An ant colony optimization approach for maximizing the lifetime of heterogeneous wireless sensor networks

Maximizing the lifetime of wireless sensor networks (WSNs) is a challenging problem. Although some methods exist to address the problem in homogeneous WSNs, research on this problem in heterogeneous WSNs have progressed at a slow pace. Inspired by the promising performance of ant colony optimization (ACO) to solve combinatorial problems, this paper proposes an ACO-based approach that can maximize the lifetime of heterogeneous WSNs. The methodology is based on finding the maximum number of disjoint connected covers that satisfy both sensing coverage and network connectivity. A construction graph is designed with each vertex denoting the assignment of a device in a subset. Based on pheromone and heuristic information, the ants seek an optimal path on the construction graph to maximize the number of connected covers. The pheromone serves as a metaphor for the search experiences in building connected covers. The heuristic information is used to reflect the desirability of device assignments. A local search procedure is designed to further improve the search efficiency. The proposed approach has been applied to a variety of heterogeneous WSNs. The results show that the approach is effective and efficient in finding high-quality solutions for maximizing the lifetime of heterogeneous WSNs

Development of two in vitro regeneration systems through leaf explant and callus culture and the application for genetic transformation in Alstroemeria

Alstroemeria is a popular ornamental crop cultivated for its flowers. Taxonomically, it belongs to a monocotyledonous family, the Alstroemeriaceae, and is commonly called by its genus name. An Alstroemeria plant consists of underground grown rhizomes, roots, and aerial shoots. The plant is grown perennially. Due to the good incorporation of plant breeding techniques combined with the modern greenhouse cultivation technologies of the last two decades, Alstroemeria has become a competitive greenhouse-grown cut flower in the Netherlands. Generally, the Alstroemeria plant is vegetatively propagated by rhizome division, but the multiplication rate is rather low. Therefore, the increasing demand for plantlets stimulated the development of in vitro propagation techniques. However, since the multiplication unit used in the in vitro method is limited to rhizome tips, the propagation rate is still rather low in comparison with other crops and the other plant organs seem to be of no use during subculture. In addition, a callus culture system has been developed in the last few years for plant propagation purpose. The multiplication efficiency of this system is expected to be higher than that of the rhizome culture system, but the commercial true-to-type requirement cannot be fulfilled, because the callus was initiated from zygotic embryos. Therefore, the development of an additional in vitro multiplication system based on other plant organs is considered to be desirable (Chapter 1).Plant regeneration of cultured explants has in general two pathways, either via organogenesis (the development of shoots directly on an explant) or via embryogenesis (the development of differentiated somatic embryos on an explant). A large part of this thesis research deals with the development of two plant regeneration systems, one based on organogenesis and the other based on embryogenesis. In Chapter 2, a two-step protocol for the induction of shoot formation from in vitro grown Alstroemeria leaf explants is described. Leaf explants were cut from seedlings still containing a leaf blade and a stem node. After 10 days of culture on an induction medium, the leaf explants were transferred to a shooting medium for eight weeks. New shoots were formed directly from the area adjacent to the region between leaf base and node tissue within three weeks on shooting medium. It was histologically demonstrated that these shoots were initiated from the epidermal cells at leaf axils (Chapter 3). There were no pre-existing axillary buds ever found on the aerial leaf axils, so that this kind of organogenesis suggests an adventitious nature. The leaf explants together with newly formed shoots were subcultured several times and many normal plantlets with rhizomes were formed, which then were suitable for transferring to the soil (Chapter 2, Chapter 4).The best induction was obtained on a Murashige and Skoog's (1962) medium supplemented with 10μM thidiazuron (TDZ) and 0.5μM indole butyric acid (IBA) (Chapter 2). The shooting medium contained MS medium with 2.2μM 6-benzylaminopurine (BAP). The shoot regeneration capacity of the excised leaf explants was related to the position of the leaf on the stem. The youngest explant which was located the nearest to the shoot apex, gave the highest response. A lower gradient response was found in the leaf explants derived from leaves cut off at a further distance from the apex. This was measured in percentage of shoot regeneration per leaf explant and in the number of shoots per regenerating explant (Chapter 3).A demonstration experiment was carried out in the greenhouse in order to investigate the similarity of plant growth morphology in between plants, which were obtained from either rhizome multiplication or leaf explant culture system. The plants were grown in the greenhouse to flowering, and the results indicated that plants obtained from both systems were morphologically identical (Chapter 4). This implicates that the leaf culture system seems to be a reliable in vitro propagation technique for the genotype we have investigated.Another advantage of the leaf explant culture system is that the leaf explants directly can be excised from in vivo full grown shoots, and that the disinfection of aerial shoots is easier than that of underground grown rhizomes (Chapter 4). Therefore, this technique is suitable for the initiation of in vitro propagation of existing cultivars.In the conventional micropropagation system, only the rhizome tips are multiplied and therefore, the aerial shoots are always discarded during subculture. In this thesis research, it is concluded that not only the rhizome tips can be used as propagation units, but also the discarded shoots can be used for the initiation of the other propagation system. The first three leaves excised from each shoot have an average regeneration capacity of 87.7%, and the average number of newly formed shoots per explant was 5.3 (Chapter 4). On the other hand, the rhizomes can be multiplied simultaneously. Therefore, combining the rhizome multiplication system with the leaf explant culture system, the multiplication efficiency will be enhanced.In Chapter 5, a somatic embryogenic callus regeneration system is described. A soft and sticky type of callus was induced initially from the stem segments of one month old seedlings of two tetraploid Alstroemeria genotypes. The soft calli turned into compact type after subculture on a medium (MS with 30 g/l sucrose) containing 6-benzylaminopurine. Subsequently, two other different morphotypes of callus, friable and granular, were obtained by subculturing the compact callus on different culture media. The friable callus can be maintained on a single medium (PCA) containing 10 mg/l picloram for a long period without loosing its friability. Subculturing the friable callus on plant growth regulator free media or on 6-benzylaminopurine containing media stimulated the granular callus formation, and the subsequent somatic embryogenesis. The somatic embryos were able to develop into complete plants.The granular callus proved to be an intermediate between friable callus, somatic embryo, and compact callus. The friable callus could also be induced from granular callus, and vice versa. Therefore, a cyclic reproduction system was established in this research. This system provides two types of callus with a high embryogenic capability, which were initially derived from the stem segments. Thus, this system is considered to be applicable for the in vitro propagation of Alstroemeria .In addition to the purpose of plant propagation, the development of a plant regeneration system is also considered to have the potential for genetic modification in Alstroemeria . Some characteristics, for example virus resistances, are very important in the continuously greenhouse-grown cultivars. However, virus resistance genes are not generally present in the Alstroemeria gene pool yet, so that the traditional breeding techniques are not sufficient for this purpose. Genetic transformation of Alstroemeria is considered to be useful for breeding in the future (Chapter 1). For genetic transformation, four important factors should be taken into account: a) an efficient DNA delivery system, b) the appropriate target cells competent for both transformation and regeneration, c) an adequate promoter, and d) a good selection system (Chapter 1).In this research, the particle bombardment delivery system was chosen for the monocot A lstroemeria , because of its expectedly higher transformation efficiency than the Agrobacterium vector system (Chapter 1). The leaf explant regeneration system was tested for gene transformation by using the particle bombardment. Although the gene expression could be detected after particle bombardment, the gene activities were only transiently expressed on leaf tissues, and they disappeared within two months (Chapter 7). On the other hand, the somatic embryogenic callus regeneration system was successfully used for particle bombardment mediated gene transformation. Two tetraploid Alstroemeria genotypes were transformed, and many transgenic plants were obtained (Chapter 6).Both granular and friable calli were used as bombardment targets, and the subsequent somatic embryogenesis resulted in the formation of complete transgenic plantlets. Two plasmids containing different selection and reporter genes were used. Firstly, a plasmid containing a firefly luciferase reporter gene, driven by the maize ubiquitin promoter ( Ubi1 ), was bombarded into both granular and friable calli. The luciferase activity was measured by a luminometer after spraying the bombarded plant material with a luciferin solution. Visual selection of the luciferase positive calli, assisted by the luminometer, was effective. This kind of selection has a nondestructive nature, without injuring the plant material, and the luciferase activity can be assayed periodically over the whole developmental process from callus to embryo and plantlet. It was shown that the granular callus is more suitable for particle bombardment mediated transformation using luciferase activity as selection marker than the friable callus (Chapter 6).Secondly, another plasmid containing the selectable Basta (herbicide) resistance gene ( bar ) encoding phosphinotricin acetyltransferase (PAT) together with an uid A reporter gene encoding ß-glucuronidase (GUS) was used. Both genes were driven by the Ubi1 promoter. The granular calli were bombarded in this experiment. Selection of the phosphinotricin (PPT) resistant calli was accomplished by culturing the bombarded calli on a medium containing 5 mg/l PPT. The PPT resistant calli were the friable type of calli which were already regenerated from the granular calli, and they developed into somatic embryos, and subsequently into the plantlets. Stable expression of the GUS gene was confirmed by histochemical staining. The blue color was detectable in all tissues of the transgenic plants tested by the GUS assay. The PPT selection proved to be a more efficient and labor-saving method compared to the luciferase selection (Chapter 6).The results described in this thesis are beneficial for both the in vitro propagation and the genetic modification of Alstroemeria . The use of leaf explants as in vitro propagation units is rather unique in Alstroemeria , which opens an alternative way for enhancing the plant propagation efficiency. The embryogenic callus regeneration system described in this thesis is not only applicable for plant propagation, but also for genetic transformation. The establishment of particle bombardment mediated transformation techniques will push the molecular breeding in Alstroemeria forward into a luminous future.</p

Intensity-modulated abrupt tapered Fiber Mach-Zehnder Interferometer for the simultaneous sensing of temperature and curvature

AbstractAn abrupt tapered fiber In-Line Mach-Zehnder Interferometer sensor for simultaneous measurement of temperature and curvature is proposed and experimentally demonstrated. The sensor head is fabricated by arcing Corning SMF-28 using a commercial arc fusion splicer. The individual parameters discrimination was achieved by manipulating the unequal sensitivities of optical power to temperature and curvature obtained at two wavelengths within the sensing spectrum. The curvature and temperature sensitivities at λ1 (1537nm) and λ2 (1568.7nm) were found to be 11.8264dBm/m−1, 12.4885dBm/m−1 and 0.0829dBm/°C, 0.0833dBm/°C, respectively. The experimental results show unperturbed readings with rms deviation of ±0.1801m−1 and ±0.0826°C, for curvature and temperature measurements, respectively, through measurement of optical power response of the sensor. With this simultaneous sensing technique, the proposed sensor can be deployed for many field applications such as nondestructive structural health monitoring of civil infrastructure

Energy Release During Slow Long Duration Flares Observed by RHESSI

Slow Long Duration Events (SLDEs) are flares characterized by long duration of rising phase. In many such cases impulsive phase is weak with lack of typical short-lasting pulses. Instead of that smooth, long-lasting Hard X-ray (HXR) emission is observed. We analysed hard X-ray emission and morphology of six selected SLDEs. In our analysis we utilized data from RHESSI and GOES satellites. Physical parameters of HXR sources were obtained from imaging spectroscopy and were used for the energy balance analysis. Characteristic time of heating rate decrease, after reaching its maximum value, is very long, which explains long rising phase of these flares.Comment: Accepted for publication in Solar Physic

CODE: Coherence based decision boundaries for feature correspondence

A key challenge in feature correspondence is the difficulty in differentiating true and false matches at a local descriptor level. This forces adoption of strict similarity thresholds that discard many true matches. However, if analyzed at a global level, false matches are usually randomly scattered while true matches tend to be coherent (clustered around a few dominant motions), thus creating a coherence based separability constraint. This paper proposes a non-linear regression technique that can discover such a coherence based separability constraint from highly noisy matches and embed it into a correspondence likelihood model. Once computed, the model can filter the entire set of nearest neighbor matches (which typically contains over 90 percent false matches) for true matches. We integrate our technique into a full feature correspondence system which reliably generates large numbers of good quality correspondences over wide baselines where previous techniques provide few or no matches

Eruptions of Magnetic Ropes in Two Homologous Solar Events on 2002 June 1 and 2: a Key to Understanding of an Enigmatic Flare

The goal of this paper is to understand the drivers, configurations, and scenarios of two similar eruptive events, which occurred in the same solar active region 9973 on 2002 June 1 and 2. The June 2 event was previously studied by Sui, Holman, and Dennis (2006, 2008), who concluded that it was challenging for popular flare models. Using multi-spectral data, we analyze a combination of the two events. Each of the events exhibited an evolving cusp-like feature. We have revealed that these apparent ``cusps'' were most likely mimicked by twisted magnetic flux ropes, but unlikely to be related to the inverted Y-like magnetic configuration in the standard flare model. The ropes originated inside a funnel-like magnetic domain whose base was bounded by an EUV ring structure, and the top was associated with a coronal null point. The ropes appear to be the major drivers for the events, but their rise was not triggered by reconnection in the coronal null point. We propose a scenario and a three-dimensional scheme for these events in which the filament eruptions and flares were caused by interaction of the ropes.Comment: 22 pages, 11 figure

Energy-Dependent Timing of Thermal Emission in Solar Flares

We report solar flare plasma to be multi-thermal in nature based on the theoretical model and study of the energy-dependent timing of thermal emission in ten M-class flares. We employ high-resolution X-ray spectra observed by the Si detector of the "Solar X-ray Spectrometer" (SOXS). The SOXS onboard the Indian GSAT-2 spacecraft was launched by the GSLV-D2 rocket on 8 May 2003. Firstly we model the spectral evolution of the X-ray line and continuum emission flux F(\epsilon) from the flare by integrating a series of isothermal plasma flux. We find that multi-temperature integrated flux F(\epsilon) is a power-law function of \epsilon with a spectral index (\gamma) \approx -4.65. Next, based on spectral-temporal evolution of the flares we find that the emission in the energy range E= 4 - 15 keV is dominated by temperatures of T= 12 - 50 MK, while the multi-thermal power-law DEM index (\gamma) varies in the range of -4.4 and -5.7. The temporal evolution of the X-ray flux F(\epsilon,t) assuming a multi-temperature plasma governed by thermal conduction cooling reveals that the temperature-dependent cooling time varies between 296 and 4640 s and the electron density (n_e) varies in the range of n_e= (1.77-29.3)*10^10 cm-3. Employing temporal evolution technique in the current study as an alternative method for separating thermal from non-thermal components in the energy spectra, we measure the break-energy point ranging between 14 and 21\pm1.0 keV.Comment: Solar Physics, in pres

On Vanishing Theorems For Vector Bundle Valued p-Forms And Their Applications

Let $F: [0, \infty) \to [0, \infty)$ be a strictly increasing $C^2$ function with $F(0)=0$. We unify the concepts of $F$-harmonic maps, minimal hypersurfaces, maximal spacelike hypersurfaces, and Yang-Mills Fields, and introduce $F$-Yang-Mills fields, $F$-degree, $F$-lower degree, and generalized Yang-Mills-Born-Infeld fields (with the plus sign or with the minus sign) on manifolds. When $F(t)=t, \frac 1p(2t)^{\frac p2}, \sqrt{1+2t} -1,$ and $1-\sqrt{1-2t},$ the $F$-Yang-Mills field becomes an ordinary Yang-Mills field, $p$-Yang-Mills field, a generalized Yang-Mills-Born-Infeld field with the plus sign, and a generalized Yang-Mills-Born-Infeld field with the minus sign on a manifold respectively. We also introduce the $E_{F,g}-$energy functional (resp. $F$-Yang-Mills functional) and derive the first variational formula of the $E_{F,g}-$energy functional (resp. $F$-Yang-Mills functional) with applications. In a more general frame, we use a unified method to study the stress-energy tensors that arise from calculating the rate of change of various functionals when the metric of the domain or base manifold is changed. These stress-energy tensors, linked to $F$-conservation laws yield monotonicity formulae. A "macroscopic" version of these monotonicity inequalities enables us to derive some Liouville type results and vanishing theorems for $p-$forms with values in vector bundles, and to investigate constant Dirichlet boundary value problems for 1-forms. In particular, we obtain Liouville theorems for $F-$harmonic maps (e.g. $p$-harmonic maps), and $F-$Yang-Mills fields (e.g. generalized Yang-Mills-Born-Infeld fields on manifolds). We also obtain generalized Chern type results for constant mean curvature type equations for $p-$forms on $\Bbb{R}^m$ and on manifolds $M$ with the global doubling property by a different approach. The case $p=0$ and $M=\mathbb{R}^m$ is due to Chern.Comment: 1. This is a revised version with several new sections and an appendix that will appear in Communications in Mathematical Physics. 2. A "microscopic" approach to some of these monotonicity formulae leads to celebrated blow-up techniques and regularity theory in geometric measure theory. 3. Our unique solution of the Dirichlet problems generalizes the work of Karcher and Wood on harmonic map

Polarimetric Properties of Flux-Ropes and Sheared Arcades in Coronal Prominence Cavities

The coronal magnetic field is the primary driver of solar dynamic events. Linear and circular polarization signals of certain infrared coronal emission lines contain information about the magnetic field, and to access this information, either a forward or an inversion method must be used. We study three coronal magnetic configurations that are applicable to polar-crown filament cavities by doing forward calculations to produce synthetic polarization data. We analyze these forward data to determine the distinguishing characteristics of each model. We conclude that it is possible to distinguish between cylindrical flux ropes, spheromak flux ropes, and sheared arcades using coronal polarization measurements. If one of these models is found to be consistent with observational measurements, it will mean positive identification of the magnetic morphology that surrounds certain quiescent filaments, which will lead to a greater understanding of how they form and why they erupt.Comment: 22 pages, 8 figures, Solar Physics topical issue: Coronal Magnetis

Noncommutative Electromagnetism As A Large N Gauge Theory

We map noncommutative (NC) U(1) gauge theory on R^d_C X R^{2n}_{NC} to U(N -> \infty) Yang-Mills theory on R^d_C, where R^d_C is a d-dimensional commutative spacetime while R^{2n}_{NC} is a 2n-dimensional NC space. The resulting U(N) Yang-Mills theory on R^d_C is equivalent to that obtained by the dimensional reduction of (d+2n)-dimensional U(N) Yang-Mills theory onto R^d_C. We show that the gauge-Higgs system (A_\mu,\Phi^a) in the U(N -> \infty) Yang-Mills theory on R^d_C leads to an emergent geometry in the (d+2n)-dimensional spacetime whose metric was determined by Ward a long time ago. In particular, the 10-dimensional gravity for d=4 and n=3 corresponds to the emergent geometry arising from the 4-dimensional N=4 vector multiplet in the AdS/CFT duality. We further elucidate the emergent gravity by showing that the gauge-Higgs system (A_\mu,\Phi^a) in half-BPS configurations describes self-dual Einstein gravity.Comment: 25 pages; More clarifications, to appear in Eur. Phys. J.