猪全胰十二指肠移植空肠引流及门静脉回流模型的建立

目的 建立猪的全胰十二指肠移植空肠内引流 ,门静脉回流模型。方法 40头杂种猪分为供体组和受体组 ,对供体组 ( n=2 0 )进行 U W液低温灌注 ,切取全胰十二指肠以及部分腹主动脉和门静脉。修剪移植胰腺和十二指肠 ,U W液保存移植物的肠系膜上动脉开口和腹腔动脉开口分别与供体的髂内外动脉端 -端吻合呈“Y”形。切除受体组胰腺建成 型糖尿病模型 ,移植物的门静脉与受体的肠系膜上静脉吻合 ,移植物“Y”形的髂总动脉与受体腹主动脉端侧吻合。十二指肠与空肠侧侧吻合。结果 本实验完成全胰十二指肠移植 2 0例 ,胰腺移植手术中因麻醉过深呼吸抑制死亡 1例 ,2例手术后移植胰腺形成血栓、梗死。 17例手术后 2 4h外周血检测血糖正常 ,移植胰腺存活时间平均 18.6± 2 .6d。

两相湍浮力回流模型及热污染预报

本文把研究精细的热污染预报模型作为基本目标,广泛地涉及了两相湍流精细模拟的理论和方法。用Eulerian坐标系中多流体模型统一描述热水和冷水两相各自的运动,并分别对热水和冷水本身的湍流输运规律以及相间相互作用规律进行模拟,建立了两相湍浮力回流模型及相应的数值计算方法。选定了包含有浮力和回流的两相复杂湍流作为模拟对象,对模型进行了数值验证,并与实测资料作了对比。结果表明,模型的模拟效果较为满意。

基于热风回流焊机热平衡机理模型的简化解耦控制

从热学机理出发建立了基于热平衡机理的热风回流焊机模型,针对该模型阶数极高,且具有强耦合性的特点,应用Padé逼近法把模型各通道的传递函数简化成经典的二阶系统,结合不变性原理对系统进行解耦补偿设计,从仿真效果来看,任一温区的温度控制基本不再受其它温区的温度变化影响,达到了更精确的控制要求。

渣油气化的过程分析与三区模型

基于渣油气化炉冷态流场测试与停留时间分布测试以及工业现象,提出了渣油气化的三区模型,即燃烧区、回流区、二次反应区.二次反应区的主要气相化学反应为CO_2+H_2=CO+H_2O

压裂支撑剂回流影响因素及控制措施

为了充分认识影响压裂支撑剂回流的因素,降低压裂后放喷测试过程中压裂支撑剂回流引起的储层伤害,解决阀门砂卡以及地面管线、油嘴套、分离器冲蚀等井口隐患治理,以四川盆地威远地区某页岩气平台压裂后放喷测试过程为研究对象,分析了4类压裂支撑剂回流预测模型中各种因素对压裂支撑剂回流的影响程度;在此基础上,利用计算流体力学(CFD)与离散单元方法(DEM)耦合并行计算方法(即CFD-DEM技术)进行压裂支撑剂回流过程数值模拟研究,同时在该页岩气井开展了矿场实验进行验证。研究结果表明:①影响压裂支撑剂回流的因素较多,主要包括压裂支撑剂性质、作用在压裂支撑剂上的流体性质及其流速、裂缝的性质,其中临界返排流速是影响压裂支撑剂回流的主要因素;②采用CFD-DEM技术能够研究复杂工况条件下各因素对压裂支撑剂回流的影响规律,并从矿场试验得到印证。结论认为:在保证压裂后返排流体临界携液流速和防止天然气水合物生成的基础上,合理优选油嘴尺寸是减少压裂支撑剂回流的有效控制措施。

支撑剂回流理论研究

压裂是低渗透油藏的重要开发手段,而压裂返排施工关乎压裂成败。通过对压裂过程中的支撑剂进行受力分析,利用牛顿第二定律分析了支撑剂在水平和竖直方向上的运动状态,建立了支撑剂回流模型。利用室内模拟实验,模拟了在单条裂缝中的支撑剂运动,分析了不同返排流量下的支撑剂运动状态,验证了支撑剂回流模型的准确性。通过室内模拟实验和回流模型计算分析了实际压裂过程中支撑剂在裂缝中的运动,得到支撑剂在裂缝中的运动距离相对于裂缝半长很小,为现场施工过程中进行顶替返排提供理论支撑。

川陈皮素自微乳的制备及其大鼠在体肠吸收动力学

目的:制备川陈皮素自微乳制剂,以期提高其口服生物利用度,并研究其在大鼠小肠各部位的吸收情况。方法:测定川陈皮素自微乳的粒径、Zeta电位等理化参数,初步考察其稳定性;运用大鼠在体肠回流模型,采用HPLC法测定回流液中药物的浓度,考察药物的吸收。结果:制得的川陈皮素自微乳平均粒径为(17.9±1.5)nm,Zeta电位为-4.9mV,稳定性好。川陈皮素微乳在空肠的吸收速率最快,吸收速率常数Ka为(0.5298±0.0507)h-1;川陈皮素胶束在空肠段的吸收显著低于微乳组(P<0.05)。结论:川陈皮素自微乳制剂稳定,微乳对川陈皮素在大鼠小肠的吸收有明显的促进作用。

盐酸青藤碱在大鼠肠道吸收特性的研究

目的研究盐酸青藤碱 (SM)不同肠段的吸收特性。方法采用大鼠在体回流模型。应用高效液相色谱法测定回流液中药物和酚红的浓度。结果十二指肠与空肠之间单位面积的吸收速度常数有显著性差异 (P <0 0 5 ) ,而十二指肠与回肠、结肠之间无显著性差异 ,并且空肠与回肠、空肠与结肠以及回肠与结肠之间均无显著性差异。结论SM在大鼠肠道的不同部位吸收特性相似。

大气污染防治审计结果运用影响因素研究——来自我国市级行政区的经验证据

以2008年—2016年我国市级审计机关数据为样本,基于超效率DEA模型和Tobit模型进行面板数据检验,分别从正反馈层面和负反馈层面研究了内外生因素对大气污染防治审计结果运用的影响。结果表明:季节因素和政府自我干预因素与大气污染防治审计结果运用情况指标显著负相关;法律权威因素、审计机关绩效考核重视度因素及综合效应因素与之显著正相关;审计人员接受执业培训水平因素与之显著正相关;审计项目规定时间长度与之显著负相关。以上结果群能够构成大气污染防治审计结果运用交互影响回流模型。该研究结论对调整大气污染防治审计结果运用工作着力点以及提升大气污染防治审计结果运用工作成效具有重要的启示作用。

Physical activity, obesity and gastroesophageal reflux disease in the general population

AIM: To clarify the association between physical activity and gastroesophageal reflux disease (GERD) in nonobese and obese people. METHODS: A Swedish population-based cross-sectional survey was conducted. Participants aged 40-79 years were randomly selected from the Swedish Registry of the Total Population. Data on physical activity, GERD, body mass index (BMI) and the covariates age, gender, comorbidity, education, sleeping problems, and tobacco smoking were obtained using validated questionnaires. GERD was self-reported and defined as heartburn or regurgitation at least once weekly, and having at least moderate problems from such symptoms. Frequency of physical activity was categorized into three groups: (1) "high" (several times/week); (2) "intermediate" (approximately once weekly); and (3) "low" (1-3 times/mo or less). Analyses were stratified for participants with "normal weight" (BMI < 25 kg/m 2 ), "overweight" (BMI 25 to ≤ 30 kg/m 2 ) and "obese" (BMI > 30 kg/m 2 ). Multivariate logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (CIs), adjusted for potential confounding by covariates. RESULTS: Of 6969 eligible and randomly selected individuals, 4910 (70.5%) participated. High frequency of physical activity was reported by 2463 (50%) participants, GERD was identified in 472 (10%) participants, and obesity was found in 680 (14%). There were 226 (5%) individuals with missing information about BMI. Normal weight, overweight and obese participants were similar regarding distribution of gender and tobacco smoking status, while obese participants were on average slightly older, had fewer years of education, more comorbidity, slightly more sleeping problems, lower frequency of physical activity, and higher occurrence of GERD. Among the 2146 normal-weight participants, crude point estimates indicated a decreased risk of GERD among individuals with high frequency of physical activity (OR: 0.59, 95% CI: 0.39-0.89), compared to low frequency of physical activity. However, after adjustment for potential confounding factors, neither intermediate (OR: 1.30, 95% CI: 0.75-2.26) nor high (OR: 0.99, 95% CI: 0.62-1.60) frequency of physical activity was followed by decreased risk of GERD. Sleeping problems and high comorbidity were identified as potential confounders. Among the 1859 overweight participants, crude point estimates indicated no increased or decreased risk of GERD among individuals with intermediate or high frequency of physical activity, compared to low frequency. After adjustment for confounding, neither intermediate (OR: 0.75, 95% CI: 0.46-1.22) nor high frequency of physical activity were followed by increased or decreased risk of GERD compared to low frequency among nonobese participants. Sleeping problems and high comorbidity were identified as potential confounders for overweight participants. In obese individuals, crude ORs were similar to the adjusted ORs and no particular confounding factors were identified. Intermediate frequency of physical activity was associated with a decreased occurrence of GERD compared to low frequency of physical activity (adjusted OR: 0.41, 95% CI: 0.22-0.77). CONCLUSION: Intermediate frequency of physical activity might decrease the risk of GERD among obese individuals, while no influence of physical activity on GERD was found in non-obese people.

Paste-like cemented backfilling technology and rheological characteristics analysis based on jigging sands

To make backfilling body meet strength requirement,physical-chemical evaluation and proportioning tests were conducted on several backfilling materials.Jigging sands,#32.5 cement and fly ash were determined as backfilling aggregate,binding material and modified material,respectively.An optimized proportion of backfilling materials with a solid mass fraction of 78%and cement:fly ash:jigging sands mass ratio of 1:2:14,was suggested to Jiangan Pyrite Mine,China.The slurry made by optimized proportion produced obvious shear thinning phenomena,and was confirmed as paste-like slurry.To analyze its rheological characteristics,L-type pipeline test and Haake VT550 rotational viscometer test were conducted.Bingham and Casson fluid models were applied to several paste-like slurry samples to simulate flow and stress states;Casson fluid model was proved to have better simulation effect on paste-like slurry with shear thinning phenomena;rheological parameters of backfilling slurry made by suggested proportion were measured.Initial yield stress,average apparent viscosity and limiting viscosity are 55.35 Pa,1.216 Pa-s and 0.48 Pa-s,respectively.Compared with Bingham fluid model,Casson fluid model has a better simulation effect on paste-like slurry with shear thinning phenomena,through calculating the residual standard deviations.

Impacts of Climatic Change on River Runoff in Northern Xinjiang of China over Last Fifty Years

The characteristics of climatic change and fiver runoff, as well as the response of fiver runoff to climatic change in the northern Xinjiang are analyzed on the basis of the hydrological and meteorological data over the last 50 years by the methods of Mann-Kendall nonparametric test and the nonlinear regression model. The results show that： 1） The temperature and the precipitation increased significantly in the whole northern Xinjiang, but the precipitation displayed no obvious change, or even a decreasing trend in the northern mountainous area of the northern Xinjiang. 2） River runoff varied in different regions in the northern Xinjiang. It significantly increased in the northern slope of the Tianshan Mountains and the north of the northern Xinjiang （p = 0.05）, while slightly ificreased in the west of the northern Xinjiang. 3） North Atlantic Oscillation （NAO） affects fiver runoff by influencing temperature and precipitation. The NAO and precipitation had apparent significant correlations with the fiver runoff, but the temperature did not in the northern Xinjiang. Since the mid-1990s fiver runoff increase was mainly caused by the increasing temperature in the northern slope of the Tianshan Mountains and the north of the northern Xinjiang. Increased precipitation resulted in increased fiver runoff in the west of the northern Xinjiang.

Indirect heat integration across plants using hot water circles

Total site heat integration(TSHI) provides more opportunities for energy saving in industry clusters. Some design methods including direct integration using process streams and indirect integration using intermediate-fluid circuits, i.e., steam, dowtherms and hot water, have been proposed during last few decades. Indirect heat integration is preferred when the heat sources and sinks are separated in independent plants with rather long distance. This improves energy efficiency by adaption of intermediate fluid circle which acts as a utility provider for plants in a symbiotic network. However, there are some significant factors ignored in conventional TSHI, i.e. the investment of pipeline, cost of pumping and heat loss. These factors simultaneously determine the possibility and performance of heat integration. This work presents a new methodology for indirect heat integration in low temperature range using hot water circuit as intermediate-fluid medium. The new methodology enables the targeting of indirect heat integration across plants considering the factors mentioned earlier. An MINLP model with economic objective is established and solved. The optimization results give the mass flow rate of intermediate-fluid, diameter of pipeline, the temperature of the circuits and the matches of heat exchanger networks(HENS) automatically. Finally, the application of this proposed methodology is illustrated with a case study.

Statistically Downscaled Summer Rainfall over the Middle-Lower Reaches of the Yangtze River

The summer rainfall over the middle-lower reaches of the Yangtze River valley (YRSR) has been estimated with a multi-linear regression model using principal atmospheric modes derived from a 500 hPa geopotential height and a 700 hPa zonal vapor flux over the domain of East Asia and the West Pacific.The model was developed using data from 1958 92 and validated with an independent prediction from 1993 2008.The independent prediction was efficient in predicting the YRSR with a correlation coefficient of 0.72 and a relative root mean square error of 18%.The downscaling model was applied to two general circulation models (GCMs) of Flexible Global Ocean-Atmosphere-Land System Model (FGOALS) and Geophysical Fluid Dynamics Laboratory coupled climate model version 2.1 (GFDL-CM2.1) to project rainfall for present and future climate under B1 and A1B emission scenarios.The downscaled results pro-vided a closer representation of the observation compared to the raw models in the present climate.In addition,compared to the inconsistent prediction directly from dif-ferent GCMs,the downscaled results provided a consistent projection for this half-century,which indicated a clear increase in the YRSR.Under the B1 emission scenario,the rainfall could increase by an average of 11.9% until 2011 25 and 17.2% until 2036 50 from the current state;under the A1B emission scenario,rainfall could increase by an average of 15.5% until 2011 25 and 25.3% until 2036 50 from the current state.Moreover,the increased rate was faster in the following decade (2011 25) than the latter of this half-century (2036 50) under both emissions.

Gas-solid flow field numerical simulation of different feeding and returning formations of flue-gas circulating fluidized bed

3D Euler double-fluid model was applied and three different feedstocks and reverts formations were simulated. By calculating and analyzing the state of gas and solid fluxion in absorber using three different methods of the feedstocks and reverts in recirculating fluidized bed, described the behavior of gas and solid through the gas-phase velocity, turbulence intensity, gas-solid sliding velocity, and density of particles. The results show that the feedstocks and reverts enters into absorption tower through two symmetrical feedings and are mixed with flue gas. Based on the respective analysis of each model and the com- parison analysis of the three models, this paper drew conclusions. The turbulence intensity of absorption tower is high, gas-solid sliding speed is big, and granule concentration near the axis is high, which has advantages for desulfurization and im- proving the utilization rate of absorbent.

The Study on Trade Policy and Openness of Mongolia： Influences on Trade Flows Between China-Mongolia-Russia （Past and Future）

This paper aimed to highlight the effects of conflict in Mongolia on trade policy and openness, by estimating the trade flows with neighbor countries （China and Russia）. Fourteen years＇ （2000-2013） data of Mongolian imports and exports were collected and gone through principal component analysis （PCA） and empirical analysis for grouping various trades with China and Russia. The empirical analysis identified the determining factors of Mongolian trade flow and openness with China and Russia. Empirical analysis evidenced that Mongolian trade and openness policy raised bilateral trade between China and Russia, leaving a great influence on economic size. Two main questions represented as empirically tested by each sample country. How did Mongolian trade policy and openness influence trade flows between China and Russia and economic growth of Mongolia？ Did Mongolian trade policy and the bilateral trade with China and Russia increase on trade openness？ Finally, the study focused on the forecasts from 2016 to 2018 to examine Mongolian trade flows with China and Russia using ordinary least squares method and autoregressive-moving-average （ARMA） model. China-Mongolia-Russia trade flows will continue to dominate during the forecasted period. As shown by the structure of export and import, goods with China and Russia influenced the mutual trade amount. Moreover, China and Russia traded to continue with Mongolia for goods in long run. Trade policy and openness, the major contributor in Mongolian economy, are significantly playing roles in trade and economy.

A nonlinear rheological model of backfill material for retaining roadways and the analysis of its stability

The long-term stability of backfill material is the key to retaining roadways successfully. In order to study the rheological deformation of backfill material and its long-term stability, given the visco-elastoplastic properties of this material, we introduced a softening and a hardening function for a new nonlinear the- ological model with time-varying parameters. Based on this, we presented the instability condition of this model by using the principle of minimum potential energy. Combined with engineering practice, we cal- culated the urlstable time period of backfill material. The results show that the time of instability of the backfill material relate to the initial parameters of the material, ＂the coefficients decided by temperature and the ratio of the plastic zone of the backfill material. Based on the results of our analysis from the point of view of energy, we can quickly obtain the time of instability of this model from our graphical analysis. The time of instability of the backfill material obtained from our investigation coincides with an actual project.

New empirical model to evaluate groundwater flow into circular tunnel using multiple regression analysis

There are various analytical, empirical and numerical methods to calculate groundwater inflow into tun- nels excavated in rocky media. Analytical methods have been widely applied in prediction of groundwa- ter inflow to tunnels due to their simplicity and practical base theory. Investigations show that the real amount of water infiltrating into jointed tunnels is much less than calculated amount using analytical methods and obtained results are very dependent on tunnel＇s geometry and environmental situations. In this study, using multiple regression analysis, a new empirical model for estimation of groundwater seepage into circular tunnels was introduced. Our data was acquired from field surveys and laboratory analysis of core samples. New regression variables were defined after perusing single and two variables relationship between groundwater seepage and other variables. Finally, an appropriate model for estima- tion of leakage was obtained using the stepwise algorithm. Statistics like R, R2, R2e and the histogram of residual values in the model represent a good reputation and fitness for this model to estimate the groundwater seepage into tunnels. The new experimental model was used for the test data and results were satisfactory. Therefore, multiple regression analysis is an effective and efficient way to estimate the groundwater seeoage into tunnels.

An Artificial Neural Network-Based Snow Cover Predictive Modeling in the Higher Himalayas

With trends indicating increase in temperature and decrease in winter precipitation, a significant negative trend in snow-covered areas has been identified in the last decade in the Himalayas. This requires a quantitative analysis of the snow cover in the higher Himalayas. In this study, a nonlinear autoregressive exogenous model, an artificial neural network （ANN）, was deployed to predict the snow cover in the Kaligandaki river basin for the next 30 years. Observed climatic data, and snow covered area was used to train and test the model that captures the gross features of snow under the current climate scenario. The range of the likely effects of climate change on seasonal snow was assessed in the Himalayas using downscaled temperature and precipitation change projection from - HadCM3, a global circulation model to project future climate scenario, under the AIB emission scenario, which describes a future world of very rapid economic growth with balance use between fossil and non-fossil energy sources. The results show that there is a reduction of 9% to 46% of snow cover in different elevation zones during the considered time period, i.e., 2Oll to 2040. The 4700 m to 52oo m elevation zone is the most affected area and the area higher than 5200 m is the least affected. Overall, however, it is clear from the analysis that seasonal snow in the Kaligandaki basin is likely to be subject to substantialchanges due to the impact of climate change.

Updating Methods for Real Time Flood Forecasting： A Comparison through Senegal River Basin Upstream Bakel

Heavy floods occur frequently in the Senegal River Basin, causing catastrophic flooding downstream the river rating station of Bakel. Anticipating the occurrence of such phenomena is the only way to reduce the resulting damages. Flood forecasting is a necessity. Flood forecasting plays also an important role in the implementation of flood management scenarios and in the protection of hydro electric structures. Many methods are applied. The most complete are based on the conservation laws of physics governing the free surface flow. These methods need a complete description of the geometry of the river and their implementation requires also huge investments. In practice the river basin can be considered as a system of inputs-outputs related by a transfer function. In this paper the authors first used a multiple linear regression model with constant parameters estimated by the ordinary least square method to simulate the propagation of the floods in the upstream part of the Senegal river basin. The authors then apply statistical and graphical criteria of goodness-of-fit to test the suitability of this model. Three procedures of parameters updating have then been added to this linear model： the Kalman filter method, the recursive least square method, and the stochastic gradient method The criteria of goodness-of-fit used above have shown that the stochastic gradient method, although more rudimentary, represents better the flood propagation in the head basin of the Senegal river upstream Bakel. This result is particularly interesting because data influenced by Manantali Dam are used.