Enhanced MAC Protocol and Scheduling Algorithm for High Rate WPANs

The demands for higher data rate in Wireless personal area network （WPAN） than one in Bluetooth has been completed with IEEE 802.15.3 standard. The standard, named High-rate WPAN （HR-WPAN）, adopts TDMA-based Medium access control （MAC） protocol. In this paper, we propose novel MAC protocol and scheduling algorithm to achieve efficient time-slots allocation. Time slots for data transmissions are allocated by two steps. In the first step, the time slots are initially allocated using a proposed allocation algorithm based on statistical packet inter-arrival time. Then, the initial allocation is dynamically adjusted by utilizing feedback information coming from each device. Performance evaluations are carried out through extensive simulations and significant performance enhancements are observed.     

PFQ-OS： A Packet Fair Queueing Based Opportunistic Scheduler in Wireless Networks

In this paper, we investigate the issues of extending the Packet fair queueing （PFQ） algorithms into continuous channel model. We present a PFQ-based Opportunistic scheduler （PFQ-OS）, which can improve user throughput while satisfying strict short-term fairness. We decouple the conflicting design objectives of fairness and user throughput improvement by introducing a Search radius （SR） into the framework of PFQ. We develop an analytical model and derive the fairness properties of PFQ-OS, which are related to the SR. Thereby system operators can focus on opportunistic scheduling for the users within the SR without violating the fairness guarantee. We further investigate the designing of scheduling policy under the strict fairness constraints, and propose that in order to utilize the opportunistic scheduling all the time, the selection rule should provide all the users with equal chance in being scheduled at each selection. Accordingly, we present Maximum relative SNR （Max-rSNR） selection rule for PFQ-OS. We derive the bounds in terms of user throughput under Rayleigh fading channel. An extensive set of simulations testifies our derived theoretical properties that PFQ-OS can significantly improve user throughput while providing excellent short-term fairness guarantee.     

青霉素发酵过程的模型仿真与补料优化

补料分批式青霉素发酵的机理模型已得到深入研究,但是模型往往难以用于补料的优化和批次内的控制。为了对模型进行优化控制,针对Birol等提出的青霉素发酵非结构动力学模型,合理调整了温度和pH变化的影响,得到了青霉素发酵过程的简化机理模型。反应基质的补料是青霉素优化控制的关键,选择对补料速率进行优化来提高青霉素的产量。由于机理模型具有非线性和约束条件,采用序贯二次规划算法来进行求解,其中将补料轨线进行分段处理提高了优化效率。优化计算结果表明改进的补料过程可以提高青霉素的浓度和产量。     

Parametric control of structural responses using an optimal passive tuned mass damper under stationary Gaussian white noise excitations

In this study, the structural control strategy utilizing a passive tuned mass damper (TMD) system as a seismic damping device is outlined, highlighting the parametric optimization approach for displacement and acceleration control. The theory of stationary random processes and complex frequency response functions are explained and adopted. For the vibration control of an undamped structure, the optimal parameters of a TMD, such as the optimal tuning frequency and optimal damping ratio, to stationary Gaussian white noise acceleration are investigated by using a parametric optimization procedure. For damped structures, a numerical searching technique is used to obtain the optimal parameters of the TMD, and then the explicit formulae for these optimal parameters are derived through a sequence of curve-fitting schemes. Using these specified optimal parameters, several different controlled responses are examined, and then the displacement and acceleration based control effectiveness indices of the TMD are examined from the view point of RMS values. From the viewpoint of the RMS values of displacement and acceleration, the optimal TMDs adopted in this study shows clear performance improvements for the simplified model examined, and this means that the effective optimization of the TMD has a good potential as a customized target response-based structural strategy.     

Effect of second non-singular term of mode I near the tip of a V-notched crack

The effect of a second non-singular term of mode I in the vicinity of the tip of a V-notched crack is discussed. The undetermined eigenvector coefficients of singular and non-singular terms of eigenfunction expansion were calculated by the numerical analysis method using the reciprocal work contour integral method (RWCIM) based on Betti's reciprocal work theorem and finite-element analysis. This study demonstrates that the second non-singular term of mode I can have a significant effect on the size and shape of plastic zones as an additional fracture mechanics parameter along with the conventional parameter K .     

ENZYMATIC PROPERTIES OF A PROTEASE FROM THE HEPATOPANCREAS OF SHRIMP, PENAEVS OMENTAIM

The protease purified from hepatopancreas of shrimp, Penaeus orientals, had high proteolytic activity in the pH range of 7.0 to 9.5. Temperature optimum for hydrolysis of casein was 70C. The protease was stable at neutral and alkaline pH and unstable at acidic pH. The apparent Michaelis‐Menten constant (K_m) and the turnover number (V_max) of the protease on hydrolysis of N‐CBZ‐L‐tyrosine p‐nitrophenyl ester (CBZ‐Tyr‐NE) and N‐CBZ‐L‐phenylalanine p‐nitrophenyl ester (CBZ‐Phe‐NE) ‐were similar, however, those for N‐CBZ‐L‐cysteine p‐nitropher.yl ester (CBZ‐Cys‐NE) were different. K_m and V_max for hydrolysis of casein by the protease were determined to be 0.31% and 5.21s^‐1, respectively. The N‐terminal sequence of the protease showed higher homology with the collagenase of crab and trypsins from Crustacea. Myosin heavy chain (MHC) was the primary substrate during proteolysis with the protease. Actin/tropomyosin were degraded progressively during 2 h incubation but to a lesser extent than MHC.     

Effects of TiN film coating on electrochemical behaviors of nanotube formed Ti-xHf alloys

Ti-xHf (x=10%, 20%, 30% and 40%, mass fraction) alloys were prepared by arc melting, and the microstructure was controlled for 24 h at 1 000 °C in argon atmosphere. The formation of nanotube was conducted by anodizing on Ti-Hf alloys in 1.0 mol/L H₃PO₄ electrolytes with small amounts of NaF at room temperature. And then TiN coatings were coated by DC-sputtering on the anodized surface. Microstructures and nanotube morphology of the alloys were examined by field emission scanning electron microscopy(FE-SEM) and X-ray diffractometry(XRD). The corrosion properties of the specimens were examined through potentiodynamic test (potential range from −1 500 to 2 000 mV) in 0.9 % NaCl solution by potentiostat. The microstructure shows the acicular phase and α′ phase with Hf content. The amorphous oxide surface is transformed to crystalline anatase phase. TiN coated nanotube surface has a good corrosion resistance.     

Effect of process parameters on electrical, optical properties of IZO films produced by inclination opposite target type DC magnetron sputtering

IZO films were deposited onto PET substrate at room temperature with the inclined opposite target type DC magnetron sputtering equipment, in which a sintered oxide IZO target (doped with 10% ZnO, packing density of 99.99%) was used. The effects of total sputtering pressure and film thickness on IZO films properties were studied. All the films produced at room temperature have a amorphous structure, irrespective of the total sputtering pressure and film thickness. A resistivity of the order of 10⁻⁴ Ω·cm was obtained for IZO films deposited at lower pressure (film thickness of 190 nm). The resistivity of IZO films deposited at room temperature depends on film thickness and shows a minimum at a thickness of 530 nm.     

Electrodeposited Ni,Fe,Co and Cu single and multilayer nanowire arrays on anodic aluminum oxide template

The Ni, Fe, Co and Cu single and multilayer nanowire arrays to make perpendicular magnetic recording media were fabricated with nanoporous anodic aluminum oxide (AAO) templates from Watt solution and additives by the DC electrodeposition. The results show that the diameters of Ni, Fe, Co and Cu single and multilayer nanowires in AAO templates are 40–80 nm and the lengths are about 30 μm with the aspect ratio of 350–750. The magnetic properties of the prepared nanowires are different under different electrodepositing conditions. The remanences (B_r) of Ni/Cu/Fe multilayer nanowires are lower than those of others multilayer nanowires, and coercivity (H_c) of Ni/Cu/Fe multilayer nanowires are lower than those of others multilayer nanowires. These are compatible with the required conditions of high density magnetic media devices that should have the low coercivity to easily success magnetization and high remanence to keep magnetization after removal of magnetic field.