Photolithography in Fabrication of Thin-film Solar Cells

Solar energy has steadily increased its efficiency and cost-effectiveness throughout the past three decades and seems poised to compete with current primary energy (natural gas, oil, coal) as the need for alternative energy sources rises. One type of solar cell, thin-film cells, often relies on use of permanent photomasks in order to imprint a pattern onto the front metal contact. However, these machined metal masks are rigid and do not allow for different designs to be explored as current masks encounter difficulties in machining grids thin enough for optimization. Photolithography, traditionally used in the microfabrication field, provides a method in creating flexible and easily interchangeable designs to duplicate patterns onto solar cell contacts. First, a positive photoresist was spun onto a glass plate with a deposited conductor (ITO). Second, exposure of the photoresist was performed in a dark environment through near UV LEDs in order to polymerize the photoresist in accordance with the mask. Third, photoresist was developed and processed with a nickel/aluminum coating through an electron beam depositor. Parameters were optimized at each individual step of the procedure along with a variety of photoresist thicknesses and designs. Photomasks were printed on a laser-jet printer featuring grids of .5mm wide and produced clean copies of the masks with minimal walling. The implementation of photolithography in exploring more options to engineer more efficient inorganic solar cells hints at a promising future through its flexibility

The Effects of the Board on Corporate Performance. Evidence from Cameroon Banks

Using a sample of 10 selected banks annual reports covering 2010-2015, this study examines the relationship between corporate governance and performance in Cameroon banking sector. Based on the econometric model, the result indicates that improved performance of the banking sector is not dependent on increasing the number of executive directors and board composition. It shows further that when there are more external board members; performance of banks tends to be worse. The study concludes a need for increase in board size and decrease in board composition as measured by the ratio of outside directors to the total number of directors in order to increase the bank performance

Parameter Optimization for Preparing Carbon Fiber/Epoxy Composites by Selective Laser Sintering

Carbon fiber (CF) reinforced thermosetting resin composites offer a wide range of high performance features including excellent strength, modulus and thermal resistance and light weight. Consequently, they are increasingly demanded by aerospace and automotive industries due to the tighter requirements of the transport vehicles for lightweight as well as higher payloads. Although thermoplastics and their composites have been widely used in additive manufacturing (AM), to date it is difficult to manufacture carbon fibers reinforced thermosetting composite parts via AM technologies. Therefore, this study developed a novel method based on selective laser sintering (SLS) to fabricate high-performance carbon fiber/epoxy resin composites. The response surface method was employed to study the processing parameters affecting the quality of final parts, and an optimized processing condition was obtained.Mechanical Engineerin

A simulation data-driven design approach for rapid product optimization

Traditional design optimization is an iterative process of design, simulation, and redesign, which requires extensive calculations and analysis. The designer needs to adjust and evaluate the design parameters manually and continually based on the simulation results until a satisfactory design is obtained. However, the expensive computational costs and large resource consumption of complex products hinder the wide application of simulation in industry. It is not an easy task to search the optimal design solution intelligently and efficiently. Therefore, a simulation data-driven design approach which combines dynamic simulation data mining and design optimization is proposed to achieve this purpose in this study. The dynamic simulation data mining algorithm—on-line sequential extreme learning machine with adaptive weights (WadaptiveOS-ELM)—is adopted to train the dynamic prediction model to effectively evaluate the merits of new design solutions in the optimization process. Meanwhile, the prediction model is updated incrementally by combining new “good” data set to reduce the modeling cost and improve the prediction accuracy. Furthermore, the improved heuristic optimization algorithm—adaptive and weighted center particle swarm optimization (AWCPSO)—is introduced to guide the design change direction intelligently to improve the search efficiency. In this way, the optimal design solution can be searched automatically with less actual simulation iterations and higher optimization efficiency, and thus supporting the rapid product optimization effectively. The experimental results demonstrate the feasibility and effectiveness of the proposed approach

Antiperovskite Li3OCl Superionic Conductor Films for Solid-State Li-Ion Batteries.

Antiperovskite Li3OCl superionic conductor films are prepared via pulsed laser deposition using a composite target. A significantly enhanced ionic conductivity of 2.0 × 10-4 S cm-1 at room temperature is achieved, and this value is more than two orders of magnitude higher than that of its bulk counterpart. The applicability of Li3OCl as a solid electrolyte for Li-ion batteries is demonstrated

The Innovation Waltz: Unpacking Developers’ Response to Market Feedback and Its Effects on App Performance

To remain competitive in the intensely competitive mobile app market, developers often rely on user feedback to fuel the innovation process. Past studies, however, have rarely examined the impact of developers’ incremental innovation strategies by treating app innovation as a continuous process. This knowledge gap prompted us to advance a framework of developers’ incremental innovation strategies comprising four coping strategies: sailing, optimizing, supplementing, and patching. Employing a multi-state Markov model to capture the probability of a developer employing an incremental innovation strategy in response to distinct types of market feedback during the app innovation process, we analyze data sourced from the Android app store that consists of 4,583 apps, 29,307 updates, and 231,817 reviews. We discovered that market feedback affects the adoption of the four incremental innovation strategies differently. Additionally, we found that sailing, supplementing, and optimizing strategies boost app downloads, while supplementing, optimizing, and patching strategies improve app ratings

Characterization and Modulation of PI3K-Akt Signaling Following Contusive SCI

poster abstractSpinal cord injury (SCI) is devastating, with most injuries being contusive/compressive injuries at the cervical spinal level. There are two mechanisms of damage after acute contusive SCI: a primary mechanical insult to the cord, and secondary injury induced by many biological events, including inflammation and signal-mediated cell death. The extent of tissue damage correlates with functional loss after SCI, therefore it is critical to protect neural tissue for preservation of functional ability. Focusing on cellular signaling events following SCI is a promising direction of investigation, as modulation of such pathways can promote neuroprotection or regeneration following injury. Two particular signaling pathways have been highlighted as mediators of cellular survival post-central nervous system (CNS) injury, the MEK-Erk and PI3K-Akt pathways. Reducing Erk activity has been shown to promote neuroprotection and reduced reactive gliosis, while reduction of PI3K-Akt signaling likely results in initiation of cellular death. Recent studies have demonstrated promotion of regrowth of adult corticospinal (CST) neurons and protection of motor neuron atrophy by disinhibition of PI3K via PTEN deletion or knock-down in these cells. Understanding the signal pathways and mechanisms involved in different cell types, when such response occurs, and the potential interaction between pathways is essential for maximizing development of optimal approaches to treatment following SCI. This study highlights PI3K-Akt signaling involvement following injury, with future directions aimed at better understanding this pathway for targeting therapies to mediate anatomical and functional preservation and recovery following SCI

Contribution of the vertical movement of dissolved organic carbon to carbon allocation in two distinct soil types under Castanopsis fargesii Franch. and C. carlesii (Hemsl.) Hayata forests

International audienceAbstractKey messageThe vertical transport of dissolved organic carbon (DOC) is an important determinant of carbon distribution across a soil profile. The transport of DOC down a soil profile can be largely influenced by incoming DOC and soil organic carbon (SOC) levels, which insulate DOC from adsorption processes regulated by soil texture and Fe/Al mineralogy.ContextUncertainties about how soil properties affect DOC transport through the soil profile require study because soils can differ strongly with respect to texture or Fe/Al mineralogy and yet retain similar quantities of DOC.AimsThis study aimed to assess the role of incoming DOC and native SOC in regulating DOC migration in soils and investigate the contribution of DOC movement to SOC allocation.MethodsWe leached a standard DOC solution extracted from Castanopsis carlesii litter through two distinct soil types, using two leaching strategies: single leaching and sequential leaching. The two soil types under a natural Castanopsis carlesii (Hemsl.) Hayata forest and a natural Castanopsis fargesii Franch. forest, respectively, differ strongly with respect to soil texture, Fe/Al oxide abundances, and SOC nature.ResultsWith single leaching, where each of six soil layers making up an entire 0–100-cm soil depth profile received single doses of standard DOC solution, deeper soil layers retained more DOC than upper soil layers, with native SOC largely masking the effects of soil texture and Fe/Al mineralogy on DOC migration. Following sequential leaching, where a sixfold larger amount of standard DOC solution sequentially percolated through the six soil layers, the upper soil layers generally retained more DOC than deeper layers. Nevertheless, in sequential leaching, desorption-induced transfer of carbon from upper soil layers to deeper soil layers resulted in greater total carbon retention than in single leaching.ConclusionForest subsoils (40–100 cm) are well below C saturation, but DOC vertical movement from top soils only transfers limited organic carbon to them. However, DOC vertical movement may greatly alter SOC allocation along the top soil profile (0–40 cm), with part of outer sphere native SOC displaced by incoming DOC and migrating downwards, which is a natural way to preserve SOC