R-3 Repository :: Browsing by Author "Zhang, Y."

Browsing by Author "Zhang, Y."

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A Modified Predictor-Corrector Algorithm for Locating Weighted Centers in Linear Programming
(1992-06) Zhang, Y.; El-Bakry, A.S.
In certain applications of linear programming, some particular solutions called the weighted centers of the solution set are often desired, giving rise to the need of algorithms capable of locating such centers. In this note, we modify the Mizuno-Todd-Ye predictor-corrector algorithm so that the modified algorithm is guaranteed to converge to the weighted center for given weights. The key idea is to ensure that iterates remain in a sequence of shrinking neighborhoods of the weighted central path. The modified algorithm also possesses polynomiality and superlinear convergence.
A next-generation liquid xenon observatory for dark matter and neutrino physics
(IOP Publishing, 2022) Aalbers, J.; AbdusSalam, S.S.; Abe, K.; Aerne, V.; Agostini, F.; Maouloud, S. Ahmed; Akerib, D.S.; Akimov, D.Y.; Akshat, J.; Musalhi, A.K. Al; Alder, F.; Alsum, S.K.; Althueser, L.; Amarasinghe, C.S.; Amaro, F.D.; Ames, A.; Anderson, T.J.; Andrieu, B.; Angelides, N.; Angelino, E.; Angevaare, J.; Antochi, V.C.; Martin, D. Antón; Antunovic, B.; Aprile, E.; Araújo, H.M.; Armstrong, J.E.; Arneodo, F.; Arthurs, M.; Asadi, P.; Baek, S.; Bai, X.; Bajpai, D.; Baker, A.; Balajthy, J.; Balashov, S.; Balzer, M.; Bandyopadhyay, A.; Bang, J.; Barberio, E.; Bargemann, J.W.; Baudis, L.; Bauer, D.; Baur, D.; Baxter, A.; Baxter, A.L.; Bazyk, M.; Beattie, K.; Behrens, J.; Bell, N.F.; Bellagamba, L.; Beltrame, P.; Benabderrahmane, M.; Bernard, E.P.; Bertone, G.F.; Bhattacharjee, P.; Bhatti, A.; Biekert, A.; Biesiadzinski, T.P.; Binau, A.R.; Biondi, R.; Biondi, Y.; Birch, H.J.; Bishara, F.; Bismark, A.; Blanco, C.; Blockinger, G.M.; Bodnia, E.; Boehm, C.; Bolozdynya, A.I.; Bolton, P.D.; Bottaro, S.; Bourgeois, C.; Boxer, B.; Brás, P.; Breskin, A.; Breur, P. A.; Brew, C.A.J.; Brod, J.; Brookes, E.; Brown, A.; Brown, E.; Bruenner, S.; Bruno, G.; Budnik, R.; Bui, T.K.; Burdin, S.; Buse, S.; Busenitz, J.K.; Buttazzo, D.; Buuck, M.; Buzulutskov, A.; Cabrita, R.; Cai, C.; Cai, D.; Capelli, C.; Cardoso, J.M.R.; Carmona-Benitez, M.C.; Cascella, M.; Catena, R.; Chakraborty, S.; Chan, C.; Chang, S.; Chauvin, A.; Chawla, A.; Chen, H.; Chepel, V.; Chott, N.I.; Cichon, D.; Chavez, A. Cimental; Cimmino, B.; Clark, M.; Co, R.T.; Colijn, A.P.; Conrad, J.; Converse, M.V.; Costa, M.; Cottle, A.; Cox, G.; Creaner, O.; Garcia, J.J. Cuenca; Cussonneau, J.P.; Cutter, J.E.; Dahl, C.E.; D’Andrea, V.; David, A.; Decowski, M.P.; Dent, J.B.; Deppisch, F.F.; Viveiros, L. de; Gangi, P. Di; Giovanni, A. Di; Pede, S. Di; Dierle, J.; Diglio, S.; Dobson, J.E.Y.; Doerenkamp, M.; Douillet, D.; Drexlin, G.; Druszkiewicz, E.; Dunsky, D.; Eitel, K.; Elykov, A.; Emken, T.; Engel, R.; Eriksen, S.R.; Fairbairn, M.; Fan, A.; Fan, J.J.; Farrell, S.J.; Fayer, S.; Fearon, N.M.; Ferella, A.; Ferrari, C.; Fieguth, A.; Fieguth, A.; Fiorucci, S.; Fischer, H.; Flaecher, H.; Flierman, M.; Florek, T.; Foot, R.; Fox, P.J.; Franceschini, R.; Fraser, E.D.; Frenk, C.S.; Frohlich, S.; Fruth, T.; Fulgione, W.; Fuselli, C.; Gaemers, P.; Gaior, R.; Gaitskell, R.J.; Galloway, M.; Gao, F.; Garcia, I. Garcia; Genovesi, J.; Ghag, C.; Ghosh, S.; Gibson, E.; Gil, W.; Giovagnoli, D.; Girard, F.; Glade-Beucke, R.; Glück, F.; Gokhale, S.; Gouvêa, A. de; Gráf, L.; Grandi, L.; Grigat, J.; Grinstein, B.; Grinten, M.G.D. van der; Grössle, R.; Guan, H.; Guida, M.; Gumbsheimer, R.; Gwilliam, C. B.; Hall, C.R.; Hall, L.J.; Hammann, R.; Han, K.; Hannen, V.; Hansmann-Menzemer, S.; Harata, R.; Hardin, S.P.; Hardy, E.; Hardy, C.A.; Harigaya, K.; Harnik, R.; Haselschwardt, S.J.; Hernandez, M.; Hertel, S.A.; Higuera, A.; Hils, C.; Hochrein, S.; Hoetzsch, L.; Hoferichter, M.; Hood, N.; Hooper, D.; Horn, M.; Howlett, J.; Huang, D.Q.; Huang, Y.; Hunt, D.; Iacovacci, M.; Iaquaniello, G.; Ide, R.; Ignarra, C.M.; Iloglu, G.; Itow, Y.; Jacquet, E.; Jahangir, O.; Jakob, J.; James, R.S.; Jansen, A.; Ji, W.; Ji, X.; Joerg, F.; Johnson, J.; Joy, A.; Kaboth, A.C.; Kalhor, L.; Kamaha, A.C.; Kanezaki, K.; Kar, K.; Kara, M.; Kato, N.; Kavrigin, P.; Kazama, S.; Keaveney, A.W.; Kellerer, J.; Khaitan, D.; Khazov, A.; Khundzakishvili, G.; Khurana, I.; Kilminster, B.; Kleifges, M.; Ko, P.; Kobayashi, M.; Kodroff, D.; Koltmann, G.; Kopec, A.; Kopmann, A.; Kopp, J.; Korley, L.; Kornoukhov, V.N.; Korolkova, E.V.; Kraus, H.; Krauss, L.M.; Kravitz, S.; Kreczko, L.; Kudryavtsev, V.A.; Kuger, F.; Kumar, J.; Paredes, B. López; LaCascio, L.; Laha, R.; Laine, Q.; Landsman, H.; Lang, R.F.; Leason, E.A.; Lee, J.; Leonard, D.S.; Lesko, K.T.; Levinson, L.; Levy, C.; Li, I.; Li, S.C.; Li, T.; Liang, S.; Liebenthal, C.S.; Lin, J.; Lin, Q.; Lindemann, S.; Lindner, M.; Lindote, A.; Linehan, R.; Lippincott, W.H.; Liu, X.; Liu, K.; Liu, J.; Loizeau, J.; Lombardi, F.; Long, J.; Lopes, M.I.; Asamar, E. Lopez; Lorenzon, W.; Lu, C.; Luitz, S.; Ma, Y.; Machado, P.A.N.; Macolino, C.; Maeda, T.; Mahlstedt, J.; Majewski, P.A.; Manalaysay, A.; Mancuso, A.; Manenti, L.; Manfredini, A.; Mannino, R.L.; Marangou, N.; March-Russell, J.; Marignetti, F.; Undagoitia, T. Marrodán; Martens, K.; Martin, R.; Martinez-Soler, I.; Masbou, J.; Masson, D.; Masson, E.; Mastroianni, S.; Mastronardi, M.; Matias-Lopes, J.A.; McCarthy, M.E.; McFadden, N.; McGinness, E.; McKinsey, D.N.; McLaughlin, J.; McMichael, K.; Meinhardt, P.; Menéndez, J.; Meng, Y.; Messina, M.; Midha, R.; Milisavljevic, D.; Miller, E.H.; Milosevic, B.; Milutinovic, S.; Mitra, S.A.; Miuchi, K.; Mizrachi, E.; Mizukoshi, K.; Molinario, A.; Monte, A.; Monteiro, C.M.B.; Monzani, M.E.; Moore, J.S.; Morå, K.; Morad, J.A.; Mendoza, J.D. Morales; Moriyama, S.; Morrison, E.; Morteau, E.; Mosbacher, Y.; Mount, B.J.; Mueller, J.; Murphy, A. St J.; Murra, M.; Naim, D.; Nakamura, S.; Nash, E.; Navaieelavasani, N.; Naylor, A.; Nedlik, C.; Nelson, H.N.; Neves, F.; Newstead, J.L.; Ni, K.; Nikoleyczik, J.A.; Niro, V.; Oberlack, U.G.; Obradovic, M.; Odgers, K.; O’Hare, C.A.J.; Oikonomou, P.; Olcina, I.; Oliver-Mallory, K.; Oranday, A.; Orpwood, J.; Ostrovskiy, I.; Ozaki, K.; Paetsch, B.; Pal, S.; Palacio, J.; Palladino, K.J.; Palmer, J.; Panci, P.; Pandurovic, M.; Parlati, A.; Parveen, N.; Patton, S.J.; Pěč, V.; Pellegrini, Q.; Penning, B.; Pereira, G.; Peres, R.; Perez-Gonzalez, Y.; Perry, E.; Pershing, T.; Petrossian-Byrne, R.; Pienaar, J.; Piepke, A.; Pieramico, G.; Pierre, M.; Piotter, M.; Pizzella, V.; Plante, G.; Pollmann, T.; Porzio, D.; Qi, J.; Qie, Y.; Qin, J.; Quevedo, F.; Raj, N.; Silva, M. Rajado; Ramanathan, K.; García, D. Ramírez; Ravanis, J.; Redard-Jacot, L.; Redigolo, D.; Reichard, S.; Reichenbacher, J.; Rhyne, C.A.; Richards, A.; Riffard, Q.; Rischbieter, G.R.C.; Rocchetti, A.; Rosenfeld, S. L.; Rosero, R.; Rupp, N.; Rushton, T.; Saha, S.; Salucci, P.; Sanchez, L.; Sanchez-Lucas, P.; Santone, D.; Santos, J.M.F. dos; Sarnoff, I.; Sartorelli, G.; Sazzad, A.B.M.R.; Scheibelhut, M.; Schnee, R.W.; Schrank, M.; Schreiner, J.; Schulte, P.; Schulte, D.; Eissing, H. Schulze; Schumann, M.; Schwemberger, T.; Schwenk, A.; Schwetz, T.; Lavina, L. Scotto; Scovell, P.R.; Sekiya, H.; Selvi, M.; Semenov, E.; Semeria, F.; Shagin, P.; Shaw, S.; Shi, S.; Shockley, E.; Shutt, T.A.; Si-Ahmed, R.; Silk, J.J.; Silva, C.; Silva, M.C.; Simgen, H.; Šimkovic, F.; Sinev, G.; Singh, R.; Skulski, W.; Smirnov, J.; Smith, R.; Solmaz, M.; Solovov, V.N.; Sorensen, P.; Soria, J.; Sparmann, T.J.; Stancu, I.; Steidl, M.; Stevens, A.; Stifter, K.; Strigari, L.E.; Subotic, D.; Suerfu, B.; Suliga, A.M.; Sumner, T.J.; Szabo, P.; Szydagis, M.; Takeda, A.; Takeuchi, Y.; Tan, P.-L.; Taricco, C.; Taylor, W.C.; Temples, D.J.; Terliuk, A.; Terman, P.A.; Thers, D.; Thieme, K.; Thümmler, T.; Tiedt, D.R.; Timalsina, M.; To, W.H.; Toennies, F.; Tong, Z.; Toschi, F.; Tovey, D.R.; Tranter, J.; Trask, M.; Trinchero, G.C.; Tripathi, M.; Tronstad, D.R.; Trotta, R.; Tsai, Y.D.; Tunnell, C.D.; Turner, W.G.; Ueno, R.; Urquijo, P.; Utku, U.; Vaitkus, A.; Valerius, K.; Vassilev, E.; Vecchi, S.; Velan, V.; Vetter, S.; Vincent, A.C.; Vittorio, L.; Volta, G.; Krosigk, B. von; Piechowski, M. von; Vorkapic, D.; Wagner, C.E.M.; Wang, A.M.; Wang, B.; Wang, Y.; Wang, W.; Wang, J.J.; Wang, L.-T.; Wang, M.; Wang, Y.; Watson, J.R.; Wei, Y.; Weinheimer, C.; Weisman, E.; Weiss, M.; Wenz, D.; West, S.M.; Whitis, T.J.; Williams, M.; Wilson, M.J.; Winkler, D.; Wittweg, C.; Wolf, J.; Wolf, T.; Wolfs, F.L.H.; Woodford, S.; Woodward, D.; Wright, C.J.; Wu, V.H.S.; Wu, P.; Wüstling, S.; Wurm, M.; Xia, Q.; Xiang, X.; Xing, Y.; Xu, J.; Xu, Z.; Xu, D.; Yamashita, M.; Yamazaki, R.; Yan, H.; Yang, L.; Yang, Y.; Ye, J.; Yeh, M.; Young, I.; Yu, H.B.; Yu, T.T.; Yuan, L.; Zavattini, G.; Zerbo, S.; Zhang, Y.; Zhong, M.; Zhou, N.; Zhou, X.; Zhu, T.; Zhu, Y.; Zhuang, Y.; Zopounidis, J.P.; Zuber, K.; Zupan, J.
The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.
A Quadratically Convergent O(sqrt{n}L)-Iteration Algorithm for Linear Programming
(1991-08) Ye, Y.; Güller, O.; Tapia, R.A.; Zhang, Y.
Recently, Ye et al. proposed a large step modification of the Mizuno-Todd-Ye predictor-corrector interior-point algorithm for linear programming. They demonstrated that the large-step algorithm maintains theO (sqrt{n}L)-iteration complexity while exhibiting superlinear convergence of the duality gap to zero under the assumption that the iteration sequence converges, and quadratic convergence of the duality gap to zero under the assumption of nondegeneracy. In this paper we establish the quadratic convergence result without any assumption concerning the convergence of the iteration sequence or nondegeneracy. This surprising result, to our knowledge, is the first instance of polynomiality and superlinear (or quadratic) convergence for an interior-point algorithm which does not assume the convergence of the iteration sequence or nondegeneracy.
A Study of Indicators for Identifying Zero Variables in Interior-Point Methods
(1991-06) El-Bakry, A.; Tapia, R.A.; Zhang, Y.
The ability to identify zero variables early on in an iterative method is of considerable value and can be used to computational advantage. In this work we first give a formal presentation of the notion of indicators for identifying zero variables, and then study various indicators proposed in the literature for use with interior-point methods for linear programming. We present both theory and experimentation that speaks strongly against the use of the variables as indicators; perhaps the most frequently used indicator in the literature. Our study implies that an indicator proposed by Tapia in 1980 is particularly effective in the context of primal-dual interior-point methods.
A Superlinearly Convergent O(sqrt{n}L)-Iteration Algorithm for Linear Programming
(1991-07) Ye, Y.; Tapia, R.A.; Zhang, Y.
In this note we consider a large step modification of the Mizuno-Todd-Ye O (sqrt{n}L) predictor-corrector interior-point algorithm for linear programming. We demonstrate that the modified algorithm maintains its O (sqrt{n}L)-iteration complexity, while exhibiting superlinear convergence for general problems and quadratic convergence for nondegenerate problems. To our knowledge, this is the first construction of a superlinearly convergent algorithm with O (sqrt{n}L)-iteration complexity.
An Efficient TVL1 Algorithm for Deblurring Multichannel Images Corrupted by Impulsive Noise
(2008-08) Yang, J.; Zhang, Y.; Yin, W.
We extend the alternating minimization algorithm recently proposed in [38, 39] to the case of recovering blurry multichannel (color) images corrupted by impulsive rather than Gaussian noise. The algorithm minimizes the sum of a multichannel extension of total variation (TV), either isotropic or anisotropic, and a data fidelity term measured in the L1-norm. We derive the algorithm by applying the well-known quadratic penalty function technique and prove attractive convergence properties including finite convergence for some variables and global q-linear convergence. Under periodic boundary conditions, the main computational requirements of the algorithm are fast Fourier transforms and a low-complexity Gaussian elimination procedure. Numerical results on images with different blurs and impulsive noise are presented to demonstrate the efficiency of the algorithm. In addition, it is numerically compared to an algorithm recently proposed in [20] that uses a linear program and an interior point method for recovering grayscale images.
Experimental observation of incoherent-coherent crossover and orbital-dependent band renormalization in iron chalcogenide superconductors
(American Physical Society, 2015) Liu, Z.K.; Yi, M.; Zhang, Y.; Hu, J.; Yu, R.; Zhu, J.-X.; He, R.-H.; Chen, Y.L.; Hashimoto, M.; Moore, R.G.; Mo, S.-K.; Hussain, Z.; Si, Q.; Mao, Z.Q.; Lu, D.H.; Shen, Z.-X.
The level of electronic correlation has been one of the key questions in understanding the nature of superconductivity. Among the iron-based superconductors, the iron chalcogenide family exhibits the strongest electron correlations. To gauge the correlation strength, we performed a systematic angle-resolved photoemission spectroscopy study on the iron chalcogenide series Fe1+ySexTe1−x (0
FAUST - V. Hot methanol in the [BHB2007] 11 protobinary system; hot corino versus shock origin
(EDP Sciences, 2022) Vastel, C.; Alves, F.; Ceccarelli, C.; Bouvier, M.; Jiménez-Serra, I.; Sakai, T.; Caselli, P.; Evans, L.; Fontani, F.; Gal, R. Le; Chandler, C.J.; Svoboda, B.; Maud, L.; Codella, C.; Sakai, N.; Lόpez-Sepulcre, A.; Moellenbrock, G.; Aikawa, Y.; Balucani, N.; Bianchi, E.; Busquet, G.; Caux, E.; Charnley, S.; Cuello, N.; Simone, M. De; Dulieu, F.; Durân, A.; Fedele, D.; Feng, S.; Francis, L.; Hama, T.; Hanawa, T.; Herbst, E.; Hirota, T.; Imai, M.; Isella, A.; Johnstone, D.; Lefloch, B.; Loinard, L.; Maureira, M.; Murillo, N.M.; Mercimek, S.; Mori, S.; Menard, F.; Miotello, A.; Nakatani, R.; Nomura, H.; Oba, Y.; Ohashi, S.; Okoda, Y.; Ospina-Zamudio, J.; Oya, Y.; Pineda, J.E.; Podio, L.; Rimola, A.; Cox, D. Segura; Shirley, Y.; Testi, L.; Viti, S.; Watanabe, N.; Watanabe, Y.; Witzel, A.; Xue, C.; Zhang, Y.; Zhao, B.; Yamamoto, S.
Aims.Methanol is a ubiquitous species commonly found in the molecular interstellar medium. It is also a crucial seed species for the build-up of chemical complexity in star forming regions. Thus, understanding how its abundance evolves during the star formation process and whether it enriches the emerging planetary system is of paramount importance.Methods. We used new data from the ALMA Large Program FAUST (Fifty AU STudy of the chemistry in the disc/envelope system of solar protostars) to study the methanol line emission towards the [BHB2007] 11 protobinary system (sources A and B), where a complex structure of filaments connecting the two sources with a larger circumbinary disc has previously been detected.Results. Twelve methanol lines have been detected with upper energies in the [45–537] K range along with one ^{13^{CH_{3_{OH transition and one methyl formate (CH_{3_{OCHO) line blended with one of the methanol transitions. The methanol emission is compact (FWHM ~ 0.5″) and encompasses both protostars, which are separated by only 0.2″ (28 au). In addition, the overall methanol line emission presents three velocity components, which are not spatially resolved by our observations. Nonetheless, a detailed analysis of the spatial origin of these three components suggests that they are associated with three different spatial regions, with two of them close to 11B and the third one associated with 11A. A radiative transfer analysis of the methanol lines gives a kinetic temperature of [100–140] K, an H_{2_{volume density of 10^{6^{–10^{7^{cm^{−3^{and column density of a few 10^{18^{cm^{−2^{in all three components with a source size of ~0.15″. Thus, this hot and dense gas is highly enriched in methanol with an abundance as high as 10^{−5^{. Using previous continuum data, we show that dust opacity can potentially completely absorb the methanol line emission from the two binary objects.Conclusions. Although we cannot firmly exclude other possibilities, we suggest that the detected hot methanol is resulting from the shocked gas from the incoming filaments streaming towards [BHB2007] 11A and B, respectively. Higher spatial resolution observations are necessary to confirm this hypothesis.}}}}}}}}}}}}}}}}}}}}
FAUST - XIII. Dusty cavity and molecular shock driven by IRS7B in the Corona Australis cluster
(EDP Sciences, 2024) Sabatini, G.; Podio, L.; Codella, C.; Watanabe, Y.; Simone, M. De; Bianchi, E.; Ceccarelli, C.; Chandler, C. J.; Sakai, N.; Svoboda, B.; Testi, L.; Aikawa, Y.; Balucani, N.; Bouvier, M.; Caselli, P.; Caux, E.; Chahine, L.; Charnley, S.; Cuello, N.; Dulieu, F.; Evans, L.; Fedele, D.; Feng, S.; Fontani, F.; Hama, T.; Hanawa, T.; Herbst, E.; Hirota, T.; Isella, A.; Jímenez-Serra, I.; Johnstone, D.; Lefloch, B.; Gal, R. Le; Loinard, L.; Liu, H. B.; López-Sepulcre, A.; Maud, L. T.; Maureira, M. J.; Menard, F.; Miotello, A.; Moellenbrock, G.; Nomura, H.; Oba, Y.; Ohashi, S.; Okoda, Y.; Oya, Y.; Pineda, J.; Rimola, A.; Sakai, T.; Segura-Cox, D.; Shirley, Y.; Vastel, C.; Viti, S.; Watanabe, N.; Zhang, Y.; Zhang, Z. E.; Yamamoto, S.
Context.The origin of the chemical diversity observed around low-mass protostars probably resides in the earliest history of these systems.Aims. We aim to investigate the impact of protostellar feedback on the chemistry and grain growth in the circumstellar medium of multiple stellar systems. Methods. In the context of the ALMA Large Program FAUST, we present high-resolution (50 au) observations of CH3OH, H2CO, and SiO and continuum emission at 1.3 mm and 3 mm towards the Corona Australis star cluster.Results. Methanol emission reveals an arc-like structure at ∼1800 au from the protostellar system IRS7B along the direction perpendicular to the major axis of the disc. The arc is located at the edge of two elongated continuum structures that define a cone emerging from IRS7B. The region inside the cone is probed by H2CO, while the eastern wall of the arc shows bright emission in SiO, a typical shock tracer. Taking into account the association with a previously detected radio jet imaged with JVLA at 6 cm, the molecular arc reveals for the first time a bow shock driven by IRS7B and a two-sided dust cavity opened by the mass-loss process. For each cavity wall, we derive an average H 2 column density of ∼7 × 1021 cm−2, a mass of ∼9 × 10−3 M⊙, and a lower limit on the dust spectral index of 1.4.Conclusions. These observations provide the first evidence of a shock and a conical dust cavity opened by the jet driven by IRS7B, with important implications for the chemical enrichment and grain growth in the envelope of Solar System analogues.
FAUST - XVII. Super deuteration in the planet-forming system IRS 63 where the streamer strikes the disk
(EDP Sciences, 2024) Podio, L.; Ceccarelli, C.; Codella, C.; Sabatini, G.; Segura-Cox, D.; Balucani, N.; Rimola, A.; Ugliengo, P.; Chandler, C. J.; Sakai, N.; Svoboda, B.; Pineda, J.; Simone, M. De; Bianchi, E.; Caselli, P.; Isella, A.; Aikawa, Y.; Bouvier, M.; Caux, E.; Chahine, L.; Charnley, S. B.; Cuello, N.; Dulieu, F.; Evans, L.; Fedele, D.; Feng, S.; Fontani, F.; Hama, T.; Hanawa, T.; Herbst, E.; Hirota, T.; Jiménez-Serra, I.; Johnstone, D.; Lefloch, B.; Gal, R. Le; Loinard, L.; Liu, H. Baobab; López-Sepulcre, A.; Maud, L. T.; Maureira, M. J.; Menard, F.; Miotello, A.; Moellenbrock, G.; Nomura, H.; Oba, Y.; Ohashi, S.; Okoda, Y.; Oya, Y.; Sakai, T.; Shirley, Y.; Testi, L.; Vastel, C.; Viti, S.; Watanabe, N.; Watanabe, Y.; Zhang, Y.; Zhang, Z. E.; Yamamoto, S.
Context. Recent observations suggest that planet formation starts early, in protostellar disks of ≤105 yr, which are characterized by strong interactions with the environment, such as through accretion streamers and molecular outflows.Aims. To investigate the impact of such phenomena on the physical and chemical properties of a disk, it is key to understand what chemistry planets inherit from their natal environment. Methods. In the context of the ALMA large program Fifty AU Study of the chemistry in the disk/envelope system of solar-like protostars (FAUST), we present observations on scales from ∼1500 au to ∼60 au of H2CO, HDCO, and D2CO toward the young planet-forming disk IRS 63. Results. The H2CO probes the gas in the disk as well as in a large scale streamer (∼1500 au) impacting onto the southeast disk side. We detected for the first time deuterated formaldehyde, HDCO and D2CO, in a planet-forming disk and HDCO in the streamer that is feeding it. These detections allowed us to estimate the deuterium fractionation of H2CO in the disk: [HDCO]/[H2CO] ∼ 0.1 − 0.3 and [D2CO]/[H2CO] ∼ 0.1. Interestingly, while HDCO follows the H2CO distribution in the disk and in the streamer, the distribution of D2CO is highly asymmetric, with a peak of the emission (and [D]/[H] ratio) in the southeast disk side, where the streamer crashes onto the disk. In addition, D2CO was detected in two spots along the blue- and redshifted outflow. This suggests that (i) in the disk, HDCO formation is dominated by gas-phase reactions in a manner similar to H2CO, while (ii) D2CO is mainly formed on the grain mantles during the prestellar phase and/or in the disk itself and is at present released in the gas phase in the shocks driven by the streamer and the outflow. Conclusions. These findings testify to the key role of streamers in the buildup of the disk concerning both the final mass available for planet formation and its chemical composition.
Logarithmic Indicators and the Identification of Subgroups of Variables in Interior-Point Methods
(1993-09) El Bakry, A.S.; Tapia, R.A.; Zhang, Y.
The identification of certain groups of variables in optimization problems is an important issue and can be used to computational advantage. In this paper new logarithmic indicators are introduced. It is demonstrated that the logarithmic Tapia indicators have superior ability for identifying several subgroups of variables in the context of primal-dual interior-point methods.
Modeling radiation belt dynamics using a 3-D layer method code
(Wiley, 2017) Wang, C.; Ma, Q.; Tao, X.; Zhang, Y.; Teng, S.; Albert, J.M.; Chan, A.A.; Li, W.; Ni, B.; Lu, Q.; Wang, S.
A new 3-D diffusion code using a recently published layer method has been developed to analyze radiation belt electron dynamics. The code guarantees the positivity of the solution even when mixed diffusion terms are included. Unlike most of the previous codes, our 3-D code is developed directly in equatorial pitch angle (α0), momentum (p), and L shell coordinates; this eliminates the need to transform back and forth between (α0,p) coordinates and adiabatic invariant coordinates. Using (α0,p,L) is also convenient for direct comparison with satellite data. The new code has been validated by various numerical tests, and we apply the 3-D code to model the rapid electron flux enhancement following the geomagnetic storm on 17 March 2013, which is one of the Geospace Environment Modeling Focus Group challenge events. An event-specific global chorus wave model, an AL-dependent statistical plasmaspheric hiss wave model, and a recently published radial diffusion coefficient formula from Time History of Events and Macroscale Interactions during Substorms (THEMIS) statistics are used. The simulation results show good agreement with satellite observations, in general, supporting the scenario that the rapid enhancement of radiation belt electron flux for this event results from an increased level of the seed population by radial diffusion, with subsequent acceleration by chorus waves. Our results prove that the layer method can be readily used to model global radiation belt dynamics in three dimensions.
Nematic Energy Scale and the Missing Electron Pocket in FeSe
(American Physical Society, 2019) Yi, M.; Pfau, H.; Zhang, Y.; He, Y.; Wu, H.; Chen, T.; Ye, Z.R.; Hashimoto, M.; Yu, R.; Si, Q.; Lee, D.-H.; Dai, Pengcheng; Shen, Z.-X.; Lu, D.H.; Birgeneau, R.J.
Superconductivity emerges in proximity to a nematic phase in most iron-based superconductors. It is therefore important to understand the impact of nematicity on the electronic structure. Orbital assignment and tracking across the nematic phase transition prove to be challenging due to the multiband nature of iron-based superconductors and twinning effects. Here, we report a detailed study of the electronic structure of fully detwinned FeSe across the nematic phase transition using angle-resolved photoemission spectroscopy. We clearly observe a nematicity-driven band reconstruction involving dxz, dyz, and dxy orbitals. The nematic energy scale between dxz and dyz bands reaches a maximum of 50 meV at the Brillouin zone corner. We are also able to track the dxz electron pocket across the nematic transition and explain its absence in the nematic state. Our comprehensive data of the electronic structure provide an accurate basis for theoretical models of the superconducting pairing in FeSe.
On the Convergence of the Iteration Sequence in Primal-Dual Interior-Point Methods
(1991-08) Tapia, R.A.; Zhang, Y.; Ye, Y.
This research is concerned with the convergence of the iteration sequence generated by a primal-dual interior-point method for linear programming. It is known that this sequence converges when both the primal and the dual problems have unique solutions. However, convergence for general problems has been an open question now for quite some time. In this work we demonstrate that for general problems, under mild conditions, the iteration sequence converges.
On the Convergence of the Tapia Indicators in the Absence of Strict Complementarity
(1993-09) El Bakry, A.S.; Tapia, R.A.; Zhang, Y.
The convergence and the convergence rate of the Tapia indicators were established in El-Bakry and El-Bakry, Tapia and Zhang in the context of primal-dual interior-point method under the assumption of strict complementarity. In the current work we use a recent result of Monteiro and Wright to extend this theory to the case when strict complementarity does not hold.
On the Convergence Rate of Newton Interior-Point Methods in the Absence of Strict Complementarity
(1995-05) El-Bakry, A.S.; Tapia, R.A.; Zhang, Y.
In the absence of strict complementarity, Monteiro and Wright proved that the convergence rate for a class of Newton interior-point methods for linear complementarity problems is at best linear. They also established an upper bound of ¼ for the Q1 factor of the duality gap sequence when the steplengths converge to one. In the current paper, we prove that the Q1 factor of the duality gap sequence is exactly ¼. In addition, the convergence of the Tapia indicators is also discussed.
Superlinear and Quadratic Convergence of Primal-Dual Interior-Point Methods for Linear Programming Revisited
(1991-08) Zhang, Y.; Tapia, R.A.
Recently, Zhang, Tapia and Dennis produced a superlinear and quadratic convergence theory for the duality gap sequence in primal-dual interior-point methods for linear programming. In this theory, a basic assumption for superlinear convergence is the convergence of the iteration sequence; and a basic assumption for quadratic convergence is nondegeneracy. Several recent research projects have either used or built on this theory under one or both of the above mentioned assumptions. In this paper, we remove both assumptions from the Zhang-Tapia-Dennis theory.

Browsing by Author "Zhang, Y."

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