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RISS 인기검색어
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Formulation and evaluation of incompatible but convergent rational quadrilateral membrane elements
Batoz, J.L.,Hammadi, F.,Zheng, C.,Zhong, W. Techno-Press 2000 Structural Engineering and Mechanics, An Int'l Jou Vol.9 No.2
This paper presents four incompatible but convergent Rational quadrilateral elements, two four-node elements (RQ4Z and RQ4B) and two five-node elements (RQ5Z and RQ5B). The difference between the so-called Rational Finite Element (Zhong and Zeng 1996) and the Free Formulation (Bergan and Nygard 1984) are discussed and compared. The importance of the mode completeness in these formulations is emphasized. Numerical results for several benchmark problems show the good performance of these elements. The two five-nodes elements RQ5Z and RQ5B, which can be viewed as complete quadratic mode elements (with seven stress modes), always give better results than the four nodes elements RQ4Z and RQ4B.
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Abdelmonaam Abid,Moncef Hammadi,Maher Barkallah,Jean-Yves Choley,Jamel Louati,Alain Rivière,Mohamed Haddar 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.12
Globalization and mass customization are demanding a higher level of productivity. The relevance of modelling approaches to the study and design of reconfigurable manufacturing system (RMS) is widely claimed to achieve the highest productivity. Principally, reconfigurability in manufacturing systems should support the changeability with precisely the production capacity and functionality needed and exactly when needed. Simulation of such reconfigurable systems has become more and more difficult with the increasing complexity of system requirements. In spite of the promising methodology for designing RMS, an effective framework that bridges the gap between conceptual modelling level process and simulation level process is still a major challenge for Scientist. For this reason, we propose in this paper a generic framework especially designed for building and running executable agent-based models of RMS. This framework relies on SysML (Systems Modelling Language) models specifications, the holonic system techniques and multi-agent system in order to generate executable models of RMS. The considered case study for this paper is based on a steel converter process. Results showed an increase in the productivity rate after simulating the reconfigurability test cases through the developed agent-based models.
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A new shear deformation shell theory for free vibration analysis of FG sandwich shells
Omar Slimani,Zakaria Belabed,Fodil Hammadi,Noureddine Taibi,Abdelouahed Tounsi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.6
In recent years, many researches have been published dealing with the mechanical responses of shells with variable cross-sectional mechanical properties such as sandwich, functionally graded and laminated composites shells. In the present paper, a simple and efficient shear deformation theory is formulated for the free vibration response of functionally graded sandwich shells. The main advantage of this theory is its reduced number of unknowns and their related governing equations and theses tend to be highly compared to others shear deformation shell theories. Two kinds of FG sandwich shells are studied with respect to their geometrical configuration and material properties. The first kind is composed of FG facesheet and homogeneous core and the other is formed by homogeneous facesheet and FG core. The governing equations of motion for the free vibration analysis are obtained using Hamilton’s principle. The closed form solutions are sought by using the Navier’s method for eigenvalue problems. The accuracy and efficiency of the present theory are established and proved by comparing obtained numerical results with those predicted by other higher order shear deformation shell theories. The influences of various parameters such as material distribution, thickness of the core and the facesheet of sandwich shell and curvature ratios are studied, discussed and reported as significant rate sensitivity to predict the fundamental frequencies of FG sandwich shells.
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Vandenplas, Yvan,Abuabat, Ahmed,Al-Hammadi, Suleiman,Aly, Gamal Samy,Miqdady, Mohamad S.,Shaaban, Sanaa Youssef,Torbey, Paul-Henri The Korean Society of Pediatric Gastroenterology 2014 Pediatric gastroenterology, hepatology & nutrition Vol.17 No.2
Presented are guidelines for the prevention, diagnosis, and treatment of cow's milk protein allergy (CMPA) which is the most common food allergy in infants. It manifests through a variety of symptoms that place a burden on both the infant and their caregivers. The guidelines were formulated by evaluation of existing evidence-based guidelines, literature evidence and expert clinical experience. The guidelines set out practical recommendations and include algorithms for the prevention and treatment of CMPA. For infants at risk of allergy, appropriate prevention diets are suggested. Breastfeeding is the best method for prevention; however, a partially hydrolyzed formula should be used in infants unable to be breastfed. In infants with suspected CMPA, guidelines are presented for the appropriate diagnostic workup and subsequent appropriate elimination diet for treatment. Exclusive breastfeeding and maternal dietary allergen avoidance are the best treatment. In infants not exclusively breastfed, an extensively hydrolyzed formula should be used with amino acid formula recommended if the symptoms are life-threatening or do not resolve after extensively hydrolyzed formula. Adherence to these guidelines should assist healthcare practitioners in optimizing their approach to the management of CMPA and decrease the burden on infants and their caregivers.
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Yvan Vandenplas,Ahmed Abuabat,Suleiman Al-Hammadi,Gamal Samy Aly,Mohamad S Miqdady,Sanaa Youssef Shaaban,Paul-Henri Torbey 대한소아소화기영양학회 2014 Pediatric gastroenterology, hepatology & nutrition Vol.17 No.2
Presented are guidelines for the prevention, diagnosis, and treatment of cow’s milk protein allergy (CMPA) which is the most common food allergy in infants. It manifests through a variety of symptoms that place a burden on both the infant and their caregivers. The guidelines were formulated by evaluation of existing evidence-based guidelines, literature evidence and expert clinical experience. The guidelines set out practical recommendations and include algorithms for the prevention and treatment of CMPA. For infants at risk of allergy, appropriate prevention diets are suggested. Breastfeeding is the best method for prevention; however, a partially hydrolyzed formula should be used in infants unable to be breastfed. In infants with suspected CMPA, guidelines are presented for the appropriate diag-nostic workup and subsequent appropriate elimination diet for treatment. Exclusive breastfeeding and maternal diet-ary allergen avoidance are the best treatment. In infants not exclusively breastfed, an extensively hydrolyzed formula should be used with amino acid formula recommended if the symptoms are life-threatening or do not resolve after extensively hydrolyzed formula. Adherence to these guidelines should assist healthcare practitioners in optimizing their approach to the management of CMPA and decrease the burden on infants and their caregivers.
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Disassembly Process Planning and Its Lines Balancing Prediction
Mahdi Aicha,Imen Belhadj,Moncef Hammadi,Nizar Aifaoui 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.6
Design centers and industrial organizations emphasize that process planning is one of the most important pillars that guarantee an efficient production system, as it represents the principal link between design and manufacturing in target of avoiding time and cost wastes. In order to ensure an effective assembly/disassembly process implementation, several parameters have to be properly treated during the planning phase: product data collection and analysis, alignment with customer demand forecast, capacity calculation and equipment/tools planning, in addition to identify layout steps and process setting-up phases. One of the most important procedures that initiate a product remanufacturability and recyclability is disassembly process. That’s why it is mandatory to predict the disassembly process planning and predefine it in advance. This research paper proposes an analytical formulation of disassembly process planning prediction: it is a proactive procedure which model need of equipment, layout and line balancing from the early design phase of product. The disassembly process elements are defined with reference to a previously extracted disassembly plans (DP) from literature, and the disassembly process planning prediction is applied on an optimal disassembly plan selected based on two combined indicators which are Quality index (Qi) and timing index (Ti).
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Akram Alaya,Abdellatif Nouri,Mohsen Belgith,Hammadi Saad,Riadh Jouini,Mohamed Fadhel Najjar 대한진단검사의학회 2012 Annals of Laboratory Medicine Vol.32 No.3
Background: Studies that evaluate the effect of age on stone composition are scarce. The aim of this study was to highlight the changes in epidemiological characteristics (stone composition and location) of urolithiasis according to patients’ age. Methods: We studied 1,301 urolithiasis patients with age ranging from 6 months to 92 yr (781 males and 520 females). Stone analysis was performed using a stereomicroscope and infrared spectroscopy to determine the morphological type and molecular composition of each stone. Results: The annual average incidence of new stone formation was 31.7 per 100,000 persons. In 71.8% of cases, calculi were located in the upper urinary tract. Compared to other age groups, children and old men were more affected by bladder stones. Calcium oxalate monohydrate was the most frequent stone component, even though its frequency decreased with age (59.5% in young adults and 43.7% in the elderly, P<0.05) in favor of an increase in uric acid stones (11.5% in young adults and 36.4% in the elderly, P<0.05). Struvite stones were rare (3.8%) and more frequent in children than in adults. Conclusions: The analysis of these data showed that urinary stones in Tunisian patients are tending to evolve in the same direction as the stones in patients from industrialized countries. Background: Studies that evaluate the effect of age on stone composition are scarce. The aim of this study was to highlight the changes in epidemiological characteristics (stone composition and location) of urolithiasis according to patients’ age. Methods: We studied 1,301 urolithiasis patients with age ranging from 6 months to 92 yr (781 males and 520 females). Stone analysis was performed using a stereomicroscope and infrared spectroscopy to determine the morphological type and molecular composition of each stone. Results: The annual average incidence of new stone formation was 31.7 per 100,000 persons. In 71.8% of cases, calculi were located in the upper urinary tract. Compared to other age groups, children and old men were more affected by bladder stones. Calcium oxalate monohydrate was the most frequent stone component, even though its frequency decreased with age (59.5% in young adults and 43.7% in the elderly, P<0.05) in favor of an increase in uric acid stones (11.5% in young adults and 36.4% in the elderly, P<0.05). Struvite stones were rare (3.8%) and more frequent in children than in adults. Conclusions: The analysis of these data showed that urinary stones in Tunisian patients are tending to evolve in the same direction as the stones in patients from industrialized countries.
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Mahdi Aicha,Imen Belhadj,Moncef Hammadi,Nizar Aifaoui 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.6
Every industrial organization, whether it deals with an assembly or a disassembly process, is definitely putting a huge focus on how to optimize its operative mode by reducing: process variation, frequent changes of production tools, quality issues, wastes. That’s why, disassembly plan generation (DP) is a very supportive tool that detects and identifies difficulties and probable blocking assembly/disassembly situations from the early design steps and avoid them. This anticipation is quite beneficial to manufactories point of view cost, time and quality of products as it returns with a remarkable reduction in production stopping time and products’ defects, as a result reduction in cost of production. In order to ameliorate DP algorithm decision generation and make it very similar to real manufacturing circumstances, this article comes with a new approach that combines between two main metrics, which are the Quality index (Qi) and the Timing index (Ti), as criteria while selecting optimal and feasible DP. Qi is calculated based on the failure mode, effects and criticality analysis method (FMECA), on the other side, Ti represents the real processing time index with reference to real manufacturing constraints (workplace, lay-out, work-flow, tools, machines…). To highlight the effectiveness of the proposed approach, an industrial gear box example is simulated and compared to a literature study.
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