厦门港国际船舶压舱水交换的CDOM示踪研究

通过对2007年10月-2008年4月经停厦门港的不同航线9条国际船舶29个压舱水中有色溶解有机物(CDOM)的三维荧光光谱和吸收光谱分析,探讨了利用CDOM光谱参数检验进出我国港口的国际船舶是否进行了远洋压舱水交换(BWE)国际公约规定的可行性.利用平行因子分析(PARAFAC)对三维荧光光谱进行解潜,共鉴别出压舱水CDOM具有2个类腐殖质及2个类蛋白质荧光组分,其中长波类腐殖质组分C2(250,345/458 nm)可作为判断压舱水是否进行BWE的合适指标.压载舱中各荧光组分垂直分布基本均匀.利用C2组分结合吸收光谱斜率比值SR、盐度等指标.对七述船舶是否进行BWE作出了准确判断.研究结果表明,3类指标的综合应用将能更有效地对国际船舶是否进行BWE进行可靠的检验,对今后在厦门港乃至国内其他港口开展压舱水水源的快速检测提供了技术支撑.     

Continuous-wave mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate

This paper reports a continuous-wave (CW) mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate (PPLN) pumped by a diode-end-pumped CW Nd:YVO$_{4}$ laser. Considering the thermal lens effects, it adopted an optical ballast lens and the near-concentric cavity for better operation. At the PPLN's grating period of 28.5\,$\mu$m and the temperature of 140\du, the maximum idler output power of 155\,mW at 3.86\,$\mu$m has been achieved when the 808\,nm pump power is 8.5\,W, leading to an optical-to-optical conversion efficiency of 1.82{\%}.     

High efficiency continuous-wave tunable signal output of an intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate

In this paper we report on a continuous-wave (CW) intracavity singly resonant optical parametric oscillator (ICSRO) based on periodically poled LiNbO₃ (PPLN) pumped by a diode-end-pumped CW Nd:YVO₄ laser. Considering the thermal lens effects and diffraction loss, an optical ballast lens and a near-concentric cavity are adopted for better operation. Through varying the grating period and the temperature, the tunable signal output from 1406~nm to 1513~nm is obtained. At a PPLN grating period of 29~μ m and a temperature of 413~K, a maximum signal output power of 820~mW at 1500~nm is achieved when the 808~nm pump power is 10.9~W, leading to an optical-to-optical conversion efficiency of 7.51%.     

Pulsed method for measuring the capacitance of semiconductor structures using a ballast capacitor

An easily implemented method for measuring the capacitance of semiconductor structures using small-amplitude current pulses is described. It is shown that the accuracy of the method described can be improved significantly when a ballast capacitor is employed and, in addition, a calibration procedure is performed. The influence of the ballast capacitor on the measurement process is analyzed in detail. Zh. Tekh. Fiz. 69, 82–84 (March 1999)     

The ballast resistor; An electro-thermal instability in a conducting wire II; Fluctuations around homogeneous stationary states

The correlation function of temperature fluctuations around homogeneous stationary states of the ballast resistor is evaluated by extending the theory of thermal fluctuations around equilibrium states to non-equilibrium situations. It is found that equal-time temperature fluctuations become correlated over large distances if one approaches the critical point. At the “critical point” of the ballast resistor the correlation length and the amplitude of the temperature fluctuations diverge. Furthermore the theory predicts a critical slowing down for the time-dependent temperature fluctuation correlation function. The electric noise of the system is also analyzed.     

The pulsed optogalvanic effect in a low-pressure mercury discharge

Experiments are described in which a low-pressure mercury discharge is irradiated with a 10 ns dye laser pulse tuned resonant to one of 6 ³P-7 ³S₁ transitions. The time behaviour of the induced optogalvanic effect is found to be dependent on the value of the ballast resistance in the discharge circuit. The qualitative explanation for this phenomenon is that the ratio of the relative change in the electron temperature and the relative change in electron density depends on the value of the ballast resistance.     

The research on the pulsed arc electrohydraulic discharge and its application in treatment of the ballast water

Since the tech of Pulsed Arc Electrohydraulic Discharge (PAED) found wide application, immense amounts of concrete research have been put into use on seawater treatment. When the breakdown of electrodes submerged in ballast water, strong pressure wave, ultraviolet ray, active groups, etc. can be generated, accompanying with the distinct electrohydraulic effect. Therefore, it shows the best performance on the inactivation of bacterium and seaweeds lives in the seawater. The experiment of the PAED reactor with different volume (from 10 L to 2 T) was performed step by step. The PAED power supply is 1 kJ/pulse and discharge frequency is 0.5 Hz. The best performance for the inactivation of bacterium and seaweeds by PAED is related to the conductivity of ballast water, the capacity of the treatment cell and the pulse energy. The inactivation mechanisms of PAED on ballast water will be discussed based on the electrohydraulic effect.     

用电容和二极管改进低压钠灯、汞灯电源中的镇流器

本介绍了用电容器和二极管代替低压钠灯、汞灯中镇流器的方法。     

直流大气压辉光放电高能电子密度的空间分布

利用针阴极和水阳极,在6 mm的空气隙产生了大气压空气辉光放电。该大气压辉光放电具有明显的负辉区、正柱区和阳极辉区等明亮的发光区。通过研究放电的电压电流特性,发现该放电处于亚辉光放电到正常辉光放电阶段。由于氮分子第二正带系337.1 nm的光谱强度反映高能电子密度,对337.1 nm谱线的强度进行了空间分辨测量。结果发现高能电子在针尖附近密度最大,而其他区域相差不多。随电压升高,高能电子密度减少。增大限流电阻,高能电子密度也减少。氧原子对杀菌消毒具有重要作用,利用发射光谱法对氧原子谱线强度的空间分布进行了测量,发现氧原子谱线强度与高能电子的空间分布及其随参数的变化关系一致。     

电子镇流器进一步节能的实验研究

对预热启动式电子镇流器进一步节能的途径和实验方法进行了研究，从实验中得出实验数据和结论。     

Application of MetaRail railway noise measurement methodology: comparison of three track systems

Within the fourth RTD Framework Programme, the European Union has supported a research project dealing with the improvement of railway noise (emission) measurement methodologies. This project was called MetaRail and proposed a number of procedures and methods to decrease systematic measurement errors and to increase reproducibility. In 1999 the Austrian Federal Railways installed 1000 m of test track to explore the long-term behaviour of three different ballast track systems. This test included track stability, rail forces and ballast forces, as well as vibration transmission and noise emission. The noise study was carried out using the experience and methods developed within MetaRail. This includes rail roughness measurements as well as measurements of vertical railhead, sleeper and ballast vibration in parallel with the noise emission measurement with a single microphone at a distance of 7.5 m from the track. Using a test train with block- and disc-braked vehicles helped to control operational conditions and indicated the influence of different wheel roughness.It has been shown that the parallel recording of several vibration signals together with the noise signal makes it possible to evaluate the contributions of car body, sleeper, track and wheel sources to the overall noise emission. It must be stressed that this method is not focused as is a microphone-array. However, this methodology is far easier to apply and thus cheaper. Within this study, noise emission was allocated to the different elements to answer questions such as whether the sleeper eigenfrequency is transmitted into the rail.     

Continuous-wave mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate

This paper reports a continuous-wave （CW） mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate （PPLN） pumped by a diode-end-pumped CW Nd：YVO4 laser. Considering the thermal lens effects, it adopted an optical ballast lens and the near-concentric cavity for better operation. At the PPLN＇s grating period of 28.5 μm and the temperature of 140℃, the maximum idler output power of 155 mW at 3.86 μm has been achieved when the 808 nm pump power is 8.5 W, leading to an optical-to-optical conversion efficiency of 1.82%.     

波峰系数对灯寿命影响的实验研究

由实验中测出不同的灯电流波峰系数与灯开关次数的对比结果，说明了灯电流波峰系数偏高对灯寿命的影响，从而推出一种高性能低成本的电子镇流器。     

Limit cycles of the ballast resistor caused by intrinsic instabilities

Spatio-temporal patterns of the ballast resistor are investigated. It is well known that in a voltage-controlled ballast resistor an electrothermal instability leads to stable stationary states consisting of hot and cold domains. Such states may become oscillatory unstable, giving rise to the bifurcation of limit cycles. These limit cycles are not caused by the external circuit but by a recently proposed novel intrinsic mechanism. There are two types of oscillatory instabilities: bulk instabilities and boundary-induced instabilities. The bulk instabilities are caused by resistivities which are not monotonically increasing functions of the temperature. The boundary-induced instabilities occur in small systems with Neumann boundary conditions. To find the bulk instability, experiments with materials showing a metal-semiconductor transition or high-temperature superconductors are suggested. To understand these new phenomena, the equation of motion is reduced to ordinary differential equations where the instabilities can be discussed analytically.     

A railway track dynamics model based on modal substructuring and a cyclic boundary condition

This article presents a technique for modelling the coupled dynamics of a railway vehicle and the track. The method is especially useful for simulating the dynamics of high speed trains running on nonlinear tracks. The main hypothesis is a cyclic system: an infinite track on which there is an infinite set of identical vehicles spaced at a regular interval of distance. Thus the main problems of the finite-length track models (e.g. the waves that reflect at the end of the track and interact with the vehicle; and the time interval of integration must be shorter than the track length divided by the velocity) are avoided. The flexibility of the method can be observed from the case studies presented in the present work: a vehicle passing over a hanging sleeper, and the vehicle-track dynamics for different ballast compaction cases. The results show the influence of the hanging sleeper gap on the wheel-rail contact forces, and the bending moment at the sleeper for different ballast compaction cases.     

On stabilization of multipoint negative corona by using ballast resistances

The I-V characteristics of a negative corona discharge initiated by a multipoint cathode in an argon flow are experimentally studied. It is found that adjustable ballast resistances connected to the corona points provide stable operation and uniform filling of the discharge gap by the plasma.     

Self-sustained oscillations in a low-current discharge with a semiconductor serving as a cathode and ballast resistor: I. Experiment

Self-sustained current oscillations in a Townsend discharge that is excited in a short plane discharge gap and is uniform along the electrode surface are investigated experimentally. A thin semiconductor plane serves as a discharge cathode, a ballast resistor, and an additional capacitor in the dc power supply circuit. The domain of existence and the frequency and waveform of oscillations are determined over a wide pressure range.     

Two types of current oscillations in a low-current spark discharge initiated in a nonuniform electric field

Experimental data for a spark discharge in the tip-plane electrode configuration in argon are considered for the case when the discharge current is limited by a high-resistivity ballast resistor. It is shown that the current passing in the thin plasma channel of a low-current spark represents a steady sequence of regular pulses. It is found that low-frequency current pulses of the low-current spark are accompanied with high-frequency current oscillations of nanosecond duration.     

Indications of marine bioinvasion from network theory

The transport of huge amounts of small aquatic organisms in the ballast tanks and at the hull of large cargo ships leads to ever increasing rates of marine bioinvasion. In this study, we apply a network theoretic approach to examine the introduction of invasive species into new ports by global shipping. This is the first stage of the invasion process where it is still possible to intervene with regulating measures. We compile a selection of widely used and newly developed network properties and apply these to analyse the structure and spread characteristics of the directed and weighted global cargo ship network (GCSN). Our results reveal that the GCSN is highly efficient, shows small world characteristics and is positive assortative, indicating that quick spread of invasive organisms between ports is likely. The GCSN shows strong community structure and contains two large communities, the Atlantic and Pacific trading groups. Ports that appear as connector hubs and are of high centralities are the Suez and Panama Canal, Singapore and Shanghai. Furthermore, from robustness analyses and the network’s percolation behaviour, we evaluate differences of onboard and in-port ballast water treatment, set them into context with previous studies and advise bioinvasion management strategies.     

Enhanced efficiency of a mutually coupled parallel spark preioniser

The enhanced efficiency, almost by a factor of 9, of preionisation when the laser is self-switched by a mutually coupled parallel spark preioniser as against its conventional operation with inductively ballasted preioniser, has been demonstrated in the operation of a TEA CO₂ laser. The increased preionisation peak current due to the near ballast free operation of the mutually coupled parallel spark channels is shown to be responsible for the observed behavior.