| 1. |
- Ademuyiwa, Adesoji O., et al.
(författare)
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Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries
- 2016
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Ingår i: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
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| 2. |
- Chabuk, Ali, et al.
(författare)
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Noise Level in Textile Industries: Case Study Al-Hillah Textile Factory-Company for Textile Industries, Al-Hillah-Babylon-Iraq
- 2021
-
Ingår i: First International Virtual Conference on Environment & Natural Resources. - : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- In this study, Al-Hillah Textile Factory, in Al-Hillah city-Iraq follows to State Company for Textile Industries was selected to study the intensity of noise in 2014. Measurements of the noise level were carried out in different workshops for each of the production stages including the spinning machinery workshop (parts 1 and 2), the rotating machinery room, the preparations room, and the textile machinery room (Roti model), weaving machines: Techmash model room Russian-made model room, Sheets' machinery room, and operator machines room; using two noise meters (model 2237 Fulfici). Fifty samples were collected in each part of these rooms to give realistic results for the noise level. After recording the noise level data, the highest and lowest values and the average of noise intensity readings were calculated in each of the rooms and compared with the global standards permitted by the EPA for industrial facilities. The results of this study showed that the general rate of noise intensity in all rooms exceeded the permissible limits, which impose a noise level of 65-70dB for such industrial establishments according to EPA recommendations in 2008.
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| 3. |
- Falih, Ali Hasan, et al.
(författare)
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Comparative study on salinity removal methods: an evaluation-based stable isotopes signatures in ground and sea water
- 2023
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Ingår i: Applied water science. - : Springer. - 2190-5487 .- 2190-5495. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- This research aims to attain the optimal method of removing the high salinity concentrations without its effect on the balance or accuracy of stable isotopes measurement of deuterium and oxygen-18 (δ18O, δ2H). Four treatment methods (i.e., distillation, vacuum distillation, electro dialysis and ion exchange) were applied for nine samples, which were obtained from different water sources (sea, groundwater, river).l Worth to notice that the samples have Electrical Conductivity (EC) ranged (1000–60,000 µs/cm). Liquid–Water Isotope Analyzer used to measure the isotope concentration of δ18O, δ2H. The research findings of the four applied methods revealed their effectiveness with various percentages (normal distillation: 92.37%; vacuum distillation: 88.31%; electro dialysis: 94.85%; ion exchange: 99.62%). In addition, the investigation was conducted a clear correspondence measurement of (δ18O, δ2H) isotopes before and after treatment. The four methods results indicated that samples with EC ranged (1000–5000 µs/cm) have no effect on stable isotope readings. Whereas, samples with EC higher than 10,000, have substantial influence on the stable isotope readings. Finally, vacuum distillation method attained the best results among the treatment methods for EC ranged (10,000–60,000 µs/cm) without affecting the isotopic content of (δ18O, δ2H). There is a clear correspondence of the stable isotopic measurements before and after treatment, for all the selected samples.
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| 4. |
- Altaee, Mohammed J., et al.
(författare)
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Evaluation of Existing Bond-Slip Relations for CFRP-Steel Joints and New Model for Linear and Nonlinear Adhesives
- 2022
-
Ingår i: Advances in Civil Engineering / Hindawi. - : Hindawi Publishing Corporation. - 1687-8086 .- 1687-8094. ; 2022
-
Tidskriftsartikel (refereegranskat)abstract
- Existing bond-slip (τ-s) relations for fibre-reinforced polymer (FRP)-steel joints employ different shapes and mathematical expressions, inferring that their predictions of failure load and mode, and other interface properties, might be inconsistent or inaccurate. In this study, predictions of four widely used τ-s relations are evaluated using a large experimental database of 78 double-lap FRP-steel specimens. To facilitate the evaluation process, a robust finite element (FE) model is developed for each test, implementing data from either of the existing τ-s relations to define the FRP-steel interface. Comparisons between test and FE results indicated that the existing τ-s models were unable of predicting the ultimate load (Pu) and effective bond length (Leff) of FRP-steel joints, or the relation between Pu and bond length and that between Leff and FRP modulus (Ef). A new τ-s model is developed based on an inverse FE simulation, comparison with experimental results, and regression analysis. It considers the effects of Ef, the type of FRP reinforcement (sheet or plate), and applies to both linear and nonlinear adhesives. The model predictions were validated by comparing with results from small bond tests and large FRP-strengthened steel beams tested under bending, yielding excellent results for Pu, failure mode, and all other interfacial properties.
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| 5. |
- Kadhim, Majid M. A., et al.
(författare)
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Review on NSM CFRP Strengthened RC Concrete Beams in Shear
- 2021
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Ingår i: Advances in Civil Engineering / Hindawi. - : Hindawi Limited. - 1687-8086 .- 1687-8094. ; 2021
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Forskningsöversikt (refereegranskat)abstract
- The use of NSM FRP strengthening of concrete structures has become an attractive option to retrofit the existing structures against shear and flexure. This paper reviews only the utilization of NSM for shear in previous review articles. A database of tests of NSM strengthened beams in shear is presented to evaluate the existing design formulations of calculating the NSM contribution in shear. These formulations were in agreement with the experimental results in the database. Further research topics are also identified such as the shape of NSM FRP bars, combined effects of existing steel stirrups, and NSM FRP reinforcement and analytical formulations.
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| 6. |
- Al Maliki, Ali, et al.
(författare)
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Comparison between inductively coupled plasma and X-ray fluorescence performance for Pb analysis in environmental soil samples
- 2017
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Ingår i: Environmental Earth Sciences. - : Springer. - 1866-6280 .- 1866-6299. ; 76:12
-
Tidskriftsartikel (refereegranskat)abstract
- Comparison of two conventional analytical techniques such as X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) for measuring Pb concentrations in soil samples was achieved using field and laboratory work. Seventy-three samples were collected from urban areas surrounding the large lead smelter at South Australia, as an indicator of the environment impact of smelter activity. Soil Pb concentrations were determined using hand-held XRF analyser under laboratory conditions. ICP-MS analysis on digested soils (using a microwave-assisted nitric acid digestion-extraction) was applied to validate p-XRF data. The analysis showed that Pb concentrations determined by XRF correlated with high linearity with Pb concentrations determined by ICP-MS measurements (R2 = 0.89). Statistical test (t test) was applied to the data of both methods applied without any significant difference between the two techniques. These results indicated that ICP-MS corroborated XRF for Pb soil measurements and suggests that XRF was a reliable and quick alternative to traditional analytical methods in studies of environmental health risk assessment, allowing for much larger sampling regimes in relatively shorter times and could be applied in the field.
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| 7. |
- Al-Mutawqi, Kareem Ghafel, et al.
(författare)
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Hydrogeochemical processes and evaluation of groundwater in Al-Salman area - Iraqi Southern Desert
- 2021
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Ingår i: Journal of Water and Land Development. - : Polish Academy of Sciences. - 1429-7426. ; 50, s. 220-228
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Tidskriftsartikel (refereegranskat)abstract
- A field survey has been conducted for the study area using the Global Positioning System (GPS) and geological and geomorphological maps of the area. The study area is one of the important areas in Iraq characterized by scarce water resources. The purpose of the study is to determine the hydro-chemical processes and their relationship to groundwater quality carried out in the southwestern desert region of Iraq, where the region lacks extensive studies of water resources. Twenty-eight groundwater samples were collected from wells distributed between the eastern borders of Saudi Arabia and the West Bank of the Euphrates River. For the purpose of hydrogeochemical analyses, the Fetter method was used to collect and examine samples. A large part of the recharge area is located in Saudi Arabia, where the groundwater bearing aquifer represented by the Dammam formation extends to Iraq and Saudi Arabian International borders. The analysis determined the order of cations (Na+ > Ca2+ > Mg2+ > K+) and anions (Cl- > SO42- > HCO3-). High values of the variation coefficient (CV) correspond to the concentration of potassium, sodium and chloride ions (CV: 68.7, 64.7 and 64 respectively). To identify the hydrochemical water facies, the Piper diagram was used. It was found that 53% of the water samples belong to the Na-Cl type and 40% are of the Ca-Mg-Cl type, while the rest of the samples are the Ca-Cl type. To identify geochemical processes, it was found that ion exchange processes via chloroalkaline indices 1 and 2 are prevalent between Ca2+, Mg2+ in the groundwater and Na+, K+ in water bearing rocks. To learn more about the processes that led to the concentration of certain ions, such as sodium, it was found that they tend to be of silicate minerals related to surface runoff of water in recharge areas and carbonic rocks. It was also found that rock/soil-groundwater interaction and evaporation processes were the formal processes in the saturated zone and evaporation in the unsaturated zone are prevalent processes of groundwater ion concentration.
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| 8. |
- Alhelfi, Ali Kadhim Hadi, et al.
(författare)
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A Condition Monitoring for Collapsing Bubble Mechanism for Sonoluminescence and Sonochemistry
- 2015
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Ingår i: Journal of Thermal Science and Engineering Apllications. - : ASME International. - 1948-5093 .- 1948-5085. ; 7:2, s. 8-021014
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- The acoustic cavitation phenomenon is a source of energy for a wide range of applications such as sonoluminescence and sonochemistry. The behavior of a single bubble in liquids is an essential study for acoustic cavitation. The bubbles react with the pressure forces in liquids and reveal their full potential when periodically driven by acoustic waves. As a result of extreme compression of the bubble oscillation in an acoustic field, the bubble produces a very high pressure and temperature during collapse. The temperature may increase many thousands of Kelvin, and the pressure may approach up to hundreds of bar. Subsequently, short flashes can be emitted (sonoluminescence) and the high local temperatures and pressures induce chemical reactions under extreme conditions (sonochemistry). Different models have been presented to describe the bubble dynamics in acoustic cavitation. These studies are done through full numerical simulation of the compressible Navier–Stokes equations. This task is very complex and consumes much computation time. Several features of the cavitation fields remain unexplained. In the current model, all hydrodynamics forces acting on the bubble are considered in the typical solution. Bubble oscillation and its characteristics under the action of a sound wave are presented in order to improve and give a more comprehensive understanding of the phenomenon, which is considered to have a significant role in different areas of science and technology.
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| 9. |
- Alhelfi, Ali Kadhim Hadi, et al.
(författare)
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Assessing Learning in Higher Education
- 2012
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Rapport (populärvet., debatt m.m.)abstract
- Assessment is a key activity within the higher education system. From the student´s perspective, assessment shapes what is to be learned; from the perspective of the educator it gives clear inputs about the quality of learning. Thus, as defined by the term, ‘Constructive alignment’, by careful planning of the assessment strategy and wise selection of the assessment methods, the teaching-learning experience can be designed in an aligned manner towards the achievement of the learning outcomes. Although, defined in different ways, the basic purpose of assessment is to work as a feedback tool to both, students and teachers, to improve the student learning. In this work, we review and comment on theoretical aspects of assessment including its significance and characteristics. Moreover, some important considerations regarding the design of the assessment activities are presented, together with the description of some methods for assessing learning. With this work we would like to invite the reader to reevaluate the significance of assessment within the learning experience, and by this, hopefully the educator is “inspired” to improve the assessment activities in the classroom or another less conventional learning space.
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| 10. |
- Alhelfi, Ali Kadhim Hadi, et al.
(författare)
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Bubble Power and Ultrasound
- 2013
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Ingår i: International Journal of Enhanced Research in Science Technology & Engineering. - 2319-7463. ; 2:11, s. 130-134
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- If anyone begins to think about the term ultrasound, the first thing that comes to the mind is the fact that it is used in animal communications (e.g., bat navigation and dog whistles). Also, one may start to think that this term is familiar in daily life and has been used many times in medicine applications for foetal imaging, (SONAR). However, many questions come to the mind, such as, what is happening when ultrasound is transmitted through the body? If it is sound, he asks himself why I cannot hear any sound? The interaction between bubbles and sound waves in liquids leads to the phenomenon of acoustic cavitation. The meaning of the word cavitation is not known or understandable for many people. This paper is to contribute the knowledge of bubble power under the action of ultrasound and to give a more comprehensive description of this phenomenon.
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| 11. |
- Alhelfi, Ali Kadhim Hadi, et al.
(författare)
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Design Considerations for Solid Oxide Fuel Cell Auxiliary Power Units for Luxury Passenger Vehicle
- 2013
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Ingår i: The proceeding of 8th International Conference on Multiphase Flow, 2013.
-
Konferensbidrag (refereegranskat)abstract
- SOFC systems, working at high temperatures of about 800°C, have recently attracted significant interests for application as automotive and stationary power supply systems. This paper explores the possibilities and limitations for achievement of solid oxide fuel cells (SOFCs) as 7 kW auxiliary power units on luxury passenger vehicles operating on diesel fuel. Various issues are discussed, e.g., the requirements and specifications for the unit as well as the advantages, challenges, and development issues for SOFCs in such applications. System design and analysis are carried out. The calculations are performed for two voltage systems 12/14 V and 36/42 V, respectively. The influences of others parameters like the mass flow rates of air and gases, water production and heat production are also evaluated for the two voltage systems.
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| 12. |
- Alhelfi, Ali Kadhim Hadi
(författare)
-
Development and Assessment of Methods for the Prediction of Hydrodynamic and Ultrasound induced Cavitation
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The cavitation phenomenon has today become a keystone for different areas of science and technology including various industrial processes and medicine. Recently increasing interest and much attention have been paid to study this phenomenon. The last two decades have witnessed the development of numerous devices for different important applications of considerable practical interest, and the range of these applications is in continuous increase. This thesis aims to gain more knowledge about the mechanisms and dynamics of the cavitation phenomenon. In the present study, various techniques are developed and investigated. The major principal parameters associated with these phenomena are all presented in order to improve and give more comprehensive understanding of the phenomenon. The study presents enhanced numerical models to analyze the cavitation phenomenon and simulated results of formation and collapse of a single bubble in a liquid are provided. A convenient model is applied and its enhancements are examined numerically. The validity and comparison with the available experimental data were found favorable. The model is employed to deduce the bubble dynamics in flow domains for the following situations, 1. Bubble dynamics in an acoustic field. The sound waves create pressure variations through the medium and cause regions of rarefaction and compression. These pressure variations can set a tiny bubble into radial motions, i.e., expansion and compression. The bubble in an acoustic field grows as the pressure associated with the sound waves gives rarefaction. When the pressure turns to compression, the bubble is compressed and may reach an unstable size and then collapse violently. During this process, the nonlinear motion of the bubble is a complicated process. Despite many efforts, the demand of creating more suitable models with a realistic applicability calls for numerical calculations of the bubble motion in an acoustic field. This will provide improved knowledge about the real situation and the main results associated with this phenomenon. 2. Bubble dynamics close to a rigid boundary. In fact, the simulation of non-spherical bubble dynamics and its interaction with solid boundaries has received much less attention due to the complexity of the problem. A main reason of the structural damages in the cavitation phenomenon is due the formation of micro jets generated due to the bubble collapse and impingement on the solid surfaces or boundaries. The boundary integral method (BIM) is employed to compute the bubble motion and explosion of a cavitation bubble close to a rigid boundary. The liquid is considered to be incompressible, inviscid, and irrotational around the bubble. These assumptions satisfy the conditions for the Laplacian equation.
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| 13. |
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| 14. |
- Alhelfi, Ali Kadhim Hadi
(författare)
-
Heat Transfer in Liquid Film over the Surface of a Rotating Disk Subjected to Impinging Jet
- 2012
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Rapport (populärvet., debatt m.m.)abstract
- This work is theoretical analyses of heat transfer across film a flowing over the surface of a rotating disk. This field has wide industrial applications in Turbomachinery, chemical, and food industries. An analytical study is developed to investigate the heat transfer characteristics in the liquid film due to jet impinging at the center of the disk. A theoretical model is based on heat balance and energy equations developed for a rotating disk heated by a constant heat flux and the free surface are subjected to the surrounding. Local Nusselt number and temperature were found for different selected parameters such as Prandtl number and Reynolds number. Nusselt number obtained from the present model was compared with that obtained by Thomas et al., and the agreement between the results was acceptable.
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| 15. |
- Alhelfi, Ali Kadhim Hadi, et al.
(författare)
-
Modeling of Spherical Gas Bubble Oscillation in Acoustic Pressure Field
- 2013
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Ingår i: Proceedings Of The 8th International Conference on Multiphase Flow, 2013.
-
Konferensbidrag (refereegranskat)abstract
- Different applications of high power ultrasound in industry and medical applications are based on the propagation and collapse of acoustic cavitation bubbles. This paper presents an enhanced numerical model and simulated results of formation and collapse of a single bubble in a liquid for two cases: bubble with uniform pressure and a bubble with variable pressure inside. For the two cases, both heat transfer inside the bubble and heat transfer to the surrounding liquid are taken into account. Various fundamental properties of oscillating bubbles in ultrasonic acoustic field, such as pressure, temperature and velocity fields inside the bubble under the influence of time-dependent acoustic pressure, have been investigated and the results show that neglecting the pressure gradient inside the bubble affects considerably the bubble dynamics.
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| 16. |
- Alhelfi, Ali Kadhim Hadi, et al.
(författare)
-
NUMERICAL INVESTIGATION OF AN OSCILLATING GAS BUBBLE IN AN ULTRASONIC FIELD
- 2014
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Konferensbidrag (refereegranskat)abstract
- The discovery of acoustic cavitation phenomenon is an important role in the design of a wide range of devices handling liquids and it has led to a renewed interest in the bubble dynamics in a sound field.In this study, the nonlinear behaviour of individual gas bubble in liquid under the action of ultrasound fields has been analysed, and simulated results of formation and collapse of a bubble have been provided. The characterization of acoustic cavitation bubbles under theinfluence of periodic pressure field, e.g., the motion of the bubble surface, pressure, temperature and density fields inside the bubble have been investigated and the results are compared with experimental data. The numerically calculated results reveal that the assumption of polytropic approximation inside the bubble predicts that a radius-time curve does not fit to the observed data. Also, the results indicate that the pressure gradient and the heat transfer inside the bubble and across the bubble surface play a major role to predict the extreme conditions associated with the bubble collapse.
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| 17. |
- Alhelfi, Ali Kadhim Hadi
(författare)
-
On Bubble Dynamics in Acoustic Cavitation
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nyligen har mycket uppmärksamhet ägnats åt studier rörande ickelinjära oscillationer av sfäriska gasbubblor i pulserande tryckfält. Denna lic-avhandlning syftar till att utöka kunskapen kring kavitationsfenomenet. I detta arbete undersöks olika modeller och en förbättrad numerisk modell har utvecklats för att analysera akustiska kavitationsfenomen. Resultaten från den utvecklade modellen innefattar bildande och kollaps av enstaka gasbubblor i en vätska under inverkan av ultraljud som en funktion av tiden. Modellen valideras och jämförs för tre huvudfall. Dessa fall är: enhetligt tryck och temperatur inne i bubblan, enhetligt tryck och varierande temperatur inne i bubblan, samt varierande tryck och temperatur inne i bubblan. För fall 2 och fall 3 tas hänsyn både till värmeöverföringen inne i bubblan och till den omgivande vätskan. Olika grundläggande egenskaper hos oscillerande bubblor i ett ultraljud akustiskt fält såsom tryck, temperatur, densitet, hastighet och acceleration inne i bubblan under påverkan av tidsberoende ljudtryck har undersökts och resultaten för varje enskilt fall jämförs med motsvarande experimentella data. De numeriskt beräknade resultaten visar att antagandet om ett enhetligt tryck och temperatur inuti bubblan predikterar ett samband mellan radien och tiden som avviker starkt från de uppmätta värdena. Vidare visades det att för att prediktera de extrema tillstånd som förknippas med en kollaps måste bubblans dynamik ta hänsyn både till tryckgradienten och värmeöverföringen inne i bubblan samt över bubblans yta.
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| 18. |
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| 19. |
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| 20. |
- Alhelfi, Ali Kadhim Hadi, et al.
(författare)
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Simulations of Cryogenic Cavitation of Low Temperature Fluids with Thermodynamics Effects
- 2015
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Ingår i: International Journal of Mechanical, Aerospace, Industrial and Mechatronics Engineering. ; 9:1, s. 65-69
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Cavitation in cryogenic liquids is widely present in contemporary science. In the current study, we re-examine a previously validated acoustic cavitation model which was developed for a gas bubble in liquid water. Furthermore, simulations of cryogenic fluids including the thermal effect, the effect of acoustic pressure amplitude and the frequency of sound field on the bubble dynamics are presented. A gas bubble (Helium) in liquids Nitrogen, Oxygen and Hydrogen in an acoustic field at ambient pressure and low temperature is investigated numerically. The results reveal that the oscillation of the bubble in liquid Hydrogen fluctuates more than in liquids Oxygen and Nitrogen. The oscillation of the bubble in liquids Oxygen and Nitrogen is approximately similar.
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| 21. |
- Alhelfi, Ali Kadhim Hadi
(författare)
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Solar Thermal Technology
- 2012
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Rapport (populärvet., debatt m.m.)abstract
- Abstract in Undetermined This project aims to explain the solar thermal technology and support a real technical revolution to help the power industry to become cleaner than before. Also, in this project the technologies and systems developed thus far and their approximate costs will be described.
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| 22. |
- Alhelfi, Ali Kadhim Hadi, et al.
(författare)
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Solid Oxide Fuel Cell Auxiliary Power Units for Heavy Duty Trucks
- 2012
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Ingår i: Proceedings Of The ASME 10th Fuel Cell Science, Engineering, and Technology Conference, 2012. ; , s. 317-325
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Konferensbidrag (refereegranskat)abstract
- This paper explores the potentials of solid oxide fuel cells (SOFCs) as 3 kW auxiliary power units for trucks and military vehicles operating on diesel fuel. Various issues are discussed, e.g., the requirements and specifications for the unit as well as the advantages, challenges, and development issues for SOFCs in such applications. System design and analysis are carried out. The major component of the system is the fuel cell stack. The calculations are performed for two voltage systems 12/14 V and 36/42 V, respectively. The influences of others parameters like the mass flow rates of air and gases, water production and heat production are also evaluated for the two voltage systems.
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| 23. |
- Alhelfi, Ali Kadhim Hadi, et al.
(författare)
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THE BOUNDARY INTEGRAL METHOD APPLIED TO NON-SPHERICAL CAVITATION BUBBLE GROWTH AND COLLAPSE CLOSE TO A RIGID BOUNDARY
- 2015
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Ingår i: ASME 2015 International Mechanical Engineering Congress and Exposition. - 9780791857496 ; 8A
-
Konferensbidrag (refereegranskat)abstract
- Recently much attention has been paid to studies concerning bubble dynamics in the cavitation phenomena and this topic has been the subject of many research works. In fact, the simulation of non-spherical bubble dynamics and its interaction with solid boundaries have received much less attention due to the complexity of the problem. One of the main reasons of the structural damages in the cavitation phenomenon is due to the formation of micro jets generated due to the bubble collapse and impinging on the solid surfaces or boundaries. The boundary integral method (BIM) based on Green’s function is used to model the oscillation and collapse of a cavitation bubble close to a rigid boundary. The liquid is considered to be incompressible, inviscid, and irrational around the bubble. These assumptions satisfy the conditions for the Laplacian equation. The theory permits one to predict correctly the interaction between the bubble and the rigid boundary, which is of great importance in the study of cavitation damage due to a bubble collapsing close to the boundaries. The results reveal that the amplitude of bubble oscillation depends on the bubble location away from a rigid surface. Also, the theory for the cavitation bubble dynamics presented in this study has many advantages in various situations and might be helpful to understand effects of the cavitation phenomenon such as generation of excessive vibration, surface erosion and undesirable acoustic emission.
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| 24. |
- Alhelfi, Ali Kadhim Hadi, et al.
(författare)
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The Cavitation Phenomenon: A Literature Survey
- 2014
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Ingår i: Transactions of the Wessex Institute.
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Konferensbidrag (refereegranskat)abstract
- The meaning of the word cavitation is not known or understandable for many people. The definition which is commonly known about such phenomena is that the formation of cavities or bubbles is encouraged by a pressure change in the surroundings. However, cavitation is much more complex. A large amount of research work and studies on the dynamics of the cavitation phenomenon via numerical investigations or by means of experimental studies have been performed in this sense over past years in order to improve the understanding of the various physical processes involved in this phenomenon. This paper presents a literature survey of existing studies on the cavitation phenomenon and aims to give a comprehensive collection of knowledge about it. The present work does not aim to review all published results in this field. The paper focuses on specific available published results, concerning the most common cavitation types especially acoustic cavitation. The authors like to provide some recommended notices and the main efforts which must be carried out to develop and contribute more efficient knowledge about the real situation and the main results associated with this phenomenon.
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| 25. |
- Castaño Arranz, Miguel, et al.
(författare)
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On Guided and Automatic Control Configuration Selection : Application on a Secondary Heating System
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This technical report provides supplementary materialto the research paper entitled ”On Guided and AutomaticControl Configuration Selection”, presented at the ETFA 2017.In that paper, different Control Configuration Selection (CCS)tools are reviewed and integrated into guided and automaticCCS methodologies. The guided CCS is a heuristic step-by-stepmethodology to be applied by practitioners, while the automaticCCS methodologies target the adaptation of such heuristicsinto algorithms which can be run in a computer and assist thepractitioners in the decision making. This report summarizesthe results of applying the introduced methodologies to a reallifeprocess: the Secondary Heating System. For an introductorybackground, preliminaries, and details on the methodologies,the reader is referred to the original research paper.
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| 26. |
- Castaño Arranz, Miguel, et al.
(författare)
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On Guided and Automatic Control Configuration Selection
- 2018
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Ingår i: IEEE International Conference on Emerging Technologies and Factory Automation (ETFA). - Piscataway, Nj : Institute of Electrical and Electronics Engineers (IEEE). - 9781509065059
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Konferensbidrag (refereegranskat)abstract
- This paper discusses the guided and automatic control configuration selection in large scale complex systems. Due to the trend of increasesd level of automation and connectedness which is promoted by the Industry 4.0 strategy and supported by technologies relating to cyber-physical systems and the industrial internet of things, selecting appropriate control strategies becomes increasingly important and complex. This is especially important as a control strategies will limit the achievable performance of the process system, and there are trade-offs between complexity of the control strategies, achievable performance, vulnerability and maintainability.The paper reviews the state of the art of methodologies that support the practitioners in taking decisions on control strategies, where two main approaches are considered, the guided one and a fully automatic one. It is shown how both approached can be conducted and examples are used to clarify the selection process.
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| 27. |
- Kadhim, Ali, et al.
(författare)
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Automated Control Configuration Selection Considering System Uncertainties
- 2017
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 56:12, s. 3347-3359
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes an automated pairing approach for configuration selection of decentralized controllers which considers system uncertainties. Following the Relative Interaction Array (RIA) pairing rules, the optimal control configuration, i.e. the configuration that fits best the pairing rules, is obtained automatically by formulating the control configuration selection problem as an Assignment Problem (AP). In this AP, the associated costs related to each input-output pairing are given by the RIA coefficients. The Push-Pull algorithm is used to solve the AP for the nominal system and to obtain the set of costs for which the resulting configuration remains optimal, also called the perturbation set. The introduction of uncertainty bounds on the RIA-based costs enables the testing of the possible violation of the optimality conditions. Examples to illustrate the proposed approach for a 3×3 system and 4×4 gasifier plant are given.
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| 28. |
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| 29. |
- Kadhim, Ali, et al.
(författare)
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Dynamic Relative Gain Array Estimation using Local Polynomial Approximation Approach
- 2016
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Ingår i: Modeling, Identification and Control. - : Norwegian Society of Automatic Control. - 0332-7353 .- 1890-1328. ; 37:4, s. 247-259
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Tidskriftsartikel (refereegranskat)abstract
- This article presents a procedure that utilizes the local polynomial approximation approach in the estimation of the Dynamic Relative Gain Array (DRGA) matrix and its uncertainty bounds for weakly nonlinear systems. This procedure offers enhanced frequency resolution and noise reduction when random excitation is used. It also allows separation of nonlinear distortions with shorter measuring time when multisine excitation is imposed. The procedure is illustrated using the well-known quadruple tank process as a case study in simulation and in real life. Besides, a comparison with the pairing results of the static RGA, nonlinear RGA and DRGA based on linearized quadruple tank model for different simulation cases is performed.
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| 30. |
- Kadhim, Ali
(författare)
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Estimation of the Dynamic Relative Gain Array for Control Configuration Selection
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The control of multi-input multi-output systems (MIMO) is more difficult than for single-input single-output systems (SISO) due to the multitude of input-output couplings. Coupling, simply means that a change in any input leads to changes in many outputs. Nevertheless, in many cases, a simple decentralised controller is usually sufficient to achieve desired performance goals. However, there is a need for systematic techniques that can suggest the most promising configurations or pairings for the decentralized controller.The relative gain array (RGA) has proven itself to be an efficient tool to solve the pairing problem. It is easily calculated and does not depend on input-output scaling. However, it gives misleading results in some cases where system dynamics are involved and hence Dynamic Relative Gain Array (DRGA) used instead. The commonplace procedure to estimate DRGA values from the input-output data is to identify a parametric system model. Thus, the user needs to decide a model structure and a model order to calculate the system frequency response. Eventually, DRGA values are obtained based on that system frequency response over the frequency range of interest. In this work, a method which requires less user interaction is proposed. The system frequency response, and subsequently the DRGA, is directly estimated from the input-output data by employing a non-parametric identification approach. Such an approach reduces the uncertainties arising from incorrect user decisions by avoiding the parametric model identification. However, DRGA values obtained by the nonparametric identification are subject to different uncertainty sources such as system nonlinearity and noise. In this thesis various strategies are presented to reduce the effect of these uncertainties. In that direction, RGA (DRGA) of linear systems is first analysed using a random excitation signal. Due to the nonperiodic nature of the random signal, the frequency response is susceptible to leakage. To reduce the leakage effect, data is divided into sub-records and the frequency response was averaged over these sub-records. Although the data division proved to be efficient in limiting the leakage effect it has a drawback of reducing the frequency resolution. Moreover, RGA (DRGA) of weakly nonlinear systems is analysed using a multisine excitation signal. The multisine excitation is used to distinguish between the nonlinear distortion and the output noise. It is very difficult to make such distinction using the random excitation. However, long experimental time is needed in returns. To overcome the shortcomings represented by low frequency resolution and the experiment running time, local polynomial approximation approach (LPA) is investigated using both random and multisine excitation.In that direction, RGA (DRGA) of linear systems is first analysed using a random excitation signal. Due to the nonperiodic nature of the random signal, the frequency response is susceptible to leakage. To reduce the leakage effect, data is divided into sub-records and the frequency response was averaged over these sub-records. Although the data division proved to be efficient in limiting the leakage effect it has a drawback of reducing the frequency resolution. Moreover, RGA (DRGA) of weakly nonlinear systems is analysed using a multisine excitation signal. The multisine excitation is used to distinguish between the nonlinear distortion and the output noise. It is very difficult to make such distinction using the random excitation. However, long experimental time is needed in returns. To overcome the shortcomings represented by low frequency resolution and the experiment running time, local polynomial approximation approach (LPA) is investigated using both random and multisine excitation.It can be concluded that the proposed approach achieves quite accurate RGA values with the advantage of exempting the user from deriving a complete parametric model of the plant. Hence, efforts of identifying the parameters of all MIMO subsystems can be saved by finding the parameters of the most significant subsystems of a multivariable system.
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| 31. |
- Kadhim, Ali, et al.
(författare)
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Evaluation of vehicle tracking for traffic monitoring based on road surface mounted magnetic sensors
- 2013
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Ingår i: The Third IFAC Symposium on Telematics Applications (TA 2013)Applications. - Red Hook, NY : Curran Associates, Inc.. - 9781629937243 ; , s. 13-18
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Konferensbidrag (refereegranskat)abstract
- The aim of this work is to evaluate a vehicle tracking scheme as a means of monitoring traffic on roads. The scheme can be used as a component in a traffic monitoring system which can provide traffic management systems and road maintainers with traffic information. Vehicle tracking is achieved by determining vehicle position, velocity and magnetic moment using a nonlinear weighted least squares method (NWLS) on readings from two 3-axes magnetic sensors.The tracking was performed both in simulation and in real life. The traffic monitoring system is composed of two adjacently glue attached wireless sensor nodes, which are placed at a distance of 1 m along the road. A potential misalignment of the sensors due to placement errors is analysed in simulation and addressed.
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| 32. |
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| 33. |
- Kadhim, Ali, et al.
(författare)
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Relative Gain Array Estimation Based on Non-Parametric Frequency Domain System Identification
- 2014
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Ingår i: 2014 IEEE International Conference on Control Applications (CCA 2014). - Piscataway, NJ : IEEE Communications Society. - 9781467345033 ; , s. 110-115
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Konferensbidrag (refereegranskat)abstract
- Since the introduction of the Relative Gain Array (RGA) by Bristol in 1966, it has received a high level of attention as a practical tool for solving the input-output pairing problem in decentralized control. Moreover, many extensions have been proposed like e.g. for the dynamic case and non-square system matrices. Recently, extensions that provide tools for uncertain parametric process models were suggested. In order to removethe dependency of these tools on a parametric description and accurate knowledge of a nominal model this paper proposes a method to calculate the RGA directly from a non-parametric frequency response matrix (FRM), derived from frequency domain system identification approach. The proposed method reduces the influence of model uncertainties on the calculation of the RGA and derives the RGA at frequencies of interest. Using Monte-Carlo principles, the variance of the estimated RGA is derived and compared with recently proposed methods. The results are exemplified on 2 by 2, 2 by 3 and 3 by 3 systems. It concluded that the proposed methods performs well and robust, while simplifying the estimation of the RGA.
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| 34. |
- Kadhim, Ali, et al.
(författare)
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Relative Gain Array Estimation Based on Non-parametric Process Identification for Uncertain Systems
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Since the introduction of the Relative Gain Array (RGA) by Bristol in 1966, it has become awidely used practical tool for solving the input-output pairing problems in decentralized control. In order to remove the dependency of this tool on a parametric description and accurate knowledge of a nominal model, this work proposes a method to estimate the RGA directly from a non-parametric frequency response matrix (FRM) derived from a frequency domain system identification approach. The proposed method reduces the influence of model uncertainties on the calculation of the RGA and derives the RGA at frequencies of interest. The results are exemplified using a 2x3 LTI systems and a 2x2 uncertain system.
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| 35. |
- Kadhim, Ali, et al.
(författare)
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Relative Gain Array of Weakly Nonlinear Systems using a Nonparametric Identification Approach
- 2015
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Ingår i: 2015 IEEE International Conference on Control Applications (CCA 2015). - Piscataway, NJ : IEEE Communications Society. - 9781479977871 ; , s. 1612-1617
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Konferensbidrag (refereegranskat)abstract
- This article presents a procedure to estimate the relative gain array (RGA) matrix for weakly nonlinear systems by means of nonparametric identification of the frequency response matrix (FRM). Specifically, the best linear approximation of nonlinear systems and the covariance of the nonlinear distortions are used in the relative gain array estimation. For the estimation neither process model nor model structure need to be known which is an advantage over methods that require accurate knowledge of a parametric process model. The proposed approach is compared with the original RGA and a nonlinear RGA calculation using the well-known quadruple tank process as a case
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| 36. |
- Kadhim, Ali, et al.
(författare)
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Relative Gain Array Variation for Norm Bounded Uncertain Systems
- 2015
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Ingår i: IEEE 54th Annual Conference on Decision and Control (CDC). - Piscataway, NJ : IEEE Communications Society. - 9781479978847 ; , s. 5959-5965
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Konferensbidrag (refereegranskat)abstract
- This article proposes computationally tractable, easyto expand and tight relative gain variation bound for uncertain systems. The proposed bound is a further development of previous work, which is summarized anddiscussed. Using several examples, the new method is compared with previous results and the advantages are highlighted. The prediction of sign changes in relative gain array elements due to uncertainties is important for pairing decisions. Based on the proposed bound,a method for the prediction of the uncertainty levels which render sign changes is suggested. The prediction method is currently limited to certain classes of systems.In this prediction method neither prior knowledge of the uncertainty nor numerous calculations are needed.
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| 37. |
- Kadhim, Ali
(författare)
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Selection of Decentralized Control Configuration for Uncertain Systems
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Industrial processes nowadays involve hundreds or more of variables to be maintained within predefined ranges to achieve the production demands. However, the lack of accurate models and practical tools to design controllers for such large processes motivate the engineers/practitioners to break the processes down into smaller subsystems and applying decentralized controllers.In contrast to the centralized controller, the decentralized controller is favourable in large-scale systems due to its robustness against loop failures and model uncertainties as well as being easier to tune and update. Yet, two steps are required prior to synthesizing these single-input single-output (SISO) controllers that comprise the decentralized controller. In the first step, a set of manipulated and the controlled variables need to be selected while the second step deals with pairing these variables to close the SISO control loops in a manner that limits the interaction between the loops. The latter step, called "input-output pairing", is usually performed by means of interaction measures (IM) tools using a nominal system model. Taking model uncertainties into consideration when deciding the pairing selection of the decentralized controller is necessary since adopting the pairing based on the nominal system model might be misleading and resulting in poor system performance or instability. It is therefore essential to have tools indicating the extent to which the pairing based on the nominal model persists against gain variations due to uncertainties.The work in this thesis presents a methodology that determines whether the effect of gain uncertainty would invalidate the selected pairing. This has been done following the definition of the most established IM tool used in the industry, the relative gain array (RGA), and some of its variants. Further, a procedure has been developed to automatically obtain the optimal input-output pairing by formulating the pairing rules of relative interaction array (RIA) method as an \textit{assignment problem} (AP), and thus, simplifying the pairing selection for large-scale systems. Thereafter, uncertainty bounds of the RIA elements are employed to validate the pairing selection under the effect of given variations of the system gain. Moreover, following the RIA pairing rules, a method is proposed to calculate a minimum amount of uncertainty that renders a perturbed system for which the pairing, obtained from the nominal system model, becomes invalid.In the aforementioned methodologies, a parametric system model is assumed to be known. To relax this constraint, an approach is therefore proposed and evaluated which identifies the pairing of the decentralized controller directly from the input-output data. This approach has the advantage of exempting the user from deriving a complete parametric model of the plant to decide the input-output pairing, and hence saves the efforts by finding the parameters of the most significant subsystems in a multivariable system. The frequency response of the system and its covariance, and subsequently the dynamic RGA (DRGA) and corresponding uncertainty bounds, are estimated from the input-output data by employing a nonparametric system identification approach. In short, the work presented in this thesis provides beneficial methodologies for researchers in academia as well as engineers in industry to predict the influence of the system gain uncertainty on the pairing selection of decentralized controllers.
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| 38. |
- Kadhim, Ali, et al.
(författare)
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System Uncertainty Effect on Optimal Control Configuration Selection
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An approach to investigate the effect of system uncertainty on the optimal controlconfiguration selection in multivariable systems is proposed. An optimal control configuration,i.e the configuration which best agrees with input-output pairing rules according to certaininteraction measure (IM) can be obtained automatically by formulating the control configurationselection as a Transportation Problem (TP). The proposed approach then checks whetherthis optimal control configuration is valid for given system uncertainties or if a change in theconguration could be expected.
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| 39. |
- Kadhim Al-lami, Ahmed, et al.
(författare)
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Using Vegetation Indices for monitoring the spread of Nile Rose plant in the Tigris River within Wasit province, Iraq
- 2021
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Ingår i: Remote Sensing Applications: Society and Environment. - : Elsevier. - 2352-9385. ; 22
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Tidskriftsartikel (refereegranskat)abstract
- The Nile rose or water hyacinth (Eichhornia crassipes) is an aquatic species threaten socio-economic and ecological systems, by invading freshwater ecosystems, affecting their productivity and functionality, as well as causing unfixable damage to key hydrological processes. Spectral signature differences can play a common role through using remote identification for these invasive plants, by using hyperspectral data, while many other studies showed that textural and phrenological differences are also can be considered as an effective strategy in this critical problem. New generation sensors like Sentinel 2 and Landsat 8 sensors of recently launched crop with improved sensing characteristics, unlike the previous broadband multispectral sensors has been provided untapped prospective alternatives. New insights were introduced in the detecting, mapping, and monitoring the spread of Nile Rose aquatic plant in the Tigris River at Wasit province in Iraq which has caused damage to fishing nets and make it difficult for fishermen to paddle on the river. Vegetation indices have been used to assess the impacts on major socio-economic activities in the study area. Spectral reflectance of Landsat 8 operational land imager OLI (acquired at 6 Oct 2016) was used to differentiate the spectral signature of the water hyacinth from other plants. These indices recorded the highest reflection of the Nile Rose plant relative to the rest of the plants. The result showed that the green Chlorophyll Index (CL Green) with overall accuracy of 89% which proved that this study has established a promising method for monitoring the invasion of the Nile Rose in the Tigris River to insure the availability of safe drinking water as a main source for the people such as in the study area nearby the part of Tigris River.
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