First Principles Studies Of Pattern Formations And Reactions On Catalyst Surfaces

This dissertation undertakes theoretical research into the adsorption, pattern formation, and reactions of atoms, molecules, and layered materials on catalyst surfaces. These investigations are carried out from first-principles calculations of electronic and geometric structures using density functional theory (DFT) for predictions and simulations at the atomic scale. The results should be useful for further study of the catalytic activities of materials and for engineering functional nanostructures. The first part of the dissertation focuses on systematic first-principles simulations of the energetic pathways of CO oxidation on the Cu2O(100) surface. These simulations show CO to oxidize spontaneously on the O-terminated Cu2O(100) surface by consuming surface oxygen atoms. The O-vacancy on Cu2O(100) then is subsequently healed by dissociative adsorption of atmospheric O2 molecules. The second part discusses the pattern formation of hydrogen on two and three layers of Co film grown on the Cu(111) surface. It is found that increasing the pressure of H2 changes the hydrogen structure from 2H-(2 × 2) to H-p(1 × 1) through an intermediate structure of 6H-(3 × 3). The third part compares the results of different ways of introducing van der Waals (vdW) interactions into DFT simulations of the adsorption and pattern formation of various molecules on certain substrates. Examinations of the physisorption of five nucleobases on iii graphene and of n-alkane on Pt(111) demonstrate the importance of taking vdW interactions into account, and of doing so in a way that is best suited to the particular system in question. More importantly, as the adsorption of 1,4 diaminebenzene molecules on Au(111) shows inclusion of vdW interactions is crucial for accurate simulation of the pattern formation. The final part carries out first-principles calculations of the geometric and electronic structure of the Moir´e pattern of a single layer of Molybdenum disulfide (MoS2 ) on Cu(111). The results reveal three possible stacking types. They also demonstrate that the MoS2 layer to be chemisorbed, albeit weakly, and that, while Cu surface atoms are vertically disordered, the layer itself is not strongly buckled

Understanding and Leveraging Virtualization Technology in Commodity Computing Systems

Commodity computing platforms are imperfect, requiring various enhancements for performance and security purposes. In the past decade, virtualization technology has emerged as a promising trend for commodity computing platforms, ushering many opportunities to optimize the allocation of hardware resources. However, many abstractions offered by virtualization not only make enhancements more challenging, but also complicate the proper understanding of virtualized systems. The current understanding and analysis of these abstractions are far from being satisfactory. This dissertation aims to tackle this problem from a holistic view, by systematically studying the system behaviors. The focus of our work lies in performance implication and security vulnerabilities of a virtualized system.;We start with the first abstraction---an intensive memory multiplexing for I/O of Virtual Machines (VMs)---and present a new technique, called Batmem, to effectively reduce the memory multiplexing overhead of VMs and emulated devices by optimizing the operations of the conventional emulated Memory Mapped I/O in hypervisors. Then we analyze another particular abstraction---a nested file system---and attempt to both quantify and understand the crucial aspects of performance in a variety of settings. Our investigation demonstrates that the choice of a file system at both the guest and hypervisor levels has significant impact upon I/O performance.;Finally, leveraging utilities to manage VM disk images, we present a new patch management framework, called Shadow Patching, to achieve effective software updates. This framework allows system administrators to still take the offline patching approach but retain most of the benefits of live patching by using commonly available virtualization techniques. to demonstrate the effectiveness of the approach, we conduct a series of experiments applying a wide variety of software patches. Our results show that our framework incurs only small overhead in running systems, but can significantly reduce maintenance window

Viet Nam Law on the Rights of Partys in the Tourism Accommodation Business and Some Complete Solutions

Vietnam's Law on Tourism 2017 has provisions related to the rights of business enterprises, service providers as well as paying customers. However, the Law still has some shortcomings. Specifically, there are no specific regulations regarding the cases where tourist accommodation establishments have the right to turn down guests; no regulations requiring accommodation businesses to provide warning information about potential risks, dangers, handling and prevention and no regulations concerning protecting the rights of tourists and guests in the case a travel agency is dissolved goes bankrupt, etc. Therefore, the article aims to point out the shortcomings and proposes some solutions to put them right. Keywords: Complete solution, tourist accommodation, rights of the parties, Vietnam's law on tourism. DOI: 10.7176/JLPG/136-05 Publication date:September 30th 202

I. Synthetic approaches to 1, 1-dilithiocyclopropanes ll. A method for the synthesis of functionalized 2, 4-dimethyl-1, 3-pentadienes III. Electrophilic additions to [4.3.1] propellenes

Organopolylithium compounds have recently been the subjects of numerous theoretical calculations which predicted intriguing structural features; among them is the planar geometry at C-1 of 1,1-dilithiocyclopropane, 21;Lithium (alpha)-lithiocyclopropanecarboxylate, a possible precursor to 21, was alkylated by iodomethane, allyl bromide, benzyl chloride or bromide in contrary to an earlier report. Treatments of 1,1-dibromotetramethylcyclopropane with excess n-butyllithium or t-butyllithium in various solvent systems showed no evidence for a consecutive double Li-Br exchange but the usual products from coupling, disproportionation, and exchange. Pentamethylcyclopropyl lithium and 2,2,3,3-tetramethylcyclopropyl lithium were iodinated unexpectedly with iodomethane;2,3-trans-Dimethoxymethyl-2,3-dimethylcyclopropylidene bromolithiocarbenoid, 72, were studied with (\u2713)C NMR ((\u2713)C-enriched compound was used) and (\u277)Li NMR. Spectroscopic evidences for the inversion at the carbenoid carbon and a mechanism for the inversion process were presented. Carbenoid 72 formed a hitherto unknown stable cyclopropylidene carbenoid: alkyllithium complex below -40(DEGREES)C with n-butyllithium. Treatments of 72 with t-butyllithium gave, among others, the 1,1-dilithio species whose C-1 was observed only by (\u277)Li decoupled (\u2713)C NMR;1,1-Dibromotetramethylcyclopropane was converted to various 1-substituted-2,2,3,3-tetramethylcyclopropyl bromide, 99, by trapping the carbenoid with methanol, iodomethane, chlorotrimethylsilane, ethyl formate, acetic anhydride, chloro ethylformate, and carbon dioxide. Flash pyrolysis of 99 constituted a convenient method for the synthesis of functionalized 2,4-dimethyl-1,3-pentadienes;Electrophilic additions to 4.3.1propell-3-ene showed a preference for the endo approach. In case of 10,10-dibromo4.3.1propell-3-ene or allylic derivatives of 10,10-dibromo4.3.1propell-2-ene, the endo approach was exclusive regardless of the allylic substitution. The steric effect of the syn bromine was dominating and led to unexpected products

Designing to Support Workspace Awareness in Remote Collaboration using 2D Interactive Surfaces

Increasing distributions of the global workforce are leading to collaborative workamong remote coworkers. The emergence of such remote collaborations is essentiallysupported by technology advancements of screen-based devices ranging from tabletor laptop to large displays. However, these devices, especially personal and mobilecomputers, still suffer from certain limitations caused by their form factors, that hinder supporting workspace awareness through non-verbal communication suchas bodily gestures or gaze. This thesis thus aims to design novel interfaces andinteraction techniques to improve remote coworkers’ workspace awareness throughsuch non-verbal cues using 2D interactive surfaces.The thesis starts off by exploring how visual cues support workspace awareness infacilitated brainstorming of hybrid teams of co-located and remote coworkers. Basedon insights from this exploration, the thesis introduces three interfaces for mobiledevices that help users maintain and convey their workspace awareness with their coworkers. The first interface is a virtual environment that allows a remote person to effectively maintain his/her awareness of his/her co-located collaborators’ activities while interacting with the shared workspace. To help a person better express his/her hand gestures in remote collaboration using a mobile device, the second interfacepresents a lightweight add-on for capturing hand images on and above the device’sscreen; and overlaying them on collaborators’ device to improve their workspace awareness. The third interface strategically leverages the entire screen space of aconventional laptop to better convey a remote person’s gaze to his/her co-locatedcollaborators. Building on the top of these three interfaces, the thesis envisions an interface that supports a person using a mobile device to effectively collaborate with remote coworkers working with a large display.Together, these interfaces demonstrate the possibilities to innovate on commodity devices to offer richer non-verbal communication and better support workspace awareness in remote collaboration

What are the factors associated with sanitation and hygiene behaviours, an investigation in Giong Trom district, Ben Tre province in the Mekong river Delta region of Vietnam?

Poor sanitation and hygiene are still one of the pressing challenges in the developing world with not only serious health and but also non-health consequences. Diarrheal diseases, for example, are preventable by handwashing and hygienic latrine, still kill more than 4500 children every day, more than that of measles, malaria and HIV combined. Its non-health consequences include welfare loss, dignity, economic and financial losses...Vietnam had a rural sanitation coverage of only 65% despite the great amount of investment (mainly in hardware provision) in rural sanitation and hygiene over the last 25 years. Behaviour change interventions, therefore, are necessary if the country is to achieve Universal Sanitation and good hygiene by 2030 as it committed. Consequently, an understanding of the population’s sanitation and hygiene behavioural determinants is required in order to design efficient and effective intervention programs. This thesis is based on the RANAS model using data surveyed in Giong Trom district, Ben Tre Province (of the provinces with lowest rural sanitation coverage in Vietnam). It has 3 objectives: to identify behavioural determinants and factors associated to a range of sanitation and hygiene behaviours; to identify, measure and compare to health and non-health impact associated with different sanitation conditions; to propose and recommend evidence-backed interventions aimed at improving rural sanitation and hygiene. Having employed the logistic and multiple linear regression analysis, the thesis found the key factors associated with the following sanitation and hygiene behaviours: • Hygienic latrine ownership: Source of income, poverty certificate possession, instrumental beliefs, perceived cost. • Unhygienic latrine ownership (while already having hygienic latrine ownership): Location, disgust, user preference, personal norm. • Hygienic latrine regular use: Gender, vulnerability perception, Instrumental beliefs, user preference, descriptive norm. • Handwashing with soap: Knowledge, user preference, disgust, volitional self-efficacy. • Forgetting handwashing with soap: Gender, knowledge, user preference, disgust, descriptive norm, injunctive norm, volitional self-efficacy, motivational self-efficacy. In addition, the thesis didn't find clear cut evidence on the health impact of different sanitation conditions due to the fact that it isn't possible to attribute any diseases solely to poor sanitation. However, it found strong evidence that poor sanitation conditions had significant negative welfare impact on the households. Finally, it demonstrated how a recent intervention program -the WASOBA project- was successful in Ben Tre in increasing hygienic latrine ownership because it addressed directly the key determinant factors identified by this thesis