Outcome of hip and knee arthroplasty in persons aged 80 years and older

Recent studies have established the cost effectiveness and safety of total joint arthroplasties. As the population ages, it is important to determine whether these procedures are equally beneficial in the elderly. The short term safety and efficacy of total hip and knee arthroplasties in subjects 80 years of age and older was evaluated. Between 1988 and 1993, preoperative and postoperative physical and functional information was collected on 99 consecutive elective hip and knee arthroplasties in subjects 80 years of age or older. These data were compared with those derived from a younger otherwise matched control group. Data collected included subject demographics and characteristics, information concerning the acute and postacute hospital stay, comorbid conditions, postoperative complications, discharge disposition, Hospital for Special Surgery knee and Harris hip scores, pain scores, and functional capacity. The average age of the subjects was 83 years; osteoarthritis was the most common diagnosis; and the average followup was 25 months. Complication rates and length of stay in acute care facilities were not significantly different than for the control group. Mean preoperative Hospital for Special Surgery knee and Harris hip scores were 58 and 60, respectively, with postoperative scores of 77 and 88, respectively. Pain dramatically improved with 98% of total knee arthroplasty and 100% of total hip arthroplasty subjects reporting mild or no pain at followup. Preoperatively, none of the knee or hip subjects could walk unlimited distances. Postoperatively 51% of the total knee arthroplasty and 54% of the total hip arthroplasty subjects could walk more than five blocks; 71% of the total knee arthroplasty and 86% of the total hip arthroplasty subjects walked with a cane or no assistive device. The most dramatic postoperative functional gains were seen in the most disabled subjects. Total charges of care for patients 80 years of age and older was slightly greater than for a younger group. It was established that total joint arthroplasty can be performed safely in patients 80 years of age and older, promising excellent pain relief and improved functional outcome.     

BP神经网络在射流冲击压力预测中的应用

紊流射流冲击压力的影响因素很多,且存在着复杂的非线性关系,因此难以用传统的数学方法建立冲击压力的理论模型。基于BP神经网络理论,结合射流冲击压力的实验结果,建立了冲击压力的神经网络预测模型。经验证,对于给定的泵压、围压、喷距和径向距离等输入量,该模型能够准确地预测水射流的冲击压力。     

Microwave-absorbing properties of silver nanoparticle/carbon nanotube hybrid nanocomposites

Silver (Ag) nanoparticles fabricated by chemical reduction process were grafted onto the surface of carbon nanotubes (CNTs) to prepare hybrid nanocomposites. The Ag/CNT hybrid nanomaterials were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The Ag/CNT hybrid nanomaterials were then loaded in paraffin wax, and pressed into toroidal shape with thickness of 1 mm to evaluate their complex permittivity and complex permeability by scattering parameters measurement method in reflection mode using vector network analyzer. The reflection loss of the samples was calculated according to the transmission line theory using their measured complex permittivity and permeability. The minimum reflection loss of the Ag/CNT hybrid nanocomposite sample with a thickness of 1 mm reached 21.9 dB (over 99 % absorption) at 12.9 GHz, and also exhibited a wide response bandwidth where the frequency bandwidth of the reflection loss of less than ?10 dB (over 90 % absorption) was from 11.7 to 14.0 GHz. The Ag/CNT hybrid nanocomposite with thickness of 6 mm showed a minimum reflection loss of ~?32.1 dB (over 99.9 % absorption) at 3.0 GHz and was the best absorber when compared with the other samples of different thickness. The reflection loss shifted to lower frequency as the thickness of the samples increased. The capability to modulate the absorption band of these samples to suit various applications in different frequency bands simply by manipulating their thickness indicates that these hybrid nanocomposites could be a promising microwave absorber.     

自激振荡脉冲射流喷嘴雾化特性试验研究

试验采用了SD150测试系统和数码摄像技术,对自激振荡脉冲射流和连续射流的时域和频域特性进行了分析。研究了雾化锥角、雾化距离及雾化粒度与泵压的变化规律。试验结果表明,泵压升高,雾化锥角和雾化距离增大,雾化粒度减少。与连续射流相比,脉冲射流的雾化质量更高。     

High-power, multioutput piezoelectric transformers operating at the thickness-shear vibration mode

In this study, a piezoelectric transformer operating at the thickness shear vibration mode and with dual or triple outputs is proposed. It consists of a lead zirconate titanate (PZT) ceramic plate with a high mechanical quality factor Qm and a size of 120 x 20 x 4 mm3. The PZT ceramic plate is poled along the width direction. The electrodes of input and output parts are on the top and bottom surfaces of the ceramic plate and separated by narrow gaps. A new construction of support and lead wire connection is used for the transformer. At a temperature rise less than 20 degrees C and efficiency of 90%, the piezoelectric transformer with dual outputs has a maximum total output power of 169.8 W, with a power of 129.5 W in one output and 40.3 W in another. The one with triple outputs has a maximum total output power of 163.1 W, with a power of 36.9 W in the first output, 13.0 W in the second output and 113.2 W in the third output. The maximum efficiency of the piezoelectric transformer with dual outputs and triple outputs is 98% and 95.7%, respectively. The voltage gains of the transformers are less than one, and different outputs have different gains. Also, there is a driving frequency range in which the load resistance of one output has little effect on the voltage gain of another output.     

The -method and Fredholm integral equations

Instead of using approximate methods on the equation

$\text{f(x) = g(x) + λ}\text{∫}\text{0}\text{1}\text{K(x,t)f(t) dt}$

, the τ-method is employed to obtain the exact solution of the equation

$\text{h(x) = g(x) + λ}\text{∫}\text{0}\text{1}\text{K(x,t)h(t) dt + R(x,λ)}$

,The analytical from of R(x, λ) determines the type of approximation which results. In this paper R(x, λ) is chosen to be a function which is rational in the parameter λ in which case, the approximation to the true solution has the same character. An example is given.     

液体燃料射流最不稳定频率的理论分析（1）——液体燃料射流的最不？…

利用线性不稳定性理论,对粘性液体燃料射流射入气体介质的射流模型所对应的色散方程进行了数值求解。利用计算结果,分析了液体燃料射流不稳定性研究中的３个最重要的无量纲参数参韦韦伯数Ｗｅ、雷诺数Ｒｅ及密度比Ｑ,对分别处于瑞利模式和泰勒模式下的液体射流的最不稳定频率及对应的最大扰动增长率的影响。     

浅谈手机设计中的时尚化

设计一直是流行与经典的共同载体。人们在崇拜设计经典的同时,设计在手机等数码领域中的时尚化演绎更是让人为之折服。当今社会,手机不仅代表着移动电话,更逐渐成为一个多元化发展的通讯工具,并和普通人生活息息相关。在其发展过程中,时尚逐渐在手机设计中占据了重要地位,这也是科技人性化的必然结果。