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Aqueous and Biphasic Coupling of Furfural and Cyclopentanone for the Synthesis of Bio-Jet Fuel Precursors
Get PDFWe report on the aldol condensation of furfural and cyclopentanone in aqueous and biphasic mediums as a promising step for producing sustainable aviation fuel. Key parameters, including catalyst concentration, reactant concentration, temperature, and solvent, were found to significantly influence conversion and product selectivity. Alkaline conditions were essential for aldol coupling, with significant conversion observed at pH 12 and higher. The activation energies for the formation of the dimeric and trimeric aldol adducts were similar at 74 and 76 kJ/mol, respectively. Biphasic conditions were employed to prevent product precipitation, leading to reactor and equipment fouling. For biphasic conditions, the extraction of the reactants and dimeric intermediates to the organic phase affected rate and selectivity, resulting in the dilemma. Good product extraction leads to inevitable reactant extraction. Based on these findings, an integrated biphasic process design was proposed, utilizing process-owned solvents to optimize the separation and recycling of aqueous streams and improve the overall process efficiency.</p
Continuous extraction of xylose to Dowtherm A via esterification with 1-napthalene boronic acid from bagasse acid hydrolysate
Get PDFPrevious studies identified esterification with 1-napthalene boronic acid and subsequent extraction to Dowtherm A as a means of separating xylose from an aqueous stream. It was also shown that the xylose-boronate ester can be converted to furfural at high yields. To further investigate the possibilities of a large-scale continuous process for converting biomass (in this case sugarcane bagasse) to furfural, the reactive extraction is further studied in this work. A kinetic model for the extraction rate of xylose in both a batch and continuous system is made and verified using a model solution of xylose in water, the findings are also confirmed for actual biomass, and a multistage countercurrent mixer-settler cascade is modeled. This demonstrated the possibility of recovering more than 90 % of the xylose in a 50 g/L feed stream with 3 stages and a total residence time of 10 minutes.</p
Specifying and testing differences between variables in structural equation modeling using the H-O specification
No full textIn social sciences, differences can be found across a range of disciplines such as economics, sociology, and psychology. Yet, approaches employed in structural equation modeling (SEM) to studying differences are limited. For instance, they do not model the difference or can only include the difference as a predictor, rather than as an outcome variable. As a consequence, researchers are revented from exploiting SEM's full potential when it comes to studying differences.In my presentation, I address this limitation and present a modification of the recently introduced refined Henseler-Ogasawara (H-O) specification to model differences in SEM. This specification allows for flexibly modeling differences in SEM and can mimic the results of extant approaches. In addition, it allows to assess whether a difference fully transmits the effects of its components. To demonstrate the application of the proposed specification, an illustrative example is provided
Centralized urgency to autonomous caution:A Q-method exploration of Dutch citizens’ energy transition visions
Get PDFThis study explores varied sociotechnical visions on the Dutch energy transition from an engaged citizen perspective, thereby moving beyond a binary of support or opposition that often dominates public and policy debates. Existing energy transition literature has primarily emphasized formal and institutionalized visions or imaginaries of incumbent actors, overlooking the viewpoints of citizens that move past this for-or-against stance. Employing Q-methodology, four sociotechnical visions are identified: the Eco-Equitable, Pragmatic Project, Centralized Urgency, and Autonomous Caution. These visions showcase the multiple dimensions on which visions are held, each reflecting their own priorities for the energy transition. The visions diverge in the assessment of the urgency of climate change mitigation and their views on implementation, whether centralized or localized, or with or without an emphasis on social justice. Ultimately, the study accentuates the necessity for nuanced, inclusive dialogues to comprehend the multifaceted nature of citizen-centric energy transitions and how they expand on institutionalized visions of desirable energy transition orders
Urban digital infrastructuring and the (re)production of privilege
Get PDFA global digital and data revolution governs future urban strategies and profoundly influences the infrastructures built in cities. Numerous digital urban infrastructures remain hidden to city dwellers, all the while concurrently shaping, if not dictating, urban rhythms
Rigorous analysis of local search heuristics
Get PDFLocal search heuristics are standard methods in the optimizer's toolbox. These algorithms take as an input a candidate solution to an optimization problem and iteratively compute better solutions. Heuristics typically provide close-to-optimal solutions in much less running time than exact or approximation algorithms. Despite their practical usefulness, local search heuristics often have poor performance in the worst case. For many problems we know of instances where commonly used heuristics take prohibitively long to return a solution, or where they may return solutions that are far from optimal. This considerable gap between theory and practice is not satisfactory, as we would like to have some theoretical justification for using local search heuristics in practice. This dissertation broadly aims to enhance our understanding of local search heuristics. We analyze several heuristics using rigorous mathematical tools. We focus on three computational problems: the Travelling Salesperson Problem (TSP), k-Means clustering, and Max Cut. We consider these heuristics from the perspective of worst-case and beyond-worst-case analysis.For the TSP, we perform a smoothed analysis of the well-known 2-opt heuristic, improving and simplifying previous results for the Euclidean TSP. We then consider two polynomial-time variants of 2-opt, showing that one has poor approximation performance while the other performs similary to 2-opt. We moreover analyze the complexity of counting 2-optimal tours, and estimate the number of such tours in random instances. For k-Means clustering, we rigorously analyze the Hartigan-Wong method. This heuristic performs well in practice, but little was previously known about it theoretically. We show that even in one-dimensional instances, where k-Means can be solved optimally in polynomial time, the Hartigan-Wong method can take exponential time to find locally optimal clusterings. We also show that the heuristic leads to a PLS-complete local search problem. To augment these results we also perform the first smoothed analysis of the Hartigan-Wong method.Finally, we analyze the Flip heuristic for Max Cut, and show that also this simple heuristic yields a PLS-complete local search problem even in Euclidean instances
The added value of physical examination for breast cancer recurrence detection in women:A systematic review
Get PDFAs the number of curatively treated breast cancer patients grows and the burden on healthcare increases, effective use of methods to detect recurrences is becoming more important. This systematic review aims to examine the added value of physical examination (PE) in addition to mammography for breast cancer recurrence detection. PubMed, Web of Science, and Scopus were searched. Observational studies including women with a primary diagnosis of invasive or in situ breast cancer without metastases, which reported method of detection for locoregional recurrences (LRRs), and in which PE was defined as examination by a healthcare provider in an asymptomatic patient were included. Quality was assessed using the ROBINS-1 tool. Nine studies were included with data on 14,406 women, 613 LRRs and 349 secondar y primar y breast cancers. Of the total LRRs, 46.3% were detected by patients, 23.3% by mammography, and 14.8% by PE. PE detected 11% of the LRRs in patients who had breast conserving surgery and 28% of the LRRs in mastectomy patients. PE detected 7.1% of the contralateral breast cancers and 18.8% of ipsilateral lymph node recurrences, compared to 43.9% and 29.2% by mammography. PE detected a LRR in 0.6% of the patients (91/14,406) and mammography in 1.5% of the patients (143/9614). For detection of breast cancer recurrences, PE is of limited added value alongside mammography and self-detection, although it seems more beneficial for mastectomy patients. Further research is required to determine the effectiveness of the most efficient interval for PE across different patient groups
The Development of Pusara Finder:Muslim Grave Finder Mobile Application
Get PDFIn Islam, visiting graves reflects and reminds us of death and life in the Barzakh. The cemeteries must be adequately cared for and maintained since they play a significant role in the community as an important location for remembering and lamenting. However, remembering or finding the specific grave can sometimes be challenging. Thus, this project aims to develop a mobile application in which users can track their loved one’s grave to help them locate, save, and share the grave’s location by utilising the GPS sensors on the mobile phone. It is easier for them to track their loved ones and build a community for the Muslim cemetery community. The objectives of this project are to identify user requirements and to design and develop Pusara Finder – Muslim Grave Finder Mobile Application. This project uses the Android platform, and the mobile application has been developed using Visual Studio or Android Studio. There is a novelty of this project in which Pusara Finder is anl app designed to simplify the process of locating and navigating to Muslim graves in Shah Alam. This apps offers a seamless and intuitive experience, making it easier to pay tribute to the loved ones. The user also can access the complete database of Muslim graves with ease. The target user of this project was Muslim Public Users or people who want to find their specific grave. The methodology used for this project will be the Mobile Application Development Life Cycle (MADLC) Model. This project, however, has been developed up until the testing phase only. The project has been developed, and it’s in a prototype. In order to develop the mobile application, Flutter and Firebase has been implemented in this project. There were 11 users who had been involved in testing the usability of the mobile application by using System Usability Scale method with the score of 76.59 which in adjective rating is good.</p
Sand Dunes as a Nature‐Based Solution to Mitigate Salt Intrusion in Stratified Estuaries
Get PDFSalt intrusion in estuaries can pose a threat to drinking water extraction, irrigation, industries, and ecology. Key factors influencing the salt intrusion length include freshwater river flushing and vertical salt mixing. This study investigates the potential of estuarine sand dunes, that is, large-scale rhythmic patterns, to serve as a nature-based solution to mitigate salt intrusion. To this end, we adopt a two-dimensional vertical (2DV) modeling approach, which numerically solves the flow and salt transport in an idealized single-channel estuary. By varying the tidal amplitude and river discharge, three types of estuaries are modeled; a salt wedge, a strongly stratified and a strain-induced periodic stratification estuary. Two types of dune configurations are considered: ’depth-neutral’ dunes (preserving mean water depth) and ’deepening’ dunes (crest level equal to original bed level, rest of dune profile entirely below). Model results demonstrate that the presence of dunes can effectively reduce the salt intrusion length by several kilometers, compared to the scenario without dunes. Systematically varying dune geometry demonstrates that steeper (higher and shorter) dunes yield a stronger reduction in the salt intrusion length. Deepening dunes have the potential to generate sufficient mixing to overcome the adverse effects of channel deepening and, as such, can mitigate salt intrusion while maintaining navigability. As a naturally existing bedform, estuarine sand dunes present a promising nature-based solution against salt intrusion without compromising accessibility to seaports.</p