Measurement of functional residual capacity through the transientphase of He dilution in newborns

Helium dilution maneuver is used to determine the functional residual capacity (FRC) 14 newborns ages 1-5 mo. The model equation describes the changing alveolar fractions of He and the ventilation promoted by a rebreathing procedure that does not exceed 40 s. The model does not involve the volume of the rebreathing bag usually needed when applying rebreathing technique and which is a source of error. The equation is discretized and solved for recorded data obtained with equipment adapted to newborns. Results show a strong relationship between FRC and the biometrical indexes, and confirm those found in the literature featuring that the measurement duration of FRC can be considerably shortened.     

Noninvasive measurement of cardiac output using partial CO2 rebreathing

A noninvasive algorithm for estimating cardiac output is discussed. The technique is based on a differential form of the CO₂ Fick equation applied during normal ventilation and a 30-s period of partial rebreathing using additional deadspace. Using the Fick equation in a differential form eliminates the need to estimate mixed venous pCO₂, also the sensitivity of the cardiac output estimate to changes in the alveolar deadspace fraction is greatly reduced. The procedure is fully automated, requires minimal staff supervision, and provides cardiac output estimates every 3 1/2-min. Estimates of cardiac output when compared to thermodilution yielded a correlation coefficient of 0.92 with a linear regression slope of 0.92 ( n=451). Temporary increases in alveolar deadspace did not significantly alter this relationship. Cardiac output estimates obtained during period of increased pulmonary shunt due to oleic acid infusion yielded a correlation coefficient of 0.90 with a linear regression slope of 0.92 when compared to direct thermodilution measurements     

Anomalous gain in an isotopically mixed CO2 laser andapplication to absolute wavelength calibration

Measurements are reported on a grating-tuned CO₂ laser, containing an isotopic mixture of ¹⁶O¹²C¹⁶ O, ¹⁶O¹²C¹⁸O, and ¹⁸O ¹²C¹⁸O. The P₆ and R ₁₄ lines of ¹⁶O¹²C¹⁶O were found to have anomalously high intensities. These anomalies are produced by the near coincidence of the transition frequencies in two distinct isotopes, permitting them to act as a single indistinguishable population. These two lines can be used to identify the rotational quantum numbers in the P and R branch spectra, thereby permitting absolute wavelength calibration to be achieved     

Relaxation oscillations in optically pumped molecular lasers

We report the observation of relaxation oscillations in both the C¹³H3F and C¹²H3F optically pumped lasers. Expressions are derived for the oscillation frequency and its temperature and pressure dependences using a four-level rate equation model. We observe excellent agreement between measured frequencies and the theory presented. Models are considered for using this phenomenon to determine the rotational and vibrational relaxation mechanisms of the laser gases.     

Beat-frequency between measurements between C12O216and C12O218lasers

Several beat frequencies in the range below 6 GHz have been measured using a C¹²O2¹⁶laser and a C¹²O2¹⁸laser operating on several pairs of closely spaced lines in the 9.3-μm region.     

Observation and assignment of D218O FIR laserlines optically pumped by a waveguide CO2 laser

By means of a detailed analysis of the v₂ infrared band of D₂¹⁸O, it has been possible to assign most of the FIR emissions reported in the literature. Moreover, two FIR laser lines which fall in the range of tunability of the CW waveguide CO₂ laser have been predicted and observed. The frequency of the stronger line was measured and found to be 2611.4185(10) GHz, thus filling a gap in the presently available comb of FIR laser lines whose frequencies have been measured. The wavelength precision of the assigned lines was improved by about two orders of magnitude     

Observation of a strong vibrational population inversion by CO laser excitation of pure solid carbon monoxide

Under irradiation of a pure solid CO sample at low temperature by a CW CO laser beam,¹³C¹⁶O,¹²C¹⁸O and¹³C¹⁸O molecules are excited to high vibrational levels, up toupsilon = 23, and a strong population inversion is observed. The¹²C¹⁶O molecules are pumped to theupsilon = 1level by laser line absorption in the low frequency phonon sideband, and the vibrational energy is subsequently transferred to the other isotopes. Quantum yield, efficiency, and heat release are discussed to clarify the mechanism.     

Infrared microwave sideband laser spectroscopy in the CO laserregion

The method of infrared microwave sideband laser spectroscopy developed by G. Magerl, et al. (ibid, vol.18, p.1214-20, 1982) for application in the 9-11-μm region with a CO₂ laser has been extended to application in the 5-6-μm region with a CO laser. The experimental details, performance of the system, and typical spectra are described. Frequency measurements of spectra in the 01¹1←00⁰0 band of ¹⁴N₂ ¹⁶O and the 20⁰←00⁰0 band of ¹⁶O¹²C³²S are compared to the results of previous precise measurements by heterodyne techniques to show that the accuracy is limited mainly by the resettability of the CO laser frequency     

The identification of candidate transitions for optically pumped far infrared lasers: Methyl halides and D2O

Two hundred and forty-four candidate transitions for optically pumped far infrared lasers have been identified in C¹²H3F, C¹³H3F, C¹²D3F, C¹²H3Cl³⁵, C¹²H3Cl³⁷, C¹²H3Br⁷⁹, C¹²H3Br⁸¹, and D2O using as candidate pump lines, 781 in number, the isotopic forms of CO2, the sequence and hot bands of C¹²O2¹⁶, and the N2O bands. The dominant transition parameters responsible for strong emission from TEA, CW, and long pulse modes of operation were identified by a correlation between known experimental behavior and the pertinent transition parameters, the results being that strong TEA laser emission correlates with ground state population while strong CW and long pulse emission correlate with absorption coefficient. The candidate transitions were subsequently selected on the basis of these parameters using calculated transitions and assignments based on band data from high resolution laser-Stark spectroscopy and measured candidate pump frequencies.     

Moving naval C4I into the next century

The combination of command, control, communications, computers and intelligence is known in the military as C⁴I. The naval C⁴I initiative is defining a future architecture that is based on information management with one objective in mind: to bring naval C⁴I to the next level of integration and interoperability in the joint war fighting arena for the advantages it brings to the warrior. We discuss the path we are taking to a more integrated C⁴I (IC⁴I) system. We also discuss what we have done to both define and bound the naval C⁴I universe; where we are on the path to the IC⁴I system; the challenges we face on our way; and how we intend to surmount them     

Active spectral stabilization of cleaved-coupled-cavity (C3) lasers

A stabilization technique which will maintain a cleaved-coupled-cavity (C³) laser in single-mode operation over a wide current and temperature range is proposed and demonstrated.     

一种基于随机森林的激光大气传输效应评估方法北大核心CSCD

针对现有的激光大气传输效应评估方法(定标律评估和波动光学仿真评估)较难有良好的模型正则性和应用普适性的困难,提出一种基于随机森林的激光大气传输效应评估方法。该方法首先以烟台某地大气环境数据(温度、风速、湍流强度(C^(2)_(n))等)的随机采样和激光发射参数(传输距离、激光功率等)作为输入数据和多层相位屏模型仿真生成的环围功率(PIB)作为输出数据,然后利用随机森林进行训练和预测。结果表明,随机森林较支持向量机能更好的表征输入与输出间的多元回归关系,预测均方根误差优于0.021%;传输距离、C^(2)_(n)与PIB相关性最强,对PIB影响最大。本方法可为机器学习在激光大气传输效应评估的应用提供更加完善的理论依据,具备一定的应用价值。     

Maximum operating frequency in Si bipolar master-slave toggleflip-flop circuit

This paper presents a propagation-delay equation which is expressed as the influence of the individual device and circuit parameters on the maximum operating frequency of Si bipolar master-slave toggle flip-flop (MS-TFF) circuit with double feedback emitter followers. This equation shows that optimizing the size of individual transistors can enhance the operating speed. Test results show a 10% increase in operating frequency by adopting this design technique. It is also shown that the time constants R_BC_jC, R_B C_D, T_F, R_LCj_C, and R _CCj_C of the upper-level current switch and T_F of the second feedback emitter follower greatly affect the operating speed of circuits using recently developed Si bipolar transistors. The results predicted by the equation are in good agreement with both the experimental ones and SPICE simulations     

A powerful new optically pumped FIR laser--Formylfluoride

Intense FIR laser action is reported in formylfluoride (HFCO) with 7 lines of the normal CO2laser and 4 lines of the C¹⁸O2laser.     

Timing constraints for high-speed counterflow-clocked pipelining

With the escalation of clock frequencies and the increasing ratio of wire-to gate-delays, clock skew is a major problem to be overcome in tomorrow's high-speed very large scale integration (VLSI) chips. Also, with an increasing number of stages switching simultaneously comes the problem of higher peak power consumption. In our prior work, we have proposed a novel scheme called counterflow-clocked (C²) pipelining to combat these problems, and discussed methods for composing C² pipelined stages. In this paper, we analyze in great detail the timing constraints to be obeyed in designing basic C² pipelined stages, as well as in composing C² pipelined stages. C² pipelining is well suited for systems that exhibit mostly unidirectional data flows as well as possess mostly nearest neighbor connections. C² pipelining eases the distribution of high-speed clocks, shortens the clock period by eliminating global clock signals, allows natural use of level-sensitive dynamic latches, and generates less internal switching noises due to the uniformly distributed latch operation. By applying C² pipelining and its composition methods to build a system, VLSI designers can substitute the global clock-skew problem with many local one-sided delay constraints     

Mixed isotope multiatmosphere CO2laser

A sealed transversely excited multiatmosphere pulsed laser is reported in which the active media is a combination of three isotopes:¹²C¹⁶O2,¹²C¹⁸O2, and¹²C¹⁶O¹⁸O. Lasing action is obtained on all 12 vibrational-rotational bands with continuous tuning observed between line centers at pressuresfrac{1}{2}tofrac{1}{4}of those required with conventional¹²C¹⁶O2lasers.     

Transport properties of Mn-doped Ru2Si3

Transport properties of Mn-doped ruthenium silicide Ru₂Si₃ were studied both experimentally and theoretically. The precipitation-free Ru₂Si₃ single crystals were grown by the zone melting technique with radiation heating. The temperature dependence of the electrical resistivity and Hall coefficients of the crystals were measured. The electrical resistivity of 1% Mn-doped Ru₂Si₃ was lower than that of undoped crystals. The carrier concentration in the doped samples is about 10¹⁸ cm⁻³ at room temperature. Mn-doped Ru₂Si₃ has a twice higher carrier mobility compared to the undoped one. Theoretical calculation of the charge carrier mobility is based on the effective masses which are estimated from the ab initio electronic band structure and classical scattering mechanisms.     

Molecular beam epitaxy growth of TmP/GaAs and transistor action inGaP/TmP/GaAs heterostructures

The growth of thulium phosphide (TmP) by molecular beam epitaxy (MBE) on GaAs substrate is reported. Good epilayer quality was demonstrated through X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM) analysis. The closely lattice matched TmP layer was n-type with an electron concentration of 1.6×10²¹ cm^-3 and a room temperature mobility of 4.8 cm²V^-1s^-1. The Schottky barrier height determined from 1/capacitance² (1/C²) versus voltage (V) measurements is about 0.81 eV which agrees well with the value obtained through the current-voltage (I-V) measurements. In this work, we also report transistor action in a GaP/TmP/GaAs structure, for which chemical bonding techniques were employed. From I-V measurements, a common base current gain α≈0.55 at V_CB=0 was obtained at room temperature     

三种典型化学物质释放变态电离层的数值模拟研究

电离层人工变态会影响短波通信及卫星通信,对空间物理研究具有重要意义.基于中性气体扩散方程、离子化学反应方程及等离子体扩散方程,模拟了三种典型化学物质（氢气H₂、二氧化碳CO₂和三氟溴甲烷CF₃Br）经点源和多源释放后导致的电离层三维扰动变化,并利用自适应变步长的三维数字射线追踪技术讨论了化学释放变态电离层对不同频率短波传播的影响.结果表明:点源释放时产生的"空洞"在水平面上沿磁场线方向的轴长略大于其垂直方向;在释放量及释放高度相同的前提下,H₂扩散最快,CF₃Br扩散最慢,但就t=100 s时电子密度最大相对变化率而言,CF₃Br最大,CO₂次之,H₂最小;CF₃Br释放形成的"空洞"垂直范围最小,开始发生穿透现象所需的短波频率最高;H₂扰动下"空洞"边界的电子密度梯度最小,射线聚焦点明显偏高,聚焦效应最弱;多源释放产生类抛物线管状的电离层"空洞"结构,射线的传播路径更加多样,此时仍有聚焦效应出现,且聚焦点随射线频率增加而升高,聚焦效应减弱.     

Sensitivity of Rs-measurement of HTS thin films by threeprime resonant techniques: cavity resonator, dielectric resonator, andmicrostrip resonator

The microwave surface resistance, R_s measurement of YBa ₂Cu₃0_{7 -δ} (YBCO) thin film deposited on 10 mm × 10 mm LaAlO₃ substrate using three prime resonating techniques, namely, cavity end plate substitution technique (20 GHz), dielectric resonator technique (18 GHz), and microstrip resonator technique (5 GHz), is reported. In addition, theoretical analysis for each technique has been performed to calculate the relative percentage error in the measured R_s -value of the YBCO thin film as a function of temperature. It has been found that the shielded dielectric resonator provides far better sensitivity for R.-measurement of the YBCO thin film with minimum relative percentage error (<4%) in the temperature range from 20 K to transition temperature of YBCO thin film compared to the other two techniques