• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.778-789
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• 2017

This paper presents an improved subdomain method to predict the magnet field distributions and electromagnetic performance of the surface-mounted permanent magnet (SPM) machines with static or dynamic eccentricity. Conventional subdomain models are either based on the scalar magnet potential to predict the rotor eccentricity effect or dependent on the magnetic vector potential without considering the eccentric rotor. In this paper, both the magnetic vector potential and the perturbation theory are introduced in order to accurately calculate the effect of rotor eccentricity on the open-circuit and armature reaction performance. The calculation results are presented and validated by the corresponding finite-element method (FEM) results.

• Journal of Electrical Engineering and information Science
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• v.1 no.1
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• pp.29-38
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• 1996

To improve the reliability of control systems, certain robustness to plant uncertainties and disturbance inputs is required in terms of well founded mathematical basis. Robust control theory was set up and developed until now from this motivation. In this field, H$_2$or H\ulcorner norm performance measures are frequently used nowadays. Moreover a mixed H$_2$/H\ulcorner control problem is introduced to combine the merits of each measure since H$_2$control usually makes more sense for performance while H\ulcorner control is better for robustness to plant perturbations. However only some partial analytic solutions are developed to this problem under certain special cases at this time. In this paper, the mixed H$_2$/H\ulcorner control problem is considered. The analytic(or semi-analytic) solutions of (sub)optimal mixed H$_2$/H\ulcorner state-feedback controller are derived for the scalar plant case and the multivariable plant case, respectively. An illustrative example is given to compare the proposed analytic solution with the existing numerical one.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.574-581
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• 2014

This paper presents the design and evaluation of the optical zoom system for an LWIR camera. The 12.8operating wavelength range of this system is from $7.7{\mu}m$ to $12.8{\mu}m$. Through a paraxial design and optimization process, we have obtained the extended four-group inner-focus zoom system with focal lengths of 10 to 100 mm, which consists of the six lenses including four aspheric surfaces and two diffractive surfaces. The diffractive lenses were used to balance the higher-order aberrations, and its diffraction properties were evaluated by scalar diffraction theory. We have calculated the polychromatic integrated diffraction efficiency and the MTF drop generated by background noise. The f-number of the zoom system is F/1.4 at all positions. Fields of view are given by $51.28^{\circ}{\times}38.46^{\circ}$ at wide field and $5.50^{\circ}{\times}4.12^{\circ}$ at narrow field positions. In conclusion, this design procedure results in a $10{\times}$ compact zoom lens system useful for an LWIR camera.

• Korean Journal of Optics and Photonics
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• v.28 no.5
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• pp.241-249
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• 2017

This paper presents the design and evaluation of the optical system for an uncooled thermal-imaging camera. The operating wavelength range of this system is from $7.7{\mu}m$ to $12.8{\mu}m$. Through optimization, we have obtained a LWIR (Long Wave Infrared) optical system with a focal length of 5.44 mm, which consists of four aspheric surfaces and two diffractive surfaces. The f-number of the optical system is F/1.2, and its field of view is $90^{\circ}{\times}67.5^{\circ}$. The hybrid lens was used to balance the higher-order aberrations, and its diffraction properties were evaluated by scalar diffraction theory. We calculated the polychromatic integrated diffraction efficiency, and the MTF drop generated by background noise. We have evaluated the thermal compensation of a LWIR fixed optical system, which is optically passively athermalized to maintain MTF performance in the focal depth. In conclusion, these design results are useful for an uncooled thermal-imaging camera.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.189-196
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• 2002

The components and alignment parameters of a flat-field soft x-ray spectrometer used in the wavelength range below 50 $\AA$ are determined, and the characteristics of the spectrometer are analyzed. It consists of a toroidal mirror, a slit, a varied line-spacing concave grating, and a soft x-ray detector. The space-resolved spectral image of a source is formed on a single plane using the tordidal mirror and the 2400-grooves/mm varied line-spacing concave grating. The former is used to compensate for the astigmatism caused by the grazing incidence of soft x-ray light on the concave grating. The spectral and spatial resolutions of the spectrometer are calculated by applying the wave front aberration theory, and the diffraction efficiency is calculated by applying the scalar diffraction theory.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.8
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• pp.1059-1068
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• 1993

We will put the emphasis on the analysis of arbitrarily shaped microstrip antennas. The most general and rigorous treatment of microstrip antennas is given by the electric field integral equation(EFIE), usally formulated in the spectral domain. In this paper, we use a modification of EFIE, called the mixed potential integral equation(MPIE) , and we solve it in the space domain. This technique uses Green's functions associated with the scalar and vector potential which are calculated by using stratified media theory and are expressed as Sommerfeld integrals. The integral equation is solved by a moment's method using rooftop subsectional basis function. Thus, microstrip patches of any shape can be analysed at any frequency and for any substrate. Numerical results for a rectangular patch and for a L-shaped patch are given and compared with measured values.

• Journal of the Korean association of regional geographers
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• v.23 no.1
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• pp.1-22
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• 2017

This paper is to consider conceptually a formation of food-networks and border-crossing of transnational marriage migrant households on the basis of actor-network theory, and to analyze empirical data on the issues collected by interview with marriage migrant women living around Daegu, S.Korea. Some research results can be argued as follows: First, food can be seen, not as a single material object, but as a multiple and hybrid network of human and nonhuman (material and institutional) actors, in which activities of food cooking and eating are regulated by and (re)construct social relations and placeness of households. Secondly, food-networks in marriage migrant households implement relationships of micro-power (and attachment) in the process of its (re)formation, and hence the food-network, it can be argued, is a field of power in which conflicts and compromising around food cooking and eating are intersecting each others. Thirdly, food-networks in marriage migrant households in both their origin country and in the Korean home are not only affected by macro natural and social environments but also by micro placeness of the households, both of which constitute the food-networks and operate in relations with other actors in the netwroks. Finally, food-networks in marriage migrant households reflect multiple and multi-scalar spatial mobility and placeness of transnational food culture, through which they express topologically 'fluid space' and 'absent presence', in which marriage migrant women can (or cannot) conduct social and cultural border-crossing.