34 research outputs found
A New DoF Upper Bound and Its Achievability for -User MIMO Y Channels
This work is to study the degrees of freedom (DoF) for the -user MIMO Y
channel. Previously, two transmission frameworks have been proposed for the DoF
analysis when , where and denote the number of antennas at
each source node and the relay node respectively. The first method is named as
signal group based alignment proposed by Hua et al. in [1]. The second is named
as signal pattern approach introduced by Wang et al. in [2]. But both of them
only studied certain antenna configurations. The maximum achievable DoF in the
general case still remains unknown. In this work, we first derive a new upper
bound of the DoF using the genie-aided approach. Then, we propose a more
general transmission framework, generalized signal alignment (GSA), and show
that the previous two methods are both special cases of GSA. With GSA, we prove
that the new DoF upper bound is achievable when . The DoF
analysis in this paper provides a major step forward towards the fundamental
capacity limit of the -user MIMO Y channel. It also offers a new approach of
integrating interference alignment with physical layer network coding.Comment: 6 pages, 3 figures, submitted to IEEE ICC 2015. arXiv admin note:
text overlap with arXiv:1405.071
Exploiting Tradeoff Between Transmission Diversity and Content Diversity in Multi-Cell Edge Caching
Caching in multi-cell networks faces a well-known dilemma, i.e., to cache
same contents among multiple edge nodes (ENs) to enable transmission
cooperation/diversity for higher transmission efficiency, or to cache different
contents to enable content diversity for higher cache hit rate. In this work,
we introduce a partition-based caching to exploit the tradeoff between
transmission diversity and content diversity in a multi-cell edge caching
networks with single user only. The performance is characterized by the system
average outage probability, which can be viewed as the sum of the cache hit
outage probability and cache miss probability. We show that (i) In the low
signal-to-noise ratio(SNR) region, the ENs are encouraged to cache more
fractions of the most popular files so as to better exploit the transmission
diversity for the most popular content; (ii) In the high SNR region, the ENs
are encouraged to cache more files with less fractions of each so as to better
exploit the content diversity.Comment: Accepted by IEEE International Conference on Communications (ICC),
Kansas City, MO, USA, May 201
Generalized Signal Alignment For MIMO Two-Way X Relay Channels
We study the degrees of freedom (DoF) of MIMO two-way X relay channels.
Previous work studied the case , where and denote the number of
antennas at the relay and each source, respectively, and showed that the
maximum DoF of is achievable when by
applying signal alignment (SA) for network coding and interference cancelation.
This work considers the case where the performance is limited by the
number of antennas at each source node and conventional SA is not feasible. We
propose a \textit{generalized signal alignment} (GSA) based transmission
scheme. The key is to let the signals to be exchanged between every source node
align in a transformed subspace, rather than the direct subspace, at the relay
so as to form network-coded signals. This is realized by jointly designing the
precoding matrices at all source nodes and the processing matrix at the relay.
Moreover, the aligned subspaces are orthogonal to each other. By applying the
GSA, we show that the DoF upper bound is achievable when ( is even) or ( is odd). Numerical results also demonstrate
that our proposed transmission scheme is feasible and effective.Comment: 6 pages, 6 figures, to appear in IEEE ICC 201
Soliton generation in CaF crystalline whispering gallery mode resonators with negative thermal-optical effects
Calcium fluoride (CaF) crystalline whispering gallery mode resonators
(WGMRs) exhibit ultrahigh intrinsic quality factors and a low power anomalous
dispersion in the communication and mid-infrared bands, making them attractive
platforms for microresonator-based comb generation. However, their unique
negative thermo-optic effects pose challenges when achieving thermal
equilibrium. To our knowledge, our experiments serve as the first demonstration
of soliton microcombs in Q > 109 CaF WGMRs. We observed soliton
mode-locking and bidirectional switching of soliton numbers caused by the
negative thermo-optic effects. Additionally, various soliton formation dynamics
are shown, including breathing and vibrational solitons, which can be
attributed to thermo-photomechanical oscillations. Thus, our results enrich the
soliton generation platform and provide a reference for generating solitons
from WGMRs that comprise other materials with negative thermo-optic effects. In
the future, the ultrahigh quality factor of CaF crystal cavities may enable
the generation of sub-milliwatt-level broad-spectrum soliton combs.Comment: 4 pages,5 pictures,description of soliton generation in a calcium
fluoride whisper gallery mode microresonators with negative thermo-optical
effect,ready for publication in optics lette
Towards a compact soliton microcomb fully referenced on atomic reference
A fully stabilized soliton microcomb is critical for many applications of
optical frequency comb based on microresonators. However, the current
approaches for full frequency stabilization require either external
acousto-optic or electro-optic devices or auxiliary lasers and multiple
phase-locked loops, which compromises the convenience of the system. This study
explores a compact atomic referenced fully stabilized soliton microcomb that
directly uses a rubidium atomic optical frequency reference as the pump source,
and complements the repetition rate (7.3 GHz) of the soliton microcomb was
phase-locked to an atomic-clock-stabilized radio frequency (RF) reference by
mechanically tuning the resonance of the optical resonator. The results
demonstrate that the stability of the comb line (0.66 THz away from the pump
line) is consistent with that of the Rb87 optical reference, attaining a level
of approximately 4 Hz @100 s, corresponding to the frequency stability of 2E-14
@100 s. Furthermore,the frequency reproducibility of the comb line was
evaluated over six days and it was discovered that the standard deviation (SD)
of the frequency of the comb line is 10 kHz, resulting in a corresponding
absolute deviation uncertainty of 1.3E-10, which is technically limited by the
locking range of the soliton repetition rate. The proposed method gives a
low-power and compact solution for fully stabilized soliton micorcombs.Comment: 6 pages, 5 figure
How to Survive between "Standardized Resident Training " and "Professional Master" -On the Difficulties Encountered in Undergraduate Clinical Practice
To review on the difficulties encountered by medical bachelor students for their career development after graduation, and to explore potential solutions to their current situation, thus provide them possibilities of making good use of professional training and skills acquired in campus
Effects of mulberry twig alkaloids(Sangzhi alkaloids) and metformin on blood glucose fluctuations in combination with premixed insulin-treated patients with type 2 diabetes
IntroductionWe aimed to evaluated the effect of premixed insulin (Ins), premixed insulin combined with metformin (Ins+Met) or mulberry twig alkaloids(Ins+SZ-A) on blood glucose fluctuations in patients with type 2 diabetes (T2DM) using continuous glucose monitors (CGM).MethodsThirty patients with T2DM and poor blood glucose control using drugs were evaluated for eligibility during the screening period. Subsequently, their original hypoglycemic drugs were discontinued during the lead-in period, and after receiving Ins intensive treatment for 2 weeks, they were randomly assigned to receive either Ins, Ins+Met, or Ins+SZ-A treatment for the following 12 weeks. The main efficacy endpoint comprised changes in their CGM indicators changes (mean blood glucose level [MBG], standard deviation of blood glucose [SDBG], mean amplitude of glycemic excursions [MAGE], postprandial glucose excursions [PPGE], the largest amplitude of glycemic excursions [LAGE], mean of daily difference [MODD], time in range between 3.9–10.0 mmol/L [TIR] and area under the curve for each meal [AUCpp]) during the screening, lead-in, and after 12-week treatment period. Changes in glycosylated hemoglobin (HbA1c), fasting blood glucose (FBG), 1-h postprandial blood glucose (1h-PBG), 2-h postprandial blood glucose (2h-PBG), fasting blood lipids and postprandial blood lipids were also measured at baseline and after 12 weeks of treatmentResultsThe CGM indicators of the three groups during the lead-in period all showed significant improvements compared to the screening period (P<0.05). Compared with those in the lead-in period, all of the CGM indicators improved in the the Ins+Met and Ins+SZ-A groups after 12 weeks of treatment (P<0.05), except for MODD. After 12-week treatment, compared with the Ins group, Ins+Met and Ins+SZ-A groups showed improved MBG, SDBG, TIR, breakfast AUCpp,lunch AUCpp, HbA1c, FBG, 1h-PBG, fasting blood lipid and postprandial blood lipid indicators (P<0.05). Further, the LAGE, PPGE, MAGE, dinner AUCpp and 2h-PBG levels of the Ins+SZ-A group were significantly lower than those of the Ins+Met and Ins groups (P<0.05).ConclusionOur findings highlight the efficacy of combination therapy (Ins+SZ-A or Ins+Met) in improving blood glucose fluctuations, as well as blood glucose and lipid levels. Ins+SZ-A reduces postprandial blood glucose fluctuations more than Ins+Met and Ins groups.Trial registration numberISRCTN20835488
Analysis of the Constituents in Rat Serum after Oral Administration of Fufang Zhenzhu Tiaozhi Capsule by UPLC–Q–TOF–MS/MS
A rapid and sensitive UPLC/Q–TOF–MS method has been established for analysis of the constituents in rat serum after oral administration of Fufang Zhenzhu Tiaozhi (FTZ) capsule, an effective compound prescription for treating hyperlipidemia in the clinic. The UPLC/MS information of samples was obtained first in FTZ preparation and FTZ-treated rat serum. Mass spectra were acquired in both negative and positive ion modes. Thirty-six constituents in rat serum after oral administration of FTZ were detected, including the alkaloids, ginsenosides, pentacyclic triterpenes, and their metabolites. These chemicals were identified based on the retention time and mass spectrometry data with those of authentic standards or comparison of the literatures reports. Twenty-seven prototype components originated from FTZ and nine were the metabolites of the FTZ constituents. These results shed light on the potential active constituents of the complex traditional Chinese medicinal formulas