• Journal of Intelligence and Information Systems
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• v.24 no.3
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• pp.45-66
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• 2018

Crowdfunding has become more popular than angel funding for fundraising by venture companies. Identification of success factors may be useful for fundraisers and investors to make decisions related to crowdfunding projects and predict a priori whether they will be successful or not. Recent studies have suggested several numeric factors, such as project goals and the number of associated SNS, studying how these affect the success of crowdfunding campaigns. However, prediction of the success of crowdfunding campaigns via non-numeric and unstructured data is not yet possible, especially through analysis of structural characteristics of documents introducing projects in need of funding. Analysis of these documents is promising because they are open and inexpensive to obtain. We propose a novel method to predict the success of a crowdfunding project based on the introductory text. To test the performance of the proposed method, in our study, texts related to 1,980 actual crowdfunding projects were collected and empirically analyzed. From the text data set, the following details about the projects were collected: category, number of replies, funding goal, fundraising method, reward, number of SNS followers, number of images and videos, and miscellaneous numeric data. These factors were identified as significant input features to be used in classification algorithms. The results suggest that the proposed method outperforms other recently proposed, non-text-based methods in terms of accuracy, F-score, and elapsed time.

• Tunnel and Underground Space
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• v.24 no.2
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• pp.155-165
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• 2014

Multiple thermal energy storage (TES) caverns can be used for storing thermal energy on a large scale and for a high-aspect-ratio heat storage design to provide good thermal performance. It may also be necessary to consider the use of multiple caverns with a reduced length when a single, long tunnel-shaped cavern is not suitable for connection to aboveground heat production and injection equipments. When using multiple TES caverns, the separation distance between the caverns is one of the significant factors that should be considered in the design of storage space, and the optimal separation distance should be determined based on a quantitative stability criterion. In this paper, we described a numerical approach for determining the optimal separation distance between multiple caverns for large-scale TES utilization. For reliable stability evaluation of multiple caverns, we employed a probabilistic method which can quantitatively take into account the uncertainty of input parameters by probability distributions, unlike conventional deterministic approaches. The present approach was applied to the design of a conceptual TES model to store hot water for district heating. The probabilistic stability results of this application demonstrated that the approach in our work can be effectively used as a decision-making tool to determine the optimal separation distance between multiple caverns. In addition, the probabilistic results were compared to those obtained through a deterministic analysis, and the comparison results suggested that care should taken in selecting the acceptable level of stability when using deterministic approaches.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.3
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• pp.269-282
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• 2008

In general, the effects of steel ribs are not considered in the numerical analysis of tunnel design. However, attempts have been increased recently to consider these effects in the analysis of shallow tunnels in soft ground, based on the fact that the steel ribs embedded in the shotcrete take a role to support some portion of the redistributed load due to excavation. In such analyses, the steel ribs can be considered in four different methods: (1) a conventional method where the steel ribs are not considered, (2) a method using the equivalent composite cross section in which the bending moment of shotcrete is not considered, (3) a method using the equivalent composite cross section in which both the compressive stress and the bending moment for the shotcrete and steel rib are considered, and (4) a method using beam elements for the shotcrete and the steel rib, respectively. These methods are adopted in the numerical analysis using FLAC 2D to investigate stresses of both the shotcrete and the steel rib. The overall results show that the analyses are more practical and economical when the effects of steel rib are considered fer the methods (2), (3), and (4). Since the results of those analyses considering steel rib capacity may be different according to the ground condition, it will be necessary to consider the appropriate method among them in accordance with design conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2B
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• pp.113-121
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• 2012

When a heavy rain brings flooding, a high turbid water is flowing into a reservoir. In this study, the effectiveness of the intake structures for the selective withdrawal from the various levels of a stratified reservoir was evaluated by the field experiments and the numerical modeling of the three-dimensional approaching flows. The temperature, the turbidity, and the velocity fields for the selective withdrawal were measured using both YSI6600EDS and YSI6600ADV, respectively. A threedimensional model, FLOW-3D, was used to predict the performance of the intake tower in Imha reservoir. The comparisons of the vertical velocity field showed a good agreement with the field measurements. The efficiency of the turbid-water elimination of the selective withdrawal method from low levels was higher up to 46% than that of the surface withdrawal. From the analysis of the numerical simulation, the efficiency of turbidity elimination increased by 10% for the selective withdrawal from middle levels, and by 30% from low levels. These results showed that the selective withdrawals from middle and low levels are more effective than the surface-water intake. The similar results were obtained by the one-dimensional model, SELECT, which is much more computationally time-efficient.

• Spatial Information Research
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• v.15 no.4
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• pp.363-370
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• 2007

This study has been carried for the development of the basic algorithm of helicopter navigation system based on TRN (Terrain Referenced Navigation) with information input from the GPS. The helicopter determines flight path due to Origination-Destination analysis on the Cartesian coordinate system of 3-D DTM. This system shows 3-D mesh map and the O-D flight path profile for the pilot's acknowledgement of the terrain, at first. The system builds TCF (terrain clearance floor) far the buffer zone upon the surface of ground relief to avid the ground collision. If the helicopter enters to the buffer zone during navigation, the real-time warning message which commands to raise the body pops up using Matlab menu. While departing or landing, control of the height of the body is possible. At present, the information (x, y, z coordinates) from the GPS is assumed to be input into the system every 92.8 m of horizontal distance while navigating along flight path. DTM of 3" interval has been adopted from that which was provided by ChumSungDae Co., Ltd..

• Journal of Engineering Education Research
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• v.3 no.1
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• pp.12-20
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• 2000

In this paper, we are trying to explain an education method using the studio class where a lecturer can teach the theoretical approach for goals of theme, simulation for the theoretical results by using commercial CAD tools, and experiments for the simulation and design results. In order to apply the education skill using studio class to electrical engineering field efficiently, the theoretical approach, simulation procedure, and experiments should be coincided with each other. In this paper, the design procedure of low pass filter for undergraduate and graduate is chosen as an example of studio class In order to show the validity of the proposed education method. By considering the example, the efficiency of the method will be discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.1
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• pp.87-94
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• 1986

Under natural condition, many rivers had shallow and gently curved shape in plane. A two dimensional mathematical model of the flow was a very attractive one. The flow characteristics in bended open channels were analyzed. The mathematical model based on the mass and the momentum equation of the two-dimensional unsteady flow was developed by introducing finite difference method and the double sweep algorithm. For the purpose of the verification of this model, the modeling results were applied to the L.F.M flume and the I.I.H.R flume. The results had a good agreement with the experimental data of the flumes. The results could be more close to the experimental data by controlling Chezy Coefficients in order to reduce the effect of friction around side wall, and be studied the importance of the convective term. The water surface profile, the direction and scale of depth average mean velocity and the path of the thread of maximum velocity in bended open channels could be computed.

• Tunnel and Underground Space
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• v.27 no.5
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• pp.303-311
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• 2017

The correlation analysis between the results obtained from DFN flow model and equivalent continuum flow model were conducted on total of 72 DFN blocks having various fracture geometry and domain size. A strong linear relation seems to exist between the two approaches under condition that normalized relative error for continuum behavior (ER) is less than 0.2, and the results from both methods are found to almost identical. To explore the field applicability of equivalent continuum flow model in DFN media, a total of 48 numerical schemes related to inflow of underground circular openings were implemented under various DFN configurations. The equivalent continuum flow model in DFN media with a constant hydraulic aperture was evaluated as valid. However, as the anisotropy increases due to variation of the hydraulic aperture, the results are likely to be overestimated compare to the DFN flow model.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.209-209
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• 1999

현재 magnetron sputter는 반도체, LCD 등을 포함하는 microelectronics 산업에서 박막형성을 위한 주요 장비로 널리 쓰이고 있으며, 소자의 고집적화 및 대형화 추세에 따라 그 이용가치는 더욱 증대되고 있다. 본 연구엣는 TFT-LCD용 Color Filter 제조시 ITO박막형성을 위해 사용하는 magnetron sputter 내부의 플라즈마 분포 및 ion kinetic energy에 대한 해석을 실시하였으며, ITO target의 erosion 형상의 원인을 실험결과와 비교하였다. Magnetron sputtering은 target에 가해지는 bias 전압(DC 혹은 RF)에 의해 target과 shield 혹은 target과 substrate 사이에서 생성될 수 잇는 플라즈마를 target 및 부분에 붙어있는 영구자석을 이용하여 target 근처에 집중시키고, target 표면과 플라즈마 사이의 전위차에 의해 가속된 이온들이 target 표면과 충돌하여 이차 전자방출을 일으킴과 동시에 target 표면에서 sputtering을 일으키고, 이들 sputtered 된 중성의 atom 들이 substrate로 날아가 박막을 형성하는 원리로 작동된다. 이때 target에서 방출되는 이차전자들은 영구자석에 의한 자기장 효과에 의해 target 근처에 갇히게 되어 중성 기체분자들과 이온화반응을 통해 플라즈마를 유지하고 그 밀도를 높혀주는 역할을 담당하게 된다. 즉 낮은 압력 및 bias 전압에서도 플라즈마 밀도를 높일수 있고 sputtering 공정이 가능한 장점을 가지고 있다. Magnetron sputtering 현상에 대한 시뮬레이션은 크게 magnetron discharge와 sputtering에 대한 해석 두가지로 나누어 볼 수 있는데, sputtering 현상 자체를 수치묘사할 수 있는 정량적인 모델은 아직까지 명확하게 정립되어 있지 않다. 따라서 본 연구에서는 magnetron plasma 자체에 대한 수치해석에 주안점을 두고 아울러 bulk plasma 영역에서 target으로 입사하는 이온들의 입사에너지 및 입사각도 등을 Monte Carlo 방법으로 추적하여 sputtering 현상을 유추해보았다. Sputtering 현상을 살펴보기 위해 magnetron sputter 내 플라즈마 밀도, 전자온도, 특히 target 및 substrate를 충돌하는 이온의 입사에너지 및 입사각 분포등을 계산하는데 hybrid 방법으로 시뮬레이션을 하였다. 즉 ion과 bulk electron에 대해서는 fluid 방식으로 접근하고, 이차전자 운동과 그로 인한 반응관계 및 target으로 입사하는 이온의 에너지와 입사각 분포는 Monte-Carlo 방법으로 처리하였다. 정지기장해석의 경우 상용 S/W인 Vector Fields를 사용하였다. 이를 통해 sputter 내 플라즈마 특성, target으로 입사하는 이온에너지 및 각 분포, 이들이 target erosion 형상에 미치는 영향을 살펴보았다. 또한 이들 결과로부터 간단한 sputtering 모델을 사용하여 target으로부터 sputter된 입자들이 substrate에 부착되는 현상을 Monte-Carlo 방법으로 추적하여 성막특성도 살펴보았다.

• Journal of Korean Society of Forest Science
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• v.97 no.4
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• pp.445-451
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• 2008

This study was carried out to develop Tablet PC based customizing system for fine mapping of forest cover type. The major contents and characteristics of FIS developed in this study were as follows. Field Investigation System (FIS) has a merit of accessibility to display exact location in various spatial data with position information received from the GPS. FIS can be used to record and manage many field information on which field investigation is done, with the help of the memo tool, field-sheet tool, calculating distance and area with measuring tool as well as editing forest type. It is possible to do field investigation effectively using FIS developed in this study. Accordingly, investigation and time costs can be reduced and field-work productivity will be improved.