The historical datasets at operating mine sites are usually large. Directly applying large datasets to build prediction models may lead to inaccurate results. To overcome the real-world challenges, this study aimed to handle these large datasets using Gaussian mixture modelling (GMM) for developing a novel and accurate prediction model of truck productivity. A large dataset of truck haulage collected at operating mine sites was clustered by GMM into three latent classes before the prediction model was built. The labels of these latent classes generated a latent variable. Two multiple linear regression (MLR) models were then constructed, including the ordinary-MLR (O-MLR) and the hybrid GMM-MLR models. The GMM-MLR model incorporated the observed input variables and a latent variable in the form of interaction terms. The O-MLR model was the baseline model and did not involve the latent variable. The GMM-MLR model performed considerably better than the O-MLR model in predicting truck productivity. The interaction terms quantitatively measured the differences in how the observed input variables affected truck productivity in three classes (high, medium, and low truck productivity). The haul distance was the most crucial input variable in the GMM-MLR model. This study provides new insights into handling massive amounts of data in truck haulage datasets and a more accurate prediction model for truck productivity.

Heavy metal pollutants in the leachate of waste landfill are a potential threat to the environment. In this study, the feasibility of using municipal sewage sludge as barrier material for the containment of heavy metal pollutants from solid waste landfills was evaluated by compaction test and hydraulic conductivity test concerning compaction property, impermeability and heavy metal retardation. Results of the compaction test showed that the maximum dry density of 0.79 g·cm−3 was achieved at the optimum water content of about 60%. The hydraulic conductivities of compacted sewage sludge permeated with synthetic heavy metal solutions were in the range of 1.3×10−8 – 6.2×10−9 cm·s−1, less than 1.0 ×10−7cm·s−1 recommended by regulations for barrier materials. Chemical analyses on the effluent from the hydraulic conductivity tests indicated that the two target heavy metals, Zn and Cd in the permeants were all retarded by compacted sewage sludge, which might be attributed to the precipitation and adsorption of heavy metal ions. The results of this study suggest that specially prepared material from sewage sludge could be used as a barrier for waste landfills for its low permeability and strong retardation to heavy metal pollutants.

In this study, a pilot-scale subsurface wastewater infiltration system (SWIS) was deployed to study landscape water treatment. The goal of the study was to investigate the effects of hydraulic loading on pollutant removal and the spatial distribution of biofilm properties in SWIS. Results showed that the efficiencies of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removal degraded as hydraulic loading increased. Furthermore, quantities of the biofilm properties parameter s increased with the hydraulic loading. Polysaccharide and protein levels ranged from 560 to 1110 μg/g filler and 60 to 190 μg/g filler, respectively, at a hydraulic loading of 0.2 m/d. At a hydraulic loading of 0.4 m/d, the quantities of polysaccharide and protein ranged from 1200 to 3300 μg/g filler and 80 to 290 μg/g filler, respectively. Biofilm intensity and biofilm activity per unit weight decreased with the increase in hydraulic loading.

Abstract In this study, wheat (Triticum aestivum L.) roots were treated with hypoxic water. The staining of cell preparations with DAPI revealed morphological changes of the cells such as nuclear condensation, deformation and fragmentation. Under TEM, cellular membrane shrinkage and breakage, chromatin condensation and apoptotic-like bodies were displayed. The number of mitochondria increased dramatically; their cristae were damaged; the interior became a cavitation and only some flocculent materials were distributed. Indirect immunofluorescence staining indicated that cytochrome C diffused from mitochondria to nucleoplasm and cytoplasm. TUNEL positive nuclei indicated double strand breaks of DNA. DAB staining was used for the identification of hydrogen peroxide and examination showed that the longer the treating time, the darker the staining of the meristematic zones of the roots which suggested the increased accumulation of these Reactive Oxygen Species (ROS). The elevation of hydrogen peroxide production was paralleled with the increase of SOD and POD activities. A negative correlation between the exposure time under hypoxia and the contents of soluble proteins was found. No obvious effect of hypoxia on MDA was established. The obtained results demonstrate that hypoxia causes programmed cell death in the root-tip meristematic cells of Triticum aestivum L. which is most probably attributed to the accumulation of large amounts of ROS.

Brushless DC motors are often used as the power sources for modern ship electric propulsion systems. Due to the electromagnetic torque ripple of the motor, the traditional control method reduces the drive performance of the motor under load changes. Aiming at the problem of the torque ripple of the DC brushless motor during a non- commutation period, this paper analysis the reasons for the torque ripple caused by pulse- width modulation (PWM), and proposes a PWM_ON_PWM method to suppress the torque ripple of the DC brushless motor. Based on the mathematical model of a DC brushless motor, this method adopts a double closed-loop control method based on fuzzy control to suppress the torque ripple of the DC brushless motor. The fuzzy control technology is integrated into the parameter tuning process of the proportional–integral–derivative (PID) controller to effectively improve the stability of the motor control system. Under the Matlab/Simulink platform, the response performance of different PID control methods and the torque characteristics of different PWM modulation methods are simulated and compared. The results show that the fuzzy adaptive PID control method has good dynamic response performance. It is verified that the PWM_ON_PWM modulation method can effectively suppress the torque ripple of the motor during non-commutation period, improve the stability of the double closed-loop control system and meet the driving performance of the motor under different load conditions.

In order to predict the distribution of shrinkage porosity in steel ingot efficiently and accurately, a criterion R√L and a method to obtain its

threshold value were proposed. The criterion R√L was derived based on the solidification characteristics of steel ingot and pressure

gradient in the mushy zone, in which the physical properties, the thermal parameters, the structure of the mushy zone and the secondary

dendrite arm spacing were all taken into consideration. The threshold value of the criterion R√L was obtained with combination of

numerical simulation of ingot solidification and total solidification shrinkage rate. Prediction of the shrinkage porosity in a 5.5 ton ingot of

2Cr13 steel with criterion R√L>0.21 m･℃1/2･s

-3/2 agreed well with the results of experimental sectioning. Based on this criterion,

optimization of the ingot was carried out by decreasing the height-to-diameter ratio and increasing the taper, which successfully eliminated

the centreline porosity and further proved the applicability of this criterion.

A novel magneto-optical current sensor (MOCS) with two sensing arms is proposed to improve the temperature stability. One of the arms, with a highly stable permanent magnet attached and orthogonal to the other one, is designed to provide a reference that follows the temperature characteristics of the sensing material. By a normalization operation between two arms, the temperature drift is compensated adaptively and a sensing output proportional to the measured current can be reached. A dual-input and dual-output structure is specially designed for the reference sensing arm to demodulate the DC Faraday rotation angle. This scheme compensates simultaneously two main temperature influence factors, the Verdet constant and linear birefringence. Validation tests were carried out and are discussed.

Abstract Water level fluctuation and inorganic nitrogen enrichment are two serious problems caused by anthropogenic disturbances in aquatic ecosystems. They cause resource fluctuation and thus might influence the invasive-ness of alien plants. Alternanthera philoxeroides is an amphibious and widespread clonal plant which exhibits significant invasiveness. This experimental study examined the plant's morphological traits under different nitrogen concentrations and water levels. The responses of A. philoxeroides to water levels and nitrogen concentrations were similar for both land-like and riverbank-like initial conditions. A. philoxeroides showed an escape strategy of shoot elongation when its growth was suppressed by shallow submergence. No toxic symptoms but increased clonal spread was observed at high nitrogen concentrations, suggesting that A. philoxeroides not only tolerated but benefitted from nitrogen-polluted water. High nitrogen level mitigated the negative effects of submergence on its leaf survival, thereby enhancing its adaptation to water level fluctuation. Such strong adaptability and clonal spread helps A. philoxeroides to grow and invade successfully in shallow eutrophic water.

The increase of ship’s energy utilization efficiency and the reduction of greenhouse gas emissions have been high lightened in recent years and have become an increasingly important subject for ship designers and owners. The International Maritime Organization (IMO) is seeking measures to reduce the CO2emissions from ships, and their proposed energy efficiency design index (EEDI) and energy efficiency operational indicator (EEOI) aim at ensuring that future vessels will be more efficient. Waste heat recovery can be employed not only to improve energy utilization efficiency but also to reduce greenhouse gas emissions. In this paper, a typical conceptual large container ship employing a low speed marine diesel engine as the main propulsion machinery is introduced and three possible types of waste heat recovery systems are designed. To calculate the EEDI and EEOI of the given large container ship, two software packages are developed. From the viewpoint of operation and maintenance, lowering the ship speed and improving container load rate can greatly reduce EEOI and further reduce total fuel consumption. Although the large container ship itself can reach the IMO requirements of EEDI at the first stage with a reduction factor 10% under the reference line value, the proposed waste heat recovery systems can improve the ship EEDI reduction factor to 20% under the reference line value.

In order to recover the low grade waste heat and increase system fuel economy for main engine 10S90ME-C9.2-TII(part load, exhaust gas bypass) installed on a 10000 TEU container ship, a non-cogeneration and single-pressure type of waste heat recovery system based on organic Rankine cycle is proposed. Organic compound candidates appropriate to the system are analyzed and selected. Thermodynamic model of the whole system and thermoeconomic optimization are performed. The saturated organic compound vapor mass flow rate, net electric power output, pinch point, thermal efficiency and exergy efficiency varied with different evaporating temperature are thermodynamically analyzed. The results of thermodynamic and thermoeconomic optimization indicate that the most appropriate organic compound candidate is R141b due to its highest exergy efficiency, biggest unit cost benefit and shortest payback time.

In this paper, a discrete wavelet transform (DWT) based approach is proposed for power system frequency estimation. Unlike the existing frequency estimators mainly used for power system monitoring and control, the proposed approach is developed for fundamental frequency estimation in the field of energy metering of nonlinear loads. The characteristics of a nonlinear load is that the power signal is heavily distorted, composed of harmonics, inter-harmonics and corrupted by noise. The main idea is to predetermine a series of frequency points, and the mean value of two frequency points nearest to the power system frequency is accepted as the approximate solution. Firstly the input signal is modulated with a series of modulating signals, whose frequencies are those frequency points. Then the modulated signals are decomposed into individual frequency bands using DWT, and differences between the maximum and minimum wavelet coefficients in the lowest frequency band are calculated. Similarities among power system frequency and those frequency points are judged by the differences. Simulation results have proven high immunity to noise, harmonic and inter-harmonic interferences. The proposed method is applicable for real-time power system frequency estimation for electric energy measurement of nonlinear loads.

An integrated Z-source inverter for the single-phase single-stage grid-connected photovoltaic system is proposed in this paper. The inverter integrates three functional blocks including maximum-power-point-tracking, step-up/down DC-side voltage and output grid-connected current. According to the non-minimum-phase characteristic presented in DC-side and the functional demands of the system, two constant-frequency sliding-mode controllers with integral compensation are proposed to guarantee the system robustness. By using two controllers, the effects caused by the non-minimum-phase characteristic are mitigated. Under the circumstance of that the input voltage or the grid-connected current changes suddenly, the notches/protrusions following the over-shoot/ under-shoot of the DC-bus voltage are eliminated. The quality of grid-connected current is ensured. Also, a small-signal modelling method is employed to analyze the close-loop system. A 300W prototype is built in the laboratory. A solar-array simulator (SAS) is used to verify the systematic responses in the experiment. The correctness and validity of the inverter and proposed control algorithm are proved by simulation and experimental results.

The Bulletin of the Polish Academy of Sciences: Technical Sciences (Bull.Pol. Ac.: Tech.) is published bimonthly by the Division IV Engineering Sciences of the Polish Academy of Sciences, since the beginning of the existence of the PAS in 1952. The journal is peer‐reviewed and is published both in printed and electronic form. It is established for the publication of original high quality papers from multidisciplinary Engineering sciences with the following topics preferred: Artificial and Computational Intelligence, Biomedical Engineering and Biotechnology, Civil Engineering, Control, Informatics and Robotics, Electronics, Telecommunication and Optoelectronics, Mechanical and Aeronautical Engineering, Thermodynamics, Material Science and Nanotechnology, Power Systems and Power Electronics.

Journal Metrics: JCR Impact Factor 2018: 1.361, 5 Year Impact Factor: 1.323, SCImago Journal Rank (SJR) 2017: 0.319, Source Normalized Impact per Paper (SNIP) 2017: 1.005, CiteScore 2017: 1.27, The Polish Ministry of Science and Higher Education 2017: 25 points.

Abbreviations/Acronym: Journal citation: Bull. Pol. Ac.: Tech., ISO: Bull. Pol. Acad. Sci.-Tech. Sci., JCR Abbrev: B POL ACAD SCI-TECH Acronym in the Editorial System: BPASTS.

The key to fingerprint positioning algorithm is establishing effective fingerprint information database based on different reference nodes of received signal strength indicator (RSSI). Traditional method is to set the location area calibration multiple information sampling points, and collection of a large number sample data what is very time consuming. With Zigbee sensor networks as platform, considering the influence of positioning signal interference, we proposed an improved algorithm of getting virtual database based on polynomial interpolation, while the pre-estimated result was disposed by particle filter. Experimental result shows that this method can generate a quick, simple fine-grained localization information database, and improve the positioning accuracy at the same time.