• Journal of Radiation Protection and Research
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• 제41권4호
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• pp.339-343
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• 2016

Background: Evaluation of deoxyribonucleic acid (DNA)-strand break is important to elucidate the biological effect of ionizing radiations. The conventional methods for DNA-strand break evaluation have been achieved by Agarose gel electrophoresis and others using an electrical property of DNAs. Such kinds of DNA-strand break evaluation systems can estimate DNA-strand break, according to a molecular weight of DNAs. However, the conventional method needs pretreatment of the sample and a relatively long period for analysis. They do not have enough sensitivity to detect the strand break products in the low-dose region. Materials and Methods: The sample is water, methanol and plasmid DNA solution. The plasmid DNA pUC118 was multiplied by using Escherichia coli JM109 competent cells. The resonance frequency and Q-value were measured by means of microwave dielectric absorption spectroscopy. When a sample is located at a center of the electric field, resonance curve of the frequency that existed as a standing wave is disturbed. As a result, the perturbation effect to perform a resonance with different frequency is adopted. Results and Discussion: The resonance frequency shifted to higher frequency with an increase in a concentration of methanol as the model of the biological material, and the Q-value decreased. The absorption peak in microwave power spectrum of the double-strand break plasmid DNA shifted from the non-damaged plasmid DNA. Moreover, the sharpness of absorption peak changed resulting in change in Q-value. We confirmed that a resonance frequency shifted to higher frequency with an increase in concentration of the plasmid DNA. Conclusion: We developed a new technique for an evaluation of DNA damage. In this paper, we report the evaluation method of DNA damage using microwave dielectric absorption spectroscopy.

• Steel and Composite Structures
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• 제12권1호
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• pp.31-51
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• 2012

Local buckling can be ignored for hot-rolled ordinary strength steel equal angle compression members, because the width-to-thickness ratios of the leg don't exceed the limit value. With the development of steel structures, Q420 high strength steel angles with the nominal yield strength of 420 MPa have begun to be widely used in China. Because of the high strength, the limit value of the width-to-thickness ratio becomes smaller than that of ordinary steel strength, which causes that the width-to-thickness ratios of some hot-rolled steel angle sections exceed the limit value. Consequently, local buckling must be considered for 420 MPa steel equal angles under axial compression. The existing research on the local buckling of high strength steel members under axial compression is briefly summarized, and it shows that there is lack of study on the local buckling of high strength steel equal angles under axial compression. Aiming at the local buckling of high strength steel angles, this paper conducts an axial compression experiment of 420MPa high strength steel equal angles, including 15 stub columns. The test results are compared with the corresponding design methods in ANSI/AISC 360-05 and Eurocode 3. Then a finite element model is developed to analyze the local buckling behavior of high strength steel equal angles under axial compression, and validated by the test results. Following the validation, a finite element parametric study is conducted to study the influences of a range of parameters, and the analysis results are compared with the design strengths by ANSI/AISC 360-05 and Eurocode 3.

• 재무관리연구
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• 제27권2호
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• pp.63-84
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• 2010

본 논문에서는 환헤지가 기업가치에 미치는 직접적인 영향을 실증분석한다. 2000~2008년 기간의 환변동보험 데이터를 이용하며 종속변수로는 Tobin's Q, 설명변수로는 환헤지 대용변수를 사용하는 패널분석모형을 설계하였다. 패널자료의 특성을 반영할 수 있도록 샘플기업의 헤징행태(hedging behavior)의 변화에 주목하였으며, 환헤지 더미, 환헤지비율 두 변수를 헤징대용변수로 각각 사용하였다. 실증분석 결과, 유가증권시장에 상장된 기업 중 환변동보험에 가입한 기업의 경우 환헤지가 기업가치에 긍정적인 것으로 나타났다. 환헤지를 하는 경우가 환헤지를 하지 않는 경우에 비하여 기업가치를 7.4% 높이는 것으로 나타났다. 이는 환헤지로 인한 헤징프리미엄이 7.4%라는 것을 의미한다. 그리고 환헤지비율이 높을수록 기업가치는 제고되는 것으로 나타났다. 기타 통제변수들인 기업규모, 수익성, 부채비율 등도 기업가치에 긍정적인 결과를 나타내었다. 본 논문의 의의는 학술적으로 환헤지의 경제적 효과를 직접 실증분석하였다는 점이다. 지금까지 헤징과 기업가치간의 관계를 직접 실증한 국내 연구문헌은 찾을 수 없었다. 기업경영 면에서는 기업가치 제고를 위한 최적 헤징전략이 존재하며, 회사 실정에 맞는 헤징정책이 필요하다는 점을 발견하였다. 정책적으로는 환변동보험의 활성화 필요성을 제기하였다. 정보비대칭으로 인해 시장을 통한 환리스크 관리가 쉽지 않은 중소수출기업들이 환변동보험을 보다 쉽고 공정하게 활용할 수 있어야 한다.

• 기술혁신연구
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• 제25권3호
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• pp.265-297
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• 2017

본 연구는 연구개발스톡과 6개의 지식스톡(특허의 질적 가치)이 기업의 시장가치에 미치는 영향을 포함하는 연구모형을 설정하여 기업의 시장가치와의 상관관계를 분석하였다. 구체적으로 토빈Q 모형을 사용하여 우리나라 402개 기업의 미국특허등록 108,851건(연도관측치 2,795건)의 특허를 분석하였다. Hall모형의 확장 모형 분석결과, 연구개발스톡/자산, 청구항스톡/특허스톡, 인용스톡/특허스톡 등이 기업의 시장가치에 긍정적인 영향을 미치는 것으로 나타났으며, 유의수준이 높진 않지만 피인용스톡/특허스톡, 발명자스톡/특허스톡 등도 기업의 시장가치에 긍정적인 영향을 미칠 수 있는 것으로 분석되었다. 이러한 결과에 따라 특허경영시대에 특허의 질적 수준 고도화와 특허의 가치 제고를 위한 정책 방안이 마련되어야 할 것으로 보인다.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• 제21권1호
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• pp.17-30
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• 1993

해양에서의 전선형성에 관해 그 발생기작을 중심으로 검토되었으며, 특히 조석혼합에 의해 발생하는 연안전선의 발생기작이 조석전선 형성에 관계되는 미세구조의 변화를 포함하는 연안의 해수 수직면에 대한 일차원 모형을 통해 이해되었다. 이로부터 조석전선의 형성을 예측하는 새로운 기준을 설정하였다. 모형으로부터 계산된 해수의 밀도 및 난류에네지의 시간에 따른 발달은 수온약층의 형성하기 위한 조건은 $\delta$가 클 때는 (${\delta}>0.5$)$R{\delta}^{-}$ constant로서 주어지지만, $\delta$가 0에 접근함에 따라 $\delta$에 점점 무관하게 됨을 보여준다. 여기서, $R=H^4Q/{K_b}^3,{\;}{\delta}=1-D_o/H$, Q는 해수면에서의 부력속, $K_b$는 해저에서의 와확산 계수, $D_o$ 아래서 수온약층의 깊이는 조석혼합이 증가함에 따라 감소하는 것이 발견되었다. 그 결과는 기존의 연구와 비교 검토되었다.

• 한국기계기술학회지
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• 제20권6호
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• pp.809-817
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• 2018

The model predictive controller performance of the mobile robot is set to an arbitrary value because it is difficult to select an accurate value with respect to the controller parameter. The general model predictive control uses a quadratic cost function to minimize the difference between the reference tracking error and the predicted trajectory error of the actual robot. In this study, we construct a predictive controller by transforming it into a quadratic programming problem considering velocity and acceleration constraints. The control parameters of the predictive controller, which determines the control performance of the mobile robot, are used a simple weighting matrix Q, R without the reference model matrix $A_r$ by applying a quadratic cost function from which the reference tracking error vector is removed. Therefore, we designed the predictive controller 1 and 2 of the mobile robot considering the constraints, and optimized the controller parameters of the predictive controller using a genetic algorithm with excellent optimization capability.

• 아태비즈니스연구
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• 제12권3호
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• pp.71-85
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• 2021

Purpose - Prior studies have found that the characteristics of managers, corporate governance structure, corporate social responsibility and so on affect firm value. This study explores whether managerial overconfidence affects firm value through empirical analysis. Design/methodology/approach - Korean-listed non-financial companies from 2011 - 2017 are collected as the research sample. Firm value is measured by Tobin's Q, and managerial overconfidence is measured using a composite index encompassing various financial data. OLS and fixed effect model are used to investigate the relationship between managerial overconfidence and firm value. Findings - Managerial overconfidence is positively associated with firm value. Additional analysis reveals the following: (1) In the three subsamples of large, backbone, and small- and medium-sized enterprises, managerial overconfidence is beneficial to firm values. (2) Managerial overconfidence increases firm value on the t+1 year. Research implications or Originality - We use a comprehensive index with higher trust and feasibility to measure manager overconfidence and empirically confirm that managerial overconfidence can become a factor to improve firm value. Thus, it is necessary for shareholders to adopt an objective and neutral attitude and reasonably understand the psychological characteristics of managers when selecting CEOs. In addition, it is necessary to continue to optimize the measurement method of managerial overconfidence.

• 한국세라믹학회지
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• 제36권9호
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• pp.915-922
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• 1999

Microwave dielectric properties and far infrared reflectivity spectra of the (Zr0.8Sn0.2)TiO4 ceramics were inves-tigated with the various cooling rate. Dielectric constant was nearly same value while the unloaded Q value was largely affected by cooling rate. The Q.f of 42,140 at 7 GHz was obtained for the specimens with cooling rate of 1$^{\circ}C$/min. The effect of the cooling rate on the change of the ionic the electronic polarization and the intrinsic microwave loss of the specimens were investigated by the infrared reflectivity spectra from 50 to 4000cm-1 which were calculated by Kramers-Kroning analysis and the classical oscillator model. The relative tendency of microwave dielectric properties of the specimens calculated from the relfectivity data were in good agreement with the results by the post resonant method.

• 한국전기전자재료학회논문지
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• 제22권4호
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• pp.285-289
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• 2009

Small RFID tag antenna were fabricated on Si substrate and their physical and electrical properties were evaluated. With decreasing the size of tag antenna on Si substrate, small SMD-type RFID tags could be fabricated, which is very useful for various applications including PCB tracking. Firstly, electromagnetic properties on tag antenna pattern were simulated with HFSS. The setup frequency was 13.56 MHz of HF-band RFID. The line-width and line-gap were modeled in the range of $50{\sim}200{\mu}m$. S parameters, SRF, and Q value were calculated from the model. When the line-width and line-gap were 100 urn and the loop-turn was 10, the SRF was 80 MHz and the Q value was ca. 9. When the microstrip antenna pattern of aluminum was fabricated by using DC sputtering, Vpp of ca. 1.6 V was obtained when the reader-tag distance was 40 mm.

• Geomechanics and Engineering
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• 제28권4호
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• pp.359-374
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• 2022

Geology conditions are crucial in decision-making during the planning and design phase of a tunnel project. Estimation of the geology conditions of road tunnels is subject to significant uncertainties. In this work, the effectiveness of a novel regression method in estimating geological or geotechnical parameters of road tunnel projects was explored. This method, called Gaussian process regression (GPR), formulates the learning of the regressor within a Bayesian framework. The GPR model was trained with data of old tunnel projects. To verify its feasibility, the GPR technique was applied to a road tunnel to predict the state of three geological/geomechanical parameters of Rock Mass Rating (RMR), Rock Structure Rating (RSR) and Q-value. Finally, in order to validate the GPR approach, the forecasted results were compared to the field-observed results. From this comparison, it was concluded that, the GPR is presented very good predictions. The R-squared values between the predicted results of the GPR vs. field-observed results for the RMR, RSR and Q-value were obtained equal to 0.8581, 0.8148 and 0.8788, respectively.