A Security Trade-Off Scheme of Anomaly Detection System in IoT to Defend against Data-Tampering Attacks

Internet of Things(IoT)is vulnerable to data-tampering(DT)attacks.Due to resource limitations,many anomaly detection systems(ADSs)for IoT have high false positive rates when detecting DT attacks.This leads to the misreporting of normal data,which will impact the normal operation of IoT.To mitigate the impact caused by the high false positive rate of ADS,this paper proposes an ADS management scheme for clustered IoT.First,we model the data transmission and anomaly detection in clustered IoT.Then,the operation strategy of the clustered IoT is formulated as the running probabilities of all ADSs deployed on every IoT device.In the presence of a high false positive rate in ADSs,to deal with the trade-off between the security and availability of data,we develop a linear programming model referred to as a security trade-off(ST)model.Next,we develop an analysis framework for the ST model,and solve the ST model on an IoT simulation platform.Last,we reveal the effect of some factors on the maximum combined detection rate through theoretical analysis.Simulations show that the ADS management scheme can mitigate the data unavailability loss caused by the high false positive rates in ADS.

Compression Behaviors of Parallel Bamboo Strand Lumber Under Static Loading

In order to investigate the influence of length and compression directions upon behaviour of parallel bamboo strand lumber(PBSL)specimens,240 axial compression tests have been performed.With three similar one different typical failure modes,the mechanical performance for PBSL specimens under compression parallel to grain and perpendicular to grain are different as a whole.From the point of the characteristic values,the compression strength parallel to grain is 2.1 times of the compression strength perpendicular to grain.The elastic modulus for compression parallel to grain is 3.64 times of the compression strength perpendicular to grain.While the compression ratios along two compression directions are equal to each other.The bigger Poisson ratios for one typical side surface is 3.93 times of that for another typical side surface for PBSL specimens under compression perpendicular to grain,and the bigger value is equal to that for PBSL specimens under compression parallel to grain.Length can influence the mechanical properties of the PBSL specimens.The size 50 mm×50 mm×100 mm should be good choice for the standard or code to measure the compression strength.PBSL materials have better ductility under compression parallel to grain than that under compression perpendicular to grain.Stress-strain relationship models were proposed for PBSL specimens under compression parallel to grain and perpendicular to grain,respectively.These proposed models gave a good agreement with the test results.

Mechanical Properties and Stress Strain Relationship Models for Bamboo Scrimber

In order to investigate the basic mechanical properties and stress strain relationship model for bamboo scrimber manufactured based on a new technique,a large quantities of experiments have been carried out.Based on the analysis of the test results,the following conclusions can be drawn.Two main typical failure modes were classified for bamboo scrimber specimens both under tension parallel to grain and tension perpendicular to grain.Brittle failure happened for all tensile tests.The slope values for the elastic stages have bigger discreteness compared with those for the specimens under tensile parallel to grain.The failure modes for bamboo scrimber specimens under compression parallel to grain could be divided into four.Only one main failure mode happened both for the bending specimens and the shear specimens.With the COV values of 28.64 and 25.72 respectively,the values for the strength and elastic modulus under tensile perpendicular to grain have the largest discreteness for bamboo scrimber.From the point of CHV values,the relationship among the mechanical parameters for bamboo scrimber were proposed based on the test results.Compared with other green building materials,bamboo scrimber manufactured based on a new technique has better mechanical performance and could be used in construction area.Three stress strain relationship models which are four-linear model,quadratic function model,and cubic function model were proposed for bamboo scrimber specimens manufactured based on a new technique.The latter two models gives better prediction for stress strain relationship in elastic plastic stage.

Upgrading CO_(2) into acetate on Bi_(2)O_(3)@carbon felt integrated electrode via coupling electrocatalysis with microbial synthesis

Upgrading of atmospheric CO_(2) into high-value-added acetate using renewable electricity via electrocatalysis solely remains a great challenge.Here,inspired by microbial synthesis via biocatalysts,we present a coupled system to produce acetate from CO_(2) by bridging inorganic electrocatalysis with microbial synthesis through formate intermediates.A 3D Bi_(2)O_(3)@CF integrated electrode with an ice-sugar gourd shape was fabricated via a straightforward hydrothermal synthesis strategy,wherein Bi_(2)O_(3) microspheres were decorated on carbon fibers.This ice-sugar gourd-shaped architecture endows electrodes with multiple structural advantages,including synergistic contribution,high mass transport capability,high structural stability,and large surface area.Consequently,the resultant Bi_(2)O_(3)@CF exhibited a maximum Faradic efficiency of 92.4%at−1.23 V versus Ag/AgCl for formate generation in 0.5 M KHCO_(3),exceeding that of Bi_(2)O_(3)/CF prepared using a conventional electrode preparation strategy.Benefiting from the high formate selectivity,unique architecture,and good biocompatibility,the Bi_(2)O_(3)@CF electrode attached with enriched CO_(2)-fixing electroautotrophs served as a biocathode.As a result,a considerable acetate yield rate of 0.269±0.009 g L^(−1) day^(−1)(a total acetate yield of 3.77±0.12 g L^(−1) during 14-day operation)was achieved in the electrochemical–microbial system equipped with Bi_(2)O_(3)@CF.