Dimensionality reduction and prediction of soil consolidation coefficient using random forest coupling with Relief algorithm

The consolidation coefficient of soil (C_v) is a crucial parameter used for the design of structures leaned on soft soi. In general, the C_v is determined experimentally in the laboratory. However, the experimental tests are time-consuming as well as expensive. Therefore, researchers tried several ways to determine C_v via other simple soil parameters. In this study, we developed a hybrid model of Random Forest coupling with a Relief algorithm (RF-RL) to predict the C_v of soil. To conduct this study, a database of soil parameters collected from a case study region in Vietnam was used for modeling. The performance of the proposed models was assessed via statistical indicators, namely Coefficient of determination (R²), Root Mean Squared Error (RMSE), and Mean Absolute Error (MAE). The proposal models were constructed with four sets of soil variables, including 6, 7, 8, and 13 inputs. The results revealed that all models performed well with a high performance (R² > 0.980). Although the RF-RL model with 13 variables has the highest prediction accuracy ( R² = 0.9869), the difference compared with other models was negligible (i.e., R² = 0.9824, 0.9850, 0.9825 for the cases with 6, 7, 8 inputs, respectively). Thus, it can be concluded that the hybrid model of RF-RL can be employed to predict C_v based on the basic soil parameters.     

Fine-spray (water mist) protection of shipboard engine rooms

Twenty-three fire tests were conducted to determine the ability of current fine-spray (water mist) technologies to extinguish fires specified in the International Maritime Organization (IMO) fire test procedure for engine rooms greater than 3000 m³. The tests were conducted using nozzle installed at a 5 m height and 1·5 m spacing in a large test facility (2800 m² area and 18 m height). Two types of nozzles were tested: a low pressure nozzle operating between 1·2 and 1·5 MPa with flow per nozzle between 12·0 and 13·41/m and a multi-nozzle high-pressure prototype consisting of seven nozzles operating at 6·9 MPa flowing at 5·3 1/m per prototype. These nozzles were selected because they had been shown to extinguish IMO fire tests in enclosures with a protected area of 83 m² and a ceiling height of 4·5 m. The fire tests selected from the IMO procedure included 6 MW diesel spray fires on top of the IMO engine mock-up, a shielded 6 MW diesel spray fire adjacent to the mock-up, a 1 MW shielded diesel spray fire adjacent to the mock-up, and a wood crib within a 2 m² pan filled with heptane. In tests in which no additional enclosure surrounded the nozzles other than the test facility, fires were not significantly affected by the water mist using either nozzle. To further investigate mist-system capabilities, a ceiling was then placed directly over the nozzles at a 5 m height covering an area of 188 m². Using 90 high-pressure prototype nozzles, the test fires were not extinguished. A 940 m³ enclosure was then formed by dropping tarpaulins to the floor from the ceiling. A 4 m² vent was placed in the wall. With the 90 high-pressure prototype nozzles, the 6 MW spray fire on top of the mock-up was extinguished. When the 6 MW fire was shielded beside the mock-up, the fire was not extinguished. With the vent closed, the 6 MW shielded spray fire was extinguished. Under the same test conditions, a 1 MW shielded diesel spray fire and a 0·1 m² heptane pool fire were not extinguished. The fire test results indicated that protection of engine rooms with volumes of about 1000 m³ is possible by optimizing current fine-spray technology while significantly larger volumes will require improved discharge characteristics.     

Influence of inter-annual variations in climatic factors on fecal coliform levels in Mississippi Sound

Information on the effects of inter-annual variations in climatic factors on fecal coliform levels in coastal waters is scarce. We used 11 years (1990–2001) of rainfall, water temperature, Pearl River stage and salinity data to assess the effects of the 1991–1992 and 1997–1998 El Niño events on fecal coliform levels in Mississippi Sound. El Niño-Southern Oscillation had major effects on Pearl River stage and water quality in the Sound. The geometric mean fecal coliform number differed among years (P=0.0001), being highest during 1991–1992 El Niño years (14.22 MPN per 100 ml) and lowest during 1999–2000 La Niña years (<1.8 MPN per 100 ml). Mean salinity varied among years (P=0.0001) from 9 ppt (1991–1992) to 21 ppt (1999–2000). Mean water temperature was lowest in 1997–1998 (14.5 °C) and highest in 1998–2000 (19.4 °C). Pearl River stage differed among years (P=0.0001), ranging from 1.96 m (1999–2000) to 3.57 m (1997–1998). Inverse relationships were observed between fecal coliform levels and salinity (r²=0.74; P=0.001) and water temperature (r²=0.69; P=0.001), whereas positive relationships were obtained with total rainfall (r²=0.52; P=0.013) and Pearl River stage (r²=0.90; P=0.0001). These relationships are useful for evaluating the potential effects of climate change on water quality and classification of shellfish growing waters in order to protect humans from consuming contaminated shellfish in shallow river-influenced estuaries.     

Application of machine learning technique for predicting and evaluating chloride ingress in concrete

The degradation of concrete structure in the marine environment is often related to chloride-induced corrosion of reinforcement steel. Therefore, the chloride concentration in concrete is a vital parameter for estimating the corrosion level of reinforcement steel. This research aims at predicting the chloride content in concrete using three hybrid models of gradient boosting (GB), artificial neural network (ANN), and random forest (RF) in combination with particle swarm optimization (PSO). The input variables for modeling include exposure condition, water/binder ratio (W/B), cement content, silica fume, time exposure, and depth of measurement. The results indicate that three models performed well with high accuracy of prediction (R²≥ 0.90). Among three hybrid models, the model using GB_PSO achieved the highest prediction accuracy (R² = 0.9551, RMSE = 0.0327, and MAE = 0.0181). Based on the results of sensitivity analysis using SHapley Additive exPlanation (SHAP) and partial dependence plots 1D (PDP-1D), it was found that the exposure condition and depth of measurement were the two most vital variables affecting the prediction of chloride content. When the number of different exposure conditions is larger than two, the exposure significantly impacted the chloride content of concrete because the chloride ion ingress is affected by both chemical and physical processes. This study provides an insight into the evaluation and prediction of the chloride content of concrete in the marine environment.     

Algal growth in warm temperate reservoirs: kinetic examination of nitrogen, temperature, light, and other nutrients

Nutrient limited growth of the phytoplankton assemblage in two Texas reservoirs was studied by a combination of nutrient addition experiments and statistical modeling. Dilution bioassays were run to ascertain the qualitative and quantitative patterns in nutrient limitation. Algal growth was frequently and strongly nutrient limited, particularly when temperature was >22°C. By itself, N was more often stimulatory than P, though strong additional enhancement of growth by P and trace nutrients was often detected. Monod growth kinetics indicated that half-saturation constants for N limited growth for the entire algal assemblage were in the range 20–200 μg N/L, relatively high compared to literature values, and increased with increasing temperature. Maximal growth was also an increasing function of temperature. A single temperature-dependent model was fit to the growth dynamics for all experiments showing N-limitation. The model μ=0.0256·T([DIN]/66.0+[DIN]) where μ is specific growth rate (d⁻¹), T is temperature (°C) and [DIN] is dissolved inorganic N (μmol/L) fit the experimental results reasonably well (r²=0.82). However, only a modest predictive power for growth in the controls (our best estimate of growth in situ) was achieved (r²=0.26). Thus, even with unusually detailed, site-specific fitting of model parameters, accurately modeling algal growth in natural ecosystems can remain a challenge.     

The energy balance of an exterior window surface, Inuvik, N.W.T., Canada

This paper examines the energy loss of an exterior window surface during the month of January, 1975, in Inuvik, N.W.T., Canada. Radiative exchanges (L^*) were measured and the energy loss through the window was calculated (Q_F). Since an energy balance exist at the exterior window surface, a heat transfer coefficient (h) was determined by residual: h=(Q_F−L^*)/(T_s−T_a). Calculated values for the heat transfer coefficient compare favourably with those of other studies. The atmospheric controls (i.e. wind speed and cloud cover) on radiative and convective heat losses and their influence on urban climate are discussed with respect to the observational data.     

Modeling of unconfined compressive strength of soil-RAP blend stabilized with Portland cement using multivariate adaptive regression spline

The recycled layer in full-depth reclamation (FDR) method is a mixture of coarse aggregates and reclaimed asphalt pavement (RAP) which is stabilized by a stabilizer agent. For design and quality control of the final product in FDR method, the unconfined compressive strength of stabilized material should be known. This paper aims to develop a mathematical model for predicting the unconfined compressive strength (UCS) of soil-RAP blend stabilized with Portland cement based on multivariate adaptive regression spline (MARS). To this end, two different aggregate materials were mixed with different percentages of RAP and then stabilized by different percentages of Portland cement. For training and testing of MARS model, total of 64 experimental UCS data were employed. Predictors or independent variables in the developed model are percentage of RAP, percentage of cement, optimum moisture content, percent passing of #200 sieve, and curing time. The results demonstrate that MARS has a great ability for prediction of the UCS in case of soil-RAP blend stabilized with Portland cement (R² is more than 0.97). Sensitivity analysis of the proposed model showed that the cement, optimum moisture content, and percent passing of #200 sieve are the most influential parameters on the UCS of FDR layer.     

Toxicity of chlorine to juvenile spot, Leiostomus Xanthurus

The sensitivity of juvenile spot, Leiostomus xanthurus, to total residual chlorine (TRC) in flowing sea-water was investigated. Incipient LC₅₀ bioassays, histopathology, avoidance tests and the combined effect of thermal stress and TRC were used to assess sensitivity.

Estimated incipient LC₅₀ values were 0.12 mg 1⁻¹ TRC at 10°C and 0.06 mg 1⁻¹ TRC at 15°C. Histological examination of spot used in the incipient LC₅₀ bioassay at 15°C and sacrificed while alive indicated pseudobranch and gill damage occurred in individuals exposed to a measured TRC concentration of 1.57 mg 1⁻¹. Spot exposed to lower concentrations of TRC, 0.02 0.06 mg 1⁻¹ at 15°C and sacrificed alive showed no consistent tissue damage.

Spot demonstrated temperature dependent avoidance responses to TRC. At 10°C, a concentration of 0.18 mg 1⁻¹ was required for significant (X²; P < 0.05) avoidance; at 15 and 20°C, spot showed significant avoidance of TRC concentrations as low as 0.05 mg 1⁻¹.

Simultaneous exposure of spot to thermal stress (5, 10 or 13°C above the acclimation temperature of 15°C) at measured TRC concentrations of 0.05 0.07 and 0.34–0.52 mg 1⁻¹ demonstrated a significant, (Z²) with Yates correction, P < 0.05) increase in sensitivity to TRC with increased temperature and exposure times for some of the groups tested.     

机场道面混掺纤维混凝土强度与抗弯韧性试验

为了降低机场道面混凝土脆性,通过混掺高性能粗聚烯烃纤维（PP）和细聚乙烯醇纤维（PVA）来提高道面混凝土韧性。通过四点弯曲试验,测得了梁试件荷载 挠度曲线,分析了2种纤维体积掺率混掺对改善三级配机场道面混凝土弯曲韧性的效果。结果表明:纤维混掺可明显改善混凝土抗弯韧性;PP的掺入使荷载 挠度曲线出现了2次峰值;PVA体积掺率为0.2%或0.4%时,随着PP掺率增加,韧性指标值P₃₀₀,P₇₅,P₅₀均呈增大趋势;PP掺率的增加对后期韧性指标值P₇₅,P₅₀的提高更为显著;增加PVA掺率对提高第一峰值强度较为显著;PP和PVA分别以体积掺率1.1%和0.4%混掺时,机场道面混凝土抗弯韧性提高最为明显。     

Modeling the pavement serviceability ratio of flexible highway pavements by artificial neural networks

The term “present serviceability” was adopted to represent the momentary ability of pavement to serve traffic, and the performance of the pavement was represented by its serviceability history in conjunction with its load application history. Serviceability was found to be influenced by longitudinal and transverse profile as well as the extent of cracking and patching. The amount of weight to assign to each element in the determination of the over-all serviceability is a matter of subjective opinion.In this study, artificial neural networks (ANN) is used in modeling the present serviceability index of the flexible pavements. Experimental data obtained from AASHTO include slope variance, rut depth, patches, cracking and longitudinal cracking. The developed ANN model has higher regression value than AASHO model. This approach can be easily and realistically performed to solve the problems which do not have a formulation or function about the solution.     

Fuzzy multi-attribute decision making in pavement management

A methodology for ranking pavement sections according to maintenance urgency has been developed using fuzzy multi-attribute decision-making concepts. First. the pavement sections in a highway network are grouped according to their maintenance needs, using fuzzy pavement serviceability indices. Then, the attributes relevant to each category of maintenance are identified, and an expert knowledge base containing priority values for selected combinations of attribute values is formed in collaboration with decisionmakers. Finally, it is shown how the fuzzy attribute values for each pavement section can interact with the expert knowledge base to produce a unique set of rankings for these sections. This ranking scheme is capable of handling possible fuzziness in the priorities assigned by the decision makers.     

FRP筋混凝土梁挠度与裂缝宽度计算模型分析

收集国内外218组纤维增强复合材料(FRP)筋混凝土梁受弯性能试验结果,重点研究了正常使用阶段和极限状态下梁挠度和裂缝宽度的发展规律,基于试验数据修正了FRP筋应变不均匀系数ψ与强度配筋影响系数的关系,建立了该类梁受弯挠度计算模型;深入分析了FRP筋混凝土梁受弯截面内力臂系数η、构件受力特征系数α_cr对构件裂缝宽度计算精度的影响,确定η,α_cr的合理取值,优化计算模型,并与规范GB 50608—2010建议模型计算值进行对比分析。结果表明:根据建立的ψ与强度配筋影响系数关系,选取η=0.88,α_cr=1.5得到的建议模型能够较好预测FRP筋混凝土梁受弯挠度和裂缝宽度,比规范计算结果吻合好,验证了建议模型的准确性和合理性。     

Adsorption of chlorinated organic compounds on activated carbon from water

The adsorption capacities and rates of seven principal chlorinated organic compounds for six commercial GACs were investigated. All the adsorption isotherms were expressed by the Freundlich equation, and the isotherms for the chloroethylenes such as trans - 1,2-dichloroethylene, trichloroethylene and tetrachloroethylene could be shown by the modified Freundlich equation Q′ = k′ (C/C_s)^l/n for each GAC. The magnitude of adsorption of the chlorinated organic compounds was in the order of: tetrachloroethylene > trichloroethylene > trans - 1,2-dichloroethylene > 1,1-dichloroethane > carbontetrachloride > 1.1,1-trichloroethane > chloroform. The value of k for a certain GAC could be predicted from the quantity of pores smaller than 2 nm in diameter. The adsorbed amounts were decreased by 10–20% when humic substances coexisted. The working periods of a fixed bed adsorber before regeneration were predicted by calculating breakthrough curves for various influent concentrations of trichloroethylene and tetrachloroethylene at the space velocities of 5 or 10 h⁻¹, and it was certified that the adsorption method by GAC was feasible for removing these compounds from water.     

Evaluation of kinetic parameters of a sulfur-limestone autotrophic denitrification biofilm process

In this study, four kinetic parameters of autotrophic denitrifiers in fixed-bed sulfur–limestone autotrophic denitrification (SLAD) columns were evaluated. The curve-matching method was used by conducting 22 non-steady-state tests for estimation of half-velocity constant, K_s and maximum specific substrate utilization rate, k. To estimate the bacteria yield coefficient, Y and the decay coefficient, k_d, two short term batch tests (before and after the starvation of the autotrophic denitrifiers) were conducted using a fixed-bed SLAD column where the biofilm was fully penetrated by nitrate-N. It was found that K_s=0.398 mg NO₃⁻–N/l, k=0.15 d⁻¹, k_d=0.09–0.12 d⁻¹, and Y=0.85–1.11 g VSS/g NO₃⁻–N. Our results are consistent with those obtained from SLAD biofilm processes, but different from those obtained from suspended-growth systems with thiosulfate or sulfur powders as the S source. The method developed in this study might be useful for estimation of four Monod-type kinetic parameters in other biofilm processes. However, cautions must be given when the estimated parameters are used because the measurements of the biomass and the biofilm thickness could be further improved, and the assumption of sulfur being a non-limiting substrate needs to be proved.     

循环剪切作用下泥质软岩本构模型研究

库区微震频发现象使泥质软岩受循环剪切动力作用。基于分数阶西原模型,将Able黏壶进行改进,获得相应条件下的本构模型,并通过泥质软岩试样循环剪切试验对该本构模型进行了验证。研究表明:①原有分数阶西原本构模型可归纳为本模型正弦函数(循环作用)为零时的特殊解;②模型表现出较好的适用性(R²∈(0.96,0.98)),且方程曲线具备试验曲线的“单双拐点”特征;③模型主要影响因素为分数阶阶数n,其中稳定型方程n∈(0,0.6)、破坏型方程n∈(0.6,1.0);④随n的增加,抗剪模量G与黏滞系数η大致呈现降低趋势,可较好反映宏观现象;⑤从参数扰动的角度解释了以往文献出现的η随n增加可能表现出的无规律波动现象。研究成果可为微震条件下含泥质软岩边坡长期稳定性控制提供理论参考。     

Estimation of flexible pavement structural capacity using machine learning techniques

The most common index for representing structural condition of the pavement is the structural number. The current procedure for determining structural numbers involves utilizing falling weight deflectometer and ground-penetrating radar tests, recording pavement surface deflections, and analyzing recorded deflections by back-calculation manners. This procedure has two drawbacks: falling weight deflectometer and ground-penetrating radar are expensive tests; back-calculation ways has some inherent shortcomings compared to exact methods as they adopt a trial and error approach. In this study, three machine learning methods entitled Gaussian process regression, M5P model tree, and random forest used for the prediction of structural numbers in flexible pavements. Dataset of this paper is related to 759 flexible pavement sections at Semnan and Khuzestan provinces in Iran and includes “structural number” as output and “surface deflections and surface temperature” as inputs. The accuracy of results was examined based on three criteria of R, MAE, and RMSE. Among the methods employed in this paper, random forest is the most accurate as it yields the best values for above criteria (R=0.841, MAE=0.592, and RMSE=0.760). The proposed method does not require to use ground penetrating radar test, which in turn reduce costs and work difficulty. Using machine learning methods instead of back-calculation improves the calculation process quality and accuracy.     

Removal of cadmium and manganese by a non-toxic strain of the freshwater cyanobacterium Gloeothece magna.

The ability of both living and dry cells of Gloeothece magna, a non-toxic freshwater cyanobacterium, to adsorb cadmium and manganese is demonstrated in this study. Chlorophyll a content of living cells was not influenced by either cadmium or manganese concentrations, indicating that adsorption of both Cd²⁺ and Mn²⁺ by living cells of G. magna, was independent of the metabolic state of the organism. Moreover, the adsorption of both Cd²⁺ and Mn²⁺ to living cells and dry cells, was dependent on the metal concentrations, and fitted the Freundlich adsorption isotherm. However, dry cells had larger binding capacity for both Cd²⁺ (K_f=912.6) and Mn²⁺ (K_f=2398) than living cells (K_f=151.4 & 63, respectively). The role of the capsular polysaccharides, the main constituents of the cyanobacterial envelope, in binding these two metals was also studied. Polysaccharide extracts of this organism adsorbed high amounts of both Cd²⁺ (115–425 μg mg⁻¹) and Mn²⁺ (473–906 μg mg⁻¹). This study suggests that G. magna would probably be cultured in water bodies contaminated by heavy metals to ameliorate their toxicity. Also dry material of this cyanobacterium being a non-toxic species, could be used as a safe biofilter to remove toxic metals from drinking water.     

Degradation of polychlorinated dibenzo-p-dioxin and dibenzofuran contaminants in 2,4,5-T by photoassisted iron-catalyzed hydrogen peroxide

The objective of this study was to determine the fate of polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) contaminants in the herbicide 2,4,5-trichlorophenoxyacetic acid after treatment by photoassisted Fe³⁺-catalyzed hydrogen peroxide oxidation, which is being investigated for waste treatment. Toluene-extraction of aqueous reagent grade 2,4,5-T gave 30 quantifiable PCDD/F isomer peaks, some of which represented more than one congener. They included 13 tetra- through heptachloro PCDDs totalling 18.4 ng/g, and 17 tetra- through octachloro PCDFs totalling 12.9 ng/g. Treatment with Fe³⁺/H₂O₂/hv (mole ratio 2,4,5-T:Fe³⁺:H₂O₂ = 1:10:200; visible fluorescent light, 300 nm cutoff) in aerated solution at pH 2.8 resulted in 89–100% removal of all PCDD/F peaks except that for OCDF, which was 66% removed. The 2,4,5-T was shown previously to be completely mineralised to HCl and CO₂. Direct photolysis of the PCDD/Fs was negligible. The 2,3,7,8-tetra-CDD referenced “toxic equivalent” used in risk assessment was reduced by 99.9% (U.S. Environmental Protection Agency method) or 99.6% (international method). Reaction mixtures supplemented with 2,3,7,8-(UL-¹⁴C)-tetra-CDD and 2,3,4,7,8-(dichlorophenyl-¹⁴C)-penta-CDF evolved up to 45 and 64%, respectively, theoretical yield of ¹⁴CO₂. Most of the remaining ¹⁴C was converted to hydrophilic forms not extractable by toluene. Dark (Fe³⁺/H₂O₂) treatment was somewhat less effective overall.     

基于敏感性分析的围岩力学参数反演方法研究

由于影响隧道变形的围岩强度参数和变形参数较多,现有的反分析研究主要集中在算法的优化上,因而忽略了工程应用的便利性和实用性。针对这种状况,以南京某隧道工程为依托,结合数值模拟,提出了基于敏感性分析的反演方法。根据工程实际,将围岩和支护结构综合考虑分为初始围岩区(简称Z₁),松动圈与锚杆锚固共同作用区(简称Z₂)以及钢支撑和喷射砼等效作用区(简称Z₃);通过安排试算初始值,利用FLAC^3D程序计算并分析不同的力学参数对不同隧道变形的敏感性,从而确定反演流程;根据反演流程结合各测点的实测变形值获取合理、准确的围岩力学参数。研究结果表明:与常规的反演方法相比,通过敏感性分析确定隧道不同变形的主控因素,以此变形来反演该主控因素参数在很大程度上提高了工程应用的效率与可靠度;拱顶下沉受Z₁区弹性模量E₁、Z₂与Z₁区弹性模量比值n的影响较大,受围岩泊松比μ₁的影响相对较小;隧道收敛受E₁、n、μ₁ 三者的影响都较大;围岩力学参数反演结果为E₁=362.6 MPa、n=0.62、μ₁=0.30;现场应用证明了该方法的有效合理性。     

Framework for developing a static strength test for measuring deformation resistance of asphalt concrete mixtures

This study deals with a strength property which is showing high correlation with rutting resistance of asphalt mixtures. The test procedure was developed by applying a load to the compacted asphalt samples and calculating the strength by using the deformation of the mixture at the failure point. To evaluate the validity of this test, various mixtures were prepared with two aggregates and seven binders using four loading head types at the loading speed of 50.8 mm/min at 60 °C. Maximum load and deformation were recorded for each test and deformation strength, S_D, was calculated using a newly developed equation. For the same mixture, wheel tracking test was performed and two rut parameters, depth of rut and dynamic stability were obtained. The relationship between S_D and rut parameters was evaluated using regression analyses. In most cases, R² values were found to be over 0.9. This test procedure is still under development; however, current results indicate that it might be a simple test to predict the deformation resistance of asphalt mixtures at high temperatures.