Gap Height Research Articles

Teflon AF–Coated Nanotextured Aluminum Surfaces for Jumping Droplet Thermal Rectification

AbstractJumping droplet thermal diodes (JDTDs) are promising candidates to achieve thermal rectification for next‐generation thermal control. However, most prior demonstrations of JDTDs have relied on monolayer‐coated copper‐based superhydrophobic (SHPB) surfaces, while lower‐cost aluminum JDTDs with more durable thin polymeric coatings have not been explored. In this work, a JDTD is constructed that employs SHPB aluminum surfaces coated with protective thin films of Teflon AF (amorphous fluoropolymer) 1601. Measurements for different heating orientations, gap heights (H), and fill ratios (ϕ) show that a maximum thermal rectification ratio of 7 can be achieved for H = 2.4 mm and ϕ = 10%. A thermal circuit is demonstrated that uses the JDTD to rectify time‐periodic temperature profiles, achieving thermal circuit effectiveness values up to 30% of the ideal‐diode limit. Coupon‐level durability tests and device‐level cycling show that dip coated Teflon AF enables stable operation of Al JDTDs over >20 cycles, improving on the performance of a monolayer‐coated surface that fails after 5 cycles. The findings of this work signify that Teflon AF coated Al SHPB surfaces can be used for thermal rectification and motivate future research into Al JDTDs for advanced thermal management applications.

Impacts of gaps below both door and partition walls of cubicles on odorous gas transport and respiratory infection in a public lavatory

Odorous gas transport and respiratory infection in a public lavatory are highly subject to the adopted ventilation system. The gaps below both the cubicle door and the partition walls can affect the ventilation performance. This study employed a validated computational fluid dynamics (CFD) program to investigate a public lavatory containing four cubicles with squat toilets. The airflow, concentrations of hydrogen sulfide and methyl mercaptan, and respiratory infection risk during use of the toilet were modeled. Odorous gases were released from the squat pan, while the pathogens resulting in respiratory infection were released by the exhalation of the toilet users. A total of seven different gap designs were considered, including designs without any gap, with a gap below only the cubicle door in three different gap heights, and gaps in three different heights below both the door and the partition walls. In addition, the use of a single central air exhaust and the use of multiple air exhausts were compared. The results revealed that the air from the gap below each cubicle door can effectively dilute the odorous gases released from the squat pan, whereas the gap below the partition walls was not shown to be favorable. The use of multiple air exhausts restrains the pollutant's spread and reduces the respiratory infection risk.

Assessing ground stability of a vertical backfilled stope considering creep behaviors of surrounding rocks

Backfill is often employed in mining operations for ground support, with its positive impact on ground stability acknowledged in many underground mines. However, existing studies have predominantly focused only on the stress development within the backfill material, leaving the influence of stope backfilling on stress distribution in surrounding rock mass and ground stability largely unexplored. Therefore, this paper presents numerical models in FLAC3D to investigate, for the first time, the time-dependent stress redistribution around a vertical backfilled stope and its implications on ground stability, considering the creep of surrounding rock mass. Using the Soft Soil constitutive model, the compressibility of backfill under large pressure was captured. It is found that the creep deformation of rock mass exercises compression on backfill and results in a less void ratio and increased modulus for fill material. The compacted backfill conversely influenced the stress distribution and ground stability of rock mass which was a combined effect of wall creep and compressibility of backfill. With the increase of time or/and creep deformation, the minimum principal stress in the rocks surrounding the backfilled stope increased towards the pre-mining stress state, while the deviatoric stress reduces leading to an increased factor of safety and improved ground stability. This improvement effect of backfill on ground stability increased with the increase of mine depth and stope height, while it is also more pronounced for the narrow stope, the backfill with a smaller compression index, and the soft rocks with a smaller viscosity coefficient. Furthermore, the results emphasize the importance of minimizing empty time and backfilling extracted stope as soon as possible for ground control. Reduction of filling gap height enhances the local stability around the roof of stope.

Investigations on wagon–track interaction and running safety with unsupported sleepers

Unsupported sleeper defects are not rare for the ballasted track. Based on the status quo of the railway in Kosovo, this paper presents a study on the wagon–track interaction and running safety risk with unsupported sleepers. A three-dimensional wagon–track dynamic model is first developed and validated through a full-scale field experiment. The dynamic response features of wagon and track components are respectively presented and analysed under the sleeper hanging condition. Parameter studies and safety analysis are then conducted with different wagon speeds, including gap height, unsupported quantity, wagon load, and asymmetric effects of the unsupported sleeper. The results indicate that unsupported sleepers will induce wheel–rail impact and significantly exacerbate the vibrations of the wagon and track. The wavelength corresponding to the dominant frequency for the wagon vertical acceleration (ACC) is equal to the wheelbase. Moreover, adjacent ballasts of the unsupported zone exhibit maximal displacements and ACCs, which could be the compelling evidence to explain the extension of the unsupported zone. The derailment risk is typically higher when the unsupported sleepers are asymmetrically distributed compared to the scenarios with symmetrically unsupported sleepers. Additionally, the combined effects of unsupported sleepers and wheel flat will further deteriorate the wagon running safety. The presented results can provide a significant reference for the wagon speed increase and track maintenance in Kosovo and other countries with deficient railway infrastructure.

Numerical investigation on the viscoelastic polymer flow in material extrusion additive manufacturing

In this paper, high-fidelity direct numerical simulations (DNSs) are carried out to explore the behavior of viscoelastic polymer flow in direct ink writing (DIW) additive manufacturing. The impact of ink elasticity on the stress for the strand deposition process has been examined. The exponential Phan-Thien Tanner (PTT) model is used to characterize the shear-thinning viscoelastic rheological behavior of polymeric fluids, and the gas-polymer interface is captured by the volume of fluid (VOF) method. Focusing on the extrusion and deposition of polymer, the effects of ink elasticity represented by the Weissenberg number (Wi), normalized printing speed and gap height on the formation of the printed strand have been studied. The results indicate that the polymer flow out of the nozzle is quite stable with time, and the polymeric stress balance is disturbed in the middle of the printed strand. For high Wi, the strand has significant deformation and an obvious large head (the earliest printed bulge in the deposited strand), whereas a larger normalized printing speed leads to a large stress region. In particular, a small normalized gap height has a squeezing effect on the deposited strand, and a visible depression in the middle of the strand can be obtained for large heights. Additionally, the degree of polymer deformation exhibits a major monotonic dependence on the normalized printing speed and gap height. The nonlinear relationships between the maximum stress components and process parameters show that the maximum stress decreases with Wi, but different printing speeds and gap heights have almost no effect on the stress components in the build platform-normal direction. The above analysis contributes to the inference of the deformation effects in different flow states, which can provide guidance to DIW additive manufacturing.

Aerothermal performance of cavity tip with flow structure effects in a transonic high-pressure turbine blade

Understanding the mechanisms of leakage flow control and heat load distribution is important in optimizing the structure of cavity tips in gas turbines. This paper investigates the aerothermal performance of cavity tip in a transonic high-pressure turbine stage. By analyzing flow structure, the effects of squealer height, squealer width and gap height on aerothermal performance are explained. It has been found that both the leakage flow and heat load distribution are influenced by the structure of vortices in the cavity. The leakage flow is controlled by the suction-side cavity vortex and the scraping vortex. The heat load distribution relates to the “M-shaped” leakage flow induced by the scraping vortex. The geometric parameters can affect the structure of vortices, which then impacts the aerothermal performance of cavity tip. As the squealer height is 2.5τ0, both the leakage flow rate and average heat transfer coefficient decrease by 0.64 % and 6.6 %, respectively. A multi-objective optimization with a feedforward neural network prediction is conducted to determine the distribution characteristics of optimal design parameters. The optimal values are approximately 2.34 for the expansion ratio, 0.5τ0 for the squealer width and 0.5τ0 for the gap height. The optimal squealer height ranges from 1.5τ0 to 2.5τ0.

Analysis of Flow Characteristics between Tandem Flexible Structures Based on PIV: Substantial Applications for the Removal of Microplastics.

This study emphasizes the potential risk posed by microplastics, particularly in tap water. Numerous studies have reported the removal of microplastics, but the limitations in addressing this issue remain challenging. To tackle this problem, a new method is introduced using tandem flexible structures (FSs) for microplastic removal. The present study focused on understanding the hydrodynamic characteristics between FSs to utilize microplastic removal. This comprehension of fluid flow and FSs offers valuable insights for improving the efficiency of microplastic removal methods. Therefore, the optimal conditions for removing microplastics were experimentally investigated inside the FSs gap region. Based on the gap distance and height, the flow structures between FSs were investigated. A small secondary vortex structure that could trap particles from upstream was continuously maintained behind the upstream FSs under certain geometric conditions. It is shown that this vortex structure has an effective way of confining the particles from upstream. The persistency of a small secondary vortex was also evaluated. This study may be helpful to researchers working on microplastic removal and FSs with a tandem arrangement.

Effect of Increasing Occlusal Vertical Dimension on Smile Parameters

Introduction: Increasing Occlusal Vertical Dimension (OVD) becomes important aspect of complex prosthodontic treatment for maintaining balance between form of oral structures and function of stomatognathic system. The purpose of this study is to determine the effect of increasing OVD on various smile parameters during posed smile. Methodology: This observational descriptive study included 30 patients, 14 male and 16 females, visiting dental department of National Academy of Medical Sciences (NAMS), Bir Hospital. Four polyvinyl siloxane bite records were fabricated on stone cast mounted on a semi-adjustable articulator increasing OVD by +1 mm, +2 mm, +3 mm and +4 mm taking incisal pin as a reference. Photographs of posed smile were taken at OVD of +0 mm, +1 mm, +2 mm, +3 mm and +4 mm using a DSLR camera mounted on a tripod. Head position was stabilized using a head positioning device of a cephalometric unit during photography. Adobe photoshop CS6 extended was used to calculate the various measurement in pixel which was converted into mm with help of conversion ratio obtained. Data were then processed and analyzed using SPSS software at the 5 % significance level. Result: One-way repeated measures ANOVA found statistically significant differences in interlabial gap height, incisal edge to lower lip distance, smile index and display zone area with increasing OVD. No statistically significant differences were found for intercommisural width and incisal edge to upper lip distance. Conclusion: Within the limitations of this study, the excessive increase of OVD may lead to excessive interlabial gap height, incisal edge to lower lip distance, and display zone area. Also, the increase of OVD may lead to reduced smile index. No change may be expected in the position of the upper lip with increase of OVD. In addition, a change in the intercommisural width of the smile should not be expected with increasing OVD.

A novel step-gap design on the top-cover of the microchannel cold plate to improve the flow boiling stability and heat transfer performance

The current study investigates the impact of incorporating the step gap in the cover above the microchannel heat sink subject to two-phase convective boiling. The microchannel heat sink size is 49 mm × 52 mm, with a channel width of 200 μm and a height of 3 mm, with a fin thickness of 200 μm. The effect of the step gap above the microchannels (SGAM) was compared at different heights, one 1 mm, which represents 1/3 fin height, and 3 mm, which means the same fin height with the same sample with no step gap above the microchannels (NSGAM). The working fluid used dielectric fluid HFE-7000 at the mass flux ranges from 30 to 260 kg/m2·s, while the heat flux ranges from 50 to 156 W/cm2. Providing a step gap above the microchannels in the cover reduces pressure drop significantly, around 37 ∼ 48% lower than the NSGAM. The experimental results demonstrate that the SGAM configuration reduces wall superheat temperatures by approximately 4 ∼ 6 °C compared to the NSGAM configuration. Flow visualizations indicate that the SGAM design avoids flow reversal, where the pressure drop fluctuations are significantly reduced by more than three times. The experimental outcomes for excessive temperatures and total thermal resistance exhibit a high level of concordance with the analytical results, with a deviation being less than 11%. The spreading resistance comprises the major portion of the total resistance, accounting for approximately 52∼58%. The SGAM samples effectively reduce local wall temperature downstream for step gap heights 1 mm, and 3 mm are 4 ∼ 6 °C, and 2 ∼ 4 °C, respectively. Overall, these findings demonstrate the potential of the step gap above microchannels to improve flow boiling stability and heat transfer performance appreciably while offering a much lower pressure drop penalty.

An experimentally validated cavitation inception model for spring-driven autoinjectors

Cavitation, the formation and collapse of vapor-filled bubbles, poses a problem in spring-driven autoinjectors (AIs). It occurs when the syringe accelerates abruptly during activation, causing pressure fluctuations within the liquid. These bubbles expand and then collapse, generating shock waves that can harm both the device and the drug molecules. This issue stems from the syringe’s sudden acceleration when the driving rod hits the plunger. To better understand cavitation in AIs, we explore how design factors like drive spring force, air gap size, and fluid viscosity affect its likelihood and severity. We use a dynamic model for spring-driven autoinjectors to predict and analyze the factors contributing to cavitation initiation and severity. This model predicts the motion of AI components, such as the displacement and velocity of the syringe barrel, and allows us to investigate pressure wave propagation and the subsequent dynamics of cavitation under various operating conditions. We investigated different air gap heights (from 1 to 4 mm), drive spring forces (from 8 to 30 N), and drug solution viscosities (from 1 to 18 cp) to assess cavitation inception based on operational parameters. Results reveal that AI dynamics and cavitation onset and severity strongly depend upon AI operating parameters, namely drive spring force and air gap height. The maximum syringe acceleration increases with spring stiffness and decreases with air gap height; increases in air gap height prolong the time interval of syringe acceleration but diminish the maximum syringe acceleration. From actuation to injection, air gap pressure peaks twice, first due to impact with the rod/plunger and secondly due to the deacceleration event upon injection. The maximum air gap pressure increases with spring stiffness and decreases with air gap height. Results show that maximum cavitation bubble radii and collapse-driven extension rates occur with higher driver spring forces, smaller air gap heights, and less viscous solutions. A cavitation criterion is developed for cavitation in autoinjectors that concludes that cavitation in autoinjectors depends on the peak syringe acceleration.

Vibration Damping and Noise Reduction of a New Non-Newtonian Fluid Damper in a Washing Machine

Due to friction vibration dampers’ inability to effectively dampen low loads during high-frequency dewatering, drum washing machines vibrated intensively. In order to address this problem, in this paper, a novel type of low-cost non-Newtonian fluid damper is proposed and investigated based on the non-Newtonian fluid shear thinning properties’ effect on vibration suppression during the high-frequency dewatering process of the washing machine. In contrast to other commonly used dampers, the homemade non-Newtonian fluid damper significantly suppresses the growth trend of the apparent elastic coefficient at high frequencies. A systematic investigation of damper structural parameters reveals that smaller gap height, higher piston head number, and more viscous fluid viscosity are adequate for vibration suppression and noise reduction. These results demonstrate that the non-Newtonian fluid damper can produce an excellent vibration-damping effect for the entire washing process of the washing machine, especially for the high-frequency dewatering process. The acceleration attenuation ratio can reach up to 83.49%, the energy attenuation is up to 98.44%, and the noise reduction is up to 10.38 dB.

DCB Bonding Energy Measurement Using Confocal IR Microscopy

Direct bonding is a widely used technique in the semiconductor industry. Many materials can be assembled and stacked together with this technique, enabling the fabrication of many useful structures. The direct bonding technique is, for instance, a major step of the Smart Cut ™ process flow enabling the industrial-scale production of Silicon-On-Insulator (SOI) substrates [1][2]. Material diversification in the microelectronics industry (i.e. “More than Moore” approach) imposes new technological constraints. The substrate bonding process control has to be improved calling for more and more accurate bonding energy measurement protocols.In this work, a new technique is assessed in order to measure, at the wafer scale, direct bonding energies. It is derived from the standard Double Cantilever Beam (DCB) method [3] and uses interferometry in confocal IR laser source microscopy to measure crack openings (Fig. 1A) [4][5][6]. Such a bonding energy measurement protocol shows a better accuracy compared to other techniques (Fig. 1B & 1D). This is due to a better confocal microscopy resolution and the high intensity of the laser source. The elastic energy stored in bent wafers is obtained by measuring the beam curvature [7][8]. DCB deformation models are discussed from short-range crack opening to long distance beam-bending theories. Comparison is done between results from analytic models, Finite Element Model (FEM) and experiments (Fig. 1C).Near-bonding edge zone modeled with FEM simulation accurately matches experimental data. A new mechanical and universal bending model, valid at both small and large scales, is proposed. With this model, bonding energy extraction is then reduced to a simple scaling parameter extraction directly linked to the stored elastic strain energy (Fig 1C & 1D) [9]. This work opens prospects for deformation and bonding energy measurements in various configurations including bonded heterostructures, polymer, and metal bonding. [1] Bruel, Electron. Lett. 31, 1201 (1995).[2] K. Celler, A.-J. Auberton-Hervé, B. Aspar, C. Lagahe-Blanchard, and C. Maleville, in Wafer Bonding Applications and Technology, Springer Series in Materials Science, edited by M. Alexe and U. Gosele, Springer, Berlin (2004).[3] Maszara, G. Goetz, A. Caviglia, and J. B. Mckitterick, J. Appl. Phys. 64, 4943 (1988).[4] Wu, S. Gowrishankar, R. Huang et al., Int. J. Fract. 202, 1–19 (2016).[5] Gowrishankar, H. Mei, K. M. Liechti et al., Int. J. Fract. 177, 109–128 (2012).[6] Pallares, L. Ponson, A. Grimaldi, M. George, G. Prevot, and M. Ciccotti, Int. J. Fract. 156, 11–20 (2009).[7] Bertholet, “Measurement, optimization and multiscale modeling of silicon wafer bonding interface fracture resistance,” Ph.D. thesis (Catholique de Louvain, 2006).[8] Olbrechts, B. Lejeune, Y. Bertholet, T. Pardoen, and J.-P. Raskin, ECS Trans. 3(6), 279–289 (2006).[9] Colonel, A. Calvez, F. Fournel et al., J. Appl. Phys. 132, 215106 (2022). Fig. 1: A – (Top) Four pasted IR confocal microscope images acquired during the DCB testing (the vertical red dashed line shows the closing point’s fitted position). (Bottom) Air gap height measured as a function of pixel position.B – Simulated reflected intensity (left y-axis) and experimental reflected intensity (right y-axis), both as functions of the estimated distance from the closure point x. The vertical dashed grey line shows the real experimental closing point.C – Air gap height as a function of the position/thickness ratio (in log/log scales) for different analytical and numerical models and experimental data.D – Bonding energies including errors obtained with the standard length measurement method, the curvature interpolation method, the scaling method, or J-integral calculation from FEM as functions of the annealing temperature. Figure 1

Anthropometric evaluation of side, sex and age by radiological examination of the normal ankle joint among adult Egyptian population

PurposeSex and age estimation is important, particularly when information about the deceased is unavailable. There are limited radiological studies investigating side, sex and age differences in normal ankle morphometric parameters. The authors’ goal was to evaluate different ankle joint morphometric measurements and document variations among Egyptians.Design/methodology/approachA prospective study was conducted throughout 23 months on 203 (100 males and 103 females) adult Egyptians, aged between 20-69 years old, who were referred for a plain x-ray of bilateral normal ankle joints.FindingsAnkle parameters showed no statistical difference between both sides, except for tarsal width (TaW) which was significantly higher on right than left side (26.92 ± 2.66 vs 26.18 ± 2.65 mm). Males showed significantly higher morphometric values except for anteroposterior gap (APG) and talus height (TaH) which were significantly higher in females (2.29 ± 0.80 vs 1.80 ± 0.61 mm and 13.01 ± 1.68 vs 11.87 ± 1.91 mm, respectively). There was significant increase in tibial arc length, APG, distance of level of MTiTh from anterior limit of mortise, distance of level of MTiTh from vertex of mortise, sagittal distance between tibial and talar vertices and sagittal radius of trochlea tali arc in old age group compared to young one. A significant decrease in tibial width, malleolar width, TaW and TaH was noted in old age group compared to young one.Originality/valueAnkle joints of both sides are mostly symmetrical; however, there are significant differences in most morphometric values due to sex and age factors. These findings may be essential during side, sex and age determination.

The effect of valve design on the pressure losses in a high-pressure homogenizer – An improved pressure drop correlation for estimating gap height

Understanding how the design of high-pressure homogenizer valves influence pressure losses in the device is of general interest for performance optimizing, and of special importance for developing correlations for predicting gap heights and gap velocities. The traditionally used correlation is from 1975 and based on a limited experimental dataset on gaps that are longer and often of lower capacity than contemporary ones. This study uses well-validated best-practice CFD to develop an improved correlation for how homogenizing pressure depends on valve designs, extending previous investigations to also include the effect of seat and forcer incline angles. The suggested correlation differs substantially from the traditional ones, shows a marked effect on inlet and exit loss coefficients of Reynolds number and of inlet seat incline angle. For cases with Reynolds number comparable to pilot- and production-scale homogenizers, the gap height can be predicted to within 10% of the set value, using the suggested correlation.

Investigation the influence of inclination angle for flat plate solar air collector through experiment and simulation

The heat behaviour of a flat plate solar collector (FPSC) has been analyzed experimentally and numerically under natural convection air flow. The thermal energy transferred through the air by heat convection and heat radiation. The data collections for the solar collector includes various of the inclination angles (15°, 30°, 45°, and 60°). The conventional glazed solar collector has a very low efficiency. Hence, the collector is unglazed in this study. It also covered with the insulation on both sides and at the bottom plate to prevent heat loss. The analysis concluded that rising solar radiation causes temperature to rise. Besides that, it is found that the studies conducted simultaneously on the experimental and numerical models on the different inclination angles are still lacking. Hence, the numerical model was simulated through the utilization of Computational Fluid Dynamics (CFD) method. A comparison between the numerical model and experiment has revealed that the simulation results of FPSC are closer to the experiment result with less than 5% error. Thus, the numerical model that incorporates design parameters can be utilized for forecasting the way FPSC will operate properly. The results concluded that the FPSC with a 5 cm height of air gap has the highest heat output when inclined at 15 degrees.

Toward a continuum description of lubrication in highly pressurized nanometer-wide constrictions: The importance of accurate slip laws.

The Reynolds lubrication equation (RLE) is widely used to design sliding contacts in mechanical machinery. While providing an excellent description of hydrodynamic lubrication, friction in boundary lubrication regions is usually considered by empirical laws, because continuum theories are expected to fail for lubricant film heights h0 ≪ 10 nm, especially in highly loaded tribosystems with normal pressures pn ≫ 0.1 GPa. Here, the performance of RLEs is validated by molecular dynamics simulations of pressurized (with pn = 0.2 to 1 GPa) hexadecane in a gold converging-diverging channel with minimum gap heights h0 = 1.4 to 9.7 nm. For pn ≤ 0.4 GPa and h0 ≥ 5 nm, agreement with the RLE requires accurate constitutive laws for pressure-dependent density and viscosity. An additional nonlinear wall slip law relating wall slip velocities to local shear stresses extends the RLE's validity to even the most severe loading condition pn = 1 GPa and h0 = 1.4 nm. Our results demonstrate an innovative route for continuum modeling of highly loaded tribological contacts under boundary lubrication.

A Novel 2D/3D X-ray Microscopy Alignment and Inspection Solution for Thermocompression Bonding (TCB) in a Highly Integrated Flip Chip Fan-Out Wafer Level Package (FO-WLP)

As packaging drives to extend the capabilities of Moore’s Law via heterogenous integration, numerous bonding technologies have emerged as potential pathways, allowing for integration of both a variety of devices in the lateral space as well as vertical integration of chips via stacking. As vertical integration on interposer becomes more complex due to shrinking CDs and increasing die layers, alignment and shape control in the bonding process becomes critical. Thermocompression bonding (TCB) is particularly well-suited for larger die, where localized reflow allows a better control of chip gap height and tilt throughout the bonding process. TCB systems require both high accuracy and repeatability in all dimensions to provide a reliable system in package. While a 2D system can provide a plan view assessment of a single bond layer between two chips, it falls short in characterizing the critical z-dimension in a highly integrated chip stacking scenario. Therefore a robust solution is needed for both system alignment validation in the x,y plane as well as a capability to explore gap height and bump quality/buried issues in high aspect ratio TSV. This paper will explore an x-ray application of a stacked 15-layer die-to-interposer structure to qualitatively validate overall health of the TSV (bond, pad, fill) via a nondestructive volumetric method as well as quantitatively evaluate stacked die for via/ball/pad alignment to determine overall alignment shift during the bonding process. In the test vehicle for a flip chip FO-WLP process flow first presented by IMEC, a silicon (Si) bridge is utilized to connect the logic and through-package via dies with a bump pitch of 20µm for the logic die interconnect. This is done by carefully aligning the logic dies on the carrier and then placing the through-package dies aligned to the carrier and logic dies. In the final step, a high accuracy placement and stacking TCB tool attaches the Si bridge. To perform an accurate assessment for bump alignment and bond quality, an initial high-resolution 3D x-ray scan is performed on a 1.5mm3 region of interest with over 2,000 individual projections at a 1.4µm voxel resolution with a 4x objective, taking approximately two hours. The dataset is put through a deep-learning algorithm which generates an AI model. This model is then applied to a faster scan of 15 minutes with a 1.4µm voxel resolution for the same field of view (FOV) on a nearby array and the data is collected and processed. To verify alignment of the entire sample, data is collected on the tightest pitch (in this case 20µm) oriented in both the vertical (x) and horizontal (y) plane in the through-silicon via (TSV) region. The z-plane is analyzed and processed by computer vision algorithms, and individual interconnects are then quantified and sorted for solder height (z), width (x,y) and TSV misalignment (deviation from expected center, x1y1 → x2y2). To validate the model, a high-resolution uncorrected 20h scan and a 15min scan based on deep learning are collected for the same region of interest (ROI). The data is comparable. Furthermore, the global misalignment data between both datasets demonstrates similar misalignment propagating through the 15-layer stack.

Preliminary Wear Investigations With Pressure Actuated Leaf Seals for Superheated Steam Turbine Application

Abstract Pressure actuated leaf seals (PALS) are a promising technology for the modern load-follow operation of power plants and turbines. Their strength lies in their radial adaptivity, which enables a significantly smaller radial gap height than conventional labyrinth seals. In this paper, which is a continuation of ISUAAAT16-022 from 2022, the operating behavior with compressed air and shaft rotation up to 3000 rpm is investigated, including an analysis of the wear caused by frictional contact between the shaft and the seal leaves. This includes both concentric and eccentric contact behavior. The test seal with a nominal diameter of 300 mm is designed in such a way that it can be used in a similar design in subsequent industry-related superheated steam tests. In addition to the seal performance before, during, and after the wear-in process, the frictional torques, temperatures in the flow and on the shaft-contacting leaves as well as the material removal on leaves and shaft running surface are analyzed. The results show a basically robust operating behavior of the seal with moderate performance deterioration, which can be directly attributed to the increase in the clear gap. However, the shaft wear is higher than for other contact seals, so further investigations are necessary before use in practice is feasible.

Building energy-saving potential of a dual-functional solar heating and radiative cooling system

Space heating and cooling devices that rely on renewable resources are in demand amid energy crises in parts of the world. However, common renewable space heating and cooling devices are mono-functional. For regions with heating and cooling seasons, using two mono-functional devices might double the installation and maintenance costs, and prolong the payback period. This study proposed a dual-functional renewable heating and cooling device by utilising solar power and nocturnal radiative cooling. The device is a modified solar heating (SH) collector that optimises the nocturnal radiative cooling (RC) to become an SHRC collector. Investigation of the SHRC collector’s performance and energy-saving potential of a building-integrated SHRC collector was conducted using CFD and EnergyPlus. Analysis of the SHRC collector’s performance in various environmental conditions shows that the SHRC collector can reach 42 % thermal efficiency at zero-reduced temperature and > 50 W/m2 of net cooling power. Also, studies on the optimal air duct and air gap height reveal that a 1 cm air duct and 4 cm air gap as the best options for the SHRC collector design. Simulations of the building-integrated SHRC with a collector area of 9.43 m2 for a typical 100 m2 house building demonstrate the multi-seasonal advantage of the SHRC collector, with at least 1.5 kWh more daily savings than the SH and RC collectors in typical winter and summer days. Furthermore, the simulations estimate the annual combined heating and cooling energy savings by the SHRC collector around 32.7 % in Madrid, 25.5 % in Tokyo, and 14.0 % in Isfahan.

The evolution of print defects in inkjet printers at elevated print gap height

Image uniformity is a key requirement for inkjet printers. When the gap between the print-face and media is large, one of the main causes of non-uniformity is the misplacement of droplets due to air-flow instabilities. Here, we characterise the onset of printed image non-uniformity by measuring the optical density variation of images printed with varying numbers of active nozzles. The optical density data are obtained by scanning printed images, which are corrected to remove any scanner-related effects. Several transects across the image are extracted, the peak spatial frequency is computed using Fourier transform analysis, and the results from these different transects are averaged. The amplitude of the main frequency peak in image density variation exhibits the same onset behaviour as seen in numerical simulations of the fluid flow in the printhead-media gap. Using numerical simulation, we extend the range of the study to estimate the operating envelope for the printing system.