Numerical and Experimental Analysis of Portable Underwater Robots with a Movable Float Device

This report describes a numerical and experimental study of a posture control device based on a movable float for portable underwater robots. We numerically analyzed the static stability using a stability curve and allowable spatial range of a center-of-gravity shift caused by a payload shift or manipulator configuration. Further, we proposed a feedback controller based on direct pitch and roll signals to change and maintain robot posture. We tested the feedback control using a numerical simulator and conducted experiments in a water tank using two portable underwater robots to demonstrate the effectiveness of the movable float device and proposed controller. The results of the field experiments showed that the device and proposed controller can be employed for effective underwater operations of portable underwater robots.

Risk Assessment Fishing Vessel Based for the Intact Ship Stability

Application of safety assessment and risk analysis using a risk-based approach for ship stability in ship operations at sea. However, there are currently no specific criteria and computational methods for risk assessment of ship stability. Based on the stability requirements for fishing activities at sea, the ship stability criteria will be explained in detail in this study. Calculation of stability used to obtain the GZ enforcement arm is carried out with the help of software for the shaking period using the International Maritime Organization (IMO) formula. Next, how to calculate parameters and determine certain coefficients for risk assessment of ship stability, and how to redraw the stability curve. Finally, proposed method is applied to ship model with comments and recommendations for monitoring to provide and overview. The study result indicate that the five loading conditions that occur on the ship have good stability by the criteria set by the International Maritime Organization (IMO). The value of GMt in each condition includes condition 1 and so on, 0.48; 0.48; 0.47; 0.46; 0.43. The results are presented in the form of F-N. Finally the sensitivity of the model is evaluated along with the assessment of associated uncertainties. The FN graph represents acceptable areas and unacceptable areas. Based on the results of data processing, the highest GM at GM Load-case 5 0.638 meters is in the Acceptable area. While Load-case 1 to Load-case 4 GM values sequentially Load-case 1: 0.487 meters; Load-case 2: 0.488 meters; Load-case 3: 0.47 meters; Load-case 4: 0.468 meters; is in an unacceptable area Unacceptable.

Stability of Viscous Flow in a Curved Porous Channel with Radial Flow

In this paper, we present a linear hydrodynamic stability analysis of the fluid, flowing in a porous curved channel. The motion is due to Pressure gradient acting round the curved channel and an imposed radial flow. The analytical solution of the eigen value problem is obtained by using the Galerkin’s method, for the wide gap case. Results for critical wave number and Dean Number are obtained and are compared with earlier result. The agreement is very good. Also, the stability curve, amplitude of the radial velocity and the cell-pattern are shown on graphs. The results show that the flow is strongly stabilized by an outward radial flow and weakly stabilized by a strong inward radial flow, while it is destabilized by a weak inward radial flow. In presence of outward flow, wide gap systems show stronger stability than the small gap system.

THE DEPLOYING BUOYDING SYSTEM DESIGN IN A STATIONARY FLOW AS A PART OF A MEDIUM-FREQUENCY HYDRO-ACOUSTIC COMPLEX AND ITS CHARACTERISTICS RESEARCH

The present study provides a designing the floating buoy system. The floating buoy is designed to determine the mid-frequency hydroacoustic set location, located in the underwater position, using sonar communication signals. The approach considers the stability at large angles of inclination analysis. For this reason, the main stability criteria is recovery moment. As a result, the following diagrams are plotted – statical stability curve and dynamical stability curve to estimate the research. Moreover, the study includes defining spatial configuration at steady flow. It is also important to mention the basic requirements for the construction of the buoy are ensuring positive buoyancy according to the terms of reference, lack of sea water absorption, sustainability to hydrostatic pressure and corrosion resistance. The study reveals designing the construction, which is able to prevent capsizing. Consequently, the buoy has positive stability, sufficient recovery moment enable to return the structure to its original position and meet the claimed buoyancy requirements.

A new lattice hydrodynamic model for bidirectional pedestrian flow with consideration of pedestrians’ honk effect

Understanding the pedestrian behavior contributes to traffic simulation and facility design/redesign. In practice, the interactions between individual pedestrians can lead to virtual honk effect, such as urging surrounding pedestrians to walk faster in a crowded environment. To better reflect the reality, this paper proposes a new lattice hydrodynamic model for bidirectional pedestrian flow with consideration of pedestrians’ honk effect. To this end, the concept of critical density is introduced to define the occurrence of pedestrians’ honk event. In the linear stability analysis, the stability condition of the new bidirectional pedestrian flow model is given based on the perturbation method, and the neutral stability curve is also obtained. Based on this, it is found that the honk effect has a significant impact on the stability of pedestrian flow. In the nonlinear stability analysis, the modified Korteweg–de Vries (mKdV) equation of the model is obtained based on the reductive perturbation method. By solving the mKdV equation, the kink-antikink soliton wave is obtained to describe the propagation mechanism and rules of pedestrian congestion near the neutral stability curve. The simulation example shows that the pedestrians’ honk effect can mitigate the pedestrians crowding efficiently and improve the stability of the bidirectional pedestrian flow.

On the neutral stability curve for shallow conical shells subjected to lateral pressure

This work presents a detailed asymptotic description of the neutral stability envelope for the linear bifurcations of a shallow conical shell subjected to lateral pressure. The eighth-order boundary-eigenvalue problem investigated originates in the Donnell shallow-shell theory coupled with a linear membrane pre-bifurcation state, and leads to a neutral stability curve that exhibits two distinct growth rates. By using singular perturbation methods we propose accurate approximations for both regimes and explore a number of other novel features of this problem. Our theoretical results are compared with several direct numerical simulations that shed further light on the problem.

The temperature dependence of the Hofmeister series: thermodynamic fingerprints of cosolute–protein interactions

Ion-specific effects induce characteristic shifts of the protein stability curve leading to a temperature-dependent Hofmeister model, replacing the homologous series.