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A complete edge-weighted directed graph on vertices 1,2,...,n that assigns cost c(i,j) to the edge (i,j) is called Monge if its edge costs form a Monge array, i.e., for all i < k and j < l, c[i, j]+c[k,l]{le} < c[i,l]+c[k,j]. One reason Monge graphs are interesting is that shortest paths can be computed quite quickly in such graphs. In particular, Wilber showed that the shortest path from vertex 1 to vertex n of a Monge graph can be computed in O(n) time, and Aggarwal, Klawe, Moran, Shor, and Wilber showed that the shortest d-edge 1-to-n path (i.e., the shortest path among all 1-to-n paths with exactly d edges) can be computed in O(dn) time. This paper`s contribution is a new algorithm for the latter problem. Assuming 0 {le} c[i,j] {le} U and c[i,j + 1] + c[i + 1,j] {minus} c[i,j] {minus} c[i + 1, j + 1] {ge} L > 0 for all i and j, our algorithm runs in O(n(1 + 1g(U/L))) time. Thus, when d {much_gt} 1 + 1g(U/L), our algorithm represents a significant improvement over Aggarwal et al.`s O(dn)-time algorithm. We also present several applications of our algorithm; they include length-limited Huffman coding, finding the …

We are seeking to find biological methods to remove carboxylic functionalities from low-rank coals and to assess the properties of the modified coal towards coal liquefaction. The main objectives for this quarter were : continuation of microbial consortia development and maintenance, evaluation of commercial decarboxylase, decarboxylation of lignite, demineralized Wyodak coal and model polymer, and characterization of biotreated coals. Specifically we report that two batch fermentor systems were completed and three other fermentors under optimum conditions for coal decarboxylation are in progress; that inhibition of growth of methanogens in the batch fermentor system enhanced the carbon dioxide production; that adapted microbial consortium produced more gas from lignite than Wyodak subbituminous coal; that phenylalanine decarboxylase exhibited insignificant coal decarboxylation activity; that two different microbial consortia developed on coal seem to be effective in decarboxylation of a polymer containing free carboxylic groups; and that CHN analyses of additional biotreated coals reconfirm increase in H/C ratio by 3--6%.

We have measured solute trapping of several solutes in Al and Ni during rapid solidification. We have also made preliminary measurements of solute trapping of As in Si, trapped 20 atomic percent As in Si, and made a preliminary measurement of the T{sub o} curve in Si-As. 5 figs.

We have measured solute trapping of several solutes in Al and Ni during rapid solidification. We have also made preliminary measurements of solute trapping of As in Si, trapped 20 atomic percent As in Si, and made a preliminary measurement of the T{sub o} curve in Si-As. 5 figs.

We are seeking to find biological methods to remove carboxylic functionalities from low-rank coals and to assess the properties of the modified coal towards coal liquefaction. The main objectives for this quarter were : continuation of microbial consortia development and maintenance, evaluation of commercial decarboxylase, decarboxylation of lignite, demineralized Wyodak coal and model polymer, and characterization of biotreated coals. Specifically we report that two batch fermentor systems were completed and three other fermentors under optimum conditions for coal decarboxylation are in progress; that inhibition of growth of methanogens in the batch fermentor system enhanced the carbon dioxide production; that adapted microbial consortium produced more gas from lignite than Wyodak subbituminous coal; that phenylalanine decarboxylase exhibited insignificant coal decarboxylation activity; that two different microbial consortia developed on coal seem to be effective in decarboxylation of a polymer containing free carboxylic groups; and that CHN analyses of additional biotreated coals reconfirm increase in H/C ratio by 3--6%.

Atmospheric transport and diffusion models have been developed by the Environmental Technology Section (ETS) of the Savannah River Technology Center to calculate the location and concentration of toxic or radioactive materials during an accidental release at the Savannah River Site (SRS). The output from these models has been used to support initial on-site and off-site emergency response activities such as protective action decision making and field monitoring coordination. These atmospheric transport and diffusion models have been incorporated into an automated computer-based system called the (Weather Information and Display) System and linked to real-time meteorological and radiological monitoring instruments to provide timely information for these emergency response activities (Hunter, 1990). This study will compare two of the WIND System annospheric models, PUFF/PLUME and 2DPUF, with a select group of MATS experiments and examine the results in detail to determine the performance of the models. Additional results from this study can be found in Fast et al. (1991).

Atmospheric transport and diffusion models have been developed by the Environmental Technology Section (ETS) of the Savannah River Technology Center to calculate the location and concentration of toxic or radioactive materials during an accidental release at the Savannah River Site (SRS). The output from these models has been used to support initial on-site and off-site emergency response activities such as protective action decision making and field monitoring coordination. These atmospheric transport and diffusion models have been incorporated into an automated computer-based system called the (Weather Information and Display) System and linked to real-time meteorological and radiological monitoring instruments to provide timely information for these emergency response activities (Hunter, 1990). This study will compare two of the WIND System annospheric models, PUFF/PLUME and 2DPUF, with a select group of MATS experiments and examine the results in detail to determine the performance of the models. Additional results from this study can be found in Fast et al. (1991).

The objective of this project is to conduct extensive studies on the surface reactivity and surface hydrophobicity of coal-pyrites using various surface characterization techniques and to correlate the alteration of the coal-pyrite surface with the efficiency of pyrite rejection in coal flotation. The flotation characteristics of coal-pyrites under various conditions was studied and compared with ore-pyrite and coal to determine the causes of pyrite rejection difficulties in coal flotation. Both the native and induced floatabilities of pyrites were investigated. It was found that both coal- and ore-pyrites, ff prepared by dry-grinding, show little or no floatability in the absence of any chemical reagents. After ultrasonic pretreatment, ore-pyrite floats effectively in the acidic to neutral pH range. Kentucky No. 9 coal-pyrite (KYPY) shows significant flotation in the pH range 7--10. With ethyl xanthate as collector, ore-pyrite floats well up to pH = 10; while coal-pyrite reveals no flotation above pH = 6. For the first time, the effect of coal collector on the floatability of coal-pyrite has been studied. It was shown that in the presence of fuel oil--a widely used collector for promoting coal flotation, coal-pyrite, particularly for the fine sizes, shows good flotation below pH = 11, whereas ore-pyrite …

The objective of this project is to conduct extensive studies on the surface reactivity and surface hydrophobicity of coal-pyrites using various surface characterization techniques and to correlate the alteration of the coal-pyrite surface with the efficiency of pyrite rejection in coal flotation. The flotation characteristics of coal-pyrites under various conditions was studied and compared with ore-pyrite and coal to determine the causes of pyrite rejection difficulties in coal flotation. Both the native and induced floatabilities of pyrites were investigated. It was found that both coal- and ore-pyrites, ff prepared by dry-grinding, show little or no floatability in the absence of any chemical reagents. After ultrasonic pretreatment, ore-pyrite floats effectively in the acidic to neutral pH range. Kentucky No. 9 coal-pyrite (KYPY) shows significant flotation in the pH range 7--10. With ethyl xanthate as collector, ore-pyrite floats well up to pH = 10; while coal-pyrite reveals no flotation above pH = 6. For the first time, the effect of coal collector on the floatability of coal-pyrite has been studied. It was shown that in the presence of fuel oil--a widely used collector for promoting coal flotation, coal-pyrite, particularly for the fine sizes, shows good flotation below pH = 11, whereas ore-pyrite …