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인공 신경망을 이용한 보청기용 실시간 환경분류 알고리즘
서상완,육순현,남경원,한종희,권세윤,홍성화,김동욱,이상민,장동표,김인영,Seo, Sangwan,Yook, Sunhyun,Nam, Kyoung Won,Han, Jonghee,Kwon, See Youn,Hong, Sung Hwa,Kim, Dongwook,Lee, Sangmin,Jang, Dong Pyo,Kim, In Young 대한의용생체공학회 2013 의공학회지 Vol.34 No.1
Persons with sensorineural hearing impairment have troubles in hearing at noisy environments because of their deteriorated hearing levels and low-spectral resolution of the auditory system and therefore, they use hearing aids to compensate weakened hearing abilities. Various algorithms for hearing loss compensation and environmental noise reduction have been implemented in the hearing aid; however, the performance of these algorithms vary in accordance with external sound situations and therefore, it is important to tune the operation of the hearing aid appropriately in accordance with a wide variety of sound situations. In this study, a sound classification algorithm that can be applied to the hearing aid was suggested. The proposed algorithm can classify the different types of speech situations into four categories: 1) speech-only, 2) noise-only, 3) speech-in-noise, and 4) music-only. The proposed classification algorithm consists of two sub-parts: a feature extractor and a speech situation classifier. The former extracts seven characteristic features - short time energy and zero crossing rate in the time domain; spectral centroid, spectral flux and spectral roll-off in the frequency domain; mel frequency cepstral coefficients and power values of mel bands - from the recent input signals of two microphones, and the latter classifies the current speech situation. The experimental results showed that the proposed algorithm could classify the kinds of speech situations with an accuracy of over 94.4%. Based on these results, we believe that the proposed algorithm can be applied to the hearing aid to improve speech intelligibility in noisy environments.
서상완,임지선 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
피치는 크게 콜타르와 석유계 잔사유의 중합을 통해 만들어진다. 석유계 잔사유는 콜타르에 비해 분자량이 낮아 반응기 내에서 쉽게 휘발된다. 또한 콜타르와 비교해 많은 관능기를 가지고 있다. 이로 인해 낮은 온도에서 쉽게 coking이 일어나 이방성 피치를 제조하는데 한계가 있다. 본 연구에서는 석유계 잔사유 중 PFO의 휘발성물질을 압력조절을 통해 이방성 피치제조 공정을 연구 하였다. 피치제조공정은 2단에 걸쳐 진행하였고 첫 번째 단은 가압, 상압, 감압으로 열처리를 진행하고 두 번째 단은 상압으로 진행하였다. 가압, 감압의 효과로는 휘발성분들의 대한 GCSIMDIS를 통해 고찰하였다. 피치에 대한 분석은 연화점 측정장치와 MALDITOF 등을 통해 전체적인 피치물성과 분자량을 확인하였고, 편광현미경을 통해 이방성 함량을 확인 하였다.
서상완,곽철환,이영석,임지선 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Activated carbon is extensively investigated as an electrode for electric double layer capacitor (EDLC) due to its high specific surface area with developed pore structure. The development of pore structure in activated carbon, however, decreases electro-conductivity because the activation process causes defects of carbon crystal structure. It should be, thus, considered that the control of pore structure is an important factor for application in EDLC. In this study, the effect of pore structure on the capacitance and electro-conductivity of EDLC was investigated. The activated carbon was prepared using oxidized pitch as a raw material. The pore structure and electro-conductivity of activated carbon were analyzed using BET and the measurement of sheet resistance, respectively. The capacitance was finally calculated using CV curve.
Control of activation property of petroleum pitch via oxygen functional groups
서상완,이영석,임지선 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
During a heat treatment process under air, oxygen functional groups are introduced into the pitch, it becomes an infusible state. It also change by the heat treatment time, with increasing the treatment time, C-O is changed to C=O. These introduced functional groups generate carbon dioxide or carbon monoxide, in this process, the carbon materials are formed a porous structure. In this study, it is investigated that the effect of oxygen functional groups in the pitch during the activation process. The oxygen functional group of pitch was controlled by heat treatment time under air condition, and the activation property of the pitch was determined. The oxygen content of the pitch and the type of oxygen functional group were investigated by XPS analysis. The activation was proceeded by chemical activation, and the pore characteristics of prepared activated carbon was examined by BET analysis.
Micropore-structured activated carbon prepared by waste PET/petroleum-based pitch
서상완,최윤정,김지홍,조종훈,이영석,임지선 한국탄소학회 2019 Carbon Letters Vol.29 No.4
In this study, pitch crosslinked by oxygen function groups was made into activated carbon (AC) and pore structure was observed. The oxygen functional groups were introduced by the addition of waste PET for pitch synthesis. Activation agent ratios used to obtain the AC during the activation process were 1:1, 1:2 and 1:4 (pitch:KOH, w/w). The oxygen content in the prepared pitch was characterized by elemental analysis. Also, the molecular weight of pitch was investigated by MALDI-TOF. Specific surface area and micropore volume of the prepared AC were determined by the argon adsorption–desorption analysis and calculated using the Brunauer–Emmett–Teller and Horvath–Kawazoe equations, respectively. Micropore fraction of PET-free AC was smaller than that of PET-added AC. At high activation agent ratio, mesopores were created when the micropore structure collapsed. However, in the PET-added AC, due to the oxygen crosslinking effect, the micropore structure and micropore size were maintained even at a high activation agent ratio. Therefore, PET AC was found to have a higher micropore fraction than that of PET-free AC.
A standardization model based on image recognition for performance evaluation of an oral scanner
서상완,이완선,변재영,이규복 대한치과보철학회 2017 The Journal of Advanced Prosthodontics Vol.9 No.6
PURPOSE. Accurate information is essential in dentistry. The image information of missing teeth is used in optically based medical equipment in prosthodontic treatment. To evaluate oral scanners, the standardized model was examined from cases of image recognition errors of linear discriminant analysis (LDA), and a model that combines the variables with reference to ISO 12836:2015 was designed. MATERIALS AND METHODS. The basic model was fabricated by applying 4 factors to the tooth profile (chamfer, groove, curve, and square) and the bottom surface. Photo-type and video-type scanners were used to analyze 3D images after image capture. The scans were performed several times according to the prescribed sequence to distinguish the model from the one that did not form, and the results confirmed it to be the best. RESULTS. In the case of the initial basic model, a 3D shape could not be obtained by scanning even if several shots were taken. Subsequently, the recognition rate of the image was improved with every variable factor, and the difference depends on the tooth profile and the pattern of the floor surface. CONCLUSION. Based on the recognition error of the LDA, the recognition rate decreases when the model has a similar pattern. Therefore, to obtain the accurate 3D data, the difference of each class needs to be provided when developing a standardized model.