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A mathematical model for the two-learners problem
Mü,ller, Jan Saputra,Vidaurre, Carmen,Schreuder, Martijn,Meinecke, Frank C,von Bü,nau, Paul,Mü,ller, Klaus-Robert IOP 2017 Journal of neural engineering Vol.14 No.3
<P> <I>Objective</I>. We present the first generic theoretical formulation of the co-adaptive learning problem and give a simple example of two interacting linear learning systems, a human and a machine. <I>Approach</I>. After the description of the training protocol of the two learning systems, we define a simple linear model where the two learning agents are coupled by a joint loss function. The simplicity of the model allows us to find learning rules for both human and machine that permit computing theoretical simulations. <I>Main results</I>. As seen in simulations, an astonishingly rich structure is found for this eco-system of learners. While the co-adaptive learners are shown to easily stall or get out of sync for some parameter settings, we can find a broad sweet spot of parameters where the learning system can converge quickly. It is defined by mid-range learning rates on the side of the learning machine, quite independent of the human in the loop. Despite its simplistic assumptions the theoretical study could be confirmed by a real-world experimental study where human and machine co-adapt to perform cursor control under distortion. Also in this practical setting the mid-range learning rates yield the best performance and behavioral ratings. <I>Significance</I>. The results presented in this mathematical study allow the computation of simple theoretical simulations and performance of real experimental paradigms. Additionally, they are nicely in line with previous results in the BCI literature.</P>
Simulations of Therapeutic Proton Beam Formation with GEANT4
Aram Kim,김종원,한인식,Jonathan Farr,Niek Schreuder 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.1
The proton beam formation for therapy has been studied with Monte Carlo simulations. This numerical study was performed in conjunction with the measurements made in the horizontal beam line of the Midwest Proton Radiotherapy Institute (MPRI) in the USA. The simulations included necessary beam-modifying devices of the beam line, and were compared to the dose distributions measured in water and in air using an ionization chamber. Therapeutic beams were produced using a double-scattering method in the transverse planes and using a rotating modulator in the beam direction. The results showed that important physical parameters of a therapy beam such as lateral penumbra and source to axis distance (SAD) can be simulated to agree with experimental values within 5 %.
The Efficacy of Steroid Injection in the Treatment of Trigger Finger
Benan M. Dala-Ali,Amir Nakhdjevani,Mary A. Lloyd,Frederik B. Schreuder 대한정형외과학회 2012 Clinics in Orthopedic Surgery Vol.4 No.4
Background: Trigger finger is one of the most common reasons for referral to a hand specialist clinic. The purpose of this study is to investigate the efficacy of steroid injections for treating trigger digits. Methods: Ninety digits were investigated with at least a year follow up. The study mainly focused on the efficacy of the injections, as well as co-morbidities, presence of a nodule, actual digit injected and the severity at presentation using Green’s classification. Results: The study found that 66% of trigger digits were effectively treated using steroid injections. There was a difference between the efficacy of the injection in the different digits, with a statistical significance between the thumb and the fingers. The results also showed that there was no statistical relationship between the severity of the condition, the presence of a nodule or co-morbidities and the efficacy of the steroid injections. Conclusions: The study found that steroid injections are an effective first-line intervention for the treatment of trigger digit. It also found an increased efficacy for treating the thumb compared to other digits. Both the severity of the condition at presentation and the presence of a nodule had no significant impact on the efficacy of the injections.