Performance enhancement and size reduction of near-eye display

Near-eye display (NED) paved its way in a variety of applications of modern virtual reality (VR). However, current NEDs have lots of limitations, which lead to compromised user experience and strongly limit their potential in real-world scenarios. Two of the most noticeable features that demanding improvements are resolution and size. On the one hand, applications of modern VR devices introduce more detailed textures and increased field-of-view (FoV), altogether create excessive demand for resolution. On the other hand, more mobile application scenarios of virtual reality and augmented reality (AR) bring the requirement of size reduction. The trend of developing high-resolution NED with small form-factor is with no doubt. During the last several decades, attempts were made to improve the resolution of NED. However, the utilization of eye-tracking and optical tiling adds a fairly amount of complexity to the NED system, which in turn makes the device even bulkier. Thus, a compact near-eye display device that can deliver excellent image quality is still in great demand by society. In this thesis, theory and methods are demonstrated to improve key performance factors in modern NED, including resolution, depth perception, and size. In Chapter 3, to solve the main conflict between resolution and device size, a versatile resolution enhancement method for NED is implemented by overlapping multiple display panel images. Based on display super-resolution, this overlapping method effectively increases the perceived resolution without optical complexity. By investigating the algorithm theory of image generation and calibration, the perceived resolution can be enhanced and overcome the physical resolution of a single display panel. A NED prototype based on a semi-transparent mirror is designed and fabricated. The experiment demonstrated decent results of resolution enhancement. Compare with the conventional method of display tiling, my method offers an equivalent level of performance yet reduces system complexity, brings more flexibility to the design of NED. Free-form optics enable innovative ways of implementing compact size NED. In Chapter 4, a design routine of off-axis near-eye display system is implemented. A compact near-eye display system described by x-y polynomial function is developed with a 4mm diameter exit pupil, a 21.5° diagonal full field-of-view (FoV) and 23 mm eye relief. Freeform surfaces are used to effectively reduce the size of NED while correcting the off-axis aberration. The designed system yields good optical performance yet very compact in terms of size, compared to traditional NED. A prototype is demonstrated with components available from the market. The prototype effectively indicated the feasibility of the design as a compact NED. Light field receives great research attention in recent years as a feasible way to solve convergence-accommodation conflict in NED and stereoscopic display. Based on either microlens or pinhole, light field NED demonstrates an effective size reduction on the longitudinal direction of the device. In chapter 5, a light field NED with random pinhole design is demonstrated with unique viewing zone and optical simplicity. Further research is recommended in chapter 6 to combine the individual technique as a hybrid device, where multiple light field display module can be used for super-resolution, with the design flexibility of free-form optics. My research can act as guidance in the design of future NED to reduce device size, enhance resolution, and incorporate the depth sense of current virtual reality headset, thus further improve virtual reality user experience.Doctor of Philosoph

Reduced stomatal frequency with rising elevation for Kobresia royleana on the Tibetan Plateau

Knowledge about within-species variation in stomatal frequency with varying elevation at very high elevations is rare, which is crucial for us to understand how alpine plants are adapted to the extreme environment. Here, we focus on the variation in stomatal frequency in Kobresia royleana (Nees) Boeckeler (Cyperaceae, Cyperales) along two altitudinal transects (elevation ranges from 3723 m to 5081 m) in the center of the Tibetan Plateau. The result shows the stomatal density (SD) varied from 303 +/- 55.6 mm(-2) to 542 +/- 81.8 mm(-2), and stomatal index (SI) ranged from 21.0% to 29.6%. In contrast with most cases, an unexpected negative response of stomatal frequency to rising elevation was observed. Among abiotic factors, the growing season mean temperature and CO2 partial pressure significantly declined with increasing elevation, while the growing season precipitation did not vary. Therefore, the decreasing SD and SI were mainly due to the declining temperature rather than the decreasing CO2 partial pressure. Further, SD and SI were negatively related to leaf functional traits of specific leaf area (SLA), leaf nitrogen concentration (N) and stable carbon isotope ratios (delta C-13), and all these morphological and physiological traits tended to covary with rising elevation and declining temperature. Meanwhile, the increasing delta C-13, N and SLA with elevation seem to be strategies for alpine plants to cope with the low-temperature environments. Therefore, the observed covariance between stomatal frequency and leaf functional traits also suggests that the low temperature rather than low CO2 partial pressure mainly leads to the elevational pattern of stomatal frequency for this alpine species. (C) 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license

Appendix S2 Fossil records of Annonaceae

Appendix S2 Fossil records of Annonacea

Data from: The early history of Annonaceae (Magnoliales) in Southeast Asia suggests floristic exchange between India and Pan-Indochina by the late Oligocene

The collision between India and Eurasia in the mid‐Palaeogene facilitated terrestrial floristic exchange. However, due to the complexity of this geological event and scarcity of fossil record, the plant migration patterns between the two plates are still highly debated. In this study, we focus on the Oligocene floristic exchange between India and Pan‐Indochina mainly based on a carpological study of Annonaceae, an emblematic family unique in its pantropical distribution and frugivore‐based dispersal strategy. A new seed species, Anonaspermum orientalis sp. nov., is described from the upper Oligocene Yongning Formation of Guangxi, southern China. The species represents the earliest known occurrence of this family in Pan‐Indochina. The specimens are characterized by ovate–elliptic seed shape, thicker seed testa, two‐lobed organization, lamelliform rumination and an obvious cone‐like plug. The palaeobiogeographical reconstruction of Annonaceae indicates that the most parsimonious dispersal scenario for the annonaceous taxon from the late Oligocene of China is the Out‐of‐India route, in parallel with other plant genera inferred to have migrated between India and Pan‐Indochina during that period

Design of a 360-deg panoramic capture system based on a smart phone

A panoramic imaging system has been developed using two afocal lenses and a smart phone that consists of cameras on both sides. An individual afocal lens has been developed with a large field of view (FOV) and a large exit pupil, which can enlarge the FOV of a smart phone camera to above 180 deg. Some issues with the smart phone-based 360-deg panoramic system, such as relative illuminance and assembly tolerance, were analyzed in detail and taken into consideration during the design procedure. A prototype has been developed with a low fabrication cost, yet producing impressive panoramic image quality.Published versio

Middle Miocene lotus (Nelumbonaceae, Nelumbo) from the Qaidam Basin, Northern Tibet Plateau

The Neogene environment and paleovegetation of today’s semi-arid and arid Central Asia remain elusive. Little is known about the effect of paleoclimatic change on the distribution and ecological response mechanisms of aquatic plants, especially on the Tibetan Plateau. Here, we report a new species of Nelumbo Adanson, including leaves, receptacles, and fruits, namely Nelumbo delinghaensis sp. nov., from the Upper Youshashan Formation of the upper Middle Miocene in the northern Qaidam Basin on the Tibetan Plateau. The new species comprises centrally peltate leaves with 12–15 actinodromous primary veins and a receptacle embedded with ca. 15–30 fruits, with an unlobed central disc. Megafossils of lotus from northwest China broaden the geographical and stratigraphic ranges of Nelumbo. Our findings suggest that a large freshwater lake body surrounded by temperate forests and grassland developed in the Qaidam Basin during the late Middle Miocene, in sharp contrast to the present desert vegetation. The climate used to be sufficiently warm and moist enough to support a forest-steppe ecosystem with abundant freshwater bodies

Poly(A)-seq: A method for direct sequencing and analysis of the transcriptomic poly(A)-tails.

Poly(A) tails at the 3' end of eukaryotic messenger RNAs control mRNA stability and translation efficiency. Facilitated by various NGS methods, alternative polyadenylation sites determining the 3'-UTR length of gene transcripts have been extensively studied. However, poly(A) lengths demonstrating dynamic and developmental regulation remain largely unexplored. The recently developed NGS-based methods for genome-wide poly(A) profiling have promoted the study of genom-wide poly(A) dynamics. Here we present a straight forward NGS-method for poly(A) profiling, which applies a direct 3'-end adaptor ligation and the template switching for 5'-end adaptor ligation for cDNA library construction. Poly(A) lengths are directly calculated from base call data using a self-developed pipeline pA-finder. The libraries were directly sequenced from the 3'-UTR regions into the followed poly(A) tails, firstly on NextSeq 500 to produce single-end 300-nt reads, demonstrating the method feasibility and that optimization of the fragmented RNA size for cDNA library construction could detecting longer poly (A) tails. We next applied Poly(A)-seq cDNA libraries containing 40-nt and 120-nt poly(A) tail spike-in RNAs on HiSeq X-ten and NovaSeq 6000 to obtain 150-nt and 250-nt pair-end reads. The sequencing profiles of the spike-in RNAs demonstrated both high accuracy and high quality score in reading poly(A) tails. The poly(A) signal bleeding into the 3' adaptor sequence and a sharp decreased quality score at the junction were observed, allowing the modification of pA-finder to remove homopolymeric signal bleeding. We hope that wide applications of Poly(A)-seq help facilitate the study of the development- and disease-related poly(A) dynamics and regulation, and of the recent emerging mixed tailing regulation

Additional file 9: Table S9. of Transcriptome analysis reveals the complexity of alternative splicing regulation in the fungus Verticillium dahliae

aJAS & Intronic intron-2nd dataset. (XLSX 74 kb