A flexible and adaptive Simpler GMRES with deflated restarting for shifted linear systems

In this paper, two efficient iterative algorithms based on the simpler GMRES method are proposed for solving shifted linear systems. To make full use of the shifted structure, the proposed algorithms utilizing the deflated restarting strategy and flexible preconditioning can significantly reduce the number of matrix-vector products and the elapsed CPU time. Numerical experiments are reported to illustrate the performance and effectiveness of the proposed algorithms.Comment: 17 pages. 9 Tables, 1 figure; Newly update: add some new numerical results and correct some typos and syntax error

THE FATE OF DISCHARGED POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) IN WATER STREAMS

Polycyclic aromatic hydrocarbons (PAHs), also known as polynuclear aromatic hydrocarbons, are potent atmospheric pollutants consisting of fused aromatic rings and do not carry or contain heteroatoms/substituents. 16 of PAHs have been classified by Environmental Protection Agency (EPA) for possible carcinogenic properties. It is discovered that PAHs are found abundant in water stream. Most of the PAHs are discharged without getting treated properly at sewage treatment plant. When exposed to the environment, the PAHs will be degraded either in microbial degradation or photo degradation pathway. The PAHs will be then transformed to various metabolites, creating ‘daughters’ and byproducts along its degradation. They may also be mutagenic or carcinogenic even if their parent compounds are not (International Association of Oil and Gas Producers, 2005). A research study was conducted on former works on PAHs and its metabolites. This included the current study to identify various sources of PAHs in water stream in river of Sungai Perak near the area Teluk Kepayang. Samples were obtained from influent of water treatment plant (WTP) in Teluk Kepayang and were analysed with Gas Chromatography/Mass Spectrometry (GC/MS) to formulate conversion path of carcinogenic PAHs. Tests were performed as well on influent and effluent of Universiti Teknologi PETRONAS (UTP) sewage treatment plant (STP) for studies on sewage polluted urban streams. The samples were then used as test solution for guppy (Poecilia reticulate) as their living environment to establish toxicity intensity of carcinogenic PAHs parents and daughter products through 96hours acute toxicity test. GC/MS analysis identified phthalic acid and benzoic acid as major derivatives found in all samples. The analysis showed the detection of Naphthalene and few other suspected derivatives in influent WTP Teluk Kepayang sample. Mortality rate of Poecilia reticulate against time exposure of 96 hours was 20% for influent Teluk Kepayang WTP and 10% for influent UTP STP whereas the rate is 0% for effluent UTP STP. It was observed that the amount of PAHs and its derivatives detected in both effluent and influent of UTP STP and influent of Teluk Kepayang WTP are not harmful to the environment