Holographic Optical Elements and Application

Holographic optical element has a high diffraction efficiency and a narrow-band frequency characteristic, and it has a characteristic that is able to implement several features in a single flat device. It is widely applied in various fields. In this chapter, the principle and characteristics of the holographic optical elements are described in detail, and few typical holographic optical element-based applications, such as head-mounted display, lens array, and solar concentrator, are introduced. Finally, the futuristic research concepts for holographic optical element-based applications and contents are discussed

Scaffolding in Technology-Enhanced Science Education

This dissertation focuses on the effectiveness of scaffolding in technology-enhanced science learning environments, and specifically the relative merits of computer- and teacher-based scaffolding in science inquiry. Scaffolding is an instructional support that helps learners solve problems, carry out tasks, or achieve goals that they are unable to accomplish on their own. Although support such as scaffolding is necessary when students engage in complex learning environments, many issues must be resolved before educators can effectively implement scaffolding in instruction. To achieve this, this dissertation includes two studies: a systematic literature review and an experimental study. The two studies attempted to reveal some important issues which are not widely recognized in the existing literature. The primary problem confronting the educator is how to determine which of the numerous kinds of scaffolding will allow them to educate students most effectively. The scaffolding forms that researchers create are often confusing, overlapping, or contradictory. In response to this, the first study critically analyzed the ways that researchers have defined and applied scaffolding, and provided suggestions for future scaffolding design and research. Moreover, studies tend to focus only on computer-based scaffolding rather than examining ways to integrate it with teacher-based instruction. Although researchers generally recognize that teacher-based support is important, research in this area is limited. The second study of this dissertation employed a quasi-experimental design with four experimental conditions, each of which include a type of computer-based procedural scaffolding (continuous vs. faded) paired with a type of teacher-based metacognitive scaffolding (early vs. late). Each class was assigned to use one of the four conditions. The findings indicated that students receiving continuous computer-based procedural and early teacher-based metacognitive scaffolding performed statistically better at learning scientific inquiry skills than other treatment groups. Students using faded computer-based procedural and early teacher-based metacognitive scaffolding showed the worst performance. However, among the four groups there existed no statistically significant difference in terms of the effect on students? ability to learn science knowledge. Moreover, teacher-based metacognitive scaffolding did not have a significant impact on either science content knowledge or scientific inquiry skills

Alkaloid content and essential oil composition of Mahonia breviracema cultivated under different light environments

Light can affect the yields of alkaloid and essential oil in the synthesis of secondary metabolites directly or indirectly through plant growth. Despite Mahonia breviracema being an endemic medicinal species in China, research on the influence of light on production of alkaloid and essential oil is scarce. Thus, this research evaluated the influence of various lighting conditions on alkaloid yields and the composition and yields of the essential oils of M. breviracema. The results revealed significant differences in alkaloid yields, oil yieldsand chemical characteristics of M. breviracema grown in four different light intensities from 10 to 100% full sun shine. The total amount of alkaloids in plants under I30 and I50 was higher than that under I10 and I100 due to the higher biomass of plants. Oil yield of M. breviracema leaf increased linearly with the increase of lightincidence. Plants grown under I10 had less plastoglobuli, which coincided with the lowest oil yield (1.91 g kg-1). The plastoglobuli in chloroplasts increased when the irradiance levels increased, resulting in the highest oil yields under I100 (4.53 g kg-1). The principal components in the leaves of M. breviracema were hexadecanoic acid (10.54-72.19%) and α-ionone (1.25-42.39%). The highest hexadecanoic acid content was obtained under I50, followed by I30, and the highest α-ionone content was obtained under I100. Therefore, it is necessary to control the light environment to obtain raw materials with high quality

On the denominators of harmonic numbers. IV

Let $\mathcal{L}$ be the set of all positive integers $n$ such that the denominator of $1+1/2+\cdots +1/n$ is less than the least common multiple of $1, 2, \dots , n$. In this paper, under a certain assumption on linear independence, we prove that the set $\mathcal{L}$ has the upper asymptotic density $1$. The assumption follows from Schanuel’s conjecture

On the denominators of harmonic numbers. IV

Let $\mathcal{L}$ be the set of all positive integers $n$ such that the denominator of $1+1/2+\cdots +1/n$ is less than the least common multiple of $1, 2, \dots , n$. In this paper, under a certain assumption on linear independence, we prove that the set $\mathcal{L}$ has the upper asymptotic density $1$. The assumption follows from Schanuel’s conjecture