National Cheng Kung University

About: National Cheng Kung University is a education organization based out in Tainan City, Taiwan. It is known for research contribution in the topics: Population & Thin film. The organization has 49723 authors who have published 69799 publications receiving 1437420 citations. The organization is also known as: NCKU.

Sun Tracking Systems: A Review

Abstract: The output power produced by high-concentration solar thermal and photovoltaic systems is directly related to the amount of solar energy acquired by the system, and it is therefore necessary to track the sun's position with a high degree of accuracy. Many systems have been proposed to facilitate this task over the past 20 years. Accordingly, this paper commences by providing a high level overview of the sun tracking system field and then describes some of the more significant proposals for closed-loop and open-loop types of sun tracking systems.

Band Gap Engineering of Chemical Vapor Deposited Graphene by in Situ BN Doping

Abstract: Band gap opening and engineering is one of the high priority goals in the development of graphene electronics. Here, we report on the opening and scaling of band gap in BN doped graphene (BNG) films grown by low-pressure chemical vapor deposition method. High resolution transmission electron microscopy is employed to resolve the graphene and h-BN domain formation in great detail. X-ray photoelectron, micro-Raman, and UV–vis spectroscopy studies revealed a distinct structural and phase evolution in BNG films at low BN concentration. Synchrotron radiation based XAS-XES measurements concluded a gap opening in BNG films, which is also confirmed by field effect transistor measurements. For the first time, a significant band gap as high as 600 meV is observed for low BN concentrations and is attributed to the opening of the π–π* band gap of graphene due to isoelectronic BN doping. As-grown films exhibit structural evolution from homogeneously dispersed small BN clusters to large sized BN domains with embedded d...

An integrative approach to understanding bird origins

Abstract: Background The origin of birds is one of the most enduring and dramatic evolutionary debates. The hypothesis that the primarily small-sized birds are nested within a theropod dinosaur group that includes the gigantic Tyrannosaurus rex has been supported by strong fossil evidence, but until recently, several important issues remained unresolved, including the origins of feathers and flight, the “temporal paradox” (the coelurosaurian theropods occur too late in the fossil record to be ancestral to the Jurassic bird Archaeopteryx), and supposed homological incongruities (e.g., the suggested homologies of three fingers in tetanuran theropods are different from those of living birds). Recent discoveries of spectacular dinosaur fossils from China and elsewhere provide new information to address these issues, and also prompt numerous studies in disciplines other than paleontology that help explain how bird characteristics originated and evolved. Evolutionary history of selected bird features inferred from multidisciplinary data. Recent studies demonstrate that major bird characteristics have evolved in a sequential way, and many of them initiated transformation early in dinosaur evolution, with some approaching modern conditions well before the origin of birds, whereas others appear only near the origin of the crown group birds. Advances The discoveries of feathered dinosaur fossils from the Jurassic and Cretaceous sediments of China and elsewhere document a diverse range of feathers from monofilamentous feathers to highly complex flight feathers, which show a general evolutionary trend of increasing complexity leading to the cladogenesis of birds. The wide occurrence of foot feathers in Mesozoic theropods (i.e., short filamentous forms in relatively basal theropods and large vaned forms in derived theropods, including early birds) clarifies feather-scale relations and integumentary evolution pertinent to flight origins and also shows that bird flight likely had evolved through a four-winged stage. With numerous discoveries of well-preserved dinosaur fossils covering a wide range of geological periods, the morphological, functional, and temporal transition from ground-living to flight-capable theropod dinosaurs is now one of the best-documented major evolutionary transitions. Meanwhile, studies in disciplines other than paleontology provide new insights into how bird characteristics originated and evolved—such as feathers, flight, endothermic physiology, unique strategies for reproduction and growth, and an unusual pulmonary system. The iconic features of extant birds, for the most part, evolved in a gradual and stepwise fashion throughout theropod evolution. However, new data also highlight occasional bursts of morphological novelty at certain stages particularly close to the origin of birds and an unavoidable complex, mosaic evolutionary distribution of major bird characteristics on the theropod tree. Research into bird origins provides a model example of how an integration of paleontological and neontological data can be used to gain a comprehensive understanding of the complexity surrounding major evolutionary transitions and to set new research directions. Outlook A refined, more robust phylogeny will be imperative to move our studies forward. A larger data set will help to increase the accuracy of phylogenetic reconstructions, but better character formulation and more accurate scorings are imperative at the current stage. In terms of character evolution, an integrative approach combining paleontological, neontological, developmental, temporal, and even paleoenvironmental data is particularly desirable. Greater examination of fossils pertaining to molecular information is also a potentially fruitful avenue for future investigation. Evolutionary scenarios for various aspects of the origin of birds have sometimes been constructed from neontological data, but any historical reconstruction must ultimately be tested using the fossil record. Consequently, dense fossil sampling along the line to modern birds and better understanding of transitional forms play key roles in such reconstructions.