起的衍射光强变化的弛豫行为。得出了弛豫过程的唯象表达式,发现其中的弛豫参数依赖于温度和电压的大小以及所加电压为同号或异号电压,且随样品的不同而变化。在低温下,衍射会被“冻结”:即在“冻结”温度(~—25℃)以下加电压,衍射增强不显著;在“冻结”温度以上加电压,然后降至“冻结”温度以下,衍射光强度仍保持高温时增强后的数值;撤去电压,因加电压所增加的衍射并不消失。  相似文献   

7.
血管低温保存是满足临床移植的重要保证手段。从影响动脉血管低温保存的因素,低温保存后的活性恢复、细胞水平上的血管低温损伤机理、冻结/复温过程中的热物理性质和力学性质变化,以及低温断裂现象等方面综述了血管低温保存研究进展。  相似文献   

8.
在以前工作的基础上,利用在频率平面上进行空间滤波的方法,研究了α-LiIO3单晶在静电场作用下,空间电荷分布引起的衍射光强变化的弛豫行为。得出了弛豫过程的唯象表达式,发现其中的弛豫参数依赖于温度和电压的大小以及所加电压为同号或异号电压,且随样品的不同而变化。在低温下,衍射会被“冻结”:即在“冻结”温度(~-25℃)以下加电压,衍射增强不显著;在“冻结”温度以上加电压,然后降至“冻结”温度以下,衍射光强度仍保持高温时增强后的数值;撤去电压,因加电压所增加的衍射并不消失。 关键词:  相似文献   

9.
报道了掺Zn的重电子金属CeCu6-xZnx(x=0.05,0.1,0.15,0.2,0.3)样品的非常规制备方法以及低温电阻和低温比热容的测量结果,研究Zn含量对CeCu6-xZnx低温性质的影响及其物理原因.发现低温下Kondo散射项系数c随Zn含量的加大而减小,电阻极大值温度Tmax随Zn含量的加大而降低,CeCu6-xZnx的德拜温度ΘD随Zn含量的加大而略有上升 关键词: 重费密子系统 低温比热容 低温电阻 相干散射  相似文献   

10.
低温阀门冷态试验的稳态传热模拟与分析   总被引:1,自引:0,他引:1  
利用有限元分析软件ANSYS对为控制20 K温度的氦气而设计的低温阀门在正常运行和冷态试验状态下的温度场进行模拟与分析。针对冷态试验状态下拉杆处出现冻结的问题,提出在上阀体处添加绝热层的方案,通过进一步的模拟计算预测其改进的效果。  相似文献   

11.
Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.  相似文献   

12.
A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.  相似文献   

13.
The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.  相似文献   

14.
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.  相似文献   

15.
16.
A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.  相似文献   

17.
A transient suppression method for piezoelectric ceramic transducer is presented. By adding some special pedestal pulses to the original transmitted signal, the transient effects in the output of the transducer can be just precisely transmission by use of a narrowband transducer. canceled, thereby achieving the broadband The experimental results show that the transient responses of the sinusoid pulses and coded signals are suppressed successfully and the acoustic waveforms radiated into the surrounding water are improved significantly.  相似文献   

18.
We experimentally demonstrate amplitude squeezed soliton utilizing intensity-dependent self-phase modulation in an asymmetric Sagnac interferometer.The system.whose components are connected via ferrule connector/physical connection(FC/PC)fiber connectors,constitutes all-fiber configuration to generate squeezed soliton.Soliton amplitude reduction measured by homodyne detection is near 4.0 dB below the shot-noise level.Optimal squeezing fields in both simple and compact all-fiber configuration are obtained.  相似文献   

19.
The(2 1)-dimensional nonlinear Schr(o)dinger(NLS)equation with spatially inhomogeneous nonlinearities is investigated,which describes propagation of light in(2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities.New types of optical modes and nonlinear effects in optical media are presented numerically.The results reveal that the regular split of beam can be obtained in (2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities,by adjusting the guiding parameter.Furthermore,the stability of beam regular split is discussed numerically,and the results reveal that the beam regular split is stable to the finite initial perturbations.  相似文献   

20.
In the real-world application of face recognition system, owing to the difficulties of collecting samples or storage space of systems, only one sample image per person is stored in the system, which is so-called one sample per person problem. Moreover, pose and illumination have impact on recognition performance. We propose a novel pose and illumination robust algorithm for face recognition with a single training image per person to solve the above limitations. Experimental results show that the proposed algorithm is an efficient and practical approach for face recognition.  相似文献   

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