• Journal of the Optical Society of Korea
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• v.16 no.1
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• pp.63-69
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• 2012

This paper presents a method to derive the theoretical requirements for the development of a 400 mm optical window that transmits dual-band wavelengths and had a stable structure. We also present design and fabrication results. Among the required specifications, the surface figure error was defined by the transmitted wavefront deformation (TWD), ${\lambda}$/15 rms at 632.8 nm. This value was derived by estimating the predicted performances with respect to five independent items that could cause system performance degradation and then calculating the required wavefront error (WFE) to satisfy the performance goals. We measured the image resolution at each performance level to trace and verify the requirements. The article also describes a design optimization process that could minimize the weight and volume of the optical window attached to the payload securing the FOV of the camera. In addition, we accurately measured the deformation that occurred in the series of fabrication steps including processing, coating, assembly, bonding and bolting, and investigated the effects by comparing them to the results of a simulation performed in advance to derive the predicted performance.

• The Journal of the Acoustical Society of Korea
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• v.34 no.5
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• pp.360-370
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• 2015

In case that an infinite length waveguide structure is connected with a finite length structure, it is required to combine a wave approach for the waveguide structure and a modal approach for the finite length structure to investigate the dynamic response of the connected target structure. In this study, the wavenumber finite element (WFE) analysis is adopted for the infinite length waveguide substructure and a finite element (FE) method is applied for the finite length substructure and then their results are coupled in terms of the impedance or mobility at the connected points between the substructures. As a structural model, an infinite length cylindrical shell with a rectangular plate inside is regarded. These two substructures are connected at the four corner points of the plate, rigidly or resiliently. From this investigation, it was confirmed that the wave approach (WFE method) and modal approach (FE method) can be combined by the impedance coupling.

• Asian-Australasian Journal of Animal Sciences
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• v.21 no.11
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• pp.1576-1584
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• 2008

In this study, canonical correlation analysis (CCA) was applied to estimate the relationship between three different sexual maturity traits (X set: days to first egg (DFE), weight of the first egg (WFE), body weight at first egg (BWFE)) and level of nutrient intake (Y set: energy (EI) and protein intake (PI)) or the egg production traits at two different periods (Z set: number of egg (NE1 and NET) and weight of egg (WE1 and WET) from 22 to 25 (Wfirst) and 22 to 33 wk of age (Wall), respectively), which were measured from 64 egg-type pullets (Isa Brown) manipulated for time of access to energy and protein sources to onset of egg production. Partial CCA (PCCA) was used to eliminate the contribution of differences in the levels of nutrient intake to canonical variables for X and Z sets at the first production period. Estimated canonical correlation coefficients between X set and Y set (0.429, p = 0.042), X set and Z set (0.390, p = 0.007 for Wfirst) and within Z set (between Wfirst and Wall; 0.780, p<0.001), and partial canonical correlation coefficient between X set and Z set (0.415, p = 0.009) were significant. Canonical weights and loadings from CCA indicated that the BWFE had the largest contribution compared to the DFE and WFE to variation of egg number produced at two different periods. The results from PCCA indicated that the contribution of PI and EI to the degree of the correlation between canonical variables for X and Z sets were unfavourable. In conclusion, the effect of body weight at sexual maturity upon the availability of nutrients can have a higher contribution to variation of egg production in pullets if the contribution of differences in nutrient intakes to onset of egg production were eliminated.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.906-913
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• 1992

The polymeric compound [{$W(NO)_2Cl_2$}$_n$] were prepared by reductive nitrosylation of $WNaNO_2$ and acidified $WFeSO_4$ with $WWCl_6$ at room temperature. The reactions of [{$W(NO)_2Cl_2$}$_n$] with unidentate and bidentate ligands afforded neutral monomeric [$W(NO)_2Cl_2L_2$(or L-L)] in a relative high yields (70$\sim$90%). 3,5-lutidine, ${\gamma}$-cyanopyridine, 1,2-phenylenediamine, 1,10-phenanthroline, sym-diphenylethylenediamine, 9,10-phenanthrenequinone, 1,3-bis(diphenylphosphino)propane, 1,1'-bis(diphenylphosphino)ferrocene and 8-hydroxyquinoline were used as coordinating ligands. These dinitrosyltungsten complexes were characterized by elemental analysis, $^1H$-NMR, infrared, and UV-visible spectroscopy are reported. The spectral data indicated that geometric structures of the products were cis-dinitrosyl-trans-dichloro-cis-$L_2$ of $C_{2v}$ symmetry.

• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.307-314
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• 2013

Infrared optical systems are operated at low temperature and vacuum (LT-V) condition, whereas the assembly and alignment are performed at room temperature and non-vacuum (RT-NV) condition. The differences in temperature and pressure between assembly/alignment environments and operation environment change the physical characteristics of optical and opto-mechanical parts (e.g., thickness, height, length, curvature, and refractive index), and the resultant optical performance changes accordingly. In this study, using input relay optics (IO), among the components of the Immersion GRating INfrared Spectrograph (IGRINS) which is an infrared spectrograph, a simulation based on the physical information of this optical system and an actual experiment were performed; and optical performances in the RT-NV, RT-V, and LT-V environments were predicted with an accuracy of $0.014{\pm}0.007{\lambda}$ rms WFE, by developing an adaptive fitting line. The developed adaptive fitting line can quantitatively control assembly and alignment processes below ${\lambda}/70$ rms WFE. Therefore, it is expected that the subsequent processes of assembly, alignment, and performance analysis could not be repeated.

• Advances in aircraft and spacecraft science
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• v.6 no.6
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• pp.463-478
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• 2019

The present work investigates the effect on the flow-induced vibrations of the lay-up sequence of composite laminated axisymmetric structures, using an hybrid approach based on a wave finite element and a transfer matrix method. The structural vibrations, under deterministic distributed pressure loads, diffuse acoustic field and turbulent boundary layer excitations, are analysed and compared. A multi-scale approach is used for the dynamic analysis of finite structures, using an elementary periodic subsystem. Different flow regimes and shell curvatures are analysed and the computational efficiency is also discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.791-796
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• 2011

In order to understand long range wave propagation in railway tracks, it is required to identify how far vibrations can travel along a rail. To answer this question, the attenuation characteristics of the main propagating waves are required as a function of distance. In this work, it is identified which wave types predominantly propagate on various regions of the rail cross-section. Then decay rates of propagating waves in railway tracks are investigated for frequencies up to 80 kHz. A numerical method called the Wavenumber Finite Element (WFE) method is utilized to predict dispersion curves and decay rates for a rail on a continuous foundation. In order to validate the simulated results, measurements have been performed on a test track and an operational railway track. The measured results are compared with the output of the simulations and good agreements are found between them.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.1
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• pp.142-148
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• 2014

The mirror which is considered in designing a MFD is off-axis primary one and its dimension is wide 556mm height 345mm. The MFD(Mirror Fixation Device) load specification is generated for the high resolution mirror. The optical WFEs for unit loads are calculated from mirror sensitivity analysis and they are compared with allocated allowable optical WFE. The parasite load for the MFD is calculated from their comparison. The MFD compliant with the parasite load is designed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.8
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• pp.698-706
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• 2013

Structural vibration induced by excitation forces under turbulent boundary layer is investigated in terms of the numerical analysis in this paper. Since the responses of structures excited by the wall pressure fluctuation(WPF) are described by the power spectral density functions, they are calculated and reviewed theoretically for finite and infinite length beams. For the use of numerical approaches, the WPF needs to be discretized but conventional finite element method is not much effective for that purpose because the WPF lose the spatial correlation characteristics. As an alternative numerical technique for WPF modelling, a wavenumber domain finite element approach, called waveguide finite element method, is examined here for infinite length beams. From the comparison between the numerical and theoretical results, it was confirmed that the WFE method can effectively and easily cope with the excitation from WPF and hence the suitable approach.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.434-438
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• 2018

The sintering behavior of $BaFe_{12}O_{19}$ with the addition of one and three weight % of $CuWO_4$ as a liquid phase sintering aid is studied. Samples are sintered in the temperature range $900-1250^{\circ}C$ and the effect of $CuWO_4$ addition on density, microstructure, phase composition and magnetic properties is examined. Compared to $BaFe_{12}O_{19}$ with no sintering aid addition, addition of 1 wt % $CuWO_4$ retards densification. Addition of 3 wt % $CuWO_4$ promotes densification at lower sintering temperatures but retards densification at temperatures > $1050^{\circ}C$. Three wt % $CuWO_4$ addition induces the formation of $BaWO_4$ and $Ba_3WFe_2O_9$ secondary phases at temperatures ${\geq}1100^{\circ}C$. Addition of $CuWO_4$ causes a decrease in saturation magnetization, remanent magnetization and coercivity.