Noise Rise Research Articles

Photoresponse characteristics of bulk gallium nitride schottky barrier metal-semiconductor-metal ultraviolet photodetectors

Photoresponse characteristics of bulk gallium nitride schottky barrier metal-semiconductor-metal ultraviolet photodetectors

Investigation on skidding behavior of a lubricated rolling bearing with fluid–solid-heat coupling effect

Investigation on skidding behavior of a lubricated rolling bearing with fluid–solid-heat coupling effect

A diamond detector based dosimetric system for instantaneous dose rate measurements in FLASH electron beams.

A reliable determination of the instantaneous dose rate (I-DR) delivered in FLASH radiotherapy treatments is believed to be crucial to assess the so-called FLASH effect in preclinical and biological studies. At present, no detectors nor real-time procedures are available to do that in Ultra High Dose Rate (UH-DR) electron beams, typically consisting of μs pulses characterized by I-DRs of the order of MGy/s. A dosimetric system is proposed possibly overcoming the above reported limitation, based on the recently developed flashDiamond (fD) detector (model 60025, PTW-Freiburg, Germany).
Approach. A dosimetric system is proposed, based on a flashDiamond detector prototype, properly modified and adapted for very fast signal transmission. It was used in combination with a fast transimpedance amplifier and a digital oscilloscope to record the temporal traces of the pulses delivered by an ElectronFlash linac (SIT S.p.A., Italy).
The proposed dosimetric systems was investigated in terms of the temporal characteristics of its response and the capability to measure the absolute delivered dose and instantaneous dose rate (I DR). A "standard" flashDiamond was also investigated and its response compared with the one of the specifically designed prototype.
Main Results. Temporal traces recorded in several UH-DR irradiation conditions showed very good signal to noise ratios and rise and decay times of the order of a few tens ns, faster than the ones obtained by the current transformer embedded in the linac head. By analyzing such signals, a calibration coefficient was derived for the fD prototype and found to be in agreement within 1% with the one obtained under reference 60Co irradiation. I-DRs as high as about 2 MGy/s were detected without any undesired saturation effect. Absolute Dose Per Pulse (DPP) values extracted by integrating the I DR signals were found to be linear up to at least 7.13 Gy and in very good agreement with the ones obtained by connecting the fD to a UNIDOS electrometer (PTW-Freiburg, Germany). A good short term reproducibility of the linac output was observed, characterized by a pulse-to-pulse variation coefficient of 0.9%. Negligible differences were observed when replacing the fD prototype with a standard one, with the only exception of a somewhat slower response time for the latter detector type.
Significance. The proposed fD-based system was demonstrated to be a suitable tool for a thorough characterization of UH-DR beams, providing accurate and reliable time resolved I-DR measurements from which absolute dose values can be straightforwardly derived.
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Modeling of Josephson Traveling Wave Parametric Amplifiers

The recent developments in quantum technologies, as well as advanced detection experiments, have raised the need to detect extremely weak signals in the microwave frequency spectrum. To this aim, the Josephson travelling wave parametric amplifier, a device capable of reaching the quantum noise limit while providing a wide bandwidth, has been proposed as a suitable cryogenic front-end amplifier. This work deals with the numerical study of a Josephson travelling wave parametric amplifier, without approximations regarding the nonlinearity of the key elements. In particular, we focus on the investigation of the system of coupled nonlinear differential equations representing all the cells of the Josephson travelling wave parametric amplifier, with proper input and output signals at the boundaries. The investigation of the output signals generated by the parametric amplification process explores the phase-space and the Fourier spectral analysis of the output voltage, as a function of the parameters describing the pump and signal tones that excite the device. Beside the expected behavior, i.e., the signal amplification, we show that, depending on the system operation, unwanted effects (such as pump tone harmonics, incommensurate frequency generation, and noise rise), which are not accounted for in simple linearized approaches, can be generated in the whole nonlinear system.

Research Status and Prospect for Vibration, Noise and Temperature Rise-Based Effect of Food Transport Pumps on the Characteristics of Liquid Foods.

In the field of food processing, the processing of liquid foods has always played an important role. Liquid foods have high requirements for the processing environment and equipment. As the core equipment in liquid foods processing, food transport pumps are widely used in liquid foods production, processing and transportation. Most liquid foods are non-Newtonian and vulnerable to vibration, noise, and temperature rise produced by rotary motions of food transport pumps in operation, which can finally affect foods safety. Therefore, this review summarizes the impact of mechanical vibration, noise, and temperature rise on liquid food products, with the aim of ensuring food safety while designing a cleaner, safer and more reliable food transport pumps in the future.

Digital Circuit Performance Evaluation of Parallel Gated Junctionless Field Effect Transistor

This paper reports the modeling and performance enhancement of complementary metal-oxide-semiconductor (CMOS) inverters using parallel-gated junctionless field-effect transistors (PGJLFET). A mathematical model for different parameters, namely, low and high input voltage, low and high output voltage, noise margin, rise time, fall time, propagation delay, and power dissipation of the inverter circuit was established. To establish the model for various parameters, potential models at the source-channel boundary and the potential at the drain-channel boundary are considered. The variations in the voltage transfer characteristics of the output current with respect to the input voltage and the power dissipation with respect to the input voltage for steady-state conditions and transient states were investigated for different gate dielectrics, gap lengths, and gate oxide thicknesses. The models were validated by comparing them with technology computer-aided design (TCAD) simulation results. The noise margin, rise time, fall time, and propagation delay of the PGJLFET-based inverter are estimated and compared with those of a conventional junctionless transistor. It has been observed that the PGJLFET exhibits an improvement in the noise margin and propagation delay compared with conventional junctionless transistors.

Tin sulfide thin films by spin coating of laser ablated nanocolloids for UV–Vis–NIR photodetection

Tin sulfide (SnS) has emerged in the field of layered metal chalcogenides (LMCs) as one of the preferred semiconductors due to its prominent optical properties and high absorption coefficient. In this work, SnS nanocolloids were obtained by pulsed laser ablation in liquid (PLAL) using Nd:YAG laser wavelengths of 532 and 1064 nm. Furthermore, thin films of SnS were spin-coated using nanocolloids and annealed in vacuum at 350 and 450 ℃. Morphology and crystal structure of SnS nanoparticles (NPs) were studied using Transmission electron microscopy and particle sizes calculated were in the range of 8–12 nm. X-ray diffraction results reproduced the same orthorhombic crystal structure for the SnS films as that of SnS NPs. The elemental composition and chemical states were analyzed by X-ray photoelectron spectroscopy. Morphological analysis of the films by scanning electron microscopy reveals surfaces having interconnected spherical grains. The energy bandgap values of the nanocolloids were 1.9, 2.8 eV and the films were between 1.4 and 2.1 eV. The photodetection abilities of the films exhibit wavelength response in the UV–Visible as well as NIR (785, 840 and 980 nm) regions. The photodetector shows a specific detectivity of 10 6 Jones. Photodetector parameters such as sensitivity, responsivity, noise equivalent power (NEP), rise time and decay time were also estimated. The study of thin films fabricated from nanocolloids by combining the aspects of PLAL and spin-coating provides a new insight to synthesize reproducible semiconducting thin films for optoelectronics. • First report on SnS thin films by spin coating of nanocolloids prepared by PLAL. • Annealing under vacuum improved their morphology and crystalline nature. • SnS films of adequate optical properties for UV–Vis–NIR photodetection. • Photodetectors with high sensitivity and extended detection up to 980 nm. • Photodetection parameters show appropriate detectivity, responsivity, and NEP.

A deep-learning reconstruction algorithm that improves the image quality of low-tube-voltage coronary CT angiography

To assess the image quality (IQ) of low tube voltage coronary CT angiography (CCTA) images reconstructed with deep learning image reconstruction (DLIR). According to body mass index (BMI), eighty patients who underwent 70kVp CCTA (Group A, N=40, BMI≤26kg/m2) or 80kVp CCTA (Group B, N=40, BMI>26kg/m2) were prospectively included. All images were reconstructed with four algorithms, including filtered back-projection (FBP), adaptive statistical iterative reconstruction-Veo at a level of 50% (ASiR-V50%), and DLIR at medium (DLIR-M) and high (DLIR-H) levels. Image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and edge rise distance (ERD) within aorta root and coronary arteries were calculated. The IQ was subjectively evaluated by using a 5-point scale. Compared with FBP, ASiR-V50% and DLIR-M, DLIR-H led to the lowest noise (Group A: 24.7±5.0HU; Group B, 21.6±2.8 HU), highest SNR (Group A, 24.9±5.0; Group B, 28.0±5.8), CNR (Group A, 42.2±15.2; Group B, 43.6±10.5) and lowest ERD (Group A, 1.49±0.30mm; Group B, 1.50±0.22mm) with statistical significance (all P<0.05). For the objective assessment, the percentages of 4 and 5 IQ scores were significantly higher for DLIR-H (Group A, 93.8%; Group B,90.0%) and DLIR-M (Group A, 85.6%; Group B,86.9 %) compared to ASiR-V50% (Group A, 58.8%; Group B, 58.8%) and FBP (Group A, 34.4%; Group B, 33.1%) algorithms (all P<0.05). The application of DLIR significantly improves both objective and subjective IQ in low tube voltage CCTA compared with ASiR-V and FBP, which may promote a further radiation dose reduction in CCTA.

Temperature Coefficient Reduction of AC-Bridge Circuit for Cryogenic Temperature Control System

Precise temperature control is crucial for the development of sensitive instruments, as temperature fluctuations will introduce many negative effects. In temperature control systems, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1/{f}$ </tex-math></inline-formula> noise is dominant in the low-frequency range, which limits the temperature control precision. To suppress the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1/{f}$ </tex-math></inline-formula> noise, AC bridges based on the modulation-demodulation method are commonly used. While the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1/{f}$ </tex-math></inline-formula> noise is suppressed, other types of noise rise to domination, further limiting the precision of the temperature control system. The response of the AC-bridge readout circuit to temperature fluctuation is the most serious. This paper proposes a method for suppressing the response of the AC-bridge readout circuit to temperature fluctuations. Using this method, the temperature coefficient of the readout circuit is reduced by matching the temperature coefficients of the used electro-components according to their weights of impact. This method has been verified in the test of a precise temperature control system designed for a superconducting gravimeter. The temperature coefficient of the AC-bridge circuit was reduced by approximately 57.4 times compared with the unmatched AC-bridge circuit, and the temperature fluctuation in the vacuum chamber of the superconducting gravimeter was controlled within <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm 5~\mu \text{K}$ </tex-math></inline-formula> .

Deep Learning Algorithm for Simultaneous Noise Reduction and Edge Sharpening in Low-Dose CT Images: A Pilot Study Using Lumbar Spine CT.

ObjectiveThe purpose of this study was to assess whether a deep learning (DL) algorithm could enable simultaneous noise reduction and edge sharpening in low-dose lumbar spine CT.Materials and MethodsThis retrospective study included 52 patients (26 male and 26 female; median age, 60.5 years) who had undergone CT-guided lumbar bone biopsy between October 2015 and April 2020. Initial 100-mAs survey images and 50-mAs intraprocedural images were reconstructed by filtered back projection. Denoising was performed using a vendor-agnostic DL model (ClariCT.AI™, ClariPI) for the 50-mAS images, and the 50-mAs, denoised 50-mAs, and 100-mAs CT images were compared. Noise, signal-to-noise ratio (SNR), and edge rise distance (ERD) for image sharpness were measured. The data were summarized as the mean ± standard deviation for these parameters. Two musculoskeletal radiologists assessed the visibility of the normal anatomical structures.ResultsNoise was lower in the denoised 50-mAs images (36.38 ± 7.03 Hounsfield unit [HU]) than the 50-mAs (93.33 ± 25.36 HU) and 100-mAs (63.33 ± 16.09 HU) images (p < 0.001). The SNRs for the images in descending order were as follows: denoised 50-mAs (1.46 ± 0.54), 100-mAs (0.99 ± 0.34), and 50-mAs (0.58 ± 0.18) images (p < 0.001). The denoised 50-mAs images had better edge sharpness than the 100-mAs images at the vertebral body (ERD; 0.94 ± 0.2 mm vs. 1.05 ± 0.24 mm, p = 0.036) and the psoas (ERD; 0.42 ± 0.09 mm vs. 0.50 ± 0.12 mm, p = 0.002). The denoised 50-mAs images significantly improved the visualization of the normal anatomical structures (p < 0.001).ConclusionDL-based reconstruction may enable simultaneous noise reduction and improvement in image quality with the preservation of edge sharpness on low-dose lumbar spine CT. Investigations on further radiation dose reduction and the clinical applicability of this technique are warranted.

Laser noise control in the optoacoustical gravitational antenna

It is shown that the metric sensitivity theory of the OGRAN project contains description of the Fabry-Perot cavity displacement readout scheme proposed by Braginsky. In theories a quality factor defines laser noise. As an alternative, two phenomenological intrinsic controlled parameters of laser noise are proposed to analyze readout resolution: spectral densities of frequency deviations and power random modulation P(t) = P 0[1 + £(t)]. The formula for vibration noise is derived. The new theory of instrumental sensitivity is applied to explain the effect of readout noise rise while increasing digitization time. To reduce the readout threshold signal from real value of 2 · 10−15 cm/Hz1/2 to required value of 3 · 10−16 cm/Hz1/2 there are proposed actions: 1) to limit temperature drift difference between laser and bar cavity frequencies by value of 250 Hz; 2) to suppress by circuitry means vibration disturbance voltage at the discriminator output while increasing by 20 dB width of feedback frequency range and feedback gain in this range.

P234 Giant right atrial myxoma presenting as right heart failure

Abstract Introduction Myxomas are the most frequent primary cardiac neoplasms. It is currently believed that myxomas are derived from multipotent mesenchymal cells capable of both neural and epithelial differentiation Histologically, these tumors are composed of dispersed cells within a stroma of mucopolysaccharides Myxomas produce vascular endothelial growth factor, which probably contributes to the growth induction at the initial stages of tumor growth. Tumors vary widely in size, ranging from 1 to 15 cm in diameter and weighing between 15 and 180 g. About 35 percent of myxomas are friable, and they tend to present emboli. The clinical characteristics of these tumors are closely related to their location, size, and mobility; there are no specific signs and symptoms that suggest the presence of a myxoma. There are several mechanisms by which cardiac tumors can cause symptoms. The blockage of circulation through the heart or heart valves produces symptoms of heart failure. Atrial myxoma can interfere with the valves of the heart and cause regurgitation. They can also produce systemic embolisms and constitutional signs. Clinical Case We present a 29-year-old female patient who started with fatigue, weight loss, increased abdominal perimeter and dyspnea of one month"s effort that progressed to dyspnea at rest in the last week associated with syncope, so she decided to go to the emergency department of our institution. Upon arrival at the emergency room, the patient was found with vital signs within normal parameters, however with dyspnea at rest, jugular plethora and important lower limb edema. On auscultation, a systolic-diastolic murmur was found with an increase in the Rivero Carvallo maneuver, with reinforcement of the pulmonary component of the second noise and parasternal high-left rise. In clinical analysis, NT-proBNP 5698pg/mL, AST 34, INR 1.65 and serum lactate of 4.2 was found. A Transthoracic Echocardiogram (TTE) was performed, where a 10cm mass effusion was documented that occupied the entire right atrium and protruded into the right ventricular outflow tract. With these findings, medical treatment was started for right heart failure and it was to cardiac surgery for resection of the right atrium where it had been performed, however during the immediate postoperative state, presented biventricular failure and later asystole without achieving a return of spontaneous circulation despite resuscitation maneuvers. Conclusion In this case, it is an unusual presentation of a rare cardiac pathology that started with symptoms of right heart failure due to the obstruction of the right ventricular outflow tract. We consider that it is an interesting clinical case and with important educational aspects to take into consideration the differential clinical diagnoses of a patient presenting to the emergency department with right heart failure. Abstract P234 Figure. Giant Myxoma

Joint mode selection and power allocation for better traffic offloading in D2D communications

Device-to-Device (D2D) technology underlying the cellular network is an attractive solution for future generation network to increase cellular traffic offloading. When two devices are close enough, D2D communication allows a direct communication between them without the mediation of the cellular base station. However, since D2D communication shares the same uplink cellular network radio resource, D2D communication mode selection remains challenging to limit the mutual interference between D2D and cellular links. In this paper, a new D2D mode selection scheme based on a new criterion is proposed aiming at maximizing the cellular traffic offload while respecting the quality of service of cellular users. More precisely, we introduce a noise rise parameter which takes into account the cellular link distance, the D2D link distance, and user’s required throughput. The D2D links are admitted under the constraint of a certain noise rise threshold. To further enhance the achieved throughput of D2D users while respecting the overall interference level in the network, a new power control algorithm is also proposed. Simulation results show that our proposed mode selection scheme provides a tradeoff between traffic offloading and the overall radio capacity in the network. They also prove that the D2D communication mode is more attractive at the cell edge and when D2D users are close enough to each other. In addition, we show the effectiveness of our proposed power control scheme as compared to both static and Rate-Adaptive Water Filling power allocation schemes.

Tribological behavior of ZnO-Si3N4 nanoparticles-based lubricating grease

Currently, nanoparticles have been widely used as lubricant additives, few researches have investigated their applications as additives for lubricating grease. In this paper, mixtures of ZnO and Si3N4 nanoparticles were added into grease as additives. XRD and TEM were utilized to the investigate phase composition, microstructure and morphology of the nanomaterials. The composite grease was prepared by introducing ZnO and Si3N4 nanoparticles into the grease matrix through ultrasonic dispersion. Then, tribological properties of the composite grease were measured through a MMW-1A universal friction tester. Results showed that the best lubrication performance was achieved when the composite grease contains 1 wt% ZnO and 0.5 wt%Si3N4. Under this condition, the friction coefficient and wear scar diameter decreased to 0.0701 and 0.727, which is 34.3% and 8.3% lower than that of the base greases, respectively. The morphology of composite nanoparticles is beneficial to the enhancement of antifriction property, which can be seen from SEM images. In addition, EDS analysis illuminated the accumulation of Zn and Si on the friction surface. Further researches proved its great potentials in alleviation of vibration, noise and temperature rise for high speed bearings, since the ZnO-Si3N4 nanoparticles-based composite grease showed excellent lubrication and antifriction properties.

An Enhanced PRACH Preamble Detector for Cellular IoT Communications

We propose an enhanced physical random access channel (PRACH) preamble detector, which efficiently identifies non-orthogonal preambles while suppressing the noise rise. The proposed PRACH preamble detector reconstructs preambles from the received signal and efficiently utilizes them to improve the detection performance. Through simulations, we verify that the proposed detector successfully detects the desired preambles while suppressing the undesired noise rise, and, thus, it can detect ten non-orthogonal preambles simultaneously with an extremely low mis-detection probability lower than $10^{-5}$ , while achieving a false alarm probability of approximately $10^{-3}$ .

Analog electro-optical readout of SiPMs achieves fast timing required for time-of-flight PET/MR

The design of combined positron emission tomography/magnetic resonance (PET/MR) systems presents a number of challenges to engineers, as it forces the PET system to acquire data in a space constrained environment that is sensitive to electro-magnetic interference and contains high static, radio frequency and gradient fields. In this work we validate fast timing performance of a PET scintillation detector using a potentially very compact, very low power, and MR compatible readout method in which analog silicon photomultipliers (SiPM) signals are transmitted optically away from the MR bore with little or even no additional readout electronics. This analog ‘electro-optial’ method could reduce the entire PET readout in the MR bore to two compact, low power components (SiPMs and lasers). Our experiments show fast timing performance from analog electro-optical readout with and without pre-amplification. With 3 mm × 3 mm × 20 mm lutetium–yttrium oxyorthosilicate (LYSO) crystals and Excelitas SiPMs the best two-sided fwhm coincident timing resolution achieved was 220 +/− 3 ps in electrical mode, 230 +/− 2 ps in electro-optical with preamp mode, and 253 +/− 2 ps in electro-optical without preamp mode. Timing measurements were also performed with Hamamatsu SiPMs and 3 mm × 3 mm × 5 mm crystals. In the future the timing degradation seen can be further reduced with lower laser noise or improvements SiPM rise time or gain.

Investigation on High-Performance CMOS With p-Ge and n-InGaAs MOSFETs for Logic Applications

CMOS circuits built using Ge-channel p-MOSFETs and InGaAs-channel n-MOSFETs have shown promise for high-performance logic applications. In this paper, we investigate for the first time the performance of such circuits using extensive device simulations. The digital performance of a CMOS inverter is evaluated in terms of noise margins, rise time, fall time, and propagation delay. Furthermore, frequency of oscillations of a three-stage ring oscillator is obtained for varying ratio of the channel width of the p- and the n-MOSFETs, respectively (W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> /W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> ). Our investigations reveal that the CMOS circuits comprising of p-Ge and n-InGaAs MOSFETs outperform their equally sized Si counterpart. Moreover, superior performance of Ge/InGaAs-based CMOS is obtained for In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.75</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.25</sub> As channel with width ratio (W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> /W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> ) of 10: 1. Also, Ge/InGaAs CMOS is found to lose its advantages over Si CMOS for 5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> eV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> · cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> .

Distributed Inter-Cell Interference Mitigation Via Joint Scheduling and Power Control Under Noise Rise Constraints

Consider the problem of joint uplink scheduling and power allocation. Being inherent in almost any wireless system, this resource allocation problem has received extensive attention. Yet, most common techniques either adopt classical power control, in which mobile stations are received with the same Signal-to-Interference-plus-Noise Ratio, or use centralized schemes, in which base stations coordinate their allocations. In this work, we suggest a novel scheduling approach in which each base station, besides allocating the time and frequency according to given constraints, also manages its uplink power budget such that the aggregate interference, "Noise Rise", caused by its subscribers at the neighboring cells is bounded. Our suggested scheme is distributed, requiring neither coordination nor message exchange between the base stations. We rigorously define the allocation problem under noise rise constraints. Inspired by the fact that under the noise-rise constraints, interference experienced by base stations is bounded and its variance is expected to be low, we suggested an approximation in which each base station assumes fixed interference. Under this approximation we formalize the joint scheduling and power control under the noise rise constraints as an optimization problem and characterize the optimal solution. For the special case of homogeneous deployment we give the optimal solution and derive an efficient iterative algorithm to achieve it. We then discuss a relaxed problem, where the noise rise is constrained separately for each sub-channel or resource unit. While sub-optimal, this view renders the scheduling and power allocation problems separate, yielding an even simpler and more efficient solution, while the essence of the scheme is kept. Via extensive simulations, we show that the suggested approach increases overall performance dramatically, with the same level of fairness and power consumption.

Linearized Shallow-water Wave Theory of Tsunami Generation and Propagation by Three-dimensional Stochastic Seismic Bottom Topography

Tsunami generation and propagation resulting from lateral spreading of a stochastic seismic fault source model driven by two Gaussian white noises in the x- and y- directions are investigated. Tsunami waveforms within the frame of the linearized shallow water theory for constant water depth are analyzed analytically by transform methods (Laplace in time and Fourier in space) for the random sea floor uplift represented by a sliding Heaviside step function under the influence of two Gaussian white noise processes in the x- and y- directions. This model is used to study the tsunami amplitude amplification under the effect of the noise intensity and rise times of the stochastic fault source model. The amplification of tsunami amplitudes builds up progressively as time increases during the generation process due to wave focusing while the maximum wave amplitude decreases with time during the propagation process due to the geometric spreading and also due to dispersion. We derived and analyzed the mean and variance of the random tsunami waves as a function of the time evolution along the generation and propagation path.

Development of a Totally Enclosed Fan-Cooled Traction Motor

The intake of dust and dirt contained outside the air into the motor while driving causes the maintenance of dismantling and clean-up operation once every three years. Moreover, excessive acoustic noise during high-speed operation is produced by the cooling fan on the rotor. Totally enclosed airtight motor was developed not only to deal with the dust-intake problem but also to reduce acoustic noise. This motor eliminates the requirement of periodical dismantling and clean-up operation. Excessive noise of internal cooling fan was decreased by newly developed uneven pitch blade fan. Further, traction motor without external fan was developed by thermofluid simulation. Acoustic noise and temperature rise of these motor were measured and compared.