• Journal of the Society of Naval Architects of Korea
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• v.43 no.1 s.145
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• pp.22-31
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• 2006

Recent studies have shown that the short time solution of the equation of motion for the rolling of ships is important in deciding the possibility of capsize of ships due to the excessive heel. Since most of known solutions for nonlinear equations of motion are long time or steady periodic solutions, here a simple way is described to get the short time solutions of the Duffing equation, which was chosen for deriving a criterion for the capsize of the ship. With the small external rolling moment, we first assume the state of the small damping and near resonance. Then, for cases when the frequency of the external moment is higher than the resonant one, an inequality was derived as a criterion for the capsize. This gives the range of the initial condition and the magnitude of the external moment which should be avoided for a ship to be safe from capsize. Furthermore, from the linearized equation, it is also shown that a simple and self-explanatory solution can be obtained consistent with that for the case of no damping, which yields the well-known linear growth with time.

• Journal of Convergence for Information Technology
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• v.8 no.1
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• pp.173-177
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• 2018

This study compared the muscle on-set time of fully immersive virtual reality motions with that of actual motions to if there difference. The subjects were 30 healthy adults subjects and compared the virtual reality moction group(punch, archery) and actual motion group(punch, archery) muscle on-set time. In this study, there was no significant difference between the virtual reality motion group and actual motion group muscle on-set time(p>0.05). Fully immersive virtual reality is deemed to be applicable for use in physical therapy. In future studies, it is necessary to investigate whether a fully immersive virtual reality can be applied to patients.

• Journal of International Academy of Physical Therapy Research
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• v.11 no.4
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• pp.2229-2236
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• 2020

Background: Few comparative studies have been conducted on strengthening the anterior and posterior muscles of the trunk via lumbar stabilization exercises. Objectives: To compare the effects of forward leaning exercise and supine bridging exercise in stability exercise. Design: Randomized controlled clinical trial (single blind). Methods: Thirty subjects with spondylolisthesis were participated in this study. Fifteen subjects performed the bridging exercises and fifteen subjects performed the forward leaning exercises. Each exercise was held for ten seconds per repetition, and four repetitions were considered one sub-session. A total of four sub-sessions were performed in one full exercise session. The full exercise session required thirty minutes, including rest time. Trunk strength and range of motion and Oswestry disability index were measured. Results: Two weeks later, trunk flexion strength and trunk extension range of motion were significantly increased in the forward leaning exercise group than in the supine bridging group, trunk extension strength were significantly increased in the supine bridging exercise group than in the forward leaning group. After two weeks, the pain score was significantly lower in the forward leaning exercise group than in the supine bridging group. Conclusion: This study has shown that stabilization exercises are effective in increasing range of motion and strength in spondylolisthesis subjects. It was especially confirmed that the method of strengthening the anterior muscles of the trunk is more effective than the standard stabilization exercise method.

• Computational Structural Engineering : An International Journal
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• v.1 no.1
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• pp.1-9
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• 2001

Collapse behavior of Mission-Gothic Undercrossing under Northridge earthquake is studied by performing nonlinear time-history analysis and three-dimensional nonlinear finite element method for flared columns. Bridge structural model is characterized as three-dimensional with consideration of columns, superstructures, and abutment conditions. Three components of ground motion, corresponding to bridge's longitudinal, transverse, and vertical direction and their combinations are used to investigate bridge collapse. Studies indicate that bridge collapse is dominantly caused by transverse ground motion and the consideration of three-dimensional ground motion leads to a more accurate assessment. Failure mechanism of flared columns is analyzed applying nonlinear finite element method. Reduction of column capacity is observed due to orientation of flare. Further investigation demonstrates that the effects of flare play an important role in predicting of bridge failure mechanism. Suggestions are offered to improve the performance of bridges during severe earthquake.

• Cartoon and Animation Studies
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• s.30
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• pp.27-57
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• 2013

Animation which appeared with films in the late 19th century was a medium which came on obtaining nourishment from art historical style of modernism. However, the relation establishment between animation and modernism has been focused mainly on animation shapes, namely painted images. This sprang from explaining the relationship between animation and paintings, and for this reason, discussions of movements in animation were understood in tradition of chromophotograph of Muybridge and Jules Marey, or some characteristics owned by the live-action film. However, movements of animation were essentially different from the indexical sign of films or photogram, and objects of reproduction were different between them. Movements reproduced by animation are not ordinary movements, but expressions of or compressed movements and considerably systematic movements. As a result, these movements are far from reproduction of live-action film photogram. Rather, the logic of movements reproduced by animation comes near to controlling their motion scopes, time, distance etc. after dividing each part of the body. This is concluded in a standpoint of modern mechanism which is represented by Descartes and La Mettrie who tried to understand human body as a exchangeable machine. Design of modern mechanism ranging from modern society to industrial society and the age of modernism came to lead to analysis of physical motions of modern industrial society called composition of efficient movements understanding them as the law of nature rather than movements as nature. In the late 19th century, Taylor, F. W. and Gilbreth, Frank Bunker's studies of workers' working hours and 'motion study' were a way of constituting the frame of machine-human, which indicates that tradition of modern mechanism affected the entire modernism passing through industrial society. Further, we can see that motion studies conducted by them have almost similar characteristics to action analysis to study animation later in the name of 'timing'.

• Journal of the Korean earth science society
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• v.39 no.4
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• pp.305-316
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• 2018

Satellite-derived sea surface winds (SSWs) and atmospheric motion vectors (AMVs) over the global ocean, particularly including the areas in and around tropical cyclones (TCs), have been provided in a real-time and continuous manner. More and better information is now derived from technologically improved multiple satellite missions and wind retrieving techniques. The status and prospects of key SSW products retrieved from scatterometers, passive microwave radiometers, synthetic aperture radar, and altimeters as well as AMVs derived by tracking features from multiple geostationary satellites are reviewed here. The quality and error characteristics, limitations, and challenges of satellite wind observations described in the literature, which need to be carefully considered to apply the observations for both operational and scientific uses, i.e., assimilation in numerical weather forecasting, are also described. Additionally, on-going efforts toward merging them, particularly for monitoring three-dimensional TC wind fields in a real-time and continuous manner and for providing global profiles of high-quality wind observations with the new mission are introduced. Future research is recommended to develop plans for providing more and better SSW and AMV products in a real-time and continuous manner from existing and new missions.

• Publications of The Korean Astronomical Society
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• v.22 no.4
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• pp.151-168
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• 2007

We have analyzed the comet records in the Korean history books: Samguksagi, Goryeosa, and Joseonwangjosillok. For a comparison, the Chinese and Japanese comet records collected by Kronk (1999) have also been analyzed. Power spectrum of the time series of the comet records is used to find periodic comets. Statistically significant periodicities in the power spectrum are detected at the periods of 38-40 years, about 76 years, and 300-400 years for all Korean, Chinese, and Japanese comet records. We have also calculated the past orbits of some comets that have been recently observed, to check whether or not they were recorded in the history books. We use a multistep method to numerically integrate the comet's orbital motion backward in time to 51 B.C. The gravitational force due to the Sun and the nine planets, non-gravitational force, and the relativistic effects have been considered. Comparison of comet's perihelion passage time and the position on the sky with the historical records shows that the comet Halley were recorded at every passage in both Goryeo and Joseon periods. The orbital motion of the comet Pons-Brooks has also been compared with the Korean records. For the comet Tempel-Tuttle, Swift-Tuttle, and Ikeya-Zhang, we have compared our calculation of the orbital motions with those of the previous studies.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.1
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• pp.12-27
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• 2007

This fundamental studies on for the productivity improvement and laborsaving of purse seine fishery. Given the difficulty posed from the distortion of net shape caused by the external forces, such as tide, at the time of shooting and pursing, we set the 4 steps of 0, 2, 4 and 6cm/sec in flow velocity in the flume tank for the experiment in order to examine those characteristics. We used two model seines designed on the scale of 1 to 180 based on the power block seine, which is the mackerel purse seine generally used in the near sea of Jeju Island and triplex seine, which is the mackerel purse seine of one boat system fishing expected in the future, for the experiment, and interpreted the characteristics of several motion in water, such as the shape of seine, the change in tension and area during pursing and its the analysis results are as follows. Though the experiment could be conducted up to 6cm/sec of flow velocity that was defined, the experiment could not go on because of the severe distortion in the seine at the flow velocity in excess of 6cm/sec. As for the depth of leadline and reduction rate of side area of seine when the pursing is connected, P seine turned out to be slightly higher than T seine, and the hauling speed and reduction rate of upper area of seine were found similar to each other. The correlation between the hauling time (Ht) and depth of lead line (Dhp, Dht) of P seine and T seine can be expressed by the equation, that is, Dhp=(0.99Pt-7.63)Pt+69.01, Dht=(1.03Pt-7.73)Pt+66.74. The correlation between the hauling time and hauling velocity (Hpp, Hpt) can be expressed by the equation, that is, $Hpp=-0.06Ht^2+0.88Ht+0.78,\;Hpt=-0.05Ht^2+0.81Ht+0.98$ here, Pt is pursing time. And the correlation between the pursing time and the reduction rate of side area (sArp, sArt) can be expressed by the equation, that is, $sArp=-0.48Pt^2+14.79Pt-16.74,\;sArt=-0.45Pt^2+14.56Pt-16.48$. The reduction rate of upper area of seine (tArp, tArt) can be expressed by the equation, that is, $tArp=0.34Pt^2-0.66Pt-0.74,\;tArt=0.34Pt^2-0.27Pt-1.80$. In addition, the correlation between the pursing time and tension of purse line (Tep, Tet) can be expressed by the equation, that is, $Tep=2.79Pt^2+2.26Pt-0.60,\;Tet=2.14Pt^2+8.08Pt-27.50$.

• Structural Engineering and Mechanics
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• v.26 no.6
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• pp.709-723
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• 2007

Considering the vast usage of time-history dynamic analyses to calculate structural responses and lack of sufficient and suitable earthquake records, generation of artificial accelerograms is very necessary. The main target of this paper is to present a novel method based on nonstationary Kanai-Tajimi model and wavelet transform to generate more artificial earthquake records, which are compatible with target spectrum. In this regard, the generalized nonstationary Kanai-Tajimi model to include the nonstationary evaluation of amplitude and dominant frequency of ground motion and properties of wavelet transform is used to generate ground acceleration time history. Application of the method for El Centro 1940 earthquake and two Iranian earthquakes (Tabas 1978 and Manjil 1990) is presented. It is shown that the model and identification algorithms are able to accurately capture the nonstationary features of these earthquake accelerograms. The statistical characteristics of the spectral response of the generated accelerograms are compared with those for the actual records to demonstrate the effectiveness of the method. Also, for comparison of the presented method with other methods, the response spectra of the synthetic accelerograms compared with the models of Fan and Ahmadi (1990) and Rofooei et al. (2001) and it is shown that the response spectra of the synthetic accelerograms with the method of this paper are close to those of actual earthquakes.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.920-932
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• 1994

The combustion phenomena of a reciprocating engine is one of the most important processes affecting performance and emissions. One effective way to improve the engine combustion is to control the motion of the charge inside a cylinder by means of optimum induction system design, because the flame speed is mainly determined by the turbulence at compression(TDC) process in S.I. engine. It is believed that the tumble and swirl motion generated during intake breaks down into small-scale turbulence in the compression stroke of the cycle. However, the exact nature of their relationship is not well known. This paper describes cycle resolved LDV measurement of turbulent flow inside the cylinder of a 4-valve engine under motoring(non-firing) conditions, and studies the effect of intake port configurations on the turbulence characteristics using following parameters ; Eulerian temporal autocorrelation coefficient, turbulence energy spectral density function, Taylor micro time scale, integral time scale, and integral length scale.