• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2043-2052
• /
• 2008

The increasing heat generation rates in CPU of notebook computers motivate a research on cooling technologies with low thermal resistance. This paper develops a closed-loop two-phase cooling system using a micropump to circulate a dielectric liquid(PF5060). The cooling system consists of an evaporator containing a boiling enhancement microstructure connected to a condenser with mini fans providing external forced convection. The cooling system is characterized by a parametric study which determines the effects of volume fill ratio of coolant, existence of a boiling enhancement microstructure and pump flow rates on thermal performance of the closed loop. Experimental data shows the optimal parametric values which can dissipate 33.9W with a film heater maintained at $95^{\circ}C$.

• Journal of the Korea Society of Computer and Information
• /
• v.23 no.4
• /
• pp.51-56
• /
• 2018

This paper proposes the efficient preprocessing method based on curvelet transform for edge enhancement in image. The propose method is generated the edge map by using the Canny algorithm to wavelet transform, which is the sub-step of the curvelet transform. In order to improve the part of edge feature, the selective sharpening according to the generate edge map is applied. In experimental result, the propose method achieves that the enhancement of edge feature is better than conventional methods. This leads that peak to signal noise ratio, edge intensity are improvement on average about 1.92, 1.12dB respectively.

• ETRI Journal
• /
• v.33 no.6
• /
• pp.841-848
• /
• 2011

A signal-to-noise ratio (SNR) enhancement algorithm using multiple chirp symbols with clock drift is proposed for accurate ranging. Improvement of the ranging performance can be achieved by using the multiple chirp symbols according to Cramer-Rao lower bound; however, distortion caused by clock drift is inevitable practically. The distortion induced by the clock drift is approximated as a linear phase term, caused by carrier frequency offset, sampling time offset, and symbol time offset. SNR of the averaged chirp symbol obtained from the proposed algorithm based on the phase derotation and the symbol averaging is enhanced. Hence, the ranging performance is improved. The mathematical analysis of the SNR enhancement agrees with the simulations.

• Journal of Information Processing Systems
• /
• v.19 no.4
• /
• pp.465-473
• /
• 2023

An image enhancement algorithm and image defogging method are studied in this paper. The formation of fog and the characteristics of fog image are analyzed, and the fog image is preprocessed by histogram equalization method; then the additive white noise is removed by foggy image attenuation model, the atmospheric scattering physical model is constructed, the image detail characteristics are enhanced by image enhancement method, and the visual effect of defogging image is enhanced by guided filtering method. The proposed method has a good defogging effect on the image. When the number of training iterations is 3,000, the peak signal-to-noise ratio of the proposed method is 43.29 dB and the image structure similarity is 0.9616, indicating excellent image defogging effect.

• Investigative Magnetic Resonance Imaging
• /
• v.21 no.3
• /
• pp.148-153
• /
• 2017

Purpose: To identify the differences between injected cement volumes during vertebroplasty procedures according to the enhancement pattern of pre-procedure magnetic resonance imaging (MRI) findings. Materials and Methods: Thirty-two patients who underwent 52 vertebroplasty procedures as well as pre-procedure contrast-enhanced spine MRI in the authors' institution were reviewed retrospectively. The 52 procedures were divided into two groups according to different enhancement patterns shown by pre-procedure MR imaging [E(+) and E(-)]. The volumes of the enhancing/non-enhancing portions of the fractured vertebral body shown by pre-procedural MR imaging were calculated and compared to the volumes of the injected cement during the vertebroplasty procedures. Results: The 52 injections included 28 (56%) in Group E(+) and 24 (44%) in Group E(-). The actual volume ratio of the injected cement to the volume of the non-enhanced or enhanced region calculated based on the contrast-enhanced MRI was $0.22{\pm}0.11(cc/cm^3)$ in the E(+) group and $0.93{\pm}0.62(cc/cm^3)$ in the E(-) group. The average amount of injected cement was significantly different between Group E(+) and Group E(-) (P < 0.001). In addition, the ratio of the injected cement amount to the volume of the enhanced or non-enhanced portion based on the contrast-enhanced MRI in Group E(-) was significantly higher than that of Group E(+) (P < 0.001). Conclusion: Different enhancement patterns shown by pre-procedure MRI can predictors of the injected cement volume during vertebroplasty procedures for osteoporotic fractures.

• The KIPS Transactions:PartB
• /
• v.16B no.4
• /
• pp.263-270
• /
• 2009

Histogram Equalization (HE) is a very popular technique for enhancing the contrast of an image. HE stretches the dynamic range of an image using the cumulative distribution function of a given input image, therefore improving its contrast. However, HE has a well-known problem : when HE is applied for the contrast enhancement, there is a significant change in brightness. To resolve this problem, we propose An Adaptive Contrast Enhancement Algorithm using Subhistogram Area-Ratioed Histogram Redistribution, a new method that helps reduce excessive contrast enhancement. This proposed algorithm redistributes the dynamic range of an input image using its mean luminance value and the ratio of sub-histogram area. Experimental results show that by this redistribution, the significant change in brightness is reduced effectively and the output image is able to preserve the naturalness of an original image even if it has a poor histogram distribution.

• The Journal of the Acoustical Society of Korea
• /
• v.40 no.3
• /
• pp.234-240
• /
• 2021

In this paper, the mask-based speech enhancement is improved for effective speech recognition in noise environments. In the mask-based speech enhancement, enhanced spectrum is obtained by multiplying the noisy speech spectrum by the mask. The VoiceFilter (VF) model is used as the mask estimation, and the Spectrogram Inpainting (SI) technique is used to remove residual noise of enhanced spectrum. In this paper, we propose a combined loss to further improve speech enhancement. In order to effectively remove the residual noise in the speech, the positive part of the Triplet loss is used with the component loss. For the experiment TIMIT database is re-constructed using NOISEX92 noise and background music samples with various Signal to Noise Ratio (SNR) conditions. Source to Distortion Ratio (SDR), Perceptual Evaluation of Speech Quality (PESQ), and Short-Time Objective Intelligibility (STOI) are used as the metrics of performance evaluation. When the VF was trained with the mean squared error and the SI model was trained with the combined loss, SDR, PESQ, and STOI were improved by 0.5, 0.06, and 0.002 respectively compared to the system trained only with the mean squared error.

• Journal of Veterinary Clinics
• /
• v.37 no.5
• /
• pp.255-260
• /
• 2020

The purpose of this retrospective study was to describe the characteristics of magnetic resonance imaging (MRI) findings in dogs with meningoencephalitis of unknown etiology (MUE), and to evaluate the usefulness of meningeal enhancement. Thirty-two dogs were included in MUE group on the basis of clinical signs, MRI findings and cerebrospinal fluid (CSF) results, and for comparison of the meningeal enhancement, twenty-three dogs with normal MRI, normal CSF and no clinical sign were included in the control group. The evaluated MRI findings included lesion site, lesion number, signal intensity of each MRI sequence, mass effect, perilesional edema, contrast enhancement, and meningeal enhancement. The MUE was most frequently associated with multiple lesions (50%) with perilesional edema (72%) in forebrain (66%) that were hyperintense (92%) in T2W and FLAIR images. Of the meningeal enhancement, there was no significant difference between the control group and the MUE groups in the pachymeningeal enhancement. However, leptomeningeal (or both) enhancement was found relatively high proportion in the MUE group than in the control group (P < 0.001, Odd ratio = 10.26), and based on this result, leptomeningeal (or both) enhancement is considered to be significant finding for indicating MUE.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.8
• /
• pp.627-634
• /
• 2006

Evaporation heat transfer characteristics by pulsating flow in a plate heat exchanger have been investigated experimentally in this study. R-l34a is evaporated by receiving heat from the hot water in the plate heat exchanger. The pulsating frequency in refrigerant side of the plate heat exchanger is varied in the range of 5-25 Hz. The operating pressure of R-l34a and mass flux of hot water are also varied 0.6-0.9 MPa and $45-105 kg/m^2s$, respectively. The experimental results indicate that evaporation heat transfer coefficient of pulsating flow is improved up to 6.3% compared with that of the steady flow at 10 Hz and $G_w=45 kg/m^2s$. It is also found that the evaporation heat transfer enhancement ratio is decreased with an increase in mass flux of hot water, and the evaporation heat transfer enhancement is little influenced by operating pressure of R-l34a.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.62 no.2
• /
• pp.90-94
• /
• 2013

In this paper, we propose a new algorithm to improve the contrast ratio, to preserve information of bright regions and to maintain the color of backlight image that appears with a great relative contrast. Backlight images of the natural environment have characteristics for difference of local brightness; the overall image contrast improvement is not easy. To improve the contrast of the backlight images, MSR (Multi-Scale Retinex) algorithm using the existing multi-scale Gaussian filter is applied. However, existing multi-scale Gaussian filter involves color distortion and information loss of bright regions due to excessive contrast enhancement and noise because of the brightness improvement of dark regions. Moreover, it also increases computational complexity due to the use of multi-scale Gaussian filter. In order to solve these problems, a linear MSR is performed that reduces the amount of computation from the HSV color space preventing the color distortion and information loss due to excessive contrast enhancement. It can also remove the noise of the dark regions which is occurred due to the improved contrast through edge preserving filter. Through experimental evaluation of the average color difference comparison of CIELAB color space and the visual assessment, we have confirmed excellent performance of the proposed algorithm compared to conventional MSR algorithm.