Run-time efficient probabilistic model checking

Since the inception of discontinuous Galerkin (DG) methods for elliptic problems, there has existed a question of whether DG methods can be made more computationally efficient than continuous Galerkin (CG) methods. Fewer degrees of freedom, approximation properties for elliptic problems together with the number of optimization techniques, such as static condensation, available within CG framework made it challenging for DG methods to be competitive until recently. However, with the introduction of a static-condensation-amenable DG method—the hybridizable discontinuous Galerkin (HDG) method—it has become possible to perform a realistic comparison of CG and HDG methods when applied to elliptic problems. In this work, we extend upon an earlier 2D comparative study, providing numerical results and discussion of the CG and HDG method performance in three dimensions. The comparison categories covered include steady-state elliptic and time-dependent parabolic problems, various element types and serial and parallel performance. The postprocessing technique, which allows for superconvergence in the HDG case, is also discussed. Depending on the direct linear system solver used and the type of the problem (steady-state vs. time-dependent) in question the HDG method either outperforms or demonstrates a comparable performance when compared with the CG method. The HDG method however falls behind performance-wise when the iterative solver is used, which indicates the need for an effective preconditioning strategy for the method

System identification and control of a flexible manipulator

The Observabilty Range Space Extraction (ORSE) algorithm used to identify a an initially overparameterized discrete-time state-space model for a single-link flexible manipulator. A controller named PDPC is designed to control rigid body motion, have a zero tracking error and minimum vibration.--Abstract.The Observability Range Space Extraction (ORSE) algorithm is successfully applied to identify an initially overparameterized discrete-time state-space model for a single-link flexible manipulator. Several critical issues related to the experiments and the implementation of the ORSE algorithm are addressed. A new model reduction and updating technique is proposed and applied to reduce the identified models. To quantify the contribution of individual modes to the responses, a new measure referred to as modal response magnitude (MRM) is developed and successfully applied to obtain a lower-order model by retaining the most significant modes. To correct errors caused by the model reduction, either the reduced input or output matrix is recalculated by a least squares solution. Based on the updated reduced-order models, a controller named as PDPC is designed to ensure a good tracking accuracy and robustness to payload changes. The experimental results show that the PDPC control structure is effective in controlling rigid body motion to have a zero tracking error and the minimum vibration as well

Channel parameter tuning in a hybrid Wi-Fi-Dynamic Spectrum Access Wireless Mesh Network

This work addresses Channel Assignment in a multi-radio multi-channel (MRMC) Wireless Mesh Network (WMN) using both Wi-Fi and Dynamic Spectrum Access (DSA) spectrum bands and standards. This scenario poses new challenges because nodes are spread out geographically so may have differing allowed channels and experience different levels of external interference in different channels. A solution must meet two conflicting requirements simultaneously: 1) avoid or minimise interference within the network and from external interference sources, and 2) maintain connectivity within the network. These two requirements must be met while staying within the link constraints and the radio interface constraints, such as only assigning as many channels to a node as it has radios. This work's original contribution to the field is a unified framework for channel optimisation and assignment in a WMN that uses both DSA and traditional Wi-Fi channels for interconnectivity. This contribution is realised by providing and analysing the performance of near-optimal Channel Assignment (CA) solutions using metaheuristic algorithms for the MRMC WMNs using DSA bands. We have created a simulation framework for evaluating the algorithms. The performance of Simulated Annealing, Genetic Algorithm, Differential Evolution, and Particle Swarm Optimisation algorithms have been analysed and compared for the CA optimisation problem. We introduce a novel algorithm, used alongside the metaheuristic optimisation algorithms, to generate feasible candidate CA solutions. Unlike previous studies, this sensing and CA work takes into account the requirement to use a Geolocation Spectrum Database (GLSD) to get the allowed channels, in addition to using spectrum sensing to identify and estimate the cumulative severity of both internal and external interference sources. External interference may be caused by other secondary users (SUs) in the vicinity or by primary transmitters of the DSA band whose emissions leak into adjacent channels, next-toadjacent, or even into further channels. We use signal-to-interference-plus-noise ratio (SINR) as the optimisation objective. This incorporates any possible source or type of interference and makes our method agnostic to the protocol or technology of the interfering devices while ensuring that the received signal level is high enough for connectivity to be maintained on as many links as possible. To support our assertion that SINR is a reasonable criterion on which to base the optimisation, we have carried out extensive outdoor measurements in both line-of-sight and wooded conditions in the television white space (TVWS) DSA band and the 5 GHz Wi-Fi band. These measurements show that SINR is useful as a performance measure, especially when the interference experienced on a link is high. Our statistical analysis shows that SINR effectively differentiates the performance of different channels and that SINR is well correlated with throughput and is thus a good predictor of end-user experience, despite varying conditions. We also identify and analyse the idle times created by Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) contention-based Medium Access Control (MAC) operations and propose the use of these idle times for spectrum sensing to measure the SINR on possible channels. This means we can perform spectrum sensing with zero spectrum sensing delay experienced by the end user. Unlike previous work, this spectrum sensing is transparent and can be performed without causing any disruption to the normal data transmission of the network. We conduct Markov chain analysis to find the expected length of time of a sensing window. We also derive an efficient minimum variance unbiased estimator of the interference plus noise and show how the SINR can be found using this estimate. Our estimation is more granular, accurate, and appropriate to the problem of Secondary User (SU)-SU coexistence than the binary hypothesis testing methods that are most common in the literature. Furthermore, we construct confidence intervals based on the probability density function derived for the observations. This leads to finding and showing the relationships between the number of sampling windows and sampling time, the interference power, and the achievable confidence interval width. While our results coincide with (and thus are confirmed by) some key previous recommendations, ours are more precise, granular, and accurate and allow for application to a wider range of operating conditions. Finally, we present alterations to the IEEE 802.11k protocol to enable the reporting of spectrum sensing results to the fusion or gateway node and algorithms for distributing the Channel Assignment once computed. We analyse the convergence rate of the proposed procedures and find that high network availability can be maintained despite the temporary loss of connectivity caused by the channel switching procedure. This dissertation consolidates the different activities required to improve the channel parameter settings of a multi-radio multi-channel DSA-WMN. The work facilitates the extension of Internet connectivity to the unconnected or unreliably connected in rural or peri-urban areas in a more cost-effective way, enabling more meaningful and affordable access technologies. It also empowers smaller players to construct better community networks for sharing local content. This technology can have knock-on effects of improved socio-economic conditions for the communities that use it

Multi-sensor activity recognition of an elderly person.

The rapid increase in the number of ageing population brings major issues to health care including a rise in care cost, high demand in long- term care, burden to caregivers, and insufficient and ineffective care. Activity recognition can be used as the key part of the intelligent sys- tems to allow elderly people to live independently at homes, reduce care cost and burden to the caregivers, provide assurance for the fam- ilies, and promote better care. However, current activity recognition systems mainly focus on the technical aspect i.e. systems accuracy and neglects the practical aspects such as acceptance, usability, cost and privacy. The practicality of the system is the vital indication whether the system will be adopted. This research aims to develop the activity recognition system which considers both practical and technical aspects using multiple wrist-worn sensors. An extensive literature review in wearable sensor based activity recog- nition and its applications in healthcare have been carried out. Novel multi-sensor activity recognition utilising multiple low-cost, non-intrusive, non-visual wearable sensors is proposed. The sensor fusion is per- formed at feature and classi er levels using the proposed feature se- lection and classi er combination techniques. The multi-sensor ac- tivity recognition data sets have been collected. The rst data set contains data from accelerometer collected from seven young adults. The second data set contains data from accelerometer, altimeter, and temperature sensor collected from 12 elderly people in home environ- ment performing 10 activities. The third data set contains sensor data from accelerometer, gyroscope, temperature sensor, altimeter, barometer, and light sensor worn on the users wrist and a heart rate monitor worn over the users chest. The data set is collected from 12 elderly persons in a real home environment performing 13 activities. This research proposes two feature selection methods, Feature Com- bination (FC) and Maximal Relevancy and Maximal Complementary (MRMC), based on the relationship between feature and classes as well as the relationship between a group of features and classes. The experimental studies show that the proposed techniques can select an optimum set of features from irrelevant, overlapped, and partly over- lapped features. The studies also show that FC and MRMC obtain higher classi cation performances than popular techniques including MRMR, NMIFS, and Clamping. Two classi er combination tech- niques based on Genetic Algorithm (GA) are proposed. The rst technique called GA based Fusion Weight (GAFW), uses GA nd the optimum fusion weights. The results indicate that 99% of classi er fusion using GAFW achieves equal or higher accuracy than using only the best classi er. While other fusion weight techniques cannot guar- antee accuracy improvement, GAFW is a more suitable method for determining fusion weight regardless which fusion techniques are used. Another algorithm called GA based Combination Model (GACM) is proposed to nd the optimal combination between classi er, weight function, and classi er combiners. The algorithm does not only nd the model which has the minimum classi cation error but also select the one that is simpler. Other criteria e.g. select the classi er with low computation can also be easily added to the algorithm. The re- sults show that in general GACM can nd the optimum combinations automatically. The comparison against manually selection revealed that there is no statistical signi cant in the performances. Applications of the proposed work in home care and decision support system are discussed The results of this research will have a signi cant impact on the future health care where people can be health monitored from their homes to promote healthy living, detect any changes in behaviour, and improve quality of care

충수염 의증 청소년 및 젊은 성인에서 2-mSv CT와 기존 선량 CT의 민감도 및 특이도: LOCAT의 사후 하위그룹 분석

학위논문(박사)--서울대학교 대학원 :융합과학기술대학원 융합과학부,2019. 8. 이경호.Introduction: To explore heterogeneity across patient or hospital characteristics in the diagnostic sensitivity and specificity of 2-mSv CT relative to conventional-dose CT (CDCT) in adolescents and young adults with suspected appendicitis. Methods: We used the per-protocol analysis set of a large randomized controlled noninferiority trial conducted between Dec 2013, and Aug 2016, comparing 2-mSv CT and CDCT (typically 7 mSv). The data included 2,773 patients (median age [interquartile range], 28 [21–35] years) and 160 radiologists from 20 hospitals. We tested for heterogeneity in sensitivity and specificity for the diagnosis of appendicitis across predefined subgroups by patient sex, body size, clinical risk scores for appendicitis, time of CT examination (i.e., working hours [typically 08:00–17:00 of working days] vs. after hours), CT machines, radiologists experience, previous site experience in 2-mSv CT, and site practice volume. We drew forest plots and tested for additive or multiplicative treatment-by-subgroup interaction on sensitivity and specificity. Results: The 95% CIs for the between-group differences, particularly for sensitivity, were wide due to small sizes (< 200) for the subgroups of extreme body sizes, high clinical risk score for appendicitis, newer CT machines, hospital with prior experience in 2-mSv CT, and hospitals with small appendectomy volume. Otherwise, the 95% CIs in most subgroups contained the previously reported overall between-group differences as well as null hypothesis value (i.e., 0). There was no significant additive or multiplicative interaction for either sensitivity or specificity. Conclusions: We found no notable subgroup heterogeneity, which implies that 2-mSv CT can replace CDCT in diverse populations. Further studies are needed for the populations for which our subgroups were small.서론: 본 연구는 충수염 의증 청소년 및 젊은 성인에서 기존 CT와 비교하여 2-mSv CT의 진단 민감도 및 특이도에서 환자 또는 병원의 특성에 따른 이질성이 있는지를 탐색하는 연구임. 방법: 본 연구는 2013년 12월에서 2016년 8월 사이에 15–44세의 환자에서 2-mSv CT와 기존 선량 CT (일반적으로 7 mSv)를 비교한 대규모 비열등성 무작위배정 임상시험의 프로토콜 별 분석세트를 사용함. 본 연구에는 20개 병원에서 2,773명의 환자 (중앙값 연령 [사분위수 범위], 28 [21–35]세)가 포함되었으며, 160명의 판독의가 참여함. 환자의 성별, 신체 크기, 충수염에 대한 임상 위험 점수, CT 검사시간 (일과시간 [근무일 기준 오전 8시부터 오후5시] 또는 일과시간 이후), CT 장비, 판독의의 경험정도, 2-mSv CT에 대한 이전 경험 여부, 그리고 병원의 임상규모 등의 사전 정의된 하위 그룹에서 충수염 진단을 위한 민감도 및 특이도의 이질성을 테스트함. 두 군의 차이를 숲그림으로 제시하고, 민감도와 특이도에 대한 덧셈 및 곱셈 상호작용을 테스트함. 결과: 많이 날씬하거나 뚱뚱한 경우, 충수염 염증 반응 점수가 높은 경우, 최신 CT 기기를 사용한 경우, 2-mSV CT 의 이전 경험이 있는 병원, 그리고 충수절제술 규모가 작은 병원의 경우 등 특정 하위 그룹은 작은 크기 (< 200)로 인해 민감도에 대한 95 % 신뢰구간이 넓었음. 그 외, 대부분의 하위 그룹에서 그룹 간 차이에 대한 95 % 신뢰구간은 이전 보고된 전체 그룹 간 차이 및 귀무 가설 값 (즉, 0)을 포함하였음. 2-mSv CT 군과 기존 선량 CT 군 간에 민감도 및 특이도에서 덧셈 또는 곱셈 상호작용을 보이는 하위 그룹은 없었음. 결론: 충수염 의증 청소년과 젊은 성인에서 2-mSv CT와 기존 선량 CT 간에 민감도와 특이도에서 이질성을 보이는 하위그룹은 없었음. 이는 2-mSv CT가 다양한 집단에서 기존 선량 CT를 대체할 수 있음을 의미함. 다만, 본 연구에서 작은 크기를 가진 일부 하위 그룹에 대해서는 추가적인 연구가 필요함.INTRODUCTION 1 Motivations of LOCAT 1 Purposes of LOCAT 3 Motivations of Dissertation Research 4 Purposes of Dissertation Research 5 BACKGROUND 7 Epidemiology of Appendicitis and CT utilization 7 Imaging Utilization 7 Popularity of CT 8 CT Radiation 9 Radiation Dose Level 10 Typical Radiation Dose for Multi-purpose Abdomen CT 10 Typical Radiation Dose for Appendiceal CT 11 Low Doses Explored in Research Settings 12 Carcinogenic Risk Associated with CT Radiation 12 Controversy 13 ALARA Principle 14 Efficacy and Effectiveness of LDCT Compared to CDCT 15 Clinical Outcome 19 Diagnostic Performance 20 Inter-observer Agreement 21 Differentiation between Complicated vs. Uncomplicated Appendicitis 22 Image Quality 24 Visualization of the Appendix 24 Alternative Diagnoses 25 Step-wise Multimodal Diagnostic Approach Incorporating LDCT 27 Patient Subgroups Less Benefited from LDCT 27 Selective Utilization of LDCT 29 Additional Imaging Test(s) Following LDCT 30 Imaging Techniques for LDCT for Suspected Appendicitis 31 Intravenous Contrast Enhancement 31 Contrast-enhancement Phase 31 Enteric Contrast 32 Anatomical Coverage 32 Tube Current 33 Tube Potential 34 Iterative Reconstruction 34 Image Reconstruction Thickness 35 Coronal Reformation 35 Sliding-Slab Averaging Technique 36 Image Interpretation and Reporting for LDCT 37 Diagnostic Criteria for Appendicitis 37 Structured Reporting 38 Other Practical Issues in Implementing LDCT 39 Dedicated Protocol for Appendiceal CT 40 Education for Referring Physicians and Surgeons 41 Education for Radiologists 42 Dose Calibration and Monitoring 43 MATERIALS AND METHODS 47 Study Overview 47 Practice Setting 48 Pre-registration Procedures 48 Study Organization and Site Recruitment 49 Site Activation 50 Patients 51 Eligibility Criteria 54 Clinical Suspicion for Appendicitis 55 The Need for CT Examination 55 Generalizability 56 Representativeness of Study Sample 57 Withdrawal Criteria 58 Randomization 58 Index Test 59 CT Image Acquisition and Archiving 66 Radiation Doses 69 Record of Modulated Radiation Dose 71 Target Median DLP Values for the 2-mSv CT and CDCT groups 71 Calibration of Radiation Doses 72 Estimation of Carcinogenic Risk Associated with CT Examination 74 Image Interpretation 75 Radiologists and CT Reports 76 Radiologist Training 78 Considerations Regarding Technical Advantages over Previous Studies 79 Image Submission 80 Co-intervention 81 Additional Imaging 82 General Treatment Guidelines 82 Follow-up 84 Endpoints in LOCAT 85 Primary Endpoint 86 Secondary Endpoints 86 Considerations for NAR and APR 89 Changes in Endpoints 89 Reference Standards 91 Overview of Reference Standards 91 Definition of Acute Appendicitis 92 Mild or Early Acute Appendicitis 92 Appendiceal Diverticulitis 93 Cases of Delayed Appendectomy 93 Periappendicitis 93 Definition of Appendiceal Perforation 94 Reporting AEs 95 Definition of AE 96 Definition of SAE 97 AE Characteristics 97 Grade 98 Expected/Unexpected AEs 98 Attribution 98 Individual Symptoms vs. Single Diagnosis 99 Who Should Report AEs 99 How to Report AEs 99 Follow-up for AEs 100 Ethical Considerations 100 Ethics and Responsibility 100 Informed Consent Form 101 Data Security and Participant Confidentiality 101 Early Stopping Rules in LOCAT 101 Data Management 102 Case Report Forms 103 Monitoring Participant Accrual 103 Monitoring Data Quality 103 Data and Safety Monitoring Board 105 Statistical Analysis 105 Considerations for Primary Endpoint 105 Analysis Plans 107 Sample Size 108 Sample Size Considerations 108 Final Sample Size 110 Rationale for the Noninferiority Margin 111 Reported NARs Following Preoperative CT 111 Reported NARs in Patients Without Preoperative CT 112 Sample Size Considerations on APR 113 Subgroup Analyses for APR and NAR 114 Subgroup Analyses for Diagnostic Performance 116 RESULTS 119 Patient Characteristics 119 Overall Diagnostic Performance 123 Subgroups of Limited Comparison 123 Between-group Differences for Subgroups 123 Heterogeneity 131 DISCUSSION 132 CONCLUSION 139 REFERENCES 140 APPENDIX 164 Abstract in Korean 176Docto