A QoS index for IP services to effectively support usage-based charging

The goal of this letter is to present a model to compute a quality-of-service (QoS) index to characterize IP services. Then, we show how such a score may be used in a clear and flexible way for defining advanced usage-based tariff criteria to charge QoS guaranteed network services to address the dynamics of the expected future telecommunications scenario.     

Successful Aging

This issue's Works in Progress department presents six abstracts for projects that are developing interesting solutions to the elderly's quality of life challenges. The first two abstracts discuss projects that will help provide the elderly with freedom and independence by instrumenting their environments with supportive technology. The next two abstracts discuss projects building specialized user interfaces for addressing some of the challenges associated with aging, such as vision impairment. The final two abstracts present projects that will aid independence for the elderly by providing remote monitoring and assistance.     

立方相GaN的持续光电导

研究了金属有机物化学气相外延 (MOVPE)方法生长的非故意掺杂的立方相 Ga N的持续光电导效应 .在六方相 Ga N中普遍认为持续光电导效应与黄光发射有关 ,而实验则显示在立方 Ga N中 ,持续光电导效应与其中的六方相 Ga N夹杂有关系 ,而与黄光发射没有关系 .文中提出 ,立方相 Ga N与其中的六方相 Ga N夹杂之间的势垒引起的空间载流子分离是导致持续光电导现象的物理原因 .通过建立势垒限制复合模型 ,解释了立方相 Ga N的持续光电导现象的物理过程 ,并对光电导衰减过程的动力学作了分析 .对实验数据拟合的结果证明以上的模型和推导是与实验相符的 .     

Modified register-exchange Viterbi decoder for low-power wireless communications

In this paper, a new implementation of the Viterbi decoder (VD), based on a modified register-exchange (RE) method, is proposed. Conceptually, the RE method is simpler and faster than the trace-back (TB) method. However, the disadvantage of the RE method is that every bit in the memory must be read and rewritten for each bit of information decoded. The proposed implementation adopts the "pointer" concept: a pointer is assigned to each register. Instead of copying the contents of one register to another, the pointer which points to the first register is altered to point to the second register. Power-dissipation, performance, memory size, and the speed of the survivor sequence management are analyzed for both the TB method, and the proposed RE method. The analysis indicates an average power reduction of 23% for the new VD, compared to the power dissipation of the VD described in the literature for the third generation of wireless applications. The bit-error rate is 10/sup -5/ with a signal-to-noise ratio of approximately 6.3 dB for a continuous, uncontrolled encoded sequence. Moreover, the memory requirements of the new implementation are reduced by half. All the read and write operations in the survivor sequence management are executed at the data rate frequency which increases the maximum frequency.     

Hydrogen limitation--a method for controlling the performance of membrane biofilm reactor for autotrophic denitrification of wastewater.

Hydrogen-driven denitrification using the fiber membrane biofilm reactor (MBfR) was evaluated for consistent operation in tertiary wastewater treatment. The possibility of controlling the process rates, as well as biofilm parameters by supplying limited amounts of electron donor (hydrogen), was tested. Limiting the hydrogen supply proved to be efficient in controlling the biofilm growth and performance of the MBfR. Denitrification rates remained unchanged for both synthetic wastewater (SWW) and real municipal wastewater (MWW) effluent as well through the fluctuations in the substrate (NO3-N) concentration. The average denitrification rates were 0.50 (+/- 0.02) g NO3-N per day per m2 for SWW and 0.59 (+/- 0.04) g NO3-N per day per m2 for MWW. Biofilm density rather than thickness was the determining factor in substrate diffusion and biofilm sloughing, ultimately determining operating stability. Limited hydrogen supply assured constant volatile solids (VS) concentration in the biofilm. It was determined that VS/TS ratio higher than 0.25 assured stable biofilm operation. Decrease of VS/TS ratio below 0.25 led to shearing of the nonbiological outer layers of the biofilm. The values of chemical oxygen demand (COD), volatile suspended solids (VSS) and total suspended solids (TSS) in the final effluent were stable and well below wastewater effluent guidelines. Substitutions of bicarbonate with gaseous carbon dioxide as the carbon source did not affect denitrification rates despite lower than optimum pH conditions.     

Enhance Cyanide Recovery by UsingAir‐Sparged Hydrocyclone

Human health and environmental concerns dictate that industrial processes be improved or replaced. Recovery or recycling is an important activity that allows cyanide residue from the industrial processes to be re‐used, reducing its production cost and disposal problems. In this regard, the air‐sparged hydrocyclone (ASH) has been used as a reactor for the treatment of cyanide solutions for cyanide recycling by acidification/volatilization using the Mexican modification of the Mills‐Crowe process. Aqueous cyanide‐ion concentration can be reduced from 250 ppm to below 20 ppm in the ASH with recoveries greater than 80 % in a single stage.     

FDTD simulation of 30 /spl mu/m diameter polymer micro-ring

Numerical results on polymer surrounded by an air micro-ring coupled to waveguides are presented. The FDTD method predicts a filter width of 1.4 nm and an extraction efficiency of almost 80% for a gap of 0.15 /spl mu/m.