Improving Quality of Crane-Lorry Assignments With Constraint Programming

The ability to maximize service quality while minimizing cost is very important to service-oriented businesses, such as lorry leasing. Very often, the ability to consistently offer higher quality service is the main differentiating factor between a business and its competitors. For lorry leasing businesses, service quality and cost are directly related to how resources-vehicles, cranes, and drivers-are allocated to jobs. The ability to assign the right combination of resources is crucial to daily operations. This paper presents how we modeled this assignment problem as a constraint-satisfaction problem (CSP) and implemented using constraint programming (CP) with an algorithm that we call the crane-lorry optimizing engine (CLOE). CLOE was implemented for the largest crane-lorry company in Hong Kong. Furthermore, plans are generated within seconds compared to close to an hour if done manually. All necessary constraints and criteria are considered systematically. We have experimented with many different types of search heuristics and have analyzed their effects on plan quality. We have found that by considering both the experience of the crane-lorry-driver combination and maximizing on the order assignment, we were able to generate plans that were significantly better than those produced by human planners, and within a substantially shorter time. Although the use of constraint-based assignment techniques is still limited in the vehicle leasing industry, we hope our combination of automated assignment with Internet portal technology that streamlines business-to-business, business-to-consumer, and business-to-employee communications can excite interest in this area     

GaN and AlGaN high-voltage rectifiers grown by metal-organic chemical-vapor deposition

In this paper, we report the study of the electrical characteristics of GaN and AlGaN vertical p-i-n junctions and Schottky rectifiers grown on both sapphire and SiC substrates by metal-organic chemical-vapor deposition. For GaN p-i-n rectifiers grown on SiC with a relatively thin “i” region of 2 μm, a breakdown voltage over 400 V, and forward voltage as low as 4.5 V at 100 A/cm² are exhibited for a 60-μm-diameter device. A GaN Schottky diode with a 2-μm-thick undoped layer exhibits a blocking voltage in excess of ∼230 V at a reverse-leakage current density below 1 mA/cm², and a forward-voltage drop of 3.5 V at a current density of 100 A/cm². It has been found that with the same device structure and process approach, the leakage current of a device grown on a SiC substrate is much lower than a device grown on a sapphire substrate. The use of Mg ion implantation for p-guard rings as planar-edge terminations in mesageometry GaN Schottky rectifiers has also been studied.     

Adhesion improvement of thermoplastic isotropically conductive adhesive

Generally, isotropically conductive adhesive formulations include epoxy resin as the polymeric matrix. Although epoxy has superior adhesion capability, its drawbacks include the tendency to absorb moisture and lack of reworkability (thermosetting polymer). In this study, a thermoplastic polymer with low moisture absorption (0.28 wt%), called polyarylene ether (PAE2), is used in isotropically conductive adhesive (ICA) formulation. Previous research work by Lu et al. showed that the moisture absorbed into epoxy caused galvanic corrosion, which result in the formation of metal oxide . By using a polymer with low moisture absorption, the amount of water present in ICA will be small, and the corrosion rate and formation of metal oxide can be reduced. However, previous measurements of contact resistance stability of PAE2-based ICA showed that they are not stable on all surface finishes. It was determined that for thermoplastic-based ICA, poor adhesion was the main mechanism for unstable contact resistance. Two methods of adhesion improvement will be evaluated in this work. The first is to use coupling agents and the second is to blend the thermoplastic with epoxy. Both methods showed promise in improving the contact resistance stability of polyarylene ether based ICA.     

Optimal diagonal precoder for multiantenna communication systems

In this paper, we examine a multiantenna single-user wireless communication system fitted with a QR-based successive cancellation receiver (QR receiver). Initially, our consideration is confined to uncoded binary phase shift keying (BPSK) signals transmitted through independent and identically distributed (IID) Rayleigh fading channels and to the design of an optimum precoder for the transmitter. For minimum feeding back of the channel state information (CSI) to the transmitter from the receiver, we stipulate the precoder to be in the form of a power loading square diagonal matrix. We proceed to develop the theory for the design of this diagonal matrix based on the minimization of the lower bound of the average bit error rate (BER) of transmission. The design obtained provides substantially lower error rates than most of other existing schemes under the same environment. The corresponding gain in signal-to-noise ratio (SNR) can be several decibels. To further improve the performance, we extend the design to include an optimal detection order of the received bits using an iterative approach. This iterative process proves to have fast convergence and results in a design providing significant SNR gain. We also propose a subchannel dropping scheme for cases in which SNR is low, and when the minimum BER precoder is equipped with this scheme, its average performance can be substantially superior to the Vertical Bell Laboratories Layered Space-Time (V-BLAST) detection. We extend our design of the optimum precoder to quadrature amplitude modulation (QAM) modulation scheme and similar performance gain has been observed.     

Moisture-induced failures of adhesive flip chip interconnects

Adhesive flip chip interconnect has been recognized as a promising substitute for solder interconnection due to its fine-pitch, lead-free, and low-temperature processing capabilities. As adhesives are made of polymers, moisture absorption by the polymeric resin remains as one of the principal contributors to adhesive joint failure mechanisms. In this research, the reliability performance of the adhesive flip chip in the pressure cooker test and moisture sensitivity test conditions was investigated. The failure modes were found to be interfacial delamination and bump/pad opening which may eventually lead to total loss of electrical contact. Different sizes of bump/pad opening in the interconnections were discussed in the context of the significance of mismatch in coefficient of moisture expansion (CME) between adhesive and other components in the package, which induces a hygroscopic swelling stress. The effect of moisture diffusion in the package and the CME mismatch were also evaluated from the standpoint of finite element modeling. In this study, it is concluded that hygroscopic swelling assisted by loss of adhesion strength upon moisture absorption is responsible for the moisture-induced failures in these adhesive flip chip interconnects.     

Study of specific absorption rate (SAR) induced in two child head models and in adult heads using mobile phones

This paper gives a first comparison of specific absorption rate (SAR) induced in a child-sized (CS) head and an adult head using a dual-band mobile phone. In the second study, the visible human head is considered and comparison of SAR induced in a CS or child-like (CL) head and an adult head using a dual-band mobile phone is given. All the peaks of average SAR over a mass of 10 and 1 g in the head and the power budget are determined in the two comparisons using the finite-difference time-domain method. The differences between the results for adult and CS or CL heads are given at 900 and 1800 MHz. No important differences are noted for the peak SAR averaged over 10 g (SAR10 g), between the two adult head models, as well as between the two child head models. The peak SAR10 g in the brain of the CS or CL head is slightly more significant than that for the adult one.     

WLAN chip antenna mountable above the system ground plane of a mobile device

A novel wireless local-area network (WLAN) chip antenna suitable to be mounted above the system ground plane of a mobile device is presented. The antenna in the study is easily fabricated from folding a single metal plate onto a foam base, and mainly comprises a short-circuited radiating strip and an antenna ground. The antenna ground occupies the bottom surface and two adjacent side surfaces of the foam base. When the antenna is mounted at the corner of the system ground plane, this antenna ground structure is expected to effectively reduce the antenna's possible fringing electromagnetic fields inside the mobile device. In this case, when the associated element such as the radio-frequency shielding metal case is placed under the proposed antenna, small or negligible variations in the antenna performance are obtained. Design considerations of the proposed antenna for WLAN operation in the 2.4 GHz band are described, and results of the constructed prototypes are presented.     

Coupling efficiency enhancement in organic light-emitting devices using microlens array-theory and experiment

Microlens arrays are introduced on glass substrates to improve the out-coupling efficiency of organic light-emitting devices (OLEDs). The microlenses suppress waveguiding loss in the substrate. A theoretical model, based on electromagnetic wave propagation and geometric ray tracing, is developed to simulate the enhancement effects and optimize the structure parameters of the lens pattern. A simple soft-lithography approach is employed to fabricate the microlens array on glass substrates. With the use of an optimized lens pattern, an increase of over 85% in the coupling efficiency of the OLED is expected theoretically. An increase of 70% in the coupling efficiency is achieved experimentally, without detrimental effect to the electrical performance of the OLED.     

玻璃衬底上MIUC Poly-Si TFT显示驱动电路

以高性能的金属诱导单一方向横向晶化多晶硅薄膜晶体管(MIUC poly-Si TFT)为基础,研制出性能能满足AM-LCD和AM-OLED要求、版图和象素尺寸适配、制备工艺和象素电路兼容的多晶硅TFT行扫描和列驱动电路.该行扫描电路工作电压为3.5-10V;当工作电压为5V、负载电容为22pf时,下降沿约为150ns,上升沿约为205ns,最高工作频率在1MHz以上;列驱动电路工作电压为3.5-8V;当工作电压为5V、负载电容为22pf时,上升沿约为200ns,信号衰减率为15%(64μs扫描周期),最高工作频率达到4MHz.将该MIUC poly-Si TFT多晶硅行扫描、列驱动电路和有源选址电路集成到同一基板上,制备出象素数为80×RGB×60、动态显示效果良好的全集成型LCD屏样品.     

Characterization and modeling of on-chip spiral inductors for Si RFICs

The paper presents a complete characterization of on-chip inductors fabricated in BiCMOS technology. First, a study of the scaling effect of inductance on geometry and structure parameters is presented to provide a clear guideline on inductor scaling with suitable quality factors. The substrate noise analysis and noise reduction techniques are then investigated. It is shown that floating well can improve both quality factor and noise elimination by itself under 3 GHz and together with a guard ring above 3 GHz. Finally, for accurate circuit simulations, a new inductor model is developed for predicting the skin effect and eddy effect and associated quality factor and inductance.