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[en] This thesis concerns two aspects of the relation between chiral symmetry breaking and confinement. The first aspect is the relations between different topological objects. The relation between monopoles and center vortices and the relation between instantons and monopoles are well established, in this thesis, we explore the relation between instantons (of finite temperature, called calorons) and center vortices in SU(2) and SU(3) gauge theory in Chapter 3 and Chapter 4, respectively. The second aspect is about the order parameters. The dual condensate introduced by E. Bilgici et al. is a novel observable that relates the order parameter of chiral symmetry breaking (chiral condensate) and confinement (Polyakov loop). In this thesis, we investigate the dual condensate on dynamical staggered fermions and explore a new dual operator: the dual quark density in Chapter 5.
[en] This paper investigates the noise sources in a single-ended class D amplifier (SECDA) and suggests corresponding ways to lower the noise. The total output noise could be expressed as a function of the gain and noises from different sources. According to the function, the bias voltage (VB) is a primary noise source, especially for a SECDA with a large gain. A low noise SECDA is obtained by integrating a filter into the SECDA to lower the noise of the VB. The filter utilizes an active resister and an 80 pF capacitance to get a 3 Hz pole. A noise test and fast Fourier transform analysis show that the noise performance of this SECDA is the same as that of a SECDA with an external filter. (semiconductor integrated circuits)
[en] Highlights: • H_2 addition eased cyclic variation of ethanol engine at unthrottled condition. • H_2-blended ethanol engine gains better efficiency at lean conditions. • Bmep of H_2-blended ethanol engine could be controlled by lean burning. • H_2 addition results in reduced exhaust loss and HC emissions. - Abstract: Concerning the throttling loss under part load conditions, it is feasible to further improve the engine thermal efficiency through operating the engine under the unthrottled condition and controlling its load by changing the excess air ratio. However, the narrow flammability of ethanol may lead the ethanol engine to encounter high cyclic variations under unthrottled and lean conditions. The addition of hydrogen is potentially helpful for solving this problem. In this test, the engine was run under an speed of 1400 rpm and unthrottled conditions. The hydrogen volume fractions in the intake were respectively kept at 0% and 3%. For a given hydrogen blending level, the ethanol flow rate was reduced to enable the engine to run under lean conditions. The results showed that the engine efficiency was improved with the blending of hydrogen. The highest thermal efficiency was improved by 6.07% after blending 3% hydrogen to the intake air. The addition of hydrogen could increase the engine torque output at lean conditions. Both cooling and exhaust losses were decreased after the hydrogen enrichment while adopting the lean combustion strategy. The hydrogen addition contributed to the extended lean burn limit and decreased cyclic variation under lean conditions. HC and CO emissions were decreased whereas NOx emissions were increased after the blending of hydrogen.
[en] In this paper, we prepared the binary Cu-Ti nanoglass films by composite deposition technique. The X-ray diffraction and atomic force microscopy indicate that as-synthesized films are consisted of nanoglass with apparent interfaces. The room temperature creep behavior and strain rate sensitivity of as-synthesized nanoglass films were investigated with nanoindetation and explored that Cu58Ti42 has a better creep-resistance property at room temperature but Cu42Ti58 has a more relaxed structure. The as-synthesized nanoglass films exhibit anomalously negative strain rate sensitivity.
[en] The big problems facing solar-assisted MED (multiple-effect distillation) desalination unit are the low efficiency and bulky heat exchangers, which worsen its systematic economic feasibility. In an attempt to develop heat transfer technologies with high energy efficiency, a mathematical study is established, and optimization analysis using FSP (field synergy principle) is proposed to support meaning of heat transfer enhancement of a pre-heater in a solar-assisted MED desalination unit. Numerical simulations are performed on fluid flow and heat transfer characteristics in a circular and elliptical tube bundle. The numerical results are analyzed using the concept of synergy angle and synergy number as an indication of synergy between velocity vector and temperature gradient fields. Heat transfer in elliptical tube bundle is enhanced significantly with increasing initial velocity of the feed seawater and field synergy number and decreasing of synergy angle. Under the same operating conditions of the two designs, the total average synergy angle is 78.97° and 66.31° in circular and elliptical tube bundle, respectively. Optimization of the pre-heater by FSP shows that in case of elliptical tube bundle design, the average synergy number and heat transfer rate are increased by 22.68% and 35.98% respectively. - Highlights: • FSP (field synergy principle) is used to investigate heat transfer enhancement. • Numerical simulations are performed in circular and elliptical tubes pre-heater. • Numerical results are analyzed using concept of synergy angle and synergy number. • Optimization of elliptical tube bundle by FSP has better performance
[en] Considering two assumptions on the molecular state, i.e. the S-wave anti Λ-K- and S-wave barΣ0-K- molecular states, we study the possible decays of anti NX(1625) that include anti NX(1625)→K- anti Λ,π0 anti p,ηanti p,π- anti n. Our results indicate that (1) if anti NX(1625) is the anti Λ-K- molecular state, K- anti Λ is the main decay mode of anti NX(1625), and the branching ratios of the rest decay modes are tiny; (2) if anti NX(1625) is the anti Σ0-K- molecular state, the branching ratio of anti NX(1625)→K- anti Λ is one or two orders smaller than that of anti NX(1625)→π0 anti p,ηanti p,π- anti n. Thus the search for anti NX(1625)→π0 anti p,ηanti p,π- anti n will be helpful to shed light on the nature of anti NX(1625). (orig.)
[en] In this paper the correlations dynamics of two atoms in the case of a micromaser-type system is investigated. Our results predict certain quasi-periodic collapse and revival phenomena for quantum discord and entanglement when the field is in Fock state and the two atoms are initially in maximally mixed state, which is a special separable state. Our calculations also show that the oscillations of the time evolution of both quantum discord and entanglement are almost in phase and they both have similar evolution behavior in some time range. The fact reveals the consistency of quantum discord and entanglement in some dynamical aspects. - Highlights: • The correlations dynamics of two atoms in the case of a micromaser-type system is investigated. • A quasi-periodic collapse and revival phenomenon for quantum discord and entanglement is reported. • A phenomenon of correlations revivals different from that of non-Markovian dynamics is revealed. • The oscillations of time evolution of both quantum discord and entanglement are almost in phase in our system. • Quantum discord and entanglement have similar evolution behavior in some time range
[en] Highlights: • H_2 addition avails improving thermal efficiency of n-butanol engines. • Lean burn limit of n-butanol engine is extended by H_2 addition. • H_2 addition shortens the n-butanol engine combustion duration. • HC and CO from the n-butanol engine are decreased by H_2 addition. - Abstract: n-Butanol is a feasible fuel candidate for spark-ignition engines. The current paper carried out an experiment to explore effects of hydrogen addition on further improving the performance of a n-butanol engine under the part load and lean conditions. Within the test, the engine intake pressure and speed were respectively kept at 61.5 kPa and 1400 rpm. The volumetric fractions of hydrogen in the total intake gas (hydrogen + air) were constrained at 0 and 3%, respectively. Under a certain hydrogen blending level, the global excess air ratio of in-cylinder charge which was changed from the stoichiometric to near the lean burn limit was adjusted by varying the n-butanol injection duration. The experimental results confirmed that the brake thermal efficiency was heightened and the lean burn limit was extended after the hydrogen addition. Besides, compared with the pure n-butanol combustion, the hydrogen enrichment enables the engine to gain dropped ignition delay and rapid combustion duration. Moreover, CO and HC from the pure n-butanol engine were reduced by the hydrogen addition. NOx were generally reduced when the excess air ratio was raised. This suggested that NOx from the hydrogen-enriched butanol engine could also be controlled by lean combustion.
[en] Highlights: • Au-Ag alloy nanoparticles modified ZnO films were prepared by a chemical method. • The alloy modified ZnO films exhibited higher photocatalytic activity. • The enhanced activity is related to the process of photocatalytic reaction. -- Abstract: Au–Ag alloy modified ZnO nanocomposite films have been prepared by sol–gel and spin-coating method. A visible-light absorption ability in the region of 450–550 nm due to the surface plasmon resonance effect of Au–Ag alloy was attained in the nanocomposite films along with a quasilinear relationship between the wavelength of the plasmon bands and Ag/Au precursor’s molar ratio. The photocatalytic activity of the nanocomposite films for Rhodamine B (RhB) degradation under UV-light irradiation is enhanced by alloy-modification, which is related to the process of photocatalytic reaction as confirmed by the TOC results. The enhancement degree of photocatalytic activity strongly depends on the Ag/Au molar ratio, among which the Ag0.1Au0.2/ZnO photocatalyst provided the highest photocatalytic activity that is more than 2 times higher than the pristine ZnO photocatalyst as fabricated and tested under the same conditions
[en] Element mercury (Hg"0) from flue gas is difficult to remove because of its low solubility in water and high volatility. A new technology for photooxidative removal of Hg"0 with an ultraviolet (UV)/H_2O_2 advanced oxidation process is studied in an efficient laboratory-scale bubble column reactor. Influence of several key operational parameters on Hg"0 removal efficiency is investigated. The results show that an increase in the UV light power, H_2O_2 initial concentration or H_2O_2 solution volume will enhance Hg"0 removal. The Hg"0 removal is inhibited by an increase of the Hg"0 initial concentration. The solution initial pH and pH conditioning agent have a remarkable synergistic effect. The highest Hg"0 removal efficiencies are achieved at the UV light power of 36W, H_2O_2 initial concentration of 0.125 mol/L, Hg"0 initial concentration of 25.3 - g/Nm"3, solution initial pH of 5, H_2O_2 solution volume of 600 ml, respectively. In addition, the O_2 percentage has little effect on the Hg"0 removal efficiency. This study is beneficial for the potential practical application of Hg"0 removal from coal-fired flue gas with UV/H_2O_2 advanced oxidation process