• Journal of Aerospace System Engineering
• /
• v.16 no.2
• /
• pp.39-48
• /
• 2022

The purpose of this paper was to study how to improve the occurrence of abnormal altitude values of radio altimeter, due to RF interference signals during the flight of aircraft. In flight missions, since it performs a roll-out after several high maneuvers, accurate altitude must be displayed to effectively perform flight missions. Thus, a root cause analysis and trouble shooting were performed for the display of abnormal altitude values of radar altimeters, and a method of reducing RF interference signals by installing an attenuator was examined. Additionally, the verification results for the improvements are also described.

• Journal of architectural history
• /
• v.18 no.6
• /
• pp.23-46
• /
• 2009

The history to have used lime in building construction was much long without distinction of the East or the West. The ancient nations of korean peninsula had used lime as construction material. The witness was discovered in the kings' tombs of fifth century. In the Joseon dynasty(15~19c), what applied several developed lime compounds to the kings' tombs have been recorded in 'Sanleong-Uigwe(山陵儀軌)' & 'Yeonggeon-Uigwe(營建儀軌)' of those days documents. Therefore, this paper is to examine the whole procedures from the product and provision of lime to its application through those days documents. Following conclusions have been reached through the study. Three lime compounds to be developed for the kings' tombs was extendedly applied to residential government buildings step by step within the current of time. These compounds to be used in the kings' tombs of the Joseon dynasty had been correlated to those of the ancient nations, which were nations of korean peninsula in narrow range, chinese and orient nations in broad range. These compounds have possibilities of development as the environmental-friendly building material. And these compounds should provide a standard specification for conservation & restoration of the traditional and cultural properties. I could confirm that the whole procedures had not been developed within limited space-time of the specified nation & period, but within interactions of the nations & periods. In the periods which disturb its interaction, the expansion of productivity in building construction was interfered.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• v.y2005m4
• /
• pp.269-273
• /
• 2005

A practical, 30-tonf-class fullscale thrust chamber has been combustion tested using real propellants for the first time in the domestic technology scene. The very first combustion test was conducted at a low mass flow rate condition for the preliminary assessment of any problems associated with its function and performance while reducing risks from a high chamber pressure never achieved before. A test for the design condition achieved through a low-pressure stage shows stable characteristics of all the static pressures and thrust. Dynamic pressures measured in the manifolds and the chamber did not reveal any distinct wave coupled to a specific frequency and their intensities reside in the allowable range. Moreover, it is encouraging to find no physical failures with a thrust chamber hardware.

• The Korean Journal of Ecology
• /
• v.23 no.3
• /
• pp.217-221
• /
• 2000

The vegetation of Maemul, Somaemul and Eoyu islets in Tongyeong-si was investigated from September, 1996 through August, 1997. In order to analyze the vegetation of this islets, synthesis table, actual vegetation map were prepared. The predominant species of the islets was Camellia japonica. and the vegetation in this study area was classfied into 4 communties (included 1 afforestation) and 7 subcommunities 1 . Camellia japonica community 1) Typical subcommunity 2) Machilus thunbergii subcommunity 3) Castanopsis cuspidata var, thunbergii subcommunity 4) Ligustrum obtusifolium subcommunity 5) Carpinus coreana subcommunity 6) Selaginella tamariscina subcommunity 7) Pinus thunbergii subcommunity 2. Pinus thunbergii community 3. Alnus firma afforestation 4. Miscanthus sinensis var. purpurascens community.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.1
• /
• pp.89-95
• /
• 2015

A surge phenomenon cause noise and pulsations in a turbo compressor, which is an unstable operating regime. Because surge protection ensures a safe compressor operation, it is important to understand the physics of the surge phenomenon. In this study, the surge characteristics of a 250-hp class turbo-compressor were evaluated experimentally. The experimental parameters were the rotational speed, opening angles of the inlet guide vane and exit valve, and inlet pipe diameter and flow rates of the inlet gases. The results showed that the compressor surge was very sensitive to the gas flow rates, exit pressure, rotational speed, and bypass flow rates.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.12
• /
• pp.1039-1044
• /
• 2013

We propose a cancellation algorithm based on Alamouti coded OFDM to mitigate ICI due to Frequency Offset (FO) between distributed antennas in the frequency selective fading channel. In the cancellation algorithm, the interference signal is estimated by using the initial detection symbol and then the estimated interference signal is subtracted from the received signal. As the accuracy of initial symbol increases, ICI cancellation becomes more significant. Therefore, the accuracy of the initial detection symbols is very important in the cancellation algorithm. The proposed scheme improves the accuracy of the initial detection symbol by employing an ICI self-cancellation scheme. The proposed cancellation scheme with only one iteration achieves better performance compared to the conventional cancellation schemes with many times iterations based on the conventional Alamouti coded OFDM.

• Progress in Medical Physics
• /
• v.21 no.1
• /
• pp.78-85
• /
• 2010

The compatibility with GammaMed-12i brachytherapy machine for an Ir-192 encapsulated source (IRRS20, KAERI, Korea) manufactured by Korea atomic energy research institute (KAERI) has been investigated. As a mechanical testing of compatibility, precise measurement of step movement with channels, measurement of curvature of radius for wire, and emergency return testing were performed. Periodic measurements of air kerma strength for 45 days were carried out to evaluate decay characteristics of Ir-192 radioisotope and comparison of dose distributions in phantom between KAERI and old sources previously used were performed by film dosimetry. KAERI source has a good compatibility with GammaMed12i machine as a result of mechanical testing. There are in good agreement with calculated values in activity characteristics and there were small differences in dose distributions around the source in comparison between KAERI and old source.

• Journal of Korean Society of Steel Construction
• /
• v.9 no.2 s.31
• /
• pp.193-204
• /
• 1997

In order to quantify the relationships of the important physical factors relating failure to strong earthquake loading, the plastic fatigue problems for structural components under repeated loading were reviewed first. A new concept of very low cycle fatigue failure for structural components under severe cyclic excitations as in strong earthquakes was represented. Also, an experimental study was made of the very low cycle fatigue failure of structural steel elements. It was attempted to realize the ultimate failure in the course of loading repetitions of the order of several to twenty. The test specimen had a form of rectangular plate, representing a thin-plated element in a steel member as wide-flange cross section. It was subjected to uniaxial loading repeatedly, until complete failure takes place after undergoing inelastic buckling, plastic elongation and/or their combination. It was seen as a result that the state of the ultimate failure is closely related to the maximum strain at the extreme fiber in the cross section.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.11a
• /
• pp.69-73
• /
• 2009

Combustion test results of 1/2.5-scale thrust chamber for 75tonf-class liquid rocket engine were described. The thrust chamber has chamber pressure of 60 bar, propellant mass flow rate of 89 kg/s, and nozzle expansion ratio of 12. The combustion tests were conducted to verify the combustion performance, the regenerative cooling performance and the durability of thrust chamber at design point condition, and then were performed to confirm the operation and the combustion performance at low combustion pressure condition. All the tests had been successfully executed without the damage of the hardware. These test results present a possibility of hot firing test at low combustion pressure condition, and can be used as fundamental data to predict the combustion performance at design point condition for 75 tonf thrust chamber.

• Journal of Korean Society of Forest Science
• /
• v.28 no.1
• /
• pp.36-42
• /
• 1975

In the beginning of the germination of Castanea creata seeds, seedlings with identical genetic characteristics from only one seed were produced by longitudinally splitting the radicle and epicotyl in half with a razor blade. The results are summarized as follows: 1. 2-8 genetically identical Castanca crenata seedlings were produced by longitudinally splitting the radicles and epicotyles from one to four in number in half with a razor blade 1-3 times about 7 days apart, while the seeds were germinating. 2. The proportion of success of splitting seedlings was very high (90-100%). When some of the spliting seedlings were withered a sprout appeared again and it was possible the seedling to revive. 3. The production rate, growth and T/R rate of seedlings which were split only once were lower that those of the seedlings which were split several times. 4. The growth and T/R rate of split seedlings which were one of no more than four seedlings produced from one seed showed no difference in comparison with normal seedlings, but in seedlings which were one of more than four, the growth and T/R rate were considerably decreased. 5. With the progress of growth, the external shapes of splitting seedlings completely returned to the original state, and no problems in growth, were found.