• Journal of the Korean Chemical Society
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• v.67 no.6
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• pp.407-414
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• 2023

The present study uses quasi-classical trajectory procedures to examine the vibrational relaxation and dissociation of the methyl and ring C-H bonds in excited methylpyrazine (MP) during collision with either N₂ or O₂. The energy-loss (-ΔE) of the excited MP is calculated as the total vibrational energy (E_T) of MP is increased in the range of 5,000 to 40,000cm^-1. The results indicate that the collision-induced vibrational relaxation of MP is not large, increasing gradually with increasing E_T between 5,000 and 30,000 cm^-1, but then decreasing with the further increase in E_T. In both N₂ and O₂ collisions, the vibrational relaxation of MP occurs mainly via the vibration-to-translation (V→T) and vibration-to-vibration (V→V) energy transfer pathways, while the vibration-to-rotation (V→R) energy transfer pathway is negligible. In both collision systems, the V→T transfer shows a similar pattern and amount of energy loss in the ET range of 5,000 to 40,000cm^-1, whereas the pattern and amount of energy transfer via the V→V pathway differs significantly between two collision systems. The collision-induced dissociation of the C-H_methyl or C-H_ring bond occurs when highly excited MP (65,000-72,000 cm^-1) interacts with the ground-state N₂ or O₂. Here, the dissociation probability is low (10^-4-10^-1), but increases exponentially with increasing vibrational excitation. This can be interpreted as the intermolecular interaction below E_T = 71,000 cm^-1. By contrast, the bond dissociation above E_T = 71,000 cm^-1 is due to the intramolecular energy flow between the excited C-H bonds. The probability of C-H_methyl dissociation is higher than that of C-H_ring dissociation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.143-150
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• 2005

In this study, to evaluate the collision behaviors of the navigating vessel and the dolphin protective system protecting the substructures of bridges, the numerical simulation was performed. The analysis model of vessel bow that the plastic deformations are concentrated was composed by shell elements, and the main body of vessel was modeled by beam elements to represent the mass distribution and the change of potential energy. The material model reflecting the confining condition was used for the modeling of the filling soil of dolphin system. The surrounding soil of the dolphin system was modeled as nonlinear springs. As results, it is verified that the dolphin system can adequately dissipate the kinematic energy of the collision vessel. The surrounding soil of the dolphin system is able to resist the collision force of the vessel. And the major energy dissipation mechanism of collision energy is the plastic deformation of the vessel bow and the dolphin system.

• Journal of the Korean Society for Railway
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• v.3 no.1
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• pp.27-33
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• 2000

In this paper, numerically evaluated is the crashworthiness of the new design of the standard Korea Electric Multiple Unit Train(K-EMU)[developed by the Korea Railway Research Institute]. The 4-car consist of K-EMU is analyzed under collision conditions such as normal coupling, heavy shunting, light collision and heavy collision to collide against another stationary one at 5 kph, 10 kph, 25 kph and 32 kph, respectively. Energy absorbing capacity of its draftgear commercially available in the market and to be equipped in K-EMU is evaluated under each collision condition. Analytical results show that draftgear only is not enough to provide necessary energy absorbing capacity. It is therefore concluded that additional energy absorbers like mechanical fuses should be adopted to improve the crashworthiness of K-EMU.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.238-244
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• 2006

The Light Collision Safety Device is used to protect the important part of trains and passengers at the low velocity accidents. The Light Collision Safety Device comprises mainly tension bolts, shear bolts and an energy absorber. The work mechanism of this device is that first, the tension bolts break at designed collapse load and second, the energy absorber absorb rest collision energy. In this paper, the tension bolt characteristics were validated by the simple tension test using the FEM(Finite Element Method) and the characteristic of the two types of energy absorber were compared by using the load-displacement curves and absorbed energy. Last, in order to determine integrated load-displacement curve of tension bolts and the energy absorber, the unified analysis was conducted by using the FEM.

• Korean Journal of Materials Research
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• v.29 no.9
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• pp.525-531
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• 2019

The widespread use of automobiles has greatly increased energy demand and exhaust gas pollution. In order to save energy, reduce emissions and protect the environment, making lightweights automobiles is an effective measure. In this paper, carbon fiber composites and automobile B-pillars are briefly introduced, and then the mechanical properties and impact resistance of the DC590 steel B-pillars and carbon fiber composites B-pillars are simulated by the ABAQUS finite element software. The results show that the quality of compound B-pillars is reduced by 50.76 % under the same dimensions, and the mechanical property of unit mass is significantly better than that of metal B-pillars. In the course of a collision, the kinetic energy of the two B-pillars is converted into internal energy, but the total energy remains the same; the converted internal energy of the composite B-pillars is greater, the deformation is smaller and the maximum intrusion and intrusion speed is also smaller, indicating that the anti-collision performance of the composite B-pillars is excellent. In summary, the carbon fiber composites can not only reduce the quality of the B-pillars, but also improve their anti-collision performance.

• Journal of Ship and Ocean Technology
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• v.5 no.4
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• pp.19-28
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• 2001

A comparative study of the new flexible double hull structure is presented as a collision energy absorbing system, which is constructed with mixed stringers comprising slant and straight stringers for the double hull tanker, The dimension and disposition of this mixed stringers are selected to give the maximum absorbing energy. From the viewpoint of collision energy absorbing efficiency, this structural system is compared with three other types of the double hull constructions with trapezoidal stiffener, stringer type and standard type of VLCC, 310K DWT, Based on the constant hull weight, the proposed double hull structure with mixed stringers shows a improved crashworthiness as the results.

• Bulletin of the Korean Chemical Society
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• v.27 no.4
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• pp.495-502
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• 2006

Intramolecular energy flow and C-$H_{methyl}$ and C-$H_{ring}$ bond dissociations in vibrationally excited toluene in the collision with HF have been studied by use of classical trajectory procedures. The energy lost by the vibrationally excited toluene upon collision is not large and it increases slowly with increasing total vibrational energy content between 20,000 and 45,000 $cm ^{-1}$. Above the energy content of 45,000 $cm ^{-1}$, however, energy loss decreases. Furthermore, in the highly excited toluene, toluene gains energy from incident HF. The temperature dependence of energy loss is negligible between 200 and 400 K. Energy transfer to or from the excited methyl C-H bond occurs in strong collisions with HF transferring relatively large amount of its translational energy (>> $k_BT$) in a single step, whereas energy transfer to the ring C-H bond occurs in a series of small steps. When the total energy content $E_T$ of toluene is sufficiently high, either C-H bond can dissociate. The C-$H_{methyl}$ dissociation probability is higher than the C-$H_{ring}$ dissociation probability. The dissociation of the ring C-H bond is not the result of the intermolecular energy flow from the direct collision between the ring C-H and HF but the intramolecular flow of energy from the methyl group to the ring C-H stretch. The C-$H_{ring}$${\cdot}{\cdot}{\cdot}$HF interaction is not important in transferring energy and in turn bond dissociation.

• Bulletin of the Korean Chemical Society
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• v.17 no.8
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• pp.745-749
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• 1996

Fluorescence from the electronically excited thiophosgene (Cl2CS) in its first excited singlet state (S1) is efficiently quenched by collision. Rates of the collision-induced electronic relaxation were obtained for various vibrational levels in the S1 state by measuring the fluorescence lifetimes. We found that the relaxation process is strongly energy-dependent; the rate consistently increases by a factor of ~40 with the increase of vibrational energy from 0 to 1450 cm-1. Collision-induced intersystem crossing from the S1 to the first triplet state (T1) is attributed to the major process responsible for the electronic relaxation.

• Journal of the Korean Chemical Society
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• v.42 no.3
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• pp.297-301
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• 1998

Linkage positions in oligosaccharides may be obtained by FAB CAD MS/MS (Fast Atom Bombardment Collision Activated Dissociation Mass Spectrometry/Mass Spectrometry). Acetylated derivatives of the linkage-isomeric trisaccharides exhibited more useful product ion patterns than the free trisaccharides and provided specific fragmentation patterns according to linkage positions. The reason for the useful linkage dependent spectra patterns of acetylated forms is related to the ability of each linkage in the oligosaccharides to absorb different levels of collision energy and rotational freedom of the individual glycosidic linkage.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.119-126
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• 2001

The potential pollution problems resulting from tanker collision necessitate the requirement for an effective structural design and the development of relevant safety regulation. During a few decades, the great effort has been made by International Maritime Organization and the Administration, etc, to reduce oil spillage from collision accidents. However there is still a need for investigation in the light of structural evaluation method for the experiments and rational analysis, and design development for an operational purpose of ships. This study is aimed at investigating a complicated structural response of bow structures of oil carriers for assessing the energy dissipation and crushing mechanics of striking vessel through a methodology of the numerical analysts for the various models and its design changes. Through this study an optimal bow construction absorbing great portion of kinetic energy in the least penetration depth prior to reach to the cargo area and an effective location of collision bulkhead are investigated. In order to obtain a rational results in this study, three stages of response analysis procedures are performed as follows; 1). 16 simplified ship models are used to investigate the structural response against bow collision with variation of primary and secondary members. Mass and speed are also varied in two conditions. 2). 21 models conisted of 5 size of full scaled oil carriers are used to perform the collision simulation with the various sizes and deadweight delivered in a recent which are complied with SOLAS and MARPOL. 3). 36 models of 100k oil carrier are used to investigate the structural response and its influence to the collision bulkhead against bow collision in variation with location of collision bulkhead, primary mombers, framing system and colliding conditions, etc.