Power Regression Equation Research Articles

Анализ технологических и энергетических параметров шаровых мельниц

The paper considers issues related to the analysis of the most important process parameters of ball mills, such as changes in productivity, power consumption, amount of water entering the mill, oil pressure in the mill hydraulic system, pulp density during mill unloading. It was found that the power consumed by the mills varies within 836–1260 kW. The energy characteristics of the mills, as well as specific power consumption, correlation coefficients and regression equations are presented. The values of the coefficients of variation, asymmetry and excess show good agreement with the normal distribution law of random variables. Specific power consumption for mills varies within 6.71–9.94 kWh/t. In the future, it is planned to carry out a verification calculation of the drive electric motors of the mills in order to establish that the actual power of the electric motor corresponds to the calculated one. Such a check allows to objectively assess whether the actual power consumption corresponds to the adopted technology of the grinding process in the autogenous grinding body of the mining and processing plant.

Modeling root effects on soil detachment capacity using critical flow depth and unit energy of cross section in soils under Fraxinus excelsior L. species

The flow depth is an important hydraulic parameter for calculating other hydraulic parameters of overland flow. There is notable changes in hydraulic parameter when the roots of a plant develop in the topsoil. A power regression equation between soil detachment capacity (Dc) and unit energy of cross section (UEC) was established in soils under Fraxinus excelsior L. species based on the Froude number. For measuring Dc, samples collected from soils under the studied species and subjected to five slopes (from 13.9 to 33.9%) and five water discharges (from 0.39 to 0.77 l m−1 s−1) by a hydraulic flume. Compared with the soil with absence of root, the soil with presence of root had lower Dc. The results showed a strong power relationship between the unit energy of cross section and Dc, suggesting that soil detachment rate in rill erosion can be estimated using this hydraulic parameter (R2 = 0.84). This finding is particularly relevant for hillslopes with slopes from 12% to 31%, where the proposed mathematical model could be applied to predict Dc. Overall, this investigation supports a broader use of native species (such as the european ash Fraxinus excelsior L.), as a useful eco-engineering conservation practice and an alternative technique instead of utilizing artificial and expensive conservation practices.

Исследование тока утечки по струе тонкораспылённой воды из автоматической установки пожаротушения на электрооборудование под напряжением

Purpose. The article is devoted to the safety issue of applying an automatic fine water spray suppression system for extinguishing fires of live electrical equipment. The study examined the worst-case scenario, in which fire suppression system is manually activated by an operator. The results of a series of experiments to determine the leakage current when discharging extinguishing agent from automatic fire suppression systems onto live electrical equipment are presented. Methods. To achieve the goal of the research the authors used analysis and experiment methods. Findings. An experimental study on automatic water spray fire suppression system was carried out, and as a result of the experiment the values of leakage current on the pumping unit body and nozzle-head were determined. Power and linear regression equations were obtained by the least squares method. Based on regression equations, diagrams of dependence of the leakage current value on the intensity (k-factor) supply of fine water spray to the nozzle-head and the pumping unit body were created. Research application field. The obtained experimental data confirm the possibility of safely using automatic suppression systems with fine water spray for live electrical equipment extinguishment while meeting certain values of the intensity of extinguishing agent supply. Conclusions. Based on the analysis of experimental data and the obtained regression equations, it can be concluded that the intensity of the extinguishing agent supply (k-factor) has a significant impact on the leakage current on the body of an automatic fire suppression system and nozzle-head.

Unraveling the Relationship between Percentage Cover and Biomass of Various Herbaceous Species in the Dry Tropical Grassland

The estimation of biomass and cover is an ideal variable for determining ecosystem productivity, vegetation abundance, and community structure of any ecosystem. Biomass estimation by harvest method causes a huge loss of biomass and biodiversity. Non-destructive methods are helpful for repeated and regular sampling of the same plot to measure any change in biomass at the fixed time interval. There are already several regression equations established between biomass and cover in various ecosystems for finding above-ground biomass but there was an urgent need for such studies in dry tropical grasslands. The experiment was performed in the entire campus of Banaras Hindu University, Varanasi. 115 Quadrats were sampled in the entire university campus during year 2019-2020. For each quadrat, species-wise individual numbers were recorded and above-ground biomass was estimated by harvest method. Herbage cover was recorded for each species and measured by gridding each 1×1 m2 quadrat into 100 cells of 10 × 10 cm cells, each representing 1% cover. We found 59 herbaceous species of 28 different families. The family Asteraceae was the most common while only single species represented the other seventeen families. Most of the species like Dichanthium annulatum, Sida acuta, Ageratum conyzoides, Malvastrum coromandelianum, Rungia pectinate, and Vernonia cinerea showed linear regression equation, Parthenium hysterophorus, Alternenthera sessilis, Boerhavia diffusa showed quadratic polynomial trendlines. Species like Zephyranthes citrina and Ruellia tuberosa showed a power regression equation. Only Andrographis paniculata, and Chenopodium album showed an exponential regression equation. A power regression equation was found between pooled biomass and cover. Using the regression equations biomass of the listed 59 species could be calculated easily without disturbing the vegetation of the study area which will eventually help in the conservation of nature.

CURRENT CHALLENGES AND PROSPECTS OF LOAN PORTFOLIO QUALITY MANAGEMENT IN WARTIME: THE CASE OF UKRAINE

The purpose of the study is to develop effective ways to solve the problems of managing the quality of the loan portfolio of the Ukrainian banking sector in the context of the financial crisis caused by the russian-Ukrainian war. In the course of the study, such scientific methods as fundamental provisions of the credit portfolio theory, multifactor regression analysis, extrapolation, trend analysis, mathematical programming, etc. have been used. A methodical approach to the study of contemporary problems and prospects of loan portfolio quality management under martial law, consisting in modelling the profitability of the Ukrainian banking sector, taking into account the quality of the loan portfolio, has been proposed. This approach is implemented by constructing a two-factor power regression equation; forecasting with the establishment of confidence intervals and the development of 3 forecast scenarios (realistic, pessimistic and optimistic); solving the target function to maximize the profit of the banking sector, taking into account the restrictions formed on the basis of forecasting results. A power model of dependence of Ukrainian banking sector profitability on the volume of loan portfolio and non-performing loans has been built and its statistical significance has been established on the basis of official statistics for 2012–2022. It has been determined that an increase in the volume of the bank loan portfolio by 1% leads to an increase in bank income by 3.1%, while an increase in the volume of non-performing loans by 1% leads to a 0.28% reduction in revenues of the banking sector of Ukraine. The loan portfolio and NPL series have been extrapolated to 2023–2025, which is consistent with the medium-term, as long-term projections would be unreliable under martial law and deep recession. According to the results of medium-term forecasting and optimization, it has been proved that the maximum growth of bank revenues by 60.4%, compared to 2022, is possible with an increase in the loan portfolio by 18.9%, a reduction of non-performing loans by 26% and a reduction of their share in the loan portfolio by 13.9%. It has been justified that the key condition for maximising bank revenues is the soonest termination of the russian-Ukrainian war and further expansion of effective government concessional lending programs. In particular, the effectiveness of the state program “Affordable Loans 5–7–9%”, which provided 19% of the bank loan portfolio in Ukraine and became a key mechanism of anti-crisis business support both during the COVID-19 pandemic and during the large-scale invasion from 2022 during the russian-Ukrainian war, has been substantiated.

Warming Stimulated Soil Respiration in a Subalpine Meadow in North China

In order to explore the response of soil respiration in grassland to global warming, we carried out a warming experiment with open top chambers (OTCs) in the subalpine meadow, Mount Wutai in north China. Our results showed in the subalpine meadow across 2 500-2 700 m above the sea level (ASL), with OTCs, soil respiration increased by 2.00 μmol·m-2·s-1 as soil temperature increased by 1.25 ℃ on average. Warming decreased soil moisture over the experiment periods except in October 2019 when snow melted in OTCs. Warming effect on soil respiration peaked at 178.31% in October 2019. In control and warming treatment, based on exponential regression equations, soil temperature alone accounted for 85.3% and 61.2% of soil respiration variation, respectively. In control treatment soil moisture alone explained 23.2% of soil respiration variation based on the power regression equation while in warming treatment they were not significantly correlated with each other. The response of soil respiration to warming relied on altitudes as well as the time of the year, but was not inhibited by soil moisture, labile carbon pool, and available nitrogen. We concluded soil temperature was the main factor influencing soil respiration, and global warming would stimulate soil respiration in the subalpine meadows of Mount Wutai in the future. Our analysis provided new data on characteristics and mechanisms of the response of soil respiration to warming, and helped to further understand the relationship between carbon cycle and climate change.

여객기 개념설계 초기 사이징 통계 분석

본 논문에서는 제트 여객기의 초기 사이징(initial sizing)에 요구되는 설계변수(design parameter)를 통계적인 방법으로 추정하였다. 항공공학과 및 항공정비학과의 항공기 개념설계(aircraft conceptual design) 수업에서 활용되는 기존의 초기 사이징 통계 관계식은 제한된 수의 구형 제트 여객기의 형상 및 성능 데이터에 기반하고 있다. 이러한 단점을 보완하기 위하여 총 109가지의 개발연도, 좌석수, 중량, 항속거리, 속도 등 형상 및 성능이 다른 제트 여객기의 데이터를 활용하였다. 이를 토대로 지수함수 회귀 방정식(power regression equation)을 도출하고 기존의 분석 결과와 비교하였다. 그리고 최대이륙중량(maximum takeoff weight)을 기준으로 공허중량(operational empty weight), 유상하중(payload), 연료중량(fuel weight)을 통계적 방법으로 추정하였다. 또한, 좌석수(seating capacity) 및 최대항속거리(range) 등의 성능요구조건에 부합하는 제트 여객기의 익면하중(wing loading)과 추력대중량비(thrust to weight ratio) 등의 설계변수를 추정하는 다양한 비선형 회귀 방정식을 도출하고 검증하였다. 본 논문에서 제시된 결과는 항공기 개념설계 수업에서 절충연구(trade study)와 설계반복(design iteration) 과정을 최소화하기 위한 현실적인 항공기 기준형상(baseline configuration)을 정의하는데 활용할 수 있을 것으로 판단된다.

THE ECONOMIC ROLE OF TOURISM IN EUROPEAN COUNTRIES’ SUSTAINABLE DEVELOPMENT

With the coronacrisis caused by the COVID–19 pandemic, the tourism industry in Europe suffered the most in 2020, experiencing huge losses, lay-offs of workers, mass bankruptcies of firms, etc. Undoubtedly, the tourism economy contributes to the sustainable development of European countries, but how? The answer to this question is contained in the proposed study. Algorithm method, correlation and regression analysis, and non-linear programming were used to address the economic contribution of tourism to sustainable development. The modelling of the multiple power regression equation was based on freely available official statistical data from 40 European countries for the year 2020. A multiple power regression equation modelling algorithm for the impact of tourism on the sustainable development of European countries has been proposed and validated. The challenge of maximising the Sustainable Development Goals Index is set and solved. It is justified that in order to increase the average European level of sustainable development by 1 % in the post-pandemic period, the average annual number of tourists per European country should be increased by 14 %, the tourist attractiveness of destinations should be increased to increase revenues per tourist by 17 %, and the sectoral structure of the European economy should be optimised so as to reduce dependence on tourist revenues by 0.4 percentage points.

The decline in immunity and circulation of pertussis among Chinese population during the COVID-19 pandemic: A cross-sectional sero-epidemiological study

BackgroundIn recent years, the resurgence of pertussis has posed a public health challenge in many countries. This study aimed to evaluate the immunity levels against pertussis among populations of different ages in China. MethodsWe conducted a cross-sectional serological survey in Zhejiang Province, China in 2020. Serum IgG antibodies against pertussis toxin (anti-PT), filamentous hemagglutinin (anti-FHA), and pertactin (anti-PRN) were quantitatively measured. The geometric mean concentration (GMC) of three antibodies was calculated. An anti-PT level < 5 IU/mL was considered undetectable, ≥20 IU/mL as seropositive and ≥80 IU/mL as an indicator of recent infection. Mathematical models were fitted for anti-PT concentrations over time in children after four doses of the pertussis vaccination. ResultsA total of 4459 participants aged 0–59 years were included in the analyses. The overall positivity rate of anti-PT was 29.80% with the highest (81.44%) rate in the 1–2 years old and the lowest (4.72%) in 10–14 years old. The GMCs of anti-PT, anti-FHA and anti-PRN for the whole participants were 9.67 (95%CI: 9.25–10.10),18.93 (18.24–19.67), and 8.99 (8.61–9.38) IU/mL, respectively. Over 50% of subjects aged ≥ 7 years had undetectable anti-PT IgG antibodies (<5IU/mL). The proportions of the populations with anti-PT IgG ≥ 80 IU/mL were approximately 0.9%, 0.3% and 1.1% among the 10–14, 15–29, and 40–59 years old groups, respectively. The power regression equation of the attenuation model after last dose of pertussis vaccine was y = 41.088x-1.238 (R2 = 0.935, p < 0.001). The fitted anti-PT concentrations was only 5.60 IU/mL at 5 years following the last vaccination dose. ConclusionThe prevalence of pertussis decreased during the study period in the COVID-19 pandemic; however, there was still a certain proportion of adolescents and adults with evidence of recent infection. The decline in antibody levels after pertussis vaccination was observed, and booster doses are in urgent need in China.

Length estimation of Atlantic bluefin tuna (Thunnus thynnus) using vertebrae

AbstractAtlantic bluefin tuna (Thunnus thynnus; BFT) is a large (up to 3.3 m in length) pelagic predator which has been exploited throughout the eastern Atlantic and Mediterranean since prehistoric times, as attested by its archeological remains. One key insight derivable from these remains is body size, which can indicate past fishing abilities, the impact of fishing, and past migration behavior. Despite this, there exists no reliable method to estimate the size of BFT found in archeological sites. Here, 13 modern Thunnus spp. skeletons were studied to provide power regression equations that estimate body length from vertebra dimensions. In modern specimens, the majority of BFT vertebrae can be differentiated by their morphological features, and thus, individual regression equations can be applied for each rank (position in vertebral column). In an archeological context, poor preservation may limit one's ability to identify rank; hence, “types” of vertebrae were defined, which enable length estimates when rank cannot be determined. At least one vertebra dimension, height, width, or length correlated highly with body length when vertebrae were ranked (R2 &gt; 0.97) or identified to types (R2 &gt; 0.98). Whether using rank or type, length estimates appear accurate to approximately ±10%. Finally, the method was applied to a sample of Roman‐era BFT vertebrae to demonstrate its potential. It is acknowledged that further studies with larger sample sizes would provide more precision in BFT length estimates.

Determination of Discharge Coefficient for both Semicircular and Triangular Labyrinth Weirs

A Labyrinth weir is a type of nonlinear weir folded in plan-view, with the ability to pass a large flow at low heads due to an increase in the effective length of the weir crest for a given channel width. The discharge coefficients (Cd) were experimentally determined for both semicircular and triangular labyrinth weirs of varying sidewall angles (α) under free-flow conditions using eight physical models. Dimensional analyses are conducted using the Buckingham π theorem to find the dependent and non-dependent variables. A nonlinear empirical equation was developed using (Statistical Package for the Social Sciences 22) software. The findings show that the discharge coefficient decreases with the increase of headwater to (Ht/P) for both types of labyrinth weir with different plan forms. It is found that the efficiency of the semicircular and triangular labyrinth is higher than linear weir for (Ht/P ≤ 0.45) and decreases with increasing the value of (Ht/P) due to interference of flow between the layers in downstream. The obtained results revealed that the discharge coefficient (Cd) values obtained empirically using multivariable power regression and 5th degree polynomial equations considerably agree with the experimental data, for both of the semicircular and triangular labyrinth weirs. Furthermore, the correlation coefficient R2was (0.9951) and (0.9637) using 5th degree polynomial equation, and their values were (0.9643) and (0.9274) using multivariable power regression equation for both semicircular and triangular labyrinth weir models, respectively. The results in the present study compared quite well with the predicted results of the proposed equations obtained by other investigators.

Quantifying lung and diaphragm morphology using radiographs in normative pediatric subjects, and predicting CT-derived lung volume.

To quantify the effect of age on two-dimensional (2D) radiographic lung and diaphragm morphology and determine if 2D radiographic lung measurements can be used to estimate computer tomography (CT)-derived lung volume in normative pediatric subjects. Digitally reconstructed radiographs (DRRs) were created using retrospective chest CT scans from 77 pediatric male and female subjects aged birth to 19 years. 2D lung and diaphragm measurements were made on the DRRs using custom MATLAB code, and Spearman correlations and exponential regression equations were used to relate 2D measurements with age. In addition, 3D lung volumes were segmented using CT scans, and power regression equations were fitted to predict each lung's CT-derived volume from 2D lung measurements. The coefficient of determination (R2 ) and standard error of the estimate (SEE) were used to assess the precision of the predictive equations with p < .05 indicating statistical significance. All 2D radiographic lung and diaphragm measurements showed statistically significant positive correlations with age (p < .01), including lung major axis (Spearman rho ≥ 0.90). Precise estimations of CT-derived lung volumes can be made using 2D lung measurements (R2 ≥ 0.95), including lung major axis (R2 ≥ 0.97). The reported pediatric age-specific reference data on 2D lung and diaphragm morphology and growth rates could be clinically used to identify lung and diaphragm pathologies during chest X-ray evaluations. The simple, precise, and clinically adaptable radiographic method for estimating CT-derived lung volumes may be used when pulmonary function tests are not readily available or difficult to perform.

The possibilities of using thermal infrared imaging data for detecting the main parameters of arable soil fertility

The analysis of the possibility of using the thermal infrared images for detecting soil fertility parameters of gray forest and alluvial arable soils was carried out by the example of a test filed in Tula region of Russia. Together with the sampling of 25 soil probes from the 0–10 cm layer, the open surface of the soil was photographed using a FLIR VUE 512 thermal imager, and the spectral reflectance of the soil was measured. According to the results of the correlation analysis, it was found that the closest correlations for thermal images are observed with the following parameters of soil fertility: the content of humus, nitrogen, exchangeable magnesium and potassium. The correlation coefficient between the humus content and the reflectance in the visible and near IR-regions, as well as with the average value of the reflectance in thermal band exceeds 0.81. In different diapasons of the visible spectrum, the spectral reflectance correlation with the content of exchangeable magnesium and potassium is lower than in the thermal band, where the correlation coefficient with the content of exchangeable magnesium is 0.81, and with the content of exchangeable potassium is 0.65. Power regression equations were constructed for detecting such soil fertility parameters as humus content (R 2 = 0.74), exchangeable potassium content (R 2 = 0.68), and exchangeable magnesium content (R 2 = 0.72) by reflection in the thermal band of the spectrum. The regressions obtained with the thermal imager data and with the spectral reflectance data in the visible and near IR- band s are similar in quality for detecting humus and exchangeable potassium content, while for detecting exchangeable magnesium content they are a bit higher. The obtained results show that thermal infrared images are applicable for detecting the most significant parameters of soil fertility in the test field and can be used as a basis for their real-time remote sensing monitoring.

Microstructure Analysis and Chemical and Mechanical Characterization of the Shells of Three Freshwater Snails.

The shells of freshwater snails are discarded as waste, which qualify as biological materials with prospective multiple uses. To substantiate this proposition, an attempt was made to elucidate the physical and chemical properties of the shells of three freshwater snails, namely, Bellamya bengalensis, Pila globosa, and Brotia costula. The shells were prepared for electron microscopy and assessment of the calcium carbonate content, apart from the Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and nanoindentation studies. The results indicated that the calcium carbonate content (y) of the shells ranged between 87 and 96% of the total weight (x) and complied with a power regression equation: y = 0.801x1.016; R2 = 0.994; r = +0.998; P < 0.001. Observations through SEM depicted different snail species-specific arrangement patterns of calcium carbonate crystals in the diverse layers of shells. The XRD, FTIR, and EDS observations revealed the dominance of the aragonite form of the calcium carbonate crystal in the microstructures of each snail shell with the occurrence of different shell surface functional groups. The Brunauer–Emmett–Teller analysis elucidated the surface textures of shell dust taken from each snail species; in addition, the nanohardness properties indicate the shells as a tough biocomposite exoskeleton. Species-specific variations in the shell morphology, microstructure, and calcium carbonate content were prominent for the three freshwater snails considered for the study. Nonetheless, the physical and chemical properties substantiate that the shells of B. bengalensis, P. globosa, and B. costula qualify as biological materials for sustainable use in various fields including bioremediation, biocatalyst, biomedical applications, and a source of lime. Since the shells of the freshwater snails are discarded as aquaculture waste, subsequent use as a biological material will support the “waste made useful” paradigm in sustainability, both from ecological and economic perspectives.

Water supply volumes and temperature regime influence on rice productivity in the Lower Kuban reclamation complexes

The statistical analysis of the irrigation water volume and air temperatures sum influence on the average rice productivity in the irrigation systems of the Lower Kuban is presented in the article. The analysis was performed by using quadratic and power regression equations; the each factor contribution to the productivity value was estimated by the statistical significance of the regression, correlation and determination coefficients. The rice culture sensitivity to the irrigation regime - to the water volume supplied to irrigation systems, and to the temperature regime according to the vegetation months, was analyzed. It was found that only during two months of the growing season - July and September, high temperatures and irrigation water scarcity lack provide a synergistic effect in relation to the high yield formation.

Modeling rainfall interception loss components of forests

Interception loss, I, the amount of precipitation intercepted by forests and evaporated back to the atmosphere plays important roles in the water balance and the climate system by removing approximately one quarter of the annual precipitation from the terrestrial hydrologic cycle. Models are critical for simulating I and its components; the canopy storage, S, and the evaporation rate during the storm, Er. The energy and the water balance methods commonly yield different Er assessments. Hence, there is an urgent need for further model development, testing, and simplification in order to independently evaluate I, S, and Er. The objectives of this study were to: (i) develop an independent model to assess I, S and Er; (ii) compare the model based on its fitness to cumulative and event based measured data of I; and (iii) identify the strengths and limitations of the proposed model. By breaking the linear and power regression equations commonly fitted to the I vs. P, gross precipitation, relationship, the model analytically isolates S and Ep (L L−1) as a function of P. Field measurements of 44 I case studies collected from Mexico and classified into arid & semi-arid, A&S (N = 13), tropical montane cloud, TMC (N = 6), temperate, T (N = 4), and tropical dry, TD (N = 21), forests were used to calibrate the model. Results showed that even though the model was constructed independently of the common equations; it isolates S, Er and Ep and reproduces remarkably well the conventional empirical linear and power regression equations of I vs. P; and simulates unbiased cumulative and individual-storm I values. When coupled with the function of rainfall duration, the model projects lower Er rates than previously anticipated using other empirical approaches. Statistical analysis revealed the likely oscillation of the I vs. P relationship between the linear and power functions depending on rainfall, canopy and climate conditions. The model represents an important advancement in forest hydrology by analytically isolating S, Er, Ep and simulating compatible I values for individual as well as for assemblages of storms. It further clarifies the large variability of Er and helps to explain the role of forests in the water budget and the climate system.

MORFOMETRICS OF MALE PASUNDAN CALVES ON DIFFERENT AGES UNDER EXTENSIVE REARING

ABSTRACTThis research on Morphometrics of Male Pasundan on Various Age was carried out in July 2018 in Cibalong District, South Garut Regency, West Java. This study aims to determine the relationship between body size of male calves at various ages and estimation of body weight using body size. The object in this study was 28 male calves at the age of 1-12 months. The results showed a relationship (R2 approaching 1) with the equation of each measurement, namely the Logarithmic regression equation for body lenght and chest deep (96,837ln(x) – 311,88), Polinomial regression equation for body and length body height (-0144x2 + 2,9524x – 48,433), Power regression equation for chest deep and chest girth (0,5317x0,9285), Logarithmic regression equation for body length and chest deep (34,974ln(x) – 110,5), Polynomial regression equation for body height and chest deep (0,004x2 - 0,1438x + 19,89). The result also show that the best model of estimating the body weight of Pasundan cattel is to use the the Polynomial formula with the equation y= 0.218x2 – 2.2536x + 76.074 where x is the size of the calf’s chest girth.Keyword: Extensive, morphometrics, pasundan male calf, weight estimation, polynomial

Prediction of Parameters which Affect Beach Nourishment Performance Using MARS, TLBO, and Conventional Regression Techniques

Artificial beach nourishment is one of the most important environmentally friendly coastal protection methods since it protects the aesthetic and recreational values of the beach and increases its protective properties. Therefore, the main aim of the current study is to assess the accuracy of multivariate adaptive regression splines (MARS) in predicting the parameters, namely sediment transport coefficients (K) and the diffusion rate (Ω), which affect beach nourishment performance. The performance of the MARS was determined by comparison of the models using exponential, linear, and power regression equations trained by conventional regression analyses (CRA) and the teaching-learning based optimization (TLBO) algorithm. In all models, two different input data obtained from the experimental study were used, one dimensional and one non-dimensional. The results presented that the MARS models gave lower error values than the CRA and TLBO models according to the root mean square error, mean absolute error, and scattering index criteria. When the models were evaluated, it was revealed that dimensional and non-dimensional models gave approximate results. We proved that the dimensional and non-dimensional MARS models can be used to estimate the (K) and (Ω) values.

Effects of rice straw ash and micro silica on mechanical properties of pavement quality concrete

This research deals with improvement in the mechanical strength of Pavement Quality Concrete (PQC) when admixed with Rice Straw Ash (RSA) and Microsilica (MS). Nine mixes were prepared by partially substituting Ordinary Portland Cement (OPC) by MS (2.5%, 5%, 7.5%, and 10%), RSA (10%) and RSA-MS composite (5%–5%, 5%–7.5%, 10%–5% and 10%–7.5%). Maximum improvement was found when OPC was partially replaced by 7.5% in the case of MS and 5%–7.5% in case of RSA-MS composite. All the mix showed increased strength, w.r.t the control mix. X-Ray powder diffraction (XRD) and Scanning Electron Microscope (SEM) techniques were employed for characterization of the selected samples. Power regression equations were established to predict split tensile and flexural strength from compressive strength. They were compared with universally accepted equations and were found to be more accurate for RSA and MS admixed concrete. Mix R1M3 (5% RSA, 7.5% MS) is recommended based on the findings.

Bedload transport measurements in the Gilgel Abay River, Lake Tana Basin, Ethiopia

Little is known about the contribution of bedload flux to the total sediment load exported from tropical sand-bed rivers. Yet, predicting bedload transport rates contributes to better river management, more appropriate river engineering works design, accurate knowledge of sediment delivery rates, which greatly benefits sediment-related water resources management. Therefore, bedload, suspended load and runoff discharge were measured at the lower Gilgel Abay River in the Blue Nile catchment of Ethiopia. Catchment area is 3887 km2, average stream discharge in the rainy season 315 (±164) m3 s−1, and the stream surface gradient at the sampling station 0.0007 m m−1. A standard Helley-Smith (U.S. BL-84) cable-suspended sampler was used to take 315 samples to measure bedload fluxes for the 2017 rainy season. The bedload predominantly comprises well to moderately well sorted, medium-sized sand (250–500 µm) with a symmetric and leptokurtic distribution. The mean daily observed bedload discharge varies from 0.7 to 427.5 Mg d−1 with an average rate of 175.1 Mg d−1. Field observations also show that the bedload dynamics become larger near the river banks and decrease towards the middle of the river section due to the presence of a central bridge pier. The average suspended sediment load ranges from 247 to 220,028 Mg d−1 and dominates the total sediment yield (>94.6%). The bedload accounts for only 0.1 to 5.4% of the total sediment load. The area-specific bedload and suspended load are also 0.6 and 22 Mg ha−1 yr−1 respectively. The elongated planform growth of the Gilgel Abay River delta in Lake Tana is also in line with the predominance of very fine, suspended load in the sediment transport of this river, in addition to limited alongshore drifting given the low waves of Tana lake. Among the tested bedload prediction criteria, the stream-power based equations of Martin and modified Bagnold performed better. Yet, the bedload prediction performance of simple power regression equations based on runoff discharge and excess unit stream power parameters provided the best agreement with the observed bedload data (Adj. R2 0.82–0.87). Finally, this study provides plausible estimates of bedload fluxes that are within predicted ranges reported for sand-bed rivers in Africa and other tropical regions.