Zur qualitativen Theorie gleichstromvormagnetisierter Eisendrosseln

Zusammenfassung und Schluß An Hand einer idealisierten Magnetisierungskurve, aus mathematischen Gründen durch den Hyperbelsinus dargestellt, wird für erzwungene sinusförmige Induktionsänderung der zugehörige Feldstärkeverlauf einer gleichstromvormagnetisierten Eisendrossel abgeleitet. Es wird gezeigt, daß eine magnetische Gleichrichtung auftritt und deren Größe und Wirkung dargelegt. Die bekannten Regelkurven, sowohl für die Grundwelle der Feldstärke als auch ihren Effektivwert, werden ermittelt und besprochen. Da das Ergebnis in Form einer Fourierreihe erscheint, können auch alle Oberwellenfragen sofort übersehen werden. In diesem Zusammenhange wird insbesondere auf den Einfluß der Polarität der Vormagnetisierung und auf die Wirkung von Induktionsoberwellen hingewiesen, mit deren Hilfe bekanntlich einzelne Feldstärkeoberwellen unterdrückt werden können.Die obigen Ausführungen stellen einen Versuch dar, einen Teil der Aufgaben, und zwar den Grenzfall für erzwungene sinusförmige Spannung an der Drossel in einphasiger Schaltung, mathematisch zu beschreiben. Der andere Grenzfall für erzwungenen sinusförmigen Strom, sowie das Zusammenwirken derartiger Drosseln in mehrphasigen Schaltungen soll späteren Mitteilungen vorbehalten bleiben.     

阿德莱德的安利路：关于大城市地区中心大街环境中的适度折衷

安利路位于阿德莱德大城市地区南部近郊，它是澳大利亚大城市中相当常见的“中心大街”的一个缩影。本文通过南澳大利亚大学规划专业学生在社区调查基础上进行的项目研究，反映了安利路作为中心大街商业区的主要特征、对安利路形成竞争的因素、对安利路产生影响的问题，并探讨了从社区愿望出发对安利路进行改善的方法和管理战略。     

Dual Knockdown of Musashi RNA-Binding Proteins MSI-1 and MSI-2 Attenuates Putative Cancer Stem Cell Characteristics and Therapy Resistance in Ovarian Cancer Cells

In ovarian cancer, therapy resistance mechanisms complicate cancer cell eradication. Targeting Musashi RNA-binding proteins (MSI) may increase therapeutic efficacy. Database analyses were performed to identify gene expression associations between MSI proteins and key therapy resistance and cancer stem cell (CSC) genes. Then, ovarian cancer cells were subjected to siRNA-based dual knockdown of MSI-1 and MSI-2. CSC and cell cycle gene expression was investigated using quantitative polymerase chain reaction (qPCR), western blots, and flow cytometry. Metabolic activity and chemoresistance were assessed by MTT assay. Clonogenic assays were used to quantify cell survival post-irradiation. Database analyses demonstrated positive associations between MSI proteins and putative CSC markers NOTCH, MYC, and ALDH4A1 and negative associations with NOTCH inhibitor NUMB. MSI-2 expression was negatively associated with the apoptosis regulator p21. MSI-1 and MSI-2 were positively correlated, informing subsequent dual knockdown experiments. After MSI silencing, CSC genes were downregulated, while cell cycle progression was reduced. Metabolic activity was decreased in some cancer cells. Both chemo- and radioresistance were reduced after dual knockdown, suggesting therapeutic potential. Dual knockdown of MSI proteins is a promising venue to impede tumor growth and sensitize ovarian cancer cells to irradiation and chemotherapy.     

Nonuniform and Unsteady Solute Transport in Furrow Irrigation. I: Model Development

A cross-section-averaged advection-dispersion equation (ADE) model was developed to simulate the transport of fertilizer in furrow irrigation. The advection and dispersion processes were solved separately at each time step by implementing a method of characteristics with cubic-spline interpolation and a time-weighted finite-difference scheme, respectively. The upstream boundary condition was a prescribed concentration. Downstream, a zero-flux boundary condition during advance and a concentration gradient following completion of advance were prescribed. Local pseudosteady state was assumed in order to apply Fischer’s longitudinal dispersion equation under nonuniform and unsteady furrow flow conditions. Statistical parameters were used to evaluate the ADE model performance.     

Evaluation of operational control strategies applicable to solar chimney power plants

Numerical simulations are carried out to study the performance of two schemes of power output control applicable to solar chimney power plants. Either the volume flow or the turbine pressure drop is used as independent control variable. Values found in the literature for the optimum ratio of turbine pressure drop to pressure potential vary between 2/3 and 0.97. It is shown that the optimum ratio is not constant during the whole day and it is dependent of the heat transfer coefficients applied to the collector. This study is a contribution towards understanding solar chimney power plant performance and control and may be useful in the design of solar chimney turbines.     

Über die Korrelation der ödometrischen und der “dynamischen” Steifigkeit nichtbindiger Böden

On the correlation of the oedometric and the “dynamic” stiffness of non‐cohesive soils. The “dynamic” shear modulus G_dyn of the soil, i.e. the secant stiffness of the shear stress – shear strain – hysteresis at very small strain amplitudes is often estimated my means of a diagram correlating the dynamic constrained elastic modulus E_s,dyn with the oedometric stiffness E_s for first loading. However, the assumptions and limits of this correlation are not clear. In the context of this paper the correlation E_s ↔ E_s,dyn is checked for four sands with different grain size distribution curves. For this purpose tests with oedometric compression and measurements of the compression wave velocity in a triaxial cell were performed. Partially, significant deviations of the measured data from the correlation approach actually used were obtained. On the basis of the wave velocity measurements and supplementing resonant column tests this paper also discusses the “dynamic” Poisson's ratio ν and presents a modified correlation E_s ↔ G_dyn.     

Development of an expert system for preliminary risk assessment of existing concrete dams

The paper presents an expert system to assist in the field inspection of existing concrete dams within the context of a preliminary risk assessment. The paper describes the engineering knowledge and reasoning required to conduct a deterministic field evaluation of the structural stability of the dam. The symptoms and failure modes identified by the expert system along with the required knowledge and procedures are organized in a structured knowledge tree. The instantiation of the frames and firing of the rules for each consultation traces part of the inference tree contained in the structured knowledge tree. Interaction between nearly decomposable problems are executed with metaknowledge procedures, shared rule groups, and active values. Examples are provided.     

Accumulation and desorption of free radicals in emulsion copolymerization

The emulsion copolymerization of styrene with acrylonitrile, seeded on a polybutadiene support and initiated either potassium persulfate or γ-rays has been studied. The original technique of support activation consists of two steps: the start of the copolymerization in the presence of a small fraction of monomers, followed by the addition of the rest of monomers, which leads to a great increase in the reaction rate. The experimental data provide evidence for a new mechanism that takes into account the desorption–reentry of the free oligoradicals into another particle, their transfer to the polybutadiene support, which results in the accumulation of trapped free radicals. As a consequence of free radicals' accumulation, the overall copolymerization rate increases. The accumulation as well as the desorption processes place this type of copolymerization far from Smith–Ewart theory case II.     

Observation of Unconventional Dynamics of Domain Walls in Uniaxial Ferroelectric Lead Germanate

Application of scanning probe microscopy techniques such as piezoresponse force microscopy (PFM) opens the possibility to re‐visit the ferroelectrics previously studied by the macroscopic electrical testing methods and establish a link between their local nanoscale characteristics and integral response. The nanoscale PFM studies and phase field modeling of the static and dynamic behavior of the domain structure in the well‐known ferroelectric material lead germanate, Pb₅Ge₃O₁₁, are reported. Several unusual phenomena are revealed: 1) domain formation during the paraelectric‐to‐ferroelectric phase transition, which exhibits an atypical cooling rate dependence; 2) unexpected electrically induced formation of the oblate domains due to the preferential domain walls motion in the directions perpendicular to the polar axis, contrary to the typical domain growth behavior observed so far; 3) absence of the bound charges at the 180° head‐to‐head (H–H) and tail‐totail (T–T) domain walls, which typically exhibit a significant charge density in other ferroelectrics due to the polarization discontinuity. This strikingly different behavior is rationalized by the phase field modeling of the dynamics of uncharged H–H and T–T domain walls. The results provide a new insight into the emergent physics of the ferroelectric domain boundaries, revealing unusual properties not exhibited by conventional Ising‐type walls.