• Water Engineering Research
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• 제3권2호
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• pp.93-111
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• 2002

In this paper, mixing characteristics and dilution of the merging buoyant discharges from array of multiple jets has been extensively studied in the hydraulic model experiments. New equations for dilution, which include the merging effects correctly, were derived. Experiments were constructed in a 20-m long, 4.9-m wide and 0.6-m deep flume, and the model diffuser was manufactured to indicate the typical characteristics of the existing ocean wastewater outfall in South Korea. Buoyant discharge from the diffuser was reproduced using heated water. Water temperature was measured using CC-Type thermocouple sensors, which were connected to a 40-channel data logger. Experimental results show that merging between ports in a particular riser is dependent upon the discharge densimetric Froude number, whereas merging between two ports which are facing each other at 90$\circ$ at the adjacent risers is dependent upon the discharge densimetric Froude number and distance from the port and port spacing. Centerline dilution increase with distance from the port outlet until two plumes has merged. However, after merging occurs, increase of the centerline dilution almost stops. Further distance from the position where merging occurs, centerline dilution increases again.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.78-78
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• 2015

Metamaterials, artificially structured nanomaterials, have enabled unprecedented phenomena such as invisibility cloaking and negative refraction. Especially, hyperbolic metamaterials also known as indefinite metamaterials have unique dispersion relation where the principal components of its permittivity tensors are not all with the same signs and magnitudes. Such extraordinary dispersion relation results in hyperbolic dispersion relations which lead to a number of interesting phenomena, such as super-resolution effect which transfers evanescent waves to propagating waves at its interface with normal materials and, the propagation of electromagnetic waves with very large wavevectors comparing they are evanescent waves and thus decay quickly in natural materials. In this abstract, I will focus discussing our efforts in achieving the unique optical property overcoming diffraction limit to achieve several extraordinary metamaterials and metadevices demonstration. First, I will present super-resolution imaging device called "hyperlens", which is the first experimental demonstration of near- to far-field imaging at visible light with resolution beyond the diffraction limit in two lateral dimensions. Second, I will show another unique application of metamaterials for miniaturizing optical cavity, a key component to make lasers, into the nanoscale for the first time. It shows the cavity array which successfully captured light in 20nm dimension and show very high figure of merit experimentally. Last, I will discuss the future direction of the hyperbolic metamaterial and outlook for the practical applications. I believe our efforts in sub-wavelength metamaterials having such extraordinary optical properties will lead to further advanced nanophotonics and nanooptics research.

• Journal of electromagnetic engineering and science
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• 제12권1호
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• pp.26-31
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• 2012

We have proposed a metamaterial lens that enables sub-wavelength focusing, which is shorter than an operating wavelength. Our lens is a two dimensional array of a unit cell consisting of a metallic dual-plate printed on a dielectric substrate. The unique dual-plate structure provides negativeness both in permittivity and permeability, with no help from conventional additional structures, which are normally printed on the opposite of metallic patterns. Therefore, we can focus a source (or an image) in a tiny distance shorter than the free space wavelength (${\lambda}$) at the frequencies of interest. Furthermore, since the proposed geometry does not need separate supplementary structures to acquire negative permittivity or permeability, our lens is much simpler than conventional metamaterial lenses, which is a strong point in practical applications. We have validated sub-wavelength focusing ability in a 6 GHz frequency band through an experiment of near field scanning, which provided the width of about 0.19 ${\lambda}$ at a half maximum of a peak value of an measured image. The width of the focused image through the lens is more than 4 times shorter than that without the lens, which confirms the validity of our design approach.

• 한국항해항만학회지
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• 제35권4호
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• pp.323-334
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• 2011

Suspended and sinking particles were collected in austral summer during ODP Leg 119 to the Indian Ocean sector of the Antarctic Ocean. Field work was carried out at four sampling sites in Prydz Bay. Two of these sites were located in the Outer Bay, and two in the Inner Bay. At the four locations, a total of ten deployments of a sediment trap array were made. The concentrations of chlorophylls and their degradation products both in suspended and sinking particulate matter in Prydz Bay were analyzed using HPLC. Chlorophylls a and c were the dominant algal pigments both in suspended and sinking particles. Because of the abundance of fecal pellets at Site 740, the mean fluxes at 200 m averaged 6 fold greater than that at 50 m. This implies that a dense swarm of zooplankters, presumably large copepods and/or salps, may "feed and excrete" mainly in between 100-200 m depths at this site, closest to land in Prydz Bay. Interestingly, The flux of phaeophorbide a was generally similar in magnitude to that of chlorophyll a throughout the study areas. This is an evidence that materials escaping from near-surface regions in austral summer derive mainly from the gazing of zooplankters. "New production" from sediment-trapped CHL pigment fluxes in Prydz Bay was estimated using f-ratio of 0.15, ranging from 520 to $1,605\;{\mu}gC\;m^{-2}\;day^{-1}$.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.889-896
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• 2004

A series of filed tests have been performed to investigate the aerodynamic effects on platform of the railway station during the passage of train that can be unpleasant and even dangerous to the pedestrians. To assess the aerodynamic effects on the platform, two aerodynamic properties has been measured; one is the wind gust induced by the train and the other is the pressure pulses generated when the nose and the tail of train passes. To measure these aerodynamic properties during the train passage, an array of hot-wire type anemometers and several sets of pressure transducers have been used, respectively. This paper deals with the filed test on conventional railway at about l00km/h operational speed, in which total 34 measurements has been made at the Bugok station in Seoul-Busan line for Saemaul and Mugungwha train. The results showed dramatic differences in the aerodynamic features between the two trains that are supposed to originate from the contrasting nose shapes of the trains.

• 한국철도학회논문집
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• 제7권2호
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• pp.137-141
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• 2004

A series of filed tests have been performed to investigate the aerodynamic effects on platform of the railway station during the passage of train that can be unpleasant and even dangerous to the pedestrians. To assess the aerodynamic effects on the platform, two aerodynamic properties has been measured; one is the wind gust induced by the train and the other is the pressure pulses generated when the nose and the tail of train passes. To measure these aerodynamic properties during the train passage, an array of hot-wire type anemometers and several sets of pressure transducers have been used, respectively. This paper deals with the filed test on conventional railway at about 100km/h operational speed, in which total 34 measurements has been made at the Bugok station in Seoul-Busan line for Saemaul-ho and Mugungwha-ho train. The results showed dramatic differences in the aerodynamic features between the two trains that are supposed to originate from the contrasting nose shapes of the trains.

• Nuclear Engineering and Technology
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• 제23권3호
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• pp.275-284
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• 1991

핵연료봉의 정방형 또는 삼각형 배열내의 2차 난류 유동의 해석은 연료봉내의 온도분포와 열전달 과정의 해석에 있어서 중요한 문제이다. 비등방성 난류모델과 등방성 난류모델을 사용하여 속 도장을 구하였고 열수력학적 성질이 일정하다는 가정하에 지배방정식을 유한 요소법을 사용하여 수치해석적인 방법으로 해를 구하였다. 또한 연료봉 표면 근처에서는 유체의 유동이 난류가 아니기 때문에 축 방향 속도는 벽의 법칙에 의해서 계산하였다. 이러한 방법에 의해서 구해진 해는 실험 결과와 비교되었고 비교적 잘 일치하였다.

• Applied Microscopy
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• 제46권4호
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• pp.184-187
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• 2016

Neuronal connectivity determines brain function. Therefore, understanding the full map of brain connectivity with functional annotations is one of the most desirable but challenging tasks in science. Current methods to achieve this goal are limited by the resolution of imaging tools and the field of view. Macroscale imaging tools (e.g., magnetic resonance imaging, diffusion tensor images, and positron emission tomography) are suitable for large-volume analysis, and the resolution of these methodologies is being improved by developing hardware and software systems. Microscale tools (e.g., serial electron microscopy and array tomography), on the other hand, are evolving to efficiently stack small volumes to expand the dimension of analysis. The advent of mesoscale tools (e.g., tissue clearing and single plane ilumination microscopy super-resolution imaging) has greatly contributed to filling in the gaps between macroscale and microscale data. To achieve anatomical maps with gene expression and neural connection tags as multimodal information hubs, much work on information analysis and processing is yet required. Once images are obtained, digitized, and cumulated, these large amounts of information should be analyzed with information processing tools. With this in mind, post-imaging processing with the aid of many advanced information processing tools (e.g., artificial intelligence-based image processing) is set to explode in the near future, and with that, anatomic problems will be transformed into informatics problems.

• Journal of Biosystems Engineering
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• 제34권5호
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• pp.382-389
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• 2009

An in-situ probe-based spectrophotometer has been developed. This system used two spectrometers to measure soil reflectance spectra from 450 nm to 2200 nm. It collects soil electrical conductivity (EC) and insertion force measurements in addition to the optical data. Six fields in Kansas were mapped with the VIS-NIR (visible-near infrared) probe module and sampled for calibration and validation. Results showed that VIS-NIR correlated well with carbon in all six fields, with RPD (the ratio of standard deviation to root mean square error of prediction) of 1.8 or better, RMSE of 0.14 to 0.22%, and $R^2$ of 0.69 to 0.89. From the investigation of carbon variability within the soil profile and by tillage practice, the 0-5 cm depth in a no-till field contained significantly higher levels of carbon than any other locations. Using the selected calibration model with the soil NIR probe data, a soil profile map of estimated carbon was produced, and it was found that estimated carbon values are highly correlated to the lab values. The array of sensors (VIS-NIR, electrical conductivity, insertion force) used in the probe allowed estimating bulk density, and three of the six fields were satisfactory. The VIS-NIR probe also showed the obtained spectra data were well correlated with nitrogen for all fields with RPD scores of 1.84 or better and coefficient of determination ($R^2$) of 0.7 or higher.

• 한국축산시설환경학회지
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• 제20권3호
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• pp.117-124
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• 2014

The objectives were to assess the use of near-infrared reflectance spectroscopy (NIRS) as a tool for estimating nutrient compositions of corn kernel, and to apply an NIRS-based indium gallium arsenide array detector to the system for collecting spectra and analyzing calibration equations using equipments designed for field application. Partial Least Squares Regression (PLSR) was employed to develop calibration equations based on representative data sets. The kennard-stone algorithm was applied to induce a calibration set and a validation set. As a result, the method for structuring a calibration set significantly affected prediction accuracy. The prediction of chemical composition of corn kernel resulted in the following (kennard-stone algorithm: relative) moisture ($R^2=0.82$, RMSEP=0.183), crude protein ($R^2=0.80$, RMSEP=0.142), crude fat ($R^2=0.84$, RMSEP=0.098), crude fiber ($R^2=0.74$, RMSEP=0.098), and crude ash ($R^2=0.81$, RMSEP=0.048). Result of this experiment showed the potential of NIRS to predict the chemical composition of corn kernel.