Buckling resistance of hot‐finished CHS beam‐columns using FE modelling and machine learning

The use of circular hollow sections (CHS) has increased in recent years owing to its excellent mechanical behaviour including axial compression and torsional resistance as well as its aesthetic appearance. They are popular in a wide range of structural members including beams, columns, trusses and arches. The behaviour of hot-finished CHS beam-columns made from normal and high strength steel is the main focus of this paper. A particular attention is given to predict the ultimate buckling resistance of CHS beam-columns using the recent advancement of the artificial neural network (ANN). FE models were established and validated to generate an extensive parametric study. The ANN model is trained and validated using a total of 3439 data points collected from the generated FE models and experimental tests available in the literature. A comprehensive comparative analysis with the design rules in Eurocode 3 is conducted to evaluate the performance of the developed ANN model. It is shown that the proposed ANN based design formula provides a reliable means for predicting the buckling resistance of the CHS beam-columns. This formula can be easily implemented in any programming software, providing an excellent basis for engineers and designers to predict the buckling resistance resistance of the CHS beam-columns with a straightforward procedure in an efficient and sustainable manner with least computational time

Ergonomic evaluation of subjects involved in orange (Citrus sinensis) handling operations in Yanlemo Market Kano State

Ergonomic evaluation of subjects involved in orange handling operation in Kano State was conducted. Anthropometric parameters were evaluated, where they were found to vary with age amongst the subjects selected. 20th and 80th percentiles of the dimensions were computed and recommended for usage in design of the relevant orange handling equipment. To evaluate the Physiological parameters, sorting/grading operations and washing operations were selected for this study. Results obtained revealed that, heart beat rate, oxygen consumption and energy expenditure varied amongst the subjects with age. Muscular stress and postural disorder were also studied. Comparing the parameters obtained during sorting/grading operation and that obtained during washing operations revealed that orange operations resulted to superior drudgery and musculoskeletal disorders.Keywords: Anthropometrics, Energy expenditure, Drudgery, Operations and Musculoskeletal disorde

QED for a Fibrillar Medium of Two-Level Atoms

We consider a fibrillar medium with a continuous distribution of two-level atoms coupled to quantized electromagnetic fields. Perturbation theory is developed based on the current algebra satisfied by the atomic operators. The one-loop corrections to the dispersion relation for the polaritons and the dielectric constant are computed. Renormalization group equations are derived which demonstrate a screening of the two-level splitting at higher energies. Our results are compared with known results in the slowly varying envelope and rotating wave approximations. We also discuss the quantum sine-Gordon theory as an approximate theory.Comment: 32 pages, 4 figures, uses harvmac and epsf. In this revised version, infra-red divergences are more properly handle

UTILIZATION OF CASCADE STRUCTURE ORGANIC RANKINE CYCLE IN PETROLEUM INDUSTRY

In the last few years in petroleum industry the focus of innovation has turned to the increase of energy efficiency and the reduction of carbon dioxide emission. One of the most difficult engineering challenges is the utilization of low temperature process streams (<180 °C) although the largest part of waste heat has been generated in this segment. Installation of Organic Rankine Cycle (ORC) system to the waste heat source unit is providing an adequate solution for handling of loss energy and yielding “green” electricity for the facility. This system involves the same devices as in the usual steam power plant (a boiler, a work-producing expansion device, a generator, a condenser and a pump). However, for such a system, the working fluid is an organic compound having a lower ebullition temperature than water and allowing reduced evaporating temperatures. The success of this technology is coming from its box module application: a similar ORC system can be used, with little modifications for handling various heat sources. Moreover, unlike the conventional Rankine cycle, local and small scale power generation is made possible by this technology. Today, Organic Rankine Cycles are commercially available even in the MW power range.The object of our examination in this paper is a unit having three technical points for future ORC utilization: i) a small quantity of liquid naphtha side draw at 165 °C; ii) a higher amount of vapor column overhead at 140 °C; iii) a furnace flue gas at 250 °C. We investigated the utilization of these streams in a cascade structure using isopentane as working fluid. Cascade structure has two working fluid cycles: a relatively high pressure (12.5 bar) for the utilization of higher temperature streams and a relatively low pressure (5.5 bar) for the utilization of lower temperature level streams. Analysis of the potential of energy saving has been made by supporting the steady-state process flowsheeting and simulation. As the result of this investigation promising results were brought for the industrial scale utilization of cascade ORC system. One can see the dimensions of this system including needed area of heat exchangers, calculated expander performances, efficiency of the system etc

New solutions of relativistic wave equations in magnetic fields and longitudinal fields

We demonstrate how one can describe explicitly the present arbitrariness in solutions of relativistic wave equations in external electromagnetic fields of special form. This arbitrariness is connected to the existence of a transformation, which reduces effectively the number of variables in the initial equations. Then we use the corresponding representations to construct new sets of exact solutions, which may have a physical interest. Namely, we present new sets of stationary and nonstationary solutions in magnetic field and in some superpositions of electric and magnetic fields.Comment: 25 pages, LaTex fil

Geochemical investigation of the mixed Máriahalom vertebrate fauna at the Paleogene–Neogene boundary in the Central Paratethys: environmental conditions and age constrain

The fossil vertebrate fauna of Máriahalom contains remains from a wide range of ecologies including terrestrial and aquatic mammals, crocodiles, sharks, and rays among others. All these were found mixed in mollusc-rich, shallow water, coastal deposits. The aim of the study is to trace the origin of the fossils using their rare earth element (REE) content and their respective ecology with stable oxygen isotopic compositions. In addition, marine vertebrates and calcareous marine fossils were analysed for their Sr isotope composition to provide a new age estimate for the locality. The REE content and their distribution in the fossils indicate similar early diagenetic environments and possible contemporaneous fossilization for the entire vertebrate assemblage. Reworked fossils of significantly different age can be excluded. The enamel/enameloid-derived phosphate oxygen isotope composition of selected fossil taxa fit well with previously inferred habitats that include marine, brackish, and terrestrial environments. Notably, the stem-pinniped Potamotherium valletoni is best interpreted as freshwater dweller instead of marine, consistent with the sedimentology of other occurrences. Our novel 87Sr/86Sr data suggest an Aquitanian age (21.4 ± 0.5&nbsp;Ma) for the Máriahalom site that is younger than the previously proposed Late Oligocene age based on biostratigraphy (MP28–30 European Mammal Paleogene Reference Levels). An Aquitanian age raises the possibility that the index fossil taxon, the anthracothere mammal Microbunodon minimum, may have vanished earlier in Western Europe than in the Central Paratethys region

Machine learning for optimal design of circular hollow section stainless steel stub columns: A comparative analysis with Eurocode 3 predictions

Stainless steel has many advantages when used in structures, however, the initial cost is high. Hence, it is essential to develop reliable and accurate design methods that can optimize the material. As novel, reliable soft computation methods, machine learning provided more accurate predictions than analytical formulae and solved highly complex problems. The present study aims to develop machine learning models to predict the cross-section resistance of circular hollow section stainless steel stub column. A parametric study is conducted by varying the diameter, thickness, length, and mechanical properties of the column. This database is used to train, validate, and test machine learning models, Artificial Neural Network (ANN), Decision Trees for Regression (DTR), Gene Expression Programming (GEP) and Support Vector Machine Regression (SVMR). Thereafter, results are compared with finite element models and Eurocode 3 (EC3) to assess their accuracy. It was concluded that the EC3 models provided conservative predictions with an average Predicted-to-Actual ratio of 0.698 and Root Mean Square Error (RMSE) of 437.3. The machine learning models presented the highest level of accuracy. However, the SVMR model based on RBF kernel presented a better performance than the ANN, GEP and DTR machine learning models, and RMSE value for SVMR, ANN, GEP and DTR is 22.6, 31.6, 152.84 and 29.07, respectively. The GEP leads to the lowest level of accuracy among the other three machine learning models, yet, it is more accurate than EC3. The machine learning models were implemented in a user-friendly tool, which can be used for design purposes

Spectrum of ultrasonographic findings in gynaecological emergencies in a Nigerian Tertiary Hospital

Background: Gynaecological emergencies are a common cause of morbidity and mortality among women of reproductive age group worldwide and can be life threatening. They can be easily managed if diagnosed early. Ultrasonography (USS) is a readily available and excellent diagnostic tool in the prompt and accurate diagnosis of these conditions. This is a comparative study aimed at evaluating the ultrasonographic findings in gynaecological emergencies and comparing with the clinical diagnosis. Methods: 400 patients presenting with suspected gynaecological emergencies at the National Hospital, Abuja were evaluated. The USS findings of these patients were recorded and matched with their socio-demographic parameters and the radiological diagnosis was then compared with the clinical diagnosis at presentation. Results: The mean age of participants was 34.2±7.5 years. Pregnancy related emergencies were the most common, making up 65.8%. Abortion was the most common emergency seen. Pregnancy related cases were commoner in the younger age group 20-39 years. A higher proportion of USS diagnosis for pregnancy related cases (96.7%) corresponded with the clinical diagnosis when compared to a smaller proportion for non-pregnancy related cases (80.6%), and this had significant correlation (x2=256.12, df=1, p&lt;0.0001) Conclusions: USS evaluation of gynaecological emergencies as seen in this study, allows for quick and accurate diagnosis so that appropriate emergent care can be instituted to improve the outcome in these cases

Atomic levels in superstrong magnetic fields and D=2 QED of massive electrons: screening

The photon polarization operator in superstrong magnetic fields induces the dynamical photon "mass" which leads to screening of Coulomb potential at small distances $z\ll 1/m$, $m$ is the mass of an electron. We demonstrate that this behaviour is qualitatively different from the case of D=2 QED, where the same formula for a polarization operator leads to screening at large distances as well. Because of screening the ground state energy of the hydrogen atom at the magnetic fields $B \gg m^2/e^3$ has the finite value $E_0 = -me^4/2 \ln^2(1/e^6)$.Comment: 12 pages, 2 figure

Machine learning-driven web-post buckling resistance prediction for high-strength steel beams with elliptically-based web openings

The use of periodical elliptically-based web (EBW) openings in high strength steel (HSS) beams has been increasingly popular in recent years mainly because of the high strength-to-weight ratio and the reduction in the floor height as a result of allowing different utility services to pass through the web openings. However, these sections are susceptible to web-post buckling (WPB) failure mode and therefore it is imperative that an accurate design tool is made available for prediction of the web-post buckling capacity. Therefore, the present paper aims to implement the power of various machine learning (ML) methods for prediction of the WPB capacity in HSS beams with (EBW) openings and to assess the performance of existing analytical design model. For this purpose, a numerical model is developed and validated with the aim of conducting a total of 10,764 web-post finite element models, considering S460, S690 and S960 steel grades. This data is employed to train and validate different ML algorithms including Artificial Neural Networks (ANN), Support Vector Machine Regression (SVR) and Gene Expression Programming (GEP). Finally, the paper proposes new design models for WPB resistance prediction. The results are discussed in detail, and they are compared with the numerical models and the existing analytical design method. The proposed design models based on the machine learning predictions are shown to be powerful, reliable and efficient design tools for capacity predictions of the WPB resistance of HSS beams with periodical (EBW) openings