Frequency limits of sequential readout for sensing AC magnetic fields using nitrogen-vacancy centers in diamond

The nitrogen-vacancy (NV) centers in diamond have ability to sense alternating-current (AC) magnetic fields with high spatial resolution. However, the frequency range of AC sensing protocols based on dynamical decoupling (DD) sequences has not been thoroughly explored experimentally. In this work, we aimed to determine the sensitivity of ac magnetic field as a function of frequency using sequential readout method. The upper limit at high frequency is clearly determined by Rabi frequency, in line with the expected effect of finite DD-pulse width. In contrast, the lower frequency limit is primarily governed by the duration of optical repolarization rather than the decoherence time (T$_2$) of NV spins. This becomes particularly crucial when the repetition (dwell) time of the sequential readout is fixed to maintain the acquisition bandwidth. The equation we provide successfully describes the tendency in the frequency dependence. In addition, at the near-optimal frequency of 1 MHz, we reached a maximum sensitivity of 229 pT/$\sqrt{\mathrm{Hz}}$ by employing the XY4-(4) DD sequence.Comment: 7 pages, 5 figure

Quantum diamond microscopy with sub-ms temporal resolution

Quantum diamond magnetometers using lock-in detection have successfully detected weak bio-magnetic fields from neurons, a live mammalian muscle, and a live mouse heart. This opens up the possibility of quantum diamond magnetometers visualizing microscopic distributions of the bio-magnetic fields. Here, we demonstrate a lock-in-based wide-field quantum diamond microscopy, achieving a mean volume-normalized per pixel sensitivity of 43.9 $\mathrm{nT\cdot\mu m^{1.5}/Hz^{0.5}}$. We obtain the sensitivity by implementing a double resonance with hyperfine driving and magnetic field alignment along the $$ orientation of the diamond. Additionally, we have demonstrated that sub-ms temporal resolution ($\sim$ 0.4 ms) can be achieved at a micrometer scale with tens of nanotesla per-pixel sensitivity using quantum diamond microscopy. This lock-in-based diamond quantum microscopy could be a step forward in mapping functional activity in neuronal networks in micrometer spatial resolution

A New Query Processing Technique for XML Based on Signature

XML is represented as a tree and the query as a regular path expression. The query is evaluated by traversing each node of the tree. Several indexes are proposed for regular path expressions. In some cases these indexes may not cover all possible paths because of storage requirements. In this paper, we propose a signature-based query optimization technique to minimize the number of nodes retrieved from the database when the indexes cannot be used. The signature is a hint attached to each node, and is used to prune unnecessary sub-trees as early as possible when traversing nodes. For this goal, we propose a signature-based DOM(s-DOM) as a storage model and a signature-based query executor(s-NFA). Our experimental results show that the signature method outperforms the original. 1

ICT Infrastructure, OTT Market Growth, Economic Freedom, and International Tourism: A Cross-Country Empirical Study

This study examined whether information and communication technology (ICT), over the top (OTT) market growth, and economic freedom affect tourism at the global level. Toward this end, the present study tested regression models of inbound tourism and outbound tourism with panel data from 50 countries covering the years 2013 to 2020. The results of the panel-data analysis suggest that high levels of OTT advertising revenue and mobile broadband penetration contribute to high levels of inbound tourism. The results also reveal that high OTT advertising revenue, labor freedom, and income are associated with high levels of outbound tourism. The obtained results underscore that ICT and media play key roles in promoting international tourism

Examining Factors Influencing Early Paid Over-The-Top Video Streaming Market Growth: A Cross-Country Empirical Study

This study examines the factors influencing early paid Over-The-Top (OTT) video streaming market growth in 50 countries. The results of the panel data analysis suggest that Netflix’s market entry, traditional pay TV market size, broadband infrastructure, and OTT platform competition contribute to the early market growth of paid OTT video streaming services, such as subscription video-on-demand (SVOD) services. The results also reveal that the traditional pay TV subscription market and the paid OTT video streaming market initially grow together in many countries. However, the findings also reveal a negative association between the market entry of Netflix and the subscription revenue growth rate of traditional pay TV services. The results of this study suggest industry and policy implications for paid OTT video streaming market growth and the sustainable development of the media industry

A Net Diffusion Model of Mobile Application: Considering Self-referencing, Within-category Dependency, and Drop-out Process

The diffusion process of mobile application has several distinctive features. First, unlike other products, there is little cost to acquire and abandon mobile applications. This easy-come-easy-go makes the issue of assimilation gap most prevalent in the mobile application diffusion. Second, many applications are tested on a popular platform before the market introduction or promoted from already popular applications, which can form the early market and accelerate the diffusion of such applications. This self-referencing can make the unique diffusion pattern, particularly in the early stage of the market introduction. Lastly, the diffusion process of applications, especially for those in the same category, can be interrelated with each other. This within-category dependency might require the diffusion of applications in the same category to be modeled together. We develop and empirically validate a flexible diffusion model to accommodate aforementioned distinctive features in the diffusion process of mobile applications

System Software for Flash Memory: A Survey

Abstract. Recently, flash memory is widely adopted in embedded ap-plications since it has several strong points: non-volatility, fast access speed, shock resistance, and low power consumption. However, due to its hardware characteristic, namely “erase before write”, it requires a software layer called FTL (Flash Translation Layer). This paper surveys the state-of-the-art FTL software for flash memory. This paper also de-scribes problem definitions, several algorithms proposed to solve them, and related research issues. In addition, this paper provides performance results based on our implementation of each of FTL algorithms