Optical pumping and population transfer of nuclear-spin states of caesium atoms in high magnetic fields

Nuclear-spin states of gaseous-state Cs atoms in the ground state are optically manipulated using a Ti：sapphire laser in a magnetic field of 1.516 T, in which optical coupling of the nuclear-spin states is achieved through hyperfine interactions between electrons and nuclei. The steady-state population distribution in the hyperfine Zeeman sublevels of the ground state is detected by using a tunable diode laser. Furthermore, the state population transfer among the hyperfine Zeeman sublevels, which results from the collision-induced modification δa（S·I） of the hyperfine interaction of Cs in the ground state due to stochastic collisions between Cs atoms and buffer-gas molecules, is studied at different buffer-gas pressures. The experimental results show that high-field optical pumping and the small change δa（S · I） of the hyperfine interaction can strongly cause the state population transfer and spin-state interchange among the hyperfine Zeeman sublevels. The calculated results maybe explain the steady-state population in hyperfine Zeeman sublevels in terms of rates of optical-pumping, electron-spin flip, nuclear spin flip, and electron-nuclear spin flip-flop transitions among the hyperfine Zeeman sublevels of the ground state of Cs atoms. This method may be applied to the nuclear-spin-based solid-state quantum computation.

A Novel All-pMOS AC to DC Charge Pump with High Efficiency

A novel AC to DC charge pump with high performance is presented. Due to the pMOS structure and threshold voltage canceling technology, the efficiency and the output voltage are greatly improved. Test results show that the output voltage and power efficiency are improved by 125% and 104% respectively at 13.56MHz for a 1V sinusoidal input compared to the traditional MOS diodes structure.

Numerical and Experimental Investigation of High-efficiency Axial-flow Pump

The experimental investigation of axial-flow pump has been rapidly developed to meet the needs of South-to-North Water Diversion Project of China. Owing to the boundary conditions of hub, blade tip clearance, much of the physical phenomena and laws involved in this complex flow field can＇t be fully determined. The flow characteristics of the high efficiency axial-flow pump have been simulated by RNG k-e turbulence model and SIMPLEC arithmetic based on FLUENT software. Numerical results indicate that the data from the prediction show agreement with the experimental results, static pressure on pressure side of blades increases slightly at circumferential direction with radius increasing, and keep almost constant at the same radial while increasing gradually from inlet to exit on the suction side along flow direction at design conditions. The static pressure, total pressure and velocity at inlet, impeller outlet and vane outlet were measured by a five-hole probe, and a contrastive experiment was done to investigate the influence of hub leakage. The experimental results show that inlet flow is almost axial and the prerotation is very small at various conditions. The meridional velocity and circulation distribution are almost identical at impeller outlet at design conditions due to steady flow and high efficiency. The residual circulation exits at downstream of the guide vane, and the circumferential velocity component increases linearly from hub to tip at small flow rate conditions. Hub leakage in adjustable blades results in the decrease of the meridional velocity and circulation at blade exit near hub. The results of numerical simulation and experiments supply important flow structure information for the high-efficiency axial-flow pump.

Experimental Performance of Moderate and High Temperature Heat Pump Charged with Refrigerant Mixture BY-3

Theoretical and experimental analysis of a new refrigerant mixture BY-3 was conducted based on a single-stage vapor compression refrigeration system. The water-water heat pump system used BY-3 to produce hot water when the low temperature was 20 ℃. The following results were obtained: the highest temperature at the condenser outlet reached about 85 ℃; when the difference between the water temperatures at the condenser outlet and the evaporator inlet was less than 40 ℃, the coefficient of performance (COP) was larger than 4; when the difference reached 55 ℃, the COP still kept 3; the discharge temperature of BY-3 was lower than 100 ℃, and the refrigerant vapor pressure kept lower than 1.8 MPa. When the water temperature at the condenser outlet reached over 85 ℃, nearly a 5 ℃ superheating temperature was maintained.

A Flexible Valve Based Piezoelectric Pump for High Viscosity Cooling Liquid Transportation

A piezoelectric pump with flexible valve has been developed to pump high viscosity cooling liquid in the nanosats thermal control system. The structure of the flexible valve is designed according to the characteristics of the human aortic shape with the aim to simulate the bionic pumping function of the human heart. Dynamic stress-strain features of the flexible valve are analyzed by the finite element method,and the results show that the proposed flexible valve is suitable and functional for the piezoelectric pump. Then the cylinder and diffuser/nozzle piezoelectric pumps based on flexible valves have been developed and fabricated. Experimental results of the output performance indicate that the maximum flow rate of the cylinder piezoelectric pump with flexible valve is 15.38 mL/min,170.77% higher than the diffuser/nozzle piezoelectric pump with flexible valve. The ability of the cylinder piezoelectric pump with flexible valve for transmitting high viscosity liquid has been validated. The piezoelectric pump with flexible valve has potential applications in the nanosats thermal control system.

Performances of the High Strength Low Heat Pump Concrete (HLPC)

The effects of mineral admixtures on fluidity,mechanical and hydrational exothermic behavior were studied.The results show that,double adding ways,i e,fly ash and slag were added at the same time,not only improves the fluidity of fresh concrete with low W/B and compensates the lower early compressive strength of harden concrete caused by high adding amount of fly ash, but also greatly reduces the highest temperature rise, exothermic rate and total heat liberation of 3 day of binder pastes in HLPC, and postponed the arrival time of the highest temperature rise. HLPC was prepared and applied to project practice successfully.

EXPERIMENTAL STUDY ON HIGH-SPEED CENTRIFUGAL PUMPS WITH DIFFERENT IMPELLERS

The experimental study is carried out on high-speed centrifugal pumps withthree different impellers. The experimental results and analysis show that high-speed centrifugalpumps with a closed complex impeller can achieve the highest efficiency and the lowest headcoefficient followed by those with half-open impeller and open-impeller, and can obtain much easilystable head-capacity characrastic curve, while those with a half-open complex impeller can't. Thecharacteristic curve with a open impeller is almost constant horizontal line before droppingsharply. The results also show that the axial clearance between pump casing and impeller caninfluence greatly on the performance of centrifugal pumps.

Synchronously Pumped Mode-Locked 1.89 μm Tm-Doped Fiber Laser with High Detuning Toleration

We propose and demonstrate a synchronously pumped mode-locked Tm-doped fiber（TDF） laser without any extra mode-locking elements. Pumped by a 1.56 μm pulse fiber laser, the TDF laser generates 1.17 ps pulses with a spectral width of 9.7 nm and a repetition rate of 9.33 MHz. The emission wavelength is tunable along with the cavity length detuning in a wide range of 3 mm. The high detuning toleration is beneficial to achieve high temperature and vibration stability in all-fiber configuration lasers.

High-dose vs low-dose proton pump inhibitors for upper gastrointestinal bleeding:A meta-analysis

AIM:To evaluate the efficacy of high-dose proton pump inhibitors(PPIs)vs low-dose PPIs for patients with upper gastrointestinal bleeding.METHODS:PubMed,Embase,the Cochrane Library,and Web of Science were searched to identify relevant randomized controlled trials(RCTs).Eligible trials were RCTs that compared high-dose PPI with low-dose PPI following endoscopic hemostasis.The primary endpoint was rebleeding;secondary endpoints were patient numbers that needed surgery,and mortality.The meta-analysis was performed with a fixed effects model or random effects model.RESULTS:Nine eligible RCTs including 1342 patients were retrieved.The results showed that high-dose intravenous PPI was not superior to low-dose intra-venous PPI in reducing rebleeding[odds ratio(OR)= 1.091,95%confidential interval(CI):0.777-1.532],need for surgery(OR=1.522,95%CI:0.643-3.605) and mortality(OR=1.022,95%CI:0.476-2.196).Subgroup analysis according to different region revealed no difference in rebleeding rate between Asian patients(OR=0.831,95%CI,0.467-1.480)and European patients(OR=1.263,95%CI:0.827-1.929).CONCLUSION:Low-dose intravenous PPI can achieve the same efficacy as high-dose PPI following endoscopic hemostasis.

High power external-cavity surface-emitting laser with front and end pump

High power optically pumped vertical-external-cavity surface-emitting lasers with front and end pump are re- ported. The gain chip consists of 15 repeats of In0.26GaAs/GaAsP0.02 multiple quantum wells and 30 pairs of Alo.2GaAs/Alo.98GaAs distributed Bragg reflectors. The maximum output power of 3 W, optical-to-optical conversion efficiency of 22.4%, and slope efficiency of 29.8% are obtained with 5-℃ heatsink temperature under the front pump, while the maximum output power of 1.1 W, optical-to-optical conversion efficiency of 23.2%, and slope efficiency of 30.8% are reached with 5-℃ heatsink temperature under the end pump. Influences of thermal effects on the output power of the laser with front and end pump are discussed.

Effect of Viscosity on Pumping-Up of Newtonian Fluid Driven by a Rotating Cone

Effect of viscosity on flow patterns of pumping-up of liquid generated by a cone rotating at the liquid surface has been experimentally studied with various concentrations of glycerol aqueous solution. We have previously found that the higher viscous non-Newtonian fluid was lifted-up along the conical surface with a radial filament-wise pattern, which is quite different from the monotonic thin film-wise pattern observed for the lower viscous fluid such as water. In order to elucidate the pumping-up mechanism, a transition diagram indicating the critical rotation rate is obtained as a function of viscosity?of Newtonian fluid in this study, varying from the lower value of water (μ?=?0.890 mPa·s) to the higher one of glycerin (μ?= 910?mPa·s). It is found that there are three categories depending on the viscosity classified as?1) film-wise pumping-up region for the viscosity?μ?≤?134?mPa·s,?2) filament-wise pumping-up one for the viscosity?μ?≥?520?mPa·s, and?3) no pumping-up phenomenon occurs?for 134??μ??mPa·s.

A cladding-pumping based power-scaled noise-like and dissipative soliton pulse fiber laser

We report a high-average-power noise-like pulse(NLP) and dissipative soliton(DS) pulse fiber laser. Average power as high as 4.8 W could be obtained at the fundamental mode-locked repetition rate. The NLP can also be transformed into a more powerful DS mode-locking state by optimizing the polarization and losses of intra-cavity pulses in the nonlinear polarization evolution regime. The operation mode between the NLP and DS can be switched, and the laser output performance in both modes has been studied. The main advantage of this work is switchable high-power operation between the NLP and DS. In comparison with conventional single-mode NLP fiber lasers, the multi-function high-power optical source will greatly push its application in supercontinuum generation, coherence tomography, and industrial processing.

LD Pumped High Efficient Intracavity Frequency-Doubled Green Laser

A laser diode (LD) pumped Q switched high efficient intracavity frequency doubled Nd ∶YAG laser is reported here. The authors have designed an optical coupler and pointed out that the key to increasing harmonic conversion efficiency is to decrease the loss of fundamental wave. In the experiments, a fundamental mode output laser was acquired. When the pumping power was 12 W, 2.6 W average output power at 1 064 nm with AO Q switch was obtained. 2.1 W average output power at 532 nm was obtained with intracavity frequency doubling, and the highest second harmonic conversion efficiency was 82 0 0.

Development and Application of a Surface High-pressure Injection Device Using a Submersible Electric Pump

Injection recovery is an important measure for increasing the oil recovery rate of an oil field. One way is that centrifugal pumps or plunger pumps are used in an injection station to responsible for injection over a large area under the same pressure. This method is ineffective for low-permeability layers. For the oilfields in dispersed distribution in the marginal areas of Daqing, the low water-absorbing section needs an injection with a high delivery pressure and a low discharge capacity; another way is to install the submersible electric pump upside down, but because the submersible electric pump and the motor are underground, it is difficult for installation and maintenance. Introduced in this paper is the development and application of a surface high-pressure injection device with a submersible electric pump. Bysuccessful resolving some problems, such as the axial force of the submersible electric pump, sealing, level regulation of the pump, coaxiality and vibration, the device has the good points of running smoothly, moving easily, installation and maintains quickly and long period of running. This device can effectively solve the injection of the low water-absorbing section and of oilfields in dispersed locations. The recovery rate of oilfields is also enhanced.

Sapo Fills the Gaps of 200 W 1064 nm Diode Pumping Modules in China

Wuhan Sapo Laser Industry Ltd．has recently introduced HipoweTM series 1064 nm high power doide laser pumping modules,which not only fill the gaps in Chinese market and end the history of importing this kind products from abroad,but also have great influence on Chinese laser industry and medical laser market．

Design and optimization methods towards a 10 kW high beam quality fiber laser based on the counter tandem pumping scheme

In this study,we investigated the influence of fiber parameters on stimulated Raman scattering(SRS)and identified a unique pattern of SRS evolution in the counter tandem pumping configuration.Our findings revealed that the SRS threshold in counter-pumping is predominantly determined by the length of the output delivery fiber rather than the gain fiber.By employing the counter tandem pumping scheme and optimizing the fiber parameters,a 10 kW fiber laser was achieved with beam quality M^(2)of 1.92.No mode instability or severe SRS limitation was observed.To our knowledge,this study achieved the highest beam quality in over 10 kW fiber lasers based on conventional double-clad Yb-doped fiber.

基于Charge Pump技术的低压高频Antiringing MOS开关驱动电路

本文给出了一种基于Charge Pump适用于低压高频Antiringing MOS开关的驱动电路。该驱动电路工作电压最低可达1.8V,工作频率最高达5MHz。文章从Charge Pump及Antiringing的基本原理出发详细介绍了此驱动电路设计思想,并且给出最终设计电路。该电路基于Samsung 0.65-μm BiCMOS工艺设计,经过HSPICE仿真验证。

The Flow Simulation and Experimental Study of Low-Specific-Speed High-Speed Complex Centrifugal Impellers＊

Based on the Navier-Stokes equations and the Spalart-Allmaras turbulence model, three-dimensional turbulent flow in four low-specific-speed centrifugal impellers are simulated numerically and analyzed. The relative velocity distribution, pressure distribution and static pressure rise at the design point are obtained for the regular impeller with only long blades and three complex impellers with long, mid or short blades. It is found that the back flow region between long-blade pressure side and mid-blade suction side is diminished and is pushed to pressure side of short blades near the outlet of impeller at suction side by the introduction of mid, short blades, and the size of back flow becomes smaller in a multi-blade complex impeller. And the pressure rises uniformly from inlet to outlet in all the impellers. The simulated results show that the complex impeller with long, mid and short blades can improve the velocity distribution and reduce the back flow in the impeller channel. The experimental results show that the back flow in the impeller has an important influence on the performance of pump and a more-blade complex impeller with long, mid and short blades can effectively solve low flow rate instability of the low-specific-speed centrifugal pump.

Design and Verification of an Auxiliary System for High Vacuum Die Casting

Vacuum die casting is the optimal method to produce high quality aluminum alloy components.At present,there are still very few systematic studies on vacuum die casting theory and equipment design.On the basis of the existing theories of the vacuum die casting pumping and venting systems,a simplified model is established in this research.The model has an aggregate unit consisted of ＂vacuum pump ＋ buffer tank＂ and a cylindrical container（including the shot sleeve,cavity and exhaust channel）.The theoretical analysis is carried out between the cavity pressure and the pumping time under different volume models.An auxiliary system for high vacuum die casting is designed based on the above analysis.This system is composed of a vacuum control machine and a new vacuum stop valve.The machine has a human-computer control mode with ＂programmable logic controller（PLC） ＋ touch screen＂ and a real-time monitoring function of vacuum degree for buffer tank and die cavity.The vacuum stop valve with the ＂compressed gas ＋ piston rod ＋ labyrinth groove＂ structure can realize the function of whole-process vacuum venting.The new system shows great advantages on vacuuming the cavity with a much faster speed by making tests on an existing die casting mold and a 250 t die casting machine.A die cavity pressure less than 10 kPa can be reached within 0.8 s in the experiment and the porosity of castings can be greatly decreased.The systematic studies on vacuum die casting theory and equipment have a great guiding significance for high vacuum die casting,and can also be applied to other high vacuum forming in related theoretical and practical research.