基于半导体光放大器交叉增益调制的波长转换的理论分析

本文利用小信号理论模型分析了基于半导体光放大器交叉增益调制的波长转换 ,获得了波长转换效率的解析表达式。结果表明 ,波长转换的频带响应宽度受到光放大器驱动电流、波导中的光功率以及转换波长的影响。     

矿产资源价值与价格

本文比较了国内外有关矿产资源价值的六种不同的观点,主张按马克思劳动价值论的原理,矿产资源本身不是劳动的产物,自身没有价值,但它有价格,它是由矿产原稀缺性、资源所有权的垄断和使用矿产品的边际效用决定的,本文还讨论了资源的价格构成。     

SrWO4晶体的紫外受激拉曼散射

使用提拉法生长了高光学质量的SrWO₄晶体,尺寸为22mm×40mm,重72.3g.测量了SrWO₄ 晶体的透过光谱,其短波截止边为263nm,长波截止边大于3200nm,因此可在较宽波长范围内实现拉曼频移.采用无腔的单次通过方式,在SrWO₄晶体中实现了紫外光激发的受激拉曼散射.当抽运光为355nm皮秒激光脉冲时获得了3级斯托克斯谱线（366.44、379.25、392.98nm）,其中一级斯托克斯线的抽运阈值仅为169.76MW/cm²,相应的拉曼增益高达49.09cm/GW.实验表明,SrWO₄具有透光波段宽、抗光损伤能力强、拉曼阈值低、增益系数大等优点,在紫外激光的拉曼变频方面表现出良好应用前景.     

纸张性能对印刷品网点扩大和呈色范围的影响

测试了胶版纸和铜版纸的白度、平滑度、光泽度和吸收性等参数,及其打印样条不同区域的网点百分比和各实地色块的三刺激值,通过计算出它们的网点增大值和x,y色度坐标,绘制了不同印样的网点扩大曲线和色域图.研究结果表明,当印刷条件相同时,由于铜版纸具有较高的平滑度、光泽度、白度和较小的吸收性,其网点扩大值较小,色域范围较大,故印刷网点复制效果好;而胶版纸的平滑度、光泽度、白度等指标均低于铜版纸,吸收性较大,因此其网点扩大值较大,色域范围较铜版纸小.     

伪码调相与正弦调频复合引信抗噪声 调频干扰性能研究

研究伪码复合体制引信的抗干扰性能对这类体制引信的发展乃至应用都具有重要的理论指导意义.文章以信干比增益作为衡量标准来研究伪码调相与正弦调频复合引信抗噪声调频干扰性能.首先介绍了该复合引信的工作原理,详细推导了存在噪声调频干扰时复合引信接收机的总信干比增益,分析了n阶贝塞尔函数、多普勒频率、伪码序列周期、码元宽度、瞄准误差对其抗干扰性能的影响,分析结果为提高该引信的抗干扰性能提供了重要理论依据.     

《二值噪声作用下线性系统的随机共振》

研究了二值噪声用下的二阶过阻尼线性系统的随机共振现象。基于线性系统理论和相关删去法方法,得到了系统平均输出幅度增益的精确表达式。研究表明：输出幅度增益是噪声的强度和相关时间、系统阻尼系数,以及激励信号的频率的非单调函数;另外,适当的噪声参数和系统参数可以使噪声情况下的输出幅度增益大于无噪声时的输出幅度增益。     

Residual renal function and arterial stiffness mediated the blood pressure change during interdialytic weight gain in hemodialysis patients

Volume overload is thought to be the main cause of hypertension in dialysis patients. However, the effect of interdialytic weight gain (IDWG) in hemodialysis (HD) patients, which was considered as an increase in extracellular water (ECW), on blood pressure (BP) change, was controversial. Our aim was to examine the changes in hemodynamics and arterial stiffness during IDWG in HD patients and attempt to explore the possible mechanism of diverse BP change. Thirty prevalent patients on HD were enrolled. The height, weight, BP, blood chemistry, volume status assessed by bioelectrical impedance analysis, hemodynamic parameters obtained by echocardiography, and pulse wave velocity (PWV) were collected within 1 hour postdialysis and again just before the next dialysis session. Meanwhile, blood samples were drawn to analyze vasoactive hormones, including renin, angiotensin II, catecholamine, and endothelin. The patients' weights and ECWs during the next predialysis were significantly higher than those during the postdialysis. The BP showed no difference between postdialysis and the next predialysis. There was an obvious increase in cardiac output and decrease in total peripheral resistance as a whole during the next predialysis than that during postdialysis. When patients were divided into the BP increase group (BPI group, 13 patients) and BP decrease group (BPD group, 11 patients) according to the change in systolic BP higher than 10 mmHg, both groups displayed a significant increase in weight, ECW, cardiac output, and a decrease in total peripheral resistance. As compared with the BPI group, patients in the BPD group had significantly lower IDWG, shorter time on dialysis treatment, and higher residual renal function. A decrease in catecholamine and endothelin in the next predialysis was obvious in the BPD group. There was a significant decrease in PWV at the next predialysis in the BPD group while the PWV did not change significantly in the BPI group. Our results showed that the diverse BP change during IDWG was significantly affected by residual renal function, PWV, and vasoactive substances.     

造纸机的增益自适应神经元控制

针对多纸种造纸机定量控制系统的特点,综合运用神经元控制和自适应控制思想,提出了神经元增益自适应整定的神经元控制方法,并对某造纸机定量控制系统进行了控制器的设计和仿真实验研究,取得了令人满意的结果。     

Optimal selection of ARQ parameters in QAM channels

For a quadrature amplitude modulation (QAM) communication channel with forward error correction (FEC) and automatic repeat request (ARQ), the bit error rate (BER) is estimated as a function of the channel signal‐to‐noise ratio (SNR). A method is presented for trading off the number of allowed transmissions and the level of margin (or the line ARQ gain) applied to the channel SNR. The line ARQ gain maximizing the channel throughput is shown to be a sum of the channel SNR and some function of the bit load and FEC parameters. Using this result, we formulate a fast method of determining the optimum ARQ parameters at the actual channel conditions, based on their values at some reference conditions, the latter being either stored in the modem memory or pre‐calculated prior to channel initialization. The derivations are presented both for AWGN and slowly fading channel conditions. Copyright © 2004 John Wiley & Sons, Ltd.     

Influences of the initial parameters on the performance of a coaxial-waveguide cyclotron autoresonance maser (CARM) amplifier

Nonlinear simulations demonstrate the possibility for a coaxial-waveguide cyclotron autoresonance maser (CARM) amplifier to operate at a frequency of 140?GHz emitting hundreds of watts with an ultrahigh gain of 68?dB. Careful design of the operating magnetic field is of importance to the power of the device, although the other initial parameters such as electron-beam radius and voltage also affect the power. Like a cylindrical-waveguide CARM, a coaxial-waveguide CARM amplifier is sensitive to the velocity spread of the electron beam.