• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.4
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• pp.285-295
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• 2001

This study describes the analysis on the dynamic characteristics of model as a fundamental studies for the horn fish Hemiramphus sajor surface pair trawl gear. The model experiments were carried out in a flume tank by using model net for the horn fish surface par trawl gear. The model net was made to the scale of 1/40 by scaling down two surfce par trawl boats of 6.67 and 9.98 ton used for sea experiment in the coast of Jeju Island. Dimensions of the model net were 1.2m for stretch length of net, 1.3m for float line, 1.0m for sinker line, 2.5g for floats, and 0.86g for sinkers. Experiments were conducted in the observation channel of a flume tank with experimental equipments used to change the distance between paired boats and towing velocity. Motion of model net during towing was recorded by two sets of digital camera which were placed in the top and side of the model net. The leading coordinate of net height and net mouth width was captured by the photograph analysis system. Through the experiment, we obtained the following results: 1. The relationship between the net hight(Nh) and towing velocity(Vt) during towing was found to be Nh=(2.39Db-$^{0.62})Vt^{0.56}$ and the relationship between the net mouth width (Nw) and towing velocity during towing was Nw=(0.96Db^{0.62})Vt^{0.11}$, where Db is the distance between paired boats. 2. The relationship between the net tension(Nt) and towing velocity during towing was found to be Nt=106.94Vt+1.43 and the model net becomes parallel to the water surface at the towing velocity larger than 1.5 Knot. 3. The relationship between the net opening area(Na) and towing velocity during towing was found to be Na=(2.28Db0.37)Vt.-0.45, and the relationship between the filtering volume(Fv) and towing velocity during towing was Fv=(69.9Db$^{0.37})Vt^{0.55}$. The net opening area and filtering volume reach maximum value at the distance of 25m between paired boats.

• Journal of the Korean Society for Railway
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• v.7 no.1
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• pp.20-25
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• 2004

Railroad geotechnical information management system was developed by using Web GIS and DB in this study. The standardization of railroad geotechnical information is progressed by classifying three groups as like basic informations, vibration informations along railway lines and design drawings. The basic informations consisted of basic and dynamic properties of soils, geophysical exploration and seismic survey/exploration. And the specification for 'human exposure to whole-body vibration' was adopted to construct the vibration informations along railway lines. The informations as like drawings and photographs were saved by changing to graphic files in the standardization of design drawings. In the case of standardization of geographical information, the topographical maps(NGIS, 1:5000) were primarily used as digital maps. Another digital maps(KRRI, 1:5000) and their geographical DB based on NGI code system were added on this maps. The standardized informations were used to construct their database. And railroad information management system was developed using Entity-Relation(ER) model which had a good feasibility for expansion and transition to other system in designing stage of database. This system consisted of layer selection, search and analysis of geotechnical informations and Zeus DB was adopted for GIS operating and user interface. This system could be a good tool for saving, searching and analyzing the geotechnical and geophysical informations. These DB systems would offered the basic informations to plans, design and construction of railroad lines etc. in practical use.

• International Journal of Computer Science & Network Security
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• v.22 no.12
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• pp.107-115
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• 2022

Recently, big data applications need another database different from the Relation database. NoSQL databases are used to save and handle massive amounts of data. NoSQL databases have many advantages over traditional databases like flexibility, efficiently processing data, scalability, and dynamic schemas. Most of the current applications are based on the web, and the size of data is in increasing. NoSQL databases are expected to be used on a more and large scale in the future. However, NoSQL suffers from many security issues, and one of them is access control. Many recent applications need Fine-Grained Access control (FGAC). The integration of the NoSQL databases with FGAC will increase their usability in various fields. It will offer customized data protection levels and enhance security in NoSQL databases. There are different NoSQL database models, and a document-based database is one type of them. In this research, we choose the CouchDB NoSQL document database and develop an access control mechanism that works at a fain-grained level. The proposed mechanism uses role-based access control of CouchDB and restricts read access to work at the document level. The experiment shows that our mechanism effectively works at the document level in CouchDB with good execution time.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.8
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• pp.795-801
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• 2014

This paper presents an efficiency enhancement for the high power amplifier using DDBS(Digitally-controlled Dynamic Bias Switching) method which dynamically provides the power amplifier with two bias voltage levels according to the input envelope signal. It is quite easy to adjust the control signal by using a digital processing. The fabricated DDBS PA was evaluated using an 64 QAM FDD LTE signal, which has a center frequency of 2.6 GHz, a bandwidth of 10 MHz and a PAPR of 9.5 dB. The DDBS increases the power amplifier's PAE(Power-Added Efficiency) from 40.9 % to 48 %, at an average output power level of 43 dBm.

• Tunnel and Underground Space
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• v.9 no.2
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• pp.131-140
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• 1999

Although there have been lots of geological or geotechnical surveys for construction sites, most of data obtained from these surveys have not been reused properly for the future construction work due to the absence of systematic management of data management system. This research, therefore, has focused on the development of DB system, Rockmass Information Management System(RIMS), to save, manage and reuse these abandoned data, specially test data of rock and rockmass with site conditions. RIMS has not only the basic functions of inputting, modifying, and dynamic searching of data but also several data control modules which can manage, input and correct, analyse and report data. Furthermore it saves data such as strata status, laboratory test results, in-site test results, and so on using 3-dimensional data stacking up structure. It is using x, y coordinates to represent horizontal positions and depth to represent vertical position of data. With the development of RIMS, this research has analyzed and classified present conditions of data in RIMS according to region, rock type, etc.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1344-1348
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• 2008

HMS(Hydrological Modelling system)는 유역의 지형자료와 강우와 같은 기상관련 시계열 자료 등 수문 유출과 관련되는 많은 매개변수를 포함하고 있으며, 모형의 구동을 위해서는 다양한 공간 비공간 자료 및 시계열 자료가 요구된다. 특히 다양한 비공간 정보의 경우 이를 모형에 적용하기 위해서는 비공간 정보에 대한 열람, 선택, 편집, 적용 시나리오의 설정, 입력변수의 적절성 평가, 모형 구동결과의 검 보정 등 복잡한 절차가 필요하다. 최근 들어 공간자료의 효율적 처리를 위해서 지리정보시스템과 수리 수문모델들 간의 연계를 통한 자료 생성과 입력 및 분석과정을 일괄적으로 처리하고자 하는 연구들이 발표되고 있다. 본 연구에서는 한국형 수자원지리정보시스템인 HyGIS와 HMS 모형의 연계 시스템인 HyGIS-HMS의 개t선과 적용성 평가를 목표로 하고 있다. 이를 위하여 HyGIS-HMS 데이터 모델을 기반으로 하는 시스템의 운영 프로세스를 재정립하였다. HyGIS에서 구축된 공간 DB를 이용하여 HMS 모형의 입력 지형인자를 계산하고 있으며, 수문시계열 자료는 HyGIS의 시계열 DB를 이용하고 있다. HMS에서는 공간 자료와 시계열 자료 외에도 다양한 비공간 자료를 이용하고 있다. 이러한 비공간 정보를 DB기반 시스템에 맞추어 효과적으로 관리 및 사용하기 위하여 HyGIS-HMS에서는 Static DB를 이용하고 있으며, Static DB에서 모형의 입력자료로 직접 이용되는 자료와 모형의 수행결과는 Dynamic DB를 이용하고 있다. 또한 개발된 시스템을 경안천 유역에 적용하여 2006년과 2007년의 유출특성을 분석하였다. 이러한 개발환경의 적용을 통해 HyGIS 데이터모델과 HyGIS-Model의 운영환경이 HyGIS-HMS개발에 효과적으로 이용될 수 있는 것으로 나타났다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.701-702
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• 2011

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1A
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• pp.39-49
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• 2008

Dynamic responses of steel plate girder bridges considering road surface roughness of bridge and bridge-vehicle interaction are investigated by numerical analysis. Simply supported steel plate girder bridges with span length of 20 m, 30 m, and 40 m from "The Standardized Design of Highway Bridge Superstructure" published by the Korean Ministry of Construction are used for bridge model and the road surface roughness of bridge decks are generated from power spectral density(PSD) function for different road. Three different vehicles of 2- and 3-axle dump trucks, and 5-axle tractor-trailer(DB-24), are modeled three dimensionally. For the bridge superstructure, beam elements for the main girder, shell elements for concrete deck, and rigid links between main girder and concrete deck are used. Impact factor and DLA of steel plate girder bridges for different spans, type of vehicles and road surface roughnesses are calculated by the proposed numerical analysis model and compared with those specified by several bridge design codes.

• Journal of Broadcast Engineering
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• v.22 no.1
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• pp.42-50
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• 2017

A Bit-depth expansion is a method to increase the number of bit. It is getting important as the needs of HDR (High Dynamic Range) display or resolution of display have been increased because the level of luminance or expressiveness of color is proportional to the number of bit in the display. In this paper, we present effective bit-depth expansion algorithm for conventional standard 8 bit-depth content to display in high bit-depth device (10 bits). Proposed method shows better result comparing with recently developed methods in quantitative (PSNR) with low complexity. The proposed method shows 1db higher in PSNR measurement with 40 times faster in computational time.

• Journal of the Korean Institute of Gas
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• v.12 no.1
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• pp.7-12
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• 2008

In order to estimate the integrity and identify the dynamic characteristics of buried gas pipelines subjected to vehicle loads, FE analysis is performed based on the 'Highway and Local Road Design Criteria' and the 'KOGAS Guideline for Pipeline Management'. The FE model describes the current burial condition of Korea properly, and the DB-24 load model is adopted for this research. This study considers a varying velocity in the range of $40{\sim}160\;km/h$ and $P_i=8$ MPa(internal pressure) with depth cover, Z=1.5 m. Maximum stress occurs at v=80 km/h and decreases after v=80 km/h. The maximum induced stress by DB-24 loads is about 10 MPa. Under the design pressure, however, the analysis results show that API 5L Gr. X65 pipelines have sufficient integrity to withstand the vibration of vehicle loads.