• Proceedings of the KSR Conference
• /
• 2011.05a
• /
• pp.1774-1785
• /
• 2011

In this paper, Rigid Reinforced Roadbed(RRR) which is expected to have highly applicability to railroad roadbed, was introduced and field tests results were analyzed. Full scale model with 5m height concerning a single track railroad roadbed was constructed. The model had four different sections, which was to assess the effect of geogrid length, spacing, and connection method on deformation characteristics of RRR. Laser displacement meter, earth pressure cell, piezometer, and strain gauge were installed in order to analyze the behavior of reinforced embankment during construction. Horizontal displacements caused by compaction at each section were 20~30% below the displacement limit that of general reinforced retaining wall, which showed that RRR was very stable structure. Maximum tensile strength of reinforcement was withing 10% of the long-term design strength.

• Journal of the Korean Wood Science and Technology
• /
• v.19 no.3
• /
• pp.35-44
• /
• 1991

In this study, thickness 40mm glulams were composed of thickness 5mm, 10mm Quercus laminas and Pinus koraiensis laminas to study on the effect of load variation on transition of neutral axis of laminated veneer lumber(LVL). The transition of neutral axis was examined by strain variation, which was checked by strain gauge. amplifier, recorder, and strain meter. The elasticity of glulam was estimated by E = $\Sigma(E_i\;I_ i)$/I and this estimated elasticity values were compared with the elasticity values of glulam in bending. The result obtained can be summarized as follows: 1. The location of neutral axis of glulam was effected by glulam composition methods 2. The neutral axis did not shift by load variation within proportional limit. 3. The estimated elasticity of glulam by E = $\Sigma(E_i\;I_ i)$/I showed much lower value than the elasticity of glulam in bending.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1998.03a
• /
• pp.94-99
• /
• 1998

The CAD system which enables to design and draw the screw thread gauges was developed and constructed. This system was proposed based on Visual C++ Version 5.0. Even beginner can get drawings as well as concerned data for the manufacturing of screw thread limit gauges by selecting the input data. This system was constructed from relevant standards and regulations (based on the Korean Standard and referred to ISO and JIS), handbooks and textbooks. The system shall provide more powerful and user friendly tool for design and drawing for screw thread gauges such as metric fine and coarse threads, unified fine and coarse threads, Parallel and taper pipe threads. The results of this system are proved to be in good agreement with concerned standards and regulations.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.7 no.5
• /
• pp.85-91
• /
• 1998

The CAD system which enables to design and draw the screw thread gauges was developed and constructed. This system was proposed based on Visual C++ Version 5.0. Even beginners can get drawings as well as concerned data for the manufacturing of screw thread limit gauges by selecting the input data. This system was constructed form relevant standards and regulations and was developed based on the Korean Standard and referred to ISO, JIS, handbooks and textbooks. This system shall provide more powerful and user friendly tool for design and drawing for screw thread gauges such as metric fine and coarse threads, unified fine and coarse threads, parallel and taper pipe threads. The results of this system are proved to be in good agreement with concerned standards and regulations.

• Proceedings of the KSRS Conference
• /
• 2002.10a
• /
• pp.312-316
• /
• 2002

Satellite radar interferometry data shows a strong coherent signal on oyster sea farms where artificial structures installed on the bottom. We obtained 21 highly coherent interferograms from eleven JERS-1 SAR data sets despite of large orbital baseline (~2 km) or large temporal baseline (~l year). The phases observed in sea farms are probably induced by double bouncing on sea surface, and consequently reveal a tide height variation. To restore the absolute sea level changes we counted the number of wrapping by exploiting the intensity of backscattering. Backscattering intensity is closely correlated with the change in water surface height, while interferometry gives the detailed variation within the limit of 2$\pi$ (or 15.3 cm). Comparing the radar measurements with the tide gauge records yielded a correlation coefficient of 0.96 and an ms error of 6.0 cm. The results demostrate that radar interferometry is promising to measure sea level.

• Journal of the Korean Society of Safety
• /
• v.35 no.6
• /
• pp.85-92
• /
• 2020

Wet Scrubber reacts the incoming pollutant gas with cleaning water (water + absorbent) to absorb pollutants and release the clean air to the atmosphere. Wet scrubbers and packed tower scrubbers using this principle are widely used in businesses that emit acid gases. In particular, in the etching process using hydrochloric acid (HCl), alkaline washing water (NaOH) having a pH of about 8 to 11 is used to absorb a large amount of acid gas. However, These salts are attached to the injection nozzle (nozzle), filling material (packing), and the demister (Demister), causing air pollution, human damage, and inoperability due to clogging and acid gas discharge. Therefore, In this study, an improvement plan was proposed to manage the washing water with pH 3~4 acidic washing water. The test method takes samples from the Wet Scrubber flue measurement laboratory twice a month for 1 year. Hydrogen chloride (HCl) concentration (ppm) was measured, and nozzle clogging and scale conditions were measured, compared, and analyzed through a differential pressure gauge and a pressure gauge. As a result of the check, it was visually confirmed that the scale was reduced to 50% or less in the spray nozzle, filler, and demister. In addition, the emission limit of hydrogen chloride in accordance with the Enforcement Regulation of the Air Quality Conservation Act [Annex 8] met 3 ppm or less. Therefore, even if the washing water is operated in an acidic pH range of 3 to 4, it is expected to reduce air pollution and human damage due to clogging of internal parts, and it is expected to reduce maintenance costs such as regular cleaning or replacement of parts.

• Korean Journal of Remote Sensing
• /
• v.35 no.5_2
• /
• pp.831-840
• /
• 2019

Recently, the span length of long-span bridges is getting longer. As a result, it has been suggested that a new concept called 'super long-span bridge'. In case of super long span bridges, the structure is being complicated and the importance of structural stability is being emphasized. However, until recently, the most commonly used sensors (dual axis clinometer, anemometer, strain gauge, etc.) have got limit about the bridge monitoring. Consequently, we researched the application of a Global Navigation Satellite System (GNSS) to improve the limit of the existing sensors. In this study, the dual axis clinometer, the anemometer and the strain gauge together with the GNSS were used to analyze the behavior of a super-long suspension bridge. Also, we propose the detailed method of bridge monitoring using the GNSS. This study consisted of three steps. First step calculated the absolute coordinates of the towers and the longitudinal axis direction of the study bridge using the GNSS. In second step, through the analysis of the long-term behavior in shortly after construction, we calculated the permanent displacement and evaluated the stability of main towers. Third step analyzed the behavior of bridge by the wind direction and was numerically indicated. Consequently, the bridge measurement using the GNSS appeared that the acquired data is able to easy processing according to the analysis purpose. If we will use together the existing measurement sensors with the GNSS on the maintenance of the super long-span bridge, we figure each error of measurement data and improve the monitoring system through calibration. As a result, we acquire the accurate displacement of bridge and figure the behavior of bridge. Consequently, we identified that it is able to construct the effective monitoring system.

• Journal of the Korean Magnetics Society
• /
• v.25 no.3
• /
• pp.87-91
• /
• 2015

This paper reports the design of solenoid in a coilgun for high velocity of projectile in a coilgun system, according to diameter of coil. Coilgun using a magnetic force means a mechanism that can control the magnetic material. When momentarily supply a large current to the solenoid instantaneous magnetic field is created around the coil, the projectile is fired by receiving a magnetic force towards the center of the coil, based on the right-hand rule of Fleming. The velocity of projectile is proportional to the magnetic force generated by the electromagnetic coil. The current affects the life of the coil and the current limit exists. Therefore, the coilgun design, which does not exceed the current limit and the magnetic forces are at the maximum, is required. In this paper, whether it is possible fire looking for the optimal number of turns according to the diameter of the coil from AWG #6 to AWG #18 for the design of the solenoid coil, and comparative analysis firing rate associated with it.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.11 no.2
• /
• pp.72-78
• /
• 2009

The demand for rainfall data in gridded digital formats has increased in recent years due to the close linkage between hydrological models and decision support systems using the geographic information system. One of the most widely used tools for digital rainfall mapping is the PRISM (parameter-elevation regressions on independent slopes model) which uses point data (rain gauge stations), a digital elevation model (DEM), and other spatial datasets to generate repeatable estimates of monthly and annual precipitation. In the PRISM, rain gauge stations are assigned with weights that account for other climatically important factors besides elevation, and aspects and the topographic exposure are simulated by dividing the terrain into topographic facets. The size of facet or grid cell resolution is determined by the density of rain gauge stations and a $5{\times}5km$ grid cell is considered as the lowest limit under the situation in Korea. The PRISM algorithms using a 270m DEM for South Korea were implemented in a script language environment (Python) and relevant weights for each 270m grid cell were derived from the monthly data from 432 official rain gauge stations. Weighted monthly precipitation data from at least 5 nearby stations for each grid cell were regressed to the elevation and the selected linear regression equations with the 270m DEM were used to generate a digital precipitation map of South Korea at 270m resolution. Among 1.25 million grid cells, precipitation estimates at 166 cells, where the measurements were made by the Korea Water Corporation rain gauge network, were extracted and the monthly estimation errors were evaluated. An average of 10% reduction in the root mean square error (RMSE) was found for any months with more than 100mm monthly precipitation compared to the RMSE associated with the original 5km PRISM estimates. This modified PRISM may be used for rainfall mapping in rainy season (May to September) at much higher spatial resolution than the original PRISM without losing the data accuracy.

• Korean Journal of Remote Sensing
• /
• v.18 no.5
• /
• pp.255-261
• /
• 2002

Strong and coherent radar backscattering signals are observed over oyster sea farms that consist of artificial structures installed on the bottom. We successfully obtained 21 coherent interferograms from 11 JERS-1 SAR data sets even though orbital baselines (up to 2 km) or temporal baselines (up to 1 year) were relatively large. The coherent phases preserved in the sea farms are probably formed by double bouncing from sea surface and the sea farming structures, and consequently they are correlated with tide height (or instantaneous sea level). Phase unwrapping is required to restore the absolute sea level. We show that radar backscattering intensity is roughly correlated with the sea surface height, and utilize the fact to determine the wrapping counts. While the SAR image intensity gives a rough range of absolute sea level, the interferometric phases provide the detailed relative height variations within a limit of $2{\pi}$ (or 15.3 cm) with respect to the sea level at the moment of the master data acquisition. A combined estimation results in an instantaneous sea level. The radar measurements were verified using tide gauge records, and the results yielded a correlation coefficient of 0.96 with an r.m.s. error of 6.0 cm. The results demonstrate that radar interferometry is a promising approach to sea level measurement in the near coastal regions.