Rod Assembly Research Articles

FAP20 is required for flagellum assembly in Trypanosoma brucei.

Trypanosoma brucei is a human and animal pathogen that depends on flagellar motility for transmission and infection. The trypanosome flagellum is built around a canonical "9+2" axoneme, containing nine doublet microtubules (DMTs) surrounding two singlet microtubules. Each DMT contains a 13-protofilament A-tubule and a 10-protofilament B-tubule, connected to the A-tubule by a conserved, non-tubulin inner junction (IJ) filament made up of alternating PACRG and FAP20 subunits. Here we investigate FAP20 in procyclic formT. brucei. A FAP20-NeonGreen fusion protein localized to the axoneme as expected. Surprisingly, FAP20 knockdown led to a catastrophic failure in flagellum assembly and concomitant lethality. This differs from other organisms, where FAP20 is required for normal flagellum motility, but generally dispensable for flagellum assembly and viability. Transmission electron microscopy demonstrates failed flagellum assembly in FAP20 mutants is associated with a range of DMT defects and defective assembly of the paraflagellar rod, a lineage-specific flagellum filament that attaches to DMT 4-7 in trypanosomes. Our studies reveal a lineage-specific requirement for FAP20 in trypanosomes, offering insight into adaptations for flagellum stability and motility in these parasites and highlighting pathogen versus host differences that might be considered for therapeutic intervention in trypanosome diseases. [Media: see text] [Media: see text].

Structural basis for Vipp1 membrane binding: from loose coats and carpets to ring and rod assemblies.

Vesicle-inducing protein in plastids 1 (Vipp1) is critical for thylakoid membrane biogenesis and maintenance. Although Vipp1 has recently been identified as a member of the endosomal sorting complexes required for transport III superfamily, it is still unknown how Vipp1 remodels membranes. Here, we present cryo-electron microscopy structures of Synechocystis Vipp1 interacting with membranes: seven structures of helical and stacked-ring assemblies at 5-7-Å resolution engulfing membranes and three carpet structures covering lipid vesicles at ~20-Å resolution using subtomogram averaging. By analyzing ten structures of N-terminally truncated Vipp1, we show that helix α0 is essential for membrane tubulation and forms the membrane-anchoring domain of Vipp1. Lastly, using a conformation-restrained Vipp1 mutant, we reduced the structural plasticity of Vipp1 and determined two structures of Vipp1 at 3.0-Å resolution, resolving the molecular details of membrane-anchoring and intersubunit contacts of helix α0. Our data reveal membrane curvature-dependent structural transitions from carpets to rings and rods, some of which are capable of inducing and/or stabilizing high local membrane curvature triggering membrane fusion.

Enhancing fuel breed-burn performance in a sodium-cooled fast reactor using a novel reactivity control method

This study aims to enhance the fuel cycle and fissile breeding performance of a sodium-cooled fast breeder reactor (FBR) by utilizing minor actinides (MAs) as a means of reactivity control alongside partially-inserted control rods. Choosing the PFBR-500 as the reference design, four core models, designated as Cases A, B, C, and D, utilizing various proportions of minor actinides (MAs) were built and simulated using OpenMC. The MA concentrations were optimized to compensate for the withdrawal of control rods and ensure the same initial reactivity for all cores. Burnup analysis over 365 EFPDs revealed a significant increase in cycle length and burnup for the modified cores along with a modest rise in breeding ratio. Notably, Case C, employing 3.45 wt.% MAs in the 88 inner-core fuel subassemblies achieved an extra 62.25 EFPDs cycle length, a 33.74% rise in single-cycle burnup, and a 3.86% increase in breeding gain compared to the reference. Loading MAs into the inner-core region proved to be more effective in enhancing both fertile-to-fissile conversion (thus extending the cycle length and fuel burnup) and transmutation than utilizing MAs throughout the core due to greater neutron flux at the core center. While Case D utilizing 2.2 wt.% MAs both in the inner and outer core fuel subassemblies had the highest overall MA loading, it demonstrated lower increments in cycle length, burnup, and breeding gain compared to Case C. Case C also exhibited the highest overall destruction rate (approximately 24%/y) for Np and Am isotopes, and successfully transmuted around 24.08 kg 237Np, 9.33 kg 241Am and 3.82 kg 243Am over the course of a single year. The addition of MAs also achieved a slight flattening of the axial and radial flux profile and a decrease in the flux peaking factor. However, it slightly lowered the beta-effective, Doppler constant, and control rod assembly worth, and shifted the coolant void reactivity worth to the positive side.

INCREASING THE DURABILITY OF HYDRAULIC CYLINDERS OF LIFTING AND TRANSPORTING MACHINES

Most lifting and transporting and loading and unloading machines have a hydraulic drive. One of the most common actuators that perform reciprocating and rotary movements are hydraulic cylinders, characterised by one-sided wear of the rod seals. Known rod assemblies are elastic sleeves mounted in the hydraulic cylinder housing, which covers the rod with a guaranteed gap. During the unit operation, a gap seal forms in the gap between the rod and the sleeve, which prevents the leakage of the working fluid from the high-pressure cavity and centres the rod in the sleeve. However, to ensure the reliable centring of the rod, the intensive flow of the working fluid through the gaps is required, which leads to significant leaks of the working fluid and a decline in the unit efficiency. The optimal gap does not ensure centring, leading to reduced unit durability due to uneven wear of the sleeve and rod. Therefore, the development of new designs of rod seals that ensure self-centring is an urgent task. The development trends of modern hydraulic drives of construction, track, and loading and unloading machines aim at increasing the pressure of the working fluid up to 32 MPa. It imposes specific requirements on the designs of seals of hydraulic cylinders – the core executive bodies. The analysis of the factors that reduce the durability of reciprocating pair seals shows that it is possible to divide them into several types: wear, aging, operational, and design factors. The article aims to develop and describe a fundamentally new design of a self-centring rod seal, which can increase the durability of hydraulic cylinders of lifting-transporting and loading-unloading machines without using additional devices. The analysis of trends in the development of constructions of rod units of hydro cylinders showed that fundamentally new types have emerged among the existing designs, which simultaneously perform two functions – rod guides and sealing. The most notable among them are combined active and passive rod seals. Passive combined seals of rod assemblies of hydro cylinders differ from traditional ones in that they allow rod movements in the radial direction and allow slight distortions of the rod, compensating for assembly and installation inaccuracies of the assembly. Active combined seals have the same advantages as passive combined seals but additionally compensate for the wear of the guide sleeve, which increases the durability of the entire rod assembly of the hydraulic cylinder. Keywords: hydraulic drive of lifting and transporting machines, hydraulic cylinder rod assembly, sealing, one-sided wear of the rod assembly, self-centring.

Euler–Euler modeling of turbulent annular regime

Euler–Euler methods are one of the many approaches available in literature for modeling droplet-laden flows. These models consider both the gas and droplet phases as inter-penetrating continua, thereby separate sets of transport equations are solved for these phases. The current work focuses on modeling of thin liquid films on solid surfaces in the context of the two-fluid approach to multiphase simulation. In majority of the literature, liquid films are modeled using a 2D Laminar approximation with a parabolic profile for the velocity across the film. However, a number of industrial applications demonstrate a turbulent behavior of the film which would affect the effective viscosity and thereby the thickness of the film. In the current work, a turbulent model for liquid films is proposed based on the Universal Velocity Profile. Additional models are employed to capture the deposition of droplets onto solid surface and stripping off of droplets from the film due to surface waves. The liquid film model is validated on experimental data from available literature. Finally, the newly implemented turbulent film model is applied to study the flow over a fuel rod assembly in a Boiling Water Reactor.

Study on failure of a tie rod for two-wheeler automotive gear mechanism

ABSTRACT Failure studies of gear shifter tie rod assemblies are crucial for enhancing automotive system reliability and safety. The origin of a tie rod assembly failure is analysed through chemical, mechanical, microstructural, and fractographic analysis in this paper. Optical imaging reveals the microstructure of heat-treated steel, while fractography shows fatigue striations, indicating a progressive fracture. According to the analysis, the penultimate thread likely had a fracture due to the minimal radial space between the external thread and the head. The macroscopic and microscopic characteristics indicate failure from reverse bending under cyclic loading. A crack propagation and ultimate fracture mechanism has been proposed to provide a better understanding of tie rod thread part failures. The importance of factors like fatigue, reverse bending, corrosion, misalignment, and material properties in tie rod failures is highlighted in this study.

Reconfigurable frequency demultiplexer using coupled-resonator elastic waveguides

Reconfigurable coupled-resonator elastic waveguides are formed using defects composed of threaded rods, fixed with nuts and attached to a perforated two-dimensional phononic crystal slab. The resonant frequency of the defect can be tuned continuously within a complete phononic bandgap by adjusting the length of the threaded rod. Straight waveguides are formed from a line of defects. Phononic circuits are created by coupling three parallel straight waveguides. Through precise manipulation of the length of the threaded rod assembly, frequency demultiplexing of Lamb waves is achieved. Numerical and experimental results are found to be in good agreement. This work is of significance for the practical design of phononic devices including reconfigurable circuits.

Nascent flagellar basal bodies are immobilized by rod assembly in Bacillus subtilis.

Bacteria insert flagella in a species-specific pattern on the cell body, but how patterns are achieved is poorly understood. In bacteria with a single polar flagellum, a marker protein localizes to the cell pole and nucleates the assembly of the flagellum at that site. Bacillus subtilis assembles ∼15 flagella over the length of the cell body in a grid-like pattern and lacks all proteins associated with targeted assembly in polarly flagellated bacteria. Here we show that B. subtilis basal bodies are mobile soon after assembly and become immobilized when the flagellar rod transits the peptidoglycan wall. Moreover, defects in the flagellar rod lead to an asymmetric distribution of flagella with respect to the midcell. We conclude that the patterning of flagella is different in B. subtilis , and we infer that the B. subtilis rod probes the peptidoglycan for holes that can accommodate the machine.

FlhE functions as a chaperone to prevent formation of periplasmic flagella in Gram-negative bacteria

The bacterial flagellum, which facilitates motility, is composed of ~20 structural proteins organized into a long extracellular filament connected to a cytoplasmic rotor-stator complex via a periplasmic rod. Flagellum assembly is regulated by multiple checkpoints that ensure an ordered gene expression pattern coupled to the assembly of the various building blocks. Here, we use epifluorescence, super-resolution, and transmission electron microscopy to show that the absence of a periplasmic protein (FlhE) prevents proper flagellar morphogenesis and results in the formation of periplasmic flagella in Salmonella enterica. The periplasmic flagella disrupt cell wall synthesis, leading to a loss of normal cell morphology resulting in cell lysis. We propose that FlhE functions as a periplasmic chaperone to control assembly of the periplasmic rod, thus preventing formation of periplasmic flagella.

MTIR-SCP nuclear safety concept

The MTIR-SCP reactor is a research reactor with a light-water coolant having a fast neutron spectrum in nominal operation. None of the existing or projected reactors has a set of these features, therefore, special attention should be paid to the choice of the design of control rods and their location. The article considers various designs of control rods characteristic of the VVER-SCP power reactor currently under development, as well as existing research reactors with a liquid metal coolant having a fast neutron spectrum, taking into account the features of the MTIR-SCP: a seven-element control rod assembly design, as well as a ring-type absorbing element. Efficiency calculations are carried out for each of the structures under consideration and it was determined that the design of a control rod with an annular type of absorbing element has the highest specific efficiency. This design is chosen as the main one for the MTIR- SCP reactor. Criteria are proposed and optimization of the placement of control rods in the reactor core is carried out in order to reduce the uncertainty of obtaining neutron-physical characteristics in the central autonomous loop channel and increase the flow density in it. When optimizing the placement of control rods in the research reactor, their influence on the main neutron-physical characteristics, and especially on their distribution during operation under nominal conditions, is taken into account. Emergency protection and compensating rods that compensate for temperature and density effects when the reactor reaches the nominal power level have been removed, therefore their effect on the neutron-physical characteristics of the reactor and the loop channel during operation at power is not significant, and the compensating rods are located in the core and are removed as the fuel burns out, therefore their effect on the spatial The distribution of neutron-physical characteristics will be significant. To reduce this effect, burnout compensators and automatic regulators are proposed to be moved outside the core into the reflector. For various reactor conditions, the efficiency of the control and protection system was evaluated. It is shown that in various states, the control rods transfer the reactor to the required level of subcriticality, in accordance with NP-009-17.

Local characteristics of bubbly flow in rods assembly 3 × 3

This study focuses on the experimental investigation of local characteristics of upward bubble flow in a 3 × 3 square rod bundle assembly. The experiments were conducted at Reynolds numbers ranging from 4000 to 11000 and gas void fractions up to 10%. The distribution of the gas phase around the central rod of the assembly was measured using a frontal conductivity probe, while the wall shear stress on the central rod was obtained through the electrodiffusion method. It is shown that the gas phase distribution does not exhibit the symmetry characteristic of the assembly cross-section. Furthermore, as the distance from the spacer grid increases, a reconfiguration of void fraction profiles is observed. This explains the non-monotonic dependence of wall shear stress and wall shear stress fluctuations on the distance to the spacer grid.

CFD analysis in effects of spacer-vane on thermal–hydraulic performance of two-phase flow in annular channel

Spacer performs a key function in the construction of nuclear rod assembly. It is utilized to ensure the appropriate spacing and firmness of the rods in assembly. In rod bundle structures, spacers are typically incorporated with vanes to promote turbulence and improve heat transfer. The aim of this work is to analyze the impacts of spacer-vane on the thermal–hydraulic performance of two-phase flow in an annular channel. CFD model of an upward flow annular channel with spacer-vane has been developed. In addition, an annular channel model with a spacer but without vane has been generated and modeled in order to examine the impact of the spacer-vane in a two-phase flow. Transient simulations were performed with flow considerations of mass flux 714.4 kg/m2s, liquid temperature 330 K, volume fraction 0.35, heat flux 197.2 kW/m2, and atmospheric pressure conditions. CFD results have been validated with experimental data. Results show that the core zone of the annulus gap exhibits the highest level of turbulent intensity, and the outer pipe wall temperature is lower for spacer-vane relative to spacer alone. It is observed that the majority of water vapor is concentrated at the center of the channel in the farthest downstream location.

Study of energy transfer and stress wave propagation during SPT through energy measurement and PIV

The blow counts in standard penetration tests (SPT) require suitable corrections to account for energy losses. Over 4,000 energy measurement data collected from four test sites across Hong Kong have been collected and analysed in this study. On average for all instrumented hammer blows, approximately 62% of the theoretical hammer potential energy is transferred to the drill rod assembly. Using high-speed camera imagery and particle image velocimetry (PIV), the detailed mechanism of stress wave propagation has been visualised and assessed. This has revealed new details and allowed nuances in the results of routine energy measurements to be interpreted in new light. It has been confirmed that the initial compressive wave is reflected as a tensile wave for low end-restraint at the SPT sampler and as a second compressive wave for high end-restraint. The commonly observed discrepancy between the theoretical and measured speeds of wave propagation is highlighted and explored. Energy loss arises from friction during free-fall of the hammer, at the anvil, and from other sources such as the horizontal motion of the hammer-anvil system. The proportion of each major source of energy loss is quantified.

Threshold of Keulegan–Carpenter instability within a 6 × 6 rod bundle

The literature is rich in fluid–structure interaction studies of a single rod in oscillating fluid (or the reciprocate), however, there is a dearth of experimental data for rod bundle oscillation, particularly if the bundle is in a confined environment. The presence of the fluid surrounding the moving solid is modeled with force coefficients such as inertial and drag. In case of small amplitudes oscillating flow, these force coefficients depend non-linearly on the Keulegan–Carpenter number KC. The dependence present different regimes, separated by threshold KC numbers. At different regimes correspond different fluid dynamics, hence different force coefficients. The aim of this paper is to experimentally investigate the fluid dynamic for a rod bundle oscillating in a stagnant fluid. The velocity fields have been measured with Particle Image Velocimetry (PIV). Both the rod bundle and the fluid have the same refractive index, which allow to measure the velocity fields within the rod bundle in an non intrusive manner. The bundle is hosted in a double tank, immersed in a refractive index matched solution and placed on an earthquake shake table. The shake table sets the bundle into motion along a single direction.Data enable the identification of a threshold effect in the fluid response to the oscillating assembly. This threshold effect is due to the formation of vortexes in the fluid. Data show a clear trend on how the development of turbulence occurs firstly inside the rod assembly and then in the bypass between the assembly and the tank wall. The experimental results indicate the presence of a viscous boundary layer developed along the rod, above the threshold KC. The results presented in this paper represent a step forward the comprehension of the damping effect induced by the fluid at different oscillating amplitudes and frequencies, due to different KC regimes.

Core Optimization for Extending the Graphite Irradiation Lifespan in a Small Modular Thorium-Based Molten Salt Reactor

The lifespan of core graphite under neutron irradiation in a commercial molten salt reactor (MSR) has an important influence on its economy. Flattening the fast neutron flux (≥0.05 MeV) distribution in the core is the main method to extend the graphite irradiation lifespan. In this paper, the effects of the key parameters of MSRs on fast neutron flux distribution, including volume fraction (VF) of fuel salt, pitch of hexagonal fuel assembly, core zoning, and layout of control rod assemblies, were studied. The fast neutron flux distribution in a regular hexagon fuel assembly was first analyzed by varying VF and pitch. It was demonstrated that changing VF is more effective in reducing the fast neutron flux in both global and local graphite blocks. Flattening the fast neutron flux distribution of a commercial MSR core was then carried out by zoning the core into two regions under different VFs. Considering both the fast neutron flux distribution and burnup depth, an optimized core was obtained. The fast neutron flux distribution of the optimized core was further flattened by the rational arrangement of control rod channels. The calculation results show that the final optimized core could reduce the maximum fast neutron flux of the graphite blocks by about 30% and result in a more negative temperature reactivity coefficient, while slightly decreasing the burnup and maintaining a fully acceptable core temperature distribution.

A connecting rod assembly deformation cognition method based on quality characteristics probability network

As the core component of marine diesel engines, the connecting rod quality directly affects the reliability and life of diesel engines. However, the deformation problem of the connecting rod assembly process, which caused the low pass rate of one-time assembly, has not been well solved. The deformation of connecting rod assembly is difficult to analyze by mechanism because it is influenced by many quality characteristics with complex and cross-process correlations. To address this issue, this paper proposes a connecting rod assembly deformation cognition method based on the quality characteristics probability network. Firstly, a quality characteristics probabilistic network model for the connecting rod assembly process is established. Secondly, based on the quality characteristics probability network model and the complexity of cross-process correlation, the K-shell entropy weight model is used to identify the key quality characteristics and construct their correlation model. Then, to deal with the uncertainty of the influence degree between quality characteristics, a Bayesian network is used to establish an influence analysis model of key quality characteristics and analyze their influence relationship from qualitative and quantitative perspectives. Finally, the simulation and actual assembly data of marine diesel engine connecting rod assembly process are used to train and verify the cognition method. The results show that the method can effectively analyze the relationship between the connecting rod assembly process quality characteristics and predict the connecting rod deformation degree. The proposed method can comprehensively consider the influence of multiple processes and quality characteristics, improve the accuracy of analysis and prediction of connecting rod deformation, and can be used to guide the dynamic adjustment of the connecting rod assembly process to increase the pass rate of one-time. Moreover, the proposed method can also provide a reference for other multi-process and multi-factor problem analyses.

Investigation of Steel Plate Washer Thickness for Column Anchor Rod Applications

Since the 13th edition, the AISC Steel Construction Manual has included provisions regarding the recommended minimum plate washer thickness used in a column base plate and anchor rod assembly. Each plate washer must have sufficient strength and stiffness to fully develop the anchor rod to which it is fastened without succumbing to pull-through, flexural, or cracking failure. Laboratory tensile testing of an anchor rod, nut, and plate washer assembly was conducted at the University of Cincinnati to study plate washer performance. This testing investigated the capacity of ASTM A572/A572M Grade 50 plate washers using the recommended minimum thicknesses as listed in Table 14-2 of the 15th edition of the AISC Steel Construction Manual, with anchor rods having ¾, 1, 1½, 2, and 2½ in. diameter. A total of 94 tests were conducted, after which the plate washers were visually assessed for signs of failure, including measurement of permanent out-of-plane deformation. This assessment established that a 40% relative deformation in plate washers could reasonably be judged as a failure threshold due to excessive deformation. Testing and assessment revealed that while 10 plate washers exhibited relative deformations in excess of 40%, the recommended minimum plate washer thicknesses found in AISC Manual Table 14-2 were sufficient in fully developing most anchor rods. The notable exception to the current minimum thickness recommendations were for washers in use with anchor rods with diameters of ¾, 1, and 1½ in. made from Grade 105 steel. For these anchor rods, a thicker plate washer than that currently specified is recommended. Testing also found that the anchor rod orientation and the variations of ultimate strength in individual anchor rods did not appear to be significantly associated with the performance of plate washers in these tests.

DNBR Limit Analysis for the Inner channel of Annular Fuel

The departure from nucleate boiling ratios (DNBR) limit for annular fuel might vary from that of conventional nuclear fuel rod assemblies due to the distinct features of annular fuel assemblies. Precise estimation of DNBR is crucial for ensuring the safe and optimal functioning of nuclear reactors equipped with annular fuel assemblies. This study examines the DNBR limit of inner channel for annular fuel, using the look up table-2006 (LUT-2006).A comprehensive database having data for both normal operation and accident situations in pressurized water reactors (PWRs) using annular fuel was built to analyze the DNBR limit of the inner channel of annular fuel. The critical heat flux (CHF) data in this database were categorized into two groups with the limiting quality as the boundary. The prediction accuracy of LUT-2006 and the DNBR limits were evaluated respectively. Given that the inner diameter of the inner channel of annular fuel in mainstream designs typically ranges from 8-9 mm, and considering the potential occurrence of the limiting quality phenomenon in the inner channel, it would be more suitable to utilize the LUT-2006 based on an 8 mm tube standard to establish the DNBR limit for the inner channel of annular fuel. A conservative DNBR limit of 1.308 is determined for the inner channel of an annular fuel using the LUT-2006. In future thermal-hydraulic optimization designs of annular fuel, it is advisable to utilize LUT-2006 for calculating the DNBR of the inner channel of the fuel.

Numerical Analysis of Effects of Vane Deflection Angle on Flow-Thermal Characteristics in a Fuel Rod Assembly

The utilization of a grid spacer with vane is a significant component within reactor fuel channels. The presence of the vane has a notable impact on the mixing of flow and the enhancement of heat transfer within subchannels. The purpose of this work was to perform a numerical analysis of the effects of the vane deflection angle on the flow-thermal characteristics in a fuel rod assembly. In the current analysis, a square array consisting of a 5 × 5 rod bundle was utilized. The pitch-to-rod diameter ratio was set to 1.33, while the blockage ratio of the grid spacer was determined to be 0.16. A relative study was made for flow-thermal characteristics with four different vane deflection angles, such as 21 deg, 25 deg, 29 deg, and 33 deg. Analyses were made for a fluid pressure of 15.5 MPa, an inlet temperature of 583 K, and a velocity of 4.74 m/s. The present study investigated the Shear Stress Transport (SST) k-ω and Renormalization Group (RNG) k-ε turbulence models to analyze flow phenomena and thermal performance. The numerical results were validated through experimental data and also compared with correlations proposed by researchers. The analysis of the results was carried out using various methods, including the examination of data curves and streamlines, as well as vector and contour plots. The results indicate that a higher deflection angle leads to a greater reduction in temperature at the grid spacer. The swirl ratio was observed to be maximum close downstream to the grid spacer, and the persistence of the swirl ratio in the downstream can enhance the performance of departure of nucleate boiling. The vane on the grid spacer with a higher deflection angle enhances the coefficient of heat transfer remarkably close to the downstream grid spacer.

Modulation of flow meandering in the gap of a model of a peripheral subchannel of a fuel rod assembly

Modulation of flow meandering in the gap of a model of a peripheral subchannel of a fuel rod assembly