Ruling out small stopping sets and small girth in Tanner graph of QC-LDPC code

The existing constructions of quasi-cyclic low-density parity-check （QC-LDPC） codes do not consider the problems of small stopping sets and small girth together in the Tanner graph, while their existences will lead to the bit error rate （BER） performance of QC-LDPC codes being much poorer than that of randomly constructed LDPC codes even decoding failure. To solve the problem, some theorems of the specific chosen parity-check matrix of QC-LDPC codes without small stopping sets and small girth are proposed. A novel construction for QC-LDPC codes with long block lengths is presented by multiplying mmin or the multiple of mmin, which is the minimum order of the identity matrix for the chosen parity-check matrix. The simulation results show that the specific chosen parity-check matrix of QC-LDPC codes can effectively avoid specified stopping sets and small girth and exhibit excellent BER performance than random LDPC codes with the same longer codes length.

Simulation and Experimental Design of Load Adaptive Braking System on Two Wheeler

The braking quality is considered the main execution of the adaptive control framework that impacts the vehicle safety and rides solace astoundingly notably the stopping distance.This research work aims to create a pattern and design of an electromechanically adjusted lever that multiplies the applied braking force depending on the inputs given by the sensors to reduce the stopping distance of the vehicle.It is carried out using two main parts of the two-wheeler vehicle:thefirst part deals with the detection of load acting on the vehicle and identifying the required braking force to be applied,and the second part deals with the micro-controller which activates the stepper motor for varying the mechanical leverage ratio from various loads on the vehicle using two actively movable wedges.The electromechanically operated variable braking force system is developed to actuate the braking system based on the load on the motorcycle.The MATLAB simulation and experimental work are carried out for various loading(driver and pillion)conditions on a two-wheeler.The results indicate that the proposed electronically operated braking system is more effective than the conventional braking system for various loads and vehicle speeds.Specifically,the stopping distance of the vehicle is decreased significantly by about 4.9%between the con-ventional braking system and the simulated proposed system.Further,the experi-mental results show that the stopping distance is condensed by about 4.1%.The validation between simulated and experimental results revealed a great deal with the least error percentage of about 0.8%.

Design of good QC-LDPC codes without small girth in the p-plane

A construction method based on the p-plane to design high-girth quasi-cyclic low-density parity-check （QC-LDPC） codes is proposed. Firstly the good points in every line of the p-plane can be ascertained through filtering the bad points, because the designed parity-check matrixes using these points have the short cycles in Tanner graph of codes. Then one of the best points from the residual good points of every line in the p-plane will be found, respectively. The optimal point is also singled out according to the bit error rate （BER） performance of the QC-LDPC codes at last. Explicit necessary and sufficient conditions for the QC-LDPC codes to have no short cycles are presented which are in favor of removing the bad points in the p-plane. Since preventing the short cycles also prevents the small stopping sets, the proposed construction method also leads to QC-LDPC codes with a higher stopping distance.

Influence of rainfall on skid resistance performance and driving safety conditions of asphalt pavements

To study the influence of rainfall on pavement skid-resistance performance and driving safety,the water film thickness(WFT)concept considering the longitudinal and transverse slopes of the pavement was utilized based on the total discharge formulation and turbulence theory of slope flow.Using experimental data measured using the British pendulum test under varying WFT levels,a model for calculating the skid resistance,namely the British pendulum number(BPN),was formulated and used to quantitatively evaluate the effects of rainfall intensity,transverse,and longitudinal slopes on the computed BPN.The study results reveal that skid resistance is linearly proportional to the pavement transverse slope and inversely proportional to the rainfall intensity and the pavement longitudinal slope.In particular,rainfall intensity,along with pavement texture depth,exhibited a significant impact on the tire-pavement friction and skid-resistance performance.The results further indicate that driving safety under wet weather is predominantly governed by skid resistance and visibility.The BPN and sideway force coefficient(SFC60)values for new asphalt pavements under different rainfall intensities are provided along with some modification to the stopping sight distance(SSD)criteria.Safe driving speed limits are also determined using a safe-driving model to develop the appropriate speed limit strategies.The overall study results provide some insights,methodology approach,and reference data for the evaluation of pavement skid-resistance performance and driving safety conditions under different pavement slopes and rainfall intensities.

A Note on the Stopping Redundancy of Linear Codes

In this paper, we study the stopping sets, stopping distance and stopping redundancy for binary linear codes. Stopping redundancy is a new concept proposed by Schwartz and Vardy recently for evaluating the performance of a linear code under iterative decoding over a binary erasure channel （BEC）. Since the exact value of stopping redundancy is difficult to obtain in general, good lower and upper bounds are important. We obtain a new general upper bound on the stopping redundancy of binary linear codes which improves the corresponding results of Schwartz and Vardy.