Academic literature on the topic 'Super-short forms'
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Journal articles on the topic "Super-short forms"
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Vishwasrao, S. S., and A. Jadhav. "STUDIES ON FORMULATION AND EVALUATION OF ORALLY DISINTEGRATING TABLETS USING MUSA ACUMINATA AS A NATURAL DISINTEGRANT FOR PAEDIATRIC USE." INDIAN DRUGS 53, no. 12 (December 28, 2016): 55–58. http://dx.doi.org/10.53879/id.53.12.10628.
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The aim of the present study was to optimize an orally disintegrating tablet of ibuprofen (~100mg) using Musa acuminata (dehydrated banana powder) as a natural super disintegrant. In this work, dehydrated banana powder was used as pharmaceutical excipient because of natural origin and high nutrition properties for paediatric formulation. These tablets were prepared by direct compression technique and compared with formulations made by using synthetic super disintegrants Croscarmellose sodium, micro crystalline cellulose and Cross povidone. FTIR studies of formulations have shown no interactions between drug and excipients. In vitro disintegration and in vitro dissolution profiles were shown that comparative disintegration properties of dehydrated banana powder to that of commonly used synthetic super disintegrants. Short term stability study indicated that formulations were stable for three months. It can be concluded that dehydrated banana powder can be used as natural super disintegrant effectively in paediatric dosage forms and also shows promise as a nutritional pharmaceutical excipient.
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Burke, Mary, Shobhana Chelliah, and Melissa Robinson. "Excrescent vowels in Lamkang prefix sequences." Journal of South Asian Languages and Linguistics 6, no. 2 (February 25, 2020): 185–213. http://dx.doi.org/10.1515/jsall-2019-2012.
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AbstractLamkang is a Trans-Himalayan language spoken in the Chandel District of Manipur, India by under 10,000 ethnically Naga people. Due to a complex person indexation system in Lamkang clauses, multiple prefixes with the shape C- are attached to a verb stem creating lexemes with the shape CCCCVC. To make such forms pronounceable, speakers insert super-short vowel-like segments between the C- prefixes. Combining acoustic analysis with speakers’ intuitions about syllable structure, we examine the nature of these segments, arguing that an accurate phonetic description of Lamkang vowels must include these super-short vowels, as well as long and short vowels, which are phonemically distinct. We call these super-short vowels excrescent, following the terminology discussed in Hall (2011. Vowel epenthesis. In Marc van Oostendorp, Colin J. Ewen, Elizabeth V. Hume & Keren Rice (eds.), The blackwell companion to phonology, 1576–1596. Oxford: Blackwell. doi: 10.1002/9781444335262.wbctp0067: 1584). The excrescent vowel is a type of epenthetic vowel, sometimes also called “intrusive”, and is typified by its short duration and centralized quality distinct from lexical vowels. It is unstressed and has the phonetic effect of helping to transition between consonants. We show that the excrescent vowels in Lamkang have formant structures that barely resemble the characteristic formant profiles of the short and long vowels. While excrescent vowels are not contrastive, they are phonologically relevant because they have just enough sonority to form nuclei of CiVCii syllables where Cii is often ambisyllabic with the following syllable. The Lamkang data show that while any language-specific phonotactic constraints must reference the syllable, what constitutes a syllable must include the possibility of excrescent vowels as nuclei.
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Shi, Run Ping, Cheng Yong Wang, and Xi Wang. "Preliminary Study on Carbon Fibre Composites Cutting Technology and Cutting Tools." Materials Science Forum 723 (June 2012): 25–29. http://dx.doi.org/10.4028/www.scientific.net/msf.723.25.
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Carbon fiber reinforced plastics (CFRP)/Ti super hybrid laminates are newly developed structural materials with excellent properties. But they are restricted in aircraft manufacturing because of their poor machining quality and short tool life. The machining quality and tool life are determined by machining ways, tool materials, drill point forms and drilling sequence. Spiral milling, drilling from Ti side, using the PCD tools and carbide drills with special point angle can improve the quality of hole and prolong tool life.
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Wang, Wen Yan, Jian Xu, and Jing Pei Xie. "Study of the Impact Abrasive Wear of New Super-High Manganese Steel." Key Engineering Materials 575-576 (September 2013): 550–53. http://dx.doi.org/10.4028/www.scientific.net/kem.575-576.550.
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Based on the traditional Mn13, the super-high manganese steel Mn18 was melted by means of adjusting the amount of C, Mn, adding a certain amount of alloying elements Cr, Mo etc and modification. The results show that with low-impact energy abrasive wear for 60 minutes, the wear resistance of super-high manganese steel Mn18 was greatly improved by contrast with that of Mn13, and the hardness of wear surface was increased slowly with the elapse of the wear time. However, under the high impact energy, the wear resistance of Mn18 is 1.5 times as high as that of Mn13, and the hardness of wear surface was increased to HB440 in a short time. The main wear forms were: cutting, gouging wear and plastic deformation. Typical TEM morphologies of subsurface wear structure consist mostly of high density dislocations, deformation bands.
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Hillier, Grant, Raymond Kan, and Xiaolu Wang. "GENERATING FUNCTIONS AND SHORT RECURSIONS, WITH APPLICATIONS TO THE MOMENTS OF QUADRATIC FORMS IN NONCENTRAL NORMAL VECTORS." Econometric Theory 30, no. 2 (October 17, 2013): 436–73. http://dx.doi.org/10.1017/s0266466613000364.
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Recursive relations for objects of statistical interest have long been important for computation, and they remain so even with hugely improved computing power. Such recursions are frequently derived by exploiting relations between generating functions. For example, the top-order zonal polynomials that occur in much distribution theory under normality can be recursively related to other (easily computed) symmetric functions (power-sum and elementary symmetric functions; Ruben, 1962, Annals of Mathematical Statistics 33, 542–570; Hillier, Kan, and Wang, 2009, Econometric Theory 25, 211–242). Typically, in a recursion of this type the kth object of interest, dk, say, is expressed in terms of all lower order dj’s. In Hillier et al. (2009) we pointed out that, in the case of top-order zonal polynomials and other invariant polynomials of multiple matrix argument, a fixed length recursion can be deduced. We refer to this as a short recursion. The present paper shows that the main results in Hillier et al. (2009) can be generalized and that short recursions can be obtained for a much larger class of objects/generating functions. As applications, we show that short recursions can be obtained for various problems involving quadratic forms in noncentral normal vectors, including moments, product moments, and expectations of ratios of powers of quadratic forms. For this class of problems, we also show that the length of the recursion can be further reduced by an application of a generalization of Horner’s method (cf. Brown, 1986, SIAM Journal on Scientific and Statistical Computing 7, 689–695), producing a super-short recursion that is significantly more efficient than even the short recursion.
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Hering, Benjamin, Anne-Kathrin Wolfrum, Tim Gestrich, and Mathias Herrmann. "Thermal Stability of TiN Coated Cubic Boron Nitride Powder." Materials 14, no. 7 (March 27, 2021): 1642. http://dx.doi.org/10.3390/ma14071642.
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Wear-resistant, super hard ceramic composites based on cubic boron nitride (cBN) are of great interest to industry. However, cBN is metastable under sintering conditions at normal pressure and converts into the soft hexagonal BN (hBN). Therefore, efforts are being made to avoid this process. Besides short sintering times, the use of coated cBN-particles is a way to minimize this process. Therefore, the thermal stability of TiN coated cBN powders in high purity argon and nitrogen atmospheres up to temperatures of 1600 °C was investigated by thermogravimetry, X-ray phase analysis, scanning electron microscopy and Raman spectroscopy. The TiN coating was prepared by the atomic layer deposition (ALD)-method. The investigations showed that the TiN layer reacts in Ar at T ≥ 1200 °C with the cBN and forms a porous TiB2 layer. No reaction takes place in nitrogen up to temperatures of 1600 °C. Nevertheless, the 20 and 50 nm thin coatings also undergo a recrystallization process during heat treatment up to temperatures of 1600 °C.
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Lisman, John. "Glutamatergic synapses are structurally and biochemically complex because of multiple plasticity processes: long-term potentiation, long-term depression, short-term potentiation and scaling." Philosophical Transactions of the Royal Society B: Biological Sciences 372, no. 1715 (March 5, 2017): 20160260. http://dx.doi.org/10.1098/rstb.2016.0260.
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Synapses are complex because they perform multiple functions, including at least six mechanistically different forms of plasticity. Here, I comment on recent developments regarding these processes. (i) Short-term potentiation (STP), a Hebbian process that requires small amounts of synaptic input, appears to make strong contributions to some forms of working memory. (ii) The rules for long-term potentiation (LTP) induction in CA3 have been clarified: induction does not depend obligatorily on backpropagating sodium spikes but, rather, on dendritic branch-specific N -methyl- d -aspartate (NMDA) spikes. (iii) Late LTP, a process that requires a dopamine signal (and is therefore neoHebbian), is mediated by trans-synaptic growth of the synapse, a growth that occurs about an hour after LTP induction. (iv) LTD processes are complex and include both homosynaptic and heterosynaptic forms. (v) Synaptic scaling produced by changes in activity levels are not primarily cell-autonomous, but rather depend on network activity. (vi) The evidence for distance-dependent scaling along the primary dendrite is firm, and a plausible structural-based mechanism is suggested. Ideas about the mechanisms of synaptic function need to take into consideration newly emerging data about synaptic structure. Recent super-resolution studies indicate that glutamatergic synapses are modular (module size 70–80 nm), as predicted by theoretical work. Modules are trans-synaptic structures and have high concentrations of postsynaptic density-95 (PSD-95) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor. These modules function as quasi-independent loci of AMPA-mediated transmission and may be independently modifiable, suggesting a new understanding of quantal transmission. This article is part of the themed issue ‘Integrating Hebbian and homeostatic plasticity.’
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Riandi, Riandi, and Hayati Nupus. "Kebijakan Bahasa dalam Lanskap Linguistik di Era Super-Diversity: Bahasa Asing (Bahasa Inggris) di Ruang Publik." MENDIDIK: Jurnal Kajian Pendidikan dan Pengajaran 8, no. 2 (October 1, 2022): 278–83. http://dx.doi.org/10.30653/003.202282.238.
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This conceptual paper presents a literature review of language landscape studies on the interaction of multilingualism, multiculturalism, and globalization in the reality of English learning education (ESL). Language has a great influence on human life through the forms of expression it conveys. Likewise in the social life of the wider community in general. In addition, language also plays an important role. In addition, the central government has rules and guidelines that affect local governments. The same applies to government language policies. Language policy is followed by language planning, which leads to social change. The areas of language policy include education, economics, politics, regional languages and literature, and law. All of that is inseparable from the language policies regulated by the governments of each country or region that use the language environment in the public sphere. Therefore, English cannot be used without another language, although it is subject to national and regional language policies. As a result, the use of English in public places requires the use of language equivalents in multilingual public forms, both in historical and cultural contexts, such as signage. However, because the unit of analysis in the linguistic landscape is the symbol, it provides the linguistic context of a particular region (roads, villages, buildings, countries, and environments), the linguistic landscape in this social conception, or the diversity of populations. English cannot be the only language used to represent signs. In the public sphere, taking into account the rise of bilingualism, the dominance of the national language, and a common language policy. However, the diversity of English is still growing. In short, English as used in this study of the linguistic landscape in the public sphere is a contradiction between language practice and language policy, and public understanding.
Keywords: Language Policy, Linguistic Landscape, Era of Super Diversity, Foreign Languages (English).
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Golovaneva, T. A., and N. N. Fedina. "Written Texts in Unwritten Languages as a Sociolinguistic Phenome- non (On the Material of the Chalkan and Alyutor Languages)." Critique and Semiotics 38, no. 2 (2020): 167–90. http://dx.doi.org/10.25205/2307-1737-2020-2-167-190.
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The Chalkan and Alyutor languages are not related, however their current conditions are simlar, meaning that they exist in comparable sociolin- guistic environments of uneven bi- and triligualism. The writing systems of the- se unwritten languages are still being developed, which is being further compli- cated by the influence of the writing norms of the dominant languages. The handwritten and published materials in Chalkan and Alyutor demonstrate the variety in graphic forms of national texts. The choice of graphemes for the spe- cific sounds of national speech is also a major issue. For the Alyutor writing system, the graphic representations of the super-short vowel [ә], the fricative [ɣ], the glottal stop [ʔ] and the epiglottal stop [ʕ] have not yet been developed. In the following article, we present the analysis of three versions of Alyutor writing systems developed by native Alyutor speakers M. I. Popov, M. V. Nu- tayulgin, A. A. Sorokin. The problem of graphic variety of the written form of the Chalkan languages stems from the following two reasons: the absence of graphemes for specific Chalkan sounds ғ [ɣі], җ [ʒ”], қ [q], њ [n’] and the in- fluence of the Standard Altai orthographic norms.
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Fialko, N. S., and V. D. Lakhno. "Numerical Simulation of Small Radius Polaron in a Chain with Random Perturbations." Mathematical Biology and Bioinformatics 14, no. 1 (April 10, 2019): 126–36. http://dx.doi.org/10.17537/2019.14.126.
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In a number of publications about biophysical experiments on the transfer of a charge to DNA, it is assumed that charge is transferred via a super-exchange mechanism at short distances of 2–3 nucleotide pairs, and in long fragments the charge forms a polaron that moves along the chain under the influence of temperature fluctuations. Using numerical simutation, we investigate the dynamics of a polaron of small radius in a homogeneous chain plaiced in constant electric field at a finite temperature. It is shown that there is no charge transfer by the polaron mechanism, i.e. there is no sequential movement of the polaron from site to site, in chains with parameter valuess corresponding to homogeneous adenine DNA fragments. The “polaron or delocalized state” check is based on the control of the average characteristics: the delocalization parameter, the position of the maximum probability, and the maximum modulus displacement. The dynamics of individual trajectories is also considered. Without electric field, there is a mode of switching between the states "stationary polaron – delocalized state", and a new polaron arises at a random site of the chain. In the chain placed in field with constant intensity, the averaged charge moves in the direction of the field, but the transfer occurs in a delocalized state.
Book chapters on the topic "Super-short forms"
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Hall, E. Dawn. "Growth: Ode; Then, a Year; and Travis." In ReFocus: The Films of Kelly Reichardt. Edinburgh University Press, 2018. http://dx.doi.org/10.3366/edinburgh/9781474411127.003.0004.
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This chapter discusses all three of Reichardt’s experimental short films. Each contain elements of feminist ideology highlighting a mixture of social and cultural tensions pulled from news headlines. All three short films share a haptic sensibility via form and content. Ode based on Bobbie Gentry’s song “Ode to Billie Joe” follows an adolescent boy’s struggle with his sexuality, ending in suicide, set in the rural south. Ode is a 48 minute narrative shot on Super-8 and mixes the tension between homosexuality and extreme religious ideologies. Then, A Year is a collage of images with voice-overs discussing real life news stories: the statutory rape case perpetrated by Mary Kay Letourneau and the murder of a woman by her husband. Travis is based on a National Public Radio interview with a mother struggling to understand the loss of her son during the Iraq war. This chapter connects the influence of documentary style realism in all of these early films to her later narrative features as she explores social and cultural issues.
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Targowski, Andrew. "Civilization Life Cycle." In Information Technology and Societal Development, 45–61. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-004-2.ch002.
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The purpose of this study is to define the role of civilization’s critical powers in the civilization life cycle. The role of information-communication processes is particularly crucial in this quest. The terms “rise” and “fall” of civilization reflect this chronic issue in comparative civilization studies. Spengler, in his book The Decline of the West (1918), argued that all cultures are subject to the same cycle of growth and decay in accordance with predetermined “historical destiny.” Toynbee in his Study of History (1934), compared civilizations to organisms and perceived their existence in a life cycle of four stages: genesis, growth, breakdown, and disintegration. A mechanism of “challenge-response” facing civilizations influences their abilities at self-determination and self-direction. However, according to him, all civilizations that grow eventually reach a peak, from which they begin to decline. It seems that Toynbee’s civilization life cycle is too short, since his “breakdown of growth” phase is in fact a point in time and the “disintegration” phase is too pessimistic in its title, only perceiving the “universal state,” often under a form of “empire,” as an ancient regime which only wants to maintain the status quo and is doomed to fail. But history shows that some civilizations may last a long time in relatively good shape without being in imminent danger of disintegration. Sorokin argued in Social and Cultural Dynamics (1937) that three cultural mentalities, ideational (spiritual needs and goals), sensate (“wine, women, and song”), and idealistic (a balance of needs and ends) are the central organizing principles of a civilization’s life cycle, and that they succeed each other always in the same order according to super-rhythms of history. According to Sorokin, Western civilization has for the last 500 years been in the sensate stage, reaching now its limit, and will soon pass to the next idealistic stage (which, according to this author, could be the universal civilization).
Conference papers on the topic "Super-short forms"
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Janssen, D. D., J. M. Dixon, S. J. Young, and F. A. Kulacki. "Flow Boiling in a Short Narrow Gap Channel." In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17437.
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Heat transfer coefficients in sub-cooled flow boiling in symmetrically heated narrow gap channels are reported at power densities of 1 kW/cm3 and greater. A pair of parallel ceramic resistance heaters in a nearly adiabatic housing forms the flow passage with length-to-gap ratios of 16:1 and 34:1. Water, Novec™ 7200 and 7300 are used as the heat transfer fluids at a mass flux of 100 to 1000 kg/m2s. Reynolds numbers range from ∼200 to ∼5600, Weber numbers range from ∼0.75 to ∼173, and boiling numbers from O(10−4) to O(10−2). Flow regimes span single-phase convection to nucleate flow boiling depending on mass flux and inlet sub-cooling, and exit quality can reach 40% in some cases. Results include overall two-phase heat transfer coefficients, wall temperature, exit quality and coefficient of performance. The initiation of flow boiling demonstrates that mean heater temperatures can be maintained below 95 °C over a wide range of power density and up to and exceeding 1 kW/cm3. A super position principle is suggested as an analytical framework to estimate exit quality and heat transfer coefficients. Highly favorable coefficients of performance across the data set indicate that the pumping power penalty within the heated zone is very small. Thus convective boiling in which the mechanism is nucleate boiling appears to hold the greatest potential to increase heat transfer coefficients, especially in small scale, inter-chip cooling strategies.
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Wills, Kendall Scott, Omar Diaz de Leon, Kartik Ramanujachar, and Charles P. Todd. "Super-Conducting Quantum Interference Device Technique: 3-D Localization of a Short within a Flip Chip Assembly." In ISTFA 2001. ASM International, 2001. http://dx.doi.org/10.31399/asm.cp.istfa2001p0069.
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Abstract In the current generations of devices the die and its package are closely integrated to achieve desired performance and form factor. As a result, localization of continuity failures to either the die or the package is a challenging step in failure analysis of such devices. Time Domain Reflectometry [1] (TDR) is used to localize continuity failures. However the accuracy of measurement with TDR is inadequate for effective localization of the failsite. Additionally, this technique does not provide direct 3-Dimenstional information about the location of the defect. Super-conducting Quantum Interference Device (SQUID) Microscope is useful in localizing shorts in packages [2]. SQUID microscope can localize defects to within 5um in the X and Y directions and 35um in the Z direction. This accuracy is valuable in precise localization of the failsite within the die, package or the interfacial region in flipchip assemblies.
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Cao, Jianming, Timothy Dimond, and Paul Allaire. "Numerical Analysis of Flexible Rotor With Nonlinear Bearings and Squeeze Film Dampers." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37365.
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This paper presents dynamic behaviors of a flexible rotor supported on nonlinear bearings and nonlinear squeeze film dampers. The nonlinear bearing and damper forces, which depend on instantaneous nodal displacements and velocities, are calculated at each time step through closed form solutions of Reynolds equation. Such combinations of fluid film bearings and squeeze film dampers are often used in industrial machines such as compressors and steam turbines to increase system damping. No previous works have studied the nonlinear time transient analysis of a fluid film bearing and damper combination. To describe the coupled motion of shaft, bearing and squeeze film damper, a method of assembling both the linear rotor and the nonlinear components is developed. The numerical transient analyses are applied to a 3-disk rotor supported with nonlinear short plain journal bearings and nonlinear short squeeze film dampers. Squeeze film dampers, introduced to the system, increase dynamic stability of the system under a wide range of system rotational speeds, and decrease the bearing forces under severe unbalance forces. Different nonlinear rotor dynamic behavior, such as sub-harmonic, super-harmonic and torus orbits are shown in transient analyses. This type of analysis can be employed to study whether a centering spring is required in the damper or not.
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Islam, Nazrul, and Suhail Ahmad. "Random Wave Response of Double Pendulum Articulated Off-Shore Tower." In ASME 2003 22nd International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2003. http://dx.doi.org/10.1115/omae2003-37296.
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Present study investigates the non-linear dynamic behavior of Double Hinged Articulated Tower (DHAT) under long crested random Sea and directional random sea. The non-linearities due to time wise variation of submergence, buoyancy, added mass, instantaneous tower orientation and resulting hydrodynamic loading have been taken into account for modeling the forcing functions of equation of motion which is derived by Largrangian approach. A long crested random sea has been modeled by Monte-Carlo Simulation using P-M spectrum. The non-linear equations of motion are solved by an iterative time integration scheme using Newmark’s β integration scheme. Various important parameters such as heel angles, deck displacements, base share for double hinged articulated tower under long and short crested random sea are compared and presented in the form of time-histories and their respective PSDFs. Statistical studies of random time histories have been carried out and important characteristics like mean, maxima, minima, standard deviations etc. have been analyzed. The dynamic behaviors have been investigated in detail in terms of various parametric combinations. Effect of current, and significant wave height are also studied. Sub and super harmonic excitations are highlighted through power spectra. A multi-hinged articulated tower is found to be economical and suitable for various offshore activities in adverse environmental and deep sea conditions.
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Munro, Chris, Jonathan Rodriguez, Terry Thain, Sabatino Di Mario, Danilo Iglesias, and Steven Dornic. "Enhancing Well Integrity and Well Completion Flexibility with a Remotely Operated Multi-Cycle RFID Sub-Surface Isolation Valve." In ADIPEC. SPE, 2022. http://dx.doi.org/10.2118/211565-ms.
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Abstract Sub-surface isolation valves that form part of the well barrier envelope are required to have the most stringent qualification standards whilst also facilitating flexibility and functionality to complete the well safely and efficiently. By incorporating RFID technology into a hydraulically operated downhole ball valve, oil and gas wells can now be completed using remote electronic communication methods to actuate the barrier valve throughout the completion and well test phase. The mechanical closure of the isolation valve, which is qualified to API 19v V1 CC classification, after any reservoir treatment can present significant well integrity problems should issues arise. To address this, an RFID microchip was to be incorporated into the work string as a contingency close trigger mechanism, should the shifting tool fail. Surface applied pressure cycles were sent to the isolation valve commanding it to re-open to allow well flow-back. Post well testing, an additional RFID microchip was deployed to the isolation valve to re-close it and form part of the well barrier envelope for P&A operations. The well was completed and successfully tested by installing a set of completion equipment across the reservoir section. After the completion was installed the isolation valve was closed with a shifting tool isolating the reservoir section which allowed a safe well environment for running the upper completion. Having the electronic contingency option available significantly increases built-in contingency whilst reducing overall risk. With the reservoir isolated the upper completion was installed, pressure cycles were sent from surface to remotely trigger the valve to open. The short and specific sequence means that it is easily applied but hard to inadvertently trigger, therefore improving overall well completion flexibility and efficiency. The micro-hydraulic power technology on-board operates independently of hydrostatic pressure, ensuring that the valve opens regardless of the setting depth. Once the well flow-back was successfully completed the valve was electronically closed by deploying an RFID microchip into the well for the final time, finalizing the P&A barrier envelope. In conclusion, the combination of RFID on-demand multi-cycle technology with stringent sub-surface isolation valve qualification standards is now providing the industry with the integrity, flexibility, and reliability that it has long sought after, which adds up to a more robust and efficient well performance. Shifting tools with built-in electronic triggers, advanced barrier valve qualification testing and high-performance sub-surface isolation valves are critical to well performance and safety within the oil and gas industry. This paper will focus on how these aspects were delivered to a super-major client to enable them to complete their well safely and efficiently.
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Cipolla, Leonardo, Augusto Di Gianfrancesco, Dario Venditti, Giuseppe Cumino, and Stefano Caminada. "Microstructural Evolution During Long Term Creep Tests of 9%Cr Steel Grades." In ASME 2007 Pressure Vessels and Piping Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/creep2007-26030.
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In the last two decades the service pressure and temperature of components for advanced power plants increased significantly and more severe requirements on strength, corrosion resistance and creep properties were imposed on high temperature steels. To comply with these requirements, several new 9–12%Cr martensitic steels were developed and some of them, such as ASTM Grades 91, 911 and 92 are currently used in new high efficiency Ultra Super Critical power plants. The initial evaluation of their creep strength above 550°C was defined with relatively short term tests, but the long experience in service and long term creep laboratory tests showed that the original estimation of creep strength values were not reliable and a reduction of the creep resistance occurred at long service time. Short creep tests (elaborated with time-temperature-parameter methods, i.e. Larson Miller equation) usually give an over-estimation of the long-term creep properties of 9%Cr steels. The results of the creep assessments of Grade 92 (Japanese NF616) are an example of the significant lowering of the creep properties: the creep resistance of this grade was initially evaluated in 600°C/160MPa/105h by means extrapolation of short creep tests, within 103 hours; recently the creep strength was reduced down to 113MPa (ECCC assessment, 2005). Moreover some premature failures of Japanese Grade PI 22 took place and similar problems appeared on other 12%Cr steels. The lowering of creep strength in 9–12%Cr steels at long times is a consequence of the evolution of their microstructure during high temperature service. The causes of this phenomenon in Grades 91, 911 and 92 are examined in this article, paying special attention to the metallurgical explanation. The most evident changes in the microstructure of 9%Cr steels occur with the nucleation of Laves-phase as well as the nucleation of Z-phase at longer times. The precipitation of Laves phase has two relevant aspects by the creep strength point of view. On one hand, high amounts of Mo and W contents are incorporated in this phase, causing a depletion of these elements from the solid solution and thus a reduction of their contribution to the overall creep resistance. On the other hand, the increased volume fraction of secondary phases leads to a higher precipitation strengthening during the first precipitation phase: at the beginning, the precipitation of fine Laves phase increases the creep resistance; however if the coarsening rate is not taken under control, the mean diameter of these particles reaches micrometric dimensions with a detrimental effect on creep behaviour within 103 hours in the range 600°C–650°C. The high coarsening rate of Laves phase is therefore the major cause of the lowering of creep properties of Grades 91, 911 and 92. Coarsening of Laves phase particles over a critical size triggers the cavity formation and the consequent brittle intergranular fracture. Transition from ductile fracture to brittle intergranular fracture often occurs in long-term creep at the onset of coarsening of Laves particles, which result to be the preferential site for cavities nucleation in the 9%Cr steels. Z-phase was recognized in 9%Cr steels after long term exposure, but in far smaller amount than on 12%Cr steels: no dramatic drop in volume fraction of MX was observed in association to the nucleation of this phase, therefore it is believed that the modified Z-phase does not affect significantly the long term creep properties of Grades 91, 911 and 92. The dimple pattern is typical of ductile fracture, which occurs for short service period (hence highest stress). At low stresses, cavities are formed at the triple grain junctions at which Laves particles are often found, causing wedge crack, otherwise isolated cavities can form independently at coarse Laves phase particles (Figure 13). The latter type is often observed after long-term creep in the interganular fracture region. In both cases, brittle fracture occurs at the onset of coarsening of Laves particles, which result to be the preferential site for cavities nucleation in the 9%Cr steels.
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Wang, Haibin, Nikoletta Trivyza, Evangelos Boulougouris, and Foivos Mylonopoulos. "Comparison of Decarbonisation Solutions for Shipping: Hydrogen, Ammonia and Batteries." In SNAME 14th International Marine Design Conference. SNAME, 2022. http://dx.doi.org/10.5957/imdc-2022-297.
Full textAbstract:
Recent regulations are targeting the carbon footprint of ships and the International Maritime Organisation (IMO) has set a target to reduce the GHG emissions by 50% until 2050, compared to the 2008 levels. Therefore, attention has been placed on the variety of available fuels and technologies that can be potential pathways for decarbonisation and special focus has been given to developing practical design options for the new generation ships. Shipping applications of batteries, hydrogen and ammonia powered fuel cells have a critical role to meet the IMO requirements by 2050. Hydrogen and batteries are emerging technologies that can be effective solutions, especially for short shipping routes. On the other hand, ammonia is also an attractive alternative option and with further development, it can potentially be utilised for ocean-going vessels. However, safety and risk assessments must be performed to support the endorsement of any new marine system design. Therefore, this work aims to guide safe and practical design solutions that can comply with the decarbonising regulatory framework. Therefore, a qualitative Hazard Identification (HAZID) approach was conducted for potential solutions with hydrogen, battery and ammonia and guidance for potential safe designs were proposed. Considering the lack of past accident statistics due to the novelty of applications, the HAZID results were discussed with experts. Hydrogen is usually stored in liquefied form in double-walled super-insulated tanks to reduce the risk of large accumulations of gas in the air, in case of potential leakage, which can induce fire (4-75% gas concentrations in the air) or explosion risks (18-59% gas concentrations in the air). Fuel cells, which produce the electricity required, should be placed within gastight enclosures in a well-ventilated space with redundant hydrogen or ammonia detection systems. Batteries use stored energy to produce electric energy, however, their use is associated with high fire risk. They are placed in battery holds/compartments in which fire doors and effective firefighting systems are mandatory to prevent the escalation of fire in adjacent places and reduce the fire duration respectively. Leakage in the fuel cell room due to pipe damage and fire in the battery room was considered the most severe hazards for hydrogen and battery version respectively. On the other hand, ammonia is considered as a low reactive gas and explosion should be a concern of only enclosed spaces at concentrations close to the stoichiometry. However, ammonia is a highly toxic gas and in high concentration, it can even be even fatal. Therefore, one of the main hazards for ammonia is the ammonia leakage from different parts of the system that can lead to injuries or fatalities to the crew due to the high toxicity of ammonia. This can be prevented with various measures, among which are sufficient ventilation and identification of hazardous zones. Overall, all the designs seem feasible in terms of safety provided that proper safety measures are considered. Redundancy of equipment and proper arrangement of safety valves, ventilation and detection systems as well as firefighting protection are amongst the most effective risk control options to mitigate the hazards.