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We study tunable optomechanically induced transparency by controlling the dark-mode effect induced by two mechanical modes coupled to a common cavity field. This is realized by introducing a phase-dependent phonon-exchange interaction, which is used to form a loop-coupled configuration. Combining this phase-dependent coupling with the optomechanical interactions, the dark-mode effect can be controlled by the quantum interference effect. In particular, the dark-mode effect in this two-mechanical-mode optomechanical system can lead to a double-amplified optomechanically induced transparency (OMIT) window and a higher efficiency of the second-order sideband in comparison with the standard optomechanical system. This is because the effective mechanical decay rate related to the linewidth of the OMIT window becomes a twofold increase in the weak-coupling limit. When the dark-mode effect is broken, controllable double transparency windows appear and the second-order sideband, as well as the light delay or advance, is significantly enhanced. For an N-mechanical-mode optomechanical system, we find that in the presence of the dark-mode effect, the amplification multiple of the linewidth of the OMIT window is nearly proportional to the number of mechanical modes, and that the OMIT with a single window becomes the one with N tunable windows by breaking the dark-mode effect. The study will be useful in optical information storage within a large-frequency bandwidth and multichannel optical communication based on optomechanical systems., 14 pages, 7 figures

In this study, laboratory-scale magnetic flocculation systems were set up and the optimal coagulant and flocculent dosage, magnetic seed immersion, pH, stirring intensity, and precipitation time were all evaluated. A total of 729 expansion reaction conditions were generated, and 700 of the expansion reaction conditions were used to train a back-propagation neural network (BPNN) and general regression neural network (GRNN). The other 29 conditions were used to verify the networks’ regression ability. The optimum coagulant was poly-aluminum chloride at a dosage of 100 mg/L; the optimum flocculent was anionic polyacrylamide at a dosage of 4 mg/L; the optimum size of the magnetic seed was 200 mesh at a dosage of 1 g/L; and the optimum stirring intensities were 300 r/min for the coagulation tank, 200 r/min for the mixing tank, and 100 r/min for the flocculation tank. Comparing BPNN and GRNN, the GRNN’s regression performance better matched the relationship between the reaction conditions and results.

A series of manganese oxide catalysts loaded on thermally modified Dolomite-palygorskite clay (MnOx/M-DPC) were synthesized by adopting impregnation, precipitation and citric acid methods and investigated for the selective catalytic reduction of NOx by NH3 (NH3-SCR) at low temperature. The results showed that the precipitated sample was more active (with 83% NOx conversion at 120 °C) by comparing it with the other MnOx/M-DPC samples prepared by impregnation and citric acid methods. Almost all NOx were completely removed by using this sample in the studied temperature range between 180 °C and 300 °C. In addition, all samples offered high N2 selectivity (> 94%) in the whole temperature range, and their SCR performance were affected by H2O introduction and NO oxidation to NO2 in the absence of NH3, but dependent on reaction temperature. The studied samples were characterized by specific surface area, pore size distribution, X-ray diffraction (XRD), Scanning electron microscope (SEM), electron diffraction spectra (EDS) and X-ray photoelectron spectroscopy (XPS). The results of specific surface area and pore size distribution suggested that the surface area and pore structure of catalysts obtained from various preparation methods were different, resulting in great difference in the catalytic performance. The irregular multi-modal mesoporous structure played a crucial role in the high catalytic activity over the precipitated MnOx/M-DPC sample. In addition, the results from XRD, SEM, EDS and XPS analyses indicated that Mn3O4 phase, good dispersion of manganese oxide, higher concentration of Mn as well as higher surface Mn4 + species, high lattice oxygen content on the surface were also beneficial to the superior catalytic efficiency of the precipitated sample.

In this study, the oxidation kinetics, mechanisms, effects and products of metalaxyl (MTL) by two different S(IV)-based processes (i.e., Mn(VII)/S(IV) and Cr(VI)/S(IV)) were systematically investigated and compared. The results showed that the concentration of S(IV) was primarily responsible for driving Mn(VII) and Cr(VI) consumption with a measured second order rate constant (k), and the k of Mn(VII) was less dependent on pH than that of Cr(VI), ranging from 104.7 M−1 s−1 to 104.9 M−1 s−1 and 10−0.4 M−1 s−1 to 101.6 M−1 s−1, respectively. Moreover, the reaction stoichiometry of [Cr(VI)]0:[S(IV)]0 was estimated to about 1:30–1:40 in the presence of O2, which was significantly different from the molar ratio of [Mn(VII)]0 to [S(IV]0 (1:5–1:10). Sulfur radical (SO4 −) was determined to be a major active oxidant in both the systems based on the chemical probes and radical scavenging experiments. Besides, carbonate and chloride have greater inhibitory effects than other coexisting solutes (e.g., nitrate and organic matter) because of the higher reactivity with radical species. In addition, the proposed degradation of MTL mainly proceeded through hydroxylation, demethylation, and carboxylation reactions. All these results indicated that Mn(VII) outperforms Cr(VI) in the activation of S(IV) auto-oxidation for the degradation of MTL. An extremely fast degradation rate, high mineralization and strong adaptation to the water matrices were observed in the process, which were attributed to ultra-fast production of high concentrations of radical species such as SO4 −, HO and high valent manganese intermediates (e.g., Mn(III) and Mn(V)).

We propose a domino-cooling method to realize simultaneous ground-state cooling of a coupled mechanical-resonator chain through an optomechanical cavity working in the unresolved-sideband regime. This domino-effect cooling is realized by combining the cold-damping feedback on the first mechanical resonator with nearest-neighbor couplings between other neighboring mechanical resonators. We obtain analytical results for the effective susceptibilities, noise spectra, final mean phonon numbers, and cooling rates of these mechanical resonators, and find the optimal-cooling condition for these resonators. Particularly, we analyze a two-mechanical-resonator case and find that by appropriately engineering either the laser power or the feedback, a flexible switch between symmetric and asymmetric ground-state cooling can be achieved. This could be used for preparing symmetric quantum states in mechanical systems. We also simulate the cooling performance of a coupled $N$-mechanical-resonator chain and confirm that these resonators can be simultaneously cooled to their quantum ground states in the unresolved-sideband regime. Under proper parameter conditions, the cooling of the mechanical-resonator chain shows a temperature gradient along the chain. This study opens a route to quantum manipulation of multiple mechanical resonators in the bad-cavity regime., Comment: 12 pages, 7 figures

The simultaneous ground-state cooling of multiple degenerate or near-degenerate mechanical modes coupled to a common cavity-field mode has become an outstanding challenge in cavity optomechanics. This is because the dark modes formed by these mechanical modes decouple from the cavity mode and prevent extracting energy from the dark modes through the cooling channel of the cavity mode. Here we propose a universal and reliable dark-mode-breaking method to realize the simultaneous ground-state cooling of two degenerate or nondegenerate mechanical modes by introducing a phasedependent phonon-exchange interaction, which is used to form a loop-coupled configuration. We find an asymmetrical cooling performance for the two mechanical modes and expound this phenomenon based on the nonreciprocal energy transfer mechanism, which leads to the directional flow of phonons between the two mechanical modes. We also generalize this method to cool multiple mechanical modes. The physical mechanism in this cooling scheme has general validity and this method can be extended to break other dark-mode and dark-state effects in physics., Comment: 42 pages, 21 figures

The absorption of single-cavity and double-cavity optomechanical systems and periodic optomechanical lattices has previously been investigated extensively. In this paper, we present the absorption of a nonperiodic cavity chain, where the absorption value on the resonance point shows switchable dips or peaks, according to whether the optomechanical interaction is at an odd or even-numbered position in the chain. Meanwhile, the value of absorption due to the optomechanical interaction varies with the number of the bare cavities. The calculated results may have some novel applications, such as detecting the position of the movable mirror in a long cavity chain, which would be useful in quantum information processing based on optomechanical systems.

The occurrence of antibiotics in the environment has recently raised serious concern regarding their potential threat to aquatic ecosystem and human health. In this study, the magnetic ion exchange (MIEX) resin was applied for removing three commonly-used antibiotics, sulfamethoxazole (SMX), tetracycline (TCN) and amoxicillin (AMX) from water. The results of batch experiments show that the maximum adsorption capacities on the MIEX resin for SMX, TCN and AMX were 789.32, 443.18 and 155.15μg/mL at 25°C, respectively, which were 2-7 times that for the powdered activated carbon. The adsorption kinetics of antibiotics on the MIEX resin could be simulated by the pseudo-second-order model (R2=0.99), and the adsorption isotherm data were well described by the Langmuir model (R2=0.97). Solution pH exhibited a remarkable impact on the adsorption process and the absorbed concentrations of the tested antibiotics were obtained around the neutral pH. The MIEX resin could be easily regenerated by 2mol/L NaCl solution and maintained high adsorption removal for the tested antibiotics after regeneration. Anion exchange mechanism mainly controlled the adsorption of antibiotic and the formation of hydrogen binding between the antibiotic and resin can also result in the increase of adsorption capacity. The high adsorption capacity, fast adsorption rate and prominent reusability make the MIEX resin a potential adsorbent in the application for removing antibiotics from water.

Vacuum ultraviolet (VUV) and ultraviolet (UV)/chlorine processes are regarded as two of many advanced oxidation processes (AOPs). Because of the similar cost of VUV/UV and UV lamps, a combination of VUV and UV/chlorine (i.e., VUV/UV/chlorine) may enhance the removal of organic pollutants in water but without any additional power input. In this paper, a mini-fluidic VUV/UV photoreaction system (MVPS) was developed for bench-scale experiments, which could emit both VUV (185 nm) and UV (254 nm) or solely UV beams with a nearly identical UV photon fluence. The photon fluence rates of UV and VUV output by the MVPS were determined to be 8.88 × 10(-4) and 4.93 × 10(-5) einstein m(-2) s(-1), respectively. The VUV/UV/chlorine process exhibited a strong enhancement concerning the degradation of methylene blue (MB, a model organic pollutant) as compared to the total performance of the VUV/UV and UV/chlorine processes, although the photon fluence of the VUV only accounted for 5.6% of that of the UV. An acidic pH favored MB degradation by the VUV/UV/chlorine process. The synergistic mechanism of the VUV/UV/chlorine process was mainly ascribed to the effective use of (•)OH for pollutant removal through formation of longer-lived secondary radicals (e.g., (•)OCl). This study demonstrates that the new VUV/UV/chlorine process, as an enhanced AOP, can be applied as a highly effective and energy-saving technology for small-scale water and wastewater treatment.

In this study, the performance of catalytic ozonation in the treatment of bio-treated coking wastewater (BCW) using pilot- and full-scale systems was investigated. Additionally, the removal efficiency of organic pollutants from BCW, the deactivation mechanism of MnxCe1-xO2/γ-Al2O3, and backflushing optimization for in-situ catalyst regeneration, which have not been previously investigated, were analysed. Results of the 12-month pilot scale experiments showed that catalytic ozonation resulted in the effective removal of organic pollutants when backflushing was applied as an in-situ catalyst regeneration strategy. The effluent chemical oxygen demand (COD) content decreased from 150 to 78 mg L−1, and remained below a discharge limitation of 80 mg L−1, and the stable COD removal efficiencies (from 56.0% to 47.9%) indicated that catalyst deactivation, which primarily resulted from the deposition of inorganic salts on the surface of the catalyst that limited interaction between ozone and active sites and/or prevented electrons transfer, was primarily inhibited by backflushing. The catalyst regeneration via in-situ air- and water-backflushing was attributed to the scrubbing, collision, and/or the loosing effect. Additionally, in the full-scale experiment, the catalytic ozonation process with in-situ alternative backflushing exhibited a stable COD removal efficiency (above 45.6%) for 885 days when water- and air-flushing strengths of 10 L m−2 s−1 and 15 L m−2 s−1, respectively, were applied with a 7-day regeneration interval. Therefore, the results of this study provide new insights into catalytic ozonation and support its engineering application in BCW treatment.

Optical nonreciprocity in a three-mode optomechanical system within a common optical reservoir is considered. It is found that optomechanically induced nonreciprocity is generated by the interference between the incoherent coupling induced by the common reservoir and the optomechanical coupling mediated by the interactions of two optical modes with a mechanical mode. There exist two symmetric nonreciprocal regimes that respectively correspond to the forward and backward photon transmissions, and the optical nonreciprocity for the relative phase φ between the optomechanical couplings is in opposite direction to that for the phase 2 π − φ . Additionally, it is shown that the optimal nonreciprocity as well as the nonreciprocal amplification can be achieved only by adjusting the optomechanical couplings. To compare nonreciprocity induced by incoherent coupling with that in the case of coherent coupling, we consider the optomechanically induced nonreciprocity created by interference between the optomechanical and direct couplings between the two optical modes. The nonreciprocal behaviors and their differences in these two cases are explained by using analytic findings.

Quantum manipulation of coupled mechanical resonators has become an important research topic in optomechanics because these systems can be used to study the quantum coherence effects involving multiple mechanical modes. A prerequisite for observing macroscopic mechanical coherence is to cool the mechanical resonators to their ground state. Here we propose a theoretical scheme to cool two coupled mechanical resonators by introducing an optomechanical interface. The final mean phonon numbers in the two mechanical resonators are calculated exactly and the results show that the ground-state cooling is achievable in the resolved-sideband regime and under the optimal driving. By adiabatically eliminating the cavity field in the large-decay regime, we obtain analytical results of the cooling limits, which show the smallest achievable phonon numbers and the parameter conditions under which the optimal cooling is achieved. Finally, the scheme is extended to the cooling of a chain of coupled mechanical resonators., 14 pages, 8 figures

The environmental risk controllability assessment system and its method of controlling volatile organic compounds (VOCs) during remediation of contaminated sites are established in this article based on soil vapor extraction (SVE) technology. According to the properties of VOCs and the technical and operational characteristics of the site remediation process, the environmental risk controllability index system includes environmental risk identification, risk source analysis, and risk assessment. Environmental risk management during site remediation was focused on technical control methods and engineering control technologies. Specifically, acceptance based on risk management was suitable for low-risk levels such as RRI3 and RRI4. Furthermore, control methods for high-level risk (RRI1 or RRI2) could be developed along with transformation and control, combined with the necessary emergency risk plan.

In order to obtain a high adsorption capacity for perchlorate, the epoxide-forming quaternary ammonium (EQA) compounds were chemically bonded onto granular activated carbon (GAC) surface by cationic reaction. The optimum preparation condition of the cationic GAC was achieved while applying softwood-based Gran C as the parent GAC, dosing EQA first at a pH of 12, preparation time of 48 h, preparation temperature of 50 °C, and mole ratio of EQA/oxygen groups of 2.5. The most favorable cationic GAC that had the QUAB360 pre-anchored exhibited the highest perchlorate adsorption capacity of 24.7 mg/g, and presented the longest bed volumes (3000 BV) to 2 ppb breakthrough during rapid small scale column tests (RSSCTs), which was 150 times higher than that for the pristine Gran C. This was attributed to its higher nitrogen amount (1.53 At%) and higher positive surface charge (0.036 mmol/g) at pH 7.5. Also, there was no leaching of the quaternary ammonium detected in the effluent of the RSSCTs, indicating there was no secondary pollution occurring during the perchlorate removal process. Overall, this study provides an effective and environmental-friendly technology for improving GAC perchlorate adsorption capacity for groundwater treatment.

We consider the probe absorption properties in a mechanically coupled optomechanical system in which the two coupled nanomechanical oscillators are driven by the time-dependent forces, respectively. It is found that the mechanical interaction splits the transparency window for a usual single-mode optomechanical system into two parts and then leads to appearance of the double optomechanically induced transparency. The distance between the two transparency positions (the frequency for the maximal transparency) is determined by the mechanical interaction amplitude. This can be explained by using optomechanical dressed-mode picture which is analogue to the interacting dark resonances in coherent atoms. When the mechanical resonators are driven by the external forces, the transparencies in the double-transparency spectrum can be increased into amplifications or be suppressed by tuning the amplitude of the forces. Additionally, it is shown that the double transparencies or the amplifications oscillate with the initial phases of the forces with a period of 2π. These investigations will be useful for more flexible controllability of multi-channel optical communication based on the optomechanical systems.

The squeezing transfer from a squeezed vacuum injected in one cavity to the output spectrum of the other cavity in an optomechanical system is investigated. By calculating the noise spectrum of the output field, it is found that two squeezing dips appear symmetrically located about the resonant point. Besides the contribution from the destructive interference between the noise fluctuation of the input field and its optomechanically modified one, the major part of the squeezing is transferred from the squeezed vacuum injected in the cavity. Additionally, it is shown that the adverse effects of the environment temperature on the output spectrum can be strongly suppressed by the injected squeezed field. This study can be useful in quantum communications via the optomechanical interface.

Polypyrrole modified activated carbon was used to remove sulfate from acid mine drainage water. The polypyrrole modified activated carbon created positively charged functionality that offered elevated sorption capacity for sulfate. The effects of the activated carbon type, approach of polymerization, preparation temperature, solvent, and concentration of oxidant solution over the sulfate adsorption capacity were studied at an array of initial sulfate concentrations. A hardwood based activated carbon was the more favorable activated carbon template, and this offered better sulfate removal than when using bituminous based activated carbon or oak wood activated carbon as the template. The hardwood-based activated carbon modified with polypyrrole removed 44.7 mg/g sulfate, and this was five times higher than for the pristine hardwood-based activated carbon. Various protocols for depositing the polypyrrole onto the activated carbon were investigated. When ferric chloride was used as an oxidant, the deposition protocol that achieved the most N+ atomic percent (3.35%) while also maintaining the least oxygen atomic percent (6.22%) offered the most favorable sulfate removal. For the rapid small scale column tests, when processing the AMD water, hardwood-based activated carbon modified with poly pyrrole exhibited 33 bed volume compared to the 5 bed volume of pristine activated carbons.

We consider the optomechanically induced transparency in the double quadratically coupled optomechanical cavities within a common reservoir, in which the two cavities are driven by the coupling fields. It is shown that the probe transparency is improved by increasing the coupling field (the left coupling field) applied on the probing cavity, but the transparency position (the probe frequency of the maximal transparency) is shifted to high frequency. The coupling field (the right coupling field) applied on the other quadratically coupled cavity can lead to a low-frequency shift for the transparency position, which can be used to fix the transparency position by adjusting the right coupling field. We get the quantitative findings that the transparency position is exactly determined by the intensity difference between the two coupling fields. On the other hand, it is found that when the two coupled optomechanical cavities interact with their common reservoir, the cross decay induced by the common reservoir can improve the probe transparency and widen the transparency window. Finally, the effects of the environment's temperature on the transparency are investigated. This will be useful in cooling the membrane, squeezing and entangling the output fields.

The cross-Kerr effects between the cavity and the mechanical oscillator in a parity-time symmetric optomechanical system are investigated. It is found that in the double-passive case there appears an asymmetric optomechanically induced transparency (OMIT) spectrum which is composed of a broad absorption peak located around the resonant point and a absorption line at the frequency position mainly determined by the Kerr interaction. The distinctive asymmetry induced by the cross-Kerr coupling is precisely demonstrated by the analytic findings. In the passive-active case, the resonance peaks in the OMIT spectrum are increased with the weak tunnel coupling, which is contrary to that in the double-passive case. When the tunnel coupling is increased up in the strong coupling region, the broad absorption peak and the absorption line in the OMIT spectrum are sequentially changed into the amplification ones, and the central amplification dip is split into two parts due to the normal mode splitting induced by the strong tunnel coupling. This can be used to realize a switching from absorption to amplification by only adjusting the tunnel interaction.

The absorption properties in double optomechanical cavities coupled by the photonic and phononic paths are investigated. The sideband absorption peaks and the transparency dips, located symmetrically around the resonant point, characterize the respective effects of the photonic and phononic interactions on the transparency spectra: the sideband absorption peaks move outward with increase of the photonic interaction due to the normal-mode splitting, and the distance between the two sideband transparency dips is determined by the phononic interaction strength. Meanwhile, the study reveals the competition and the harmonization between the photonic and phononic interactions. When simultaneously switching on the photonic and phononic paths, it is shown from the absorption spectra that the features of the interacting path with stronger strength dominate over the other one with weaker strength. Additionally, the transparency around the resonant point manifests the destructive interference between the photonic and phononic coupling paths when the strength of two paths are comparable. These findings display the flexible tunability of the transparency, and can be used to distinguish between the two quantum paths in the absorption spectrum.