A simple method to determine ductile fracture strain in a tensile test of plane specimen’s

The ultimate ductile fracture strain determination method for the specimen of circular cross-section has been presented by FEM method. The state of stress in individual locations of tensile tested specimen in successive process phases has been determined unequivocally with the stress triaxiality k. It has been demonstrated that the plane specimen’s fracture strain value in the fracture location varies and depends on the state of stress, which is present in the final specimen’s tension phase. The ductile fracture strain values in various fracture locations for steel, copper and aluminum specimen have been experimentally determined and compared. The simple and practical method to determine this strain has been proposed

Analytical approximations for the amplitude and period of a relaxation oscillator

<p>Abstract</p> <p>Background</p> <p>Analysis and design of complex systems benefit from mathematically tractable models, which are often derived by approximating a nonlinear system with an effective equivalent linear system. Biological oscillators with coupled positive and negative feedback loops, termed hysteresis or relaxation oscillators, are an important class of nonlinear systems and have been the subject of comprehensive computational studies. Analytical approximations have identified criteria for sustained oscillations, but have not linked the observed period and phase to compact formulas involving underlying molecular parameters.</p> <p>Results</p> <p>We present, to our knowledge, the first analytical expressions for the period and amplitude of a classic model for the animal circadian clock oscillator. These compact expressions are in good agreement with numerical solutions of corresponding continuous ODEs and for stochastic simulations executed at literature parameter values. The formulas are shown to be useful by permitting quick comparisons relative to a negative-feedback represillator oscillator for noise (10× less sensitive to protein decay rates), efficiency (2× more efficient), and dynamic range (30 to 60 decibel increase). The dynamic range is enhanced at its lower end by a new concentration scale defined by the crossing point of the activator and repressor, rather than from a steady-state expression level.</p> <p>Conclusion</p> <p>Analytical expressions for oscillator dynamics provide a physical understanding for the observations from numerical simulations and suggest additional properties not readily apparent or as yet unexplored. The methods described here may be applied to other nonlinear oscillator designs and biological circuits.</p

Jednostavna metoda odredjivanja plastičnoga prijeloma i čvrstoće plošnih uzoraka

The ultimate ductile fracture strain determination method for the specimen of circular cross-section has been presented by FEM method. The state of stress in individual locations of tensile tested specimen in successive process phases has been determined unequivocally with the stress triaxiality k. It has been demonstrated that the plane specimen’s fracture strain value in the fracture location varies and depends on the state of stress, which is present in the final specimen’s tension phase. The ductile fracture strain values in various fracture locations for steel, copper and aluminum specimen have been experimentally determined and compared. The simple and practical method to determine this strain has been proposed.U članku je data metoda proračuna određivanja plastičnoga loma uzoraka s okruglim prijesekom sa MKE metodom. Stanje naprezanja u pojedinačnim mjestima vlačnog pokusnog uzorka u pojedinim fazama procesa su bile određene koeficientom troosnog naprezanja k. Dokazano je, vrijednosti naprezanja pri lomu plošnih uzoraka u oblasti prijeloma se mjenjaju u ovisnosti od stanja naprezanja koje je pokazano u završnoj fazi vučenog uzorka. Vrijednosti deformacije pri plastičnom razaranju u raznim mjestima prijeloma za čelik, bakar i aluminij su bile eksperimentalne proračunate i uspoređene. Određena je jednostavna i praktička metoda pri proračunu tih deformacija

EMC studies on systems with hybrid filter circuits for modern aircraft applications

In this contribution, a new approach for EMC-filter design is presented. Due to the increasing electrification of modern aircraft, as a result of the More Electric Aircraft concept, new strategies and approaches are required to fulfill the strict EMC aircraft standards (DO-160/ED-14 – Sec. 20). Consequently the weight and volume of the used filter components can be reduced. A promising approach could be a combination of passive and active filters. For the same attenuation effect, so-called hybrid filters achieve either savings in weight and volume, or can obtain an additional filtering effect with minimal weight increase of an existing system. In this paper, the underlying theory is explained in detail, carried out in a simulation tool and the gained insight is demonstrated with a sample measurement

Component procurement strategies in decentralized assembly systems under supply uncertainty

Copyright © 2015 “IIE” In this article we analyze the interactions among the assembler and two component suppliers in their procurement decisions under a Vendor-Managed Inventory (VMI) contract. Under the VMI contract, the assembler first offers a unit price for each component and will pay component suppliers only for the amounts used to meet the actual demand. The two independent component suppliers then decide on the production quantities of their individual components before the actual demand is realized. We assume that one of the component suppliers has uncertainty in the supply process, in which the actual number of components available for assembly is equal to a random fraction of the production quantity. Under the assembly structure, both component suppliers need to take into account the underlying supply uncertainty in deciding their individual production quantities, as both components are required for the assembly of the final product. We first analyze the special case under deterministic demand and then extend our analysis to the general case under stochastic demand. We derive the optimal component prices offered by the assembler and the corresponding equilibrium production quantities of the component suppliers

Coordinating supply and demand on an on-demand service platform with impatient customers

We consider an on-demand service platform using earning-sensitive independent providers with heterogeneous reservation price (for work participation) to serve its time and price-sensitive customers with heterogeneous valuation of the service. As such, the supply and demand are “endogenously” dependent on the price the platform charges its customers and the wage the platform pays its independent providers. We present an analytical model with endogenous supply (number of participating agents) and endogenous demand (customer request rate) to study this on-demand service platform. To coordinate endogenous demand with endogenous supply, we include the steady-state waiting time performance based on a queueing model in the customer utility function to characterize the optimal price and wage rates that maximize the profit of the platform. We first analyze a base model that uses a fixed payout ratio (i.e., the ratio of wage over price), and then extend our model to allow the platform to adopt a time-based payout ratio. We find that it is optimal for the platform to charge a higher price when demand increases; however, the optimal price is not necessarily monotonic when the provider capacity or the waiting cost increases. Furthermore, the platform should offer a higher payout ratio as demand increases, capacity decreases or customers become more sensitive to waiting time. We also find that the platform should lower its payout ratio as it grows with the number of providers and customer demand increasing at about the same rate. We use a set of actual data from a large on-demand ride-hailing platform to calibrate our model parameters in numerical experiments to illustrate some of our main insights

Different paths to the modern state in Europe: the interaction between domestic political economy and interstate competition

Theoretical work on state formation and capacity has focused mostly on early modern Europe and on the experience of western European states during this period. While a number of European states monopolized domestic tax collection and achieved gains in state capacity during the early modern era, for others revenues stagnated or even declined, and these variations motivated alternative hypotheses for determinants of fiscal and state capacity. In this study we test the basic hypotheses in the existing literature making use of the large date set we have compiled for all of the leading states across the continent. We find strong empirical support for two prevailing threads in the literature, arguing respectively that interstate wars and changes in economic structure towards an urbanized economy had positive fiscal impact. Regarding the main point of contention in the theoretical literature, whether it was representative or authoritarian political regimes that facilitated the gains in fiscal capacity, we do not find conclusive evidence that one performed better than the other. Instead, the empirical evidence we have gathered lends supports to the hypothesis that when under pressure of war, the fiscal performance of representative regimes was better in the more urbanized-commercial economies and the fiscal performance of authoritarian regimes was better in rural-agrarian economie

High Acute Myeloid Leukemia derived VEGFA levels are associated with a specific vascular morphology in the leukemic bone marrow

Acute Myeloid Leukemia (AML) bone marrow biopsies at diagnosis display enhanced angiogenesis and increased VEGFA expression. In a xenograft mouse model it was described that availability of free VEGFA versus bound VEGFA is related to different vascular morphology. In this study we investigate the relationship between vascular morphology within AML bone marrow biopsies and AML derived VEGFA levels. Vessel count and surface area (Chalkley count) were calculated in AML bone marrow biopsies at diagnosis (n = 32), at remission (n = 8) and Normal Bone Marrow (n = 32) using immunohistochemical staining for FVIII, CD31, CTIV, SMA and VEGFA. VEGFA protein levels were measured. High vessel count was associated with an immature vessel status. Combining vessel count and Chalkley count different vessel morphology patterns were quantified within AML bone marrow biopsies. Three different subgroups could be distinguished. The subgroup (37.5% of the samples) exhibiting a high vessel count and vessels with predominantly large lumen (normal Chalkley count) was associated with high secreted VEGFA protein levels. Different vasculature patterns are seen in AML bone marrow biopsies, defined by combining number and size of vessel. These quantified morphology patterns, combined with VEGFA levels, might be of value in the success of VEGF/VEGFR-signaling interference approaches

Chicken cGAS Senses Fowlpox Virus Infection and Regulates Macrophage Effector Functions

The anti-viral immune response is dependent on the ability of infected cells to sense foreign nucleic acids. In multiple species, the pattern recognition receptor (PRR) cyclic GMP-AMP synthase (cGAS) senses viral DNA as an essential component of the innate response. cGAS initiates a range of signaling outputs that are dependent on generation of the second messenger cGAMP that binds to the adaptor protein stimulator of interferon genes (STING). Here we show that in chicken macrophages, the cGAS/STING pathway is essential not only for the production of type-I interferons in response to intracellular DNA stimulation, but also for regulation of macrophage effector functions including the expression of MHC-II and co-stimulatory molecules. In the context of fowlpox, an avian DNA virus infection, the cGAS/STING pathway was found to be responsible for type-I interferon production and MHC-II transcription. The sensing of fowlpox virus DNA is therefore essential for mounting an anti-viral response in chicken cells and for regulation of a specific set of macrophage effector functions