Showing papers by "Nanjing University published in 1994"
TL;DR: Three tests based on fossil data indicate that high rates of extinction recorded in the penultimate (Guadalupian) stage of the Paleozoic era are not artifacts of a poor fossil record, but represent an abrupt mass extinction that was one of the largest to occur in the past half billion years.
Abstract: Three tests based on fossil data indicate that high rates of extinction recorded in the penultimate (Guadalupian) stage of the Paleozoic era are not artifacts of a poor fossil record. Instead, they represent an abrupt mass extinction that was one of the largest to occur in the past half billion years. The final mass extinction of the era, which took place about 5 million years after the Guadalupian event, remains the most severe biotic crisis of all time. Taxonomic losses in the Late Permian were partitioned among the two crises and the intervening interval, however, and the terminal Permian crisis eliminated only about 80 percent of marine species, not 95 or 96 percent as earlier estimates have suggested.
414 citations
TL;DR: The Kuqa depression along the northern flank of the Tarim basin is filled with a thick sequence of Neogene and Quaternary coarse elastic continental sediments as discussed by the authors, which is part of a large foreland basin that lies south of the Tianshan.
Abstract: The Kuqa depression along the northern flank of the Tarim basin is filled with a thick sequence of Neogene and Quaternary coarse elastic continental sediments. This structural depression is part of a large foreland basin that lies south of the Tianshan—an orogenic belt of intracontinental convergence resulting from the northward propagation of stress following the collision of India with the southern margin of Eurasia.
108 citations
TL;DR: Using data on formation of the Loess Plateau of central China, Loess-palaeosol sequences, pollen analysis, historical geography, and long-term experimentation on rates of soil erosion, it is demonstrated that current serious erosion on the loess plateau is mainly due to human destruction of the natural vegetation and irrational land use as mentioned in this paper.
Abstract: Using data on formation of the Loess Plateau of central China, loess-palaeosol sequences, pollen analysis, historical geography, and long-term experimentation on rates of soil erosion, it is demonstrated that current serious erosion on the Loess Plateau is mainly due to human destruction of the natural vegetation and irrational land use. These two modifications greatly reduce soil-infiltration capacity and resistance of the soil to erosion. The increase of soil erosion began ca. 5000 BP at which time a hunting and pastoral life began to change gradually to a sedentary life centred around cultivation. Using the volume of Holocene loessic sediments on the continental shelf of the Bohai, Yellow, and East China Seas, it is estimated that the present sediment load of the lower Yellow River is at least three times greater than it was during the Holocene. Although human-induced soil erosion in the Loess Plateau began earlier, it was not until the Tang dynasty (about 1000 BP) that it began to increase rapidly. Ac...
103 citations
TL;DR: In this article, the authors analyzed the evolution of vector magnetograms and vertical current over a 6-day period (October 17-22) in the active region, and found that two magnetic fluxes of opposite polarities emerged synchronously with their separating motion, one of which converged with an old magnetic structure and caused a number of flares.
Abstract: NOAA 5747 was a flare-productive active region during its transit across the solar disk in October 1989. After the resolution of the 180° ambiguity of the transverse field synthetically, and transformation of vector magnetograms from the image plane to the heliographic frame, we have determined the distribution of the photospheric vertical electric current density in the active region. By analyzing the evolution of vector magnetograms and vertical current over a 6-day period (October 17–22) in the active region, we get the following results: (1) Two magnetic fluxes of opposite polarities emerged synchronously with their separating motion, one of which converged with an old magnetic structure and caused a number of flares. (2) There appeared a new current system, with the emergence of the fluxes. (3) The initial Hβ bright kernels occurred in the vicinity of the neutral line of vertical current (Jz = 0) with a steep gradient, but not just on the sites of vertical current peaks. (4) The flares were probably triggered by the interaction between the new emerging electric current system and old current system.
96 citations
TL;DR: In this paper, a linear projection equation for unconstrained optimization problems is presented, where the search directions of these methods are straighforward extensions of the directions in traditional methods.
Abstract: Many interesting and important constrained
optimization problems in mathematical programming can be translated into an
equivalent linear projection equation
$$
u = P_{\Omega} [ u - (Mu+q)] .
$$
Here,
$P_{\Omega}(\cdot)$
is the orthogonal projection on some convex set
$\Omega$
(e.g.
$\Omega=
{\Bbb R}^n_+$
)
and
$M$
is a positive semidefinite
matrix.
This paper presents some new methods for solving a class of linear projection
equations. The search directions of these methods are straighforward
extensions of
the directions in traditional methods for unconstrained optimization.
Based on the idea of a projection and contraction method [7] we get a
simple step length rule and are able to obtain global linear
convergence.
94 citations
TL;DR: In this article, the SHRIMP zircon U-Pb isotopic study suggests that the crystallization age of a highly fractionated magma in the NE Jiangxi ophiolite suite is 968±23 Ma.
Abstract: The new SHRIMP zircon U-Pb isotopic study suggests that the crystallization age of a highly fractionated magma in the NE Jiangxi ophiolite suite is 968±23 Ma. Re-calculated Sm-Nd isochron age of 955±44 Ma is within analytical errors. consistent with the zircon U-Pb age. With the exception of two anomalous Sm-Nd data, the remaining 15 analyses so far obtained for the ophiolite gaveeNd (T) values falling into a limited range from +4.3 to +6.7, indicating that the ophiolite was derived from a relatively strongly depleted mantle source. Sm-Nd isotopic systematics in some samples may have been strongly affected by post-magmatic events, such as alteration, deformation and metamorphism, resulting in anomalouseNd (T) values. Combined with published40Ar39Ar age data, it can be concluded that the collision between the Yangtze and South China Blocks occurred during 0.97-0.80 Ga.
83 citations
TL;DR: In this paper, it was shown that invariant tori still exist in perturbed integrable Hamiltonian systems with n degrees of freedom H(p, q) = N(p) + P(p, q) if the hypothesis of nondegeneracy is replaced by a much weaker one that the rank of the mapping ∂N/∂p can be any positive integer smaller than n provided the image of any open set under the mapping includes a Cn + 2 curved one-dimensional submanifold.
71 citations
TL;DR: In this article, a new method for synthesis of Mo(W)-S cluster compounds by solid state reactions at low heating temperatures is introduced, and the factors which may influence solid-state reactions are discussed.
70 citations
TL;DR: The results show that carp has low ability to take up the REEs under the experimental conditions, and the order of maximum bioconcentration factors was mostly internal organs > gills > skeleton > muscle.
68 citations
TL;DR: In this paper, convective effects in the electrodeposition of iron from FeSO4 solution were shown to generate a mesh-like pattern, a morphology that has not been reported previously.
Abstract: ELECTRODEPOSITION of metals such as copper and zinc from solutions of their salts may give rise to ramified metal deposits which show a range of growth morphologies1–9. Our understanding of the factors that determine growth morphology is still very limited, in part because different morphologies may be observed even under similar growth conditions4,5. It is thought9 that uncontrolled convective processes at the tips of the deposit branches may play a role in these discrepancies. Here we show that convective effects, which we can visualize directly, in the electrodeposition of iron from FeSO4 solution, can generate a mesh-like pattern, a morphology that has not been reported previously. Convection can be diminished by altering the pH, whereupon we see a transition to a dense branching morphology. Our results show that convective effects do indeed play an important part in determining pattern selection during electrodeposition.
66 citations
TL;DR: In this article, the applicability of the coupling model to some relaxations in metals including precipitates and the Snoek-Koster relaxation has been discussed and summarized and discussed by participants of ICIFUAS-10.
TL;DR: In this article, the third member (Hg-1223) of the homologous series HgBa2Can−1CunO2n+2+δ, having a Tc of 118 K (as synthesized sample) and 133 K (oxygen-annealed sample), was successfully prepared by the solid state reaction and short-time annealing technique using mixtures of the metal oxides.
Abstract: The third member (Hg-1223) of the recently discovered homologous series HgBa2Can−1CunO2n+2+δ, having a Tc of 118 K (as synthesized sample) and 133 K (oxygen-annealed sample), was successfully prepared by the solid state reaction and short-time annealing technique using mixtures of the metal oxides HgO, BaO, CaO and CuO with starting composition HgBa2Ca2Cu3O8+δ. We found that the combination of very short annealing times with optimum temperatures 715–725°C gives rise to a very effective sintering of the constituents and avoids an excessive loss of Hg. Samples so obtained display a sharp superconducting transition determined both magnetically and resistively. The X-ray diffraction patterns of both the 118 K phase and the 133 K phase indicate a nearly single phase, corresponding to the tetragonal structure of space group P4/mmm and with lattice parameters a= 3.85 A and c= 15.85 A . The resistivity ϱ of such a sample was very low, ∼ 12x10-3 Ω cm at 300 K, and the ϱ versus T curve was linearly extrapolated to zero resistance at 0 K, being similar to the cases of high-quality high-Tc cuprates. Energy dispersive X-ray analysis (EDX) data of several grains of the Hg-1223 sample are in agreement with the proposed chemical formula.
TL;DR: Wang et al. as discussed by the authors discussed the background of human resource man agement and labour-management relations in China and concluded that as the economic reforms deepen and a market economy is established, changes will take place in the nature of labour- management relations and human resource management in Chinese enterprises.
Abstract: Human resource management and labour-management relations in China are different from those in other countries because of different political and economic systems and social and cultural backgrounds. Lots of changes have taken place in human resource management since the 1978 economic reforms. This paper discusses the general background of human resource man agement and labour-management relations in China. It describes the cultural values, political and economic systems shaping Chinese human resource man agement and explores labour-management relations in Chinese enterprises. The author concludes that as the economic reforms deepen and a market economy is established, changes will take place in the nature of labour- management relations and human resource management in Chinese enterprises.
TL;DR: This kind of anomaly can cause hematometra and endometriosis leading to acute abdominal pain, infertility, rupture of pregnant rudimentary horn and obstetrical complications with pregnant semi‐uterus, and Rudimentary horn should be removed if detected.
TL;DR: In this article, microcalorimetry was used to determine the differential enthalpy changes of adsorption versus coverage on HZSM-5 and Hmordenite of reactants and products of methylamine synthesis.
TL;DR: In this article, the authors considered that the length of pendant groups has an influence on the height of tan δ in the interpenetrating structure of SINs and found that loss factor of PU/PEMA and PU/PEA is much higher than that of PU/(PMMA) and PU/(PMA).
Abstract: Simultaneous Interpenetrating Networks (SINs) were synthesized based on polyepichlorohydrin glycol (PECG), toluene diiocyanate (TDI), and trihydroxymethyl propane (TMP) as network I; and methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA), and ethyleneglycol dimethylacrylate (EGLM), respectively as network II. Damping behavior of the SINs was studied by a dynamic viscoelastometer. It was found that loss factor, tan δ, of PU/PEMA and PU/PEA is much higher than that of PU/PMMA and PU/PMA. The present authors consider that the length of pendant groups has an influence on the height of tan δ in the interpenetrating structure. Transmission electron microscopy (TEM) photos show that the SINs possess multiphase structures. These two networks are dispersed in a system microheterogeneously. © 1994 John Wiley & Sons, Inc.
TL;DR: In this paper, the effect of adding tin oxide to δ-Al2O3 has been studied in microcalorimetric and infrared spectroscopic studies of ammonia and carbon dioxide adsorption.
Abstract: Microcalorimetric and infrared spectroscopic studies of ammonia and carbon dioxide adsorption have been used to study the effects on the acid/base properties of adding tin oxide toγ-Al2O3. The addition of SnO2 toγ-Al2O3 decreases the number of strong acid sites (heats of ammonia adsorption higher than 140 kJ/mol), increases the number of weaker acid sites (heats from 110 to 130 kJ/mol), and decreases slightly the number of basic sites (heats of carbon dioxide adsorption from 70 to 150 kJ/mol). In contrast, the presence of SnO onγ-Al2O3 decreases the total number of acid sites (heats of ammonia adsorption higher than 70 kJ/mol) and eliminates most of the basic sites. Infrared spectroscopy of adsorbed ammonia reveals interactions between aluminum cations and stannous ions, leading to a decrease in the strength of the Lewis acid sites associated with aluminum cations.
25 Aug 1994
TL;DR: It is shown that every nc-random set in E has nk-random predecessors in E for any k ≥ 1, whereas the amount of randomness of the successors is bounded, and that there are weakly complete problems which are not p-btt-complete for E.
Abstract: We introduce and study resource bounded random sets based on Lutz's concept of resource bounded measure ([5, 6]). We concentrate on nc-randomness (c ≥ 2) which corresponds to the polynomial time bounded (p-) measure of Lutz, and which is adequate for studying the internal and quantative structure of E = DTIME(2lin). First we show that the class of nc-random sets has p-measure 1. This provides a new, simplified approach to p-measure 1-results. Next we compare randomness with genericity (in the sense of [1, 2]) and we show that nc+1-random sets are nc-generic, whereas the converse fails. From the former we conclude thatnc-random sets are not p-btt-complete for E. Our technical main results describe the distribution of the nc-random sets under p-m-reducibility. We show that every nc-random set in E has nk-random predecessors in E for any k ≥ 1, whereas the amount of randomness of the successors is bounded. We apply this result to answer a question raised by Lutz [8]: We show that the class of weakly complete sets has measure 1 in E and that there are weakly complete problems which are not p-btt-complete for E.
TL;DR: The complexes Co(BBP)Cl2, Co( BBP)2SO4·H2O, CoBBP2(NO3)2·H 2O, COBBPCl2(MeOH)2 and Co(CBP−H)2−H 2 O 2 2 O, where BBP is 2,6-bis(benzimidazol-2′-yl) pyridine, were prepared and characterized by elemental analysis, electrical conductance, i.r.t. and electronic spectra as discussed by the authors.
Abstract: The complexes Co(BBP)Cl2, Co(BBP)2SO4·H2O, Co(BBP)2(NO3)2·H2O, Co(BBP)2(ClO4)2 and Co(BBP−H)2· 2H2O, where BBP is 2,6-bis(benzimidazol-2′-yl) pyridine, were prepared and characterized by elemental analysis, electrical conductance, i.r. and electronic spectra. The electrochemical behaviour of the complexes was recorded and the X-ray crystal structure of Co(BBP)Cl2(MeOH)2 was determined. The geometry about cobalt is a distorted octahedron.
TL;DR: According to historical records, vegetation destruction occurred nationwide and frequently in preindustrial China; the four most frequent causes were firewood collection, charcoal making for heating in winter, land reclamation, and brick making and construction of houses and palaces.
TL;DR: In this article, the relative amount of cations in Ba-W-Ce complex oxides with perovskite superstructure interstitial oxygen species can be created which benefits C2 selectivity.
Abstract: Ce4+ doped Ba3 WO6 complex oxides were used as catalysts for methane oxidative coupling (MOC), and characterized by XPS and O2-TPD-MS techniques. The results indicate that the ratio of electrophilic oxygen species O− and O
2
−
to lattice oxygen on the surface is crucial for C2 selectivity. By adjusting the relative amount of cations in Ba-W-Ce complex oxides with perovskite superstructure interstitial oxygen species can be created which benefits C2 selectivity by raising the relative amount of (O− + O
2
−
) on the surface.
TL;DR: A number of tetraimine macrocycles were synthesized by using 2,6-diformyl-4-methylphenolate as a precursor to undergo Schiff base condensation with a series of diamino compounds as mentioned in this paper.
TL;DR: It is shown that the large activation enthalpy of the relaxation time and the breadth of the internal-friction peak associated with the Snoek-K\"oster relaxation can be explained quantitatively by this model for various foreign atoms in several bcc metals.
Abstract: The importance of the effects of mutual interactions between the interstitial solute atoms in the Cottrell atmosphere on the Snoek-K\"oster relaxation in cold-worked bcc metals is emphasized in a theoretical approach based on the coupling model. It is shown that the large activation enthalpy of the relaxation time and the breadth of the internal-friction peak associated with the Snoek-K\"oster relaxation can be explained quantitatively by this model for various foreign atoms in several bcc metals.
TL;DR: In this paper, phase-like transitions (PLTs) characterized by a small jump of lattice parameters in the range 100-300 K always exist in high-Tc (near 100 K) superconducting Y-Ba-Cu-O, Bi-Sr-Ca-cu-O and Tl-Ba-,Ca-Cu,O. The energy dissipation (Qp-1 and alpha p) related to carriers can be explained reasonably by using a coupling model of carriers with local dynamic distortion.
Abstract: Acoustic measurements from 10-2 to 107 Hz show that phase-like transitions (PLTs) characterized by a small jump of lattice parameters in the range 100-300 K always exist in high-Tc (near 100 K) superconducting Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O. Ferroelastic loops associated with the elastic softening of C'=((C11+C22)/2-C12)/2 and C66 invariably occur at the PLT temperatures, and in some cases the shape memory effect may be observed. For various samples of Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O with different Tc, the acoustic attenuation (Q-1, alpha ) from the kilohertz to megahertz range reveals a plateau (Qp-1, alpha p) above Tc and drops obviously below Tc with the turning point at Tc. This kind of anomaly has not been observed for non-superconducting samples. Qp-1 is found to be closely related to the carrier density for YBa2Cu3O7- delta , Y1-xPrxBa2Cu3O7 and Gd1-xPrxBa2Cu3O7, and the drop of Q-1 and a below Tc is considered to be caused by superconducting condensation. The energy dissipation (Qp-1 and alpha p) related to carriers can be explained reasonably by using a coupling model of carriers with local dynamic distortion. Furthermore, taking account of the smearing of the superconducting gap structure and by using the modified Bardeen-Cooper-Schrieffer (BCS) relative jump rate, S(E, E', Gamma )=Re(1- Delta 2/((E-i Gamma )(E'-i Gamma ))), the calculated results of acoustic attenuation below Tc are in fairly good agreement with the experimental data. The superconducting gap Delta and the damping rate Gamma for both Bi-Sr-Ca-Cu-O and TI-Ba-Ca-Cu-O have also been obtained.
TL;DR: In this article, the pore system of L zeolite proved to be beneficial for Pt clusters, exhibiting a high benzene selectivity in n-hexane aromatization, and the secondary pores of L had a negative influence on the aromatisation over Pt/BaKL.
Abstract: L, Y zeolites were used as carrier to support Pt, and the catalytic properties of the supported Pt catalysts in n-hexane aromatization were investigated. The pore system of L zeolite proved to be beneficial for Pt clusters, exhibiting a high benzene selectivity in n-hexane aromatization. The secondary pores of zeolite L had a negative influence on the aromatization over Pt/BaKL. With these secondary pores blocked, the 0.4% Pt/BaKL-I sample could keep up with the excellent aromatization properties of 0.6% Pt/BaKL zeolite. Pt dispersed on KL basic zeolite exhibited dehydrogenation activity in isopropanol decomposition. Pt supported on NH4L acidic zeolite enhanced the conversion of isopropanol to form water and propene. IR results of linear CO adsorbed on Pt/L zeolites suggested the Pt on NH4L acidic zeolite was “electron deficient”, and Pt on KL basic zeolite exhibited some electron excess, which results from the interaction of Pt and zeolites with different acidic-basic properties.
TL;DR: In the [ital J]/[psi] plus two pion mass spectrum, the tentative observation of a structure at a mass of 3.527 GeV/[ital c][sup 2] is observed.
Abstract: A search has been made in 300 GeV/[ital c] [pi][sup [plus minus]]- and proton-Li interactions for production of states that decay into [ital J]/[psi] or [psi][prime] plus one or two pions. A 2.5[sigma] enhancement in the [ital J]/[psi] [pi][sup 0] spectrum, possibly the recently reported [sup 1][ital P][sub 1] state of charmonium, is observed at a mass of 3.527 GeV/[ital c][sup 2]. In the [ital J]/[psi] plus two pion mass spectrum, we report, together with the expected [psi][prime][r arrow][ital J]/[psi] [pi][sup +][pi][sup [minus]], the tentative observation of a structure at a mass of 3.836 GeV/[ital c][sup 2]. No enhancements are seen in the [ital J]/[psi] [pi][sup [plus minus]][pi][sup [plus minus]], [ital J]/[psi] [pi][sup [plus minus]][pi][sup 0], [ital J]/[psi] [pi][sup [plus minus]], or [psi][prime] [pi][sup [plus minus]] mass spectra.
TL;DR: In this paper, a single crystal structure of [Cu(bpc)(H 2 O) 2 ] (bpc = 2,2-bipyridyl-3,3′-dicarboxylate) has been constructed and the magnetic susceptibility has been measured in the range 7-300 K and obeys the Curie-Weiss law.
TL;DR: In this article, the plate-tectonic evolution of the Tarim basin and nearby western Tianshan region during Paleozoic time is reconstructed in an effort to further constrain the tectonic development of Central Asia, providing insights into the formation and distribution of oil and gas resources.
Abstract: The plate-tectonic evolution of the Tarim basin and nearby western Tianshan region during Paleozoic time is reconstructed in an effort to further constrain the tectonic evolution of Central Asia, providing insights into the formation and distribution of oil and gas resources. The Tarim plate developed from continental rifting that progressed during early Paleozoic time into a passive continental margin. The Yili terrane (central Tianshan) broke away from the present eastern part of Tarim and became a microcontinent located somewhere between the Junggar ocean and the southern Tianshan ocean. The southern Tianshan ocean, between the Tarim craton and the Yili terrane, was subducting beneath the Yili terrane from Silurian to Devonian time. During the Late Devonian-Early Carboniferous, the Tarim plate collided with the Yili terrane by sinistral accretional docking that resulted in a late Paleozoic deformational episode. Intracontinental shortening (A-type subduction) continued through the Permian with the crea...
TL;DR: A simplified enzyme-based fiber optic sensor system has been developed for selective determination of hydrogen peroxide using co-immobilized oxidase and horseradish peroxidase and a new fluorimetric substrate, thiamine is used to indicate the sensing process.
TL;DR: TPR, TPO and FTIR were used to study the elementary processes occurred in the calcination of Pt (NH3)2Cl2 supported on Kβ zeolite as discussed by the authors.
Abstract: TPR, TPO and FTIR were used to study the elementary processes occurred in the calcination of Pt (NH3)2Cl2 supported on Kβ zeolite. Using CO–FTIR, we found directly that while the Pt ammine complexes decomposed at about 300°C, autoreduction of Pt2+ ions by NH3 groups occurred and led to the formation of Pt° atoms prematurely. Reoxidation of the reduced sample could decrease the extent of Pt agglomeration caused by autoreduction. The unique effect of Ba2+ ions on Pt dispersion was also studied. Aromatization of n-hexane and methylcyclopentane were used to study the effect of Pt dispersion on catalytic properties.