Initial Start-up Research Articles

Simple model for the nonlinear radiation field of a free electron laser

It is shown that Jacobi elliptic function solutions of the nonlinear Duffing equation model the radiation field in a high-gain free electron laser through early saturation. After initial start-up, the field can be expressed equivalently with a hyperbolic secant. The model is derived for arbitrary detuning from resonance, which enables study of the spectral properties in the early nonlinear regime.

Analysis of the whole process tritium transport based on fuel cycle modeling for CFETR

Abstract Tritium self-sustain is crucial for the successful operation of China Fusion Engineering Test Reactor (CFETR). In this work, tritium fuel cycle model is developed based on the practical tritium plant. The retention values caused by different purification technology which can’t be extracted during the fuel cycle is considered in several sub-systems like Isotope Separation System-Inner cycle(ISS-I). The typical inventory in each sub-system is calculated which resulting that the minimum initial startup inventory (Im) is about 3131 g and tritium breeding ratio that required to satisfy tritium self-sustain (TBRreq) is about 1.13 under typical parameters. The sensitivity relation of Im and TBRreq are analyzed. We found that the fractional burnup is a key factor to affect both.

Research on viscoelastic fluid unsteady flow model based on torque loss correction

To address the complexity of unsteady shear flow in the initial start-up stage of rheometers, a model considering torque losses in motors and fixtures was developed based on the true torque balance relationship at the rotor boundary of the rheometer and the constitutive equation of the viscoelastic rheological model. The viscoelastic fluid transient flow model was established, and the real wall stress expression of unsteady shear flow of the viscoelastic fluid in the initial stage was obtained. The reliability of the model was verified by comparing the result from the analytical model with numerical calculation. The impact of the geometric dimensions of the test system and the material viscoelastic characteristics on the transient test was analyzed. The results show that the non-uniform velocity distribution has little effect on the initial strain response in the gap of the actual test system of the rheometer. The oscillation curves of strain and stress obtained by numerical and analytical methods coincide completely, proving the reliability of the model in characterizing the transient flow. For a Jeffery fluid, the elastic modulus G mainly affects the oscillation period and amplitude, the parallel viscosity pots η1 mainly impact the amplitude and oscillation attenuation speed, and the series clay pots η2 mainly influence the slope of the strain curve. The greater the system inertia, the more significant the creep oscillation in the unsteady flow process. The coupling between the test system inertia and the viscoelasticity fluid is the essential cause of the creep oscillation. Combined with the mechanical response characteristics of rheometer, a Jeffery model based on short term correction and torque loss was established. The model can accurately describe the strain time curve of gelled crude oil in the initial unsteady flow stage. The results of this study can help understand the rheological properties of materials in the transient start-up process.

ECONOMIC AND LEGAL PROSPECTS OF ACTIVATION OF SCIENCE PARKS ACTIVITY JN THE WAY TO NEOECONOICS

The author researches and substantiates by generalizing the scientific points of view improving the legal regulation of the created science parks on the initiative of higher education institutions and / or research institutions, taking into account the economic and legal prospect of intensifying their activities. National and foreign experience of scienceparks activity is considered. The content of using the founding agreement on creation of a science park and the agreement on partnership of business entities with a science park is provided. Problems that have not yet been resolved in the process of creating science parks and using innovative developments are noted. The classical content of entrepreneurship in innovation is provided and considered from thestandpoint of clarifying the content of the innovation structure, which is based on the commercialization of intellectual property rights by their types, which is a part of the intellectual capital cycle with a corresponding effective result. There is substantiated the procedure of formation of the statutory capital of the science park, to which higher educational institutions and / or scientific institutions cannot use intellectual property rights to the objects, created at the expense of budgetary funds, but can only under the conclusion of a license agreement with business entity,having non-state and state form of ownership as transferred assets, which does not require the alienation of the object of intellectual property rights as part of intangible assets. It is proposed to use the target budget funds as the initial start-up capital, which is provided on reverse terms to the state budget in case of closure (liquidation) of the science park by the decision of the founders or on the basis of a court decision. Alternatively, in the absence of target budget funds, it is proposed as a source of money to contribute to the statutory capital of the science park as a start-up capital to send part of the special fund of the state budget. It is justified the creation of a technology transfer office, which will be a structural unit of higher education institutions and / or research institutions, which will deal with the process of filing and reviewing a patent application and subsequent licensing. It is noted that the science park can be the founder (co-founder) of small innovative enterprises and enter into partnership agreements with them for the implementation of certain innovative projects.

Analysis of diesel engine injector nozzle spray characteristics fueled with residual fuel oil

Experimental analysis on the spray characteristics of a diesel engine injector nozzle fueled with Residual Fuel Oil (RFO) was carried out in this study. To achieve this, the fuel was characterized to determine its physicochemical properties, and an experimental set up was designed to visualize and capture the spray pattern of the fuel. The images obtained were processed and analysed using Image J software to determine the spray length, spray cone angle, spray area, spray volume, and spray velocity values of the fuel. Experimental results obtained agree with validation models and reveal that spray parameter values of RFO are higher than those of diesel fuel. The values of spray parameters of RFO such as 456mm spray length, 2.85mm Sauter Mean Diameter (SMD) and the low spray cone angle of 12.69°, led to a higher spray volume causing the engine to run on a rich mixture after initial start-up conditions. This would create such challenges as reduction in power and clogging of injector nozzle tip due to an increase in carbon deposits. Regression models generated reveal that these challenges could be eliminated when the spray parameters run on optimal values of 256mm, 6.41cm2, 16.18cm3, 0.96 mm/s and 13.59° for the spray length, spray area, spray volume, spray velocity and the spray angle respectively. These optimal values were obtained when the engine fuel injection time was set to 500μs while running on fuel of viscosity 4.305 mPa.s and temperature of 48 °C.

Evaluation of PCR conditions for characterizing bacterial communities with full-length 16S rRNA genes using a portable nanopore sequencer

MinION (Oxford Nanopore Technologies), a portable nanopore sequencer, was introduced in 2014 as a new DNA sequencing technology. MinION is now widely used because of its low initial start-up costs relative to existing DNA sequencers, good portability, easy-handling, real-time analysis and long-read output. However, differences in the experimental conditions used for 16S rRNA-based PCR can bias bacterial community assessments in samples. Therefore, basic knowledge about reliable experimental conditions is needed to ensure the appropriate use of this technology. Our study concerns the reliability of techniques for obtaining accurate and quantitative full-length 16S rRNA amplicon sequencing data for bacterial community structure assessment using MinION. We compared five PCR conditions using three independent mock microbial community standard DNAs and established appropriate, standardized, better PCR conditions among the trials. We then sequenced two mock communities and six environmental samples using Illumina MiSeq for comparison. Modifying the PCR conditions improved the sequencing quality; the optimized conditions were 35 cycles of 95 °C for 1 min, 60 °C for 1 min and 68 °C for 3 min. Our results provide important information for researchers to determine bacterial community using MinION accurately.

Large eddy simulation of thermally induced oscillatory flow in a thermoacoustic engine

In this paper, a comprehensive high-fidelity three-dimensional computational fluid dynamic research using large eddy simulation has been conducted to investigate a standing-wave quarter-wavelength thermoacoustic engine that consists of a hot buffer, a stack and a resonator. The performance of the thermoacoustic engine has been analysed in four aspects. Firstly, the dynamic characteristics of the engine during the initial start-up process are investigated when changing the temperature gradient imposed on the stack. Numerical results are compared with those from a system-wide reduced-order network model based on linear thermoacoustic theory. Secondly, the acoustic behaviour of the engine operating at steady state is studied. Fourier Series Model is utilized to decompose the steady-state acoustic pressure oscillations which reveals the unstable longitudinal acoustic modes excited in the engine. The stack serves as an energy source for the fundamental mode while it extracts acoustic power from the second harmonic. Thirdly, the hydrodynamic performances of the engine are inspected, and the obtained three-dimensional flow fields inside the engine enable us to probe into rich nonlinear phenomena including minor losses, mass streaming, etc. Finally, the heat transfer characteristics have been analysed by examining the mean temperature field and transversal heat fluxes along the engine. This research demonstrates that the large eddy simulation framework is effective in simulating the thermally induced oscillatory flow inside thermoacoustic engines. The multi-perspective analytical methodologies are valuable in comprehending the engine performance and provide guidelines for the design and optimization of efficient thermoacoustic engines for recovering waste thermal energy from various sources.

Computational modelling of nasal respiratory flow

CFD has emerged as a promising diagnostic tool for clinical trials, with tremendous potential. However, for real clinical applications to be useful, overall statistical findings from large population samples (e.g., multiple cases and models) are needed. Fully resolved solutions are not a priority, but rather rapid solutions with fast turn-around times are desired. This leads to the issue of what are the minimum modelling criteria for achieving adequate accuracy in respiratory flows for large-scale clinical applications, with a view to rapid turnaround times. This study simulated a highly-resolved solution using the large eddy simulation (LES) method as a reference case for comparison with lower resolution models that included larger time steps and no turbulence modelling. Differences in solutions were quantified by pressure loss, flow resistance, unsteadiness, turbulence intensity, and hysteresis effects from multiple cycles. The results demonstrated that sufficient accuracy could be achieved with lower resolution models if the mean flow was considered. Furthermore, to achieve an established transient result unaffected by the initial start-up quiescent effects, the results need to be taken from at least the second respiration cycle. It was also found that the exhalation phase exhibited strong turbulence. The results are expected to provide guidance for future modelling efforts for clinical and engineering applications requiring large numbers of cases using simplified modelling approaches.

Initial rotor alignment method for doubly salient electromagnetic machine position sensorless startup

The initial rotor alignment process plays an important role in `align and go' which is a simple, implementable and widely industrial used position sensorless startup method. To deal with the possible jitter and reverse in the initial startup process, this Letter proposes a novel initial rotor alignment method for the position sensorless startup of the doubly salient electromagnetic machine (DSEM). According to the analysis of the generated electromagnetic torque, the relation between the alignment pulse and stable locating position is studied at first. Then, to improve the initial startup performance, the alignment pulse of switching on two upper transistors and one lower transistor is proposed to be injected as the alignment pulse since the stable locating position is around the middle point of rotor sector; it owns the benefit of better selection for the initial energising phase windings. The initial sensorless startup performance is desired to be improved in terms of no jitter or reverse. The experiments of initial alignment, as well as, the full process of the sensorless startup based on `align and go' on a 12/8-pole DSEM validate the flexibility and effectiveness of the proposed method.

Heat-Transfer Characteristics of a Cryogenic Loop Heat Pipe for Space Applications

Infrared detectors on satellites and spacecraft require cooling to increase their measurement sensitivity. To efficiently cool infrared detectors in a zero gravity environment and in limited spaces, a cryogenic loop heat pipe (CLHP) can be used to transfer heat over a certain distance by the capillary forces generated from porous wicks without a mechanical power source. The CLHP presented in this study transfers the heat load to a condenser 0.5 m away from an evaporator at temperatures below −150 °C. The CLHP with two evaporators includes a subloop for initial start-up, and uses a pressure reduction reservoir (PRR) for the supercritical start-up from room to cryogenic temperature. Nitrogen is used as the working fluid to verify the thermal behavior of the CLHP, and the heat-transfer capacity according to the nitrogen charging pressure of the PRR is investigated. To simulate a cryogenic environment, the CLHP is installed inside a space environment simulator, including a single-stage GM (Gifford McMahon) cryocooler to cool the condenser. The CLHP is horizontally installed to simulate zero gravity. The heat-transfer characteristics are experimentally evaluated through the loop circulation of the CLHP.

Viscous fluid flow inside an oscillating cylinder and its extension to Stokes’ second problem

We present the analytical solution for the fluid motion inside a cylindrical tank whose angular velocity starts from rest and undergoes a harmonic oscillation. This problem, which has not yet been reported, is an extension to Stokes’ second problem where the fluid motion is governed by an outer moving cylindrical boundary and a zero velocity condition at the cylinder center. Different from the flow on the outside of a cylinder, the cylinder radius has a large influence on the internal fluid motion. We show that the fluid approaches solid body rotation for cylinders with outer radii similar to the characteristic viscous length scale of the flow, whereas the motion approaches that of Stokes’ original flat plate solution within very large cylinders. We detail both the transient starting condition and the quasi-steady fluid motion, which we present along with a particle image velocimetry experiment for validation. After decay of the initial startup transient, both quasi-steady analytical and experimental results predict that the oscillatory flow inside has an amplitude of velocity that decreases toward the center of the cylinder. The thickness of the Stokes layer, which is proportional to the penetration depth of the viscous wave, is altered by the size of the cylinder and/or the frequency of oscillation. We show that the penetration depth of the Stokes layer reaches its maximum thickness at intermediate cylinder sizes. The solution and results presented herein are potentially of value to describe the fluid motion in many applications where fluids are contained within cylindrical geometries.

Nitrate removal and secondary effects of a woodchip bioreactor for the treatment of subsurface drainage with dynamic flows under pastoral agriculture

While enabling economically viable use of poorly drained soils, artificial subsurface drainage has also been found to be a significant pathway for nutrient transfers from agricultural land to surface waters. Thus, mitigating the impacts of agriculture on surface water quality needs to address nutrient transfers via subsurface drainage. Woodchip bioreactors are a promising mitigation option as demonstrated under arable agriculture in the mid-west of the USA. However, research is needed to ascertain their efficiency in removing nutrients from very flashy drainage flows common in New Zealand (NZ) pastoral agriculture and any possible pollution swapping (e.g. reduction of leaching losses vs. greenhouse gas emissions). Accordingly, a lined 78-m3 woodchip bioreactor was constructed on a dairy farm in the Hauraki Plains (Waikato, NZ) with a drainage area of 0.65 ha. Rainfall, flow, hydrochemistry and dissolved gases in the inflow and outflow were monitored for two drainage seasons (part of 2017, 2018). Based on the nitrate-N fluxes, the estimated nitrate removal efficiency of the bioreactor was 99 and 48% in 2017 and 2018, respectively. The higher removal efficiency in 2017 could be attributed to two reasons. Firstly, the substantially longer hydraulic residence time (HRT) of the water in the bioreactor (mean = 21.1 days vs 4.7 days in 2018) provided more opportunity for microorganisms to reduce the nitrate. A strong positive relationship between HRT and removal efficiency was also observed within the 2018 drainage season. Secondly, denitrification was supported in 2017 by greater electron donor availability. Evidence of this was the higher mass of DOC discharge from the bioreactor (318 mg C L−1 of bioreactor volume vs 165 mg C L−1 in 2018). Removal rates in the bioreactor varied from 0.67–1.60 g N m−3 day−1 and were positively correlated with inflow nitrate loads. Pollution swapping was observed during the start-up phase of the bioreactor in both years (DOC, and DRP only in 2017) and during periods with very long HRTs (hydrogen sulphide (H2S) and methane (CH4) production). Substantially elevated discharges of DOC and DRP, as compared to inlet conditions, occurred during the initial start-up phase of the bioreactor in 2017 (3 to 3.5 pore volumes of the bioreactor), but only slightly elevated DOC and decreased DRP discharges were observed when drainage flow resumed at the start of the 2018 drainage season. Unexpectedly, cumulative DRP removal during the 2018 drainage season amounted to 89% of the DRP inflow into the bioreactor. Long HRTs (>5 days) enabled high nitrate removal efficiency (≥59%) and promoted complete reduction of nitrate to harmless dinitrogen gas but also promoted strongly reduced conditions, resulting in the production of H2S and CH4. On the other hand, short HRTs (<4 days) only allowed for moderate nitrate removal efficiency (≤43%) and constrained complete reduction of nitrate resulting in higher nitrous oxide concentrations in the outflow as compared to the inflow. Thus, nitrate removals above 50% were not able to be achieved without inducing H2S and CH4 generation. However, it may be achievable when the microbial community is provided with an additional source of readily available carbon during the critical periods when hydraulic flow and concomitant N load peaks occur.

A Novel Sensorless Initial Position Estimation and Startup Method

In this article, a low noise and simple initial position estimation and startup method based on high-frequency rotating sinusoidal voltage injection is proposed for interior permanent magnet synchronous machine. Different from the conventional method that uses negative sequence current and closed-loop position observer, the proposed method simply compares the three-phase high-frequency current amplitudes calculated by discrete Fourier transform to detect the rotor sector. The initial position can be obtained within only half of the injection cycle without parameter tuning. Thus, it is fast and simple compared to the conventional method. Both discrete and continuous rotor positions can be obtained and used for startup. Furthermore, to mitigate the acoustic noise during starting, a multifrequency injection strategy is introduced to reduce the noise emission caused by high-frequency voltage injection. Experiments are carried out to verify the effectiveness of the proposed method.

The liquid regime of waxy oils suspensions: A magnetic resonance velocimetry analysis

In view of better understanding the properties of waxy crude oils of great practical importance, we study the rheological behavior evolution of model waxy suspensions during transient shear tests, and its variation with concentration in a wide range. Macroscopic tests show a strong destructuring process with the increasing imposed shear rate (starting from rest), while negligible restructuring is observed during shear rate decrease. MRI (Magnetic Resonance Imaging) velocimetry of the suspension during the same tests allow to observe that, in most of the concentration range tested, the material flows only in a limited thickness close to the inner cylinder, and the thickness of this shear-band decreases for increasing concentration but marginally evolves as the apparent shear rate is widely increased then decreased. This means that the extent of the liquid region is governed by the initial start-up flow conditions, and the apparent viscosity variations during the next steps (at other shear rate values) are not associated with an increase of the flowing region but with the evolution of the structure in the liquid region. For the specific case of the lowest wax content analyzed, the thickness of the unsheared region decreases considerably after shearing at a high shear rate. In this case the torque balance in the sample is capable of overcoming the yield stress of the unsheared region. We also show that despite very different (initial) elastic moduli and yield stresses in the solid regime (a factor of several orders of magnitude over the whole range of concentration), we essentially have the same power-law behavior of the fluid in the shear-band, even when the shear-band thickness is close to the particle size.

A dynamic model for rapid startup of high-speed landslides based on the mechanism of friction-induced thermal pressurization considering vaporization

The friction-induced thermal pressurization mechanism in the shear band is an important reason for the transition of motion state of landslides from creeping to high-speed sliding during their initial startup phase. In this paper, a dynamic model for the startup phase of high-speed landslides with thermo-hydro-vapor-mechanical (THVM) coupling in shear band is established and applied to the Vaiont landslide for case study. The model consists of three governing equations: the equation of motion controls the motion of the overlying slide mass, the heat equation controls the heat or temperature change in the shear band at the bottom, and the pore pressure equation controls the change of excess pore pressure in the shear band. The main variables of these equations interact with each other. In addition to the thermal expansion pressurization of pore water, vaporizing pressurization is systematically considered for the first time in this model. The analysis results of the model applied to the Vaiont landslide show that, at 10 s, the excess pore pressure in the shear band is up to 4.5 MPa, the maximum temperature is 295 °C, and the velocity of each block is in the range of 24~31 m/s. The evolution of excess pore pressure in the shear band is divided into four stages which have been discussed in detail. The THVM model established in this paper can reflect the physical mechanism of thermal pressurization inside the shear band of high-speed landslides during their startup process to a certain extent, and it could also explain why some landslides quickly turn to catastrophic high-speed sliding after they start.

Numerical analysis on the start behavior of rough journal bearings during the gear pump meshing cycle

In this paper, the transient lubrication characteristics of hydrodynamic journal bearings during the external gear pump meshing cycle are studied. In the bearings lubrication calculation part, a numerical model is developed to assess the transient lubrication during the initial start-up of an aero gear pump. The model takes into account the effects of surface topography, asperities contact, and pump start-up speed. In the pump simulation part, the flow inside pump and bearing load environment are analyzed by a computational fluid dynamics model. Then a simulation method is presented to solve the problem of pump-bearings system, considering the pump’s influence during bearings lubrication calculation. To gain insight, results of a series of simulations with illustrative examples are presented. The variation of the startup lubrication performance under load conditions corresponding to the pump internal flow field is acquired. The results show that bearings operate from mixed-lubrication to hydrodynamic-lubrication state with changed load-supporting effects during the startup. The load-supporting effects and film rupture boundary are directly related to the pump load fluctuation, but the center trace is slightly influenced except on the hydrodynamic-lubrication state.

Economically Sustainable Growth of Perovskite Photovoltaics Manufacturing

Summary The significant capital expense of photovoltaics manufacturing has made it difficult for new cell and module technologies to enter the market. We present two technoeconomic models that analyze the sustainable growth of perovskite manufacturing for an R2R single-junction technology and a perovskite-silicon tandem module, focusing on the impacts of economies of scale and average selling price on profitability. We establish a cost range of $3.30/W to $0.53/W for flexible modules manufactured in factory sizes ranging from 0.3 MW/year to 1 GW/year. In addition, we model the cost to manufacture a tandem module consisting of a single-junction perovskite cell stacked in 4-terminal configuration onto a silicon cell and show how an existing manufacturer can grow at a faster rate by co-investing in tandems. Our analyses highlight potential routes to market for perovskite photovoltaics and the possibility to sustainably grow a photovoltaics manufacturing company even in markets with higher labor rates.

Initial Start-up Characteristics of Anaerobic Ammonium Oxidation in a UASB Reactor

Initial Start-up Characteristics of Anaerobic Ammonium Oxidation in a UASB Reactor

The Binns Program for Cord Blood Research: A Novel Program for Cord Blood Procurement in an Academic Setting for Biomedical Research

<h3>Introduction</h3> Umbilical cord blood (UCB) is a vital source of hematopoietic stem and progenitor cells (HSPCs). Since 1991, UCB has been collected and stored in public cord blood banks to be primarily used as a source for allogeneic hematopoietic stem cell transplantation (HSCT). Since the seminal UCB transplant reported in 1988 by Gluckman et al., UCB has contributed to advances in HSCT and clinical trials. However, UCB-derived cells remain costly and difficult to procure for pre-clinical research. Here we present a protocol for a multidisciplinary, self-sustaining cord blood program dedicated to biomedical research: The Binns Program for Cord Blood Research, piloted at the Stanford University School of Medicine. <h3>Objectives</h3> The primary objective of this study was to educate others on the benefits of implementing a self-sustaining cord blood program that increases biomedical research throughout the medical community. <h3>Methods</h3> Eligible donors are identified using IRB-approved inclusion criteria. UCB samples are then collected in utero, with informed consent, by obstetric providers at the time of delivery. Within 24-48 hours of isolation, deidentified samples are processed into three fractions: (1) plasma, (2) hematopoietic stem and progenitor cells (HSPCs) by immunomagnetic separation, and (3) non-HSPC cellular flow-through. UCB-derived fractions are then distributed to researchers upon request. <h3>Results</h3> Between November 2015 and April 2019, 1,385 women gave informed consent to donate their cord blood following delivery. Of those participants, 1,147 (83%) samples were collected and 927 (81%) distributed for research purposes. The median post-enrichment cell count per cord following positive selection for CD34+ HSPCs was 1.25 × 10⁶ (Figure 1). Corresponding median post-enrichment sample purity was 90% following single-step purification. By October 2016, a protocol had been developed and optimized for the Binns Program to begin providing UCB-derived products to six laboratories. Now, the program supports 47 laboratories across Stanford. The research being supported spans a broad array of topics including normal and abnormal hematopoiesis, genetic engineering, and novel approaches to HCST. <h3>Conclusions</h3> After initial start-up funding, the Binns Program became self-sustaining, representing a feasible model for cord blood banking to support the advancement of research by providing fresh or cryopreserved UCB-derived cells to the research community. We hope this model may be useful for other institutions and centers where the need to support research is high and the traditional model for public cord blood banking may not be a suitable option.

Estimation of effective thermal conductivity of packed bed with internal heat generation

Test Blanket Module (TBM) of the fusion reactor has the vital role of removing heat generated from the fusion reactor along with the heat generated internally due to tritium breeding reaction. In the initial startup phase of fusion reactor, neutron flux has a climbing ramp nature and heat gets generated in discrete locations of TBM due to non-uniform nature of neutron irradiation. Thus, there is need to establish mathematical method to estimate Effective Thermal Conductivity (ETC) of packed bed with randomly scattered internal heat sources. Novel Induction Heating technique was used to simulate above mentioned conditions in packed bed of Li2TiO3 pebbles. An input-output FDM (Finite Difference Method) based model has been developed to estimate ETC of packed beds with non-uniform and discrete Internal Heat Generation (IHG). The inputs to the FDM based model are experimental results along with various operating and process parameters of the packed bed system under consideration. Also, an empirical correlation has been proposed to yield ETC of above mentioned packed bed systems valid for bed voidage of 0.44-0.47. The experimental and analytical methods used for this study are detailed in this paper.