Cumulative Frequency Distributions for Hourly Clearness Indices Through Generalized Parameters

2010 ◽  
Author(s):  
V. V. Satyamurty ◽  
P. RaviKumar
Keyword(s):  
Time Scale ◽  
Cumulative Frequency ◽  
Clearness Index ◽  
Frequency Distributions ◽  
The Difference ◽  
Generalized Parameters ◽  
Different Climates

The objective of the present investigation is to develop generalized cumulative frequency distributions for hourly clearness indices applicable for different climates. The distributions have been developed in terms of suitable normalized variables relevant on hourly time scale, and include the swing (the difference between the maximum and minimum values of the hourly clearness index for a particular hour over the days in a month) in the hourly clearness index. The adequacy of the distributions developed in predicting the hourly clearness index has been established by comparing with the data values of the 183 secondary locations in addition to the 56 primary locations in USA for which the data are available.

Cumulative Frequency Distributions for Daily Global Illuminance

Solar Energy ◽  
2004 ◽  
Author(s):  
V. V. Satyamurty ◽  
P. RaviKumar
Keyword(s):  
Standard Deviation ◽  
Data Base ◽  
Linear Form ◽  
Large Data ◽  
Cumulative Frequency ◽  
Clearness Index ◽  
Frequency Distributions ◽  
Large Data Base ◽  
Average Value ◽  
Monthly Average

The present article describes the development of cumulative frequency distributions (similar to clearness index distributions) for daily global horizontal illuminance based on the modeled data of 56 US locations. Normalized variables have been employed to account for seasonal and location dependencies. The normalized variables contain the maximum and minimum illuminance values in the array of daily values in addition to the daily illuminance (the variable to be related to cumulative frequency) and the monthly average daily illuminance. The distributions thus developed discrete in terms of the normalized monthly average daily global illuminance have been presented in a convenient linear form which accommodates continuous values for the parameter. When data are not available, the maximum and minimum of the daily values needed in estimating the parameter first and eventually the daily illuminance values have been correlated to other more readily available predictors. Present distributions have been validated by comparing against the daily illuminance values available in the large data base employed. Daily global illuminance has been predicted with a standard deviation of 23.44 klux and rms difference of 4.64%. The present correlations can be conveniently applied to obtain the 30 or 31 daily illuminance values in a month from the monthly average value.

scholarly journals Fast Comparison of High-Precision Time Scales Using GNSS Receivers

2017 ◽  
Vol 2017 ◽  
pp. 1-4
Author(s):  
Vojtech Vigner ◽  
Jaroslav Roztocil
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
High Performance ◽  
Data Format ◽  
Common View ◽  
Log Files ◽  
Gnss Receivers ◽  
Precision Time ◽  
The Common ◽  
The Difference

Comparison of high-performance time scales generated by atomic clocks in laboratories of time and frequency metrology is usually performed by means of the Common View method. Laboratories are equipped with specialized GNSS receivers which measure the difference between a local time scale and a time scale of the selected satellite. Every receiver generates log files in CGGTTS data format to record measured differences. In order to calculate time differences recorded by two receivers, it is necessary to obtain these logs from both receivers and process them. This paper deals with automation and speeding up of these processes.

Weak Coupling Strategy for Multi-Physics CFD Simulation in Engineering Problems

2011 ◽  
Author(s):  
Makoto Yamamoto ◽  
Masaya Suzuki
Keyword(s):  
Strong Coupling ◽  
Time Scale ◽  
Weak Coupling ◽  
Particle Deposition ◽  
Cfd Simulation ◽  
The Other ◽  
Cfd Simulations ◽  
Sand Erosion ◽  
Coupling Strategy ◽  
The Difference

Multi-Physics CFD Simulation will be one of key technologies in various engineering fields. There are two strategies to simulate a multi-physics phenomenon. One is “Strong Coupling”, and the other is “Weak Coupling”. Each can be employed, based on time-scales of physics embedded in a problem. That is, when a time-scale of one physics is nearly same as that of the other physics, we have to use Strong Coupling to take into account the interaction between two physics. On the other hand, when one time-scale is quite different from the other one, Weak Coupling can be applied. Considering the present computer performance, Strong Coupling is difficult to be used in engineering design processes now. Therefore, we are focusing on Weak Coupling, and it has been applied to a number of multi-physics CFD simulations in engineering. We have successfully simulated sand erosion, ice accretion, particle deposition, electro-chemical machining and so on, with using Weak Coupling method. In the present study, the difference between strong and weak couplings is briefly described, and two examples of our multi-physics CFD simulations are expressed. The numerical results indicate that Weak Coupling strategy is promising in a lot of multi-physics CFD simulations.

Effect of Ethanol on Drug Levels in Blood in Fatal Cases

1982 ◽  
Vol 22 (4) ◽  
pp. 232-234 ◽  
Author(s):  
L. A. King
Keyword(s):  
Blood Levels ◽  
Cumulative Frequency ◽  
Frequency Distributions ◽  
Drug Levels ◽  
Postmortem Blood

The cumulative frequency distributions of postmortem blood levels of four centrally-acting drugs (pentobarbitone, amitriptyline, chlormethiazole and dextropropoxyphene) have been derived from fatalities involving either the named drug only or the drug in association with ethanol only. For each drug, the presence of ethanol markedly reduced the concentration at which a given proportion of fatalities occurred.

scholarly journals The effects of clouds and aerosols on net ecosystem CO<sub>2</sub> exchange over semi-arid Loess Plateau of Northwest China

2010 ◽  
Vol 10 (5) ◽  
pp. 13337-13372
Author(s):  
X. Jing ◽  
J. Huang ◽  
G. Wang ◽  
K. Higuchi ◽  
J. Bi ◽  
...  
Keyword(s):  
Loess Plateau ◽  
Air Temperature ◽  
Northwest China ◽  
Co2 Uptake ◽  
Observation Data ◽  
Light Use Efficiency ◽  
Clearness Index ◽  
Use Efficiency ◽  
The Difference ◽  
Semi Arid

Abstract. The impacts of clouds and atmospheric aerosols on the terrestrial carbon cycle at semi-arid Loess Plateau in Northwest China are investigated, by using the observation data obtained at the SACOL (Semi-Arid Climate and Environment Observatory of Lanzhou University) site. Daytime (solar elevation angles of larger than 50°) NEE of CO2 obtained during the midgrowing season (July–August) are analyzed with respect to variations in the diffuse radiation, cloud cover and aerosol optical depth (AOD). Results show a significant impact by clouds and aerosols on the CO2 uptake by the grassland (with smaller LAI values) located in a semi-arid region, quite different from areas covered by forests and crops. The light saturation levels in canopy are lower, with a value of about 434.8 W m−2. Thus, under overcast conditions of optically thick clouds, the CO2 uptake increases with increasing clearness index, and a maximum CO2 uptake and light use efficiency of vegetation occur with the clearness index of about 0.37 and lower air temperature. Under other sky conditions the CO2 uptake decreases with the cloudiness but the light use efficiency is enhanced, due to increase in the fraction of diffuse PAR. Additionally, under cloudy conditions, changes in the NEE of CO2 also result from the interactions of many environmental factors, especially the air temperature. In contrast to its response to changes in solar radiation, the carbon uptake shows a negative response to increased AOD. The reason for the difference in the response of the semi-arid grassland from that of the forest and crop lands may be due to the difference in the canopy's architectural structure.

Adaptation and Natural Selection

2021 ◽  
pp. 125-154
Author(s):  
Áki J. Láruson ◽  
Floyd A. Reed
Keyword(s):  
Natural Selection ◽  
Allele Frequency ◽  
Levels Of Selection ◽  
Frequency Data ◽  
Selection Coefficient ◽  
Frequency Distributions ◽  
Single Allele ◽  
Selection Strength ◽  
The Difference ◽  
Over Time

Here non-random shifts in allele frequencies over time are introduced, as well as how to incorporate varying levels of selection into a model of a single population through time. This chapter highlights the difference between weak and strong selection, the dynamics of single allele versus genotype-level selection, and how selection strength and population size affect allele frequency distributions over time. Finally the inference of the selection coefficient from allele frequency data is discussed, alongside the concepts of overdominance and underdominance.

The growth pattern of the African tortoise Geochelone pardalis and other chelonians

1999 ◽  
Vol 77 (2) ◽  
pp. 181-193 ◽  
Author(s):  
Adrian Hailey ◽  
Ian M Coulson
Keyword(s):  
Growth Pattern ◽  
High Growth ◽  
Growth Patterns ◽  
Growth Rings ◽  
Frequency Distributions ◽  
The North ◽  
Body Sizes ◽  
Biased Sex Ratio ◽  
The Difference ◽  
North And South

Growth rings were measured in dead African leopard tortoises, Geochelone pardalis, collected in the seasonal tropics of Zimbabwe over an 11-year period. A series of Ford-Walford plots using growth measured from annuli showed that growth fitted a logistic by mass curve best, logistic by length and Gompertz curves less well, and a Bertalanffy curve least well. The Bertalanffy curve, often fitted to growth of chelonians, is characterised by particularly high growth rates of juveniles compared with larger individuals. It is suggested that this growth pattern is likely to be found in species showing a marked decrease in diet quality with size. This hypothesis is supported by a review of growth patterns in chelonians: Bertalanffy curves are associated with an omnivorous (and thus potentially variable) diet and other growth patterns with an obligate carnivorous or herbivorous diet. Geochelone pardalis in Zimbabwe showed significant sexual size dimorphism, the mean asymptotic mass of females being 1.7 times that of males, unlike populations with larger body sizes to the north and south. Annual survival estimated from age-frequency distributions was significantly higher in males (0.80) than in females (0.72), the difference being sufficient to account for the male-biased sex ratio of live animals.

Cumulative Frequency Distributions for Hourly Global Illuminance

2011 ◽  
Author(s):  
V. V. Satyamurty ◽  
P. RaviKumar
Keyword(s):  
Present Article ◽  
Cumulative Frequency ◽  
Frequency Distributions

In the present article, cumulative frequency distributions for hourly global horizontal illuminance based on the modeled data of 56 US locations have been presented. Measured illuminance information from other sources also has been utilized. Suitable normalized variables have been introduced to depict the generalized cumulative frequency distributions for hourly global illuminance. The cumulative distributions developed based on representative set locations have been shown to be applicable for another set of locations. In addition, the present article brings out, the major differences between daily and hourly cumulative frequency distributions and, a method to generate hourly (synthetic) global illuminance data from the frequency distributions.

Frequency Distributions for Hourly and Daily Clearness Indices

2001 ◽  
Author(s):  
Manuel Ibañez ◽  
William A. Beckman ◽  
Sanford A. Klein
Keyword(s):  
Solar Radiation ◽  
Recent Literature ◽  
Weather Data ◽  
Clearness Index ◽  
Frequency Distributions ◽  
The Us ◽  
Daily Frequency ◽  
Better Than ◽  
Exponential Probability

Abstract The clearness index for hourly and daily radiation is an important parameter in describing solar radiation. Liu and Jordan demonstrated that the monthly average daily clearness index could be used to predict the long-term distribution of daily solar radiation in a month. This paper reviews recent literature on the prediction of hourly and daily frequency distributions and cumulative frequency distributions of clearness indices. Ten years of measured weather data for six cities in the US are used to investigate the nature of the hourly and daily frequency distributions. A second set of ten years of data for six cities is used to verify the predictions. A bi-exponential probability density function is proposed that fits the observed bimodal nature of the data better than existing models. A case is made for the function being universal.

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