User location privacy protection mechanism for location-based services

With the rapid development of the Internet of Things(IoT),Location-Based Services(LBS)are becoming more and more popular.However,for the users being served,how to protect their location privacy has become a growing concern.This has led to great difficulty in establishing trust between the users and the service providers,hindering the development of LBS for more comprehensive functions.In this paper,we first establish a strong identity verification mechanism to ensure the authentication security of the system and then design a new location privacy protection mechanism based on the privacy proximity test problem.This mechanism not only guarantees the confidentiality of the user s information during the subsequent information interaction and dynamic data transmission,but also meets the service provider's requirements for related data.

Silicon photonic integrated interrogator for fiber-optic distributed acoustic sensing

Distributed acoustic sensing(DAS)technology has been a promising tool in various applications.Currently,the large size and relatively high cost of DAS equipment composed of discrete devices restrict its further popularization to some degree,and the photonic integration technology offers a potential solution.In this paper,we demonstrate an integrated interrogator for DAS on the silicon-on-insulator(SOI)platform.The design of the chip revolves around a Mach–Zehnder modulator(MZM)transmitter and a dual-quadrature and dualpolarization coherent receiver.The integrated interrogator supports multiple DAS schemes,including the time-gated digital optical frequency domain reflectometry(TGD-OFDR),which is adopted for system performance evaluation.59■strain resolution in 12.1km sensing fiber with 1.14 m spatial resolution(SR)is realized.Besides,along 49.0 km sensing fiber,81■strain resolution with 3.78 m SR is achieved.The results show that the integrated interrogator has comparable performance to the discrete DAS system.To the best of our knowledge,this is the first dedicated on-chip DAS interrogator,which validates the effectiveness of the blend of photonics integration and DAS technology.

Flexible ternary carbon black/Bi_(2)Te_(3) based alloy/polylactic acid thermoelectric composites fabricated by additive manufacturing

Flexible ternary carbon black/Bi_(2)Te_(3) based alloy/polylactic acid(CB/BTBA/PLA)composites were fabricated by additive manufacturing and their thermoelectric properties were investigated from 300 K to 360 K.At 300 K,as the mass ratios of BTBAs in the composites increased from 38.5% to 71.4%,both the electrical conductivity and Seebeck coefficient of the composites increased from 5.8 S/cm to 13.3 S/cm,and from 60.2 mV/K to 119.9 mV/K,respectively,and the thermal conductivity slightly increased from 0.15 W m^(-1)K^(-1) to 0.25 W m^(-1)K^(-1),as a result,the ZT value of the composites increased from 0.004 to 0.023.As the temperature increased from 300 K to 360 K,the electrical conductivity of all the composites slightly decreased,while the thermal conductivity slowly increased,and a highest ZT value of 0.024 was achieved for the composites with 71.4% BTBAs at 320 K.Unlike traditional sterolithography,fused deposition modeling,selective laser melting,etc.,this additive manufacturing process can directly print the solutions which contain inorganic fillers and polymer matrixes into almost any designed intricate geometries of thermoelectric composites,therefore this process has great potential to be used for fabrication of flexible polymer based thermoelectric composites and devices.

A post-processing method for true random number generators based on hyperchaos with applications in audio-based generators

True random number generators(TRNG)are important counterparts to pseudorandom number generators(PRNG).especially for high security applications such as cryptography.They produce unpredictable,non-repeatablerandom sequences.However,most TRNGs require specialized hardware to extract entropy from physical phenomena and tend to be slower than PRNGs.These generators usually require post-processing algorithms to eliminate biases but in tun.reduces performance.In this paper.a newpost-processing method based on hyperchaos is proposed forsoftware-based TRNGs which not only eliminates statisticalbiases but also provides amplification in order to improve the performance of TRNGs.The proposed method utilizes the inherent characteristics of chaos such as hypersensitivity to input shanugeri,diffusisn,and csnfusion sapabilities to ushievethese goals.Quantized bits of a physical entropy source areused to perturb the parameters of a hyperchaotic map,which is then iterated to produce a set of random output bits.To de-pict the feasibility of the proposed post-processing algorithm.it is applied in designing TRNGs based on digital audio.Thegenerators are analyzed to identify statistical defects in addition to forward and backward security.Results indicate that the proposed generators are able to produce secure true random sequences at a high throughput,which in turn reflects on the effectiveness of the proposed post-processing method.