• Journal of the Korean Society of Industry Convergence
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• v.25 no.5
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• pp.773-782
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• 2022

Estimation of cable tension through proper measurements is one of the essential tasks in evaluating the safety of cable structures. In this paper, a study on cable tension estimation using the built-in accelerometer and camera in a smartphone was conducted. For the experimental study, visual displacement measurement using a smartphone camera and acceleration measurement using a built-in accelerometer were performed in the cable-stayed bridge model. The estimated natural frequencies and transformed tensions from these measurements were compared with the theoretical values and results from the normal visual displacement method. Through comparison, it can be seen that the error between the method using the smartphone and the normal visual displacement is sufficiently small to be acceptable. It has also been shown that those errors are much smaller than the difference between the values calculated by the theoretical model. These results show that the deviation according to the type of measurement method is not large and it is rather important to use an appropriate mathematical model. In conclusion, in the case of cable tension estimation, it can be said that the visual displacement measurement and acceleration using a smartphone can be a sufficiently applicable method, just like the normal visual displacement method. It is also noteworthy that the smartphone accelerometer has a larger magnitude error and has more limitations such as high-frequency sampling instability compared to the visual displacement method, but shows almost the same performance as the visual displacement method in this cable tension estimation.

• Water for future
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• v.19 no.3
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• pp.249-258
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• 1986

The purpose of this study is to estimate the PMP frequency factor for evaluation of the Probable Maximum Precipitation (PMP) in Korea. The value of PMP is the criterion of the determination of design rainfall in Planning and designing hydraulic structures, and water resources management. To obtain the object, 12 key stations were selected in which have the automatic rain0recording paper of 20 years, and the annual maximum rainfall values were calculated for each 7 durations(10 min., 1, 2, 4, 6, 12, 24 hr.). The statistics(mean, standard deviation)were estimated, and diagram which shows the relationship between mean annual maximum rainfall($$) and frequency factor for each durations were drawn. PMP was estimated by statistical method using the PMP frequency factor obtained from the diagram and statistics($$, Sn). The PMP-Duration Equation was derived from the envelope curve in order to obtain the PMP for an arbitrary duration. The isohyetal map of 24 hours PMP and PMP. DAD curve for the whole of Korea were drawn in accordance with the point PMP values.

• Journal of the Korean housing association
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• v.18 no.3
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• pp.103-113
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• 2007

The purpose of this study is calling attention to the silver town by analyse preference attributes diversely and suggest alterative plan. Also, offering basic data which needs for the establishment of comfortable and ideal old age residence culture by developing silver town which is appropriate for our circumstances and emotion. The survey population of this study focused on 40s and 50s' middle aged both genders living in the Seoul and national capital region, we used random sampling method. The analytical methods used in this study were frequency, mean, standard deviation, Factor Analysis, t-test, ANOVA, post-hoc estimation (Duncan test), multiple regression, To verify the reliability of each measure, Cronbach's alpha coefficient was used.

• Journal of Families and Better Life
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• v.21 no.6
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• pp.97-106
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• 2003

This study explored the relationship between housing values and condominium purchasing behavior. The participants of this study were married women who had bought a condominium at least once and who also were dwelling in one. Survey questionnaires were conducted on 1103 married women from three residential areas in Daegu. The analytical methods used in this study were frequency, mean, standard deviation, factor analysis, 1-test, one-way ANOVA, post-hoc estimation (Scheff test), and correlation analysis. The results show that the more the women were oriented toward convenience, education, and investment, the more likely they were to make a rational purchase. Also, the more the women's values were oriented toward conspicuous consumption and investment, the more they were likely to make an investment and ostentatious purchase. The women who valued ostentation and location tended to rely on other people's opinions and advertisement more, and were more likely to be impulsive shoppers. Women who valued convenience, education, and location, made their purchase decisions based on the housing prices.

• Journal of the Korean housing association
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• v.18 no.5
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• pp.143-150
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• 2007

The purpose of this research is to example the general trend of the service environment evaluation of the silver town and classify based on the service environment evaluation to suggest a effective method and alternatives fur development companies. The survey population of this study focused on 40s and 50s' middle aged both genders living in the Seoul and national capital region, we used random sampling method. The analytical methods used in this study were frequency, mean, standard deviation, factor analysis, Chi-Squae analysis, ANOVA, cluster Analysis, post-hoc estimation (Duncan test), To verify the reliability of each measure, Cronbach's alpha coefficient was used. As a result of classifying the environment evaluation elements, it was classified into 5 groups for the differentiating strategy on each group. The groups are: life support service type, medical and health support service type, cultural support service type, indifference type, and food support service type.

• ETRI Journal
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• v.45 no.4
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• pp.713-723
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• 2023

Game bots are illegal programs that facilitate account growth and goods acquisition through continuous and automatic play. Early detection is required to minimize the damage caused by evolving game bots. In this study, we propose a game bot detection method based on action time intervals (ATIs). We observe the actions of the bots in a game and identify the most frequently occurring actions. We extract the frequency, ATI average, and ATI standard deviation for each identified action, which is to used as machine learning features. Furthermore, we measure the performance using actual logs of the Aion game to verify the validity of the proposed method. The accuracy and precision of the proposed method are 97% and 100%, respectively. Results show that the game bots can be detected early because the proposed method performs well using only data from a single day, which shows similar performance with those proposed in a previous study using the same dataset. The detection performance of the model is maintained even after 2 months of training without any revision process.

• Journal of Positioning, Navigation, and Timing
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• v.5 no.3
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• pp.157-163
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• 2016

Clocks for time synchronization using radio signals such as global navigation satellite system (GNSS) may lose reference signals by intentional or unintentional jamming. This is called as holdover. When holdover occurs, a clock goes into free run in which synchronization performance is degraded considerably. In order to maintain the required precise time synchronization during holdover, accurate estimation on main parameters such as frequency offset and frequency drift is needed. It is necessary to implement an optimum filter through various simulation tests by creating clock noise in accordance with given specifications in order to estimate the main parameters accurately. In this paper, a method that creates clock noise in accordance with given specifications is described.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.8 s.251
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• pp.897-905
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• 2006

This study considers an experimental design of disturbance compensation control to improve stabilization performance of main battle tanks. An adaptive non-parametric design technique based on the Filtered-x Least Mean Square(FXLMS) algorithm is applied in the consideration of model uncertainties. The optimal compensator is designed by two-step design procedures: determination of frequency response function of the disturbance compensator which can cancel the disturbance of series of single harmonics by using the FXLMS algorithm and determination of the compensator polynomial which can fit the frequency response function obtained in the first step optimally by using a curve fitting technique. The disturbance compensator is applied to a simple experimental gun-torsion bar-motor system which simulates gun driving servo-system. Along with experimental results, the feasibility of the proposed technique is illustrated. Experimental results demonstrate that the proposed control reduces the standard deviation of stabilization error to 47.6% that by feedback control alone. The directional properties of the FXLMS Algorithm such as the direction of convergence and its convergence speed are also verified experimentally.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.8 no.2
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• pp.76-81
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• 1983

PCM-NRZ/FM Telemetry system is constructed on the basis of RF link with FM modulatedand NRZ-L binary coded PCM data are assumed to transmit through 5th-order Bessel filter. Upon demodulated by the limiter-discriminator at the receiver, the probability of bit error, which is important for performance estimation of digital system, is analyzed against SNR. The analysis based on the following parameters, that is bit rate 140kHz, frequency of pre-modulation filter f-100kHz, maximum frequency deviation of transmitter 2f=300kHz, was performed. As a result, when the telemetry system with the parameters above is designed, the probability of bit error is obtained as 10 along with fT=0.7 and h=2, T=2.

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.1
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• pp.25-29
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• 1980

For the preliminary estimation of the vertical hull natural frequency, the Schlick's or Schlick-type formulae have been traditional ones and are still in common use today. Some investigators have made their efforts, based on statistical data of ships' system parameters, to extend the applicability of Schlick-type formulae to higher modes, or to utilize the Rayleigh method. For instance, the work done by Dinsenbacher et al.[5] belongs to the former and that of Nagamoto et al.[6] to the latter. In a part of his previous paper[7], the author, investigating the case of a cargo ship of medium size, suggested that provided statistically simplified curves such as trapezoid of system parameter distributions are available in hands, direct utlization of an ordinary computer program can be also an another convenient method by which we can obtain both natural frequencies and normal mode shapes. In this paper, to confirm the feasibility of the above suggestion, four high speed boats are investigated. The system parameters of them are originally given in [5]. The computer program used here is one confiled based on a calculation method derived from Myklestal-Prohl modeling of hull, transfer matrix formulation and an extended Gumbel's initial value method for solving frequency equation. The results of the investigation show that the direct calculation based on statistically oriented and reasonably assumed trapezoidal mean curves of system parameter distributions can give us natural frequencies within about 5% deviation up to several-noded modes and normal mode shapes serviceable at least up to 4- or 5-noded modes in comparision with those based on actual distributions of system parameters. For this simplified method the actual data required for input are only of ship length, displacement, total added mass, bending and shear rigidity at amidship. They are available at the early stage of design. By this method we can also easily trace variations of vibration characteristics in the course of ship design cycles.