Transverse stability in a Stark decelerator

The traditional structure of the upper structure of the track on the main railways of Ukraine in curved sections with a radius of less than 350 m is a link structure of the track with wooden sleepers. This track design is not rational under current operating conditions. The use of a more advanced jointless track design in curves with a radius of less than 350 m is limited primarily by the condition of ensuring the transverse stability of the rail-sleeper lattice. To be able to expand the use of jointless track construction in curved sections with a radius of less than 350 m, it is necessary to know the values of the transverse forces of interaction of the structures of the upper track structure with the moving carriage. Knowing the forces of interaction, it is possible to estimate by what value the transverse stability of the rail-sleeper lattice will be provided and to make constructive decisions on its increase. The method of determination of transverse horizontal forces of interaction of track and moving carriage in curves of radius less than 350 m taking into account quasi-static compressive forces in a train is given. The reasons for these forces are related to the presence of eccentricity of the autoclutch shank in the horizontal and vertical planes. Theoretical calculations of horizontal transverse forces of interaction are carried out according to the given technique and coefficients of stability of a rail-sleeper lattice in curved sites are defined. The main conclusions concerning the possibility of operation of the jointless track structure in curved sections with a radius of 350 m and less are made.

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PERBANDINGAN KAPAL MONOHULL, CATAMARAN, TRIMARAN BERDASARKAN TINJAUAN OPERASIONAL PENGGUNAAN BAHAN BAKAR

ALE Proceeding ◽

10.30598/ale.4.2021.30-36 ◽

2021 ◽

Vol 4 ◽

pp. 30-36

Author(s):

Jacobus Tupan ◽

Richard Benny Luhulima

Keyword(s):

Data Analysis ◽

Energy Requirements ◽

Energy Usage ◽

Fishing Vessel ◽

Fishing Vessels ◽

Initial Stage ◽

Transverse Stability ◽

Fishing Fleets

In general, fishing fleets operating in Maluku waters and managed by local entrepreneurs consist of monohull and trimaran fishing vessels with outriggers. Monohull fishing vessels have limited deck space and poor transverse stability, while trimaran-type vessels have better deck space and transverse stability than monohull vessels, but because they are still in the form of outriggers, the space is limited. This study aims to examine the development of the trimaran fishing vessel in terms of energy requirements, safety, and comfort of the crew during fishing operations. The initial stage of this research begins with data analysis and the basic size of monohull fishing vessels operating in Maluku waters, from this data the shape of the trimaran hull is designed. Calculation of resistance using CFD, then analyzed the calculation of resistance and stability, safety, and comfort of the ship using Maxsurf. The drag Trimaran is 8.86% smaller than a monohull and 3.25% smaller than a catamaran. Energy Usage (EHP) is proven by trimaran ships more than other ship modes. The average trimaran period is 10.5 seconds which meets IMO standards and is declared operationally good.

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The Transverse Plane Motions of Ships

Marine Technology and SNAME News ◽

10.5957/mt1.1991.28.2.55 ◽

1991 ◽

Vol 28 (02) ◽

pp. 55-72

Author(s):

Bruce L. Hutchison

Keyword(s):

Transverse Plane ◽

Irregular Waves ◽

Hydrodynamic Coefficients ◽

Important Process ◽

Regular Waves ◽

Hull Form ◽

Fishing Vessels ◽

Transverse Stability ◽

Roll Axis ◽

The One

A detailed exposition of the kinematics of the transverse plane motions of ships is provided, with particular attention to the important process of total transverse acceleration in vessel coordinates. The loci of sway, sway velocity and sway acceleration are shown to follow hyperbolic distributions with respect to elevation in both regular and irregular waves. In regular waves the transverse acceleration in earth-fixed and vessel-fixed coordinates are shown to be congruent with a vertical shift in elevation of g/ω2 = λ/(2π). Expressions are given for the elevations minimizing transverse plane processes in regular and irregular waves. In long waves the elevation minimizing total transverse acceleration in vessel coordinates is shown to be g/ωn2 = g[Tn/ /(2π)]2 below the waterline. This is the roll center, which should be used in the traditional analysis of foundation loads. Its location, far below the keel for most vessels, is surprising. The elevation (OP) of the roll axis, which must be used when solving the one-degree-of-freedom equation for roll, is given and is shown to require hydrodynamic coefficients for sway as well as roll. In general, OP does not correspond to an elevation that minimizes any of the transverse plane processes. The effect of hull form, transverse stability and natural roll period on transverse plane motions are examined in an attempt to resolve the dichotomy of views between those who favor ships with low GMT and long natural roll periods and those who favor high GMT with short natural roll periods. It is demonstrated that large values of the beam-to-draft ratio (6/7) with low natural roll periods are advantageous at modest elevations above the waterline. This explains the favorable offshore experience in vessels meeting this description, such as tugs, supply vessels and fishing vessels. At higher elevations long natural periods are shown to present a clear advantage, which supports the preference for low GMT for large passenger vessels, containerships and ships with deck-loads of logs. The trends identified would seem to support the conjecture that, with regard to natural roll period, there is a "forbidden middle" that should be avoided in design.

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An Alternative Operation Scheme to Improve the Efficiency of a Stark Decelerator

Chinese Physics Letters ◽

10.1088/0256-307x/38/12/123201 ◽

2021 ◽

Vol 38 (12) ◽

pp. 123201

Author(s):

Mei Du ◽

Dongdong Zhang ◽

Dajun Ding

Keyword(s):

High Voltage ◽

Polar Molecules ◽

Cold Molecules ◽

Trajectory Simulation ◽

Alternative Method ◽

Order Of Magnitude ◽

Focusing Property ◽

Stark Decelerator

A Stark decelerator can slow down polar molecules to very low velocities. When the velocities are very low, the number of cold molecules obtained is very small. In order to obtain a higher quantity of cold molecules, inspired by the work of Reens et al. [Phys. Rev. Res. 2 (2020) 033 095], we propose an alternative method of operating a Stark decelerator. Through the trajectory simulation of OH molecules in the decelerator, we find that the number of cold molecules can be greatly increased by one order of magnitude at both low and high final velocities on a Stark decelerator consisting of around 150 electrodes. This development is due to the improved longitudinal and the transverse focusing property provided by the new switching schemes and the high-voltage configurations on the decelerator unit.

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Study of Double Hull Tanker Lolling and Its Prevention

Marine Technology and SNAME News ◽

10.5957/mt1.1996.33.3.183 ◽

1996 ◽

Vol 33 (03) ◽

pp. 183-202

Author(s):

Michael J. Goodwin ◽

James C. Card ◽

John S. Spencer

Keyword(s):

Oil Spills ◽

Size Range ◽

Loading Conditions ◽

Risk Of Injury ◽

Intact Stability ◽

Sufficient Stability ◽

Transverse Stability ◽

Double Hull

Lolling is an uncontrollable list caused by inadequate transverse stability in the upright condition. With the advent of double hull tankers, lolling incidents have begun to occur, usually while loading or unloading cargo. These lolling incidents have damaged loading arms and piers and resulted in ship damage. There is also the risk of injury or death to personnel, a risk of fire, and a risk of polluting oil spills from damaged loading facilities. This study considers the problem of lolling of double hull, single tank across tankers in the 35,000 DWT to 150,000 DWT range. This is the size range of tankers which have experienced incidents of lolling. Below this range are mostly product tankers which have greater cargo tank subdivision. Above 150,000 DWT, strength and tank size considerations dictate against the single tank across configuration. The study recommends that new tankers be required to have sufficient intact stability to prevent the occurrence of lolling, preferably by design without having to consider cargo or ballast loading sequences. The study also provides an approach on how to demonstrate that sufficient stability is available under all loading conditions possible.

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A Concept of the Triple-Hull Frigate

Marine Technology and SNAME News ◽

10.5957/mt1.2000.37.3.141 ◽

2000 ◽

Vol 37 (03) ◽

pp. 141-145

Author(s):

Victor A. Dubrovskiy

Keyword(s):

Hydrodynamic Interaction ◽

Bending Moment ◽

Resistance Coefficient ◽

Residual Resistance ◽

Advantages And Disadvantages ◽

General Arrangement ◽

Hull Structure ◽

Longitudinal Bending ◽

Transverse Stability ◽

Wetted Area

Ships with outriggers, such as multihull vessels, are defined and their advantages and disadvantages described. The general feasibility of a hull with a small waterplane area is considered as a method for development of an outriggered frigate design. The main dimensions, general arrangement, and hull structure of this design are offered along with calculations of initial transverse stability, longitudinal bending moment in waves, wetted area, residual resistance coefficient of the single hull, as well as the hydrodynamic interaction of the main hull with the outriggers.

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