An Improved Method for the Determination of 3D Cutting Force Coefficients and Runout Parameters in End Milling

A simple improved method is suggested for determining constant cutting force coefficients, irrespective of the cutting condition and cutter rotation angle. This can be achieved through the combination of experimentally deternimed cutting forces with those from simulation, performed by a mechanistic cutting force model and a geometric uncut chip thickness model. Additionally, this study presents an approach that estimates runout-related parameters, and the runout offset and its location angle, using only one measurement of cutting force. This method of estimating 3D end milling force coefficients was experimentally verified for a wide range of cutting conditions, and gave significantly better predictions of cutting forces than any other methods. The estimated value of the runout offset also agreed well with the measured value.     

Neighborhood spillover effects between rezoning and housing price

The objective of this research was to investigate neighborhood spillover effects between rezoning of vacant parcels and housing price in the Knoxville, TN area. The study is unique in that it correctly highlights the need to analyze the dynamics of zoning structure and accommodates the neighborhood spillover effects associated with the real estate market. Results indicate that the probability of rezoning vacant land is expected to increase as housing price in a neighboring location increases. The rise in the housing price in a neighboring location implies increasing pressure on housing demand. This increased pressure on housing demand likely contributes to greater demands for residential development and commercial development that complements residential use. Currently, the major guidelines for the approval of rezoning petitions, according to the planners in the Knoxville area, are consistency with long-and short-range land use plans adopted by state, municipality, and county governments, and consistency with surrounding land use and environmental constraints, e.g., slope, flooding, and drainage. Local planning authorities can modify and update consistency measures in the current guidelines by accounting for varying degrees of housing demand pressure. For example, consistency measures can be strengthened in areas with greater housing-price increases, if preservation is desirable because these areas are likely to experience greater rezoning pressure.     

Prediction of the combination of failure modes for an arch bridge system

An innovative prediction method for the combination of failure modes of an arch bridge is proposed for its probabilistic risk assessment and is compared with the conventional system reliability analysis method. The suggested method reveals various combinations of failure modes in significantly reduced time and efforts in comparison to the previous permutation method or the conventional system reliability analysis method. Additionally, the suggested method can be used for the verification of the system reliability with more specific predictions of the failure modes.Component reliabilities of girders have been evaluated by using response surfaces of the design variables at the selected critical sections, i.e. the maximum shear and negative moment locations. Response Surface Method (RSM) is successfully applied for the reliability analyses of complex structure with relatively small probability of failure. Previous methods such as Monte Carlo Simulations or First Order Second Moment method cannot easily calculate the derivative terms of implicit limit state functions. Hence, the target bridge system is modeled as a series-connection system for the analysis of its system reliability. The upper and lower bound of the probabilities of failure for the structural system have been evaluated and are compared with the suggested prediction method for all possible combination of failure modes.     

Sorbed atrazine shifts into non-desorbable sites of soil organic matter during aging

Soil-chemical contact time (aging) is an important determinant of the sorption and desorption characteristics of the organic contaminants and pesticides in the environment. The effects of aging on mechanism-specific sorption and desorption of atrazine were studied in soil and clay slurries. Sorption isotherm and desorption kinetic experiments were performed, and soil-water distribution coefficients and desorption rate parameters were evaluated using linear and non-linear sorption equations and a three-site desorption model, respectively. Aging time for sorption of atrazine in sterilized soil and clay slurries ranged from 2 days to 8 months. Atrazine sorption isotherms were nearly linear (r(2)>0.97) and sorption coefficients were strongly correlated to soil organic carbon content. Sorption distribution coefficients (K(d)) increased with increase in age in all five soils studied, but not for K-montmorillonite. Sorption non-linearity did not increase with increase in age except for the Houghton muck soil. Desorption profiles were well described by the three-site desorption model. The equilibrium site fraction (f(eq)) decreased and the non-desorbable site fraction (f(nd)) increased as a function of aging time in all soils. For K-montmorillonite, f(nd) approximately 0 regardless of aging, showing that aging phenomena are sorbent/mechanism specific. In all soils, it was found that when normalized to soil organic matter content, the concentration of atrazine in desorbable sites was relatively constant, whereas that in non-desorbable site increased. This, and the lack of aging effects on desorption from montmorillonite, suggests that sorption into non-desorbable sites of soil organic matter is primary source of increased atrazine sorption in soils during aging.     

Novel membrane bioreactor (MBR) coupled with a nonwoven fabric filter for household wastewater treatment

Conventional and modified membrane bioreactors (MBRs) are increasingly used in small-scale wastewater treatment. However, their widespread applications are hindered by their relatively high cost and operational complexity. In this study, we investigate a new concept of wastewater treatment using a nonwoven fabric filter bag (NFFB) as the membrane bioreactor. Activated sludge is charged in the nonwoven fabric filter bag and membrane filtration via the fabric is achieved under gravity flow without a suction pump. This study found that the biofilm layer formed inside the NFFB achieved 10 mg/L of suspended solids in the permeate within 20 min of initial operation. The dynamic biofilter layer showed good filterability and the specific membrane resistance consisted of 0.3-1.9 × 10¹² m/kg. Due to the low F/M ratio (0.04-0.10 kg BOD₅/m³/d) and the resultant low sludge yield, the reactor was operated without forming excess sludge. Although the reactor provided aerobic conditions, denitrification occurred in the biofilm layer to recover the alkalinity, thereby eliminating the need to supplement the alkalinity. This study indicates that the NFFB system provides a high potential of effective wastewater treatment with simple operation at reduced cost, and hence offer an attractive solution for widespread use in rural and sparsely populated areas.     

Dynamic P‐Δ effects for multistorey steel columns in long‐span tube‐in‐tube tall buildings

An Euler–Bernoulli beam–column model is employed to investigate the dynamic P‐Δ effects of steel columns located at the external tube of a long‐span tube‐in‐tube tall building. A steel column with multistorey lateral open‐web beam supports is modelled as a beam–column element supported by elastic springs, from which a governing partial differential equation is established for the vibration of the column subjected to an axial compression force, lateral beam forces and base excitations. The problem is solved by a modal superposition method for both transient and steady‐state solutions. A numerical example is illustrated and the results indicate that the secondary moment of a steel column induced from dynamic multistorey P‐Δ effects is essential and should not be ignored in a practical design. The influences of the factors including flexural rigidity of the column, axial stiffness of the open‐web beams and the magnitude of the compressive axial force are discussed. Copyright © 2005 John Wiley & Sons, Ltd.     

Thermal error analysis for a CNC lathe feed drive system

The development of high-speed feed drive systems has been a major issue in the machine tool industry for the past few decades. The resulting reduction in the time needed for tool changes and the rapid travel time can enhance productivity. However, a high-speed feed drive system naturally generates more heat and resultant thermal expansion, which adversely affects the accuracy of machined parts. This paper divides the feed drive system into two parts: the ball screw and the guide way. The thermal behavior model for each part is developed separately, in order to estimate the position errors of the feed drive system caused by thermal expansion. The modified lumped capacitance method (MLCM) and genius education algorithm (GEA) are used to analyse the linear positioning error of the ball screw. Thermal deformation of the guide way affects straightness and introduces angular errors, as well as affecting linear positioning. The finite element method is used to estimate the thermal behavior of the guide way. The effectiveness of the proposed models is verified through experiments using a laser interferometer.     

Identification and control for micro-drilling productivity enhancement

Micro-hole drilling (holes less than 0.5 mm in diameter with aspect ratios larger than 10) is gaining increased attention in a wide spectrum of precision production industries. Alternative methods such as EDM, laser drilling, etc. can sometimes replace mechanical micro-hole drilling, but are not acceptable in PCB manufacture because they yield inferior hole quality and accuracy. The major difficulties in micro-hole drilling are related to the wandering motions during the inlet stage, high aspect ratios, high temperature, etc. However, of all the difficulties, the most undesirable ones are the increases in drilling force and torque as the drill penetrates deeper into the hole. This is mainly caused by chip-related effects. Peck-drilling is thus widely used for deep hole drilling despite the fact that it leads to low productivity. Therefore, in this paper, a method for cutting force regulation is proposed to achieve continuous drilling. A proportional plus derivative (PD) and a sliding mode control algorithm will be implemented and compared for controlling the spindle rotational frequency. Experimental results will show that sliding mode control reduces the nominal torque and cutting force and their variations better than PD control, resulting in a number of advantages, such as an increase in drill life, fast stabilization of the wandering motion, and precise positioning of the holes.     

The adverse effects of fine particle air pollution on respiratory function in the elderly

There is increasing concern that airborne particles are critical risk factors for adverse health conditions in susceptible populations. The objective of this panel study is to investigate an association between particulate matter and the peak expiratory flow rate (PEFR) in the elderly and to compare estimated risks using PM10 or PM2.5 levels as a measure of exposure. During a 2-year longitudinal follow-up study, we contacted subjects living in an asylum for the elderly, provided them with a mini-Wright peak flow meter, and instructed to record all the flow readings, any respiratory symptoms, passive smoking activity, and hours spent outdoors for that given day. Daily levels of particulate matter were measured by two separate mini-volume air samplers (for PM10 and PM2.5) placed on the rooftop of the two-story residence asylum building. In our statistical models, we assumed that the expected response varied linearly for each participant with a slope and intercept that depended on fixed or time-varying covariates using a mixed linear model. The daily mean levels of PM10 and PM2.5 were 78 microg/m3 and 56 microg/m3, respectively. For every 10 microg/m3 increase in PM10 and PM2.5 levels, there was an estimated PEFR change of -0.39 l/min (95% CI, -0.63, -0.14) and -0.54 l/min (95% CI, -0.89, -0.19), respectively. These data also suggest that fine particles have a more adverse respiratory health impact for sensitive individuals such as the elderly and that more research and control strategies should focus on the smaller particles associated with air pollution.     

Phosphorous retention capacity of filter media for estimating the longevity of constructed wetland

The filter medium could be selected and the longevity of the filter medium by the phosphorus saturation could be predicted in the constructed wetland system, accordingly proposing the scheme to remove the phosphorus for a long period. The phosphorus adsorption capacities of various filter media were investigated in relation to the size and types of filter media to screen the optimal condition. The objective of this study was to evaluate the constructed wetland longevity by improving P adsorption capacity. The maximum P adsorption capacities of filter media A (4--10 mm), B (2--4 mm), and C (0.1--2 mm) were 7.7, 11.6, and 22.5 mg/kg, respectively, showing that they increased as the filter media size decreased. Among the experimental media, the optimal filter media size was 0.1--2 mm. When Ca, Mg, Al and Fe were added to the filter medium C, which is the optimal filter medium, the addition of Ca improved mostly the P adsorption capacity. In the alternative proposal to use these facts, the oyster shell was added to the filter medium and the P adsorption capacity was examined: adding 2% oyster shell increased the P adsorption capacity from 23 to 36 mg/kg. In the column where the oyster shell was mixed, when the oyster shell content was 5%, 10%, 20%, 40%, 60%, 80%, and 100% in the filter medium C, the respective saturation times of the P adsorption were about 6, 9, 17, 30, 43, 56, and 70 days. When the oyster shell content was 0%, 5%, 10%, 20%, 40%, 60%, 80%, and 100% after 1 month in the column, the P adsorption amount was about 180, 600, 1560, 4280, 6157, 7089, 7519, and 7925 mg/kg, respectively. The increment of the P adsorption amount was small if the oyster shell content was 60% or more, because the filter medium with more than 60% oyster shell content did not approach the saturation time by the P adsorption yet. The P adsorption amount for 60%, 80%, and 100% could be predicted as about 9702, 12,879, and 16,056 mg/kg, respectively. The largest amount of extracted P in the filter media with oyster shell after 30 days of P solution application was bound to Ca, followed by water soluble-P, Al--P, and Fe--P. Therefore, it was concluded that the adsorption amount of the phosphorus could be increased by adding the oyster shell to the filter medium. Also, it was concluded that adding the oyster shell to the filter medium in the constructed wetland was the scheme to extend the longevity of the constructed wetland by the phosphorus saturation, and using the oyster shell would be useful in aspect of economical efficiency and easiness. Especially, it would be the alternative proposal to reduce the environmental pollution in aspect of recycling wastes.