Membrane Potential Distribution Adjustment and Parametric Surrogate Gradient in Spiking Neural Networks

As an emerging network model, spiking neural networks (SNNs) have aroused significant research attentions in recent years. However, the energy-efficient binary spikes do not augur well with gradient descent-based training approaches. Surrogate gradient (SG) strategy is investigated and applied to circumvent this issue and train SNNs from scratch. Due to the lack of well-recognized SG selection rule, most SGs are chosen intuitively. We propose the parametric surrogate gradient (PSG) method to iteratively update SG and eventually determine an optimal surrogate gradient parameter, which calibrates the shape of candidate SGs. In SNNs, neural potential distribution tends to deviate unpredictably due to quantization error. We evaluate such potential shift and propose methodology for potential distribution adjustment (PDA) to minimize the loss of undesired pre-activations. Experimental results demonstrate that the proposed methods can be readily integrated with backpropagation through time (BPTT) algorithm and help modulated SNNs to achieve state-of-the-art performance on both static and dynamic dataset with fewer timesteps.Comment: 10 pages, 8 figure

Effects of fear factors in disease propagation

Upon an outbreak of a dangerous infectious disease, people generally tend to reduce their contacts with others in fear of getting infected. Such typical actions apparently help slow down the spreading of infection. Thanks to today's broad public media coverage, the fear factor may even contribute to prevent an outbreak from happening. We are motivated to study such effects by adopting a complex network approach. Firstly we evaluate the simple case where connections between individuals are randomly removed due to fear factor. Then we consider a different case where each individual keeps at least a few connections after contact reduction. Such a case is arguably more realistic since people may choose to keep a few social contacts, e.g., with their family members and closest friends, at any cost. Finally a study is conducted on the case where connection removals are carried out dynamically while the infection is spreading out. Analytical and simulation results show that the fear factor may not easily prevent an epidemic outbreak from happening in scale-free networks. However, it significantly reduces the fraction of the nodes ever getting infected during the outbreak.Comment: 19 pages, 10 figure

AOBA VELOX-IV: 2U CubeSat for the technological demonstration of lunar horizon glow mission

AOBA VELOX-IV is a 2U-sized CubeSat that has been developed by the Kyushu Institute of Technology and Nanyang Technological University for the technological demonstration of a future lunar mission. Decades ago, Surveyor and Apollo programs reported light scattering observations on the horizon of the Moon; however, only a limited number of investigations were performed after the Apollo program to observe the lunar horizon glow (LHG). It is still unknown what conditions produce the light glow on the horizon of the Moon. The lunar mission of the AOBA VELOX project is planning to send CubeSats to the Moon and to capture images of the LHG on the lunar orbit while determining the conditions that can support light scattering above the lunar horizon. Before the satellites go into the lunar orbit, the necessary technologies must first be confirmed in Earth orbit. AOBA VELOX-IV was launched to low earth orbit via a JAXA Epsilon rocket in 18th January 2019. This paper explains the LHG mission first, and presents an overview of AOBA VELOX-IV, its payloads, technical issues, and the flight model

Development of high performance distributed multimedia systems

The report investigates the role, and relationships between multimedia database/server systems in a distributed environment.RP 45/9

An efficient mechanism for dynamic survivable multicast traffic grooming

Recent advances in wavelength division multiplexing (WDM) networks have helped enhance the popularity of multicasting services. However, as a single network failure may disrupt the information transmission to multiple end-users, protecting multicast requests against network failures becomes an important issue in network operation. This paper investigates the sub-wavelength level protection for dynamic multicast traffic grooming. A new method named lightpath-fragmentation based segment shared protection (LF-SSP) scheme is proposed. By carefully splitting primary/backup lightpaths into segments to improve resource sharing for both traffic grooming and protection, LF-SSP aims to minimize the network resources allocated for request protection. Extensive simulations are carried out to compare the performance of LF-SSP to some existing approaches, on sub-wavelength-level as well as wavelength-level multicast protections in different cases. Results show that LF-SSP steadily outperforms these existing methods as long as the network resources are not too limited. Influences of the add/drop port resources and the average number of destinations per connection request on the LF-SSP performance are also evaluated.Accepted versio

Dynamic multicast traffic grooming in optical WDM mesh networks : lightpath versus light-tree

With the rising popularity of multicast applications, various algorithms using either lightpath or light-tree schemes have been proposed for dynamic multicast traffic grooming in meshed wavelength division multiplexing (WDM) networks. To the best of our knowledge, however, no systematic comparison has ever been made between the performance of the two schemes in minimizing network blocking probability. In this paper, we address the dynamic multicast traffic grooming problem in WDM networks and present comprehensive comparisons between these two schemes in different cases. Our main contributions are twofold: first, we compare the performance of the existing lightpath- and light-tree-based grooming algorithms and show that, in most cases, the lightpath-based methods outperform the light-tree-based ones. We discuss and explain such observations. Second, we propose a lightpath-based algorithm, called the LightPath Fragmentation (LPF) method, to further improve the network blocking performance. Numerous simulations show that the LPF method steadily outperforms the existing algorithms in different cases. Effects of the ratio of unicast traffic loads versus overall traffic loads and the average number of destinations of each multicast request are also studied.Published versio

Routing and wavelength assignment algorithms for translucent optical networks

Due to transmission impairments, optical regeneration is needed to extend the length of a lightpath beyond its transparent length. Spare transmitter (Tx) and receiver (Rx) modules in an optical network node can be used for optical regeneration. A Max-spare algorithm for locating the regeneration nodes for a lightpath is proposed and compared with a Greedy algorithm in conjunction with two routing algorithms, namely, wavelength weighted (WW) and length weighted (LW) routing algorithms. Through simulation we find that significant number of lightpaths that cannot be established due to the violation of transparent length can be established if the regeneration algorithm is used to select transit nodes that have spare Tx and Rx for 3R regeneration. The translucent optical network with limited number of transceivers can still perform close to a transparent optical network with full set of transceivers. We find that for the same routing algorithm, the Max-spare algorithm yields better results than the Greedy algorithm. In addition; for the same regeneration nodes selection algorithm, the WW algorithm has better performance than the LW algorithm

Performance comparisons between lightpath and light-tree schemes in dynamic multicast traffic grooming process

To support multicast applications while improving wavelength capacity utilization in wavelength division multiplexing (WDM) networks, dynamic multicast traffic grooming problem has been extensively studied in recent years, and various algorithms using either lightpath or light-tree schemes have been proposed. To the best of our knowledge, however, no systematic comparison has ever been made between the blocking performances of these two different types of schemes. In this paper, we firstly present a brief survey of the various existing algorithms for dynamic multicast traffic grooming, followed by a short discussion on the pros and cons of lightpath and lightp-tree schemes respectively. By conducting extensive numerical simulations, we carefully compare the blocking performances of these two types of schemes. Our study results show that, in most cases, the lightpath-based methods outperform the light-tree based ones, typically with only a slightly higher consumption of O/E/O resources. We provide an explanation to such interesting observations. Effects of the ratio of multicast traffic to overall network traffic and the average number of destinations of each multicast request are also studied

Telecommunication techniques and systems 1 : fibre lasers for optical communication systems

The project fabricates and characterizes fibre lasers and to explore new fabrication techniques and laser configurations to make fibre lasers suitable for optical communication system applications.RGM 2219