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16 results on '"Su, S.-W."'

1. Rashba-type Spin-orbit Coupling in Bilayer Bose-Einstein Condensates

Author

Su, S. -W., Gou, S. -C., Sun, Q., Wen, L., Liu, W. -M., Ji, A. -C., Ruseckas, J., and Juzeliunas, G.

Subjects
Condensed Matter - Quantum Gases, Physics - Atomic Physics, Quantum Physics
Abstract

We explore a new way of producing the Rashba spin-orbit coupling (SOC) for ultracold atoms by using a two-component (spinor) atomic Bose-Einstein condensate (BEC) confined in a bilayer geometry. The SOC of the Rashba type is created if the atoms pick up a {\pi} phase after completing a cyclic transition between four combined spin-layer states composed of two spin and two layer states. The cyclic coupling of the spin-layer states is carried out by combining an intralayer Raman coupling and an interlayer laser assisted tunneling. We theoretically determine the ground-state phases of the spin-orbit-coupled BEC for various strengths of the atom-atom interaction and the laser-assisted coupling. It is shown that the bilayer scheme provides a diverse ground-state phase diagram. In an intermediate range of the atom-light coupling two interlacing lattices of half- skyrmions and half-antiskyrmions are spontaneously created. In the strong-coupling regime, where the SOC of the Rashba-type is formed, the ground state represents plane-wave or standing-wave phases depending on the interaction between the atoms. A variational analysis is shown to be in a good agreement with the numerical results., Comment: 13 pages, 9 figures

Published
2016
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2. Position-dependent spin-orbit coupling for ultracold atoms

Author

Su, S. -W., Gou, S. -C., Liu, I. -K., Spielman, I. B., Santos, L., Acus, A., Mekys, A., Ruseckas, J., and Juzeliūnas, G.

Subjects
Condensed Matter - Quantum Gases, Physics - Atomic Physics, Quantum Physics
Abstract

We theoretically explore atomic Bose-Einstein condensates (BECs) subject to position-dependent spin-orbit coupling (SOC). This SOC can be produced by cyclically laser coupling four internal atomic ground (or metastable) states in an environment where the detuning from resonance depends on position. The resulting spin-orbit coupled BEC phase-separates into domains, each of which contain density modulations - stripes - aligned either along the x or y direction. In each domain, the stripe orientation is determined by the sign of the local detuning. When these stripes have mismatched spatial periods along domain boundaries, non-trivial topological spin textures form at the interface, including skyrmions-like spin vortices and anti-vortices. In contrast to vortices present in conventional rotating BECs, these spin-vortices are stable topological defects that are not present in the corresponding homogenous stripe-phase spin-orbit coupled BECs.

Published
2014
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3. Crystallized merons and inverted merons in the condensation of spin-1 Bose gases with spin-orbit coupling

Author

Su, S. -W., Liu, I. -K., Tsai, Y. -C., Liu, W. M., and Gou, S. -C.

Subjects
Condensed Matter - Quantum Gases
Abstract

The non-equilibrium dynamics of a rapidly quenched spin-1 Bose gas with spin-orbit coupling is studied. By solving the stochastic projected Gross-Pitaevskii equation, we show that crystallization of merons can occur in a spinor condensate of ^{87}Rb. Analytic form and stability of the crystal structure are given. Likewise, inverted merons can be created in a spin-polarized spinor condensate of ^{23}Na. Our studies provide a chance to explore the fundamental properties of meron-like matter., Comment: 5 pages, 6 figures

Published
2011
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4. Spontaneous Crystallization of Skyrmions and Fractional Vortices in the Fast-rotating and Rapidly-quenched Spin-1 Bose-Einstein Condensates

Author

Su, S. -W., Hsueh, C. -H., Liu, I. -K., Horng, T. -L., Tsai, Y. -C., Gou, S. -C., and Liu, W. M.

Subjects
Condensed Matter - Quantum Gases
Abstract

We investigate the spontaneous generation of crystallized topological defects via the combining effects of fast rotation and rapid thermal quench on the spin-1 Bose-Einstein condensates. By solving the stochastic projected Gross-Pitaevskii equation, we show that, when the system reaches equilibrium, a hexagonal lattice of skyrmions, and a square lattice of half-quantized vortices can be formed in a ferromagnetic and antiferromagnetic spinor BEC, respetively, which can be imaged by using the polarization-dependent phase-contrast method.

Published
2011
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5. Copper and Zinc Uptake by Pakchoi and Rice as Affected by Applying Manure Compost with Different Levels of Cu and Zn Concentrations

Author

Huang T. H., Su S. W., Chang H. Y., Huang C. C., and Chen Z. S.

Subjects
Cu, Zn, manure, compost, pakchoi, paddy rice, bioavailability, Environmental sciences, GE1-350
Abstract

Cu and Zn are frequently added to livestock diets as additives to increase feed efficiency and production. This practice resulted in the higher contents of Cu and Zn in excrement of livestock. The aim of this study is to evaluate the effect of Cu and Zn concentration of manure compost and its application rates on the production and quality of pakchoi and rice. The pot experiments were conducted and the six manure compost were applied at 3 rates (20, 40, and 80 ton/ha), including the control and chemical fertilizer treatments. Results showed that the yield of the crops was enhanced by the compost application, and the Cu and Zn concentration in the edible part of crops were in normal range (pakchoi: Cu 1.8-10.4 mg/kg, Zn 39-160 mg/kg; rice grain: Cu 0.6-4.0 mg/kg, Zn 58-79 mg/kg). The potential risk of long-term manure compost application on soil quality was also evaluated. The total Zn concentration in soils may reach the regulation standard after 22 years of manure compost application at the rate of 40 ton/ha/year.

Published
2013
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6. Position-dependent spin-orbit coupling for ultracold atoms

Author

Su, S.-W., Gou, S.-C., Liu, I.-K., Spielman, I.B., Santos, Luis, Acus, A., Mekys, A., Ruseckas, J., Juzeliunas, G., Su, S.-W., Gou, S.-C., Liu, I.-K., Spielman, I.B., Santos, Luis, Acus, A., Mekys, A., Ruseckas, J., and Juzeliunas, G.

Abstract

We theoretically explore atomic Bose-Einstein condensates (BECs) subject to position-dependent spin-orbit coupling (SOC). This SOC can be produced by cyclically laser coupling four internal atomic ground (or metastable) states in an environment where the detuning from resonance depends on position. The resulting spin-orbit coupled BEC (SOBEC) phase separates into domains, each of which contain density modulations-stripes-aligned either along the x or y direction. In each domain, the stripe orientation is determined by the sign of the local detuning. When these stripes have mismatched spatial periods along domain boundaries, non-trivial topological spin textures form at the interface, including skyrmions-like spin vortices and anti-vortices. In contrast to vortices present in conventional rotating BECs, these spin-vortices are stable topological defects that are not present in the corresponding homogenous stripe-phase SOBECs.

Published
2015

7. HVAC integrated control for energy saving and comfort enhancement

Author

Vakiloroava, V., Su, S. W., and Quang Ha

Abstract

The overall attainable reduction in energy consumption and enhancement of human comfort of Heating, Ventilating, and Air Conditioning (HVAC) systems are dependant on thermodynamic behavior of buildings as well as performance of HVAC components and device control strategies. In this paper by refining the models of HVAC components, the influence of integrated control of shading blinds and natural ventilation on HVAC system performance is discussed in terms of energy savings and human comfort. An actual central cooling plant of a commercial building in the hot and dry climate condition is used for experimental data collection, modeling and strategy testing. Subject to comfort constraints, interactions between the building's transient hourly load and system performance are considered to show how the system energy consumption varies at different control strategies. For validation, a holistic approach is proposed to integrate dynamic operations of shading devices with direct and indirect ventilation of a commercial building equipped with a central cooling plant. Simulation results are provided to show possibility of significant energy saving and comfort enhancement by implementing proper control strategies.

Published
2011

10. DUAL-WIDEBAND, MULTI-MONOPOLE-ANTENNA SYSTEM WITH A TRIANGULAR-CYLINDER SHIELDING WALL FOR WIRELESS, SURVEILLANCE-CAMERA APPLICATIONS.

Author

Chang, F. -S., Chen, W. -C., and Su, S. -W.

Subjects
MONOPOLE antennas, ANTENNAS (Electronics), WIRELESS LANs, ELECTRIC impedance, ANTENNA radiation patterns, ELECTROMAGNETIC fields
Abstract

A multi-monopole-antenna system capable of generating two wide operating bands with good input matching by a voltage standing wave ratio (VSWR) of 1.5 to cover the 2.4 GHz (2400-2484 MHz), 5.2 GHz (5150-5350 MHz), and 5.8 GHz (5725-5825 MHz) bands for wireless local area network (WLAN) applications is introduced. The design mainly comprised three, metal-plate monopole antennas symmetrically located on a main, hexagonal ground plane and backed by vertical, step-shaped grounds protruding thereon. The step- shaped grounds not only facilitated the attaining of wide impedance bandwidth but also good port isolation. In addition, directional antenna radiation was also produced. Further, a triangular-cylinder shielding wall was placed in the center of the main ground plane for integration of the wireless, surveillance-camera module into the proposed antenna system. Details of the design prototype are described and discussed in the article. [ABSTRACT FROM AUTHOR]

Published
2012
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11. COMPACT, PRINTED, STANDALONE PENTA-BAND ANTENNA FOR WWAN OPERATION.

Author

Su, S.-W. and Chang, Y.-W.

Subjects
MONOPOLE antennas, WIDE area networks, WIRELESS communications, INTRANETS (Computer networks), RADIATION
Abstract

A standalone, printed monopole antenna with a two-branch shorting strip and a grounding wire to achieve a small size and yet multi-band operation for penta-band wireless wide area network (WWAN) operation (824-960/1710-2170 MHz) is presented. The antenna was formed on a low-cost, single-layered dielectric substrate with the dimensions 10mm x 50 mm. By applying the proposed grounding wire and the dual-shorting strip, two resonant modes in close proximity in the antenna's lower band were obtained to cover the GSM850/900 operation. Further, the proposed shorting strip led to two additional, higher-order resonance excitation at about 1700 and 1800MHz to assist in the formation of a wide upper band to cover the GSM1800/1900/UMTS operation. The proposed antenna also showed good radiation properties. Details of the design are described and discussed in the article. [ABSTRACT FROM AUTHOR]

Published
2012

12. A COMPACT, PLANAR PLATE-TYPE ANTENNA FOR 2.4/5.2/5.8-GHz TRI-BAND WLAN OPERATION.

Author

Lee, C.-T., Su, S.-W., and Chang, F.-S.

Subjects
ANTENNAS (Electronics), WIRELESS LANs, DIPOLE antennas, SIGNAL processing, COAXIAL cables
Abstract

A novel, tri-band, planar plate-type antenna made of a compact metal plate for wireless local area network (WLAN) applications in the 2.4GHz (2400-2484MHz), 5.2GHz (5150- 5350MHz), and 5.8GHz (5725-5825MHz) bands is presented. The antenna was designed in a way that the operating principle includes dipole and loop resonant modes to cover the 2.4/5.2 and 5.8GHz bands, respectively. The antenna comprises a larger radiating arm and a smaller loop radiating arm, which are connected to each other at the signal ground point. The antenna can easily be fed by using a 50 Ω mini-coaxial cable and shows good radiation performance. Details of the design are described and discussed in the article. [ABSTRACT FROM AUTHOR]

Published
2011
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16. Microgrid state estimation and control using Kalman filter and semidefinite programming technique

Author

Rana, M. M., Li Li, and Su, S. W.

Abstract

The design of environment-friendly microgrids at the smart distribution level requires a stable behaviour for multiple state operations. This paper develops a Kalman filter based optimal feedback control method for the microgrid state estimation and stabilization. First, the microgrid is modelled by a discrete-time state space equation. Then the cost-effective smart sensors are deployed in order to obtain the required system information. From the communication point of view, the recursive systematic convolution code is adopted to add the redundancy in the system. At the end, the soft output Viterbi decoder is used to recover the system information from the noisy measurements and transmission uncertainties. Thereafter, the Kalman filter is utilized to estimate the system states, which acts as a precursor for applying the control algorithm. Finally, this paper proposes an optimal feedback control method to stabilize the microgrid based on semidefinite programming. The performance of the proposed approach is demonstrated by extensive numerical simulations.

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