bluuebunny/crossref_metadata_2025 huggingface dataset:
Digitalization and Digital Twins in Long Term Management of Radioactive Waste
Authors: Jacques Diederik , Kolditz Olaf , Szőke István , Churakov Sergey V. , García David , Laloy Eric , Montoya Vanessa , Prasianakis Nikolaos I. , Samper Javier
Published: November 2023

Digitalization and Artificial Intelligence is the fastest emerging paradigms in engineering and natural science applications. As an example data-driven and physics-inspired machine learning methods have been developed and evaluated to accelerate numerical simulations; evaluating their usability for applications related to the radioactive waste management cycle is therefore of high relevance. Under the umbrella of the European Joint Programme on Radioactive Waste Management (EURAD) and on Pre-disposal Management of Radioactive Waste (PREDIS), different initiatives have been established to facilitate evaluation and implementation of digitalization technologies (and specifically digital twins mirroring their corresponding physical assets) for long-term radioactive waste management. Previous studies indicate that digitalization is an important tool, to improve processes throughout the whole waste management cycle including pre-disposal activities like waste treatment, conditioning, storage and aspects related to the operation and long-term performance of disposal systems. However, before implementation, several challenges related to different facets of digital twins and digitalization need further research. At this stage, the specific potential and role of different aspects of digital transformation for different topics of waste management is still somewhat vague. In this contribution, an overview will be given addressing selected research developments s based on activities that are ongoing in EURAD and PREDIS or in closely related activities.
Influence of Blending Phosphogypsum to Mitigate Radium Leaching and Enhance Reuse As Road Base Material
Authors: Weiksnar Kate D. , Lott Dreyton J. , Townsend Timothy G.
Published: November 2023

The processing of phosphate rock to produce phosphoric acid results in a calcium sulfate byproduct known as phosphogypsum (PG). This byproduct is regulated in the United States as a Technologically Enhanced Naturally Occurring Radioactive Material (TENORM) and is managed indefinitely in monofills or gypstacks. Reuse of this material is inhibited by regulations surrounding radon release and total and leachable 226Ra concentrations, however increased interest in using PG as a road base material has developed. Many sources of PG cannot be used as a road base material alone largely due to insufficient strength and potential for 226Ra leaching. This paper investigates the influence of blending PG with common alkaline road base aggregates such as limerock and recycled concrete aggregate (RCA) to reduce 226Ra leaching from PG amended road base and provide an avenue for widespread reuse. Two sources of PG were investigated for 226Ra leaching at various pH conditions and blended with each of the two aggregate sources at up to 0,25,50, and 75% (by mass) PG to understand the behavior of 226Ra leaching. The results reveal an amphoteric leaching behavior from the PG sources alone. The blending experiment indicates an increase in leaching from PG:limerock blends initially, followed by a reduction with increasing limerock addition, and a decrease in leaching from PG:RCA blends. The amphoteric behavior of the PG paired with the leaching curves for these material blends indicates a mechanism of control of 226Ra mobility aside from change in pH, perhaps due to binding of radium by elevated concentrations of Ba, Sr, or Ca in the RCA blends. This data provides novel insight into controlling a limiting factor to PG reuse as a road base material and suggests that blending with RCA could allow for lower 226Ra mobility from PG blends and allow a larger application of PG reuse and an alternative scenario to end-of-life stacking.
Man-Portable LINAC-Based X-Ray Sources for NDT and Nuclear Security Applications
Authors: Kutsaev Sergey V. , Agustsson Ronald , Araujo-Martinez Aurora , Berry Robert , Boucher Salime , Ivanov Evgeny , Kaneta Kenichi , Kravchenko Maksim , Murokh Alex , Pronikov Alexey , Ruelas Marcos , Smirnov Alexander
Published: November 2023

Electron accelerators operating at energies in the MeV range and kW power levels are used for many industrial applications, including medical device sterilization, nondestructive testing cargo inspection, and radiotherapy. However, many of these applications, especially novel ones, require that size, weight, and costs of the accelerators are significantly reduced to be considered as a suitable source of radiation. Some examples of such applications include field radiography, mobile cargo inspection, radioactive source replacement and industrial irradiation. The dramatic level of miniaturization and cost-reduction is achieved thanks to the implementation of such innovative technologies as high-frequency magnetrons, novel fabrication technology, and solid-state power supplies.

In this paper we will cover the examples of man-portable accelerator-based X-ray sources for NDT and nuclear security applications, where our case studies of the accelerator system optimization for specific applications could be of interest to the broader community.
Safety Study on Korean Deep Geological Repository for High-Level Radioactive Waste: (2) Use of GoldSim for Risk Assessment
Authors: Choi Karyoung , Son Kibeom , Kim Hyungdae , Chang Kunok , Heo Gyunyoung
Published: November 2023

Risk, which is a quantitative representation for the degree of health risk caused by radiation exposure from disposed radioactive waste, is a main indicator for the safety of High-Level radioactive Waste (HLW) in Korean regulation, and it should be calculated by an appropriate methodology, which is not yet officially setup. Following the previous companion paper, which gives the overall description of the safety assessment, this paper shows the overall algorithm for risk assessment, actual example of a simple model by GoldSim, and the Monte Carlo simulation results for the model. This study may be an enabling step for developing deep-geological repository and carrying out the risk assessment afterwards in Korea.
Effect of High Active Raffinate Waste Composition and Loading on Early Age and Hardened Properties of Radioactive Cemented Waste Forms
Authors: Ghosh Debabrata , Ferreira Eduardo , Tri Phung Quoc , Cizer Özlem
Published: November 2023

This research focuses on the effects of waste loading and composition (specifically Ca(NO3)2, Ba(NO3)2 and NaNO3) on the early age properties and mechanical strength of nuclear cementitious waste forms, which are subjected to accelerated alkali-silica reaction (ASR) test. A laboratory-prepared acidic liquid waste simulating a high active raffinate (HAR) generated from the PUREX process is neutralized to a pH of 10 with a mixture of Ca(OH)2 and Ba(OH)2. The neutralized waste is then immobilized at 50, 53 and 56% by volume waste loadings (WL50, WL53 and WL56, respectively), with water/binder ratios of 0.33, 0.38 and 0.45, respectively. The immobilization matrix contains CEM I and supplementary cementitious materials such as blast furnace slag and silica fume, along with other components such as limestone fillers and lime. The mixture is cast in 40 × 40 × 160 mm3 molds and subjected to the accelerated ASR test using 1M NaOH solution at 80°C for 28 days. Afterwards, the compressive strengths are measured to check if they conform to the Waste Acceptance Criteria for homogenous cementation process (ACRIA) of ONDRAF/NIRAS in Belgium. Hydration heat and setting time are measured for the three different mixes using an isothermal calorimeter and automatic Vicat apparatus, respectively, to investigate the effect of waste loading on the early age properties. The initial heat of hydration is found to be the highest for WL50, which may be attributed to the highest percentage of cement present in the designated volume of mix. Although at a later stage, the hydration heat of WL53 and WL56 become similar to WL50, which may be due to the accelerating effect of Ca(NO3)2 in the waste sludge on the hydration kinetics.

This effect is proportional to the waste loading. Vicat data shows that the initial setting time is the lowest for WL50 followed by WL53 and WL56. One possible explanation to this is the proportional increase of Ba(NO3)2 within the designated volume with respect to waste loading. It may progressively retard the set of the mix by decomposing ettringite. However, this may also be a combined effect of increased Ba(NO3)2 and water content. A mineralogical and microstructural analysis of the samples is needed in order to examine these assumptions. Compressive strength tests after 28 days reveal average values of 42, 35 and 23 MPa for 50, 53 and 56% waste loadings respectively, which are well above the ACRIA criteria.
Securing Capacities for Safe and Sustainable Management of Contaminated Metals From Decommissioning
Authors: Larsson Arne , Schultz Bastian , Krause Gregor
Published: November 2023

For 35 years, Cyclife, a specialized company within the EDF Group, has provided metal treatment services to the domestic and international nuclear industry with the aim to qualify the metal for clearance and recycling for manufacturing of new products, for the manufacturing of shielding arrangements or for volume reduction.

The acceptance of free released material for conventional recycling and/or reuse within the nuclear industry has been in focus for multiple years. Now, when the treatment and recycling concepts are well established and accepted by most stakeholders, the shortage of production capacity is a new challenge to be overcome. This to secure the schedule, the logistics and overall efficiency in the decommissioning, lifetime extension and power upgrade projects.

The paper presents the current facilities within the EDF Group incl. concepts and processes for treatment and recycling as well as the ongoing extension and new-build projects.
Innovative Non-Destructive Techniques for Radioactive Waste Packages Monitoring
Authors: Chierici Andrea , Ciolini Riccardo , Lo Frano Rosa , D’Onofrio Antonio , Sabbarese Carlo , Pandalone Antonio , Romoli Mauro , di Meo Paolo , Finocchiaro Paolo , Conti Enrico , Gonella Franco , Andreetto Paolo , Checchia Paolo , Niederleithinger Ernst , d’Errico Francesco
Published: November 2023

A monitoring and surveillance system is a mandatory element to ensure that a radioactive waste disposal facility provides and meets the required level of safety during both its operational and closure periods. In this study an innovative approach for the identification and monitoring of the structural integrity of stored radioactive drums is presented. The activities were carried out in the context of the European Project PREDIS, whose goal is the development of a robust and reliable sensing technology for monitoring and long-term storage of radioactive waste packaging systems.

Specifically, the focus was set on the development of innovative and smart sensor technologies, non-destructive examination tools, and/or devices capable to improve the safety of the storage by minimizing the number of interventions of cemented waste packages. Both conventional and innovative techniques, such as muon-tomography, SiLiF neutron and SciFi gamma detection, or contactless and smart radio transceiver technology provided with radiation monitoring sensors, have been considered and adapted for the use under repository conditions. Indeed, gamma and neutron detection techniques exploit the radiological information coming from inside the drums, while imaging techniques proved to be effective in spotting high density objects embedded inside the concrete: together, they allow to improve safety and security and can provide an early alert on behavioral changes hinting at anomalies in the drums.
Tailoring Nuclear Waste Glass Properties for Joule Heated Ceramic Melter Technique With Bottom Drain Glass Pouring
Authors: Weiser Martin , Willberger Christian , Finck Nicolas , Xiangda Meng , Xiaorui Qu , Jing Zhao , Weisenburger Siegfried
Published: November 2023

Detailed investigations during the glass formulation development for the future Diwopu plant are described. Three different glass formulations were developed including two base glasses for the different waste streams present at Diwopu site and a corresponding Start Glass that allows commissioning of the liquid-fed ceramic melters (LFCM) and later switch-over from glass production operation of the melter to idling mode for maintenance. The waste glasses have to possess similar physical properties to be processed within the same LFCM. Therefore, all three developed glasses were tailored to lie within given margins for rheological and electrical resistivity data as well as to allow a high waste glass loading and high chemical durability. Further in-depth research was conducted to clarify the crystallization behavior of the waste glasses as it is known that the crystallization tendency has to be minimized to exclude relevant impacts on the viscosity. Increase of the viscosity due to crystallization might otherwise lead to unfavorable conditions for the bottom drain up to blockage in the worst case.
The Enhanced Sealing Project (ESP) at the Underground Research Laboratory in Canada: Sixteen Years and Counting?
Authors: Priyanto Deni G.
Published: November 2023

Established in 2008, the Enhanced Sealing Project (ESP) was the final full-scale experiment at the Underground Research Laboratory (URL) in Manitoba, Canada. As of January 2023, the project has been monitoring the evolution and performance of the full-scale composite shaft seal at the URL for over 16 years. The shaft seal was constructed in a 5-m-diameter circular shaft across a water bearing fracture zone at the depth of c. 270 m and comprises of 6-m-thick clay component that is sandwiched between two 3-m-thick concrete components. The clay component was made of 40% (by dry mass) of bentonite and 60% of fine aggregate mixture. This paper highlights the ESP results until early 2023. The ESP results, combined with the URL results from 1980s to 2013, provide 45+ years of unique data sets representing a lifecycle of an underground facility from pre-construction, operation, decommissioning, closure, and post-closure phases. This paper also examines the feasibility of the ESP extension beyond 2023 and proposes additional efforts that will enable to observe the evolution of the seal and URL for the longer term (e.g., several decades).
MPS Method Simulation for Estimating Fuel Debris Distributions Under the Damaged Reactor Pressure Vessel of 1F Unit-2
Authors: Bando Yamato , Yamaji Akifumi , Yamashita Takuya
Published: November 2023

The internal investigations of TEPCO’s Fukushima Daiichi Nuclear Power Station (1F) Unit 2 indicate multiple breaches in the lower head of the reactor pressure vessel (RPV), which led to discharges of molten core materials. In addition, a large enough breach(es) is expected near the vessel periphery, which allowed relocation of a fuel assembly upper tie plate to the pedestal floor. However, the muon radiography indicates that massive fuel debris are still retained within the RPV lower head. This study aims to provide a comprehensive explanation of such observations by considering interactions of the fuel debris with the thermal insulation plates below the RPV lower head at the time of the accident. The Moving Particle Semi-implicit (MPS) method has been developed and pieces of the debris were modeled by rigid bodies to analyze thermal behavior of the fuel debris and their interactions with the insulation plate. The results showed that whether the insulation plate failed or not depended on the initial enthalpy and temperature distribution of the relocated fuel debris on the plate. The results implied that thermal load on the plate was greater below the outer region of the vessel than the central region, because there was larger space between the plate and the vessel for the debris to pileup.
Additively Manufactured Hybrid Two-Phase Cold Plate
Authors: Shaeri Mohammad Reza , Bonner Richard , Catuche Jana
Published: November 2023

The performance of a capillary-driven two-phase cold plate (CP) for thermal management of high heat flux electronic devices was investigated. The CP was a key component of a hybrid two-phase cooling system (HTPCS). The HTPCS operated with the refrigerant R245fa and integrated the benefits of a pumped two-phase cooling with a capillary-driven two-phase cooling. The significance of the present study is to fabricate the CP integrated with evaporator wicks through one single additive manufacturing (AM) process. The CP was a compact enclosure including eight heaters located on both sides of the CP. The evaporator wicks were lattice structures, and individual heater was cooled down by its own evaporator. Compared to the CP without evaporator wicks, the capillary-driven CP (CDCP) led to 39% enhancement in the upper limit heat flux, as well as over 44% improvement in the non-uniformity of the thermal resistance of the CP. The equivalent heat fluxes achieved by the CDCP was 203–212 W/cm2 over areas less than 0.1 cm2. The measured thermal resistances at those ranges of heat fluxes were ∼ 0.16–0.30 K-cm2/W, while operating within a low pumping power below 0.3 W.
Cold Gas Spraying Copper Metal on AlN Ceramics as an Alternative to Thick DBC Substrates for Power Electronics
Authors: Guerrero Margie , Quintero Pedro , Ozdemir Ozan Cagatay
Published: November 2023

This study investigates the use of cold gas spraying (CGS) as a low-temperature additive manufacturing method to bond copper onto aluminum nitride (AlN) substrates for electronic packaging of high-power applications. While direct bond copper (DBC) technique is commonly used, it has limitations due to the large mismatch in coefficient of thermal expansion, which affects substrate reliability. This work employed cold gas spraying (CGS) to mechanically bond Cu on AlN. The study explores the effect of multiple sprays, spray angle and spraying direction on deposition thickness, coating surface roughness, and deposited volume through a factorial design of experiments (DOE). The results, based on optical and scanning electron microscopy combined with profilometry data, showed that coatings sprayed at a 60° angle had a smoother profile topography and less surface roughness than those sprayed at a 90° angle. After depositing 10 layers, a surface roughness (Sa) of around 30 μm and a coating thickness of over 300 μm were successfully attained. These findings provide valuable insights into the processing factors affecting the growth and quality of copper coatings on AlN substrates via multiple sprays, thus enabling the realization of CGS technology as a potential solution to DBC substrates for electronic packaging of wide-bandgap semiconductors.
Thermal and Hydraulic Performance Analyses of Machined and Hybrid Printed Oblique-Fin Cold Plates
Authors: Law Matthew , Soh Sin Liang , Wang Wei , Lee Poh Seng , Lu Wen Feng
Published: November 2023

The computational capabilities of central processing unit (CPU) and graphics processing unit (GPU) are rising steadily with every generation thanks to advancement in electronics and packaging techniques. However, this brings about issues in effective heat dissipation as the thermal design point (TDP) of the chips increases as well. In view of the higher TDPs, traditional air-cooling solutions, such as air-cooled CPU heat sinks and built-in fan modules on the GPU card are no longer sufficient in addressing this problem. This causes the CPU and GPU temperatures to hover very close to their maximum allowable limit. When this occurs, the performance of the chips degrades due to thermal throttling. Thus, the introduction of liquid cooling to high-performance computing (HPC) servers is inevitable due to the above issue. Liquid-cooled HPC servers using finned cold plates not only effectively dissipates higher heat flux but also reduces power consumption of the chip by significantly lowering the chip operating temperature. In this work, the oblique-fin cold plate was fabricated using a hybrid manufacturing technique, whereby the fins were additively manufactured (AM) directly on a solid machined base plate. The fins were fabricated by selective laser melting using copper chromium zirconium, CuCrZr powder, which is a high thermal conductivity copper-based alloy. The base plate, on which the fins were printed, was machined from solid copper. Hybrid printing reduced fabrication time and saves cost, as bulk of the printing time and cost came from the base plate. On the other hand, the benchmark oblique-fin cold plate was machined using wire-cut (WC) electro-discharge machining (EDM), which is a form of subtractive manufacturing. The AM oblique fins reduced material wastage compared to the machined fins. Liquid cooling experiments were conducted on a 1U server running on a 32-core AMD CPU with a TDP of 180 W. Water flow rates were varied between 400 ml/min to 2000 ml/min with an inlet temperature of 25°C. Thermal and hydraulic performance analyses revealed that the hybrid printed oblique-fin cold plate managed to maintain lower CPU temperature compared to the WC oblique-fin cold plate. However, the associated pressure drop penalty was slightly higher due to higher surface roughness of the AM fins. Nevertheless, the pressure drop penalty incurred was justified due to its better cooling performance, as the AM oblique-fin cold plate exhibited higher overall performance when evaluated using the thermal resistance vs pumping power curve. As a result, AM, in particular hybrid printing, can be considered as an alternative to fabricate finned cold plates, especially irregular fin designs that are otherwise not realizable using conventional machining techniques, without compromising cooling performance.
Investigation of Silicon Carbide Embedded Cooling Technology for Compact Electronic Systems
Authors: Wilhite Jarred , Kharangate Chirag
Published: November 2023

A compact, high heat flux cooling design is in development that can enable high-powered electronic systems to achieve greater thermal reliability and sustained functionality for a wide variety of applications. The design and development of this embedded cooling technology involves microfabrication of a 3-D manifold structure in silicon carbide (SiC) which is bonded to a SiC microchannel substrate to form a manifold-microchannel (MMC). The flow manifold geometries in conjunction with the embedded microchannel array provides the MMC with the ability to enable high heat transfer rates while maintaining reasonably low pressure drops, thereby minimizing the pumping power of the system. Microfabrication processes and techniques used to manufacture the MMC are presented. Modeling results are also presented to demonstrate the benefits of the MMC design over traditional cooling designs. This MMC fabricated from SiC is capable of meeting heat dissipation targets of 100 W/cm2 while maintaining thermal resistance below 2 K/W and ΔP within 1 kPa utilizing single-phase working fluid.
A New Low-GWP Dielectric Fluid for Two-Phase Immersion Cooling
Authors: Pottker Gustavo , Van Wassen Abigail , Brandt Drew R.
Published: November 2023

Two-phase immersion cooling (2-PIC) is one the most promising technologies for thermal management of next generation servers and chips. 2-PIC can help data centers dramatically reduce energy and water usage, physical footprint while providing much higher heat rejection rates for chips versus air cooling. Given that many commercial two-phase immersion fluids have limitations of either high GWP, poor dielectric properties or challenges such as chemical stability, a new dielectric fluid candidate (DF-50) is proposed in this paper. Experimental results showed that the dielectric constant and dissipation factor of DF-50 are only about 1.75 and 1 × 10−3, respectively, under frequencies up to 67GHz. A signal integrity analysis of cable and microstrip traces showed that the insertion losses of these components when immersed in DF-50 are almost identical to those in air. The actual thermal performance of multiple GPUs equipped with boiler plates and immersed in DF-50 is also investigated. The total thermal resistance based on the average GPU temperature was estimated to be about 0.04°C/W, with further opportunities for improvement.
Condition Monitoring of Semiconductors Using Wide Band Acoustic Emission Sensors
Authors: Frankhouse Josef , Marsh Jackson , Hu Han
Published: November 2023

Electric vertical takeoff and landing (eVTOL) aircraft require a significant amount of power to operate and fly efficiently over long distances. Nevertheless, long-distance flights of electric vehicles are limited by the energy density of batteries and the specific power of electronics. Mid-voltage power electronics can increase the voltage of the power supply and reduce the current, allowing the eVTOL aircraft to operate more efficiently. However, the breakdown voltage in aircraft is significantly lower than ground due to Paschen’s effect. As such, condition monitoring of power electronics has become critical to the safe operation of eVTOL. In recent years, acoustic emissions (AE) sensors have gained traction within the electronics space, due to their resistance to electromagnetic interference and high temperatures. In this study, acoustic emissions from an integrated circuit are experimentally measured and analyzed for condition monitoring. An AE sensor was applied onto a NE555PCR oscillator placed upon an epoxy substrate to characterize the electromagnetic waves emitted from the device under various input loads. Acoustic emissions were detected upon applying voltage to the oscillator, in which correlates with the output of the device, as well as its input state.
Effect of Thermal Cycling on Interfacial Fracture Toughness of Electronic Mold Compound-to-Substrate Interface Subjected to Monotonic and Fatigue Loading
Authors: Lall Pradeep , Kasturi Madhu
Published: November 2023

Electronics used in automotive underhood applications are subjected to extremely high operating temperatures ranging from 125 to 150°C for up to 10 years or longer over the vehicle’s use-life. Semiconductors in area-array packaging on laminate substrates are encapsulated in electronic mold compounds in microelectronic assemblies to meet unique functional needs. The robustness of the EMC-Substrate interface may also be influenced by the thermal mismatch stresses owing to the differences in the coefficients of thermal expansion between the glass-impregnated epoxy substrate and the silica-filled epoxy. This paper investigates the interface fracture toughness in bimaterial pre-cracked specimens made of PBGAs during thermal cycling exposure. Two EMC materials are subjected to 1000 automotive-grade thermal cycles. The samples are subjected to thermal cycling from −40°C to +125°C. Bi-material EMC-Substrate beam samples are created by polishing the solder balls from PBGA packages. Fracture toughness is measured under exposure to automotive-grade thermal cycling. Interfacial crack initiation, propagation, and failure mechanisms are investigated.
Comparative Study of SMD Components Attached Using Electrically Conductive Adhesive and Magnetically Oriented Anisotropic Conductive Adhesive on Inkjet Printed Structures
Authors: Lall Pradeep , Kulkarni Shriram , Narangaparambil Jinesh , Miller Scott
Published: November 2023

Due to its high resolution and ability to deposit a variety of functional materials, including conductive inks, insulators, and dielectrics, inkjet printing is a viable method for constructing such devices. In this study, the authors sought to examine the electrical and mechanical performance of surface-mounted device (SMD) components mounted on inkjet-printed circuits using two adhesives: Electrically Conductive Adhesive (ECA) and Magnetically Oriented Anisotropic Conductive Adhesive (MOACA). The study is carried out this investigation in two phases. In the initial phase, SMD components such as resistors, inductors, and capacitors were mounted using ECA and MOACA on conductive traces with pads, and their electrical performance was compared to their rated values. In the second phase, the behavior of inkjet-printed Circuits was studied, including Non-Inverting Amplifier Circuit and Schmitt Trigger Circuit. These functional circuits were constructed on polyimide substrates. The researchers utilized silver nanoparticle ink. Evaluation of the electrical and mechanical performance of the circuits was done. Overall, this study gives invaluable insight into inkjet-printed circuits’ electrical and mechanical behavior, particularly in the context of attached components.
Single-Phase Immersion Cooling Multi-Design Variable Heat Sink Optimization for Natural Convection
Authors: Herring Joseph , Gupta Gautam , Lamotte-Dawaghreh Jacob , Bansode Pratik , Agonafer Dereje
Published: November 2023

This paper proposes a computational fluid dynamics (CFD) simulation methodology for the multi-design variable optimization of heat sinks for natural convection single-phase immersion cooling of high power-density Data Center server electronics. Immersion cooling provides the capability to cool higher power-densities than air cooling. Due to this, retrofitting Data Center servers initially designed for air-cooling for immersion cooling is of interest. A common area of improvement is in optimizing the air-cooled component heat sinks for the fluid and thermal properties of liquid cooling dielectric fluids. Current heat sink optimization methodologies for immersion cooling demonstrated within the literature rely on a server-level optimization approach. This paper proposes a server-agnostic approach to immersion cooling heat sink optimization by developing a heat sink-level CFD to generate a dataset of optimized heat sinks for a range of variable input parameters: inlet fluid temperature, power dissipation, fin thickness, and number of fins. The objective function of optimization is minimizing heat sink thermal resistance. This research demonstrates an effective modeling and optimization approach for heat sinks. The optimized heat sink designs exhibit improved cooling performance and reduced pressure drop compared to traditional heat sink designs. This study also shows the importance of considering multiple design variables in the heat sink optimization process and extends immersion heat sink optimization beyond server-dependent solutions. The proposed approach can also be extended to other cooling techniques and applications, where optimizing the design variables of heat sinks can improve cooling performance and reduce energy consumption.
Direct Write Thermoformed Additive Silver Circuits With SMDs Attachment for In-Mold Electronics
Authors: Lall Pradeep , Sarwar Md Golam , Soni Ved , Miller Scott
Published: November 2023

Additively printed thermoformable circuitry for In-Mold Electronics (IME) is getting tremendous research focus because of its numerous advantages: design flexibility, cost-effectiveness, weight reduction, and potential for seamless integration into structural components. This study uses a direct write printing technique to produce conductive FWR circuits using stretchable silver ink. A stretchable ink capable of thermoforming was used for circuit fabrication. Once the conductive traces were printed, SMDs were joined to the circuit using ECA. An impedance analyzer was used to examine the performance of the additively printed FWR circuit. Thermo-forming capable High Impact Polystyrene sheet and Polycarbonate substrates have been used for this study. The cross-section of the printed lines has been measured using white-light interferometry. The effect of the process parameters on the printed line resistivity has been studied. Optimized parameters from the printing process and sintering analysis are used to print FWR circuitry. The OrCAD software is used to simulate the FWR circuit. The simulated performance of the circuit is compared to the actual output of the printed thermoformed circuit. This work highlights the possibility of an additively printed FWR circuit in IME using a direct write process with thermoformable silver conductive ink and ECA.
Reparability Test of Aerosol-Jet Printed Sustainable Silver Ink Circuit
Authors: Lall Pradeep , Bimali Sabina , Miller Scott
Published: November 2023

The earlier generation of additive printable inks was based on volatile organic solvent carrier fluids. Increased awareness of the environmental impact of electronic waste has resulted in the emergence of environmentally friendly water-based inks with low-impact waste. The repairability of additively printed circuits can be used to reduce electronic waste and enable life extensions of deployed electronics through repair and replacement. However, the repairability potential, processes, and impact on reliability are relatively unexplored for new sustainable materials. This study consists of a thorough study of component attachment and the reparability of the components on performance and reliability. Repair procedures have been pursued on circuits printed with sustainable conductive ink on an aerosol jet printer (AJP). Adhesives are printed on the pads at the location where the component is to be attached using a direct-write technique that can print highly viscous materials such as ECA. This procedure entails attaching a component to a flexible printed circuit, measuring the output response, removing the attached component from the circuit, replacing it with a new component of the same rated value, measuring the output again, and comparing it to the prior output and the simulated output. Furthermore, the mechanical strength of the attached components is characterized in terms of shear load to failure. The force required to remove the attached component using a metal tip before and after the repair is compared for each of the passive components. Finally, a functional differentiator circuit is used to validate the findings.
Experimental and Numerical Investigation of Single-Phase Liquid Cooling for Heterogeneous Integration Multi-Chip Module
Authors: Gharaibeh Ahmad R. , Soud Qusai , Manaserh Yaman , Tradat Mohammad , Sammakia Bahgat
Published: November 2023

The variety of new electronic packaging technologies has grown significantly over the last 20 years as a result of market demands for higher device performance at lower costs and in less space. Those demands have pushed for heterogeneous packaging, where computer chips with different stack heights are closely packed, creating non-uniform multicore chip heat flux and temperature and additional challenges for thermal management. Without implementing an appropriate thermal management strategy for heterogeneous packages, large temperature gradients can be observed within the package, which would increase the thermal stresses on the chip and raise reliability issues. Therefore, removing excessive heat flux will improve the reliability and efficiency of those electronic components. The development of high-heat flux applications is straining the capabilities of air-cooling systems, which are nearing their limitations. Single-phase liquid cooling methods have proven to be reliable, usable, and energy-efficient methods for cooling high-heat flux devices. With the introduction of packages with multiple-chip modules (MCMs), the cold plates of future generations are expected to handle multiple hot spots at the same time. To enable the effective removal of heat from the chips, special cold plate designs for each type of package are required. Many methods may be used to improve thermohydraulic performance, including the use of improved fin designs, flow restriction to breakdown the boundary layer, and the integration of mixing mechanisms to improve the mixing between the fluid and channel walls. To mimic this real-life scenario of such packaging in high-heat flux applications, an experimental setup was designed and built. The design of the new experimental setup consists of four identical 1.2 cm × 1.2 cm ceramic heaters, each of which is connected to a separate power supply and can reach a heat flux of 140 W/cm2. Accordingly, this mock package is capable of delivering different power levels to mimic different multicore microprocessor conditions. To give the heater the ability to move precisely in the x, y, and z directions with high precision, each heater is mounted to an XYZ linear stage. Deionized water (DI) was used as the working fluid, and a commercially available pin-fin heat sink was used to run the initial steady-state tests on the experimental rig. The tests showed how different flow rates at a constant fluid temperature and input power affect the temperatures of the heaters and the thermohydraulic performance of the heat sink. In addition, a three-dimensional numerical model has been developed and validated with experimental data in terms of heat sink pressure drop and temperatures of the heaters.
Characterization of SAC305 Solder Joints Under Elevated Current, Temperature, and Varying Shear Stress Conditions
Authors: Ruby Collin , Huitink David R.
Published: November 2023

With the densification and increased power and operating temperatures of power electronics, solder joint reliability is increasingly important to study at high temperature, current, and mechanical stresses. This paper demonstrates the application of an accelerated stress test using a novel combined loading apparatus where a constant shear stress is applied to a test sample in an oven, with an applied constant current. Average shear stress is varied for three conditions, and it is demonstrated that increasing shear stress reduces lifetime of the solder joints. Cross-sectioned solder joints show corroboration between resistance measurement and joint failure. Further studies will develop a combined stress reliability model, and will include varying temperatures and constant current, as well as the individual measurement of the solder spheres in the circuit. High temperature solder alloys such as gold tin (AuSn) will also be considered.
Reliability of Copper Inverse Opal Surfaces for Extreme-Heat-Flux Micro-Coolers in Low-Global-Warming-Potential Refrigerant R-1233zd Pool Boiling Experiments
Authors: Kekelia Bidzina , Wu Qianying , Narumanchi Sreekant , Major Joshua , Moreno Gilbert , Asheghi Mehdi , Dede Ercan M. , Palko James , Goodson Kenneth
Published: November 2023

This paper explores copper inverse opal (CIO) surface reliability in pool boiling experiments in water and a new, low-global-warming-potential (GWP = 1) hydrofluoroolefin (HFO) refrigerant R-1233zd. The CIO-based structure is intended to develop enhanced two-phase heat transfer surfaces for extreme-heat-flux (∼1 kW/cm2) micro-coolers. In this study, a limited number of pool boiling experiments were performed using water and HFO-1233zd fluid, and the reliability of the CIO-based surfaces was evaluated. Critical heat flux (CHF) values in HFO-1233zd at 40°C–45°C saturation temperatures and the corresponding saturation pressures were also measured. The CHF values with the refrigerant are significantly lower compared to those with water, but the refrigerant allows for a wider usable temperature range in the end application of the micro-coolers and is not limited to data centers with controlled ambient conditions.

Reliability experiments with CIO surface samples — involving pool boiling with water on the CIO surfaces for approximately 48 hours and with HFO-1233zd for 144 hours — showed no structural degradation of the enhanced surface or any significant performance drop in heat transfer coefficients. The CIO surface samples in water were oxidized, most likely due to the presence of air in water and in the experimental vessel.
Water Entry Dynamics of Avian Inspired Divers
Authors: Boom Bart , Truscott Tadd , Fish Frank , Summers Adam , Habtour Ed
Published: November 2023

The mechanics of water entry has been investigated extensively for rigid and deformable media, for a wide range of engineering applications. Limited attention has been paid to understanding the water entry process of structural systems with both rigid and deformable components. Inspired by diving animals such as the gannet, the paper experimentally investigates the dynamic characteristics of diving systems (divers) with different springs and head shapes. While the body shape plays an important role in dissipating the impact energy due during water entry, introducing springs into the neck assembly of a rigid diver reduces its maximum impact acceleration and the jerk by more than 50%, regardless of the tested head shapes. The experimental investigation examines the water entry performance of two diving systems: round and cone head. The effect of the stiffness of water-entry mechanics of each system is compared for rigid (no spring), firm spring, and soft spring, totaling six experimental cases. The impact velocity ranges from approximately 3.1 to 5.9 m/s. Introducing rigid-deformable interfaces into the design of a diving system holds great promise in improving the impact survivability of the system.
A Novel Design of Shape-Memory Alloy Actuated Grippers
Authors: John Benjamin , Schubert Thomas , Casper Matthias , Karl Tino , Pagel Kenny , Drossel Welf-Guntram
Published: November 2023

Given the increasing requirements for enhanced performance, accuracy, space efficiency and complexity in industry, there is a need for robots and industrial grippers to become faster, lighter, and more precise. Moreover, due to various reasons including energy efficiency concerns, there is a growing demand for compressed air-free production or, at the very least, severely curtailed compressed air usage. To address this challenge, this paper introduces a novel approach for industrial grippers that employs shape memory wires, leveraging injection molding automation as a specific use case. Three different concepts of implementing a gripping mechanism were developed, considering the functional and structural degradation of shape memory wires during the design process to meet the requirements throughout its entire cyclic lifetime. Subsequently, a characterization study was conducted on the manufactured gripper system to evaluate its performance. To enable a comprehensive evaluation, a control strategy was devised prior to the study, with the objectives of preventing thermal overheating, enhancing dynamics, and achieving a substantial reduction in power consumption.
Environmental Tests of a Parabolic Self-Deployable Tapespring Boom for CubeSat Applications
Authors: Mhadgut Deven , Thomas Patrick , Du Minzhen , Phoenix Austin , Davaria Sheyda , Black Jonathan
Published: November 2023

The need for composite booms in deployable space structures is ever-increasing. This study aims to investigate the effects of environmental conditions on the material properties of a self-deployable carbon fiber boom with a parabolic cross-section. A similar boom will fly as the primary payload on Ut ProSat-1 (UPS-1), a 3U CubeSat designed and manufactured by students at Virginia Tech. The boom will be deployed repeatedly at different locations along the spacecraft’s orbit. In addition, the boom has a flexible circuit near its tip. This circuit houses an inertial measurement unit (IMU) to measure the acceleration experienced by the boom during and at the end of each deployment sequence. A second IMU embedded on the payload control module near the root of the boom measures the vibration response at that location. The transfer function between these two IMUs will give qualitative and quantitative information about the deployment shock perceived by the CubeSat chassis. The on-orbit data will help validate the data obtained from the ground experiments described here. The boom was deployed inside a Tenney environmental chamber to simulate the space environment. The thermal cycling was typical, with hot and cold survival cycles going from 4°C to 70°C, followed by a series of operational cycles with dwell periods at each. A low vacuum of 9 Torr was maintained throughout the test. The effect of temperature on the deployment velocities and shocks has been presented here. The same tests were performed with the TVAC chamber door open, and the differences were noted. These results will provide insight into the characterization of NASA’s tape springs and aid in making informed decisions for future missions.
Development of a Laser Vibrometer-Based Shear Wave Sensing System for Characterizing Mechanical Properties of Viscoelastic Materials
Authors: Cai Bowen , Shen Liang , Pei Zhe , Li Teng , Li Jiali , Bo Luyu , Du Yingshan , Tian Zhenhua
Published: November 2023

Characterizing the mechanical properties of viscoelastic materials is critical in biomedical applications such as detecting breast cancer, skin diseases, myocardial diseases, and hepatic fibrosis. Current methods lack the consideration of dispersion curves that depend on material properties and shear wave frequency. This paper presents a novel method that combines noncontact shear wave sensing and dispersion analysis to characterize the mechanical properties of viscoelastic materials. Our shear wave sensing system uses a piezoelectric stack (PZT stack) to generate shear waves and a laser Doppler vibrometer (LDV) integrated with a 3D robotic stage to acquire time-space wavefields. Next, an inverse method is employed for the wavefield analysis. This method leverages multi-dimensional Fourier transform and frequency-wavenumber dispersion curve regression. Through proof-of-concept experiments, our sensing system successfully generated shear waves and acquired its timespace wavefield in a customized viscoelastic phantom. After dispersion curve analysis, we successfully characterized two material properties (shear elasticity and shear viscosity) and measured shear wave velocities at different frequencies.
Active Implant System Based on SMA Actuators for Improved Bone Fracture Healing
Authors: Welsch Felix , Kirsch Susanne-Marie , Ehl Lukas , Britz Rouven , Pohlemann Tim , Ganse Bergita , Seelecke Stefan , Motzki Paul
Published: November 2023

Shape memory alloys (SMAs) are an attractive technology in actuators and sensors because of their versatile geometry, low weight, high energy density, and low cost.

Recent scientific research found that a switchable stiffness of an implant for bone fracture treatment with individual stimulation patterns to be applied to the fracture site may improve the patient’s healing process.

The first intelligent implant system was developed and realized. This active implant system consists of two actuation mechanisms. The first SMA actuator system generates a switching capability between rigid and soft states in cooperation with an incompressible element. A second set of SMA actuators generates controlled stimulation of the fracture site in the soft implant state by contracting and restoring with an adaptable stroke.

This work first introduces the mechanism of the active implant with a short overview of the mechanical parts. Next, the novel batterie-driven electronic control unit is presented with its realized miniaturized PCB, and the user interface is introduced, enabling wireless control and monitoring via the internet. Following the manual measuring setup, the demonstration case is presented, which is also equipped with an electronic control unit and the terminal where the user interface allows the control of the implant.