Ladder Type Research Articles

Research on the influence of labyrinth ring configuration on runaway characteristics of pump-turbines

The labyrinth ring can reduce the volume loss, mitigate the influence of force characteristics when the unit is operating, and ensure the efficient, safe, and stable operation of the unit. It is usually installed in the upper crown and lower ring of the pump-turbines runner. When the pump-turbines unit is running in runaway condition, the internal flow field structure is more complicated due to the different forms of labyrinth ring, so a new method needs to be adopted to analyze it from a new perspective. In this paper, a high head pump-turbines was selected as the research object. Combined with the experimental and numerical simulation results, the flow field structure corresponding to different upper labyrinth ring forms under runaway condition was analyzed and visualized in many aspects. The results show that the mixed type labyrinth ring can improve the undesirable flow regime in the runner and draft tube. The guide vanes under the serrated type labyrinth ring are more likely to be damaged due to greater force. The influence of the mixed type labyrinth ring on the radial force of the runner is only half that of the ladder type, which has a great advantage in maintaining the radial stability of the runner. The ladder and serrated type labyrinth ring can make the unit obtain less axial water thrust. In addition, based on the Finite-Time Lyapunov Exponent (FTLE) method, the flow field structure in the vaneless region was analyzed, and it was found that the labyrinth ring may affect the flow in the flow path of the guide vane and the vaneless region, thus causing the change of axial water thrust. This study reveals the internal flow and force characteristics of pump-turbines with different types of labyrinth rings under runaway condition and provides a technical reference for further understanding and studying the influence of labyrinth ring forms on pump-turbines performance and force characteristics.

The impact of land-use policy on household energy transition: Evidence from China's conversion of cropland to forestland program

The implementation of the Conversion of Cropland to Forestland Program (CCFP) has affected land-use patterns and biomass availability in China, consequently reshaping household energy consumption patterns. Utilizing data from the China Health and Retirement Longitudinal Study, this study employs a multinomial logit model to examine the impact of CCFP subsidies on household energy transitions, analyzed through the lenses of the energy ladder and energy types. Additionally, this study differentiates the effects of CCFP subsidies across households with varying characteristics. The empirical results reveal that, from the energy ladder perspective, CCFP subsidies hinder household energy transitions from biomass to both traditional and advanced commercial energy sources. From the energy type perspective, the subsidies impede transitions from biomass energy to coal, electricity, and LPG/LNG. These adverse effects may be attributed to the CCFP subsidy's role in increasing biomass supply and encouraging the use of biomass energy equipment. Moreover, the impacts of CCFP subsidies differ among households based on education level, location, and degree of engagement in farming. Overall, this study highlights the importance of considering land use policies and patterns in the formulation of energy policies aimed at promoting energy transition and alleviating energy poverty.

Laser enrichment of the 62Ni isotope for betavoltaic devices

We have studied the laser isotope separation of the 62Ni isotope using a three-step ladder type photoionization scheme. Using density matrix formalism, optimum conditions for the efficient separation of the 62Ni isotope have been derived. The optimum bandwidth of the excitation lasers has been found to be 200 MHz, 1200 MHz, and 1200 MHz for the enrichment of the 62Ni isotope. It has also been shown that it is possible to produce 75 mg/day of 90% enriched 62Ni using the optimized experimental operating parameters derived in this work. Upon irradiation of this enriched 62Ni isotopic mixture, it is possible to produce ∼19mg/day of the 63Ni isotope, which is sufficient to manufacture a 100 µW betavoltaic device each day.

Modulation on the twinning microstructure of Cu nanowires and its effect on oxidation behaviour

In this study, nanotwinned Cu nanowires (nt-Cu NWs) with varying twin characteristics were fabricated via pulse electrodeposition using a novel H3BO3 based electrolyte, and their impact on the oxidation process was investigated. The density and direction of twin lamellas within nt-Cu NW were adjusted by modifying the concentration of H3BO3 and the current density. Specifically, the average twinning thickness of Cu NWs increases from 26.7 nm to 424.5 nm as the concentration of H3BO3 increases from 0 g/L to 6 g/L. Moreover, three types of nt-Cu NWs with distinct twinning directions, namely waterfall type, bevel type, and ladder type were fabricated by changing the current density from −0.16 ASD to -1.6 ASD (vs Ag/AgCl). A nanowire Winand (NWW) diagram was established to describe the change of twin density and direction based on the difference between the growth behaviour of thin films and nanowires. The thermogravimetric analysis (TGA) and transmission electron microscopy (TEM) were further used to characterize the oxidation process of nt-Cu NWs. It revealed that the oxide thickness was closely related to the thickness of twin lamellas for the ladder type nt-Cu NWs. Also, the waterfall type Cu NWs exhibited a unique bead-chain like oxide morphology and a slower oxidation rate through the impact on the nanoscale Kirkendall effect (NKE). This study provides valuable insights into the controllable fabrication of nt-Cu NWs and Cu oxide NWs.

Temporal mode switching during polariton condensation

Multimode behavior plays a key role in a wide range of nonlinear optical phenomena. Multiple exciton-polariton modes can attain macroscopic population as observed in time-integrated measurements. Recent theory work has shown that, rather than being simultaneously in many modes, the population may temporally switch between the modes. However, the origin and the dynamics of multimode condensation has not been experimentally addressed. Here, we study the dynamics of exciton-polariton condensation into multiple modes of Gaussian defect microcavities filled with ladder type polymer gain material methyl-substituted ladder-type poly(p-phenylene) MeLPPP. We deploy a second-order cumulant model to simulate the dynamics of the system and find picosecond-timescale switching between condensate modes. By interferometric measurements we reveal the experimental signatures of such mode competition behaviour.

Dynamic Analysis on a Sub-Scaled Physical Model of a 4-Ton Truck Composite Ladder Type Cassis

Dynamic Analysis on a Sub-Scaled Physical Model of a 4-Ton Truck Composite Ladder Type Cassis

A rare femoral venous ladder encircling the femoral artery.

Femoral vein is increasingly used for venous cannulation procedures. Its anomalies in the femoral triangle could complicate these procedures. We report an extremely rare type of femoral venous ladder observed during routine cadaveric dissections. The variation was found in the left lower limb of an adult male cadaver aged 70 years. The femoral vein was a single vein in initial 3cm and terminal 4cm of its course. The middle part of the vein showed a duplication and a complex ladder pattern and encircled the femoral artery in the femoral triangle. This anomaly could predispose the vein for deep vein thrombosis. Knowledge of this anomaly could be useful during radiological procedures, femoral hernia repair and femoral triangle abscess and lymph node clearance.

Ladder type covalent organic frameworks constructed with natural units for the oxygen and carbon dioxide reduction reactions

Covalent organic frameworks (COFs) constructed with metallocyclophane units and organic linkers have found application as electrocatalytic systems. Nevertheless, the majority of linkers within COFs necessitate intricate design and synthesis. Conversely, the potential utilization of natural building blocks in COF construction remains largely unexplored. In this study, we constructed a natural COF (CoPc-EA-COF) by employing a natural phenolic molecule (ellagic acid (EA)) as the linker and Co-hexadecafluorophthalocyanine (CoPc) as blocks. This framework serves as an electrocatalyst for both the oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO2RR). The incorporation of EA units imparts the CoPc-EA-COF with elevated electronic conductivity, enhanced CO2 binding affinity, and superior reductive capacity compared to the controlled COF lacking EA units. The CoPc-EA-COF demonstrated enhanced performance in the ORR, as evidenced by a half-wave potential of 0.80 V. Moreover, it showcased elevated activity and selectivity in the CO2RR, achieving a maximum CO faradic efficiency of 97.32 % at − 0.8 V, along with turnover frequency (TOF) values reaching 2092 h−1. Theoretical calculations revealed that the presence of EA units facilitated the generation of OOH* and COOH* species, which are pivotal in the rate-determining stages of both ORR and CO2RR processes. The contribution of EA units significantly bolstered the overall catalytic activity.

Influence of phase diffusion on atomic grating in a three-level ladder-type system in lower-level microwave-driven scheme

In this paper, we consider a scheme for electromagnetically induced grating (EIG) in a three-level ladder-type system. A microwave field of finite bandwidth making a standing-wave pattern is applied on lower levels. In addition, we have also introduced an indirect pump in our system. A weak probe field is then applied to study the effects of phase diffusion associated with the microwave control field on EIG. It is found that phase diffusion associated with the strong microwave control field strongly affect the diffraction. We have incorporated the effect of different system parameters such as the strength of the microwave field, indirect pumping mechanism, interaction length, and detuning in the weak probe field. Interestingly, the stronger microwave control field retrieves the loss in diffraction intensity caused by the phase diffusion. Our results show that the introduction of detuning in the optical probe field results in the enhancement of the phase grating effect. Furthermore, our results show that an optimized indirect pump field can slightly improve the first-order diffraction intensities both in the absence and presence of phase diffusion.

Emergence of exotic electronic and magnetic phases upon electron filling in Na2BO3 (B = Ta, Ir, Pt, and Tl): a first-principles study.

Competition between spin-orbit interaction and electron correlations can stabilize a variety of non-trivial electronic and magnetic ground states. Using density functional theory calculations, here we show that different exotic electronic and magnetic ground states can be obtained by electron filling of the B-site cation in the Na2BO3 family of compounds (B = Ta, Ir, Pt and Tl). Electron filling leads to a Peierls insulator state with a direct band gap to j = 1/2 spin-orbit assisted Mott-insulator to band insulator and then to negative charge-transfer half-metal transition. The magnetic ground state also undergoes a transition from a non-magnetic state to a zigzag antiferromagnetic state, a re-entrant non-magnetic state and finally to a ferromagnetic state. The electron localization function shows a ladder type dimerization or Peierls instability in Na2TaO3. Maximally localized Wannier function calculations reveal delocalization of electrons through the eg orbitals, which form a π bond, and localization of electrons through the t2g orbitals, which form a σ bond, between the neighbouring tantalum ions. Na2TlO3 shows Stoner or band ferromagnetism due to the localized moments with up-spin on oxygen ligands created by the negative charge-transfer character, interacting via the down-spin itinerant electrons of the Tl 5d-O 2p hybridized band. These findings are significant for practical applications; for instance the direct band gap insulator Na2TaO3 shows potential for utilisation in solar cells, while Na2TlO3, which exhibits ferromagnetic half metallicity, holds promise for spintronic device applications.

Effect of neighboring transitions on the transformation between electromagnetically induced transparency and two-photon absorption

We report the effect of neighboring transitions on the transformation between electromagnetically induced transparency (EIT) and two-photon absorption (TPA) in an open multi-level ladder type system of 87Rb atom, the EIT peak exhibits split and asymmetric line feature owing to a neighboring transition line with a stronger relative hyperfine transition strength factor. By comparing the signals of the 5S1/2−5P3/2−5D3/2,5/2 transitions when increasing the power of the coupling laser, it can be found that avoiding neighboring effects due to Doppler broadening in a real atom, a lower decay rate of the excited state and a higher hyperfine transition strength ratio between the coupling and probe lasers are the crucial factors that enhance the transformation efficiency between TPA and EIT and the resolution of the switched spectra. Detailed theoretical calculations, considering the crucial factors, are consistent with the experimental results.

Low-carbon economy dispatching of integrated energy system with P2G-HGT coupling wind power absorption based on stepped Carbon emission trading

To improve the renewable energy consumption capacity of integrated energy system (IES) and reduce the carbon emission level of the system, a low-carbon economic dispatch model of IES with coupled power-to-gas (P2G) and hydrogen-doped gas units (HGT) under the stepped carbon trading mechanism is proposed. On the premise of wind power output uncertainty, the operating characteristics of the coupled electricity-to-gas equipment in the system are used to improve the wind abandonment problem of IES and increase its renewable energy consumption capacity; HGT is introduced to replace the traditional combustion engine for energy supply, and on the basis of refined P2G, a part of the volume fraction of hydrogen obtained from the production is extracted and mixed with methane to form a gas mixture for HGT combustion, so as to improve the low-carbon economy of the system. The ladder type carbon trading mechanism is introduced into IES to guide the system to control carbon emission behavior and reduce the carbon emission level of IES. Based on this, an optimal dispatching strategy is constructed with the economic goal of minimizing the sum of system operation cost, wind abandonment cost, carbon trading cost and energy purchase cost. After linearization of the established model and comparison analysis by setting different scenarios, the wind power utilization rate of the proposed model is increased by 24.5%, and the wind abandonment cost and CO2 emission are reduced by 86.3% and 10.5%, respectively, compared with the traditional IES system, which achieves the improvement of renewable energy consumption level and low carbon economy.

Custom-designed 3D printed feed spacers and TFN membranes with MIL-101(Fe) for water recovery by forward osmosis

ABSTRACT In this work, a dual-pronged approach– (i) novel thin-film nanocomposite polyether sulfone (PES) membrane with MIL-101 (Fe) and (ii) 3D printed spacers were explored to enhance water recovery by forward osmosis. The concentration of PES, pore former, draw solution, and MIL-101(Fe) was optimised for maximum pure water flux (PWF) and minimum specific reverse solute flux (SRSF). The best membrane exhibited a PWF of 7.52 Lm−2 h−1 and an SRSF of 0.33 ± 0.03 gL−1 using 1.5 M NaCl and DI water feed. The M22 membrane with the diamond-type spacer demonstrated a PWF of 2.53 Lm−2 h−1 and SRSF of 0.75 gL−1 for emulsified oily wastewater feed. The novel spacer design imparted significant turbulence to the feed flow and a lower foulant resistance of 1.3 m−1 as compared to the ladder type (1.5 m−1) or commercial spacer (1.7 m−1). This arrangement could recover 19% pure water within 12 h of operation (98% oil rejection) with a ∼ 94% flux recovery after hydraulic wash.

Development Law of Mining Fracture and Disaster Control Technology under Hard and Thick Magmatic Rock

Hard and thick magmatic rocks are widely distributed in many mining areas in China. Their fracture migration could cause mechanical effects such as the evolution of overburden structure, the sudden change of surface subsidence, and the transformation of accumulated elastic properties, inducing strong dynamic phenomena and even coupled geo dynamic disasters. In this study, by means of theoretical analysis and similar material simulation testing, the fracture of hard thick magmatic rock and the fracture development characteristics of stope are analyzed, and the following research results are obtained: (1) the mechanical model of an elastic foundation beam is established, and it is found that the bending moment in the middle of hard thick magmatic rock is greater than the bending moment at the end, and the magmatic rock first produces fractures in the middle, and then the initial fracture occurs. (2) The existence of hard thick magmatic rock blocks the development of fractures in the longitudinal direction. The bed separation and fracture undergo three processes of generation, development and closure. When the working face advances 160 m, 200 m and 270 m, the maximum bed separation shape on the strike section experiences triangle trapezoid crescent shape. (3) A ladder type fissure channel is formed above the working face side and the open cut hole side. When the working face is advanced 160 m, the ladder type fissure channel develops to the bottom of the hard thick rock layer, providing a ladder type channel for gas flow. After the hard thick rock layer is broken, a large number of elastic properties are released, which produces a strong impact force on the gas rich area of the bed separation, and also causes a sharp rise in the gas pressure of the bed separation at the bottom of the magmatic rock. A large amount of high-pressure gas in the bed separation space flows reversely to the working face along the ladder type gas channel, which can easily induce a gas outburst, coal and gas outburst or other disasters. (4) The correctness of the similar simulation experiment is verified by the field data. Technical measures for preventing gas outbursts in bed separation by surface drilling and pressure relief gas extraction are put forward. The research results have a certain guiding role for the prevention and control of dynamic disasters and the design of roadway support under the condition of a hard and thick key stratum overlying the working face.

Electromagnetically induced transparency and absorption cross-over with a four-level Rydberg system

Electromagnetically induced transparency (EIT) and absorption (EIA) are quantum coherence phenomena which result from the interference of excitation pathways. Combining these with Rydberg atoms have opened up many possibilities for various applications. We introduce a theoretical model to study Rydberg-EIT and Rydberg-EIA effects in cold Cs and Rb atomic ensembles in a four-level ladder type scheme taking into account van der Waals type interactions between the atoms. The proposed many-body method for analysis of such systems involves a self-consistent mean field approach and it produces results which display a very good agreement with recent experiments. Our calculations also successfully demonstrate experimentally observed EIT-EIA cross-over in the Rb case. Being able to simulate the interaction effects in such systems has significant importance, especially for controlling the optical response of these.

Influence of higher-order nonlinear effects on optical solitons of the complex Swift-Hohenberg model in the mode-locked fiber laser

The complex Swift-Hohenberg equation (CSHE) has been widely studied in recent years. It is a more real model in the mode-locked fiber laser with the saturable absorber due to the addition of the diffraction term compared with the complex Ginzburg-Landau equation. In this work, the dynamics process of the traditional soliton and M−type soliton pulses in the mode-locked fiber laser is demonstrated based on the CSHE model with higher-order nonlinear effects. The results show that with the increase of the small signal gain coefficient, the number of soliton molecules adds gradually. Under the same transmission conditions, the transmission of M−type solitons in the laser are more stable than that of single solitons. By adding the self-steepening effect, it can be found that the time-domain shift due to higher-order dispersion effects is compensated. The self-frequency shift effect caused by the Raman scattering can produce not only time domain shift, but also frequency domain shift. Moreover, the addition of higher-order diffraction term can describe the spectral response of multiple peaks, and makes the pulse spectrum show the asymmetric propagation in the transmission process. Finally, the increase of the length of the single-mode fiber on the right side of the gain fiber in the optical circuit will not only shift the center position of the output pulse backward, but also make the pulse energy show a ladder type downward trend.

Microcontroller Controlled Inverter Application

The limited use of fossil fuels has increased the interest in renewable energy sources. Renewable energy sources are generally direct current (DC) production. The popularity of inverters converting from DC to AC is increasing due to the generation of the generated DC signal and the current grid being alternating current (AC). In this study, a computer-controlled inverter was designed with the 16F877 microcontroller chosen as the model, and frequency and amplitude controls were realized with the serial communication system of this structure. A digital-analog converter (DAC) circuit is formed by connecting the R-2R ladder type resistor to the relevant ports of the microprocessor. With the codes written to the microprocessor, the signal response was taken from the DAC circuit, and the signal response at the ports was combined with the inverter and collector operational amplifier (op-amp) circuits, and the inverter design was completed.

Design and In Situ Growth of Cu2O‐Blended Heterojunction Directed by Energy‐Band Engineering: Toward High Photoelectrochemical Performance

AbstractIn the field of photoelectrochemical (PEC) water splitting, cuprous oxide (Cu2O) is one of the most promising photocathode materials, but its performance is restricted by poor carrier separation ability and low photovoltage. In order to overcome these limitations, a new kind of Cu2O‐ZnO blended heterojunction photocathode is designed and prepared by novel one‐step thermal oxidation method. ZnO granules are uniformly distributed in Cu2O film matrix, forming a granular structure, which enhances the band bending of Cu2O in the electrolyte and improves the photovoltage. In addition, the formed ladder type band alignment of Cu2O‐ZnO facilitates the spatial separation of photoexcited carriers. Different from the conventional layered heterojunction, the granular structured heterojunction proposed in this work extends the built‐in electric field region and further promotes the transmission of photoexcited carriers from the photoelectrode to the electrolyte. At 0 V vs reversible hydrogen electrode (RHE), the photocurrent density of Cu2O‐ZnO film is as high as −8.7 mA cm−2, which is over 6 times that of bare Cu2O (−1.3 mA cm−2). The onset potential positively shifts from 0.57 V vs RHE to 0.78 V vs RHE. This work provides an effective strategy for improving the PEC performance from the perspective of band alignment and material structure.

Structural analysis and weight optimization of automotive chassis by Latin hypercube sampling using metal matrix composites

Automotive chassis is used for supporting the functioning structure and balancing on the road. Being an initial requirement chassis vehicles like trucks, trailers, and semi-trailers have stepping skeleton (ladder chassis). Automotive chassis comprise of two bars organized corresponding to the longitudinal hub of the casing and a transverse beam arrangement laterally. Such chassis, the side elements of the lead frames generally consist of open channels or other sections. The work involves a ladder type frame of a heavy-duty truck considering the MMCs Al GA 7-230 and Al6092/SiC/17.5p MMC materials respectively using in comparison with ST52E steel. Latin hyper cube scheme of response surface method is used for the optimization purpose on ANSYS 18.1. Results shows that, the mass of chassis is 62.564Kg and 71.502 Kg using Graphite Al GA 7-230 and Al6092/SiC/17.5p MMC respectively whereas the actual mass is 214 Kg in case of conventionally used Structural steel alloy. Therefore, a significant amount of mass is reduced considering a number of other performance factors.

Electromagnetic field induced strong two photon blockade with hyperradiant behavior

We theoretically study the electromagnetic field controlled photon correlation and radiation properties in a two-atom-cavity quantum electrodynamic (QED) system with different atom-cavity coupling strengths. When two three-level atoms are coherently driven by a probe field and a strong control field, forming a ladder type electromagnetically induced transparency configuration, there exist four different excitation pathways via the two photon processes, yielding four different frequencies for realizing two photon blockades. Carefully choosing the intensity of the control field, resonant single-photon and two-photon excitation can be achieved at the same probe field frequency. Thus, two photon blockade phenomenon can be significantly improved and the collective radiation behavior becomes superradiance or even hyperradiance. Our system presented here can be considered to be a converter of a weak coherent light to two correlated photons.