International Journal of Photoenergy The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Investigating the Effect of Thermal Annealing Process on the Photovoltaic Performance of the Graphene-Silicon Solar Cell Wed, 28 Jan 2015 14:16:42 +0000 Graphene-silicon (Gr-Si) Schottky solar cell has attracted much attention recently as promising candidate for low-cost photovoltaic application. For the fabrication of Gr-Si solar cell, the Gr film is usually transferred onto the Si substrate by wet transfer process. However, the impurities induced by this process at the graphene/silicon (Gr/Si) interface, such as H2O and O2, degrade the photovoltaic performance of the Gr-Si solar cell. We found that the thermal annealing process can effectively improve the photovoltaic performance of the Gr-Si solar cell by removing these impurities at the Gr/Si interface. More interestingly, the photovoltaic performance of the Gr-Si solar cell can be improved, furthermore, when exposed to air environment after the thermal annealing process. Through investigating the characteristics of the Gr-Si solar cell and the properties of the Gr film (carrier density and sheet resistance), we point out that this phenomenon is caused by the natural doping effect of the Gr film. Lifei Yang, Xiaolei Wu, Xin Shen, Xuegong Yu, and Deren Yang Copyright © 2015 Lifei Yang et al. All rights reserved. Solar Energy and Clean Energy: Trends and Developments 2014 Wed, 28 Jan 2015 08:09:08 +0000 Ching-Song Jwo, Ho Chang, Chao-Rong Chen, Yen-Lin Chen, and Mohammad Yusri Hassan Copyright © 2015 Ching-Song Jwo et al. All rights reserved. Enhanced Light Trapping in Thin Film Solar Cells Using a Plasmonic Fishnet Structure Wed, 28 Jan 2015 07:43:51 +0000 Incorporating plasmonic structures into the back spacer layer of thin film solar cells (TFSCs) is an efficient way to improve their performance. The fishnet structure is used to enhance light trapping. Unlike other previously suggested discrete plasmonic particles, the fishnet is an electrically connected wire mesh that does not result in light field localization, which leads to high absorption losses. The design was verified experimentally. A silver fishnet structure was fabricated using electron beam lithography (EBL) and thermal evaporation. The final fabricated structure optically resembles a TFSC. The results predicted by numerical simulations were reproduced experimentally on a fabricated sample. We show that light absorption in the a-Si absorber layer is enhanced by a factor of 10.6 at the design wavelength of 690 nm due to the presence of the fishnet structure. Furthermore, the total absorption over all wavelengths was increased by a factor of 3.2. The short-circuit current of the TFSC was increased by 30% as a result of including the fishnet. Sayan Seal, Vinay Budhraja, Liming Ji, and Vasundara V. Varadan Copyright © 2015 Sayan Seal et al. All rights reserved. The Application Study in Solar Energy Technology for Highway Service Area: A Case Study of West Lushan Highway Low-Carbon Service Area in China Tue, 27 Jan 2015 08:39:03 +0000 A lot of research works have been made concerning highway service area or solar technology and acquired great achievements. However, unfortunately, few works have been made combining the two topics together of highway service areas and solar energy saving to make a systemic research on solar technology application for highway service area. In this paper, taking West Lushan highway low-carbon service area in Jiangxi Province of China as the case study, the advantages, technical principles, and application methods of solar energy technology for highway service area including solar photoelectric technology and solar water heating technology were discussed based on the analysis of characteristics of highway low-carbon service area; the system types, operation mode, and installing tilt angle of the two kinds of solar systems suitable for highway service areas were confirmed. It was proved that the reduction of the cost by electricity savings of solar system was huge. Taking the investment of the solar systems into account, the payback period of solar photoelectric systems and solar water heating systems was calculated. The economic effect of the solar systems in West Lushan highway service area during the effective operation periods was also calculated and proved very considerable. Xiaochun Qin, Yi Shen, and Shegang Shao Copyright © 2015 Xiaochun Qin et al. All rights reserved. Solubility Characteristics and Slow-Release Mechanism of Nitrogen from Organic-Inorganic Compound Coated Urea Thu, 22 Jan 2015 12:13:37 +0000 A soil incubation method was used to investigate the solubility characteristics and slow-release mechanism of organic-inorganic compound coated urea at temperature of 10, 20, and 30°C. The membrane microstructure with and without incubation was tested via scanning electron microscopy (SEM). Slow release of nitrogen (N) from different inorganic minerals was analysed by the activation energy from the nutrient solubility system. The rate of nitrogen solubility increased with temperature increasing. The first-order reaction kinetic equation described the solubility process of coated urea. The rate constant also increased with temperature increasing. Moreover, the SEM images showed that the microstructure of the coating layer changed into a flocculent structure and the number of tiny pores and holes on the membrane surface increased significantly with temperature increasing, which increased N solubility rate. The Arrhenius equation indicated that activation energy was closely related to during the solubility process; the activation energy was reduced with rising, which resulted in N solubility rate increasing. Overall, the N solubility rate of coated urea was affected by temperature. Hongtao Zou, Yao Ling, Xiuli Dang, Na Yu, YuLing Zhang, YuLong Zhang, and Jianghui Dong Copyright © 2015 Hongtao Zou et al. All rights reserved. Ultraviolet Radiation Emissions and Illuminance in Different Brands of Compact Fluorescent Lamps Thu, 22 Jan 2015 11:23:06 +0000 Introduction. Replacing incandescent lamps with compact fluorescent lamps (CFLs), which are three to six times more efficient, is one of the easiest methods to achieve energy efficiency. The present study aimed to evaluate relationships between UV emissions radiated and illuminance CFLs. Material and Methods. This pilot study was conducted on 16 single envelope CFLs. The illuminance and UV irradiance of various types of CFLs are measured on a three-meter long optical bench, using a calibrated lux meter and UV meter, and measurement was done in 10, 25, 50, 100, 150, and 200 cm, in three angles, including 0°, 45°, and 90°, at the ages of 0, 100, and 2000 hours. Result. UVC irradiance was not observed at the distance of 10 cm in all of lamps. The lowest value of UVB irradiance was recorded in Pars Khazar lamp, while the highest value was recorded in Etehad lamps. UVR values measured at different times showed negligible differences; the highest asset value was detected in zero times. One way ANOVA indicated that relationships between UVA irradiance and illuminance were significant (). Conclusion. UVB irradiance in most of the lamp in 10 and 25 cm was more than occupational exposure and UVA except for the fact that Pars Khazar 60 watts and Nama Noor 60 watts were less than occupational exposure. Shahram Safari, Sina Eshraghi Dehkordy, Meghdad Kazemi, Habibollah Dehghan, and Behzad Mahaki Copyright © 2015 Shahram Safari et al. All rights reserved. Improving Efficiency of Evaporated Cu2ZnSnS4 Thin Film Solar Cells by a Thin Ag Intermediate Layer between Absorber and Back Contact Thu, 22 Jan 2015 09:30:51 +0000 A 20 nm Ag coating on Mo back contact was adopted to improve the back contact of evaporated Cu2ZnSnS4 (CZTS) solar cells. The Ag layer helped reduce the thickness of MoS2 which improves fill factor (FF) significantly; additionally, it reduced secondary phases ZnS and SnS2−x, which may help carrier transport; it was also involved in the doping of the absorber layer, which compensated the intrinsic p-type doping and therefore drags down the doping level. The doping involvement may enlarge the depletion region and improve lifetime of the absorber, which led to enhancing open circuit voltage (), short circuit current density (), and efficiency significantly. However, it degrades the crystallinity of the material slightly. Hongtao Cui, Chang-Yeh Lee, Wei Li, Xiaolei Liu, Xiaoming Wen, and Xiaojing Hao Copyright © 2015 Hongtao Cui et al. All rights reserved. Matlab-Based Modeling and Simulations to Study the Performance of Different MPPT Techniques Used for Photovoltaic Systems under Partially Shaded Conditions Mon, 19 Jan 2015 09:30:14 +0000 A pulse-width-modulator- (PWM-) based sliding mode controller is developed to study the effects of partial shade, temperature, and insolation on the performance of maximum power point tracking (MPPT) used in photovoltaic (PV) systems. Under partially shaded conditions and temperature, PV array characteristics become more complex, with multiple power-voltage maxima. MPPT is an automatic control technique to adjust power interfaces and deliver power for a diverse range of insolation values, temperatures, and partially shaded modules. The PV system is tested using two conventional algorithms: the Perturb and Observe (P&O) algorithm and the Incremental Conductance (IncCond) algorithm, which are simple to implement for a PV array. The proposed method applied a model to simulate the performance of the PV system for solar energy usage, which is compared to the conventional methods under nonuniform insolation improving the PV system utilization efficiency and allowing optimization of the system performance. The PWM-based sliding mode controller successfully overcomes the issues presented by nonuniform conditions and tracks the global MPP. In this paper, the PV system consists of a solar module under shade connected to a boost converter that is controlled by three different algorithms and is generated using Matlab/Simulink. Jehun Hahm, Jaeho Baek, Hyoseok Kang, Heejin Lee, and Mignon Park Copyright © 2015 Jehun Hahm et al. All rights reserved. Luminance Conversion Property of Er and Yb Doped KZnF3 Nanocrystal Synthesized by Hydrothermal Method Mon, 12 Jan 2015 14:03:58 +0000 In order to make full use of exposure energy, one feasible way is to modify the luminance of crystal by rare earth doping technique. KZnF3:Er3+ and KZnF3:Er3+/Yb3+ nanocrystals of uniform cuboid perovskite type morphology, with average diameter of 130 nm, has been synthesized by hydrothermal method. When Yb3+ ions were codoped with Er3+, absorption peak at 970 nm has been heightened and widened, and the photon absorption cross section increased. The common xenon lamp exposure cannot initiate obvious nonlinear phenomenon of the doped Er3+ and Yb3+, and exposing at 245 nm only excites the fluorescence around 395 nm. Contrarily, under high power IR exposure at 980 nm, obvious upconversion photoluminescence (PL) has been observed due to the two-photon process. The PL mechanism of the doped Er3+ ion in KZnF3:Er3+/Yb3+ nanocrystals is confirmed. Furthermore, Yb3+ codoped as sensitizer has modified the PL intensity of Er3+ from green light range to red range, and the primary channel is changed from 4S3/2(Er3+) → 4I15/2(Er3+) of only Er3+ doped KZnF3 nanocrystal to 4F9/2(Er3+) → 4I15/2(Er3+) of Er3+/Yb3+ codoped sample. With exposure energy increasing, such primary transition channel after two-photon excitation is unchanged. Weidong Lai, Xinzheng Li, Lu Han, Huiqing Liu, Yingjuan Chen, Pingguang Duan, and Xiaowei Li Copyright © 2015 Weidong Lai et al. All rights reserved. A Low Cost Shading Analyzer and Site Evaluator Design to Determine Solar Power System Installation Area Sun, 11 Jan 2015 07:04:36 +0000 Shading analyzer systems are necessary for selecting the most suitable installation site to sustain enough solar power. Afterwards, changes in solar data throughout the year must be evaluated along with the identification of obstructions surrounding the installation site in order to analyze shading effects on productivity of the solar power system. In this study, the shading analysis tools are introduced briefly, and a new and different device is developed and explained to analyze shading effect of the environmental obstruction on the site on which the solar power system will be established. Thus, exposure duration of the PV panels to the sunlight can be measured effectively. The device is explained with an application on the installation area selected as a pilot site, Denizli, in Turkey. Selami Kesler, Sinan Kivrak, Hilmi Gurleyen, Furkan Dincer, Saban Yilmaz, and Hasan Riza Ozcalik Copyright © 2015 Selami Kesler et al. All rights reserved. Influence of Secondary Phases in Kesterite-Cu2ZnSnS4 Absorber Material Based on the First Principles Calculation Tue, 06 Jan 2015 06:46:36 +0000 The influence of secondary phases of ZnS and Cu2SnS3 (CTS) in Cu2ZnSnS4 (CZTS) absorber material has been studied by calculating the band offsets at the CTS/CZTS/ZnS multilayer heterojunction interfaces on the basis of the first principles band structure calculation. The ZnS/CZTS heterointerface is of type I and since ZnS has a larger band gap than that of CZTS, the ZnS phase in CZTS is predicted to be resistive barriers for carriers. The CTS/CZTS heterointerface is of type I; that is, the band gap of CTS is located within the band gap of CZTS. Therefore, the CTS phase will act as a recombination site in CZTS. Wujisiguleng Bao and Masaya Ichimura Copyright © 2015 Wujisiguleng Bao and Masaya Ichimura. All rights reserved. Distribution of Energy Density and Optimization on the Surface of the Receiver for Parabolic Trough Solar Concentrator Mon, 05 Jan 2015 14:16:09 +0000 The geometrical optics model about the offset effect of solar rays by the thickness of concentrating mirror and the diametric solar model were established. The radiant flux density on the surface of the receiver for parabolic trough solar concentrator was obtained by numerical calculation with the established models. Charge-coupled device (CCD) was used for testing gray image on the surface of the receiver for parabolic trough solar concentrator. The image was analyzed by Matlab and the radiant flux density on the surface of the receiver for parabolic trough solar concentrator was achieved. It was found that the result of the theory is consistent with that of the experiment, and the relative deviation on the focal length width was 8.7%. The geometrical structure of receiver based on parabolic trough solar concentrator was optimized, a new parabolic receiver has been proposed, and it has been shown that the optimized geometrical structure of receiver was beneficial to improve the working performance of the entire system. Fei Chen, Ming Li, and Peng Zhang Copyright © 2015 Fei Chen et al. All rights reserved. Novel Photomedicine Wed, 31 Dec 2014 13:40:57 +0000 Victor Loschenov, Rudolf Steiner, Alexander Potapov, and Alexander Douplik Copyright © 2014 Victor Loschenov et al. All rights reserved. Solar Energy Conversion by Nanostructured TiO2 Mon, 22 Dec 2014 11:51:38 +0000 Jia Hong Pan, Detlef W. Bahnemann, Qing Wang, Chuanyi Wang, and Xiwang Zhang Copyright © 2014 Jia Hong Pan et al. All rights reserved. Photovoltaic Materials and Devices 2014 Mon, 22 Dec 2014 09:35:41 +0000 Bhushan Sopori, Peter Rupnowski, Sudhakar Shet, and Prakash Basnyat Copyright © 2014 Bhushan Sopori et al. All rights reserved. Solar Energy and PV Systems Mon, 22 Dec 2014 09:29:26 +0000 Ismail H. Altas and Adel M. Sharaf Copyright © 2014 Ismail H. Altas and Adel M. Sharaf. All rights reserved. Study on Mitigation Method of Solder Corrosion for Crystalline Silicon Photovoltaic Modules Mon, 22 Dec 2014 08:49:28 +0000 The corrosion of 62Sn36Pb2Ag solder connections poses serious difficulties for outdoor-exposed photovoltaic (PV) modules, as connection degradation contributes to the increase in series resistance () of PV modules. In this study, we investigated a corrosion mitigation method based on the corrosion mechanism. The effect of added sacrificial metal on the reliability of PV modules was evaluated using the oxidation-reduction (redox) reaction under damp heat (DH) conditions. Experimental results after exposure to DH show that the main reason for the decrease in power was a drop in the module’s fill factor. This drop was attributed to the increase of . The drop in output power of the PV module without added sacrificial metal is greater than that of the sample with sacrificial metal. Electroluminescence and current-voltage mapping analysis also show that the PV module with sacrificial metal experienced less degradation than the sample without sacrificial metal. Ju-Hee Kim, Jongsung Park, Donghwan Kim, and Nochang Park Copyright © 2014 Ju-Hee Kim et al. All rights reserved. Review of Polymer, Dye-Sensitized, and Hybrid Solar Cells Sun, 14 Dec 2014 00:11:06 +0000 The combination of inorganic nanoparticles semiconductor, conjugated polymer, and dye-sensitized in a layer of solar cell is now recognized as potential application in developing flexible, large area, and low cost photovoltaic devices. Several conjugated low bandgap polymers, dyes, and underlayer materials based on the previous studies are quoted in this paper, which can provide guidelines in designing low cost photovoltaic solar cells. All of these materials are designed to help harvest more sunlight in a wider range of the solar spectrum besides enhancing the rate of charge transfer in a device structure. This review focuses on developing solid-state dye-synthesized, polymer, and hybrid solar cells. S. N. F. Mohd-Nasir, M. Y. Sulaiman, N. Ahmad-Ludin, M. A. Ibrahim, K. Sopian, and M. A. Mat-Teridi Copyright © 2014 S. N. F. Mohd-Nasir et al. All rights reserved. UV Blocking Glass: Low Cost Filters for Visible Light Photocatalytic Assessment Mon, 08 Dec 2014 11:52:36 +0000 A number of commercially available art protection products have been compared and assessed for their suitability as UV blocking filters in the application of “visible light” photocatalytic research. Many groups claiming visible light photocatalytic success employ filters to block out stray UV radiation in order to justify that their photocatalysts are indeed visible light photocatalysts and not UV light photocatalysts. These filters come in varying degrees of ability and price and many authors fail to correctly characterise their filters in individual papers. The use of effective filters to prevent both false positive and false negative results is important to maintain scientific rigor and create accurate understanding of the subject. The optimum UV filter would have the highest UV blocking properties (<390 nm) and simultaneously the highest visible light transmission (390–750 nm). Single and double layers of each of the glass products were assessed as well as laminate products. The conclusions show an inexpensive and highly effective setup for the conduction of visible light photochemistry that should be incorporated as a standard part in any researcher’s work where the claim of visible light activity is made. Charles W. Dunnill Copyright © 2014 Charles W. Dunnill. All rights reserved. Highly Reliable and Low-Cost Fabrication of Warm-White LEDs Using Composite Silica Photonic Crystals Wed, 03 Dec 2014 11:59:05 +0000 We demonstrated a technique requiring little phosphor that used white light-emitting diodes (WLEDs) containing composite silica colloidal photonic crystals (c-SCPhCs) for developing the warm-WLEDs (w-WLEDs). WLEDs containing c-SCPhCs enhanced luminous efficacy 5.6% more than commercial w-WLEDs did. We used a UV adhesive curing method to improve the adhesion properties of the c-SCPhCs. A reliability analysis (RA) test was performed on the WLEDs containing c-SCPhCs, applying a high temperature and high relative humidity (85°C/85 RH) during WLEDs operation at 120 mA. During a RA test of 2500 h, no visible degradation in optical performance was observed. We implemented a novel, inexpensive technique for producing high luminous flux w-WLEDs that can be used in residential light. Chun-Feng Lai, Yu-Chun Lee, Tzong-Liang Tsai, Chung-Chieh Chang, and Mau-Kuen Wu Copyright © 2014 Chun-Feng Lai et al. All rights reserved. Photocatalysis and Photoelectrochemistry for Solar Fuels Mon, 01 Dec 2014 12:11:30 +0000 Zhigang Zou, Jinhua Ye, Michael R. Hoffmann, and Wenjun Luo Copyright © 2014 Zhigang Zou et al. All rights reserved. Surfactant-Free Synthesis of Single Crystalline SnS2 and Effect of Surface Atomic Structure on the Photocatalytic Property Mon, 01 Dec 2014 11:45:30 +0000 Sheetlike tin disulfide (SnS2) single crystal exposed with well-defined facets and flowerlike SnS2 mainly exposed with facets were prepared through a surfactant-free solvothermal process. Photocatalytic degradation of methyl orange (MO) under visible light irradiation indicated that the sheetlike SnS2 showed a much higher activity than flowerlike SnS2. Theoretical and experimental results revealed that the band structure derived from the surface atomic structure played a more important role than the surface energy in the photocatalytic property. The present work has provided a deep insight into the important role of the surface energy and band structure, both of which are derived from the surface atomic structure, in the photocatalytic activity. Mengyi Li, Enzuo Liu, Huilin Hu, Shuxin Ouyang, Hua Xu, and Defa Wang Copyright © 2014 Mengyi Li et al. All rights reserved. Structure, Optical Properties, and Photocatalytic Activity towards H2 Generation and CO2 Reduction of GaN Nanowires via Vapor-Liquid-Solid Process Mon, 01 Dec 2014 07:58:14 +0000 High quality single crystalline GaN nanowires with large aspect ratio (>100) are synthesized on n-type Si (111) substrate via Au-catalyzed vapor-liquid-solid process. Morphology, crystal structure, and optical property of the as-synthesized GaN nanowires are characterized by means of X-ray diffraction, scanning/transmission electron microscopy, UV-vis diffuse reflection spectroscopy, and room temperature photoluminescence. The results indicate that the as-prepared GaN nanowires with a large aspect ratio are well crystallized in the hexagonal wurtzite structure, and a slight blue shift appears in both the absorption edge and emission peak probably due to the quantization effect. Photocatalytic H2 evolution over the as-prepared GaN nanowires is performed with the incorporation of Pt or Rh as the cocatalyst, exhibiting greatly enhanced capability compared to the GaN powder tested under the same conditions. Moreover, photocatalytic CO2 reduction over the GaN nanowires is also successfully realized using Pt or Rh as the cocatalyst, depending on which the products show a strong selectivity inherently related to the reductive electrons transferred by cocatalyst. Hong Pang, Lequan Liu, Shuxin Ouyang, Hua Xu, Yunxiang Li, and Defa Wang Copyright © 2014 Hong Pang et al. All rights reserved. Preparation of Cerium Modified Titanium Dioxide Nanoparticles and Investigation of Their Visible Light Photocatalytic Performance Mon, 01 Dec 2014 00:10:11 +0000 Mesoporous Ce/TiO2 nanoparticles have been successfully synthesized using titanate nanotubes as precursor through the hydrothermal-calcination method. The as-prepared materials were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), UV-vis diffuse reflectance spectra and nitrogen adsorption-desorption isotherm analysis. All the obtained Ce/TiO2 materials exhibit anatase phase. Ce element existed in two valance states of Ce3+ and Ce4+. Introduction of Ce species can effectively extend the spectral response from UV to visible light region. N2 adsorption-desorption analysis revealed that all the samples belong to mesoporous structure and have large BET surface area compared with P25. The Ce/TiO2 nanoparticles showed excellent photocatalytic activity in the degradation of MB under visible light irradiation. Jinfeng Liu, Haiyan Li, Qiuye Li, Xiaodong Wang, Min Zhang, and Jianjun Yang Copyright © 2014 Jinfeng Liu et al. All rights reserved. Bottom-Up Enhancement of g-C3N4 Photocatalytic H2 Evolution Utilising Disordering Intermolecular Interactions of Precursor Sun, 30 Nov 2014 13:58:49 +0000 Disordered intermolecular interaction carbon nitride precursor prepared by water-assisted grinding of dicyandiamide was used for synthesis of g-C3N4. The final sample possesses much looser structure and provides a broadening optical window for effective light harvesting and charge separation efficiency, which exhibits significantly improved H2 evolution by photocatalytic water splitting. The bottom-up mechanochemistry method opens new vistas towards the potential applications of weak interactions in the photocatalysis field and may also stimulate novel ideas completely different from traditional ones for the design and optimization of photocatalysts. Xue Lu Wang, Wen Qi Fang, Yu Hang Li, Pengfei Liu, Haimin Zhang, Yun Wang, Porun Liu, Yefeng Yao, Huijun Zhao, and Hua Gui Yang Copyright © 2014 Xue Lu Wang et al. All rights reserved. Electrochemical Impedance Spectra of Dye-Sensitized Solar Cells: Fundamentals and Spreadsheet Calculation Thu, 27 Nov 2014 14:22:37 +0000 Electrochemical impedance spectroscopy (EIS) is one of the most important tools to elucidate the charge transfer and transport processes in various electrochemical systems including dye-sensitized solar cells (DSSCs). Even though there are many books and reports on EIS, it is often very difficult to explain the EIS spectra of DSSCs. Understanding EIS through calculating EIS spectra on spreadsheet can be a powerful approach as the user, without having any programming knowledge, can go through each step of calculation on a spreadsheet and get instant feedback by visualizing the calculated results or plot on the same spreadsheet. Here, a brief account of the EIS of DSSCs is given with fundamental aspects and their spreadsheet calculation. The review should help one to develop a basic understanding about EIS of DSSCs through interacting with spreadsheet. Subrata Sarker, A. J. Saleh Ahammad, Hyun Woo Seo, and Dong Min Kim Copyright © 2014 Subrata Sarker et al. All rights reserved. Improved Synthesis of Global Irradiance with One-Minute Resolution for PV System Simulations Wed, 26 Nov 2014 12:58:01 +0000 High resolution global irradiance time series are needed for accurate simulations of photovoltaic (PV) systems, since the typical volatile PV power output induced by fast irradiance changes cannot be simulated properly with commonly available hourly averages of global irradiance. We present a two-step algorithm that is capable of synthesizing one-minute global irradiance time series based on hourly averaged datasets. The algorithm is initialized by deriving characteristic transition probability matrices (TPM) for different weather conditions (cloudless, broken clouds and overcast) from a large number of high resolution measurements. Once initialized, the algorithm is location-independent and capable of synthesizing one-minute values based on hourly averaged global irradiance of any desired location. The one-minute time series are derived by discrete-time Markov chains based on a TPM that matches the weather condition of the input dataset. One-minute time series generated with the presented algorithm are compared with measured high resolution data and show a better agreement compared to two existing synthesizing algorithms in terms of temporal variability and characteristic frequency distributions of global irradiance and clearness index values. A comparison based on measurements performed in Lindenberg, Germany, and Carpentras, France, shows a reduction of the frequency distribution root mean square errors of more than 60% compared to the two existing synthesizing algorithms. Martin Hofmann, Stefan Riechelmann, Cristian Crisosto, Riyad Mubarak, and Gunther Seckmeyer Copyright © 2014 Martin Hofmann et al. All rights reserved. Effect of UV Irradiation and Temperature on Free Radical Properties in Dehydrocholic and Ursodeoxycholic Acids: An EPR Study Tue, 25 Nov 2014 11:56:06 +0000 The effect of UV irradiation and temperature on the formation and properties of free radicals in two pharmaceutical important bile acids, such as dehydrocholic (DH) and ursodeoxycholic acids (UDC), was examined. Electron paramagnetic resonance (EPR) spectroscopy was applied to determine the paramagnetic character of UV irradiated and thermally sterilized drugs. Thermal and UV irradiation sterilizations of both compounds were carried out at different conditions according to pharmaceutical norms. The performed EPR measurements of UV irradiated and thermally sterilized DH and UDC samples proved the existence of the complex free radical systems in examined bile acids. Significant influence of UV irradiation in comparison with applied thermal sterilization on free radical concentrations in DH and UDC samples was observed. The results pointed out that thermal method is most suitable for bile acid sterilization. Therefore, this kind of sterilization should be applied in practice. Małgorzata Dołowy, Paweł Ramos, and Barbara Pilawa Copyright © 2014 Małgorzata Dołowy et al. All rights reserved. The Development of LED-Based Dental Light Using a Multiplanar Reflector Design Tue, 18 Nov 2014 08:14:06 +0000 A multiplanar reflector was designed to enhance the application efficiency of light-emitting diode (LED) light sources that can be employed as LED-based dental lights. This study used a high-power LED developed by Nichia, that is, a single LED capable of providing a total luminous flux of 120 lm, as the primarily light source to design and develop an LED-based dental light. This LED complies with the international standards and regulations stipulated in ISO 9680:2007. The light spots produced by the prototype were rectangular, with a length of 200 mm and a width of 100 mm. These light spots achieved maximum illumination of 12,000 lux. The use of LEDs can reduce energy consumption from 50 W to 3 W, providing an energy saving of more than 90%. Chi-Chang Hsieh and Yan-Huei Li Copyright © 2014 Chi-Chang Hsieh and Yan-Huei Li. All rights reserved. Reversible Visualization for Synchrotron Radiation Using Photochromic Dye and Photostimulable Phosphor Composite Film Tue, 11 Nov 2014 00:00:00 +0000 The study reported herein is undertaken to visualize reversibly synchrotron radiation by using a composite film comprised of two components: a photochromic SP with the conversion characteristics of UV-to-visible color and PSP BaFCl:Eu2+ particles with the conversion characteristics of X-rays-to-UV emission. Kenji Kinashi, Kazuya Jimbo, Takahiro Okabe, Sono Sasaki, and Hiroyasu Masunaga Copyright © 2014 Kenji Kinashi et al. All rights reserved.