An Improved Slant Path Attenuation Prediction Method in Tropical Climates

An improved method for predicting slant path attenuation in tropical climates is presented in this paper. The proposed approach is based on rain intensity data R_0.01 (mm/h) from 37 tropical and equatorial stations; and is validated by using the measurement data from a few localities in tropical climates. The new method seems to accurately predict the slant path attenuation in tropical localities, and the comparative tests seem to show significant improvement in terms of the RMS of the relative error variable compared to the RMS obtained with the SAM, Crane, and ITU-R prediction models

Development Of Rain And Scintillation Models At Ku-Sand In Southeast Asia Tropical Countries

A two year rainfall rate, attenuation and scintillation measurement was conducted in Southeast Asia Tropical countries (USM, KMITL,USP, AdMU and ITB). The data obtained are useful to investigate the impairment due to rainfall in satellite links operating in tropical and equatorial climates. The cumulative distributions of rainfall rate, attenuation and scintillation derived from the measured data are presented and compared with those obtained with existing prediction models. Existing model for prediction of slant-path have not shown good agreement with available experimental data, confirming the need of suitable models for tropical region. Results were analysed in order to understand the potentials and the limits of each prediction model. Based on the limitations of the existing models, 1-minute rainfall rate and attenuation prediction model was developed from the knowledge of the ground point rainfall rate and attenuation cumulative distribution representative of the area where the earth station is located. Comparison between predicted and experimental results has shown significant improvements in terms of reduced prediction error over existing models. The proposed models were also used for prediction against the measured data from different location such as Brazil, Singapore and Papua New Guinea. The proposed model gave a good representation of cumulative distribution with an overall low rms for measurement sites and the three different locations mentioned above. The agreement with the measured data was found to be mainly dependent on the proper parameterization of the proposed models to the radiometeorological variables along the satellite link. Therefore, it can be concluded that the proposed models has high prediction accuracy for the whole cumulative distribution of rainfall and scintillation data

Usporedba modela intenziteta oborine za područja s ekvatorijalnom klimom u jugoistočnoj Aziji

Statistics of 1 minute rain rate has a major impact in the design of satellite communication systems at frequencies above 10 GHz. The effect of rain causes serious degradation of radio signals at frequencies above about 10 GHz; therefore, models for the prediction of statistics of excess path attenuation needed for the design of communication propagation paths requires a statistical description of rain-rate occurrences. In this paper, the tasks are tackled by processing 3 years rain rate data for selected sites in the equatorial region. A comparison between rain rate data set with a sampling period of 1 minute and existing rain rate prediction models is presented.Statistika minutnih intenziteta oborine ima veliki utjecaj na modeliranje satelitskih komunikacijskih sustava koji rade na frekvencijama višim od 10 GHz. Utjecaj kiše uzrokuje jaku degradaciju radio signala na frekvencijama 10 GHz i višim; stoga modeli za predviđanje prekoračenja dozvoljenog propagacijskog gušenja, koje je potrebno za izbor komunikacijskih pravaca, zahtijevaju statistički opis intenziteta oborine na tim pravcima. U ovom su radu obrađeni trogodišnji nizovi podataka s intenzitetima oborine za odabrane postaje u ekvatorijalnom području. Uspoređeni su rezultati dobiveni s nizovima podataka intenziteta oborine koji su uzorkovani s periodom jedne minute s onima dobivenima prognostičkim modelima intenziteta oborine

ANALYSIS OF RAIN RATE AND RAIN ATTENUATION FOR EARTH-SPACE COMMUNICATION LINKS OVER UYO - AKWA IBOM STATE

Rain rate and rain attenuation predictions are vital when designing microwave satellite and terrestrial communication links, such as in the Ku and Ka bands. This paper presents the cumulative distribution functions (CDFs) of the predicted rain rate and rain attenuation for Uyo, Akwa Ibom State (AKS) (Latitude: 4.88°N, Longitude: 8.09°E, Height above Sea Level: 51.2 m), a typical rain forest zone in Nigeria, using rainfall data for three years spanning between January 2010 and December 2012. These measurements were recorded by the meteorology department of the Akwa Ibom International Airport (AIIA), Uyofor percentage availabilities 99.9 to 99.999. Rain-rate measurements were carried out using the Moupfouma and Chebil models – models purposely designed for tropical zones, while the International Telecommunications Union Radio-wave propagation (ITU-R P) models were used for estimating rain-attenuation. The results obtained will serve as a good preliminary design tool for both terrestrial and earth-satellite microwave links. http://dx.doi.org/10.4314/njt.v35i1.2

Stress and deformation of optimally shaped silicon microneedles for transdermal drug delivery

In this study, we demonstrated the fabrication of the concave conic shape microneedle with the aid of COMSOL Multiphysics simulation. The stress and buckling of the microneedle structure were simulated by applying various loads ranging from 50 to 800 g perpendiculars to the tip in order to predict the occurrence of microneedles structure deformation. The simulation study indicated that the surface buckling deformation does not occur to the microneedle structure with the increment of the load. The microneedles with dimensions of height and diameter tip ranging from 60 to 100 μm and 1 to 4 μm, respectively had been fabricated via an etching process in a mixture of hydrofluoric acid, nitric acid, and acetic acid. Three optimized microneedles but different in the structures were fabricated via the acidic etching process. The reproducibility of three different microneedle structures was 15, 20, and 60%, respectively. Stress and buckling analyses of the fabricated microneedles were further carried out on the rat skin. The obtained experimental results show promising applications for the deep dermis, stratum corneum to epidermis layer penetration

Statistics of rainfall rate at 60 minutes integration time in Malaysia

Background: This paper presents the statistics of rainfall at 60- minute integration time in Malaysia for the period of 12 months from January to December 2009. Objective: To analyze the statistics and characteristics of rainfall intensity measurement at KLIA, Malaysia. To study the behavior of measured rainfall intensity and represent the annual distribution of the measured rainfall through cumulative distribution functions together with different types of rainfall that occurred in 2009. Results: The results obtained show the cumulative distribution functions and amount of the rainfall rate for that particular year. The results also show the different cumulative distribution functions for four different rainfall types that occur in 2009. Conclusion: The study of the 12-month tipping bucket data has given the characteristics of the collected rainfall. From the results obtained, it shows that Malaysia is within equatorial region with the characteristics of two distinguishable rainfall rates that occurs during the whole year

Review of Rain Attenuation Measurements On Earth - Space Links in Nigeria

Due to the prevailing impact of rain on microwave and millimetre wave propagation in tropical climates, fade margins derived from experimental campaigns would provide more practical estimates for planning. In this paper, the extent of work done on the experimental assessment of the attenuation induced by rain on practical earth-space links in Nigeria is presented. The cumulative rain rate distributions derived from the instantaneous precipitation indices for propagation modelling and the estimation of fade margin is presented for Ile-Ife, Akure, Ilorin, Ota, Osogbo and Ogbomoso. Results reveals the spatial variability of the point rainfall rate across these stations. Although the stations engaged with measurement on rain attenuation are limited in number, preliminary results from new stations are presented, while addition data from ongoing campaigns will provide a robust indices for modelling the digital DTH links and for evaluating the performance of pre-existing models over Nigeria

On requirements for a satellite mission to measure tropical rainfall

Tropical rainfall data are crucial in determining the role of tropical latent heating in driving the circulation of the global atmosphere. Also, the data are particularly important for testing the realism of climate models, and their ability to simulate and predict climate accurately on the seasonal time scale. Other scientific issues such as the effects of El Nino on climate could be addressed with a reliable, extended time series of tropical rainfall observations. A passive microwave sensor is planned to provide information on the integrated column precipitation content, its areal distribution, and its intensity. An active microwave sensor (radar) will define the layer depth of the precipitation and provide information about the intensity of rain reaching the surface, the key to determining the latent heat input to the atmosphere. A visible/infrared sensor will provide very high resolution information on cloud coverage, type, and top temperatures and also serve as the link between these data and the long and virtually continuous coverage by the geosynchronous meteorological satellites. The unique combination of sensor wavelengths, coverages, and resolving capabilities together with the low-altitude, non-Sun synchronous orbit provide a sampling capability that should yield monthly precipitation amounts to a reasonable accuracy over a 500- by 500-km grid