• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.15 no.5
• /
• pp.12-19
• /
• 2016

An average of 20 million individual transit unit activities per day on the Seoul-Gyeonggi-Incheon public transportation network are provided as transportation card analysis data by the metropolitan district (99.02% by 2014 standard, Humanlive, 2015.4). The metropolitan transportation card data can be employed in a comprehensive analysis of public transportation users' current transit patterns and by means of this, an effective use plan can be explored. In enhancing the existing information on the bus and rail integrated network of the metropolis with public transportation card data, the constraints in the existing methodology of metropolitan transit analysis, which functions on a zone unit origin and destination basis, can be overcome. Framework for metropolitan public transportation card data based integrated public transportation analysis, which consists of bus and rail integrated transport modes, is constructed, and through this, a single passenger's transit behavior transit volume can be approximated. This research proposes that in the use of metropolitan public transportation card data, integrated public transportation usage, as a part of individual passenger spatial movements, can be analyzed. Furthermore, metropolitan public transportation card usage data can provide insights into understanding not only movements of populations taking on transit activities, but also, characteristics of metropolitan local space.

• Management & Information Systems Review
• /
• v.37 no.2
• /
• pp.87-108
• /
• 2018

This article explores the international trade flow of Bangladesh's ready-made garments (RMG). We first suggest the brief history and an international structure of trade among countries by using the trade volume. Then we implemented a gravity model regression with the sample of 38 major partner countries in order to investigate the potential export market for the RMG industry. The fixed effect and random effect model for the panel data during the period of 1990 to 2011 are estimated. Our result shows that Bangladesh's RMG exports are affected positively by the size of economy, inflation, exchange rate, foreign direct investment(FDI) and trade openness. On the other hand, the distance between trading partners are related negatively with the trade volume. We used the estimated coefficients from the panel regression in order to predict RMG export potential of Bangladesh. This might show which country is the promising export market for Bangladesh RMG industry. We found that Bangladesh has the highest potential of RMG export with Japan and USA, which seem to have considerable room for export growth if trade barriers and constraints are removed. We added some policy implications for encouraging the RMG export of Bangladesh by using the results from the analysis.

• Journal of the Geological Society of Korea
• /
• v.54 no.6
• /
• pp.641-656
• /
• 2018

Although an amount of hydrocarbon has been discovered in the West Korea Bay Basin (WKBB), located in the North Korean offshore area, geophysical investigations associated with these hydrocarbon reservoirs are not permitted because of the current geopolitical situation. Interpretation of satellite derived potential field data can be alternatively used to image three-dimensional (3D) density distribution in the sedimentary basin associated with hydrocarbon deposits. We interpreted the TRIDENT satellite-derived gravity field data to provide detailed insights into the spatial distribution of sedimentary density structures in the WKBB. We used 3D forward density modeling for the interpretation that incorporated constraints from existing geological and geophysical information. The gravity data interpretation and 3D forward modeling showed that there are two modeled areas in the central subbasin that are characterized by very low density structures, with a maximum density of about $2,000kg/m^3$, indicating some type of hydrocarbon reservoir. One of the anticipated hydrocarbon reservoirs is located in the southern part of the central subbasin with a volume of about $250km^3$ at a depth of about 3,000 m in the Cretaceous/Jurassic layer. The other hydrocarbon reservoir should exist in the northern part of the central subbasin, with an average volume of about $300km^3$ at a depth of about 2,500 m. A comparison between the TRIDENT derived gravity field and the ship-based gravity field measured in 1980s shows us that our results are highly reliable and there is a very high probability to detect another low-density layer existings in the northwestern part of the central subbasin.

• Explosives and Blasting
• /
• v.30 no.2
• /
• pp.52-58
• /
• 2012

A TBM launching shaft in DTL2 Contract 915 site is located in a typical hard Bukit Timah granite formation and lots of blasting work is required for shaft sinking. The original blast design used the electric detonator and ANFO blasts consisting of 30 holes per one blast with 1.5 m depth of drilling hole. However, significant delay of work and poor progress were expected due to the limitation of the number of blasting hole and strict vibration regulation on retaining systems. To overcome such constraints, an efficient new blasting method which can improve productivity and satisfy vibration limit was required. The revised blast design, using triple-deck blasts with electronic detonators and cartridge emulsion explosives, gives better construction performance and can reduce construction time. Such a new blasting technique can be effectively used for similar underground projects in the future where the volume of rock blasting is significant.

• Journal of Astronomy and Space Sciences
• /
• v.31 no.1
• /
• pp.67-72
• /
• 2014

The next generation small satellite-1 (NEXTSat-1) program has been kicked off in 2012, and it will be launched in 2016 for the science missions and the verification of space core technologies. The payloads for these science missions are the Instrument for the Study of Space Storms (ISSS) and NIR Imaging Spectrometer for Star formation history (NISS). The ISSS and the NISS have been developed by Korea Advanced Institute of Science and Technology (KAIST) and Korea Astronomy and Space science Institute (KASI) respectively. The ISSS detects plasma densities and particle fluxes of 10 MeV energy range near the Earth and the NISS uses spectrometer. In order to verify the spacecraft core technologies in the space, the total of 7 space core technologies (SCT) will be applied to the NEXTSat-1 for space verification and those are under development. Thus, the operation modes for the ISSS and the NISS for space science missions and 7 SCTs for technology missions are analyzed for the required operation time during the NEXTSat-1's mission life time of 2 years. In this paper, the operational concept of the NEXTSat-1's science missions as well as the verification of space core technologies are presented considering constraints of volume, mass, and power after launch.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.10
• /
• pp.5149-5167
• /
• 2017

Reducing energy consumption in a wireless video sensor network (WVSN) is a crucial problem because of the high video data volume and severe energy constraints of battery-powered WVSN nodes. In this paper, we present an adaptive dynamic resizing approach for a SRAM communication buffer in a WVSN node in order to reduce the energy consumption and thereby, to maximize the lifetime of the WVSN nodes. To reduce the power consumption of the communication part, which is typically the most energy-consuming component in the WVSN nodes, the radio needs to remain turned off during the data buffer-filling period as well as idle period. As the radio ON/OFF transition incurs extra energy consumption, we need to reduce the ON/OFF transition frequency, which requires a large-sized buffer. However, a large-sized SRAM buffer results in more energy consumption because SRAM power consumption is proportional to the memory size. We can dynamically adjust any active buffer memory size by utilizing a power-gating technique to reflect the optimal control on the buffer size. This paper aims at finding the optimal buffer size, based on the trade-off between the respective energy consumption ratios of the communication buffer and the radio part, respectively. We derive a formula showing the relationship between control variables, including active buffer size and total energy consumption, to mathematically determine the optimal buffer size for any given conditions to minimize total energy consumption. Simulation results show that the overall energy reduction, using our approach, is up to 40.48% (26.96% on average) compared to the conventional wireless communication scheme. In addition, the lifetime of the WVSN node has been extended by 22.17% on average, compared to the existing approaches.

• International Journal of Precision Engineering and Manufacturing
• /
• v.2 no.2
• /
• pp.65-72
• /
• 2001

The design of multi-stage gear drives is a time-consuming process, since on includes more complicated problems, which are not considered in the design of single-stage gear drives. The designer has th determine the number of reduction stages and the gear ratios of each reduction state. In addition, the design problems include not only the dimensional design but also the configuration design of gear drive elements. There is no definite rule and principle for these types of design problems. Thus the design practices largely depend on the sense and the experiences of the designer , and consequently result in undesirable design solution. We propose a new generalized design algorithm to support the designer at the preliminary design phase of multi-stage gear drives. The proposed design algorithm automates the design process by integrating the dimensional design and the configuration design process. The algorithm consists of four steps. In the first step, a designer determines the number of reduction stage. In the second step. gear ratios se chosen by using the random search method. In the third step, the values of basic design parameter are chosen by using the generate and test method. Then, the values of other dimension, such ad pitch diameter, outer diameter, and face width, are calculated for the configuration design in the final step. The strength and durability of a gear is guaranteed by the bending strength and the pitting resistance rating practices by using the AGMA rating formulas. In the final step, the configuration design is carried out b using the simulated annealing algorithm. The positions of gears and shafts are determined to minimize the geometrical volume(size) of a gearbox, while satisfying spatial constraints between them. These steps are carried out iteratively until a desirable solution is acquired. The propose design algorithm has been applied to the preliminary design of four-stage gear drives in order to validate the availability. The design solution have shown considerably good results in both aspects of the dimensional and the configuration design.

• Radiation Oncology Journal
• /
• v.20 no.1
• /
• pp.68-72
• /
• 2002

This study was done to implement intensity-modulated radiation therapy (IMRT) for the treatment of primary prostate cancer and to compare this technique with conventional treatment methods. A 72-year-old male patient with prostate cancer stage T2a was treated with IMRT delivered with dynamic multi-leaf collimation. Treatment was designed using an inverse planning algorithm, which accepts dose and dose-volume constraints for targets and normal structures. The IMRT plan was compared with a three-dimensional (3D) plan using the same 6 fields technique. Lower normal tissue doses and improved target coverage were achieved using IMRT at current dose levels, and facilitate dose escalation to further enhance locoregional control and organ movement during radiotherapy is an important issue of IMRT in prostate cancer.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.23 no.5
• /
• pp.501-507
• /
• 2010

Structural optimization is performed to minimize the weight of a RC building structure, which has eight floors above ground and three underground, under gravity, wind, and seismic loads. Design optimization problem is formulated to find the values of the design variables that minimize the volume while satisfying various design and side constraints. To solved the optimization problem posed, several design techniques equipped in PIAnO, a commercial PIDO tool, are used. DOE is used to generate training points and structural analysis is performed using MIADS Gen, a general-purpose structural analysis CAE tool. Then, meta-models are generated from structural analysis results and accuracies of meta-models are evaluated. Next, design optimization is performed by using the verified meta-models and optimization technique equipped in PIAnO. Finally, we obtained optimal results, which could demonstrate the effectiveness of our design method.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.3
• /
• pp.309-314
• /
• 2014

The structural layout of mechanical and civil structures is commonly obtained using conventional methods. For example, the shape of structures such as electric transmission towers and offshore substructures can be generated systematically. However, with rapid advancements in computer graphic technology, advanced structural analyses and optimum design technologies have been implemented. In this study, the structural shape of a jacket substructure for an offshore wind turbine is investigated using a topology optimization technique. The structure is subjected to multiple loads that are intended to simulate the loading conditions during actual operation. The optimization objective function is defined as one that ensures compliance of the structure under the given boundary conditions. Optimization is carried out with constraints on the natural frequency in addition to the volume constraint. The result of a first step model provides quick insights into the optimum layout for the second step structure. Subsequently, a 3D model in the form of the frustum of a quadrilateral pyramid is developed through topology optimization.