可区分回波通道变化和双端话音的检测算法研究

自适应声回波对消器中,可区分回波通道变化EPC(Echo Pass Change)和双端话音DT(Double-Talk)的检测算法非常重要,以确保自适应滤波器在EPC时更新权系数,在DT期间冻结权系数.提出了两种检测算法:算法1利用自适应滤波器误差信号的平均幅度,并结合误差信号和自适应滤波器输出信号的互相关系数来区分DT和EPC;算法2借助一个辅助滤波器来完成EPC和DT的检测,同时能加快主滤波器的收敛.仿真结果表明,所提出的检测算法能有效区分EPC和DT,提高了回波对消器性能.

多通道变化盲:理论、方法与进展

人们在特定条件下通常难以探测到事物的变化,这种现象发生在视、听、触感觉通道分别称为变化盲视、变话盲听和变化盲触。文章主要对以下四个方面进行详细的探讨:变化盲视及视觉表征理论、变化盲听及听觉信息加工机制、变化盲触及体表空间表征、多通道变化盲及空间注意和空间表征跨通道一致性本质。此外,文章还对多通道变化盲的理论深度和拓展方向及相关应用研究进行了展望。

肌浆网Ca^(2+)-ATP酶和L型-Ca^(2+)通道功能变化对肥厚心室肌电重构的影响

为探讨肌浆网Ca2 + ATP酶和L型 Ca2 +通道功能变化在左室肥厚 (LVH)心室肌电重构发生中的作用。将 60只日本大耳白兔随机分为 6组 :单纯实验组、实验组 +维拉帕米、实验组 +Thapsigargin、单纯对照组、对照组 +维拉帕米和对照组 +Thapsigargin。实验组行腹主动脉部分结扎术 ,喂养 1 0周制作LVH模型。对照组在游离出腹主动脉后 ,不予结扎。均采用以Langendorff离体灌流方法。对单纯实验组和单纯对照组 ,在心外膜左室心尖部部位以 2 31ms为基础周长 (BCL)测定心室有效不应期 (VERP)后 ,于右房行电刺激 ,刺激频率为 2 60次 /分 ,持续 30min ,保持 1 1房室传导。刺激结束后 ,重复测定VERP值。对其余 4组 ,先测定未加药物时各组的VERP值 ,随后改用加入药物的灌流液后再次测定VERP值 ,最后进行右房刺激及VERP的测定 (同前 )。结果 :单纯实验组在快速刺激后 ,VERP显著延长 ,其延长程度显著大于单纯对照组 ;而在加用维拉帕米的实验组和对照组中 ,快速刺激后无VERP延长的表现 ;相反 ,Thapsigargin则可增强快速刺激后VERP延长的表现。结论 :L 型Ca2 +通道的激活可能是LVH心室肌电重构发生的重要原因。其中 ,心室肌细胞肌浆网Ca2 + ATP酶的功能降低参与了此过程 ,并可能导致了LVH与正常心室肌的频率相关性电重构?

Microecosystem of ostiomeatal complex and the changes via functional endoscopic sinus surgery

Objective: To study the composition of microecosystem in ostiomeatal complex (OMC) of adults and the changes via functional endoscopic sinus surgery. Methods: 220 adults with chronic sinusitis(20 as control) were classified into pre- and post-operative groups, and categorised according to its type of sinusitis. Swab specimens were taken from three different sites of ostiomeatal complex in each individual, and cultivations and identifications of aerobes, anaerobes and fungi were performed simultaneously. The microecosystem was analysed. Results: Cultured aerobes belonged to 30 species from 13 genera, anaerobes species, and fungi 3 major species, most of which have none or less virulence. The difference of mi-croecological status between type Ⅰ and Ⅱ was not significant (P > 0.05). Aerobic culture rates between preoperative group and control group had significance(P < 0.01);culture rate descended in postoperative group while the difference was not significant compared to preoperative group (P > 0. 05); difference of rate of same aerobic culture from three sites (RSAC) , which reflects the microecological integrity of OMC, between preoperative and control group was significant (P < 0.01), while was not between postoperative group and control one(P > 0. 05). Taking fungi into account, differences among all groups had no significance(P>0.05); anaerobes were rare in all groups. Conclusion: Being a microecosystem under normal condition, ostiomeatal complex is relatively clean and exists as a whole space. Chronic inflammations separate different parts of which from each other with multimicrobial existence.FESS reverses separation of the microecosystem and rebuild it as a whole again, thus promote the recovery.

SEQUENCE VARIABILITY OF HUMAN CYTOMEGALOVIRUS UL144 OPEN READING FRAME IN LOW-PASSAGE CLINICAL ISOLATES

Objective To explore the relationship between human cytomegalovirus (HCMV) UL144 sequence variability and clinical disease. Methods HCMV UL144 open reading frame (ORF) was amplified by PCR assay in 72 lowpassage isolates [65 con-genitally infective children and 7 healthy children who were HCMV-DNA positive by quantitative PCR (qPCR)]. All positive PCR products were analyzed by heteroduplex mobility assay and single-stranded conformation polymorphism (HMA-SSCP) and 32 of them were sequenced. Results Fifty-five patient isolates and five healthy children isolates were HCMV-UL144 positive by PCR. Sequencing and HMA-SSCP analysis showed that significant strain-specific variability was present in the UL144 ORF. Phylogenetic analysis indicated that the nucleotide sequences could be separated into 3 major genotypes. Comparing between UL144 se-quences and the corresponding symptoms showed that genotype 2 did not exist in megacolon isolates. And genotype 1 and 3 were the major types among microcephaly and jaundice isolates respectively. Conclusions HCMV-UL144 existed in most of low passage isolates and sequences were hypervariable. The UL144 ORF and its predicted product with the high level of sequence variability in different kinds of isolates suggest that UL144 ORF might play a role in HCMV infectivity and subsequent diseases.

A novel low-cost and environment-friendly cathode with large channels and high structure stability for potassium-ion storage

Potassium-ion batteries (KIBs) are promising candidates for large-scale energy storage due to the abundance of potassium and its chemical similarity to lithium.Nevertheless,the performances of KIBs are still unsatisfactory for practical applications,mainly hindered by the lack of suitable cathode materials.Herein,combining the strong inductive effect of sulphate and the feasible preparation of Fe^(2+)-containing compounds in oxalate system,a compound with novel architecture,K_(4)Fe_(3)(C_(2)O_(4))_(3)(SO_(4))_(2),has been identified as a lowcost and environmentally friendly cathode for stable potassium-ion storage.Its unique crystal structure possesses an unprecedented two-dimensional framework of triple layers,with 3.379Åinterlayer distance and large intralayer rings in the size of 4.576×6.846Å.According to first-principles simulations,such a configuration is favorable for reversible K-ion migration with a very low volume change of 6.4%.Synchrotron X-ray absorption spectra and X-ray diffraction characterizations at different charging/discharging states and electrochemical performances based on its half and full cells further verify its excellent reversibility and structural stability.Although its performance needs to be improved via further composition tuning with multi-valent transition metals,doping,structural optimization,etc.,this study clearly presents a stable structural model for K-ion cathodes with merits of low cost and environmental friendliness.

Kinetic calculation for the reaction of H with Si_2H_6 using the variational transition state theory

The reaction of disilane with atomic hydrogen has been studied. This reaction involves both substitution and abstraction. Calculations show that the hydrogen abstraction is the strongest competing channel. The canonical variational transition state theory with a small curvature tunneling correction (SCT) has been used for the kinetic calculation. The theoretical results are in good agreement with the available experimental data. Comparing the reactions of atomic hydrogen with disilane and silane, it can be seen that the reactivity of the Si-H bond is higher in Si2H6than that in SiH4.

Changes in the sediment load of the Lancang-Mekong River over the period 1965-2003

Changes in the sediment load of a river can have important impacts on river channel evolution,nutrient fluxes,aquatic ecology and delta erosion and sedimentation,and the possibility of changes in the sediment load of the Lancang-Mekong River has attracted increasing concern in recent years.Existing studies present conflicting findings regarding the nature and magnitude of recent changes in the sediment load of the Lancang-Meking River and the authors have attempted to assemble the most reliable data on annual sediment loads for the period 1965-2003,to assess recent trends in the sediment load of the river.The changes in annual sediment load at 7 stations on the river are analyzed.Important sediment contributing areas are found in the reaches between Gajiu and Yunjinghong,Chiang Saen and Luang Prabang and downstream of Nong Khai.The sediment load increased at Gajiu,Yunjinghong and Chiang Saen over the period 1985-1992 because of serious soil erosion caused by the expansion of cultivation,the replacement of natural forest by plantations and land disturbance associated with hydropower dam construction.A marked reduction in sediment load occurred at Gajiu after the impoundment of the Manwan Hydropower dam on the Lancang River,but this reduction was not evident downstream at Yunjinghong and the stations further downstream.Significant increases in sediment load appeared at Mukdahan and Khong Chiam.These contrasting patterns of change reflect the influence of sediment contributions from the intervening catchment areas and channel systems as well as storage and remobilization of sediment from the channel system and the impact of hydraulic works such as irrigation systems.The long term mean annual sediment load of the Mekong River at its mouth is estimated to be ca.145×106ta-1,which is lower than previously reported values and it seems likely that this will be reduced in the foreseeable future.

Study on the pre-ignition characteristics of wire insulation in the narrow channel setup

A narrow channel setup was established and experiments were conducted to study the pre-ignition characteristics of wire insulation under overload conditions in weak buoyancy environment.The pre-ignition temperature variation trend of both the wire insulation and its nearby temperature monitoring points,the movement characteristics of smoke produced from the wire insulation and the ignition delay time of wire insulation were investigated.The results indicated that the narrow channel setup with a height of 10-15 mm was effective to suppress the effect of buoyancy,and the pre-ignition characteristics of wire insulation in microgravity could be predicted well by the narrow channel method.

Analysis of Internal Cooling Geometry Variations in Gas Turbine Blades

The present investigation analyzes the effects of major geometrical modifications to the interior of a convectioncooled gas turbine rotor blade. The main focus lies on the flow of the leading edge channels and the impact on theheat transfer. An experimental approach is performed with flow visualization via paint injection into water. Alsonumerical calculations are carried out in two sets, on the one hand water calculations accompanying the experimentsand on the other hand conjugate heat transfer calculations under realistic engine conditions. The latter calculationsare still ongoing delivering preliminary results.Five geometry configurations are investigated, three of them with differing turbulator arrangements in the leadingedge channels. The operating point of the base configuration is set to Re = 50,000 at the inlet while for the modifiedgeometries the pressure ratio is held constant compared to the base.Among several investigated configurations one could be identified that leads to a heat transfer enhancement inone leading edge channel 7 % larger compared to the base.

Effect of rib height on turbulent flow and heat transfer of kerosene in rectangular duct

The coupling effects of rib heights and fluid properties on turbulent convective heat transfer of kerosene flow through the rectangular duct on the ribbed bottom wall are studied numerically in this paper.The numerical simulation is based on the ten components surrogate model of kerosene and the Reynolds average method combined with the re-normalized group(RNG)k-εturbulence model.The turbulent vortex structures and heat transfer characteristics of kerosene flowing over rectangular ribs of different heights are obtained.The results show that three dimensional vortices are generated by the ribs,and the vortices alter local flow significantly,leading to both enhanced and reduced convective heat transfer at different locations near the ribs.In addition,it is found that with the increase of rib height,the average Nusselt number and the wall friction factor on the ribbed wall also increase.For the present study,the maximum heat transfer enhancement rate of kerosene flow is 72.16%,and the ratio of rib-to-duct height is 0.75.