• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.621-628
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• 2005

Recently, it is noticed that autogenous shrinkage of high-performance concrete causes early crack in high performance concrete structures. The purpose of the present study is to derive a realistic equation to estimate the autogenous shrinkage of high performance concrete and to apply to structural analysis. For this purpose, several series of concrete specimens have been tested. When water-binder ratio is fixed to $30\%$, major test variables were the type and contents of mineral admixture. The autogenous shrinkage of HPC with fly ash slightly decreased than that of OPC concrete, but the use of blast furnace slag increased with the autogenous shrinkage. A prediction equation to estimate the autogenous shrinkage of HPC with mineral admixture was derived and proposed in this study. The proposed equation show reasonably good correlation with test data on autogenous shrinkage of HPC with mineral admixture. The finite element program developed in this study provides the useful tool for the flexural analysis including the autogenous shrinkage model. By this program, we know that the tensile stress considering the autogenous shrinkage of reinforced concrete structures increase $20\~27\%$ than that not considering.

• Journal of Internet Computing and Services
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• v.25 no.1
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• pp.123-136
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• 2024

The U.S. Department of Defense, leading global cybersecurity policies, has two main cybersecurity frameworks: the Cybersecurity Maturity Model Certification (CMMC) for external defense industry certification, and the Risk Management Framework (RMF) for internal organizational security assessments. For Republic of Korea military, starting from 2026, the Korean version of RMF (K-RMF) will be fully implemented. Domestic defense industry companies participating in projects commissioned by the U.S. Department of Defense must obtain CMMC certification by October 2025. In this paper, a new standard compliance meta-model (R3C) development methodology that can simultaneously support CMMC and RMF security audit readiness tasks is introduced, along with the implementation results of a compliance solution based on the R3C meta-model. This research is based on practical experience with the U.S. Department of Defense's cybersecurity regulations gained during the joint project by the South Korean and U.S. defense ministries' joint chiefs of staff since 2022. The developed compliance solution functions are being utilized in joint South Korean-U.S. military exercises. The compliance solution developed through this research is expected to be available for sale in the private sector and is anticipated to be highly valuable for domestic defense industry companies that need immediate CMMC certification.

• Land and Housing Review
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• v.6 no.2
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• pp.67-77
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• 2015

Now that it is the current situation that the smooth supply and demand are necessary for 2nd phase of beginning construction and stable development of Gaesung Industrial Complex, this study was willing to offer the planning criteria and model to establish the lodging for the workers in Gaesung Industrial Complex based on the agreement that both South and North Korea agreed in 2007. Regarding the plan, its standard and the alternative were reviewed considering welfare of workers, economic efficiency, technical validity, possibility of agreement and long-term development. The exclusive area per capita was calculated through Labor Standards Act of Korea and status survey of lodging for the workers provided to border line area between China and North Korea and the economic alternative based on one room for 6 persons with the public restroom was compared with that of development type based on one room for 4 persons with indoor restroom. Especially regarding the proposed site, the area with the optimized position was set by considering gradient, accessibility and convenience of development out of the area of Dongchang-ri where was agreed already and the priority of the proposed site that can keep the existing building site and provide was offered. The necessary period for whole construction was set as approximately 36 months. Regarding construction method, RC Rahmen method was selected as the optimized alternative considering the workmanship of manpower of North Korea and conditions of supply and demand of materials and cluster-type vehicle allocation plan based on 4~6 units considering the efficiency of supplying service facilities and convenient facilities along the simultaneous accommodation of 15,000 people was offered. It was analyzed that total business expenses of approximately 80~100 billion Korean Won would required though there were the difference for each alternative in the charged rental way that the development business owner develops by lending the inter-Korea Cooperation Fund and withdraws the rent by the benefit principle. The possibility of withdrawing the rent was analyzed assuming that the period of withdrawing the investment is 30 years. Especially for the operation management after moving, the establishment of the committee of operating the lodging for the workers of Gaesung Industrial Complex (tentative name) was offered with the dualized governance that the constructor takes charge of operational management, collecting fees and management of infrastructure and human resource management is delegated to North Korea.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.449-454
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• 1998

전립선 비대증 및 각종 고형암 조직을 제거하기 위해 이용되는 고강도 집속형 초음파 시스템은 초음파의 조직에 대한 열 효과를 이용한다. 이 경우 수MPa의 고 압력 초음파를 사용하기 때문에 수술시 초음파에 의한 조직내의 공동 현상이 수반되고 이로 인해 초음파의 집속 효과가 감소하게 된다. 본 논문에서는 초음파 공동 현상을 억제하기 위하여 초음파의 주파수 특성을 고려하였다. 초음파의 크기는 일정하게 유지하면서 증가하는 주파수로 변조된 초음파와 비선형 고저파 (nonlinear harmonics) 성분을 포함한 왜곡된 초음파에 대한 기포의 반응을 Gilmore 기포 모델을 이용하여 관찰하였다. 초음파의 주파수 변조는 10 $\mu\textrm{s}$ 동안 초기 주파수 1 MHz부터 시작하여 7 MHz까지 선형적으로 증가하도록 하였다. 파형을 왜곡시키는 고저파 성분의 크기는 주파수에 역 비례 하도록 하였다. 초음파의 기본 주파수는 1 MHz로 하였고, 압력은 0.1 MPa과 1 MPa의 두 경우를 고려하였다. 초기 기포의 반경은 1 $\mu\textrm{m}$으로 하였고, 기포 주위의 유체는 물로 가정하였다. 시뮬레이션 결과로부터, 주파수를 변조시키거나 파형을 왜곡시킨 초음파에 대한 기포의 진동은, 동일한 압력의 정현파에 대한 경우 보다 작은 것으로 나타났다. 주파수 변조된 초음파에 반응한 기포의 진동은 압력이 낮을 때 (0.1 MPa), 변조된 주파수가 기포의 공진 주파수인 3 MHz 부근에서 최대치를 보이다가 이후 급격히 감소하는 경향을 보였다. 반면, 압력이 높아지면 (1 MPa) 기포의 진동은 주파수의 증가와 함께 감소하다가 3 MHz 이상으로 변조 될 경우, 유의한 변화를 보이지 않는 것으로 나타났다. 이 결과는 초음파의 적절한 주파수 성분 조절로 초음파 공동 현상을 일정 수준 억제할 수 있음을 시사한다. 고려가 수반되어야 할 것으로 보인다. 다음 내용을 정리해 보고자 한다.리해 보고자 한다.rc$ 구입할 때 중점적으로 살펴보는 사항은 신선도와 순수재래종 여부, 위생상태였다. 한편 소비자가 언제나 구입할 수 없다는 의견이 85.2%나 되어 원활한 공급과 시장조성이 아직 정착되지 않고 있었다. $\bigcirc$ 현재 유통되고 있는 재래종닭은 소비자 대부분이 잡종으로 인식하고 있었으며, 재래종과 일반육계와의 구별은 깃털색, 피부색, 정강이색등 외관상으로 구별하고 있었다. 체중에 대한 반응은 너무 작다는 의견이었고, 식품으로의 인식도는 비교적 고급식품으로 인식하고 있다. $\bigcirc$ 재래종닭고기의 브랜드화에 대한 견해는 젊고 소득이 높은 계층에서 브랜드화의 필요성을 강조하고 있다. $\bigcirc$ 재래종달걀의 소비형태는 대부분의 소비자가 좋아하였으나 아직 먹어보지 못한 응답자가 많았다. 재래종달걀의 맛에 대해서는 고소하고 독특하여 차별성을 느끼고 있었다. $\bigcirc$ 재래종달걀의 구입장소는 계란판매점(축협.농협), 슈퍼, 백화점, 재래닭 사육 농장등 다양하였으며 포장단위는 10개를 가장 선호하였고, 포장재료는 종이, 플라스틱, 짚의 순으로 좋아하였다. $\bigcirc$ 달걀의 가격은 200원정도를 적정하다고 하였으며, 크기는 (평균 52g)는 가장 적당하다고 인식하고 있으며, 난각색은 대부분의 응답자가 갈색을 선호하였다. $\bigcirc$ 재래종달걀의 구입시 애로사항은 믿을수 없고, 구입장소를 몰라서, 값이 싸다 등이었고, 앞으로 신뢰할 수 있고 위생적인 생산 및 유통체계가 확립될 경우 더 많이 소비하겠다는 의견이었다. $\bigcirc$ 재래닭 판매업소(식당)의 판매형태는 66.7%인 대부분

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.25-35
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• 2012

For a member subjected to direct shear forces, forces are transferred across interface concrete area and resisted by shear transfer capacity. Shear-friction equations in recent concrete structural design provisions are derived from experimental test results where shear-friction capacity is defined as a function of steel reinforcement area contained in the interface. This empirical equation gave too conservative values for concrete members with large amounts of reinforcement. This paper presents a method to evaluate shear transfer strengths and to define ultimate conditions which result in crushing of concrete struts after yielding of longitudinal reinforcement perpendicular to the interface concrete. This method is based on the bi-axial stress field theory where different constitutive laws are applied in various means to gain accurate shear strengths by considering softening effects of concrete struts based on the modified compression-field theory and the softened truss model. The validity of the proposed method is examined by applying to some selected test specimens in literatures and results are compared with recent design code provisions. A general agreement is observed between predicted and measured values at ultimate loading stages in initially uncracked normal-strength concrete test.

• Journal of the Korea Concrete Institute
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• v.25 no.3
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• pp.271-281
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• 2013

The current seismic design code prescribes that a structural wall should be designed as a special shear wall when the building height is more than 60 m and its seismic design category is classified as D. However, the use of a special shear wall has a negative effect on constructability and economic efficiency. In the present study, the seismic performance of a special shear wall and a special shear wall with relaxed reinforcement detail was evaluated through a cyclic reversal loading test. The specimens were constructed to measure the results of the experimental variable regarding the reinforcement details of the special boundary element. Next, the seismic performances of a special shear wall structural system and that of a special shear wall structural system with relaxed reinforcement detail was evaluated by methods proposed in the FEMA P695. The cyclic reversal loading test results of this study showed that the performance of the shear wall with relaxed reinforcement detail was almost similar to the performance of a special shear wall and has the performance which requested from standard. The results of the seismic evaluation showed that all special shear walls with relaxed reinforcement detail are satisfied with the design code and seismic performance.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.2
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• pp.9-19
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• 2002

Steel piers and concrete-filled steel(CFS) piers, in spite of reasonable strength, high ductility, small section, and fast construction, have not been considered as one of alternatives to RC piers even in the highly populated urban area where aseismic safety, limited space and fast construction are indispensably required. This paper, the first of two companion papers for the seismic performance of steel and CFS piers, tests steel and CFS piers under quasi-static cyclic loading to estimate their ductility and strength. Additional details such as rebars and base ribs are added to increase the ductility of a concrete-filled steel pier with minimum additional cost. Also, simplified numerical analyses using nonlinear spring and shell elements are examined for the estimation of the ductility and strength of concrete-filled steel piers and a steel pier. The result shows that concrete-filled steel peirs have higher energy absorption, i.e., ductility and strength than those of steel pier and increasing bonding between in-filled concrete and lower diaphragm, and the improved details of stress concentrated region would be important for the ductility and strength of a pier. Numerical results show that simplified modeling with nonlinear springs and shells has potential to be effective modeling technique to estimate the seismic performance of a concrete-filled steel pier.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.396-402
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• 2021

A cross section in RC flexural members must be designed to satisfy flexural strength and ductility requirements simultaneously. In design provisions, ductile behavior is ensured by a sufficient reinforcement ratio or depth of the neutral axis. If the reinforcement ratio is less than the balanced reinforcement ratio, ductile behavior is secured, and this value is theoretically the maximum reinforcement ratio. But for a cross section with less steel, brittle failure can occur regardless of ductile behavior because of unqualifying a cracking moment. Recently, designs with a minimum steel ratio have been increasing along with the use of high-strength material, so in design provisions, a minimum amount of reinforcement is suggested. In the KCI(2012) standard, a minimum amount of reinforcement was suggested in terms of strength of steel and concrete. But in the revised KCI(2017) standard, a minimum amount of reinforcement was suggested by a relationship between the design flexural strength and cracking moment indirectly. This code can reflect the effect of cover thickness, but a material model must be defined. Therefore, the minimum amount of reinforcement in KCI(2012) and KCI(2017) was examined, and a rational review method was studied by parametric analysis.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.43-53
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• 2004

The current Korean Concrete Design Code(KCI Code) requires the minimum and maximum content of shear s in order to prevent brittle and noneconomic design. However, the required content of the steel reinforcement In KCI Code is quite different to those of the other design codes such as fib-code, Canadian Code, and Japanese Code. Furthermore, since the evaluation equations of the minimum and maximum shear reinforcement for the current KCI Code were based on the experimental results, the equations can not be used for the RC members beyond the experimental application limits. The concrete tensile strength, shear stress, crack inclination, strain perpendicular to the crack, and shear span ratio are strongly related to the lower and upper limits of shear reinforcement. In this research, an evaluation equation for the minimum content of shear reinforcement is theoretical proposed from the Wavier's three principals of the mechanics of materials.

• Journal of Dairy Science and Biotechnology
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• v.32 no.1
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• pp.47-53
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• 2014

In this study, our aim was to investigate the changes in ginsenosides and polyphenols in red ginseng extract fermented by Lactobacillus acidophilus and to manufacture fresh cheese using fermented red ginseng extract. Red ginseng extract (3%, w/v) was fermented by L. acidophilus for 24 h. On performing lactic acid bacteria counts, we determined that L. acidophilus reached its maximum growth phase after 16 h; this was followed by decrease in growth. During fermentation, the levels of ginsenosides Rg3 (20S) and Rg3 (20R) as well as protopanaxadiol (20R), F1, and compound K increased, while those of s Rb2, Rd, Rf, and Rg1 decreased. The pH, titratable acidity, and viable cell counts in fresh cheese prepared using fermented red ginseng extract were measured during the storage period. The pH decreased over time, while titratable acidity and viable cell counts increased with increase in the duration of the storage period. Sensory tests showed that the overall sensory properties of fresh cheese prepared using 1% fermented red ginseng extract were similar to those of the control groups. This result suggests that L. acidophilus-fermented red ginseng has potential for development as a new bioactive material.