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[IEEE 2019 Second Balkan Junior Conference on Lighting (Balkan Light Junior) - Plovdiv, Bulgaria (2019.9.19-2019.9.21)] 2019 Second Balkan Junior Conference on Lighting (Balkan Light Junior) - Investigating the Influence of Environmental and Design Parameters on the Thermal Regime of a LED Lamp
摘要： The increase of the LED’s temperature above a certain threshold decreases significantly their live expectancy. Therefore, it is important to investigate LEDs’ thermal regime during exploitation. The influence of the construction and the environment parameters on the thermal regime of LED lamp was investigated in this paper. The study was done with a specially developed software, based on a model, describing the thermal regime of LED lamps. Next, a methodology for the research has been developed and a simulation study was carried out. The results of this investigation are represented graphically.
关键词： simulation,model,LED lamp,investigation
更新于2025-09-11 14:15:04
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Preliminary experiment on a novel photovoltaic-thermoelectric system in summer
摘要： Compared with the PV electricity generation, the hybrid Photovoltaic-thermoelectric (PV-TE) can generate more electricity due to its ability to utilize a wider solar spectrum than the PV. The PV-TE employing micro-channel heat pipe array is a novel PV-TE-MCHP system which is capable of providing high cost performance compared to the traditional PV-TE due to the use of the micro-channel heat pipe array. In this paper, the experimental investigation of this new system in summer in Hefei city, China is presented for the first time. The comparison between this system and PV alone is made, and the details are presented. The power output, PV temperature, and the hot and cold sides temperatures of the TE are all tested. The results show that the novel system has a higher electrical output than the PV alone. The electrical efficiencies of this system during the test are all higher than 14.0% and the PV temperatures are about 20 (cid:1)C higher than the ambient temperature. Based on this experiment, the results also verify the feasibility of the new system, which will give a valuable reference for the PV-TE design.
关键词： Micro-channel heat pipe,Power output,Experimental investigation,Photovoltaic-thermoelectric
更新于2025-09-11 14:15:04
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Numerical Study of Amplification of Subnanosecond Radiation Pulses in the Gas Amplifier of the THL-100 Laser System
摘要： Methods for increasing the energy characteristics of the THL-100 hybrid laser system are investigated by numerical modeling. The influence of the input laser radiation energy and system of mirrors on the energy and maximal laser radiation intensity in the amplifier is investigated. The systems of amplifier mirrors in which the number of passes of the active medium changed from Nm = 27 to 39 are considered. It is shown that at Nm =27, an increase in the pump energy of the amplifier from 270 to 400 J allows the output radiation energy to be increased by a factor of 2.6 (to 8.34 J) with a maximal radiation intensity in the amplifier no more than 7 GW?cm–2. Pulse compression to an initial duration of 50 fs will allow the average output power of the THL-100 system to be increased up to 160 TW.
关键词： amplification of subnanosecond pulses,numerical investigation,THL-100 laser system
更新于2025-09-11 14:15:04
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First-principle study of the polarization, atomic displacements and electronic structure of angular-deformed barium titanate
摘要： The in?uence of β and γ angular deformation on polarization, TieO(3) bond distances, atomic displacements, number of states, valence charge distributions and valance charge asymmetry of barium titanate (BaTiO3) has been investigated using local density approximation. The results show that for all angles of 89.5°≤ β&γ ≤ 90.5°, there is a clear correlation between polarization, TieO(3) bond distances, atomic displacements and number of 2 orbital. For the case of γ-deformation the values of polarization and the other parameters are approximately constant in the range of 89.8°≤γ ≤ 90.2° and an abnormal behavior is observed at γ = 89.6°. In this case valence charge asymmetry of Ti 3d orbital has a direct relation with the polarization and atomic displacements of Ti atoms for the whole region of γ, especially at γ = 89.6°. In the case of β-deformation, an approximately symmetrical behavior versus β variations is observed for all above-mentioned parameters. In this case, a direct relation between valence charge asymmetry of Ti 3d orbital, polarization and atomic displacements is remarkable only for β > 89.8° and the region of β < 89.8° does not reveal such a direct relation.
关键词： Electronic investigation,Angular deformation,DFT,Atomic displacements,Barium titanate
更新于2025-09-11 14:15:04
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Structural Optimization For Accurate Characterization Of Urban Areas In Hyperspectral Datasets
摘要： Accurately estimating the urbanization process is a key-factor for the actual implementation of the sustainable development goals identified by transnational institutions and agencies. In order to retrieve precise characterization of the anthropogenic extents and a sound human-environment interaction assessment, the analysis of Earth observations (EOs) plays a crucial role. Especially, the use of nonlinear spectral investigation can improve the description of geometrically and morphologically complex scenes, so that anthropogenic settlements and dynamics can be properly outlined. In this paper, we propose a novel method for directly assessing the distribution of materials and elements in hyperspectral images by means of a structural optimization approach. Experimental results show how the proposed approach is able to deliver accurate and reliable characterization of urban materials and extents.
关键词： nonlinear spectral investigation,structural optimization,hyperspectral imaging,urban materials characterization
更新于2025-09-10 09:29:36
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Gunshot residue on dark materials: a comparison between infrared photography and the use of an alternative light source
摘要： The pattern of gunshot residue (GSR) includes important information about muzzle-target distance since a larger GSR distribution diameter indicates a larger shooting distance. GSR may not be visible to the naked eye when, for example, it is located on dark textiles. In such cases, further procedures need to be performed in order to visualize the pattern of GSR. Besides chemical procedures, an alternative light source or infrared photography can be utilized for non-destructive GSR visualization. In the work presented, these two techniques are compared based on shooting experiments using 26 different dark textiles. Within the range of the alternative light source, the use of a 440-nm light in combination with an orange-colored filter led to the best visualization of GSR in the form of fluorescent particles. Infrared photography, on the other hand, visualized GSR as dark particles, whereas—ideally—the dark textile reflected the infrared light and appeared bright. The comparison of both techniques revealed that the GSR distribution visualized by infrared photography was not identical to the GSR distribution visualized with 440-nm illumination in combination with an orange-colored filter. We concluded that infrared photography visualizes the inner powder soot zone, whereas illumination at 440 nm leads to fluorescence of the outer powder soot zone, which can be visualized using an orange-colored filter. Knowledge of this difference in visualization of the two powder soot zones is important for forensic practitioners assessing firing distances. In the literature, however, this difference is not noted as clearly.
关键词： Gunshot residue GSR,Alternative light source,Forensic light source,Crime scene investigation,Shooting distance,Infrared photography
更新于2025-09-10 09:29:36
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On the Influence of Collector Size on the Solar Chimneys Performance
摘要： Performance of solar chimney power plant system is highly influenced by the design geometries. The collector size is logically enhances the solar chimney performance, but the trend of enhancement is not yet investigated. In the present work, experimental and numerical investigations have been carried out to ascertain, in terms of qualitative and quantitative evaluation, the effect of the collector diameter. Daily thermal efficiency has been determined at four different collector diameter. Two different collector diameters, 3.0 and 6.0 m, have been investigated experimentally, and then scaled up, to 9.0 and 12.0 m, by numerical simulation using ANSYS-FLUENT?15 software. Results demonstrated that collector diameter has effectively influenced the system performance. Larger collector diameter imposed increase in the velocity, temperature and the daily average thermal efficiency of the system. From the experimental results, increasing the collector diameter from 3.0 to 6.0 m has increased the daily average thermal efficiency of the collector from 9.81 to 12.8. Simulation results at 800 W/m2 irradiation revealed that the velocity in the chimney have increased from 1.66 m/s at 3.0 m collector diameter to 2.34, 2.47 and 2.63 m/s for 6.0, 9.0 and 12.0 m collector diameters, respectively.
关键词： experimental investigation,thermal efficiency,solar chimney,numerical simulation,collector diameter
更新于2025-09-10 09:29:36
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Multi-objective Optimization of Rotary Ultrasonic Machining Parameters for Quartz Glass Using Taguchi-Grey Relational Analysis (GRA)
摘要： Rotary ultrasonic machining has the capability to process the materials which are very hard, brittle and electrically non-conductive, with efficiency and cost-effectiveness. The current investigation is focused on the use of Taguchi-Grey relational analysis to improve the machining performance of Rotary ultrasonically machined quartz glass. Ideal machining parameters were calculated by grey relational grade calculated in grey relational analysis which was designed for simultaneous optimization of material removal rate and surface roughness. The rotary ultrasonic machining parameters setting with tool rotational speed of 5000 rpm, tool feedrate of 0.75 mm/min, and ultrasonic power of 55% were found to have the highest grey relation grade resulting in the high material removal rate and low surface roughness of the processed material. The tool feed rate was found to be the most critical parameter followed by ultrasonic power and tool rotational speed on the rotary ultrasonic machining characteristics. Confirmatory experiments were also executed to authenticate the forecasted results obtained from the Taguchi-Grey relational analysis. Furthermore, the microstructural investigation was carried out to comprehend the mechanism of material removal in the rotary ultrasonic machining of quartz glass at optimum parameter setting. It was found that the material was removed in the brittle mode and abrasion during the machining at optimum parameter setting. The sharp cutting edges of the diamond grits have caused the abrasive wear and brittle fracture of the quartz material. The interlinking of the cracks results in the pullout of the grains and consequently deeper grooves are formed on the machined surface.
关键词： RUM,Fused silica,Taguchi method,Machining performance,Grey relational analysis,Microstructural investigation
更新于2025-09-09 09:28:46