• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.75-81
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• 2002

In the re-entry comtrol system, errors apt to induce because the time deriviative of drag acceleration is analytically estimated. Still more, the difficulty of estimation of th exact drag coefficient in hypersonic velocity and the non-reality of the scale height cause a steady-state drag errer. In the Space-Shuttle, a steady-state drag error is reduced by the addition of the integral term of drag acceleation error into the control system. This method, however, induces a difficulties in respect to the modern controller composition due to the multi-poles in a closed-loop system. Thus, this paper proposes the additional method of the disturbance observer. This reduces the steady-state drag error according to the following by the analytic calculation, and then creates the new drag acceleration time derivative using the estimated error. The performance of the re-entry control system is verified about 32 refernce trajectories.

• Journal of the Korean Home Economics Association
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• v.44 no.8
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• pp.181-198
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• 2006

The purpose of this study is to understand modernization process of korean housing during the past one century. To following up the changes of everyday lives of common peoples, magazines, news papers, tourist's records and gossip items were collected and interpreted from the microscopic point of view. In this study arguments on 'modernity' of korean housing was focused on some issues, thus, separation, differentiation, individualization, as well as privatization. Concrete discourses are; firstly, spatial isolation of housing and urban place each other, secondly, functional division of inner spaces of housing, and lastly, guarantee of privacy sphere. Historical changes of housing showed some meaningful phenomena. Before modernization housing was place of reproduction and consume at the same time. However after modern urban space came into existence and work and rest were separated, housing gained only mono function. Thus, housing have only one meaning as private place for nuclear family, that is "Home, Sweet Home." Instead of past multi-functional rooms, functional prescribed rooms, for example, dinning room, were newly born. In the past, the boundary between public and private sphere was not clear. For examples, everyday experiences of family were extended to the street and in the house in most cases spaces were shared. But after modernization the scale of individual spaces become larger and private life can be secured. Consequently, history of everyday life from traditional agricultural society to industrialized modern society demonstrates the structural context between the micro and macro dimension in the fields of human life. In other words, everyday lives and macro history response each other and create new perception of time-space structure in the modern housing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12C
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• pp.1239-1247
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• 2005

It is important to improve TCP performance in Self-similar TCP network where signalling between the same end nodes through bidirectional traffic routes. In wireless link, the traffic limitation pattern occurred in two or more TCP connections is applied into MPEC video control as multi time-interval congestion control. For TCP update variable, we extend TCP and perform as function call, and we study a method of relating TCP with LTS module controlling with the information type that is overcoming the limit of feedback loop determined by RTT. For comparison, we measure the TCP throughput without LTS and verify the fairness by means of meta control. The improved TCP performance is shown by that the number of connections of traffic congestion control increases when RTT increases.

• Journal of Pharmacopuncture
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• v.27 no.2
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• pp.123-130
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• 2024

Objectives: Post-operative urinary retention (POUR) is a frequent complication following surgical procedures, characterized by an acute inability to void, leading to additional complications and extended hospitalization. Acupuncture has been shown to be effective in facilitating spontaneous urination and alleviating anxiety in patients experiencing poor urination. The present study aims to evaluate the effectiveness of electroacupuncture in the management of POUR in patients who have undergone lumbar spine surgery. Methods: This retrospective study conducted at the National Hospital of Acupuncture in Vietnam and reviewed the medical records of patients over 18 years old who underwent lumbar spine surgery and were diagnosed with POUR between January to December 2019. Electroacupuncture was administered at five specific acupuncture points: Qugu (CV2), Zhongji (CV3), Zhibian (BL54), Pangguanshu (BL28), and Kunlun (BL60). This study monitored key parameters related to the effectiveness of the acupuncture treatment, including the number of acupuncture treatment sessions required until a patient was successfully treated was recorded, with a maximum of three acupuncture treatment sessions per patient, the time elapsed until urination following the treatment (minutes), and urinary bladder volume before and after treatment (mL). Results: The study demonstrated a 93.3% success rate in treating POUR with electroacupuncture. A significant reduction in post-void residual volume was noted, and patients could void within 30 minutes post-treatment. No significant differences in treatment effectiveness were observed across difference genders and age groups. Conclusion: Electroacupuncture proved to be a highly effective treatment for POUR in patients post-lumbar spine surgery, with a rapid response time and substantial reduction in PVR. However, the retrospective nature of the study and single-center focus limit its generalizability. Future research incorporating randomized controlled trials or multi-center observational studies are recommended to validate these findings and explore the potential of acupuncture in POUR management on a broader scale.

• Smart Media Journal
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• v.13 no.4
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• pp.23-32
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• 2024

Large-scale fires and their consequential damages are becoming increasingly common, but confidence in fire detection systems is waning. Recently, widely-used chemical fire detectors frequently generate lots of false alarms, while video-based deep learning fire detection is hampered by its time-consuming and expensive nature. To tackle these issues, this study proposes a fire detection model utilizing an autoencoder approach. The objective is to minimize false alarms while achieving swift and precise fire detection. The proposed model, employing an autoencoder methodology, can exclusively learn from normal data without the need for fire-related data, thus enhancing its adaptability to diverse environments. By amalgamating data from five distinct sensors, it facilitates rapid and accurate fire detection. Through experiments with various hyperparameter combinations, the proposed model demonstrated that out of 14 scenarios, only one encountered false alarm issues. Experimental results underscore its potential to curtail fire-related losses and bolster the reliability of fire detection systems.

• Tunnel and Underground Space
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• v.34 no.5
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• pp.571-598
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• 2024

Nuclear power generation, which belongs to the eco-friendly energy category, has a comparative advantage over other power generation methods in terms of cost and efficiency, and its share of electricity energy has recently shifted to an increasing trend worldwide. In Korea, various empirical studies have been conducted centering on KURT (KEARI Underground Research Tunnel) to secure elemental technology necessary for safe and efficient disposal of high-level radioactive waste inevitably generated during the operation of nuclear power plants. Considering the domestic rock type and geological conditions, the multi-barrier system is evaluated as the most effective among various high-level radioactive waste disposal methods. The objectives of this study were, first, to evaluate the hydraulic characteristics of deep and low-permeable rock masses and second, to secure quantitative information on the hydraulic connectivity between boreholes for establishing a large-scale in-situ test system necessary for the proper design and stability evaluation of the multi-barrier system. In this regard, diverse borehole tests using DHTS (Deep borehole Hydraulic Testing System) were performed in the two research modules in KURT, and in particular, the injection type cross-hole hydraulic connectivity tests were successfully completed for the first time in Korea. In this paper, we briefly introduced MDST (Mini Downhole Shut-in Tool) developed to update the performance of DHTS and mainly discussed the key results obtained from the stepwise in-situ borehole tests.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.5
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• pp.249-257
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• 2022

This paper presents an improved computational framework for the direct-solution-based finite element tearing and interconnecting (FETI) algorithm. The FETI-local algorithm is further improved herein, and localized Lagrange multipliers are used to define the interface among its subdomains. Selective inverse entry computation, using a property of the Boolean matrix, is employed for the computation of the subdomain interface stiffness and load, in which the original FETI-local algorithm requires a full matrix inverse computation of a high computational cost. In the global interface computation step, the original serial computation is replaced by a parallel multi-frontal method. The performance of the improved FETI-local algorithm was evaluated using a numerical example with 64 million degrees of freedom (DOFs). The computational time was reduced by up to 97.8% compared to that of the original algorithm. In addition, further stable and improved scalability was obtained in terms of a speed-up indicator. Furthermore, a performance comparison was conducted to evaluate the differences between the proposed algorithm and commercial software ANSYS using a large-scale computation with 432 million DOFs. Although ANSYS is superior in terms of computational time, the proposed algorithm has an advantage in terms of the speed-up increase per processor increase.

• Smart Media Journal
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• v.11 no.10
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• pp.65-75
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• 2022

Deep learning is used as a creative tool that could overcome the limitations of existing analysis models and generate various types of results such as text, image, and music. In this paper, we propose a method necessary to preprocess audio data using the Niko's MIDI Pack sound source file as a data set and to generate music using Bi-LSTM. Based on the generated root note, the hidden layers are composed of multi-layers to create a new note suitable for the musical composition, and an attention mechanism is applied to the output gate of the decoder to apply the weight of the factors that affect the data input from the encoder. Setting variables such as loss function and optimization method are applied as parameters for improving the LSTM model. The proposed model is a multi-channel Bi-LSTM with attention that applies notes pitch generated from separating treble clef and bass clef, length of notes, rests, length of rests, and chords to improve the efficiency and prediction of MIDI deep learning process. The results of the learning generate a sound that matches the development of music scale distinct from noise, and we are aiming to contribute to generating a harmonistic stable music.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.40.3-41
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• 2017

Korea Astronomy and Space Science Institute The observation of particles and waves using a single satellite inherently suffers from space-time ambiguity. Recently, such ambiguity has often been resolved by multi-satellite observations; however, the inter-satellite distances were generally larger than 100 km. Hence, the ambiguity could be resolved only for large-scale (> 100 km) structures while numerous microscale phenomena have been observed at low altitude satellite orbits. In order to resolve those spatial and temporal variations of the microscale plasma structures on the topside ionosphere, SNIPE mission consisted of four (TBD) nanosatellites (~10 kg) will be launched into a polar orbit at an altitude of 700 km (TBD). Two pairs of satellites will be deployed on orbit and the distances between each satellite will be from 10 to 100 km controlled by a formation flying algorithm. The SNIPE mission is equipped with scientific payloads which can measure the following geophysical parameters: density/temperature of cold ionospheric electrons, energetic (~100 keV) electron flux, and magnetic field vectors. All the payloads will have high temporal resolution (~ 16 Hz (TBD)). This mission is planned to launch in 2020. The SNIPE mission aims to elucidate microscale (100 m-10 km) structures in the topside ionosphere (below altitude of 1,000 km), especially the fine-scale morphology of high-energy electron precipitation, cold plasma density/temperature, field-aligned currents, and electromagnetic waves. Hence, the mission will observe microscale structures of the following phenomena in geospace: high-latitude irregularities, such as polar-cap patches; field-aligned currents in the auroral oval; electro-magnetic ion cyclotron (EMIC) waves; hundreds keV electrons' precipitations, such as electron microbursts; subauroral plasma density troughs; and low-latitude plasma irregularities, such as ionospheric blobs and bubbles. We have developed a 6U nanosatellite bus system as the basic platform for the SNIPE mission. Three basic plasma instruments shall be installed on all of each spacecraft, Particle Detector (PD), Langmuir Probe (LP), and Scientific MAGnetometer (SMAG). In addition we now discuss with NASA and JAXA to collaborate with the other payload opportunities into SNIPE mission.

• The Journal of Engineering Geology
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• v.29 no.2
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• pp.137-151
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• 2019

Geophysical exploration techniques are effective for monitoring changes in the ground condition around the excavation project to prevent subsidence risks during excavation work, therefore, improving analysis techniques is required for applying and supplementing various geophysical exploration technologies. In this study, a field-scale on-site test was conducted to detect possible ground subsidence hazards and areas of relaxation zone that may occur during excavation work and due to underground water level changes. In order to carry out the field test, a real-scale excavation test bed was constructed and the geophysical exploration methods, such as electrical resistivity survey and multi-channel analysis of surface wave (MASW) survey for urban sites condition, have researched for optimal geophysical exploration parameter, design and correlation analysis between the results by reviewing the validity of each individual geophysical exploration and modeling. The results of this study showed the impact of each geophysical exploration on the relaxation zone and, in particular, the location of the underground water surface and the effects of excavation were identified using electrical resistivity survey. Further research on modeling will be required, taking into account the effects of excavation and groundwater.