Area Spectral Efficiency Analysis and Energy Consumption Minimization in Multi-Antenna Poisson Distributed Networks

This paper aims at answering two fundamental questions: how area spectral efficiency (ASE) behaves with different system parameters; how to design an energy-efficient network. Based on stochastic geometry, we obtain the expression and a tight lower-bound for ASE of Poisson distributed networks considering multi-user MIMO (MU-MIMO) transmission. With the help of the lower-bound, some interesting results are observed. These results are validated via numerical results for the original expression. We find that ASE can be viewed as a concave function with respect to the number of antennas and active users. For the purpose of maximizing ASE, we demonstrate that the optimal number of active users is a fixed portion of the number of antennas. With optimal number of active users, we observe that ASE increases linearly with the number of antennas. Another work of this paper is joint optimization of the base station (BS) density, the number of antennas and active users to minimize the network energy consumption. It is discovered that the optimal combination of the number of antennas and active users is the solution that maximizes the energy-efficiency. Besides the optimal algorithm, we propose a suboptimal algorithm to reduce the computational complexity, which can achieve near optimal performance.Comment: Submitted to IEEE Transactions on Wireless Communications, Major Revisio

Reassessing China’s Growing Presence in the Arctic: A World-System perspective

This paper intends to provide an analytical framework to interpret China’s growing presence in the Arctic from the perspective of world-system theory. I have set up the analytical framework from the following four aspects. Firstly, China’s externalizing behavior in the Arctic region is governed by the internalized law of value of the modern world-system, i.e., the endless accumulation of capital. Secondly, China has benefited and is still benefiting from the division of labor, with Southeast Asia, Latin America, Africa, and most recently the Arctic serving as a relatively subordinated resource periphery. Thirdly, driven by a strong upward mobility, China has leapfrogged the periphery and semi-periphery and gained a semi-core position with an upward trend towards the core, by offering a favorable external environment to the Arctic (invitation to promote). Lastly, since the world-economy is currently in a Kondratieff B-phase, China, as an emerging global core power, is logically dedicated to the relocation of productive activity and the probability of alternative profitable outlets, where the Arctic is highly compatible. Keywords: China, Arctic, world-system theory, endless accumulation of capital, division of labor, upward mobility, Kondratieff B-phas

Learn from Unpaired Data for Image Restoration: A Variational Bayes Approach

Collecting paired training data is difficult in practice, but the unpaired samples broadly exist. Current approaches aim at generating synthesized training data from the unpaired samples by exploring the relationship between the corrupted and clean data. This work proposes LUD-VAE, a deep generative method to learn the joint probability density function from data sampled from marginal distributions. Our approach is based on a carefully designed probabilistic graphical model in which the clean and corrupted data domains are conditionally independent. Using variational inference, we maximize the evidence lower bound (ELBO) to estimate the joint probability density function. Furthermore, we show that the ELBO is computable without paired samples under the inference invariant assumption. This property provides the mathematical rationale of our approach in the unpaired setting. Finally, we apply our method to real-world image denoising and super-resolution tasks and train the models using the synthetic data generated by the LUD-VAE. Experimental results validate the advantages of our method over other learnable approaches

Airline Network Choice and Configuration

As an increasing number of countries liberalize their skies, some airlines, notably carriers in the Middle East, have been able to extend their hub-and-spoke networks beyond domestic borders. This allows them to serve international destinations without going through traditional gateway hubs, so that they can compete with airline alliances relying on the traditional dual-gateway, or the so-called “dog-bone” networks. This paper proposes a stochastic model to investigate the competition between airlines running traditional dog-bone and hub-and-spoke networks in a liberalizing inter-continental market. The proposed model considers the interactions among three types of stakeholders, namely a regulator that aims to maximize the expected social welfare by designating the locations of new gateways; airlines that maximize profits by optimizing the service offerings and airfares; passengers that minimize their own travel disutility. Such a model is applied to analyze the Europe - China aviation market, so that the comparative advantages of different networks can be examined and quantified. The modeling results provide evidence-based recommendations on airline competition and airport development, and infrastructure investment needs in markets being liberlized

Post Pandemic Aviation Market Recovery: Focus on Changes in China

China was the first aviation market in the world hit hard by the COVID-19 and has been recovering gradually as the pandemic became largely under control within mainland China. This study reviews the recovery pattern influenced by the Chinese government’s aviation policy choices, in the hope that our discussions and findings will help improve aviation policy responses elsewhere. While the domestic market in mainland China has enjoyed a quick recovery to about 80% of the pre- crisis level by July, 2020, the recovery of international services has been much slower, due to the bilateral route and flight frequency/capacity control and strict requirements for health check and quarantine. China’s domestic aviation market was recovered by about 80% in two months after the pandemic became under good control. Most other countries with a “curve flatting” strategy, instead of full pandemic control, may not expect the fast recovery path China has achieved. A British “travel corridor” approach may be more practical for Western countries to follow, albeit more likely to be subject to serious setbacks and disruptions. The aviation fee reductions and cost support China and many other countries have been using are helpful but not sufficient. Capital injection and/or credit guarantee may be needed for many airlines to survive. Airlines based in open economies that have small domestic markets will face particularly serious challenges during the recovery process

Research on the impact mechanism of major public health emergency on China's economic growth

Under different transmission mechanisms, major public health emergencies have different effects on economic growth. Based on the specific economic impact of COVID-19, a literature analysis method was used to systematically explain the economic impact of different channels and specific transmission mechanisms caused by major public health emergencies. Major public health emergencies caused serious damage to life and health, and had a huge impact on the entire economic environment. However, different economic sectors have different levels and channels of impact from the pandemic. The existing literature has analysed the various impact mechanisms of major public health emergencies on the economic development process from many angles, but there are still problems that need in-depth discussion and supplementary research

Modeling the Potential for Aviation Liberalization in Central Asia - Market analysis and implications for the Belt and Road initiative

This study analyzes aviation markets in the five land-locked countries in Central Asia. Panel data spanning from 2007 to 2015 are used to estimate airline entry patterns in origin-destination markets. Econometric estimates for domestic and international markets are subsequently benchmarked, and route groups are paired by alternative matching algorithms so that counter-factual analysis can be conducted. Our investigation suggests that although the Central Asia–China markets are characterized by poor connectivity and high airfares, great benefits could be achieved if more liberal aviation policies such as those proposed by the Belt and Road initiative were introduced. In particular, our counterfactual analysis suggests that if the Central Asia–China markets were regulated and operated in a similar way to the routes between Central Asia and other states, the probability of having aviation services between cities in China and Central Asia would increase by 27%, even by conservative estimates. The number of Chinese destinations could increase by more than 150%. Our study finds strong negative effects of the restrictive regulations on the international aviation markets, and calls for further liberalizations between Central Asia and the region’s major trade partners

Baicalin Ameliorates Experimental Liver Cholestasis in Mice by Modulation of Oxidative Stress, Inflammation, and NRF2 Transcription Factor

Experimental cholestatic liver fibrosis was performed by bile duct ligation (BDL) in mice, and significant liver injury was observed in 15 days. Administration of baicalin in mice significantly ameliorates liver fibrosis. Experimental cholestatic liver fibrosis was associated with induced gene expression of fibrotic markers such as collagen I, fibronectin, alpha smooth muscle actin (SMA), and connective tissue growth factor (CTGF); increased inflammatory cytokines (TNFα, MIP1α, IL1β, and MIP2); increased oxidative stress and reactive oxygen species- (ROS-) inducing enzymes (NOX2 and iNOS); dysfunctional mitochondrial electron chain complexes; and apoptotic/necrotic cell death markers (DNA fragmentation, caspase 3 activity, and PARP activity). Baicalin administration on alternate day reduced fibrosis along with profibrotic gene expression, proinflammatory cytokines, oxidative stress, and cell death whereas improving the function of mitochondrial electron transport chain. We observed baicalin enhanced NRF2 activation by nuclear translocation and induced its target genes HO-1 and GCLM, thus enhancing antioxidant defense. Interplay of oxidative stress/inflammation and NRF2 were key players for baicalin-mediated protection. Stellate cell activation is crucial for initiation of fibrosis. Baicalin alleviated stellate cell activation and modulated TIMP1, SMA, collagen 1, and fibronectin in vitro. This study indicates that baicalin might be beneficial for reducing inflammation and fibrosis in liver injury models