Practical Conditions Of Use Research Articles

Hydrochloric acid diffusion coefficients at acid-fracturing conditions

The reaction of a 15% HCl solution with Indiana Limestone was investigated at 93 °C and 34.5 MPa using an annular flow reactor that was erected vertically. The laminar flow conditions were such that both free and forced convections contributed to the overall mass-transfer rate. The experimental results correlated well with theory when the forced and free convections were in the same direction (assisting flow) and when free-convection mass transfer dominated the mass-transfer process. Deviation from theory, however, occurred when free convection was in the opposite direction to forced convection (opposing flow). Correlating the experimental results with theory provided a method for the determination of the effective diffusion coefficient of HCl at the high temperature, pressure and acid concentrations encountered in acid-fracturing treatments. An HCl effective diffusion coefficient of 5.25 × 10 −5 cm 2/s was found from correlating the present experimental results with theory. Recent trend in designing acid-fracturing treatments is to use computer models to predict and optimize the etched length of the created fracture. The accuracy and reliability of such computer model predictions depend heavily on the accuracy of the values used for physical parameters such as reaction rate and diffusion coefficient of HCl. The annular flow reactor and the correlations discussed here provide a way to obtain reaction rates and diffusion coefficients at practical conditions for use in computer models and design of acid-fracturing treatments.

The response characteristics of GafChromic dosimetry media to 60Co gamma rays

The dosimetric characteristics of GafChromic Dosimetry Media after being irradiated by 60Co gamma rays have been studied and the dependence of the radiation-induced absorbance on the temperature during irradiated and during reading and the postirradiated effect are reported. The dose-response characteristics of the films to 60Co gamma rays at the reading wavelengths of 400 and 580 nm have been analyzed, and the suitable range (0.1–45 kGy) and conditions of practical use are recommended according to the results.

Electrochemical behavior of [octaethylporphyrin iron(III)-σ-bonded pyrrole] and its electrocatalytic activity for the reduction of dioxygen

The electrochemistry of [octaethylporphyrin iron(III)-σ-bonded pyrrole] (abbreviated as (OEP)Fe III(Pyr)) was investigated in CH 2Cl 2 + TBAP solution by cyclic voltammetry (CV) and in situ UV-visible electronic absorption spectrometry. It was found that (OEP)Fe III(Pyr) can undergo a quasi-reversible one-electron reduction step to form (OEP)Fe II(Pyr), and two sorts of irreversible one-electron oxidation step: one was the formation of [(OEP)Fe III(Pyr)] + firstly, followed by loss of the σ-bonded pyrrole to produce [(OEP)Fe III] +; the other was probably the direct formation of [(OEP)Fe III] + with simultaneous loss of the σ-bonded pyrrole. It was also found that (OEP)Fe III(Pyr) adsorbed on the surface of glassy cardon (GC) exhibited high activity for the electrocatalytic reduction of dioxygen, but this activity was not stable. However, this catalyst can be buried in polypyrrole (PPyr) film, resulting in more stable activity. Rotation ring-disk experiments (RRDE) demonstrated that (OEP)Fe III(Pyr) whether adsorbed on a GC surface or buried in PPyr film could catalyze the reduction of dioxygen to give water predominantly. In these two cases, the catalytic mechanisms were found to be the same and the water production efficiencies were nearly 90% in the potential region −0.30 to 0.35 V (vs. SCE) in O 2 saturated 0.05 M H 2 SO 4 solution. The slope of the Tafel curve suggested that the one-electron transfer from [(OEP)Fe II(Pyr)O 2] to [(OEP)Fe III(Pyr)O 2 −] was the rate-controlling step before the limiting disk current was reached. 1. (i) The electrochemistry and in situ UV-visible absorption spectra suggested that the electrochemical oxidation of (OEP)Fe III(Pyr) might produce the porphyrin ring cation with the loss of its σ-bonded pyrrole, resulting in irreversible oxidation of (OEP)Fe III(Pyr) to form [(OEP)Fe III] + species. The electrochemical reduction of (OEP)Fe III(Pyr) seems to be a reversible process in which the porphyrin ring anion is formed first, followed by electron transfer from the porphyrin ring to the central iron to yield (OEP)Fe II(Pyr). 2. (ii) There may be two different forms of (OEP) Fe III(Pyr) adsorbed on the GC surface. The so-called “different adsorption form” is resulted probably from the different distance between the active sites on which (OEP)Fe III(Pyr) could adsorb. This might lead to a different interaction pattern of bonding with dioxygen. For type I sites (as described in Section 3.3.4) perhaps the side-on and/or end-on interactions occurred favorably, whereas for type II sites perhaps the bridge interaction was predominant [36,37]. 3. (iii) Burying (OEP)Fe III(Pyr) in PPyr film might proceed only at the beginning of the electrochemical polymerization of pyrrole monomers. The concentration of (OEP)Fe III(Pyr) buried in the PPyr film appeared to be independent of the thickness of the film. (OEP)Fe III(Pyr), whether buried in PPyr film or adsorbed on the GC surface, exhibited a similar electrocatalytic activity for dioxygen reduction. The catalytic mechanisms were found to be the same. Furthermore, the burying method clearly could increase the stability of this activity. 4. (iv) In the low polarization region where the potential is higher than −0.120 V, the catalytic reduction of dioxygen by (OEP)Fe(Pyr)] ad/GC underwent successive 2e − reduction steps to form water, whereas in the higher polarization region, the direct 4e − reduction occurred to give water predominantly. The Tafel slope in the kinetic controlled region suggested that the reaction rate was controlled by the first one-electron transfer step. In the more negative potential region, the reaction rate was controlled by the diffusion of dioxygen in solution phase. Thus, (OEP)Fe III(Pyr) has a high activity for the electrocatalytic reduction of dioxygen with an efficiency of water production of 75%–90%, which is close to the activity observed on a Pt electrode. This activity appeared very unstable, probably resulting from the loss of (OEP)Fe III(Pyr) from the GC surface. However, it was satisfactory to find that the burying method, for example burying (OEP)Fe III(Pyr) in a PPyr film, could increase the catalytic activity and its stability markedly. Furthermore, it was interesting to find that this kind of σ-bonded metalloporphyrin could be used as the cathodic catalyst in a full cell if further research into increasing its stability were accomplished, according to the conditions for practical use.

Magnetic Field Characteristics in the Quadri-Layered M-O Film with Overwritability

The authors investigated the external magnetic field characteristics of exchange-coupled quadrilayer magnetooptic film in direct overwriting by optical modulation. The external field dependence of the recording characteristics was studied through the temperature dependence of the reversal field and the mechanism of direct overwriting. In direct overwriting by optical modulation, an upper limit to the external field exists due to the "low" process. Here the process of initialization of the writing layer, unique to the quadrilayer film, did not affect the lower limit of the external field. A wide external field margin was obtained under conditions of practical use, and effective fluctuations in the external field did not affect the recording laser power margin.

French administrative practice and design codes for nuclear vessels

French codes for nuclear components are presented, emphasizing the conditions of practical use. They are strongly linked to French regulations and the first part of the paper is devoted to presentation of these regulations and to the ways they are applied by authorities. The most important part is the decree of February 26, 1974, which defines the frame for codes and standards. Two codes are presented. The first one is dealing with components for water-cooled nuclear boilers (RCC-M). The second with components of Fast-Breeder Reactors (RCC-MR).

Evaluation des paramétres thermiques d'un milieu poreux: optimisation d'outils de mesure “in situ”

A synthetic presentation of the different methods of measuring in a transient way the thermal parameters with ‘thermal shock probes’ is made by using the point of view of systems dynamics. The corresponding heat transfer models and the associated identification techniques are described. Particular attention is focused on the problem of the influence of a thermal contact resistance between the probe and the material. A method to study this problem is proposed. Solutions are given to improve the accuracy of the different treatments which can be used. It is shown that using probes with very low thermal inertia is particularly well adapted to “in situ” measurement in porous media. Indications are given on the realization of this type of probe, their conditions of practical use and the estimation of their performances.

On the practical applications of MBE surface phase diagrams

This paper reports detailed surface phase diagrams for (100) GaAs and (100)InAs. In the case of GaAs, growth rates from 0.07 to 3.0 μm/h, As 4 : Ga flux ratios from 0.25:1 to 100:1 and growth temperatures from 300°C to 800°C were used, covering the whole range of growth conditions of practical use in MBE. Results on the nucleation of the (100) InAs/GaAs heterojunction are also presented. The correlation between material properties, surface reconstruction and growth conditions is discussed for both GaAs and homo- and heteroepitaxial InAs. The emphasis of the paper is on the practical application of the results as an aid to optimising (and reproducing) MBE growth conditions with reasonable efficiency.

Isolation and identification of new oligomers in aqueous solution of glutaraldehyde.

Commercially available aqueous solutions of glutaraldehyde (GA) sometimes contain GA polymers as impurities which can cause undesirable effects. We found new type oligomers present in a GA solution as impurities and isolated them by reverse-phase high performance liquid chromatography. These compounds were identified as GA trimer, pentamer and heptamer having a 1, 3, 5-trioxane skeleton. In particular, GA trimer, 2, 4, 6-tris (4-oxobutyl) -1, 3, 5-trioxane, was named “paraglutaraldehyde” (para-GA). These compounds showed absorption maxima at 280 nm (the same position as GA), and hence could not be distinguished from GA itself by the conventional ultraviolet absorption method. These impurities were not detected in highly purified GA solution after storage under the conditions of practical use. Accordingly, these oligomers seemed to be formed by the intermolecular cyclization of GA monomer during the processes of synthesis.

Significance of mode of exposure in aerosol inhalation toxicity studies - head only versus whole body exposure.

The purpose of this study was to investigate differences in acute inhalation toxicity (LC50 values) using different types of exposure systems with five agricultural chemicals (three insecticides and two herbicides). Rats of both sexes were exposed during a period of four hours and observed for 14 days. During exposure air flow rate, concentration, particle size distribution, temperature, relative humidity and oxygen content were monitored within the inhalation chamber, toxic signs and death rate were recorded during the exposure and observation period. Of the three insecticides tested two were liquid OP type compounds - one of which was hydrophilic and one lipophilic - and one was a moderately hydrophilic solid insecticidal carbamate. Upon whole body exposure the hydrophilic OP was slightly less toxic and the lipophilic OP slightly more toxic. The carbamate was equally toxic regardless of type of exposure. The results demonstrate that it is advisable to have both systems available in view of the importance of exposures under practical conditions of use. For gaseous materials the whole body exposure is preferred.

An experimental study of some effects of solid surface roughness on wetting

An experimental study was made of the influence of surface roughness on the equilibrium spreading of liquid on solids, employing well-characterized rough surface and a well-defined technique of attaining drop equilibrium. The surfaces were prepared under practical conditions for use, e.g. in adhesion, i.e. without rigorous purification or attempting to eliminate anisotropy or micro-heterogeneities in surface free energy. Two limiting cases of surface roughness were examined: spiral grooves yielding a stick-jumps contact line movement which agreed reasonably well with the theory for a concentric groove model; and radial grooves on which the advancing contact angle agreed with Wenzel's classical equation. On the forms of roughness such as parallel grooves, hexagonal sinusoidal grooves, bead-blasted and composite surface , stick-jump movements become less evident as capillary channeling increased, so that spreading accordingly varied between these limiting cases. Wetting hysteresis occurred on all surfaces, exceeding that predicted theoretically from the roughness measurements made by surface profilometry. Scanning electron microscopic observation suggest that the enhanced hysteresis may have resulted from added complications introduced by microscopic roughness features such as sharp edges which are known to inhibit movement of the contact line.

エダマメ収穫後の品質変化とその防止

Green soybeans, a common crop in Japan, is harvested at the green-pod stage and its somewhat immature seeds are eaten as a snack etc. The taste of the seeds, however, deteriorates much more rapidly than the visual quality. This paper reports the investigation on the factors concerning the post-harvest quality deterioration and the means of keeping quality, especially applicable under non-refrigerated conditions for practical use. Shirayama-and Komagi-dadachamame cultivars were used and their pods were packaged in perforated polyethylene (PE) bags and held at 0°, 5° and 20°C, respectively.Organoleptic test showed that the taste of soybean became flat in 2 days at 20°C. Yellowing or browning of pods began after several days at 20°C, and 2 weeks at 5 °C. At 0°C, the loss of freshness of pods was noticed after about a month, while green color remained.Sugar content, index of free amino acid content (ninhydrin-positive substances), and L-ascorbic acid content in seeds drastically decreased in 2 days at 20°C. At 5 °C, marked decrease in sugar and amino acid was found after a week. At 0°C, amino acid considerably decreased after 2 weeks of storage while sugar content showed little change. Post-harvest deterioration in the taste of the green soybeans is supposed to be principally attributable to the decrease of sugar and amino acid.When metabolic inhibitors were applied to the seeds by vacuum infiltration, change of the sugar content was retarded with NaF and 2, 4-dinitrophenol (DNP), and that of amino acid with cycloheximide and DNP.Some other pods were packed in PE bags of 0.07mm film-thickness, and the atmosphere in bags was replaced by N2or CO2, or withdrawn under vacuum. These treatments brought about a retardation of sugar loss, and an increase of amino acid in contrast with a sharp decrease in non-treated pods. Simple sealing also had a comparable effect to the a bove-mentioned treatments, showing high CO2 and low O2 concentrations in the bag during the days succeeding the sealing. At 20°C, however, shelf life reduced to 3-4 days since a symptom of gas injury developed on the surface of pod and seed. At 5°C, no injury was found during 2 weeks of storage and loss of sugar and amino acid was considerably retarded.Packaging of a whole plant with leaves and pods attached in a PE bag of 0.03mm-thickness exhibited a marked effect on keeping quality, and preferable taste was kept for several days even at 20°C. External appearance was also maintained by this means, and pod color remained green without any gas injury for more than 10 days at 20°C.

45—THE TENSILE AND BURSTING PROPERTIES OF STITCHED CLOSURES IN POLYPROPYLENE-TAPE SACKS FILLED WITH NYLON GRANULES AND SUBJECTED TO COMPRESSIVE FORCES

An investigation is reported of the tensile and bursting properties of stitched closures in polypropylene-tape sacks filled with nylon granules and subjected to compressive forces. It is shown that, in a ‘flat’ configuration, the main features of the mechanics of closure deformation and failure by inflation are reproduced during the compression of sacks filled with mobile nylon granules and tightly sealed to eliminate ullage space. The inflation technique provides a method of sack-testing under biaxial tensile forces that simulates more closely the conditions of practical use.

The Long-Term Stability of Fixed Resistors

The causes of long-term failure under practical conditions of use or storage of different types of fixed resistors commonly used in electronic equipment have been investigated. Some reported life tests have proceeded without interruption for almost four years. Carbon-composition (grade 2) resistors under load fail by slow thermal degradation of the resistive material. Drift of value may also occur if unloaded resistors of this type are stored in a damp atmosphere. Vitreous-enamelled wire-wound resistors made with fine wire may fail during tropical exposure both unloaded and especially when lightly loaded with direct current. This is owing to electrochemical corrosion taking place at faults in the vitreous coating. High-stability cracked-carbon (grade 1) resistors may fail rapidly under light dc load by electrochemical action if moisture condensation occurs and the protective paint or varnish coating is inadequate. Tests for long-term resistor stability are critically discussed.

Suggested methods of testing and standards of resistance for respiratory protective devices.

There is need to establish a method of bench testing and standards of allowable resistance for respiratory protective devices. It is suggested that a technique for recording pressure-volume diagrams using a sine-wave pump is satisfactory. Standards of resistance are proposed which are expressed as total rate of respiratory work done on the apparatus, and the percentage of this which is done in expiration. It is suggested that apparatus should be tested at minute volumes up to 100 l/min. Other information derivable by this technique is discussed. Fundamental principles of aerodynamics are also considered in relation to closed-circuit breathing apparatus. It is shown that under conditions of practical use of such systems, flow is only laminar in rare instances. Useful information can be gained about the frictional resistance of a respiratory circuit from simple bench tests at various constant rates of flow of air, and from the results of such experiments theoretical calculations can be made of the rate of work done. They are shown to correspond well with the measured rates of work done by human volunteers when breathing against the same resistance at all levels of exertion on a treadmill. Submitted on March 7,1960

Design and Performance of Field-Defining Apertures for Neutron Capture Therapy

The purpose of this report is to present some of the special radiological problems which arise when a nuclear reactor or atomic pile is used in medical research and experimental radiation therapy. While there are many and various ways in which this new tool can be used, the principal emphasis here will be toward the means and the devices which are utilized in order to control the energy spectrum of the external neutron stream and to direct it selectively to the treatment site. It has become possible to investigate these problems under practical conditions of use now that a nuclear reactor has been built expressly for and as an integral part of a Medical Research Center (1). Figure 1 shows the general external aspect of the Medical Research Center at Brookhaven National Laboratory, with the reactor housed in the cylindrical building in the background. The initial exploratory phase of its operation has turned up the acute problem of extracting from the machine the kinds and the numbers of neutrons required for experimental therapy, and the concurrent problem of keeping the gamma-ray contamination down to an acceptable level. Except for some pertinent details of power level and neutron fluxes, the nuclear engineering aspects of the machine are not related here. The emphasis is instead placed on the machine as a device for studies on man and the diseases of man. Its design began with the establishing of criteria for the treatment situation in terms of human convenience as well as of radiation. The beginning point was the patient and a suitable radiation exposure room around him. The neutron aperture was stipulated to be at the appropriate location and to have the desired flow of neutrons controlled by a shutter. The situation is thus entirely medical in nature; the reactor was designed to provide the factors demanded. Other conveniences were, of course, included, and flexibility of application was built in at every possible point. Other kinds of investigation are planned and still others—as yet not imagined—must surely present themselves. The reactor will run typically at a power of 1,000,000 watts (1 megawatt). Performance of the reactor has actually been satisfactory in terms of its internal and operational characteristics. Its pattern of control, heat transfer, and other engineering attributes have been good enough that permission has been granted to run at power levels up to 3 megawatts. For the typical operating condition at the 1-MW power level, central core flux figures are greater than 1013 n/cm.2·sec., as predicted. On the other hand, the primary reason for building this reactor is to use streams of neutrons external to the reactor shield. To provide for this, the design includes specialized shielding components to minimize the delivery distance. The channel combines elements arranged for best neutron optics, planned from studies made during the criticality experiments.

The long-term stability of fixed resistors

The causes of long-term failure under practical conditions of use or storage of different types of fixed resistors commonly used in electronic equipment have been investigated. Some reported life tests have proceeded without interruption for almost four years. Carbon-composition (grade 2) resistors under load fail by slow thermal degradation of the resistive material. Drift of value may also occur if unloaded resistors of this type are stored in a damp atmosphere. Vitreous-enamelled wire-wound resistors made with fine wire may fail during tropical exposure both unloaded and especially when lightly loaded with direct current. This is owing to electrochemical corrosion taking place at faults in the vitreous coating. High-stability cracked-carbon (grade 1) resistors may fail rapidly under light d.c. load by electrochemical action if moisture condensation occurs and the protective paint or varnish coating is inadequate.Tests for long-term resistor stability are critically discussed.

The long-term stability of fixed resistors

The causes of long-term failure under practical conditions of use or storage of different types of fixed resistors commonly used in electronic equipment have been investigated. Some reported life tests have proceeded without interruption for almost four years. Carbon-composition (grade 2) resistors under load fail by slow thermal degradation of the resistive material. Drift of value may also occur if unloaded resistors of this type are stored in a damp atmosphere. Vitreous-enamelled wire-wound resistors made with fine wire may fail during tropical exposure both unloaded and especially when lightly loaded with direct current. This is owing to electro-chemical corrosion taking place at faults in the vitreous coating. High-stability cracked-carbon (grade 1) resistors may fail rapidly under light d.c. load by electro-chemical action if moisture condensation occurs and the protective paint or varnish coating is inadequate.Tests for long-term resistor stability are critically discussed.

An Analysis of Insect Environments and Response

It has become increasingly evident of late years that a detailed study of the environment is of first importance in dealing with control measures for injurious insects. All forms of life are most intimately related to their respective environments, being so nicely adjusted to them that any considerable change in the conditions exerts a very marked influence either in favor of the organism or to its detriment. The organism is, in other words, what its environment makes it. Thus, if we know accurately the conditions of its environment, we know how to change the whole economy of the organism by perverting certain of the controlling conditions. It is axiomatic that the best method of control in the case of a given insect is to substitute for its normal environment an inimical one. Moreover, during its life cycle, the insect is subjected in most cases to several distinct environments, and it is important to know which one of these may be most profitably manipulated for its destruction. It is clear that the study of environments will be the first and last steps toward control in the entomological work of the future. But the question has always been how to approach and encompass this subject, how to determine accurately the influence of all the various conditions on the particular insect under consideration. Everyone realizes that the whole life cycle and economy of the insect, its habits, its physiological and structural characters, are the result of the environmental conditions which constantly surround and affect it. But how to get an accurate and tangible expression of these conditions for practical use is a matter that has long been the subject of earnest investigation in both Europe and America. The writer has for very many years, and especially during the past fifteen years, attempted to elucidate the study of insect environment, and reduce it to a comprehensive, tangible, and workable form. Only within the past year or two has he succeeded in securing results which partially satisfy him in this regard. The purpose of this paper is to present briefly these results. Early in his work, the writer perceived that environment students were constantly confusing various elements of the environment. It seemed to be commonly accepted that the environment consisted entirely of factors, or forces acting on the organism, and that factors and responses constituted the whole subject. In reality, the environment consists of several classes of elements, as is demonstrated by a thorough analysis of it; and, if all these elements be indiscriminately interpreted as factors, it is impossible to get a clear idea of environmental functions.