An improved posture evaluation method of cylindrical intersecting holes on large aerospace component based on monocular vision

Cylindrical intersecting holes(CIHs) are common connection and location reference features in assembly of large aerospace structures such as missile and rocket cabins. The posture accuracy of assembly holes significantly impacts the relative position accuracy of joined parts and fatigue strength of finished product. At present, monocular vision measurement is widely used in automatic drilling of assembly holes for its integration simplicity and lower cost, but in most research, only the front face edge of the hole is used in the measurement model, and the hole end surface is usually assumed to be plane, which inevitably leads to precision loss. In this research, a novel posture measurement method for CIHs is proposed. Firstly, by introducing an ambiguity removal strategy, a coarse posture estimation method based on plane hypothesis of the two end surfaces of CIHs is suggested. Secondly, considering that there is no simply explicit expression for CIHs edge, thus it is difficult to adopt the conventional model projection based pose optimization method. In view of this, the three-dimensional points corresponding to the edge pixels of CIHs image are derived, and the pose optimization model is established by minimizing the deviations between the distance from the points to the CIHs axis and the hole radius. Moreover, to better control the direction parameters of CIHs during the global optimization process, the approximately perpendicular and intersection constraints between CIHs axis and cylindrical component axis are involved in solution. The effectiveness of the posture measurement method is verified by comparative experiments with current methods and CMM, which demonstrates improvements on both measurement accuracy and robustness.

Morphological, hydrodynamic and sedimentary characteristics of the Northeastern coast of Cuba

The absence of the marine platform, the presence of emerged and submerged terraces with tide notches on its front face and the increase in the number of beaches constituted by terrigenous sands towards the east end of this coastal stretch are the main geomorphological features that characterize the northeastern coast of Cuba. The lower rocky terrace is the best represented type of coastline on the Northeastern coast, exposed to the direct action of ocean waves. Considering the inland coast, mangroves are the most abundant type of coast and occupy most of the bays on this coastal stretch. From the hydrodynamic point of view, the highest wave heights of the north coast of Cuba take place there. In addition, the biggest tidal range of the Cuban archipelago is recorded. From the sedimentary point of view, these beaches have a greater amount of fragments of mollusks and corals and fewer fragments of calcareous algae than the other beaches of the Cuban archipelago. These beaches, unlike the other beaches of Cuba, show cumulative processes at the end of winter and early spring, with a maximum accumulation in April, while eroding at the beginning of autumn, with maximum values in the months of September and October. Keywords: Coastal characteristic, beach, genesis sand, Northeastern coast of Cuba.

Evaluation of Hydrophilic and Lipophilic Antioxidant Capacity in Spanish Tomato Paste: Usefulness of Front-Face Total Fluorescence Signal Combined with Parafac

The hydrophilic and lipophilic antioxidant activities due to the main bioactive components present in Spanish tomato paste samples were studied, using standardized and fluorescent methods. After extraction, phenolic antioxidants (Folin-Ciocalteu method) and total antioxidant activity (TEAC assay) were evaluated, examining differences between hydrophilic and lipophilic extracts corresponding to different samples. Total fluorescence spectra of extracts (excitation-emission matrices, EEMs) were recorded in the front-face mode at two different ranges: 210–300 nm/310–390 nm, and 295–350 nm/380–480 nm, for excitation and emission, respectively, in the hydrophilic extracts. In the lipophilic extracts, the first range was 230–283 nm/290–340 nm, while the second range was 315–383 nm/390–500 nm for excitation and emission, respectively. EEMs from a set of 22 samples were analyzed by the second-order multivariate technique Parallel Factor Analysis (PARAFAC). Tentative assignation of the different components to the various fluorophores of tomato was tried, based on literature. Correlation between the antioxidant activity and score values retrieved for different components in PARAFAC model was obtained. The possibility of using EEMs-PARAFAC to evaluate antioxidant activity of hydrophilic and lipophilic compounds in these samples was examined, obtaining good results in accordance with the Folin-Ciocalteu and TEAC assays.

Analysis of the oscillation behavior during ultrasonic welding of EN AW-1070 wire strands and EN CW004A terminals

For fulfilling the demand of durable yet lightweight electrical connections in transportation industries, ultrasonic metal welding (USMW) sees widespread use in these branches. As the ultrasound oscillations utilized in the welding procedure occur at a range of only a few micrometers at frequencies of 20–100 kHz for an overall duration of only 50–1500 ms, it is not possible to observe the compaction behavior with the bare eye. This paper focusses on investigating the oscillation behavior of the horn, the anvil, and the joining partners during the welding procedure by utilizing an array of synchronized laser vibrometers and performing welds with incrementing time stages. The oscillation data is correlated with temperature measurements in the welding zone as well as tensile testing results. Inter alia the formation of sidebands at the fundamental frequency as well as 2nd- and 3rd-order harmonics has been observed for the anvil, terminal, and wire front face when exceeding optimal weld time which would lead to maximum joint strength. Following the assumption of other research groups, the cause of these sidebands could be a change in relative motion of these components. As the terminal is slipping with increasing weld time, it could be assumed that the reason for the sidebands is low-frequency movement of the anvil, modulated onto the fundamental frequency, additionally indicating successful bonding of the stranded wire and the terminal. Furthermore, this slipping of the terminal on the anvil could lead to increased wear of the anvil knurls.

Chemically Insignificant Social Parasites Exhibit More Anti-Dehydration Behaviors than Their Hosts

Social parasites have evolved adaptations to overcome host resistance as they infiltrate host colonies and establish there. Among the chemical adaptations, a few species are chemically “insignificant”; they are poor in recognition cues (cuticular hydrocarbons) and evade host detection. As cuticular hydrocarbons also serve a waterproofing function, chemical insignificance is beneficial as it protects parasites from being detected but is potentially harmful because it exposes parasites to desiccation stress. Here I tested whether the social parasites Polistes atrimandibularis employ behavioral water-saving strategies when they live at Polistes biglumis colonies. Observations in the field showed that parasites were less active than their cohabiting host foundresses, spent more time at the nest, and rested in the shadowy, back face of the nest, rather than at the front face, which contradicted expectations for the use of space for dominant females—typically, dominants rest at the nest front-face. These data suggest that behavioral adaptations might promote resistance to desiccation stress in chemical insignificant social parasites.

Parasitic Capillary Waves on Small-Amplitude Gravity Waves with a Linear Shear Current

This paper describes a numerical investigation of ripples generated on the front face of deep-water gravity waves progressing on a vertically sheared current with the linearly changing horizontal velocity distribution, namely parasitic capillary waves with a linear shear current. A method of fully nonlinear computation using conformal mapping of the flow domain onto the lower half of a complex plane enables us to obtain highly accurate solutions for this phenomenon with the wide range of parameters. Numerical examples demonstrated that, in the presence of a linear shear current, the curvature of surface of underlying gravity waves depends on the shear strength, the wave energy can be transferred from gravity waves to capillary waves and parasitic capillary waves can be generated even if the wave amplitude is very small. In addition, it is shown that an approximate model valid for small-amplitude gravity waves in a linear shear current can reasonably well reproduce the generation of parasitic capillary waves.

Blast Loading and Its Effects on Building

Terrorist assaults have become more common in recent years. Their main purpose is to destroy important structures such as areas of defense, hospitals, schools, buildings. Due to the explosion, high pressure is generated and the blast time is also very short, but it can damage the structure from outside and inside. Which can cause a lot of damage to human life. There has an influence on the nation's economy. Like the earthquake and wind load, the blast load should also be designed, keeping in mind the important structures that have to be avoided from the explosion. In this research paper, six story R.C.C. Structures exposed to explosion loads are analyzed. We study the effect on the building by changing the weight of the explosive and the distance between the explosion source and the building. The IS 4991-1968 code has been used to calculate the parameters of the explosion pressure waves. The program ETabs 2019 has been used to analyze the effect of blast load. The structure has been modified by providing shear walls to reduce excessive displacement due to blast loading on the building. The results of the analysis are compared after adding the shear wall with the general building model. The result was that after the addition of the shear wall, the effect of blast loading is greatly reduced. Keywords: Blast phenomena, Standoff distance, detonation charge weight (TNT), Front face pressure, Side face pressure, ETABS, RCC, Blast waves, explosive effects, Story Displacement, Storey Drift, Overturning Moment, Shear wall.

A new electrically small antenna for on-demand 3.6/5.8 GHz wireless applications

This article presents a highly miniaturized dual-band electrically small antenna (ESA) for on-demand 3.6 and 5.8 GHz wireless applications. A partial rectangle-shaped structure is printed on the back face of the dielectric material, forming the antenna's ground (GND) plane. The radiating structure of the antenna consists of a C-shaped structure and a U-shaped ring connected to it, which is printed on the dielectric material's front face. The overall dimensions of the designed antenna are 0.160λo × 0.160λo × 0.02λo at the lowest operating frequency. The proposed antenna has a ka value of 0.56 at the lowest operating frequency, which is 3.59 GHz. Thus, the proposed antenna is considered as electrically small. The characteristic mode analysis is adopted to provide a clear understanding of the antenna's resonance behavior. The antenna has been fabricated and the simulation results were validated through measurements. Good agreement between simulated and measured results was obtained. Dual-band operation at 3.62 and 5.75 GHz was achieved, according to the measured reflection coefficient. The proposed antenna offers an adequate performance in terms of gain and efficiency, based on simulation and measurement results. Because of these characteristics, the antenna is well-suited to new wireless applications.