Wang Shaoqing

Investigation on quenching at a high-angle Cu grain boundary on an atomic scale

We have performed molecular dynamics simulations of structural changes due to quenching the melting interface at a Cu Σ5(310)/[001] symmetrical tilt grain boundary. The simulation results suggest that the grain boundary structures due to quenching are different from those due to heating up to the same temperature. The calculated atom density profiles show that the grain boundary structures can be significantly changed as they are quenched to quite low temperatures.

SEAWATER INTRUSION TYPES AND REGIONAL DIVISIONS IN THE SOUTHERN COAST OF LAIZHOU BAY

The southern coast of Laizhou Bay, Bohai Sea, is one of the areas in China most seriously impacted by seawater intrusion. Based on the sources of intruding waterbodies, seawater intrusion can be divided into two types: intrusion of saline water derived from modern seawater, and intrusion of subsurface brine and saline water derived from paleo-seawater in shallow Quaternary sediments. There are some distinct differences in their formation, mechanism and damage. The subsurface brine intrusion is a special type, which can cause very serious disaster.The coastal landform and the Quaternary hydrogeological environment are predominant factors in the classification of seawater intrusion types. Various coastal environments in different coastal sections result in three types of intrusion: seawater intrusion, saline groundwater intrusion, and mixed seawater and saline water intrusion, in the southern coast of Laizhou Bay, which can be divided into four areas: the seawater intrusion area in the northern Laizhou City coast, the mixed seawater and saline groundwater intrusion area in the Baisha River-Jiaolai River mouth plain area, the mixed seawater and saline groundwater intrusion area in the Weihe River mouth plain area northern Changyi county coast, and the saline ground-water intrusion area in the northern Shouguang plains.

Characterization of Ag adsorption on TiC(001) substrate: an ab initio study

Ag adsorptions at 0.25-3 monolayer (ML) coverage on a perfect TiC(001) surface and at 0.25ML coverage on C vacancy are separately investigated by using the pseudopotential-based density functional theory. The preferential adsorption sites and the adsorption-induced modifications of electronic structures of both the substrate and adsorbate are analysed. Through the analyses of adsorption energy, ideal work of separation, interface distance, projected local density of states, and the difference electron density, the characteristic evolution of the adatom-surface bonding as a function of the amount of deposited silver is studied. The nature of the Ag/TiC bonding changes as the coverage increases from 0.25 to 3 MLs. Unlike physisorption in an Ag/MgO system, polar covalent component contributes to the Ag/TiC interfacial adhesion in most cases, however, for the case of 1-3 ML coverage, an additional electrostatic interaction between the absorption layer and the substrate should be taken into account. The value of ideal work of separation, 1.55 J/m(2), for a 3-ML-thick adlayer accords well with other calculations. The calculations predict that Ag does not wet TiC(001) surface and prefers a three-dimensional growth mode in the absence of kinetic factor. This work reports on a clear site and coverage dependence of the measurable physical parameters, which would benefit the understanding of Ag/TiC(001) interface and the analysis of experimental data.

Middle Holocene warm period and sea level high in coastal areas, North China

Relevant geological, geographical, archaeological data were collected to study the characteristics of middle Holocene warm period and sea level high on North China coast. Middle Holocene climate and sea level change on North China coast were correlated to warm marine environment events in about 8-3 ka B.P. The sea level in about 8 ka B.P. was higher than present mean sea level, then fluctuated for 5 000 years and after that it became even in 3 ka B.P. The highest sea level occurred in about 6-5 ka B.P.; the maximum was about 2–3 m and minimum was about 1–2 m.

Sporo-pollen assemblage and paleoclimate events in shelf area of the southern Yellow Sea since 15 ka B. P.

Based on the authors’ 1986 to 1994 sporo-pollen assemblage analysis in the southern Yellow Sea area, data from 3 main cores were studied in combination with14C, palaeomagnetic and thermoluminescence data. The evolution of the paleoclimate environments in the southern Yellow Sea since 15ka B. P. was revealed that, in deglaciation of the last glacial period, the climate of late glaciation transformed into that of postglaciation, accompanied by a series of violent climate fluctuations. These evolution events happened in a global climate background and related to the geographic changes in eastern China. We distinguished three short-term cooling events and two warming events. Among them, the sporo-pollen assemblage of subzone A1 showed some cold climate features indicating that a cooling event occurred at about 15-14ka. B. P. in early deglaciation. This subzone corresponds to the Oldest Dryas. In subzone A3, many drought-enduring herbal pollens and some few pollens of cold-resistantPicea, Abies, etc. were found, which indicated that a cooling event, with cold and arid climate, occurred at about 12-11ka. B. P. in late deglaciation. This subzone corresponds to the Younger Dryas. The sporo-pollen assemblage of zone B showed warm and arid climate features in postglaciation. Although the assemblage of subzone B2 indicated a cold and arid climate environment, the development of flora in subzone B2 climate was less cold than that in A3. Subzone B2 indicated a cooling event which occurred at about 9ka B. P. in early olocene. Subzone A2, with some distinct differences from subzone A1 and A3, indicated a warming event which occurred at 14-13ka. B.P. and should correspond to a warming fluctuation. The sporo-pollen assemblage of zone C showed features of warn-moist flora and climate, and indicated a warming event which universally occurred along the coast of eastern China at 8-3 ka B. P. in middle Holocene, and its duration was longer than that of any climate events mentioned above. This period was climatic optimum and belonged to an altithermal period in postglaciation.

FIRST-PRINCIPLES INVESTIGATION OF THE THERMODYNAMICS PROPERTIES OF Al3Sc AND Al3Zr INTERMETALLICS

A first-principles investigation of the structural and thermodynamic properties of Al3Sc and Al3Zr intermetallics has been conducted using the norm-conserving pseudopotentials within the local density approximation in the frame of the density functional theory (DFT) and the density functional perturbation theory (DFPT) with the ABINIT code. The calculated formation enthalpy and cohesive energy results show that both phases have strong alloying ability and Al3Zr has a higher structural stability than Al3Sc phase. By means of calculations, the relationships of the vibrational free energy constant-volume specific heats entropy bulk modulus and thermal expansion with the elevated temperatures are given. The calculated bulk modulus indicates that Al3Sc and Al3Zr phases can improve the high-temperature creep resistance properties of aluminum alloys. The calculated datum of the thermal expansion and the diffusion speed of Sc and Zr in Al can explain the mechanism that the solder wire with Sc and Zr can improve the strength of welding gap and the resistance ability of hot crack.

The forming-storing environment and abundance conditions of quaternary underground brine in the embayed coast of Qingdao

The discovery of useful brine resources in the embayed coastal zone of Qingdao is an important achievement in research on potential underground brine resources stored in Quaternary littoral facies in the North China coast. The Holocene transgression in this area provided the ancient seawater sources for forming brine. In spite of the unfavorable geological conditions (narrow littoral plain, shallow and thin Quaternary sedimentary strata) Qingdaos embayed coast has deposition basins with bay-in-bay and weir dam ideal for gathering brine. The geologic structure of the littoral Quaternary deposition basin and hydrologic condition (deficient runoff) comprise favorable environment for the formation and abundance of underground brine.The embayed coast geomorphy controls the distribution of brine in patches that form small mineral zones in some parts. The brine aquifer sediment series formed under Quaternary littoral plain sedimentary and hydrogeologic environment are usually single phreatic ones. Part of the thick deposit areas consists of phreatic and poorly confined aquifers. Near the river mouth, there can sometimes be brine aquifers interbedded with saline water ones. The basement of the brine ore deposits is comprised of Mesozoic rock formations. Underground brine is scattered almost all over the littoral plain and only in the larger plains area is the narrow saline water belt distributed beyond the brine zone. The structural features of the brine aquifer sediment series along the Jiaozhou Bay Coast are typical of those in the North China coast. We name it “Jiaozhou Bay Type”. Its features are different from those of other brine aquifer sediment series such as “Laizhou Bay Type” and “Bohai Bay Type” in the littoral plain of the Bohai Sea.

FIRST-PRINCIPLES STUDY OF THE PHASE STRACTURES OF Al-Sc ALLOYS

The formation enthalpies of the Al-Sc compounds and the Al-rich solid solution phase have been studied from first-principles based on plane-wave pseudopotential method. To calculate the electronic structure of the disordered Al-Sc alloys, the small-size special quasirandom structures (SQS), which exhibited similar structure environments as that of the disordered Al-Sc alloys, are employed. It is shown that the Sc atoms in supersaturated solid solution tend to segregation forming ordered Al3Sc (L12) and AlSc (L10) precipitations. The nucleation mechanism of Al3Sc precipitation phase in the supersaturated Al(Sc) solid solution is analyzed in terms of the calculated densities of states and distributions of electron densities.