18 research outputs found
Investigating Combined Extreme Weather Effects on Solar Module Through Hardware and Simulink Performance Evaluation
No full textWorldwide adoption of photovoltaic (PV) cells, which use the photovoltaic effect to convert solar energy into electricity, has led to their emergence as a significant source of electricity production. As the number of PV installations continues to grow, understanding the impact of environmental factors on solar module performance becomes paramount.
Factors such as intermittency, cloud cover, shading, and nighttime unavailability significantly affect the efficiency and longevity of solar modules. However, there is a shortage of research connecting extreme weather conditions to overall module performance, hindering informed implementation decisions.
This study addresses the need for continuous monitoring of solar systems under various extreme conditions to evaluate their initial performance and optimize energy output. In order to achieve this, we conducted a hardware experiment where we tested solar cell performance under varying conditions; simultaneously, a MATLAB Simulink model was built and tested, and the results from hardware and software were compared. Both hardware and simulation experiments showed effective results that helped us to draw significant conclusions
Adapting authoritarianism: institutions and co-optation in Egypt and Syria
No full textThis PhD thesis compares Egypt and Syria’s authoritarian political systems. While the tendency in social science political research treats Egypt and Syria as similarly authoritarian, this research emphasizes differences between the two systems with special reference to institutions and co-optation. Rather than reducibly understanding Egypt and Syria as sharing similar histories, institutional arrangements, or ascribing to the oft-repeated convention that “Syria is Egypt but 10 years behind,” this thesis focuses on how events and individual histories shaped each states current institutional strengthens and weaknesses. Specifically, it explains the how varying institutional politicization or de-politicization affects each state’s capabilities for co-opting elite and non-elite individuals.
Beginning with a theoretical framework that considers the limited utility of democratization and transition theoretical approaches, the work underscores the persistence and durability of authoritarianism. Chapter two details the politicized institutional divergence between Egypt and Syria that began in the 1970s. Chapter three and four examines how institutional politicization or de-politicization affects elite and non-elite individual co-optation in Egypt and Syria. Chapter five discusses the study’s general conclusions and theoretical implications.
This thesis’s argument is that Egypt and Syria co-opt elites and non-elites differently because of the varying degrees of institutional politicization in each governance system. Rather than view one country as more politically developed than the other, this work argues that Syria’s political institutions are more politicized than their Egyptian counterparts. Syria’s political arena is, thus, described as politicized-patrimonialism. Syria’s politicized-patrimonial arena produces uneven co-optation of elites and non-elites as they are diffused through competing institutions. Conversely, the Egyptian political arena remains highly personalized as weak institutions and individuals are manipulated and molded according to the president’s ruling clique. This is referred to as personalized-patrimonialism. As a consequence, Egypt’s political establishment demonstrates more flexibility in ad hoc altering and adapting its arena depending on the emergence of crises.
This study’s theoretical implications suggest that, contrary to modernization and democratization theory’s adage that institutions lead to a political development, politicized institutions within a patrimonial order actually hinder regime adaptation because consensus is harder to achieve and maintain. It is within this context that Egypt’s de-politicized institutional framework advantages its top political elite. In this reading of Egyptian and Syrian politics, Egypt’s personalized political arena is more adaptable than Syria’s. These conclusions do not indicate that political reform is a process underway in either state
Recommended from our members
GEODESICS IN LORENTZIAN MANIFOLDS
No full textWe present an extension of Geodesics in Lorentzian Manifolds (Semi-Riemannian Manifolds or pseudo-Riemannian Manifolds ). A geodesic on a Riemannian manifold is, locally, a length minimizing curve. On the other hand, geodesics in Lorentzian manifolds can be viewed as a distance between ``events\u27\u27. They are no longer distance minimizing (instead, some are distance maximizing) and our goal is to illustrate over what time parameter geodesics in Lorentzian manifolds are defined. If all geodesics in timelike or spacelike or lightlike are defined for infinite time, then the manifold is called ``geodesically complete\u27\u27, or simply, ``complete\u27\u27. It is easy to show that the magnitude of a geodesic is constant, so one can characterize geodesics in terms of their causal character: if this magnitude is negative, the geodesic is called timelike. If this magnitude is positive, then it is spacelike. If this magnitude is 0, then it is called lightlike or null. Geodesic completeness can be considered by only considering one causal character to produce the notions of spacelike complete, timelike complete, and null or lightlike complete. We illustrate that some of the notions are inequivalent
Error-Bounded Approximation of Pareto Fronts in Robot Planning Problems
No full textMany problems in robotics seek to simultaneously optimize several competing objectives under constraints. A conventional approach to solving such multi-objective optimization problems is to create a single cost function comprised of the weighted sum of the individual objectives. Solutions to this scalarized optimization problem are Pareto optimal solutions to the original multi-objective problem. However, finding an accurate representation of a Pareto front remains an important challenge. Using uniformly spaced weight vectors is often inefficient and does not provide error bounds. Thus, we address the problem of computing a finite set of weight vectors such that for any other weight vector, there exists an element in the set whose error compared to optimal is minimized. To this end, we prove fundamental properties of the optimal cost as a function of the weight vector, including its continuity and concavity. Using these, we propose an algorithm that greedily adds the weight vector least-represented by the current set, and provide bounds on the error. Finally, we illustrate that the proposed approach significantly outperforms uniformly distributed weights for different robot planning problems with varying numbers of objective functions.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Learning & Autonomous Contro
Optimizing Task Waiting Times in Dynamic Vehicle Routing
No full textWe study the problem of deploying a fleet of mobile robots to service tasks
that arrive stochastically over time and at random locations in an environment.
This is known as the Dynamic Vehicle Routing Problem (DVRP) and requires robots
to allocate incoming tasks among themselves and find an optimal sequence for
each robot. State-of-the-art approaches only consider average wait times and
focus on high-load scenarios where the arrival rate of tasks approaches the
limit of what can be handled by the robots while keeping the queue of
unserviced tasks bounded, i.e., stable. To ensure stability, these approaches
repeatedly compute minimum distance tours over a set of newly arrived tasks.
This paper is aimed at addressing the missing policies for moderate-load
scenarios, where quality of service can be improved by prioritizing
long-waiting tasks. We introduce a novel DVRP policy based on a cost function
that takes the -norm over accumulated wait times and show it guarantees
stability even in high-load scenarios. We demonstrate that the proposed policy
outperforms the state-of-the-art in both mean and percentile wait
times in moderate-load scenarios through simulation experiments in the
Euclidean plane as well as using real-world data for city scale service
requests.Comment: Accepted for publication in IEEE Robotics and Automation Letters
(RA-L
Current trends in retraction of plastic surgery and reconstruction research
No full textBackground: Various studies regarding retractions of publications have determined the rate of retraction has increased in recent years. Although this trend may apply to any field, there is a paucity of literature exploring the publication of erroneous studies within plastic and reconstructive surgery. The present study aims to identify trends in frequency and reasons for retraction of plastic and reconstructive surgery studies, with analysis of subspecialty and journals. Methods: A database search was conducted for retracted papers within plastic and reconstructive surgery. The initial search yielded 2347 results, which were analyzed by two independent reviewers. 77 studies were jointly identified for data collection. Results: The most common reasons for retractions were duplication (n = 20, 25.9 %), request of author (n = 15, 19.5 %), plagiarism (n = 9, 11.6 %), error (n = 9, 11.6 %), fraud (n = 2, 2.6 %), and conflict of interest (n = 1, 1.3 %). 15 were basic science studies (19.4 %), 58 were clinical science studies (75.3 %), and 4 were not categorized (5.2 %). Subspecialties of retracted papers were maxillofacial (n = 29, 37.7 %), reconstructive (n = 17, 22.0 %), wound healing (n = 8, 10.4 %), burn (n = 6, 7.8 %), esthetics (n = 5, 6.5 %), breast (n = 3, 3.9 %), and trauma (n = 1, 1.3 %). Mean impact factor was 2.9 and average time from publication to retraction was 32 months. Conclusion: Analysis of retracted plastic surgery studies revealed a recent rise in frequency of retractions, spanning a wide spectrum of journals and subspecialties
Clinical Predictors of Gastrointestinal Bleeding Source before Computed Tomography Angiography
No full textBackground: Acute gastrointestinal bleeding (GIB) is a commonly encountered medical emergency. In cases of negative endoscopic evaluations, computed tomography angiography (CTA) is usually the next diagnostic step. To date, data regarding positive CTA examinations are lacking. We aimed to assess the clinical and laboratory parameters that predict a positive CTA examination, as demonstrated by the extravasation of contrast material into the bowel lumen. Methods: We performed a single-center retrospective study, including all patients who were admitted with GIB and who underwent CTA. Analysis was performed to compare patients’ characteristics, and logistic regression was used to explore parameters associated with a positive CTA. Results: We included 154 patients. Of them, 25 patients (16.2%) had active GIB on CTA vs. 129 patients (83.8%) who did not. On univariate analysis, several parameters were positively associated with active GIB, including congestive heart failure (OR 2.47, 95% CI 1.04–5.86, p = 0.04), warfarin use (OR 4.76, 95% CI 1.49–15.21, p = 0.008), higher INR (OR 1.33, 1.04–1.69, p = 0.02), and low albumin level (OR 0.37, 95% CI 0.17–0.79, p = 0.01). On multivariate logistic regression analysis, only high INR (OR 1.34, 95% CI 1.02–1.76, p = 0.03) and low albumin (OR 0.3, 95% CI 0.12–0.7, p = 0.005) kept their positive association with active bleeding, while a high ASA score was negatively associated with an active GIB. Conclusions: We could identify high INR and low albumin as strong predictors of active GIB, as demonstrated by positive CTA. On the other hand, comorbid patients classified by a high ASA score did not experience a higher rate of active GIB
Wafer classification using support vector machines
No full textIncreasing yield is a primary concern to integrated circuit manufacturing companies as it dictates the readiness of a new process for high volume manufacturing. In order to expedite the process of discovering yield issues, companies have started looking for ways to perform early prediction for such issues. This paper suggests the use of the support vector machines (SVMs) for early wafer classification. The choice of SVM is motivated by the model's ability to effectively classify multivariate, multimodal, and inseparable data points. This model uses multidimensional hyperplanes to separate and classify wafers into low-yield and high-yield classes. This paper includes a proposal for how the classification model can be applied for yield classification and how it can be adaptively updated in a manufacturing environment. We show how the values for the SVM parameters can be selected for best yield classification. Furthermore, performance evaluation is conducted on real manufacturing data, comparing the proposed SVM classifier to state of the art. Results show that in all cases, SVM consistently outperforms other methods with and without adaptive model updates. The experiments also show that all classifiers' performances depend on yield thresholds. It is also shown that the classification model can be built and executed using a reduced set without compromising its accuracy. © 1988-2012 IEEE.Abe S., 2005, SUPPORT VECTOR MACHI; Boser B, 1992, P 5 ANN WORKSH COMP, V5, P144, DOI DOI 10.1145-130385.130401; Botros Y, 2003, P SOC PHOTO-OPT INS, V5044, P121, DOI 10.1117-12.485311; Botros Y., 2003, P AEC APC S 4; Chapelle O, 2002, MACH LEARN, V46, P131, DOI 10.1023-A:1012450327387; Chin W. W., 2010, HDB PARTIAL LEAST SQ; Dasarathy B. V., 1991, NEAREST NEIGHBOR NN; Dupret Y., 2005, P IEEE SEM ADV SEM M, P118; Fayed A., 2003, P AEC APC S 25 SEP; Fenner J., 2000, P AEC APC S 12 SEP, VXII; Hajj H., 1998, P FLEX AUT INT MAN C; Hajj H., 2006, P AEC APC S 18, VXVIII; Hajj H, 2007, P SOC PHOTO-OPT INS, V6730, pQ7300, DOI 10.1117-12.746844; Hall M., 2000, P 17 INT C MACH LEAR, P359; Han J., 2001, DATA MINING CONCEPTS; He QP, 2008, P AMER CONTR CONF, P1606, DOI 10.1109-ACC.2008.4586721; He QP, 2007, IEEE T SEMICONDUCT M, V20, P345, DOI 10.1109-TSM.2007.907607; Khan AA, 2008, J PROCESS CONTR, V18, P961, DOI 10.1016-j.jprocont.2008.04.014; Kittler R., 2000, P INT C MOD AN SEM M, P270; Li TS, 2006, J INTELL MANUF, V17, P355, DOI 10.1007-s10845-005-0008-7; Lin TH, 2009, IEEE T SEMICONDUCT M, V22, P204, DOI 10.1109-TSM.2008.2011185; MACGREGOR JF, 1995, CONTROL ENG PRACT, V3, P403, DOI 10.1016-0967-0661(95)00014-L; May G. S., 2006, FUNDAMENTALS SEMICON; Moore G. E., 1975, P IEEE INT EL DEV M, P11; Moyne J, 2001, RUN TO RUN CONTROL S; Moyne JR, 2007, IEEE T SEMICONDUCT M, V20, P408, DOI 10.1109-TSM.2007.907617; Quinlan J. R., 1993, C4 5 PROGRAMS MACHIN; SPECHT DF, 1991, IEEE T NEURAL NETWOR, V2, P568, DOI 10.1109-72.97934; Wong A. Y., 1996, Proceedings. 1996 IEEE International Symposium on Defect and Fault Tolerance in VLSI Systems (Cat. No.96TB100081), DOI 10.1109-DFTVS.1996.57201274
An analysis of productivity app strengths: An environmental scan
No full textBACKGROUND
In recent years, productivity apps have become the most commonly used apps. While some may feel productivity apps work solely as a result of the placebo effect , productivity apps have been shown to have three major benefits: accountability, assessment, and improvement. Stress levels were especially reduced in the two meditation groups as opposed to the muscle relaxation group . Furthermore, there has been reported evidence on the effectiveness of app-based meditation and mindfulness in reducing stress and increasing productivity for users.
METHODS
In order to answer the research question, published articles from ProQuest, Business Source Premier and Web of Science were used. Additionally, Harvard Business Review was also used as a source of grey literature. Information was collected in order to determine the strengths of competing productivity apps and how they could limit or be applied to the Felicity App. The research was reviewed based on screening tools that assessed validity and relevance. Included studies were published within Asia, North America, Australia, or Europe, and were either quantitative, qualitative, randomized controlled trial (RCT), surveys, experiments with participants, or academic studies. Study screening and extraction were completed independently among two authors. Disagreements following reconciliation between the two authors were settled by a third author.
RESULTS
The selected articles discuss information including methods of improving productivity, mobile-based interventions that are effective at improving either overall health or productivity, and techniques that may be applicable to the Felicity App as a mobile-based intervention.
CONCLUSION
The results show that the Felicity App can improve user outcomes by integrating features from other applications
