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1.
B. Tong Z. -C. Tan X. C. Lv L. X. Sun F. Xu Q. Shi Y. S. Li 《Journal of Thermal Analysis and Calorimetry》2007,90(1):217-221
The molar heat capacities C
p,m of 2,2-dimethyl-1,3-propanediol were measured in the temperature range from 78 to 410 K by means of a small sample automated
adiabatic calorimeter. A solid-solid and a solid-liquid phase transitions were found at T-314.304 and 402.402 K, respectively, from the experimental C
p-T curve. The molar enthalpies and entropies of these transitions were determined to be 14.78 kJ mol−1, 47.01 J K−1 mol− for the solid-solid transition and 7.518 kJ mol−1, 18.68 J K−1 mol−1 for the solid-liquid transition, respectively. The dependence of heat capacity on the temperature was fitted to the following
polynomial equations with least square method. In the temperature range of 80 to 310 K, C
p,m/(J K−1 mol−1)=117.72+58.8022x+3.0964x
2+6.87363x
3−13.922x
4+9.8889x
5+16.195x
6; x=[(T/K)−195]/115. In the temperature range of 325 to 395 K, C
p,m/(J K−1 mol−1)=290.74+22.767x−0.6247x
2−0.8716x
3−4.0159x
4−0.2878x
5+1.7244x
6; x=[(T/K)−360]/35. The thermodynamic functions H
T−H
298.15 and S
T−S
298.15, were derived from the heat capacity data in the temperature range of 80 to 410 K with an interval of 5 K. The thermostability
of the compound was further tested by DSC and TG measurements. The results were in agreement with those obtained by adiabatic
calorimetry. 相似文献
2.
B. Tong Z. C. Tan J. N. Zhang S. X. Wang 《Journal of Thermal Analysis and Calorimetry》2009,95(2):469-475
The low-temperature heat capacity C
p,m of erythritol (C4H10O4, CAS 149-32-6) was precisely measured in the temperature range from 80 to 410 K by means of a small sample automated adiabatic
calorimeter. A solid-liquid phase transition was found at T=390.254 K from the experimental C
p-T curve. The molar enthalpy and entropy of this transition were determined to be 37.92±0.19 kJ mol−1 and 97.17±0.49 J K−1 mol−1, respectively. The thermodynamic functions [H
T-H
298.15] and [S
T-S
298.15], were derived from the heat capacity data in the temperature range of 80 to 410 K with an interval of 5 K. The standard
molar enthalpy of combustion and the standard molar enthalpy of formation of the compound have been determined: Δc
H
m0(C4H10O4, cr)= −2102.90±1.56 kJ mol−1 and Δf
H
m0(C4H10O4, cr)= − 900.29±0.84 kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. DSC and TG measurements were performed to study the thermostability of the compound. The results were in agreement
with those obtained from heat capacity measurements. 相似文献
3.
I. E. Paukov Yulia A. Kovalevskaya Elena V. Boldyreva 《Journal of Thermal Analysis and Calorimetry》2008,93(2):423-428
Heat capacity C
p(T) of the orthorhombic polymorph of L-cysteine was measured in the temperature range 6–300 K by adiabatic calorimetry; thermodynamic functions were calculated
based on these measurements. At 298.15 K the values of heat capacity, C
p; entropy, S
m0(T)-S
m0(0); difference in the enthalpy, H
m0(T)-H
m0(0), are equal, respectively, to 144.6±0.3 J K−1 mol−1, 169.0±0.4 J K−1 mol−1 and 24960±50 J mol−1. An anomaly of heat capacity near 70 K was registered as a small, 3–5% height, diffuse ‘jump’ accompanied by the substantial
increase in the thermal relaxation time. The shape of the anomaly is sensitive to thermal pre-history of the sample. 相似文献
4.
J. Leitner K. Růžička D. Sedmidubský P. Svoboda 《Journal of Thermal Analysis and Calorimetry》2009,95(2):397-402
Heat capacity and enthalpy increments of calcium niobates CaNb2O6 and Ca2Nb2O7 were measured by the relaxation time method (2–300 K), DSC (260–360 K) and drop calorimetry (669–1421 K). Temperature dependencies
of the molar heat capacity in the form C
pm=200.4+0.03432T−3.450·106/T
2 J K−1 mol−1 for CaNb2O6 and C
pm=257.2+0.03621T−4.435·106/T
2 J K−1 mol−1 for Ca2Nb2O7 were derived by the least-squares method from the experimental data. The molar entropies at 298.15 K, S
m0(CaNb2O6, 298.15 K)=167.3±0.9 J K−1 mol−1 and S
m0(Ca2Nb2O7, 298.15 K)=212.4±1.2 J K−1 mol−1, were evaluated from the low temperature heat capacity measurements. Standard enthalpies of formation at 298.15 K were derived
using published values of Gibbs energy of formation and presented heat capacity and entropy data: Δf
H
0(CaNb2O6, 298.15 K)= −2664.52 kJ molt-1 and Δf
H
0(Ca2Nb2O7, 298.15 K)= −3346.91 kJ mol−1. 相似文献
5.
Lebedev B. V. Bykova T. A. Lobach A. S. 《Journal of Thermal Analysis and Calorimetry》2000,62(1):257-265
The temperature dependence of the molar heat capacity (C0
p) of hydrofullerene C60H36 between 5 and 340 K was determined by adiabatic vacuum calorimetry with an error of about 0.2%. The experimental data were
used for the calculation of the thermodynamic functions of the compound in the range 0 to340 K. It was found that at T=298.15 K and p=101.325 kPa C0
p (298.15)=690.0 J K−1 mol−1,Ho(298.15)−Ho(0)= 84.94 kJ mol−1,So(298.15)=506.8 J K−1 mol−1, Go(298.15)−Ho(0)= −66.17 kJ mol−1. The standard entropy of formation of hydrofullerene C60H36 and the entropy of reaction of its formation by hydrogenation of fullerene C60 with hydrogen were estimated and at T=298.15 K they were ΔfSo= −2188.4 J K−1 mol−1 and ΔrSo= −2270.5 J K−1mol−1, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Molar heat capacity and thermodynamic properties of 1,2-cyclohexane dicarboxylic anhydride [C8H10O3]
X. -C. Lv X. -H. Gao Z. -C. Tan Y. -S. Li L. -X. Sun 《Journal of Thermal Analysis and Calorimetry》2008,92(2):523-527
The molar heat capacity C
p,m of 1,2-cyclohexane dicarboxylic anhydride was measured in the temperature range from T=80 to 390 K with a small sample automated adiabatic calorimeter. The melting point T
m, the molar enthalpy Δfus
H
m and the entropy Δfus
S
m of fusion for the compound were determined to be 303.80 K, 14.71 kJ mol−1 and 48.43 J K−1 mol−1, respectively. The thermodynamic functions [H
T-H
273.15] and [S
T-S
273.15] were derived in the temperature range from T=80 to 385 K with temperature interval of 5 K. The thermal stability of the compound was investigated by differential scanning
calorimeter (DSC) and thermogravimetry (TG), when the process of the mass-loss was due to the evaporation, instead of its
thermal decomposition. 相似文献
7.
J. N. Zhang Z. C. Tan Q. F. Meng Q. Shi B. Tong S. X. Wang 《Journal of Thermal Analysis and Calorimetry》2009,95(2):461-467
The heat capacities (C
p,m) of 2-amino-5-methylpyridine (AMP) were measured by a precision automated adiabatic calorimeter over the temperature range
from 80 to 398 K. A solid-liquid phase transition was found in the range from 336 to 351 K with the peak heat capacity at
350.426 K. The melting temperature (T
m), the molar enthalpy (Δfus
H
m0), and the molar entropy (Δfus
S
m0) of fusion were determined to be 350.431±0.018 K, 18.108 kJ mol−1 and 51.676 J K−1 mol−1, respectively. The mole fraction purity of the sample used was determined to be 0.99734 through the Van’t Hoff equation.
The thermodynamic functions (H
T-H
298.15 and S
T-S
298.15) were calculated. The molar energy of combustion and the standard molar enthalpy of combustion were determined, ΔU
c(C6H8N2,cr)= −3500.15±1.51 kJ mol−1 and Δc
H
m0 (C6H8N2,cr)= −3502.64±1.51 kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. The standard molar enthalpy of formation of the crystalline compound was derived, Δr
H
m0 (C6H8N2,cr)= −1.74±0.57 kJ mol−1. 相似文献
8.
Z. H. Zhang L. X. Sun Z. C. Tan F. Xu X. C. Lv J. L. Zeng Y. Sawada 《Journal of Thermal Analysis and Calorimetry》2007,89(1):289-294
The molar heat capacities of the room temperature ionic liquid 1-butylpyridinium tetrafluoroborate (BPBF4) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity
on temperature is given as a function of the reduced temperature X by polynomial equations, C
p,m [J K−1 mol−1]=181.43+51.297X −4.7816X
2−1.9734X
3+8.1048X
4+11.108X
5 [X=(T−135)/55] for the solid phase (80–190 K), C
p,m [J K−1 mol−1]= 349.96+25.106X+9.1320X
2+19.368X
3+2.23X
4−8.8201X
5 [X=(T−225)/27] for the glass state (198–252 K), and C
p,m[J K−1 mol−1]= 402.40+21.982X−3.0304X
2+3.6514X
3+3.4585X
4 [X=(T−338)/52] for the liquid phase (286–390 K), respectively. According to the polynomial equations and thermodynamic relationship,
the values of thermodynamic function of the BPBF4 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition
of BPBF4 was observed at 194.09 K, the enthalpy and entropy of the glass transition were determined to be ΔH
g=2.157 kJ mol−1 and ΔS
g=11.12 J K−1 mol−1, respectively. The result showed that the melting point of the BPBF4 is 279.79 K, the enthalpy and entropy of phase transition were calculated to be ΔH
m = 8.453 kJ mol−1 and ΔS
m=30.21 J K−1 mol−1. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BPBF4 was determined to be Δc
H
m0 = −5451±3 kJ mol−1. The standard molar enthalpy of formation of BPBF4 was evaluated to be Δf
H
m0 = −1356.3±0.8 kJ mol−1 at T=298.150±0.001 K. 相似文献
9.
J. Leitner M. Hampl K. Růžička M. Straka D. Sedmidubský P. Svoboda 《Journal of Thermal Analysis and Calorimetry》2008,91(3):985-990
The heat capacity and the enthalpy increments of strontium metaniobate SrNb2O6 were measured by the relaxation method (2-276 K), micro DSC calorimetry (260-320 K) and drop calorimetry (723-1472 K). Temperature
dependence of the molar heat capacity in the form C
pm=(200.47±5.51)+(0.02937±0.0760)T-(3.4728±0.3115)·106/T
2 J K−1 mol−1 (298-1500 K) was derived by the least-squares method from the experimental data. Furthermore, the standard molar entropy
at 298.15 K S
m0 (298.15 K)=173.88±0.39 J K−1 mol−1 was evaluated from the low temperature heat capacity measurements. The standard enthalpy of formation Δf
H
0 (298.15 K)=-2826.78 kJ mol−1 was derived from total energies obtained by full potential LAPW electronic structure calculations within density functional
theory. 相似文献
10.
M. Hampl J. Leitner K. Růžička M. Straka P. Svoboda 《Journal of Thermal Analysis and Calorimetry》2007,87(2):553-556
The heat capacity and the heat content of
bismuth niobate BiNb5O14 were
measured by the relaxation time method, DSC and drop method, respectively.
The temperature dependence of heat capacity in the form C
pm=455.84+0.06016T–7.7342·106/T
2 (J K–1
mol–1) was derived by the least squares method
from the experimental data. Furthermore, the standard molar entropy at 298.15
K S
m=397.17 J K–1
mol–1 was derived from the low temperature
heat capacity measurement. 相似文献
11.
I. E. Paukov Yulia A. Kovalevskaya Irina A. Kiseleva Tatiana N. Shuriga 《Journal of Thermal Analysis and Calorimetry》2010,99(2):709-712
Low-temperature heat capacity of natural zinnwaldite was measured at temperatures from 6 to 303 K in a vacuum adiabatic calorimeter.
An anomalous behavior of heat capacity function C
p(T) has been revealed at very low temperatures, where this function does not tend to zero. Thermodynamic functions of zinnwaldite
have been calculated from the experimental data. At 298.15 K, heat capacity C
p(T) = 339.8 J K−1mol−1, calorimetric entropy S
o(Т) – S
o(6.08) = 329.1 J K−1 mol−1, and enthalpy Н
o(Т) − Н
o(6.08) = 54,000 J mol−1. Heat capacity and thermodynamic functions at 298.15 K for zinnwaldite having theoretical composition were estimated using
additive method of calculation. 相似文献
12.
Z. H. Zhang T. Cui J. L. Zhang H. Xiong G. P. Li L. X. Sun F. Xu Z. Cao F. Li J. J. Zhao 《Journal of Thermal Analysis and Calorimetry》2010,101(3):1143-1148
The molar heat capacities of the room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluoroborate (BMIPF6) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity
on temperature is given as a function of the reduced temperature (X) by polynomial equations, C
P,m (J K−1 mol−1) = 204.75 + 81.421X − 23.828 X
2 + 12.044X
3 + 2.5442X
4 [X = (T − 132.5)/52.5] for the solid phase (80–185 K), C
P,m (J K−1 mol−1) = 368.99 + 2.4199X + 1.0027X
2 + 0.43395X
3 [X = (T − 230)/35] for the glass state (195 − 265 K), and C
P,m (J K−1 mol−1) = 415.01 + 21.992X − 0.24656X
2 + 0.57770X
3 [X = (T − 337.5)/52.5] for the liquid phase (285–390 K), respectively. According to the polynomial equations and thermodynamic relationship,
the values of thermodynamic function of the BMIPF6 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition
of BMIPF6 was measured to be 190.41 K, the enthalpy and entropy of the glass transition were determined to be ΔH
g = 2.853 kJ mol−1 and ΔS
g = 14.98 J K−1 mol−1, respectively. The results showed that the milting point of the BMIPF6 is 281.83 K, the enthalpy and entropy of phase transition were calculated to be ΔH
m = 20.67 kJ mol−1 and ΔS
m = 73.34 J K−1 mol−1. 相似文献
13.
Igor E. Paukov Yulia A. Kovalevskaya Alexei E. Arzamastcev Natalia A. Pankrushina Elena V. Boldyreva 《Journal of Thermal Analysis and Calorimetry》2012,108(1):243-247
Heat capacity of methacetin (N-(4-methoxyphenyl)-acetamide) has been measured in the temperature range 5.8–300 K. No anomalies in the C
p(T) dependence were observed. Thermodynamic functions were calculated. At 298.15 K, the values of entropy and enthalpy are equal
to 243.1 J K−1 mol−1 and 36360 J mol−1, respectively. The heat capacity of methacetin in the temperature range 6–10 K is well fitted by Debye equation C
p = AT
3. The thermodynamic data obtained for methacetin are compared with those for the monoclinic and orthorhombic polymorphs of
paracetamol. 相似文献
14.
Z. H. Zhang Z. C. Tan Y. S. Li L. X. Sun 《Journal of Thermal Analysis and Calorimetry》2006,85(3):551-557
The molar heat capacities of the room temperature
ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4)
were measured by an adiabatic calorimeter in temperature range from 80 to
390 K. The dependence of the molar heat capacity on temperature is given as
a function of the reduced temperature X
by polynomial equations, C
P,m
(J K–1 mol–1)=
195.55+47.230 X–3.1533 X
2+4.0733 X
3+3.9126 X
4 [X=(T–125.5)/45.5] for the solid phase (80~171
K), and C
P,m (J
K–1 mol–1)=
378.62+43.929 X+16.456 X
2–4.6684 X
3–5.5876 X
4 [X=(T–285.5)/104.5] for the liquid phase (181~390
K), respectively. According to the polynomial equations and thermodynamic
relationship, the values of thermodynamic function of the BMIBF4
relative to 298.15 K were calculated in temperature range from 80 to 390 K
with an interval of 5 K. The glass translation of BMIBF4
was observed at 176.24 K. Using oxygen-bomb combustion calorimeter, the molar
enthalpy of combustion of BMIBF4 was determined to
be Δc
H
m
o=
– 5335±17 kJ mol–1. The standard
molar enthalpy of formation of BMIBF4 was evaluated
to be Δf
H
m
o=
–1221.8±4.0 kJ mol–1 at T=298.150±0.001 K. 相似文献
15.
The heat capacity of crystalline α-platinum dichloride was measured for the first time in the temperature intervals from 11
to 300 K (vacuum adiabatic microcalorimeter) and from 300 to 620 K (differential scanning calorimetry). In the 300–620 K temperature
interval, the C°
p
values for α-PtCl2 (cr) coincide with the heat capacity of CrCl2 (cr) within the limits of experimental error, which made it possible to estimate the heat capacity of α-PtCl2 (cr) at higher temperatures. The approximating equation of the temperature dependence of the heat capacity in the interval
from 298 to 900 K C°
p
(±0.8) = 63.5 + 21.4·10−3
T + 0.883·105/T
2 (J mol−1 K−1) was derived using the experimental values, as well as the literature data on the heat capacity of CrCl2 (cr). For the standard conditions, the C°
p,298.15 and S°298.15 values are 70.92±0.08 and 100.9±0.33 J mol−1 K, respectively; H°298.15 − H°0 = 14 120±42 J mol−1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1136–1138, June, 2008. 相似文献
16.
Ju-Lan Zeng Sai-Bo Yu Bo Tong Li-Xian Sun Zhi-Cheng Tan Zhong Cao Dao-Wu Yang Jing-Nan Zhang 《Journal of Thermal Analysis and Calorimetry》2011,103(3):1087-1093
An N-tert-butyloxycarbonylated organic synthesis intermediate, (S)-tert-butyl 1-phenylethylcarbamate, was prepared and investigated by means of differential scanning calorimetry (DSC) and thermogravimetry
(TG). The molar heat capacities of (S)-tert-butyl 1-phenylethylcarbamate were precisely determined by means of adiabatic calorimetry over the temperature range of 80-380 K.
There was a solid–liquid phase transition exhibited during the heating process with the melting point of 359.53 K. The molar
enthalpy and entropy of this transition were determined to be 29.73 kJ mol−1 and 82.68 J K−1 mol−1 based on the experimental C
p–T curve, respectively. The thermodynamic functions, [HT0 - H298.150 H_{T}^{0} - H_{298.15}^{0} ] and [ST0 - S298.150 S_{T}^{0} - S_{298.15}^{0} ], were calculated from the heat capacity data in the temperature range of 80–380 K with an interval of 5 K. TG experiment
showed that the pyrolysis of the compound was started at the temperature of 385 K and terminated at 510 K within one step. 相似文献
17.
Zhi-Heng Zhang Guo-Yin Yin Zhi-Cheng Tan Yan Yao Li-Xian Sun 《Journal of solution chemistry》2006,35(10):1347-1355
The molar heat capacities of an aqueous Li2B4O7 solution were measured with a precision automated adiabatic calorimeter in the temperature range from 80 to 356 K at a concentration of 0.3492 mol⋅kg−1. The occurrence of a phase transition was determined based on the changes in the curve of the heat capacity with temperature. A phase transition was observed at 271.72 K corresponding to the solid-liquid phase transition; the enthalpy and entropy of the phase transition were evaluated to be Δ H
m = 4.110 kJ⋅mol−1 and Δ S
m = 15.13 J⋅K−1⋅mol−1, respectively. Using polynomial equations and thermodynamic relationship, the thermodynamic functions [H
T
−H
298.15] and [S
T
−S
298.15] of the aqueous Li2B4O7 solution relative to 298.15 K were calculated in temperature range 80 to 355 K at intervals of 5 K. Values of the relative apparent molar heat capacities of the aqueous Li2B4O7 solution, C
p,φ, were calculated at every 5 K in temperature range from 80 to 355 K from the experimental heat capacities of the solution and the heat capacities of pure water. 相似文献
18.
L. Abate E. Badea I. Blanco D. D’Angelo G. Della Gatta 《Journal of Thermal Analysis and Calorimetry》2007,90(2):575-580
Molar heat capacities of twelve linear alkane-α,ω-diamides H2NOC-(CH2)(n-2)-CONH2, (n=2 to 12 and n=14) were measured by differential scanning calorimetry at T=183 to 323 K. Heat flow rate calibration of the Mettler DSC 30 calorimeter was carried out by using benzoic acid as reference
material. The calibration was checked by determining the molar heat capacity of urea in the same temperature range as that
of measurements. The molar heat capacities of alkane-α,ω-diamides increased in function of temperature and fitted into linear
equations. Smoothed values of C
p,m at 298.15 K displayed a linear increase with the number of carbon atoms. The C
p,m contribution of CH2 group was (22.6±0.4) J K−1 mol−1, in agreement with our previous results concerning linear alkane-a,ω-diols and primary alkylamides as well as the literature
data on various series of linear alkyl compounds.
On leave from the Faculty of Chemistry, University of Craiova, Calea Bucureşti 165, Craiova 1100, Romania 相似文献
19.
F. Xu L.-X. Sun Z.-C. Tan J.-G. Liang Y.-Y. Di Q.-F. Tian T. Zhang 《Journal of Thermal Analysis and Calorimetry》2004,76(2):481-489
Molar heat capacities (C
p,m) of aspirin were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range
from 78 to 383 K. No phase transition was observed in this temperature region. The polynomial function of C
p,m
vs. T was established in the light of the low-temperature heat capacity measurements and least square fitting method. The corresponding
function is as follows: for 78 K≤T≤383 K, C
p,m/J mol-1 K-1=19.086X
4+15.951X
3-5.2548X
2+90.192X+176.65, [X=(T-230.50/152.5)]. The thermodynamic functions on the base of the reference temperature of 298.15 K, {ΔH
T -ΔH
298.15} and {S
T-S
298.15}, were derived. Combustion energy of aspirin (Δc
U
m) was determined by static bomb combustion calorimeter. Enthalpy of combustion (Δc
H
o
m) and enthalpy of formation (Δf
H
o
m) were derived through Δc
U
m as - (3945.26±2.63) kJ mol-1 and - (736.41±1.30) kJ mol-1, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
Liang Xue Feng-Qi Zhao Xiao-Ling Xing Zhi-Ming Zhou Kai Wang Hong-Xu Gao Jian-Hua Yi Rong-Zu Hu 《Journal of Thermal Analysis and Calorimetry》2010,102(3):989-992
The thermal decomposition behavior of 3,4,5-triamino-1,2,4-triazole dinitramide was measured using a C-500 type Calvet microcalorimeter
at four different temperatures under atmospheric pressure. The apparent activation energy and pre-exponential factor of the
exothermic decomposition reaction are 165.57 kJ mol−1 and 1018.04 s−1, respectively. The critical temperature of thermal explosion is 431.71 K. The entropy of activation (ΔS
≠), enthalpy of activation (ΔH
≠), and free energy of activation (ΔG
≠) are 97.19 J mol−1 K−1, 161.90 kJ mol−1, and 118.98 kJ mol−1, respectively. The self-accelerating decomposition temperature (T
SADT) is 422.28 K. The specific heat capacity of 3,4,5-triamino-1,2,4-triazole dinitramide was determined with a micro-DSC method
and a theoretical calculation method. Specific heat capacity (J g−1 K−1) equation is C
p = 0.252 + 3.131 × 10−3
T (283.1 K < T < 353.2 K). The molar heat capacity of 3,4,5-triamino-1,2,4-triazole dinitramide is 264.52 J mol−1 K−1 at 298.15 K. The adiabatic time-to-explosion of 3,4,5-triamino-1,2,4-triazole dinitramide is calculated to be a certain value
between 123.36 and 128.56 s. 相似文献