Mixed Zone Research Articles

Friction behavior of quenched and tempered steel in partial and gross slip conditions in fretting point contact

Tangential traction caused by friction in contacting surfaces is a major factor in fretting fatigue that increases stress levels and leads to a reduction in fatigue life. Friction in fretting contact was studied in partial, mixed and gross slip conditions on quenched and tempered steel. Measurements were made with sphere-on-plane contact geometry for polished and ground surfaces. Friction was evaluated from on-line energy ratio and, after the tests, from wear marks. A maximum friction coefficient of over 1.0 was measured at mixed slip zone with polished surfaces, whereas ground surfaces promote lower values in similar operating conditions. The friction coefficient dependence on load cycles and loading frequency is also presented and briefly discussed. The friction data and understanding thus gained is to be used for evaluation of crack initiation with the numerical fretting fatigue model.

On the mixing of a confined stratified fluid by a turbulent buoyant plume

We investigate the mixing of a stratified fluid of finite volume by a turbulent buoyant plume. We develop a model to describe the mixing and apply this to both the cases of a two-layer stratification and a continuous stratification. With a two-layer stratification, the plume intrudes at the interface where it supplies an intermediate layer of fluid. This new layer gradually deepens, primarily mixing the original near-source layer of fluid through entrainment. Eventually, this intermediate layer becomes sufficiently buoyant that the plume penetrates into the more distal layer, leaving a partially mixed region between the original layers of fluid. Analysis of new experiments shows that the growth of the intermediate layer depends primarily on the ratio λ of (i) the filling box time, during which the plume entrains a volume of fluid equal to that in the near-source layer, and (ii) the time for the buoyancy of the near-source layer to increase to that of the more distal layer. For small values of λ, the near-source layer becomes approximately well mixed, and the penetration time of the plume scales with the buoyancy evolution time of the near-source layer. In the limit λ ~ O(1), however, the plume penetrates through into the distal layer long before the near-source layer becomes well mixed; instead, at the time of penetration, the plume leaves an intermediate partially mixed zone between the two original layers. We develop a new phenomenological model to account for the mixing in this intermediate layer based on the effective turbulent diffusion associated with the kinetic energy in the plume and compare this with the model for penetrative entrainment proposed by Kumagai (J. Fluid Mech., vol. 147, 1984, p. 105). In comparison with the experimental data, the models provide a reasonably accurate prediction of the plume penetration time, while the diffusive mixing model provides a somewhat more accurate description of the evolution of the density profile for a range 0 < λ < 1. The diffusive mixing model also leads to predictions which are consistent with some new experimental data for the case in which a plume mixes a continuously stratified layer. In particular, the model is able to predict the initial transient mixing of the region between the source and the height at which the plume intrudes laterally in the ambient fluid, thereby providing an advance on the late-time mixing model of Cardoso and Woods (J. Fluid Mech., vol. 250, 1993, p. 277). We consider the implications of these results on the turbulent penetrative entrainment associated with buoyant plumes.

Separating of dislocation ring at finite temperature

We constructed a partial dislocation ring with Burgers vector b=［112］/6 in the glide plane （111） of copper crystal, and studied its self-contraction process in the temperature range, from 0 to 350 K by using molecular dynamics simulations. The results reveal that, at zero temperature the dislocation ring cannot pass the Peierls-Ｎabarro potential barrier, so its migrating velocity is zero; below 50 K, the screw part and the edge part of the dislocation have nearly the same migrating velocity. With the increasing of temperature, the edge dislocation migrates more quickly than the screw dislocation. At a higher temperature, the dislocation core becomes wider, consequently, it may contain more complex internal structures and becomes easier for separating. At the same time, local stress gradient within the mixed dislocation zone becomes steeper and results in the generation of four partial dislocation rings. The four new dislocation rings first grow with time under the influence of original dislocation ring. When the original ring finally disappears, the newly created rings begin to shrink and finally disappear. This is a new dislocation source, different from the Frank-Read，L or double cross-slip type.

Analysis of Crack Tip Plastic Zone for Composites under Small Scale Yielding

Based on mechanics of composite materials, the Tsai-Hill strength criterion expressions are derived under plane stress and plane strain conditions. The analytic solutions of mode Ⅰ, mode Ⅱ and Ⅰ/Ⅱ mixed mode crack tip plastic zone are obtained for an infinite composites plate with a central crack under small scale yielding. The crack tip plastic zones are analyzed for different crack inclination angle β, Poisson ratio v31 and v32. The obtained results show that the size of crack tip plastic zone under plane strain condition is less than that of crack tip plastic zone under plane stress condition, the parameters of β, v31 and v32 affect the size and shape of crack tip plastic zone obviously, and the difference among crack tip plastic zone results for different value of parameters is great. In addition, the solution is applicable to composites as well as isotropy materials.

A novel approach to planting grass - legume pastures in the mixed farming zone of southern inland Queensland, Australia

Reliable establishment of pasture systems with a desirable composition of grasses and legumes remains a challenge in the highly variable climates of the northern grain belt of southern inland Queensland. In this paper, an alternative system is proposed whereby legumes and grasses are planted simultaneously in alternative strips. A 4-year study tested the establishment, production, and botanical composition of the tropical legume species Macroptilium bracteatum cvv. Cardaga and Juanita, Lablab purpureus cv. Endurance, and Clitoria ternatea cv. Milgarra sown as pure stands or with grass strips. The grass strips, and a grass-only treatment, both contained a mix of Panicum maximum cv. Petrie, Dichanthium aristatum cv. Floren, and Bothriochloa insculpta cv. Bisset. L. purpureus was relatively unproductive, yielding ~2000 kg/ha dry matter (DM) produced in each of the first 2 years. M. bracteatum produced 2050 and 3300 kg/ha DM in Years 1 and 2, with declining plant populations and DM in subsequent years. C. ternatea produced 960 kg/ha DM in Year 1, 2730 kg/ha DM in Year 2, and continued to persist throughout the trial, albeit at low DM production levels. The grass-only treatment was dominated by the sown grass species, while the legume-based treatments were dominated by a colonising native species, Dichanthium sericeum, in the fourth and final year. Sowing grass strips adjacent to the legume areas proved a successful strategy, with the proportion of sown grasses in the legume strips increasing to >20% of total DM by Year 4. Soil carbon changes did not differ between treatments, but total C in the top 0.15 m increased from 0.99% in Year 1 to 1.13% in Year 4, representing a net gain of 6.5 t/ha in C over 3 years.

Wear mechanisms in metal-on-metal bearings: The importance of tribochemical reaction layers

Metal-on-metal (MoM) bearings are at the forefront in hip resurfacing arthroplasty. Because of their good wear characteristics and design flexibility, MoM bearings are gaining wider acceptance with market share reaching nearly 10% worldwide. However, concerns remain regarding potential detrimental effects of metal particulates and ion release. Growing evidence is emerging that the local cell response is related to the amount of debris generated by these bearing couples. Thus, an urgent clinical need exists to delineate the mechanisms of debris generation to further reduce wear and its adverse effects. In this study, we investigated the microstructural and chemical composition of the tribochemical reaction layers forming at the contacting surfaces of metallic bearings during sliding motion. Using X-ray photoelectron spectroscopy and transmission electron microscopy with coupled energy dispersive X-ray and electron energy loss spectroscopy, we found that the tribolayers are nanocrystalline in structure, and that they incorporate organic material stemming from the synovial fluid. This process, which has been termed "mechanical mixing," changes the bearing surface of the uppermost 50 to 200 nm from pure metallic to an organic composite material. It hinders direct metal contact (thus preventing adhesion) and limits wear. This novel finding of a mechanically mixed zone of nanocrystalline metal and organic constituents provides the basis for understanding particle release and may help in identifying new strategies to reduce MoM wear.

ElectroData: a FORTRAN Program to Evaluate Rotating Disc Electrode Data

The Rotating Disk Electrode (RDE) hydrodynamic technique is well known as an important tool for obtaining the kinetic parameters of catalytic electrochemical reactions. Using RDE, a significant amount of data can be obtained and mathematical treatment is necessary for the elucidation of the catalytic behavior of materials. This mathematical procedure is normally performed using a spreadsheet through several repetitive steps applied to some hundred current-potential data pairs. To eliminate errors in these tedious calculations, it is convenient to have a computer program that makes calculations feasible and efficient. In this work we selected the FORTRAN language to build the required program. The most important characteristics of ElectroData are the automatic mixed control zone delimitation of RDE curves using a Stavitzky-Golay numerical derivation and smoothing, and the feasibility of obtaining Tafel curves through a Koutecký-Levich procedure to calculate the kinetic parameters of a certain reaction.

Microsatellites Reveal Clonal Growth and Genetically Distinct Groups in Cryptocarya chinensis in Fragmented Lower Subtropical Forest, China

AbstractThe lower subtropical monsoon evergreen broadleaved forest in South China (about 22° ~ 24° N) has a high conservation status, because of its uniqueness and high biodiversity. During the last few decades, most of these forests have been destroyed, and the remaining are being degraded by fragmentation. However, genetic information concerning the effects of fragmentation is currently lacking for plant species in these forests. In this study, therefore, eight microsatellites were used to study six Cryptocaya chinensis fragmented populations in Guangdong Province South China, and the results revealed a complex pattern of genetic variation within and among C. chinensis populations. Firstly, genetic variations demonstrate hitherto undetected clonal growth in C. chinensis. Secondly, current population structure of C. chinensis reflects an interaction between ancient homogeneous level of genetic variation and contemporary bottleneck via fragmentation. Small populations maintain substantial genetic variation of the initial populations through clonal growth, and do not show genetic depauperation compared to larger populations. Finally, two genetically distinct groups (West and Middle- East groups) are found in this area, connected by highly mixed contact zone.

A model of tidally dominated ocean processes near ice shelf grounding lines

Glaciological processes at grounding lines, which divide floating ice shelves from grounded ice sheets, may strongly influence the dynamics and evolution of inland ice. Therefore, understanding the oceanic forcing on ice shelves in this region is of importance to predictions of cryospheric change and sea level rise. As the ocean cavity shallows toward the grounding line, tidal mixing becomes proportionately more important until a tidal front forms, beyond which the water properties are vertically homogenized. The extent of this mixed zone is relevant to several questions because a fully mixed region behaves differently to the stratified ocean offshore. In this study a highly simplified one‐dimensional model is used to examine the size, properties, and sensitivities of the mixed zone. The model suggests that most grounding line mixed zones are small, implying that the usual models representing a stratified ocean are generally valid if tidal mixing is also taken into account. Modeled mixed zones can be significant in near‐freezing regions with vigorous tides and a shallowly sloping cavity, but even these areas are smaller than previously proposed. It therefore seems that upwelling of warm water, rather than mixing in tidal zones, generally maintains ice shelf basal melting near grounding lines. Where mixed zones are present, the model suggests that they insulate the grounding line from offshore ocean waters. The model illustrates the origin of Ice Shelf Water plumes and confirms that unlike elsewhere in the cavity, melting in the mixed zone increases linearly in response to ocean warming.

Improvement of EB-PVD thermal barrier coatings by treatments of a vacuum plasma-sprayed bond coat

The lifetime of electron beam physical vapor deposited (EB-PVD) thermal barrier coating (TBC) systems with conventional 7 YSZ ceramic top layers was investigated in 1 h thermal-cyclic testing at 1100 °C. The single crystal alloy CMSX-4 and the polycrystalline IN 100 alloy that had been coated with a vacuum plasma-sprayed MCrAlY bond coat were chosen as substrate materials. A fully plasma-sprayed TBC system was studied as well. Several bond coat treatments such as smoothing, annealing in vacuum or air, and grit blasting were employed in order to study their effects on TBC life, and particularly the underlying mechanisms of thermally grown oxide (TGO) formation. Variations in TGO microstructure and especially occurrence or absence of the mixed zone have been correlated to the bond coat treatments. Spallation of the TBCs is mainly related to TGO formation that is influenced by the bond coat pre-treatment. The longest lifetime has been achieved by smoothing the bond coat prior to any heat treatment, followed by vacuum annealing prior to EB-PVD top coat deposition. TBC lifetimes were longer on CMSX-4 than on IN100 substrates. The surface roughness of the bond coat did not influence TBC life much.

Effects of nutrient enrichment on Distichlis spicata and Salicornia bigelovii in a marsh salt pan

We investigated how nutrient addition affects the abundance, nutrient storage, and competition between Distichlis spicata and Salicornia bigelovii, two dominant species in salt pans of Northern Gulf of Mexico marshes. Namely, we compared fertilized and unfertilized plots in monospecific areas colonized respectively by D. spicata or S. bigelovii, and in a mixed area colonized by the two species. Nutrient addition generally increased the aboveground biomass and percent cover of the two species, and those increases were moderate to large in relation to the increases found for other marsh plant species. Nutrient addition also generally decreased the carbon:nitrogen and carbon:phosphorus ratios of aboveground and belowground tissues of the two species. Our results provide evidence that, under enhanced nutrient availability, D. spicata is a superior competitor over S. bigelovii in the mixed zone of the salt pan where the two species grow together. However, we did not detect large changes in biomass dominance by D. spicata following fertilization, possibly because the experiment only lasted 10 months. Our results suggest that nutrient addition, by increasing the structural complexity of the leaf canopy and the nutritional quality of plant tissues for first-order consumers, may enhance the value of salt pans as habitat for organisms

Depth-stratified phytoplankton dynamics in Cyclone Opal, a subtropical mesoscale eddy

Abstract As part of E-Flux III cruise studies in March 2005, we investigated phytoplankton community dynamics in a cyclonic cold-core eddy (Cyclone Opal) in the lee of the Hawaiian Islands. Experimental incubations were conducted under in situ temperature and light conditions on a drift array using a two-treatment dilution technique. Taxon-specific estimates of growth, grazing and production rates were obtained from analyses of incubation results based on phytoplankton pigments, flow cytometry and microscopy. Cyclone Opal was sampled at a biologically and physically mature state, with an 80–100 m doming of isopycnal surfaces in its central region and a deep biomass maximum of large diatoms. Depth-profile experimentation defined three main zones. The upper (mixed) zone (0–40 m), showed little compositional or biomass response to eddy nutrient enrichment, but growth, grazing and production rates were significantly enhanced in this layer relative to the ambient community outside of the eddy. Prochlorococcus spp. dominated the upper mixed layer, accounting for 50–60% of its estimated primary production both inside and outside of Opal. In contrast, the deep zone of 70–90 m showed little evidence of growth rate enhancement and was principally defined by a ∼100-fold increase of large (>20-μm) diatoms and a shift from Prochlorococcus to diatom dominance (∼80%) of production. The intermediate layer of 50–60 m marked the transition between the upper and lower extremes but also contained an elevated biomass of physiologically unhealthy diatoms with significantly depressed growth rates and proportionately greater grazing losses relative to diatoms above or below. Microzooplankton grazers consumed 58%, 65% and 55%, respectively, of the production of diatoms, Prochlorococcus and the total phytoplankton community in Cyclone Opal. The substantial grazing impact on diatoms suggests that efficient recycling was the major primary fate of diatom organic production, consistent with the low export fluxes and selective export of biogenic silica, as empty diatom frustules, in Cyclone Opal.

Scale length of mantle heterogeneities: Constraints from helium diffusion

A model of coupled He production/diffusion is used to constrain the question of whether Earth's peridotitic mantle contains ubiquitous mesoscale veins or slabs of other lithologies. The high diffusion rates of helium preclude survival of He isotope heterogeneities on scales smaller than a few tens of meters, especially if they represent long term in-growth of 4He in the mantle. For 1.5 Gyr residence times, and a diffusion coefficient of 10 − 10 m 2/s, 0.5 km slabs or 2 km cylinders will lose > 90% of in-grown 4He. However, substantial 3He/ 4He variations may persist in slabs or be induced in adjacent mantle, depending on initial He, U and Th contents. We have modeled three cases of 3He/ 4He equilibration between mantle domains: an ocean crust (OC) slab in depleted upper mantle (DMM) or in enriched mantle (BSE), and a BSE slab in DMM. For a 1 km OC slab in DMM (8 Ra today), the slab today will have 3He/ 4He of only 3 Ra, and will have influenced the surrounding mantle with 4He for > 7 km on either side. The average 3He/ 4He of this mixed zone will be < 7 Ra, even when sampled by melts over a total width of 20–50 km. For the case of a 1 km BSE slab in DMM (8 Ra today), the slab will be 37 Ra today, and will have infected a mantle domain > 16 km wide. Even with a 60 km melt sampling width, the average 3He/ 4He will be > 15 Ra. Slabs may lose their He signature by diffusion, but their presence will be recorded in the surrounding mantle. We have evaluated 3 along-axis N-MORB ridge-crest data sets in this context (MAR 25.7–26.5°S; EPR 19–23°S; SWIR 16–24° E), with a view to defining scale-lengths of He isotope variability. The average 3He/ 4He variability for these 3 areas is very small, and independent of spreading rate: 0.13, 0.19 and 0.21 Ra (± 1 σ). Since these ridges range from ultra-slow to very fast-spreading, the variability in size of along-axis magma chambers will lead inevitably to various scales of melt averaging. We conclude that these ridge areas are not sampling mantle that contains enriched veins or recycled oceanic crust slabs of significant size (> tens of meters). It appears difficult to sustain a view of the upper mantle as a ubiquitous mixture of veins and depleted matrix, with MORB always representing an averaging of this mixture.

Seasonal variation and flux of dissolved nutrients in the Danshuei Estuary, Taiwan: A hypoxic subtropical mountain river

Comprehensive bimonthly field surveys were carried out from September 2000 to June 2002 to study the seasonal dynamics and the inter-annual variability of dissolved inorganic nitrogen (DIN; nitrate, nitrite and ammonium) and dissolved inorganic phosphorus (DIP) in a subtropical mountain river system, the Danshuei tributary, the largest urbanized estuarine system in Taiwan. The headwaters were found to be well aerated, saturated with oxygen, with low ambient DIN (<9 μM) and DIP (<0.2 μM) concentration. As the river flows through the city of Taipei, the river becomes hypoxic because re-aeration rates cannot keep up with elevated oxygen consumption, and the concentrations of DIP (7.53 μM) and DIN (∼390 μM) increase drastically. Conservative mixing was mostly observed for silicate while DIP and DIN mostly showed non-conservative removal characteristics. Silicate originates from weathering and erosion of bedrocks in the watershed, whereas nitrogen- and phosphorus-bearing nutrients come mainly from urban discharges. Ammonium is the predominant dissolved nitrogenous species, ranging from 10 to 1000 μM. The nutrient chemistry is complex and dynamic due to anthropogenic perturbations and reactions in the tidally mixed zone of strong redox gradients. On average, the annual loading rates of dissolved phosphate and dissolved inorganic nitrogen from the Danshuei River to the ocean are 0.1 and 3.2 Gmol/year, respectively, which represent 0.1% and 0.2% of the world's total river discharge of dissolved inorganic nitrogen and phosphate.

Two chloride sources in soils of the McMurdo Dry Valleys, Antarctica

Sulfate, nitrate, and chloride are major water‐soluble anions in soils of the McMurdo Dry Valleys (MDV), Antarctica. We measured the chloride stable isotope composition of 40 soil samples from 16 different soil profiles. The soil profiles come from three different microclimate zones in the MDV: a coastal thaw zone, which fosters a seasonally saturated active layer; a stable upland zone, in which air and soil temperatures are too cold to foster active layers and/or significant snowmelt; and an intermediate, inland mixed zone. Results show that the total water‐soluble chloride content is low in both the coastal and the upland zones, but highly variable in the inland mixed zone (average 770 to 11520 ppm). Individual soil δ37Cl values range from −2.10‰ to +0.56‰, with profile average δ37Cl values broadly decreasing from the coast toward upland valleys. Vertically, the δ37Cl increases with depth in soil profiles developed on basal tills but decreases on sublimation tills. We propose that the spatial [Cl−] and δ37Cl patterns are the result of continuous influx and leaching of two major chloride sources, an airborne sea‐salt chloride (SSC) with a δ37Cl value ≥ ∼0.0‰ and a secondary atmospheric chloride (SAC) with a δ37Cl value ≤ −2.10‰. Our model suggests that sublimation tills have their Cl− input from two boundaries: a till‐atmosphere interface at the top and a buried‐ice‐till interface at the bottom, differing distinctively from basal tills where there is no salt contribution from the bottom. Our model also suggests a higher influx of SSC relative to SAC in the MDV in the past. Overall, characterizing the sources, budgets, and spatial/vertical patterns of chloride constitutes a first step toward unraveling climate, tectonic, and landscape changes archived in MDV soil profiles.

Geochemical behavior of rare earth elements in hydrothermally altered rocks of the Kuroko mining area, Japan

In this study we analyzed the chemical composition of hydrothermally altered dacite and basalt from the Kuroko mining area, northeastern Honshu, Japan, by REE (rare earth element). Features of rare earth element analyses include: (1) altered footwall dacite exhibits a negative Eu anomaly compared with fresh dacite, suggesting preferential removal of Eu 2+ from the altered dacite via hydrothermal solutions, (2) altered hangingwall dacite and basalt and dacite and basalt adjacent to ore deposits exhibit positive Eu anomalies compared with fresh dacite and basalt, suggesting addition of Eu 2+ from hydrothermal solutions, (3) LREE ratio (∑LREE/∑REE) from altered dacite of chlorite–sericite zone and K-feldspar zone show a negative relationship with δ 18O, and La/Sm ratios show a positive correlation with the K 2O index. These trends indicate the addition of light rare earth elements such as La to the altered dacite from hydrothermal solution and/or leaching of heavy rare earth elements such as Sm and Yb, (4) Principal component analysis (PCA) indicates that light rare earth elements enrichment is related to the formation of sericite zone near the Kuroko deposits but not to the formations of chlorite and K-feldspar zones, and (5) The correlations among REE features (LREE ratio, MREE ratio, HREE ratio, Eu/Eu⁎), δ 18O and K 2O index are not found for montmorillonite zone, mixed layer clay mineral zone and mordenite zone. Therefore, it is inferred that sericite, chlorite and K-feldspar alterations are related to the Kuroko and vein-type mineralization, but montmorillonite and mordenite alterations are not related to the mineralizations, and probably they formed at the post-mineralization stage. We conclude that rare earth elements provide a useful geochemical index for the exploration of submarine massive sulfide ore deposits such as the Kuroko-type deposits.

Al-Mg-Si系合金摩擦攪拌スポット接合継手の疲労挙動に及ぼす後熱処理の影響

In this paper, the effect of post heat treatment on fatigue behaviour of friction stir spot welded Al-Mg-Si aluminium alloy was investigated. The microstructure of the weld zone was classified into two regions: stir zone (SZ) and mixed zone (MZ), where fine equiaxed grains due to dynamic recrystallization were observed. Two kinds of post heat treatment, namely aging and T6 treatment, were applied to the as-welded joints. The grains in the SZ and MZ were extremely enlarged only by T6 treatment, but some fine grains still remained near the boundary of MZ. Fatigue tests were conducted using lap-shear specimens at a stress ratio R = 0.1. Post heat treatments exhibited little influence on fatigue strength, but fatigue fracture morphology was dependent on both load level and post heat treatment. At high applied loads, fatigue fracture took place through the MZ in the as-welded and aged joints, while along the boundary of MZ in the T6 treated joint. At low applied loads, fatigue crack initiated at the edge of the nugget and then propagated through the upper sheet in the as-welded joint, while the lower sheet in the aged and T6 treated joints. The dependence of fracture morphology on post heat treatment was attributed to the change of microstructures and hardness distribution around the nugget by post heat treatment.

Advances in Diffusivity Measurement of Solvents in Oil Sands

Abstract This work deals with the prediction of mass transfer of solvents in bitumen in the presence and absence of sand through a unified model that uses magnetic resonance response information. Experiments were performed with pairs of solvents and bitumen in the presence of sand and without sand. Low field NMR was used to acquire spectra of the migrating solvent in bitumen or oil sand as a function of time. The experimental results of this work, along with data collected previously on similar systems in the Tomographic Imaging and Porous Media Laboratory, were fit together in a one-dimensional Fickian model. The novelty of the presented approach is not only that the new model matches all the experiments to date, but also that this matching can be done independently and without external input parameters. In previous work, matching could only be achieved if the depth of solvent penetration was provided through external measurements. The present model predicts diffusivities of solvents in bitumen in the presence of sand to be in the same order of magnitude and a bit lower than diffusivities of solvent in bulk bitumen. It is anticipated that this method would be of value when estimates of mass transfer in solvent-based heavy oil processes are attempted in the field. Introduction In solvent-based recovery processes for heavy oil and bitumen, mass transfer phenomena compete with viscous forces, gravity and capillary forces as the predominant means for oil recovery or trapping. In order to understand the relative merit of such forces, one must be able to measure mass transfer at reservoir conditions and potentially verify such measurements in the field. There is considerable literature on the measurement of recovery mechanisms and recovery efficiency through solvent-based processes for heavy oil and bitumen. The bulk of the work presented in the recent literature focuses around the VAPEX (Vapour Extraction) process, but the fundamental work presented can easily apply to any solvent displacement process. If we were to measure mass transfer phenomena in the field, it appears that a possible logging tool with significant potential is magnetic resonance. Thus, the TIPM group has embarked in a project whereby magnetic resonance is used for the determination of bitumen (or heavy oil) solvent interactions. As two miscible fluids are in contact, they will slowly diffuse into each other. This molecular transport of one substance relative to another is known as diffusion. With time, the interface between the fluids will appear as a diffused mixed zone grading from one pure fluid to the other. The mechanism of diffusion happens due to the random motion of molecules(1,2). The diffusion flux between solvent and heavy oil can be defined as the flow due to concentration gradient between solvent and heavy oil. The diffusion phenomena take place when there is no mixing in the system and the only driving force is the concentration gradient, unlike dispersion that is caused due to convective fluid mixing in the porous medium. It was observed that as solvent and heavy oil diffuse into each other, the mobility of hydrogen bearing molecules of both oil and solvent change(3).

Late Holocene vegetation changes and human impact in the Changbai Mountains area, Northeast China

Pollen analytical data from Jinchuan site in the Changbai Mountains, located within the mixed temperate broadleaved forest zone of Northeast China, were used for the reconstruction of vegetation changes and dynamics of human habitation activities in the last 6000 cal. years in the periphery to the Chinese civilization areas of former Manchuria. The beginning of the present type of vegetation dominated by mixed forests with the characteristic tree species Korean pine ( Pinus koraiensis Siebold & Zuccarini) was dated to 3100 cal. BC. Expansion of Korean pine occurred in two steps. The second phase of enhanced expansion of pine along with other coniferous taxa of higher altitudes such as Abies and Picea was dated to around 70 AD. The pattern of Late Holocene spread of coniferous elements ( P. koraiensis, Picea, Abies) and retreat of deciduous oaks was associated with phases of climatic cooling and presumably changes in effective precipitation. The oldest record of habitation processes identified in pollen assemblages from Jinchuan was dated to around 140 AD. The buckwheat ( Fagopyrum esculentum) cultivation was documented since the first half of the 9th century AD. The 18th century immigration of the Chinese population of Han ethnicity was reflected in the fossil archive, due to economic activities of the settlers connected with exploitation of forest resources through cutting of pine trees, protection of walnut stands, and cultivation of Hordeum/ Triticum cereals.

Growth Pattern Study of Closed Surface Flaw under Compression

Under extra compressive stress, some phenomena of rock spallings and fractures often exist on rock mass located in sidewalls of underground house and tunnels. It is the reason that the crack growth and coalescence initiation from original flaws (or faults) in rock mass. In the previous studies, many researchers took a flaw as a through flaw (2-dimentional model), but the flaws are not always through the whole rock mass in fact, most of them are only near the surface of rock mass, These are so named as surface flaws. They belong to three dimensional (2-D) flaws. Now, the reports on initiation and growth of 3-D surface flaw are few. So, for the investigation on growth patterns of 3-D surface flaw, a series of samples containing a surface flaw were carried out using frozen casting resin material at about -30°C temperatures. The surface flaw was made of a polyester film was used to model a single closed flaw on rock mass. The experimental results show that the wrapping wing crack (Mode I) initiated at the ends (or tips) of surface flaw first, and then formed a kinking zone (mixed crack zone) at a certain place at the middle of surface flaw region. Some petal cracks (Mode III) and shell-shaped cracks (Mode III) would grow at the middle place of flaw. A big fin crack (Mixed Mode) also emerged in middle of flaw and grown along loading direction. Finally, a team of large cracking curved faces deformed inside the resin specimen; the whole specimen would be splitted off by the initiation and growth of the cracks. The reasons lead to the fracture patterns of 3-D closed surface flaw were provided with brittle fracture mechanics theory in the article, preliminarily.