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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Ultrashort Impulse Radiation from Plane Disk with Uniform Current Distribution
摘要： The problem of transient radiation from plane disk with uniform current distribution solved by Evolutionary Equation method in Time Domain. The solution for all components of electromagnetic field is received by means of Riemann function method for Klein-Gordon equation for time dependence of current in form of Heaviside function. Using Duhamel integral the generalization of the solution for arbitrary time dependence is obtained. Amplitude and energy characteristics of radiated field are investigated for different observation distances and angles as well as time shapes of exciting current. The solution for an arbitrary time dependence of plane disk radiation is used to investigate the applicability of impulse radiation in radio communication and radar problems.
关键词： plane disk radiation,impulse communication,time domain,ultrawideband ultrashort pulse (UWB-SP),Duhamel integral,electromagnetic missile
更新于2025-09-23 15:21:21
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[IEEE 2018 7th International Conference on Computer and Communication Engineering (ICCCE) - Kuala Lumpur, Malaysia (2018.9.19-2018.9.20)] 2018 7th International Conference on Computer and Communication Engineering (ICCCE) - CPW-Fed Patch Antenna with Reflecting Metasurface Covering for WLAN and WiMAX Applications
摘要： A coplanar waveguide (CPW)-fed multiband patch antenna with the integration reflecting metasurface covering has been designed and performance characteristics are critically analyzed. The proposed low profile antenna can offers the wireless communications services for WLAN and WiMAX applications. The rectangular shaped patch antenna consists of pair of C-, L- and splitted-T shape slotted radiator, and 2D reflective metasurface covering at the back of patch which is separated by dielectric layer of substrate. The details of the antenna design structure and performance criteria are discussed through numerical simulation using full-wave electromagnetic simulator. The simulation results shows that by employing the reflecting metasurface covering, the -10dB impedance bandwidth has considerably increased than the typical CPW-fed patch antenna: from 440 MHz to 570 MHz (29%), 390 MHz to 480 MHz (23%) and 900 MHz to 1060 MHz (18%) for three different operating bands centered at 2.5, 3.5 and 5.5 GHz respectively. The simulated result shows the antenna with RMC integration achieves peak gain of 6.56 dBi, 6.43 dBi and 6.97 dBi with average gain of 6.45 dBi, 6.27 dBi and 6.82 dBi at three operating bands respectively which are higher than the typical patch antenna.
关键词： patch antenna,low-profile,reflecting metasurface covering,CPW-fed,WiMAX/WLAN Applications,radiation pattern improvement
更新于2025-09-23 15:21:21
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Proximal remote sensing of tree physiology at northern treeline: Do late-season changes in the photochemical reflectance index (PRI) respond to climate or photoperiod?
摘要： Relatively little is known of how the world's largest vegetation transition zone – the Forest Tundra Ecotone (FTE) – is responding to climate change. Newly available, satellite-derived time-series of the photochemical reflectance index (PRI) across North America and Europe could provide new insights into the physiological response of evergreen trees to climate change by tracking changes in foliar pigment pools that have been linked to photosynthetic phenology. However, before implementing these data for such purpose at these evergreen dominated systems, it is important to increase our understanding of the fine scale mechanisms driving the connection between PRI and environmental conditions. The goal of this study is thus to gain a more mechanistic understanding of which environmental factors drive changes in PRI during late-season phenological transitions at the FTE – including factors that are susceptible to climate change (i.e., air- and soil-temperatures), and those that are not (photoperiod). We hypothesized that late-season phenological changes in foliar pigment pools captured by PRI are largely driven by photoperiod as opposed to less predictable drivers such as air temperature, complicating the utility of PRI time-series for understanding climate change effects on the FTE. Ground-based, time-series of PRI were acquired from individual trees in combination with meteorological variables and photoperiod information at six FTE sites in Alaska. A linear mixed-effects modeling approach was used to determine the significance (α = 0.001) and effect size (i.e., standardized slope b*) of environmental factors on late-seasonal changes in the PRI signal. Our results indicate that photoperiod had the strongest, significant effect on late-season changes in PRI (b* = 0.08, p < 0.001), but environmental variables susceptible to climate change were also significant (i.e., daily mean solar radiation (b* = ?0.03, p < 0.001) and daily mean soil temperature (b* = 0.02, p < 0.001)). These results suggest that interpreting PRI time-series of late-season phenological transitions may indeed facilitate our understanding of how northern treeline responds to climate change.
关键词： PRI,Climate change,Photoperiod,Photosynthetic phenology,MODIS,Solar radiation,Northern treeline,Forest Tundra Ecotone
更新于2025-09-23 15:21:21
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Directional Statistics in Solar Potential of Rooftops at Three Different Neighborhoods of a Medium Size City
摘要： The utilization of solar energy is one of the best effective methods to combat the climate change. The estimation of solar potential in urban areas can vary depending on the urban morphology. This paper performs a directional statistical analysis of the distribution of the monthly solar potential of rooftops in Cáceres city, related to the orientation of the rooftops in different neighborhoods. The orientation values of the roofs will be treated as a directional data and the radiation values as a linear data. The circular graphics representing the orientation data is a suitable representation of the distribution of the buildings being related with the urban framework.
关键词： rooftop orientation,directional data,solar potential,solar radiation
更新于2025-09-23 15:21:21
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Study of materials structure physics of isomorphic LiNbO <sub/>3</sub> and LiTaO <sub/>3</sub> ferroelectrics by synchrotron radiation X-ray diffraction
摘要： Electron charge density studies of stoichiometric LiNbO3 and LiTaO3 ferroelectrics have been carried out by analyzing the synchrotron radiation X-ray powder di?raction data using a combination of the Rietveld and maximum entropy methods. The clear relationships between the Nb(Ta)–O bond length, the electron charge density on the Nb(Ta)–O bond, and the phase transition temperature TC are revealed for isomorphic structures. Nb(Ta)–O bonding plays an important role in the elevation of TC. The TC in LiNbO3 being higher than that in LiTaO3 is attributed to the larger lattice distortion of the Nb–O oxygen octahedron in LiNbO3. The validity of estimating TC for LiNbO3 family crystals from the degree of lattice distortion in the ferroelectric structure is discussed.
关键词： ferroelectric,LiTaO3,X-ray diffraction,synchrotron radiation,LiNbO3,phase transition temperature,electron charge density
更新于2025-09-23 15:21:21
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[Advances in Intelligent Systems and Computing] Emerging Trends in Expert Applications and Security Volume 841 (Proceedings of ICETEAS 2018) || Bone Fracture Detection from X-Ray Image of Human Fingers Using Image Processing
摘要： Orthopaedics deals with surgery and treatment of the human musculoskeletal system. It also involves degenerative conditions, trauma, sports injury, tumors, and congenital issues. Orthopaedic doctors are always interested to take an X-Ray image of injured parts of patient’s body for better diagnosis. In an X-Ray imaging, electronic radiation is passed in the human body for capturing bone images. After X-Ray image retrieval, a doctor examines X-Ray image manually. It is not that easy to detect most of the major diseases/issues related with the bones just by visualizing an X-Ray image, although in some cases, it is possible, but till that time, diseases may reached towards next or serious stage for example bone fracture. The main problem with X-Ray images is that they may be blurred, out of focus, improperly bright and noisy, which makes examination more dif?cult. One of the solutions to all above problems can be computerized image processing of human being’s X-Ray images. In this research paper, we have presented an algorithm to detect bone fracture from X-Ray images of human ?ngers using image processing.
关键词： Trauma,Orthopaedics,Image processing,Musculoskeletal,X-Ray,Electronic radiation
更新于2025-09-23 15:21:21
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Design and performance analysis of volumetric solar receiver based on porous foam ceramics
摘要： Volumetric solar receiver is one of three main categories of solar receivers. It has great application prospect due to the simple structure, high thermal efficiency, and the air exit temperature can reach above more than 800℃. The porous material is used instead of tube as absorber in volumetric solar receiver to heat the working medium, and the incident radiation can be absorbed gradually from outside to inside. In this study, an one-dimensional volumetric solar receiver calculating model based on porous foam ceramics is constructed. The temperature distributions and radiation absorption efficiencies at different conditions are analyzed, and a kind of secondary heating volumetric solar receiver is put forward to further improve its thermal efficiency. The results show that both the outlet air temperature and the depth for the temperature of air and ceramic solid reaching to stability decreases apparently with decrease of porosity of ceramic foam, but the temperature of front surface of the receiver increases gradually. With decrease of porous ceramic diameter, the air exit temperature decreases gradually, and the depth for the temperature of air and ceramic solid reaching to stability is decreasing, while, the diameter change has little effect on the temperature of front surface. The air exit temperature increases apparently with decrease of air flow rate and rise of inlet air temperature, and increases with increase of incident radiation intensity. The energy absorbing efficiency is decreasing with decrease of air flow rate and rise of inlet air temperature, and decreases with increase of incident radiation intensity. The presented secondary heating type of receiver can improve the energy absorbing efficiency, although the feasibility and economy of this consideration need further verification in future.
关键词： volumetric solar receiver,porous foam ceramics,temperature distribution,radiation absorption efficiency,secondary heating
更新于2025-09-23 15:21:21
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Monitoring investigation of solar diffuse fraction in Taiwan
摘要： Global solar radiation, which passes through the atmosphere and arrives on earth’s ground, is composed of two constituents, that is, beam and diffuse radiation. It is agreed that the beam radiation is the only effective part for use of solar energy in concentrating either photovoltaic or solar thermal energy application, which concentrates the incident sunlight to attain high performance of either electrical power or high-temperature thermal energy generation, respectively. Information of beam radiation quantity incident upon an absorbing surface is, thus, a prerequisite for the performance evaluation of concentrating optic device. However, very few data of diffuse fraction, defined as the ratio of diffuse radiation to global radiation, is available in Taiwan. A long-time monitoring investigation in the main island (Taiwan proper) and one offshore islet (Penghu) were conducted over recent years. It was found that the annually averaged diffuse fractions, calculated with the time duration from sunrise to sunset, in the east (Taitung) and west (Tainan) sides of the main island were about 0.49 and 0.53, respectively, while about 0.50 in the offshore islet (Penghu). Seasonal variations due to geographical/topographical effects on diffuse fraction are also reported and discussed. It is found that Northeast Monsoon has remarkable effects on increment of diffuse fraction in Taitung and Penghu, while insignificant effect in Tainan.
关键词： Solar diffuse fraction,Concentrating solar energy application,Solar energy,Solar diffuse radiation
更新于2025-09-23 15:21:21
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A dose monitoring system for dental radiography
摘要： Purpose: The current study investigates the feasibility of a platform for a nationwide dose monitoring system for dental radiography. The essential elements for an unerring system are also assessed. Materials and Methods: An intraoral radiographic machine with 14 X-ray generators and five sensors, 45 panoramic radiographic machines, and 23 cone-beam computed tomography (CBCT) models used in Korean dental clinics were surveyed to investigate the type of dose report. A main server for storing the dose data from each radiographic machine was prepared. The dose report transfer pathways from the radiographic machine to the main sever were constructed. An effective dose calculation method was created based on the machine specifications and the exposure parameters of three intraoral radiographic machines, five panoramic radiographic machines, and four CBCTs. A viewing system was developed for both dentists and patients to view the calculated effective dose. Each procedure and the main server were integrated into one system. results: The dose data from each type of radiographic machine was successfully transferred to the main server and converted into an effective dose. The effective dose stored in the main server is automatically connected to a viewing program for dentist and patient access. conclusion: A patient radiation dose monitoring system is feasible for dental clinics. Future research in cooperation with clinicians, industry, and radiologists is needed to ensure format convertibility for an efficient dose monitoring system to monitor unexpected radiation dose. (Imaging Sci Dent 2016; 46: 103-8)
关键词： Radiography,Protection,Radiation monitoring,Radiation,Dental,Radiation Dosage
更新于2025-09-23 15:21:01
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Evaluation of a Ultraviolet B Light Emitting Diode (LED) for Producing Vitamin D <sub/>3</sub> in Human Skin
摘要： Aim: A commercially available light emitting diode (LED) that transmitted narrow band ultraviolet B (UVB) radiation was evaluated for its efficacy and efficiency to produce vitamin D3 in human skin. Materials and Methods: Human skin samples were obtained from surgical procedures. The LED had peak emission wavelength of 295 nm. Skin samples were exposed to the UVB-LED for varying times and then were analyzed by high-pressure liquid chromatography (HPLC) to determine the vitamin D3 content. Results: There was a statistically significant time- and dose- dependent increase in the percent of 7-dehydrocholesterol that was converted to vitamin D3 in the skin type II samples; 1.3%±0.5, 2.3%±0.6 and 4.5%±1.67 after exposure to 0.75 (11.7 mJ/cm2), 1.5 (23.4 mJ/cm2) and 3 (46.8 mJ/cm2) minimal erythemal doses (MEDs), respectively. Conclusion: The UVB-LED was effective and efficient in generating vitamin D3 in human skin, in vitro. The amount of vitamin D3 production increased in a dose-dependent fashion with increased UVB energy. UVB-LEDs can be developed for devices that can efficiently produce vitamin D3 in human skin.
关键词： vitamin D3,human skin,ultraviolet B radiation,Previtamin D3,ultraviolet radiation light emitting diode (LED)
更新于2025-09-23 15:21:01