5 research outputs found
A study on the analysis of hull damage assessment in wreck and salvage process of ship
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Όλ¬Έ (μμ¬) -- μμΈλνκ΅ λνμ : 곡과λν μ‘°μ ν΄μ곡νκ³Ό, 2021. 2. μ₯λ²μ .ν΄μμμ μ΄μ©λλ μ λ°μ λΆμμ μ¬κ³ λ‘ μΈν΄ μΉ¨λͺ°ν μ μμΌλ©°, μ΄λ‘ μΈν΄ κ²½μ μ μμ€ λ° ν΄μ νκ²½μ€μΌ λ± λ€μν λΆμμ©μ λ°μμν¨λ€. νΉν λν μ¬κ°μ μ κ²½μ° λΉκ°μμ μΈ λ€λμ μΈλͺ
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λ° μλ°©μ κΈ°μ¬ν κ²μΌλ‘ κΈ°λλλ€.The ship that operating at sea can be sunk by an unexpected accident, resulting in various side effects such as economic loss and marine environmental pollution. Especially, in the case of large passenger ships, a large amount of irreversible loss of life is accompanied, so efforts to prevent ship sinking accidents are more urgent.
Basically, in order to prevent accidents, it is necessary to prioritize the identification of the cause of the accident. and in case of the external damage on shipwreck can be an important evidence to determine the cause of the accident. Therefore, evaluation of the external damage on shipwreck is necessary to determine the cause of the accident.
In this study, the damage assessment for shipwreck appearance occurring during the lifting process from the sinking of the hull is to be performed through 3D structural analysis. The techniques for the damage assessment for shipwreck established as follows.
First, situations in which major damage applied to the hull that may occur during the process from the sinking to the lifting are estimated. then with this, the load applied for each major situation is calculated and applied step by step in 3D structural analysis. because the sinking and lifting process takes a long time, so it is very inefficient in terms of time and economy to perform the analysis at once for the entire process.
After that, each structural analysis result was continuously accumulated over time to maintain the accuracy of the analysis even the individual classified loads were applied independently with each analysis. The application of this continuous analysis technique was verified through a case study comparing the final damage state of the case to which the technique was applied and the case not applied to the simplified box shaped 3D model.
At the last, an analysis was performed in which the above-established technique was applied to a 3D model using an actual sunk and lifted passenger ship as an example. At this time, the steps were subdivided in order to perform a quasi-static analysis of the sinking process occurring over a long period of time.
then it can be confirmed that the overall damage tendency is consistent. when comparing the actual ship's external damage of the shipwreck and the analysis results,
Based on these results, it was verified that the established impairment evaluation analysis technique can secure time and economic efficiency while maintaining the accuracy of the damage tendency. Furthermore, it is expected to contribute to the identification and prevention of the cause of accidents by effectively carrying out damage assessment of possible shipwreck and lifting ships.1. μλ‘ 1
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Abstract 65Maste
μμ μ기곡λͺ λΆκ΄μμ λ₯λ¬λμ μ΄μ©ν μ λ¨λ μμ μ λκ°μ λ‘λΆν°μ μ€ννΈλΌ 볡μ
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Όλ¬Έ(μμ¬)--μμΈλνκ΅ λνμ :μκ³Όλν μκ³Όνκ³Ό,2020. 2. κΉνμ§.Introduction: Reconstruction of the spectrum from a truncated free induction decay (tFID) has long been a challenging issue in NMR(nuclear magnetic resonance). A simple approach is to zero-fill the missing data followed by Fourier transform (FT). However, for a substantially truncated FID the resulting spectrum suffers from strong truncation artifact. To address this issue various signal processing algorithms have been reported.
Deep learning has gained great attention due to its remarkable success in a variety of different fields including medical imaging. Among the artificial neural network classes in deep learning a convolutional neural network (CNN) is actively used in undersampled MRI(magnetic resonance imaging) reconstruction where the network is trained in the image-domain only or frequency-domain only.
Given the promising results of the CNN-based undersampled MRI, we explored the potential applicability of CNNs in the reconstruction of the spectra from tFIDs in 1H-MRS.
Methods: Rat brain FIDs were simulated at 9.4T based on in vivo data (n=11), and randomly truncated by retaining 8, 16, 32, 64, 128, 256, 512, and 1024 (null-truncation) points (denoted as tFID8, tFID16, β¦ tFID1024).
Using a U-net, three CNNs were individually trained (n=40,000) in time-domain only (FID-to-FID (FIDCNNFID)), in frequency-domain only (spectrum-to-spectrum (specCNNspec)), and across the domains (FID-to-spectrum (FIDCNNspec)) to map the truncated data to their fully sampled versions.
The CNNs were tested on the simulated data (n=5,000) and the CNN with the best performance was further tested on the in vivo data, for which the CNN-predicted fully sampled data were analyzed using the LC model and the results were compared with those from the original, fully sampled data.
Results: The best result on the simulated data was obtained with specCNNspec, which effectively recovered the spectral details even for those input spectra that appear as a hump due to substantial FID truncation (spectra from tFID16 and tFID32).
Overall, its performance was significantly degraded on the in vivo data. Nonetheless, using specCNNspec, several coupled spins in addition to the major singlets can be quantified from tFID128 with the error no larger than 10%.
Conclusion: Upon the availability of more realistically simulated training data, CNNs can also be used in the reconstruction of spectra from truncated FIDs.μλ‘ : μ λ¨λ μμ μ λκ°μ (truncated free induction decay; tFID)λ‘λΆν°μ μ€ννΈλΌ 볡μμ ν΅μ기곡λͺ
(NMR)μμ μ€λ«λμ λν΄ν μ΄μ μ€ νλμ΄λ€. κ°λ¨ν 볡μ λ°©λ² μ€ νλλ λλ½λ λ°μ΄ν°λ₯Ό 0μΌλ‘ μ±μ°κ³ νΈλ¦¬μ λ³ν(fourier transform)μ μ€ννλ λ°©λ²μ΄μ§λ§, μ¬νκ² μ λ¨λ μμ μ λκ°μ λ‘λΆν°μ μ€ννΈλΌμ μ λ¨ μΈκ³΅λ¬Ό(truncation artifact)μ ν¬κ² μν₯μ λ°λλ€. μ΄λ¬ν λ¬Έμ λ₯Ό ν΄κ²°νκΈ° μν΄ λ€μν μ νΈ μ²λ¦¬ μκ³ λ¦¬μ¦λ€μ΄ λ³΄κ³ λ λ° μλ€.
μ΅κ·Ό, λ₯λ¬λμ μλ£ μμμ ν¬ν¨ν λ€μν λΆμΌμμ λλλ§ν μ±κ³Όλ₯Ό κ±°λλ©° ν° μ£Όλͺ©μ λ°κ³ μλ€. νΉν, λ₯λ¬λμμ μΈκ³΅ μ κ²½λ§ ν΄λμ€ μ€ νλμΈ ν©μ±κ³± μ κ²½λ§(convolutional neural network; CNN)μ μμ μμ(image-domain) λλ μ£Όνμ μμ(frequency-domain)μμμ νμ΅μ ν΅ν΄ λΆμΆ©λΆν λ°μ΄ν° point μλ₯Ό κ°μ§(undersampled) μ기곡λͺ
μμ(MRI)μ 볡μμ μ κ·Ήμ μΌλ‘ μ΄μ©λκ³ μλ€.
μ΄λ¬ν ν©μ±κ³± μ κ²½λ§μ μ기곡λͺ
μμ 볡μλ₯μ μ°Έκ³ νμ¬, λ³Έ λ
Όλ¬Έμ μμ μ기곡λͺ
λΆκ΄(1H-MRS)μμ μ λ¨λ μμ μ λκ°μ λ‘λΆν°μ μ€ννΈλΌ 볡μμμμ ν©μ±κ³± μ κ²½λ§μ νμ© κ°λ₯μ±μ νꡬνμλ€.
λ°©λ²: μΈκ³΅ μ κ²½λ§ νλ ¨μ μν μμ μ λκ°μ λ€μ 9.4Tμ μκΈ°μ₯μ κΈ°μ€μΌλ‘ λ«λμ λ(Rat brain)λ‘λΆν°μ μ체(in vivo) λ°μ΄ν°λ₯Ό μ°Έκ³ νμ¬ λͺ¨μ¬(simulation) λμκ³ , μ΄ 1024κ°μ λ°μ΄ν° point μμμ κ°κ° 8, 16, 32, 64, 128, 256, 512, 1024κ°μ λ°μ΄ν° point μλ₯Ό κ°λλ‘ μμλ‘ μ λ¨λμλ€.
U-netμ μ΄μ©νμ¬, 40,000κ°μ μ λ¨λ μμ μ λκ°μ λ€μ μμ ν λ°μ΄ν° point μλ₯Ό κ°μ§ λ°μ΄ν°(μμ μ λκ°μ λλ μ€ννΈλΌ)λ‘ λ³΅μνκΈ° μν΄ κ°κ° μμ μ λκ°μ μμ μμ μ λκ°μ λ‘(FID-to-FID (FIDCNNFID)), μ€ννΈλΌμμ μ€ννΈλΌμΌλ‘(spectrum-to-spectrum (specCNNspec)), μμ μ λκ°μ μμ μ€ννΈλΌμΌλ‘(FID-to-spectrum (FIDCNNspec)) μΆλ ₯νλ μΈ κ°μ§μ ν©μ±κ³± μ κ²½λ§μ νμ΅μμΌ°λ€.
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μ€νΈλμκ³ , κ°μ₯ μ’μ μ±λ₯μ κ°μ§ ν©μ±κ³± μ κ²½λ§μ μ λ³νμ¬ μ€μ μ체μμ μ»μ΄μ§ λ°μ΄ν°λ€λ‘ μΆκ° ν
μ€νΈλ₯Ό μ§ννμλ€. κ·Έλ¦¬κ³ κ·Έ ν©μ±κ³± μ κ²½λ§μΌλ‘ 볡μλ λ°μ΄ν°λ€μ LC modelμ μ΄μ©νμ¬ λμ¬μ²΄ μ λλΆμμ μ§ννμ¬, κ·Έ μ λλΆμ κ²°κ³Όλ₯Ό μλ λ°μ΄ν°μ LC modelμ μ΄μ©ν μ λλΆμ κ²°κ³Όμ λΉκ΅νμλ€.
κ²°κ³Ό: λͺ¨μ¬λ λ°μ΄ν°λ₯Ό ν΅ν ν
μ€νΈμμ, μ€ννΈλΌμμ μ€ννΈλΌμΌλ‘(specCNNspec)μΌλ‘ μΆλ ₯νλ ν©μ±κ³± μ κ²½λ§μ΄ κ°μ₯ μ’μ κ²°κ³Όλ₯Ό 보μ¬μ£Όμλ€. νΉν, μ΄ ν©μ±κ³± μ κ²½λ§μ μμ μ λκ°μ μ μ λ¨μΌλ‘ μΈν΄ κ±°μ νΉμ²λΌ 보μ΄λ μ
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μ€νΈμμλ§νΌ μ’μ κ²°κ³Όλ₯Ό μ»μ§λ λͺ»νμλ€. κ·Έλ¬λ, 128κ°μ λ°μ΄ν° point μλ₯Ό κ°μ§ μ λ¨λ μμ μ λκ°μ λ‘λΆν° 볡μλ μ€ννΈλΌμ κ²½μ°, singletμΌλ‘ κ΄μΈ‘λλ λνμ μΈ λμ¬μ²΄λ€λΏ μλλΌ multipletμΌλ‘ κ΄μΈ‘λλ λͺλͺ λμ¬μ²΄λ€μ λν΄μλ 10% λ―Έλ§μ μ λν μ€λ₯λ₯Ό μ»μ μ μμλ€.
κ²°λ‘ : λ³΄λ€ μ€μ μ κ°κΉμ΄ λͺ¨μ¬ λ°μ΄ν°λ₯Ό λ€νΈμν¬μ νμ΅μ μ΄μ©νλ€λ©΄, ν©μ±κ³± μ κ²½λ§μ μ λ¨λ μμ μ λκ°μ λ‘λΆν°μ μ€ννΈλΌ 볡μμλ μ¬μ©λ μ μλ€.1. Introduction 1
2. Methods 3
3. Results 13
4. Discussion 26
5. Conclusion 35
6. References 36
7. κ΅λ¬Έμ΄λ‘ 42Maste