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This article has been accepted for publication and undergone full peer review but has
not been through the copyediting, typesetting, pagination and proofreading process,
which may lead to differences between this version and the Version of Record. Please
cite this article as doi: 10.1111/pbi.12923
DR. PEISONG HU (Orcid ID : 0000-0002-8568-5621)
Article type : Research Article
OsPK2 encodes a plastidic pyruvate kinase involved in rice endosperm starch
synthesis, compound granule formation and grain filling
Yicong Cai 1, #, Sanfeng Li 1, #, Guiai Jiao 1, Zhonghua Sheng 1, Yawen Wu 1, Gaoneng
Shao 1, Lihong Xie 1, Cheng Peng 2, Junfeng Xu 2, Shaoqing Tang 1, Xiangjin Wei 1, *,
Peisong Hu 1, *
1 State Key Laboratory of Rice Biology, China National Rice Research Institute,
Hangzhou, 310006, China
2 State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease
Control, Institute of Quality and Standard for Agro-products, Zhejiang Academy of
Agricultural Sciences; Hangzhou, 310021, China
#These authors contributed equally to this work.
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e*Authors for correspondence:
Peisong Hu: peisonghu@https://www.doczj.com/doc/37760981.html,, hupeisong@https://www.doczj.com/doc/37760981.html,
Xiangjin Wei: weixiangjin@https://www.doczj.com/doc/37760981.html,
Phone: +86-571-63370221, Fax: +86-571-63371532
Running title: OsPK2 affects rice quality and grain weight
Keywords: Grain filling; Amyloplast development; Pyruvate kinase; Starch
biosynthesis, Rice.
Summary
Starch is the main form of energy storage in higher plants. Although several enzymes
and regulators of starch biosynthesis have been defined, the complete molecular
machinery remains largely unknown. Screening for irregularities in endosperm
formation in rice represents valuable prospect for studying starch synthesis pathway.
Here, we identified a novel rice white-core endosperm and defective grain filling
mutant, ospk2, which displays significantly lower grain weight, decreased starch
content and alteration of starch physicochemical properties when compared to
wild-type grains. The normal starch compound granules were drastically reduced and
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e more single granules filled the endosperm cells o
f ospk2. Meanwhile, the
germination rate of ospk2 seeds after one year storage was observably reduced
compared to wild-type. Map-based cloning of OsPK2 indicated that it encodes a
pyruvate kinase (PK, ATP: pyruvate 2-O-phosphotranferase, EC 2.7.1.40), which
catalyzes an irreversible step of glycolysis. OsPK2 has a constitutive expression in rice
and its protein localizes in chloroplasts. Enzyme assay showed that the protein
product from expressed OsPK2 and the crude protein extracted from tissues of
wild-type exhibits strong PK activity however the mutant presented reduced protein
activity. OsPK2 (PKpα1) and three other putative rice plastidic isozymes, PKpα2,
PKpβ1 and PKpβ2 can interact to form heteromer. Moreover, the mutation leads to
multiple metabolic disorders. Altogether, these results denote new insights into the
role of OsPK2 in plant seed development, especially in starch synthesis, compound
granules formation and grain filling,which would be useful for genetic improvement
of high yield and rice grain quality.
Introduction
Starch is the essential carbohydrate storage material in plants. Because of its
relevance as staple crop, rice has been used to study starch formation in seeds.
Starch synthesis is a complex process involving a series of biosynthetic enzymes such
as ADP-Glc pyrophosphorylase (AGPase), starch synthase (SS), starch branching
enzyme (SBE), and starch debranching enzyme (DBE) (Toyosawa et al., 2016).
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e Mutation o
f those genes changes the appearance of the endosperm and alters the
characteristics of storage starch. For instance, mutations in AGPase subunits create a
wrinkled endosperm and significantly reduce the starch content (Akihiro et al., 2005;
Lee et al,, 2007; Tuncel et al., 2014; Wei et al., 2017). Loss-of-function mutations of
the GBSSI gene produce a complete lack of endosperm amylose (Sato et al., 2002;
Tian et al., 2009). Knockout of OsSSIIIa causes a white-core floury endosperm and
changes starch granules morphology, starch structure and gelatinization
temperature (Ryoo et al., 2007). Mutation of BEIIb causes a chalkiness endosperm
and has great influence on the properties of starch (Tanaka et al., 2004).
Loss-of-function mutations of ISA1, encoding a starch debranching enzyme, cause a
serious defect in amylopectin structure and a sugary endosperm (Kawagoe et al.,
2005; Kubo et al., 1999). Besides starch biosynthesis enzymes, other factors
associated to starch formation can also affect endosperm development in rice. For
example, FLOURY ENDOSPERM4 (FLO4), encoding a pyruvate orthophosphate
dikinase (PPDK; EC 2.7.9.1), was shown to regulate carbon flow from starch and lipid
biosynthesis during seeding stage (Kang et al., 2005). Some other factors such as
flo2, flo6, flo7, OsbZIP58, OsBT1 (ADP-glucose transporter), RPBF (rice P-box binding
factor), OspPGM (plastidic phosphor-glucomutase) and RSR1 (rice starch regulator1)
have also been shown to influence starch synthesis and endosperm development in
rice (She et al., 2010; Peng et al., 2014; Zhang et al., 2016; Li et al., 2017; Wang et al.,
2013; Lee et al., 2016; Yamamoto et al., 2006; Fu and Xue, 2010). Mutants of
SUBSTANDARD STARCH GRAIN4 (SSG4) and SSG6 show enlarged starch grains (SGs)
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e in the rice endosperm (Matsushim et al., 2014; 2016).All these data evidence that
the genetic basis of starch synthesis and grain development imply a complex
regulatory network. Therefore, identification and characterization of different rice
endosperm defective mutants are necessary for further understanding this process
in rice.
Pyruvate kinase (PK, ATP: pyruvate 2-O-phosphotranferase, EC 2.7.1.40) is a key
enzyme that regulates and adjusts the final step of the glycolysis pathway. It
catalyses the irreversible transfer of the high-energy phosphate group from
phosphoenolpyruvate (PEP) to ADP to synthesize pyruvate and ATP (Ambasht and
Kayastha, 2002; Valentini et al., 2000). The glycolytic pathway provides
intermediates for other crucial metabolic reactions. The product pyruvate can be
decarboxylated by pyruvate dehydrogenase complex (PDC) to generate acetyl-CoA,
which can be used as the initial substrate to participate in the tricarboxylic acid (TCA)
cycle to generate ATP under aerobic condition or be converted into lactic acid or
ethanol under hypoxia. Besides, acetyl-CoA can be involved in fatty acid (FA)
biosynthesis and the mevalonate pathway (Grodzinski et al., 1999).PEP, as the
intermediate product in glycolysis pathway, can also be catalyzed by
phosphoenolpyruvate carboxylase (PEPC) to form oxaloacetic acid (OAA) which is
required for amino acid synthesis (Schwender et al., 2004). Therefore, PK plays an
important role in the cellular metabolic flux (Zhang et al., 2012). PKs in plant exist as
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e cytosolic (PKc) and plastidic (PKp) isozymes (Plaxton, 1996). In most organisms, PKs
are usually present as a homotetramer (Schramm et al., 2000), but can also be found
in a monomer (Knowles et al., 1989) or in complexes as homodimer (Plaxton et al.,
2002) or in different heteromeric forms (αnβn) (Andre, 2007; Plaxton, 1989). For
example, PKc in castor oil seed germinating endosperm is existed as 240 kDa
heterotetramers comprised by 56 and 57 kDa subunits (Hu and Plaxton, 1996). PKp
purified from castor bean had been reported to exist as a 334 kDa α3β3
heterohexameric (63.5 kDa and 54 kDa polypeptides considered as α-subunit and
β-subunit, respectively) (Plaxton, 1991). There are 14 genes encoding putative PK
isoforms in Arabidopsis (Initiative, 2000). At least 6 PKc potato genes were identified
by southern blot analyses (Oliver et al., 2008). Cotton has at least 19 PKc and 14 PKp
genes (Zhang and Liu, 2016). In rice, at least 11 genes have been predicted to encode
putative PK isozymes (Zhang et al., 2012). Thus, the component forms of PK in higher
plant display abundant diversity.
In plants, a ‘bottom up’ allosteric regulatory mechanism regulates the glycolysis
pathway where PEP is considered as a potent inhibitor for ATP- and PPi-dependent
phosphofructokinase (PFK) (Plaxton and Podestá, 2006). Meanwhile, PK as an
allosteric enzyme can be inhibited by glutamate and activated by aspartate (Hu and
Plaxton 1996; Smith et al. 2000). Allosteric activation by 6-p-gluconate (G6P) in
Brassica napus PKp has been described (Andre et al., 2007). The major role of PKc is
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e to produce a precursor and ATP for various synthetic metabolic pathways (Smith et
al., 2000). Transgenic tobacco plants lacking the leaf PKc display decreased root
elongation and delayed bud differentiation and flowering (Knowles et al., 1998). The
cotton PKc gene GhPK6 is primarily expressed in cotton fibers and its expression
negatively correlates with the rate of fiber cell elongation (Zhang and Liu, 2016).
Identification of the rice OsPK1 gene suggested that PKc might affect plant
morphological development, causing dwarfism and panicle enclosure in rice (Zhang
et al., 2012). On the other hand, PKp is thought to provide pyruvate and ATP to
support biosynthetic pathways in plastids (Andre and Benning, 2007). Besides the
defects in oil accumulation and delayed germination found in Arabidopsis pkp1
mutants (Andre et al., 2007; Baud et al., 2007), research on PKp is limited and
defined roles in growth and development are unknown.
In this study, we identified a white-core endosperm and defective grain filling
mutant, ospk2. Map-based cloning showed that OsPK2 encodes a plastidic PK
enzyme that can interact with three other putative PKp subunits to form a polymer
which affects starch synthesis, compound granule formation and grain weight during
rice seed development. This deep dissection of OsPK2 will enhance our
understanding of the genetic basis of endosperm starch synthesis and grain filling in
rice, and provides useful information for genetic improvement of high yield and grain
quality.
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e Results
The rice ospk2 mutant displays defects in endosperm appearance and grain filling
A chalky endosperm and defective grain filling mutant, named ospk2, was identified
from an ethyl methane sulfonate (EMS)-mutagenized rice population. Compared to
the wild-type, the mature grains of ospk2 displayed an opaque endosperm, and
presented a white-core in the interior whereas the peripheral endosperm was
transparent (Figure 1a-c). Scanning electron microscopy (SEM) analysis of the
endosperm transverse sections showed that wild-type endosperm cells were filled
with densely packed and irregularly polyhedral starch grains (SGs; Figure 1d, e),
whereas the ospk2 endosperm cells presented spherical and loosely packed SGs
(Figure 1f, g). The grain-filling rate in the ospk2 mutant was significant slower than
the wild-type from 10 days after fertilization (DAF), resulting in a significantly
reduced grain weight and grain yield per plant in ospk2 (Figure 1h, i, and Figure S1a).
Quantification of seed size showed no significant difference in grain length but the
grain width and the grain thickness of ospk2 were reduced compared to the
wild-type (Figure 1j-l). Furthermore, germination rates of fresh harvested seeds were
not significant different between wild-type and ospk2, but the buds of ospk2 were
weaker. However, the seed germination rates after one year of storage was strongly
reduced in ospk2 compared to wild-type (Figure S2). Besides these grain endosperm
defects, no other obvious differences in plant architecture between wild-type and
the ospk2 mutant were observed (Figure S1b-g).
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e The structure o
f starch compound granules is abnormal in ospk2 endosperm cells
Semi-thin sections of developing endosperms at 10 DAF were prepared to observe
the structure of starch compound granules in wild-type and ospk2. Fewer well
developed compound granules and some immature starch granules were observed
in the peripheral endosperm cells of both wild-type and ospk2 (Figure 2a, e). In
central endosperm cells of wild-type seeds, several polyhedral and sharp-edged
starch granules congregate to form well-developed amyloplasts (Figure 2a, c). In
central endosperm cells of ospk2, however, abundant single, smaller, scattered and
weakly stained starch granules were also observed (Figure 2f, g). The morphology of
individual starch granules were also analyzed using SEM. The starch granules in
wild-type endosperm appear polygonal with sharp edges and similar size, whereas in
the mutant they were smaller and with irregular shape (Figure 2d, h). Amyloplasts at
earlier developmental stages (3, 6, and 9 DAF) were observed by transmission
electron microscopy (TEM). Wild-type amyloplasts were filled with polyhedral starch
granules and the interior space was quickly occupied during grain development,
eventually forming a typical complex structure (Figure 3a-c). Similar to wild-type,
there were few well developed amyloplasts in the endosperm cells of the ospk2
mutant (Figure 3d-f), however the majority of the starch granules in ospk2
endosperm cells existed as small, single and disperse granules rather than
aggregated (Figure 3g-i). This was consistent with our observations of the semi-thin
sections (Figure 2f, g). These results suggest that OsPK2 affects the formation of
starch compound granules in endosperm cells during grain development.
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e Starch physicochemical properties in ospk2
Because the starch granules were abnormal in both mature and developing
endosperm in the ospk2 mutant, the starch physicochemical properties were also
examined. The total starch and amylose contents significantly decreased in the
endosperm of ospk2 compared to wild-type (Figure 4a, b). Nonetheless, the contents
of protein and lipid in ospk2 were higher than these in wild-type (Figure 4c, d). In the
case of lipids, the contents of the C16:0 (palmitic acid), C18:0 (stearic acid), C18:1
(oleic acid), C18:2 (linoleic acid) and C22:0 (behenic acid) all increased (Figure S3). To
further analyze the fine structure of amylopectin, its chain length distribution was
determined. Compared to wild-type, the proportion of short chains with degree of
polymerization (DP) values between 6 and 12 decreased, whereas the proportion of
intermediate chains with DP values between 13 and 25 was elevated in the ospk2
mutant (Figure 4e).
The pasting properties of starch were analyzed with a Rapid Visco Analyzer (RVA;
Figure 4f). The RVA profile showed significant differences in pasting properties of the
starch derived from wild-type and ospk2. The viscosity of pasting starch in ospk2 was
maintained at a very low level and did not show the distinct characteristics of the
peak viscosity and breakdown when the temperature rose. When the temperature
was lowered, the viscosity of pasting starch in wild-type augmented quickly and
showed a high final value, whereas that of ospk2 almost did not increase and the
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e final viscosity was only 16.68% o
f that of wild-type. The gelatinization properties of
the SGs also were examined, and the result showed that SGs in ospk2 had a
significantly shorter gel consistency than wild-type (Figure 4g). Starch solubility in
urea solutions was measured. Mixing powdered starch with varying concentrations
(0–9 M) of urea solutions showed that the ospk2 starch was more difficult to
gelatinize and exhibited significant different gelatinization characteristics in 4-9 M
urea compared to that of wild-type (Figure 4h). In brief, the physicochemical
properties of the starch in ospk2 endosperm were significantly different from those
in wild-type.
Map-based cloning and complementation of the ospk2 mutation
To identify the gene controlling the ospk2 phenotypes, map-based cloning was
conducted using an F2 mapping population that was generated by crossing the ospk2
mutant (japonica) with Nanjing11 (NJ-11, indica). The mutation locus was first
mapped on the short arm of chromosome 7 between the simple sequence repeat
(SSR) markers RM21078 and RM3484. Over 978 individuals showing the o s pk2
phenotypes were chosen from this F2 population. The o s pk2 locus was further
narrowed down to a 90.8-kb region between InDel markers In18 and In20 located on
the BAC clone OSJ1119_A04, which included nine putative open reading frames
(ORFs, Figure 5a; Table S1). Sequence analysis of the ORFs revealed a single
nucleotide substitution from a cytosine (C) to thymine (T) on the 4th exon in ORF4
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e(Os07g0181000) in the ospk2 mutant, which led a Serine296 replaced by a Leucine296
(Figure 5b). Os07g0181000 was predicted to encode a putative pyruvate kinase (PK)
of about 63.58 kDa with 578 amino acids (http://smart.embl-heidelberg.de). Among
a total of eleven Oryza sativa PK isozymes, OsPK2 (Os07g0181000, also named
PKpα1) belongs to the α-subunit type within the plastidic clade (Figure S4). Protein
sequence alignment showed that the mutation site lies in a highly conserved Serine
(S) residue on the PK domain among the OsPK2 homologues and that OsPK2 shares
74.33% identity with Arabidopsis AtPKp1(Figure S5) which was reported as a
plastidic PK involved in embryo development and control of carbon flux in maturing
Arabidopsis seeds (Andre et al., 2007).
To verify whether OsPK2 (Os07g0181000) is the gene responsible for the mutant
phenotypes, a vector carrying the OsPK2 genomic sequence including its native
promoter and another vector with the OsPK2 coding region driven by the UBIQUTIN1
promoter were constructed and introduced into the ospk2 mutant. The expression of
OsPK2 in complementation and overexpression transgenic lines was significant
higher than that in ospk2 and wild-type plants (Figure S6). Seeds harvested from
independent complementation and overexpression positive transgenic T1 lines
showed similar phenotypes to wild-type (Figure 5c). The total starch content,
1000-brown grain weight, grain length, width and thickness of brown rice of the
complementation and overexpression lines achieved the same levels of those of
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e wild-type (Figure 5d, e, and Figure S7a-d). SGs in endosperm cells o
f these positive
transgenic lines also presented the polyhedral and densely packed granule
morphology, similar to those of wild-type (Figure 5c). RNAi knock-down plants (Ri) of
OsPK2 (Os07g0181000) were generated in a wild-type genetic background resulting
in lines with significant lower expression levels of OsPK2 than in wild-type (Figure
S6). The grains of those Ri lines displayed opaque endosperm (Figure 5c). The total
starch content and grain weight, grain length, width and thickness of brown rice of Ri
were all markedly decreased compared to wild-type (Figure 5d, e, and Figure S7e-h).
CRISPR/Cas9 technology was also applied to confirm that the phenotypic was due to
the knock out the OsPK2 gene (Figure 5c-e and Figure S8). Therefore,it was deduced
that the abnormal grain phenotypes and starch physicochemical properties observed
in the mutant were due to the mutation detected in the OsPK2 gene.
Expression pattern, subcellular localization, and enzyme assay of OsPK2
Temporal and spatial expression analysis showed that OsPK2 is constitutively
expressed in all tested organs. Transcript levels of OsPK2 were higher in stems,
panicles and leaves but less abundant in roots and developing grains. Compared to
the wild-type, OsPK2 transcription level in the mutant was much lower in most
organs (Figure 6a). To confirm these results, a vector with the GUS reporter gene
driven by the OsPK2 promoter was transformed into rice. Histochemical analysis of
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e GUS activity in transgenic plants corroborated that OsPK2 presents a constitutive
expression pattern (Figure 6b).
OsPK2 was predicted as a chloroplast-targeted protein by the online tools
Plant-PLoc (https://www.doczj.com/doc/37760981.html,/cgi-bin/PlantPLoc.cgi) and WoLF PSORT
(http://wolf https://www.doczj.com/doc/37760981.html,). To verify the predicted subcellular localization and the length
and position of the chloroplast-targeting signal in OsPK2, GFP fusions driven by the
CaMV 35S promoter, OsPK2-GFP, ospk2-GFP, OsPK21–451aa -GFP, OsPK21–97aa –GFP and
OsPK298–578aa -GFP were constructed and transiently expressed in rice protoplasts
and tobacco leaves. The GFP control protein was widely present in the cytoplasm
and nuclei, however, both OsPK2-GFP and ospk2-GFP fusion proteins were localized
in chloroplasts, evidenced by the exclusive co-localization with the chlorophyll
autofluorescence signal (Figure 6c and Figure S9a, b). GFP signals of OsPK21–451aa-GFP
and OsPK21–97aa -GFP fusion proteins were also targeted to the chloroplasts, while the
signal of OsPK298–578aa -GFP was not (Figure S9c-e). These results suggest that OsPK2
is a chloroplast-located protein and that the 97-amino acid N-terminal sequence is
essential for targeting OsPK2 to chloroplasts.
The proteins encoded by OsPK2 and ospk2 were expressed in baculovirus system
and purified by His-tag (Figure S10) and used to examine PK activity. The result
showed that both OsPK2 and ospk2 present PK activity. However, the activity of
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e ospk2 (~60.98 nmol/min/mg) was significantly lower than that o
f wild-type
(~112.09nmol/min/mg) (Figure 6d). The PK activity was also detected in seeds (10
DAF) and leaves of wild-type and ospk2, and the results indicated that the PK activity
was also significantly decreased in the mutant (Figure 6e and Figure S11a).
Additionally, the content of pyruvate (product of PK) in seeds (10 DAF) and leaves
was also significantly reduced in ospk2 compared to wild-type (Figure 6f and Figure
S11b). All these results demonstrate that the protein encoded by OsPK2 has PK
activity and a single amino acid substitution (Ser296 to Leu296) in the PK domain
compromised its enzymatic activity.
OsPK2 can interact with other plastidic pyruvate kinases to form heteropolymers
There are at least eleven genes predicted to encode putative PK isoforms in rice
(Zhang et al., 2012), among them, OsPK2(PKpα1), Os03g0672300 (PKpα2,53.48%
amino acid sequence identity with OsPK2),Os01g0660300 (PKpβ1, 39.47% identity
with OsPK2) and Os10g0571200 (PKpβ2, 39.43% identity with OsPK2)exist as
plastidic PK isozymes (Baud et al., 2007). Transcription levels of the PK family were
analyzed in wild-type and ospk2 mutant. The results showed that the expression of
OsPK2 and PKpβ2were significantly decreased, and that of PKpα2, PKpβ1 and two
plant cytoplasmic PK isozyme genes, Os01g0276700 and Os11g0216000,were
significantly increased in the ospk2 mutant (Figure S12). Usually, PKs exist as
homotetramers, but are also present as monomers, homodimers, heterodimers,
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e heterotetramers or heteropolymers (Andre et al., 2007; Knowles et al., 1989;
Plaxton, 1989; Plaxton, 1990; Plaxton et al., 2002). Approaches to test recombinant
subunits of rice PKps were applied in our study. The possible interactions of PKp
subunits with OsPK2 were examined by yeast two-hybrid analysis (Y2H) and
bimolecular fluorescence complementation (BiFC). Results showed that three putative
PKp subunits (PKpα2, PKpβ1 and PKpβ2) can interact with OsPK2 in yeast cells
(Figure 7a). The BiFC assay in tobacco epidermal cells also confirmed that OsPK2
(PKpα1) can physically interact with PKpα2, PKpβ1 and PKpβ2 (Figure 7b). In addition,
Y2H and BiFC revealed that PKpβ1 and PKpβ2 can interact with each other to form a
heteromer (Figure 7a, b). Moreover, we found that OsPK2 (PKpα1) and PKpα2 can
interact with themselves. However, pKpβ1 and PKpβ2 cannot interact with
themselves and no interaction was detected between PKpα2 and pKpβ1 or PKpβ2
(Figure 7a, b and Figure S13). These results suggest that OsPK2 can form polymeric
protein complexes in vivo by interacting with other PKp.
Expression of glycolysis-, pyruvate metabolism-, FA metabolism- and starch
synthesis-related genes was affected in the ospk2 mutant
PK is a key enzyme involved in the glycolytic pathway, thus, the expression of ten
putative enzyme genes related to glycolysis, pyruvate metabolism and FA
metabolism was analyzed in developing grains of wild-type and ospk2. Compared to
wild-type, expression levels of OsFBP1 encoding fructose-1,6-bisphosphatase
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e(FBPase, EC: 3.1.3.11), a key enzyme in gluconeogenesis or Calvin cycle converting
fructose-1,6-bisphosphate to fructose-6-phosphate (F6P), and triose phosphate
isomerase (TIM, EC: 5.3.1.1), which reversibly interconvert dihydroxyacetone
phosphate (DHAP) and 3-phosphoglyceraldehyde (GA3P), were significantly
increased in the ospk2 mutant. The expression level of a gene encoding the putative
plastidic pyruvate dehydrogenase (PDH, EC: 4.1.1.1, the dehydrogenase E1
component of PDC) which converts pyruvate to acetyl CoA was also significantly
increased. Whereas no differences were observed for the expression of the gene
encoding glucose-6-phosphate isomerase (GPI, EC: 5.3.1.9) that interconvert G6P
and F6P (Figure 8a). Otherwise, expression levels of pyruvate metabolism-related
genes PEPC-2 encoding PEP carboxylase, PEPCK for PEP carboxykinase and ATL-2 for
alanine transaminase were all significantly increased in ospk2. Meanwhile,
expression of the genes that encode a chloroplastic NADP-dependent malic enzyme
(ME6, Os01g0188400) and OsAlaATL1 (Os10g0390500) were lower in the ospk2
mutant(Figure 8b). The expression of OsKASI, encoding a β-ketoacyl-[acyl carrier
protein] synthase I which participates in FA synthesis, was significantly higher in the
mutant. Genes for lipolytic enzymes such as THIS1 and Lipase-II displayed lower
expression in ospk2 (Figure 8c). The expression of starch synthesis related genes
were also evaluated in 12 DAF grains. Results showed that transcript levels of three
AGP genes (OsAGPL2, OsAGPS1 and OsAGPS2b), six amylopectin synthesis related
genes (OsSSI, OsSSIVb, OsGBSSI, OsISA1, OsISA3, and OsPUL), Susy3 and pyruvate
phosphate dikinase gene PPDKB were all significantly lower in ospk2 than in the
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e wild-type. Conversely, the transcript levels o
f OsBEIIb, OsSSIIIa, OsPHOL, OsISA2,
Susy1 and Susy2 were markedly higher in ospk2 mutant (Figure 8d).
Discussion
OsPK2 can interact with other plastidic PKs to form heteropolymers
PK isoforms vary in different tissues and subcellular components (Andre et al., 2007).
In cytosol, PKc exists as homotetramer in both germinating cotyledons and
developing endosperm of castor oil seeds (Podestá and Plaxton, 1994; Turner et al.,
2005). In plastids, native enzyme PKp in developing endosperm of castor oil seeds
was present as a heterohexamer (α2β2; Plaxton et al., 1990). PKp in Arabidopsis was
as appeared to be a 460 kDa heterooctamer (α4β4) containing four α subunits (59.6
kDa) and four β subunits (56.8 kDa; Andre et al., 2007). In this work, we identified
and characterized OsPK2 encoding a PKp isozyme in rice. Subcellular localization
analysis confirmed that the green ?uorescent signals of OsPK2-GFP were small
dot-like structures and only co-localized with the auto?uorescent signals of
chlorophyll (Figure 6c and Figure S9), implying that OsPK2 localizes in the chloroplast
nucleoids, similar to what was observed for AtPKp1 and AtPKp2 in Arabidopsis (Baud
et al., 2007). In developing castor oil seeds, the N-terminal 44 and 60 amino acids of
PKp α- and β-subunit contain their respective transit peptides which were
responsible for their import to the leucoplast (Negm et al., 1995). Here, we found
that the first 97 N-terminal amino acids were necessary for the chloroplast location
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f OsPK2 (Figure S9). Y2H and BiFC assays indicated that OsPK2 (PKpα1) can
interacted with three other putative PKp subunits (PKpα2, PKpβ1, and PKpβ2) and
that OsPK2 (PKpα1)and PKpα2can also interacted with themselves (Figure 7a, b and
Figure S13). These results suggest that the PKp in rice can exist as heteromeric
complex. Meanwhile, BiFC assays also showed the green ?uorescent signals of
PKpα1&PKpα2, PKpα1&PKpβ1, PKpα1&PKpβ2, and PKpβ1&PKpβ2 overlapping with
the chlorophyll autofluorescence signal in tobacco cells (Figure 7b), supporting the
idea that PKpα2, PKpβ1 and PKpβ2, with OsPK2 (PKpα1) are all plastidic isozymes,
consistent with the phylogenetic analysis of OsPK2 homologous proteins (Figure S4).
Therefore, the enzyme complexes formed by OsPK2 subunit coordinated with three
other subunits would fulfill PKp function in rice. Together, these results suggest that
the PKp complex in rice might be more multifaceted and diverse than in other plants
due to the multiple interactions between different subunits.
Mutation in OsPK2 leads to multiple disorders in metabolic processes
PK catalyzes the final step in glycolysis which produces ATP and NADH by breakdown
glucose into pyruvate. Pyruvate can then be converted to acetyl-CoA and NADH by
the PDC which contains two distinct forms, mitochondrial (mtPDC) and plastidial
(plPDC). I n the cytosol, pyruvate produced by PKc is transported into mitochondria
to undergo oxidative decarboxylation by mtPDC and offer carbon (acetyl-CoA) to the
TCA cycle (Smith et al., 2000). In plastids, the main role of PKp is to generate ATP and
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e substrate (pyruvate) which can be catalyzed by plPDC to synthesize acetyl-CoA for
FA biosynthesis (Andre et al., 2007). Pyruvate and acetyl-CoA are also important
products in the conversion of lipids to sugars via gluconeogenesis and the glyoxylate
cycle. In addition, the intermediate PEP can be catalyzed by PEPC to produce OAA
which can enter the mitochondria to fuel the TCA pathway or amino acids synthesis.
Malate produced by OAA in the cytosol can also enter the mitochondria (Agrawal
and Rakwal, 2012; Sweetlove et al., 2010). Therefore, pyruvate is an important
intermediate for sucrose/starch, lipid and amino acid metabolism. In our study,
mutation in OsPK2 significantly reduced the PK activity in ospk2 (Figure 6e and Figure
S10b), which led to alteration of the expression of genes involved in multiple
metabolic processes. For instance, the expression of TIM, OsFBP1 and PDH was
significantly higher in ospk2 (Figure 8a). The transcription level of OsKASI encoding a
FA synthesis enzyme was significantly higher in the mutant than in the wild-type,
while that of THIS1 and Lipase-II gene encoding the lipolytic enzyme was lower in
ospk2 (Figure 8c). In addition, expression of Susy1 and Susy2 was significantly higher
in ospk2 (Figure 8d). These data imply that OsPK2 can directly or indirectly affect the
TCA cycle, FA and sugar metabolism. In addition, the expression of starch synthesis
related genes was also changed in ospk2 (Figure 8d). Therefore, mutation in OsPK2
leads to a variety of metabolic disorders in the ospk2 mutant.
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变电所母线桥的动稳定校验 随着用电负荷的快速增长，许多变电所都对主变进行了增容，并对相关设备进行了调换和校验，但往往会忽视主变母线桥的动稳定校验，事实上此项工作非常重要。当主变增容后，由于阻抗发生了变化，短路电流将会增大许多，一旦发生短路，产生的电动力有可能会对母线桥产生破坏。特别是户内母线桥由于安装时受地理位置的限制，绝缘子间的跨距较长，受到破坏的可能性更大，所以应加强此项工作。 下面以我局35kV/10kv胡店变电所#2主变增容为例来谈谈如何进行主变母线桥的动稳定校验和校验中应注意的问题。 1短路电流计算 图1为胡店变电所的系统主接线图。(略) 已知#1主变容量为10000kVA，短路电压为7.42%，#2主变容量为12500kVA，短路电压为7.48%(增容前短路电压为7.73%)。 取系统基准容量为100MVA，则#1主变短路电压标么值 X1＝7.42/100×100×1000/10000＝0.742， #2主变短路电压标么值 X2＝7.48/100×100×1000/12500＝0.5984 胡店变电所最大运行方式系统到35kV母线上的电抗标么值为0.2778。 ∴#1主变与#2主变的并联电抗为： X12=X1×X2/(X1+X2)＝0.33125； 最大运行方式下系统到10kV母线上的组合电抗为： X＝0.2778+0.33125＝0.60875
∴10kV母线上的三相短路电流为：Id=100000/0.60875*√3*10.5，冲击电流：I sh=2.55I =23032.875A。 d 2动稳定校验 (1)10kV母线桥的动稳定校验： 进行母线桥动稳定校验应注意以下两点： ①电动力的计算，经过对外边相所受的力，中间相所受的力以及三相和二相电动力进行比较，三相短路时中间相所受的力最大，所以计算时必须以此为依据。 ②母线及其支架都具有弹性和质量，组成一弹性系统，所以应计算应力系数，计及共振的影响。根据以上两点，校验过程如下： 已知母线桥为8×80mm2的铝排，相间中心线间距离为210mm，先计算应力系数： ∵频率系数N f＝3.56，弹性模量E＝7×10.7 Pa，单位长度铝排质量M＝1.568kg/m，绝缘子间跨距2m，则一阶固有频率: f’=(N f/L2)*√(EI/M)=110Hz 查表可得动态应力系数β＝1.3。 ∴单位长度铝排所受的电动力为： f ph＝1.73×10-7I sh2/a×β＝568.1N/m ∵三相铝排水平布置，∴截面系数W＝bh2/6＝85333mm3，根据铝排的最大应力可确定绝缘子间允许的最大跨距为： L MAX=√10*σal*W/ f ph=3.24m ∵胡店变主变母线桥绝缘子间最大跨距为2m，小于绝缘子间的最大允许跨距。
母线电动力及动热稳定性计算 1 目的和范围 本文档为电气产品的母线电动力、动稳定、热稳定计算指导文件，作为产品结构设计安全指导文件的方案设计阶段指导文件，用于母线电动力、动稳定性、热稳定性计算的选型指导。 2 参加文件 表1 3 术语和缩略语 表2 4 母线电动力、动稳定、热稳定计算 4.1 载流导体的电动力计算 4.1.1 同一平面内圆细导体上的电动力计算
? 当同一平面内导体1l 和2l 分别流过1I 和2I 电流时（见图1），导体1l 上的电动力计 算 h F K I I 4210 π μ= 式中 F ——导体1l 上的电动力（N ） 0μ——真空磁导率，m H 60104.0-?=πμ； 1I 、2I ——流过导体1l 和2l 的电流（A ）； h K ——回路系数，见表1。 图1 圆细导体上的电动力 表1 回路系数h K 表 两导体相互位置及示意图 h K 平 行 21l l = ∞=1l 时，a l K h 2= ∞≠1l 时，?? ? ???-+=l a l a a l K h 2)(12 21l l ≠ 22 2) ()(1l a m l a l a K h ++-+= 22)()1(l a m +-- l a m =
? 当导体1l 和2l 分别流过1I 和2I 电流时，沿1l 导体任意单位长度上各点的电动力计 算 f 124K f I I d μ= π 式中 f ——1l 导体任意单位长度上的电动力（m N ）； f K ——与同一平面内两导体的长度和相互位置有关的系数，见表2。 表2 f K 系数表
4.1.2 两平行矩形截面导体上的电动力计算 两矩形导体（母线）在b ＜＜a ，且b ＞＞h 的情况下，其单位长度上的电动力F 的 计算见表3。 当矩形导体的b 与a 和h 的尺寸相比不可忽略时，可按下式计算 712 210x L F I I K a -=? 式中 F -两导体相互作用的电动力，N ； L -母线支承点间的距离，m ； a -导体间距，m ； 1I 、2I -流过两个矩形母线的电流，A ； x K -导体截面形状系数； 表3 两矩形导体单位长度上的电动力 4.1.3 三相母线短路时的电动力计算
对比导购稿日系美系家轿大P K三厢利亚纳A6对比新赛欧
【对比导购稿】 日系美系家轿大PK 利亚纳A6对比新赛欧 随着国内汽车市场需求不断多元化，家用轿车在“大气、个性”的一贯形象的基础上，更注重自己的家族特色。一般来说，美系车大气粗矿，日系车精致节油，现在我们以三厢利亚纳A6与三厢新赛欧为例，综合各个方面为举棋不定的朋友们做一番详细解析。 外观：各有千秋 外观方面，利亚纳A6三厢整体传承了Liana日系家族高大外观，且采用“二次元”透视梦幻大灯，如“精灵之翼”般的上格栅，浮雕感线条、侧面大轮辋，更显时尚动感大气。潮流尾灯红白均衡布置，行李箱特征线横向造型，下部轮廓线条从车门护板过渡到后保险杠，至角部布置回复反射器连贯一体，在平稳和更具运动感的同时有种年轻气盛的冲动。 新赛欧沿袭了雪佛兰家族特征和美系风格，线条更为硬朗。上扬的前大灯与倒梯形进气格栅组成了前脸造型，一条粗壮的线条横跨进气格栅，整体形象中规中矩。不足的是整体外形尺寸比利亚纳A6小一号，钢辋加轮罩略显低档。
内饰配置：新贵PK老派 利亚纳A6的内饰体现出日系车细致用心的一贯特点：深色仪表台，配以银色装饰，三幅方向盘造型有力度感，仪表板造型锐化，控制面板造型细腻，颇具精度感。配以触摸屏和行车电脑、自动空调等数字显示清晰，科技感十足。 新赛欧采用了简洁朴实的设计风格，左右两侧的圆形出风口为整车带来了一些动感。手动空调按钮大小适中，仪表盘的设计非常的新颖，中间一个大的速度表，两边集成了数字式的转速表和里程表，橘红色的背景很温馨。唯一不足的是淡灰色内饰比较老气，驾驶空间没有利亚纳A6宽畅。 配置方面，利亚纳A6拥有一般装配于高级轿车的自动空调系统，此系统可以按照人体舒适软件根据周围环境自动调节车内空调的工作状态，对于驾驶和乘客，这样全自动控制模式的人性化科技非常便捷可心。高智能化的无钥匙系统使车主只要在智能钥匙随身携带且位于一定半径范围内的情况下，无需取出钥匙即可通过感应随手执行开闭车门等操作，并且在进入车内后，同样可以在不取出智能钥匙的前提下通过安全认证启动汽车。另外，四轮独立悬挂系统的装配有效减小车身的倾斜和振动，增强抗颠簸性，平行连接主车架加强梁式优化设计可以更好的起到减震隔噪作用。同样属于越级配置的还有利亚纳A6装配的多功能方向盘、一系列中控多媒体科技、6.5英寸触摸式多媒体
筠连县分水岭煤业有限责任公司 井 下 高 压 电 缆 热 稳 定 性 校 验 计 算 书 巡司二煤矿 编制：机电科 筠连县分水岭煤业有限责任公司
井下高压电缆热稳定校验计算书 一、概述： 根据《煤矿安全规程》第453条及456条之规定，对我矿入井高压电缆进行热稳定校验。 二、确定供电方式 我矿高压供电采用分列运行供电方式，地面变电所、井下变电所均采用单母线分段分列供电方式运行，各种主要负荷分接于不同母线段。 三、井下高压电缆明细： 矿上有两趟主进线，引至巡司变电站不同母线段，一趟931线，另一趟925线。井下中央变电所由地面配电房10KV输入。 入井一回路：MYJV22-8.7/10KV 3*50mm2--800m(10KV) 入井二回路：MYJV22-8.7/10KV 3*50mm2--800m(10KV) 四、校验计算 1、井下入井回路高压电缆热稳定性校验 已知条件：该条高压电缆型号为，MYJV22-8.7/10KV 3*50mm2 ,800m，电缆长度为800m=0.8km。 （1）计算电网阻抗 查附表一，短路电流的周期分量稳定性为 电抗：X=0.072*0.8=0.0576Ω； 电阻：R=0.407*0.8=0.3256 Ω； (2)三相短路电流的计算
A Z I 5.174693305 .0310000 3v 3=?== ∞ （3）电缆热稳定校验 由于断路器的燃弧时间及固有动作时间之和约为t=0.05S; 查附表二得热稳定计算系数取K=142; 故电缆最小热值稳定截面为 23mm 51.2705.0142/5.17469t )/(min ===∞）（K I S Smin<50mm 2 故选用 MYJV 22 -8.7/10KV 3*50 电缆热稳定校验合格，符合要求。 附表一：三相电缆在工作温度时的阻抗值（Ω/Km ） 电缆截面S （mm 2 ） 4 6 10 16 2 5 35 50 70 95 120 150 185 240 交联聚乙烯 R 4.988 3.325 2.035 1.272 0.814 0.581 0.407 0.291 0.214 0.169 0.136 0.11 0.085 X 0.093 0.093 0.087 0.082 0.075 0.072 0.072 0.069 0.069 0.069 0.07 0.07 0.07 附表二 不同绝缘导体的热稳定计算系数 绝缘材料 芯线起始温度（° C ） 芯线最高允许温度（°C ） 系数K 聚氯乙烯 70 160 115（114） 普通橡胶 75 200 131 乙丙橡胶 90 250 143（142） 油浸纸绝缘 80 160 107 交联聚乙烯 90 250 142
井下高压开关、供电电缆动热稳定性校验 一、-350中央变电所开关断路器开断能力及电缆热稳定性校验 1 23 G 35kV 2 Uz%=7.5△P N.T =12kW △P N.T =3.11kW S N.T =8MVA 6kV S1点三相短路电流计算： 35kV 变压器阻抗： 2 22.1. u %7.5 6.30.37()1001008z N T N T U Z S ?===Ω? 35kV 变压器电阻：2 22.1.22. 6.30.0120.007()8 N T N T N T U R P S =?=?=Ω 35kV 变压器电抗：10.37()X = ==Ω 电缆电抗：02(x )0.415000.08780 0.66()1000 1000i L X ??+?== =Ω∑ 电缆电阻：02(x )0.11815000.118780 0.27()1000 1000 i L R ??+?== =Ω∑ 总阻抗： 21.370.66) 1.06( Z ==Ω S1点三相短路电流：(3)1 3.43()d I KA === S2点三相短路电流计算： S2点所用电缆为MY-3×70+1×25，长400米，变压器容量为500KV A ，查表的：(2)2d I =2.5KA
S2点三相短路电流：32 d d =2.88I I KA = 1、架空线路、入井电缆的热稳定性校验。已知供电负荷为3128.02KV A ，电压为6KV ，需用系数0.62，功率因数cos 0.78φ=，架空线路长度1.5km ，电缆长度780m (1)按经济电流密度选择电缆，计算容量为 3128.020.62 2486.37cos 0.78 kp S KVA φ?= ==。 电缆的长时工作电流Ig 为239.25 Ig === A 按长时允许电流校验电缆截面查煤矿供电表5-15得MYJV42-3×185-6/6截面长时允许电流为479A/6kV 、大于239.25A 符合要求。 (2)按电压损失校验，配电线路允许电压损失5%得 60000.1300Uy V ?=?=，线路的实际电压损失 109.1L U COS DS φφ?====，U ?小于300V 电压损失满足要求 (3)热稳定性条件校验，短路电流的周期分量稳定性为 电缆最小允许热稳定截面积： 3 2min d =S I mm 其中：i t ----断路器分断时间，一般取0.25s ； C----电缆热稳定系数，一般取100，环境温度35℃，电缆温升不超过120℃时，铜芯电缆聚乙烯电缆熔化温度为130℃，电
全球汽车车型中英文对照表 车型（中文）车型（英文）车型（中文）车型（英文） 奥迪奥迪AUDI伊兰特ELANTRA 宝马宝马BMW特拉卡Terracan 迷你Mini途胜Tucson mini One mini One御翔NF 奔驰奔驰benz雅绅特Accent 东风雪铁龙东风雪铁龙DONGFENG CITROEN 圣达菲SantaFe 爱丽舍Elysee酷派coupe 毕加索Picasso君爵XG 世嘉quatre特杰Trajet 凯旋triomphe美佳Matrix 大众(上汽)大众(上汽)VW(Shangha i) 雅科仕EQUUS 波罗Polo维拉克斯Veracruz 帕萨特领驭PASSAT悦达起亚起亚KIA 高尔GOL千里马 桑塔纳SANTANA赛拉图CERATO 途安Touran嘉华Carnival 大众(一汽)大众(一汽)faw-volksw agen 远舰Optima 捷达JETTA RIO RIO 宝来BORA索兰托SORENTO 高尔夫Golf佳乐Carens 开迪Caddy狮跑Sportage 速腾 Sagitar Sagitar欧迪玛Optima 迈腾magotan 阿尔法-罗 米欧 阿尔法-罗米欧Alfa Romeo 甲壳虫beetle保时捷保时捷porsche 辉腾Phaeton新款Boxster porsche Boxster 康比Combi卡宴Cayenne VR6VR6卡曼cayman 途锐Touareg宾利宾利Bentley 面包车multivan雅致Arnage 高尔夫Golf GTI欧陆飞驰Continental Flying Spur 辉腾Phaeton大陆Continental GT 东风标致东风标致Dongfeng 大陆Continental
1.试求出圆柱坐标系的尺度系数，并由此导出圆柱坐标系中的导热微分方程。 2 .一无限大平板，初始温度为T 0；τ>0时，在x = 0表面处绝热；在x = L 表面以对流方式向温度为t f 的流体换热。试用分离变量法求出τ>0时平板的温度分布（常物性）。（需求出特征函数、超越方程的具体形式，范数（模）可用积分形式表示）。（15分） , 3.简述近似解析解——积分法中热层厚度δ的概念。 答：近似解析解：既有分析解的特征：得到的结果具有解析函数形式，又有近似解的特征：结果只能近似满足导热解问题。在有限的时间内，边界温度 的变化对于区域温度场的影响只是在某一有限的范围内，把这个有限的范围定义为热层厚度δ。 4.与单相固体导热相比，相变导热有什么特点 答：相变导热包含了相变和导热两种物理过程。相变导热的特点是 1.固、液两相之间存在着 移动的交界面。 2.两相交界面有潜热的释放（或吸收） | 对流部分（所需量和符号自己设定） 1 推导极坐标系下二维稳态导热微分方程。 2 已知绕流平板流动附面层微分方程为 y u y u V x u u 22??=??+??ν 取相似变量为： x u y νη∞ = x u f νψ∞= 写出问题的数学模型并求问题的相似解。 3 已知绕流平板流动换热的附面层能量积分方程为： ?=∞?? =-δ00)(y y t a dy t t u dx d 当Pr<<1时，写出问题的数学模型并求问题的近似积分解及平均Nu （取三次多项式）。 4 ] O x
5写出常热流圆管内热充分发展流动和换热问题的数学模型并求出速度和温度分布及Nu x.辐射 1．请推导出具有n个表面的净热流法壁面间辐射换热求解公式，并简要说明应用任一种数值方法的求解过程。 2．试推导介质辐射传递方程的微分形式和积分形式，要求表述出各个步骤和结果中各个相关量的含义。 3．根据光谱辐射强度表示下面各量：1）光谱定向辐射力；2）定向辐射力；3）光谱辐射力；4）辐射力；5）辐射热流量。要求写清各量的符号、单位。 4．说明下列术语（可用数学表达式）（每题4分） a)光学厚度 b)漫有色表面 c)? d)兰贝特余弦定律 e)光谱散射相函数 f)定向“灰”入射辐射
*作品编号：DG13485201600078972981* 创作者：玫霸* 筠连县分水岭煤业有限责任公司 井 下 高 压 电 缆 热 稳 定 性 校 验 计 算 书 巡司二煤矿
编制：机电科 筠连县分水岭煤业有限责任公司 井下高压电缆热稳定校验计算书 一、概述： 根据《煤矿安全规程》第453条及456条之规定，对我矿入井高压电缆进行热稳定校验。 二、确定供电方式 我矿高压供电采用分列运行供电方式，地面变电所、井下变电所均采用单母线分段分列供电方式运行，各种主要负荷分接于不同母线段。 三、井下高压电缆明细： 矿上有两趟主进线，引至巡司变电站不同母线段，一趟931线，另一趟925线。井下中央变电所由地面配电房10KV输入。 入井一回路：MYJV22-8.7/10KV 3*50mm2--800m(10KV) 入井二回路：MYJV22-8.7/10KV 3*50mm2--800m(10KV) 四、校验计算 1、井下入井回路高压电缆热稳定性校验 已知条件：该条高压电缆型号为，MYJV22-8.7/10KV 3*50mm2 ,800m，电缆长度为800m=0.8km。 （1）计算电网阻抗 查附表一，短路电流的周期分量稳定性为
电抗：X=0.072*0.8=0.0576Ω； 电阻：R=0.407*0.8=0.3256 Ω； (2)三相短路电流的计算 （3）电缆热稳定校验 由于断路器的燃弧时间及固有动作时间之和约为t=0.05S; 查附表二得热稳定计算系数取K=142; 故电缆最小热值稳定截面为 Smin<50mm2故选用 MYJV22 -8.7/10KV 3*50 电缆热稳定校验合格，符合要求。 附表一：三相电缆在工作温度时的阻抗值（Ω/Km）
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2004年上海理工大学硕士研究生入学考试试题考试科目：传热学准考证号：得分： 一、问答题(每题5分) 1. 一无内热源平板沿厚度x方向发生一维稳态导热，其一侧表面上的温度梯度 =30 ℃/m，导热系数λ1=40W/(m.℃)，如果其另一侧表面上的导热系数λ2=50W/(m.℃)，问这一侧表面上的温度梯度是多少? 2. 解释毕渥准则数Bi的物理含义，并说明为什么用Bi判别非稳态导热问题能否采用集总参数法求解。 3. 图1.1示出了常物性、有均匀内热源、二维稳态导热问题局部边界区域的网格配置，试用元体平衡法建立节点0关于温度t的有限差分方程式（设 ，所需参数的符号自己设定）。 4. 当条件相同时，物体在空气中冷却快还是在水中冷却快？这一现象说明对流换热与什么因素相关？ 5. 试用简图表示流体沿平板流动时速度边界层的发展并说明速度边界层内分成哪些区域？ 6. 试解释普朗特数Pr的物理意义,并示意性的画出Pr>1时的速度边界层和热边界层厚度沿板长的变化(速度边界层和热边界层要画在同一图上以便比较)。 7. 说明温度附面层的概念及附面层能量微分方程在物理上忽略了哪部分换热。 8. 在应用管内旺盛紊流实验关联式时，当流体与换热壁面温差较大时需要对计算结果修正，为什么? 9. 试说明为什么一个细长圆柱水平放置时自然对流换热一般大于竖直放置时的自然对流换热？ 10.在稳定膜态沸腾过程中，为什么换热系数随 增加而迅速上升？
11.试说明大气中CO2含量增高为什么会出现大气温室效应？ 二、计算题 1. （10分）一直径为5cm的钢球，其初始温度为500℃，突然被置于温度为 30℃的空气中。设钢球表面与周围环境的对流换热系数为10 W/m2℃，试计算钢球非稳态导热的时间常数及其被冷却到300℃所需的时间。已知钢球的比热为c=0.48kJ/kg℃, ρ=7753kg/m3, λ=33W/m℃。 2. （20分）长10m、外径133mm的水平管道通过一大房间，房间壁面及其内 的空气温度均为30℃。若管道表面温度为90℃、黑度为0.9，求管道的散 热量（自然对流换热的努塞尔特数用下式计算）。3. （22分）如图2所示为一半径R=1m的半球，球冠3绝热。底面1和2的 温度分别为500℃和100℃，黑度都为0.9，求底面1和2间的辐射散热量。 4. （23分）温度为95℃的热空气流经一内径100mm、厚度6mm的圆管，管 壁导热系数为22 W/m℃。管外环境温度为30℃，管外壁与环境的总换热系数为10 W/m2℃。若管内空气质量流量为407kg/h，求管出口空气温度降低到65℃时的管长(不需考虑修正)。 三、理论题 1.（8分）一厚度为2δ的无内热源薄平板，其导热系数和初始温度分别为 λ和t0，突然被插在温度为t f的流体中。平板表面与流体的换热系数为h，给出问题的完整数学描述。 2. （12分）绕流平板换热的附面层积分方程为： 平板温度为t W，来流速度和温度分别为u∞和t∞，若Pr<<1，可以忽略速
案例--变电所母线桥的动稳定校验 朱时光修改 下面以35kV/10kv某变电所#2主变增容为例来谈谈如何进行主变母线桥的动稳定校验和校验中应注意的问题。 1短路电流计算 图1为某变电所的系统主接线图。(略) 已知#1主变容量为10000kVA，短路电压为7.42%，#2主变容量原为1000为kVA 增容为12500kVA，短路电压为7.48%。 取系统基准容量为100MVA，则#1主变短路电压标么值 X1＝7.42/100×100×1000/10000＝0.742， #2主变短路电压标么值 X2＝7.48/100×100×1000/12500＝0.5984 假定某变电所最大运行方式系统到35kV母线上的电抗标么值为0.2778。 ∴#1主变与#2主变的并联电抗为： X12=X1×X2/(X1+X2)＝0.33125； 最大运行方式下系统到10kV母线上的组合电抗为： X＝0.2778+0.33125＝0.60875 ∴10kV母线上的三相短路电流为：Id=100000/0.60875*√3*10.5=9.04KA，冲击电流：I s h=2.55I d=23.05KA。 2动稳定校验
(1)10kV母线桥的动稳定校验： 进行母线桥动稳定校验应注意以下两点： ①电动力的计算，经过对外边相所受的力，中间相所受的力以及三相和二相电动力进行比较，三相短路时中间相所受的力最大，所以计算时必须以此为依据。 ②母线及其支架都具有弹性和质量，组成一弹性系统，所以应计算应力系数，计及共振的影响。 根据以上两点，校验过程如下： 已知母线桥为8×80mm2的铝排，相间中心线间距离A为210mm，先计算应力系数： 6Kg/Cm2， ∵频率系数N f＝3.56，弹性模量E＝0.71×10 -4kg.s2/cm2，绝缘子间跨距2m， 单位长度铝排质量M＝0.176X10 截面惯性矩J=bh3/12=34.13c m4或取惯性半径（查表）与母线截面的积， ∵三相铝排水平布置，∴截面系数W＝bh2/6＝8.55Cm3， 则一阶固有频率: f0=(3.56/L2)*√(EJ/M)=104(Hz) 查表可得动态应力系数β＝1.33。 ∴铝母排所受的最大机械应力为： σMAX＝1.7248×10-3I s h2（L2/Aw）×β＝270.35 kg/c m2<σ允许=500 根据铝排的最大应力可确定绝缘子间允许的最大跨距为：（简化公式可查表） L MAX=1838√a/ I s h=366(c m) ∵某变主变母线桥绝缘子间最大跨距为2m，小于绝缘子间的最大允许跨距。
K14B利亚纳维修手册 （电喷系统） 德尔福MT22.1发动机管理系统 目录 1.2. 系统功能介绍 ............................................................................................................................................. 2.3.电子节流阀体功能限制模式 ....................................................................................................................... 3.8．油压调节器 ................................................................................................................................................ 4.2. 故障指示灯（MI）说明 (18) 5.1. 燃油及润滑油 (29)
6.2. 发动机故障指示灯 .....................................................................................................................................
1. 系统介绍 1.1. 系统特点 K14B利亚纳的德尔福MT22.1发动机管理系统基于扭矩和电子节气门控制，其特征是电脑闭环控制、多点燃油顺序喷射、无分电器顺序点火和三元催化器后处理。 系统主要功能包括： - 发动机气体热力学空气流量及温度计算； - 发动机扭矩输出控制模式； - 整车主电源继电器控制； - 闭环控制多点燃油顺序喷射； -无回油供油方式的控制； - 燃油油泵工作控制； - ECM内置点火驱动模块，无分电器式顺序点火； - 点火模式为顺序点火； - 线性EGR控制(选用)； - 爆震控制； - 电子节气门控制控制； - 即插即用式空调控制； - 冷却液箱风扇控制； - 碳罐电磁阀控制； - 系统自诊断功能； - 过电压保护； - 即插即用式ECM防盗控制(防盗器需经德尔福认证)； 1.2. 系统功能介绍 发动机气体热力学模型空气流量计算 ECM通过进气温度压力传感器对进入气缸的空气流量进行计算，并通过控制供油量，使空燃比符合各工况的要求。 扭矩控制模式 系统根据油门踏板位置传感器，估算输出扭矩，对发动机的输出动力进行控制。 曲轴位置基准及转速测量 系统根据曲轴位置传感器信号判断曲轴位置及测量发动机转速，精确控制发动机点火及喷油正时。发动机各缸工作顺序判断
2020年传热学考研大纲——上海理工大学材料科 学与工程学院 传热学A《传热学》杨世铭、陶文铨，高等教育出版社，2006年 二、基本要求 1.掌握热量传递的三种方式(导热、对流和辐射)的基本概念和基本定律; 2.能够对常见的导热、对流、辐射换热及传热过程进行定量的计算，并了解其物理机理和特点，进行定性分析; 3.对典型的传热现象能进行分析，建立合适的数学模型并求解; 4.能够用差分法建立导热问题的数值离散方程，并了解其计算机求解过程。 三、主要知识点 第一章绪论：热量传递的三种基本方式;导热、对流和热辐射的基本概念和初步计算公式;热阻;传热过程和传热系数。 第二章导热基本定律和稳态导热：温度场、温度梯度;傅里叶定律和导热系数;导热微分方程、初始条件与边界条件;单层及多层平壁的导热;单层及多层圆筒壁的导热;通过肋端绝热的等截面直肋的导热;肋效率;一维变截面导热;有内热源的一维稳态导热。 第三章非稳态导热：非稳态导热的基本概念;集总参数法;描述非稳态导热问题的数学模型(方程和定解条件); 第四章导热问题的数值解法：导热问题数值解法的基本思想;用差分法建立稳态导热问题的数值离散方程。 第五章对流换热：对流换热的主要影响因素和基本分类、牛顿冷却公式和对流换热系数的主要影响因素;速度边界层和热边界层的概念;横掠平板层流换热边界层的微分方程组;横掠平板层流换热边界
层积分方程组;动量传递和热量传递比拟的概念;相似的概念及相似 准则;管槽内强制对流换热特征及用实验关联式计算;绕流单管、管 束对流换热特征及用实验关联式计算;大空间自然对流换热特征及对流换热特征及用实验关联式计算。 第六章凝结与沸腾换热：凝结与沸腾换热的基本概念;珠状凝结与膜状凝结特点;膜状凝结换热计算;影响膜状凝结的因素;大容器饱和沸腾曲线;影响沸腾换热的因素。 第七章热辐射基本定律及物体的辐射特性：热辐射的基本概念;黑体、白体、透明体;辐射力与光谱辐射力;定向辐射强度;黑体辐射基本定律：普朗克定律，维恩定律，斯忒藩—玻尔兹曼定律，兰贝 特定律;实际固体和液体的辐射特性、黑度;灰体、基尔霍夫定律。 第八章辐射换热的计算：角系数的概念、性质、计算;两固体表面组成的封闭系统的辐射换热计算;表面热阻;空间热阻;多表面系统辐射换热的网络法计算;辐射换热的强化与削弱、遮热板;辐射换热 系数和复合换热表面传热系数;气体辐射特点。 第九章传热过程分析与换热器计算：传热过程及传热系数的计算;临界绝热直径;换热器型式及对数平均温差;用平均温差法进行换热 器的热计算;换热器效能ε的概念和定义;强化传热。
都是需要考虑的，特别是母桥距离比较长的时候。需要计算出现短路故障时的电动力，绝缘子类固定件的安装距离、绝缘子安装件的抗屈服力等。不很少有人会特别计算，我感觉是大家都自觉不自觉的把母线规格放大了，所以基本上不用计算。 4 母线的热效应和电动力效应 4.1母线的热效应 4.1.1母线的热效应是指母线在规定的条件下能够承载的因电流流过而产生的热效应。在开关设备和控制设备中指在规定的使用和性能条件下，在规定的时间内,母线承载的额定短时耐受电流（IK）。 4.1.2根据额定短时耐受电流来确定母线最小截面 根据GB3906-1991《3.6-40.5kV交流金属封闭开关设备和控制设备》[附录F]中公式：S=（I/a）(t/△θ)1/2来确定母线的最小截面。 式中： S—母线最小截面,mm2； I--额定短时耐受电流，A； a—材质系数，铜为13，铝为8.5； t--额定短路持续时间，s； △θ—温升（K）,对于裸导体一般取180K，对于4s持续时间取215K。 如对于31.5kA/4S系统,选用铜母线最小截面积为： S=（31500/13）×（4/215）1/2=330 mm2 铝母线最小截面积与铜母线最小截面积关系为： SAl=1.62SCu 式中, SAl为铝母线的最小截面积；SCu为铜母线的最小截面积。 如对于31.5kA/4S系统,铝母线最小截面积为： SAl=1.62×330 =540 mm2 根据DL404-1997《户内交流高压开关柜订货技术条件》中7.4.3条规定，接地汇流排以及与之连接的导体截面，应能通过铭牌额定短路开断电流的87%，可以计算出各种系统短路容量下（短路时间按4S）的接地母线最小截面积。 如对于31.5kA/4S系统,接地铜母线最小截面积为： S=330×86.7% =287mm2 根据以上公式计算，对应各种额定短时耐受电流时，开关设备和控制设备中对应几种常用的额定短时耐受电流，母线最小截面及所用铜母线和铝母线的最小规格见表1： 表1 母线kA/4s 25 31.5 40 63 80 设备中铜母线规格50×6 60×6 80×6或60×8 80×10 100×10 接地铜母线规格50×5 50×6 50×8 80×8 80×10 设备中铝母线规格80×6或60×8 80×8 100×8或80×10 设备中铜母线 最小截面（mm2）260 330 420 660 840 设备中铝母线 最小截面（mm2）425 540 685 1075 1365 4.2 母线的电动力效应 母线是承载电流的导体，当有电流流过时势必在母线上产生作用力。母线受电流的作用力与
2004年上海理工大学硕士研究生入学考试试题 考试科目：传热学准考证号：得分： 一、问答题(每题5分) 1. 一无内热源平板沿厚度x方向发生一维稳态导热，其一侧表面上的温度梯度=30 ℃/m，导热系数λ1=40W/(m.℃)，如果其另一侧表面上的导热系数λ2=50W/(m.℃)，问这一侧表面上的温度梯度是多少? 2. 解释毕渥准则数Bi的物理含义，并说明为什么用Bi判别非稳态导热问题能否采用集总参数法求解。 3. 图1.1示出了常物性、有均匀内热源、二维稳态导热问题局部边界区域的网格配置，试用元体平衡法建立节点0关于温度t的有限差分方程式（设，所需参数的符号自己设定）。 4. 当条件相同时，物体在空气中冷却快还是在水中冷却快？这一现象说明对流换热与什么因素相关？ 5. 试用简图表示流体沿平板流动时速度边界层的发展并说明速度边界层内分成哪些区域？ 6. 试解释普朗特数Pr的物理意义,并示意性的画出Pr>1时的速度边界层和热边界层厚度沿板长的变化(速度边界层和热边界层要画在同一图上以便比较)。 7. 说明温度附面层的概念及附面层能量微分方程在物理上忽略了哪部分换热。
8. 在应用管内旺盛紊流实验关联式时，当流体与换热壁面温差较大时需要对计算结果修正，为什么? 9. 试说明为什么一个细长圆柱水平放置时自然对流换热一般大于竖直放置时的自然对流换热？ 10.在稳定膜态沸腾过程中，为什么换热系数随增加而迅速上升？ 11.试说明大气中CO2含量增高为什么会出现大气温室效应？ 二、计算题 1. （10分）一直径为5cm的钢球，其初始温度为500℃，突然被置于温度为30℃的空 气中。设钢球表面与周围环境的对流换热系数为10 W/m2℃，试计算钢球非稳态导热 的时间常数及其被冷却到300℃所需的时间。已知钢球的比热为c=0.48kJ/kg℃, ρ =7753kg/m3, λ=33W/m℃。 2. （20分）长10m、外径133mm的水平管道通过一大房间，房间壁面及其内的空气温 度均为30℃。若管道表面温度为90℃、黑度为0.9，求管道的散热量（自然对流换 热的努塞尔特数用下式计算）。 3. （22分）如图2所示为一半径R=1m的半球，球冠3绝热。底面1和2的温度分别为 500℃和100℃，黑度都为0.9，求底面1和2间的辐射散热量。 4. （23分）温度为95℃的热空气流经一内径100mm、厚度6mm的圆管，管壁导热系数 为22 W/m℃。管外环境温度为30℃，管外壁与环境的总换热系数为10 W/m2℃。若
02年传热学课程考试题 学 校 系 别 考试时间 150分钟 专业班号 考试日期 年 月 日 姓 名 学号 一、问答题 (42分，每小题7分) 1． 图1示出了常物性、有均匀内热源 、二导热问题局部边界区域的网格配置，试用热平衡法建立节点0的有限差分方程式（设?=?x y ）。 2 ． 蒸气与温度低于饱和温度的壁面接触时，有哪两种不同的凝结形式？产生不同凝结形式的原因是什么？ 3． 有人说：“常温下呈红色的物体表示该物体在常温下红色光的光谱发射率较其它单色光（黄、绿、蓝等）的光谱发射率高”。你认为这种说法正确吗？为什么？ 4． 一块厚度为2()δδδ-≤≤x 的大平板，与温度为f t 的流体处于热平衡。当时间0τ>时，左侧流体温度升高并保持为恒定温度2f t 。假定平板两侧表面传热系数相同，当 0δλ =→h Bi 时，试确定达到新的稳态时平板中心及两侧表面的温度，画出相应的板 内及流体侧温度分布的示意性曲线，并做简要说明。 5． 有人说，在电子器件的多种冷却方式中，自然对流是一种最可靠（最安全）、最经济、无污染（噪音也是一种污染）的冷却方式。试对这一说法作出评价，并说明这种冷却方式有什么不足之处？有什么方法可作一定程度的弥补？ 6． 强化空气－水换热器传热的主要途径有哪些，请列出任意三种途径？ ? Φ
二、计算题 (58分) 1．(18分) 一块大平板，厚度5cm δ=，有内热源? Φ，平板中的一维稳态温度分布为 2=+t b cx ，式中o 200C =b ，2200K/m =-c 。假定平板的导热系数50W/(m K)λ= ，试确定： （1） 平板中内热源? Φ之值； （2） 0=x 和δ=x 边界处的热流密度。 2．(15分) 有一圆柱体，如图2所示，表面1温度1550K =T ，发射率10.8ε=，表面2温度2275K =T ，发射率20.4ε=，圆柱面3为绝热表面，角系数3,10.308=X 。求：（1）表面1的净辐射损失；（2）绝热面3的温度。 3．(25分) 为了得到热水，0.361 MPa (t s =140℃) 的水蒸气在管外凝结（如图3所示），其表面传热系数29500W/(m K)= o h 。冷却水在盘管内流动，流速为0.8m/s ，黄铜管外径为18mm ，壁厚为1.5mm ，导热系数为132W/(m K)λ= ，盘管的弯曲半径为90mm 。冷水进换热器时的温度为o 25C ，加热到o 95C 。试求所需的换热面积及盘管长度。不计管内入口效应修正及温差修正。 附注： (1) 管内湍流强制对流换热实验关联式为： n f f Pr Re Nu 8.0023.0= (流体被加热n =0.4；流体被冷却n =0.3) (2) 60o C 时水的物性：ρ＝983.1 kg/m 3, c p =4.179 kJ/(kg ?K)，λ=65.9×10-2 W/(m ?K)， ν=0.478×10-6 m 2/s ， Pr =2.99； (3) 弯管修正系数：3)(3.101R d c R += 图 3 饱和蒸气 冷 "53.6110Pa =?s 图2
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