• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.47-59
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• 2023

In this research, laboratory tests were conducted on clayey sand (SC) to analyze its physical properties, compaction/permeability characteristics, and stress-strain behavior. The main objective was to determine the transitional fines content at which the mechanical properties of sand transition to those of clay, resulting in a change in the geotechnical behavior of the material. Additionally, to assess the practical applicability of SC soil, field data from a soft ground improvement site with significant settlement issues were collected. The settlement characteristics derived from laboratory tests and numerical simulations were then compared and analyzed in relation to the actual settlement data obtained from the field, aiming to evaluate the suitability of the SC soil as a compaction target layer. The laboratory tests and compaction analysis showed that the SC soil exhibited a distinct change in mechanical properties, shifting from sandy behavior to clayey behavior when the fines content exceeded 25%. This transition in mechanical behavior was found to be closely correlated with the content of clay particles within the material. Through numerical simulations of the soft ground site, it was verified that the use of clayey sand with a fines content exceeding the transitional level as a compaction target layer resulted in settlements that closely aligned with the measured settlements, with an average agreement of 91.2%. Based on these findings, it is deemed advisable to incorporate clayey sand with a fines content exceeding the transitional level as part of the compaction target layer in the design of soft ground improvements.

• Journal of the Korean Geotechnical Society
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• v.22 no.10
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• pp.77-91
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• 2006

Domestic practices in shotcrete use have developed in many respects even now, but it still has issues about material, construction, quality standard and so on. In overseas, the construction using high strength shotcrete with $39.2{\sim}58.8 MPa$ of compressive strength is becoming common based on the shotcrete technology of high strength and durability. However, domestic shotcrete design strength is low at around 20.6 MPa of compressive strength and a long term durability is also insufficient. In this paper, field tests using high-quality additives and accelerators were performed to obtain the improvement of shotcrete strength and EFNARC standard was used to evaluate the field test results. In addition, deterioration test combined with the freezing-thawing and carbonation was also performed in order to investigate a long-term durability of high-strength shotcrete. As a result of the field test, the promotion ratio of early strength was $90{\sim}97%$ in case of using alkali-free accelerators. And the compressive strength of the shotcrete using Micro-silica fume was $45.2{\sim}55.8MPa$ and flexible strength was $5.01{\sim}6.66MPa$, so the promotion ratio of strength was $37{\sim}79%$ and $17{\sim}61%$ respectively. The promotion effect of strength by silica fine additives ratio of $7.5{\sim}10%$ for cement mass was much superior to the other cases. It was especially examined that using Micro-silica fume reduced deterioration due to mixed steel fiber and improved a long-term durability of shotcrete.

• Food Science of Animal Resources
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• v.31 no.3
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• pp.451-459
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• 2011

We investigated melting points and sensory characteristics by adding rice bran and roasted soybean to the finishing diet of Hanwoo steers. Thirty-six Hanwoo steers (average age, 20.92 mon-old; average weight, 599.89 kg) were assigned to either Control, Treatment 1 (rice bran) or Treatment 2 (roasted soybean) groups (12 steers/group), considering body weight and age. Supplementation levels of rice bran and roasted soybean were determined to meet total 5% crude fat in the concentrates, and the experimental animals were fed for 314 d until they reached 31.2 mon old. No significant differences were found in the moisture and crude fat content among groups. Melting points of lipid extracted from M. longissimus dorsi, subcutaneous fat, and perirenal fats were 25.83-26.17, 17.26-18.53 and $32.40-33.15^{\circ}C$, respectively, resulting in remarkable differences depending on fat depots. Contents of free amino acids in M. longissimus dorsi related to sweet taste were 39.48 mg/100 g for Treatment 1, which was significantly (p<0.05) higher than those for Control (32.24 mg/100 g), whereas those related to bitter taste were 25.93 mg/100 g for Treatment 2, which was the lowest (p<0.05) among the groups. Fatty acid composition, such as $C_{14:0}$, $C_{16:0}$, $C_{16:1}$, $C_{18:0}$, and $C_{18:1}$, in M. longissimus dorsi was not different among the groups. Results of a panel test on M. longissimus dorsi showed that Treatment 1 scored the highest (p<0.05) in juiciness, and both Treatments 1 and 2 scored higher (p< 0.05) in overall palatability than the Control group. $C_{18:1}$ showed a positive (+) relationship with tenderness (r = 0.650; p<0.05), and $C_{18:0}$ with flavor (0.698; p<0.05). The results suggest that rice bran and roasted soybean are beneficial for improving M. longissimus dorsi sensory characteristics, whereas no significant differences were found in the physico-chemical characteristics among the groups.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.491-496
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• 2010

The direct design modification of problematic component is disallowed in order to sacrifice other major factors such as a stability or a major performance. So, the best design policy is to risvise the immature structural medchanism under the minimal design change as soon as possible. For this paper presents a new design sensitivity analysis based on transmissibility rtio (TR) of response acceleration to find a proper candidate for the minimal design modification. The new sensitivity analysis is based on the fact that the sensitivity of TR over a small design change is inversly proportinal to the magnitude of TR. The theory of proposed design sensitivity analysis is simulated with the variance of TR over a dynamic change. Then, new methodology is appplied for a linear elastic specimen to detect the most sensitive node over a design change using measured accleration data during uni-axial vibration test, The physical verification of the sensitivity method is conducted on the CAE model of a linear elastic specimen by adding concentration mass and the vibration fatigue of the simple specimen is analyzed to estimate the relationship between fatigue behaviors and sensitivity consequences.

• Journal of the Korean Geosynthetics Society
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• v.7 no.2
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• pp.7-13
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• 2008

Geosynthetic damage has attracted a major attention since the introduction of geotextiles for civil construction applications. Geotextile is one of the most useful and effective polymer material in civil construction works and the main function of geotextile is separation, reinforcement, filtering and drainage. Recently, because of the shortage of natural rock, traditional forms of river and coastal structures have become very expensive to build and maintain. This study tries to suggest the method of estimating valid stitching rate and the methodology of sea dyke construction over soft soils for more reasonable application of geotextile mat by studying tensile strength, bursting strength, punching strength, tear strength that are considered when analyzing and designing geotextile mat of a field.

• Journal of Satellite, Information and Communications
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• v.4 no.1
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• pp.8-13
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• 2009

Software-Based GNSS Simulation Tool is being developed by ETRI as a part of development of software-based GNSS Test & Evaluation Facility which will provide test and evaluation environment for various software level application and navigation algorithm in GNSS. The simulation tool will provide digitized GNSS signal generator and receiver including GPS and Galileo. The detailed design and module implementation for the Software GNSS signal generation and signal processing simulation tool and its modular implementation is presented in this paper.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.618-623
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• 2011

A pressure control law to regulate pressure of gas generator is suggested. To design a model based control law, the governing equation which is consisted of Robert and conservation equation is built and verified through the ground burning test. PID and nonlinear adaptive control laws are designed to evaluate the loop response characteristics under the system which has varying eigen properties as combustor volume is increased. It is suggested that new approach, gain scheduling design, is required to overcome the defects identified from numerical simulation results of the two control laws. The newly suggested scheme showed good control performance even under disturbances and measurement noise.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.854-856
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• 2011

A vent relief valve for oxidizer tank has been designed for liquid propellant feeding system of the space launch vehicle. The vent relief valve ensures oxidizer tank ventilation during filling and its protection from overpressure after filling. Tank ventilation during filling is ensured by vent valve and tank protection is ensured by combined operation of relief valve and vent valve. Numerical analysis predicted that pneumatic behavior and dynamic characteristics met the valve requirements. After manufacturing the prototype model, we have been conducting the tests to evaluate the performance of the vent relief valve.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.3 s.96
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• pp.272-279
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• 2005

In this study the optimal isolation system for the prototype HIFD(high impulsive force device) is investigated. For this purpose, firstly, the dynamic behavior of a human body and a transmitted force under specific operation conditions are analyzed through a series of experimental works using the devised test setup. In order to design the optimal dynamic absorbing system, the parameter optimization process is performed using the simplified isolation system model based on the experimental results of linear impulse and transmitted force. Finally, under the parameters satisfying the constraints of the buffering displacement and the transmitted force, the performance of the designed isolation system for the prototype HIFD is evaluated by experiment.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.10a
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• pp.8-8
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• 1999

로켓 엔진 설계는 연소 과정 동안에 발생하는 모든 복잡한 현상을 고려하여 이루어져야하지만 이러한 물리적 변수들을 만족시키면서 설계를 하는 것은 불가능하기 때문에 최근 수치 해석의 발달로 내부 연소 과정에 대환 체계적 접근이 활발히 진행되고는 있으나 아직은 경험과 직관에 따라 각 변수의 중요성을 판단하고 있다고 해도 과언은 아니다. 최근 RP-1과 액체 산소를 추진제로 하는 연소실 압력 200psi, 최대 추력 2.8$\times$$10^{5}$lbf의 액체 엔진 개발을 목표로 본 연구팀은 분사기용 소형 엔진(연소실 압력 200psi, 추력 350lbf) 실험을 시점으로 단계적으로 추력을 증가시키면서 단열재의 삭마 실험과 연소 불안정성을 위한 실험을 준비하고 있다. 첫걸음으로서 135$^{\circ}C$로 FOOF형의 비동류형(unlike) 충돌 제트로 구성되는 3개의 인젝터가 배열된 분사기 시험용 엔진에 관한 실험을 수행 중에 있으나 상대적으로 매우 간단한 엔진임에도 불구하고 실험적으로 내부 연소 과정을 정확히 이해하는 것도 현재로서는 여전히 용이하지 않다.다.