Transverse Bragg-resonant enhancement of modulation and switching

We demonstrate theoretically that the electrooptic phase retardation, hence, modulation, can be enhanced very substantially in transverse Bragg resonance (TBR) waveguides. This enhancement is due fundamentally to the strong dependence of the dispersion of the TBR waveguide on the Bragg condition. Both theoretical and numerical analysis show that this enhancement can be used to improve the performance of directional coupler switches and electroabsorption modulators, leading potentially to major reductions in the device size or the switching voltage/current

Direct Virtual Memory Access from FPGA for High-Productivity Heterogeneous Computing

Heterogeneous computing utilizing both CPU and FPGA requires access to data in the main memory from both devices. While a typical system relies on software executing on the CPU to orchestrate all data movements between the FPGA and the main memory, our demo presents a complementary FPGA-centric approach that allows gateware to directly access the virtual memory space as part of the executing process without involving the CPU. A caching address translation buffer was implemented alongside the user FPGA gateware to provide runtime mapping between virtual and physical memory addresses. The system was implemented on a commercial off-the-shelf FPGA add-on card to demonstrate the viability of such approach in low-cost systems. Experiment demonstrated reasonable performance improvement when compared to a typical software-centric implementation; while the number of context switches between FPGA and CPU in both kernel and user mode was significantly reduced, freeing the CPU for other concurrent user tasks. © 2013 IEEE.published_or_final_versio

A perceptual based rate control scheme for MPEG-2

In this paper, a new perceptual based rate control algorithm for MPEG-2 is presented. The algorithm first determines the target bit count for each frame using simple statistical models. Precise bit allocation is used to adjust the macroblock quantization scale factors to meet the given bit count, with the uniform visual fidelity as the primary objective. Since the buffer is very stable, it is less sensitive to transmission delay, Experimental results showed that it gave better visual quality and less buffer variations as compared to the TM5 rate control scheme.published_or_final_versio

A new fast motion estimation algorithm using hexagonal subsampling pattern and multiple candidates search

In this paper we present a fast algorithm to reduce the computational complexity of block motion estimation. The reduction is obtained from the use of a new hexagonal subsampling pattern and the domain decimation method introduced by Cheng and Chan (see Proc. IEEE ICASSP, vol.4, p.2313, 1996). The multiple candidates search method is also introduced to improve the robustness of the algorithm. Computer simulation shows that the performance is very close to that of the full search.published_or_final_versio

Post-processing of transform coded images using selective filtering and fuzzy-based enhancement

Transform coding often leads to artifacts called blocking when the image or video is compressed to low bit-rate. In this paper, a new post-processing scheme using selective low-pass filtering and fuzzy-based enhancement is proposed. The merit of the scheme is that it can remove most of the blocking artifacts found in image or video coding while preserving most of the fine details. Simulation results demonstrated that the proposed algorithm can significantly improve the visual quality of the decoded image.published_or_final_versio

Multiresolution motion compensation coding for video compression

Motion estimation using block matching algorithm (BMA) is frequently used to reduced the temporal redundancy found in video coding. The performance of the mean squared error (MSE) is usually better than the mean absolute difference (MAD). However, the computational complexity is higher due to the squaring operations. In this paper, we propose a multiple candidates approach to shorten the gap between the two methods with slight increase in computational complexity. Application of the proposed algorithm to subband motion-estimation is studied and simulation results demonstrate that great improvement in performance can be obtained with similar computational complexity as the MAD measure.published_or_final_versio

Social Comparisons in Social Exercise Apps

A key strategy to combat sedentary lifestyle is to encourage fitness exercises. Traditional wellness and lifestyle management programs focus on inducing health awareness and providing fitness activity support. The growing pervasive use of smartphones allows individualized and cost-effective digital wellness programs to be administrated through mobile fitness apps. Drawing on the social comparison theory, this study plans to explore ways to effectively design social comparison mechanisms to help promote physical exercises. Additionally, this study proposes a unique field experiment that enables fine- grained manipulation of social comparisons and present an opportunity to observe network evolutions over time

{3,14-Dimethyl-2,6,13,17-tetra­aza­tricyclo­[16.4.0.07,12]docosane-κ4 N,N′,N′′,N′′′)bis­(nitrato-κO)copper(II)

The CuII atom in the title compound, [Cu(NO3)2(C20H40N4)], is N,N′,N′′,N′′′-chelated by the macrocyclic ligand: the four N atoms form a square, above and below which are located the O atoms of the nitrate ions. The metal atom exists in a tetra­gonally distorted octa­hedron, on a special position of site symmetry. One of the amino groups is hydrogen bonded to an O atom of the nitrate ion. The other amino group is hydrogen bonded to O atom of an adjacent mol­ecule, generating a supra­molecular dimeric hydrogen-bonded dinuclear aggregate

Unstable angina early after aortic valve replacement surgery in a female patient with normal coronary arteries preoperatively – a case report

<p>Abstract</p> <p>Background</p> <p>Angina pectoris early after aortic valve replacement surgery in patients with previously normal coronary arteries may be life threatening and has to be assessed immediately.</p> <p>Case report</p> <p>12 weeks after aortic valve replacement surgery, a 60-year-old female patient was referred for evaluation of recent onset of severe chest pain on mild exertion and at rest. Coronary angiography showed severe stenosis nvolving the left coronary ostium and the left main stem. The patient was urgently referred for bypass surgery and had an uneventful postoperative recovery.</p> <p>Conclusion</p> <p>A high degree of suspicion is needed for early recognition and aggressive management of this rare but serious complication.</p