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Systematic information integration of multiple related microarray studies has become an important issue as the technology has become significant mature and more prevalent in public health relevance over the past decade. The aggregated information provides more robust and accurate biomarker detection. So far, published meta-analysis methods for this purpose mostly consider two-class comparison. Methods for combining multiclass studies and expression pattern concordance are rarely explored. We first consider a natural extension of combining p-values from the traditional ANOVA model. Since p-values from ANOVA do not guarantee to reflect the concordant expression pattern information across studies, we propose a multi-class correlation measure (MCC) to specifically look for biomarkers of concordant inter-class patterns across a pair of studies. For both approaches, we focus on identifying biomarkers differentially expressed in all studies (i.e. ANOVA-maxP and min-MCC). The min-MCC method is further extended to identify biomarkers differentially expressed in partial studies using an optimally-weighted technique (OW-min-MCC). All methods are evaluated by simulation studies and by three meta-analysis applications to multi-tissue mouse metabolism data sets, multi-condition mouse trauma data sets and multi-malignant-condition human prostate cancer data sets. The results show complementary strength of ANOVA-based and MCC-based approaches for different biological purposes. For detecting biomarkers with concordant inter-class patterns across studies, min-MCC has better power and performance. If biomarkers with discordant inter-class patterns across studies are expected and are of biological interests, ANOVA-maxP better serves this purpose.

Geomagnetically induced currents (GIC) could saturate a transformer core. Two significant effects are the abnormal stray flux in transformers and extremely large harmonic contents in excitation currents, which can lead to serious equipment damage and power system misoperation. Such incidents have occurred during the March 1989 K-9 solar magnetic disturbance. This dissertation starts with a systematically study of transformer magnetization under GIC. It reviews both dc and ac saturation patterns of five transformer core designs. Magnetic fields along various traverses for dc excitation are presented. Impedance matrix entries of a single phase transformer are compared for normal and dc operations. New observations have been formed based on the simulation results. The study helps to reveal the fundamental transformer magnetization mechanism under GIC in order to assess potential stray flux heating possibilities of geologically vulnerable transformer units. Based on the finite element analysis, an improved method of modeling transformer excitation under dc bias using equivalent magnetic circuit is developed. There are two unique points in this approach: first, information of 3D finite element magnetic flux distribution analysis is used to construct and verify the circuit model; second, the effect of the transformer tank: is included The model is capable of simulating transformer excitation currents under different levels of dc bias with good accuracy. As a consequence, the complete variations of excitation current harmonics with respect to an extended range of dc bias are revealed. The sensitivity of transformer winding impedances and core loss on the excitation characteristics are examined. The saturated transformer under no-load and various loading conditions is simulated. A laboratory test is performed on a small scale transformer and compared with the model results. Excitation harmonics generated from dc biased three phase transformer banks with different types of equivalent loads are also simulated The effect of both unbalanced dc excitations and unbalanced loads are investigated The results of this study contribute in understanding transformers as harmonic sources and the impact on power systems during a geomagnetic disturbance.

A wideband microwave balun is designed to adapt unbalanced to balanced transmission line networks. The balun is realized by a planar microstrip line configuration on a double copper c1added teflon-ceramic C0I11posite board. The microstrip line conductor pattern was formed on the board using the chemical etching process. The fabricated balun is measured and evaluated in both the time domain and frequency domain, indicating a 5 GHz bandwidth. The time domain modeling technique is used to characterize the balun's performance. Based on physical analysis of the balun's configuration, the discontinuities through the transmission paths are modeled as distributed and lumped elements, resulting in an equivalent network model for the balun structure. The obtained model successfully simulates the balun's performance.