• Korean Journal of Agricultural Science
• /
• v.44 no.4
• /
• pp.595-603
• /
• 2017

Crop growth and production cost are greatly influenced by management of environmental factors such as ambient temperature, humidity, and $CO_2$, especially in protected horticulture. Opening and closing of greenhouses is the most important operation for control of these ambient environmental factors, and precise and stable operation requires high performance window motors. In this study, a 400 W precise window motor was constructed, and its performance was evaluated for plastic and glass greenhouses. First, the motor was designed and fabricated by benchmarking of an advanced foreign product. Then, the performance was evaluated through vibration, PCB (Process Control Block), and load tests. Vibration tests resulted in averaged vibration displacement and velocity of the developed motor of 0.002 mm and 0.2267m/s, which were statistically significantly different from those of the target motor. Average vibration acceleration ($0.26m/s^2$) of the developed motor was also significantly different from that ($0.51m/s^2$) of the target motor. PCB tests showed 2 - 4 mm deviation from the target values, and confirmed the operating status and precision of the control. Load tests with a 300 kg load also showed acceptable operating status and durability. Current values were $1.31{\pm}0.06A$ and RPMs were in the range of 2.9 - 3.0. Considering the above results, the developed window motor would be competitive to the target foreign product.

• Journal of the Korean GEO-environmental Society
• /
• v.4 no.4
• /
• pp.25-34
• /
• 2003

This paper is focused on an experimental study in order to investigate the utilization of sewage sludge ash as the cover and liner materials for the waste disposal landfill or as construction materials. A series of tests were performed to evaluate the basic properties, compaction, compressive strength, consolidation, permeability, and CBR of sewage ash. Specially, clay bricks were made as increasing replacement ratio of sewage ash (such as 5, 10, 15, 20, 25, 30%). And tests were fulfilled for its quality. Bentonite and lime were used as the additives to improve permeability properties of sewage sludge ash. As a result of tests, it was shown that the permeability coefficient decreases as increasing bentonite content and the percentage of bentonite was roughly needed 20% to keep the permeability coefficient below $1{\times}10^{-7}cm/sec$. The results of unconfined compression tests show that sewage ash meets the criteria of the unconfined compression strength for cover material. It was shown that the compressive strength decreases as increasing the replacement ratio of sewage sludge ash and the maximum replacement ratio of sewage sludge ash to satisfy the quality standards of the third degree bricks was about 15%.

• Journal of the Korean GEO-environmental Society
• /
• v.4 no.4
• /
• pp.17-23
• /
• 2003

Accurate prediction of consolidation behaviors of the soft ground improved by plastic board drains is not easy because the consolidation characteristics of the improved ground has not been fully elucidated yet. The shape of drains is one of the most important factors which affect the consolidation characteristics of the improved ground. In this paper, a series of model consolidation tests of soft clay ground improved by plastic board drain were carried out, in order to investigate the effect of both plastic board width and stress level on consolidation characteristics of the improved ground. As the results, behaviors of both settlement and excess pore pressure dissipation were elucidated. Also, the non-uniform distribution of water content in the model ground was obtained. Then, in order to investigate the effect of vertical drainage on the consolidation behavior in the model tests, the comparison between experimental consolidation behaviors and Barron's theoretical ones were carried out. As the results, it was elucidated that the consolidation behavior in the model tests was affected not only by radial drainage but also by vertical drainage.

• Journal of the Korean GEO-environmental Society
• /
• v.4 no.3
• /
• pp.19-26
• /
• 2003

Recently, for the design of pile foundations on the soft ground condition, it is recognized that set-up effects are another important factor which influence the characteristics of bearing capacity of pile. In this paper, the thirteen dynamic pile loading tests were performed at the two different construction sites and the end of initial driving(EOID) were also performed and then restrike tests were performed after certain time lag. The H-pile, pipe pile, PHC pile are installed by driving into the loose silty soil and then restrike tests were performed. Nine days after pile driving, the bearing capacity of H and pipe pile were increased whereas there is not bearing capacity increasement with PHC pile. When the dense silty soil, the restrike test results showed that the bearing capacity of H and pipe pile increased up to 1.17 times. The 1-st and 2-nd restrike tests performed after 6 and 12 day, respectively. The results showed that the bearing capacity of PHC pile was decreased but the bearing capacity of piles were increased up to 1.38 times after 13 days with the third restrike test.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.9
• /
• pp.91-99
• /
• 2012

This study describes the investigation based on centrifuge model tests for the clay ground improved by sand compaction pile. In order to clarify the failure behavior of composite ground improved by partly and fully penetrated SCPs. And, in order to compare the effect of the penetration ratio and the replacement area ratio, nine of the centrifuge tests were carried out. From the test results, settlement reduce ratio in the fully penetrated SCPs ground is bigger than that in the partly penetrated SCPs ground. It is also evaluated that angle of the failure of composite ground improved by SCP are 26, 25, $34^{\circ}$ for As=10%, 22, $29^{\circ}$ for As=30%. And as a result of rigid loading tests, surface displacement decreases linearly with the partly penetration ratio increased.

• Journal of the Korean GEO-environmental Society
• /
• v.2 no.2
• /
• pp.13-22
• /
• 2001

In this study, centrifuge model tests were fulfilled to investigate the characteristics of bearing capacity of paper ash as a filling material. The model tests were done varying the footing width and gravity level. The settlement and vertical soil pressure by loading were measured. The results from the tests were compared with the one from FLAC program using finite difference method and bearing capacity theory. After all, it was shown that the characteristics of load-settlement represented the local shear failure, which the settlement ratio s/B showed inflection point around 25~30%. As g-level and footing width were increasing, the load strength was increasing. The ultimate bearing capacity from the tests was very closed the results from Terzaghi's theory. As the distance from footing center was increasing, the vertical soil pressure was decreasing. If E/B is higher than 7, the stress by loading was almost increasing. The vertical displacement from loading was the largest one around under the footing and was almost occurred when the depth>4cm and E/B is higher than 5.0.

• Journal of the Korean GEO-environmental Society
• /
• v.14 no.1
• /
• pp.69-75
• /
• 2013

Suction stress is evaluated from soil water retention curves in order to deduce effective stress in unsaturated soils. $K_0$ consolidated triaxial tests were performed for silty sand to interpret effective stress in consolidation and shearing of unsaturated soils. Suction stresses from both consolidation stress and shear strength in triaxial tests were compared with those from soil water retention curves. The effective stresses on consolidation and shear strength are on each unique line, which are the same as that of the saturated case. It was found that the effective stress from soil water retention curves agrees with those from consolidation and shear strength in triaxial tests.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.4
• /
• pp.45-51
• /
• 2012

The shear strength of weathered granite soils under unsaturated condition was evaluated by $K_0$ consolidated triaxial tests. Various matric suctions in the unsaturated triaxial tests were applied using suction-controlled triaxial test apparatus for weathered granite soils obtained in Daegu. Soil water characteristic curve (SWCC) laboratory tests for drying and wetting procedure were performed and van Genuchten curves were fitted by experimental results. The contribution of matric suction in unsaturated soils is directly correlated to effective stress and evaluated from SWCCs. The effective stresses were estimated from these SWCCs and the relationship between effective stress and unsaturated shear strength was determined. In the effective stress description, the unsaturated shear strength with respect to various suctions indicates unique relationship and almost the same as that of the saturated envelope.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.4
• /
• pp.53-59
• /
• 2012

In this study, strength and durability of a geo-polymer grout material(HIT) was investigated through unconfined compression strength tests(UCS)), scanning electron microscope(SEM), elution tests, and surface observations. UCS tests showed high initial strength and rapid continuous strength increments when compared to labile wasser glass(LW) and space grouting rocket system (SGR) grout materials, which showed strength reduction after 28 days. The higher strength was also reflected in SEM results which showed calcium silicate hydroxide(C-S-H) gels of the dense hydrate range, indicating higher strength and durability. Additionally, elution tests and grout surface observations showed HIT was in good condition and the decrease in weight was minor when under water for six months. LW and SGR showed the grout surface to be constricted and lower durability due to higher weight increase. These results and observations show HIT to be better suited for coastal structural applications than LW and SGR in long terms of strength and durability.

• Journal of the Korean GEO-environmental Society
• /
• v.9 no.2
• /
• pp.31-37
• /
• 2008

Diffused Aeration System (DAS) is one of the remediation methods used for removing contaminants in groundwater and this method brings air bubbles in contact with contaminated water, afterwards transferring contaminants in liquid phase into air phase. In this study, three applicability tests using DAS were conducted in two highly contaminated sites. For these tests, diffused air bubbles are generated with a in-flow rate of 17.1, 44.8 and 76.5 (1/min), respectively. The concentrations of TCE in grounwater and air phase were measured during the tests. The measured results showed that TCE concentration hit the highest value after 6~8 min and afterwards decreased gradually. Also, it was observed that the TCE concentration in air phase changed depending on the rate of diffused aeration. In addition, $K_La$ values from liquid to air phase were calculated based on the test results and those of three tests (test 1, 2 3) were 0.444, 1.158 and 1.836(1/hr), respectively. From the comparison of $K_La$ values, the faster air in-flow rate is, the higher the efficiency of the DAS is.