• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.1
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• pp.37-45
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• 2011

Reduction of ship's rolling is the most important performance requirement for improving the safety of the crew on board and preventing damage to cargo as well as improving the comfort of the ride. It is a common experience for mariners, to see that steering with a rudder generally induces rolling of the ship, though the original aim of the rudder is to keep the ship's heading to the required course. At the first stage, when a rudder is steered, usually a ship heels in an inward direction, due to the roll moment acting on the rudder. At the next stage in steering, the main heel may change to an outward. This coupling between rudder and roll motion has become an attractive problem from the point of view of roll stabilization using the rudder, because it is a natural in sight that if the rudder action is skillfully related to the change of roll as well as to the course deviation, the roll can be reduced to a certain degree. The main aim of this paper is to discuss the results of the actual full-scale sea trials carried out on steer gear No.1 and No.1 2, the individual quartermaster and to make clear their statistical properties, using the actual data which included measurement of roll angle, roll rate and the comparative tests were carried out immediately after each other, in order to minimize any statistical variation in sea conditions. It can be concluded that the steer gear No. 1 2 reduced the roll motion on average by about 21% in comparison with the No.1 and confirmed the some difference as per a ability of quarter-master's maneuver.

• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.139-146
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• 2007

The objective of the present study is to provide statistical resistance statistics for steel-concrete composite plate girder sections under positive and negative moments. Statistical properties on yield strength, tensile strength, elongation, and fracture toughness of domestic structural steel products, gathered from an analysis of over 16,000 samples, were evaluated. Using the steel samples for the plate girder, the bias factor and the coefficient of variation of the ultimate flexural resistance for representative composite plate girder sections under positive and negative flexures were presented. In calculating the ultimate flexural resistance of the composite section, the moment curvature relationships were developed using the incremental load approach considering material nonlinearity for the steel girder. The predicted statistics can be used in the future for the efficient calibration of LRFD code.

• Advances in Energy Research
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• v.8 no.2
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• pp.95-110
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• 2022

Wind energy can be utilized for the generation of electricity, due to significant wind potential at different parts of the world, some countries have already been generating of electricity through wind. Pakistan is still well behind and has not yet made any appreciable effort for the same. The objective of this work was to add some new strategies to calculate Weibull parameters and assess wind energy potential. A new approach calculates Weibull parameters; we also developed an alternate formula to calculate shape parameters instead of the gamma function. We obtained k (shape parameter) and c (scale parameter) for two-parameter Weibull distribution using five statistical methods for five different cities in Pakistan. Maximum likelihood method, Modified Maximum likelihood Method, Method of Moment, Energy Pattern Method, Empirical Method, and have been to calculate and differentiate the values of (shape parameter) k and (scale parameter) c. The performance of these five methods is estimated using the Goodness-of-Fit Test, including root mean square error, mean absolute bias error, mean absolute percentage error, and chi-square error. The daily 10-minute average values of wind speed data (obtained from energydata.info) of different cities of Pakistan for the year 2016 are used to estimate the Weibull parameters. The study finds that Hyderabad city has the largest wind potential than Karachi, Quetta, Lahore, and Peshawar. Hyderabad and Karachi are two possible sites where wind turbines can produce reasonable electricity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.197-205
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• 2008

In order to estimate mean wind speed in the Gwangyang-Myodo Region, the probability distribution model of extreme values has been used in the statistical analysis of joint distribution probability of daily maximum wind speed and corresponding direction in this paper. For this purpose frequency of daily maximum records at respective stations is inquired into and sample of largest yearly wind speed of sixteen compass direction and non-direction is extracted from daily data of maximum wind speed and appropriate direction of the meteorological observing stations nearby the bridge construction site. These extreme speed records are applied to Gumbel and Weibull distribution model and parameters are estimated through method of moment and method of least squares etc. And also, distribution and parameters are inquired into whether it is fitted through the probability plot correlation coefficient examination. From fitted parameters the largest yearly wind speed of sixteen compass direction and non-direction is extrapolated taking into account factors regarding sample size of data and distance from the bridge construction site according to the appropriate stations.

• The Korean Journal of Applied Statistics
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• v.26 no.5
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• pp.713-723
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• 2013

An objective Bayesian estimation procedure of the two-parameter Pareto distribution is presented under the reference prior and the noninformative prior. Bayesian estimators are obtained by Gibbs sampling. The steps to generate parameters in the Gibbs sampler are from the shape parameter of the gamma distribution and then the scale parameter by the adaptive rejection sampling algorism. A numerical study shows that the proposed objective Bayesian estimation outperforms other estimations in simulated bias and mean squared error.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.3
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• pp.250-257
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• 2017

This paper investigates minimum safe distances relative to a ship's four cardinal sides, as perceived by Filipino navigators when encountering dangerous elements and in adverse weather conditions when maneuvering in and around harbors. It uses a descriptive research method in the form of a questionnaire survey for experienced Filipino navigators of various ranks. During the course of research, 71 responses were colleted and the resulting data is presented in graphical and tabulated forms. Statistical methods including Pearson-product moment correlations, Cronbach's Alpha and ANOVA were used to identify internal associations, consistencies and significances, respectively. It has been proven that there are no significant differences in minimum safe distances relative to a ship's four cardinal sides, whether maneuvering while approaching a port or within an inner harbor. This study has been deemed significant for training future navigators, managing traffic in fairways, and designing harbors and maneuvering areas in the approaches to ports, among other applications. This work can also be used as a preliminary study for comparison with the well known safe domains presently in use.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.4
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• pp.341-349
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• 2018

Recently, it has been reported that the whipping response, which is the elastic phenomenon of the ship, may be one of the causes of the ship accident. Unfortunately, the commonly used methodology for evaluating the whipping effect effectively has not been developed yet. In this study, we developed a procedure to estimate the whipping effect of hull in actual design stage. Fluid-structure interaction analysis was performed for a dominant short term sea state to obtain the time series data of vertical wave bending moment including the whipping response by slamming. In order to estimate the whipping effect by using the time series, some signal processing and statistical techniques such as low pass filtering, Weibull fitting and so on, were applied. the hydro-elasticity analysis was performed on container ships of various sizes to evaluate the whipping effect. The parameters that can affect the response of the hull vibration was selected and the effect of these parameters on whipping was analyzed.

• Korean Journal of Child Studies
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• v.14 no.1
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• pp.167-177
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• 1993

The purpose of the present study to investigate relationships among family background factors (i. e. adolescents' sex, mother's educational level and employment status. family's SES, and family types), mother-adolescent communication patterns and ego-identity development of adolescents. The subjects were 169 mother-adolescent dyads living in Seoul. Statistical methods used for the data analysis were frequencies, percentiles, Mean, ANOVA, Duncan's multiple range test, Pearson's product-moment correlation, regression analysis, ANCOVA, and Cronbach's ${\alpha}$. The results were as follows: (1) Significant differences of the adolescents were between family's SES and open communication patterns, between family types and problematic communication patterns. (2) Significant differences of the mothers were between family's SES and open communication patterns, and among family's SES, mother's educational level and problematic communication patterns. (3) There were significant differences in ego-identity of adolescents according to family's SES. (4) There were significant relationships between mother-adolescent communication patterns and the ego-identity development of adolescents. (5) The most influential variable explaining adolescents' ego-identity development was found to be problematic communication patterns perceived by adolescents. Family background factors and mother's communication patterns were not found to have significant effects.

• The Journal of Korea CHUNA Manual Medicine
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• v.5 no.1
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• pp.85-92
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• 2004

Low back pain(LBP) is known as one of the diseases that produce severe pains with 80% of the whole population having experienced it and reported that, even at this moment, 20-30% of the world population is suffering from it. The writer has performed 'Conservative remedies (non-surgical procedures taken)' from $1^{st}$ of January 2003 to $31^{st}$ of December the same year for 76 cases who have been hospitalized in Jaseng Hospital and adopted as having been diagnosed either HIVD L4-5 or HIVD L5-S1 or as having both. The clinical analysis was made through statistical researches which include : the changing degree in SLR test of the Cheongpa-Jeon(CP) taking patient group and the non-taking group, the change of VAS(Visual analogue scale) against pains, and the days of hospital treatment. The result demonstrated that the CP taking group showed higher changes in SLR test, bigger reduction in VAS changes and the days for hospitalization shorter than the group that didn't take CP.

• The Korean Journal of Applied Statistics
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• v.28 no.3
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• pp.511-527
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• 2015

For time series analysis, power transformation (especially log-transformation) is widely used for variance stabilization or normalization for stationary ARMA(p, q) model. A simple and naive back transformed forecast is obtained by taking the inverse function of expectation. However, this back transformed forecast has a bias. Under the assumption that the log-transformed data is normally distributed. The unbiased back transformed forecast can be obtained by the expectation of log-normal distribution; consequently, the property of this back transformation was studied by Granger and Newbold (1976). We investigate the sensitivity of back transformed forecasts under several different underlying distributions using simulation studies.