统计学在垃圾焚烧飞灰浸提液重金属检测准确性研究中的应用

为提高复杂基体重金属检测准确性,在使用电感耦合等离子体发射光谱法检测生活垃圾焚烧飞灰浸提液时,进行标准曲线法、标准加入法和内标法3种定量校准方法比对。3种方法报出结果经过加标回收率换算后的样品原值具有明显一致性,使用统计学方差齐性和单因素方差分析验证了该一致性成立,表明内标法的精密度和准确度与标准曲线法、标准加入法无显著性差别。以3种方法样品原值的算数平均值作为样品最佳估计值评价各方法实际报出结果准确性,标准加入法准确性最好;稀释后的样品内标法加标回收率明显优于标准规定,受稀释倍数影响不大,工作效率高,满足HJ 781—2016质控要求,建议可作为该标准的补充;建议批量样品检测时优先采用内标法。3种方法样品原值一致性的验证,有助于执法、科研中对于复杂基体重金属物质含量的准确判断。     

Prediction of high-density polyethylene pyrolysis using kinetic parameters based on thermogravimetric and artificial neural networks

● Reducting the sampling frequency can enhance the modelling process. ● The pyrolysis of HDPE was investigated at three different heating rates. ● The average E_a and k₀ were calculated by Friedman, KAS, FWO, and CR methods. ● ANN was employed to predict the HDPE weight loss with the optimal MSE and R². Pyrolysis is considered an attractive option and a promising way to dispose waste plastics. The thermogravimetric experiments of high-density polyethylene (HDPE) were conducted from 105 °C to 900 °C at different heating rates (10 °C/min, 20 °C/min, and 30 °C/min) to investigate their thermal pyrolysis behavior. We investigated four methods including three model-free methods and one model-fitting method to estimate dynamic parameters. Additionally, an artificial neural network model was developed by providing the heating rates and temperatures to predict the weight loss (wt.%) of HDPE, and optimized via assessing mean squared error and determination coefficient on the test set. The optimal MSE (2.6297 × 10⁻²) and R² value (R² > 0.999) were obtained. Activation energy and pre-exponential factor obtained from four different models achieves the acceptable value between experimental and predicted results. The relative error of the model increased from 2.4 % to 6.8 % when the sampling frequency changed from 50 s to 60 s, but showed no significant difference when the sampling frequency was below 50 s. This result provides a promising approach to simplify the further modelling work and to reduce the required data storage space. This study revealed the possibility of simulating the HDPE pyrolysis process via machine learning with no significant accuracy loss of the kinetic parameters. It is hoped that this work could potentially benefit to the development of pyrolysis process modelling of HDPE and the other plastics.     

Factors influencing NOx emission of a stationary diesel engine fuelled with crude rice bran oil methyl ester blend – Taguchi approach

The main objective of this work is to control the NO_x emission of a stationary diesel engine fuelled with crude rice bran oil methyl ester blend with less sacrifice on smoke density and brake thermal efficiency (BTE) and also to investigate the factors influencing the objective. Fuel injection timing, percentage of exhaust gas recirculation and fuel injection pressure are chosen as the promising factors for the objective and NO_x emission, smoke density and BTE are considered as response variables. Tests were conducted as per Taguchi’s L₉ orthogonal array and the most influencing factor for each response variable and also the significance of each factor on the same was found out through analysis of variance (ANOVA). Response graph was drawn for each response variable and from the results of response graph and ANOVA the optimum combination of the factor levels in achieving the objective was obtained and the same was confirmed experimentally.     

Compound dependence of the relationship log Kow and log BCFL

Linear relatinships between log bioconcentration factor (BCF) and log K^ow for a variety of compounds have been reported many times in the literature. Analysis of the thermodynamics of the two partition processes has, however, shown that they are not analogous and that linear relationships can be expected to have different slopes for structurally unrelated compounds. In this study a set of literature lipid normalized BCF (BCF_L) values of chlorbenzenes (CBs) for rainbow trout and polycyclic aromatic hydrocarbons (PAHs) forDaphnia was put together with literature K_ow values. The slopes of the regression lines for log BCF_L versus log K_ow for the two groups of compounds proved to differ significantly in a statistical test using analysis of variance (ANOVA). The difference, which is of significance for estimates of BCFs in environmental modelling of these types of compounds, is explained by the differences in chemical structure of the two groups of compounds.     

Can variations in visual behavior measures be good predictors of driver sleepiness? A real driving test study

Objective: The primary purpose of this study was to examine the association between variations in visual behavior measures and subjective sleepiness levels across age groups over time to determine a quantitative method of measuring drivers' sleepiness levels.

Method: A total of 128 volunteer drivers in 4 age groups were asked to finish 2-, 3-, and 4-h continuous driving tasks on expressways, during which the driver's fixation, saccade, and blink measures were recorded by an eye-tracking system and the subjective sleepiness level was measured through the Stanford Sleepiness Scale. Two-way repeated measures analysis of variance was then used to examine the change in visual behavior measures across age groups over time and compare the interactive effects of these 2 factors on the dependent visual measures.

Results: Drivers' visual behavior measures and subjective sleepiness levels vary significantly over time but not across age groups. A statistically significant interaction between age group and driving duration was found in drivers' pupil diameter, deviation of search angle, saccade amplitude, blink frequency, blink duration, and closure duration. Additionally, change in a driver's subjective sleepiness level is positively or negatively associated with variation in visual behavior measures, and such relationships can be expressed in regression models for different period of driving duration.

Conclusions: Driving duration affects drivers' sleepiness significantly, so the amount of continuous driving time should be strictly controlled. Moreover, driving sleepiness can be quantified through the change rate of drivers' visual behavior measures to alert drivers of sleepiness risk and to encourage rest periods. These results provide insight into potential strategies for reducing and preventing traffic accidents and injuries.     

The effect of model structure and data in modeling land conditions in disturbed complex ecosystems

Off-road vehicles increase soil erosion by reducing vegetation cover and other types of ground cover, and by changing the structure of soil. The investigation of the relationship between disturbance from off-road vehicles and the intensity of the activities that involve use of vehicles is essential for water and soil conservation and facility management. Models have been developed in a previous study to predict disturbance caused by off-road vehicles. However, the effect of data on model quality and model performance, and the appropriate structure of models have not been previously investigated. In order to improve the quality and performance of disturbance models, this study was designed to investigate the effects of model structure and data. The experiment considered and tested: (1) two measures of disturbance based on the Vegetation Cover Factor (C Factor) of the Revised Universal Soil Loss Equation (RUSLE) and Disturbance Intensity; (2) model structure using two modeling approaches; and (3) three subsets of data. The adjusted R-square and residuals from validation data are used to represent model quality and performance, respectively. Analysis of variance (ANOVA) is used to identify factors which have significant effects on model quality and performance. The results of the ANOVA show that subsets of data have significant effects on both model quality and performance for both measures of disturbance. The ANOVA also detected that the C Factor models have higher quality and performance than the Disturbance models. Although modeling approaches are not a significant factor based on the ANOVA tests, models containing interaction terms can increase the adjusted R-squares for nearly all tested conditions and the maximum improvement can reach 31%.     

STREAM DEPTH SIGNIFICANCE DURING IN‐SITU SEDIMENT OXYGEN DEMAND MEASUREMENTS IN SHALLOW STREAMS1

ABSTRACT: Ninety‐one sediment oxygen demand (SOD) samples from six designated sites along the stretch of Lower Rapid Creek, South Dakota, were conducted using an in‐situ SOD chamber. Inside the chamber, readings of dissolved oxygen (DO), water temperature, pH, and specific conductance were recorded every minute for more than one hour using the Datasonde 3 Hydrolab. Initial readings of such parameters were recorded for the overlaying water before the deployment of the SOD chamber. Characteristics of the stream conditions, air temperature, barometric pressure, average flow velocity of the stream, depth of the stream, and the flow velocity by the chamber were recorded. Single and multiple linear regression analyses on all parameters indicated that the velocity of the stream is the least critical parameter for SOD in shallow streams.     

Reality and risk of contact-type head injuries related to bicycle-mounted child seats

Objective

The authors have treated numerous children who have been injured by falling from bicycle-mounted child seats. Despite the greatly increased use of such seats, the understanding of their risk and the importance of helmet use remains alarmingly poor. The objective of this study was to confirm the risk of bicycle-mounted child seats and to evaluate the efficacy of helmets, seat belts, and back seat height in terms of preventing or mitigating contact-type head impacts that occur in falls from bicycle-mounted child seats.

Materials and methods

Biometrical dummy tests were performed to examine contact-type head injuries in falls from stationary bicycles. A bicycle with an anthropometric test dummy placed in a bicycle-mounted child seat was tipped over. Each test was repeated three times and three-dimensional acceleration was measured using accelerometer. Head Injury Criteria (HIC) were calculated and the respective influences of a helmet, a seat belt, and increased height of the back of the seat on such impacts were evaluated.

Results

Only helmets unequivocally lowered maximal acceleration and/or HIC values with statistical significance. The seat belt lowered HIC values as long as it was used with the high-back seat. Only when the dummy wore a helmet sitting in a high-back seat did the HIC show less than the threshold of 570 for three-year-old children. The HIC showed the lowest score of 161.5 when the dummy wore both a helmet and a seat belt sitting in a high-back seat.

Conclusions

Riders in bicycle-mounted child seats definitely have higher risks of contact-type head injuries. In transporting a child on a bicycle-mounted child seat, parents must use both a child-bicycle helmet and a high-back child seat at least; a seat belt is highly recommended as long as it is used with the other safety devices.

Impact on Industry

The bicycle-mounted child seat should have a high enough back and an appropriate seat belt to protect the head of the child from a contact-type injury.     

In vivo and in vitro metabolism of tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), by the freshwater planarian, Dugesia japonica

Cigarette smoke is a risk factor for human health, and many studies were conducted to investigate its adverse effects on humans and other mammals. However, since large amounts of cigarette products are produced and consumed, it is possible that tobacco chemicals can end up in aquatic environments through several routes, thus influencing aquatic organisms. In this study, the presence of tobacco-specific nitrosamine (TSNA), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), in aquatic environment was demonstrated. Since toxic effects on and distribution patterns of tobacco chemicals in aquatic organisms were rarely studied, after results of an acute toxicity pretest were obtained, experiment was conducted to investigate the bioaccumulation pattern of NNK and distribution patterns of its metabolites, mainly 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), in NNK-treated freshwater planarians, Dugesia japonica. Results from in vivo and in vitro studies showed that NNK was readily converted to NNAL through the carbonyl reduction in bodies of NNK-treated planarians. Tissue concentrations of both chemicals increased in time- and dose-dependent manners. Furthermore, we examined the end products of NNK/NNAL α-hydroxylation in NNK-treated planarians, but only 1-(3-pyridyl)-1,4-butanediol was detected, suggesting that NNK metabolism in planarians partially differs from that in mammalian systems. This is the first report on NNK metabolism in an aquatic organism and can be used as a foundation for developing freshwater planarians as a new in vivo model for the study of NNK toxicology in the future.     

不同填料组合的曝气生物滤池前置反硝化工艺特性的比较研究

研究了2组不同填料组合的前置反硝化曝气生物滤池(BAF)脱氮工艺:陶粒-沸石工艺(C-Z BAF)和沸石-陶粒工艺(Z-C BAF),比较二者在不同的水力停留时间(HRT)、气水比和回流比条件下的工艺特性。当进水COD、氨氮和TN容积负荷分别为0.72～5.97、0.09～0.60和0.11～0.78 kg/(m3.d)时,C-Z BAF和Z-C BAF的最佳HRT、气水比和回流比分别为1.5 h、5∶1、1∶1和1.5 h、5∶1、2∶1,相应COD、氨氮和TN的平均去除率分别为94.7%、99.0%、62.2%和93.2%、99.5%、70.1%。单因素方差分析结果表明,HRT对2组工艺的各种污染物的去除率均有显著影响;回流比对Z-C BAF的TN去除率存在显著的影响,而对C-Z BAF的TN去除率几乎没有影响。污染物沿程分布分析结果表明,两组工艺的COD去除主要发生在缺氧滤池以及好氧滤池0～0.3 m的填料区;硝化作用主要发生在好氧滤池的0～0.6 m填料区,Z-C BAF工艺的硝化速率高于C-Z BAF工艺。Z-C BAF工艺存在明显的同步硝化反硝化作用,且Z-C BAF工艺的脱氮性能优于C-Z BAF工艺。