L'efficience des marchés financiers face à la crise financière de 2007

La récente crise financière de 2007 a amené plusieurs questionnements sur la structure architecturale de la théorie financière; des critiques se sont mises à prendre cible la théorie de l'efficience des marchés financiers. Considérée comme la pire crise financière que le monde a connue depuis la Grande Dépression, la crise financière de 2007 a fourni des arguments de taille à ceux considérant la théorie de l'efficience comme dépassée. Le travail présent consiste à analyser la validité de la théorie de l'efficience des marchés à travers la crise financière de 2007. Le modèle d'un marché efficient demeure important dans le quotidien des multiples transactions sur le marché bousier. Ainsi, une approche employant des indices bousiers majeurs constitue une bonne source pour l'étude. Divers outils économétriques traditionnels et modernes tels que le test d'autocorrélation, le "runs test", le test du ratio de variance et le test du ratio de variance basé sur les rangs et les signes sont utilisés à cette fin. Les résultats obtenus ont démontré que l'efficience des marchés est toujours validée lorsque nous avons employé les tests d'autocorrélation et le "runs test". Dans le cas des tests du ratio de variance et celle basée sur les rangs et les signes, l'efficience n'a pu être validée dans certains cas. Cependant, l'explication de ce résultat s'explique par la présence de variance variable. En tenant compte de cet effet, les résultats ont soutenu la présence d'un marché efficient. Suite aux résultats trouvés, l'idée de renoncer à la théorie d'efficience des marchés n'a pas pu être retenue.\ud ______________________________________________________________________________ \ud MOTS-CLÉS DE L’AUTEUR : efficience du marché, crise financière, marche aléatoire, test paramétrique, test non paramétriqu

Position control for haptic device based on discrete-time proportional integral derivative controller

Haptic devices had known as advanced technology with the goal is creating the experiences of touch by applying forces and motions to the operator based on force feedback. Especially in unmanned aerial vehicle (UAV) applications, the position of the end-effector Falcon haptic sets the velocity command for the UAV. And the operator can feel the experience vibration of the vehicle as to the acceleration or collision with other objects through a forces feedback to the haptic device. In some emergency cases, the haptic can report to the user the dangerous situation of the UAV by changing the position of the end-effector which is be obtained by changing the angle of the motor using the inverse kinematic equation. But this solution may not accurate due to the disturbance of the system. Therefore, we proposed a position controller for the haptic based on a discrete-time proportional integral derivative (PID) controller. A Novint Falcon haptic is used to demonstrate our proposal. From hardware parameters, a Jacobian matrix is calculated, which combines with the force output from the PID controller to make the torque for the motors of the haptic. The experiment was shown that the PID has high accuracy and a small error position

An Efficient Design of the Piezoresistive Pressure Sensor Applied for Micro Aerial Vehicle

In this research, the developing process of a piezoresistive pressure sensor working in the atmosphere environment applied in micro aerial vehicle using the MEMS fabrication method is introduced. The sensor consists of four Au/Cr piezoresistors in a Wheatstone bridge configuration on a wet oxidized silicon diaphragm. To fabricate the sensor, three lithographic steps were conducted: the first one is to define the resistors and Au/Cr lines/pads, the second and the third ones are to determine the width and the thickness of the square SiO2/Si diaphragm, respectively. The sensor diaphragm shape and thickness were defined by the anisotropic etching of Si in tetramethylammonium hydroxide (TMAH) solution, and the resistors array are formed by sputtering and wet etching method. The sensor size is ~6000 µm by 6000 µm. The sensor output voltage was measured for various applied pressure levels from 0 to 1.2 bar with 5V voltage supply. The fabricated sensor also exhibits a sensitivity of 50.01 mV/bar

An Efficient Design of the Piezoresistive Pressure Sensor Applied for Micro Aerial Vehicle

In this research, the developing process of a piezoresistive pressure sensor working in the atmosphere environment applied in micro aerial vehicle using the MEMS fabrication method is introduced. The sensor consists of four Au/Cr piezoresistors in a Wheatstone bridge configuration on a wet oxidized silicon diaphragm. To fabricate the sensor, three lithographic steps were conducted: the first one is to define the resistors and Au/Cr lines/pads, the second and the third ones are to determine the width and the thickness of the square SiO2/Si diaphragm, respectively. The sensor diaphragm shape and thickness were defined by the anisotropic etching of Si in tetramethylammonium hydroxide (TMAH) solution, and the resistors array are formed by sputtering and wet etching method. The sensor size is ~6000 µm by 6000 µm. The sensor output voltage was measured for various applied pressure levels from 0 to 1.2 bar with 5V voltage supply. The fabricated sensor also exhibits a sensitivity of 50.01 mV/bar

The Correlation between the Structures of the Nasal Tip on the Ultrasound and the Anthropometry of the Nose in Vietnamese

BACKGROUND: Nowadays, there are few types of research held in Vietnam to investigate the anthropometric index of the nose as well as analysis the structure of nasal tip on ultrasound to identify the relationship between these parameters. AIM: determine the relationship between the height and the width of the nasal tip and the structures constructed these areas by anthropometric and ultrasound measurement. METHODS: a descriptive study in Thanh Van Hospital from December 2017 to April 2019. RESULTS: There were 94 women (62.7%), and 56 men (37.3%) and the average age were 33.6 years old. The height and width of the nasal tip are 10.1 mm and 21.7 mm, respectively. Through the ultrasound, the thickness of the adipose tissues is 3 mm. The width of the interdomal fat pad is 6.5 mm and the distance between two tip point is 5.6 mm. There are the relationships between the distance of two tip points and the width of the tip (r = 0.341), and the width of the interdomal fat pad (r = 0.72). There is also the correlation between the width of the nasal tip with the distance of two tip points (r = 0.46) and the height of the tip with the thickness of the interdomal fat pad (r = 1.23). CONCLUSION: The thickness of the interdomal fat affects the height of the tip, and the distance of two tip points influences the width of the tip

How Foreign Ownership and Competition Affect the Credit Growth of Commercial Banks: Evidence from A Transitional Economy

This study examines the relationship between foreign ownership and market competition, proxied by bank market power, affecting the credit growth of 32 commercial banks in Vietnam from 2010 to 2020. The Random Effects Model and the Dynamic System Generalized Method of Moments were used to analyze an unbalanced panel of 278 annual observations. The findings report that foreign ownership reduces credit growth, with each percentage increase in foreign ownership reducing credit growth by 0.74%. The results indicate an inverse U-shaped relationship between competitive advantage and credit growth, with a turning point of 0.46. The main findings were found to be robust after employing an alternative market power proxy. The study recommends that bank managers and policymakers limit foreign ownership and control commercial banks’ market power to promote sustainable credit growth

Research on Macroanatomic and Histologic Characteristics of the Lower Lateral Nasal Cartilages in Vietnamese

BACKGROUND: There are recently many studies about the anatomy of lower lateral cartilage (LLC). However, the microanatomic studies to identify the segments of most LLC at the nasal tip in Vietnamese are very rare. AIM: Investigate the macroanatomic and microanatomic characteristics of the LLC and the structures of the nasal tip. METHODS: Descriptive study, 30 cadaver noses fixed by 10% formalin, 2 cadaver noses fixed by HE in 69 Institutes in Vietnam from December 2017 to April 2019. RESULTS: The average length of the medial crus is 12.3 mm on the right and 13.2 mm on the left. The maximum intercrural distance is 10.7 mm. The average length of the dome is 3.7 mm and 3.9 mm on the right and left side separately, with 2 subunits are the domal and lobular segment. The average thickness of the tip points is 1.0 mm. The width of the interdomal and intercrural ligaments are 0.5-fold the height and 2-fold the thickness. The thickness of the interdomal fat pad is 3mm and about 0.5-fold the wide. CONCLUSION: The LLC has 3 parts: intermediate, medial and lateral crus. The microanatomic structures of tip consist of the interdomal ligaments, intercrural ligaments, SMAS and interdomal fat pad

Optimization Parameters of Milling Process of Mould Material for Decreasing Machining Power and Surface Roughness Criteria

Improving milling performances is an effective solution to decrease the costs required. This paper addressed a multi-response optimization to simultaneously decrease the machining power consumed Pm, arithmetical roughness Ra, and ten-spot roughness Rz. The Grey-Response Surface Method-Multi Island Genetic Algorithm (GRMA) consisting of grey relational analysis (GRA), response surface method (RSM), and multi-island genetic algorithm (MA) was proposed to predict the optimal parameters and yield optimum milling performances. The experimental trials were conducted with the support of a CNC milling center. The influences of spindle speed (S), depth of cut (ap), feed rate (fz), and tip radius (r) were explored using GRA. The nonlinear relationship between machining parameters and grey grade (GG) model was developed using RSM. Finally, two optimization techniques, including desirability approach (DA) and MA were performed to observe the optimal values. The results indicated that the machining power was greatly affected by processing factors and the radius has a significant impact on the roughness criteria. The measured reductions using optimal parameters of Pm, Ra, and Rz are approximately 77.05%, 50.00%, and 58.02%, respectively, as compared to initial settings. The GRMA can be considered as an effective approach to generate reliable values of processing conditions and technological performances in the milling process

Least Expected Time Paths in Stochastic Schedule-Based Transit Networks

We consider the problem of determining a least expected time (LET) path that minimizes the number of transfers and the expected total travel time in a stochastic schedule-based transit network. A time-dependent model is proposed to represent the stochastic transit network where vehicle arrival times are fully stochastically correlated. An exact label-correcting algorithm is developed, based on a proposed dominance condition by which Bellman’s principle of optimality is valid. Experimental results, which are conducted on the Ho Chi Minh City bus network, show that the running time of the proposed algorithm is suitable for real-time operation, and the resulting LET paths are robust against uncertainty, such as unknown traffic scenarios