• Korean Journal of Applied Biomechanics
• /
• v.25 no.3
• /
• pp.283-291
• /
• 2015

Objective : The purpose of this study was to determine the differences in the head and tibial acceleration signal magnitudes, and their powers and shock attenuations between flat-footed and normal-footed running. Methods : Ten flat-footed and ten normal-footed subjects ran barefoot on a treadmill with a force plate at 3.22m/s averaged from their preferred running speed using heel-toe running pattern while the head and tibial acceleration in the vertical axis data was collected. The accelerometers were sampled at 2000 Hz and voltage was set at 100 mv, respectively. The peak magnitudes of the head and tibial acceleration signals in time domain were calculated. The power spectral density(PSD) of each signal in the frequency domain was also calculated. In addition to that, shock attenuation was calculated by a transfer function of the head PSD relative to the tibia PSD. A one-way analysis of variance was used to determine the difference in time and frequency domain acceleration variables between the flat-footed and normal-footed groups running. Results : Peaks of the head and tibial acceleration signals were significantly greater during flat-footed group running than normal-footed group running(p<.05). PSDs of the tibial acceleration signal in the lower and higher frequency range were significantly greater during flat-footed running(p<.05), but PSDs of the head acceleration signal were not statistically different between the two groups. Flat-footed group running resulted in significantly greater shock attenuation for the higher frequency ranges compared with normal-footed group running(p<.05). Conclusion : The difference in impact shock magnitude and frequency content between flat-footed and normal-footed group during running suggested that the body had different ability to control impact shock from acceleration. It might be conjectured that flat-footed running was more vulnerable to potential injury than normal-footed running from an impact shock point of view.

• Journal of Communications and Networks
• /
• v.18 no.2
• /
• pp.218-226
• /
• 2016

Coordination among users is an inevitable but time-consuming operation in wireless networks. It severely limit the system performance when the data rate is high. We present FC-MAC, a novel MAC protocol that can complete a contention within one contention slot over a joint frequency-code domain. When a node takes part in the contention, it generates randomly a contention vector (CV), which is a binary sequence of length equal to the number of available orthogonal frequency division multiplexing (OFDM) subcarriers. In FC-MAC, different user is assigned with a distinct signature (i.e., PN sequence). A node sends the signature at specific subcarriers and uses the sequence of the ON/OFF states of all subcarriers to indicate the chosen CV. Meanwhile, every node uses the redundant antennas to detect the CVs of other nodes. The node with the minimum CV becomes the winner. The experimental results show that, the collision probability of FC-MAC is as low as 0.05% when the network has 100 nodes. In comparison with IEEE 802.11, contention time is reduced by 50-80% and the throughput gain is up to 200%.

• Nuclear Engineering and Technology
• /
• v.56 no.2
• /
• pp.745-752
• /
• 2024

A method for gamma/neutron event classification based on frequency-domain analysis for mixed radiation environments is proposed. In contrast to the traditional charge comparison method for pulse-shape discrimination, which requires baseline removal and pulse alignment, our method does not need any preprocessing of the digitized data, apart from removing saturated traces in sporadic pile-up scenarios. It also features the identification of neutron events in the detector's full energy range with a single device, from thermal neutrons to fast neutrons, including low-energy pulses, and still provides a superior figure-of-merit for classification. The proposed frequency-domain analysis consists of computing the fast Fourier transform of a triggered trace and integrating it through a simplified version of the transform magnitude components that distinguish the neutron features from those of the gamma photons. Owing to this simplification, the proposed method may be easily ported to a real-time embedded deployment based on Field-Programmable Gate Arrays or Digital Signal Processors. We target an off-the-shelf detector based on a small CLYC (Cs2LiYCl6:Ce) crystal coupled to a silicon photomultiplier with an integrated bias and preamplifier, aiming at lightweight embedded mixed radiation monitors and dosimeter applications.

• Journal of Institute of Control, Robotics and Systems
• /
• v.17 no.2
• /
• pp.135-138
• /
• 2011

Although most of control methods have been studied in the continuous-time domain, the actual control systems have been implemented using MCU (Micro Control Unit) and/or microprocessors so that the overall systems turn to be sampled-data systems. In this case, the stability criterion of the closed-loop system is not easy to derive. In this paper, a simple stability criterion for the sampled-data system with sliding mode controller is derived.

• Proceedings of the IEEK Conference
• /
• 2002.06d
• /
• pp.101-104
• /
• 2002

This paper proposes a unique data embedding algorithm for the video sequence. It describes two processings: shot boundary detection and robust data embedding. First, for the shot boundary detection, instead of using absolute frame differences, block by block based relative frame differences are employed. Frame adaptive thresholding values are also employed for the better detection. Second, for the robust data embedding, we generate message template and then convolve and correlate it with carrier signal. And then we embed data on the time domain video sequence. By using these two methods, watermarks into randomly selected frames of shots. Watermarks are detected well even if several certain shots are damaged because we embed watermark into each shot equally.

• Journal of the Korean Institute of Navigation
• /
• v.19 no.4
• /
• pp.1-8
• /
• 1995

Although ship's draught information onboard is substantial for both the safety of navigation and the estimation of loaded cargoes, its accuracy depends, in conventional surveying method, on the skillfulness of observers and the condition of the sea surface round the vessel. To obtain more accurate information accessibly, measuring instruments with sophisticated sensors such as mechanical, electronic and ultrasonic transducers have been developed. However, they have still limitation in accuracy and in making up a system due to the complexity of processing signal. In this paper, we propose a new technique for analyzing ultrasonic pulse signal, in order to improve the measurement accuracy and simplify a remote sensing system of draught by ultrasonic waves. In this technique, pulse signal is translated into phase curve which is composed of the phase value defined in time domain. Then, the time interval between two signals different in waveform, is waveform, is analytically determined by calculating average time difference on phase curves. Also, analytical procedure can be carried out in real time with the successive five data sampled at T/4, for high speed digital processing with computer and A/D converter. This technique is useful for measuring draught under the influence of sea condition and for interfacing its data briefly to the integrated bridge system.

• 제어로봇시스템학회:학술대회논문집
• /
• 1998.10a
• /
• pp.295-300
• /
• 1998

In this paper, a real time diagnostic algorithm fur estimating the impact location by loose parts is proposed. It is composed of two modules such as the alarm discrimination module (ADM) and the impact-location estimation module(IEM). ADM decides whether the detected signal that triggers the alarm is the impact signal by loose parts or the noise signal. When the decision from ADM is concluded as the impact signal, the beginning time of burst-type signal, which the impact signal has usually such a form in time domain, provides the necessary data fur IEM. IEM by use of the arrival time method estimates the impact location of loose parts. The overall results of the estimated impact location are displayed on a computer monitor by the graphical mode and numerical data composed of the impact point, and thereby a plant operator can recognize easily the status of the impact event. This algorithm can perform the diagnosis process automatically and hence the operator's burden and the possible operator's error due to lack of expert knowledge of impact signals can be reduced remarkably. In order to validate the application of this method, the test experiment with a mock-up (flat board and reactor) system is performed. The experimental results show the efficiency of this algorithm even under high level noise and potential application to Loose Part Monitoring System (LPMS) for improving diagnosis capability in nuclear power plants.

• The Journal of Information Systems
• /
• v.31 no.3
• /
• pp.67-87
• /
• 2022

Purpose This study quantified companies' views on the COVID-19 pandemic with sentiment analysis of U.S. public companies' disclosures. It aims to provide timely insights to shareholders, investors, and consumers by analyzing and visualizing sentiment changes over time as well as similarities and differences by industry. Design/methodology/approach From more than fifty thousand Form 10-K and Form 10-Q published between 2020 and 2021, we extracted over one million texts related to the COVID-19 pandemic. Using the FinBERT language model fine-tuned in the finance domain, we conducted sentiment analysis of the texts, and we quantified and classified the data into positive, negative, and neutral. In addition, we illustrated the analysis results using various visualization techniques for easy understanding of information. Findings The analysis results indicated that U.S. public companies' overall sentiment changed over time as the COVID-19 pandemic progressed. Positive sentiment gradually increased, and negative sentiment tended to decrease over time, but there was no trend in neutral sentiment. When comparing sentiment by industry, the pattern of changes in the amount of positive and negative sentiment and time-series changes were similar in all industries, but differences among industries were shown in neutral sentiment.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.7A
• /
• pp.756-765
• /
• 2004

Using single carrier frequency RFID system in one-to-multiple wireless communications, might be generated data loss because of data collisions. Conventional Anti-collision method prevent data loss from data collisions which are binary tree method and ALOHA. However, those two preventive measures also have week points which are strongly dependent on the time and space when passing through the recognition area. This paper suggests the full-length instruction code method which fits in to half-duplex method, prevents data collision effectively by calculating the non-transmitting time of multiple tags considering approaching time to the recognition area. After full-length instruction code method test using 13.56MHz bandwidth RFID system shows that full-length instruction code method could make better result than any other methods. Moreover, the record shows O(n) result after analyzing O-notation of conventional time-domain procedure.

• Journal of the Korean Society of Food Culture
• /
• v.15 no.4
• /
• pp.259-268
• /
• 2000

The purpose of this study was to describe the levels of market goods substitution of housework and find out the determinants on it in the domain of food among married female home-based workers. The data were collected from 169 married female home-based workers in Pusan and Kyungnam province, by self-administered questionnaires. Frequencies, percentiles, Cronbach's alpha, Pearson's correlations, and multiple regression were used to analyze the data. In the convenience foods, frozen foods had the highest substitution level, whereas prepared stew had the lowest. The substitution level of Korean traditional storage foods was the middle. And in dining-out service, the substitution level was mostly high: the level of delivery service was higher than that of dining-out. Compared to the previous research, these results showed that market goods substitution tended to increase, and its level in the domain of food will promote continually over time. The variables affecting the substitution level of convenience food were the number of family members, occupation, the existence of elderly/disabled person in the family, sex-role attitude, and weekly hours at home-based work. The substitution level of Korean traditional storage foods was influenced by sex-role attitude, occupation, education, monthly household income, and the existence of elderly/disabled person in the family. The significant variables affecting the substitution level of dining-out service were weekly hours at home-based work, the number of family members, occupation, monthly household income, education, and sex-role attitude.