• Nuclear Engineering and Technology
• /
• v.51 no.2
• /
• pp.526-532
• /
• 2019

In this study, an in-house $^{152}Eu$ calibration source was produced from a custom epoxy matrix with a density of ${\rho}=1.14g\;cm^{-3}$, which is chemically stable and durable form after its solidification. The homogeneity of $^{152}Eu$ in matrix was obtained better than 98%. For a Marinelli beaker geometry, an efficiency calibration procedure was applied to a n-type, coaxial, 78.5% relative efficient HPGe detector in the energy range of 121.7-1408.0 keV by using in-house $^{152}Eu$ calibration source. Then the measured efficiencies for Marinelli geometry were compared with the results calculated by MEFFTRAN and ANGLE softwares for the validation. Although MEFFTRAN and ANGLE have two different efficiency transfer algorithms to calculate the efficiencies, they usually need to use a reliable and accurate reference efficiency values as input data. Hence, reference efficiency values were obtained experimentally from a multinuclide standard source for the same detector-Marinelli geometry. In the present source characterization, the corrections required for self-absorption and true coincidence summing effects for $^{152}Eu$ gamma-rays were also obtained for a such close counting geometry condition. The experimental results confirmed the validity of efficiency calculations obtained by MEFFTRAN and ANGLE softwares that are calculation tools.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.3
• /
• pp.1-11
• /
• 2020

In this study, a hot-firing test of a lab-scale gel rocket motor using liquid kerosene and gelled kerosene as fuel was performed in order to analyze the discrepancy of the static and dynamic pressure between the two fuels. The static pressure, characteristic velocity, and characteristic velocity efficiency of the liquid kerosene and gelled kerosene did not show any significant difference. However, in the case of dynamic pressure characteristics, the pressure oscillation amplitude in a specific high frequency region of the gelled kerosene demonstrated a significantly higher amplitude than liquid kerosene case. This is considered to be the effect of an intrinsic combustion mechanism of the gel propellant, and it can be postulated that this may act as a dominant factor influencing the high frequency combustion instability of the gel rocket motor.

• Smart Structures and Systems
• /
• v.30 no.3
• /
• pp.327-332
• /
• 2022

In building envelope, transparent components play an important role. The structural glazing systems are the weak element of the casing in terms of mechanical resistance, thermal and acoustic insulation. In the present work, new structural glass panels with granular aerogel in interspace were investigated from different points of view. In particular, the mechanical characterization was carried out in order to assess the resistance to bending of the single glazing pane. To this end, a special instrument system was built to define an alternative configuration of the coaxial double ring test, able to predict the fracture strength of glass large samples (400 × 400 mm) without overpressure. The thermal and lighting performance of an innovative double-glazing façade with granular aerogel was evaluated. An experimental campaign at pilot scale was developed: it is composed of two boxes of about 1.60 × 2 m² and 2 m high together with an external weather station. The rooms, identical in terms of size, construction materials, and orientation, are equipped with a two-wing window in the south wall surface: the first one has a standard glazing solution (double glazing with air in interspace), the second room is equipped with the innovative double-glazing system with aerogel. The indoor mean air temperature and the surface temperature of the glass panes were monitored together with the illuminance data for the lighting characterization. Finally, a brief energy characterization of the performance of the material was carried out by means of dynamic simulation models when the proposed solution is applied to real case studies.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.3A
• /
• pp.417-423
• /
• 2000

A broadband antenna available in the range of 30MHz for electromagnetic interference (EMI) test is proposed in this paper, This antenna is configurated in a disk-loaded cylindrical dipole (DLCD) connected to an 180。 hybrid balun consisting of two coaxial feeders. The performance of EMI antenna is characterized with its accurate antenna factor. The antenna factor for this antenna is obtained by using the method of moments and the calculated results are compared with the measured ones. Normalized site attenuation (NSA) is also measured by using this antenna. The results present that the propose antenna could be used for a reference antenna having measurement reproducibility and represented by a theoretically accurate analysing model in EMI measurement.

• Proceedings of the KIEE Conference
• /
• 1999.07d
• /
• pp.1538-1540
• /
• 1999

For the development of electro magnetic shielding materials by use of the conductive polymer, measuring technique related to their shielding effect should be well established. For this propose, several commercialized techniques based on different conception have been well compared in order to adopt appropriate method to our materials under development and then, flanged coaxial holder type fixture device has been fabricated and tested satisfied performance has been obtained showing over 90dB in dynamic range with accuracy of +/-2dB.

• Proceedings of the KIEE Conference
• /
• 1995.07c
• /
• pp.1126-1128
• /
• 1995

In order to investigate the electrical properties for transformer oils due to electron bean irradition, the dielectric properties was made researches by dose of irradition To measure the dielectric loss of irradiated specimen, coaxial cylindrical liquid electrode was used, geometric capacitance was confirmed to 16[pF]. Experiments for measuring the dielectric loss were performed at $20{\sim}120[^{\circ}C]$ in temperature range, $30{\sim}1.5{\times}10^5$[Hz] in frequency range and $300{\sim}1500$[mV] in voltage range and then, the result of experiment for the movement of carrier and the physical constants to contribute dielectric properties of specimen due to electron beam irradiation introduced.

• Journal of Biosystems Engineering
• /
• v.24 no.2
• /
• pp.123-134
• /
• 1999

The electrical properties such as dielectric constant, dielectric loss factor and AC conductivity of grain were presented to measure the moisture content of grain using RF impedance. At frequency ranging from 1 to 10MHz and room temperature, $20^{\circ}C$, vector network analyzer(HP4195) and coaxial type sample holder were used to analyze the electrical properties of paddy(11∼24%w.b.), brown rice(11∼18%w.b.), barley(11∼21%w.b.) and wheat(11∼23%w.b.) depending on the moisture content, frequency and bulk density. The dielectric constant and AC conductivity of grain samples increased with moisture content and bulk density. The dielectric constants decreased with frequency and could be expressed as function of the moisture density(decimal moisture $content{\times}bulk$ density).

• Journal of the Korean Society of Industry Convergence
• /
• v.14 no.4
• /
• pp.135-142
• /
• 2011

Convergence between telecom and broadcasting is today a worldwide phenomenon. Diverse services like VoD, mobile broadcasting, IPTV and interactive services have already made their market debut or are currently being commercialized. Regulatory systems are also being revised to appropriately regulate this new breed of services. We propose the new model of educational broadcasting system using the internet network, it is not different conventional coaxial cable methods. Especially, we design the multicast method of the network using the limited channel and resource, propose the method of intercommunication in the school between the broadcasting system and database system.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.1
• /
• pp.331-337
• /
• 2015

A novel fully-printed microstrip antenna with negative first resonance and dual polarization is proposed. The radiator is printed on the 1-layer substrate instead of multilayers. The -1st resonance results from a composite right- and left-handed(CRLH) structure that has a circumferentially interlocked gap capacitively coupling a patch with a shorted-ring. This compact antenna is provided with a dual-polarization capability by creating two orthogonal linear polarizations in one body with coaxial feeds. The design is carried out by doing full-wave EM field simulation which is compared with the measurement of the fabricated antenna prototype. The measured results give the gain of 5 dBi and the efficiency of 78% at the -1st resonance mode as the center frequency of a downlink channel of the bandwidth over 20 MHz with 29 dB polarization isolation for mobile communication.

• Structural Engineering and Mechanics
• /
• v.48 no.1
• /
• pp.17-39
• /
• 2013

In the present paper, a coaxial rotating smeared crack model is proposed for mass concrete in three-dimensional space. The model is capable of applying both the constant and variable shear transfer coefficients in the cracking process. The model considers an advanced yield function for concrete failure under both static and dynamic loadings and calculates cracking or crushing of concrete taking into account the fracture energy effects. The model was utilized on Koyna Dam using finite element technique. Dam-water and dam-foundation interactions were considered in dynamic analysis. The behavior of dam was studied for different shear transfer coefficients considering/neglecting fracture energy effects. The results were extracted at crest displacement and crack profile within the dam body. The results show the importance of both shear transfer coefficient and the fracture energy in seismic analysis of concrete dams under high hydrostatic pressure.