• 한국언론정보학보
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• 제73권
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• pp.35-55
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• 2015

언론행위는 사회적 실천행위다. 따라서 무엇이 옳고 그런가에 대한 판단이 전제되어야 한다. 언론에 철학이 필요한 이유다. 언론철학의 빈곤은 언론의 도구화를 촉진한다. 어떤 권력이나 자본도 언론의 본질적인 철학을 침범하도록 해서는 안 된다. 언론은 언론의 본질적 가치를 지켜야 한다. 언론의 본질적 가치를 침해당했음에도 불구하고 침묵하는 것은 언론 스스로 존재가치를 부정하는 것이다. 즉 자기 배반이다. 언론의 사회적 실천은 언론의 본질적 가치를 지키고 실현하는 과정이다. 따라서 역사적이다. 언론이 역사와 만나는 지점이다. 역사의식 없는 언론은 곧 철학의 빈곤이다. 철학 없는 언론은 역사적 소명의식을 가질 수 없다. 언론철학은 역사를 통해서 현실로서 들어난다. 역사적 현실을 통해 언론철학의 구체성은 들어난다. 언론철학과 언론역사 연구 간의 대화가 필요한 이유다. 따라서 본 연구는 언론철학이 언론역사 속에서 어떻게 형성되고 재구성되는지 살펴본다. 동시에 언론역사 속에서 언론철학은 어떻게 구체화 되는지, 역사적 주체들이 어떻게 언론을 실천하는지, 그것의 언론사적 의미가 무엇인지를 탐구한다.

• Smart Structures and Systems
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• 제20권1호
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• pp.61-74
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• 2017

One of the most reliable and simplest tools for structural vibration control in civil engineering is Tuned Mass Damper, TMD. Provided that the frequency and damping parameters of these dampers are tuned appropriately, they can reduce the vibrations of the structure through their generated inertia forces, as they vibrate continuously. To achieve the optimal parameters of TMD, many different methods have been provided so far. In old approaches, some formulas have been offered based on simplifying models and their applied loadings while novel procedures need to model structures completely in order to obtain TMD parameters. In this paper, with regard to the nonlinear decision-making of fuzzy systems and their enough ability to cope with different unreliability, a method is proposed. Furthermore, by taking advantage of both old and new methods a fuzzy system is designed to be operational and reduce uncertainties related to models and applied loads. To design fuzzy system, it is required to gain data on structures and optimum parameters of TMDs corresponding to these structures. This information is obtained through modeling MDOF systems with various numbers of stories subjected to far and near field earthquakes. The design of the fuzzy systems is performed by three methods: look-up table, the data space grid-partitioning, and clustering. After that, rule weights of Mamdani fuzzy system using the look-up table are optimized through genetic algorithm and rule weights of Sugeno fuzzy system designed based on grid-partitioning methods and clustering data are optimized through ANFIS (Adaptive Neuro-Fuzzy Inference System). By comparing these methods, it is observed that the fuzzy system technique based on data clustering has an efficient function to predict the optimal parameters of TMDs. In this method, average of errors in estimating frequency and damping ratio is close to zero. Also, standard deviation of frequency errors and damping ratio errors decrease by 78% and 4.1% respectively in comparison with the look-up table method. While, this reductions compared to the grid partitioning method are 2.2% and 1.8% respectively. In this research, TMD parameters are estimated for a 15-degree of freedom structure based on designed fuzzy system and are compared to parameters obtained from the genetic algorithm and empirical relations. The progress up to 1.9% and 2% under far-field earthquakes and 0.4% and 2.2% under near-field earthquakes is obtained in decreasing respectively roof maximum displacement and its RMS ratio through fuzzy system method compared to those obtained by empirical relations.

• Earthquakes and Structures
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• 제13권1호
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• pp.59-66
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• 2017

Modern seismic codes rely on performance-based seismic design methodology which requires that the structures withstand inelastic deformation. Many studies have focused on the inelastic deformation ratio evaluation (ratio between the inelastic and elastic maximum lateral displacement demands) for various inelastic spectra. This paper investigates the inelastic response spectra through the ductility demand ${\mu}$, the yield strength reduction factor $R_y$, and the inelastic deformation ratio. They depend on the vibration period T, the post-to-preyield stiffness ratio ${\alpha}$, the peak ground acceleration (PGA), and the normalized yield strength coefficient ${\eta}$ (ratio of yield strength coefficient divided by the PGA). A new inelastic deformation ratio $C_{\eta}$ is defined; it is related to the capacity curve (pushover curve) through the coefficient (${\eta}$) and the ratio (${\alpha}$) that are used as control parameters. A set of 140 real ground motions is selected. The structures are bilinear inelastic single degree of freedom systems (SDOF). The sensitivity of the resulting inelastic deformation ratio mean values is discussed for different levels of normalized yield strength coefficient. The influence of vibration period T, post-to-preyield stiffness ratio ${\alpha}$, normalized yield strength coefficient ${\eta}$, earthquake magnitude, ruptures distance (i.e., to fault rupture) and site conditions is also investigated. A regression analysis leads to simplified expressions of this inelastic deformation ratio. These simplified equations estimate the inelastic deformation ratio for structures, which is a key parameter for design or evaluation. The results show that, for a given level of normalized yield strength coefficient, these inelastic displacement ratios become non sensitive to none of the rupture distance, the earthquake magnitude or the site class. Furthermore, they show that the post-to-preyield stiffness has a negligible effect on the inelastic deformation ratio if the normalized yield strength coefficient is greater than unity.

• Earthquakes and Structures
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• 제12권4호
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• pp.397-407
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• 2017

To estimate the structural seismic demand, some methods are based on an equivalent linear system such as the Capacity Spectrum Method, the N2 method and the Equivalent Linearization method. Another category, widely investigated, is based on displacement correction such as the Displacement Coefficient Method and the Coefficient Method. Its basic concept consists in converting the elastic linear displacement of an equivalent Single Degree of Freedom system (SDOF) into a corresponding inelastic displacement. It relies on adequate modifying or reduction coefficient such as the inelastic deformation ratio which is usually developed for systems with known ductility factors ($C_{\mu}$) and ($C_R$) for known yield-strength reduction factor. The present paper proposes a rational approach which estimates this inelastic deformation ratio for SDOF bilinear systems by rigorous nonlinear analysis. It proposes a new inelastic deformation ratio which unifies and combines both $C_{\mu}$ and $C_R$ effects. It is defined by the ratio between the inelastic and elastic maximum lateral displacement demands. Three options are investigated in order to express the inelastic response spectra in terms of: ductility demand, yield strength reduction factor, and inelastic deformation ratio which depends on the period, the post-to-preyield stiffness ratio, the yield strength and the peak ground acceleration. This new inelastic deformation ratio ($C_{\eta}$) is describes the response spectra and is related to the capacity curve (pushover curve): normalized yield strength coefficient (${\eta}$), post-to-preyield stiffness ratio (${\alpha}$), natural period (T), peak ductility factor (${\mu}$), and the yield strength reduction factor ($R_y$). For illustrative purposes, instantaneous ductility demand and yield strength reduction factor for a SDOF system subject to various recorded motions (El-Centro 1940 (N/S), Boumerdes: Algeria 2003). The method accuracy is investigated and compared to classical formulations, for various hysteretic models and values of the normalized yield strength coefficient (${\eta}$), post-to-preyield stiffness ratio (${\alpha}$), and natural period (T). Though the ductility demand and yield strength reduction factor differ greatly for some given T and ${\eta}$ ranges, they remain take close when ${\eta}>1$, whereas they are equal to 1 for periods $T{\geq}1s$.

• 한국언론정보학보
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• 제60권
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• pp.5-27
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• 2012

2008년 이후 정부의 공영방송 사장 임명과 정부 비판 보도의 제한, 시사 프로그램의 폐지 압력, 그리고 재벌과 보수언론의 방송진출을 허용한 언론법 개정 등은 언론 민주화를 위협하고 있다. 이러한 상황에서 권위주의 정부 시절 언론 민주화를 위해 노력했던 언론인의 정신과 실천을 되돌아보고 숙고해서 한국 저널리즘의 미래상을 재설계 할 필요성이 있다. 송건호는 정부의 언론 장악 시도에 정면으로 맞서 보도통제를 반대하고, 국민을 위한 언론의 역할에 대해 진지한 성찰과 고민을 계속한 점에서 오늘날의 언론인이 언론 민주화의 위기를 극복할 수 있도록 현실적인 언론사상을 제시해 준다. 송건호의 언론사상을 살펴보기 위해 문헌연구 및 관련 언론인과의 인터뷰를 진행했다. 송건호의 언론사상은 민족언론, 민주언론, 독립언론 등으로 요약됐다. 첫째, 민족언론은 분단된 남북관계와 주변 강대국의 영향이 지속되는 상황 속에서 언론이 민족의 자긍심을 세우고 통일의 책무를 강조하며, 우리나라와 세계 역사에 대한 지식과 통찰력을 가져야 함을 의미한다. 둘째, 민주언론은 언론이 민주주의 사회의 기반이자 유지, 발전 양식이라는 점에서 포기할 수 없는 원칙이다. 셋째, 독립언론은 언론이 기업의 형태로 존재, 운영되는 과정에서 내외의 압력에서 자유로울 때 언론의 책무가 구현됨을 강조한다. 송건호의 언론사상은 언론 민주화의 위기를 회복하기 위한 철학과 방법론 모색의 기초 자료라는 점에서 언론학적 의미가 매우 크다.