bluuebunny/crossref_metadata_2025 huggingface dataset:
Review of Cross-Leg Flaps in Reconstruction of Posttraumatic Lower Extremity Wounds in a Microsurgical Unit
Authors: Mahajan Ravi K. , Srinivasan Krishnan , Ghildiyal Harish , Singh Mahipal , Jain Adish , Kapadia Taha , Tambotra Ankush
Published: May 2019

Since the advent of microsurgery, and expanding expertise in the field, extensive traumatic wounds of leg have been managed successfully with free tissue transfer. Various patient-related factors may preclude the use of free flaps even in units with available expertise and infrastructure. It is in such situations that the “cross-leg flap” comes into play. In these cases, instead of attempting complicated anastomotic techniques or anastomosis in the zone of trauma, it is better to perform the simpler and more reliable cross-leg flap. In this study, we try to show the utility of a cross-leg flap based on a retrospective study of 198 patients who underwent cross-leg flap in our institute over a period of 15 years extending from November 2003 to March 2018. Materials and methods: Case sheets of all patients who underwent cross-leg flap from November 2003 to March 2018 were reviewed. The location of defect in the leg, the indication for cross-leg flap, the pattern of cross-leg flap, and perioperative complications were noted. Results: A total of 198 patients underwent cross-leg flap for traumatic soft tissue injury of leg during this period. The most common reason for performing cross-leg flap was poor pulsatility of the recipient artery as seen intraoperatively, followed by the economics of the procedure wherein the initial cost of free flap was found significantly higher compared with cross-leg flap. All flaps survived with partial necrosis occurring in 23 patients. All flaps settled well by 2 years’ time. Bony union/fracture healing evaluation was not a part of this study. Conclusion: Cross-leg flap is still a useful tool for leg wound coverage even in microsurgical unit in situations precluding free flap coverage.
Alternating activity patterns and a chimeralike state in a network of globally coupled excitable Morris-Lecar neurons
Authors: Kaminker Vitaliy , Wackerbauer Renate
Published: May 2019

Spatiotemporal chaos collapses to either a rest state or a propagating pulse in a ring network of diffusively coupled, excitable Morris–Lecar neurons. Adding global varying synaptic coupling to the ring network reveals complex transient behavior. Spatiotemporal chaos collapses into a transient pulse that reinitiates spatiotemporal chaos to allow sequential pattern switching until a collapse to the rest state. A domain of irregular neuron activity coexists with a domain of inactive neurons forming a transient chimeralike state. Transient spatial localization of the chimeralike state is observed for stronger synapses.
Experimental investigation of the effects of sideslip on canard-configuration aircraft at high angle of attack
Authors: Dong Yizhang , Shi Zhiwei , Chen Kun , Chen Jie
Published: May 2019

Sideslip-induced asymmetrical vortices are critical to the performance of canard-configuration aircraft. In this paper, a canard-configuration model was found to roll around a nonzero trim angle in a free-to-roll experiment, indicating a loss of lateral static stability. This loss was also evidenced by the positive slope of the rolling-moment versus sideslip curve. To reveal the underlying mechanism of this phenomenon, we focused on sideslip effects, taking surface-pressure measurements and conducting PIV (particle image velocimetry) tests. At the attack angle of 16°, sideslip causes inward extension of the windward low-pressure area on the main wings, which leads to a decrease in rolling moment. The inferred cause is the inward movement of the windward reattachment point. At the attack angle of 35°, complex multi-vortex structures were analyzed using PIV for three forms of the model: with all components; without canard; with neither canard nor strake. The effects of sideslip on vortex flow at high attack angle were then studied. As sideslip angle changed from -1° to 1°, sideslip promotes the breakdown of windward vortices, causing a sharp decrease in windward suction. Subsequently, as sideslip angle changed from 1° to 4°, the backward movement of the breakdown point and an increase in strength of vortices are observed on the leeward side, which coincides with an increase in both leeward suction and the rolling moment. As the sideslip angle continues to increase, the inboard vortex on the leeward side rises and becomes weak, which leads to a decrease in leeward suction, and hence, the recovery of lateral static stability. Moreover, the coiling of leeward vortices weakens under sideslip.
Solution-based synthesis of NiSb nanoparticles for electrochemical activity in hydrogen evolution reaction
Authors: Qian Yin-yin , Yang Jing , Li Huan-ran , Xing Shi-qi , Yang Qing
Published: May 2019

A cost-effective, facile solution-based hot-injection synthetic route has been developed to synthesize NiSb nanoparticles in oleylamine (OAm) using commercially available inexpensive precursor with reducing toxicity at a relatively low temperature of 160 °C. Especially, an organic reductant of borane-tert-butylamine complex is intentionally involved in the reaction system to promote a fast reduction of metallic Ni and Sb for the formation of the NiSb nanoparticles. Structural characterizations reveal that the NiSb nanoparticles are hexagonal phase with space group P63/mmc and they are composed of small granules with size about 10 nm that tend to form agglomerates with porous-like geometries. This is the first report on the generation of transition metal antimonide via solution-based strategy, and the as-fabricated nanoparticles possess actively electrocatalytic hydrogen evolution reaction (HER) property in acidic electrolytes when the long-chain ligand of OAm adhered on the surface of the nanoparticles is exchanged by ligand-removal and exchange procedure. It is found that the NiSb nanoparticles as a new kind of non-noble-metal HER electrocatalysts only require overpotentials of 437 and 531 mV to achieve high current densities of 10 and 50 mA/cm2 respectively, as well as exhibit low charge transfer resistance and excellent HER stability.
Ring-polymer molecular dynamics studies of thermal rate coefficients for reaction F + H2O → HF + OH
Authors: Li Jun
Published: May 2019

The prototype tetra-atomic reaction F + H2O → HF + OH plays a significant role in both atmospheric and astronomical chemistry. In this work, thermal rate coefficients of this reaction are determined with the ring polymer molecular dynamics (RPMD) method on a full-dimensional potential energy surface (PES). This PES is the most accurate one for the title reaction, as demonstrated by the correct barrier height and reaction energy, compared to the benchmark calculations by the focal point analysis and the high accuracy extrapolated ab initio thermochemistry methods. The RPMD rate coefficients are in excellent agreement with those calculated by the semiclassical transition state theory and a two-dimensional master equation technique, and some experimental measurements. As has been found in many RPMD applications, quantum effects, including tunneling and zero-point energy effects, can be efficiently and effectively captured by the RPMD method. In addition, the convergence of the results with respect to the number of beads is rapid, which is also consistent with previous RPMD applications.
Superabsorbent capability and high retention ability of China clay (Kaolinite)/polyacrylic acid composites for aqueous solution
Authors: Shah Tanveer-Ul-Hassan , Tahir Mudassir Hussain , Rahman Ata ur , Liu He-wen
Published: May 2019

Majority of superabsorbent polymers (SAPs) yet reported either have low gel strength or high production cost. Therefore, we synthesized a novel polyacrylic acid-grafted China clay (Kaolinite) super-absorbent polymer composite (SAPC) with high thermal stability, low cost of production and superior sorption and retention capability for water and salt solution. The resulting SAPCs were extensively characterized and analysed by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Results suggested that the composites were thermally stable. Water absorbency increased with increase of clay content up to 45%, while further increase in clay content decreased the water absorbency. Percentage of acrylic acid (AA) and clay by weight shows the optimum absorbency in 35% and 40% respectively. Crosslinker and initiator contents were optimized to be 0.5% and 0.3% by weight respectively. The resulting polymer composite showed high water absorbency of about 785 g/g and 103 g/g of 1% NaCl solution with above 90% retention ability at 50 °C.
Functional roles of ammonium (NH4+) and nitrate (NO3–) in regulation of day- and night-time transpiration in Phaseolus vulgaris
Authors: Naku Mandilakhe , Kambizi Learnmore , Matimati Ignatious
Published: May 2019

Nitrogen may regulate transpiration and consequently the delivery of nutrients to root surfaces. It remains unclear whether both NO3– and NH4+ regulate transpiration and nutrient acquisition. In this study we investigated the functional role of NO3– or NH4+ in regulating both day- and night-time transpiration for potential ‘mass-flow’ delivery of nutrients. Phaseolus vulgaris L. plants were grown in troughs with a poly vinyl chloride (PVC) ‘root-barrier’ with a 25-µm mesh window designed to create an N-availability gradient by restricting roots from intercepting a slow-release NO3– or NH4+ fertiliser. ‘Root-barrier’ plants had their fertiliser placed at one of four distances behind the mesh from which nutrient acquisition was by diffusion or mass-flow. Control plants had direct access to fertiliser, termed ‘no root-barrier’ plants. NO3–-fed ‘root-barrier’ plants closest to the N source had 2-fold higher stomatal conductance, 2.6-fold higher transpiration, 1.8-fold higher night-time stomatal conductance, and 1.5-fold higher night-time transpiration than NO3–-fed ‘no-barrier’ plants, despite having comparable photosynthetic rates and biomass. Day- and night-time transpiration of NO3–-fed ‘root-barrier’ plants, however, was downregulated with further distance from the N source. All NH4+-fed plants displayed ammoniacal toxicity symptoms. NH4+-fed ‘no root-barrier’ plants had higher root biomass, 2-fold higher stomatal conductance and photosynthetic rate, 1.7-fold higher transpiration but had the same night-time stomatal conductance and transpiration compared with NH4+-fed ‘root-barrier’ plants closest to the N source. Unlike with NO3–-fed ‘root-barrier’ plants, NH4+-fed ‘root-barrier’ plants continuously increased their water fluxes with distance of N source. Thus, under N-limited conditions plants may be opportunistic in their water uptake, transpiring more when the water is available, in order to acquire nutrients through mass-flow. NH4+-fed plants prone to ammoniacal toxicity allocated their biomass towards the roots at non-limiting N levels, which may be linked to their extensive root system and enhanced photosynthetic rate. Thus, root hydraulic conductivity in response to NH4+-N requires further scrutiny, given that previous studies indicated that NH4+ may not alter the expression of root aquaporins or root hydraulic conductance.
Combined elevated temperature and soil waterlogging stresses limit fibre biomass accumulation and fibre quality formation by disrupting protein activity during cotton fibre development
Authors: Chen Yinglong , Chen Binglin , Wang Haimiao , Hu Wei , Wang Shanshan , Zhou Zhiguo
Published: May 2019

Soil waterlogging and high temperature conditions generally occur together, especially in the Yangtze River Valley, China, negatively affecting cotton (Gossypium hirsutum L.) fibre development. Therefore, combined elevated temperature (34.1/29.0°C) and soil waterlogging (6 days) were imposed to study their combined effects on fibre biomass and fibre qualities (length, strength and micronaire). The results showed that in the boll cohort exposed to waterlogging and/or elevated air temperature, combined elevated temperature and soil waterlogging decreased final fibre length (by 8.9–11.3%) and fibre biomass (by 25.8–33.9%) more than either stress individually. A total of 113, 263 and 290 differential abundance proteins were identified related to elevated temperature, waterlogging and the two treatments combined, respectively, in fibres at 15 days after anthesis via the isobaric tags for relative and absolute quantitation technique, which were classified as: carbohydrate and energy metabolism (21.7%), protein metabolism (16.6%), amino acid metabolism (12.8%), intracellular structural components (6.6%), transport (7.9%), oxidation–reduction process (7.9%), signal transduction (5.2%), lipid metabolism (5.2%), stress response (5.2%), nucleic acid metabolism (4.5%), organic acid metabolism (3.4%) and others (2.1%). Both vacuolar ATPase (V-ATPase) and plasma membrane H+-ATPase (PMH+-ATPase) were responsible for fibre length formation, although V-ATPase expression may play a major role in determining fibre cell elongation rather than PM H+-ATPase expression. It was concluded that fibre cell elongation and secondary wall thickening were inhibited mainly by reduced accumulation of osmolytes, blocked synthesis and transport of secondary wall components, and disruption of the cytoskeleton system under combined elevated temperature and soil waterlogging.
Shift from slow- to fast-twitch muscle fibres in skeletal muscle of newborn heterozygous and homozygous myostatin-knockout piglets
Authors: Xuan Mei-Fu , Luo Zhao-Bo , Wang Jun-Xia , Guo Qing , Han Sheng-Zhong , Jin Song-Shan , Kang Jin-Dan , Yin Xi-Jun
Published: May 2019

Myostatin (MSTN) is a member of the transforming growth factor-β superfamily that negatively regulates skeletal muscle development. A lack of MSTN induces muscle hypertrophy and increases formation of fast-twitch (Type II) muscle fibres. This study investigated muscle development in newborn heterozygous (MSTN+/−) and homozygous (MSTN−/−) MSTN-knockout piglets. Detailed morphological and gene and protein expression analyses were performed of the biceps femoris, semitendinosus and diaphragm of MSTN+/−, MSTN−/− and wild-type (WT) piglets. Haematoxylin–eosin staining revealed that the cross-sectional area of muscle fibres was significantly larger in MSTN-knockout than WT piglets. ATPase staining demonstrated that the percentage of Type IIb and IIa muscle fibres was significantly higher in MSTN−/− and MSTN+/− piglets respectively than in WT piglets. Western blotting showed that protein expression of myosin heavy chain-I was reduced in muscles of MSTN-knockout piglets. Quantitative reverse transcription–polymerase chain reaction revealed that, compared with WT piglets, myogenic differentiation factor (MyoD) mRNA expression in muscles was 1.3- to 2-fold higher in MSTN+/− piglets and 1.8- to 3.5-fold higher MSTN−/− piglets (P<0.05 and P<0.01 respectively). However, expression of myocyte enhancer factor 2C (MEF2C) mRNA in muscles was significantly lower in MSTN+/− than WT piglets (P<0.05). MSTN plays an important role in skeletal muscle development and regulates muscle fibre type by modulating the gene expression of MyoD and MEF2C in newborn piglets.
Effects of temperature and exercise on metabolism of three species of Australian freshwater turtles: implications for responses to climate change
Authors: Chessman Bruce C.
Published: May 2019

Oxygen consumption () of Chelodina expansa, C. longicollis and Emydura macquarii (Pleurodira: Chelidae) was measured at rest and during induced exercise at 8, 13, 18, 22, 26, 30 and 34°C. Resting varied significantly among species, being lowest in C. expansa, which is the most sedentary of the three species in nature, and highest in E. macquarii, which is the most energetic, but active did not differ significantly among the three species overall. For both Chelodina species, resting was appreciably lower than expected from regression of on body mass for non-marine turtles globally, a result that reinforces previous evidence of low resting metabolism in Australian chelid turtles. Active of all three species at higher temperatures was similar to reported for active freshwater cryptodires. Resting of all three species increased similarly with temperature, but active and aerobic scope did not. In C. expansa and E. macquarii, active and aerobic scope increased over the full temperature range assessed but in C. longicollis these variables reached a plateau above 22°C. Projected increases in freshwater temperatures in south-eastern Australia as a result of global warming are likely to enhance activity, feeding and growth of the three species (subject to food availability), especially in cooler seasons for C. longicollis and warmer seasons for C. expansa and E. macquarii. However, other aspects of predicted climate change, especially increased drought, are likely to be detrimental.
The Neurocognition of Translation and Interpreting
Authors: García Adolfo M.
Published: May 2019

This groundbreaking work offers a comprehensive account of brain-based research on translation and interpreting. First, the volume introduces the methodological and conceptual pillars of psychobiological approaches vis-à-vis those of other cognitive frameworks. Next, it systematizes neuropsychological, neuroscientific, and behavioral evidence on key topics, including the lateralization of networks subserving cross-linguistic processes; their relation with other linguistic mechanisms; the functional organization and temporal dynamics of the circuits engaged by different translation directions, processing levels, and source-language units; the system’s susceptibility to training-induced plasticity; and the outward correlates of its main operations. Lastly, the book discusses the field’s accomplishments, strengths, weaknesses, and requirements. Its authoritative yet picturesque, didactic style renders it accessible to researchers in cognitive translatology, bilingualism, and neurolinguistics, as well as teachers and practitioners in related areas. Succinctly, this piece establishes a much-needed platform for translation and interpreting studies to fruitfully interact with cognitive neuroscience.
Old English wolde and sceolde
Authors: Wischer Ilse
Published: May 2019

The Old English (OE) pre-modals willan and *sculan are generally considered less grammaticalized than their Modern English counterparts will and shall; nevertheless they most often function as auxiliary verbs (cf. Wischer, 2006: 173). Their present tense forms have already been studied in considerable detail, often in the context of their development into future tense markers, while their morphologically past tense forms have received comparatively little attention. In this paper I examine the past forms of willan and *sculan in the poetry texts from the Dictionary of Old English Corpus and categorize them according to their syntactic contexts and the lexical or grammatical meanings they express. Thus, the aim of this paper is to shed light on their past and non-past time-reference, their main verb use versus auxiliary use and the type of modality or other function they can express in periphrastic constructions, and hence their degree of grammaticalization in Old English.
Counterfactuality and aktionsart
Authors: Huber Judith
Published: May 2019

In Middle English (ME), manner of motion verbs occur in perfect periphrases with both BE and HAVE as auxiliaries (e.g. is/has run, is/has ridden), the BE-variant being the older, the HAVE-variant the more recent form with these verbs. Los (2015) hypothesizes that the choice of auxiliary with manner of motion verbs in ME might depend systematically on aktionsart in that HAVE is chosen when the verb denotes a controlled process (e.g. he has run fast for an hour), and BE when the verb denotes a change of location (e.g. he is run into town), much as in Present-Day Dutch. Also taking into account other factors that have been suggested to influence the choice of BE vs. HAVE in Middle English (such as counterfactuality, infinitive, or past perfect), I test this hypothesis on data from the Corpus of Middle English Prose and Verse. I show that aktionsart is indeed a very reliable predictor, but overridden by counterfactuality.
Signs of grammaticalization
Authors: Schwarz Sarah
Published: May 2019

In this study, I examine a large number of get-passives from different genres and time periods in the Corpus of Historical American English for signs of grammaticalization by looking for evidence of semantic bleaching and morphosyntactic generalization. A comparable set of be-passives is included as a control group throughout. The study shows a dramatic increase in the frequency of central get-passives between the 1870s and the 1990s. Changes in situation type, subject type, and range of past-participle collocates, which are traced through all four genres in the corpus, provide further indications that the get-passive is continuing to grammaticalize over the period.
Further explorations in the grammar of intensifier marking in Modern English
Authors: Rohdenburg Günter
Published: May 2019

Picking up on earlier analyses, this paper explores a number of further issues bearing on the replacement of unmarked intensifiers by suffixed ones. While the evolutions of individual intensifiers may vary enormously, almost all grammatical constraints on intensifier marking can be accounted for in terms of a verbality cline: Structures displaying a high degree of verbality promote the establishment of suffixed intensifiers whereas less verbal structures tend to delay the process. The major findings supporting this generalization include the following:

Past participles, which virtually always function as predicatives, represent one of the earliest categories to implement the change. In this respect, they contrast with present participles, which tend to behave like ordinary adjectives.

Compared with predicative adjectives, attributive adjectives have been slow to replace unmarked intensifiers by suffixed ones.

The establishment of the suffix is further advanced with complemented (non-attributive) adjectives than uncomplemented ones.
“Splendidly prejudiced”
Authors: Chapman Don
Published: May 2019

This paper examines terms used for disapproval in usage guides during the 19th and 20th centuries. Two corpora are used for this investigation: the Hyper Usage Guide of English database (HUGE) and a corpus of 29 usage guides representing nearly all decades of the 19th and 20th centuries. The terms of disapproval fall into four groups: terms emphasizing correctness (wrong, error), communication (confusing, awkward), varieties of English (variant, slang), and social judgments (silly, ignorant). The examination shows that terms emphasizing correctness are most dominant today and have predominated over time. In contrast, judgmental terms have declined over time, while variation and communication terms have increased. The paper further notes that for shibboleths – prescriptive rules with high salience for “some readers” – a common formulation is that “some writers” or even “many writers” use the disapproved term, thus paralleling the “some readers” who notice the shibboleths.
Paradigm shifts in 19th-century British grammar writing
Authors: Busse Beatrix , Gather Kirsten , Kleiber Ingo
Published: May 2019

Systematic and comprehensive linguistic studies of 19th-century British grammar books are scarce. This is surprising since the 19th century has often been claimed to constitute a turning point in English grammar writing, particularly due to the assumed paradigm shift from prescriptive works to predominantly descriptive grammars, the emergence of the comparative-historical approach around 1830, and phonetics gaining importance in the 1890s.

Combining methods from network analysis and historical corpus linguistics, we aim to reassess these assumed (meta)linguistic developments in grammar writing by examining authors’ references to other grammarians in a corpus of 19th-century British grammars. We will show that changes, such as the turn away from prescriptive grammar writing, can indeed be further enhanced and systematically supported by quantitative results from the analysed network of referenced grammars and grammarians. Further, the analysis of the grammars’ lexical inventory shows which authors take the lead in terminological progress.
The proverbial discourse tradition in the history of English
Authors: Lückert Claudia
Published: May 2019

The present contribution sheds light on the mental representation of proverbs in relation to the norms and conventions of discourse traditions (cf. Koch, 1997; Oesterreicher, 1997). While the proverbial tradition is seen as a very important discourse tradition of medieval England (for example Schaefer, 1992; Shippey, 1994; Aurich, 2012a), it is widely acknowledged that it is no longer as influential in modern times. The article introduces a new model of mental representation (“dual layer storage model of proverb representation”) which is a modified version of the “superlemma model of idiom representation” (Sprenger et al., 2006). This new model incorporates a facilitation process in line with the usage-based view (e.g. Bybee, 2013). The article argues that the particular norms and conventions of discourse traditions in the history of English which are connected with the proverbial tradition have an effect on the strength of the representation of proverbs in the mind.
Evidentiality and stance in YouTube comments on smartphone reviews
Authors: Parini Alejandro , Fetzer Anita
Published: May 2019

Online participatory environments have become saturated spaces in terms of the opportunities that they offer for the
display of different viewpoints and ideologies. YouTube, as a popular video-sharing and networking site,
constitutes a new media space that invites both individual and collaborative stance-taking by participants who gather, virtually,
to address a particular topic, issue or event depicted visually and discussed textually through the comments that are posted on
the site. This interactional dynamics triggers a dialogic sequence of follow-ups through which stances are formulated following up
on previous stances or counterstances. Against this background, this paper reports on a case study of individual and
collaborative, and interdiscursive and intradiscursive stance-taking in participants’ comments to an online review focusing on the
strategic use of direct (tactile) and indirect (inferential) references to evidentiality and their co-occurrence with
argumentative markers. In this multilayered context stance-taking does not only contribute to evaluation but also to the
construction of collective identities.
Gender inequality by design: does successful implementation of childcare policy deliver gender-just outcomes?
Authors: Plomien Ania
Published: May 2019

The intractability of complex forms of gender inequality and the normalisation of gender equality policies on public policy agendas continue to challenge feminist research and activism concerned with gender-just outcomes. Through integrative multi-level analysis of policy design-implementation-outcomes building on the feminist policy implementation framework, this article illuminates how dominant discursive framing supports divergent policy approaches by different actors within state-institutional sites. Based on a decade of childcare policy implementation in Poland, the analysis shows that a shared family well-being frame is deployed by political actors to design and implement contrasting models for childcare. These have profound implications for the attainment of gender-just outcomes by sometimes challenging, but more frequently, reconstituting gender hierarchies. The policy design-implementation-outcome lens highlights the centrality of gender throughout the policy process and thus helps account for the persistence of inequalities through their construction and re-construction. It also suggests that, politically, the policy effort can be deployed towards alternative processes and policies, and thus towards the attainment of gender-just outcomes.
Chiral phase transition from the Dyson-Schwinger equations in a finite spherical volume *
Authors: Zhao Ya-Peng , Zhang Rui-Rui , Zhang Han , Zong Hong-Shi
Published: May 2019

Within the framework of the Dyson-Schwinger equations and by means of Multiple Reflection Expansion, we study the effect of finite volume on the chiral phase transition in a sphere, and discuss in particular its influence on the possible location of the critical end point (CEP). According to our calculations, when we take a sphere instead of a cube, the influence of finite volume on phase transition is not as significant as previously calculated. For instance, as the radius of the spherical volume decreases from infinite to 2 fm, the critical temperature

, at zero chemical potential and finite temperature, drops only slightly. At finite chemical potential and finite temperature, the location of CEP shifts towards smaller temperature and higher chemical potential, but the amplitude of the variation does not exceed 20%. As a result, we find that not only the size of the volume but also its shape have a considerable impact on the phase transition.
Triple α -particle resonances in the decay of hot nuclear systems *
Authors: Zhang S. , Wang J. C. , Bonasera A. , Huang M. R. , Zheng H. , Zhang G. Q. , Kohley Z. , Ma Y. G. , Yennello S. J.
Published: May 2019

The Efimov (Thomas) trimers in excited 12C nuclei, for which no observation exists yet, are discussed by means of analyzing the experimental data of 70(64)Zn(64Ni) + 70(64)Zn(64Ni) reactions at the beam energy of E/A = 35 MeV/nucleon. In heavy ion collisions,

-particles interact with each other and can form complex systems such as 8Be and 12C. For the 3

-particle systems, multi-resonance processes give rise to excited levels of 12C. The interaction between any two of the 3

-particles provides events with one, two or three 8Be. Their interfering levels are clearly seen in the minimum relative energy distributions. Events with the three

-particle relative energies consistent with the ground state of 8Be are observed with the decrease of the instrumental error for the reconstructed 7.458 MeV excitation level in 12C, which was suggested as the Efimov (Thomas) state.
Study of the a1 (1269) resonance in the γp →π+π+π-n
reaction *
Authors: Zhang Xu , Xie Ju-Jun
Published: May 2019

Within an effective Lagrangian approach and resonance model, we study the

and

reactions via the

-exchange mechanism. For the

reaction, we perform a calculation of the differential and total cross-sections by considering the contributions of the

intermediate resonance decaying into

and then into

. Besides, the non-resonance process is also considered. With a lower mass of

, the experimental data for the invariant

mass distributions can be fairly well reproduced. For the

reaction, with the model parameters, the total cross-section is of the order of 10 μb at the photon beam energy

~2.5 GeV. It is expected that the model calculations in this work could be tested by future experiments.
Projection algorithm for simulation of fluid flow around moving objects with immersed boundary method
Authors: Abbati Alessia , Chierici Andrea , Chirco Leonardo , Da Vià Roberto , Manservisi Sandro
Published: May 2019

The simulations of fluid flow around moving objects are usually done using body conforming meshes, but recently there is growing interest in algorithms using non conforming grids, known as immersed boundary methods (IB). In particular the resolution of the flow around objects with moving boundary may involve a high meshing work that has to be repeated at each time step. In the present work the immersed boundary method is applied to an in-house finite element code, in order to simulate transient applications involving the movement of immersed solid interfaces. The distinguishing feature of this method is that the entire simulation is carried out on a grid which cover the entire domain and do not conform to the geometry of the rigid objects. A second mesh independent from the first one and built on the immersed body is considered. The presented method consists in the projection of fields, including boundary conditions, from the second mesh mentioned to the first one, that cover the whole domain. The projection is carried out considering the movement of the immersed objects, through the handling of the second mesh. The proposed algorithm is built in order to satisfy the mass conservation in the entire fluid region and to avoid any numerical instability. For the projection of such fields we develop a multiphysics open-source coupling platform, based on the open-source SALOME platform. MED (Modèle d’Échange de Donné) data structure has been used for all field operations, allowing the algorithm to be used with all the numerical codes where a MED duplicate of the field solution can be created. Applications of this approach will be presented and we provide results that show the consistency of the proposed algorithm.
Distributed optimal control applied to Fluid Structure Interaction problems
Authors: Chierici A , Chirco L , Da Vià R , Manservisi M , Magnaniand S
Published: May 2019

In this paper we focus on an optimal control problem based on Lagrangian multipliers and adjoint variables applied to the steady state Fluid-structure interaction problem. FSI systems consist of one or more solid structures that deform by interacting with a surrounding fluid flow. We consider the Fluid-structure interaction problem written in variational monolithic form in order to balance automatically solid and liquid forces at the interface. The objective of the control problem is the minimization of a velocity matching functional and it is obtained with a distributed force control that deforms the shape of the solid domain. This distributed control for Fluid-structure interaction systems can be easily used to control the shape of the solid domain and the flow effects of the fluid-solid interactions. The optimality system is derived from the first order optimality conditions by taking the Fréchet derivatives of the Lagrangian with respect to all the variables involved. The optimal solution is then obtained through a steepest descent algorithm applied to the optimality system. To support this approach we report a few numerical tests where the distributed force deforms the solid structure in order to match the desired velocity profile. The results obtained show the feasibility and robustness of this approach and its possible use in many industrial relevant applications.
A new surface tension VOF evaluation by using variational representation and Galerkin interpolation projection
Authors: Chirco L. , Chierici A. , Da Vià R. , Manservisi S.
Published: May 2019

In this work we propose a new algorithm for studying two-phase interface advection problems dominated by surface tension. We use a Volume Of Fluid (VOF) algorithm for studying the evolution of the two-phase interface on a Cartesian grid and a finite element numerical scheme for the velocity-pressure state. The velocity field that drives the evolution of this interface is obtained by solving the weak form of the Navier-Stokes equation where the surface tension force is not defined in a singular way. With standard numerical approaches that solve the strong form of the Navier-Stokes equations the surface force is determined by taking the divergence of the surface tension tensor. The computation of the divergence term results in a force which is non-convergent when the grid is refined since the tensor is computed in a discontinuous cell-by-cell way. In the past this approach was proposed with artificial different smoothing schemes in order to compute such a singular force. In this work we use the variational formulation of the Navier-Stokes equation and avoid differentiation. The tensor which is a function of the unit normal is evaluated by a Galerkin projection over regular Sobolev spaces. This allows the piece-wise continuous representation of the surface tensor and the unit normal based on the VOF reconstruction. Tests on convergence for two and three-dimension in the static and dynamical cases are reported to show the correct representation in the desired spaces. This method is also natural for coupling non uniform grid computation of the fluid with Cartesian grid of the VOF algorithm.
Optimal Control of the Wilcox turbulence model with lifting functions for flow injection and boundary control
Authors: Chirco L , Chierici A , Da Vià R , Giovacchini V , Manservisi S
Published: May 2019

This paper deals with boundary optimal control problems for the Navier-Stokes equations and Wilcox turbulence model. In this paper we study adjoint optimal control problems for Navier-Stokes equations to improve the advantages of using simulations where turbulence models play a significant role in designing engineering devices. We assess first distributed optimal control problems with the purpose to control the fluid behavior by injecting a flow on the boundary solid region to obtain a desired control over the fluid velocity and the kinetic turbulence energy in specific parts of the domain. Then, with the same purpose, we use lifting functions and boundary control. For this reason we reformulate the boundary optimal control problem into a distributed problem through a lifting function approach. The stronger regularity requirements which are imposed by standard boundary control approaches can then be avoided. The state, adjoint and control equations are derived and the optimality system solved for some simple cases with a finite element. Furthermore, we propose numerical strategies that allow to solve the coupled optimality system in a robust way for a large number of unknowns. The approach presented in this work is general and can be used to assess different objectives and types of control.
Numerical modelling of flashing flow phase change in convergent-divergent nozzle: A sensitivity analysis
Authors: Quang Dang Le , Mereu Riccardo , Besagni Giorgio , Dossena Vincenzo , Inzoli Fabio
Published: May 2019

A sensitivity analysis of a computational fluid dynamics (CFD) model of flashing flow phenomenon including the thermal non-equilibrium effect is proposed in the present paper. The model uses a two-phase mixture approach and the phase-change process is based on the difference between the vaporization pressure and the vapour partial pressure. Thermal non-equilibrium effect is included in the model by a sub-routine for the boiling delay. A two-dimensional axisymmetric convergent-divergent nozzle is used as benchmark for the proposed study. Such geometry is representative of well-known applications in nuclear, refrigeration and energy engineering (e.g., primary flow in the motive nozzle of ejectors). The results are compared to experimental data and previous numerical results available in literature. Present results show good agreement with global and local experimental fluid dynamic quantities used to validate the model. The paper includes in the first part a brief description of physical phenomenon of flashing flow, the experimental benchmark geometry and operating conditions. In the second part, the physical model and the numerical modeling approach are reported, showing the validation and the results related to the sensitivity analyses of the artificial coefficients characterizing the modelling approach.
Comparison between cooling strategies for power electronic devices: fractal mini-channels and arrays of impinging submerged jets
Authors: Baraldi N , Fregni A , Sabato M , Stalio E , Brusiani F , Tranchero M , Baritaud T
Published: May 2019

Power electronic devices like Insulated Gate Bipolar Transistors (IGBTs) and diodes are often characterized by power densities and dimensions that could result in very high heat flux densities. In order to guarantee the expected performance and lifetime for these components, dedicated active cooling devices are usually adopted. In the present paper, the comparison between two different cooling strategies for power electronics is presented: fractal-channel design and submerged impinging jets. Each cooling strategy is tested on two different geometrical configurations. Water is used as coolant in all cases. Assessment of the considered cooling methods is done through application of the selected configuration in a simplified system composed by a rectangular chip (heat source) separated from the coolant by a solid block.

Three-dimensional conjugated heat transfer simulations are performed by using RANS solver implemented in OpenFOAM and two-equations turbulence models, resolving also the viscous sublayer. Numerical results allow to compare the cooling strategies in terms of maximum chip temperature, overall chip-to-coolant thermal resistance, and pumping power required. In summary, the fractal-channel design shows limitations in guaranteeing low chip temperatures at an affordable pumping power. The submerged impinging jets approach shows very high local heat transfer coefficient by which it is possible to tailor the cooling effect on specific hot spots.
Finite heating duration based-sensitivity analysis in transient heat conduction
Authors: D’Alessandro G , de Monte F
Published: May 2019

In the parameter estimation the sensitivity analysis of the temperature to the unknown parameter (such as thermal conductivity, heat capacity) plays a fundamental role. In the experimental setup for thermal properties measurements of solid materials, the heater in contact with the specimen can be modelled through an high conductivity thin layer. In such a case the one dimensional finite rectangular body, representing the sample, is subject to a boundary condition of the 4th kind at the heated boundary. Also, a constant heat flux applied for a finite period of time is considered in the analysis and the sample backside is assumed insulated. The temperature field within the finite body is obtained by using the superposition principle. Then, the scaled sensitivity coefficients are computed analytically for two different locations: at the interface between the heater and the sample, and at the sample backside. The results show that the sensitivity coefficients with respect to the thermal conductivity and to the volumetric heat capacity of the sample are uncorrelated.
Occupancy modelling of buildings based on CO2 concentration measurements: an experimental analysis
Authors: Franco Alessandro , Leccese Francesco , Marchi Lorenzo
Published: May 2019

The problem of real-time estimation of occupancy of buildings (number of people in various zones at every time instant) is relevant to a number of emerging applications that achieve high energy efficiency through feedback control. The measurement of CO2 concentration can be considered an important indicator that allows to define the occupation of closed and crowded spaces. Interesting cases can be school buildings and other buildings used in civil and residential (shopping centers, hospitals, etc.). This paper starting from an experimental analysis conducted of a University campus in different operating conditions, with different model for occupancy simulation in multi-zone multi-occupant buildings and its preliminary validation from experimental data acquired in different cases. The acquired data are used to present some graphical models and perform occupancy estimates. Starting from an accurate analysis of the data, attempts are made to define a preliminary estimation method through the development of a mathematical models of occupancy dynamics in a building, which show promising results.
Experimental study of PM emissions from wood pellet stoves with an innovative burning pot
Authors: Polonini L F , Petrocelli D , Parmigiani S P , Lezzi A M
Published: May 2019

In this study, results of an extensive set of experiments on a wood pellet stove model equipped with innovative burning pots are presented. Tests have been performed to investigate the relations between design data and operation parameters of the stove and its emissions. In particular, carbon monoxide (CO) and particulate matter (PM) emissions are correlated to the burning-pot depth.

The burning pot A, adopted by AICO S.p.A, allows to obtain near-to-zero CO emissions and low PM emissions: however, PM emissions reduction with respect to standard burning pots is not as enhanced as CO emission reduction. Here it is shown that a further reduction of PM emissions (down to 6-16 mg/Nm3) can be attained increasing the burning pot depth.

Experiments show also an increment of PM emissions in subsequent tests in the same day: there is an apparent dependence of PM release on the time from ignition. It is likely that this effect is due to ashes accumulation on the bottom of the burning pot and to their interaction with the primary air stream that flows over them.
Experimental analysis of steam condensation patterns within a pressure suppression system operating at sub-atmospheric pressure conditions
Authors: Lo Frano R , Aquaro D , Mazed D , Del Serra D , Giambartolomei G
Published: May 2019

For some specific applications, the pressure suppression systems should be maintained at sub-atmospheric pressure, such as in fusion plants systems. This operation conditions differ considerably from those experienced in the suppression pools of BWR operating at atmospheric pressure.

The steam condensation in water at sub-atmospheric conditions is not sufficiently known, if not at all; therefore its effectiveness has to be investigated experimentally. In fact the steam condensation at sub-atmospheric pressure requires a subcooling capacity 2.5 times higher than that at atmospheric pressure.

In consideration of that, a low scale experimental facility was designed and built at the University of Pisa. More than 350 steam condensation tests were performed in broad influencing parameters range (e. g. pressure within the condensation tank, water temperature and steam mass flux) to study of effectiveness of the steam condensation. In doing that, different sparger configurations (with single or multiple holes) were considered to check possible interference of condensing steam jets and bubble coalescence.

Results indicate a high efficiency of condensation for all the examined conditions. The 3D map of the condensation regimes demonstrate they are dependent only on the downstream exit pressure, the water temperature and the steam mass flux per hole.
The ultrasounds as a mean for the enhancement of heat exchanger performances: an analysis of the available data
Authors: Franco Alessandro , Bartoli Carlo
Published: May 2019

The aim of this paper is to investigate the potential use of ultrasounds for improving the performances of heat exchangers. In a heat exchanger, the effect of ultrasonic vibrations is important both for heat transfer intensification and for the possibility of obtaining fouling reduction: the cumulative effect can determine an interesting advantage in term of overall heat transfer coefficient increase. After a general analysis of the topic, the paper analyse the results recently obtained in the two main fields of analysis, heat transfer coefficient enhancement and fouling reduction. The perspective of the use of acoustic fields and ultrasound for optimization of heat exchangers operation is some particular fields of application are discussed.