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1

Historical and projected land-use / land cover changes of the Welmel River Watershed, Genale Dawa Basin, Ethiopia

Ayalew Solomon E., Nigussie Tewodros A.

Journal of Water and Land Development

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2023

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no. 58

89--98

EN

Human activities on land have grown significantly changing the entire landscape, while most of the changes have occurred in the tropics. The change has become a serious environmental concern at the local, regional and global scales. The intensity, speed, and degree of land use / land cover (LULC) changes are nowadays quicker compared to the past because of the development of society. Moreover, the rapid increase in population resulted in disturbing a large number of landscapes on the Earth. The main objective of this study was to detect historical (1990-2020) and predicted (2020-2050) LULC changes in the Welmel River Watershed, which is located in the Genale-Dawa Basin, South Eastern Ethiopia. The dataset of 1990, 2005, and 2020 was generated from Landsat 5, Landsat 7 and Landsat 8 respectively to determine the historical LULC map. The result of this study revealed that agriculture/ settlement increased by 6.85 km2 ∙y-1, while forestland declined by 9.16 km2 ∙y-1 over the last 31 years between 1990 and 2020. In the coming 31 years (by 2050), if the existing trend of the LULC change continues, agriculture/settlement land is expected to increase from 290.64 km2 in 2020 to 492.51 km 2 in 2050 at the rate of 6.73 km2 ∙y-1, while forestland is expected to shrink from 690.48 km2 in 2020 to 427.01 km2 in 2050 by a rate of 8.78 km2 ∙y-1.

2

The Effects of Various Organic Materials on Dactylis glomerata Yield and Content of Selected Macroelements

Malinowska Elżbieta, Wiśniewska-Kadżajan Beata, Ostaszewska Urszula, Horaczek Tomasz

Journal of Ecological Engineering

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2023

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Vol. 24, nr 7

108--118

EN

The aim of the experiment was to assess the effects of various organic materials on Dactylis glomerata yield, on the content of selected macroelements (K, Ca and Mg) and on K:Ca, K:Mg and K:(Ca + Mg) ratios. As a valuable forage plant, Dactylis glomerata (cocksfoot grass) is a common grass in Poland both in grassland and in arable fields. Its rapid spring growth and its resistance to drought, low temperatures, but also to frequent mowing and pests, makes it a common species in meadows, pastures and grassland, both permanent and alternating. In order to achieve the research goal, a three-year pot experiment was established in a greenhouse. The experiment was conducted in a completely random design, in four replications. In the autumn before the experiment, soil was mixed with organic materials (chicken manure, mushroom substrate and rye straw) and put into pots. To selected units, an additional amount of mineral N was applied in the first year and NPK fertilizers in consecutive years. Mineral fertilizers were applied at the beginning of the growing period. Compared to control, the application of mineral and organic fertilizers resulted in a significant increase in Dactylis glomerata yield. The highest biomass yield (average over the growing periods) was recorded on the unit treated with manure, straw and mineral fertilizers (27.64 g•pot-1) and on the one with mushroom substrate applied together with rye straw and mineral fertilizers (26.47 g•pot-1). The K:(Ca+Mg) ratio in the forage was normal and averaged 0.933, but mineral fertilizers, compared to other treatments, narrowed it.

3

Practical Approach to IP Scheduled Throughput Measurements in Dual Connectivity Systems

Zięba Arkadiusz, Kollar Martin, Tatarczyk Krzysztof, Sadowski Jarosław

International Journal of Electronics and Telecommunications

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2023

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Vol. 69, No. 4

645--654

EN

IP scheduled throughput defined according to 3GPP TS 36.314 reflects user throughput regardless of traffic characteristics, and therefore has become one of the most important indicators for monitoring Quality of Service (QoS) of the end user in Evolved Universal Terrestrial Radio Access Network (E-UTRAN). However, networks built on a distributed architecture make the above definition impossible to be applied directly due to the implementation challenges. This paper gives an overview of the classical Long Term Evolution (LTE) architecture as opposed to Dual Connectivity (DC) topology and focuses on a novel method of solving the calculation issue with the IP scheduled throughput measurement in edge computing environment. Experimental results show a good agreement with the real end user perception.

4

Creep model of cement and asphalt (CA) mortar based on micro‑meso structure

Zhu Huasheng, Zeng Xiaohui, Lan Xuli, Long Guangcheng, Xie Youjun

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e10, 2023

EN

CA mortar, as a filling layer, has been widely used in slab ballastless track. Since the creep deformation directly determines the track regularity and the train ride comfort, we investigated the effect of various stress levels on CA mortar creep. Results showed that the creep strain of CA mortar increased by 10 times when the stress level increased from 10%σp to 40%σp . Furthermore, it was first discovered that creep of CA mortar was attributed to the organic-inorganic interface slip and the propagation of microcracks. This work proposed a new CA mortar creep model based on the micro-meso structure characteristics, and its accuracy of prediction was much higher than previous models, R2 > 0.93.

5

Development of Renewable Material Hydrochar-Based CaAl Layered Double Hydroxide to Overcome Methyl Red Dyes Contaminant

Mohadi Risfidian, Juleanti Novie, Palapa Neza Rahayu, Hidayati Nurlisa, Lesbani Aldes

Journal of Ecological Engineering

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2022

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Vol. 23, nr 3

17--25

EN

The preparation of the CaAl/HC composite was carried out with a supporting material in the form of hydrochar from duku skin. The success of the preparation was demonstrated by XRD, FT-IR, and BET analysis. The diffractogram of CaAl/HC showed diffraction peaks at 2θ = 10.16° (003), 18.0° (002), 20.15° (006) and 65.4° (110). The diffraction showed similarity to diffraction in CaAl and hydrochar double layer hydroxyl. The FT-IR spectrum of CaAl/HC also showed similarity to the CaAl/HC double layer hydroxyl at 3448, 1635, and 1381 cm-1. The characteristic spectrum of the hydrochar also appeared in CaAl/HC at 20.15. BET analysis showed an increase in the surface area of CaAl/HC before modification of 11.842 m2/g and increased to 22.635 m2/g of CaAl/HC. The ability of CaAl/HC as an adsorbent is determined through several parameters including selectivity, regeneration, isotherm, and thermodynamics. The results of dye selectivity showed that CaAl/HC was more likely to absorb MR dyes in a mixture of dyes (DG, MO, PR, MR, CR, and DR). The regeneration results showed the ability of CaAl/HC which lasted up to 73.26% in the fifth cycle.

6

Comparison Environmental Conditions and Economic Efficiency Between Organic and Non-Organic Integrated Mangrove – Shrimp Farming Systems in Ca Mau Province, Vietnam

Van Cong Nguyen, Khanh Huynh Cong

Journal of Ecological Engineering

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2022

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Vol. 23, nr 5

130--136

EN

Mangrove forest protection is an essential solution for mitigating the impacts of natural disasters in coastal zones and climate change. Integrated mangrove-shrimp farming (IMSF) system has been promoted as a sustainable livelihood that can provide income for farmers and protect mangrove forests. However, the productivity of shrimp is limited. Therefore, to enhance the revenue for farmers, improving the value of shrimp products is a good option. Organic shrimp farming practices following the EU aquaculture organic standards have been previously applied in some areas of the Mekong delta. This study was conducted to compare technical, financial characteristics and environmental parameters between the applied (i.e., organic farms) and non-applied (i.e., non-organic farms) standards of Naturland, aiming to support the development of ecological shrimp farming and contribute towards green development. The study was carried out in Nhung Mien mangrove forest, Ngoc Hien district, Ca Mau province, Vietnam. Fifty organic farms and 50 non-organic farms were directly interviewed using structured questionnaires. And then, three farms in each system were selected for monitoring water quality. Results showed that the average mangrove coverage was 54.1% in the organic IMSF system and significantly different from the non-organic IMSF system (p<0.05). Total shrimp yield, total income and total profits tended to increase in organic IMSF system and the selling shrimp price increased by 10% compared to the conventional price. The study showed that following organic farming methods could provide higher income for farmers and a better chance to mitigate natural disasters and climate change impacts.

7

Catalytic pyrolysis of metal free PCBs with ZSM-5 and Ca(OH)2

Pandere Vaibhav, Gautam Alok, Gautam Shina

Chemical and Process Engineering

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2022

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Vol. 43, nr 2

171-–182

EN

Presence of heavier molecules and toxic brominated compounds in pyrolysis products of printed circuit boards (PCB) make their use difficult. In the present work to overcome this problem PCBs were pyrolyzed in presence of catalysts such as ZSM-5 and Ca(OH)2 to study their effect on pyrolysis products. The comparison of non-catalytic pyrolysis of PCB was done with oil and gas compositions produced by both techniques. Pyrolysis experiments were done at a lab scale set-up. However, the increased concentrations of ZSM-5 were found to increase char and gases were found to be rich in CH4 and O2. The composition of oils was mainly composed of phenols, phenol derivatives and aromatic compounds, which increased with pyrolysis with ZSM-5 and Ca(OH)2. Ca(OH)2 was found effective in removing brominated compounds from oil and no halogens were observed in oil. Char produced during pyrolysis was mesoporous in nature and composed of some fractions of metals and glass fibers.

8

Contact Stress Simulation for Mg-0.5Ca-xMn Alloys used for Medical Application

Nastasa Roxana Oana, Tufescu Ana, Munteanu Corneliu, Istrate Bogdan, Przybył Anna, Ianus Gelu

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 2

405--408

EN

In the past decades, Mg alloys have been studied intensively as potential orthopedic applications. The present research work, the FEA of the obtained contact stresses in the case of the load applied on Mg-0.5Ca-xMn alloys has been investigated. It has been used the NCB Curved Femur Shaft Plate type as a model in order to establish the necessary modeling parameters. The objective of the present work was to highlight the strain values at the contact point on the surface of the Mg-0.5Ca-xMn alloys. The results showed that the highest stresses observed near the gaps of the plate and in the screws. It means that all mechanical loads are sustained by the plate and screws, and the patient’s femur can be recovered.

9

Osobliwa mineralizacja rudna w serpentynitach antygorytowych kopalni Nasławice koło Sobótki (Dolny Śląsk)

Heflik Wiesław, Dumańska-Słowik Magdalena, Kotowski Mirosław

Przegląd Górniczy

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2021

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T. 77, nr 7-9

1--8

PL

W pracy przedstawiono charakterystykę mineralogiczno-petrograficzną grubokrystalicznej mineralizacji dolomitowo-magnetytowej napotkanej w obrębie północno-zachodniej części kopalni serpentynitów w Nasławicach koło Sobótki (Dolny Śląsk). Takie grubokrystaliczne wykształcenie tych dwóch minerałów w obrębie serpentynitów Wzgórz Nasławickich napotkano po raz pierwszy. Mineralizacja ta występuje w strefie kontaktu tektonicznego serpentynitu z wczesnowaryscyjską intruzją gabrową. W wyniku badań mikroskopowych w świetle przechodzącym oraz mikrospektroskopii Ramana stwierdzono, że asocjacja tych dwóch minerałów (dolomitu i magnetytu) stanowi produkt krystalizacji roztworów hydrotermalnych. Składniki chemiczne, żelazo i magnez, potrzebne do krystalizacji tych faz pochodzą głównie z rozkładu piroksenów i oliwinów oraz produktów protokrystalizacji obecnych w protolicie serpentynitowym. Wapń doprowadzony został pogabrowymi roztworami hydrotermalnymi.

EN

The paper presents mineralogical and petrographical characteristics of coarse-crystalline dolomite-magnetite mineralization found within the north-western part of the serpentinite mine in Nasławice near Sobótka (Lower Silesia). Such a coarse-crystalline formation of these two minerals within the serpentinites of the Nasławice Hills was encountered here for the first time. The mineralization occurs in the tectonic contact zone of the serpentinite with the Early Variscan gabbroic intrusion. The observations under polarized transmitted light microscopy and analyses of Raman microspectroscopy revealed that the association of these two minerals (dolomite and magnetite) has been a product of post-magmatic, hydrothermal activity. The chemical components, i.e. iron and magnesium, required for the crystallisation of these phases were mainly derived from the decomposition of pyroxenes and olivines and the products of protocrystallisation found in the serpentinite protolith. Calcium was supplied by post-gabbroic hydrothermal solutions.

10

Design of Construction and Controlling of Automation Technics in Order to Improve Skills of Students

Hrušková Erika, Matúšová Miriam, Václav Václav

Multidisciplinary Aspects of Production Engineering

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2021

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Vol. 4, Iss. 1

120--131

EN

The article summarizes the experience, skills of the students of technical subjects teaching methodologies using a number of software products. Solve specific assigned tasks described in this paper. Task is about the problems of automation and mechanization in the industry. That helps to improve the skills of praxis, through the design of construction and of controlling. Specifically it focuses on introducing automation in the wood industry. Article describes the design of the automation process for marking wooden hammers. Similar problems are solved by students in Computer Aided (CA) systems. The control process of automation is realized through the electro-pneumatic circuits. These circuits are creating in software FluidSIM 4 that is used as a simulation tool. FluidSIM 4 is comprehensive software for creation, simulation, instruction and study of electro-pneumatic, electro-hydraulic and digital circuits.

11

Evidence of amorphous Ca-phosphate precipitate caused by bio mineralisation in 4-5th CE lime plasters of the previously submerged east coastal monument of Salvankuppam

Singh Manager R., Kumar S. Vinodh, Ganaraj Kuntikana

Mineralogia

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2021

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Vol. 52, iss. 1

19--30

EN

The lime plasters of the excavated monument of Salvankuppam, previously submerged and exposed by the Tsunami occurred in the Indian Ocean on 26th December 2004 was studied with different analytical techniques. The temple is dated 4-5th century CE. The XRF, XRD, FTIR, NMR, SEM-EDX analysis of the lime plasters evidenced particular occurrence of phosphatised bacterial remains in saline conditions. The formation of amorphous Ca-phosphate by bio mineralization was identified in the plasters by the analyses. The plasters are made of air-lime with coarse aggregates and seashells inclusion as confirmed by the thermal and chemical analysis. The microstructure and morphological investigations of mineralized microbial structures by SEM-EDX indicated the formation of amorphous Ca-phosphate. The unordered and fibrous spherulites have hardened and reduced porosity of the plaster by bio mineralization as observed through MIP analysis. The 16S rRNA sequencing has identified the Pseudomonas strains mainly responsible for the clustering of amorphous Ca-phosphate particles around the bacterial colony.

12

Purification of Synthetic Gas from Fine Coal Waste Gasification as a Clean Fuel

Faizal Muhammad, Said Muhammad, Nurisman Enggal, Aprianti Nabila

Journal of Ecological Engineering

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2021

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Vol. 22, nr 5

114--120

EN

The presence of CO2 in the syngas is attracting more attention in terms of reducing the greenhouse gas emissions in its utilisation. The aim of this study was to purify syngas from the CO2 content of fine coal gasification. Fine coal is gasified with and without absorption using CaO, which is hydrated to Ca(OH) 2 in the modified updraft gasifier at 450–700 °C. Apart from investigating the CO2 absorption process, the gasification process also evaluates the influence of temperature in terms of its synergy with Ca(OH) 2. The best conditions for the gasification process are achieved at 700 °C. The content of CO2 was proven to be well absorbed, which is characterised by a decrease in the CO2 content and an increase in H2 in syngas. After the absorption process, the H2 content obtained increased from 42.6 mole% to 48.8 mole% of H2 at 700°C. The H2 ratio also increased after absorption to 2.57 from the previous value of 2.23. The highest absorption efficiency of CO2 by Ca(OH) 2 occurred at 700°C at 50.63%. With an increase in temperature in the gasification process with absorption, the CO2 content decreased dramatically from 16.9 mole% to 3.9%. Ca(OH) 2 has good absorption power at CO2 at high temperatures.

13

Integrated Access and Backhaul based 5G Connectivity for Rural Indian Sectors : Ending the Digital Divide

Biswas Ardhendu Shekhar, Sil Sanjib, Bera Rabindranath, Mitra Monojit

International Journal of Electronics and Telecommunications

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2021

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Vol. 67, No. 4

655--663

EN

The world is heading towards deployment of 5G commercially by the year 2020. But providing broadband 5G connectivity to remote rural regions is a significant challenge. Fiber connectivity has attempted to penetrate rural regions but last mile connectivity is still a problem in many rural sectors due to improper land demarcation and hostile terrain. A scheme which is based on the Integrated Access and Backhaul (IAB) concept is proposed to provide last mile 5G connectivity to satisfy the broadband needs of rural subscribers. A wireless 5G downlink environment following 3GPP NR specifications with a significantly high throughput is simulated. The last mile link is provided through a 28GHz carrier from a proposed IAB node delivering a data throughput of 4.301 Gbps for single-user carrier aggregation and 5.733 Gbps for multi-user carrier aggregation which is quite promising for broadband service, like high-speed Internet and streaming video. The results presented in this work are observed to agree favourably with the results of other researchers in the field.

14

CaO-based high temperature CO2 sorbents – Literature review

Konopacka-Łyskawa Donata, Czaplicka Natalia, Szefer Andrzej

Chemical and Process Engineering

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2021

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Vol. 42, nr 4

411–-438

EN

The use of CaO-based adsorbents has a high potential to capture CO2 from various systems due to its high reactivity with CO2, high capacity, and low cost of naturally derived CaO. The application of CaO-based sorbents to remove carbon dioxide is based on a reversible reaction between CaO and CO2. However, multiple carbonation/calcination cycles lead to a rapid reduction in the sorption capacity of natural CaO, and therefore efforts are made to reduce this disadvantage by doping, regenerating, or producing synthetic CaO with stable sorption properties. In this review, the synthesis methods used to obtain CaO-based sorbents were collected, and the latest research on improving their sorption properties was presented. The most commonly used models to describe the CO2 sorption kinetics on CaO-based sorbents were also introduced. The methods of sorbent regeneration and their effectiveness were summarized. In the last part of this review, the current state of advancement of work on the larger scale, possible problems, and opportunities during scale-up of the calcium looping process were presented. Concluding (i) the presented methods of adsorbent synthesis allow for the production of doped CaO adsorbents on a laboratory scale, characterized by high CO2 capture efficiency and good cyclic stability, (ii) the most commonly used in practice models describing CO2 chemisorption are empirical models and the shrinking core model, (iii) the use of sorbent regeneration allows for a significant improvement in sorption capacity, (iv) the scale-up of both the production of new CaO adsorbents and the CO2 capture technology with their use requires further development.

15

Zero net energy public library for the San Benito County in Hollister, CA

Kaczmarek Andrzej, Kirschke Paweł

Architectus

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2021

|

Nr 1 (65)

99--109

EN

The objective of this paper is to demonstrate the use of elements of sustainable design in public buildings in the context of contemporary architectural design solutions and zero-energy standards for newly designed buildings in California, USA. The paper presents a detailed overview of the main task of the "Architecture at Zero 2020" international architectural competition, organised by the American Institute of Architects California – a design of the San Benito County Public Library in Hollister, CA. The paper also features a detailed analysis of the competition's outcome, with a specific focus on Andrzej Kaczmarek's design, which was given the merit award in the competition’s student projects category. The competition resulted in the presentation of the library's design alternatives, each suited to contextspecific environmental and climate determinants and optimised in terms of energy. Andrzej Kaczmarek's design met these requirements, as demonstrated via calculations performed using eQuest 3–64 software. The design was recognised not only because of its optimised energy balance, but also the excellence with which it satisfied the needs of local citizens and how it reflected a thorough understanding of the site's placebased character. The library was successfully blended in with its historical context via its simple form that was partially embedded underground. The building was designed to feature an array of advanced engineering solutions intended to secure it against earthquakes and optimise its heat balance, including kinetic façades and retractable glazed roof elements, photovoltaic panels, wind turbines and Pavegen floor surfaces.

PL

Celem artykułu było ukazanie sposobów wykorzystania elementów projektowania zrównoważonego we współczesnych budynkach użyteczności publicznej, w kontekście architektonicznych rozwiązań projektowych i standardów zeroenergetycznych przewidzianych dla nowo projektowanych budynków w Kalifornii. Przedmiotem szczegółowych prac był projekt biblioteki publicznej hrabstwa San Benito w Hollister w Kalifornii, stanowiący zadanie w międzynarodowym konkursie architektonicznym „Architecture at Zero 2020”, organizowanym przez American Institute of Architect California. W artykule przeanalizowano wyniki tego konkursu, a w szczególności projekt autorstwa Andrzeja Kaczmarka, który zdobył równorzędną nagrodę w kategorii prac studenckich. Efektem konkursu było uzyskanie alternatywnych rozwiązań biblioteki dopasowanych do uwarunkowań środowiska naturalnego i klimatu, a przede wszystkim zoptymalizowanych pod względem energetycznym. Projekt Andrzeja Kaczmarka spełnił jego wymagania, co wykazano, przeprowadzając obliczenia za pomocą programu eQuest 364. Projekt ten został nagrodzony nie tylko za zoptymalizowanie bilansu energetycznego, ale również za znakomite spełnienie potrzeb mieszkańców i zrozumienie charakteru miejsca. Dobre wkomponowanie biblioteki w historyczne otoczenie uzyskano, nadając budynkowi prostą formę̨ i zagłębiając go częściowo pod ziemię. W obiekcie zastosowano wiele zaawansowanych rozwiązań technicznych mających na celu zabezpieczenie budowli przed trzęsieniami ziemi i prowadzących do optymalizacji bilansu ciepła, w tym: kinetyczne fasady i ruchome oszklone dachy, panele fotowoltaiczne, turbiny wiatrowe i posadzki typu Pavegen.

16

Surface modified bentonite mineral as a sorbent for Pb2+ and Zn2+ ions removal from aqueous solutions

Selim K.haled A., Rostom Merit, Youssef Mohhamed A., Abdel-Khalek Nagui A., Abdel-Khalek Mohhamed A., Hassan El-Sayed R. E.

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 6

145--157

EN

Environmental pollution by lead (Pb2+) and zinc (Zn2+) ions has become an important issue due to its harmful effects on human health and environment. This work aims to evaluate the application of surface modified Egyptian bentonite mineral by acid activation using H2SO4 and thermal treatment as an adsorbent to remove lead (Pb2+) and zinc (Zn2+) ions from aqueous solution. X-ray diffraction (XRD), Fourier Transformed Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) techniques were used to investigate the modified bentonite. The impact of organic and inorganic dispersants on rheological characteristics of bentonite suspensions was investigated. Adsorption of Pb2+ and Zn2+ ions using modified bentonite mineral was performed with different adsorbent doses and pH values. Removal efficiencies of lead and zinc are 99.67% and 99%, respectively with adsorbent dose of 25 g/l at pH of 6.2.

17

Evaluation of water treatment plants quality in Basrah Province, by factor and cluster analysis

Al Saad Zainb A.A., Hamdan Ahmed N.A.

Journal of Water and Land Development

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2020

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no. 46

10--19

EN

The Shatt Al Arab River (SAAR) is a major source of raw water for most water treatment plants (WTP’s) located along with it in Basrah province. This study aims to determine the effects of different variables on water quality of the SAAR, using multivariate statistical analysis. Seventeen variables were measured in nine WTP’s during 2017, these sites are Al Hussain (1), Awaissan (2), Al Abass (3), Al Garma (4), Mhaigran (5), Al Asmaee (6), Al Jubaila (7), Al Baradia (8), Al Lebani (9). The dataset is treated using principal component analysis (PCA) / factor analysis (FA), cluster analysis (CA) to the most important factors affecting water quality, sources of contamination and the suitability of water for drinking and irrigation. Three factors are responsible for the data structure representing 88.86% of the total variance in the dataset. CA shows three different groups of similarity between the sampling stations, in which station 5 (Mhaigran) is more contaminated than others, while station 3 (Al Abass) and 6 (Al Asmaee) are less contaminated. Electrical conductivity (EC) and sodium adsorption ratio (SAR) are plotted on Richard diagram. It is shown that the samples of water of Mhaigran are located in the class of C4-S3 of very high salinity and sodium, water samples of Al Abass station, are located in the class of C3-S1 of high salinity and low sodium, and others are located in the class of C4-S2 of high salinity and medium sodium. Generally, the results of most water quality parameters reveal that SAAR is not within the permissible levels of drinking and irrigation.

18

Modeling and Analysis of Additional Clear Channel Assessment to Improve Performance of IEEE 802.15.4-based MAC Protocol

Asuti Manjunath G., Basarkod Prabhugoud I.

Journal of Telecommunications and Information Technology

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2020

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nr 3

10--21

EN

Design of the MAC protocol is crucial in all wireless sensor networks (WSNs) due to its inﬂuence on the performance of the transceiver, i.e. the most energy-consuming component of each sensor node. A mechanism known as “carrier sense multiple access with collision avoidance” (CSMA/CA) is used for accessing the wireless channel in the IEEE 802.15.4 standard-based MAC protocol in order to avoid collisions between the network’s communicating nodes. CSMA/CA relies on two clear channel assessments (CCA=2) for checking the status of the channel. In this paper, we develop an additional CCA algorithm for the two scenarios encountered in star topology-enabled WSNs. Next, we investigate the impact of an additional clear channel assessment (CCA=3) on performance in IEEE 802.15.4. We develop a Markov chain model for the proposed methodology, and validate it using Matlab. Simulation results show that there is a signiﬁcant improvement of performance metrics in the IEEE 802.15.4 standard-based MAC protocol with an additional CCA.

19

Flow Assurance Study on Offshore Marginal Oil Field Development in Vietnam: The Case of Ca Ngu Vang Oil Field

Nguyen Van Tinh, Nguyen Thi Hai Yen, Trinh Tien Thang, Tong Canh Son, Le Dinh Hoe

Inżynieria Mineralna

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2020

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no. 2, vol. 1

15--22

EN

Over the last few years, PetroVietnam has discovered and exploited several marginal oil fields such as Ca Ngu Vang, Te Giac Trang, Hai Su Den, Hai Su Trang, etc. however the reserves are modest. Test results received during drilling exploratory wells within these fields indicated that the maximum total daily production rate from the wells could promisingly range to about 20,000 barrels of oil per day (BOPD). Unfortunately, the optimum development of these offshore oil fields still offers numerous challenges to oil engineers due to the limitations of equipment and technology. Oil production activities worldwide show that if the daily production of an offshore oilfield is less than 20,000 BOPD, a connection of the marginal fields to their nearest larger oil field should be taken into consideration in order to efficaciously recover more crude oil. Often, this method of production requires a long subsea pipeline system. Besides, the transportation of the fluids from these fields to the processing platform will undergo several serious problems caused by the deposition of wax. All these matters should be handled to guarantee the performance of transportation. A number of models using PIPESIM, PIPEPHRASE and OLGA have been applied to design and examine the operations of the subsea pipeline in different working conditions. Results of the simulations proposed the use of passive insulation to economically eliminate wax deposition and recommended proper pipeline shutdown operations to minimize several problems related to flow assurance issues in the region of interest.

PL

W ciągu ostatnich kilku lat w Vietnamie odkryto i eksploatowano kilka marginalnych pól naftowych, takich jak Ca Ngu Vang, Te Giac Trang, Hai Su Den, Hai Su Trang, itd.… Jednak zasoby są skromne. Wyniki testów otrzymane podczas wiercenia odwiertów poszukiwawczych na tych polach wykazały, że maksymalny całkowity dzienny poziom wydobycia z odwiertów może potencjalnie sięgać około 20 000 baryłek ropy dziennie (BOPD). Niestety, optymalny rozwój tych przybrzeżnych pól naftowych nadal stwarza liczne wyzwania dla inżynierów naftowych ze względu na ograniczenia sprzętu i technologii. Działalność wydobywcza ropy naftowej na całym świecie pokazuje, że jeśli dzienna produkcja morskiego pola naftowego jest mniejsza niż 20 000 BOPD, należy wziąć pod uwagę połączenie pól marginalnych z ich najbliższym większym polem naftowym, aby efektywnie odzyskać więcej ropy. Często ta metoda produkcji wymaga długiego systemu rurociągów podmorskich. Poza tym transport płynów z tych pól na platformę obróbkową będzie wiązał się z kilkoma poważnymi problemami spowodowanymi osadzaniem się wosku. Wszystkie te sprawy powinny być załatwione, aby zagwarantować wykonanie transportu. Szereg modeli wykorzystujących PIPESIM, PIPEPHRASE i OLGA zostało zastosowanych do projektowania i badania działania rurociągu podmorskiego w różnych warunkach pracy. W wynikach symulacji zaproponowano zastosowanie izolacji pasywnej w celu ekonomicznego wyeliminowania osadzania się wosku oraz zalecono prawidłowe operacje wyłączania rurociągu, aby zminimalizować kilka problemów związanych z kwestiami zapewnienia przepływu w obszarze zainteresowania.

20

Phase Transformation Analysis of the Amorphous Mg72Zn24Ca4 Alloy

Lelito J.

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 3

21--24

EN

The paper presents research of metallic glass based on a Mg72Zn24Ca4 alloy. Metallic glass was prepared using induction melting and further injection on a spinning copper wheel. The X-ray diffractometer and differential scanning calorimeter (DSC) were used to investigate the phase transformation of the amorphous ribbon. The heat released in the crystallization process, during isothermal annealing, based on the differential scanning calorimeter investigation, was determined to be 166.18 Jg-1. The effect of isothermal annealing temperature on the kinetics of the amorphous alloy crystallization process using differential scanning calorimeter was investigated. For this purpose, two isothermal annealing temperatures were selected. The incubation time decreases as the temperature of the isothermal annealing increases from 300 to 252 seconds. The same relationship is visible in the case of duration of the phase transformation, which also decreases as the temperature of the isothermal annealing increases from 360 to 228 seconds. The obtained results show a significant influence of isothermal annealing temperature on the degree of phase transformation.