Multidimensional Modulation Research Articles

Experimental study on two-dimensional film flow with local measurement methods

In an accident condition of a nuclear reactor, multidimensional two-phase flows may occur in the reactor vessel downcomer and reactor core. Therefore, those have been regarded as important issues for an advanced thermal-hydraulic safety analysis. In particular, the multi-dimensional two-phase flow in the upper downcomer during the reflood phase of large break loss of coolant accident appears with an interaction between a downward liquid and a transverse gas flow, which determines the bypass flow rate of the emergency core coolant and subsequently, the reflood coolant flow rate. At present, some thermal-hydraulic analysis codes incorporate multidimensional modules for the nuclear reactor safety analysis. However, their prediction capability for the two-phase cross flow in the upper downcomer has not been validated sufficiently against experimental data based on local measurements. For this reason, an experimental study was carried out for the two-phase cross flow to clarify the hydraulic phenomenon and provide local measurement data for the validation of the computational tools. The experiment was performed in a 1/10 scale unfolded downcomer of Advanced Power Reactor 1400 (APR1400). Pitot tubes, a depth-averaged PIV method and ultrasonic thickness gauge were applied for local measurement of the air velocity, the liquid film velocity and the liquid film thickness, respectively. The uncertainty of the depth-averaged PIV method for the averaged velocity of the liquid film was discussed. Also the local velocity profiles of air and liquid film and the liquid film thickness distribution were presented. These local experimental data of two-dimensional film flow which simulated the two-phase cross flow can be used to validate the multidimensional models in the system analysis codes and CFD codes.

Flexible multi-dimensional modulation method for elastic optical networks

We demonstrate a flexible multi-dimensional modulation method for elastic optical networks. We compare the flexible multi-dimensional modulation formats PM-kSC-mQAM with traditional modulation formats PM-mQAM using numerical simulations in back-to-back and wavelength division multiplexed (WDM) transmission (50GHz-spaced) scenarios at the same symbol rate of 32Gbaud. The simulation results show that PM-kSC-QPSK and PM-kSC-16QAM can achieve obvious back-to-back sensitivity gain with respect to PM-QPSK and PM-16QAM at the expense of spectral efficiency reduction. And the WDM transmission simulation results show that PM-2SC-QPSK can achieve 57.5% increase in transmission reach compared to PM-QPSK, and 48.5% increase for PM-2SC-16QAM over PM-16QAM. Furthermore, we also experimentally investigate the back to back performance of PM-2SC-QPSK, PM-4SC-QPSK, PM-2SC-16QAM and PM-3SC-16QAM, and the experimental results agree well with the numerical simulations.

Treg Induced Impairment of DC Function and Its Impact on GvH Reactions

Promising results from murine models and early stage clinical trials have shown that adoptive transfer of regulatory T cells (Treg) prevents graft-versus-host disease (GvHD). However, the primary target of Treg mediated protection against GvHD is yet to be fully defined. We have previously shown that the presence of Treg during effector T cell priming is able to ameliorate cutaneous GvH reactions in vitro by blocking effector cell migration. This has led to the hypothesis that Treg modulation of dendritic cells (DC) could be a key mechanism by which Treg exert their protective role in GvHD. DC are fundamental for the initiation of allo-reactive immune responses and are critical in GvHD pathogenesis. We investigated the effect of Treg on the phenotypic profile and allo-reactive functions of DCs. Furthermore, the impact of Treg treatment on the ability of DCs to induce GvH target tissue damage was examined for the first time using an in vitro human GvHD skin explant model.Immature, mature and Treg treated DCs were generated from immuno-magnetic isolated monocytes (im-DC, mat-DC and Treg-DC respectively). The three moDC populations were generated using the well-established 6 day culture with GM-CSF and IL-4 followed by 24 hour LPS maturation. Treg were added on day 3 of moDC culture. Im-DC, mat-DC and Treg-DC were harvested on day 7 and tested in parallel as stated below. Prior to functional assays Treg-moDC were isolated by FACS sorting via FSC/SSC/CD3neg gating to remove Treg present in the co-culture.Our results revealed that Treg-DC displayed a semi-mature phenotype with CD83, CD80 and CD86 expression significantly lower than mat-moDC (p<0.005) but significantly higher than im-moDC (P<0.05) whilst HLA-DR levels were comparable to mat-moDC but significantly higher than imDC (p<0.005). Treg-DC also expressed CCR7 comparable to that of im-DC but markedly higher than mat-DC (p=0.052). Distinct morphology of Treg-DC, defined by Giemsa staining, corroborated their semi-mature status. Data from FITC-dextran uptake showed a significant reduction in antigen-capture capacity of Treg treated im-DC compared to untreated im-DC (p=0.047). The Treg mediated functional impairment of DCs was also associated with significantly higher expression of LAP-TGFβ1 on Treg-DC when compared to that of mat-DC (P<0.05). Treg-DC were also markedly defective in stimulating activation and proliferation of allo-reactive CD8 T cells, detected by CD25 expression and CFSE dilution respectively (p=0.009, p=0.046). Interestingly the presence of Treg throughout the entire allo-response induction resulted in a more potent reduction in activation and proliferation than when only the DC were treated with Treg (p=0.009, p=0.0085). Furthermore, allo-reactive CD8 T cells primed with Treg treated moDC were less able to mediate cutaneous GvH tissue damage (Figure 1).In conclusion, attenuation of DC signature and function is key for Treg mediated protection against GvHD. However, isolated DC modulation by Treg was less effective in suppressing CD8 T cell allo-responses compared to the continued presence of Treg during the CD8 T cell priming, activation and proliferation, suggesting that Treg exert most effective function via multidimensional modulation on the DC, T cells and DC-T cell interactions simultaneously. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Imaging through a highly scattering medium with structural similarity and genetic algorithm

A method to recover the image of an object behind a highly scattering medium with higher accuracy is presented. Instead of the Pearson correlation coefficient (PCC) used in the existing methods, structural similarity (SSIM), which is known as an excellent evaluation indicator of image quality, is employed as the cost function for the wavefront optimization. Compared to PCC, better imaging quality can be acquired with SSIM, because the latter comprehensively analyzes the luminance, the contrast, and the structure of imaging results. By comparing the performances of the three commonly used global optimization algorithms, including a genetic algorithm (GA), particle swarm optimization and differential evolution algorithm, we verify that GA has the best reliability and stability to solve this multidimensional wavefront modulation problem among these global optimization algorithms, including in strong noise environments. This work can improve the quality of imaging through a highly scattering medium with a wavefront optimization technique and can be applied to the fields of optical detection or biomedical imaging.

Multi-dimensional modulations of α and γ cortical dynamics following mindfulness-based cognitive therapy in Major Depressive Disorder.

To illuminate candidate neural working mechanisms of Mindfulness-Based Cognitive Therapy (MBCT) in the treatment of recurrent depressive disorder, parallel to the potential interplays between modulations in electro-cortical dynamics and depressive symptom severity and self-compassionate experience. Linear and nonlinear α and γ EEG oscillatory dynamics were examined concomitant to an affective Go/NoGo paradigm, pre-to-post MBCT or natural wait-list, in 51 recurrent depressive patients. Specific EEG variables investigated were; (1) induced event-related (de-) synchronisation (ERD/ERS), (2) evoked power, and (3) inter-/intra-hemispheric coherence. Secondary clinical measures included depressive severity and experiences of self-compassion. MBCT significantly downregulated α and γ power, reflecting increased cortical excitability. Enhanced α-desynchronisation/ERD was observed for negative material opposed to attenuated α-ERD towards positively valenced stimuli, suggesting activation of neural networks usually hypoactive in depression, related to positive emotion regulation. MBCT-related increase in left-intra-hemispheric α-coherence of the fronto-parietal circuit aligned with these synchronisation dynamics. Ameliorated depressive severity and increased self-compassionate experience pre-to-post MBCT correlated with α-ERD change. The multi-dimensional neural mechanisms of MBCT pertain to task-specific linear and non-linear neural synchronisation and connectivity network dynamics. We propose MBCT-related modulations in differing cortical oscillatory bands have discrete excitatory (enacting positive emotionality) and inhibitory (disengaging from negative material) effects, where mediation in the α and γ bands relates to the former.

New Methods for the Visualization of Incommensurately Modulated Structures

While the theory of incommensurate structure and composite crystallography is well established, methods for the visualization of modulated and composite crystal structures are few.[1] At the same time, databases featuring such structures have arisen [2], and there is a growing need for web-based tools that allow users to interactively explore such structures. This presentation is by the principal developer of Jmol, an international open-source collaborative molecular visualization project. It will focus on recent developments that have been made in this area. Jmol provides a flexible and crystallographically rich suite of functionality, including depiction of specific symmetry operations and selective sets of unit cells, selection of specific modes of modulation, use of color to show long-range low-frequency modulation components, and the depiction of relative modulation phasing through animation. From an archival perspective, Jmol development has been an opportunity to test the basic ontology of the IUCr msCIF standard [3], and a number of issues relating to this standard will be discussed, particularly in relation to multidimensional modulation. From an general educational perspective, Jmol for the first time allows easy access to a wide variety of examples of incommensurately and commensurately modulated structures and composite structures. Being accessible on virtually all platforms and within all major browsers, Jmol offers a novel mechanism for the wide-spread dissemination of understanding of this important class of crystal structure.

Multidimensional Constellations for Power-Efficient and Flexible Optical Networks

Multidimensional constellations and time domain hybrid QAM both realize a non-integer ratio of bits per complex 2D symbol in order to allow for flexibility of spectral efficiency. We compare both approaches in terms of symbol error probability, asymptotic power efficiency, and bit error probability. In order to achieve 400G transmission, as an example for a non-integer ratio, an average number of 3.33 bits per complex 2D symbol was chosen, resulting in a symbol rate of 67.2 GBd including 12% FEC overhead. We show a 0.34-dB gain of multidimensional 16-QAM modulation over a hybrid 8-QAM/16-QAM scheme in terms of asymptotic power efficiency.

Joint source-channel coded multidimensional modulation for variable-length codes

Resource-constrained networks such as deep space communications and mobile communications have the phenomena such us large-scale path loss, small-scale fading, and multipath effect, which are very hostile for information transmission. Combining Shannon’s source-channel coding theory with multidimensional modulation, an en/decoding method is proposed in this article called variable-length symbol-level joint source-channel and multidimensional modulation. Utilizing symbol-level source a priori information, an optimized symbol-level L-dimensional M-ary phase shift keying (LD-MPSK) constellation mapping function has been derived, which can increase free Euclidean distance between modulated symbols and enhance the decoding performance. It has been shown in the simulation results that the proposed scheme can achieve more than 2 dB signal-to-noise ratio gains compared with the conventional bit-level schemes under the condition of the same error rate.

Advanced Digital Signal Processing and Coding for Multi-Tb\/s Optical Transport [From the Guest Editors

The articles in this special section aims to highlight diverse recent advances in digital signal processing (DSP)and coding, enabling TbE and multi-TbE optical transport while addressing bandwidth and energy constraints. The addressed topics range from sophisticated modulation and coding schemes to advanced detection schemes. The multi-Tb/s optical transports over either singlemode fibers or few-mode/few-core fibers are also topics covered in this special issue. The main technologies covered by this special issue comprise multiple-input, multiple-output (MIMO) signal processing, advanced multilevel and multidimensional modulation schemes, advanced multiplexing schemes, signal processing for superchannel transmission, advanced DSP for signal detection and equalization, and advanced coding, all aiming at achieving multi-Tb/s optical transports.

Matrix factorization methods for integrative cancer genomics.

With the rapid development of high-throughput sequencing technologies, many groups are generating multi-platform genomic profiles (e.g., DNA methylation and gene expression) for their biological samples. This activity has generated a huge number of so-called "multidimensional genomic datasets," providing unique opportunities and challenges to study coordination among different regulatory levels and discover underlying combinatorial patterns of cellular systems. We summarize a matrix factorization framework to address the challenge of integrating multiple genomic datasets, as well as a semi-supervised variant of the method that can incorporate prior knowledge. The basic idea is to project the different kinds of genomic data onto a common coordinate system, wherein genetic variables that are strongly correlated in a subset of samples form a multidimensional module. In the context of cancer biology, such modules reveal perturbed pathways and clinically distinct patient subgroups that would have been overlooked with only a single type of data. In summary, the matrix factorization framework can uncover associations between distinct layers of cellular activity and explain their biological implications in multidimensional data.

Unitary Differential Space-Time-Frequency Codes for MB-OFDM UWB Wireless Communications

In a multiple-input multiple-output (MIMO), multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) system, coherent detection requires the transmission of a large number of symbols for channel estimation, thus reducing the bandwidth efficiency. For the first time, this paper proposes unitary differential space-time-frequency codes (DSTFCs) for MB-OFDM UWB communications, which increase the system bandwidth efficiency because no channel state information (CSI) is required. The proposed system would be useful when CSI is unavailable at the receiver, such as when the transmission of multiple channel estimation symbols is impractical or uneconomical. The coding and decoding algorithms for the proposed DSTFCs are then derived for both constant envelope modulation scheme, such as PSK (phase shift keying) and 4QAM (quadrature amplitude modulation), and multi-dimensional modulation scheme, such as DCM (dual carrier modulation). The paper also quantifies for the first time the diversity order of a DSTFC MB-OFDM system. Simulation results show that the application of DSTFCs can significantly improve the bit error performance of conventional differential MB-OFDM system (without MIMO), and even provide much better bit error performance than the conventional coherent MB-OFDM system (without MIMO) at high signal-to-noise ratios.

Experimental Investigations of 3-D-/4-D-CAP Modulation With Directly Modulated VCSELs

In this letter, we present experimental investigations of multidimensional multilevel carrierless amplitude phase (CAP) modulation with directly modulated vertical cavity surface-emitting lasers. The signals are transmitted over 20 km of standard single-mode fiber (SSMF). For multilevel 3-D-CAP, bit rates of 468.75 and 937.5 Mb/s are achieved at two levels/dimension and four levels/dimension, respectively. For 4-D-CAP, bit rates of 416.67 and 833.3 Mb/s are achieved at two levels/dimension and four levels/dimension, respectively. For all signals, a bit-error rate below the forward error correction limit of 2.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> for error-free reception is achieved after 20 km of SSMF transmission. Spectral efficiencies of 2.68 and 2.08 b/s/Hz are reported for 3-D-CAP and 4-D-CAP, respectively. We believe that multidimensional modulation formats represent an attractive solution for providing more flexibility for optical fiber systems.

A Pragmatic Approach to Assessing Structure-specific Dosimetric Error of VMAT Delivery

VMAT adopts a multi-dimensional modulation methodology. However, multi-dimensional modulations present multi-dimensional challenges. Firstly, electro-mechanically, the multi-dimensional modulation paradigm tends to perform less reliably than its one-dimensional pre-cursor. Secondly, for plans demanding extensive gantry angular speed modulation, persistent acceleration and deceleration could lead to dosimetric error due to mechanical constraint. Temporal dose rate modulation with high frequency and amplitude results in the same dosimetric consequences because of the time delay and imperfect beam pulses. More significantly, beam hold-off signals are not asserted for VMAT due to the excessive rotational inertia of the LINAC head. Consequently, it is not surprising to observe larger leaf RMS errors for VMAT plans than those for IMRT plans. The compounding effects of all these impose a significant technical challenge in clinical situations where steep dose gradients need to be accurately verified and faithfully delivered. Although there are QA tools to measure delivered doses, they, in general, either lack the required spatial resolution or detect the peripheral dose only or require extensive post-irradiation processing and are not structure-specific. Here, we present a practical and efficient approach to retrospectively calculating actually delivered dose using VMAT Dynalog files. The VMAT DynaLog file was an extensive treatment log file that contained the theoretical and actual leaf positions at the MLC physical plane at a given gantry angle and was automatically saved on the 4-Dimensional Integrated Treatment Console (4DITC). The leaf positions were sampled at a time interval of 50 ms. Due to beam divergence and rounded-leaf-end design, the physical leaf positions were converted to the projected positions at the iso-plane using a polynomial model. The actually delivered DVA file was then reconstructed iteratively and fed back to our homegrown VMAT planning system for forward dose calculation. Dosimetric parameters of clinical significance between the planned and reconstructed were then compared. It was found that there were observable differences between the planned and delivered doses in several important dosimetric parameters. For D95, the planned and delivered doses were 98.97% and 96.55%, respectively. The same trend was also observed for V95, which was 99.04% and 97.12% for the planned and delivered. The PTV Dmin was 105.09% and 103.46%, respectively. The same dosimetric behavior was detected for a group of randomly sampled VMAT patients, revealing potential delivery hardware deficiency. We developed a pragmatic and efficient technique to assess delivered VMAT doses to specific structures. The method provides concrete dosimetric evidence for adaptive VMAT treatment planning.

Discovery of multi-dimensional modules by integrative analysis of cancer genomic data

Recent technology has made it possible to simultaneously perform multi-platform genomic profiling (e.g. DNA methylation (DM) and gene expression (GE)) of biological samples, resulting in so-called ‘multi-dimensional genomic data’. Such data provide unique opportunities to study the coordination between regulatory mechanisms on multiple levels. However, integrative analysis of multi-dimensional genomics data for the discovery of combinatorial patterns is currently lacking. Here, we adopt a joint matrix factorization technique to address this challenge. This method projects multiple types of genomic data onto a common coordinate system, in which heterogeneous variables weighted highly in the same projected direction form a multi-dimensional module (md-module). Genomic variables in such modules are characterized by significant correlations and likely functional associations. We applied this method to the DM, GE, and microRNA expression data of 385 ovarian cancer samples from the The Cancer Genome Atlas project. These md-modules revealed perturbed pathways that would have been overlooked with only a single type of data, uncovered associations between different layers of cellular activities and allowed the identification of clinically distinct patient subgroups. Our study provides an useful protocol for uncovering hidden patterns and their biological implications in multi-dimensional ‘omic’ data.

Crystalline chiral condensates off the tricritical point in a generalized Ginzburg-Landau approach

We present an extensive study on inhomogeneous chiral condensates in QCD at finite density in the chiral limit using a generalized Ginzburg-Landau (GL) approach. Performing analyses on higher harmonics of one-dimensionally (1D) modulated condensates, we numerically confirm the previous claim that the solitonic chiral condensate characterized by Jacobi's elliptic function is the most favorable structure in 1D modulations. We then investigate the possibility of realization of several multidimensional modulations within the same framework. We also study the phase structure far away from the tricritical point by extending the GL functional expanded up to the eighth order in the order parameter and its spatial derivative. On the same basis, we explore a new regime in the extended GL parameter space and find that the Lifshitz point is the point where five critical lines meet at once. In particular, the existence of an intriguing triple point is demonstrated, and its trajectory consists of one of those critical lines.

Study on Modular Design Method for CNC Lathe

A multi-dimensional module partition methodology is put forward for CNC lathe, in which not only the functional module partition and the physical structure module partition of CNC machine tools are taken into account, but the characteristics of different stages of in the whole life-cycle of machine tools is considered as well. On the basis of this the principle of module partition for CNC machine tools are presented. The mechanical structure system of CNC lathe is elaborated on the functional module and structural module. A CNC machine tool company’s HTC Series CNC lathes modular design is illustrated as an example.

Spatial-domain-based multidimensional modulation for multi-Tb/s serial optical transmission

The multidimensional channel capacity studies indicate that the employment of multiple photon degrees of freedom-such as subcarrier, amplitude, phase, polarization, and space-can improve the spectral efficiency by several orders of magnitude higher than that claimed in any fiber-optic experiment reported to date. This dramatic increase in spectral efficiency through multiple photon degrees of freedom can provide revolutionary capabilities for future optical networks. Moreover, photons can carry both spin angular momentum (SAM) associated with polarization, and orbital angular momentum (OAM) associated with the azimuthal phase of the complex electric field. Because OAM eigenstates are orthogonal, an arbitrary number of bits per photon can be transmitted in principle. The ability to generate the OAM modes, such as Bessel modes, in multimode fibers (MMFs) will allow realization of fiber-optic communication networks with ultra-high bits-per-photon efficiencies. To this end, we propose here a spatial-domain-based multidimensional coded-modulation scheme as an enabling technology for multi-Tb/s serial optical transport. To demonstrate the capabilities of the proposed scheme, we show that an eight-dimensional (8D) spatial-domain-based coded modulation scheme outperforms a prior-art 128-point 4D scheme by 3.88 dB at BER of 10(-8) while providing 120 Gb/s higher aggregate information bit rate. The proposed 8D scheme also outperforms its conventional polarization-multiplexed QAM counterpart by even a larger, and indeed striking, margin of 8.39 dB (also at the BER of 10(-8)).

DPC Rates and Multiplexing Gains for MIMO Broadcast Systems with Multi-Dimensional Space-Time Modulation

This paper considers multiple-antenna broadcast channels (BCs) with multi-dimensional space-time modulation schemes, created by various allocations of signal dimensions to transmit antennas. The signal dimensions are divided into disjoint subsets, where one is shared between all users, and each of the others are assigned to different users. This model encompasses several practical single point to multi-point wireless communication systems employing multiple antennas. Assuming space and time dispersive channels, we consider the transmission rates that are achieved by applying dirty paper coding (DPC) at the transmitter, present inner and outer bounds for the DPC rate region, and study the effects of space-time modulation formats. At high SNR, we consider the limit form of these bounds, derive an achievable multiplexing gain region, and study the effects of sharing signal dimensions between users.

Numerically Optimized Uniformly Most Powerful Alphabets for Hierarchical-Decode-and-Forward Two-Way Relaying

We address the issue of the parametric performance of the Hierarchical-Decode-and-Forward (HDF) strategy in a wireless 2-way relay channel. Promising HDF, representing the concept of wireless network coding, performs well with a pre-coding strategy that requires Channel State Information (CSI) on the transceiver side. Assuming a practical case when CSI is available only on the receiver side and the channel conditions do not allow adaptive strategies, the parametrization causes significant HDF performance degradation for some modulation alphabets. Alphabets that are robust to the parametrization (denoted Uniformly Most Powerful (UMP)) have already been proposed restricting on the class of non-linear multi-dimensional frequency modulations. In this work, we focus on the general design of unrestricted UMP alphabets. We formulate an optimization problem which is solved by standard non-linear convex constrained optimization algorithms, particularly by Nelder-Mead global optimization search, which is further refined by the local interior-pointsmethod.

Traversing the Chasm from School to University in South Africa: A student perspective

Under‐preparedness of students entering university has become increasingly challenging as South African universities struggle to ensure student success where schooling no longer provides sufficient preparation for university. Understanding the gap between being eligible and being ready for university study is of critical importance. Using Conley's multidimensional module of college readiness, the perspectives of first‐year students regarding their transition from school to university are explored. The paper argues that greatest difficulty is faced in the facets of academic behaviours and “university knowledge”, and that one worrying coping mechanism is a growing acceptance of mediocrity or failure.