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--------------------------Page1------------------------------摘要地铁交通事业快速发展给地铁火灾防范提出了更严格的要求，而我国地铁消防工程起步较晚，地铁火灾烟气控制方案还不成熟。因此，必须加强地铁系统火灾安全工程的研究，为确保地铁安全运营和火灾烟气控制提供理论依据和技术支撑。一般火灾系统最根本的特性是非线性，而火灾烟气分岔行为是非线性现象的一种。本文结合中国科学院中国科技大学火灾科学国家重点实验室的开放课题采用理论分析、模型实验和数值模拟相结合的方法对地铁隧道火灾分岔性这一典型非线性现象开展研究。主要研究内容是：一、从理论上分析地铁隧道中火灾烟气羽流传播与火灾烟气逆流两种分岔现象：描述火灾烟气羽流和逆流的数学描述方程并指出其影响因素同时推导了临界风速的理论计算公式。二、参考相似理论，在北京工业大学的地铁隧道模型基础进行实验方案的设计和测量设备的研制，测量所需要的各种参数并整理分析了相关的实验数据。三、采用CFD软件PHOENICS对地铁隧道火灾的烟流分布进行了数值模拟计算，在火灾烟气羽流的模拟计算中发现火灾危险距离随火源功率的关系近似呈抛物线变化。在火灾烟气逆流的模拟计算中验证了实验与计算公式所得出的产生火灾烟气逆流的临界风速。关键词：地铁隧道火灾；分岔；数值模拟；临界风速--------------------------Page2------------------------------北京交通大学硕士论文ABSTRACTTheneedstobeforwardstricterquicklydevelopedsubwaytransportationputforthethisstartedlateinourprohibitingfire，butrequirementsubwaysubjectveryhaven’tamaturedtocontrolthesmokeintunnel．Socountry，wegotsystemsubwayhavetowetheresearchaboutfireinthetunneltOmakesurewedeepensafetysubwaycanhaveareliabletheoreticalreferenceandinthetechnologicalsupportoperatingsubway．Thebasictraitsofthefirearenonlinearthefractiongeneralsystemcharacter,andisoneofthesenonlinearcharacters．BasedontheofphenomenonUSTC，openprojectwethefractionwiththreeapproachtypicalphenomenonways：theoreticalanalysis，andnumericalexperimentssimulation．1、Wethesmokeflowandsmokeflowwhicharekindsanalyzedplumeupstreamtwooffractionthemathematicofthetwophenomenontheoretically：Describedequationkindsoffractionandthenouttheinfecteddeducedphenomenonpointedfactor，thenthecalculationformulaofthecriticalventilatingvelocity．to2、Madeareferencethetheories，wetheschemeanalogicaldevelopedexperimentalandfacilitiesinthemodelinoftestingsubwayUniversityBeijingTechnology，thentestedtheneededdataandneatenedandthem．analyzed3、WeCFDsoftwaretousedPHOENICScalculatethefireandsmokedistributionindiscoveredthefireanddistancethefiresubwaytunnel，thendangerouspowerainsmokeflowweattestedthepresentingparabolavarietyplumecalculation，alsocriticalinsmokeflowcalculationwhichwefromtheventilatingvelocityupstreamgotandtheoretic
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你可能喜欢Phonetics and Phonology
Linguistics 001 & Lectures 6 & 7&&& Sound Structure
of Language
Background
Learning about the sound structure of language requires covering a lot of
ground. Some of the key topics are the anatomy, physiology, and acoustics
of t the nomenclature for the vocal articulations and
sounds used in speech, as represented by the International Phonetic A
hypotheses about the nature of phonological features and their organization&
into segments, the way that features like tone align
and spread relative to c the often-extreme changes
in sound of morphemes i the way that knowledge of language
sound structure unfolds as chi the variation in sound
structure across dialects and across time.
You can't learn all of this in a few days. If we tried to cover all of
these topics quickly, the result would be little more than a dry terminological
list with brief definitions, accompanied by a few diagrams and an abstract
discussion of the associated theories. It would not be especially useful
for us to require you to memorize these terms with learning anything much
about the underlying realities.
Instead of giving a whirlwind tour of the whole of phonetics and phonology,
this portion of ling001 has two more limited goals.
The first goal is
to put language sound structure in context. Why do human languages have
a sound structure about which we need to say anything more than &vocal
communication is based on noises made with the eating and breathing apparatus&?
What are the apparent "design requirements" for this system, and how does
are they fulfilled?
The second goal is to give you a concrete sense of
what the language sound systems are like. In order to do this, we will
go over, in a certain amount of detail, a few aspects of the phonetics
and phonology of English, and also a bit about the phonetic and phonology
of Mawukakan, a language spoken in the Ivory Coast and Guinea. Along the way,
a certain amount of the terminology and theory of phonetics and phonology
will emerge.
Apparent design features of human spoken
We can list a few characteristics of human spoken languages:
Large vocabulary: 10,000-100,000 items
Open vocabulary: new items are added easily
Variation in space and time: different languages and "local accents"
Messages are typically structured sequences of vocabulary items
Compare what is known about the "referential" part of the vocal signaling
system of other primates:
Small vocabulary: &35 items
Closed vocabulary: new "names" or similar items are not added
System is fixed across space and time: widely separated populations
use the same signals
Messages are usually single items, perhaps with repetition
Some general characteristics of other primate vocalizations that are retained
by human speech:
Vocalizations communicate individual identity
Vocalizations communicate attitude and emotional state
Some potential advantages of the human innovations:
Easy naming of new people, groups, places, etc.
Signs for arbitrarily large inventory of abstract concepts
Language learning is a large investment in social identity
How can it work?
Experiments on vocabulary sizes at different ages suggest that children
must learn an average of more than 10 items per day, day in and day out,
over long periods of time.
A sample calculation:
40,000 items learned in 10 years
10 x 365 = 3,650
40,000 / 3,650 = 10.96
Most of this learning is without explicit instruction, just from hearing
the words used in meaningful contexts. Usually, a word is learned after
hearing only a handful of examples. Experiments have shown that young children
can often learn a word (and retain it for at least a year) from hearing just one
casual use.
Let's put aside the question of how to figure out the meaning of a new
word, and focus on how to learn its sound.
You only get to hear the word a few times -- maybe only once. You have
to cope with many sources of variation in pronunciation: individual, social
and geographical, attitudinal and emotional. Any particular performance
of a word simultaneously expresses the word, the identity of the speaker,
the speaker's attitude and emotional state, the influence of the performance
of adjacent words, and the structure of the message containing the word.&
Yet you have tease these factors apart so as to register the sound of
the word in a way that will let you produce it yourself, and understand
it as spoken by anyone else, in any style or state of mind or context
In subsequent use, you (and those who listen to you speak) need to distinguish
this one word accurately from tens of thousands of others.
(The perceptual error rate for spoken word identification is less than
one percent, where words are chosen at random and spoken by arbitrary
and previously-unknown speakers. In more normal and natural contexts,
performance is better).
Let's call this the pronunciation learning problem. If every word
were an arbitrary pattern of sound, this problem would probably be impossible
What makes it work?
In human spoken languages, the sound of a word is not defined directly (in
terms of mouth gestures and noises). Instead, it is mediated by encoding
in terms of a phonological system:
A word's pronunciation is defined as a structured combination of
a small set of elements
The available phonological elements and structures
are the same for all words (though each word uses only some of them)
The phonological system is defined in terms of patterns of
mouth gestures and noisesi
This "grounding" of the system is called phonetic interpretation
Phonetic interpretation is the same for all words
How does the phonological principle help solve the pronunciation learning
problem? Basically, by splitting it into two problems, each one easier to
Phonological representations are digital, i.e. made up of discrete
elements in discrete structural relations.
Copying can be exact: members of a speech community can share identical
phonological representations
Within the performance of a given word on a particular occasion,
the (small) amount of information relevant to the identity of the
word is clearly defined.
Phonetic interpretation is general, i.e. independent of word identity
Every performance of every word by every member of the speech community
helps teach phonetic interpretation, because it applies to the phonological
system as a whole, rather than to any particular word.
The linguist Charles Hockett (1960) used the phrase "duality of patterning" to describe this two-stage encoding of the basic elements of a communication system, in which a large set of elements that refer to concepts or to things in the world (e.g. words) are created as combinations of a small set of discrete elements (e.g. phonemes), which are meaningless except for their role in connecting words to concepts.
Andr& Martinet (1965) used the phrase &double articulation& for the same idea. A more contemporary description might say that the lexicon of human languages is digitally encoded.
A simple example of phonological elements
and structures
To illustrate, let's start with the (excessively simple) phonological system
of a made-up language.
Outlandish has three vowels -- /a/, /i/, /u/ -- and every
Outlandish syllable must contain one of these. There are seven
consonants that can start syllables --- /p/, /t/, /k/, /b/, /d/,
/g/, /s/ -- and a syllable may also lack an initial consonant. Syllables
may optionally end with the consonant /n/.
Outlandish thus has 48 possible syllables: the syllable onset
has 8 options (/p/, /t/, /k/, /b/, /d/, /g/, /s/ or nothing), the syllable
nucleus has three options (/a/, /i/, /u/), and the syllable coda
has two options (/n/ or nothing), and 8 x 3 x 2 = 48.
Outlandish words are made up of from 1 to 4 syllables. In consequence,
there are 5,421,360 possible Outlandish words& -- 48x48x48x48 + 48x48x48
+ 48x48 + 48 = 5,421,360.
Thus the phonological elements of Outlandish, as we have described them,
are /i/, /a/, /u/, /p/, /t/, /k/, /b/, /d/, /g/, /s/, /n/. The phonological
structures of Outlandish include the notions of syllable, onset,
nucleus, and coda.
Some examples of Outlandish words might /kanpiuta/ "electronic calculator",
/kaa/ "automobile", /pi/ "climbing annual vine with edible seeds", /bata/
"emulsion of milkfat, water and air".
In giving the phonological encoding of these words, we've omitted the
structure, because it is unambiguously recoverable from the string of
elements. For instance, /kanpiuta/ must be a four-syllable word whose
first syllable contains the onset /k/, the nucleus /a/, and the coda /n/,
Real languages all have more complex phonological systems than our made-up
language Outlandish does. However, it remains true that phonological structures
are mostly recoverable from strings of phonological elements, and therefore
can be omitted for convenience in writing. In this way of writing down
phonological representations as strings of letter-like phonological elements,
the "letters" are usually called phonemes.
From phonemes to mouth gestures
and noises (and back again)
We've exemplified half of the situation: the "Outlandish" example explains
what kind of thing a phonological system is, and how the pronunciation of
words can be specified by "spelling" them in phonological terms.
What about the phonetic interpretation of words, that is, the interpretation
of phonemic strings in terms of mouth gestures and the accompanying noises?
How does that work?
notes, we'll give only a very basic overview. This topic is covered in
more detail in Ling 330 (Introduction to Phonetics and Phonology). Ling
520 (graduate Introduction to Phonetics) is a laboratory courses that
goes into considerably more detail, and is open to interested undergraduates
with appropriate background.
Basic sound production in the vocal
tract: buzz, hiss and pop
There are three basic modes of sound production in the human vocal tract
that play a role in speech: the buzz of vibrating vocal cords, the hiss
of air pushed past a constriction, and the pop of a closure released.
Laryngeal buzz
is a rather complex little
structure of cartilage, muscle and connective tissue, sitting on top of
the trachea. It is what lies behind your "adam's apple." The original
role of the larynx is to seal off the airway, in order to prevent aspiration
of food or liquid, and also to permit the thorax to be pressurized to provide
a more rigid framework for heavy lifting and pushing.
Part of the airway-sealing system in the larynx is a pair of muscular
flaps, the vocal cords or vocal folds,& which can be
brought together to form a seal, or moved apart to permit free motion
of air in and out of the lungs. When any elastic seal is not quite strong
enough to resist the pressurized air it restricts, the result is an erratic
release of the pressure through the seal, creating a sound. Some homely
examples are the Bronx cheer, where the leaky seal is provided
the belch, where the opening of the esophagus provides
or the rude noises made by grade school boys with their
hands under their armpits.
The mechanism of this sound production is very simple and general: the
air pressure forces an opening, through whic the
flow of air generates a so-called Bernoulli force at right angles
to the flow, which combines with the elasticity of the tissue to close
and then the cycle repeats, as air pressure again forces
an opening. In many such sounds, the pattern of opening and closing is
irregular, producing a belch-like sound without a clear pitch. However,
if the circumstances are right, a regular oscillation can be set up, giving
a periodic sound that we perceive as having a pitch. Many animals have
developed their larynges so as to be able to produce particularly loud
sounds, often with a clear pitch that they are able to vary for expressive
The hiss of turbulent flow
Another source of sound in the vocal tract -- for humans and for other animals
-- is the hiss generated when a volume of air is forced through a passage
that is too small to permit it to flow smoothly. The result is turbulence,
a complex pattern of swirls and eddies at a wide range of spatial and temporal
scales. We hear this turbulent flow as some sort of hiss.
In the vocal tract, turbulent flow can be created at many points of constrictions.
For instance, the lower teeth can be pressed against the upper lip --
if air is forced past this constriction, it makes the sound associated
with the letter (and IPA symbol) [f].
When this kind of turbulent flow is used in speech, phoneticians call
it frication, and sounds that involve frication are called fricatives.
The pop of closure and release
When a constriction somewhere in the vocal tract is complete, so that air
can't get past it as the speaker continues to breath out, pressure is built
up behind the constriction. If the constriction is abruptly released, the
sudden release of pressure creates a sort of a pop. When this kind of closure
and release is used as a speech sound, phoneticians call it a stop
(focusing on the closure) or a plosive (focusing on the release).
As with frication, a plosive constriction can be made anywhere along
the vocal tract, from the lips to the larynx. However, it is difficult
to make a firm enough seal in the pharyngeal region to make a stop, although
a narrow fricative constriction in the pharynx is possible.
Sound shaping by the vocal tract: vowel color and nasality
Between the larynx and the world at large is about 15 centimeters of throat
and mouth. This passageway acts as an acoustic resonator, enhancing some
frequencies and attenuating others. The properties of this resonator depend
on the position of the tongue and lips, and also on whether the velum
is lowered so as to open a side passage to the nasal cavities. Some examples
of shapes in a computer model of the human vocal tract, the corresponding
resonance patterns, and the sounds that result when a laryngeal buzz in
shaped by these resonances, can be found .
Different positions of the tongue and lips make the difference between
one vowel sound and another. As you can easily determine for yourself
by experiment, you can combine any vowel sound with any pitch -- or with
a whisper, which is a hiss created by turbulent flow at the vocal folds.
You can see (some aspects of) the coordination
of the articulators in this old x-ray movie:
And here's a video showing something invisible in the x-ray, namely (some of) what happens in your larynx as you talk:
a high-speed video that gives a better sense of how the vocal folds generate air-pressure variation at the time scale of voice pitch (about 60 to 600 oscillations per second):
And, if you're interested, here's a bit more about the anatomy:
Phonetic syllables: the scale and cycle of sonority
Human speech, like many animal vocalizations, tends to involve repetitive
cycles of opening and closing the vocal tract. In human speech, we call
these cycles syllables. A syllable typically begins with the vocal
tract in a relatively closed position -- the syllable onset -- and
procedes through a relatively open nucleus. The degree of vocal tract
openness correlates with the loudness of the sound that can be made. Speech
sounds differ on a scale of sonority, with vowels at one end (the
most sonorous end!) and stop consonants at the other end. In between are
fricatives, nasal consonants like [m] and [n], and so on. Languages tend
to arrange their syllables so that the least sonorous sounds are restricted
to the margins of the syllable -- the onset in the simplest case -- and
the most sonorous sounds occur in the center of the syllable.
However, there are some cases where the same -- or at least very similar
-- sounds can occur in several different syllabic roles. For example,
the glides (sometimes called approximants) that begin syllables
like "you" and "we" are almost exactly like vowels, except for their syllabic
position. In fact, the mouth position and acoustic content of the "consonant"
at the start of "you" and of the "vowel" at the end of "we" are just about
exactly the same.
In the International Phonetic Alphabet (IPA), the English word "you"
(in standard pronunciations) would be written something like [ju], where
the [j] refers to the sound we usually write as "y", and the [u] refers
to the vowel as in "boo" or "pool". The English word "we" would be written
in the IPA as [wi], where the [w] is familiar, and the [i] refers to the
vowel found in "see" or "eat".
In fact, the articulation and sound of IPA [j] is quite a lot like the
articulation and sound of IPA [i], while the articulation and sound of
IPA [w] is quite like that of IPA [u]. What is different is the role in
the syllabic cycle -- [j] and [w] are consonants, while [i] and [u] are
This means that the English words "you" and "we" are something like a
phonetic palindrome -- though "you" played backwards sounds more like
"oowee" than "we". More important, this underlines that point that phonetics
is the study of speech sounds, not just the study of vocal noises.
The International Phonetic Alphabet
Bell's VISIBLE SPEECH
In the mid-19th century, Melville Bell invented a writing system that he
called "Visible Speech." Bell was a teacher of the deaf, and he intended
his writing system to be a teaching and learning tool for helping deaf students
learn spoken language.& However, Visible Speech was more than
a pedagogical tool for deaf education -- it was the first system for notating
the sounds of speech independent of the choice of particular language or
dialect. This was an extremely important step -- without this step, it is
nearly impossible to study the sound systems of human languages in any sort
of general way.
In the 1860's, Melville Bell's three sons -- Melville, Edward and Alexander
-- went on a lecture tour of Scotland, demonstrating the Visible Speech
system to appreciative audiences. In their show, one of the brothers would
leave the auditorium, while the others brought volunteers from the audience
to perform interesting bits of speech -- words or phrases in a foreign
language, or in some non-standard dialect of English. These performances
would be notated in Visible Speech on a blackboard on stage.
When the absent brother returned, he would imitate the sounds produced
by the volunteers from the audience, solely by reading the Visible Speech
notations on the blackboard. In those days before the phonograph, radio
or television, this was interesting enough that the Scots were apparently
happy to pay money to see it!
[There are some interesting
connections between the "visible speech" alphabet and the later career
of one of the three performers,&
who began following in his father's footsteps as a teacher
of the dear, but then went on to invent the telephone. For example, look
at the discussion of Bell's && and artificial vocal tract.]
Phonetic notation for elocution lessons --
and for linguistic description
After Melville Bell's invention, notations like Visible Speech were widely
used in teaching students (from the provinces or from foreign countries)
how to speak with a standard accent. This was one of the key goals of early
phoneticians like
(said to have been the model for Henry
Higgins, who teaches Eliza
Doolittle to speak "properly" in
and its musical
adaptation ).
(IPA) was founded in 1886 in Paris, and has been ever
since the official keeper of the Inernational Phonetic Alphabet (also
IPA), the modern equivalent of Bell's Visible Speech. Although the IPA's
emphasis has shifted in a more descriptive direction, there remains a
lively tradition in Great Britain of teaching standard pronunciation using explicit training in the IPA.
The IPA and the dimensions of speech production
If you look at the IPA's table of "pulmonic" consonants (roughly, those
made while exhaling normally), you will see that it is organized along two
main dimensions.
The columns are labelled by positions of constriction, moving from the
lips (bilabial) past the teeth (dental) and the hard palate
(palatal) and soft palate (velar) to the larynx (glottal).
The rows are labelled by the type of manner of constriction: plosive,
nasal, fricative, and so forth. The side-by-side pairs of
plosives and fricatives are differentiated by whether layrngeal buzz is
present during the constriction. You can feel the difference yourself
if you put your finger on your adam's apple while saying an& extended
[s] or [z].
Thus the dimensions along which the IPA is organized are basically the
physical and functional dimensions of the human vocal tract, as shown
in . The same was
true of Bell's Visible Speech.
Sound Structure of Mawukakan
An essential part of learning about the sound structure of language is
to look at a particular case in detail. We don't have time to teach the
appropriate level of detail in this course. However, those of you who
are interested in such things can learn a lot on your own, and of course
you can go on to take other courses at Penn that take up language sound
in detail.
For this course, we will go over in class a
book chapter on some aspects of the sound structure of an African language, Mawukakan,
available on line via .. You will not be responsible
for the details of this material -- if any of it is used in any exam question,
all needed facts will be presented in the question.
The information in this section was developed a few years ago in the
course Ling 505/202
(Introduction to Field Linguistics), with the help of Dr. Moussa Bamba,
an accomplished linguist who happens to be a native speaker of Mawu.
Mawukakan is
more commonly known as &Mawu& (or &Mau&, or &Mahou&,
among other spellings). For its speakers, the region where they live is
called mawu, the people who live there are the mawuka (adding
a suffix /-ka/ that turns a name for a place into a name for the people
who live there), and the way they speak is called mawukakan (adding
another suffix /-kan/ that turns the name for a people into a name for
the language they speak). Since Mawukakan is not normally written down,
the different ways of spelling the name arise from different transliterations
into other languages, or different ideas about writing systems for Mawukakan
itself: the
gives six versions.
The Mawukakan region is near the city of Touba, in the northwestern region
of the , near the border with
Guinea. The traditions of the Mawuka people say that they migrated from
the city of , in what
in now Mali.. The Manding people, of which the Mawuka are a branch, are
known among other things for the
and poetry of their bards, known as griots, and for their spectacular
traditional architecture (here is a picture of the )