Automatic Detection of Clear-Sky Periods From Irradiance Data

Recent degradation studies have highlighted the importance of considering cloud cover when calculating degradation rates, finding more reliable values when the data are restricted to clear sky periods. Several automated methods of determining clear sky periods have been previously developed, but parameterizing and testing the models has been difficult. In this paper, we use clear sky classifications determined from satellite data to develop an algorithm that determines clear sky periods using only measured irradiance values and modeled clear sky irradiance as inputs. This method is tested on global horizontal irradiance (GHI) data from ground collectors at six sites across the United States and compared against independent satellite-based classifications. First, 30 separate models were optimized on each individual site at GHI data intervals of 1, 5, 10, 15, and 30 min (sampled on the first minute of the interval). The models had an average F0.5 score of 0.949 ± 0.035 on a holdout test set. Next, optimizations were performed by aggregating data from different locations at the same interval, yielding one model per data interval. This paper yielded an average F0.5 of 0.946 ± 0.037. A final, 'universal' optimization that was trained on data from all sites at all intervals provided an F0.5 score of 0.943 ± 0.040. The optimizations all provide improvements on a prior, unoptimized clear sky detection algorithm that produces F0.5 scores that average to 0.903 ± 0.067. Our paper indicates that a single algorithm can accurately classify clear sky periods across locations and data sampling intervals

Simulations of solar cell absorption enhancement using resonant modes of a nanosphere array

We propose an approach for enhancing the absorption of thin-film amorphous silicon solar cells using periodic arrangements of resonant dielectric nanospheres deposited as a continuous film on top of a thin planar cell. We numerically demonstrate this enhancement using 3D full field finite difference time domain simulations and 3D finite element device physics simulations of a nanosphere array above a thin-film amorphous silicon solar cell structure featuring back reflector and anti-reflection coating. In addition, we use the full field finite difference time domain results as input to finite element device physics simulations to demonstrate that the enhanced absorption contributes to the current extracted from the device. We study the influence of a multi-sized array of spheres, compare spheres and domes and propose an analytical model based on the temporal coupled mode theory

Student Center Opens

Articles in the student newspaper, the KEN, regarding the opening of the Student Center and Student Union Buildin

The Effects of Absent Father Figures on the Social Functioning of Teens

Problem: In America, children under the age of 18 are being negatively affected by the absence of a father in the home. This is important because fatherlessness is on the rise (Census Bureau, 2016) and can harm a child’s future opportunities (Snyder, McLaughlin, & Findeis, 2006). Specifically, depressive symptoms and delinquent behavior have been recognized as two tangible outcomes of growing up without a father. Trending research suggests that delinquency and depressive symptoms are linked to a lack of parental monitoring (Markowitz & Ryan, 2016), yet the aspects of socialization (early father departure) and emotional distress (late father departure) should be further researched. Research Question: How does the level of social functioning in teens without father figures compare to teens with father figures? Design/sample: We will use a cross-sectional descriptive research design. Teens between the ages of 13-19 in enrolled in education, juvenile court/detention center, and local service agencies located in Miami Valley, Ohio will be studied using multistage cluster random sample. Collection/Analysis: A voluntary mobile-online survey will be sent out to the teachers, social workers in the court system and social workers at the social service agencies to distribute to their teenage students and clients. Three statistical tests will be run using SPSS software. Frequency distribution and Chi-square will compare teens living with a biological father, a father figure, or no father figure. One-way ANOVA will examine the differences in social functioning among teens with a biological father, father figure, or no father figure. Expected Findings: We expect to find higher social function in teens with an involved biological father who lives in the home. We also expect to find teens with father figures to have lower social functioning than those with biological fathers living in the home, while having higher social functioning than those with no biological father or father figure. Keywords: Father-figure, social functioning, teens, fatherless, biological fathe

Effects of bulk and grain boundary recombination on the efficiency of columnar-grained crystalline silicon film solar cells

Columnar-grained polycrystalline silicon films deposited at low temperatures are promising materials for use in thin-film photovoltaics. We study the effects of recombination at grain boundaries, bulk intragranular recombination, grain size, and doping in such structures with two-dimensional device physics simulations, explicitly modeling the full statistics and electrostatics of traps at the grain boundary. We characterize the transition from grain-boundary-limited to bulk-lifetime-limited performance as a function of intergranular defect density and find that higher bulk lifetimes amplify grain boundary recombination effects in the intermediate regime of this transition. However, longer bulk lifetimes ultimately yield higher efficiencies. Additionally, heavier base doping is found to make performance less sensitive to grain boundary defect density

Design of Nanostructured Solar Cells Using Coupled Optical and Electrical Modeling

Nanostructured light trapping has emerged as a promising route toward improved efficiency in solar cells. We use coupled optical and electrical modeling to guide optimization of such nanostructures. We study thin-film n-i-p a-Si:H devices and demonstrate that nanostructures can be tailored to minimize absorption in the doped a-Si:H, improving carrier collection efficiency. This suggests a method for device optimization in which optical design not only maximizes absorption, but also ensures resulting carriers are efficiently collected

Contrahelicase activity of the mitochondrial transcription termination factor mtDBP

The sea urchin mitochondrial D-loop binding protein (mtDBP) is a transcription termination factor that is able to arrest bidirectionally mitochondrial RNA chain elongation. The observation that the mtDBP binding site in the main non-coding region is located in correspondence of the 3′ end of the triplex structure, where the synthesis of heavy strand mitochondrial (mt) DNA is either prematurely terminated or allowed to continue, raised the question whether mtDBP could also regulate mtDNA replication. By using a helicase assay in the presence of the replicative helicase of SV40, we show that mtDBP is able to inhibit the enzyme thus acting as a contrahelicase. The impairing activity of mtDBP is bidirectional as it is independent of the orientation of the protein binding site. The inhibition is increased by the presence of the guanosine-rich sequence that flanks mtDBP binding site. Finally, a mechanism of abrogation of mtDBP contrahelicase activity is suggested that is based on the dissociation of mtDBP from DNA caused by the passage of the RNA polymerase through the protein–DNA complex. All these findings favour the view that mtDBP, besides serving as transcription termination factor, could also act as a negative regulator of mtDNA synthesis at the level of D-loop expansion

Outdoor performance of a thin-film gallium-arsenide photovoltaic module

We deployed a 855 cm2 thin-film, single-junction gallium arsenide (GaAs) photovoltaic (PV) module outdoors. Due to its fundamentally different cell technology compared to silicon (Si), the module responds differently to outdoor conditions. On average during the test, the GaAs module produced more power when its temperature was higher. We show that its maximum-power temperature coefficient, while actually negative, is several times smaller in magnitude than that of a Si module used for comparison. The positive correlation of power with temperature in GaAs is due to temperature-correlated changes in the incident spectrum. We show that a simple correction based on precipitable water vapor (PWV) brings the photocurrent temperature coefficient into agreement with that measured by other methods and predicted by theory. The low operating temperature and small temperature coefficient of GaAs give it an energy production advantage in warm weather

MTERF factors: a multifunction protein family

The MTERF family is a large protein family, identified in metazoans and plants, which consists of four subfamilies, MTERF1, 2, 3 and 4. Mitochondrial localisation was predicted for the vast majority of MTERF family members and demonstrated for the characterised MTERF proteins. The main structural feature of MTERF proteins is the presence of a modular architecture, based on repetitions of a 30-residue module, the mTERF motif, containing leucine zipperlike heptads. The MTERF family includes transcription termination factors: human mTERF, sea urchin mtDBP and Drosophila DmTTF. In addition to terminating transcription, they are involved in transcription initiation and in the control of mtDNA replication. This multiplicity of functions seems to flank differences in the gene organisation of mitochondrial genomes. MTERF2 and MTERF3 play antithetical roles in controlling mitochondrial transcription: that is, mammalian and Drosophila MTERF3 act as negative regulators, whereas mammalian MTERF2 functions as a positive regulator. Both proteins contact mtDNA in the promoter region, perhaps establishing interactions, either mutual or with other factors. Regulation of MTERF gene expression in human and Drosophila depends on nuclear transcription factors NRF-2 and DREF, respectively, and proceeds through pathways which appear to discriminate between factors positively or negatively acting in mitochondrial transcription. In this emerging scenario, it appears that MTERF proteins act to coordinate mitochondrial transcription