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Two dimensional magnetic recording (TDMR) is one of the leading technologies proposed to achieve ultra high storage density in the next generation hard disk drives. A typical read channel of TDMR can be approximated by a multihead multitrack (MHMT) model which is characterized by the intersymbol interference (ISI) in the downtrack direction and intertrack interference (ITI) in the crosstrack direction. In this dissertation, we aim to address two challenging problems that can potentially make the maximum likelihood (ML) detection for the MHMT channel impractical. One problem associated with the conventional ML detector is the ITI dependency of the ML trellis, which makes it inefficient to adapt to a time-varying ITI environment. We propose a novel detection method, called the weighted sum-subtract joint detection (WSSJD), to solve this issue. We show that the ITI interfering channels in MHMT system can be transformed to several parallel subchannels, whose joint trellis is independent of ITI. For the case when the receiver lacks the knowledge of ITI, we propose a gain loop structure which can be incorporated into WSSJD to efficiently track the ITI estimates. We present the implementation of WSSJD and simulation results for several widely-studied MHMT models including the 2H2T channel, the 3H3T channel, and the 3H2T channel.Another challenging problem is the exponentially increased computational complexity of the ML detector due to its multitrack processing scheme. We propose to use the reduced-state sequence estimation (RSSE) to mitigate this issue. The underlying idea is to drop less likely paths at early state during the detection by using a heavily reduced subset trellis. To apply RSSE to the MHMT channel, we find that the channel transformation developed in WSSJD offers a natural set partition principle on the input constellation that is necessary to successfully implement RSSE. The theoretical error event analysis shows a good consistency with the simulation results.Flash memory has faster access speed, lower power consumption, and better data integrity, which make it more attractive than the magnetic recording in many applications. However, the lifetime of flash memory is limited by the program/erase cycles. Write-once memory (WOM) codes are proposed to extend the flash memory lifetime by constraining the unidirectional changes of cell levels. In this work, we study the expected performance of WOM codes. Dynamic programming based algorithm is proposed to construct the optimal WOM updating function of a given labeling function.

The query image is usually a simple and single object in image retrieval, and the reference images in the database usually have many distractions. The precision of image retrieval can be greatly improved If the target regions in the database image are extracted during retrieval. So this paper proposes a Bow image retrieval method based on SSD target detection. First, the training gallery is manually annotated to record the location and size information. Second, the SSD target detection model is trained with the labeled training gallery to obtain the target object SSD model. Third, the SSD model is used to locate the similar target regions of the reference image and the query graph. Finally, the target region information is mapped into the convolutional features, and these feature vectors are used for image similarity matching. The performance of the proposed method is evaluated on Paris6k, Oxford5k, Paris106k and Oxford105k databases. The experimental results show that the accuracy of image retrieval will be greatly improved by adding optimization methods in the proposed image retrieval framework. The image retrieval accuracy of this method is higher than that of similar methods in recent years.

Meat adulteration, mainly for the purpose of economic pursuit, is widespread and leads to serious public health risks, religious violations, and moral loss. Rapid, effective, accurate, and reliable detection technologies are keys to effectively supervising meat adulteration. Considering the importance and rapid advances in meat adulteration detection technologies, a comprehensive review to summarize the recent progress in this area and to suggest directions for future progress is beneficial. In this review, destructive meat adulteration technologies based on DNA, protein, and metabolite analyses and nondestructive technologies based on spectroscopy were comparatively analyzed. The advantages and disadvantages, application situations of these technologies were discussed. In the future, determining suitable indicators or markers is particularly important for destructive methods. To improve sensitivity and save time, new interdisciplinary technologies, such as biochips and biosensors, are promising for application in the future. For nondestructive techniques, convenient and effective chemometric models are crucial, and the development of portable devices based on these technologies for onsite monitoring is a future trend. Moreover, omics technologies, especially proteomics, are important methods in laboratory detection because they enable multispecies detection and unknown target screening by using mass spectrometry databases.

As the support networks of the electric power grid, power communication networks (PCNs) become more complex and vulnerable due to the increasing scale of the electric power grid. Identifying and protecting the critical nodes in PCNs in advance is an effective way to reduce network vulnerability. Owing to the large differences in vulnerability indicators of different layers in the PCN, it is difficult to find the critical nodes, which have great impacts on all vulnerability indicators. Therefore, the goal of this study is to identify the critical nodes that have greater impacts on different layers, rather than nodes that have the greatest impact on a single layer. Therefore, the authors present a model to analyse the node in the PCNs from the physical topology, traffic distribution, and service importance distribution to calculate the node importance in the physical topology layer, the transport layer, and the service layer, respectively. Combined with a multi-layer critical nodes identification algorithm (MCNIA) proposed, the node critical degree is obtained so that it can identify the critical nodes in the PCNs. The vulnerability analyses of PCNs under critical nodes attacking prove that MCNIA can identify critical nodes in the PCNs precisely.

Background: Rolling mill vibration mechanism is very complex, and people haven't found a satisfactory vibration control method. Rolling interface is one of the vibration sources of the rolling mill system, and its friction and lubrication state has a great impact on the vibration of the rolling mill system. It is necessary to establish an accurate friction model for unsteady lubrication process of roll gap and a nonlinear vibration dynamic model for rolling process. In addition, it is necessary to obtain more direct and real rolling mill vibration characteristics from the measured vibration signals, and then study the vibration suppression method and design the vibration suppression device. Methods: This paper summarizes the friction lubrication characteristics of rolling interface and its influence on rolling mill vibration, as well as the dynamic friction model of rolling interface, the tribological model of unsteady lubrication process of roll gap, the non-linear vibration dynamic model of rolling process, the random and non-stationary dynamic behavior of rolling mill vibration, etc. At the same time, the research status of rolling mill vibration testing technology and vibration suppression methods were summarized. Time-frequency analysis of non-stationary vibration signals was reviewed, such as wavelet transform, Wigner-Ville distribution, empirical mode decomposition, blind source signal extraction, rolling vibration suppression equipment development. Results: The lubrication interface of the roller gap under vibration state presents unsteady dynamic characteristics. The signals generated by the vibration must be analyzed in time and frequency simultaneously. In the aspect of vibration suppression of rolling mill, the calculation of inherent characteristics should be carried out in the design of rolling mill to avoid dynamic defects such as resonance. When designing or upgrading the mill structure, it is necessary to optimize the structure of the work roll bending and roll shifting system, such as designing and developing the automatic adjustment mechanism of the gap between the roller bearing seat and the mill stand, adding floating support device to the drum shaped toothed joint shaft, etc. In terms of rolling technology, rolling vibration can be restrained by improving roll lubrication, reasonably distributing rolling force of each rolling mill, reducing rolling force of vibration prone rolling mill, increasing entrance temperature, reducing rolling inlet tension, reducing strip outlet temperature and reasonably arranging roll diameter. The coupling vibration can also be suppressed by optimizing the hydraulic servo system and the frequency conversion control of the motor. Conclusion: Under the vibration state, the lubrication interface of roll gap presents unsteady dynamic characteristics. The signal generated by vibration must be analyzed by time-frequency distribution. In the aspect of vibration suppression of rolling mill, the calculation of inherent characteristics should be carried out in the design of rolling mill to avoid dynamic defects such as resonance. It is necessary to optimize the structure of work roll bending and roll shifting system when designing or reforming the mill structure. In rolling process, rolling vibration can be restrained by improving roll lubrication, reasonably distributing rolling force of each rolling mill, increasing billet temperature, reasonably arranging roll diameter and reducing rolling inlet tension. Through the optimization of the hydraulic servo system and the frequency conversion control of the motor, the coupling vibration can be suppressed. The paper has important reference significance for vibration suppression of continuous rolling mill and efficient production of high quality strip products.