Flux Density Characteristics Research Articles

Illuminance Distribution and Photosynthetic Photon Flux Density Characteristics of LED Lighting with Periodic Lattice Arrangements

LED lighting systems that combine lighting capability, emotional and physiological characteristics are required for lighting source and multifunctional applications. In this work, Simulation studies using optical analysis software packages, Light Tools, are presented. This is done to estimate the uniformity ratio of illuminance and photosynthetic photon flux density (PPFD) of the periodic 2D lattice arrangements, such as square, diamond, two-way bias quadrangular, hexagonal, and Kagome lattices, under the same transmissivity, absorptance and reflectivity. It has been found out that the two-dimensional Kagome lattice arrangement exhibited high uniformity ratio of illuminance and PPFD compared to other lattices. Accordingly, these results can be used to guide a design and improve the lighting environment which in turn would maximize the uniform distributions of illuminance.

2-D Magnetic Field Analysis of Air Cylinder with MR Sensor

As a type of solid state switch, MR (magnetoresistive) sensor detects the air cylinder piston’s position in pneumatic control system. The construction and working principle of the air cylinder with MR sensor are introduced. Using 2-D magnetic field finite element analysis (FEA) method, the magnetic field distribution of air cylinder with piston motion is analyzed. Simulation results are given. The magnetic flux density characteristics are compared between piston wear or not.

Wall material and roughness effects on transmittable shear stresses of magnetorheological fluids in plate–plate magnetorheometry

A direct comparison of plate–plate magnetorheometry results for nonmagnetic (titanium/brass) and ferromagnetic plates is presented, using a modified Anton Paar magnetocell MRD180/1T. Necessary corrections to derive the true flux density in the magnetorheological fluid (MRF) from the online Hall probe reading and to account for the gap opening effect caused by normal forces on shear stress and flux density are addressed. The measured shear stress versus magnetic flux density characteristics agree in the low flux density regime <0.1 T but yield distinctly higher transmittable shear stresses for ferromagnetic plates at elevated flux densities (49% increase at 1 T for 90% by weight carbonyl iron powder (CIP) and 84% for 85% by weight CIP). Remarkably, the normal force, if corrected for its magnetostatic part, remains independent of the type of plates up to about 0.6 T. We address the role of normal forces, of magnetic interactions between CIP and wall, as well as the role of wall roughness in a solid body friction model. A systematic variation of wall properties and materials was achieved by introducing both a modular rotor and stator, which ease the variation of the walls in contact to the MRF. The transmittable shear stress of nonmagnetic plates (e.g., brass) may be increased up to the level of ferromagnetic disks by a higher wall roughness or by grooves. No shear stress increase is obtained for grooves in ferromagnetic plates, which is explained by the different local flux density modulation at the grooves for ferromagnetic compared to nonmagnetic plates. Finally, we address the effect of ferromagnetic and nonmagnetic coatings on brass and steel disks, and show that, e.g., a layer of CIP on brass efficiently increases the transmittable shear stress.

Permanent Magnet Remagnetizing Physics of a Variable Flux Memory Motor

The finite-element method incorporating with a hysteresis model has been used to analyze the variation characteristics of flux density of permanent magnets (PM) in the variable flux memory motor (VFMM). It accounts for the local hysteresis curves of PMs under different remagnetizing magnetomotive forces. Excellent agreement between the FEA predicted and measured phase back EMFs and air gap flux per pole has been achieved. It shows that the analysis method is suitable for evaluating the PM remagnetizing state in VFMM machines, and the remagnetization of PM is more difficult than the demagnetization, several times the full demagnetizing MMF is required in order to achieve the full remagnetization of PM.

Permanent Magnet Demagnetization Physics of a Variable Flux Memory Motor

The variation characteristics of flux density and field intensity of trapezoidal permanent magnets (PM) in the variable-flux memory motor (VFMM) under different demagnetizing magnetomotive forces are analyzed using the finite element method. A prototype machine is fabricated and tested. Good agreement between the calculated and experimental results is achieved. It confirms the easy controllability of air gap flux of the developed VFMM with trapezoidal PMs.

Analysis of 3D electromagnetic field for three-phase low voltage and heavy current busbar bridge system

In this paper, the three-dimensional finite element model of a low voltage and heavy current three-phase busbar bridge system is established. The edge element is used to discretize the finite element equations of the electromagnetic field. The main characteristics of magnetic flux density and electromagnetic force in the system are obtained. Through the comparison between calculation results and measured ones, the reliability of the calculation is validated. The influence of the operating current, different arrangements of three-phase busbars, space between each phase busbar and frequency on electro-magnetic parameters, especially magnetic flux density and electromagnetic force, are also studied. The low voltage and heavy current busbar bridge is a new type of transmission facility, which is widely applied to transmitting current and power in power plants, large and medium-sized enterprises as well as transformer substations. The electric performance and reliability of busbar bridge systems have gained a good market and brought considerable economic benefits. However, the working noise of such facilities is remarkable, especially when the power consumption increases. On-the-spot investigations show that the working noise is mainly composed of electromagnetic noise and ventilating noise, which have three possible generating sources: the vibration of busbars and steel boxes caused by the alternating electromagnetic force; the aeolian vibration caused by air convection when the temperature inside the bridge rises; the vibration of the magnetic components of the busbar bridge system caused by the magnetostrictive effect. In order to understand the underlying mechanism, energy sources and propagation paths of the working noise, an analysis of the electromagnetic field for busbar bridge systems is required, so that the magnetic field distribution and the electromagnetic force on busbars and steel boxes can be obtained. The analysis is the basis of studying the working noise and it also plays an important role in optimizing the structure of busbar bridge systems.

Vascular Epiphyte Communities in the Inner‐Crown of Hyeronima alchorneoides and Lecythis ampla at La Selva Biological Station, Costa Rica

ABSTRACTThe community composition and percent cover of vascular epiphytes were examined in relation to photosynthetic photon flux density (PFD), temperature, vapor pressure, and tree characteristics in the inner‐crown of two emergent tree species, Hyeronima alchorneoides and Lecythis ampla, at La Selva Biological Station, Costa Rica. A total of 53 species were found in a total sampled branch area of 32 m2 in eight trees—four trees per species. Community composition varied both among individuals of the same tree species and between tree species. However, percent cover patterns of vascular epiphytes were significantly different between the two tree species; Hyeronima had a significantly greater percent cover of epiphytes than Lecythis. The higher percent light transmittance as well as lower humidity in Lecythis are likely causes of its lower percent cover of epiphytes.

Fabrication of Sr-Ferrite Plastic-Bonded Magnet Rotor by Injection Molding

A plastic-bonded strontium-ferrite rotor assembly for brushless dc motors is fabricated by injection molding to produce a four-pole arrangement of anisotropic SrO·6Fe2O3 plastic-bonded magnets. The resultant rotor has superior magnetic flux density characteristics to a conventional four-pole plastic-bonded rotor. The degree of anisotropy and hence magnetic flux of the magnets is found to be dependent on the injection time, with faster injection times producing magnets with higher flux densities. The proposed fabrication method and rotor design eliminate the need for a magnetic path and dynamic balancing of the rotor. The resultant motor therefore operates at a significantly lower noise level compared to motors based on conventional rotors.

Feasibility of iron-sheathed MgB2 wires for magnet applications

Although the development of MgB2 wires has been very intensive there is only a little information about their performance in magnet applications. In this study the possibility to use an iron-sheathed MgB2 wire in magnet applications is studied computationally. The calculations are based on the short sample critical current–magnetic flux density characteristics measured for a four-filament MgB2/Fe wire. Maximum obtainable magnetic field, field homogeneity and stored energy are determined as a function of the coil dimensions. Magnetic field in coils is calculated with finite element method. The influence of ferromagnetic sheath material on magnet performance is clarified by examining coils wound of conductors with non-magnetic sheath. For comparison, the study is repeated with coils wound of NbTi wires. The first quantitative analysis about the performance of state-of-the-art MgB2 wires in magnet applications is presented and particulars for MgB2 magnet design are discussed.

Characteristics of a disc permanent magnet linear synchronous machine with back iron

A disc permanent magnet linear synchronous machine (DPMLSM) with back iron is presented in this paper. The proposed machine is to fulfil the requirements of high efficiency and large torque for electric vehicle (EV) applications. The back iron plays an important role in enhancing flux linkage and reducing flux leakage so that the designed machine has characteristics of high flux and power density to reduce the physical volume of EV. The steady-state, dynamic operating characteristics, and three-dimensional (3-D) finite element analyses are obtained to demonstrate the performance of the machine. Experimental results show that the proposed machine has a very low line current distortion with just a six-step inverter and a very wide range of operating speed without gear-ratio devices.

Ultraviolet-B and photosynthetically active radiation environment of inclined leaf surfaces in a maize canopy and implications for modeling

The potential increase in ultraviolet-B (UVB) flux density and potential decrease in productivity of agricultural crops due to stratospheric ozone loss requires knowledge of the characteristics of UVB flux density above and within crops. Measurements of the photosynthetically active (PAR) and UVB radiation on inclined surfaces above and within a maize ( Zea mays L.) canopy were made in 1990. Sunlit surfaces within the canopy had similar UVB and PAR relative flux density levels to that above the canopy. Shaded surfaces within the canopy had very different relative flux density in the UVB and PAR as a result of differences in sky view, diffuse fraction, and orientation. These differences can be expected to result in canopy transmittance estimation errors of the order of 0.1 in the UVB and 0.05 in the PAR when one assumes an invariant diffuse radiation of leaves with differing aspect. The diffuse fraction of global radiant flux density influenced the radiation regimes present in the canopy. Two distinct radiation regimes were found for surfaces throughout the canopy in the relatively low diffuse fraction PAR waveband; a sunlit regime and a deep shade regime. Three distinct radiation regimes were evident for the relatively high diffuse fraction UVB waveband for surfaces at a height with cumulative leaf area index (LAI) of 1; a sunlit regime, a deep shade regime, and a light shade regime. At greater cumulative LAI, this additional light shade regime in the UVB was absent. Therefore, the bi-modal approach of modeling sunlit or shaded radiation regimes is adequate to estimate the photosynthetically active photon flux density throughout the canopy as well as to estimate the UVB radiant flux density when the cumulative canopy LAI was 2. At lower LAI, the UVB radiant flux density should be modeled using either a three-dimensional model or a model partitioning the gap probability into large and small gaps in the canopy. The necessity for two shade sub-models to model the UVB radiation environment apparently depends on the size distribution of gaps in the canopy.

Preparation of Garnet Films for Hybrid Head by RF-Sputtering

Garnet films have the low saturation flux density characteristics required for use in the ring head gap sections of hybrid heads. Conditions for preparation of garnet films by the RF sputter technique were studied. Oxygen density, annealing time, and power supplied were the most important film formation factors, while target material composition was also significant, with a critical level of 5 percent. It was found that annealing from 950°C for 30 min after film growth under 50 W applied power in an argon atmosphere including 2 percent oxygen produced the best garnet film with characteristics close to those of bulk material.

General Catalogue of Discrete Radio Sources

view Abstract Citations (39) References (138) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS General Catalogue of Discrete Radio Sources Howard, William E., III ; Maran, Stephen P. Abstract A catalogue of 1292 discrete radio sources observed at two or more frequencies or by two or more observers is presented, giving for each source available data on frequency, flux density, position, polarization, brightness distribution, and optical characteristics. Publication: The Astrophysical Journal Supplement Series Pub Date: March 1965 DOI: 10.1086/190105 Bibcode: 1965ApJS...10....1H full text sources ADS |