Both reverse osmosis(RO) and nanofiltration(NF) membranes have been increasingly used for water purification and desalination. However, the salt rejection of NF membranes is quite different from that of RO membranes,w...Both reverse osmosis(RO) and nanofiltration(NF) membranes have been increasingly used for water purification and desalination. However, the salt rejection of NF membranes is quite different from that of RO membranes,which makes a significant distinction in their process designs. This work started from the performance investigation of a single NF membrane element and then focused on the process design of the NF system for surface water treatment. In experimental tests, it was found that the observed rejection of the NF element becomes nearly constant when the concentrate flow is large enough, while the membrane flux of the NF element is quite stable regardless of the water flow across the membrane surface. These findings can be used to instruct the process design of the NF system for surface water treatment. In process design, a two-stage arrangement is sufficient for the NF system to reach the highest water recovery, while the RO system requires a three-stage arrangement.展开更多
In this work, the synthesis of epichlorohydrin(ECH) from 1,3-dichloropropanol(DCP) by using solid sodium hydroxide(NaOH) is carefully investigated. Inert organic solvent, 1-octanol, is introduced to ensure reaction in...In this work, the synthesis of epichlorohydrin(ECH) from 1,3-dichloropropanol(DCP) by using solid sodium hydroxide(NaOH) is carefully investigated. Inert organic solvent, 1-octanol, is introduced to ensure reaction intensity under control. The reaction performances with respect to apparent kinetics and selectivity are determined to explore optimized reaction conditions and confirm potentials for enhancing productivity in one batch. The dissolution and liquid phase reaction mechanism and instant reaction assumption are proposed and verified through process analysis. A process design towards free additional water is schematically figured out to manipulate solid NaOH, by-product,and unreacted starting materials to realize a nearly closed circuit. This process allows high selectivity over 97% and complete DCP conversion at 323.2 K within a reaction time less than 20 min. Other advantages include near-zero wastewater emission, economically possible NaOH regeneration from NaCl, and robust operating condition window.展开更多
The main objective of this work is to use the CFD (Computational Fluid Dynamics) technique to study the effects of pitch ratio on the controllable pitch propeller's thrust characteristic. The propeller analyzed is ...The main objective of this work is to use the CFD (Computational Fluid Dynamics) technique to study the effects of pitch ratio on the controllable pitch propeller's thrust characteristic. The propeller analyzed is at the following design condition: diameter of 3.65 m, speed of 200 rpm, blade number of 4, average pitch of 2.459 m, pitch ratio at 0.7 of 0.6737. The first stage involves the mesh generation and refinement on domain of the designed propeller. The second stage deals with the identification of initial and boundary conditions of the mesh-equipped module. In the final stage, various results are calculated and analyzed for pitch ratio affecting on the propeller's thrust characteristic. The achieved results are the basis design and improving efficiency of the controllable pitch propeller.展开更多
Inspired by the idea that bionic non-smooth surfaces(BNSS) can reduce fluid adhesion and resistance, and the effect of bionic V-riblet non-smooth structure arranged in tire tread pattern grooves surface on anti-hydrop...Inspired by the idea that bionic non-smooth surfaces(BNSS) can reduce fluid adhesion and resistance, and the effect of bionic V-riblet non-smooth structure arranged in tire tread pattern grooves surface on anti-hydroplaning performance was investigated by using computational fluid dynamics(CFD). The physical model of the object(model of V-riblet surface distribution, hydroplaning model) and SST k-ω turbulence model were established for numerical analysis of tire hydroplaning. With the help of a orthogonal table L16(45), the parameters of V-riblet structure design compared to the smooth structure were analyzed, and obtained the priority level of the experimental factors as well as the best combination within the scope of the experiment. The simulation results show that V-riblet structure can reduce water flow resistance by disturbing the eddy movement in boundary layers. Then, the preferred type of V-riblet non-smooth structure was arranged on the bottom of tire grooves for hydroplaning performance analysis. The results show that bionic V-riblet non-smooth structure can effectively increase hydroplaning velocity and improve tire anti-hydroplaning performance. Bionic design of tire tread pattern grooves is a good way to promote anti-hydroplaning performance without increasing additional groove space, so that tire grip performance and roll noise are avoided due to grooves space enlargement.展开更多
In order to investigate the effect of priming on Chickpea seed performance under drought stress, a study was carried out at the Seed Research Laboratory of Razi University, Kermanshah, Iran. The experiment was a facto...In order to investigate the effect of priming on Chickpea seed performance under drought stress, a study was carried out at the Seed Research Laboratory of Razi University, Kermanshah, Iran. The experiment was a factorial with three factors arranged in a completely randomized design with four replications. The first factor was seed priming (control (untreated), HB-101 (Completely organic herbal extracts, derived from the bark of dark cones), KNO3 and distilled water), the second was drought stress levels (0.0, -0.3, -0.6, -0.9, -1.2 MPa) and the third was chickpea cultivars (Arman and Azar). Results indicated that for both cultivars germination percentage (GP), mean germination rate (MGR), radicle length (RL), plumule length (PL) and seedling dry weight (SDW) were reduced when drought stress level were increased from 0 to -!.2 Mpa, although, the cultivars showed different responses to the increased drought stress level. For all of the traits under study, the best results due to the priming treatments were obtained at the drought stress levels higher than -0.6 or -0.9 MPa. So that, at the -1.2 MPa of drought stress level, GP, MGR, and SDW were increased 53.75, 0.49, and 13.85, respectively by HB -101 when compared with control. However, seeds primed with HB-101 showed better performance than those primed with distilled water and KNO3. In general, this study revealed that seed priming especially with HB-101 improved chickpea seed performance under drought stress condition. However, the improvements were more obvious at the higher levels of drought stress.展开更多
In recent major earthquakes, the researchers have found the need for consideration of vertical seismic acceleration for the stability analysis of the man-made and natural slopes. However, in most past studies, the per...In recent major earthquakes, the researchers have found the need for consideration of vertical seismic acceleration for the stability analysis of the man-made and natural slopes. However, in most past studies, the performance of slopes has been assessed by accounting only the horizontal seismic component of the ground motion, without giving due weightage to the effect of vertical component. In the present study, analytical expressions are derived to determine the factor of safety, yield seismic coefficient and consequently the seismic displacement of cohesionless soil slope under combined horizontal and vertical components of the ground motion. The derivation uses the Newmark's sliding block approach, in which the soil slope with a planar failure surface within the framework of conventional pseudo-static analysis is assumed to follow the Mohr-Coulomb failure criterion. The effects of vertical seismic coefficient on the stability of cohesionless slope have been studied through a set of graphical presentations for a specific range of soil parameters. It is observed that overlooking the effect of the vertical component of the ground motion on factor of safety and the displacement while designing the slope may be detrimental, resulting in the slope failure. The general expressions presented in this paper may be highly useful in the field of earthquake geotechnical engineering practice for designing the cohesionless soil slopes under combined horizontal and vertical seismic loads.展开更多
Groundwater as an alternative source still does not contribute to the water supply in area of Parit Raja because of the limitation of water availability in the ground. This lacking of groundwater could be caused by th...Groundwater as an alternative source still does not contribute to the water supply in area of Parit Raja because of the limitation of water availability in the ground. This lacking of groundwater could be caused by the circumstance that the top layer of soil is dominated by compacted clay around 2 meters in which its permeability is small, so the water is difficult to infiltrate the ground. The recharge well technique was designed based on the flat area problems, layer of real condition, flow water table and low infiltration rate. Resistivity soundings were made at existing wells to assess the subsurface layers. Beside that, the past records on floods event, sub surface and surface studies were collected around study area as a preliminary studies. It was presented that the study area promised good prospects to increase the capability of groundwater and contribute to the drainage system by reducing the volume of rainfall runoff using the recharge well technique.展开更多
Darcy's law only applying to the flow domain is extended to the entire fracture network domain including the dry domain.The partial differential equation(PDE) formulation for unconfined seepage flow problems for d...Darcy's law only applying to the flow domain is extended to the entire fracture network domain including the dry domain.The partial differential equation(PDE) formulation for unconfined seepage flow problems for discrete fracture network is established,in which a boundary condition of Signorini's type is prescribed over the potential seepage surfaces.In order to reduce the difficulty in selecting trial functions,a new variational inequality formulation is presented and mathematically proved to be equivalent to the PDE formulation.The numerical procedure based on the VI formulation is proposed and the corresponding algorithm has been developed.Since a continuous penalized Heaviside function is introduced to replace a jump function in finite element analysis,oscillation of numerical integration for facture elements cut by the free surface is eliminated and stability of numerical solution is assured.The numerical results from two typical examples demonstrate,on the one hand the effectiveness and robustness of the proposed method,and on the other hand the capability of predicting main seepage pathways in fractured rocks and flow rates out of the drainage system,which is very important for performance assessments and design optimization of complex drainage system.展开更多
Developing transition metal-based electrocatalysts with rich active sites for water electrolysis plays important roles in renewable energy fields. So far, some strategies including designing nanostructures, incorporat...Developing transition metal-based electrocatalysts with rich active sites for water electrolysis plays important roles in renewable energy fields. So far, some strategies including designing nanostructures, incorporating conductive support or foreign elements have been adopted to develop efficient electrocat- alysts. Herein, we summarize recent progresses and propose in-situ electrochemical activation as a new pretreating technique for enhanced catalytic performances. The activation techniques mainly comprise facile electrochemical processes such as anodic oxidation, cathodic reduction, etching, lithium-assisted tuning and counter electrode electro-dissolution. During these electrochemicaI treatments, the catalyst surfaces are modified from bulk phase, which can tune local electronic structures, create more active spe- cies. enlarge surface area and thus improve the catalytic performances. Meanwhile, this technique can couple the atomic, electronic structures with electrocatalysis mechanisms for water splitting. Compared to traditional chemical treatment, the in-situ electrochemical activation techniques have superior advantages such as facile operation, mild environment, variable control, high efficiency and flex- ibility. This review may provide guidance for improving water electrolysis efficiencies and hold promis- ing for application in many other energy-conversion fields such as supercapacitors, fuel cells and batteries.展开更多
基金Sponsored by the National Natural Science Foundation of China(51578485,L1422037)the National Basic Research Program of China(2015CB655303)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China(No.20130101110064)the National Sustain Plan Program of China(2015BAB11B01)
文摘Both reverse osmosis(RO) and nanofiltration(NF) membranes have been increasingly used for water purification and desalination. However, the salt rejection of NF membranes is quite different from that of RO membranes,which makes a significant distinction in their process designs. This work started from the performance investigation of a single NF membrane element and then focused on the process design of the NF system for surface water treatment. In experimental tests, it was found that the observed rejection of the NF element becomes nearly constant when the concentrate flow is large enough, while the membrane flux of the NF element is quite stable regardless of the water flow across the membrane surface. These findings can be used to instruct the process design of the NF system for surface water treatment. In process design, a two-stage arrangement is sufficient for the NF system to reach the highest water recovery, while the RO system requires a three-stage arrangement.
基金Supported by the National Natural Science Foundation of China(21176136,21422603)the National Science and Technology Support Program of China(2011BAC06B01)
文摘In this work, the synthesis of epichlorohydrin(ECH) from 1,3-dichloropropanol(DCP) by using solid sodium hydroxide(NaOH) is carefully investigated. Inert organic solvent, 1-octanol, is introduced to ensure reaction intensity under control. The reaction performances with respect to apparent kinetics and selectivity are determined to explore optimized reaction conditions and confirm potentials for enhancing productivity in one batch. The dissolution and liquid phase reaction mechanism and instant reaction assumption are proposed and verified through process analysis. A process design towards free additional water is schematically figured out to manipulate solid NaOH, by-product,and unreacted starting materials to realize a nearly closed circuit. This process allows high selectivity over 97% and complete DCP conversion at 323.2 K within a reaction time less than 20 min. Other advantages include near-zero wastewater emission, economically possible NaOH regeneration from NaCl, and robust operating condition window.
文摘The main objective of this work is to use the CFD (Computational Fluid Dynamics) technique to study the effects of pitch ratio on the controllable pitch propeller's thrust characteristic. The propeller analyzed is at the following design condition: diameter of 3.65 m, speed of 200 rpm, blade number of 4, average pitch of 2.459 m, pitch ratio at 0.7 of 0.6737. The first stage involves the mesh generation and refinement on domain of the designed propeller. The second stage deals with the identification of initial and boundary conditions of the mesh-equipped module. In the final stage, various results are calculated and analyzed for pitch ratio affecting on the propeller's thrust characteristic. The achieved results are the basis design and improving efficiency of the controllable pitch propeller.
基金Project(51405201)supported by the National Natural Science Foundation of ChinaProject(1291120046)supported by the Jiangsu University Advanced Talents Initial Funding,China+1 种基金Project(QC201303)supported by the Open Fund of Automotive Engineering Key Laboratory,ChinaProject(2014M551509)supported by the China Postdoctoral Science Foundation
文摘Inspired by the idea that bionic non-smooth surfaces(BNSS) can reduce fluid adhesion and resistance, and the effect of bionic V-riblet non-smooth structure arranged in tire tread pattern grooves surface on anti-hydroplaning performance was investigated by using computational fluid dynamics(CFD). The physical model of the object(model of V-riblet surface distribution, hydroplaning model) and SST k-ω turbulence model were established for numerical analysis of tire hydroplaning. With the help of a orthogonal table L16(45), the parameters of V-riblet structure design compared to the smooth structure were analyzed, and obtained the priority level of the experimental factors as well as the best combination within the scope of the experiment. The simulation results show that V-riblet structure can reduce water flow resistance by disturbing the eddy movement in boundary layers. Then, the preferred type of V-riblet non-smooth structure was arranged on the bottom of tire grooves for hydroplaning performance analysis. The results show that bionic V-riblet non-smooth structure can effectively increase hydroplaning velocity and improve tire anti-hydroplaning performance. Bionic design of tire tread pattern grooves is a good way to promote anti-hydroplaning performance without increasing additional groove space, so that tire grip performance and roll noise are avoided due to grooves space enlargement.
文摘In order to investigate the effect of priming on Chickpea seed performance under drought stress, a study was carried out at the Seed Research Laboratory of Razi University, Kermanshah, Iran. The experiment was a factorial with three factors arranged in a completely randomized design with four replications. The first factor was seed priming (control (untreated), HB-101 (Completely organic herbal extracts, derived from the bark of dark cones), KNO3 and distilled water), the second was drought stress levels (0.0, -0.3, -0.6, -0.9, -1.2 MPa) and the third was chickpea cultivars (Arman and Azar). Results indicated that for both cultivars germination percentage (GP), mean germination rate (MGR), radicle length (RL), plumule length (PL) and seedling dry weight (SDW) were reduced when drought stress level were increased from 0 to -!.2 Mpa, although, the cultivars showed different responses to the increased drought stress level. For all of the traits under study, the best results due to the priming treatments were obtained at the drought stress levels higher than -0.6 or -0.9 MPa. So that, at the -1.2 MPa of drought stress level, GP, MGR, and SDW were increased 53.75, 0.49, and 13.85, respectively by HB -101 when compared with control. However, seeds primed with HB-101 showed better performance than those primed with distilled water and KNO3. In general, this study revealed that seed priming especially with HB-101 improved chickpea seed performance under drought stress condition. However, the improvements were more obvious at the higher levels of drought stress.
文摘In recent major earthquakes, the researchers have found the need for consideration of vertical seismic acceleration for the stability analysis of the man-made and natural slopes. However, in most past studies, the performance of slopes has been assessed by accounting only the horizontal seismic component of the ground motion, without giving due weightage to the effect of vertical component. In the present study, analytical expressions are derived to determine the factor of safety, yield seismic coefficient and consequently the seismic displacement of cohesionless soil slope under combined horizontal and vertical components of the ground motion. The derivation uses the Newmark's sliding block approach, in which the soil slope with a planar failure surface within the framework of conventional pseudo-static analysis is assumed to follow the Mohr-Coulomb failure criterion. The effects of vertical seismic coefficient on the stability of cohesionless slope have been studied through a set of graphical presentations for a specific range of soil parameters. It is observed that overlooking the effect of the vertical component of the ground motion on factor of safety and the displacement while designing the slope may be detrimental, resulting in the slope failure. The general expressions presented in this paper may be highly useful in the field of earthquake geotechnical engineering practice for designing the cohesionless soil slopes under combined horizontal and vertical seismic loads.
文摘Groundwater as an alternative source still does not contribute to the water supply in area of Parit Raja because of the limitation of water availability in the ground. This lacking of groundwater could be caused by the circumstance that the top layer of soil is dominated by compacted clay around 2 meters in which its permeability is small, so the water is difficult to infiltrate the ground. The recharge well technique was designed based on the flat area problems, layer of real condition, flow water table and low infiltration rate. Resistivity soundings were made at existing wells to assess the subsurface layers. Beside that, the past records on floods event, sub surface and surface studies were collected around study area as a preliminary studies. It was presented that the study area promised good prospects to increase the capability of groundwater and contribute to the drainage system by reducing the volume of rainfall runoff using the recharge well technique.
基金supported by the National Natural Science Foundation of China (Grant No. 51079110)the National Basic Research Program of China ("973" Project) (Grant No. 2011CB013506)
文摘Darcy's law only applying to the flow domain is extended to the entire fracture network domain including the dry domain.The partial differential equation(PDE) formulation for unconfined seepage flow problems for discrete fracture network is established,in which a boundary condition of Signorini's type is prescribed over the potential seepage surfaces.In order to reduce the difficulty in selecting trial functions,a new variational inequality formulation is presented and mathematically proved to be equivalent to the PDE formulation.The numerical procedure based on the VI formulation is proposed and the corresponding algorithm has been developed.Since a continuous penalized Heaviside function is introduced to replace a jump function in finite element analysis,oscillation of numerical integration for facture elements cut by the free surface is eliminated and stability of numerical solution is assured.The numerical results from two typical examples demonstrate,on the one hand the effectiveness and robustness of the proposed method,and on the other hand the capability of predicting main seepage pathways in fractured rocks and flow rates out of the drainage system,which is very important for performance assessments and design optimization of complex drainage system.
基金financially supported by Shandong Provincial Natural Science Foundation,China (ZR2017MB059)the National Natural Science Foundation of China (21776314)the Fundamental Research Funds for the Central Universities (18CX05016A)
文摘Developing transition metal-based electrocatalysts with rich active sites for water electrolysis plays important roles in renewable energy fields. So far, some strategies including designing nanostructures, incorporating conductive support or foreign elements have been adopted to develop efficient electrocat- alysts. Herein, we summarize recent progresses and propose in-situ electrochemical activation as a new pretreating technique for enhanced catalytic performances. The activation techniques mainly comprise facile electrochemical processes such as anodic oxidation, cathodic reduction, etching, lithium-assisted tuning and counter electrode electro-dissolution. During these electrochemicaI treatments, the catalyst surfaces are modified from bulk phase, which can tune local electronic structures, create more active spe- cies. enlarge surface area and thus improve the catalytic performances. Meanwhile, this technique can couple the atomic, electronic structures with electrocatalysis mechanisms for water splitting. Compared to traditional chemical treatment, the in-situ electrochemical activation techniques have superior advantages such as facile operation, mild environment, variable control, high efficiency and flex- ibility. This review may provide guidance for improving water electrolysis efficiencies and hold promis- ing for application in many other energy-conversion fields such as supercapacitors, fuel cells and batteries.