• The Journal of Korean Institute of Communications and Information Sciences
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• v.9 no.1
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• pp.39-44
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• 1984

Three types of parabolic antenna to reduce the sidelobes and backlobe are compared to determine the best suppressive effect under same conditions which are side rim loading parabilic antenna, flanged prabolic antenna. The hooded parabolic antenna adhered polyurethan form impregnated carbon powder in shows the best shape of suppressed the side back lobes that is 5 to 10 dB suppression of sidelobe and 15dB suppression of back lobe for E-plane.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.9
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• pp.93-99
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• 1998

A novel four-channel narrowband wavelength demultiplexer using integrated four vertical directional coupler structures is proposed and theoretically investigated. Four ridge waveguide with different ridge width are vertically coupled to a strip-loaded waveguide which results four different wavelengths filtered out to each ridge waveguide. In order to reduce the side-lobes, the coupling coefficients are varied along the propagation direction. The spectral responses of channels were found to be quite uniform. An average channel spacing of 7 nm with power coupling efficiency of ~90%, 3-dB passband width of 2 nm, and 20 dB side-lobe suppression ratio was achieved.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.4
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• pp.413-422
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• 2011

An improved split-beam transducer for a 50 kHz fish-sizing echo sounder was developed. The main objective of this study was to minimize the side lobe level in the beam pattern and the distance between acoustic centers for adjacent transducer quadrants in the geometrical arrangement of array elements while maintaining a given number of transducer elements and beam width. To achieve these goals, a 32-element planar array transducer ($6{\times}6$ array with one element in each corner missing) was designed using the Dolph-Chebyshev shading function to suppress side lobes in the array beam pattern and fabricated by arranging the inter-element spacing to be substantially equal to half the wavelength using the transducer element of 0.4 times the wavelength in diameter. The performance characteristics of this split-beam transducer were evaluated in the experimental water tank of $5m{\times}5m{\times}6m$ (length${\times}$height${\times}$width). In this study, the design goal of the beam width and side lobe level for transmitting a beam pattern was initially set at $21^{\circ}$ and -30 dB, respectively. However, the measured beam width at 3 dB was $21^{\circ}$ in both directions with side lobe levels of -24.7 dB in the horizontal plane and -25.6 dB in the vertical plane. The averaged beam width at -3 dB of the receiving beam patterns for four receiving quadrants was $31.4^{\circ}$. The transmitting voltage response was 161.5 dB (re $1{\mu}Pa$/V at 1 m) at 50.23 kHz with a bandwidth of 2.16 kHz, and the averaged receiving sensitivity for four receiving quadrants was -178.13 dB (re 1 V/${\mu}Pa$) at 49.8 kHz with a bandwidth of 2.64 kHz.

• The Journal of the Acoustical Society of Korea
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• v.41 no.5
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• pp.525-533
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• 2022

We propose an effective method for suppressing both side and grating lobes by applying 2-dimensional Fourier Transform to the received channel data during the receive focusing process of an ultrasound imaging system. When the signal from the image point is focused, the channel signals have the same DC value across the channels. However, even after echoes from outside an imaging point are focused, they are manifested as having different spatial frequencies depending on their incident angles. Therefore, after the receive focusing delay time is applied, 2-D Fourier Transform is performed on the time-channel data to separate the DC component and other frequency components in the spectral domain, and the weighting value is defined using the ratio of the two values. The side lobe and grating lobe were suppressed by multiplying the ultrasound image by a weighting value. Ultrasound images with a frequency of 5 MHz were simulated in a 64-channel linear array. The grating lobe appearing in the ultrasound image was completely removed by applying the proposed method. In addition, the side lobe was reduced and the lateral resolution was greatly increased. Results of computer simulation on a human organ mimicking image show that the proposed method can aid in better lesion diagnosis by increasing the image contrast.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.4
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• pp.181-190
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• 2014

The underwater acoustic lens system is one of the systems getting high-resolution images on the seafloor by the beam forming method using acoustic lens. The beam forming using acoustic lenses reduces complexity and driving power. When receiving an incoming beam with the acoustic lens array, beam pattern analysis and arrangement problem of the array sensor must be addressed. Introducing SIR (Signal to Interference Ratio), the relationship among sensor interval, beam pattern and image quality would be analyzed. Generally if the sensor interval getting wider, the less effect of the side lobes makes SIR high. If the amplitude of a side lobe is high, SIR is generally getting low. The type of the apodization function changes the width, shape and amplitude of both main lobe and side lobes. Thus an appropriate apodization function can improve SIR. In this paper, SIR is stable at the sensor interval of 13mm with 0-10dB, which is not high relatively. By applying the Chebyshev function, the SIR becomes 80dB over the sensor interval of 37 mm or higher. The Hann and triangular functions demonstrate better SIR when the sensor interval becomes narrower.

• Journal of Convergence for Information Technology
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• v.10 no.3
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• pp.16-21
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• 2020

This paper describes the jamming characteristics of a stand-off jammer jamming the LPI radar. The LPI radar reduces the side lobes of the receiving antenna to reduce the effect of jamming. It is easy a radar to predict the effect of jamming on a self-protection jammer where the jammer is in the same position as the target. However, for stand-off jammer jamming at different locations from the target, the prediction of jamming effect is complex. In this paper, the jamming effect of LPI radar is analyzed using signal to jamming ratio and burn-through range. Also, when the antenna's side lobe decreases below -30 dB, the stand-off jamming effect in the side lobe direction is weak. So we proposed a new jamming method for the main lobe and analyzed the jamming effect. This study is expected to be useful for the design and operation of aircraft jammers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9B
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• pp.1676-1682
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• 1999

In this paper, the double circular array microstrip patch antenna was designed to minimize the side lobe in which a cooperate feeding network was used to supply the same amplitude and equi-phase to each antenna element. Eight microstirip patch antenna(MPA) elements were arrayed with $45^{\circ}$ interval in the inner circle and the outer circle respectively. The simulation results showed that when the radii of the inner circle and the outer circle were 0.7 $\lambda$0 and 1.45 $\lambda$0, the side lobes of beam pattern were minimized. As the results of the measurements, the return loss of the designed antenna was -14.5[dB] at 11.75[GHz] in the input terminal. When the level of the main lobe was normalized at 0[dB], those of the first and the second side lobe were -18[dB] and -26[dB] respectively. The radiation patterns agree well with the simulated patterns.

• Physical Therapy Korea
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• v.9 no.3
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• pp.67-76
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• 2002

We report the reorganization of motor network resulted from intensive unilateral coordination training and the effect of cross education on the untrained side in patient with traumatic brain injury using functional magnetic resonance imaging (fMRI). A 22 year-old male patient who had suffered from diffuse axonal injury for 58 months showed coordination deficit in the left hand at initial examination. Intensive motor training including complex finger movements and coordination activities using a metronome was introduced to the patient 4 hours per day for a week. FMRI was performed on a 3T ISOL Forte scanner. All functional images were analyzed using SPM-99 software. Hand function was improved after training not only in the trained left hand, but also in the untrained right hand. There was no activation in the right primary motor area (M1) during left hand movement before training whereas robust activation of left M1 was demonstrated by the right hand movement. Profuse activation of bilateral prefrontal lobes was seen during both hand movements before training. After training of left hand, right M1 became prominently activated during the left hand motion. The activation of bilateral prefrontal lobes disappeared after training not only for the left hand movement but also for the right, which clearly demonstrated the effect of cross education. This case report demonstrated the learning-dependent reorganization of the M1 and the effect of cross education.

• Dementia and Neurocognitive Disorders
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• v.17 no.3
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• pp.110-119
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• 2018

Background and Purpose: To analyze $^{18}F-THK5351$ positron emission tomography (PET) scans of patients with clinically diagnosed nonfluent/agrammatic variant primary progressive aphasia (navPPA). Methods: Thirty-one participants, including those with Alzheimer's disease (AD, n=13), navPPA (n=3), and those with normal control (NC, n=15) who completed 3 Tesla magnetic resonance imaging, $^{18}F-THK5351$ PET scans, and detailed neuropsychological tests, were included. Voxel-based and region of interest (ROI)-based analyses were performed to evaluate retention of $^{18}F-THK5351$ in navPPA patients. Results: In ROI-based analysis, patients with navPPA had higher levels of THK retention in the Broca's area, bilateral inferior frontal lobes, bilateral precentral gyri, and bilateral basal ganglia. Patients with navPPA showed higher levels of THK retention in bilateral frontal lobes (mainly left side) compared than NC in voxel-wise analysis. Conclusions: In our study, THK retention in navPPA patients was mainly distributed at the frontal region which was well correlated with functional-radiological distribution of navPPA. Our results suggest that tau PET imaging could be a supportive tool for diagnosis of navPPA in combination with a clinical history.

• Journal of Chest Surgery
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• v.24 no.11
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• pp.1098-1106
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• 1991

Atelectasis may be defined as collapse of the lung due to absence of air within the alveoli. It may involve anatomic segments, lobes, or whole lungs but also may be a diffuse miliary process, as in the adult respiratory distress syndrome. The key to treatment are the anticipation and prevention of atelectasis in various clinical situations, the recognition and treatment of underlying disease, and the prompt initiation of vigorous treatment once atelectasis is found. Repeated assessment by physical examination is necessary to determine the presence of atelectasis and its response to treatment. During the period of January, 1981 to October, 1990, 100 patients with atelectasis were treated in the department of Thoracic and Cardiovascular Surgery, Pusan National University Hospital. There were 70 males and 30 females ranging from 3 days to 79 years of age. The occurrence ratio of right to left side was 2.1 : 1. The underlying pathologic lesions of atelectasis were pneumonia with effusion(28), lung ca.(24), pulmonary tuberculosis(24), and chronic empyema(9), The treatment procedure for atelectasis were closed thoracostomy in 26 cases, ressection in 21 cases, therapeutic bronchoscopy in 14 cases and etc.