• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.825-828
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• 2004

The objective of this study is to examine mechanical properties of ductile fiber-reinforced mortar designed based on micromechanics. This mortar was produced by employing raw materials commercially available in Korea. To verify property level of this material in uniaxial tension, a series of direct tensile tests were performed with varying water cement ratio. In addition to this, flexural tests as well as compressive tests were carried out. Experiments revealed that the fiber reinforced mortar exhibited high ductility represented by strain hardening behavior in uniaxial tension. Significant enhancements of ductility, in terms of strain at peak stress and post-peak behavior, were also observed during the tests in compression and in bending.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.4
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• pp.239-244
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• 1998

Susceptibility of soybean cultivars to Calonectria illicicola was evaluated in a greenhouse by inoculating seedlings with mycelium in agar discs placed on the stems at the soil line. A range of responses was detected among cultivars following inoculation with a virulent isolate of C.ilicicola. Rankings of cultivars between greenhouse tests 1 and 2 were similar for disease severity and areas under the disease progress curves (AUDPC). In addition, rankings of cultivars for Final disease severity were highly correlated with AUDPC in test 1 ($r_s$ =0.88, t =5.48, p<0.001), test 2 ($r_s$ =0.99, t =22.10, p<0.001), and when tests were combined ($r_s$=0.89, t=5.82, p<0. 001). Final disease severity and AUDPC consistently identified Asgrow 7986, Braxton, Cajun, and Forrest as soybean cultivars least susceptible to red crown rot. In 1993 and 1994 field tests, a range in disease susceptibility was observed for tested cultivars but none was completely resistant. Soybean cultivars Braxton, Cajun, and Forrest, which were least susceptible to red crown rot in greenhouse tests, also ranked among cultivars with the lowest disease incidence and AUDPC in field tests. Comparisons .between rankings of the eight cultivars common to greenhouse and field tests showed a correlation between final disease severity from combined greenhouse tests and both final disease incidence ($r_s$=0.63, t =1.99, p<0.1) and AUDPC ($r_s$=0.60, t =1.82, p < 0.2) from the combined field tests. However, AUDPC from greenhouse tests did not correlate with either final disease incidence or AUDPC from field tests. The green-house screening method provided consistent results between greenhouse and field tests and successfully identified the least susceptible cultivars Braxton, Cajun, and Forrest.

• Journal of Multimedia Information System
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• v.7 no.2
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• pp.175-188
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• 2020

The paper focuses on conception and development of complex systems composed mainly by a pump syringe subsystem and an electronically injector that facilitates patients saving data operation for medical staff use. We successfully developed conventional approaches for medical system staff requirements, such as system boundary conditions. Decisions at a given level are studied. We propose a complex system architecture, based mainly on patients collected data and ordered stepper injection parameters. System is successfully simulated and prototyped. Design and implement tests are accomplished, the proposed system ensures both the electric syringe pump and the electric injector operation. In addition, this new system introduces several additional options as patient database development and automation injection operation. Development and software operating tests to create a visualization control interface are validated. The solution performs syringe function and electronic injector. User can manage a syringe in two C modes of technology. We propose a program composed of two linked parts. If an error such radiologist bad target selection is made, an image with lower intrinsic quality emerges. Developed Shoot syringe different electronic cards are simulated and prototyped, in addition, maps are driven, prototype. All tests results are accomplished.

• Computers and Concrete
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• v.18 no.3
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• pp.337-354
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• 2016

To study the influence on fracture properties of reinforced concrete wedge splitting test specimens by the addition of reinforcement, and the restriction of steel bars on crack propagation, 7 groups reinforced concrete specimens of different reinforcement position and 1 group plain concrete specimens with the same size factors were designed and constructed for the tests. Based on the double-K fracture criterion and tests, fracture toughness calculation model which was suitable for reinforced concrete wedge splitting tensile specimens has been obtained. The results show that: the value of initial craking load Pini and unstable fracture load Pun decreases gradually with the distance of reinforcement away from specimens's top. Compared with plain concrete specimens, addition of steel bar can reduce the value of initial fracture toughness KIini, but significantly increase the value of the critical effective crack length ac and unstable fracture toughness KIun. For tensional concrete member, the effect of anti-cracking by reinforcement was mainly acted after cracking, the best function of preventing fracture initiation was when the steel bar was placed in the middle of the crack, and when the reinforcement was across the crack and located away from crack tip, it plays the best role in inhibiting the extension of crack.

• Advances in concrete construction
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• v.11 no.1
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• pp.59-71
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• 2021

This research aims to study the utilization of olive waste ash (OWA) in the production of concrete as a partial substitute for cement. Effects of using OWA on the physical and mechanical properties of concrete mixtures have been investigated. This is done by carrying out tests involving the addition of various percentages of OWA to cement (0%, 5%, 10% and 15%). For each percentage, tests were performed on both fresh and hardened concrete; these included slump test, unit weight test and compressive strength test after 7, 28 and 90 days. Durability tests were investigated in solutions containing 5% NaOH and MgSO4 by weight of water. In addition, resistance to high temperatures was tested by subjecting the cubes to high temperatures of up to 170℃. The results of this research indicate that a higher percentage of OWA gives a lower compressive strength and lower workability but higher performance in terms of durability against both different weather conditions and high temperatures.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.4 no.1
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• pp.49-62
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• 2023

Phthalates are animal carcinogens. Potassium hydrogen phthalate (KHP), which has the least complicated structure among phthalates, is used for the analysis of total organic carbon and formaldehyde. However, its toxicity has not been confirmed. A 24-hour acute toxicity test was performed using Daphnia magna, a water flea used to evaluate aquatic toxicity owing to its high sensitivity. The lowest observed effect concentration of KHP was found to be 240 mg/L. The effects of phosphorus, nitrogen, and Cr(6+), which are able to be discharged along with KHP, were also confirmed using tests. At 240 mg/L KHP, toxicity increased as phosphorus, nitrogen, and Cr(6+) increased. In addition, tests were performed to confirm the half maximal effective concentration of KHP. Through 10 test repetitions, the average ecotoxicity value was found to be 0.3, the average half maximal effective concentration was 327.75 mg/L, and the coefficient of variation (%) was 3.16%; because the latter value is lower than 25%, which is what is generally suggested for the water pollution standard method, the reproducibility of the tests is sufficient to replace the existing standard reference toxicity test that uses potassium dichromate. In addition, the half maximum effective concentration of potassium hydrogen phthalate is approximately 218 times more than that of potassium dichromate; therefore, toxicity is relatively low. In conclusion, KHP is a feasible alternative to the highly toxic potassium dichromate for performing the standard reference toxicity test.

• KSTLE International Journal
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• v.8 no.1
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• pp.11-15
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• 2007

The mechanical face seal has been tested in Korea Aerospace Research Institute (KARl) for turbopump applications. In the turbopump under current development, the mechanical face seal is installed between fuel pump and turbine to prevent a mixture of fuel and combustion gas. Generally the mechanical face seal in turbopump is exposed to severe environment because of great rotational speed, high temperature of combustion gas and high level of pressure difference. Thus a series of tests were performed to guarantee the reliability of mechanical face seal by means of simulating the practical operating conditions. The tests were conducted up to 20,000 rpm with pressure difference of 800 kPa and temperature of 620 K In addition several carbon materials for mechanical face seal were conducted to the tests to compare the life time. During the tests, the performance against leakage was monitored and the carbon wear was also measured to estimate the life of a mechanical face seal The results show that the leakage flow rates of mechanical face seal is ignorable compared to an overall flow rate of fuel pump. The carbon material which has the finest wear resistance was found during the tests. Lastly no critical failure of mechanical face seal was found during the tests and the reliability of mechanical face seal for turbopump was successfully proved.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.50-57
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• 2004

In this study reinforcing effect of soil nailed-drilled shafts subjected to axial and lateral loads were evaluated. Special attention was given to the reinforcing effects of soil nails placed from the drilled shafts to surrounding weathered- and soft-rocks based on model tests, numerical analyses and load tests. The model tests and numerical analyses are conducted to analyze the reinforcing effect of various conditions of number, inclination, position and length. The results of 1/40 scale model tests and numerical analyses show that as the number of reinforcing level increases, the incremental effect of reinforcement tends to increase, whereas the reinforcing effect on relative position is negligible. In addition there is a reinforcing effect as the inclination angle increaes up to 30 degrees. Based on the results of tensile load tests, soil nailed-drilled shafts has a considerably smaller settlement to reach the ultimate level when compared with the result of un-reinforced drilled shafts. For compression tests, there is a reinforcing effect of about 200% measured.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.129-134
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• 2003

The importance of understanding the response of structural composites to impact and CAI cannot be overstated to develop analytical models for impact damage and CAI strength predictions. This paper presents experimental findings observed from quasi-static lateral load tests, low velocity impact tests, CAI strength and open hole compressive strength tests using 3mm thick composite plates ($[45/-45/0/90]_{3s}$ - IM7/8552). The conclusion is drawn that damage areas for both quasi-static lateral load and impact tests are similar and the curves of several drop weight impacts with varying energy levels (between 5.4 J and 18.7 J) fallow the static curve well. In addition, at a given energy the peak force is in good agreement between the static and impact cases. From the CAI strength and open hole compressive strength tests, it is identified that the failure behaviour of the specimens was very similar to that observed in laminated plates with open holes under compression loading. The residual strengths are in good agreement with the measured open hole compressive strengths, considering the impact damage site as an equivalent hole. The experimental findings suggest that simple analytical models for the prediction of impact damage area and CAI strength can be developed on the basis of the failure mechanism observed from the experimental tests.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.4
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• pp.230-240
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• 2020

The aim of this study was to investigate the manoeuvrability of a ship in different Center of Gravity (CG) conditions. Free Running Model Tests (FRMT), such as 35°turning circle tests, 20/20 zigzag manoeuvring tests, and 10/10 zigzag manoeuvring tests, were conducted in three GM and three trim conditions with 1/65.83 scaled KRISO Container Ship (KCS). The test results indicated that KCS in the lower GM condition and the trim by bow condition showed reduced advance and tactical diameter in turning circle tests and increased overshoot angles in zigzag tests, and those manoeuvring indices were strongly related with roll angle. In addition, sensitivity indices for three-axis CG position were suggested with prior research, and it showed that y-axis CG position significantly affected manoeuvrability of KCS due to the low GM. Therefore, in the case of KCS, it is evident that the roll angle during manoeuvre is closely related with manoeuvring indices.