Quantum radiation reaction force on a one-dimensional cavity with two relativistic moving mirrors

We consider a real massless scalar field inside a cavity with two moving mirrors in a two-dimensional spacetime, satisfying Dirichlet boundary condition at the instantaneous position of the boundaries, for arbitrary and relativistic laws of motion. Considering vacuum as the initial field state, we obtain formulas for the exact value of the energy density of the field and the quantum force acting on the boundaries, which extend results found in previous papers. For the particular cases of a cavity with just one moving boundary, non-relativistic velocities, or in the limit of infinity length of the cavity (a single mirror), our results coincide with those found in the literature.Comment: 6 pages 9 figure

Pad Temperature In High Speed, Lightly Loaded Tilting Pad Journal Bearings.

LecturePg. 73-84The principal results from an extensive experimental investigation of the steady state characteristics of tilting pad journal bearings are presented. The conditions examined were primarily concerned with operation at high speed (>200ft/sec) and light load (<50 psi specific pressure). The stimulus for this work was the observation of significantly higher than predicted pad temperatures in several steam turbine service applications. The bearings involved were of the conventional pressurized supply (flooded), centrally pivoted, self-aligning type, loaded between pad. High temperatures occurred on both four and five inch diameter bearings designed to operate at shaft speeds up to 14,000 rpm. To investigate this, four and five inch diameter bearings of almost identical design to the service bearings were tested in a laboratory steam turbine at shaft speeds up to 16,000 rpm. The test data acquired show the relationships that exist between the steady state characteristics of pad temperature and power loss, and the parameters of speed, bearing geometry, oil flowrate, and pad material. These results are compared with predicted values from the same tilting pad journal bearing computer program used to evaluate the service bearings. Of primary interest in the data gathered is the observation of an apparent laminar to turbulent transition region. The results verify the actual behavior of the service bearings and identify limitations of the theoretical model used for predicting steady state performance. It is anticipated that the results presented will be of use to bearing designers, and of general interest to manufacturers of rotating machinery

Retrofitting A Large Steam Turbine With A Mechanically Centered Squeeze Film Damper.

LecturePg. 29-40Reviewed is the application of a squeeze film damper to a large steam turbine that addresses high vibration passing through the first critical speed. The turbine was the fifth near identical machine purchased over the course of several expansion projects at a large LNG plant. The original machine was designed in the early 1970s, and had a highly responsive first critical speed with an amplification factor in the upper teens. With a rotor this sensitive to unbalance, heavy rubs and operational difficulties were often encountered during start up and shut down transients. For the fifth machine, it was inquired how the rotor's response sensitivity could be improved without compromising rotor interchangeability with the sister units. A squeeze film damper bearing, being the only practical solution, was proposed and implemented. The design and analysis methodology used in the development of the squeeze film damper bearing is discussed. To maintain rotor interchangeability, the design covers how the damper bearing was optimized to fit the available limited envelope. The systematic analytical approach demonstrates the importance of including support stiffness effects beyond the damper bearing. Test results are presented that illustrate the accuracy of the analysis, and the reduction in synchronous rotor response at the first critical speed

Influence of aerosol acidity on the chemical composition of secondary organic aerosol from β-caryophyllene

The secondary organic aerosol (SOA) yield of β-caryophyllene photooxidation is enhanced by aerosol acidity. In the present study, the influence of aerosol acidity on the chemical composition of β-caryophyllene SOA is investigated using ultra performance liquid chromatography/electrospray ionization-time-of-flight mass spectrometry (UPLC/ESI-TOFMS). A number of first-, second- and higher-generation gas-phase products having carbonyl and carboxylic acid functional groups are detected in the particle phase. Particle-phase reaction products formed via hydration and organosulfate formation processes are also detected. Increased acidity leads to different effects on the abundance of individual products; significantly, abundances of organosulfates are correlated with aerosol acidity. To our knowledge, this is the first detection of organosulfates and nitrated organosulfates derived from a sesquiterpene. The increase of certain particle-phase reaction products with increased acidity provides chemical evidence to support the acid-enhanced SOA yields. Based on the agreement between the chromatographic retention times and accurate mass measurements of chamber and field samples, three β-caryophyllene products (i.e., β-nocaryophyllon aldehyde, β-hydroxynocaryophyllon aldehyde, and β-dihydroxynocaryophyllon aldehyde) are suggested as chemical tracers for β-caryophyllene SOA. These compounds are detected in both day and night ambient samples collected in downtown Atlanta, GA and rural Yorkville, GA during the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS)

Profiled Leading Edge Groove Tilting Pad Journal Bearing For Light Load Operation.

LecturePg. 1-16Optimization of a leading edge groove tilting pad journal bearing for application in a small, high speed, multistage steam turbine is described. Rotordynamics constraints to meet a design objective maximum operating speed of 1 8000 rpm resulted in a rotor with a 51.0 in bearing span and 5.0 in diameter tilting pad journal bearings. This configuration yielded a design with projected bearing loads of less than 25 psi, and journal surface speeds that could approach 400 ft/sec. Under these conditions, the applicable limits of conventional style tilting pad journal bearings are stretched, since operation is well into the turbulent flow regime. This can result in significantly higher than predicted operating pad temperatures and increased frictional losses. Furthermore, at very light pad loads, bearing dynamic performance and influence on rotor behavior often does not correlate well with theory. For this application, high efficiency leading edge groove bearings (journal and thrust) were used, due to their preferred steady state operating characteristics at high speed. However, as is often observed with lightly loaded conventional style journal bearings, dynamic performance did not precisely match that predicted by theory. This was investigated by profiling the exit side of the leading edge groove with both a tapered and pocket geometry. Two case histories are presented demonstrating their effect on rotor-bearing stability and unbalance response. The modified bearings yielded greater system stability at high speeds, reduced overall vibration amplitudes, and greatly improved effective damping on passing through the rotor's first peak response speed

Subtracting Residual Unbalance For Improved Test Stand Vibration Correlation.

LecturePg. 7-18The importance of correlating rotordynamic analytical results to actual test data has become extremely important in recent years. Many user specifications require the verification of vendor generated analytical results in conjunction with shop unbalance testing. This correlation generally includes critical speed, amplification factor, and vibration magnitude. Several problems arise during shop unbalance testing. First, it is not always feasible to place an unbalance test weight in a location where it will logically excite the mode in question. This can lead to test runs where, despite a large unbalance weight, the residual unbalance is more influential than the test weight. Thus, the resulting rotor vibration is controlled by the residual unbalance and not the test unbalance. Consequently, any type of analytical correlation for this situation is extremely difficult. Another problem with test stand data is that it usually comes from four different vibration probe locations. This results in four vibration plots and, in many cases, four different critical speeds, amplification factors, and vibration magnitudes. Again, the analytical correlation for this situation is extremely difficult, since determining the actual values for these parameters is somewhat nebulous. These problems are addressed herein and a solution is offered. Several examples of analytical and test stand results are presented for steam turbines and centrifugal compressors. These examples highlight and discuss the problem areas identified. A method is presented for subtracting the vibration due to residual unbalance from that of the verification test. The resulting vibration with residual subtraction isolates the effect of the unbalance weight, and leads to improved correlation with analytical predictio

The Household Responsibility System, Karl Marx’s Theory of Property and Antony M. Honoré’s Concept of Ownership

The Household Responsibility System (HRS) has improved agricultural productivity and promoted economic growth and thus relieved poverty in the rural population of China. However, the prevailing assumptions about its nature are that it was the result of de-collectivization and privatization (or at least semi-privatization) of land and thus an adaptation of capitalism or semi-capitalism. Moreover, the property rights structure of the HRS in China is also often assumed to be ambiguous and insecure. Grasping the principal characteristics of the HRS requires historical analysis of its origin, development and eventual legislation and institutionalization. Marx's theory of property is the key to understanding the institutional change from the Commune System to the HRS. It reveals that the HRS is one kind of “individual property” that Marx envisioned in post-capitalist society. Antony M. Honoré's theoretical framework of ownership is usefully viewed as a development of Marx's theory; within that framework, the HRS emerges as a kind of “split ownership” and its property rights structure can be judged to be well-defined

Moment analysis of the probability distributions of different sandpile models

We reconsider the moment analysis of the Bak-Tang-Wiesenfeld and the Manna sandpile model in two and three dimensions. In contrast to recently performed investigations our analysis turns out that the models are characterized by different scaling behavior, i.e., they belong to different universality classes.Comment: 6 pages, 6 figures, accepted for publication in Physical Review

Untargeted Metabolomic Characterization of Glioblastoma Intra-Tumor Heterogeneity Using OrbiSIMS

Glioblastoma (GBM) is an incurable brain cancer with a median survival of less than two years from diagnosis. The standard treatment of GBM is multimodality therapy comprising surgical resection, radiation, and chemotherapy. However, prognosis remains poor, and there is an urgent need for effective anticancer drugs. Since different regions of a single GBM contain multiple cancer subpopulations ("intra-tumor heterogeneity"), this likely accounts for therapy failure as certain cancer cells can escape from immune surveillance and therapeutic threats. Here, we present metabolomic data generated using the Orbitrap secondary ion mass spectrometry (OrbiSIMS) technique to investigate brain tumor metabolism within its highly heterogeneous tumor microenvironment. Our results demonstrate that an OrbiSIMS-based untargeted metabolomics method was able to discriminate morphologically distinct regions (viable, necrotic, and non-cancerous) within single tumors from formalin-fixed paraffin-embedded tissue archives. Specifically, cancer cells from necrotic regions were separated from viable GBM cells based on a set of metabolites including cytosine, phosphate, purine, xanthine, and 8-hydroxy-7-methylguanine. Moreover, we mapped ubiquitous metabolites across necrotic and viable regions into metabolic pathways, which allowed for the discovery of tryptophan metabolism that was likely essential for GBM cellular survival. In summary, this study first demonstrated the capability of OrbiSIMS for in situ investigation of GBM intra-tumor heterogeneity, and the acquired information can potentially help improve our understanding of cancer metabolism and develop new therapies that can effectively target multiple subpopulations within a tumor