The Reliability Function of Lossy Source-Channel Coding of Variable-Length Codes with Feedback

We consider transmission of discrete memoryless sources (DMSes) across discrete memoryless channels (DMCs) using variable-length lossy source-channel codes with feedback. The reliability function (optimum error exponent) is shown to be equal to $\max\{0, B(1-R(D)/C)\},$ where $R(D)$ is the rate-distortion function of the source, $B$ is the maximum relative entropy between output distributions of the DMC, and $C$ is the Shannon capacity of the channel. We show that, in this setting and in this asymptotic regime, separate source-channel coding is, in fact, optimal.Comment: Accepted to IEEE Transactions on Information Theory in Apr. 201

Transport improvement, agglomeration effect and urban productivity: The case of Chinese cities

Improvement in the transport sector will increase accessibility to economic activities, which in turn benefit urban productivity by enabling agglomeration economies. This paper aims to establish the link between agglomeration effect and wider economic benefits of transport, and test the magnitude of city-level agglomeration elasticity in China. Based on the measure of effective employment density, this paper finds that a doubling of effective density will improve the productivity in urban areas by 10.9 percent. Agglomeration elasticities vary across different regions. With improvements in transport conditions, the agglomeration elasticity on productivity will increase, but will reach a threshold value of around 17.010

The capacity-C torch problem

The torch problem (also known as the bridge problem or the flashlight problem) is about getting a number of people across a bridge as quickly as possible under certain constraints. Although a very simply stated problem, the solution is surprisingly non-trivial. The case in which there are just four people and the capacity of the bridge is two is a well-known puzzle, widely publicised on the internet. We consider the general problem where the number of people, their individual crossing times and the capacity of the bridge are all input parameters. We present two methods to determine the shortest total crossing time: the first expresses the problem as an integer-programming problem that can be solved by a standard linear-programming package, and the second expresses the problem as a shortest-path problem in an acyclic directed graph, i.e. a dynamic-programming solution. The complexity of the integer-programming solution is difficult to predict; its main purpose is to act as an independent test of the correctness of the results returned by the second solution method. The dynamic-programming solution has best- and worst-case time complexity proportional to the square of the number of people. An empirical comparison of the efficiency of both methods is also presented. This manuscript has been accepted for publication in Science of Computer Programming. The manuscript has undergone copyediting, typesetting, and review of the resulting proof before being published in its final form. Please note that during the production process errors may have been discovered which could affect the content, and all disclaimers that apply to the journal apply to this manuscript

Secrecy outage probability of a NOMA scheme and impact imperfect channel state information in underlay cooperative cognitive networks

Security performance and the impact of imperfect channel state information (CSI) in underlay cooperative cognitive networks (UCCN) is investigated in this paper. In the proposed scheme, relay R uses non-orthogonal multiple access (NOMA) technology to transfer messages e1, e2 from the source node S to User 1 (U-1) and User 2 (U-2), respectively. An eavesdropper (E) is also proposed to wiretap the messages of U-1 and U-2. The transmission's security performance in the proposed system was analyzed and performed over Rayleigh fading channels. Through numerical analysis, the results showed that the proposed system's secrecy performance became more efficient when the eavesdropper node E was farther away from the source node S and the intermediate cooperative relay R. The secrecy performance of U-1 was also compared to the secrecy performance of U-2. Finally, the simulation results matched the Monte Carlo simulations well.Web of Science203art. no. 89

Suggestions for Improving Vietnam Laws on Marine Environment Protection from Contamination Caused by Ship’s Garbage

Due to the fact that Vietnam legal system on marine environmental protection is still inconsistent and deficient, as focusing only on the protection of marine environment either in general or environmental pollution from oil and noxious liquid substances, but lacking a concentration on marine contamination caused by ship’s garbage. It is explained that Vietnam only joined Annexes I and II of International Convention for the Prevention of Pollution from Ships, 1973 as modified by the Protocol of 1978 (hereinafter referred to as the MARPOL 73/78), which serves as a prerequisite condition and fundament of researches and legal system on protection of marine environment. Owing to the lack of in-depth study of the issues, this article is written to describe and analyze the current status of Vietnam laws on the marine environment preservation. Moreover, suggestions for improving the Vietnam legal system on the marine protection from ship’s garbage are suggested in this paper. Keywords: International conventions, improve, Vietnam laws, suggestions, ship’s garbag

Conservation of Natural and Cultural Heritage in the Huong Son Complex of Natural Beauty and Historical Monuments, Northern Vietnam

The Huong Son Complex has long been recognised as an important sacred landscape in Vietnam due to its spiritual and cultural values. The area also retains many aesthetic and biological values. Unfortunately, its cultural and natural treasures are currently at risk due to anthropogenic impacts, mainly associated with increased spiritual tourist activities. Some urgent solutions have been implemented, but they give priority to protecting cultural values and sometimes conflict with nature conservation efforts. This problem was encountered during our recent bat conservation research in Huong Son. Our preliminary findings revealed symbiotic relationships between natural and cultural heritage in Huong Son; thus, linking nature and culture in conservation planning and management is critical for the sustainable development of the site. However, the application of this approach in Huong Son, and other sacred places in Vietnam, is challenged by gaps in basic research and the inadequate attention of local stakeholders