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	Longitudinal wave - Wikipedia, the free encyclopedia
		Longitudinal waves, also referred to as compressional waves or pressure waves, are waves that have vibrations along or parallel to their direction of travel.
		Examples of non-electromagnetic longitudinal waves include sound waves (alternation in pressure, particle displacement, or particle velocity propagated in an elastic material) and seismic P-waves (created by earthquakes and explosions).
		Maxwell's equations lead to the prediction of electromagnetic waves in a vacuum, which are transverse (in that the electric fields and magnetic fields vary perpendicularly to the direction of propagation).
	en.wikipedia.org /wiki/Longitudinal_wave (537 words)

	Sound is a Longitudinal Wave (Site not responding. Last check: 2007-11-06)
		Longitudinal waves are waves in which the motion of the individual particles of the medium is in a direction which is parallel to the direction of energy transport.
		Sound waves are longitudinal waves because particles of the medium through which the sound is transported vibrate parallel to the direction which the sound moves.
		And the essential characteristic of a longitudinal wave which distinguishes it from other types of waves is that the particles of the medium move in a direction parallel to the direction of energy transport.
	www.glenbrook.k12.il.us /gbssci/phys/Class/sound/u11l1b.html (490 words)

	Warren Savary's Home Page
		Longitudinally oriented larvae (Figures 3, 4) are borne in a single layer, are aligned parallel to the longitudinal axis of the mother, face anteriorly, and typically have their prosomas directed downward and their metasomas curled so that the aculeus points towards their mother's dorsum (see also Stahnke 1944, Williams 1969).
		This association is corroborated by at least one morphological synapomorphy: in those taxa which exhibit longitudinal orientation of the larvae, the lamellar hooks of the spermatophore are elevated along, and adnate to, the lamella.
		One of the characteristics of the longitudinal pattern of orientation is the presence of a single layer of larvae, which contrasts with the multiple layers found in the other known orientation patterns.
	pw1.netcom.com /~wsavary/larvae.html (1759 words)

	The Physics Classroom
		Longitudinal waves are always characterized by particle motion being parallel to wave motion.
		While waves which travel within the depths of the ocean are longitudinal waves, the waves which travel along the surface of the oceans are referred to as surface waves.
		In longitudinal and transverse waves, all the particles in the entire bulk of the medium move in a parallel and a perpendicular direction (respectively) relative to the direction of energy transport.
	www.physicsclassroom.com /Class/waves/u10l1c.html (1558 words)

	Courses
		A longitudinal study is defined as a study in which the response for each experimental unit in the study is observed on two or more occasions.
		Because several types of data may be regarded as longitudinal, methods for the analysis of social change may also vary substantially: from time-series techniques for repeated cross-section data to logistic and log-linear models; from structural equation models to longitudinal multilevel methods; from regression analysis to event history analysis (Davies and Dale 1994).
		Longitudinal data are collected in a time sequence that clarifies the direction as well as the magnitude of change among variables.
	www.stat.ufl.edu /~ssaha/LDAworkshop/Courses.htm (3766 words)

	Acoustoelastic Phenomena of Wood
		The first objective of this study is to investigate experimentally the changes in the velocities of ultrasonic waves propagating transverse to the direction of applied stress in wood, and the second objective is to estimate the bending stress distribution by the acoustoelastic method.
		Their dimensions were 6 cm (longitudinal) by 3 cm (tangential) by 2 cm (radial) for compressive loading, and 29 cm (longitudinal) by 5 cm (tangential) by 1.5 cm (radial) for tensile loading specimen.
		The signs of the constants in longitudinal waves for compressive stress, shown in table 1, seemed to depend on the species and the structural directions of wood, suggesting a relationship between the acoustoelastic phenomena and the anatomical structure of wood.
	www.ndt.net /article/v04n11/sasaki/sasaki.htm (3245 words)

	Indicators of Child, Family and Community Connections: Longitudinal Indicators of the Social Context of Families: ...
		A longitudinal indicator is a measure of a family or individual behavior, interaction, attitude, or value that is measured consistently or comparably across multiple points in time and cumulated to provide a portrait over time of an important aspect of family life.
		The key to a longitudinal indicator is not the way in which the data are collected; the data for such an indicator can be collected either retrospectively from a single survey or by combining data from longitudinal surveys across waves.
		Our discussion of potential longitudinal indicators for each of the social contexts of families that we have considered for this project indicates that many cross-sectional indicators have a corresponding longitudinal indicator that provides a useful perspective on the stability or duration of that indicator across families.
	aspe.hhs.gov /HSP/connections-papers04/paper3.htm (8609 words)

	Nat' Academies Press, Leveraging Longitudinal Data in Developing Countries: Report of a Workshop (2002)
		Longitudinal community studies, also known as population laboratories or demographic surveillance studies, systematically collect data (generally on fertility, mortality, and in- and out-migration) from all individuals (at least all individuals of interest in all households) in geographically demarcated communities.
		To maximize the time devoted to comparing longitudinal approaches, workshop participants did not address topics related to cross-sectional data, including a comparison of longitudinal and cross-sectional approaches, and to techniques such as synthetic cohort analysis and retrospective data, which can be used with cross-sectional data to simulate longitudinal data.
		As discussed in previous sections, longitudinal community studies often work with massive amounts of data that are continually collected, and they have goals and relationships with communities that differ greatly from those associated with other longitudinal studies thus data collectors involved with those studies face multiple demands.
	www.nap.edu /books/0309084504/html/1.html (5280 words)

	NLS Overview
		In 1979, a longitudinal study of a cohort of young men and women aged 14 to 22 was begun.
		In 1986, the NLSY79 was expanded to include surveys of the children born to women in that cohort and called the NLSY79 Children and Young Adults.
		This new cohort is the National Longitudinal Survey of Youth 1997 (NLSY97).
	www.bls.gov /nls/nlsview.htm (350 words)

	Encyclopedia: Longitudinal redundancy check (Site not responding. Last check: 2007-11-06)
		In telecommunication, a longitudinal redundancy check (LRC) or horizontal redundancy check is a form of redundancy check based on the formation of a block check following preset rules.
		A combination of longitudinal and vertical redundancy check allows the detection and correction of single bit errors.
		A longitudinal redundancy check character, which is used to verify that data has been received without error, may be computed from any sequence of characters by the following algorithm:
	www.nationmaster.com /encyclopedia/Longitudinal-redundancy-check (217 words)

	An Overview on Regression Models for Discrete Longitudinal Responses, Brajendra C. Sutradhar
		In the longitudinal regression setup, interest may be focused primarily on the regression parameters for the marginal expectations of the longitudinal responses, the longitudinal correlation parameters being of secondary interest.
		In one approach, true longitudinal correlations are modeled and the regression and the true correlation parameters are jointly estimated based on a GEE approach.
		In the first new approach, the true longitudinal correlations are estimated by the method of moments, whereas the regression estimates are obtained based on a generalized quasi-likelihood (GQL) estimation approach.
	projecteuclid.org /Dienst/UI/1.0/Summarize/euclid.ss/1076102426 (436 words)

	Thematic Keynote Highlights - Advances in Longitudinal Research Methodology (Site not responding. Last check: 2007-11-06)
		The recognition that longitudinal data were needed to understand development was not necessarily followed immediately by a full recognition of how cross-sectional and longitudinal data were related, and what kind of information could or could not be inferred from one to the other.
		But longitudinal studies are also fraught with methodological problems, the most serious of which have been described by Campbell and Stanley [9] as threats to internal validity common to all quasi-experiments, that is studies that do not allow completely random assignment to levels of the independent variable.
		Although longitudinal studies are generally conceptualised as a sequence of data gathered on the same individuals over a long period of time, it is also possible to conceptualise the reconstruction of events occurring over a person's life by means of autobiographical data as a form of longitudinal inquiry.
	www.cas.flinders.edu.au /iag/proceedings/proc0028.htm (4688 words)

	[No title]
		The longitudinal layer of the muscularis can be separated into two different categories: a longitudinal layer that is common with the esophagus and ends in the corpus, and a longitudinal layer that originates in the corpus and spreads into the duodenum.
		Structure of Gastric Muscularis: A -- the longitudinal layer (the area where the longitudinal fibers split is marked with a fl circle); B - the circular layer; C - the oblique layer.
		The area in the corpus around the greater curvature, where the split of the longitudinal layers takes place, is considered to be anatomically correlated with the origin of gastric electrical activity (11).
	www.ee.ualberta.ca /~mintchev/stomach.html (387 words)

	Longitudinal Data Analysis in the Social Sciences
		Longitudinal data are important for many social science disciplines as such data facilitates the investigation of empirical research questions relating to social change and social stability.
		At the current time there is a shortage of social scientists with skills appropriate for longitudinal data analysis.
		In the UK there is an increasing number of large-scale longitudinal datasets, and currently most remain under-analysed.
	www.longitudinal.stir.ac.uk (352 words)

	Longitudinal Study
		The ONS Longitudinal Study (LS) contains linked census and vital event data for one per cent of the population of England and Wales.
		All about the Longitudinal Study: What is it, what does it contain, what are its strengths and weaknesses, and how to access the information.
		Why the Longitudinal Study was set up, how the sample is drawn, and how the data are linked.
	www.statistics.gov.uk /about/data/methodology/specific/population/LS (138 words)

	Railway Track and Structures: Development of guidelines for longitudinal forces in bridges
		In Chapter 15 of the 1968 AREA manual, a factor L/1200 (where L is the length of the bridge in feet) was introduced to be applied to the 15 percent of the Cooper train load with an exception for bridges with non-continuous rail (as with movable spans, expansion joints, or switches).
		The longitudinal force due to braking was reinstated as 15 percent of the Cooper train load.
		The longitudinal force due to traction was reinstated as 25 percent of the Cooper locomotive load, except that all locomotive axles were to be used, not just driving axles.
	www.findarticles.com /p/articles/mi_m0BFW/is_2_97/ai_71963392 (1433 words)

	Transverse and Longitudinal Waves (Site not responding. Last check: 2007-11-06)
		In longitudinal waves the displacement of the medium is parallel to the propagation of the wave.
		The air motion which accompanies the passage of the sound wave will be back and forth in the direction of the propagation of the sound, a characteristic of longitudinal waves.
		Physics professor Clint Sprott of the University of Wisconsin shows one way to visualize these longitudinal pressure waves in his "Wonders of Physics" demonstration show.
	hyperphysics.phy-astr.gsu.edu /hbase/sound/tralon.html (282 words)

	Gifted-Longitudinal Studies FAQ
		Longitudinal studies represent one of the best ways to determine educational practice because they view children and adults over an extended period of time.
		This longitudinal case study investigated issues that influence successful talent development in the arts and examined the effects of long-term artistic involvement on the lives of 23 artistically talented young people (ages 10-26) in New York City, all of whom had participated in a dance or music program in their elementary years.
		Longitudinal, retrospective, and cross-sectional data on the relationship between giftedness in childhood and adulthood indicate that children who became eminent adults did not necessarily fit conceptions of giftedness driving current school programs.
	www.hoagiesgifted.org /eric/faq/gt-long.html (1803 words)

	Social Research Update 28: Longitudinal Research in the Social Sciences
		Longitudinal surveys usually combine both extensive and intensive approaches (Davies and Dale 1994).
		Thus, longitudinal analysis presupposes the development of a methodological mix where neither of the two aspects alone is sufficient to produce an accurate picture of social dynamics (Mingione 1999).
		Longitudinal Research: a Bridge between Quantitative and Qualitative Social Research?’, in Ruspini, E. (Ed.) ‘Longitudinal Analysis: A Bridge between Quantitative and Qualitative Social Research’, Special Issue of Quality and Quantity, vol.
	www.soc.surrey.ac.uk /sru/SRU28.html (2634 words)

	SPD - Longitudinal File Information
		These three weights are referred to as the traditional longitudinal panel weight, the 1999 quasi‑longitudinal panel weight, and the 2000 quasi‑longitudinal panel weight.
		To provide a means for estimating the annual or calendar characteristics of young children based on the data on the SPD second longitudinal file, the characteristics of the non‑original sample children born after Wave 1 of the SIPP Panels 1992 and 1993 must be also taken into account.
		Thus, we refer to these three SPD longitudinal annual weights as the traditional longitudinal annual weight, the 1999 quasi‑longitudinal annual weight, and the 2000 quasi‑longitudinal annual weight which are derived from the tradition longitudinal panel final weight, the 1999 quasi‑longitudinal panel final weight, and the 2000 quasi‑longitudinal panel final weight, respectively.
	www.bls.census.gov /spd/long/fileinfo_2ndl.htm (3669 words)

	Committee on Population - Workshop on Leveraging Longitudinal Data in Developing Countries (Site not responding. Last check: 2007-11-06)
		Longitudinal data collection and analysis remain critical tools for social, demographic, and health research as well as policy and practice.
		Thus, most presenters have been asked to prepare short papers, which will be distributed to participants in advance of the workshop, and to make short (5-10 minute) presentations highlighting the main points of their papers to stimulate discussion around the session issues.
		Two sessions have slightly longer and more formal papers: the session on the comparative advantages and disadvantages of longitudinal community studies, panel studies, and cohort studies and the session on ethics in longitudinal demographic and health research in developing countries.
	www7.nationalacademies.org /cpop/Longitudinal_data_developing_countries.html (833 words)

	Longitudinal and Transverse Wave Motion (Site not responding. Last check: 2007-11-06)
		Mechanical Waves are waves which propagate through a material medium (solid, liquid, or gas) at a wave speed which depends on the elastic and inertial properties of that medium.
		In a longitudinal wave the particle displacement is parallel to the direction of wave propagation.
		Water waves are an example of waves that involve a combination of both longitudinal and transverse motions.
	www.gmi.edu /~drussell/Demos/waves/wavemotion.html (528 words)

	Amazon.com: Books: Linear Mixed Models for Longitudinal Data (Site not responding. Last check: 2007-11-06)
		Longitudinal data are important in biostatistics and particularly in the analysis of clinical trials.
		There are effective methods for handling longitudinal data using linear models with covariance structures that represent the time dependence of the repeated observations.
		There are many subtle issues in the analysis and many who analyze longitudinal data apply incorrect linear models and are often not aware of the consequences of their decisions.
	www.amazon.com /exec/obidos/tg/detail/-/0387950273?v=glance (1024 words)

	Social Dimensions of Health Institute - Research
		Scotland is singularly disadvantaged relative to England in the poverty of its longitudinal databases (i.e.
		Under the auspices of the Longitudinal Studies Centre - Scotland [link to LSCS website], we are establishing the Scottish Longitudinal Study (SLS) which will link administrative records for a 5% sample of the Scottish population.
		This will be the largest longitudinal database in Scotland, including information on approximately 270,000 people, and will allow a range of social science and health questions to be addressed.
	www.sdhi.ac.uk /research/longitudinal.htm (391 words)

	Amazon.com: Books: Applied Longitudinal Data Analysis: Modeling Change and Event Occurrence (Site not responding. Last check: 2007-11-06)
		Using Longitudinal Data is a unique contribution to the literature on research methods and will be useful to a wide range of behavioral and social science researchers.
		It is divided into two main sections -- one on longitudinal analysis per se, and another on time-to-event, or survival analysis, models.
		This is a great book, it tells you in a straightforward way how to analyze your longitudinal data to answer questions of critical importance in the social sciences.
	www.amazon.com /exec/obidos/tg/detail/-/0195152964?v=glance (1398 words)

	The Physics Classroom
		In a transverse wave, particles of the medium are displaced in a direction perpendicular to the direction of energy transport.
		In a longitudinal wave, particles of the medium are displaced in a direction parallel to energy transport.
		In this type of wave - a longitudinal wave - the particles of the medium move in a direction parallel to the direction of energy transport.
	www.physicsclassroom.com /mmedia/waves/lw.html (245 words)

	The High School Sophomore Class of 2002: A Demographic Description-First Results From the Base Year of the Education ...
		The sample survey data are from the Education Longitudinal Study of 2002 (ELS:2002).
		The data for this report, The High School Sophomore Class of 2002: A Demographic Description, describe the demographic characteristics and tested achievement of a cohort based on a nationally representative probability sample of 15,362 10th-graders in 752 public, Catholic, and other private schools who were studied in the spring term of the 2001–02 school year.
		The base-year data collection for the Education Longitudinal Study of 2002 (ELS:2002) is the first wave of a new longitudinal study of high school students that continues a series of nationally representative longitudinal studies conducted by the U.S. Department of Education's National Center for Education Statistics (NCES) in recent decades.
	nces.ed.gov /programs/quarterly/vol_6/1_2/4_1.asp (782 words)

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