105,211 research outputs found
Local momentum balance in electromagnetic gyrokinetic systems
Get PDFORCID 0000-0001-5444-1758The Eulerian variational formulation is presented to obtain governing equations of the electromagnetic turbulent gyrokinetic system. A local momentum balance in the system is derived from the invariance of the Lagrangian of the system under an arbitrary spatial coordinate transformation by extending the previous work [H. Sugama et al., Phys. Plasmas 28, 022312 (2021)]. Polarization and magnetization due to finite gyroradii and electromagnetic microturbulence are correctly described by the gyrokinetic Poisson equation and Ampère's law which are derived from the variational principle. Also shown is how the momentum balance is influenced by including collisions and external sources. Momentum transport due to collisions and turbulence is represented by a symmetric pressure tensor, which originates in a variational derivative of the Lagrangian with respect to the metric tensor. The relations of the axisymmetry and quasi-axisymmetry of the toroidal background magnetic field to a conservation form of the local momentum balance equation are clarified. In addition, an ensemble-averaged total momentum balance equation is shown to take the conservation form even in the background field with no symmetry when a constraint condition representing the macroscopic Ampère's law is imposed on the background field. Using the WKB representation, the ensemble-averaged pressure tensor due to the microturbulence is expressed in detail and it is verified to reproduce the toroidal momentum transport derived in previous works for axisymmetric systems. The local momentum balance equation and the pressure tensor obtained in this work present a useful reference for elaborate gyrokinetic simulation studies of momentum transport processes.journal articl
Tinjauan terhadap terjadinya tindak pidana perlindungan konsumen dari penyalahgunaan bahan berbahaya dalam produk pangan / oleh Yessy Sugama Halim
No full textabstrak (A) Nama : Yessy Sugama Halim (NIM : 205040133) (B) Judul Skripsi : Tinjauan Terhadap Terjadinya Tindak Pidana Perlindungan Konsumen dari Penyalahgunaan Bahan Berbahaya dalam Produk Pangan. (C) Halaman : x + 120 + lampiran, 2009 (D) Kata Kunci : Tindak Pidana Perlindungan Konsumen (E) Isi : Masalah Perlindungan Konsumen merupakan masalah klasik yang telah ada sejak dahulu. Masalah Konsumen yang berkaitan dengan Penyalahgunaan Bahan Berbahaya dalam Produk Pangan itu telah ada sejak tahun 1980-an. Masalah ini tidak pernah dapat terselesaikan dan selalu akan muncul bila menjadi bahan pemberitaan dalam berbagai media pemberitaan. Munculnya pemberitaan ini, karena adanya suatu hal yang salah pastinya, baik dilihat dari hukum/sistem hukum itu sendiri, penegakkan hukum mapun yang dikaitkan dengan masyarakat serta kebudayaannya yang menjadi satu kesatuan menjadi masalah perlindungan konsumen. Masalah Konsumen ini dapat dikatakan sebagai suatu Tindak Pidana Konsumen, jika pelaku sampai merugikan hak-hak masyarakat sebagai konsumen dan perbuatannya tersebut dianggap melanggar peraturan hukum (hukum normatif) yang ada, terutama melanggar Undang-Undang Perlindungan Konsumen (UU Nomor 8 Tahun 1999) dan UU Pangan. Pelanggaran yang biasa dilakukan oleh pihak pelaku usaha dengan memasukkan bahan berbahaya seperti Formalin, Boraks, Metanil Yellow, serta Rhodamin B ke dalam dagangannya, denganalasan agar lebih awet serta tahan lama. Pihak pelaku usaha tidak memperdulikan dampak yang diakibatkan perbuatannya tersebut, karena ia hanya peduli dengan keuntungan materi semata. Untuk menanggulangi masalah konsumen ini, diperlukan kerjasama dengan berbagai pihak dalam penegakkan hukumnya. Kerjasama penegakkan hukum ini harus dilakukan tidak hanya pemerintah saja melainkan pemerintah dengan masyarakat, organisasi yang terkait ;BPOM dan BPSK, serta dengan pihak kepolisian juga. Selain itu, pihak produsen sebagai pelaku usaha juga harus menyadari bahwa tindakannya tersebut merupakan suatu tindak pidana konsumen yang dapat dikenakan sanksi pidana pula. Penggunaan serta pengonsumsian bahan berbahaya dalam produk pangan ini secara terus menerus maka akan membawa dampak menurunnya kesehatan bahkan mengakibatkan kematian, sehingga penggunaan BTP ini haruslah segera dihentikan. (F) Acuan : 42 (1992-2007) (G) Pembimbing : Soetan Budhi Satria, SH., MH. (H) Penulis : Yessy Sugama Hali
Moment-equation methods for calculating neoclassical transport coefficients in general toroidal plasmas
Get PDFA detailed comparison is made between moment-equation methods presented by H. Sugama and S. Nishimura [Phys. Plasmas 9, 4637 (2002)] and by M. Taguchi [Phys. Fluids B 4, 3638 (1992)] for calculating neoclassical transport coefficients in general toroidal plasmas including nonsymmetric systems. It is shown that these methods can be derived from the drift kinetic equation with the same collision model used for correctly taking account of collisional momentum conservation. In both methods, the Laguerre polynomials of the energy variable are employed to expand the guiding-center distribution function and to obtain the moment equations, by which the radial neoclassical transport fluxes and the parallel flows are related to the thermodynamic forces. The methods are given here in the forms applicable for an arbitrary truncation number of the Laguerre-polynomial expansion so that their accuracies can be improved by increasing the truncation number. Differences between results from the two methods appear when the Laguerre-polynomial expansion is truncated up to a finite order because different weight functions are used in them to derive the moment equations. At each order of the truncation, the neoclassical transport coefficients obtained from the Sugama?Nishimura method show the Onsager symmetry and satisfy the ambipolar-diffusion condition intrinsically for symmetric systems. Also, numerical examples are given to show how the transport coefficients converge with the truncation number increased for the two methods.journal articl
Numerical implementation of the improved Sugama collision operator using a moment approach
No full textThe numerical implementation of the linearized gyrokinetic and drift-kinetic improved Sugama (IS) collision operators, recently introduced by Sugama et al. [Phys. Plasmas 26, 102108 (2019)], is reported. The IS collision operator extends the validity of the widely used original Sugama (OS) operator [Sugama et al., Phys. Plasmas 16, 112503 (2009)] to the Pfirsch-Schluter collisionality regime. Using a Hermite-Laguerre velocity-space decomposition of the perturbed gyrocenter distribution function that we refer to as the gyro-moment approach, the IS collision operator is written in a form of algebraic coefficients that depend on the mass and temperature ratios of the colliding species and perpendicular wavenumber. A comparison between the IS, OS, and Coulomb collision operators is performed, showing that the IS collision operator is able to approximate the Coulomb collision operator in the case of trapped electron mode in H-mode pedestal conditions better than the OS operator. In addition, the IS operator leads to a level of zonal flow residual which has an intermediate value between the Coulomb and the OS collision operators. The IS operator is also shown to predict a parallel electrical conductivity that approaches the one of the Coulomb operator within less than 1%, while the OS operator can underestimate the parallel electron current by at least 10%. Finally, closed analytical formulas of the lowest order gyro-moments of the IS, OS, and Coulomb operators are given, which are ready to use to describe the collisional effects in reduced gyro-moment fluid models. Published under an exclusive license by AIP Publishing.SP
A convergence study for the Laguerre expansion in the moment equation method for neoclassical transport in general toroidal plasmas
Get PDFThe dependence of neoclassical parallel flow calculations on the maximum order of Laguerre polynomial expansions is investigated in a magnetic configuration of the Large Helical Device [ S. Murakami, A. Wakasa, H. Maaßberg, et al., Nucl. Fusion 42, L19 (2002) ] using the monoenergetic coefficient database obtained by an international collaboration. On the basis of a previous generalization (the so-called Sugama–Nishimura method [ H. Sugama and S. Nishimura, Phys. Plasmas 15, 042502 (2008) ]) to an arbitrary order of the expansion, the 13 M, 21 M, and 29 M approximations are compared. In a previous comparison, only the ion distribution function in the banana collisionality regime of single-ion-species plasmas in tokamak configurations was investigated. In this paper, the dependence of the problems including electrons and impurities in the general collisionality regime in an actual nonsymmetric toroidal configuration is reported. In particular, qualities of approximations for the electron distribution function are investigated in detail
Conservation of energy and momentum in nonrelativistic plasmas
Get PDFConservation laws of energy and momentum for nonrelativistic plasmas are derived from applying Noether's theorem to the action integral for the Vlasov-Poisson-Amp?re system [Sugama, Phys. Plasmas 7, 466 (2000)]. The symmetric pressure tensor is obtained from modifying the asymmetric canonical pressure tensor with using the rotational symmetry of the action integral. Differences between the resultant conservation laws and those for the Vlasov-Maxwell system including the Maxwell displacement current are clarified. These results provide a useful basis for gyrokinetic conservation laws because gyrokinetic equations are derived as an approximation of the Vlasov-Poisson-Amp?re system.journal articl
Local momentum balance in electromagnetic gyrokinetic systems
Get PDFThe Eulerian variational formulation is presented to obtain governing
equations of the electromagnetic turbulent gyrokinetic system. A local momentum
balance in the system is derived from the invariance of the Lagrangian of the
system under an arbitrary spatial coordinate transformation by extending the
previous work [H. Sugama et al., Phys. Plasmas 28, 022312 (2021)]. Polarization
and magnetization due to finite gyroradii and electromagnetic microturbulence
are correctly described by the gyrokinetic Poisson equation and Amp\`{e}re's
law which are derived from the variational principle. Also shown is how the
momentum balance is influenced by including collisions and external sources.
Momentum transport due to collisions and turbulence is represented by a
symmetric pressure tensor which originates in a variational derivative of the
Lagrangian with respect to the metric tensor. The relations of the axisymmetry
and quasi-axisymmetry of the toroidal background magnetic field to a
conservation form of the local momentum balance equation are clarified. In
addition, an ensemble-averaged total momentum balance equation is shown to take
the conservation form even in the background field with no symmetry when a
constraint condition representing the macroscopic Amp\`{e}re's law is imposed
on the background field. Using the WKB representation, the ensemble-averaged
pressure tensor due to the microturbulence is expressed in detail and it is
verified to reproduce the toroidal momentum transport derived in previous works
for axisymmetric systems. The local momentum balance equation and the pressure
tensor obtained in this work present a useful reference for elaborate
gyrokinetic simulation studies of momentum transport processes.Comment: 25 pages, submitted to Phys. Plasma
Collisionless kinetic-fluid closure and its application to the three-mode ion temperature gradient driven system
Get PDFA novel closure model is presented to give a set of fluid equations which describe a collisionless kinetic system. In order to take account of the time reversal symmetry of the collisionless kinetic equation, the new closure model relates the parallel heat flux to the temperature and the parallel flow in terms of the real-valued coefficients in the unstable wave number space. Effects of the closure model on turbulence saturation and anomalous transport are investigated based on kinetic and fluid entropy balances. When the closure model is applied to the three-mode ion temperature gradient (ITG) driven system, the fluid system of equations reproduces the exact nonlinear kinetic solution found by Watanabe, Sugama, and Sato [Phys. Plasmas 7, 984 (2000)]. Oscillatory behaviors and initial amplitude dependence of other numerical kinetic solutions of the three-mode ITG problem can also be accurately described by the fluid system.journal articl
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L-H confinement mode dynamics in three-dimensional state space
Get PDFThe dynamical model for the L-H confinement mode transitions consisting of three ordinary differential equations (3-ODE model) for the essential state variables is proposed. The model is derived from the energy balance equations for the resistive pressure-gradient-driven turbulence and describes temporal evolutions of three characteristic variables (u.k.f) the potential energy contained in the pressure gradient, the turbulent kinetic energy and the shear flow energy. The energy input to the peripheral plasma region is included as an external control parameter in the model. The model equations have stationary solutions corresponding to the L and H modes. The authors obtain the L to H and H to L transition with the energy input parameter changed. The type of the L-H transition, whether a first-order or second-order transition, is shown to be determined by the shear flow damping coefficient. They also find the parameter region in which the H mode stationary solution becomes unstable and bifurcates to the limit cycle which shows periodic oscillations characteristic of the ELM confinement state
Linear Landau damping, Schrödinger equation, and fluctuation theorem
Get PDFORCID 0000-0001-5444-1758A linearized Vlasov–Poisson system of equations is transformed into a Schrödinger equation, which is used to demonstrate that the fluctuation theorem holds for the relative stochastic entropy, defined in terms of the probability density functional of the particle velocity distribution function in the Landau damping process. The difference between the energy perturbation, normalized by the equilibrium temperature, and the entropy perturbation constitutes a time-independent invariant of the system. This invariant takes the quadratic form of the perturbed velocity distribution function and corresponds to the squared amplitude of the state vector that satisfies the Schrödinger equation. Exact solutions, constructed from a discrete set of Hamiltonian eigenvectors, are employed to formulate and numerically validate the fluctuation theorem for the Landau damping process. The results offer new insight into the formulations of collisionless plasma processes within the framework of nonequilibrium statistical mechanics.journal articl
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