Extraction robuste de primitives géométriques 3D dans un nuage de points et alignement basé sur les primitives

Dans ce projet, nous étudions les problèmes de rétro-ingénierie et de contrôle de la qualité qui jouent un rôle important dans la fabrication industrielle. La rétro-ingénierie tente de reconstruire un modèle 3D à partir de nuages de points, qui s’apparente au problème de la reconstruction de la surface 3D. Le contrôle de la qualité est un processus dans lequel la qualité de tous les facteurs impliqués dans la production est abordée. En fait, les systèmes ci-dessus nécessitent beaucoup d’intervention de la part d’un utilisateur expérimenté, résultat souhaité est encore loin soit une automatisation complète du processus. Par conséquent, de nombreux défis doivent encore être abordés pour atteindre ce résultat hautement souhaitable en production automatisée. La première question abordée dans la thèse consiste à extraire les primitives géométriques 3D à partir de nuages de points. Un cadre complet pour extraire plusieurs types de primitives à partir de données 3D est proposé. En particulier, une nouvelle méthode de validation est proposée pour évaluer la qualité des primitives extraites. À la fin, toutes les primitives présentes dans le nuage de points sont extraites avec les points de données associés et leurs paramètres descriptifs. Ces résultats pourraient être utilisés dans diverses applications telles que la reconstruction de scènes on d’édifices, la géométrie constructive et etc. La seconde question traiée dans ce travail porte sur l’alignement de deux ensembles de données 3D à l’aide de primitives géométriques, qui sont considérées comme un nouveau descripteur robuste. L’idée d’utiliser les primitives pour l’alignement arrive à surmonter plusieurs défis rencontrés par les méthodes d’alignement existantes. Ce problème d’alignement est une étape essentielle dans la modélisation 3D, la mise en registre, la récupération de modèles. Enfin, nous proposons également une méthode automatique pour extraire les discontinutés à partir de données 3D d’objets manufacturés. En intégrant ces discontinutés au problème d’alignement, il est possible d’établir automatiquement les correspondances entre primitives en utilisant l’appariement de graphes relationnels avec attributs. Nous avons expérimenté tous les algorithmes proposés sur différents jeux de données synthétiques et réelles. Ces algorithmes ont non seulement réussi à accomplir leur tâches avec succès mais se sont aussi avérés supérieus aux méthodes proposées dans la literature. Les résultats présentés dans le thèse pourraient s’avérér utilises à plusieurs applications.In this research project, we address reverse engineering and quality control problems that play significant roles in industrial manufacturing. Reverse engineering attempts to rebuild a 3D model from the scanned data captured from a object, which is the problem similar to 3D surface reconstruction. Quality control is a process in which the quality of all factors involved in production is monitored and revised. In fact, the above systems currently require significant intervention from experienced users, and are thus still far from being fully automated. Therefore, many challenges still need to be addressed to achieve the desired performance for automated production. The first proposition of this thesis is to extract 3D geometric primitives from point clouds for reverse engineering and surface reconstruction. A complete framework to extract multiple types of primitives from 3D data is proposed. In particular, a novel validation method is also proposed to assess the quality of the extracted primitives. At the end, all primitives present in the point cloud are extracted with their associated data points and descriptive parameters. These results could be used in various applications such as scene and building reconstruction, constructive solid geometry, etc. The second proposition of the thesis is to align two 3D datasets using the extracted geometric primitives, which is introduced as a novel and robust descriptor. The idea of using primitives for alignment is addressed several challenges faced by existing registration methods. This alignment problem is an essential step in 3D modeling, registration and model retrieval. Finally, an automatic method to extract sharp features from 3D data of man-made objects is also proposed. By integrating the extracted sharp features into the alignment framework, it is possible implement automatic assignment of primitive correspondences using attribute relational graph matching. Each primitive is considered as a node of the graph and an attribute relational graph is created to provide a structural and relational description between primitives. We have experimented all the proposed algorithms on different synthetic and real scanned datasets. Our algorithms not only are successful in completing their tasks with good results but also outperform other methods. We believe that the contribution of them could be useful in many applications

Evaluate the Results at Minimum 2-Years of Treating Rotator Cuff Tear by Arthroscopic Surgery

BACKGROUND: Rotator cuff tear (RCT) is a common injury of the shoulder, especially middle-aged people. Nonoperative treatment, cortisone injections are only effective at an early stage. Open surgery causes postoperative atrophy of the deltoid muscle, so results are limited. Arthroscopic rotator cuff repair surgery has been performed in Vietnam for about ten years, with many advantages such as the ability to accurately assess the lesions and less invasive procedure. In order to have a clearer view, we performed a mid-term assessment of the effectiveness of this surgery. AIM: Evaluate results over 2 years of patients with rotator cuff tears treated with arthroscopic surgery and their quality of life. METHOD: A group of 30 patients were diagnosed with RCT and surgery by arthroscopy to treat at Hanoi Medical University Hospital and Saint Paul Hospital between Jun 2015 and April 2017. The results of the surgeries were assessed by the degree of pain, muscle power, motion of the shoulder joint according to UCLA shoulder score. Evaluate the quality of life through the Rotator Cuff-Quality of Life (RC-QoL) index. RESULTS: The average age was 60.7 years. Female / male ratio was 1.3. Thirty-six months ± 6.41 was the average follow-up time (min 27 – max 50 months). The shoulder function is recorded according to UCLA has an average score of 30.9, therein good and excellent result were 90 %. The mean RC-QoL index was 91.5%. CONCLUSION: Treatment of RCT by arthroscopic surgery that has been evaluated for a minimum of 2 years follow-up showed good results and high quality of patient’s life

Energy harvesting-based spectrum access with incremental cooperation, relay selection and hardware noises

In this paper, we propose an energy harvesting (EH)-based spectrum access model in cognitive radio (CR) network. In the proposed scheme, one of available secondary transmitters (STs) helps a primary transmitter (PT) forward primary signals to a primary receiver (PR). Via the cooperation, the selected ST finds opportunities to access licensed bands to transmit secondary signals to its intended secondary receiver (SR). Secondary users are assumed to be mobile, hence, optimization of energy consumption for these users is interested. The EH STs have to harvest energy from the PT's radio-frequency (RF) signals to serve the PTPR communication as well as to transmit their signals. The proposed scheme employs incremental relaying technique in which the PR only requires the assistance from the STs when the transmission between PT and PR is not successful. Moreover, we also investigate impact of hardware impairments on performance of the primary and secondary networks. For performance evaluation, we derive exact and lower-bound expressions of outage probability (OP) over Rayleigh fading channel. Monte-Carlo simulations are performed to verify the theoretical results. The results present that the outage performance of both networks can be enhanced by increasing the number of the ST-SR pairs. In addition, the outage performance of both primary and secondary networks is severely degraded with the increasing of hardware impairment level. It is also shown that fraction of time used for EH and positions of the secondary users significantly impact on the system performance.Web of Science26125024

A Comparative Survey on 3D Models Retrieval Methods

In computer vision many studies have been conducted in order to perform the matching and comparison of 3D models of objects. The main goal of matching is to group the models into different categories according to their similarity in order to allow their retrieval for recognition purposes and for further usage. So, in most of the cases, the comparison is run on a large dataset containing various models whether they belong to the same type of object or not and generally having similar or different shapes and poses. The objects’ nature and characteristics are important factors to be taken into consideration before performing the comparison step. We distinguish between two main categories of objects: rigid objects and deformable objects whose treatment and handling differ in the modeling as well as in the comparison phases. In this paper, we will be focusing on the comparison of deformable objects, and thus dealing with objects whose shapes might vary in different instances. For this purpose two main approaches used in the retrieval of 3D deformable models will be reviewed and implemented: the spectral approach and the bag-of-features approach. The deformation or variation in shape involves different aspects depending on the type of object. It could be a change in the posture of an articulated or bendable model, or it could result from a variation (loss or gain) in the total mass leading to a change in the surface and thus in the shape of the object. Even more complex situations occur when both cases are combined together

“False Patellar Duplication†Originated from Synovial Osteochondromatosis in Knee Joint: A Rare Case Report

BACKGROUND: “False patellar duplication†is a situation where there are two pieces in the position of a knee-joint like patella. It can derive from cartilage tumors, soft tissue tumors, or gout tumors, or due to the heterotopic ossification, forming a sub patella in the knee joint. CASE REPORT: A woman, 57 years old, healthy history, she has hospitalized for right knee joint pain since 2 years. Diagnosis: the synovial osteochondromatosis of the right knee. We decided to conduct and arthroscopy and removal. After 18 months surgery, the patient knee joint is currently good, range of motion (ROM) (-10)°- 0°-160°, Lysholm Knee Scoring Scale 85/100 point. CONCLUSION: This is the second case in the world and the first case in Vietnam. This is an experience in the process of diagnosis, arthroscopic treatment and differentiation from the "double patellae" status

FACTORS INFLUENCING VIETNAMESE STUDENTS’ CHOICES TO ATTAIN ENGLISH PROFICIENCY STANDARDS IN A UNIVERSITY IN VIETNAM

In the current era of globalization, English is considered a necessary skill for education and work and a criterion for evaluation in recruitment and graduation assessments in many places in Vietnam. According to the project entitled "Teaching and Learning Foreign Languages in the National Education System Phase 2008 - 2020", non-English majored university students must achieve a minimum of Level 3 according to the 6-level Foreign Language Proficiency Framework used in Vietnam. Several universities have diversified their ways to meet these standards to facilitate students in meeting the English language outcomes, allowing students more opportunities to choose ways that are suitable for them. However, this also indicates that various influencing factors will impact students' selection of ways to meet these standards. This research explores the primary ways students choose to fulfill English language standards as stipulated and analyzes the factors influencing the choices of non-English major students in universities in Vietnam.  Article visualizations

Anatomical Study of Femoral Condylar Index in Magnetic Resonance Imaging: Implication to Total Knee Replacement Surgery for Vietnamese People

BACKGROUND: The femoral rotation angle is important element in total knee replacement (TKR). AIM: To measure this angle, we determine through the axes: the transepicondylar axis (cTEA and sTEA), the posterior condylar axis (PCA), the anteroposterior axis (APA – Whiteside axis). METHODS: Measuring the angles created by the four axes: cTEA, sTEA, PCA and APA in magnetic resonance imaging (MRI); determining the femoral rotation angle and application TKR. RESULTS: the angle between APA and cTEA: 90.41° ± 3.35°, the angle between APA and sTEA: 94.47° ± 3.31°, the angle between APA and PCA: 96.40° ± 4.59°, the angle between cTEA and sTEA: 4.00° ± 1.02°, the angle between cTEA and PCA: 6.53° ± 2.55°, the angle between sTEA and PCA: 3.48° ± 1.91°. CONCLUSION: The angle between sTEA and PCA is the angle that best represents the femoral rotation angle. However, in case of sTEA or PCA is difficult to identify, it can be measure via the APA or cTEA. These angles don’t differ by age, gender and place of knee joint

Primary Cementless Bipolar Long Stem Hemiarthroplasty for Unstable Osteoporotic Intertrochanteric Fracture in the Elderly Patients

BACKGROUND: Intertrochanteric fracture (ITF) is a major part of fracture in femoral head fracture. 95% of ITF are found in elderly patients. Osteosynthese is the preferred method of choice. However, elderly patients had osteoporotic, combined with many of chronic disease conditions that increase the rate of osteosynthese failure. Hemiarthroplasty bipolar long-stem is a surgical method that helps patients relieve pain, facilitate early rehabilitation, limit long-term complications, and improve quality of life for patients. AIM: The aim of our study is to evaluate the clinical of result of primary cementless bipolar long stem hemiarthroplasty in treatment for unstable ITF in the elderly patients who have severe osteoporosis. METHODS: Between 01/2016 and 12/2017, 35 patients with ITF type A2.2 and A2.3 (AO) were included in our prospective study. These patients were over 70 years old and treatment by hemiarthroplasty cementless long stem at E hospital and Saint Paul hospital by one group surgeons. RESULTS: Mean age of studied subjects was 84.29 ± 6.17, the lowest was 71, the highest was 96; ratio male/female was 1/4. Follow-up of 35 patients for at least 6 months showed 88.6% caused by a low-energy injury; Average rehabilitation time was 4.63 ± 1.7 days. The average Harris point at the end was 90.4 ± 4.72. CONCLUSION: Primary cementless bipolar long stem hemiarthroplasty is one of good choices in treatment unstable ITF in elderly patients with severe osteoporosis helped patients improve the quality of life

Preliminary Result of Arthroscopic Anterior Cruciate Ligament Reconstruction Using Anterior Half of Peroneus Longus Tendon Autograft

BACKGROUND: Anthroscopic anterior cruciate ligament reconstruction is one of the most successful operations in sports medicine. At present, ligament autografts have been the best method due to good histocompatibility, rapid healing, no cross-contamination, and low cost of treatment. However, autografts do not have infinite amount and are also not always feasible. Anterior half of peroneus longus tenden autograft is likely to become a source of autograft with many advantages. This study aims to evaluate the clinical outcomes of anthroscopic anterior cruciate ligament reconstruction using anterior half of peroneus longus tendon autograft (AHPLT). AIM: To evaluate the initial outcome of ACL reconstruction arthroscopy by anterior half of peroneus longus tendon. METHODS: This is a prospective non-controlled case series. RESULTS: A prospective study on 30 patients (from 9 / 2016 to 01 / 2019) had both ACL and MCL injury who had operated ACL reconstruction using anterior half of peroneus longus tendon autograft (AHPLT) at Department of General Orthopaedic and Trauma, Viet Duc hospital. Our outcome: the year average 35.4 ys, the rate of ACL rupture combined with meniscus injury was 40%. The average diameter AHPLT autograft is 7.0 mm. The function Lysholm scores improved from 59 to 94.27 postoperative 6 months. No difference beetwen the AOFAS scale of preoperative and postoperative. CONCLUSION: Peroneus longus tendon is recommended to be a safe and practical autograft resource for anthroscopic anterior cruciate ligament reconstruction