A feasible direction procedure for general multiple objective optimization

The Feasible Direction Finding Problem (DFP) of Zoutendijk is adapted to create a general Mathematical Programming (MP) algorithm for treating optimization problems with multiple objective functions. Classically such problems are reduced to standard MP form by converting them to single objective function problems by the use of weighting functions. Unfortunately not all practical problems can be so reduced. Consider the problem of maximizing the strength of a structure. Typically there are several, or even many, failure modes. All active failure modes must be included in the optimal search in such a way that resistance to one active mode can not be increased at the expense of another. Thus this problem can not be treated by reduction. The search must seek to increase resistance to all active modes. The DFP formulation seeks to improve the objective function by including said function as a constraint in the DFP Linear Programming problem. Multiple objective functions can be treated by simply including each such function as a constraint in the DFP. Thus the solution to such a DFP improves all the objective functions considered. There is no need to resort to reduction to a single objective function. An algorithm based on the DFP is described. This procedure locates a variable set where, at least locally, no further improvement in all objective functions is available (a Parato Optimum). A general multiple objective formulation is developed defining a wide range of optimization problems. It is shown that this formulation also includes the problem of locating the feasible region, either from an infeasible starting point, or for feasibility restoration during the search. Thus the method is of value in single objective function optimization. The procedure is applied to a six variable problem with eleven constraints where the objective is to separate the two lowest natural frequencies of a stiffened thin shell. Four active frequencies are considered. Several two-variable, constrained and unconstrained, problems are also treated. The procedure was found to efficiently locate Parato Optima and was effective in feasible region location and restoration

Estimation Of Time Of Concentration Using Triangulated Irregular Network Method

In Malaysia, Manual Saliran Mesra Alam (MSMA) has proposed two calculation methods to obtain areas between the isochrones that have been widely practiced at the moment. They are Grid method and Conventional method. However, these methods pose certain problems of their own. Although the Grid method is more detail and accurate when compared to the Conventional method, but that is extremely tedious and time consuming. Conventional method on the other hand is simpler to use. But, the results are not consistent. The results are very subjective because it depends on each user’s experience and judgement. Therefore, a new calculation method named Triangulated Irregular Network (TIN) method has been designed and developed in this research to improve the Time-Area method calculation. This method is computer based and thus the algorithm of TIN method was developed. The algorithm of the TIN method is explained in this research. A study site was constructed and eight sets of rainfall data were collected. All the results from each calculation method were verified with the collected site data to compare their accuracy. Investigation upon their efficiency and reliability were also presented in this research. The comparison showed that TIN method has higher accuracy. In the correlation coefficient comparison among the methods, TIN method has average accuracy of 0.988, Grid method has average accuracy of 0.936 and Conventional method has average accuracy of 0.948. When calculating their difference against the observed data in percentage, TIN method has average difference of 14.29%, Grid method has average difference of 25.67% and Conventional method has average difference of 24.52%. When using the peak flow comparison for the difference against the observed data, the results shows that TIN method has average difference of 3.48%, Grid method has average difference of 5.88% and Conventional method has average difference of 7.72%. Lastly, the methods were compared using the total flow volume. It was demonstrated that the TIN method has different of 0.19%, Grid method has different of 0.43% and Conventional method has different of 4.80% when compared to the observed data. The TIN method has the highest accuracy and reliability among the three methods. Besides, this research also showed that the newly developed TIN method algorithm is easier to use, less time consuming and more reliable

Nonlinear silicon photonics

Session - Silicon Photonics and Photonic Integrated Circuits IIAn intriguing optical property of silicon is that it exhibits a large third-order optical nonlinearity, with orders-ofmagnitude larger than that of silica glass in the telecommunication band. This allows efficient nonlinear optical interaction at relatively low power levels in a small footprint. Indeed, we have witnessed a stunning progress in harnessing the Raman and Kerr effects in silicon as the mechanisms for enabling chip-scale optical amplification, lasing, and wavelength conversion - functions that until recently were perceived to be beyond the reach of silicon. With all the continuous efforts developing novel techniques, nonlinear silicon photonics is expected to be able to reach even beyond the prior achievements. Instead of providing a comprehensive overview of this field, this manuscript highlights a number of new branches of nonlinear silicon photonics, which have not been fully recognized in the past. In particular, they are two-photon photovoltaic effect, mid-wave infrared (MWIR) silicon photonics, broadband Raman effects, inverse Raman scattering, and periodically-poled silicon (PePSi). These novel effects and techniques could create a new paradigm for silicon photonics and extend its utility beyond the traditionally anticipated applications. © 2010 Copyright SPIE - The International Society for Optical Engineering.published_or_final_versionThe 2010 Conference of the International Society for Optical Engineering (SPIE) Photonics Europe, Brussels, Belgium, 12-16 April 2010. In Proceedings of SPIE, 2010, v. 7719, article no. 77190

Pixel super-resolution of time-stretch imaging by an equivalent-time sampling concept

Optical time-stretch imaging entails a stringent requirement of state-of-the-art high-speed data acquisition unit in order to preserve high image resolution at an ultrahigh frame rate-hampering the widespread application of such technology. We here propose a pixel super-resolution (pixel SR) technique tailored for time-stretch imaging that can relax the sampling rate requirement. It harnesses a concept of equivalent-time sampling, which effectively introduces sub-pixel shifts between frames. It involves no active opto-mechanical subpixel-shift control and any additional hardware. We present the system design rules and a proof-of-principle experiment which restores high-resolution images at a relaxed sampling rate of 5 GSa=s. © 2016 SPIE.published_or_final_versio

Green silicon photonics

Silicon photonics have provided low-cost communication components for Internet applications and are now aimed towards providing environmentally friendly and green optical solutions. The need for energy-efficient photonics is due to the excessive energy dissipated in advanced electronics and an increase in power density that has posed a challenge to the most advanced chip-cooling technologies. The two-photon absorption (TPA)-generated free carriers need to be actively removed from the waveguide cover to eliminate any event of light absorption and a subsequent conversion to heat. Researchers have proposed an electro-optic modulator that takes advantage of the two-photon photovoltaic (TPPV) effect to attain negative static power dissipation. Photovoltaic power converters (PPC) are used for remote power delivery and are optimized for a wavelength range from 1,200 to 1,550 nm.published_or_final_versio

Amplified Dispersive Fourier-Transform Imaging for Ultrafast Displacement Sensing and Barcode Reading

Dispersive Fourier transformation is a powerful technique in which the spectrum of an optical pulse is mapped into a time-domain waveform using chromatic dispersion. It replaces a diffraction grating and detector array with a dispersive fiber and single photodetector. This simplifies the system and, more importantly, enables fast real-time measurements. Here we describe a novel ultrafast barcode reader and displacement sensor that employs internally-amplified dispersive Fourier transformation. This technique amplifies and simultaneously maps the spectrally encoded barcode into a temporal waveform. It achieves a record acquisition speed of 25 MHz -- four orders of magnitude faster than the current state-of-the-art.Comment: Submitted to a journa

Periodically poled silicon (PePSi) for efficient and electronically-tuned nonlinear optics in silicon

Periodically poled silicon (PePSi) induces substantial 2nd order optical nonlinearity and at the same time achieves quasi-phase matching. PePSi is made by alternating strain gradients along the waveguide using periodic arrangement of stressed cladding layers. © 2013 OSA.published_or_final_versio

Pixel super-resolution in optical time-stretch microscopy using acousto-optic deflector

Session - Biosensing and Bio-Manipulation Techniques II (BW2A): paper BW2A.7Bio-Optics: Design and Application (BODA)We present experimental demonstration of pixel super-resolution time-stretch imaging by high-speed agile-beam-steering with the use of synchronized acousto-optic deflector--enabling high-resolution imaging rate of 1MHz whereas relaxing the stringent requirement on extreme data acquisition. © 2015 OSApostprin

Vancouver School Optimization

Vancouver has undergone extreme population growth in the last 20 years. Many city services have struggled to keep up with this increase in demand. The Vancouver school system is a prime example of this struggle. Many of the existing schools are showing clear signs of ageing and were not built with today’s needs in mind. This is particularly apparent in the higher density, and typically lower-income, areas of the city. The number of students per classroom has increased, especially in these areas. Larger class sizes have been linked to decreased academic performance, which is further compounded among economically disadvantaged students. Structural changes to the Vancouver school system must be made in order to provide all students with the same standard of education