Absorption Coefficient Of Radiation Research Articles

Study on the thermal behavior of aluminum reticulated shell structures considering solar radiation

The aluminum dome has been more and more widely adopted in industrial and civil buildings, and the span is up to 140m. Because the thermal expansion coefficient of aluminum with a value of 2.3×10−5 is almost two times than that of steel, the temperature change will induce significant thermal deformation and thermal stress, especially for the large span aluminum domes under solar radiation. In this paper, the solar radiation absorption coefficient was firstly measured using spectrophotometer, and then a numerical simulation method was presented and verified by test dada. To take a aluminum dome project with a span of 125m for an example, the non-uniform temperature distribution and change under solar radiation were analyzed using the presented method, and following conclusions were obtained: (1) The thermal load is the key load for the aluminum domes, and the solar radiation has a significant effect on the thermal behavior of the aluminum domes. Therefore, the non-uniform thermal load considering solar radiation has to be considered in the future design. (2) There is a remarkable variation of member stress, and it is necessary to study the fatigue behavior of the aluminum domes under solar radiation.

Studies on the temperature distribution of steel plates with different paints under solar radiation

Thermal effects on steel structures exposed to solar radiation are significant and complicated. Furthermore, the solar radiation absorption coefficient of steel surface with different paintings is the main factor affecting the non-uniform temperature of spatial structures under solar radiation. In this paper, nearly two hundreds steel specimens with different paintings were designed and measured to obtain their solar radiation absorption coefficients using spectrophotometer. Based on the test results, the effect of surface color, painting type, painting thickness on the solar radiation absorption coefficient was analyzed. The actual temperatures under solar radiation for all specimens were also measured in summer not only to verify the absorption coefficient but also provide insight for the temperature distribution of steel structures with different paintings. A numerical simulation and simplified formula were also conducted and verified by test, in order to study the temperature distribution of steel plates with different paints under solar radiation. The results have given an important reference in the future research of thermal effect of steel structures exposed to solar radiation.

Effect of vacuum ultraviolet on the surface properties of high-filled polymer composites

The effect of vacuum ultraviolet radiation (λ = 90–115 nm) on the surface structure and optical properties of high-filled polymer composites based on high-impact polystyrene and organosiloxane filler is investigated. It is ascertained that VUV exposure leads to the surface smoothing and solar radiation absorption coefficient increasing by ∼15%.

Synthesis and Characterisation of Thin Films of Bismuth Triiodide for Semiconductor Radiation Detectors

Bismuth iodide is a potentially active material for room temperature radiation detector, as it is well reported in the literature that it has both wide energy band gap and high atomic absorption coefficient. Crystalline films of high atomic number and high radiation absorption coefficient can absorb the X-rays and convert them directly into electrical charges which can be read by imaging devices. Therefore, it was proposed to grow thin films of Bismuth iodide on glass substrate using thermal evaporation technique in vacuum to avoid the inclusion of impurities in the films. The structural studies of the films were carried out using XRD and optical absorption measurement was carried out in the UV/VIS region using spectrophotometer. All Bismuth iodide films grown at room temperature are polycrystalline and show X-ray diffraction peaks at angles reported in research papers. The optical transmission spectra of BiI3 films show a high transmission of about 80% in visible region with a sharp fall near the fundamental absorption at 650 nm. Resistivity of the as-grown film was found to be around 1012 ohm-cm suitable value for X-ray detection application. Films were subjected to scanning electron microscopy to study the growth features of both as-grown and annealed films.

Quantitative analysis for CIGS thin films by surface analytical techniques

The compound semiconductor Cu(In,Ga)Se2 (CIGS) is well known as the next‐generation solar cell material because of its high absorption coefficient for solar radiation, suitable band gap, ability to be deposited on flexible substrate materials, and producing highly flexible and lightweight solar panels. In order to improve the performance of solar cells, a quantitative and depth‐resolved elemental analysis of photovoltaic thin films is strongly required. In this study, we determined the average concentration of the major elements, Cu, In, Ga, and Se in fabricated CIGS thin films, using inductively coupled plasma atomic emission spectrometry, X‐ray fluorescence, and electron probe microanalysis. Depth profiling results for CIGS samples using AES, XPS, magnetic sector SIMS, and time of flight SIMS were also obtained to compare their atomic concentration results. In the SIMS technique, detection of MCs+ clusters reduced possible matrix effects because of the variant concentrations of In and Ga. The reproducibility and accuracy of quantitative analysis were investigated as a function of ion sputtering energy. The compositional distributions of CIGS absorber layers as measured by MCs+–SIMS showed good agreement with those of AES and XPS. Copyright © 2014 John Wiley & Sons, Ltd.

Quantitative analyses of photovoltaic CIGS thin films via SIMS depth profiling with elemental ions and MCs+ clusters

Polycrystalline copper–indium–gallium–diselenide (CIGS) is used as an absorber in thin‐film solar cells because of its appropriate band gap and high absorption coefficient for solar radiation. Many research groups have determined the CIGS compositions related to solar cell efficiency. In this work, three different Cu(In,Ga)Se2 thin films were prepared on molybdenum back contacts deposited on soda‐lime glass substrates via a three‐stage evaporation or, alternatively, a two‐step selenized process. Surface analyses via AES, XPS, and SIMS were used to characterize the CIGS thin films and compare their depth profiles. The MCs+ clusters were detected to improve the quantification of major compositions in the CIGS thin films while suppressing the matrix effect in the SIMS depth profiles. The compositional distribution in the MCs+‐SIMS was in good agreement with the AES and XPS depth profiles. The MCs+‐SIMS results proved more quantitatively accurate than those from the elemental SIMS while comparing to ICP‐AES data. Copyright © 2014 John Wiley & Sons, Ltd.

High-quality laser cutting of stainless steel in inert gas atmosphere by ytterbium fibre and lasers

Processes of cutting stainless steel by ytterbium fibre and lasers have been experimentally compared. The cut surface roughnesses for 3- and -thick stainless steel sheets are determined. The absorption coefficient of laser radiation during cutting is measured. It is established that the power absorbed by metal during cutting by the laser exceeds that for the ytterbium laser (provided that the cutting speed remains the same). The fact that the maximum cutting speed of the laser is lower than that of the ytterbium fibre laser is explained.

Spectral diagnostics of a vapor-plasma plume produced during welding with a high-power ytterbium fiber laser

We have conducted spectroscopic studies of the welding plasma formed in the process of welding with an ytterbium fiber laser delivering output power of up to 20 kW. The influence of shielding gases (Ar, He) on different parts of the welding plume is investigated. The absorption coefficient of the laser radiation by the welding-plume plasma is estimated. Scattering of 532-nm probe radiation from particles of the condensed metal vapor within the caustic of a high-power fiber laser beam is measured. Based on the obtained results, conclusions are made on the influence of the plasma formation and metal vapor condensation on the radiation of the high-power fiber laser and the stability of the welding process.

Bremsstrahlung and Thermal Microwave Radiation from an Air Explosion

reason, once again, it is important to develop methods to monitor the atmosphere and to detect and identify dangerous objects. One promising method is to detect electromagnetic radiation in the milli- and centimeter ranges. The mechanisms of generation and the structure of a microwave signal in the case of explosions in the stratosphere and the characteristics of the radiation from contact explosions and others have been studied in [3‐6]. In the present communication, we shall examine the characteristics of the generation of an incoherent signal by nuclear explosions in the lower atmosphere. It is known that at the initial stage in a time not exceeding 1 sec the cloud from a nuclear explosion is a symmetric fireball. At this stage, the upward motion of the fireball can be neglected. The region of hot plasma is surrounded by a cold region of partial ionization created by the emission of neutrons and γ-rays. The region of partial ionization is a source of microwave Bremsstrahlung in the first 1‐20 μsec [3, 4]. The duration of this part of the signal depends strongly on the energy and type of nuclear explosion. The remaining part of the incoherent radiation lasts for about 0.1‐1 sec and is due to the radiation from the front of an expanding shock wave [4, 5]. In the present work, the results were obtained by computer modeling of six-component plasma formed by a nuclear explosion in air. A package of modeling codes was used [7]. These codes made it possible to calculate the Bremsstrahlung from charged particles in the partial ionization region and the thermal radio radiation from a shock wave front. In this package, the Runge‐Kutta method is used to solve the kinetic equations for the six components of the plasma in the group approximation; the particle concentrations, the conductivity of the air plasma, and the absorption coefficients for the microwave radiation are calculated, the radiation transfer equation is solved, and the optical thickness and radio brightness temperature of the plasma along the line of sight are calculated. Let us examine the problem of an atmospheric nuclear explosion at the altitude H = 1 km above the Earth’s surface. The positions of the source (explosion) S and the detector (radiometer) Ra and the direction of the line of sight 1 are shown in Fig. 1. For simplicity, the source, radiometer, and line of sight are located in the same plane. A dashed line marks the boundary of the fireball. The radiometer can be placed in an airplane or satellite on altitude h > H. Let h = 10 km. The ray 1 passes at impact distance p from the center of the explosion. The form and parameters of the detected radiation depend not only on the conditions chosen for the explosion but also on the orientation of the axis of the directional pattern of the radiometer. We shall confine our attention to the case where the impact distance is less than the radius of the fireball p < r fr . Then, the line of sight intersects the region of high ionization. In this case, the radiation from the shock wave and the Bremsstrahlung from the charged particles in the region of partial ionization encompassing the fireball will be detected.

Influences of properties and heating characteristics on the thermal decomposition of polymer/carbon nanotube nanocomposites

A comprehensive transport model (conductive, convective and radiative heat transfer, convective mass transport) is applied to simulate the thermal decomposition of thermoplastic polymer/carbon nanotube nanocomposites and corresponding neat polymers (poly(methylmethacrylatye), polypropylene, polystyrene). The flame retardant effectiveness of nanocomposites is confirmed and good quantitative agreement with measurements is shown. The effects of flame retardance are enhanced by increasing the intensity of the radiative heat flux and/or the sample thickness. Moreover, extensive parametric and sensitivity analyses, carried out by varying kinetic constants and polymer physical properties, indicate that activation energy, density, reaction heat and thermal conductivity exert the most significant role. Finally a crucial aspect in relation to the differences in the initial degradation behavior of neat polymers versus nanocomposites is played by the in-depth radiation absorption coefficient.

Computer study of methane adsorption by water clusters

Methane adsorption by water clusters including 50 molecules was studied by the molecular dynamics (MD) technique. The calculated frequency dependence of the real and imaginary parts of the dielectric permittivity points to the prevalence of a high-frequency mode in the spectra of these parameters after methane is adsorbed by water clusters. Such changes are also observed in the spectrum of the IR radiation absorption coefficient; however, the average value of this coefficient remains nearly the same. Methane adsorption causes a considerable increase in the reflection coefficient of the disperse water medium and the integrated power of IR radiation emission.

Testing Amorphous, Multi-component, Organic Dielectrics According to Their Electronic Spectrums and Color Charcteristics

The original methods of determining physicochemical properties (e.g. relative density, fixed carbon coking ability, viscous flow activation energy, number-average molecular weight, initial material destruction temperature) and characteristics of electronic structure (ionization potentials and electron affinity) of hydrocarbon systems were generalized. In the considered methods for testing dielectrics based on these systems named characteristics are estimated according to radiation absorption coefficients, color characteristics of substance solutions and integral oscillator strength in visible and UV spectrum region. The proved regularities are confirmed with statistical processing of data.

Terahertz free-electron laser radiation to determine water concentration in flames

The possibility of measuring the concentration of H2O molecules in flames based on the absorption of terahertz free-electron laser radiation was studied. These measurements were performed using the 177.32 cm−1 absorption line in the rotational spectrum of H2O. This line has a low intensity at room temperature, and at about 1000 K, its intensity is comparable to that of the strongest lines. The temperature dependence of the radiation absorption coefficient at a frequency of 77.32 cm−1 was studied theoretically and experimentally. It is shown that the method can be used for measurements in a sooty C2H4/O2/Ar flame, which strongly scatters visible and UV radiation.

HOURLY CALCULATION METHOD OF BUILDING ENERGY DEMAND FOR SPACE HEATING AND COOLING BASED ON STEADY-STATE HEAT BALANCE EQUATIONS

Correct evaluation of solar heat gains through fenestration into the rooms has a great impact on energy demand calculations for buildings. This article presents an hourly energy demand calculation method for heating and cooling, which considers the fact that the solar radiation flow passed through the transparent fenestration into the rooms is not adequate to the thermal energy flow. This method considers that the thermal energy flow in the rooms transformed from solar thermal radiation depends on the short-wave thermal radiation absorption coefficient of internal surfaces of the rooms. The value of short-wave thermal radiation absorption coefficient forms a considerable impact on the flow of thermal energy gains in the room. The presented method differs from others on that score that it considers additionally physical lows, according to which the solar short-wave thermal radiation energy admitted into the room is converted into the thermal energy. This hourly method enables precise calculating the hourly mean of indoor temperature and energy demand for heating and cooling of the buildings during the day.

Influence of Nitrogen Fertilizer on Ash, Organic Carbon, Phosphorus, Potassium, and Fiber of Forage Corn Intercropped by Three Cultivars of Berseem Clover as Cover Crops in Semi Arid Region of Iran

Supplementation of animal feeds with high quality needs new agriculture management, like intercropping system. In order to determine qualitative characteristics of forage corn intercropped by berseem clover cultivars in different levels of nitrogen fertilizer, an experiment was conducted in 2010 at Research Farm, Faculty of Agriculture, Islamic Azad University, Khorasgan Branch, Esfahan. A factorial layout within randomized complete block design with 3 replications was used. Cultivars were Karaj, Sacromont and Multicut, and nitrogen levels were included 0, 40 and 60 kg/ha. The nitrogen fertilizer was provided from urea source (46% pure N). Cultivar had significant effect on ash percentage, P, organic carbon of soil and soil nitrogen percentage. Nitrogen had significant influence on ash, K, organic carbon of soil, soil nitrogen percentage, light transmission, solar radiation absorption and extinction coefficient. Organic carbon of soil and soil nitrogen percentage just significantly influenced by cultivar and nitrogen interaction. In this experiment the highest ash percentage, organic carbon of plant, ENDF was obtained in forage corn intercropped by Multicut. The maximum organic carbon of soil and soil nitrogen percentage also related to forage corn and Multicut intercropping. The highest ash percentage, organic carbon, ENDF, organic carbon of soil, soil nitrogen percentage and solar radiation absorption was obtained in forage corn and Multicut intercropping.

Absorption and scattering of laser radiation by the diffusion flame of aviation kerosene

The absorption coefficient of the radiation of a repetitively pulsed Nd : YAG laser with an average output power up to 6 W and of a cw ytterbium optical fibre laser with an output power up to 3 kW was measured in the diffusion flame of aviation kerosene burning on a free surface in the atmospheric air. The absorptioncoefficient as a function of flame length, radiation power, and radiation intensity, which was varied in the ∼103 — 5×104 W cm-2 range, was obtained for two distances (1 and 2 cm) between the laser beam axis and the surface. The coefficient of radiation absorption by kerosene flame was compared with that in ethanol and kerosene — ethanol mixture flames. The radiation power scattered by a small segment of the kerosene flame irradiated by Nd : YAG laser radiation was measured as a function of longitudinal and azimuthal coordinates. An estimate was made of the total scattered radiation power.

Responses of phenological and physiological stages of spring safflower to complementary irrigation

In order to investigate impact of complementary irrigation on phenological stages, chlorophyll content, radiation absorption and extinction coefficient, as well as some aspects concerning the yield of spring safflower, a split-plot experiment based on randomized complete block design with three replication was conducted at the Ardabil Research Center For Agriculture And Natural Resources, Ardabil, Iran in 2009. Experimental treatments included irrigations (non- irrigation, irrigation at the head appearance and irrigation at the flowering stage) and safflower cultivars (Jila, native Isfahan and Pi-537636). Irrigation levels showed significant effects on flowering initiation, flowering period, seed filing period, maturing, number of head, number of seed per head, shoot dry weight, seed yield, extinction coefficient, radiation absorption and chlorophyll content. There were significant differences among cultivars in terms of head appearance, flowering, flowering period, maturing, number of head per plant, number of seed per head, shoot dry weight, seed yield per plant and seed oil content. Also, interactions between irrigation and cultivar were significant for flowering period and seed yield. The highest flowering period was observed by applying irrigation at the head appearance for the native Isfahan cultivar which caused the highest seed yield at the flowering stage. Complementary irrigation increased chlorophyll content and radiation absorption and decreased extinction coefficient at both stages compared to no irrigation. Key words : Safflower, complementary irrigation, absorption of radiation, extinction coefficient.

Experimental investigation of X-ray spectral absorption coefficients in heated Al and Ge on the Iskra-5 laser facility

We set forth the data of experimental investigation of X-ray spectral absorption coefficients in the 1.1 — 1.6 keV photon energy range for Al and Ge specimens bulk heated by soft X-ray radiation. Two experimental techniques are described: with the use of one facility channel and the heating of specimens by the X-ray radiation from a plane burnthrough target, as well as with the use of four channels and the heating by the radiation from two cylindrical targets with internal input of laser radiation. The X-ray radiation absorption coefficients were studied by way of transmission absorption spectroscopy using backlighting X-ray radiation from a point source. The results of investigation of X-ray spectral absorption coefficients on the 1s — 2p transitions in Al atoms and the 2p — 3d transitions in Ge atoms are presented.

Optical breakdown in supersonic air jet

The characteristics of a free supersonic air jet with a diameter of 10 mm and Mach numbers within 1.7–3.7 have been studied in the presence of energy supply via pulsed optical discharge generated by a periodic-pulsed mechanically-Q-switched CO2 laser. The coefficient of laser radiation absorption by optical discharge plasma in supersonic air jet has been studied and it is established that this parameter can reach 60%. It is demonstrated for the first time that a threshold density of air corresponding to sharp growth in the absorption efficiency amounts to 1.8–2 kg/m3 and is independent of the Mach number in airflow. Distributions of the gasdynamic parameters (including dynamic pressure and temperature) in supersonic air jet with energy supply via optical discharge have been determined.

Optical properties of SbI 3 single crystalline platelets

Optical parameters of platelets of crystalline antimony triiodide (SbI 3) have been evaluated using spectrogoniometric interference spectroscopy technique. Spectral characteristics of real parts of refractive indices of radiation with electric vector normal and parallel to the optical c-axis of SbI 3 crystalline platelets (i.e. n o , n e – refractive indices for ordinary and extraordinary rays) have been shown. The temperature dependences of spectra of optical parameters ( n o and absorption coefficient of radiation with electric vector normal to the optical c-axis) have been presented. The temperature dependences of fitted optical indirect allowed energy gap of SbI 3, Urbach energy and phonons energies are the main findings of the presented work. The obtained results have been compared with literature data.