Showing papers in "Journal of Zhejiang University Science in 2010"
TL;DR: In this article, the authors discuss the process parameters of FDM Prodigy Plus (Stratasys, Inc., Eden Prairie, MN, USA). Various selected parameters were tested and the optimum condition was proposed.
Abstract: Fused deposition modelling (FDM) is one of rapid prototyping (RP) technologies which uses an additive fabrication approach. Each commercially available FDM model has different types of process parameters for different applications. Some of the desired parts require excellent surface finish as well as good tolerance. The most common parameters requiring setup are the raster angle, tool path, slice thickness, build orientation, and deposition speed. The purpose of this paper is to discuss the process parameters of FDM Prodigy Plus (Stratasys, Inc., Eden Prairie, MN, USA). Various selected parameters were tested and the optimum condition was proposed. The quality of the parts produced was accessed in terms of dimensional accuracy and surface finish. The optimum parameters obtained were then applied in the fabrication of the master pattern prior to silicone rubber moulding (SRM). These parameters would reduce the post processing time. The dimensional accuracy and surface roughness were analyzed using coordinate measuring machine (CMM) and surface roughness tester, respectively. Based on this study, the recommended parameters will improve the quality of the FDM parts produced in terms of dimensional accuracy and surface roughness for the application of SRM.
127 citations
TL;DR: In this paper, an adaptive cruise control (ACC) algorithm with multi-objectives is proposed based on a model predictive control (MPC) framework, where the requirements of comfort and car-following are considered to be the performance criteria and some optimal reference trajectories are introduced to increase fuel economy.
Abstract: For automated vehicles, comfortable driving will improve passengers’ satisfaction. Reducing fuel consumption brings economic profits for car owners, decreases the impact on the environment and increases energy sustainability. In addition to comfort and fuel-economy, automated vehicles also have the basic requirements of safety and car-following. For this purpose, an adaptive cruise control (ACC) algorithm with multi-objectives is proposed based on a model predictive control (MPC) framework. In the proposed ACC algorithm, safety is guaranteed by constraining the inter-distance within a safe range; the requirements of comfort and car-following are considered to be the performance criteria and some optimal reference trajectories are introduced to increase fuel-economy. The performances of the proposed ACC algorithm are simulated and analyzed in five representative traffic scenarios and multiple experiments. The results show that not only are safety and car-following objectives satisfied, but also driving comfort and fuel-economy are improved significantly.
120 citations
TL;DR: Experimental results demonstrated that all four multiscale entropies outperformed single-scale ones, whilstMultiscale FSampEn was superior to other multiscales methods, especially when analyzed signals were contaminated by heavy noise.
Abstract: Feature extraction from vibration signals has been investigated extensively over the past decades as a key issue in machine condition monitoring and fault diagnosis. Most existing methods, however, assume a linear model of the underlying dynamics. In this study, the feasibility of devoting nonlinear dynamic parameters to characterizing bearing vibrations is studied. Firstly, fuzzy sample entropy (FSampEn) is formulated by defining a fuzzy membership function with clear physical meaning. Secondly, inspired by the multiscale sample entropy (multiscale SampEn) which is originally proposed to quantify the complexity of physiological time series, we placed approximate entropy (ApEn), fuzzy approximate entropy (FApEn) and the proposed FSampEn into the same multiscale framework. This led to the developments of multiscale ApEn, multiscale FApEn and multiscale FSampEn. Finally, all four multiscale entropies along with their single-scale counterparts were employed to extract discriminating features from bearing vibration signals, and their classification performance was evaluated using support vector machines (SVMs). Experimental results demonstrated that all four multiscale entropies outperformed single-scale ones, whilst multiscale FSampEn was superior to other multiscale methods, especially when analyzed signals were contaminated by heavy noise. Comparisons with statistical features in time domain also support the use of multiscale FSampEn.
54 citations
TL;DR: The fatigue and fracture behavior of nickel-based superalloy Inconel 718 was investigated up to the very high cycle regime under rotary bending tests at room temperature.
Abstract: The fatigue and fracture behavior of nickel-based superalloy Inconel 718 was investigated up to the very high cycle regime under rotary bending tests at room temperature. It was found that this superalloy can still fracture after exceeding 107 cycles. Fractographic analysis revealed that there was a transition from fatigue crack initiation at multi-sites to single initiation with decreasing stress levels. The fracture surface can be divided into four areas according to the appearance, associated with fracture mechanics analysis of the corresponding stress intensity factors. The fracture mechanism dominant in each area was disclosed by scanning electron microscope examination and analyzed in comparison with those obtained from the crack growth tests. Subsequently, life prediction modeling was proposed by estimating the crack initiation and propagation stage respectively. It was found that Chan (2003)’s model for initiation life and the Paris law for growth life can provide comparable predictions against the experimental life.
53 citations
TL;DR: In this article, the integration of water quality analysis simulation program (WASP) with a geographical information system (GIS) is presented to enhance the data analysis and management ability of the widely used water quality model.
Abstract: The integration of water quality analysis simulation program (WASP) with a geographical information system (GIS) is presented. This integration was undertaken to enhance the data analysis and management ability of the widely used water quality model. Different types of data involved in WASP modeling were converted and integrated into GIS using a database method. The spatial data modeling and analysis capability of GIS were used in the operation of the model. The WASP water quality model was coupled with the environmental fluid dynamics code (EFDC) hydrodynamic model. A case study of the Lower Charles River Basin (Massachusetts, USA) water quality model system was conducted to demonstrate the integration process. The results showed that high efficiency of the data process and powerful function of data analysis could be achieved in the integrated model, which would significantly improve the application of WASP model in water quality management.
53 citations
TL;DR: In this article, the recycling of carbon steel slag (CSS) to produce self-consolidating concrete (SCC) was examined, and the results showed that the design and performance of all the concrete mixtures used in this investigation were comparable to those of SCC and high performance concrete (HPC).
Abstract: This study deals with the recycling of carbon steel slag (CSS) to produce self-consolidating concrete (SCC). Since the chemical composition of CSS is similar to that of Portland cement or blast furnace slag (BFS), it is expected to behave similarly. In the current study, the pozzolanic activity index of CSS is examined. Furthermore, the use of CSS as a pozzolanic material to partially replace Portland cement in the production of SCC is tested. We designed concrete mixtures with different water-to-cementitious material ratios (w/cm) keeping water and superplasticizer (SP) contents constant. Results showed that the design and performance of all the concrete mixtures used in this investigation were comparable to those of SCC and high performance concrete (HPC). However, compared to ordinary plain concrete (OPC), the additional CSS content increases the setting time. In the CSS mixtures set for 90 d, compressive strengths of 86%, 134% and 121% were attained as compared to the control concrete; the corresponding w/cm ratios were 0.28, 0.32 and 0.40, respectively. Verifying the soundness of the SCC for meeting the criteria for HPC, the ultrasonic pulse velocity (UPV) of CSS was found to be comparable to that of ordinary concrete. In conclusion, the recycling of CSS can be advantageously employed in the production of SCC.
37 citations
TL;DR: In this paper, the single cylinder and multi-cylinder pumping dynamics model of a swash plate piston pump were improved, with particular attention paid to the design influences of key parts of the valve plate such as relief groove, precompression/expansion and fluid inertia effect of the unsteady flow.
Abstract: The single cylinder and multi-cylinder pumping dynamics model of a swash plate piston pump were improved. Particular attention has been paid to the design influences of key parts of the valve plate such as relief groove, pre-compression/expansion and fluid inertia effect of the unsteady flow. Some important parameters, such as the discharge area, discharge coefficient, fluid bulk modulus, were especially analyzed using numerical methods or by experiment-based estimation. Consequently, the mathematical results of pressure pulsation and flow ripple agree well with experimental results from the test-rig of the flow ripple. Therefore, the cross angle and the pre-compression angle of the valve plate was optimized, based on the pumping dynamics model. Considering both the flow ripple and the cylinder pressure of the pump, the cross angle is set to be 2.2° to 2.7° with a pre-compression angle of 1.7° to 2.2°, so the pumping dynamics character can obtain the best result.
36 citations
TL;DR: In this paper, a model of syngas production from municipal solid waste (MSW) gasification with air in fixed bed reactors is proposed, and the results indicate that higher temperature improves gasification, and higher air equivalence ratio increases the carbon conversion.
Abstract: This study proposes a model of syngas production from municipal solid waste (MSW) gasification with air in fixed bed reactors. The model (using Aspen plus simulator) is used to predict the results of MSW gasification and to provide some process fundamentals concerning syngas production from MSW gasification. The effects of gasification temperature, air equivalence ratio and moisture concentration on the composition of syngas, lower heating value (LHV) of syngas, heat conversion efficiency, and carbon conversion are discussed. The results indicate that higher temperature improves gasification, and higher air equivalence ratio increases the carbon conversion while decreasing syngas LHV. Heat conversion efficiency increases and reaches the maximum and then decreases with the increase of air equivalence ratio. Higher moisture concentration increases the carbon conversion and increases the heat conversion efficiency at lower ratios. Higher temperature and a lower equivalence ratio are favorable for obtaining a higher LHV of syngas at the same moisture concentration.
34 citations
TL;DR: In this paper, a new approach based on Bayesian configuration against pipe condition to generate factor weights was employed to assess the condition of water pipes, and informative prior factor weight distribution based on the literature and previous knowledge of water pipe assessment was used.
Abstract: An accurate understanding of the condition of a pipe is important for maintaining acceptable levels of service and providing appropriate strategies for maintenance and rehabilitation in water supply systems. Many factors contribute to pipe deterioration. To consolidate information on these factors to assess the condition of water pipes, this study employed a new approach based on Bayesian configuration against pipe condition to generate factor weights. Ten pipe factors from three pipe materials (cast iron, ductile cast iron and steel) were used in this study. The factors included size, age, inner coating, outer coating, soil condition, bedding condition, trench depth, electrical recharge, the number of road lanes, material, and operational pressure. To address identification problems that arise when switching from pipe factor information to actual pipe condition, informative prior factor weight distribution based on the literature and previous knowledge of water pipe assessment was used. The influence of each factor on the results of pipe assessment was estimated. Results suggested that factors that with smaller weight values or with weights having relative stable posterior means and narrow uncertainty bounds, would have less influence on pipe conditions. The model was the most sensitive to variations of pipe age. Using numerical experiments of different factor combinations, a simplified model, excluding factors such as trench depth, electrical recharge, and the number of road lanes, is provided. The proposed Bayesian inference approach provides a more reliable assessment of pipe deterioration.
32 citations
TL;DR: Wang et al. as discussed by the authors developed a land use regression model using regulatory monitoring data to predict the spatial distribution of air pollutant concentrations in Jinan, China, where traffic, land use and census data, and meteorological and physical conditions were included as candidate independent variables, and were tabulated for buffers of varying radii.
Abstract: SO2, NO2, and PM10 are the major outdoor air pollutants in China, and most of the cities in China have regulatory monitoring sites for these three air pollutants. In this study, we developed a land use regression (LUR) model using regulatory monitoring data to predict the spatial distribution of air pollutant concentrations in Jinan, China. Traffic, land use and census data, and meteorological and physical conditions were included as candidate independent variables, and were tabulated for buffers of varying radii. SO2, NO2, and PM10 concentrations were most highly correlated with the area of industrial land within a buffer of 0.5 km (R2=0.34), the distance from an expressway (R2=0.45), and the area of residential land within a buffer of 1.5 km (R2=0.25), respectively. Three multiple linear regression (MLR) equations were established based on the most significant variables (p<0.05) for SO2, NO2, and PM10, and R2 values obtained were 0.617, 0.640, and 0.600, respectively. An LUR model can be applied to an area with complex terrain. The buffer radii of independent variables for SO2, NO2, and PM10 were chosen to be 0.5, 2, and 1.5 km, respectively based on univariate models. Intercepts of MLR equations can reflect the background concentrations in a certain area, but in this study the intercept values seemed to be higher than background concentrations. Most of the cities in China have a network of regulatory monitoring sites. However, the number of sites has been limited by the level of financial support available. The results of this study could be helpful in promoting the application of LUR models for monitoring pollutants in Chinese cities.
32 citations
TL;DR: In this paper, the relationship among tool wear, surface topography, and surface roughness when high-speed end milling Ti-6Al-4V alloy was investigated, and an optimal flank wear criterion for the cutting tool was defined.
Abstract: The objective of the present research is to investigate the relationship among tool wear, surface topography, and surface roughness when high-speed end milling Ti-6Al-4V alloy, and also to define an optimal flank wear criterion for the cutting tool to integrate tool life and the surface roughness requirements of the finish milling process An annealed Ti-6Al-4V alloy was selected as the workpiece material, undergoing end milling with uncoated carbide inserts The flank wear of the insert was observed and measured with the toolmaker’s microscope To examine machined surfaces, 3D surface topography was provided by the white light interferometer, and the arithmetical mean roughness (R
a) was calculated with the WYKO Vision32 software The flank wear increases with cutting time, and the maximal flank wear is set as the flank wear criterion As the cutting process progresses, tool wear is the predominant factor affecting the variation of surface roughness According to the plots for the tool wear propagation and surface roughness variation, an optimal flank wear criterion can be defined which integrates the tool life and the surface roughness requirements for the finish milling process
TL;DR: In this paper, the authors presented regression analysis on two classical datasets, the Lincoln and Holland tunnels, with different possible OVFs, demonstrating that these functions give results similar to those of the famous Bando OVF (Bando et al., 1995).
Abstract: The integral part of the optimal velocity car-following models is the optimal velocity function (OVF), which can be derived from measured velocity-spacing data. This paper discusses several characteristics of the OVF and presents regression analysis on two classical datasets, the Lincoln and Holland tunnels, with different possible OVFs. The numerical simulation of the formation of traffic congestion is conducted with three different heuristic OVFs, demonstrating that these functions give results similar to those of the famous Bando OVF (Bando et al., 1995). Also an alternative method is present for determining the sensitivity and model parameters based on a single car driving to a fixed barrier.
TL;DR: In this article, a numerical approach is proposed for the laying of pipelines in the so-called J-lay method, taking into account the importance of both pipe embedment and ocean currents.
Abstract: The pipe configuration and internal loads along the pipeline during the pipeline laying process have long been the focus of engineers. Most researchers simplify the seabed to be rigid and the water to be calm, ignoring the pipe embedment into the seabed and the influence of ocean currents. In this paper, a novel numerical approach is proposed for the laying of pipelines in the so-called J-lay method, taking into account the importance of both pipe embedment and ocean currents. The pipeline is divided into two parts, one part suspended in water, and the other laid on the seabed. The continuity of the two parts at the touch down point (TDP) is guaranteed to make a whole. The feasibility of the model is proved by the comparison between the present model and an analytical model, which shows good agreement in both pipeline configuration and bending moment distribution. Finally, parametric study was performed to consider the influence of current velocity, water depth, top inclination angle, and seabed stiffness, and conclusions are drawn.
TL;DR: In this article, the effects of water quality parameters (bromide concentration, pH value and ammonia concentration), chlorination conditions (chlorine dose, reaction time) and ratios of Br −/DOC and Br − /Cl2 consumption on the formation and distribution of brominated trihalomethanes (THMs-Br) in chlorination were assessed.
Abstract: The formation of brominated trihalomethanes (THMs-Br) which is proved more carcinogenic than their chlorinated analogues reported was very different at various water qualities. This study was performed to assess the effects of water quality parameters (bromide concentration, pH value and ammonia concentration), chlorination conditions (chlorine dose, reaction time) and ratios of Br − /DOC and Br − /Cl2 consumption on the formation and distribution of THMs-Br in chlorination. The results showed good correlation between the bromine incorporation factor (BIF) n(Br) and Br − /Cl2 consumption ratio. The formation of total THM (TTHM) was found to decrease with increasing ammonia concentration but to increase with bromide concentration and pH value. The n(Br) trends were significantly affected by the presence of bromide concentration. The effects on the molar yields of THMs were more strongly influenced by bromide concentration and dissolved organic carbon (DOC) concentration than pH value and natural organic matter (NOM) source. High Br − /DOC and Br − /Cl2 favor the formation of THMs-Br over chlorinated THMs (THMs-Cl). The experimental data including the main parameters such as bromide, DOC, ammonia, pH and reaction time were used for developing the predictive model for THMs-Br.
TL;DR: It is outlined problems and potential solutions for feasible human-machine interfaces using cable-based parallel manipulators for physiotherapy applications and the design constraints related to acceptance by patients and physiotherapist users are discussed.
Abstract: We outline problems and potential solutions for feasible human-machine interfaces using cable-based parallel manipulators for physiotherapy applications. From an engineering perspective, we discuss the design constraints related to acceptance by patients and physiotherapist users. To date, most designs have focused on mobile platforms that are designed to be operated as an end-effector connected to human limbs for direct patient interaction. Some specific examples are illustrated from the authors’ experience with prototypes available at Laboratory of Robotics and Mechatronics (LARM), Italy.
TL;DR: In this paper, an improved response surface method (RSM) based on weighted regression for the anti-slide reliability analysis of concrete gravity dam was designed and constructed, which not only saves the arithmetic operations but also greatly enhances the calculation efficiency and storage efficiency.
Abstract: The aim of this study was to design and construct an improved response surface method (RSM) based on weighted regression for the anti-slide reliability analysis of concrete gravity dam. The limitation and lacuna of the traditional RSM were briefly analyzed. Firstly, based on small experimental points, research was devoted to an improved RSM with singular value decomposition techniques. Then, the method was used on the basis of weighted regression and deviation coefficient correction to reduce iteration times and experimental points and improve the calculation method of checking point. Finally, a test example was given to verify this method. Compared with other conventional algorithms, this method has some strong advantages: this algorithm not only saves the arithmetic operations but also greatly enhances the calculation efficiency and the storage efficiency.
TL;DR: In this paper, an auto-regressive model with exogenous input (ARX) of second-order including a forgetting coefficient as a weighting coefficient is used for the estimation of modal parameters.
Abstract: Temporal variation of dynamical modal properties of a base-isolated building is investigated using earthquake records in the building. A batch processing least-squares estimation method is applied to segment-wise time-series data. To construct an input-output system, an auto-regressive model with exogenous input (ARX) of second-order including a forgetting coefficient as a weighting coefficient is used for the estimation of modal parameters. The fundamental and second natural frequencies and the damping ratios of the fundamental and second natural modes of the base-isolated building are identified in the time domain. The identified results are consistent with the results obtained from the micro-tremor vibration data, forced-vibration test data and earthquake records in the present base-isolated building in the case of taking into account the amplitude-dependency of the isolators and viscous dampers. It is finally pointed out that several factors, e.g., amplitude dependency of the isolator and damper system and special characteristics of the series-type viscous damper system, may be related complicatedly with the temporal variation in modal properties of the above-mentioned system.
TL;DR: In this article, the structural strength and driving force of flexible bags with the nonlinear finite element analysis (FEA) software ABAQUS were analyzed. And the authors derived an empirical equation of driving force.
Abstract: The purpose of this study was to build a flexible mechanical system with a hydrostatic skeleton The main components of this system are two type flexible bags One is a structural bag with constant inner pressure The other is an actuator bag with controlled inner pressure To design the system, it was necessary to estimate both structural deformation and driving force Numerical analysis of flexible bags, however, is difficult because of large nonlinear deformation This study analyzed structural strength and driving force of flexible bags with the nonlinear finite element analysis (FEA) software ABAQUS The stress concentration dependency on the bag shape is described and the driving force is calculated to include the large deformation From the analytical results, this study derives an empirical equation of driving force The validity of the equation was confirmed by condition-changed analyses and experimental results
TL;DR: In this article, the performance optimization of a single-stage Linde-Hampson refrigerator operating with six different binary refrigerants (R23/R134a, R 23/R227ea, R23/ R236ea, and R170/R290) with ozone depletion potentials (ODPs) of zero was conducted using a new approach at the temperature level of −60 °C.
Abstract: The optimization of the performance of a single-stage Linde-Hampson refrigerator (LHR) operating with six different binary refrigerants (R23/R134a, R23/R227ea, R23/R236ea, R170/R290, R170/R600a and R170/R600) with ozone depletion potentials (ODPs) of zero was conducted using a new approach at the temperature level of −60 °C. Among these binary refrigerants, the 0.55 and the 0.6 mole fractions of R23 for R23/R236ea are the most prospective nonflammable ones for the medium and low suction pressure compressors, respectively. For these two kinds of compressors, the 0.6 and the 0.65 mole fractions of R170 for R170/R600, respectively, are the most prospective binary refrigerants with low global warming potentials (GWPs). The results of optimization of pressure levels indicate that the optimum low pressure value for coefficients of performance (COP) is achieved when the minimum temperature differences occur at both the hot and the cold ends of the recuperator at a specified composition and pressure ratio. Two useful new parameters, the entropy production per unit heat recuperated and the ratio of heat recuperating capacity to the power consumption of the compression, were introduced to analyze the exergy loss ratio in the recuperator. The new approach employed in this paper also suggests a promising application even to the optimization of the performance with multi-component refrigerants.
TL;DR: In this article, the effects of nonlocal stress field on the natural frequencies and vibration modes are investigated for three different types of boundary conditions: simple supports, clamped supports and elastically-constrained supports.
Abstract: The transverse free vibration of nanobeams subjected to an initial axial tension based on nonlocal stress theory is presented. It considers the effects of nonlocal stress field on the natural frequencies and vibration modes. The effects of a small scale parameter at molecular level unavailable in classical macro-beams are investigated for three different types of boundary conditions: simple supports, clamped supports and elastically-constrained supports. Analytical solutions for transverse deformation and vibration modes are derived. Through numerical examples, effects of the dimensionless nanoscale parameter and pre-tension on natural frequencies are presented and discussed.
TL;DR: In this paper, the effectiveness of surface treatments on the durability of concrete was evaluated by measuring chloride diffusion, charge passing capacity, air permeability and water absorption, and the results showed that the concrete specimens with a coating procedure have a better long-term performance and effectiveness than the specimens with the penetrant treatments.
Abstract: This paper reports on a laboratory-based study carried out to evaluate the effectiveness of surface treatments on the durability of concrete and suggests a number of different evaluation methodologies for assessing the performance of various surface treatments. Durability of untreated and treated concrete specimens was evaluated by measuring chloride diffusion, charge passing capacity, air permeability and water absorption. A total of six concrete surface treatments were selected to represent different generic types, including coating, penetrant and mixed-use treatments. Results show that the concrete specimens with a coating procedure have a better long-term performance and effectiveness than the specimens with the penetrant treatments. This work also indicates that the wetting and drying cycles test can be used to assess the weatherability of the surface treatments. The ASTM C 1202 and the Autoclam air permeability test can be used to evaluate the effectiveness of surface treatments quantitatively. Further work is needed, however, to assess the longevity of the various surface treatments.
TL;DR: In this article, the uniaxial ratcheting behavior of polyetherimide (PEI) polymer was studied using stress-controlled cyclic loading at room temperature, including both cyclic tension-compression with non-zero tensile mean stress and tension-unloading tests.
Abstract: The uniaxial ratcheting behavior of a polyetherimide (PEI) polymer ‘TECAPEI’ was studied using stress-controlled cyclic loading at room temperature, including both cyclic tension-compression with non-zero tensile mean stress and tension-unloading tests. The experimental observations were focused on the time-dependent ratcheting of the PEI polymer revealed in cyclic tests at diverse stress rates and with different peak stress holding times. The results showed that the PEI polymer shows obvious ratcheting deformation; i.e., the ratcheting strain accumulates progressively in the tensile direction during stress-controlled cyclic tests with non-zero mean stress. The ratcheting is highly dependent on the applied mean stress and stress amplitude, and is also characterized by a strong time-dependency during the cyclic stressing at diverse stress rates and with different peak stress holding times. The time-dependent ratcheting of the PEI polymer is caused mainly by its remarkable viscosity. A comparison of the ratcheting occurring before and beyond the ultimate stress point of the PEI polymer showed that the ratcheting beyond the ultimate stress point is more significant than that occurring before that point.
TL;DR: In this paper, the surface roughness of two types of inserts, C and T, was compared using a lathe machine Colchester 6000, and it was found that the C type resulted in 40% lower roughness compared to the T type due to the difference in insert geometry.
Abstract: Surface roughness is an important parameter for ensuring that the dimension of geometry is within the permitted tolerance. The ideal surface roughness is determined by the feed rate and the geometry of the tool. However, several uncontrollable factors including work material factors, tool angle, and machine tool vibration, may also influence surface roughness. The objective of this study was to compare the measured surface roughness (from experiment) to the theoretical surface roughness (from theoretical calculation) and to investigate the surface roughness resulting from two types of insert, ‘C’ type and ‘T’ type. The experiment was focused on the turning process, using a lathe machine Colchester 6000. The feed rate was varied within the recommended feed rate range. We found that there were large deviations between the measured and theoretical surface roughness at a low feed rate (0.05 mm/r) from the application of both inserts. A work material factor of AISI D2 steel that affects the chip character is presumably responsible for this phenomenon. Interestingly, at a high feed rate (0.4 mm/r), the ‘C’ type insert resulted in 40% lower roughness compared to the ‘T’ type due to the difference in insert geometry. This study shows that the geometry of an insert may result in a different surface quality at a particular level of feed rate.
TL;DR: In this paper, a computer model has been generated to analyze the performance of the domestic rainwater harvesting system (DRHS) with different ratios of D/(AR) (water demand/average annual collected runoff) and S/(ARM) (storage capacity/average daily collected runoff).
Abstract: The domestic rainwater harvesting system (DRHS) is an important freshwater source for Zhoushan, China to meet water demands. A computer model has been generated to analyze the performance of the DRHS with different ratios of D/(AR) (water demand/average annual collected runoff) and S/(AR) (storage capacity/average annual collected runoff). The performance of the DRHS was analyzed by means of the model simulation, which is described by its water shortage rate (WSR) and water loss rate (WLR). Using the data, a set of dimensionless design calculation chart is introduced. When the water demand and requirement of the design are known, the established chart can be used to easily determine the storage capacity and catchment (roof and other surface) area required to achieve a desired performance level.
TL;DR: Based on the coupled periodic finite element-boundary element (FE-BE) method, a 3D dynamic track-tunnel-soil interaction model for metro line 8 has been used to predict vibrations in the free field induced by trains running at variable speeds between 30 km/H and 80 km/h as discussed by the authors.
Abstract: This paper mainly discusses the problem of ground-borne vibrations due to the planned line 8 of Beijing metro which passes under the National Measurement Laboratory. A lot of vibration sensitive equipments are placed in the laboratory. It is therefore necessary to study the impact of vibrations induced by metro trains on sensitive equipments and important to propound a feasible vibration mitigation measure. Based on the coupled periodic finite element-boundary element (FE-BE) method, a 3D dynamic track-tunnel-soil interaction model for metro line 8 has been used to predict vibrations in the free field induced by trains running at variable speeds between 30 km/h and 80 km/h. Four types of track structures commonly used on the Beijing metro network have been considered: (1) high resilience direct fixation fasteners, (2) Vanguard fasteners, (3) a floating slab track and (4) a floating ladder track. For each of these track types, the vibration isolation efficiency has been compared. The results of the numerical study can be used to predict vibrations in nearby buildings and to decide upon effective vibration countermeasures.
TL;DR: In this paper, a two-level strength criterion of lightweight aggregate concrete in both octahedral stress coordinate and principal stress coordinate was suggested, and a quadratic formula was suggested for the expression of strength criterion under triaxial compression.
Abstract: Lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) and plate specimens (100 mm×100 mm×50 mm) were tested under biaxial compression-compression (CC) and compression-tension (CT) load combinations. For comparison, normal concrete plate specimens (100 mm×100 mm×50 mm) were tested under the same load combinations. Based on the test results, a two-level strength criterion of lightweight aggregate concrete in both octahedral stress coordinate and principal stress coordinate was suggested. The lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) were then tested under triaxial compression-compression-compression (CCC) load combination with corresponding tests on normal concrete cube specimens (100 mm×100 mm×100 mm). The effect of intermediate principal stress on triaxial compressive strength is further examined. A “plastic flow plateau” area was apparent in principal compressive stress-strain relationships of lightweight aggregate concrete but not in normal concrete. A quadratic formula was suggested for the expression of strength criterion under triaxial compression.
TL;DR: In this article, the thermolysis of urea-water solution and its product, HNCO hydrolysis is investigated in a dual-reactor system, where the reaction is initiated by instigating the reaction HNHO+H·→·NH2+CO and high temperature has positive effect on H radical.
Abstract: The thermolysis of urea-water solution and its product, HNCO hydrolysis is investigated in a dual-reactor system. For the thermal decomposition below about 1073 K, the main products are ammonia (NH3) and isocyanic acid (HNCO) whereas at higher temperatures the oxidation processes take effect and the products include a low concentration of nitric oxide (NO) and nitrous oxide (N2O). The gas HNCO is quite stable and a high yield of HNCO is observed. The ratio of NH3 to HNCO increases from approximately 1.2 to 1.7 with the temperature. The chemical analysis shows that H radical is in favor of HNCO hydrolysis by instigating the reaction HNCO+H·→·NH2+CO and high temperature has positive effect on H radical. The hydrolysis of HNCO over an alumina catalyst made using a sol-gel process (designated as γ-Al2O3) is investigated. The conversion of HNCO is high even at the high space velocities (6×105 h−1) and low temperatures (393–673 K) in the tests with catalysts, which enhances HNCO hydrolysis and raises the ratio of NH3 to HNCO to approximately 100. The pure γ-Al2O3 shows a better catalytic performance than CuO/γ-Al2O3. The addition of CuO not only reduces the surface area but also decreases the Lewis acid sites which are recognized to have a positive effect on the catalytic activity. The apparent activation energy of the hydrolysis reaction amounts to about 25 kJ/mol in 393–473 K while 13 kJ/mol over 473 K. The overall hydrolysis reaction rate on catalysts is mainly determined by external and internal mass-transfer limitations.
TL;DR: Based on the mechanics of the needle placement robot, detailed kinematic analysis is conducted, including a combined numerical algorithm and coordinate mapping, which proves the feasibility of this robotic system.
Abstract: Hepatocellular carcinoma (HCC) is the second most common malignancy in China. As microwave ablation (MWA) is an effective method for liver cancer, a robotic surgical system with ultrasound-directed was designed to assist surgeons on positioning the needles. This robotic system includes a surgical robot with 5 degrees of freedom, a workstation for path-planning and image processing, a conventional 2D ultrasound device, and an electromagnetic (EM) tracking system. Surgery space, clinical operation requirements and optimal mechanical structure are the key factors to be considered in designing a medical robot suitable for use by surgeons. Based on the mechanics of the needle placement robot, we have conducted detailed kinematic analysis, including a combined numerical algorithm and coordinate mapping. Finally, the feasibility of the needle placement robot has been validated by experiment.
TL;DR: In this paper, a computational fluid dynamics (CFD) simulation of the wind flow over an airport terminal building was performed to study the effect of the building wake on landing aircraft.
Abstract: Turbulence in the wake generated by wind flow over buildings or obstacles may produce complex flow patterns in downstream areas. Examples include the recirculating flow and wind deficit areas behind an airport terminal building and their potential impacts on the aircraft landing on nearby runways. A computational fluid dynamics (CFD) simulation of the wind flow over an airport terminal building was performed in this study of the effect of the building wake on landing aircraft. Under normal meteorological conditions, the studied airport terminal building causes limited effects on landing aircraft because most of the aircraft have already landed before entering the turbulent wake region. By simulating the approach of a tropical cyclone, additional CFD sensitivity tests were performed to study the impacts of building wake under extreme meteorological conditions. It was found that, in a narrow range of prevalent wind directions with wind speeds larger than a certain threshold value, a substantial drop in wind speed (>3.6 m/s) along the glide path of aircraft was observed in the building wake. Our CFD results also showed that under the most critical situation, a drop in wind speed as large as 6.4 m/s occurred right at the touchdown point of landing aircraft on the runway, an effect which may have a significant impact on aircraft operations. This study indicated that a comprehensive analysis of the potential impacts of building wake on aircraft operations should be carried out for airport terminals and associated buildings in airfields to ensure safe aviation operation under all meteorological conditions and to facilitate implementation of precautionary measures.
TL;DR: In this article, a 3D finite element model for the Taizhou Yangtze River Bridge, the first triple-tower long-span suspension bridge in China, is established based on the nonlinear finite element software ABAQUS, and the dynamic characteristics of the bridge are analyzed using the LANCZOS eigenvalue solution method.
Abstract: A 3D finite element model for the Taizhou Yangtze River Bridge, the first triple-tower long-span suspension bridge in China, is established based on the nonlinear finite element software ABAQUS, and the dynamic characteristics of the bridge are analyzed using the LANCZOS eigenvalue solution method. The study focuses on the effects of the vertical, lateral and torsional stiffness of the steel box girder, the rigid central buckle and the elastic restraints connecting the towers and the steel box girder on the dynamic characteristics of the triple-tower suspension bridge. Our results show that, in general, the dynamic characteristics of the triple-tower suspension bridge are similar to those of two-tower suspension bridges. The vertical, lateral and torsional stiffness of the steel box girder have different effects on the dynamic characteristics of triple-tower suspension bridges. The elastic restraints have a more significant effect on the dynamic characteristics than the central buckle, and decreasing the stiffness of the elastic restraints results in the appearance of a longitudinal floating vibration mode of the bridge. Also, rigid central buckles have a greater influence on the dynamic characteristics of triple-tower suspension bridges than on those of two-tower suspension bridges. The results obtained could serve as a valuable numerical reference for analyzing and designing super-long-span triple-tower suspension bridges.