Academic literature on the topic 'Loose Cycle'

A subsetCof edges in ak-uniform hypergraphHis aloose Hamilton cycleifCcovers all the vertices ofHand there exists a cyclic ordering of these vertices such that the edges inCare segments of that order and such that every two consecutive edges share exactly one vertex. The binomial randomk-uniform hypergraphHkn,phas vertex set [n] and an edge setEobtained by adding eachk-tuplee∈ ($\binom{[n]}{k}$) toEwith probabilityp, independently at random.Here we consider the problem of finding edge-disjoint loose Hamilton cycles covering all buto(|E|) edges, referred to as thepacking problem. While it is known that the threshold probability of the appearance of a loose Hamilton cycle inHkn,pis$p=\Theta\biggl(\frac{\log n}{n^{k-1}}\biggr),$the best known bounds for the packing problem are aroundp= polylog(n)/n. Here we make substantial progress and prove the following asymptotically (up to a polylog(n) factor) best possible result: forp≥ logCn/nk−1, a randomk-uniform hypergraphHkn,pwith high probability contains$N:=(1-o(1))\frac{\binom{n}{k}p}{n/(k-1)}$edge-disjoint loose Hamilton cycles.Our proof utilizes and modifies the idea of ‘online sprinkling’ recently introduced by Vu and the first author.

We establish a relation between two uniform models of randomk-graphs (for constantk⩾ 3) onnlabelled vertices: ℍ(k)(n,m), the randomk-graph with exactlymedges, and ℍ(k)(n,d), the randomd-regulark-graph. By extending the switching technique of McKay and Wormald tok-graphs, we show that, for some range ofd = d(n)and a constantc> 0, ifm~cnd, then one can couple ℍ(k)(n,m)and ℍ(k)(n,d)so that the latter contains the former with probability tending to one asn→ ∞. In view of known results on the existence of a loose Hamilton cycle in ℍ(k)(n,m), we conclude that ℍ(k)(n,d)contains a loose Hamilton cycle whend≫ logn(or justd⩾Clogn, ifk= 3) andd=o(n1/2).

The purpose of this study is to describe the process and learning outcomes through STEAM based on loose parts that can improve the creativity of working children aged 5-6 years in group B Kindergarten Juara Bekasi City in 2019. The subjects of this study were 12 children. The research method used in this study is Classroom Action Research by Kemmis and Mc. Taggart which includes four stages, namely planning, action, observation, and reflection. This study consisted of 2 cycles, each cycle consisting of 4 meetings. The data analysis technique used in this study is qualitative and quantitative data analysis. Qualitative data analysis by analyzing data from observations, documentations, and interviews. Quantitative data analysis uses descriptive statistical analysis that compares results obtained from pre-intervention, first cycle and second cycle. The results of this study indicate an increase in early childhood creativity through STEAM learning based on loose parts, it can be proved completeness of pre-intervention creativity by 31%. Then it increased in the first cycle by 56,50% and the second cycle by 83,70%. It was concluded that to improve the creativity of working children aged 5-6 years, teachers can use STEAM learning based on loose parts. Abstrak Tujuan penelitian ini untuk mendeskripsikan proses dan hasil pembelajaran Jarak Jauh berbasis STEAM dengan Media loose parts yang dapat meningkatkan kreativitas berkarya anak usia 5-6 tahun kelompok B TK Juara Bekasi Tahun 2020. Subjek penelitian ini berjumlah 12 anak. Metode penelitian yang digunakan dalam penelitian ini adalah Penelitian Tindakan Kelas model Kemmis dan Mc. Taggart yang meliputi empat tahap yaitu perencanaan, tindakan, pengamatan, dan refleksi. Penelitian ini terdiri dari 2 siklus, masing-masing siklus terdiri dari 4 kali pertemuan. Teknik analisis data yang digunakan dalam penelitian ini adalah analisis data kualitatif dan kuantitatif. Analisis data kualitatif dengan cara menganalisis data dari hasil observasi, dokumentasi, dan wawancara selama penelitian. Analisis data kuantitatif menggunakan analisis statistik deskriptif yaitu membandingkan hasil yang diperoleh dari pra-siklus, siklus pertama dan siklus kedua. Hasil penelitian ini menunjukkan adanya peningkatan kreativitas berkarya anak usia5-6 tahun melalui pembelajaran berbasis STEAM dengan media loose parts, dapat dibuktikan ketuntasan kreativitas pra-intervensi sebesar 31%. Kemudian mengalami peningkatan pada siklus I sebesar 56,50% dan siklus II sebesar 83,70%. Disimpulkan bahwa untuk meningkatkan kreativitas berkarya anak usia 5-6 tahun, guru dapat menggunakan pembelajaran Jarak Jauh berbasis STEAM dengan media loose parts. Kata Kunci: Kreativitas, STEAM, Loose Parts

It is known that the 3-uniform loose 3-cycle decomposes the complete 3-uniform hypergraph of order \(v\) if and only if \(v \equiv 0, 1,\text{ or }2 (\operatorname{mod} 9)\). For all positive integers \(\lambda\) and \(v\), we find a maximum packing with loose 3-cycles of the \(\lambda\)-fold complete 3-uniform hypergraph of order \(v\). We show that, if \(v \geq 6\), such a packing has a leave of two or fewer edges.

In living cells, molecular motors convert chemical energy into mechanical work. Its thermodynamic energy efficiency, i.e. the ratio of output mechanical work to input chemical energy, is usually high. However, using two-state models, we found the motion of molecular motors is loosely coupled to the chemical cycle. Only part of the input energy can be converted into mechanical work. Others are dissipated into environment during substeps without contributions to the unidirectional movement.

While the production costs and logistical benefits of biomass pelleting have been widely discussed in the literature, the downstream economic and environmental benefits of processing pelleted biomass have been largely neglected. To investigate those benefits, we performed a comparative techno-economic analysis and life cycle assessment of producing ethanol using loose and pelleted forms of biomass. Analyses of a 2000 metric tons (dry)/d biorefinery showed that using pelleted biomass is more economical than using loose or baled biomass. The lowest minimum ethanol selling price (MESP) for pelleted biomass was USD 0.58/gal less than the lowest MESP for loose biomass. Among all processing conditions analyzed, MESP for ethanol produced with pelleted biomass was always lower than when produced with loose biomass. Shorter pretreatment and hydrolysis times, higher pretreatment solids loadings, lower ammonia requirements, and reduced enzyme loadings were the primary factors contributing to lower MESP with pelleted biomass. Similarly, pelleted biomass also demonstrated a 50% lower life cycle greenhouse gas emission compared to loose biomass. Emissions from higher pelleting energy were offset by downstream advantage in lower chemical needs.

The asymptotics of 2-colour Ramsey numbers of loose and tight cycles in 3-uniform hypergraphs were recently determined [16, 17]. We address the same problem for Berge cycles and for 3 colours. Our main result is that the 3-colour Ramsey number of a 3-uniform Berge cycle of length n is asymptotic to $\frac{5n}{4}$. The result is proved with the Regularity Lemma via the existence of a monochromatic connected matching covering asymptotically 4n/5 vertices in the multicoloured 2-shadow graph induced by the colouring of Kn(3).

Cette étude a pour objectifs la caractérisation expérimentale des frottements saccadés dans les matériaux granulaires modèles constitués des billes de verre monodisperses en compression triaxiale drainée et l'identification des paramètres de contrôle. Cinq paramètres macroscopiques caractérisent ces frottements saccadés : la chute de déviateur et la contraction volumique, l'intermittence de déformation axiale, le module d'Young et le coefficient de Poisson. Les frottements saccadés affectent simultanément le déviateur et la déformation volumique. Le comportement macroscopique est globalement contractant tandis que le matériau tend vers un état limite critique en grandes déformations, à la manière des sables lâches. Cependant il présente localement, dans les phases de blocage qui suivent immédiatement les ruptures temporaires, le comportement dilatant des sables denses, qui obéit à une relation contrainte-dilatance linéaire et unique. Les frottements saccadés disparaissent au-delà d'une vitesse critique d'écrasement axial, qui dépend de la contrainte de confinement et de la taille des grains. Le module d'Young dynamique par propagation d'ondes varie avec la contrainte de confinement selon une loi de puissance. Le module d'Young quasi-élastique au départ des phases de blocage est constant à l'intérieur du domaine élastique, de même que le coefficient de Poisson. Le suivi par granulométrie laser et par analyse d'images des matériaux après un ou plusieurs essais triaxiaux permet de suivre l'évolution de la taille moyenne et de la forme des grains. Tandis que les instabilités par saccade disparaissent suite à un certain nombre d'essais, on observe, simultanément à une légère diminution du volume moyen, l'apparition progressive de populations d'objets non sphériques par une fusion des grains analogue au frittage.

abstract: Extremal graph theory results often provide minimum degree conditions which guarantee a copy of one graph exists within another. A perfect $F$-tiling of a graph $G$ is a collection $\mathcal{F}$ of subgraphs of $G$ such that every element of $\mathcal{F}$ is isomorphic to $F$ and such that every vertex in $G$ is in exactly one element of $\mathcal{F}$. Let $C^{3}_{t}$ denote the loose cycle on $t = 2s$ vertices, the $3$-uniform hypergraph obtained by replacing the edges $e = \{u, v\}$ of a graph cycle $C$ on $s$ vertices with edge triples $\{u, x_e, v\}$, where $x_e$ is uniquely assigned to $e$. This dissertation proves for even $t \geq 6$, that any sufficiently large $3$-uniform hypergraph $H$ on $n \in t \mathbb{Z}$ vertices with minimum $1$-degree $\delta^1(H) \geq {n - 1 \choose 2} - {\Bsize \choose 2} + c(t,n) + 1$, where $c(t,n) \in \{0, 1, 3\}$, contains a perfect $C^{3}_{t}$-tiling. The result is tight, generalizing previous results on $C^3_4$ by Han and Zhao. For an edge colored graph $G$, let the minimum color degree $\delta^c(G)$ be the minimum number of distinctly colored edges incident to a vertex. Call $G$ rainbow if every edge has a unique color. For $\ell \geq 5$, this dissertation proves that any sufficiently large edge colored graph $G$ on $n$ vertices with $\delta^c(G) \geq \frac{n + 1}{2}$ contains a rainbow cycle on $\ell$ vertices. The result is tight for odd $\ell$ and extends previous results for $\ell = 3$. In addition, for even $\ell \geq 4$, this dissertation proves that any sufficiently large edge colored graph $G$ on $n$ vertices with $\delta^c(G) \geq \frac{n + c(\ell)}{3}$, where $c(\ell) \in \{5, 7\}$, contains a rainbow cycle on $\ell$ vertices. The result is tight when $6 \nmid \ell$. As a related result, this dissertation proves for all $\ell \geq 4$, that any sufficiently large oriented graph $D$ on $n$ vertices with $\delta^+(D) \geq \frac{n + 1}{3}$ contains a directed cycle on $\ell$ vertices. This partially generalizes a result by Kelly, K\"uhn, and Osthus that uses minimum semidegree rather than minimum out degree.
Dissertation/Thesis
Doctoral Dissertation Mathematics 2019

‘Shakespeare’s Loose Ends and the Contemporary Poet’ contains detailed readings of individual poems with a Shakespearean theme by John Ashbery (‘Friar Laurence’s Cell’), Elizabeth Bishop (‘Twelfth Morning; or What You Will’), Roy Fisher (‘Barnardine’s Reply’), alongside passages from Geoffrey Hill’s ‘Funeral Music’ and The Triumph of Love, as well as observations about a number of other Shakespeare-inspired poems. It deploys them to sustain and illustrate an argument that contrasts with the noted attempts by earlier modernist poets such as Yeats, Eliot, Auden, and Ted Hughes to incorporate theories of Shakespeare’s organic creative unity into their oeuvres. Rather, this chapter proposes that it is the heterogeneity, the loose ends and frayed edges of the Shakespearean corpus that have inspired contemporary poets, prompting them to come at their own materials by means of the oblique angles provided by minor characters, such as Barnardine in Measure for Measure or the poet Cinna in Julius Ceasar, and less highly regarded plays, such as the early Henry VI cycle, finding thematic suggestions in implications that remain to be spelt-out in Shakespearean scenes, dialogues, and plot trajectories.

‘It was the time when the rush for spoils filled a corner of the forest with the yelping of hounds, the cracking of whips, the flaring of torches. The appetites let loose were satisfied at last, shamelessly, amid the sound of crumbling neighbourhoods and fortunes made in six months. The city had become an orgy of gold and women.’ The Kill (La Curée) is the second volume in Zola's great cycle of twenty novels, Les Rougon-Macquart, and the first to establish Paris – the capital of modernity - as the centre of Zola's narrative world. Conceived as a representation of the uncontrollable ‘appetites’ unleashed by the Second Empire (1852–70) and the transformation of the city by Baron Haussmann, the novel combines into a single, powerful vision the twin themes of lust for money and lust for pleasure. The all-pervading promiscuity of the new Paris is reflected in the dissolute and frenetic lives of an unscrupulous property speculator, Saccard, his neurotic wife Renée, and her dandified lover, Saccard's son Maxime.

The study tries to analyze the morphological and hydrological changes and to establish their relationship in the Sandwip Island through the integration of Remote Sensing (RS) and Geographic Information Systems (GIS). The study concludes from the recent 30 years' data that the different parts of the island response different cycle of coastline change associated with hydrological dynamics. The resulted net loss of the coastline is about 6.98 km (0.23 km/y) and the net loss of the coastal area is about 23.99 km2 (0.8 km2/y). The erosion processes (increase in the water depth near shore) were active along the western and the south-western shores. This erosion of the island is facilitated by the steep slope of the bank, high tidal water pressure and loose bank materials. In contrast, the accretions (decrease in the water depth near shore) were taken place in the larger parts of the northern and the north-eastern shores of the island. This is due to the backwash sediment deposition with the favor of gentle topographic slope along shores.

The study tries to analyze the morphological and hydrological changes and to establish their relationship in the Sandwip Island through the integration of Remote Sensing (RS) and Geographic Information Systems (GIS). The study concludes from the recent 30 years' data that the different parts of the island response different cycle of coastline change associated with hydrological dynamics. The resulted net loss of the coastline is about 6.98 km (0.23 km/y) and the net loss of the coastal area is about 23.99 km2 (0.8 km2/y). The erosion processes (increase in the water depth near shore) were active along the western and the south-western shores. This erosion of the island is facilitated by the steep slope of the bank, high tidal water pressure and loose bank materials. In contrast, the accretions (decrease in the water depth near shore) were taken place in the larger parts of the northern and the north-eastern shores of the island. This is due to the backwash sediment deposition with the favor of gentle topographic slope along shores.

Pediculosis pubis gives an overview of the aetiology, epidemiology and transmission, clinical features, diagnosis, and finally, management of infestations with the pubic louse, Pthirus pubis. The life cycle of this tiny human parasite, which has been found in fossilized form dating back 10,000 years, is explained. The classical clinical features and diagnostic tips are given together with up to date management advice. The use of malathion and permethrin as mainstays of treatment are explained. There is also a specific section for the management of pediculosis ciliaris (infestation of the eyelashes by the pubic louse) a rare, but recognized clinical presentation.

The widespread practices of viniculture (the study of production of grapes for wine) and oenology (the study of winemaking) affirm the generalization that grapevines have fewer problems with mineral deficiency than many other crops. Only occasionally is the addition of iron (Fe), phosphorus (P), magnesium (Mg), and manganese (Mn) supplements to the soil needed. Addition of potassium (K), zinc (Zn), and boron (B) to the soil is more common. And, of course, nitrogen (N) is critical for the production of proteins. Over the years, various transition metals (metals in groups three through twelve [3– 12] of the periodic table, Appendix 1) have been shown to be generally important. These groups include iron (Fe), magnesium (Mg), manganese (Mn), zinc (Zn), and copper (Cu). Many metals are bound to organic molecules that are important for life. Some of the metals, such as copper (Cu) and iron (Fe), are important in electron transport while others, including manganese (Mn) and iron (Fe), inhibit reactive oxygen (O) species (ROSs) that can destroy cells. Metals serve both to cause some reactions to speed up, called positive catalysis while caus¬ing others (e.g., unwanted oxidation) to slow down (negative catalysis). It is not uncommon to add nitrogen (N), in the form of ammonium salts such as ammonium nitrate (NH4NO3), as fertilizer to the soil in which the vines are growing. It is also common to increase the nitrogen (N) content in the soil by planting legumes (legumes have roots that are frequently colonized by nitrogen-fixing bacteria). Nitrogen- fixing bacteria convert atmospheric nitrogen (N2), which plants cannot use, to forms, such as ammonia (NH3) or its equivalent, capable of absorption by plants. Nitrogen, used in plant proteins, tends to remain in the soil after harvest or decomposition. With sufficient nitrogen present in the soil the growth cycle can begin again in the following season without adding too much fertilizer. In a more general sense, however, it is clear (as mentioned earlier) that the soil must be capable of good drainage so the sub-soil parts of the plant do not rot and it must be loose enough to permit oxygen to be available to the growing roots.

Gas turbine combined cycles (GTCC) using a steam bottoming cycle are a widely used technology for electric power generation. From [1] it is known that the best current large GTCC’s loose around 25% of the fuel exergy just by combusting the fuel while all other exergy losses sum up to around 15%. For the net efficiency of such plants 60% is remaining. This paper shows thermodynamic calculation results of GTCC’s with variable pressure ratio and turbine inlet temperature (TIT) aimed at understanding the efficiency potential associated with further increases of the TIT thus reducing the exergy loss by combustion. The assumptions of these calculations correspond to published industrial experience and standard assumptions in two different scenarios. The results are curves showing net efficiency and specific power as functions of TIT. Other data like the related pressure ratio and compressor exit temperature are shown too. The conclusion shows that a net efficiency of 63…65% is feasible with a hot gas temperature of around 1750°C based on the two scenarios. The winning cycle arrangement uses an adiabatic compressor. A GTCC with GT-compressor having one intercooling stage is clearly less favorable in several respects.

Manual transmission gear rattle is the result of repetitive impacts of gear meshing teeth within their backlash. This NVH phenomenon is a major industrial concern and can occur under various loaded or unloaded conditions. It fundamentally differs from other transient NVH phenomena, such as clonk or thud, which are due to impulsive actions. However, they all have their lowest common denominator in the action of contact/impact forces through lubricated contacts. Various forms of rattle have, therefore, been defined: idle rattle, drive rattle, creep rattle and over-run rattle. This paper presents a dynamic transmission model for creep rattle conditions (engaged gear at low engine RPM). The model takes into account the lubricated impact force between a gear teeth pair during a meshing cycle as well as the friction between their flanks. Hertzian contact conditions are applied to the gear pair along the torque path. Additionally, isoviscous hydrodynamic regime of lubrication is assumed for unselected (loose gear pairs) with lightly loaded impact conditions. The highly non-linear impacts induce a range of system response frequencies. These include engine order harmonics, harmonics of meshing frequency and natural frequencies related to contact stiffness. The last of these are dependent on the contact geometry and lubricant rheology. The analysis includes lubricant viscosity variation due to generated contact pressures as well as temperature. For loose gears, subject to oscillations on their retaining bearings, bearing friction is also considered.

A last stage (L-0) turbine blades failure was experienced in a 110 MW geothermal unit after one year of operation period. This unit has two tandem-compound intermediate/low-pressure turbines (turbine A and turbine B) with 23-inch/3600 rpm last-stage blades. There were flexible blades continuously coupled 360 degrees around the row by loose cover segment at the tip and loose sleeve and lug at the mid-span (pre-twist design). The failed blades were in the L-0 row of the LP turbine B connected to the generator. The visual examination indicated that the group of 12 L-0 blades of rotor B on the generator side was bent and another group of 5 blades at 140 degrees from the first damaged group was also bent. The cover segments were spread out from the damaged blades and had cracks. Laboratory evaluation of the cracking in the cover segments indicates the failure mechanism to be high cycle fatigue (HCF), initiating at the cover segment holes outer fillet radius. The L-0 blades failure investigation was carried out. The investigation included a metallographic analysis of the cracked cover segments and bent blades, Finite Element Method (FEM) stress and natural frequency analysis (of blades/cover segments), fracture mechanics and crack propagation analysis. This paper provides an overview of the L-0 blades failure investigation, which led to the identification of the blades vibrations within the range 250 Hz to 588 Hz induced due to unstable flow excitation (stall flutter) as the primary contribution to the observed failure.

To face challenges associated with reduced shipbuilding budgets and the need for increased material availability, the Machine Readable Material Transaction was proposed, accepted and is currently in development at Ingalls Shipbuilding. Machine Readable Material Transaction is the processes and tools required to provide a machine readable identification (i.e. license plate) and scanning capability for tracking and identifying individual items, containers of material, and loose materials at various locations and workflows throughout the shipyard. The effort facilitates: * reduced cycle time of material transactions by moving from paper driven processes to electronic driven processes * increased accuracy by minimizing the manual entry of material transaction data by utilizing scanning technology and bar-coding * reduced re-buys by locating lost, damaged or cannibalized material * retention of material identification and history during consumption by capturing: * “what” is the material * “when” was it received or last moved * “where” was its last known location * “why” was it moved, and * “who” was the last person to touch it The purpose of the effort is to ensure visibility, traceability, and accountability for material (purchased and fabricated) from receipt through delivery to the end user. This paper discusses the use of these processes and tools to support U.S. Navy ship construction modernization and cost reduction goals at Ingalls Shipbuilding.

Steam dryers in Boiling Water Reactors (BWRs), located in the upper steam dome of the reactor pressure vessel, are not pressure retaining components and are not designed and constructed to American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Section III safety class. Although the steam dryers in BWRs perform no safety function, they must maintain the structural integrity in order to avoid the generation of loose parts that may adversely impact the capability of other plant equipment to perform their safety functions. The majority of licensees of many operating nuclear plants are applying for extended power uprate (EPU), which increases the thermal power output up to 20% above the original licensed thermal power (OLTP). Nuclear power plant components such as steam dryers can be subjected to strong fluctuating loads and can experience unexpected high cycle fatigue due to adverse flow effects while operating at EPU conditions. However, there are some unique challenges for operation of dryers at EPU conditions requiring special considerations to prevent fatigue damage from the effects of flow induced vibration (FIV). This paper examines the FIV considerations and margin recommendations for fatigue stresses due to many uncertainties in the prediction of the fluctuating pressure loading acting on the steam dryer and the structural analysis of the steam dryer, very limited bench marking of the methods, and operating experience with some dryer failures.

Steam dryers in Boiling Water Reactors, located in the upper steam dome of the reactor pressure vessel, are not pressure retaining components and are not designed and constructed to the provisions of Section III of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code. As such, these components do not correspond to any specific safety class referenced in the Code. Although the steam dryers in BWRs perform no safety function, they must maintain the structural integrity in order to avoid the generation of loose parts that may adversely impact the capability of other plant equipment to perform their safety functions. Therefore guidance from Section III of the ASME Code is utilized in the design and fabrication of replacement dryers as well as for design modifications of the existing dryers for extended power uprates. The majority of licensees of operating nuclear plants are applying for EPU, which generally increases the thermal power output to 20% above the original licensed thermal power. Nuclear power plant components such as steam dryers can be subjected to strong fluctuating loads and can experience unexpected high cycle fatigue due to adverse flow effects while operating at EPU conditions. However, there are some unique challenges related to steam dryer operation at EPU conditions requiring special considerations to prevent fatigue damage from the effects of flow induced vibration. This paper examines the issues and lessons learned related to FIV considerations during EPU reviews of BWR steam dryers.

ASME code explicitly addresses design for fatigue due to pressure or temperature cycles. Protection against fatigue failure due to cyclic external mechanical loads (e.g. piping loads) is not tackled in depth. This paper provides a less-tedious yet fit-for-purpose approach to evaluate the effect of cyclic external mechanical loads as well as the pressure fluctuations — as a result of piping slug flow — on nozzles fatigue life. The evaluation compares between two types of nozzles construction (configuration); separate reinforcement nozzle and readily radiographed (lip type) integrally reinforced nozzle. Within the analysis, a unity fatigue damage ratio or exceeding the ratcheting allowable limits was selected as the indication for the inadequacy of the reinforcement configuration. COMPRESS® FEA software results comprehensively predict that the separate reinforcement nozzles can’t withstand the imposed cyclic loads since the accumulated fatigue damage are greater than 1 (one) implying that the nozzle will experience fatigue failure before the end of its life time. COMPRESS® FEA results were examined at four locations, namely “shell next to nozzle”, “nozzle next to shell”, “nozzle thickness transition” and “shell away from nozzle”. The maximum stress of the four locations was always at “shell next to nozzle”. These results have been verified against SOLIDWORKS® simulation FEA results. The results show that the separate reinforcement nozzle construction, although adequate for static loadings, has less fatigue life compared to the integral reinforcement nozzle construction. Moreover, progressive distortion of the non-integral (separate) reinforcement connection is predicted showing that the mating members may become loose at the end of each complete operating cycle which could eventually cause disengagement. Additionally, the results support ASME 2004, VIII-2 para. 5-112 recommendations in prohibiting fillet welds in joints of category D for components subject to fatigue service. The paper concludes the advantage of integral reinforced readily radiographed nozzle construction in protection against fatigue failure and ratcheting and also provides a roadmap for simplified fatigue analysis using commercially available software.

The differences of flow field in bowed blade cascade and that in straight blade cascade are systematically studied in this paper. To bow a blade means to change its geometric boundary condition. This change not only affect the pressure distribution along the blade profile exit Mach number but also has great effect on the original position and development of the passage vertex. All of the changes mentioned above have great influence on the loss. Numerical simulation result showed that blade bowing can decrease the cross-pressure gradient near the end wall. This trend will be more obvious with the increase of the bow angle. The pressure gradient decrease is beneficial to weaken the passage vortex strength and reduces the secondary loss near the endwalls. In addition, Pressure gradient from endwalls to midspan can be established near suction surface in positively bowed blade. With the increase of bow angle, this C-type pressure distribution is remarkable. It is also found that this C-type pressure distribution will influence the position of corner vortex near the suction surface and will also influence the position and size of the passage vortex. Blade bowing also has great influence on the position of the saddle point near the leading edge and the separated line of the horseshoe vortex. It is found that the position of the saddle point and the separated line of both legs of the horseshoe vortex move forward in a positively bowed blade. The passage vortex structure in bowed cascade is also presented. It can be concluded that a bowed blade can make the passage vortex stable and helps change its structure from loose to compact. Blade bowing is also beneficial to limit the influence domain of the unstable passage vortex core by the stable limit cycle.

Buried pipelines can be locally buckled (wrinkled) by a load combination of axial deformations and rotations. Previous test results show that those wrinkled pipes do not lose their safety and integrity if they possess sufficient ductility. However, if those wrinkled pipes are going to continue operating under the condition of cyclic loading, their low cycle fatigue (LCF) behaviours have to be thoroughly investigated. This paper presents LCF tests for two full-scale pipes and the relevant results. Those two pipes were tested under a complicated loading procedure. The entire loading consisted of two stages: the monotonic loading stage and the cyclic loading stage. The monotonic loading was designed to form an enclosed wrinkle around the pipe under a locked curvature, and the cyclic loading was planned to fracture the wrinkled pipe. Firstly, the loading procedure was demonstrated by viewing the spectra of MTS load, MTS stroke, jack load, internal pressure, as well as pipe end average rotation. Secondly, the global behaviour was investigated by examining the relation between bending moment and global curvature, the relation between pivot axial load and relative axial deformation (RAD) between pivots, and the relation between internal pressure and RAD between pivots. Thirdly, the phenomenon of ‘deformation localization’ was studied by investigating the relation between the global RAD and the local RAD, and it was found that the global deformation was totally localized into the wrinkle area. Fourthly, the failure modes were discussed and it was found that the seam weld was more liable to be fractured under the condition of cyclic axial deformation. At last, the failure mechanism was investigated by macroscopically examining fracture surfaces. It found out that the cracks initiated from multi-locations on surfaces, then those cracks propagated from surfaces into the interior and finally fractured the pipe wall. Moreover, it found out that more damage was generated from the inside surface than from the outside surface.

Abstract Double network (DN) elastomers are a class of reinforced gels that benefit from a significantly high stretch-ability and toughness. However, DN gels lose their toughness due to the accumulation of damage under cyclic loading during their lifetime. While recent advances in the process and characterization of the DN gels have led to significant improvements in their properties, our understandings of the accumulated damage mechanisms within the material remain sparse and inconclusive. Here, a physically motivated constitutive model is presented for DN gels subjected to a high number of cyclic deformations, which will eventually approach a steady-state after thousands of cycles. The model can be particularly used to elucidate the inelastic features, such as permanent damage during deformation of each cycle. The observed damage may be induced from the chain scission, chain slippage, or polymer relaxation. Therefore, irreversible chain detachment and decomposition of the first network due to its highly cross-linked structure are explored as the underlying reasons for the nonlinear stress softening phenomenon. The model is validated against the experimental tests. The model contains a few numbers of material constants and shows good agreement with cyclic uni-axial tensile test data.

1.1 Macroeconomic summary Economic recovery has consistently outperformed the technical staff’s expectations following a steep decline in activity in the second quarter of 2020. At the same time, total and core inflation rates have fallen and remain at low levels, suggesting that a significant element of the reactivation of Colombia’s economy has been related to recovery in potential GDP. This would support the technical staff’s diagnosis of weak aggregate demand and ample excess capacity. The most recently available data on 2020 growth suggests a contraction in economic activity of 6.8%, lower than estimates from January’s Monetary Policy Report (-7.2%). High-frequency indicators suggest that economic performance was significantly more dynamic than expected in January, despite mobility restrictions and quarantine measures. This has also come amid declines in total and core inflation, the latter of which was below January projections if controlling for certain relative price changes. This suggests that the unexpected strength of recent growth contains elements of demand, and that excess capacity, while significant, could be lower than previously estimated. Nevertheless, uncertainty over the measurement of excess capacity continues to be unusually high and marked both by variations in the way different economic sectors and spending components have been affected by the pandemic, and by uneven price behavior. The size of excess capacity, and in particular the evolution of the pandemic in forthcoming quarters, constitute substantial risks to the macroeconomic forecast presented in this report. Despite the unexpected strength of the recovery, the technical staff continues to project ample excess capacity that is expected to remain on the forecast horizon, alongside core inflation that will likely remain below the target. Domestic demand remains below 2019 levels amid unusually significant uncertainty over the size of excess capacity in the economy. High national unemployment (14.6% for February 2021) reflects a loose labor market, while observed total and core inflation continue to be below 2%. Inflationary pressures from the exchange rate are expected to continue to be low, with relatively little pass-through on inflation. This would be compatible with a negative output gap. Excess productive capacity and the expectation of core inflation below the 3% target on the forecast horizon provide a basis for an expansive monetary policy posture. The technical staff’s assessment of certain shocks and their expected effects on the economy, as well as the presence of several sources of uncertainty and related assumptions about their potential macroeconomic impacts, remain a feature of this report. The coronavirus pandemic, in particular, continues to affect the public health environment, and the reopening of Colombia’s economy remains incomplete. The technical staff’s assessment is that the COVID-19 shock has affected both aggregate demand and supply, but that the impact on demand has been deeper and more persistent. Given this persistence, the central forecast accounts for a gradual tightening of the output gap in the absence of new waves of contagion, and as vaccination campaigns progress. The central forecast continues to include an expected increase of total and core inflation rates in the second quarter of 2021, alongside the lapse of the temporary price relief measures put in place in 2020. Additional COVID-19 outbreaks (of uncertain duration and intensity) represent a significant risk factor that could affect these projections. Additionally, the forecast continues to include an upward trend in sovereign risk premiums, reflected by higher levels of public debt that in the wake of the pandemic are likely to persist on the forecast horizon, even in the context of a fiscal adjustment. At the same time, the projection accounts for the shortterm effects on private domestic demand from a fiscal adjustment along the lines of the one currently being proposed by the national government. This would be compatible with a gradual recovery of private domestic demand in 2022. The size and characteristics of the fiscal adjustment that is ultimately implemented, as well as the corresponding market response, represent another source of forecast uncertainty. Newly available information offers evidence of the potential for significant changes to the macroeconomic scenario, though without altering the general diagnosis described above. The most recent data on inflation, growth, fiscal policy, and international financial conditions suggests a more dynamic economy than previously expected. However, a third wave of the pandemic has delayed the re-opening of Colombia’s economy and brought with it a deceleration in economic activity. Detailed descriptions of these considerations and subsequent changes to the macroeconomic forecast are presented below. The expected annual decline in GDP (-0.3%) in the first quarter of 2021 appears to have been less pronounced than projected in January (-4.8%). Partial closures in January to address a second wave of COVID-19 appear to have had a less significant negative impact on the economy than previously estimated. This is reflected in figures related to mobility, energy demand, industry and retail sales, foreign trade, commercial transactions from selected banks, and the national statistics agency’s (DANE) economic tracking indicator (ISE). Output is now expected to have declined annually in the first quarter by 0.3%. Private consumption likely continued to recover, registering levels somewhat above those from the previous year, while public consumption likely increased significantly. While a recovery in investment in both housing and in other buildings and structures is expected, overall investment levels in this case likely continued to be low, and gross fixed capital formation is expected to continue to show significant annual declines. Imports likely recovered to again outpace exports, though both are expected to register significant annual declines. Economic activity that outpaced projections, an increase in oil prices and other export products, and an expected increase in public spending this year account for the upward revision to the 2021 growth forecast (from 4.6% with a range between 2% and 6% in January, to 6.0% with a range between 3% and 7% in April). As a result, the output gap is expected to be smaller and to tighten more rapidly than projected in the previous report, though it is still expected to remain in negative territory on the forecast horizon. Wide forecast intervals reflect the fact that the future evolution of the COVID-19 pandemic remains a significant source of uncertainty on these projections. The delay in the recovery of economic activity as a result of the resurgence of COVID-19 in the first quarter appears to have been less significant than projected in the January report. The central forecast scenario expects this improved performance to continue in 2021 alongside increased consumer and business confidence. Low real interest rates and an active credit supply would also support this dynamic, and the overall conditions would be expected to spur a recovery in consumption and investment. Increased growth in public spending and public works based on the national government’s spending plan (Plan Financiero del Gobierno) are other factors to consider. Additionally, an expected recovery in global demand and higher projected prices for oil and coffee would further contribute to improved external revenues and would favor investment, in particular in the oil sector. Given the above, the technical staff’s 2021 growth forecast has been revised upward from 4.6% in January (range from 2% to 6%) to 6.0% in April (range from 3% to 7%). These projections account for the potential for the third wave of COVID-19 to have a larger and more persistent effect on the economy than the previous wave, while also supposing that there will not be any additional significant waves of the pandemic and that mobility restrictions will be relaxed as a result. Economic growth in 2022 is expected to be 3%, with a range between 1% and 5%. This figure would be lower than projected in the January report (3.6% with a range between 2% and 6%), due to a higher base of comparison given the upward revision to expected GDP in 2021. This forecast also takes into account the likely effects on private demand of a fiscal adjustment of the size currently being proposed by the national government, and which would come into effect in 2022. Excess in productive capacity is now expected to be lower than estimated in January but continues to be significant and affected by high levels of uncertainty, as reflected in the wide forecast intervals. The possibility of new waves of the virus (of uncertain intensity and duration) represents a significant downward risk to projected GDP growth, and is signaled by the lower limits of the ranges provided in this report. Inflation (1.51%) and inflation excluding food and regulated items (0.94%) declined in March compared to December, continuing below the 3% target. The decline in inflation in this period was below projections, explained in large part by unanticipated increases in the costs of certain foods (3.92%) and regulated items (1.52%). An increase in international food and shipping prices, increased foreign demand for beef, and specific upward pressures on perishable food supplies appear to explain a lower-than-expected deceleration in the consumer price index (CPI) for foods. An unexpected increase in regulated items prices came amid unanticipated increases in international fuel prices, on some utilities rates, and for regulated education prices. The decline in annual inflation excluding food and regulated items between December and March was in line with projections from January, though this included downward pressure from a significant reduction in telecommunications rates due to the imminent entry of a new operator. When controlling for the effects of this relative price change, inflation excluding food and regulated items exceeds levels forecast in the previous report. Within this indicator of core inflation, the CPI for goods (1.05%) accelerated due to a reversion of the effects of the VAT-free day in November, which was largely accounted for in February, and possibly by the transmission of a recent depreciation of the peso on domestic prices for certain items (electric and household appliances). For their part, services prices decelerated and showed the lowest rate of annual growth (0.89%) among the large consumer baskets in the CPI. Within the services basket, the annual change in rental prices continued to decline, while those services that continue to experience the most significant restrictions on returning to normal operations (tourism, cinemas, nightlife, etc.) continued to register significant price declines. As previously mentioned, telephone rates also fell significantly due to increased competition in the market. Total inflation is expected to continue to be affected by ample excesses in productive capacity for the remainder of 2021 and 2022, though less so than projected in January. As a result, convergence to the inflation target is now expected to be somewhat faster than estimated in the previous report, assuming the absence of significant additional outbreaks of COVID-19. The technical staff’s year-end inflation projections for 2021 and 2022 have increased, suggesting figures around 3% due largely to variation in food and regulated items prices. The projection for inflation excluding food and regulated items also increased, but remains below 3%. Price relief measures on indirect taxes implemented in 2020 are expected to lapse in the second quarter of 2021, generating a one-off effect on prices and temporarily affecting inflation excluding food and regulated items. However, indexation to low levels of past inflation, weak demand, and ample excess productive capacity are expected to keep core inflation below the target, near 2.3% at the end of 2021 (previously 2.1%). The reversion in 2021 of the effects of some price relief measures on utility rates from 2020 should lead to an increase in the CPI for regulated items in the second half of this year. Annual price changes are now expected to be higher than estimated in the January report due to an increased expected path for fuel prices and unanticipated increases in regulated education prices. The projection for the CPI for foods has increased compared to the previous report, taking into account certain factors that were not anticipated in January (a less favorable agricultural cycle, increased pressure from international prices, and transport costs). Given the above, year-end annual inflation for 2021 and 2022 is now expected to be 3% and 2.8%, respectively, which would be above projections from January (2.3% and 2,7%). For its part, expected inflation based on analyst surveys suggests year-end inflation in 2021 and 2022 of 2.8% and 3.1%, respectively. There remains significant uncertainty surrounding the inflation forecasts included in this report due to several factors: 1) the evolution of the pandemic; 2) the difficulty in evaluating the size and persistence of excess productive capacity; 3) the timing and manner in which price relief measures will lapse; and 4) the future behavior of food prices. Projected 2021 growth in foreign demand (4.4% to 5.2%) and the supposed average oil price (USD 53 to USD 61 per Brent benchmark barrel) were both revised upward. An increase in long-term international interest rates has been reflected in a depreciation of the peso and could result in relatively tighter external financial conditions for emerging market economies, including Colombia. Average growth among Colombia’s trade partners was greater than expected in the fourth quarter of 2020. This, together with a sizable fiscal stimulus approved in the United States and the onset of a massive global vaccination campaign, largely explains the projected increase in foreign demand growth in 2021. The resilience of the goods market in the face of global crisis and an expected normalization in international trade are additional factors. These considerations and the expected continuation of a gradual reduction of mobility restrictions abroad suggest that Colombia’s trade partners could grow on average by 5.2% in 2021 and around 3.4% in 2022. The improved prospects for global economic growth have led to an increase in current and expected oil prices. Production interruptions due to a heavy winter, reduced inventories, and increased supply restrictions instituted by producing countries have also contributed to the increase. Meanwhile, market forecasts and recent Federal Reserve pronouncements suggest that the benchmark interest rate in the U.S. will remain stable for the next two years. Nevertheless, a significant increase in public spending in the country has fostered expectations for greater growth and inflation, as well as increased uncertainty over the moment in which a normalization of monetary policy might begin. This has been reflected in an increase in long-term interest rates. In this context, emerging market economies in the region, including Colombia, have registered increases in sovereign risk premiums and long-term domestic interest rates, and a depreciation of local currencies against the dollar. Recent outbreaks of COVID-19 in several of these economies; limits on vaccine supply and the slow pace of immunization campaigns in some countries; a significant increase in public debt; and tensions between the United States and China, among other factors, all add to a high level of uncertainty surrounding interest rate spreads, external financing conditions, and the future performance of risk premiums. The impact that this environment could have on the exchange rate and on domestic financing conditions represent risks to the macroeconomic and monetary policy forecasts. Domestic financial conditions continue to favor recovery in economic activity. The transmission of reductions to the policy interest rate on credit rates has been significant. The banking portfolio continues to recover amid circumstances that have affected both the supply and demand for loans, and in which some credit risks have materialized. Preferential and ordinary commercial interest rates have fallen to a similar degree as the benchmark interest rate. As is generally the case, this transmission has come at a slower pace for consumer credit rates, and has been further delayed in the case of mortgage rates. Commercial credit levels stabilized above pre-pandemic levels in March, following an increase resulting from significant liquidity requirements for businesses in the second quarter of 2020. The consumer credit portfolio continued to recover and has now surpassed February 2020 levels, though overall growth in the portfolio remains low. At the same time, portfolio projections and default indicators have increased, and credit establishment earnings have come down. Despite this, credit disbursements continue to recover and solvency indicators remain well above regulatory minimums. 1.2 Monetary policy decision In its meetings in March and April the BDBR left the benchmark interest rate unchanged at 1.75%.