Metal–Ligand Based Mechanophores Enhance Both Mechanical Robustness and Electronic Performance of Polymer Semiconductors

The backbone of diketopyrrolopyrrole-thiophene-vinylene-thiophene-based polymer semiconductors (PSCs) is modified with pyridine (Py) or bipyridine ligands to complex Fe(II) metal centers, allowing the metal–ligand complexes to act as mechanophores and dynamically crosslink the polymer chains. Mono- and bi-dentate ligands are observed to exhibit different degrees of bond strengths, which subsequently affect the mechanical properties of these Wolf-type-II metallopolymers. The counter ion also plays a crucial role, as it is observed that Py-Fe mechanophores with non-coordinating BPh₄^– counter ions (Py-FeB) exhibit better thin film ductility with lower elastic modulus, as compared to the coordinating chloro ligands (Py-FeC). Interestingly, besides mechanical robustness, the electrical charge carrier mobility can also be enhanced concurrently when incorporating Py-FeB mechanophores in PSCs. This is a unique observation among stretchable PSCs, especially that most reports to date describe a decreased mobility when the stretchability is improved. Next, it is determined that improvements to both mobility and stretchability are correlated to the solid-state molecular ordering and dynamics of coordination bonds under strain, as elucidated via techniques of grazing-incidence X-ray diffraction and X-ray absorption spectroscopy techniques, respectively. This study provides a viable approach to enhance both the mechanical and the electronic performance of polymer-based soft devices.     

Wirebond profiles characterized by a modified linkage-spring model which includes a looping speed factor

The linkage-spring model based on a quasi-static looping has been used to determine the design rules to reduce the loop heights and the sagging altitude of gold wire in the package. In order to further simulating the capillary trajectory which includes a looping speed factor from the first bond to the second bond stages, a linkage-spring model is modified in this study. The factors of the inertia mass and variations in material properties with different strain-rates need to be considered due to a high speed looping.It is found that the looping speed effects on the wirebond profiles due to the inertia mass can be neglected at a regular looping process of 3–5g acceleration even up to around 10g acceleration. However, variations in the material properties during deformation at different strain-rates could be an important factor on the wirebond profiles. Fortunately, a pure annealed state like pure gold wire would be little strain-rate sensitivity. The effects of the strain-rate in pure gold wire, therefore, can be excluded in analysis. Accordingly, a linkage-spring model based on the quasi-static looping is still applicable in analyzing the wirebond profiles.     

Control of linear motor machine tool feed drives for end milling: Robust MIMO approach

Linear motors are getting promising for use as high speed, high accuracy machine tool feed drives. The cutting force in the machining process are directly reflected to the linear motor due to no gearing mechanism. To achieve high accuracy machining, the controller for the linear motor system should be designed to compensate for the cutting force.

In this work, a MIMO H_∞ controller for the linear motor machine tool feed drives has been designed to reduce tracking errors induced by cutting forces for end milling. The controller is designed using normalized coprime factorization method for the dynamic model of the linear motor system. The model includes constant in-line and cross coupling force gain, since the feedback cutting force can be considered as the product of the constant gain and the moving velocity of each axis.

Analysis of the structured singular value shows that the designed controller has good robust performance despite wide variations of the cutting force and physical parameters. It is directly implemented on a linear motor X–Y table which is mounted on a milling machine to have cutting experiments via a DSP board. Experimental results verified effectiveness of the proposed scheme to suppress the effects of the cutting force in the high feed rate.     

Improving the R-score of an adaptive VoIP codec in IEEE 802.16 networks

Worldwide Interoperability for Microwave Access (WiMAX) technology, which is based on the IEEE 802.16 standard, supports different quality of service (QoS) for different services. WiMAX is expected to support QoS in real-time applications such as Voice over Internet Protocol (VoIP). When network congestion occurs, the VoIP bit rate needs to be adjusted to achieve the best speech quality. In this study, we propose a new scheme called Adaptive VoIP Level Coding (AVLC). This scheme takes into consideration network conditions (packet delay and packet loss) and a connection’s modulation scheme. The amount of data that can be transmitted increases with the speed of the modulation scheme. When network congestion occurs, AVLC scheme prioritizes reducing the bit rate of a connection that has a slower modulation scheme to mitigate congestion. Depending on network conditions, such as modulation scheme, packet delay, packet loss, and residual time slot, we use the G.722.2 codec to adjust each connection’s bit rate. Simulations are conducted to test the performance (network delay, packet loss, number of modulation symbols, and R-score) of the proposed scheme. The simulation results indicate that speech quality is improved by the use of AVLC.     

Performance evaluation of fault-branch detection in TDM passive optical networks by spectral analysis of interferometric signals

A new fault-branch detection scheme is proposed to troubleshoot the breaks of any distribution fibers in a time-division multiplexing (TDM) passive optical network. We employ a continuous optical frequency sweeper at the optical line terminal (OLT) and an interferometric (IF) device at each optical network unit (ONU). By analyzing the spectrum of the returned combined signals at the OLT, we can obtain the status of all branches. This detection method not only uses a small optical frequency band for surveillance monitoring, but is also simple to operate. Furthermore, a modified architecture is proposed to relax the specifications of IF devices. The tolerance of the IF device length was analyzed using the Monte–Carlo simulation method.     

Spectral-domain analysis of circular patch frequency selective surfaces

A computationally efficient method is presented for analyzing the scattering from frequency selective surfaces (FSS) comprised of circular metal patches. The formulation is carried out in the spectral domain where the convolution form of the integral equation for the induced current reduces to an algebraic one and the spectral-Galerkin technique is used to solve the resulting equation. Entire-domain basis functions that satisfy the edge condition are introduced to expand the unknown induced current on the metal patches. Calculated results using this procedure show good agreement with data reported by other authors.     

Flash Process-Based Complex Programmable Logical Device with 72 Macro Cells

A complex programmable logical device （CPLD） based on conventional embedded Flash memory process with 72 macro cells is studied in the paper. Compared with the Flash cell array technology employed by foreign companies, this architecture exhibiting insystem reconfiguration and rapid response was manufactured by low cost fabrication process. The device architecture and critical cell design are also analyzed in detail in the paper. The CPLD was designed by full-custom ASIC technology and manufactured by 0.35 pm 3P3M Flash process with 72 macro cells and 5 V voltage supply. The measurement results indicate that the devices are able to operate above the frequency of 66.7 MHz with the pin delay less than 10 ns.     

A 110-MHz 84-dB CMOS programmable gain amplifier with integrated RSSI function

This paper describes a CMOS programmable gain amplifier (PGA) that maintains a 3-dB bandwidth greater than 110 MHz and can provide an 84-dB gain control range with 1-dB step resolution. The PGA can also be operated in a low-power mode with 3-dB bandwidth greater than 71 MHz. Integrated with this PGA is a CMOS successive logarithmic detecting amplifier with a /spl plusmn/0.7-dB logarithmic accuracy over an 80-dB dynamic range. It achieves -83-dBm sensitivity and consumes 13 mA from a single 3-V supply in the normal power mode. The chip area, including pads, occupies 1.5/spl times/1.5 mm/sup 2/.     

Versatile,Benzimidazole/Amine‐Based Ambipolar Compounds for Electroluminescent Applications: Single‐Layer,Blue, Fluorescent OLEDs,Hosts for Single‐Layer,Phosphorescent OLEDs

A series of compounds containing arylamine and 1,2‐diphenyl‐1H‐benz[d]imidazole moieties are developed as ambipolar, blue‐emitting materials with tunable blue‐emitting wavelengths, tunable ambipolar carrier‐transport properties and tunable triplet energy gaps. These compounds possess several novel properties: (1) they emit in the blue region with high quantum yields; (2) they have high morphological stability and thermal stability; (3) they are capable of ambipolar carrier transport; (4) they possess tunable triplet energy gaps, suitable as hosts for yellow‐orange to green phosphors. The electron and hole mobilities of these compounds lie in the range of 0.68–144 × 10^?6 and 0.34–147 × 10^?6 cm² V^?1 s^?1, respectively. High‐performance, single‐layer, blue‐emitting, fluorescent organic light‐emitting diodes (OLEDs) are achieved with these ambipolar materials. High‐performance, single‐layer, phosphorescent OLEDs with yellow‐orange to green emission are also been demonstrated using these ambipolar materials, which have different triplet energy gaps as the host for yellow‐orange‐emitting to green‐emitting iridium complexes. When these ambipolar, blue‐emitting materials are lightly doped with a yellow‐orange‐emitting iridium complex, white organic light‐emitting diodes (WOLEDs) can be achieved, as well by the use of the incomplete energy transfer between the host and the dopant.     

A reliability model for real-time rule-based expert systems

This paper uses two modeling tools to analyze the reliability of real-time expert systems: (1) a stochastic Petri net (SPN) for computing the conditional response time distribution given that a fixed number of expert system match-select-act cycles are executed, and (2) a simulation search tree for computing the distribution of expert system match-select-act cycles for formulating a control strategy in response to external events. By modeling the intrinsic match-select-act cycle of expert systems and associating rewards rates with markings of the SPN, the response time distribution for the expert system to reach a decision can be computed as a function of design parameters, thereby facilitating the assessment of reliability of expert systems in the presence of real-time constraints. The utility of the reliability model is illustrated with an expert system characterized by a set of design conditions under a real-time constraint. This reliability model allows the system designers to: (1) experiment with a range of selected parameter values; and (2) observe their effects on system reliability