• Advances in aircraft and spacecraft science
• /
• v.3 no.3
• /
• pp.271-298
• /
• 2016

In this paper, we study a problem of passive suppression of helicopter Ground Resonance (GR) using a single degree freedom Nonlinear Energy Sink (NES), GR is a dynamic instability involving the coupling of the blades motion in the rotational plane (i.e. the lag motion) and the helicopter fuselage motion. A reduced linear system reproducing GR instability is used. It is obtained using successively Coleman transformation and binormal transformation. The analysis of the steadystate responses of this model is performed when a NES is attached on the helicopter fuselage. The NES involves an essential cubic restoring force and a linear damping force. The analysis is achieved applying complexification-averaging method. The resulting slow-flow model is finally analyzed using multiple scale approach. Four steady-state responses corresponding to complete suppression, partial suppression through strongly modulated response, partial suppression through periodic response and no suppression of the GR are highlighted. An algorithm based on simple criterions is developed to predict these steady-state response regimes. Numerical simulations of the complete system confirm this analysis of the slow-flow dynamics. A parametric analysis of the influence of the NES damping coefficient and the rotor speed on the response regime is finally proposed.

• Journal of the Korean Geographical Society
• /
• v.41 no.2 s.113
• /
• pp.188-194
• /
• 2006

Three-dimensional topological data is essential for 3D modeling and application such as emergency management and 3D network analysis. This paper reviewed current 3D topological data model and developed a method to construct 3D topological node-relation data structure from 2D computer aided design (CAD) data. The method needed two steps with medial axis-transformation and topological node-relation algorithms. Using a medial-axis transformation algorithm, the first step is to extract skeleton from wall data that was drawn polygon or double line in a CAD data. The second step is to build a topological node-relation structure by converting rooms to nodes and the relations between rooms to links. So, links represent adjacency and connectivity between nodes (rooms). As a result, with the conversion method 3D topological data for micro-level sub-unit of each building can be easily constructed from CAD data that are commonly used to design a building as a blueprint.

• (The)Korea Educational Review
• /
• v.22 no.3
• /
• pp.169-192
• /
• 2016

The purpose of this study is to investigate the relations between religious socialism and education of Martin Buber(1878~1965), a theistic existentialist. Buber suggested religious socialism as an alternative to modern capitalist society which has many problems. Buber's religious socialism is based on the communitarianism of Hasidism. Buber considered 'true' socialism must be based on decentralized associations, not based on centralized state apparatuses. For establishing this kind of socialism, human will and mind are the most important. Thus, education takes a very important role in the process of social transformation. According to Buber, education and pedagogy should contribute to overcoming modern society's problems by pursuing the construction of community(true socialist society). For Buber, education for individuals' character and education for building community are not separated but combined. That is, although education takes a main role in the social transformation, it should not be considered just as an instrument for the social transformation. This is the main distinction between Buber's thought and other key socialists' thoughts on social transformation and education, because many of socialists who stress the role of education in the process of social transformation, tend to regard education as an instrument for the social transformation. According to Buber, education can contribute to social transformation without being an instrument for the social transformation. These ideas of Buber on religious socialism and education have important implications for educators and educationalists who hope education contributes to solving problems of modern society.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.8
• /
• pp.57-64
• /
• 2009

In this study, a method using equivalent transformation for estimation of the axial load capacity of tapered piles is proposed. While preexistent methods for estimating the axial load capacity of tapered piles have been based on the effect of soil state and taper angle, a new design method is proposed considering cone resistance $q_c$ and equivalent transformation in sand. Through tapered pile simplified by using equivalent transformation, a new method fur quick and easy estimation of the axial load capacity of tapered pile is proposed for practical use. In order to verify the proposed method, calibration chamber test and field test were conducted. In calibration chamber test, comparison of estimated axial load capacity with measured one showed that the standard deviation and COV (Coefficient Of Variation) of estimated $Q_t$ is $0.05{\sim}0.121$, $0.04{\sim}0.05$ respectively. For field test, axial load capacity by proposed method shows 2.5% under-estimation in comparison with measured value. As a result, it is found that proposed method produces satisfactory predictions for tapered piles.

• Journal of International Area Studies (JIAS)
• /
• v.22 no.2
• /
• pp.305-330
• /
• 2018

The purpose of this article is to examine whether Myanmar's experience in which dealing with the most exemplary change among rogue states or pariah state in the 21st century is feasible for North Korea's case. Recently, North Korea's willingness to dialogue, reform and open is similar to the precedent in which the Myanmar military junta dismantled its ruling system and turned over transition period through general elections in 2010 and 2015 each. The so-called 'Myanmar Model' refers to a country branded as a rogue state which has been under the international sanctions and pressure, and opening its political system and the market by choosing transformation. However, rapid changes in speed across the entire society after opening up are impossible because the political elite is only the leading role and implementation in the transition. In case of Myanmar, military culture has penetrated into society due to such a long-lasting military dictatorship, and even democratic bloc has become accustomed to authoritarian decision-making process. Furthermore, the "reserved area" of the old regime still exists in a deformed political structure that can not retrieve the interests of the military. Therefore there could not be achieved political development in term of qualification. North Korea also appears unlikely to achieve political and economic assessment in a short period of time, as civil society has not appeared due to its long dictatorship and very low economic development levels. Like Myanmar, North Korea is also likely to control the pace and direction of upcoming reforms and open, as the dictator or most powerful person chose to reform and open up. Therefore, if North Korea moves toward the 'Myanmar Model', there will be high expectations of new changes in the short term, but it could be delayed or stalled in the mid and long term.

• Journal of Power Electronics
• /
• v.12 no.4
• /
• pp.548-558
• /
• 2012

In this paper, a novel offset-based single-state pulse width modulation (PWM) method for achieving zero common-mode voltage (CMV) and reducing switching losses in multilevel inverters is presented. The specific active switching state of the zero common-mode (ZCM) voltage that approximates the reference voltage can be deduced from the switching state sequence of the reduced CMV phase disposition PWM (CMV PD PWM) method. From the reference leg voltages for the zero common-mode voltage, an N-to-2-level transformation defines a virtual two-level inverter and the corresponding nominal leg voltage references. The commutation process of the reduced CMV PD PWM method in a multilevel inverter and its outputs can be simply followed in a nominal switching time diagram for the virtual inverter. The characteristics of the reduced CMV PD PWM and the single-state PWM for zero common-mode voltage are analyzed in detail in this paper. The theoretical analysis of the proposed PWM method is verified by experimental results.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.20 no.6
• /
• pp.768-773
• /
• 2010

This paper presents the performance verification of the optimal state feedback controller via inverted pendulum systems. The proposed method generates the optimal control inputs satisfying both the constrained input and the performance specification. In addition, it reduces the steady-state error by adopting the integral control technique. In order to verify the performance of the proposed method, we apply both the proposed method and the general state feedback control to an inverted pendulum, CEM-IP-01 in the experiment.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.1
• /
• pp.41-52
• /
• 1992

An algorithm of transforming continuous-time state feedback gains into equivalent discrete-time feedback gains or vice versa is proposed using bilinear transformation. The proposed method is evaluated experimentally by an application control of a mobile crane system which is implemented by 16bits micro computer with A/D and D/A converters. It has been shown from the experimental result that the transformed feedback gains are virtually identical to the optimal discrete gain over range of significant sampling time. Since the transformed matrix is composed by a distinct relationship between continuous-time gain and discrete-time gain, it is noted that the proposed method can be regarded as an explicit gain transformation method compared to the other methods using series expansion.

• Korean Journal of Pharmacognosy
• /
• v.22 no.1
• /
• pp.26-32
• /
• 1991

The study aimed to confirm transformation, morphology, steroid alkaloidal TLC pattern and growth rate of hairy roots. The Solanum nigrum plantlets were inoculated with Agrobacterium rhizogenes strain 15834. Hairy roots were induced by plasmid. Agropine and mannopine were detected in the hairy roots. The organization of hairy roots on the transactional morphology was undifferentiated. Culture on the medium containing hormone(IBA 2, kinetin 0.1mg/l) altered hairy roots into callus. The growth rate of hairy roots on the NN30 liquid medium was 52 times heavier than in the original state and this was higher than on the other media. The results of TLC analysis indicated that the hairy roots produced steroidal alkaloids resembling those of normal roots.

• Korean Journal of Optics and Photonics
• /
• v.5 no.1
• /
• pp.25-30
• /
• 1994

We derive a set of formuale which show one-to-one correspondence between the the unitary Jones matrices of transparent anisotropic media and the rotational transformations on the Poincare sphere. By using the formuale one can determine the vectorial representation of the rotational transformation on the Poincare sphere which specifies the direction of the axis and the angle of the rotation in terms of the three parameters specific to the corresponding unitary Jones matrix, and conversely the the three parameters of the uniatry Jones matrix in terms of the vectorial representation of the corresponding rotational transformation on the Poincare sphere. To understand the polarization transmission characteristics of an optical system consisting of transparent linear anisotropic media, start with the Jones calculus to get the unitary Jones matrix for the whole system and then convert it to a rotational transformation on the Poincare sphere, from which we can intuitively understand the effect of the optical system on the polarization state of the light passing through the system.