There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

“Unpaired Image-to-Image Translation using Cycle-Consistent Adversarial Networks”の学習報告

The distributed nature and dynamic topology of Wireless Sensor Networks (WSNs) introduces very special requirements in routing protocols that should be met. The most important feature of a routing protocol, in order to be efficient for WSNs, is the energy consumption and the extension of the network's lifetime. During the recent years, many energy efficient routing protocols have been proposed for WSNs. In this paper, energy efficient routing protocols are classified into four main schemes: Network Structure, Communication Model, Topology Based and Reliable Routing. The routing protocols belonging to the first category can be further classified as flat or hierarchical. The routing protocols belonging to the second category can be further classified as Query-based or Coherent and non-coherent-based or Negotiation-based. The routing protocols belonging to the third category can be further classified as Location-based or Mobile Agent-based. The routing protocols belonging to the fourth category can be further classified as QoS-based or Multipath-based. Then, an analytical survey on energy efficient routing protocols for WSNs is provided. In this paper, the classification initially proposed by Al-Karaki, is expanded, in order to enhance all the proposed papers since 2004 and to better describe which issues/operations in each protocol illustrate/enhance the energy-efficiency issues.

Energy-Efficient Routing Protocols in Wireless Sensor Networks: A Survey

https://hal.archives-ouvertes.fr/hal-01009386/document

Energy efficiency in wireless sensor networks: A top-down survey

In this paper, we address the problem of lossless, offline compression of climate data. We propose a technique for compression of climate data using combination of differential encoding and Huffman coding. This technique gives lossless data compression and reduces the number of bits required to encode a set of symbols,thereby leading to high compression. Performance of this method is measured using the compressed file sizes and finding the compression ratio. Our data set consists of three parameters from the Nevada climate data portal – solar radiation, photo synthetically active radiation, and data logger power system voltage.

Lossless Compression of Climate Data

https://www.cs.clemson.edu/stabiliz/Papers/MICRO-PUBLISHED.pdf

Loop detection in MPLS for wireless sensor networks

This paper aims to discuss a comprehensive list of demerits associated with the use of Diffusing Update Algorithm compared to its link-state counterpart, namely, Shortest Path First algorithm which is a variant of Dijkstra's algorithm. Such a comparison was neglected for the past two decades due to the proprietary nature of the former protocol. This has led to the prevalence of the latter which is why many computer network professionals adamantly recommend implementing link-state protocols in campus implementations. However, this is of importance today pursuant to the release of several IETF Internet drafts in an attempt to standardize the Enhanced Interior Gateway Routing Protocol. Dynamic routing protocols rely on algorithms computing the shortest paths using weighted digraphs and tree traversals. In this paper, not only are the algorithms discussed but also an in-depth analysis of the various features of the aforementioned protocols is conducted. Abandoning the periodicity of update massages and operating in an event- driven fashion with automatic failover capability are some of the features that will be analyzed. Part of the novelty of this paper lies in the mathematical representation of decision-making processes and metric computation. One of the notable findings of this paper is an evaluative analysis of convergence times achieved in a typical university campus routing implementation. Moreover, using wide metric vectors contributes to energy-aware routing and improved performance for jitter-sensitive services.

Will an Emerging Standard Take Over the Routing Realm? An Evaluative Analysis of DUAL and SPF

Recent developments in remote sensing technologies have provided various images with high spatial and spectral resolutions. However, multispectral images have low spatial resolution and panchromatic images have low spectral resolution. Therefore, image fusion techniques are necessary to improve the spatial resolution of spectral images by injecting spatial details of high-resolution panchromatic images. The objective of image fusion is to provide useful information by improving the spatial resolution and the spectral information of the original images. The fusion results can be utilized in various applications, such as military, medical imaging, and remote sensing. This paper addresses two issues in image fusion: i) image fusion method and ii) quality analysis of fusion results. First, a new contourlet-based image fusion method is presented, which is an improvement over the wavelet-based fusion. This fusion method is then applied to a case study to demonstrate its fusion performance. Fusion framework and scheme used in the study are discussed in detail. Second, quality analysis for the fusion results is discussed. We employed various quality metrics in order to analyze the fusion results both spatially and spectrally. Our results indicate that the proposed contourlet-based fusion method performs better than the conventional wavelet-based fusion methods.

Fusion and Quality Analysis for Remote Sensing Images Using Contourlet Transform

Spectral images have relatively low spatial resolution, compared to high-resolution single band panchromatic (PAN)
images. Therefore, fusing a spectral image with a PAN image has been widely studied to produce a high-resolution
spectral image. However, raw spectral images are too large to process and contain redundant information that is not
utilized in the fusion process. In this study, we propose a novel fusion method that employs a spectral band reduction
and contourlets. The band reduction begins with the best two band combination, and this two-band combination is
subsequently augmented to three, four, and more until the desired number of bands is selected. The adopted band
selection algorithm using the endmember extraction concept employs a sequential forward search strategy. Next, the
image fusion is performed with two different spectral images based on the frequency components that are newly
obtained by contourlet transform (CT). One spectral image that is used as a dataset is multispectral (MS) image and the
other is hyperspectral (HS) image. Each original spectral image is pre-processed by spectrally integrating over the entire
spectral range to obtain a PAN source image that is used in the fusion process. This way, we can eliminate the step of
image co-registration since the obtained PAN image is already perfectly aligned to the spectral image. Next, we fuse the
band-reduced spectral images with the PAN images using contourlet-based fusion framework. The resultant fusion
image provides enhanced spatial resolution while preserving the spectral information. In order to analyze the band
reduction performance, the original spectral images are fused with the same PAN images to serve as a reference image,
which is then compared to the band-reduced spectral image fusion results using six different quality metrics.

Shahram Latifi

Papers

Lossless Compression of Climate Data

Loop detection in MPLS for wireless sensor networks

Will an Emerging Standard Take Over the Routing Realm? An Evaluative Analysis of DUAL and SPF

Fusion and Quality Analysis for Remote Sensing Images Using Contourlet Transform

Spectral image fusion using band reduction and contourlets