PAST events

Department of Physics and Materials Science
Centre of Super-Diamond and Advanced Films (COSDAF)
Joint Seminar

Title: Designing molecules and materials by optimizing potentials

Speaker: Prof Weitao Yang
Department of Chemistry
Duke University
USA 

Date: 15 December 2006 (Friday)
Time: 3:30 pm (tea reception: 3:20 pm)

Venue: P4906, Academic Building, City University of Hong Kong

ABSTRACT
The astronomical number of accessible discrete chemical structures makes rational molecular and material design extremely challenging.  We formulate the design of molecules and materials with specific tailored properties as performing a continuous optimization in the space of electron-nuclear attraction potentials.  The optimization is facilitated by using a linear combination of atomic potentials (LCAP), a general framework that creates a smooth property landscape from an otherwise unlinked set of discrete molecular-property values.  A demonstration of this approach is given for the optimization of molecular electronic polarizability, hyperpolarizability. And the optimization of a figure of merit for n-type organic semiconductors. We show that the optimal structures can be determined without enumerating and separately evaluating the characteristics of the combinatorial number of possible structures, a process that would be much slower or impossible.  The! LCAP approach may be used with quantum or classical Hamiltonians, with possible applications to drug design and new
materials discovery.

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CityU Department of Physics and Materials Science
Centre of Super-Diamond and Advanced Films (COSDAF)

Joint Seminar

Title: Materials Integrity in Microsystems

Speaker: Prof W K Liu
Department of Mechanical Engineering
Northwestern University

Date: 21 December 2006 (Thursday)
Time: 4:00 pm (tea reception: 3:45 pm)

Venue: B5-208
Academic Building
City University of Hong Kong

ABSTRACT
It is fair to say that microsystems have become an integral part of our lives nowadays - computers, cell phones, iPods, automobiles, aerospace systems, and biomedical systems all consist of these ever-shrinking microsystems. For example, a hard drive in a computer/cell phone/iPod is a micromachined cantilever system that reads and writes information. An accelerometer microsystem in a car is used to activate the airbag when a preset threshold acceleration is reached. A gyroscope microsystem in an aerospace system such as satellite and space station is utilized for stabilization and navigation. Microfluidic devices are used to collect and analyze blood samples. The advances in microsystem technologies have brought and will continue to bring convenience to our daily lives, enhance health and safety, and help to make major scientific discoveries among many other advantages. In 2004, annual sales of microsystems have exceeded 5 billion dollars, and an annual growth ra! te of more than 20% is expected in the rest of the decade.

Major hurdles remain in ensuring the long term performance and reliability of microsystems in aerospace applications despite the redundancies with which the microsystems are often designed. Guided by both Boeing and Honeywell Microsystems technologies and our past and on-going leverage projects, a micro-gyroscope has been chosen as the focus application to develop verified and validated probabilistic reliability modeling topics and predictive capabilities relevant for national interests and future security needs. Predictive science topics include thermal-mechanical-chemical-electrical aging and materials instability, radiation-enhanced diffusion, damage, fatigue, fracture, stiction, and energy dissipation mechanisms. A key focus of the proposed work is to develop multiscale methodologies to bridge both the space and time scales based on adaptive concurrent, hierarchical, and statistical power equivalence coupling of methods at various scales depending on th! e scale of the physics involved. Challenges and Limitations in Multiscale Predictive Science Simulations are presented.

Vita: Dr. Wing Kam Liu, Walter P. Murphy Professor at Northwestern University and Director of NSF Summer Institute on Nano Mechanics and Materials, received his Ph.D. from Caltech. His research activities include bridging scale computational mechanics and materials, multi-scale analysis, and computational biology. Selected Liu's honors include the Gustus L. Larson Memorial Award, the Pi Tau Sigma Gold Medal and the Melville Medal, all from ASME; the Thomas J. Jaeger Prize by the International Association for Structural Mechanics in Reactor Technology; the SAE Ralph R. Teetor Educational Award; the Computational Structural Mechanics Award and Computational Mechanics Award from USACM and IACM, respectively; and the JSME Computational Mechanics Award. Liu serves on both the executive committee of the ASME applied mechanics division (Chair 2005-2006) and the International Association for Computational Mechanics. He was the past president of USACM. Liu is cited by Institute for S! cientific Information as one of the most highly cited, influential researchers in Engineering, and an original member, highly cited researchers database. He is the editor and honorary editors of many Journals. Dr. Liu has acted as a consultant to the many organizations.

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City University of Hong Kong, Department of Physics and Materials Science
Seminar

Fifty Years of Seeing and Experimenting with Surface Atoms

Prof Tien T Tsong

Institute of Physics, Academia Sinica
Taiwan

Date: 22 December 2006 (Friday)

Time: 3:30 pm (tea reception: 3:20 pm)

Venue: P4906

Academic Building

City University of Hong Kong

ABSTRACT
The field ion microscope (FIM) and the atom-probe FIM are the two instruments that have achieved for the first time the two most important aspects of atomic resolution microscopy, namely the atomic resolution imaging of the sample and the chemical analysis of pre-selected sample atoms. I will describe here some of our atomic scale studies on the dynamics of single surface atoms and surface nanostructures and surface analyses using field ion microscopy. As microscopy progresses, now both electron microscope and scanning probe microscope have also achieved atomic image resolution. SPM may one day be able to do non-destructive chemical analysis of surface atoms using a thermally stable and chemically inert single atom sharp probe tip of known apex atom through mapping of the electronic density of states and atomic interactions. Here, I will discuss how field ion microscopy studies have instigated some of the later studies, including ours, of scanning probe microscopy in surface and nano science applications.

Enquiry: 2788-7413

7:00pm	Chan Ka Cheung	Ultrasonic motor as an application of piezoelectric materials
7:20pm	Lo Yuk Kuen Andrew	Comparison Study of the Properties of Concrete of Unmodified and Modified Recycled Aggregates
7:40pm	Chau Chi Hang	Wavelength-tuning of Fiber Bragg Gratings using Magnerostrictive Transducers

Program Highlight

Speaker

International Practices for Sustainable Building

22 December 2006 (Friday), 3:00 p.m. – 4:00 p.m., Chen Kuan Cheng Forum (LTH) (Near Lift 27/28), The Hong Kong University of Science and Technology