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δ13C-δ18O Covariance:An Effective Indicator of Hydrological Closure for Lakes?

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Acta Geologica Sinica(English Edition) 2008年第5期82卷 975-981页

作者： CHEN Jing＇an WANG Fushun WAN Guojiang TANG Degui david Dian ZHANG HUNAG Ronggui LI Jian XIAO Tangfu State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang550002 Guizhou Department of Geography University of Hong Kong Pokfulam Road Hong Kong

The correlation between the δ^13C and δ^13C-δ^18O in primary carbonates is affected by several factors such as hydrological balance, total CO2 concentrations, climatic condition and lake productivity. The influence of these factors on the δ^13C-δ^18O correlation may be different on different time scales. In this paper, two different-type lakes in southwestern China, Lake Erhai and Lake Chenghai, are selected to investigate the influence of climatic pattern on the δ^13C-δ^18O correlation and to evaluate the reliability of the δ^13C-δ^18O covariance as an indicator of hydrological closure. The results show that there exists good correlation between the δ^13C and δ^18O in Lake Erhai （overflowing open lake） and in Lake Chenghai （closed lake）. This suggests that the δ^13C-δ^18O covariance may be not an effective indicator of hydrological closure for lakes, especially on short time scales. On the one hand, a hydrologically open lake may display covariant δ^13C and δ^18O as a result of climatic influence. The particular alternate warm-dry and cold-wet climatic pattern in southwestern China may be the principal cause of the δ^13C-δ^18O covariance in Lake Erhai and Lake Chenghai. On the other hand, a hydrologically closed lake unnecessarily displays covariant trends between δ^13C and δ^18O because of the buffering effect of high CO2 concentration on the δ^13C shift in hyper-alkaline lakes. We should be prudent when we use the covariance between δ^13C and δ^18O to judge the hydrological closure of lake.

关键词： carbonates δ^13C-δ^18O covariance hydrological closure climatic pattern

Prevalence of hyponatremia in acute medical admissions in tropical Asia Pacific Australia

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Asian Pacific Journal of Tropical Medicine 2014年第1期7卷 40-43页

作者： Usman H.Malabu david Porter Venkat N.Vangaveti Monsur Kazi R.Lee Kennedy Department of Medicine Townsville Hospital/James Cook UniversityQueenslandAustralia Department of Pathology Townsville Hospital/James Cook UniversityQueenslandAustralia Department of Medicine Deakin UniversityVictoriaAustralia

Objective:To determine prevalence of hyponatremia in acute medical admissions in Northern ***:We studied 469 consecutive acute medical admissions to a hospital in Australia's Far North Queensland during the colder months of June and July *** of hyponatremia and its relationship with gender,age,diagnosis and prognosis in acute medical admissions were ***:On admission,hyponatremia(plasma sodiumgood for this population with a high prevalence of electrolyte *** prospective analysis on a larger population in the area is needed to confirm our findings.

关键词： Hyponatremia Prevalence Acute admissions Tropical Asia Pacific Australia

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智能井非线性预测控制器设计

控制工程 2013年第3期20卷 489-492,496页

作者：杨青 david Davies 西南石油大学电气信息学院四川成都610500 Institute of Petroleum Engineering Heriot-Watt UniversityEdinburghUKEH14 4AS

随着石油开采中出现的新技术——智能井的应用,井控由地面转移到地下。为了解决地层物理属性难以准确获得以及流体流动的强非线性给井下控制带来的困难,研究了带有模型不确定性的非线性预测控制器。首先建立了带有不确定性的预测控制模... 详细信息

随着石油开采中出现的新技术——智能井的应用,井控由地面转移到地下。为了解决地层物理属性难以准确获得以及流体流动的强非线性给井下控制带来的困难,研究了带有模型不确定性的非线性预测控制器。首先建立了带有不确定性的预测控制模型;然后基于反馈线性化和反步设计的思想设计非线性预测控制器。该控制器在模型带有不确定性时更易使闭环系统稳定,且动态特性良好。以北海油田某区块为例进行的仿真研究结果验证了控制器是有效的。

关键词：智能井非线性预测控制反馈线性化反步设计

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Eat by Colour

英语自学 2004年第2期 14-15页

作者： david Heber 谢琼 Dr

COLOUR is the key to good nutrition. Yet what colour is an increasing number of people’s diet? *** a physician who has studied nutrition and cancer prevention for more than 20 years, I believe that bland diets actually account for the most common diseases, including heart disease, cancer and what I call diabesity-a booming epidemic of obesity and diabetes.

关键词： nutrition obesity actually physician epidemic colo

Severe morbidity after pancreatectomy is accurately pre dicte d by preoperative pancreatic resection score(PREPARE): A prospective validation analysis from a medium-volume center

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Hepatobiliary & Pancreatic Diseases International 2018年第6期17卷 559-565页

作者： Mario Rodriguez-Lopez Francisco J. Tejero-Pintor Baltasar Perez-Saborido Asterio Barrera-Rebollo Martin Bailon-Cuadrado david Pacheco-Sanchez General and Digestive Surgery Department Rio-Hortega University Hospital

Background: Major morbidity in pancreatic surgery remains high. Different scores for predicting complications have been described. Preoperative pancreatic resection(PREPARE) score is based on objective preoperative variables and offers good predictive accuracy for Clavien ≥ III complications. This study aimed to validate this score and analyze other preoperative variables in a prospective study performed in a medium-volume center. Methods: A total of 50 pancreatic resections were included. Preoperative variables were registered and PREPARE was calculated. The main outcome was severe morbidity(Clavien ≥ III) up to 30 days after discharge. The secondary outcomes were length of stay(LOS) and readmission. Statistical validation was performed to compare severe morbidity rate among the scores categories. Association with other preoperative variables(not included in PREPARE) was also tested. Results: Of the 50 pancreatic resections, the severe morbidity was 34.0%, with median LOS of 11 days. Readmission rate was 25.5%. Severe morbidity rates according to PREPARE categories were 18.5% in lowrisk group, 41.7% in intermediate-risk group, and 63.6% in high-risk group, respectively( P = 0.023). The accuracy was 72%(Hosmer–Lemeshow, P = 0.86). ROC curve was obtained both for PREPARE score expressed as incremental values and categorized as the three risk groups, showing an area under curve(AUC) of 0.736(95% CI: 0.586–0.887; P = 0.007) and 0.712(95% CI: 0.555–0.869; P = 0.015), respectively. PREPARE was significant in multivariate analysis. Median LOS was statistically higher as PREPARE category increases(9, 11 and 15 days in low-, intermediate-and high-risk groups, respectively; P = 0.009). Readmission was not associated with any variables. Conclusions: PREPARE behaves as an independent risk factor for severe morbidity after pancreatic surgery. Score validation shows good accuracy prediction. Increasing PREPARE category is also associated with longer LOS.

关键词： Pancreatic surgery Morbidity Complications Preoperative pancreatic resection score Validation

Anion exchange membranes based on long side-chain quaternary ammonium-functionalized poly(arylene piperidinium)s for vanadium redox flow batteries

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Science China Materials 2022年第3期65卷 683-694页

作者： Xuefu Che Weiqin Tang Jianhao Dong david Aili Jingshuai Yang Department of Chemistry College of SciencesNortheastern UniversityShenyang 110819China Department of Energy Conversion and Storage Technical University of DenmarkElektrovejBuilding 3752800 LyngbyDenmark

A new series of poly(arylene piperidinium)-based anion exchange membranes(AEMs)are proposed for vanadium redox flow batteries(VRFBs).The AEMs are fabricated via the Menshutkin reaction between poly(arylene piperidine)without ether bonds in the backbone and various quaternizing agents,including iodomethane,1-bromopentane,and(5-bromopentyl)-trimethylammonium *** properties of the AEMs are investigated in terms of sulfuric acid doping content,swelling,vanadium permeability,ion selectivity,area-specific resistance,mechanical properties,VRFB performance,and cyclic ***,a method of measuring the H^(+) permeability of the AEM is *** demonstrates that the poly(p-terphenyl-N-methylpiperidine)-quaternary ammonium(PTP-QA)membrane with a QA cation-tethered alkyl chain exhibits high H^(+) permeability,resulting in low area *** with its low vanadium permeance,the PTP-QA membrane achieves nearly 370 times higher ion selectivity than Nafion *** VRFB based on PTP-QA-based AEM displays high Coulombic efficiencies above 99% at current densities of 80-160 mA cm^(-2).The higher energy efficiency of 89.8% is achieved at 100 mA cm^(-2)(vs.73.6% for Nafion 115).Meanwhile,the PTPQA-based AEM shows good cycling stability and capacity retention,proving great potential as the ion exchange membrane for VRFB applications.

关键词： vanadium redox flow battery anion exchange membrane poly(arylene piperidinium) quaternary ammonium H+permeability

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氮化镓功率晶体管三电平驱动技术

电工技术学报 2013年第5期28卷 202-207页

作者：任小永 david Reusch 季澍穆明凯 Fred C Lee 南京航空航天大学江苏省新能源发电与电能变换重点实验室南京210016 VirginiaPolytechnicInstituteandStateUniversityBlacksburgVA24061

作为第三代半导体材料的典型代表,宽禁带半导体氮化镓(GaN)材料具有许多硅材料所不具备的优异性能,是高频、高压、高温和大功率应用的优良半导体材料,无论在民用或是军事领域都具有广阔的应用前景。随着GaN技术的进步,大直径硅(Si)基Ga... 详细信息

作为第三代半导体材料的典型代表,宽禁带半导体氮化镓(GaN)材料具有许多硅材料所不具备的优异性能,是高频、高压、高温和大功率应用的优良半导体材料,无论在民用或是军事领域都具有广阔的应用前景。随着GaN技术的进步,大直径硅(Si)基GaN外延技术逐步成熟并向商用化方向发展。2010年以来,多家国际著名半导体厂商相继推出GaN功率晶体管器件。与硅半导体功率器件一样,合理的驱动方式也是GaN功率晶体管优越性能得以体现的重要保障。本文将以GaN功率器件在同步整流Buck变换器中的应用为例,提出一种三电平的驱动方式,以充分发挥GaN功率晶体管器件的优越性。实验结果表明,本文提出的三电平驱动方式可以有效提高变换器的效率。

关键词：氮化镓 GaN 三电平驱动方式

Follow-Up Care of HIV-Positive Pregnant Women in North Central Nigerian: A 15-Year Review

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World Journal of AIDS 2023年第4期13卷 147-160页

作者： Nathaniel david Adewole Vivian Kwaghe Department of Obstetrics and Gynaecology University of Abuja Teaching Hospital Federal Capital Territory Nigeria Department of Medicine University of Abuja Teaching Hospital Federal Capital Territory Nigeria

Background: Pregnant women bear the greatest burden of people living with HIV in the West Africa sub-region, and the country requires continuous optimal follow-up care for their disease after delivery. Documentation of such very important services is rarely done in this high-burden environment, and hence the present study. Method: A 15-year retrospective review of medical records of HIV-positive pregnant women who attended antenatal care services from January 2006 to December 2020 at the prevention of the mothers-to-child transmission unit of the health facility was carried out to document the HIV service provided at the unit, and the follow-up care at the adult HIV special treatment clinic for the continuation of their HIV treatment. Results: Of the 1245 HIV-positive pregnant mothers reviewed during the period, 702 (56.4%) were between the ages of 26 - 35 years, 1043 (83.8%) were on HIV treatment before their index pregnancy, 202 (16.2%) were diagnosed of HIV infection during their last trimester and labor, while 878 (70.5%) continued their HIV services at adult HIV special treatment clinic after delivery. The predictors of continuous care include: maternal parity with [OR] 0.51 (0.35 - 0.73), p = 0.02, time of presentation in trimester with [OR] 1.54 (1.15 - 2.06), p = 0.003, duration on antiretroviral therapy [OR] 2.14 (1.57 - 2.9) p Conclusion: The high rate of optimal follow-up care of HIV-positive mothers after delivery in the adult special treatment clinic in this study speaks of the preparedness and good supportive services provided to these mothers in the health facility. However, the high rate of loss to follow-up among this cohort of women requires a more focused intervention during their postpartum period for a better outcome.

关键词： Follow-Up HIV Quality of Life Pregnant Women

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基于速度的显式等效力控制方法的研究

工程力学 2016年第6期33卷 15-22,33页

作者：周惠蒙吴斌王涛 david Wagg 戴君武中国地震局工程力学研究所地震工程与工程振动重点实验室黑龙江哈尔滨150080 哈尔滨工业大学土木工程学院黑龙江哈尔滨150090 谢菲尔德大学机械工程系英国谢菲尔德S1 3TD

该文采用等效力控制(EFC)来求解在实时子结构试验中的速度差分方程,采用反馈控制取代数学迭代来求解非线性动力方程。谱半径分析表明,由于准确地模拟了速度响应,结合显式Newmark-?算法的等效力控制方法的稳定界限与系统的阻尼系数无关,... 详细信息

该文采用等效力控制(EFC)来求解在实时子结构试验中的速度差分方程,采用反馈控制取代数学迭代来求解非线性动力方程。谱半径分析表明,由于准确地模拟了速度响应,结合显式Newmark-?算法的等效力控制方法的稳定界限与系统的阻尼系数无关,在不同阻尼比下稳定界限保持为?=2,具有良好的数值特性。而直接预测速度的中心差分法和采用线性插值模拟速度的平均加速度等效力控制方法,其稳定界限随着系统阻尼比的增大而降低,对于过阻尼结构(阻尼比大于1),原本无条件稳定的平均加速度等效力控制方法变为条件稳定:对于阻尼比为1.05的动力系统,其稳定界限为?=1.45。最后,采用该文方法对安装磁流变(MR)阻尼器的单自由度结构的地震响应进行数值分析,结果表明该文方法能正确跟踪结构速度和位移命令,因而对于速度相关型结构体系,具有良好的适用性和精确性。

关键词：实时子结构试验等效力控制速度控制显式Newmark-β方法稳定性

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