QuickPool: Privacy-Preserving Ride-Sharing Service

Online ride-sharing services (RSS) have become very popular owing to increased awareness of environmental concerns and as a response to increased traffic congestion. To request a ride, users submit their locations and route information for ride matching to a service provider (SP), leading to possible privacy concerns caused by leakage of users\u27 location data. We propose QuickPool, an efficient SP-aided RSS solution that can obliviously match multiple riders and drivers simultaneously, without involving any other auxiliary server. End-users, namely, riders and drivers share their route information with SP as encryptions of the ordered set of points-of-interest (PoI) of their route from their start to end locations. SP performs a zone based oblivious matching of drivers and riders, based on partial route overlap as well as proximity of start and end points. QuickPool is in the semi-honest setting, and makes use of secure multi-party computation. We provide security proof of our protocol, perform extensive testing of our implementation and show that our protocol simultaneously matches multiple drivers and riders very efficiently. We compare the performance of QuickPool with state-of-the-art works and observe a run time improvement of 1.6 - 2$\times$, and communication improvement of at least 8$\times$

Sol-gel preparation of silica glass

This paper is a preliminary report on the preparation of silica glass containing very low amount of hydroxyl by the sol-gel processing technique. Gels were prepared from optimized amounts of tetraethyl orthosilicate, fumed silica and water. Acids and bases in small quantities were added for catalysing hydrolysis and adjusting the pH. Dried gels were heated up to 1400-degrees-C in various atmospheres to obtain transparent silica glass of the required density and very low (< 5 ppm) hydroxyl content

Exchange bias effect in alloys and compounds

The phenomenology of exchange bias effects observed in structurally single-phase alloys and compounds but composed of a variety of coexisting magnetic phases such as ferromagnetic, antiferromagnetic, ferrimagnetic, spin-glass, cluster-glass and disordered magnetic states are reviewed. The investigations on exchange bias effects are discussed in diverse types of alloys and compounds where qualitative and quantitative aspects of magnetism are focused based on macroscopic experimental tools such as magnetization and magnetoresistance measurements. Here, we focus on improvement of fundamental issues of the exchange bias effects rather than on their technological importance

A copper-benzotriazole based coordination polymer catalyzes the efficient one-pot synthesis of (N'-substituted)-hydrazo-4-aryl-1,4-dihydropyridines from azines

A series of new (N’-substituted)-hydrazo-4-aryl-1,4 dihydropyridines were successfully synthesized via a facile one pot catalytic pathway utilizing azines and propiolate esters as starting materials and 1D Cu benzotriazoles based coordination polymer as catalyst. In the absence of catalyst, the corresponding 5-substituted 4,5-dihydro pyrazoles were formed in moderate to high yields. Fine-tuning the catalysts allowed us to gain more insights regarding the plausible reaction mechanism

Assessment of biomass energy potential for SRC willow woodchips in a pilot scale bubbling fluidized bed gasifier

The current study investigates the short rotation coppice (SRC) gasification in a bubbling fluidized bed gasifier (BFBG) with air as gasifying medium. The thermochemical processes during combustion were studied to get better control over the air gasification and to improve its effectiveness. The combustion process of SRC was studied by different thermo-analytical techniques. The thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) were performed to examine the thermal degradation and heat flow rates. The product gas composition (CO, CO2, CH4 and H2) produced during gasification was analyzed systematically by using an online gas analyzer and an offline GC analyzer. The influence of different equivalence ratios on product gas composition and temperature profile was investigated during SRC gasification. TG/DTG results showed degradation occur in four stages; drying, devolatilization, char combustion and ash formation. Maximum mass loss ~70% was observed in devolatilization stage and two sharp peaks at 315–500 °C in TG/DSC curves indicate the exothermic reactions. The temperature of gasifier was increased in the range of 650–850 °C along with the height of the reactor with increasing equivalent ratio (ER) from 0.25 to 0.32. The experimental results showed that with an increment in ER from 0.25 to 0.32, the average gas composition of H2, CO, CH4 decreased in the range of 9–6%, 16–12%, 4–3% and CO2 concentration increased from 17 to 19% respectively. The gasifier performance parameters showed a maximum high heating value (HHV) of 4.70 MJ/m3, Low heating value (LHV) of 4.37 MJ/m3 and cold gas efficiency (CGE) of 49.63% at 0.25 ER. The ER displayed direct effect on carbon conversion efficiency (CCE) of 95.76% at 0.32 ER and tar yield reduced from 16.78 to 7.24 g/m3 with increasing ER from 0.25 to 0.32. All parametric results confirmed the reliability of the gasification process and showed a positive impact of ER on CCE and tar yield

High-temperature abrasive wear characteristics of H13 steel modified by laser remelting and cladded with Stellite 6 and Stellite 6/30% WC

The study is aimed to analyse the comparative behaviour of the high-temperature abrasive wear of H13 steel surfaces modified by laser melting and cladding with Stellite 6 and Stellite 6 + 30 wt% WC. 3-body abrasive tests were conducted at room temperature, 450 °C, 550 °C, and 650 °C. The microstructural evolution, microhardness, wear surface morphology and mechanisms, and various phases formed during laser surface modifications were also studied. The laser remelting of H13 steel surface increased its room temperature microhardness to 750 ± 35 HV0.01, whereas laser cladding of Stellite 6 powder yielded hardness of around 600 ± 20 HV0.01 in the clad layer; and Stellite 6/WC composite clad layer had marginally higher hardness than the Stellite 6 clad layer in the matrix and much higher hardness of ~3000 HV0.01 at the sporadically distributed WC particle sites. Though the room temperature microhardness of laser remelted H13 surface is the highest, the volumetric wear loss in it was comparable to that of the Stellite 6 cladding. However, Stellite 6/WC composite layer recorded a relatively less volumetric loss as WC particles resisted the abrasive wear. With increasing temperature, the wear loss in laser remelt surfaces increased at a fast rate, while that in Stellite 6 and composite clad layers varied marginally with no definite trend. Overall, Stellite 6/WC composite cladding performed better than others in the current temperature range. © 2021 Elsevier B.V

Effect of scan strategy and heat input on the shear strength of laser cladded Stellite 21 layers on AISI H13 tool steel in as-deposited and heat treated conditions

Coating of hard-facing, wear and corrosion resistant materials on working surfaces of engineering parts made of relatively lower grade materials plays an important role in their service life as this is dictated by the coating material rather than the substrate material. However, the quality of coating in terms of pores- and crack- free deposition, low dilution and good bond strength is vital for the working life of coatings. In this work, bond strength of laser cladded Stellite 21 layers deposited on AISI H13 tool steel with different scanning strategies and line energy is investigated by subjecting the clad-substrate interface to shear force. As Stellite 21 is deposited to improve surface property of high-temperature dies and also for refurbishing worn out dies, bond strength of cladded specimens subjected to a high thermal cycle was also measured. Three sets of shear test specimens of rectangular clad build-up were made with different deposition strategies. First two sets have same laser line energy, but interfacial layers have overlapped clad tracks deposited in two orthogonal directions to study the effect of track orientation on the bond strength. In the third set line energy was doubled by reducing the scan speed. Bond strength was more for shear force applied along the direction of clad tracks. Higher interfacial bond strength of clad tracks parallel to shear stress direction compared to transverse tracks could be resulting by the similar effect that the orientation of fibers in a composite have on its strength. Deposition with higher line energy also had higher bond strength because of more uniform overlapped clad interface. However, specimens subjected to heating up to 1000 °C followed by furnace cooling had much reduced bond strength due to grain coarsening. Results are supported by the micro-structure, micro-hardness, dilution and elemental analyses of cladding and fractured surfaces

Performance of additive manufactured Stellite 6 tools in friction stir processing of CuCrZr sheet

In the recent time friction stir welding (FSW), a solid state welding process has rapidly gained attention for joining high melting point materials like Cu, Fe, Ti and their alloys apart from Al alloys due to its several advantages over fusion welding techniques. AISI H13, a versatile chromium–molybdenum hot work hardened steel, has been the most commonly used as a tool material for aluminium alloys. However, low tool life due to plastic deformation and wear at elevated temperatures is limiting its application in welding of high melting point materials. In the present work the performances of as-received, heat treated, laser remelted and Stellite 6 hardfaced H13 steel tools in friction stir processing (FSP) of CuCrZr have been investigated. Stellite 6 hardfaced FSW tools are developed by additive manufacturing (AM) process on H13 steel as a base material. In all these cases except the Stellite 6 hardfaced tool, the shoulder and pin are found to deform plastically with significant wear of shoulder along with the diffusion of CuCrZr into tool from tool pin-shoulder interface. However, tools developed by AM process are found to remain intact without any significant deformation or wear

Asterisk\textsf{Asterisk}: Super-fast MPC with a Friend

Secure multiparty computation (MPC) enables privacy-preserving collaborative computation over sensitive data held by multiple mutually distrusting parties. Unfortunately, in the most natural setting where a majority of the parties are maliciously corrupt (also called the $\textit{dishonest majority}$ setting), traditional MPC protocols incur high overheads and offer weaker security guarantees than are desirable for practical applications. In this paper, we explore the possibility of circumventing these drawbacks and achieving practically efficient dishonest majority MPC protocols with strong security guarantees by assuming an additional semi-honest, non-colluding helper party $\mathrm{HP}$. We believe that this is a more realistic alternative to assuming an honest majority, since many real-world applications of MPC involving potentially large numbers of parties (such as dark pools) are typically enabled by a central governing entity that can be modeled as the $\mathrm{HP}$. In the above model, we are the first to design, implement and benchmark a practically-efficient and general multi-party framework, $\textsf{Asterisk}$. Our framework requires invoking $\mathrm{HP}$ only a constant number of times, achieves the strong security guarantee of $\textit{fairness}$ (either all parties learn the output or none do), scales to hundreds of parties, outperforms all existing dishonest majority MPC protocols, and is, in fact, competitive with state-of-the-art honest majority MPC protocols. Our experiments show that $\textsf{Asterisk}$ achieves $288-228\times$ speedup in preprocessing as compared to the best dishonest majority MPC protocol. With respect to online time, $\textsf{Asterisk}$ supports $100$-party evaluation of a circuit with $10^6$ multiplication gates in approximately $20$ seconds. We also implement and benchmark practically efficient and highly scalable instance of dark pools using $\textsf{Asterisk}$. The run times showcase the effectiveness of $\textsf{Asterisk}$ in enabling efficient realizations of real-world privacy-preserving applications with strong security guarantees