Extra-Soft Tactile Sensor for Sensitive Force/Displacement Measurement with High Linearity Based on a Uniform Strength Beam

The soft sensing system has drawn huge enthusiasm for the application of soft robots and healthcare recently. Most of them possess thin-film structures that are beneficial to monitoring strain and pressure, but are unfavorable for measuring normal displacement with high linearity. Here we propose soft tactile sensors based on uniform-strength cantilever beams that can be utilized to measure the normal displacement and force of soft objects simultaneously. First, the theoretical model of the sensors is constructed, on the basis of which, the sensors are fabricated for testing their sensing characteristics. Next, the test results validate the constructed model, and demonstrate that the sensors can measure the force as well as the displacement. Besides, the self-fabricated sensor can have such prominent superiorities as follows—it is ultra-soft, and its equivalent stiffness is only 0.31 N·m−1 (approximately 0.4% of fat); it has prominent sensing performance with excellent linearity (R2 = 0.999), high sensitivity of 0.533 pF·mm−1 and 1.66 pF·mN−1 for measuring displacement and force; its detection limit is as low as 70 μm and 20 μN that is only one-tenth of the touch of a female fingertip. The presented sensor highlights a new idea for measuring the force and displacement of the soft objects with broad application prospects in mechanical and medical fields.

DEVELOPMENT OF UNIFORM STRENGTH DESIGN OF CABLE-NET MID-WATER TRAWL

The article implements the previously outlined proposal [1] on the feasibility of calculating the diameters of cables and threads of the cable-net part of a mid-water trawl based on ensuring their strength is equal to the cables in the first net piece. The case study was carried out regarding a commonly used trawl “Atlantic-1920 m, Nizin” developed by the company “Fishering Service”. The calculation algorithm is described which includes determination of resistance forces of the cable-net part and tensions in the cables and threads of net pieces. The safety factor is determined on the basis of the permissible stresses for the respective materials of which cables and threads are manufactured. After that, the values of diameters for cables and threads are calculated so as to ensure that the safety factor in the net pieces is equal to the cables in the first net piece. As a result, the formula is derived, which is able to calculate the diameters of cables and threads of the cable-net part of a mid-water trawl based on ensuring their strength is equal to the cables in the first net piece.

Problem scientific basis equal strengthe construction of cable-net part of the midwater trawl

The article outlined the R&D activities that would create a theory and methodology for designing the uniform strength cable-net mid-water trawls. To manage the mentioned problems a large volume of research is needed, however, the transition to cable-net design of trawls' parts will provide significant economic benefits. It therefore seems rather relevant and important.

Polyethylene glycol oligomers as siloxane modificators in consolidation of carbonate stones

The overall performance of alkoxysilanes as stone consolidants is constrained by stone mineralogy (particularly in the carbonate varieties) and by their tendency to crack during drying. In an attempt to overcome these problems, polyethylene glycol “chains” with two carboxylic acid end-groups (PEG-CA) were introduced in siloxane sols obtained by sol-gel chemistry using tetraethoxysilane (TEOS) as precursor. Different pre-condensation degrees (by varying the stirring times of sol-gel reaction: 10 min, 2, and 24 h) and PEG-CA chains with different molecular weights were studied as variables affecting the initial efficacy of the consolidants when applied into a limestone. The sol containing siloxanes with the lowest pre-condensation degree (10 min stirring) was quite susceptible to the carbonate media and thus a poor consolidation was achieved. The sol with the highest pre-condensation degree (24 h stirring) together with the PEG-CA chains with intermediate molecular weight produced significant and uniform strength gains along the stone depth. The consolidation also showed to be highly dependent on the molecular weight of the PEG-CA chains, the PEG-CA with highest molecular weight produced a non-uniform strength increase with potential harmful side effects. The results confirmed the role of carboxylic acid end-groups as efficient sol-gel catalysts and their ability to be incorporated into the silica matrix in the presence of carbonate stone.