Impact Fatigue Characteristics of Valve Leaves for Small Hermetic Reciprocating Compressors

This paper presents an investigation on the impact fatigue characteristics of valve leaves that are prevalently used in hermetic reciprocating compressors especially for the household type refrigerators. The investigation relates the impact fatigue lifetime of the valve leaves that is the heart of the compressor, with the working temperature, material type (carbon steel, stainless steel and improved stainless steel grade) and tumbling duration after the manufacturing process. The investigation provides a better understanding of the impact fatigue characteristics of valve leaves while designing a high performance compressor to decrease the energy consumption. \ud A unique automated impact fatigue test system was designed and produced, which enables to carry out impact fatigue tests of the compressor valve leaves under the desired impact velocities. In the test system, original valve plate and valve leaf couple was utilized through the experimentation in order to simulate the real behavior in the compressor. A fixture was designed to mount the valve plate. The main principle of the system is to create pulsating airflow through a high frequency solenoid valve. The impact fatigue life was determined for various impact velocities and at different operating temperatures

Multicomponent bi-superHamiltonian KdV systems

It is shown that a new class of classical multicomponent super KdV equations is bi-superHamiltonian by extending the method for the verification of graded Jacobi identity. The multicomponent extension of super mKdV equations is obtained by using the super Miura transformation

Vitamin K catabolite inhibition of ovariectomy-induced bone loss: Structure–activity relationship considerations

The potential benefit of vitamin K as a therapeutic in osteoporosis is controversial and the vitamin K regimen being used clinically (45 mg/day) employs doses that are many times higher than required to ensure maximal gamma‐carboxylation of the vitamin K‐dependent bone proteins. We therefore tested the hypothesis that vitamin K catabolites, 5‐carbon (CAN5C) and 7‐carbon carboxylic acid (CAN7C) aliphatic side‐chain derivatives of the naphthoquinone moiety exert an osteotrophic role consistent with the treatment of osteoporosis

Novelty-seeking might underlie curiosity and the novelty dimension of creativity, but not the usefulness dimension

We question the perspective that curiosity and creativity stem from a shared novelty- seeking process. We emphasize that creativity has two distinct dimensions: novelty and usefulness, each involving separate cognitive processes. These dimensions may not necessarily mutually reinforce each other. We contend that a more comprehensive model that encompasses the full scope of the creativity construct is needed

Volume changes during active shape fluctuations in cells

Cells modify their volume in response to changes in osmotic pressure but it is usually assumed that other active shape variations do not involve significant volume fluctuations. Here we report experiments demonstrating that water transport in and out of the cell is needed for the formation of blebs, commonly observed protrusions in the plasma membrane driven by cortex contraction. We develop and simulate a model of fluid mediated membrane-cortex deformations and show that a permeable membrane is necessary for bleb formation which is otherwise impaired. Taken together our experimental and theoretical results emphasize the subtle balance between hydrodynamics and elasticity in actively driven cell morphological changes.Comment: Phys. Rev. Lett. in press. 13 pages 4 figures, 9 supplementary figure

The efficacy of endogenous gibberellic acid for parthenocarpy in eggplant (Solanum melongena L.)

Eggplants are generally grown by winter in Mediterranean areas. Therefore, growers prefer to use parthenocarpic fruit and plant growth regulators. This study determined the relationship between flower development and gibberellic acid (GA3) levels in parthenocarpic and non-parthenocarpic eggplant (Solanum melongena L.) genotypes. A single crop was grown in an unheated greenhouse at the Bati Akdeniz Agricultural Research Institute, Antalya, Turkey, and samples were collected from November to March, GA3 levels were measured with reverse phase high performance liquid chromatography at five different stages between small buds and small fruits. The results showed that there was no relationship between flower development and GA3 levels in parthenocarpic and non-parthenocarpic eggplant genotypes.Key words: HPLC, relation, cultivation, greenhouse, genotype, flower

Equivalent Circuit-Based Analysis of CMUT Cell Dynamics in Arrays

Cataloged from PDF version of article.Capacitive micromachined ultrasonic transducers (CMUTs) are usually composed of large arrays of closely packed cells. In this work, we use an equivalent circuit model to analyze CMUT arrays with multiple cells. We study the effects of mutual acoustic interactions through the immersion medium caused by the pressure field generated by each cell acting upon the others. To do this, all the cells in the array are coupled through a radiation impedance matrix at their acoustic terminals. An accurate approximation for the mutual radiation impedance is defined between two circular cells, which can be used in large arrays to reduce computational complexity. Hence, a performance analysis of CMUT arrays can be accurately done with a circuit simulator. By using the proposed model, one can very rapidly obtain the linear frequency and nonlinear transient responses of arrays with an arbitrary number of CMUT cells. We performed several finite element method (FEM) simulations for arrays with small numbers of cells and showed that the results are very similar to those obtained by the equivalent circuit model

Rayleigh-Bloch waves in CMUT arrays

Cataloged from PDF version of article.Using the small-signal electrical equivalent circuit of a capacitive micromachined ultrasonic transducer (CMUT) cell, along with the self and mutual radiation impedances of such cells, we present a computationally efficient method to predict the frequency response of a large CMUT element or array. The simulations show spurious resonances, which may degrade the performance of the array. We show that these unwanted resonances are due to dispersive Rayleigh-Bloch waves excited on the CMUT surface-liquid interface. We derive the dispersion relation of these waves for the purpose of predicting the resonance frequencies. The waves form standing waves at frequencies where the reflections from the edges of the element or the array result in a Fabry-Pérot resonator. High-order resonances are eliminated by a small loss in the individual cells, but low-order resonances remain even in the presence of significant loss. These resonances are reduced to tolerable levels when CMUT cells are built from larger and thicker lates at the expense of reduced bandwidth. © 2014 IEEE

Emergency crowd simulation for outdoor environments

Cataloged from PDF version of article.We simulate virtual crowds in emergency situations caused by an incident, such as a fire, an explosion, or a terrorist attack. We use a continuum dynamics-based approach to simulate the escaping crowd, which produces more efficient simulations than the agent-based approaches. Only the close proximity of the incident region, which includes the crowd affected by the incident, is simulated. We use a model-based rendering approach where a polygonal mesh is rendered for each agent according to the agent's skeletal motion. To speed up the animation and visualization, we employ an offline occlusion culling technique. We animate and render a pedestrian model only if it is visible according to the static visibility information computed. In the pre-processing stage, the navigable area is decomposed into a grid of cells and the from-region visibility of these cells is computed with the help of hardware occlusion queries. (C) 2009 Elsevier Ltd. All rights reserved