Architecture value mapping: using fuzzy cognitive maps as a reasoning mechanism for multi-criteria conceptual design evaluation

The conceptual design phase is the most critical phase in the systems engineering life cycle. The design concept chosen during this phase determines the structure and behavior of the system, and consequently, its ability to fulfill its intended function. A good conceptual design is the first step in the development of a successful artifact. However, decision-making during conceptual design is inherently challenging and often unreliable. The conceptual design phase is marked by an ambiguous and imprecise set of requirements, and ill-defined system boundaries. A lack of usable data for design evaluation makes the problem worse. In order to assess a system accurately, it is necessary to capture the relationships between its physical attributes and the stakeholders\u27 value objectives. This research presents a novel conceptual architecture evaluation approach that utilizes attribute-value networks, designated as \u27Architecture Value Maps\u27, to replicate the decision makers\u27 cogitative processes. Ambiguity in the system\u27s overall objectives is reduced hierarchically to reveal a network of criteria that range from the abstract value measures to the design-specific performance measures. A symbolic representation scheme, the 2-Tuple Linguistic Representation is used to integrate different types of information into a common computational format, and Fuzzy Cognitive Maps are utilized as the reasoning engine to quantitatively evaluate potential design concepts. A Linguistic Ordered Weighted Average aggregation operator is used to rank the final alternatives based on the decision makers\u27 risk preferences. The proposed methodology provides systems architects with the capability to exploit the interrelationships between a system\u27s design attributes and the value that stakeholders associate with these attributes, in order to design robust, flexible, and affordable systems --Abstract, page iii

Multi-objective Stochastic Heuristic Methodology for Tradespace Exploration of a Network Centric System of Systems

System of systems (SoS) architecting techniques rely on traditional, static tools that were designed for classical stove-piped systems. There is a need for tools that can capture the complex adaptive nature of such SoS. An architecture search methodology using genetic algorithms and a fuzzy assessor was applied to the conceptual architecture design of a generic smart grid and a set of architectures with high fitness was obtained. This set of architectures is intended to serve as a starting point for a systems architect to ultimately be able to converge on the best system design. The SoS architecting process has largely remained heuristic in nature and there exists a need for quantitative and analytical models. The research presented in this paper provides a starting point for a mathematical basis to the SOS architecting process

Using Quality Attributes and Computational Intelligence to Generate and Evaluate System Architecture Alternatives

This paper proposes an evolutionary algorithm based approach for evolving architecture alternatives using quality attributes as design drivers. A novel fuzzy architecture assessment approach is presented to quantitatively evaluate the set of possible solutions based on linguistic assessments of architecture quality attributes elicited from the stakeholders. The proposed approach makes a valuable contribution to the systems architecting knowledge base by presenting a measurable and quantifiable approach to architecture design and evaluation

Neural Network Controller Development and Implementation for Spark Ignition Engines with High EGR Levels

Past research has shown substantial reductions in the oxides of nitrogen (NOx) concentrations by using 10% -25% exhaust gas recirculation (EGR) in spark ignition (SI) engines (see Dudek and Sain, 1989). However, under high EGR levels, the engine exhibits strong cyclic dispersion in heat release which may lead to instability and unsatisfactory performance preventing commercial engines to operate with high EGR levels. A neural network (NN)-based output feedback controller is developed to reduce cyclic variation in the heat release under high levels of EGR even when the engine dynamics are unknown by using fuel as the control input. A separate control loop was designed for controlling EGR levels. The stability analysis of the closed-loop system is given and the boundedness of the control input is demonstrated by relaxing separation principle, persistency of excitation condition, certainty equivalence principle, and linear in the unknown parameter assumptions. Online training is used for the adaptive NN and no offline training phase is needed. This online learning feature and model-free approach is used to demonstrate the applicability of the controller on a different engine with minimal effort. Simulation results demonstrate that the cyclic dispersion is reduced significantly using the proposed controller when implemented on an engine model that has been validated experimentally. For a single cylinder research engine fitted with a modern four-valve head (Ricardo engine), experimental results at 15% EGR indicate that cyclic dispersion was reduced 33% by the controller, an improvement of fuel efficiency by 2%, and a 90% drop in NOx from stoichiometric operation without EGR was observed. Moreover, unburned hydrocarbons (uHC) drop by 6% due to NN control as compared to the uncontrolled scenario due to the drop in cyclic dispersion. Similar performance was observed with the controller on a different engine

Comparative analysis of COVID-19 case fatality rate between two waves in Nepal

The first COVID-19 case in Nepal was reported on January 23, 2020. Then infection, then, started to spread gradually, and October marked the most devastating increase in COVID-19 cases of the year 2020. Compared with the October 2020 peak in Nepal, the May 2021 peak of COVID-19 observed 2- and 10-fold rise in new cases and deaths per day, respectively. Given that this surprising increase in the death rate was not observed in other countries, this study analyzed the COVID-19 case fatality rates between the two peaks in Nepal. We found an increase in death rates among younger adults and people without comorbidities

An analysis and comparison of modal extraction techniques in power system modeling

Modal Analysis methodologies are being investigated as a means to model power system behavior, in recent times...This work compares and contrasts three modal extraction methods, namely the Prony method, the Levenberg-Marquardt method, and the Hilbert Transform method. --Abstract, page iii

Evaluation of serum magnesium levels in patients with acute myocardial infarction

Aim: To evaluate the serum magnesium levels in patients with acute myocardial infarction. Material and method: The present prospective observational study was conducted in the department of Medicine among 50 patients with acute myocardial infarction. Patients who presented to the hospital within 24 hours of onset of symptoms and diagnosed with acute myocardial infarction were included in the study. Blood samples collection were taken within 24 hours of onset of symptoms. All patients were evaluated for their ECG and cardiac enzymes and serum magnesium level by taking 5 cc venous blood sample in a disposable syringe and sent to biochemistry laboratory for analysis in fluoride bulb and plain bulb respectively. Results: Smoking was reported in 82% of the subjects whereas hypertension and diabetes mellitus in 64% and 46% of the subjects respectively. Sixteen percent, 24% and 60% of the subject’s time of presentation was 3-6 hours, 6-12 hours and 12-18 hours respectively. On day 5, only six percent (3) of the subjects with arrhythmia were having serum magnesium level (mg/dL) <1.6 while 14% of the subjects with arrhythmia reported 1.7-2.4 serum magnesium level (mg/dL). There was an increase in serum magnesium from Day-1 to Day-5 with statistically significant difference.&nbsp

Incorporating Security and Survivability into the System of Systems Architecting

System of systems (SoS) security and survivability issues have found prominence in the wake of increased importance of such large scale interconnected systems. The threats and risks associated with SoS architectures present unique challenges to system architects. SoS security and survivability practices are needed to ensure the performance and survival of the system under an intrusion. Current security engineering activities are performed independent of the system architecting process, leading to ad hoc solutions and after-the-fact reactions to vulnerabilities as discussed in (Evans et al. 2005). Literature on security and survivability oriented system architecting activities is far and few in between. This paper studies the major classes of threats and risks associated with SoS and the response to such vulnerabilities. Existing works were researched to outline the key characteristics of an effective security and survivability process that can be integrated with systems engineering activities. Overviews of three survivability architectures are provided on the basis of the identified criteria. Comments on the currently available solutions and future areas of emphasis are presented

Evaluation of serum magnesium levels in patients with acute myocardial infarction

Aim: To evaluate the serum magnesium levels in patients with acute myocardial infarction. Material and method: The present prospective observational study was conducted in the department of Medicine among 50 patients with acute myocardial infarction. Patients who presented to the hospital within 24 hours of onset of symptoms and diagnosed with acute myocardial infarction were included in the study. Blood samples collection were taken within 24 hours of onset of symptoms. All patients were evaluated for their ECG and cardiac enzymes and serum magnesium level by taking 5 cc venous blood sample in a disposable syringe and sent to biochemistry laboratory for analysis in fluoride bulb and plain bulb respectively. Results: Smoking was reported in 82% of the subjects whereas hypertension and diabetes mellitus in 64% and 46% of the subjects respectively. Sixteen percent, 24% and 60% of the subject’s time of presentation was 3-6 hours, 6-12 hours and 12-18 hours respectively. On day 5, only six percent (3) of the subjects with arrhythmia were having serum magnesium level (mg/dL) <1.6 while 14% of the subjects with arrhythmia reported 1.7-2.4 serum magnesium level (mg/dL). ance in acute MI