K-factor Values Research Articles

Application of a Combined Measurement and Modeling Method to Quantify Windblown Dust Emissions from the Exposed Playa at Mono Lake, California

ABSTRACT Particulate matter ≤10 μm (PM10) emissions due to wind erosion can vary dramatically with changing surface conditions. Crust formation, mechanical disturbance, soil texture, moisture, and chemical content of the soil can affect the amount of dust emitted during a wind event. A refined method of quantifying windblown dust emissions was applied at Mono Lake, CA, to account for changing surface conditions. This method used a combination of real-time sand flux monitoring, ambient PM10 monitoring, and dispersion modeling to estimate dust emissions and their downwind impact. The method identified periods with high emissions and periods when the surface was stable (no sand flux), even though winds may have been high. A network of 25 Cox sand catchers (CSCs) was used to measure the mass of saltating particles to estimate sand flux rates across a 2-km2 area. Two electronic sensors (Sensits) were used to time-resolve the CSC sand mass to estimate hourly sand flux rates, and a perimeter tapered element oscillating microbalance (TEOM) monitor measured hourly PM10 concentrations. Hourly sand flux rates were related by dispersion modeling to hourly PM10 concentrations to back-calculate the ratio of vertical PM10 flux to horizontal sand flux (K-factors). Geometric mean K-factor values (K f) were found to change seasonally, ranging from 1.3 × 10−5 to 5.1 × 10−5 for sand flux measured at 15 cm above the surface (q 15). Hourly PM10 emissions, F, were calculated by applying seasonal K-factors to sand flux measurements (F = K f × q 15). The maximum hourly PM10 emission rate from the study area was 76 g/m2·hr (10-m wind speed = 23.5 m/sec). Maximum daily PM10 emissions were estimated at 450 g/m2·day, and annual emissions at 1095 g/m2·yr. Hourly PM10 emissions were used by the U.S. Environmental Protection Agency (EPA) guideline AERMOD dispersion model to estimate downwind ambient impacts. Model predictions compared well with monitor concentrations, with hourly PM10 ranging from 16 to over 60,000 μg/m3 (slope = 0.89, R 2 = 0.77). IMPLICATIONS Under a U.S. Environmental Protection Agency (EPA)-approved plan, the method described in this paper has been used since 2000 at Owens Lake, CA, to identify and successfully mitigate dust from over 100 km2 of the dry lakebed. It continues to be used to monitor dust control compliance at Owens Lake. Scaled-down versions of the Owens Lake network can be implemented in other areas in a manner similar to the Mono Lake study. Once K-factors are established, low-cost CSC samplers (about $35 U.S.) may be used for periodic monitoring (e.g., daily, weekly, or monthly) to estimate PM10 emissions or to evaluate dust control compliance.

Partner Selection in Indoor-to-Outdoor Cooperative Networks: An Experimental Study

In this paper, we develop a partner selection protocol for enhancing the network lifetime in cooperative wireless networks. The case-study is the cooperative relayed transmission from fixed indoor nodes to a common outdoor access point. A stochastic bivariate model for the spatial distribution of the fading parameters that govern the link performance, namely the Rician K-factor and the path-loss, is proposed and validated by means of real channel measurements. The partner selection protocol is based on the real-time estimation of a function of these fading parameters, i.e., the coding gain. To reduce the complexity of the link quality assessment, a Bayesian approach is proposed that uses the site-specific bivariate model as a-priori information for the coding gain estimation. This link quality estimator allows network lifetime gains almost as if all K-factor values were known. Furthermore, it suits IEEE 802.15.4 compliant networks as it efficiently exploits the information acquired from the receiver signal strength indicator. Extensive numerical results highlight the trade-off between complexity, robustness to model mismatches and network lifetime performance. We show for instance that infrequent updates of the site-specific model through K-factor estimation over a subset of links are sufficient to at least double the network lifetime with respect to existing algorithms based on path loss information only.

Stress Intensity Factor Calculations for the Compressor Blade with Half-Elliptical Surface Crack Using Raju-Newman Solution

Stress Intensity Factor Calculations for the Compressor Blade with Half-Elliptical Surface Crack Using Raju-Newman Solution This paper presents results of the stress intensity factor calculations for the compressor blade including a half-elliptical crack, subjected to vibration. In this analysis, the Raju-Newman empirical solution for stress intensity factor calculations in the rectangular plate with a half-elliptical flaw was used. The bending stress used in the Raju-Newman solution was computed for the real blade using the finite element method. The K-factor values were calculated only at one point of the crack front, where the crack tip contacts the free surface, because the crack length during experimental investigations was measured just in this direction. In order to determine the stress intensity factors for different crack sizes, ten diverse flaws in the blade were defined. Results of the experimental fatigue tests performed for the blade without preliminary defects showed that the cracks developed from the convex blade surface. On the blade fracture, the beach marks typical of the fatigue damage were visible. The dimensions of cracks in the rectangular plate were defined based on the beach marks shape. In the next part of the work, the stress intensity factor values were used as an input data into the Paris-Erdogan equation. As a result of this calculation, the crack growth rate for the compressor blade vibrating at constant amplitude was estimated. The results obtained were finally compared with the results of the experimental crack growth analysis performed for 1st stage compressor blades of the helicopter turbo-engine.

Distribution of radio refractivity gradient and effective earth radius factor ( k-factor) over Akure, South Western Nigeria

Refractivity gradient and k-factor variations, based on measurements of atmospheric pressure, temperature and relative humidity made in Akure North (7.15°N, 5.12°E), South Western Nigeria, is reported. The measurement was made using wireless weather stations (Integrated Sensor Suite, ISS) positioned at five different height levels beginning from the ground surface and at intervals of 50 m to a height of 200 m on a 220 m idled TV tower. The study utilised 2 years of meteorological data measured from January 2007 to December 2008 to calculate refractivity, its gradient and the effective Earth radius factor ( k-factor). From the results, refractivity values were observed to be generally high during the rainy season (April–October) and the values decreased with increasing altitude. The average refractivity gradient was −52.8 N-units/km and the average value of k-factor is 1.51 for the 2 year period of this report.

Modeling of Localization Error in Wireless Sensor Network

This letter presents the variation of localization error to network parameters, the number of range estimation results from anchor nodes (ANs) and average distance between ANs in centralized Wireless Sensor Network (WSN). In sensor network, ANs estimate the relative range to Target Node (TN) using Time-Of-Arrival (TOA) information of Ultra WideBand (UWB) radio and a fusion center determines the final localization of TN based on estimation results reported. From simulation results, the variation of localization error, which is defined as the difference between localization result of TN and its actual location, is represented as the function of number of estimation results to average distance between ANs. The distribution of localization error is matched to the Rician distribution whose K-factor value is given by the proposed formula as well. Finally, the normalized error function for the efficient localization network design is characterized.

An Empirical Model for Nonstationary Ricean Fading

Ricean fading is common in dense urban cellular networks and, as a mobile moves through that environment, the K-factor of the Ricean fading will change. This paper presents a statistical model for dense urban vehicular nonstationary Ricean fading, where the K-factor gradually changes due to movement through changing surroundings. This model is empirical and is based on K-factor fluctuations that are observed in dense urban cellular radio channel measurements. The K -factor is modeled using a random process with a distribution that is fit to the measured K-factor values. An autoregressive (AR) model is also used to ensure that the autocorrelation of the simulated K-factor process matches the empirical data. The nonstationary Ricean fading envelope that is generated using this model is verified by comparing it with the fading envelope that is observed in the measurements.

Microstructural Evolution and Examination of α’-Martensite during a Multi-Pass Dissimilar Stainless Steel GTAW Process

This study discusses the microstructural evolution and examination of α'-martensite in fusion zones and heat-affected zones under multi-pass dissimilar stainless steels welding. The morphology, quantity, grain size, and chemical composition of the α'-martensite and δ-ferrite were analyzed using optical microscopy (OM), an image analyzer (IA), a ferritscope (FS), field emission scanning electron microscopy (FESEM), energy dispersive spectrometry (EDS), respectively. Recrystallization induced grain refinement of α'-martensite in over-lapping heat-affected zones (HAZ1 > 2 and HAZ2 > 3) after the second and third pass of welding. The Creq, Nieq, and K-factor values were calculated in an elemental analysis according to the Kaltenhauser equation. The higher Nieq (8.0–9.26) and lower K-factor (7.73–9.50) were examined for α'-martensite in the second pass fusion zone (FZ-2) as opposed to δ-ferrite. Comparatively, the a-ferrite indicated higher Creq (22.30–22.91) and K-factor (15.72–16.68) values.

Revised soil erodibility K-factor for soils in the Czech Republic

In the territory of the Czech Republic there are more than 50% of agricultural soils exposed to water erosion; it is a very urgent problem both at present and for the future. It must be solved now when there is still something to be protected. It is rather complicated to describe the soil properties in terms of soil susceptibility to water erosion because it is a complex relation in which many factors participate. For the complex evaluation of all main factors participating in erosion origination it is possible to apply the Universal Soil Loss Equation (USLE). It consists of six factors interacting with each other and participating in the origination of soil erosion. One of these factors is the soil erodibility factor (K-factor), the revision of which for soil conditions of the CR is the subject of this study. In total ca. 5000 soil pits from the whole territory of the country were processed and evaluated in detail. The main results of this study are K-factor values (means and variances) for the soil types, subtypes and varieties (represented in the database) according to the Taxonomic Classification System of Soils of the Czech Republic.

A Novel Simple Semi-Empirical Model for the Effective Earth Radius Factor

This paper presents a dual cumulative probability distribution model for predicting the cumulative distribution of the probability that a particular value of the propagation k-factor will be exceeded. The distributions relate to so-called dry and wet (or climatic) components. The model is based on meteorological radiosonde data observed over a period of some 11 years and published by other workers. The model is extended by a simple height regression analysis in order to predict the cumulative behavior of the k-factor at different ground level heights in the summer rainfall area of South Africa during different months. Comparisons are made between predicted and observed data. The model may have potential applications in other parts of the world where data on k-factor behavior are scarce

On the k-factor distribution and diffraction fading for Southern Africa

In previous presentations, we have discussed models for determining the probability density function (pdf) of the effective earth radius factor for Botswana as a means of predicting k-factor variation. These models are based on the radiosonde measurement data obtained over three years in Botswana. In this presentation, we compare the k values obtained via the curve-fitting model for Botswana and Durban, South Africa. We compare the median k-factor values and k values exceeded 99.9% of the time. Two design examples show that the type of terrain plays a major role in diffraction fading resulting from k-factor variation. While designing with k=4/3 only results in losses of 2 dB and 5 dB for Durban and Botswana links, respectively, multiple obstructions would result in higher fades. Moreover, the gentler terrain in Botswana results in lower losses that would have been the case if the k-factor for Durban had been 1.1. Also we observe that 99.9% link availability would be harder to attain in Durban than in Botswana, due to the higher k-factor variability and hillier terrain in Durban.

Tunable BST:MgO Dielectric Composite by Microwave Sintering

Microwave sintering route was used for obtaining minimum chemical reactivity between the two phases (for sharp grain boundaries) and controlled microstructure in the composites of Ba1 − xSrxTiO3 (BST) and MgO. Composites of desirable compositions of ferroelectric BST and non-ferroelectric MgO were microwave sintered at a frequency of 2.45 GHz. Low dielectric constant, controlled microstructure, high relative density, and sharp grain boundary in BST:MgO composites were achieved. The depressed dielectric constant and tangent loss, high tunability and K-factor values are measured in the sintered composites. This paper describes the detailed studies on the microwave sintered BST:MgO composites and their tunable dielectric properties and microstructure development.

Dielectric Tunability of BST:MgO Composites Prepared by Using Nano Particles

The dielectric properties of ferroelectric Ba0.5Sr0.5TiO3 and non-ferroelectric MgO composites synthesized by using nano particles are investigated for tunable microwave applications. Dielectric properties are studied in the temperature range of −250°C to 100°C, with and without an electrical field. The dielectric tunability is ∼50% for BST:MgO composites under the field of 80 KV/cm. at around the Curie peak. The use of nano particle sizes of materials considerably reduces dielectric losses and shows comparatively high K-factor values in the resulted composites. The ferroelectric phase is well connected and thus enhances the overall dielectric properties of the composites.

Analysis of Soil Hydraulic Conductivity in Palm Plantations in the Saline Soils of the Oued Rhir

The aim of the study was to determine K-factors of homogeneous zones in palm-groves in order to make possible the interpolation of these values to other similar areas, and by this way to help the calculation of draining parameters. Another goal was to interpret the agronomical aspects of the results. Investigations for the determination of conductivity factors (K-factors) were carried out in the palm-groves of the Oued Rhir Valley. The measurements - conducted three times - were made by the auger-hole method. After boring the hole, a perforated cylinder was placed into it to prevent falling in. K-factor values were calculated after van Beers. The mean of the three calculations was given as the end result for the K-factors. Our results show that K-factor values are influenced by the porosity, type, bulk density and texture of soils, their salt content and the form of gypsum. The K-factor was extremely high in case of sandy soils and soils containing crystallized gypsum. Water conductivity was moderate in case gley and pseudogley were located in deeper layers. The lowest values occurred when gypsum was found in cemented coherent particles. Salinization in deeper layers influenced hydraulic conductivity only in case it was associated with finer texture and airless layers. Besides date production, the traditional growing of nitrogen-fixing perennial legumes (alfalfa, Egyptian clover, melilot, etc.) in palm-groves is essential. Systemic flooding irrigation decreases the salt content of soils, increases date and legumes yields. Legumes - by their root-system - improve the nitrogen balance, structure and water drainage of soils. The green parts of the cultivated legumes serve as fodder for animals (goats, sheep, cows), which turn it to manure. This manure increases the nutrient supply of the soils for palm-trees and vegetables. The positive results of stubble and root manuring (green manuring) of legumes is also confirmed by experiments on sandy soils. The elaboration of a good plant rotation is possible. At last, date and vegetables produced in this way could be sold better on the world market as bioproducts.

Silicon avalanche photodiodes for particle detector:: modelling and fabrication

Large-area arrays (30×30) of metal/resistive layer/silicon (MRS) avalanche photodiodes as 150×150 μm sub-pixels were developed and fabricated to detect short-wavelength scintillator signals for high-energy particle detection. Modelling of MRS photodiodes was performed using McIntyre's approach of local electric field to optimize semiconductor doping profiles and resistive layer parameters and to obtain the minimum value of effective k-factor (the holes to electrons ionization coefficients ratio) less than 0.01 under low excess noise factor and high gain. The resistive layer/silicon surface barrier suppresses minority carriers injection to decrease dark current and effective k-factor. Test samples of silicon avalanche photodiodes arrays have been fabricated using low-rate epitaxial growth of silicon layer, impurity doping, and resistive layer deposition processing. The integral gain for experimental specimens was ∼100.

Comparison of Technology and New Developments with Hydrocarbon Blown Rigid Foams Shows a Clear Tendency to Cyclopentane/Hydrocarbon Blends

Rigid foams blown with hydrocarbons have shown a great progress since this technology was implemented in 1992 in Europe, and culminated, last year, in the introduction of blends of hydrocarbons and more particularly cyclopentane/isobutane. Also recently, other blends have found favor where the more complicated handling of butane may present some difficulties. In the hydrocarbon family, cyclopentane is the best option in terms of gas k-factor, but its high boiling point requires higher density and shot weights in cabinets to guarantee long term dimensional stability. The best cost option is provided by the iso-/n-pentane blend. However, the foams produced show inferior k-factor, although final energy consumption is not affected to the same degree. In general, the addition of another co-blowing hydrocarbon such as isobutane, isopentane or c-pentane negatively affects the insulation performance of the foam, but recent polyurethane system developments have allowed the retention of the same k-factor values as those of pure cyclopentane blown foams. This paper aims to compare the different hydrocarbon blowing agent alternatives introduced during the past period and includes theoretical cell gas modeling, creep performance and compressive strength ageing tests. These methods have been used to evaluate and predict, during the foam development phase, the short and long term dimensional stability of the foam. An attempt will be made to understand if the combination of all of them is necessary for getting reliable information. Results from cabinets foamed with these cyclopentane based hydrocarbon blends have confirmed the initial findings and are discussed. It is a further objective of this paper to give the OEMs the data that they require to select the optimum technology to answer their needs in terms of cost, processing performance and insulation value.

Equal-gain combining of multichannel DPSK in Doppler-spread Ricean fading

A method for computing the bit error probability (BEP) of multichannel differentially coherent phase-shift keying (DPSK) with equal gain combining in Doppler spread Ricean fading is given. It is based on Gauss-Chebyshev quadrature integration of the moment generating function of the decision statistic at the combiner output. The method allows nonuniform power delay profiles for the received multipath rays. Applications to multicarrier spread spectrum modulation and spread spectrum with RAKE reception systems are discussed. It is found that for moderate values of the Ricean K-factor (ratio of specular to diffuse fading signal power) an optimum order of diversity exists whereas, for large K-factors, diversity does not improve performance.

In vitro and in vivo microdialysis calibration using retrodialysis for the study of the cerebrospinal distribution of bupivacaine

Microdialysis coupled to HPLC was used to study the disposition of local anesthetics in the cerebrospinal fluid (CSF) because of the difficulty in sampling CSF. A retrodialysis method for the microdialysis calibration was investigated in vitro and in vivo. Calibration by retrodialysis was simultaneously validated through the use of the zero net flux method. Two local anesthetics (bupivacaine and ropivacaine), which differ structurally by only one methyl group, were respectively utilized as substance of interest and as internal standard. Different parameters were tested in vitro to compare the relative recovery ( RR) of bupivacaine and the relative loss ( RL) of ropivacaine. Several flow rates were tried to select an optimal in vivo flow rate (1 μl/min). The RR and RL values were not influenced by the variation of bupivacaine concentration. A significant variability among different probes within a batch was established ( RR ranging from 41.1–65.3%; RL ranging from 30.7–61.0%). The K-factor values, defined as RL ropivacaine/ RL bupivacaine, were calculated in vitro and in vivo. This ratio decreased in vivo but was constant ( K in vitro=1.06±0.04, K in vivo=0.87±0.03). The extracellular tissue concentration of the compound of interest was given by C= C in dialysate×( K/ RL). Following in vivo implantation in rabbit CSF during 4 h, the probes were tested again in vitro and no deterioration of probe during the in vivo experiment was found. After administration of bupivacaine in the epidural space of rabbits, plasma and microdialysis CSF samples were simultaneously collected. Plasma and CSF disposition of bupivacaine displayed different kinetics. The maximum CSF concentration of B averaged 394±170 μg ml −1, with a mean T max of 3.8±1.8 min. The maximum plasma concentration of B averaged 0.44±0.09 μg ml −1 with a mean T max occurring at 1 min. Microdialysis, combined with accurate calibration, should be a reliable technique to gain further insight in the spinal disposition of local anesthetics.

Adequação de métodos indiretos para estimativa da erodibilidade de solos com horizonte B textural no Brasil

O conhecimento da erodibilidade dos solos (fator K) é de fundamental importância para a aplicação da equação universal de perdas de solo (EUPS). O objetivo deste trabalho foi verificar a adequação de diferentes métodos indiretos para estimativa da erodibilidade de solos com horizonte B textural (Bt) de várias regiões geográficas do Brasil. Coletaram-se amostras superficiais de 22 solos com Bt, cujo fator K foi determinado diretamente no campo. Realizaram-se diversas análises químicas e físicas, de modo que o fator K pudesse ser estimado por treze diferentes métodos indiretos. Correlacionaram-se os valores dos fatores K medidos no campo com os obtidos indiretamente. Verificou-se que nenhum dos métodos indiretos testados é adequado para a estimativa do fator K de todo o conjunto de solos com Bt estudados.

Estimativa da erodibilidade a partir de atributos de solos com horizonte B textural no Brasil

Os métodos existentes para estimar a erodibilidade dos solos (fator K) não se têm mostrado adequados quando aplicados a solos brasileiros. Este trabalho teve por objetivo o desenvolvimento de método indireto para estimar a erodibilidade, visando obter esse fator, a partir de propriedades do solo facilmente determináveis. Assim, os horizontes A e Bt (B textural) de 22 solos de várias regiões geográficas do Brasil foram submetidos a diversas análises químicas e físicas, e a descrição morfológica do perfil foi considerada. Tais resultados (variáveis independentes) foram submetidos à análise de regressão linear múltipla em "stepwise", e relacionados com a erodibilidade (fator K) medida diretamente no campo (variável dependente). Obtiveram-se várias equações com graus crescentes de complexidade e precisão. A partir das variáveis selecionadas, tanto do horizonte A quanto do Bt, e da distribuição do tamanho das partículas, obtida com e sem dispersante químico, foi possível estimar, satisfatoriamente, a erodibilidade desses solos. As informações contidas na descrição morfológica dos perfis de solo, especialmente as referentes à estrutura, bem como os teores de carbono orgânico, foram de grande importância para a determinação indireta da erodibilidade (fator K).

ASSESSMENT OF Hll,LSLOPE DESIGNS USING RUSLE AT THE COEUR ROCHESTER MINE, LOVELOCK, NV

The Coeur Rochester Mine is a mountain-top, open-pit, heap-leach operation engaged in the production of silver and gold. The Revised Universal Soil Loss Equation (RUSLE) was used to assess the erosion potential of various reclamation-hillslope designs at this mine. Soil-loss estimates were computed for reclaimed rock-disposal and leach-pad sites as well as natural, undisturbed, sites. Factor inputs reflected the expected post-reclamation hillslope characteristics. The estimated average annual soil loss from the natural hillslopes ranged from 0.16-1.77 T/ha (0.07-0.79 t/ac). The estimated soil loss from the various designs for hillslopes developed on rock-disposal sites ranged from 0.22-3.41 T/ha/yr (0.10-1.52 t/ac/yr). The estimated soil loss from the various designs for hillslopes developed on leach-pad sites ranged from 0.04-0.22 T/ha/yr (0.02-0.10 t/ac/yr). The low soil-loss rates are the result of low R- and C-factor values coupled with a low to moderate K-factor values. These estimates were carefully considered in the selection of appropriate hillslope designs. RUSLE is a powerful tool for assessing the erosion potential of various hillslope designs during the reclamation-planning process.