Shock amplification, curve veering and the role of damping

The circumstances are investigated under which high peak acceleration can occur in the internal parts of a system when subjected to impulsive driving on the outside. Previous work using a coupled beam model has highlighted the importance of veering pairs of modes. Such a veering pair can be approximated by a lumped system with two degrees of freedom. The worst case of acceleration amplification is shown to occur when the two oscillators are tuned to the same frequency, and for this case closed-form expressions are derived to show the parameter dependence of the acceleration ratio on the mass ratio and coupling strength. Sensitivity analysis of the eigenvalues and eigenvectors indicates that mass ratio is the most sensitive parameter for altering the veering behaviour in an undamped system. Non-proportional damping is also shown to have a strong influence on the veering behaviour. The study gives design guidelines to allow permissible acceleration levels to be achieved by the choice of the effective mass and damping of the indirectly driven subsystem relative to the directly driven subsystem. © 2013 Elsevier Ltd.

Parameterizing Unconditional Skewness in Models for Financial Time Series

In this paper we consider the third-moment structure of a class of time series models. It is often argued that the marginal distribution of financial time series such as returns is skewed. Therefore it is of importance to know what properties a model should possess if it is to accommodate unconditional skewness. We consider modeling the unconditional mean and variance using models that respond nonlinearly or asymmetrically to shocks. We investigate the implications of these models on the third-moment structure of the marginal distribution as well as conditions under which the unconditional distribution exhibits skewness and nonzero third-order autocovariance structure. In this respect, an asymmetric or nonlinear specification of the conditional mean is found to be of greater importance than the properties of the conditional variance. Several examples are discussed and, whenever possible, explicit analytical expressions provided for all third-order moments and cross-moments. Finally, we introduce a new tool, the shock impact curve, for investigating the impact of shocks on the conditional mean squared error of return series.

A low-mass impact sensor for high-speed firmness sensing of fruits.

A low-mass impact sensor for high-speed firmness sensing of fruits was built and tested. Results of tests with a rubber ball indicated that the impact measurement was not sensitive to the distance between the impactor and the impacting surface of the sample within the range of 8 to 23 mm, and was not sensitive to how the sample was held. Tests with kiwifruits and peaches show good correlation between firmness readings obtained with the impact sensor and those obtained with the penetrometer. The best correlation was between the slope of the impact curve (at mid-point) and the force-deformation firmness. Preliminary test showed that the sensor could sense fruit firmness at a speed of 5 fruits/s.

A family of autoregressive conditional duration models

This paper develops a family of autoregressive conditional duration (ACD) models that encompasses most specifications in the literature. The nesting relies on a Box-Cox transformation with shape parameter λ to the conditional duration process and a possibly asymmetric shocks impact curve. We establish conditions for the existence of higher-order moments, strict stationarity, geometric ergodicity and β-mixing property with exponential decay. We next derive moment recursion relations and the autocovariance function of the power λ of the duration process. Finally, we assess the practical usefulness of our family of ACD models using NYSE transactions data, with special attention to IBM price durations. The results warrant the extra flexibility provided either by the Box-Cox transformation or by the asymmetric response to shocks.

A family of autoregressive conditional duration models

This paper develops a family of autoregressive conditional duration (ACD) models that encompasses most specifications in the literature. The nesting relies on a Box-Cox transformation with shape parameter λ to the conditional duration process and a possibly asymmetric shocks impact curve. We establish conditions for the existence of higher-order moments, strict stationarity, geometric ergodicity and β-mixing property with exponential decay. We next derive moment recursion relations and the autocovariance function of the power λ of the duration process. Finally, we assess the practical usefulness of our family of ACD models using NYSE price duration data on the IBM stock. The results warrant the extra flexibility provided either by the Box-Cox transformation or by the asymmetric response to shocks.

I. Impact spallation experiments: fracture patterns and spall velocities. II. Craters in carbonate rocks: an electron paramagnetic resonance analysis of shock damage

This work is divided into two independent papers.

PAPER 1.

Spall velocities were measured for nine experimental impacts into San Marcos gabbro targets. Impact velocities ranged from 1 to 6.5 km/sec. Projectiles were iron, aluminum, lead, and basalt of varying sizes. The projectile masses ranged from a 4 g lead bullet to a 0.04 g aluminum sphere. The velocities of fragments were measured from high-speed films taken of the events. The maximum spall velocity observed was 30 m/sec, or 0.56 percent of the 5.4 km/sec impact velocity. The measured velocities were compared to the spall velocities predicted by the spallation model of Melosh (1984). The compatibility between the spallation model for large planetary impacts and the results of these small scale experiments are considered in detail.

The targets were also bisected to observe the pattern of internal fractures. A series of fractures were observed, whose location coincided with the boundary between rock subjected to the peak shock compression and a theoretical "near surface zone" predicted by the spallation model. Thus, between this boundary and the free surface, the target material should receive reduced levels of compressive stress as compared to the more highly shocked region below.

PAPER 2.

Carbonate samples from the nuclear explosion crater, OAK, and a terrestrial impact crater, Meteor Crater, were analyzed for shock damage using electron para- magnetic resonance, EPR. The first series of samples for OAK Crater were obtained from six boreholes within the crater, and the second series were ejecta samples recovered from the crater floor. The degree of shock damage in the carbonate material was assessed by comparing the sample spectra to spectra of Solenhofen limestone, which had been shocked to known pressures.

The results of the OAK borehole analysis have identified a thin zone of highly shocked carbonate material underneath the crater floor. This zone has a maximum depth of approximately 200 ft below sea floor at the ground zero borehole and decreases in depth towards the crater rim. A layer of highly shocked material is also found on the surface in the vicinity of the reference bolehole, located outside the crater. This material could represent a fallout layer. The ejecta samples have experienced a range of shock pressures.

It was also demonstrated that the EPR technique is feasible for the study of terrestrial impact craters formed in carbonate bedrock. The results for the Meteor Crater analysis suggest a slight degree of shock damage present in the β member of the Kaibab Formation exposed in the crater walls.

Evaluation of the Electric Vehicle Impact in the Power Demand Curve in a Smart Grid Environment

Smart grids with an intensive penetration of distributed energy resources will play an important role in future power system scenarios. The intermittent nature of renewable energy sources brings new challenges, requiring an efficient management of those sources. Additional storage resources can be beneficially used to address this problem; the massive use of electric vehicles, particularly of vehicle-to-grid (usually referred as gridable vehicles or V2G), becomes a very relevant issue. This paper addresses the impact of Electric Vehicles (EVs) in system operation costs and in power demand curve for a distribution network with large penetration of Distributed Generation (DG) units. An efficient management methodology for EVs charging and discharging is proposed, considering a multi-objective optimization problem. The main goals of the proposed methodology are: to minimize the system operation costs and to minimize the difference between the minimum and maximum system demand (leveling the power demand curve). The proposed methodology perform the day-ahead scheduling of distributed energy resources in a distribution network with high penetration of DG and a large number of electric vehicles. It is used a 32-bus distribution network in the case study section considering different scenarios of EVs penetration to analyze their impact in the network and in the other energy resources management.

The impact of a permanent Income shock on the situation of women in the household: the case of a pension reform in Argentina

Transfers to women may affect their bargaining power within the household and consequently their well-being. We analyze the effects of the 2004/2005 pension reform in Argentina, that resulted in an unexpected and substantial increase in permanent income for around 1.8 million women, on outcomes arguably related to women’s bargaining power within the household. We estimate the effects of the reform in the probability of divorce/separation, the distribution of household chores, and the probability of women being the head of the household, using a Difference-in-Differences approach. Our results show that despite the low divorce probability among seniors, transfers to senior women have substantial effects on their situation in the household. More specifically, we find that the reform had statistically significant effects on the probability of divorce/separation increasing it by 1.8 − 2.7 percentage points implying an increase of around 18 − 19% on the divorce/separation rate of 60 − 65 year old women. Moreover, the probability of being the head of the household also increased by 2.8−3.3 percentage points representing an increase of 7−19% in the probability amongst women of 60 − 65 years of age. In the case of married women, the probability of being the head of the household increased by 1.3 − 1.5 percentage points, which represents an increase of 20 − 22%. Results show that the distribution of household chores within the couples was also affected by the reform. More precisely, the probability that the wife is the only person in charge of the housework decreased by 5 percentage points, an 11% decrease. The participation of husbands in housework, however, did not change significantly.

Future shock or e-hype?: the impact of online shopping on UK retail property

This research examines the impact of ecommerce on sales and rental values and on the future space and ownership/leasing requirements of UK retailers for 2000-2005. The independent study, commissioned by BCSC (and funded by BCSC Educational Trust with support from the RICS Education Trust), included a major postal survey, follow-up interviews, a retail focus group, and shopper survey and case study of Cyberton, a town in the South East of England. The study was conducted by the Research Department of The College of Estate Management between June and December 2000.

Determination of the maximum force due to skull impact in fights between sheep of the Ovis aries species

The present article presents a means of determining the maximum impact force between two bodies from the determination of the involved impulse in the impact and the sound emitted by the shock of the bodies during this impact.It also presents a case study applied to the shock between the skulls of male sheep of the Ovis aries species. These animals do not possess horns and dispute the territorial leadership by fighting, during which the skull is used as a weapon of attack, similar to a battering ram.Initially, a revision of basic physics approaching the theory of impulse is made, which shows that the average force during an impact can be obtained by the quantity of movement of the bodies. In its turn, the quantity of movement is obtained through the average speed of approach and the mass of the bodies. The maximum force is obtained from the average force, using the approach of the Force X Time curve with the Sonorous Intensity X Time Curve.In order to study the case of a shock between two sheep, the mass of the bodies was obtained through direct weighing and the average speed of approach obtained indirectly through filming, thus making possible the calculation of the average force. The Sonorous Intensity X Time Curve was obtained through the recording of the sound of the impact during a filmed fight, with later manipulation through computer programs. With this data the maximum force exercised between the skull of the sheep during the impact was obtained, which will be used in later studies.

Blood concentration curve of cyclosporine: impact of itraconazole in lung transplant recipients

Although the influence of cytochrome P450 inhibitory drugs on the area under the curve (AUC) of cyclosporine (CsA) has been described, data concerning the impact of these substances on the shape of the blood concentration curve are scarce. By assessment of CsA blood levels before and 1, 2, and 4 hr after oral intake (C0, C1, C2, and C4, respectively) CsA profiling examinations were performed in 20 lung transplant recipients taking 400 mg, 200 mg, and no itraconazole, respectively. The three groups showed comparable results for C0, C2, and AUC(0-12). Greater values were found for Cmax, Cmax-C0, peak-trough fluctuation and rise to Cmax in favor of the non-itraconazole group. Additionally, tmax was shorter in the non-itraconazole group. Comedication with the metabolic inhibitor itraconazole is associated with a flattening of the CsA blood concentration profile in lung transplant recipients. These changes cannot be assessed by isolated C0, C2, or AUC(0-12) values alone.

Impact of epinephrine and norepinephrine on two dynamic indices in a porcine hemorrhagic shock model

Abstract BACKGROUND: Pulse pressure variations (PPVs) and stroke volume variations (SVVs) are dynamic indices for predicting fluid responsiveness in intensive care unit patients. These hemodynamic markers underscore Frank-Starling law by which volume expansion increases cardiac output (CO). The aim of the present study was to evaluate the impact of the administration of catecholamines on PPV, SVV, and inferior vena cava flow (IVCF). METHODS: In this prospective, physiologic, animal study, hemodynamic parameters were measured in deeply sedated and mechanically ventilated pigs. Systemic hemodynamic and pressure-volume loops obtained by inferior vena cava occlusion were recorded. Measurements were collected during two conditions, that is, normovolemia and hypovolemia, generated by blood removal to obtain a mean arterial pressure value lower than 60 mm Hg. At each condition, CO, IVCF, SVV, and PPV were assessed by catheters and flow meters. Data were compared between the conditions normovolemia and hypovolemia before and after intravenous administrations of norepinephrine and epinephrine using a nonparametric Wilcoxon test. RESULTS: Eight pigs were anesthetized, mechanically ventilated, and equipped. Both norepinephrine and epinephrine significantly increased IVCF and decreased PPV and SVV, regardless of volemic conditions (p < 0.05). However, epinephrine was also able to significantly increase CO regardless of volemic conditions. CONCLUSION: The present study demonstrates that intravenous administrations of norepinephrine and epinephrine increase IVCF, whatever the volemic conditions are. The concomitant decreases in PPV and SVV corroborate the fact that catecholamine administration recruits unstressed blood volume. In this regard, understanding a decrease in PPV and SVV values, after catecholamine administration, as an obvious indication of a restored volemia could be an outright misinterpretation.