• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.11
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• pp.1113-1120
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• 2014

In this paper, general methods for enhancing the transmission efficiency through the small subwavelength aperture in an infinite conducting plane are considered first by use of the transmission-resonant aperture like the ridged circular aperture structure, second by employing the transmission-resonant cavity structure. In particular, the maximum transmission cross section is found to be $\frac{2G{\lambda}^2}{4{\pi}}[m^2]$ for the two structures, where G is the gain of the aperture in the output half space. As experimental works, the impedance matching characteristics are investigated for the cases that above two structures are incorporated as a potential near field microscopic probe in the waveguide end. As a complementary problem to the above transmission-resonant aperture problem, some discussions are also given on the scattering resonance by the scattering object much smaller than the wavelength. This discussion may provide a good understanding of the physics for the phenomena that the maximum scattering cross section is much larger than the physical size of the atom in atomic physics area.

• Journal of Korean Neurosurgical Society
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• v.61 no.6
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• pp.707-715
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• 2018

Objective : To investigate the potential risk of approach-related complications at different access angles in minimally invasive lateral lumbar interbody fusion. Methods : Eighty-six axial magnetic resonance images were obtained to analyze the risk of approach-related complications. The access corridor were simulated at different access angles and the potential risk of neurovascular structure injury was evaluated when the access corridor touching or overlapping the corresponding structures at each angle. Furthermore, the safe corridor length was measured when the corridor width was 18 and 22 mm. Results : When access angle was $0^{\circ}$, the potential risk of ipsilateral nerve roots injury was 54.7% at L4-L5. When access angle was $45^{\circ}$, the potential risk of abdominal aorta, contralateral nerve roots or central canal injury at L4-L5 was 79.1%, 74.4%, and 30.2%, respectively. The length of the 18 mm-wide access corridor was largest at $0^{\circ}$ and it could reach 44.5 mm at L3-L4 and 46.4 mm at L4-L5. While the length of the 22 mm-wide access corridor was 42.3 mm at L3-L4 and 44.1 mm at L4-L5 at $0^{\circ}$. Conclusion : Changes in the access angle would not only affect the ipsilateral neurovascular structures, but also might adversely influence the contralateral neural elements. It should be also noted to surgeons that alteration of the access angle changed the corridor length.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.2 s.72
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• pp.195-202
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• 2006

Thin-walled structures are efficiently utilized an automobiles, aircraft, satellite and ship as well as needed light weight simultaneously. This paper presents new shape of automobile hood reinforcement that rotating parts as engine, transmission are protected by thin-walled structures. The automobile hood is concerned about the resonance occurs due to the frequency of the rotating parts. The hood must be designed by supporting the stiffness of design loads and considering the natural frequencies. Hence, it is sustained the stiffness and considered the vibration by resonance. It is deep related to ride. Therefore, the topology, shape and size optimization methods are used to design the automobile hood. Topology technique is applied to determine the layout of a structural component optimum size with maximized natural frequency by volume reduction. In this research, The optimal structure layout of an inner reinforcement of an automobile hood for the natural frequency of a designated mode is obtained by using topology optimization method. The optimum size and the optimum shape are determined by PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm.

• Journal of Korean Association for Spatial Structures
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• v.8 no.2
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• pp.63-72
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• 2008

One of the most important matters in keeping membrane structures in healthy condition is to maintain the proper tension distribution over the membrane. However, it is not easy to know the real stress level in the membrane quantitatively after completion of the structures. Authors suggested measurement method that can measure membrane stress using sound wave, and have been holding experimental tests of membrane stress measurement that used the sound external excitation with sine wave and white noise. The concept of the method is the fact that measurement of resonance frequency by vibrating membrane having rectangular boundary by audible frequency can measure membrane stress indirectly. In this paper, through the experimental tests it is proved that the equipment can be used for not only the membrane material of type A but also for types B and C. In addition, it is proved that the developed measurement equipment is available to stably measure the membrane stress which exists in the membrane material of the actual membrane structures.

• Smart Structures and Systems
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• v.21 no.5
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• pp.695-703
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• 2018

Based on monitoring data collected from the Nanjing Dashengguan Bridge over the last five years, this paper systematically investigates the effects of temperature field and train loadings on the structural responses of this long-span high-speed railway bridge, and establishes the early warning thresholds for various structural responses. Then, some lessons drawn from the structural health monitoring system of this bridge are summarized. The main context includes: (1) Polynomial regression models are established for monitoring temperature effects on modal frequencies of the main girder and hangers, longitudinal displacements of the bearings, and static strains of the truss members; (2) The correlation between structural vibration accelerations and train speeds is investigated, focusing on the resonance characteristics of the bridge at the specific train speeds; (3) With regard to various static and dynamic responses of the bridge, early warning thresholds are established by using mean control chart analysis and probabilistic analysis; (4) Two lessons are drawn from the experiences in the bridge operation, which involves the lacks of the health monitoring for telescopic devices on the beam-end and bolt fractures in key members of the main truss.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.6
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• pp.505-508
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• 2017

This paper analyzes the effect of metal dummy structures in CMOS on antenna performances of a sub-terahertz on-chip microstrip patch antenna. A 400-GHz on-chip antenna is designed in a 45-nm CMOS process, and the resonance frequency and efficiency of the antenna are analyzed depending on the density of metal dummy structures. Antennas integrated with an oscillator are designed and fabricated for verification, and measurements are performed using quasi-optical methods with an FTIR and bolometer. The measurement results shows that the radiated power drops from 420 nW to 90 nW by 6.8 dB due to the dummy structures with the density of 27 %.

• Journal of Korean Association for Spatial Structures
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• v.22 no.3
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• pp.49-56
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• 2022

Tuned mass damper (TMD) is widely used to reduce dynamic responses of structures subjected to earthquake loads. A smart tuned mass damper (STMD) was proposed to increase control performance of a traditional passive TMD. A lot of research was conducted to investigate the control performance of a STMD based on analytical method. Experimental study of evaluation of control performance of a STMD was not widely conducted to date. Therefore, seismic response reduction capacity of a STMD was experimentally investigated in this study. For this purpose, a STMD was manufactured using an MR (magnetorheological) damper. A simple structure presenting dynamic characteristics of spacial roof structure was made as a test structure. A STMD was made to control vertical responses of the test structure. Two artificial ground motions and a resonance harmonic load were selected as experimental seismic excitations. Shaking table test was conducted to evaluate control performance of a STMD. Control algorithms are one of main factors affect control performance of a STMD. In this study, a groundhook algorithm that is a traditional semi-active control algorithm was selected. And fuzzy logic controller (FLC) was used to control a STMD. The FLC was optimized by multi-objective genetic algorithm. The experimental results presented that the TMD can effectively reduce seismic responses of the example structures subjected to various excitations. It was also experimentally shown that the STMD can more effectively reduce seismic responses of the example structures conpared to the passive TMD.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11A
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• pp.912-920
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• 2003

This paper is about the design of a small wide-band slot loop antenna, which consists of dual offset-fed and rectangular loop within the slot on a substrate. The proposed antenna is a novel structure generating a multi-resonances due to three geometrical resonance structures. The impedance matching of this antenna can be accomplished by changing the offset position of dual-fed at resonance frequencies. In this experiment, the slot of a fabricated antenna has a center frequency of 6.755㎓, 12.5mm${\times}$50mm in size and the rectangular loop has 10.5mm${\times}$27.5mm in size. The measured result is fractional bandwidth 63.21% with VSWR 2:1, which is agreed with the simulated result within 5% of error, and the maximum antenna gain is 7.42㏈i.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1317-1322
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• 2014

Membrane disruption by an antimicrobial peptide (AMP) was investigated by measuring the $^2H$ solid-state nuclear magnetic resonance spectra of 1-palmitoyl-$d_{31}$-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC_$d_{31}$) in mixtures of POPC_$d_{31}$/cholesterol and either magainin 2 or aurein 3.3 deposited on thin cover-glass plates. The line shapes of the experimental $^2H$ solid-state nuclear magnetic resonance (SSNMR) spectra were best simulated by assuming the coexistence of a mosaic spread of bilayers containing pore structures and a fasttumbling isotropic phase or a hexagonal phase. Within a few days of incubation in a hydration chamber, an isotropic phase and a pore structure were induced by magainin 2, while in case of aurein 3.3 only an isotopic phase was induced in the presence of a bilayer phase. After an incubation period of over 100 days, alignment of the bilayers increased and the amount of the pore structure decreased in case of magainin 2. In contrast with magainin 2, aurein 3.3 induced a hexagonal phase at the peptide-to-lipid ratio of 1/20 and, interestingly, cholesterol was not found in the hexagonal phase induced by aurein 3.3. The experimental results indicate that magainin 2 is more effective in disrupting lipid bilayers containing cholesterol than aurein 3.3.

• Journal of the Korean Magnetic Resonance Society
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• v.22 no.2
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• pp.26-33
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• 2018

Xanthium sibiricum is used as a traditional folk medicine for the treatment of cancer, fever, headache, nasal sinusitis, and skin pruritus. This study aimed to identify components from Xanthium sibiricum extracts using an SPE-800MHz NMR-MS hyphenated system. The simultaneous acquisition of MS and NMR spectra from the same chromatographic peaks significantly increases the depth of information acquired for the compound and allows the elucidation of structures that would not be possible using MS or NMR data alone. LC -NMR analysis was conducted using a HPLC separation system coupled to 800 MHz spectrometer equipped with a cryoprobe, and a SPE unit was used to automatically trap chromatographic peaks using a HPLC pump. LC-MS analysis was conducted with a Q-TOF MS instrument using ESI ionization in the negative ion mode. Using the hyphenated analysis, several secondary metabolites were identified, such as 3',5'-O-dicaffeoylquinic acid, 1',5'-O-dicaffeoyl- quinic acid, and ethyl caffeate. These results demonstrate that the SPE-800MHz NMR-MS hyphenated system can be used to identify metabolites within natural products that have complex mixtures.