System reconstruction from higher order spectra slices

We consider the problem of system reconstruction from higher order spectra (HOS) slices. We establish that the impulse response of a complex system can be reconstructed up to a scalar and a shift based on any pair of HOS slices, as long as the distance between the two slices satisfies a certain condition. One slice is sufficient for the reconstruction in the case of a real system. We propose a cepstrum-based method for system reconstruction. We also propose a new method for the reconstruction of the system Fourier phase based on the phase of any odd-indexed bispectrum slice. Being able to choose the slices to be used in the reconstruction allows us to avoid bispectrum regions dominated by noise     

非正交多址接入系统中基于受限马尔科夫决策过程的网络切片虚拟资源分配算法

针对无线接入网络切片虚拟资源分配优化问题,该文提出基于受限马尔可夫决策过程(CMDP)的网络切片自适应虚拟资源分配算法。首先,该算法在非正交多址接入(NOMA)系统中以用户中断概率和切片队列积压为约束,切片的总速率作为回报,运用受限马尔可夫决策过程理论构建资源自适应问题的动态优化模型;其次定义后决策状态,规避最优值函数中的期望运算;进一步地,针对马尔科夫决策过程(MDP)的“维度灾难”问题,基于近似动态规划理论,定义关于分配行为的基函数,替代决策后状态空间,减少计算维度;最后设计了一种自适应虚拟资源分配算法,通过与外部环境的不断交互学习,动态调整资源分配策略,优化切片性能。仿真结果表明,该算法可以较好地提高系统的性能,满足切片的服务需求。     

Classification of normal and abnormal brain MRI slices using Gabor texture and support vector machines

In computational and clinical environments, autoclassification of brain magnetic resonance image (MRI) slices as normal and abnormal is challenging. The purpose of this study is to investigate the computer vision and machine learning methods for classification of brain magnetic resonance (MR) slices. In routine health-care units, MR scanners are being used to generate a massive number of brain slices, underlying the anatomical details. Pathological assessment from this medical data is being carried out manually by the radiologists or neuro-oncologists. It is almost impossible to analyze each slice manually due to the large amount of data produced by MRI devices at each moment. Irrefutably, if an automated protocol performing this task is executed, not only the radiologist will be assisted, but a better pathological assessment process can also be expected. Numerous schemes have been reported to address the issue of autoclassification of brain MRI slices as normal and abnormal, but accuracy, robustness and optimization are still an open issue. The proposed method, using Gabor filter and support vector machines, classifies brain MRI slices as normal or abnormal. Accuracy, sensitivity, specificity and ROC-curve have been used as standard quantitative measures to evaluate the proposed algorithm. To the best of our knowledge, this is the first study in which experiments have been performed on Whole Brain Atlas-Harvard Medical School (HMS) dataset, achieving an accuracy of 97.5%, sensitivity of 99%, specificity of 92% and ROC-curve as 0.99. To test the robustness against medical traits based on ethnicity and to achieve optimization, a locally developed dataset has also been used for experiments and remarkable results with accuracy (96.5%), sensitivity (98%), specificity (92%) and ROC-curve (0.97) were achieved. Comparison with state-of-the-art methods proved the overall efficacy of the proposed method.     

Optical communication with synchronized hyperchaos generated electrooptically

We propose a method based on a scalar second-order difference-differential equation to obtain intensity chaos from a laser diode with a nonlinear delayed feedback. The method can be used for encrypting, transmitting, and decrypting a signal in a chaos-based communication system. The core of the chaotic transmitter and receiver is formed by an electrooptic modulator that is used to generate a strong reproducible nonlinearity and chaotic waveforms of extremely high Lyapunov dimensionality. The system opens the way to ultrafast chaotic communications.     

Bias field inconsistency correction of motion-scattered multislice MRI for improved 3D image reconstruction

A common solution to clinical MR imaging in the presence of large anatomical motion is to use fast multislice 2D studies to reduce slice acquisition time and provide clinically usable slice data. Recently, techniques have been developed which retrospectively correct large scale 3D motion between individual slices allowing the formation of a geometrically correct 3D volume from the multiple slice stacks. One challenge, however, in the final reconstruction process is the possibility of varying intensity bias in the slice data, typically due to the motion of the anatomy relative to imaging coils. As a result, slices which cover the same region of anatomy at different times may exhibit different sensitivity. This bias field inconsistency can induce artifacts in the final 3D reconstruction that can impact both clinical interpretation of key tissue boundaries and the automated analysis of the data. Here we describe a framework to estimate and correct the bias field inconsistency in each slice collectively across all motion corrupted image slices. Experiments using synthetic and clinical data show that the proposed method reduces intensity variability in tissues and improves the distinction between key tissue types.     

基于镜像对称参考切片的多扫描链测试数据压缩方法

为了减少测试数据和测试时间,该文提出一种基于镜像对称参考切片的多扫描链测试数据压缩方法。采用两个相互镜像对称的参考切片与扫描切片做相容性比较,提高了相容概率。若扫描切片与参考切片相容,只需要很少的几位编码就可以表示这个扫描切片,并且可以并行载入多扫描链;若不相容,参考切片被该扫描切片替换。提出一种最长相容策略,用来处理扫描切片与参考切片同时满足多种相容关系时的选取问题。根据Huffman编码原理确定不同相容情况的编码码字,可以进一步提高测试数据的压缩率。实验结果表明所提方法的平均测试数据压缩率达到了69.13%。     

Semantic image retrieval in magnetic resonance brain volumes

Practitioners in the area of neurology often need to retrieve multimodal magnetic resonance (MR) images of the brain to study disease progression and to correlate observations across multiple subjects. In this paper, a novel technique for retrieving 2-D MR images (slices) in 3-D brain volumes is proposed. Given a 2-D MR query slice, the technique identifies the 3-D volume among multiple subjects in the database, associates the query slice with a specific region of the brain, and retrieves the matching slice within this region in the identified volumes. The proposed technique is capable of retrieving an image in multimodal and noisy scenarios. In this study, support vector machines (SVM) are used for identifying 3-D MR volume and for performing semantic classification of the human brain into various semantic regions. In order to achieve reliable image retrieval performance in the presence of misalignments, an image registration-based retrieval framework is developed. The proposed retrieval technique is tested on various modalities. The test results reveal superior robustness performance with respect to accuracy, speed, and multimodality.     

Incentive Scheme for Slice Cooperation Based on D2D Communication in 5G Networks

In the 5th generation(5G)wireless communication networks,network slicing emerges where network operators(NPs)form isolated logical slices by the same cellular network infrastructure and spectrum resource.In coverage regions of access points(APs)shared by slices,device to device(D2D)communication can occur among different slices,i.e.,one device acts as D2D relay for another device serving by a different slice,which is defined as slice cooperation in this paper.Since selfish slices will not help other slices by cooperation voluntarily and unconditionally,this paper designs a novel resource allocation scheme to stimulate slice cooperation.The main idea is to encourage slice to perform cooperation for other slices by rewarding it with higher throughput.The proposed incentive scheme for slice cooperation is formulated by an optimal problem,where cooperative activities are introduced to the objective function.Since optimal solutions of the formulated problem are long term statistics,though can be obtained,a practical online slice scheduling algorithm is designed,which can obtain optimal solutions of the formulated maximal problem.Lastly,the throughput isolation indexes are defined to evaluate isolation performance of slice.According to simulation results,the proposed incentive scheme for slice cooperation can stimulate slice cooperation effectively,and the isolation of slice is also simulated and discussed.     

A semidistributed HEMT model for accurate fitting and extrapolationof S-parameters and noise parameters

A model is described for a low noise millimeter-wave HEMT device. It takes account of the distributed nature of the gate and drain electrodes by dividing the active region of the device into a number of slices. Each slice is modeled as an intrinsic HEMT with thermal noise sources and the slices are connected together through lossy reactances. The parameters of the first slice are made different from those of the remaining slices, in order to account for the inevitable differences in the field distribution in the gate feed region. The model parameters have been optimized numerically to fit the manufacturer's measured S-parameters and all four noise parameters, for a commercially available HEMT chip. A good fit has been achieved simultaneously to all of these parameters, and the model therefore provides a reasonable basis for extrapolation to higher frequencies. The significance of the distributed gate effect and the unequal slice effect is assessed by comparing the best fit achievable when these effects are not included     

MRI of moving subjects using multislice snapshot images with volume reconstruction (SVR): application to fetal, neonatal, and adult brain studies

Motion degrades magnetic resonance (MR) images and prevents acquisition of self-consistent and high-quality volume images. A novel methodology, Snapshot magnetic resonance imaging (MRI) with Volume Reconstruction (SVR) has been developed for imaging moving subjects at high resolution and high signal-to-noise ratio (SNR). The method combines registered 2-D slices from sequential dynamic single-shot scans. The SVR approach requires that the anatomy in question is not changing shape or size and is moving at a rate that allows snapshot images to be acquired. After imaging the target volume repeatedly to guarantee sufficient sampling every where, a robust slice-to-volume registration method has been implemented that achieves alignment of each slice within 0.3 mm in the examples tested. Multilevel scattered interpolation has been used to obtain high-fidelity reconstruction with root-mean-square (rms) error that is less than the noise level in the images. The SVR method has been performed successfully for brain studies on subjects that cannot stay still, and in some cases were moving substantially during scanning. For example, awake neonates, deliberately moved adults and, especially, on fetuses, for which no conventional high-resolution 3-D method is currently available. Fine structure of the in-utero fetal brain is clearly revealed for the first time and substantial SNR improvement is realized by having many individually acquired slices contribute to each voxel in the reconstructed image.     

Differentiation and function of osteoclasts cultured on bone and cartilage

We examined the differentiation and resorptive function of osteoclasts (OC) cultured on the slices of calcified bone, decalcified bone and hyaline cartilage, and found that OC differentiation depends on the co-cultured substratum, as well as osteoblast-derived factors. Bone marrow-derived macrophages (BMM) were formed from marrow cells of 5 week old ddY mice and cultured for 3 days on freeze-dried slices of calcified bone, decalcified bone or cartilage, all prepared from rabbit costal bone. BMM cultured on calcified bone slices exhibited tartrate-resistant acid phosphatase (TRAP) activity and were structurally characterized by multinucleation and ruffled border development. However, on decalcified bone slices, BMM seldom became multinucleated and exhibited weak TRAP activity. BMM cultured on cartilage slices were mononuclear, devoid of TRAP activity and structurally resembled mononuclear phagocytes. In SEM observations of co-cultured slices, resorption lacunae were formed only on calcified bone slices, and not on slices of decalcified bone and cartilage. Our results, therefore, indicated that BMM could differentiate into functional OC only on calcified bone slices, suggesting a key role of calcified components in the bone matrix for the terminal OC differentiation. Then, we cultured BMM on the same slices with yeast particles. In cultures with yeast particles, BMM exhibited intense TRAP activity, developed a ruffled border-like structure and formed resorption lacunae even on decalcified bone and cartilage slices. Vacuolar-type H+-ATPase was strongly expressed along the ruffled border membranes of these OC. Only the BMM that had not incorporated yeast particles developed a ruffled border, whereas the BMM that had incorporated yeast particles did not become multinucleated and lacked a ruffled border structure. Thus, our results further suggest that, even on uncalcified substrata, the terminal differentiation of BMM into functional OC is induced by an unidentified external stimulus, which may be contained in the cell membrane of yeast particles.     

Medical image compression by using three-dimensional wavelet transformation

This paper proposes a three-dimensional (3-D) medical image compression method for computed tomography (CT) and magnetic resonance (MR) that uses a separable nonuniform 3-D wavelet transform. The separable wavelet transform employs one filter bank within two-dimensional (2-D) slices and then a second filter bank on the slice direction. CT and MR image sets normally have different resolutions within a slice and between slices. The pixel distances within a slice are normally less than 1 mm and the distance between slices can vary from 1 mm to 10 mm. To find the best filter bank in the slice direction, the authors use the various filter banks in the slice direction and compare the compression results. The results from the 12 selected MR and CT image sets at various slice thickness show that the Haar transform in the slice direction gives the optimum performance for most image sets, except for a CT image set which has 1 mm slice distance. Compared with 2-D wavelet compression, compression ratios of the 3-D method are about 70% higher for CT and 35% higher for MR image sets at a peak signal to noise ratio (PSNR) of 50 dB, In general, the smaller the slice distance, the better the 3-D compression performance.     

A flexible perforated microelectrode array for extended neuralrecordings

A flexible and perforated 32-element planar microelectrode array has been fabricated and used to measure evoked potentials in brain slices. Electrodes are spaced 200 microns apart in a 4 x 8 array and are sandwiched between layers of insulating polyimide. The polyimide sandwich is lifted off its substrate, making it flexible so that it could shape to contoured tissues. Prior to lift off, holes are etched to expose recording sites 15 microns in diameter and to create perforations which allow increased circulation of artificial cerebrospinal fluid to the recording surface of the tissue and, hence, increased viability. Comparisons of evoked potentials measured over time showed an average increase of 10 h to the viability of the slice while using the perforated versus nonperforated arrays.     

Yield analysis of large integrated-circuit chips

It has been experimentally observed that integrated-circuit yields decrease as their size increases and various attempts have been made to explain the variation. The authors analyze yield in terms of the geometrical factors involved in producing large chips from circular slices. It is shown that the qualitatively correct dependence of yield on area is obtained when a defect density that is higher near the outside of the slice is assumed. Results of computer program calculations of the maximum possible number of chips that can be obtained from a slice are given, assuming both random and nonrandom defect distributions.     

System reconstruction based on selected regions of discretizedhigher order spectra

We consider the problem of system reconstruction from arbitrarily selected slices of the nth-order output spectrum. We establish that unique identification of the impulse response of a system can be performed, up to a scalar and a circular shift, based on any two one-dimensional (1-D) slices of the discretized nth-order output spectrum, (n⩾3), as long as the distance between the slices and the grid size satisfy a simple condition. For the special case of real systems, one slice suffices for system reconstruction. The ability to choose the slices to be used for reconstruction enables us to avoid regions of the nth-order spectrum, where the estimation variance is high, or where the ideal polyspectrum is expected to be zero, as is the case for bandlimited systems. We show that the obtained system estimates are asymptotically unbiased and consistent. We propose a mechanism for selecting slices that result in improved system estimates. We also demonstrate via simulations the superiority, in terms of estimation bias and variance, of the proposed method over existing approaches in the case of bandlimited systems     

Blind reconstruction of non-minimum-phase systems from 1-D obliqueslices of bispectrum

The author considers the problem of identifying a non-minimum-phase signal from one-dimensional slices of its output bispectra. It is proved that any single slice of the bispectrum carries sufficient information to estimate the impulse response of a complex valued system within a time shift, as long as the chosen slice is not parallel to any one of the frequency axes or to the diagonal at 135 degrees. The author also derives identifiability criteria associated with complex valued signals that admit finite-dimensional ARMA representations. One-dimensional techniques are proposed for signal reconstruction from bispectrum slices and their performance is investigated through Monte-Carlo simulations. The slices required for the proposed method can be estimated on a polar raster directly from observations, avoiding the heavy computational burden associated with cumulant estimates. The freedom to choose arbitrarily oriented and shifted slice(s) allows bispectrum regions dominated by larger estimation variance and higher noise to be avoided     

Experimental validation of resource allocation in transport network slicing using the ADRENALINE testbed

Transport network virtualization provides the necessary data and control plane technologies as key enablers of future networks. The interaction between network slicing and optical transport network virtualization architectures is under study to automate effective network resource orchestration. In this paper, we present an harmonized network slicing and transport network virtualization architecture, including a network slice planner tool, which is designed and implemented enabling in-operation execution of network slice resource allocation algorithms. We validate the proposed architecture by providing a novel resource allocation algorithm, evaluating its performance and deploying two different slices on top of the ADRENALINE testbed, while measuring both slices key performance indicators.

     

Synchronized chaotic mode hopping in DBR lasers with delayedopto-electric feedback

We propose and demonstrate a scheme for generating synchronized chaotic mode hopping in two wavelength-tunable lasers. Chaotic mode hopping resulting in large hops in wavelength is induced by delayed feedback of an electrical signal proportional to the intensity of the laser output which passes through an optical filter. Mode hopping among up to 11 modes was experimentally observed and optical signals in each wavelength band show a different on-off modulation time series. Analysis of the time series indicates high dimensionality. By using a unidirectional coupling method that injects part of the output of one laser into another, we can synchronize the chaotic mode hopping of two separate lasers and obtain synchronized chaotic on-off modulation patterns in multiple corresponding wavelength bands. The robustness of the synchronization with respect to the parameter mismatch and the effects of the coupling strength are investigated. The chaotic mode hopping dynamics and synchronization are well described with a numerical model that includes the characteristics of the laser tuning and the filter transmission. A multiplexed data transmission scheme using chaotic carriers is proposed and experiments demonstrate that multiple messages can be simultaneously recovered when chaos synchronization is achieved     

LTE无线网络虚拟化中切片调度策略

研究了未来移动通信网络切片机制,针对LTE系统下行在基站内建立媒体接入控制(MAC)层流级别的切片调度器,使得运营商之间可以按照预设比例共享资源.运营商作为切片的拥有者可以根据不同的服务等级协议(SLA)来对其资源比例进行设定.比较固定切片与网络虚拟化基片(NVS)框架下切片的资源块利用率,进行了系统级仿真实验.相对于固定切片方法,NVS方法在不同切片间用户相互隔离的情况下有更好的资源利用率.此外,针对实时(RT)业务和非实时(NRT)业务在时延上的差异建立业务切片,定制化地选择其调度算法策略,从而在降低分组丢失率的同时提升整个系统的性能.     

An Elastic Sub-carrier and Power Allocation Algorithm Enabling Wireless Network Virtualization

Wireless mobile network virtualization enables physical mobile network operators (PMNO) to partition their network resources into smaller slices and assign each slice to an individual virtual mobile network operator and then manages these virtual networks in a more dynamic and cost-effective fashion. How a PMNO allocates resources to individual slices while ensuring resource elasticity is a key issue. This paper presents a resource allocation algorithm in such a network virtualization scenario where resource considered here includes both sub-carriers and transmission power. The overall algorithm involves the following two major processes: firstly to virtualize a physical wireless network into multiple slices each representing a virtual network, where resources are allocated elastically based on traffic loads and channel state information during virtualization; secondly, to carry out physical resource allocation within each virtual network (or slice). In particular the paper adopts orthogonal frequency division multiplexing as its physical layer to achieve more efficient resource utilization. A multi-step dynamic optimization approach is proposed to achieve sub-carrier allocation using binary integer programming and power allocation using nonlinear programming. The aim is to achieve the following design goals: virtual network isolation, and resource efficiency. The simulation results show that the above goals have been achieved.