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Bias-dependent photoresponsivity of multi-layer MoS <sub>2</sub> phototransistors
Park, Jinwu,Park, Youngseo,Yoo, Geonwook,Heo, Junseok Springer US 2017 NANOSCALE RESEARCH LETTERS Vol.12 No.1
<P>We studied the variation of photoresponsivity in multi-layer MoS<SUB>2</SUB> phototransistors as the applied bias changes. The photoresponse gain is attained when the photogenerated holes trapped in the MoS<SUB>2</SUB> attract electrons from the source. Thus, the photoresponsivity can be controlled by the gate or drain bias. When the gate bias is below the threshold voltage, a small amount of electrons are diffused into the channel, due to large barrier between MoS<SUB>2</SUB> and source electrode. In this regime, as the gate or drain bias increases, the barrier between the MoS<SUB>2</SUB> channel and the source becomes lower and the number of electrons injected into the channel exponentially increases, resulting in an exponential increase in photoresponsivity. On the other hand, if the gate bias is above the threshold voltage, the photoresponsivity is affected by the carrier velocity rather than the barrier height because the drain current is limited by the carrier drift velocity. Hence, with an increase in drain bias, the carrier velocity increases linearly and becomes saturated due to carrier velocity saturation, and therefore, the photoresponsivity also increases linearly and becomes saturated.</P>
Park, Junseok,Kim, Hyungdae Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.8
Direct-contact heat transfer of a single saturated droplet upon colliding with a heated wall in the regime of film boiling was experimentally investigated using high-resolution infrared thermometry technique. This technique provides transient local wall heat flux distributions during the entire collision period. In addition, various physical parameters relevant to the mechanistic modelling of these phenomena can be measured. The obtained results show that when single droplets dynamically collide with a heated surface during film boiling above the Leidenfrost point temperature, typically determined by droplet collision dynamics without considering thermal interactions, small spots of high heat flux due to localized wetting during the collision appear as increasing We<sub>n</sub>. A systematic comparison revealed that existing theoretical models do not consider these observed physical phenomena and have lacks in accurately predicting the amount of direct-contact heat transfer. The necessity of developing an improved model to account for the effects of local wetting during the direct-contact heat transfer process is emphasized.
BIPRODUCT BIALGEBRAS WITH A PROJECTION ONTO A HOPF ALGEBRA
Junseok Park 충청수학회 2013 충청수학회지 Vol.26 No.1
Let (D;B) be an admissible pair. Then recall that B £LHD À¼DiDD are bialgebra maps satisfying ¼D ± iD = I: We have solved a converse in case D is a Hopf algebra. Let D be a Hopf algebra with antipodesD and be a left H-comodule algebra and a left H-module coalgebra over a¯eld k: Let A be a bialgebra over k: Suppose A À¼ i D are bialgebra maps satisfying ¼ ± i = ID: Set ¦ = ID ¤ (i ± sD ± ¼);B = ¦(A) and j : B ! A be the inclusion. Suppose that ¦ is an algebra map. We show that (D;B)is an admissible pair and B ¿¦ j A À¼ i D is an admissible mapping system and that the generalized biproduct bialgebra B £LH D is isomorphic to A as bialgebras.
Fast Scheduling of Semiconductor Manufacturing Facilities Using Case-Based Reasoning
Junseok Lim,Moon-Jung Chae,Yongseok Yang,In-Beom Park,Jaeyong Lee,Jonghun Park Institute of Electrical and Electronics Engineers 2016 IEEE transactions on semiconductor manufacturing Vol.29 No.1
<P>This paper presents a scheduling method for semiconductor manufacturing systems through utilizing a case-based reasoning approach that consists of modeling, casebase building, and reasoning steps. Petri nets are employed as a model for representing the behavior of a system and accommodating various types of constraints. Casebase contains the cases, composed of pairs of a state and the decision made at the state, and it is built from the solutions of previously solved problems. Subsequently, a schedule for a new problem with different production requirements, initial setup status, and number of setup change operators is obtained by sequentially retrieving and reusing the cases that are most similar to the states encountered during schedule generation in the reasoning step. Extensive experiments demonstrate the performances of the proposed approach, compared to those of dispatching rule and meta-heuristic methods, and also show the robustness against possible perturbations in terms of production requirements and initial setup status based on real world scale datasets. The proposed method significantly outperformed a meta-heuristic algorithm in terms of computation time while requiring much less sacrifice in a performance metric than the competitive dispatching rules.</P>