36,591 research outputs found
Three dimensions of biodiversity: New perspectives and methods
No full textAlthough the knowledge and understanding of biodiversity is rapidly increasing, very little of the total biodiversity is currently considered in applied conservation actions. In this sense, it is crucial to integrate independent fields of biodiversity models and perspectives with conservation issues, in particular, the views that address the links between biodiversity, ecosystem services and human well-being, species interaction, and focal charismatic species. This study overcomes the lack of framework necessary for this integration, and proposes three perspectives and approaches to assess biodiversity. The first perspective is biodiversity potential. It considers the correlation between renewable resources in local ecosystems and biodiversity potential, in terms of the possibility of maintaining a high degree of biodiversity. The energy cost is evaluated using both static and dynamic methods, based on the measure of the emergy of local renewable resources and of the total emergy throughput needed by components in ecosystem food webs, respectively, also highlighting the link between biodiversity and ecosystem services, species interactions via energy transfer respectively. The second perspective considers the contribution of biodiversity to human well-being, such as domestication. In this approach, we assess the contribution of biodiversity to humans by calculating the emergy of non-renewable resources required to domesticate animals or plants into agricultural products. The third perspective highlights the significance of local focal charismatic species to global biodiversity conservation. Taking rare species as an example, the emergy required to maintain rare species per unit area is used as a quantitative indicator of the role of local rare species in maintaining global biodiversity. By measuring biodiversity from these three perspectives (potential, contribution and significance) simultaneously, biodiversity conservation strategies are addressed for different regions. Taking China as a case study, it shows that the provinces featuring high potential, low contribution and low significance can moderately increase biodiversity development. The provinces with high significance to global biodiversity should strengthen conservation to halt biodiversity loss. The areas exhibiting overexploitation of biodiversity should in turn restrict biodiversity exploitation. The general approaches proposed in this study could be applied to different cases, situations and species, promoting the integration to biodiversity conservation actions at different scales. © 2021 The Author(s
Spin Representations of the q-Poincare Algebra
No full textIn der Quantenmechanik können freie Elementarteilchen durch irreduzible Darstellungen der Poincare-Algebra beschrieben werden. Im Rahmen der Darstellungtheorie der q-deformierten Poincaré-Algebra untersucht diese Arbeit den Spin von Teilchen auf einer nichtkommutativen Geometrie.
Zunaechst wird eine Uebersicht ueber die Konstruktion der q-Lorentz-Algebra gegeben. Ausgehend von q-Spinoren, wird die q-Lorentz-Gruppe und die zu ihr duale q-Lorentz-Algebra konstruiert. Dabei soll gezeigt werden, dass die q-Lorentz-Algebra weitgehend durch mathematische Konsistenzbedingungen festgelegt ist.
Anschliessend wird die Struktur der q-Lorentz-Algebra untersucht. Ihre Darstellungstheorie einschliesslich expliziter Formeln fuer die q-Clebsch-Gordan-Koeffzienten wird zusammengefasst. Nach einer allgemeinen Betrachtung von Tensor-Operatoren in Hopf-Algebren werden die Vektorgeneratoren der Quantenalgebra der Drehungen berechnet. Zwei weitere Formen der q-Lorentz-Algebra, die vektorielle oder RS-Form (Wess) und die Quantendoppel-Form (Woronowicz), werden vorgestellt. Ein Isomorphismus zwischen beiden Formen wird gefunden.
Die Darstellungstheorie der q-Lorentz-Algebra wird verwendet, um die Algebra des q-Minkowski-Raumes zu konstruieren. Vertauschungsregeln zwischen den Erzeugern der q-Minkowski-Algebra und den verschiedenen Formen der q-Lorentz-Algebra werden angegeben. Die Struktur der von Rotationen und Translationen erzeugten q-Euklidischen Algebra wird eingehend untersucht und dadurch ihr Zentrum bestimmt. Daraus können zunaechst die nullte Komponente und schliesslich alle Komponenten des q-Pauli-Lubanski-Vektor bestimmt werden. Mit dem q-Pauli-Lubanski-Vektor können die Algebren der Spin-Symmetrie, die kleinen Algebren, berechnet werden, sowohl fuer den massiven als auch den masselosen Fall.
Irreduzible Spin-Darstellungen der q-Poincaré-Algebra werden konstruiert. Zunaechst werden Darstellungen in einer physikalisch interpretierbaren Drehimpuls-Basis berechnet. Die Berechnungen werden dabei durch die Verwendung des q-Wigner-Eckart-Theorems stark vereinfacht. Anschliessend wird gezeigt, wie Darstellungen durch die Methode der Induktion gewonnen werden können. Ausgehend von einer darstellungstheoretischen Interpretation von Wellengleichungen werden schlielich freie q-relativistische Wellengleichungen bestimmt. Dazu werden zunächst allgemeine Betrachtungen zu q-Lorentz-Spinoren, konjugierten Spinoren und dem Verhaeltnis von q-Impulsen und q-Ableitungen auf den Spinor-Darstellungen angestellt. Als Beispiele werden die q-Dirac-Gleichung, die q-Weyl-Gleichungen und die q-Maxwell-Gleichungen eindeutig bestimmt
Ecosystem restoration programs challenges under climate and land use change
No full textEcological restoration programs have significantly contributed to the improvement of ecosystem services in the past two decades. However, due to climate change and rapid land use change, planning and management of ecosystem services restoration programs are still challenging, particularly how to identify and quantify the specific contribution of natural and human drivers of ecosystem services dynamics, how to assess and simulate the integrated impacts of climate-land use change interactions on changes in ecosystem services, insufficient simulation of mid- and long-term impacts of different ecological restoration programs, and lack of identification of ecological restoration thresholds. To overcome the challenges, we propose a new framework for restoring ecosystem services programs as potential solutions to the challenges. The framework includes attribution analysis of changes in ecosystem services, assessment and projections of ecosystem services dynamics under the integrated impacts of climate-land use change interactions, simulation of mid- and long-term effects of ecological programs and identification of ecological restoration threshold, which forms the logic chain of the framework, i.e. theory foundation-techniques support-application cases-policy implications. We finally recommend four related research directions and steps forward to overcome the challenges, including (1) Step 1: establish attribution analysis method of ecosystem services dynamics based on ecological thermodynamics and partial differential equation; (2) Step 2: Assess and simulate the impacts of coupled climate-land use change interactions on ecosystem services dynamics; (3) Step 3: Simulate the mid- and long-term impacts of different ecological restoration programs; and (4) Step 4: Identify ecological restoration thresholds. This study could provide insights for improving management of ecosystem services restoration programs in the context of rapid land use change and continuous climate change
Three dimensions of biodiversity: New perspectives and methods
No full textAlthough the knowledge and understanding of biodiversity is rapidly increasing, very little of the total biodiversity is currently considered in applied conservation actions. In this sense, it is crucial to integrate independent fields of biodiversity models and perspectives with conservation issues, in particular, the views that address the links between biodiversity, ecosystem services and human well-being, species interaction, and focal charismatic species. This study overcomes the lack of framework necessary for this integration, and proposes three perspectives and approaches to assess biodiversity. The first perspective is biodiversity potential. It considers the correlation between renewable resources in local ecosystems and biodiversity potential, in terms of the possibility of maintaining a high degree of biodiversity. The energy cost is evaluated using both static and dynamic methods, based on the measure of the emergy of local renewable resources and of the total emergy throughput needed by components in ecosystem food webs, respectively, also highlighting the link between biodiversity and ecosystem services, species interactions via energy transfer respectively. The second perspective considers the contribution of biodiversity to human well-being, such as domestication. In this approach, we assess the contribution of biodiversity to humans by calculating the emergy of non-renewable resources required to domesticate animals or plants into agricultural products. The third perspective highlights the significance of local focal charismatic species to global biodiversity conservation. Taking rare species as an example, the emergy required to maintain rare species per unit area is used as a quantitative indicator of the role of local rare species in maintaining global biodiversity. By measuring biodiversity from these three perspectives (potential, contribution and significance) simultaneously, biodiversity conservation strategies are addressed for different regions. Taking China as a case study, it shows that the provinces featuring high potential, low contribution and low significance can moderately increase biodiversity development. The provinces with high significance to global biodiversity should strengthen conservation to halt biodiversity loss. The areas exhibiting overexploitation of biodiversity should in turn restrict biodiversity exploitation. The general approaches proposed in this study could be applied to different cases, situations and species, promoting the integration to biodiversity conservation actions at different scales
MOTIF PENGGUNAAN TREN Q&A ANONYMOUS DI MEDIA SOSIAL INSTAGRAM PADA GENERASI Z
No full textABSTRAK
Nama : Rizka Rahmani Z Jurusan : Ilmu Komunikasi
Judul : Motif Penggunaan Tren Q&A Anonymous Di Media Sosial Instagram Pada Generasi Z
Penelitian ini bertujuan untuk mengetahui dan menganalisis motif penggunaan tren Q&A Anonymous di media sosial Instagram pada generasi Z. Metode penelitian yang digunakan adalah metode kualitatif. Teknik pengumpulan data dengan observasi, wawancara dan dokumentasi. Teknik analisis data dengan tahapan reduksi data, penyajian data, dan verifikasi. Hasil penelitian menunjukkan terdapat 3 motif informan generasi Z dalam penggunaan Q&A Anonymous di media sosial Instagram yaitu mengikuti tren pada saat itu, untuk merasakan keseruan dalam bertanya dan menjawab lewat penggunaan fitur tersebut, dan rasa penasaran ini mendorong informan untuk mencoba pengalaman baru menggunakan fitur ini. Terdapat 2 makna dari Generasi Z dalam memandang Q&A Anonymous di media sosial Instagram yakni Q&A Anonymous Instagram menjadi sarana yang ideal sebagai tempat bertanya yang cocok untuk mengungkapkan pertanyaan-pertanyaan yang sensitif tanpa diketahui identitas si penanya, dan yang kedua, Q&A Anonymous Instagram menjadikan Instagram tambah seru berkat aplikasi ini pengguna terhibur dengan pertanyaan-pertanyaan lucu, menarik, dan unik dari anonim. Terdapat bermacam-macam pengalaman dari Generasi Z dalam memandang Q&A Anonymous yakni generasi Z merasakan pengalaman yang menyenangkan setelah menggunakan Q&A Anonymous Instagram karena bisa bertukar informasi misalnya mengenai tempat yang menarik dikunjungi jika ke sebuah kota, informasi mengenai film, dan informasi mengenai makanan. Q&A Anonymous Instagram menjadi media atau wadah bagi Generasi Z untuk dapat intropeksi diri juga, misalnya jika saya ingin meminta pengikut untuk menyebutkan hal-hal yang mereka tidak sukai dari pengguna yang bertanya, lewat jawaban-jawaban mereka tersebut pengguna dapat mengambil pelajaran dan bisa berbenah ke depannya. Pengguna juga mengalami pengalaman yang tidak mengenakkan karena ada anonim yang memanfaatkan fitur tersebut untuk membully akun yang bertanya dengan pertanyaan-pertanyaan yang aneh.
Kata Kunci : Motif, Q&A Anonymous, Motif, Makna, Pengalama
q-Differential equations for q-classical polynomials and q-Jacobi-Stirling numbers
No full textWe introduce, characterise and provide a combinatorial interpretation for the so-called q-Jacobi–Stirling numbers.
This study is motivated by their key role in the (reciprocal) expansion of any power of a second order
q-differential operator having the q-classical polynomials as eigenfunctions in terms of other even order operators,
which we explicitly construct in this work. The results here obtained can be viewed as the q-version of
those given by Everitt et al. and by the first author, whilst the combinatorics of this new set of numbers is a
q-version of the Jacobi–Stirling numbers given by Gelineau and the second author
-analogues of two supercongruences of Z.-W. Sun
No full textsummary:We give several different -analogues of the following two congruences of \hbox {Z.-W. Sun}: where is an odd prime, is a positive integer, and is the Jacobi symbol. The proofs of them require the use of some curious -series identities, two of which are related to Franklin's involution on partitions into distinct parts. We also confirm a conjecture of the latter author and Zeng in 2012
On the mechanics of granular shear. The effect of normal stress and layer thickness on stick-slip properties
No full textSeismic stress drop is one of the most important earthquake source parameters, playing a key role in elastic energy release and in scaling relations for seismic moment and fault length. While stress drop does not scale systematically with earthquake size, it varies greatly within seismic catalogs and there is much broad interest in understanding how such variations relate to fault zone properties. Here, we address connections between stress drop and fault zone properties via laboratory experiments that investigate the role of normal stress and layer thickness during frictional sliding. We sheared granular layers at normal stresses from 4 to 22 MPa and document both elastic and inelastic processes that couple with layer dilation to determine the granular fragility and stress drop during stick-slip failure. Stick-slip stress drop scales directly with fault normal stress and inversely with layer thickness. Thicker layers exhibit, greater dilation during shear loading, however shear driven dilatant volume strain is independent of layer thickness. We posit that force chains form rapidly after a dynamic slip event and that bulk inelastic creep occurs via formation and destruction of force chains, interparticle slip, and rolling. Stick-slip recurrence time and stress drop vary with fault normal stress and stiffness, which increases with shear strain, consistent with a model in which stiffness increases as porosity decreases and fault zone density increases. We propose a micromechanical model that accounts for force chains and spectator regions where granular processes are dominated by inelastic slip. We document the role of elastic and inelastic processes during three stages of the stick-slip cycle and show how these change systematically as a function of normal stress and layer thickness. Our work shows that dilation during shear loading contributes to frictional strength via volume strain and that apparent friction scales inversely with the granular thinning ratio
Evolutionary programming with q-Gaussian mutation for dynamic optimization problems
No full textThis article is posted here with permission from IEEE - Copyright @ 2008 IEEEThe use of evolutionary programming algorithms with self-adaptation of the mutation distribution for dynamic optimization problems is investigated in this paper. In the proposed method, the q-Gaussian distribution is employed to generate new candidate solutions by mutation. A real parameter q, which defines the shape of the distribution, is encoded in the chromosome of individuals and is allowed to evolve. Algorithms with self-adapted mutation generated from isotropic and anisotropic distributions are presented. In the experimental study, the q-Gaussian mutation is compared to Gaussian and Cauchy mutation on three dynamic optimization problems.This work was supported by Brazil FAPESP under Grant 04/04289-6 and UK EPSRC under Grant No. EP/E060722/01
Investigation and development of an advanced virtual coordinate measuring machine
No full textThis thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel UniversityDimensional measurement plays a critical role in product development and quality control. With the continuously increasing demand for tighter tolerances and more complex workpiece shapes in the industry, dimensional metrology often becomes the bottleneck of taking the quality and performance of manufacturing to the next level. As one kind of the most useful and powerful measuring instruments, coordinate measuring machines (CMMs) are widely employed in manufacturing industries. Since the accuracy and efficiency of a CMM have a vital impact on the product quality, productivity and manufacturing cost, the evaluation and improvement of CMM performance have always been important research topics since the invention of CMM.
A novel Advanced Virtual Coordinate Measuring Machine (AVCMM) is proposed against such a background. The proposed AVCMM is a software package that provides an integrated virtual environment, in which user can plan inspection strategy for a given task, carry out virtual measurement, and evaluate the uncertainty associated with the measurement result, all without the need of using a physical machine. The obtained estimate of uncertainty can serve as a rapid feedback for user to optimize the inspection plan in the AVCMM before actual measurement, or as an evaluation of the result of a performed measurement. Without involving a physical CMM in the inspection planning or evaluation of uncertainty, the AVCMM can greatly reduce the time and cost needed for such processes. Furthermore, as the package offers vivid 3D visual representation of the virtual environment and supports operations similar to a physical CMM, it does not only allow the user to easily plan and optimise the inspection strategy, but also provide a cost-effective, risk-free solution for training CMM operators.
A modular, multitier architecture has been adopted to develop the AVCMM system, which incorporates a number of functional components covering CMM and workpiece modelling, error simulation, inspection simulation, feature calculation, uncertainty evaluation and 3D representation. A new engine for detecting collision/contact has been developed and utilized, which is suitable for the virtual environment of simulated CMM inspections. A novel approach has been established to calculate errors required for the error simulation, where the data are obtained from FEA simulations in addition to conventional experimental method. Monte Carlo method has been adopted for uncertainty evaluation and has been implemented with multiple options available to meet different requirements.
A prototype of the proposed AVCMM system has been developed in this research. Its validity, usability and performance have been verified and evaluated through a set of experiments. The principles for utilising the AVCMM in practical use have also been established and demonstrated.
The results have indicated that the proposed AVCMM system has great potentials to improve the functionalities and overall performance of CMMs.ORSAS and the School of Engineering and Design of Brunel University
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