What really caused the ROKS Cheonan warship sinking?

This paper is concerned with the sinking of the Korean naval warship (ROKS Cheonan) and the reported spectra of the seismic signals recorded at the time of the incident. The spectra of seismic signals show prominently amplitude peaks at around 8.5 Hz and its harmonics. These frequencies were explained with the vibrations of a water column due to an underwater explosion. This explanation is highly doubtful and concerns about its validity have already been raised in the scientific community. In this work an alternative explanation is presented: it is shown that the recorded seismic spectra are consistent with the natural frequencies of vibrations of a large submarine with a length of around 113 m. This finding raises the possibility that the ROKS Cheonan sunk because of the collision with a large submarine rather than the explosion of a torpedo or an underwater mine.Peer Reviewe

EXPRESSIVE SPEECH ACTS ANALYSIS ON THE COMMENT SECTION OF PRINCE EA’S YOUTUBE CHANNEL

ABSTRACT This research was driven by the prevalence of netizens' comments expressing their feelings on Prince Ea's youtube channel, raising concerns about the education system. Netizens' expressions in the comments section have specific meanings and functions, Understanding the meaning and function of netizen comments that contained expressions of their feelings was important because this could avoid misunderstandings and ensure that communication in the comments section ran smoothly. Pragmatics offers insight into this phenomenon through the theory of expressive speech acts. The study focused on three objectives: (1) to find the types of expressive speech acts on the comment section of Prince Ea's YouTube Channel, (2) to describe the meanings of expressive speech acts used in the comment section of Prince Ea's YouTube Channel, and (3) to know the functions of expressive speech acts used on the comment section of Prince Ea's YouTube Channel. The research employed descriptive qualitative analysis, using comments from Prince Ea's videos, "I Just Sued the School System" and "Student Vs. Teacher." The analysis involved data condensation, display, and drawing conclusions. Moreover, investigator triangulation was employed to enhance the data's validity. Results revealed 7 out of 8 expressive speech act types in the comments, including agreement, volition, thanking, exclamations, sorrow, and greetings. Among these, thanking was the most frequent, with a total of 36 occurrences. The reason was that the two Prince Ea videos conveyed inspirational messages that reflected experiences and problems often experienced in educational contexts. Then, to describe the meaning of expressive speech acts in the comment section, researcher first examine the context, namely the content of two Prince Ea videos. Four distinct functions emerged: competitive, convivial, collaborative, and conflictive. The convivial function dominated, being used 60 times. It happened because of the positive responses from netizens, including their support, praise, and expressions of gratitude in their comments on Prince Ea's videos. Keywords: expressive speech act comment, prince ea, youtube channe

) Australian Nuclear Science and Technology Organisation (ANSTO)

ABSTRACT The aim of this work is to model the vibrational behaviour of thin plates joined to a stiff orthogonal side plate using the technique of 'roll swaging'. Swage joints are typically found in plate-type fuel assemblies for nuclear reactors. Since they are potentially liable to flow-induced vibrations, it is crucial to be able to predict their dynamic characteristics. It is shown that the contact between the plates resulting from the swage can be modelled assuming a perfect clamp of all the degrees of freedom but the rotational around the axis parallel to the swage. A modal analysis was performed on different specimens and the values of the first natural frequencies are used to find the equivalent torsional spring stiffness, by matching these frequencies with the results obtained from a finite element model (FEM)

Acoustic signature of a submarine hull

A model to predict the acoustic signature of a submarine resulting from the radial vibration of the hull under axial excitation is presented. The simplified physical model of the submarine hull includes complicating effects such the presence of bulkheads, end enclosures, ring stiffeners and fluid loading due to the interaction with the surrounding medium. Under an axial symmetric force, only the ‘breathing’ modes of the cylinder corresponding to the n=0 circumferential modes are excited. To show the sound radiation due to the higher order n≥1 modes, a point axial force acting at one end of the shell has been considered. At low frequencies, the structural wavenumbers are generally subsonic. However, due to the finite cylinder, the wavenumber spectrum is a convolution of the spectrum of an infinite structure and a window generating radiation by means of the presence of supersonic components. The effect of the bulkheads on the structural and acoustic responses of the hull is also presented

Low frequency structural and acoustic responses of a submarine hull under eccentric axial excitation from the propulsion system

A model to describe the low frequency dynamic and acoustic responses of a submarine hull subject to an eccentric harmonic propeller shaft excitation is presented. The submarine is modelled as a fluid-loaded, ring stiffened cylindri-cal shell with internal bulkheads and conical end caps. The stiffeners are introduced using a smeared approach. A harmonic axial force is introduced by the propeller and is transmitted to the hull through the shaft. It results in excita-tion of the accordion modes only if the force is symmetrically distributed to the structure. Otherwise the excitation can be modelled as the sum of a distributed load and a moment applied to the edge of the hull. This leads to excitation of the higher order circumferential modes that can result in high noise signature. Structural and acoustic responses are presented in terms of deformation shapes and directivity patterns for the radiated sound pressure. Results for the case of purely axisymmetric excitation and the case in which an eccentricity is introduced are compared

Lipid Peroxidation and Antioxidant Consumption as Early Markers of Neurosurgery-Related Brain Injury in Children

BACKGROUND AND AIMS: Lipid peroxidation represents a marker of secondary brain injury both in traumatic and in non-traumatic conditions-as in major neurosurgical procedures-eventually leading to brain edema amplification and further brain damage. Malondialdehyde (MDA), a lipid peroxidation marker, and ascorbate, a marker of antioxidant status, can represent early indicators of this process within the cerebrospinal fluid (CSF). We hypothesized that changes in cerebral lipid peroxidation can be measured ex vivo following neurosurgery in children. METHODS: Thirty-six children (M:F = 19/17, median age 32.9 months; IQR 17.6-74.6) undergoing neurosurgery for brain tumor removal were admitted to the pediatric intensive care unit (PICU) in the postoperative period with an indwelling intraventricular catheter for intracranial pressure monitoring and CSF drainage. Plasma and CSF samples were obtained for serial measurement of MDA, ascorbate, and cytokines. RESULTS: An early brain-limited increase in lipid peroxidation was measured, with a significant increase from baseline of MDA in CSF (p = 0.007) but not in plasma. In parallel, ascorbate in CSF decreased (p = 0.05). Systemic inflammatory response following brain surgery was evidenced by plasma IL-6/IL-8 increase (p 0.0022 and 0.0106, respectively). No correlation was found between oxidative response and tumor site or histology (according to World Health Organization grading). Similarly, lipid peroxidation was unrelated to the length of surgery (mean 321 ± 73 min), or intraoperative blood loss (mean 20.9 ± 16.8% of preoperative volemia, 44% given hemotransfusions). Median PICU stay was 3.5 days (IQL range 2-5.5 d.), and postoperative ventilation need was 24 h (IQL range 20-61.5 h). The elevation in postoperative MDA in CSF compared with preoperative values correlated significantly with postoperative ventilation need (P = 0.05, r2 0168), while no difference in PICU stay was recorded. CONCLUSIONS: Our results indicate that lipid peroxidation increases consistently following brain surgery, and it is accompanied by a decrease in antioxidant defences; intraventricular catheterization offers a unique chance of oxidative process monitoring. Further studies are needed to evaluate whether monitoring post-neurosurgical oxidative stress in CSF is of prognostic utility

Predicting the broadband response of a layered cone-cylinder-cone shell

The dynamic response of an aerospace layered structure composed of a combination of conical and cylindrical shells is hereby modelled. In the low and the mid-frequency ranges a WFEM derived ESL approach implemented within a FEM is used in order to predict the response of the shell. Furthermore, in the high frequency range the CLF of the connected subsystems are calculated using a WFEM/FEM approach. These CLF are implemented within a SEA approach in order to predict the structural response. The accuracy and robustness of the developed approaches are exhibited by comparisons to experimental measurements on a layered conical-shell-conical configuration