Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
Volume 40 , Issue 451
Showing 1-22 articles out of 22 articles from the selected issue
  • Mitsuharu TABUCHI, Yasunari KANEKO, Hiromichi IWASAKI
    1991 Volume 40 Issue 451 Pages 367-373
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    A new process of synthesizing metal and metal nitride powders by spark discharge between two metal electrodes in liquid nitrogen has been studied. In this paper, the phase and shape of the synthesized powders by using titanium (Ti), aluminium (Al) and tungsten (W) electrodes are reported.
    In the cases of the same metal electrode couple, titanium nitride (TiN), Al and aluminium nitride (AlN), W and beta-tungsten (β-W) were formed from Ti, Al and W electrodes, respectively. Spherical particles appeared in all the cases. In the cases of different metal electrode couple, the powders were the mixture of particles forming from each electrodes, since the particle compositions were not uniform in BSE images and EDX spectra.
    Download PDF (2801K)
  • Jisun JIN, Hiromitsu KOZUKA, Sumio SAKKA
    1991 Volume 40 Issue 451 Pages 374-378
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Suppression of the bloating of the Y-Ba-Cu-O metal acetate gels during heating for the conversion of gel-to-superconducting oxide was attempted by three different approaches: the use of metal formates characterized with less numbers of carbon and hydrogen atoms in a molecule than corresponding metal acetates, the vacuum drying of the gel fiber before heating, and the reduction of the rate of heating of the acetate gel. Vigorous bloating was seen in metal formate gels as well in the temperature range where the copper formate complexes were decomposed, and thus the use of metal formates as the starting materials was not effective in suppressing the bloating. The vacuum drying of the gel was not effective either. On the other hand, the reduction in the rate of heating for gel-to-superconductor conversion was effective in suppressing vigorous bloating, leading to the formation of solid ceramic superconducting fibers with Tc (end) of 86.3K.
    Download PDF (1641K)
  • Yoshinari MIURA, Toshio KAWAMURA, Jun TAKADA, Kiichi ODA, Akiyoshi OSA ...
    1991 Volume 40 Issue 451 Pages 379-384
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    ZnO films were prepared on silica glass substrates by the use of an R.F. activated reactive evaporation (ARE) method, and were examined by X-ray diffraction (XRD) and scanning electron micrograph. XRD indicated that they were c-axis oriented and that an R.F. plasma of Zn and O was necessary for the film deposition. The optimum conditions for a dense film with a fine texture of the surface and having good crystallinity were as follows; R.F. power: 150-200W, the substrate temperature: 400°C, the oxygen pressure: 2.0×10-4 Torr, the evaporation rate: 5.0Å/s. The standard devitation σ of the X-ray rocking curve of (002) for the film was 1.9°, smaller than that of the film prepared by using an R.F. sputtering method.
    Download PDF (1437K)
  • Keisuke KAGEYAMA, Mitsuhiro TAKATA
    1991 Volume 40 Issue 451 Pages 385-389
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    In order to survey new microwave dielectric resonators, complex perovskite compounds having A(B'1/2/B"1/2)O3 composition have been investigated. It was reported previously that the dielectric ceramics fabricated from a stoichiometric powder mixture in Sr(Sm1/2Ta1/2)O3 composition (SST ceramics) had a high Q value at microwave frequencies and a negative temperature coefficient, and also reported that long time sintering had considerable effects on the densification, grain growth and the improvement of microwave Q for SST ceramics.
    In this study, HIP'ed SST ceramics were prepared in order to investigate the relation between grain growth and microwave Q with taking notice of the effect of HIP process on the acceleration of grain growth under certain conditions. The results were summarized as follows:
    (1) Long time sintering was effective to the densification and grain growth of SST ceramics. HIP after long time sintering accelerated the densification and grain growth of SST ceramics.
    (2) The relative dielectric constants of both normally sintered and HIP'ed SST ceramics increased according to the densification of SST ceramics.
    (3) Microwave Q of HIP'ed SST ceramics was not improved from that of normally sintered ceramics in spite of the increases of density and grain size.
    Download PDF (1317K)
  • Makoto ISHIKAWA, Mitsuru WAKAMATSU, Nobuyuki TAKEUCHI, Tetsuyuki HATTO ...
    1991 Volume 40 Issue 451 Pages 390-394
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Six kinds of pressureless sintered Si3N4 with three different additives (CeO2-Al2O3-MgO, Y2O3-Al2O3, Y2O3-Al2O3-MgO) were rapidly heated up to 1400°C and then held at this temperature for 15h in pure oxygen. During the oxidation, N2, NO and CO2 concentrations in the exhaust gas were continuously measured by a mass spectrometer. In every sample, a good correlation was observed between the amount of N2 formed and weight gain. The amount of N2 formed and weight gain after oxidation of Si3N4 increased with decreasing sintering temperature. The rates of N2 and NO formation increased rapidly for 5min after the heating temperature reached 1400°C and then decreased rapidly. After rapid decrease, the N2 formation curve showed different behavior with three additives. The maximum N2 formation rate was in the order Y2O3-Al2O3-MgO>CeO2-Al2O3-MgO>Y2O3-Al2O3. The total amount of N2 formed was in the order Y2O3-Al2O3-MgO>CeO2-Al2O3-MgO≈Y2O3-Al2O3. From the Si3N4 with CeO2-Al2O3-MgO, a large amount of CO2 was released and the surface of oxide scale was rough.
    Download PDF (1083K)
  • Rikuo OTA, Hideyuki KURIBAYASHI, Jiro FUKUNAGA
    1991 Volume 40 Issue 451 Pages 395-399
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Critical cooling rate Q* for glass formation was determined by means of DTA method for a non-alkali multicomponent system of 39.8SiO2·10.1Al2O3·24.4CaO·12.6ZnO·11.1TiO2·2.0B2O3mol% composition. Q* was found to be 1.5×10-2°C/sec. Viscosity of the system was measured by the beambending and the counter balancing method. The liquidus temperature T1 of the system was determined by DTA method. From the viscosity and T1 data, the Liquidus viscosity η1 was obtained (logη1/PaS=0.94). The Q*1 relationship of the non-alkali system was compared with those of alkali silicate and alkali borate systems.
    It was found that the present non-alkali system has a critical cooling rate equivalent to 94SiO2·6Li2O, 75B2O3·25Li2O or 85B2O3·15Na2O glass. The fusion entropy ΔSf was calculated from eq. (2) using the values of liquid parameters of the non-alkali system. It became apparent that the non-alkali system has a considerably high ΔSf value compared with the alkali borate or alkali silicate system. This was regarded to indicate that the present system is composed of various polyhedra, including SiO4, AlO4 or TiO4 tetrahedra, thus easing a glass formation of a SiO2 poor melt.
    Download PDF (605K)
  • Kazuyuki HIRAO, Zuyi ZHANG, Hirokazu MORITA, Naohiro SOGA
    1991 Volume 40 Issue 451 Pages 400-404
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Densified alkali borate glasses were prepared by applying hydrostatic pressure up to 6GPa near the glass transition temperature. The mechanical properties such as Young's modulus and hardness were measured. The yield stress for 5Na2O·95B2O3 and 10Na2O·90B2O3 glasses was calculated from the interference fringes of the indented surface. Young's modulus and Knoop hardness increased with an increase of the degree of densification. The yield stress increased and tended to approach a constant value with the densification. These variations with densification were explained by the decrease of void and the increase of two-dimensional structural groups in glass network.
    Download PDF (1020K)
  • Kunio HAYASHI, Shinji TSUJIMOTO, Yasunori OKAMOTO, Tomozo NISHIKAWA
    1991 Volume 40 Issue 451 Pages 405-410
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Fracture toughness (KIC) values were measured on the major planes of single-crystal silicon using the controlled surface flaw (CSF) and indentation fracture (IF) methods at room temperature. The values of KIC on the surface orientations {100}, {110}, {111} and {112} obtained by the CSF method were found to be 1.13, 1.12-1.14, 1.18 and 1.11-1.18MPa·m0.5, respectively. It was found that these KIC values increased slightly with increasing the Young's modulus perpendicular to the fracture surfaces. Though KIC values obtained by the IF method, on the other hand, were scattered significantly (0.82-1.18MPa·m0.5), its Young's modulus dependence was similar to that obtained by CSF method.
    Download PDF (1860K)
  • Toshihiko NISHIDA, Ichiro KAMEYAMA, Tomozo NISHIKAWA
    1991 Volume 40 Issue 451 Pages 411-415
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The crack propagation stability of chevron notched specimens during bending test was discussed on the basis of the dimensionless equilibrium Gibbs free energy diagram of elastic fracture system proposed by Sakai. The free energy diagram was also used for designing a new type of crack stabilizer which provides reliable and stable fracture of brittle ceramics in bending. A pair of elastic rectangular bend-bars were arranged on both sides and parallel to a bend-bar chevron notched SiC specimen as a crack stabilizer. Thus the stable fracture of the specimen was achieved by the simultaneous loading on both the specimen and the stabilizer arranged in this way.
    Download PDF (651K)
  • Mikio HIGASHI, Keijiro TERASHITA, Kei MIYANAMI
    1991 Volume 40 Issue 451 Pages 417-423
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Preparation of composite conductive particles was attempted by coating fine electric conductive powders on insulative core particles so called dry coating. Compressive crushing mill was utilized for the dry coating process. Polymethylmethacrylate (PMMA, 8μm in diameter) was used as core particles. TiO2 coated with Ag (0.5μm in diameter), TiO2 coated with SnO2 (0.2μm) and SnO2 particles (less than 0.1μm) were employed as fine electric conductive powders. In the experiments, the rotation speed of the mill and the treatment time were changed. The coating condition and electric conductivity of the prepared particles were determined by volume specific resistivity, SEM observation of the particle surfaces and the compression moldings of the particles and X-ray micro-analysis.
    As a result, composite particles with the functions of charge prevention and electromagnetic shield were procured by the dry coating process. In the conductive compression moldings, electric conductive routes were formed by the contacts of fine electric conductive particles and aggregates, coated or dispersed on the core particles. A network of good electric conductive routes was obtained when primary particles of the conductive powder were dispersed uniformly. It was obvious that the excellent conductive composite particles (coated with the fine electric conductive powder) were obtained when the particles were acted by shearing force and compression force.
    Download PDF (3716K)
  • Kenzo FUKAURA, Hisakichi SUNADA, Yasuyuki MISAWA, Hisashi IZUMI
    1991 Volume 40 Issue 451 Pages 424-430
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    SiC whisker reinforced aluminum composites with whisker volume fraction ranging from 0 to 20% were fabricated by a powder metallurgy method, that is, a combination of hot pressing and hot extrusion. The relation between the microstructure and the tensile properties of the composites was discussed.
    The main results obtained were as follows;
    (1) The SiC/Al composites fabricated by the appropriate combination of hot pressing and hot extrusion had theoretical density. The deviation of whiskers from the extruded direction was within about ±4 degree.
    (2) The tensile strength of SiC/Al composites increased with increasing the volume fraction of SiC whisker; for example, 20 v% SiC/Al composite had the tensile strength of 387MPa. The experimental tensile strength exceeded the predicted one. The possible reason was that the real value of shear yield stress of the matrix was larger than our estimate.
    (3) The tensile fracture behavior of SiC/Al composites was as follows. At first the interfacial voids were formed at whiskers ends, then grew gradually and finally joined each other along the shear direction.
    (4) The tensile strength of SiC/Al composites at elevated temperatures decreased with increasing temperature, but the tensile strength of 20 v% SiC/Al composite at 723K was two times as strong as that of pure aluminum.
    Download PDF (3831K)
  • Yoshifumi TANIGUCHI, Junichi KITAZUMI, Toshiro YAMADA
    1991 Volume 40 Issue 451 Pages 431-437
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Following the previous report, the strength distribution of ceramics was simulated by the Monte-Carlo method for the case in which the lower limit existed in the strength of ceramics. In this study, the tensile strength, 3-point and 4-point bending strengths of specimens of four different sizes were calculated, by using the model specimens with a number of penny-shaped inner cracks. In order to investigate the change of strength distribution of ceramics due to the size effect, the strength obtained was plotted on the Weibull probability paper. It was found that the shape of strength distribution was convex for the specimens of large effective volume, while it was concave for those of small effective volume. The strength distribution function for this model was also expressed and compared with the simulation results. As a result, both distributions showed good agreement in the range of fracture probability greater than a few percents.
    Furthermore, the relation between the mean strength and the effective volume was discussed. As the strength of the specimens varied between the lower and upper limits, its relation was represented by a inverse S-shape curve on the logarithmic graph paper.
    Download PDF (939K)
  • Nobushige KOISO
    1991 Volume 40 Issue 451 Pages 438-443
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Flexural strength tests and fracture toughness tests on two kinds of ceramics (silicon nitride and silicon carbide) were carried out by four-point bending at room temperature and elevated temperatures. The fracture toughness was measured by using the chevron-notched specimens and by using the controlled surface flaw specimens which have a semi-circular surface crack induced by a knoop indenter.
    Furthermore, the fracture toughness of smooth specimen was evaluated by using √area, which is the square root of the area of the defect projected to the direction of the principal stress. These results were discussed in comparison with the fracture toughness values obtained by the chevron-notched specimens and the controlled surface flaw specimens.
    The results obtained are as follows:
    (1) The fracture toughness values depended on the method of measurement. The values of silicon nitride and silicon carbide obtained from the chevron-notched specimens were higher than those obtained from the controlled surface flaw specimens at elevated temperatures.
    (2) The fracture toughness values of silicon nitride obtained from the controlled surface flaw specimens decreased rapidly when the temperature exceeded 1000°C. It was clear that its rapid decrease was caused by slow crack growth.
    (3) The fracture toughness values of silicon carbide obtained from the controlled surface flaw specimens were influenced by the healing of crack at about 1200°C.
    (4) The temperature dependency of the fracture toughness value of silicon nitride obtained from the smooth specimens coincided with that of the fracture toughness obtained from the controlled surface flaw specimens.
    Download PDF (2046K)
  • Keiro TOKAJI, Takeshi OGAWA, Makoto FUJIMURA
    1991 Volume 40 Issue 451 Pages 444-450
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Tensile properties and fatigue behaviour under rotating bending were investigated on both underaged and overaged specimens of two aluminum-lithium alloys, 2090 and 8090. The results were compared with those of the peakaged specimens of the same materials and conventional aluminum alloys, 2024 and 7075, obtained in a previous report.
    The metastable δ'-phase precipitated and grew during aging, and the diameters of the particles were approximately 10nm, 20nm and 30nm for the underaged, peakaged and overaged conditions, respectively. The elongation of the underaged and overaged specimens slightly increased compared with that of the peakaged specimens, while the proof stress and tensile strength decreased. The fatigue strength was decreased by the underaging and overaging process. This was due to the decrease in both crack initiation and growth resistances. The crack initiation and growth were discussed based on the observation of precipitation of δ'-phase during aging.
    Download PDF (3182K)
  • Susumu MITANI, Hisayoshi TAKAZAWA, Eiichi SAKITA, Mikio NISHIHATA
    1991 Volume 40 Issue 451 Pages 451-457
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The effect of cold-working on hydrogen embrittlement of metastable austenitic stainless steels has been investigated. The specimens were made of SUS302 and SUS304, which had different austenite stabilities, and were cold-worked by 20% to 80%. Hydrogen embrittlement of H-charged specimens was measured by bend testing. The main results are as follows:
    (1) The bend deformation resistance decreased due to hydrogen charging.
    (2) Hydrogen embrittlement depended on Vickers hardness or strain-induced martensite content but not on the type of specimen.
    (3) The decrease in bend deformation resistance by hydrogen charging was recorvered by keeping the specimen at room temperature.
    (4) Hydrogen embrittlement did not depend on the amount of hydrogen absorbed. The amount of hydrogen absorbed by SUS302 increased with cold-working, whereas that absorbed by SUS304 decreased with cold-working.
    (5) Hydrogen charging caused blisters on SUS302 and cracks on SUS304. Blisters tended to be induced on the severely cold-worked specimens and cracks on the mildly cold-worked ones. The difference in surface state between H-charged SUS302 and SUS304 specimens indicated different hydrogen absorption mechanisms for these two steels.
    Download PDF (2026K)
  • Kiyohisa TAKAHASHI, Naomoto ISHIKAWA, Toshio KOHNO, Heung-Soo YOON
    1991 Volume 40 Issue 451 Pages 458-463
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    In a preceding paper, the chemical resistance of the epoxy resin cured with 1, 3, 5-trichloro-1, 3, 5-tri (dimethylamino) cyclotriphosphazene (CL3) was investigated, and it was shown that the epoxy resin cured with CL3 was degradated by acid and was resistant to alkali. In this paper, the water resistance of EPIKOTE154 cured with CL3 has been investigated in detail and the effect of glass flake reinforcement has been also investigated. The results obtained are as follows:
    (1) The curing reaction may proceed further in the presence of water. This is considered because the curing reaction of the EPIKOTE154/CL3 is difficult to proceed completely in an ordinary curing condition, and also because the cured epoxy resin is not degradated by water.
    (2) When the epoxy resin was filled with glass flakes, the modulus of rigidity increased and the glass transition was observed at 15-25°C higher temperature. When the glass flakes were surface treated, the experimental results of the modulus of rigidity showed relatively good agreement with the theoretical prediction, in which the interfacial perfect adhesion between the glass and epoxy was assumed. On the other hand, when the glass flakes were not surface treated, the reinforcing effect was remarkably lower than that of the surface treated case.
    (3) After the glass flake filled specimens were immersed into water, the effect of surface treatment vanished.
    Download PDF (772K)
  • Takako HONZYO, Yoichiro NAKANISHI
    1991 Volume 40 Issue 451 Pages 464-469
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The influence of water absorption on the deterioration of carbon fiber reinforced plastics (CFRP) was investigated from the viewpoint of the interfacial change in bonding. Carbon fiber braids impregnated with epoxy resin were made and cured. And they were tested by torsional braid analysis (TBA) after immersion in boiling water. The followings are the results.
    (1) The glass transition temperature (Tg) obtained from TBA data for CFRP with suface-treated carbon fibers was higher by 22-36°C than that with surface-untreated carbon fibers. This difference of Tg was attributed to the interfacial bonding.
    (2) Tg dropped with the immersion time of 15-50 hours, but rose again after the immersion of more than 100 hours. For example, Tg of the after-cured sample with surface-treated carbon fibers dropped from 200°C to 146°C in 50 hours of immersion, and rose to 174°C in 200 hours.
    From these results, it is considered that, though the fiber-resin interface of CFRP is destroyed by hot water in the early stage of immersion into boilding water, weak chemical bridging is generated in epoxy resin after long immersion. The extent of the bridging is enough to make the strength of the resin higher, but not enough to make the modulus higher. And some new weak bonding is also generated in the fiber-resin interface, making gradual increase in Tg of CFRP.
    Download PDF (854K)
  • Akira TODOROKI, Hideo KOBAYASHI, Kunio ADACHI
    1991 Volume 40 Issue 451 Pages 470-476
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    High strength type CFRP has low delamination resistance, although it has high mechanical properties. In this low delamination resistance, an opening mode (mode I) delamination crack growth resistance is the most important because this mode shows relatively lower resistance and usually occurs in actual structures. Recently, the energy release rate concept has been applied to estimate this mode I delamination resistance. Various test methods have been proposed to measure it using double cantilever beam test specimens. The test method, however, has not been established yet and the micromechanism of delamination is still unknown. In this study, therefore, various factors affecting the testing, such as large deformation of beam, jig and loading rate, are discussed based on a beam theory and the experiments of mode I delamination resistance using high strength type CFRP (T-400/epoxy). The results obtained are as follows. (1) It was reconfirmed that the effects of large deflection and jig are negligible under the condition of low deflection value (0.1<δ/a<0.25). (2) It is considered that the fiber bridging breaks by time depended fracture mechanisms. (3) Stick-slip delamination growth occurs under a low loading rate condition. (4) The modeling of the stick-slip delamination growth can be successfully made by considering visco-elastic property of resin.
    Download PDF (1489K)
  • Yoshiaki KAWAGUCHI, Yoshiaki YAMADE, Teruo KISHI
    1991 Volume 40 Issue 451 Pages 477-482
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Sometimes in ceramics remarkable slow crack growth appears even at room temperature and in air. The evaluation of fracture toughness in such a case is one of the most important problems for the development and practical use of ceramics.
    This paper deals with the case of mullite. Two kinds of mullite were tested by using the precracked and chevron-notched specimens at room temperature and in air. Especially in the chevron-notched specimens, remarkable slow crack growth was detected. The compliance method obtained from the notch mouth opening displacement gave the slow crack growth quantatively and the acoustic emission measurement indicated that qualitatively. The fracture toughness obtained from the three point bending tests was evaluated from the viewpoint of the material resistance against slow crack growth.
    Download PDF (727K)
  • Juhachi ODA, Yoshifumi TANIGUCHI, Masayuki HANZAWA
    1991 Volume 40 Issue 451 Pages 483-489
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The static and impact three point bending tests were carried out to evaluate the fracture toughness of alumina. A precrack was introduced into the specimen by BI method. In order to eliminate the influence of residual stress caused by the roughness of the crack surface, a notch was made on the crack with diamond cutter, leaving the crack tip.
    The static fracture toughness was evaluated by SEPB method. Because of rising R-curve behavior of alumina, the fracture toughness calculated from the maximum load would be greater than the inherent one. In this experiment, the fracture toughness was calculated from the load at the onset of crack extension, which was detected by the output of a strain gage glued near the crack tip. This value was almost the same as the fracture toughness obtained by IF method. In addition, the relation between load and strain near the crack tip observed in the static three point bending test was explained by using a simple model.
    In the impact three point bending test, the impact forces were loaded on the specimen by dropping a cylindrical bar from various heights. It was found that the fracture toughness had a tendency to increase with an increase of impact velocity. Furthermore, the time variation of dynamic stress intensity factor measured in this test was compared with the calculated value by a simple evaluating method which was proposed in the previous paper. As a result, both values showed good agreement until the crack began to extend.
    Download PDF (1470K)
  • Tadao IKEJIRI
    1991 Volume 40 Issue 451 Pages 490-494
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    In order to discuss the arc resistance of synthetic resin, it is quite important to know the relation between arc resistance time and applied voltage. In this study, an attempt was made to derive the arc resistance time-applied voltage curve under the consideration that the arc deterioration of insulating materials is completed when the sum of deterioration caused by each discharge becomes above a limiting value. Several assumptions were used in the present step, but it is considered that those assumptions must be improved and be proven by the experimental and theoretical studies in future.
    Furthermore, the progress of deterioration was defined here and the tendency of its variation with the elapsed time was clarified.
    Download PDF (607K)
  • K. Tanaka, T. Kurokawa
    1991 Volume 40 Issue 451 Pages 495-502
    Published: April 15, 1991
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Download PDF (1067K)
feedback
Top