Two-Way Training for Discriminatory Channel Estimation in Wireless MIMO Systems

This work examines the use of two-way training to efficiently discriminate the channel estimation performances at a legitimate receiver (LR) and an unauthorized receiver (UR) in a multiple-input multiple-output (MIMO) wireless system. This work improves upon the original discriminatory channel estimation (DCE) scheme proposed by Chang et al where multiple stages of feedback and retraining were used. While most studies on physical layer secrecy are under the information-theoretic framework and focus directly on the data transmission phase, studies on DCE focus on the training phase and aim to provide a practical signal processing technique to discriminate between the channel estimation performances at LR and UR. A key feature of DCE designs is the insertion of artificial noise (AN) in the training signal to degrade the channel estimation performance at UR. To do so, AN must be placed in a carefully chosen subspace based on the transmitter's knowledge of LR's channel in order to minimize its effect on LR. In this paper, we adopt the idea of two-way training that allows both the transmitter and LR to send training signals to facilitate channel estimation at both ends. Both reciprocal and non-reciprocal channels are considered and a two-way DCE scheme is proposed for each scenario. {For mathematical tractability, we assume that all terminals employ the linear minimum mean square error criterion for channel estimation. Based on the mean square error (MSE) of the channel estimates at all terminals,} we formulate and solve an optimization problem where the optimal power allocation between the training signal and AN is found by minimizing the MSE of LR's channel estimate subject to a constraint on the MSE achievable at UR. Numerical results show that the proposed DCE schemes can effectively discriminate between the channel estimation and hence the data detection performances at LR and UR.Comment: 1

Combined analysis of the γn→K0Σ0\gamma n \to K^0\Sigma^0 and γn→K+Σ−\gamma n \to K^+\Sigma^- reactions

The recently released data on differential cross sections for $\gamma n \to K^0\Sigma^0$ from the A2 and BGOOD Collaborations are used to examine the theoretical model constructed in our previous work [Phys. Rev. D \textbf{105}, 094017 (2022)] for $\gamma n \to K^+\Sigma^-$, and it is found that the model predictions are able to qualitatively reproduce the A2 data but fail to describe the BGOOD data. Then, a combined analysis of the $\gamma n \to K^0\Sigma^0$ and $\gamma n \to K^+\Sigma^-$ reactions is performed to revise the theoretical model. Due to the inconsistency problem, the A2 and BGOOD data are included in fits separately. In the case of including the A2 data, both the data for $\gamma n \to K^0\Sigma^0$ and $\gamma n \to K^+\Sigma^-$ can be fairly well described, and the contributions from the $N(1710)1/2^+$, $N(1880)1/2^+$, $N(1900)3/2^+$, and $\Delta(1920)3/2^+$ resonances are found to dominate the reactions in the lower energy region. While in the case of including the BGOOD data, although most of the data for the $\gamma n \to K^+ \Sigma^-$ reaction can be described with the exception of some noticeable discrepancies on beam asymmetries at lower energies, the BGOOD data for $\gamma n \to K^0\Sigma^0$ can be only qualitatively described, and the contributions from the $N(1710)1/2^+$, $N(1900)3/2^+$, and $\Delta(1910)1/2^+$ resonances are found to dominate the reactions in the lower energy region. In both cases, the $t$-channel $K^\ast(892)$ exchange is found to play a crucial role at forward angles in the higher energy region. Further precise measurements of data for $\gamma n \to K^0\Sigma^0$ are called on to disentangle the discrepancies between the data sets from the A2 and BGOOD Collaborations.Comment: 14 pages,17 figures; Accepted for publication in Physical Review

Effects of natto extract on endothelial injury in a rat model

Vascular endothelial damage has been found to be associated with thrombus formation, which is considered to be a risk factor for cardiovascular disease. A diet of natto leads to a low prevalence of cardiovascular disease. The aim of the present study was to investigate the effects of natto extract on vascular endothelia damage with exposure to laser irradiation. Endothelial damage both in vitro and in vivo was induced by irradiation of rose bengal using a DPSS green laser. Cell viability was determined by MTS assay, and the intimal thickening was verified by a histological approach. The antioxidant content of natto extract was determined for the free radical scavenging activity. Endothelial cells were injured in the presence of rose bengal irradiated in a dose-dependent manner. Natto extract exhibits high levels of antioxidant activity compared with purified natto kinase. Apoptosis of laser-injured endothelial cells was significantly reduced in the presence of natto extract. Both the natto extract and natto kinase suppressed intimal thickening in rats with endothelial injury. The present findings suggest that natto extract suppresses vessel thickening as a synergic effect attributed to its antioxidant and anti-apoptosis properties

Failure and Repair of the Slope of Railway Embankments and Expansive Soils

This paper mainly discusses the stability of the slope of the four sections of railway embankments of expansive soils, describes their basic condition and the properties of the soil materials, analyzes the types and causes of slope failures, discusses the repair of such slopes, and the remedial measures to prevent recurrent of the slides, and sums up experience of using expansive soils to construct railway embankments

Hookworm infestation, an old but not vanished disease

AbstractHookworms, together with other helminthes infestations, were serious health problems in Taiwan before. With improvements in public health and medicine, the prevalence of parasite infestations drops significantly and current attention has been shifted to foreign laborers coming from the Southeast Asia. Herein we reported a case of hookworm infestation who presented as subacute diarrhea. Initially, only peripheral eosinophilia was revealed. Anti-helminth treatment, but not the immunosuppressant for eosinophilic gastroenteritis, was given when the hookworm ova were finally harvested after repeated stool examinations. Please remember the old diseases when you meet a patient with gastrointestinal complaints and peripheral eosinophilia, especially when there are intermittent skin atopic manifestations. Repeated parasite ova checks with concentration method are necessary in acute stage, especially when the worm burden is not heavy