一种软件流水的反流水算法

软件流水是一种循环程序的优化技术,已经广泛应用于现代优化编译器中.为了充分利用VLIWDSP处理机的指令级并行性,必须使用软件流水技术对DSP程序进行优化.然而,在串行源代码不存在的情况下,对软件流水后的原始代码进行变换、理解、测试和调试,并转换成其他处理机的代码是非常困难的.提出了一种反流水技术,它能够将软件流水后的优化汇编代码反向转换成语义等价的相应代码.通过20个程序的初步实验,验证了所提出的反流水算法的正确性.

IA-64软件流水的反流水算法研究

软件流水是一种开发循环程序指令级并行性的技术,它通过并行执行连续的多个迭代来加快循环的执行速度。而在逆向工程中,软件流水却为逆向翻译带来了困难。为此,基于IA-64平台,提出了一种反流水算法,针对循环中包含软件流水的汇编代码进行处理,将其反向转换成语义等价的串行代码,并通过实验验证了该算法的有效性,为在二进制翻译中处理软件流水代码奠定了基础。

一种IA-64下的反软件流水算法

软件流水是一种循环程序的优化技术,它可以有效地提高指令级并行性。由于处理机的实现方法各不相同,在一种处理机上经过软件流水优化后的循环代码很难在其它处理机中移植和使用。反软件流水是软件流水的逆向操作,它可以消除循环代码中的软件流水特性,以便于代码在不同平台上的移植。基于IA-64体系结构,分析了软件流水的代码特点,提出了反流水算法,用于将ICC编译器编译后的可执行二进制代码消除软件流水特性,转换成语义等价的C代码。

IA-64二进制翻译中软件流水代码消除技术

IA-64体系结构使用软件流水提高程序的执行性能,但产生的二进制代码跟机器特性紧密相关,给代码跨平台移植造成了困难。该文针对IA-64体系结构下软件流水的特点,提出2种软件流水代码消除方法,它能够将软件流水代码转换成语义等价无硬件依赖的串行代码,实验验证了这2种方法的有效性。

Recent advances in design of hydrogen evolution reaction electrocatalysts at high current density:A review

The electrolysis of water powered by renewable energy sources offers a promising method of"green hydrogen"production,which is considered to be at the heart of future carbon-neutral energy systems.In the past decades,researchers have reported a number of hydrogen evolution reaction(HER)electrocatalysts with activity comparable to that of commercial Pt/C,but most of them are tested within a small current density range,typically no more than 500 mA cm^(-2).To realize the industrial application of hydrogen production from water electrolysis,it is essential to develop high-efficiency HER electrocatalysts at high current density(HCD≥500 mA cm^(-2)).Nevertheless,it remains challenging and significant to rational design HCD electrocatalysts for HER.In this paper,the design strategy of HCD electrocatalysts is discussed,and some HCD electrocatalysts for HER are reviewed in seven categories(alloy,metal oxide,metal hydroxide,metal sulfide/selenide,metal nitride,metal phosphide and other derived electrocatalysts).At the end of this article,we also pro-pose some viewpoints and prospects for the future development and research directions of HCD electrocatalysts for HER.

Coupled effect of cement hydration and temperature on rheological properties of fresh cemented tailings backfill slurry

The fluidity of fresh cemented tailings backfill（CTB） slurry depends on its rheological properties. Hence, it is crucial to understand the rheology of fresh CTB slurry, which is related to the cement hydration progress and temperature evolution within CTB mixtures. For this reason, a numerical model was developed to predict the evolution of the rheological properties of fresh CTB slurry under the coupled effect of cement hydration and temperature. Experiments were conducted to investigate the rheological behaviours of the fresh CTB slurry. By comparing the simulated results with the experimental ones, the availability of this developed model was validated. Thereafter, the model was used to demonstrate the coupled effect of cement hydration and temperature on the evolution of fresh CTB slurry＇s rheological properties, under various conditions（initial CTB temperature, cement to tailings ratio, and water to cement ratio）. The obtained results are helpful to better understanding the rheology of CTB slurry.

IA-64二进制翻译中旋转寄存器的处理方法

寄存器旋转技术为每一个循环迭代都提供一组专用的寄存器,从而减少对循环展开的需求。针对如何在IA-64二进制翻译中处理旋转寄存器的问题,提出一种在二进制翻译器的后端直接模拟寄存器旋转特性的解决方案,实验结果证明了该方法在二进制翻译中处理软件流水操作代码的有效性。

Energy Recovery Device with a Fluid Switcher for Seawater Reverse Osmosis System

Energy recovery device （ERD） is an important part of the seawater reverse osmosis （SWRO） desalination system. There are principally two kinds of ERDs, the centrifugal type and the positive displacement （PD） type. The PD type is of extensive concern and is preferred in large-scale plants. In this article, an innovative fluid switcher was presented and a two-cylinder hydraulic energy recovery unit with a lab-scale fluid switcher was set up. Tap water was used as the working medium instead of the actual seawater and brine in SWRO desalination plants. Under steady state operating conditions, the experimental results were obtained on the variations of the pressure and flow rate to and from the energy recovery unit. The hydraulic recovery efficiency （En） of the energy recovery unit with the fluid switcher reached up to 76.83%.

Reaction thrust characteristics of high-pressure submerged water jet of cylinder nozzles

The shapes and geometrical parameters of nozzles are key factors for fluidics. The relationship among the reaction thrust, flow rate pressure, diameter do and length L of a cylinder nozzle is analyzed theoretically. The simulation of the flow field characteristics was conducted via the FLUENT computational fluid dynamics package. Effects of the inlet conditions and the nozzle dimensions on the reaction thrust of a water jet were addressed particularly. The reaction thrust experiments were performed on a custom-designed test apparatus. The experimental results reveal that a） the nozzle diameter and the inlet conditions exert great influence on the water jet reaction thrust; and b） for L≤4d0, where the nozzle is treated as a thin plate-orifice, the reaction thrust is independent of nozzle length; for L〉4d0, where the nozzle is treated as a long orifice, the reaction thrust can reach maximum under the condition of a certain flow rate. These findings lay a theoretical foundation for the design of nozzles and have significant value, especially for the future development of high-oressure water-let orooulsion technology.

Streamflow response to shrinking glaciers under changing climate in the Lidder Valley,Kashmir Himalayas

The study investigated the streamflow response to the shrinking cryosphere under changing climate in the Lidder valley, Upper Indus Basin(UIB), Kashmir Himalayas. We used a combination of multitemporal satellite data and topographic maps to evaluate the changes in area, length and volume of the glaciers from 1962 to 2013. A total of 37 glaciers from the Lidder valley, with an area of 39.76 km^2 in 1962 were selected for research in this study. It was observed that the glaciers in the valley have lost ~28.89 ±0.1% of the area and ~19.65 ±0.069% of the volume during the last 51 years, with variable interdecadal recession rates. Geomorphic and climatic influences on the shrinking glacier resources were studied. 30-years temperature records(1980-2010) in the study area showed a significant increasing trend in all the seasons. However, the total annual precipitation during the same period showed a nonsignificant decreasing trend except during the late summer months(July, August and September), when the increasing trend is significant. The depletion of glaciers has led to the significant depletion of the streamflows under the changing climate in the valley. Summer streamflows(1971-2012) have increased significantly till mid-nineties but decreased significantly thereafter, suggesting that the tipping point of streamflow peak, due to the enhanced glacier-melt contribution under increasing global temperatures, may have been already reached in the basin. The observed glacier recession and climate change patterns, if continued in future, would further deplete the streamflows with serious implications on water supplies for different uses in the region.

Numerical Simulations on Countercurrent Gas-Liquid Flow in a PWR Hot Leg with Air-Water Flow in a 1/15th Scale-Model

To clarify the countercurrent flow in a PWR hot leg under reflux condensation, numerical simulations of countercurrent air-water flow for a 1/15th scale model of the PWR hot leg were conducted using the two-fluid model implemented in CFD software. In this paper, the effect of expansion of the inclined pipe, which is the actual plant geometry, was evaluated. When increasing the air velocity, CCFL characteristics and the mechanism of flow pattern transition had significant differences between the case with and without expansion of the inclined pipe. CCFL characteristics were mitigated in the case with expansion. The effect of computational grid size was also discussed. When the supplied water velocity was small, the predicted flow pattern transition point agreed well with the measured data by increasing the number of cells. On the other hand, when the air velocity was decreasing, there were no significant differences in each case.

Preparation of Fe_3O_4/Mn OOH core–shell nanoparticles by a high-frequency impinging stream reactor

Well-defined Fe3O4/Mn OOH nanoparticles with 61.1 emu·g-1in magnetization intensity and 90.53 m2·g-1in surface area have been synthesized by a new-style of high-frequency impinging stream(HFIS)reactor.In this reactor,two streams first collided together to form nano Fe3O4suspension,which subsequently flew through an S-shaped main channel to generate high-frequency reversing high-gravity fields.At the same time,24 thin liquid sheets impinged into the main channel at the frequencies higher than 100 Hz to create nano Fe3O4/Mn OOH colloids.The obtained powders were characterized by transmission electron microscopy/energy dispersive spectrometer(TEM/EDS),X-ray diffraction(XRD),Brunner–Emmet–Teller(BET)and vibrating sample magnetometer(VSM).Experimental results indicated that low coating ratio prolonged the induction period of heterogeneous nucleation.The high-frequency impingements of 24 thin liquid sheets greatly accelerated the macro-mixing and the initial dispersion.The high-frequency reversing high-gravity fields promoted the mesoand micro-mixing.As a result,nano Fe3O4cores were fleetly and uniformly covered by Mn OOH precursor.As a continuously operated and static high-gravity reactor,the high-frequency impinging stream(HFIS)reactor is being developed to the large-scaled and low-cost production of various nanocomposites.

Backward Calculation Based on the Advection and Diffusion of Oil Spills on the Sea Surface

In the light of the problem of oil pollution brought about by ships, in this paper we present the concept of backward tracing oil spills. In the course of backward calculation of the two-dimensional convection & diffusion equation, on the one hand, the advection term itself has the strong unilateral property, which means information in the upper reaches is transmitted downstream via the advection term; on the other hand, because of the opposite direction of calculation, it is essential for information to be conveyed upstream by means of the advection term. In addition, unlike that in the forward calculation, the diffusion term in the backward calculation is prone to accumulate errors, and thus renders the whole scheme unstable. Therefore, we adopt the central difference to deal with both the convectional term and the diffusion term. By examining two practical examples (1) under the unlimited boundary condition, and (2) under the limited boundary condition, it is proven that this method could achieve fundamentally satisfactory results not only in the open ocean but also in the closed or semi-closed bay.

Responses of Hydrological Processes to Climate Change in the Zhujiang River Basin in the 21st Century

In this study, discharge at the outlet of Xijiang River, the biggest sub-basin of the Zhujiang River, was simulated and projected from 1961 to 2099 using the hydrological model HBV-D. The model uses precipitation and temperature data from CISRO/MK3 5, MPI/ECHAM5, and NCAR/CCSM3 under three greenhouse gas emission scenarios (SRES A2, A1B, B1). The results in water resources and flood frequency suggest that annual precipitation and annual runoff would increase after 2050 relative to the reference period of 1961-1990. In addition, increasing trends have been projected in area averaged monthly precipitation and runoff from May to October, while decreasing trends in those from December to February. More often and larger floods would occur in future. Potential increase in runoff during the low-flow season could ease the pressure of water demand until 2030, but the increase in runoff in the high-flow season, with more often and larger floods, more pressure on flood control after 2050 is expected.

Water-recycled Cassava Bioethanol Production Integrated with Two-stage UASB Treatment

Considering limited success in target-hitting discharge from alcohol industry, our attention was directed toward a recycling use of distillery spentwash (DS) in cassava bioethanol production by using a two-stage up-flow anaerobic sludge blanket bioremediation (TS-UASBB). With the TS-UASBB, 2 4 SO , COD, N and P in the effluent from the DS degraded significantly and their concentrations were kept at 0.2 g·L -1 , 2.0 g·L -1 , 1.0 g·L -1 and 15 mg·L -1 , respectively, in 13 batch processes for water-recycled ethanol fermentation. With the effluent used directly as dilution water, no heat-resistant bacteria were found alive. The thirteen-batch ethanol production individually achieved 10% after 48 h fermentation. The starch utilization ratio and total sugar consumption were 90% and 99.5%, respectively. The novel water-recycled bioethanol production process with ethanol fermentation and TS-UASBB has a considerable potential in other starchy and cellulosic ethanol production.

Oxygen Transfer and Hydrodynamics in a Flexible Fibre Biofilm Reactor for Wastewater Treatment

A flexible fibre biofilm reactor was developed for treatment of organic wastewaters.The hydrodynamic characteristics and mass transfer coefficients of oxygen were studied and compared with those of the conventional activated sludge processes.Tracer experiments were performed to obtain the residence time distributions of the reactors.The results indicated that both reactors could be treated as mixed flow reactors.The effects of flow rates of water and air on the overall mass transfer coefficient of oxygen were investigated,and the correlations between the mass transfer coefficient and the ratio of flow rates were obtained.Compared to the conventional activated sludge reactor,the mass transfer coefficients in the flexible fibre reactor were similar to but slightly lower,and less sensitive to the variation in the ratio of flow rates.It indicated that the fibre packing in the reactor hindered the oxygen transfer to some extent.

Hydrodynamics research of wastewater treatment bioreactors

To optimize the design and improve the performance of wastewater treatment bioreactors,the review concerning the hydrodynamics explored by theoretical equations,process experiments,modeling of the hydrodynamics and flow field measurement is presented. Results of different kinds of experiments show that the hydrodynamic characteristics can affect sludge characteristics,mass transfer and reactor performance significantly. Along with the development of theoretical equations,turbulence models including large eddy simulation models and Reynolds-averaged Navier-Stokes (RANS) models are widely used at present. Standard and modified k-ε models are the most widely used eddy viscosity turbulence models for simulating flows in bioreactors. Numerical simulation of hydrodynamics is proved to be efficient for optimizing design and operation. The development of measurement techniques with high accuracy and low intrusion enables the flow filed in the bioreactors to be transparent. Integration of both numerical simulation and experimental measurement can describe the hydrodynamics very well.

Modified two-phase anaerobic baffled process for low-concentration wastewater treatment

In this study low-concentration wastewater was investigated in the integral two-phase anaerobic baffled reactor by determining the removal of COD at various HRT,reflex ratios,and temperatures. Results indicate that the removal efficiency of COD is more than 90% at 25 ℃ and 10-h HRT with no wastewater recycled,and the removal efficiency is up to 88% at 8-h HRT and reflex ratio of 150%. The removal efficiency is decreased with the decreasing temperature and HRT. The removal efficiency of COD is approximately 60% at 10 ℃,which proves that the temperature does not affect it apparently. This research has significance for reducing the cost of wastewater and sludge treatment in cold area.

Hydrodynamics and Mass Transfer of Oily Micro-emulsions in An External Loop Airlift Reactor

This study reports an experimental investigation on hydrodynamics and mass transfer characteristics in a 15.6x10-3 m3 external loop airlift reactor for oil-in-water micro-emulsions with oil to water volume ratio （φ） rang- ing from 3% to 7% （by volume）. For comparative purposes, experiments were also carried out with water. Increase in φ of micro-emulsion systems results in an increment in the gas holdup and a decrease in the volumetric gas-liquid oxygen transfer coefficient and liquid circulation velocity, attributed to the escalation in the viscosity of mi- cro-emulsions. The gas holdup and volumetric mass transfer coefficient for micro-emulsion systems are signifi- cantly higher than that of water system. Two correlations are developed to predict the gas holdup and oxygen trans- fer coefficient

Experimental and CFD Simulations of Pressure Loss through Perforated Plates

This paper presents the experimental pressure loss of water flow through perforated plates with geometry similar to the ones of the bottom end piece of a Pressurized Water Reactors （PWR） fuel element. Geometric features like the number, pattern and diameter of holes were evaluated as well as different inlet chamfers. The recovering pressure profile downstream of the plates was also measured. The experimental results were compared with numerical modeling performed with the commercial Computational Fluid Dynamics （CFD） code CFX 11.0. The analysis of the results shows that the standard k-e turbulence model presents the best compromise between computing time and accuracy for the calculation of the total pressure loss through the perforated plates tested.