Mechanical Properties of Concrete and Mortar Containing Low Density Polyethylene Waste Particles as Fine Aggregate

Iraq industrial activities related to huge amounts of solid, non-biodegradable waste, waste low density Polyethylene (LDPE) plastic being among the well-known. So in this study, the scarped LDPE food boxes were transformed into fine particles and used as a sand for cement mortar and concrete. LDPE wastes were utilized to alter 0 to 25% of fine aggregates in mortar mixtures and 0% to 30% in concrete mixes at an increment of 5%. Compressive strength and dry density were tested for all mortar and concrete specimens.  In addition, splitting tensile strength and ultrasonic pulse speed were tested for specimens of concrete.  Results show that mass, pulse speed of ultrasonic, splitting and compressive tensile strengths were lowered as the size of LDPE raised. The lowest value of dry density, compressive strength and splitting strength was 2240 kg/m3, 18.7 MPa and 1.68 MPa, respectively, for 15% replacement of sand by the LDPE waste in concrete specimens. Whilst, the value of ultrasonic pulse velocity of LDPE concrete mixtures tends to decline lower than the reference values, but it remains nearly to the stander concrete mixtures and can be classified as excellent quality concrete. The density and compressive strength were decreased by using LDPE waste in mortar mixes for all replacement ratios reaching 12% and 42% respectively for 25% substitute

A multifaceted analysis of COVID-19 propagation in confined spaces: a techno-economic assessment of ventilation, heating, and renewables integration

vii, 73 p., xiiThe outbreak of novel coronavirus disease 2019 (COVID19) has spread rapidly, affecting nearly all countries and territories around the globe, impacting every aspect of human life. Governments and various organizations worldwide have issued mitigation measures to counteract COVID-19 virus propagations, whether in indoor spaces or outdoors. Although the underlying uncertainty concerning COVID-19 transmission details, most international organizations such as WHO, ECDC, ASHRAE, REHVA, and CIBSE agree on the important role of ventilation to minimize the causes and reduce the viability of SARS-CoV-2 in confined spaces. Given that natural ventilation is variable, which depends on the intermittent wind source, mechanical ventilation systems provide stable airflow rates that ensure reliability and adequacy to meet the minimum ventilation rates for building users in a controlled environment. Thus, a paradigm shift in the mechanical ventilation system is needed to steer the focus from the predominant energy efficient space-based design to occupant-based design. This study will discuss the cost-related effects to ensure stable and adequate ventilation by setting up ventilation scenarios with parameters derived from the recommendations published in recent guidelines focusing on HVAC operations. A working methodology is applied to a case study on two zones, an office, and a nursery. The results show that maintaining a minimum of five and seven air changes per hour for office and nursery, respectively, with proper indoor air distribution can reduce the risk of infection by more than half while ensuring an economic balance between ventilation costs and infection risk. Additionally, the study suggests using photovoltaics installations to power ventilation rates higher than five air changes per hour which can save at least forty-five tons of CO2 while reaching a payback period in thirteen years. Based on the achieved results, the paper presents recommendations to operate the two zones’ ventilation, space heating, and photovoltaics cost-effectively while ensuring COVID-19 probability of infection reduction

Relationships Between Reflectance and Soil Physical and Chemical Properties

Soil chemical and physical properties are important to farm productivity, and they vary within fields, so farmers are interested in managing inputs like fertilizer according to local soil conditions within fields. Thus, they must have knowledge of soil conditions of interest, which have historically been measured at a few locations with tedious soil sampling and laboratory analyses. Advantageous to farmers would be a measurement method that provided more geographically detailed information at similar or lower cost. Remote and ground-based optical sensing are possibilities for gathering detailed soil information rapidly and inexpensively. This study considers the possibility of optically measuring soil characteristics. The first objective was to determine relationships between spectral reflectance in the 250- to 2500-nm range and the following soil constituents: clay, sand, Ca, K, Mg, Na, P, Zn, and acidity (pH). The second objective was to find wavebands for estimating certain soil properties, with the goal of sensor development. Physical, chemical, and spectral-reflectance measurements were made on 969 soil samples collected from two Mississippi fields over two years. Reflectances were averaged over 50-nm wavebands and analyzed with simple- and multiple-linear regression and canonical correlation in relation to soil properties. No single waveband was highly correlated to any soil property in this study, but waveband groups exhibited strong correlations with some soil properties. Clay was the only property consistently strongly correlated (R2 ¡Ý 0.50) to waveband groups over different fields and years. In general, waveband groups that were most highly correlated with a specific soil property in one field in one year were not similar to waveband groups most highly correlated with that property in a different field or year. Thus, it was difficult to select a waveband group for sensor development regarding a specific soil property. However, a group of nine promising wavebands was considered for estimating clay, and results for data in this study indicated the feasibility of grossly estimating clay content with spectral reflectance. Canonical correlation analysis demonstrated strong correlations among certain groups of soil-properties and wavebands. Clay appeared as the most promising property for sensor development from this portion of the study also

The school-to-work transition and youth unemployment in Saudi Arabia : the case of Al-Hasa province

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

An experimental and numerical study of two-phase flow in horizontal tube bundles

An effective design for a kettle reboiler is dependent on fitness for purpose while reducing costs. Thus, accurate information concerning two-phase flow behaviour within it is important. Experimental and numerical studies have been carried out in this research to gain a more detailed understanding of the phenomena associated with two-phase flow in a thin-slice kettle reboiler. The kettle reboiler contained 241 electrically heated tubes arranged as 17 rows of 17 columns in an in-line layout with an outside diameter of 19 mm and a pitch-to-diameter ratio of 1.34. The working fluids used in this investigation were pentane and the refrigerant R113. They were boiled at atmospheric pressure at uniform heat fluxes in the range of 10 to 40 kW/m2. The patterns of flow inside the kettle reboiler were investigated experimentally using ordinary and high speed cameras. Visual observation of the flow patterns showed that the flow in the tube bundle was two-dimensional at heat fluxes of 20 kW/m2 and above. The quantity of foam and recirculation above the tube bundle were found to depend on both the heat flux and the working fluid used. Observations of the two-phase flow pattern in the shell indicated that the movement of fluid from the centre column of the bundle was affected by the down flow into the top of the tube bundle. Two flow patterns in the tube bundle were identified: bubbly and intermittent. At low heat fluxes, bubbly flow dominated, then, with increasing heat flux, bubble coalescence led to the development of vapour slugs and intermittent flow was observed. Pressure drop measurements were made in three columns within the tube bundle. The results showed that at heat fluxes below 20 kW/m2, the pressure drop remained nearly constant and equal to the all-liquid value. At a heat flux of 20 kW/m2 and above, the pressure drop was found to increasingly fall below the all-liquid value as the bundle row number increased. This effect was especially evident in the centre of the bundle. A change in the flow pattern caused the pressure distribution up the tube bundle to change from roughly constant to decaying with height. Based on a number of assumptions, the two-fluid model has been applied. The two-fluid model’s drag coefficient and tube resistance were deduced from a one-dimensional model. The two-fluid model predictions show good agreement with the experimental results for the pressure distribution and flow distribution. Grid sizes of 10, 8 and 4 mm for the bundle and the pool were considered. It was found that the predicted bundle results were not affected by changing the grid size. However, in the pool region, a small grid size was needed. A grid size of 10 mm was used in the bundle while 4 mm was used in the pool. The pool velocity predictions compared well with measured values available in the open literature. The results indicated that the bundle flow is not significantly affected by the pool flow. This allows the two-fluid model to be further refined: simplifying it and reducing the computational time. A bundle-only two fluid model has been developed to accurately predict two-phase flow behaviour in the kettle reboiler tube bundle. Information available from earlier studies has been used to develop this model because of the difficulties associated with measuring the void fraction and velocities within the tube bundle. The model uses two different boundary conditions: (1) static liquid pressure in the pool and (2) variation of pressure in the pool based on the flow pattern transition. The results predicted by the model have been compared with experimental data and with one and two-fluid models at different heat fluxes. Boundary condition (1) was found to be in good agreement with experimental data and the one and two-fluid models at a heat flux of 10 kW/m2. This was because the transition flow pattern was not achieved and the bundle was surrounded by a static pool. Boundary condition (2) is based on the Kutateladze number (Ku), which sets the transition point from bubbly to intermittent flow at a certain height in the bundle. For Ku ≤ 1.09, the bundle flow would be surrounded by liquid, and if Ku > 1.09, the bundle flow would be surrounded by two-phase flow. At heat fluxes of 20 kW/m2 and above, boundary condition (2) has been found to be in good agreement with experimental data and the values predicted from the one and two-fluid models for liquid velocities, vertical mass flux and void fraction. The bundle-only model accurately predicts the trend line of constant and decaying pressure drop measured at low and high heat fluxes, respectively, and the observed flow phenomena in the kettle reboiler. The key feature of the model presented is that it allows two-phase flow in the kettle reboiler to be simulated by only modelling the tube bundle. Thus the model is simplified and less computational time is required. A central column model was developed using the minimum pressure gradient approach. The predicted results from this model were compared with experimental data and the values predicted by the two-fluid model and the bundle-only model. Reasonable agreement was obtained indicating that the flow distribution may be linked to the minimum pressure gradient

Modelling, analysis and feedback control design for upright standing sways

Human body upright standing is inherently unstable, and as a bipedal creature, the body can implement several functions such as upright standing, walking and running, with the help of the central nervous system. Understanding the stability control of the human body during upright standing is important for prosthetic design and joint prostheses, walking restoration, diagnosis of nervous system diseases. Also, it is essential to anthropology, clinical research, aerospace science and kinesiology.Therefore, the objective of this work is to model the musculoskeletal system of human upright standing posture for analysis and control design of body sway. An asymmetric Gaussian function is proposed to model the force-length relationship and compared with other existing force-length models. By using least square curve fitting tools with a set of rabbit experimental data, and simulated data that represent sarcomere of the frog. Also, the implicit and explicit ordinary differential equations, are used to model muscle-tendon unit and compare the simulation results in term of singularity.In addition to, the equilibrium analysis is used to determine sway ranges during upright standing, and the equilibrium points can be used to linearize the model for feedback control design and stability analysis of the musculoskeletal system. Furthermore, a switching function is designed to model the intermittent activity of the MG muscle, where the parameters are optimised using the centre of gravity and electromyography data with Genetic Algorithm tool. The musculoskeletal system of the human body is modelled as a single inverted pendulum, which rotates around the ankle joint, in the sagittal plane only. The calf muscles especially the medial gastrocnemius activated intermittently, and soleus activated continuously are included in the model of the musculoskeletal system. The developed musculoskeletal system model is linearized in order to have clear stability analysis using Routh-Hurwitz stability criterion and eigenvalue analysis.The results show that the musculoskeletal system cannot be stabilised at the upright standing without feeding back angular velocity. The equilibrium analysis reveals how the sway range (sway points) depends on the used anatomical and anthropometry data. Finally, the stability analysis shows that during forwarding sway the calf muscles are shortening paradoxically and lengthening during backwards sway, which supports some existing experimental results. The model-based analysis which used in modelling the body upright standing, will help in analysis and understands the dynamics of the body during upright standing. Also, it assists in medical research, in clinical diagnostics and application

Evaluation and testing of a novel photocatalytic reactor with model water pollutants.

Semiconductor photocatalysis is a newly emerging technology for the elimination of harmful chemical compounds from air and water. It couples low-energy ultraviolet light with semiconductors acting as photocatalyst and thereby overcoming many of the drawbacks that exist for the traditional water treatment methods. Recent literature has established the potential of this powerful technology to destroy toxic pollutants dissolved or dispersed in water. However, to date, very few viable pilot plants exist using this technology. In this study, the application of photocatalysis for the removal of contaminants from waste water discharges such as produced water from oil rigs and other organic contaminants in industrial wastewater, were investigated. A novel photocatalytic reactor, which employs a commercial pellet titanium dioxide (TiO2) catalyst, was tested for water treatment capability by investigating the photocatalytic degradation of contaminants from waste water discharges such as; hydrocarbons in produced water from the oil industry and synthetic dyes from the textile industrys waste processing fluids, using titanium dioxide (TiO2) as photocatalyst in an aqueous suspension under UV irradiation. Experiments were conducted to investigate the effects of parameters such as catalyst loading, pollutant adsorption rate on the pellet TiO2 catalyst and reactor circulation flow rate. In this work, the batch adsorption of methylene blue from aqueous solution (10ï­M) onto the Hombikat-KCO pellet TiO2 catalyst was studied, adsorption isotherms and kinetics were determined from the experimental data. A modest catalyst loading of 30g per 1L TiO2 was choosen for further experiments since its shows gradual and consistent degradation results and approximately 98% degradation of methylene blue was achieved within 60 minutes irradiation in the optimization experiment. Photodegradation of methylene blue dye was monitored by UV- spectroscopy. Complete degradation of methylene blue was achieved within 60 minutes illumination with the various loads of catalyst (30-200g). Experimental results indicate that this novel reactor configuration has a high effective mass transfer rate and UV light penetration characteristics. The use of TiO2 Hombikat KOC pellets catalyst means the system is free from the need of filtration of catalyst following photocatalysis and provides a higher surface area for catalyst illumination and a high contact of catalyst surface area with contaminated water

Educational, financial, and social needs of families of children with multiple disabilities in Saudi Arabia.

Studies on the needs of families of children with multiple disabilities are few and limited, and none of these studies have been conducted in the Arab world, in general, nor in Saudi Arabia, in particular. Even though many families suffer from problems that affect their needs and the needs of their children with disabilities, social work research in the Arab world have not focused on the families and their needs. The information collected from such research can help in developing new and superior services to help children with multiple disabilities and their families. Thus, the present study will contribute to a better understanding of the needs of families of children with multiple disabilities and will help to fill the gap in the literature. The purpose of this dissertation was to identify the families’ educational, financial, and social needs, and to explore the differences in needs among families based on the parents\u27 demographic information (i.e., educational backgrounds and financial status) and the children\u27s characteristics (i.e., type of disability, gender of the child). Using a questionnaire, the data for this study were collected between May 2016 and September 2016 from 196 fathers and mothers (98 couples) of children with multiple disabilities (male and female, between 5 and 18 years of age) enrolled in multiple-disability programs from 10 institutes each supervised through the Ministry of Education in Riyadh, Saudi Arabia. The data were analyzed using the Statistical Package for the Social Sciences (IBM SPSS-22). Descriptive statistics were used to ascertain the sample description. In addition, one-way ANOVA and two-way ANOVA were used for answer research questions. Generally, parents reported that families\u27 needs are still falling short of being fulfilled in Saudi Arabia. Moreover, there was a significant difference between parents\u27 gender regarding social needs; mothers reported a stronger need for social support than did fathers. Thus, the results suggest that the perceived social needs of the mothers are more important to them than the perceived education and financial needs. Moreover, the educational needs based on the parent\u27s level of education was significant with the mothers who had high school diploma. The financial needs based on the interaction between parents\u27 gender and child\u27s gender was significant in favor of fathers with female children. Finally, the educational needs based on a child\u27s type of disability was significant for both parents when the child had both deafness and another type of disability. This exploratory research study served to extend research related to social work with families, social work with special groups, as well as provide further support for this specialized field of social work practice

Risk Assessment for Marine Construction Projects

Marine-construction projects are becoming increasingly important for the development of the maritime industry. However, such increases are hampered by various risks that can significantly impact growth. Natural forces, political events, administrative and operational mistakes, equipment failures, external attacks such as arson, and economic events are some of the major risks faced by firms in this industry. Researchers have paid little attention on marine- construction risk assessment, despite the importance of such research. This study sought to develop a generic risk-levels predictor framework, using the integrated definition function model (IDEF0) and the case-based reasoning approach (CBR), to predict levels of risk associated with a new marine-construction project. This framework can be developed through the following three phases: (a) Cases collection: previous marine-construction projects (cases) were investigated for identification, classification, and evaluation of risk factors and triggers, (b) Cases classification: the cases were organized and stored in a marine construction database (MCDB) and compiled into risk-triggers and risk-levels data for each case, (c) Cases reasoning: using the information from previous phases, when risk-triggers data for a new case is entered into a system knowledge database (i.e., a temporary database that keeps the new risks triggers and proposes prediction data for further knowledge and validation) looking for risk-levels prediction, the system searches into the MCDB for known risk-triggers that are similar to the new case. The similar cases are retrieved, and their risk-levels data are used to propose a risk -levels prediction for the new case. Finally, when the proposed prediction is revised and approved by users, the risk-triggers and risk-levels prediction data for the new case are stored in the system knowledge database for further learning. The implementation of the proposed risk-level predictor framework (RLPF) was tested in this study on 10 hypothetical marine construction projects conducted in Saudi Arabia. The automated systematic approach—the RLPF proposed in this study—can address specific and time-urgent decisions invariably and accurately. Future researchers should use the RLPF to gain knowledge on risk aspects in marine construction projects

E-Learning Security Challenges, Implementation and Improvement in Developing Countries: A Review

The application of e-learning technology in teaching and learning environment in developing countries has created a significant impact especially to students and staff. Despite the fact that it attended a high level of acceptability, there are various security threats and implementation challenges militating against effective utilization of the e-learning platform. This paper, reviewed the impact associated with security vulnerabilities and implementation issues that impede successful e-learning implementation. Specifically, the review examined the effect of security challenges in e-learning and viability of e-learning implementation. This review found that there is need to develop a viable and holistic approach model that combines both biometric fingerprint and cryptography authentication techniques for the e-learning platform. It is recommended that there is need for adequate and uninterruptable bandwidth and power supply for e-learning sustainability. Keywords: security challenges, implementation, e-learning, ICT and trustworthiness