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Evaluating four remote sensing based models to estimate latent heat flux in semi-arid climate for heterogeneous surface coverage of western Algeria

Oualid Tewfik A., Hamimed Abderahmane, Khaldi Abdelkader

Journal of Water and Land Development

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2022

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no. 55

259--275

EN

Optimal estimation of water balance components at the local and regional scales is essential for many applications such as integrated water resources management, hydrogeological modelling and irrigation scheduling. Evapotranspiration is a very important component of the hydrological cycle at the soil surface, particularly in arid and semi-arid lands. Mapping evapotranspiration at high resolution with internalised calibration (METRIC), trapezoid interpolation model (TIM), two-source energy balance (TSEB), and soil-plant-atmosphere and remote sensing evapotranspiration (SPARSE) models were applied using Landsat 8 images for four dates during 2014-2015 and meteorological data. Surface energy maps were then generated. Latent heat flux estimated by four models was then compared and evaluated with those measured by applying the method of Bowen ratio for the various days. In warm periods with high water stress differences and with important surface temperature differences, METRIC proves to be the most robust with the root-mean-square error (RMSE) less than 40 W∙m-2. However, during the periods with no significant surface temperature and soil humidity differences, SPARSE model is superior with the RMSE of 35 W∙m-2. The results of TIM are close to METRIC, since both models are sensitive to the difference in surface temperature. However, SPARSE remains reliable with the RMSE of 55 W∙m-2 unlike TSEB, which has a large deviation from the other models. On the other hand, during the days when the temperature difference is small, SPARSE and TSEB are superior, with a clear advantage of SPARSE serial version, where temperature differences are less important.

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Wpływ cząstek grafitowych lub metalowych na wytrzymałość termiczną silikonowego smaru termicznego

Araźna A., Janeczek K., Stęplewski W., Sitek J., Lipiec K.

Elektronika : konstrukcje, technologie, zastosowania

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2018

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Vol. 59, nr 12

43--46

PL

Stosowanie bardziej złożonych i miniaturowych elementów zintegrowanych w jednej obudowie w technologii mikroelektroniki skutkuje wysoką gęstością wytwarzanego ciepła. Dlatego efektywne zarządzanie ciepłem stało się kluczowym wymogiem przy projektowaniu nowoczesnych pakietów elektronicznych. Jedną z wielu metod zarządzania ciepłem generowanym w pakietach elektronicznych jest użycie materiałów termoprzewodzących (TIM). Materiały TIM mają za zadanie wyeliminowanie szczelin powietrznych uformowanych pomiędzy chipem IC a radiatorem i zwiększenie wymiany ciepła między nimi. Dlatego właściwości termiczne materiałów TIM odgrywają kluczową rolę w procesie rozpraszania ciepła. Celem pracy jest określenie wpływu cząstek grafitu, srebra lub miedzi na stabilność termiczną silikonowego smaru termicznego metodami termograwimetrii (TGA) i skaningowej kalorymetrii różnicowej (DSC). W pracy badano stabilność termiczną próbek TIM w oparciu wartości temperatury maksymalnej utraty masy, energi aktywacji reakcji rozkładu i początkowej temperatury rozkładu próbek. Wyniki pokazują, że proces degradacji wszystkich testowanych próbek TIM w warunkach analizy ma charakter wieloetapowy. Dodatki grafitu i cząstek metalu zmieniły stabilność termiczną silikonowego smaru termicznego.

EN

The use more complex and smaller components in one packaging in microelectronics technology results in high density of heat generated. In this sense, efficient thermal management has become a critical requirement for the design of modern electronic packages. One of the many methods to manage the heat generated within the electronics components is using Thermal Interface Materials (TIMs). The function of TIMs is to eliminate the interstitial air gaps formed between IC chip and heat sink and to improve heat transfer between them. Therefore, thermal properties of TIMs materials play a key role in heat dissipation. The goal of this work is to determine influence of graphite, silver or copper particles on thermal stability of the silicone based thermal grease by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The weight loss behavior and the thermal stability based on temperatures of maximum rate of weight loss, the activation energy of the decomposition reactions and the initial decomposition temperature were studied. The results reveal that degradation process of all the tested TIMs materials under the analysis condition is multistage. Addition of graphite and metal particles changed thermal behavior of the silicone based thermal grease.

3

Growth of intermetallic compound between indium-based thermal interface material and copper substrate: molecular dynamics simulations

Fałat T., Płatek B.

Materials Science Poland

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2015

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Vol. 33, No. 2

445--450

EN

The diffusion phenomenon occurring between copper and indium was investigated by molecular dynamics simulations. The calculations were carried out in various temperatures in aging domain with the use of the commercially available Materials Studio v.6. software. The results showed that the intermetallic compound (IMC) growth followed the parabolic law, which indicated this growth to be mainly controlled by volume diffusion. The growth activation energy was estimated at 7.48 kJ.mol(-1).