Vent Holes Research Articles

Development and Application of Catheter Electrodes for Rat Airway High-Voltage Pulsed Electric Field Ablation

High-voltage pulsed electric field (HV-PEF) ablation technology has demonstrated promising applications in the clinical treatment of chronic obstructive pulmonary disease (COPD). However, its use has been limited to exploratory applications in a small number of cases, and the underlying mechanisms remain largely undefined. To facilitate broader clinical implementation, comprehensive molecular mechanism studies via extensive animal experimentation are essential. Rats, due to their ease of modeling COPD and the availability of comprehensive molecular reagents, serve as an optimal model for such studies. Consequently, the development of electrodes specifically designed for HV-PEF respiratory ablation in SD rats is of significant importance. In this study, we meticulously examined the anatomical structure of rat airways and investigated various equipment parameters, including material composition, rigidity, diameter, electrode ring dimensions, spacing between positive and negative poles, insulation coating for the catheters, welding techniques between the guidewire and electrode ring, and the design of vent holes in the catheter. Based on these considerations, we fabricated PVC ablation electrode catheters with integrated ventilation functionality. Subsequently, we employed finite element simulation to estimate the field strengths that could be applied by these electrodes. The simulation results were then validated in normal rats to assess the electrical safety and efficacy of the electrodes. These findings laid the groundwork for further investigation into the mechanisms of HV-PEF treatment for COPD.

Fabrication of organic thin films using slit nozzle with a wide viscosity spectrum

A slit nozzle with a broad viscosity spectrum is highly demanded for slit coating of various materials with different viscosities without a compromise on the film quality. To this end, we have fabricated a multi-cavity slit nozzle with the inlet and vent holes for each cavity. Compared with a slit nozzle with a high-volume single cavity, such a multi-cavity slit nozzle further reduces the dead volume and thus material waste. As a design parameter in computational fluid dynamics (CFD) simulations for the multi-cavity slit nozzles, we have calculated the coefficient of variation in the internal pressure (Pcv) of the cavity and investigated the correlation between the simulated Pcv value and the measured thickness uniformity of low-viscosity (tens of cPs) poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), medium-viscosity (5000 cPs) polydimethylsiloxane (PDMS), and high-viscosity (18,000 cPs) hard-PDMS films. It is addressed that the Pcv value that can ensure the thickness non-uniformity of less than 5 % is of the order of 1 %, and the internal pressure of the nozzle should not exceed a specific upper limit to protect a coating system against overload. Based on the design guideline provided, we have found that the upper limit of the viscosity spectrum of the triple-cavity slit nozzle with the 800-μm-thick shim is 79,000 cPs when the flow rate is 50 ml/min. Using the multi-cavity slit nozzle, we have fabricated a highly uniform PDMS film exhibiting the tensile strain as high as 180 %, which can be used as a substrate for stretchable displays. Furthermore, we have successfully fabricated flexible OLED stripes on the slit-coated conductive PEDOT:PSS stripes, showing the average luminance of 72.8 cd/m2 at 5 V and inter-stripe luminance non-uniformity as low as 8.2 %.

Modified Two-Step Impressions via the Incorporation of Venting Holes: A Technical Report.

This study presents a methodology for obtaining a precise impression of the crown margin of prepared teeth by utilizing a two-step impression technique. The method begins with the fabrication of a custom tray made from heat-cured acrylic resin, followed by the acquisition of an initial impression using putty elastomeric material. Subsequently, the impression is relieved around the prepared teeth, and vent holes are strategically placed through both the impression and the tray. Finally, a light-body consistency impression material is applied. This streamlined technique enhances efficiency and minimizes the errors commonly encountered with traditional two-step impression methods.

Heat transfer within a multi-package: Assessing the impact of package design on the cooling of strawberries

Perishable horticultural products may necessitate multi-packaging for preservation. The optimized primary and secondary packaging designs allow to reduce cooling time and ensure uniform product temperature, thereby enhancing fruit quality. This study examined how the secondary package design impacts the cooling of strawberries in airtight clamshells (AC) during precooling. The AC design simulates heat transfer within Modified Atmosphere Package (MAP) where there is no direct interaction between the external cooling air and the internal environment of the clamshell. Laboratory experiments were conducted to simulate one level of a pallet, using artificial material instead of real strawberries in order to have a better control of thermophysical properties and thus to better investigate heat transfer mechanisms. The thermal performance of an existing tray design was compared to three new alternative designs. The effect of air headspace, vent holes area and inlet airflow rate on the cooling efficiency was investigated.Experimental results revealed significant cooling heterogeneities among different AC positions, with the largest observed disparities being 1.8 h for half cooling time (HCT) and 3.7 h for seven-eight cooling time (SECT) in the current tray design. Incorporating vent holes into the current commercialized tray design demonstrated superior cooling performance, with 8% improvement of the overall average HCT. Analysis showed increasing the thickness of the air headspace above the AC increased 91% and 113% the overall average HCT and SECT, respectively. The research found that airflow distribution in a tray has a critical effect on the heat transfer between the AC walls and the surrounding air temperature. Thus, the packaging design is crucial in ensuring proper ventilation around the ACs.The alternative designs or operating under a lower airflow rate revealed a potential to cut down on energy use for ventilation. Specifically, when the airflow rate was reduced by one-quarter, there was a remarkable 94% decrease in energy usage. However, this benefit is counterbalanced by a 100% increase in the overall average HCT, which might adversely affect the product quality. Hence, optimizing the packaging design is essential to ensure the right balance between energy efficiency and product quality.The HCT exhibited a linear correlation with the external resistance, which is influenced by the airflow behavior, whatever the AC positions and tray designs.

Osteotomy Site Venting Enhances Femoral Bone Consolidation With Magnetic Intramedullary Lengthening Nails.

Magnetic intramedullary lengthening nailing has demonstrated benefits over external fixation devices for femoral bone lengthening. These include avoiding uncomfortable external fixation and associated pin site infections, scarring, and inhibition of muscle or joint function. Despite this, little has changed in the field of biologically enhanced bone regeneration. Venting the femoral intramedullary canal at the osteotomy site before reaming creates egress for bone marrow during reaming. The reamings that are extruded from vent holes may function as a prepositioned bone graft at the distraction gap. The relationship between venting and the consolidation of regenerating bone remains unclear. (1) Do bone marrow reamings extruded through venting holes enhance the quality of bone regeneration and improve healing indices and consolidation times? (2) Is venting associated with a higher proportion of complications than nonventing? We performed a retrospective study of femoral lengthening performed at one hospital from December 2012 to February 2022 using a magnetic intramedullary lengthening nail with or without venting at the osteotomy site before reaming. This was a generally sequential series, in which the study groups were assembled as follows: Venting was performed between July 2012 and August 2016 and again from November 2021 onward. Nonventing was used between October 2016 and October 2021 because the senior author opted to create drill holes after the reaming procedure to avoid commitment to the osteotomy level before completing the reaming procedure. Outcomes were evaluated based on bone healing time, time to achieve full weightbearing, and complications. Sixty-one femoral lengthening procedures were studied (in 33 male and 28 female patients); two patients were excluded because of implant breakage. The mean age was 17 ± 5 years. The mean amount of lengthening was 55 ± 13 mm in the venting group and 48 ± 16 mm in the nonventing group (mean difference 7 ± 21 [95% CI 2 to 12]; p = 0.07). The healing index was defined as the time (in days) required for three cortices to bridge with new bone formation divided by the length (in cm) lengthened during the clinical protocol. This index signifies the bone formation rate achieved under the specific conditions of the protocol. Full weightbearing was allowed upon bridging the regenerated gap on three sides. Consolidation time was defined as the total number of days from the completion of the lengthening phase until adequate bone union (all three cortices healed) was achieved and full weightbearing was permitted. This time frame represents the entire healing process after the lengthening is complete divided by the amount of lengthening achieved (in cm). Patient follow-up was conducted meticulously at our institution, and we adhered to a precise schedule, occurring every 2 weeks during the distraction phase and every 4 weeks during the consolidation phase. There were no instances of loss to follow-up. Every patient completed the treatment successfully, reaching the specified milestones of weightbearing and achieving three cortexes of bone bridging. The mean healing index time in the venting group was faster than that in the nonventing group (21 ± 6 days/cm versus 31 ± 22 days/cm, mean difference 10 ± 23 [95% CI 4 to 16]; p = 0.02). The mean consolidation time was faster in the venting group than the nonventing group (10 ± 6 days/cm versus 20 ± 22 days/cm; mean difference 10 ± 23 [95% CI 4 to 15]; p = 0.02). No medical complications such as deep vein thrombosis or fat or pulmonary embolism were seen. Two patients had lengthy delays in regenerate union, both of whom were in the nonventing group (healing indexes were 74 and 62 days/cm; consolidation time was 52 and 40 days/cm). Femoral lengthening with a magnetic intramedullary lengthening nail healed more quickly with prereaming venting than with nonventing, and it allowed earlier full weightbearing without any major associated complications. Future studies should evaluate whether there is a correlation between the number of venting holes and improvement in the healing index and consolidation time. Level III, therapeutic study.

An ultra‐miniaturized single‐layer multiband frequency selective surface with vent for wireless communication

SummaryA novel single‐layer ultra‐miniaturized multi‐band Frequency Selective Surface (FSS) with a circular vent is designed for shielding LTE and ISM bands. The top layer of the proposed FSS unit cell incorporates a circular patch along with convoluted arms. The designed FSS unit cell exhibits band‐rejection characteristics with a resonance of 800 MHz, 2.45 GHz, and 5 GHz and bandwidths of 523 MHz, 687 MHz, and 725 MHz, respectively. The periodicity of an ultra‐miniaturized FSS unit cell is 0.024λօ x 0.024λօ, encompassing a spatial vent hole of 0.01λօ, where λօ corresponds to the lowest operating frequency. Moreover, the proposed FSS unit cell remains unaltered angular stability up to 75° with less than 1% frequency deviation in TE and TM modes. Good polarization insensitivity for the designed four‐fold symmetrical FSS unit cell is achieved. Further, an Equivalent Circuit Model (ECM) analysis is developed to infer the physical insight of the proposed FSS unit cell. The FSS prototype is measured for the assertion, and the good agreement between the findings from simulation and measurement is validated. For real‐time assertion, the FSS prototype is verified using the Amitech SDR04. Thus, FSS is a promising candidate with good ventilation for shielding the LTE, Bluetooth, and Wi‐Fi application bands.

Optimizing ventilated packaging design for strawberries: Assessing the impact on fruit quality from farm to retailer using physics-based modeling

Amongst fruits and vegetables, strawberries (Fragaria × ananassa) are one of the most perishable products. Consequently, it is challenging to maintain their quality until they reach the consumer. Therefore, keeping optimal hygrothermal conditions around the berries from farm to the consumer is crucial to preserving them and avoiding food loss. Using ventilated packaging design is an established way to address this technological, economic, and environmental problem. Until now, strawberry packaging is often designed using a trial-and-error approach, and a multitude of packaging designs exist. Ideally, the packaging should be designed in such a way that it provides the best preservation of the fruit all the way from farm to retailer. This is challenging since the hygrothermal conditions change significantly along the supply chain. In this study, we use physics-based modeling to evaluate new strawberry packaging designs in regard to cooling performance, risk of condensation, mass loss, and respiration-driven shelf life of the fruit and assess their performance along the whole post-harvest export supply chain from Spain to Switzerland. Twelve packaging designs for strawberries with existing and newly-designed vent hole configurations were investigated. Simulations quantified how the berries physiologically and hygrothermally evolve inside these packages along the whole post-harvest supply chain. Implementing appropriate ventilation in open-and top-sealed trays for strawberries can help to minimize losses along the post-harvest supply chain. As commonly known, strawberries cool significantly faster in better-ventilated trays than in unventilated trays, and condensation-based time of wetness could be reduced by 45% by adding additional ventilation holes in a top-sealed tray. The height of the secondary packaging, the total opening area (TOA), the size, and the placement of the vents have a substantial influence on the performance of the packaging. We recommend a TOA between 5.5% and 7% and a diameter of the vents between 5 and 12 mm. Also, they should be evenly distributed. However, there is always a trade-off in packaging design: a reduced risk of condensation comes along with a higher mass loss of the strawberries. Strawberry packaging models enabled a unique insight into the evolution of the fruits along the supply chain and visualized the spatial distribution of condensation and mass loss inside the package.

The Effect of Different Angled Abutments with Peripheral Groove and Vent Hole on the Retention of Cement Retained Implant – Supported Restorations

Background: The purpose of this study was to analyze the effect of vent hole or peripheral groove on retention of differently angled (15 ° and 30 o) abutments in of cement retained implant supported restorations. Methods: A total of sixty standart implant abutments were used. Abutments were divided into two groups at 15 ° and 30 ° angles on CNC. According to the modification, each group were divided into 3 subgroups; (1) no modifications, (2) with peripheral groove and (3) with vent hole. Sixty metal frameworks were prepared using laser sintering to fit all abutments. All laser sintered frameworks were cemented with eugenol-free provisional cement. Then, all specimens were thermocycled. The frameworks were removed from the abutments by using the universal test machine and the peak removal force was recorded. Statistical analysis were performed with two-way ANOVA, post hoc Tukey’s (HSD) test-adjusted independent samples t-tests. Results: According to the results, there were significant differences between 15 ° and 30 ° groups in terms of retention values (p < 0.001). Additional hole and grooves enhanced retention in both groups. The highest mean value of vertical pull-out strength (185.00 ± 23.08 N) was showed in 15 ° additional grooves group, and the lowest mean value of vertical pull-out strength (27.60 ± 14.84 N) was showed in 30° control group. Means values of additional groove specimens had the highest scores in both groups. In all groups, there were significant differences between all subgroups (p < 0.05). Conclusion: Increased abutment angle decreases retention, while addition of hole and groove increases.

Acoustical behaviour of “baroque” trumpets with vent holes

The trumpets for which baroque composers including Bach and Handel wrote viruoso solo parts were natural (valveless) instruments approximately twice the length of a modern C trumpet. Playing chromatically in the high register of a natural trumpet requires great skill, since only the approximately harmonic resonances of the fixed-length air column are available. In the second half of the twentieth century several makers collaborated with performers to develop variants of the natural trumpet incorporating three or four finger-holes. Such instruments, widely used in modern ensembles playing baroque music, are best described as ‘vented trumpets’. The way in which the finger-holes are used differs from the use of tone-holes on the cornett, the keyed trumpet and the keyed bugle. In general, vented trumpets are designed to approach the timbre of natural trumpets while facilitating control of intonation and accuracy in playing. In the present paper, the acoustical foundations for the function of the three- and four hole systems are explored. The study draws on input impedance measurements, computational modelling, and playing tests of typical vented and natural trumpets. Parameters quantifying the timbre of vented trumpets are compared with corresponding values for natural trumpets.

Volatile organic compounds (VOCs) emissions from internal floating-roof tank in oil depots in Beijing: Influencing factors and emission reduction strategies analysis

The internal floating-roof tank is the main type of storage tank for refined oil products. The volatile organic compounds (VOCs) emission from the internal floating-roof tank plays a dominant role in the unorganized emission source of the oil depot. In this study, we selected six typical oil depots in Beijing to investigate VOC emission characteristics from the tank top vent hole using infrared imaging technology and flame ionization detector (FID). The results reveal that infrared thermal imager is efficient in quickly identifying the emission level of the tank discharge point. The ambient temperature and wind speed have a direct effect on sealing loss, the turnover can greatly influence the wall hanging loss, and the concentration of VOCs emitted from the tank top vent hole is negatively correlated with liquid height. Furthermore, the influence of accessories type of the internal floating-roof tank on the concentration of VOCs emission from the top vent hole is also studied when other parameters remain unchanged, and find the floating deck type and sealing mode have a significant influence on their VOCs emissions, of which the combination of pontoon type floating deck and secondary seal are effective in controlling the concentration of VOCs emitted from the tank top vent hole. Finally, based on our experimental results, several feasible emission reduction strategies are proposed in terms of source prevention and process control in order to achieve the fine management of the whole process. This paper provides important technical support and policy thoughts for VOCs emission control during oil storage.

Enhancing Dimensional Geometry Casting using Computer Modeling

Sand casting method is used to produce many useful products for many applications. The aim of the study is to manufacture a product with excellent dimensional geometry is achieved in sand casting process at low cost. We would expect manuscripts to show how design and/or manufacturing problems have been solved using computer modeling, simulation and analysis. In this work, the important mechanical properties of hardness and surface roughness are investigated on Aluminum 6063 cast material with and without incorporating the copper tubes as a vent hole in sand casting process. Since copper has high thermal conductivity when compared to other metals, the heat transfer rate will be varying from existing system. The copper tubes have made different diameters of holes on outer surfaces with selective distance of intervals. The specific number of copper tubes with various diameters are designed by CATIA modeling software and analyzed with Taguchi Design of Experiment. Taguchi L9 orthogonal array is used proficiently in the optimal value of hardness and surface roughness. The results are revealed that the maximum hardness value of 104 BHN is attained for 10mm distance of holes made on copper tube with an angle of 90o degree. The minimum surface roughness of 2.11 micron is achieved for 20mm distance of holes made on copper tube with 45o of angle as a vent hole in sand casting process.

An on-site inspection system for explosives in a container using dust collection through a vent cover and ion mobility spectrometric detection.

Rapid and accurate cargo-inspection systems are required for shipping containers, because illegal and hazardous items, such as explosives and drugs, can be easily concealed in large containers. Dust in a container is suspended in the air and deposited in vent covers. The vapor and particulate matter of explosives can be adsorbed onto the dust. In this study, a model vent cover system was developed for a container and explosive-adsorbed dust specimens were modeled using organic [cotton fabric (CF) and sawdust (SD)] and inorganic substances [clay (CL) and silica (SL)]. The dust was placed in the inner part of the vent cover and collected through the vent holes, and the explosive components present in the dust were rapidly analyzed using ion mobility spectrometry (IMS). Three explosives, namely 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and pentaerythritol tetranitrate (PETN), were investigated along with two different collection filters, namely poly(tetrafluoroethylene) (PTFE) and lens cleansing paper (LCP). The dust collection rate decreased when the dust was located away from the vent holes. The order of the dust collection rate was SD > CF > SL > CL. The limit of detection (LOD) of TNT was considerably lower than those of RDX and PETN. The LODs of the explosives when using the LCP collection filter were lower than those when using the PTFE filter. The LOD order was CF < SD < CL < SL for the PTFE collection filter and CL < SL < CF < SD for the LCP filter. The technique developed in this study can be employed as a rapid and accurate cargo inspection system for shipping containers.

Improving design features and air bubble manipulation techniques for a single-step sandwich electrochemical ELISA incorporating commercial electrodes into capillary-flow driven immunoassay devices.

Integrating electrochemistry into capillary-flow driven immunoassay devices provides unique opportunities for quantitative point-of-care testing. Although custom electrodes can be inexpensive and are tunable, they require skilled fabrication. Here, we report the incorporation of a commercial electrode into a capillary-flow driven immunoassay (iceCaDI) device for a single end-user step sandwich electrochemical enzyme-linked immunosorbent assay (ELISA). The iceCaDI device is a pump-free portable microfluidic device with an integrated commercial screen-printed electrode and flow driven by capillary action. The iceCaDI device is composed of alternating polyester transparency film and double-sided adhesive film layers that are patterned with a laser cutter. This platform was designed to address known limitations of laminated device fabrication methods and operation. First, we developed a foldable laminated device fabrication using hinges for easy assembly and precise alignment. Second, reagent dispersing was achieved by incorporating a 1 mm wide arrow-shaped notch in the middle of the channel that trapped an air bubble and formed a baffle that facilitated reagent spreading to cover the detection area. Third, small vent holes were added to the top layer of the channels to prevent air bubbles from blocking flow. Finally, we fabricated a CRP immunosensor with a detection range of 0.625 to 10.0 μg mL-1 as a proof-of-concept to demonstrate an automatically driven sandwich electrochemical ELISA using the iceCaDI device. Three concentrations of CRP were successfully measured under flow conditions within 8 min. Our proposed device is a promising approach and a step forward in the development of point-of-care (POC) devices for techniques that traditionally require multiple user steps.

Failure analysis and reliability assessment of a type of aero-engine combustion chamber thermal barrier coatings

During a routine hole probe inspection, the aviation division found that the combustion chamber flame tube of a V2500 aero engine had failed early and that the TBCs around the vent holes on the flame tube liner panel 4 had peeled off over a large area, causing the flame tube liner to burn through. This work studies the premature failure of the V2500 aero-engine flame tube and, using modeling and simulation tests, finds the reason for premature failure as a substantial area of thermal barrier coating peeling owing to sintering. The sintering procedure significantly increases the thermal barrier coating's Young's modulus, which reduces the coating's resistance to thermal mismatch strain. The reliability of the TBCs was then evaluated using a probabilistic approach. Owing to the non-uniformity of temperature distribution induced by the hot airflow, the lifetime of the TBCs in the high temperature region is only around 3000 h, but the lifetime in the low temperature region is at least 25,000 h. Using the method of hole-probing, the values of the calculated and real outcomes are compared. The relative error is less than 5 %, demonstrating that the suggested approach for evaluating dependability has high credibility and applicability.

Comprehensive investigation of corrugated fiberboard boxes with edge vents for ambient loading of chinese cabbage: Part I - Computational fluid dynamics simulation and experimental validation

The ambient (warm) loading of perishable products is widely practiced during their storage and transport. The vent hole design in a corrugated fiberboard box is crucial for providing effective airflow to maintain the freshness of products during ambient loading. In this study, four different corrugated fiberboard boxes with vent hole areas of 0, 2, 3, and 4 % were prepared. The cooling behavior of the Chinese cabbage in the corrugated fiberboard boxes with different air vent holes was verified using a computational fluid dynamics (CFD) simulation model. The results indicated that the cooling rate of the Chinese cabbage in the top and bottom layers of the seven-layer box stacks decreased substantially faster than those in the middle layers of the boxes, regardless of the air vent hole areas. The experimental analysis indicated significant differences in the cooling rates of the Chinese cabbages among the seven-layer box stacks with 0, 2, 3, and 4 % air vent holes; however, the CFD simulation exhibited no significant differences in the cooling rates of the Chinese cabbages among those stacks. The compression strength of the corrugated fiberboard box designed with a 4 % air vent hole area exhibited the lowest value, which was nearly 20 % lower than that of the box with 0 % air vent hole area. Moreover, highly humid conditions were observed in the headspace of boxes, which was a critical factor causing a further decrease in its mechanical property in addition to the inevitable reduction caused by the vent hole design. Thus, the study findings can form the scientific basis for improving the edge-vent corrugated fiberboard box design used for transporting Chinese cabbage by ambient loading.

Experimental and numerical study on unsteady entrainment behaviour of ventilated air mass in underwater vehicles

The hydrodynamic characteristics of underwater vehicles are significantly affected by the ventilated cavity covered by the vehicle surface. In this paper, the unsteady flow characteristics of this ventilated cavity are studied using experimental and numerical methods, and the unsteady entrainment behaviour of the ventilated air mass is emphasised. The flow pattern of the ventilated air mass is recorded using a high-speed camera. The large eddy simulation turbulence model is employed for the numerical simulations, and a good agreement is observed between the experimental and numerical results. In the early stage of the formation of the ventilated air mass, the internal structure exhibits a symmetric kidney vortex system, while the ventilated cavity below the vent hole has a continuous hairpin vortex structure. The ventilated air mass experiences a growth stage, an entrainment stage, and a shedding stage. The entrainment behaviour enables the ventilated air mass to quickly fill the ventilated cavity and modifies the surface pressure distribution of the vehicle. As the cavitation number decreases, the radial size of the ventilated cavity increases, and the contact area between the cavity and the water body increases, thus enhancing the vertical drag coefficient of the vehicle.

Steel corrosion in precast reinforced concrete column-beam joint with grouted sleeve connections under chloride-rich environment

Due to the existence of pump and vent holes, precast reinforced concrete (RC) structure with grouted sleeve connections may have serious durability issues, which have almost never been studied. In this paper, a precast RC column-beam joint specimen with grouted sleeve (GS) connections, as a comparison of a cast-in-place specimen, was exposed to chloride-rich environments for 4 years. The steel corrosion and its impacts on specimen were investigated by visual inspections, X-ray computed tomography (X-ray CT) and data analysis. The test results showed that the precast RC specimen exhibited porous and loose interfaces between PVC tubes, sleeve and cement-based materials within the GS connections, leading to more severe stirrup corrosion compared to the cast-in-place specimen. In contrast, the sleeve, grouting material and their interfaces were dense so that the longitudinal bars inside had been well protected. Besides, the chloride diffusion coefficient of concrete cover in the two specimens were quantified. The corrosion level of precast RC structures with GS connections was found to grow more rapidly versus service year. On this basis, several precautions for alleviating the negative impact of GS connections on steel corrosion were proposed.

Pore Forming Agent–Assisted Fabrication of Porous Platinum Vent Frits and Their Suitability Evaluation for Radioisotope Power Sources

Disc-shaped porous platinum sintered frits were fabricated employing a pore forming agent (PFA) via a powder-metallurgical process. Porous vent frits using several platinum-PFA compositions were prepared after characterizing the starting materials (platinum and PFA powders) for particle size (D50) and distribution (D10 to D90), morphology, Brunauer-Emmet-Teller surface area, density (apparent and tap), etc. The sintered platinum vent frits were extensively characterized to evaluate their suitability for application in terms of surface microstructure analysis by scanning electron microscopy, helium/air permeability parameters, and particulate filtration characteristics. This paper reports for the first time on the measurement of retention efficiency of vent frits for particulate sizes 0.3, 0.5, and 1 µm. The platinum frits made using 10 and 20 vol % PFA were found to be suitable as a vent hole filter for radioisotope power sources.

Estimation of Discharge Coefficient of Compartment Venting during Atmospheric Reentry of the Space Capsule

The problem of re-pressurization of compartment of reentry space capsule through vent holes is formulated using equation of mass conservation, isentropic relation and perfect gas equation of state. Resulting, a one-dimensional nonlinear compressible transient equation is numerically integrated employing fourth-order Runge-Kutta scheme in order to obtain compartment pressure using knowledge of the discharge coefficient of the orifice. An inverse venting analysis is carried out to estimate the discharge coefficient using measured and computed compartment pressure time history during the reentry phase of the space capsule. The inverse venting problem is solved using the Newton-Raphson method coupled with a direct-search algorithm utilizing pseudo-random numbers. The inverse venting algorithm estimates the discharge coefficient of the vent holes in a stepwise manner as a function of the reentry flight Mach number. The reconstructed compartment differential pressure is compared with pre- and post-flight data. It is observed that the estimated values of the discharge coefficient depend on the accuracy of the transmitted telemetry data, dispersion of the reentry trajectory, pressure acting on the base of the capsule and atmospheric pressure.

Design for the Vent Holes of Gas Turbine Flow Guide Disks Based on the Shape Optimization Method

Two shape optimization methods, based on non-parametric and geometric parameters, were developed to address stress concentrations in the vent holes of gas turbine flow guide disks. The design optimization focused on reducing the maximum equivalent stress at the hole edge in an aero-engine gas turbine flow guide disk. The effectiveness of both methods in achieving this objective was studied. The results indicated that the non-parametric-based optimization method reduced the maximum equivalent stress at the hole edge by 24.5% compared to the initial design, while the geometric parameter-based optimization method achieved a reduction of 20.2%. Both shape optimization methods proved effective in reducing stress concentrations and improving fatigue life. However, the non-parametric shape optimization method resulted in a better design for the vent holes based on the study’s findings.