Three-Dimensional Water Quality Model Based on FVCOM for Total Load Control Management in Guan River Estuary,Northern Jiangsu Province

Guan River Estuary and adjacent coastal area(GREC) suffer from serious pollution and eutrophicational problems over the recent years.Thus,reducing the land-based load through the national pollutant total load control program and developing hydrodynamic and water quality models that can simulate the complex circulation and water quality kinetics within the system,including longitudinal and lateral variations in nutrient and COD concentrations,is a matter of urgency.In this study,a three-dimensional,hydrodynamic,water quality model was developed in GREC,Northern Jiangsu Province.The complex three-dimensional hydrodynamics of GREC were modeled using the unstructured-grid,finite-volume,free-surface,primitive equation coastal ocean circulation model(FVCOM).The water quality model was adapted from the mesocosm nutrients dynamic model in the south Yellow Sea and considers eight compartments:dissolved inorganic nitrogen,soluble reactive phosphorus(SRP),phytoplankton,zooplankton,detritus,dissolved organic nitrogen(DON),dissolved organic phosphorus(DOP),and chemical oxygen demand.The hydrodynamic and water quality models were calibrated and confirmed for 2012 and 2013.A comparison of the model simulations with extensive dataset shows that the models accurately simulate the longitudinal distribution of the hydrodynamics and water quality.The model can be used for total load control management to improve water quality in this area.

Predicting Net Cross-Shore Total Load Transport: A Phase-Averaging, Quasi-Steady Approach Incorporating Undertow Contribution

Wave shapes that induce velocity skewness and acceleration asymmetry are usually responsible for onshore sediment transport, whereas undertow and bottom slope effect normally contribute to offshore sediment transport. By incorporating these counteracting driving forces in a phase-averaged manner, the theoretically-based quasi-steady formula of Wang （2007） is modified to predict the magnitude and direction of net cross-shore total load transport under the coaction of wave and current. The predictions show an excellent agreement with the measurement data on medium and fine sand collected by Dohmen-Janssen and Hanes （2002） and Schretlen （2012） in a full-scale wave flume at the Coastal Research Centre in Hannover, Germany. The modified formula can predict the net onshore transport of fine sand in sheet flows. In particular, it can predict the net offshore transport of medium sand in rippled beds through enlarged bed roughness, as well as the net offshore transport of fine-to-coarse sand in sheet flows with the aid of a new criterion to judge the occurrence of net offshore transport.

Optimal allocation method of electric/air braking force of high-speed train considering axle load transfer

Reasonable distribution of braking force is a factor for a smooth,safe,and comfortable braking of trains.A dynamic optimal allocation strategy of electric-air braking force is proposed in this paper to solve the problem of the lack of consideration of adhesion difference of train wheelsets in the existing high-speed train electric-air braking force optimal allocation strategies.In this method,the braking strategy gives priority to the use of electric braking force.The force model of a single train in the braking process is analyzed to calculate the change of adhesion between the wheel and rail of each wheelset after axle load transfer,and then the adhesion of the train is estimated in real time.Next,with the goal of maximizing the total adhesion utilization ratio of trailer/motor vehicles,a linear programming distribution function is constructed.The proportional coefficient of adhesion utilization ratio of each train and the application upper limit of braking force in the function is updated according to the change time point of wheelset adhesion.Finally,the braking force is dynamically allocated.The simulation results of Matlab/Simulink show that the proposed algorithm not only uses the different adhesion limits of each trailer to reduce the total amount of braking force undertaken by the motor vehicle,but also considers the adhesion difference of each wheelset.The strategy can effectively reduce the risk and time of motor vehicles during the braking process and improve the stability of the train braking.

Total loads modeling and geological adaptability analysis for mixed soil-rock tunnel boring machines

Rock-soil interface mixed ground(RSI)is often encountered in tunnel construction.The excavation loads of tunnel boring machines(TBMs)are controlled by the interaction characteristics between TBM and rock/soil layers.The different properties of rock and soil cause the varying interaction range and stress distribution.Currently,there have been several studies available to estimate excavation loads under RSI,and the conclusion is that the total loads increase with increasing the rock layer proportion in the excavation face.However,the previous studies cannot take the difference of rock/soil properties into account,except for the calculation of cutters loads.Therefore,the interaction characteristics between RSI and TBM is unclear.This paper analyzes the interaction characteristics between TBM’s main components and complex geological conditions(e.g.,layered soil,layered rock,and RSI condition).A model is proposed to calculate the total thrust and total torque assuming quasi-static equilibrium of the tunneling equipment.The rationality and applicability of the model are discussed and verified by two typical projects.Furthermore,the geological adaptability is discussed in terms of the excavation difficulty and the matching relationship between total torque and total thrust.The results indicate that when the rock layer proportion in the excavation face increases,the reduction of overall extrusion and friction loads is 1.5 times higher than the increase of disc cutters breaking load.The total loads and the ratio of the total torque to total thrust decrease approximately linearly.There is a power function relationship between the excavation difficulty index and the penetration depth.The results of this study provide an important reference for the total loads design of equipment propulsion systems and the parameter adjustment during tunnel construction.

Determination of influential parameters for prediction of total sediment loads in mountain rivers using kernel-based approaches

It is important to have a reasonable estimation of sediment transport rate with respect to its significant role in the planning and management of water resources projects. The complicate nature of sediment transport in gravel-bed rivers causes inaccuracies of empirical formulas in the prediction of this phenomenon. Artificial intelligences as alternative approaches can provide solutions to such complex problems. The present study aimed at investigating the capability of kernel-based approaches in predicting total sediment loads and identification of influential parameters of total sediment transport. For this purpose, Gaussian process regression(GPR), Support vector machine(SVM) and kernel extreme learning machine(KELM) are applied to enhance the prediction level of total sediment loads in 19 mountain gravel-bed streams and rivers located in the United States. Several parameters based on two scenarios are investigated and consecutive predicted results are compared with some well-known formulas. Scenario 1 considers only hydraulic characteristics and on the other side, the second scenario was formed using hydraulic and sediment properties. The obtained results reveal that using the parameters of hydraulic conditions asinputs gives a good estimation of total sediment loads. Furthermore, it was revealed that KELM method with input parameters of Froude number(Fr), ratio of average velocity(V) to shear velocity(U*) and shields number(θ) yields a correlation coefficient(R) of 0.951, a Nash-Sutcliffe efficiency(NSE) of 0.903 and root mean squared error(RMSE) of 0.021 and indicates superior results compared with other methods. Performing sensitivity analysis showed that the ratio of average velocity to shear flow velocity and the Froude number are the most effective parameters in predicting total sediment loads of gravel-bed rivers.

Total Maximum Allocated Loads on Stoichiometry of Nitrogen and Identification of Critical Form in Jiaozhou Bay, China

Total pollutant load control management for total dissolved nitrogen(TDN) is an urgent task required to gain a good water quality status in Jiaozhou Bay(JZB), China. In this paper, the stoichiometry of multiform TDN on land-ocean interactions associated with marine biogeochemical reaction(LOIMBR) was studied by modeling the load-response relationship based on a three-dimensional water quality model of nitrogen in JZB. The results showed that the stoichiometry on LOIMBR of dissolved organic nitrogen(DON), NO3-N and NH4-N was 3:1:1, with one-third of the contribution on the concentration of dissolved inorganic nitrogen(DIN) in JZB for the land-based DON loads to DIN loads. Based on the stoichiometric relationship of nitrogen forms, the total maximum allocated load(TMAL) of equivalent TDN(ETDN) was approximately 5300 t a^-1 in JZB, equivalent to the TMAL of 5700, 5800 and 15600 t a^-1 for NH4-N, NO3-N and DON, respectively. According to the loads of ETDN, there were four outfalls overloaded in JZB in 2015, which lie in the head of the bay. In the four overloaded outfalls, besides NO3-N, NH4-N was the critical nitrogen control form for Moshui River, while DON for Dagu River and Haibo River. The results of numerical experiments further showed that JZB will achieve good water quality after 7 years by implementation of the 'different emission reduction' based on TMAL of ETDN, which is significantly better than 'equal percent removal'.

Use of antibiotic-loaded cement in total knee arthroplasty

Bone cement has the capacity to release antibiotic molecules if any antibiotic is included in it, and these elution properties are improved as cement porosity is increased. In vitro studies have shown high local antibiotic concentration for many hours or few days after its use. Antibiotic loaded bone cement(ALBC) is helpful when treating an infection in total knee arthroplasty(TKA) revision surgery. The purpose of this paper was to review the evidence for the routine use of ALBC in TKA in the literature, its pros and cons. Many authors have recommended the use of ALBC also in primary TKA for infection prophylaxis, but the evidence based on data from National Registries, randomized clinical trials and meta-analysis suggest a protective effect of ALBC against infection when used in hips, but not(or only mild) in knees. A possible explanation to this finding is that the duration and quantity of locally elevated antibiotic levels after surgery are smaller in TKA, due to the smaller amount of cement used for fixation in TKA-only a layer in the bone surface. There are some concerns about the routine use of ALBC in primary TKA as prophylaxis against infection: Firstly, there is a risk of hypersensivity or toxicity even when the chance is highly improbable. Secondly, there is a reduction in the mechanical properties of the cement, but this can be probably neglected if the antibiotic is used in low doses, not more than 1 g per 40 g cement package. Another significant concern is the increased economic cost, which could be overlooked if there were enough savings in treating fewer prosthetic infections. Finally, there is also a risk of selection of antibiotic-resistant strains of bacteria and this could be the main concern. If used, the choice of the antibiotic mixed in ALBC should consider microbiological aspects(broad antimicrobial spectrum and low rate of resistant bacteria), physical and chemical aspects(thermal stability, high water solubility), pharmacological characteristics(low risk to allergic reactions or toxicity) and economic aspects(not too expensive). The most commonly used antibiotics in ALBC are gentamicin, tobramycin and vancomycin. In conclusion, there is a paucity of randomized clinical trials in the use of ALBC in primary TKAs and the actual evidence of the effect of ALBC in reducing the risk of infection is insufficient. This, in addition to concerns about patient safety, risks of increase in the antibiotic resistance of microorganisms and the increase in costs in the procedure, lead us to recommend a cautious use of ALBC, perhaps only in high-risk patients(immunocompromised, morbidly obese, diabetic and patients with previous history of fracture or infection around the knee) unless the benefits of ALBC use were fully proven. Meanwhile, the rigorous use of peri-operative prophylactic systemic antibiotics and adoption of efficient antiseptic procedures and improved surgical techniques must be considered the gold standard in infection prevention in TKA surgery.

血浆致动脉粥样硬化指数与脑小血管病总负荷的相关性研究进展

脑小血管病(CSVD)是一组由不同病因造成的临床症状和影像学表现相似的疾病,它主要影响着脑内的小动脉及小静脉等高级血管网。目前,CSVD的病理生理机制仍不完全清楚,但动脉粥样硬化(AS)是众所周知的脑部血管疾病的主要病理机制之一,而血脂在AS的发病机制中又起着非常重要的作用。随着大量学者的深入研究,目前认为血浆致动脉粥样硬化指数(AIP)及其相关传统血脂指标与CSVD联系密切。此研究从AIP与CSVD的发生发展入手,深入探讨了AIP及相关传统血脂指标与CSVD各分型之间的相关性,整合CSVD影像学总负荷来体现CSVD的严重程度,进一步探讨AIP及传统血脂指标与CSVD总负荷的相关性,最终确定了AIP与CSVD严重程度的相关性。本文对AIP及其相关传统指标与CSVD总负荷的相关性研究进展做一综述,全面阐述了血脂对CSVD总负荷的影响,为临床建立CSVD总负荷综合性评价指标提供新依据。

CTCA定量参数对冠心病患者短期病死预测价值

目的探讨CT冠状动脉造影(CTCA)定量参数对冠心病患者短期病死预测价值。方法选取2021年3月—2023年3月收治的冠心病200例,比较不同冠状动脉病变程度冠心病患者CTCA定量参数(动脉阻力指数、总斑块负荷和斑块最小密度CT值),分析CTCA定量参数与冠心病患者冠状动脉病变程度相关性,探讨术后1年冠心病患者病死情况,分析CTCA定量参数与冠心病患者短期病死风险关联性,评价CTCA定量参数对冠心病患者短期病死预测价值。结果不同冠状动脉病变程度冠心病患者动脉阻力指数、总斑块负荷逐渐升高,斑块最小密度CT值逐渐降低(P<0.05)。冠心病患者动脉阻力指数、总斑块负荷与疾病类型、病变支数及狭窄程度呈正相关,斑块最小密度CT值与疾病类型、病变支数及狭窄程度呈负相关(P<0.05)。冠心病200例中39例(19.50%)术后1年病死。动脉阻力指数、总斑块负荷和斑块最小密度CT值与冠心病患者短期病死有关(P<0.01)。对冠心病患者短期病死预测的受试者工作特征曲线下面积动脉阻力指数、总斑块负荷和斑块最小密度CT值三者联合明显高于单独预测(P<0.05)。结论CTCA定量参数与冠心病患者冠状动脉病变程度密切相关,且联合各参数预测冠心病患者短期病死价值较高。

不同影像学类型脑小血管病及其MRI总负荷与认知功能障碍的研究进展

脑小血管病(cerebral small vessel disease,CSVD)是引起人群认知功能障碍最重要的原因之一,随着我国人口老龄化趋势的加重及医学影像技术的发展,CSVD的发病率呈逐年上升趋势,其所引起的认知功能障碍也越来越受到关注。因脑小血管病起病隐匿、进展缓慢、早期无明显临床表现,出现症状时已进入认知功能障碍的中晚期或者已经形成痴呆,往往带给患者不能逆转的损伤及沉重的医疗负担。本文就不同影像学类型脑小血管病及其MRI总负荷对认知功能的影响进行综述,进一步了解CSVD与认知功能的关系,为CSVD所致认知功能障碍的识别和预防提供帮助。

基于HYPE模型的汉江安康断面以上流域非点源污染模拟

基于空间数据和属性数据,构建了汉江安康断面以上流域环境水文预测(HYPE)模型,模拟了2012—2016年安康水文站的降水量和径流以及研究区非点源总氮、总磷污染负荷。结果表明:HYPE模型日径流量和月径流量模拟结果率定期纳升效率系数分别为0.78、0.90,验证期分别为0.69、0.87;总氮、总磷负荷模拟结果率定期纳什效率系数分别为0.71、0.69,验证期分别为0.68、0.63,表明HYPE模型在研究区具有良好适用性;汉江安康断面以上流域总氮和总磷非点源污染负荷主要集中在6—10月,主要来源于农业化肥施用与水土流失;研究区总氮单位面积负荷流失量为0.354~6.139 kg,总磷单位面积负荷流失量为0.012~0.395 kg,总氮、总磷流失最严重的区域主要分布在流域偏南部,合理使用化肥、加强防治水土流失是控制研究区非点源污染的有效措施。

LID设施布局对城市径流与污染负荷影响评估

关于低影响开发(LID)空间布局对水量水质控制效果影响的研究较为缺乏。针对上述问题,以郑州市中原区为对象,基于SWMM模型原理构建布设LID设施的研究区城市水量水质模型。所提模型依据城市综合径流系数的经验值以及研究区实际情况,将中原区划分为城市建筑高、中、低密集区,并在研究区高、中、低密集子汇水区布设不同比例的LID设施(S1~S5),计算不同雨量级别下不同空间格局下的LID设施对水量水质的控制效果。结果表明:随着雨量级别的增大,LID方案的径流总量削减率、峰值流量削减率和TSS负荷削减率不断减小。在降雨级别为暴雨、大雨和中雨时,在高、中、低密集子汇水区布设占比分别为35%、35%和30%的LID方案(S5),其径流总量削减率超过80%,峰值流量削减率超过70%,且TSS负荷削减率超过50%。从各事件下水量与水质综合指标评估来看,该方案表现最佳。

脑小血管病总负荷与血红细胞分布宽度的相关性分析

目的探究脑小血管病(CSVD)总负荷与血红细胞分布密度(RDW)的相关性,旨在为脑小血管总体负荷寻找更为简单、廉价的血清学指标。方法选取2018年9月至2023年3月我院的133例CSVD患者作为分析对象。根据磁共振影像诊断结果将患者分别按照CSVD总负担评分分为0分,1分,2分,3分和4分五组。采用Spearman相关性分析探讨CSVD总负荷评分与红细胞分布宽度(RDW)的相关性。结果年龄、高血压、卒中史、颈动脉硬化、总胆固醇(TC)、低密度脂蛋白胆固醇(LDL-C)、平均红细胞血红蛋白浓度(MCHC)、RDW在不同CSVD总负荷分组均有差异。相关性分析结果显示,CSVD与RDW呈正相关(r=2.203,P=0.002)。结论血红细胞分布宽度与脑小血管病总负荷呈正相关性。

脑小血管病与血管储备及认知障碍相关性研究进展

脑小血管病(CSVD)发病率逐年上升,CSVD的早期筛查与诊治具有重要意义,认知障碍是CSVD中对患者生活质量影响较大的表现之一。经颅多普勒超声(TCD)可以早期判断CSVD患者血管储备能力,CSVD患者MRI总负荷相较于独立的病灶能够更全面的计算出CSVD病变程度,本文旨在探讨CSVD与CSVD患者MRI总负荷、血管储备及认知障碍的相关性研究进展,研究CSVD的早期筛查与诊疗。

NRG1联合MRI总负荷量对脑小血管病认知功能障碍的预测价值

目的 分析探究神经调节蛋白1(NRG1)与磁共振成像(MRI)总负荷评分对脑小血管病认知功能障碍的预测价值。方法 选择2021年10月至2022年10月河南科技大学第二附属医院收治的符合标准的124例脑小血管病(CSVD)高危人群及血管性认知功能障碍(VCI)住院患者进行回顾性分析研究。根据蒙特利尔认知评估量表(MoCA)以及血管性认知障碍程度将其分为非痴呆型血管性认知障碍(VCIND)组、血管性痴呆(VD)组、认知功能正常(CN)组。通过酶联免疫吸附实验检测血清中NRG1表达水平;根据MRI检查结果,计算CSVD影像学标志物总体负荷评分。将血清NRG1表达水平、MRI总负荷评分与CSVD认知功能障碍进行相关性分析。用NRG1与MRI负荷量构建对血管性认知功能障碍的预测模型。结果 VD组患者血清NRG1表达水平均明显高于CN组,差异具有统计学意义(P <0.05)。Pearson分析显示三组患者血清中NRG1表达水平、MRI总负荷评分与MoCA评分均呈负相关,具有统计学意义(P <0.05)。Logistic回归分析显示血清NRG1、MRI总负荷量均是CSVD认知功能下降的独立危险因素。受试者工作特征(ROC)曲线分析显示血清NRG1和MRI总负荷值单独和联合检测对CSVD所致认知功能障碍均具有较高的诊断价值,具有统计学意义(P <0.05);其中联合检测的诊断价值最高(AUC=0.923)。结论 血清NRG1检测联合MRI总负荷量对CSVD认知功能障碍具有良好的预测价值。

河流水质采样策略与频率对氮磷负荷估算的影响

为探究适合的流域水质监测频率与采样策略,提高氮磷污染物负荷估算的精度,基于云南省洱源县凤羽河流域2011~2013年间逐日流量与总氮､总磷浓度的每日数据,在7d/次,14d/次,21d/次,28d/次4种采样频率下设定了3种不同的采样情景(情景a:普通随机取样､情景b:随机取样的基础上增加降水量超过10mm的水样样品采集,情景c:随机取样的基础上增加降水量超过25mm的水样样品采集).基于采样频率与采样情景的组合,利用LOADEST模型估算的总氮与总磷负荷,并与逐日连续水量水质数据计算的实测值进行比较,评估了不同取样频率和取样情景下LOADEST模型的负荷估算精度.结果表明:在LOADEST模型的估算过程中,同种采样频率下,增加降雨时期的浓度数据将会提高LOADEST模型的模拟精度;在降雨事件期间进行加密采样,不仅加大了工作量,且增加的采样次数过多(如情景b)使总氮的RMSE值由1.92增至2.26,总磷的RMSE值由0.08增至0.19,高估氮磷负荷,模型模拟精度降低.在四种不同的采样频率下,情景c中总氮的RMSE值范围为1.92~2.07,总磷的RMSE值范围为0.06~0.13,均取得了该频率下最低的RMSE值,模型估算精度最高;从不同频率与采样情景对模型估算结果的影响来看,对总氮负荷估算结果(RMSE值范围为1.92~2.52)影响要大于总磷(RMSE值范围为0.06~0.18).其中,情景a与情景b的负荷估算结果精度随着采样频率降低而降低.情景c的估算结果受现有取样频率降低的影响不明显.本研究表明,在常规固定频率水质监测基础上结合气象预报适量增加降雨时的采样可在28d/次的较低取样频率下得到较高的氮磷负荷估算精度,符合我国各地区环境水质采样频率,可为相关研究的水质采样策略提供一定的参考作用.

环巢湖地区沙河流域污染负荷总量控制及削减措施

针对巢湖污染负荷总量控制的问题,以巢湖二级子流域沙河流域为研究对象,基于对沙河流域水文特征、河道水质受损情况、污染源分布及源强评估分析,建立了陆域污染物负荷与水质定量响应关系,识别了流域重点控制区域,通过水文模拟模型(HSPF)模拟了流域污染负荷总量控制目标值,并制定了污染负荷削减分配方案。结果表明:在工业点源污染、生产区径流污染、村镇生活污水处理严格执行巢湖流域地方排放标准,镇区截污纳管率提高到80%,村镇坑塘治理率达到85%以上等削减措施情景下,各管控区域出口断面水质可达到目标水质考核要求。

基于流域分区的鄱阳湖流域入湖总磷负荷估算

随着江西省和环鄱阳湖经济带的快速发展,鄱阳湖湖区总磷超标且浓度日益上升。针对鄱阳湖流域内主要磷污染来源成因问题,基于污染源普查的流域分区技术方法,开展全流域总磷污染负荷核算和入湖磷污染源系统定量解析。结果表明:2021年鄱阳湖入湖总磷污染负荷为1.49万t,主要污染来源于陆域输入,其贡献占比为87.73%,湖体内污染源主要来自于内源释放(5.52%)和水土流失(4.60%);污染源按贡献权重大小排序依次为畜禽养殖(48.63%)>城镇生活(20.01%)>种植业(9.71%)>水产养殖(7.37%)>内源释放(5.52%)>水土流失(4.6%)>工业企业(1.12%)>农村生活(0.89%)>候鸟粪便(0.46%)>旅游业(0.12%);在空间分布上,总磷入湖负荷高贡献流域主要集中在赣江集水区和滨湖区,贡献占比分别为50.67%、25.92%,抚河和信江集水区总磷产生量集中,贡献率分别为7.64%、8.34%;各分区的总磷污染源贡献结构类似,主要呈现为农业源为主,城镇源为次要来源。研究显示,鄱阳湖总磷污染来源具有明显的空间差异性,但不同区域对总磷入湖主控污染源具有相似性,建议优先管控滨湖区和赣江集水区等高贡献流域,并针对农业源、城镇生活等主控贡献源提出相应的防控削减措施,以改善鄱阳湖流域生态环境。

血清同型半胱氨酸水平对脑小血管病总负荷的影响

目的观察脑小血管病(cerebral small vessel disease,CSVD)总负荷的影响因素及血清同型半胱氨酸(Homocysteine,Hcy)水平与CSVD总负荷的相关性。方法选取2018年1月~2022年11月承德市中心医院神经内科确诊的CSVD患者242例,根据CSVD总负荷评分进行分组,0~2分为低负荷组,3~4分为高负荷组。比较两组患者一般人口学资料、合并症、总胆固醇(TC)、三酰甘油(TG)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)、空腹血糖(FPG)、红细胞沉降率(ESR)、尿酸(UA)、肌酐(Cr)、Hcy水平,分析影响CSVD总负荷的风险因素,使用Spearman相关分析Hcy水平与CSVD总负荷的相关性。结果低负荷组共115例,高负荷组共127例。高负荷组年龄、TC、LDL-C、UA、Hcy水平均高于低负荷组[(66.81±10.23)岁vs.(60.28±11.40)岁、(4.96±1.18)mmol L vs.(4.54±1.02)mmol L、(3.36±0.97)mmol L vs.(3.04±1.01)mmol L、(308.84±48.61)μmol L vs.(292.79±50.04)μmol L、(14.78±3.91)μmol L vs.(13.64±4.04)μmol L],高血压、动脉粥样硬化占比均高于低负荷组[(79.53%vs.50.43%)、(72.44%vs.53.04%)],组间差异有统计学意义(t=4.696、2.948、2.513、2.529、2.229,χ^(2)=22.667、9.766,P<0.05)。多因素分析显示高龄、合并高血压、动脉粥样硬化、LDL-C、Hcy水平升高为CSVD总负荷增加的独立危险因素(P<0.05)。Hcy水平与CSVD总负荷呈弱正相关(r=0.028,P=0.013)。结论年龄、高血压、动脉粥样硬化、脂代谢异常等多种因素可影响CSVD总负荷,关注Hcy水平,早期干预可能优化CSVD的防治方案。

PBA暗挖区段单跨隧道施工阶段增量法与全量法结构计算分析

以北京轨道交通22号线(平谷线)为依托工程,以3种施工阶段结构受力和变形为研究重点,对PBA暗挖区段单跨隧道施工阶段的增量法和全量法进行了分析,对比了单跨PBA暗挖隧道增量法与全量法的计算结果,介绍了增量法与全量法的基本原理和应用,并结合Midas GTS NX岩土有限元分析软件对在建工程模型施工阶段结构受力进行了分析。研究结果表明:PBA暗挖逆筑隧道采用增量法与全量法计算出的结果有差异。其主要原因是增量法需考虑分步施工,构件和荷载是分步施加的,内力和变形也是分阶段达到平衡;全量法需考虑力和变形的同时性,不能真实反映施工的分步性。故在设计时需采用增量法进行计算。该研究成果可为相似隧道工程的设计与施工提供借鉴参考。