489 research outputs found
Three-dimensional analysis of pile behaviour
No full textOften, any form of ground activities will have an influence on the structures which the ground carries and in some instances of piles, an induced lateral load may act on the piles. Serviceability limit of the pile may be undermined resulting in cracks in the pile or in more disastrous cases, ultimate limit state of the pile will be reached and the pile fails. Numerous research have been carried out to investigate the effects of such lateral loads on piles and in this project, a numerical study has been attempted to understand the effects of lateral soil movement on pile behaviour. Three dimensional numerical analyses were carried out with the use of a finite element analysis program, PLAXIS 3D Foundation. The versatile software was proven to be able to assist in investigating the underlying problem. Three-dimensional models of an embankment were built and a special feature, “embedded pile” was used in the model. The results of the analyses match well with the proposed parametric studies from the literature. The parameters studied were embankment pressure, clay thickness, pile stiffness, soil undrained shear strength and modulus of elasticity of clay. For all the parameters, the bending moment of the pile proved to be very sensitive to any degree of changes while the deflections of the pile were less significant. The study also indicated that the “embedded pile” feature in PLAXIS 3D Foundation was not suitable to model pile group behaviour.Bachelor of Engineering (Civil
Investigating male factors and their relationships with reproductive health outcomes: a case-control study protocol for Towards Optimal Fertility, Fathering, and Fatherhood studY (TOFFY) in Singapore
No full textIntroduction: despite the global prevalence of low fertility rates, male contributions to fertility and reproductive health outcomes have been understudied. This study aims to investigate the male contribution to fertility and explore the underlying biological mechanisms. Specifically, we aim to (1) identify male factors associated with successful pregnancy; (2) develop a fertility index incorporating modifiable factors for both males and females to predict pregnancy rate; and (3) explore the relationship of male modifiable factors with semen parameters and molecular characteristics.Methods and analysis: we will conduct an unmatched case-control study involving 240 couples with impaired male fertility (cases) and 240 couples with normal male fertility (controls). Between July 2024 and June 2026, we will recruit the 480 eligible couples from KK Women’s and Children’s Hospital, Singapore. Male and female participants will complete questionnaires on socio-demographics, general health and lifestyle factors, and their anthropometry and body fat composition will be measured. Blood and semen samples from the male participants will be collected for biochemical, molecular, and semen analyses. Predictive male factors will be identified using the least absolute shrinkage and selection operator method, accounting for female factors. We will construct a logistic regression model incorporating both male and female factors to derive a fertility index, which will be evaluated using cross-validation on subsets of the study population. Multivariable linear regression will be used to explore relationships between male modifiable exposures and semen parameters.Ethics and dissemination: the study protocol has received approval from the Centralised Institutional Review Board of SingHealth (2024/2120), Singapore. Participants will provide written informed consent. Study results will be disseminated through conferences and peer-reviewed scientific journals.<br/
Toxic exposure in a clinical pathology laboratory as a potential occupational hazard causing small fibre neuropathy
No full textMetabolic health status and fecundability in a Singapore preconception cohort study
No full textBackground: obesity compromises metabolic health and female fertility, yet not all obese women are similar in metabolic status. The extent to which fecundability is influenced by the metabolic health status of women who are overweight or obese before conception is unknown.Objective: this study aimed to: (1) determine the metabolic health status, and (2) examine the association between metabolic health status and fecundability of overweight and obese women trying to conceive in the Singapore PREconception Study of long-Term maternal and child Outcomes cohort study.Study Design: we conducted a prospective preconception cohort study of Asian women (Chinese, Malay, and Indian) aged 18 to 45 years trying to conceive who were treated from 2015 to 2017 in KK Women’s and Children’s Hospital in Singapore (n=834). We defined women to have metabolically unhealthy status if they: (1) met 3 or more modified Joint Interim Statement metabolic syndrome criteria; or (2) had homeostasis model assessment-insulin resistance index ≥2.5. Body mass index was categorized as normal (18.5–22.9 kg/m2), overweight (23–27.4 kg/m2), or obese (≥27.5 kg/m2) on the basis of cutoff points for Asian populations. Fecundability was measured by time to pregnancy in menstrual cycles within a year of enrolment. Discrete-time proportional hazards models were used to estimate fecundability odds ratios, with adjustment for confounders and accounting for left truncation and right censoring.Results: of 232 overweight women, 28 (12.1%) and 25 (10.8%) were metabolically unhealthy by metabolic syndrome ≥3 criteria and homeostasis model assessment-insulin resistance ≥2.5, respectively. Of 175 obese women, 54 (30.9%) and 93 (53.1%) were metabolically unhealthy by metabolic syndrome ≥3 criteria and homeostasis model assessment-insulin resistance ≥2.5, respectively. Compared with metabolically healthy normal-weight women, lower fecundability was observed in metabolically unhealthy overweight women on the basis of metabolic syndrome criteria (fecundability odds ratios, 0.38 [95% confidence interval, 0.15–0.92]) and homeostasis model assessment-insulin resistance (fecundability odds ratios, 0.68 [95% confidence interval, 0.33–1.39]), with metabolic syndrome criteria showing a stronger association. Metabolically unhealthy obese women showed lower fecundability than the healthy normal-weight reference group by both metabolic syndrome (fecundability odds ratios, 0.35; 95% confidence interval, 0.17–0.72) and homeostasis model assessment-insulin resistance criteria (fecundability odds ratios, 0.43; 95% confidence interval, 0.26–0.71). Reduced fecundability was not observed in overweight or obese women who showed healthy metabolic profiles by either definition.Conclusion: overweight or obesity was not synonymous with having metabolic syndrome or insulin resistance. In our preconception cohort, metabolically unhealthy overweight and obese women showed reduced fecundability, unlike their counterparts who were metabolically healthy. These findings suggest that metabolic health status, rather than simply being overweight and obese per se, plays an important role in fecundability
Strain-tuning of periodic optical devices : tunable gratings and photonic crystals
No full textThesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003.Includes bibliographical references (p. [161]-173).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.The advancement of micro- and nano-scale optical devices has heralded micromirrors, semiconductor micro- and nano-lasers, and photonic crystals, among many. Broadly defined with the field of microphotonics and microelectromechanical systems, these innovations have targeted applications in integrated photonic chips and optical telecommunications. To further advance the state-of-the-art, dynamically tunable devices are required not only for demand-based reconfiguration of the optical response, but also for compensation to external disturbances and tight device fabrication tolerances. In this thesis, specific implementations of strain-tunability in two photonic devices will be discussed: the fundamental diffractive grating element, and a photonic band gap microcavity waveguide. For the first part, we demonstrate high-resolution analog tunability in microscale diffractive optics. The design concept consists of a diffractive grating defined onto a piezoelectric-driven deformable membrane, microfabricated through a combination of surface and bulk micromachining. The grating is strain-tuned through actuation of high-quality thin-film piezoelectric actuators. Device characterization shows grating period tunability on the order of a nanometer, limited by measurement uncertainty and noise. The results are in good agreement with analytical theory and numerical models, and present immediate implications in research and industry. For the second part, we generalize the piezoelectric strain-tunable membrane platform for strain-tuning of a silicon photonic band gap microcavity waveguide. Additional motivation for this strain-tuning approach in silicon photonic crystals lies in:(cont.) (a) the virtual absence of electro-optic effects in silicon, and (b) the ability to achieve tuning with low power requirements through piezoelectric actuation. Compared to current thermo-optics methods, piezoelectric actuation affords faster and more localized tuning in high-density integrated optics. The small-strain perturbation on the optical resonance is analyzed through perturbation theory on unperturbed full 3D finite-difference time-domain numerical models. Device fabrication involves X-ray nanolithography and multi-scale integration of micro- and nano-fabrication methods. Experimental characterization achieved dynamically-tunable resonances with 1.54 nm tunable range (at 1.55 Mum optical wavelengths), in good agreement with theory. This is the first demonstration of strain tunability in photonic crystals and contributes to the development of smart micro- and nano-scale photonics.by Chee Wei Wong.Sc.D
Sub-fm/Hz(1/2) displacement measurement on MgF2 whispering gallery mode microcavity
No full textWe present sub-fm/Hz(1/2) displacement measurement on the MgF2 whispering gallery mode microcavity. We analyze power spectral density of the displacement from 1 Hz to 100 kHz of the Fourier offset frequency. (C) 2020 The Author(s
Security framework for Android applications
No full textFrauds, infringement of privacy, hacking, loss of data and many more acts are somethings everyone faces in modern society. One of the biggest issue is mobile security, in this case the focus is on the Android platform, given its wide spread usage it is important to build safeguards for it. There are many security applications out there in the market and this application would not be out of the original. It would seek to put in place Rules that would mimic current identifiers of security breaches that could only be used on a more capable device like a workstation. The outstanding thing about this app is that it is an informative app which seeks to place as much details to the user, hoping it will allow the user to know of the dangers with in the device. This is still first and foremost, a work-in progress and the first in it iteration. The whole idea is based on the noble and tedious task to weed out malicious apps that might be rampaging through private data and to hopefully in future put a stop to it.Bachelor of Engineerin
Security framework for Android applications
No full textFrauds, infringement of privacy, hacking, loss of data and many more acts are somethings everyone faces in modern society. One of the biggest issue is mobile security, in this case the focus is on the Android platform, given its wide spread usage it is important to build safeguards for it. There are many security applications out there in the market and this application would not be out of the original. It would seek to put in place Rules that would mimic current identifiers of security breaches that could only be used on a more capable device like a workstation. The outstanding thing about this app is that it is an informative app which seeks to place as much details to the user, hoping it will allow the user to know of the dangers with in the device. This is still first and foremost, a work-in progress and the first in it iteration. The whole idea is based on the noble and tedious task to weed out malicious apps that might be rampaging through private data and to hopefully in future put a stop to it.Bachelor of Engineerin
Prediction of solar energy and radiation in Singapore
No full textThis project was to perform prediction of solar energy and radiation in Singapore. Artificial Neural Network (ANN) was used in this project for prediction purpose. Data obtained from National Weather Study Project (NWSP) were used as data sources. Java Object Oriented Neural Engine (JOONE) was used to run the network designed.
In this report, the data used were in between 9am to 10am, all together there were 664 datasets. 564 datasets were used for training and the 100 datasets were used for validating the output of network. The error was evaluated by using the 100 validating datasets and their respective network outputs. The accuracies were evaluated within 5% error.
In this project, we used the training datasets to teach the ANN so that the network could give us the desired output. The learning algorithm selected in this project was BackPropagation (BP). BP was a method using the difference between the target output value and the network output value to modify the weights of the network. The changes of weights were accumulated during the network learning process. After the learning process, the network was tested with validating data so as to evaluate the accuracy of the network.Bachelor of Engineerin
Numerical studies of thermal flying height control slider in hard disk drive
No full textAs thermal flying height control (TFC) slider has been widely used in today's hard disk drive (HDD) industry for its advantages of easier control of flying height (FH) and less risk of contacts with the disk over conventional slider. The concept of a TFC slider is to use a heater embedded near the read/write element. When a current is applied through the heater, the pole-tip protrusion caused by the mismatch of thermal expansion of various materials occurs and reduces the slider-disk spacing accordingly. Test, analysis and design of the air bearing slider with thermal protrusion are essential for both research and development work, and industrial products.
In this report, a series of numerical simulations is done to gain an insightful knowledge on the heater designs of the thermal actuated sliders and their effects on the protrusion profiles, temperature and distribution and flying height reduction by using the commercial software ANSYS and DSI self-developed simulation code ABSolution respectively.Bachelor of Engineerin
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