Temperature dependence of common-emitter I-V andcollector breakdown voltage characteristics in AlGaAs/GaAs andAlInAs/GaInAs HBT's grown by MBE

Temperature-dependent measurements from 25 to 125°C have been made of the DC I-V characteristics of HBTs with GaAs and In_0.53Ga_0.47As collector regions. It was found that the GaAs HBTs have very low output conductance and high collector breakdown voltage BV_CEO>10 V at 25°C, which increases with temperature. In striking contrast, the In_0.53Ga_0.47As HBTs have very high output conductance and low BV_CEO~2.5 V at 25°C, which actually decreases with temperature. This different behavior is explained by the >10⁴ higher collector leakage current, I_CO, in In_0.53Ga_0.47As compared to GaAs due to bandgap differences. It is also shown that device self-heating plays a role in the I-V characteristics     

Evaluation of relative nutritive value in cultivars of triticale with shrivelled grain characteristics,using Aspergillus flavus

Aspergillus flavus Link ex Fr., was used to evaluate the Relative Nutritive Value (RNV) in a set of triticale cultivars having shrivelled grain characteristics. The protein content in these samples ranged from 11.8 to 24.0%. The milled material was tested at 3 mg nitrogen level. Biomass of the fungus was measured as the total dry weight of the mycelium produced after 72 h of shaking and taken as the index of Relative Nutritive Value. The fungal biomass was negatively correlated with protein content and dye binding capacity while a positive correlation existed with protein index. With the use of glucose as an extra energy source, the basic pattern of response remained the same but the magnitude of correlation decreased.     

Dynamic provisioning of low-speed unicast/multicast traffic demands in mesh-based WDM optical networks

This paper addresses the problem of dynamically provisioning both low-speed unicast and multicast connection requests in mesh-based wavelength division multiplexing (WDM) optical networks. Several routing/provisioning schemes to dynamically provision both unicast and multicast connection requests are presented. In addition, a constraint-based grooming strategy is devised to utilize the overall network resources as efficiently as possible. Based on this strategy, several different sequential multicast grooming heuristics are first presented. Then, we devise a hybrid grooming approach and combine it with sequential approaches to achieve a grooming scheme that is biased toward serving multicast traffic demands in comparison with all other sequential grooming approaches. To achieve our objective, we decompose the problem into four subproblems: 1) routing problem; 2) light-tree-based logical-topology-design problem; 3) provisioning problem; and 4) traffic-grooming problem. The simulation results of the proposed schemes are compared with each other and with those of conventional nongrooming approaches. To the best of our knowledge, this is the first detailed paper to address and examine the problem of grooming dynamic multicast traffic demands.     

Effect of chemical doping on the electrical conductivity of poly(2,6-dimethyl-1,4-phenylene oxide)

The electrical conductivity of solution-grown poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) films doped with TCNQ, TCNE, TNF, and I₂ has been studied as a function of dopant concentration, temperature (298–353 K), and field (50–2000 V). PPO forms a conductive complex on doping with these strong electron-acceptor organic molecules. As with PPO, two distinct ohmic and nonohmic conduction regions at low and higher fields, respectively, are observed. The conduction properties of doped PPo films result from the formation of an isotropic continuous charge-transfer complex. The existence of such a complex is confirmed by UV-visible absorption spectra measurements. A possible mechanism for the electrical conduction process is discussed. © 1994 John Wiley & Sons, Inc.     

Evolving simple fault-tolerant routing rules using geneticprogramming

A novel approach to solving network routing and restoration problems using the genetic programming (GP) paradigm is presented, in which a single robust and fault-tolerant program is evolved which determines the near-shortest paths through a network subject to link failures     

Studies on an araldite-based membrane of copper hexacyanoferrate (III) as a caesium ion-sensitive electrode

Solid membranes of copper hexacyanoferrate (III) in araldite are evaluated as a caesium ion-sensitive electrode. The electrode can be used for caesium determination in the concentration range of 10⁻¹ to 10-⁴M . The potentials generated across the membrane are reproducible and steady potentials are attained in about 1 to 2min. The same electrode can be used over a period of 6 months without significant change in potential. The electrode can be used in the pH ranges 2.5–6.0 at 10⁻² M Cs⁺ and 3.0–6.0 at 10⁻³ M CS⁺, and in presence of a number of interfering ions. Potentiometric titration of caesium nitrate with 12-moIybdophosphoric acid was also carried out using the membrane as an end point indicator.     

Electrical conductivity of seeded combustion products of water gas-air system

The dependence of the electrical conductivity of seeded combustion products of water gas-air system on preheating and oxygen enrichment of air has been analytically investigated. Optimum oxygen enrichment is estimated to be around 40% while preheating could be carried for temperatures in the range of 1100 to 1400 K. The conductivity of the system is found to increase with the addition of extra CO to the fuel.     

Robust QoS Control for Single Carrier PMP Mode IEEE 802.16 Systems

The IEEE 802.16 WirelessMAN standard provides a comprehensive quality-of-service (QoS) control structure to enable flow isolation and service differentiation over the common wireless network interface. By specifying a particular set of service parameters, the media access control (MAC) mechanisms defined in the standard are able to offer predefined QoS provisioning on a per-connection basis. However, the design of efficient, flexible, and yet robust MAC scheduling algorithms for such QoS provisioning still remains an open topic. This paper proposes a new QoS control scheme for single-carrier point-to-multipoint mode wireless metropolitan area network (WirelessMAN) systems, which enables the predefined service parameters to control the service provided to each uplink and downlink connection. By MAC-PHY cross-layer resource allocation, the proposed scheme is robust against particular wireless link degradation. Detailed simulation experiments are presented to study the performance and to validate the effectiveness of the proposed QoS control scheme.