• 대한조선학회논문집
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• 제47권3호
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• pp.410-420
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• 2010

When ships are sailing with large motions in rough waves, the slamming phenomenon occurs and the ships suffer from impulsive pressure loadings. Recently, ships are becoming lager and faster than before and it becomes more possible that the ships experience larger impacts on their bows and sterns. Many researchers have been performing the investigations on slamming experimentally and theoretically for a long time. Most of the research reported in the open literature focused on how to accurately estimate the amplitude of the peak pressure of slamming. According to the results of a recently published work, not only the amplitude of peak pressure but also the width of the peak may play an important role in predicting the extents of damage of impacted structures. The uncertainty of impulsive pressure loadings due to slamming has been indicated by many researchers. However, probabilistic treatments of the impulsive pressure loadings are few. In this study, drop tests were conducted on wedges having dead-rise angles of $0^{\circ}$ and $10^{\circ}$. Not only the amplitude of peak pressure but also the width of peak pressure were measured. Furthermore, the variations of those values are also provided for the probabilistic approach of the slamming problem.

• Annals of Clinical Neurophysiology
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• 제25권1호
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• pp.32-37
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• 2023

Background: Type 2 diabetic mellitus (T2DM) is an emerging global pandemic which is associated with lots of co-morbidities and reported vascular dysfunctions. T2DM associated vascular dysfunctions leads to vasculopathy in the form of altered peripheral vascular dynamics. Cold stress test (CST) is a reliable sympathetic reactivity test used for assessing vascular dysfunctions. In this study we are trying to quantify vascular dysfunctions in T2DM patients non invasively by various parameters of photoplethysmography (PPG) of cold stress test. Methods: Case control study had done in referral health center AIIMS, Raipur. Parameters are recorded by finger-PPG before, during and after CST (1 min) in 2 groups, control (n = 20 healthy volunteers) and case (n = 20 diagnosed T2DM patients). Results: Due to cold stress, PPG parameter peak amplitude was significantly decreased in both healthy and T2DM groups (p <0.001 and p <0.001, respectively). However, recovery trend of amplitude was significantly slow in T2DM compared to healthy subjects. Another PPG parameter peak to peak interval was significantly higher in healthy group compared to T2DM patients. Conclusions: This study showed that T2DM patients has significant deranged pulse volume parameters like amplitude and peak to peak interval can be used to objectively quantify the vasculopathy in T2DM patients by using sympathetic reactivity to cold stress.

• Current Optics and Photonics
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• 제6권3호
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• pp.252-259
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• 2022

In this paper, a dual-function dynamically tunable metamaterial absorber is proposed. At frequency points of 1.545 THz and 3.21 THz, two resonance peaks with absorption amplitude of 93.8% (peak I) and 99.4% (peak II) can be achieved. By regulating the conductivity of photosensitive silicon with a pump laser, the resonance frequency of peak I switches to 1.525 THz, and that of peak II switches to 2.79 THz. By adjusting the incident polarization angle by rotating the device, absorption amplitude tuning is obtained. By introducing two degrees of regulation freedom, the absorption amplitude modulation and resonant frequency switching are simultaneously realized. More importantly, dynamic and continuous adjustment of the absorption amplitude is obtained at a fixed resonant frequency, and the modulation depth reaches 100% for both peaks. In addition, the sensing property of the proposed MMA was studied while it was used as a refractive index sensor. Compared with other results reported, our device not only has a dual-function tunable characteristic and the highest modulation depth, but also simultaneously possesses fine sensing performance.

• 한국전기전자재료학회논문지
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• 제24권1호
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• pp.47-51
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• 2011

The superconducting fault current limiter (SFCL) with a peak current limiting function according to the initial fault current with the different amplitudes was suggested. The proposed SFCL, which consists of two limiting components, causes only the first superconducting element among two limiting components to be quenched in case that the initial fault current with the lower peak amplitude happens. On the other hand, the initial fault current with the higher peak amplitude makes both the superconducting elements of two limiting components to be quenched, which contributes to the peak current limiting function of the SFCL. To confirm the fault current limiting operation of the proposed SFCL, the short-circuit tests of the SFCL according to the fault angle were carried out and its effective fault current limiting operations could be discussed.

• ETRI Journal
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• 제29권2호
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• pp.231-233
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• 2007

One of the drawbacks in an OFDM system is the high peak-to-average power ratio (PAPR). Among a number of techniques to reduce the high PAPR, simple amplitude predistortion (SAP), a form of active constellation extension, has been proposed to effectively achieve the desired PAPR. In this letter, a novel scheme, simple amplitude and phase predistortion (SAPP), is proposed. In SAP the carriers' amplitude is utilized to combat the peak signal. Each amplitude is amplified according to its degree of contribution as a metric. In addition to amplitude, SAPP also utilizes the phase. Simulation results indicate that the proposed scheme provides better PAPR reduction than SAP.

• Corrosion Science and Technology
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• 제19권4호
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• pp.163-173
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• 2020

Cavitation corrosion in many industrial plants has recently become a serious issue. Cavitation corrosion has generally been investigated using a vibratory method based on ASTM G32 standard, and the test can be divided into direct cavitation and indirect cavitation. Cavitation corrosion test uses the vibration frequency of the horn of 20 kHz with constant peak-to-peak displacement amplitude. In this work, the peak-to-peak amplitude was controlled from 15 ㎛ to 85 ㎛, and electrochemical measurements were obtained during indirect cavitation. The relationship between cavitation corrosion rate and electrochemical properties was discussed. Corrosion steps of carbon steel at the initial stage under cavitation condition in 3.5 % NaCl can be proposed. When the cavitation strength is relatively low, corrosion of the steel is more affected by the electrochemical process than by the mechanical process; but when the cavitation strength is relatively high, corrosion of the steel is affected more by the mechanical process than by the electrochemical process. This work confirmed that the critical ultrasonic amplitude of 0.42 %C carbon steel is 53.8 ㎛, and when the amplitude is less than 53.8 ㎛, the corrosion effect during the cavitation corrosion process is higher than the mechanical effect.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권4호
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• pp.312-319
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• 2016

Measured wave data covering two years simultaneously at 3 locations along the eastern Arabian Sea reveals the presence of long-period (peak wave period > 18 s) low-amplitude waves (significant wave height < 1 m) and the characteristics of these waves are described in this article. In a year, 1.4-3.6% of the time, the low-amplitude long-period swells were observed, and these waves were mainly during the nonmonsoon period. The wave spectra during these long-period swells were multi-peaked with peak wave period around 18.2 s, the secondary peak period around 13.3 s and the wind-sea peak period at 5 s. The ratio of the spectral energy of the wind-sea peak and the primary peak (swell) was slightly higher at the northern location (0.2) than that at the southern location (0.15) due to the higher wind speed present at the northern location.

• Journal of Oral Medicine and Pain
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• 제24권1호
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• pp.9-24
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• 1999

Pumping into the upper joint cavity of the TMJ was done on patients who had reducible disc displacement with pain. This article discusses the change in TMJ sounds before and after the Pumping treatment. 20subjects(mean age of $32.1{\pm}10.2yr$)were selected among those who visited the department of Oral Medicine of Yonsei University for the treatment of craniomandibular dysfunctions. Through a thorough history taking, clinical exam and X-ray taking these subjects were diagnosed as reducible disc displacement patients, and they were subdivided into two groups as acute and chronic according to the time the TMJ sound was made. Sonopak was used to measure the TMJ sound before, right after and one-week after the Pumping treatment. VAS was used to measure the degree of subjective TMJ complaints(sounds and pain) before and one-week after the Pumping treatment. Vibration related items included total integral, high integral, low integral, ratio of high integral to low integral, peak amplitude, peak frequency and median frquency. 1. It was not statistically significant between the acute and chronic groups before the treatment. However, total integral, high integral, low integral, peak amplitude, peak frequency, median frequency showed to be greater in the chronic group. 2. In all the subjects, just after the Pumping treatment was done, total integral, high and low integral, peak amplitude and peak frequency significantly decreased (p<0.05). Even after one week, low integral, peak frequency and median frequency significantly decreased (p<0,05), and the TMJ sound diminished accordingly. 3. Comparing the two groups(before and right after the Pumping treatment), there was the following difference ; in the acute group, high integral, high amplitude, high frequency and median frequency significantly decreased(p<0.05). In the chronic group, total integral, high integral, low integral, ratio, peak amplitude and peak frequency significantly decreased(p<0,05). It was not statistically significant between the acute and chronic group. 4. Comparing the two groups(right after and one week after the Pumping treatment), there was the following difference : in the acute group, high integral, high amplitude, high frequency and median frequency significantly decreased(p<0.05), In the chronic group, low integral significantly decreased(p<0.05). However, although it was not statistically significant, after one week, there was an increase in total integral, ratio, peak amplitude and peak frequency compared to right after the treatment group. 5. In the VAS of before and one week after the Pumping treatment of the TMJ pain and sound, the TMJ pain significantly decreased(p<0.05) in both the acute and chronic group. However, it was not statistically significant between the two groups. There was a statistically significant decrease(p<0.05) in the TMJ sound in the acute group after one week of Pumping treatment, but no change was notable in the chronic group and it was not statistically significant between the two groups. From the above results, we can conclude that Pumping into the upper joint cavity of patients having reducible disc displacement is effective in reducing clicking and pain. Therefore, it can be applied in diverse clinical fields.

• Journal of Oral Medicine and Pain
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• 제25권1호
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• pp.87-97
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• 2000

This study was performed to investigate the effects of repetitive mandibular opening movement and change of head posture on the vibration of temporomandibular(TM) joint. For this study, 23 patients with internal derangement of TM joint were selected. All they had clinically noticeable TM joint sound. Observation of the joint vibration were performed in four head postures, namely, natural head posture (NHP), forward head posture(FHP), upward head posture(UHP), and downward head posture(DHP). For recording of joint sound vibration, Sonopak of Biopak system(Bioresearch Inc., Milwaukee, USA) was used, The author could take results related to integral higher than 300Hz, integral lower than 300Hz, ratio of integral higher than 300Hz to integral lower than 300Hz, total integral which was sum of higher and lower integral, peak amplitude, and peak frequency in each opening movement, which was carried out three times in each head posture. Integral means amount of vibration. The data obtained were analysed by SPSS windows program and the results of this study were as follows : 1. In NHP, total integral in right TM joint was 5O.3Hz in the first opening, 67.9Hz in the second opening, and 74.0Hz in the third opening movement, bur there was no significant increase of total integral with repetitive opening movement. This finding was similar in left TM joint. Integral lower than 300Hz were higher than integral higher than 300Hz in almost every opening movement. 2. There was no significant difference of total integral between right and left side of TM joint, but there was a tendency of higher total integral in right TM joint than that in left TM joint except for results in DHP. 3. Peak amplitude in NHP ranged from 2.0 to 4.7, and peak frequency in NHP were 101.4-170.0Hz. And there was no consistent findings related to increase or decrease of these value according to repetitive opening in each head posture. 4. Change of head posture did not result any difference in integral, peak amplitude, and peak frequency. In conclusion, change of head posture and repetitive mandibular opening movement did not make any significant effect on the vibration of temporo-mandibular joint, especially, on total integral, peak amplitude, and peak frequency.

• Structural Engineering and Mechanics
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• 제55권5호
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• pp.913-929
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• 2015

The ratcheting and strain cyclic behaviour of joined conical-cylindrical shells under uniaxial strain controlled, uniaxial and multiaxial stress controlled cyclic loading are investigated in the paper. The elasto-plastic deformation of the structure is simulated using Chaboche non-linear kinematic hardening model in finite element package ANSYS 13.0. The stress-strain response near the joint of conical and cylindrical shell portions is discussed in detail. The effects of strain amplitude, mean stress, stress amplitude and temperature on ratcheting are investigated. Under strain symmetric cycling, the stress amplitude increases with the increase in imposed strain amplitude. Under imposed uniaxial/multiaxial stress cycling, ratcheting strain increases with the increasing mean/amplitude values of stress and temperature. The abrupt change in geometry at the joint results in local plastic deformation inducing large strain variations in the vicinity of the joint. The forcing frequency corresponding to peak axial ratcheting strain amplitude is significantly smaller than the frequency of first linear elastic axial vibration mode. The strains predicted from quasi static analysis are significantly smaller as compared to the peak strains from dynamic analysis.