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Krishnan R.,National University of Singapore | Krishnan R.,Institute of Chemical and Engineering Sciences, Singapore | Sundarrajan S.,National University of Singapore | Sundarrajan S.,Institute of Technical Education | Ramakrishna S.,National University of Singapore
Macromolecular Materials and Engineering | Year: 2013

Electrospinning of polymer scaffolds is mostly carried out using organic solvents, but the drawbacks are: solvent costs, environmental hazards, and presence of traces of solvent impurities. The use of water-soluble polymers (WSPs), water or aqueous solutions as an electrospinning medium (green processing) is a very attractive method to avoid such issues. However, a few WSP such as polyelectrolytes are not spinnable as such, but have been electrospun by addition of WSPs, additives, and salts. This paper covers solution properties, polyelectrolyte nanofibrous scaffolds (polysaccharides, biopolymers, etc.), fabrication through green processing, and their regenerative medical applications such as wound dressing, drug delivery, and tissue engineering. This is the first review to cover the above issues, the drawbacks of current methods, and future challenges. The fabrication of polyelectrolyte nanofiber scaffolds from aqueous polymer solution via a green electrospinning process is described. Generation of different architectures under various spinning conditions, application of polysaccharides and biopolymers scaffolds (for skin, cartilage, heart, and bone applications), drawbacks of the current methods, and future challenges are reviewed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Chandra Rao B.S.S.,National University of Singapore | Weng J.,National University of Singapore | Shen L.,Institute of Materials Research and Engineering of Singapore | Lee T.K.,Institute of Technical Education | Zeng K.Y.,National University of Singapore
Microelectronic Engineering | Year: 2010

This paper presents the studies to determine hardness and elastic modulus of intermetallic compound (IMC) layers in lead-free solder joints using nanoindentation technique. Two types of surface finishes, i.e., organic solderability preservative (OSP) and electrolytic Ni/Au on Cu pad, with Sn3.5Ag0.5Cu solder balls of 330 μm in diameter are studied, and the intermetallic layers are identified to be Cu6Sn5, Cu3Sn and (Niy,Cu1-y)3Sn4. The thicknesses of these IMC layers are only few microns at reflowed conditions (less than 2.3 μm). Therefore, probing mechanical properties of thinner IMCs using nanoindentation techniques poses immense difficulties and challenges. In this study, taper-mounted samples are used rather than standard cross-sectional mounted for solder joints. This taper sample gives a larger area for nanoindentation measurements. The elastic modulus and hardness of IMC layers are determined based on the parameter P/S2 (load/stiffness2) as a function of the indentation depth to minimise the effects of underlying UBM or solder materials. The modulus of Cu6Sn5, Cu 3Sn, (Cux,Ni1-x)6Sn 5 and (Niy,Cu1-y)3Sn 4 layer are found to be 112.0 ± 5.1 GPa, 135.5 ± 4.3 GPa, 165.0 ± 11.3 GPa and 136.8 ± 5.8 GPa; whereas the hardness values are found to be 6.8 ± 0.4 GPa, 6.6 ± 0.5 GPa, 7.2 ± 0.9 GPa and 8.2 ± 1.0 GPa, respectively. Thus, the IMC layers in the order of increasing hardness and modulus are found to be Cu6Sn 5, Cu3Sn, (Cux,Ni1- x)6Sn5 and (Niy,Cu1- y)3Sn4. © 2010 Elsevier Ltd. All rights reserved.


Menkhoff T.,Singapore Management University | Yian T.T.,Institute of Technical Education | Wah C.Y.,SIM University Singapore | Kee W.Y.,Singapore Management University
VINE | Year: 2011

Purpose: The purpose of this paper is to examine how to successfully blend an e-learning module into a knowledge management (KM) course aimed at getting KM students interested in the respective subject matter (= KM) in a web-based learning environment. Design/methodology/approach: Based on data obtained from 138 undergraduate business management students at a university in Singapore, practical aspects of effectively implementing an e-learning system with a focus on KM are analyzed and the importance determined of three conceptual variables in the context of successful blended learning approaches: online faculty to student interaction, social presence and personal e-learning experiences. Findings: The study shows some positive correlations between online faculty to student interaction, the degree of presence in a web-based learning environment, as well as personal e-learning experiences as potential drivers of students' desire to learn more about the subject matter KM. Research limitations/implications: There has been reliance on self-reported data in both the strengths, weaknesses, opportunities and threats study and the student survey. The causal effects of students' perceptions on actual learning need to be explored in a future study with a larger sample size. Practical implications: To increase students' acceptance of a web-based KM course, instructors must ensure quality interaction between them and their students, strong social presence via intrinsically rewarding group interactions and enriching, personal e-learning experiences on the basis of real-life KM problems. Games, systematic performance monitoring and graded knowledge tests are critical, too. Originality/value: This study highlights several good design features of an effective student interface vis-à-vis the development of an effective online learning environment from the perspective of KM student learners. Implications for e-learning designers and instructors, as well as issues for further research, are outlined. © Emerald Group Publishing Limited.


Koo Y.X.,National University of Singapore | Kang M.L.,National University of Singapore | Auyong A.,National University of Singapore | Liau G.Z.,National University of Singapore | And 6 more authors.
Public Health Nutrition | Year: 2013

Objective The objectives of the present study were to assess the nutritional status, identify factors for malnutrition risk and evaluate barriers to adequate nutrition among recipients of the Public Assistance (PA) scheme for socio-economically disadvantaged Singaporeans. Design Using a cross-sectional study design, we assessed PA recipients' malnutrition risk using the DETERMINE Nutritional Health checklist and the full Mini-Nutritional Assessment (MNA), as well as their nutritional knowledge, co-morbidity burden, depression risk, instrumental and basic activities of daily living (IADL and BADL), and awareness and utilization of available food services. In-depth interviews were also conducted on malnourished individuals (MNA score < 17) to understand barriers to adequate nutrition. Setting Homes of community-living older adults and nursing homes of institutionalized older adults. Subjects All PA recipients aged ≥55 years in Central Singapore District. Results Four hundred and sixty-five of 511 (91·0 %) eligible PA recipients participated in the study. The prevalence of malnutrition in the study population was 2·8 %. However, 50·3 % were at risk of malnutrition. Among community-dwelling respondents, the risk of malnutrition was independently associated with age >75 years, currently unmarried, BADL impairment, depression risk and BMI < 19·0 kg/m2. Qualitative analysis revealed that financial, social and physical barriers and lack of knowledge were the main contributors to poor nutritional status. Only half were aware of subsidized food services and education increased interest in utilizing food services. Among nursing home respondents, those who were BADL impaired were more likely to be at risk of malnutrition. Conclusions Among PA recipients, the prevalence of malnutrition is low but the risk of malnutrition is high. Education on adequate nutrition and food services are recommended. © The Authors 2013.


Chen H.,Nepes Pte. Ltd. | Tee T.Y.,Nepes Pte. Ltd. | Siew G.,Nepes Pte. Ltd. | Soh S.,Nepes Pte. Ltd. | And 7 more authors.
2011 IEEE 13th Electronics Packaging Technology Conference, EPTC 2011 | Year: 2011

WLP with various design configurations is fast becoming a common package for high performance applications. Besides large-die or embedded WLPs in System-in-Package, technology development in the industry also focuses on cost-effective WLP with acceptable level of functional and reliability performances, suitable for low-pin-count or small-die applications. Nepes is developing a series of low-cost wafer level packages (LCWLPs) to address the cost and technology demands. This paper will focus on prototyping of a non-UBM LCWLP with RDL, to be used as a baseline for relative cost, functional and reliability performances comparison with conventional WLPs and future LCWLPs of the same die sizes and ball layout. Previously, simulations were performed to confirm good electrical, mechanical (warpage and thermal cycling) and thermal performances of LCWLP. Here, process development is carried out to fabricate prototype of LCWLP. Several process issues are successfully resolved. Subsequently, LCWLP is qualified under package level reliability tests, including multi-reflow, solder shear/pull tests, pressure cooker test (PCT), and high temperature storage (HTS) test. After package level qualification, effort will be spent on board level tests. Here, board level drop test simulations are conducted for 3 different sizes of LCWLP. They are shown to have reasonable drop test performance, comparable to typical BGAs. © 2011 IEEE.

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