• Investigative Magnetic Resonance Imaging
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• v.11 no.2
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• pp.95-102
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• 2007

Purpose: To acquire high-resolution spiral-scan images at higher magnetic field, high homogeneous magnetic field is needed. Field inhomogeneity mapping and in-vivo shimming are important for rapid imaging such as spiral-scan imaging. The rapid scanning sequences are very susceptible to inhomogeneity. In this paper, we proposed a higher-order shimming method to obtain homogeneous magnetic field. Materials and Methods: To reduce measurement time for field inhomogeneity mapping, simultaneous axial/ sagittal, and coronal acquisitions are done using multi-slice based Fast Spin echo sequence. Acquired field inhomogeneity map is analyzed using the spherical harmonic functions, and shim currents are obtained by the multiplication of the pseudo-inverse of the field pattern with the inhomogeneity map. Results: Since the field inhomogeneity is increasing in proportion to the magnetic field, higher order shimming to reduce the inhomogeneity becomes more important in high field imaging. The shimming technique in which axial, sagittal, and coronal section inhomogeneity maps are obtained in one scan is developed, and the shimming method based on the analysis of spherical harmonics of the imhomogenity map is applied. The proposed technique is applicable to a localized shimming as well. High resolution spiral-scan imaging was successfully obtained with the proposed higher order shimming. Conclusion: Proposed pulse sequence for rapid measurement of inhomogeneity map and higher order shimming based on the inhomogeneity map work very well at 3 Tesla MRI system. With the proposed higher order shimming and localized higher order shimming techniques, high resolution spiral-scan images are successfully obtained at 3 T MRI system.

• Asian Journal of Atmospheric Environment
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• v.9 no.1
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• pp.78-85
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• 2015

In the past several decades, biofuels have emerged as candidates to help mitigate the issues of global warming, fossil fuel depletion and, in some cases, atmospheric pollution. To date, the only biofuels that have achieved any significant penetration in the global transportation sector are ethanol and biodiesel. The global consumption of biodiesel was rapidly increased from 2005. The goal of this study was to examine the chemical composition on particulate pollutant emissions from a diesel engine operating on several different biodiesels. Tests were performed on non-road diesel engine. Experiments were performed on 5 different fuel blends at 2 different engine loading conditions (50% and 75%). 5 different fuel blends were ultra-low sulfur diesel (ULSD, 100%), soy biodiesel (Blend 20% and Blend 100%) and canola biodiesel (Blend 20% and Blend 100%). The chemical properties of particulate pollutants were characterized using an Aerodyne High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS). Organic matter and nitrate were generally the most abundant aerosol components and exhibited maximum concentration of $1207{\mu}g/m^3$ and $30{\mu}g/m^3$, respectively. On average, the oxidized fragment families ($C_xH_yO_1{^+}$, and $C_xH_yO_z{^+}$) account for ~13% of the three family sum, while ~87% comes from the $C_xH_y{^+}$ family. The two peaks of $C_2H_3O_2$ (m/z 59.01) and $C_3H_7O$ (m/z 59.04) located at approximately m/z 59 could be used to identify atmospheric particulate matter directly to biodiesel exhaust, as distinguished from that created by petroleum diesel in the AMS data.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.1
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• pp.36-40
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• 2004

To observe and analysis ultra-microscopically barley aleurone cell surface, atomic force microscope (AFM) was used. Seed coat of early maturing germplasm, eam9, was dehulled and scanned by non-contact mode. We have obtained the high resolution topographic 3-dimensional image of barley aleurone layer with high resolution. These images showed the membrane proteins in barley aleurone cell. One channel protein and numerous peripheral or integral proteins were detected in a area of 100 $\mu\textrm{m}^2$. Furthermore, we found that their widths were ranged from 50 to 750nm and lengths from 0 to 66 $\mu\textrm{m}$. The thickness of aleurone layer was measured by scanning electron microscope. The thickness at early developmental stage was about 16 and then the aleurone cell enlarged upto 57 $\mu\textrm{m}$${\mu}{\textrm}{m}$ at least until 42 days after anthesis. In this study, we firstly reported on the ultrastructural AFM analysis of living aleurone cell as a biological specimen. It was clearly suggested that AFM will become an powerful tool for probing both the structural properties of biological samples.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.45-48
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• 1996

In the case of $^{123}I$ from the $^{124}Te$ (p,2n)reaction, the radionuclidic impurity is the high-energy gamma-emitting $^{124}I$, which interferes greatly with nuclear medicine images. The choice of a collimator can affect the quality of clinical SPECT images of [I-123]MIBG or [I-123]TPT. The tradeoffs that two different collimators make among spatial resolution, sensitivity, and scatter were studied by imaging a line source at 5cm, 10cm, 15cm distance using a number of plexiglass sheets between source and collimator, petri dist two-dimensional Hoffman brain phantom, and Jaszczak phantom after filling with $^{123}I$ (FWHM, FWTM, Sensitivity) for low energy ultra high resolution parallel hole(LEUHRP) collimator and medium energy general purpose (MEGP) collimator were measured as (9.27mm, 61.27mm $129CPM/[\mu}$ Ci) and (10.53m 23.17mm $105CPM/{\mu}$ Ci), respectively. The image quality of two-dimensional Hoffman brain Phantom with LEUHRP looked better than the one with MEGP. However, the image quality of Jasgczak phantom with LEUHRP looked much worse than the one with MEGP, The results suggest that the MEGP is preferable to LEUHRP for SPECT studies of [I-123]MIBG or [I-123]IPT.

• Journal of radiological science and technology
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• v.24 no.2
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• pp.35-40
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• 2001

Performance of SPECT imaging systems which use a rotating gamma camera, are affected by characteristics of the detector-collimator assembly, the data acquisition method, and the filter used in imaging reconstruction. The purpose of this study Is to examine image qualifies of SPECT with different types of low energy collimators. The SPECT imaging system in this study is a digital gamma camera system GCA-901A(Toshiba) and a data processing unit Scintipac-700(Shimadzu). The four types of collimators compared are UHR(ultra high resolution), LEHR(low energy high resolution), LEGP(low energy general purpose), and I-123 PAR(Parallel), with 0.27, 0.66, 1.00, and 2.06 relative sensitivity, respectively. In this case of the same collimators, the spatial resolutions measured in the slice plane showed a slight difference in the FWHM values(mean values of UHR, LEHR, LEGP, and I-123 PAR were 11.3 mm, 13.6 mm, 15.8 mm, and 20.4 mm, respectively) between the center and the circumference of the field of view, in the radial direction, but a large difference in the tangential direction, with lower FWHM values(values of UHR, LEHR, LEGP, and I-123 PAR were 8.4 mm, 8.7 mm, 9.3 mm, and 10.8 mm at 12 cm from the center, respectively). In comparison of SPECT images with the four types of collimators, except for the I-123 PAR collimator, image qualities of UHR, LEHR, and LEGP collimators showed only a slight difference. From the point of for, it is expected that the LEGP collimator would be suitable for SPECT imaging with $^{99m}Tc$.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.35 no.6
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• pp.563-572
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• 2017

The purpose of the study is to investigate the effect of flight height, flight speed, exposure time of camera shutter and autofocusing on the visual resolution of the image in order to obtain ultra-high resolution images with a GSD less than 1cm. It is also aimed to evaluate the ease of recognition of various types of aerial targets. For this purpose, we measured the visual resolution using a 7952*5304 pixel 35mm CMOS sensor and a 55mm prime lens at 20m intervals from 20m to 120m above ground. As a result, with automatic focusing, the visual resolution is measured 1.1~1.6 times as the theoretical GSD, and without automatic focusing, 1.5~3.5 times. Next, the camera was shot at 80m above ground at a constant flight speed of 5m/s, while reducing the exposure time by 1/2 from 1/60sec to 1/2000sec. Assuming that blur is allowed within 1 pixel, the visual resolution is 1.3~1.5 times larger than the theoretical GSD when the exposure time is kept within the longest exposure time, and 1.4~3.0 times larger when it is not kept. If the aerial targets are printed on A4 paper and they are shot within 80m above ground, the encoded targets can be recognized automatically by commercial software, and various types of general targets and coded ones can be manually recognized with ease.

• Journal of the Korean Vacuum Society
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• v.21 no.6
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• pp.348-353
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• 2012

We investigated chemical states of a $Sb_2Te_3$ thin film with the polycrystalline phase by using high-resolution x-ray photoelectron spectroscopy with synchrotron radiation. The $Sb_2Te_3$ thin film was formed by sputtering. The rhombohedral phase was confirmed by x-ray diffraction. To remove the surface oxide, we performed $Ne^+$ ion sputtering for 1 hour with the beam energy of 1 kV and post-annealing at $100^{\circ}C$ for 5 min in ultra-high vacuum. We obtained the Te and Sb 4d core-levels spectra with the peaks at the binding energies of 40.4 and 33.0 eV, respectively. The full-width of half maximum of both the Te and Sb $4d_{5/2}$ core-levels is 0.9 eV. The Te and Sb core-levels only show a single chemical state, and we also confirmed the stoichiometry of approximately 2 : 3.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.4
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• pp.238-246
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• 2011

A 3-5 GHz UWB radar chip in 0.13 ${\mu}m$ CMOS process is presented in this paper. The UWB radar transceiver for surveillance and biometric applications adopts the equivalent time sampling architecture and 4-channel time interleaved samplers to relax the impractical sampling frequency and enhance the overall scanning time. The RF front end (RFFE) includes the wideband LNA and 4-way RF power splitter, and the analog signal processing part consists of the high speed track & hold (T&H) / sample & hold (S&H) and integrator. The interleaved timing clocks are generated using a delay locked loop. The UWB transmitter employs the digitally synthesized topology. The measured NF of RFFE is 9.5 dB in 3-5 GHz. And DLL timing resolution is 50 ps. The measured spectrum of UWB transmitter shows the center frequency within 3-5 GHz satisfying the FCC spectrum mask. The power consumption of receiver and transmitter are 106.5 mW and 57 mW at 1.5 V supply, respectively.

• Journal of the Korean Chemical Society
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• v.40 no.12
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• pp.719-723
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• 1996

An inverse photoemission spectrometer has been built and tested to study the unoccupied electron energy states of solid surfaces. It consists of a low energy electron gun and a band pass photon detector in an ultra-high vacuum chamber. The electron ray tracing simulation and current measurement of the electron gun show a good focus and a high flux of electron current. The overall resolution of the spectrometer is 0.74 eV and the sensitivity of the photon detector is about 10 counts/$sec{\cdot}{\mu}A.$ As a test experiment, the inverse photoemission spectra of a Ge(111) sample is in good agreement with the theoretical result.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.1
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• pp.121-131
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• 2023

Although the utilization of drone photogrammetry that can generate spatial information using ultra-high-resolution images is increasing in the civil engineering and construction fields, analysis of areas that can be used is insufficient. Therefore, this study attempted to determine how far drone photogrammetry can be used in the civil engineering and construction fields by applying a detailed analysis method. The status map and cross-sectional map were actually vectorized using drone photogrammetry outcomes, compared and analyzed with the results acquired in the field, and the qualitative aspects of traffic safety facilities were analyzed to determine their usability. As a result, the accuracy of the plane position using drone photogrammetry was reliable, but the height accuracy was difficult to trust. Accordingly, although there is a possibility of preparing a status map, the use of it in areas requiring high accuracy such as cross-sectional plans was limited, and it is believed that it can be used in the construction management field where qualitative analysis is conducted.