关于信源的Tunstall编码方法

在信源编码理论中，Ｔｕｎｓｔａｌｌ码是渐近最优的Ｖ－Ｂ码（Ｖ代表变长消息，Ｂ代表定长码字）．本文进一步研究了Ｔｕｎｓｔａｌｌ码的性质，给出了Ｔｕｎｓｔａｌｌ码的码率的新的上界，刻划了Ｔｕｎｓｔａｌｌ树和扩展次数之间的一些较深刻的内在联系，并且给出了一个寻找ε－最优的Ｔｕｎｓｔａｌｌ码的扩展次数的算法．

Comparison of the ability of wavelet index and bispectral index for reflecting regain of consciousness in patients undergone surgery

Background Wavelet index （WLI） is a new parameter for monitoring depth of anesthesia based on Wavelet analysis. We observed the change of WLI and bispectral index （BIS） in patients regain of consciousness （ROC） in the absence of frontalis electromyographic （EMG） interference. The aim of this study was to compare the ability of WLI and BIS for reflecting ROC in patients undergone surgery. Methods Twelve patients who were scheduled for maxillofacial surgeries were enrolled in the study. BIS and WLI values were monitored continually. After being given midazolam and remifentanil, patients were asked to squeeze the investigator＇s hand ever 30 seconds. Patients were continuously given propofol until loss of consciousness （LOC1）. Tunstalrs isolated forearm technique was used to test the surgical consciousness in patients. After total muscle relaxation endotracheal intubations were performed, and the patients were connected to a ventilator. Then, propofol was withdrawn until the patients showed regain of consciousness （ROC1） and an awareness reaction. After the command test, patients were readministered with propofol until loss of consciousness （LOC2）. After surgery, all of the sedatives were withdrawn, and the patients were let to regain consciousness （ROC2）, Results The BIS values of twelve patients at ROC1 after using muscle relaxant were much lower than those at LOC1 and ROC2 without using muscle relaxant, showing statistical significance （P 〈0.05）. Meanwhile, the WLI values of twelve patients at ROC1 after using muscle relaxant were much higher than those at LOC1 and equal to ROC2 without using muscle relaxant, showing statistical significances （P 〈0.05） between ROC1 and LOCI. Conclusions This study showed that under muscle relaxation or facial paralysis, when there is no EMG signal, BIS can not accurately reflect regain of consciousness in surgical patients, but WLI can reflect it accurately. So WLI may have advantages for reflecting state of consciousness in surgical patients.

Indexing structures for the PLS blockchain

This paper studies known indexing structures from a new point of view:minimisation of data exchange between an IoT device acting as a blockchain client and the blockchain server running a protocol suite that includes two Guy Fawkes protocols,PLS and SLVP.The PLS blockchain is not a cryptocurrency instrument;it is an immutable ledger offering guaranteed non-repudiation to low-power clients without use of public key crypto.The novelty of the situation is in the fact that every PLS client has to obtain a proof of absence in all blocks of the chain to which its counterparty does not contribute,and we show that it is possible without traversing the block's Merkle tree.We obtain weight statistics of a leaf path on a sparse Merkle tree theoretically,as our ground case.Using the theory we quantify the communication cost of a client interacting with the blockchain.We show that large savings can be achieved by providing a bitmap index of the tree compressed using Tunstall's method.We further show that even in the case of correlated access,as in two IoT devices posting messages for each other in consecutive blocks,it is possible to prevent compression degradation by re-randomising the IDs using a pseudorandom bijective function.We propose a low-cost function of this kind and evaluate its quality by simulation,using the avalanche criterion.

Indexing structures for the PLS blockchain

This paper studies known indexing structures from a new point of view:minimisation of data exchange between an IoT device acting as a blockchain client and the blockchain server running a protocol suite that includes two Guy Fawkes protocols,PLS and SLVP.The PLS blockchain is not a cryptocurrency instrument;it is an immutable ledger offering guaranteed non-repudiation to low-power clients without use of public key crypto.The novelty of the situation is in the fact that every PLS client has to obtain a proof of absence in all blocks of the chain to which its counterparty does not contribute,and we show that it is possible without traversing the block’s Merkle tree.We obtain weight statistics of a leaf path on a sparse Merkle tree theoretically,as our ground case.Using the theory we quantify the communication cost of a client interacting with the blockchain.We show that large savings can be achieved by providing a bitmap index of the tree compressed using Tunstall’s method.We further show that even in the case of correlated access,as in two IoT devices posting messages for each other in consecutive blocks,it is possible to prevent compression degradation by re-randomising the IDs using a pseudorandom bijective function.We propose a low-cost function of this kind and evaluate its quality by simulation,using the avalanche criterion.