42 research outputs found
An experimental study on friction reducing polymers in turbulent pipe flow
No full textAn experimental study was conducted to search the reduction of friction in fully developed turbulent pipe flow using different types of polyacrylamides as friction reducing polymers. Pressure drop measurements determined the friction reduction. Three different polymer types Superfloc A110, Superfloc A130 and Superfloc A150 were used to examine the effect of polymer concentration, Reynolds number and polymer type on friction reduction. The Darcy friction factor was obtained for each polymer type at the polymer concentration ranging from 0 to 500 wppm and a Reynolds number range of 10000-80000. It was observed that friction factor decreased with increment in polymer concentration and Reynolds number for each polymer. Higher molecular weight polymers are more effective at reducing friction. With increasing concentration of polymer, the measured data approaches the Virk asymptote, which represents the maximum friction reduction limit by the polymers. The percentage of friction reduction increased with increasing concentration of polymer up to 100 wppm for each polymer type and then began to decrease for polymer concentrations higher than 100 wppm. An empirical formula was obtained to calculate the Darcy friction factor as a function of Reynolds number and polymer concentration for Superfloc A110.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.Marine and Transport Technolog
Ultrasound Imaging Methods for Breast Cancer Detection
No full textThe main focus of this thesis is on modeling acoustic wavefield propagation and implementing imaging algorithms for breast cancer detection using ultrasound. As a starting point, we use an integral equation formulation, which can be used to solve both the forward and inverse problems. This thesis contains three main topics: forward modeling, imaging and inversion methods, and a short description of essential steps needed to work with measured data. First, acoustic wavefield propagation using a full-wave method and the Born approximation are discussed. The first method is used to investigate the effect of variations in compressibility, volume density of mass and attenuation separately and combined. The accuracy of the full-wave method is confirmed using an analytical solution. The results of both the Born approximation and the full-wave method are compared using a 3D example, and the results show that the full-wave method provides more accurate results compared to the Born approximation. It is also shown that the spatially dependent attenuation plays an important role in wave propagation. Considering the significant effect of the attenuation coefficient, it might be a useful medium parameter for imaging. The full-wave method is used to generate noise-free synthetic data, which includes typical wave phenomena such as multiple scattering, refraction and dispersion. In addition, it is a useful tool to test a particular imaging system with respect to the required frequency and minimum number of transducers. Secondly, imaging and inversion methods such as inverse Radon, refraction corrected tomography, synthetic aperture focusing technique, back-propagation, Born inversion, and contrast source inversion are discussed. The advantages and disadvantages of all methods are expressed, and they are compared using a 2D synthetic example. Of all methods, the nonlinear inversion method, CSI, provides the best reconstruction results. It also provides extra information for the inner structure of the breast by accurately reconstructing the speed of the sound profile. Moreover, CSI is more stable than Born inversion, and a regularization may be applied such as total variation to increase the stability. CSI is applied on a 3D synthetic example, to estimate the required number of sources/receivers, frequency and number of iterations. Although not tested, attenuation profiles of the breast can also be obtained using CSI. This additional information may help to detect malignant tumors. Finally, we mention several essential steps that should be applied before working with measured data. These steps are important to analyze and understand the data. Methods for finding the sound speed of the background medium are suggested and some methods are recommended to find a correlation between modeled and measured data. Furthermore, the sampling criterion is discussed and it is shown that increasing the number of receivers has a stronger positive impact on image quality than increasing the number of sources. In adition, it is stated that using less sources will lead to a larger reduction of computational time and memory than reducing the number of receivers. The reconstruction results for the synthetic examples are very promising and definitely warrants testing with real experiments. Applying the nonlinear inversion methods to the data obtained from the current scanning systems is challenging due to limitations in computer technology. Since the modeling results indicate that attenuation may have a significant effect, it would be a valuable addition to include attenuation during imaging.Imaging Science & TechnologyApplied Science
Visual inspirations of A Little Life
No full textHanya Yanagihara's critically acclaimed second novel A Little Life was published in 2015 and despite its length and disturbing thematic concerns soon became a bestseller. Yanagihara has laid her creative process bare in various interviews and has been open about the intermedial inspiration she has drawn from photography and painting. These sources provide an opportunity for the scholar to accurately and precisely trace how visual arts interact with the text before, during, and even after its conception. Critics predominantly responded to the novel about how comprehensively the author depicted child sexual abuse, violence, and trauma. The author merges generic conventions such as the Bildungsroman and fairy tale while constructing her plot and draws a significant amount of her inspiration from images. Seemingly contrasting affective impressions emanating from the images and the text converge in harmony and lead to an apt portrayal of the protagonist's psyche and the reader's ambiguous perception of his trauma. The article scrutinizes the use of photographs, paintings, and other visual material in the creative process of the novel in an ekphrastic mode both descriptively and non-descriptively, the latter to create a mood in the story rather than present a realistic depiction of the objects in question
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No full textHyoscyamus reticulatus (Solanaceae) is distributed in the Mediterranean, East and Central Anatolia regions of Turkey. In the present study, antioxidant properties of the various extracts of H. reticulatus were evaluated by seven different chemical assays, namely total phenolics and flavonoids content, total antioxidant capacity, free radical (2,2-diphenyl-1-picrylhydrazyl)-scavenging assay, beta-carotene/linoleic acid test system, and ferric- and cupric ion-reducing power. The strongest antioxidant properties were obtained by ethanolic extract. The order of the antioxidant properties of extracts were ethanolic > methanolic > acetone. Fatty acid composition of the aerial parts of H. reticulatus was analyzed by gas chromatography. The main fatty acids of the oil gave the proportions C 12:0 (lauric acid), C 10:0 (capric acid) and C 11:0 (undecanoic acid). Results of the present study demonstrated that the extracts and oil of H. reticulatus may be used as a source of natural antioxidant and lauric acid in the food and pharmaceutical industries. PRACTICAL APPLICATIONS Hyoscyamus species contain important tropane alkaloids, which have antispasmodic, anticholinergic, analgesic and sedative effects. In this study, antioxidant properties of the various extracts of Hyoscyamus reticulatus were investigated by seven different chemical assays. The results of the present study may be important as an indication of pharmacological and food processing utility of the plant. H. reticulatus can be considered as a source of both natural antioxidants and lauric acid in food industry and pharmacological applications.Selcuk University Scientific Research Foundation (BAP)This study was financed by Selcuk University Scientific Research Foundation (BAP). The author wishes to acknowledge their support of this project
ABOUT TABARANI'S TAFSIR: The Problem of the Attribution of Al-Tafsir Al-Kabir to Al-Tabarani
No full textBased on the reference inscribed on it, a manuscript found in the National and University Library of Strasbourg published in Jordan under the name of Al-Tafsir al-Kabir: Tafsir Al-Qur'an Al-Azim has been attributed to the famous muhaddith Abu'l-Qasim Al-Tabarani (360/971). The manuscript in question is actually Hanafi faqih Abu Bakr Al-Haddad's (800/1398) well known and printed as Tafsir Al-Haddad, tafsir named Kashf al-tanzil fi tahqiq al-mabahith wa-al-ta'wil. The copy of the tafsir present in Strasbourg is one of the three existing copies used during the impression of Tafsir Al-Haddad. Consequently, the copy used for Haddad's tafsir and Tabarani's tafsir is the same. This article will deal with the attribution of the author of Al-Tafsir Al-Kabir. In this context, the book will be compared with the tafsir copy present in Strasbourg and Abu Bakr Al-Haddad's tafsir. Besides, a detailed study of the sources, method and content of Al-Tafsir Al-Kabir will be realized. The quotations in the book of the work of mufassir's who have lived after Tabarani will be shown. Moreover, we will indicate the impossibility to attribute the book to Tabarani proposing
A guided internet-based intervention targeting procrastination in college students: Protocol for an open trial (Preprint)
No full textBackground: Academic procrastination is a widespread problem among college students. It is linked to poor academic performance and increased college dropout intentions, as well as several mental health problems such as depression, anxiety, and stress. Guided web-based interventions can help reduce procrastination. However, guidance by professional clinicians draws upon valuable and limited societal resources, and a more efficient, scalable form of guidance is needed. Guidance by trained clinical psychology students has not yet been examined.Objective: The aim of this open trial is to examine the feasibility and acceptability of a web-based procrastination intervention for college students under the guidance of student digital coaches (e-coaches).Methods: We developed a single-arm trial of a guided web-based intervention targeting procrastination for the Dutch student population. Guidance is delivered by trained clinical psychology students asynchronously in the form of textual feedback on intervention progress, with the aim of supporting and motivating the participant. Participants are recruited at 7 Dutch universities. Primary outcomes are intervention satisfaction, usability, and adherence, which are assessed by the Client Satisfaction Scale (CSQ-8), System Usability Scale (SUS-10), and number of completed modules, respectively. The primary outcomes will be examined by calculating descriptive statistics. Secondary outcomes are e-coach satisfaction and changes to procrastination, depression, stress, and quality of life from pre- to posttest and follow-up. Results: The project was funded in 2019, and recruitment began in January 2021. As of May 2023, a total of 985 participants were enrolled, of which 372 had completed the posttest and 192 had completed the follow-up. The expected date of analysis and publication of the results is 2024.Conclusions: The results are expected to contribute to the body of literature regarding eHealth in 3 ways. First, we will examine whether students who procrastinate adhere to and are satisfied with an eHealth intervention targeting this problem. Second, we will explore whether an intervention targeting procrastination can also decrease depression and stress. Lastly, we will investigate whether trained psychology students can effectively guide their peers in web-based interventions. Given the shortage of licensed psychologists, exploring alternative sources of guidance is much needed in order to provide students with the mental health support they need.</p
Effectiveness of a guided internet-based intervention for procrastination among university students – A randomized controlled trial study protocol
No full textProcrastination is a widespread problem that is highly prevalent among the young adult population and is associated with several negative consequences. However, current evidence on the effectiveness of e-health interventions for procrastination either lack a comparison to an inactive control, do not include a student population or are of poor quality. This protocol describes the design of a trial that will overcome these limitations and examine the effectiveness of a guided internet-based intervention (GetStarted) to reduce problematic procrastinating behaviors in college students compared to a waitlist control. This study will be a two-armed randomized controlled trial with a calculated sample size of N = 176. Participants will be students from seven universities in the Netherlands. The intervention group will receive a four-week e-coach-guided intervention for procrastination. The waitlist control group will get access to treatment four weeks after randomization. Assessments will take place at baseline, post-test (4 weeks post-baseline) and follow-up (6 months post-baseline). Data will be analyzed with an intent-to-treat principle. The primary outcome is change in procrastination behaviors measured on the Irrational Procrastination scale (IPS). Secondary outcomes are depression, anxiety, stress, and quality of life. Additionally, sociodemographic characteristics of the participants, satisfaction with treatment, program usability, satisfaction with e-coach and treatment adherence will be examined as potential moderators. The results from this study can build evidence for the effectiveness of a guided internet-based intervention for treating procrastination in college students. Should it be effective, GetStarted could provide a flexible, low-intense and cost-effective treatment for procrastination and prevent common mental health problems in college students. Trial registration: This trial is registered at ClinicalTrials.gov Protocol Registration and Results System (Trial number: NCT05478096)
Suvokiamo m-komercijos programėlių privatumo politikos veiksmingumas naudotojų norui dalytis asmenine informacija.
No full textWith the introduction of digitalization and information technologies into our lives, businesses continued to develop their services online. With the transition to the online environment, consumers began to purchase services through online services, and this caused the concept of data privacy to come to the fore. As consumers shopped online, they had to share different personal data with service providers. With data privacy coming to the fore, governments have introduced laws and regulations to protect data privacy, and privacy policies have entered our lives. The purpose of privacy policies was to legally protect the rights of users and service providers. However, it has been observed that the perceived effectiveness of privacy policies can have different effects on the user. Therefore, it has been observed that privacy policies play an important role in creating a sense of trust in the user and reducing privacy concerns, and have a great impact on users' willingness to share their personal information. Therefore, the author's aim is to analyze the impact of the perceived effectiveness of the privacy policy on users' willingness to share their personal information while considering the factors of trust, privacy concern and privacy awareness for the respondents from Lithuania. In order to achieve the purpose of the research and evaluate the hypotheses, data was collected using the survey method, correlation analysis was made using the SPSS program and the hypotheses were tested. Lithuanian users' attitudes towards privacy policy, willingness to share personal data, levels of trust, privacy concerns and privacy awareness were measured with different survey questions, and by analyzing the results, all five hypotheses developed were confirmed. The findings of the survey show that the perceived effectiveness of the privacy policy has a significant impact on the user's willingness to share personal data. In addition, the author added a different dimension to the research and contributed to the literature by addressing the factors of trust, privacy concern and privacy awareness at the stage of users' willingness to share their personal data. As a result, for Lithuanian users, the perceived effectiveness of the privacy policy appeared to increase the sense of trust and reduce privacy concern. On the other hand, it has been concluded that the privacy concerns of users with high awareness and knowledge about privacy also increase, and as a result, their willingness to share personal information decreases. To summarize, the current research is helpful to both the academic and business communities in terms of m-commerce companies and service providers
Quantitative ultrasound tomography
No full textTomogrophic ultrasound imaging is gaining popularity in breast cancer detection. Reconstructing the acoustic properties of a breast from the ultrasound measurements is stated as a nonlinear inverse problem, which is usually solved by linearized methods because of computational efficiency. However, linearization of the problem reduces the quality of the reconstruction. To improve the accuracy, we developed and tested a three-dimensional nonlinear inversion method that allow for three-dimensional reconstruction of the breast in terms of speed of sound. The method, referred to as contrast source inversion (CSI), uses an integral equation formulation to describe the inverse acoustic scattering problem. The resulting integral equation is solved to reconstruct the unknown contrast (speed-of-sound profile of the breast). The contrast and contrast sources (the product of the contrast with the total field) are iteratively updated by minimizing a cost functional using conjugate gradient directions. In this study, we tested the CSI method on synthetic data retrieved form full-wave simulations for a realistic three-dimensional cancerous breast model. Results show that the CSI method outer performs other conventional methods as it yields speed-of-sound reconstructions that are akin to the model. This shows that the approach offers a contribution to the detection of breast cancer.IST/Imaging Science and TechnologyApplied Science
A contrast source inversion method for breast cancer detection
No full textTomogrophic ultrasound imaging is gaining popularity in breast cancer detection. Reconstructing the acoustic properties of a breast from the ultrasound measurements is stated as a nonlinear inverse problem, which is usually solved by linearized methods because of computational efficiency. However, linearization of the problem reduces the quality of the reconstruction. To improve the accuracy, we developed and tested a three-dimensional nonlinear inversion method that allow for three-dimensional reconstruction of the breast in terms of speed of sound. The method, referred to as contrast source inversion (CSI), uses an integral equation formulation to describe the inverse acoustic scattering problem. The resulting integral equation is solved to reconstruct the unknown contrast (speed-of-sound profile of the breast). The contrast and contrast sources (the product of the contrast with the total field) are iteratively updated by minimizing a cost functional using conjugate gradient directions. In this study, we tested the CSI method on synthetic data retrieved form full-wave simulations for a realistic three-dimensional cancerous breast model. Results show that the CSI method outer performs other conventional methods as it yields speed-of-sound reconstructions that are akin to the model. This shows that the approach offers a contribution to the detection of breast cancer.IST/Imaging Science and TechnologyApplied Science
