OPTIMAL OPERATION OF MULTIQUALITY WATER SUPPLY SYSTEMS-III: THE Q-C-H MODEL

A new technique for optimal operation of multiquality water supply systems is proposed. The technique, which is known as a Q-C-H (flow-quality-head) model, combines previously developed Sow-quality (Q-C) and flow-head (Q-H) models for optimal operation of water supply systems. The decision variables in the model are the operation of treatment plants, pumps and valves. The model minimizes the cost of water at sources, treatment, energy, and loss of agricultural yield when water quality is low. The model uses an iterative modified projected gradient method combined with the Complex method. As in the Q-C and Q-H models, the solution method is based on decomposition, dis-aggregation/aggregation approach, involving internal and external optimization. The decision variables of the external model are the flows in the loops of the network and the removal ratios at the treatment plants. The operation of the pumps and valves are the decision variables of the internal model. The method is demonstrated by application to an example problem.     

OPTIMAL OPERATION OF MULTI-QUALITY WATER SUPPLY SYSTEMS-I: INTRODUCTION AND THE Q-C MODEL

One of three complementary models for optimal operation of multi-quality water supply systems is presented. The other two models are the subject of companion papers. The model, which is known as the Q-C (flow-quality) model, includes mass continuity of water and constituents. However, the hydraulic constraints do not appear explicitly. To prevent infeasibilities or unreasonable hydraulic conditions arising from the lack of hydraulic constraints, limits and a cost are associated with the flow in each pipe. The constraints in the model include dilution conditions which depend on flow direction. These dilution conditions are introduced into the model by an exponential function, resulting in a smooth continuous nonlinear programming problem, which is transformed into an equivalent problem and solved by a modified projected gradient method. The method is insensitive to scaling of variables, and the computational complexity depends only slightly on the number of water quality parameters. The method is demonstrated by application to two examples: the solution for a small network is presented in detail, and main results are shown for a larger one. The results of these two applications indicate the method's applicability to real networks.     

中空纤维超滤系统的水锤分析及防护

超滤系统的物理清洗是通过阀门频密开启和关闭、水泵的交替起动和停机来实现的,这使液体流速产生急剧变化;并引起很高的水锤压力,造成管道及膜元件损坏.分析了超滤系统出现关阀水锤及停泵水锤的成因,提出相应的防护措施.     

Quantitative Ratio of Heat Flows Due to Second Sound to Dissipation in Superfluid 3He-4He Mixtures

In this paper we compare two hydrodynamic modes in superfluid ³He-⁴He mixtures, focusing on which mode gives greater contribution to propagation of heat in superfluid liquids. Starting from the two-fluid hydrodynamic model, the quantitative contributions of second sound mode and dissipative thermal conductivity mode to the total heat flow are studied. The problem is considered in a cell with heat source of a form Q ₀cos²(ωt) at one side. Analytical expressions for space-time temperature and heat flow dependence are obtained and discussed.     

Numerical Investigation of the Hydrodynamics of a Twisted Flow in a Vortex Chamber Based on the Two‐Parameter Model of Turbulence

An approach based on solution of complete averaged Navier–Stokes equations in vortex chambers using a lowReynolds k– model of turbulence is considered. The problem is solved in the variables vortex, stream function, and circular component of the velocity. The method of oriented pseudoconvection is used for problems of the dynamics of twisted flows. The method allows one to retain second order of accuracy of convective terms and provide stability of the solution for rather high Reynolds numbers. The problem of formulation of boundary conditions of second order of accuracy for vorticity on a solid wall at angular points is considered. An analysis of the results obtained shows that numerical calculations within the framework of the considered model of turbulence agree with experimental data rather well.     

Concerning closed-streamline flows with discontinuous boundary conditions

High-Reynolds-number (Re) flow containing closed streamlines (Prandtl-Batchelor flows), within a region enclosed by a smooth boundary at which the boundary conditions are discontinuous, is considered. In spite of the need for local analysis to account fully for flow at points of discontinuity, asymptotic analysis for Re 1 indicates that the resulting mathematical problem for determining the uniform vorticity ₀) in these situations, requiring the solution of periodic boundary-layer equations, is in essence the same as that for a flow with continuous boundary data. Extensions are proposed to earlier work [3] to enable ₀ to be computed numerically; these require coordinate transformations for the boundary-layer variables at singularities, as well as a two-zone numerical integration scheme. The ideas are demonstrated numerically for the classical circular sleeve.     

Optimal joint maintenance and operation policies to maximise overall systems effectiveness

In this paper, the problem of determining the optimal maintenance and operation policies for a multi-state, multi-stage machine maintenance problem is considered. This problem has been formulated in the literature as a Partially Observed Markov Decision Process (POMDP). A new formulation that explicitly ties maintenance, operation, and quality within the POMDP framework is provided. The new formulation maximises Overall Systems Effectiveness for an n-state system with multiple speed and maintenance actions. The model provides, for each time epoch, a set of optimal maintenance and production-rate actions. The decision-maker (controller) can select the optimal policy depending on the system state occupancy vector (belief state). A realistic numerical model is presented to demonstrate the model utility.     

On some helical flows of Oldroyd-B fluids

Summary In this study the velocity fields and the associated tangential stresses corresponding to some helical flows of Oldroyd-B fluids between two infinite coaxial circular cylinders and within an infinite circular cylinder are determined in forms of series in terms of Bessel functions. At time t = 0 the fluid is at rest and the motion is produced by the combined action of rotating and sliding cylinders. The solutions that have been obtained satisfy the governing differential equations and all imposed initial and boundary conditions. For λ _r = 0, λ = 0 or λ _r = λ = 0 they reduce to the similar solutions for a Maxwell, second grade or Newtonian fluid, respectively. Finally, for comparison, the velocity profiles corresponding to the four models are plotted for different values of t.     

Self-contained, fully integrated biochip for sample preparation, polymerase chain reaction amplification, and DNA microarray detection

A fully integrated biochip device that consists of microfluidic mixers, valves, pumps, channels, chambers, heaters, and DNA microarray sensors was developed to perform DNA analysis of complex biological sample solutions. Sample preparation (including magnetic bead-based cell capture, cell preconcentration and purification, and cell lysis), polymerase chain reaction, DNA hybridization, and electrochemical detection were performed in this fully automated and miniature device. Cavitation microstreaming was implemented to enhance target cell capture from whole blood samples using immunomagnetic beads and accelerate DNA hybridization reaction. Thermally actuated paraffin-based microvalves were developed to regulate flows. Electrochemical pumps and thermopneumatic pumps were integrated on the chip to provide pumping of liquid solutions. The device is completely self-contained: no external pressure sources, fluid storage, mechanical pumps, or valves are necessary for fluid manipulation, thus eliminating possible sample contamination and simplifying device operation. Pathogenic bacteria detection from approximately milliliters of whole blood samples and single-nucleotide polymorphism analysis directly from diluted blood were demonstrated. The device provides a cost-effective solution to direct sample-to-answer genetic analysis and thus has a potential impact in the fields of point-of-care genetic analysis, environmental testing, and biological warfare agent detection.     

Eliminating nuisance parameters: two characterizations

Given a statistical modelP = {P_θ : θ ∈ x} and a surjective functiong: ϑ→Λ the problem of transformingP into a new modelQ= {_λ : λ ∈ Λ} indexed by Λ is investigated. Two characterizations are given for those modelsQ of the form Q_λ = ∫ P_θ π_λ(dθ), where π_λ is some probability such that π_λ(g=λ)=1. The first is related to a geometric property ofQ, while the second rests on the inferential implications of adoptingQ. Also, in the first π_λ is allowed to be finitely additive, while in the second π_λ is σ-additive. Finally, integrated likelihoods are revisited in light of the second characterization.     

Transient stages during the chemical vapour deposition of silicon carbide from CH3SiCl3/H2: impact on the physicochemical and interfacial properties of the coatings

Transient chemical vapour deposition experiments were produced from MTS/H₂ mixtures by varying the deposition temperature or the gas flow rates (Q_MTS or Q_H2) versus time. The gas phase, deposition rates and properties of the transient coating (φ_Tr) were investigated and adhesion assessments of SiC/φ_Tr/SiC bilayers were performed by scratch testing. Transient stages resulting from a decrease of Q_MTS or temperature lead to silicon co-deposition, but do not affect interfacial properties. Transient stages resulting from a decrease of Q_H2 eventually lead to carbon co-deposition. Thick and continuous carbon interlayers lead to a poor adhesion whereas thin and discontinuous layers do not.     

Hydrodynamics of Rotory‐Pulsatory Apparatuses

A kinematic and dynamic analysis of flows in a rotorypulsatory apparatus has been carried out. Based on this analysis, a method for calculating the main parameters of the apparatus with the use of minimum initial experimental information (the head at zero transit flow rate H ₀ and the flow rate at zero head Q ₀) has been developed.     

Torsion by a circular die of a nonhomogeneous elastic layer bonded to a nonhomogeneous half-space

The title problem is equivalent to a torsional mixed boundary value problem in the theory of elasticity in which the only non-zero displacement component is specified inside the circular area r ? l and the shearing stress σ_θz, is zero in the area r > 1 on the face z = 0; the continuity of the displacement and the shearing stress σ_θz is assumed at the interface z = h between the layer and the half-space having different modulii of rigidity. The modulii of rigidity are assumed to be continuous functions of 2. The problem is reduced to the solution of a Fredholm integral equation of the second kind whose iterative solution has been obtained valid for values of h >l, for a few particular cases. Expression for the torque T required to rotate the die through an angle ω has been obtained for the general as well as particular cases.     

Theory of helium under heat flow near the λ point. II. Dynamics of phase change

The He I-He II interface is a crucial aspect in the transformation processes between the superfluid and normal fluid phases. Its motion is investigated when temperatures and heat flows at boundaries deviate from those of a stationary coexistence state. As a unique feature, the heat flow to the interface from the He I side can be mostly transmitted to the He II side by thermal counterflow, and the latent heat generation (or absorption) at the interface becomes negligibly small. In any case the interfacial motion is so slow that the temperature on the He II sideT is still given by the stationary relationT –T Q ^3/4, whereT is the critical temperature and Q is the heat flow. The temperature profile and the interfacial position are calculated in some nonstationary cases. To this end a simple approximation scheme is developed. First, the interface can propagate with a constant velocity and the superfluid region can expand as a shock wave. Second, if the heat flow at the warmer boundaryQ _w and that in the He II regionQ _– are fixed at different values, the length of the He I region y_i changes in time as (d/dt)y _i ^1+p = const Q _w – Q_–, wherep=1/(1–x), and x is the critical exponent of the thermal conductivity. In particular, ify _i=0 att=0 andQ _w>Q_–, the normal fluid region emerges asy _it ^1/(1+p) at the warmer boundary. Third, ifQ _– and the temperature at the warmer boundary are fixed, the interfacial position approaches an equilibrium position exponentially in time. The uniqueness of the problem arises from the superfluidity on the He II side and the strong critical singularity of the thermal conductivity on the He I side.     

Biological artificial fluid-induced non-lamellar phases in glyceryl monooleate: the kinetics pathway and its digestive process by bile salts

Background: The cubic (Q_II) phase is a promising sustained-release system. However, its rigid gel-like propensity is highly viscous, which makes it difficult to handle in pharmaceutical applications. To circumvent this problem, a less viscous lamellar (L_α) phase that could spontaneously transform to Q_II phase by the introduction of water or biological artificial fluid can be used. However, the kinetics pathway of phase transition, susceptibility to digestive processes and impact of the transition on drug release are not yet well understood.

Method: We investigated various biological artificial fluid-induced L_α to inverse Q_II phase transition over time in glyceryl monooleate (GMO) by water penetration scan and light polarizing microscopy. To reveal the structure stability, fluorescence spectroscopy studies were conducted using pyrene as a probe. Furthermore, the release mechanism of pyrene as a lipophilic drug model in the spontaneously formed Q_II was investigated.

Result: Although hexagonal (H_II) mesophases occurred when phosphate buffered saline (PBS) 7.4, 0.1?M HCl or sodium taurocholate (NaTC) solutions were introduced to GMO at room temperature, they disappear with the exception of 0.1?M HCl at 37?°C. Compared with 25?°C, L_α to Q_II phase transition was in a faster rate as almost completely transforms were observed after 2?h post-immersion. The spontaneously formed mesophases were stable over 24?h immersions in PBS or pancreatic lipase solutions as proven by the extremely low fluorescence signal, however they were digestible by bile salts. This result indicated that digestion by bile salts was the major pathway instead of digestion by lipases. Moreover, pyrene fluorescence spectroscopy confirmed that the digestion by bile salts induced the formation of GMO–bile salt mixed micelles whose performance depended on the bile salt concentrations. This dependence influenced the drug release from the spontaneously formed Q_II phase.

Conclusion: All the results concluded that temperature, pH and ionic strength tendencies for the formation of non-lamellar structures greatly influenced the self-assembly process, thereby affecting the final mesophase structure. The results of this study are important to understand the lamellar to non-lamellar lipid-phase transitions and their possible pharmaceutical applications.     

Study of high-pressure air curtain and combined dedusting of gas water spray in multilevel ore pass based on CFD-DEM

In order to solve the problem of dust pollution caused by ore unloading in ore pass, this paper, taking Li Lou Mining as a case study, conducted the wind speed variation law in the fluid domain and the impact of the collision between the ore in the unloading process on the fluid to determine the key dust control point based on the CFD-DEM coupling software. By Fluent software, the air curtain dust-proof efficiency under the action of unloading airflow is analyzed, and the relationship between the dust-control wind speed and the impinging airflow is known. And an experimental model of gas water spray is established to analyze the effect of spray dust removal. By analyzing the impact airflow and dust migration caused by ore unloading and the effect of air curtain dust control through numerical simulation, it can be seen that when the ore discharging quantity M_o = 4000 kg, the dust production is mainly concentrated in the fourth middle section. By high-pressure air shield assisting dust removal, dust diffusion can be better controlled when the ratio of impact wind speed of ore pass wellhead (denoted as λ) to high-pressure air curtain wind speed (denoted as ζ) is at least 1:8. When the dust removal effect is optimal, the ratio δ of the water supply amount q_l and the gas supply amount Q_g is determined by the gas water spray dust control experimental platform.     

A new monitor set for the determination of neutron flux parameters in short-time k0-NAA

Multipurpose research reactors such as LVR-15 in ?e? require monitoring of the neutron flux parameters (f, α) in each batch of samples analyzed when k₀ standardization in NAA is to be used. The above parameters may change quite unpredictably, because experiments in channels adjacent to those used for NAA require an adjustment of the reactor operation parameters and/or active core configuration. For frequent monitoring of the neutron flux parameters the bare multi-monitor method is very convenient. The well-known Au-Zr tri-isotopic monitor set that provides a good tool for determining f and α after long-time irradiation is not optimal in case of short-time irradiation because only a low activity of the ⁹⁵Zr radionuclide is formed. Therefore, several elements forming radionuclides with suitable half-lives and Q₀ and ē_r parameters in a wide range of values were tested, namely ¹⁹⁸Au, ⁵⁶Mn, ⁸⁸Rb, ¹²⁸I, ¹³⁹Ba, and ²³⁹U. As a result, an optimal mixture was selected consisting of Au, Mn, and Rb to form a well suited monitor set for irradiation at a thermal neutron fluence rate of 3×10¹⁷ m⁻² s⁻¹. The procedure of short-time INAA with the new monitor set for k₀ standardization was successfully validated using the synthetic reference material SMELS 1 and several matrix reference materials (RMs) representing matrices of sample types frequently analyzed in our laboratory. The results were obtained using the Kayzero for Windows program.     

Influence of a dc heat flux on the velocity of second sound nearT fλ

We have measured the speed of second soundu ₂ in He II in the presence of a heat fluxQ. ForT _f–1 mK>T>T _f–3.5 mK it is found thatu ₂ reduces linearly withQ ², for 2 mW/cm ² <Q<6 mW/cm ² . By extrapolating the data we have deduced that the lambda transition temperature reduces linearly withQ.     

Stress–strain relationships of polycarbonate over a wide range of strain rate,including a shock wave regime

Stress–strain relationships of polycarbonate (PC) are determined over a very wide range of strain rates, including a shock wave regime. Plate impact tests, drop-weight tests, and quasi-static tests using universal and Instron testing machines are used for the high strain rate (10⁷ s⁻¹), medium strain rate (10² s⁻¹) and low strain rate (10⁻⁴ s⁻¹) tests, respectively. A newly modified unsteady wave sensing system (NM-UWSS) for plate impact tests is developed to determine the stress–strain relationships of PC. The system consists of a powder gun for plate impact tests, three embedded polyvenyliden fluoride (PVDF) gauges, and NM-UWSS. As originally proposed, UWSS is aimed at obtaining experimental inputs for the Lagrangian analysis used in determining the dynamic behavior of materials. We revise this standard system (UWSS) twice to gain a higher time resolution. In the past, the conventional charge mode (Q₂ method) was used. The first modified system (M-UWSS) has been used to study two classes of materials: (1) metallic materials and (2) polymeric materials, where the Q₁ method coupled with a transient differential equation for the equivalent circuit of the measurement circuit for the PVDF stress gauge was used. The latest method (Q_t method) for gaining the highest time resolution of shock wavefront structure by considering the effects of a piezofilm's thickness is proposed for PC at particle velocities of up to 1 km/s. Here we show from basic equations of piezoelectricity that the charge density q, i.e., the charge release per unit area, of the active electrode is proportional to the ratio of the thickness of the shocked region to the total thickness of the piezofilm. It is demonstrated that the rise time of shock charge density q in the piezofilm induced by such shock in the Q₂, Q₁ and Q_t methods, in this order, is becoming much shorter. The latest Q_t method has the highest accuracy among these three methods. Power law relations between stress and strain rate are observed again with PC under conditions of uniaxial strain over a very wide range of strain rates, i.e., 10⁻⁴–10⁷ s⁻¹ including a shock wave regime. For the PC, the effects of strain rate on the stress–strain relationships are estimated using empirical formula.     

‘Heat from Above’ Heat Capacity Measurements in Liquid 4He

We have made heat capacity measurements of superfluid ⁴He at temperatures very close to the lambda point, T _λ, in a constant heat flux, Q, when the helium sample is heated from above. In this configuration the helium enters a self-organized (SOC) heat transport state at a temperature T _soc(Q), which for Q≥100 nW/cm² lies below T _λ. At low Q we observe little or no deviation from the Q=0 heat capacity up to T _SOC(Q); beyond this temperature the heat capacity appears to be sharply depressed, deviating dramatically from its bulk behaviour. This marks the formation and propagation of a SOC/superfluid two phase state, which we confirm with a simple model. The excellent agreement between data and model serves as an independent confirmation, of the existence of the SOC state. As Q is increased (up to 6 µW/cm²) we observe a Q dependent depression in the heat capacity that occurs just below T _SOC(Q), when the entire sample is still superfluid, This is due to the emergence of a large thermal resistance in the sample, which we have measured and used to model the observed heat capacity depression. Our measurements of the superfluid thermal resistivity are a factor of ten larger than previous measurements by Baddar et al.