Towards a Secure Zero-rating Framework with Three Parties

Zero-rating services allow mobile users to access contents from contracted CP free of data charge. In this thesis, we introduce attacks against the zero rating service which allows extra non-contracted traffic to be transported free of charge. We call this types of attack the \u27free-riding\u27 attack. Specifically, we create two types of free-riding attacks: 1) masquerade zero-rating CP attack; 2) response packets modification attack. We conducted multiple experiments on several major commercial cellular and WiFi ISPs in the United States and China. The experimental results show that all these ISPs are vulnerable to free-riding attacks.In this thesis, we also propose a secure and backward compatible zero-rating framework, called ZFree. ZFree authorizes network traffic from valid CP to be zero-rated. Next, we perform a formal security verification using ProVerif on ZFree. The formal verification results show that ZFree is secure in preserving packet integrity and CP server authenticity. Our evaluation shows that ZFree is lightweight, scalable and secure

A Game-Theoretic Approach to Energy-Efficient Resource Allocation in Device-to-Device Underlay Communications

Despite the numerous benefits brought by Device-to-Device (D2D) communications, the introduction of D2D into cellular networks poses many new challenges in the resource allocation design due to the co-channel interference caused by spectrum reuse and limited battery life of User Equipments (UEs). Most of the previous studies mainly focus on how to maximize the Spectral Efficiency (SE) and ignore the energy consumption of UEs. In this paper, we study how to maximize each UE's Energy Efficiency (EE) in an interference-limited environment subject to its specific Quality of Service (QoS) and maximum transmission power constraints. We model the resource allocation problem as a noncooperative game, in which each player is self-interested and wants to maximize its own EE. A distributed interference-aware energy-efficient resource allocation algorithm is proposed by exploiting the properties of the nonlinear fractional programming. We prove that the optimum solution obtained by the proposed algorithm is the Nash equilibrium of the noncooperative game. We also analyze the tradeoff between EE and SE and derive closed-form expressions for EE and SE gaps.Comment: submitted to IET Communications. arXiv admin note: substantial text overlap with arXiv:1405.1963, arXiv:1407.155

Nuclear Magnetic Resonance Implementation of a Quantum Clock Synchronization Algorithm

The quantum clock synchronization algorithm proposed by I. L. Chuang (Phys. Rev. Lett, 85, 2006(2000)) has been implemented in a three qubit nuclear magnetic resonance quantum system. The effective-pure state is prepared by the spatial averaging approach. The time difference between two separated clocks can be determined by reading out directly through the NMR spectra.Comment: 13 pages, 5 figure

Protrusion of Cu-TSV under different strain states

A phase-field-crystal (PFC) model is used to investigate the protrusion of blind TSVs under different strain states. The direction of loading applied to the TSVs has an effect on the protrusion, which is closely related to the copper grains and their orientations at the TSV edges. A nonlinear relation between protrusion and strain rate has been found, which can be explained by different mechanisms of deformation. A higher strain occurring near the top end of the TSVs leads to a larger protrusion of the bind TSVs

Processing-structure-protrusion relationship of 3D Cu TSVs: control at the atomic scale

A phase-field-crystal model is used to investigate the processing-structure-protrusion relationship of blind Cu through-silicon vias (TSVs) at the atomic scale. A higher temperature results in a larger TSV protrusion. Deformation via dislocation motion dominates at temperatures lower than around 300∘C, while both diffusional and dislocation creep occur at temperatures greater than around 300∘C. TSVs with smaller sidewall roughness Ra and wavelength λa exhibit larger protrusions. Moreover, different protrusion profiles are observed for TSVs with different grain structures. Both protrusions and intrusions are observed when a single grain is placed near the TSV top end, while the top surface protrudes near both edges when it contains more grains. Under symmetric loading, coalescence of the grains occurs near the top end, and a symmetric grain structure can accelerate this process. The strain distributions in TSVs are calculated, and the eigenstrain projection along the vertical direction can be considered an index to predict the TSV protrusion tendency

Main ecological drivers of woody plant species richness recovery in secondary forests in China

Identifying drivers behind biodiversity recovery is critical to promote efficient ecological restoration. Yet to date, for secondary forests in China there is a considerable uncertainty concerning the ecological drivers that affect plant diversity recovery. Following up on a previous published meta-analysis on the patterns of species recovery across the country, here we further incorporate data on the logging history, climate, forest landscape and forest attribute to conduct a nationwide analysis of the main drivers influencing the recovery of woody plant species richness in secondary forests. Results showed that regional species pool exerted a positive effect on the recovery ratio of species richness and this effect was stronger in selective cutting forests than that in clear cutting forests. We also found that temperature had a negative effect, and the shape complexity of forest patches as well as the percentage of forest cover in the landscape had positive effects on the recovery ratio of species richness. Our study provides basic information on recovery and resilience analyses of secondary forests in China

Local Buckling of Concrete Filled Rectangular Steel Tube with Longitudinal Stiffener under Axial Compression

Width-thickness ratio was an important parameter for designing Concrete Filled Rectangular Steel Tube (CFRST). Welding longitudinal stiffener on the internal wall of steel pipe could delay the local buckling, which increased the limit of width-thickness ratio. If there was not enough stiffener and its sectional dimension was too small, the local buckling of steel pipe would occur, inducing its bearing capacity seriously. If the stiffener sectional dimension was too large, concrete filled in steel tube would be broken up, which reduces its bearing capacity. To solve that problem, this paper studied local buckling of CFRST with longitudinal stiffener under axial compression and design of longitudinal stiffener. It established buckling analysis model, simplified local buckling analysis as calculating buckling load of thin plate clamped on loading side and unloading side under axial force. It deduced buckling load and buckling coefficient based on the principle of energy. The results showed that buckling mode depended on stiffening rigidity. Therefore, it put forward minimum stiffening rigidity ratio that controlled the stiffener design. This paper also came up with a formula to calculate minimum stiffening rigidity ratio. It provided guidance on designing number, sectional dimension and material performance

Distance-rank Aware Sequential Reward Learning for Inverse Reinforcement Learning with Sub-optimal Demonstrations

Inverse reinforcement learning (IRL) aims to explicitly infer an underlying reward function based on collected expert demonstrations. Considering that obtaining expert demonstrations can be costly, the focus of current IRL techniques is on learning a better-than-demonstrator policy using a reward function derived from sub-optimal demonstrations. However, existing IRL algorithms primarily tackle the challenge of trajectory ranking ambiguity when learning the reward function. They overlook the crucial role of considering the degree of difference between trajectories in terms of their returns, which is essential for further removing reward ambiguity. Additionally, it is important to note that the reward of a single transition is heavily influenced by the context information within the trajectory. To address these issues, we introduce the Distance-rank Aware Sequential Reward Learning (DRASRL) framework. Unlike existing approaches, DRASRL takes into account both the ranking of trajectories and the degrees of dissimilarity between them to collaboratively eliminate reward ambiguity when learning a sequence of contextually informed reward signals. Specifically, we leverage the distance between policies, from which the trajectories are generated, as a measure to quantify the degree of differences between traces. This distance-aware information is then used to infer embeddings in the representation space for reward learning, employing the contrastive learning technique. Meanwhile, we integrate the pairwise ranking loss function to incorporate ranking information into the latent features. Moreover, we resort to the Transformer architecture to capture the contextual dependencies within the trajectories in the latent space, leading to more accurate reward estimation. Through extensive experimentation, our DRASRL framework demonstrates significant performance improvements over previous SOTA methods

Mechanisms of copper protrusion in through-silicon-via structures at the nanoscale

Thermal stress-induced copper protrusion is frequently observed in through-silicon-vias (TSVs) based three-dimensional (3D) system integration. In this study, the detailed process of Cu protrusion is reproduced on the atomic scale using a two-mode phase-field-crystal (PFC) model, and the mechanisms of protrusion are identified. To simulate thermal loading, a “penalty term” is added to the governing equation of the PFC model. The application of loading on the TSVs induces copper grain deformation and grain boundary migration at the nanoscale. Furthermore, the simulation results suggest that the Cu protrusion is resulted from diffusional creep, involving both Nabarro-Herring creep and Coble creep. The obtained power index of diffusional creep is around 2.16, suggesting that lattice diffusion contributes more to protrusion than grain boundary diffusion does. The protrusion height in micron-scale TSVs predicted by extrapolating the relationship between the protrusion height and diameter of nanoscale TSVs agrees with the experimental data