bluuebunny/crossref_metadata_2025 huggingface dataset:
Climate drivers and animal host use determine kelp performance over decadal scales in the kelp Pleurophycus gardneri (Laminariales, Phaeophyceae)
Authors: Pfister Catherine A. , Betcher Samuel P.
Published: October 2017

Primary producers respond to climate directly and indirectly due to effects on their consumers. In the temperate coastal ocean, the highly productive brown algae known as kelp have both strong climate and grazer linkages. We analyzed the demographic response of the kelp Pleurophycus gardneri over a 25‐year span to determine the interaction between ocean climate indicators and invertebrate infestation rates. Pleurophycus hosts amphipod species that burrow in the stipe, increasing mortality. Although kelp performance is generally greater with more negative values of the Pacific Decadal Oscillation (PDO) and colder seawater temperatures, Pleurophycus showed the opposite pattern. When we compared the 1990s, a period of positive values for the PDO and warmer sea surface temperatures, with the following decade, a period characterized by negative PDO values, we documented a contradictory outcome for proxies of kelp fitness. In the 1990s, Pleurophycus unexpectedly showed greater longevity, faster growth, greater reproductive effort, and a trend toward decreased amphipod infestation compared with the 2006–2012 period. In contrast, the period from 2006 to 2012 showed opposite kelp performance patterns and with a trend toward greater amphipod infestation. Pleurophycus performance metrics suggest that some coastal primary producers will respond differently to climate drivers, particularly if they interact strongly with grazers.
Molecular determinants of beta‐adrenergic signaling to voltage‐gated K+ channels in the cerebral circulation
Authors: Rhee Sung W. , Rusch Nancy J.
Published: October 2017

Voltage‐gated K+ (Kv) channels are major determinants of membrane potential in vascular smooth muscle cells (VSMCs) and regulate the diameter of small cerebral arteries and arterioles. However, the intracellular structures that govern the expression and function of vascular Kv channels are poorly understood. Scaffolding proteins including postsynaptic density 95 (PSD95) recently were identified in rat cerebral VSMCs. Primarily characterized in neurons, the PSD95 scaffold has more than 50 known binding partners, and it can mediate macromolecular signaling between cell‐surface receptors and ion channels. In cerebral arteries, Shaker‐type Kv1 channels appear to associate with the PSD95 molecular scaffold, and PSD95 is required for the normal expression and vasodilator influence of members of this K+ channel gene family. Furthermore, recent findings suggest that the β1‐subtype adrenergic receptor is expressed in cerebral VSMCs and forms a functional vasodilator complex with Kv1 channels on the PSD95 scaffold. Activation of β1‐subtype adrenergic receptors in VSMCs enables protein kinase A‐dependent phosphorylation and opening of Kv1 channels in the PSD95 complex; the subsequent K+ efflux mediates membrane hyperpolarization and vasodilation of small cerebral arteries. Early evidence from other studies suggests that other families of Kv channels and scaffolding proteins are expressed in VSMCs. Future investigations into these macromolecular complexes that modulate the expression and function of Kv channels may reveal unknown signaling cascades that regulate VSMC excitability and provide novel targets for ion channel‐based medications to optimize vascular tone.
Protective efficacy of an IL‐12‐expressing baculoviral malaria vaccine
Authors: Iyori M. , Blagborough A. M. , Sala K. A. , Nishiura H. , Takagi K. , Yoshida S.
Published: October 2017

Interleukin‐12 (IL‐12) plays an important role in antigen‐specific adaptive immunity against Plasmodium sporozoites, and this requirement allows for a new approach to developing an effective malaria vaccine. In this study, we examined whether IL‐12 could enhance protective efficacy of a baculovirus‐based malaria vaccine. For this aim, a baculoviral vector expressing murine IL‐12 (mIL‐12) under the control of CMV promoter (BES‐mIL‐12‐Spider) and a baculoviral vector expressing Plasmodium falciparum circumsporozoite protein (PfCSP) with post‐transcriptional regulatory element of woodchuck hepatitis virus (BDES‐sPfCSP2‐WPRE‐Spider) were generated. BES‐mIL‐12‐Spider produced bioactive IL‐12 which activates splenocytes, resulting in induction of IFN‐γ. When co‐immunized with BES‐mIL‐12‐Spider and BDES‐sPfCSP2‐WPRE‐Spider, the mouse number for high IgG2a/IgG1 ratios and the geometric mean in this group were both increased as compared with those of the other groups, indicating a shift towards a Th1‐type response following immunization with BES‐mIL‐12‐Spider. Finally, immunization with BDES‐sPfCSP2‐WPRE‐Spider plus BES‐mIL‐12‐Spider had a higher protective efficacy (73%) than immunization with BDES‐sPfCSP2‐WPRE‐Spider alone (30%) against challenge with transgenic Plasmodium berghei sporozoites expressing PfCSP. These results suggest that co‐administration of IL‐12 expressing baculoviral vector, instead of IL‐12 cDNA, with viral‐vectored vaccines provides a new feasible vaccine platform to enhance Th1‐type cellular immune responses against Plasmodium parasites.
China's Public Diplomacy for International Public Goods
Authors: Zhao Kejin
Published: October 2017

Since the late 1970s, the question of how to balance national and global interests has been one of the important considerations in China's grand strategy. Since 2012, China's top leaders have argued that China should provide international public goods (IPGs) and pay more attention to public diplomacy as a new model of big power diplomacy. Nevertheless, based on an examination of the recent literature, this article finds that most of the discussions highlight China's responsibility to provide IPGs rather than the motivations behind it. To obtain an accurate understanding of the real strategic motivations behind China's IPG public diplomacy, a necessary methodological innovation from normative to empirical studies should be undertaken. Drawing on case studies relevant to the topic, this article concludes that power advantage, institutional, and social ecological factors play determinative roles in understanding the motivations behind China's new IPG public diplomacy. Further, IPGs are regarded as core to China's new public diplomacy for global leadership in the foreseeable future. Within the context of emerging antiglobalization movements around the world, China's public diplomacy for IPGs aims to drive the nation further along the track of global leadership alongside the United States.
Indo‐Pacific Diplomacy: A View from the Pacific Islands
Authors: Naupa Anna
Published: October 2017

Pacific diplomacy has entered a new chapter in the twenty‐first century; it should chart a strategic course among diverse geopolitical agendas, new and multiple actors, including beyond the traditional nation state, and evolving regional identity politics. Often on the receiving end of “soft diplomacy” from the established and rising powers of the Indo‐Pacific seeking to exert influence, the Pacific Island nations face real consequences of transnational challenges such as climate change and marine resource depletion, and are crafting their own pragmatic diplomacy. The emerging Pacific approach suggests that aspects of network diplomacy—leveraging bilateral, multilateral, and multi‐actor relations to forge issues‐based coalitions around a common goal—will increasingly become a necessary feature of Pacific states seeking to navigate shifting geopolitics, and situate themselves within an emerging Indo‐Pacific region.
CT versus thoracic ultrasound for discriminating uncomplicated and complicated parapneumonic pleural effusions – Reply
Authors: Porcel José M.
Published: October 2017

See Letter
The use of question tags in different text types of Trinidadian English
Authors: WILSON GUYANNE , WESTPHAL MICHAEL , HARTMANN JOHANNA , DEUBER DAGMAR
Published: October 2017

We investigate the use of question tags in Trinidadian English. Using a variationist pragmatics approach and spoken material from the Trinidad and Tobago component of the International Corpus of English, we describe the distribution and pragmatic functions of variant and invariant tags across four text types. Variant question tags are rare in Trinidadian English, but a range of invariant question tags is present in the corpus. Tags serve a number of pragmatic functions, and can serve multiple functions simultaneously. Text type is a strong factor influencing the frequency of tag forms and functions, with tags associated with the local creole mainly found in informal text types.
Personalization of learning situations within a virtual environment for training based on fuzzy clustering
Authors: Fahim Mohamed , Jakimi Abdeslam , El Bermi Lahcen
Published: October 2017

Advances in networks, computers and multimedia technology have changed traditionalmethods for learning and skills training. Nowadays, Virtual Environments for Training (VET) havebeen popular, they can provide an environment where virtual reality can be used to createinteractive interfaces and real-time software that can control every response and action madeby the user. VET have proven to be advantageous to put learners into varied trainingsituations to acquire knowledge and competencies, especially when these situations are taking place in uncontrolled circumstances, or when they are dangerous, unrealizable, or expensive to establish in reality. However individual learners find it difficult to select suitablelearning situations for their particular situation because often, there is no personalized serviceto response to the user needs. Personalization of learning in a VET is a very important way ofimproving the effectiveness and the quality of the training, yet it also a complex process thatrequires consideration of several factors such as learner‘s profiles. The goal is to associatesuitable learning situations to each learner based on his profile.However, personalization of learning becomes an issue with the uncertainty and imprecisionof data that may contains a learner profile. To address this issue, this study is an attempt tointegrate a fuzzy clustering into the process of the personalization of learning.
Immediate cortical adaptation in visual and non‐visual areas functions induced by monovision
Authors: Zeri Fabrizio , Berchicci Marika , Naroo Shehzad A. , Pitzalis Sabrina , Di Russo Francesco
Published: October 2017

Key points

Monovision is an optical correction for presbyopes that consists of correcting one eye for far distance and the other for near distance, creating a superimposition of an in‐focus with a blurred image.

Brain adaptation to monovision was studied in unexperienced observers by measuring visual evoked potentials from 64‐channels.

The first clear effect of monovision on visual evoked potentials was the C1 amplitude reduction, indicating that the unilateral blurring induced by monovision reduces feed‐forward activity in primary visual area.

Monovision led also to an increased amplitude of the P1 and pP1 components, with the latter originating in prefrontal regions. This effect probably works as an attentional compensatory activity used to compensate for the degraded V1 signal.

A common and often successful option to correct presbyopia with contact lenses is monovision. This is an unbalanced correction across the two eyes where one eye is corrected for far vision and the other eye is corrected for near vision. Monovision is therefore a form of acquired anisometropia that causes a superimposition of an in‐focus image with a blurred image. In spite of this visual anisometropia, monovision has been successfully used for many decadesl however the brain mechanism supporting monovision is not well understood. The present study aimed to measure the visual evoked potentials with a high‐density electrode array (64‐channel) in a group of presbyopes and to provide a detailed spatiotemporal analysis of the cortical activity after a short period of adaptation to monovision with contact lenses. When compared with a balanced eye near correction, monovision produced both a clear reduction of the earliest visual evoked potential components, the C1 and the N1, and an amplitude increase of the P1 and pP1. These results indicate that the unilateral blurring induced by wearing monovision contact lenses reduces feed‐forward activity in the primary visual area and feedback activity in extrastriate areas (C1 and N1 reduction). Interestingly, other brain activities in both extrastriate visual areas (the P1 component) and in the anterior insula (the pP1 component) appear to compensate for this dysfunction, increasing their activity during monovision. These changes confirm the presence of fluid brain adaptation in visual and non‐visual areas during monocular interferences.
Ups and downs of calcium in the heart
Authors: Eisner David A.
Published: October 2017

Contraction and relaxation of the heart result from cyclical changes of intracellular Ca2+ concentration ([Ca2+]i). The entry of Ca2+ into the cell via the L‐type Ca2+ current leads to the release of more from the sarcoplasmic reticulum (SR). Compared to other regulatory mechanisms such as phosphorylation, Ca2+ signalling is very rapid. However, since Ca2+ cannot be destroyed, Ca2+ signalling can only be controlled by pumping across membranes. In the steady state, on each beat, the amount of Ca2+ released from the SR must equal that taken back and influx and efflux across the sarcolemma must be equal. Any imbalance in these fluxes will result in a change of SR Ca2+ content and this provides a mechanism for regulation of SR Ca2+ content. These flux balance considerations also explain why simply potentiating Ca2+ release from the SR has no maintained effect on the amplitude of the Ca2+ transient. A low diastolic [Ca2+]i is essential for cardiac relaxation, but the factors that control diastolic [Ca2+]i are poorly understood. Recent work suggests that flux balance is also important here. In particular, decreasing SR function decreases the amplitude of the systolic Ca2+ transient and the resulting decrease of Ca2+ efflux results in an increase of diastolic [Ca2+]i to maintain total efflux.

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Optimal Vibration Absorber With a Friction Damper
Authors: Sinha Alok , Trikutam Krishna T.
Published: October 2017

The response of a single degree-of-freedom spring mass system connected to a vibration absorber with a friction damper and subjected to a sinusoidal excitation is considered in this paper. Two possible configurations of the friction damper, rigid and flexible, are explored in details. Optimization of the parameters of absorbers with both these damper configurations to minimize the peak value of the frequency response of the primary system is presented. Results from this minimax optimization approach are compared to the classical solutions for a vibration absorber with linear viscous damper.
Mechanical Behavior of Thermal Interface Materials in Electronic Components Under Dynamic Loading Conditions
Authors: Poshtan Emad A. , Hegde Sudarshan , Roessle Andreas
Published: October 2017

The miniaturization of Control Units (CUs), consequently increasing power and reduced component size justifies a growing need for significantly improved Thermal Interface Material (TIM) which is a pivotal material for transferring heat from a die to a heat-spreader. However, it also has a crucial effect on the thermomechanical and dynamic behavior of the attached components. In this paper, the effect of frequency dependency of TIM on dynamic behavior of the attached capacitor is investigated analytically, numerically and experimentally. The results show that it is crucial to consider the frequency dependent material properties of TIM, for reliability assessment of the attached components under dynamic loading conditions.
Copper Inverse Opal Surfaces for Enhanced Boiling Heat Transfer
Authors: Lee Hyoungsoon , Maitra Tanmoy , Palko James , Zhang Chi , Barako Michael , Won Yoonjin , Asheghi Mehdi , Goodson Kenneth E.
Published: October 2017

Enhanced boiling is one of the popular cooling schemes in thermal management due to its superior heat transfer characteristics. This study demonstrates the ability of copper inverse opal (CIO) porous structures to enhance pool boiling performance using a thin CIO film with a thickness of ∼ 10 μm and pore diameter of 5 μm. The microfabricated CIO film increases microscale surface roughness that in turn leads to more active nucleation sites thus improved boiling performance parameters such as heat transfer coefficient and critical heat flux compared to those of smooth Si surfaces. The experimental results for CIO film show a maximum critical heat flux of 225 W/cm2 (at 16.2°C superheat) or about 3 times higher than that of smooth Si surface (80 W/cm2 at 21.6°C superheat). Optical images showing bubble formation on the microporous copper surface are captured to provide detailed information of bubble departure diameter and frequency.
Relationship Between Threshold Current Density of Electromigration Damage Considering Void and Hillock Formation and Reservoir Shape in Interconnect Line
Authors: Takaya Ryuji , Sasagawa Kazuhiko , Fujisaki Kazuhiro , Moriwaki Takeshi
Published: October 2017

Reservoir structures are often constructed in the interconnection to prevent the electromigration damages. In this study, a numerical simulation technique for analyzing the atomic density distributions in the line under high current density was used to evaluate the effects of reservoir length and location on the threshold current density considering void and hillock generations.

The threshold current density is determined when the local atomic density in the line reaches the upper critical value for hillock creation or the lower critical value for void generation. Atomic density distributions in the line were simulated when cathode and anode reservoir lengths were changed.

The threshold current density considering void formation became higher with longer cathode reservoir and shorter anode reservoir. However, opposite results obtained in the case of hillock formation. It was found that there was an optimum value of reservoir length, corresponding to both critical values of hillock and void initiation.
Comparison and Evaluation of Different Monitoring Methods in a Data Center Environment
Authors: Tradat M. , Khalili S. , Sammakia B. , Ibrahim M. , Peddle Th. , Calder A. , Dawson B. , Seymour M. , Nemati K. , Alissa H.
Published: October 2017

The operation of today’s data centers increasingly relies on environmental data collection and analysis to operate the cooling infrastructure as efficiently as possible and to maintain the reliability of IT equipment. This in turn emphasizes the importance of the quality of the data collected and their relevance to the overall operation of the data center. This study presents an experimentally based analysis and comparison between two different approaches for environmental data collection; one using a discrete sensor network, and another using available data from installed IT equipment through their Intelligent Platform Management Interface (IPMI). The comparison considers the quality and relevance of the data collected and investigates their effect on key performance and operational metrics. The results have shown the large variation of server inlet temperatures provided by the IPMI interface. On the other hand, the discrete sensor measurements showed much more reliable results where the server inlet temperatures had minimal variation inside the cold aisle. These results highlight the potential difficulty in using IPMI inlet temperature data to evaluate the thermal environment inside the contained cold aisle.

The study also focuses on how industry common methods for cooling efficiency management and control can be affected by the data collection approach. Results have shown that using preheated IPMI inlet temperature data can lead to unnecessarily lower cooling set points, which in turn minimizes the potential cooling energy savings. It was shown in one case that using discrete sensor data for control provides 20% more energy savings than using IPMI inlet temperature data.
Experimental Investigation of Parameters Affecting Performance of Pulsating Heat Pipe
Authors: Kathait Pawan Singh , Sharma Rajnish N.
Published: October 2017

Pulsating heat pipe (PHP) is a two phase highly efficient heat transfer device, due to its simple and flexible construction; it can be manufactured for a variety of applications. PHP works on thermally induced self-sustaining oscillation of liquid plugs and vapor slugs, so it does not have any moving parts either. Ease of manufacturing, potential for high efficiency at different scales and the ability to handle large heat fluxes has the PHP a suitable candidate for microscale electronics cooling or power electronics cooling. However, this technology is still in developing phase and there is at present no comprehensive model which can be used to design a PHP for a specific application. There are many parameters which affect PHP operation and a thorough understanding of the relation between all the variables is first required. The present study is an attempt to investigate experimentally the effects of various parameters on PHP startup, based on startup temperature measurements under varying heat input and carefully controlled conditions. It has been observed that the oscillations in PHP start (startup) as soon as it reaches a minimum temperature corresponding to the minimum Etvos number required for vapor bubble rise.
Power Packaging Thermal and Stress Model for Quick Parametric Analyses
Authors: Boteler L. M. , Miner S. M.
Published: October 2017

This work presents an easy to use approach to quickly estimate the device temperatures and thermal stresses in a generic high power module. A low order model was developed in MATLAB using a combination of numerical-analytical approach and a 3D nodal resistor network to calculate device temperatures and thermal stresses. The model assumes a heat flux generated at the top of each device which is dissipated through the packaging structure and removed by convection. The temperature distribution is used to calculate thermal stresses throughout the package. This method eliminates computer aided drawings (CAD) in favor of numerical parameters that can be easily and quickly varied over a wide range. The resistor network solves quickly in MATLAB, enabling fast, iterative thermal analyses and design through parametric studies of the chip dimensions, number of chips, chip layout, material types, cooling solutions, etc. The model is adaptable to any number of devices and board layers. The MATLAB model reduced the computational time by 97% compared to an equivalent SOLIDWORKS finite element analysis (FEA) model and that does not include the time required to generate the CAD model and verify mesh convergence and mesh independence. Temperatures from the network model were within 5°C and stresses were within 30% of the values obtained from the FEA model. The ability to quickly assess the thermal and stress effects of a wide variety of power module design parameters during the initial design process, without the complexity of a full FEA analysis, with reasonable results can significantly improve the final module.
The Effect of Surface Texture on Thermal Sensation and Comfort
Authors: Zhang Han , Hedge Alan
Published: October 2017

The study investigated how the material roughness of a tablet computer surface can affect thermal sensation and comfort of users fingers and palms at different surface temperatures. Three levels of pattern spacing were tested, and it was shown that rough material surface provided higher thermal comfort comparing to a smooth surface. In addition, the surface temperature of the material also moderates participants′ physical sensation of the roughness of the materials. The results of the study have shown evidences of the potentials to use materials with spatial patterns to improve thermal comfort while dissipating heat from electronic devices.
Knowledge Based Qualification Process to Evaluate Vibration Induced Failures in Electronic Components
Authors: Meyyappan Karumbu , Vujosevic Milena , Wu Qifeng , Malatkar Pramod , Hill Charles , Parrott Ryan
Published: October 2017

Electronic products used in autonomous vehicles can be subjected to harsh road conditions. Transportation induced vibration is one such reliability risk to be addressed as part of qualification. Vibration use data and reliability models are very extensively studied for fully packaged systems exposed to vibration risks during shipping. MIL-STD-810G and ISTA4AB are some of the industry standards that address these risks. On the other hand, USCAR-2 and GMW-3172 are couple of standards that may be more relevant for electronics used in automotive applications, where electronic components are exposed to vibration risks during their entire lifetime. Even though the usage model and duration for fully packaged systems in shipping and automotive electronics are different, the source of energy (road conditions), driving the risks are similar. The industry standards based damage model appear to be generic, covering a wide variety of products. In this paper, a knowledge based qualification (KBQ) framework, is used to map use conditions to accelerated test requirements for two failure modes: solder joint fatigue and socket contact fretting. The mechanisms chosen are distinct with different damage metric and drivers. The KBQ obtained qualification requirements were discussed relative to standard requirement with the objective to verify how well industry standard models reflect field reliability risks. For the chosen failure mechanisms and use condition data, it was observed that the industry standards lead to erroneous conclusions about vibration risk in the field.
Effect of Static and Dynamic Aging on Fatigue Behavior of Sn3.0Ag0.5Cu Solder Alloy
Authors: Li Yiran , Singh Yuvraj , Subbarayan Ganesh
Published: October 2017

In this paper, the effect of pretest isothermal aging and in-test aging on the fatigue behavior of Sn3.0Ag0.5Cu alloy are examined using the microstructurally adaptive creep model (MACM) and the maximum entropy fracture model (MEFM). Compared to traditional constitutive models, the MACM considers the effect of thermal history. Two microstructural parameters, the average Ag3Sn particle size and the average primary-Sn cell size, are identified as critical to capturing the aging behavior of SnAgCu alloys and are incorporated into a modified Dorn creep form. The MEFM is next utilized to characterize the damage accumulation rate in the Sn3.0Ag0.5Cu solder alloy. The MEFM uses a single damage accumulation parameter, which connects the accumulated damage to the accumulated in-elastic dissipation. This parameter is independent of sample geometry, test temperature and strain rate. The concepts of static aging and dynamic aging are utilized to describe pretest aging and in-test aging. In 25° C tests, with longer static aging, a faster fatigue damage accumulation results. Through the relationship between the damage accumulation rate and the average primary-Sn cell size, the influence of microstructural evolution introduced by static aging on fatigue behavior is confirmed. In 100° C tests, the dynamic aging causes further rapid damage accumulation relative to the 25° C tests.
Effect of Alloy Composition and Aging on the Survivability of Leadfree Solders in High Temperature Vibration in Automotive Environments
Authors: Lall Pradeep , Yadav Vikas , Zhang Di , Suhling Jeff
Published: October 2017

Current trends in the automotive industry point to increasing role of electronics for vehicle control, safety, efficiency and entertainment. Examples include lane-departure warning systems, collision avoidance systems, vehicle stability systems, and drive assist systems. Many of the automotive electronics systems are located under the hood of the vehicle mounted directly on engine or on transmission with sustained exposure to temperatures greater than 150°C in conjunction with vibration. Solder joint fatigue is a dominant failure modes under high-temperature vibration. Industry migration to lead-free solders has resulted in a proliferation of a wide variety of solder alloy compositions many of which are based on formulation of Sn, Ag and Cu. While it is well known that solder interconnects, accrue damage much faster when vibrated at elevated temperatures, the models for assessment of life under simultaneous temperature and vibration are scarce. State-of-art reliability models for solder joints focus on single stresses of vibration or thermal cycling. There is need for models for evaluating the survivability of leadfree solder assemblies to ensure 10-years, 100,000 miles life in automotive environments. In this paper, a new model has been proposed for life prediction of electronics under simultaneous temperature-vibration.
Effect of Corner Staking on the Fatigue Life of BGA Under Thermal Cycling
Authors: Chen Deng Yun , Osterman Michael
Published: October 2017

Solder interconnects in electronic assemblies are susceptible to failures due to environmental high strain rate impact and cyclic stresses. To mitigate the failures, adhesive bonds can be added after the solder assembly process to provide additional mechanical support. For ball grid array (BGA) packages, the adhesive is normally applied to the corners of the package and referred to as corner staking. In addition to corner staking, underfill is also a strategy used to mitigate the stresses on the solder joints. While components with underfill has been widely studied, the study of the impact of corner staking on the reliability of packages remains limited. This paper presents a study of corner-staked BGA packages with tin-3.0 silver-0.5 copper (SAC305) solder subjected to temperature cycling. Experimental temperature cycling is conducted to examine impact of the selected corner staking material on the fatigue life of BGAs. Further, finite element analysis is conducted to understand the influence of material properties of staking material on the fatigue life of BGAs. The result of the study indicates that the presence of corner staking, with selected material properties, reduces the damage on the solder joints under thermal cycling, and thus increases its fatigue life by about 80%. This paper may serve as a guidance for staking material selection to improve the fatigue life of solder joints of BGAs under thermal cycling.
Advancements in Silver Wire Bonding
Authors: Manoharan Subramani , Patel Chandradip , McCluskey Patrick
Published: October 2017

Silver is a leading competitor to gold and copper in fine pitch wire bonding used in the interconnection of microelectronic devices. Primary material for wire bonding has been gold, which gave way to copper in order for original equipment manufacturers to realize cost benefits. However, copper wire bonding has exhibited several reliability issues, especially in industrial and high temperature applications. Corrosion is the major problem, which was mitigated by coating the wire with palladium, which increased overall cost of production. Other concerns include harder free air ball (FAB) leading to under pad metallization cracking, smaller process window, excessive aluminum splash especially in fine pitch bonding, and lower throughput and yield arising from the hardness and stiffness of copper. Due to the above concerns, automotive, military and aerospace industries are still reluctant to fully adopt copper wire bonding. Light emitting diodes (LEDs) are also not manufactured with copper wires due to its low reflectance. Some of these industries are still using gold wire bonds in most of their packages, but are continually looking for an alternative. Silver wire bonds have good electrical and thermal conductivity, are less prone to corrosion than copper, have low melting points and comparable hardness to gold. Also, cost of silver has been shown to be similar to that of palladium coated copper wire, hence making it a good alternative. Silver wire bonding, a relatively new area of research, has attracted a lot of research focused on wire dopant material, bonding process, quality and reliability. This paper is aimed to serve as a comprehensive review of research done in this area, by summarizing the literature on silver wire bonding, establishing benefits and drawbacks over other wire bond materials and indicating reliability concerns along with failure modes and mechanisms.
Anand Parameters for SAC305 Alloys After Prolonged Storage up to 1-Year
Authors: Lall Pradeep , Zhang Di , Suhling Jeff , Locker David
Published: October 2017

Electronics in automotive underhood environments may be subjected to high temperatures in the neighborhood of 175°C while subjected to high strain rate mechanical loads of vibration. Portable products such as smartphones and tablets stay in the powered on condition for a majority of their operational life during which time the device internals are maintained at higher than ambient temperature. Thus, it would be expected for interconnects in portable products to be at a temperature high than room temperature when subjected to accidental drop or shock. Furthermore, electronics in missile-applications may be subjected to high strain rates after prolonged period of storage often at high temperature. Electronics systems including interconnects may experience high strain rates in the neighborhood of 1–100 per sec during operation at high temperature. However, the material properties of SAC305 leadfree solders at high strain rates and high operating temperatures are scarce after long-term storage. Furthermore, the solder interconnects in simulation of product drop are often modeled using elastic-plastic properties or linear elastic properties, neither of which accommodate the effect of operating temperature on the solder interconnect deformation at high operating temperature. SAC305 solders have been shown to demonstrate the significant degradation of mechanical properties including the tensile strength and the elastic modulus after exposure to high temperature storage for moderate periods of time. Previously, Anand’s viscoplastic constitutive model has been widely used to describe the inelastic deformation behavior of solders in electronic components under thermo-mechanical deformation. Uniaxial stress-strain curves have been plotted over a wide range of strain rates (ε. = 10, 35, 50, 75 /sec) and temperatures (T = 25, 50, 75, 100, 125, 150, 175, 200°C). Anand viscoplasticity constants have been calculated by non-linear fitting procedures. In addition, the accuracy of the extracted Anand constants has been evaluated by comparing the model prediction and experimental data.
True Concurrent Modulation of a Multi-Channel Ring Modulator Transmitter Driven by a Comb Laser
Authors: Seyedi Ashkan , Fiorentino Marco , Beausoleil Ray
Published: October 2017

This paper presents experimental data of concurrent modulation of a multi-channel transmitter that uses carrier-injection ring modulators at 10Gb/s/channel that is optically driven by a quantum-dot comb laser with 50GHz channel spacing.
Impact of Tile Design on Thermal Performance of Open and Enclosed Aisles
Authors: Khalili Sadegh , Tradat Mohammad I. , Nemati Kourosh , Seymour Mark , Sammakia Bahgat
Published: October 2017

In raised floor data centers, tiles with high open area ratio or complex understructure are used to fulfill the demand of today’s high-density computing. Using more open tiles reduces pressure drop across the raised floor with the potential advantages of increased airflow and lower noise. However, it introduces the disadvantage of increased non-uniformity of airflow distribution. In addition, there are various tile designs available on the market with different opening shapes or understructures. Furthermore, a physical separation of cold and hot aisles (containment) has been introduced to minimize the mixing of cold and hot air. In this study, three types of floor tiles with different open area, opening geometry, and understructure are considered. Experimentally validated detail models of tiles were implemented in CFD simulations to address the impact of tile design on the cooling of IT equipment in both open and enclosed aisle configurations. Also, impacts of under-cabinet leakage on the IT equipment inlet temperature in the provisioned and under-provisioned scenarios are studied. Finally, a predictive equation for the critical under-provisioning point that can lead to a no-flow condition in IT equipment with weaker airflow systems is presented.
Temperature-Based Request Distribution for Effective CRAC and Equipment Life-Cycle Extension
Authors: Nakajo Yusuke , Nishi Hiroaki
Published: October 2017

With the growth of Internet-based services, data centers must deal with increasing data traffic. Load-balancing technologies can help data centers process data effectively and stably; however, the current load-balancing methods do not take into account the heat generated by servers. Excessive heat can increase the failure rate of IT devices and the energy consumption of air conditioning systems, both of which lead to higher data center maintenance costs. This paper aims to simultaneously increase the coefficient of performance (COP) of the data center’s air-conditioning equipment and decrease the semiconductor-based equipment failure rate. To do so — and, consequently, reduce the operation and maintenance costs — we propose a novel request distribution system based on server-temperature and evaluate the proposed system by creating a thermal model of a data center. As a result, it is suggested that using the proposed load-balancing method the semiconductor failure rate can be reduced by 32 % when compared with the common round-robin distribution method, and by 19 % when compared with a load-balancing method based on CPU utilization. Moreover, the COP of the air-conditioning equipment obtained with the proposed method is recognized to be higher than those obtained with either the round-robin or the CPU-utilization-based methods.
Application of Computed Tomography for the Examination of Pressure Retaining Nuclear Plant Components
Authors: Gratton Robert , Wilson James , Skuse Kevin
Published: October 2017

Pressure retaining nuclear plant components require high levels of quality assurance to support the rigorous requirements of the modern safety case and the ASME Boiler and Pressure Vessel Code. Part NB-2500 of the ASME BPVC requires 100% volumetric examination of pressure retaining components and attachment welds utilising suitably demonstrated ultrasonic and radiographic examination techniques respectively. The capability of the inspection technique is particularly important for thin-walled components where the typical size of manufacturing defects tend to make up a greater proportion of the wall thickness.

Computed Tomography (CT) is a development of conventional radiography and makes use of computer-processed combinations of many X-ray images taken from different angles to produce cross-sectional images of specific areas of a scanned object. This technique can be used to compliment and add strength to the standard volumetric examinations; ie the detection capability for conventional radiography is often dependent on alignment of the source to defect and ultrasonic methods are more suited to targeting planar flaws.

Rather than the technical challenges placed on the Non-Destructive Examination (NDE) practitioner, this paper focuses on the benefits of application of CT to thin-walled nuclear plant components from the viewpoint of the nuclear plant component Design Engineer.

The CT examples presented in this paper demonstrate reliable detection of voids measuring 4% of thickness including those located at features which are difficult to examine using standard techniques. These CT examinations compliment the standard volumetric inspections and provide high confidence that the component is free of structurally significant defects.
An Experimental Setup for Determining the Failure Locus of ASME Tubular Pressure Vessel Steel Grades
Authors: Al Khaled M. A. , Barsoum I.
Published: October 2017

Pressure vessels designed in accordance with the ASME BPVC code are protected against local ductile failure. Recent work has shown that local ductile failure highly depends on the stress state characterized by both stress triaxiality (T) and the Lode parameter (L). In this paper, the effect of stress state on the ductility of a tubular steel is studied. Two ring specimen configurations were optimized to allow the determination of the ductile failure locus of both tensile and plane strain loadings. The geometry of both ring specimen configurations was optimized to achieve a plane strain (L = 0) condition and a generalized tension (L = −1) condition. Notches with different radii were machined on both types to achieve a wide range of stress triaxiality levels. Specimens were manufactured from SA-106 carbon tubular steel and were tested to determine the ductile failure loci as a function of T and L. Failure locus of SA-106 steel was constructed based on the failure instants and was found to be independent of the variation in the Lode parameter. The ASME-BPVC local failure criterion showed close agreement with experimental results.
Failure Analysis of a Large Knife Gate Valve Subjected to Multiaxial Loading
Authors: Barsoum Imad , Muñoz Alberto
Published: October 2017

Knife gate valves are common in process piping plants in the petrochemical industry. In this study a failure analysis is undertaken on a large knife gate valve attached on top of a Y-piece as part of a purge bin outlet in a polyethylene production facility. A large crack was discovered on the knife gate valve shortly after its installation and operation of the facility. The study outlines a methodology, based on the finite element method, to analyze failure of such units. It starts out by determining the stress intensification factors for a Y-piece by conducting an FEA, which are used in CAESER II piping software to determine the operational loads on the valve. The loads are used as inputs for a non-linear FEA model of the valve accounting for material failure based on continuum damage mechanics approach. The FEA results suggest that the operational loads are not the root cause to the observed failure on the gate valve. It is rather attributed to internal casting defects and the lack of post-heat treatment of the valve.
Statistical Approach to Establishing Tuned Simulation Parameters
Authors: Westwater Gregory D. , Mann J. Adin , Speichinger Jared R.
Published: October 2017

The data needed to fully benchmark a simulation is frequently inadequate. The analyst is then challenged to make assumptions or otherwise determine how the simulation can be appropriately used to predict future outcomes. A thermal analysis will be presented where temperature data is available at several locations throughout the structure, but information on boundary conditions and thermal properties of the structure is limited. The unknown variables are parameterized and bounded based on the underlying physics and available data for ‘typical’ values. Simulations are then run and a fitting score is used to determine the ranges of the inputs which gave the best overall fit to the test data for the entire structure, avoiding bias of focusing on the single location of interest. In this process, multiple combinations are found that yield similar fit scores, but the variables were confounded and the available data could not support one set of values over another. The resulting ranges of input values were then used in the follow-on analysis work, allowing results to be found as a range of likely values in terms of the input uncertainties. Statistical methods were also applied to the results, allowing determination of which inputs had the greatest impact on the results, and thus identifying where future efforts should be focused to distinguish the variables and provide greater accuracy in the method.
Full Scale Blasting Test and Finite Element Analysis of Nozzle Repair Pipeline
Authors: Wu Xu , Shuai Jian
Published: October 2017

Nozzle repair is one of the common repair methods for oil and gas pipelines. As a means to test the applicability of the pipeline, the pressure test is widely used in the integrity evaluation of oil and gas pipelines. To avoid possible failure accidents of nozzle repair pipeline, hydrostatic burst tests were performed. The finite element model of the pipeline was established. The effects of nozzle diameter and nozzle wall thickness parameters on the stress-strain response of the nozzle repair pipeline were discussed. The results show that the yield stress of the specimen is about 11.2MPa, and the blasting pressure is 12.9MPa. Due to the effect of nozzle structure, the change of strain for each point with the internal pressure is inconsistent. The ratio of axial strain to circumferential strain decreases with the increase of pressure, which shows that the yield mainly occurs in the hoop direction, and the axial deformation increases with the increase of the pressure. Under the condition of the_constant wall thickness, the stress distribution of pipeline is uniform and the yield pressure increases with the decrease of nozzle diameter. The smaller the nozzle diameter, the better the bearing capacity. The selection for the wall thickness of nozzle should be greater than or equal to the thickness of the pipe wall.
Construction of Dynamic Model of Planar and Rocking Motion for Free Standing Spent Fuel Rack
Authors: Sakamoto Kazuya , Kan Ryosuke , Takai Akihiro , Kaneko Shigehiko
Published: October 2017

Spent nuclear fuel is settled in racks and stored in spent fuel pool. A free standing rack (FS rack) is a type of a spent fuel rack, which is not fixed to walls unlike conventional ones. For this characteristic, movement of an FS rack during an earthquake can be reduced by fluid force and friction force. However, collision between a rack and another rack or a wall must be avoided. Therefore, it is necessary for designing an FS rack to figure out how it moves under seismic excitation. In this research, a dynamic model of FS racks is constructed considering seismic inertial force, friction force and fluid force. This model consists of two sub-models: translation model, which simulates planar translational and rotational motion; and rocking model, which simulates rocking motion. Moreover, we developed two kinds of rocking model: slide-rocking considered model, which considers the equations of both slide-rocking motion and non-slide-rocking motion; and non-slide-rocking model, which considers only the equation of non-slide-rocking motion. Then, simulations with sinusoidal inertial force input were conducted, changing values of friction coefficient. To validate this dynamic model, a miniature experiment was conducted. It is found that the non-slide-rocking model simulates movement of an FS rack well and better than the slide-rocking considered model in the aspect of translational and rocking movement. However, planar rotational movement is not simulated well with either model. Through this research, the knowledge is acquired that friction force plays a significant role in motion of an FS rack so that estimating and controlling friction coefficient is important in designing an FS rack.