• 설비공학논문집
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• 제7권1호
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• pp.1-12
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• 1995

In order to seek various relationships among many design parameters employed in the design of the axial-flow fans the program which generates acoustic spectrum has been developed and its validity verified. Outputs of the program, with other outputs from a formerly developed performance prediction program, have been used to form a multi-objective function, for which an optimal design process was carried out. The present analysis shows that overall noise level and efficiency has contrasting trends, and the chord length turns out to be the most critical design variable. In the chosen design case of requirements $Q=2000m^2/min$, ${\Delta}P_s=67mmAq$, D=1.4m, the chord length of 0.2059m minimizes the overall noise level, while chord length of 0.1254m maximizes the efficiency. The resulting chord length in the balanced optimization is 0.1809m.

• 한국수소및신에너지학회논문집
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• 제31권3호
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• pp.314-321
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• 2020

In this work, a preliminary design of an inlet guide vane and runner for developing a 2.5 kW hydraulic turbine was conducted by using computational fluid dynamic analysis. Three-dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were used to analyze the fluid flow in the hydraulic turbine. The hexahedral grid system was used to construct computational domain, and the grid dependency test was performed to obtain the optimal grid system. Velocity triangle diagram considering the flow angles of the inlet guide vane and runner was analyzed to obtain a basic geometry of the inlet guide vane and runner. Through modification of the preliminary design, the hydraulic performances of the turbine have improved under overall drop conditions. Especially, the efficiency and power of the turbine increased by 0.95% and 1.45%, respectively, compared to those of the reference model.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.417-420
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• 2006

In these days, mobile application dealing with information contents on mobile or handheld devices such as mobile communicator, PDA or WAP device face the most important industrial needs. The motivation of this study is the design and implementation of mobile application using high resolution satellite imagery, large-sized image data set. Although major advantages of mobile devices are portability and mobility to users, limited system resources such as small-sized memory, slow CPU, low power and small screen size are the main obstacles to developers who should handle a large volume of geo-based 3D model. Related to this, the previous works have been concentrated on GIS-based location awareness services on mobile; however, the mobile 3D terrain model, which aims at this study, with the source data of DEM (Digital Elevation Model) and high resolution satellite imagery is not considered yet, in the other mobile systems. The main functions of 3D graphic processing or pixel pipeline in this prototype are implemented with OpenGL|ES (Embedded System) standard API (Application Programming Interface) released by Khronos group. In the developing stage, experiments to investigate optimal operation environment and good performance are carried out: TIN-based vertex generation with regular elevation data, image tiling, and image-vertex texturing, text processing of Unicode type and ASCII type.

• 한국인터넷방송통신학회논문지
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• 제17권6호
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• pp.27-31
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• 2017

본 논문에서는 낮은 삽입 손실을 가지는 광대역 DSPSL (double-sided parallel-stripline) - CPS (coplanar stripline) 전이구조를 제안하였다. 제안하는 전이구조는 자연스러운 전계분포의 필드 변환과 DSPSL과 CPS 사이의 임피던스 정합의 관점에서 설계되었다. 전이구조의 명확한 설계방법을 제시하여 바닥면 그라운드의 변화와 전이구조의 길이를 결정할 수 있게 하였다. 설계의 제작된 전이구조의 특성은 전이구조 당 6.2 ~ 18.2 GHz의 대역에서 0.7 dB의 낮은 삽입 손실을 가지고 있으며, 6.2 ~ 30 GHz 이상의 대역에서 1.25 dB의 삽입 손실을 가짐을 확인하였다.

• 한국산학기술학회논문지
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• 제10권8호
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• pp.1817-1823
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• 2009

본 논문에서는 출력전력이 협대역 정합에서 최대 23dBm 정도인 중간전력급 증폭소자를 이용하여 광대역 이득을 갖는 직렬 분포형 증폭기 설계에 대하여 기술한다. 일반적으로 병렬 분포형 증폭기는 1단 증폭기처럼 이득이 낮고, 직렬 분포형 증폭기는 이득이 높은 반면에 출력전력의 크기가 10dBm 이내인 소신호 증폭기였던데 비하여, 본 논문에서는 광대역에서 출력 전력이 20dBm급인 직렬 분포형 증폭기에 대하여 기술한다. 실제로 제작한 증폭기는 $300MHz{\sim}2GHz$에서 $18.15{\pm}0.75dB$의 평탄한 이득과 $19{\sim}20dBm$의 출력전력 특성을 보이는 것으로 측정되어, 광대역에서 구동증폭기로 사용할 수 있음을 보여준다.

• 융합신호처리학회논문지
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• 제9권2호
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• pp.129-134
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• 2008

본 논문에서는 적자생존 원리에 기반한 유전자 알고리즘을 이용하여 일차원 비선형 광자 결정 구조에 대해 분석하고, 광 트랜지스터로의 적용 가능성을 컴퓨터 시뮬레이션에 의해 증명한다. 이와 같은 형태의 최적 설계는 해석식이 필요한 steepest decent 최적 알고리즘과 달리 유전자 알고리즘은 탁월한 성능을 낼 수 있으며, 광 트랜지스터 뿐만 아니라 다른 광자 결정 광소자의 설계에 유용하게 적용될 수 있다. 또한, global minimum 최적해 부근에서 여러 가지의 해가 얻어지기 때문에 광 트랜지스터가 어떤 모양을 가져야 되는지 분석하는데 많은 도움을 주는 장점을 갖는다. 완전 광 필터 트랜지스터를 설계하기 위해 신경회로망 모델을 이용하여 초기 설계를 수행한 후, 유전자 알고리즘에 의해 최종적인 최적화 설계가 수행된다. 시뮬레이션으로부터 얻어진 일차원 광자 결정 트랜지스터의 스위칭 On/Off 비는 약 27dB 였다.

• Journal of Microbiology and Biotechnology
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• 제27권11호
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• pp.2010-2018
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• 2017

Mixotrophic microalgal growth gives a great premise for wastewater treatment based on photoautotrophic nutrient utilization and heterotrophic organic removal while producing renewable biomass. There remains a need for a control strategy to enrich them in a photobioreactor. This study performed a series of batch experiments using a mixotroph, Chlorella sorokiniana, to characterize optimal guidelines of mixotrophic growth based on a statistical design of the experiment. Using a central composite design, this study evaluated how temperature and light irradiance are associated with $CO_2$ capture and organic carbon respiration through biomass production and ammonia removal kinetics. By conducting regressions on the experimental data, response surfaces were created to suggest proper ranges of temperature and light irradiance that mixotrophs can beneficially use as two types of energy sources. The results identified that efficient mixotrophic metabolism of Chlorella sorokiniana for organics and inorganics occurs at the temperature of $30-40^{\circ}C$ and diurnal light condition of $150-200{\mu}mol\;E{\cdot}m^{-2}{\cdot}s^{-1}$. The optimal specific growth rate and ammonia removal rate were recorded as 0.51/d and 0.56/h on average, respectively, and the confirmation test verified that the organic removal rate was $105mg\;COD{\cdot}l^{-1}{\cdot}d^{-1}$. These results support the development of a viable option for sustainable treatment and effluent quality management of problematic livestock wastewater.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.437-438
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• 2006

Generally, the vertical roll process is used to achieve extensive width reduction in hot strip mill. However, it is difficult to avoid the defects such as dog-bone and seam-defect. The sizing press has been developed in response to the defects mentioned above. Especially, this study is carried out to investigate the deformation of slab by two-step sizing press. The deformation behavior in the width sizing process is more favorable than that in conventional vertical rolling edger. The objective of this study is to determine the optimal anvil shape parameters in the sizing press with two-step die from the viewpoint of edge-seam length. In general, the edge-seam defect occurs parallel to the rolling direction at both edges in horizontal rolling process after sizing press. The optimal combination of the parameters is determined by FE-simulation and Artificial Neural Network (ANN). The slab deformation in sizing press with convex anvil is analyzed by FE-simulation. The most suitable profile of the anvil is also discussed fur the improvement of trimming loss because of the side seam defect by FE-simulation and ANN.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권10호
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• pp.4759-4780
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• 2017

Full Dimension multiple input multiple output (FD-MIMO) architecture employs a planar array design at the Base Station (BS) to provide high order multi-user MIMO (MU-MIMO) via simultaneous data transmission to large number of users. With FD-MIMO, the BS can also adjust the beam direction in both elevation and azimuth direction to concentrate the energy on the user of interests while minimizing the interference leakage to co-scheduled users in the same cell or users in the neighboring cells. In a typical highly populated macrocell environment, modelling the elevation angular characteristics of three-dimensional (3D) channel is critical to understanding the performance limits of the FD-MIMO system. In this paper, we study the throughput performance of FD-MIMO system with varying elevation angular spread and inter-element spacing using a 3D spatial channel model. Our results show that for a typical urban scenario, horizontal beamforming with correlated antenna spacing achieves optimal performance but by restricting the spread of elevation angles of departure, elevation beamforming achieves high array gain with wide inter-element spacing. We also realize significant gains due to spatial array processing via modelling the elevation domain and varying the inter-element spacing for both the transmitter and receiver.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권7호
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• pp.13-22
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• 2015

In this study, we have developed the performance evaluation model for the optimal soil remediation technology selection. Performance evaluation model is composed in the evaluation of two steps. In the first stage, the candidate technologies are derived according to the conditions of drilling, type and concentration of pollutants, and the saturated/unsaturated of target site. In the second stage, each individual candidate technology is evaluated by performance evaluation model. The performance evaluation model has 5 groups of evaluation items and 12 evaluation items which have their own evaluation index and their own weights through the AHP approach surveying 40 experts. From the case study of actual design cases, the applicability of the performance evaluation model was confirmed.