Achieving Secrecy Capacity of the Gaussian Wiretap Channel with Polar Lattices

In this work, an explicit wiretap coding scheme based on polar lattices is proposed to achieve the secrecy capacity of the additive white Gaussian noise (AWGN) wiretap channel. Firstly, polar lattices are used to construct secrecy-good lattices for the mod-$\Lambda_s$ Gaussian wiretap channel. Then we propose an explicit shaping scheme to remove this mod-$\Lambda_s$ front end and extend polar lattices to the genuine Gaussian wiretap channel. The shaping technique is based on the lattice Gaussian distribution, which leads to a binary asymmetric channel at each level for the multilevel lattice codes. By employing the asymmetric polar coding technique, we construct an AWGN-good lattice and a secrecy-good lattice with optimal shaping simultaneously. As a result, the encoding complexity for the sender and the decoding complexity for the legitimate receiver are both O(N logN log(logN)). The proposed scheme is proven to be semantically secure.Comment: Submitted to IEEE Trans. Information Theory, revised. This is the authors' own version of the pape

Chinese international students' experience of studying online in New Zealand.

Reasons distance students seek online study options include pursuing subjects of interest, taking subjects not available to them locally, or gaining a qualification from an institution of specialisation or reputation. However, when students travel to another country for study, what prompts these students to elect to study online? International students in New Zealand have the opportunity to study online through most tertiary institutions. This paper reports on a research project investigating Chinese graduate students' experience of learning online while in New Zealand, and the impact of culture on their learning. This study highlights the benefits of particular aspects of instructional design and makes recommendations to help eEducation educators maximise the benefits of online learning for international students

The impact of Chinese culture in online learning: Chinese tertiary students’ perceptions

This thesis looks at Chinese students' understanding of online learning, investigates how culture impact on students online learning attitude, behaviour, and achievement, and seeks their recommendations for eLeaming and eTeaching guidelines and/or professional development. This study used a qualitative framework and took place over a year period. The research involved the methods of email surveys and interviews. The literature identifies many factors including the online learning and teaching pedagogy, aspects of Chinese culture, the implications for online Chinese students' learning, and Chinese students learning in another country. This review helps to identity some research findings of this research. This finding of this research identified participants' experience and their perceptions of learning online, explored their beliefs about Chinese cultural impact on their online learning, and sought their recommendations to eTeachers and other Chinese students about eTeaching and eLearning. In the light of literature, this research found that participants had different opinions about the impact of Chinese culture on their online learning. Participants had seen both positive and negative impacts on their online learning. The acknowledgment of individuals' differences and willingness of adapting to a new culture was viewed as a reason why some participants thought the cultural impact varied with individuals and could not be generalized. The invisibility of culture was also explained why some participants disagreed with the cultural impact. Participants' perceptions on the impact of Chinese culture on their online learning would help eTeachers to understand the learning difficulties for Chinese students to study online, and in what ways the Chinese culture influences on their online learning. The recommendations participants made to eTeachers were related to the effective eTeaching pedagogy such as to give timely feedback and more encouragements to students, to cater for students' different needs and interests by selecting some course contents or examples relevant to Chinese students' backgrounds. Participants suggested eTeachers to arrange the group meeting beside the course study, and to give more introductions about what online learning was before the online course started. Based on the consideration of the English language difficulties for Chinese students and some negative impacts from Chinese culture, participants made recommendations to other Chinese students such as to be willing to share ideas, to speak out their thoughts and to be active in asking for assistance, and to find more information before they chose online learning. Participants' those recommendations could help eTeachers to make some changes of eTeaching pedagogy and learn about Chinese students' culture in order to cater for Chinese students' interests and needs. Therefore, these recommendations could be helpful for eLearning and eTeaching guidelines and/or professional development on supporting Chinese students learning online both in New Zealand and China. This study raised some concerns about possible future research such as how to maximise librarian's assistance in online course, and in what ways both Chinese students' written and spoken English language could be improved through learning online

NEW ISOMERIC SILICONES: SYNTHESIS, COMPOSITIONS AND SURFACE PROPERTIES

This dissertation presents research performed in the field of silicone polymer science, which refers to polymers with alternating silicon-oxygen backbones. Three research topics will be explored. The first topic involves the synthesis of trimethylsiloxysilsesquioxane (MT) copolymers with vinyl and hydride functionalities as reactive liquid silicone precursors. The second topic describes titration of dimethylsiloxy (D) composition into trimethylsiloxysilsesquioxane (MT) copolymers for the purpose of controlling the mechanical properties and thermal stabilities of the material. The last topic explores the modification of hydrophobic silicone surfaces with oxygen plasma to form silica-like, hydrophilic surfaces and the behaviors of hydrophobic recovery. The first chapter provides a general review of silicone polymers with an emphasis on the simplicity of the chemistry and rational science that underpins the experiments that were carried out in this thesis research. The history of silicone polymers is introduced, as well as the key chemistry reactions that are utilized in the thesis research: (1) hydrolysis and condensation of methoxysilanes, and (2) hydrosilylation of olefins and hydridosilanes. Finally, some basic concepts of surface wetting including contact angles and contact angle hysteresis are presented. Three separate, but interrelated projects are presented after this introduction. In the first project described in Chapter 2, trimethylsiloxy-terminated phenylsilsesquioxane (MTϕ) copolymers were prepared using modifications of procedures used to prepare (homo)poly(phenylsilsesquioxane) (pTϕ), the structures of which are discussed in detail. With the addition of trimethylsiloxy monomers with vinyl (MV) or hydride (MH) functionalities, MTϕ copolymers were obtained as precursors with control over silanol content and M to T ratio. These reactive MTϕ copolymers were crosslinked by hydrosilylation between vinyl and hydride, and hard silicone materials were formed with excellent thermal stabilities. In the second project described in Chapter 3, the mechanical properties of crosslinked silicones were controlled by titrating dimethylsiloxy (D) composition into trimethylsiloxymethylsilsesquioxane (MT) silicones. The intrinsic rigidity of the crosslinked MT network results in a high modulus of the material. By bringing the flexibility of D composition into the network, the moduli of the crosslinked materials are able to be controlled. D composition was titrated during the preparation of reactive liquid precursors, and was controlled by D:T feed ratio, which could predict the moduli of final crosslinked materials. The structure-property relationships were also explored in terms of this network structures. The last project described in Chapter 4, entails research involving the hydrophobic recovery of silicone surfaces. Oxygen plasma was utilized to generate hydrophilic surfaces with silica reactivity on some of the crosslinked silicones discussed in the first and second projects. The hydrophobic recovery process was monitored by dynamic contact angle using water as a probe fluid. The MT networks exhibited slower recovery compared with common PDMS networks

Construction of Capacity-Achieving Lattice Codes: Polar Lattices

In this paper, we propose a new class of lattices constructed from polar codes, namely polar lattices, to achieve the capacity \frac{1}{2}\log(1+\SNR) of the additive white Gaussian-noise (AWGN) channel. Our construction follows the multilevel approach of Forney \textit{et al.}, where we construct a capacity-achieving polar code on each level. The component polar codes are shown to be naturally nested, thereby fulfilling the requirement of the multilevel lattice construction. We prove that polar lattices are \emph{AWGN-good}. Furthermore, using the technique of source polarization, we propose discrete Gaussian shaping over the polar lattice to satisfy the power constraint. Both the construction and shaping are explicit, and the overall complexity of encoding and decoding is $O(N\log N)$ for any fixed target error probability.Comment: full version of the paper to appear in IEEE Trans. Communication