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Angelica albicans is being used in the cure of different, respiratory, neuromuscular, and cutaneous diseases in traditional eastern medicine. The pharmacokinetic (PK) characteristics of imperatorin (IM) and isoimperatorin (ISOIM), the main effective components in Angelica albicans, were investigated. The rapid, subtle, and measuring the PKs of a drug, a validated UPLC/MS/MS methodology was designed for a total of 2 furanocoumarins in 2,4,6-trinitrobenzene sulfonic acid-stimulated and untreated mice. After that, blood samples were obtained. Angelica albicans (0.5 and 1.0 g/kg) was given orally, taken regularly from the tail vein. The time it takes for colitis rats to achieve their maximal concentration ( T max ) imperatorin and isoimperatorin was considerably postponed. In comparison to normal rats, all furanocoumarins had lesser peak plasma concentrations ( C max ) and higher represent residence durations. The area below the C max time-curve or clearance half-life did not differ significantly. In normal rats, all two furanocoumarins attained maximal plasma levels between 40 and 75 minutes, demonstrating fast oral absorption. The periods to attain T max of the two furanocoumarins, on the other hand, were shorter than in earlier studies. Therefore, colitis-linked alterations in the drug-absorption stage may result in a late T max and lowered C max , which have no effect on its clearance in half-life. Hence, conclusively, as a result, more consideration should be given to the prescription and administration of Angelica albicans in colitis individuals, and more research is needed to determine whether the changed PK profile was clinically meaningful for medicinal dose.

Soil salinization is one of the major forms of land degradation processes from all over the world. The dielectric constant plays an important role in the process of soil salinity retrieval by using microwave remote sensing. The Dobson model has been widely used to simulate the dielectric constant of nonsaline soil, but the estimated result of the Dobson model did not perform well for saline soil. Moreover, the ions' concentration is related to soil salinity, and the electrical conductance is a critical factor that influences the imaginary part of the dielectric constant. Therefore, the relationship between them needs to further explore. In addition, saturation is neglected in the current dielectric model of saline soil. In this letter, the relationship between the electrical conductance and ions' concentration was analyzed based on the experimental data. The saturation as a new parameter was introduced into the Dobson model to improve the estimated accuracy of the dielectric constant of saline soil in the C-band. The comparison between the revised model, the Dobson model, the Hu Qingrong (HQR) model, and the Wu Yueru (WYR) model was presented. The results indicate that there is a significant linear relationship between the electrical conductance and ions' concentration, with R² of 0.996, a slope of 0.1456, and an intercept of 0.0252. Once the new parameter is implemented, the improved dielectric model based on the C-band reproduces the dielectric constant of saline soil satisfactorily in each soil sample. The simulated results of the improved model are consistent with the laboratory measurement results, with an RMSE of 0.97 and R² of 0.953. Compared with other commonly used three dielectric models of the saline soil, the improved dielectric model performs well in simulating the imaginary part of the dielectric constant. The improved agreements between the simulations and the measurements indicate that the revised dielectric model is appropriate for simulating the dielectric constant of saline soil. The revised dielectric model of saline soil will provide a scientific foundation for the soil salinity retrieval from the microwave remote sensing technology.

Overprinting of an earlier formed deposit may obscure the nature of the deposit and hinder our understanding of regional metallogeny. The Qiaoxiahala Fe(-Cu/Au) deposit in eastern Junggar, NW China, is characterized by magnetite mineralization later replaced by sulfide minerals such as chalcopyrite. To reveal the genesis of Qiaoxiahala, we conducted Re-Os dating on post-magnetite molybdenite separated from chalcopyrite and rare earth elements (REEs) for basaltic volcanic rock, magnetite, chalcopyrite and diorite. An isochron age of 377±7 Ma was obtained together with a weighted mean age of 375±3 Ma, which is indistinguishable from mineralization ages determined in previous studies. Rare earth element (REE) data for basaltic volcanic rocks hosting the ore are comparable to that of the magnetite, while the REE signatures of chalcopyrite from the Cu ore and local intrusive diorite share a similar pattern. These suggest that two distinct fluid sources are responsible for the deposition of Fe and Cu in the Qiaoxiahala deposit. According to these experimental results, we consider that the iron mineralization in Qiaoxiahala is the result of fluid exsolution from basaltic volcanism which was further overprinted by fluids that deposited copper and gold, which may have been sourced from nearby dioritic intrusions.

The housing vacancy rate (HVR) is an important index in assessing the healthiness of residential real estate market. In China, it is hardly to take advantage of the basic data of real estate information due to the opaque of those data. In this paper, the HVR is estimated to two scales. At the grid level, urban area ratio was calculated by nighttime images after eliminating outliers of nighttime images and night light intensity of non-residential pixels in mixed pixels by a proposed modified optimal threshold method, and built-up areas in each pixel were extracted from the land-cover data. Then, the HVR is calculated by comparing the light intensity of specific grid with the light intensity of full occupancy rate regions. At the administrative scale, the GCI (‘ghost city’ index) is constructed by calculating the ratio of the total light radiation intensity of a city to the total construction land area of the city. The overall spatial differentiation pattern of the vacant houses in the national prefecture level administrative regions is analyzed. The following conclusions were drawn: vacant housing is rare in certain eastern coastal cities and regions in China with relatively fast economic development. Cities based on exhausted resources, some mountainous cities, and cities with relatively backward economic development more typically showed high levels of housing vacancy. The GCI of prefecture-level administrative units gradually declined from north to south, whereas the east-west distribution showed a parabolic shape. As city level decreased, the GCI registered a gradual upward trend. China’s urban housing vacancy can be divided into five categories: industry or resources driven, government planned, epitaxy expansionary, environmental constraint and speculative activate by combining the spatial distribution of housing vacancy with the factors of natural environment, social economic development level, and population density into consideration.

The absolute crystallization ages of minerals from hydrothermal fluids measured in situ can unravel the timing of key events leading to the formation of, for instance, ore deposits and hydrothermally derived geological terrains. In this study, a skarn iron deposit from northwest (NW) China is shown to have U-Pb garnet and U-Pb zircon ages of 254.2 ± 1.7 Ma and 255.5 ± 1.0 Ma, respectively, which are both significantly younger than magmatism and metamorphism of the region. This skarn age instead correlates with the occurrence of strike-slip and thrust faulting in the region. The water/rock mass ratio of 0.065~0.115 suggests the δ18O garnet composition is ~1‰ at temperatures ranging from 250–450 °C. The low oxygen isotopic composition indicates the role of meteoric water in the garnet formation. These measurements can be interpreted as the shear along faults circulating meteoric water ~10 km below the hanging wall of meta-volcanic sedimentary rock. Meteoric water in this hydrothermal system would leach cations from the meta-volcano-sedimentary rocks necessary for mineralization. Silica-rich hydrothermal fluid reacts with calcic-rich materials in the meta-volcano-sedimentary rocks, depositing the garnet and magnetite. Our work suggests that the shear zone is rich in ores, rendering this deposit for NW China a prospective source for future mineral resource exploration.

Moving Kriging interpolation (MKI) is an important approximation method to construct shape functions in meshless methods. We analyzed the stability of MKI and found that it will become unstable when the nodal spacing decreases. Thus, we developed a stabilized MKI method by using shifted and scaled polynomial basis functions. Then, we applied the stabilized MKI to boundary node method for Laplace's problems and Poisson's problems to study the advantages. For Poisson's problems, the radial integration method is introduced to compute the domain integrals. We also applied the stabilized MKI to element-free Galerkin method to solve elastodynamic problems. Examples are provided to show the accuracy and stability of the stabilized MKI and the boundary node method and element-free Galerkin method based on the stabilized MKI.

There are many Miocene collision- and subduction-related porphyry Cu deposits in the Eastern Tethyan orogenic belt. However, the petrogenesis of the ore-related magmas and the mechanism of metal enrichment remain controversial. Here, we present a geochemical study and comparison of the major Miocene ore-related porphyries and coeval ore-barren magmatic rocks in the Urumieh-Dokhtar magmatic arc in Iran and the Chagai belt in Pakistan, and the Eastern Gangdese belt of the Himalaya. The results show that ore-related porphyries are characterized by relatively depleted mean Sr isotopic compositions (0.704217–0.706859 in the Urumieh-Dokhtar magmatic arc; 0.705052–0.706588 in the Eastern Gangdese belt; 0.705252–0.706708 in the Chagai belt), but higher maximum Sr/Y ratios (40–149 in Urumieh-Dokhtar; 79–178 in Eastern Gangdese; 52–178 in Chagai). In contrast, the coeval ore-barren magmatic rocks yield relatively enriched, mean Sr isotopic compositions (0.704722–0.707653 in Urumieh-Dokhtar; 0.704701–0.707802 in Eastern Gangdese; 0.705982–0.707856 in Chagai), but lower maximum Sr/Y (2–88 in Urumieh-Dokhtar; 61–136 in Eastern Gangdese; and 19–35 in Chagai). A deep crustal hot zone model provides a robust explanation of these data. Melts derived from a deeper melt source in juvenile mafic lower crust, where mantle-derived materials are common, have a greater potential to yield a higher tonnage of metallic Cu, such as the Sar-Cheshmeh deposit in Iran, which is derived from a deep melt zone, and characterized by a low radioactive mean Sr isotopic value of 0.704851, but a huge tonnage of metallic Cu of 7.2 Mt and a high maximum Sr/Y value of 117 (representative of a deeper depth of the melt zone), whereas the Dalli deposit in Iran derived from a relatively shallow melt zone has a more radioactive mean Sr isotopic value of 0.706859, but a smaller amount of metallic Cu of 0.04 Mt and a lower maximum Sr/Y ratio of 40. Conversely, re-melting the contact between newly-formed and pre-existing crust where mantle-derived materials are absent will produce ore-barren rocks. Additionally, the ore-barren rocks with low Sr/Y ratios (

The newly discovered Katbasu gold deposit in the South Tianshan region has a gold reserve of 76 t at an average grade of 3.84 g/t. It is the first large gold deposit in the central segment of the South Tianshan. Gold mineralization is hosted within granite, and is associated with potassic, phyllic and chloritic alteration. Gold-bearing pyrite occurs as disseminations in the host rock and as quartz-sulfide veins cross-cutting the potassic and phyllic alteration assemblage. Rubidium (Rb) - strontium (Sr) analyses on sericite within five individual pyrite grains from a phyllic alteration sample yield an isochron age of 322.5 ± 6.8 Ma (MSWD = 3.2). The host granite has a SIMS U-Pb zircon age of 351.4 ± 1.1 Ma (MSWD = 0.13). The Rb-Sr isochron age represents the mineralizing age of the Katbasu gold deposit, which significantly postdates the ore-hosting granite but is consistent with the age of regional porphyry type mineralization at ~ 320 Ma in the South Tianshan. Discovery of the Katbasu gold deposits indicates huge potential for gold exploration in the central segment of the South Tianshan as it is geologically similar to the western and eastern segments of the South Tianshan, which both host many world-class gold deposits.

Porphyry copper deposits are the world's largest source of copper, but their ultimate source and deep process are disputed. We compare the Sr/Y ratios and Nd isotopes of coeval ore-bearing and ore-barren intermediate rocks from collisional and subduction settings to unravel the sourced depth and nature. During the Miocene mineralization epoch in the Iranian plateau, the median Sr/Y ratios and the median eNd(T) values of ore-bearing rocks (56 ± 38, 1.1 ± 1.5) are slightly higher than those of the ore-barren rocks (30 ± 31, −0.3 ± 2.4), respectively. Such patterns also exist at mineralization epochs during the Miocene collision in the eastern Gangdese, and the early Cretaceous subduction in Southeast China. These results indicate that all ore-bearing and ore-barren rocks are from the thickened (>1.2 Gpa) juvenile dominated (>70% mantle contribution) lower crust, and the ore-bearing rocks are sourced from slightly deeper and more juvenile sources compared to the coeval ore-barren rocks. The subtle geochemical difference but contrasting ore-potentials indicate heterogeneous origins, and the ore-bearing rocks may be related to ore-enriched sources at the lower crust. A deep crustal hot zone with melting at different depths with heterogeneous sources can account for such phenomena. Delamination of a thickened orogenic root induces asthenosphere upwelling and generates abnormal heat flow in the lower crust. The porphyry mineralization is an indication of the balancing between the melting of thickened lower crust and mantle upwelling, which explains the rarity of mineralization compared to the prolonged orogenic magmatism.

The Axi and Jingxi-Yelmand gold deposits, being the largest gold deposits in the Chinese North Tianshan, NW China, are located ca. l0 km apart in the Tulasu Basin, and are hosted by the Late Devonian - Early Carboniferous Dahalajunshan Formation. In situ LA-ICP-MS titanium analyses on quartz from the Axi and Jingxi-Yelmand deposits are broadly identical. Accordingly, the calculated ore-forming temperatures by Ti-in-quartz thermometer give average temperatures of 279 °C and 294 °C, respectively. Results of in situ SIMS analyses of oxygen and sulfur isotopes on quartz and pyrite from these two deposits are similar. Temperature-corrected fluids of the Axi deposit have δ 18 O values of 2.6–8.1‰ and δ 34 S values of 0.8–2.4‰, whereas the fluids of the Jingxi-Yelmand deposit have δ 18 O of 6.4–8.9‰ and δ 34 S of −0.4 to 4.0‰. The oxygen and sulfur isotopes from the two deposits indicate a magmatic origin. LA-ICP-MS zircon U-Pb ages of Aqialehe Formation sandstone provided a lower limit for the mineralization timing of the Axi deposit (288 Ma). In situ SIMS U-Pb analyses on entrapped zircon (297 Ma) and newly recognized 284.5 Ma columnar rhyolite implies that the Jingxi-Yelmand deposit formed in the Early Permian. Based on the magmatic affinity of the ore fluids, similar age and ore-formation temperatures, we propose that the Axi and Jingxi-Yelmand deposits comprise an epithermal gold system, which was driven by the same Permian magma in the Tulasu Basin. The ore geological features together with our new results indicate that the Axi and Jingxi-Yelmand deposits are intermediate and high sulfidation type epithermal deposits, respectively.

An experimental study has been carried out on the characteristics of the fouling process from Water-CaSO4 solutions to the heat transfer surface with and without bulk precipitation. Effects of rotational bulk solution Reynolds number (Re) and surface temperature ( T S ) on the fouling mechanism, fouling behaviour and fouling rate, under surface crystallization (SC) and bulk precipitation (BP) conditions, are investigated. It is found that fouling can enhance the overall heat transfer when Re is high enough in the lack of BP. Under SC conditions, the fouling resistance ( R f ) and the fouling rate ( d R f / d t ) decrease with an increase in Re. The effects of T S on R f and d R f / d t depend on Re, with exponential increases with Re under low Re of 16000, and negligible influence under high Re of 80000. The presence of BP markedly increases d R f / d t by 3.6 times, while decreases the length of the initial period by 4.5 times. The presence of BP alters the overall precipitation fouling mechanisms. A critical Re of 57600 is found separating two distinct fouling mechanisms under the same T S . When Re CaS O 4 solutions, which could provide a benchmark for fouling model development and help develop an effective fouling mitigation strategy.

Accurate quantification of evaporation loss from irrigation canals at an irrigation district scale is very useful for developing efficient irrigation strategies, particularly in water-deficient regions. The double-deck surface air layer (DSAL) model, a new aerodynamic method proposed by Kobayashi et al. (2013), is used for estimating the evaporation loss from a running water surface in irrigation canals. In this study, based on the long-term meteorological measurements made at automatic weather stations in 2013 and the field experiment conducted at - midstream areas of the Heihe River Basin (HRB), northwestern China, the DSAL model was applied to estimate the long-term evaporation loss from irrigation canals, which was the remarkable highlight of the study. The results showed that the rate of evaporation from irrigation canals exhibited a concave-up trend for the period from June to September, with higher values in June and September (20 to 50 mm day&minus, 1) and lower values in July and August (around 10 mm day&minus, 1). During the four months, for the Yingke and Daman irrigation districts in the Zhangye Oasis, the total water losses from irrigation canals due to evaporation were approximately 23.9 &times, 105 m3 and 36.6 &times, 105 m3, or 3.2% and 4.8% of the total amount of irrigation water, respectively. Results of the study are not only important for improving the irrigation water use efficiency, but also are beneficial to develop sustainable water resource management in the midstream areas of the HRB.

An analytical model is given to investigate the end-fitting effect on slip and stress of tensile armors in unbonded flexible pipes under tension, torsion and varying bending in the absence of friction. An exponentially decaying curvature distribution is assumed to represent controlled curvature over the end region. The deviation from the initial helical angle is taken to describe the armor wire path as the pipe is stretched, twisted and bent, which is determined by minimization of the strain energy functional using the Euler equation. The obtained simultaneous differential equations are numerically solved by transforming them into a boundary value problem. An analytical solution is found by neglecting the twisting rotation of the wire cross-section. The developed model is validated with a finite element simulation and geodesic based analytical expressions for constant curvature and with a current numerical model for varying curvature. Reasonable correlations are observed between the model predictions and the results from other methods. The validated model is then applied to typical flexible pipe designs to find the level and location of the greatest increases in stress. The results show that the end restraint could cause a significant stress increase in the armor wire at the end fitting vicinity and the critical location is close to the extreme fiber position on the compressive side of the pipe for typical cases. The effect of end restraint on layer bending stiffness is also evaluated.

In this paper, we proposed the complex variable moving Kriging interpolation (CVMKI) to approximate functions on two-dimensional (2D) boundaries. The CVMKI is based on complex variable theory and the moving Kriging interpolation (MKI). It requires no curvilinear coordinate, and can construct shape functions possessing Kronecker delta function property and partition of unity property. Further, the complex variable boundary node method (CVBNM) is proposed for potential problems based on CVMKI and boundary integration equation (BIE). CVBNM is an efficient and accurate method that can directly impose the boundary conditions. Three 2D example problems are presented to verify the accuracy and efficiency of CVBNM.

Understanding how seasonal and annual variations in dew formation are controlled by environmental elements of a crop field is necessary for utilizing dew as a water resource for agricultural production. Radiative cooling intensity, wind speed, and water vapor pressure are the key environmental elements for the dew formation. However, a detailed investigation of how seasonal and annual variations in these environmental elements affect the variation in dew formation is unexplored. We examined the relationship between dew characteristics (frequency, amount, and duration) and environmental elements of a semiarid crop field during the cultivation period of corn (April–September) for three years. In spring (April–June), though large nighttime negative net radiation, which indicates strong radiative cooling intensity, was observed, dew rarely occurred and only in small amounts. Conversely, in summer (July–September), dew frequently occurred and in larger amounts despite the lower radiative cooling intensity. In spring, lower water vapor pressure was observed, and thus dew formation was limited by the lack of water source of dew. In summer, water vapor pressure was high, and dew formation was predominantly limited by the radiative cooling intensity. The dew amount during the cultivation period accounted for 5.4% of the rainfall amount on average over the 3 years. However, dew occurred more frequently than rainfall at 53% of the days comprising the cultivation period. Additionally, the occurrence of dew wet the leaves for approximately 10 h indicating the significant impact of leaf wetting by dew on plant eco-physiological functions. The results of this study should advance the understanding of how dew formation is controlled by variations in the environmental elements of a semiarid crop field, which will contribute to improving the utilization of dew as a water resource for agricultural production.

This paper deals with the effect of termination restraint due to end fitting on the stress evaluation of tensile armors in unbonded flexible pipes under axial tension. The problem is characterized by one single armoring tendon helically wound on a cylindrical supporting surface subjected to traction. The deviation from the initial helical angle is taken to describe the armor wire path as the pipe is stretched. The integral of this angle change gives the lateral displacement of the wire, which is determined by minimizing the energy functional that consists of the strain energy due to axial strain, local bending and torsion, and the energy dissipated by friction, leading to a variational problem with a variable endpoint. The governing differential equation of the wire lateral displacement, together with the supplementary condition, is derived using the variational method and solved analytically. The developed model is verified with a finite element (FE) simulation. Comparisons between the model predictions and the FE results in terms of the change in helical angle and transverse bending stress show good correlations. The verified model is then applied to study the effects of imposed tension and friction coefficient on the maximum bending stress. The results show that the response to tension is linear, and friction could significantly increase the stress at the end fitting compared with the frictionless case.

An analytical model is given to investigate the behavior of unbonded flexible pipes under biaxial dynamic bending. The stick-slip conditions of each wire are studied in the framework of incremental analysis by an operator splitting of the time step into a stick-state prediction and a slip-state correction step. The tension gradient is calculated using the classical return-mapping algorithm and the obtained tension gradients are integrated numerically to find the axial tension by imposing appropriate boundary conditions. From the axial tension the bending moments with respect to the principal bending axes of the pipe are obtained. Poisson's effect, bending induced tension in the wire, shear deformations of the supporting plastic layer and the changes of the effective torsion and curvature increments of the wire after slip occurs are taken into account in the model. The results of bending moment–curvature relationship from this model are compared with the test data from simple bending and good correlations are found. The comparison of the biaxial bending moment results between this model and the available model also shows good agreement.

An analytical model is given to investigate the tensile armour behaviour of unbonded flexible pipes close to end fittings under axial tension with no friction. The deviation from the initial lay angle is taken to describe the path of the single armour wire and is determined by minimisation of the strain energy functional using the Euler equation. The obtained simultaneous differential equations are transformed into a boundary value problem which is solved numerically. An analytical solution is found by neglecting the twist of the wire cross-section with respect to the wire centre-line. The developed model is verified with a finite element simulation. Good agreement of armour wire path and maximum lateral bending moment is observed between the model predictions and the finite element results. The discrepancies in the bending and twisting moment distributions are attributed to the twisting constraint assumed in the analytical solutions. The verified model is then applied to typical flexible pipe designs to ...

Rigorous analytical formulations are given to describe the gross slip initiation and progression in tensile armor layers of unbonded flexible pipes. Then two mechanisms are thought to contribute to the decrease of layer stiffness before gross slip begins. The first one considers the micro-slip occurred at the interlayer contact interfaces. The relative displacement between an armor wire and the underlying layer is determined according to the theory of contact mechanics. Shear deformations of the supporting plastic layer are taken into account in the other mechanism where plane sections no longer remain plane. The results of bending moment-curvature relationship from the presented models are compared with the available test data and good correlations are found. The shear model is seen to describe the slip transition better than other models do.

An evaluation method of the crack tip reverse plastic zone size (CTRPZS) for the center cracked steel plate under tension–compression cyclic loading is proposed. In this method, the variable quantity of maximum crack opening displacement (VMCOD) is used to study the effect of compressive loads on CTRPZS. In the compressive loading stage, CTRPSZ increases linearly with increasing of the compressive load on basis of the existing CTRPZS after the tensile loading and tensile unloading processes. The maximum CTRPZS can be expressed with respect to VMCOD. This expression is suitable for center cracked finite plates with different materials under tension–compression cyclic loading.

The high stress region around weld joints accelerates corrosion and may induce non-uniform corrosion. In this study, the effect of loading on corrosion behavior of the steel in NaCl solution was investigated. The relationship between the corrosion rate and applied loading was deduced based on the electrochemical theory. Electrochemical experiments were carried out to investigate the interaction between loading and corrosion rate on Q235 steel. A butt weld joint of ship deck structure was selected as a case study. Time-dependent stress concentration factor of welded joint as a function of the corrosion deterioration was analyzed, and the iterative process of stress and corrosion degeneration of plate thickness was used to simulate the coupling effect based on results of the experiment. The hot spot stress approach was adopted to calculate the fatigue damage.

This paper deals with the effect of termination restraint due to end fitting on the stress evaluation of tensile armors in unbonded flexible pipes under axial tension. The problem is characterized by one single armoring tendon helically wound on a cylindrical supporting surface subjected to traction. The deviation from the initial helical angle is taken to describe the armor wire path as the pipe is stretched. The integral of this angle change gives lateral displacement of the wire, which is determined by minimization of the energy functional consists of the strain energy due to axial strain, local bending and torsion, and the energy dissipated by friction, leading to a variational problem with a variable endpoint. The governing differential equation of the wire lateral displacement, together with the supplementary condition, is derived using the variational method and solved analytically. The developed model is validated with a finite element simulation. Comparisons between the model predictions and the finite element results in terms of the change in helical angle and transverse bending stress show good correlations. The validated model is then applied to study the effects of imposed tension and friction coefficient on the maximum bending stress. The results show that the response to tension is linear and friction could significantly increase the stress at the end fitting compared with the frictionless case.

Katbasu is a gold (and copper) deposit located in an arc on the southern margin of the Ili-Central Tianshan micro-continent. An in-situ method was conducted to acquire trace element concentrations to elucidate the origins and chemistry of the fluid in the Katbasu deposit. This included oxygen isotopes in quartz, as well as sulfur isotopes and trace elements concentrations in pyrite. Trace elements in gold deficient veins have higher concentrations compared to those in the gold bearing veins. The δ18O values of gold deficient veins are between 3.9 and 8.1‰, which imply a magmatic oxygen isotope signature. In contrast, oxygen isotopes in gold bearing veins range between −1.3 and 5.8‰, indicating the involvement of meteoric water in the mineralization system. This data, combined with evidence from alteration style and metal assemblages, shows that the ore-forming fluids at the Katbasu gold deposit is of a magmatic origin. The data also indicates that meteoric water diluted the magmatic fluid and caused an oversaturation of gold, causing precipitation of native gold grains. Trace elements in pyrite show no difference among the veins analyzed. However, they have distinctly different trace element patterns of pyrite from orogenic gold deposits. Based on the δ34S values of pyrite (8.3–12.9‰), and the lack of coeval regional metamorphism, we conclude that the enriched 34S at the Katbasu gold deposit is derived from a subducted slab during the Late Carboniferous.

An analytical model is proposed to investigate the local torsion and bending behavior of tensile armors in unbonded flexible pipes. The general expressions of torsion and curvature increments, including the effects of axial strain and twisting rotation of tendon cross-section, are firstly derived based on the generalized Frenet–Serret equations. Then the expressions corresponding to the strained helix assumption are obtained, which are further simplified by ignoring the twisting rotation. Afterwards, explicit expressions are given for axisymmetric case and tendon stick and slip states when bending is included. The developed model is finally verified with a finite element simulation. The results show that the model prediction of normal curvature increment is in good agreement with the numerical solution while the changes in torsion and transverse curvature cannot be obtained accurately through simple analytical formulas. Several earlier models are also discussed briefly and are demonstrated to be special cases of the present general model.

Analytical formulations are presented to determine the bending moment-curvature relationship of a helical layer in unbonded flexible pipes. Explicit expressions describing the variation of both bending stiffness and moment as a function of the applied curvature are given. The approach takes into account the nonlinearity of the response caused by the interlayer slip. The contribution of local bending and torsion of individual helical elements to the bending behavior of helical layers is included. Theoretical results for a typical unbonded flexible pipe using the nonlinear formulation for helical layers are compared with experimental data from the available literature. Encouraging correlations are found and the importance of the initial interlayer pressures is seen. The influence of local bending and torsion of individual helical elements on the bending behavior of the entire pipe is also evaluated. The results show that the inclusion of this local behavior significantly influences the full-slip bending stiffness.

Riser long-term fatigue performance is an important design consideration. Although extensive application of irregular sea analysis in time domain with the rainflow counting technique for post-processing is regarded as the most accurate of the approaches for fatigue analysis, it does suffer from some limitations, such as the computational effort. For this reason, two computationally efficient approaches are employed to perform the fatigue analysis of a deepwater top-tensioned riser, based on the Longuet-Higgins distribution and time domain scaling respectively. With Longuet-Higgins distribution irregular wave sea states are expanded into their individual wave bins. These regular wave simulations are of short duration and consequently run quickly. Using the time domain scaling technique, the number of irregular wave runs can be performed for a comparatively small number of load cases and hence reduces the calculation time. The results showed a reasonable accuracy and significant efficiency for both approaches, compared with those from the equivalent rainflow analysis. With much less computational effort and disk storage requirement, the approaches outlined in this paper can therefore be used for the fatigue assessment of deepwater risers in industry practice.

The connection of a flexible riser to the floating production system is identified as a critical area with respect to extreme deformation and fatigue damage. Bend stiffeners are designed to provide a gradual stiffness transition at the riser–vessel interface, protecting the riser against overbending and from the accumulation of fatigue damage. Thus, they are of vital importance to deep-water oil and gas production systems. A methodology for the bend-stiffener taper design is firstly outlined in this paper. The exact expression of the angle at the tip of the bend stiffener required for the design is derived. Then, a mathematical formulation and the numerical solution procedure for the geometrical and material non-linear analysis of the riser-stiffener system are developed. The governing differential equations are obtained from geometrical compatibility, equilibrium of forces and moments, and non-linear material constitutive relations. An analytical approach to predict the bending moment versus curvature re...