内外共振联合作用下索-梁组合结构非线性振动分析

研究内共振和外共振联合作用下的索-梁组合结构非线性振动问题。利用Hamilton原理推导索-梁组合结构非线性动力学方程,同时考虑索的垂度以及由梁和索之间模态耦合引起的非线性影响。利用Galerkin方法将索-梁组合结构非线性运动偏微分方程离散为一组常微分方程。最后对数学模型进行数值计算,得到了不同内外共振联合作用下梁和索的模态时程曲线。研究表明,梁的稳态运动呈现周期性振荡,而索在不同的内外共振联合作用下,分别呈现出混沌或周期性振荡,并且索和梁之间持续的模态交替现象只能在特定的内外共振下出现。

门式框架结构出平面外参数共振试验研究

本文对一个门式框架结构出平面外参数共振(动力失稳)问题进行了试验研究,采用振动台激发了门式框架结构的出平面外参数共振,观测和分析了门式框架结构出平面外参数共振的现象和机理,测量并探究了结构参数共振的稳定边界,研究了参数共振下激励频率与稳态响应幅值的变化关系。结果表明,当外部周期激励的频率大约是结构出平面外自振频率的两倍时,门式框架结构发生出平面外参数共振;在不稳定区域内,当固定激励幅值时,非线性稳态响应的幅值随激励频率的增大近似地呈线性减小。This paper reports an experimental study on the out-of-plane parametric resonance (dynamic instability) of a portal frame structure. A vibration table is used to induce the out-of-plane parametric resonance of the portal frame, and the phenomenon and mechanism of this resonance are observed and analyzed. The stable boundary of the structural parametric resonance is measured and investigated. The relationship between the excitation frequency and the steady-state response amplitude under parametric resonance is investigated. The results show that out-of-plane parametric resonance occurs in the portal frame structure when the frequency of the external periodic excitation is approximately twice the natural frequency of the structure’s out-of-plane vibration. Within the unstable region, when the excitation amplitude is fixed, the amplitude of the nonlinear steady- state response decreases approximately linearly with the increase of the excitation frequency.

外腔共振和频系统中阻抗匹配的理论研究

外腔共振是提高和频效率的有效方法.实现外腔共振高效和频需要基频光高效地耦合到外部谐振腔中,因此系统要达到阻抗匹配.本文分别建立了双波长和单波长外腔共振和频系统的理论模型,分析了腔增强因子与耦合腔镜反射率、入射基频光功率等参数的依赖关系,通过数值模拟获得最优化的共振光耦合腔镜反射率,使系统达到阻抗匹配,提高和频效率.研究表明,无论双波长还是单波长外腔共振和频系统,共振基频光的最佳耦合腔镜反射率只会随着另一束共振或者不共振的基频光入射功率的增加而减小,而其本身的入射功率变化则影响较小;进一步分析表明,若共振基频光的耦合腔镜反射率超过阻抗匹配值,和频光功率将会迅速减小,而小于阻抗匹配值时,和频光功率减少速度相对较慢,因此实验过程中要尽量避免过耦合的情况出现.本文的理论分析过程将对外腔和频实验有一定的指导意义.

索-梁耦合结构非线性分析

研究内、外共振联合激励下索-梁耦合结构的非线性行为,用多尺度法探讨索-梁耦合结构内共振模式。分析表明,耦合结构存在多种内共振形式;考虑梁与索在1∶2内共振作用下分别研究索-梁耦合结构在梁主共振且索自参数共振时与梁亚谐波共振且索主参数共振时的非线性特性,并具体讨论索-梁耦合结构的垂跨比、质量比、刚度比及外激励幅值等参数对索-梁耦合结构中梁、索的非线性特性影响。研究表明,由于模态耦合影响,索-梁耦合结构存在两种外共振机制,梁表现出非线性特性,索表现出两自由度特性;刚度比参数对耦合结构非线性特性有显著影响。

参数振动系统频响特性研究

采用矩阵谱分解中常用的Sylvester理论和Fourier级数展开法,推导了单自由度参数振动系统的频响函数,并得到了系统外激励共振条件。在此基础上,以直齿轮副参数振动系统为例仿真了系统的频响特性,并讨论了系统参数稳定性、时变参数以及阻尼的影响。结果表明,参数振动系统的频响特性主要有以下一些特点:(1)系统具有多个频响函数,分别对应于多频响应中的各个频率成分;(2)系统存在多个外激励共振区。除了外激励频率等于系统固有频率的共振区外,当激励频率等于系统固有频率与参数激励频率的组合值时,同样存在共振现象;(3)参数振动系统共振响应时,主导频率成分为系统固有频率;(4)阻尼使得频响函数峰值有明显下降,而对非共振区的频响曲线影响不大。

基于单波长外腔共振和频技术产生波长可调谐589nm激光及钠原子饱和荧光谱的测量

本文基于新型单波长外腔共振和频技术实现了转换效率高、波长可调谐589nm激光的输出,其中基频光波长分别为1583nm和938nm,和频晶体为周期极化铌酸锂.在1583nm激光频率被锁定到外部环形腔腔模后,通过对938nm激光的频率扫描实现了输出功率4.96mW,调谐范围7GHz的589nm激光输出,并采用声光调制器的伺服反馈技术有效提高了输出功率的稳定性.最后采用该光源对钠原子在348—413K(75—140C)时D2线的饱和荧光谱进行了测量.观察到了多普勒背景下钠D2a,D2b以及Crossover的亚多普勒结构,其均可为589nm频率的锁定提供参考信号.

参数振动系统响应的频谱成分及其分布规律

采用Sylvester理论和Fourier级数展开方法分别研究了参数振动系统自由响应和强迫响应的频谱特性(频谱成分及其分布规律),讨论了系统稳定性和阻尼对于频谱幅值的影响,并给出了系统外激励共振条件.理论研究结果表明:由于参数激励作用使得系统响应具有多频特点,这些频谱成分与系统固有频率、参数激励频率和外激励频率具有密切联系,而且其在频域分布也呈现出一定的规律.此外,参数振动系统具有多个外激励共振点,除了外激励频率等于系统固有频率将发生共振外,当外激励频率等于系统固有频率和参数激励频率的组合值时,同样将发生外激励共振现象.

双波长外腔共振和频中Boyd-Kleinman因子优化的理论研究

双波长外腔共振是提高和频转换效率的有效手段,然而基于Boyd-Kleinman(BK)理论,和频效率除了受基频光功率密度影响外,主要受BK因子限制。本文通过分析BK因子随腔结构参数的变化关系,给出基于外腔频率转换过程中BK因子优化的一般方案,从而为搭建相关实验提供必要的理论基础。

NORMAL APPEARANCE OF LARGE FIELD DIFFUSION WEIGHTED IMAGING ON 3.0T MRI

Objective To evaluate the normal appearance of large field diffusion weighted imaging (DWI) on 3.0T magnetic resonance imaging (MRI). Methods Twenty healthy volunteers and thirty patients with benign prostate hyperplasia were included in this study. All patients were examined with large field DWI on 3.0T MRI. Normal tissue appearance was analyzed and apparent diffusion coefficient (ADC) of normal tissue with high signal intensity was measured. The ADC values of bilateral symmetrical tissue were also compared. The ADC values of intervertebral disks of healthy people younger than 50 years and exceeding 50 years were compared. Results Salivary gland, spleen, kidney, gallbladder, bladder, prostate, seminal vesicle, testis, intervertebral disk, liquid in articular cavity and lymph node showed high signal intensity on large field DWI, while lung, liver and bone showed hypo-signal intensity. The mean ADC values of partial hyperintensity tissue were as followed: parotid gland (1.088 ± 0.114) ×10-3 mm2/s, submaxillary gland (1.309 ± 0.189) ×10-3 mm2/s, kidney (1.909 ± 0.143) ×10-3 mm2/s, seminal vesicle (1.669 ± 0.168) ×10-3 mm2/s, testis (1.028 ± 0.075) ×10-3 mm2/s, spleen (0.963 ± 0.108) ×10-3 mm2/s, bladder (2.898 ± 0.267) ×10-3 mm2/s, prostate (1.448 ± 0.132) ×10-3 mm2/s, intervertebral disks (1.360 ± 0.140) ×10-3 mm2/s. No statistical significance was found between the ADC values of bilateral symmetrical tissues. The difference of ADC values of intervertebral disks of healthy people younger than 50 years [(1.372 ± 0.142) ×10-3 mm2/s] and exceeding 50 years [(1.344 ± 0.134) ×10-3 mm2/s] showed statistical significance (P = 0.040). Conclusion Understanding the high signal intensity of normal tissue on large field DWI may help to differentiate the normal tissues and abnormal ones.

MRI of gastric carcinoma:Results of T and N-staging in an in vitro study

AIM： To determine the accuracy of 1.5-T magnetic resonance imaging （MRI） in the evaluation of gastric wall invasion and perigastric lymph node metastasis in gastric adenocarcinoma.METHODS： Twenty resected gastric specimens containing 20 tumors were studied with a 1.5-T MR system using a commercial head surface coil. MR scanning was performed with a T1 weighted image （TR/TE = 500/20）, and a T2 weighted image （TR/TE = 2500/90）. MR findings were compared with pathologic findings.RESULTS： A T1-weighted image demonstrated three layers in the normal gastric wall. All of the gastric tumors were well demonstrated by lesions and location. In a MRI findings of gastric wall invasion, there was 1 case of T1, 7 of T2, 11 of T3. Pathologic results of resected specimens included 3 cases of pT1, 4 of pT2, and 12 of pT3. The accuracy of T staging with MRI was 74% （14 of 19）. MRI findings of lymph node metastasis included 6 cases of NO, 13 cases of N1. The accuracy of the N staging with MRI was 47% （9 of 19）.CONCLUSION： MRI has a high diagnostic accuracy in the evaluation of the T staging of gastric cancerin vitro and thus potentially enables preoperative histopathologic staging.

New Progress in the Application of Satellite Thermal Infrared Imagery to Earthquake Prediction

The concept of stochastic resonance (SR) has been introduced into the analysis of satellite thermal infrared images. Six kinds of anomalous phenomena related to crustal movement were recognized in satellite thermal infrared images. Six diagnostic indicators for the prediction of global earthquakes with magnitude ≥6.0 and their quantitative evaluation standards have been established. The microscopic behavior of global crustal movement is successfully controlled by using satellite thermal infrared imagery, and the occurrence time and magnitude of over 80% of global strong earthquakes occurred since the foundation of the observation station have been successfully predicted. It is believed that the combination of satellite thermal infrared information with macroscopic anomalous phenomena will play an important role in earthquake hazard reduction.

Experimental and Density Functional Theory Calculation Studies on Raman and Infrared Spectra of 1,1＇-Binaphthyl-2,2＇-diamine

The IR absorption, visible excited normal Raman, and UV-excited near-resonant Raman （UVRR） spectra of 1,1＇-binaphthyl-2,2＇-diamine （BINAM） were measured and analyzed. Density functional theory calculations were carried out to investigate its vibrational frequencies, infrared absorption, normal Raman, and near-resonance Raman intensities. The observed Raman and IR bands of BINAM were assigned with respect to the local vibrations of substituted 2-naphthylamine. Several Raman bands of BINAM were found selectively enhanced in the UVRR in comparison with the normal Raman spectrum. Possible excited state geometry distortion was discussed based on the resonance Raman intensity analysis.

IR, 1H NMR, Electronic Properties and Conductivity Studies of N1 ,N4-Bis（Diphme）Benzene-l,4-Diamine Chloride Zirconium （IV） [{（Ar）2NC6H5N（Ar）2}ZrCl4] （Ar = C6H5）

A range of new compounds such as N1,N4-bis（diphenylmethlene）benzene-l,4-diamine zirconium （IV） chloride [{（Ar）2NC6HsN（Ar）z}ZrCl4] （Ar = C6H5） complex counting the chelating amine and chloride in position trans have been prepared. Well-defined NI,N4-bis（diphenylmethlene）benzene-l,4-diamine zirconium （IV） chloride [{（Ar）2NC6H5N（Ar）2}ZrCl4] （Ar = C6H5） was obtained by stoichiometric addition of {（Ar）2NC6H5N（Ar）2} （Ar = C6H5） and {ZrC14} in ethanol at reflex temperature. IR, 1H NMR, electronic properties using hyperchem program study has been improved for this compound such as bond distance, and this compound was also defined as electric conductivity which proves to be useful for conductively compound.

Synthesis and Characterization of Oxy-Vanadium （Ⅳ） Complex of 4-（2, 4-dihydroxybenzaldimine） Antipyrine

The reaction of VCl3 with 4-（2, 4-dihydroxybenzaldimine） antipyrine （LH） in a l ： 1 molar ratio results in formation of the general complex of [VOL（CI）OH]. The nature of bonding and stereochemistry of the complex was deduced from the elemental analysis, IR, UV-Vis, 1H and ^13C NMR spectroscopy. This complex has a coordination number five （square pyramidal） as known for many vanadyl complexes. The formation of the vanadyl ion （VO^2＋） and the mode of bonding of the Schiff base through the oxygen of the pyrazol ring and the nitrogen of the azomethine group to the vanadyl ion were established by IR technique.

Identification of Superoxide O2^- during KNO3-NaNO2-NaNO3 Salt by Electron UV-Vis Absorption Spectroscopy Thermal Decomposition of Molten Paramagnetic Resonance and

On account of excellent thermal physical properties, molten nitrates/nitrites salt has been widely employed in heat transfer and thermal storage industry, especially in concentrated solar power system. The thermal stability study of molten nitrate/nitrite salt is of great importance for this system, and the decomposition mechanism is the most complicated part of it. The oxide species O2^2- and O2^- were considered as intermediates in molten KNO3-NaNO3 while hard to been detected in high temperature molten salt due to their trace concentration and low stability. In this work, the homemade in situ high temperature UV- Vis instrument and a commercial electron paramagnetic resonance were utilized to supply evidence for the formation of superoxide during a slow decomposition process of heat transfer salt （HTS, 53 wt% KNO3/40 wt% NaNO2/7 wt% NaNO3）. It is found that the superoxide is more easily generated from molten NaNO2 compared to NaNO3, and it has an absorption band at 420-440 nm in HTS which red shifts as temperature increases. The band is assigned to charge-transfer transition in NaO2 or KO2, responsible for the yellow color of the molten nitrate/nitrite salt. Furthermore, the UV absorption bands of molten NaNO2 and NANO3 are also obtained and compared with that of HTS.

Synthesis and Structure of Chromium Complexes with New Tetradentate Schiff Base N202-Type Ligand

In this research two chromium（II][） and （VI） complexes of tetradentate Schiff bases have been prepared by condensing of salicylaldehyde with 4-methyl 1,2-phenylenediamine. Schiff base complexes of chromium（Ill） have been employed to design and synthesize polynuclear complexes. So they have played an important role in molecular magnetism. Synthesized complexes were characterized by elemental analysis, IR, molar conductivity and NMR. The free ligands were alsc characterized by 1H, 13C NMR spectra. The 13C NMR and IR spectra of free ligand and the complexes are compared and discussed.

Curing Mechanism of Condensed Polynuclear Aromatic Resin and Thermal Stability of Cured Resin

In order to improve the thermal stability of condensed polynuclear aromatic(COPNA) resin synthesized from vacuum residue, 1,4-benzenedimethanol was added to cure COPNA resin. The curing mechanism was investigated by proton nuclear magnetic resonance spectrometry, solid carbon-13 nuclear magnetic resonance spectrometry and Fourier transform infrared spectroscopy. Microstructures of the uncured and the cured COPNA resins were studied by scanning electron microscopy and X-ray diffractometry. The thermal stability of COPNA resins before and after curing was tested by thermogravimetric analysis. The element composition of the cured COPNA resin heated at different temperatures was analyzed by an element analyzer. The results showed that the uncured COPNA resin reacted with the cross-linking agent during the curing process, and the curing mechanism was confirmed to be the electrophilic substitution reaction. Compared with the uncured COPNA resin, the cured COPNA resin had a smooth surface, well-ordered and streamlined sheet structure with more crystalline solids, better molecular arrangement and orientation. The weight loss process of the uncured and cured COPNA resins was divided into three stages. Carbon residue of the cured COPNA resin was 41.65% at 600 ℃, which was much higher than 25.02% of the uncured COPNA resin, which indicated that the cured COPNA resin had higher thermal stability.

Some New Derivatives of 3H-benzo[b]Furo[3,2-f]- Benzimidazole with Expected Biological Activity

On the base of benzimidazole and benzofuran containing heterocyclic system, several derivatives with expected biological activity were synthesized. 2,3-diaminodibenzofuran was the primary substance. Adding various cyclic agents, 2-phenil was got, 2-（o-chlorophenil）, 2-（o-oxyphenil）, 2-chlorometyl- and 2-hydroximethyl-3H-benzo[b[furo（3,2-f] benzimidazoles. The aforementioned substances were characterized by IR and NMR spectroscopy.

Resonant Continuum in Extended RMF Plus BCS Approximation

The contribution of the resonant continuum to pairing correlations is investigated in the relativistic mean field theory plus Bardeen–Cooper–Schrieffer (BCS) approximation with a constant pairing strength. The resonance states with their widths in the continuum are considered explicitly. The numerical study is performed in an effective Lagrangian with the parameter set NLSH for neutron-rich nucleus 84Ni. The results show that the effect of the proper treatment of the resonant continuum on pairing correlations for nucleus close to neutron drip line is important. It is found that the problem of an unphysical particle gas could be overcome when the pairing correlation is performed by using the resonant states instead of the discretized states in the continuum.

基于KTP键合晶体的Hansch-Couillaud双波长外腔频率锁定机理

基于KTP键合晶体采用Hansch-Couillaud频率锁定技术实现了双波长外腔同时共振,理论和实验上分别研究了基于键合KTP晶体的HC频率锁定方案.研究表明,与采用单KTP晶体的结果相比,采用键合KTP晶体进行HC锁频时,能将激光频率分别锁定到e1光或e2光的共振峰值.实验中将环形腔腔模频率锁定到938nm激光器的输出频率上,1583nm激光器的输出频率锁定到环形腔腔模频率上,从而实现了三者之间的相位关联锁定.