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2021 ◽  
Author(s):  
Yufeng Sun ◽  
Ou Ma

Abstract Visual inspections of aircraft exterior surface are usually required in aircraft maintenance routine. It becomes a trend to use mobile robots equipped with sensors to perform automatic inspections as a replacement of manual inspections which are time-consuming and error-prone. The sensed data such as images and point cloud can be used for further defect characterization leveraging the power of machine learning and data science. In such a robotic inspection procedure, a precise digital model of the aircraft is required for planning the inspection path, however, the original CAD model of the aircraft is often inaccessible to aircraft maintenance shops. Thus, sensors such as 3D Laser scanners and RGB-D (Red, Green, Blue, and Depth) cameras are used because of their capability of generating a 3D model of an interested object in an efficient manner. This paper presents a two-stage approach of automating aircraft scanning with a UAV (Unmanned Aerial Vehicle) equipped with an RGB-D camera for reconstructing a digital replica of the aircraft when its original CAD model is not available. In the first stage, the UAVcamera system follows a predefined path to quickly scan the aircraft and generate a coarse model of the aircraft. Then, a full-coverage scanning path is computed based on the coarse model of the aircraft. In the second stage, the UAV-Camera system follows the computed path to closely scan the aircraft for generating a dense and precise model of the aircraft. We solved the Coverage Path Planning (CPP) problem for the aircraft scanning using Monte Carlo Tree Search (MCTS) which is a reinforcement learning technique. We also implemented the Max-Min Ant System (MMAS) strategy, a population-based optimization algorithm, to solve the CPP problem and demonstrate the effectiveness of our approach.


2021 ◽  
Author(s):  
Alison C Leonard ◽  
Jonathan Weinstein ◽  
Paul J Steiner ◽  
Annette Erbse ◽  
Sarel J Fleishman ◽  
...  

Stabilizing antigenic proteins as vaccine immunogens or diagnostic reagents is a stringent case of protein engineering and design as the exterior surface must maintain recognition by receptor(s) and antigen specific antibodies at multiple distinct epitopes. This is a challenge, as stability-enhancing mutations must be focused on the protein core, whereas successful computational stabilization algorithms typically select mutations at solvent-facing positions. In this study we report the stabilization of SARS-CoV-2 Wuhan Hu-1 Spike receptor binding domain (S RBD) using a combination of deep mutational scanning and computational design, including the FuncLib algorithm. Our most successful design encodes I358F, Y365W, T430I, and I513L RBD mutations, maintains recognition by the receptor ACE2 and a panel of different anti-RBD monoclonal antibodies, is between 1-2°C more thermally stable than the original RBD using a thermal shift assay, and is less proteolytically sensitive to chymotrypsin and thermolysin than the original RBD. Our approach could be applied to the computational stabilization of a wide range of proteins without requiring detailed knowledge of active sites or binding epitopes, particularly powerful for cases when there are multiple or unknown binding sites.


Buildings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 568
Author(s):  
Silje Kathrin Asphaug ◽  
Berit Time ◽  
Tore Kvande

Building façades must endure severe climatic exposure throughout their lifetimes. To prevent damage and expensive repairs, ageing tests are used in durability assessments. The NT Build 495 describes an artificial ageing procedure to address building material and component resistance to ultraviolet (UV) light, heat, water, and frost using a climate simulator. The test has been used for decades to investigate exterior surface materials and façade products but has only recently been adopted for multi-layered systems. This study investigates moisture accumulation in a façade system for retrofitting based on concrete and thermal insulation. Hygrothermal simulations of the façade system subjected to ageing were conducted. Moisture accumulation was considered theoretically for the current test procedure and compared to a modified setup in which the interior climate was controlled at 21 °C. Physical measurements were performed in the climate simulator to determine the boundary conditions. Results showed that moisture accumulation in the thermal insulation was largely affected by the type of concrete, that applying a water-repellent surface treatment reduced moisture accumulation, and that the current setup resulted in less moisture accumulation compared to the modified setup. The latter implicates accelerated degradation with the modified setup.


Author(s):  
Т. Ю. Гречкина ◽  
А. А. Выборнов ◽  
Ю. С. Лебедев

Статья посвящена результатам исследования жилища на стоянке Байбек в Северном Прикаспии. Планиграфические данные позволили представить его конфигурацию, размеры и конструктивные особенности. Стратиграфические наблюдения свидетельствуют о специфике его функционирования. Технико-типологические признаки керамического и каменного инвентаря подтверждают культурное единство комплекса и его отношение к каиршакскому типу. Радиоуглеродные даты указывают на начало первой четверти VI тыс. до н. э. и подтверждают сооружение заглубленных в материк жилищ на данной территории уже в раннем неолите. Палинологические образцы дают информацию не только о природно-климатической ситуации в этот период, но и о строительных деталях жилища. В археозоологических определениях представлены лишь дикие виды животных (преобладают кулан и благородный олень) и рыб. Липидный анализ показал, что в нагаре содержатся признаки растительной и животной пищи. Вся совокупность данных свидетельствует, что Северный Прикаспий был одним из наиболее ранних регионов перехода к неолиту в Восточной Европе. . The paper presents results of studying a dwelling at Baybek in the northern Caspian region. Planigraphic data enabled the authors to describe its configuration, size and design features. Stratigraphical observations demonstrate specific features of its use. Technical and typological traits of ceramic and stone tools confirm that all objects from this assemblage belong to the same culture of the Kairshak type. Radiocarbon dates put the site around the beginning of the first quarter of 6 mill. BC and confirm that sunken-bottomed dwellings were constructed in this area in the Early Neolithic. Palynological samples provide information not only on the nature and the climatic situation in that period, but also on construction elements of the dwellings. Archaeozoological assemblage includes only wild species of animals (kulan and red deer prevailing) and fish. According to the lipid analysis, encrusted deposits adhering to the interior or exterior surface of vessels are associated with plant and animal food. The corpus of data clearly demonstrates that the northern Caspian region was one of the earliest territories in Eastern Europe where transition to the Neolithic took place.


PLoS Genetics ◽  
2021 ◽  
Vol 17 (11) ◽  
pp. e1009886
Author(s):  
Megan S. Behrmann ◽  
Himasha M. Perera ◽  
Joy M. Hoang ◽  
Trisha A. Venkat ◽  
Bryan J. Visser ◽  
...  

Helicase regulation involves modulation of unwinding speed to maintain coordination of DNA replication fork activities and is vital for replisome progression. Currently, mechanisms for helicase regulation that involve interactions with both DNA strands through a steric exclusion and wrapping (SEW) model and conformational shifts between dilated and constricted states have been examined in vitro. To better understand the mechanism and cellular impact of helicase regulation, we used CRISPR-Cas9 genome editing to study four previously identified SEW-deficient mutants of the bacterial replicative helicase DnaB. We discovered that these four SEW mutations stabilize constricted states, with more fully constricted mutants having a generally greater impact on genomic stress, suggesting a dynamic model for helicase regulation that involves both excluded strand interactions and conformational states. These dnaB mutations result in increased chromosome complexities, less stable genomes, and ultimately less viable and fit strains. Specifically, dnaB:mut strains present with increased mutational frequencies without significantly inducing SOS, consistent with leaving single-strand gaps in the genome during replication that are subsequently filled with lower fidelity. This work explores the genomic impacts of helicase dysregulation in vivo, supporting a combined dynamic regulatory mechanism involving a spectrum of DnaB conformational changes and relates current mechanistic understanding to functional helicase behavior at the replication fork.


Research ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Yuecheng Xiong ◽  
Fei Yu ◽  
Stefanie Arnold ◽  
Lei Wang ◽  
Volker Presser ◽  
...  

Faradaic electrode materials have significantly improved the performance of membrane capacitive deionization, which offers an opportunity to produce freshwater from seawater or brackish water in an energy-efficient way. However, Faradaic materials hold the drawbacks of slow desalination rate due to the intrinsic low ion diffusion kinetics and inferior stability arising from the volume expansion during ion intercalation, impeding the engineering application of capacitive deionization. Herein, a pseudocapacitive material with hollow architecture was prepared via template-etching method, namely, cuboid cobalt hydroxide, with fast desalination rate (3.3 mg (NaCl)·g-1 (h-Co(OH)2)·min-1 at 100 mA·g-1) and outstanding stability (90% capacity retention after 100 cycles). The hollow structure enables swift ion transport inside the material and keeps the electrode intact by alleviating the stress induced from volume expansion during the ion capture process, which is corroborated well by in situ electrochemical dilatometry and finite element simulation. Additionally, benefiting from the elimination of unreacted bulk material and vertical cobalt hydroxide nanosheets on the exterior surface, the synthesized material provides a high desalination capacity (117±6 mg (NaCl)·g-1 (h-Co(OH)2) at 30 mA·g-1). This work provides a new strategy, constructing microscale hollow faradic configuration, to further boost the desalination performance of Faradaic materials.


Chemistry ◽  
2021 ◽  
Vol 3 (4) ◽  
pp. 1203-1214
Author(s):  
Garrett D. Jackson ◽  
Max B. Tipping ◽  
Christopher G. P. Taylor ◽  
Jerico R. Piper ◽  
Callum Pritchard ◽  
...  

New synthetic routes are presented to derivatives of a (known) M8L12 cubic coordination cage in which a range of different substituents are attached at the C4 position of the pyridyl rings at either end of the bis(pyrazolyl-pyridine) bridging ligands. The substituents are (i) –CN groups (new ligand LCN), (ii) –CH2OCH2–CCH (containing a terminal alkyne) groups (new ligand LCC); and (iii) –(CH2OCH2)3CH2OMe (tri-ethyleneglycol monomethyl ether) groups (new ligand LPEG). The resulting functionalised ligands combine with M2+ ions (particularly Co2+, Ni2+, Cd2+) to give isostructural [M8L12]16+ cage cores bearing 24 external functional groups; the cages based on LCN (with M2+ = Cd2+) and LCC (with M2+ = Ni2+) have been crystallographically characterised. The value of these is twofold: (i) exterior nitrile or alkene substituents can provide a basis for further synthetic opportunities via ‘Click’ reactions allowing in principle a diverse range of functionalisation of the cage exterior surface; (ii) the exterior –(CH2OCH2)3CH2OMe groups substantially increase cage solubility in both water and in organic solvents, allowing binding constants of cavity-binding guests to be measured under an increased range of conditions.


2021 ◽  
Vol 9 (3A) ◽  
Author(s):  
Ashfaque Ahmed Jhatial ◽  
◽  
Wan Inn Goh ◽  
Noridah Mohamad ◽  
Kim Hung Mo ◽  
...  

Increased usage of concrete contributes to urban thermal discomfort due to the Urban Heat Island effect. At the same time, the corresponding increased consumption of cement also causes a significant rise in carbon dioxide (CO2) gas emissions. This experimental work aims at evaluating the thermal and mechanical performance of 1800 kg/m3 dry density green sustainable foamed concrete (GFC) incorporating agroindustrial waste such as Palm Oil Fuel Ash (POFA) and Eggshell Powder (ESP) as supplementary cementitious materials (SCMs). The POFA content varied from 15 to 35%, with increments of 5%, while being supplemented with 5% ESP. To evaluate the performance of the developed GFC, the flowability, mechanical strengths (compressive and splitting tensile strengths), and thermal performances (thermal conductivity and surface temperature) were investigated. Incorporation of 15-25% of POFA supplemented with 5% ESP as partial cement replacement materials resulted in enhanced mechanical strengths. Although usage of POFA can reduce the thermal conductivity, the POFA content must be limited to 15–25% to prevent excessive heat absorption by the exterior surface of the concrete. Overall, the optimum use of 15% POFA in a combination of 5% ESP is desirable to produce an eco-friendly sustainable foamed concrete.


2021 ◽  
Vol 16 (4) ◽  
pp. 199-225
Author(s):  
Elif Özer Yüksel ◽  
Nil Türkeri

ABSTRACT Using vegetated facade systems (VFS) as a sustainable solution for existing and new buildings and evaluating thermal performance of these sytems are not a new concept. However, there is a gap in literature about measuring thermal performance of VFS applied on an insulated wall. Also, in the research literature, there are few studies measuring thermal performance of felt type VFS in temperate climates, and data about the thermal performance of VFS during winter periods is still scarce. Thus, the aim of the present study is to measure the thermal performance of a felt type VFS applied on a thermal insulated existing wall that us located in Kocaeli, Turkey, under Csa climate conditions during heating and cooling periods. Test results indicate that the felt type VFS acts as a shading device and has a positive contribution to the thermal performance of building walls during a cooling period. In daytime when there is a high amount of solar radiation, felt type VFS decreased exterior surface temperatures of the insulated existing wall by a maximum of 24.4°C, 32.2°C and 37.2°C, in spring, summer and fall periods, respectively. Additionally, indoor air temperatures of the vegetated facade were lower than indoor air temperatures of the reference facade with the maximum difference of 1.8°C during the cooling period. Also, test results indicate that the vegetated facade never dropped to below 0°C while exterior surface temperatures of the reference facade dropped below 0°C at nighttime in the winter period. Thus, it can be claimed that the felt type VFS behaves as a thermal buffer and enhances the thermal performance of the exterior wall of the existing building during heating periods at nighttime. As a conclusion, although differences between exterior surface temperatures of vegetated and reference walls were high, differences between interior surface temperatures of vegetated and reference walls were not meaningful. That is due to the fact that the existing building exterior wall assembly includes 5 cm thickness thermal insulation material which enhance the thermal performance of the brick wall. Finally, according to solar reflectance results, it can be claimed that vegetated facade systems have a positive effect on reducing urban heat island effect.


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