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By Toru H. Okabe

As part of a systematic study on the thermodynamic properties of complex nitrides, phase equilibria of the system Li-M-N (M Mg, AI, Ga) at 900 K were investigated. An attempt to determine the thermodynamic properties of complex nitrides was made by using the galvanic cell method, which utilizes LiMgN as an electrolyte under nitrogen atmosphere. The electromotive force (Emf) of ilie cell at temperatures between 800 and 1100 K was measured. Whilc the Emf of the cell at 900 K was measured to be 0.137 V, data discrepancies of ±0.03V were found. It was difficult to determine temperature dependence of ilie Emf. The Gibbs energy change for the reaction, 113 LbN (s) + 1/3 Mg3N2 (s) = LiMgN (s), at 900 K was determined to be tJ.Gor (LiMgN) -13.2 (±2.9) kJ/mol. Using thermodynamic information on ilie binary nitride from literature, the standard Gibbs energy of LiMgN was derived to be AGO f (LiMgN)= - 121 kJ at 900 K. The thermodynamic stability range of nitride was discussed by constructing isothermal chemical potential diagrams that provide a better understanding of ilie stability region of the LiMgN phase. The diagram was found to be in good agreement with the isoiliermal phase diagram determined by ilie alloy equilibration meiliod. Although the obtained data includes large uncertainties, the results provide a better understanding of the iliermodynamic stability of nitrides. The potential application of this complex nitride to nitrogen chemical sensors or a medium for controlling nitrogen potential is also shown.

Jan 1, 2003

By Andrew B. Suttie

The lead-acid battery recycling industry was seriously affected during the 1980s by increasing environmental protection costs and poor lead prices. The process is now being repeated in the 1990s causing further difficulties, for recyclers. In Europe, many lead-acid battery recycling plants use rotary furnaces. The Darley Dale smelter, redeveloped between 1984-87, uses only rotary furnaces. A review of options for this plant has been completed and 'concluded in favour of further investment to exploit more fully the benefits of rotary furnace technology.

Jan 1, 1995

By Christian Bernhard, Mario Hartl, Susanne K. Michelic

"One aspect of an efficient process and product optimization of the liquid steelmaking process is the understanding of reactions and interactions between the components steel, slag and nonmetallic inclusions. The present paper focuses on a fundamental study of this topic by combining the powerful methods of thermodynamic modeling with systematic experiments on a laboratory scale and subsequent SEM/EDS analyses. The modeling aspect is addressed by the commercial software FactSage 6.1; laboratory experiments are performed for a low-alloyed, Ca-treated carbon steel combined with varying slag compositions. The consequent SEM/EDS analyses provide a detailed insight into the inclusion landscape which offers a strong tool for characterizing the modification of inclusions. In the present study the combination of these methods is mainly applied to oxides, due to their crucial influence on the final product quality, thus giving important indications for further optimizing the secondary metallurgy processes.IntroductionIn recent years, the range of application for steels has been enlarged continuously; also resulting in extreme surrounding conditions combined with considerable stresses for the material. This trend is directly linked with higher demands on the properties of steels. In order to optimize the final product quality, the cleanness of steels is an important criterion. For this reason, the broad topic ""Steel Cleanness"" has become one of the main research points at the Chair of Metallurgy. Next to the continuous optimization of methods for the characterization of cleanness, the primary aim is to combine thermodynamic modeling and laboratory experiments in order to describe the changes in inclusion landscape under different conditions.The steel cleanness can particularly be influenced in the processes of secondary metallurgy. In different processes the reactions and interactions between the components steel, slag and nonmetallic inclusions (NMI) are essential for the final inclusion landscape. Consequently, the understanding of the occurring reactions is a fundamental aspect for further development and process optimization. In secondary metallurgy especially oxide-slag systems consisting of the components Ca0-Ah03-Mg0-Si02, which significantly influence the modification of NMI, are of importance. Several works dealing with the interactions of oxide non-metallic inclusions with different slag systems have been published in the last years [1-4]. In order to observe the dissolution of oxides in different slag compositions a Laser Scanning Electron Microscope is frequently used. A very detailed study on the ternary system Ah03-Ca0-Mg0 and its subsystems was also done by De Aza et al. [5, 6]."

Jan 1, 2011

By Leon E. Laforest

An early commitment by Kidd Creek Mines Ltd. (formerly Texasgulf Canada) to follow a stringent environmental control programme from the initial stages of design and development of its metallurgical facilities in Timmins, Ontario, has resulted in the on-going attainment of extremely low levels of industrial waste emissions. This paper outlines the monitoring programme initiated and maintained by the company's environmental control section. Comparative results of environmental sampling for the periods before and after the copper smelter start-up are highlighted.

Jan 1, 1983

By E. Gutierrez-Miravete

A computational method for the simulation of mold filling processes is described. The method is based on the representation of the flowing or deforming medium as a collection of mutually interacting parcels of material. Instantaneous positions of individual material parcels are calculated by numerical integration of the dynamic equations, subject to appropriate initial and boundary conditions. So far, the method has been used to produce qualitative simulations of some flowing and deforming systems encountered in mold filling technology, and our findings are summarized herein. In all cases, individual material particle motions can be followed in detail, allowing critical examination of potentially problematic mold design features.

Jan 1, 1992

By E. S. Geskin, W. L. Chen, A. Vora

"This paper is concerned with the application of an abrasive waterjet for metal shaping. The waterjet cutting technology uses water compressed to the pressure up to 55,000 psia which is accelerated in a cylindric nozzle. Abrasive particles are then supplied into the water stream and accelerated by the water. Cutting occurs via the interaction between the water-particles stream and a workpiece that causes material erosion at the impingement zone. The mechanism of this interaction enables shaping of practically any material with a minimal effect on the metallurgy of subsurface. The motion of the jet penetrating through a material body is guided by a robotic arm. A waterjet cutter is becoming one of the principal tools for shaping titanium, super-alloys and other hard-to-machine metals and composites. The shaping, resulting from the waterjet cutter, is very similar to laser beam cutting. However, unlike laser processing, there is no damage to the subsurface structure.The presented work discusses the experimental study of cutting of titanium plates. The results of these experiments demonstrate the potential of the abrasive waterjet as a shaping tool. IntroductionOne of the main avenues in the development of metal shaping is the use of high energy beams as cutting tools (1,2). There are a number of advanced beam oriented material removal technologies, such as laser, electron beam, plasma and abrasive waterjet (AWJ) cutting. The advantages of AWJ cutting are well understood and documented (3-14). This technology has the potential of becoming the principal tool for netshaping and netsurfacing of parts. However, the use of AWJ is currently limited to cutting of hard-to-machine materials such as titanium, superalloys, glass, composites, etc. The cost of A W J cutting is much higher and the productivity is much lower than those of the thermal cutting. At the same time abrasive waterjet can be used for shaping any existing technological material from fabrics, plastics, aluminum to glass, composites, and diamonds. The material losses during AWJ shaping are minimal. The roughness and waveness of the surfaces generated during AWJ cutting are substantially less than those of the thermal cutting. Due to the size of the jet cross-section total force exerted by the jet on a workpiece does not exceed 30-50 newtons. This terminates the need in the use of complex fixture for material holding. Low applied forces and low surface temperature prevent the damage of metal subsurface in the course of cutting. The small size of the impingement area will determine the limited width of the kerf. Due to the size of kerf and unidirectional character of the water jet the formation of practically any metal contour is possible."

Jan 1, 1988

By O. Ryosuke Suzuki

A new metallurgical process via sulfide is proposed: a sulfide is produced at a high temperature from its metallic oxide using gaseous CS2, and this sulfide is electrochemically reduced to its metallic state using molten salt. This combined process via sulfide is effective to obtain high purity of metallic powder, even if the metal in its oxide is strongly combined with oxygen. For example, it is not easy to reduce stable oxide TiO2, and only Ca can remove oxygen to form α-Ti. However, a fairly large amount of oxygen remains as Ti–O solid solution. Because the solubility of S in Ti is very small, this proposal was examined experimentally both on the conversion of TiO2 to TiS2 and on the successive reduction of TiS2 to Ti. TiO2 powder was exposed to CS2 gas flow at 1073 K, and the conversion to TiS2 was confirmed. TiS2 could be reduced to Ti powder either by calciothermic reduction or electrolysis in a CaCl2 melt. By Ca reduction at 1133 K in CaCl2 melt, sulfur concentration decreased to 0.03 mass%S when the amount greater than twice the stoichiometric calcium amount is added. By electrochemical reduction at 1173 K in CaCl2–CaS melt, S concentration significantly decreased to 0.01 mass% S when four times larger amount of electric charge was supplied.

By Mingmei Zhu, Xin Qiu, Xiaofei Dou, Yu Wang, Tiancheng Lin, Bing Xie

In this study, the slag forming route of the single-slag steel melting when smelting medium phosphorus hot metal was investigated. The CaO-SiO2-FeO-MgO-MnO-P2O5 as hexahydric slag system was adopted in the converter. The effect of slag composition on liquidus was calculated by FactSage, the isogram of phosphorus distribution ratio was calculated by using the regular ion solution model, combining these two tasks, the theoretical slag forming route was obtained. Through experiments, the actual melting point ofthe corresponding components on theoretical slag forming route was obtained, in this way, the theoretical slag forming route was confirmed. Then, the theoretical slag forming route was applied to industrial test in a 210t BOF. After using the new slag formating route, the dephosphorization ratio was increased 3.6% while the auxiliary materials consumption was reduced, and the cost of steelmaking was reduced.

Jan 1, 2015

By Jorge A. S. Tenorio, Girley F. Rodrigues, Joner O. Alves, Denise C. R. Espinosa

"Rock wools are mineral fibers composed of amorphous silicates, due to their thermo-acoustic characteristics this material has a broad consumer market in the construction, automotive, and electric-electronics industries. This work studied the recovery of wastes from ornamental rocks (granite and marble) as partial raw materials in the production of rock wools. Residues from granite and marble cuttings are industrial wastes with considerable production and limited applications. These wastes should be appropriately managed because when discharged in rivers or lakes can cause siltation, and also they can cause serious human health problems, such as silicosis. Samples of produced materials with thickness smaller than 500µm were characterized by chemical analyses, XRD, and DTA. Results showed that the rock wools produced using granite or marble wastes have important properties, especially the melting point. This process decreases the extraction of mineral resources and provides a profitable destination for the ornamental rock wastes.IntroductionThe ornamental rocks industry is a sector with large production of wastes. During the granite and marble extraction processes and specifically during the rocks cutting (see Figure 1), approximately 35 tons of powdered rock per month can be produced. These residues should be appropriately managed, because when discharged in rivers, lakes or watersheds, they can cause siltation. Also, these wastes can cause serious human health problems, such as silicosis [1].Currently, the granite and marble wastes are mainly used in civil construction to produce materials in the form of mortar, bricks and tiles. However, due the current produced volumes and the average growth of world production estimated at 6% per year, new applications for these wastes are necessary [2]."

Jan 1, 2011

By Qiang Yu

This paper reports on a research project supported by NSF, which aims at developing a multi-scale methodology for systematic microstructure prediction in thermo-mechanical processing of metals. This methodology is based on combining mesoscopic microstructure models with macroscopic process formulations and involves the following three main steps: (I) based on the given global processing conditions, the gross deformation patternof the entire workpiece is modeled using a continuum-based algorithm, (2) the resulting parameters are then extracted from the continuum-based simulation, post-processed and passed on to the mesoscopic numerical module, and (3) the microstructural changes are finally modeled at the mesoscopic scale. This approach is expected to overcome the disadvantages of current microstructure prediction practice employing empirical relationships between microstructural features and processing parameters. Keywords: Thermo-mechanical processing, Microstructure, Grain growth; Recrystallization; Mesoscopic models; Finite Element Method

Jan 1, 2003

By J. T. Stanley

The identification of crystal phases and crystal chemistry can be critical to understanding the mechanisms of waste material interaction with native soils. Understanding these mechanisms can suggest correct methods for remediation and treatment. A program is outlined and examples are given of the development of effective techniques for rapid phase identification of environmental samples using electron microscopy. The program concentrates on the development of integrated object oriented software to aid rapid searching of online databases and rapid simulation of potential crystal diffraction patterns. Examples come from dried sludge taken from a former hard-chrome plating facility.

Jan 1, 1993

By F. Patisson

One of the major issues with multiparticle reactors is to handle their multiscale aspect. For modeling, it usually comes to coupling a reactor model (describing the phenomena at the macroscopic scale) with a so-called grain model (simulating the behavior of a single grain or a particle). An interesting approach proposed by H.Y. Sohn (1978) is to use the law of additive reaction times in order to calculate, approximately but analytically, the reaction rate of a particle in the reactor model. Its great advantage, compared to a numerical grain model, is to drastically reduce the computation time, particularly in the case of complex reactor models. This is the approach we retained for modeling the moving bed furnace, a counter-current gas-solid reactor used in the nuclear fuel-making route for producing uranium tetrafluoride from uranium trioxide. The numerical model we developed is 2-dimensional, steady-state and based on the finite volume method. It describes solid and gas flow, convective, conductive and radiative heat transfers, and six chemical reactions involved in the process. The law of additive reaction times is used to calculate analytically the rate of the three principal gas-solid reactions at every discrete point in the reactor. We have demonstrated the validity of this approach by comparing its results with those calculated from a numerical grain model. Also detailed in the paper are the main results of the moving bed furnace model itself and the possibilities of optimizing the process revealed by the calculations.

Jan 1, 2006

By D. C. Foguel, J. L. R. Bravo

For several years, Caraiba Metais S.A. (CMSA) had to stock the arsenic sludge generated from the electrolyte purification process of its tankhouse. The amount stocked · reached approximately 3,500 tonnes, as the effects of its recycling during the smelting process and consequently in the sulfuric acid plant were unknown. Besides, it had as limiting factors the high content of arsenic in the copper concentrates supplied by foreign countries as well as the reduced capacity of the tankhouse's purification plant. The choice for selling the mentioned residue, which generally contains more than 50% of Cu, was attractive, but the environmental policies and regulations had not allowed this option. Other alternatives, such as the production of bicupric arsenic by means of a solvent extraction process or arsenic trioxide, were considered but the economic feasibility was not attractive due to the absence of a domestic market and a poor international market. After a study of the arsenic partition in the metallurgical process, it was verified that the residue could be recycled without causing any operational problems or damage to the environment. To make this possible, the capacity of the purification plant was increased and the way of removing the arsenic sludge from the cells was modified from manual to mechanical, therefore avoiding the direct contact of the workers with this poisonous substance. Moreover, procedures for recycling in the smelter were established and tolerance limits were set for both the smelter and the sulfuric acid plant. The main amount of arsenic to be recycled is released with the smelting furnace off-gas, which is washed during the purification stage of the sulfuric acid plant. The acid water, rich in arsenic, is then treated in the waste plant and the arsenic, in its stabilized condition, is confined in an appropriate area.

Jan 1, 2000

By Klaus Bauckhage

Phase-Doppler-anemometry (PDA)-measurements have to be taken from representative measuring positions from inside the spray cone, helping - with the support of simulated data of improved process models - to describe the multiphase flow situations within the spray cone - and accordingly to that - the heat transfer conditions for the rapid cooling and (partly) solidifying melt droplets before their impact onto the substratddeposit. Simulations and PDA-measurements thus give the base to confirm the hypothesis of the existence of a semisolid mixed-layer and it's influence on the resulting material structure during compaction. The dispersed particles in the spray cone exhibit a cooling and solidification process within a split of a second, which leads - as far as the particles solidify - to a dendritic structure with very short dendritic arm spacings. This causes within the particles extremely short distances for the following equalizing diffision processes taking place on a high temperature level (between liquidus and solidus) in the semisolid mixed-layer of the deposit and explaining the short residence times within this zone of only seconds up to a few minutes. This and the fact that the globular structure of the mushy zone (in the semisolid mixed-layer) leads to an unidirectional crystallization process over very short distances also explains the chemical and morphological ,homogeneity of the sprayed material. The dynamics of these process steps, the very special buffer function of the mixing layer during parameter variations as well as the controlled cooling process of the preform in order to avoid hot cracks influence the quality of the material. Due to the necessity of measuring and controlling the particle bound mass-, momentum- and enthalpy- fluxes to the deposit the PDA-technique has been adapted and modified in order to receive in-line and (in the future) also on-line data from the dynamics of the multiphase flow conditions within the spray chamber.

Jan 1, 1999

By Yuanyuan Wang, Hong Li, Xueting Liu, Hao Bai, Kang Zhou

"Phase change materials are widely used in efficient utilization of energy and new energy technology. Especially, more attention has been paid to composite phase material, which is applied on architectural energy-saving and efficient working fluid. In this paper, stearic acid-silicon dioxide composite material was prepared by sol-gel process from tetraethyl orthosilicate (TEOS) and stearic acid (SA). The material was investigated by Field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and Differential scanning calorimeter (DSC). The FE-SEM results show that 3D-grids of silicon dioxide were formed clearly and SA was encapsulated in the silicon dioxide shell. The FT-IR results show that there were no chemical reactions between silicon dioxide and SA, which is the chemical property of the composite material, is stable. The DSC results show that the composite phase change material has favorable heat capacity. This material is expected to be used to make a cooling working fluid.1. IntroductionEnergy thermal storage becomes increasingly prominent issue in recent years, because thermal storage has been used in many aspects, for example, it can be added into building materials to improve heat conditioning. Another potential application of thermal storage materials is that the intermittent waste heat can be collected and recycled effectively by using the thermal storage facility. Thus, energy thermal storage plays a significant role in conserving available energy and improving its utilization [1]. Energy thermal storage includes sensible heat storage and latent heat storage. The latent heat storage has great heat density with a constant temperature during the phase change process [2-5]. Large quantities of latent heat storage will be absorbed and released when phase change takes place. Based on the former researches, some phase change material (PCM), such as fatty acid and paraffin waxes, has been proved to have high latent heat storage capacity and appropriate thermal properties [5-6]. However, using the PCM in energy storage systems directly is restricted, e.g. some properties of organic PCM, like form-stability and thermal conductivity, are not good enough to use. Meanwhile, almost all the inorganic PCMs are corrosive and most materials may cause sub cooling and segregation [7-9].The other problem is that the leakage when the temperature reaches the phase change point. Therefore, encapsulated composite phase change material (CPCM) emerged in order to solve the problem of leaking out, minimize the sub cooling and prevent phase segregation. [10-13] However, the easy flammability of fatty acid also has hindered the development of PCM. Accordingly, it has been found out that silicon compounds are environmentally friendly promising substitutes for halogen-containing flame retardants. Especially, silsesquioxanes are excellent in the flame retardancy. So CPCM can be encapsulated with SiO2 acting supporting material."

Jan 1, 2014

By R. E. Fanning

"IntroductionThe Aluminum industry is one of many materials industries which strive to make their material the preferred choice for large volume products. In some applications one material has a natural advantage over others, but more frequently several materials compete with one another, each providing one or more advantages and some trade-offs. Customers may design their product with several objectives such as minimum system cost, maximum customer appeal or maximum manufacturing flexibility, choosing materials which best combine cost and performance. In such markets it may become necessary for a material supplier to enhance the attractive features of the particular material to outweigh its disadvantages.It is difficult, if not impossible, to predict how various materials will evolve. Technological breakthrough, government regulations, material availability or sociological issues may redefine the balance between competing materials. In spite of some uncertainty regarding the competitive position of competing materials, there is little doubt that unrelenting pursuit of product quality improvement and cost reduction are essential to future viability of the aluminum industry. It is the intent of this paper to identify some areas where technological improvement would be beneficial. Thus this paper is a collection of briefly described problems that will hopefully stimulate the thoughts and research required for knowledge based solutions. Rolling ProcessA particular example is the beverage can industry where aluminum, steel, glass and plastics vie for a share of the m.arket. The high cost of aluminum relative to steel or glass requires minimizing the amount of metal per can. The high intrinsic value of aluminum has led to extensive recycling of cans although net metal cost is still higher than that of the competing materials. Intensive engineering of the beverage can led to improved design and better understanding of material requirements. These improvements permitted substantial reduction in sheet thickness over the past decade. The downward trend in metal thickness for beverage can sheet is shown in Figure 1."

Jan 1, 1988

By G. S. Hanumanth

Sedimentation of particles during the liquid metal processing of particulate metal-matrix composites can affect the homogeneity, and thereby the properties, of the cast product. A novel electrical probe has been developed to measure the in-situ volume fraction of ceramic particles in molten metal baths. Using this probe, sedimentation rates for 90 pm silicon carbide particles dispersed in molten aluminum A356 alloy were measured over a wide range of particle volume fraction, 0.05 to 0.3. The sedimentation rate was found to depend strongly on particle volume fraction; the time to clarify a 0.15 m depth increased from approximately 60 to 500 seconds as the volume fraction increased from 0.05 to 0.3. Measured sedimentation rates agree well with the predictions of a sedimentation model based on one-dimensional, two-phase flow theory in which the inter-phase drag function is derived from the momentum equation, utilizing the Richardson-Zaki Equation for sedimentation in aqueous systems. The implications for solidification are discussed.

Jan 1, 1993

By S. Yokoya

With increasing requirement of steel productivity and quality in continuous casting in the conventional casting system using an immersion nozzle, it is very difficult to establish a reasonable molten flow pattern. In order to overcome this difficulty, we propose a new method of imparting swirling motion onto the flow in the immersion nozzle and to control the flow pattern in the mold. Following results have been obtained during the studies. For the case of slab continuous casting mold: High amplitudes of oscillation with a period of 10 to 15 seconds are observed in the outlet flow of the immersion nozzle and meniscus flow in the conventional casting system, while these phenomena are remarkably suppressed using swirling motion in the immersion nozzle, which leads to very calm and uniform flow pattern at the outlets of the immersion nozzle, in the mold and on the meniscus in the mold; For the case of billet continuous casting mold: (1) heat and mass transfer near the meniscus can be remarkably activated compared with a conventional straight type immersion nozzle without swirl, and (2) Quite different mold flow patterns are observed between the divergent and straight immersion nozzles. Heat and mass transport in the mold using the divergent nozzle is much more reasonable compared to that of straight nozzle. The findings, mentioned above, are very useful to control the flow pattern in the slab, and billet continuous casters. Such effectiveness of swirling flow in the SEN on the mold flow has been put into practical use. As a result, remarkable progress on the quality and production of continuous casting products has been observed in practical application.

Jan 1, 2006

By Yan Beygelzimer, Alexander Spuskanyuk, Victor Varyukhin

"The main idea of the report is that the yield surface can be presented as thick, ""foamed surface"" with dimensionality exceeding two. By other words, perhaps, the yield surface is fractal, i.e. it belongs to the class of geometric objects with fractional dimensionality. Apparently, fractal structure of the yield surface is determined by the fractal structure of natural materials. ""Cloud of internal stresses"" term is introduced to describe the stress distribution in representative volume element. Its plastic flow is determined by the interaction of this cloud with the thick yield surface. Thick yield surface and internal stress cloud concepts allow to determine an additional correlation between micro mechanical models of polycrystals and phenomenological theory of plasticity.1. IntroductionClassical plastic flow models are not satisfying the modem requirements. There are two main directions in their development. The first, mathematical, is connected with the development of the general theory of rheological relationships; the second, physical, is connected with the development of the representative volume element (RVE) models which are based on specific ideas about deformation mechanisms. Within the framework of the first direction, the macroscopic experimental data is formalized; the second approach deals with the generalization of physical research results for the different scale levels that are involved in plastic deformation.These approaches have advantages and disadvantages. In phenomenological theories, the advantages are the mathematical simplicity and laconic formulation of constitutive relations, which allows using them in practical calculations. However, the mathematical models of this class can not be considered as general, they are useful only for the description of limited range of deforming processes. On the other hand, physical theories that are based on the description of real plastic deformation mechanisms are very explanatory and predictive, but they lack mathematical simplicity. The above circumstances lead us to the necessity of compromise that can be found in determining the constitutive relations for RVE, which structure and parameters would bear the information about rnicrolevel and mesolevel phenomena. In this synthesis direction, the fundamental role belongs to [1,2], etc."

Jan 1, 2001

By Tor Lindstad

Specific C02-emissions are given for the production of silicon-metal, ferrosilicon, ferromanganese and silicomanganese. Emissions taken into account come from reduction materials, from coke production and generation of electric energy. C02-emissions can be abated by direct and by indirect methods. A direct method is to replace fossil carbon as reduction material wholly or partially by endogenous carbon (biocarbon, charcoal). Another possibility is to produce metals by electrolysis instead of the present electric smelting furnace. Indirectly CO2-emissions can be reduced by energy recovery, thus saving coal, oil or natural gas for heat generation. Some reduction in global C02-emissions can be obtained by giving credit for the use of silica dust partially replacing cement in concrete. In addition to give an overview of possible methods, costs will be discussed.

Jan 1, 1999