Numerical modeling of fracture propagation of supercritical CO_(2)compound fracturing

The exploitation of shale gas is promising due to depletion of the conventional energy and intensification of the greenhouse effect.In this paper,we proposed a heat-fluid-solid coupling damage model of supercritical CO_(2)(SC-CO_(2))compound fracturing which is expected to be an efficient and environmentally friendly way to develop shale gas.The coupling model is solved by the finite element method,and the results are in good agreement with the analytical solutions and fracturing experiments.Based on this model,the fracture propagation characteristics at the two stages of compound fracturing are studied and the influence of pressurization rate,in situ stress,bedding angle,and other factors are considered.The results show that at the SC-CO_(2)fracturing stage,a lower pressurization rate is conducive to formation of the branches around main fractures,while a higher pressurization rate inhibits formation of the branches around main fractures and promotes formation of the main fractures.Both bedding and in situ stress play a dominant role in the fracture propagation.When the in situ stress ratio(δ_(x)/δ_(y))is 1,the presence of bedding can reduce the initiation pressure and failure pressure.Nevertheless,it will cause the fracture to propagate along the bedding direction,reducing the fracture complexity.In rocks without bedding,hydraulic fracturing has the lengthening and widening effects for SC-CO_(2)induced fracture.In shale,fractures induced at the hydraulic fracturing stage are more likely to be dominated by in situ stresses and have a shorter reorientation radius.Therefore,fracture branches propagating along the maximum principal stress direction may be generated around the main fractures induced by SC-CO_(2)at the hydraulic fracturing stage.When the branches converge with the main fractures,fracture zones are easily formed,and thus the fracture complexity and damage area can be significantly increased.The results are instructive for the design and application of SC-CO_(2)compound fracturing.

Adsorption of 2-naphthalenesulfonic acid/sulfuric acid/sulfurous acid from aqueous solution by iron-impregnated weakly basic resin：Equilibrium and model

Commercial grade weakly basic resin D301 was impregnated with iron through a simple method using ferric chloride. Experiments for single, bisolute and trinary competitive adsorption were carried out to investigate the adsorption behavior of 2-naphthalenesulfonic acid(NSA), sulfuric acid and sulfurous acid from their solution at 298 K onto the novel hybrid iron impregnated D301(Fe-D301). Adsorption affinity of NSA on Fe-D301 was found to be much higher than that of sulfuric acid, while adsorption affinity of sulfuric acid was slightly higher than that of sulfurous acid. The data of single-solute adsorption were fitted to the Langmuir model and the Freundlich adsorption model. The non-ideal competitive adsorbed model coupled with the single-solute adsorption models were used to predict the bisolute and trinary-solute competitive adsorption equilibria. The NICM coupled with the Langmuir model yields the favorable representation of the bisolute and trinary-solute competitive adsorption behavior.

TiAl和Mo_5Si_3金属间化合物基高温结构材料及其合金化研究

对比分析了TiAl和Mo_5Si_3金属间化合物的性能特点、应用前景和存在问题,并对这两种金属间化合物的合金化研究作了综述和展望。近来研究微量镁和镍在TiAl合金中的作用发现,微合金化可提高变形合金的热加工工艺性能和促进铸造合金组织的细化,是TiAl金属间化合物进一步合金化研究的重要方向。根据模量计算和常用合金元素在Mo_5Si_3相中溶解度的测定结果,讨论了以合金化韧化Mo_5Si_3化合物的潜力。

Removal atrazine using two anion-exchange resins supported nanohydrous metal-oxide particle

Hydrous iron oxide and hydrous aluminum oxide were loaded successfully onto a polymeric adsorbent(D301) to modify adsorbing materials(HIOD301 and HAOD301). The adsorptive equilibrium of atrazine was investigated in an aquatic environment using HIOD301 and HAOD301 under different experimental conditions. The results indicated that both HIOD301 and HAOD301 showed good adsorption capacities for atrazine at p H 4. The Langmuir and Freundlich isotherm equations were used to study the interactions between the adsorbate and adsorbent.The adsorption kinetics of atrazine at different concentrations was well described in terms of a pseudosecond-order equation in regard to the correlation coefficients and adsorption capacity. The removal percentages of atrazine for HIOD301 and HAOD301 were still more than 95% in the presence of sodium chloride.

Tectonic Evolution of Southeast Central Asian Orogenic Belt: Evidence from Geochronological Data and Paleontology of the Early Paleozoic Deposits in Inner Mongolia

In this study, we present detrital zircon U-Pb dating and paleontological data for the newly identified Ayadeng Formation in the northern margin of the North China Block(NCB) and Xibiehe Formation(molasse) in the Bainaimiao arc belt(BAB), which could provide strong evidence indicating the affinity of the BAB and the evolution of the southeast Central Asian orogenic belt(CAOB). Zircon U-Pb data of siltstone samples and paleontological data indicate the Ayadeng Formation dates back to the Early Ordovician. Although its location is near the NCB, its zircon age spectra and paleontology share a closer affinity with those of Tarim and NE Gondwana, as the U-Pb data suggest an age range of 490–2 192 Ma(peak age=629, 788, 965 and 1 935 Ma), and similar gastropod fossils are found in Tarim and NE Gondwana. The U-Pb ages of meta-sandstone samples in the Xuniwusu Formation indicate a shared inheritance with the Ayadeng Formation(before 440 Ma), and the U-Pb ages of sandstone samples in the Xibiehe Formation are concentrated, with age peaks centered at ca. 420 Ma. Fossil corals occur in these two formations, and their age components also indicate a collisional setting. Therefore, it is speculated that the BAB drifted away from Tarim or NE Gondwana during the Ordovician and became attached to northern NCB between 440–420 Ma as an exotic terrane. During the Early Paleozoic, there may have occurred a collision between an arc and a continental block.

Safety and tolerability of available drugs for hyperuricemia:a critical review and an update on recent developments

Hyperuricemia(HUA)is a metabolic disease caused by excessive production of serum uric acid(s UA)or decreased excretion of s UA in the body.HUA is an independent risk factor for chronic kidney disease,hypertension,cardiovascular and cerebrovascular diseases,and diabetes mellitus.Timely and effective treatment for reducing s UA plays a key role in reducing urate deposition,preventing gout attacks,and reducing kidney damage and the occurrence of other accompanying diseases.Four pharmacological methods can be used to treat HUA:decrease urate production,increase urate excretion,prevent urate formation,and catabolize urate.To provide a reference for clinical treatment and new medical research for HUA,the drugs and potential drugs for HUA were reviewed in the present work.

Surgical treatment of hepato-pancreato-biliary disease in China:the Tongji experience

Hepato-pancreato-biliary(HPB) tumors are common in China. However, these tumors are often diagnosed at intermediate/advanced stages because of the lack of a systemic surveillance program in China. This situation creates many technical challenges for surgeons and increases the incidence of postoperative complications. Therefore, Dr. Xiao-Ping Chen has made many important technical improvements, such as Chen's hepatic portal occlusion method, the anterior approach for liver resection of large HCC tumors, the modified technique of Belghiti's liver-hanging maneuver, inserting biliary-enteric anastomosis technique, and invaginated pancreaticojujunostomy with transpancreatic U-sutures. These techniques are simple, practical, and easy to learn. Owing to these advantages, complicated surgical procedures can be simplified, and the curative effects are greatly improved. These improved techniques have been widely applied in China and will benefit many additional patients. In this review, we introduce our experience of surgically treating intermediate/advanced hepatocellular carcinoma(HCC), hilar cholangiocarcinoma(HC), and pancreatic carcinoma, mainly focusing on technical innovations established by Dr. Chen in HPB surgery.

Experimental Study on Elevated Fires in a Ceiling Vented Compartment

The impacts of elevation on fires in a ceiling vented compartment were investigated experimentally. The flame behavior of elevated fires was recorded. Various parameters including the fuel mass loss rate, the light extinction coefficient, the oxygen concentration and the gas temperature were measured. Results indicated that the variations of the flame behavior were consistent with that of the fuel mass loss rate. The fire location significantly impacted the light extinction coefficient, the oxygen concentration and the gas temperature, which all showed distinct stratification phenomena. For a higher elevated f＇we, the average fuel loss rate and the overall light extinction co- efficient were smaller, the oxygen concentration was higher and the gas temperature was lower. In addition, the smoke descending was slower. From the perspective of those parameters the fire was less hazardous if the fire was elevated higher, which was totally different from the elevated fires in closed compartments.

Correlation of rate of gas temperature rise with mass loss rate in a ceiling vented compartment

n-heptane pool fire and industrial alcohol pool fire in a ceiling vented compartment were studied experimentally. The parameters including mass loss rate and rate of gas temperature rise were investigated. The results suggest that the rate of gas temperature rise, whose variations were highly coincident with those of the mass loss rate, minimized at the moment of extinction. The correlation of the rate of average nondimensional temperature rise with mass loss rate was established. It was found that the rate of average nondimensional temperature rise may be correlated with mass loss rate via the gas heat absorption coefficient which was found to be a quadratic function of the nondimensional heat release rate for the ceiling vented compartment under study. The present study may be of practical use for estimation of the time-dependent changes in mass loss rate from the gas temperature curves.