293 research outputs found
Integrating new assessment strategies into mathematics classrooms: an exploratory study in Singapore primary and secondary schools
No full textEducational researchers and practitioners have in recent years paid mounting attention to the importance of new assessment (or the so-called alternative assessment) strategies in Mathematics instruction to better reflect the new desired educational goals and shifted values in education. However, research is wanting in this area, particularly in Singapore's educational setting. This project seeks to investigate the influence of using new assessment strategies in Mathematics teaching and learning on students' achievements, in both the cognitive and affective domains, in our local school settings. A quasi-experimental study with about 15-20 teachers at primary and lower secondary levels will be carried out to assess the impact of using a variety of strategies (e.g., projects, journal writing, oral presentation, performance tasks, student self-assessment, classroom observation and interview, etc.) for three school semesters on students' learning. The project will also look into issues concerning how to use new assessment strategies effectively in classrooms in local schools. For this purpose, data will be collected from classroom observation, interviews with teachers and students, and questionnaire surveys. It is hoped that the project will provide research-based evidence and practical suggestions for promoting the effective use of alternative assessment in Singapore Mathematics classrooms. <br/
Update on the treatment of gastrointestinal stromal tumors (GISTs): role of imatinib
No full textRichard Quek1, Suzanne George21Visiting Fellow, Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, Boston, MA, USA; 2Clinical Director, Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, Boston, MA, USAAbstract: In the last decade a tremendous amount has been learned about the biology and treatment of gastrointestinal stromal tumor (GIST). Imatinib mesylate has revolutionized the treatment of metastatic GIST. In addition, the role of imatinib in localized GIST has gained much interest and may improve patient outcomes. Additionally, research efforts aimed at understanding the biology and the molecular heterogeneity of GIST both at initial presentation and at the time of resistance to imatinib, has helped guide rational approaches to treatment as well as future efforts aimed at treating imatinib-resistant GIST.Keywords: gastrointestinal stromal tumors, GIST, review, imatinib, tyrosine kinase inhibitor, TK
Local modification and characterization of the electronic structure of carbon nanotubes
No full textIn december 1959, in his famous lecture "There's Plenty of Room at the
Bottom" given at Caltech, Richard Feynman imagined the possibility to
manufacture objects at the nanometer scale (1 nm = 10¡9 m) by maneu-
vering matter atom by atom. This revolutionary idea paved the way to
envision systems designed and engineered at the ultimate length scale rele-
vant to material science. Such systems have become a reality today and the
efforts to understand, build and use them encompass what is called nan-
otechnology. Today, nanoscience and nanotechnology constitute very active
and promising multidisciplinary research areas, bringing together engineers
and scientists from several ¯elds like physics, chemistry, materials science,
electronics, biology and medicine. A strong focus is given to the understand-
ing of the correlations between the structure of a material at the atomic
level and its optical, chemical and electronic properties. But nanoscience
and nanotechnology also aim at developing and improving techniques for
manufacturing nanomaterials for new applications.
When the dimensions of an object are shrunk down to a scale of the
order of the Fermi wavelength of the electrons, the said object will behave
according to the rules of quantum mechanics, and novel properties will
emerge that may be completely different from the bulk properties. One
well-known example for this is provided by graphite.
Graphite is a carbon allotrope whose structure consists of a stacking of
two-dimensional, sp2-bonded carbon layers interacting with each other by
van-der-Waals interactions. Because of these weak inter-layer interactions,
graphite is known as a mechanically soft material which is used in pencil
leads or, due to its high melting point and good electrical conductivity, in
the electrodes of arc lamps and arc furnaces. Now, if one imagines isolating a
small sheet of a graphite monolayer and roll it into a cylinder with nanome-
ter scale diameter, one will obtain a nano-object with amazing mechanical,
thermal and electronic properties. Such objects called carbon nanotubes
(CNT) have been discovered in 1991 1 and since then have led to an explo-
sion of research activities in many labs worldwide. In terms of mechanical
properties, carbon nanotubes are among the strongest and most resilient
materials known to exist in nature, with a Young's modulus approaching
1.2 TPa and a tensile strength 80 times higher than high strength steel.
Their electronic properties are unique in the sense that they are completely
determined by the tube geometry, resulting in semiconducting or metallic
character, with observed ballistic transport properties up to a few microm-
eters for the latter 2. During the last decade, CNT-based device prototypes
like single-electron transistors (SET) 3, ¯eld-effect transistor (FET) 4, logic
gates or memories 5;6 could be realized. Especially, it was demonstrated
that a CNTFET has superior performance over standard Si MOSFETs 7.
CNT based FETs are then very promising to be used as building blocks for
future large-scale integrated circuits as the actual silicon technology might
soon reach its limits in terms of miniaturization. Recent progress in separa-
tion techniques where individual chiralities can be isolated further sustain
this assumption 8. Also, growth techniques got improved with regard to
high purity of the raw material 9 and still constitute an active research
¯eld towards a highly desired chirality selective growth. Despite all these
advances, the development of a reliable and massively parallel integration
technology for CNT-based electronic devices that can compete in yield and
structure size with silicon technology is still missing and it is not yet clear
if such a technology can be established.
Up to now, especially in the worldwide race towards the realization of
the most competitive SWNT-based transistor, research focussed on mainly
defect free nanotubes. Nevertheless, researchers reported interesting results
from the investigation of intrinsic defects. For example, a classical p ¡ n
rectifying behavior has been reported for an intramolecular junction in a
single-walled carbon nanotube (SWNT), due to a special arrangement of
the C-C bonds at a tube kink 10. Furthermore, two separated intrinsic
defects in a metallic SWNT embodied in a source-drain-gate device showed
gate-dependent resonant backscattering properties 11. And more recently, a
high gate sensitivity at the position of individual defects of unknown nature
in similar devices has been observed 12.
These ¯ndings show that whereas a defect can be considered as a nui-
sance, on the other hand it can be regarded as an opportunity to tailor the
electronic properties of CNTs. Thus, the question arises to know how and
to which extent different types of defects can change the electronic proper-
ties of SWNTs. This is important in view to possibly modify and improve
the properties of existing CNT-based electronic devices such as CNTFETs,
or even further to de¯ne new kind of quantum devices with possibly new
properties entirely designed by a controlled creation of speci¯c defects.
The fundamental questions put above constitute the main motivation
of this Ph.D thesis. Here, we propose a study of the interplay between ar-
ti¯cially created defects and the electronic structure of SWNTs by means
of low temperature scanning tunneling microscopy and spectroscopy (LT-
STM/STS). LT-STM/STS constitutes the perfect investigation tool to achieve\ud
this goal since it enables us to directly probe the electronic structure of solids
with atomic resolution. The defects we investigate here are created by ion
bombardment. In order to study the effect of well-de¯ned individual de-
fects, a low invasive method for their creation must be privileged. To serve
this purpose, we have chosen an ECR plasma source producing low energy
ions of the order of a few eV.
In a ¯rst phase, we investigated hydrogen ion-induced defects, motivated
by a earlier work on graphite where it was shown that such defects act as
scattering centers leading to large momentum scattering. In a second phase,
we studied the effects of an exposition of the tubes to nitrogen plasma. This
is motivated by the fact that the intrinsic p-type doping of CNTFETs draws
up a demand on techniques allowing n-type doping in view to de¯ne p-n
junctions, which are indispensable key-blocks towards a future SWNT-based
technology. Different approaches like deposition of K donor atoms 13 or
attempts to create substitutional N sites during the tube growth 14 present
inhomogeneity problems. A controlled substitution technique is thus highly
desirable.
In the last phase, we were interested to create harsher defects like va-
cancies and double vacancies, which have shown to largely increase the
resistivity of SWNTs 15. This could be achieved by medium energy argon
ions of 200 eV and 1.5 keV produced by an ion gun.
Outline
The present Ph.D thesis is organized as follows:
Chapter 1 gives a brief introduction on the geometrical structure, synthe-
sis and electronic structure of SWNTs. The actual knowledge on the
effects of structural defects on the electronic and transport properties
of SWNT will be given in the form of an overview of the literature.
Chapter 2 describes the experimental methods used in this work. As the
principal investigation tool, the basic theoretical principles of STM
and STS will be described, followed by a technical description or our
LT-STM/STS setup. A short introduction to tmAFM will also be
given. And ¯nally, the basic principles of cold plasma physics will be
described, with emphasis on ECR plamsa and DC glow discharge.
Chapter 3 describes in details the different steps involved in the sample
preparation, from the SWNT suspension to the defect free SWNT
sample characterization by means of tmAFM and LT-STM/STS.
Chapter 4 and 5 present topography and spectroscopy investigations on
ECR H- and N-plasma-induced defects. In both cases, new defect-
induced gap states in semiconducting SWNTs could be observed.
For the ECR-H plasma treatment, STM/STS investigations combined
with ¯rst principle ab initio calculations demonstrated that a corre-
lated chemisorption of H-adatoms on the SWNT wall gives rise to
symmetric paired gap states.
Chapter 6 presents topography and spectroscopy investigations on 200
eV and 1.5 keV Ar+ion-induced defects. From ¯rst principle ab initio
calculations combined with our experimental results, we concluded
on the formation of two main defect types: vacancies and C-adatoms
giving rise to new states in the semiconducting gap. An increase of
the complexity of the defect con¯guration has been observed for 1.5
keV treatement, compared to 200 eV.
Chapter 7 gives an extended discussion on the often observed NDR be-
havior in the I ¡ V curves recorded at defect sites. Within a simple
tunneling model, we could explain this phenomenon by a voltage de-
pendence of the tunneling barrier height.
Chapter 8 describes electronic con¯nement effects observed between con-
secutive defects in metallic SWNTs. The capability of our method to
create su±ciently strong scattering centers shows the possibility to de-
¯ne room temperature active intra-tube quantum dots. The discussion
of the experimental observations mainly based on a Fourier analysis of
the spatial variation of the differential conductance is made on the ba-
sis of a scattering matrix formalism as well as a geometrical approach
within the Fourier projection-slice theorem.
Details on the ab initio calculations for different defect structures and ad-
ditional calculation results are given in Appendices A and B, respectively
Stock prediction, trading simulation and options volatility prediction using FASCOM++ (fuzzy associative cortical maps architecture)
No full textFuzzy Associative Cortical Maps Architecture (FASCOM) is inspired from the cortical maps found in many biological and artificial neural systems. The cortical maps organise and represent information obtained from sensory inputs and play important roles in learning and memory processes. FASCOM uses features inspired by the structure and functions of cortical maps and is integrated a linguistic fuzzy model to perform associative learning of input-output pairs. The project undertakes to improve the architecture of FASCOM to incorporate a learning mechanism, so that the network is capable of modifying its properties on the basis of the incoming data leading to better prediction and higher accuracy.
The author aims to validate the modified architecture of FASCOM by conducting benchmarking experiments and observing the improvement in the performance of the system over other systems. For this purpose, various classical datasets for classification and regression problems were used.
The author worked on many real-life application to observe FASCOM++’s performance on real-life data. One of the applications is stock data prediction where the author used Hong Kong stock data and predicted prices using FASCOM++ and compared the results with the actual prices. The analysis of FASCOM++’s performance helps in gauging its practical use in real-life applications such as stock trading. The author simulated a simple stock trading algorithm to compare and evaluate FASCOM++’s performance against other architectures.
The author explored other areas of applications and worked on options volatility prediction which is one of the core areas of research in the financial industry. By exploiting on the online learning capabilities FASCOM++ was able to perform better than the other architectures and demonstrated its capability to be a potential architecture for real-life purpose.Bachelor of Engineering (Computer Science
Appointment capacity planning in specialty clinics: a queueing approach
No full textSpecialty clinics provide specialized care for patients referred by primary care physicians, emergency departments, or other specialists. Urgent patients must often be seen on the referral day, whereas nonurgent referrals are typically booked an appointment for the future. To deliver a balanced performance, the clinics must know how much “appointment capacity” is needed for achieving a reasonably quick access for nonurgent patients. To help identify the capacity that leads to the desired performance, we model the dynamics of appointment backlog as novel discrete-time bulk service queues and develop numerical methods for efficient computation of corresponding performance metrics. Realistic features such as arbitrary referral and clinic appointment cancellation distributions, delay-dependent no-show behaviour, and rescheduling of no-shows are explicitly captured in our models. The accuracy of the models in predicting performance as well as their usefulness in appointment capacity planning is demonstrated using real data. We also show the application of our models in capacity planning in clinics where patient panel size, rather than appointment capacity, is the major decision variable
BBIPS : a blackboard based intergrated process supervision
No full textThe research effort undertaken by the author attempts to investigate the use of the blackboard architecture to realize the Integrated Process Supervision paradigm in a heterogeneous control environment that supports dynamic switching of control regimes and their corresponding techniques.Master of Engineering (SCE
Recurrent correlation associative memories
No full textThe online technique of neuro-fuzzy system has been increasing in popularity in the recent years. In actuality external factors play an important role in the time-variant dataset, changing its pattern. This change in pattern is known as drift and shift. To tackle these changes, Hebbian learning was introduced. However this learning is characterised by uni-directional learning, resulting in the instability of the model.
Hence, the BCM theory was developed to overcome the problem of Hebbian learning through the provision of Hebbian and Anti-Hebbian learning.
However, time variant data possesses both dynamic and temporal problems. The purpose of the author is to address this issue through the modification of the current recurrent fuzzy neural network. The underlying principle is to store past information to be recalled later for application in the current context.
The existing recurrent neuro-fuzzy system shows promising results that motivates the author to further the efficacy of the recurrent neuro-fuzzy system.
This report proposes a recurrent neuro-fuzzy system that uses the BCM theory of online learning with self-organizing effectiveness. In addition, rules are represented using the Takagi Sugeno Kang model to achieve a better accuracy compared to the Mamdani model which focuses on interpretability.
The performance of Recurrent SeroTSK is evaluated and compared against neuro-fuzzy systems through various time-series benchmark experiments and prediction for cancer diagnosis which is a classification data. The results show that Recurrent SeroTSK is better for time-series prediction and it works for classification data as well.Bachelor of Engineering (Computer Science
Values as resources in career counselling methods: case studies with integrative approach for clients with disabilities in Malaysia
No full textThis article responds to the Government\u27s call for counsellors to extend career guidance, which includes counselling Malaysians for enhancing human capital development with inclusiveness for attaining Vision 2020. This research paper does not study the types and degrees of severity of clients\u27 disabilities or explain the methodology for the integrative approach. It aims at creating awareness among career counsellors in: (1) understanding the integration of values for facilitating clients with disabilities in the counselling processand (2) using this insight for enabling clients to integrate into their society as productive and valued individuals. Hence, three cases of career counselling which were conducted by the author were selected to highlight the uses of values: (1) in Case I to develop objectivity, (2) in Case 2 to build therapeutic goals and (3) in Case 3 to cope with contextual barriers at work and at home. Using case studies, the relevance of the integrative approach is discussed within the context of the clients\u27 own values in the counselling process, facilitating them in integrating into society as productive contributors. However, it is cautioned that career counsellors refrain from imposing their values on clients in using the integrative approach. More dialogue from the counselling fraternity is invited to address the use of the integrative approach in improving inclusiveness at the cross-cultural level
From Cars to Complete Streets: Integrating Bicycles Into Seattle\u27s Transportation Network
No full textThis thesis explores the process of integrating cycling infrastructure into transportation networks in major cities. It starts by contextualizing the process in Copenhagen, Denmark (often called the best bike city in the world) during its cycling movement in the mid-20th Century. The findings from Copenhagen show that cycling is both viewed as a legitimate and respected mode of transportation and that the city layout, density, and topography is conducive to cycling. In the United States, this thesis explores the federal policies that have been created in support of the Complete Streets movement and makes the case that Complete Streets generally yield many benefits. In the final section, this thesis contextualizes these studies with a case study of Seattle and explores the challenges that have been associated with implementing Seattle’s Bicycle Master Plan. Although the city has made some small-scale cycling infrastructure, the number of cyclists in the city remains low and the bike network remains disconnected. There has been tremendous citizen pushback against lanes for fear of increased traffic and gentrification, and Seattle’s layout and topography presents additional challenges. While the author is in support of bicycling and cycle networks, she believes it is important to consider the opposition to implementing this infrastructure so that we can be more deliberate, sensitive, and inclusive with creating cycle networks in the future. The author proposes that cycling infrastructure may need to be done in smaller pockets before a citywide network can be successfully developed
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