• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.2
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• pp.33-39
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• 2004

Sandblasting has recently been developed into a powder blasting technique for brittle materials. In this study, the machinability of $Si_3N_4$-hBN based machinable ceramics are evaluated for micro - pattern making processes using powder blasting. Material properties of the developed machinable ceramics according to the variation of h-BN contents give a good machinability to the ceramics. The effect of scanning times, the size of patterns and variation of BN contents on the erosion depth of samples without mask and samples with different mask patterns in powder blasting of $Si_3N_4$-hBN ceramics are investigated. The Parameters are the impact angle of $90^{\circ}$, the scanning times of nozzle up to 40, and the stand-off distances of 100mm The widths of masked pattern are 0.1mm 0.5mm and 1mm. The powder used is Alumina particles, WA#600. and the blasting pressure of powder is 0.2MPa. Through required experiments, the results are investigated and analyzed. As the results, the machinability of the developed ceramics increases as the BN contents in the ceramics.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3319-3338
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• 2016

Cloud storage is becoming more and more popular because of its elasticity and pay-as-you-go storage service manner. In some cloud storage scenarios, the data that are stored in the cloud may be shared by a group of users. To verify the integrity of cloud data in this kind of applications, many auditing schemes for shared cloud data have been proposed. However, all of these schemes do not consider the access authorization problem for users, which makes the revoked users still able to access the shared cloud data belonging to the group. In order to deal with this problem, we propose a novel public auditing scheme for shared cloud data in this paper. Different from previous work, in our scheme, the user in a group cannot any longer access the shared cloud data belonging to this group once this user is revoked. In addition, we propose a new random masking technique to make our scheme preserve both data privacy and identity privacy. Furthermore, our scheme supports to enroll a new user in a group and revoke an old user from a group. We analyze the security of the proposed scheme and justify its performance by concrete implementations.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.8 no.1
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• pp.9-17
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• 2014

Electrical compound action potential (ECAP) can be recorded on cochlear implant. This study will investigate stimulation and recording to enhance the efficacy of ECAP. 34 articles was used. We analyzed pulse and stimulating condition, artifact suppression, recording condition. The cathod-leading biphasic pulse was used with as short as possible pulse width and inter phase gap for the efficacy of neural firing, stable threshold and preventing neural degeneration. Around C-level was stimulated to apical, middle and basal turn of cochlea. Artifact was eliminated by forward-masking, template-subtraction technique. For clearer waveform, we need to change distance between stimulating and recording electrode, the gain of amplification, number of average.

• Korean Journal of Remote Sensing
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• v.24 no.5
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• pp.445-452
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• 2008

Preliminary results are reported on ship detection using coherence images computed from cross-correlating images of multi-look-processed dual-polarization data (HH and HV) of ENVISAT ASAR. The traditional techniques of ship detection by radars such as CFAR (Constant False Alarm Rate) rely on the amplitude data, and therefore the detection tends to become difficult when the amplitudes of ships images are at similar level as the mean amplitude of surrounding sea clutter. The proposed method utilizes the property that the multi-look images of ships are correlated with each other. Because the inter-look images of sea surface are covered by uncorrelated speckle, cross-correlation of multi-look images yields the different degrees of coherence between the images and water. In this paper, the polarimetric information of ships, land and intertidal zone are first compared based on the cross-correlation between HH and HV images, In the next step, we examine the technique when the dual-polarization data are split into two multi-look images, It was shown that the inter-look cross-correlation method could be applicable in the performance improvement of small ship detection and the land masking, It was also found that a simple combination of coherence images from each co-polarised (HH) inter-look and cross-polarised (HV) inter-look data can provide much higher target-detection possibilities.

• Korean Journal of Remote Sensing
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• v.8 no.2
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• pp.105-123
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• 1992

A study was made on the feature extraction for non-metallic one deposits and their related geology using the Remote Sensing and Airborne Radiometric data. The area chosen is around the Haenam area, where dickite and Quarzite mines are distributed in. The geology of the area consists mainly of Cretaceous volcanics and PreCambrian metamorphic. The methods applied are study on the reflectance characteristics of minerals and rocks sampled in the study area, and the feature extraction extraction of histogram normalized images for Landsat TM and Airborne Radiometric data, and finally evaluation of applicability of some useful pattern recognition techniques for regional lithological mapping. As a result, reflectances of non-metallic minerals are much higher than rock samples in the area. However, low grade dickites are slightly higher than rock samples, probably due to their greyish colour and also their textural features which may scatter the reflectance and may be capable of capturing much hychoryl ions. The reflectances of rock samples may depend on the degree of whiteness of samples. The outcrops or mine dumps in the study area were most effectively extracted on the histogram normalized image of TM Band 1, 2 and 3, due to their high reflectivity. The Masking technique using the above bands may be the most effective and the natural colour composite may provide some success as well. The colour composite image of PCA may also be effective in extracting geological features, and airborne radiometric data may be useful to some degree as an complementary tool.

• Journal of the Korean earth science society
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• v.26 no.1
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• pp.58-65
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• 2005

Homomorphic filtering improves image by enhancing high components and reducing low components in the Sequency domain based on FFT, as one of useful digital image processing techniques. In this study, the application program f3r homomorphic filtering was developed. Using this program, satellite imageries and geophysical image such as magnetic image data were processed and their results were analyzed. In case of applying to other techniques suck as histogram equalization and kernel-based masking f3r the same purpose. they often cause the slight distortion of boundary or overall change of brightness values on the whole image. Whereas. homomorphic filtering has ability to enhance selectively detailed components in a target image. Therefore. this technique can be effectively used for extraction or separation of complex types of characteristics contained in the satellite imagery. In addition, this technique would be applicable to investigate anomalous zone in various geophysical image data.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2006.06a
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• pp.730-736
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• 2006

In this paper, we propose a rotation resistant robust logo embedding watermarking technique. Geometric manipulations make the detection process very complex and difficult. Watermark embedding ill the normalized image directly suffers from smoothing effect due to the interpolation during the image normalization. This can be avoided by estimating the transform parameters using image normalization technique, instead of embedding in the normalized image. Conventional rotation resistant schemes that use full frame transform. In this paper, we adopt $8{\times}8$ block DCT and calculate masking using a spatio-frequency localization of the $8{\times}8$ block DCT coefficients. Experimental results show that the proposed algorithm is robust against rotation process.

• Journal of Radiation Industry
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• v.9 no.3
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• pp.137-141
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• 2015

A single-shot dual-energy x-ray imaging technique has been developed using a sandwich detector by stacking two detectors, in which the front and rear detectors respectively produce relatively lower and higher x-ray energy images. Each detector layer is composed of a phosphor screen coupled with a photodiode array. The front detector layer employs a thinner phosphor screen, whereas the rear detector layer employs a thicker phosphor screen considering the quantum efficiency for x-ray photons with higher energies. We have applied the proposed method into the inspection of printed circuit boards, and obtained dual-energy images with background clutter suppressed. In addition, the single-shot dual-energy method provides sharper-edge images than the conventional radiography because of the unsharp masking effect resulting from the use of different thickness phosphors between the two detector layers. It is promising to use the single-shot dual-energy x-ray imaging for high-resolution nondestructive testing. For the reliable use of the developed method, however, more quantitative analysis is further required in comparisons with the conventional method for various types of printed circuit boards.

• The Korean Journal of Applied Statistics
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• v.28 no.6
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• pp.1275-1288
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• 2015

A microscale weather analysis module (about 1km or less) is a microscale numerical weather prediction model designed for operational forecasting and atmospheric research needs such as radiant energy, thermal energy, and humidity. The accuracy of the module is directly related to the usefulness and quality of real-time microscale weather information service in the metropolitan area. This paper suggests an object based verification method useful for spatio-temporal evaluation of the accuracy of the microscale weather analysis module. The method is a graphical method comprised of three steps that constructs a lattice field of evaluation statistics, merges and identifies objects, and evaluates the accuracy of the module. We develop lattice fields using various evaluation spatio-temporal statistics as well as an efficient object identification algorithm that conducts convolution, masking, and merging operations to the lattice fields. A real data application demonstrates the utility of the verification method.

• Journal of Animal Science and Technology
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• v.48 no.3
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• pp.467-478
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• 2006

Maintenance of an optimal air quality in the enclosed pig building is potentially important in terms of pig performance and farmer health. The objective of this on-site experiment is to evaluate and compare efficiencies of currently utilized biological additives to reduce odor emissions from the enclosed pig building. As a result, generally all the additives except for salt water, artificial spice and essential oil were proved ineffective in reducing odor generation. The beneficial effects of salt water, artificial spice and essential oil on odor reduction were highlighted on ammonia, odor intensity and offensiveness, and sulfuric odorous compounds, respectively. To efficiently utilize odor masking agent such as the artificial spice, ventilation rate should keep slightly lower than the optimal level. Essential oil functioned well as not only masking agent but also antimicrobial agent for reducing odor. To precisely quantify odor concentration, it should be measured by not the odor sensor but the olfactometry technique.