Why Bitcoin Will Fail to Scale?

Bitcoin falls dramatically short of the scale provided by banks for payments. Currently, its ledger grows by the addition of blocks of ∼2,000 transactions every 10 minutes. Intuitively, one would expect that increasing the block capacity would solve this scaling problem. However, we show that increasing the block capacity would be futile. We analyze strategic interactions of miners, who are heterogeneous in their power over block addition, and users, who are heterogeneous in the value of their transactions, using a game-theoretic model. We show that a capacity increase can facilitate large miners to tacitly collude—artificially reversing back the capacity via strategically adding partially filled blocks in order to extract economic rents. This strategic partial filling crowds out low-value payments. Collusion is sustained if the smallest colluding miner has a share of block addition power above a lower bound. We provide empirical evidence of such strategic partial filling of blocks by large miners of Bitcoin. We show that a protocol design intervention can breach the lower bound and eliminate collusion. However, this also makes the system less secure. On the one hand, collusion crowds out low-value payments; on the other hand, if collusion is suppressed, security threatens high-value payments. As a result, it is untenable to include a range of payments with vastly different outside options, willingness to bear security risk, and delay onto a single chain. Thus, we show economic limits to the scalability of Bitcoin. Under these economic limits, collusive rent extraction acts as an effective mechanism to invest in platform security and build responsiveness to demand shocks. These traits are otherwise hard to attain in a disintermediated setting owing to the high cost of consensus. This paper was accepted by Kartik Hosanagar, information systems.

Effects of Grain Morphology on Flow Behavior of Semi-Solid Slurries

The flow behavior of semi-solid slurry determines the quality of the castings produced by the semi-solid forming process. Many studies have done to investigate the flow behavior of slurry under different conditions, and results show that the rheological behavior of slurry with dendritic structure is inappropriate for semi-solid forming. In this study, slurries with varying morphologies of grain for the same alloy with the same fraction solid have tested using a partial filling method. The SEED process was employed, and the pouring temperature adjusted to prepare semi-solid slurries with different grain morphologies. The flow pattern, entrapped air during the filling process, and also microstructure of the samples were examined to characterize the macro and micro flow behavior. The results show that a turbulent macro-flow, leading to entrapped air, and severe segregation appeared in the sample using slurry of Tpour ≥ 660 °C . For the slurry of Tpour < 660 °C, none of the three phenomena found in the sample. This investigation further showed that the detriment of dendrite on the semi-solid forming process, and implied that large size dendrite in semi-solid slurry must avoided.

Mathematical modeling of monochromatic acoustic wave diffraction on a system of bodies and on flat screens

Some problems of diffraction of a monochromatic acoustic wave on surfaces of complex shapes are considered. To solve such problems, an approach is applied, in which the problem is reduced to a boundary hypersingular integral equation, where the integral is understood in the sense of a finite value according to Hadamard. Such approach allows solving diffraction problems both on solid objects and on thin screens. To solve the integral equation, the method of piecewise constant approximations and collocations, developed in the previous works of the author, is used. In the present study, examples of modeling the diffraction of an acoustic wave by bodies with partial filling are given. It is shown how the filling of bodies influences the acoustic pressure field, and the field direction patterns are given. An example of applying this approach to solving the problem of sound propagation in an urban area is also given: the diffraction of an acoustic wave from a point source on a system of buildings is considered. The presented results demonstrate that this method allows constructing reflected fields and analyze their characteristics on surfaces of complex shapes.

Effect of PCM fill ratio and heat sink orientation on the thermal management of transient power spikes in electronics

The goal of this paper is to investigate the usefulness of Phase Change Material based heat sinks in power surge operations. Experiments have been carried out on a PCM based heat sink for different fill ratios (0, 33, 66, and 99%) of the PCM and different orientations (0, 90, 180°) of the heat sink under constant and power surge heat loads. The heat sink with a fill ratio of 0% is considered as the baseline case for comparison. The heat sink with a fill ratio of 66% at 0° orientation recorded lower temperatures among all the fill ratios and orientations under both constant and power surge heat loads. Partial filling (66% fill ratio) of the PCM in the cavity is more effective than complete filling (99% fill ratio) in handling both constant and power surge heat loads.

Bile Salts in Chiral Micellar Electrokinetic Chromatography: 2000–2020

Bile salts are naturally occurring chiral surfactants that are able to solubilize hydrophobic compounds. Because of this ability, bile salts were exploited as chiral selectors added to the background solution (BGS) in the chiral micellar electrokinetic chromatography (MEKC) of various small molecules. In this review, we aimed to examine the developments in research on chiral MEKC using bile salts as chiral selectors over the past 20 years. The review begins with a discussion of the aggregation of bile salts in chiral recognition and separation, followed by the use of single bile salts and bile salts with other chiral selectors (i.e., cyclodextrins, proteins and single-stranded DNA aptamers). Advanced techniques such as partial-filling MEKC, stacking and single-drop microextraction were considered. Potential applications to real samples, including enantiomeric impurity analysis, were also discussed.

SIMULATION OF MICROBIOLOGICAL DESTRUCTION PROCESS OF OIL POLLUTION IN SHALLOW WATER

The paper covers the research of microbiological destruction processes of petroleum origin pollutants in a shallow water taking into account a number of determining factors that affect the distribution of pollution in the researched water area: the oil fractional composition, the processes of evaporation, dissolution, biological oxidation of petro-hydrocarbons by microorganisms, as well as hydrodynamic and chemical-biological features of the water. A complex of interrelated spatially inhomogeneous mathematical models was proposed that allow researching the dynamics of microbiological destruction processes of petroleum hydrocarbons in shallow water. Schemes with weight taking into account the partial filling of computational cells of the simulated domain were developed at model discretization that made it possible to significantly increase the accuracy of calculations and reduce the calculation time. Based on a multiprocessor computer system, experimental software has been developed for predictive modeling of the ecological situation of shallow water in the event of accidental pollution by oil and other harmful substances during natural and technogenic challenges.

Sloshing Effects on FLNG and LNGC Side-by-Side Offloading

A side-by-side moored offloading configuration has relatively stronger hydrodynamic and mechanical interactions compared to a tandem moored offloading configuration. For instance, due to the narrow gap between FLNG and LNG Carrier, the trapped water resonance induces higher relative motions between the FLNG and LNG Carrier. In addition, due to the partial filling conditions during the offloading operations, the sloshing loads excite ship motions which induce higher loading on the offloading arms. In this research, a time domain sloshing-ship motion coupling analysis module has been developed for analyzing interactions of the side-by-side moored multiple floating platforms. This paper presents the numerical modeling, the validation analysis results, and the sloshing-ship motion coupled effects on the side-by-side offloading analysis.