Showing papers by "Technical University of Denmark published in 1979"
TL;DR: In this paper, a phenomenological flow theory of plasticity is proposed which models time-independent incremental behavior at a corner of the yield surface of a polycrystalline metal.
Abstract: A class of phenomenological flow theories of plasticity is proposed which models time-independent incremental behavior at a corner of the yield surface of a polycrystalline metal. The proposal is consistent with the physical theories of plasticity based on single crystal slip. Conditions for convexity, ensuring invertibility of the incremental relations, are derived. The simplest candidate, called J 2 corner theory, coincides with the J 2 deformation theory of plasticity for nearly proportional stress increments and incorporates a smooth transition to elastic unloading for increasingly non-proportional increments. The theory is applied to the bifurcation and imperfection-sensitivity analysis of necking in a thin sheet. For this example, like many others involving bifurcation in the plastic range, the corner theory appears to circumvent some of the difficulties associated with use of the standard phenomenological plasticity laws.
260 citations
TL;DR: In this article, the authors discuss the interaction between battery requirements, in particular for vehicle propulsion, and electrochemical and constructional factors, and show that the energy obtainable at a given load is limited by saturation of the surface layers of cathode particles with cations, and that the time before saturation is determined by diffusion of cations and electrons into the host lattice.
Abstract: Battery systems based on alkali metal anodes and solid solution cathodes,i.e., cathodes based on the insertion of the alkali cation in a "host lattice," show considerable promise for high energy density storage batteries. This paper discusses the interaction between battery requirements, in particular for vehicle propulsion, and electrochemical and constructional factors. It is argued that the energy obtainable at a given load is limited by saturation of the surface layers of cathode particles with cations, and that the time before saturation occurs is determined by diffusion of cations and electrons into the host lattice. Expressions are developed for plane, cylindrical, and spherical particles, giving the relation between battery load and the amount of cathode material utilized before saturation. The particle shape and a single parameter is used to describe cathode performance. is the ratio between discharge time at 100% utilization of the cathode at the given load, and the time constant for diffusion through the cathode particles. This description is extended to cover short peak loads characteristic of vehicle propulsion. On the basis of estimated parameters for the couple with electrolyte the properties of plane cathodes or cathodes consisting of few layers of particles are examined in relation to traction requirements. In this context limiting currents in the electrolyte phase are discussed, and a relation between the maximal allowed values for particle size and electrode spacing is derived. For nonporous electrodes the limiting factor is cathode surface saturation. A qualitative discussion of porous cathodes indicates that the cathode thickness, and thus the over‐all specific energy, is limited by cation transport in the pore electrolyte when the cation diffusion coefficient in the solid exceeds 10−10 cm2 sec−1. On the basis of an approximate relation between cathode thickness and electrode spacing the specific energy for the system with organic electrolyte is estimated to be 120–150 W‐hr/kg in agreement with published values.
202 citations
153 citations
TL;DR: In this article, the single crystal elastic constants of aluminum have been measured using a piezoelectric composite oscillator from room temperature to just 20 K below the melting point, and the elastic moduli differ markedly from previous high temperature results, but match in well with previous cryogenic results.
149 citations
TL;DR: Four alternative flow injection methods based on the concept of merging zones have been developed for the assay of glucose in serum with glucose dehydrogenase, with the optimal procedure allowing the assay to be done at a rate of 100 determinations per hour.
121 citations
TL;DR: Eleven nickel‐hypersensitive patients with chronic, dyshidrotic hand eczema aggravated by oral challenge with 0.6–2.5 mg nickel were treated with 100 mg tetraethylthiuramdisulfide (Antabuse®) two to four times daily for 4–10 weeks.
Abstract: Eleven nickel-hypersensitive patients with chronic, dyshidrotic hand eczema aggravated by oral challenge with 0.6-2.5 mg nickel were treated with 100 mg tetraethylthiuramdisulfide (Antabuse) two to four times daily for 4-10 weeks. Nine of the patients experienced a flare of the dermatitis shortly after initiation of the treatment. During the course of treatment the dermatitis of seven patients cleared, improvement was seen in two patients, and in two the dermatitis remained unchanged. Flare was seen in six patients when the treatment was discontinued. Seven patients experienced side effects such as fatigue, headache and dizziness. The treatment of four patients was discontinued due to side effects. During the treatment high levels of nickel were found in the serum and urine.
104 citations
TL;DR: The lead taken up by grass in a remote rural area is predominantly from the atmosphere as discussed by the authors, and it is said that airborne lead is not a significant source of lead in crops in general.
Abstract: LEAD in the atmosphere of the Northern Hemisphere originates mostly from lead-alkyl petrol additives emitted from car exhausts1 A small proportion of this lead—estimated at about 10%2,3—is deposited within 50–100 m of the road while the rest is presumably transported long distances before deposition There are reports of increasing concentrations of lead in roadside vegetation with decreasing distance from the edge of the road1,4,5 This apparent lead contamination ceases beyond 100–200 m from the road, and it is said therefore that airborne lead is not a significant source of lead in crops in general5–7, although there is circumstantial evidence to the contrary8,9 We report here, however, that the lead taken up by grass in a remote rural area is predominantly from the atmosphere
98 citations
TL;DR: The formation, growth and interaction of small metal particles (10-100 nm) produced by gas evaporation has been studied in this paper, where single metal atoms diffuse radially out from the gas source until they condense at a temperature of roughly 0.35-0.40 T m, where T m is the absolute melting temperature.
87 citations
TL;DR: Experiments on a pilot plant demonstrate that a self-tuning pH-regulator including exponential forgetting and quadratic optimal control has satisfactory static and dynamic properties even though the process is nonlinear.
81 citations
66 citations
TL;DR: In addition to the known iridoid glucosides loganin, sweroside and cantleyoside, Dipsacus sylvestris has provided 4 novel bis-iridoid glucose derivatives named Sylvestrosides I, II and III as discussed by the authors.
TL;DR: In this article, changes in dune properties due to a sudden change in the water discharge are analysed. But the authors assume that the transport of sediment is assumed to occur mainly as bed load and the square of the Froude number must be much smaller than unity.
Abstract: Changes in dune properties due to a sudden change in the water discharge are analysed. The transport of sediment is assumed to occur mainly as bed load and the square of the Froude number must be much smaller than unity. The theory is based on similarity in the bed-shear distribution close to the dune top just before and just after the change in the water discharge. The model is found to agree with laboratory experiments. Further, by use of this model, flow in a river where the water discharge oscillates weakly around a constant mean value has been treated. Hereby the variation in the phase differences between sediment transport, water depth and water discharge with the period of the oscillation is calculated. The results agree qualitatively with observations.
TL;DR: In this article, it is suggested that the zeolite lattice may have a very specific action in assisting the production of rhodium centers which are active in carbonylation.
TL;DR: In this paper, the principles of using radiating microstrip resonators as elements in a frequency scanning antenna array are described, where the resonators are cascade-coupled, giving a scan of the main lobe due to the phase shift in the resonator in addition to that created by the transmission line phase-shift.
Abstract: The principles of using radiating microstrip resonators as elements in a frequency scanning antenna array are described. The resonators are cascade-coupled. This gives a scan of the main lobe due to the phase-shift in the resonator in addition to that created by the transmission line phase-shift. Experimental results in X -band, in good agreement with the theory, show that it is possible to scan the main lobe an angle of \pm30\deg by a variation of the frequency \pm300 MHz, and where the 3 dB beamwidth is less than 10\deg . The directivity was 14.7 dB, while the gain was 8.1 dB. The efficiency might be improved by a trade-off between the efficiency and the scanning angle, or by using a better amplitude distribution.
TL;DR: In this article, the authors used convergent energy minimisation in a simple force field for β-maltose conformations and found four local minima on the φ,ψ-map; the free enthalpy differences are 2.8, 3.4, and 5.6 kJ.
TL;DR: Seeds of Moringa peregrina (Moringaceae), on treatment with myrosinase, produce 2-propyl, 2-butyl and 2-methylpropyl isothiocyanate in addition to 5,5-dimethyl-oxazolidine-2-thione, all new to the family but known as natural derivatives from other sources.
TL;DR: In this article, the four independent material parameters of plane orthotropic elasti city are introduced as the effective stiffness, the effective Poisson ratio, the stiffness ratio and the shear parameter.
Abstract: The four independent material parameters of plane orthotropic elasti city are introduced as the effective stiffness, the effective Poisson ratio, the stiffness ratio and the shear parameter. It is proved that stress boundary value problems with zero resulting force on internal contours lead to stress fields that are independent of the effective stiffness and the effective Poisson ratio, and a general transformation is described which is equivalent to a change of the stiffness ratio. These properties suggest the importance of the remaining shear parameter, that has the interesting property of being invariant with respect to a 90 degree rotation of the principal axes of the material.
TL;DR: In this article, the interaction between two nickel atoms in the configurations (3d)8(4s)2 and 3d)9 (4 s)1 has been calculated using ab initio methods (Hartree-Fock and configuration interaction).
Abstract: The interaction between two nickel atoms in the configurations (3d)8(4s)2 and (3d)9 (4s)1 has been calculated using ab initio methods (Hartree–Fock and configuration interaction). The results of the calculations compare favorably with the optical spectrum. The discrepancy between the calculated and the experimental dissociation energy is discussed, and a new estimate of the dissociation energy is given. The configuration-interaction calculations show that the interaction between the two nickel atoms is of a very complex nature. In spite of this the binding can be interpreted in a simple way. The bond is minly due to the 4sσg molecular orbital while the 3d orbitals of the two nuclei are exchange coupled.
TL;DR: In this paper, the reaction of L -ascorbic acid with hydrogen bromide in acetic acid gave 6bromo-6deoxy-L-ascorbIC acid, which was converted into 5,6-dideoxy- D - glycero -hex-2,3-enono-1,4-lactone.
TL;DR: In this article, various subproblems for DH lasers such as field distribution, carrier profile, and temperature distribution are investigated and solutions to these problems are obtained either analytically or by precise numerical methods.
Abstract: The various subproblems for DH lasers such as field distribution, carrier profile, and temperature distribution are investigated. Solutions to these problems are obtained either analytically or by precise numerical methods. By combining the subproblems, a detailed model for the static properties is obtained. The model is applicable as well below as above threshold and properties of interest in the application of DH lasers such as threshold current, field distribution at a given current, and light current characteristics can be found. Nonlinear characteristics are found even for ideal symmetrical lasers. These "kinks" are associated with higher order modes and appear at relatively high values of the optical power.
TL;DR: In this article, a potential energy function was devised, comprising harmonic terms for bond length and valence angle deformations, and Lennard-Jones and Coulomb terms for non-bonded interactions.
TL;DR: The elution patterns demonstrate that beer antigens, originating from barley or yeast macromolecules, can be separated from carbohydrates, from ‘proteose-like’ material and from each other in a few preparative chromatographic steps.
Abstract: The macromolecules of an antigen-rich beer fraction X were characterized by column chromatography. Elution profiles of protein, carbohydrate and immunochemically distinct antigens were recorded after separation on gels of Sephacryl, Sephadex, Sepharose, DEAE-Sephadex, SP-Sephadex, Bio-gel HT hydroxylapatite, Con A-Sepharose, and two types of antibody-Sepharose. The elution patterns demonstrate that beer antigens, originating from barley or yeast macromolecules, can be separated from carbohydrates, from ‘proteose-like’ material and from each other in a few preparative chromatographic steps. Affinity chromatography on a column of immobilized antibodies towards fraction X indicated that the antigenic material constitutes about 25% of the fraction. More than 20% of the protein in fraction X seems to originate from a distinct barley protein Z.
TL;DR: The incorporation of dietary isomeric fatty acids into the membranes of liver mitochondria was investigated and the content oftrans fatty acids in the lipids of the mitochondrial membranes was 15–19% of the total fatty acids.
Abstract: The incorporation of dietary isomeric fatty acids into the membranes of liver mitochondria was investigated. Three groups of rats were fed diets containing 3% sunflower seed oil plus 15%, 20%, or 25% partially hydrogenated arachis oil. A fourth group was fed 25% partially hydrogenated arachis oil, but no sunflower seed oil. All diets were given for 3, 6, or 10 weeks. After 10 weeks, the content oftrans fatty acids in the lipids of the mitochondrial membranes was 15–19% of the total fatty acids. The composition of thetrans- and thecis-octadecenoic acids in the lipids of the mitochondrial membranes was similar for all groups supplemented with sunflower seed oil (SO), irrespective of time and dietary level of partially hydrogenated arachis oil (HAO). Thecis 18∶1 (n−8), which was a major isomer of the partially hydrogenated arachis oil, was almost excluded from the mitochondrial fatty acids. Likewise, the content oftrans 18∶1 (n−8) was considerably lower in the mitochondrial lipids than in the diet. On the contrary, the content oftrans 18∶1 (n−6) was higher in the mitochondrial lipids than in the diet. In the group fed without sunflower seed oil, isomers of linoleic acid and arachidonic acid were observed in the lipids of mitochondrial membranes.
TL;DR: In this paper, the authors present the problem of remodeling a given structure such that it improves structural performance optimally within a specified available resource, where the mode of structural response is governed by an extremum principle.
Abstract: We present the problem of remodeling a given structure such as to improve structural performance optimally within a specified available resource. The development pertains to all types of problems where the mode of structural response is governed by an extremum principle. A variational formulation is used, and the idea is illustrated for maximum-stiffness remodeling of single-purpose structures.
TL;DR: Focusing on a small firm and its special problems a case from the glass industry is presented and it is shown that the waste can be reduced by approximately 50% in comparison to the solution normally used by the company.
Abstract: A description of some examples of the application of cutting stock problems is given. Focusing on a small firm and its special problems a case from the glass industry is presented. The case leads to a two-dimensional cutting stock problem where large rectangles have to be cut into smaller rectangles. At the same time a group of additional constraints have to be satisfied. The solution method is a near optimal method using knapsack functions. It is shown that the waste can be reduced by approximately 50% in comparison to the solution normally used by the company. Furthermore a sequencing procedure for the ordering of the glass sheets is suggested.
01 Feb 1979
TL;DR: In this article, the authors describe the application of a hydraulic pump/motor and a hydro-pneumatic energy storage as a supplement to the conventional internal combustion engine in a city bus.
Abstract: The paper describes the application of a hydraulic pump/motor and a hydro-pneumatic energy-storage as a supplement to the conventional internal combustion engine in a city bus. The resultant hybrid-system makes it possible to smooth out the combustion engine power output and to regenerate the braking-energy which in conventional busses dissipate as heat. Computer-simulation and supplementary experiments with a model-system have shown that, depending on the driving pattern of the bus, this type of hybrid-system would lead to a 10-30% fuel saving provided that an appropriate control strategy is used.
TL;DR: In this paper, the incorporation of excess PPh 3 into the catalysts leads to an increase in regioselectivity for n-aldehyde production and to a greater stability.
TL;DR: In this article, the authors showed that methyl 4-O -benzoyl-2,3- O -isopropylidene-α- l -rhamnopyranoside and methyl 5-O-benzyl-2.3-OISOPropylIDene-β- d -ribofuranoside with dibromomethyl methyl ether gave 2-bromo-2-deoxy-3 O -formyl glycosyl bromides in good yields.
TL;DR: In this article, minimal basis set SCF-MO computations on conformations of α-D -gluco-pyranose, β- D -glucopyranoses, and β-maltose resulting from empirical energy minimisation reproduce known trends in relative energy.