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Ultrasonic Vibration-Assisted Machining (UVA) is a machining process that adds a micro-scale high frequency vibration to the motion of a cutting tooltip to interrupt the continuous interaction of tool - workpiece surface. A good point of machining with UVA is more effective than conventional processes such as lower machining forces, higher machining stability, less tool wear and better surface finishes. In molds fabrication with some narrow cavities having a conversion space diameter of less than 3mm will face many difficulties while low surface roughness is required. Low stiffness of technological system in these cases of finishing machining is the reason of a weak machining in high-speed cutting. The ability to achieve cutting speeds for surface finishing of this type in tight spaces is also an interesting application for UVA tools. This paper discusses the finishing machining tool design with UVA for milling machine in such as analyze of the main parameters, adding diagonal split and simulation of the generated vibration effects to evaluate the achieved results before fabrication by using the help of ANSYS.

International audience

International audience

Arsenic (As) contaminated groundwater has been a major concern due to the negative impacts to exposed people. This research was conducted to assess and compare the removal efficiency of As from groundwater by laterite, sand, and ash. The experiment was carried out in 14 days in a household scale in Son Dong commune, Hoai Duc district, Ha Noi. Groundwater was pumped directly from a well and flowed through 20 cm (diameter) x 80 cm (length) columns. The initial As concentration in groundwater was 526 µg/L decreasing to an average of 189, 192 and 154 µg/L after being filtrated using sand, ash, and laterite, respectively. Average removal efficiency of sand, ash and laterite during the experiment was 63.3, 63.9, and 70.5%, respectively. Laterite had higher As removal efficiency may be due to higher content of goethite and kaolinite in this sorbent which resulted in better adsorption of As. The concentrations of As in the outflow water were higher than the allowable limit set by the national technical regulation on drinking water quality (QCVN 01:2009/BYT). Therefore, it requires higher volume of sorbents or additional treatment technologies for removal of As from groundwater. Ô nhiễm asen (As) trong nước ngầm hiện nay là một vấn đề cấp bách đối với xã hội bởi những rủi ro tiềm ẩn với sức khoẻ con người. Nghiên cứu được thực hiện nhằm đánh giá và so sánh khả năng hấp phụ As trong nước ngầm của đá ong, cát và tro. Thí nghiệm được tiến hành trong vòng 14 ngày đặt tại một hộ gia đình có nguồn nước ngầm bị ô nhiễm As thuộc xã Sơn Đồng, huyện Hoài Đức, Hà Nội. Nước ngầm được bơm từ giếng và chảy qua các cột đựng vật liệu có đường kính và chiều dài lần lượt là 20 cm và 80 cm. Nồng độ As ban đầu là 526 µg/L đã giảm xuống còn 189, 192 và 154 µg/L sau khi lọc bằng cát, tro và đá ong. Hiệu suất xử lý As trung bình của cát, tro và đá ong lần lượt là 63,3, 63,9 và 70,5 µg/L. Đá ong xử lý As tốt hơn có thể do hàm lượng goethit và kaolinit cao hơn trong vật liệu hấp phụ này dẫn đến khả năng hấp phụ As tốt hơn. Tuy nhiên hàm lượng As trong nước đầu ra vẫn chưa đạt quy chuẩn cho nước uống (QCVN 01:2009/BYT). Do đó, cần tăng thêm lượng vật liệu hoặc kết hợp với các phương pháp khác để xử lý As hiệu quả hơn., Journal of Vietnamese Environment, Vol 9 No 4 (2018)

National audience

Real-time embedded systems (RTES) are subject to timing constraints. In these systems, the total correctness depends not only on the logical correctness of the computation but also on the time in which the result is produced (Stankovic, 1988). The systems must be highly predictable in the sense that the worst case execution time of each task must be determined. Then, scheduling analysis is performed on the system to ensure that there are enough resources to schedule all of the tasks.Cache memory is a crucial hardware component used to reduce the performance gap between processor and main memory. Integrating cache memory in a RTES generally enhances the whole performance in term of execution time, but unfortunately, it can lead to an increase in preemption cost and execution time variability. In systems with cache memory, multiple tasks can share this hardware resource which can lead to cache related preemption delay (CRPD) being introduced. By definition, CRPD is the delay added to the execution time of the preempted task because it has to reload cache blocks evicted by the preemption. It is important to be able to account for CRPD when performing schedulability analysis.This thesis focuses on studying the effects of CRPD on uniprocessor systems and employs the understanding to extend classical scheduling analysis methods. We propose several priority assignment algorithms that take into account CRPD while assigning priorities to tasks. We investigate problems related to scheduling simulation with CRPD and establish two results that allows the use of scheduling simulation as a verification method. The work in this thesis is made available in Cheddar - an open-source scheduling analyzer. Several CRPD analysis features are also implemented in Cheddar besides the work presented in this thesis.; Les systèmes embarqués en temps réel (RTES) sont soumis à des contraintes temporelles. Dans ces systèmes, l'exactitude du résultat ne dépend pas seulement de l'exactitude logique du calcul, mais aussi de l'instant où ce résultat est produit (Stankovic, 1988). Les systèmes doivent être hautement prévisibles dans le sens où le temps d'exécution pire-cas de chaque tâche doit être déterminé. Une analyse d’ordonnancement est effectuée sur le système pour s'assurer qu'il y a suffisamment de ressources pour ordonnancer toutes les tâches. La mémoire cache est un composant matériel utilisé pour réduire l'écart de performances entre le processeur et la mémoire principale. L'intégration de la mémoire cache dans un RTES améliore généralement la performance en terme de temps d'exécution, mais malheureusement, elle peut entraîner une augmentation du coût de préemption et de la variabilité du temps d'exécution. Dans les systèmes avec mémoire cache, plusieurs tâches partagent cette ressource matérielle, ce qui conduit à l'introduction d'un délai de préemption lié au cache (CRPD). Par définition, le CRPD est le délai ajouté au temps d'exécution de la tâche préempté car il doit recharger les blocs de cache évincés par la préemption. Il est donc important de pouvoir prendre en compte le CRPD lors de l'analyse d’ordonnancement. Cette thèse se concentre sur l'étude des effets du CRPD dans les systèmes uni-processeurs, et étend en conséquence des méthodes classiques d'analyse d’ordonnancement. Nous proposons plusieurs algorithmes d’affectation de priorités qui tiennent compte du CRPD. De plus, nous étudions les problèmes liés à la simulation d'ordonnancement intégrant le CRPD et nous établissons deux résultats théoriques qui permettent son utilisation en tant que méthode de vérification. Le travail de cette thèse a permis l'extension de l'outil Cheddar - un analyseur d'ordonnancement open-source. Plusieurs méthodes d'analyse de CRPD ont été également mises en oeuvre dans Cheddar en complément des travaux présentés dans cette thèse.

Real-time embedded systems (RTES) are subject to timing constraints. In these systems, the total correctness depends not only on the logical correctness of the computation but also on the time in which the result is produced (Stankovic, 1988). The systems must be highly predictable in the sense that the worst case execution time of each task must be determined. Then, scheduling analysis is performed on the system to ensure that there are enough resources to schedule all of the tasks.Cache memory is a crucial hardware component used to reduce the performance gap between processor and main memory. Integrating cache memory in a RTES generally enhances the whole performance in term of execution time, but unfortunately, it can lead to an increase in preemption cost and execution time variability. In systems with cache memory, multiple tasks can share this hardware resource which can lead to cache related preemption delay (CRPD) being introduced. By definition, CRPD is the delay added to the execution time of the preempted task because it has to reload cache blocks evicted by the preemption. It is important to be able to account for CRPD when performing schedulability analysis.This thesis focuses on studying the effects of CRPD on uniprocessor systems and employs the understanding to extend classical scheduling analysis methods. We propose several priority assignment algorithms that take into account CRPD while assigning priorities to tasks. We investigate problems related to scheduling simulation with CRPD and establish two results that allows the use of scheduling simulation as a verification method. The work in this thesis is made available in Cheddar - an open-source scheduling analyzer. Several CRPD analysis features are also implemented in Cheddar besides the work presented in this thesis.; Les systèmes embarqués en temps réel (RTES) sont soumis à des contraintes temporelles. Dans ces systèmes, l'exactitude du résultat ne dépend pas seulement de l'exactitude logique du calcul, mais aussi de l'instant où ce résultat est produit (Stankovic, 1988). Les systèmes doivent être hautement prévisibles dans le sens où le temps d'exécution pire-cas de chaque tâche doit être déterminé. Une analyse d’ordonnancement est effectuée sur le système pour s'assurer qu'il y a suffisamment de ressources pour ordonnancer toutes les tâches. La mémoire cache est un composant matériel utilisé pour réduire l'écart de performances entre le processeur et la mémoire principale. L'intégration de la mémoire cache dans un RTES améliore généralement la performance en terme de temps d'exécution, mais malheureusement, elle peut entraîner une augmentation du coût de préemption et de la variabilité du temps d'exécution. Dans les systèmes avec mémoire cache, plusieurs tâches partagent cette ressource matérielle, ce qui conduit à l'introduction d'un délai de préemption lié au cache (CRPD). Par définition, le CRPD est le délai ajouté au temps d'exécution de la tâche préempté car il doit recharger les blocs de cache évincés par la préemption. Il est donc important de pouvoir prendre en compte le CRPD lors de l'analyse d’ordonnancement. Cette thèse se concentre sur l'étude des effets du CRPD dans les systèmes uni-processeurs, et étend en conséquence des méthodes classiques d'analyse d’ordonnancement. Nous proposons plusieurs algorithmes d’affectation de priorités qui tiennent compte du CRPD. De plus, nous étudions les problèmes liés à la simulation d'ordonnancement intégrant le CRPD et nous établissons deux résultats théoriques qui permettent son utilisation en tant que méthode de vérification. Le travail de cette thèse a permis l'extension de l'outil Cheddar - un analyseur d'ordonnancement open-source. Plusieurs méthodes d'analyse de CRPD ont été également mises en oeuvre dans Cheddar en complément des travaux présentés dans cette thèse.

A generated resistance force in the deformation process is considered to increase the resistance torque of a Magneto-Rheological (MR) brake when a variable stiffness material is rolled under the cylindrical form of a roller. This paper proposes a new approach to increase the resistance torque of an MR brake using a large-size magnetic particle which can be considered as the roller mentioned above (steel roller or rolling pin). Due to the cylindrical form of the roller and a line contact between the roller and the surface of the motion part, the steel roller can contribute to create a stronger magnetic field and larger resistance force than the conventional one. In this paper, a new MR brake is successfully designed to generate a higher braking torque than the conventional one, which only uses typical MR fluid. To verify the effect of the roller, the proposed MR brake is compared with the conventional one. Both of the MR brakes are designed with the same magnetic circuit and the same material parameters. The performance of the proposed MR brake is compared with that of the conventional MR brake. The proposed MR brake is verified to have about 200% larger torque than the conventional one.

National audience; This article is a presentation of the Cheddar toolset.Cheddar is a GPL open-source scheduling analysis tool.It has been designed and distributed to allow students to understand the main concepts of the real-time scheduling theory.The tool is built around a simplified ADL (Architecture Description Language)devoted to real-time scheduling theory. Students can directly build their real-time systems models with this ADL andits associated editor, however, it is expected that they use modeling tools to illustrate how scheduling analysis fits in an engineering process.In this article, we introduce the Cheddar ADL and the scheduling analysis features of Cheddar. We alsopresent how Cheddar is implemented and how it can be adapted to specific requirements.Two examples of use of Cheddar are then described.Finally, in the annex of this article, teachers may find a sample of hand-outs that may be used to illustrate real-time scheduling theory with their students.

International audience; Handling cache related preemption delay (CRPD) in pre-emptive scheduling context for real-time systems stays an open issue despite of its practical importance. Priority assignment algorithms and feasibility tests are usually based on the assumption that the preemption cost is negligible. Then, a system that could be schedulable on design time can fail to meet its timing constraints in practice due to preemption costs. In this article, we propose a simple approach to take into account the CRPD when performing priority assignment. The goal is to have a priority assignment algorithm which guarantees the schedulability of systems when tasks suffer CRPD on run-time. For such a purpose, we propose an extension of the feasibility test of Audsley and illustrate it with some examples. An implementation of our priority assignment method has been integrated to the Cheddar scheduling analyzer. A comparison of the proposed algorithm with classical priority assignment algorithms is achieved.

This paper proposed the face detection and tracking system using a embedded computing system for humanoid robot environment which allows the user to observe of recognize an unknown person. For detection faces in image sequence, the system uses the skin color model and deformable ellipse matching. Faces in a view are detected by maximizing the image gradient magnitude around the perimeter of the ellipse (or face line) and the number of skin color pixels in the ellipse area. The information of detected face regions are stored on-line into a face state table and are evaluated for tracking in real-time. Results of this processing are applied to embedded humanoid robot The applied robot acts to detect human's fate and react to it. After this processing, the result is sent to embedded humanoid robot through zigbee wireless module. The robot that got this data acts to detect human's face and react to it.

Nowadays, conventional Magneto-Rheological (MR) fluid has been commonly used in many types of device operating within three its modes that have widely known as valve, shear and squeeze film modes. Except valve mode, shear and squeeze film modes just can generate the weak resistance force. Therefore, this paper proposes a new approach with the purpose that it can help to increase the weak force in shear mode by the application of a large size magnetic particle which is a small steel roller. This kind of particle with its hydrodynamic form helps the new MR brake device which can generate the higher braking torque than the conventional one. The theory of this proposed approach is based on the deformation theory with the support of the improved magnetic field. The practical application of this approach has been examined by experimental results.

This paper presents a novel magnetorheological (MR) brake design incorporating a rotary disk with a waveform boundary that generates a resistance force based on the effects of a material deformation process. This force is transmitted from an external agent and creates the necessary energy for breaking the structure of the hardened MR fluid. Its minimum destructive ability is proportional to the variable stiffness of an MR fluid in a magnetic field. In this design, the waveform wall of a rotary disk crushes the particles chains (fibrils) of the MR fluid together instead of breaking them via strain in a conventional MR brake. The resistance forces and braking torques generated by this crush action are stronger than those produced by strain action. To verify our proposed MR brake, the proposed and conventional MR brakes are designed using similar magnetic circuits and material parameters. We compared the performance of our novel MR brake to the performance of a conventional MR brake, and demonstrated that the measured resistance torque of the proposed MR brake is approximately 600% greater than resistance torques generated by conventional brakes.