Amplitude truncation of Gaussian 1/f(alpha) noises: Results and problems

An interesting property of Gaussian 1/f noise was found experimentally a few years ago: The amplitude truncation does not change the power spectral density of the noise under rather general conditions. Here we present a brief theoretical derivation of this invariant property of band-limited Gaussian 1/f noise and include 1/f(alpha) noises also with 0 less than or equal to alpha <2. It is shown that when alpha less than or equal to1, a transformation of keeping only the sign of the zero-mean 1/f(alpha) noise does not alter the shape of the spectral density. The theoretical results are extended to truncation levels differing significantly from the mean value. Numerical simulation results are also presented to draw attention to unsolved problems of amplitude truncation using asymmetric levels. (C) 2001 American Institute of Physics

REVIEW OF SPENT FUEL INTEGRITY EVALUATION FOR DRY STORAGE

Among the several options to solve PWR spent fuel accumulation problem in Korea, the dry storage method could be the most realistic and applicable solution in the near future. As the basic objectives of dry storage are to prevent a gross rupture of spent fuel during operation and to keep its retrievability until transportation, at the same time the importance of a spent fuel integrity evaluation that can estimate its condition at the final stage of dry storage is very high. According to the national need and technology progress, two representative nations of spent fuel dry storage, the USA and Japan, have established different system temperature criteria, which is the only controllable factor in a dry storage system. However, there are no technical criteria for this evaluation in Korea yet, it is necessary to review the previously well-organized methodologies of advanced countries and to set up our own domestic evaluation direction due to the nation's need for dry storage. To satisfy this necessity, building a domestic spent fuel test database should be the first step. Based on those data, it is highly recommended to compare domestic data range with foreign results, to build our own criteria, and to expand on evaluation work into recently issued integrity problems by using a comprehensive integrity evaluation code

A Statistical Performance Analysis of Named Data Ultra Dense Networks

Named data networking (NDN) is a novel communication paradigm that employs names rather than references to the location of the content. It exploits in-network caching among different nodes in a network to provide the fast delivery of content. Thus, it reduces the backhaul traffic on the original producer and also eliminates the need for a stable connection between the source (consumer) and destination (producer). However, a bottleneck or congestion may still occur in very crowded areas, such as shopping malls, concerts, or stadiums, where thousands of users are requesting information from a device that resides at the edge of the network. This paper provides an analysis of content delivery in terms of the interest satisfaction rate (ISR) in ultra-dense network traffic situations and presents a final and an adequate statistical model based on multiple linear regression (MLR) to enhance ISR. A four-way factorial design was used to generate the dataset by performing simulations in ndnSIM. The results show that there is no significant interaction between four predictors: number of nodes (NN), number of interests (NI) per second, router bandwidth (RB), and router delay (RD). Moreover, the NI has a negative effect, and log(RB) has a positive effect on the ISR. The NN less than 10 has a significantly higher effect on the ISR compared with other nodes&rsquo; densities

A 3D-Printed Sensor for Monitoring Biosignals in Small Animals

Although additive manufacturing technologies, also known as 3D printing, were first introduced in the 1980s, they have recently gained remarkable popularity owing to decreased costs. 3D printing has already emerged as a viable technology in many industries; in particular, it is a good replacement for microfabrication technology. Microfabrication technology usually requires expensive clean room equipment and skilled engineers; however, 3D printing can reduce both cost and time dramatically. Although 3D printing technology has started to emerge into microfabrication manufacturing and medical applications, it is typically limited to creating mechanical structures such as hip prosthesis or dental implants. There have been increased interests in wearable devices and the critical part of such wearable devices is the sensing part to detect biosignals noninvasively. In this paper, we have built a 3D-printed sensor that can measure electroencephalogram and electrocardiogram from zebrafish. Despite measuring biosignals noninvasively from zebrafish has been known to be difficult due to that it is an underwater creature, we were able to successfully obtain electrophysiological information using the 3D-printed sensor. This 3D printing technique can accelerate the development of simple noninvasive sensors using affordable equipment and provide an economical solution to physiologists who are unfamiliar with complicated microfabrication techniques

Multichannel EEG Recordings on PTZ-induced Zebrafish Epilepsy Model

Despite recent interests in using zebrafish for human disease studies, sparked by their economics, fecundity, easy handling, and homologies to humans, the electrophysiological tools or methods for zebrafish are still inaccessible. Although zebrafish exhibit more significant larval-adult duality than any other animals1, most electrophysiological studies using zebrafish are biased in using larvae these days. The results of larval studies not only differ from those conducted with adults, but also are unable to delicately manage electroencephalographic montages due to their small size. Hence, we developed a methodology of non-invasive long-term multichannel electroencephalographic recording on adult zebrafish using a custom-designed electrode array and perfusion system. The multichannel EEG array was prepared as a flexible printed circuit board (FPCB) based on polymide film. The array had a thickness of 80 μm and was flexible enough to adhere to the curved head surface of zebrafish. Zebrafish were anesthetized by 15 ppm of eugenol, until they were anesthetized in stage 3. When they did not show reflex responses, their head skin was gently dried using cotton swabs. Then, the electrode array was attached onto zebrafish heads. During the recordings, 7.5 ppm of eugenol (2~3ml/min) was orally injected continuously through an intubator. By providing 7.5 ppm of eugenol, animals were successfully maintained in the anesthesia state. After 10 minutes of baseline recording, 15 mM of pentylenetetrazole (PTZ) was orally injected to evoke seizure activities. All recording sessions were performed for 60 minutes using 17 zebrafish, and all the animals survived through the sessions. During the one hour of recording, animals exhibited 4.93 seizures per hour. The seizure activities showed two patterns, high amplitude theta activities and absence-like seizure activities. The high amplitude theta activity events were comparable to seizure pattern in all other species2,3. Our techniques with multichannel recording capability allowed for studying seizure dynamics on epileptic zebrafish for the first time. 71% of seizure activities were onset from telencephalon as expected4. In addition, our results suggested that there is a possibility that some seizures started from the cerebellum, which rarely happens in human5. Our results provide a new pathway for future neuroscience research using zebrafish by overcoming the challenges for aquatic organisms such as precision, serviceability, and continuous water seepage

A Reconstruction Method of Blood Flow Velocity in Left Ventricle Using Color Flow Ultrasound

Vortex flow imaging is a relatively new medical imaging method for the dynamic visualization of intracardiac blood flow, a potentially useful index of cardiac dysfunction. A reconstruction method is proposed here to quantify the distribution of blood flow velocity fields inside the left ventricle from color flow images compiled from ultrasound measurements. In this paper, a 2D incompressible Navier-Stokes equation with a mass source term is proposed to utilize the measurable color flow ultrasound data in a plane along with the moving boundary condition. The proposed model reflects out-of-plane blood flows on the imaging plane through the mass source term. The boundary conditions to solve the system of equations are derived from the dimensions of the ventricle extracted from 2D echocardiography data. The performance of the proposed method is evaluated numerically using synthetic flow data acquired from simulating left ventricle flows. The numerical simulations show the feasibility and potential usefulness of the proposed method of reconstructing the intracardiac flow fields. Of particular note is the finding that the mass source term in the proposed model improves the reconstruction performance