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"ABSTRAKA direct solvent-extraction method was evaluated to assess its application for the extraction and analysis of PAHs (polycyclic aromatic hydrocarbons) in coal-tar-contaminated soils. Eight individual solvents and two combined solvents were used in a screening test to determine the suitability of different solvents for the direct solvent-extraction method. Based on the extracted concentrations of the Total PAH, noncarcinogenic ride - were selected for further investigation by testing these solvents on four coal-tar-contaminated soils and a certified PAH -contaminated soil. The extraction results for the Total PAH and N-PAH concentrations showed that there were no statistical differences for the three solvents at a confidence interval of 95%. However, ethanol gave lower concentrations of C-PAH than acetone and methylene chloride. Fifteen coal-tar-contaminated soil samples from a land farming treatment unit were used to compare the direct solvent-extraction method using acetone as the extraction solvent with the conventional Soxhlet extraction method (EPA method 3540) and ultrasonic extraction method (EPA Method 3550). The results showed that the direct solvent-extraction method gave higher mean PAH concentrations than the Soxhlet and ultrasonic extraction method and that the direct extraction method was equivalent to the Soxhlet method at a confidence interval of 99%. Because of its simplicity of use and its equivalent extraction capability with the Soxhlet extraction method, the direct solvent-extraction method may be used as a technique for the extraction and analysis of PAHs in contaminated soil."

"Selecting a procurement strategy for construction projects is inherently subjective. The decision is often intuitively based on the previous experience and knowledge of the decision marker. An objective-subjective procurement selection method is proposed. The method takes into account the need to have an objective base for strategy comparison through the use of multiattribute utility technology. Allowing the desicion maker to assign importance ratings for the selection criteri also accommodates individual preferences and project specificities. The analytical hierarchical process based importance ratings assingment method improves both the objectivity and the realibility of the assessment. Application in real cases suggest positive potential use of the method. "

"The measurement of susoended sediment, particularly in field settings, is important in the documentation of sediment transport and deposition. Many measurement techniques have been used euth varying degrees of success. "

"ABSTRAKThe stable pools formed by spur dikes can be a significant factor for improving aquatic habitat in unstable degraded streams. Prediction of the volume and geometry of the scour hole associated with a spur dike yields information that is valuable for assessing the potential benefit to the aquatic habitat. Volumes of the scour hole in the vicinity of model spur dikes were measured in a laboratory flume under clear-water overtopping flows. Spur dike length, flow depth and shear velocity ratio were varied in the experiments and found to significantly influence the volume of the scour hole. For overtopping flows, the ratio of the flow depth to the spur dike height was found to be an important control on the geometry of the resulting scour hole. At higher flow depth to spur dike height ratios, the location of the maximum depth of scour changed from the upstream point of the dike toward the channel bank and caused a secondary scour zone to form downstream of the spur dike. A preliminary technique is proposed to predict the volume of scour for spur dikes perpendicular to the bank."

"ABSTRAKFor dynamic excitation, it is convenient to idealize homogeneous soil under a base mat by a semi-infinite truncated cone. It is easy to analyze the cone model for vertical and horizontal translation, as well as for rocking and torsional rotation. The accuracy by comparison to rigorous half-space solutions is quite adequate for practical applications. Time-domain computational methods for translational and rotational motions are described in both the stiffness and flexibility formulations and elucidated by examples. The infinite cone is dynamically equivalent to a discrete element representation of the soil, consisting of an interconnection of a small number of masses, springs, and dashpots. As an alternative to the physical-component model, the response may be determined directly by simple recursive numerical procedures. The recursive methods are exact and particularly well suited for hand calculations of short-duration excitations."

"ABSTRAKThe current design practice for concrete bridge decks requires a top mat and a bottom mat of reinforcing bars. The chloride attack of the top mat reinforcing bars is a major cause of deterioration of bridge decks. Emprical evidence has indicated that the top transverse reinforcing bars can essentially be eliminated without jeopardizing the structural integrity of a deck. To explore this issue, the behavior of a four-span highway bridge deck subjected to a test truck and normal traffic loads is being investigated. The behavior of the bridge under the test truck and various combinations of truck loads has been analyzed with the finite-element method. These result confirm the fact that a properly designed bridge deck does not requiere top transverse reinforcement for sustaining the negative bending moment induced by traffic loads. "

"ABSTRAK The aircraft gate reassignment problem occurs when the departure of an incoming aircraft is delayed or a delay occurs in a flight. If the delay is significant enough to delay the arrival of subsequent incoming aircraft at the assigned gate, the airline must revise the gate assignments to minimize extra delay times. This paper describes a genetic algorithm approach to solving the gate reassignment problem. By using a global search technique on quantified information, this genetic algorithm approach can efficiently find minimum extra delayed time solutions that are as effective or more effective than solutions generated by experienced gate managers. "