为系统研究无巷旁充填切顶卸压沿空留巷矿压规律及关键支护技术,理论分析了无巷旁充填切顶卸压沿空留巷矿压显现规律,基于恒源煤矿Ⅱ632机巷工程实践,在巷道内布设位移观测点和顶板恒阻锚索测力计对巷道变形及恒阻锚索工作阻力进行连续...为系统研究无巷旁充填切顶卸压沿空留巷矿压规律及关键支护技术,理论分析了无巷旁充填切顶卸压沿空留巷矿压显现规律,基于恒源煤矿Ⅱ632机巷工程实践,在巷道内布设位移观测点和顶板恒阻锚索测力计对巷道变形及恒阻锚索工作阻力进行连续观测,得到巷道在留巷期间巷道变形量、变形速率及恒阻锚索受力的变化规律。结果表明:切顶之后,由于顶板快速下沉所产生的冲击载荷,留巷围岩变形剧烈,尤其是强烈的底鼓现象;留巷段围岩变形受动压影响,变形更加剧烈;无巷旁充填切顶卸压沿空留巷顶部恒阻锚索总体平均受力为259.721 k N,最大受力达到275.76 k N,当工作面推过测点后,恒阻锚索受力趋于稳定;提出了"强化恒阻锚索配合锚杆(索)支护以增加顶板支护强度"、"当底板较软时,适当强化底板支护"和"注意留巷阶段的加强支护"的无巷旁充填切顶卸压沿空留巷关键支护技术。展开更多
Glycerol(GLY) aerobic oxidation in an aqueous solution is one of the most prospective pathways in biomass transformation, where the supported catalysts based on noble metals(mainly Au, Pd, Pt) are most commonly employ...Glycerol(GLY) aerobic oxidation in an aqueous solution is one of the most prospective pathways in biomass transformation, where the supported catalysts based on noble metals(mainly Au, Pd, Pt) are most commonly employed. Herein, Pt nanoparticles supported on rehydrated MgxAl1-hydrotalcite(denoted as re-MgxAl1-LDH-Pt) were prepared via impregnation-reduction method followed by an in situ rehydration process, which showed high activity and selectivity towards GLY oxidation to produce glyceric acid(GLYA) at room temperature. The metal-support interfacial structure and catalyst basicity were modulated by changing the Mg/Al molar ratio of the hydrotalcite precursor, and the optimal performance was achieved on re-Mg6Al1-LDH-Pt with a GLY conversion of 87.6% and a GLYA yield of 58.6%, which exceeded the traditional activated carbon and oxide supports. A combinative study on structural characterizations(XANES, CO-FTIR spectra, and benzoic acid titration) proves that a higher Mg/Al molar ratio promotes the formation of positively charged Ptd+species at metal-support interface, which accelerates bond cleavage of a-C–H and improves catalytic activity. Moreover, a higher Mg/Al molar ratio provides a stronger basicity of support that contributes to the oxidation of terminal-hydroxyl and thus enhances the selectivity of GLYA. This catalyst with tunable metal-support interaction shows prospective applications toward transformation of biomass-based polyols.展开更多
Rate of penetration(ROP) of a tunnel boring machine(TBM) in a rock environment is generally a key parameter for the successful accomplishment of a tunneling project. The objectives of this work are to compare the accu...Rate of penetration(ROP) of a tunnel boring machine(TBM) in a rock environment is generally a key parameter for the successful accomplishment of a tunneling project. The objectives of this work are to compare the accuracy of prediction models employing partial least squares(PLS) regression and support vector machine(SVM) regression technique for modeling the penetration rate of TBM. To develop the proposed models, the database that is composed of intact rock properties including uniaxial compressive strength(UCS), Brazilian tensile strength(BTS), and peak slope index(PSI), and also rock mass properties including distance between planes of weakness(DPW) and the alpha angle(α) are input as dependent variables and the measured ROP is chosen as an independent variable. Two hundred sets of data are collected from Queens Water Tunnel and Karaj-Tehran water transfer tunnel TBM project. The accuracy of the prediction models is measured by the coefficient of determination(R2) and root mean squares error(RMSE) between predicted and observed yield employing 10-fold cross-validation schemes. The R2 and RMSE of prediction are 0.8183 and 0.1807 for SVMR method, and 0.9999 and 0.0011 for PLS method, respectively. Comparison between the values of statistical parameters reveals the superiority of the PLSR model over SVMR one.展开更多
Background:Hepatitis B virus-related acute-on-chronic liver failure(HBV-ACLF)has a high short-term mortality.However,the treatment progression for HBV-ACLF in China in the past decade has not been well characterized.T...Background:Hepatitis B virus-related acute-on-chronic liver failure(HBV-ACLF)has a high short-term mortality.However,the treatment progression for HBV-ACLF in China in the past decade has not been well characterized.The present study aimed to determine whether the HBV-ACLF treatment has significantly improved during the past decade.Methods:This study retrospectively compared short-term(28/56 days)survival rates of two different nationwide cohorts(cohort I:2008-2011 and cohort II:2012-2015).Eligible HBV-ACLF patients were enrolled retrospectively.Patients in the cohorts I and II were assigned either to the standard medical therapy(SMT)group(cohort I-SMT,cohort II-SMT)or artificial liver support system(ALSS)group(cohort IALSS,cohort II-ALSS).Propensity score matching analysis was conducted to eliminate baseline differences,and multivariate logistic regression analysis was used to explore the independent factors for 28-day survival.Results:Short-term(28/56 days)survival rates were significantly higher in the ALSS group than those in the SMT group(P<0.05)and were higher in the cohort II than those in the cohort I(P<0.001).After propensity score matching,short-term(28/56 days)survival rates were higher in the cohort II than those in the cohort I for both SMT(60.7%vs.53.0%,50.0%vs.39.8%,P<0.05)and ALSS(66.1%vs.56.5%,53.0%vs.44.4%,P<0.05)treatments.The 28-day survival rate was higher in patients treated with nucleos(t)ide analogs than in patients without such treatments(P=0.046).Multivariate logistic regression analysis revealed that ALSS(OR=0.962,95%CI:0.951-0.973,P=0.038),nucleos(t)ide analogs(OR=0.927,95%CI:0.871-0.983,P=0.046),old age(OR=1.028,95%CI:1.015-1.041,P<0.001),total bilirubin(OR=1.002,95%CI:1.001-1.003,P=0.004),INR(OR=1.569,95%CI:1.044-2.358,P<0.001),COSSH-ACLF grade(OR=2.683,95%CI:1.792-4.017,P<0.001),and albumin(OR=0.952,95%CI:0.924-0.982,P=0.002)were independent factors for 28-day mortality.Conclusions:The treatment for patients with HBV-ACLF has improved in the past decade.展开更多
文摘为系统研究无巷旁充填切顶卸压沿空留巷矿压规律及关键支护技术,理论分析了无巷旁充填切顶卸压沿空留巷矿压显现规律,基于恒源煤矿Ⅱ632机巷工程实践,在巷道内布设位移观测点和顶板恒阻锚索测力计对巷道变形及恒阻锚索工作阻力进行连续观测,得到巷道在留巷期间巷道变形量、变形速率及恒阻锚索受力的变化规律。结果表明:切顶之后,由于顶板快速下沉所产生的冲击载荷,留巷围岩变形剧烈,尤其是强烈的底鼓现象;留巷段围岩变形受动压影响,变形更加剧烈;无巷旁充填切顶卸压沿空留巷顶部恒阻锚索总体平均受力为259.721 k N,最大受力达到275.76 k N,当工作面推过测点后,恒阻锚索受力趋于稳定;提出了"强化恒阻锚索配合锚杆(索)支护以增加顶板支护强度"、"当底板较软时,适当强化底板支护"和"注意留巷阶段的加强支护"的无巷旁充填切顶卸压沿空留巷关键支护技术。
基金supported by the National Natural Science Foundation of China (21871021 and 21521005)the National Key Research and Development Program (2017YFA0206804)the Fundamental Research Funds for the Central Universities (buctylkxj01 and XK1802-6)
文摘Glycerol(GLY) aerobic oxidation in an aqueous solution is one of the most prospective pathways in biomass transformation, where the supported catalysts based on noble metals(mainly Au, Pd, Pt) are most commonly employed. Herein, Pt nanoparticles supported on rehydrated MgxAl1-hydrotalcite(denoted as re-MgxAl1-LDH-Pt) were prepared via impregnation-reduction method followed by an in situ rehydration process, which showed high activity and selectivity towards GLY oxidation to produce glyceric acid(GLYA) at room temperature. The metal-support interfacial structure and catalyst basicity were modulated by changing the Mg/Al molar ratio of the hydrotalcite precursor, and the optimal performance was achieved on re-Mg6Al1-LDH-Pt with a GLY conversion of 87.6% and a GLYA yield of 58.6%, which exceeded the traditional activated carbon and oxide supports. A combinative study on structural characterizations(XANES, CO-FTIR spectra, and benzoic acid titration) proves that a higher Mg/Al molar ratio promotes the formation of positively charged Ptd+species at metal-support interface, which accelerates bond cleavage of a-C–H and improves catalytic activity. Moreover, a higher Mg/Al molar ratio provides a stronger basicity of support that contributes to the oxidation of terminal-hydroxyl and thus enhances the selectivity of GLYA. This catalyst with tunable metal-support interaction shows prospective applications toward transformation of biomass-based polyols.
基金Project(2010CB732004)supported by the National Basic Research Program of ChinaProjects(50934006,41272304)supported by the National Natural Science Foundation of China
文摘Rate of penetration(ROP) of a tunnel boring machine(TBM) in a rock environment is generally a key parameter for the successful accomplishment of a tunneling project. The objectives of this work are to compare the accuracy of prediction models employing partial least squares(PLS) regression and support vector machine(SVM) regression technique for modeling the penetration rate of TBM. To develop the proposed models, the database that is composed of intact rock properties including uniaxial compressive strength(UCS), Brazilian tensile strength(BTS), and peak slope index(PSI), and also rock mass properties including distance between planes of weakness(DPW) and the alpha angle(α) are input as dependent variables and the measured ROP is chosen as an independent variable. Two hundred sets of data are collected from Queens Water Tunnel and Karaj-Tehran water transfer tunnel TBM project. The accuracy of the prediction models is measured by the coefficient of determination(R2) and root mean squares error(RMSE) between predicted and observed yield employing 10-fold cross-validation schemes. The R2 and RMSE of prediction are 0.8183 and 0.1807 for SVMR method, and 0.9999 and 0.0011 for PLS method, respectively. Comparison between the values of statistical parameters reveals the superiority of the PLSR model over SVMR one.
基金supported by grants from the Science&Technology Key Program of Zhejiang China(2017C03051)the National Science&Technology Major Project of China(2017ZX10203201)。
文摘Background:Hepatitis B virus-related acute-on-chronic liver failure(HBV-ACLF)has a high short-term mortality.However,the treatment progression for HBV-ACLF in China in the past decade has not been well characterized.The present study aimed to determine whether the HBV-ACLF treatment has significantly improved during the past decade.Methods:This study retrospectively compared short-term(28/56 days)survival rates of two different nationwide cohorts(cohort I:2008-2011 and cohort II:2012-2015).Eligible HBV-ACLF patients were enrolled retrospectively.Patients in the cohorts I and II were assigned either to the standard medical therapy(SMT)group(cohort I-SMT,cohort II-SMT)or artificial liver support system(ALSS)group(cohort IALSS,cohort II-ALSS).Propensity score matching analysis was conducted to eliminate baseline differences,and multivariate logistic regression analysis was used to explore the independent factors for 28-day survival.Results:Short-term(28/56 days)survival rates were significantly higher in the ALSS group than those in the SMT group(P<0.05)and were higher in the cohort II than those in the cohort I(P<0.001).After propensity score matching,short-term(28/56 days)survival rates were higher in the cohort II than those in the cohort I for both SMT(60.7%vs.53.0%,50.0%vs.39.8%,P<0.05)and ALSS(66.1%vs.56.5%,53.0%vs.44.4%,P<0.05)treatments.The 28-day survival rate was higher in patients treated with nucleos(t)ide analogs than in patients without such treatments(P=0.046).Multivariate logistic regression analysis revealed that ALSS(OR=0.962,95%CI:0.951-0.973,P=0.038),nucleos(t)ide analogs(OR=0.927,95%CI:0.871-0.983,P=0.046),old age(OR=1.028,95%CI:1.015-1.041,P<0.001),total bilirubin(OR=1.002,95%CI:1.001-1.003,P=0.004),INR(OR=1.569,95%CI:1.044-2.358,P<0.001),COSSH-ACLF grade(OR=2.683,95%CI:1.792-4.017,P<0.001),and albumin(OR=0.952,95%CI:0.924-0.982,P=0.002)were independent factors for 28-day mortality.Conclusions:The treatment for patients with HBV-ACLF has improved in the past decade.
