关于钢材力学性能试验试样断口厚向开裂的若干问题

针对钢铁产品力学性能试验试样(包括拉伸、弯曲、静压、冲击、落锤撕裂和断裂韧度试验试样)断口厚向开裂现象中涉及的试样断口厚向开裂的原因、试样断口分离/分层开裂如何界定,是否认定为欠缺/缺陷,船板静压大断口试验的合理性以及钢材的合乎使用性等若干问题进行了讨论分析,提出了一些新的观点和建议。

AN APPROACH TO IMPROVE PSEUDORANGE DIFFERENTIAL GPS

The pseudorange residual error of imperfect correction of the ionospheric time delay in pseudorange (PR) differential global positioning system (DGPS) is analyzed. The different vertical total electron content (TEC) and slant factors at the pierce points of satellite signals are the reasons of the residual error. An improved pseudorange differential approach is proposed and the effect of this new PR differential operation verified by using the simulation.

Separation and analysis of aromatic hydrocarbons from two Chinese coals

Separation and analysis of aromatic hydrocarbons (AHs) from coals is of considerable significance for both fuel and non-fuel use of the coals. In present work two Chinese bituminous coals were selected for separation of AHs by ultrasonic extrac-tion with CS2 followed by column chromatography using hexane as eluent. A series of AHs were separated from the two coals and analyzed by GC/MS. FTIR was employed to characterize the raw coals and the extracted residues. The results of GC/MS analysis show that the separated AHs are mono- to tetracyclic arenes, among which the principle AHs are alkyl naphthalenes and phenan-threnes. Obvious differences in the composition and the structure of AHs exist between the two coals, i.e., the AHs from Tongting coal tend to be higher rings compared to those from Pingshuo coal both from the variety and from the abundance of the AHs. FTIR analysis shows that the raw and extracted coals are similar in terms of functional groups, suggesting that the composition and structure of CS2 extract, especially the AHs, from coals can be used to interpret the coal structure to some extent.

Dynamic mechanical properties and instability behavior of layered backfill under intermediate strain rates

To obtain dynamic mechanical properties and failure rule of layered backfill under strain rates from10to80s-1,impactloading test on layered backfill specimens(LBS)was conducted by using split Hopkinson pressure bar system.The results indicatethat positive correlation can be found between dynamic compressive strength and strain rate,as well as between strength increasefactor and strain rate.Dynamic compressive strength of LBS gets higher as the arithmetic average cement-sand ratio increases.Compared with static compressive strength,dynamic compressive strength of LBS is enhanced by11%to163%.In addition,theenergy dissipating rate of LBS lies between that of corresponding single specimens,and it decreases as the average cement contentincreases.Deformation of LBS shows obvious discontinuity,deformation degree of lower strength part of LBS is generally higherthan that of higher strength part.A revised brittle fracture criterion based on the Stenerding-Lehnigk criterion is applied to analyzingthe fracture status of LBS,and the average relevant errors of the3groups between the test results and calculation results are4.80%,3.89%and4.66%,respectively.

Discrete AKNS-D Hierarchy

In this paper, we consider the discrete AKNS-D hierarchy, make the construction of the hierarchy, prove the bilinear identity and give the construction of the τ-functions of this hierarchy.

STUDY ON DETERMINATION OF TRACE Fe BY Fe(Ⅱ)-VA THIN LAYER RESIN PHASE SPECTROPHOTOMETRY

A new method for the determination of Fe by thin layer resin phase spectrophotometry in alkali condition was reported. The complex anion formed by Fe（Ⅱ） and VA was absorbed on the 717w resin and Fe was determined by making thin layer. This method had a high sensitivity （ε620= 3.0×10^5L/mol.cm）, which was 15 times higher than that of liquid phase spectrophotometry. It had been proved a satisfactory precision （5.01μg Fe, n=6, RSD=1.8%）. The trace Fe in natural water was determined and the recovery was 97%.

Separation of Recombinant Geranylgeranyl Diphosphate Synthase of Deinococcus radiodurans from Expressed Strain Cell Homogenate by Immobilized Metal Affinity Chromatography on a Characterized Monolithic Cryogel Column

Geranylgeranyl diphosphate synthase （GGPPS） plays a key role in the biosynthesis of antioxidative carotenoid from the extremely radioresistant bacterium Deinococcus radiodurans. In this work, the recombinantGGPPS expressed in Escherichia coli by cloning and transforming the gene dr1395 of D. radiodurans was isolated rapidly by an immobilized metal affinity supermacroporous cryogel, i.e., Cu2＋-iminodiacetic acid （IDA）-cryogel. The properties of the Cu2＋-IDA-cryogel were characterized using capillary-based mathematical model and experi- mental measurements. The obtained protein samples were analyzed by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis （SDS-PAGE）. The porosity of the present Cu2＋-IDA-cryogel is 90.4% and the water permeability is 5.04x10-12 m2. From the capillary-based model, this cryogel presents a slightly wide normal pore （capillary） size distribution with the mean diameter of 55.2 μm, the standard deviation of 28.0 μm and the half of skeleton wall thickness of 2.8 μm. The pore size distribute from about 10 to 141 μm and the effective tortuosity of these capillary pores increases from 2.60 to 9.05. The isolation of the GGPPS from cell homogenate can be achieved at the flow velocity of 3.40x 10-4μm. s-1 by the Cu2＋-IDA-cryogel bed. High-purity GGPPS （about 91.4%） is obtained according to the SDS-PAGE analysis of the elution samples, indicating that the present method is a promising, simple and ef- fective atmroach to isolate GGPPS from cell homoenate of engineering, strains.

Experimental Investigation of Flow Instabilities in a Laminar Separation Bubble

The present paper reports the results of a detailed experimental study aimed at investigating the dynamics of a laminar separation bubble, from the origin of separation up to the breakdown to turbulence of the large scale co- herent structures generated as a consequence of the Kelvin-Helmholtz instability process. Measurements have been performed along a fiat plate installed within a double contoured test section, designed to produce an adverse pressure gradient typical of Ultra-High-Lift turbine blade profiles, which induces the formation of a laminar separation bubble at low Reynolds number condition. Measurements have been carried out by means of comple- mentary techniques： hot-wire （HW） anemometry, Laser Doppler Velocirnetry （LDV） and Particle Image Veloci- metry （PIV）. The high accuracy 2-dimensional LDV results allow investigating reverse flow magnitude and both Reynolds normal and shear stress distributions along the separated flow region, while the high frequency response of the HW anemometer allows analyzing the amplification process of flow oscillations induced by instability mechanisms. PIV results complement the flow field analysis providing information on the generation and evolu- tion of the large scale coherent structures shed as a consequence of the separated shear layer roll-up, through in- stantaneous velocity vector maps. The simultaneous analysis of the data obtained by means of the different meas- uring techniques allows an in depth view of the instability mechanisms involved in the transition/reattachrnent processes of the separated shear layer.

Numerical investigation on synthetic jet flow control inside an S-inlet duct

The high degree of centerline curvature and cross-stream pressure gradient in S-inlet ducts gives rise to boundary layer separation and secondary flows, which result in poor pressure recovery and non-uniform flow in the outlet interface with the engine. The flowfield in ducts is three-dimensional due to the existence of secondary flow, so ordinary two-dimensional actuations have poor effect on reforming the flow. Synthetic jet actuations extended in different spanwise positions were employed to manipulate the flow, and compared with the two-dimensional actuation, The interaction mechanics between flow separation and secondary flow was studied at first. It was found that the secondary flow enhanced Ol~ weakened flow separation depending on the spanwise position of synthetic jet actuators. Moreover, the J flow separation enhanced the secondary flow, thus causing lower pressure recovery and flow distortion in the duct outlet. The actuators located at different spanwise positions will weaken the secondary flows by improving the flow separation to get energetic and uniform main flow.

High-performance polyamide nanofiltration membrane with arch-bridge structure on a highly hydrated cellulose nanofiber support

Nanofiltration(NF)membranes with outstanding performance are highly demanded for more efficient desalination and wastewater treatment.However,improving water permeance while maintaining high solute rejection by using the current membrane fabrication techniques remains a challenge.Herein,polyamide(PA)NF membrane with archbridge structure is successfully prepared via interfacial polymerization(IP)on a composite support membrane of saltreinforced hydrophilic bacterial cellulose nanofibers(BCNs)nanofilm/polytetrafluoroethylene(BCNs/PTFE).The strong hydration of BCNs promotes Marangoni convection along water/organic solvent interface during the IP process,which creates extra area for interfacial reaction and produces a thin PA active layer with arch-bridge structures.These arch-bridge structures endow the resulting PA active layer with substantial larger active area for water permeation.Consequently,the PA NF membrane exhibits exceptional desalination performance with a permeance up to 42.5 L m^-2h^-1bar^-1 and a rejection of Na2SO4as high as 99.1%,yielding an overall desalination performance better than almost all of the state-of-the-art NF membranes reported so far in terms of perm-selectivity.

Analysis of the ionospheric variability based on wavelet decomposition

In this work,the ionospheric variability is analyzed by applying the wavelet decomposition technique to the noontime fo F2,F10.7,interplanetary magnetic field(IMF)Bz,Ap,and lower thermospheric temperature at pressure of 10?4 h Pa in 2002.Results show that the variance of periodic oscillations in the ionosphere is largest in the 2–4-day period and declines with the increase of the period.The maximum variance of the periodic oscillations in solar irradiation is in the 16–32-day period.For geomagnetic activities,most of the variance is about equally distributed on intervals of periods shorter than 32 days.Variance distributions of IMF Bz and lower thermospheric temperature are similar to those of the ionosphere.They show the maximum in the 2–4-day period and decline with the increase of the period.By analyzing the distributions of the variances,the potential connections between the ionosphere and the external sources are discussed.