Calculation of the Power Density in the Fredholm Equation That Yields a Weibull PDF (Power Level Density Function)

1988 ◽  
Author(s):  
M. W. Kim
Keyword(s):  
Density Function ◽  
Power Density ◽  
Level Density ◽  
Power Level ◽  
Fredholm Equation ◽  
Weibull Pdf

Spectral analysis of palaeomagnetic time series and the geomagnetic spectrum

1982 ◽  
Vol 306 (1492) ◽  
pp. 203-209 ◽  
Keyword(s):  
Time Series ◽  
Spectral Analysis ◽  
Spectral Density ◽  
Density Function ◽  
Power Density ◽  
Spectral Density Function ◽  
Power Spectral Density Function ◽  
Power Spectral ◽  
Polarity Reversals ◽  
The Continuum

There are now sufficient archaeomagnetic data from rapidly deposited sediments and baked clays to start bridging the gap in the geomagnetic spectrum between the frequency ranges covered by observatory records and polarity reversals. The form of the continuum spectrum of internal origin can be only loosely constrained but is broadly consistent with earlier speculations. The power spectral density function appears to increase rapidly with period up to periods of about 60 years, then more slowly up to a plateau in the region of 10 4 to 10 5 years, and thereafter starts to fall. There is somewhat inconclusive evidence for a drop in power density at periods around 10 2 years. Prospects for refining the spectrum are excellent.

Superlattice Thin-film Thermoelectric Materials and Devices

2003 ◽  
Vol 793 ◽  
Author(s):  
Rama Venkatasubramanian ◽  
Brooks O'Quinn ◽  
Edward Siivola ◽  
Kip Coonley ◽  
Pratima Addepally ◽  
...  
Keyword(s):  
Thin Film ◽  
Power Density ◽  
Power Efficiency ◽  
Power Level ◽  
Active Device ◽  
Structured Materials ◽  
Conversion Unit ◽  
Small Footprint ◽  
Near Term ◽  
P Type

ABSTRACTThin-film nano-structured materials offer the potential to enhance the performance of thermoelectrics, with near-term capabilities like small-footprint coolers for lasers and microprocessors. Our recent focus has been to transition the enhanced figure-of-merit (ZT) in p-type Bi2Te3/Sb2Te3 and n-type Bi2Te3/Bi2Te3-xSex superlattices to performance at the module level with several device demonstrations. We have been able to obtain a best ZT of ∼2 in a p-n couple, the fundamental cooling or power conversion unit in an operational module. In addition, we have been able to demonstrate p-n couple ZT of as much as 1.6 from heat-to-power efficiency data. The thermal interface resistances between the active device and the external heat source have been optimized. A power level of 38 mW per couple for a ΔT of about 107K, with 4-micron-thick element, was obtained. This translates to an active power density of ∼54 W/cm2 and a mini-module power density of ∼10.5 W/cm2. In short, power devices with thin-film superlattices are a real possibility. In the cooling arena, we have been able to obtain over 50K active cooling with thin-film modules, useable in several laser and microprocessor cooling needs. This is in spite of severe thermal management issues that had to be overcome noting that the “true” hot-side temperature, and hence the “true” ΔT, across the device are much higher. Even so, we have p-n superlattice couples that show twice the cooling ΔTmax, compared to the best bulk p-n couples at cryogenic temperatures. Some of the challenges that remain to be addressed in the full development of this materials technology and thoughts on further progress in nano-structured materials are presented.

scholarly journals Application of surface frequency functions to assess the state of the kinematic pair elements

2018 ◽  
Vol 182 ◽  
pp. 02019
Author(s):  
Maciej Matuszewski ◽  
Małgorzata Słomion ◽  
Janusz Musiał ◽  
Andres Bustilo
Keyword(s):  
Surface Layer ◽  
Density Function ◽  
Power Density ◽  
Spectral Power ◽  
Spectral Power Density ◽  
The State ◽  
Surface Structures ◽  
Kinematic Pair ◽  
Tribological Tests ◽  
Frequency Functions

In this paper the possibility of using frequency functions of the kinematic pair surface layer elements was analyzed for evaluation of the surface layer condition. The function of spectral power density and autocorrelation which were accepted for analysis was characterized. Evaluation of the elements condition was made on the quantify way as changes in degree of isotropy and in the qualitative way based on the graphs of the analyzed frequency functions. After tribological tests the surface structures were adopted to assess the changes. Spectral graphs for structures without cooperation (directly after-machining) and for the different friction distance, were analyzed. Conditions during tribological tests were taken as permanent. The determined degree of isotropy basis on the frequency functions and received graphs of spectra power density function and autocorrelation become useful in evaluation of the surface layer changes during its transformation.

The Effects of the Total Number of Regions and Average Power Density on the Overall Performance of Modified CANDLE Burn-Up Scheme Based Gas Cooled Fast Reactors

2014 ◽  
Vol 983 ◽  
pp. 284-287
Author(s):  
Indah Rosidah ◽  
Maryam Afifah ◽  
Zaki Suud ◽  
Hiroshi Sekimoto ◽  
A. Ferhat
Keyword(s):  
Power Density ◽  
Cycle Length ◽  
Power Level ◽  
Average Power ◽  
General Remark ◽  
Significant Drop ◽  
Mixed Effect ◽  
Original Case ◽  
Overall Performance ◽  
Effective Multiplication

In this study the effects of the total number of regions and average power density in Modified CANDLE burn-up scheme are studied. In the previous studies usually 10 equal axial regions are applied in Modified CANDLE burn-up scheme, and in this study 6, 8 and 10 regions Modified CANDLE burn-up scheme performance is compared and discussed. The core power level varied from 800-1000MWt. Several comparisons are performed between 10 and 8 regions Modified CANDLE, 8 and 6 regions Modified CANDLE and some additional comparison which include some changing in power level. Some general remark which we can get from this study is that reducing region with the same cycle length and power level will resulted in significant drop of effective multiplication constant especially at the beginning of life and the reduction of discharge burn-up level. On the other hand the increase of the power level with the same region number and cycle length resulted in higher effective multiplication constant value especially at the beginning of life, while at the end of life the differences are decrease. Then when we reduce the region number and increase the power level at the same time we get the mixed effect in which the system performance is relatively go back to the original case.

scholarly journals An Improved Method for Estimating the Wind Power Density Distribution Function

2010 ◽  
Vol 27 (7) ◽  
pp. 1153-1164 ◽  
Author(s):  
Mark L. Morrissey ◽  
Werner E. Cook ◽  
J. Scott Greene
Keyword(s):  
Wind Speed ◽  
Density Function ◽  
Wind Power ◽  
Power Density ◽  
Distribution Curve ◽  
Parametric Method ◽  
Reliable Estimate ◽  
Hermite Expansion ◽  
Usual Practice ◽  
Wind Power Density

Abstract The wind power density (WPD) distribution curve is essential for wind power assessment and wind turbine engineering. The usual practice of estimating this curve from wind speed data is to first estimate the wind speed probability density function (PDF) using a nonparametric or parametric method. The density function is then multiplied by one-half the wind speed cubed times the air density. Unfortunately, this means that minor errors in the estimation of the wind speed PDF can result in large errors in the WPD distribution curve because the cubic term in the WPD function magnifies the error. To avoid this problem, this paper presents a new method of estimating the WPD distribution curve through a direct estimation of the curve using a Gauss–Hermite expansion. It is demonstrated that the proposed method provides a much more reliable estimate of the WPD distribution curve.

Quantification of the energy required for the destruction ofBalanus amphitritelarva by ultrasonic treatment

2010 ◽  
Vol 90 (7) ◽  
pp. 1475-1482 ◽  
Author(s):  
Nishant Seth ◽  
Piyul Chakravarty ◽  
Lidita Khandeparker ◽  
Arga Chandrashekar Anil ◽  
Aniruddha B. Pandit
Keyword(s):  
Power Density ◽  
Ultrasonic Treatment ◽  
Bacterial Abundance ◽  
Treatment Time ◽  
Power Level ◽  
Acoustic Power ◽  
Water Disinfection ◽  
Balanus Amphitrite ◽  
Marine Fouling ◽  
System Operating

Ultrasonic treatment, a relatively less explored technology in water disinfection, was used to quantify the energy required for the destruction of larvae of barnacleBalanus amphitrite, which is a major marine fouling and a potential invasive organism. Since the power used and treatment time for disinfection are economically, and practically, the most important parameters, the energy required to pulverize the larvae into pieces ≤30 µm was determined as a function of the acoustic power density. The present investigation suggests that an ultrasonic system operating at 20 kHz and 0.0975 W/cm3can effectively pulverize barnacle larvae having length (~440 µm) and breadth (~350 µm) within 45 seconds using 0.1 mJ/larva of pulverization energy. It was also observed that following pulverization of the larvae, the bacterial abundance increased and the rate of release of bacteria was dependent on power level and treatment time, which in turn decided the pulverization rate and hence the rate of release of bacteria.

scholarly journals A Survey on Bidirectional DC/DC Power Converter Topologies for the Future Hybrid and All Electric Aircrafts

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4883
Author(s):  
Álvaro Ojeda-Rodríguez ◽  
Pablo González-Vizuete ◽  
Joaquín Bernal-Méndez ◽  
María A. Martín-Prats
Keyword(s):  
Power Density ◽  
Power Distribution ◽  
Distribution Systems ◽  
High Efficiency ◽  
Low Voltage ◽  
Power Level ◽  
Power Converter ◽  
Dc Power ◽  
Converter Topologies ◽  
Converter Topology

DC-DC isolated converters allowing a bidirectional flow of energy between High-Voltage DC and Low-Voltage DC networks have been proposed to be integrated in future on board power distribution systems. These converters must meet the specially stringent efficiency and power density requirements that are typical of the aeronautic industry. This makes it specially challenging to determine which converter topology is best suited for each particular application. This work presents a thorough review of several topologies of bidirectional DC-DC power converters that are considered good candidates to meet certain important aeronautic requirements, as those related with high efficiency and high power density. We perform simulations on virtual prototypes, constructed by using detailed component models, and optimized following design criteria that are in accordance with those typically imposed by aeronautic requirements. This comparative analysis is aimed to clearly identify the advantages and drawbacks of each topology, and to relate them with the required voltage and power levels. As an outcome, we point out the topologies that, for the required power level at the chosen switching frequencies, yield higher efficiency in the whole range of required operation points and that are expected to allow more important weight reductions.

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