The Causes of Propeller Pitching Moment and the Conditions for its Significance

Recent development of vertical takeoff and landing (VTOL) aircraft has renewed interest in the study of propellers. One metric in particular, the propeller pitching moment, has been observed to be important to VTOL aircraft stability and control in the past. Propellers at angles of attack could not be accurately modeled in generations past due to a lack of computational power, but even with advances in computer technology, modern designers seem to possess insufficient knowledge in this area. In this dissertation, we study the physics behind propeller pitching moment in the context of an isolated propeller and a propeller upstream of a wing. An unsteady 3D vortex lattice method is developed specifically to model propellers at angles of attack and is validated by comparing to high-fidelity CFD analyses. We then use the model to isolate velocity influences to show that the propeller pitching moment is largely caused by two effects: a skewed wake and the presence of wing circulation. Generated maps of propeller pitching moment over a range of operational parameters corresponding to VTOL transition show that the low flight speeds and high angles of attack encountered during transition lead to significant magnitudes of propeller pitching moment that would be difficult to trim using passive methods. Also, derivation of a generalizable metric of significance shows that the peak contribution of propeller pitching moment to aircraft stability is comparable to a longitudinal displacement of the center of gravity by several percent of the wing chord. Finally, we give a concluding discussion on the impact of propeller pitching moment on VTOL aircraft design.Ph.D

Preparation and pre-clinical characterization of sustainedrelease ketoprofen implants for the management of pain and inflammation in osteoarthritis

Purpose: To prepare and evaluate sustained-release ketoprofen implants for prolonged drug release and activity.Methods: Ketoprofen implants were prepared with poly (lactic-co-glycolic acid) (PLGA) and chitosan in the form of tablets. The implants were analyzed for drug loading, thickness, hardness, swelling, in vitro drug release, as well as in vivo analgesic and anti-inflammatory activities.Results: The implants were round, smooth in appearance, uniform in thickness and showed no cracks or physical defects on the surface. Their friability was < 1 % while drug content ranged from 89.98 ± 2.06 to 92.95 ± 1.65 %. In vitro drug release ranged from 70.23 to 92.04 % at the end of 5 days. Implants containing higher amounts of PLGA produced the highest swelling (40.24 ± 1.08 %). Implant IKT3 showed maximum analgesic activity (7.75 ± 1.00 s) and shortest time of maximum analgesia (2.5 h) in hot plate method. Inhibition of rat paw edema for IKT1, IKT2 and IKT3 was 79.95, 69.98 and 82.24 %, respectively, after 24 h.Conclusion: Ketoprofen-loaded implant IKT3 (4:4:2 ratio of PLGA, chitosan and ketoprofen) provides relatively quick onset and prolonged duration of analgesic effect. Thus, ketoprofen implants have a potential for development into therapeutic products for prolonged management of pain and inflammation in osteoarthritis.Keywords: Osteoarthritis, Ketoprofen implant, Prolonged analgesia, Poly(lactic-co-glycolic acid), Chitosa

An Exploration of the Performance and Acoustic Characteristics of UAV-Scale Stacked Rotor Configurations

As interest grows in rotor- and propeller-driven electric vertical takeoff and landing (eVTOL) aircraft for the Urban Air Mobility market, there is a potential for previously studied concepts to reemerge due to the opportunities afforded by novel technologies and operating modes. One such concept is the stacked rotor, which consists of multiple co-rotating rotors positioned co-axially with a small axial offset. The goal of the work presented in this paper is to determine whether stacked rotors offer a compelling advantage for eVTOL aircraft in terms of both performance and acoustic characteristics. Results are presented for new experimental tests and computational modeling of multiple stacked rotor configurations, and comparisons are made with conventional rotor configurations. Testing of thirteen separate configurations each using the same blade shaperevealed a configuration that resulted in an increase in the rotor power loading efficiency by more than 7% and reduced noise by more than 3 dBA when compared with a conventional rotor with all blades located in the same rotational plane

The water lily genome and the early evolution of flowering plants

Water lilies belong to the angiosperm order Nymphaeales. Amborellales, Nymphaeales and Austrobaileyales together form the so-called ANA-grade of angiosperms, which are extant representatives of lineages that diverged the earliest from the lineage leading to the extant mesangiosperms1–3. Here we report the 409-megabase genome sequence of the blue-petal water lily (Nymphaea colorata). Our phylogenomic analyses support Amborellales and Nymphaeales as successive sister lineages to all other extant angiosperms. The N. colorata genome and 19 other water lily transcriptomes reveal a Nymphaealean whole-genome duplication event, which is shared by Nymphaeaceae and possibly Cabombaceae. Among the genes retained from this whole-genome duplication are homologues of genes that regulate flowering transition and flower development. The broad expression of homologues of floral ABCE genes in N. colorata might support a similarly broadly active ancestral ABCE model of floral organ determination in early angiosperms. Water lilies have evolved attractive floral scents and colours, which are features shared with mesangiosperms, and we identified their putative biosynthetic genes in N. colorata. The chemical compounds and biosynthetic genes behind floral scents suggest that they have evolved in parallel to those in mesangiosperms. Because of its unique phylogenetic position, the N. colorata genome sheds light on the early evolution of angiosperms.Supplementary Tables: This file contains Supplementary Tables 1-21.National Natural Science Foundation of China, the open funds of the State Key Laboratory of Crop Genetics and Germplasm Enhancement (ZW201909) and State Key Laboratory of Tree Genetics and Breeding, the Fujian provincial government in China, the European Union Seventh Framework Programme (FP7/2007-2013) under European Research Council Advanced Grant Agreement and the Special Research Fund of Ghent University.http://www.nature.com/naturecommunicationsam2021BiochemistryGeneticsMicrobiology and Plant Patholog

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Performance of Turbo-TCM in wireless channel and its application for image transmission

In designing a wireless communication transceiver, the main objective is to achieve high-speed high-spectral-efficient data transmission with low error probability. Therefore, powerful channel coding is a major requirement in such a harsh wireless environment. Recently a novel class of parallel concatenated recursive convolutional codes called turbo-codes has attracted great attention by its surprising error correcting capability. In this thesis, we study the performance of turbo-codes in a wireless environment. In order to achieve high spectral efficiency, turbo-codes with multilevel modulation (turbo-TCM) are utilized. We simulated turbo-TCM in a frequency selective fading channel with two kinds of the time delay spread profiles, namely, the equal-amplitude two-ray profile and the one-sided exponential profile. It is found that turbo-TCM achieves unmatched performance of average irreducible BER compared to the conventional TCM, especially in channels with high delay spread (i.e., strong intersymbol interference). Therefore, it suggests that high-speed high-spectral-efficient data transmission in a wireless environment can be achieved by utilizing turbo-TCM. Wireless multimedia is being discussed actively among researchers and developers. Powerful and effective channel coding is necessary for high quality image and video transmission through a wireless environment. To see an application of turbo-codes, we study its performance for the transmission of compressed images over a flat Rayleigh fading channel and a frequency selective fading channel. We find that the excellent error correcting capability, the iterative decoding scheme and the soft channel information utilization of turbo-codes are especially suitable for compressed image transmission. In addition, a joint source/channel coding scheme and an unequal error protection (UEP) are also studied in this thesis. A lot of simulation results are presented and compared with a soft decision convolutional code

Effects of time delay spread on Turbo-TCM in a wireless communication channel

This paper presents some simulation results on the performances of turbo-codes with multilevel modulation (Turbo-TCM) in a wireless environment. The wireless channel is modeled as a frequency selective fading channel with two time delay spread profiles, namely, a two-ray profile and a one-sided exponential profile. Turbo-TCM codes constructed from punctured turbo-codes combined with different modulation schemes are studied. It is found that Turbo-TCM achieves unmatched performance of average irreducible BER. Turbo-TCM has much lower error probability than conventional TCM, especially in channels with high delay spread

NaOH-Thiourea Aqueous Solution Treatment of Cellulose Fiber and its Effects on Bulk and Softness

Bleached kraft pulp of hardwood was pretreated in a NaOH-thiourea aqueous solution to modify the bulk and softness of the cellulose fibers with minimal reduction in paper strength. The effects of soaking time, fiber concentration, alkali dosage, and freezing time were evaluated through single factor experiments. The optimal conditions were determined to be a soaking time of 15 min, fiber concentration of 15%, alkali dosage of 9%, and freezing time of 75 min. Under the optimal conditions, the bulk and softness of the treated cellulose fibers were increased by 28.7% and 21.6%, respectively, compared with those of untreated cellulose fibers. The tensile and burst indices were only reduced by 1.2% and 5.1%, respectively, under these conditions. Also, there were almost no effects on the polymerization degree, the thermostability, and the structure of the functional groups or crystalline regions

Simulating the IPOD, East Asian summer monsoon, and their relationships in CMIP5

This paper evaluates the simulation performance of the 37 coupled models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) with respect to the East Asian summer monsoon (EASM) and the Indo-Pacific warm pool and North Pacific Ocean dipole (IPOD) and also the interrelationships between them. The results show that the majority of the models are unable to accurately simulate the interannual variability and long-term trends of the EASM, and their simulations of the temporal and spatial variations of the IPOD are also limited. Further analysis showed that the correlation coefficients between the simulated and observed EASM index (EASMI) is proportional to those between the simulated and observed IPOD index (IPODI); that is, if the models have skills to simulate one of them then they will likely generate good simulations of another. Based on the above relationship, this paper proposes a conditional multi-model ensemble method (CMME) that eliminates those models without capability to simulate the IPOD and EASM when calculating the multi-model ensemble (MME). The analysis shows that, compared with the MME, this CMME method can significantly improve the simulations of the spatial and temporal variations of both the IPOD and EASM as well as their interrelationship, suggesting the potential for the CMME approach to be used in place of the MME method