血管回声跟踪技术评价糖尿病患者颈动脉弹性与下肢动脉粥样硬化的相关性

目的：利用血管回声跟踪技术（ET）研究糖尿病（DM）患者颈动脉弹性与下肢动脉粥样硬化病变的相关性。方法：选择116例糖尿病患者分别进行颈动脉弹性检查和下肢血管彩超检查,根据血管彩超检查结果分为无下肢动脉粥样硬化病变组（对照组A）和下肢动脉粥样硬化病变组,下肢动脉粥样硬化病变组又根据下肢动脉血管的狭窄程度由轻至重依次分为B、C、D、E四组。分析比较各组间应用髓检查获得的颈动脉弹性参数,即压力应变弹性系数（Ep）、僵硬度（β）、顺应性（AC）、增大指数（AI）、脉冲波传导速度（PWVβ）。结果：下肢动脉粥样硬化病变组Ep取PWvp值较对照组明显增高,Ac值较对照组明显降低,差异有统计学意义（P〈0．01或P〈0．05）,随着各组间下肢动脉病变程度的不断加重,Ep取Pw邯值增加明显,差异有统计学意义（P〈0．01或P〈0．05）,参数AI在各组间差异无统计学意义（P〉0．05）。结论：血管回声跟踪技术能揭示糖尿病患者颈动脉弹性参数与下肢动脉粥样硬化病变程度的相关性,是评价糖尿病下肢动脉粥样硬化病变的有效方法。     

光子回声量子存储器中非均匀展宽频谱对存储效率的影响

本文提出了一个利用光子回声技术探究非均匀展宽频谱线形(如高斯、洛伦兹分布)对存储效率影响的简捷方法。我们发现当信号光脉冲的持续时间与介质频谱线宽的乘积远大于1时,可将分布函数的傅里叶变换近似成狄拉克函数,使得研究非均匀展宽频谱对存储效率的影响变得非常容易;通过计算发现不同线形分布达到最佳存储效率的光学深度有所不同,频谱线形趋于均匀时达到最优存储效率的存储介质光学深度最小。该研究对实验上实现最优化光量子态存储具有指导意义。     

Linear absorbing boundary conditions for surface water wave propagation

Summary The meaning of linear absorbing boundary conditions for periodic water waves in elliptical approaches is discussed. It is found that the direction of propagation of the waves must be known for reliable boundary conditions and that the energy dissipation of waves running parallel to a boundary in general cannot be modelled in the framework of a linear theory. Work presented at the Euromech Colloquium 240 on ?Dispersive waves in dissipative fluids?, Bologna, August 30–September 2, 1988.     

模数模保密机改进的回波抵消技术

自适应回波抵消技术是模数模保密机走向实用的关键。详细介绍了如何用TMS320C50实现自适应回波抵消技术。由于使用了本方无话检测和双向通话检测,回波抵消的收敛速度和精度达到了满意的效果。     

Thermal expansion of a rig

Summary We have estimated and measured the daily thermal expansion of an oceanographic platform. This has been found negligible as far as the calibration of a satellite altimeter is concerned.     

卫星通信中的回波抑制与回波抵消

本文叙述了卫星通信中回波的产生及其抑制的原理，分析了ＪＵＥ－４５Ａ Ｍ Ⅱ ＩＮＭＡＲＳＡＴ－Ａ船站中回波抑制器电路，阐述了一种用横向滤波器实现的回波抵消的原理。     

Cost-Effective Joint Echo-NEXT Canceller Designs for 10GBase-T Ethernet Systems Based on a Shortened Impulse Response Filter (SIRF) Scheme

Echo canceller plays an important role in the full-duplex communication system. Conventional implementations of echo cancellers are often the adaptive transversal filter architectures due to the simplicity and robustness of stability and convergence. However, the conventional echo cancellers suffer from high cost problem especially when the response time of the echo is long. In this paper, a new cost-efficient architecture of echo cancellers, targeting on 10GBase-T Ethernet System, is presented. The proposed scheme inherits the concept of channel shortening which is widely employed in DSL systems. A shortened impulse response filter is implemented at the receiver to shorten the impulse response of the echo signal. Hence, the overall cost of echo cancellers can be reduced. We generalize the channel shortening architecture to a joint multi-channel shortening scheme. The joint multi-channel shortening architecture can be applied to multiple-input multiple-output wireline communication systems to further reduce both the cost of echo and near-end crosstalk (NEXT) cancellers. We apply the proposed scheme to 10GBase-T Ethernet system. The simulation results show that the proposed echo and NEXT cancellers can save up to 35% hardware cost compared to the conventional transversal implementations.

Analysis of prediction performance in wavelet minimum complexity echo state network

Echo state network （ESN） has become one of the most popular recurrent neural networks （RNN） for its good prediction performance of non-linear time series and simple training process. But several problems still prevent ESN from becoming a widely used tool. The most prominent problem is its high complexity with lots of random parameters. Aiming at this problem, a minimum complexity ESN model （MCESN） was proposed. In this paper, we proposed a new wavelet minimum complexity ESN model （WMCESN） to improve the prediction accuracy and increase the practical applicability. Our new model inherits the characters of minimum complexity ESN model using the fixed parameters and simple circle topology. We injected wavelet neurons to replace the original neurons in internal reservoir and designed a wavelet parameter matrix to reduce the computing time. By using different datasets, our new model performed better than the minimum complexity ESN model with normal neurons, but only utilized tiny time cost. We also used our own packets of transmission control protocol （TCP） and user datagram protocol （UDP） dataset to prove that our model can deal with the data packet bit prediction problem well.     

Transient Nutation EPR Spectroscopy of Condensed Media (Review)

The application of transient nutations in EPR spectroscopy of condensed media is considered. The main methods of formation and observation of transient nutations are presented. The laws governing this phenomenon in twolevel and multilevel spin systems and also in inhomogeneous broadening of EPR lines are described. Recent advances in the use of transient nutations to separate overlapping spectra, identify quantum numbers and quantum transitions, investigate the kinetics of photoinduced paramagnetic centers, and determine relaxation times for a wide range of crystalline and disordered media are presented.     

Feasibility of post-gadolinium three-dimensional gradient-echo sequence to evaluate the pulmonary arterial vasculature

Purpose

To determine the feasibility of post-gadolinium three-dimensional gradient-echo (3D-GE) sequence for the evaluation of the pulmonary arterial vasculature in patients with suspected pulmonary embolism (PE) and in patients with a variety of other disease processes.

Materials and Methods

Twenty-six consecutive patients (18 females, 8 males; mean age±S.D., 46.6±21.1 years) who underwent chest magnetic resonance imaging (MRI) including post-gadolinium 3D-GE sequence for the evaluation of PE (Group A, n=13) and a variety of other disease processes (Group B, n=13) were included in the study. Post-gadolinium 3D-GE MR sequences were retrospectively, independently and blindly evaluated by two reviewers for the image quality of pulmonary arterial vasculature, and findings of PE and other disease processes. Clinical and imaging follow-up data for all patients were obtained. Interobserver agreement was calculated by kappa statistics.

Results

All central and lobar pulmonary arteries, 71.4–89.6% of segmental arteries and 46.7–52.7% of subsegmental arterial units in both groups were visualized with sufficient diagnostic image quality on post-gadolinium 3D-GE sequences. PE involving lobar and segmental arteries was diagnosed in two patients in each group. Other disease processes including pneumonia, lung nodules, superior vena cava stenosis, lung metastases, chronic lymphocytic leukemia and aortic aneurysm were detected in 10 of 26 patients. There was good to excellent interobserver agreement (0.73 to 1.00) for all findings.

Conclusion

Post-gadolinium 3D-GE sequence may be an alternative technique for the visualization of central, lobar and segmental arteries, and may diagnose PE and other pathologies involving the chest in different patient populations.