• Title/Summary/Keyword: design procedure

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An Empircal Model of Effective Path Length for Rain Attenuation Prediction (강우감쇠 유효경로 길이 예측을 위한 경험 모델)

  • 이주환;최용석;박동철
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.11 no.5
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    • pp.813-821
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    • 2000
  • The engineering of satellite communication systems at frequencies above 10GHz requires a method for estimating rain-caused outage probabilities on the earth-satellite path. A procedure for predicting a rain attenuation distribution from a point rainfall rate distribution is, therefore, needed. In order to predict rain attenuation on the satellite link, several prediction models such as ITU-R, Global, SAM, DAH model, have been developed and used at a particular propagation condition, they may not be appropriate to a propagation condition in Korean territory. In this paper, a new rain attenuation prediction method appropriate to a propagation condition in Korea is introduced. Based on the results from ETRI measurements, a new method has been derived for an empirical approach with an identification on the horizontal correction factor as in current ITU-R method, and the vertical correction factor has been suggested with decreasing power law as a function of rainfall rate. This proposed model uses the entire rainfall rate distribution as input to the model, while the ITU-R and DAH model approaches only use a single 0.01% annual rainfall rate and assume that the attenuation at other probability levels can be determined from that single point distribution. This new model was compared with several world-wide prediction models. Based on the analysis, we can easily know the importance of the model choice to predict rain attenuation for a particular location in the radio communication system design.

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An Assessment of Technological Competitiveness in Core Products of Foreign Design & Construction markets (해외 유망 건설상품의 기술 경쟁력 평가)

  • Choi, Seok-In;Kim, Sang-Bum;Lee, Young-Whan;Kim, Woo-Young;Jang, Hyoun-Seung
    • Korean Journal of Construction Engineering and Management
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    • v.9 no.1
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    • pp.107-117
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    • 2008
  • In this study, surveys and interviews are used to evaluate technological competitiveness of each product with respect to that of foreign leading firms, for seven leading domestic construction products which have been determined to have competitive edge in offshore markets, Such evaluation provides a more in depth study than previously conducted research, and is meaningful in that corporate level, rather than industry level, perspective is projected. Major findings of such evaluations are the following. First, as expected, it has been evaluated that domestic technological competitiveness in desalination plant and power plant has reached the point where it can compete with foreign leading firms. Moreover, a noteworthy result of the evaluation is that development program sector, including urban development of satellite cities, has reached considerable level of competitiveness in offshore market. In the case of the development market, domestic firms have accumulated sufficient experience in domestic market and engineering technology is not a decisive factor as in plant sector, and these factors lead to such an evaluation. Second, in the cases of gas, oil refinery and petro-chemical plants, domestic products' technological competitiveness that can contest in offshore market is still centered around production and construction. On the other hand, there are still weaknesses in license technology and basic design capabilities, which constitute the "value added" area. Third, skyscrapers, a promising product in offshore construction market and a product group which domestic firms have much performance record and projects in progress both in domestic and offshore markets, are considered. While direct comparison between skyscrapers and plant sector is not feasible, with the exception of production and construction, overall domestic capability in this sector has been assessed to be the lowest amongst those products that were surveyed. Fourth, it has been indicated that competitiveness is relatively higher in common technology than in key technology. In project management capability, it has been assessed that there are weaknesses in procedure document area. Also, a characteristic is the point that low overall assessments have been given across all product groups for corporate and management areas, not technological areas. Especially, financing, contracting/claim, risk management and investment on research and development received low evaluations. Fifth, it has been assessed that overall corporate and governmental supports are weak. This result is especially evident for corporate management and support areas across all product groups surveyed.

Temperature Prediction of Cylinder Components in Medium-Speed Diesel Engine Using Conjugate Heat Transfer Analysis (복합 열전달 해석을 이용한 중속 디젤엔진 실린더 부품 온도 분포 예측)

  • Choi, Seong Wook;Yoon, Wook Hyoen;Park, Jong Il;Kang, Jeong Min;Park, Hyun Joong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.8
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    • pp.781-788
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    • 2013
  • Predicting the engine component temperature is a basic step to conduct structural safety evaluation in medium-speed diesel engine design. Recent trends such as increasing power density and performance necessitate more effective thermal management of the engine for achieving the desired durability and reliability. In addition, the local temperatures of several engine components must be maintained in the proper range to avoid problems such as low- or high-temperature corrosion. Therefore, it is very important to predict the temperature distribution of each engine part accurately in the design stage. In this study, the temperature of an engine component is calculated by using steady-state conjugate heat transfer analysis. A proper approach to determine the thermal load distribution on the thermal boundary area is suggested by using 1D engine system analysis, 3D transient CFD results, and previous experimental data from another developed engine model. A Hyundai HiMSEN engine having 250-mm bore size was chosen to validate the analysis procedure. The predicted results showed a reasonable agreement with experimental results.

Estimation of Coefficient of Earth Pressure At Rest During SCP Installation by Drained Triaxial Compression Test (배수삼축압축시험을 통한 SCP 시공과정 중 정지토압계수 평가)

  • Kwon, Youngcheul
    • Journal of the Korean GEO-environmental Society
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    • v.13 no.11
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    • pp.93-101
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    • 2012
  • SCP is a construction method that maximizes the effects of ground improvement by creating sand piles, which are formed by the compaction within soft ground. SCP is mainly used for consolidation and drain effects in clayey soils, and as a liquefaction countermeasure through effects such as compaction in loose sandy soils. In the design of SCP, if the sand piles with high stiffness are not taken into account, it can become a design that overly considered safety, and increased construction costs are highly likely to cause economic disadvantages. The changes in stress conditions and compaction mechanisms in the subsurface have been identified to a certain extent by study findings to date. However, the studies that considered SCP and in-situ ground as composite ground are fairly limited, and therefore, those studies have not achieved enough results to fully explain the relevant topics. In this study, the ground improved by SCP was regarded as the composite ground that consists of SCP and in-situ ground. Moreover, employing a CID test, this study examined the changes in the stress conditions of in-situ ground according to the installation of SCP through the relations between $K_0$ and SCP replacement ratio. At the same, whether the SCP installation procedure can be recreated in a laboratory was examined using a cyclic triaxial test. According to the test results, the changes in the stress conditions of the original ground occurred most largely in an initial stage of SCP installation, and after a certain time point, the vibration for SCP installation did not have a great influence on the changes in the stress conditions of the ground. Moreover, in order to recreate the behaviors of in-suit ground according to SCP in a laboratory, cyclic loading, which corresponds to casing vibration, was concluded to be essentially required.

A Suggestion of Mix, Construction Method and Quality Control Criteria of Fine-size Exposed Aggregate PCC Pavement by Experimental Construction (시험시공을 통한 소입경 골재노출 콘크리트 포장의 배합, 시공 및 품질관리 기준 제안)

  • Lee, Seung-Woo;Kim, Young-Kyu;Choi, Don-Hwa;Shim, Jae-Won;Yoo, Tae-Seok
    • International Journal of Highway Engineering
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    • v.13 no.3
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    • pp.51-63
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    • 2011
  • Surface of fine-size exposed aggregate portland cement concrete pavements(FS-EAPCC) is consist by exposed coarse aggregate to remove upper 2~3mm mortar of concrete slabs. Advantages of FS-EAPCC are maintaining low-noise and adequate skid-resistance level during the performance period. However, FS-EAPCC is required rational management criteria for field application, since it is early stage for application. Design construction and quality control criteria of FS-EAPCC was temporary laboratory tests which including optimum mix and exposing method, selection of adequate aggregate, resistance against, environmental loading and etc. However, these criteria need to be validated base on field application. In this study, experimental constructions were performed and construction procedure and quality control criteria were suggested based on the performance of the FS-EAPCC.

Pre/Post processor for structural analysis simulation integration with open source solver (Calculix, Code_Aster) (오픈소스 솔버(Calculix, Code_Aster)를 통합한 구조해석 시뮬레이션 전·후처리기 개발)

  • Seo, Dong-Woo;Kim, Jae-Sung;Kim, Myung-Il
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.9
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    • pp.425-435
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    • 2017
  • Structural analysis is used not only for large enterprises, but also for small and medium sized ones, as a necessary procedure for strengthening the certification process for product delivery and shortening the time in the process from concept design to detailed design. Open-source solvers that can be used atlow cost differ from commercial solvers. If there is a problem with the input data, such as with the grid, errors or failures can occur in the calculation step. In this paper, we propose a pre- and post-processor that can be easily applied to the analysis of mechanical structural problems by using the existing structural analysis open source solver (Caculix, Code_Aster). In particular, we propose algorithms for analyzing different types of data using open source solvers in order to extract and generate accurate information,such as 3D models, grids and simulation conditions, and develop and apply information analysis. In addition, to improve the accuracy of open source solvers and to prevent errors, we created a grid that matches the solver characteristics and developed an automatic healing function for the grid model. Finally, to verify the accuracy of the system, the verification and utilization results are compared with the software used.

Design, Analysis, and Equivalent Circuit Modeling of Dual Band PIFA Using a Stub for Performance Enhancement

  • Yousaf, Jawad;Jung, Hojin;Kim, Kwangho;Nah, Wansoo
    • Journal of electromagnetic engineering and science
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    • v.16 no.3
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    • pp.169-181
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    • 2016
  • This work presents a new method for enhancing the performance of a dual band Planer Inverted-F Antenna (PIFA) and its lumped equivalent circuit formulation. The performance of a PIFA in terms of return loss, bandwidth, gain, and efficiency is improved with the addition of the proposed open stub in the radiating element of the PIFA without disturbing the operating resonance frequencies of the antenna. In specific cases, various simulated and fabricated PIFA models illustrate that the return loss, bandwidth, gain, and efficiency values of antennas with longer optimum open stub lengths can be enhanced up to 4.6 dB, 17%, 1.8 dBi, and 12.4% respectively, when compared with models that do not have open stubs. The proposed open stub is small and does not interfere with the surrounding active modules; therefore, this method is extremely attractive from a practical implementation point of view. The second presented work is a simple procedure for the development of a lumped equivalent circuit model of a dual band PIFA using the rational approximation of its frequency domain response. In this method, the PIFA's measured frequency response is approximated to a rational function using a vector fitting technique and then electrical circuit parameters are extracted from it. The measured results show good agreement with the electrical circuit results. A correlation study between circuit elements and physical open stub lengths in various antenna models is also discussed in detail; this information could be useful for the enhancement of the performance of a PIFA as well as for its systematic design. The computed radiated power obtained using the electrical model is in agreement with the radiated power results obtained through the full wave electromagnetic simulations of the antenna models. The presented approach offers the advantage of saving computation time for full wave EM simulations. In addition, the electrical circuit depicting almost perfect characteristics for return loss and radiated power can be shared with antenna users without sharing the actual antenna structure in cases involving confidentiality limitations.

Determination of Optimum Heating Regions for Thermal Prestressing Method Using Artificial Neural Network (인공신경망을 이용한 온도프리스트레싱 공법의 적정 가열구간 설정에 관한 연구)

  • Kim, Jun Hwan;Ahn, Jin-Hee;Kim, Kang Mi;Kim, Sang Hyo
    • Journal of Korean Society of Steel Construction
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    • v.19 no.6
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    • pp.695-702
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    • 2007
  • The Thermal Prestressing Method for continuous composite girder bridges is a new design and construction method developed to induce initial composite stresses in the concrete slab at negative bending regions. Due to the induced initial stresses, prevention of tensile cracks at the concrete slab, reduction of steel girder section, and reduction of reinforcing bars are possible. Thus, the construction efficiency can be improved and the construction can be made more economical. The method for determining the optimum heating region of the thermal prestressing method has not been established although such method is essential for improving the efficiency of the design process. The trial-and-error method used in previous studies is far from efficient, and a more rational method for computing optimal heating region is required. In this study, an efficient method for determining the optimum heating region in using the thermal prestressing method was developed based on the neural network algorithm, which is widely adopted to pattern recognition, optimization, diagnosis, and estimation problems in various fields. Back-propagation algorithm, commonly used as a learning algorithm in neural network problems, was used for the training of the neural network. Through case studies of two-span and three-span continuous composite girder bridges using the developed procedure, the optimal heating regions were obtained.

A Study on the Improvement of Huff's Method for Applying in Korea : II. Improvement of Huff's Method (Huff 강우시간분포방법의 개선방안 연구 : II. Huff 방법의 개선방안)

  • Jang Su-Hyung;Yoon Jae-Young;Yoon Yong-Nam
    • Journal of Korea Water Resources Association
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    • v.39 no.9 s.170
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    • pp.779-786
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    • 2006
  • In this study, we propose a new method that utilizes rainfall data in and out of a basin, which is greater than 25.4mm for point rainfall or 12.7mm for areal mean rainfall respectively. From our analysis, most frequent quartile for point and areal mean rainfall were found to be the same in general for various rainfall duration intervals. From an evaluation of design rainfall per each rainfall duration distributed in time by the MOCT(Ministry of Construction and Transportation) version of Huff's method and this study, peak rainfall intensity by this study was found to be greater than the one by MOCT, but there were no consistent increase or decrease of this difference with rainfall durations. Using the distributed design rainfall per each duration by MOCT and this study, corresponding flood inflow hydrographs were simulated and compared each other. Contrary to the case of peak rainfall intensity, difference in peak flow by both methods per each rainfall duration started to increase from about 12-hr duration. Especially, the difference in peak flow was significant when critical rainfall duration was considered, and this trend was similar for peak flows of other rainfall durations. Therefore, the method proposed in this study is thought to be the effective procedure for the construction of dimensionless cumulative rainfall curve that is representative of a basin while considering time distribution characteristics for different rainfall durations.

Characteristics and Energy Absorbing Capacity for Rockfall Protection Fence from In-Situ Rockfall Tests (현장 낙석실험을 통한 낙석방지울타리의 특성 및 성능 평가)

  • 구호본;박혁진;백영식
    • Journal of the Korean Geotechnical Society
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    • v.17 no.6
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    • pp.111-121
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    • 2001
  • Rockfall protection fences are used for diminishing rockfall damage in roads side slopes. In order to install the fences in effective way, the conditions of rock slopes and total predicted impact energy of fa11ing rock should be considered. However, the fences have been constructed without any consideration for lithology, height and slope angle of rock slope in Korea. In addition, the information about the performance of the protection fences, which should be evaluated by in-situ test or laboratory test in order to check out the practical use in the field, is not available. Therefore, in design manual for the rockfall protection fence, the specific details for the installation of this type of fence are not provided yet. The full sized rockfall in situ test was carried out for the calculation of falling energy of rock and the evaluation of the maximum energy absorbing capacity of fence. For this test, the rock slopes whose heights are about 20 m and dip angle of 65 degree, have been chosen. This is because those geometries are mean height and slope angle of most road cut slopes along Korean national highway. Based on the preliminary simulation procedure, four different sizes of concrete ball (0.7, 1.3, 2.3 and 4.3 ton) were prepared and flour different types of protection fence were constructed. The results of this test provide information about the maximum energy absorbing capacity of the fence, kinetic energy of rockfall and restitution coefficient, and these results can be utilized in the establishment of rockfall fence design and construction manual.

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