Critical experiments analysis by ABBN-90 constant system
Energy Technology Data Exchange (ETDEWEB)
Tsiboulia, A.; Nikolaev, M.N.; Golubev, V. [Institute of Physics and Power Engineering, Obninsk (Russian Federation)] [and others
1997-06-01
The ABBN-90 is a new version of the well-known Russian group-constant system ABBN. Included constants were calculated based on files of evaluated nuclear data from the BROND-2, ENDF/B-VI, and JENDL-3 libraries. The ABBN-90 is intended for the calculation of different types of nuclear reactors and radiation shielding. Calculations of criticality safety and reactivity accidents are also provided by using this constant set. Validation of the ABBN-90 set was made by using a computerized bank of evaluated critical experiments. This bank includes the results of experiments conducted in Russia and abroad of compact spherical assemblies with different reflectors, fast critical assemblies, and fuel/water-solution criticalities. This report presents the results of the calculational analysis of the whole collection of critical experiments. All calculations were produced with the ABBN-90 group-constant system. Revealed discrepancies between experimental and calculational results and their possible reasons are discussed. The codes and archives INDECS system is also described. This system includes three computerized banks: LEMEX, which consists of evaluated experiments and their calculational results; LSENS, which consists of sensitivity coefficients; and LUND, which consists of group-constant covariance matrices. The INDECS system permits us to estimate the accuracy of neutronics calculations. A discussion of the reliability of such estimations is finally presented. 16 figs.
ZEMO system for generating group constants
International Nuclear Information System (INIS)
The code system ZEMO for generating 26 group and 140-group constant sets for fast breeder reactors neutronics is considered. Group constant libraries, calculational techniques, formats of generated group constant sets and code control parameters are described. Results of one-dimensional model calculations for some critical assemblies and results of investigation of sodium void reactivity effect calculational error caused by 26-group approximation for two-dimensional model of BN-800 are presented. 14 refs.; 1 fig.; 3 tabs
21 CFR 1250.42 - Water systems; constant temperature bottles.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Water systems; constant temperature bottles. 1250...; constant temperature bottles. (a) The water system, whether of the pressure or gravity type, shall be... at all times as to prevent contamination of the water. (e) Constant temperature bottles and...
New multitarget constant modulus array for CDMA systems
Institute of Scientific and Technical Information of China (English)
Zhang Jidong; Zheng Baoyu
2006-01-01
A new multitarget constant modulus array is proposed for CDMA systems based on least squares constant modulus algorithm. The new algorithm is called pre-despreading decision directed least squares constant modulus algorithm (DDDLSCMA). In the new algorithm, the pre-despreading is first applied for multitarget arrays to remove some multiple access signals, then the despreaded signal is processed by the algorithm which united the constant modulus algorithm and decision directed method. Simulation results illustrate the good performance for the proposed algorithm.
ON SOLUTIONS TO SINGULAR FRACTIONAL DIFFERENTIAL SYSTEMS WITH CONSTANT COEFFICIENTS
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
In this paper, we consider solutions to singular fractional differential systems with constant coefficients involving Riemann-Liouville differential operator. At first, we study the solvability of the systems. Then we discuss the general solution to the system.
Equilibrium Constant as Solution to the Open Chemical Systems
Zilbergleyt, B.
2008-01-01
According to contemporary views, equilibrium constant is relevant only to true thermodynamic equilibria in isolated systems with one chemical reaction. The paper presents a novel formula that ties-up equilibrium constant and chemical system composition at any state, isolated or open as well. Extending the logarithmic logistic map of the Discrete Thermodynamics of Chemical Equilibria, this formula maps the system population at isolated equilibrium into the population at any open equilibrium at...
Assessment of fast radiographic systems by the constant exposure technique
International Nuclear Information System (INIS)
The constant exposure technique was applied to compare the radiographic image quality and relative speed of different fast radiographic systems. Conventional industrial X-ray films, exposed with lead intensifying screens, special fast film with fluorometallic screens as well as different brands of radiographic paper exposed both with fluorescent as well as fluorometallic screens were tested and compared. ISO wire IQI's and ASTM penetrameters were used together with 30-mm aluminium and 10-mm steel plates. For all the fast radiographic systems wire sensitivity better than 2 per cent was obtained. The constant exposure technique proved to be adequate for the assessment of fast radiographic systems. (author)
Constant-space P systems with active membranes
A. Leporati; Manzoni, L; Mauri, G; Porreca, A; Zandron, C
2014-01-01
We show that a constant amount of space is sufficient to simulate a polynomial-space bounded Turing machine by P systems with active membranes. We thus obtain a new characterisation of PSPACE, which raises interesting questions about the definition of space complexity for P systems. We then propose an alternative definition, where the size of the alphabet and the number of membrane labels of each P system are also taken into account. Finally we prove that, when less than a logarithmic number ...
Constant-Space P Systems with Active Membranes
Leporati, Alberto; Manzoni, Luca; Mauri, Giancarlo; Porreca, Antonio E.; Zandron, Claudio; Research Group on Natural Computing (Universidad de Sevilla) (Coordinador)
2014-01-01
We continue the investigation of the computational power of space- constrained P systems. We show that only a constant amount of space is needed in order to simulate a polynomial-space bounded Turing machine. Due to this result, we propose an alternative de nition of space complexity for P systems, where the amount of information contained in individual objects and membrane labels is also taken into ac- count. Finally, we prove that, when less than a logarithmic number of membr...
Spectral Gap and Logarithmic Sobolev Constant for Continuous Spin Systems
Institute of Scientific and Technical Information of China (English)
Mu Fa CHEN
2008-01-01
The aim of this paper is to study the spectral gap and the logarithmic Sobolev constant for continuous spin systems. A simple but general result for estimating the spectral gap of finite dimensional systems is given by Theorem 1.1, in terms of the spectral gap for one-dimensional marginals. The study of this topic provides us a chance, and it is indeed another aim of the paper, to justify the power of the results obtained previously. The exact order in dimension one (Proposition 1.4), and then the precise leading order and the explicit positive regions of the spectral gap and the logarithmic Sobolev constant for two typical infinite-dimensional models are presented (Theorems 6.2 and 6.3). Since we are interested in explicit estimates, the computations become quite involved. A long section (Section 4) is devoted to the study of the spectral gap in dimension one.
Contact position sensor using constant contact force control system
Sturdevant, Jay (Inventor)
1995-01-01
A force control system (50) and method are provided for controlling a position contact sensor (10) so as to produce a constant controlled contact force therewith. The system (50) includes a contact position sensor (10) which has a contact probe (12) for contacting the surface of a target to be measured and an output signal (V.sub.o) for providing a position indication thereof. An actuator (30) is provided for controllably driving the contact position sensor (10) in response to an actuation control signal (I). A controller (52) receives the position indication signal (V.sub.o) and generates in response thereto the actuation control signal (I) so as to provide a substantially constant selective force (F) exerted by the contact probe (12). The actuation drive signal (I) is generated further in response to substantially linear approximation curves based on predetermined force and position data attained from the sensor (10) and the actuator (30).
Bifurcation in a Discrete-Time Piecewise Constant Dynamical System
Directory of Open Access Journals (Sweden)
Chenmin Hou
2013-01-01
Full Text Available The study of recurrent neural networks with piecewise constant transition or control functions has attracted much attention recently because they can be used to simulate many physical phenomena. A recurrent and discontinuous two-state dynamical system involving a nonnegative bifurcation parameter is studied. By elementary but novel arguments, we are able to give a complete analysis on its asymptotic behavior when the parameter varies from 0 to . It is hoped that our analysis will provide motivation for further results on large-scale recurrent McCulloch-Pitts-type neural networks and piecewise continuous discrete-time dynamical systems.
Controllability and Observability Criteria for Linear Piecewise Constant Impulsive Systems
Directory of Open Access Journals (Sweden)
Hong Shi
2012-01-01
Full Text Available Impulsive differential systems are an important class of mathematical models for many practical systems in physics, chemistry, biology, engineering, and information science that exhibit impulsive dynamical behaviors due to abrupt changes at certain instants during the dynamical processes. This paper studies the controllability and observability of linear piecewise constant impulsive systems. Necessary and sufficient criteria for reachability and controllability are established, respectively. It is proved that the reachability is equivalent to the controllability under some mild conditions. Then, necessary and sufficient criteria for observability and determinability of such systems are established, respectively. It is also proved that the observability is equivalent to the determinability under some mild conditions. Our criteria are of the geometric type, and they can be transformed into algebraic type conveniently. Finally, a numerical example is given to illustrate the utility of our criteria.
Macroscopic multigroup constants for accelerator driven system core calculation
International Nuclear Information System (INIS)
The high-level wastes stored in facilities above ground or shallow repositories, in close connection with its nuclear power plant, can take almost 106 years before the radiotoxicity became of the order of the background. While the disposal issue is not urgent from a technical viewpoint, it is recognized that extended storage in the facilities is not acceptable since these ones cannot provide sufficient isolation in the long term and neither is it ethical to leave the waste problem to future generations. A technique to diminish this time is to transmute these long-lived elements into short-lived elements. The approach is to use an Accelerator Driven System (ADS), a sub-critical arrangement which uses a Spallation Neutron Source (SNS), after separation the minor actinides and the long-lived fission products (LLFP), to convert them to short-lived isotopes. As an advanced reactor fuel, still today, there is a few data around these type of core systems. In this paper we generate macroscopic multigroup constants for use in calculations of a typical ADS fuel, take into consideration, the ENDF/BVI data file. Four energy groups are chosen to collapse the data from ENDF/B-VI data file by PREPRO code. A typical MOX fuel cell is used to validate the methodology. The results are used to calculate one typical subcritical ADS core. (author)
Solar System motions and the cosmological constant: a new approach
Iorio, Lorenzo
2007-01-01
In this paper we use the corrections to the Newton-Einstein secular precessions of the perihelia of some planets (Mercury, Earth, Mars, Jupiter, Saturn) of the Solar System, phenomenologically estimated as solve-for parameters by the Russian astronomer E.V. Pitjeva in a global fit of almost one century of data with the EPM2004 ephemerides, in order to put on the test the expression for the perihelion precession induced by an uniform cosmological constant $\\Lambda$ in the Schwarzschild-de Sitter (or Kottler) space-time. We compare such an extra-rate to the estimated corrections to the planetary perihelion precessions by taking their ratio for different pairs of planets instead of using one perihelion at a time for each planet separately, as done so far in literature. The answer is neatly negative, even by further re-scaling by a factor 10 (and even 100 for Saturn) the errors in the estimated extra-precessions of the perihelia released by Pitjeva. However, caution is advised because it would be relevant to repe...
A Piecewise-Conserved Constant of Motion for a Dissipative System
Burko, Lior M.
1999-01-01
We discuss a piecewise-conserved constant of motion for a simple dissipative oscillatory mechanical system. The system is a harmonic oscillator with sliding (dry) friction. The piecewise-conserved constant of motion corresponds to the time average of the energy of the system during one half-period of the motion, and changes abruptly at the turning points of the motion. At late times the piecewise-conserved constant of motion degenerates to a constant of motion in the usual sense.
One-dimensional relativistic dissipative system with constant force and its quantization
López, G; Hernández, H; L\\'opez, Gustavo; L\\'opez, Xaman-Ek; Hern\\'andez, Hector
2005-01-01
For a relativistic particle under a constant force and a linear velocity dissipation force, a constant of motion is found. Problems are shown for getting the Hamiltoninan of this system. Thus, the quantization of this system is carried out through the constant of motion and using the quantization of the velocity variable. The dissipative relativistic quantum bouncer is outlined within this quantization approach.
One-Dimensional Relativistic Dissipative System with Constant Force and its Quantization
López, G.; López, X. E.; Hernández, H.
2006-04-01
For a relativistic particle under a constant force and a linear velocity dissipation force, a constant of motion is found. Problems are shown for getting the Hamiltonian of this system. Thus, the quantization of this system is carried out through the constant of motion and using the quantization on the velocity variable. The dissipative relativistic quantum bouncer is outlined within this quantization approach.
Constant of Motion for One-Diemnsional Non Autonomous Linear Systems and Harmonic Oscillator
Lopez, Gustavo
1999-01-01
For a one-dimensional motion, a constant of motion for non autonomous an linear system (position and velocity) is given from the constant of motion associated to its autonomous system. This approach is used in the study of the harmonic oscillator with an additional time depending force.
Institute of Scientific and Technical Information of China (English)
Xu Yumei
2005-01-01
In this paper we consider the Cauchy problem for quasilinear hyperbolic systems with characteristics with constant multiplicity. Without restriction on characteristics with constant multiplicity (＞ 1), a blow-up result is obtained for the C1 solution to the Cauchy problem under the assumptions where there is a simple genuinely nonlinear characteristic and the initial data possess certain weaker decaying properties.
CAUCHY PROBLEM FOR QUASILINEAR HYPERBOLIC SYSTEMS WITH CHARACTERISTICS WITH CONSTANT MULTIPLICITY
Institute of Scientific and Technical Information of China (English)
Wang Libin
2004-01-01
For quasilinear hyperbolic systems with characteristics of constant multiplicity, suppose that characteristics of constant multiplicity(＞1) are linearly degenerate, by means of generalized normalized coordinates we get the global existence and the blow-up phenomenon of the C1 solution to the Cauchy problem under an additional hypothesis.
Institute of Scientific and Technical Information of China (English)
王利彬
2003-01-01
In this paper we consider the Cauchy problem for quasilinear hyperbolic systems with characteristics with constant multiplicity. Without restriction on characteristics with constant multiplicity(＞ 1), under the assumptions that there is a genuinely nonlinear simple characteristic and the initial data possess certain decaying properties, the blow-up result is obtained for the C,1 solution to the Cauchy problem.
Comment on "Global Positioning System Test of the Local Position Invariance of Planck's Constant"
Berengut, J C
2012-01-01
In their Letter, Kentosh and Mohageg [Phys. Rev. Lett. 108, 110801 (2012)] seek to use data from clocks aboard global positioning system (GPS) satellites to place limits on local position invariance (LPI) violations of Planck's constant, h. It is the purpose of this comment to show that discussing limits on variation of dimensional constants (such as h) is not meaningful; that even within a correct framework it is not possible to extract limits on variation of fundamental constants from a single type of clock aboard GPS satellites; and to correct an important misconception in the authors' interpretation of previous Earth-based LPI experiments.
Decay constants of a subcritical system by two-group diffusion theory
International Nuclear Information System (INIS)
The effects of a neutronic pulse applied to a subcritical multiplicative medium are analyzed on the basis of the diffusion theory for one and two groups. The decay constants of the system were determined from the experimental data, for various values geometric buckling. A natural uranium light-water configuration was pulsed employing a Texas Nuclear 9905 neutron generator. The least square method was employed in the data reduction procedures to determine the decay constants. The separation of the decay constants associated with thermal and epithermal fluxes are verified through two groups formulation. (Author)
ℋ∞ constant gain state feedback stabilization of stochastic hybrid systems with Wiener process
Directory of Open Access Journals (Sweden)
E. K. Boukas
2004-01-01
Full Text Available This paper considers the stabilization problem of the class of continuous-time linear stochastic hybrid systems with Wiener process. The ℋ∞ state feedback stabilization problem is treated. A state feedback controller with constant gain that does not require access to the system mode is designed. LMI-based conditions are developed to design the state feedback controller with constant gain that stochastically stabilizes the studied class of systems and, at the same time, achieve the disturbance rejection of a desired level. The minimum disturbance rejection is also determined. Numerical examples are given to show the usefulness of the proposed results.
Perturbation approach and the constant of motion for on-dimensional dynamical systems
International Nuclear Information System (INIS)
A perturbation technic is used to find the constant of motion of a one-dimensional autonomous system. The convergence of the method is discussed through some examples. In addition, the approach is extended to one-dimensional non-autonomous systems where some examples are given
The Control System Simulation of Variable-Speed Constant-Frequency Wind Turbine
Institute of Scientific and Technical Information of China (English)
窦金延; 曹娜
2010-01-01
<正>In general,Variable-Speed Constant Frequency (VSCF)Wind generation system is controlled by stator voltage orientation method which based on the mathematic model of VSCF Wind generation system and discussed the control strategy.Present the whole dynamic control model of variable-speed wind generator system in MATLAB/ Simulink,and the simulation results confirm the validity and effectiveness of the proposed control strategy.
Bracken, Paul
2007-05-01
The generalized Weierstrass (GW) system is introduced and its correspondence with the associated two-dimensional nonlinear sigma model is reviewed. The method of symmetry reduction is systematically applied to derive several classes of invariant solutions for the GW system. The solutions can be used to induce constant mean curvature surfaces in Euclidean three space. Some properties of the system for the case of nonconstant mean curvature are introduced as well.
International Nuclear Information System (INIS)
A one-vessel crystal growth system has been built to grow KD P crystals of up to 10 cm in length. The process is based on transfer of saturated solution under constant temperature-constant supersaturation. Ca ry 17 D X spectrophotometer transmission spectra from (100) planes of the grown crystals show 89% transmission in the visible region. The system provides a reduction in capping time and growth rate of 25 mm/day for the first day and 1.5 mm/day for the 7th day
Optimal Control of Production-Inventory Systems with Constant and Compound Poisson Demand
Germs, Remco; Foreest, Nicky D. van
2014-01-01
In this paper, we study a production-inventory systems with finite production capacity and fixed setup costs. The demand process is modeled as a mixture of a compound Poisson process and a constant demand rate. For the backlog model we establish conditions on the holding and backlogging costs such t
High dielectric constant materials and their application to IC gate stack systems
Institute of Scientific and Technical Information of China (English)
TU; Hailing
2005-01-01
High dielectric constant (high-k) materials are vital tothe nanoelectronic devices.The paper reviews research development of high-k materials, describes a variety of manufacture technologies and discusses the application of the gate stack systems to non-classical device structures.
Queueing systems with constant service time and evaluation of M/D/1,k
DEFF Research Database (Denmark)
Iversen, Villy Bæk
1997-01-01
Systems with constant service times have the particular property that the customers leave the servers in the same order in which they areaccepted for service. Probabilitites of integral waiting times can be expressed by the state probabilities, and non-integral waiting timescan be expressed...
CONVERGENCE OF NEWTON'S METHOD FOR SYSTEMS OF EQUATIONS WITH CONSTANT RANK DERIVATIVES
Institute of Scientific and Technical Information of China (English)
Xiubin Xu; Chong Li
2007-01-01
The convergence properties of Newton's method for systems of equations with constant rank derivatives are studied under the hypothesis that the derivatives satisfy some weak Lipschitz conditions. The unified convergence results, which include Kantorovich type theorems and Smale's point estimate theorems as special cases, are obtained.
High-Performance Constant Power Generation in Grid-Connected PV Systems
DEFF Research Database (Denmark)
Sangwongwanich, Ariya; Yang, Yongheng; Blaabjerg, Frede
2016-01-01
An advanced power control strategy by limiting the maximum feed-in power of PV systems has been proposed, which can ensure a fast and smooth transition between maximum power point tracking and Constant Power Generation (CPG). Regardless of the solar irradiance levels, high-performance and stable...
Criteria for the Degree of Stability of the Linear Constant Systems
Institute of Scientific and Technical Information of China (English)
王广彬; 潘宝珍; 侯文渊
2004-01-01
There are various applications of the stability theory of the first-order dynamical systems. And the stability of the non-linear control systems can be determined by its linear part. In practice, it is not enough to know the stability of the dynamical systems. Sometimes we must know the degree of stability of these systems. In this paper, we present some criteria for the degree of stability of the linear constant systems, by using the entries of the coefficient matrix A only.
Thermal energy storage system using phase change materials: Constant heat source
Directory of Open Access Journals (Sweden)
Reddy Meenakshi R.
2012-01-01
Full Text Available The usage of phase change materials (PCM to store the heat in the form of latent heat is increased, because large quantity of thermal energy is stored in smaller volumes. In the present experimental investigation paraffin and stearic acid are employed as PCMs in thermal energy storage (TES system to store the heat as sensible and latent heat also. A constant heat source is used to supply heat transfer fluid (HTF at constant temperature to the TES system. In the TES system PCMs are stored in the form of spherical capsules of 38 mm diameter made of high density poly ethylene (HDPE. The results of the investigation are related to the charging time and recovery of stored energy from the TES system.
A new constant-pressure molecular dynamics method for finite system
Sun, D. Y.; Gong, X. G.
2001-01-01
In this letter, by writing the volume as a function of coordinates of atoms, we present a new constant-pressure molecular dynamics method with parameters free. This method is specially appropriate for the finite system in which the periodic boundary condition does not exist. Simulations on the carbon nanotube and the Ni nanoparticle clearly demonstrate the validity of the method. By using this method, one can easily obtain the equation of states for the finite system under the external pressure.
Rogers, Keith Eric
1994-01-01
The basic concepts of command preshaping were taken and adapted to the framework of systems with constant amplitude (on-off) actuators. In this context, pulse sequences were developed which help to attenuate vibration in flexible systems with high robustness to errors in frequency identification. Sequences containing impulses of different magnitudes were approximated by sequences containing pulses of different durations. The effects of variation in pulse width on this approximation were examined. Sequences capable of minimizing loads induced in flexible systems during execution of commands were also investigated. The usefulness of these techniques in real-world situations was verified by application to a high fidelity simulation of the space shuttle. Results showed that constant amplitude preshaping techniques offer a substantial improvement in vibration reduction over both the standard and upgraded shuttle control methods and may be mission enabling for use of the shuttle with extremely massive payloads.
DEFF Research Database (Denmark)
Ghotbi, Abdoul R; Barari, Amin
2009-01-01
Due to wide range of interest in use of bio-economic models to gain insight in to the scientific management of renewable resources like fisheries and forestry, variational iteration method (VIM) is employed to approximate the solution of the ratio-dependent predator-prey system with constant effort...... prey harvesting. The results are compared with the results obtained by Adomian decomposition method and reveal that VIM is very effective and convenient for solving nonlinear differential equations....
A Novel Constant-Pressure Pumped Hydro Combined with Compressed Air Energy Storage System
Directory of Open Access Journals (Sweden)
Erren Yao
2014-12-01
Full Text Available As intermittent renewable energy is receiving increasing attention, the combination of intermittent renewable energy with large-scale energy storage technology is considered as an important technological approach for the wider application of wind power and solar energy. Pumped hydro combined with compressed air energy storage system (PHCA is one of the energy storage systems that not only integrates the advantages but also overcomes the disadvantages of compressed air energy storage (CAES systems and pumped hydro energy storage systems to solve the problem of energy storage in China’s arid regions. Aiming at the variable working conditions of PHCA system technology, this study proposes a new constant-pressure PHCA. The most significant characteristics of this system were that the water pump and hydroturbine work under stable conditions and this improves the working efficiency of the equipment without incurring an energy loss. In addition, the constant-pressure PHCA system was subjected to energy and exergy analysis, in expectation of exploring an attractive solution for the large-scale storage of existing intermittent renewable energy.
The measurement system of birefringence and Verdet constant of optical fiber
Huang, Yi; Chen, Li; Guo, Qiang; Pang, Fufei; Wen, Jianxiang; Shang, Yana; Wang, Tingyun
2013-12-01
The Faraday magneto-optical effect of optical fiber has many applications in monitoring magnetic field and electric current. When a linearly polarized light propagates in the direction of a magnetic field, the plane of polarization will rotate linearly proportional to the strength of the applied magnetic field, which following the relationship of θF =VBl. θF is the Faraday rotation angle, which is proportional to the magnetic flux density B and the Verdet constant V . However, when the optical fiber contains the effect of linear birefringence, the detection of Faraday rotation angle will depend on the line birefringence. In order to determine the Verdet constant of an optical fiber under a linear birefringence, the fiber birefringence needs to be accurately measured. In this work, a model is applied to analyze the polarization properties of an optical fiber by using the Jones matrix method. A measurement system based on the lock-in amplifier technology is designed to test the Verdet constant and the birefringence of optical fiber. The magnetic field is produced by a solenoid with a DC current. A tunable laser is intensity modulated with a motorized rotating chopper. The actuator supplies a signal as the phase-locked synchronization reference to the signal of the lock-in amplifier. The measurement accuracy is analyzed and the sensitivity of the system is optimized. In this measurement system, the Verdet constant of the SMF-28 fiber was measured to be 0.56±0.02 rad/T·m at 1550nm. This setup is well suitable for measuring the high signal-to-noise ratio (SNR) sensitivity for lock-in amplifier at a low magnetic field strength.
BLIND EQUALIZATION OF MIMO SYSTEMS BASED ON ORTHOGONAL CONSTANT MODULUS ALGORITHM
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
This paper investigates adaptive blind source separation and equalization for Multiple Input Mul-tiple Output (MIMO) systems. To effectively recover input signals, remove Inter-Symbol Interference (ISI)and suppress Inter-User Interference (IUI), the array input is first transformed into the signal subspace, thenwith the derived orthogonality between weight vectors of different input signals, a new orthogonal ConstantModulus Algorithm (CMA) is proposed. Computer simulation results illustrate the promising performance ofthe proposed method. Without channel identification, the proposed method can recover all the system inputssimultaneously and can be adaptive to channel changes without prior knowledge about signals.
The Vlasov-Poisson System for Stellar Dynamics in Spaces of Constant Curvature
Diacu, Florin; Ibrahim, Slim; Lind, Crystal; Shen, Shengyi
2016-09-01
We obtain a natural extension of the Vlasov-Poisson system for stellar dynamics to spaces of constant Gaussian curvature {κ ≠ 0}: the unit sphere {S^2}, for {κ > 0}, and the unit hyperbolic sphere {H^2}, for {κ singular than the classical analogue of the Vlasov-Poisson system. In the analysis of this reduced model, we study the well-posedness of the problem and derive Penrose-type conditions for linear stability around homogeneous solutions in the sense of Landau damping.
Non-constant positive steady-states of a diffusive predator-prey system in homogeneous environment
Ko, Wonlyul; Ryu, Kimun
2007-03-01
In this paper, we investigate the existence and non-existence of non-constant positive steady-states of a diffusive predator-prey interaction system under homogeneous Neumann boundary condition. In homogeneous environment, we show that the predator-prey model with Leslie-Gower functional response has no non-constant positive solution, but the system with a general functional response may have at least one non-constant positive steady-state under some conditions.
Rare events in many-body systems: reactive paths and reaction constants for structural transitions
International Nuclear Information System (INIS)
This PhD thesis deals with the study of fundamental physics phenomena, with applications to nuclear materials of interest. We have developed methods for the study of rare events related to thermally activated structural transitions in many body systems. The first method involves the numerical simulation of the probability current associated with reactive paths. After deriving the evolution equations for the probability current, a Diffusion Monte Carlo algorithm is implemented in order to sample this current. This technique, called Transition Current Sampling was applied to the study of structural transitions in a cluster of 38 atoms with Lennard-Jones potential (LJ-38). A second algorithm, called Transition Path Sampling with local Lyapunov bias (LyTPS), was then developed. LyTPS calculates reaction rates at finite temperature by following the transition state theory. A statistical bias based on the maximum local Lyapunov exponents is introduced to accelerate the sampling of reactive trajectories. To extract the value of the equilibrium reaction constants obtained from LyTPS, we use the Multistate Bennett Acceptance Ratio. We again validate this method on the LJ-38 cluster. LyTPS is then used to calculate migration constants for vacancies and divacancies in the α-Iron, and the associated migration entropy. These constants are used as input parameter for codes modeling the kinetic evolution after irradiation (First Passage Kinetic Monte Carlo) to reproduce numerically resistivity recovery experiments in α-Iron. (author)
Constant Power Generation of Photovoltaic Systems Considering the Distributed Grid Capacity
DEFF Research Database (Denmark)
Yang, Yongheng; Blaabjerg, Frede; Wang, Huai
2014-01-01
With an imperative demand of clean and reliable electricity generation in some countries, the increasing adoption of new photovoltaic (PV) systems pushes the Distribution System Operators (DSOs) to expand the transmission/distributed lines. However, the potential cost brought by such extensions...... and increased maintenances introduce new obstacles. In view of this concern, the DSOs starts to reduce PV installations in order to avoid an extension of the power infrastructure. Besides, another alternative solution is to limit the maximum feed-in power of the existing PV systems to a certain level. It can...... contribute to a weakened requirement of grid expansion and at the same time an increased penetration level. Therefore, to meet the need of this emerging ancillary service provided by future PV systems, a Constant Power Generation (CPG) control concept of PV inverters is proposed in this paper. Accordingly...
Choi, Yang-Ho
2016-09-01
An observation system consists of the world lines of rest observers in the system. Recently a coordinate transformation between an isotropic and a rotating observation system has been presented which was derived through a relativistic circular approach based on the Lorentz transformation. It was formulated such that the relative speeds between the two systems are the same, but the two-way speed of light is not constant in the rotating observation system. The constancy of the two-way speed of light in inertial frames has been known to be experimentally verified. This paper presents the transformation that holds the constancy in the rotating system as well. Though the rotating system is in motion with acceleration, it can be regarded as locally inertial. Thus, in the limit, a transformation into a rotating system should be reduced to a transformation into an inertial systems. The transformation presented is consistent with the one between inertial systems so that the latter can be derived from the former in the limit. Moreover it allows us to theoretically analyze the generalized Sagnac effect, which involves rectilinear motion as well as circular motion. The theoretical analysis corresponds to the experimental results.
Optimal Control of Production-Inventory Systems with Constant and Compound Poisson Demand
Germs, Remco; Foreest, Nicky D. van
2014-01-01
In this paper, we study a production-inventory systems with finite production capacity and fixed setup costs. The demand process is modeled as a mixture of a compound Poisson process and a constant demand rate. For the backlog model we establish conditions on the holding and backlogging costs such that the average-cost optimal policy is of (s, S)-type. The method of proof is based on the reduction of the production-inventory problem to an appropriate optimal stopping problem and the analysis ...
Blümler, Peter
2015-01-01
A design for a permanent magnet system is proposed that generates spatially homogeneous, constant magnetic field gradients, thus creating conditions suitable for MRI without gradient coils and amplifiers. This is achieved by superimposing a weak Halbach quadrupole on a strong Halbach dipole. Rotation of either the quadrupole or the entire magnet assembly can be used to generate 2D images via filtered back-projection. Additionally, the mutual rotation of two quadrupoles can be used to scale the resulting gradient. If both gradients have identical strength the gradient can even be made to vanish. The concept is demonstrated by analytical considerations and FEM-simulations.
Ashtekar, Abhay; Bonga, Béatrice; Kesavan, Aruna
2016-02-01
There is a deep tension between the well-developed theory of gravitational waves from isolated systems and the presence of a positive cosmological constant Λ, however tiny. In particular a generalization of Einstein's 1918 quadrupole formula that would allow a positive Λ is not yet available. We first explain the principal difficulties and then show that it is possible to overcome them in the weak field limit. These results also provide concrete hints for constructing the Λ>0 generalization of the Bondi-Sachs framework for full, nonlinear general relativity. PMID:26894695
Salinas-Rodriguez, Sergio G.
2015-02-18
Reliable methods for measuring and predicting the fouling potential of reverse osmosis (RO) feed water are important in preventing and diagnosing fouling at the design stage, and for monitoring pre-treatment performance during plant operation. The Modified Fouling Index Ultrafiltration (MFI-UF) constant flux is a significant development with respect to assessing the fouling potential of RO feed water. This research investigates (1) the variables influencing the MFI-UF test at constant flux filtration (membrane pore size, membrane material, flux rate); and (2) the application of MFI-UF into pre-treatment assessment and RO fouling estimation. The dependency of MFI on flux, means that to assess accurately particulate fouling in RO systems, the MFI should be measured at a flux similar to a RO system (close to 20 L/m2/h) or extrapolated from higher fluxes. The two studied membrane materials showed reproducible results; 10% for PES membranes and 6.3% for RC membranes. Deposition factors (amount of particles that remain on the surface of membrane) were measured in a full-scale plant ranging between 0.2 and 0.5. The concept of “safe MFI” is presented as a guideline for assessing pre-treatment for RO systems.
Wang, Shilong; Yin, Changchun; Lin, Jun; Yang, Yu; Hu, Xueyan
2016-03-01
Cooperative work of multiple magnetic transmitting sources is a new trend in the development of transient electromagnetic system. The key is the bipolar current waves shutdown, concurrently in the inductive load. In the past, it was difficult to use the constant clamping voltage technique to realize the synchronized shutdown of currents with different peak values. Based on clamping voltage technique, we introduce a new controlling method with constant shutdown time. We use the rising time to control shutdown time and use low voltage power source to control peak current. From the viewpoint of the circuit energy loss, by taking the high-voltage capacitor bypass resistance and the capacitor of the passive snubber circuit into account, we establish the relationship between the rising time and the shutdown time. Since the switch is not ideal, we propose a new method to test the shutdown time by the low voltage, the high voltage and the peak current. Experimental results show that adjustment of the current rising time can precisely control the value of the clamp voltage. When the rising time is fixed, the shutdown time is unchanged. The error for shutdown time deduced from the energy consumption is less than 6%. The new controlling method on current shutdown proposed in this paper can be used in the cooperative work of borehole and ground transmitting system.
Cosmological variation of the MOND constant: secular effects on galactic systems
Milgrom, Mordehai
2014-01-01
The proximity of the MOND acceleration constant with cosmological accelerations -- for example, a0~ cH0/2pi -- points to its possibly decreasing with cosmic time. I begin to consider the secular changes induced in galactic systems by such presumed variations, assumed adiabatic. It is important to understand these effects, in isolation from other evolutionary influences, in order to identify or constrain a0 variations by detection of induced effects, or lack thereof. I find that as long as the system is fully in the deep-MOND regime -- as applies to many galactic systems -- the adiabatic response of the system obeys simple scaling laws. For example, in a system that would be stationary for fixed a0, the system expands homologously as a0^{-1/4}, while internal velocities decrease uniformly as a0^{1/4}. If a0 is proportional to cH at all relevant times, this change amounts to a factor of ~ 2.5 since redshift 10. For a system stationary in a rotating frame, the angular frequency decreases as a0^{1/2}. The acceler...
Quantum logic gates from time-dependent global magnetic field in a system with constant exchange
Energy Technology Data Exchange (ETDEWEB)
Nenashev, A. V., E-mail: nenashev@isp.nsc.ru; Dvurechenskii, A. V. [Rzhanov Institute of Semiconductor Physics SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Zinovieva, A. F. [Rzhanov Institute of Semiconductor Physics SB RAS, 630090 Novosibirsk (Russian Federation); Gornov, A. Yu.; Zarodnyuk, T. S. [Institute for System Dynamics and Control Theory SB RAS, 664033 Irkutsk (Russian Federation)
2015-03-21
We propose a method that implements a universal set of one- and two-quantum-bit gates for quantum computation in a system of coupled electron pairs with constant non-diagonal exchange interaction. In our proposal, suppression of the exchange interaction is performed by the continual repetition of single-spin rotations. A small g-factor difference between the electrons allows for addressing qubits and avoiding strong magnetic field pulses. Numerical experiments were performed to show that, to implement the one- and two-qubit operations, it is sufficient to change the strength of the magnetic field by a few Gauss. This introduces one and then the other electron in a resonance. To determine the evolution of the two-qubit system, we use the algorithms of optimal control theory.
Hall normalization constants for the Bures volumes of the n-state quantum systems
Slater, Paul B.
1999-11-01
We report the results of certain integrations of quantum-theoretic interest, relying, in this regard, upon recently developed parametrizations of Boya et al (1998 Preprint quant-ph/9810084) of the n × n density matrices, in terms of squared components of the unit (n - 1)-sphere and the n × n unitary matrices. Firstly, we express the normalized volume elements of the Bures (minimal monotone) metric for n = 2 and 3, thereby obtaining `Bures prior probability distributions' over the two- and three-state systems. Then, as a first step in extending these results to n>3, we determine that the `Hall normalization constant' (Cn) for the marginal Bures prior probablity distribution over the (n - 1)-dimensional simplex of the n eigenvalues of the n × n density matrices is, for n = 4, equal to 71 680/icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/>2. Since we also find that C3 = 35/icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/>, it follows that C4 is simply equal to 211C3/icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/>. (C2 itself is known to equal 2/icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/>.) The constant C5 is also found. It too is associated with a remarkably simple decomposition, involving the product of the eight consecutive prime numbers from 3 to 23. We also preliminarily investigate several cases n>5, with the use of quasi-Monte Carlo integration. We hope that the various analyses reported will prove useful in deriving a general formula (which evidence suggests will involve the Bernoulli numbers) for the Hall normalization constant for arbitrary n. This would have diverse applications, including quantum inference and universal quantum coding.
Hall normalization constants for the Bures volumes of the n-state quantum systems
International Nuclear Information System (INIS)
We report the results of certain integrations of quantum-theoretic interest, relying, in this regard, upon recently developed parametrizations of Boya et al (1998 Preprint quant-ph/9810084) of the nxn density matrices, in terms of squared components of the unit (n-1)-sphere and the nxn unitary matrices. Firstly, we express the normalized volume elements of the Bures (minimal monotone) metric for n=2 and 3, thereby obtaining 'Bures prior probability distributions' over the two- and three-state systems. Then, as a first step in extending these results to n>3, we determine that the 'Hall normalization constant' (Cn) for the marginal Bures prior probability distribution over the (n-1)-dimensional simplex of the n eigenvalues of the nxn density matrices is, for n=4, equal to 71 680/π2. Since we also find that C3=35/π, it follows that C4 is simply equal to 211C3/π. (C2 itself is known to equal 2/π.) The constant C5 is also found. It too is associated with a remarkably simple decomposition, involving the product of the eight consecutive prime numbers from 3 to 23. We also preliminarily investigate several cases n>5, with the use of quasi-Monte Carlo integration. We hope that the various analyses reported will prove useful in deriving a general formula (which evidence suggests will involve the Bernoulli numbers) for the Hall normalization constant for arbitrary n. This would have diverse applications, including quantum inference and universal quantum coding. (author)
Institute of Scientific and Technical Information of China (English)
Yong-gang PENG; Jun WANG; Wei WEI
2014-01-01
In view of the high energy consumption and low response speed of the traditional hydraulic system for an injection molding machine, a servo motor driven constant pump hydraulic system is designed for a precision injection molding process, which uses a servo motor, a constant pump, and a pressure sensor, instead of a common motor, a constant pump, a pressure pro-portion valve, and a flow proportion valve. A model predictive control strategy based on neurodynamic optimization is proposed to control this new hydraulic system in the injection molding process. Simulation results showed that this control method has good control precision and quick response.
Iacob, N.; Schinteie, G.; Bartha, C.; Palade, P.; Vekas, L.; Kuncser, V.
2016-07-01
A quantitative treatment of the effects of magnetic mutual interactions on the specific absorption rate of a superparamagnetic system of iron oxide nanoparticles coated with oleic acid is reported. The nanoparticle concentration of the considered ferrofluid samples varied from a very low (0.005) to a medium (0.16) value of the volume fraction, whereas the amplitude of the exciting AC magnetic field ranged from 14–35 kA m‑1. It was proved that a direct effect of the interparticle interactions resides in the regime of the modified superparamagnetism, dealing, besides the usual increase in the anisotropy energy barrier per nanoparticle, with the decrease in the specific time constant {τ0} of the relaxation law, usually considered as a material constant. Consequently, the increase in the specific absorption rate versus the volume fraction is significantly diminished in the presence of the interparticle interactions compared to the case of non-interacting superparamagnetic nanoparticles, with direct influence on the magnetic hyperthermia efficiency.
AB INITIO CALCULATIONS OF ELASTIC CONSTANTS OF BCC V-NB SYSTEM AT HIGH PRESSURES
Energy Technology Data Exchange (ETDEWEB)
Landa, A; Klepeis, J; Soderlind, P; Naumov, I; Velikokhatnyi, O; Vitos, L; Ruban, A
2005-05-02
First-principles total energy calculation based on the exact muffin-tin orbital and full potential linear muffin-tin orbital methods were used to calculate the equation of state and shear elastic constants of bcc V, Nb, and the V{sub 95}Nb{sub 05} disordered alloy as a function of pressure up to 6 Mbar. We found a mechanical instability in C{sub 44} and a corresponding softening in C at pressures {approx} 2 Mbar for V. Both shear elastic constants show softening at pressures {approx} 0.5 Mbar for Nb. Substitution of 5 at. % of V with Nb removes the instability of V with respect to trigonal distortions in the vicinity of 2 Mbar pressure, but still leaves the softening of C{sub 44} in this pressure region. We argue that the pressure induced shear instability (softening) of V (Nb) originates from the electronic system and can be explained by a combination of the Fermi surface nesting, electronic topological transition, and band Jahn-Teller effect.
Constant-Power Engines in Flights to L4 point of the Earth-Moon System
Directory of Open Access Journals (Sweden)
Mircea DUMITRACHE
2012-03-01
Full Text Available The transfer is studied in the context of the classical Circular Restricted Three-Body Problem. The initial state is on a geosinchronous orbit and the terminal state is the L4 triangular Lagrangian point. The use of controllable acceleration engine by minimization of a time integral of the squared engine acceleration, the optimization problem is separated into two sub-problems: dynamical and parametric ones. Initial mass to constant output power ratio variation is mainly studied, depending on the transfer duration and initial thrust acceleration for fixed power jet (specific impulse is within the limits of the VASIMR magneto-plasma engine. The Two Point Boundary Value Problem is solved when the startup speed is circular or when the initial thrust acceleration is given. Time variation of the obtained state and control variables is represented relative to Earth in geocentric equatorial inertial system.
Table 5.1. Exchange current densities and rate constants in aqueous systems
Holze, R.
This document is part of Volume 9 `Electrochemistry', Subvolume A, of Landolt-Börnstein - Group IV `Physical Chemistry'. This document lists the exchange current densities and the electrode reaction rate constants of the following metallic electrodes in aqueous systems for various electrolyte reactions: silver (Ag), aluminium (Al), gold (Au), bismuth (Bi), carbon (C), cadmium (Cd), cobalt (Co), chromium (Cr), cesium (Cs), copper (Cu), iron (Fe), gallium (Ga), mercury (Hg), indium (In), iridium (Ir), potassium (K), lithium (Li), molybdenum (Mo), natrium (Na), niobium (Nb), nickel (Ni), lead (Pb), palladium (Pd), platinum (Pt), rubidium (Rb), rhodium (Rh), ruthenium (Ru), antimony (Sb), tin (Sn), tantalum (Ta), titanium (Ti), thallium (Tl), vanadium (V), tungsten (W), zinc (Zn). For each electrolyte reaction the electrolyte solution, the educt, product and concentration are specified along with the temperature of determination of the given values.
ADAPTIVE STEP-SIZE CONSTANT MODULUS ALGORITHM FOR BLIND MULTIUSER DETECTION IN DS-CDMA SYSTEMS
Institute of Scientific and Technical Information of China (English)
Sun Liping; Hu Guangrui
2004-01-01
Blind Adaptive Step-size Constant Modulus Algorithm (AS-CMA) for multiuser detection in DS-CDMA systems is presented. It combines the CMA and the concept of variable step-size, uses a second LMS algorithm for the step size. It adjusts the step-size according to the minimum output-energy principle within a specified range, thus overcomes the problems of bad effect of fixed step-size LMS algorithm. Compared with Adaptive Step-size LMS (AS-LMS) algorithm, through simulations, this algorithm can adapt the changes of the environment, suppress multiple access interference in the dynamic environment and the stability of Signal to Interference Ratio (SIR) is superior to that of AS-LMS.
GRUCAL: a program system for the calculation of macroscopic group constants
International Nuclear Information System (INIS)
Nuclear reactor calculations require material- and composition-dependent, energy-averaged neutron physical data in order to decribe the interaction between neutrons and isotopes. The multigroup cross section code GRUCAL calculates these macroscopic group constants for given material compositions from the material-dependent data of the group constant library GRUBA. The instructions for calculating group constants are not fixed in the program, but are read in from an instruction file. This makes it possible to adapt GRUCAL to various problems or different group constant concepts
DEFF Research Database (Denmark)
Sangwongwanich, Ariya; Yang, Yongheng; Blaabjerg, Frede;
2016-01-01
active power control methods are required. As a cost-effective solution to avoid overloading, a Constant Power Generation (CPG) control scheme by limiting the feed-in power has been introduced into the currently active grid regulations. In order to achieve a CPG operation, this paper presents three CPG...... strategies based on: 1) a power control method (P-CPG), 2) a current limit method (I-CPG) and 3) the Perturb and Observe algorithm (P&O-CPG). However, the operational mode changes (e.g., from the maximum power point tracking to a CPG operation) will affect the entire system performance. Thus, a benchmarking...... of the presented CPG strategies is also conducted on a 3-kW single-phase grid-connected PV system. Comparisons reveal that either the P-CPG or I-CPG strategies can achieve fast dynamics and satisfactory steady-state performance. In contrast, the P&O-CPG algorithm is the most suitable solution in terms of high...
DEFF Research Database (Denmark)
Sangwongwanich, Ariya; Yang, Yongheng; Blaabjerg, Frede;
2016-01-01
active power control methods are required. As a cost-effective solution to avoid overloading, a Constant Power Generation (CPG) control scheme by limiting the feed-in power has been introduced into the currently active grid regulations. In order to achieve a CPG operation, this paper proposes three CPG...... strategies based on: 1) a power control (P-CPG), 2) a current limit method (I-CPG) and 3) the Perturb and Observe algorithm (P&O-CPG). However, the operational mode changes (e.g., from the maximum power point tracking to a CPG operation) will affect the entire system performance. Thus, a benchmarking...... of the proposed CPG strategies is also conducted on a 3-kW single-phase grid-connected PV system. Comparisons reveal that either the P-CPG or I-CPG strategies can achieve fast dynamics and satisfactory steady-state performance. In contrast, the P&OCPG algorithm is the most suitable solution in terms of high...
Cold leg injection reflood test results in the SCTF Core-I under constant system pressure
International Nuclear Information System (INIS)
The Slab Core Test Facility (SCTF) was constructed to investigate two-dimensional thermal-hydrodynamics in the core and the interaction in fluid behavior between the core and the upper plenum during the last part of blowdown, refill and reflood phases of a postulated loss-of-coolant accident (LOCA) of a pressurized water reactor (PWR). The present report describes the analytical results on the system behavior observed in the SCTF Core-I cold leg injection tests, S1-14 (Run 520), S1-15 (521), S1-16 (522), S1-17 (523), S1-20 (530), S1-21 (531), S1-23 (536) and S1-24 (537), performed under constant system pressure condition during transient. Major discussion items are: (1) steam binding, (2) U-tube oscillations, (3) bypass of ECC water (4) core cooling behavior, (5) effect of vent valve and (6) other parameter effects. These results give us very useful information and suggestion on reflood behavior. (author)
Surface induced constant composition crystal growth kinetics studies. The brushite gypsum system
Hina, A.; Nancollas, G. H.; Grynpas, M.
2001-02-01
The possible oriented growth of one crystalline phase on the surface of another is especially important in systems containing both phosphate and sulfate salts of calcium. Whether the overgrowth results from a true epitaxial relationship is dependent on factors such as the thermodynamic driving forces and the free energies of the surfaces. Despite the fact that calcium sulfate dihydrate (CSD, gypsum) and calcium hydrogen phosphate dihydrate (DCPD, brushite) show many crystallographic and structural analogies, their surface reactions are quite different. The nucleation and growth of gypsum on brushite surfaces has been investigated in supersaturated solutions of calcium sulfate dihydrate at 25.0°C using the constant composition (CC) method. During the kinetics experiments, the harvested solid phases were examined by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDS). Induction periods, τ, preceding the initial formation of gypsum crystals at the brushite surfaces, varied markedly with relative supersaturation, σ. A thin layer wicking method was used to investigate the interfacial free energies of the growing phases, and these data were also calculated from the kinetics results. The interfacial free energy, γ, estimated from initial growth rates was 8.4 mJ m -2, while that calculated from the induction times was 8.9 mJ m -2. These values were in agreement with those determined directly using thin layer wicking.
Optical constants and nonlinear calculations of fluorescein/FTO thin film optical system
Zahran, H. Y.; Iqbal, Javed; Yahia, I. S.
2016-11-01
The organic thin films of fluorescein dye were deposited on fluorine-doped tin oxide glass substrate by using low-cost spin coating technique. The surface of the deposited film was characterized by using AFM and X-ray diffraction spectroscopy, which shows that the film is uniform and amorphous. The spectrophotometric study was carried out at the wavelength range of 300-2500 nm. The spectral dependences of the linear refractive index and absorption index were found to decrease as the wavelength was increased. Tauc's plot study revealed that the film shows the direct transition and energy band gap values were found 1.75 eV and 3.55 eV for the thin film and the substrate, respectively. Optical constants were found nearly the same in the higher energy domain (1.0-4.5 eV). Spectroscopic method was employed to study the nonlinear optical susceptibility χ (3). The deposited thin film is a promising optical system for new generation of optoelectronics.
Units Based on Constants: The Redefinition of the International System of Units
Stenger, J.; Ullrich, J. H.
2016-03-01
Recent decisions of the General Conference on Weights and Measures of the Metre Convention have opened the door to a fundamental change of the International System of Units, the SI, in 2018. The revised SI will be based on fixing the numerical values of seven defining constants corresponding to the seven traditional base units. This will bring about basic modifications in the definition of the kilogram, the ampere, the kelvin, and the mole and will have consequences for units derived from them. In contrast, the second, the meter, and the candela will not be affected. This paper describes the motivation and rationale behind this endeavor, introduces the new definitions, and reviews the requirements for the redefinitions as well as the status of the experiments that are currently being carried out to fulfill them. Benefits and a wide-reaching impact for the realization and dissemination of the units are anticipated because innovative technologies with ever-increasing accuracy will emerge, enabling the direct realization over widespread measurement ranges without the definitions themselves having to be changed.
American Society for Testing and Materials. Philadelphia
2008-01-01
1.1 This practice covers procedures for the dynamic verification of cyclic force amplitude control or measurement accuracy during constant amplitude testing in an axial fatigue testing system. It is based on the premise that force verification can be done with the use of a strain gaged elastic element. Use of this practice gives assurance that the accuracies of forces applied by the machine or dynamic force readings from the test machine, at the time of the test, after any user applied correction factors, fall within the limits recommended in Section 9. It does not address static accuracy which must first be addressed using Practices E 4 or equivalent. 1.2 Verification is specific to a particular test machine configuration and specimen. This standard is recommended to be used for each configuration of testing machine and specimen. Where dynamic correction factors are to be applied to test machine force readings in order to meet the accuracy recommended in Section 9, the verification is also specific to the c...
Calculations on the hyperfine constants of the ground states for lithium-like system
Institute of Scientific and Technical Information of China (English)
Wu Xiao-Li; Yu Kai-Zhi; Gou Bing-Cong; Zhang Meng
2007-01-01
In this paper a relativistic many-body perturbation calculation is performed to calculate the hyperfine constants of the ground states for lithium-like isoelectronic sequence. Zeroth-order hyperfine constants are calculated with Dirac-Fock wavefunctions, and the finite basis sets of the Dirac-Fock equations are constructed by B splines. With the finite basis sets, the core polarization and the correlation effect are evaluated.
Piekarczyk, Wojciech; Kata, Dariusz
2016-09-01
The paper presents the methodology and results of the ultrasound determination of material constants of anisotropic materials belonging to the transversely isotropic system. Ultrasound through-transmission method was used for determining material constants. Based on the measurements of velocities of longitudinal and transverse ultrasounds waves propagation, respectively polarized in required directions all the elastic and the material constant of the test materials were determined. Measurements of all the velocities necessary to determine the elastic constants were performed on a specially prepared individual samples. The tests were carried out on porous polycrystalline anisotropic graphites of anisotropy in Young's modulus of up to 26% and Al2O3 composites with up to 30% of hBN causing anisotropy of Young's modulus of up to 50%. It was found that for all tested samples the value of Young's modules and modules stiffness decreasing with increasing porosity in the graphites and increasing content of hBN in Al2O3. PMID:27395009
International Nuclear Information System (INIS)
We propose a novel circuit to be applied to the front-end integrated circuits of gamma-ray spectroscopy systems. Our circuit is designed as a type of current conveyor (ICON) employing a constant-gm (transconductance) method which can significantly improve the linearity in the amplified signals by using a large time constant and the time-invariant characteristics of an amplifier. The constant-gm method is obtained by a feedback control which keeps the transconductance of the input transistor constant. To verify the performance of the propose circuit, the time constant variations for the channel resistances are simulated with the TSMC 0.18μm transistor parameters using HSPICE, and then compared with those of a conventional ICON. As a result, the proposed ICON shows only 0.02% output linearity variation and 0.19% time constant variation for the input amplitude up to 100 mV. These are significantly small values compared to a conventional ICON's 1.39% and 19.43%, respectively, for the same conditions.
Energy Technology Data Exchange (ETDEWEB)
Jung, I.I. [School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Lee, J.H. [Institute of Innovative Functional Imaging, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Lee, C.S. [Department of Physics, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Choi, Y.-W., E-mail: ychoi@cau.ac.k [School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 156-756 (Korea, Republic of)
2011-02-11
We propose a novel circuit to be applied to the front-end integrated circuits of gamma-ray spectroscopy systems. Our circuit is designed as a type of current conveyor (ICON) employing a constant-g{sub m} (transconductance) method which can significantly improve the linearity in the amplified signals by using a large time constant and the time-invariant characteristics of an amplifier. The constant-g{sub m} method is obtained by a feedback control which keeps the transconductance of the input transistor constant. To verify the performance of the propose circuit, the time constant variations for the channel resistances are simulated with the TSMC 0.18{mu}m transistor parameters using HSPICE, and then compared with those of a conventional ICON. As a result, the proposed ICON shows only 0.02% output linearity variation and 0.19% time constant variation for the input amplitude up to 100 mV. These are significantly small values compared to a conventional ICON's 1.39% and 19.43%, respectively, for the same conditions.
Energy Technology Data Exchange (ETDEWEB)
Kolowrocki, Krzysztof [Gdynia Maritime University, Gdynia (Poland)
2009-07-01
In the paper the multi-state approach to the analysis and evaluation of systems' reliability, risk and availability is practically applied. Theoretical definitions and results are illustrated by the example of their application in the reliability, risk and availability evaluation of an oil pipeline transportation system. The pipeline transportation system is considered in the constant in time operation conditions. The system reliability structure and its components reliability functions are not changing in constant operation conditions. The system reliability structure is fixed with a high accuracy. Whereas, the input reliability characteristics of the pipeline components are not sufficiently exact because of the lack of statistical data necessary for their estimation. The results may be considered as an illustration of the proposed methods possibilities of applications in pipeline systems reliability analysis. (author)
Sun, H. G.; Chen, W.; Wei, H.; Chen, Y. Q.
2011-03-01
How to characterize the memory property of systems is a challenging issue in the modeling and analysis of complex systems. This study makes a comparative investigation of integer-order derivative, constant-order fractional derivative and two types of variable-order fractional derivatives in characterizing the memory property of systems. The advantages and potential applications of two variable-order derivative definitions are highlighted through a comparative analysis of anomalous relaxation process.
Wilczek, Frank
2007-01-01
The notion of ``fundamental constant'' is heavily theory-laden. A natural, fairly precise formulation is possible in the context of the standard model (here defined to include gravity). Some fundamental constants have profound geometric meaning. The ordinary gravitational constant parameterizes the stiffness, or resistance to curvature, of space-time. The cosmological term parameterizes space-time's resistance to expansion -- which may be, and apparently is at present, a {\\it negative} resistance, i.e. a tendency toward expansion. The three gauge couplings of the strong, electromagnetic, and weak interactions parameterize resistance to curvature in internal spaces. The remaining fundamental couplings, of which there are a few dozen, supply an ungainly accommodation of inertia. The multiplicity and variety of fundamental constants are esthetic and conceptual shortcomings in our present understanding of foundational physics. I discuss some ideas for improving the situation. I then briefly discuss additional con...
Damour, Thibault Marie Alban Guillaume
2003-01-01
We review some string-inspired theoretical models which incorporate a correlated spacetime variation of coupling constants while remaining naturally compatible both with phenomenological constraints coming from geochemical data (Oklo; Rhenium decay) and with present equivalence principle tests. Barring unnatural fine-tunings of parameters, a variation of the fine-structure constant as large as that recently ``observed'' by Webb et al. in quasar absorption spectra appears to be incompatible with these phenomenological constraints. Independently of any model, it is emphasized that the best experimental probe of varying constants are high-precision tests of the universality of free fall, such as MICROSCOPE and STEP. Recent claims by Bekenstein that fine-structure-constant variability does not imply detectable violations of the equivalence principle are shown to be untenable.
Barrow, J D
2005-01-01
We review properties of theories for the variation of the gravitation and fine structure 'constants'. We highlight some general features of the cosmological models that exist in these theories with reference to recent quasar data that are consistent with time-variation in the fine structure 'constant' since a redshift of 3.5. The behaviour of a simple class of varying-alpha cosmologies is outlined in the light of all the observational constraints.
Operation of the Run IIB D0 Luminosity System and Determination of the Run IIB Luminosity Constant
Energy Technology Data Exchange (ETDEWEB)
Prewitt, Michelle Victoria; /Rice U.
2010-04-01
The luminosity system is an integral part of the D0 detector that must be properly maintained to provide accurate luminosity measurements for physics analysis. After the addition of a readout layer to the silicon vertex detector in 2006, it was necessary to re-calculate the effective inelastic cross section to which the luminosity monitor is sensitive. The preliminary analysis showed that the luminosity constant did not change with the addition of the extra layer of silicon. A full study of the revised luminosity constant including a complete analysis of systematic uncertainties has been completed. The luminosity constant was determined to be {sigma}{sub eff} = 48.3 {+-} 1.9 {+-} 0.6 mb, which reduces the D0 contribution to the luminosity measurement uncertainty by almost 3%.
Stary, J
1979-01-01
Critical Evaluation of Equilibrium Constants Involving 8-Hydroxyquinoline and Its Metal Chelates presents and evaluates the published data on the solubility, dissociation, and liquid-liquid distribution of oxine and its metal chelates to recommend the most reliable numerical data. This book explores the dissociation constants of oxine in aqueous solutions.Organized into four chapters, this book begins with an overview of the characteristics of 8-hydroxyquinoline (oxine). This text then examines the total solubility of oxine in aqueous solution at different pH values. Other chapters consider th
Variable Frequency Constant Pressure Water Supply System Design%变频恒压供水系统设计
Institute of Scientific and Technical Information of China (English)
尤志强
2016-01-01
小区供水是变频恒压供水系统经常应用的例子。随着人民的生活条件越来越好，所以供水方式要越来越高效节能。小区供水系统是用PLC和变频器制作的供水控制系统。%District water supply is an example of constant frequency and constant pressure water supply system.In recent years, the development of people's living conditions are getting better and better, so the way to water supply more and more efficient and energy saving.District water supply system is a water supply control system with PLC and frequency changer.
Decay constants and mixing parameters in a relativistic model for q\\barQ system
Ahmady, M. R.; Mendel, R. R.; Talman, J.D.
1996-01-01
We extend our recent work, in which the Dirac equation with a ``(asymptotically free) Coulomb + (Lorentz scalar $\\gamma_0\\sigma r$) linear '' potential is used to obtain the light quark wavefunction for $q\\bar Q$ mesons in the limit $m_Q\\to \\infty$, to estimate the decay constant $f_P$ and the mixing parameter $B$ of the pseudoscalar mesons. We compare our results for the evolution of $f_P$ and $B$ with the meson mass $M_P$ to the non-relativistic formulas for these quantities and show that t...
Sakamoto, Sadaaki; Adachi, Hiroshige; Kaneko, Kazuhiro; Sugimoto, Yasutaka; Takada, Takahiro
2013-09-01
We found that the co-firing low temperature co-fired ceramic (LTCC) materials of different dielectric constants (ɛr) with Cu wiring is achievable using a novel, original design. It was confirmed that the dielectric characteristics of the dielectrics designed in this study are very suitable for the use of the dielectrics in electronic components such as filters mounted in high-speed radio communication equipment. The dielectric constants of the lower- and higher-dielectric-coefficient materials were 8.1 and 44.5, respectively, which are sufficiently effective for downsizing LTCC components. Observing the co-fired interface, it was confirmed that excellent co-firing conditions resulted in no mechanical defects such as delamination or cracks. On the basis of the results of wavelength dispersive X-ray spectrometry (WDX) and X-ray diffractometry (XRD), it was confirmed that co-firing with minimal interdiffusion was realized using the same glass for both dielectrics. It is concluded that the materials developed are good for co-firing in terms of the mechanical defects and interdiffusion that appear in them.
Institute of Scientific and Technical Information of China (English)
师宇腾; 魏蓓; 周京华
2016-01-01
The advanced design of the remote monitoring system of the constant-temperature constant-humidity unit stacks room for Sikuquanshu of the National Library of China is presented. The system achieves the real-time monitoring and real-time displaying of the temperature and the humidity for each of the constant-temperature constant-humidity units, also can realize the relevant alarming, clearing, recording and inquiring. The advanced design of the system ensures the high efficiency and safe operation of the constant-temperature constant-humidity units.%国家图书馆四库全书书库恒温恒湿机组远程监控系统的建立，实现了对各恒温恒湿机组温湿度的实时显示和运行状态的实时监控，也能够实现对报警状态的显示、清除和记录及对温度、湿度的记录和查询。恒温恒湿机组监控系统运行稳定、操作方便，它的设计使用确保了恒温恒湿机组的高效、安全运行。
Bhattacharjee, Suraka; Chaudhury, Ranjan
2016-11-01
The generalized spin stiffness constant for a doped quantum antiferromagnet has been investigated both analytically and numerically as a function of doping concentration at zero temperature, based on the strongly correlated t-J model on two-dimensional square lattice. The nature of the theoretical dependence of the stiffness constant on doping shows a striking similarity with that of the effective exchange constant, obtained from the combination of other theoretical and experimental techniques in the low doping region. This correspondence once again establishes that spin stiffness can very well play the role of an effective exchange constant even in the strongly correlated semi-itinerant systems. Our theoretical plot of the stiffness constant against doping concentration in the whole doping region exhibits the various characteristic features like a possible crossover in the higher doping regions and persistence of short range ordering even for very high doping with the complete vanishing of spin stiffness occurring only close to 100% doping. Our results receive very good support from various other theoretical approaches and also brings out a few limitations of some of them. Our detailed analysis highlights the crucial importance of the study of spin stiffness for the proper understanding of magnetic correlations in a semi-itinerant magnetic system described by the strongly correlated t-J model. Moreover, our basic formalism can also be utilized for determination of the effective exchange constant and magnetic correlations for itinerant magnetic systems, in general in a novel way.
Directory of Open Access Journals (Sweden)
Agneta M. BALINT
2010-12-01
Full Text Available In this paper we build up a flight control system for an unmanned aircraft whose flightcontrol system fails during a longitudinal flight with constant forward velocity. This task isaccomplished using only the system of differential equations, which governs the movement of theaircraft around its center of mass. Numerical simulation is given.
Lithium-ion Battery Charging System using Constant-Current Method with Fuzzy Logic Based ATmega16
Rossi Passarella; Ahmad Fali Oklilas; Tarida Mathilda
2014-01-01
In this charging system, constant-current charging technique keeps the current flow into the battery on its maximum range of 2A. The use of fuzzy logic control of this charging system is to control the value of PWM. PWM is controlling the value of current flowing to the battery during the charging process. The current value into the battery depends on the value of battery voltage and also its temperature. The cutoff system will occur if the temperature of the battery reaches its maximum range
Lithium-ion Battery Charging System using Constant-Current Method with Fuzzy Logic Based ATmega16
Directory of Open Access Journals (Sweden)
Rossi Passarella
2014-10-01
Full Text Available In this charging system, constant-current charging technique keeps the current flow into the battery on its maximum range of 2A. The use of fuzzy logic control of this charging system is to control the value of PWM. PWM is controlling the value of current flowing to the battery during the charging process. The current value into the battery depends on the value of battery voltage and also its temperature. The cutoff system will occur if the temperature of the battery reaches its maximum range
Energy Technology Data Exchange (ETDEWEB)
Tazhibayeva, Irina, E-mail: tazhibayeva@ntsc.kz [Institute of Atomic Energy NNC RK, Kurchatov (Kazakhstan); Kulsartov, Timur; Gordienko, Yuri [Institute of Atomic Energy NNC RK, Kurchatov (Kazakhstan); Mukanova, Aliya [Al’ Farabi Kazakh National University, Almaty (Kazakhstan); Ponkratov, Yuri; Barsukov, Nikolay; Tulubaev, Evgeniy [Institute of Atomic Energy NNC RK, Kurchatov (Kazakhstan); Platacis, Erik [University of Latvia (IPUL), Riga (Latvia); Kenzhin, Ergazy [Shakarim Semey State University, Semey (Kazakhstan)
2013-10-15
Highlights: • The experiments with Li CPS sample were carried out at reactor IVG-1.M. • The gas absorption technique was used to study hydrogen isotope interaction with lithium CPS. • The temperature dependence of constants of interaction rate was obtained for various power rates of the reactor. • Determination of the activation energies, and pre-exponents of Arrhenius dependence. • The effect of increase of the rate constant under reaction irradiation. -- Abstract: Experiments with a sample of a lithium capillary-porous system (CPS) were performed at the reactor IVG-1.M of the Institute of Atomic Energy NNC RK to study the effects of neutron irradiation on the parameters of hydrogen isotope interactions with a lithium CPS. The absorption technique was used during the experiments, and this technique allowed the temperature dependences of the hydrogen isotope interaction rate constants with the lithium CPS to be obtained under various reactor powers. The obtained dependencies were used to determine the main interaction parameters: the activation energies and the pre-exponents of the Arrhenius dependence of the hydrogen interaction rate constants with lithium and the lithium CPS. An increase of the hydrogen isotope interaction rate with the lithium CPS was observed under reactor irradiation.
Determination of the Rubidium Decay Constant by Age Comparison Against the U-Pb System
Nebel, O.; Mezger, K.; Scherer, E. E.; Davies, G. R.
2006-12-01
The currently accepted Rb decay constant (λ 87Rb) was suggested by the Subcommission on Geochronology [1] is 1.42 x 10-11yr-1, and has a potential precision at the percent level at best [2]. This value has been used in most Rb-Sr studies in the last three decades. Several attempts to refine λ87Rb by different techniques yielded results that, despite excellent reported precisions, differed from the proposed value and also from each other. In a recent evaluation of published calibrations of the decay constant, Begemann et al. [2] suggested a lower value [~ 1.40 x 10-11yr-1] but also called for a re-determination of λ87Rb to check its accuracy and significantly improve the precision. Subsequent re-determinations [3,4] yielded values that differ significantly from each other and from that proposed by the Subcommission on Geochronology [1], one of which being higher [3], the other one lower [4] than the recommended value. Therefore, at present, there is no consensus on the λ87Rb to be used in Rb-Sr chronology. Here we report three individual determinations of λ87Rb by the method of age comparison. This entails solving for λ87Rb using 1) the measured slopes of high precision Rb-Sr isochrons from igneous rocks and minerals and 2) the emplacement ages of these samples as determined by the precise and presumably accurate U-Pb method. The precision of the measured 87Rb/86Sr has been improved to ~0.2% by measuring Rb concentrations by isotope dilution MC-ICPMS [5] (cf. ~1% for TIMS data). A challenging aspect of Rb-Sr studies is that of spike calibration, which is generally performed using standards prepared from salts of Rb and Sr rather than pure metals. The Rb/Sr values of individual spikes calibrated against two standard solutions made from different salts (iodide and carbonate) agree to within 0.15%, strongly suggesting that the stoichiometry of the salts, after careful dehydration, is sufficiently ideal for accurate spike calibrations. The calibration was checked
De Martino, S; Illuminati, F; Martino, Salvatore De; Siena, Silvio De; Illuminati, Fabrizio
1999-01-01
The possibility is discussed of inferring or simulating some aspects of quantum dynamics by adding classical statistical fluctuations to classical mechanics. We introduce a general principle of mechanical stability and derive a necessary condition for classical chaotic fluctuations to affect confined dynamical systems, on any scale, ranging from microscopic to macroscopic domains. As a consequence we obtain, both for microscopic and macroscopic aggregates, dimensional relations defining the minimum unit of action of individual constituents, yielding in all cases Planck action constant.
Institute of Scientific and Technical Information of China (English)
王农; 韩冰; 贺青; 张钟华; 李小亭
2011-01-01
A constant current source with high stability is required in establishing measuring system of Planck' s constant. The technique based on series compensation type for special constant current source for magnetic field was described. Therewith the constant current source with 4. 5 X 10 ~ /30min stability was constructed through designing the extraordinary sampling resistor, selecting stable voltage reference and operational amplifier with outstanding properties, offsetting the phase shift of inductive load. As a special constant current source for magnetic field, it presently could serve for the measuring system of Planck' s constant.%在建立我国普朗克常数h测定系统中,对高稳定度直流电源提出了新的要求.本文提出一种基于串联补偿型的专用磁场稳流源.通过设计特殊的采样电阻,选用稳定的基准电压,优选性能突出的运放,并针对感性负载进行关键的补偿,搭建了一套稳定度达到4.5×10 -6/30min的稳流源,可用作现阶段普朗克常数h测定系统的磁场稳流源.
International Nuclear Information System (INIS)
The Cauchy problem for the system of linear pseudodifferential equations is considered. For two classes of such systems including partial differential systems with conbstant and rapidity decreasing variable coefficients a solution by series is obtained. The series is represented in the form of feynman integral in phase space of chronological exponent of operator-valued symbol of pseudodifferential operator
Sparavigna, Amelia Carolina
2012-01-01
As proposed in a previous paper, the decorations of ancient objects can provide some information on the approximate evaluations of constant {\\pi}, the ratio of circumference to diameter. Here we discuss some disks found in the tomb of Hemaka, the chancellor of a king of the First Dynasty of Egypt, about 3000 BC. The discussion is based on measurements of the dimensionless ratio of lengths.
Energy Technology Data Exchange (ETDEWEB)
Robinson, H.P.; Potter, Elinor
1971-03-01
This collection of mathematical data consists of two tables of decimal constants arranged according to size rather than function, a third table of integers from 1 to 1000, giving some of their properties, and a fourth table listing some infinite series arranged according to increasing size of the coefficients of the terms. The decimal values of Tables I and II are given to 20 D.
Nungesser, Ernesto
2014-01-01
We show future global non-linear stability of surface symmetric solutions of the Einstein-Vlasov system with a positive cosmological constant. Estimates of higher derivatives of the metric and the matter terms are obtained using an inductive argument. In a recent research monograph Ringstr\\"{o}m shows future non-linear stability of (not necessarily symmetric) solutions of the Einstein-Vlasov system with a non-linear scalar field if certain local estimates on the geometry and the matter terms are fulfilled. We show that these assumptions are satisfied at late times for the case under consideration here which together with Cauchy stability leads to our main conclusion.
Bracken, Paul; Grundland, Alfred M.
1999-01-01
Analysis of the generalized Weierstrass-Enneper system includes the estimation of the degree of indeterminancy of the general analytic solution and the discussion of the boundary value problem. Several different procedures for constructing certain classes of solutions to this system, including potential, harmonic and separable types of solutions, are proposed. A technique for reduction of the Weierstrass-Enneper system to decoupled linear equations, by subjecting it to certain differential co...
Higashi, K. K.; Minges, G. P.; Price, G. D.
1982-10-01
The use of a wound rotor variable speed, constant frequency generator with small wind systems was investigated. The main initial objective was to demonstrate proof of concept under controlled conditions. The feasibility of this application was confirmed and it was shown that improved performance could be expected over a constant speed, constant frequency generator systems. The ability to maintain a constant tip speed ratio near the maximum rotor performance coefficient over a wide range of wind speeds is noted. A substantial increase in annual energy output can be expected from VSCF operation. Controlled start up and shutdown can also reduce the high transient torques and concomitant inrush currents common to induction generator systems.
System Lifetimes, The Memoryless Property, Euler's Constant, and Pi
Agarwal, Anurag; Marengo, James E.; Romero, Likin Simon
2013-01-01
A "k"-out-of-"n" system functions as long as at least "k" of its "n" components remain operational. Assuming that component failure times are independent and identically distributed exponential random variables, we find the distribution of system failure time. After some examples, we find the limiting…
PULSING A 4.1 MW MOTOR GENERATOR SYSTEM TO 34 MW PEAK POWER UNDER CONSTANT INPUT POWER OPERATION.
Energy Technology Data Exchange (ETDEWEB)
MARNERIS,I.; BADEA,V.; BANNON,M.; BONATI,R.; DANOWAKI,G.; SANDBERG,J.; SOUKAS,A.
1999-03-29
Brookhaven operates a 9 MW motor generator, made by Siemens, as part of the main magnet power supply of the Alternating Gradient Synchrotron (AGS) accelerator. A cycloconverter power supply system is utilized to ensure that during pulsing the main magnets of the AGS up to 50 MW peak power, the input power of the motor generator remains constant. There is also another motor generator (MG set) at Brookhaven, a 40 year old system manufactured by Westinghouse. This MG set could be pulsed up to 34 MW peak power while the input average power should not exceed. 4.1 M&V. A project is underway to upgrade this MG system and it's controls, so it could be used as a spare while doing maintenance on the Siemens MG and thus not interrupting the RHIC physics program. The purpose of this paper is to show that it is possible to pulse the AGS magnets using the Westinghouse MG system without utilizing a cycloconverter power supply, and still be able to maintain the input power to the motor generator constant. Calculations will be provided to show that we can pulse the position of the liquid rheostat in the motor rotor circuit to support the above, while taking out the power necessary to pulse the AGS magnets. This solution is being implemented due to budget constraints and overall simplicity. The hydraulic system to accomplish this task will also be described.
Optical timing receiver for the NASA laser ranging system. Part I. Constant-fraction discriminator
International Nuclear Information System (INIS)
Position-resolution capabilities of the NASA laser ranging system are essentially determined by time-resolution capabilities of its optical timing receiver. The optical timing receiver consists of a fast photoelectric device, primarily a standard of microchannel-plate-type photomultiplier or an avalanche photodiode detector, a timing discriminator, a high-precision time-interval digitizer, and a signal-processing system. The time-resolution capabilities of the receiver are determined by the photoelectron time spread of the photoelectric device, the time walk and resolution characteristics of the timing discriminator, and the time-interval digitizer. It is thus necessary to evaluate available fast photoelectronic devices with respect to their time-resolution capabilities, and to design a very low time walk timing discriminator and a high-precision time digitizer which will be used in the laser ranging system receiver. (auth)
Systemizing: A Cross-Cultural Constant for Motivation to Learn Science
Zeyer, Albert; Çetin-Dindar, Ayla; Md Zain, Ahmad Nurulazam; Juriševic, Mojca; Devetak, Iztok; Odermatt, Freia
2013-01-01
The present study is based on the empathizing-systemizing (E-S) theory of cognitive science. It was hypothesized that the influence of students' gender on their motivation to learn science is often overestimated in the research literature and that cognitive style is more important for motivation than students' gender. By using structural…
Di Francesco, Marco
2011-04-01
The dependence of tumor on essential nutrients is known to be crucial for its evolution and has become one of the targets for medical therapies. Based on this fact a reaction-diffusion system with chemotaxis term and nutrient-based growth of tumors is presented. The formulation of the model considers also an influence of tumor and pharmacological factors on nutrient concentration. In the paper, convergence of solutions to constant, stationary states in the one-dimensional case for small perturbation of the equilibria is investigated. The nonlinear stability results are obtained by means of the classical symmetrization method and energy Sobolev estimates. © 2010 Elsevier Ltd.
International Nuclear Information System (INIS)
The program system FEDGROUP was originally released for general distribution in June 1976. It is widely applied for the generation of group constant libraries used by different spectral codes. In this revised version of report INDC/HUN/-13 errors, deficiencies and misprints in the original report have been removed and an extension is introduced and described. The basic computer of FEDGROUP is the CDC-3300. There exist, however, CYBER-72, BESM-6 and IBM-360 versions, too. The problems connected with the various computer versions are discussed. Results of test calculations are quoted and errata to the report INDC/HUN/-13 are given
On the Formulation of Flexible Multibody Systems with Constant Mass Matrix
DEFF Research Database (Denmark)
Pedersen, Niels Leergaard
1997-01-01
A flexible body in a multibody system isdescribed only by the position of the nodes in theinertial frame. With this description we can formulatethe mass matrix of the flexible multibody as aconstant matrix. This matrix can be inverted in apreprocessing stage which yields a more efficientaccelerat...... of this formulation is that neither thecentrifugal nor the Coriolis forces appear in theequations due to the description of the flexible body....
Constant-coefficient FIR filters based on residue number system arithmetic
Directory of Open Access Journals (Sweden)
Stamenković Negovan
2012-01-01
Full Text Available In this paper, the design of a Finite Impulse Response (FIR filter based on the residue number system (RNS is presented. We chose to implement it in the (RNS, because the RNS offers high speed and low power dissipation. This architecture is based on the single RNS multiplier-accumulator (MAC unit. The three moduli set {2n+1,2n,2n-1}, which avoids 2n+1 modulus, is used to design FIR filter. A numerical example illustrates the principles of residue encoding, residue arithmetic, and residue decoding for FIR filters.
Xu, Jinxin; Zhang, Zhonghua; Li, Zhengkun; Bai, Yang; Wang, Gang; Li, Shisong; Zeng, Tao; Li, Chen; Lu, Yunfeng; Han, Bing; Wang, Nong; Zhou, Kunli
2016-02-01
The joule balance experiment has been carried out at the National Institute of Metrology, China (NIM) since 2007. By the end of 2013 the first generation of the joule balance (NIM-1) achieved a measurement uncertainty of 7.2 × 10-6 (k = 1). To reduce the measurement uncertainty further, the next generation of the joule balance apparatus (NIM-2) system is under construction. A new coil system using ferromagnetic material is being adopted in NIM-2 to reduce self-heating in the coils. However, the effects on the measurement of the mutual inductance from the nonlinearity and hysteresis of the ferromagnetic material will bring a considerable measurement uncertainty. Inspired by the watt balance, the measurement of the mutual inductance is replaced by an equivalent measurement of the magnetic flux linkage difference. The nonlinearity and hysteresis will not be a problem in the measurement of the magnetic flux linkage difference. This technique comes from the watt balance method. It is called the generalized joule balance method, which is actually a modification of the watt balance method. However, it still represents a valid change that can reduce the difficulty of dynamic measurement experienced using the watt balance. Permanent magnets can also be adopted in the generalized joule balance. To check the feasibility of the generalized joule balance method, some preliminary experiments have been performed on NIM-1. A yokeless permanent magnet system has been designed and used to replace the exciting coils in NIM-1. In this paper, the structure of the yokeless permanent magnet system is introduced. Furthermore, a determination of the Planck constant with the permanent magnet system is presented. The value of the Planck constant h we obtained is 6.626 069(17) × 10-34 J s with a relative standard uncertainty of 2.6 × 10-6.
Institute of Scientific and Technical Information of China (English)
PIAO; Daxiong
2001-01-01
., Wampler, E. J., Gaskell, C. M., Emission-line properties of optically and radio-selected complete quasars samples, Astrophys. J., 1989, 338: 630.［13］Yong, P., Sargent, W. L. W. A., High-resolution study of the absorption spectra of three QSOs: evidence for cosmological evolution in the lyman-alpha lines, Astrophys. J., 1982, 252: 10.［14］Lawrence, J., Zucker, J. R., Readhead, A. C. S. et al., Optical spectra of a complete sample of radio sources I. The spectra, Astrophys. J. Suppl., 1996, 107: 541.［15］Junkkarinen, V. T. , Burbidge E. M. , Smith, H. E. , Spectrophyotometry of six broad absoption line QSOs, Astrophys. J. ,1987, 317, 460.［16］Laor, A., Babcall, J. N., Jannuzi, B. T. et al., The ultraviolet emission properties of 13 quasars, Astrophys. J. Suppl.,1995, 99: 1.［17］Baldwin, J. A., Rees, M. J., Longair, M. S. et al., QSOs with narrow emission lines, Astrophys. J., 1988, 327: 103.［18］Shaver, P. A. , Boksenberg A. , Robertson, J. G. , Spectroscopy of the QSO pair Q0028 + 003/Q0029 + 003, Astrophys.J., 1982, 261: L7.［19］Baldwin, J. A., Netzer, H., The emission-line regions of high-redshift QSOs, Astrophys. J., 1978, 226: 1.［20］Wills, B. J., Thompson, K. L., Han, M. et al. , The Hubble space telescope sample of radio-loud quasars: Ultraviolet spectra of the first 31 quasars, Astrophys. J., 1995, 447: 139.［21］Osmer, P. S., Smith, M. G. , Discovery and spectroscopic observations of 27 optical selected quasars with 1.4 ＜ z ＜ 2.5,Astrophys. J., 1977, 213: 607.［22］Storrie-Lombardi, L. J., McMabon, R. G., Irwin, M. J. et al., APM Z ＞ = 4 QSO Survey: Spectra and Intervening Ab-sorption Systems, Astrophys. J., 1996, 468: 121.［23］Young, P. , Sargent, W. L. W. , Boksenberg, A. , Clv absorption in an unbiased sample of 33 QSOs: evidence for the inter-vening galaxy hypothesis, Astrophys. J. Suppl., 1982, 48: 455.［24］Zitelli, V., Mignoli, M., Zarano, B. et al., A spectroscopically complete sample of quasars with Bj ≤ 22
International Nuclear Information System (INIS)
A device for measuring the exposure rate from neutron-activated indium foil, under constant geometry, has been designed, constructed, and tested. The device is intended for use with the Juno ionization chambers, although it adapts to Victoreen CDV-700 and Victoreen 193 G-M instruments. Juno dose-response data for low (53 rad) and high (226 rad) doses were compiled and modeled. This model was compared to that assumed from the indium foil dose-response model in current use; plots of fitted and assumed models are congruent. An analysis of data from both Juno and CDV-700 instruments indicates that the constant geometry device may be used effectively to monitor the decay of In-116m. Tolerance limits for the Juno dose-response curve increase with time after activation, which results in diminished precision of dose estimates made by indium foil measurement. From the data collected in these experiments, the system appears to be most useful if activation is measured within 250 min after exposure. 5 references, 7 figures, 1 table
International Nuclear Information System (INIS)
Graphical abstract: The work aimed at studying the performance of a steam jet refrigeration system with (i) a constant area ejector and (ii) a variable area ejector under different operating conditions both experimentally and computationally. The boiler temperature was varied from 90 °C to 120 °C, the evaporator temperature was varied from 5 °C to 15 °C and the entertainment ratio, variation of Mach number along the ejector and the Coefficient of Performance were obtained. With proper design, the shock phenomenon in the variable area ejector was eliminated as shown in the left figure, which resulted in a better performance of the variable area ejector over a range of evaporator temperatures. The study also confirmed that the system can operate steadily at a boiler temperature of 90 °C which can be obtained from waste heat. - Highlights: • Experimental and computational studies on steam jet refrigeration system carried out. • Constant area and variable area ejectors were designed for low heat input. • Evaporator temperature was varied from 5 °C to 15 °C and the boiler temperature from 90 °C to 120 °C. • At the lower boiler temperature, no shock formed in the variable area ejector resulting in better performance. • A steam jet refrigeration system can operate steadily at boiler temperature of 90 °C. - Abstract: This paper first presents the results from an experimental study of a conventional steam jet ejector refrigeration system and compares the performance with the computational fluid dynamics (CFD) results of the same. Secondly, it describes a method of developing a variable area supersonic ejector and presents experimental results of the operating performance of the variable area ejector over the same operating conditions. The two ejectors were experimentally tested for boiler temperatures below 120 °C and an evaporator temperature below 15 °C. It was found that the steam jet refrigeration system can operate with stability at low boiler
Cosmological Constant, Fine Structure Constant and Beyond
Wei, Hao; Li, Hong-Yu; Xue, Dong-Ze
2016-01-01
In this work, we consider the cosmological constant model $\\Lambda\\propto\\alpha^{-6}$, which is well motivated from three independent approaches. As is well known, the evidence of varying fine structure constant $\\alpha$ was found in 1998. If $\\Lambda\\propto\\alpha^{-6}$ is right, it means that the cosmological constant $\\Lambda$ should be also varying. In this work, we try to develop a suitable framework to model this varying cosmological constant $\\Lambda\\propto\\alpha^{-6}$, in which we view it from an interacting vacuum energy perspective. We propose two types of models to describe the evolutions of $\\Lambda$ and $\\alpha$. Then, we consider the observational constraints on these models, by using the 293 $\\Delta\\alpha/\\alpha$ data from the absorption systems in the spectra of distant quasars, and the data of type Ia supernovae (SNIa), cosmic microwave background (CMB), baryon acoustic oscillation (BAO). We find that the model parameters can be tightly constrained to the narrow ranges of ${\\cal O}(10^{-5})$ t...
收放系统恒张力研究%Research on Constant Tension Control of Retractable System
Institute of Scientific and Technical Information of China (English)
鄢华林; 周超; 姜飞龙; 赵瑞; 李亚南; 袁威
2012-01-01
以收放系统作为研究对象,讨论缆绳收放系统的储缆绞车和绞盘之间的同步问题.采用SEW变频器实现对交流电机速度与力矩的控制,分析采用变频器实现恒张力的工作原理.针对平台上升过程中电动机发电的问题,提出负功率的平衡方法.%The retractable system was taken as the research object. Synchronization between the cable storage winch and winch was discussed. SEW inverter was used to control the speed and torch of AC motor. The principle of constant tension control with inverter was analyzed. As to the power problem during the platform rising, balanced approach based on negative power was proposed.
Marvola, Janne; Kanerva, Hanna; Slot, Lillian; Lipponen, Maija; Kekki, Tommi; Hietanen, Heikki; Mykkänen, Sirpa; Ariniemi, Kari; Lindevall, Kai; Marvola, Martti
2004-08-20
This paper is a report from a pharmacoscintigraphic study with an Egalet constant-release system containing caffeine and natural abundance samarium oxide. First the formulation was tested in vitro to clarify integrity during irradiation in the nuclear reactor. Then six healthy male volunteers were enrolled into the in vivo study. The in vitro release of caffeine obeyed all the time linear zero-order kinetics. The in vivo release of radioactive Sm2O3 consisted of three consequent linear phases with different slopes. The release rate was fastest while the product was in the small intestine and slowest when the product was in the descending colon. In terms of the bioavailability of caffeine, the most important factor seemed to be the residence time in the ascending and transverse colon. A long residence time in these sections led to high AUC values for caffeine.
Energy Technology Data Exchange (ETDEWEB)
Layadi, A. [LESIMS, Departement de Physique, Université Ferhat Abbas, Sétif 19000 (Algeria)
2015-05-15
The ferromagnetic resonance intrinsic field linewidth ΔH is investigated for a multilayer system such as a coupled trilayer and a spin valve structure. The magnetic coupling between two ferromagnetic layers separated by a nonmagnetic interlayer will be described by the bilinear J{sub 1} and biquadratic J{sub 2} coupling parameters. The interaction at the interface of the first ferromagnetic layer with the antiferromagnetic one is account for by the exchange anisotropy field, H{sub E}. A general formula is derived for the intrinsic linewidth ΔH. The explicit dependence of ΔH with H{sub E}, J{sub 1} and J{sub 2} will be highlighted. Analytical expressions for each mode field linewidth are found in special cases. Equivalent damping constants will be discussed.
Institute of Scientific and Technical Information of China (English)
常国宾; 柳明
2015-01-01
In inertial navigation system (INS) and global positioning system (GPS) integrated system, GPS antennas are usually not located at the same location as the inertial measurement unit (IMU) of the INS, so the lever arm effect exists, which makes the observation equation highly nonlinear. The INS/GPS integration with constant lever arm effect is studied. The position relation of IMU and GPS’s antenna is represented in the earth centered earth fixed frame, while the velocity relation of these two systems is represented in local horizontal frame. Due to the small integration time interval of INS, i.e. 0.1 s in this work, the nonlinearity in the INS error equation is trivial, so the linear INS error model is constructed and addressed by Kalman filter’s prediction step. On the other hand, the high nonlinearity in the observation equation due to lever arm effect is addressed by unscented Kalman filter’s update step to attain higher accuracy and better applicability. Simulation is designed and the performance of the hybrid filter is validated.
Institute of Scientific and Technical Information of China (English)
金文敬
2011-01-01
The situation of astronomical constant system adopted by the IAU since 1900 has been briefly reviewed. The mathematical relation between some astronomical constants and the main reason for the change of astronomical constant system each time in the past are described. Especially, the work on the IAU astronomical constant system, including the establishment of working groups and adoption of the current best estimates since 1991, is introduced. The background of the IAU 2009 astronomical constant system instead of the IAU 1976 astronomical constant system is given. As for this change the reasons are the appearance of new measurements of astronomical constants with exploration of the Solar system, application of the Barycentric Celestial Reference System and Geocentric Celestial Reference System under the relativistic reference frame after 1991 and the adoption of new models for precession and nutation after 2006. The comparison between the IAU 2009 and 1976 astronomical constant system is given. Finally, the work on astronomical constants in China, such as determination of precession constant from proper motion, the definition of astronomical unit under the relativistic reference frame, determination of nutation constant from globe optical classical observations during 1962.0-1982.0, Corrections to the IAU 1976 precession constant and the coefficients of the IAU nutation series from VLBI data by using various networks during April 1980-December 1995, establishment of a new nutation model of a non-rigid earth with ocean and atmosphere etc. is briefly mentioned. Some suggestions for the further work on astronomical constants are proposed as follows:(1) Shanghai Astronomical Observatory (SHAO) incorporates the international organizations of ILRS, IVS and IGS. The globe solution are given from processing the observational data of SLR、 GPS and VLBI routinely. By using these globe data not only the Earth Orientation Parameters, plate motion and regional crustal
Pogliano, U.; Durbiano, F.; Serazio, D.
2011-05-01
The development of an electrochemical system for the Faraday constant determination has been undertaken at I.N.RI.M. In this system a new two-electrode cell for processing silver dissolution has been set up. The parts of this cell have been carefully designed to avoid sources of undue influence. New elements for monitoring the Ag+ ion concentration in the two half-cells have been introduced and the operations necessary to keep the electrochemical reactions under strict control have been identified and tested. The solution stability, the residue recovery, the O2 prevention and the solution filtering process without its transfer to other containers are other merits. The electrical charge measurement equipment has been assembled and integrated with the one for monitoring the reaction parameters. A control apparatus displaying when some specific operations in the two half-cells are required has been added. The measurements showed that by employing the setup assembled with some proper precautions an uncertainty of about 1-2 parts in 105 can be reached, mainly limited by the silver purity, and the evolution toward a measurement system at a metrological level (parts in 106 or better) is attainable.
Energy Technology Data Exchange (ETDEWEB)
Solaimani, M.; Morteza, Izadifard [Faculty of Physics, Shahrood University of technology, Shahrood (Iran, Islamic Republic of); Arabshahi, H., E-mail: arabshahi@um.ac.ir [Department of Physics, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Physics Department, Payame Noor University, P.O. Box 19395-3697, Tehran (Iran, Islamic Republic of); Reza, Sarkardehi Mohammad [Physics Department, Al-Zahra University, Vanak, Tehran (Iran, Islamic Republic of)
2013-02-15
In this work, we have studied the effect of the number of the wells, in a multiple quantum wells structure with constant total effective length, on the optical properties of multiple quantum wells like the absorption coefficient and the refractive index by means of compact density matrix approach. GaAs/Al{sub x}Ga{sub (1-x)}As multiple quantum wells systems was selected as an example. Besides, the effect of varying number of wells on the subband energies, wave functions, number of bound states, and the Fermi energy have been also investigated. Our calculation revealed that the number of wells in a multiple quantum well is a criterion with which we can control the amount of nonlinearity. This study showed that for the third order refractive index change there is two regimes of variations and the critical well number was six. In our calculations, we have used the same wells and barrier thicknesses to construct the multiple quantum wells system. - Highlights: Black-Right-Pointing-Pointer OptiOptical Non-Linear. Black-Right-Pointing-Pointer Total Effective Length. Black-Right-Pointing-Pointer Multiple Quantum Wells System - genetic algorithm Black-Right-Pointing-Pointer Schroedinger equation solution. Black-Right-Pointing-Pointer Nanostructure.
Ashenfelter, T P; Olive, Keith A; Ashenfelter, Timothy P.; Mathews, Grant J.; Olive, Keith A.
2004-01-01
Evidence from a large sample of quasar absorption-line spectra in damped Lyman-alpha systems has suggested a possible time variation of the fine structure constant alpha. The most statistically significant portion of this sample involves the comparison of Mg and Fe wavelength shifts using the many-multiplet (MM) method. However, the sensitivity of this method to the abundance of heavy isotopes, especially Mg, is enough to imitate an apparent variation in alpha in the redshift range 0.5 < z < 1.8. We implement recent yields of intermediate mass (IM) stars into a chemical evolution model and show that the ensuing isotope distribution of Mg can account for the observed variation in alpha. As such, these observations of quasar absorption spectra can be used to probe the nucleosynthetic history of low-metallicity damped Lyman-$\\alpha$ systems in the redshift range 0.5 < z < 1.8. This analysis, in conjunction with other abundance measurements of low-metallicity systems, reinforces the mounting evidence ...
JIANG Xing-fang; LIYan-ji; Jiang, Hong
2012-01-01
The Planck constant is an important constant inmodern physics. Its experimental verification isgenerally by the experiment of photoelectric effect.The data processing is very complex. In order tosimplify the complex question the intelligent system“Measuring of the Planck constant withphotoelectric effect” had been developed withmultimedia authoring tool Multimedia ToolBook. Theexperimental data was of large number that obtainedby user after the leakage current between electrodesand the anode ...
Radiographic constant exposure technique
DEFF Research Database (Denmark)
Domanus, Joseph Czeslaw
1985-01-01
The constant exposure technique has been applied to assess various industrial radiographic systems. Different X-ray films and radiographic papers of two producers were compared. Special attention was given to fast film and paper used with fluorometallic screens. Radiographic image quality...... was tested by the use of ISO wire IQI's and ASTM penetrameters used on Al and Fe test plates. Relative speed and reduction of kilovoltage obtained with the constant exposure technique were calculated. The advantages of fast radiographic systems are pointed out...
Brokaw, R. S.; Brabbs, T. A.; Snyder, C. A.
1985-01-01
Exponential free radical growth constants have been measured for ethane carbon monoxide oxygen mixtures by monitoring the growth of oxygen atom concentration as manifested by CO flame band emission. Data were obtained over the temperature range of 1200 to 1700 K. The data were analyzed using an ethane oxidation mechanism involving seven elementary reaction steps. Calculated growth constants were close to experimental values at lower temperatures, up to about 1400 K, but at higher temperatures computed growth constants were considerably smaller than experiment. In attempts to explain these results additional branching reactions were added to the mechanism. However, these additional reactions did not appreciably change calculated growth constants.
Kotuš, Srđan M; Carswell, Robert F
2016-01-01
The brightest southern quasar above redshift $z=1$, HE 0515$-$4414, with its strong intervening metal absorption-line system at $z_{abs}=1.1508$, provides a unique opportunity to precisely measure or limit relative variations in the fine-structure constant ($\\Delta\\alpha/\\alpha$). A variation of just $\\sim$3 parts per million (ppm) would produce detectable velocity shifts between its many strong metal transitions. Using new and archival observations from the Ultraviolet and Visual Echelle Spectrograph (UVES) we obtain an extremely high signal-to-noise ratio spectrum (peaking at S/N $\\approx250$ pix$^{-1}$). This provides the most precise measurement of $\\Delta\\alpha/\\alpha$ from a single absorption system to date, $\\Delta\\alpha/\\alpha=-1.42\\pm0.55_{\\rm stat}\\pm0.65_{\\rm sys}$ ppm, comparable with the precision from previous, large samples of $\\sim$150 absorbers. The largest systematic error in all (but one) previous similar measurements, including the large samples, was long-range distortions in the wavelengt...
Fenner, Y; Gibson, B K
2005-01-01
At redshifts z_abs < 2, quasar absorption-line constraints on space-time variations in the fine-structure constant, alpha, rely on the comparison of MgII and FeII transition wavelengths. One potentially important uncertainty is the relative abundance of Mg isotopes in the absorbers which, if different from solar, can cause spurious shifts in the measured wavelengths and, therefore, alpha. Here we explore chemical evolution models with enhanced populations of intermediate-mass (IM) stars which, in their asymptotic giant branch (AGB) phase, are thought to be the dominant factories for heavy Mg isotopes at the low metallicities typical of quasar absorption systems. By design, these models partially explain recent Keck/HIRES evidence for a smaller alpha in z_abs < 2 absorption clouds than on Earth. However, such models also over-produce N, violating observed abundance trends in high-z_abs damped Lyman-alpha systems (DLAs). Our results do not support the recent claim of Ashenfelter, Mathews & Olive (2004...
Structure of the group-constant-library GRUBA and its management by the program-system GRUMA
International Nuclear Information System (INIS)
For nuclear calculations of Fast Reactors a chain of programs and associated data libraries has been established and successfully applied at KfK. Starting from energy-dependent probabilities for interactions between neutrons and isotopes, they allow to derive - as an intermediate step - averaged energygroup-dependent data stored on the GRUBA-file, which eventually are used to calculate the characteristic nuclear parameters of a reactor under investigation. The GRUBA-file contains material- and reaction-type-dependent group-cross-sections and similar quantities combined in a so called set of group-constants. The file is managed by the program-system GRUMA, which allows to open a new file and to change an existing one, to prepare input-files, to document changes and to print data contained in the GRUBA-file. For practical work with GRUMA and GRUBA the present report replaces the old report KfK 1815; it includes all new options of general character. (orig.)
Stearn, A E
1927-01-20
From the solubility minimum the value of the basic ionization constant of sulfanilic acid is shown to lie probably between the values 1.7 x 10(-15) and 3.2 x 10(-15). From solubility measurements the value of this same constant is shown to lie probably between 2.0 and 2.2 x 10(-15), and the isoelectric point of sulfanilic acid is thus at a cH of 0.056 or a pH of 1.25. From conductivity ratios the acid ionization constant of sulfanilic acid is shown to be 7.05 x 10(-4) at room temperature (21 degrees C.). Calculations are made, from data published in preceding papers, of the ionization constants of glycine, K(a) being 2.3 x 10(-10), and K(b) being 2.2 x 10(-12).
Institute of Scientific and Technical Information of China (English)
蔡红梅
2015-01-01
通过设计回转窑熟料烧成系统分解炉(DDF炉)自动恒温控制系统,提高系统的稳定性和可靠性.传统的DDF炉自动恒温控制系统的数据采集及温度控制单元采用有源晶振A/D时钟采样控制方法,导致基线漂移,恒温控制性能不好.提出一种基线漂移交流耦合控制的DDF炉自动恒温控制系统设计方法.在炉内温度离散采集的基础上,进行温度控制曲线拟合,设计基线漂移交流耦合控制的DDF炉自动恒温控制算法,实现对DFF炉温度控制的优化预测,进行硬件电路设计,实现对自动恒温控制系统设计和改进.仿真结果表明,该系统能有效避免恒温控制中的基线漂移,温度跟踪性能较好,具有较好的稳定输出,能有效应用在DDF炉恒温控制中.%The automatic constant temperature control system of the clinker burning system of rotary kiln (DDF) is designed, and the stability and reliability of the system are improved.. Traditional DDF furnace automatic constant temperature con-trol system of the data acquisition system and the temperature control unit using active crystal A/D sampling clock control method, resulting in the baseline drift and constant temperature control performance is not good. A design method of auto-matic constant temperature control system for DDF furnace is presented, which is controlled by the exchange and coupling of the baseline drift. In furnace based on discrete temperature acquisition, temperature control curve fitting and control de-sign baseline drift AC coupled DDF furnace automatic constant temperature control algorithm to achieve on DFF furnace temperature control optimization prediction, hardware circuit design and Realization of automatic constant temperature con-trol system design and improvement. The simulation results show that the system can effectively avoid the baseline drift in the constant temperature control, the temperature tracking performance is good, and has good stable output
The Vehicle Hydraulic Constant Speed Power Generation System%一种车载液压恒速发电系统
Institute of Scientific and Technical Information of China (English)
卢学渊; 杨红; 白清鹏
2015-01-01
The parking or driving in the car engine with constant or variable speed drive L10V constant pressure/flow variable pump, using the fixed throttle hole in the outlet of the variable pump and the throttle pressure feedback back to the control variable pump export, so that the output and load constant flow independent drive hydraulic motor constant speed, constant speed hydraulic motor to drive the permanent magnet generator to generate electricity. The vehicle constant speed hydraulic power generation system has the features of parking or driv-ing power generation, control, large unit weight, compact size and so on..%驻车或行驶中的汽车发动机以恒定或变化转速驱动L10V恒压/流量变量泵,在变量泵出口采用所需的固定节流孔,并把节流孔后压力反馈回变量泵控制口,使之输出与负载无关的恒定流量驱动液压马达恒速运转,恒速液压马达再驱动永磁发电机进行发电.该车载恒速液压发电系统具有驻车或行车发电功能、控制简单、单位重量功率大、体积小巧等特点.
International Nuclear Information System (INIS)
A method is presented for the calculation of association constants and the concentration of binding sites in a reaction of a ligand with a heterogeneous system of binding sites. The Scatchard plot for such a system is curvelinear and the method employs previously established relationships between the parameters of the limiting slopes to such a curve and the above mentioned association constants and concentrations of binding sites. The special case of a system with two different and non-interacting groups of binding sites was solved. The expressions thus obtained were used to characterize the reaction of a polypeptide neurotoxin with its specific binding sites in a membranal preparation from insect central nervous system. Moreover it is evident from these expressions that the widely accepted method to analyze such system, by an intuitive generalization of the method applicable to homogeneous systems, is erroneous and should be avoided. (author)
Little, Steven G.; Akin-Little, Angeleque; Newman-Eig, Lynne M.
2010-01-01
The present study sought to evaluate the efficacy of an interdependent group contingency program on increasing homework completion and accuracy rates in fourth grade students in an elementary school. In addition, the present study attempted to determine whether randomized reinforcement was more effective than constant reinforcement. Overall, the…
Heffler, Michael A.; Walters, Ryan D.; Kugel, Jennifer F.
2012-01-01
An undergraduate biochemistry laboratory experiment is described that will teach students the practical and theoretical considerations for measuring the equilibrium dissociation constant (K[subscript D]) for a protein/DNA interaction using electrophoretic mobility shift assays (EMSAs). An EMSA monitors the migration of DNA through a native gel;…
International Nuclear Information System (INIS)
The reaction of the immune system on the constant exposure to the radiation of the Chernobyl discharge during the life of several generations of laboratory animals. It has been shown that the exposed animals (irrespective of the line, generation and sex) differ considerably from the controls both in definite immune characteristics (30-70% of the studied parameters) and in sensitivity to grippe virus
Eggert, Th.; Geilenkeuser, R.; Jäckel, M.
2000-07-01
We have measured the dielectric response ε( ω) and the thermal conductivity κ of polystyrene (PS) and of polycarbonate (PC) under high hydrostatic pressure (0.1 MPa
constant Ci can be determined. These results show that the product P¯γ l,t2 of the standard tunnelling model (STM) scales with the pressure-dependent elastic constants c11 and c44.
Criteria for the Degree of Stability of the Linear Constant Systems%线性定常系统稳定度的判据
Institute of Scientific and Technical Information of China (English)
王广彬; 潘宝珍; 侯文渊
2004-01-01
There are various applications of the stability theory of the first-order dynamical systems.And the stability of the non-linear control systems can be determined by its linear part.In practice, it is not enough to know the stability of the dynamical systems.Sometimes we must know the degree of stability of these systems.In this paper, we present some criteria for the degree of stability of the linear constant systems, by using the entries of the coefficient matrix A only.
Institute of Scientific and Technical Information of China (English)
杨德福
2016-01-01
Introduced the characteristics of the ancient library and HVAC system in the library of Liaoning Province, analyzes the scheme selection of the constant temperature and humidity air conditioning system and the cold and heat sources, summarizes the necessary technical measures and experience during the design of constant temperature and humidity air conditioning system, in order to provide a reference for design.%介绍了辽宁省图书馆古籍库及其暖通空调系统的特点，分析了其恒温恒湿空调系统方案选择及冷热源选择，总结了古籍库恒温恒湿空调系统设计的必要技术措施和体会，以供设计参考。
International Nuclear Information System (INIS)
As of February 3, 1975, 175 neutron group constants had been derived from the Evaluated Nuclear Data Library (ENDL) at LLL. In this volume, tables and graphs of the constants are presented along with the conventions used in their preparation. (U.S.)
Energy Technology Data Exchange (ETDEWEB)
Correa, Eduardo de L.; Vivolo, Vitor; Potiens, Maria da Penha A., E-mail: vivolo@ipen.b, E-mail: mppalbu@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)
2011-07-01
The PPV is an electrical quantity that relates the peak voltage with the radiological image contrast, thus having a larger clinical application. By definition, in an X-ray system, the 'PPV is a quantity based on the concept that the radiation generated by a high voltage source with an arbitrary wave source produces the same radiographic contrast that the radiation generated by a high voltage source with an equivalent constant potential'. The Instruments Calibration Laboratory (LCI) of IPEN has the mammography qualities established in a constant potential system (industrial X-ray system), and also in a clinical system (mammograph). The objective of this study was to analyze the PPV behavior in these systems, and try to reach calibration conditions that are more similar to the work conditions in hospitals and clinics. For this, it was used an industrial X-ray (constant potential) and a mammography system (high frequency). The first system has a tungsten (W) target, and additional filtration of aluminum (Al) and molybdenum (Mo), and the second one has a Mo target and additional filtration of Mo and rhodium (Rh). A non-invasive measuring system from PTW model Diavolt was used to PPV determination. The voltages used were 25 kV, 28 kV, 30 kV and 35 kV (calibration qualities in mammography, according to the IEC 61267). The Diavolt was placed one meter from the focal spot in the industrial X-ray system, and 60 cm for the clinical system. (author)
Cosmological Hubble constant and nuclear Hubble constant
International Nuclear Information System (INIS)
The evolution of the Universe after the Big Bang and the evolution of the dense and highly excited nuclear matter formed by relativistic nuclear collisions are investigated and compared. Values of the Hubble constants for cosmological and nuclear processes are obtained. For nucleus-nucleus collisions at high energies the nuclear Hubble constant is obtained in the frame of different models involving the hydrodynamic flow of the nuclear matter. Significant difference in the values of the two Hubble constant - cosmological and nuclear - is observed
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In this paper, the air-water vapor-water system is taken as an example, and the formula of constantpressure specific heat during non-equilibrium phase change process in the two-phase flow system is deduced using the theory of two-phase flow and thermophysics. The constant-pressure specific heat of non-equilibrium phase change process is calculated with the corresponding numerical model, and the numerical results are compared to those of the equilibrium phase change process. It is shown that in evaporation process, the variational rate of the non-equilibrium specific heat increases with increasing initial fluid temperature and particle mass fraction. The smaller particle radius is, the faster the variational rate is. Meanwhile, the constant-pressure specific heat of equilibrium process is higher than that of the non-equilibrium process all the time.
Mohammed, Saif Khan
2011-01-01
We consider downlink cellular multi-user communication between a base station (BS) having N antennas and M single-antenna users, i.e., an N X M Gaussian Broadcast Channel (GBC). Under an average only total transmit power constraint (APC), large antenna arrays at the BS (having tens to a few hundred antennas) have been recently shown to achieve remarkable multi-user interference (MUI) suppression with simple precoding techniques. However, building large arrays in practice, would require cheap/power-efficient Radio-Frequency(RF) electronic components. The type of transmitted signal that facilitates the use of most power-efficient RF components is a constant envelope (CE) signal. Under certain mild channel conditions (including i.i.d. fading), we analytically show that, even under the stringent per-antenna CE transmission constraint (compared to APC), MUI suppression can still be achieved with large antenna arrays. Our analysis also reveals that, with a fixed M and increasing N, the total transmitted power can b...
International Nuclear Information System (INIS)
Highlights: • A new set of Henry’s constant for the system carbon dioxide-aqueous deep eutectic solvents were measured. • The DESs used were: ethaline, glyceline, and maline. • The measured data were reported as functions of temperature and composition. • The measured data were represented satisfactorily by the applied correlations. -- Abstract: In this study, we present a new set of Henry’s constant data for the system carbon dioxide-aqueous deep eutectic solvent (DES) (20 to 80 wt% DES) at T = (303.15, 308.15, and 313.15) K. The DESs used were choline chloride-based: ethaline (choline chloride/ethylene glycol), glyceline (choline chloride/glycerol), and maline (choline chloride/malonic acid). A differential Henry’s coefficient model was used to describe the behaviour of Henry’s constant, and correlate it with temperature and concentration of DES in the aqueous DES solution. The correlation was found satisfactory such that the proposed model can be used in engineering calculations with reasonable accuracy
Benard, P
2003-01-01
The linearization of the meteorological equations around a specified reference state, usually applied in NWP to define the linear system of constant-coefficients semi-implicit schemes, is outlined as an unnecessarily restrictive approach which may be detrimental in terms of stability. It is shown theoretically that an increased robustness can sometimes be obtained by choosing the reference linear system in a wider set of possibilities. The potential benefits of this new approach are illustrated in two simple examples. The advantage in robustness is not obtained at the price of an increased error or complexity.
Ion exchange equilibrium constants
Marcus, Y
2013-01-01
Ion Exchange Equilibrium Constants focuses on the test-compilation of equilibrium constants for ion exchange reactions. The book first underscores the scope of the compilation, equilibrium constants, symbols used, and arrangement of the table. The manuscript then presents the table of equilibrium constants, including polystyrene sulfonate cation exchanger, polyacrylate cation exchanger, polymethacrylate cation exchanger, polysterene phosphate cation exchanger, and zirconium phosphate cation exchanger. The text highlights zirconium oxide anion exchanger, zeolite type 13Y cation exchanger, and
Varying constants, Gravitation and Cosmology
Uzan, Jean-Philippe
2010-01-01
Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. It is thus of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We thus detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, Solar system observations, meteorites dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describ...
Surfaces of a Constant Negative Curvature
Directory of Open Access Journals (Sweden)
G. M. Gharib
2012-01-01
Full Text Available I study the geometric notion of a differential system describing surfaces of a constant negative curvature and describe a family of pseudospherical surfaces for the nonlinear partial differential equations with constant Gaussian curvature .
Nadia Afrin; Monirul Islam; Anarul Islam
2015-01-01
Recently, transformerless inverters are becoming more attractive for grid-tied photovoltaic (PV) system because of high efficiency and low cost. Unfortunately, leakage current may flow through the whole grid-tied PV system due to fluctuating common mode (CM) voltage that depends on the topology structure and control strategy. Therefore, to meet the safety regulations, leakage current of transformerless PV inverter has to be addressed carefully. In this paper, a new microcontroller based trans...
Lie, Svenn Arne
2006-01-01
When studying the party system formation in post-communist Lithuania, the Western European theoretical framework is a useful, although not sufficient tool to understand this process. Weak alignments between voters and parties and unstable party systems have made it difficult to apply the Western European theoretical framework because it prerequisites a high degree of party institutionalisation. In addition to unstable electoral support for the established parties, new parties s...
International Nuclear Information System (INIS)
A modular code system RADHEAT-V4 has been developed for performing precisely neutron and photon transport analyses, and shielding safety evaluations. The system consists of the functional modules for producing coupled multi-group neutron and photon cross section sets, for analyzing the neutron and photon transport, and for calculating the atom displacement and the energy deposition due to radiations in nuclear reactor or shielding material. A precise method named Direct Angular Representation (DAR) has been developed for eliminating an error associated with the method of the finite Legendre expansion in evaluating angular distributions of cross sections and radiation fluxes. The DAR method implemented in the code system has been described in detail. To evaluate the accuracy and applicability of the code system, some test calculations on strong anisotropy problems have been performed. From the results, it has been concluded that RADHEAT-V4 is successfully applicable to evaluating shielding problems accurately for fission and fusion reactors and radiation sources. The method employed in the code system is very effective in eliminating negative values and oscillations of angular fluxes in a medium having an anisotropic source or strong streaming. Definitions of the input data required in various options of the code system and the sample problems are also presented. (author)
Directory of Open Access Journals (Sweden)
Rongsheng Liu
2015-01-01
Full Text Available Vibration of the boom system is inevitably caused by periodic disturbances, which are induced by pumping concrete. In this paper, an active control strategy of constant-position commandless input shaping technique is developed to suppress vibration. Based on a set of independent modal equations obtained by adopting modal approach, the double-impulse control with reverse direction is proposed, which is aiming at not only suppressing vibration, but also avoiding the variation of the equilibrium position of the boom system after active control action. And the characteristic of time-lag existing in real system is also taken into account for optimizing the control action. Experiments of vibration control were implemented on a 52-meter-long five-boom system to verify the proposed control strategy.
Meagher, Daniel T; Latimer, Federico G; Sutter, W Wes; Saville, William J A
2006-06-15
OBJECTIVE-To determine clinical findings and outcome in horses treated by means of a balloon constant rate infusion system. DESIGN-Retrospective case series. ANIMALS-23 horses. PROCEDURES-Medical records of horses examined at The Ohio State University veterinary teaching hospital from 2002 to 2005 that had septic arthritis, septic tenosynovitis, or penetration of a synovial structure and in which treatment involved a balloon constant rate infusion system were searched. Information pertaining to signalment, history, physical examination findings, clinicopathologic data, treatment, and duration of hospitalization was recorded. RESULTS-Mean+/- SD duration of hospitalization was 11.5+/-5.26 days. No correlation between duration of clinical signs and duration of hospitalization or duration of infusion pump use was detected, but correlations between WBC count and duration of hospitalization and WBC and duration of infusion-pump use were observed. All horses survived to discharge. Follow-up information was obtained on 17 horses, 16 of which were alive at the time of follow-up. Twelve of 13 horses for which followup information was available for at least 5 months were alive 5 months or longer after discharge. Thirteen of the 16 horses alive at follow-up were reported by owners as not lame, whereas the remaining 3 were mildly lame or intermittently moderately lame or had developed angular limb deformity in the contralateral limb. CONCLUSIONS AND CLINICAL RELEVANCE-Balloon constant rate infusion systems may be used effectively in treatment of septic arthritis, septic tenosynovitis, and contaminated synovial wounds. Clinical response and long-term outcome appeared to be comparable to results obtained with other techniques.
Varying Constants, Gravitation and Cosmology
Uzan, Jean-Philippe
2011-12-01
Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.
Varying Constants, Gravitation and Cosmology
Directory of Open Access Journals (Sweden)
Jean-Philippe Uzan
2011-03-01
Full Text Available Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.
Spruit, Martijn A.; Troosters, Thierry; Gosselink, Rik; Kasran, Ahmad; Decramer, Marc
2007-01-01
Study objectives: To explore the acute systemic inflammatory and anabolic effects of cycling in hospital admitted patients with chronic obstructive pulmonary disease (COPD) and in patients with clinically stable disease. Design: Cross-sectional comparative study. Setting: University Hospital Gasthuisberg, a tertiary care setting. Patients: 16 patients with clinically stable COPD (no acute exacerbation in the past 12 weeks; median age: 73 years (IQR: 60 to 75); median forced expiratory volume ...
De Martino, Salvatore; De Siena, Silvio; Illuminati, Fabrizio
1999-01-01
The possibility is discussed of inferring or simulating some aspects of quantum dynamics by adding classical statistical fluctuations to classical mechanics. We introduce a general principle of mechanical stability and derive a necessary condition for classical chaotic fluctuations to affect confined dynamical systems, on any scale, ranging from microscopic to macroscopic domains. As a consequence we obtain, both for microscopic and macroscopic aggregates, dimensional relations defining the m...
Directory of Open Access Journals (Sweden)
S. M. Tebcheran
2003-04-01
in small concentrations as densifying aids for this oxide. In the present study the sintering kinetics of tin oxide was studied considering the effect of sintering atmosphere and of the MnO2 concentration. SnO2-MnO2 systems were prepared from the polymeric precursors method and the obtained powders were characterized by surface area by the BET method. SnO2 powders with varied MnO2 concentrations were pressed in cylindrical shape, and sintered in a dilatometer furnace with constant heating rate and controlled atmospheres. Sintered samples were characterized by scanning electron microscopy. The influence of atmosphere (argon, air or CO2 as well as of the MnO2 concentrations on the sintering kinetics was determined. The kinetics data of linear shrinkage were analyzed in terms of kinetic models for the initial stage of sintering (Woolfrey and Bannister as well as for the global sintering (Su e Johnson allowing the determination of the apparent activation energy. Following the determination of the master sintering curve the apparent activation energy of all sintering process were determined as well as its dependence with the atmosphere and manganese concentrations. Based on these values and on the n exponent, determined by the classical grain growth equation, it was concluded that the most probable sintering mechanism is grain boundary diffusion with surface redistribution controlling the kinetics.
International Nuclear Information System (INIS)
The library of atomic masses and characteristic constants for nuclear ground states, a sub-library of Chinese Evaluated Nuclear Parameter Library (CENPL), consists of two parts: the data file and management-retrieval code system. The former stores the nuclear basic data, such as the mass excesses, abundances and half-lives, spines and parities of the nuclear ground states. The latter is developed to retrieve the data stored in the data file. It can also derive the separation energies of some particles and particle groups and β-decay energies; nuclear reaction energies and the corresponding threshold energies for some neutron reaction channels including the third reaction process could also be obtained as combinations of different mass excesses. The function, feature and operation instruction of the code system are described briefly
Local Experiments See Cosmologically Varying Constants
Shaw, D J; Barrow, John D.; Shaw, Douglas J.
2006-01-01
We describe a rigorous construction, using matched asymptotic expansions, which establishes under very general conditions that local terrestrial and solar-system experiments will measure the effects of varying `constants' of Nature occurring on cosmological scales to computable precision. In particular, `constants' driven by scalar fields will still be found to evolve in time when observed within virialised structures like clusters, galaxies, and planetary systems. This provides a justification for combining cosmological and terrestrial constraints on the possible time variation of many assumed `constants' of Nature, including the fine structure constant and Newton's gravitation constant.
风电互补恒压供水系统控制器的设计%Controller Design of Wind Power Constant Pressure Water Supply System
Institute of Scientific and Technical Information of China (English)
齐保良; 杨宝昆
2011-01-01
For reducing the energy consumption of constant pressure water supply system? Wind power is used as assistant energy and wind power constant pressure water supply system is designed on the basis of fuzzy control and PLC controller. When the wind power is enough to driving pump, the PLC controls electric regulating valve to cope with discharge of water supply branch for making the water pressure of pipe networks within the given range. Otherwise, the PLC keeps the head of the water supply branch within the designed scope. At the same time, the rotational speed of pump is adjusted to supplement the system requirement by PLC variable-frequency control. Thus, it realizes the reduction of power consumption by the automatic operation wind power.%为降低恒压供水系统的耗电量,将风能作为辅助动力源,通过PLC控制器,采用模糊控制技术设计了一种风电互补恒压供水系统.当风力机驱动泵供水量充足时,PLC调节电动调节阀以控制风力供水支路的流量,使管网压力保持于设定范围内;当风力供水不足时,PLC调节电动调节阀使风力供水支路的扬程达到设定值.同时,PLC通过变频调速方式,调节电动泵的转速以补充系统所需,实现了风力自动投入以减少电力消耗的目的.
Ziganshin, Ayrat M; Schmidt, Thomas; Lv, Zuopeng; Liebetrau, Jan; Richnow, Hans Hermann; Kleinsteuber, Sabine; Nikolausz, Marcell
2016-10-01
The effects of hydraulic retention time (HRT) reduction at constant high organic loading rate on the activity of hydrogen-producing bacteria and methanogens were investigated in reactors digesting thin stillage. Stable isotope fingerprinting was additionally applied to assess methanogenic pathways. Based on hydA gene transcripts, Clostridiales was the most active hydrogen-producing order in continuous stirred tank reactor (CSTR), fixed-bed reactor (FBR) and anaerobic sequencing batch reactor (ASBR), but shorter HRT stimulated the activity of Spirochaetales. Further decreasing HRT diminished Spirochaetales activity in systems with biomass retention. Based on mcrA gene transcripts, Methanoculleus and Methanosarcina were the predominantly active in CSTR and ASBR, whereas Methanosaeta and Methanospirillum activity was more significant in stably performing FBR. Isotope values indicated the predominance of aceticlastic pathway in FBR. Interestingly, an increased activity of Methanosaeta was observed during shortening HRT in CSTR and ASBR despite high organic acids concentrations, what was supported by stable isotope data.
Vidal, C. R.; Stwalley, W. C.
1982-01-01
The molecular constants and their adiabatic corrections have been determined for the (A 1 Sigma +) - (X 1 Sigma +) system of the isotopic lithium hydrides: (Li-6)H, (Li-7)H, (Li-6)D, and (Li-7)D. Using a fully quantum mechanical variational method, the potential energy curves (IPA potentials) are determined. Extending the variational method, we have obtained for the first time adiabatic corrections of potential energy curves from isotopic spectroscopic data. A significant difference between the potential energy curves of the lithium hydrides and the lithium deuterides has been observed. When Li-6 was replaced by Li-7, a significant difference was only observed for the (A 1 Sigma +) state, but not for the (X 1 Sigma +) state.
Ziganshin, Ayrat M; Schmidt, Thomas; Lv, Zuopeng; Liebetrau, Jan; Richnow, Hans Hermann; Kleinsteuber, Sabine; Nikolausz, Marcell
2016-10-01
The effects of hydraulic retention time (HRT) reduction at constant high organic loading rate on the activity of hydrogen-producing bacteria and methanogens were investigated in reactors digesting thin stillage. Stable isotope fingerprinting was additionally applied to assess methanogenic pathways. Based on hydA gene transcripts, Clostridiales was the most active hydrogen-producing order in continuous stirred tank reactor (CSTR), fixed-bed reactor (FBR) and anaerobic sequencing batch reactor (ASBR), but shorter HRT stimulated the activity of Spirochaetales. Further decreasing HRT diminished Spirochaetales activity in systems with biomass retention. Based on mcrA gene transcripts, Methanoculleus and Methanosarcina were the predominantly active in CSTR and ASBR, whereas Methanosaeta and Methanospirillum activity was more significant in stably performing FBR. Isotope values indicated the predominance of aceticlastic pathway in FBR. Interestingly, an increased activity of Methanosaeta was observed during shortening HRT in CSTR and ASBR despite high organic acids concentrations, what was supported by stable isotope data. PMID:26853042
International Nuclear Information System (INIS)
A constant of motion is defined for a one-dimensional and nth-differenital-order autonomous svstem. A generalization of the Legendre transformation is given that allows one to obtain a relation among the constant of motion the Lagrangian, and the Hamiltonian. The approach is used to obtain the constant of motion associated with the nonrelativistic third-differential-order Abraham-Lorentz radiation damping equation
Variation of Fundamental Constants
Flambaum, V. V.
2006-11-01
Theories unifying gravity with other interactions suggest temporal and spatial variation of the fundamental ``constants'' in expanding Universe. The spatial variation can explain a fine tuning of the fundamental constants which allows humans (and any life) to appear. We appeared in the area of the Universe where the values of the fundamental constants are consistent with our existence. We present a review of recent works devoted to the variation of the fine structure constant α, strong interaction and fundamental masses. There are some hints for the variation in quasar absorption spectra. Big Bang nucleosynthesis, and Oklo natural nuclear reactor data. A very promising method to search for the variation of the fundamental constants consists in comparison of different atomic clocks. Huge enhancement of the variation effects happens in transition between accidentally degenerate atomic and molecular energy levels. A new idea is to build a ``nuclear'' clock based on the ultraviolet transition between very low excited state and ground state in Thorium nucleus. This may allow to improve sensitivity to the variation up to 10 orders of magnitude! Huge enhancement of the variation effects is also possible in cold atomic and molecular collisions near Feshbach resonance.
Algorithm for structure constants
Paiva, F M
2011-01-01
In a $n$-dimensional Lie algebra, random numerical values are assigned by computer to $n(n-1)$ especially selected structure constants. An algorithm is then created, which calculates without ambiguity the remaining constants, obeying the Jacobi conditions. Differently from others, this algorithm is suitable even for poor personal computer. ------------- En $n$-dimensia algebro de Lie, hazardaj numeraj valoroj estas asignitaj per komputilo al $n(n-1)$ speciale elektitaj konstantoj de strukturo. Tiam algoritmo estas kreita, kalkulante senambigue la ceterajn konstantojn, obeante kondicxojn de Jacobi. Malsimile al aliaj algoritmoj, tiu cxi tauxgas ecx por malpotenca komputilo.
Huchra, John P.
1992-01-01
The Hubble constant is the constant of proportionality between recession velocity and distance in the expanding universe. It is a fundamental property of cosmology that sets both the scale and the expansion age of the universe. It is determined by measurement of galaxy radial velocities and distances. Although there has been considerable progress in the development of new techniques for the measurements of galaxy distances, both calibration uncertainties and debates over systematic errors remain. Current determinations still range over nearly a factor of 2; the higher values favored by most local measurements are not consistent with many theories of the origin of large-scale structure and stellar evolution.
Energy Technology Data Exchange (ETDEWEB)
Nobrega, Juraci Carlos de Castro
1989-07-01
The stead-state analysis of a Wind Energy Conversion Systems, consisting on a Windmill, Synchronous Generator, transmission Line and Induction Motor driving a Centrifugal Pump is developed. The performance of the system operating at variable Speed with a flux control is examined using mathematical and digital simulation. The control scheme is proposed and tested in laboratory and a tested in laboratory and a test centre to be compared with simulation results. (author)
Scott, Tricia
2015-11-01
Compassion is a powerful word that describes an intense feeling of commiseration and a desire to help those struck by misfortune. Most people know intuitively how and when to offer compassion to relieve another person's suffering. In health care, compassion is a constant; it cannot be rationed because emergency nurses have limited time or resources to manage increasing demands.
1995-08-01
about the distances to galaxies and thereby about the expansion rate of the Universe. A simple way to determine the distance to a remote galaxy is by measuring its redshift, calculate its velocity from the redshift and divide this by the Hubble constant, H0. For instance, the measured redshift of the parent galaxy of SN 1995K (0.478) yields a velocity of 116,000 km/sec, somewhat more than one-third of the speed of light (300,000 km/sec). From the universal expansion rate, described by the Hubble constant (H0 = 20 km/sec per million lightyears as found by some studies), this velocity would indicate a distance to the supernova and its parent galaxy of about 5,800 million lightyears. The explosion of the supernova would thus have taken place 5,800 million years ago, i.e. about 1,000 million years before the solar system was formed. However, such a simple calculation works only for relatively ``nearby'' objects, perhaps out to some hundred million lightyears. When we look much further into space, we also look far back in time and it is not excluded that the universal expansion rate, i.e. the Hubble constant, may have been different at earlier epochs. This means that unless we know the change of the Hubble constant with time, we cannot determine reliable distances of distant galaxies from their measured redshifts and velocities. At the same time, knowledge about such change or lack of the same will provide unique information about the time elapsed since the Universe began to expand (the ``Big Bang''), that is, the age of the Universe and also its ultimate fate. The Deceleration Parameter q0 Cosmologists are therefore eager to determine not only the current expansion rate (i.e., the Hubble constant, H0) but also its possible change with time (known as the deceleration parameter, q0). Although a highly accurate value of H0 has still not become available, increasing attention is now given to the observational determination of the second parameter, cf. also the Appendix at the
International Nuclear Information System (INIS)
A new definition for the electrochemical cell constant in conductivity measurements is presented in this paper. Electrochemical Impedance Spectroscopy and DC pulses measurements have been carried out in non-Faradaic conditions in order to evaluate the effects of the cell geometry. The results obtained demonstrate that conductivity measurements are affected not only by the electrodes surface and separation but also by the cross section of the electrochemical cell. In order to obtain a linear behavior of the resistance versus the distance between electrodes, the cross section of the cell should be equal to the electrodes surface. Differences between the cell cross section and the electrodes surface produce a heterogeneous distribution of the electric field that causes the non-linear behavior for low values of the electrodes separation. This study shows that the reproducibility in electronic tongue and humid electronic nose measurements can be improved by designing an electrochemical cell structure that warrants a homogeneous distribution of the electrical field, which results in a reduction of the detection threshold in these types of system
Studies in the system MgO-SiO2-CO2-H2O(I): The activity-product constant of chrysotile
Hostetler, P.B.; Christ, C.L.
1968-01-01
Chrysotile dissolves congruently in water according to the reaction: Mg3Si2O6(OH)4c + 5H2Ol = 3Mgaq2+ + 6OHaq- + 2H4SiO4aq. Experimental determination of the activity-product constant of chrysotile, Kchr = [Mg2+]3[OH-]6[H4SiO4aq]2, at 90??C, yields the value of Kchr = 10-49.2 ?? 100.5. A synthetic sample and a natural sample from New Idria, California, were used in the determination. Values of Kchr were calculated for temperatures ranging from 0??C to 200??C, using the thermochemical data of King et al. (1967) for chrysotile and antigorite, various solubility data for silica, and ionic partial molal heat capacities estimated by the method of criss and Cobble (1964a). Kchr is 10-54.1 at 0??C, rises to a maximum value of 10-48.5 at approximately 135??C, and is 10-49.1 at 200??C (all values for the three-phase system, chrysotile plus solution plus vapor). The calculated 90??C value is 10-49.1, in excellent agreement with the experimental value; for 25??C, the calculated value is 10-50.8. ?? 1968.
Variation of fundamental constants
Flambaum, V V
2006-01-01
We present a review of recent works devoted to the variation of the fine structure constant alpha, strong interaction and fundamental masses. There are some hints for the variation in quasar absorption spectra, Big Bang nucleosynthesis, and Oklo natural nuclear reactor data. A very promising method to search for the variation of the fundamental constants consists in comparison of different atomic clocks. Huge enhancement of the variation effects happens in transition between accidentally degenerate atomic and molecular energy levels. A new idea is to build a ``nuclear'' clock based on the ultraviolet transition between very low excited state and ground state in Thorium nucleus. This may allow to improve sensitivity to the variation up to 10 orders of magnitude! Huge enhancement of the variation effects is also possible in cold atomic and molecular collisions near Feschbach resonance.
Aurich, R.; Steiner, F.
1992-07-01
Dynamical zeta functions, defined as Euler products over classical periodic orbits, have recently received enhanced attention as an important tool for the quantization of chaos. Their representation as a Dirichlet series over pseudo-orbits has proven to be particularly useful, since these series seem to possess in the general case much better convergence properties than the original Euler product. The convergence of the Dirichlet series depends crucially on the asymptotic distribution of the pseudo-orbits and thus on the ergodicity of the underlying dynamical system. It is shown that the lengths ln (or rather expln) of the classical periodic orbits play mathematically the role of generalized prime numbers. Based on the theory of Beurling's generalized prime numbers, we derive an exact law for the proliferation of psuedo-orbits for the Hadamard-Gutzwiller model, which is one of the main testing grounds of our ideas about quantum chaos. The strength of growth of the pseudo-orbits is determined by the ratio ZETA(2)/ZETA'(1), where ZETA(s) denotes the Selberg zeta function. Two explicit, complementary representations are given that allow the computation of this ratio solely from the length spectrum \\{ln\\} of the classical periodic orbits, or from the quantal energy spectrum \\{En\\}. One of these relations depends exponentially on the generalized Euler constant γΔ, which is therefore also studied. The formulas are applied to two strongly chaotic systems. It turns out that our asymptotic law describes the mean proliferation of pseudo-orbits very well not only in the asymptotic region, but also surprisingly well down to the shortest pseudo-orbit.
U.S. Geological Survey, Department of the Interior — This digital data set represents the constant head-boundary used to simulate ground-water inflow or outflow at the lateral boundary of the Death Valley regional...
Time-Varying Fundamental Constants
Olive, Keith
2003-04-01
Recent data from quasar absorption systems can be interpreted as arising from a time variation in the fine-structure constant. However, there are numerous cosmological, astro-physical, and terrestrial bounds on any such variation. These includes bounds from Big Bang Nucleosynthesis (from the ^4He abundance), the Oklo reactor (from the resonant neutron capture cross-section of Sm), and from meteoretic lifetimes of heavy radioactive isotopes. The bounds on the variation of the fine-structure constant are significantly strengthened in models where all gauge and Yukawa couplings vary in a dependent manner, as would be expected in unified theories. Models which are consistent with all data are severly challenged when Equivalence Principle constraints are imposed.
Institute of Scientific and Technical Information of China (English)
郑敦衍; 詹培德; 洪晓斌
2013-01-01
Facing to multistage hydraulic control problem of dishwasher and its feedwater electromagnetic valve performance testing, the process of electromagnetic valve performance testing was introduced and constant pressure&flow water supply system was designed based on the requirements of electromagnetic valve performance test. The constant pressure control circuit, constant flow control circuit, signal detection circuit of hall flow sensor and control software were designed through the analysis of constant pressure&flow water supply system principle. Finally, experiments were conducted in the constant pressure&flow water supply system. The experiment results showed that constant pressure&flow regulation was rapid, and the error between prevalue after the regulation and actual value was very small. Therefore, the constant pressure & flow water supply system can meet the testing requirements of various kinds of hydraulic pressures and water flow.%针对洗衣机及洗碗机进水电磁阀性能检测中的多级水压控制问题，首先介绍电磁阀性能测试流程，根据电磁阀性能测试要求进行恒压恒流供水系统设计。通过分析恒压恒流供水系统原理，设计出恒压控制电路、恒流控制电路、霍耳型流量传感器信号检测电路及控制流程，最后对恒压恒流供水系统进行应用实验。实验结果表明：恒压恒流调节控制快速，且调节后预置值与实际值误差较小，可以满足各种水压、水流量测试要求。
Institute of Scientific and Technical Information of China (English)
陈逸; 孙剑波; 韦忠朝
2012-01-01
在matlab／simulink中对一台三相12／8极开关磁阻发电机的变速恒压工作情况进行了建模仿真，通过SRMFEM建立了开关磁阻发电机非线性本体模型，这在一定程度上保证了仿真结果的准确性在自励发电模式下，通过对电压、电流的两点式闭环，探讨了变速恒压情况下开关磁阻发电机的动静态响应．仿真结果表明：开关磁阻发电系统在变速的情况下依然有很不错的发电特性．但是，在仿真结果中，同样也可以发现，因为开关磁阻发电机是一个多变量、强耦合的非线性系统，在能量转换的过程中，虽然有滤波电容的平波作用，输出直流电压的脉动还是无法避免，在一些应用要求较高的场合，须在动态响应和发电质量两者之间权衡优化控制策略及相关拓扑电路的设计是下一步研究的问题．%Due to the characteristics of high reliability, wide speed scope with high efficiency, and low cost, Switched Reluctance Generator （SRG） system is suitable for applications in the field of variable-speed con- stant-voltage generation, such as wind power generation, flywheel energy storage, electric vehicle, aircraft power generator, and so on. In this paper, a nonlinear model of SRG was established by means of Matlab/ Simulink. Furthermore, a power generation plan of SRG about variable-speed constant-voltage generation control system was designed. Variable-speed simulation results show that the control system has favorable dynamic and static characteristics.
Directory of Open Access Journals (Sweden)
Neal Jackson
2015-09-01
Full Text Available I review the current state of determinations of the Hubble constant, which gives the length scale of the Universe by relating the expansion velocity of objects to their distance. There are two broad categories of measurements. The first uses individual astrophysical objects which have some property that allows their intrinsic luminosity or size to be determined, or allows the determination of their distance by geometric means. The second category comprises the use of all-sky cosmic microwave background, or correlations between large samples of galaxies, to determine information about the geometry of the Universe and hence the Hubble constant, typically in a combination with other cosmological parameters. Many, but not all, object-based measurements give H_0 values of around 72–74 km s^–1 Mpc^–1, with typical errors of 2–3 km s^–1 Mpc^–1. This is in mild discrepancy with CMB-based measurements, in particular those from the Planck satellite, which give values of 67–68 km s^–1 Mpc^–1 and typical errors of 1–2 km s^–1 Mpc^–1. The size of the remaining systematics indicate that accuracy rather than precision is the remaining problem in a good determination of the Hubble constant. Whether a discrepancy exists, and whether new physics is needed to resolve it, depends on details of the systematics of the object-based methods, and also on the assumptions about other cosmological parameters and which datasets are combined in the case of the all-sky methods.
Approximations to Euler's constant
International Nuclear Information System (INIS)
We study a problem of finding good approximations to Euler's constant γ=lim→∞ Sn, where Sn = Σk=Ln (1)/k-log(n+1), by linear forms in logarithms and harmonic numbers. In 1995, C. Elsner showed that slow convergence of the sequence Sn can be significantly improved if Sn is replaced by linear combinations of Sn with integer coefficients. In this paper, considering more general linear transformations of the sequence Sn we establish new accelerating convergence formulae for γ. Our estimates sharpen and generalize recent Elsner's, Rivoal's and author's results. (author)
Black holes with constant topological Euler density
Bargueño, Pedro
2016-01-01
A class of four dimensional spherically symmetric and static geometries with constant topological Euler density is studied. These geometries are shown to solve the coupled Einstein-Maxwell system when non-linear Born-Infeld-like electrodynamics is employed.
Local experiments see cosmologically varying constants
International Nuclear Information System (INIS)
We describe a rigorous matched asymptotic expansion, which establishes under very general conditions that local terrestrial and solar-system experiments will measure any variations in 'constants' of Nature occurring on cosmological scales
New Quasar Studies Keep Fundamental Physical Constant Constant
2004-03-01
certain spectral lines with present-day values. Quasars are here only used as a beacon - the flame - in the very distant Universe. Interstellar clouds of gas in galaxies, located between the quasars and us on the same line of sight and at distances varying from six to eleven thousand of million light years, absorb parts of the light emitted by the quasars. The resulting spectrum consequently presents dark "valleys" that can be attributed to well-known elements. If the fine-structure constant happens to change over the duration of the light's journey, the energy levels in the atoms would be affected and the wavelengths of the absorption lines would be shifted by different amounts. By comparing the relative gaps between the valleys with the laboratory values, it is possible to calculate alpha as a function of distance from us, that is, as a function of the age of the Universe. These measures are however extremely delicate and require a very good modelling of the absorption lines. They also put exceedingly strong requirements on the quality of the astronomical spectra. They must have enough resolution to allow very precise measurement of minuscule shifts in the spectra. And a sufficient number of photons must be captured in order to provide a statistically unambiguous result. For this, astronomers have to turn to the most advanced spectral instruments on the largest telescopes. This is where the Ultra-violet and Visible Echelle Spectrograph (UVES) and ESO's Kueyen 8.2-m telescope at the Paranal Observatory is unbeatable, thanks to the unequalled spectral quality and large collecting mirror area of this combination. Constant or not? ESO PR Photo 07/04 ESO PR Photo 07/04 Relative Changes with Redshift of the Fine Structure Constant [Preview - JPEG: 496 x 400 pix - 36k] [Normal - JPEG: 991 x 800 pix - 320k] Captions: ESO PR Photo 07/04 shows measured values of the relative change of alpha from the sample of absorption systems studied by Hum Chand and his colleagues, plotted as
Decay constants in geochronology
Institute of Scientific and Technical Information of China (English)
IgorM.Villa; PaulR.Renne
2005-01-01
Geologic time is fundamental to the Earth Sciences, and progress in many disciplines depends critically on our ability to measure time with increasing accuracy and precision. Isotopic geochronology makes use of the decay of radioactive nuclides as a help to quantify the histories of rock, minerals, and other materials. Both accuracy and precision of radioisotopic ages are, at present, limited by those of radioactive decay constants. Modem mass spectrometers can measure isotope ratios with a precision of 10-4 or better. On the other hand, the uncertainties associated with direct half-life determinations are, in most cases, still at the percent level. The present short note briefly summarizes progress and problems that have been encountered during the Working Group's activity.
The Standard Association Constant of Ion Pair [GaCl]2+in the System of HCl+GaCl3+H2O
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The standard association constants of ionic pair [GaCl]2+, Kas, were determined by emf(electromotive force) method at 278.15 to 318.15 K. The thermodynamic quantities for the ionic association process were calculated and it was pointed that the association entropy is driving force to form the ionic pair.
Hofmann, A.F.; Middelburg, J.J.; Soetaert, K.; Meysman, F.J.R.
2009-01-01
A new pH modelling approach is presented that explicitly quantifies the influence of biogeochemical processes on proton cycling and pH in an aquatic ecosystem, and which accounts for time variable acid-base dissociation constants. As a case study, the method is applied to investigate proton cycling
Bubble Universes With Different Gravitational Constants
Takamizu, Yu-ichi
2015-01-01
We argue a scenario motivated by the context of string landscape, where our universe is produced by a new vacuum bubble embedded in an old bubble and these bubble universes have not only different cosmological constants, but also their own different gravitational constants. We study these effects on the primordial curvature perturbations. In order to construct a model of varying gravitational constants, we use the Jordan-Brans-Dicke (JBD) theory where different expectation values of scalar fields produce difference of constants. In this system, we investigate the nucleation of bubble universe and dynamics of the wall separating two spacetimes. In particular, the primordial curvature perturbation on superhorizon scales can be affected by the wall trajectory as the boundary effect. We show the effect of gravitational constant in the exterior bubble universe can provide a peak like a bump feature at a large scale in a modulation of power spectrum.
Institute of Scientific and Technical Information of China (English)
李文信
2011-01-01
This paper mainly introduces the solution and application of the constant lighting control of ABB i-bus intelligent building control system.%本文主要阐述了ABBi-bus。智能建筑控制系统恒照度方案的原理及应用。
Institute of Scientific and Technical Information of China (English)
DARBAN D.A.; GOWEN S.R.; PEMBROKE B.; MAHAR A.N.
2005-01-01
Growth room and glasshouse experiment was conducted to investigate the effect of constant and fluctuating temperatures on the development of Pasteuria penetrans a hyperparasite of root-knot nematodes. Tomato plants (Lycopersicon esculentum Mill) were inoculated with Meloidogynejavanica second-stage juveniles attached with endospores ofP. penetrans and were grown in growth room at 26-29 ℃ and in glasshouse at 20-32 ℃. The tomato plants were sampled from the growth room after 600 degree-days based on 17 ℃/d, accumulating each day above a base temperature of 10 ℃ and from the glasshouse after 36 calendar days. Temperature affected the development ofP. penetrans directly. The rate of development at constant temperature in growth room was faster than that in the glasshouse at fluctuating temperatures.
Martins José C; Hendrickx Pieter MS
2008-01-01
Abstract Background The advent of combinatorial chemistry has revived the interest in five-membered heterocyclic rings as scaffolds in pharmaceutical research. They are also the target of modifications in nucleic acid chemistry. Hence, the characterization of their conformational features is of considerable interest. This can be accomplished from the analysis of the 3JHH scalar coupling constants. Results A freely available program including an easy-to-use graphical user interface (GUI) has b...
The Interacting and Non-constant Cosmological Constant
Verma, Murli Manohar
2009-01-01
We propose a time-varying cosmological constant with a fixed equation of state, which evolves mainly through its interaction with the background during most of the long history of the universe. However, such interaction does not exist in the very early and the late-time universe and produces the acceleration during these eras when it becomes very nearly a constant. It is found that after the initial inflationary phase, the cosmological constant, that we call as lambda parameter, rolls down from a large constant value to another but very small constant value and further dominates the present epoch showing up in form of the dark energy driving the acceleration.
Adelic Universe and Cosmological Constant
Makhaldiani, Nugzar
2003-01-01
In the quantum adelic field (string) theory models, vacuum energy -- cosmological constant vanish. The other (alternative ?) mechanism is given by supersymmetric theories. Some observations on prime numbers, zeta -- function and fine structure constant are also considered.
Quantum Theory without Planck's Constant
Ralston, John P
2012-01-01
Planck's constant was introduced as a fundamental scale in the early history of quantum mechanics. We find a modern approach where Planck's constant is absent: it is unobservable except as a constant of human convention. Despite long reference to experiment, review shows that Planck's constant cannot be obtained from the data of Ryberg, Davisson and Germer, Compton, or that used by Planck himself. In the new approach Planck's constant is tied to macroscopic conventions of Newtonian origin, which are dispensable. The precision of other fundamental constants is substantially improved by eliminating Planck's constant. The electron mass is determined about 67 times more precisely, and the unit of electric charge determined 139 times more precisely. Improvement in the experimental value of the fine structure constant allows new types of experiment to be compared towards finding "new physics." The long-standing goal of eliminating reliance on the artifact known as the International Prototype Kilogram can be accompl...
EFFECTS OF CONSTANT EXCITATION ON LOCAL BIFURCATION
Institute of Scientific and Technical Information of China (English)
WU Zhi-qiang; CHEN Yu-shu
2006-01-01
The effects of the constant excitation on the local bifurcation of the periodic solutions in the 1:2 internal resonant systems were analyzed based on the singularity theory. It is shown that the constant excitation make influence only when there exist some nonlinear terms, in the oscillator with lower frequency. Besides acting as main bifurcation parameter, the constant excitation, together with coefficients of some nonlinear terms,may change the values of unfolding parameters and the type of the bifurcation. Under the non-degenerate cases, the effect of the third order terms can be neglected.
Institute of Scientific and Technical Information of China (English)
杨洪升
2015-01-01
Using frequency control method to enable water pump motor keep the pressure constant in water supply system of high-rise building’s construction, can reach the target that high-rise building's water supply capacity changes with the water flow. By the use of Siemens frequency converter to control the water pump motor, the article introduces the composi⁃tion of variable frequency constant pressure water supply system, the PID regulatory function of Siemens inverter, the set⁃ting method of PID parameters and briefly introduces the control scheme of frequency converter in constant pressure water supply system of high-rise building’s construction . Results show that the constant pressure water supply system con⁃trolled by Siemens inverter in high-rise building’s construction can ensure the of constant pressure water supply, at the same time has achieved remarkable energy saving effect. At present, constant pressure water supply system controlled by the Siemens inverter has been widely used.%采用对水泵电机变频调速的方法，使高层建筑施工供水系统压力恒定，可达到高层建筑供水能力随用水流量而变化的目标。本文通过使用西门子变频器控制水泵电机，介绍了变频恒压供水系统的构成、西门子变频器的PID调节功能、PID参数的设置方法并简要介绍了变频器在高层建筑施工恒压供水系统中的控制方案。结果表明西门子变频器控制的恒压供水系统在实现高层建筑施工恒压供水的同时，达到了显著的节能效果。目前西门子变频器控制的恒压供水系统已经得到了广泛的应用。
Directory of Open Access Journals (Sweden)
ELENA ANGHEL
2011-04-01
Full Text Available "Are we watching, in the succession of history, the appearance and disappearance of legal systems or assisting, in a greater or lesser extent, to what might be considered, in a sense, an evolution of those systems?"1 Law, indissolubly linked to the general evolution of society, has recorded a number of differences in time and space, both in terms of content of various types and positive law systems, and also in terms of forms that take the rules of law, authorities who have the ability to edict it or the procedure to be followed.Indeed, there is no law for all times and all places, as law is not an abstract product of our reason, it comes from the human experience, it is a product of history and that is why institutions of each society can only be different from one society to another.2 But, as in reality there are not quantities of history - many, little or very little - but just history3, we can say that in typology there is not socialist law absolutely different from bourgeois, feudal or slave law, so there is just law. By this approach, I wanted to bring back into question the existence of some factors of constancy in law, those "legal permanencies” investigated by Edmond Picard, believing that "there is something in the legal relationship that necessarily subsist anywhere”.4
Selby, David; Creaser, Robert A.; Stein, Holly J.; Markey, Richard J.; Hannah, Judith L.
2007-04-01
The past decade has seen renewed interest in 187Re- 187Os geochronology using a variety of matrices including sulfide minerals, shales and meteorites. The most widely used value of the 187Re decay constant ( λ187Re) is 1.666 ± 0.005 × 10 -11 a -1 (±0.31%), which is based on cross calibration of Re-Os and Pb-Pb chronometers for certain meteorites [Smoliar M. I., Walker R. J., and Morgan J. W. (1996) Re-Os isotope constraints on the age of Group IIA, IIIA, IVA, and IVB iron meteorites. Science271, 1099-1102]. However, other recent studies have yielded alternate values of λ187Re, based upon either direct counting experiments or analysis of meteorites. Here, we provide an independent assessment of λ187Re, using methodology, sample materials, and preparation of Os standard solutions different from those of Smoliar et al. (1996). Combining Re-Os age data for molybdenite formed in magmatic ore deposits, with the U-Pb zircon age of the magmatic rocks, a refined λ187Re value is determined by averaging 11 individual cross-calibration experiments spanning ca. 2700 Ma of Earth history. Using the U decay constants of Jaffey [Jaffey A. H., Flynn K. F., Glendenin L. E., Bentley W. C., and Essling A. M. (1971) Precision measurement of half-lives and specific activities of 235U and 238U. Phys. Rev.4, 1889-1906], a value for λ187Re of 1.6668 ± 0.0034 × 10 -11 a -1 is determined. Using the λ238U value of Jaffey et al. (1971) and λ235U value of Schoene [Schoene B., Crowley J. L., Condon D. J., Schmitz M. D., and Bowring S. A. (2006) Reassessing the uranium decay constants for geochronology using ID-TIMS U-Pb data. Geochim. Cosmochim. Acta70, 426-445], a value for λ187Re of 1.6689 ± 0.0031 × 10 -11 a -1 is determined. These values are nominally higher (ca. 0.1 and ca. 0.2%) than the value determined by Smoliar et al. [Smoliar M. I., Walker R. J., and Morgan J. W. (1996) Re-Os isotope constraints on the age of Group IIA, IIIA, IVA, and IVB iron meteorites. Science271
Institute of Scientific and Technical Information of China (English)
陈江; 章云
2001-01-01
本文以某自来水加压站为例，介绍了一种可编程控制器恒压供水监控系统的原理、结构、特点以及其在实际中的应用。%In this paper, the principle of the constant pressure water supply system controlled by PLC is introduced together with its characteristics and application in a tap water pressure station.
Forward recursions and normalizing constant
Guyon, Xavier; Hardouin, Cécile
2009-01-01
Maximum likelihood parameter estimation is frequently replaced by various techniques because of its intractable normalizing constant. In the same way, the literature displays various alternatives for distributions involving such unreachable constants. In this paper, we consider a Gibbs distribution $\\pi $ and present a recurrence formula allowing a recursive calculus of the marginals of $\\pi $ and in the same time its normalizing constant$.$ The numerical performance of this algorithm is eval...
Basic constant of matter world
International Nuclear Information System (INIS)
It was analysed how to gain constant 46 hidden among elementary units of matter world, which is divided into, 1, 2, 4, 8, 16, 8, 4, 2, 1. Here it shows the unity of opposites on philosophy and simple symmetric beauty of mathphysics. The constant specifically shows that scope constant 44 in nuclides layer of matter world and chromosome number of mankind is 23 pairs, which is the highest form of matter motion, the basic cause of existing constant 46 is that matter exists in space-time with 4-dimensions, and it obeys the principle of the most lower energy
Energy Technology Data Exchange (ETDEWEB)
Diaz S, A.; Fuentes C, P.; Merino C, F. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)], e-mail: angeles.diaz@inin.gob.mx
2009-10-15
Whit the objective of to complete the existent techniques for susceptibility evaluation to phenomenon of stress corrosion cracking in laboratories of Applied Sciences Area of National Institute of Nuclear Research; was realized and documented the modification of a high pressure and temperature equipment, identified as MEX-03 to carry out the implementation of a growth and crack propagation assay, using a constant load method. The assay was realized to a specimen of stainless steel AISI 304l type CT of an inch, which was previously thermally sensitize, simulating the typical degradation of this materials type below operation conditions in a BWR. The MEX-03 system, consist from an annexed auto key to a load system which originally was controlled by displacement; therefore were carried out modifications to achieve the control by load. The realized adjustments allowed to maintain a constant load during all the experiment, and as much the temperature conditions (T = 288 C) as of pressure (P = 8 Mpa) were controlled during the assay realization. The steel was exposed to a conditioned ambient with hydrogen gas addition; simulating a well-known alternative chemistry as hydrogen water chemistry that is used to mitigate the phenomenon of stress corrosion cracking, main degradation mechanism of austenitic stainless steels. The continuation of the crack behavior was realized by means of electric potential fall technique and later was validated of visual form through the fractographic analysis of cracked surface. The modification and control of equipment for realization of this experiment is necessary, for what should be carried out new assays, whose results will allow to establish the effect of dynamic and static methods in velocity determination of crack growth to laboratory level; to be considered in the existent models of crack propagation in systems and components in operation. (Author)
Spectrophotometric determination of association constant
DEFF Research Database (Denmark)
Spanget-Larsen, Jens
2016-01-01
Least-squares 'Systematic Trial-and-Error Procedure' (STEP) for spectrophotometric evaluation of association constant (equilibrium constant) K and molar absorption coefficient E for a 1:1 molecular complex, A + B = C, with error analysis according to Conrow et al. (1964). An analysis of the Charge...
Institute of Scientific and Technical Information of China (English)
周文源; 袁越; 傅质馨; 惠东; 杨凯
2012-01-01
该文以提高跟踪速度、减少最大功率点附近功率振荡和减少误判为多重目标,提出了恒电压结合牛顿法的最大功率点跟踪策略,并利用朗伯W(LambertW)函数在光伏电池实用模型的基础上对其原理进行了理论推导和证明.该方法仅依赖于当前工作点的信息计算下一工作点的参考电压,有效地减少了误判；借助于牛顿法的良好收敛性,速度和稳定性都有提高.通过三种不同光照模式算例,与传统方法进行仿真对比,验证了方法的有效性.%This paper proposed a novel multi-objective maximum power point tracking (MPPT) strategy combined constant voltage tracking and Newton method in order to improve tracking speed, minimize the power oscillation near maximum power point (MPP) and reduce erroneous results. A theoretical derivation and a demonstration based on practical photovoltaic (PV) cell model were also given by using LambertW function. The proposed method only uses the information of the actual working point to calculate the reference voltage of the next working point, thus the erroneous result is thus reduced. With the help of Newton method's good convergence, the proposed method shows a better tracking speed and less oscillation. Numerical simulations were conducted based on various radiation types to test the effectiveness of the proposed method. The results validate its effectivity and efficiency.
Timelike Constant Mean Curvature Surfaces with Singularities
DEFF Research Database (Denmark)
Brander, David; Svensson, Martin
2014-01-01
We use integrable systems techniques to study the singularities of timelike non-minimal constant mean curvature (CMC) surfaces in the Lorentz–Minkowski 3-space. The singularities arise at the boundary of the Birkhoff big cell of the loop group involved. We examine the behavior of the surfaces at ...
Directory of Open Access Journals (Sweden)
Orlando Ragnisco
2010-12-01
Full Text Available A novel family of exactly solvable quantum systems on curved space is presented. The family is the quantum version of the classical Perlick family, which comprises all maximally superintegrable 3-dimensional Hamiltonian systems with spherical symmetry. The high number of symmetries (both geometrical and dynamical exhibited by the classical systems has a counterpart in the accidental degeneracy in the spectrum of the quantum systems. This family of quantum problem is completely solved with the techniques of the SUSYQM (supersymmetric quantum mechanics. We also analyze in detail the ordering problem arising in the quantization of the kinetic term of the classical Hamiltonian, stressing the link existing between two physically meaningful quantizations: the geometrical quantization and the position dependent mass quantization.
Institute of Scientific and Technical Information of China (English)
姜素霞; 闫艳霞; 杨小亮
2011-01-01
For the need to build an intelligent building life and fire water supply system, a design was proposed, which was composed of PLC, frequency converter and PID regulator and could achieve AC dual-constant-pressure,dual-frequency-convert close-loop speed governing control. According to water-out pressure and flow rate,the system can provide constant pressure alternating quantity water supply by controlling the speed of motor unit and switchover from variable frequency to power-frequency. Simulation of the above system in MCGS showed that the system has pressure stability, simple structure and good reliability.%针对城市智能楼宇建筑生活及消防供水系统需求,利用PLC,变频器和PID调节器构建交流双恒压双变频闭环调速控制系统.该系统根据供水系统出口处的水压和流量,利用PLC控制变频/工频及电动机泵组的速度和切换,实现了闭环自动调节恒压变量供水.利用MCGS组态软件对该系统进行模拟调试,运行结果表明:该系统可靠性高、扩展性好,动态响应速度快,启动时压力波动小.
Directory of Open Access Journals (Sweden)
Belyaev Valeriy L’vovich
2016-02-01
Full Text Available The concept of a geoinformation system for urban geoenvironment is concerned. Geological data is necessary for the sustainable development of city infrastructure. The municipal departments should use geological and environmental information for perspective planning, selecting the location for important infrastructure objects, solving ecologycal problems, and in decision making. The concept includes a preliminary list of system’s users, their informational needs, main functionalities, methodical approaches to the system design and development. Geological data must contain source documents from geological archives “as is” and geodata based on its interpretation for various tasks. These data must be checked carefully and updated with new engineering-geological investigations. Geoinformation system must integrate various geological, engineering-geological, hydrogeological, and environmental data. Sophisticated procedures must be provided to check complicated logical dependences in the system database and to analyze contradictions between source documents. 3D modeling is an adequate language for presenting geological data, therefore, the considered system must include 3D models of various scales. In the suggested concept 3D modeling is considered as a tool for investigations, not only for presentations. The end users should have possibilities to get results of their queries in various formats: tables, geological and thematic maps, geological cross-sections, 2D and 3D grids as source data for mathematical modeling, etc. In conclusion, the paper briefly describes IEG RAS activities in GIS technologies for geological cartography and 3D modeling.
Directory of Open Access Journals (Sweden)
E. M. Karchevskii
2014-01-01
Full Text Available We present new numerical methods for the solution of inverse spectral problem to determine the dielectric constants of core and cladding in optical fibers. These methods use measurements of propagation constants. Our algorithms are based on approximate solution of a nonlinear nonselfadjoint eigenvalue problem for a system of weakly singular integral equations. We study three inverse problems and prove that they are well posed. Our numerical results indicate good accuracy of new algorithms.
International Nuclear Information System (INIS)
A new, completely rewritten version of the FEDGROUP program system is presented in this report. The formulae and the algorithm underlying the calculation are revised. The FEDGROUP-3 is able to calculate group averaged infinite diluted and screened cross-sections, elastic and inelastic transfer matrices, point-wise cross-section sets from evaluated data in ENDF/B, KEDAK and UKNDL format. The program system is written mainly in FORTRAN-IV of IBM-OS but it can be adapted relatively easily to other type of computers. (author)
Fundamental Constants and Conservation Laws
Roh, Heui-Seol
2001-01-01
This work describes underlying features of the universe such as fundamental constants and cosmological parameters, conservation laws, baryon and lepton asymmetries, etc. in the context of local gauge theories for fundamental forces under the constraint of the flat universe. Conservation laws for fundamental forces are related to gauge theories for fundamental forces, their resulting fundamental constants are quantitatively analyzed, and their possible violations at different energy scales are...
Inflation and the cosmological constant
Directory of Open Access Journals (Sweden)
FENG Chaojun
2014-08-01
Full Text Available By assuming the cosmological “constant” is no longer a constant during the inflation epoch,it is found that the cosmological constant fine-tuning problem is solved.In the meanwhile,inflation models could predict a large tensor-to-scalar ratio,correct power spectral index and a larger running of it.Furthermore,the e-folding number is large enough to overcome the horizon,flatness problems in the Big Bang cosmology.
基于PLC的恒压供水系统设计%The constant pressure water supply system based on PLC design
Institute of Scientific and Technical Information of China (English)
李珊珊
2014-01-01
With the rapid development of social economy, people on the requirement of increasing the quality of water supply and water supply system reliability, however, today's water supply system original deficiencies exist - lack of water and electricity supply pressure. Complete water supply system is through the automatic control technology, computer technology and communication technology to build, the water supply system can achieve high performance and low power consumption.%随着社会经济的迅速发展，人们对供水质量和供水系统可靠性的要求不断提高，然而现如今的供水系统存在着原始不足之处-水电供应压力不足。完善的供水系统是通过自动控制技术、计算机技术以及通信技术来构建的，这样的供水系统可以达到高性能、低能耗的目标。
Directory of Open Access Journals (Sweden)
Rathore Umesh C.
2016-01-01
Full Text Available This paper presents the experimental evaluation of the performance of 3-φ self-excited induction generator (SEIG suitable for pico-hydro power generation system feeding domestic load in remote mountainous region. The use of induction generators is most suitable for renewable energy conversion systems due to their enormous advantages over conventional synchronous generators. Important features of induction generators include the simplicity in construction, ruggedness, simplified control, ease in maintenance and small size per generated kW. The performance characteristics of 3-φ SEIG feeding isolated load are evaluated using MATLAB-Simulink model based on the prevalent renewable energy sources inputs and loading conditions in mountainous terrain of Himalayas. The results are validated using an experimental set-up comprising of 3-φ, 3 HP induction motor run as 3- φ induction generator driven by 5HP, 4-pole DC shunt motor acting as prime-mover.
Goodrich, John W.
1995-01-01
Two methods for developing high order single step explicit algorithms on symmetric stencils with data on only one time level are presented. Examples are given for the convection and linearized Euler equations with up to the eighth order accuracy in both space and time in one space dimension, and up to the sixth in two space dimensions. The method of characteristics is generalized to nondiagonalizable hyperbolic systems by using exact local polynominal solutions of the system, and the resulting exact propagator methods automatically incorporate the correct multidimensional wave propagation dynamics. Multivariate Taylor or Cauchy-Kowaleskaya expansions are also used to develop algorithms. Both of these methods can be applied to obtain algorithms of arbitrarily high order for hyperbolic systems in multiple space dimensions. Cross derivatives are included in the local approximations used to develop the algorithms in this paper in order to obtain high order accuracy, and improved isotropy and stability. Efficiency in meeting global error bounds is an important criterion for evaluating algorithms, and the higher order algorithms are shown to be up to several orders of magnitude more efficient even though they are more complex. Stable high order boundary conditions for the linearized Euler equations are developed in one space dimension, and demonstrated in two space dimensions.
From the Rydberg constant to the fundamental constants metrology
International Nuclear Information System (INIS)
This document reviews the theoretical and experimental achievements of the author since the beginning of his scientific career. This document is dedicated to the spectroscopy of hydrogen, deuterium and helium atoms. The first part is divided into 6 sub-sections: 1) the principles of hydrogen spectroscopy, 2) the measurement of the 2S-nS/nD transitions, 3) other optical frequency measurements, 4) our contribution to the determination of the Rydberg constant, 5) our current experiment on the 1S-3S transition, 6) the spectroscopy of the muonic hydrogen. Our experiments have improved the accuracy of the Rydberg Constant by a factor 25 in 15 years and we have achieved the first absolute optical frequency measurement of a transition in hydrogen. The second part is dedicated to the measurement of the fine structure constant and the last part deals with helium spectroscopy and the search for optical references in the near infrared range. (A.C.)
Effective cosmological constant induced by stochastic fluctuations of Newton's constant
de Cesare, Marco; Lizzi, Fedele; Sakellariadou, Mairi
2016-09-01
We consider implications of the microscopic dynamics of spacetime for the evolution of cosmological models. We argue that quantum geometry effects may lead to stochastic fluctuations of the gravitational constant, which is thus considered as a macroscopic effective dynamical quantity. Consistency with Riemannian geometry entails the presence of a time-dependent dark energy term in the modified field equations, which can be expressed in terms of the dynamical gravitational constant. We suggest that the late-time accelerated expansion of the Universe may be ascribed to quantum fluctuations in the geometry of spacetime rather than the vacuum energy from the matter sector.
Effective cosmological constant induced by stochastic fluctuations of Newton's constant
de Cesare, Marco; Sakellariadou, Mairi
2016-01-01
We consider implications of the microscopic dynamics of spacetime for the evolution of cosmological models. We argue that quantum geometry effects may lead to stochastic fluctuations of the gravitational constant, which is thus considered as a macroscopic effective dynamical quantity. Consistency with Riemannian geometry entails the presence of a time-dependent dark energy term in the modified field equations, which can be expressed in terms of the dynamical gravitational constant. We suggest that the late-time accelerated expansion of the Universe may be ascribed to quantum fluctuations in the geometry of spacetime rather than the vacuum energy from the matter sector.
Benard, P; Vivoda, J; Smolikova, P; Benard, Pierre; Laprise, Rene; Vivoda, Jozef; Smolikova, Petra
2003-01-01
The aim of this paper is to investigate the response of this system/scheme in terms of stability in presence of explicitly treated residual terms, as it inevitably occurs in the reality of NWP. This sudy is restricted to the impact of thermal and baric residual terms (metric residual terms linked to the orography are not considered here). It is shown that conversely to what occurs with Hydrostatic Primitive Equations, the choice of the prognostic variables used to solve the system in time is of primary importance for the robustness with Euler Equations. For an optimal choice of prognostic variables, unconditionnally stable schemes can be obtained (with respect to the length of the time-step), but only for a smaller range of reference states than in the case of Hydrostatic Primitive Equations. This study also indicates that: (i) vertical coordinates based on geometrical height and on mass behave similarly in terms of stability for the problems examined here, and (ii) hybrid coordinates induce an intrinsic inst...
Pole placement with constant gain output feedback
Sridhar, B.; Lindorff, D. P.
1972-01-01
Given a linear time invariant multivariable system with m inputs and p outputs, it was shown that p closed loop poles of the system can be preassigned arbitrarily using constant gain output feedback provided (A circumflex, B circumflex) is controllable. These data show that if (A circumflex, B circumflex, C circumflex) is controllable and observable, and Rank B circumflex = m, Rank C circumflex = p, then max (m,p) poles of the system can be assigned arbitarily using constant gain output feedback. Further, it is shown that in some cases more than max (m,p) poles can be arbitrarily assigned. A least square design technique is outlined to approximate the desired pole locations when it is not possible to place all the poles.
How fundamental are fundamental constants?
Duff, M. J.
2015-01-01
I argue that the laws of physics should be independent of one's choice of units or measuring apparatus. This is the case if they are framed in terms of dimensionless numbers such as the fine structure constant, ?. For example, the standard model of particle physics has 19 such dimensionless parameters whose values all observers can agree on, irrespective of what clock, rulers or scales? they use to measure them. Dimensional constants, on the other hand, such as ?, c, G, e and k ?, are merely human constructs whose number and values differ from one choice of units to the next. In this sense, only dimensionless constants are 'fundamental'. Similarly, the possible time variation of dimensionless fundamental 'constants' of nature is operationally well defined and a legitimate subject of physical enquiry. By contrast, the time variation of dimensional constants such as ? or ? on which a good many (in my opinion, confusing) papers have been written, is a unit-dependent phenomenon on which different observers might disagree depending on their apparatus. All these confusions disappear if one asks only unit-independent questions. We provide a selection of opposing opinions in the literature and respond accordingly.
How fundamental are fundamental constants?
Duff, M J
2014-01-01
I argue that the laws of physics should be independent of one's choice of units or measuring apparatus. This is the case if they are framed in terms of dimensionless numbers such as the fine structure constant, alpha. For example, the Standard Model of particle physics has 19 such dimensionless parameters whose values all observers can agree on, irrespective of what clock, rulers, scales... they use to measure them. Dimensional constants, on the other hand, such as h, c, G, e, k..., are merely human constructs whose number and values differ from one choice of units to the next. In this sense only dimensionless constants are "fundamental". Similarly, the possible time variation of dimensionless fundamental "constants" of nature is operationally well-defined and a legitimate subject of physical enquiry. By contrast, the time variation of dimensional constants such as c or G on which a good many (in my opinion, confusing) papers have been written, is a unit-dependent phenomenon on which different observers might...
Effect constant and natural illumination on physiological state in rats
Directory of Open Access Journals (Sweden)
Ilyukha Viktor Alexandrovitch
2012-03-01
Full Text Available The influences of constant and natural illumination on antioxidant system, leukocytes differential count, speed of pubescence and life span of male laboratory rats was investigated. The changes of melatonin level secretion by constant and natural illumination leads to connected reorganization in physiological systems functioning and speed of ageing.
Learning Read-constant Polynomials of Constant Degree modulo Composites
DEFF Research Database (Denmark)
Chattopadhyay, Arkadev; Gavaldá, Richard; Hansen, Kristoffer Arnsfelt;
2011-01-01
is not known to be learnable in any reasonable learning model. In this paper, we provide a deterministic polynomial time algorithm for learning Boolean functions represented by polynomials of constant degree over arbitrary finite rings from membership queries, with the additional constraint that each variable...
Energy Technology Data Exchange (ETDEWEB)
Nez, F
2005-06-15
This document reviews the theoretical and experimental achievements of the author since the beginning of his scientific career. This document is dedicated to the spectroscopy of hydrogen, deuterium and helium atoms. The first part is divided into 6 sub-sections: 1) the principles of hydrogen spectroscopy, 2) the measurement of the 2S-nS/nD transitions, 3) other optical frequency measurements, 4) our contribution to the determination of the Rydberg constant, 5) our current experiment on the 1S-3S transition, 6) the spectroscopy of the muonic hydrogen. Our experiments have improved the accuracy of the Rydberg Constant by a factor 25 in 15 years and we have achieved the first absolute optical frequency measurement of a transition in hydrogen. The second part is dedicated to the measurement of the fine structure constant and the last part deals with helium spectroscopy and the search for optical references in the near infrared range. (A.C.)
Mirror QCD and Cosmological Constant
Pasechnik, Roman; Teryaev, Oleg
2016-01-01
An analog of Quantum Chromo Dynamics (QCD) sector known as mirror QCD (mQCD) can affect the cosmological evolution and help in resolving the Cosmological Constant problem. In this work, we explore an intriguing possibility for a compensation of the negative QCD vacuum contribution to the ground state energy density of the universe by means of a positive contribution from the chromomagnetic gluon condensate in mQCD. The trace anomaly compensation condition and the form of the mQCD coupling constant in the infrared limit have been proposed by analysing a partial non-perturbative solution of the Einstein--Yang-Mills equations of motion.
Czechowski, Grzegorz; Zywucki, B.; Jadzyn, Jan
1993-10-01
The Frederiks transitions for the n-octyloxycyanobiphenyl (8-OCB) placed in the external magnetic and electric field as a function of the temperature have been studied. On the basis of threshold values Bc and Uc, the elastic constants for splay, bend and twist modes are determined. The magnetic anisotropy of 8-OCB as a function of temperature has been determined. The K11 and K33 elastic constants show the pretransitional nematic- smectic A effect. The values of critical exponents obtained from the temperature dependence of K11 and K33 in the vicinity of N-SA phase transition are discussed.
Variation of the fine structure constant
Lipovka, Anton A
2016-01-01
In present paper we evaluate the fine structure constant variation which should take place as the Universe is expanded and its curvature is changed adiabatically. This changing of the fine structure constant is attributed to the energy lost by physical system (consist of baryonic component and electromagnetic field) due to expansion of our Universe. Obtained ratio (d alpha)/alpha = 1. 10{-18} (per second) is only five times smaller than actually reported experimental limit on this value. For this reason this variation can probably be measured within a couple of years. To argue the correctness of our approach we calculate the Planck constant as adiabatic invariant of electromagnetic field, from geometry of our Universe in the framework of the pseudo- Riemannian geometry. Finally we discuss the double clock experiment based on Al+ and Hg+ clocks carried out by T. Rosenband et al. (Science 2008). We show that in this particular case there is an error in method and this way the fine structure constant variation c...
On constant elasticities of demand
Andrés Vázquez
1998-01-01
While the Slutsky matrix and duality theory have been used to establish that constant elasticity demand functions imply unitary income elasticities, zero cross price elasticities and own price elasticities equal to minus one, this note shows that these results can also be straightforwardly derived from the simple assumption that demand functions satisfy the budget constraint with strict equality.
Bose-Einstein condensation at constant temperature
Erhard, M.; Schmaljohann, H.; Kronjäger, J.; Bongs, K.; Sengstock, K.
2004-09-01
We present an experimental approach to Bose-Einstein condensation by increasing the particle number of the system at almost constant temperature. In particular, the emergence of a new condensate is observed in multicomponent F=1 spinor condensates of Rb87 . Furthermore, we develop a simple rate-equation model for multicomponent Bose-Einstein condensate thermodynamics at finite temperature which well reproduces the measured effects.
Elastic constants from microscopic strain fluctuations
Sengupta, Surajit; Nielaba, Peter; Rao, Madan; Binder, K.
1999-01-01
Fluctuations of the instantaneous local Lagrangian strain $\\epsilon_{ij}(\\bf{r},t)$, measured with respect to a static ``reference'' lattice, are used to obtain accurate estimates of the elastic constants of model solids from atomistic computer simulations. The measured strains are systematically coarse- grained by averaging them within subsystems (of size $L_b$) of a system (of total size $L$) in the canonical ensemble. Using a simple finite size scaling theory we predict the behaviour of th...
The 1% concordance Hubble constant
Energy Technology Data Exchange (ETDEWEB)
Bennett, C. L.; Larson, D.; Weiland, J. L. [Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Hinshaw, G., E-mail: cbennett@jhu.edu [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada)
2014-10-20
The determination of the Hubble constant has been a central goal in observational astrophysics for nearly a hundred years. Extraordinary progress has occurred in recent years on two fronts: the cosmic distance ladder measurements at low redshift and cosmic microwave background (CMB) measurements at high redshift. The CMB is used to predict the current expansion rate through a best-fit cosmological model. Complementary progress has been made with baryon acoustic oscillation (BAO) measurements at relatively low redshifts. While BAO data do not independently determine a Hubble constant, they are important for constraints on possible solutions and checks on cosmic consistency. A precise determination of the Hubble constant is of great value, but it is more important to compare the high and low redshift measurements to test our cosmological model. Significant tension would suggest either uncertainties not accounted for in the experimental estimates or the discovery of new physics beyond the standard model of cosmology. In this paper we examine in detail the tension between the CMB, BAO, and cosmic distance ladder data sets. We find that these measurements are consistent within reasonable statistical expectations and we combine them to determine a best-fit Hubble constant of 69.6 ± 0.7 km s{sup –1} Mpc{sup –1}. This value is based upon WMAP9+SPT+ACT+6dFGS+BOSS/DR11+H {sub 0}/Riess; we explore alternate data combinations in the text. The combined data constrain the Hubble constant to 1%, with no compelling evidence for new physics.
Variation of fundamental constants: theory
Flambaum, Victor
2008-05-01
Theories unifying gravity with other interactions suggest temporal and spatial variation of the fundamental ``constants'' in expanding Universe. There are some hints for the variation of different fundamental constants in quasar absorption spectra and Big Bang nucleosynthesis data. A large number of publications (including atomic clocks) report limits on the variations. We want to study the variation of the main dimensionless parameters of the Standard Model: 1. Fine structure constant alpha (combination of speed of light, electron charge and Plank constant). 2. Ratio of the strong interaction scale (LambdaQCD) to a fundamental mass like electron mass or quark mass which are proportional to Higgs vacuum expectation value. The proton mass is propotional to LambdaQCD, therefore, the proton-to-electron mass ratio comes into this second category. We performed necessary atomic, nuclear and QCD calculations needed to study variation of the fundamental constants using the Big Bang Nucleosynthsis, quasar spectra, Oklo natural nuclear reactor and atomic clock data. The relative effects of the variation may be enhanced in transitions between narrow close levels in atoms, molecules and nuclei. If one will study an enhanced effect, the relative value of systematic effects (which are not enhanced) may be much smaller. Note also that the absolute magnitude of the variation effects in nuclei (e.g. in very narrow 7 eV transition in 229Th) may be 5 orders of magnitude larger than in atoms. A different possibility of enhancement comes from the inversion transitions in molecules where splitting between the levels is due to the quantum tunneling amplitude which has strong, exponential dependence on the electron to proton mass ratio. Our study of NH3 quasar spectra has already given the best limit on the variation of electron to proton mass ratio.
WHY IS THE SOLAR CONSTANT NOT A CONSTANT?
International Nuclear Information System (INIS)
In order to probe the mechanism of variations of the solar constant on the inter-solar-cycle scale, the total solar irradiance (TSI; the so-called solar constant) in the time interval of 1978 November 7 to 2010 September 20 is decomposed into three components through empirical mode decomposition and time-frequency analyses. The first component is the rotation signal, counting up to 42.31% of the total variation of TSI, which is understood to be mainly caused by large magnetic structures, including sunspot groups. The second is an annual-variation signal, counting up to 15.17% of the total variation, the origin of which is not known at this point in time. Finally, the third is the inter-solar-cycle signal, counting up to 42.52%, which is inferred to be caused by the network magnetic elements in quiet regions, whose magnetic flux ranges from (4.27-38.01) × 1019 Mx.
Varying Fine-Structure Constant and the Cosmological Constant Problem
Fujii, Y
2003-01-01
We start with a brief account of the latest analysis of the Oklo phenomenon providing the still most stringent constraint on time-variability of the fine- structure constant $\\alpha$. Comparing this with the recent result from the measurement of distant QSO's appears to indicate a non-uniform time-dependence, which we argue to be related to another recent finding of the accelerating universe. This view is implemented in terms of the scalar-tensor theory, applied specifically to the small but nonzero cosmological constant. Our detailed calculation shows that these two phenomena can be understood in terms of a common origin, a particular behavior of the scalar field, dilaton. We also sketch how this theoretical approach makes it appropriate to revisit non- Newtonian gravity featuring small violation of Weak Equivalence Principle at medium distances.
Varying Fine-Structure Constant and the Cosmological Constant Problem
Fujii, Yasunori
We start with a brief account of the latest analysis of the Oklo phenomenon providing the still most stringent constraint on time variability of the fine-structure constant α. Comparing this with the recent result from the measurement of distant QSO's appears to indicate a non-uniform time-dependence, which we argue to be related to another recent finding of the accelerating universe. This view is implemented in terms of the scalar-tensor theory, applied specifically to the small but nonzero cosmological constant. Our detailed calculation shows that these two phenomena can be understood in terms of a common origin, a particular behavior of the scalar field, dilaton. We also sketch how this theoretical approach makes it appropriate to revisit non-Newtonian gravity featuring small violation of Weak Equivalence Principle at medium distances.
Energy Technology Data Exchange (ETDEWEB)
Wakui, T.; Yamaguchi, K. [Waseda University, Tokyo (Japan); Tanzawa, Y. [Nippon Institute of Technology, Saitama (Japan); Hashizume, T.; Ota, E. [Waseda University, Tokyo (Japan). School of Science and Engineering
1998-06-01
The effect that the set data of the load control system in a wind power generation system exerts on the dynamic behavior of a system was investigated. The wind power generation system consists of a hybrid wind turbine with combined Darrieus and Savonius rotors, load with a generator and battery in the center, and a controller. A constant-tip-speed ratio operation that holds the circumferential speed ratio in which the power coefficient is maximized irrespective of the change in wind velocity was used to extract and convert the wind energy more effectively. In a high-wind velocity area, the system is operated at a fixed speed, and the increase in rotation is suppressed to protect the wing strength. In a large system, the response characteristics are only slightly improved by the limited load operation range and influenced rotor inertial. Power cannot be fully extracted even if the control system is changed in setting, and the applicability to the wind situation remains low. During the actual operation, the adjustment value of the control system should be set so that the output operation is satisfactorily possible in the specified load operation range, that is, the change in the instantaneous value of an effective power coefficient indicates almost flat gain characteristics in frequency characteristics. 14 refs., 10 figs., 2 tabs.
Wormholes and the cosmological constant
International Nuclear Information System (INIS)
We review Coleman's wormhole mechanism for the vanishing of the cosmological constant. We show that in a minisuperspace model wormhole-connected universes dominate the path integral. We also provide evidence that the euclidean path integral over geometries with spherical topology is unstable with respect to formation of infinitely many wormhole-connected 4-spheres. Consistency is restored by summing over all topologies, which leads to Coleman's result. Coleman's argument for determination of other parameters is reviewed and applied to the mass of the pion. A discouraging result is found that the pion mass is driven to zero. We also consider qualitatively the implications of the wormhole theory for cosmology. We argue that a small number of universes containing matter and energy may exist in contact with infinitely many cold and empty universes. Contact with the cold universes insures that the cosmological constant in the warm ones is zero. (orig.)
Quaternions as astrometric plate constants
Jefferys, William H.
1987-01-01
A new method for solving problems in relative astrometry is proposed. In it, the relationship between the measured quantities and the components of the position vector of a star is modeled using quaternions, in effect replacing the plate constants of a standard four-plate-constant solution with the four components of a quaternion. The method allows a direct solution for the position vectors of the stars, and hence for the equatorial coordinates. Distortions, magnitude, and color effects are readily incorporated into the formalism, and the method is directly applicable to overlapping-plate problems. The advantages of the method include the simplicity of the resulting equations, their freedom from singularities, and the fact that trigonometric functions and tangential point transformations are not needed to model the plate material. A global solution over the entire sky is possible.
Three pion nucleon coupling constants
Ruiz Arriola, E.; Amaro, J. E.; Navarro Pérez, R.
2016-08-01
There exist four pion nucleon coupling constants, fπ0pp, ‑ fπ0nn, fπ+pn/2 and fπ‑np/2 which coincide when up and down quark masses are identical and the electron charge is zero. While there is no reason why the pion-nucleon-nucleon coupling constants should be identical in the real world, one expects that the small differences might be pinned down from a sufficiently large number of independent and mutually consistent data. Our discussion provides a rationale for our recent determination fp2 = 0.0759(4),f 02 = 0.079(1),f c2 = 0.0763(6), based on a partial wave analysis of the 3σ self-consistent nucleon-nucleon Granada-2013 database comprising 6713 published data in the period 1950-2013.
Three pion nucleon coupling constants
Arriola, E Ruiz; Perez, R Navarro
2016-01-01
There exist four pion nucleon coupling constants, $f_{\\pi^0, pp}$, $-f_{\\pi^0, nn}$, $f_{\\pi^+, pn} /\\sqrt{2}$ and $ f_{\\pi^-, np} /\\sqrt{2}$ which coincide when up and down quark masses are identical and the electron charge is zero. While there is no reason why the pion-nucleon-nucleon coupling constants should be identical in the real world, one expects that the small differences might be pinned down from a sufficiently large number of independent and mutually consistent data. Our discussion provides a rationale for our recent determination $$f_p^2 = 0.0759(4) \\, , \\quad f_{0}^2 = 0.079(1) \\,, \\quad f_{c}^2 = 0.0763(6) \\, , $$ based on a partial wave analysis of the $3\\sigma$ self-consistent nucleon-nucleon Granada-2013 database comprising 6713 published data in the period 1950-2013.
Institute of Scientific and Technical Information of China (English)
黄燕玲
2012-01-01
Abstract: In this paper, we study a cubic kolmogorov system with constant-rata prey stocking(dx)/(dt)=x(a0+a1x-a2x2-a3y-a4y2-a5xy)+k,(dy)/(dt)=y(bx2-d)The sufficient conditions of the existence and nonexistence of limit cycles areobtained.%对一类食饵种群具有常数存放率的三次kolmogorov系统：（dx）/（dt）=x（a0＋a1x-a2x2-a3y-a4y2-a5xy）＋k,（dy）/（dt）=y（bx2-d）,进行定性分析,得到该系统不存在极限环和存在极限环的充分条件.
Institute of Scientific and Technical Information of China (English)
许立滨; 尹晓
2011-01-01
In this paper, under the effect of the variance of the dead population on the internal and environmental toxicant density, a Gallopin' s resource-consumer system with constant-rate harvesting in polluted environment was studied. By using comparison theory, the sufficient condition for β-persistence ,β-extinction and zero-extinction was proved.%在考虑死亡种群对环境毒素影响的情况下,研究了污染环境中具有常数收获率的Gallopin资源-消费者种群的生存问题.利用比较原理,给出了种群β生存、β绝灭、零绝灭的充分条件.
Henry's law constants of polyols
Compernolle, S.; J.-F. Müller
2014-01-01
Henry's law constants (HLC) are derived for several polyols bearing between 2 and 6 hydroxyl groups, based on literature data for water activity, vapour pressure and/or solubility. While deriving HLC and depending on the case, also infinite dilution activity coefficients (IDACs), solid state vapour pressures or activity coefficient ratios are obtained as intermediate results. An error analysis on the intermediate quantities and the obtained HLC is included....
Henry's law constants of polyols
Compernolle, S.; J.-F. Müller
2014-01-01
Henry's law constants (HLC) are derived for several polyols bearing between 2 and 6 hydroxyl groups, based on literature data for water activity, vapour pressure and/or solubility. Depending on the case, infinite dilution activity coefficients (IDACs), solid state pressures or activity coefficient ratios are obtained as intermediary results. For most compounds, these are the first values reported, while others compare favourably with literature data in most ...
Fundamental constants and high resolution spectroscopy
Bonifacio, P; Whitmore, J B; Wendt, M; Centurion, M; Molaro, P; Srianand, R; Murphy, M T; Petitjean, P; Agafonova, I I; D'Odorico, S; Evans, T M; Levshakov, S A; Lopez, S; Martins, C J A P; Reimers, D; Vladilo, G
2013-01-01
Absorption-line systems detected in high resolution quasar spectra can be used to compare the value of dimensionless fundamental constants such as the fine-structure constant, alpha, and the proton-to-electron mass ratio, mu = m_p/m_e, as measured in remote regions of the Universe to their value today on Earth. In recent years, some evidence has emerged of small temporal and also spatial variations in alpha on cosmological scales which may reach a fractional level of 10 ppm . We are conducting a Large Programme of observations with VLT UVES to explore these variations. We here provide a general overview of the Large Programme and report on the first results for these two constants, discussed in detail in Molaro et al. and Rahmani et al. A stringent bound for Delta(alpha)/Alpha is obtained for the absorber at_abs = 1.6919 towards HE 2217-2818. The absorption profile is complex with several very narrow features, and is modeled with 32 velocity components. The relative variation in alpha in this system is +1.3+-...
Cosmology with New Astrophysical Constants
Alfonso-Faus, Antonio
2008-01-01
It is shown that Einstein field equations give two solutions for cosmology. The first one is the standard well known representative of the present status of cosmology. We identify it with the local point of view of a flat Universe with the values for the cosmological omega parameters (k = 0, lambda = 2/3, m = 1/3). The second one is a new one that we identify with a cosmic point of view, as given by free photons, neutrinos, tachyons and gravity quanta. We apply a wave to particle technique to find the matter propagation equation. Then we prove that all gravitational radii are constant, regardless of the possible time variations of the physical properties like the speed of light c, the gravitational constant G or the mass m of fundamental particles. We find two cosmological constants, c^3 /G and mc, with the condition that the field equations be derived from the action principle. With this result, and the integration of the Bianchi identity, we prove the existence of the two solutions for cosmology. We then va...
Control system of constant power consumption melting speed for vacuum arc furnace%真空自耗电弧炉恒熔速控制系统改造
Institute of Scientific and Technical Information of China (English)
王勃; 陈鼎; 孙足来
2015-01-01
为真空自耗电弧炉设备由恒电压控制升级改造至恒熔速控制系统。通过对2000kg真空自耗电弧炉熔炼钛合金的生产工艺、过程参数、产品要求进行了详细分析，选取恰当的数据采样算法，为更好的掌握真空弧电压、真空弧电流、钛合金熔炼速度等工艺参数间的耦合关系提供了良好的依据。同时对真空自耗电弧炉的控制系统现状及熔炼技术发展做了综述。在 PLC中建立弧电压、弧电流，熔炼速率等的计算公式来实现设定各级控制回路的设定值。%In this paper, the control system of electricity arc furnace equipment is upgraded from constant voltage to constant melting speed. The power consumption of vacuum arc furnace selfmelting production technology of titanium alloy, process parame-ters and product requirements are analyzed in detail. The data sampling algorithm was selected appropriately in order to better grasp the vacuum arc current, arc voltage, the coupling relationship between process parameters such as titanium alloy melting speed so as to provide good basis. At the same time, the development of the current control system and self-melting technology for power consumption vacuum arc furnace were reviewed. The calculation formula of arc voltage, arc current and melting rate were built up in PLC to implement the control circuit at various levels.
Some Dynamical Effects of the Cosmological Constant
Axenides, M.; Floratos, E. G.; Perivolaropoulos, L.
Newton's law gets modified in the presence of a cosmological constant by a small repulsive term (antigravity) that is proportional to the distance. Assuming a value of the cosmological constant consistent with the recent SnIa data (Λ~=10-52 m-2), we investigate the significance of this term on various astrophysical scales. We find that on galactic scales or smaller (less than a few tens of kpc), the dynamical effects of the vacuum energy are negligible by several orders of magnitude. On scales of 1 Mpc or larger however we find that the vacuum energy can significantly affect the dynamics. For example we show that the velocity data in the local group of galaxies correspond to galactic masses increased by 35% in the presence of vacuum energy. The effect is even more important on larger low density systems like clusters of galaxies or superclusters.
Angular momentum and separation constant in the Kerr metric
International Nuclear Information System (INIS)
Kerr metric admits a Killing tensor which yields a second order constant of motion for classical trajectories. An explicit expression is found for this constant using a particular coordinate system, the oblate spheroidal. Owing to the separability of the Hamilton - Jacobi equation in this system, it is easy to show that the second order constant is in fact the square of the total angular momentum of the particle at infinity, corrected with terms which arise from the non-inertial character of the coordinate system. (Author)
Institute of Scientific and Technical Information of China (English)
尹业宏; 高黎明
2012-01-01
随着高性能CCD传感器的发展，其在空间成像探测系统得到广泛应用。为解决传感器的成像质量和恒温控制问题，采用基于帕尔贴效应的热电制冷（Thermo—ElectricCooling，TEC）技术，以FPGA为控制芯片，运用PID控制算法，实现了小型温度控制系统。实验结果表明，该系统能快速准确地实现恒温控制，可扩展性强，具有一定的应用价值。%With the development of high performance cooling CCD imaging system in aerospace imaging detection, in order to improve sensor＇s imaging performance and keep sensor＇s temperature constant, a precision temperature control system is designed by using FPGA as digital control processor and a method of PID control and Thermo-Electric Cooling（TEC） technolo- gy, based on Peltier effect. The experiment results show that the system can work fast and accurately and can be well expanded. It has the good practicability.
Chandra Independently Determines Hubble Constant
2006-08-01
A critically important number that specifies the expansion rate of the Universe, the so-called Hubble constant, has been independently determined using NASA's Chandra X-ray Observatory. This new value matches recent measurements using other methods and extends their validity to greater distances, thus allowing astronomers to probe earlier epochs in the evolution of the Universe. "The reason this result is so significant is that we need the Hubble constant to tell us the size of the Universe, its age, and how much matter it contains," said Max Bonamente from the University of Alabama in Huntsville and NASA's Marshall Space Flight Center (MSFC) in Huntsville, Ala., lead author on the paper describing the results. "Astronomers absolutely need to trust this number because we use it for countless calculations." Illustration of Sunyaev-Zeldovich Effect Illustration of Sunyaev-Zeldovich Effect The Hubble constant is calculated by measuring the speed at which objects are moving away from us and dividing by their distance. Most of the previous attempts to determine the Hubble constant have involved using a multi-step, or distance ladder, approach in which the distance to nearby galaxies is used as the basis for determining greater distances. The most common approach has been to use a well-studied type of pulsating star known as a Cepheid variable, in conjunction with more distant supernovae to trace distances across the Universe. Scientists using this method and observations from the Hubble Space Telescope were able to measure the Hubble constant to within 10%. However, only independent checks would give them the confidence they desired, considering that much of our understanding of the Universe hangs in the balance. Chandra X-ray Image of MACS J1149.5+223 Chandra X-ray Image of MACS J1149.5+223 By combining X-ray data from Chandra with radio observations of galaxy clusters, the team determined the distances to 38 galaxy clusters ranging from 1.4 billion to 9.3 billion
MARTENSITIC TRANSFORMATION AND ELASTIC CONSTANTS
Suzuki, T
1985-01-01
The deformation energy barrier for the martensitic transformation is estimated from the data of the elastic constants. The deformation energy barrier for B.C.C → F.C.C martensitic transformation is, at most, of the order of the thermal energy at room temperature. The deformation energy barrier between B.C.C. and F.C.C can be surmounted by thermal energy at temperatures higher than Ms. The martensitic transformation is proposed to be understood as the freezing process of the non-linear lattice...
Exact constants in approximation theory
Korneichuk, N
1991-01-01
This book is intended as a self-contained introduction for non-specialists, or as a reference work for experts, to the particular area of approximation theory that is concerned with exact constants. The results apply mainly to extremal problems in approximation theory, which in turn are closely related to numerical analysis and optimization. The book encompasses a wide range of questions and problems: best approximation by polynomials and splines; linear approximation methods, such as spline-approximation; optimal reconstruction of functions and linear functionals. Many of the results are base
Henry's law constants of polyols
Directory of Open Access Journals (Sweden)
S. Compernolle
2014-05-01
Full Text Available Henry's law constants (HLC are derived for several polyols bearing between 2 and 6 hydroxyl groups, based on literature data for water activity, vapour pressure and/or solubility. Depending on the case, infinite dilution activity coefficients (IDACs, solid state pressures or activity coefficient ratios are obtained as intermediary results. For most compounds, these are the first values reported, while others compare favourably with literature data in most cases. Using these values and those from a previous work (Compernolle and Müller, 2014, an assessment is made on the partitioning of polyols, diacids and hydroxy acids to droplet and aqueous aerosol.
Kepler's Constant and WDS Orbit
Siregar, S
2012-01-01
The aim of this work are to find a Kepler's constant by using polynomial regression of the angular separation \\rho = \\rho(t) and the position angle \\theta = \\theta(t). The Kepler's constant obtained is used to derive the element of orbit. As a case study the angular separation and the position angle of the WDS 00063 +5826 and the WDS 04403-5857 were investigated. For calculating the element of orbit the Thiele-Innes van den Bos method is used. The rough data of the angular separation \\rho(t) and the position angle \\theta(t) are taken from the US Naval Observatory, Washington. This work also presents the masses and absolute bolometric magnitudes of each star.These stars include into the main-sequence stars with the spectral class G5V for WDS04403-5857and the type of spectrum G3V for WDS 00063+5826. The life time of the primary star and the secondary star of WDS 04403-5857 nearly equal to 20 Gyr. The life time of the primary star and the secondary star of WDS 00063+5826 are 20 Gyr and 19 Gyr, respectively.
Institute of Scientific and Technical Information of China (English)
赵振元; 陈维荣; 戴朝华; 张雪霞
2012-01-01
由于区域电网的互联，整个系统的惯性时间常数将会发生明显变化，继而会影响整网的暂态稳定水平。基于暂态能量函数法，通过对等值2机系统进行数学推导并作暂态稳定分析，研究了系统在各种运行方式下，2端机组惯量变化对电力系统暂态稳定水平产生的影响，比较了两端机组惯量变化分别对系统暂态稳定性的影响，并发现了系统机组惯性时间常数对系统暂态稳定水平造成的影响与系统的负荷水平及初始工况有关。在理论分析的基础上，结合相关算例在各种运行方式下进行了仿真研究，仿真结果验证了分析结果的正确性。%Due to the interconnection of regional power grids, the inertia time constant of the whole interconnected grid evidently changes, then transient stability level of the interconnected power grid will be influenced. Based on transient energy function, by means of mathematical deduce for equivalent two-machine system and analysis on its transient stability, the influences of unit inertial changes at both terminals on transient stability level of the whole system under various operation modes are researched, and respective influences of terminal unit inertial changes on transient stability of the whole grid are compared, besides, it is found that the influences of unit inertial time constants on system transient stability level are relevant to load level and initial operating condition of the power grid. Based on theoretical analysis, simulation of concerned examples under various operation modes is performed and the correctness of theoretical analysis results is verified by simulation results.
Cosmological constant and curved 5D geometry
Ito, M
2002-01-01
We study the value of cosmological constant in de Sitter brane embedded in five dimensions with positive, vanishing and negative bulk cosmological constant. In the case of negative bulk cosmological constant, we show that not zero but tiny four-dimensional cosmological constant can be realized by tiny deviation from bulk curvature of the Randall-Sundrum model.
Institute of Scientific and Technical Information of China (English)
乔玉钢; 胡勇
2015-01-01
开式节流恒功率控制液压系统在小型液压挖掘机上得到了广泛的应用。按照小型挖掘机实际工况特点，推导建立了开式节流系统主泵的动态数学模型，再结合主泵的p-q曲线，分析得出了主泵输出效率与主泵工作参数之间的特性。%Constant power controlled main pumps have been widely used in the open throttle hydraulic systems on mini hydraulic excavators. According to the characteristics of the actual condition of small excavators, a dynamic mathematical model of main pump in the open throttle system is deduced and established. Combined with the main pump p-q curve analysis, the relational characteristics between the output efficiency and the working parameters of the main pump are revealed in this paper.
Institute of Scientific and Technical Information of China (English)
刘红冰; 汪雨清; 王腾飞; 刘峰
2013-01-01
高能耗问题一直是恒温恒湿空调面临的难题。针对这一问题，设计了一种带冷凝热回收装置的变容量系统，将部分的冷凝热回收用于空气再热，节省了电能，减少了热污染。进行了可行性分析，介绍了系统的原理、控制方法、技术特点及发展前景。%The high energy consumption is the problem to an air conditioning of constant temperature and humidity. A variable capacity system with condensation heat recovery device is designed. Part of condensing heat recovery will be utilized for reheating air to conserve the power and reduce the heat pollution. The system principle, control methods, technical characteristics and developing prospect are expounded through the feasibility analysis.
Some new optimal quaternary constant weight codes
Institute of Scientific and Technical Information of China (English)
GE Gennian; WU Dianhua
2005-01-01
Constant weight codes (CWCs) are an important class of codes in coding theory. Generalized Steiner systems GS(2, k, v, g) were first introduced by Etzion and used to construct optimal nonlinear CWCs over an alphabet of size g+ 1 with minimum Hamming distance 2κ - 3, in which each codeword has length υ and weight κ. In this paper, Weil's theorem on character sum estimates is used to show that there exists a GS(2, 4, υ, 3) for any prime v ≡ 1 (mod 4) and v ＞ 13. From the coding theory point of view, an optimal nonlinear quaternary (v, 5, 4) CWC exists for such a prime v.
Timelike Constant Mean Curvature Surfaces with Singularities
Brander, David
2011-01-01
We use integrable systems techniques to study the singularities of timelike non-minimal constant mean curvature (CMC) surfaces in the Lorentz-Minkowski 3-space. The singularities arise at the boundary of the Birkhoff big cell of the loop group involved. We examine the behaviour of the surfaces at the big cell boundary, generalize the definition of CMC surfaces to include those with finite, generic singularities, and show how to construct surfaces with prescribed singularities by solving a singular geometric Cauchy problem. The solution shows that the generic singularities of the generalized surfaces are cuspidal edges, swallowtails and cuspidal cross caps.
The fundamental constants a mystery of physics
Fritzsch, Harald
2009-01-01
The speed of light, the fine structure constant, and Newton's constant of gravity — these are just three among the many physical constants that define our picture of the world. Where do they come from? Are they constant in time and across space? In this book, physicist and author Harald Fritzsch invites the reader to explore the mystery of the fundamental constants of physics in the company of Isaac Newton, Albert Einstein, and a modern-day physicist
Reduction of symplectic manifold through constants of the motion
International Nuclear Information System (INIS)
The reduction of a dynamical system on a symplectic manifold by the use of constants of the motion is described. A constant of the motion together with a symplectic structure defines a distribution, from which one obtains a foliation. The Hamiltonian dynamical system is reduced to another of lower dimension on a certain quotient manifold defined by the foljation. The role of the dynamics remaining on the leaves is discussed
Constant Proportion Debt Obligations (CPDOs)
DEFF Research Database (Denmark)
Cont, Rama; Jessen, Cathrine
2012-01-01
Constant Proportion Debt Obligations (CPDOs) are structured credit derivatives that generate high coupon payments by dynamically leveraging a position in an underlying portfolio of investment-grade index default swaps. CPDO coupons and principal notes received high initial credit ratings from...... the major rating agencies, based on complex models for the joint transition of ratings and spreads for all names in the underlying portfolio. We propose a parsimonious model for analysing the performance of CPDO strategies using a top-down approach that captures the essential risk factors of the CPDO. Our...... approach allows us to compute default probabilities, loss distributions and other tail risk measures for the CPDO strategy and analyse the dependence of these risk measures on various parameters describing the risk factors. We find that the probability of the CPDO defaulting on its coupon payments can...
Henry's law constants of polyols
Compernolle, S.; Müller, J.-F.
2014-12-01
Henry's law constants (HLC) are derived for several polyols bearing between 2 and 6 hydroxyl groups, based on literature data for water activity, vapour pressure and/or solubility. While deriving HLC and depending on the case, also infinite dilution activity coefficients (IDACs), solid state vapour pressures or activity coefficient ratios are obtained as intermediate results. An error analysis on the intermediate quantities and the obtained HLC is included. For most compounds, these are the first values reported, while others compare favourably with literature data in most cases. Using these values and those from a previous work (Compernolle and Müller, 2014), an assessment is made on the partitioning of polyols, diacids and hydroxy acids to droplet and aqueous aerosol.
Coupling constant in dispersive model
Indian Academy of Sciences (India)
R Saleh-Moghaddam; M E Zomorrodian
2013-11-01
The average of the moments for event shapes in + - → hadrons within the context of next-to-leading order (NLO) perturbative QCD prediction in dispersive model is studied. Moments used in this article are $\\langle 1 - T \\rangle, \\langle ρ \\rangle, \\langle B_{T} \\rangle$ and $\\langle B_{W} \\rangle$. We extract , the coupling constant in perturbative theory and α0 in the non-perturbative theory using the dispersive model. By fitting the experimental data, the values of $(M_{Z^{°}})$ = 0.1171 ± 0.00229 and 0 ($_{I} = 2{\\text{GeV}}$) = 0.5068 ± 0.0440 are found. Our results are consistent with the above model. Our results are also consistent with those obtained from other experiments at different energies. All these features are explained in this paper.
Institute of Scientific and Technical Information of China (English)
王新龙
2015-01-01
RTD temperature measurement system for measuring lead resistance errors brought insurmountable problem by using a constant current source drives the thermal resistance and by adding and subtracting circuit to overcome the measurement error caused by wire, which has won high precision analog signal. After AD conversion of the analog signal by returning timed sampling filter out interference and using STM32 so as to obtain a high accuracy temperature values.%针对热电阻测温系统中，导线电阻所带来的测量误差难以克服的问题，通过采用恒流源驱动热电阻以及通过加减运算电路来克服导线带来的测量误差，从而获得了具有较高精度的模拟信号。通过STM32对返回的模拟信号进行定时采样滤除干扰后进行AD转换从而获得了较高精度的温度值。
Institute of Scientific and Technical Information of China (English)
李雁飞; 王行; 庞之洋; 陈金增
2011-01-01
针对舰用变频恒压供水装置测试的需求,以虚拟仪器技术为基础,完成了进出口压力、流量、功率等参数的测量,并基于LabVIEW软件完成了参数监测、数据记录及性能分析等功能设计.应用结果表明,该测试系统在硬件上具有测量精度高、采样速度快、抗干扰能力强、可靠性高等特点,在软件上具有功能完善、人机界面友好等特点.%According to the testing requirement of constant-pressure water-supply instrument of warship, parameters including vacuum degree of inlet, pressure and flux of outlet and power of instrument are measured based on virtual instrument technology. Designed testing software has functions such as parameter monitoring, data recording and performance analysis based on Lab VIEW. Application results show that the testing system has high accuracy of measurement, high sampling speed and high reliability in hardware, and has perfect functions and friendly interface in software.
Institute of Scientific and Technical Information of China (English)
李亚; 赵鑫; 李振亮; 许玮
2013-01-01
An auto air leakage volume test system based on constant pressure method was designed. Using standard orifice plate as throttle device,after testing some original data such as the differential pressure between both sides of the throttle device,temperature of the dry-bulb and the wet-bulb,and so on,the auto air leakage volume can be calculated. The formulas and methods involved were demonstrated in detail and the experiment was designed based on an analysis of the measurement theory. According to the result of the experiment,this method proved stable and reliable and can satisfy the requirement of the measurement.% 设计了基于恒压法的汽车整车漏风量测试系统。采用标准孔板作为节流件，通过测量节流件上下游的压力差、干球温度和湿球温度等基础数据，经过计算可得到整车漏风量。在分析测量原理的基础上，详细给出了计算漏风量的公式和方法，并进行了实验。实验结果表明，该计算方法稳定可靠，可满足测量要求。
Alternative set of defining constants for redefinition of four SI units
Khruschov, V. V.
2016-01-01
We discuss different sets of defining constants, fixed values of which are considered in connection with the transition to new definitions of four SI units (the kilogram, the mole, the ampere, and the kelvin). The notion of constant's order in a given system of units is suggested. We propose an alternative set of fixed constants applicable for new definitions of the four SI units. We analyse and discuss in detail the set, which consists of the Planck constant, the Avogadro constant, the Boltz...
Alternative set of defining constants for redefinition of four SI units
Khruschov, V V
2016-01-01
We discuss different sets of defining constants, fixed values of which are considered in connection with the transition to new definitions of four SI units (the kilogram, the mole, the ampere, and the kelvin). The notion of constant's order in a given system of units is suggested. We propose an alternative set of fixed constants applicable for new definitions of the four SI units. We analyse and discuss in detail the set, which consists of the Planck constant, the Avogadro constant, the Boltzmann constant and the magnetic constant.
A Variant of Davenport's Constant
Indian Academy of Sciences (India)
R Thangadurai
2007-05-01
Let be a prime number. Let be a finite abelian -group of exponent (written additively) and be a non-empty subset of $]n[:=\\{1,2,\\ldots,n\\}$ such that elements of are incongruent modulo and non-zero modulo . Let $k ≥ D(G)/|A|$ be any integer where () denotes the well-known Davenport’s constant. In this article, we prove that for any sequence $g_1,g_2,\\ldots,g_k$ (not necessarily distinct) in , one can always extract a subsequence $g_{i_1},g_{i_2},\\ldots,g_{i_l}$ with $1 ≤ l ≤ k$ such that $$\\sum\\limits_{j=1}^l a_j g_{i_j}=0 \\text{in} G,$$ where $a_j\\in A$ for all . We provide examples where this bound cannot be improved. Furthermore, for the cyclic groups, we prove some sharp results in this direction. In the last section, we explore the relation between this problem and a similar problem with prescribed length. The proof of Theorem 1 uses group-algebra techniques, while for the other theorems, we use elementary number theory techniques.
Institute of Scientific and Technical Information of China (English)
郝丽俊; 单纯玉; 白宝丹
2015-01-01
A cell resistance measurement system based on a constant current source is designed .In the system ,AC square w ave micro‐current signal is first being applied to the cells or the cell mass ,and then an output square‐w ave volt‐age proportional to the measuring cell resistance is obtained according to Ohm's law .Finally digital display values can be attained after rectification and A/D conversion .The application of constant current source can effectively improve meas‐urement accuracy by eliminating the effect on the measuring results of the cell membrane potential and measuring elec‐trode electrolysis .And also ,as using square wave ,the DC influence can be easily filtered by the system with simple cir‐cuit .Finally ,using saline to simulate experimental cell fluid ,the experiment shows that with the increasing distance of test probes ,the measured resistance is increased in direct proportion and the results have little effect on polarization and effective .In addition , results demonstrate that the mean square error is less than 6% in the measurement range 0 -1 000 Ω and it can basically meet to the needs of isolated assisted detection in clinically .%设计实现了一个细胞电阻测量系统。该系统基于方波恒流源电路，将交流方波微电流信号施加在被测细胞或细胞群上，根据欧姆定律，输出与被测细胞电阻成正比的交流方波电压，再经滤波、整流、A／D转换后获得电阻数字显示值。系统中恒流源的应用有效消除了测量电极电解作用及细胞膜电位对测量结果的影响，方波电压的产生则便于进一步滤除直流干扰成分，提高测量准确度。利用生理盐水模拟细胞液进行实验，可以观察到随着测试表笔距离的加大，测量电阻也在做正比例增加，结果受表笔电极化影响很小，且在有效测量范围0～1000Ω内，测量均方误差小于6％，能够基本满足临床上离体辅助检测的需求。
Research and Practice of the Traceable Animal Products Constantly Monitor System%畜产品全程监管可追溯体系的研究与实践
Institute of Scientific and Technical Information of China (English)
崔先雨; 张淋江
2015-01-01
畜产品全程监管可追溯体系，是从畜产品投入品的生产、检验、销售到畜禽养殖的饲养、防疫、监督、检疫、出栏、运输、屠宰，再到畜产品的检疫、运输、销售等每个环节都建立监管和追溯体系，实现真正意义上的全过程监管与追溯。以政府监管的畜产品质量安全监督管理平台为核心，以濮阳市皇哺牛奶有限公司、河南三高农牧股份有限公司为示范企业，依托河南省奶牛生产性能测定中心奶牛生产管理信息服务平台数据，采用标准化的质量安全跟踪与追溯框架，建立畜禽产品质量安全追溯系统，实现“从养殖场到餐桌”整个供应链的全程溯源服务。%The traceable animal products constantly monitor system is a monitor and tracing system from the production, inspection, sale of animal by-products input to livestock breeding, epidemic prevention and supervision, quarantine, market, transportation and slaughter, and then to the quarantine, transport and sale of the animal by-products, aiming to realize the whole process monitor and trace in the true sense. This article takes the government regulated animal products quality and safety supervision and management platform as the core, and Puyang Huangbu Milk Co., Ltd. and Henan Sungo Agriculture and Animal Husbandry Co., Ltd. as the demonstration enterprises. Based on the data on the cow production management information service platform of Henan cow production performance test center, this article uses standard quality and safety of tracking and traceability framework to set up animal products quality safety traceability system to realize the entire tracing system of the supply chain"from farm to table".
Vacuum energy and the cosmological constant
Bass, Steven D
2015-01-01
The accelerating expansion of the Universe points to a small positive value for the cosmological constant or vacuum energy density. We discuss recent ideas that the cosmological constant plus LHC results might hint at critical phenomena near the Planck scale.
Temporal variation of coupling constants and nucleosynthesis
Oberhummer, Heinz; Fairbairn, M; Schlattl, H; Sharma, M M
2003-01-01
We investigate the triple-alpha process and the Oklo phenomenon to obtain constraints on possible cosmological time variations of fundamental constants. Specifically we study cosmological temporal constraints for the fine structure constant and nucleon and meson masses.
Temporal variation of coupling constants and nucleosynthesis
Oberhummer, H.; Csótó, A.; Fairbairn, M.; Schlattl, H.; Sharma, M. M.
2003-05-01
We investigate the triple-alpha process and the Oklo phenomenon to obtain constraints on possible cosmological time variations of fundamental constants. Specifically we study cosmological temporal constraints for the fine structure constant and nucleon and meson masses.
Dependence of Reaction Rate Constants on Density in Supercritical Fluids
Institute of Scientific and Technical Information of China (English)
WANGTao; SHENZhongyao
2002-01-01
A new method,which correlates rate constants of chemical reactions and density or pressure in supercritical fluids,was developed.Based on the transition state theory and thermodynamic principles, the rate constant can be reasonably correlated with the density of the supercritical fluid,and a correlation equation was obtained. Coupled with the equation of state (EOS) of a supercritical solvent,the effect of pressure on reaction rate constant could be represented.Two typical systems were used to test this method.The result indicates that this method is suitable for dilute supercritical fluid solutions.
Anderegg, G
2013-01-01
Critical Survey of Stability Constants of EDTA Complexes focuses on the computations, values, and characteristics of stability constants. The book emphasizes that for a critical discussion of experimentally determined stability constants, it is important to consider the precision of the values that manifests the self-consistency of the constant, taking into consideration the random errors. The publication reviews the stability constants of metal complexes. The numerical calculations affirm the reactions and transformations of metal ions when exposed to varying conditions. The text also present
Constant global population with demographic heterogeneity
Cohen, Joel E.
2008-01-01
To understand better a possible future constant global population that is demographically heterogeneous, this paper analyzes several models. Classical theory of stationary populations generally fails to apply. However, if constant global population size P(global) is the sum of all country population sizes, and if constant global annual number of births B(global) is the sum of the annual number of births of all countries, and if constant global life expectancy at birth e(global) is the populat...
Origin of cosmological constant from Bulk manifold
International Nuclear Information System (INIS)
The problem about cosmological constant is a difficult and important problem, people even don't know what it is really originated from. In this letter, the authors show up a kind of origin of the cosmological constant from the viewpoint of some extra dimensional spaces, obtain different values of the cosmological constant under different circumstances, acquire the evolution function with time t. And we achieve a cosmological constant that may be fitted with modern astronomic observation. (authors)
Fields of rational constants of cyclic factorizable derivations
Janusz Zielinski
2015-01-01
We describe all rational constants of a large family of four-variable cyclic factorizable derivations. Thus, we determine all rational first integrals of their corresponding systems of differential equations. Moreover, we give a characteristic of all four-variable Lotka-Volterra derivations with a nontrivial rational constant. All considerations are over an arbitrary field of characteristic zero. Our main tool is the investigation of the cofactors of strict Darboux ...
Motion on Constant Curvature Spaces and Quantization Using Noether Symmetries
Bracken, Paul
2014-01-01
A general approach is presented for quantizing a metric nonlinear system on a manifold of constant curvature. It makes use of a curvature dependent procedure which relies on determining Noether symmetries from the metric. The curvature of the space functions as a constant parameter. For a specific metric which defines the manifold, Lie differentiation of the metric gives these symmetries. A metric is used such that the resulting Schrodinger equation can be solved in terms of hypergeometric fu...
One-group constant libraries for nuclear equilibrium state
Energy Technology Data Exchange (ETDEWEB)
Mizutani, Akihiko; Sekimoto, Hiroshi [Tokyo Inst. of Tech. (Japan). Research Lab. for Nuclear Reactors
1997-03-01
One-group constant libraries for the nuclear equilibrium state were generated for both liquid sodium cooled MOX fuel type fast reactor and PWR type thermal reactor with Equilibrium Cell Iterative Calculation System (ECICS) using JENDL-3.2, -3, -2 and ENDF/B-VI nuclear data libraries. ECICS produced one-group constant sets for 129 heavy metal nuclides and 1238 fission products. (author)
Institute of Scientific and Technical Information of China (English)
潘庭龙; 孙承奇; 纪志成; 徐莉莉
2015-01-01
To achieve the constant power control of the above rated wind speed,pitch angle and elec-tromagnetic torque of the wind energy conversion system( WECS) must be controlled simultaneously. The nonlinearity and uncertainty of the variable speed variable pitch wind energy conversion system results in the difficulties in modeling. Combining the data-driven optimal control theory with multivariable control strategy,according to the input and output data of the variable speed variable pitch wind energy conversion system to calculate the Markov parameters. A data-driven state observer controller is constructed. A multivariable optimal feedback controller is designed by the closed form of difference Riccati equation. Simulation in MATLAB/simulink results indicate that the above rated wind,the data-driven multivariable optimal control without modelling can effectively maintain the rated power output.%为了实现风能转换系统在额定风速以上的恒功率控制，必须同时控制桨距角和电磁转矩。针对变速变桨风能转换系统具有强非线性和不确定性难于建立精确模型的问题，将数据驱动的最优控制理论和多变量控制策略相结合，根据变速变桨风能转换系统的输入输出数据得出系统的马尔可夫参数，据此构造一个基于数据的状态观测控制器，并通过差分Riccati方程的闭合解来设计多变量最优反馈控制器。在MATLAB/Simulink的仿真结果表明：在不建立模型的基础上设计的数据驱动的多变量最优控制器能够有效地实现系统的恒功率输出控制。
Institute of Scientific and Technical Information of China (English)
李加念; 洪添胜; 倪慧娜
2013-01-01
The stability of micro-irrigation system inlet water pressure affects the uniformity of the micro-irrigation and the mixed fertilizer accuracy of automatic fertilizer mixing device. In order to provide a constant inlet water pressure for small and medium-sized irrigation pipe network which adopts gravity drip irrigation, a constant pressure water supply automatic control device was developed, through employing a diaphragm pump DP-60 powered by solar energy to carry water to the reservoir built in high place, and maintaining the reservoir’ water level at a fixed height in the drip irrigation process. The water level was detected online by using a level sensor YZ-YO-LAG1, and the controller control DP-60 carrying water to the reservoir according to the water level detected. Due to the certain distance between reservoir water level detection terminal and DP-60 control terminal, two wireless communication modules CC1100 were installed in each terminal respectively to realize wireless data transmission and control between two terminals. To reduce power consumption of wireless communication, a regular communication strategy combining with sleeping mechanism was adopted, and a kind of time synchronization technology was employed to keep time synchronization between the communication parties, and the WOR (wake on radio) mode of CC1100 module was enabled while communicating, the communication success rate was 100%verified by practical test. Photovoltaic capacity of the system had been designed for obtaining an optimal capacity combination of solar cell array and lead-acid battery, and the solar panel power was determined to be 60 W and the battery capacity to be 60 A·h, the capacity combination could meet the electricity demand of 500L irrigation norm for each drip irrigation cycle, and ensure that the system operates normally in seven consecutive days without sunshine. In order to maximize the use of solar energy, the relationship between solar panel power and the
Measuring the RC time constant with Arduino
Pereira, N. S. A.
2016-11-01
In this work we use the Arduino UNO R3 open source hardware platform to assemble an experimental apparatus for the measurement of the time constant of an RC circuit. With adequate programming, the Arduino is used as a signal generator, a data acquisition system and a basic signal visualisation tool. Theoretical calculations are compared with direct observations from an analogue oscilloscope. Data processing and curve fitting is performed on a spreadsheet. The results obtained for the six RC test circuits are within the expected interval of values defined by the tolerance of the components. The hardware and software prove to be adequate to the proposed measurements and therefore adaptable to a laboratorial teaching and learning context.
Dimensionless constants, cosmology and other dark matters
Tegmark, M; Rees, M; Wilczek, F; Tegmark, Max; Aguirre, Anthony; Rees, Martin; Wilczek, Frank
2006-01-01
We identify 31 dimensionless physical constants required by particle physics and cosmology, and emphasize that both microphysical constraints and selection effects might help elucidate their origin. Axion cosmology provides an instructive example, in which these two kinds of arguments must both be taken into account, and work well together. If a Peccei-Quinn phase transition occurred before or during inflation, then the axion dark matter density will vary from place to place with a probability distribution. By calculating the net dark matter halo formation rate as a function of all four relevant cosmological parameters and assessing other constraints, we find that this probability distribution, computed at stable solar systems, is arguably peaked near the observed dark matter density. If cosmologically relevant WIMP dark matter is discovered, then one naturally expects comparable densities of WIMPs and axions, making it important to follow up with precision measurements to determine whether WIMPs account for ...
Nonlinear H-infinity robust control of constant power for wind power system%风力发电系统的恒功率非线性H∞鲁棒控制
Institute of Scientific and Technical Information of China (English)
秦生升; 胡国文; 顾春雷; 李杜
2012-01-01
风力发电系统传统控制器的缺点在于，基于某一工况点的局部线性化方法无法实现全局范围的精确控制，且传统的控制理论无法应对内外干扰．本文将精确反馈线性化方法与线性H∞理论相结合设计非线性H∞控制器．首先用微分几何精确线性化方法将非线性风电模型全局线性化，然后运用线性H∞控制理论对此线性系统设计控制器，将两者结合有原风电系统的非线性H∞变桨距控制器．最后对12m／s至24m／s阶跃风，12111／至22m／s骤变风，18m／s至20m／s随机风，以及风力机转动惯量下降10％的情况进行仿真，能实现风机转速及输出功率的恒定．验证了该控制器在全风速段的精确控制，并且具有良好鲁棒性．%The conventional wind turbine controller can not realize the global range control because of its local lineariza- tion at specific operating point. It neither provides the rejection of internal and external disturbances. In our approach, the nonlinear model of the wind turbine is converted to a global linear model by using the differential geometry method. For this global linear model, a linear H-infinity variable pitch controller is designed for the existing wind power system. Simu- lations of the control system are carried out for 12-24 m/s step wind, 12-22 m/s suddenly change wind, 18-20 m/s random wind, and 10% reduction of wind turbine rotary inertia. Results show that the wind turbine speed and the output power are maintained at constant values as desired, showing desirable performances and robustness of the control.
Effects of Cosmological Constant on Clustering of Galaxies
Hameeda, Mir; Upadhyay, Sudhaker; Faizal, Mir; Ali, Ahmed Farag
2016-09-01
In this paper, we analyse the effect of the expansion of the universe on the clustering of galaxies. We evaluate the configurational integral for interacting system of galaxies in an expanding universe by including effects produced by the cosmological constant. The gravitational partition function is obtained using this configuration integral. Thermodynamic quantities, specifically, Helmholtz free energy, entropy, internal energy, pressure and chemical potential are also derived for this system. It is observed that they depend on the modified clustering parameter for this system of galaxies. It is also demonstrated that these thermodynamical quantities get corrected because of the cosmological constant.
Effects of Cosmological Constant on Clustering of Galaxies
Hameeda, Mir; Faizal, Mir; Ali, Ahmed Farag
2016-01-01
In this paper, we analyse the effect of the expansion of the universe on the clustering of galaxies. We evaluate the configurational integral for interacting system of galaxies in an expanding universe by including effects produced by the cosmological constant. The gravitational partition function is obtained using this configuration integral. Thermodynamic quantities, specifically, Helmholtz free energy, entropy, internal energy, pressure and chemical potential are also derived for this system. It is observed that they depend on the modified clustering parameter for this system of galaxies. It is also demonstrated that these thermodynamical quantities get corrected because of the cosmological constant.
Failure to Manage Constant Change
McDonald, Ann
2010-01-01
This study examines patterns of system failure (communication, typographic, material, economic, maintenance) and the resulting workarounds in signs that are intended to communicate frequently changing information in the built environment. The observed failures and workarounds in the communication of ephemeral data and the accompanying narratives…
An Automated Approach for Finding Variable-Constant Pairing Bugs
DEFF Research Database (Denmark)
Lawall, Julia; Lo, David
2010-01-01
Named constants are used heavily in operating systems code, both as internal flags and in interactions with devices. Decision making within an operating system thus critically depends on the correct usage of these values. Nevertheless, compilers for the languages typically used in implementing...
Li, Xiaogai; von Holst, Hans; Kleiven, Svein
2013-01-01
A 3D finite element (FE) model has been developed to study the mean intracranial pressure (ICP) response during constant-rate infusion using linear poroelasticity. Due to the uncertainties in the poroelastic constants for brain tissue, the influence of each of the main parameters on the transient ICP infusion curve was studied. As a prerequisite for transient analysis, steady-state simulations were performed first. The simulated steady-state pressure distribution in the brain tissue for a normal cerebrospinal fluid (CSF) circulation system showed good correlation with experiments from the literature. Furthermore, steady-state ICP closely followed the infusion experiments at different infusion rates. The verified steady-state models then served as a baseline for the subsequent transient models. For transient analysis, the simulated ICP shows a similar tendency to that found in the experiments, however, different values of the poroelastic constants have a significant effect on the infusion curve. The influence of the main poroelastic parameters including the Biot coefficient α, Skempton coefficient B, drained Young's modulus E, Poisson's ratio ν, permeability κ, CSF absorption conductance C(b) and external venous pressure p(b) was studied to investigate the influence on the pressure response. It was found that the value of the specific storage term S(ε) is the dominant factor that influences the infusion curve, and the drained Young's modulus E was identified as the dominant parameter second to S(ε). Based on the simulated infusion curves from the FE model, artificial neural network (ANN) was used to find an optimised parameter set that best fit the experimental curve. The infusion curves from both the FE simulation and using ANN confirmed the limitation of linear poroelasticity in modelling the transient constant-rate infusion. PMID:22452461
Cosmological Constant and Soft Terms in Supergravity
Choi, Kiwoon; Kim, Jihn E.; Nilles, Hans Peter, Ramos-S\\xe1nchez, Sa\\xfal
1994-01-01
Some of the soft SUSY breaking parameters in hidden sector supergravity model depend on the expectation value of the hidden sector scalar potential, $$, whose tree level value is equal to the tree level cosmological constant. The current practice of calculating soft parameters assumes that $=0$. Quantum correction to the cosmological constant can differ from the correction to $$ by an amount of order $m^2_{3/2}M_{Pl}^2/8\\pi$. This implies that, for the vanishing cosmological constant, the $$-...
A small but nonzero cosmological constant
Ng, Y J
1999-01-01
Recent astrophysical observations seem to indicate that the cosmological constant is small but nonzero and positive. The old cosmological constant problem asks why it is so small; we must now ask, in addition, why it is nonzero, and why it is positive. In this essay, we try to kill these three metaphorical birds with one stone. That stone is the unimodular theory of gravity, which is the canonical theory of gravity, except for the way the cosmological constant arises in the theory.
Cosmological Constant and Axions in String Theory
Energy Technology Data Exchange (ETDEWEB)
Svrcek, Peter; /Stanford U., Phys. Dept. /SLAC
2006-08-18
String theory axions appear to be promising candidates for explaining cosmological constant via quintessence. In this paper, we study conditions on the string compactifications under which axion quintessence can happen. For sufficiently large number of axions, cosmological constant can be accounted for as the potential energy of axions that have not yet relaxed to their minima. In compactifications that incorporate unified models of particle physics, the height of the axion potential can naturally fall close to the observed value of cosmological constant.
Bubble Universes With Different Gravitational Constants
Takamizu, Yu-ichi; Maeda, Kei-ichi
2015-01-01
We argue a scenario motivated by the context of string landscape, where our universe is produced by a new vacuum bubble embedded in an old bubble and these bubble universes have not only different cosmological constants, but also their own different gravitational constants. We study these effects on the primordial curvature perturbations. In order to construct a model of varying gravitational constants, we use the Jordan-Brans-Dicke (JBD) theory where different expectation values of scalar fi...
A natural cosmological constant from chameleons
Energy Technology Data Exchange (ETDEWEB)
Nastase, Horatiu, E-mail: nastase@ift.unesp.br [Instituto de Física Teórica, UNESP-Universidade Estadual Paulista, R. Dr. Bento T. Ferraz 271, Bl. II, Sao Paulo 01140-070, SP (Brazil); Weltman, Amanda, E-mail: amanda.weltman@uct.ac.za [Astrophysics, Cosmology & Gravity Center, Department of Mathematics and Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7700 (South Africa)
2015-07-30
We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT)-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero) and the coincidence problem (why Λ is comparable to the matter density now)
Surprises in numerical expressions of physical constants
Amir, Ariel; Tokieda, Tadashi
2016-01-01
In science, as in life, `surprises' can be adequately appreciated only in the presence of a null model, what we expect a priori. In physics, theories sometimes express the values of dimensionless physical constants as combinations of mathematical constants like pi or e. The inverse problem also arises, whereby the measured value of a physical constant admits a `surprisingly' simple approximation in terms of well-known mathematical constants. Can we estimate the probability for this to be a mere coincidence, rather than an inkling of some theory? We answer the question in the most naive form.
Motion on constant curvature spaces and quantization using noether symmetries
Bracken, Paul
2014-12-01
A general approach is presented for quantizing a metric nonlinear system on a manifold of constant curvature. It makes use of a curvature dependent procedure which relies on determining Noether symmetries from the metric. The curvature of the space functions as a constant parameter. For a specific metric which defines the manifold, Lie differentiation of the metric gives these symmetries. A metric is used such that the resulting Schrödinger equation can be solved in terms of hypergeometric functions. This permits the investigation of both the energy spectrum and wave functions exactly for this system.
Spectral Sensitivity Measured with Electroretinogram Using a Constant Response Method
Rocha, Fernando Allan de Farias; Gomes, Bruno Duarte; Silveira, Luiz Carlos de Lima; Martins, Sonia Limara; Aguiar, Renata Genaro; de Souza, John Manuel; Ventura, Dora Fix
2016-01-01
A new method is presented to determine the retinal spectral sensitivity function S(λ) using the electroretinogram (ERG). S(λ)s were assessed in three different species of myomorph rodents, Gerbils (Meriones unguiculatus), Wistar rats (Ratus norvegicus), and mice (Mus musculus). The method, called AC Constant Method, is based on a computerized automatic feedback system that adjusts light intensity to maintain a constant-response amplitude to a flickering stimulus throughout the spectrum, as it is scanned from 300 to 700 nm, and back. The results are presented as the reciprocal of the intensity at each wavelength required to maintain a constant peak to peak response amplitude. The resulting S(λ) had two peaks in all three rodent species, corresponding to ultraviolet and M cones, respectively: 359 nm and 511 nm for mice, 362 nm and 493 nm for gerbils, and 362 nm and 502 nm for rats. Results for mouse and gerbil were similar to literature reports of S(λ) functions obtained with other methods, confirming that the ERG associated to the AC Constant-Response Method was effective to obtain reliable S(λ) functions. In addition, due to its fast data collection time, the AC Constant Response Method has the advantage of keeping the eye in a constant light adapted state. PMID:26800521
Institute of Scientific and Technical Information of China (English)
赵奇; 吴智铭
2007-01-01
为优化半导体生产系统,针对半导体生产线的特点,建立基于在制品数(Work in Process,WIP)水平控制投料的数学模型.通过仿真试验,得出不同WIP水平对生产线性能的影响;比较固定在制品数(CONstant WIP,CONWIP)投料系统与固定时间间隔投料(CONstant Release Interval,CONRIN)系统之间的性能差异.在不停线的情况下,对增加生产品种的生产线进行分析,得出一些关于影响WIP水平因素的定性规律.
Habitable sphere and fine structure constant
Kozlovskii, Miroslaw P; Kozlowski, Miroslaw; Marciak-Kozlowska, Janina
2005-01-01
Future space missions, TPF and Darwin will focus on searches of signatures of life on extrasolar planets. In this paper we look for model independ definition of the habitable zone. It will be shown that the radius of the habitable sphere depends only on the constants of the Nature. Key words: Habitable sphere, fine structure constant.
Fullerene derivatives with increased dielectric constants
Jahani, Fatemeh; Torabi, Solmaz; Chiechi, Ryan C; Koster, L Jan Anton; Hummelen, Jan C
2014-01-01
The invention of new organic materials with high dielectric constants is of extreme importance for the development of organic-based devices such as organic solar cells. We report on a synthetic way to increase the dielectric constant of fullerene derivatives. It is demonstrated that introducing trie
FLOTATION RATE CONSTANT MODEL FOR FINE COAL
Institute of Scientific and Technical Information of China (English)
LuMaixi; CaiZhang; TaoYoujun; KuangYali
1996-01-01
The density of fine coal has a major effect on the value of its floxation rate constant. The collector dose can increase the flotation rate of fine coal, especially for low ash coal, but the effect for gangue is not notable. The flotation rate of gangue is mainly governed by the water entrainment. A coal flotation rate constant model has been developed.
Atomic hydrogen and fundamental physical constants
International Nuclear Information System (INIS)
Techniques are described which allow the study, in undergraduate laboratories, of the spectrum of atomic hydrogen. The Rydberg constant, the electron-proton mass ratio, and the fine-structure constant are evaluated from the measurements. The key to the series of experiments is a discharge tube in which atomic lines dominate over the molecular lines. (author)
Fields of rational constants of cyclic factorizable derivations
Directory of Open Access Journals (Sweden)
Janusz Zielinski
2015-12-01
Full Text Available We describe all rational constants of a large family of four-variable cyclic factorizable derivations. Thus, we determine all rational first integrals of their corresponding systems of differential equations. Moreover, we give a characteristic of all four-variable Lotka-Volterra derivations with a nontrivial rational constant. All considerations are over an arbitrary field of characteristic zero. Our main tool is the investigation of the cofactors of strict Darboux polynomials. Factorizable derivations are important in derivation theory. Namely, we may associate the factorizable derivation with any given derivation of a polynomial ring and that construction helps to determine rational constants of arbitrary derivations. Besides, Lotka-Volterra systems play a significant role in population biology, laser physics and plasma physics.
Energy Technology Data Exchange (ETDEWEB)
Tiwari, Arvind [Department of Design, Production and Management, University of Twente, Enschede (Netherlands); Dubey, Swapnil; Sandhu, G.S. [Centre for Energy Studies, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India); Sodha, M.S. [Department of Education and Physics, Lucknow University, Lucknow 226007 (India); Anwar, S.I. [Indian Institute of Sugar-cane Research, Lucknow, U.P. (India)
2009-12-15
In this communication, an analytical expression for the water temperature of an integrated photovoltaic thermal solar (IPVTS) water heater under constant flow rate hot water withdrawal has been obtained. Analysis is based on basic energy balance for hybrid flat plate collector and storage tank, respectively, in the terms of design and climatic parameters. Further, an analysis has also been extended for hot water withdrawal at constant collection temperature. Numerical computations have been carried out for the design and climatic parameters of the system used by Huang et al. [Huang BJ, Lin TH, Hung WC, Sun FS. Performance evaluation of solar photovoltaic/thermal systems. Sol Energy 2001; 70(5): 443-8]. It is observed that the daily overall thermal efficiency of IPVTS system increases with increase constant flow rate and decrease with increase of constant collection temperature. The exergy analysis of IPVTS system has also been carried out. It is further to be noted that the overall exergy and thermal efficiency of an integrated photovoltaic thermal solar system (IPVTS) is maximum at the hot water withdrawal flow rate of 0.006 kg/s. The hourly net electrical power available from the system has also been evaluated. (author)
String theory, cosmology and varying constants
Damour, Thibault
In string theory the coupling `constants' appearing in the low-energy effective Lagrangian are determined by the vacuum expectation values of some (a priori) massless scalar fields (dilaton, moduli). This naturally leads one to expect a correlated variation of all the coupling constants, and an associated violation of the equivalence principle. We review some string-inspired theoretical models which incorporate such a spacetime variation of coupling constants while remaining naturally compatible both with phenomenological constraints coming from geochemical data (Oklo; Rhenium decay) and with present equivalence principle tests. Barring a very unnatural fine-tuning of parameters, a variation of the fine-structure constant as large as that recently `observed' by Webb et al. in quasar absorption spectra appears to be incompatible with these phenomenological constraints. Independently of any model, it is emphasized that the best experimental probe of varying constants are high-precision tests of the universality of free fall, such as MICROSCOPE and STEP.
String theory, cosmology and varying constants
Damour, Thibault Marie Alban Guillaume
2002-01-01
In string theory the coupling ``constants'' appearing in the low-energy effective Lagrangian are determined by the vacuum expectation values of some (a priori) massless scalar fields (dilaton, moduli). This naturally leads one to expect a correlated variation of all the coupling constants, and an associated violation of the equivalence principle. We review some string-inspired theoretical models which incorporate such a spacetime variation of coupling constants while remaining naturally compatible both with phenomenological constraints coming from geochemical data (Oklo; Rhenium decay) and with present equivalence principle tests. Barring a very unnatural fine-tuning of parameters, a variation of the fine-structure constant as large as that recently ``observed'' by Webb et al. in quasar absorption spectra appears to be incompatible with these phenomenological constraints. Independently of any model, it is emphasized that the best experimental probe of varying constants are high-precision tests of the universa...
Energy Technology Data Exchange (ETDEWEB)
Berryman, J.G.; Nakagawa, S.
2009-11-20
Poroelastic analysis has traditionally focused on the relationship between dry or drained constants which are assumed known and the saturated or undrained constants which are assumed unknown. However, there are many applications in this field of study for which the main measurements can only be made on the saturated/undrained system, and then it is uncertain what the eects of the uids were on the system, since the drained constants remain a mystery. The work presented here shows how to deduce drained constants from undrained constants for anisotropic systems having symmetries ranging from isotropic to orthotropic. Laboratory ultrasound data are then inverted for the drained constants in three granular packings: one of glass beads, and two others for distinct types of more or less angular sand grain packings. Experiments were performed under uniaxial stress, which resulted in hexagonal (transversely isotropic) symmetry of the poroelastic response. One important conclusion from the general analysis is that the drained constants are uniquely related to the undrained constants, assuming that porosity, grain bulk modulus, and pore uid bulk modulus are already known. Since the resulting system of equations for all the drained constants is linear, measurement error in undrained constants also propagates linearly into the computed drained constants.
Berryman, James G; Nakagawa, Seiji
2010-02-01
Poroelastic analysis has traditionally focused on the relationship between dry and drained constants, which are assumed known, and the saturated or undrained constants, which are assumed unknown. However, there are many applications in this field of study for which the main measurements can only be made on the saturated/undrained system, and then it is uncertain what the effects of the fluids were on the system, since the drained constants remain a mystery. The work presented here shows how to deduce drained constants from undrained constants for anisotropic systems having symmetries ranging from isotropic to orthotropic. Laboratory ultrasound data are then inverted for the drained constants in three granular packings: one of glass beads, and two others for distinct types of more or less angular sand grain packings. Experiments were performed under uniaxial stress, which resulted in hexagonal (transversely isotropic) symmetry of the poroelastic response. One important conclusion from the general analysis is that the drained constants are uniquely related to the undrained constants, assuming that porosity, grain bulk modulus, and pore fluid bulk modulus are already known. Since the resulting system of equations for all the drained constants is linear, measurement error in undrained constants also propagates linearly into the computed drained constants. PMID:20136194
GPS test of the local position invariance of Planck's constant
Kentosh, James; Mohageg, Makan
2012-01-01
Publicly available clock correction data from the Global Positioning System was analyzed and used in combination with the results of terrestrial clock comparison experiments to confirm the local position invariance (LPI) of Planck's constant within the context of general relativity. The results indicate that h is invariant within a limit of |beta_h|
DETERMINATION OF HENRY'S LAW CONSTANTS OF SELECTED PRIORITY POLLUTANTS
The Henry's law constants (H) for 41 selected priority pollutants were determined to characterize these pollutants and provide information on their fate as they pass through wastewater treatment systems. All experimental values presented for H are averages of two or more replicat...
QCD Phase Transitions and Bag Constants at Finite Chemical Potential
Institute of Scientific and Technical Information of China (English)
YANG Shu; GUO Hua; ZHAO En-Guang; L(U) Xiao-Fu
2007-01-01
The global colour model at finite temperature is further extended to study the systems at finite chemical potential. The deconfinement and chiral phase transition at finite chemical potential and at temperature T=0K are studied simultaneously. Meanwhile the evolution of the bag constants at finite chemical potential is calculated. The dependences of results on the model parameters are discussed in detail.
Theophylline: constant-rate infusion predictions.
Mesquita, C A; Sahebjami, H; Imhoff, T; Thomas, J P; Myre, S A
1984-01-01
This study was undertaken to evaluate a method of prospectively estimating appropriate aminophylline infusion rates in acutely ill, hospitalized patients with bronchospasm. Steady-state serum theophylline concentrations (Css), clearances (Cl), and half-lives (t1/2) were estimated by the Chiou method using serum concetrantions obtained 1 and 6 h after the start of a constant-rate intravenous aminophylline infusion in 10 male patients averaging 57 years of age. Using an enzyme-multiplied immunoassay (EMIT) system for theophylline analysis, pharmacokinetic estimations were excellent for Css (r = 0.9103, p less than 0.01) and Cl (r = 0.9750, p less than 0.01). The mean estimation errors were 9.4% (range 0.8-21.5) for Css and 12.3% (range 1.3-28.0) for Cl. There was no correlation between patient age and Cl. This method is useful for rapidly individualizing aminophylline therapy in patients with acute bronchospasm. PMID:6740734
Neutron stars and the cosmological constant problem
International Nuclear Information System (INIS)
The gravitational aether theory is a modification of general relativity that decouples vacuum energy from gravity, and thus can potentially address the cosmological constant problem. The classical theory is distinguishable from general relativity only in the presence of relativistic pressure (or vorticity). Since the interior of neutron stars has high pressure and as their mass and radius can be measured observationally, they are the perfect laboratory for testing the validity of the aether theory. In this paper, we solve the equations of stellar structure for the gravitational aether theory and find the predicted mass-radius relation of nonrotating neutron stars using two different realistic proposals for the equation of state of nuclear matter. We find that the maximum neutron-star mass predicted by the aether theory is 12%-16% less than the maximum mass predicted by general relativity assuming these two equations of state. We also show that the effect of aether is similar to modifying the equation of state in general relativity. The effective pressure of the neutron star given by the aether theory at a fiducial density differs from the values given by the two nuclear equations of state to an extent that can be constrained using future gravitational wave observations of neutron stars in compact systems. This is a promising way to test the aether theory if further progress is made in constraining the equation of state of nuclear matter in densities above the nuclear saturation density.
On the constants for some Sobolev imbeddings
Directory of Open Access Journals (Sweden)
Pizzocchero Livio
2001-01-01
Full Text Available We consider the imbedding inequality is the Sobolev space (or Bessel potential space of type and (integer or fractional order . We write down upper bounds for the constants , using an argument previously applied in the literature in particular cases. We prove that the upper bounds computed in this way are in fact the sharp constants if , , and exhibit the maximising functions. Furthermore, using convenient trial functions, we derive lower bounds on for in many cases these are close to the previous upper bounds, as illustrated by a number of examples, thus characterizing the sharp constants with little uncertainty.
The Determination of the Strong Coupling Constant
Dissertori, Günther
2016-10-01
The strong coupling constant is one of the fundamental parameters of the Standard Theory of particle physics. In this review I will briefly summarise the theoretical framework, within which the strong coupling constant is defined and how it is connected to measurable observables. Then I will give an historical overview of its experimental determinations and discuss the current status and world average value. Among the many different techniques used to determine this coupling constant in the context of quantum chromodynamics, I will focus in particular on a number of measurements carried out at the Large Electron-Positron Collider (LEP) and the Large Hadron Collider (LHC) at CERN.
Some Zero-Sum Constants with Weights
Indian Academy of Sciences (India)
S D Adhikari; R Balasubramanian; F Pappalardi; P Rath
2008-05-01
For an abelian group , the Davenport constant () is defined to be the smallest natural number such that any sequence of elements in has a non-empty subsequence whose sum is zero (the identity element). Motivated by some recent developments around the notion of Davenport constant with weights, we study them in some basic cases. We also define a new combinatorial invariant related to $(\\mathbb{Z}/n\\mathbb{Z})^d$, more in the spirit of some constants considered by Harborth and others and obtain its exact value in the case of $(\\mathbb{Z}/n\\mathbb{Z})^2$ where is an odd integer.
On geometrically unified fields and universal constants
Fabbri, Luca
2013-07-01
We consider the Cartan extension of Riemann geometry as the basis upon which to build the Sciama-Kibble completion of Einstein gravity, developing the most general theory in which torsion and metric have two independent coupling constants: the main problem of the ESK theory was that torsion, having the Newton constant, was negligible beyond the Planck scale, but in this {ESK}2 theory torsion, with its own coupling constant, may be relevant much further Planck scales; further consequences of these torsionally-induced interactions will eventually be discussed.
Fractional crystallization of iron meteorites: Constant versus changing partition coefficients
Jones, J. H.
1994-01-01
Analyses of magmatic iron meteorites, plotted on LogC(sub i) vs LogC(sub Ni) diagrams, often form linear arrays. Traditionally, this linearity has been ascribed to fractional crystallization under the assumption of constant partition coefficients (i.e., Rayleigh fractionation). Paradoxically, however, partition coefficients in the Fe-Ni-S-P system are decidedly not constant. This contribution provides a rationale for understanding how trends on LogC(sub i) vs LogC(sub Ni) diagrams can be linear, even when partition coefficients are changing rapidly.
Interacting universes and the cosmological constant
Energy Technology Data Exchange (ETDEWEB)
Alonso-Serrano, A. [Centro de Física “Miguel Catalán”, Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 121, 28006 Madrid (Spain); Estación Ecológica de Biocosmología, Pedro de Alvarado 14, 06411 Medellín (Spain); Bastos, C. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Avenida Rovisco Pais 1, 1049-001 Lisboa (Portugal); Bertolami, O. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Avenida Rovisco Pais 1, 1049-001 Lisboa (Portugal); Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Robles-Pérez, S., E-mail: salvarp@imaff.cfmac.csic.es [Centro de Física “Miguel Catalán”, Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 121, 28006 Madrid (Spain); Estación Ecológica de Biocosmología, Pedro de Alvarado 14, 06411 Medellín (Spain); Física Teórica, Universidad del País Vasco, Apartado 644, 48080 Bilbao (Spain)
2013-02-12
In this Letter it is studied the effects that an interaction scheme among universes can have in the values of their cosmological constants. In the case of two interacting universes, the value of the cosmological constant of one of the universes becomes very close to zero at the expense of an increasing value of the cosmological constant of the partner universe. In the more general case of a chain of N interacting universes with periodic boundary conditions, the spectrum of the Hamiltonian splits into a large number of levels, each of them associated with a particular value of the cosmological constant, that can be occupied by single universes revealing a collective behavior that plainly shows that the multiverse is much more than the mere sum of its parts.
An improved dosimeter having constant flow pump
International Nuclear Information System (INIS)
A dosemeter designed for individual use which can be used to monitor toxic radon gas and toxic related products of radon gas in mines and which incorporates a constant air stream flowing through the dosimeter is described. (U.K.)
The time constant of the somatogravic illusion
Correia Grácio, B.J.; Winkel, K.N. de; Groen, E.L.; Wentink, M.; Bos, J.E.
2013-01-01
Met desdemona hebben we gevonden dat de tijd constante van de somatografische illusie rond twee seconden is. Dit resultaat verschilt van wat was gevonden in ander onderzoek dat gebruikt maakt van een gewone centrifuge
Determination of the gravitational constant G
Institute of Scientific and Technical Information of China (English)
HU Zhong-kun; LIU Qi; LUO Jun
2006-01-01
A precise knowledge of the Newtonian gravitational constant G has an important role in physics and is of considerable meteorological interest.Although G was the first physical constant to be introduced and measured in the history of science,it is still the least precisely determined of all the fundamental constants of nature.The 2002 CODATA recommended value for G,G=(6.6742±0.0010)×10-11m3·kg-1·s-2,has an uncertainty of 150 parts per million (ppm),much larger than that of all other fundamental constants.Reviewed here is the status of our knowledge of the absolute value of G,methods for determining G,and recent high precision experiments for determining G.
Canonoid transformations and constants of motion
International Nuclear Information System (INIS)
The necessary and sufficient conditions for a canonoid transformation with respect to a given Hamiltonian are obtained in terms of the Lagrange brackets of the trasformation. The relation of these conditions with the constants of motion is discussed. (Author)
Cosmology with a time dependent cosmological constant
International Nuclear Information System (INIS)
In the context of the scalar-tensor theories we consider cosmological models with a time dependent cosmological constant. Several toy models are obtained among them there are solutions without singularity and accelerating. (Author)
Hydrolysis and formation constants at 250C
International Nuclear Information System (INIS)
A database consisting of hydrolysis and formation constants for about 20 metals associated with the disposal of nuclear waste is given. Complexing ligands for the various ionic species of these metals include OH, F, Cl, SO4, PO4 and CO3. Table 1 consists of tabulated calculated and experimental values of log K/sub xy/, mainly at 250C and various ionic strengths together with references to the origin of the data. Table 2 consists of a column of recommended stability constants at 250C and zero ionic strength tabulated in the column headed log K/sub xy/(0); other columns contain coefficients for an extended Debye-Huckel equation to permit calculations of stability constants up to 3 ionic strength, and up to 0.7 ionic strength using the Davies equation. Selected stability constants calculated with these coefficients for various ionic strengths agree to an average of +- 2% when compared with published experimental and calculated values
Low noise constant current source for bias dependent noise measurements
International Nuclear Information System (INIS)
A low noise constant current source used for measuring the 1/f noise in disordered systems in ohmic as well as nonohmic regime is described. The source can supply low noise constant current starting from as low as 1 μA to a few tens of milliampere with a high voltage compliance limit of around 20 V. The constant current source has several stages, which can work in a standalone manner or together to supply the desired value of load current. The noise contributed by the current source is very low in the entire current range. The fabrication of a low noise voltage preamplifier modified for bias dependent noise measurements and based on the existing design available in the MAT04 data sheet is also described.
The Cosmological Constant Problem from a Brane-World Perspective
Förste, S; Lavignac, Stephane; Nilles, Hans Peter; Forste, Stefan; Lalak, Zygmunt; Lavignac, St\\'ephane; Nilles, Hans Peter
2000-01-01
We point out several subtleties arising in brane-world scenarios of cosmological constant cancellation. We show that solutions with curvature singularities are inconsistent, unless the contribution to the effective four-dimentional cosmological constant of the physics that resolves the singularities is fine-tuned. This holds for both flat and curved branes. Irrespective of this problem, we then study an isolated class of flat solutions in models where a bulk scalar field with a vanishing potential couples to a 3-brane. We give an example where the introduction of a bulk scalar potential results in a nonzero cosmological constant. Finally we comment on the stability of classical solutions of the brane system with respect to quantum corrections.
Maximum Tension: with and without a cosmological constant
Barrow, John D
2014-01-01
We discuss various examples and ramifications of the conjecture that there exists a maximum force (or tension) in general relativistic systems. We contrast this situation with that in Newtonian gravity, where no maximum force exists, and relate it to the existence of natural units defined by constants of Nature and the fact that the Planck units of force and power do not depend on Planck's constant. We discuss how these results change in higher dimensions where the Planck units of force are no longer non-quantum. We discuss the changes that might occur to the conjecture if a positive cosmological constant exists and derive a maximum force bound using the Kottler-Schwarzschild-de Sitter black hole.
Synthetic Strategies for High Dielectric Constant Silicone Elastomers
DEFF Research Database (Denmark)
Madsen, Frederikke Bahrt
synthetic strategies were developed in this Ph.D. thesis, in order to create silicone elastomers with high dielectric constants and thereby higher energy densities. The work focused on maintaining important properties such as dielectric loss, electrical breakdown strength and elastic modulus...... driving voltages (several kV’s), for instance, are necessary to activate the material. Driving voltage can be lowered by increasing the energy density of the DEAP elastomer film, achieved by creating elastomers with high dielectric constants, which is a material’s ability to store electrical energy. Two....... The methodology therefore involved chemically grafting high dielectric constant chemical groups onto the elastomer network, as this would potentially provide a stable elastomer system upon continued activation of the material. The first synthetic strategy involved the synthesis of a new type of cross...
International Nuclear Information System (INIS)
Current sources are widely used in bio-impedance spectroscopy (BIS) measurement systems to maximize current injection for increased signal to noise while keeping within medical safety specifications. High-performance current sources based on the Howland current pump with optimized impedance converters are able to minimize stray capacitance of the cables and setup. This approach is limited at high frequencies primarily due to the deteriorated output impedance of the constant current source when situated in a real measurement system. For this reason, voltage sources have been suggested, but they require a current sensing resistor, and the SNR reduces at low impedance loads due to the lower current required to maintain constant voltage. In this paper, we compare the performance of a current source-based BIS and a voltage source-based BIS, which use common components. The current source BIS is based on a Howland current pump and generalized impedance converters to maintain a high output impedance of more than 1 MΩ at 2 MHz. The voltage source BIS is based on voltage division between an internal current sensing resistor (Rs) and an external sample. To maintain high SNR, Rs is varied so that the source voltage is divided more or less equally. In order to calibrate the systems, we measured the transfer function of the BIS systems with several known resistor and capacitor loads. From this we may estimate the resistance and capacitance of biological tissues using the least-squares method to minimize error between the measured transimpedance excluding the system transfer function and that from an impedance model. When tested on realistic loads including discrete resistors and capacitors, and saline and agar phantoms, the voltage source-based BIS system had a wider bandwidth of 10 Hz to 2.2 MHz with less than 1% deviation from the expected spectra compared to more than 10% with the current source. The voltage source also showed an SNR of at least 60 dB up to 2.2 MHz in
The Origin of the Constant Carbohydrate Diet
Directory of Open Access Journals (Sweden)
Charles Herbert Read
2009-01-01
Full Text Available The Constant Carbohydrate diet, based entirely on carbohydrate exchanges, is now widely used in the dietary treatment of diabetes mellitus. Being based on sound scientific principles and simple in design, the Constant Carabohydrate diet is appropriate for all those having diabetes mellitus, young or old, no matter their ethncity. This report describes why and how it was developed in 1951. Its simplicity makes it adaptable to all ethnic diets.
The Origin of the Constant Carbohydrate Diet
Directory of Open Access Journals (Sweden)
Read CharlesHerbert
2008-01-01
Full Text Available The Constant Carbohydrate diet, based entirely on carbohydrate exchanges, is now widely used in the dietary treatment of diabetes mellitus. Being based on sound scientific principles and simple in design, the Constant Carabohydrate diet is appropriate for all those having diabetes mellitus, young or old, no matter their ethncity. This report describes why and how it was developed in 1951. Its simplicity makes it adaptable to all ethnic diets.
Holographic dark energy with varying gravitational constant
Jamil, Mubasher; Saridakis, Emmanuel N.; Setare, M. R.
2009-08-01
We investigate the holographic dark energy scenario with a varying gravitational constant, in flat and non-flat background geometry. We extract the exact differential equations determining the evolution of the dark energy density-parameter, which include G-variation correction terms. Performing a low-redshift expansion of the dark energy equation of state, we provide the involved parameters as functions of the current density parameters, of the holographic dark energy constant and of the G-variation.
Holographic dark energy with varying gravitational constant
International Nuclear Information System (INIS)
We investigate the holographic dark energy scenario with a varying gravitational constant, in flat and non-flat background geometry. We extract the exact differential equations determining the evolution of the dark energy density-parameter, which include G-variation correction terms. Performing a low-redshift expansion of the dark energy equation of state, we provide the involved parameters as functions of the current density parameters, of the holographic dark energy constant and of the G-variation.
Holographic dark energy with varying gravitational constant
Jamil, Mubasher; Setare, M R
2009-01-01
We investigate the holographic dark energy scenario with a varying gravitational constant, in flat and non-flat background geometry. We extract the exact differential equations determining the evolution of the dark energy density-parameter, which include $G$-variation correction terms. Performing a low-redshift expansion of the dark energy equation of state, we provide the involved parameters as functions of the current density parameters, of the holographic dark energy constant and of the $G$-variation.
Siegel-Veech constants in H(2)
Lelièvre, Samuel
2005-01-01
Abelian differentials on Riemann surfaces can be seen as translation surfaces, which are flat surfaces with cone-type singularities. Closed geodesics for the associated flat metrics form cylinders whose number under a given maximal length generically has quadratic asymptotics in this length, with a common coefficient constant for the quadratic asymptotics called a Siegel--Veech constant which is shared by almost all surfaces in each moduli space of translation surfaces. Square-tiled surfaces ...
Emergent Gravity And The Cosmological Constant Problem
Yang, Hyun Seok
2007-01-01
We address issues on the origin of gravity and the cosmological constant problem based on a recent understanding about the correspondence between noncommutative field theory and gravity. We suggest that the cosmological constant problem can be resolved in a natural way if gravity emerges from a gauge theory in noncommutative spacetime. Especially, we elucidate why the emergent gravity implies that vacuum energy does not gravitate but only fluctuations around the vacuum generate gravity. That ...
Optimization for Hue Constant RGB Sensors
Finlayson, Graham D.; Süsstrunk, Sabine
2002-01-01
We present an optimization technique to find hue constant RGB sensors. The hue representation is based on a log RGB opponent color space that is invariant to brightness and gamma. While modeling the visual response did not derive the opponent space, the hue definition is similar to the ones found in CIE Lab and IPT. Finding hue constant RGB sensors through this optimization might be applicable in color engineering applications such as finding RGB sensors for color image encodings.
A constant elasticity of profit production function
Beard, Rodney
2007-01-01
Impact analysis of changes in production inputs may be simplified if one can apply a constant adjustment factor to profit. In particular, if a production function can be found for which the elasticity of profit is constant and this function has desirable properties, then one can use the input elasticity of profit to study the impact of input changes on profit. In this paper such a production function is derived from first principles.
Beyond lensing by the cosmological constant
Faraoni, Valerio
2016-01-01
The long-standing problem of whether the cosmological constant affects directly the deflection of light caused by a gravitational lens is reconsidered. We use a new approach based on the Hawking quasilocal mass of a sphere grazed by light rays and on its splitting into local and cosmological parts. Previous literature restricted to the cosmological constant is extended to any form of dark energy accelerating the universe in which the gravitational lens is embedded.
Prime rings with PI rings of constants
Kharchenko, V K; Rodríguez-Romo, S
1996-01-01
It is shown that if the ring of constants of a restricted differential Lie algebra with a quasi-Frobenius inner part satisfies a polynomial identity (PI) then the original prime ring has a generalized polynomial identitiy (GPI). If additionally the ring of constants is semiprime then the original ring is PI. The case of a non-quasi-Frobenius inner part is also considered.
RNA structure and scalar coupling constants
Energy Technology Data Exchange (ETDEWEB)
Tinoco, I. Jr.; Cai, Z.; Hines, J.V.; Landry, S.M.; SantaLucia, J. Jr.; Shen, L.X.; Varani, G. [Univ. of California, Berkeley, CA (United States)
1994-12-01
Signs and magnitudes of scalar coupling constants-spin-spin splittings-comprise a very large amount of data that can be used to establish the conformations of RNA molecules. Proton-proton and proton-phosphorus splittings have been used the most, but the availability of {sup 13}C-and {sup 15}N-labeled molecules allow many more coupling constants to be used for determining conformation. We will systematically consider the torsion angles that characterize a nucleotide unit and the coupling constants that depend on the values of these torsion angles. Karplus-type equations have been established relating many three-bond coupling constants to torsion angles. However, one- and two-bond coupling constants can also depend on conformation. Serianni and coworkers measured carbon-proton coupling constants in ribonucleosides and have calculated their values as a function of conformation. The signs of two-bond coupling can be very useful because it is easier to measure a sign than an accurate magnitude.
Tunneling for Dirac Fermions in Constant Magnetic Field
Choubabi, El Bouazzaoui; Bouziani, Mohamed El; Jellal, Ahmed
2009-01-01
The tunneling effect of two-dimensional Dirac fermions in a constant magnetic field is studied. This can be done by using the continuity equation at some points to determine the corresponding reflexion and transmission coefficients. For this, we consider a system made of graphene as superposition of two different regions where the second is characterized by an energy gap t'. In fact, we treat concrete systems to practically give two illustrations: barrier and diode. For each case, we discuss ...
Institute of Scientific and Technical Information of China (English)
王恒; 张志胜; 刘飏
2009-01-01
交货期设置是晶圆制造车间控制的重要任务之一.根据统计分析和排队理论提出3层结构交货期设置模型预测交货期.采用固定在制品(Constant WIP,CONWIP)投料保持系统在制品恒定和物料流程稳定,提出最大积聚未投放量法确定物料投放时间,采用基于模拟的等待时间分布估计等待时间.实例表明,该模型简单有效,提高了交货期预测的准确性.
Dynamic analysis of the CTAR (constant temperature adsorption refrigeration) cycle
International Nuclear Information System (INIS)
The basic SAR (solar-driven adsorption refrigeration) machine is an intermittent cold production system. Recently, the CO-SAR (continuous operation solar-powered adsorption refrigeration) system is developed. The CO-SAR machine is based on the theoretical CTAR (constant temperature adsorption refrigeration) cycle in which the adsorption process takes place at a constant temperature that equals the ambient temperature. Practically, there should be a temperature gradient between the adsorption bed and the surrounding atmosphere to provide a driving potential for heat transfer. In the present study, the dynamic analysis of the CTAR cycle is developed. This analysis provides a comparison between the theoretical and the dynamic operation of the CTAR cycle. The developed dynamic model is based on the D-A adsorption equilibrium equation and the energy and mass balances in the adsorption reactor. Results obtained from the present work demonstrate that, the idealization of the constant temperature adsorption process in the theoretical CTAR cycle is not far from the real situation and can be approached. Furthermore, enhancing the heat transfer between the adsorption bed and the ambient during the bed pre-cooling process helps accelerating the heat rejection process from the adsorption reactor and therefore approaching the isothermal process. - Highlights: • The dynamic analysis of the CTAR (constant temperature adsorption refrigeration) cycle is developed. • The CTAR theoretical and dynamic cycles are compared. • The dynamic cycle approaches the ideal one by enhancing the bed precooling
Environment-Dependent Fundamental Physical Constants
Terazawa, Hidezumi
2012-01-01
A theory of special inconstancy, in which some fundamental physical constants such as the fine-structure and gravitational constants may vary, is proposed in pregeometry. In the special theory of inconstancy, the \\alpha-G relation of \\alpha=3\\pi/[16ln(4\\pi/5GM_W^2)] between the varying fine-structure and gravitaional constants (where M_W is the charged weak boson mass) is derived from the hypothesis that both of these constants are related to the same fundamental length scale in nature. Furthermore, it leads to the prediction of dot{{\\alpha}}/\\alpha=(-0.8\\pm2.5)\\times10^{-14}yr^{-1} from the most precise limit of dot{G}/G=(-0.6\\pm2.0)\\times10^{-12}yr^{-1} by Thorsett, which is not only consistent with the recent observation of dot{{\\alpha}}/\\alpha=(0.5\\pm0.5)\\times10^{-14}yr^{-1} by Webb et al. but also feasible for future experimental tests. Also a theory of general inconstancy, in which any fundamental physical constants may vary, is proposed in "more general relativity", by assuming that the space-time is ...
Estimation of Stability Constants of Complex Compounds
Directory of Open Access Journals (Sweden)
Raos, N.
Full Text Available The stability constant of a complex generally depends on the electronic, stereochemical and steric factors, as well as on the chelate effect and interaction of the complex, metal and ligand with water. In the first part of the paper we discuss the Irving-Williams order of stability of bivalent transition metal ion complexes from Mn2+ to Zn2+, along with the HSAB model (hard and soft acids and bases of stability. The second part describes three kinds of models for the estimation of the stability constants of complex compounds. First are those based on molecular mechanics, which were used mainly for the estimation of the enantioselectivity effect, i. e. Gibbs energy differences between MLL and MDL isomers. The second kind of models are mechanistic, that rest on the presumption of linear dependence of measured stability constants of the complexes with the same ligand (stability constants of mono- and bis-complexes, protonation constants, etc.. The third kind of models are heuristic (QSPR, which encompass molecular descriptors calculated by the method of overlapping spheres (OS, as well as topological indices. Among the variety of topological indices, connectivity indices proved best. They were calculated for the ligand and various representations of the coordination compound structure.
The case for the cosmological constant
Indian Academy of Sciences (India)
Varun Sahni
2000-07-01
I present a short overview of current observational results and theoretical models for a cosmological constant. The main motivation for invoking a small cosmological constant (or -term) at the present epoch has to do with observations of high redshift Type Ia supernovae which suggest an accelerating universe. A ﬂat accelerating universe is strongly favoured by combining supernovae observations with observations of CMB anisotropies on degree scales which give the `best-ﬁt’ values ≃ 0.7 and m ≃ 0.3. A time dependent cosmological -term can be generated by scalar ﬁeld models with exponential and power law potentials. Some of these models can alleviate the `ﬁne tuning’ problem which faces the cosmological constant.
Bounds on Gromov Hyperbolicity Constant in Graphs
Indian Academy of Sciences (India)
José M Rodríguez; José M Sigarreta
2012-02-01
If is a geodesic metric space and 1,2,3 $\\in$ , a geodesic triangle ={1,2,3} is the union of the three geodesics [1,2], [2,3] and [31] in . The space is -hyperbolic (in the Gromov sense) if any side of is contained in a -neighborhood of the union of two other sides, for every geodesic triangle in . If is hyperbolic, we denote by () the sharp hyperbolicity constant of , i.e. ()=$inf{$≥ 0$ : is -hyperbolic}. In this paper we relate the hyperbolicity constant of a graph with some known parameters of the graph, as its independence number, its maximum and minimum degree and its domination number. Furthermore, we compute explicitly the hyperbolicity constant of some class of product graphs.
Gravitational Interactions and Fine-Structure Constant
Jentschura, U D; Nandori, I
2015-01-01
Electromagnetic and gravitational central-field problems are studied with relativistic quantum mechanics on curved space-time backgrounds. Corrections to the transition current are identified. Analogies of the gravitational and electromagnetic spectra suggest the definition of a gravitational fine-structure constant. The electromagnetic and gravitational coupling constants enter the Einstein-Hilbert-Maxwell Lagrangian. We postulate that the variational principle holds with regard to a global dilation transformation of the space-time coordinates. The variation suggests is consistent with a functional relationship of the form alpha_QED being proportional to alpha_G^(1/2), where alpha_QED is the electrodynamic fine-structure constant, and alpha_G its gravitational analogue.
The Cosmological Constant Problem (2/2)
CERN. Geneva
2015-01-01
I will review the cosmological constant problem as a serious challenge to our notion of naturalness in Physics. Weinberg’s no go theorem is worked through in detail. I review a number of proposals possibly including Linde's universe multiplication, Coleman's wormholes, the fat graviton, and SLED, to name a few. Large distance modifications of gravity are also discussed, with causality considerations pointing towards a global modification as being the most sensible option. The global nature of the cosmological constant problem is also emphasized, and as a result, the sequestering scenario is reviewed in some detail, demonstrating the cancellation of the Standard Model vacuum energy through a global modification of General Relativity.
The Cosmological Constant Problem (1/2)
CERN. Geneva
2015-01-01
I will review the cosmological constant problem as a serious challenge to our notion of naturalness in Physics. Weinberg’s no go theorem is worked through in detail. I review a number of proposals possibly including Linde's universe multiplication, Coleman's wormholes, the fat graviton, and SLED, to name a few. Large distance modifications of gravity are also discussed, with causality considerations pointing towards a global modification as being the most sensible option. The global nature of the cosmological constant problem is also emphasized, and as a result, the sequestering scenario is reviewed in some detail, demonstrating the cancellation of the Standard Model vacuum energy through a global modification of General Relativity.
Coulomb field in a constant electromagnetic background
Adorno, T C; Shabad, A E
2016-01-01
Nonlinear Maxwell equations are written up to the third-power deviations from a constant-field background, valid within any local nonlinear electrodynamics including QED with Euler-Heisenberg effective Lagrangian. Linear electric response to imposed static finite-sized charge is found in the vacuum filled by an arbitrary combination of constant and homogeneous electric and magnetic fields. The modified Coulomb field, corrections to the total charge and to the charge density are given in terms of derivatives of the effective Lagrangian with respect to the field invariants.
Black Hole Constraints on Varying Fundamental Constants
International Nuclear Information System (INIS)
We apply the generalized second law of thermodynamics and derive upper limits on the variation in the fundamental constants. The maximum variation in the electronic charge permitted for black holes accreting and emitting in the present cosmic microwave background corresponds to a variation in the fine-structure constant of Δα/α≅2x10-23 per second. This value matches the variation measured by Webb et al. [Phys. Rev. Lett. 82, 884 (1999); Phys. Rev. Lett. 87, 091301 (2001)] using absorption lines in the spectra of distant quasars and suggests the variation mechanism may be a coupling between the electron and the cosmic photon background
Atomic weights: no longer constants of nature
Coplen, Tyler B.; Holden, Norman E.
2011-01-01
Many of us were taught that the standard atomic weights we found in the back of our chemistry textbooks or on the Periodic Table of the Chemical Elements hanging on the wall of our chemistry classroom are constants of nature. This was common knowledge for more than a century and a half, but not anymore. The following text explains how advances in chemical instrumentation and isotopic analysis have changed the way we view atomic weights and why they are no longer constants of nature
Stringy mechanism for a small cosmological constant
International Nuclear Information System (INIS)
Based on the probability distributions of products of random variables, we propose a simple stringy mechanism that prefers the meta-stable vacua with a small cosmological constant. We state some relevant properties of the probability distributions of functions of random variables. We then illustrate the mechanism within the flux compactification models in Type IIB string theory. As a result of the stringy dynamics, we argue that the generic probability distribution for the meta-stable vacua typically peaks with a divergent behavior at the zero value of the cosmological constant. However, its suppression in the single modulus model studied here is modest
Optimizing constant wavelength neutron powder diffractometers
Cussen, Leo D.
2016-06-01
This article describes an analytic method to optimize constant wavelength neutron powder diffractometers. It recasts the accepted mathematical description of resolution and intensity in terms of new variables and includes terms for vertical divergence, wavelength and some sample scattering effects. An undetermined multiplier method is applied to the revised equations to minimize the RMS value of resolution width at constant intensity and fixed wavelength. A new understanding of primary spectrometer transmission (presented elsewhere) can then be applied to choose beam elements to deliver an optimum instrument. Numerical methods can then be applied to choose the best wavelength.
Hermite's Constant for Quadratic Number Fields
Baeza, Ricardo; Coulangeon, Renaud; Icaza, Maria Ines; O'Ryan, Manuel
2001-01-01
We develop a method to compute the Hermite-Humbert constants $\\gam_{K,n}$ of a real quadratic number field $K$, the analogue of the classical Hermite constant $\\gam_n$ when $\\funnyQ$ is replaced by a quadratic extension. In the case $n=2$, the problem is equivalent to the determination of lowest points of fundamental domains in $\\H^2$ for the Hilbert modular group over $K$, that had been studied experimentally by H. Cohn. We establish the results he conjectured for the...
New concepts in constant wavelength neutron powder diffractometry
International Nuclear Information System (INIS)
Complete text of publication follows. Neutron powder diffraction is an important tool in the determination of atomic structures of materials. It has become increasingly important to improve the current constant wavelength powder diffractometers to handle the increasing demand. Where once a single diffraction pattern of a 10 gram sample was the entire experiment, today the demand is for experiments using smaller samples in multiple environments (temperature, pressure, magnetic field,...). A new type of constant wavelength diffractometer is proposed using position sensitive detectors (PSD) and advanced collimators. The PSD's allow a larger out-of-scattering plane area to be collected while still affording good peak shapes; hence good resolution at increased collection rates can be obtained. With miniaturisation of many of the detector electronics, the entire system could be affordable and compact. A system of 360 x 40 cm long PSD's is envisaged. This increased density (over the typically 64 detectors) is made possible by use of new advances in neutron collimation. (author)
Institute of Scientific and Technical Information of China (English)
刘乾; 姜钦青; 蒋绿林; 陈孚江
2015-01-01
For the climatic feature of the Yangtze River Delta rigion,designed a constant temperature and humidity air-condi-tioning system driven by ground source heat pump with condensing heat recovery.Established mathematical model of constant temperature and humidity air-conditioning respectively for summer and spring,and carried the theory calculate and analyse on constant temperature and humidity air-conditioning system driven by ground source heat pump with condensing heat recovery and that with conventional electric heating.The results show that the recovery condensing heat of constant temperature and humidity air-conditioning system driven by ground source heat pump with condensing heat recovery enough to heat the air had cooled and dehumidified to the required temperature range,which can reduce energy consumption by 40.2% in summer and 77.4% in spring compared to constant temperature and humidity air-conditioning system driven by ground source heat pump with conventional elec-tric heating.%针对长三角地区气候特点，设计了一种冷凝热回收型地源热泵恒温恒湿空调系统，分别就夏季和春季，建立恒温恒湿空气处理的数学模型，对冷凝热回收型地源热泵恒温恒湿空调系统和常规电加热型地源热泵恒温恒湿空调系统的耗能进行理论计算与分析。结果表明：冷凝热回收型地源热泵恒温恒湿空调系统回收的冷凝热足以把降温除湿后的冷空气加热到所需温度范围，与常规电加热型地源热泵恒温恒湿空调系统相比，此系统在夏季节能40．2％，在春季节能77．4％。
A Constant Factor Approximation Algorithm for Reordering Buffer Management
Avigdor-Elgrabli, Noa
2012-01-01
In the reordering buffer management problem (RBM) a sequence of $n$ colored items enters a buffer with limited capacity $k$. When the buffer is full, one item is removed to the output sequence, making room for the next input item. This step is repeated until the input sequence is exhausted and the buffer is empty. The objective is to find a sequence of removals that minimizes the total number of color changes in the output sequence. The problem formalizes numerous applications in computer and production systems, and is known to be NP-hard. We give the first constant factor approximation guarantee for RBM. Our algorithm is based on an intricate "rounding" of the solution to an LP relaxation for RBM, so it also establishes a constant upper bound on the integrality gap of this relaxation. Our results improve upon the best previous bound of $O(\\sqrt{\\log k})$ of Adamaszek et al. (STOC 2011) that used different methods and gave an online algorithm. Our constant factor approximation beats the super-constant lower b...
Can compactifications solve the cosmological constant problem?
Hertzberg, Mark P.; Masoumi, Ali
2016-06-01
Recently, there have been claims in the literature that the cosmological constant problem can be dynamically solved by specific compactifications of gravity from higher-dimensional toy models. These models have the novel feature that in the four-dimensional theory, the cosmological constant Λ is much smaller than the Planck density and in fact accumulates at Λ = 0. Here we show that while these are very interesting models, they do not properly address the real cosmological constant problem. As we explain, the real problem is not simply to obtain Λ that is small in Planck units in a toy model, but to explain why Λ is much smaller than other mass scales (and combinations of scales) in the theory. Instead, in these toy models, all other particle mass scales have been either removed or sent to zero, thus ignoring the real problem. To this end, we provide a general argument that the included moduli masses are generically of order Hubble, so sending them to zero trivially sends the cosmological constant to zero. We also show that the fundamental Planck mass is being sent to zero, and so the central problem is trivially avoided by removing high energy physics altogether. On the other hand, by including various large mass scales from particle physics with a high fundamental Planck mass, one is faced with a real problem, whose only known solution involves accidental cancellations in a landscape.
The Alpha Constant from Relativistic Groups
González-Martin, G R
2000-01-01
The value of the alpha constant, known to be equal to an algebraic expression in terms of pi and entire numbers related to certain group volumes, is derived from the relativistic structure group of a geometric unified theory, its subgroups and corresponding symmetric space quotients.
The ideal Kolmogorov inertial range and constant
Zhou, YE
1993-01-01
The energy transfer statistics measured in numerically simulated flows are found to be nearly self-similar for wavenumbers in the inertial range. Using the measured self-similar form, an 'ideal' energy transfer function and the corresponding energy flux rate were deduced. From this flux rate, the Kolmogorov constant was calculated to be 1.5, in excellent agreement with experiments.
Pion decay constants in dense skyrmion matter
Directory of Open Access Journals (Sweden)
Lee H.-J.
2010-10-01
Full Text Available According to the QCD, the hadronic matter can have various phases with matter density and temperature. In general, when there is phase transition in a matter, it is known that a symmetry in the matter changes. In case of the hadronic matter, the chiral symmetry in the matter is expected to be restored when the matter density (or temperature increases. The actual order parameter with respect to the chiral symmetry in the hadronic matter is known as the quark condensate from the QCD, but the pion decay constant, corresponding to the radius of the chiral circle, plays the role of the order parameter in an eﬀective ﬁeld theoretical approach to the QCD. In this paper, by using the skyrmion model which is an eﬀective theory to the QCD, we construct the skyrmion matter as a model of the hadronic matter (nuclear matter and calculate the pion decay constant in the matter. Because of presence of the matter, the pion decay constant is split into the two components, the temporal component and the spatial component. We discuss the phase transition in the skyrmion matter and behavior of the two components of the decay constant for massless pion with density of the skyrmion matter.
Teaching Nanochemistry: Madelung Constants of Nanocrystals
Baker, Mark D.; Baker, A. David
2010-01-01
The Madelung constants for binary ionic nanoparticles are determined. The computational method described here sums the Coulombic interactions of each ion in the particle without the use of partial charges commonly used for bulk materials. The results show size-dependent lattice energies. This is a useful concept in teaching how properties such as…
Discrete Higgs and the Cosmological Constant
Amore, Paolo; Diaz-Cruz, J Lorenzo
2008-01-01
It is proposed that the Higgs vacuum possesses a small-scale structure that can explain the large discrepancy between the predicted electroweak vacuum energy density and the observed cosmological constant. An effective Lagrangian description is employed to obtain modifications to the Standard Model predictions that can be tested at collider experiments.
Varying Constants: Constraints from Seasonal Variations
Shaw, Douglas J
2010-01-01
We analyse the constraints obtained from new atomic clock data on the possible time variation of the fine structure `constant' and the electron-proton mass ratio and show how they are strengthened when the seasonal variation of Sun's gravitational field at the Earth's surface is taken into account.
The Cosmological Constant and its Interpretation
Liddle, A.; Murdin, P.
2002-12-01
The cosmological constant was first introduced into the equations of general relativity by Einstein himself, who later famously criticized this move as his `greatest blunder'. His main motivation had been to allow cosmological models featuring a static universe, but this possibility swiftly became redundant with Edwin Hubble's discovery of the expansion of the universe. Despite this, it has period...
The Elastic Constants for Wrought Aluminum Alloys
Templin, R L; Hartmann, E C
1945-01-01
There are several constants which have been devised as numerical representations of the behavior of metals under the action of loadings which stress the metal within the range of elastic action. Some of these constants, such as Young's modulus of elasticity in tension and compression, shearing modulus of elasticity, and Poisson's ratio, are regularly used in engineering calculations. Precise tests and experience indicate that these elastic constants are practically unaffected by many of the factors which influence the other mechanical properties of materials and that a few careful determinations under properly controlled conditions are more useful and reliable than many determinations made under less favorable conditions. It is the purpose of this paper to outline the methods employed by the Aluminum Research Laboratories for the determination of some of these elastic constants, to list the values that have been determined for some of the wrought aluminum alloys, and to indicate the variations in the values that may be expected for some of the commercial products of these alloys.
Monopoly price discrimination with constant elasticity demand
Aguirre Pérez, Iñaki; Cowan, Simon George
2013-01-01
This paper presents new results on the welfare e¤ects of third-degree price discrimination under constant elasticity demand. We show that when both the share of the strong market under uniform pricing and the elasticity di¤erence between markets are high enough,then price discrimination not only can increase social welfare but also consumer surplus.
Supersymmetry Breaking and the Cosmological Constant
Banks, T
2014-01-01
I review three attempts to explain the small value of the cosmological constant, and their connection to SUSY breaking. They are The String Landscape, Supersymmetric Large Extra Dimensions (SLED), and the Holographic Space-time Formalism invented by Fischler and myself.
GPS test of the local position invariance of Planck's constant
Kentosh, James
2012-01-01
Publicly available clock correction data from the Global Positioning System was analyzed and used in combination with the results of terrestrial clock comparison experiments to confirm the local position invariance (LPI) of Planck's constant within the context of general relativity. The results indicate that h is invariant within a limit of |beta_h|<0.007, where beta_h is a dimensionless parameter that represents the extent of LPI violation.
Atomic fine structure in a space of constant curvature
Energy Technology Data Exchange (ETDEWEB)
Bessis, N.; Bessis, G.; Shamseddine, R. (Lyon-1 Univ., 69 - Villeurbanne (France))
1982-10-01
As a contribution to a tentative formulation of atomic physics in a curved space, the determination of atomic fine structure energies in a space of constant curvature is investigated. Starting from the Dirac equation in a curved space-time, the analogue of the Pauli equation in a general coordinate system is derived. The theoretical curvature induced shifts and splittings of the fine structure energy levels are put in evidence and examined for the particular case of the hydrogenic n=2 levels.
Atomic fine structure in a space of constant curvature
International Nuclear Information System (INIS)
As a contribution to a tentative formulation of atomic physics in a curved space, the determination of atomic fine structure energies in a space of constant curvature is investigated. Starting from the Dirac equation in a curved space-time, the analogue of the Pauli equation in a general coordinate system is derived. The theoretical curvature induced shifts and splittings of the fine structure energy levels are put in evidence and examined for the particular case of the hydrogenic n=2 levels. (author)
The Physiology Constant Database of Teen-Agers in Beijing
Directory of Open Access Journals (Sweden)
Wei Wei-Qi
2004-01-01
Full Text Available Physiology constants of adolescents are important to understand growing living systems and are a useful reference in clinical and epidemiological research. Until recently, physiology constants were not available in China and therefore most physiologists, physicians, and nutritionists had to use data from abroad for reference. However, the very difference between the Eastern and Western races casts doubt on the usefulness of overseas data. We have therefore created a database system to provide a repository for the storage of physiology constants of teen-agers in Beijing. The several thousands of pieces of data are now divided into hematological biochemistry, lung function, and cardiac function with all data manually checked before being transferred into the database. The database was accomplished through the development of a web interface, scripts, and a relational database. The physiology data were integrated into the relational database system to provide flexible facilities by using combinations of various terms and parameters. A web browser interface was designed for the users to facilitate their searching. The database is available on the web. The statistical table, scatter diagram, and histogram of the data are available for both anonym and user according to queries, while only the user can achieve detail, including download data and advanced search.
Electronic transport in two-dimensional high dielectric constant nanosystems.
Ortuño, M; Somoza, A M; Vinokur, V M; Baturina, T I
2015-01-01
There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing electronic transport scales logarithmically with either system size or electrostatic screening length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials. PMID:25860804
International Nuclear Information System (INIS)
Statistical shape fluctuations can be calculated with two alternative assumptions: (a) the temperature remains constant as the shape fluctuates, or (b) the energy remains constant as the shape fluctuates. These two possibilities are compared for a simple model, the Landau theory, and the finite-temperature HFB cranking theory. Average electric quadrupole moments are compared for these two constraints. (orig.)
Constant pH replica exchange molecular dynamics in biomolecules using a discrete protonation model
Meng, Yilin; Roitberg, Adrian E.
2010-01-01
A constant pH replica exchange molecular dynamics (REMD) method is proposed and implemented to improve coupled protonation and conformational state sampling. By mixing conformational sampling at constant pH (with discrete protonation states) with a temperature ladder, this method avoids conformational trapping. Our method was tested and applied to seven different biological systems. The constant pH REMD not only predicted pKa correctly for small, model compounds but also converged faster than...
Frequency Dependence of Attenuation Constant of Dielectric Materials
Directory of Open Access Journals (Sweden)
A. S. Zadgaonkar
1975-01-01
Full Text Available Different dielectric materials have been studied for frequency dependence of attenuation constant. The sensitive cathode ray oscillograph method has been used to evaluate to the dielectric constant and loss factor, and from these attenuation constants have been calculated. The temperature remaining constant, a regular increase has been observed in attenuation constant, at higher frequencies of electro-magnetic propagating wave.
Hyperscaling violation and the shear diffusion constant
Kolekar, Kedar S.; Mukherjee, Debangshu; Narayan, K.
2016-09-01
We consider holographic theories in bulk (d + 1)-dimensions with Lifshitz and hyperscaling violating exponents z , θ at finite temperature. By studying shear gravitational modes in the near-horizon region given certain self-consistent approximations, we obtain the corresponding shear diffusion constant on an appropriately defined stretched horizon, adapting the analysis of Kovtun, Son and Starinets. For generic exponents with d - z - θ > - 1, we find that the diffusion constant has power law scaling with the temperature, motivating us to guess a universal relation for the viscosity bound. When the exponents satisfy d - z - θ = - 1, we find logarithmic behaviour. This relation is equivalent to z = 2 +deff where deff =di - θ is the effective boundary spatial dimension (and di = d - 1 the actual spatial dimension). It is satisfied by the exponents in hyperscaling violating theories arising from null reductions of highly boosted black branes, and we comment on the corresponding analysis in that context.
Fat Euclidean Gravity with Small Cosmological Constant
Sundrum, Raman
2003-01-01
The cosmological constant problem is usually considered an inevitable feature of any effective theory capturing well-tested gravitational and matter physics, without regard to the details of short-distance gravitational couplings. In this paper, a subtle effective description avoiding the problem is presented in a first quantized language, consistent with experiments and the Equivalence Principle. First quantization allows a minimal domain of validity to be carved out by cutting on the proper length of particle worldlines. This is facilitated by working in (locally) Euclidean spacetime, although considerations of unitarity are still addressed by analytic continuation from Lorentzian spacetime. The new effective description demonstrates that the cosmological constant problem {\\it is} sensitive to short-distance details of gravity, which can be probed experimentally. ``Fat Gravity'' toy models are presented, illustrating how gravity might shut off at short but testable distances, in a generally covariant manner...
Negative Energy Cosmology and the Cosmological Constant
Prokopec, Tomislav
2011-01-01
It is well known that string theories naturally compactify on anti-de Sitter spaces, and yet cosmological observations show no evidence of a negative cosmological constant in the early Universe's evolution. In this letter we present two simple nonlocal modifications of the standard Friedmann cosmology that can lead to observationally viable cosmologies with an initial (negative) cosmological constant. The nonlocal operators we include are toy models for the quantum cosmological backreaction. In Model I an initial quasiperiodic oscillatory epoch is followed by inflation and a late time matter era, representing a dark matter candidate. The backreaction in Model II quickly compensates the negative cosmological term such that the Ricci curvature scalar rapidly approaches zero, and the Universe ends up in a late time radiation era.
Cosmological Constant or Variable Dark Energy?
Institute of Scientific and Technical Information of China (English)
XU Li-Xin; ZHANG Cheng-Wu; LIU Hong-Ya
2007-01-01
@@ Selection statics of the Akaike information criterion (AIC) model and the Bayesian information criterion (BIC)model are applied to the Λ-cold dark matter (ΛCDM) cosmological model, the constant equation of state of dark energy, w =constant, and the parametrized equation of state of dark energy, w(z) = w0 + w1z/(1 + z),to determine which one is the better cosmological model to describe the evolution of the universe by combining the recent cosmic observational data including Sne Ia, the size of baryonic acoustic oscillation (BAO) peak from SDSS, the three-year WMAP CMB shift parameter. The results show that AIC, BIC and current datasets are not powerful enough to discriminate one model from the others, though odds suggest differences between them.
Regular Black Holes with Cosmological Constant
Institute of Scientific and Technical Information of China (English)
MO Wen-Juan; CAI Rong-Gen; SU Ru-Keng
2006-01-01
We present a class of regular black holes with cosmological constant Λ in nonlinear electrodynamics. Instead of usual singularity behind black hole horizon, all fields and curvature invariants are regular everywhere for the regular black holes. Through gauge invariant approach, the linearly dynamical stability of the regular black hole is studied. In odd-parity sector, we find that the Λ term does not appear in the master equations of perturbations, which shows that the regular black hole is stable under odd-parity perturbations. On the other hand, for the even-parity sector, the master equations are more complicated than the case without the cosmological constant. We obtain the sufficient conditions for stability of the regular black hole. We also investigate the thermodynamic properties of the regular black hole, and find that those thermodynamic quantities do not satisfy the differential form of first law of black hole thermodynamics. The reason for violating the first law is revealed.
Constant force extensional rheometry of polymer solutions
DEFF Research Database (Denmark)
Szabo, Peter; McKinley, Gareth H.; Clasen, Christian
2012-01-01
We revisit the rapid stretching of a liquid filament under the action of a constant imposed tensile force, a problem which was first considered by Matta and Tytus [J. Non-Newton. Fluid Mech. 35 (1990) 215–229]. A liquid bridge formed from a viscous Newtonian fluid or from a dilute polymer solution...... filament can be probed. In particular, we show that with this constant force pull (CFP) technique it is possible to readily impose very large material strains and strain rates so that the maximum extensibility of the polymer molecules may be quantified. This unique characteristic of the experiment...... mass is developed for simple viscous filaments. Based on these theoretical considerations we develop an expression that enables estimation of the finite extensibility parameter characterizing the polymer solution in terms of quantities that can be extracted directly from simple measurement of the time...
Quantum Exclusion of Positive Cosmological Constant?
Dvali, Gia
2014-01-01
We show that a positive cosmological constant is incompatible with the quantum-corpuscular resolution of de Sitter metric in form of a coherent state. The reason is very general and is due to the quantum self-destruction of the coherent state because of the scattering of constituent graviton quanta. This process creates an irreversible quantum clock, which precludes eternal de Sitter. It also eliminates the possibility of Boltzmann brains and Poincare recurrences. This effect is expected to be part of any microscopic theory that takes into account the quantum corpuscular structure of the cosmological background. This observation puts the cosmological constant problem in a very different light, promoting it, from a naturalness problem, into a question of quantum consistency. We are learning that quantum gravity cannot tolerate exceedingly-classical sources.
The Value of the Cosmological Constant
Barrow, John D
2011-01-01
We make the cosmological constant, {\\Lambda}, into a field and restrict the variations of the action with respect to it by causality. This creates an additional Einstein constraint equation. It restricts the solutions of the standard Einstein equations and is the requirement that the cosmological wave function possess a classical limit. When applied to the Friedmann metric it requires that the cosmological constant measured today, t_{U}, be {\\Lambda} ~ t_{U}^(-2) ~ 10^(-122), as observed. This is the classical value of {\\Lambda} that dominates the wave function of the universe. Our new field equation determines {\\Lambda} in terms of other astronomically measurable quantities. Specifically, it predicts that the spatial curvature parameter of the universe is {\\Omega}_{k0} \\equiv -k/a_(0)^(2)H^2= -0.0055, which will be tested by Planck Satellite data. Our theory also creates a new picture of self-consistent quantum cosmological history.
Incompressible flows with piecewise constant density
Danchin, Raphaël
2012-01-01
We investigate the incompressible Navier-Stokes equations with variable density. The aim is to prove existence and uniqueness results in the case of discontinuous ini- tial density. In dimension n = 2, 3, assuming only that the initial density is bounded and bounded away from zero, and that the initial velocity is smooth enough, we get the local-in-time existence of unique solutions. Uniqueness holds in any dimension and for a wider class of velocity fields. Let us emphasize that all those results are true for piecewise constant densities with arbitrarily large jumps. Global results are established in dimension two if the density is close enough to a positive constant, and in n-dimension if, in addition, the initial velocity is small. The Lagrangian formula- tion for describing the flow plays a key role in the analysis that is proposed in the present paper.
Lectures on the Cosmological Constant Problem
Padilla, Antonio
2015-01-01
These lectures on the cosmological constant problem were prepared for the X Mexican School on Gravitation and Mathematical Physics. The problem itself is explained in detail, emphasising the importance of radiative instability and the need to repeatedly fine tune as we change our effective description. Weinberg's no go theorem is worked through in detail. I review a number of proposals including Linde's universe multiplication, Coleman's wormholes, the fat graviton, and SLED, to name a few. Large distance modifications of gravity are also discussed, with causality considerations pointing towards a global modification as being the most sensible option. The global nature of the cosmological constant problem is also emphasized, and as a result, the sequestering scenario is reviewed in some detail, demonstrating the cancellation of the Standard Model vacuum energy through a global modification of General Relativity.
Variable energy constant current accelerator structure
Anderson, O.A.
1988-07-13
A variable energy, constant current ion beam accelerator structure is disclosed comprising an ion source capable of providing the desired ions, a pre-accelerator for establishing an initial energy level, a matching/pumping module having means for focusing means for maintaining the beam current, and at least one main accelerator module for continuing beam focus, with means capable of variably imparting acceleration to the beam so that a constant beam output current is maintained independent of the variable output energy. In a preferred embodiment, quadrupole electrodes are provided in both the matching/pumping module and the one or more accelerator modules, and are formed using four opposing cylinder electrodes which extend parallel to the beam axis and are spaced around the beam at 90/degree/ intervals with opposing electrodes maintained at the same potential. 12 figs., 3 tabs.
The fine structure constant and numerical alchemy
Dattoli, Giuseppe
2010-01-01
We comment on past and more recent efforts to derive a formula yielding the fine structure constant in terms of integers and transcendent numbers. We analyse these "exoteric" attitudes and describe the myths regarding {\\alpha}, which seems to have very ancient roots, tracing back to Cabbala and to medieval alchemic conceptions. We discuss the obsession for this constant developed by Pauli and the cultural "environment" in which such an "obsession" grew. We also derive a simple formula for {\\alpha} in terms of two numbers {\\pi} and 137 only. The formula we propose reproduces the experimental values up to the last significant digit, it has not any physical motivation and is the result of an alchemic combination of numbers. We make a comparison with other existing formulae, discuss the relevant limits of validity by comparison with the experimental values and discuss a criterion to recover a physical meaning, if existing, from their mathematical properties.
Varying fine-structure and gravitational constants
International Nuclear Information System (INIS)
A simple relation between the time-dependent fine-structure and gravitational constants of alpha/alpha2 approx G/G is derived from the hypothesis that both of these fundamental constants are related to the more fundamental length scale of nature as in he unified pregauge and pregeometric theory of all fundamental forces. From the latest observation of alpha/alpha = (-1.91 ± 0.54) centre dot 10-15yr-1 by Webb et al., it leads to the prediction of G/G = (-0.154 ± 0.044) centre dot 10-12yr-1, which is not only consistent with the most precise limit of G/G = (-0.6 ± 2.0) centre dot 10-12yr-1 by Thorsett but also feasible for future experimental tests
Daylight calculations using constant luminance curves
Energy Technology Data Exchange (ETDEWEB)
Betman, E. [CRICYT, Mendoza (Argentina). Laboratorio de Ambiente Humano y Vivienda
2005-02-01
This paper presents a simple method to manually estimate daylight availability and to make daylight calculations using constant luminance curves calculated with local illuminance and irradiance data and the all-weather model for sky luminance distribution developed in the Atmospheric Science Research Center of the University of New York (ARSC) by Richard Perez et al. Work with constant luminance curves has the advantage that daylight calculations include the problem's directionality and preserve the information of the luminous climate of the place. This permits accurate knowledge of the resource and a strong basis to establish conclusions concerning topics related to the energy efficiency and comfort in buildings. The characteristics of the proposed method are compared with the method that uses the daylight factor. (author)
Why all these prejudices against a constant?
Bianchi, Eugenio
2010-01-01
The expansion of the observed universe appears to be accelerating. A simple explanation of this phenomenon is provided by the non-vanishing of the cosmological constant in the Einstein equations. Arguments are commonly presented to the effect that this simple explanation is not viable or not sufficient, and therefore we are facing the "great mystery" of the "nature of a dark energy". We argue that these arguments are unconvincing, or ill-founded.
Comoving suppression mechanism and cosmological constant problem
Shen, Jian Qi
2004-01-01
In this paper, we assume that the observer is fixed in a comoving frame of reference with $g_{00}=\\frac{\\lambda}{\\Lambda}$, where $\\lambda$ and $\\Lambda$ denote the comoving parameter and the cosmological constant, respectively. By using the {\\it comoving suppression mechanism} and {\\it Mach's principle} (the latter of which is used to determine the comoving parameter $\\lambda$), we calculate the vacuum energy density of quantum fluctuation field in the above-mentioned comoving frame of refer...
Constant fraction timing with scintillation detectors
International Nuclear Information System (INIS)
A model is presented for constant fraction pick-off timing with scintillator-photomultiplier detectors based on a statistical method for leading edge timing. Many of the essential features of this technique are obtained such as prompt time-response, the dependence of FWHM on dynamic range of pulse heights and on maximum energy deposited in scintillator; also the effect of delay time on the optimum resolution in CFPHT and ARC timing. The Walk component in this technique is also satisfactory reproduced
Standard-model coupling constants from compositeness
Besprosvany, J.
2003-01-01
A coupling-constant definition is given based on the compositeness property of some particle states with respect to the elementary states of other particles. It is applied in the context of the vector-spin-1/2-particle interaction vertices of a field theory, and the standard model. The definition reproduces Weinberg's angle in a grand-unified theory. One obtains coupling values close to the experimental ones for appropriate configurations of the standard-model vector particles, at the unifica...
Physical Basis for a Constant Lag Time
Socrates, Aristotle
2012-01-01
We show that the constant time lag prescription for tidal dissipation follows directly from the equations of motion of a tidally-forced fluid body, given some basic assumptions. They are (i) the equilibrium structure of the forced body is spherically-symmetric (ii) the tidal forcing is weak and non-resonant (iii) dissipation is weak. The lag time is an intrinsic property of the tidally-forced body and is independent of the orbital configuration.
Running cosmological constant with observational tests
Geng, Chao-Qiang; Lee, Chung-Chi; Zhang, Kaituo
2016-01-01
We investigate the running cosmological constant model with dark energy linearly proportional to the Hubble parameter, $\\Lambda = \\sigma H + \\Lambda_0$, in which the $\\Lambda$CDM limit is recovered by taking $\\sigma=0$. We derive the linear perturbation equations of gravity under the Friedmann-Lema\\"itre-Robertson-Walker cosmology, and show the power spectra of the CMB temperature and matter density distribution. By using the Markov chain Monte Carlo method, we fit the model to the current ob...
Linear polarization constant of $\\R^n$
Matolcsi, Mate
2006-01-01
The present work contributes to the determination of the $n$-th linear polarization constant $c_n(H)$ of an $n$-dimensional real Hilbert space $H$. We provide some new lower bounds on the value of $\\sup_{\\|y\\|=1}| x_1,y >... x_n,y |$, where $x_1, ..., x_n$ are unit vectors in $H$. In particular, the results improve an earlier estimate of Marcus. However, the intriguing conjecture $c_n(H)=n^{n/2}$ remains open.
Noteworthy dimensionless constant in gravitation theory
Energy Technology Data Exchange (ETDEWEB)
Fayos, F.; Lobo, J.A.; Llanta, E.
1986-01-01
A simple problem of gravitation is studied classically and in the Schwarzchild framework. A relationship is found between the parameters that define the trajectories of two particles (the first in radial motion and the second in a circular orbit) which are initially together and meet again after one revolution of particle 2. Dimensional analysis is the clue to explain the appearance of a dimensionless constant in the Newtonian case.
Some constant solutions to Zamolodchikov's tetrahedron equations
Hietarinta, Jarmo
1992-01-01
In this letter we present constant solutions to the tetrahedron equations proposed by Zamolodchikov. In general, from a given solution of the Yang-Baxter equation there are two ways to construct solutions to the tetrahedron equation. There are also other kinds of solutions. We present some two-dimensional solutions that were obtained by directly solving the equations using either an upper triangular or Zamolodchikov's ansatz.
Fractional constant elasticity of variance model
Ngai Hang Chan; Chi Tim Ng
2007-01-01
This paper develops a European option pricing formula for fractional market models. Although there exist option pricing results for a fractional Black-Scholes model, they are established without accounting for stochastic volatility. In this paper, a fractional version of the Constant Elasticity of Variance (CEV) model is developed. European option pricing formula similar to that of the classical CEV model is obtained and a volatility skew pattern is revealed.
Chiral Heterotic Strings with Positive Cosmological Constant
Florakis, Ioannis
2016-01-01
We present explicit examples of semi-realistic heterotic models with spontaneously broken supersymmetry, which dynamically lead to breaking scales much smaller than $M_{\\rm Planck}$ and exponentially small positive values for the cosmological constant. Contrary to field theoretic intuition, we find that the global structure of the effective potential is significantly affected by contributions of massive and non-level matched string states and we investigate the conditions that dynamically ensure a number of desired properties.
On recent SFR calibrations and the constant SFR approximation
Cervino, M; Hidalgo, S
2016-01-01
Star Formation Rate (SFR) inferences are based in the so-called constant SFR approximation, where synthesis models are require to provide a calibration; we aims to study the key points of such approximation to produce accurate SFR inferences. We use the intrinsic algebra used in synthesis models, and we explore how SFR can be inferred from the integrated light without any assumption about the underling Star Formation history (SFH). We show that the constant SFR approximation is actually a simplified expression of more deeper characteristics of synthesis models: It is a characterization of the evolution of single stellar populations (SSPs), acting the SSPs as sensitivity curve over different measures of the SFH can be obtained. As results, we find that (1) the best age to calibrate SFR indices is the age of the observed system (i.e. about 13Gyr for z=0 systems); (2) constant SFR and steady-state luminosities are not requirements to calibrate the SFR; (3) it is not possible to define a SFR single time scale ove...
A constant current source for extracellular microiontophoresis.
Walker, T; Dillman, N; Weiss, M L
1995-12-01
A sophisticated constant-current source suitable for extracellular microiontophoresis of tract-tracing substances, such as Phaseolus vulgaris leucoagglutinin, Biocytin or Fluoro-Gold, is described. This design uses a flyback switched-mode power supply to generate controllable high-voltage and operational amplifier circuitry to regulate current and provide instrumentation. Design features include a fast rise time, +/- 2000 V supply (stable output in current and voltage monitoring, and separate pumping and holding current settings. Three features of this constant-current source make it especially useful for extracellular microiontophoresis. First, the output voltage monitor permits one to follow changes in the microelectrode resistance during current injection. Second, the voltage-limit (or out-of-compliance) indicator circuitry will sound an alarm when the iontophoretic pump is unable to generate the desired current, such as when the micropipette is blocked. Third, the high-compliance voltage power supply insures up to +/- 20 microA of current through 100 M omega resistance. This device has proven itself to be a reliable constant-current source for extracellular microiontophoresis in the laboratory. PMID:8788057
When is the growth index constant?
Polarski, David; Giacomini, Hector
2016-01-01
The growth index $\\gamma$ is an interesting tool to assess the phenomenology of dark energy (DE) models, in particular of those beyond general relativity (GR). We investigate the possibility for DE models to allow for a constant $\\gamma$ during the entire matter and DE dominated stages. It is shown that if DE is described by quintessence (a scalar field minimally coupled to gravity), this behaviour of $\\gamma$ is excluded either because it would require a transition to a phantom behaviour at some finite moment of time, or, in the case of tracking DE at the matter dominated stage, because the relative matter density $\\Omega_m$ appears to be too small. An infinite number of solutions, with $\\Omega_m$ and $\\gamma$ both constant, are found with $w_{DE}=0$ corresponding to Einstein-de Sitter universes. For all modified gravity DE models satisfying $G_{\\rm eff}\\ge G$, among them the $f(R)$ DE models suggested in the literature, the condition to have a constant $w_{DE}$ is strongly violated at the present epoch. In ...
Nonminimal coupling and the cosmological constant problem
Glavan, Dražen
2015-01-01
We consider a universe with a positive effective cosmological constant and a nonminimally coupled scalar field. When the coupling constant is negative, the scalar field exhibits linear growth at asymptotically late times, resulting in a decaying effective cosmological constant. The Hubble rate in the Jordan frame reaches a self-similar solution, $H=1/(\\epsilon t)$, where the principal slow roll parameter $\\epsilon$ depends on $\\xi$, reaching maximally $\\epsilon=2$ (radiation era scaling) in the limit when $\\xi\\rightarrow -\\infty$. Similar results are found in the Einstein frame (E), with $H_E=1/(\\epsilon_E t)$, but now $\\epsilon_E \\rightarrow 4/3$ as $\\xi\\rightarrow -\\infty$. Therefore in the presence of a nonminimally coupled scalar de Sitter is not any more an attractor, but instead (when $\\xi4/3$ at a rate $\\Gamma\\gg H$, the scaling changes to that of matter, $\\epsilon\\rightarrow \\epsilon_m$, and the energy density in the effective cosmological becomes a fixed fraction of the matter energy density, $M_{\\rm...
Stability constants for silicate adsorbed to ferrihydrite
DEFF Research Database (Denmark)
Hansen, Hans Christian Bruun; Wetche, T.P.; Raulund-Rasmussen, Karsten;
1994-01-01
required days-weeks, both reactions probably being diffusion controlled. Applying the values for specific surface area and site densities for ferrihydrite used by Dzombak & Morel (1990) (600 m2 g-1, 3.4 mumole m-2) the constants pK(al)intr 6.93 +/- 0.12, pK(a2)intr = 8.72 +/- 0.17 and log K(Si) = 3.62 were...... calculated by using the FITEQL optimization routine. Use of the specific surface area actually measured (269 m2 g-1) gave a poorer fit of the experimental data. Due to the slow adsorption of silicate and hence long shaking times, changes in the surface characteristics of the ferrihydrite seem to take place......Intrinsic surface acidity constants (K(a1)intr, K(a2)intr) and surface complexation constant for adsorption of orthosilicate onto synthetic ferrihydrite (K(Si) for the complex = FeOSi(OH)3) have been determined from acid/base titrations in 0.001-0.1 m NaClO4 electrolytes and silicate adsorption...
Twelve Elastic Constants of Betula platyphylla Suk.
Institute of Scientific and Technical Information of China (English)
Wang Liyu; Lu Zhenyou
2004-01-01
Wood elastic constants are needed to describe the elastic behaviors of wood and be taken as an important design parameter for wood-based composite materials and structural materials. This paper clarified the relationships between compliance coefficients and engineering elastic constants combined with orthotropic properties of wood, and twelve elastic constants of Betula platyphylla Suk. were measured by electrical strain gauges. Spreading the adhesive quantity cannot be excessive or too little when the strain flakes were glued. If excessive, the glue layer was too thick which would influence the strain flakes' performance, and if too little, glues plastered were not firm, which could not accurately transmit the strain. Wood as an orthotropic material, its modulus of elasticity and poisson's ratios are related by two formulas:μij /Ei =μji /Ej and μij 0.95) between the reciprocal of elastic modulus MOE-1 and the square of the ratio of depth to length (h/l)2, which indicate that shear modulus values measured were reliable by three point bending experiment.
Fundamental Constants as Monitors of the Universe
Thompson, Rodger I
2016-01-01
Astronomical observations have a unique ability to determine the laws of physics at distant times in the universe. They, therefore, have particular relevance in answering the basic question as to whether the laws of physics are invariant with time. The dimesionless fundamental constants, such as the proton to electron mass ratio and the fine structure constant are key elements in the investigation. If they vary with time then the answer is clearly that the laws of physics are not invariant with time and significant new physics must be developed to describe the universe. Limits on their variance, on the other hand, constrains the parameter space available to new physics that requires a variation with time of basic physical law. There are now observational constraints on the time variation of the proton to electron mass ratio mu at the 1.E-7 level. Constraints on the variation of the fine structure constant alpha are less rigorous, 1E-5, but are imposed at higher redshift. The implications of these limits on ne...
Pole-placement with constant gain output feedback
Sridhar, B.; Lindorff, D. P.
1973-01-01
Davison (1970) has demonstrated that it is possible to assign max (m, p) poles of a linear time-invariant controllable and observable multivariable system arbitrarily close to desired locations by using constant gain output feedback. A new proof of Davison's theorem on pole placement is developed, and a system design procedure is described which offers some advantages over Davison's method. It is shown that in some cases more than max (m, p) poles can be assigned arbitrarily, and a least square design procedure is proposed to approximate the desired pole locations when it is not possible to place all the poles.
Virial theorem and gravitational equilibrium with a cosmological constant
Nowakowski, Marek; Sanabria, Juan Carlos; García, Alejandro
2012-01-01
Starting from the Newtonian limit of Einstein's equations in the presence of a positive cosmological constant, we obtain a new version of the virial theorem and a condition for gravitational equilibrium. Such a condition takes the form ρ > λρvac, where ρ is the mean density of an astrophysical system (e.g. galaxy, galaxy cluster or supercluster), λ is a quantity which depends only on the shape of the system, and ρvac is the vacuum density. We conclude that gravitational stability might be ...
Was the fine-structure constant variable over cosmological time?
International Nuclear Information System (INIS)
Cosmological variation of the fine-structure constant (α) dependent on the redshifts of quasars. Using the emission (absorption) systems in the spectra of distant quasars, we investigate the effects of the cosmology variability in the value of the fine-structure constant (α) dependent on the redshifts of quasars during the evolution of Universe. We obtain optical spectra of fine-structure transitions in [Ne-III], [Ne-V], [O-III], [O-I], and [S-II] multiplets from a sample of 14 Seyfert 1.5 galaxies in the low-z range. 0.035 2(t)/α2(0) = (0.999965 ± 0.00005529). (authors)
Of Matter Less Repulsive than a Cosmological Constant
Cornish, N J; Cornish, Neil J.; Starkman, Glenn D.
1998-01-01
The case grows ever stronger that the average density of matter, ordinary and dark, is less than the critical density required for a flat universe. However, most of determinations of the mass density have been dynamical, hence sensitive only to matter which is clustered at or below the scale of the observed dynamical systems. The density may still be critical if there is a dark matter component which is relatively smooth on the scales of galaxies or clusters. Thoughts on this matter have focused on the possibility of an effective cosmological constant or vacuum energy. In this letter we examine an alternative possibility - that there is a second component to the dark matter which has a repulsive self-interaction. We show that given even very weak self-repulsion, this dark matter would remain unclustered. While this repulsive alternative is perhaps aptly named, it is arguably at least as palatable as a cosmological constant.
NVU dynamics. I. Geodesic motion on the constant-potential-energy hypersurface
DEFF Research Database (Denmark)
Ingebrigtsen, Trond; Toxværd, Søren; Heilmann, Ole;
2011-01-01
An algorithm is derived for computer simulation of geodesics on the constant-potential-energy hypersurface of a system of N classical particles. First, a basic time-reversible geodesic algorithm is derived by discretizing the geodesic stationarity condition and implementing the constant-potential...
Effective Torsion and Spring Constants in a Hybrid Translational-Rotational Oscillator
Nakhoda, Zein; Taylor, Ken
2011-01-01
A torsion oscillator is a vibrating system that experiences a restoring torque given by [tau] = -[kappa][theta] when it experiences a rotational displacement [theta] from its equilibrium position. The torsion constant [kappa] (kappa) is analogous to the spring constant "k" for the traditional translational oscillator (for which the restoring force…
Institute of Scientific and Technical Information of China (English)
张建民; 石秋芝
2003-01-01
In this paper the Bi (Ⅲ) -ligand(pyridine-2-carboxylic acid) system was studied by direct current sampledpolarography (DC_TAST) at a fixed ratio of total-ligand to total-metal concentration and changing pH. The po-larographic experimental complex formation curve (ECFC) and the theoretical complex formation curve (TCFC)were used for modelling the metal-ligand system and optimizing stability constants. The ECFC, in which experi-mental parameters of polarography are included (a shift in a half-wave potential and a variation in a diffusioncontrolled limiting current), appears to be a characteristic function for a particular metal-ligand system. The TCFCis a theoretical curve calculated for the designed metal-ligand model from mass-balance equation. Five bismuthcomplexes MHL, ML, ML2, ML3 and ML3(OH) with their stability constants as logβ 7.54 ±0. 10, 7.50 ±0.02,13.91 +0. 04, 18.15 ±0. 03 and 26.75 ±0. 02, respectively, are reported.
Institute of Scientific and Technical Information of China (English)
刘波; 贺志佳; 金昊
2015-01-01
双PWM变换器是目前风力发电系统广泛使用的控制电路，其直流母线是实现风电系统能量传输与转换的中间环节，母线电压的稳定与否直接关系到能否实现对机侧和网侧变换器独立控制及整个系统的安全稳定运行，减小直流母线电压波动成为双PWM变换器控制技术的研究热点，并得到了广泛的关注。对风电系统双PWM变换器直流母线电压控制技术进行综述，分析了基于电容电流直接控制、直接功率控制、协调控制及模糊控制等各种控制策略的优缺点，指出了存在的问题、今后的研究重点及发展趋势。%Dual PWM converter control system is widely used in wind power system,the DC bus is the interme-diate link of energy transfer and conversion in wind power system,bus voltage stability is directly related to the realization of the generator side and grid side converter control and the stable operation of the whole system. How to reduce the fluctuation of DC bus voltage has become the research focus of dual PWM converter control technology,and received wide attention. DC bus voltage control technology in wind power system with dual PWM converter was summarized. Analyzed the advantages and disadvantages of the direct control based on ca-pacitive current,direct power control,coordination control,fuzzy control and other control strategies. Pointed out the problem in each of control strategies and the research emphases and development trend in the future.
Institute of Scientific and Technical Information of China (English)
罗隆福; 黎涛; 邓建国; 陆格文
2011-01-01
光伏发电系统输出功率易受外部环境的影响,存在诸多不确定因素.该文采用蓄电池储能单元作为光伏并网的能量缓冲装置,以控制并网的功率输出.文中建立了基于等效电路的电池储能光伏并网系统整体动态数学模型,设计相应的控制策略,对系统的输出功率进行控制,并以随机光照强度的扰动为例,对系统输出的电能质量和稳定性进行仿真研究.结果表明,该并网系统灵活性强,能很好实现系统功率可控稳定输出.%The output power of photovoltaic(PV) system is vulnerable to the impact of changes in the external environment and exists many uncertainties. The research on the possibility of employing a battery energy storage method in PV grid-connected power generation system to enhance the performance of its power quality and stability was done. A mathematic model of battery energy storage system (BESS) based on equivalent circuit and a photovoltaic based on global dynamic mathematical model for PV-BESS grid-connected were built, and corresponding conrtol srtategy was developed to control the output power. Based on these models,illumination change random for example, a simulaiton platform of PV-BESS was developed by Simulink of the Matlab to analyze the power quality and stability. Simulation results show that it is flexible and can improve the stability of output power.
Temperature corrections for constant temperature and constant current hot-wire anemometers
International Nuclear Information System (INIS)
Changes in the ambient fluid temperature change the calibration curve for velocity measurements taken using hot-wire anemometry. New correction methods are proposed to account for the effects of relatively large temperature changes in the heat-transfer process and on the fluid properties. The corrections do not assume any particular heat-transfer correlation, and they do not require multiple calibrations over a range of temperatures. The corrections are derived for the constant temperature and constant current modes of operation
Dereli, Tekin; Yetişmişoǧlu, Cem
2016-09-01
We derive the field equations for topologically massive gravity coupled with the most general quadratic curvature terms using the language of exterior differential forms and a first order constrained variational principle. We find variational field equations both in the presence and absence of torsion. We then show that spaces of constant negative curvature (i.e. the anti-de Sitter space AdS3) and constant torsion provide exact solutions.
Dereli, T
2016-01-01
We derive the field equations for topologically massive gravity coupled with the most general quadratic curvature terms using the language of exterior differential forms and a first order constrained variational principle. We find variational field equations both in the presence and absence of torsion. We then show that spaces of constant negative curvature (i.e. the anti de-Sitter space $AdS_3$) and constant torsion provide exact solutions.
International Nuclear Information System (INIS)
The complex formation and redox decomposition of several hydroxo complexes that form in the Ce4+ - SO42- - R(OH)m systems, where R(OH)m (m = 3, 5, 6) is glycerol, xylitol, and sorbitol, respectively, were studied spectrophotometrically, pH metrically, and kinetically at the ionic strength I = 2 with the pH of the sulfate background in the range of 1.7-3.4 and temperatures of 20.0-23.0 deg C. The stability constants of the [CeOHHxL]3-x (L = R(OH)m) complexes, the ligand speciation, and the rate constants of the intramolecular redox decomposition of the complexes were determined in the sulfate background. The apparent stabilization of the +4 oxidation state of cerium in the specified complexes is demonstrated
CONSTANT LEVERAGE AND CONSTANT COST OF CAPITAL: A COMMON KNOWLEDGE HALF-TRUTH
Directory of Open Access Journals (Sweden)
IGNACIO VÉLEZ-PAREJA
2008-01-01
Full Text Available Un enfoque típico para valorar flujos de caja finitos es suponer que el endeudamiento es constante (generalmente como un endeudamiento objetivo o deseado y que por tanto, el costo del patrimonio, Ke y el costo promedio ponderado de capital CPPC, también son constantes. Para los flujos de caja perpetuos, y con el costo de la deuda, Kd como la tasa de descuento para el ahorro en impuestos o escudo fiscal, Ke y el CPPC aplicado al flujo de caja libre FCL son constantes si el endeudamiento es constante. Sin embargo esto no es verdad para los flujos de caja finitos. En este documento mostramos que para flujos de caja finitos, Ke y por lo tanto el CPPC dependen de la tasa de descuento que se utiliza para valorar el ahorro en impuestos, AI y según lo esperado, Ke y el CPPC no son constantes con Kd como la tasa de descuento para el ahorro en impuestos, aunque el endeudamiento sea constante. Ilustramos esta situación con un ejemplo simple. Analizamos cinco métodos: el flujo de caja descontado, FCD, usando APV, el FCD y la formulación tradicional y general del CPPC, el valor presente del flujo de caja del accionista, FCA más deuda y el flujo de caja de capital, FCC.
Elucidation of constant current density molecular plating
International Nuclear Information System (INIS)
The production of thin layers by means of constant current or constant voltage electrolysis in organic media is commonly known as molecular plating. Despite the fact that this method has been applied for decades and is known to be among the most efficient ones for obtaining quantitative deposition, a full elucidation of the molecular plating is still lacking. In order to get a general understanding of the process and hence set the basis for further improvements of the method, constant current density electrolysis experiments were carried out in a mixture of isopropanol and isobutanol containing millimolar amounts of HNO3 together with [Nd(NO3)3·6H2O] used as a model electrolyte. The process was investigated by considering the influence of different parameters, namely the electrolyte concentrations (i.e., Nd(NO3)3·6H2O: 0.11, 0.22, 0.44 mM, and HNO3: 0.3, 0.4 mM), the applied current (i.e., 2 mA and 6 mA), and the surface roughness of the deposition substrates (i.e., a few tens to several hundreds of nm). The response of the process to changes of these parameters was monitored recording cell potential curves, which showed to be strongly influenced by the investigated conditions. The produced layers were characterized using γ-ray spectroscopy for the evaluation of Nd deposition yields, X-ray photoelectron spectroscopy for chemical analysis of the surfaces, and atomic force microscopy for surface roughness evaluation. X-ray photoelectron spectroscopy results clearly indicate that Nd is present only as Nd3+ on the cathodic surface after molecular plating. The results obtained from this characterization and some basic features inferred from the study of the cell potential curves were used to interpret the different behaviours of the deposition processes as a consequence of the applied variables.
Localized (super)gravity and cosmological constant
International Nuclear Information System (INIS)
We consider localization of gravity in domain wall solutions of Einstein's gravity coupled to a scalar field with a generic potential. We discuss conditions on the scalar potential such that domain wall solutions are non-singular. Such solutions even exist for appropriate potentials which have no minima at all and are unbounded below. Domain walls of this type have infinite tension, while usual kink type of solutions interpolating between two AdS minima have finite tension. In the latter case the cosmological constant on the domain wall is necessarily vanishing, while in the former case it can be zero or negative. Positive cosmological constant is allowed for singular domain walls. We discuss non-trivial conditions for physically allowed singularities arising from the requirement that truncating the space at the singularities be consistent. Non-singular domain walls with infinite tension might a priori avoid recent 'no-go' theorems indicating impossibility of supersymmetric embedding of kink type of domain walls in gauged supergravity. We argue that (non-singular) domain walls are stable even if they have infinite tension. This is essentially due to the fact that localization of gravity in smooth domain walls is a Higgs mechanism corresponding to a spontaneous breakdown of translational invariance. As to discontinuous domain walls arising in the presence of δ-function 'brane' sources, they explicitly break translational invariance. Such solutions cannot therefore be thought of as limits of smooth domain walls. We point out that if the scalar potential has no minima and approaches finite negative values at infinity, then higher derivative terms are under control, and do not affect the cosmological constant which is vanishing for such backgrounds. Nonetheless, we also point out that higher curvature terms generically delocalize gravity, so that the desired lower-dimensional Newton's law is no longer reproduced
Localized (super)gravity and cosmological constant
Kakushadze, Zurab
2000-11-01
We consider localization of gravity in domain wall solutions of Einstein's gravity coupled to a scalar field with a generic potential. We discuss conditions on the scalar potential such that domain wall solutions are non-singular. Such solutions even exist for appropriate potentials which have no minima at all and are unbounded below. Domain walls of this type have infinite tension, while usual kink type of solutions interpolating between two AdS minima have finite tension. In the latter case the cosmological constant on the domain wall is necessarily vanishing, while in the former case it can be zero or negative. Positive cosmological constant is allowed for singular domain walls. We discuss non-trivial conditions for physically allowed singularities arising from the requirement that truncating the space at the singularities be consistent. Non-singular domain walls with infinite tension might a priori avoid recent "no-go" theorems indicating impossibility of supersymmetric embedding of kink type of domain walls in gauged supergravity. We argue that (non-singular) domain walls are stable even if they have infinite tension. This is essentially due to the fact that localization of gravity in smooth domain walls is a Higgs mechanism corresponding to a spontaneous breakdown of translational invariance. As to discontinuous domain walls arising in the presence of δ-function "brane" sources, they explicitly break translational invariance. Such solutions cannot therefore be thought of as limits of smooth domain walls. We point out that if the scalar potential has no minima and approaches finite negative values at infinity, then higher derivative terms are under control, and do not affect the cosmological constant which is vanishing for such backgrounds. Nonetheless, we also point out that higher curvature terms generically delocalize gravity, so that the desired lower-dimensional Newton's law is no longer reproduced.
On inflation, cosmological constant, and SUSY breaking
Linde, Andrei
2016-01-01
We consider a broad class of inflationary models of two unconstrained chiral superfields, the stabilizer $S$ and the inflaton $\\Phi$, which can describe inflationary models with nearly arbitrary potentials. These models include, in particular, the recently introduced theories of cosmological attractors, which provide an excellent fit to the latest Planck data. We show that by adding to the superpotential of the fields $S$ and $\\Phi$ a small term depending on a nilpotent chiral superfield $P$ one can break SUSY and introduce a small cosmological constant without affecting main predictions of the original inflationary scenario.
The fine structure constant and habitable planets
Sandora, McCullen
2016-08-01
We use the existence of habitable planets to impose anthropic requirements on the fine structure constant, α. To this effect, we present two considerations that restrict its value to be very near the one observed. The first, that the end product of stellar fusion is iron and not one of its neighboring elements, restricts α‑1 to be 145± 50. The second, that radiogenic heat in the Earth's interior remains adequately productive for billions of years, restricts it to be 145±9. A connection with the grand unified theory window is discussed, effectively providing a route to probe ultra-high energy physics with upcoming advances in planetary science.
TASI Lectures on the cosmological constant
Energy Technology Data Exchange (ETDEWEB)
Bousso, Raphael; Bousso, Raphael
2007-08-30
The energy density of the vacuum, Lambda, is at least 60 orders of magnitude smaller than several known contributions to it. Approaches to this problem are tightly constrained by data ranging from elementary observations to precision experiments. Absent overwhelming evidence to the contrary, dark energy can only be interpreted as vacuum energy, so the venerable assumption that Lambda=0 conflicts with observation. The possibility remains that Lambda is fundamentally variable, though constant over large spacetime regions. This can explain the observed value, but only in a theory satisfying a number of restrictive kinematic and dynamical conditions. String theory offers a concrete realization through its landscape of metastable vacua.
Infrared propagator corrections for constant deceleration
Energy Technology Data Exchange (ETDEWEB)
Janssen, T M; Miao, S P; Prokopec, T [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Leuvenlaan 4, Postbus 80.195, 3508 TD Utrecht (Netherlands); Woodard, R P [Department of Physics, University of Florida Gainesville, FL 32611 (United States)], E-mail: T.M.Janssen@uu.nl, E-mail: S.Miao@uu.nl, E-mail: T.Prokopec@uu.nl, E-mail: woodard@phys.ufl.edu
2008-12-21
We derive the propagator for a massless, minimally coupled scalar on a D-dimensional, spatially flat, homogeneous and isotropic background with arbitrary constant deceleration parameter. Our construction uses the operator formalism by integrating the Fourier mode sum. We give special attention to infrared corrections from the nonzero lower limit associated with working on finite spatial sections. These corrections eliminate infrared divergences that would otherwise be incorrectly treated by dimensional regularization, resulting in off-coincidence divergences for those special values of the deceleration parameter at which the infrared divergence is logarithmic. As an application we compute the expectation value of the scalar stress-energy tensor.
PET physiological measurements using constant infusion
International Nuclear Information System (INIS)
A wide range of study designs can be used with positron emission tomography methods to provide quantitative measurements of physiological parameters. While bolus injection of tracer is the conventional approach, use of combined bolus plus constant infusion provides a number of advantages for receptor-binding tracers. Of recent interest is the use of this approach to dynamically follow the displacement of tracer during in vivo changes in neurotransmitter concentrations. This paper provides an overview of the tradeoffs in using bolus/infusion methods versus conventional bolus injection for receptor binding studies
Characterization of a constant current charge detector.
Mori, Masanobu; Chen, Yongjing; Ohira, Shin-Ichi; Dasgupta, Purnendu K
2012-12-15
Ion exchangers are ionic equivalents of doped semiconductors, where cations and anions are equivalents of holes and electrons as charge carriers in solid state semiconductors. We have previously demonstrated an ion exchange membrane (IEM) based electrolyte generator which behaves similar to a light-emitting diode and a charge detector (ChD) which behaves analogous to a p-i-n photodiode. The previous work on the charge detector, operated at a constant voltage, established its unique ability to respond to the charge represented by the analyte ions regardless of their redox properties, rather than to their conductivities. It also suggested that electric field induced dissociation (EFID) of water occurs at one or both ion exchange membranes. A logical extension is to study the behavior of the same device, operated in a constant current mode (ChD(i)). The evidence indicates that in the present operational mode the device also responds to the charge represented by the analytes and not their conductivity. Injection of a base into a charge detector operated in the constant voltage mode was not previously examined; in the constant current mode, base injection appears to inhibit EFID. The effects of applied current, analyte residence time and outer channel fluid composition were individually examined; analyte ions of different mobilities as well as affinities for the respective IEMs were used. While the exact behavior is somewhat dependent on the applied current, strong electrolytes, both acids and salts, respond the highest and in a near-uniform fashion, weak acids and their salts respond in an intermediate fashion and bases produce the lowest responses. A fundamentally asymmetric behavior is observed. Injected bases but not injected acids produce a poor response; the effects of incorporating a strong base as the electrolyte in the anion exchange membrane (AEM) compartment is far greater than incorporating an acid in the cation exchange membrane (CEM) compartment. These
Bouncing Anisotropic Universes with Varying Constants
Barrow, John D
2013-01-01
We examine the evolution of a closed, homogeneous and anisotropic cosmology subject to a variation of the fine structure 'constant', \\alpha, within the context of the theory introduced by Bekenstein, Sandvik, Barrow and Magueijo, which generalises Maxwell's equations and general relativity. The variation of \\alpha permits an effective ghost scalar field, whose negative energy density becomes dominant at small length scales, leading to a bouncing cosmology. A thermodynamically motivated coupling which describes energy exchange between the effective ghost field and the radiation field leads to an expanding, isotropizing sequence of bounces. In the absence of entropy production we also find solutions with stable anisotropic oscillations around a static universe.
Standard-model coupling constants from compositeness
Besprosvany, J
2003-01-01
A coupling-constant definition is given based on the compositeness property of some particle states with respect to the elementary states of other particles. It is applied in the context of the vector-spin-1/2-particle interaction vertices of a field theory, and the standard model. The definition reproduces Weinberg's angle in a grand-unified theory. One obtains coupling values close to the experimental ones for appropriate configurations of the standard-model vector particles, at the unification scale within grand-unified models, and at the electroweak breaking scale.
The Fine Structure Constant and Habitable Planets
Sandora, McCullen
2016-01-01
We use the existence of habitable planets to impose anthropic requirements on the fine structure constant, $\\alpha$. To this effect, we present two considerations that restrict its value to be very near the one observed. The first, that the end product of stellar fusion is iron and not one of its neighboring elements, restricts $\\alpha^{-1}$ to be $145\\pm 50$. The second, that radiogenic heat in the Earth's interior remains adequately productive for billions of years, restricts it to be $145\\pm9$. A connection with the grand unified theory window is discussed, effectively providing a route to probe ultra-high energy physics with upcoming advances in planetary science.
The fine structure constant and habitable planets
Sandora, McCullen
2016-08-01
We use the existence of habitable planets to impose anthropic requirements on the fine structure constant, α. To this effect, we present two considerations that restrict its value to be very near the one observed. The first, that the end product of stellar fusion is iron and not one of its neighboring elements, restricts α-1 to be 145± 50. The second, that radiogenic heat in the Earth's interior remains adequately productive for billions of years, restricts it to be 145±9. A connection with the grand unified theory window is discussed, effectively providing a route to probe ultra-high energy physics with upcoming advances in planetary science.
Scalar field collapse with negative cosmological constant
Baier, R; Stricker, S A
2014-01-01
The formation of black holes or naked singularities is studied in a model in which a homogeneous time-dependent scalar field with an exponential potential couples to four dimensional gravity with negative cosmological constant. An analytic solution is derived and its consequences are discussed. The model depends only on one free parameter which determines the equation of state and decides the fate of the spacetime. Depending on the value of this parameter the collapse ends in a black hole or a naked singularity. The latter case violates the cosmic censorship conjecture.
Rugged constant-temperature thermal anemometer
Palma, J
2016-01-01
Here we report a robust thermal anemometer which can be easily built. It was conceived to measure outdoor wind speeds, and for airspeed monitoring in wind tunnels and other indoor uses. It works at a constant, low temperature of approximately 90$^\\circ$C, so that an independent measurement of the air temperature is required to give a correct speed reading. Despite the size and high thermal inertia of the probe, the test results show that this anemometer is capable of measuring turbulent fluctuations up to ~100 Hz in winds of ~14 m/s, which corresponds to a scale similar to the length of the probe.
Constant-Elasticity-of-Substitution Simulation
Reiter, G.
1986-01-01
Program simulates constant elasticity-of-substitution (CES) production function. CES function used by economic analysts to examine production costs as well as uncertainties in production. User provides such input parameters as price of labor, price of capital, and dispersion levels. CES minimizes expected cost to produce capital-uncertainty pair. By varying capital-value input, one obtains series of capital-uncertainty pairs. Capital-uncertainty pairs then used to generate several cost curves. CES program menu driven and features specific print menu for examining selected output curves. Program written in BASIC for interactive execution and implemented on IBM PC-series computer.
Fine Structure Constant: Theme With Variations
Bezerra, V B; Muniz, C R; Tahim, M O; Vieira, H S
2016-01-01
In this paper, we study the spatial variation of the fine structure constant $\\alpha$ due to the presence of a static and spherically symmetric gravitational source. The procedure consists of calculating the solution including the energy eigenvalues of a massive scalar field around that source, considering the weak-field regimen, which yields the gravitational analog of the atomic Bohr levels. From this result, we obtain several values for the effective $\\alpha$ by considering some scenarios of semi-classical and quantum gravities. Constraints on the parameters of the involved theories are calculated from astrophysical observations of the white dwarf emission spectra. Such constraints are compared with those ones obtained in the literature.
Radiation balances and the solar constant
Crommelynck, D.
1981-01-01
The radiometric concepts are defined in order to consider various types of radiation balances and relate them to the diabetic form of the energy balance. Variability in space and time of the components of the radiation field are presented. A specific concept for sweeping which is tailored to the requirements is proposed. Finally, after establishing the truncated character of the present knowledge of the radiation balance. The results of the last observations of the solar constant are given. Ground and satellite measurement techniques are discussed.
Determination of pre-emphasis constants for eddy current reduction
International Nuclear Information System (INIS)
Magnetic field gradients play a fundamental role in fast magnetic resonance imaging (MRI) methods and spectroscopy imaging. Precise information on gradient waveform shape and rise times is often very useful in experimental MRI. We present a simple method for the measurement of the gradient time course and static magnetic field changes. The method does not require any specialized hardware and can be used with a standard volume coil and a special phantom filled with deionized or doped water. The method is based on an analysis of the instantaneous frequency variation of an MR signal in the time domain, acquired from a mechanically selected thin slice of phantom located at the gradient isocentre. The measurement and approximation of the course of time gradients and of the changes in the static magnetic field result in pre-emphasis constants that substitute the constants determined manually in a time-consuming manner. The described method facilitates the determination of pre-emphasis constants for the compensation of eddy current effects in MR systems. Our results show that residual gradients in the region of interest within 0.5 ms after the gradient is switched off are smaller than 5 µT m−1 (for an applied test gradient of 72 mT m−1) and the shift of the static field is smaller than 0.2 µT. This accuracy is very important for the development of MR spectroscopic imaging technologies using samples with very short relaxation times, and for EPI pulse sequences
Is cosmological constant needed in Higgs inflation?
Directory of Open Access Journals (Sweden)
Chao-Jun Feng
2014-11-01
Full Text Available The detection of B-mode shows a very powerful constraint to theoretical inflation models through the measurement of the tensor-to-scalar ratio r. Higgs boson is the most likely candidate of the inflaton field. But usually, Higgs inflation models predict a small value of r, which is not quite consistent with the recent results from BICEP2. In this paper, we explored whether a cosmological constant energy component is needed to improve the situation. And we found the answer is yes. For the so-called Higgs chaotic inflation model with a quadratic potential, it predicts r≈0.2, ns≈0.96 with e-folds number N≈56, which is large enough to overcome the problems such as the horizon problem in the Big Bang cosmology. The required energy scale of the cosmological constant is roughly Λ∼(1014 GeV2, which means a mechanism is still needed to solve the fine-tuning problem in the later time evolution of the universe, e.g. by introducing some dark energy component.
Variation of fundamental constants: theory and observations
Flambaum, V V
2007-01-01
Review of recent works devoted to the variation of the fundamental constants is presented including atomic clocks, quasar absorption spectra, and Oklo natural nuclear reactor data. Assuming linear variation with time we can compare different results. From the quasar absorption spectra: $\\dot{\\mu}/\\mu=(1 \\pm 3) \\times 10^{-16}$ yr$^{-1}$. A combination of this result and the atomic clock results gives the best limt on variation of $\\alpha$: $\\dot{\\alpha}/\\alpha=(-0.8 \\pm 0.8) \\times 10^{-16}$ yr$^{-1}$. The Oklo natural reactor gives the best limit on the variation of $m_s/\\Lambda_{QCD}$ where $m_s$ is the strange quark mass. Huge enhancement of the relative variation effects happens in transitions between close atomic, molecular and nuclear energy levels. We suggest several new cases where the levels are very narrow. Large enhancement of the variation effects is also possible in cold atomic and molecular collisions near Feshbach resonance. Massive bodies (stars or galaxies) can also affect physical constants....
Is cosmological constant needed in Higgs inflation?
Energy Technology Data Exchange (ETDEWEB)
Feng, Chao-Jun, E-mail: fengcj@shnu.edu.cn [Shanghai United Center for Astrophysics (SUCA), Shanghai Normal University, 100 Guilin Road, Shanghai 200234 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); Li, Xin-Zhou, E-mail: kychz@shnu.edu.cn [Shanghai United Center for Astrophysics (SUCA), Shanghai Normal University, 100 Guilin Road, Shanghai 200234 (China)
2014-11-10
The detection of B-mode shows a very powerful constraint to theoretical inflation models through the measurement of the tensor-to-scalar ratio r. Higgs boson is the most likely candidate of the inflaton field. But usually, Higgs inflation models predict a small value of r, which is not quite consistent with the recent results from BICEP2. In this paper, we explored whether a cosmological constant energy component is needed to improve the situation. And we found the answer is yes. For the so-called Higgs chaotic inflation model with a quadratic potential, it predicts r≈0.2, n{sub s}≈0.96 with e-folds number N≈56, which is large enough to overcome the problems such as the horizon problem in the Big Bang cosmology. The required energy scale of the cosmological constant is roughly Λ∼(10{sup 14} GeV){sup 2}, which means a mechanism is still needed to solve the fine-tuning problem in the later time evolution of the universe, e.g. by introducing some dark energy component.
Dynamical Vacuum against a rigid Cosmological Constant
Sola, Joan; Gomez-Valent, Adria; Nunes, Rafael C
2016-01-01
When we are approaching the centenary of the introduction of the cosmological constant $\\Lambda$ by Einstein in his gravitational field equations, and after about two decades of the first observational papers confirming the existence of a non-vanishing, positive, $\\Lambda$ as the most likely explanation for the observed acceleration of the Universe, we are still facing the question whether $\\Lambda$ is truly a fundamental constant of Nature or a mildly evolving dynamical variable. In this work we compare three types of cosmological scenarios involving dynamical vacuum energy in interaction with matter. By performing an overall fit to the cosmological observables $SNIa+BAO+H(z)+LSS+CMB$, we find that the dynamical $\\Lambda$ models are significantly more favored than the $\\Lambda$CDM, suggesting that a rigid $\\Lambda$-term is excluded at $\\sim 3\\sigma$ c.l. This conclusion is strongly supported by Akaike and Bayesian information criteria which render more than 10 points of difference in favor of the dynamical v...
Ventricular fibrillation time constant for swine.
Wu, Jiun-Yan; Nimunkar, Amit J; Sun, Hongyu; O'Rourke, Ann; Huebner, Shane; Will, James A; Webster, John G
2008-10-01
The strength-duration curve for cardiac excitation can be modeled by a parallel resistor-capacitor circuit that has a time constant. Experiments on six pigs were performed by delivering current from the X26 Taser dart at a distance from the heart to cause ventricular fibrillation (VF). The X26 Taser is an electromuscular incapacitation device (EMD), which generates about 50 kV and delivers a pulse train of about 15-19 pulses s(-1) with a pulse duration of about 150 micros and peak current about 2 A. Similarly a continuous 60 Hz alternating current of the amplitude required to cause VF was delivered from the same distance. The average current and duration of the current pulse were estimated in both sets of experiments. The strength-duration equation was solved to yield an average time constant of 2.87 ms +/- 1.90 (SD). Results obtained may help in the development of safety standards for future electromuscular incapacitation devices (EMDs) without requiring additional animal tests.
In-medium pion weak decay constants
Kim, H
2002-01-01
In nuclear matter, the pion weak decay constant is separated into the two components $f^t, f^s$ corresponding to the time and space components of the axial-vector current. Using QCD sum rules, we compute the two decay constants from the pseudoscalar-axial vector correlation function in the matter $i \\int d^4x~ e^{ip\\cdot x} $. It is found that the sum rule for $f^t$ satisfies the in-medium Gell-Mann$-$Oakes$-$Renner (GOR) relation precisely while the $f^s$ sum rule does not. The $f^s$ sum rule contains the nonnegligible contribution from the dimension 5 condensate $_N + {1\\over 8} _N$ in addition to the in-medium quark condensate. Using standard set of QCD parameters and ignoring the in-medium change of the pion mass, we obtain $f^t =105$ MeV at the nuclear saturation density. The prediction for $f^s$ depends on values of the dimension 5 condensate and slightly on the Borel mass. However, the OPE constrains that $f^s/f^t \\ge 1 $, which does not agree with the prediction from the in-medium chiral perturbation ...
Ventricular fibrillation time constant for swine
International Nuclear Information System (INIS)
The strength–duration curve for cardiac excitation can be modeled by a parallel resistor–capacitor circuit that has a time constant. Experiments on six pigs were performed by delivering current from the X26 Taser dart at a distance from the heart to cause ventricular fibrillation (VF). The X26 Taser is an electromuscular incapacitation device (EMD), which generates about 50 kV and delivers a pulse train of about 15–19 pulses s−1 with a pulse duration of about 150 µs and peak current about 2 A. Similarly a continuous 60 Hz alternating current of the amplitude required to cause VF was delivered from the same distance. The average current and duration of the current pulse were estimated in both sets of experiments. The strength–duration equation was solved to yield an average time constant of 2.87 ms ± 1.90 (SD). Results obtained may help in the development of safety standards for future electromuscular incapacitation devices (EMDs) without requiring additional animal tests
Hyperscaling violation and the shear diffusion constant
Kolekar, Kedar S; Narayan, K
2016-01-01
We consider holographic theories in bulk $(d+1)$-dimensions with Lifshitz and hyperscaling violating exponents $z,\\theta$ at finite temperature. By studying shear gravitational modes in the near-horizon region given certain self-consistent approximations, we obtain the corresponding shear diffusion constant on an appropriately defined stretched horizon, adapting the analysis of Kovtun, Son and Starinets. For generic exponents with $d-z-\\theta>-1$, we find that the diffusion constant has power law scaling with the temperature, motivating us to guess a universal relation for the viscosity bound. When the exponents satisfy $d-z-\\theta=-1$, we find logarithmic behaviour. This relation is equivalent to $z=2+d_{eff}$ where $d_{eff}=d_i-\\theta$ is the effective boundary spatial dimension (and $d_i=d-1$ the actual spatial dimension). It is satisfied by the exponents in hyperscaling violating theories arising from null reductions of highly boosted black branes, and we comment on the corresponding analysis in that cont...
The Hubble Constant and the Expanding Universe
Freedman, Wendy
2003-01-01
In 1929 Edwin Hubble proved that our universe is expanding by showing that the farther a galaxy is from us, the faster it is speeding away into space. This velocity-distance relation came to be called Hubble's law, and the value that describes the rate of expansion is known as the Hubble constant, or H0 . Like the speed of light, H0 is a fundamental constant, and it is a key parameter needed to estimate both the age and size of the universe. Since the late 1950s astronomers have been arguing for an H0 value between 50 to 100 kilometers per second per megaparsec, a lack of precision that produced an unacceptably wide range of ages for the universe—anywhere from 10 to 20 billion years. Using the Hubble Space Telescope, Freedman and her colleagues measured H0 to an unprecedented level of accuracy, deriving a value of 72, with an uncertainty of 10 percent—a milestone achievement in cosmology. The new result suggests that our universe is about 13 billion years old, give or take a billion years, and it's a value that sits comfortably alongside the 12 billion years estimated for the age of the oldest stars.
Exact Values of Some Geometric Constants of Orlicz Spaces
Institute of Scientific and Technical Information of China (English)
Ya Qiang YAN
2007-01-01
We present the exact values of nonsquare constants, yon Neumann-Jordan constants, Jung constants, packing constants, weakly convergent sequence coefficients and normal structure coefficients in a class of reflexive Orlicz function spaces and sequence spaces equipped with Luxemburg norm and Orlicz norm.
Garbage-free reversible constant multipliers for arbitrary integers
DEFF Research Database (Denmark)
Mogensen, Torben Ægidius
2013-01-01
We present a method for constructing reversible circuitry for multiplying integers by arbitrary integer constants. The method is based on Mealy machines and gives circuits whose size are (in the worst case) linear in the size of the constant. This makes the method unsuitable for large constants, ......, but gives quite compact circuits for small constants. The circuits use no garbage or ancillary lines....
Decay constants and wave functions of heavy-light pseudoscalars
International Nuclear Information System (INIS)
Calculations of the pseudoscalar decay constant for mesons containing one heavy quark (i.e., fD, fB) are reported. Results at β = 6.0 using the static-quark approximation for the heavy-quark propagator are compared to results using a propagating heavy quark with Wilson fermions at (β = 6.0, β = 6.1 and β = 6.3). Further investigation into the dynamics governing these systems is made by measuring the Bethe-Salpeter wave function for each case. 15 refs., 5 figs., 1 tab
NVU dynamics. III. Simulating molecules at constant potential energy
DEFF Research Database (Denmark)
Ingebrigtsen, Trond; Dyre, J. C.
2012-01-01
standard algorithms. The conclusion was that the NVU algorithm has the same desirable properties as the Verlet algorithm for Newtonian NVE dynamics, i.e., it is time-reversible and symplectic. Additionally, it was concluded that NVU dynamics becomes equivalent to NVE dynamics in the thermodynamic limit......-terphenyl (OTP) and rigid SPC/E water. The rigid bonds introduce additional constraints beyond that of constant potential energy for atomic systems. The rigid-bond NVU algorithm conserves potential energy, bond lengths, and step length for indefinitely long runs. The quantities probed in simulations give results...
Some Unique Constants Associated with Extremal Black Holes
Sivaram, C; 10.1007/s10509-012-0983-z
2012-01-01
In recent papers we had developed a unified picture of black hole entropy and curvature which was shown to lead to Hawking radiation. It was shown that for any black hole mass, holography implies a phase space of just one quantum associated with the interior of the black hole. Here we study extremal rotating and charged black holes and obtain unique values for ratios of angular momentum to entropy, charge to entropy, etc. It turns out that these ratios can be expressed in terms of fundamental constants in nature, having analogies with other physical systems, like in condensed matter physics.
Growing oral biofilms in a constant depth film fermentor (CDFF).
Pratten, Jonathan
2007-08-01
In order to grow organisms in such a manner as to mimic their physiological growth state in vivo, it is often desirable to grow them as biofilms in the laboratory. There are numerous systems available to accomplish this; however, some are more suited to the growth of oral biofilms (dental plaque) than others. The operating parameters of one such model, the constant depth film fermentor (CDFF), are given in this unit. This model is particularly suited to studying the varied biofilms which exist in the oral cavity because environmental factors such as the substratum, nutrient source, and gas flow can be altered.
Computing magnetic anisotropy constants of single molecule magnets
Indian Academy of Sciences (India)
S Ramasesha; Shaon Sahoo; Rajamani Raghunathan; Diptiman Sen
2009-09-01
We present here a theoretical approach to compute the molecular magnetic anisotropy parameters, and for single molecule magnets in any given spin eigenstate of exchange spin Hamiltonian. We first describe a hybrid constant -valence bond (VB) technique of solving spin Hamiltonians employing full spatial and spin symmetry adaptation and we illustrate this technique by solving the exchange Hamiltonian of the Cu6Fe8 system. Treating the anisotropy Hamiltonian as perturbation, we compute the and values for various eigenstates of the exchange Hamiltonian. Since, the dipolar contribution to the magnetic anisotropy is negligibly small, we calculate the molecular anisotropy from the single-ion anisotropies of the metal centers. We have studied the variation of and by rotating the single-ion anisotropies in the case of Mn12Ac and Fe8 SMMs in ground and few low-lying excited states of the exchange Hamiltonian. In both the systems, we find that the molecular anisotropy changes drastically when the single-ion anisotropies are rotated. While in Mn12Ac SMM values depend strongly on the spin of the eigenstate, it is almost independent of the spin of the eigenstate in Fe8 SMM. We also find that the value is almost insensitive to the orientation of the anisotropy of the core Mn(IV) ions. The dependence of on the energy gap between the ground and the excited states in both the systems has also been studied by using different sets of exchange constants.
Design verification of large time constant thermal shields for optical reference cavities.
Zhang, J; Wu, W; Shi, X H; Zeng, X Y; Deng, K; Lu, Z H
2016-02-01
In order to achieve high frequency stability in ultra-stable lasers, the Fabry-Pérot reference cavities shall be put inside vacuum chambers with large thermal time constants to reduce the sensitivity to external temperature fluctuations. Currently, the determination of thermal time constants of vacuum chambers is based either on theoretical calculation or time-consuming experiments. The first method can only apply to simple system, while the second method will take a lot of time to try out different designs. To overcome these limitations, we present thermal time constant simulation using finite element analysis (FEA) based on complete vacuum chamber models and verify the results with measured time constants. We measure the thermal time constants using ultrastable laser systems and a frequency comb. The thermal expansion coefficients of optical reference cavities are precisely measured to reduce the measurement error of time constants. The simulation results and the experimental results agree very well. With this knowledge, we simulate several simplified design models using FEA to obtain larger vacuum thermal time constants at room temperature, taking into account vacuum pressure, shielding layers, and support structure. We adopt the Taguchi method for shielding layer optimization and demonstrate that layer material and layer number dominate the contributions to the thermal time constant, compared with layer thickness and layer spacing. PMID:26931831
Running cosmological constant with observational tests
Geng, Chao-Qiang; Zhang, Kaituo
2016-01-01
We investigate the running cosmological constant model with dark energy linearly proportional to the Hubble parameter, $\\Lambda = \\sigma H + \\Lambda_0$, in which the $\\Lambda$CDM limit is recovered by taking $\\sigma=0$. We derive the linear perturbation equations of gravity under the Friedmann-Lema\\"itre-Robertson-Walker cosmology, and show the power spectra of the CMB temperature and matter density distribution. By using the Markov chain Monte Carlo method, we fit the model to the current observational data and find that $\\sigma H_0/ \\Lambda_0 \\lesssim 2.63 \\times 10^{-2}$ and $6.74 \\times 10^{-2}$ for $\\Lambda(t)$ coupled to matter and radiation-matter, respectively, along with constraints on other cosmological parameters.
Running cosmological constant with observational tests
Directory of Open Access Journals (Sweden)
Chao-Qiang Geng
2016-09-01
Full Text Available We investigate the running cosmological constant model with dark energy linearly proportional to the Hubble parameter, Λ=σH+Λ0, in which the ΛCDM limit is recovered by taking σ=0. We derive the linear perturbation equations of gravity under the Friedmann–Lemaïtre–Robertson–Walker cosmology, and show the power spectra of the CMB temperature and matter density distribution. By using the Markov chain Monte Carlo method, we fit the model to the current observational data and find that σH0/Λ0≲2.63×10−2 and 6.74×10−2 for Λ(t coupled to matter and radiation-matter, respectively, along with constraints on other cosmological parameters.
Fine structure constant variation or spacetime anisotropy?
International Nuclear Information System (INIS)
Recent observations on the quasar absorption spectra supply evidence for the variation of the fine structure constant α. In this paper, we propose another interpretation of the observational data on the quasar absorption spectra: a scenario with spacetime inhomogeneity and anisotropy. Maybe the spacetime is characterized by the Finsler geometry instead of the Riemann one. The Finsler geometry admits fewer symmetries than the Riemann geometry does. We investigate the Finslerian geodesic equations in the Randers spacetime (a special Finsler spacetime). It is found that the cosmological redshift in this spacetime deviates from the one in general relativity. The modification term to the redshift could be generally revealed as a monopole plus dipole function of spacetime locations and directions. We suggest that this modification corresponds to the spatial monopole and dipole of α variation in the quasar absorption spectra. (orig.)
Explosive helium burning at constant pressures
Hashimoto, M.-A.; Hanawa, T.; Sugimoto, D.
The results of numerical calculations of nucleosynthesis under adiabatic conditions, i.e., when the only heat exchange with the external regions takes place through neutrinos, are reported. Attention is focused on explosive burning associated with shell flashes, assuming that nuclear energy is deposited in a mass element, followed by expansion and density decrease. Consideration is given to three cases, the shell flash near the surface of a degenerate star, to nuclear burning concentrated in a small region of a star, and to the heat energy being deposited in intermediate layers. A reaction network of 181 nuclear species was constructed and the thermodynamic evolution was calculated assuming constant pressure and adiabatic conditions. The final products of the reactions of H-1 to Cu-62 were projected to by O-16, Mg-24, Si-28, S-32, Ca-40, Ti-44, Cr-48, and Fe-52.
Cybersusy Solves the Cosmological Constant Problem
Dixon, John
2010-01-01
Cybersusy is a new mechanism for SUSY breaking. When the auxiliary fields are integrated in any theory like the SSM, certain special new composite superfields arise. Spontaneous breaking of internal symmetry, like SU(2) X U(1) to U(1), gives rise to a new realization of SUSY for these new superfields. This realization mixes elementary and composite states. In the resulting effective action, if the new superfield has mass, then there are SUSY anomalies. Since there are no massless supermultiplets, the SUSY anomalies must be present. They generate a spectrum for SUSY breaking that is consistent with the known particles. Supergravity does not couple to the anomalies because it does not couple to composite states. So unitarity is not violated. There is no cosmological constant generated, because SUSY is not spontaneously broken.
Tunelling with a negative cosmological constant
Gibbons, G W
1996-01-01
The point of this paper is see what light new results in hyperbolic geometry may throw on gravitational entropy and whether gravitational entropy is relevant for the quantum origin of the univeres. We introduce some new gravitational instantons which mediate the birth from nothing of closed universes containing wormholes and suggest that they may contribute to the density matrix of the universe. We also discuss the connection between their gravitational action and the topological and volumetric entropies introduced in hyperbolic geometry. These coincide for hyperbolic 4-manifolds, and increase with increasing topological complexity of the four manifold. We raise the questions of whether the action also increases with the topological complexity of the initial 3-geometry, measured either by its three volume or its Matveev complexity. We point out, in distinction to the non-supergravity case, that universes with domains of negative cosmological constant separated by supergravity domain walls cannot be born from ...
Running cosmological constant with observational tests
Geng, Chao-Qiang; Lee, Chung-Chi; Zhang, Kaituo
2016-09-01
We investigate the running cosmological constant model with dark energy linearly proportional to the Hubble parameter, Λ = σH +Λ0, in which the ΛCDM limit is recovered by taking σ = 0. We derive the linear perturbation equations of gravity under the Friedmann-Lemaïtre-Robertson-Walker cosmology, and show the power spectra of the CMB temperature and matter density distribution. By using the Markov chain Monte Carlo method, we fit the model to the current observational data and find that σH0 /Λ0 ≲ 2.63 ×10-2 and 6.74 ×10-2 for Λ (t) coupled to matter and radiation-matter, respectively, along with constraints on other cosmological parameters.
More on Lensing by a Cosmological Constant
Ishak, Mustapha; Dossett, Jason
2008-01-01
The question of whether or not the cosmological constant affects the bending of light around a concentrated mass has been the subject of some recent papers. We present here a simple, specific and transparent example where $\\Lambda$ bending clearly takes place, and where it is clearly neither a coordinate effect nor an aberration effect, as has been claimed in some of these papers. We then show that in some recent works using perturbation theory the $\\Lambda$ contribution was missed because of initial too-stringent smallness assumptions. Namely: Our method has been to insert a Kottler (Schwarzschild with $\\Lambda$) vacuole into a Friedman universe, and to calculate the total bending within the vacuole. We assume that no more bending occurs outside. It is important to observe that while the mass contribution to the bending takes place mainly quite near the lens, the $\\Lambda$ bending continues throughout the vacuole. Thus if one deliberately restricts one's search for $\\Lambda$ bending to the immediate neighbor...
Rotenberg, E.; Davis, D. W.; Amelin, Y.
2009-05-01
Despite dozens of measurements of the decay constant of 87Rb (λ87), uncertainty surrounding the value remains. Mounting evidence [e.g. 1,2,3] suggests that the actual value is 1-2% lower than the conventional value of 1.42 × 10-11a-1 [4]. Increased precision and accuracy are crucial if meaningful comparisons are to be made between Rb-Sr and U-Pb ages. We have been working on measuring the decay constant by the accumulation of radiogenic 87Sr (87Sr*) in a RbClO4 salt. Our original measurements by this method had large errors [5,6] and tended to agree with the conventional value. Because the samples contained very little common Sr, it was impossible to properly correct for instrumental fractionation, with the result that both precision and accuracy were compromised. Furthermore, the concentration of the 84Sr spike was not determined reliably, which likely affected the accuracy. In order to overcome this, a new 84-86Sr double-spike was prepared, and the experiment was repeated. The spike was calibrated against three different Sr reference solutions. Two were prepared from Sr metal and the third from SrCl2. The isotopic abundance ratios of the 84-86Sr double-spike are: 84/86 = 0.93252, 87/86 = 0.01033, and 88/86 = 0.02240. The concentration was determined to be 832.95 ± 0.26 ng Sr/g solution (MSWD = 2.5). Seventeen measurements of the decay-constant were made by measuring 87Sr* ingrowth in a RbClO4 salt over approximately 32 years. 87Sr* ranges from 125 - 616 pg. The two highest points are eliminated: one due to high procedure blank and the second due to abnormal fractionation behaviour. A weighted average of the remaining fifteen measurements yields a decay constant of 1.3981 × 10-11a-11 ± 0.0009 (0.062%; and a high MSWD = 106. The 2σ standard deviation is 0.004). The data scatter outside of their analytical errors. Recent geological calibrations [1,2] and a carefully controlled decay counting measurement [3] yield λ87 values from 1.395 ± 0.006 to 1.398 ± 0
String Phenomenology and the Cosmological Constant
de Alwis, S P
2007-01-01
It is argued that classical string solutions should not be fine tuned to have a positive cosmological constant (CC) at the observed size, since even the quantum corrections from standard model effects will completely negate any classical string theory solution with such a CC. In fact it is even possible that there is no need at all for any ad hoc uplifting term in the potential since these quantum effects may well take care of this. Correspondingly any calculation of the parameters of the MSSM has to be rethought to take into account the evolution of the CC. This considerably complicates the issue since the initial conditions for RG evolution of these parameters are determined by the final condition on the CC! The Anthropic Principle is of no help in addressing these issues.
Black holes and the positive cosmological constant
Bhattacharya, Sourav
2013-01-01
We address some aspects of black hole spacetimes endowed with a positive cosmological constant, i.e. black holes located inside a cosmological event horizon. First we establish a general criterion for existence of cosmological event horizons. Using the geometrical set up built for this, we study classical black hole no hair theorems for both static and stationary axisymmetric spacetimes. We discuss cosmic Nielsen-Olesen strings as hair in Schwarzschild-de Sitter spacetime. We also give a general calculation for particle creation by a Killing horizon using complex path analysis and using this we study particle creation in Schwarzschild-de Sitter spacetime by both black hole and the cosmological event horizons.
Higgs inflation and the cosmological constant
Energy Technology Data Exchange (ETDEWEB)
Jegerlehner, Fred [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)
2014-02-15
The Higgs not only induces the masses of all SM particles, the Higgs, given its special mass value, is the natural candidate for the inflaton and in fact is ruling the evolution of the early universe, by providing the necessary dark energy which remains the dominant energy density. SM running couplings not only allow us to extrapolate SM physics up to the Planck scale, but equally important they are triggering the Higgs mechanism. This is possible by the fact that the bare mass term in the Higgs potential changes sign at about μ{sub 0}≅1.40 x 10{sup 16} GeV and in the symmetric phase is enhanced by quadratic terms in the Planck mass. Such a huge Higgs mass term is able to play a key role in triggering inflation in the early universe. In this article we extend our previous investigation by working out the details of a Higgs inflation scenario. We show how different terms contributing to the Higgs Lagrangian are affecting inflation. Given the SM and its extrapolation to scales μ>μ{sub 0} we find a calculable cosmological constant V(0) which is weakly scale dependent and actually remains large during inflation. This is different to the Higgs fluctuation field dependent ΔV(φ), which decays exponentially during inflation, and actually would not provide a sufficient amount of inflation. The fluctuation field has a different effective mass which shifts the bare Higgs transition point to a lower value μ'{sub 0} ≅7.7 x 10{sup 14} GeV. The vacuum energy V(0) being proportional to M{sub Pl}{sup 4} has a coefficient which vanishes near the Higgs transition point, such that the bare and the renormalized cosmological constant match at this point. The role of the Higgs in reheating and baryogenesis is emphasized.
Analytical estimation of the gravitational constant with atomic and nuclear physical constants
International Nuclear Information System (INIS)
If NA represents the Avogadro's number, gravitational constant associated with atomic electromagnetic interaction can be expressed as GE ≅ N2AG. With GE and with the assumed two new pseudo numbers x ≈ 38.725 and y ≈ 47.415, value of G can be fixed for 10 digits in a verifiable approach. (x, y) can be called as the back ground analytical numbers using by which micro-macro physical constants can be interlinked qualitatively and quantitatively
Giant Static Dielectric Constant of Strained PbTiO3*
Institute of Scientific and Technical Information of China (English)
WANG Yuan-Xu
2009-01-01
First-principles density functional perturbation calculations are employed to study the dielectric and piezoelectric properties of strained tetragonal PbTi03. Lattice distortion, static dielectric constant, Born effective charge, zone-centre phonons, and piezoelectric constant are obtained. For the strained tetragonal Pb TiO3, we obtain a giant static dielectric constant (3600) under a strain 0.77%. Moreover, the calculated piezoelectric constant e15 of strained PbTiO3 reaches about 203 C/m2 which is about 20 times of that of unstrained system. The giant static dielectric constant is mainly due to the softening of the lowest-frequency phonon mode and the reduce of Ti-O bond length. This work demonstrates a route to a giant static dielectrics for electrically microwave and other devices.
Direct battery-driven solar LED lighting using constant-power control
Huang, Bin-Juine
2012-11-01
A direct battery-driven LED lighting technique using constant-power control is proposed in the present study. A system dynamics model of LED luminaire was derived and used in the design of the feedback constant-power control system. The test result has shown that the power of 18. W and 100. W LED luminaires can be controlled accurately with error at 2-5%. A solar LED street lighting system using constant-power and dimming control was designed and built for field test in a remote area. The long-term performance was satisfactory and no any failure since the installation. Since no high-power capacitor is used in the present constant-power control circuit, a longer lifetime is expected. © 2012 Elsevier Ltd.
Quick and accurate estimation of the elastic constants using the minimum image method
Tretiakov, Konstantin V.; Wojciechowski, Krzysztof W.
2015-04-01
A method for determining the elastic properties using the minimum image method (MIM) is proposed and tested on a model system of particles interacting by the Lennard-Jones (LJ) potential. The elastic constants of the LJ system are determined in the thermodynamic limit, N → ∞, using the Monte Carlo (MC) method in the NVT and NPT ensembles. The simulation results show that when determining the elastic constants, the contribution of long-range interactions cannot be ignored, because that would lead to erroneous results. In addition, the simulations have revealed that the inclusion of further interactions of each particle with all its minimum image neighbors even in case of small systems leads to results which are very close to the values of elastic constants in the thermodynamic limit. This enables one for a quick and accurate estimation of the elastic constants using very small samples.
Black Holes and Quantum Theory: The Fine Structure Constant Connection
Directory of Open Access Journals (Sweden)
Cahill R. T.
2006-10-01
Full Text Available The new dynamical theory of space is further confirmed by showing that the effective “black hole” masses M BH in 19 spherical star systems, from globular clusters to galaxies, with masses M , satisfy the prediction that M BH = α 2 M , where α is the fine structure constant. As well the necessary and unique generalisations of the Schr ̈ odinger and Dirac equations permit the first derivation of gravity from a deeper theory, showing that gravity is a quantum effect of quantum matter interacting with the dynamical space. As well the necessary generalisation of Maxwell’s equations displays the observed light bending effects. Finally it is shown from the generalised Dirac equation where the spacetime mathematical formalism, and the accompanying geodesic prescription for matter trajectories, comes from. The new theory of space is non-local and we see many parallels between this and quantum theory, in addition to the fine structure constant manifesting in both, so supporting the argument that space is a quantum foam system, as implied by the deeper information-theoretic theory known as Process Physics. The spatial dynamics also provides an explanation for the “dark matter” effect and as well the non-locality of the dynamics provides a mechanism for generating the uniformity of the universe, so explaining the cosmological horizon problem.
The Cosmological Constant Problem and Quantum Spacetime Reference Frame
Luo, M J
2015-01-01
This paper is a generalization of earlier papers [ Nucl. Phys. B 884, 344 (2014) (arXiv:1312.2759) and JHEP 6, 63 (2015) (arXiv:1401.2488) ]. Since space and time should be put on an equal footing, we generalize the idea of quantum clock time to a quantum spacetime reference frame via a physical realization of a reference system by quantum rulers and clocks. Omitting the internal degrees of freedoms (e.g. spin) of the physical rulers and clocks, only considering their metric properties, the spacetime reference frame is described by a bosonic non-linear sigma model. We study the quantum behavior of the system under given approximations, and obtain (1) a cosmological constant $(2/\\pi)\\rho_{c}$ ($\\rho_{c}$ the critical density) very close to current observational value; (2) an Einstein-Hilbert term in the quantum effective action; (3) the ratio of variance to mean-squared of spacetime distance tends to a universal constant $(2/\\pi)\\hbar^{2}$ in the infrared region. This effect is testable by observing the linear...
Effects of constant voltage and constant current stress in PCBM:P3HT solar cells
DEFF Research Database (Denmark)
Cester, Andrea; Rizzo, Aldo; Bazzega, A.;
2015-01-01
The aimof this work is the investigation of forward and reverse bias stress effects, cell self-heating and annealing in roll coated organic solar cells with PCBM:P3HT active layer. In reverse bias stress cells show a constant degradation over time. In forward current stress cells alternate degrad...
Symmetry breakdown and coupling constants of leptons
Directory of Open Access Journals (Sweden)
Gil C. Marques
2007-06-01
Full Text Available Based on a new approach to symmetries of the fundamental interactions we deal, in this paper, with the electroweak interactions of leptons. We show that the coupling constants, arising in the way leptons are coupled to intermediate bosons, can be understood as parameters associated to the breakdown of SU(2 and parity symmetries. The breakdown of both symmetries is characterized by a new parameter (the asymetry parameter of the electroweak interactions. This parameter gives a measure of the strength of breakdown of symmetries. We analyse the behaviour of the theory for three values of this parameter. The most relevant value is the one for which only the electromagnetic interactions do not break parity (the maximally allowed left-right asymetric theory. Maximamally allowed parity asymmetry is a requirement that is met for a value of Weinberg's theta-angle that is quite close to the experimental value of this parameter.Com base em uma formulação nova para simetrias das interações fundamentais nós lidamos, neste trabalho, com interações eletrofracas de leptons. Mostramos que as constantes do acoplamento, associadas aos acoplamentos de bósons intermediários, podem ser entendidas como parâmetros associados à quebra de simetrias SU(2 e paridade. A quebra de ambas as simetrias é caracterizada por um parâmetro novo (o parâmetro de assimetria das interações eletrofracas. Este parâmetro dá uma medida da intensidade com que a simetria é quebrada. Analisamos o comportamento da teoria para três valores deste parâmetro. O valor mais relevante é aquele para o qual apenas as interações eletromagnéticas não quebram a paridade (a teoria assimétrica esquerda-direita permitida da maneira máxima. A assimetria máxima permitida é uma exigência que leva a um ângulo de Weinberg cujo valor é próximo daquele observado experimentalmente.
Pure odd-order oscillators with constant excitation
Cveticanin, L.
2011-02-01
In this paper the excited vibrations of a truly nonlinear oscillator are analyzed. The excitation is assumed to be constant and the nonlinearity is pure (without a linear term). The mathematical model is a second-order nonhomogeneous differential equation with strong nonlinear term. Using the first integral, the exact value of period of vibration i.e., angular frequency of oscillator described with a pure nonlinear differential equation with constant excitation is analytically obtained. The closed form solution has the form of gamma function. The period of vibration depends on the value of excitation and of the order and coefficient of the nonlinear term. For the case of pure odd-order-oscillators the approximate solution of differential equation is obtained in the form of trigonometric function. The solution is based on the exact value of period of vibration. For the case when additional small perturbation of the pure oscillator acts, the so called 'Cveticanin's averaging method' for a truly nonlinear oscillator is applied. Two special cases are considered: one, when the additional term is a function of distance, and the second, when damping acts. To prove the correctness of the method the obtained results are compared with those for the linear oscillator. Example of pure cubic oscillator with constant excitation and linear damping is widely discussed. Comparing the analytically obtained results with exact numerical ones it is concluded that they are in a good agreement. The investigations reported in the paper are of special interest for those who are dealing with the problem of vibration reduction in the oscillator with constant excitation and pure nonlinear restoring force the examples of which can be found in various scientific and engineering systems. For example, such mechanical systems are seats in vehicles, supports for machines, cutting machines with periodical motion of the cutting tools, presses, etc. The examples can be find in electronics
Long-range carbon-proton spin-spin coupling constants in conformational analysis
International Nuclear Information System (INIS)
The author has collected a reliable set of data on long range 13C-1H coupling constants in aliphatic compounds and developed the use of long range 13C-1H coupling constants as a tool in the conformational analysis of aliphatic compounds. An empirical determination of the torsion angle dependence of the vicinal 13C-1H coupling constant for model compounds is described and the dependence of long range 13C-1H coupling constants on the electronegativity of substituents attached to the coupling pathway reported for the monohalogen substituted ethanes and propanes. The electronegativity dependence of the vicinal 13C-1H coupling was studied in monosubstituted propanes whose substituents are elements from the first row of the periodic table and it is shown that the vicinal 13C-1H coupling constant in aliphatic systems is a constitutive property. The geminal 13C-1H coupling constants in ethyl, isopropyl and tert-butyl compounds, which have been substituted by an element of the first row of the periodic table or a haline atom, are reported and the influence of electronegative substituents on the vicinal 13C-1H coupling constants in the individual rotamers of 13CH3-C(X)H-C(Y)H-1H fragments discussed. The application of long range 13C-1H coupling constants to the conformational analysis of CMP-N-Acetylneuraminic acid and 2,6-dichloro-1,4-oxathiane is described. (Auth.)
Institute of Scientific and Technical Information of China (English)
高鹏; 丁敬雷; 徐超
2011-01-01
由于直流送端交流系统"孤岛"、不联网方式运行,送端交流系统强度一般都比较弱.送端交流系统故障会导致交流系统电压和直流电压的降低.在直流送端"孤岛"运行、直流定功率控制方式下,基于实时闭环仿真系统模型,对直流电压测量时间常数对系统运行稳定性的影响进行理论分析和仿真验证.较小的直流电压测量时间常数使直流控制系统响应较快,电压降低后,直流控制系统迅速增加电流定值以维持直流输送功率的恒定,有可能导致送端交流系统凶无功不平衡而电压严重降低,甚至是电压失稳;较大的直流电压测量时间常数使直流控制系统响应较慢,在系统电压恢复后,直流电流定值有可能继续增加,从而使直流功率不断增加,有可能导致送端有功不平衡,交流系统频率严重降低,甚至失稳.还针对系统分析和实际工程给出了启示性的建议.%The sending system is islanded and not connected to the main power grid,so its stability intensity is commonly weak.The faults occurred in the sending system decrease the voltages of AC and DC systems in the sending terminal.The theoretical studies and simulation validation of the impact of the DC voltage measurement time constant on the operation of the islanded sending system of DC transmission which is in the power control mode,are given,Smaller DC voltage measurement time constant means quicker response of the DC controller When the voltage decreases,the DC control system will increase the current setting quickly in order to maintain the DC power.The imbalance of the reactive power may occur in the islanded sending AC system,and the voltage will decrease seriously or even lose stability.Large DC voltage measurement time constant means slower and laggard response of the DC controller.The DC current order may continue increase even after the voltage resumed,thus the DC power will also increase continuously
Tunnelling with a negative cosmological constant
Gibbons, G. W.
1996-02-01
The point of this paper is to see what light new results in hyperbolic geometry may throw on gravitational entropy and whether gravitational entropy is relevant for the quantum origin of the universe. We introduce some new gravitational instantons which mediate the birth from nothing of closed universes containing wormholes and suggest that they may contribute to the density matrix of the universe. We also discuss the connection between their gravitational action and the topological and volumetric entropies introduced in hyperbolic geometry. These coincide for hyperbolic 4-manifolds, and increase with increasing topological complexity of the 4-manifold. We raise the question of whether the action also increases with the topological complexity of the initial 3-geometry, measured either by its 3-volume or its Matveev complexity. We point out, in distinction to the non-supergravity case, that universes with domains of negative cosmological constant separated by supergravity domain walls cannot be born from nothing. Finally we point out that our wormholes provide examples of the type of Perpetual Motion machines envisaged by Frolov and Novikov.
Expanding Taylor bubble under constant heat flux
Voirand, Antoine; Benselama, Adel M.; Ayel, Vincent; Bertin, Yves
2016-09-01
Modelization of non-isothermal bubbles expanding in a capillary, as a contribution to the understanding of the physical phenomena taking place in Pulsating Heat Pipes (PHPs), is the scope of this paper. The liquid film problem is simplified and solved, while the thermal problem takes into account a constant heat flux density applied at the capillary tube wall, exchanging with the liquid film surrounding the bubble and also with the capillary tube outside medium. The liquid slug dynamics is solved using the Lucas-Washburn equation. Mass and energy balance on the vapor phase allow governing equations of bubble expansion to be written. The liquid and vapor phases are coupled only through the saturation temperature associated with the vapor pressure, assumed to be uniform throughout the bubble. Results show an over-heating of the vapor phase, although the particular thermal boundary condition used here always ensures an evaporative mass flux at the liquid-vapor interface. Global heat exchange is also investigated, showing a strong decreasing of the PHP performance to convey heat by phase change means for large meniscus velocities.
The Constant Comparative Method of Qualitative Analysis
Directory of Open Access Journals (Sweden)
Barney G. Glaser, Ph.D.
2008-11-01
Full Text Available Currently, the general approaches to the analysis of qualitative data are these:1. If the analyst wishes to convert qualitative data into crudely quantifiable form so that he can provisionally test a hypothesis, he codes the data first and then analyzes it. He makes an effort to code “all relevant data [that] can be brought to bear on a point,” and then systematically assembles, assesses and analyzes these data in a fashion that will “constitute proof for a given proposition.”i2. If the analyst wishes only to generate theoretical ideasnew categories and their properties, hypotheses and interrelated hypotheses- he cannot be confined to the practice of coding first and then analyzing the data since, in generating theory, he is constantly redesigning and reintegrating his theoretical notions as he reviews his material.ii Analysis with his purpose, but the explicit coding itself often seems an unnecessary, burdensome task. As a result, the analyst merely inspects his data for new properties of his theoretical categories, and writes memos on these properties.We wish to suggest a third approach
Holographic Dark Energy with Cosmological Constant
Hu, Yazhou; Li, Nan; Zhang, Zhenhui
2015-01-01
Inspired by the multiverse scenario, we study a heterotic dark energy model in which there are two parts, the first being the cosmological constant and the second being the holographic dark energy, thus this model is named the $\\Lambda$HDE model. By studying the $\\Lambda$HDE model theoretically, we find that the parameters $c$ and $\\Omega_{hde}$ are divided into a few domains in which the fate of the universe is quite different. We investigate dynamical behaviors of this model, and especially the future evolution of the universe. We perform fitting analysis on the cosmological parameters in the $\\Lambda$HDE model by using the recent observational data. We find the model yields $\\chi^2_{\\rm min}=426.27$ when constrained by Planck+SNLS3+BAO+HST, comparable to the results of the HDE model (428.20) and the concordant $\\Lambda$CDM model (431.35). At 68.3\\% CL, we obtain $-0.07<\\Omega_{\\Lambda0}<0.68$ and correspondingly $0.04<\\Omega_{hde0}<0.79$, implying at present there is considerable degeneracy bet...
Elastic stiffness constants of lead chlorophosphate glasses
International Nuclear Information System (INIS)
This paper describes the preparation of a series of binary (PbO)x(P2O5)1-x lead phosphate and ternary (PbCl2)y (PbO.2P2O5)1-5 lead chlorophosphate glasses by the melt quenching technique. Their physical as well as elastic properties have been determined at room temperature by using the ultrasonic pulse echo overlap method. The density of both series of glasses increases linearly with the mole fraction of PbO and PbCl2 respectively. The experimental results show that the elastic constants C11 and C44 of the binary lead phosphate glasses decrease linearly with the mole fraction of PbO; the addition of PbO weakens the structure of phosphate glasses due to an increase of non-bridging oxygen. An introduction of PbCl2 into the lead phosphate glassy matrix also causes the decrease of elastic modulli C11, C44 and bulk modulus; the chloride ions breaking up the bridging oxygen into non-bridging oxygen. The Debye temperatures of both series of glasses have been calculated by using the room temperature ultrasonic velocities data
Further Evidence for Cosmological Evolution of the Fine Structure Constant
Energy Technology Data Exchange (ETDEWEB)
Webb, J. K.; Murphy, M. T.; Flambaum, V. V.; Dzuba, V. A.; Barrow, J. D.; Churchill, C. W.; Prochaska, J. X.; Wolfe, A. M.
2001-08-27
We describe the results of a search for time variability of the fine structure constant {alpha} using absorption systems in the spectra of distant quasars. Three large optical data sets and two 21 cm and mm absorption systems provide four independent samples, spanning {approx}23% to 87% of the age of the universe. Each sample yields a smaller {alpha} in the past and the optical sample shows a 4{sigma} deviation: {Delta}{alpha}/{alpha}=-0.72{+-}0.18 x 10{sup -5} over the redshift range 0.5
Analysis constants for database of neutron nuclear data
Bedenko, S. V.; Jeremiah, J. Joseph; Knyshev, V. V.; Shamanin, I. V.
2016-07-01
At present there is a variety of experimental and calculation nuclear data which are rather entirely presented in the following evaluated nuclear data libraries: ENDF (USA), JEFF (Europe), JENDL (Japan), TENDL (Russian Federation), ROSFOND (Russian Federation). Libraries of nuclear data, used for neutron-physics calculations in programs: Scale (Origen-Arp), MCNP, WIMS, MCU, and others. Nevertheless all existing nuclear data bases, including evaluated ones, contain practically no information about threshold neutron reactions on 232Th nuclei; available values of outputs and cross-sections significantly differ by orders. The work shows necessity of nuclear constants corrections which are used in the calculations of grids and thorium storage systems. The results of numerical experiments lattices and storage systems with thorium.
Further Evidence for Cosmological Evolution of the Fine Structure Constant
Webb, J K; Flambaum, V V; Dzuba, V A; Barrow, John D; Churchill, C W; Prochaska, J X; Wolfe, A M
2001-01-01
We summarise the results of a search for time variability of the fine structure constant, alpha, using absorption systems in the spectra of distant quasars. Three large optical datasets and two 21cm/mm absorption systems provide four independent samples, spanning approximately 23% to 87% of the age of the universe. Each sample yields a negative Delta(alpha)/alpha (smaller alpha in the past) and the whole optical sample shows a 4-sigma deviation: Delta(alpha)/alpha = -0.72 +/- 0.18 x 10^{-5} over the redshift range 0.5 < z < 3.5. A comprehensive search for systematic effects reveals none which can explain our results. The only potentially significant systematic effects push Delta(alpha)/alpha towards positive values, i.e. our results would become more significant were we to correct for them.
Tunneling for Dirac Fermions in Constant Magnetic Field
Choubabi, El Bouazzaoui; Jellal, Ahmed
2009-01-01
The tunneling effect of two-dimensional Dirac fermions in a constant magnetic field is studied. This can be done by using the continuity equation at some points to determine the corresponding reflexion and transmission coefficients. For this, we consider a system made of graphene as superposition of two different regions where the second is characterized by an energy gap t'. In fact, we treat concrete systems to practically give two illustrations: barrier and diode. For each case, we discuss the transmission in terms of the ratio of the energy conservation and t'. Moreover, we analyze the resonant tunneling by introducing a scalar Lorentz potential where it is shown that a total transmission is possible.
Initial conditions of inhomogeneous universe and the cosmological constant problem
Totani, Tomonori
2016-06-01
Deriving the Einstein field equations (EFE) with matter fluid from the action principle is not straightforward, because mass conservation must be added as an additional constraint to make rest-frame mass density variable in reaction to metric variation. This can be avoided by introducing a constraint 0δ(√‑g) = to metric variations δ gμν, and then the cosmological constant Λ emerges as an integration constant. This is a removal of one of the four constraints on initial conditions forced by EFE at the birth of the universe, and it may imply that EFE are unnecessarily restrictive about initial conditions. I then adopt a principle that the theory of gravity should be able to solve time evolution starting from arbitrary inhomogeneous initial conditions about spacetime and matter. The equations of gravitational fields satisfying this principle are obtained, by setting four auxiliary constraints on δ gμν to extract six degrees of freedom for gravity. The cost of achieving this is a loss of general covariance, but these equations constitute a consistent theory if they hold in the special coordinate systems that can be uniquely specified with respect to the initial space-like hypersurface when the universe was born. This theory predicts that gravity is described by EFE with non-zero Λ in a homogeneous patch of the universe created by inflation, but Λ changes continuously across different patches. Then both the smallness and coincidence problems of the cosmological constant are solved by the anthropic argument. This is just a result of inhomogeneous initial conditions, not requiring any change of the fundamental physical laws in different patches.
Development of constant-power driving control for light-emitting-diode (LED) luminaire
Huang, Bin-Juine
2013-01-01
The illumination of an LED may be affected by operating temperature even under constant-current condition. A constant-power driving technique is proposed in the present study for LED luminaire. A linear system dynamics model of LED luminaire is first derived and used in the design of the feedback control system. The PI controller was designed and tuned taking into account the control accuracy and robust properties with respect to plant uncertainty and variation of operating conditions. The control system was implemented on a microprocessor and used to control a 150W LED luminaire. The test result shows that the feedback system accurately controls the input power of LED luminaire to within 1.3 per cent error. As the ambient temperature changes from 0 to 40 °C, the LED illumination varies slightly (-1.7%) for constant-power driving, as compared to that of constant-current driving (-12%) and constant-voltage driving (+50%). The constant-power driving has revealed advantage in stabilizing the illumination of LED under large temperature variation. © 2012 Elsevier Ltd. All rights reserved.