bluuebunny/crossref_metadata_2025 huggingface dataset:
A Mechanistic Approach to the Prediction of Material Removal Rates in Rotary Ultrasonic Machining
Authors: Pei Z. J. , Prabhakar D. , Ferreira P. M. , Haselkorn M.
Published: February 2008

An approach to modeling the material removal rate (MRR) during rotary ultrasonic machining (RUM) of ceramics is proposed and applied to predicting the MRR for the case of magnesia stabilized zirconia. The model, a first attempt at predicting the MRR in RUM, is based on the assumption that brittle fracture is the primary mechanism of material removal. To justify this assumption, a model parameter (which models the ratio of the fractured volume to the indented volume of a single diamond particle) is shown to be invariant for most machining conditions. The model is mechanistic in the sense that this parameter can be observed experimentally from a few experiments for a particular material and then used in prediction of MRR over a wide range of process parameters. This is demonstrated for magnesia stabilized zirconia, where very good predictions are obtained using an estimate of this single parameter. On the basis of this model, relations between the material removal rate and the controllable machining parameters are deduced. These relationships agree well with the trends observed by experimental observations made by other investigators.
A Customized Neural Network for Sensor Fusion in On-Line Monitoring of Cutting Tool Wear
Authors: Leem Choon Seong , Dornfeld D. A. , Dreyfus S. E.
Published: February 2008

A customized neural network for sensor fusion of acoustic emission and force in on-line detection of tool wear is developed. Based on two critical concerns regarding practical and reliable tool-wear monitoring systems, the maximal utilization of “unsupervised” sensor data and the avoidance of off-line feature analysis, the neural network is trained by unsupervised Kohonen’s Feature Map procedure followed by an Input Feature Scaling algorithm. After levels of tool wear are topologically ordered by Kohonen’s Feature Map, input features of AE and force sensor signals are transformed via Input Feature Scaling so that the resulting decision boundaries of the neural network approximate those of error-minimizing Bayes classifier. In a machining experiment, the customized neural network achieved high accuracy rates in the classification of levels of tool wear. Also, the neural network shows several practical and reliable properties for the implementation of the monitoring system in manufacturing industries.
In-process Identification of System Time Constant for the Adaptive Control of Grinding
Authors: Thomas D. A. , Allanson D. R. , Moruzzi J. L. , Rowe W. Brian
Published: February 2008

The forces generated during the grinding process cause deflections of the machine-grinding wheel-workpiece system which are large compared to the accuracies required. The deflections cannot be precisely predicted and the optimum grinding conditions vary because the grinding wheel sharpness changes with grinding wheel wear and dressing. In practice conservative machining conditions and feed cycles are used in order to maintain the quality of the finished workpieces. This paper presents a new method of characterizing the time constant of the system from the grinding power consumption during the infeed section of a grinding cycle. Adaptive grinding cycles have been implemented which use the measured value of system time constant to control the target axis position and the dwell time. In this way the control system adapts the machining cycle for the wheel condition at the time of grinding, and can cope with the large variations in deflection that occur when using high feedrates.
Digital Gap Monitor and Adaptive Integral Control for Auto-Jumping in EDM
Authors: Wang W. M. , Rajurkar K. P. , Akamatsu K.
Published: February 2008

This paper reports a monitoring and adaptive integral control strategy for EDM to regulate the cycle time of the periodical retraction (jumping) of the tool electrode according to the gap condition. A digital EDM gap monitor has been developed to detect the time ratios of gap states with a resolution of 0.2 μs. The theoretical and experimental analysis of the effect of sensing parameter combinations on control aspects and performance of manual setting, integral control and adaptive integral control methods have been carried out. Experimental verification shows that the proposed system results in higher erosion rate, better machining stability, and complete avoidance of arc damage.
Surface Smoothing Mechanism by Replication in Ironing Process
Authors: Wang Z. , Kondo K. , Mori T.
Published: February 2008

The purpose of this paper is to clarify the surface smoothing process under contact states with a small relative slide between the tool and workpiece. An internal ironing apparatus was developed to observe the surface during the processing. Observation revealed that the surface smoothing process is largely developed during a very short contact length from the entrance of the contact zone where the bulk material is in the elastic state and can be markedly promoted by the plastic deformation in the surface layer. It was also confirmed that the ironed surface roughness decreases by increasing the ironing reduction in thickness and reaches the surface roughness of container Ra = 0.01 μm under dry condition and 30 percent in the reduction when initial surface roughness Ra is about 0.07 μm. The surface smoothing process could be understood by the slip-line field theory.
Off-Axial, Gas-Jet-Assisted, Laser Cutting of 6.35-mm Thick Stainless Steel
Authors: Hsu M. J. , Molian P. A.
Published: February 2008

A dual gas-jet, laser-cutting technique involving coaxial and off-axial oxygen gas flows was developed to cut 6.35-mm thick AISI 304 stainless steel plates with a 1.2-kW CO2 gas transport laser at a cutting speed of 12.7 mm/sec (30 in./min). Under identical process conditions, the single, coaxial gas jet could not cut the stainless steel although the cutting speed was reduced to 2.11 mm/sec (5 in./min). Thresholds of off-axial nozzle diameter, gas-impinging angle, oxygen pressure, and other process parameters were determined to obtain clean-cut edge quality (average dross height 0.25 mm). Experimental data coupled with a fluid-dynamics model of gas flow were presented to show the effectiveness of the dual gas-jet, laser-cutting method in achieving the maximum machining rate without deteriorating the quality of cut.
A Novel Approach to the Design of Self-Piloting Drills With External Chip Removal, Part 1: Geometry of the Cutting Tip and Grinding Process
Authors: Astakhov V. P. , Galitsky V. V. , Osman M. O. M.
Published: February 2008

The performance of a self-piloting drill with external chip removal is affected by the geometry of its cutting tip. A comprehensive analysis of the cutting tip geometry and its influence on the drill performance is made. This subject is treated in two parts. In Part 1, the cutting tip geometry is analyzed. Special attention is given to the flank planes and a novel approach to the design of the drill was developed. By this approach the drill flank planes are located with minimum offset of the supporting pads’ faces relative to the plane of the drill corner’s rotation. Since several important drill angles are defined, the analysis is extended to cover the grinding process. The experimental comparison between the ordinary and newly designed self-piloting drills with external chip removal is also made to show the advantages of the latter.
A UBET-Simulation Meant for Basic Understanding of the Extrusion of Aluminum Profiles
Authors: Sta˚hlberg U. , Hou J.
Published: February 2008

A plane strain UBET-model, meant for deeper understanding of the material flow in the extrusion of complex shaped aluminum profiles is presented. In order to get the desired straight shape of the extrudate, every part of its cross-section must exit the die with the same velocity. One intention of the present work is to imitate this problem and to analyze it in a simplified way. This has been done by studying the extrusion through a two-hole die face. The flow is balanced by determining the optimum lengths of the bearing lands, i.e., those lengths which result in equal exit velocities of the extrudates. Furthermore, the material flow, as influenced by the position of the die openings along the die face, has been investigated.
On the Plastic Deformation of a Tube During Bending
Authors: Pan K. , Stelson K. A.
Published: February 2008

The objective of this study is to develop an analytical approach to calculate the relationship between the axial curvature of a bent tube and the resulting deformation of the cross-section. The model accounts for both geometrical and material nonlinearities. An approximate expression in trigonometric form is introduced for the displacement field, which reflects the change of wall thickness and neutral axis shift during bending. The total deformation theory is employed as a constitutive relation. The solution is found using a minimization approach and the energy principle. A better approach for springback prediction might be obtained from the deformation model, which predicts a more accurate moment of inertia change during bending.
Die-less Forming of Thermoplastic-Matrix Continuous Fiber Composite Materials—Process and Demonstration
Authors: Ramani K. , Miller A. K. , Cutkosky M. R.
Published: February 2008

Conventionally, large components made of thermoplastic matrices and continuous fibers are manufactured in autoclaves using dies. As the applications of composite materials increase, there is a need to reduce costs and increase manufacturing flexibility. This need has led to the development of a new concept called “die-less forming”. The concept of “kinematically admissible bending” is central to the concept of die-less forming. The concepts behind die-less forming have been tested in preliminary experiments on a two-roller demonstration machine. Induction heating was used to locally heat the composite as it moved into the forming zone, where it was bent using a specially designed cluster roller. Induction heating combined with a variable velocity profile was successful in establishing a uniform heating profile. Experiments were conducted for multidirectional APC-2 carbon/PEEK fiber composites and the composite bending behavior was explained using energy methods.
Thermal Expansion of the Workpiece in Turning
Authors: Stephenson D. A. , Barone M. R. , Dargush G. F.
Published: February 2008

Thermal expansion of the part can be a significant source of dimensional and form errors in precision machining operations. This paper describes a method for calculating the thermal expansion of an axisymmetric workpiece. The analysis is based on a commercially available boundary element code modified to properly represent concentrated moving heat sources such as those produced in machining. The inputs required are the amount of heat entering the part from the cutting zone and the thermal properties of the workpiece material. Calculations are compared with direct measurements of expansion from tests on large diameter 2024 aluminum sleeves. The agreement between calculated and measured values is generally reasonable, although calculated expansions are consistently smaller than measured expansions. This error is probably due to errors in estimating the heat input to the part, and particularly the neglect of flank friction in heat input calculations. Sample calculations for hard turning of a wheel spindle show that expansions can approach tolerances on critical surfaces. Based on sample calculations, thermal expansion is likely to be significant when hard turning parts with tolerances on the order of 0.01 mm. For these applications, critical surfaces should be machined first, before cuts on other sections heat the part, and gaging should be carried out only after the part has cooled.
A Mechanistic Approach to Predicting the Cutting Forces in Drilling: With Application to Fiber-Reinforced Composite Materials
Authors: Chandrasekharan V. , Kapoor S. G. , DeVor R. E.
Published: February 2008

In this paper models are developed to predict the thrust and torque forces at the different regions of cutting on a drill. The mechanistic approach adopted to develop these models exploits the geometry of the process, which is independent of the workpiece material. The models are calibrated to a particular material using the well-established relationships between chip load and cutting forces, modified to take advantage of the characteristics of the drill point geometry. The models are validated independently for the cutting lips and the chisel edge for drilling both metals and fiber-reinforced composite materials for a wide range of machining conditions and drill geometry. While the cutting-lips model predictions agree well with the experimental data for both materials, only the chisel-edge model proposed for metals agrees well with the experimental data.
An Adaptive Error Correction Method Using Feature-Based Analysis Techniques for Machine Performance Improvement, Part 2: Experimental Verification
Authors: Mou J. , Donmez M. A. , Cetinkunt S.
Published: February 2008

The development and derivation of an adaptive error correction method using an interactive inspection system and feature-based analysis technique for machine performance improvement were presented in Part 1 of this paper. Here, in Part 2, the experimental verification of the derived feature-based residual error models and analysis technique is described in detail. The experimental procedure and results of both the process-intermittent and the post-process gauging are presented. A polynomial regression method is used to derive the parametric functions that represent the deviation of imperfect features from nominal. The output of these polynomial functions is compared with process-intermittent inspection data to determine the machine errors and then to identify the residual systematic errors. Feature-based residual error models are used to correlate the residual errors to the systematic residual error components. Inverse kinematics technique and multiple regression methods are used to identify and characterize the contribution of each error component as a function of the machine’s temperature profile and nominal position. The residual error components are then combined with the error components identified through the pre-process characterization process to refine the geometric-thermal error model. After the error model is adaptively fine tuned, it can be used more effectively to compensate the machine tool error for more precise manufacturing.
Laser Machining for Secondary Finishing Applications
Authors: Sheng P. S. , Liu Ko-Wang
Published: February 2008

A laser-based technique for finishing axisymmetric parts is presented which allows the efficient finishing of polymers and ceramics without tool wear, tool breakage, or cutting forces. In this process, a laser beam impinges tangentially onto the surface of a cylindrical workpiece. A flexible machine tool can be developed to grind parts of differing geometries and materials by changing process parameters instead of setups or machines, as well as integrate primary machining and secondary finishing in one machine tool. The precision of laser finishing can be enhanced by using oblique beam impingement angles. Initial results show that Ra values less than 1 μm can be achieved on PMMA workpieces with a fixed beam. This paper presents the elements of the laser machine tool and preliminary results on parametric dependencies for laser finishing of polymer workpieces.
Heat Transfer in the Non-reacting Zone of a Cement Rotary Kiln
Authors: Ghoshdastidar P. S. , Unni V. K. Anandan
Published: February 2008

This paper presents a steady-state heat transfer model for a rotary kiln used for drying and preheating of wet solids with application to the non-reacting zone of a cement rotary kiln. A detailed parametric study indicates that the influence of the controlling parameters such as percent water content (with respect to dry solids), solids flow rate, gas flow rate, kiln inclination angle and the rotational speed of the kiln on the axial solids and gas temperature profiles and the total predicted kiln length is appreciable.
Recent Advances in the Study of Electrochemical Micromachining
Authors: Datta M. , Shenoy R. V. , Romankiw L. T.
Published: February 2008

The present paper reviews some fundamental aspects related to the understanding of the high rate anodic dissolution processes and their influence on thin film patterning by electrochemical micromachining. The role of convective mass transport and current distribution on the surface finish and shape evolution is discussed. Several examples of the applications of maskless and through-mask electrochemical micromachining are presented.
An Analytical and Experimental Study of the Flow of Sheet Metal Between Circular Drawbeads
Authors: Sanchez L. R. , Weinmann K. J.
Published: February 2008

This paper describes an analytical model for determining the pulling and shear forces and bending moment required to form sheet metal subject to plane strain along its width. The model is based on simplifying assumptions widely accepted in the analysis of wide thin sheet: planes remain plane and normal to the mid-surface, and plane stress state across the thickness. During deformation, any bending, unbending and reverse bending of the strip is analyzed and the constitutive law for this cyclic process is discussed. The model consists of an iterative procedure which is ended when the equation of equilibrium and all boundary conditions are satisfied. The output of the model gives the geometry of the deformed shape, the forces and moments applied along the strip, the displacement field, thickness variations, and stress and strain history fields. The model can be applied to an arbitrary die geometry, and it is used here to analyze the specific case of sheet flow through a drawbead gap consisting of circular drawbeads. The calculated resultant forces, the theoretical surface strains and thickness reductions agree reasonably well with the experimental results.
Fixture Failure Diagnosis for Autobody Assembly Using Pattern Recognition
Authors: Ceglarek D. , Shi J.
Published: February 2008

In this paper, a fault diagnostic method is proposed for autobody assembly fixtures. This method uses measurement data to detect and isolate dimensional faults of part caused by fixture. The proposed method includes a predetermined variation pattern model and a fault mapping procedure. The variation pattern model is based on CAD information about the fixture geometry and location of the measurement points. This fault mapping procedure combines Principal Component Analysis with pattern recognition approach. Simulations and one case study illustrate the proposed method.
Inverse Error Analysis for Multi-axis Machines
Authors: Lin P. D. , Ehmann K. F.
Published: February 2008

This paper discusses the problem of tolerance distribution among the links and joints of a multi-axis machine. By defining the maximum allowable tolerances for the position and orientation of the tool in the machine’s workspace, the allowable error tolerance limits of the link parameters and of the error motions of the joints are obtained. The solution of this problem, to be referred to as inverse error analysis, is of fundamental importance during the design stages of a new machine.
Prediction of Ball End Milling Forces
Authors: Yu¨cesan G. , Altıntas¸ Y.
Published: February 2008

Mechanics of milling with ball ended helical cutters are modeled. The model is based on the analytic representation of ball shaped helical flute geometry, and its rake and clearance surfaces. It is assumed that friction and pressure loads on the rake face are proportional to the uncut chip thickness area. The load on the flank contact face is concentrated on the in cut portion of the cutting edge. The pressure and friction coefficients are identified from a set of slot ball end milling tests at different feeds and axial depth of cuts, and are used to predict the cutting forces for various cutting conditions. The experimentally verified model accurately predicts the cutting forces in three Cartesian directions.
Helical Micro-Drill Point Design and Grinding
Authors: Lin C. , Kang S. K. , Ehmann K. F.
Published: February 2008

A new drill point geometry, termed the helical drill point, specifically intended for micro-drills, is developed in order to alleviate the disadvantages of existing planar micro-drill points. A mathematical model for this new drill point has been established. It is shown that this model is more general than existing drill point models. The commonly used conical, cylindrical and planar drill point models are only special cases of the helical model. For uniquely determining the grinding parameters of the new drill point as well as guiding the grinder design, the characteristics, the controllability and the sensitivity of the grinding parameters have been analyzed. Finally the geometric characteristics of this new drill point are investigated.
Geometric Modeling of Manufacturing Processes Using Symbolic and Computational Conjugate Geometry
Authors: Dhande S. G. , Karunakaran K. P. , Misra B. K.
Published: February 2008

The present paper describes a unified symbolic model of conjugate geometry. This model can be used to study the geometry of a cutting tool and the surface generated by it on a blank along with the kinematic relationships between the tool and the blank. A symbolic algorithm for modeling a variety of shape generating processes has been developed. It has been shown that using this algorithm one can develop geometric models for conventional machining processes such as milling, turning, etc. as well as unconventional or advanced machining techniques such as Electric Discharge Machining (EDM), Laser Beam Machining (LBM) etc. The proposed symbolic algorithm has been implemented using the symbolic manipulation software, MACSYMA. The algorithm is based on the concepts of envelope theory and conjugate geometry of a pair of mutually enveloping surfaces. A case study on the manufacture of a helicoidal surface and an illustrative example are given at the end of the paper.
Analysis of Flow and Heat Transfer in Twin-Roll Strip Casting by Finite Element Method
Authors: Hwang S. M. , Kang Y. H.
Published: February 2008

This paper presents a finite element approach for the analysis of the twin-roll strip casting process. Basic formulations for calculating the thermal and flow solutions are described, with emphasis on dealing with strong correlations between those solutions. Comparison with the experimental data found in the literature is made for examining the validity of the thermal solutions. A series of process simulations are carried out. The effect of various process variables on roll force, cooling rate, flow rate, and thickness of the solidified shell is investigated.
A Consideration of Optimum Conditions for Surface Smoothing Based on Lubricating Mechanisms in Ironing Process
Authors: Wang Z. , Kondo K. , Mori T.
Published: February 2008

The purpose of this paper is to clarify the mechanism of a smooth surface generation in the ironing process under contact states with a largely relative slide. In this case, the outflow behavior of lubricant trapped in the oil pits is the most important point in the surface smoothing process. It was deduced from ironing experiments that lubricant flows out from oil pits as a result of plastic deformation of the metal surface layer, mainly in the friction direction. A model has been proposed to estimate variations in the friction stress during ironing. This model can explain experimental results that the metal surface is best smoothed under the condition in which the minimum friction stress appears.
Design Optimization of a Three Degrees-of-Freedom Variable-Reluctance Spherical Wrist Motor
Authors: Roth R. B. , Lee Kok-Meng
Published: February 2008

This paper presents the basis for optimizing the design of a three degrees-of-freedom (DOF) variable reluctance (VR) spherical motor which offers some attractive features by combining pitch, roll, and yaw motion in a single joint. The spherical wrist motor offers a major performance advantage in trajectory planning and control as compared to the popular three-consecutive-rotational joint wrist. Since an improved performance estimate is required, a method for optimizing the VR spherical motor’s magnetics was developed. This paper begins with a presentation of the geometrical independent and dependent variables which fully described the design of a VR spherical motor. These variables are derived from examination of the torque prediction model. Next, a complete set of constraint equations governing geometry, thermal limitations, amplifier specifications, iron saturation, and leakage flux are derived. Finally, an example problem is presented where the motor’s geometry is determined by maximizing the output torque at one rotor position. The concept of developing a spherical motor with uniform torque characteristics is discussed with respect to the optimization methodology. It is expected that the resulting analysis will improve the analytical torque prediction model by the inclusion of constraint equations, aid in developing future VR spherical motor designs, improve estimates of performance, and therefore will offer better insight into potential applications.
Thermal-Mechanical Modelling of the Rolling-Plus-Sliding With Frictional Heating of a Locomotive Wheel
Authors: Gupta V. , Hahn G. T. , Bastias P. C. , Rubin C. A.
Published: February 2008

This paper examines finite element models for studying the long time frictional heating of locomotive wheels. The aim is to obtain the temperature distribution and the thermal and residual stresses in the wheel, for given conditions of rolling-plus-sliding, with the least computing effort. Initially a rigorous 3-D model is employed. Then this model is reduced to a much simpler but equivalent 2-D axisymmetric model with reasonable assumptions. It is shown, with the help of the 3-D model, that the actual temperature distribution is fluctuating and exhibits a sharp spike during each wheel rotation. For a part of the cycle the temperature is much higher than the steady state temperature calculated from the 2-D model.
Comparison of Antimicrobial Resistance Profiles among Extended-Spectrum-β-Lactamase-Producing and Acquired AmpC β-Lactamase-Producing
Escherichia coli
Isolates from Canadian Intensive Care Units
Authors: Baudry Patricia J. , Nichol Kim , DeCorby Melanie , Mataseje Laura , Mulvey Michael R. , Hoban Daryl J. , Zhanel George G.
Published: February 2008

Resistance profiles were compared among 18 extended-spectrum-β-lactamase-producing (ESBL) and 27 acquired AmpC β-lactamase-producing
Escherichia coli
isolates collected from Canadian intensive care units from 2005 to 2006. ESBL-producing
E. coli
isolates were more likely to be gentamicin resistant (
P
< 0.03), fluoroquinolone resistant (
P
< 0.0001), and multidrug resistant (
P
< 0.0001) than AmpC-producing
E. coli
isolates.
Comparison of the In Vitro Efficacies of Moxifloxacin and Amoxicillin against
Listeria monocytogenes
Authors: Grayo S. , Join-Lambert O. , Desroches M. C. , Le Monnier A.
Published: February 2008

Listeria monocytogenes
is a facultative intracellular bacterium that causes severe infections associated with a high mortality rate. Moxifloxacin presents extended activity against gram-positive bacteria and has recently been suggested to be a potential alternative in the treatment of listeriosis. We evaluated the in vitro efficacy of moxifloxacin against
L. monocytogenes
using a combination of epidemiological and experimental approaches. The median MIC of moxifloxacin for a large collection of
L. monocytogenes
strains of various origins (human, food, and environment) was 0.5 μg/ml (MIC range, 0.064 to 1 μg/ml). No differences were observed, irrespective of the origin of the strains. Moreover, no cross-resistance with fluoroquinolones was detected in strains that have been reported to be resistant to ciprofloxacin. The in vitro activities of moxifloxacin and amoxicillin were compared by time-kill curve and inhibition of intracellular growth experiments by using a model of bone marrow-derived mouse macrophages infected by
L. monocytogenes
EGDe. Both moxifloxacin and amoxicillin were bactericidal in broth against extracellular forms of
L. monocytogenes
. However, moxifloxacin acted much more rapidly, beginning to exert its effects in the first 3 h and achieving complete broth sterilization within 24 h of incubation. Moxifloxacin has a rapid bactericidal effect against intracellular reservoirs of bacteria, whereas amoxicillin is only bacteriostatic and appears to prevent cellular lysis and the subsequent bacterial spreading to adjacent cells. No resistant bacteria were selected during the in vitro experiments. Taken together, our results suggest that moxifloxacin is an interesting alternative to the reference treatment, combining rapid and bactericidal activity, even against intracellular bacteria.
Transcriptional and Translational Control of the
mlr
Operon, Which Confers Resistance to Seven Classes of Protein Synthesis Inhibitors
Authors: Smith Lisa K. , Mankin Alexander S.
Published: February 2008

The methyltransferase genes
erm
(B) and
cfr
are adjacent to each other in the chromosome of methicillin-resistant
Staphylococcus aureus
strain CM05. Analyses of the transcriptional organization of the
erm
(B) and
cfr
genes in the chromosome of strain CM05 showed that the two genes are organized into an operon, designated
mlr
(for modification of the large ribosomal subunit), which is controlled by the
erm
(B) promoter. Analysis of the translation control and the inducibility of the
erm
(B) and
cfr
genes in the
mlr
operon showed that despite the presence of putative regulatory short open reading frames, both genes are expressed constitutively. The combined action of the two methyltransferases encoded in the
mlr
operon results in modification of two specific residues in 23S rRNA, A2058 and A2503, and renders cells resistant to all clinically useful antibiotics that target the large ribosomal subunit. Furthermore, simultaneous modification of both rRNA sites synergistically enhances resistance to 16-member-ring macrolides.
Engineers and waterpower on the Lachine Canal, 1843–1871
Authors: Nally Larry Mc
Published: February 2008

As a result of the reconstruction of the Lachine Canal in the 1840s, waterpower became available within the city of Montreal. This power source was a strong stimulus to Montreal's rapid industrialization starting in the 1850s. However, the efforts of the Commissioners of Public Works of the Province of Canada to balance the competing demands of shipping and manufacturing resulted in many problems. The civil engineers, who designed and built the canal, were drawn into an unresolved conflict with other engineers who were interested in utilizing waterpower. Engineers were also in conflict with a variety of non-engineers over the building of waterpower installations and factories. This case study of waterpower on the Lachine Canal demonstrates the opportunities and conflicts for engineers in mid-nineteenth century Canada. Key words: waterpower, industrialization, turbine, hydraulic engineering, canal, Montreal, Lachine Canal.
Reliability-based design of wood structures: background to CSA-086.1-M89
Authors: Foschi Ricardo O. , Folz Bryan , Yao Felix
Published: February 2008

The limit states design version of the 1989 Canadian code for engineering design in wood (CSA-086.1-M89) is, for the most part, reliability-based. This paper discusses the methodology employed in the calibration procedure and the reliability levels adopted. Particular emphasis is given to the results obtained for duration of load and system (load sharing) strength adjustment factors, to serviceability limit states, and to the design of columns. Final comments address the impact of the new code in comparison to the traditional working stress design procedures. Key words: code, design, reliability, timber construction, wood.
Duration of load in wood: Canadian results and implementation in reliability-based design
Authors: Yao Felix Z. , Foschi Ricardo O.
Published: February 2008

This paper summarizes some Canadian experimental results for duration of load effects in wood, and discusses the theoretical framework utilized for their interpretation and implementation in design guidelines. The theory is based on a model for accumulation of damage, and it is used in the context of reliability assessment of a structure under load over its service life. The paper also compares results from other theoretical approaches. Finally, the background to currently recommended design adjustment factors for duration of load is discussed. Key words: fatigue, load duration, reliability, timber construction, wood.
Reflection effects on wave field within a harbour
Authors: Isaacson Michael , O'Sullivan Enda , Baldwin John
Published: February 2008

The present paper outlines a numerical model for predicting the wave field in a harbour with partially reflecting boundaries, and describes laboratory tests undertaken to assess the model. The numerical model is based on linear diffraction theory and involves the application of a partial reflection boundary condition. By utilizing a wave doublet representation of the fluid boundaries instead of the usual wave source representation, the extension is made to general harbour configurations that include breakwaters. Numerical results are compared with known solutions for specific reference configurations. Laboratory measurements have been made of the wave field within a particular harbour model having portions of the boundary corresponding to different degrees of wave reflection. A comparison with the numerical predictions is summarized and highlights the importance of adequately modelling the partial reflections within the harbour. Key words: breakwaters, coastal engineering, harbours, waves, wave diffraction, wave reflection.
Stepped spillway flows and air entrainment
Authors: Chanson Hubert
Published: February 2008

Stepped spillways have become a popular method for handling flood releases. The steps significantly increase the rate of energy dissipation taking place on the spillway face and reduce the size of the required downstream energy dissipation basin. The compatibility of stepped spillways with roller compacted concrete and gabion construction techniques results in low additional cost for the spillway. This paper presents a review of recent developments for the design of stepped spillways, provides a discussion of the effects of air entrainment, and presents new calculation methods that take into account the effects of flow aeration on the flow characteristics and the rate of energy dissipation. Key words: stepped spillway, air entrainment, dam, spillway, energy dissipation.
Subjective and interactive duration estimation
Authors: AbouRizk Simaan M. , Sawhney Anil
Published: February 2008

Scheduling of construction projects with an uncertainty content requires that the scheduler's subjective knowledge of various factors that might influence the duration of the activities comprising the project is incorporated. Depending on the participating factors and their significance, a different duration outcome is often observed for each activity. To include this uncertainty in the schedule, a statistical distribution is frequently used. This paper presents a system based on the premise that part of the information available, when duration distribution is being estimated, exists in a subjective form. We present an automated system that requires the modeler to specify the activity's minimum and maximum times and a set of linguistic descriptors of the external factors that are suspect of influencing the duration. The lower and upper end point estimates are often available from familiarity with the technology used, physical and logical constraints, or a combination of these situations. The subjective information collected by the modeler is modeled as fuzzy parameters and is quantified using fuzzy set theory. The result of the fuzzy set analysis is a sample of activity durations from the underlying distribution, which is then used to characterize the first two moments of that distribution. Since earlier research has shown that the beta distribution provides an adequate representation for construction durations, the end points specified by the user and the two moments resulting from the fuzzy set analysis are used to fit a beta distribution. The system then allows the user to visually assess the quality of the fit and modify the shape of the beta density using the visual interactive beta estimation system. The paper also presents a practical construction scheduling application to demonstrate the use of the developed system. Key words: construction management, scheduling, fuzzy sets, subjective duration estimation, beta distribution, linguistic variables.
L'utilisation du compost de boues de stations d'épuration des eaux comme substrat de culture pour la production des plants forestiers en récipients
Authors: Polan Patrick , Gagnon Jean , Jones J. Peter
Published: February 2008

The Quebec government has established a program to treat industrial and domestic wastewaters. However, this program does make it necessary to dispose of large quantities of sludge. This sludge can be burned or landfilled but such solutions do not properly draw benefit from the sludge's potential as a fertilizer. There is a considerable interest in composting of the sludge. In this study, compost from the composting plant in Plattsburgh was mixed with the growing substrate normally used for the production of containerized jack pine (Pinus banksiana Lamb.) seedlings to determine if the compost could be used for the production in containers of forest seedlings. The growth of containerized seedlings produced with proportions by volume of 80% peat moss and 20% vermiculite was compared to the growth of seedlings when the peat moss (80%) was replaced by different proportions of compost (20, 40, 60, and 80%). After one growing season in tunnel, the best growth rates in terms of shoot height, root-collar diameter, and dry biomass were obtained with the control, followed in decreasing order by the treatments compost 20, 40, 60, and 80%. In this experiment, the use of compost from wastewater treatment plants reduced significantly the growth of jack pine and this can be explained mainly by the lack of nitrogen in the tissues of jack pine seedlings. However, the adjustment of nitrogen fertilization and conditions of cultivation by using compost may permit the production of containerized seedlings having the same dimensions as the controls. The seedling growth parameters when 20% compost was incorporated in the substrate were nearly the same as the control seedling. Key words: sludge, recycling, compost, substrate, container, forest seedlings, jack pine.
Classical hydraulic jump: free surface profile
Authors: Hager Willi H.
Published: February 2008

Based on a large number of experiments, a simple formula is developed for the time-averaged free surface profile of a classical hydraulic jump. This novel approach is based on the length of the roller. The resulting surface profile fits the data well for usual inflow Froude numbers in the range of 2 to 10. Key words: backwater, channel flow, hydraulics, open channel, surface profile.
Subsocial organization and behavior in broods of the obligate burrowing wolf spider Geolycosa turricola (Treat)
Authors: Miller Gary L.
Published: February 2008

Prolonged mutual tolerance is described for spiderlings in broods of the burrowing wolf spider Geolycosa turricola (Treat) (Lycosidae). The length of the tolerant phase is compared with that of the facultative burrower Lycosa georgicola Walckenaer. Specific behaviors are described from observations of pairs of spiderlings. The frequency of occurrence of these behaviors was studied in a series of bioassay experiments designed to test questions concerning the nature of the mechanism of communication among spiderlings, the length of the tolerance phase, and the ability to recognize siblings from nonsiblings. The results indicate that chemical communication is the principal form of communication between spiderlings. Aggressive behavior increased in pairs of spiderlings of increasing disparity of size. Geolycosa turricola spiderlings showed little kin recognition ability. The advantage of prolonged tolerance within the burrowing life strategy is discussed.
Distribution and innervation of sensilla on the mouthparts of the carnivorous stonefly nymph, Paragnetina media (Walker) (Plecoptera: Perlidae)
Authors: Kapoor N. N.
Published: February 2008

The external morphology and distribution of various types of sensilla on the mouthparts of the nymphs of Paragnetina media are described, based on light and scanning electron microscopy. Hairs of various types are arranged in distinctive patterns on each mouthpart. Scolopophorous sensilla, each consisting of a pore canal and two bipolar neurons, are present in the mandibular teeth. The elliptical type of campaniform sensilla, multiporous columnar pegs, and nonporous sensilla are concentrated on the segments of the maxillary and labial palps. The tips of the maxillary and labial palps bear a cluster of uniporous multidigitate pegs, a multiporous peg, a circular type campaniform sensillum, and several nonporous sensilla. Nonsocketed uniporous pegs crown the tip of galeae and are also scattered over the surface of the glossae and paraglossae. Possible functions of these sensilla are discussed. A cleaning method is described to visualize details with the scanning electron microscope.
External morphology of the developing hemipenes of the dwarf chameleon, Bradypodion pumilum (Reptilia: Chamaeleonidae)
Authors: Rosenberg Herbert I. , Bauer Aaron M. , Russell Anthony P.
Published: February 2008

The external morphology of the hemipenes of squamate reptiles is often complex and has been widely employed in systematic studies. Little is known, however, of the development of these patterns and thus of the potential polarity of the character states used in systematic studies. Analysis of three developmental stages of the hemipenes of the chameleon Bradypodion pumilum using scanning electron microscopy reveals that the complexity of pattern emerges gradually. Initially the hemipenial anlagen appear as simple, external lobes that develop in close association with the cloaca. By stage 38 a shallow sulcus spermaticus is evident and calices have begun to appear. By stage 41 embryos possess a deep, protected sulcus and two pairs of distal lobes. These lobes will eventually differentiate into semicircular disks (rotulae) with serrated margins that are characteristic of many members of the family. The complex external morphology of the hemipenes that is of significance in systematic studies and of assumed importance in copulatory mechanics may not be expressed until sexual maturity is reached.
Mitochondrial DNA diversity among populations of striped bass in the southeastern United States
Authors: Wirgin Isaac I. , Proenca Rui , Grossfield Joseph
Published: February 2008

Mitochondrial DNA (mtDNA) genotypes were determined for Atlantic striped bass from the St. Johns River in northeastern Florida and several hatchery reared individuals from Monck's Corner, South Carolina. Adults and hatchery-reared descendants of striped bass with high lateral line scale counts were sampled from several sites in the Apalachicola River system along the Gulf coast of Florida. In addition, naturally reproduced 1985 year class juveniles from the Apalachicola system were sampled. All mtDNA genotypes were compared with those observed in our sample of approximately 200 fish from the Atlantic coastal migratory stock. Ten different restriction endonucleases were used, generating 169 mtDNA fragments in most individuals. Heteroplasmy was observed in striped bass from both the St. Johns River and the Apalachicola system. Base sequence divergence among the populations surveyed was extremely low (maximum p = 0.0004), among the lowest reported for any animal species to date. However, the restriction enzymes RsaI and XbaI both revealed base substitutions unique to populations of Gulf Coast striped bass. Approximately 57% of striped bass from the Apalachicola system displayed an XbaI genotype not seen in any of our Atlantic collections. Four discrete mtDNA size classes were detected, differing by approximately 200, 300, and 400 base pairs from the smallest mtDNA molecule observed. The largest genotype was only seen in the Apalachicola system. The smallest genotype, while restricted to Gulf Coast striped bass sampled for this study, has been frequently observed in the Atlantic coastal migratory stock. The presence of mtDNA genotypes unique to the Apalachicola systems suggests the continued existence of a maternal lineage of striped bass of Gulf ancestry and points to the use of mtDNA as a valuable tag in the management of these populations. The lack of mtDNA sequence divergence in striped bass suggests a very recent origin for these populations.
Description of a new species of Haminoea, Haminoea callidegenita (Mollusca: Opisthobranchia), with a comparison with two other Haminoea species found in the northeast Pacific
Authors: Gibson Glenys D. , Chia Fu-Shiang
Published: February 2008

A new species of Haminoea (Opisthobranchia: Cephalaspidea), Haminoea callidegenita, is described from Washington State, U.S.A. Diagnostic features are reddish brown colour, deeply bifurcate cephalic shield, reddish ovate shell with imperforate apex, tubular Hancock's organ, unarmed penis, unilobular prostate, and radula formula n.l.l.l.n (n from 12 to 21), with bicuspid first lateral uncini. The development of H. callidegenita is unusual among the Opisthobranchia in that the hatching stage includes both lecithotrophic veligers and juveniles from each egg mass. Diagnostic features were examined among animals from different populations of H. callidegenita and two other Haminoea species found in the northeast Pacific: H. vesicula Gould, 1855 and H. virescens Sowerby, 1833. Shell shape was slightly variable among individuals of all three species and radula morphologies were variable among populations of H. vesicula. Fingerlike papillae were noted on the gizzard plates and are suggested as a diagnostic character.
Influence of photoperiod on postnatal growth, sexual development, and reproduction in a semifossorial microtine, Microtus pinetorum
Authors: Derting Terry L. , Cranford Jack A.
Published: February 2008

This study examined the effect of photoperiod lengths on growth, development of reproductive organs, and litter production in pine voles (Microtus pinetorum). Between 3 and 7 weeks of age, body mass increased significantly faster under a photoperiod of 8L:16D than under 16L:8D, resulting in an 11% difference in body mass at 7 weeks of age. Prior to 3 weeks and beyond 8 weeks body mass gains were not significantly different. Animals under 8L: 16D molted, on average, at 30.5 days of age, approximately 1 week earlier than animals under 16L:8D. In general, reproductive organ masses of males and females varied only as a function of age and not of photoperiod. The exception was uterine mass, which was greater under 8L:16D than 16L:8D. Similarly, development of tertiary follicles occurred earlier under the short photoperiod.
A new crangonyctid amphipod crustacean from hypogean fresh waters of Oregon
Authors: Bousfield E. L. , Holsinger J. R.
Published: February 2008

Stygonyx courtneyi n.gen., n.sp. (Amphipoda: Crangonyctidae) is described from hypogean waters of northwestern Oregon. This new species appears most closely allied taxonomically with one subgroup of the advanced hypogean genus Stygobromus. However, the unique form of uropod 3 and the relatively unmodified (plesiomorphic) form of the coxal and pleon plates and oostegites justify its recognition as the type of a new genus that is intermediate between Stygobromus and the primitive, mainly epigean, genus Crangonyx.