A state-space approach to Walsh series solution of linear systems

A state-space procedure for solving linear dynamic systems by the Walsh series is developed. A new operational matrix plays the main role and a new Kronecker product formula is established. The laborious use of Corrington'B tables is eliminated. Several examples illustrate the process and demonstrate the power of the approach.     

Stabilization of large structural systems under mode truncation,parameter perturbations and actuator saturations

The stabilization of large structural systems (LSS) under (i) mode truncation and linear parametric perturbations, or (ii) mode truncation and actuator saturations is considered. A new robust stability condition for the perturbed LSS controlled by observer-based compensators is derived. A stability criterion is also given for the stabilization of LSS by observer-based constrained controls. Finally, a simply supported beam problem is provided for illustration.     

为下一代作准备:林后四林平地森林园区规划

林后四林平地森林园区是一处集平地造林、在地文化、栖地营造、资源利用与环境教育为一体的学习园区.在其不断的发展下,现成为大武山低海拔自然森林园区,作为生态栖地修复、区域文化体验及休闲游憩的场域.从环境修复的角度保有农垦地和草生地生态环境,并营造大武山低海拔森林的栖地环境,提供猛禽、鸟类及两栖类动物栖息繁衍之地.重视生态保育意义的同时,发挥环境教育和生态旅游的价值.因气候环境变迁,以分散排水、贮流、自然人渗及自然过滤方式为主,同时进行土壤地利改良,达到环境保全修复的功效.以现地环境保育及生态演变历史延续对自然环境的关怀,营造合宜的生态栖地、掌握水资源的保存与再利用,为下一代的自然生态环境作准备.     

Practical Vector Dirty Paper Coding for MIMO Gaussian Broadcast Channels

Recently, the vector dirty paper coding (DPC) achievable rate region has been shown to be the capacity region of a multiple-input multiple-output Gaussian broadcast channel (MIMO GBC). With DPC, the multiuser interference noncausally known at the transmitter can be completely removed. In this paper, we present a vector DPC structure for MIMO GBC. It is a generalization of the single antenna superposition dirty paper coding for the scalar Gaussian dirty paper problem proposed by Bennatan et al. In a theoretical random code setting, this construction is shown to be able to achieve the promised rate performance of the MIMO GBC. We also implement it with existing vector quantizer and capacity-achieving channel coding. Combined with iterative decoding, a design example validates the effectiveness of our methods.     

Convection Velocity of Vortex Structures in the Near Wake of a Circular Cylinder

The convection velocity of vortex structures in the near wake of a circular cylinder was experimentally investigated over the region 1.6–2.5 ? x/D ? 12.0 for R = 160–12,000. Dye injection technique of flow visualization and two completely noninvasive laser Doppler velocimeters were employed for R ? 320 and ?400, respectively. The convection velocity, Uc, is defined as the mean traveling velocity of vortex cores passing a streamwise separation during a mean elapsed time. For R ? 320, Uc was determined directly from the motion of dye-marked vortex cores filmed by a video camera. In the cases of R ≥ 400, the positions of peak vorticity and half of the half-velocity-defect width at each downstream section were first used to identify the mean path of vortex cores (i.e., the most probable trajectory of the vortex structures), along which spatial correlation measurements were then performed to determine the mean elapsed time corresponding to the maximum cross correlation. The present results show that, in laminar and transitional wakes, the ratio Uc/Uo increases from 0.53 to 0.84 over a region of 1.6 ? x/D ? 6.0 and then tends to be a constant of 0.84 for x/D ≥ 6.0. In a turbulent wake, Uc/Uo also increases from a certain value at a point downstream from the position of vortex formation to a mean value of about 0.86 at x/D ≥ 5.0–6.0, and then changes little with the increase of x/D. In addition, it is found that the dependence of Uc/Uo on R almost disappears for x/D ≥ 5.0.     

基于水质模拟的水质在线监测站点布设研究

随着水质监测连续化的需求增加,河流水质在线监测站布设成为不可忽视的问题。本文采用水文模拟模型HSPF对台湾淡水河流域进行水量水质联合模拟。水文模拟以9个测站比对,纳什效率系数多数大于0.7;相关系数r皆大于0.7。水质模拟以27个测站比对,生化需氧量、氨氮、悬浮固体、溶氧的修正平均百分误差多数小于25%。基于水质变化率和水质超标率提出水质敏感河段概念,并以此确定为补充布设水质在线监测站点的优先河段。研究指出,淡水河流域水质在线监测站目前仍缺乏且位置不尽合理,应优先补充三峡河的三峡大桥、景美溪的宝桥、基隆河的江北桥水质在线监测站。     

Fractal Dimensions of Hydrogen Induced Brittle Fracture of Titanium Aluminide

The relationship between the stress intensity factor K_1~* required for brittle crack initiation and propa-gation and the fractal dimension D_F of the fracture surface was derived,i.e,InK_1~*=(1/2)In2γE'+(1/2)In(d_f/L_0)(1-D_F)The real surface energy can be calculated based on the measured linear relation of the InK_1~* vs D_F,The equation is not only suitable for the overload fracture but also for the delayed fracture,e.g.hydrogen induced cracking (HIC) and stress corrosion cracking (SCC).The experiment resultsshowed that the hydrogen induced delayed cracking occurred in the Ti-24AI-11 Nb alloy during dy-namic charging,and the threshold stress intensity factor was very low,i.e..K_(IH)/K_(IC)= 0.43.The ex-perimental relationship between the stress intensity factor K_1~* and D_F was consistent with the theo-retical equation.     

High-sensitivity analysis of six synthetic musks by ultra-performance liquid chromatography-atmospheric pressure photoionization-tandem mass spectrometry

The occurrence and potential toxicity of synthetic musks in environmental media have aroused concerns for the impacts of these chemicals on ecosystems and human health. Here, we present the first method using ultra-performance liquid chromatography-atmospheric pressure photoionization-tandem mass spectrometry (UPLC-APPI-MS/MS) for analysis of the six most important synthetic musks. Analysis was performed on an API 3000 triple quadrupole equipped with a PhotoSpray APPI source. Two pairs of precursor/product ions are presented that are essential for confirmation. Chromatographic separation is completed in 7 min in the positive mode and 5.1 min in the negative mode. Furthermore, three dopant solutions (0.5% anisole in toluene, 0.5% 2,4-difluoroanisole (DFA) in bromobenzene, and 0.5% DFA in chlorobenzene) are compared in terms of sensitivity, linearity, precision, and accuracy. The best sensitivity is associated with 0.5% anisole in toluene as the dopant; all LODs are below 6 pg. The linear range is 5 to 500 ppb with fairly good precision and accuracy. This analytical method has also proven its applicability by analyzing real air samples. In summary, we present a fast, sensitive, and reliable UPLC-APPI-MS/MS method for six important synthetic musks; it can be readily applied to environmental studies.     

Light Amplification and Efficient Electroluminescence from a Solution-Processable Diketopyrrolopyrrole Derivative via Triplet-to-Singlet Upconversion

Over the years, achieving efficient electroluminescence (EL) while simultaneously having low light amplification thresholds under optical excitation has been the key to progression toward the long-thought objective of electrically pumped organic lasers. While significant progress in this regard has been made for organic semiconductors emitting in the blue–green region of the visible spectrum, organic laser dyes with low-energy emission (>600 nm) still suffer from high amplified spontaneous emission (ASE) thresholds and low external quantum efficiencies (EQEs) in devices. Herein, low ASE thresholds and efficient EL are reported from a solution-processable organic laser dye dithiophenyl diketopyrrolopyrrole (DT-DPP). The ASE threshold of 4 µJ cm⁻² at the wavelength of 620 nm is obtained while making constructive use of triplet excitons by doping DT-DPP in a green-emitting host matrix, which exhibits thermally activated delayed fluorescence (TADF). The organic light-emitting diode fabricated from this system gives a high EQE of 7.9% due to the efficient utilization of triplet excitons. Transient EL studies further show that a high reverse intersystem crossing rate is crucial in achieving lasing under electrical pumping from such TADF-assisted fluorescent systems.