Tribological Performance of the Head-Disk Interface in Perpendicular Magnetic Recording and Heat-Assisted Magnetic Recording

International Data Corporation (IDC) estimates that hard disk drives will still be the main storage device for storing digital data in the next 10 years, holding approximately 80% of the data inside data centers. To increase the areal density of hard disk drives, the mechanical spacing between the head and disk surface has decreased to approximately 1nm. At such a small spacing, tribology of the head-disk interface, including head-disk contacts, wear, material buildup, and lubricant transfer, become increasingly more important for the reliability of hard disk drives. In addition to small spacing, heat-assisted magnetic recording (HAMR) technology aims to deliver higher areal density recording by heating up the media surface to a few hundred Celsius degrees, facilitating the writing process. High temperature at the head and disk surfaces cause serious reliability issues for the head-disk interface (HDI). Therefore, understanding of the main factors that affect the reliability of the head-disk interface is an essential task. In this dissertation, the effect of bias voltage and helium environment on the tribological performance of the head-disk interface is investigated. To do this, we first simulated the flying characteristics of the slider as a function of bias voltage in air and helium environment. Thereafter, an experimental study was performed using custom built tester located inside a sealed environmental chamber to study the effect of air and helium on wear and lubricant redistribution at the head-disk interface during load-unload. We investigated the effect of bias voltage and relative humidity on wear, material buildup, and nano-corrosion on the slider surface. Finally, we have studied laser current and laser optical power in heat-assisted magnetic recording as a function of operating radius, head-disk clearance, media design, and their effects on the life-time of the head-disk interface. The results of this dissertation provide guidance for the effect of bias voltage, relative humidity, and helium environment on wear, material buildup, corrosion, and lubricant transfer at the head-disk interface. More importantly, our experimental study in heat-assisted magnetic recording leads to a better understanding of the main factors that cause failure of the HAMR head-disk interface. Our results are important for the improvement of the tribological performance and reliability of perpendicular magnetic recording (PMR) and heat-assisted magnetic recording (HAMR) head-disk interface

Investigation of visual cueing aids of UAV targeting for real-time warpoint re-allocation

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1998.Includes bibliographical references (p. 59).An experimental study was performed to determine the effects of two visual cueing aids for a real-time waypoint navigation system. The applications of the cueing aids would be in enhancing operator performance during real-time operation of an Unmanned Autonomous Vehicle (UAV). Subjects used a graphical user interface to perform a simulated surveillance mission. Two cueing aids were used during the missions. The cueing aids were a synthetic video camera image facing either forward or to the side, and the presence or absence of a camera ground marker that depicted the camera field of view on a map display. On average, operators using a side camera view completed the simulated surveillance mission in less time than when they used a forward camera view. With the absence of the camera ground marker, the side view yielded a 25% lower performance time, and with the presence of the marker, the side view yielded a 36% reduction in performance time. However, subjects preferred a forward camera view for initially finding the target. Also, a camera ground marker was found to have beneficial effects on reducing mission time. For cases with a forward camera view, the presence of a ground marker reduced performance time by 12%, and for cases with a side camera view, the ground marker reduction was 26%.by Tan T. Trinh.S.M

Social media’s impact on Generation Z’s purchasing behavior of sustainable products

The aim of this study is to evaluate the effects of social networks on the consumption behavior of sustainable products among Generation Z. Social networks have evolved into important technologies, making them an unavoidable option for Generation Z and the human race in general. Therefore, it is necessary to comprehensively assess how social networks have influenced the consumption behavior of Gen Z toward sustainable products in order to improve the process of community implementation while improving the quality of social networks and the durability of products. A literature review was conducted of studies linked to the suggested study model, which includes a mix of social network models and external variables influencing Gen Z's purchase of sustainable products via social networks. The suggested model was then tested on a sample of 100 Vietnamese students. Social networking techniques were used to study and evaluate the dataset. The report advises that managers and marketers should employ social media marketing tactics to communicate with Gen Z customers and promote the value of sustainability. Management and marketers should also provide sustainability information and promote sustainable goods on popular social media platforms, such as Instagram, Facebook, Twitter, and TikTok

Data Driven Customer Segmentation for Vietnamese SMEs in Big Data Era

Almost Vietnamese big businesses often use outsourcing services to do marketing researches such as analysing and evaluating consumer intention and behaviour, customers’ satisfaction, customers’ loyalty, market share, market segmentation and some similar marketing studies. One of the most favourite marketing research business in Vietnam is ACNielsen and Vietnam big businesses usually plan and adjust marketing activities based on ACNielsen’s report. Belong to the limitation of budget, Vietnamese small and medium enterprises (SMEs) often do marketing researches by themselves. Among the marketing researches activities in SMEs, customer segmentation is conducted by tools such as Excel, Facebook analytics or only by simple design thinking approach to help save costs. However, these tools are no longer suitable for the age of data information explosion today. This article uses case analysing of the United Kingdom online retailer through clustering algorithm on R package. The result proves clustering method’s superiority in customer segmentation compared to the traditional method (SPSS, Excel, Facebook analytics, design thinking) which Vietnamese SMEs are using. More important, this article helps Vietnamese SMEs understand and apply clustering algorithm on R in customer segmenting on their given data set efficiently. On that basis, Vietnamese SMEs can plan marketing programs and drive their actions as contextualizing and/or personalizing their message to their customers suitabl

Improvement of Tuning Fork Gyroscope Drive-mode Oscillation Matched using a Differential Driving Suspension Frame

This paper presents a novel design of a vibration tuning fork gyroscope (TFG) based on a differential driving suspension coupling spring between two gyroscopes. The proposed TFG is equivalent to a transistor differential amplifier circuit. The mechanical vibrations of driving frames are, therefore, well matched. The matching level depends on stiffness of spring. When three various TFG structures respond to differential stiffness of spring, their the driving frame mechanical vibration is well matched in case the input excitation driving differential phase is less than 3.5°, 2.5°, and 4°, respectively. The fabricated tuning fork gyroscope linearly operates in the range from -200 to +200 degree/s with the resolution of about 0.45 mV/degree/s

3D surface reconstruction using dense optical flow combined to feature matching: Application to endoscopy

International audienceIn structure from motion (SfM) algorithms, the surface reconstruction performance strongly depends on the quality of the determination of homologous points between images. Classical feature matching-based methods as integrated in the state-of the-art SfM-algorithms are often inoperative for scenes including weak structures and textures (e.g., as those in medical endoscopic videos). This contribution introduces an effective solution based on the combination of dense optical flow and feature matching. The accuracy and robustness of the proposed method were validated using results obtained for a phantom with known dimensions and with patient data, respectively. Apart from the high performance obtained for cystoscopy and gastroscopy, the proposed solution has a high potential in other medical and non-medical scenes.Dans les algorithmes de structures à partir du mouvement (SfM), la performance de la reconstruction des surfaces dépend fortement de la qualité de la détermination des points homologues entre images. Les méthodes SfM de référence sont souvent inopérantes pour les scènes avec peu de structures et textures faiblement contrastées car elles reposent uniquement sur l'appariement de caractéristiques. Cette contribution présente une solution associant un flot optique dense à la mise en correspondance de caractéristiques. La précision et la robustesse de la reconstruction ont été validées via des résultats obtenus pour un fantôme avec des dimensions connues et avec des données patient en cystoscopie et en gastroscopie, respectivement. Plus généralement, cette approche a un fort potentiel pour toute scène peu constrastée, médicales ou non

THE EFFECTS OF DEMOGRAPHIC VARIABLES ON KNOWLEDGE SHARING BEHAVIOUR

The purpose of this study was to explore the relationship between demographic variables and two forms of knowledge sharing behavior (KSB) to give some suggestions for managers. Data collected from 234 employees of some departments such as research and development, technology,... of some Vietnam telecommunication companies in order to test the general model: KSB = K + gender(xa) + age(xb) + educational qualification(xc) + work experience(xd). The study found that males tend to share more of their knowledge than females and staffs aged from 31 to 45 tend to share their knowledge more than those aged from 20 to 30 while 20-30 year old staffs tend to collect knowledge more than 31-45 year old staffs. Keywords: knowledge, knowledge sharing, knowledge managemen