Write-Once Read-Many-Times Memory Based on a Single Layer of Pentacene

We realized an organic electrical memory device with a simple structure based on single-layer pentacene film embedded between Al and ITO electrodes. The optimization of the thickness and deposition rate of pentacene resulted in a reliable device with an on/off current ratio as high as nearly 10(6), which was two orders of magnitude higher than previous results, and the storage time was more than 576 h. The current transition process is attributed to the formation and damage of the Interface dipole at different electric fields, in which the current conduction showed a transition from ohmic conductive current to Fowler-Nordheim tunneling current. After the transition from ON- to OFF-state, the device tended to remain in the OFF-State even when the applied voltage was removed, which indicated that the device was very promising for write-once read-many-times memory.

Efficient two-step digit-set-restricted modified signed-digit algorithm based on optoelectronic shared content-addressable memory

A two-step digit-set-restricted modified signed-digit (MSD) adder based on symbolic substitution is presented. In the proposed addition algorithm, carry propagation is avoided by using reference digits to restrict the intermediate MSD carry and sum digits into {(1) over bar ,0} and {0, 1}, respectively. The algorithm requires only 12 minterms to generate the final results, and no complementarity operations for nonzero outputs are involved, which simplifies the system complexity significantly. An optoelectronic shared content-addressable memory based on an incoherent correlator is used for experimental demonstration. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Efficient two-step digit-set-restricted modified signed-digit algorithm based on optoelectronic shared content-addressable memory

A two-step digit-set-restricted modified signed-digit (MSD) adder based on symbolic substitution is presented. In the proposed addition algorithm, carry propagation is avoided by using reference digits to restrict the intermediate MSD carry and sum digits into {(1) over bar ,0} and {0, 1}, respectively. The algorithm requires only 12 minterms to generate the final results, and no complementarity operations for nonzero outputs are involved, which simplifies the system complexity significantly. An optoelectronic shared content-addressable memory based on an incoherent correlator is used for experimental demonstration. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Optoelectronic quotient-selected modified signed-digit division

A novel optoelectronic quotient-selected modified signed-digit division technique is proposed. This division method generates one quotient digit per iteration involving only one shift operation, one quotient selection operation and one addition/subtraction operation. The quotient digit can be selected by observing three most significant digits of the partial remainder independent of the divisor. Two algorithms based on truth-table look-up and binary logic operations are derived. For optoelectronic implementation, an efficient shared content-addressable memory based architecture as well as compact logic array processor based architecture with an electron-trapping device is proposed. Performance evaluation of the proposed optoelectronic quotient-selected division shows that it is faster than the previously reported convergence division approach. Finally, proof-of-principle experimental results are presented to verify the effectiveness of the proposed technique. (C) 2001 Society of Photo-Optical Instrumentation Engineers.

基于组块及记忆的词性自动标注

基于组块及记忆的模型(BMM)采用与传统方法明显不同的标注思路,以汉语中的整句为处理单元,从组块出发,立足于单个词汇,分析更为丰富的上下文语境知识,并借助知网词典记忆词性集合,同时采用渐增式的机械学习方式获取参数值。对于棘手的稀疏数据问题只简单地设置平伏常数加以平滑,最后利用少量人工规则修正标注结果。实验表明,该模型的封闭式测试准确率将近99%,开放式测试准确率为95%以上。

One-step digit-set-restricted modified signed-digit adder using an incoherent correlator based on a shared content-addressable memory

An efficient one-step digit-set-restricted modified signed-digit (MSD) adder based on symbolic substitution is presented. In this technique, carry propagation is avoided by introducing reference digits to restrict the intermediate carry and sum digits to {1,0} and {0,1}, respectively. The proposed technique requires significantly fewer minterms and simplifies system complexity compared to the reported one-step MSD addition techniques. An incoherent correlator based on an optoelectronic shared content-addressable memory processor is suggested to perform the addition operation. In this technique, only one set of minterms needs to be stored, independent of the operand length. (C) 2002 society or Photo-Optical Instrumentation Engineers.

A nanowire magnetic memory cell based on a periodic magnetic superlattice

We analyse the operation of a semiconductor nanowire-based memory cell. Large changes in the nanowire conductance result when the magnetization of a periodic array of nanoscale magnetic gates, which comprise the other key component of the memory cell, is switched between distinct configurations by an external magnetic field. The resulting conductance change provides the basis for a robust memory effect, which can be implemented in a semiconductor structure compatible with conventional semiconductor integrated circuits.

Photon-storage in optical memory cells based on a semiconductor quantum dot-quantum well hybrid structure

We report a new type of photonic memory cell based on a semiconductor quantum dot (QD)-quantum well (QW) hybrid structure, in which photo-generated excitons can be decomposed into separated electrons and holes, and stored in QW and QDs respectively. Storage and retrieval of photonic signals are verified by time-resolved photoluminescence experiments. A storage time in excess of 100ms has been obtained at a temperature of 10 K while the switching speed reaches the order of ten megahertz.

Realization of write-once-read-many-times memory devices based on poly(N-vinylcarbazole) by thermally annealing

A nonvolatile write-once-read-many-time (WORM-time) memory device based on poly(N-vinylcarbazole) (PVK) films was realized by thermally annealing. The device can be fabricated using a simple spin coat method. It was found that the control of PVK film surface morphology by thermally annealing plays an important role in achieving the WORM memory properties. The memory device showed an ON/OFF current ratio as high as 10(4) and the retention time was over 2000 s without degradation.

Origin of negative differential resistance and memory characteristics in organic devices based on tris(8-hydroxyquinoline) aluminum

Negative differential resistance (NDR) and memory phenomenon have been realized in current-voltage (I-V) characteristics of indium tin oxide/tris(8-hydroxyquinoline) aluminum/aluminum devices. The I-V curves have been divided into three operational regions that are associated with different working regimes of the devices: (i) bistable region, (ii) NDR region, and (iii) monotonic region. The bistable region disappeared after a couple of voltage sweeps from zero to a positive voltage. The bistable nature can be reinstated by applying a suitable negative voltage.

Nonvolatile memory devices based on gold nanoparticle and poly (N-Vinylcarbazole) composite

A rewritable polymer memory device based on gold nanoparticle doped poly (N-vinylcarbazole) (PVK), which can be easily fabricated by simple spin coating, has been described. An electrical bistable phenomenon is observed in the current-voltage characteristics of this device, and it is found that the electrical bistability is repeatable by proper writing voltage and erasing voltage. The unique behavior of the devices provides an interesting approach such that doping nanoparticles in polymer can be used to realize high performance nanovolatile polymer memory devices.

Shape memory effect of poly(L-lactide)-based polyurethanes with different hard segments

A series of biodegradable polylactide-based polyurethanes (PLAUs) were synthesized using PLA diol (M-n = 3200) as soft segment, 4,4 '-diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate (TDI), and isophorone diisocyanate (IPDI) as hard segment, and 1,4-butanediol as chain extender. The structures and properties of these PLAUs were studied using infrared spectroscopy, differential scanning calorimetry, tensile testing, and thermomechanical analysis. Among them, the MDI-based PLAU has the highest T-g, maximum tensile strength, and restoration force, the TDI-based PLAU has the lowest T-g, and the IPDI-based PLAU has the highest tensile modulus and elongation at break. They are all amorphous. The shape recovery of the three PLAUs is almost complete in a tensile elongation of 150% or a twofold compression. They can keep their temporary shape easily at room temperature (20 degrees C). More importantly, they can deform and recover at a temperature below their T-g values. Therefore, by selecting the appropriate hard segment and adjusting the ratio of hard to soft segments, they can meet different practical demands for shape memory medical devices.

Biodegradable polyurethane based on random copolymer of L-lactide and epsilon-caprolactone and its shape-memory property

A series of biodegradable polyurethanes (PUs) are synthesized from the copolymer diols prepared from L-lactide and epsilon-caprolactone (CL), 2,4-toluene diisocyanate, and 1,4-butanediol. Their thermal and mechanical properties are characterized via FTIR, DSC, and tensile tests. Their T(g)s are in the range of 28-53 degrees C. They have high modulus, tensile strength, and elongation ratio at break. With increasing CL content, the PU changes from semicrystalline to completely amorphous. Thermal mechanical analysis is used to determine their shape-memory property. When they are deformed and fixed at proper temperatures, their shape-recovery is almost complete for a tensile elongation of 150% or a compression of 2-folds. By changing the content of CL and the hard-to-soft ratio, their T(g)s and their shape-recovery temperature can be adjusted. Therefore, they may find wide applications.

Shape-memory and biocompatibility properties of segmented polyurethanes based on poly(L-lactide)

A series of segmented poly (L-lactide)-polyurethanes (PLA-PU) were synthesized by a two-step method, with oligo-poly(L-lactide) (PLA) as the soft segments and the reaction product of 2,4-toluene diisocyanate(TDI) and ethylene glycol(EG) as the hard segments. The shape memory properties of PLA-PUs were examined. The processed PLA-PUs could recover almost 100% to their original shape within 10 degrees C from the lowest recovery temperature. In the recovery process, the PLA-PUs showed a maximum contracting stress of shape change in the range of 1.5-4 MPa depending on the PLA segmental length and the hard-segmental content and higher than that of poly (e-caprolactone polyurethane) (PCL-PU). Besides, the influence of deforming and fixing temperatures on shape memory properties of PLA-PU was studied in detail. They could affect not only the recovery temperature but also the maximum contracting stress. The experiments of cell incubation were used to evaluate the biocompatibility of PLA-PU. The results show that the biocompatibility of PLA-PU is comparable to that of the pure PLA. This kind of polyurethane can be used as implanted medical devices with a shape memory property.