Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

<p>Distributed real-time system consists of many tasks on different processors communicating with</p><p>each other. The communication between these tasks must occur in bounded time. In our thesis we</p><p>are considering a holistic approach to estimate the end-to-end delays between two processors</p><p>communicating with each other. For both tasks scheduled by fixed priority and dynamic priority,</p><p>the system model considered is time token passing ring. The method is described to calculate</p><p>worst-case communication delay of the message sent by certain tasks over the network. Once the</p><p>worst-case communication delay of the message is obtained, and all required parameters are</p><p>provided i.e. deadline of the message, transmission time of the packet etc, one can figure out how</p><p>many messages will successfully meet their deadline. Thus this will enable us to select</p><p>appropriate algorithm according to system requirement.</p>

Dietary factors have been implicated in the risk of head and neck squamous cell carcinoma (HNSCC). Much interest has been placed upon the effects of suspected chemopreventative agents found in fruit and vegetables associated with low HNSCC risk. However, studies investigating specific uptake of these agents have failed to show positive results. The possibility exists that single chemopreventative agents fail to provide the same beneficial effect as the various compounds found in a fruits and vegetables is examined. Curatively treated head and neck squamous cell carcinoma patients ingested Juice Plus, a F&V extract supplement containing multiple chemopreventative agents, for 12 weeks. Lymphocyte samples of participants were collect pre- and post- treatment and examined in pairs. Despite the study currently still blinded, surrogate endpoint biomarkers were evaluated to observer any modification between pre- and post treatment samples. Although a paired t-test showed no significant difference between pre- and post treatment samples on surrogate endpoint biomarkers, there is a significant difference in population distribution between treatment times signifying a modification of the surrogate endpoint biomarkers. The exact nature of this difference is pending due to the blinded status of the study.

The present research presents procedures for exploitation of level sensitive latches in wire pipelining. The user gives a Steiner tree, having a signal source and set of destination or sinks, and the location in rectangular plane, capacitive load and required arrival time at each of the destinations. The user also defines a library of non-clocked (buffer) elements and clocked elements (flip-flop and latch), also known as synchronous elements. The first procedure performs concurrent repeater and synchronous element insertion in a bottom-up manner to find the minimum latency that may be achieved between the source and the destinations. The second procedure takes additional input (required latency) for each destination, derived from previous procedure, and finds the repeater and synchronous element assignments for all internal nodes of the Steiner tree, which minimize overall area used. These procedures utilize the latency and area advantages of latch based pipelining over flip-flop based pipelining. The second procedure suggests two methods to tackle the challenges that exist in a latch based design. The deferred delay padding technique is introduced, which removes the short path violations for latches with minimal extra cost.

More than 6 million people present to emergency departments (EDs) across the US annually with chief complaints of chest pain or other symptoms suggestive of acute myocardial infarction (AMI). Of the million who are diagnosed with AMI, 350,000 die during the acute phase. Accurate triage in the ED can reduce mortality and morbidity, yet accuracy rates are low and delays in patient care are high. The purpose of this study was to explore the relationship between (a) patient characteristics, registered nurse (RN) characteristics, symptom presentation, and accuracy of ED RN triage level designations and (b) delay of care of patients with symptoms suggestive of AMI. Constructs from Donabedian’s Structure-Process-Outcome model were used to guide this study. Descriptive correlational analyses were performed using retrospective triage data from electronic medical records. The sample of 286 patients with symptoms suggestive of AMI comprised primarily Caucasian, married, non-smokers, of mean age of 61 with no prior history of heart disease. The sample of triage nurses primarily comprised Caucasian females of mean age of 45 years with an associate’s degree in nursing and 11 years’ experience in the ED. RNs in the study had an accuracy rate of 54% in triage of patients with symptoms suggestive of AMI. The older RN was more accurate in triage level designation. Accuracy in triage level designations was significantly related to patient race/ethnicity. Logistic regression results suggested that accuracy of triage level designation was twice as likely (OR 2.07) to be accurate when the patient was non-Caucasian. The patient with chest pain reported at triage was also twice as likely (OR 2.55) to have an accurate triage than the patient with no chest pain reported at triage. Electrocardiogram (ECG) delay was significantly greater in the patient without chest pain and when the RN had more experience in ED nursing. Triage delay was significantly related to patient gender and race/ethnicity, with female patients and non-Caucasian patients experiencing greater delay. An increase in RN years of experience predicted greater delay in triage. Further studies are necessary to understand decisions at triage, expedite care, improve outcomes, and decrease deaths from AMI.

Background: Schizophrenia is associated with deficits in decision-making. Aim: To determine the effects of smoking status on delay discounting in schizophrenia in comparison to non-psychiatric controls. Method: Cross-sectional comparison of delay discounting across smoking and psychiatric status. Hypotheses: Individuals with schizophrenia were hypothesized to have higher rates of delay discounting than controls; Non-smokers with schizophrenia would have higher rates of delay discounting than smokers. Control smokers would discount future rewards more than non-smokers. Results: No significant differences in delay discounting were observed between psychiatric groups. Smokers with schizophrenia exhibited more delay discounting than non-smokers. Within the psychiatric group, former smokers discount rates were similar to current smokers. Conclusion: Delay discounting deficits in schizophrenia and modulation by cigarette smoking were not supported; our pattern of results in schizophrenia does suggest that deficits in delay discounting in these patients appears to be a trait rather than a state-dependent phenomenon.

Background: Schizophrenia is associated with deficits in decision-making. Aim: To determine the effects of smoking status on delay discounting in schizophrenia in comparison to non-psychiatric controls. Method: Cross-sectional comparison of delay discounting across smoking and psychiatric status. Hypotheses: Individuals with schizophrenia were hypothesized to have higher rates of delay discounting than controls; Non-smokers with schizophrenia would have higher rates of delay discounting than smokers. Control smokers would discount future rewards more than non-smokers. Results: No significant differences in delay discounting were observed between psychiatric groups. Smokers with schizophrenia exhibited more delay discounting than non-smokers. Within the psychiatric group, former smokers discount rates were similar to current smokers. Conclusion: Delay discounting deficits in schizophrenia and modulation by cigarette smoking were not supported; our pattern of results in schizophrenia does suggest that deficits in delay discounting in these patients appears to be a trait rather than a state-dependent phenomenon.

Wireless Internet has become increasingly popular due to anywhere anytime access feature. The Internet architecture was designed underlying the existing of the end-to-end path connection. The promise of wireless Internet networks is to provide roaming users connectivity anywhere anytime. However, quality of service (QoS) is still an open issue in wireless networks, which are characterized by possible intermittent connectivity and large transmission delays, due to user mobility, sparse mobile node distribution, link failures (because of hostile propagation medium), and/or other high-priority traffc. In this thesis, a credit-based user authentication scheme is proposed for delay tolerant mobile wireless networks. The proposed authentication scheme isolates the uncertain network condition in the high delay wireless backhaul with high error rate, and accelerates the overall authentication process when the mobile terminal roams in the visited network. Furthermore, an analytical study of overall network performance is presented for the authentication scheme in terms of authentication cost and delay. Simulation results demonstrate that the proposed credit-based authentication scheme reduces the overall real time transaction cost and delay for delay tolerant mobile wireless networks.

Like many other transportation agencies, the Ministry of Transportation Ontario (MTO) is also using the same work zone closure strategies and standards that it has used for decades. However, the lane closure strategies should incorporate the impacts of construction duration and inconvenience to the road users and find the balance where users face minimal inconvenience while contractors have the appropriate amount of time to finish the work and produce a high quality product. In-order to evaluate and assess the appropriate time for lane closures, it is important to estimate the capacity of the lanes. The capacity estimates can help in determining the optimized time for lane closures to minimize the user delays while providing sufficient time for contractors to achieve the desired productivity and quality of work. There are different models, computer Software and wide variety of studies to evaluate and estimate the Workzone Capacity and associated User Delay Costs at workzones. These costs are primarily affected by traffic flows, vehicle speeds, and work zone capacities. In-view of the above, this study is designed to estimate freeway capacity of construction workzones and discuss the associated user delay costs and economic issues. For this study, the capacity at the work zones was measured as the mean queue discharge flow rate during forced-flow conditions. Forced-flow conditions were defined as congested conditions during which a sustained queue formed. There are several studies and approaches for collecting traffic volume data for estimating workzone capacity. For this study, it was decided to utilize a manual counting method for volume data. This would help provide the visual confirmation of queuing and intensity of work activity at workzones. Six sites located in Southern Ontario, were selected for this study. The data from these sites is used to develop a mathematical model for estimating workzone capacity for Ontario.

Delay- and Disruption-tolerant wireless networks (DTN), or opportunistic networks, represent a class of networks where continuous end-to-end connectivity may not be possible. DTN is a well recognized area in networking research and has attracted extensive attentions from both network designers and application developers. Applications of this emergent communication paradigm are wide ranging and include sensor networks using scheduled intermittent connectivity, vehicular DTNs for dissemination of location-dependent information (e.g., local ads, traffic reports, parking information, etc.), pocket-switched networks to allow humans to communicate without network infrastructure, and underwater acoustic networks with moderate delays and frequent interruptions due to environmental factors, etc. Security is one of the main barriers to wide-scale deployment of DTNs, but has gained little attention so far. On the one hand, similar to traditional mobile ad hoc networks, the open channel and multi-hop transmission have made DTNs vulnerable to various security threats, such as message modification/injection attack or unauthorized access and utilization of DTN resources. On the other hand, the unique security characteristics of DTNs including: long round-trip delay, frequent disconnectivity, fragmentation, opportunistic routing as well as limited computational and storage capability, make the existing security protocols designed for the conventional ad hoc networks unsuitable for DTNs. Therefore, a series of new security protocols are highly desired to meet stringent security and efficiency requirements for securing DTNs. In this research, we focus on three fundamental security issues in DTNs: efficient DTN message (or bundle) authentication, which is a critical security service for DTN security; incentive issue, which targets at stimulating selfish nodes to forward data for others; and certificate revocation issue, which is an important part of public key management and serves the foundation of any DTN security protocols. We have made the following contributions: First of all, the unique ``store-carry-and-forward'' transmission characteristic of DTNs implies that bundles from distinct/common senders may opportunistically be buffered at some common intermediate nodes. Such a ``buffering'' characteristic distinguishes DTN from any other traditional wireless networks, for which intermediate cache is not supported. To exploit such buffering opportunities, we propose an Opportunistic Batch Bundle Authentication Scheme (OBBA) to dramatically reduce the bundle authentication cost by seamlessly integrating identity-based batch signatures and Merkle tree techniques. Secondly, we propose a secure multi-layer credit based incentive scheme to stimulate bundle forwarding cooperation among DTNs nodes. The proposed scheme can be implemented in a fully distributed manner to thwart various attacks without relying on any tamper-proof hardware. In addition, we introduce several efficiency-optimization techniques to improve the overall efficiency by exploiting the unique characteristics of DTNs. Lastly, we propose a storage-efficient public key certificate validation method. Our proposed scheme exploits the opportunistic propagation to transmit Certificate Revocation List (CRL) list while taking advantage of bloom filter technique to reduce the required buffer size. We also discuss how to take advantage of cooperative checking to minimize false positive rate and storage consumption. For each research issue, detailed simulation results in terms of computational time, transmission overhead and power consumption, are given to validate the efficiency and effectiveness of the proposed security solutions.