Flow Rate and Its Relation to Velocity

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Women’s Employment and Its Relation to Children’s Health and Schooling in Developing Countries: Conceptual Links, Empirical Evidence, and Policies Peter Glick Cornell University September 2002 2 ABSTRACT This paper reviews several decades of empirical research on the effects of women’s work on investments in children’s human capital—their nutrition and schooling—in developing countries. No clear relationship between women’s work and nutrition emerges from a large body of studies examining this issue, but this is to be expected given the complexity of the relationship and the wide variation in methodological approaches. However, specific factors, such as quality of substitute care and age of the child, condition the relationship and point to areas where policy can intervene to prevent negative nutritional outcomes or enhance positive outcomes of maternal work. Less research has been done on the subject of women’s work and children’s schooling, but there is evidence that there can be negative effects on girl’s education because daughters are often obliged to substitute in the home for mothers who work. The paper considers a range of policies (including, in particular, childcare) that can reduce the potential conflicts, or increase the complementarities, between women’s need or desire to work and their children’s well-being. Also discussed are trends in developing economies and in the global economy that are affecting women’s work and its relation to children’s welfare, as well as affecting the ability of governments to intervene to ease the domestic constraints on women. 3 TABLE OF CONTENTS 1. INTRODUCTION 4 2. CONCEPTUAL FRAMEWORKS 6 3. EMPIRICAL EVIDENCE 8 3. 1 Effects of women’s employment on children’s nutrition 8 3. 2 Effects of women’s employment on children’s schooling 15 3. 3 Men’s employment and children’s welfare 19 4. PROSPECTS AND POLICIES 21 4. 1 Urbanization, changes in families, and women’s employment 23 4. 2 Implications of globalization for women’s work and children’s welfare 24 4. 3 Policies to reduce conflicts between women’s dual roles 27 Childcare services 27 Other policies 33 Globalization and constraints on policy 35 Changing gender norms 37 REFERENCES 39 4 1. INTRODUCTION Women play multiple roles in the family that affect the health and well being of all family members. In almost all societies around the world, they are assigned by custom to be the primary caregivers to infants and children (UNDP 1995). Activities carried out by women such as breastfeeding, preparing food, collecting water and fuel, and seeking preventative and curative medical care are crucial for children’s healthy development. Women also play important roles as generators of family income, whether in household farms or businesses or as wage employees. In developing countries especially, such work is likely to be essential to family survival. Because of the time constraints women face, however, their roles as care-givers and as providers of family income Flow Rate and Its Relation to Velocity Flow Rate and Its Relation to Velocity Bởi: OpenStaxCollege Flow rate Q is defined to be the volume of fluid passing by some location through an area during a period of time, as seen in [link] In symbols, this can be written as V Q= t, where V is the volume and t is the elapsed time The SI unit for flow rate is m3/s, but a number of other units for Q are in common use For example, the heart of a resting adult pumps blood at a rate of 5.00 liters per minute (L/min) Note that a liter (L) is 1/1000 of a cubic meter or 1000 cubic centimeters ( 10 − m3 or 103 cm3) In this text we shall use whatever metric units are most convenient for a given situation Flow rate is the volume of fluid per unit time flowing past a point through the area A Here the shaded cylinder of fluid flows past point P in a uniform pipe in time t The volume of the cylinder ¯ ¯ is Ad and the average velocity is v = d / t so that the flow rate is Q = Ad / t = Av Calculating Volume from Flow Rate: The Heart Pumps a Lot of Blood in a Lifetime How many cubic meters of blood does the heart pump in a 75-year lifetime, assuming the average flow rate is 5.00 L/min? Strategy 1/10 Flow Rate and Its Relation to Velocity Time and flow rate Q are given, and so the volume V can be calculated from the definition of flow rate Solution Solving Q = V / t for volume gives V = Qt Substituting known values yields V ( = 2.0 × 105 m3 5.00 L ) ( )(5.26 × 10 = (75 y) m3 10 L y ) Discussion This amount is about 200,000 tons of blood For comparison, this value is equivalent to about 200 times the volume of water contained in a 6-lane 50-m lap pool Flow rate and velocity are related, but quite different, physical quantities To make the distinction clear, think about the flow rate of a river The greater the velocity of the water, the greater the flow rate of the river But flow rate also depends on the size of the river A rapid mountain stream carries far less water than the Amazon River in Brazil, ¯ for example The precise relationship between flow rate Q and velocity v is ¯ Q = Av, ¯ where A is the cross-sectional area and v is the average velocity This equation seems logical enough The relationship tells us that flow rate is directly proportional to both the magnitude of the average velocity (hereafter referred to as the speed) and the size of a river, pipe, or other conduit The larger the conduit, the greater its cross-sectional area [link] illustrates how this relationship is obtained The shaded cylinder has a volume V = Ad, which flows past the point P in a time t Dividing both sides of this relationship by t gives V t = Ad t 2/10 Flow Rate and Its Relation to Velocity ¯ We note that Q = V / t and the average speed is v = d / t Thus the equation becomes ¯ Q = Av [link] shows an incompressible fluid flowing along a pipe of decreasing radius Because the fluid is incompressible, the same amount of fluid must flow past any point in the tube in a given time to ensure continuity of flow In this case, because the cross-sectional area of the pipe decreases, the velocity must necessarily increase This logic can be extended to say that the flow rate must be the same at all points along the pipe In particular, for points and 2, Q1 = Q2 ¯ ¯ A1 v = A2 v } This is called the equation of continuity and is valid for any incompressible fluid The consequences of the equation of continuity can be observed when water flows from a hose into a narrow spray nozzle: it emerges with a large speed—that is the purpose of the nozzle Conversely, when a river empties into one end of a reservoir, the water slows considerably, perhaps picking up speed again when it leaves the other end of the reservoir In other words, speed increases when cross-sectional area decreases, and speed decreases when cross-sectional area increases When a tube narrows, the same volume occupies a greater length For the same volume to pass points and in a given time, the speed must be greater at point The process is exactly reversible If the fluid flows in the opposite direction, its speed will decrease when the tube widens (Note that the relative volumes of the two cylinders and the corresponding velocity vector arrows are not drawn to scale.) Since liquids are essentially incompressible, the equation of continuity is valid for all liquids However, gases are compressible, and so the equation must be applied with caution to gases if they are subjected to compression or expansion Calculating Fluid Speed: Speed Increases When a Tube Narrows 3/10 Flow Rate and Its Relation to Velocity A nozzle with a radius of 0.250 cm is attached to a garden hose with a radius of 0.900 cm The flow rate through hose and nozzle is 0.500 L/s Calculate the speed of the water (a) in the hose and (b) in the nozzle Strategy We can use the relationship between flow rate and speed to find both velocities We will use the subscript for the hose and for the nozzle Solution for (a) ¯ First, we solve Q = Av for v1 ...Computational structure of generative phonology and its relation to language comprehension. Eric Sven Ristad* MIT Artificial Intelligence Lab 545 Technology Square Cambridge, MA 02139 Abstract We analyse the computational complexity of phonological models as they have developed over the past twenty years. The major results ate that generation and recognition are undecidable for segmental models, and that recognition is NP- hard for that portion of segmental phonology sub- sumed by modern autosegmental models. Formal restrictions are evaluated. 1 Introduction Generative linguistic theory and human language comprehension may both be thought of as com- putations. The goal of language comprehension is to construct structural descriptions of linguistic sensations, while the goal of generative theory is to enumerate all and only the possible (grammat- ical) structural descriptions. These computations are only indirectly related. For one, the input to the two computations is not the same. As we shall see below, the most we might say is that generative theory provides an extensional chatacterlsation of language comprehension, which is a function from surface forms to complete representations, includ- ing underlying forms. The goal of this article is to reveal exactly what generative linguistic theory says about language comprehension in the domain of phonology. The article is organized as follows. In the next section, we provide a brief overview of the com- putational structure of generative phonology. In section 3, we introduce the segmental model of phonology, discuss its computational complexity, and prove that even restricted segmental mod- els are extremely powerful (undecidable). Subse- quently, we consider various proposed and plausi- ble restrictions on the model, and conclude that even the maximally restricted segmental model is likely to be intractable. The fourth section in troduces the modern autosegmental (nonlinear) model and discusses its computational complexity. "The author is supported by a IBM graduate fellowship and eternally indebted to Morris Halle and Michael Kenstowicz for teaching him phonol- ogy. Thanks to Noam Chomsky, Sandiway Fong, and Michael Kashket for their comments and assistance. 235 We prove that the natural problem of construct- ing an autosegmental representation of an under- specified surface form is NP-hard. The article concludes by arguing that the complexity proofs are unnatural despite being true of the phonolog- ical models, because the formalism of generative phonology is itself unnatural. The central contributions of this article ate: (i) to explicate the relation between generative theory and language processing, and argue that generative theories are not models of language users primarily because they do not consider the inputs naturally available to language users; and (ii) to analyze the computational complexity of generative phonological theory, as it has developed over the past twenty years, including segmental and autosegmental models. 2 Computational structure of generative phonology The structure of a computation may be described at many levels of abstraction, principally includ- ing: (i) the goal of the computation; (ii) its in- put/output specification (the problem statement), (iii) the algorithm and representation for achiev- ing that specification, and (iv) the primitive opera- RESEARCH Research and Professional Briefs Food Label Use and Its Relation to Dietary Intake among US Adults NICHOLAS JAY OLLBERDING, PhD; RANDI L. WOLF, PhD; ISOBEL CONTENTO, PhD ABSTRACT Rates of diet-related chronic disease combined with the lack of current data on patterns of food label use by the US population warrant re-examination of the use and potential influence of this public health tool. The purpose of this study was to describe the prevalence of food label use and the association between food label use and nu- trient intake in a nationally representative sample of US adults who participated in the 2005-2006 National Health and Nutrition Examination Survey. Data on food label use were collected during the interview portion of the survey, and nutrient intake was estimated using the average of two 24-hour dietary recalls. In this sample, 61.6% of participants reported using the Nutrition Facts panel, 51.6% looked at the list of ingredients, 47.2% looked at serving size, and 43.8% reviewed health claims at least sometimes when deciding to purchase a food product. There were significant differences (PϽ0.05) in food label use across all demographic characteristics ex- amined. Significant differences (PϽ0.05) in mean nutri- ent intake of total energy, total fat, saturated fat, choles- terol, sodium, dietary fiber, and sugars were observed between food label users and non-users with label users reporting healthier nutrient consumption. The greatest differences observed were for total energy and fat and for use of specific nutrient information on the food label. Despite food label use being associated with improved dietary factors, label use alone is not expected to be sufficient in modifying behavior ultimately leading to im- proved health outcomes. J Am Diet Assoc. 2010;110:1233-1237. T he continued rise in rates of obesity and diet-related chronic disease over the past several decades has culminated in a public health crisis that warrants re-examination of approaches designed to combat these disorders. Poor dietary practices, including overconsump- tion of energy (1,2), high intakes of saturated fat and sodium (2), and low intakes of fruits, vegetables, and fiber (2-4) are contributing to diet-related chronic disease and have resulted in speculation that poor diet and physical inactivity will surpass tobacco use as the leading prevent- able cause of death among US adults (5). The 1990 Nutrition Labeling and Education Act al- lowed for the creation of a standardized food label intro- duced in May 1994 with the aim of combating obesity and diet-related chronic disease by providing consumers in- formation at the point of purchase that would assist in selecting foods in accordance with dietary recommenda- tions. Current regulations require all packaged food items regulated by the Food and Drug Administration to display on the label information on serving size, number of servings, total energy, energy from fat, total fat, satu- rated fat, cholesterol, sodium, carbohydrates, dietary fi- ber, sugar, protein, vitamin A, vitamin C, calcium, iron, and trans fat (6), with selection of these nutrients based on their role in chronic disease etiology or nutrient defi- ciency (7). The percent daily value for nutrients reflective of a 2,000-kcal/day diet and a list of ingredients must also be provided for foods with more than one A density result for random sparse oriented graphs and its relation to a conjecture of Woodall Jair Donadelli ∗ Departamento de Inform´atica Universidade Federal do Paran´a Centro Polit´ecnico, 81531–990, Curitiba PR, Brazil jair@inf.ufpr.br Yoshiharu Kohayakawa † Instituto de Matem´atica e Estat´ıstica Universidade de S˜ao Paulo RuadoMat˜ao 1010, 05508–090 S˜ao Paulo SP, Brazil yoshi@ime.usp.br Submitted: July 24, 2000; Accepted: November 16, 2002 MR Subject Classifications: 05C20, 05C38, 05C80 Abstract We prove that for all  ≥ 3andβ>0 there exists a sparse oriented graph of arbitrarily large order with oriented girth  andsuchthatany1/2+β proportion of its arcs induces an oriented cycle of length . As a corollary we get that there exist infinitely many oriented graphs with vanishing density of oriented girth  such that deleting any 1/-fraction of their edges does not destroy all their oriented cycles. The proof is probabilistic. 1 Introduction We call the pair  G =(V,E)anoriented graph if the set of vertices V is a finite set and the set of oriented edges E ⊆ V × V ,whichwecallarcs, is such that (v, v) ∈ E for any v ∈ V and if (u, v) ∈ E then (v,u) ∈ E. Our notation will basically follow [1]. The main result of this note, Theorem 1, is related to a conjecture of Woodall, which we now describe. Given an oriented graph  G =(V, E), we say that a subset B ⊆ E of E is an oriented cut in  G if there exists a subset W ⊆ V of V such that B = E(  G) ∩ (W × W ) ∗ Supported by a CNPq PhD Scholarship (Proc. 141633/1998-0). † Research supported in part by FAPESP (Proc. 96/04505-2), MCT/FINEP/CNPq through ProNEx Programme (Proc. CNPq 664107/1997–4), and by CNPq (Proc. 300334/93–1 and 468516/2000–0). the electronic journal of combinatorics 9 (2002), #R45 1 and E(  G) ∩ (W × W )=∅,whereW = V \ W. A subset F ⊆ E of E is a transversal of the family of oriented cuts of  G if F ∩ B = ∅ for all oriented cuts B in  G. In 1978, Woodall [7] conjectured that, for any oriented graph  G, a minimum oriented cut in  G has cardinality equal to the maximum cardinality of a family of pairwise disjoint transversals of oriented cuts. Woodall’s conjecture has been proved in some particular cases. Feofiloff and Younger [2], and independently Schrijver [6], proved this conjecture for source-sink connected graphs. An oriented graph is called source-sink connected if it is acyclic and each source is joined to each sink by an oriented path. Lee and Wakabayashi [5] recently proved the conjecture for series-parallel oriented graphs. To relate this conjecture to Theorem 1, we consider its dual version in the case of planar oriented graphs. By the oriented girth of  G, we mean the length of a shortest oriented cycle in  G. We call a subset D ⊆ E of the set of arcs E a transversal of the family of oriented cycles of  G if D intersects all oriented cycles of  G.Fromnowon,bya transversal in an oriented graph  G, we mean a transversal of the family of oriented cycles of  G. A dual version of Woodall’s conjecture may be stated as follows: for any planar oriented graph  G, the oriented girth of  G is equal to the maximum cardinality of a family of pairwise disjoint transversals. In other words, this version of the conjecture states that if  is the oriented girth of  G then  is the largest k ∈ for which there exists a k-colouring of E(  G), say ϕ: E(  G) → [k], such that any oriented cycle of  G meets all the k colours, that is, |ϕ(  C)| = k for all oriented cycles  C ⊆  G. We have learnt from D. Younger [8] that we cannot remove the hypothesis of planarity from the dual of Woodall’s conjecture. Indeed, Thomassen constructed a tournament T on 15 vertices with oriented girth 3 for which the smallest number of arcs we have to delete to get rid of all oriented cycles is more than one third of its arcs. Hence, the oriented girth of T is larger than the maximum cardinality of a family of pairwise disjoint transversals and, therefore, T is a Ann. For. Sci. 64 (2007) 679–690 Available online at: c  INRA, EDP Sciences, 2007 www.afs-journal.org DOI: 10.1051/forest:2007048 Original article Strength properties of thermally modified softwoods and its relation to polymeric structural wood constituents Michiel J. B a * ,JorisV  A b ,BôkeF.T c ,EdoV.K a a Plato International BV, PO Box 2159, NL-6802 CD Arnhem, The Netherlands b Laboratory of Wood Technology, Ghent University, Coupure links 653, 9000 Ghent, Belgium c SHR Hout Research, PO Box 497, 6700 AL Wageningen, The Netherlands (Received 17 October 2006; accepted 18 April 2007) Abstract – Thermal modification at relatively high temperatures (ranging from 150 to 260 ◦ C) is an effective method to improve the dimensional stability and resistance against fungal attack. This study was performed to investigate the impact of heat treatment on the mechanical properties of wood. An industrially-used two-stage heat treatment method under relative mild conditions (< 200 ◦ C) was used to treat the boards. Heat treatment revealed a clear effect on the mechanical properties of softwood species. The tensile strength parallel to the grain showed a rather large decrease, whereas the compressive strength parallel to the fibre increased after heat treatment. The bending strength, which is a combination of the tensile stress, compressive stress and shear stress, was lower after heat treatment. This decrease was less than the decrease of only the tensile strength. The impact strength showed a rather large decrease after heat treatment. An increase of the modulus of elasticity during the bending test has been noticed after heat treatment. Changes and/or modifications of the main wood components appear to be involved in the effects of heat treatment on the mechanical properties. The possible effect of degradation and modification of hemicelluloses, degradation and/or crystallization of amorphous cellulose, and polycondensation reactions of lignin on the mechanical properties of heat treated wood have been discussed. The effect of natural defects, such as knots, resin pockets, abnormal slope of grain and reaction wood, on the strength properties of wood appeared to be affected by heat treatment. Nevertheless, heat treated timber shows potential for use in constructions, but it is important to carefully consider the stresses that occur in a construction and some practical consequences when heat treated timber is used. thermal modification / mechanical properties / cellulose / hemicelluloses / lignin Résumé – Propriétés mécaniques de bois résineux modifiés par traitement thermique en r e lation avec la constitution en polymères ligneux structuraux. La modification thermique du bois à des températures relativement élevées (entre 150 et 260 ◦ C) présente une méthode efficace pour améliorer la stabilité dimensionnelle et la résistance aux attaques de champignons. Ce travail porte sur les effets du traitement thermique sur les propriétés mécaniques du bois. Les planches ont été soumises à un traitement thermique à des températures relativement modérées (< 200 ◦ C) selon un procédé industriel en deux phases. Il s’est avéré qu’un tel traitement influe nettement sur les propriétés mécaniques des bois résineux. La résistance à la traction dans la direction parallèle au fil du bois est diminuée de manière assez importante, tandis que, dans la même direction, la résistance à la compression est augmentée. La résistance au fléchissement, qui intègre la résistance aux efforts de traction, de compression et de cisaillement, était plus réduite après le traitement thermique. Cette diminution était moins importante que celle de la résistance à la traction considérée seule. La résistance aux efforts de choc a diminué de manière importante. Les tests de flexion ont permis de constater également une augmentation du module d’élasticité à la suite du traitement thermique. Des changements et/ou des modifications au niveau des principaux composants du bois ... falls when it widens to 60 m and its depth increases to an average of 40 m? 7/10 Flow Rate and Its Relation to Velocity The Huka Falls in Taupo, New Zealand, demonstrate flow rate (credit: RaviGogna,.. .Flow Rate and Its Relation to Velocity Time and flow rate Q are given, and so the volume V can be calculated from the definition of flow rate Solution Solving Q = V... ¯ The flow rate is given by Q = Av or v = Q πr2 for a cylindrical vessel Substituting the known values (converted to units of meters and seconds) gives 5/10 Flow Rate and Its Relation to Velocity