| 1. | Measurement of quartz crystal unit parameters - measurement of activity and frequency dips of quartz crystal units
石英晶体元件参数的测量.石英晶体元件的活性和频率下降的测量 |
| 2. | Measurement of quartz crystal unit parameters - part 7 : measurement of activity and frequency dips of quartz crystal units
石英晶体元件参数的测量.第7部分:石英晶体元件的放射性和频率下降测量 |
| 3. | A new method based on the frequency decrease rate for fast identification of site liquefaction from surface acceleration records was presented
摘要提出了一个以频率下降率为基本指标的依据强震记录快速识别场地液化的新方法。 |
| 4. | Testing results indicated that in the state of serviceability , the members ’ natural frequencies and dynamic - stiffness are descent because of damage . and the degree of damage can be detected by the descent degree of natural frequencies and dynamic - stiffness
试验结果表明,梁损伤后固有频率和刚度均有所下降,建议可对不同荷载下构件频率下降程度进行分析与总结,进而由固有频率下降程度来诊断结构的损伤程度。 |
| 5. | Spatial distribution and time scales of atmospheric diffusion over beijing area are revealed by means of a random walk simulation model and practical meteorological data with a specified emission source from the city . results show a southward transport pattern for wintertime while a northwest transport of pollutants in summer . the area is the least evidently influenced by the emission source in spring , while the largest in autumn . the time spent for instantly emitted material removing from the model domain varies from winter - spring to summer - autumn . the former was shorter one of less than 20 hours ; the latter was longer one of approximately 30 hours . distribution of occurrence probability for different removal times was not symmetry . reducing slowly at the end of longer removal time , probability exists for pollutants remaining in this area a long time
结果表明，冬季示踪物偏南夏季偏西北的输送明显春季扩散影响范围最小秋季最大。示踪物从200km200km模式区域输出的平均时间去除时间明显分为冬春季和夏秋季两组，前者较小，平均在20h以下，后者较大，平均约30h 。不同去除时间出现的频率分布是非对称的，在长去除时间一侧，出现频率下降缓慢，显示污染物有在该区域内长时间滞留的可能。 |
| 6. | Taking the natural frequency arid the ratio of frequency drop as input characteristic parameters , crack damage in the cylindrical supporting shell of a portal crane is diagnosed and its length and position are forecasted , applying finite element emulation and artificial neural network technologies
摘要应用有限元仿真技术和人工神经网络模型，以反映结构损伤程度的固有频率和损伤的频率下降率作为神经网络输入的特徵参数，对门座起重机筒形支柱上出现的裂纹损伤长度和位置进行了综合诊断和预测分析。 |
| 7. | Then the general plan of underwater vibrators is put forward . in chapter 3 , combining fluid - solid coupling theory and mechanical vibration theory , we get the coupling equation of moving parts and water . the dynamic characteristics of moving parts are studied with theory of finite element , and additional mass of moving parts is found in fluid - solid coupling field , which makes vibrator ' s natural frequency descend and amplitude - frequency curve downward shift
第三章运用流固耦合理论和机械振动学理论相结合的方法建立运动部件与水的耦合运动方程，利用有限元法对其的动态特性进行了研究，得到了在流固耦合场下运动部件存在的附加质量，该附加质量导致固有频率下降，单位推力下的加速度频响曲线整体下移。 |
| 8. | Our results suggested the accumulation of ft in muscle was not the only factor that affected " spectrum shift " during muscle fatigue . the decline of the firing rate of motor units , the synchronization of motor units and an inadequate cns drive may be the important mechanisms that attributed to the change of semg signal during isometric contractions
本研究认为肌肉疲劳过程中h ~ +浓度升高不是导致肌电功率谱曲线左移的唯一因素，运动单位放电频率下降、中枢驱动减弱和运动单位活动的有序性或同步化可能是肌肉活动时肌电信号变化的一种重要机制。 |
| 9. | Consider the fact that natural frequency can reflect the structure entity performance but cannot be sensitive to the structure local damage identification . in many cases , structure damage in deferent location can cause almost the same decrease in low frequency , so this method cannot ascertain the definite damage location
考虑到固有频率能够反映结构的整体性能，但对结构中局部微观损伤的识别不灵敏，在很多情况下，结构中不同位置的损伤引起的结构低阶频率下降几乎相同，因此用频率参数很难准确确定结构损伤位置。 |
