Simulation of the heating performance of the Kang system in one Chinese detached house using biomass

A traditional Chinese heating system, the Chinese Kang, is used by 175 million people in detached houses in the rural regions of China, especially in Northeast China. This system utilizes biomass such as corn stalks, straw, corncob and energy plants as the heat sources. The objective of this paper is to establish a set of models to simulate the energy performance of the Kang heating system in one Chinese detached house. An experimental field study was carried out to collect practical parameters in a newly constructed Chinese detached house. The dynamic performance of the Kang heating system was simulated by using IDA-ICE 4.0 embedded with an empirical model built in the field study. The results show that the simulation can obtain good overall agreement with the field measurement results. It was confirmed that the Kang model created by IDA-ICE 4.0 is capable of simulating the performance of the Kang system and of calculating energy consumption in the detached house. Moreover, the result reveals that the thermal environment in the present Chinese detached house is still poor during the severe cold season if only the Kang system is used to heat the whole house.     

Study of the cellular retention time and the partial biomass renovation in a fungal decolourisation continuous process

The long-term continuous decolourisation treatment of the textile dye Grey Lanaset G (150 mg/l) was carried out in an air-pulsed bed bioreactor with retained pellets of the white-rot fungus Trametes versicolor. Maximum cellular retention time (CRT) was established at 40 days. During this time period, colour reduction remained at 90% and laccase activity was over 400 AU/l. Higher CRTs involved operational problems related to biomass conglomerates formed at the top of the bioreactor, which made individual movement of the pellets difficult. In order to carry out the long-term continuous treatment, a strategy of purge and biomass renovation that had to allow fungal stable activity levels to be maintained was planned. The purge and biomass renovation strategy consists of partial biomass renovations: 1/3 of the total biomass of the system is renewed every 1/3 of the CRT. Different CRTs were tested; with a CRT of 21 days carrying out partial biomass renovations every 7 days and with a hydraulic retention time of 2 days, decolourisation percentages higher than 80% were obtained, maintaining a young culture in the bioreactor and guaranteeing microbial activity. In accordance with the strategy observed, different simulations of the age of the biomass in the bioreactor were carried out, obtaining suitable age distributions for CRT of 20-21 days.     

Simulation of closed double‐sludge retention time anoxic‐oxic process in wastewater treatment: case study for a utility model process

The ‘closed double‐sludge retention time anoxic‐oxic (SRT AO) process’ is a utility model designed by the Shanghai Urban Construction Design and Research Institute. It can quantitatively control the nitrification level by adjusting wastewater distribution and mixed sludge return during wastewater treatment, and can thus considerably reduce construction investment and operation costs. However, mixed sludge return from the sedimentation tank may dilute the concentration of nitrobacteria because the heterotrophic bacteria propagate faster. In this paper, the closed double‐SRT AO process was modelled and simulated based on its application at the Zhuyuan Second Wastewater Treatment Plant (WWTP). The distribution ratio was found to have a significant influence on the nitrobacteria's concentration but does not eliminate the existence of nitrobacteria in the system. Extension of sludge age enhanced the heterotrophic bacteria concentration and to a greater extent the nitrobacteria concentration, thus attenuated the dilution of nitrobacteria. Mixed liquid recycling showed little effect on nitrobacteria concentration. The closed double‐SRT AO process in Zhuyuan Second WWTP had enough capacity for complete nitrification, but the shortage of organic matter in the influent impeded the nitrogen removal.     

静力压桩临界深度和最小厚度探讨

根据土塑性力学基本原理 ,用空穴球形扩张理论推得了沉桩时沉桩阻力沿深度变化的理论计算方法 ,对有软弱下卧层的桩基持力层、桩尖离下卧层顶面应留的最小厚度 ,无软弱下卧层的桩基持力层、桩尖进入持力层的临界深度 ,以及最小厚度或临界深度在不同土层或土层组合时的差别等三个问题进行了讨论。计算结果与工程实测结果对比 ,二者比较接近。还就现行规范中桩基进入持力层深度或离软弱下卧层距离大小的规定进行了讨论。     

工程事故案例分析在钢筋混凝土结构课程中的引入与运用

钢筋混凝土结构是土木工程本科生专业必修课,也是他们未来从事设计、施工的重要理论基础。实际建筑工程中由于钢筋、混凝土的材料原因、施工原因、设计原因会引发各种工程事故。从结构角度分析,钢筋混凝土梁、板、柱等承重构件的破坏及变形是造成这些事故的主因。在课堂教学中,结合各章节的教学重点,有选择地对不同工程事故案例进行理论分析,在强化学生对知识点理解的同时,也增强了他们安全生产的意识,同时要求他们应用所学知识,对事故提出整改及预防措施。这种来源于工程、应用于工程的模式,培养了学生对钢筋混凝土结构学习的兴趣,为日后的工程设计、施工奠定良好的专业理论基础。     

Waste activated sludge fermentation: Effect of solids retention time and biomass concentration

Laboratory scale, room temperature, semi-continuous reactors were set-up to investigate the effect of solids retention time (SRT, equal to HRT hydraulic retention time) and biomass concentration on generation of volatile fatty acids (VFA) from the non-methanogenic fermentation of waste activated sludge (WAS) originating from an enhanced biological phosphorus removal process. It was found that VFA yields increased with SRT. At the longest SRT (10 d), improved biomass degradation resulted in the highest soluble to total COD ratio and the highest VFA yield from the influent COD (0.14 g VFA-COD/g TCOD). It was also observed that under the same SRT, VFA yields increased when the biomass concentration decreased. At a 10 d SRT the VFA yield increased by 46%, when the biomass concentration decreased from 13 g/L to 4.8 g/L. Relatively high nutrient release was observed during fermentation. The average phosphorus release was 17.3 mg PO₄-P/g TCOD and nitrogen release was 25.8 mg NH₄-N/g TCOD.     

A mine shaft case study on the accurate prediction of yield and displacements in stressed ground using lab-derived material properties

Continuum models provide a useful tool for the prediction of stress re-distribution due to excavation and induced yielding, and are used as a key analysis tool in the design of many underground excavations. Recent developments in the study of rock strength and post-yield behaviour have played a key role in improving our understanding of how plastic constitutive models can also be used to practically replicate observed phenomena in brittle rocks. In particular, new models for rock dilatancy can help to improve the applicability of plastic constitutive models as a predictive tool for excavation design. In this study, laboratory data for a heterogeneous, brittle, conglomerate unit from a mine shaft has been analysed. Using parameters from this analysis, brittle strength and dilatancy models have been implemented in a finite-difference code to predict not only stress re-distribution and yield around the shaft, but also to obtain realistic displacement values. Comparison of the modelling results to displacements measured using borehole extensometers show that the constitutive model and lab-derived parameters used were effective in predicting the rockmass behaviour. Parameters were further optimized through back analysis. One interesting finding of this analysis is that the in-situ rockmass dilation decay rate (as a function of plastic strain) appears to be faster than estimated based on laboratory data, which may be indicative of the influence of rockmass-scale natural fractures and other geological structures on the dilation decay process. It also appears possible to model the in-situ dilation decay rate using a single parameter, instead of separate parameters for unconfined and confined conditions. To conclude the study, more numerical results obtained using alternative dilatancy models are presented to illustrate the problem of non-uniqueness in plasticity back analyses.     

In situ characterization of nitrifying biofilm: Minimizing biomass loss and preserving perspective

Methods for characterizing nitrifying bacteria within biofilms are of key importance to understand and optimize the nitrification kinetics of attached growth treatment facilities. In this work, we propose an analytical protocol based upon environmental scanning electron microscopy (ESEM) and confocal laser scanning microscopy (CSLM) in combination with fluorescent in situ hybridization (FISH) to characterize the structure of nitrifying biofilm as it remains attached to the original reactor substratum. This protocol minimizes the loss of mass and distortion of in situ perspective commonly associated with traditionally applied microscopic techniques and thereby enables a more accurate estimation of the nitrifying biomass within biofilm attached to the substratum. The use of ESEM eliminates the destructive preparatory procedures associated with traditional scanning electron microscopy and thus the loss of mass and shrinking of the samples. ESEM is used in this study to evaluate the percent coverage of the substratum with biofilm and the biofilm thickness. CLSM-FISH is used to determine cell counts in the biofilm and to characterize the undisturbed substratum/biofilm interface. By hybridizing and analyzing the nitrifying biofilm using CLSM as it remains attached to the substratum, the loss of material and distortion of in situ perspective associated with the biofilm detachment process is minimized. Moreover, by conducting the CLSM analysis directly on the nitrifying biofilm as it remains attached to the substratum it is shown that cell counts at the substratum/biofilm interface differ significantly from that located above the interface.     

岩土参数随机场特性及线性预测

对利用随机场理论来研究岩土参数的几个基本问题进行了探讨 ,指出目前对岩土参数随机场的随机性描述存在半变异函数和相关函数两种理论方法 ,通过理论分析和推导研究了两种方法的内涵和联系 ,探讨了计算岩土参数的相关距离的几种方法 ,在此基础上证明加权最小二乘多项式可作为最佳线性预测函数 ,并通过大量实测资料进行了验证。     

NOM degradation during river infiltration: Effects of the climate variables temperature and discharge

Most peri-alpine shallow aquifers fed by rivers are oxic and the drinking water derived by riverbank filtration is generally of excellent quality. However, observations during past heat waves suggest that water quality may be affected by climate change due to effects on redox processes such as aerobic respiration, denitrification, reductive dissolution of manganese(III/IV)- and iron(III)(hydr)oxides that occur during river infiltration. To assess the dependence of these redox processes on the climate-related variables temperature and discharge, we performed periodic and targeted (summer and winter) field sampling campaigns at the Thur River, Switzerland, and laboratory column experiments simulating the field conditions. Typical summer and winter field conditions could be successfully simulated by the column experiments. Dissolved organic matter (DOM) was found not to be a major electron donor for aerobic respiration in summer and the DOM consumption did not reveal a significant correlation with temperature and discharge. It is hypothesized that under summer conditions, organic matter associated with the aquifer material (particulate organic matter, POM) is responsible for most of the consumption of dissolved oxygen (DO), which was the most important electron acceptor in both the field and the column system. For typical summer conditions at temperatures >20 °C, complete depletion of DO was observed in the column system and in a piezometer located only a few metres from the river. Both in the field system and the column experiments, nitrate acted as a redox buffer preventing the release of manganese(II) and iron(II). For periodic field observations over five years, DO consumption showed a pronounced temperature dependence (correlation coefficient r = 0.74) and therefore a seasonal pattern, which seemed to be mostly explained by the temperature dependence of the calculated POM consumption (r = 0.7). The river discharge was found to be highly and positively correlated with DO consumption (r = 0.85), suggesting an enhanced POM input during flood events. This high correlation could only be observed for the low-temperature range (T < 15 °C). For temperatures >15 °C, DO consumption was already high (almost complete) and the impact of discharge could not be resolved. Based on our results, we estimate the risk for similar river-infiltration systems to release manganese(II) and iron(II) to be low during future average summer conditions. However, long-lasting heat waves might lead to a consumption of the nitrate buffer, inducing a mobilization of manganese and iron.     

Mitigating ammonia inhibition of thermophilic anaerobic treatment of digested piggery wastewater: use of pH reduction, zeolite, biomass and humic acid

High free ammonia released during anaerobic digestion of livestock wastes is widely known to inhibit methanogenic microorganisms and result in low methane production. This was encountered during our earlier thermophilic semi-continuously fed continuously-stirred tank reactor (CSTR) treatment of piggery wastewater. This study explored chemical and biological means to mitigate ammonia inhibition on thermophilic anaerobic treatment of piggery wastewater with the aim to increase organic volatile carbon reduction and methane production. A series of thermophilic anaerobic batch experiments were conducted on the digested piggery effluent to investigate the effects of pH reduction (pH 8.3 to 7.5, 7.0 and 6.5) and additions of biomass (10% v/v and 19% v/v anaerobic digested piggery biomass and aerobic-anaerobic digested municipal biomass), natural zeolite (10, 15 and 20 g/L) and humic acid (1, 5 and 10 g/L) on methane production at 55 °C for 9-11 days. Reduction of the wastewater pH from its initial pH of 8.3 to 6.5 produced the greatest stimulation of methane production (3.4 fold) coupled with reductions in free ammonia (38 fold) and total volatile fatty acids (58% TVFA), particularly acetate and propionate. Addition of 10-20 g/L zeolite to piggery wastewater with and without pH reduction to 6.5 further enhanced total VFA reduction and methane production over their respective controls, with 20 g/L zeolite producing the highest enhancement effect despite the ammonia-nitrogen concentrations of the treated wastewaters remaining high. Without pH reduction, zeolite concentration up to 20 g/L was required to achieve comparable methane enhancement as the pH-reduced wastewater at pH 6.5. Although biomass (10% v/v piggery and municipal wastes) and low humic acid (1 and 5 g/L) additions enhanced total VFA reduction and methane production, they elevated the residual effluent total COD concentrations over the control wastewaters (pH-unadjusted and pH-reduced) unlike zeolite treatment. The outcomes from these batch experiments support the use of pH reduction to 6.5 and zeolite treatment (10-20 g/L) as effective strategies to mitigate ammonia inhibition of the thermophilic anaerobic treatment of piggery wastewater.     

盐源县塘房沟泥石流成因及运动特征研究

在现场勘察调查的基础上,对塘房沟泥石流的形成条件和流体的动力学特征作了较详细的分析,得出了对沟口村庄进行搬迁和对塘房沟治理工作迫在眉睫的结论,研究成果为泥石流防治工程提供了可靠的设计依据。     

新光快速路设计施工总承包模式理论研究

介绍了国内总承包模式的类型及各自特点,并结合广州新光快速路项目,对设计-施工总承包模式进行了理论研究,新光快速路工程实践证明,在我国现阶段以设计-施工联合体方式进行工程总承包具有现实意义,并提出了总承包模式进一步发展的建议。     

Bayesian posterior prediction and meta-analysis: an application to the value of travel time savings

In the evaluation of transportation infrastructure projects, some non-tradable goods such as time are usually key determinants of the result. However, obtaining monetary values for these goods is not always easy. For this purpose, this paper presents an approach that combines Bayesian posterior prediction and meta-analysis. This methodology will allow obtaining predictive distributions of the monetary values for this type of goods. Therefore, uncertainty is formally considered in the analysis. Moreover, the proposed method is easy to apply and inexpensive both in terms of time and money. Finally, an illustrative application to the value of travel time savings is also presented.     

Measuring the exposure of infants and children to indoor air pollution from biomass fuels in The Gambia

Indoor air pollution (IAP) from biomass fuels contains high concentrations of health damaging pollutants and is associated with an increased risk of childhood pneumonia. We aimed to design an exposure measurement component for a matched case-control study of IAP as a risk factor for pneumonia and severe pneumonia in infants and children in The Gambia. We conducted co-located simultaneous area measurement of carbon monoxide (CO) and particles with aerodynamic diameter <2.5 microm (PM(2.5)) in 13 households for 48 h each. CO was measured using a passive integrated monitor and PM(2.5) using a continuous monitor. In three of the 13 households, we also measured continuous PM(2.5) concentration for 2 weeks in the cooking, sleeping, and playing areas. We used gravimetric PM(2.5) samples as the reference to correct the continuous PM(2.5) for instrument measurement error. Forty-eight hour CO and PM(2.5) concentrations in the cooking area had a correlation coefficient of 0.80. Average 48-h CO and PM(2.5) concentrations in the cooking area were 3.8 +/- 3.9 ppm and 361 +/- 312 microg/m3, respectively. The average 48-h CO exposure was 1.5 +/- 1.6 ppm for children and 2.4 +/- 1.9 ppm for mothers. PM(2.5) exposure was an estimated 219 microg/m3 for children and 275 microg/m3 for their mothers. The continuous PM(2.5) concentration had peaks in all households representing the morning, midday, and evening cooking periods, with the largest peak corresponding to midday. The results are used to provide specific recommendations for measuring the exposure of infants and children in an epidemiological study. PRACTICAL IMPLICATIONS: Measuring personal particulate matter (PM) exposure of young children in epidemiological studies is hindered by the absence of small personal monitors. Simultaneous measurement of PM and carbon monoxide suggests that a combination of methods may be needed for measuring children's PM exposure in areas where household biomass combustion is the primary source of indoor air pollution. Children's PM exposure in biomass burning homes in The Gambia is substantially higher than concentrations in the world's most polluted cities.     

我国火灾损失的时间趋势分析及动态预测

利用我国火灾损失统计资料，进行时间趋势分析。结果表明，我国火灾损失呈现一定的上升趋势。在此基础上，采用灰色GM(1，1)模型预测我国火灾损失，经检验预测模型的精度满足要求，其预测结果比较可靠，可以为相关部门的决策提供一定的帮助。     

Evaluation on the impacts of predators on biomass components and oxygen uptake in sequencing batch reactor and continuous systems

An expanded unified model for the biomass fractions, soluble-organic fractions, and oxygen-uptake rates considering extracellular polymeric substances (EPS), intracellular storage products (X_STO), and predators for activated sludge is used to study the impacts of predators on biomass components and oxygen uptake. The new model is applied to evaluate how predation affects the oxygen-uptake rate (OUR) and the different forms of biomass: active bacteria (X_H), X_EPS, and X_STO, under dynamic feast-and-famine and continuous conditions. For the dynamic conditions of a sequencing batch reactor (SBR), eliminating predators from the model increases X_H and X_EPS fractions significantly, and this causes the substantial increases in OUR and MLVSS once the famine period begins. An analysis of how the OUR is distributed among the several respiration processes shows that the predation of X_H is the most significant oxygen utilization rate process in the system under famine conditions of an SBR. Application of the model to simulate the long-term operation of an SBR indicates that predators reach their maximum fraction in the MLVSS (∼4% of MLVSS) at a solids retention time of about 13 days, but they are washed out at a solids retention time less than ∼3 days. Simulation for a continuous system indicates that predators take more time (about 800 h) to reach steady state and reach their maximum fraction (∼5.5%) at an SRT of ∼14 days. Comparison of SBR and continuous systems reveals that the predators have greater impact in the continuous system because the permanent near-famine condition accentuates predation processes.     

Hypertension with elevated levels of oxidized low-density lipoprotein and anticardiolipin antibody in the circulation of premenopausal Indian women chronically exposed to biomass smoke during cooking

This study aims to investigate whether indoor air pollution (IAP) from biomass fuel use was associated with hypertension, platelet hyperactivity, and elevated levels of oxidized low-density lipoprotein (oxLDL) and anticardiolipin antibody (aCL). We enrolled 244 biomass fuel-using (median age 34 year) and 236 age-matched control women who cooked with liquefied petroleum gas (LPG). Enzyme-linked immunosorbent assay was used to measure oxLDL in plasma and aCL in serum, flow cytometry for P-selectin expression on platelet and reactive oxygen species (ROS) generation by leukocytes, aggregometry for platelet aggregation, spectrophotometry for superoxide dismutase (SOD) in erythrocytes, and laser photometer for particulate matter <10 and 2.5 μm in diameter (PM(10) and PM(2.5), respectively) in cooking areas. Biomass users had three times more particulate pollution in kitchen, had higher prevalence of hypertension (29.5 vs. 11.0% in control, P < 0.05), elevated oxLDL (170.6 vs. 45.9 U/l; P < 0.001), platelet P-selectin expression (9.1% vs. 2.4%), platelet aggregation (23.2 vs. 15.9 Ohm), raised aCL IgG (28.7% vs. 2.1%), IgM (8.6% of vs. 0.4%), and ROS (44%) but depleted (13%) SOD. After controlling potential confounders, the changes were positively associated with PM(10) and PM(2.5) in indoor air, suggesting a positive association between IAP and increased cardiovascular risk. PRACTICAL IMPLICATIONS: The study showing high risk of developing cardiovascular diseases (CVD) among poor, underprivileged women in their reproductive ages in rural India is important from public health perspectives. It may motivate the government and the regulatory agencies of the country to take a serious note of the indoor air pollution (IAP) from biomass fuel use as it threatens the health of millions of women, children, and the elderly who mostly stay indoor. We hope the findings will strengthen the demand for setting up a standard for indoor air quality in the country in the line of national ambient air quality standard. The findings may also inspire the authorities to take measures for the reduction in IAP by improving housing, kitchen ventilation, and cook stoves. Moreover, the parameters used in this study can be utilized for large, population-based studies to identify women at a higher risk of developing CVD so that medical intervention can be taken at the formative stage of a disease.     

The role of biomass, electron shuttles, and ferrous iron in the kinetics of Geobacter sulfurreducens-mediated ferrihydrite reduction

This work presents a new framework for describing biologically mediated reduction of thin layers of poorly crystalline iron oxides. The research here explores the nature of the biomass to surface area relationship and the role of biogenic ferrous iron during Geobacter sulfurreducens-mediated ferrihydrite reduction, with and without an electron shuttle, through experiments and a mathematical model. The results indicate that a saturating function of biomass most accurately describes the rate of iron reduction without electron shuttles, based on the principle of electron transfer via direct contact. This study also finds that the most appropriate model of iron reduction in the presence of electron shuttles includes both a saturating function of biomass for electron transfer via direct contact and a first-order electron transfer to ferrihydrite via the electron shuttle, strongly supporting the idea that G. sulfurreducens uses both pathways simultaneously. In all experiments, G. sulfurreducens reduced less than 60% of the total ferric iron, a phenomenon that has often been explained through the inhibitory effects of biogenic ferrous iron in the dissolved phase. However, through experiments with spikes of ferrous sulfate, this study suggests that the role of dissolved ferrous iron is passive in this case, and does not directly inhibit the extent of iron reduction in ferrihydrite coated sand. These experiments find that solid phase ferrous iron is the most probable primary product of ferrihydrite reduction, and that the conversion of solid ferric iron to solid ferrous iron depletes a fixed pool of bioavailable ferric iron, thereby accounting for the incomplete reduction of ferric iron observed here. This is the first reported model that explicitly treats solid ferrous iron as the primary product of reduction, with aqueous ferrous iron as a passive byproduct. This simple mathematical model readily translates to other systems of microbially mediated iron reduction.     

ILES of flow over low-rise buildings: Influence of inflow conditions on the quality of the mean pressure distribution prediction

The paper presents an analysis of the deformation of the horizontal velocity profile in the flow approaching low-rise buildings for large eddy simulation on coarse grids. Build-up of velocity near the ground is observed as a consequence of momentum transfer from the outer flow to the ground level due to the fluctuating flow field. As a remedy, reduction of the turbulence intensity at the inflow boundary of the computational domain with respect to the experimental values is studied. The observation is that accurate prediction of the mean pressure distribution on the building surface is obtained when the inlet turbulence is reduced such that the deformation of the velocity profile in the flow approaching the building becomes small. For reliable mean pressure prediction, it is best not to reduce the inlet turbulence more than the minimum necessary to obtain a good velocity profile in the approaching flow.