This paper presents a warm bore ferromagnetic shimming design for a high resolution NMR magnet based on spherical harmonic coefficient reduction techniques. The passive ferromagnetic shimming along with the active shimming is a critically important step to improve magnetic field homogeneity for an NMR Magnet. Here, the technique is applied to an NMR magnet already designed and built at the MIT's Francis Bitter Magnet Lab. Based on the actual magnetic field measurement data, a total of twenty-two low order spherical harmonic coefficients is derived. Another set of spherical harmonic coefficients was calculated for iron pieces attached to a 54 mm diameter and 72 mm high tube. To improve the homogeneity of the magnet, a multiple objective linear programming method was applied to minimize unwanted spherical harmonic coefficients. A ferromagnetic shimming set with seventy-four iron pieces was presented. Analytical comparisons are made for the expected magnetic field after Ferromagnetic shimming. The theoretically reconstructed magnetic field plot after ferromagnetic shimming has shown that the magnetic field homogeneity was significantly improved.

This paper presents a wireless sensor network for assessing the structural health of urban highway bridges. Sensor data were collected on two pre-stressed box beam bridges (PSBB) with eight wireless sensor nodes. The wireless sensor was able to collect one hundred Accelerometer data samples per second without losing any wireless sensor data. Application software was developed to transform the sample data into frequency domain. Sensor data from all eight wireless sensor nodes have shown the similar peak frequencies with multiple trial runs on the same bridge. The peak frequency component was unique to each highway bridge. The signal to noise ratio in frequency domain is greater than seven to one. By comparing the actual wireless sensor data with the predictions from a finite element bridge model, a hypothesis of evaluating the structural health of the bridge was presented.Index Terms -Wireless mesh networks, sensor networks, frequency domain, structural health.

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A compact power-efficient class-AB Miller op-amp is introduced. It uses a simple auxiliary circuit that enhances the op-amp's gain-bandwidth product and helps to drive a wide range of capacitive and resistive loads with high static and dynamic current efficiency. Simple Miller compensation is used to obtain stability over a wide range of loading conditions. The op-amp's simulation and experimental results in strong inversion with 15µA bias current and in sub-threshold with 250nA bias current are shown. Its performance is measured in terms of dynamic and static current efficiency figures of merit FOM CEDyn and FOM CEStat. and using the conventional small-signal figure of merit FOM SS. Experimental results of op-amps fabricated in a 130nm CMOS technology are shown that validate the proposed approach.