Search results for: fatigue crack growth rate

Authors: Marinko Skare, Malgorzata Porada Rochon

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This paper study the link between energy justice and economic growth. The link between energy justice and growth has not been extensively studied. Here we study the impact and importance of energy justice, as a part of the energy transition process, on economic growth. Our study shows energy justice growth is an important determinant of economic growth and development that should be addressed at the industry and economic levels. We use panel data modeling and causality testing to research the empirical link between energy justice and economic growth. Industry and economy-level policies designed to support energy justice initiatives are beneficial to economic growth. Energy justice is a necessary condition for green growth and sustainability targets.

Keywords: energy justice, economic growth, panel data, energy transition

Procedia PDF Downloads 95

Authors: Aboozar Aghaei

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In the present work, the dissimilar Monel400 and SS316 were joined by friction stir welding (FSW). The applied rotating speed was 400 rpm, whereas the traverse speed varied between 50 and 150 mm/min. At a constant rotating speed, the sound welds were obtained at the welding speeds of 50 and 100 mm/min. However, a groove-like defect was formed when the welding speed exceeded 100 mm/min. The mechanical properties of the joints were evaluated using tensile and fatigue tests. The fatigue strength of dissimilar FSWed specimens was higher than that of both Monel400 and SS316. To study the failure behavior of FSWed specimens, the fracture surfaces were analyzed using a scanning electron microscope (SEM). The failure analysis indicates that different mechanisms may contribute to the fracture of welds. This was attributed to the dissimilar characteristics of dissimilar materials exhibiting different failure behaviors.

Keywords: frictions stir welding (FSW), stainless steel, mechanical properties, Monel400

Procedia PDF Downloads 64

Authors: Ehsan Ahmadifar, Mohammad Ali Yousefi, Zahra Roohi

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In this study, the effects of different levels of Ergosan (control group (0), 2, 4 and 6 gr Ergosan per Kg diet) as a nutritional supplement were investigated on growth indices and stress in Zebrafish for 3 months. Larvae (4-day-old after hatching) were fed with experimental diet from the beginning of feeding until adult (adolescence) (average weight: 69.3 g, length: 5.1 cm). Different levels of Ergosan had no significant effect on rate survival (P < 0.05). The results showed that diet containing 6 gr Ergosan significantly caused the best FCR in Zebrafish (P < 0.05). By increasing the Ergosan diet, specific growth rate increased. Body weight gain and condition factor had significant differences (P < 0.05) as the highest and the lowest were observed in treatment 3 gr of Ergosan and control, respectively. The results showed that fish fed with experimental diet, had the highest resistance to environmental stresses compared to control, and the test temperature, oxygen, salinity and alkalinity samples containing 6 gr/kg, was significantly more resistance compared to the other treatments (P < 0.05). Overall, to achieve high resistance to environmental stress and increase final biomass using 6 gr/kg Ergosan in diet fish Zebrafish.

Keywords: Ergosan, stress, growth performance, Danio rerio

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Authors: Fatih Tarlak

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Predictive microbiology can be considered as an important field in food microbiology in which it uses predictive models to describe the microbial growth in different food products. Predictive models estimate the growth of microorganisms quickly, efficiently, and in a cost-effective way as compared to traditional methods of enumeration, which are long-lasting, expensive, and time-consuming. The mathematical models used in predictive microbiology are mainly categorised as primary and secondary models. The primary models are the mathematical equations that define the growth data as a function of time under a constant environmental condition. The secondary models describe the effects of environmental factors, such as temperature, pH, and water activity (aw) on the parameters of the primary models, including the maximum specific growth rate and lag phase duration, which are the most critical growth kinetic parameters. The combination of primary and secondary models provides valuable information to set limits for the quantitative detection of the microbial spoilage and assess product shelf-life.

Keywords: shelf-life, growth model, predictive microbiology, simulation

Procedia PDF Downloads 187

Authors: Sami Ali Metwally, Bedour Helmy Abou-Leila, Hussien I.Abdel-Shafy

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The work was carried out at the greenhouse of National Research Centre, Pot experiment was carried out during of 2020 and 2021 seasons aimed to study the effect of two types of water (two recycling gray water treatments((SMR (Sequencing Batch Reactor) and MBR(Membrane Biology Reactor) and three watering intervals 15, 20 and 25 days on Syangonium plants growth. Examination of data cleared that, (MBR) recorded increase in vegetative growth parameters, osmotic pressure, transpiration rate chlorophyll a,b,carotenoids and carbohydrate)in compared with SBR.As for water, intervalsthe highest values of most growth parameters were obtained from plants irrigated with after (20 days) compared with other treatments.15 days irrigation intervals recorded significantly increased in osmotic pressure, transpiration rate and photosynthetic pigments, while carbohydrate values recorded decreased. Interaction between water type and water intervals(SBR) recorded the highest values of most growth parameters by irrigation after 20 days. While the treatment (MBR)and irrigated after 25 days showed the highest values on leaf area and leaves fresh weight compared with other treatments.

Keywords: grey water, water intervals, Syngonium plant, recycling water, vegetative growth

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Authors: Touhami Tahenni

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Excessively wide cracks are harmful to the serviceability of reinforced concrete (RC) beams and may lead to durability problems in the longer term. They also reduce the rigidity of RC sections, rendering the tensile concrete ineffective structurally. To reduce the negative effects of cracks, steel fibers are added to concrete mixes in the same manner as aggregates. In the present work, steel fibers reinforced concrete (SFRC) beams, made of normal strength and high strength concretes, were tested in a four-point bending test using a digital image correlation technique. The beams had different volume fractions of fibres and different aspect ratios (fiber length/fiber diameter). The evaluation of flexural cracking widths was determined using Gom-Aramis software. The experimental crack widths were compared with theoretical values predicted by the technical document of Rilem TC 162-TDF. The model proposed in this document seems to be the only one that considers the efficiency of steel fibres in restraining the crack widths. However, the model of Rilem takes into account only the aspect ratio of steel fibres to predict the crack width of SFRC beams. It has been reported in several pieces of research that the contribution of steel fibres to the limitation of flexural cracking widths is based on three essential parameters namely, the volume fraction, the orientation and the aspect ratio of fibres. Referring to the literature on the flexural cracking behavior of SFRC beams and the experimental observations of the present work, a correction of the Rilem model by the introduction of these parameters in the formula is proposed. The crack widths predicted by the new empirical model were compared with the experimental results and assessed against other test data on SFRC beams taken from the literature. The modified Rilem model gives better results and is found more satisfactory in predicting the crack widths of fibres concrete.

Keywords: stee fibres, reinforced concrete, flexural cracking, tensile strength, crack width

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Authors: Khater N., Rahmine S., Bougoffa C., Bouguenna T., Ouanes H.

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Moringa oleifera L. species is considered one of the most useful trees in the world, possessing many interesting properties that make it of great scientific interest. It has been described as the miracle tree, the tree of a thousand virtues, the tree of life and God's gift to man. The present study aims to introduce, produce, and develop Moringa Oleifera as a species with high ecological potential (resistance to biotic and abiotic stresses and productivity), high added value, and multiple virtues. The aim of this work is to study the germination potential of this species under different temperature conditions. In this study, the germination assay was tested in two different temperature ranges: internal (laboratory ambient temperature between 22°c and 25°c) and external (seasonal temperature between 4°c and 8°c). Morphological and physiological analyses were carried out by Shoot length (SL), root length (RL), diameter at the crown (DC), fresh weight of shoots (FWS), fresh weight of roots (FWR), dry weight of shoots (DWS) and dry weight of roots (DWS). For all these variables, the results of the study reveal a significant difference between the two temperature intervals, with a high germination rate of 81. 81% and plant growth was rapid (7cm during 24h) in the laboratory temperature; in contrast to the external temperatures, a germination rate value of around 27% was recorded, and germination took place after 20 days of sowing, with slower plant growth. The results obtained show that a temperature greater than or equal to 25° is the ideal temperature for the germination and growth of moringa seeds and has a positive influence on the speed and percentage of germination.

Keywords: moringa oleifera, temperature, germination rate, growth, biomass

Procedia PDF Downloads 43

Authors: Aboozar Aghaei, Kamran Dehghani

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In the present work, the dissimilar Monel400 and SS316 were joined by friction stir welding (FSW). The applied rotating speed was 400 rpm, whereas the traverse speed varied between 50 and 150 mm/min. At a constant rotating speed, the sound welds were obtained at the welding speeds of 50 and 100 mm/min. However, a groove-like defect was formed when the welding speed exceeded 100 mm/min. The mechanical properties of the joints were evaluated using tensile and fatigue tests. The fatigue strength of dissimilar FSWed specimens was higher than that of both Monel400 and SS316. To study the failure behavior of FSWed specimens, the fracture surfaces were analyzed using a scanning electron microscope (SEM). The failure analysis indicates that different mechanisms may contribute to the fracture of welds. This was attributed to the dissimilar characteristics of dissimilar materials exhibiting different failure behaviors.

Keywords: frictions stir welding, stainless steel, Monel400, mechanical properties

Procedia PDF Downloads 67

Authors: Deniz Dincel, Sena Ardicli, Hale Samli, Mustafa Ogan, Faruk Balci

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The aim of the study was to determine the effects of some environmental and genetic factors on growth, fertility traits, milk yield and composition in Saanen goats. For this purpose, the total of 173 Saanen goats and kids were investigated for growth, fertility and milk traits in Marmara Region of Turkey. Fertility parameters (n=70) were evaluated during two years. Milk samples were collected during the lactation and the milk yield/components (n=59) of each goat were calculated. In terms of CSN3 and AGPAT6 gene; the genotypes were defined by PCR-RFLP. Saanen kids (n=86-112) were measured from birth to 6 months of life. The birth, weaning, 60ᵗʰ, 90ᵗʰ, 120ᵗʰ and 180tᵗʰ days of average live weights were calculated. The effects of maternal age on pregnancy rate (p < 0.05), birth rate (p < 0.05), infertility rate (p < 0.05), single born kidding (p < 0.001), twinning rate (p < 0.05), triplet rate (p < 0.05), survival rate of kids until weaning (p < 0.05), number of kids per parturition (p < 0.01) and number of kids per mating (p < 0.01) were found significant. The impacts of year on birth rate (p < 0.05), abortion rate (p < 0.001), single born kidding (p < 0.01), survival rate of kids until weaning (p < 0.01), number of kids per mating (p < 0.01) were found significant for fertility traits. The impacts of lactation length on all milk yield parameters (lactation milk, protein, fat, totally solid, solid not fat, casein and lactose yield) (p < 0.001) were found significant. The effects of age on all milk yield parameters (lactation milk, protein, fat, total solid, solid not fat, casein and lactose yield) (p < 0.001), protein rate (p < 0.05), fat rate (p < 0.05), total solid rate (p < 0.01), solid not fat rate (p < 0.05), casein rate (p < 0.05) and lactation length (p < 0.01), were found significant too. However, the effect of AGPAT6 gene on milk yield and composition was not found significant in Saanen goats. The herd was found monomorphic (FF) for CSN3 gene. The effects of sex on live weights until 90ᵗʰ days of life (birth, weaning and 60ᵗʰ day of average weight) were found significant statistically (p < 0.001). The maternal age affected only birth weight (p < 0,001). The effects month at birth on all of the investigated day [the birth, 120ᵗʰ, 180ᵗʰ days (p < 0.05); the weaning, 60ᵗʰ, 90ᵗʰ days (p < 0,001)] were found significant. The birth type was found significant on the birth (p < 0,001), weaning (p < 0,01), 60ᵗʰ (p < 0,01) and 90ᵗʰ (p < 0,01) days of average live weights. As a result, screening the other regions of CSN3, AGPAT6 gene and also investigation the phenotypic association of them should be useful to clarify the efficiency of target genes. Environmental factors such as maternal age, year, sex and birth type were found significant on some growth, fertility and milk traits in Saanen goats. So consideration of these factors could be used as selection criteria in dairy goat breeding.

Keywords: fertility, growth, milk yield, Saanen goats

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Authors: Reza Hedayati, Meysam Jahanbakhshi

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In this work, Fracture Mechanics is used to predict crack propagation in the adhesive joining aluminum and composite plates. Three types of loadings and two types of glass-epoxy composite sequences: [0/90]2s and [0/45/-45/90]s are considered for the composite plate. Therefore, 2*3=6 cases are considered and their results are compared. The debonding initiation load, complete debonding load, crack face profile and load-displacement diagram have been compared for the six cases.

Keywords: adhesive joint, debonding, fracture, LEFM, APDL

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Authors: S. Benbellil-Tafoughalt, J. M. Koene

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Growth strategies are often plastic and influenced by environmental conditions. Terrestrial gastropods are particularly affected by seasonal and climatic variables, and growth rate and size at maturity are key traits in their life history. Therefore, we investigated juvenile growth of Helix aperta snails under four combinations of temperature and photoperiod using two sets of young snails, born in the laboratory from adults collected in either the autumn (aestivating snails) or spring (active snails). Parental snails were collected from Bakaro (Northeastern Algeria). Higher temperature increased adult size and reduced time to reproduction. Long day photoperiod also increased the final body weight, but had no effect on the length of the growth period. The season of birth had significant effects on length of the growth period and weight of hatchings, whereas this weight difference disappeared by adulthood. The spring snails took less time to develop and reached similar adult body weight as the autumn snails. These differences may be due to differences in egg size or quality between the snails from different seasons. More rapid growth in spring snails results in larger snails entering aestivation, a period with size-related mortality in this species.

Keywords: growth, Hélix aperta, photoperiod, temperature

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Authors: Alessandro Falconieri, Sara De Vincentiis, Vittoria Raffa

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Mechanical force regulates axonal growth, elongation and maturation processes. This force is opening new frontiers in the field, contributing to a general understanding of the mechanisms of axon growth that, in the past, was thought to be governed exclusively by the growth cone and its ability to influence axonal growth in response to chemical signals. A method recently developed in our laboratory allows, through the labeling of neurons with magnetic nanoparticles (MNPs) and the use of permanent magnets, to apply extremely low mechanical forces, similar to those generated endogenously by the growth cone or by the increase of body mass during the organism growth. We found that these extremely low forces strongly enhance the spontaneous axonal elongation rate as well as neuronal sprouting. Data obtained don’t exclude that local phenomena, such as local transport and local translation, may be involved. These new advances could shed new light on what happens when the cell is subjected to external mechanical forces, opening new interesting scenarios in the field of mechanobiology.

Keywords: axon, external mechanical forces, magnetic nanoparticles, mechanotransduction

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Authors: Prashant Dhiman, Viranshu Kumar, Pradeep Joshi

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Lot of research is going on to study the effect of cryogenic treatment on materials. Cryogenic treatment is a heat treatment process which is used widely to enhance the mechanical and metallurgical properties of various materials whether the material is ferrous or non ferrous. In almost all ferrous metals, it is found that retained austenite is converted into martensite. Generally deep cryogenic treatment is done using liquid nitrogen having temperature of -195 ℃. The austenite is unstable at this stage and converts into martensite. In non ferrous materials there presents a microcavity and under the action of stress it becomes crack. When this crack propagates, fracture takes place. As the metal contract under low temperature, by doing cryogenic treatment these microcavities will be filled hence increases the soundness of the material. Properties which are enhanced by cryogenic treatment of both ferrous and non ferrous materials are hardness, tensile strength, wear rate, electrical and thermal conductivity, and others. Also there is decrease in residual stress. A large number of manufacturing process (EDM, CNC etc.) are using cryogenic treatment on different tools or workpiece to reduce their wear. In this Review paper the use of cryogenic heat treatment in different manufacturing has been shown along with their advantages.

Keywords: cyrogenic treatment, EDM (Electrical Discharge Machining), CNC (Computer Numeric Control), Mechanical and Metallurgical Properties

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Authors: Khalil Aghapouramin

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The aim of the present work is to investigate the mechanical and microstructural properties of dissimilar and similar aluminum alloys welded by Friction Stir Welding (FSW). The specimens investigated by applying different welding speed and rotary speed. Typically, mechanical properties of the joints performed through tensile test fatigue test and microhardness (HV) at room temperature. Fatigue test investigated by using electromechanical testing machine under constant loading control with similar since wave loading. The Maximum stress versus minimum got the range between 0.1 to 0.3 in the research. Based upon welding parameters by optical observation and scanning electron microscopy microstructural properties fulfilled with a cross section of welds, in addition, SEM observations were made of the fracture surfaces

Keywords: friction stir welding, fatigue and tensile test, Al alloys, microstructural behavior

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Authors: A. Mir, C. Aribi, B. Bezzazi

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Work presented is interested in the characterization of the quasistatic mechanical properties and in fatigue of a composite laminated in jute/epoxy. The natural fibers offer promising prospects thanks to their interesting specific properties, because of their low density, but also with their bio deterioration. Several scientific studies highlighted the good mechanical resistance of the vegetable fiber composites reinforced, even after several recycling. Because of the environmental standards which become increasingly severe, one attends the emergence of eco-materials at the base of natural fibers such as flax, bamboo, hemp, sisal, jute. The fatigue tests on elementary vegetable fibers show an increase of about 60% of the rigidity of elementary fibers of hemp subjected to cyclic loading. In this study, the test-tubes manufactured by the method infusion have sequences of stacking of 0/90° and ± 45° for the shearing and tensile tests. The quasistatic tests reveal a variability of the mechanical properties of about 8%. The tensile fatigue tests were carried out for levels of constraints equivalent to half of the ultimate values of the composite. Once the fatigue tests carried out for well-defined values of cycles, a series of static tests of traction type highlights the influence of the number of cycles on the quasi static mechanical behavior of the laminate jute/epoxy.

Keywords: jute, epoxy resin, mechanical, static, dynamic behavior

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Authors: Philip Rose, Markus Linke, David Busquets

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The distinction between interlaminar and intralaminar fracture toughness has already been investigated by several authors. For loading mode I, the double cantilever beam specimens were often used for the interlaminar fracture toughness and the compact tension specimen for the intralaminar fracture toughness. In order to minimize the influence of the different specimen geometries, a method was developed which allows the determination of both the interlaminar and the intralaminar fracture toughness on an almost identical specimen geometry. However, as this method is not applicable to prepreg semi-finished products, a further modification was developed, which is also suitable for prepreg laminates. After the successful application for the investigation of mode I with this method, the application of the method for loading mode II is presented in this paper. In addition to manufacturing differences, due to an additional fiber ply in which the controlled crack growth takes place, the adapted test procedure is also explained. By comparing the test results of standardized end-notched flexure (ENF) specimens with those of the modified ENF specimen, the difference between the interlaminar and intralaminar fracture toughness of the material Hexply 8552/IM7 is shown.

Keywords: ENF, fracture toughness, interlaminar, mode II

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Authors: Sanjeev Kumar, Vikas Kumar

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Inconel 718 (IN718) is a high strength nickel-based superalloy designed for high-temperature applications up to 650 °C. It is widely used in gas turbines of jet engines and related aerospace applications because of its good mechanical properties and structural stability at elevated temperatures. Because of good performance ratio and excellent process capability, this alloy has been used predominantly for aeronautic engine components like compressor disc and compressor blade. The main precipitates that contribute to high-temperature strength of IN718 are γʹ Ni₃(Al, Ti) and mainly γʹʹ (Ni₃ Nb). Various processes have been used for modification of the surface of components, such as Laser Shock Peening (LSP), Conventional Shot Peening (SP) and Ultrasonic Shot Peening (USP) to induce compressive residual stress (CRS) and development of fine-grained structure in the surface region. Surface nanostructure by ultrasonic shot peening is a novel methodology of surface modification to improve the overall performance of structural components. Surface nanostructure was developed on the peak aged IN718 superalloy using USP and its effect was studied on low cycle fatigue (LCF) life. Nanostructure of ~ 49 to 73 nm was developed in the surface region of the alloy by USP. The gage section of LCF samples was USPed for 5 minutes at a constant frequency of 20 kHz using StressVoyager to modify the surface. Strain controlled cyclic tests were performed for non-USPed and USPed samples at ±Δεt/2 from ±0.50% to ±1.0% at strain rate (ė) 1×10⁻³ s⁻¹ under reversal loading (R=‒1) at room temperature. The fatigue life of the USPed specimens was found to be more than that of the non-USPed ones. LCF life of the USPed specimen at Δεt/2=±0.50% was enhanced by more than twice of the non-USPed specimen.

Keywords: IN718 superalloy, nanostructure, USP, LCF life

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Authors: Alae Lamtai, Said Elkoun, Hniya Kharmoudi, Mathieu Robert, Carl Diez

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This study applies Taguchi's design of experiment methodology and grey relational analysis (GRA) for multi objective optimization of an industrial recycling line. This last is composed mainly of a mono and twin-screw extruder and a filtration system. Experiments were performed according to L₁₆ standard orthogonal array based on five process parameters, namely: mono screw design, screw speed of the mono and twin-screw extruder, melt pump pressure, and filter mesh size. The objective of this optimization is to improve the durability of the Polyethylene (PE) blend by decreasing the loss of Stress Crack resistance (SCR) using Notched Crack Ligament Stress (NCLS) test and Unnotched Crack Ligament Stress (UCLS) in parallel with increasing the gain of Izod impact strength of the Polyethylene (PE) blend before and after recycling. Based on Grey Relational Analysis (GRA), the optimal setting of process parameters was identified, and the results indicated that the mono-screw design and screw speed of both mono and twin-screw extruder impact significantly the mechanical properties of recycled Polyethylene (PE) blend.

Keywords: Taguchi, recycling line, polyethylene, stress crack resistance, Izod impact strength, grey relational analysis

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Authors: Vaclav Mentl, P. Zlabek, J. Volak

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New methods of mechanical testing were developed recently that are based on making use of miniature test specimens (e.g. Small Punch Test). The most important advantage of these method is the nearly non-destructive withdrawal of test material and small size of test specimen what is interesting in cases of remaining lifetime assessment when a sufficient volume of the representative material cannot be withdrawn of the component in question. In opposite, the most important disadvantage of such methods stems from the necessity to correlate test results with the results of standardised test procedures and to build up a database of material data in service. The correlations among the miniature test specimen data and the results of standardised tests are necessary. The paper describes the results of fatigue tests performed on miniature tests specimens in comparison with traditional fatigue tests for several steels applied in power producing industry. Special miniature test specimens fixtures were designed and manufactured for the purposes of fatigue testing at the Zwick/Roell 10HPF5100 testing machine. The miniature test specimens were produced of the traditional test specimens. Seven different steels were fatigue loaded (R = 0.1) at room temperature.

Keywords: mechanical properties, miniature test specimens, correlations, small punch test, micro-tensile test, mini-charpy impact test

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Authors: Raymond K. Dziwornu

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Lending rate of agriculture loan has persistently been high and attributed to risk in the sector. This study examined how food inflation and agriculture lending rate react to each other in Ghana using vector autoregressive approach. Quarterly data from 2006 to 2018 was obtained from the Bank of Ghana quarterly bulletin and the Ghana Statistical Service reports. The study found that a positive standard deviation shock to food inflation causes lending rate of agriculture loan to react negatively in the short run, but positively and steadily in the long run. This suggests the need to direct appropriate policy measures to reduce food inflation and consequently, the cost of credit to the agricultural sector for its growth.

Keywords: food inflation, agriculture, lending rate, vector autoregressive, Ghana

Procedia PDF Downloads 127

Authors: Radwa Elshorbagy, Alaa Elden Balbaa, Khaled Ayad, Waleed Reda

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Introduction: Ankle sprain is a common lower limb injury that is complicated by high recurrence rate. The cause of recurrence is not clear; however, changes in motor control have been postulated. Objective: to determine the contribution of proximal hip strategy to dynamic postural control in patients with recurrent ankle sprain. Methods: Fifteen subjects with recurrent ankle sprain (group A) and fifteen healthy control subjects (group B) participated in this study. Abductor-adductors as well as flexor-extensor hip musculatures control was abolished by fatigue using the Biodex Isokinetic System. Dynamic postural control was measured before and after fatigue by the Biodex Balance System. Results: Repeated measures MANOVA was used to compare between and within group differences, in group A fatiguing of hip muscles (flexors-extensors and abductors-adductors) increased overall stability index (OASI), anteroposterior stability index (APSI) and mediolateral stability index (MLSI) significantly (p=0.00) whereas; in group B fatiguing of hip flexors-extensors increased significantly OASI and APSI only (p= 0.017, 0.010; respectively) while fatiguing of hip abductors-adductors has no significant effect on these variables. Moreover, patients with ankle sprain had significantly lower dynamic balance after hip muscles fatigue compared to the control group. Specifically, after hip flexor-extensor fatigue, the OASI, APSI and MLSI were increased significantly than those of the control values (p= 0.002, 0.011, and 0.003, respectively) whereas fatiguing of hip abductors-adductors increased significantly in OASI and APSI only (p=0.012, 0.026, respectively). Conclusion: To maintain dynamic balance, patients with recurrent ankle sprain seem to rely more on the hip strategy. This means that those patients depend on a top to down instead of down to top strategy clinical relevance: patients with recurrent ankle sprain less efficient in maintaining the dynamic postural control due to the change in motor strategies. Indicating that health care providers and rehabilitation specialists should treat CAI as a global/central and not just as a simple local or peripheral injury.

Keywords: hip strategy, ankle strategy, postural control, dynamic balance

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Authors: J. H. Lv, W. Z. Wang, S.W. Liu

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The major concern in the aviation industry is the flight safety. Although great effort has been put onto the development of material and system reliability, the failure cases of fatal accidents still occur nowadays. Due to the complexity of the aviation system, and the interaction among the failure components, the failure analysis of the related equipment is a little difficult. This study focuses on surveying the failure cases in aviation, which are extracted from failure analysis journals, including Engineering Failure Analysis and Case studies in Engineering Failure Analysis, in order to obtain the failure sensitive factors or failure sensitive parts. The analytical results show that, among the failure cases, fatigue failure is the largest in number of occurrence. The most failed components are the disk, blade, landing gear, bearing, and fastener. The frequently failed materials consist of steel, aluminum alloy, superalloy, and titanium alloy. Therefore, in order to assure the safety in aviation, more attention should be paid to the fatigue failures.

Keywords: aerospace, disk, failure analysis, fatigue

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Authors: Bozena Leven

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The middle-income trap (MIT) describes a situation faced by countries at a relatively mature stage of development that often poses an obstacle to sustainable long-term growth. MIT is characterized by declining factor productivity from the exhaustion of labor intensive, import and Foreign Direct Investment (FDI) based strategies when middle-income status is achieved. In this paper, we focus on MIT and Poland. In the past two decades, Poland experienced steady growth based largely on imported technologies and low-cost labor. Recently, that economic growth has slowed, prompting economists to ask whether Poland is experiencing MIT. To answer this question, we analyze changes in investment in Poland; specifically- its growth and composition – as well as savings, FDI, educational attainments of the labor force, development of new technologies and products, the role of imports, diversification of exports, and product complexity. We also examine the development of modern infrastructure, institutions (including legal environment) and demographic changes in Poland that support growth. Our findings indicate that certain factors consistent with MIT are gaining importance in Poland, and represent a challenge to that country’s future growth rate.

Keywords: engines of growth, factor productivity, middle income trap, sustainable development

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Authors: Frederick Monyepao

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Crack cocaine first appeared on the scene in the form of cocaine freebasing in the late 1970s. Stockbrokers, investment bankers, rock stars, Hollywood elites, and a few pro athletes were regular users of the substance. As criminogenic factors associated with substance abuse began to surface, congress passed new legislation. The laws led to the increase of health coverage insurances and the expansion of hospitals. By the mid-1980s, crack use spread into America's inner cities among impoverished African Americans and Latinos. While substance abuse increased among minority communities, legislation pertaining to substance abuse evolved. The prison industry also expanded the number of cells available. A qualitative approach was taken, drawing from a range secondary sources for contextual analysis. This paper traces out the continued marginalisation and racist undertones towards minorities as perpetuated by certain drug policies. It was discovered that the new legislation on crack was instrumental in the largest incarcerations the United States ever faced. Drug offenders increased in prisons eightfold from 1986 to 2000. The paper concludes that American drug control policies are consistently irrational and ineffective when measured by levels of substance use and abuse. On the contrary, these policies have been successful as agents of social control in maintaining the stratification patterns of racial/ethnic minorities and women. To move beyond prohibition, radical law and policy reform may require a change in narratives on substance use.

Keywords: crack, drug policy, minorities, racism, substance abuse

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Authors: L. Torchane

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This study is devoted to defining the optimal conditions for the nitriding of pure iron at atmospheric pressure by using NH3-Ar-C3H8 gas mixtures. After studying the mechanisms of phase formation and mass transfer at the gas-solid interface, a mathematical model is developed in order to predict the nitrogen transfer rate in the solid, the ε-carbonitride layer growth rate and the nitrogen and carbon concentration profiles. In order to validate the model and to show its possibilities, it is compared with thermogravimetric experiments, analyses and metallurgical observations (X-ray diffraction, optical microscopy and electron microprobe analysis). Results obtained allow us to demonstrate the sound correlation between the experimental results and the theoretical predictions.

Keywords: gaseous nitrocarburizing, kinetic model, diffusion, layer growth kinetic

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Authors: Clara Theresia, Hardianto Iridiastadi

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Drowsiness is one of the main factors that contribute to the occurrence of accidents, particularly in the transportation sector. While the effects of sleep deprivation on cognitive functions have been reported, the exact relationships remain a critical issue. This study aimed at quantifying the effects of extreme sleep deprivation on vigilance, fatigue, and performance during simulated train driving. A total of 12 participants were asked to drive a train simulator continuously for 4 hours, either in a sleep deprived condition (2-hr of sleep) or normal (8-hr of sleep) condition. Dependent variables obtained during the task included Psychomotor Vigilance Task (PVT) parameters, degree of fatigue (assessed via Visual Analogue Scale/VAS) and sleepiness (reported using Karolinska Sleepiness Scale/KSS), and driving performance (the number of speed limit violations). Findings from this study demonstrated substantial decrements in vigilance in the sleep-deprived condition. This condition also resulted in 75% increase in speed violation and a two-fold increase in the degree of fatigue and sleepiness. Extreme sleep deprivation was clearly associated with substantially poorer response. The exact effects, however, were dependent upon the types of responses.

Keywords: cognitive function, psychomotor vigilance task, sleep deprivation, train simulator

Procedia PDF Downloads 167

Authors: Fayçal Benyahia, Abdelmohsen Albedah, Bel Abbes Bachir Bouiadjra

Abstract:

In this study the Finite element method is used to analyse the effect of the thermal residual stresses resulting from adhesive curing on the performances of the bonded composite repair in aircraft structures. The stress intensity factor at the crack tip is chosen as fracture criterion in order to estimate the repair performances. The obtained results show that the presence of the thermal residual stresses reduces considerably the repair performances and consequently decreases the fatigue life of cracked structures. The effects of the curing temperature, the adhesive properties and the adhesive thickness on the Stress Intensity Factor (SIF) variation with thermal stresses are also analysed.

Keywords: bonded composite repair, residual stress, adhesion, stress transfer, finite element analysis

Procedia PDF Downloads 399

Authors: Abubakar O. Sulaiman

Abstract:

Agriculture was the main stay of Nigeria’s economy before the oil boom of the 1970s caused a gradual but steady shift from agriculture to crude oil as the major source of revenue and foreign exchange. The economy later experienced many symptoms of the 'Dutch disease', with exchange rate appreciation and erosion of competitiveness of the non-oil tradable goods. In order to reverse the worsening economic situations -high unemployment, galloping inflation, deteriorating balance of payment, declining economic growth, and fiscal deficits among others- the government, embarked on austerity measures in 1982 and Structure Adjustment Programme (SAP) in 1986. One of the cornerstones of SAP is the diversification of the economy from oil to non-oil. In the form of stocktaking, this paper investigates the impact of non-oil revenue on economic growth in Nigeria using quarterly time-series data from 1980 to 2019. The findings revealed that a long-run relationship exists between the variables (non-oil variables) and economic growth in Nigeria. Among the variables, (agriculture revenue, manufacturing revenue, revenue from services, and company income tax) contributed substantially to economic growth. The paper recommends that the government should continue to intensify efforts and policies in the diversification of the economy as it will bring about sustainable non-oil revenue and economic growth.

Keywords: non-oil revenue, economic growth, export, long run relationship

Procedia PDF Downloads 141

Authors: Okolo Chimaobi Valentine, Obidigbo Chizoba

Abstract:

As a basic physiology need, the threat to sufficient food production is the threat to human survival. Food security has been an issue that has gained global concern. This paper looks at the food security in Nigeria by assessing the availability of food and accessibility of the available food. The paper employed multiple linear regression technique and graphic trends of growth rates of relevant variables to show the situation of food security in Nigeria. Results of the tests revealed that population growth rate was higher than the growth rate of food availability in Nigeria for the earlier period of the study. Commercial bank credit to the agricultural sector, foreign exchange utilization for food and the Agricultural Credit Guarantee Scheme Fund (ACGSF) contributed significantly to food availability in Nigeria. Food prices grew at a faster rate than the average income level, making it difficult to access sufficient food. It implies that prior to the year 2012; there was insufficient food to feed the Nigerian populace. However, continued credit to the food and agricultural sector will ensure sustained and sufficient production of food in Nigeria. Microfinance banks should make sufficient credit available to the smallholder farmer. The government should further control and subsidize the rising price of food to make it more accessible by the people.

Keywords: food, accessibility, availability, security

Procedia PDF Downloads 349

Authors: Anton A. Bykov, Irina O. Glot, Igor N. Shardakov, Alexey P. Shestakov

Abstract:

This paper presents the results of experimental and theoretical investigations of the mechanisms of crack formation in reinforced concrete beams subjected to quasi-static bending. The boundary-value problem has been formulated in the framework of brittle fracture mechanics and has been solved by using the finite-element method. Numerical simulation of the vibrations of an uncracked beam and a beam with cracks of different size serves to determine the pattern of changes in the spectrum of eigenfrequencies observed during crack evolution. Experiments were performed on the sequential quasistatic four-point bending of the beam leading to the formation of cracks in concrete. At each loading stage, the beam was subjected to an impulse load to induce vibrations. Two stages of cracking were detected. At the first stage the conservative process of deformation is realized. The second stage is an active cracking, which is marked by a sharp change in eingenfrequencies. The boundary of a transition from one stage to another is well registered. The vibration behavior was examined for the beams strengthened by carbon-fiber sheet before loading and at the intermediate stage of loading after the grouting of initial cracks. The obtained results show that the vibrodiagnostic approach is an effective tool for monitoring of cracking and for assessing the quality of measures aimed at strengthening concrete structures.

Keywords: crack formation, experiment, mathematical modeling, reinforced concrete, vibrodiagnostics

Procedia PDF Downloads 281