Browsing by Author "Chen, Po-An"

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A New High Voltage IC with Robust Isolation Design
(2018-01-01)
Ningaraju, Vivek
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Lin, Horng-Chih
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Chen, Po-An
;
Wen, Jiin-Shiarng
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交大名義發表
A new and robust isolation design for control devices integrated in the high side island region of 250V high-voltage integrated circuits (HVIC) is proposed and verified by numerical calculations, simulations and experiments. The new isolation structure can be realized using micro N-well in the P-type isolation region to achieve a higher breakdown voltage (BV). The measurement and TCAD simulation results prove this new isolation structure's BV is over 350V with negligible leakage current. In the proposed scheme BV is improved by 15% more than the conventional structure without adding additional process steps and photo layers.
Bounds on the price of anarchy for a more general class of directed graphs in opinion formation games
(2016-11)
Chen, Po-An
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Chen, Yi-Le
;
Lu, Chi-Jen
;
資訊工程學系
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資訊管理與財務金融系註：原資管所+財金所
In opinion formation games with directed graphs, a bounded price of anarchy is only known for weighted Eulerian graphs. Thus, we bound the price of anarchy for a more general class of directed graphs with conditions intuitively meaning that each node does not influence the others more than she is influenced, where the bounds depend on such difference (in a ratio). We also show that there exists an example just slightly violating the conditions with an unbounded price of anarchy. (C) 2016 Elsevier B.V. All rights reserved.
Budget-constrained multi-battle contests: A new perspective and analysis
(2018-04-18)
Cheng, Chu-Han
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Chen, Po-An
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Hon, Wing-Kai
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資訊管理與財務金融系註：原資管所+財金所
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Department of Information Management and Finance
In a multi-battle contest, each time a player competes by investing some of her budgets or resources in a component battle to collect a value if winning the battle. There are multiple battles to fight, and the budgets get consumed over time. The final winner in the overall contest is the one who first reaches some amount of total value. Examples include R & D races, sports competition, elections, and many more. A player needs to make adequate sequential actions to win the contest against dynamic competition over time from the others. We are interested in how much budgets the players would need and what actions they should take in order to perform well. We model and study such budget-constrained multi-battle contests where each component battle is a sequential first-price or all-pay auction. We focus on analyzing the 2-player budget ratio that guarantees a player's winning against the other omnipotent player. In the settings considered, we find the optimal budget ratios and the corresponding bidding strategies. Our definition of game, budget constraints, and emphasis on budget analyses provide a new perspective and analysis for multi-battle contests. (C) 2018 Elsevier B.V. All rights reserved.
Generalized mirror descents in congestion games
(2016-12)
Chen, Po-An
;
Lu, Chi-Jen
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資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Different types of dynamics have been studied in repeated game play, and one of them which has received much attention recently consists of those based on "no-regret" algorithms from the area of machine learning. It is known that dynamics based on generic no-regret algorithms may not converge to Nash equilibria in general, but to a larger set of outcomes, namely coarse correlated equilibria. Moreover, convergence results based on generic no-regret algorithms typically use a weaker notion of convergence: the convergence of the average plays instead of the actual plays. Some work has been done showing that when using a specific no-regret algorithm, the well-known multiplicative updates algorithm, convergence of actual plays to equilibria can be shown and better quality of outcomes in terms of the price of anarchy can be reached for atomic congestion games and load balancing games. Are there more cases of natural no-regret dynamics that perform well in suitable classes of games in terms of convergence and quality of outcomes that the dynamics converge to? We answer this question positively in the bulletin-board model by showing that when employing the mirror-descent algorithm, a well-known generic no-regret algorithm, the actual plays converge quickly to equilibria in nonatomic congestion games. This gives rise to a family of algorithms, including the multiplicative updates algorithm and the gradient descent algorithm as well as many others. Furthermore, we show that our dynamics achieves good bounds on the outcome quality in terms of the price-of-anarchy type of measures with two different social costs: the average individual cost and the maximum individual cost. Finally, the bandit model considers a probably more realistic and prevalent setting with only partial information, in which at each time step each player only knows the cost of her own currently played strategy, but not any costs of unplayed strategies. For the class of atomic congestion games, we propose a family of bandit algorithms based on the mirror descent algorithms previously presented, and show that when each player individually adopts such a bandit algorithm, their joint (mixed) strategy profile quickly converges with implications. (C) 2016 Elsevier B.V. All rights reserved.
Generalized Mirror Descents in Congestion Games with Splittable Flows
(2014-01-01)
Chen, Po-An
;
Lu, Chi-Jen
;
交大名義發表
;
National Chiao Tung University
Different types of dynamics have been studied in repeated game play, and one of them which has received much attention recently consists of those based on "no-regret" algorithms from the area of machine learning. It is known that dynamics based on generic no-regret algorithms may not converge to Nash equilibria in general, but to a larger set of outcomes, namely coarse correlated equilibria. Moreover, convergence results based on generic no-regret algorithms typically use a weaker notion of convergence: the convergence of the average plays instead of the actual plays. Some work has been done showing that when using a specific no-regret algorithm, the well-known multiplicative updates algorithm, convergence of actual plays to equilibria can be shown and better quality of outcomes can be reached for atomic congestion games and load balancing games. Are there more cases of natural no-regret dynamics that perform well in suitable classes of games in terms of convergence and quality of outcomes? We answer this question positively by showing that when each player individually employs the mirror-descent algorithm, a well-known generic no-regret algorithm, the actual plays converge quickly to equilibria in nonatomic congestion games. This gives rise to a family of algorithms, including the multiplicative updates algorithm and the gradient descent algorithm as well as many others. Furthermore, we show that our dynamics achieves good bounds on the quality of outcomes measured by two different social costs: the average individual cost and the maximum individual cost.
Generalized mirror descents with non-convex potential functions in atomic congestion games: Continuous time and discrete time
(2018-02-01)
Chen, Po-An
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
When playing certain specific classes of no-regret algorithms such as multiplicative updates and replicator dynamics in atomic congestion games, some previous convergence analyses were done with the standard Rosenthal potential function in terms of mixed strategy profiles (i.e., probability distributions on atomic flows), which could be non-convex. In several other works, the convergence, when playing the mirror-descent algorithm (a more general family of no-regret algorithms including multiplicative updates, gradient descents, etc.), was guaranteed with a convex potential function in terms of nonatomic flows as an approximation of the Rosenthal one. The convexity of the potential function provides convenience for analysis. One may wonder if the convergence of mirror descents can still be guaranteed directly with the non-convex Rosenthal potential function. In this paper, we answer the question affirmatively for discrete-time generalized mirror descents with the smoothness property (similarly adopted in many previous works for congestion games and markets) and for continuous-time generalized mirror descents with the separability of regularization functions. (C) 2017 Elsevier B.V. All rights reserved.
How egalitarian are Nash equilibria in network cost-sharing games?
(2015-11-01)
Chen, Po-An
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資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
We consider the egalitarian social cost, which is the maximum individual cost (instead of the sum), when analyzing Nash equilibria in fair network cost-sharing games. Intuitively, the egalitarian price of anarchy reflects how uneven cost is distributed among players at equilibrium. We first show a tight upper bound of kin general fair network cost-sharing games, where k is the total number of players. For fair network cost-sharing games with a single source-sink pair and a relaxed benchmark, we then show an upper bound of n - 1 on the egalitarian price of anarchy defined using such benchmark, where n is the network size. This gives a possibly better bound that does not depend on the number of players nor the costs. (C) 2015 Elsevier B.V. All rights reserved.
Improving breakdown voltage for 120 V level up shifter by using vertical and lateral assisted depletion layers in 0.35 mu m CMOS technology
(2020-04-01)
Ningaraju, Vivek
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Lin, Horng-Chih
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Chen, Po-An
;
Lin, Kuang-Lun
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交大名義發表
A novel isolation structure featuring a vertical assisted depletion layer (VADL) by p-buried layer (PBL) and lateral assisted depletion layer (LADL) by micro-n-well (mu NW) for 120 V level up shifter is proposed. VADL and LADL efficiently prevents the premature breakdown of level shifter by fully depleting nLDMOS drain region and p-isolation (P-ISO) region respectively. By the effect of the electric field modulation, more uniform lateral and vertical electric fields are obtained due to the insertion of the VADL and LADL, which improves the breakdown voltage (BV) and device reliability. The breakdown and reliability mechanisms are investigated in detail by theoretical analysis, TCAD simulations and experimental measurements. The measured results shows, BV of 160 V and almost no HTRB degradation is seen after 168 h of stress. In addition, the new structure is fully compatible with standard 0.35 mu m CMOS technology. Hence, it is not only a performance booster but also a low-cost solution. (C) 2020 The Japan Society of Applied Physics
Intra-cell ionic properties of twisted nematic liquid crystal cells
(2019-01-01)
Chen, Po-An
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Yang, Kei-Hsiung
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光電學院
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College of Photonics
Under 1-kHz and low-frequency driving, we report our investigation of intra-cell ionic properties of two twisted nematic (TN) liquid crystal (LC) cells made of same LC mixture but different polyimide (PI) materials for LC alignments. A heterodyne interferometry system was used to measure the phase retardations of the TN cells versus applied voltages at 1kHz. We also measured the phase retardations and currents of the TN cells versus time by applying a mid-grayscale voltage of 1.3V at 0.1Hz to the cells. Related to the above-measured data, we have developed equations to characterise the field-driven transports of mobile charge carriers within the PI films independently from that within the LC medium of same TN cell to obtain time-dependent in-cell voltages of mobile charge carries across the LC mixture and across two PI-alignment films, respectively. Our experimental methods can be used to optimise LC mixtures and PI materials for low-refresh-rate thin-film-transistor-driven liquid crystal displays (LCDs) for low power and provide bases for further investigations on mobile-charge-carrier generation and transport within thin in-cell PI-alignment films as well as within the LC mixture of same LC cell. [GRAPHICS] .
Ionic effects on electro-optics and residual direct current voltages of twisted nematic liquid crystal cells
(2018-01-01)
Chen, Po-An
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Yang, Kei-Hsiung
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光電學院
;
College of Photonics
By using electro-optical and dielectric absorption [1-4] measurements, we report our investigations of ionic effects on electro-optics and residual direct current voltages (VrDCs) of two polyimide (PI)-aligned twisted nematic (TN) cells with same liquid crystal mixture but different PI-alignment materials. We have also carried out new experimental methods to find out that the observed VrDCs were caused by LC-PI-interfacial trapped ions generated and transported from the LC medium for one TN cell, and from the PI layers for the other TN cell. Our measured VrDCs indicated that the former had two different exponential-decay rates similar to the published results by M. Mizusaki et al. [2] but the latter had only a single exponential-decay rate. [GRAPHICS] .
Playing Congestion Games with Bandit Feedbacks
(2015-01-01)
Chen, Po-An
;
Lu, Chi-Jen
;
交大名義發表
;
National Chiao Tung University
Almost all convergence results from each player adopting specific "no-regret" learning algorithms such as multiplicative updates or the more general mirror-descent algorithms in repeated games are only known in the more generous information model, in which each player is assumed to have access to the costs of all possible choices, even the unchosen ones, at each time step. This assumption in general may seem too strong, while a more realistic one is captured by the bandit model, in which each player at each time step is restricted to know only the cost of her currently chosen path, but not any of the unchosen ones. Can convergence still be achieved in such a more challenging bandit model? We answer this question positively. While existing bandit algorithms do not seem to work here, we develop a new family of bandit algorithms based on the mirror-descent algorithm with such a guarantee in atomic congestion games.
Sharp variation in coercivity and magnetic interactions in patterned CoxNi1-x nanoarrays
(2013-08-14)
Yang, Chao-Yao
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Wang, Liang-Wei
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Chen, Po-An
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Lin, Hong-Ji
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Lai, Chih-Huang
We present a study concerning the unexpectedly large coercivity increase and associated magneto-structural properties of CoxNi1-x patterned arrays. An increase in x led to an face-center-cubic (FCC)-> hexagonal-close-packed (HCP) transition in CoxNi1-x arrays, accompanied by a 6-fold increase in coercivity and strong 3d exchange interactions probed by x-ray magnetic circular dichroism. Sum-rule analysis revealed that orbital moment involved very little in the variable coercivity and magnetic anisotropy; this is distinct from other nanostructures displaying variable coercivity. The sharp rise in coercivity can be attributed to the geometrical confinement of the arrays, causing the microstructure of the nano-clusters to switch magnetization reversal mechanism from fanning to coherent with increasing x, based on the chain-of-spheres model. First-order-reversal curves revealed that the FCC and HCP arrays comprised both soft and hard ferromagnetic components; however, the soft component of the FCC was much more pronounced, leading to differences in reversibility. This type of nanostructure provides a sharp control of magnetic hardness that could be tailored in related technologies. (C) 2013 AIP Publishing LLC.
Soft and hard natures of Nd2Fe14B permanent magnet explored by first-order-reversal-curves
(2014-12-01)
Chen, Po-An
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Yang, Chao-Yao
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Chang, Shu-Jui
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Lee, Min-Han
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Tang, Nai-Kuang
Two commercial Nd2Fe14B samples, MQP-B and sintered-NdFeB were investigated using synchrotron based x-ray diffraction and first-order-reversal-curves (FORCs). Despite differing in magnetic and structural properties, the two samples were found to comprise two major ferromagnetic components in FORCs. For the sintered-NdFeB case, the soft component may originate from the intrinsically soft Nd-f site which was coupled with its local Fe atomic environment that differs in magnetic anisotropy from the Nd-g site (intrinsically hard). It may directly originate from the Nd-rich phase or microstructural imperfection, while the former possibility (Nd-f sire) appears greater than the latter While for the MQP-B, the minor second phase resulting from high structural disorder was likely in charge of the presence of the soft component. Sophisticated FORCs analyses revealed the natures of the soft and hard components, soft hard coupling and switching reversibility of the two cases, irrespective of the origins of their two components. This provides insights to the origin of magnetic stability and reversal dynamics of Nd2Fe14B that have not been fully understood by conventional magnetic analyses. The coexistence of the two components led to an incoherent reversal undermining the magnetic stability of Nd2Fe14B. This is a fundamental problem as to why the performance extremity can only be improved finitely through extrinsic tuning. From FORCs simulation we understand that the soft-hard coupling was moderate in a real Nd2Fe14B compound. A stronger soft-hard coupling is necessary to conquer the anisotropic competition to enable a coherent reversal that will promote the magnetic hardness. (C) 2014 Elsevier B.V. All rights reserved,