• Journal of Electrical Engineering and Technology
• /
• v.9 no.5
• /
• pp.1704-1711
• /
• 2014

Sandy and dusty weather condition often occurs in the high altitude areas of China, which may greatly influence the corona generated radio interference (RI) characteristics of the bundle conductors of 750 kV AC power transmission lines. Corona generated RI of the conductors of the 750 kV AC power transmission lines used in practice is measured by EMI receiver with a coupling circuit and a coupling capacitor connected between the high voltage side and the earth side in fine and sandy and dusty condition. The measuring frequency is 0.5 MHz, and the quasi-peak detection is used. RI excitation function is calculated based on the corona RI current measured by the EMI receiver. Corona generated RI characteristics were analyzed from sand concentration and sand particle size. The test result shows that the corona generated RI excitation function is influenced by the sandy and dusty condition. Corona discharge of the conductors is more serious in sandy and dusty condition with an ultraviolet (UV) detector. Corona generated RI excitation function increases with the increase of sand concentration and also increases with the increase of particle size.

• Korean Journal of Plant Resources
• /
• v.32 no.4
• /
• pp.325-337
• /
• 2019

This study was conducted to analyze character of distribution of plants by landforms and altitude in Mt. myeonbong. The chemical properties of soil in this study sites were as follows; pH 4.86, organic 52.53 g/kg, $P_2O_5$ 7.57 mg/kg, potassium $0.18cmol^+/kg$, calcium $2.45cmol^+/kg$ and magnesium $0.49cmol^+/kg$. Generalists in the upper layer were analyzed as follows; Quercus mongolica, Pinus densiflora, Quercus variabilis, and specialists; Carpinus cordata, Tilia amurensis, Morus bombycis etc. In the middle layer, generalists were Betula schmidtii, Quercus mongolica, Sorbus alnifolia and specialists; Lindera erythrocarpa, Quercus serrata, Staphylea bumalda etc. Generalist of shrubs; Lindera obtusiloba, Rhododendron mucronulatum, Sorbus alnifolia, and specialists; Morus bombycis, Pinus densiflora, Deutzia glabrata etc. Generalists of herbaceous layer; Rhus tricocarpa, Lespedeza maximowiczii, Polygonatum odoratum var. pluriflorum and specialists; Liparis kumokiri, Davallia mariesii and Chrysosplenium flagelliferum etc.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.11a
• /
• pp.299-304
• /
• 2008

Starting characteristics of the axi-symmetric second throat exhaust diffuser (STED) with zero-secondary flows are numerically investigated. Renolds-Average Navier-Stokes equations with a standard ${\kappa}-{\varepsilon}$ turbulence model incorporated with enhanced wall treatment are solved to simulate the diffusing evolutions of the nozzle plume. Minimum (optimum) starting pressure difference of 20$\sim$25% between 1-D theory and the measured data validated from previous results[5] is also applied to predict the range of an effective diffuser expansion ratio (Ad/At) in this system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2012.05a
• /
• pp.58-62
• /
• 2012

In this study, the hybrid rocket was developed that has a thrust of 1000 kgf level. The static fire test was shown that the thrust was 700 kgf level and trajectory was predicted by the maximum altitude of 12.5 km. The L/D ratio of KHyRoc-I has 28, but the KHyRoc-II were designed the small L/D ratio(18.3) using the seamless aluminium tube(Diameter : 250 mm). And KHyRoc-II has a thrust of 900 kgf level, that is designed with internal ballistics and trajectory was predicted by the maximum altitude of 7.4 km.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.50 no.2
• /
• pp.83-92
• /
• 2022

This paper analyzes the performance of the IRA(Interferometric Radar Altimeter) by terrain type for estimating reliability of TRN(Terrain Referenced Navigation). The accuracy of the altitude is one of the key parameters of TRN's accuracy. When the antenna of the IRA has wide beamwidth, its altitude accuracy is directly affected by the configuration of the earth's surface. Hence, the accuracy and reliability of TRN can also be affected and may cause ambiguity in positioning. We present analysis data for estimating the reliability of TRN by modeling several topographies and analyzing the performance of the IRA. The results of the analysis are verified by comparison with test data.

• International journal of advanced smart convergence
• /
• v.12 no.4
• /
• pp.386-394
• /
• 2023

This study investigated changes in salivary cortisol, lactic acid, and heart rate along the route during walking exercise in a forest environment for the purpose of reducing stress. Walking exercise in a forest environment was conducted on a Hill Type (Distance: 800m, Average slope 25°, Altitude 112m) and Step Type (Distance: 800m, Average slope 25°, Altitude 114m) routes for 10 female college students in their 20s. The subjects were asked to walk at a speed of 60 bpm. The resulting changes in salivary cortisol, lactate, and average heart rate during exercise were compared and analyzed using Repeated Measurement two-way ANOVA, and the maximum heart rate during exercise and average heart rate at rest were compared and analyzed using paired t-test, and the following results were obtained. First, there was no significant difference in salivary cortisol depending on the type and period of the forest, but it tended to gradually decrease. Second, there was a significant difference in lactic acid depending on the type and period, and it was higher in Step Type. Third, there was a significant difference in the average heart rate during exercise, and it was higher in Step Type. Fourth, there was a significant difference in maximum heart rate during exercise, and it was higher in Step Type. Fifth, there was no significant difference in average heart rate during rest. In summary, walking exercise in a forest environment can be effective for stress reduction for female college students in their 20s, but it appears that forest routes should be selected according to physical strength level, and walking exercise in a forest environment for long periods of time is not recommended. For this purpose, it is suggested that it is appropriate to select the Hill Type route.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.15 no.2
• /
• pp.15-22
• /
• 2011

Unlike most aerodynamic wind-tunnel, Scramjet Engine Test Facility(SETF) of Korea Aerospace Research Institute should simulate enthalpy condition at a flight condition. SETF is a blow-down type, high-enthalpy wind tunnel. To attain a flight condition, a highly stagnated air comes into the test cell through a supersonic nozzle. Also, an air ejector of the SETF is used for simulating altitude conditions of the engine, and facility starting. SETF has a free-jet type test cell and this free-jet type test cell can simulate a boundary layer effect between an airplane and engine using facility nozzle, but it is too difficult to predict the nature of the facility. Therefore it is required to understand the starting characteristics of the facility by experiments. In this paper, the starting characteristics of the SETF and modifications of the ejector are described.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.11a
• /
• pp.451-458
• /
• 2010

Unlike most aerodynamic wind-tunnel, Scramjet Engine Test Facility(SETF) of Korea Aerospace Research Institute should simulate enthalpy condition at a flight condition. SETF is a blow-down type, high-enthalpy wind tunnel. To attain a flight condition, a highly stagnated air comes into the test cell through a supersonic nozzle. Also, an air ejector of the SETF is used for simulating altitude conditions of the engine, and facility starting. SETF has a free-jet type test cell and this free-jet type test cell can simulate a boundary layer effect between an airplane and engine using facility nozzle, but it is too difficult to predict the nature of the facility. Therefore it is required to understand the starting characteristics of the facility by experiments. In this paper, the starting characteristics of the SETF and modifications of the ejector are described.

• Aerospace Engineering and Technology
• /
• v.4 no.1
• /
• pp.31-38
• /
• 2005

Conceptual design of an Aerostat was completed. Configuration was determined based on wind tunnel test results of aeostat hulls to have longitudinal static stability. Hull surface area and volume were obtained by using of Cubic spline method for given configuration and length. Final length of a hull was determined by iteration process. Cable tension and payload were estimated for conceptual design. A parametric study was performed for various weight and misson altitude. As results, a 30m class aerostat was designed and described.

• Particle and aerosol research
• /
• v.9 no.4
• /
• pp.253-260
• /
• 2013

For a vertical atmospheric aerosol distribution measurement, a very compact and light particle sampling package is developed. This package includes a compact optical particle counter (Hy-OPC), a light and small condensation particle counter (Hy-CPC), sensors (GPS, wind velocity, temperature, humidity), and a communication and system control board. This package is attached to He balloon and the altitude is controlled by a winch. Using this system the vertical particle size distribution was measured. The test results showed that the ground base atmospheric particle measurement result may be a lot different from that high above the ground.