An effective ant-colony based routing algorithm for mobile ad-hoc network

An effective Ant-Colony based routing algorithm for mobile ad-hoc network is proposed in this paper. In this routing scheme, each path is marked by path grade, which is calculated from the combination of multiple constrained QoS parameters such as the time delay, packet loss rate and bandwidth, etc. packet routing is decided by the path grade and the queue buffer length of the node. The advantage of this scheme is that it can effectively improve the packet delivery ratio and reduce the end-to-end delay. The simulation results show that our proposed algorithm can improve the packet delivery ratio by 9%-22% and the end-to-end delay can be reduced by 14%-16% as compared with the conventional QAODV and ARA routing schemes

Uniqueness of signature for simple curves

We propose a topological approach to the problem of determining a curve from its iterated integrals. In particular, we prove that a family of terms in the signature series of a two dimensional closed curve with finite p variation, 1≤p<21≤p<2, are in fact moments of its winding number. This relation allows us to prove that the signature series of a class of simple non-smooth curves uniquely determine the curves. This implies that outside a Chordal SLEκSLEκ null set, where 0<κ≤40<κ≤4, the signature series of curves uniquely determine the curves. Our calculations also enable us to express the Fourier transform of the n-point functions of SLE curves in terms of the expected signature of SLE curves. Although the techniques used in this article are deterministic, the results provide a platform for studying SLE curves through the signatures of their sample paths

Multi-infeed HVDC/AC power system modeling and analysis with dynamic phasor application

In this paper, dynamic phasor method has been applied to HVDC transmission system and FACTS device modeling. A hybrid-model simulation algorithm is suggested for transient stability analysis with HVDC transmission system and FACTS devices in dynamic phasor models and other ac system elements in electromechanical models. Computer test results show clearly that the proposed hybrid-model simulation algorithm can be applied for transient stability analysis effectively and accurately. A multi-infeed HVDC/AC (MIDC/AC) system is studied using the suggested hybrid-model transient stability program. The dynamic behaviors of MIDC/AC system under different circumstances are discussed. The characteristics of HVDC system recovery and recovery strategy for MIDC system are considered in the stability analysis. Furthermore, the impacts of advanced FACTS controllers such as STATCOM on system dynamic are studied for enhance system operation security. © 2000 IEEE.published_or_final_versio

Reversible Embedding to Covers Full of Boundaries

In reversible data embedding, to avoid overflow and underflow problem, before data embedding, boundary pixels are recorded as side information, which may be losslessly compressed. The existing algorithms often assume that a natural image has little boundary pixels so that the size of side information is small. Accordingly, a relatively high pure payload could be achieved. However, there actually may exist a lot of boundary pixels in a natural image, implying that, the size of side information could be very large. Therefore, when to directly use the existing algorithms, the pure embedding capacity may be not sufficient. In order to address this problem, in this paper, we present a new and efficient framework to reversible data embedding in images that have lots of boundary pixels. The core idea is to losslessly preprocess boundary pixels so that it can significantly reduce the side information. Experimental results have shown the superiority and applicability of our work

An Introduction to Machine Learning in Quantitative Finance

In this book, the authors provide a systematic and rigorous introduction to supervised, unsupervised and reinforcement learning by establishing essential definitions and theorems

Does evaporation paradox exist in China?

One expected consequence of global warming is the increase in evaporation. However, lots of observations show that the rate of evaporation from open pans of water has been steadily decreasing all over the world in the past 50 years. The contrast between expectation and observation is called &quot;evaporation paradox&quot;. Based on data from 317 weather stations in China from 1956 to 2005, the trends of pan evaporation and air temperature were obtained and evaporation paradox was analyzed. The conclusions include: (1) From 1956 to 2005, pan evaporation paradox existed in China as a whole while pan evaporation kept decreasing and air temperature became warmer and warmer, but it does not apply to Northeast and Southeast China; (2) From 1956 to 1985, pan evaporation paradox existed narrowly as a whole with unobvious climate warming trend, but it does not apply to Northeast China; (3) From 1986 to 2005, in the past 20 years, pan evaporation paradox did not exist for the whole period while pan evaporation kept increasing, although it existed in South China. Furthermore, the trend of other weather factors including sunshine duration, windspeed, humidity and vapor pressure deficit, and their relations with pan evaporation are discussed. As a result, it can be concluded that pan evaporation decreasing is caused by the decreasing in radiation and wind speed before 1985 and pan evaporation increasing is caused by the decreasing in vapor pressure deficit due to strong warming after 1986. With the Budyko curve, it can be concluded that the actual evaporation decreased in the former 30 years and increased in the latter 20 year for the whole China

Epitaxial lateral overgrowth of a-plane GaN by metalorganic chemical vapor deposition

We report on epitaxial lateral overgrowth (ELO) of (112¯0) a-plane GaN by metalorganic chemical vapor deposition. Different growth rates of Ga- and N-polar wings together with wing tilt create a major obstacle for achieving a smooth, fully coalesced surface in ELOa-plane GaN. To address this issue a two-step growth method was employed to provide a large aspect ratio of height to width in the first growth step followed by enhanced lateral growth in the second by controlling the growth temperature. By this method, the average ratio of Ga- to N-polar wing growth rate has been reduced from 4–6 to 1.5–2, which consequently reduced the wing-tilt induced height difference between the two approaching wings at the coalescence front, thereby making their coalescence much easier. Transmission electron microscopy showed that the threading dislocation density in the wing regions was 1.0×108 cm−2, more than two orders of magnitude lower than that in the window regions (4.2×1010 cm−2). However, a relatively high density of basal stacking faults of 1.2×104 cm−1 was still present in the wing regions as compared to c -plane GaN, where they are rarely observed away from the substrate. Atomic force microscopy(AFM) measurements showed two orders of magnitude higher density of surface pits in the window than in the wing regions, which were considered to be terminated by dislocations (partial ones related to stacking faults and full ones) on the surface. The existence of basal stacking faults was also revealed by AFM measurements on the a-plane ELO sample after wet chemical etching in hot H3PO4∕H2SO4 (1:1). The extensions of Ga-polar wings near the meeting fronts were almost free of stacking faults. The improvement of crystalline quality in the overgrown layer by ELO was also verified by near field scanning optical microscopy and time-resolved photoluminescence measurements; the former showing strongly enhanced luminescence from the wing regions, and the latter indicating longer decay times (0.25 ns) compared to a standard a-plane GaN template (40 ps)