• Korean Journal of Remote Sensing
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• v.38 no.4
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• pp.411-419
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• 2022

DPR Korea has been creating cropland across the country due to its chronic food shortage. Cropland was about 17.4% at the end of the 1980s, but it increased steadily to 19.6% at the end of the 1990s, 24.8% at the end of the first decade of 2000s, and 25.4% at the end of the 2010s. On the other hand, the forest land declined from about 74.8% in the late 1980s to 69.5% in the late 2010s. Urbanization is also progressing, increasing from about 1.15% at the end of the 1980s to 1.68% at the end of the 2010s. Most of the deforestation that occurred in DPR Korea was caused by conversion to cropland. These characteristics of land cover changes in DPR Korea provide useful information and implications for international and inter-Korean cooperation for DPR Korea.

• Electronics and Telecommunications Trends
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• v.39 no.1
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• pp.14-24
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• 2024

The O-RAN Alliance is responsible for defining the technical and testing specifications of open radio access networks, aiming for openness, virtualization, and intelligence in these networks. Recently, the application of Korea Open Testing and Integration Center (OTIC) to this alliance has been approved, enabling the issuance of O-RAN certificates and badges. An OTIC plays a crucial role as a testing facility in performing conformance verification and interoperability tests for O-RAN functions and interfaces. In addition, it enables end-to-end system verification adhering to O-RAN principles and processes. These activities can substantially contribute to enhancing the competitiveness of domestic O-RAN products and activating the corresponding ecosystem. We comprehensively describe the O-RAN certification and badging processes. Additionally, we analyze end-to-end test cases that are essential for the proper deployment and operation of 5G systems including O-RANs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.2
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• pp.974-987
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• 2018

This paper presents a novel and efficient data transmission scheme based on mobile edge computing for the massive IoT environments which should support various type of services and devices. Based on an accurate and precise synchronization process, it maximizes data transmission throughput, and consistently maintains a flow's latency. To this end, the proposed efficient software defined data transmission scheme (ESD-DTS) configures and utilizes synchronization zones in accordance with the 4 usage cases, which are end node-to-end node (EN-EN), end node-to-cloud network (EN-CN), end node-to-Internet node (EN-IN), and edge node-to-core node (EdN-CN); and it transmit the data by the required service attributes, which are divided into 3 groups (low-end group, medium-end group, and high-end group). In addition, the ESD-DTS provides a specific data transmission method, which is operated by a buffer threshold value, for the low-end group, and it effectively accommodates massive IT devices. By doing this, the proposed scheme not only supports a high, medium, and low quality of service, but also is complied with various 5G usage scenarios. The essential difference between the previous and the proposed scheme is that the existing schemes are used to handle each packet only to provide high quality and bandwidth, whereas the proposed scheme introduces synchronization zones for various type of services to manage the efficiency of each service flow. Performance evaluations show that the proposed scheme outperforms the previous schemes in terms of throughput, control message overhead, and latency. Therefore, the proposed ESD-DTS is very suitable for upcoming 5G networks in a variety of massive IoT environments with supporting mobile edge computing (MEC).

• Journal of KIISE:Information Networking
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• v.31 no.6
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• pp.608-619
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• 2004

Application layer multicast(ALM) has been developed as an alternative to support the multi-receiver applications due to the slow deployment of IP multicast. Unlike routers in IP multicast, end systems participating in a ALM session are not optimized for relaying data and have various processing and network capacity. Therefore, with the increased role of end systems, the delay incurred at the end systems occupy large portion of the end-to-end delay. In this paper, we model the end system delay of ALM sessions and analyze its impact on the performance of the existing ALM schemes. Furthermore, we propose an enhanced scheme, based on the existing mesh-based scheme, which reflects the end system delay We also evaluate the performance of the proposed scheme by simulation and show that it reduces the end-to-end delay compared with the existing scheme.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.115-120
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• 2018

This study examined the cast quality of small-sized induction motor rotors during the die casting process. Numerical analyses with 3-dimensional half models were performed to investigate the filling patterns of aluminum molten metals into a mold after high-speed injections. The following were obtained from numerical analyses and experimental results. First, molten metals started to fill the lower end ring, then moved horizontally to fill the core slot and upper end ring, and finally stopped to fill the rotor core slot. Second, circulation of molten metals occurred at the lower end ring, resulting considerable porosity at the section of lower end ring from the experimental results. Third, further work for obtaining sound quality of rotor core cast is required to develop a new shape of the rotor core cast or improve the die casting conditions.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1423-1450
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• 2015

The paper presents the details and results of an experimental study on bolted end-plate joints of industrial type steel building frames. The investigated joints are commonly used in Lindab-Astron industrial buildings and are optimized for manufacturing, erection and durability. The aim of the research was to provide an experimental background for the design model development by studying load-bearing capacity of joints, bolt force distribution, and end-plate deformations. Because of the special joint details, (i.e., joints with four bolts in one bolt-row and HammerHead arrangements), the Eurocode 3 standardized component model had to be improved and extended. The experimental programme included six different end-plate and bolt arrangements and covered sixteen specimens. The steel grade of test specimens was S355, the bolt diameter M20, whereas the bolt grade was 8.8 and 10.9 for the two series. The end-plate thickness varied between 12 mm and 24 mm. The specimens were investigated under pure bending conditions using a four-point-bending test arrangement. In all tests the typical displacements and the bolt force distribution were measured. The end-plate plastic deformations were measured after the tests by an automatic measuring device. The measured data were presented and evaluated by the moment-bolt-row force and moment-distance from centre of compression diagrams and by the deformed end-plate surfaces. From the results the typical failure modes and the joint behaviour were specified and presented. Furthermore the influence of the end-plate thickness and the pretension of the bolts on the behaviour of bolted joints were analysed.

• Journal of Ocean Engineering and Technology
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• v.24 no.1
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• pp.166-171
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• 2010

In this paper, the front-end of a digital receiver with a 25 kHz carrier frequency, 5 kHz symbol rate, and any excess-bandwidth is designed using two basic facts. The first is known as the uniform sampling theorem, which states that the sampled sequence might not suffer from aliasing even if its sampling rate is lower than the Nyquist sampling rate if the analog signal is a bandpass one. The other fact is that if the sampling rate is 4 times the center frequency of the sampled sequence, the front-end processing complexity can be dramatically reduced due to the half of the sampled sequence to be multiplied by zero in the demixing process. Furthermore, the designed front-end is simplified by introducing sub-filters and sub-sampling sequences. The designed front-end is composed of an A/D converter, which takes samples of a bandpass filtered signal at a 20 kHz rate; a serial-to-parallel converter, which converts a sampled bandpass sequence to 4 parallel sub-sample sequences; 4 sub-filter blocks, which act as a frequency shifter and lowpass filter for a complex sequence; 4 synchronized switches; and 2 adders. The designed front-end dramatically reduces the computational complexity by more than 50% for frequency shifting and lowpass filtering operations since a conventional front-end requires a frequency shifting and two lowpass filtering operations to get one lowpass complex sample, while the proposed front-end requires only four filtering operation to get four lowpass complex samples, which is equivalent to one filtering operation for one sample.

• Journal of the Korean Society of Costume
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• v.50 no.2
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• pp.167-182
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• 2000

The purpose of this study is to examine the art nouveau fashion represented in the end of the twentieth century. The characteristics of art nouveau are naturalism, medievalism , exoticism, and decadentism. The influences of art nouveau were seen in the fashion of the late nineteenth century : S-curve silhouette and organic curve motives printed on hems. Art nouveau has reappeared in modern fashion trends such as romanticism , decadence, ecology, ethno, and fusion. To sum up, art nouveau fashion at the end of the twentieth century is classified into four shapes. First, art nouveau appears in naturalism. Influenced by the arts and crafts movements and naturalistic trend, it has reappeared at the end of the twentieth century in themes like 'art & craft'. This expression technique is to objectively nature and to represented art nouveau textiles. Second, S-curve silhouette appeared at the end of nineteenth century's fashion with the art nouveau influenced rejection of the bustle style. At the end of the twentieth century, the design , emphasizing the hip, is represented in fashion collections as a phenomenon of romanticism . Especially the art nouveau silhouette of the end of the twentieth century does not represent S-curve silhouette. But , it emphasizes the hip only. Third, Art nouveau exoticism by symbolism is influenced by Chinese and Celtic art, the Middle Ages, and the exoticism that appeared in fashion at the end of the nineteenth century : harem style, kimono style, and turbans. Exoticism at the end of the twentieth century is expressed by optical flower prints and successive floral print arrangements as seen in the themes of ethno and fusion. Fourth, one of the characteristics of art nouveau, decadence is influenced by the pre-raphaelite brotherhood. This is expressed in the images of vampires, and symbolism expressing grotesque insect motives and decadent successive curves. At the end of the twentieth century decadence is represented in fashion ; grotesque insect motives, tatto looks of organic curve motives celtic hair style, see-through fashion, grotesque make-up . Besides hair style techniques, decadent expressions applying art nouveau paintings also appeared. Finally , art nouveau fashion represented as a fashion trend at the turning point to the new millennium is one of great significance as an organic, an environment-intimate and continuance-possible design in a future.

• Journal of Advanced Navigation Technology
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• v.12 no.6
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• pp.604-610
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• 2008

A 2.4 GHz CMOS RF front-end using for ZigBee application is described The front-end consists of a low noise amplifier and a down-mixer and uses a 2 MHz IF frequency. A common source with resistive feedback and an inductive degeneration are adopted for a low noise amplifier, and a 20 dB gain control step is digitally controlled. A passive mixer for low current consumption is employed. The RF front-end is implemented in 0.18 ${\mu}m$IP6M CMOS process. The measured performance is 4.44 dB NF and -6.5 dBm IIP3 while consuming 3.28 mA current from a 1.8 V supply.

• Journal of Biosystems Engineering
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• v.41 no.3
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• pp.153-160
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• 2016

Purpose: This study was conducted to experimentally investigate the structural safety of and identify critical locations in a front-end loader under impact loads. Methods: Impact and static tests were conducted on a commonly used front-end loader mounted on a tractor. In the impact test, the bucket of the front-end loader with maximum live load was raised to its maximum lift height and was allowed to free fall to a height of 500 mm above the ground where it was stopped abruptly. For the static test, the bucket with maximum live load was raised and held at the maximum lift height, median height, and a height of 500 mm from the ground. Strain gages were attached at twenty-three main locations on the front-end loader, and the maximum stresses and strains were measured during respective impact and static tests. Results: Stresses and strains at the same location on the loader were higher in the impact test than in the static test, for most of measurement locations. This indicated that the front-end loader was put under a severe environment during impact loading. The safety factors for stresses were higher than 1.0 at all locations during impact and static tests. Conclusions: Since the lowest safety factor was higher than 1.0, the front-end loader was considered as structurally safe under impact loads. However, caution must be exercised at the locations having relatively low safety factors because failure may occur at these locations under high impact loads. These important design locations were identified to be the bucket link elements and the connection elements between the tractor frame and front-end loader. A robust design is required for these elements because of their high failure probability caused by excessive impact stress.