Charge Carriers Relaxation Behavior of Cellulose Polymer Insulation Used in Oil Immersed Bushing

Cellulose insulation polymer material is widely used in oil immersed bushing. Moisture is one of the important reasons for the deterioration of cellulose polymer insulation, which seriously threatens the safe and stable operation of bushing. It is significant to study the polarization and depolarization behavior of oil-immersed cellulose polymer insulation with different moisture condition under higher voltage. Based on polarization/depolarization current method and charge difference method, the polarization/depolarization current, interfacial polarization current and electrical conductivity of cellulose polymer under different DC voltages and humidity were obtained. Based on molecular-dynamics simulation, the effect of moisture on cellulose polymer insulation was analyzed. The results show that the polarization and depolarization currents become larger with the increase in DC voltage and moisture. The higher applied voltage will accelerate the charge carrier motion. The ionization of water molecules will produce more charge carriers. Thus, high DC voltage and moisture content will increase the interface polarization current. Increased moisture content results in more charge carriers ionized by water molecules. In addition, the invasion of moisture will reduce the band width of cellulose polymer and enhance its electrostatic potential, so as to improve its overall electrical conductivity. This paper provides a reference for analyzing the polarization characteristics of charge carriers in cellulose polymer insulation.

IMPROVING THE ENERGY EFFICIENCY OF BUILDINGS BY PROVIDING BETTER PROTECTIVE STRUCTURES BASED ON THE UNIVERSITY'S KNOWLEDGE HUB

BACKGROUND AND OBJECTIVES. Modern university buildings use a large number of resources, such as heat, cold and hot water, as well as electricity, which is the main consumed energy resource and is used for lighting, office equipment, ventilation and air conditioning systems. In order to improve the energy efficiency of university buildings, it is necessary to carry out heat and energy modernization of internal and external envelopes, which will allow for internal billing and qualitative analysis of consumption, which contribute to prompt decision-making on heat and energy modernization of the premises.METHODS. To assess the potential for improving the energy efficiency of buildings by improving the quality of protective structures, methods for assessing the temperature and humidity conditions of multilayered enclosing structures in a wide range of humidity under stationary boundary conditions were developed on the basis of the University Hub of Knowledge.FINDINGS. On the basis of the University Hub of Knowledge, Kyiv National University of Technologies and Design, the moisture content profile was calculated for the general estimation of the moisture condition for building No. 4, the planes of the highest moisture content were determined to find the most dangerous, from the moisture condition point of view, section of the structure, the calculation of the enclosing structure modernization according to the maximum allowable moisture condition for the analysis of moisture accumulation in the coldest month of the year was made.CONCLUSION. The advantage of the proposed method of increasing the energy efficiency of buildings by improving the quality of protective structures based on the University Hub of Knowledge is the possibility of calculation in a wide range of moisture content of materials, including supersorption moisture zone, as well as applicability to structures with multizone condensation of moisture. The clarity and simplicity of the proposed method makes it available for the practical implementation of energy efficiency improvements in all university buildings.

Formulation of Parsimonious Urban Flash Flood Predictive Model with Inferential Statistics

The curve number (CN) rainfall–runoff model is widely adopted. However, it had been reported to repeatedly fail in consistently predicting runoff results worldwide. Unlike the existing antecedent moisture condition concept, this study preserved its parsimonious model structure for calibration according to different ground saturation conditions under guidance from inferential statistics. The existing CN model was not statistically significant without calibration. The calibrated model did not rely on the return period data and included rainfall depths less than 25.4 mm to formulate statistically significant urban runoff predictive models, and it derived CN directly. Contrarily, the linear regression runoff model and the asymptotic fitting method failed to model hydrological conditions when runoff coefficient was greater than 50%. Although the land-use and land cover remained the same throughout this study, the calculated CN value of this urban watershed increased from 93.35 to 96.50 as the watershed became more saturated. On average, a 3.4% increase in CN value would affect runoff by 44% (178,000 m3). This proves that the CN value cannot be selected according to the land-use and land cover of the watershed only. Urban flash flood modelling should be formulated with rainfall–runoff data pairs with a runoff coefficient > 50%.

An Assessment of Water Budget of Ibadan, Nigeria

The influence of climatic conditions of precipitation and evapotranspiration exercise great control on soil water budget. This is fundamental to crop production and hydrological processes. This study assessed the temporal variability of soil moisture condition of Ibadan, Nigeria using the water budget approach. Specifically the study analyzed the climatic variables of monthly rainfall and means monthly air temperature, computed the mean monthly evapotranspiration values, plots the water budget graph, and discussed the implications of the observed seasonal trend in water budget condition on agricultural activities and hydrological processes. Monthly rainfall and mean monthly air temperature data used were collected from the archives of the Nigeria meteorological agency for the period 2008-2020. Monthly potential evapotranspiration data used in the study was estimated from the mean monthly air temperature data. The monthly rainfall data and the monthly evapotranspiration data were used to plot the water budget graph. Results revealed temporal variability in soil moisture condition. Water deficit condition was observed between November and April while water surplus condition was observed between May and October. The highest water surplus condition was observed in September (111.9mm) while the highest deficit condition (-125.64mm) was observed in December. The month of October recorded the lowest water surplus condition (41.30mm) while the month of April recorded the lowest water deficit condition (-10.10mm). The implications of the observed seasonal variation in soil moisture status on agricultural activities and hydrological processes were discussed.

Discrete Element Simulation on Sand-Bed Collision Considering Surface Moisture Content

The process of aeolian sand transport is an important mechanism leading to the formation and evolution of local landforms in coastal areas and desert lakes. For a long time, the role of surface moisture in incipient motion of sand grains by wind stress has been extensively studied but, in fact, sand-bed collision is the main mechanism in steady aeolian sand flow. At present, the lack of understanding of surface moisture content on sand-bed collision limits the application of aeolian sand transport models in wet coastal areas. In this paper, we adopt numerical simulations to discuss and analyze the effect of cohesive forces formed by surface moisture content on the sand-bed collision process based on discrete element method. High density contact forces appear with the surface moisture increasing, and form a closed structure around the edge of crater to resist the avulsion in horizontal direction. Under high moisture condition, even though the ejected sand grains saltate away from the surface, the tension forces will prevent from leaving. The ejected number trend with incident velocity shows some nonlinear characteristics due to the unequally distributed force chains and liquid bridges in the unsaturated sand bed surface.

Study on the Uncertainty of Critical Rainfall for Flash Floods in Small Watersheds Based on the Random Rainfall Pattern

Flash floods cause great harm to people's lives and property safety. Rainfall is the key factor which induces flash floods, and critical rainfall (CR) is the most widely used indicator in flash flood early warning systems. Due to the randomness of rainfall, the CR has great uncertainty, which causes missed alarms when predicting flash floods. To improve the early warning accuracy for flash floods, a random rainfall pattern (RRP) generation method based on control parameters, including the comprehensive peak position coefficient (CPPC) and comprehensive peak ratio (CPR), is proposed and an early warning model with dynamic correction based on RRP identification is established. The rainfall-runoff process is simulated by the HEC-HMS hydrological model, and the CR threshold space corresponding to the RRP set is calculated based on the trial algorithm. Xinxian, a small watershed located in Henan Province, China, is taken as the case study. The results show that the method for generating the RRP is practical and simple, and it effectively reflects the CR uncertainty caused by the rainfall pattern uncertainty. The HEC-HMS model is proved to have good application performance in the Xinxian watershed. Through sensitivity analysis, the effect of the antecedent soil moisture condition, CPPC, and CPR are compared. The proposed early warning model is practical and effective, which increases the forecast lead time.

Run-off and Soil Loss Estimation Using Numerical Approach in Hard Rock Terrain.

The present study reveals the potential run-off estimation, soil erosion and scope of groundwater recharge in the Bundelkhand region in the state of U.P. , India. The estimation of run-off and soil erosion have provided a platform to evaluate the realistic potential for water conservation in the study area. The study area is characterized by occurrence of mild to severe drought conditions with significant run-off and poor infiltration. Geomorphological factors such as land use changes, slope, and nature of soil affect the run-off rate and discharge significantly. Soil map and rainfall data for the study area were acquired to evaluate the hydrological soil group (HSG) and antecedent moisture condition (AMC) respectively. Soil Conservation Services and Curve Number (SCS-CN) method has been used to calculate the run-off volume at the point where river/streams join together while soil loss has been calculated using revised universal soil loss equation of RUSLE model with the input of spatial data sets such as soil texture, rainfall, topography etc. The maximum run-off (355mm) has been estimated in watershed-1 during 2016 and minimum (1 mm) in watershed-4 respectively. The estimated run-off varies from 5.5% to 28% of the total rainfall in the study area, while soil loss is maximum (2.1x106 ton/ha) in the watershed-1. It is a fact that soil loss is in conformity with run-off. This finding provides the roadmap for the selection of suitable artificial recharge structures to augment the groundwater in the study area.

LAB-SCALE EXPERIMENTS FOR SOIL CEMENTING THROUGH BIO-CHEMICAL PROCESS

Ureolytic bacteria strains of Bacillus show its ability of calcium carbonate precipitation through metabolic activity. Different studies related to self-healing concrete material were reported associated with the generated calcium carbonate of Bacillus subtilis HU58 metabolism in recent communications. In this paper, recent findings of soil cementing with a combination of such precipitated products were presented. The experiments relied on the lab-scale studies with the use of sand-clay mixture as the controlled soil specimens. Bacillus bacteria and nutrients were mixed to introduce in the sand matrix and then curing in high moisture condition. The composition and morphology of soil specimens were characterized after solidifying by FTIR, XRD, and SEM. Water percolation and mechanical stability for the physicomechanical properties were also tested with the unconventional method. Discussing the relevant results can help to figure out the next experiments in the field of geotechnical engineering. From the perspective of this study, the sustainability factor should be considered to apply this promising technique for soil stabilization and improvement and/or for the formulation of bio-brick as an alternative to sintered clay-based brick. From the perspective of this study, this technique for soil stabilization and improvement and/or for the formulation of bio-brick can be considered a promising sustainable alternative to sintered clay-based brick.