479 research outputs found
Mean Field Analysis of Stochastic Neural Network Models with Synaptic Depression
We investigated the effects of synaptic depression on the macroscopic
behavior of stochastic neural networks. Dynamical mean field equations were
derived for such networks by taking the average of two stochastic variables: a
firing state variable and a synaptic variable. In these equations, their
average product is decoupled as the product of averaged them because the two
stochastic variables are independent. We proved the independence of these two
stochastic variables assuming that the synaptic weight is of the order of 1/N
with respect to the number of neurons N. Using these equations, we derived
macroscopic steady state equations for a network with uniform connections and a
ring attractor network with Mexican hat type connectivity and investigated the
stability of the steady state solutions. An oscillatory uniform state was
observed in the network with uniform connections due to a Hopf instability.
With the ring network, high-frequency perturbations were shown not to affect
system stability. Two mechanisms destabilize the inhomogeneous steady state,
leading two oscillatory states. A Turing instability leads to a rotating bump
state, while a Hopf instability leads to an oscillatory bump state, which was
previous unreported. Various oscillatory states take place in a network with
synaptic depression depending on the strength of the interneuron connections.Comment: 26 pages, 13 figures. Preliminary results for the present work have
been published elsewhere (Y Igarashi et al., 2009.
http://www.iop.org/EJ/abstract/1742-6596/197/1/012018
Non-contingent reinforcement as a treatment for problem behaviors in the natural contexts of a special needs school.
This study evaluate the effects of an intervention package, including non-contingent reinforcement(NCR), to reduce severe problem behaviors of a student with autism and mental retardation in the daily program of a special needs school. Prioritizing the practicality of assessment and intervention procedures, we relied on interview and direct observation to identify the function of the problem behaviors and selected a maintained reinforcer that was easily delivered among alternatives. In Intervention 1, NCR was provided, with extinction (EXT) and contingent response to communicative behaviors(CR). In Intervention 2, visual schedule and peer mediated strategy, in addition to NCR, EXT, and CR, were introduced. Reduction of the problem behaviors occured following Intervention 1, and more substantial occurred following Intervention 2. Additionally, increases in class participation were noticeable after Intervention 2. Additionally, increases in class participation were noticeable after Intervention 2 was implemented. On the basis of these results, we discussed practical ways of implementing NCR interventions in school settings where controlling environments is typically difficult
The development of “Ultimate Rudder” for EEDI
EEDI (Energy Efficiency Design Index) came into effect mandatory in Jan.
2013, and the ship owners definitely required a higher efficiency propulsion system than ever
before. Hence, the shipyards have been conducting an optimization of ESD (Energy Saving Device)
system in self-propulsion test for each project. As the results, the shipyards have
installed a rudder bulb as an effective ESD.
The rudder bulb is a popular ESD system from a long time ago. Mewis1) described that the rudder
bulb was developed by Costa in 1952 and the efficiency improve by the rudder bulb for a container
vessel was 1% on average. Fujii et al.2) developed “MIPB (Mitsui Integrated Propeller Boss)” as an
advanced rudder bulb. The feature of MIPB was a streamlined profile from propeller cap to rudder.
According to their paper, the efficiency improve by installing MIPB was 2-4%.
Recently, NAKASHIMA PROPELLER Co., Ltd. developed ECO-Cap (economical propeller
cap)3) as a new ESD with FRP (Fiber Reinforced Plastics). The strength of FRP is higher than that
of NAB (Nickel Aluminium Bronze), therefore ECO-Cap was able to adopt thin fins on propeller
caps for low resistance. Although the material used for the energy- saving propeller cap
was generally NAB, the research results on FRP showed that FRP could be used as ESD due to their
properties such as lightweight and flexibility.
As explained above, the authors thought that there was a possibility to evolve the rudder bulb
profile using the easily moldable FRP compared with NAB. This paper described about the development
of “Ultimate Rudder” of new design concept by FRP. The authors optimized the profile of “Ultimate
Rudder” by CFD and confirmed the efficiency increase from 4.9 to
5.4% in self-propulsion test
Study on the rudder characteristics of ultimate rudder by numerical calculation
The authors invented Ultimate Rudder3) as the rudder with bulb. The authors
calculated the rudder characteristics of the normal rudder and Ultimate Rudder by CFD
at several steering angles and compared these values. The result showed that regardless of the
presence or absence of the bulb, signs of separation appear on the control surface
with a steering angle of 20 deg. to 30 deg. and regarding the steering torque coefficient, it was
found that the steering torque coefficient of Ultimate Rudder is larger than the normal Rudder when
the steering angle is less than 20 deg. and also the steering torque coefficient can be decreased
by changing the shape of the rudder bulb
Geographical distribution for malignant neoplasm of the pancreas in relation to selected climatic factors in Japan
<p>Abstract</p> <p>Background</p> <p>Malignant neoplasm of the pancreas has become one of the leading causes of death from malignant neoplasm in Japan (the 5th in 2003). Although smoking is believed to be a risk factor, other risk factors remain unclear. Mortality from malignant neoplasm of the pancreas tends to be higher in northern Japan and in northern European countries. A recent study reported that standardized mortality ratios (SMRs) for malignant neoplasm of the pancreas were negatively correlated to global solar radiation level. People residing in regions with lower solar radiation and lower temperatures may be at higher risk of development of malignant neoplasm of the pancreas. Therefore, this study aimed to examine the relationship between SMRs for malignant neoplasm of the pancreas and climatic factors, such as the amount of global solar radiation and the daily maximum temperature in Japan.</p> <p>Results</p> <p>The study used multiple linear regression models. Number of deaths and demographic data from 1998 to 2002 were used for the calculation of SMR. We employed mesh climatic data for Japan published in 2006 by the Japan Meteorological Agency. Regression coefficients for the amount of global solar radiation and the daily maximum temperature in males were -4.35 (p = 0.00034) and -2.81 (p < 0.0001) respectively, and those in females were -5.02 (p < 0.0001) and -1.87 (p < 0.0001) respectively. Increased amount of global solar radiation or daily maximum temperature was significantly related to the decreased SMRs for malignant neoplasm of the pancreas in both males and females.</p> <p>Conclusion</p> <p>This study suggested that low solar radiation and low temperature might relate to the increasing risk of malignant neoplasm of the pancreas. Use of group data has a limitation in the case of evaluating environmental factors affecting health, since the impact of climatic factors on the human body varies according to individual lifestyles and occupations. Use of geographical mesh climatic data, however, proved useful as an index of risk or beneficial factors in a small study area. Further research using individual data is necessary to elucidate the relationship between climatic factors and the development of malignant neoplasm of the pancreas.</p
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