Real-time wavefront processors for the next generation of adaptive optics systems: a design and analysis

Adaptive optics (AO) systems currently under investigation will require at least two orders of magitude increase in the number of actuators, which in turn translates to effectively a 104 increase in compute latency. Since the performance of an AO system invariably improves as the compute latency decreases, it is important to study how today's computer systems will scale to address this expected increase in actuator utilization. This paper answers this question by characterizing the performance of a single deformable mirror (DM) Shack-Hartmann natural guide star AO system implemented on the present-generation digital signal processor (DSP) TMS320C6701 from Texas Instruments. We derive the compute latency of such a system in terms of a few basic parameters, such as the number of DM actuators, the number of data channels used to read out the camera pixels, the number of DSPs, the available memory bandwidth, as well as the inter-processor communication (IPC) bandwidth and the pixel transfer rate. We show how the results would scale for future systems that utilizes multiple DMs and guide stars. We demonstrate that the principal performance bottleneck of such a system is the available memory bandwidth of the processors and to lesser extent the IPC bandwidth. This paper concludes with suggestions for mitigating this bottleneck

Investigating the dynamic process of value co-creation and value co-destruction in Self-Service Technology

To a certain degree, Self-service technology (SST) has been proved to be one of successful and profitable business models, yet not always SST is implemented properly so that customers can derive expected values from such technology-based systems. Since this area has not been paid enough attention from extant scholars in both IT and service area, the current study aims to investigate the dynamic process of successful and failed SST; in other words, we employed the Service Dominant Logic lens to examine the dynamic phenomenon of value co-creation and value co- destruction when customers participating in a SST encounter process. In terms of academic contributions, our study is going to add more theoretical foundations for the “dark side” of IT integrated system lik e SST. Additionally, we also build a conceptual model which poses a dynamical nature of SST usage process. Equally important, we expect our study producing significant practical implications for SST providers

Energy-efficient precoding in multicell networks with full-duplex base stations

© 2017, The Author(s). This paper considers multi-input multi-output (MIMO) multicell networks, where the base stations (BSs) are full-duplex transceivers, while uplink and downlink users are equipped with multiple antennas and operate in a half-duplex mode. The problem of interest is to design linear precoders for BSs and users to optimize the network’s energy efficiency. Given that the energy efficiency objective is not a ratio of concave and convex functions, the commonly used Dinkelbach-type algorithms are not applicable. We develop a low-complexity path-following algorithm that only invokes one simple convex quadratic program at each iteration, which converges at least to the local optimum. Numerical results demonstrate the performance advantage of our proposed algorithm in terms of energy efficiency

Energy-efficient precoding in multicell networks with full-duplex base stations

© 2017, The Author(s). This paper considers multi-input multi-output (MIMO) multicell networks, where the base stations (BSs) are full-duplex transceivers, while uplink and downlink users are equipped with multiple antennas and operate in a half-duplex mode. The problem of interest is to design linear precoders for BSs and users to optimize the network’s energy efficiency. Given that the energy efficiency objective is not a ratio of concave and convex functions, the commonly used Dinkelbach-type algorithms are not applicable. We develop a low-complexity path-following algorithm that only invokes one simple convex quadratic program at each iteration, which converges at least to the local optimum. Numerical results demonstrate the performance advantage of our proposed algorithm in terms of energy efficiency

Trellis orthogonal reconstruction algorithm based on orthogonal space-time block code for wireless communication system in high-speed railway

A detailed analysis of open-loop (OL) and closed-loop (CL) multiple input multiple output (MIMO) scheme based on orthogonal space-time block code (OSTBC), and lays emphasis on how the velocity influences the OSTBC in high-speed railway scenario is provided. When the train moves at a fantastic speed, the fast time-varying channel destroys the orthogonality of OSTBC reducing the diversity gain which would severely degrade the bit error rate (BER) perform-ance. The trellis orthogonal reconstruction algorithm (TORA), in which the intra-code orthogonality is reconstructed through givens transformation and the transmit beamforming direction can be changed as well is proposed. In high-speed railway scenario, this proposal obtains not only the array gain by transmit beamforming, but also the same diversity gain as the train is motionless. The simulation shows that the TORA improves BER performance of MIMO schemes based on OSTBC for mobile communication system in high-speed railway

Effects of combined intervention of physical exercise and cognitive training on cognitive function in stroke survivors with vascular cognitive impairment: a randomized controlled trial

Objective: This study evaluated the possible effect of the combined intervention of physical exercise and cognitive training on cognitive function in stroke survivals with vascular cognitive impairment. Design: A single-blind (investigator-blinded but not subject-blinded) randomized controlled trial. Setting: Medical Rehabilitation Center of Shanghai General Hospital, China. Subjects: A total of 225 patients (mean age 64.59 years, SD = 4.27) who exhibited vascular cognitive impairment were included in this study. Interventions: Patients were randomly allocated into one of the four groups: (1) physical exercise (n = 56; 50-minute session), (2) cognitive training (n = 57; 60-minute session), (3) combined intervention of physical exercise and cognitive training (n = 55; 50-minute session + 60-minute session), or (4) control groups (n = 57; 45-minute session). All participants received training for 36 sessions, three days per week, for 12 weeks. Primary measures: Measures were recorded at baseline, after the intervention and at a six-month follow-up. Primary measurements included the Trail Making Part B, Stroop, forward digit span, and mental rotation tests. Results: A total of 179 participants (79.56% response rate) completed the study. Cognitive performances on all four tasks in the combined training group improved significantly after the intervention (P < 0.01). Changes in cognitive performance were greater in the combined intervention group than those in the physical exercise group (e.g. forward digit span, 13.61% vs. 2.18%, P = 0.003), the cognitive training group (e.g. mental rotation, 17.36% vs. 0.87%, P = 0.002), and the control group (e.g. Stroop, −4.11% vs. −0.72%, P = 0.026). Conclusion: The combined intervention produced greater benefits on cognitive function compared to either training alone in stroke survivors with vascular cognitive impairment.måsjekke

Effects of an acute bout of light-intensity walking on sleep in older women with sleep impairment: A randomized controlled trial

Study objective: This study aimed to explore the effects of a single bout of light-intensity walking on sleep in older women with mild sleep impairment. Methods: A total of 40 women aged 55 years or above with mild sleep impairment were randomized to either a treadmill-walking session for 50 mins or a quiet-rest control. All participants completed the study (mean age: 60.4±4.7). Sleep quality was assessed by ActiGraph for 2 nights before (pre-test) and 2 nights after exercise (post-test). A mixed-design analysis of variance was used with group as the between-subjects factor and time point as the within-subjects factor. Results: No significant group difference on demographic variables, body mass index, physical and mental status, and eight sleep parameters were observed at baseline. Significant group-time interactions existed for sleep latency (p<0.001) and sleep efficiency (p=0.025). After the intervention, the walking group reduced sleep latency by 3.3 minutes (p=0.001) and also had greater sleep efficiency (increase 3.8%, p=0.008), but no significant change was found in the control group. No significant group-time interactions were present for the other six sleep parameters (activity counts, total sleep time, wake after sleep onset, number and length of awakenings, or time in bed). Conclusion: A single session of light-intensity walking led to a modest reduction in sleep latency and improvement of sleep efficiency in older women with mild sleep impairment

Transmission scheme and capacity analysis of onboard multi-antenna system in high-speed train

Based on the three-dimensional modeling of line-of-sight SIMO (single-input multiple-output) channel for high-speed railway, which adopts uniform linear receiving array, the channel capacity of N -group receiving arrays was analyzed. The combining capacity grows but vibrates near base station and falls to Shannon capacity quickly. Instead of increasing group numbers of receiving arrays simply, stable capacity can be obtained by adjusting array parameters, grouping arrays and changing array weights among groups. The computer simulation results illustrate that proper setting would get stable channel capacity and avoid oscillation when the train is passing through the base stations