示踪气体跟踪测量方法在空调通风上的应用

论述了示踪气体跟踪测量的基本原理和基本方法。详细介绍了空调、通风工程中使用示踪气体进行检测的内容、计量和过程等,指出了该方法的优点和不足。认为示踪气候跟踪测量在空调、通风工程中能解决系统调节、测量等工作中的具体问题,应用前景广阔。认为“空气龄”应作为评价人空气质量的主要指标之一。     

Estimation of bias with the single‐zone assumption in measurement of residential air exchange using the perfluorocarbon tracer gas method

Residential air exchange rates (AERs) are vital in understanding the temporal and spatial drivers of indoor air quality (IAQ). Several methods to quantify AERs have been used in IAQ research, often with the assumption that the home is a single, well‐mixed air zone. Since 2005, Health Canada has conducted IAQ studies across Canada in which AERs were measured using the perfluorocarbon tracer (PFT) gas method. Emitters and detectors of a single PFT gas were placed on the main floor to estimate a single‐zone AER (AER_1z). In three of these studies, a second set of emitters and detectors were deployed in the basement or second floor in approximately 10% of homes for a two‐zone AER estimate (AER_2z). In total, 287 daily pairs of AER_2z and AER_1z estimates were made from 35 homes across three cities. In 87% of the cases, AER_2z was higher than AER_1z. Overall, the AER_1z estimates underestimated AER_2z by approximately 16% (IQR: 5–32%). This underestimate occurred in all cities and seasons and varied in magnitude seasonally, between homes, and daily, indicating that when measuring residential air exchange using a single PFT gas, the assumption of a single well‐mixed air zone very likely results in an under prediction of the AER.     

Heat balance and tracer gas technique for airflow rates measurement and gaseous emissions quantification in naturally ventilated livestock buildings

Experiments were performed to study the airflow rates (AFRs) in a naturally ventilated building through four summer seasons and three winter seasons. The AFRs were determined using heat balance (HB), tracer gas technique (TGT) and CO₂-balance as averages of the values of all experiments carried out through the different seasons. The statistical analyses were correlation analysis, regression model and t-test. Continuous measurements of gaseous concentrations (NH₃, CH₄, CO₂ and N₂O) and temperatures inside and outside the building were performed. The HB showed slightly acceptable results through summer seasons and unsatisfactory results through winter seasons. The CO₂-balance showed unexpected high differences to the other methods in some cases. The TGT showed reliable results compared to HB and CO₂-balance. The AFRs, subject to TGT, were 0.12 m³ s⁻¹ m⁻², 1.15 m³ s⁻¹ cow⁻¹, 0.88 m³ s⁻¹ LU⁻¹, 56 h⁻¹, 395 m³ s⁻¹ and 470 kg s⁻¹ through summer seasons, and 0.08 m³ s⁻¹ m⁻², 0.83 m³ s⁻¹ cow⁻¹, 0.64 m³ s⁻¹ LU⁻¹ 39 h⁻¹, 275 m³ s⁻¹ and 328 kg s⁻¹ through winter seasons. The AFRs are not independent values, rather they were estimated for specific reference values, which are: area, cow and LU as well as rates. The emission rates through summer seasons, subject to TGT, were 9.4, 40, 3538 and 2.3 g h⁻¹ cow⁻¹; and through winter seasons were 4.8, 19, 2332 and 2.6 g h⁻¹ cow⁻¹, for NH₃, CH₄, CO₂ and N₂O, respectively.     

Reliability analysis of tunnel using least square support vector machine

In the reliability analysis of tunnels, the limited state function is implicit and nonlinear, and is difficult to apply based on the traditional reliability method, especially for large-scale projects. Least squares support vector machines (LS-SVM) are capable of approximating the limited state function without the need for additional assumptions regarding the function form, in comparison to traditional polynomial response surfaces. In the present work, the LS-SVM method was adapted to obtain the limited state function. An LS-SVM-based response surface method (RSM), combined with the first-order reliability method (FORM), is proposed for use in tunnel reliability analysis and implementation of the method is described. The reliability index obtained from the proposed method applied to particular tunnel configurations under different conditions shows excellent agreement with Low and Tang’s (2007) method and traditional RSM results, and indicates that the LS-SVM-based RSM is an efficient and effective approach for reliability analysis in tunnel engineering.     

Efficiency measurement of the maintenance of paved lanes using data envelopment analysis

While the road maintenance performance measurement systems that are currently in use investigate maintenance level of service (i.e. effectiveness of the road maintenance), the fundamental relationship between the maintenance level of service and the budget requirements (i.e. the efficiency of road maintenance) has not received as much attention. Given that not knowing how ‘efficient’ transportation agencies are in being ‘effective’ can lead to excessive and unrealistic maintenance budget expectations, there is a need for a performance measurement system that can assess the overall efficiency of road maintenance operations. To address this need, a framework was developed and implemented to assess the relative cost efficiency of eight counties in Virginia, USA in maintaining the paved lanes of the Interstate roads. Such framework is developed using a methodology known as data envelopment analysis which is based on the production theory and principles of linear programming. The results indicate that the Rockbridge County is the most efficient and the Roanoke County is the least efficient in maintaining the paved lanes. The findings of this research are intended to be used as guides for benchmarking as well as managerial actions and policy making for decision making with respect to road maintenance.     

A new device for measurement and control of gas production by bench scale anaerobic digesters

On the basis of an analysis, in terms of desirable characteristics and main sources of error, of existing apparatus for measuring biogas production by laboratory anaerobic digesters, we have developed a new device that is precise, inexpensive, easily constructed and capable of functioning autonomously for long periods. A slightly costlier version suitable for use in automatic control systems is also described.     

基于图像相关分析的砂土模型试验变形场量测

高分辨率数码相机的出现为砂土模型试验变形场非接触量测法的研究开发提供了一条简便经济而且实用的途径,在模型试验观测面上,不再需要布置嵌入式量测标志点或描画网格,直接用数码相机在试验各阶段拍摄照片,然后对照片序列进行图像相关分析,即可得出模型试验的变形场分布。利用图像匹配技术追踪模型上点的位移,借用FEM常用的等参单元的概念进行图像校准和应变计算,采用双线性插值技术可以实现微小变形量测,并提出同时用平移和旋转搜索方法,以适应砂土模型的变形特点。精度检验试验结果表明,一个像素以下的平移量测标准方差达到0.19个像素,数值试验表明,15°旋转刚体变形量测,非旋转搜索和旋转搜索的标准方差分别为0.49和0.08个像素。最后给出一个在砂土地基承载力离心机模型试验中的应用实例,分析结果包含砂土模型位移场、最大剪应变场和体积应变场的分布图。结果表明这一方法使得砂土模型局部化变形、剪切带和渐进破坏过程的量化分析成为可能。     

基于图像分析的土坡离心模型试验变形场测量

开发了离心场条件下土坡离心模型试验变形场非接触测量技术并进行了实际应用。基于图像相关分析理论,开发了新的土坡离心模型试验过程中土体位移非接触测量系统以观测离心机运行中土坡的位移。针对简单土坡进行了离心模型试验,测量了土坡的位移场变化过程。测量结果规律性好,表明该非接触测量技术能够较好地测定离心模型试验中土体侧面任意点在任意时刻的位移,适用于离心场环境中土坡变形过程的测量。加载导致土坡在某些位置出现变形集中,意味着这些位置发生了应变局部化。应变局部化的发展与土坡破坏有着密切联系。     

Development of a remote analysis method for underground ventilation systems using tracer gas and CFD in a simplified laboratory apparatus

Following a disaster in a mine, it is important to understand the state of the mine damage immediately with limited information to manage the emergency effectively. Tracer gas technology can be used to understand the ventilation state remotely where other techniques are not practical. Computational fluid dynamics is capable of simulating and ascertaining information about the state of ventilation controls inside a mine by simulating the airflow and tracer distribution. This paper describes a simulation of tracer gas distribution in a simplified laboratory experimental mine with the ventilation controls in various states. Tracer gas measurements were taken in the laboratory experimental apparatus, and used to validate the numerical model. The distribution of the tracer gas, together with the ventilation status, was analyzed to understand how the damage to the ventilation system related to the distribution of tracer gases. Detailed error analysis was performed and the discrepancies between experimental and simulated results were discussed. The results indicate that the methodology established in this study is feasible to determine general ventilation status after incidents and can be transferred to field experiment. Because it is complex to simulate the actual condition of an underground mine in a laboratory, the model mine used is simplified to simulate the general behavior of ventilation in a mine. This work will be used to inform planned on-site experiments in the future and the proposed methodology will be used to compare collected and simulated profiles and determine the general location of ventilation damage at the mine scale.     

A data analysis method for detecting wall thermal resistance considering wind velocity in situ

To improve the accuracy of data analysis methods for the field measurement of wall thermal resistance, a method considering wind velocity is presented through an analysis of both surface heat flux and temperature samples. This analysis method takes the wall heat transfer of linear system into account, simplifying the first order differential equation of wall transient response based on the nodes of the interior and exterior wall surfaces. An approximate solution has been proposed in the form of time domain interpolation. By applying the weighted residual method for the approximate solution, the data analysis method about temperature, heat flux, and wind velocity can be achieved.A transient heat transfer model of a wall was established applying the infinite difference method, by which the proposed analysis method was validated in this paper. Additionally, the heat flow meter experiment platform considering wind velocity was built, on which the proposed method, the mean method and the dynamic analysis method suggested by the international standard ISO 9869 were applied to the test wall under different wind velocities. The wall thermal resistance value obtained in our proposed method has proven to be in better agreement with that obtained for a steady state.     

广州新光大桥钢板桩深水围堰监测及结果分析

介绍了监测设施布置、数据计算方法及精度分析,给出了部分监测数据,监测数据反映了钢板桩的非线性变形特性和钢板桩接头部位的刚度变化情况,监测结果为保证工程的顺利进行发挥了重要作用。     

Payback of natural gas turbines: A retrospective analysis with implications for decarbonizing grids

The low capital cost, low lead times, and flexible operation of natural gas combustion turbines are qualitatively different from other power generation technologies and have the potential for faster investment payback. We explore this hypothesis with a retrospective analysis of natural gas combustion turbine economics in six locations, with revenue from energy, frequency regulation, reserve, and capacity markets. Using historical data, we find payback periods from 8.5 to 15 years. Gas turbines can be financially justified with a single profitable decade of service and are thus more economically compatible with a decarbonizing grid than other types of fossil fuel infrastructure.     

大体积混凝土温控计算与测温数据分析

结合工程实例,介绍了大体积混凝土的温控计算及相关参数的取值,并将计算值与实测数据进行分析比较,由此得出的一些结论对工程实践具有参考价值。     

基坑SMW工法型钢起拔力的工程实测分析

基坑工程涉及岩土工程、结构工程等,其综合性强、影响因素多。SMW工法围护结构型钢拔出力受多种因素影响。基于对不同粘结长度及不同施工条件下型钢起拔力的实测结果整理,对比分析了不同粘结长度的SMW工法型钢起拔力及其影响因素,认为型钢粘结长度、侧向变形程度、型钢起拔先后顺序等是影响起拔力的重要因素,在工程设计、施工实际中,综合考虑多种因素对型钢起拔力的影响,可较顺利地实现型钢完整回收。     

考虑固相分解的含水合物沉积物体积应变分析模型

水合物开采通过打破固相水合物相平衡状态使其分解为水和气体,含水合物沉积物（gas hydrate-bearing sediment,GHBS）固相组分减少使孔隙体积增大,土骨架间胶结作用弱化,产生的水和气显著改变孔隙压力,造成沉积物软化和体积收缩。基于GHBS三轴压缩试验,考虑水合物降压分解过程对GHBS变形特性的影响,将固相骨架分为惰性土骨架和可分解的水合物固相,引入随水合物饱和度变化的压缩参数,建立了能够描述GHBS应力和水合物分解耦合作用、体积应变随时间变化的分析模型。该模型能够描述降压速率、降压幅值及水合物分解速率对GHBS变形特性的影响,结果表明：降压速率增大,降压阶段体积应变速率增大,达到相平衡时间缩短,降压开采时应综合考虑开采过程中储层变形速率和开采效率间的关系;不同粒径组成的沉积物水合物分解速率存在差异,分解速率对储层变形速率影响明显;降压开采稳定孔压影响储层最终沉降量,降低稳定孔压可以提高开采效率,但最终变形量增大。     

Validation of data analysis routines for a thermal probe apparatus using numerical data sets

Most thermal properties of construction materials used in the analysis of building performance have been measured under laboratory conditions, using a guarded hot box or hot plate apparatus. As a consequence, these properties seldom reflect the impact of actual conditions (especially moisture content) on the values of thermal conductivity and diffusivity. Hence there is a need to develop techniques that take into account local conditions, and measure building material properties in situ. One option available is the use of a thermal probe. The thermal probe technique is based on creating a line source in a material sample and measuring the temperature rise in the sample in reaction to heat being applied. Obviously the data analysis routines used to calculate thermal conductivity and diffusivity based on the temperature rise observed are crucial to the success of the technique. This work has used transient thermal simulation of a model representing a line source in an infinite material sample to generate a set of numerical data sets to validate analysis routines in conjunction with an experimental thermal probe apparatus. Findings show that by careful application of these routines, a close agreement with simulation input values can be achieved, with errors of less than one percent. This validates the analysis routines and provides a deeper appreciation of the theoretical behaviour of a thermal probe.     

气体分析法测定岩棉中甲醛释放量影响因素探讨

针对利用气体分析法测定岩棉中甲醛释放量的影响因素展开研究,从试验舱背景、洗瓶水的更换、硅胶有效性以及供气系统气密性等因素展开验证分析。结果表明,在洗瓶水甲醛含量未饱和的状态下,试验舱背景和洗瓶水的更换对试验结果没有明显影响,硅胶有效性和供气系统气密性对试验数据影响较大,其中供气系统气密性同时对硅胶有效性有显著影响,对试验结果影响最大。     

燃气发动机驱动热泵一次能源利用系数的计算和分析

提出描述缸内工质复杂工作过程的零维物理模型和数学模型，用P－K法求得燃气机的性能参数。利用导出的燃气发动机驱动热泵装置一次能源利用系数PER的计算公式，分析并指出了供热系数、废热利用率和有效效率对PER的影响以及增大PER的有效途径。     

免棱镜全站仪测量拱圈线形及其精度分析

为解决既有拱桥评定时拱圈线形测量的难题,提出了一种在拱桥侧面架设免棱镜全站仪测量拱圈线形的新方法,并给出了详细的操作步骤;分析了该方法的X和Z坐标测量误差的主要来源,根据误差传播定律,推导了X和Z坐标测量中误差的计算公式,并通过模拟试验和工程实例对测量精度进行了验证.研究结果表明,免棱镜全站仪测量拱圈线形具有测量精度高...     

盾构隧道管片接缝气密性模拟方法与影响因素分析

盾构隧道穿越含气地层时,施工对地层的扰动易引发气体泄漏,气体易由盾构管片接缝处进入隧道内部,极易引发爆炸等灾害.依托穿越长江高压含气地层的苏通GIL综合管廊工程,较系统地研究了影响盾构管片接缝面气体泄漏的主要因素,并提出对应改进措施.通过接缝室内模型试验,分析了气压加载下接缝面气体泄漏的全过程,从而揭示了气体在不同泄漏...