• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.1
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• pp.50-52
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• 2007

The growth of young-of-the-year blue spot mudskipper, Boleophthalmus pectinirostris, was investigated using length-frequency data for 395 individuals collected from a mud flat in southwestern Korea between August and October 2001. Three cohorts were separated by the Bhattacharya method. In October, individuals of cohort-I reached 98 mm in total length, whereas those of cohort-III reached just 66 mm. Each cohort reached hibernation in November, that could be related to the ring formation in the following year.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.27-35
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• 1998

An experimental study was performed to investigate the optimum cycle of an inverter heat pump as a function of frequency. The performance of the inverter heat pump with the rated cooling capacity of 4,141 W(3,550kcal/h) was measured with a variation of frequency, indoor and outdoor temperature, and length of capillary tube in the psychrometric test room. As a base case, the inverter heat pump with the standard capillary length of l,000mm(optimum size for the frequency of 60Hz) and ASHRAE Test condition "A" was tested by varying frequency from 30Hz to 80Hz. Then, the optimum cycles were investigated by varying the length of capillary tube at each frequency level of 30, 60 and 80Hz. Based on the experimental data, the change of system characteristics between the optimum and the base case were analyzed for each selected frequency level. Generally, for low frequency level(30Hz), the longer length of the capillary tube compared with the standard size showed the higher energy efficiency ratio(EER), while for high frequency level(80Hz) the shorter length of the capillary tube showed the higher EER.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.1
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• pp.64-72
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• 1997

An experiment study was performed to investigate the optimum cycle of an inverter heat pump as a function of frequency. The performance of the inverter heat pump with the rated cooling capacity of 4141W(3550kcal/h) was measured with a variation of frequency, indoor and outdoor temperature, and length of capillary tube in the psychrometric test room. As a base case, the inverter heat pump with the standard capillary length of 1000mm which was optimum size for the frequency of 60Hz and ARHRAE Test condition A was tested by varying frequency from 30Hz to 80Hz. Then, the optimum cycle was invesigated by varying the length of capillary tube at each frequency levels of 30, 60 and 80Hz. Based on the experimental data, the change of system characteristics between the optimum and the base case were analyzed for each selected frequency levels. Generally, for low frequency level(30Hz), the longer length of the capillary tube compared with the standard size showed the higher EER, while for high frequency level(80Hz) the shorter length of the capillary tube showed the higher EER.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.12
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• pp.164-170
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• 2010

For the surge currents like lightning or ground fault currents containing high frequency components which cause the electromagnetic interferences for the electronic devices and communication equipment, the grounding impedances give the significantly composite characteristics which are dependent on the frequency of surge currents. In this paper, the analytical model and method for determining the optimal length of the newly developed coaxial type carbon ground electrode which has a little fluctuation in grounding impedance with frequency. The length of minimizing the fluctuation of grounding impedance by changing frequency from 100[Hz] to 1[MHz] was determined, and the validity of this proposed method was confirmed by comparing with the simulated and measured data.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.1
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• pp.80-89
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• 2021

In Korea, marine fish landed at ports are randomly sampled on a periodic basis (e.g., daily or weekly), and body sizes (e.g., lengths and weights) of those sampled fish are measured. The motivation for our study is whether or not such measurements reflect the size distribution, especially the length distribution of fish landed (= a population), because such length measurements are key data for a length-based assessment model. The current sampling method is to sample fish landed at ports by body size group (e.g., very small, small, medium, large, very large), using the sampling weights as the number of boxes by body size group. In this study, we showed that length composition data about fish sampled by the current method did not represent the length frequency distribution of the fish landed, and suggested that an alternative sampling method should be applied of using the sampling weights as the number of fish landed by body size group. We also introduced a method for determining an appropriate sample size.

• Journal of The Korean Digital Architecture Interior Association
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• v.2 no.1
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• pp.24-31
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• 2002

The purpose of this study was to analyze the transition on architectural data such as valid indoor length, module, ratio of core, floor height, ceiling height and the type of structured cabling system according to the intelligent building grade through case study of the intelligent office buildings constructed in Korea since 1980. The results of this study were as follows. The average floor height was 3.80m, and it was higher in proportion to the IB grade. The average ceiling height was 2.57m, and it didn't have connection with the IB grade. The module of high frequency in application was $3.0{\times}3.0m$, and it showed 25% in the application frequency. The average valid indoor length was 12.27m. The average ratio of core was 24.49%. The type of high frequency in application for the structured cabling was Access Floor Type, and it showed 31% in the application frequency.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.240-240
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• 2000

This paper presents two algorithms based on the concept of the frequency domain adaptive filter(FDAF). First the frequency domain recursive least squares(FRLS) algorithm with the overlap-save filtering technique is introduced. This minimizes the sum of exponentially weighted square errors in the frequency domain. To eliminate discrepancies between the linear convolution and the circular convolution, the overlap-save method is utilized. Second, the sliding method of data blocks is studied Co overcome processing delays and complexity roads of the FRLS algorithm. The size of the extended data block is twice as long as the filter tap length. It is possible to slide the data block variously by the adjustable hopping index. By selecting the hopping index appropriately, we can take a trade-off between the convergence rate and the computational complexity. When the input signal is highly correlated and the length of the target FIR filter is huge, the FRLS algorithm based on the block processing technique has good performances in the convergence rate and the computational complexity.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.593-598
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• 2005

At-site analysis is not appropriate if the record length is shorter than target return period T. If the record length is longer than 27 years, then at-site analysis may be sufficient(Institute of Hydrology, 1999). However, in such a case, regional frequency analysis is recommended for purpose of comparison. Record lengths of annual maximum rainfall data in Korea are usually shorter than 50 years. It is therefore essential to apply regional frequency analysis for estimating rainfall quantiles of more than 100 years return period. In this research, regional rainfall frequency analysis is performed for hourly rainfall data of South Korea. Homogeneous regions are idntified by clusgter analysis which is a standard method of statistical multivariate analysis for dividing a data set into groups. An appropriate distribution is chosen by goodness-of-fit test. GLO is found to be an appropriate distribution as a result of goodness-of-fit measure (Hosking & Wallis, 1997). Simulation experiments are performed to check the performance of frequency analysis techniques. The effects of discordant sites on quantiles are considered.

• Computers and Concrete
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• v.31 no.1
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• pp.1-7
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• 2023

In this paper, Timoshenko-beam model is developed for the vibration of double carbon nanotubes. The resulting frequencies are gained for axial wave mode and length-to-diameter ratios. The natural frequency becomes more prominent for lower length-to-diameter ratios and diminished for higher ratios. The converse behavior is observed for axial wave mode with clamped-clamped and clamped-free boundary conditions. The frequencies of clamped-free are lower than that of clamped-clamped boundary condition. The eigen solution is obtained to extract the frequencies of double walled carbon nanotubes using Galerkin's method through axial deformation function. Computer softer MATLAB is used for formation of frequency values. The frequency data is compared with available literature and found to be in agreement.

• Fisheries and Aquatic Sciences
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• v.12 no.2
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• pp.152-161
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• 2009

The largehead hairtail (Trichiurus lepturus) is one of the most common fisheries stocks in the East China Sea and the Yellow Sea. The species is caught using a variety of fishing tools, such as a stow net or a long line, as well as jigging and trawling. Scientific investigations have been conducted throughout the world to enable evidence-based estimations for the management and protection of the main fisheries biomass. For example, inshore and offshore hydro acoustic surveys are performed annually using bottom- and mid-water trawls around the Korean Peninsula. However, to date, no acoustic survey has been conducted to estimate fish size distribution, which is necessary to construct a data bank of target strength (TS) relative to fish species, length (L), and frequency. This study describes the frequency and length dependence of TS among fishes in Korean waters for the purpose of constructing such a TS data bank. TS measurements of the largehead hairtail were carried out in a water tank (L 5 m$\times$width 6 m$\times$ height 5 m) at frequencies of 50, 75, 120, and 200 kHz, using a tethering method. The average TS patterns were measured as a function of tilt angle, ranging from $-45^{\circ}$ (head down) to $+45^{\circ}$ (head up) every $0.2^{\circ}$. The length conversion constant ($b_{20}$) was estimated under the assumption that TS is proportional to the square of the length. In addition, in situ TS measurements on live largehead hairtails were performed using a split beam echo sounder.