Research on the Key Techniques of TCP Protocol Normalization for Mimic Defense Architecture

The Mimic Defense(MD)is an endogenous security technology with the core technique of Dynamic Heterogeneous Redundancy(DHR)architecture.It can effectively resist unknown vulnerabilities,backdoors,and other security threats by schedule strategy,negative feedback control,and other mechanisms.To solve the problem that Cyber Mimic Defense devices difficulty of supporting the TCP protocol.This paper proposes a TCP protocol normalization scheme for DHR architecture.Theoretical analysis and experimental results show that this scheme can realize the support of DHR-based network devices to TCP protocol without affecting the security of mimicry defense architecture.

Particle convective heat transfer near the wall in a supercritical water fluidized bed by single particle model coupled with CFD-DEM

Supercritical water fluidized bed(SCWFB)is a promising reactor to gasify biomass or coal.Its optimization design is closely related to wall-to-bed heat transfer,where particle convective heat transfer plays an important role.This paper evaluates the particle convective heat transfer coefficient(h_(pc))at the wall in SCWFB using the single particle model.The critical parameters in the single particle model which is difficult to get experimentally are obtained by the computational fluid dynamics-discrete element method(CFD-DEM).The contact statistics related to particle-to-wall heat transfer,such as contact number and contact distance,are also presented.The results show that particle residence time(τ),as the key parameter to evaluate h_(pc),is found to decrease with rising velocity,while increase with larger thermal boundary layer thickness.τfollows a gamma function initially adopted in the gas-solid fluidized bed,making it possible to evaluate h_(pc) in SCWFB by a simplified single particle model.The theoretical predicted h_(pc) tends to increase with rising thermal gradient thickness at a lower velocity(1.5 U_(mf)),while first decreases and then increases at higher velocity(1.75 and 2 U_(mf)).h_(pc) occupies 30%-57%of the overall wall-to-bed heat transfer coefficient for a particle diameter of 0.25 mm.The results are helpful to predict the overall wall-to-bed heat transfer coefficient in SCWFB combined with a reasonable fluid convective heat transfer model from a theoretical perspective.

Wall-to-bed heat transfer in supercritical water fluidized bed using CFD-DEM

Supercritical water fluidized bed(SCWFB)reactors are designed to gasify biomass or coal with high efficiency.In this paper,the wall-to-bed heat transfer characteristics in SCWFB are studied using the computational fluid dynamics and discrete element method(CFD-DEM)coupled with a constant heat flux boundary.Two different methods are considered to deal with the multiphase heat flux boundary in CFD-DEM because there is currently no single widely accepted approach.Zhang’s method predicts a more accurate wall-to-bed heat transfer coefficient in SCWFB than Lattanzi’s method according to comparisons of the simulation results with an empirical correlation.The influences of temperature,pressure,velocity,and the solid phase properties,such as the particle diameter,particle heat capacity,particle thermal conductivity,and particle density,on the SCWFB wall-to-bed heat transfer characteristics are studied based on Zhang’s method.The simulation results help reveal the SCWFB heat transfer characteristics.

Plasmonic semiconductor nanogroove array enhanced broad spectral band millimetre and terahertz wave detection

High-performance uncooled millimnetre and terahertz wave detectors are required as a building block for a wide range of applications.The state-of-the art technologies,however,are plagued by low sensitivity,narrow spectral bandwidth,and complicated architecture.Here,we report semiconductor surface plasmon enhanced high-performance broadband millimetre and terahertz wave detectors which are based on nanogroove InSb array epitaxially grown on GaAs substrate for room temperature operation.By making a nanogroove array in the grown InSb layer,strong millimetre and terahertz wave surface plasmon polaritons can be generated at the InSb-air interfaces,which results in significant improvement in detecting performance.A noise equivalent power(NEP)of 2.2× 10^(-14)WHz^(-1/2) or a detectivity(D)of 2.7× 10^(12)cmHz^(1/2) W^(-1) at 1.75 mm(0.171 THz)is achieved at room temperature.By lowering the temperature to the thermoelectric cooling available 200 K,the corresponding NEP and D'of the nanogroove device can be improved to 3.8× 10^(-15)WHz^(-1/2) and 1.6× 10^(13) cm Hz^(-1/2) w^(-1),respectively.In addition,such a single device can perform broad spectral band detection from 0.9 mm(0.330 THz)to 9.4 mm(0.032 THz).Fast responses of 3.5μs and 780 ns are achieved at room temperature and 200 K,respectively.Such high-performance millimnetre and terahertz wave photodetectors are useful for wide applications such as high capacity communications,walk-through security,biological diagnosis,spectroscopy,and remote sensing.In addition,the integration of plasmonic semiconductor nanostructures paves a way for realizing high performance and multifunctional long-wavelength optoelectrical devices.

Vertically coupled ZnO nanorods on MoS2 monolayers with enhanced Raman and photoluminescence emission

Hybrid structures composed of layered materials have received much attention due to their exceptional tunable optical, electronic and catalytic properties. Here, we describe a hydrothermal strategy for coupling vertical ZnO nanorods on MoS2 monolayers without a catalyst. These vapor-solid-grown MoS2 monolayers aid in growing vertical ZnO nanorods via epitaxy. Enhanced Raman and photoluminescence emissions were observed from the MoS2 monolayers under the ZnO nanorods in these coupled structures, which was attributed to the light antenna effect of the ZnO nanorods. These hybrid and incorporation protocols for layered materials will provide new perspectives and opportunities for promoting the construction of heterojunctions with adjustable layered structures leading to fascinating fundamental phenomena and advanced devices.

SeBROP:blind ROP attacks without returns

Currently,security-critical server programs are well protected by various defense techniques,such as Address Space Layout Randomization(ASLR),eXecute Only Memory(XOM),and Data Execution Prevention(DEP),against modern code-reuse attacks like Return-oriented Programming(ROP)attacks.Moreover,in these victim programs,most syscall instructions lack the following ret instructions,which prevents attacks to stitch multiple system calls to implement advanced behaviors like launching a remote shell.Lacking this kind of gadget greatly constrains the capability of code-reuse attacks.This paper proposes a novel code-reuse attack method called Signal Enhanced Blind Return Oriented Programming(SeBROP)to address these challenges.Our SeBROP can initiate a successful exploit to server-side programs using only a stack overflow vulnerability.By leveraging a side-channel that exists in the victim program,we show how to find a variety of gadgets blindly without any pre-knowledges or reading/disassembling the code segment.Then,we propose a technique that exploits the current vulnerable signal checking mechanism to realize the execution flow control even when ret instructions are absent.Our technique can stitch a number of system calls without returns,which is more superior to conventional ROP attacks.Finally,the SeBROP attack precisely identifies many useful gadgets to constitute a Turing-complete set.SeBROP attack can defeat almost all state-of-the-art defense techniques.The SeBROP attack is compatible with both modern 64-bit and 32-bit systems.To validate its effectiveness,We craft three exploits of the SeBROP attack for three real-world applications,i.e.,32-bit Apache 1.3.49,32-bit ProFTPD 1.3.0,and 64-bit Nginx 1.4.0.Experimental results demonstrate that the SeBROP attack can successfully spawn a remote shell on Nginx,ProFTPD,and Apache with less than 8500/4300/2100 requests,respectively.

Epitaxial indium antimonide for multiband photodetection from IR to millimeter/terahertz wave

Conventional photodetection converts light into electrical signals only in a single electromagnetic waveband.Multiband detection technology is highly desirable because it can handle multispectral information discrimination,identification,and processing.Current epitaxial solid-state multiband detection technologies are mainly within the IR wave range.Here,we report epitaxial indium antimonide on gallium arsenide for IR and millimeter/terahertz wave multiband photodetection.The photoresponse originates from interband transition in optoelectrical semiconductors for IR wave,and surface plasmon polaritons induced nonequilibrium electrons for a millimeter/terahertz wave.The detector shows a strong response for an IR wave with a cutoff wavelength of 6.85 μm and a blackbody detectivity of 1.8×10^(9) Jones at room temperature.For a millimeter/terahertz wave,the detector demonstrates broadband detection from 0.032 THz(9.4 mm)to 0.330 THz(0.9 mm);that is,from Ka to the W and G bands,with a noise equivalent power of 1.0×10^(-13) W Hz^(-1/2) at 0.270 THz(1.1 mm)at room temperature.The detection performance is an order of magnitude better while decreasing the temperature to 170 K,the thermoelectric cooling level.Such detectors,capable of large scale and low cost,are promising for advanced uncooled multiband detection and imaging systems.