Transitional two-phase flow around 90° bends of different orientations

Considering the gap in available information and the need of the industries such as oil and gas production, energy, and food processing, this study focuses on the two phase flows around bends in process pipe lines. The aim of this study is to investigate the influence of 90° bends on the gas-liquid two phase flow behaviour in vertical and horizontal orientations using advanced two-phase flow measuring techniques. An experimental study has been conducted using silicone oil with a viscosity of 5 mPa.s and air to examine the transitional flows around 90° bends of 68 mm internal diameter (ID) with different configurations. Experiments were conducted at ambient conditions in an open system which consists of a 68 mm ID riser of 4.5 m long, vertical upward 90° bend and two horizontal sections of a 9.2m and 5.5m long in series with a horizontal 90° bend in between. The experimental matrix comprises 60 combinations of gas and liquid superficial velocities, ranging from 0.045 m.s-1 to 3.21 m.s-1 and 0.15 m.s-1 to 0.53 m.s-1 respectively. The phase distributions within the pipes were measured using Electrical Capacitance Tomography (ECT) and Wire Mesh Sensors (WMS). The behaviour of the flow was examined qualitatively using high speed imaging. To study the flow development in the riser, both ECT and WMS were placed in series and moved along three axial locations downstream of the mixing section. During the experiments at the bends, the ECT was kept immediately upstream while the WMS was moved to different positions downstream of the bend. The cross-sectional void fraction time series from the ECT and the WMS were used to quantify the main hydrodynamic parameters of the flow including cross-sectional averaged void fraction, bubble size distribution, radial void fraction profiles, slug length, slug frequency, void fraction in liquid slugs, and the slug bubble velocity. Results were compared against the available slug flow correlations. The results show that the phases separate shortly after the vertical to horizontal bend leading to stratified or wavy stratified flow. Beyond a certain threshold of the gas flow rate and liquid level, onset of slugs can be observed at a certain distance downstream of the vertical upward bend. This work suggests that the formation of hydrodynamic slugs downstream of the vertical upward bend is independent of the inlet conditions upstream. The horizontal bend, unlike the vertical upward bend, has a minor influence on the flow evolution, particularly slug flow. This is due to the influence of gravitational force on phase separation and its subsequent effect on the change of momentum in the vertical bend. The flow structures, mainly slugs and disturbance waves, are slightly accelerated as they pass through the horizontal bend with minimum change to the structure frequency and gas holdup within liquid slugs. Most of the existing correlations do not predict the measured void fractions in this work as those correlations were essentially limited to the conditions they were developed for as the basis of them lies in the curve fitting. In this work, the higher viscosity and lower surface tension led to higher gas holdup in liquid slugs causing the discrepancy

Influence of Elevated Temperature on the Mechanical Properties of Hybrid Flax-Fiber-Epoxy Composites Incorporating Graphene

Natural fibers are now becoming widely adopted as reinforcements for polymer matrices to produce biodegradable and renewable composites. These natural composites have mechanical properties acceptable for use in many industrial and structural applications under ambient temperatures. However, there is still limited understanding regarding the mechanical performance of natural fiber composites when exposed to in-service elevated temperatures. Moreover, nanoparticle additives are widely utilized in reinforced composites as they can enhance mechanical, thermal, and physical performance. Therefore, this research extensively investigates the interlaminar shear strength (ILSS) and flexural properties of flax fiber composites with graphene at different weight percentages (0%, 0.5%, 1%, and 1.5%) and exposed to in-service elevated temperatures (20, 40, 60, 80, and 100 °C). Mechanical tests were conducted followed by microscopic observations to analyze the interphase between the flax fibers and epoxy resin. The results showed that a significant improvement in flexural strength, modulus, and interlaminar shear strength of the composites was achieved by adding 0.5% of graphene. Increasing the graphene to 1.0% and 1.5% gradually decreased the enhancement in the flexural and ILSS strength. SEM observations showed that voids caused by filler agglomeration were increasingly formed in the natural fiber reinforced composites with the increase in graphene addition

Durability of hybrid flax fibre-reinforced epoxy composites with graphene in hygrothermal environment

Natural fibre composites are highly sensitive to the hygrothermal environment (humidity and elevated in-service temperature). Enhancing the long-term behaviour of such composites can be achieved through additive manufacturing using nanomaterials as a constituent. Thus, this study investigated the mechanical properties of hybrid flax fibre-reinforced epoxy composites with 0%, 0.5%, 1% and 1.5% of graphene nanoparticles after exposure to a relative humidity of 98% for 1000, 2000, and 3000 hours and at temperature of 20°C, 40°C, and 60°C. The degradation behaviour of hybrid natural fibre composites was then evaluated by flexural and inter-laminar shear tests. Hygrothermal conditioning simulation of these hybrid composites was then performed using Arrhenius model based on accelerated aging data. The results of this study showed that graphene nanoparticles played a significant role in the reduction of moisture absorption and in the improvement of mechanical properties after hygrothermal conditioning. Compared to the specimens without graphene nanoparticles, the flexural and interlaminar shear strength in hybrid composites with 0.5%, 1.0%, and 1.5% graphene increased by 77.7%, 72.0%, and 77.1%, respectively, and up to 75.5%, 70.6%, and 73.5%, respectively after exposure for 3000 hours at 40°C. However, the degradation of the hybrid composites increased with the increase of conditioning temperature and exposure duration due to the moisture diffusion into the flax fibres and resin plasticisation. Nevertheless, the 0.5% graphene nanoparticles were found optimal in retaining the mechanical properties of aged hybrid composites due to their better distribution within the matrix. Accelerated test results showed that the hybrid composites can retain at least 57% and 49% of its flexural and interlaminar shear strength, respectively, after 100 years in service in hygrothermal environment at a temperature of 30°C representing the average annual temperature in Australia

Long-Term Water Absorption of Hybrid Flax Fibre-Reinforced Epoxy Composites with Graphene and Its Influence on Mechanical Properties

Interest in the use of natural fibres as an alternative for artificial fibres in polymer composite manufacturing is increasing for various engineering applications. Their suitability for use in outdoor environments should be demonstrated due to their perceived hydrophilic behaviour. This study investigated the water absorption behaviour of hybrid flax fibre-reinforced epoxy composites with 0%, 0.5%, 1% and 1.5% graphene by weight that were immersed in water for 1000, 2000, and 3000 h. The flexural and interlaminar shear strength before and after immersion in water was then evaluated. The results showed that graphene nanoparticles improved the mechanical properties of the composites. The moisture absorption process of hybrid natural fibre composites followed the Fickian law, whereas the addition of graphene significantly reduced the moisture absorption and moisture diffusion, especially for hybrid composites with 1.5% graphene. However, the flexural and ILSS properties of the composites with and without graphene decreased with the increase in the exposure duration. The flexural strength of hybrid composites with 0%, 0.5%, 1% and 1.5% graphene decreased by 32%, 11%, 17.5% and 13.4%, respectively, after exposure for 3000 h. For inter-laminar shear strength at the same conditioning of 3000 h, hybrid composites with 0.5%, 1% and 1.5% graphene also decreased by 13.2%, 21% and 17.5%, respectively, compared to the dry composite’s strength. The specimens with 0.5% graphene showed the lowest reduction in strength for both the flexural and interlaminar tests, due to good filler dispersion in the matrix, but all of them were still higher than that of flax fibre composites. Scanning electron microscope observations showed a reduction in voids in the composite matrix after the introduction of graphene, resulting in reduced moisture absorption and moisture diffusion

Infantile Osteopetrosis in Two Siblings: Case Report

Case repor

أثر الخصائص الشخصية للمزارعين وحجم الحيازة الزراعية على تبني الزراعة التعاقدية في محافظة اللاذقية

هدف البحث إلى دراسة تأثير بعض الخصائص الشخصية للمزارع كالمستوى التعليمي والخبرة الزراعية، بالإضافة لحجم الحيازة الزراعية على تبني الزراعة التعاقدية في محافظة اللاذقية، ولتحقيق أهداف البحث تم أخذ عينة من المزارعين الذين يعملون وفق نظام التعاقد في محافظة اللاذقية قوامها 400 مزارع حيث تم اختيار ثلاث مناطق كالتالي (منطقة اللاذقية – منطقة جبلة – منطقة الحفة)، ومن كل منطقة تم اختيار قريتين، بالإضافة إلى سوق الهال. اعتمد البحث المنهج الوصفي، بهدف وصف المتغيرات المدروسة وإلقاء الضوء على جوانبها المختلفة بغرض فهمها وتحديد أسبابها باستخدام الجداول التكرارية والنسب المئوية، كما تم استخدام المنهج الكمي القياسي باستخدام المؤشرات والاختبارات كمعامل الثبات (Cronbach's Alpha) كمقياس ليكرت واختبار تحليل التباين (ANOVA) لاختبار فرضيات البحث. أظهرت نتائج البحث أن أغلب المزارعين يتعاقدون بالمناصفة ونسبة قليلة منهم تتعاقد بنظام الريع أو الأجر وآخرون يتعاقدون بكامل الأرض. كما أشارت النتائج أن مشاكل المديونية وعدم عدالة الجهات المتعاقدة في التوزيع من أهم المشكلات التي تواجه المزارعين المتعاقدين بالإضافة للتلاعب بالحصص بحيث لا يتم شراء كامل الإنتاج. أظهرت نتائج اختبار فرضيات البحث وجود آثر إيجابي دال إحصائياً لكل من خبرة المزارع، والمستوى التعليمي، وحجم الحيازة الزراعية (sig<0.05) على تبني الزراعة التعاقدية

The influence of fibres on the properties and sustainability of oil-impacted concrete

There are significant environmental and health consequences associated with oil-contaminated sand due to its toxic and persistent nature. The impacts include disrupted ecosystems with harm to plants and animals and contamination of water sources, requiring immediate and sustained remediation. Using oil-contaminated sand in construction addresses waste management and promotes sustainability by reducing waste, protecting the environment, saving energy, and driving innovation. This study investigates the impact of crude oil-contaminated sand on concrete’s physical and mechanical characteristics. It focuses on assessing the impact of incorporating four different fibres (Forta Ferro PP, ReoShore 45 PP, glass, and steel fibres) and finding the optimal quantity (0.1, 0.2, 0.3, 0.4 or 0.5%) to improve the physical and mechanical properties of concrete prepared with sand contaminated by crude oil. The impact of crude oil on the bond strength between fibres and concrete was examined. Additionally, the effect of crude oil on heat flow and cumulative heat was analysed. The results demonstrated that increasing oil content decreases concrete density and compressive strength. Nevertheless, the findings indicated that sand contaminated with 10% oil is suitable for low-strength concrete applications. Incorporating 0.1% of Forta Ferro PP, glass, and ReoShore 45 PP fibres had a negligible impact on the mechanical properties of concrete contaminated with 10% oil. Comparatively, steel fibres enhanced the concrete’s compressive strength by 30% at 0.1%, and the flexural strength improved by 9.6% at 0.5%. Concrete with a 10% crude oil content reinforced with steel fibres hinders fracture stabilisation and load transfer, making it suitable as a sustainable material for low-strength civil engineering applications

Hospital-based surveillance study of rotavirus gastroenteritis in children under 5 years of age in Lebanon

AbstractBackgroundRotavirus (RV) is a major cause of gastroenteritis (GE) in infants and young children globally, with rotavirus gastroenteritis (RVGE) causing dehydration due to diarrhea and frequently leading to hospitalization. Epidemiological data on RVGE in Lebanon are lacking, therefore this study aims to collect such baseline data.MethodsWe conducted multicenter, hospital-based surveillance across Lebanon to estimate the proportion of diarrheal hospitalizations attributable to RV in children under 5 years of age. Medical history, GE symptoms, treatment prior to hospitalization and demographics were obtained from medical records and parent/guardian interviews. The severity of GE episodes was determined using the 20-point Vesikari scale (score ⩾11 was considered severe). Stool samples were analyzed for RV using an enzyme immunoassay and for strain prevalence using reverse transcriptase polymerase chain reaction.ResultsBetween April 2007 and September 2008, a total of 534 subjects were enrolled, of whom 491 were included in the final analysis. GE attributable to RV was 27.7% and nearly 75% of the RVGE cases occurred in children under 2 years of age. No differences were observed between the severity of signs and symptoms in RV positive and negative subjects. Hospitalization occurred mainly between December–March and lasted for a median of 3 days. Treatment primarily consisted of intravenous rehydration and almost all subjects (96.1%) had recovered by the time of discharge. Prevalent circulating G and P types were G4 (36.9%), G1WT (29.2%), P[8]WT (77.7%) and P[4] (17.7%); the most common circulating RV strain was G4P[8]WT (36.9%).ConclusionRVGE hospitalizations are prevalent in children under 5 years of age in Lebanon. This baseline data might be useful for decision makers when initiating measures, such as vaccination, to prevent the disease

Fluid structure behaviour in gas-oil two-phase flow in a moderately large diameter vertical pipe

Intermittent flows in vertical pipes occur in many industrial settings including power generation and downstream oil-and gas production. This type of flows include cap bubble, slug and churn flow regimes. These regimes are of interest as downstream processes and control may heavily depend on the intermittency of the inflow. There are a number of correlations that predicts the features in such flows in vertical pipes. Most of the correlations were developed for air and water fluid pair for slug flow regime in vertical pipes with 25 to 50 mm inner diameter. In this paper, an attempt has been made to assess the suitability of several of these correlations specific to slug flow regime for a fluid pair that is different to air-water system. In this work, air-silicone oil flow development was experimentally investigated in a vertical pipe with an inner diameter of 68mm. A Wire Mesh Sensor (WMS) and an Electrical Capacitance Tomography (ECT) sensor were installed in series at four locations (15D, 30D, 45D and 65D) downstream of the mixing section. The flow was visually observed using a high speed camera. The void fraction time series obtained from the WMS and the ECT were used to establish the flow characteristics such as slug length, slug frequency, void fraction in liquid slugs and Taylor bubble velocity. A comparison showed that the void fraction measurements using ECT and WMS are in good agreement. Axial measurements shows that the flow development beyond 45D is minimal. Change in physical properties of the liquid phase is responsible for the deviation associated with the existing slug flow models, particularly those developed to predict the gas holdup in liquid slugs

Behavior of circular concrete columns reinforced with hollow composite sections and GFRP bars

Hollow concrete columns (HCCs) constitute a structurally efficient construction system for marine and offshore structures, including bridge piers and piles. Conventionally, HCCs reinforced with steel bars are vulnerable to corrosion and can lose functionality as a result, especially in harsh environments. Moreover, HCCs are subjected to brittle failure behavior by concrete crushing due to the absence of the concrete core. Therefore, this study investigated the use of glass fiber- reinforced polymer (GFRP) bars as a solution for corrosion and the use of hollow composite- reinforced sections (HCRSs) to confine the inner concrete wall in HCCs. Furthermore, this study conducted an in-depth assessment of the effect of the reinforcement configuration and reinforcement ratio on the axial performance of HCCs. Eight HCCs with the same lateral- reinforcement configuration were prepared and tested under monotonic loading until failure. The column design included a column without any longitudinal reinforcement, one reinforced longitudinally with an HCRS, one reinforced longitudinally with GFRP bars, three reinforced with HCRSs and different amounts of GFRP bars (4, 6, and 8 bars), and three reinforced with HCRSs and different diameters of GFRP bars (13, 16, 19 mm). The test results show that longitudinal reinforcement—whether GFRP bars or HCRSs—significantly enhanced the strength and displacement capacities of the HCCs. Increasing the amount of GFRP bars was more effective than increasing the bar diameter in increasing the confined strength and the displacement capacity. The axial-load capacity of the GFRP/HCRS-reinforced HCCs could be accurately estimated by calculating the load contribution of the longitudinal reinforcement, considering the axial strain at the concrete peak strength. A new confinement model considering the combined effect of the longitudinal and transverse reinforcement in the lateral confinement process was also developed