Self-Powered neutron detectors (SPND) detect current generated from interaction of neutron flux with emitter materials. They are inside a reactor in NPP (Nuclear Power Plant), and currently used to monitor the output and control the operation. Since the signal level of prompt-response SPND is very small (-nA), an analog circuit is necessary to amplify the current signal, and to convert it into voltage. This circuit needs to perform an anti-aliasing function to reduce distortion at the stage of digital conversion. In this paper, a systematic design process for high-gain amplification circuit is presented. Based on error analysis of the circuit, parameters are selected to satisfy design requirements. A third-order anti-aliasing filter is designed. A prototype circuit is built. Measured performance of the circuit confirms that the circuit satisfies all design requirements and validates the efficacy of the design to be used in practical environments.

Magnetic bearings are being actively adopted by the turbo-chiller industry because of their higher efficiency during partial load, quieter operation, and smaller footprint than that which machines with ball bearings provide. Since magnetic bearings are open-loop unstable, feedback control is necessary. In the industry, traditional PID-based control is preferred to model-based control, because of its simplicity. When traditional control algorithms are used, significant resources are required to obtain and tune control parameters, which is an impediment to the widespread use of magnetic bearing technology in the industry. In this paper, we propose a mixed optimization method by combining genetic algorithm and sequential quadratic programming. To obtain the initial guess to be used for the mixed optimization, a phase-margin maximization algorithm is also proposed, based on the rigid-body model of the system. Mixed optimization results in suitable control parameters in less than 2.8% of the time it takes a genetic algorithm only to find similar solutions. The proposed optimization also ensures the robustness of the control parameters. The output sensitivity measured from a prototype compressor with magnetic bearings confirms the validity of the control parameters.

This paper presents a proposed means of frequency-tuning a magnetostrictive energy harvester(EH). This end may be accomplished by decreasing the distance between two permanent magnets (PM) located at free end of the cantilever and at the opposite, resulting in increase of a repulsive force between the PMs. The EH consists of a coil-wound Galfenol cantilever with PMs, a mover connected to the cantilever, and a rotating wheel with PMs. The rotating wheel driven by a motor provides a forced vibration to the EH. To direct inspection, It is noted that the maximum output voltage continually changes depending upon the the distance between the PMs And itmight therefore be deduced that the resonant frequency of the harvester may be adjusted to attain maximum, or optimal, voltage output. The rotational speed of the wheel (for the purpose of attaining maximum output voltage) is changed from 325 rpm to 265 rpm at a distance of 10 mm. It can be concluded that the practice of frequency-tuning with two PMs is a potentially positive application with respect to the EH.

This study presents the development of a magnetostrictive control rod position indicator (Mag-CRPI) for improving safety of nuclear power generation. Mag-CRPI principle is based on two magnetostrictive effects: The Wiedemann effect and the Villari effect. The position may be estimated by multiplying time-of-flight (TOF) of the elastic wave from the cursor magnet to the sensing coil, and a sound speed of the magnetostrictive wire. A Mag-CRPI prototype has been designed and built. Experiments are conducted to characterize the Mag-CRPI. Change of the TOF is obtained with cursor magnet movement interval of 100 ㎜. Averaged position error is estimated to be 0.002m over the entire measuring length. Based on experimental results, the performance of Mag-CRPI is validated, thereby confirming feasibility of a nuclear reactor-internal control rod.

Magnetically levitated (Maglev) vehicles maintain a constant air gap between guideway and car bogie, and thereby achieves non-contact riding. Since the straightness and the flatness of the guideway directly affect the stability of levitation as well as the ride comfort, it is necessary to monitor the status of the guideway and to alert the train operators to any abnormal conditions. In order to develop a signal processing algorithm that extracts guideway irregularities from sensor data, virtual testing using a simulation model would be convenient for analyzing the exact effects of any input as long as the model describes the actual system accurately. Simulation model can also be used as an estimation model. In this paper, we develop a state-space dynamic model of a maglev vehicle system, running on the guideway that contains jumps. This model contains not only the dynamics of the vehicle, but also the descriptions of the power amplifier, the anti-aliasing filter and the sampling delay. A test rig is built for the validation of the model. The test rig consists of a small-scale maglev vehicle, tracks with artificial jumps, and various sensors measuring displacements, accelerations, and coil currents. The experimental data matches well with those from the simulation model, indicating the validity of the model.

This paper deals with an experimental verification of a temperature-dependent power loss model of a DC/DC converter in severe temperature conditions. The power loss of a DC/DC converter is obtained by summing the losses by the components constituting the converter including switching elements, diodes, inductors, and capacitors. MIL-STD-810F stipulates that any electronic devices must be operable in the temperature ranging from ?50°C to 70°C. We summarized the temperature-dependent loss models for the converter components. A SEPIC-type converter is designed and built as a target. Using a constant-temperature chamber, a test rig is set up to measure the power loss of the converter. The experimental results confirm the validity of the loss model within 4.5% error. The model can be useful to predict the efficiency of the converter at the operating temperature, and to provide guidelines in order to improve the efficiency.

This paper presents a proof-of-concept of a wheel-based magnetostrictive energy harvester (EH), which is a vibration-based EH. Coil-wound Galfenol cantilevers with two permanent magnets (PMs) act EH, while rotating wheels provide a forced vibration to EH. Four different cantilevers are designed and simulated for various end deflection. As expected from the simulation, the cantilever end deflection with triple cavity is the most. Three experiments are conducted to characterize the EH: the first with a magnetostrictive actuator, the second with a motor-driven wheel, and the third with the dummy weights. From the first experiment, the power reaches about 50 mV due to the relatively small displacement of the magnetostrictive actuator. From the second experiment, the power reaches about 120 mW. The power from the Galfenol cantilever is estimated to be about 60% of the total power from the wheel-based magnetostrictive EH.

This paper presents ejection of high viscosity fluids with magnetostrictive inkjet printhead(Magjet), which is not common with any other printhead. The MagJet uses a magnetostrictive material, Terfenol-D rod with 10-mm in diameter and 50-mm in length, as an actuation mechanism. It has been known that high viscosity is often an obstacle in ejecting small and mono-disperse droplets. We calculated required pressure with fluidic inertia (Bernoulli equation) and viscous loss (Hagen Poiseuille equation). The required pressure for ejecting a droplet is 1300kPa. The generated force and displacement with Terfenol-D rod are estimated to be 480N (2600kPa) and 28μm, respectively. It was enough that Magjet eject high viscosity fluid (Max 1000cP). The experiments are performed to eject the high viscosity fluid with Magjet. The ejection of high viscosity fluids is successful with the aid of Terfenol-D’s high performance.

A guitar pickup is a transducer that converts string vibration to an electrical signal. The magnetic and piezo pickups are the most commonly used for the respective electric and electroacoustic guitars. The magnetic pickups are prone to magnetic interference between the steel strings and permanent magnets, while the piezo ones are not free from signal inference between the strings. Thus, this paper presents the development of an optical pickup for the electroacoustic guitar. The proposed optical pickup has the top-to-bottom structure. It uses two of Infrared (IR) Light Emitting Diode (LED) and one photodetector. The developed optical pickup is subjected to the evaluation with commonly used piezoelectric pickup. It becomes obvious that SNR with the optical pickup is increased by 45 percent in average, compared with the piezoelectric pickup. It can be concluded that the developed optical pickup has a potential to be applied to the acoustic guitar.

The electro-acoustic guitar pickup converts the vibration of strings to the electric signals, and delivers them to an amplifier. The vibration of the strings is transferred to the piezoelectric material through the saddle. This paper aims to improve sound quality for electro-acoustic guitars through the finite element analysis of the saddle. Firstly, the conventional pickup is modeled and analyzed with a commercial program called ANSYS. It is obvious that there exists interference phenomenon of stress. A structural modification of the pickup is performed, based on the beam theory. The modified structure is modeled and analyzed. Finally, the fabricated structures are subjected to the measurements and compared with the conventional pickup. It can be concluded that the interference with the modified structure is much less than that with the conventional structure, and that the sound quality is improved with the modified structures.

This paper presents the development of a magnetostrictive microactuator. The structural and functional requirements are as follows: it must be a millimeter structure and must achieve controllable displacement with nanometer resolution. Finite Element Analysis(FEA) is used to determine the structure with the most uniform and highest magnetic flux density along the Terfenol-D rod. The microactuator prototype 1 is designed and made based on the FEA. It is observed that the microactuator show some level of hysteresis and that it produces 25 newton in force and 3 ㎛ in displacement with 1.5 amperes of current, and resolution of 250 ㎚ per 0.1 amperes.
To improve the performance of the microactuator prototype 1, microactuator prototype 2 is made again with a permanent magnet (PM). It is observed that the microactuator prototype 2 generates 3.3 ㎛ in displacement with 0.9 amperes of current. It means that the micro actuator prototype 2 performs better than the microactuator prototype 1.