• The Journal of the Acoustical Society of Korea
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• v.31 no.6
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• pp.359-366
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• 2012

Today, people are exposed to the various noisy environments, such as in the buses, subway and supermarkets where there are a lot of people. The noise issue is getting more serious as people want to use portable sound equipment and mobile phones even under this noisy condition. People want to use the portable equipment to exchange the information freely and they set the volume as 15dB higher than the noise around them, which almost reach at 110 dB. That amount of sound can cause noise induced deafness to the users and another issue to the others as additional noise source. A Bone-conduction system can be a solution to reduce noise and enhance voice signal of mobile phone. In this paper, we propose the way of cancelling noise and enhancing speech signal of mobile phones, by installing bone-conduction feedback system with ordinary mobile phones. With this system, we can reduce the environment noise and enhance the voice quality of mobile phones. Using this method, we can enhance the signal by around 17 dB.

• The Journal of the Acoustical Society of Korea
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• v.30 no.4
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• pp.207-214
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• 2011

Human auditory acuity decreases naturally due to aging. But recently cases of impaired hearing at a young age are increasing greatly. The biggest reason for such an increase of population with impaired hearing is popularization of various kinds of portable multimedia appliances. Many studies on impaired hearing due to noises caused by the earphone and headphone are being made, but there are few studies on noise-impaired hearing caused directly by mobile phone communication. Based on a precedent inquiry, this study proposes a technique for preventing noise-impaired hearing applying to an active noise reduction technique onto bone conduction speaker. This technique is a method for reducing noises by antiphase oscillation through bone conduction speaker with ambient noises. If the proposed system is applied, the noise level that is actually introduced to audition decreases by more than 12 dB, and such a decreased amount of sound volume fundamentally prevents the factors of noise-caused hearing difficulty due to mobile phone communication. Sensibility test results showed that adequate communication was possible even in such a situation where communication volume was decreased like this.

• The Journal of the Korean bone and joint tumor society
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• v.9 no.2
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• pp.139-147
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• 2003

Purpose: The purpose of this study was to determine if bony union can be obtained when a bone graft substitute is transplanted in order to treat a benign bone tumor and if there is a difference between calcium sulfate and hydroxyapatite in the healing procedure when the degree of the bony union after the bone graft are compared. Materials and Methods: This study selected 20 cases, in which a curettage on the benign bone tumors was conducted and a bone graft substitute was transplanted. The area of the focus, the new bone formation, the recurrence of the focus in the plain radiographs and histological findings were observed. Results: Twenty cases (13 males, 7 females) were evaluated. Their mean age at surgery was 15.8 years (2~45), and the mean follow-up period was 3 years. The mean area of focus was 30.7 $cm^3$ in the radiographs, and 19 cases showed successful results in the ultimate visit, while 1 case has a recurrence of the focus. Conclusion: Calcium sulfate has osteoconduction and superior bioavailability, and is absorbed in vivo in proportion to the new bone formation. On the other hand, hydroxyapatite has good osteoconduction. It can result in better bone formation when it is combined with an autologous bone graft, autologous bone marrow, and an allogenic bone graft, but is absorbed in vivo more slowly than the former.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.4 no.1
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• pp.29-34
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• 2010

The fully implantable hearing devices (FIHDs) have been studied to compensate the defect of conventional hearing aids. Typically, a microphone for FIHDs was implanted under the skin of the temporal bone. So, implantable microphone characteristics can be affected by the eating food, chattering teeth and moving artifact. In this paper, we fabricated the physical model that was similar to characteristics of human temporal bone and skin, and we measured implanted microphone sensitivity for effect of bone conducted noise signal. For the measurement of microphone sensitivity, we applied 1 kHz pure sounds that were transmitted to implanted microphone and sine wave vibrations of varied frequency were simultaneously transmitted through the artificial bone. As a result, sensitivity of implanted microphone can be modified by bone conducted signal and this phenomenon was confirmed at varied frequency band.

• The Journal of the Korean bone and joint tumor society
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• v.9 no.1
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• pp.31-37
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• 2003

Introduction: The purpose of this study is to assess the efficacy of calcium sulfate as a bone graft substitute in the treatment of benign bone tumor. Materials and Method: Between December 2000 and November 2001, 18 patients with a benign bone tumor were treated with crettage and the defects were filled with calcium sulfate (Osteoset$^{(R)}$:Wright Medical Co. USA) as a bone graft substitute. Average age was 28.4 years and mean follow up period was 12.3 months. Calcium sulfate mixed with autograft was used in 6 cases, calcium sulfate with allograft in 2 cases, and calcium sulfate alone was used in 10 cases. The degree of absorption of calcium sulfate and new bone formation at plain radiograph was analyzed at immediate postoperative and postoperative 3 months and 6 months follow up. Results: At 3 months postoperatively, 92% of calcium sulfate was absorbed, and at 6 months postoperatively, 89% of new bone formation was observed. There was no difference in the resorption and new bone formation between the group using bone graft and the group osteoset$^{(R)}$ alone, different preoperative diagnosis and even different locations. There was no complication. Conclusion: Calcium sulfate(Osteoset$^{(R)}$) is a safe and effective bone graft substitute in the treatment of benign bone tumors, especially for the children in whom autograft is not recommandable.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.11
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• pp.1237-1242
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• 2011

Calcium phosphates are very interesting materials for use as scaffolds for bone tissue engineering. These materials include hydroxyapatite (HA) and tricalcium phosphate (TCP), which are inorganic components of human bone tissue and are both biocompatible and osteoconductive. Although these materials have excellent properties for use as bone scaffolds, many researchers have used these materials as additives to synthetic polymer scaffolds for bone tissue regeneration, because they are difficult to manufacture three-dimensional (3D) scaffolds. In this study, we fabricated 3D calcium phosphate scaffolds with the desired inner and outer architectures using solid freeform fabrication technology. To fabricate the scaffold, the sintering behavior was evaluated for various sintering temperatures and slurry concentrations. After the fabrication of the calcium phosphate scaffolds, in-vitro cell proliferation and osteogenic differentiation tests were carried out.

• Journal of Periodontal and Implant Science
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• v.36 no.1
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• pp.39-49
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• 2006

1. 목 적 이 연구의 목적은 성견의 하악 골 결손부에 이식한 생체 유래 골 이식재에 대한 치조골의 반응을 알아보는 것이다. 2. 연구방법 및 재료 생후 1년 이상 된 성견 4마리의 하악 제2소구치 및 제 4 소구치를 발거하고 발치와에 금원심 폭경 8mm, 협설 폭경 5mm, 치조정에서의 깊이 6mm인 결손부를 형성하였다. 4주간의 자연 치유 후 판막을 형성하여 결손부의 크기를 확인하였다. 각각의 결손부 크기가 일정하도록 수정한 후 '이식재+차폐막'군에는 OCS-B을 이식하고 Bio-gide을 차단막으로 사용한 후 봉합하고 '이식재군'은 OCS-B 이식 후 차폐막 없이 봉합하였으며 '비이식'군은 아무런 처치없이 일차봉합하였다. 수술 4, 6주에 실험동물을 각각 희생시켜 실험부위를 적출하고 비탈회 연마 표본을 제작하여 골 치유 양성을 조직학적 및 조직계측학적으로 관찰하였다. 3. 연구결과 이식재 비이식군 및 이식군 모돼서 별다른 부작용없이 잘 치유되었다. 세 실험군 모두에서 술후 4주에 비교하여 술 후 6주에서의 결손부 산생골 형성량이 증가하였다. 술후 4주 소견에서 비이식군은 결손부 주변부위에서 골이 생성되어 나오는 양상을 보였으며 이식군은 이식재 주변으로 골침착 시작되는 것을 관찰할 수 있었다. 술후 6주 소견에서 비이식군은 결손부 경계부로부터의 지속적인 골 생성을 관찰할 수 있었으며 이식군은 이식재 주변으로 침착된 골의 양이 많아지고 신생골이 가교를 형성하는 것을 관찰할 수 있었다. 4. 결 론 차폐막 유무와 상관없이 OCS-B는 염증반응을 전혀 일으키지 않았으며 우수한 골 전도성을 보였다. 또한 결손부의 형태를 잘 유지하여 골재생을 위한 공간을 확보할 수 있었다. 이는 OCS-B가 골이식재로서의 필요조건을 갖추었음을 확인한 결과이며 보다 장기적인 관찰에서 OCS-B의 흡수 가능성을 확인하는 것이 필요할 것으로 보인다.

• Journal of Biomedical Engineering Research
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• v.25 no.4
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• pp.261-268
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• 2004

Osteoporosis is a clinical condition in which the amount of bone tissue is reduced and the likelihood of fracture is increased. It is known that the electrical property of the bone is related to its density, and, in particular, the electrical resistance of the bone decreases as the bone loss increases. This implies that the electrical property of bone may be an useful parameter to diagnose osteoporosis, provided that it can be readily measured. The study attempted to evaluate the electrical conductivity of bone using a technique of electrical impedance tomography (EIT). It nay not be easy in general to get an EIT for the bone due to the big difference (an order of 2) of electrical properties between the bone and the surrounding soft tissue. In the present study, we took an adaptive mesh regeneration technique originally developed for the detection of two phase boundaries and modified it to be able to reconstruct the electrical conductivity inside the boundary provided that the geometry of the boundary was given. Numerical simulation was carried out for a tibia phantom, circular cylindrical phantom (radius of 40 mm) inside of which there is an ellipsoidal homeogenous tibia bone (short and long radius are 17 mm and 15 mm, respectively) surrounded by the soft tissue. The bone was located in the 15 mm above from the center of the circular cross section of the phantom. The electrical conductivity of the soft tissue was set to be 4 mS/cm and varies from 0.01 to 1 ms/cm for the bone. The simulation considered measurement errors in order to look into its effects. The simulated results showed that, if the measurement error was maintained less than 5 %, the reconstructed electrical conductivity of the bone was within 10 % errors. The accuracy increased with the electrical conductivity of the bone, as expected. This indicates that the present technique provides more accurate information for osteoporotic bones. It should be noted that tile simulation is based on a simple two phase image for the bone and the surrounding soft tissue when its anatomical information is provided. Nevertheless, the study indicates the possibility that the EIT technique may be used as a new means to detect the bone loss leading to osteoporotic fractures.

• 대한예방의학회:학술대회논문집
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• 1993.10a
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• pp.115-116
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• 1993

• The Journal of the Acoustical Society of Korea
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• v.32 no.5
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• pp.423-429
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• 2013

The present study aimed to find the most sensitive placement of the skull to perceive speech through the bone vibrator in various protection methods while being exposed to noise. Twenty young normal-hearing adults (10 male and 10 female) participated in the study. As stimulus, Korean spondee words were presented via one of five skull locations (i.e., jaw angle, condyle, temple, mastoid, and vertex), while the participants wore one of four protection methods (i.e., ear form, ear plug, ear muff, and ear form and muff together) against white noise in one of four noise directions (i.e., 0, 90, 180, 270 degrees). The results showed: 1) there was a significant difference among the five skull locations with condyle being the most sensitive placement; 2) there was a significant difference among the four protection methods, with the ear form plus ear muff condition (or dual protection) providing the lowest threshold; 3) when exposed to noise from 90 degrees, the significantly lowest threshold was found; 4) there was no significant difference in results by gender. The pattern of results suggests that the communicative condition via the condyle bone conduction and the dual protection of the air conduction under any noise direction might be ideal for preventing noise-induced hearing loss, although further studies should be undertaken in this area.