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Ferroelectric and antiferroelectric smectic liquid crystalline (LC) phases are still at the center of investigations and interests for both their fundamental properties and variety of technological applications. This review aims to report the main contributions based on different nuclear magnetic resonance (NMR) techniques to the study of chiral liquid crystalline calamitic mesogens forming smectic phases, such as the SmA, the SmC* (ferroelectric), and the SmC*A (antiferroelectric) phases. 2H NMR and 13C NMR techniques and their combination were of help in clarifying the local orientational properties (i.e., the molecular and fragments' main orientational order parameters) at the transition between the SmA and the SmC* phases, and in the particular case of de Vries liquid crystals, NMR studies gave important clues regarding the actual models describing the molecular arrangement in these two phases formed by de Vries LCs. Moreover, this review describes how the combination of 2H NMR relaxation times' analysis, 1H NMR relaxometry, and 1H NMR diffusometry was successfully applied to the study of chiral smectogens forming the SmC* and SmC*A phases, with the determination of relevant parameters describing both rotational molecular and internal motions, collective dynamics, and translational self-diffusion motions. Several cases will be reported concerning NMR investigations of chiral ferroelectric and antiferroelectric phases, underlining the great potential of combined NMR approaches to the study of supramolecular, conformational, and dynamic properties of liquid crystals. [ABSTRACT FROM AUTHOR]

The dynamic motions of ion-acoustic (IA) waves in plasma are studied by considering the Kappa-Cairns electron distribution. The effect of external periodic force is also considered, here. Using the reductive perturbation technique, a Korteweg-de Vries (K-dV) equation is obtained. The quasiperiodic motions of IA waves are investigated by considering two-dimensional phase portraits and time-series analysis. The effects of non-thermal parameters (i.e., κ, α) and the strength (f0) of the external periodic force on nonlinear travelling wave structures are also discussed. [ABSTRACT FROM AUTHOR]

Ferroelectric and antiferroelectric smectic liquid crystalline (LC) phases are still at the center of investigations and interests for both their fundamental properties and variety of technological applications. This review aims to report the main contributions based on different nuclear magnetic resonance (NMR) techniques to the study of chiral liquid crystalline calamitic mesogens forming smectic phases, such as the SmA, the SmC* (ferroelectric), and the SmC*A (antiferroelectric) phases. 2H NMR and 13C NMR techniques and their combination were of help in clarifying the local orientational properties (i.e., the molecular and fragments’ main orientational order parameters) at the transition between the SmA and the SmC* phases, and in the particular case of de Vries liquid crystals, NMR studies gave important clues regarding the actual models describing the molecular arrangement in these two phases formed by de Vries LCs. Moreover, this review describes how the combination of 2H NMR relaxation times’ analysis, 1H NMR relaxometry, and 1H NMR diffusometry was successfully applied to the study of chiral smectogens forming the SmC* and SmC*A phases, with the determination of relevant parameters describing both rotational molecular and internal motions, collective dynamics, and translational self-diffusion motions. Several cases will be reported concerning NMR investigations of chiral ferroelectric and antiferroelectric phases, underlining the great potential of combined NMR approaches to the study of supramolecular, conformational, and dynamic properties of liquid crystals.

Abstract The purpose of the present study was to explore the effects of wearing knee guards on skin blood flow and skin pressure during dynamic soccer motions. Twenty-one male subjects participated in the following two experimental conditions: wearing knee guards (KG) and no knee guards (Control). Subjects performed several consecutive soccer motions along with a standing position between each motion. Skin blood flow and skin pressure on the thigh, knee, and calf were monitored. The results showed that skin pressure had the greatest value in a sitting position for both the KG condition and Control, but the smallest during instep kicking and switching directions (P

The necessity for higher speed and appropriate seakeeping performance of boats has led to extensive research. Hence, this research mainly discusses the optimal behavior of the boat against motions. From an economic point of view, reducing motions of the boat minimizes the damage caused by shock and vibration to the boat and equipment. Other benefits include comfort and safety and, as a result, improved human operating ability. Suspension systems are rarely used as motion controller in a boat. In multi-hull boats, the hull is an inseparable part of the vessels, so the wave will affect crew and equipment. This paper proposes and evaluates a novel concept boat equipped with a suspended cabin. The hull and superstructure (cabin) are separated in this new form by a simple passive suspension system. This study used numerical analysis to examine the seakeeping performance of the planing boat Fridsma model equipped with a passive suspension system under regular wave conditions. The hydrodynamics of the planing hull were modeled using commercial software, STAR-CCM+. For simulation of the passive suspension system between boat and cabin, MATLAB software was used. Results showed that the motion of the cabin, which is where the crew and equipment are located, decreased in regular waves.

The purpose of the present study was to explore the effects of wearing knee guards on skin blood flow and skin pressure during dynamic soccer motions. Twenty-one male subjects participated in the following two experimental conditions: wearing knee guards (KG) and no knee guards (Control). Subjects performed several consecutive soccer motions along with a standing position between each motion. Skin blood flow and skin pressure on the thigh, knee, and calf were monitored. The results showed that skin pressure had the greatest value in a sitting position for both the KG condition and Control, but the smallest during instep kicking and switching directions (P < 0.001). The rear calf had the greatest skin pressure for the KG condition (P < 0.001), while the side knee showed the greatest for the Control (P < 0.001). Normalized skin blood flow based on values from their standing position was the greatest during the jump motion among the various soccer motions. Interestingly, skin blood flow decreased by wearing the knee guards on the front thigh and calf (r = − 0.859; r = − 0.835; P < 0.001), while the blood flow increased on the side knee (r = 0.295, P < 0.001). Subjects felt greater skin pressure sensation during the jump motion and switching directions than other soccer positions/motions (P < 0.001). These results indicate that the knee guards result in relatively lighter pressure for dynamic motions (e.g., kick, switching directions, or jump) than for static positions (e.g., sitting or standing), and the skin blood flows for the thigh, knee, and calf are redistributed by wearing the knee guards, especially during jumping. [ABSTRACT FROM AUTHOR]

Skyscrapers cause both limited sky-view and multipath error when using Global Navigation Satellite System (GNSS) measurements for monitoring structural movements. To reduce multipath errors, cut-off elevation angle can be set to a high value such as 30°−40°. However, in the case of employing high cut-off elevation angles, the use of GPS only may not provide adequate positioning solutions. To overcome this problem, Galileo and GLONASS observations are combined with GPS observations. This study experimentally investigates the contribution of multi-GNSS for studying the effects of different cut-off elevation angles on the accuracy of high-rate GNSS results for detecting characteristics of dynamic motions for structural health monitoring (SHM). The filtration design, noise level and Signal-to-Noise Ratio (SNR) of high-rate GNSS measurements of GPS-only, GPS/Galileo, GPS/GLONASS and GPS/GLONASS/Galileo are assessed for different cut-off elevation angles. The results demonstrate that the SNR of GNSS solutions for GPS/GLONASS and GPS/GLONASS/Galileo is the highest, which signifies their use in SHM. The accuracy of the dynamic movements of structures can be attained to 2 mm, on average, using multi-GNSS measurements even when using high cut-off elevation angles up to 40°. The precision of GPS/GLONASS and GPS/GLONASS/Galileo systems with different cut-off elevation angles was high when referenced to LVDT.

To accelerate the strapdown inertial navigation system (SINS)/Doppler velocity logs (DVL) based underwater vehicle's coarse alignment process, an improved optimization based alignment (OBA) methodology is proposed, where the dynamic motions are taken into account. First, the DVL velocity measurements are analyzed to specify the extra velocity errors brought by the velocity difference between the transmitting and receiving epochs, where the influence of the dynamic motions is indicated. Then, a novel SINS/DVL coarse alignment method that accommodates dynamic motions is proposed, exploring the velocity relationship between the transmitting and receiving moments using SINS information. To evaluate the coarse alignment performance of the proposed method, simulations and field test are operated under different trajectories including various motions, such as turning and acceleration. Comparing to the traditional OBA method, the proposed coarse alignment solution shows its superiority in pitch, roll and yaw attitudes, where faster convergence rate and higher precision are obtained.

Skyscrapers cause both limited sky-view and multipath error when using Global Navigation Satellite System (GNSS) measurements for monitoring structural movements. To reduce multipath errors, cut-off elevation angle can be set to a high value such as 30°−40°. However, in the case of employing high cut-off elevation angles, the use of GPS only may not provide adequate positioning solutions. To overcome this problem, Galileo and GLONASS observations are combined with GPS observations. This study experimentally investigates the contribution of multi-GNSS for studying the effects of different cut-off elevation angles on the accuracy of high-rate GNSS results for detecting characteristics of dynamic motions for structural health monitoring (SHM). The filtration design, noise level and Signal-to-Noise Ratio (SNR) of high-rate GNSS measurements of GPS-only, GPS/Galileo, GPS/GLONASS and GPS/GLONASS/Galileo are assessed for different cut-off elevation angles. The results demonstrate that the SNR of GNSS solutions for GPS/GLONASS and GPS/GLONASS/Galileo is the highest, which signifies their use in SHM. The accuracy of the dynamic movements of structures can be attained to 2 mm, on average, using multi-GNSS measurements even when using high cut-off elevation angles up to 40°. The precision of GPS/GLONASS and GPS/GLONASS/Galileo systems with different cut-off elevation angles was high when referenced to LVDT. [ABSTRACT FROM AUTHOR]

This paper presents the theory development and numerical implementation of a new gradient-deficient-based ANCF (Absolute Nodal Coordinate Formulation) model applied to perform the nonlinear dynamic analysis of elastic line structures subject to large stretching and deformation. The derivations of model equations, introduced numerical approaches, and result validations are the focuses of this study. Different from the traditional rod theory for small stretching consideration, the present model implements the line structures' large elongation concepts into both the control mechanisms of constitutive formulations and equations of motion. The effect of external hydrodynamic forces on structures is also included in the model formulations. Based on the conservation of energy, the line model developed in this study covers the variation in strain and takes a full account of the bending effect with large stretching. A finite-element-based implicit scheme according to a modified Newmark-beta method is employed to solve the assembled system equations with unknown variables of nodal position vectors, their tangential derivatives, and strains. Selected cases with dynamic motions, such as nonlinear oscillation of a compound pendulum, free falling of a horizontal elastic beam in air with two different settings of gravity, free falling of a submerged horizontal tether with and without an attached concentrated mass, and a submerged vertical tether with a prescribed translational motion, are simulated to verify the developed model by comparing the results with analytical solutions and published experimental data and numerical results. It is found the present ANCF model, as noticed with good matched results with analytical solutions, measurements and other published solutions, is demonstrated to be able to provide converged and reasonably accurate predictions on the responses of line structures subject to large dynamic motions. [ABSTRACT FROM AUTHOR]

In order to stabilise floating wind turbines, an innovative motion stabilisation measure is proposed and verified here through conducting a series of numerical researches with the aid of SESAM. In the research, the numerical model of a spar-supported 5 MW floating turbine was developed first to investigate its motion stability in different depths water and under different wave conditions. Then, a new concept of motion stabiliser is proposed, which consists of a number of heave plates that are connected to floating turbine foundation via structural arms. The influences of both the number of heave plates and their arm length on motion reduction are then investigated in order to explore an optimal design of the proposed stabiliser. Considering the dynamic motions of a floating turbine is mainly affected by sea waves, the motion stabilising capability of the proposed stabiliser is investigated over a wide range of wave period 4–36 s. It has been found that after using the proposed motion stabiliser, both the pitch and heave motions of the floating turbine are successfully limited within the most range of wave period, especially when the wave period exceeds 12 s.

In spite of wide-ranging previous studies on synthetic macrocycles, the installation of open-close functions into the frameworks remains a challenge. We present a new polyaromatic macrocycle capable of switching between open and closed forms in response to external stimuli, namely, base and acid. The macrocycle, which is prepared in three steps, has a well-defined hydrophobic cavity with a length of around 1 nm, surrounded by four pH-responsive acridinium panels. The open and closed structures were confirmed by single-crystal X-ray analysis. The cylindrical cavity can bind long hydrophilic molecules up to 2.7 nm in length in neutral water and then release the bound guests through a reversible open-to-closed structural change upon simple addition of base. [ABSTRACT FROM AUTHOR]

Residues E402 and R404 of the Escherichia coli serine chemoreceptor, Tsr, appear to form a salt bridge that spans the interfaces between neighboring dimers in the Tsr trimer of dimers, a key structural component of receptor core signaling complexes. To assess their functional roles, we constructed full sets of single amino acid replacement mutants at E402 and R404 and characterized their signaling behaviors with a suite of in vivo assays. Our results indicate that the E402 and R404 residues of Tsr play their most critical signaling roles at their inner locations near the trimer axis where they likely participate in stabilizing the trimer-of-dimer packing and the kinase-ON state of core signaling complexes. Mutant receptors with a variety of side-chain replacements still accessed both the ON and OFF signaling states, suggesting that core signaling complexes produce kinase activity over a range of receptor conformations and dynamic motions. Similarly, the kinase-OFF state may not be a discrete conformation but rather a range of structures outside the range of those suitable for kinase activation. Consistent with this idea, some structural lesions at both E402 and R404 produced signaling behaviors that are not compatible with discrete two-state models of core complex signaling states. Those lesions might stabilize intermediate receptor conformations along the OFF–ON energy landscape. Amino acid replacements produced different constellations of signaling defects at each residue, indicating that they play distinct structure–function roles. R404, but not E402, was critical for high signal cooperativity in the receptor array. [ABSTRACT FROM AUTHOR]

This work studied the dynamic motions of disc samples with three contact surfaces on an oiled flat glass plate. A driving force was applied to the sample using elastic cords at the initial stage of motion. The sliding and rotation behaviors of the samples were determined to elucidate the effect of friction on the dynamic motions. Analytical models were also proposed for the sliding and rotation of samples based on equations of motion with damping factors. The models revealed all of the dominant features of experimental sliding and rotation, and indicated that the damping factor plays a significant role in the analysis the dynamic motions of samples under lubricated smooth surface conditions. • Dynamic motion of disk sample on oiled glass plate shows damped slide/rotation behavior. • Sliding velocity decreases sharply in early part of motion and more moderately in later part. • Owing to damping effect, rotation or angular velocity also decreased as a function of time. • Analytical models demonstrate physical aspects of sliding and rotation behavior of sample. [ABSTRACT FROM AUTHOR]

This paper demonstrates the utility of a differencing technique to transform surface EMG signals measured during both static and dynamic contractions such that they become more stationary. The technique was evaluated by three stationarity tests consisting of the variation of two statistical properties, i.e., mean and standard deviation, and the reverse arrangements test. As a result of the proposed technique, the first difference of EMG time series became more stationary compared to the original measured signal. Based on this finding, the performance of time-domain features extracted from raw and transformed EMG was investigated via an EMG classification problem (i.e., eight dynamic motions and four EMG channels) on data from 18 subjects. The results show that the classification accuracies of all features extracted from the transformed signals were higher than features extracted from the original signals for six different classifiers including quadratic discriminant analysis. On average, the proposed differencing technique improved classification accuracies by 2–8%. [ABSTRACT FROM AUTHOR]

The motions of an infinitely long, two-dimensional runway subjected to the dynamic moving load imposed by an airplane taking off are investigated. The runway is assumed to be floating in an inviscid fluid and is initially at equilibrium before the plane takes off. The deformation of the runway resulting from the take-off is wave-like and moves in the same direction as the plane. The maximum drag occurs when the plane catches up with the first wave. Three different runway configurations were considered: a baseline and ones which were ten and one hundred times more flexible than the baseline. For these runways, the added drag to the aircraft was very small, ranging from 1% for the stiffest to 10% for the most flexible runway. [ABSTRACT FROM AUTHOR]