Start-up Strategy Research Articles

Start-up process of ion optics in ion thrusters

In this study, a particle-in-cell model of ion optics was established to simulate the changing trend of an ion beam shape over time during an ion optic start-up. This model was established to study the effect of ion beam shape change on the accel grid during ion optical start-up and to discuss the start-up strategy of ion optics. The results show that the ions at the edge of the beam have a radial velocity component toward the centerline of the ion optics owing to the electric field; this causes the ion beam to shrink gradually toward the centerline over time. Furthermore, the accel grid can be prevented from being bombarded by ions by design at the operating voltage. However, the grid may still be bombarded by ions during the low-voltage start-up process, thereby affecting its life. Thus, the ion dynamics must be considered during the start-up process.

Start-up strategies of electromethanogenic reactors for methane production from cattle manure

This study qualitatively assessed the impacts of different start-up strategies on the performance of methane (CH4) production from cattle manure (CM) in electromethanogenic reactors. Single chamber MECs were operated with an applied voltage of 0.7 V and the impact of electrode acclimatization with a simple substrate, acetate (ACE) vs a complex waste, CM, was compared. Upon biofilm formation on the sole carbon source (ACE or CM), several MECs (ACE_CM and CM_ACE) were subjected to cross-feeding (switching substrate to CM or ACE) during the test period to evaluate the impact of the primary substrate. Even though there was twice as much peak current density via feeding ACE during biofilm formation, this did not translate into higher CH4 production during the test period, when reactors were fed with CM. Higher or similar CH4 production was recorded in CM_CM reactors compared to ACE_CM at various soluble chemical oxygen demand (sCOD) concentrations. Additionally, feeding ACE as primary substrate did not significantly impact either COD removals or coulombic efficiencies. On the other hand, the use of anaerobic digester (AD) seed as an inoculum in CM-fed MECs (CM_CM), relative to no inoculum added MECs (Blank), increased the initial CH4 production rate by 45% and reduced the start-up time by 20%. In CM-fed MECs, Geobacter dominated bacterial communities of bioanodes and hydrogenotrophic methanogen Methanoculleus dominated archaeal communities of biocathodes. Community cluster analysis revealed the significance of primary substrate in shaping electrode biofilm; thus, it should be carefully selected for successful start-up of electromethanogenic reactors treating wastes.

A 40.68-MHz Active Rectifier With Cycle-Based On-/Off-Delay Compensation for High-Current Biomedical Implants

This article presents a 40.68-MHz active rectifier for high-current biomedical implants. Cycle-based timing control (CBTC) is proposed to significantly extend the duration for compensating both turn-on and turn-off delays of active diodes at 40.68 MHz, thereby improving both the power conversion efficiency (PCE) and the voltage conversion ratio (VCR) of the rectifier. The supply independent ramp, the delay-mimicking sample-and-hold (DMSH) circuit, and the low-voltage (LV)-stress startup scheme are also developed to maintain high PCE and VCR, and ensure rectifier reliability over a wide input range. Implemented in standard 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS, the proposed fully integrated rectifier delivers a maximum output power of 207 mW and operates at 40.68 MHz to enable the use of a small-diameter receiver coil of 4 mm. This rectifier is the first to achieve full turn-on and turn-off delay compensation at 40.68 MHz, so its maximum PCE and VCR obtain 86% and 96.3%, respectively. Compared with the prior art, this work not only provides more stable high PCE and VCR over a wider input range from 1.9 to 3.8 V at 40.68 MHz but also uses the smallest receiver coil for wireless power delivery.

Investigation on Start-Up Characteristics of Large Axial Flow Pump Systems Considering the Influence of Auxiliary Safety Facilities

A large number of operation practices show that the reliability and stability of large axial flow pump systems will face significant challenges during the start-up process. If the start-up control mode or safety auxiliary facilities of large axial flow pump stations are unreasonable, start-up failure will easily follow. In order to find a scientific control strategy for the start-up of large axial flow pump stations, the start-up characteristics of large axial flow pump stations must be fully understood first. In this paper, based on the secondary development of Flowmaster software, a simulation study of the start-up process of a large axial flow pump system equipped with different safety aids is carried out. It is found that it is a very dangerous start-up control mode to delay the opening of the rapid-drop gate to reduce the maximum reflux value and reflux duration when the pump system is initially started. When the rapid-drop gate opens with a delay of 4 s, the power overload coefficient reaches 23.49, indicating that the possibility of start-up failure of the large axial flow pump system increases sharply the longer the gate delay is opened. The method of adding a flap valve to the rapid-drop gate can significantly weaken the instantaneous impact power of the unit and prevent the unit from overload. When safety auxiliary facilities with an additional disc valve on the fast descending gate are adopted, the backflow coefficient is within 0.2, the impact head coefficient is within 2, and the power overload coefficient is less than 0. The research results will provide an important reference value for comprehensively understanding the start-up characteristics of large axial flow pump stations and finding scientific and safe start-up control strategies.

Effect of start-up strategies with functionally redundant and efficient acetoclastic electroactive bacteria on the performance of microbial electrolysis cells fed with domestic wastewater

Different start-up strategies were investigated for enriching efficient acetoclastic electroactive bacteria (EAB) in wastewater-fed microbial electrolysis cells (MECs). Wastewater-fed MECs bioaugmented (B-MECs) at time zero with pure cultures of Geobacter sulfurreducens and Desulfuromonas acetexigens or pre-enriched anode biofilm (PEA-MECs) with G. sulfurreducens and D. acetexigens performed better than wastewater-fed MECs started with wastewater (WW-MECs) as the sole inoculum. The highest peak current (1575 ± 157 mA/m2), coulombic efficiency (70.3 ± 9 %), and CH4 production (0.27 ± 0.02 L/g-COD) was observed in PEA-MECs. The relative abundance of acetoclastic EAB was influenced by start-up strategies (Geobacter: 23.9 ± 2.6 % and Desulfuromonas: 13.7 ± 6 % for B-MECs; Geobacter: 29.6 % ± 5.1 % and Desulfuromonas: 0.45 ± 0.2 % for PEA-MECs; Geobacter: 7.9 ± 0.5 % for WW-MECs). These results provide a novel insight for enriching the anode with functionally redundant and efficient acetoclastic EAB, which is crucial for resource recovery from wastewater.

Interaction of urban management with universities and institutions of higher education and research; presenting the "Knowledge-City-University" model

Based on various indicators such as dynamic cities, world cities, top cities, livable cities, creative cities, quality of life and competitiveness, Tehran has not gained a worthy position among the cities of the world, despite having the necessary potential and capability. This is while the capacity of human, intellectual and symbolic academic capital and effective interactions and interaction with the field of urban management, can be effective in creating and promoting the network of smart cities and their creative relationship with regional and global networks. And lead to national and local development. Lack of effective interaction between universities, with public organizations such as urban management, has led to reduced productivity and efficiency in this area. In this research, the strategy of integrated and multiple methodology has been used. This methodological strategy itself consists of four approaches of positivism, pragmatism, instrumentalism and persuasion. And research, the third and fourth integrated approach and the reference theory used is the social exchange theory regarding the interaction of two institutions. The result of these approaches and theories is the presentation of the "knowledge-city- University" model. The different parts of this model are described in detail from the stakeholders of both the university and the city, as well as the supply and demand of the desired and applied knowledge.The result is that if startup strategies and complementary and executive projects are used alongside this operational model, the mentioned indicators about the city will definitely improve and its position in the world rankings will be greatly improved.

Optimisation Strategy of Carbon Dioxide Methanation Technology Based on Microbial Electrolysis Cells

Microbial Electrolytic Cell (MEC) is an electrochemical reaction device that uses electrical energy as an energy input and microorganisms as catalysts to produce fuels and chemicals. The regenerative electrochemical system is a MEC improvement system for methane gas produced by biological carbon sequestration technology using renewable energy sources to provide a voltage environment. In response to the influence of fluctuating disturbances of renewable electricity and the long system start-up time, this paper analyzes the characteristics of two strategies, regulating voltage parameter changes and activated sludge pretreatment, on the methane production efficiency of the renewable gas electrochemical system. In this system, the methane production rate of regenerative electrochemical system is increased by 1.4 times through intermittent boosting start-up strategy; based on intermittent boosting, the methane production rate of regenerative electrochemical system is increased by 2 times through sludge pyrolysis pretreatment start-up strategy, and the start-up time is reduced to 10 days. Meanwhile, according to the simulation test results of power input fluctuation and intermittency, the stability standard deviation of its system operation is 75% of the original one, and the recovery rate is about 1 times higher. This study can provide a theoretical basis and technical reference for the early industrial application of microbial CO₂ methanation technology based on renewable energy.

Порівняльний аналіз розвитку стартапів у світовій економіці

The purpose of the article is to conduct a comparative analysis of the trends in the development of startups, taking account of world practices and the possibility of their implementation in Ukraine. The impact of Industries 4.0, 5.0 on ensuring the high-tech development of national economic systems is substantiated and the need to implement startups as the basis for the formation of innovative entrepreneurship is emphasized. Changes in global financing of startups are analyzed, a decrease in the number and value of deals on the financing of startups and fluctuations in the financing due to the phased development of startups are revealed. The following reasons for the decrease in the financing are identified: a slight rise in investment in the early stages of the development of startups and a fall in the level of global financing of startups due to the unattractive investment climate in the global economic system. The need for assessing the factors in the formation of a new ecosystem for the development of startups by country, changes in the number of registered startups is emphasized. The leaders in the development of startups in the TOP-5 countries are identified, examples of highly rated startups in specific countries are provided and the main areas of their operation are determined. The trends towards the increase in the number of dismissals of IT workers in 2023 are systematized. It is found that such dismissals have a negative impact on the technological development of sectors and decrease the attractiveness of startups in innovative entrepreneurship. The global structure of startups by fields of activity and changes during 2022-2023 are analyzed, reductions in such industries as social networks and leisure, e-commerce and retail are detected. The main global trends in the development of startups and influencing factors in the development of startups are determined. It is concluded that in the conditions of global transformations there are negative changes in the development strategies of startups, the priority areas are the planning and improvement of business models, and not the growth strategies within the framework of increasing the profitability of foreign companies.

Low-Grade Syngas Biomethanation in Continuous Reactors with Respect to Gas–Liquid Mass Transfer and Reactor Start-Up Strategy

In order to utilize a wider range of low-grade syngas, the syngas biomethanation was studied in this work with respect to the gas–liquid mass transfer and the reactor start-up strategy. Two reactors, a continuous stirred tank (CSTR) and a bubble column with gas recirculation (BCR-C), were used in the experiment by feeding an artificial syngas of 20% H2, 50% CO, and 30% CO2 into the reactors at 55 °C. The results showed that the CH4 productivity was slightly increased by reducing the gas retention time (GRT), but was significantly improved by increasing the stirring speed in the CSTR and the gas circulation rate in the BCR-C. The best syngas biomethanation performance of the CSTR with a CH4 productivity of 22.20 mmol·Lr−1·day−1 and a yield of 49.01% was achieved at a GRT of 0.833 h and a stirring speed of 300 rpm, while for the BCR-C, the best performance with a CH4 productivity of 61.96 mmol·Lr−1·day−1 and a yield of 87.57% was achieved at a GRT of 0.625 h and a gas circulation rate of 40 L·Lr−1·h−1. The gas–liquid mass transfer capability provided by gas circulation is far superior to mechanical stirring, leading to a much better performance of low-grade syngas biomethanation in the BCR-C. Feeding H2/CO2 during the startup stage of the reactor can effectively stimulate the growth and metabolism of microorganisms, and create a better metabolic environment for subsequent low-grade syngas biomethanation. In addition, during the thermophilic biomethanation of syngas, Methanothermobacter is the dominant genus.

A Three-stage AC side startup strategy for hybrid MMC

When a hybrid modular multilevel converter (MMC) starts from the AC side, the capacitor voltages of full-bridge submodules (FBSMs) will be twice those of half-bridge submodules (HBSMs) in the uncontrolled charging stage due to their structural differences, making it difficult to further charge the SMs in the ensuing controlled charging stage. To solve this problem, a three-stage AC-side startup strategy for hybrid MMCs is proposed. Compared with conventional closed-loop startup strategies, it charges HBSMs and FBSMs simultaneously with the third harmonic injection method, which eliminates the inrush current. And then the HBSMs are charged separately by orthogonal decomposition of the arm voltage after FBSMs are fully charged, which avoids overcharging the FBSMs. Thus, hybrid MMCs can start from the AC side quickly without inrush current, and the unbalance between different SMs is eliminated. The necessity and feasibility of the proposed strategy are discussed in detail. Aiming at possible errors in arm voltage orthogonal decomposition and current phase tracking, control loops for HBSMs and FBSMs are derived and analyzed. Finally, the complete three-stage startup strategy is designed. Simulation results and experimental results are provided to support the theoretical analysis and validate the proposed strategy.

Mathematical simulation and experimental verification of a novel control strategy for a single stage PN/A (partial nitrification/Anammox) SBR (sequencing batch reactor)

The single reactor PN-A process offers a cost-effective solution for nitrogen removal. The successful startup and operation of the PN/A reactor requires the enrichment and balanced growth of AOB (Ammonium oxidizing bacteria) and AMX (AMAMMOX bacteria). The precise aeration supply or DO (dissolved oxygen) control was regarded to be the key for successful operation of the PN/A reactor. However, due to the low DO concentration requirement for the PN/A reactor, it is not practical to apply the precise aeration or DO concentration control. In this study, a new control strategy for the rapid startup and operation of the single stage PN/A (partial nitrification) SBR (sequencing batch reactor) was put forward. The control strategy relies on the periodic measurement of effluent NH4+, NO2-, and NO3- concentration to determine the nitrogen loading rate and aeration pump speed (i.e., not exact air supply volume). It does not require precise oxygen supply or DO (dissolved oxygen) control. This feature makes the control strategy easily applicable for practical application. A calibrated mathematical model was used to evaluate the control strategy, which was shown to be effective in achieving satisfactory nitrogen removal and NOB suppression. The control strategy was tested in a lab PN/A batch reactor, in which TN removal efficiency of 80% was achieved under low influent NH4+ concentration of 100 mg N/L and nitrogen loading rate of 0.12 Kg N/(m3•d) within 60 days of the experiment.

EVALUASI DAN REDESIGN WEBSITE STARTUP ENSIKLOTARI MENGGUNAKAN METODE SYSTEM USABILITY SCALE

Ensiklotari is a digital education startup, that provides a platform for dance performers and learners, where dance studios deliver virtual dance lessons in the form of coordinated, integrated, and directed video tutorials. Ensiklotari innovation is a blend of Design Thinking and Lean Startup strategies, or Lean Design Thinking. The strength of Design Thinking lies in the area of qualitative methods, which include details of ethnography, user research, and observation, while Lean Startup emphasizes quantitative methods that focus on metric-based analysis. Both ensure tests are conducted at each stage. The user-centered and customer-oriented implementation of the two strategies above accelerates the iterative process in the Ensiklotari software development stage. The results of the SUS measurement of the Ensiklotari application are 78 points. These results indicate that the overall usability level of the application is effective, efficient, and satisfactory for users in the promoter category or users who have the potential to give a positive response and promote the Ensiklotari website.

Air Company

One winning strategy for a chemistry start-up is to first bring a high-value, low-volume specialty chemical to market and then use the resulting cash flow to build a capacity and technology portfolio en route to higher-volume business lines. The carbon dioxide-to-chemical start-up Air Company is doing exactly that. Its rollout started in 2020 with vodka and perfume base containing ethanol made from CO 2 . Air Company’s vodka is a classically correct spirit with no odor or aftertaste, moderate astringency, and a slight warmth going down. The $75 bottle is consistently sold out in the liquor stores that carry it—something new facilities that are in the planning stages will fix, according to the company’s spirit brand manager . The new plants will indeed make ethanol, but the alcohol will be a side product to the company’s main aspiration: converting captured CO 2 into jet fuel. “Today is where our entire

Role of quorum sensing-based regulation in development of anaerobic ammonium oxidation process

Shortage of anaerobic ammonium oxidation (anammox) sludge greatly limits the extensive full-scale application of anammox-based processes. Although numerous start-up strategies have been proposed, the interaction among microbial consortia and corresponding mechanism during the process development remain unknown. In this study, three reactors were established based on different seed sludges. After 27 days, the anammox process inoculated with anammox granules and activated sludge (1:5) was firstly achieved, and the highest nitrogen removal rate was 1.17 kg N m−3 d−1. Correspondingly, the anammox activity and abundances of related functional genes increased. Notably, the dominant anammox bacteria shifted from Candidatus Kuenenia to Candidatus Brocadia. Metagenomic analysis indicated that quorum sensing-based regulation mainly contributed to the proliferation and accumulation of anammox bacteria. This work provides an insight into the quorum sensing (QS)-regulated microbial interactions in the anammox and activated sludge consortia during the process development.

Numerical Research on the Cold Start-up Strategy of a PEMFC Stack from −30°C

Numerical Research on the Cold Start-up Strategy of a PEMFC Stack from −30°C

Novel insights into aerobic duration control-based partial nitritation in source-separated blackwater treatment: Growth type, inoculation source, and comammox threat

Aerobic duration control (ADC), whereby aeration is terminated before nitrite is extremely oxidized during the nitrification process, is an effective strategy to achieve partial nitritation (PN) for blackwater. This study evaluated the effects of microbial growth type, influent ammonia-oxidizing organisms (AOO), and comammox bacteria from seeding sludge to ADC-based PN. The long-term operation of lab-scale reactors and model simulations were implemented to select the best growth type. The biofilm formed on the inner wall of the activated sludge reactor decreased the nitrite accumulation ratio (NAR) from 99.2% to 77.2%. Meanwhile, the NAR of the pure-biofilm reactor decreased from 95.9% to 47.8%. The deteriorated PN of the biofilm-related reactors was due to the extended solid retention time and increased substrate saturation constants of AOOs compared with those of nitrite-oxidizing organisms (NOO). Periodic biofilm carrier regeneration and biofilm thickness control can recover PN performance but are difficult to implement. In contrast, the optimized activated sludge reactor exhibited high (NAR >94%) and stable (>3 months) PN performance when treating real blackwater. Nitrifiers were found in blackwater, and chemically enhanced high-rate activated sludge pretreatment removed more NOOs than AOOs (41.8% vs. 24.3%) and increased the influent AOO/NOO ratio. Interestingly, the influent AOOs supported fast PN start-up in the moving-bed biofilm reactor without the initial inoculation of activated sludge. Moreover, model simulations verified that high and stable PN could also be realized in an activated sludge reactor by the continuous inoculation of influent AOOs, which is a novel PN start-up strategy. Metagenomic analyses showed that the comammox bacteria from the seeding sludge eventually disappeared owing to their intrinsic specific growth rates and free ammonia inhibition. The findings of this study will provide insightful guidelines for PN application in decentralized and semi-centralized wastewater treatment systems.

Anaerobic Digestion of Pig-Manure Solids at Low Temperatures: Start-Up Strategies and Effects of Mode of Operation, Adapted Inoculum, and Bedding Material.

The objective of this study was to obtain start-up strategies for the operation of a dry anaerobic digestion (DAD) system treating pig-manure (PM) solids at low-temperatures, and evaluate the effects of operation mode, adapted inoculum, and bedding material on the performance. A DAD system coupled with an inoculum system (two-stage DAD) was operated at 20 ± 1 °C to digest PM solids (Total Solids, TS: 27%) with wheat straw or woodchips as bedding materials (TS substrate-mixture: 45%) using a liquid inoculum. Static DAD was also operated in parallel for comparison purposes. Overall, the percolation–recirculation mode of operation was superior to the static mode; the former had more than a 3-fold increase in specific methane yield in cycle 3. Using the adapted inoculum in cycle-2 improved methane yield by 7% and 26% for cycles 1 and 3, respectively, under the percolation–recirculation mode of operation. In addition, the digestate resulting from the digestion of woodchips + PM solids had better physical characteristics than wheat straw + PM solids. Thus, anaerobic digestion of pig-manure solids at low-temperatures with appropriate start-up strategies, inoculum, and bedding material is a promising technology for transforming PM solids into biogas and using its digestate as biofertilizer.

Biosurfactant-driven synergic roles to accelerate biofilm formation in an anaerobic moving bed biofilm reactor (MBBR): A comprehensive analysis on meso and micro scale

Biofilm formation is a complex and time-consuming process, especially the attachment and growth of anaerobic biofilm, which fundamentally determines the start-up of biofilm reactor. In this study, biosurfactant, rhamnolipid, was introduced into an anaerobic moving bed biofilm reactor (AnMBBR) to promote its start-up, and the results showed that AnMBBR with rhamnolipid (RMBBR) could be successfully started within 25 days. Compared to the control AnMBBR without rhamnolipid, the start-up time was shortened by about half, the attached biomass on biocarriers was increased to 1.5 times, and the pollutants removal efficiencies were all greatly improved in the start-up phase, especially NO3− increased from 86.76 ± 1.04% to 96.93 ± 0.73%, and then these gaps were reduced in the steady-state phase. Under the action of rhamnolipid, the adhesion force of the biofilm increased from 18.9 nN to 27.4 nN eventually, and the interfacial energy between biofilm and biocarriers was transformed from repulsion (6200 KT) to weak attraction (−100 KT) by the evaluation of the extended Derjaguin–Landau–Verwey–Overbeek theory, which significantly promoted the initial attachment of biofilm. The increased metabolic activity, key enzyme activity, extracellular polymeric substances (EPS) and quorum sensing behaviors evidenced that rhamnolipid stimulated microbial internal activities and then regulated biofilm growth process. Moreover, rhamnolipid also significantly enhanced the abundance of functional bacteria in terms of metabolism or quorum sensing, including Thauera, Methylomonas, Desulfomicrobium, Azoarcus, Leptonema. Rhamnolipid would also stimulate the expression of genes that related to membrane transport, biofilm formation and nitrogen metabolism. This work provided a promising strategy for the rapid start-up of anaerobic biofilm reactor.

A Moment-of-Inertia-Driven Engine Start-Up Strategy for Four-Wheel-Drive Hybrid Electric Vehicles

During the moment-of-inertia (MoI) start-up process, an engine is cranked to ignite at 800 rpm with better fuel efficiency than at 250 rpm in the belt-driven start. As kinetic energy is employed, the work needed to crank the engine is also reduced. This article aims to develop an MoI-driven engine start-up method for a four-wheel-drive (4WD) vehicle. By modeling a 4WD hybrid electric vehicle (HEV) powertrain, a system dynamics model is developed into a state-space equation. The variable operating conditions of the engine and clutch are identified, and an adaptive model predictive controller (MPC) is designed. The goal of multioptimization is to control the engine speed trace, minimize the front and total axle torsion speed, and execute the torque demand. The optimization outputs are the engine torque set points, front electric motor (EM) torque set points, clutch nominal force set points, and rear EM set points. By predicting the engine fluctuation torque and considering the power source component constraints, an optimization algorithm is developed. This strategy is simulated and verified on the vehicle and powertrain models. The results indicate that the proposal achieves distinct fuel consumption improvement with an optimized drivability performance.

Multi-Objective Optimization of Back-to-Back Starting for Pumped Storage Plants under Low Water Head Conditions Based on the Refined Model

Pumped storage plants (PSP) must switch frequently between various working conditions. Moreover, PSPs can fall easily into an S-shaped zone under low water head conditions, especially during back-to-back starting (BTBS), which reduces the stability and safety of unit operation. In this paper, a nonlinear PSP model for BTBS is established by combining an electrical subsystem with a refined hydraulic-mechanical subsystem. The influences of the hydraulic, mechanical, and electrical factors on the BTBS process are investigated quantitatively. Choosing the speed overshoot and speed stable time as the optimization objectives, and considering a variety of constraints, the multi-objective particle swarm optimization (MOPSO) algorithm is introduced to study and optimize two typical startup strategies. The results show that: (1) The parameters of a hydraulic-mechanical-electrical system have a significant impact on BTBS process, and the most unfavorable working condition corresponds to the lowest water head; (2) In the control schemes, a novel constant excitation voltage strategy is proposed based on the multi-objective optimization scheme. Compared with the constant excitation current strategy or single-objective, the optimization strategy proposed can considerably improve the speed overshoot and the speed stable time by at least 68.27% and 3.22% under the worst working conditions. (3) It is further verified that the problem of trapping in the S-shaped region under various working conditions may be avoided by the obtained optimal control scheme. The results give prominence to the effectiveness of the proposed optimization strategy for maintaining the safety and stabilization of PSP operation.