Comparative studies of eye-safe intracavity and extracavity optical parametric oscillators with an unstable telescopic cavity

We have experimentally studied the lasing characteristics of an eye-safe optical parametric oscillator (OPO) with an unstable telescopic cavity when it is placed inside (intracavity OPO) and outside (extracavity OPO) the plane-parallel cavity of a pulsed, nearly single-mode KGW:Nd pump laser. We used a KTP crystal as the nonlinear medium for the OPO. We have shown that the intracavity OPO has the higher lasing efficiency. We have observed that the distribution of nonlinear losses introduced by the intracavity OPO, nonuniform over the cavity cross section, leads to an increase in the diameter and divergence of the radiation beam from the pump laser and a dependence of its temporal lasing dynamics on the transverse beam coordinate. We propose a physical model qualitatively explaining the spatial and temporal lasing dynamics of a radiation source with an intracavity OPO. Both OPO versions generate beams of radiation with about the same divergence. When the KGW:Nd laser has an electrical pumping energy of 7.3 J and a cavity length of 77 cm, the intracavity OPO and the extracavity OPO emit pulses with energies of 14.5 mJ and 12.0 mJ and duration 18 nsec and 13 nsec respectively. The divergence of the eye-safe radiation (λ = 1.578 μm) at 86.5% of the total pulse energy is no greater than 5.5 mrad for an OPO output beam diameter of = 2 mm. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 535–543, July–August, 2006.     

单程直驱超高压纳升泵的研制与评价

随着生命科学的发展，纳升液相色谱系统在生化分析领域有着越来越多的应用。纳升流速输液泵作为系统的关键部件之一，其性能直接影响分析结果的准确性与重复性。该文基于高精度直驱电机和十通切换阀研制了一种单程直驱超高压纳升泵，并对其进行了评价。测试结果表明，该纳升输液泵在500 nL/min下的流速准确性优于1%，稳定性优于0.7%，最大输液压强超过100 MPa，梯度输液偏差低于1%。进一步利用该纳升输液泵构建纳升液相色谱-质谱联用系统，对1 μg牛血清白蛋白（BSA）酶解液进样分析，序列覆盖率可达45%，分析1.25 μg Hela细胞蛋白质酶解液鉴定到2809个蛋白质。说明构建的单程直驱超高压纳升泵能够用于生化分析，尤其是蛋白质组学分析研究中。     

单级高压微流量电渗泵的研究

设计了一种高压微流量电渗泵。泵体主要由高压电源、电渗柱、毛细通道、导电空心电极以及气泡去除器、压力传感器等构成。单级电渗泵可以给出0～20MPa范围的输出压力和nL～μL级输出流量。输出压强和输出流量取决于电压、填充柱阻力和流体性质。     

油液颗粒污染检测仪的研制

研制了油液颗粒污染检测仪。采用高压注射泵取样系统控制取样精度,通过激光电源恒流控制电路设计提高了遮光原理颗粒计数传感器的稳定性。油基颗粒计数标准物质校准和比对测试结果表明,研制的油液颗粒污染检测仪的测试重复性和准确性达到国外同类仪器水平。     

Temperature control technology by heat capacity change upon lock and key binding

We propose an innovative temperature control technology wherein a heat capacity change upon lock and key binding is applied. A proof-of-principle calculation is performed using a three-dimensional integral equation theory of a statistical mechanics of fluid (Ornstein-Zernike theory coupled by HNC closure). Logical correctness of the temperature control technology is verified by this calculation. The performance of the heat pump is discussed. In addition, a more effective condition of the heat pump is also discussed to improve the performance.     

Assessment of scale-adaptive turbulence models for volute-type centrifugal pumps at part load operation

Unsteady three-dimensional (3D) computational fluid dynamics (CFD) simulations are conducted with the open-source software OpenFOAM to assess the scale-adaptive k-ω-SST-SAS turbulence model (SAS) on a radial, volute-type centrifugal pump at part load operation which is characterized by high unsteadiness and flow separation. SAS results are compared to spatially high resolved and ensemble-averaged flow measurement data in terms of flow angle and turbulence intensity (TI) in the rotor–stator interaction region. Differences to simulation results obtained with the statistical state-of-the-art k-ω-SST turbulence model (SST) are highlighted. The flow angle is predicted with a reasonable agreement to measurement data by both, SST and SAS models. In the highly transient flow of strong rotor–stator interaction near the volute tongue, SST results show a significant overprediction of measured TI while the SAS model yields a considerably better agreement to measurement data even with a typical URANS grid resolution. A grid refinement does not further improve the agreement to measurement data. An in-depth analysis of the SAS model on separated flow, i.e., periodic hill test case, together with a large eddy simulation (LES) reference solution is performed and reveals that with successive grid refinement, in contrast to LES, the SAS model in its present form of Egorov and Menter (2008) does not resolve a successively larger portion of the turbulence spectrum, and the modeled part is not successively reduced. For that purpose, a re-calibration or even a re-formulation of the scale-adaption source term in the transport equation of the turbulent dissipation rate may be indispensable, which will be the subject of future studies.     

Effect of turnoff time on characteristics of the output pulse in an AO Q-switched laser

A laser-end-diode-pumped actively Q-switched Nd:YVO₄ laser with acoustic-optic (AO) modulator is realized. By changing the position of AO in the cavity for changing the transit time of the acoustic-wave, the effect of the AO turnoff time on the characteristics of the output Q-switched pulse is obtained. The experimental results show that the longer transit time leads to the wider pulse duration. By considering the Gaussian spatial distribution of the intra-cavity photon density and the AO turnoff time including the electronic turnoff time and the transit time of the acoustic-wave, the numerical solutions of the coupled Q-switched rate equations are consistent with the experimental results.     

Investigation of thermodynamic properties of magnesium chloride amines by HPDSC and TG

The formation as well as the decomposition of magnesium chloride ammonia complexes was studied by high-pressure differential scanning calorimetry (HPDSC) and thermogravimetric analysis (TG). HPDSC runs were performed under constant ammonia pressure conditions to determine the transition temperatures and stability regions of the ammonia complexes. The TG technique has been employed to examine the stoichiometry of the complexes. The hexa-, di-and mono-ammines are proven to exist under our experimental conditions. The decomposition of the mono ammine to pure MgCl₂ occurs most probably in two steps.     

Frequency sweeping of emission from heterojunction quantum lasers with pump current modulation

We have used numerical modeling to study the dynamic shift of the “instantaneous” laser frequency (sweeping) as a function of the pump current modulation frequency for heterojunction quantum lasers when the lasing frequency is tuned within the gain band. As the model for the active medium, we used a two-band model with identical distribution of levels for the electron and hole subbands, in which we take into account direct transitions between the ground-state subbands. We have established that the variation in the sweep qualitatively corresponds to the behavior of the amplitude detuning characteristics of the laser. Depending on the parameters of the system during emission of pulses, the variation in the laser frequency can be monotonic or nonmonotonic. By selecting the pump current modulation frequency and setting the laser frequency within the gain band, we can realize the cases of maximum or minimum dynamic shift of the lasing frequency. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 370–374, May–June, 2006.     

某中央空调制冷实验设备中水泵的合理选择

如果中央空调制冷实验设备中水泵选择不当,会使系统运行不正常,或者导致能量消耗加大,这都将造成工程的失败,因此,合理选择循环水泵具有重要的意义。以某中央空调制冷实验设备设计为例,说明水泵的合理选择方法。其对中央空调设计具有一定的参考价值。