치료되지 않은 치주염이 치과 임플란트의 골유착에 미치는 영향

학위논문 (박사)-- 서울대학교 대학원 : 치의과학과, 2017. 2. 구영.Background: There have been previous studies on the relationship between periodontitis and periimplantitis, but limited information is available on how periodontitis affects osseointegration and wound healing of newly placed dental implants adjacent to natural teeth. The objective of the present experiment was to evaluate healing around dental implants adjacent to teeth with untreated experimental periodontitis. Methods: The experiment included 6 male beagle dogs. Scaling and plaque control procedures were performed in 3 dogs (the control group). In the other 3 dogs (the experimental group), retraction cords and ligature wires were placed subgingivally around all premolars and the first molars. Induced experimental periodontitis was confirmed after 3 months. Each control or experimental group was divided into 2 subgroups depending on the timing of implant placement (immediate/delayed). Twelve dental implants (2 implants for each dog) were placed immediately and the other 12 dental implants (2 implants for each dog) were placed two months after extraction. The animals were sacrificed 2 months after implant placement. Histological and histometric analysis were performed. Results: Four implants (3 from immediate and 1 from delayed placement) failed in the experimental group. There were significant differences in the percentage of bone-to-implant contact and marginal bone volume density between the control and the experimental groups. Both parameters were significantly lower in the experimental group than in the control group (P<0.05). There was a tendency toward more marginal bone loss in the experimental group than the control group. Conclusion: Immediately placed implants have a higher failure rate than delayed placed implants. Untreated experimental periodontitis was correlated with a compromised osseointegration in delayed placed implants.INTRODUCTION 1 MATERIALS & METHODS 5 RESULTS 11 DISCUSSION 14 References 25 국문초록 32Docto

임의 흩뿌림에 기반한 가변생체인증

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 전기·컴퓨터공학부, 2018. 8. 조남익.Nowadays biometrics systems for identification or authentication of a person are everywhere. These system have a number of advantages. In particular, biometrics traits cannot be lost or forgotten compared to passwords. Moreover biometric identification offers good accuracy. However, their uses raises several privacy concerns, especially in their storage. In fact, if a password is stolen, it can be replaced by a new password. This is not possible in biometrics. To overcome the security problems, biometric cryptosystems (BCS) and cancelable biometrics (CB) represent emerging technologies of biometrics template protection addressing this concerns and improving public confidence and acceptance of biometrics. BCS are designed to securely bind a digital key to a biometric or generate a digital key from a biometric offering solutions to biometric-dependent key-release and biometric template protection while CB consist of intentional, repeatable distortions of biometric signals based on transforms which provide a comparison templates in the transformed domain. In this dissertation, a cancelable biometric scheme for iris recognition system is proposed. The first proposed CB method uses the reduced random permutation and binary salting (RRP-BS). RRP-BS consists of random permutation of binary iris template followed by the orthogonal binary salting. The random permutation perturbs the rows of iris template structure and eliminates some rows of iris template. This guarantees the non-invertibility of CB scheme even though the all of bio-security keys is stolen. Then this CB scheme also proposes an orthogonal binary salting method, where the random binary keys are generated by Gram-Schmidt orthogonalization. The orthogonality of random keys maximizes the Hamming distances among binary-salted templates. Thus, the inter classes (different users) are discriminated while the intra class (one user) is well identified. While this method has good performance and unlinkability, its non-invertibility is vulnerable to muliplicity or hill-climbing attacks. The second proposed method uses more robust non-invertibility transform based on the first method. We use the RRP-BS as the biometric salting, and use the Hadamard product for enhancing the non-invertibility of salted data. Moreover, to overcome the shortcomings of perserving the keys of the conventional salting methods, we generate several templates for an input, and define non-coherent and coherent matching regions among these templates. We show that salting the non-coherent matching regions is less influential on the overall performance. Specifically, embedding the noise in this region does not affect the performance, while making the data difficult to be inverted to the original. For the evaluation, we use three datasets, namely CASIA V3 iris-interval, IIT Delhi iris, and ND-Iris-0405. The extensive evaluations show that the proposed algorithm yields low error rates and good intra/inter classification performances, which is better or comparable to the existing methods. Moreover, the security analysis ensures that the proposed algorithm satisfies non-invertibility and unlinkability, and is robust against several attacks as well.1 INTRODUCTION 1 1.1 Biometrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Outline of the Dissertation . . . . . . . . . . . . . . . . . . . . . . . 4 2 BACKGROUND 6 2.1 Iris Biometric Processing . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 Potential Attacks against Cancelable Biometrics . . . . . . . . . . . . 9 3 NON-INVERTIBLE CANCELABLE IRIS BIOMETRICS USING RAN- DOM PERMUTATION AND ORTHOGONAL KEYS 10 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2 Related Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.3 Proposed Non-invertible Binary Salting . . . . . . . . . . . . . . . . 15 3.3.1 Binary Salting Review . . . . . . . . . . . . . . . . . . . . . 15 3.3.2 Random permutation . . . . . . . . . . . . . . . . . . . . . . 16 3.3.3 Orthogonal random key . . . . . . . . . . . . . . . . . . . . 17 3.3.4 Cancelable Iris Biometric System . . . . . . . . . . . . . . . 18 3.3.5 Analysis of stolen key situations . . . . . . . . . . . . . . . . 18 3.4 Experiments and Discussion . . . . . . . . . . . . . . . . . . . . . . 21 3.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 4 CANCELABLE IRIS BIOMETRICS USING NOISE EMBEDDING 32 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 4.2 Related Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 4.2.1 Non-Invertible Transform Approaches . . . . . . . . . . . . . 36 4.2.2 Biometric Salting Approaches . . . . . . . . . . . . . . . . . 37 4.3 Preliminaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.3.1 Binary Salting . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.3.2 Reduced Random Permutation . . . . . . . . . . . . . . . . . 41 4.4 Proposed CIB System . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4.4.1 Template Creation . . . . . . . . . . . . . . . . . . . . . . . 42 4.4.2 Reference Template Selection . . . . . . . . . . . . . . . . . 48 4.4.3 Finding Coherent and Non-Coherent Matching Region . . . . 48 4.4.4 Noise Embedding . . . . . . . . . . . . . . . . . . . . . . . . 49 4.4.5 Modifications for Alignment . . . . . . . . . . . . . . . . . . 50 4.4.6 Authentication . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.4.7 Differences with IFO hashing . . . . . . . . . . . . . . . . . 52 4.5 Experiments and Discussion . . . . . . . . . . . . . . . . . . . . . . 53 4.5.1 Experimental Databases . . . . . . . . . . . . . . . . . . . . 53 4.5.2 Scores for evaluation . . . . . . . . . . . . . . . . . . . . . . 54 4.5.3 Effect of parameters . . . . . . . . . . . . . . . . . . . . . . 56 4.5.4 Comparison with other algorithms . . . . . . . . . . . . . . . 58 4.5.5 Unlinkability . . . . . . . . . . . . . . . . . . . . . . . . . . 67 4.6 Security Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 5 CONCLUSION 74 Bibliography 76 Abstract (In Korean) 81Docto

Research on cardiovascular ultrasound data acquisition and analysis for diagnosing coronary artery stenosis

Doctor관상동맥 협착증으로 인한 혈류의 난류는 주변 관상동맥 조직에 영향을 미치며 인접한 심근 조직에 오디오 주파수 진동을 발생시킨다. 관상 동맥 도플러 진동 측정법 (CDV)은 초음파를 사용하여 관상 동맥 협착증으로 발생한 심근의 진동을 감지하는 비침습적 진단기술이다. 최근 진행된 CDV 기술 연구는 관상동맥 질환 진단에서 상당한 민감도 및 특이도를 보여주지만, 긴 진단시간과, 정상군 피험자에게서도 고주파 진동 성분이 검출되는 문제 등이 여전히 남아있다. 이러한 문제를 극복하기 위해 우리는 아래와 같이 3 가지 데이터 수집 방법을 제안했다. 또한, 임상 연구를 통해 제안 된 접근 방식의 가능성을 검증했다. Interleaved 데이터 수집 방법에서는, 두 곳의 다른 위치로부터 초음파 펄스를 교차적으로 송수신 하여 데이터를 획득한 후, 공통 신호 성분을 제거하여 협착에 의한 진동 성분만 검출하는 것을 목표로 한다. 이 방식의 데이터 획득을 통하여 여러 영역에서 공통적으로 나타날 수 있는 개인의 고유한 고주파 진동 특성을 효과적으로 검출할 수 있다. 또한 특정 시간에 발생하는 노이즈 성분을 효과적으로 필터링 할 수 있다. Interleaved 데이터 수집 방법을 이용하여 임상 연구에서 총 11 명의 피험자를 모집했다. RCA 관상동맥의 경우 83 %의 민감도와 80 %의 특이도를 얻었으며 LAD 관상동맥의 경우 100 %의 민감도와 83 %의 특이도를 얻었다. Arrayed-range gate 데이터 수집에서는 협착에 의한 고주파 진동이 심근 조직에 어떻게 분포하는 지 분석하는 것을 목표로 하였다. 우리의 목표는 심근 조직 내에 협착이 있는 경우와 없는 경우 진동 분포의 경향성을 비교하여 관찰하는 것이다. 기존의 방식에서 밝히지 못한 협착에 의한 진동의 전파 특성을 분석하였다. 또한 협착이 존재하는 경우와 그렇지 않은 경우의 심근의 움직임에서 유의미한 차이를 확인하였다. 이 방식을 이용한 임상연구에서 총 33 명의 피험자를 모집했다. 우리의 진단 알고리즘은 정상군과 환자군을 75 %의 민감도와 83 %의 특이도로 효과적으로 분류했다. Wide range gate (WRG) 데이터 수집에서는 데이터 획득 대상에 초음파 펄스를 집중하는 방식을 이용한다. 실시간으로 데이터 획득 대상의 영역을 입력받은 후, 해당 영역으로부터 검출되는 신호가 최대가 되도록 평면파 펄스를 발생시켜 WRG 데이터 획득을 진행한다. 이 방식은 포커스드 기반 방식들이 가지고 있는 매우 긴 진단시간과 특정 부분에서만 높은 신호 대 잡음비의 문제점들을 해결할 수 있었다. 넓은 영역에서 데이터를 획득하기 때문에 정보처리에 매우 많은 양의 데이터를 활용할 수 있고, 촘촘한 영역에서 데이터 분석이 가능하기 때문에 개개인마다 다른 관상동맥의 특성 혹은 협착에 의한 진동 전파 특성을 고려한 진동 검출 알고리즘을 개발할 수 있다. 온전한 진단 알고리즘과 프로토콜을 제시하여 실제로 대상자가 병원을 방문하였을 경우, 진단 결과를 도출할 수 있었다. 임상 연구에서 총 100 명의 피험자를 모집했다. 관상 동맥 조영술 결과와 비교하여 WRG 데이터 분석의 민감도와 특이도는 각각 80 %와 84 %였다. 또한 다변량 분석에서, WRG 바이브로메트리 진단 결과는 CAD에 대한 독립적 인 예측 인자였다. 우리는 위와 같이 초음파를 사용하여 CAD를 감지하는 새로운 진단 방법들을 제안하였다. 새로운 데이터 수집 방법은 상당한 민감도와 특이도를 보이며, CAD의 초기 진단 도구로 큰 잠재력을 보여주었다.The turbulence of blood flow caused by coronary artery stenosis has an impact on the surrounding coronary artery tissue, and creates audio-frequency vibrations to the adjacent myocardial wall. Coronary Doppler vibrometry (CDV) is a non-invasive diagnosis to detect the vibrations from stenosis in coronary artery using ultrasound. Although recent CDV shows considerable sensitivity and specificity in diagnosing coronary artery disease, there still remains a serious problem that normal subjects can also have high-frequency components in vibration. To overcome these problems, we proposed three data acquisition methods. Also, we confirmed the feasibility of the proposed approach through a clinical study. In interleaved data acquisition, we transmit pulse to two different positions in an interleaved manner and obtain differential information of two reflected signals in order to eliminate common noise thereby enhancing the quality of stenosis-induced vibration. We recruited total 11 subjects in a clinical study. We obtained a sensitivity of 83% and a specificity of 80% in the right coronary artery cases and obtained a sensitivity of 100% and a specificity of 83% in the left anterior descending cases. In arrayed-range-gate data acquisition, we developed new data acquisition and analysis algorithms that focus on the spatial distribution of high-frequency vibration in the myocardial tissue. Our purpose is to observe the location-dependent variation of vibration in the myocardial tissue. We recruited total 33 subjects in a clinical study. Our proposed algorithm effectively classifies normal subjects and patients with sensitivity of 75% and specificity of 83%. In wide range gate (WRG) data acquisition, we investigated the diagnostic feasibility of a novel diagnostic method using wide range gate ultrasound data acquisition for diagnosing coronary artery disease (CAD). The WRG data acquisition detects high-frequency vibrations from coronary artery stenosis, using pulse-wave Doppler ultrasound. We recruited total 100 subjects in a clinical study. As compared with the results of coronary angiography, the sensitivity and specificity of the WRG data analysis were 80% and 84%, respectively. In a multivariate analysis, a positive vibrometry result was an independent predictive factor for CAD. We proposed a new diagnostic method for detecting CAD using ultrasound. The new data acquisition method showed good potential as an initial diagnostic tool for CAD

(A)Clinical study of alveolar bone quality using fractal dimension and implant stability quotient

Thesis(master`s)--서울대학교 대학원 :치의학과 치주과학전공,2006.Maste

GPU Implementation of Ultrasound Signal Processing for Beamforming

2

컴파일방식을 이용한 VHDL 시뮬레이션 시스템의 구현

학위논문(석사) - 한국과학기술원 : 전기및전자공학과, 1995.2, [ iii, 45 p. ]Simulation is a very important phase in digital system design. Today VHDL widens its area in the design field and a lot of VHDL simulator is emerging. Most of commercial simulation tools use the compilation technique for high speed simulation. Because those tools generates machine codes directly to obtain the highest performance, they are highly dependent of operating systems. In this thesis work, a VHDL simulation system called VS using the compilation technique was implemented in the UNIX environment. Since this system generates standard C programs, it can be ported to other operating systems with ease. From the testing through simulation of two circuits in VHDL -- one in structural level and the other in behavioral level -- it is proved that the simulator works correctly. This work has focused heavily on the correct functionality of the implemented simulator so that the the optimization for speed up has not yet been fully considered. Nevertheless the simulation speed of VS is 7 to 8 times faster than that of Quicksim -- the VHDL simulator of the Mentor Co. -- on the behavioral level benchmark. For the structural level benchmark the performance is poor-about 10 times slower than Quicksim.한국과학기술원 : 전기및전자공학과