32位双发射双流水线结构RISC微处理器设计

"龙腾R2"是西北工业大学自主研制的32位嵌入式RISC微处理器,与IBM公司的Power-PC750处理器pin-to-pin兼容。综合考虑面积、功耗、实时响应以及性能要求等因素,文章提出了一种应用于嵌入式处理器微架构设计的双发射双流水线结构。该结构的核心思想是在指令流水线前端处理阶段动态检测相邻指令的先后依赖关系,预先完成双发射判断。文中首先介绍了"龙腾R2"的微体系架构,然后重点讨论了基于双发射双流水结构的指令调度策略、相邻指令耦合关系、双发射下的相关处理以及精确异常考虑等。采用M ibench基准程序完成了性能评测,综合分析结果显示,该结构对算术计算类程序流加速明显,并且电路结构清晰,易于设计验证,同时发现优化存储系统结构是提升该处理器性能的关键。文章最后对"龙腾R2"的可测试性设计以及硅物理设计等关键技术进行了论述。"龙腾R2"已流片成功,整个处理器采用SMIC 180nm CMOS工艺,芯片面积5.9 mm×6.7 mm,核心频率266 MHz,CBGA360封装。

Creation method for bi-level positive airway pressure based on pressure and flow feedback

An airway pressure and flow data acquisition system is developed to investigate the approach to building the bi-level positive airway pressure BiPAP in a ventilator.A number of experiments under different breathing situations and states are conducted and the experimental data are recorded.According to the data from these experiments the variation characteristics of the pressure and flow are analyzed using Matlab. The data analysis results show that the pressure increases while the flow decreases in the expiratory phase contrarily the pressure decreases while the flow increases in the inspiratory phase during the apnea state both the pressure and the flow remain unchanged. According to the above variation characteristics of breath a feedback-based method for creating bi-level positive airway pressure is proposed. Experiments are implemented to verify the BiPAP model. Results demonstrate that the proposed method works effectively in following respiration and caters well to most polypnea and apnea events.

Double-diffusive Fluxes of Salt and Heat in the Upper Layer of North Pacific Intermediate Water

Almost half of the oceanic water columns exhibit double-diffusion. The importance of double-diffusion in global oceans’ salt and heat fluxes, water-mass formation and mixing, and circulation is increasingly recognized. However, such an important physical process in the ocean has not been well studied. One of the reasons is the difficulty of parameterizing and quantifying the processes. The paper presented here attempts to quantify the double-diffusive fluxes of salt and heat in the ocean. Previous qualitative analysis by applying the water-mass Turner angle, mTu, to the North Pacific Intermediate Water (NPIW) layer showed a favorable condition for salt-fingering in the upper NPIW due to the overlying warm/salty water above the cold/fresh NPIW core, and a doubly-stable condition in the lower NPIW where potential temperature decreases with depth while salinity increases, inducing double stratification with respect to both potential temperature and salinity. The present study gives a quantitative estimate of double-diffusive fluxes of salt and heat contributed by salt-fingering in the upper NPIW layer.

Liquid holdup measurement with double helix capacitance sensor in horizontal oil-water two-phase flow pipes

This paper presents the characteristics of a double helix capacitance sensor for measurement of the liquid holdup in horizontal oil–water two-phase flow. The finite element method is used to calculate the sensitivity field of the sensor in a pipe with 20 mm inner diameter and the effect of sensor geometry on the distribution of sensitivity field is presented. Then, a horizontal oil–water two-phase flow experiment is carried out to measure the response of the double helix capacitance sensor, in which a novel method is proposed to calibrate the liquid holdup based on three pairs of parallel-wire capacitance probes. The performance of the sensor is analyzed in terms of the flow structures detected by mini-conductance array probes.

A Simple Model to Determine the Trends of Electric Field Enhanced Water Dissociation in a Bipolar Membrane

This work is concentrated on elucidating the mechanism of the electric field enhanced water dissociation. A simple model was established for the theoretical current-voltage characteristics in water dissociation process on a bipolar membrane based on the existence of a depletion layer and Onsager's theory. Particular attention was given to the influence of applied voltage on depletion thickness and the dissociation constant. The factors on the water splitting process, such as water diffusivity, water content, ion exchange capacity, temperature, relative permittivity, etc. Were adequately analysed based on the derived model equations and several suggestions were proposed for decreasing the applied voltage in practical operation. The water dissociation tests were conducted and compared with both the theoretical calculation and the measured current-voltage curves reported in the literature, which showed a very good prediction to practical current-voltage behavior of a bipolar membrane at high current densities when the splitting of water actually commenced.

Heat and mass transfer enhancement in triangular pyramid solar still using CNT-water nanofluid

This work represents a 3 D numerical study of the effects of carbon nanotube(CNT)-water nanofluids on the double diffusive convection inside the triangular pyramid solar still.This numerical investigation is performed for wide ranges of governing parameters such as buoyancy ratio(-10≤N≤0),volumetric fraction of nanoparticles(0≤Φ≤0.05) and Rayleigh number(10^(3)≤Ra≤10^(5)).The results are presented in terms of flow structure,temperature field,heat and mass transfer rates variations.It was found that the buoyancy ratio can be considered as an optimizing parameter for the heat and mass transfer,and the use of CNT has a positive effect on the solar still performances.

Potential vorticity analysis of quasi-biweekly rainfall events over the Yangtze Basin in summer 2014

A series of heavy rainfall events occurred over the Yangtze River Valley(YRV)in summer 2014,which were modulated by the 10-20-day quasi-biweekly oscillation(QBWO).Thus,the strongest QBWO cycle for the period 10-24 July was used as a representative case to reveal the dynamical mechanism for the QBWO of the YRV rainfall from the potential vorticity(PV)perspective and based on MERRA-2 reanalysis data.The quasi-biweekly YRV rainfall was found to depend closely on the QBWO of the upper-tropospheric South Asian high(SAH),with the SAH configuration modified by the southward-intruding midlatitude high PV stream along with southwestward-advected high PV,altering the divergent condition over the YRV.Quantitative diagnoses for the anomalous vertical motion demonstrated that,in the wet phase of the QBWO cycle,the upper-tropospheric southward-intruding high PV stream acted as a positive PV advection,while negative PV advection was generated due to the lower-tropospheric southerlies,thereby forming a positive vertical gradient of horizontal PV advection to induce evident isentropic-displacement ascending motion.On the other hand,the southward-intruding high PV stream extended downward to the middle troposphere,causing the isentropic surfaces to become more sloping,thus producing a strong isentropic-gliding ascending component.Subsequently,the stronger diabatic heating-related ascending motion was induced to generate positive rainfall anomalies over the YRV.The opposite situation arose in the dry phase,with weak descending motion in magnitude.

Osmotic concentration of succinic acid by forward osmosis:Influence of feed solution pH and evaluation of seawater as draw solution

In this study, we investigated the essential role of feed solution pH so as to gain insights into the transport mechanisms of succinic acid concentration by osmotically-driven forward osmosis （FO） process. FO performances including water flux and bidirectional transport of succinate and chloride anions were systematically examined using cellulose triacetate-based FO membrane. Additionally, real seawater was explored as draw solution. Experimental results revealed that the pH-dependent speciation of succinic acid can affect the FO performances. Ionization of succinic acid at higher solution pH enhanced the osmotic pressure of feed solution, thus leading to lower water flux performance. A strong effect was pointed out on the succinate rejection for which nearly 100% rejections were achieved at pH above its pKa2 value. The rejection of succinate increased in the following order of chemical form： C2H4C2O4H2 〈 C2H4C2OH- 〈 C2H4C2O24-. With real seawater as the draw solution, low to moderate water fluxes （〈4 L. m- 2. h- 1 ） were observed. The divalent succinate anion was highly retained in the feed side despite differences in the succinic acid feed concentration at pH of approximately 6.90.

Palladium-Carbon Composite Nanoparticle Films with Enhanced Electrocatalytic Activity for Hydrogen Peroxide Sensors

A nanocomposite electrocatalyst was prepared with the method of cluster beam deposition of palladium nanoparticle thin lms on carbon nanoparticle supporting layers and used as sensitive nonenzyme hydrogen peroxide sensors. An enhancement on the electrocatalytic activity of the palladium nanoparticles toward H2O2 reduction was observed, which was related to the coverage of the carbon nanoparticles. With one monolayer of carbon nanoparticles, the H2O2 detection sensitivity reached the maximum, which was more than twice of that of the pure Pd nanoparticles.

Selected Experiences with Optimization Tests of the Kaplan-Type Hydraulic Turbines

The paper presents selected experience of the authors resulting from the optimization tests of double-regulated water turbines. Among the methods for measuring the discharge through the turbine used in such tests, particular attention was paid to index methods allowing to measure the relative discharge through the turbine-the index current meter method and the methods based on measuring the differential pressure between two points properly located at the turbine flow system （i.e., Winter-Kennedy method）. These methods contribute to effective reduction of the cost of optimizing the turbine that is extremely important for small hydropower plants regarding installed capacity. The paper presents selected examples of the optimization tests and experiences that arise from these tests.

Hierarchical iridium-based multimetallic alloy with double-core-shell architecture for efficient overall water splitting

The overall water splitting for hydrogen production is an effective strategy to resolve the environmental and energy crisis. Here, we report a facile approach to synthesize the Ir-based multimetallic, hierarchical, double-coreshelled architecture(HCSA) assisted by oil bath reaction for boosting overall water splitting in acidic environment. The Ir Ni Cu HCSA shows superior electrocatalytic activity for hydrogen evolution reaction(HER) and oxygen evolution reaction(OER), which are comparable to commercial Pt/C and better than IrO2. The Ir Ni Cu HCSA exhibits remarkably catalytic efficiency as bifunctional catalyst for overall water splitting where a low cell voltage of 1.53 V is enough to drive a current density of 10 mA cm^-2 and maintains stable for at least 20 h. The presented work for the design and synthesis of novel Ir-based multimetallic architecture paves the way for highperformance overall water splitting catalysis.