Study on Influencing Factors and Control Points of Design Estimate of Landscaping Engineering

In recent years,China’s landscaping projects have developed vigorously,and the growth rate of urban garden green space areas has been maintained at about 5%.Overall,with the development of the national economy and the support of macro policies,people’s demand for close to nature and beautify the environment is gradually increasing,which has brought new growth momentum for the development of the landscaping industry.Simultaneously,from the perspective of future economic development and urban development,the landscaping industry still has a lot of room for development.However,with the rapid development of landscape engineering,the problem of cost control of landscape engineering is becoming more prominent,the phenomenon of budget overestimation is common,and there are many factors affecting the cost of landscape engineering,which brings difficulties and challenges to the analysis of its influencing factors and cost management.How to scientifically analyze the influencing factors and control the cost has become an important link in the landscaping project.To solve the above problems,this paper takes the design stage of landscaping engineering as the background,takes the design estimate of landscaping engineering as the research object,through literature research and data collection,fully excavates the main influencing factors of the design estimate stage of landscaping engineering,analyzes the key points of cost control,and provides reference ideas and directions for the later cost management and control.

Characteristics of the Main Journal Bearings of an Engine Based on Non-linear Dynamics

Many simple nonlinear main journal bearing models have been studied theoretically, but the connection to existing engineering system has not been equally investigated. The consideration of the characteristics of engine main journal bearings may provide a prediction of the bearing load and lubrication. Due to the strong non-linear features in bearing lubrication procedure, it is difficult to predict those characteristics. A non-linear dynamic model is described for analyzing the characteristics of engine main journal bearings. Components such as crankshaft, main journals and con rods are found by applying the finite element method. Non-linear spring/dampers are introduced to imitate the constraint and supporting functions provided by the main bearing and oil film. The engine gas pressure is imposed as excitation on the model via the engine piston, con rod, etc. The bearing reaction force is calculated over one engine cycle, and meanwhile, the oil film thickness and pressure distribution are obtained based on Reynolds differential equation. It can be found that the maximum bearing reaction force always occurs when the maximum cylinder pressure arises in the cylinder adjacent to that bearing. The simulated minimum oil film thickness, which is 3 μm, demonstrates the reliability of the main journal bearings. This non-linear dynamic analysis may save computing efforts of engine main bearing design and also is of good precision and close connection to actual engine main journal bearing conditions.

Lubrication Performance of Connecting-Rod and Main Bearing in Di erent Engine Operating Conditions

Only the lubrication performance at rated engine operating condition was generally analyzed in current design and research of engine connecting-rod and main bearing. However, the actual engine(especially vehicle engine) does not always operate in rated operating condition and its operating condition changes constantly. In this paper, a fourstroke four-cylinder engine is taken as the studying object, the load and lubrication of connecting-rod and main bearing in di erent operating conditions are analyzed. The load of connecting-rod bearing is calculated by the dynamic calculation method, the loads of all main bearings are calculated by the whole crankshaft beam-element finite element method, and the lubrication performance of connecting-rod and main bearings are analyzed by the dynamic method. The results show that there are major di erences in the changes and numerical value at corresponding moment of the loads and lubrication performance of connecting-rod and main bearings in an engine operating cycle in di erent engine operating conditions; the most unfavorable case of the lubrication performance of connectingrod and main bearings may not take place in the rated engine operating condition. There are also major di erences between the lubrication performance of connecting-rod bearing and that of main bearing and between the lubrication performances of main bearings one another. Therefore, it will not be reasonable that the lubrication performance of a certain connecting-rod bearing or main bearing is analyzed in the design of the engine bearing. It is necessary to analyze simultaneously the lubrication performances of all bearings in di erent engine operating conditions.

Numerical Investigation of the Effects of Rate-Shaped Main Injection on Combustion and Emission in an OPOC Two-Stroke Diesel Engine

The effects of various split injection strategies on the opposed-piston opposed-cylinder(OPOC)diesel engine combustion and emission characteristics have been studied numerically using AVL-Fire CFD tools.The five rate-shaped main injections were used in split injection strategies.The results show that ignition delay from a rectangular injection rate is the shortest.Maximum pressure of the trapezoid injection rate is the largest.And the NOx emission of the rectangular injection rate is the largest.Meanwhile,the soot emission of the trapezoid injection rate is the least among the five injection rates.

A Value Engineering Analysis of Head Loss in Pumping Mains

With net zero carbon emissions targets approaching over the next 20 to 30 years, the water industry must act now to develop energy efficient techniques and designs to reduce emissions and reduce the carbon footprint of water utility providers. There is also the potential for significant energy and therefore financial savings to be realised from the adoption of more energy efficient designs approaches. Water utility providers account for a significant proportion of national electricity consumption. The purpose of this research is to determine if, over the long term, opting for a larger diameter pipe at design stage can lead to significant financial and emissions savings for water utility providers when considering pumping mains. Pumping mains are widely used throughout the water and wastewater industry where a gravity solution is not possible. 72 hypothetical water main design scenarios were analysed and the long term financial and environmental impact of each hypothetical water main was assessed. It was found across all design scenarios that larger diameter water mains were capable of delivering the same rate of flow of smaller diameter pipes at a much reduced velocity and requiring reduced pumping power. It was concluded that pumped mains of larger diameters can ultimately be more energy efficient and cost effective over the long term when selected in favour of smaller diameter pumped mains in otherwise identical design scenarios.

A comparative study of the main factors controlling geohazards induced by 10 strong earthquakes in Western China since the Wenchuan earthquake in 2008

Determining the main controlling factors of earthquake-triggered geohazards is a prerequisite for studying earthquake geohazards and post-disaster emergency response.By studying these factors,the geomorphic and geological factors controlling the nature,condition,and distribution of earthquake-induced geohazards can be analyzed.Such insights facilitate earthquake disaster prediction and emergency response planning.The authors combined field investigations and spatial data analysis to examine geohazards induced by seismic events,examining ten earthquakes including the Wenchuan,Yushu,Lushan events,to elucidate the main control factors of seismic geohazard.The authors observed that seismic geohazard occurrence is usually affected by many factors,among which active nature of the seismogenic fault,seismic peak ground acceleration(PGA),topographic slope and geomorphic height differences,and distance from the fault zone and river system are the most important.Compared with strike-slip earthquakes,thrust earthquakes induce more high-altitude and high-speed remote landslides,which can cause great harm.Slopes of 0°–40°are prone to secondary seismic geohazards,which are mainly concentrated 0–6 km from the river system.Secondary geohazards are not only related to seismogenic fault but also influenced by the associated faults in the earthquake area.The maximum seismic PGA and secondary seismic geohazard number are positively correlated,and the horizontal and vertical ground motions play leading and promoting roles in secondary geohazard formation,respectively.Through the research,the spatial distribution of seismic geohazards is predicted,providing a basis for the formulation of emergency response plans following disasters.

基于联合静动力修正的混凝土斜拉桥主梁挠度变化规律研究

针对混凝土斜拉桥服役期间主梁不断下挠的问题,该文基于修正模型分析大跨度混凝土斜拉桥服役期间主梁挠度变化规律。采用联合静动力的有限元模型修正方法,构造双目标优化问题,基于非支配排序遗传算法(NSGA-Ⅱ)求解,得到Pareto最优解集,从Pareto最优解集中找到协调最优解,从而实现有限元模型修正。模型修正后的静力位移和自振频率计算值与实测值吻合较好,能更好地反映结构的实际工作状态。在此基础上,结合主梁线形历年监测数据,分析不同徐变模式及拉索松弛效应等时变因素对主梁线形的影响,分析结果表明:采用CEB-FIP 2010徐变模式计算的挠度与实测挠度更加接近。中跨跨中下挠量最大,服役20年下挠量约为270 mm;主梁跨中挠度前5年平均增长率达33 mm/年,前5年挠度约占前40年的50%,后期主梁下挠趋于平缓。

不同海拔下甲醇替代率和主喷正时对RCCI发动机性能的影响

为探究不同海拔条件下甲醇/柴油反应活性控制压燃(reactivity controlled compression ignition, RCCI)发动机的运行特性,该研究基于甲醇/柴油双燃料发动机试验台架,试验研究1 800 r/min、100%负荷和3 200 r/min、100%负荷下不同甲醇替代率、柴油喷射正时对发动机燃烧与排放性能的影响规律。结果表明:不同海拔条件下随着甲醇替代率的增加,缸压和瞬时放热率峰值逐渐升高,燃烧始点和燃烧中心前移,当量有效燃油消耗率(equivalent brake specific fuel consumption, ESFC)降低,有效热效率升高,NO_x和碳烟排放大幅降低,THC(total hydrocarbons)和CO排放增加。1 800 r/min、100%负荷工况下,甲醇替代率由0增至20%,0、1 000、2 000 m海拔下最大缸压平均增加1.72 MPa,瞬时放热率峰值平均升高25.08 J/(°),ESFC平均降低4.67%,有效热效率平均升高4.90%,NO_x和碳烟排放分别平均降低16.63%和50%,THC和CO排放量分别平均增加142.03、388.18 mg/kg。3 200 r/min下甲醇替代率由0增至7%,不同海拔高度下ESFC平均降低1.76%,有效热效率平均升高1.79%,NO_x和碳烟排放量分别平均降低8.17%和20.70%。海拔高度由0升至2 000 m,1 800 r/min、20%甲醇替代率与3 200 r/min、7%甲醇替代率下,瞬时放热率峰值分别降低4.80和8.08 J/(°),燃烧中心分别推迟1.44°和1.43°,有效热效率分别降低0.82%和0.68%,ESFC分别升高2.10%和1.99%,NO_(x)排放量分别减少10.61%和7.35%,碳烟排放分别增加26.54%和32.12%,THC排放分别升高29.88%和15.45%,CO排放量分别增加22.42%和18.15%。固定甲醇替代率后,随着柴油主喷正时提前,不同海拔条件下缸压和放热率峰值逐渐升高,燃烧中心向上止点靠近,ESFC逐渐降低,有效热效率升高,碳烟排放减少,NO_(x)、THC和CO排放增加。1 800 r/min、15%甲醇替代率下,主喷正时从-1.5°提前至-7.5°,不同海拔高度下ESFC平均降低8.27%,有效热效率平均升高9.08%,碳烟排放平均减少90.94%。为提升高海拔条件下甲醇/柴油RCCI发动机的热效率和燃油经济性,可以适当增大柴油主喷正时。研究结果可为不同海拔环境下甲醇/柴油RCCI发动机燃烧与污染物排放控制优化提供参考。

基于工程经济性的公路悬索桥主缆最优垂跨比研究

为寻求工程经济性最优的公路悬索桥主缆垂跨比,以我国近年多座采用混凝土桥塔的单跨公路悬索桥为背景,建立主缆、锚碇、桥塔基础工程量的直接函数模型和桥塔塔身工程量的非线性函数拟合模型,对跨度750~2250 m、单层车道数4~8及双层车道数6+4、垂跨比1/14~1/6共952种布置形式的悬索桥进行大范围关于主缆垂跨比的工程经济性研究,并以2座实桥为算例分析主缆垂跨比对悬索桥静、动力性能及抗风性能的影响。结果表明:主缆垂跨比对悬索桥工程经济性影响显著;悬索桥主缆最优垂跨比与跨度相关,而车道数、加劲梁荷载集度的影响相对较小,涉水和不涉水的差异也不显著;基于工程经济性考虑,跨度750~2250 m的悬索桥主缆最优垂跨比为1/6.5~1/8.5,比经验值增大较多。2座实桥算例分析表明随着垂跨比增加,加劲梁挠度和活载应力有所增加,抗风性能略有提升,建议方案设计阶段加大垂跨比研究范围、对工程经济性和桥梁力学性能进行综合比选。

改扩建高速公路桥梁可用性评判与延寿准则

针对高速公路改扩建工程中既有桥梁是否能继续使用问题,综合考虑总体技术状况、承载力状况、剩余耐久年限状况3个层次,创建了以桥梁构件类别的外观耐久状态为一级指标、以剩余耐久年限为二级指标的评判方法,提出了表征构件剩余耐久年限的寿命系数和可用寿命系数,建立了既有桥梁的延寿准则和延寿策略,探讨了可用寿命系数与目标使用年限、单次延寿的有效保护年限、拟采取的维护措施类型数量的相互关系。以京沪高速改扩建工程为研究背景,选取9座既有桥梁为典型桥梁,按100 a目标使用年限,计算得到构件主筋和箍筋的剩余耐久年限,给出了典型桥梁主体构件剩余耐久年限。根据可用评判方法,计算得到了在相同延寿措施下的延寿年限、延寿费用及可用寿命系数,按经济最优原则提出了从A级到E级共计5种延寿方式。研究表明,京沪高速改扩建工程典型桥梁按箍筋计算得到构件耐久寿命比按主筋计算值低,建议构件年限按箍筋计算值取用;目标使用年限为100 a时,主梁构件可正常使用比例为94%,墩柱单元、盖梁单元、桥台单元的可正常使用比例分别为67%,11%,44%。实际工程表明,采用该评判方法的评判结果与结构实际状态基本相符,与工程实际采取的处置措施基本相当,验证了该方法的合理性。

复合多聚磷酸改性沥青混合料动态力学性能

为研究多聚磷酸(polyphosphoric acid,PPA)+SBS复合改性沥青混合料的动态力学性能,采用单轴压缩动态模量试验,分析温度和频率对动态模量和相位角的影响,并基于改进Havriliak-Negam(i HN)模型构建动态模量和相位角主曲线,同时与SBS改性沥青混合料相对比。结果表明:2种沥青混合料动态模量和相位角随温度和频率的变化呈现相同的趋势,HN模型可准确拟合2种沥青混合料的动态模量和相位角主曲线。相较于SBS改性沥青混合料,PPA+SBS复合改性沥青混合料的相位角在-10、20、50℃时均降低,而动态模量在-10℃时降低,20℃时变化较小,50℃时增加;较宽频域范围内,PPA+SBS复合改性沥青混合料在高温低频下动态模量变大,相位角变小,在低温高频下动态模量变小,相位角变化不大;PPA+SBS复合改性沥青混合料具有更优的动态力学性能。

低硫条件下船舶主机缸套-活塞环磨损现状与应对策略

国际海事组织(IMO)的“限硫令”于2020年1月在全球范围内实施后,燃用低硫燃油(LSFO)成为许多远洋公司的主要选择。对多家远洋公司船舶主机燃用LSFO后的运行状况进行调研,发现缸套、活塞环等零部件存在异常磨损及故障显著增多的现象。将LSFO对船舶主机的影响以及其实际应用案例进行分析与总结,并针对燃用LSFO的主机所出现的异常磨损和故障现象提出应对策略。该研究有助于解决LSFO条件下船舶主机缸套和活塞环异常磨损问题的实际需求,希望进一步推动LSFO条件下缸套和活塞环异常磨损的机理研究。

TDI发动机润滑油挤压高频噪声影响因素试验研究

针对涡轮增压柴油机的运行特点,在半消声试验室进行了发动机加速工况主轴承处润滑油挤压高频噪声的影响因素测试。研究过程基于发动机主轴承座振动测试和曲轴运动轨迹测试,重点分析了润滑系统特征和主轴承结构特征以及曲轴轴承支撑方式对高频挤压噪声的影响。结果表明:润滑油黏度、润滑油含气量、主轴承间隙、主轴颈形状和轴承支撑方式等均对主轴承座异常振动产生影响;当轴承载荷小,轴心偏心距较大,曲轴自转方向与公转方向相反时,主轴承润滑油压力升高,润滑油内的气泡被挤压产生高频的气泡破裂噪声,并伴随主轴承座异常振动;当曲轴运转稳定且轴心轨迹平顺时,主轴承座异常振动对应转速升高,高频噪声不易识别。

开州湖特大桥主塔位置研究

基于贵州瓮安至开阳高速公路开州湖特大桥主塔位置研究实例,提出主塔位置选择是一个系统工程,应从地形地貌、地层岩性、地质构造、不良地质、岸坡稳定性分析、不同主塔位置所带来的治理难度、环保等因素出发,进行多个主塔位置比选,选择技术可靠、投资最优、长期稳定的主塔位置。研究表明:瓮安岸K35+525、开阳岸K36+625适合设置主塔,为最优方案。为复杂艰险山区公路桥梁主塔选址工作提供借鉴。

化学工程与技术专业高水平创新应用型研究生人才培养模式的探索与实践

针对化学工程与技术专业研究生培养过程中,出现了培养模式单一、优质教学资源匮乏、实验操作技能差、应用思维能力弱化、科研创新能力不足等缺点,南昌航空大学环境功能材料教学团队以研究生创新能力培养为一条主线,以工程应用思维培养、功能材料实验技术方法培养和双导师制联合培养研究生为三大模式,以纳米材料、光催化分解水制氢、催化剂的设计合成及应用、催化剂可控合成及污染控制等四大创新研究方向为基石构建了独具特色的化学工程与技术专业研究生创新能力培养模式。实践发现,在此培养模式下能提升学科影响力与研究生培养质量,更利于创新型化学工程与技术专业研究生人才的培养。

船舶柴油机主轴承温度过高问题的处置及预防工作方案

船舶柴油机在使用过程中,主轴承突发故障时有发生,主要表现现象为主轴承温度过高。如未能及时有效处理,将严重影响柴油机的正常运行。本文从故障机理的角度出发,研究主轴承温度过高的各项成因,并分析故障的各种表现形式。基于滑油温度过高、滑油压力过低或无压力、曲轴箱中出现异常敲击声等主要的附加故障特征,本文分析故障发生后的主要危害,重点探讨故障的处置流程和排除方法,进而提出故障预防方案,为船舶柴油机的安全使用与维护提供理论依据。

多层建筑主体结构施工方案研究

近年来,城市化建设速度加快,城市建筑工程规模不断扩大,数量也随之增加。建筑主体结构施工技术的运用对主体结构整体质量、强度的影响较大,对工程实际使用寿命具有决定性影响,需加以重点研究。鉴于此,文章以广州华农大营养食品有限公司华农大功能性乳品生产基地为对象,根据建筑主体结构的重要性,重点阐述了该多层建筑主体结构的施工方案,以增强项目施工效果。

基于复杂网络和免疫策略的斜拉桥主梁施工安全风险耦合分析

斜拉桥主梁施工是一项复杂系统行为,施工过程中风险事故可能存在多条演化路径,因此具有复杂性和不确定性。为满足当前对施工安全风险管理的更高要求,提出一种基于复杂网络的风险耦合分析方法。首先,通过主梁施工作业程序分解及致险状态分析以识别安全风险因素;然后,基于复杂网络理论,借助邻接矩阵构建主梁施工安全风险的耦合网络模型,对特征指标进行研究分析并得出风险演化特征;最后,运用MATLAB软件对网络进行免疫仿真,包括单个节点免疫、随机免疫和蓄意免疫,以识别出关键节点并提出施工风险管控策略。结果显示:蓄意免疫的效果明显优于随机免疫,综合考虑免疫结果应优先预防和控制网络关键节点代表的风险点,从而有效降低网络效率,提高施工安全性。

AS法悬索桥锚靴及拉杆锚固可靠性研究

AS法(空中纺线法)施工的悬索桥,主缆各索股钢丝套接锚固在两岸的锚靴上,锚靴通过拉杆将索股力传递给锚固系统。锚靴与主缆钢丝相互作用后锚靴的承载能力、钢丝小曲率弯折后的应力状态、拉杆安装精度对锚固可靠性的影响均需要定性定量的研究以及试验验证。该文以AS法架设主缆悬索桥——阳宝山特大桥为背景,对锚靴及索股进行了6 150 kN设计荷载下拉杆无偏转状态、拉杆相对于锚固垫板在水平向、竖直向和45°向偏转0.5°共4种工况下的试验研究。结果表明:锚靴承载能力满足设计要求,钢丝小曲率弯折后无异常变形和破坏;锚靴及拉杆构造连接可靠,装配性好,构造采用球面垫圈结构可以保证拉杆具备约1°偏心调节能力,为保证锚靴及拉杆构造设计使用要求,建议拉杆与索股轴向安装控制精度保证在0.5°以内。

兴凯湖西部土壤-植物系统中硒含量特征、成因来源及迁移转化主控因素

硒及其有机化合物对生物体具有重要的生物活性和特殊的保健功能,开展富硒土壤硒成因来源和迁移转化研究,对富硒土地利用和富硒功能产品研发具有重要的科学和经济意义。基于区域地质特征、土壤数据和植物籽实数据,开展土壤硒空间分布和成因来源研究,运用地统计学、相关性、生物富集系数等方法探讨硒在土壤-植物系统中的迁移转化主控因素。土壤Se含量为0.11~0.70 mg/kg,均值为0.37 mg/kg,含量特征及空间分布主要受成土母质控制;富锦组黑色岩系是形成富硒土壤的物质基础和Se元素的最初来源,后期有利的古气候环境演化促进了黑色岩系的持续风化,为土壤提供了丰富的硒源;植物富集能力BCF水稻/土壤>BCF玉米/土壤,籽实Se平均含量为Se水稻>Se玉米,含量与土壤理化指标相关性揭示,硒在土壤-植物系统中迁移转化受土壤矿物组成及土壤环境等因素制约。土壤硒主要来源于富锦组黑色岩系及其风化物,硒在土壤-植物系统中迁移转化主控因素为粘土矿物的吸附/解析作用;划定天然富硒土地6550.68 hm^(2),为富硒土地科学利用和富硒功能产品开发提供地学依据,有效支撑服务地方经济发展和疾病预防。