bluuebunny/crossref_metadata_2025 huggingface dataset:
‘Ten thousand times more malignant than her mate’: destabilizing gendered assumptions underlying the defences of provocation and loss of control through a reading of Mary Shelley's Frankenstein
Authors: HUGHES‐MOORE BARBARA
Published: November 2021

This article explores how Mary Shelley's Frankenstein engages with notions relating to mens rea. It constructs a reading of the creature as Victor's double, and therefore a manifestation of his guilty mind. Utilizing interdisciplinary literary‐legal methods, the article employs the central relationship in Frankenstein as a means of illuminating and critiquing the ways in which criminal law reproduces and perpetuates gendered notions of behaviour in relation to what is deemed a justified emotional response in the partial defences of provocation and loss of control. It concludes that Frankenstein helps to expose these gaps in legal discourse and ultimately destabilizes binaries of gendered criminality.
Wild guppies from populations exposed to higher predation risk exhibit greater vasotocin brain gene expression
Authors: Reddon A. R. , Aubin‐Horth N. , Reader S. M.
Published: November 2021

Intraspecific variation in social behaviour is often observed among animal populations. Local predation risk can be a key driver of these differences, with populations that are exposed to greater threat typically showing greater aggregation and reduced intraspecific aggression. The Trinidadian guppy,Poecilia reticulata, is found in populations that vary dramatically in predation risk and show greater grouping and reduced agonism in high‐predation populations compared to low‐predation populations. The neurohormonal mechanisms that underpin these differences in behaviour across populations remain unknown and elucidating these mechanisms may help us to understand the evolution of behavioural diversity in this species. We predicted that guppies naturally exposed to higher predation risk would show greater expression of the isotocin system and reduced expression of the vasotocin system when compared to low‐predation fish, because these peptides are thought to promote gregariousness and aggressivity respectively. We collected guppies of both sexes from high‐ and low‐predation sites, replicated in two different Trinidadian rivers, and measured the brain gene expression of isotocin and vasotocin along with their central receptors. Contrary to our prediction, we found that high‐predation guppies showed greater expression of vasotocin, while we did not find evidence that the populations differed in isotocin expression, nor in the expression of the receptors. These results support the hypothesis that vasotocin may act as a neural substrate for social variation in fishes but call into question generalisations about its specific role across species.
I and thou: Challenging the barriers to adopting a relational approach to medical education
Authors: Brown Megan E. L. , Horsburgh Jo
Published: November 2021

The authors highlight barriers to a lack of engagement with relational approaches to medical education by synthesising findings from four State of the Science papers focused on Social aspects of health professional education.
Northern Ireland independence revisited
Authors: Fusco Adam
Published: November 2021

This article examines the idea of Northern Ireland independence in Unionist political thought. It focuses on three moments which compelled Ulster Unionists to re‐evaluate Northern Ireland's constitutional status as part of the United Kingdom—the Stormont parliament's cohabitation with the post‐war Labour government, Stormont's collapse in 1972, and the Anglo‐Irish Agreement of 1985. It argues that rather than being the expression of Ulster nationalism or a contractarian understanding of political obligation, Unionist arguments for independence were motivated by a classical republican concern: the arbitrary power Northern Ireland is subject to as part of the United Kingdom. This locates Unionist thought on independence within a problem of democratic self‐determination: the relationship between majority rule and the bounds of the political community. The article finds that each moment compelled particular Unionist thinkers to reconceive of Ulster Unionists as a political minority subject to arbitrary power in the UK constitution and to choose between Northern Ireland and the United Kingdom as the sovereign political community. The article is unique as there exists little scholarship on the idea of Northern Ireland independence and instructive in providing a challenging case study to assess the attraction and determinacy of classical republicanism as a theory of self‐determination.
The DNA‐dependent protease AtWSS1A suppresses persistent double strand break formation during replication
Authors: Hacker Leonie , Capdeville Niklas , Feller Laura , Enderle‐Kukla Janina , Dorn Annika , Puchta Holger
Published: November 2021

The protease WSS1A is an important factor in the repair of DNA‐protein crosslinks in plants.

Here we show that the loss of WSS1A leads to a reduction of 45S rDNA repeats and chromosomal fragmentation in Arabidopsis. Moreover, in the absence of any factor of the RTR (RECQ4A/TOP3α/RMI1/2) complex, which is involved in the dissolution of DNA replication intermediates, WSS1A becomes essential for viability.

If WSS1A loss is combined with loss of the classical (c) or alternative (a) nonhomologous end joining (NHEJ) pathways of double‐strand break (DSB) repair, the resulting mutants show proliferation defects and enhanced chromosome fragmentation, which is especially aggravated in the absence of aNHEJ. This indicates that WSS1A is involved either in the suppression of DSB formation or in DSB repair itself. To test the latter we induced DSB by CRISPR/Cas9 at different loci in wild‐type and mutant cells and analyzed their repair by deep sequencing. However, no change in the quality of the repair events and only a slight increase in their quantity was found.

Thus, by removing complex DNA‐protein structures, WSS1A seems to be required for the repair of replication intermediates which would otherwise be resolved into persistent DSB leading to genome instability.
MoErv29 promotes apoplastic effector secretion contributing to virulence of the rice blast fungus Magnaporthe oryzae
Authors: Qian Bin , Su Xiaotong , Ye Ziyuan , Liu Xinyu , Liu Muxing , Shen Danyu , Chen Han , Zhang Haifeng , Wang Ping , Zhang Zhengguang
Published: November 2021

During plant‐pathogenic fungi and host plants interactions, numerous pathogen‐derived proteins are secreted resulting in the activation of the unfolded protein response (UPR) pathway. For efficient trafficking of secretory proteins, including those important in disease progression, the cytoplasmic coat protein complex II (COPII) exhibits a multifunctional role whose elucidation remains limited.

Here, we discovered that the COPII cargo receptor MoErv29 functions as a target of MoHac1, a previously identified transcription factor of the UPR pathway. In Magnaporthe oryzae, deletion of MoERV29 severely affected the vegetative growth, conidiation and biotrophic invasion of the fungus in susceptible rice hosts.

We demonstrated that MoErv29 is required for the delivery of secreted proteins through recognition and binding of the amino‐terminal tripeptide motifs following the signal peptide. By using bioinformatics analysis, we predicted a cargo spectrum of MoErv29 and found that MoErv29 is required for the secretion of many proteins, including extracellular laccases and apoplastic effectors. This secretion is mediated through the conventional endoplasmic reticulum–Golgi secretion pathway and is important for conferring host recognition and disease resistance.

Taken together, our results revealed how MoErv29 operates on effector secretion, and our findings provided a critical link between COPII vesicle trafficking and the UPR pathway.
Type 1 diabetes affects the brain functional connectivity underlying working memory processing
Authors: Gallardo‐Moreno Geisa B. , Alvarado‐Rodríguez Francisco J. , Romo‐Vázquez Rebeca , Vélez‐Pérez Hugo , González‐Garrido Andrés A.
Published: November 2021

Visuospatial working memory (VSWM) deficits have been demonstrated to occur during the development of type‐1‐diabetes (T1D). Despite confirming the early appearance of distinct task‐related brain activation patterns in T1D patients compared to healthy controls, the effect of VSWM load on functional brain connectivity during task performance is still unknown. Using electroencephalographic methods, the present study evaluated this topic in clinically well‐controlled T1D young patients and healthy individuals, while they performed a VSWM task with different memory load levels during two main VSWM processing phases: encoding and maintenance. The results showed a significantly lower number of correct responses and longer reaction times in T1D while performing the task. Besides, higher and progressively increasing functional connectivity indices were found for T1D patients in response to cumulative degrees of VSWM load, from the beginning of the VSWM encoding phase, without notably affecting the VSWM maintenance phase. In contrast, healthy controls managed to solve the task, showing lower functional brain connectivity during the initial VSWM processing steps with more gradual task‐related adjustments. Present results suggest that T1D patients anticipate high VSWM load demands by early recruiting supplementary processing resources as the probable expression of a more inefficient, though paradoxically better adjusted to task demands cognitive strategy.
Correlating genotype with phenotype using CFTR‐mediated whole‐cell Cl− currents in human nasal epithelial cells
Authors: Noel Sabrina , Servel Nathalie , Hatton Aurélie , Golec Anita , Rodrat Mayuree , Ng Demi R. S. , Li Hongyu , Pranke Iwona , Hinzpeter Alexandre , Edelman Aleksander , Sheppard David N. , Sermet‐Gaudelus Isabelle
Published: November 2021

Dysfunction of the epithelial anion channel cystic fibrosis transmembrane conductance regulator (CFTR) causes a wide spectrum of disease, including cystic fibrosis (CF) and CFTR‐related diseases (CFTR‐RDs). Here, we investigate genotype–phenotype–CFTR function relationships using human nasal epithelial (hNE) cells from a small cohort of non‐CF subjects and individuals with CF and CFTR‐RDs and genotypes associated with either residual or minimal CFTR function using electrophysiological techniques. Collected hNE cells were either studied directly with the whole‐cell patch‐clamp technique or grown as primary cultures at an air–liquid interface after conditional reprogramming. The properties of cAMP‐activated whole‐cell Cl− currents in freshly isolated hNE cells identified them as CFTR‐mediated. Their magnitude varied between hNE cells from individuals within the same genotype and decreased in the rank order: non‐CF > CFTR residual function > CFTR minimal function. CFTR‐mediated whole‐cell Cl− currents in hNE cells isolated from fully differentiated primary cultures were identical to those in freshly isolated hNE cells in both magnitude and behaviour, demonstrating that conditional reprogramming culture is without effect on CFTR expression and function. For the cohort of subjects studied, CFTR‐mediated whole‐cell Cl− currents in hNE cells correlated well with CFTR‐mediated transepithelial Cl− currents measured in vitro with the Ussing chamber technique, but not with those determined in vivo with the nasal potential difference assay. Nevertheless, they did correlate with the sweat Cl− concentration of study subjects. Thus, this study highlights the complexity of genotype–phenotype–CFTR function relationships, but emphasises the value of conditionally reprogrammed hNE cells in CFTR research and therapeutic testing.

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Key points

The genetic disease cystic fibrosis is caused by pathogenic variants in the cystic fibrosis transmembrane conductance regulator (CFTR), an ion channel, which controls anion flow across epithelia lining ducts and tubes in the body.

This study investigated CFTR function in nasal epithelial cells from people with cystic fibrosis and CFTR variants with a range of disease severity.

CFTR function varied widely in nasal epithelial cells depending on the identity of CFTR variants, but was unaffected by conditional reprogramming culture, a cell culture technique used to grow large numbers of patient‐derived cells.

Assessment of CFTR function in vitro in nasal epithelial cells and epithelia, and in vivo in the nasal epithelium and sweat gland highlights the complexity of genotype–phenotype–CFTR function relationships.
Conventional rigid 2D substrates cause complex contractile signals in monolayers of human induced pluripotent stem cell‐derived cardiomyocytes
Authors: Huethorst Eline , Mortensen Peter , Simitev Radostin D. , Gao Hao , Pohjolainen Lotta , Talman Virpi , Ruskoaho Heikki , Burton Francis L. , Gadegaard Nikolaj , Smith Godfrey L.
Published: November 2021

Human induced pluripotent stem cell‐derived cardiomyocytes (hiPSC‐CM) in monolayers interact mechanically via cell–cell and cell–substrate adhesion. Spatiotemporal features of contraction were analysed in hiPSC‐CM monolayers (1) attached to glass or plastic (Young's modulus (E) >1 GPa), (2) detached (substrate‐free) and (3) attached to a flexible collagen hydrogel (E = 22 kPa). The effects of isoprenaline on contraction were compared between rigid and flexible substrates. To clarify the underlying mechanisms, further gene expression and computational studies were performed. HiPSC‐CM monolayers exhibited multiphasic contractile profiles on rigid surfaces in contrast to hydrogels, substrate‐free cultures or single cells where only simple twitch‐like time‐courses were observed. Isoprenaline did not change the contraction profile on either surface, but its lusitropic and chronotropic effects were greater in hydrogel compared with glass. There was no significant difference between stiff and flexible substrates in regard to expression of the stress‐activated genes NPPA and NPPB. A computational model of cell clusters demonstrated similar complex contractile interactions on stiff substrates as a consequence of cell‐to‐cell functional heterogeneity. Rigid biomaterial surfaces give rise to unphysiological, multiphasic contractions in hiPSC‐CM monolayers. Flexible substrates are necessary for normal twitch‐like contractility kinetics and interpretation of inotropic interventions.

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Key points

Spatiotemporal contractility analysis of human induced pluripotent stem cell‐derived cardiomyocyte (hiPSC‐CM) monolayers seeded on conventional, rigid surfaces (glass or plastic) revealed the presence of multiphasic contraction patterns across the monolayer with a high variability, despite action potentials recorded in the same areas being identical.

These multiphasic patterns are not present in single cells, in detached monolayers or in monolayers seeded on soft substrates such as a hydrogel, where only ‘twitch’‐like transients are observed.

HiPSC‐CM monolayers that display a high percentage of regions with multiphasic contraction have significantly increased contractile duration and a decreased lusotropic drug response.

There is no indication that the multiphasic contraction patterns are associated with significant activation of the stress‐activated NPPA or NPPB signalling pathways.

A computational model of cell clusters supports the biological findings that the rigid surface and the differential cell–substrate adhesion underly multiphasic contractile behaviour of hiPSC‐CMs.
Fisher Identifiability Analysis of Longitudinal Vehicle Dynamics
Authors: Kandel Aaron , Wahba Mohamed , Fathy Hosam K.
Published: November 2021

This article investigates the theoretical Cramér-Rao bounds on estimation accuracy of longitudinal vehicle dynamics parameters. This analysis is motivated by the value of parameter estimation in various applications, including chassis model validation and active safety. Relevant literature addresses this demand through algorithms capable of estimating chassis parameters for diverse conditions. While the implementation of such algorithms has been studied, the question of fundamental limits on their accuracy remains largely unexplored. We address this question by presenting two contributions. First, this article presents theoretical findings which reveal the prevailing effects underpinning vehicle chassis parameter identifiability. We then validate these findings with data from on-road experiments. Our results demonstrate, among a variety of effects, the strong relevance of road grade variability in determining parameter identifiability from a drive cycle. These findings can motivate improved experimental designs in the future.
A Study of Crack Growth in Sandwich Composite Beams
Authors: El-Sayed Sami I. , Sridharan Srinivasan
Published: November 2021

The paper proposes models to track the face-core interfacial delamination growth and crack kinking into the sandwich core, respectively. The models consist in interposing a cohesive layer along a pre-existing delamination or an identified plane of crack propagation. The former, designated as CLD (cohesive layer delamination model) is investigated first in detail using an example of a restrained beam specimen. The Influence of the key parameters of the model, viz. the thickness of the cohesive layer and the strength and stiffness of the cohesive layer material, have been studied. It is found that the model is fairly robust and is not sensitive to changes in parameters other than the critical strain energy release rate. The second model is a highly simplified one, but it is nevertheless a comprehensive model which can track the crack path by identifying crack planes in various elements using a maximum tensile stress criterion. This is designated as CLDK model as it deal with delamination and crack kinking — whichever is the preferred mode of fracture. The models are constructed ensuring that the crack opening is controlled by the critical value of strain energy release rate in mode I fracture. Experimental results of two sandwich specimens, viz. bottom restrained beams with 0° and −10° tilt angle respectively were used for comparison. The results indicate that the both the models are able to capture the initiation and track the growth of the interfacial delamination. The CLDK model tracks the crack kinking into the core, and its subsequent return to the facesheet-core interface.
Micromechanical Analysis of Nonlinear Response of Unidirectional Composites: A Fundamental Approach
Authors: Jadhav Virendra R. , Sridharan Srinivasan
Published: November 2021

Micromechanical models with different representative volume elements have been developed to study their ability to predict nonlinear response of unidirectional composites. A simple, square cells type micro-mechanical model similar to those widely used by other researchers is compared with a more advanced 3-phase finite element based micro-mechanical model. The models utilize the “bulk” properties of the matrix without attempting to “tune” the model to fit with experimental response of laminae. This is a more fundamental approach and constitutes a departure from current practice. The models account for shear softening, matrix cracking and the presence of residual stresses. A smeared cracking approach was used to characterize the micro-cracking in matrix. Experimental studies were performed on laminae, laminates and cylinders made from carbon epoxy composites. Experimental comparisons show that the more accurate micro-mechanical model with proper partial cracking options provides good bounds on experimental response with consistent accuracy. A square cells type model however is not consistent in its predictions, thus raising questions about its applicability in any general micro-mechanics based analysis.
Damage Assessment in Thermal Barrier Coatings Using Thermal Wave Imaging Technique
Authors: Chen X. , Newaz G. , Han X.
Published: November 2021

Thermal wave imaging (TWI) was used to investigate damage processes in electron beam-physical vapor deposited (EB-PVD) ZrO2-8% wt.%Y2O3 thermal barrier coatings (TBCs) during thermal cycling. TWI is a non-destructive and non-contact evaluation method. Small interfacial decohesions from manufacturing were captured by TWI after only two thermal cycles, but the decohesions did not grow with thermal cycling. No delamination was found in TBC specimens until failure, while surface temperature profiles of TWI indicated increases of thermal wave signal amplitude with thermal cycles. Local interfacial damage formed due to high thermal residual stresses during thermal cycling and induced thermal contact resistance in the TBCs, which resulted in the increases of thermal wave signal amplitude. The results of TWI confirmed the progressive damage evolution in TBCs observed by microscopy. The buckling propagation and spallation process were monitored by TWI.
Novel Concept of Advanced Thermal Protection Coating Based on Fullerenes
Authors: Loutfy Raouf O. , Wexler Eugene M.
Published: November 2021

Experimental study has been carried out to investigate thermal protection properties of thin fullerene coatings subjected to external heating. It was shown that due to low thermal conductivity and high emissivity, micron-scale fullerene films were capable of withstanding elevated temperatures (up to 800°C) resulting in over 100°C temperature decrease on the “cold” surface of the underlying substrate. Based on obtained results, practically important recommendations are made.
The Mechanics of Dynamic Fiber Push-Out: Experimental and Numerical Study
Authors: Lambros John , Bi Xiaopeng , Geubelle Philippe H.
Published: November 2021

This paper summarizes our recent progress on the experimental and numerical study of dynamic debonding and frictional push-out in composite systems. A modified split Hopkinson pressure bar system is adopted to perform dynamic fiber push-out experiments on model single fiber composite systems. A cohesive/volumetric finite element scheme is developed to capture the initiation and propagation of the crack along the fiber/matrix interface. Interface properties are extracted by comparison between experimental and numerical results. Effects of loading rate and surface roughness are presented. The results indicate that the combination of the experimental and numerical analysis constitutes a valuable tool to study the failure process in composites under high loading rates.
Stochastic Applications in Crashworthiness
Authors: Koganti Rama P. , Caliskan Ari G.
Published: November 2021

Due to geometrical, and material property variations, response of any structural member varies from the nominal design value. Typically the geometrical and material variations are the resultant of manufacturing variations. In this paper, the effect of these variations about the nominal values on structural response is studied using stochastic or probabilistic methods. Circular aluminum cross-sections are becoming popular in structural energy management applications. Also, significant research has been done to estimate the mean crush load for a circular section using empirical relations. An empirical relation, which is a function of thickness, outer radius, elastic modulus and yield strength, was used to estimate the mean crush load. Based on the measured thickness, outer radius and yield strength, the mean crush load is calculated using the empirical relation. Also, using the empirical relation, the variation in the mean crush load is estimated using linear statistical approach and Monte-Carlo simulation. In both the stochastic methods, actual mean and standard deviations of thickness, outer radius and yield strength are used. Also, using the extreme variations of these factors, mean crush load is predicted using an implicit Finite Element Analysis (FEA) code. The FEA prediction is in good agreement with the results of the testing. However, the designed mean crush load based on the empirical relation overestimates the crush loads by about 11%. The results of the study showed that the tube thickness and yield strength variations significantly affect the crush loads. Based on the Monte-Carlo simulation and FEA values using the extreme values for the geometrical and mechanical properties, one can design crash structures that take into account the inherent variability of components.
Mathematical Model Methodology to Compare Different Occupant Models in Frontal Impact
Authors: Marshall Rob , Altamore Paul F.
Published: November 2021

Restraint system and vehicle design rely heavily on the use of Anthropomorphic Test Devices and mathematical models of ATD’s to provide information about human occupant response in impact conditions. Recent advances in ATD’s take years to get through the prototyping and evaluation stages before they can be widely used. The recent advances in ATD development will not benefit the testing of many vehicles for quite some time.

The development of mathematical models of new ATD’s that are not yet available for widespread use, as well as mathematical models of humans can provide more information about human occupant responses to engineers. This study develops a method to utilize these mathematical models in combination with a highly detailed vehicle model to gain more understanding of how human occupants will behave in a frontal impact.
A Proposed New Brain Injury Tolerance for Minor Traumatic Brain Injury
Authors: Zhang Liying , Yang King H. , King Albert I.
Published: November 2021

Traumatic brain injuries constitute a significant portion of injury resulting from automotive collisions, motorcycle crashes, and sports collisions. Brain injuries not only represent a serious trauma for those involved but also place an enormous burden on society, often exacting a heavy economical, social, and emotional price. Development of intervention strategies to prevent or minimize these injuries requires a complete understanding of injury mechanism, response and tolerance level. In this study, an attempt is made to delineate actual injury causation and establish a meaningful injury criterion through the use of the actual field accident data. Twenty-four actual field head-to-head collisions that occurred in professional football games were duplicated using a validated finite element human head model. The injury predictors and injury levels were analyzed based on resulting brain tissue responses and were correlated with the site and occurrence of MTBI. Prediction indicated that the shear deformation around the brainstem region could be an injury predictor for concussion. Statistical analyses were performed to establish the new brain injury tolerance level and to further reduce brain injury severity.
Conducting Dynamic Impact Tests Using a “Free-Flight” Drop Tower Facility: Part I — Theory
Authors: Browne Alan L. , Johnson Nancy L.
Published: November 2021

“Free-Flight” drop tower facilities provide an inexpensive means for studying the dynamic impact response and energy absorption capabilities of structural elements. They are thus a commonly used tool, especially in the automotive industry, both for validating analytical predictions of dynamic crush and for determining the dynamic crush response itself in those cases where analytical prediction capability does not exist. This paper discusses the theory underlying drop tower impact testing. Specific topics that are discussed include a general development of the governing equations, a corrected interpretation of these equations, and quantification of (and means of correcting for) the effects of aerodynamic drag, cable friction, and “pressurization” of the test specimen.
Wheelchair Attachable System for Stepping UP
Authors: Barrigar Frederick , Johnson Christopher , Sanchez Julie , Wasiloff James
Published: November 2021

A methodology to apply contemporary mechanism design and synthesis tools to the modeling and development of a mechanical device that provides improved wheelchair mobility over vertical obstacles is presented in this paper. An advanced technique in design concept selection, Pugh Analysis, was utilized as a process to formulate, categorize and rank various design alternatives with respect to criteria such as design targets and constraints. An ADAMS model was developed to simulate the kinematics of the mechanism design selected. Simulation modeling confirmed that an initial feasible mechanism design concept that met or exceeded customer expectations had been achieved. Additional design optimization, design reliability and robustness opportunities are presented as potential follow-on efforts.
Three-Dimensional Analysis of Double Rivet-Row Lap Joints: Part I — Non-Countersunk Rivets
Authors: Iyer K. , Rubin C. A. , Hahn G. T.
Published: November 2021

Three-dimensional finite element analysis of an elastic, double rivet-row, aluminum alloy lap joint with non-countersunk aluminum rivets, is presented. The compliance of the connection, rivet tilt, peak contact pressures and slip amplitudes, in the absence of interference and clamp-up, are described. Rivet-panel slips in the double-row assembly are between 50–60% of those calculated for the single-row case. Contrary to the expectation that the second row of rivets might reduce the stress concentration factor by half, the additional row of rivets provides a reduction of only 28%.
Parameterized Design of a Supersonic Radome
Authors: Hollis Michael S. L.
Published: November 2021

Future gun-launched projectiles will have higher muzzle velocities. There currently exists a need for RF transparent radome solutions with muzzle velocities near Mach numbers equal to 3 (M = 3). Future Combat System (FCS) requirements may push these velocities as high as M = 5. Assessments of aerothermal heating requirements for specific radome geometries need to be studied. Trade-off studies involving aerodynamic shape, antenna location, materials, and RF characteristics also need to be made.

The final product of this report is twofold. The first is a short-term solution using the extruded/molded plastics to manufacture a radome. The other is a guideline for a more extensive study to find several solutions for high speed, RF transparent radomes for ballistic projectiles.
Warpage Analysis of Wafers With Film Coating
Authors: Ding Hai , Ume I. Charles , Zhang Cheng
Published: November 2021

Wafer-level packaging (WLP) is one of the trends of electronic packaging in the 21st century. Since 1994, many companies have released WLP licenses. One of the common concerns among these various approaches is wafer warpage. Warpage of wafer tends to introduces crack or delamination during dicing and low temperature storage process. After wafer dicing, warpage could reduce the quality of each package in the long run. Many documented works indicated that in the design and implementation of WLP, some key parameters have to be carefully considered and closely controlled to ensure higher packaging quality with the minimum warpage. For the case of wafer-level flip chip, the key parameters are Young’s modulus, thickness, and coefficient of thermal expansion (CTE) of underfill.

In this research, an experimental design and statistical methods have been used to identify the model structure and parameters that are critical to the warpage of wafers. Regression models were identified based on the data obtained from finite element analysis (FEA) that is verified by shadow Moiré experiments. According to the models, the CTE, the coupling of Young’s modulus and CTE, and the coupling of thickness and CTE of underfill primarily determine wafer warpage. Further FEA and shadow Moiré experiments indicate that the models are capable of predicting of wafer warpage in the process of WLP.
Vibration-Induced Droplet Atomization (VIDA) for Two-Phase Thermal Management
Authors: Vukasinovic Bojan , Heffington Samuel N. , Smith Marc K. , Glezer Ari
Published: November 2021

A novel vibration induced droplet atomization (VIDA) technology is utilized in a two-phase heat transfer cell for cooling of high-power integrated circuits. VIDA is a rapid atomization process whereby discrete liquid drops (or liquid film) are placed on the surface of a diaphragm that is vibrated near or at the coupled resonance of the system. Surface waves that develop on the liquid free surface lead to rapid bursting and the ejection of secondary droplets that are propelled away from the diaphragm. The VIDA-based heat transfer cell is similar to a heat pipe in that cooling is based on the evaporation and condensation of liquid within a closed cell. However, in contrast to a heat pipe where the liquid is delivered to the evaporator by capillary transport within a wicking material, in the VIDA cell the atomized liquid droplets are propelled towards the hot surface thus eliminating the capillary transport limit that is imposed by the wicking material. The vapor condenses near an air-side heat exchanger and the condensate is delivered to the VIDA driver. The rate of atomization and therefore the heat transfer within the cell can be actively controlled and regulated. The present paper focuses on the fundamental aspects of the VIDA atomization process of a single liquid drop. It is shown that VIDA process can be either self-intensifying or self-decaying. The global features of the VIDA, spray droplet size- and velocity distributions, and their interrelation with the external driving parameters are investigated. Finally, the performance of a current prototype of VIDA heat transfer cell is discussed.
Alternative Compliant Interconnects: Thermo-Mechanical Reliability, Design and Testing
Authors: Ma Lunyu , Zhu Qi , Sitaraman Suresh
Published: November 2021

Two types of novel compliant interconnects are being proposed in this paper. The advantages of these two types of compliant interconnects are: accommodation of the mismatch due to different thermal expansions in electronic packages, integration with wafer-level fabrication process, low cost, fine pitch and high I/O density. The first type is a highly-compliant cantilevered spring interconnect for the next generation packaging and probing technology. To understand the reliability of the package with this novel compliant spring interconnect structure and the typical behavior of sliding contact, test vehicles with different orientations of the cantilevered springs (21 μm pitch) have been fabricated, assembled and subjected to thermal cycling test. In-situ resistance and temperature measurements have been conducted. The second type is a compliant free-standing interconnect, One-Turn Helix (OTH) structure. This structure is built as an one-turn strip helix in order to get good compliance in space. It can be fabricated through conventional photolithography-based IC fabrication process. Optimal design parameters have been identified for this structure taking into consideration the thermo-mechanical and electrical behavior of this unique structure.
A Neural-Taguchi Based Quasi Time-Optimal Control Strategy for Chemical-Mechanical Polishing Processes
Authors: Wang Gou-Jen , Chou Meng-Hsian
Published: November 2021

Besides the major factors such as the down force, back pressure and the rotating speed of wafer carrier, effect of polishing time is also an important issue in CMP processes. In this study, a neural-Taguchi method based cost-effectively quasi time-optimal technique for Chemical-Mechanical Polishing. (CMP) processes is developed. Key concept of this new technique is that an optimal processes parameter set is obtained through a neural networks simulated CMP processes model. Under such an optimal parameters set, the desired material removal rate (MRR) and within-wafer-nonuniformity (WIWNU) can be reached with the optimal polishing time. It has been proved by experiments that the proposed method can offer a better polishing performance while reducing the polishing time by 1/3.
Experimental Investigation on Chemical-Mechanical Polishing of Wafers With Low-Conductivity Dielectrics
Authors: Tsai Jhy-Cherng , Liu Charls , Tsai Ming-Hsih , Dai Bao-Tong
Published: November 2021

Low conductivity (low-k) dielectric material is used in the sandwich structure of next-generation semiconductor devices in order to reduce the RC time delay. While global flatness of wafer surface becomes critical for deep sub-micro semiconductor fabrication process, chemical-mechanical polishing (CMP) becomes one of the key technologies for planarization of wafer surface. This paper investigated the effect of the low-k material on the CMP of the SiO2 cap layer of such a sandwiched wafer. Two types of wafers, blanket wafer and wafer with circuit pattern, are designed and conducted to investigate the effects of the thickness of the low-k layer under different polishing pressures and velocities. Material removal rate (RR) and non-uniformity (NU) are used as indices of the CMP process performance. The results show that the RR and NU of wafers with low-k layer, either blanket or with circuit pattern, become better when the pressure or velocity increases. The thickness of the low-k layer, however, has only tiny effect on the RR and NU.
Reliable Low-Cost Flip Chip Interconnections
Authors: Zhong Z. W.
Published: November 2021

A few reliable low-cost flip chip assembly processes using gold bumps with NCA, ACF or ACP that involved daily mass production activities in the industry are reported in this paper. Some key issues of material selection and assembly for reliable low-cost flip chip interconnections are discussed. This paper also discusses reliable low-cost processes of flip chip on FR-4 using eutectic solder bumps with possible fewer process steps compared to the full assembly process. Some interesting results with respect to the reliability performance of the processes have been obtained.
Novel Experimental-Computational Method for Quantitative Applications in Electronic Packaging
Authors: Furlong Cosme , Pryputniewicz Ryszard J.
Published: November 2021

Rapid advances in microelectronics require design and optimization of components and packages, for new and ever more demanding applications, in relatively short periods of time while satisfying electrical, thermal, and mechanical specifications, as well as cost and manufacturability expectations. In addition, reliability and durability have to be taken into consideration. As a consequence, some of the most sophisticated analytical, computational, and experimental methods are being used for development, optimization, and quantitative characterization of electronic packages. In this paper, a novel experimental-computational method, based on combined use of recent advances in laser-based optics and computational modeling, is described and its application is demonstrated by case studies of microelectronic components subjected to electro-thermo-mechanical loads. Results of these studies show that this methodology provides an effective engineering tool for nondestructive testing (NDT) applications in electronic packaging and provides indispensable quantitative data for development, optimization, and applications in electronic packaging.
Mechanical Considerations of Shin-Etsu Elastomer As a Z-Axis Interconnect
Authors: Cox C. , Schmidt W. F. , Gordon M. H. , Marsh W. , Bates G. , Lucas M.
Published: November 2021

This research effort addresses the integration of a dense z-axis interconnect technology, Shin-Etsu, into a 3D thermo-mechanical multi-chip module with two to eight stack layers. Shin-Etsu is a matrix of vertical beryllium-copper wires embedded in silicone. Since it is a composite material, accurately determining Shin-Etsu’s mechanical properties is extremely important for estimating long-term reliability of the electronic package.

Five percent compression of the Shin-Etsu elastomer was specified to maintain proper electrical contact between substrates. To determine the corresponding force, Tinius-Olsen compression tests up to 15% were conducted on both single and double layer samples of Shin-Etsu. In addition, these data were used to infer Shin-Etsu’s Young’s modulus. Both series of test were also conducted with and without alumina (A12O3) to simulate the contact surface boundary condition between Shin-Etsu and the LTCC substrate (2 pieces were used for the single Shin-Etsu case, and 3 pieces were used for the 2 layer Shin-Etsu case). All compression tests follow the same trends, though the sample to sample scatter is relatively large (+/−75%). Because Shin-Etsu’s Poisson’s ratio is near 0.5 (volume is conserved), the frictional forces between the contact surfaces is important. By carefully accounting for these frictional forces, we infer a Young’s modulus for Shin-Etsu of 3.25 MPa. Using this value with the appropriate contact model (we found that a simpler model with infinite friction is suitable in our case), we are able to successfully design a two-board test vehicle which incorporates Shin-Etsu.
Effect of Rotational Speed on the Average Flow Field at the Pump/Turbine Interface of an Automotive Torque Converter
Authors: Hotho M. , Gruber M. R. , Flack R. D. , Gillies G. T.
Published: November 2021

The internal flow fields of a pump/turbine interface in a torque converter were examined using laser velocimetry. The torque converter was operated at three different turbine/pump rotational speed ratios: 0.065 (near stall), 0.600, and 0.800 (near coupling point) and for each speed ratio three different pump and turbine speeds were used. Most importantly, the dimensional rotational speed had minimal effects on the flow fields — flow characteristics were Reynolds number independent. At the pump exit plane the flow is non-uniform in the blade-to-blade direction at all speed ratios and speeds. Velocities were fairly uniform in the core-to-shell direction. Through flow velocity non-uniformity became more pronounced as the speed ratio increased. The pump exit plane slip factors are near unity. At high speed ratios the flow in the turbine inlet plane flow is non-uniform in the blade-to-blade direction. Also at high speed ratios, velocities are fairly uniform in the core-to-shell direction but high velocities move near the shell at lower speed ratios. The turbine leading edge incidence angles were found to depend strongly on the speed ratio, ranging from positive to negative.
Fuzzy Logic Control of Constant Power Regulated Swash Plate Axial Piston Pumps
Authors: Kassem S. A. , Bahr M. K.
Published: November 2021

This paper presents a theoretical study of some aspects of the dynamics of electrically controlled constant power regulated swash plate axial piston pumps with conical cylinder blocks. The mathematical model of the pump is derived. Simulation of the pump dynamic characteristics is carried out when the controller is a conventional PD one used currently in practical applications. The good agreement between the simulation and the experimental results validates the derived model. A fuzzy logic controller (FZC) is proposed to replace the PD controller. The simulation results show that the FZC yields better dynamic performance and is more robust as compared with the PD controller. The FZC is also shown to reduce the oscillations of the proportional valve spool at each swash plate inclination angle, which increases the valve service life and reduces the generated heat in it. In case of pumps of large geometric volumes the FZC is found also to reduce the impact of the control piston at the end of the stroke.
Modelling of an Electrohydraulically-Activated Friction Damper in a Vehicle Application
Authors: Guglielmino Emanuele , Edge Kevin A.
Published: November 2021

This paper is concerned with the modelling and control of a servo-driven dry-friction damper employed as a part of a car suspension.

An accurate model of the hydraulic drive is developed, taking into consideration valve leakage flows. These affect closed-loop gain and hence the overall performance of the system. A robust Variable Structure Control (VSC) algorithm is proposed. The merits of different schemes are compared via numerical simulation. The vehicle ride model employed for the study has seven degrees of freedom.
Semiempirical Model for Variable Displacement Pump With Load Sensing Regulator and Power Restrictor
Authors: Käppi Timo J.
Published: November 2021

In this paper modeling of variable displacement pump system is discussed. The system described is typically used in mobile hydraulic applications.

An easy-to-parameterize loss model is presented which is based on the Dorey’s model. The model identification is done semi-empirically with a reduced number of parameters. Two parameters are required to identify the volumetric losses and four to determine the hydromechanical efficiency. The accuracy of the loss model is proven by comparing calculated values between the measured values of a commercial axial piston pump. The relative error in total efficiency is less than 4% over the whole range of variables and thus acceptable.

The pump system model presented includes the operation of load sensing regulator and power restrictor. The pump system model also includes the dynamic effect of a load sensing line from the mobile valve to the pump regulator and the first order dynamics of the pump itself.

The suggested model is usable in carrying out the system level simulation of mobile hydraulic machine systems. Simple examples demonstrate the application.
Relating Semiconductor Heat Sink Local and Non-Local Experimental and Simulation Data to Upper Scale Design Goals
Authors: Travkin V. S.
Published: November 2021

The primary difficulty in semiconductor heat sink (and many other types of heat exchangers) research and design is not a lack of interest or money, but rather confusion with what being looked for and adequacy of the tools used for the search. As recently shown, there are few meaningful parameters (apart from sizes and weight) or physical characteristics of interest in semiconductor cooler design are local values. Even the maximum temperature of the base Tmax or semiconductor temperature are not local. In this work outlined the description in detail of arguments on how, and for what reasons, the measured data are to be simulated or measured and represented in a way that allows design goals to be formulated primarily with bulk physical characteristics. We demonstrate why studies of only averaged local integrated variables are not enough. Four sample semiconductor heat sinks of two morphologies (three samples of round pin fin and one sample of longitudinal rib fin sinks) were studied by different techniques and models. There were changes in by-pass values, external heat flux and flow rate. The results are depicted with using new parameters that better represent the needs of a design process as well as the usual parameters used in the past. Characteristics reported are the heat transfer rate in solid phase, relative fin effectiveness, and influence of only morphology features among others. Some suggestions for heat sink design are discussed.
An Assessment of the Impact of Interconnect Strategies on Thermal Performance of GaAs Power Amplifier IC Devices
Authors: Adams V. H. , Lee T.-Y. Tom
Published: November 2021

Alternative interconnect strategies are being considered in place of the standard wire bond interconnect for GaAs power amplifier MMIC devices due to cost and electrical performance improvements. The package/die thermal performance consequences are potentially high-risk issue to these interconnect strategies and requires evaluation. Thermal simulations are conducted to compare and evaluate the thermal performances of three interconnect strategies: wire bond, gold post-flip chip, and through via interconnects. The test vehicle simulated is a three-stage, dual band power amplifier integrated circuit dissipating approximately 5 W steady-state power. Parametric studies are conducted to evaluate the impact of the printed circuit board, die thickness, solid gold vias, and design enhancements on package thermal performance.

Best thermal performance is provided by a wire bonded, thin GaAs die attached with solder die attach to a printed circuit board that maximizes the number of plated-through-holes directly under the die. This configuration results in a best case junction-to-heat sink thermal resistance of 12 °C/W. Optimum flip chip and through via designs result in degraded thermal performance compared to the above described wire bond design but may have acceptable thermal performance. For these simulations, predicted junction-to-heatsink thermal resistance is in a range of 15–20 °C/W and is better than a comparable wire bonded design that uses a conductive epoxy die attach material.