求解多约束0-1背包问题的遗传算法的改进

提出对基本遗传算法(Genetic Algorithm,GA)的改进策略,并将其应用于多约束0-1背包问题(Multi-constrained 0-1Knapsack Problems,MKP)的求解。改进策略主要有:将线性规划松弛法求得的MKP的解作为初始解,另外为了避免种群多样化的丧失,将复杂的修复操作和局部优化操作应用于每一个最近产生的解。最后,对大规模测试数据的标准集进行实验,并将该算法与先前的方法进行比较,结果表明新的遗传算法在大多数时间能够更快速地收敛到较优解。     

耐磨堆焊层中化学成分对热裂纹倾向的影响

介绍了耐磨堆焊熔敷层热袭纹的形成机理,并以１５＃钢为母材,研究了高Ｃ合金多层堆焊中化学成分对热裂纹倾向的影响。     

OPTIMAL DELAUNAY POINT INSERTION

An efficient algorithm for Delaunay triangulation of a given set of points in d dimensions is presented. Various steps of the point insertion algorithm are reviewed and many acceleration procedures are implemented to speed up the triangulation process. New features include the search for a neighbouring point by a layering scheme, locating the containing simplex by a random walk, formulas of important geometrical quantities of a new simplex based on those of an old one, a novel approach in establishing the adjacency relationship using connection matrices. The resulting scheme seems to be one of the fastest triangulation algorithms known, which enables us to generate tetrahedra in ℝ³ with a linear generation rate of 15 000 tetrahedra per second for randomly generated points on an HP 735 workstation.     

Unified field theory for space-time systems

The communication efficiency associated with the problems of transmitting information in space and time is known to be dependent upon the characteristics of the transmission medium. Notably Turin (1977), Kailath (1961), and Bello (1963) have considered the temporal channel response as a function of the channel time and delay spread processes. The physics of the medium have not been considered. Middleton and Groginsky (1965) and Wittwer (1980) have attempted to incorporate the physics of the medium in a strictly temporal channel model. This paper presents a theory that generalizes the earlier work for characterizing medium-induced effects upon deterministic and random space-time fields, and the theory is applicable to any frequency band in the electromagnetic spectrum. For a linear medium, a space-time system field function (S-TSFF) is introduced as a system model for an arbitrary (turbulent or material) medium (Lo 1988). The unified system field theory states that the output space-time field is related to the input space-time field and the S-TSFF through a set of space-time superposition integrals. The geometry between the energy source, the medium, and the observed world-point area or volume is dependent on the chosen coordinate system, and is implicitly expressed by the space-time superposition integrals. (The term world-point was used by Minkowski (1908) to denote a point in a four-dimensional space-time coordinate system. To distinguish our approach from the analysis of arbitrary events in a space-time manifold, the terms world-area and world-volume are chosen to denote the ‘simultaneity in space’ as opposed to the notation of world-line and world-space used in the theory of relativity.) For a deterministic input space-time field, the statistics of the output field are solely dependent on the S-TSFF. For a random input space-time field, the statistics of the output field are related to the statistics of the input field and the S-TSFF. In either case, the statistical characterization can be expressed in terms of a space-time correlation function, or, equivalentIy, the space-time power spectral density of the input-output fields and of the S-TSFF. The space-time correlation function of the S-TSFF generalizes the concept of the mutual coherence function (MCF) used in statistical optics (Born and Wolf 1970). A dual property for the S-TSFF is observed and it is shown to be consistent with the duality principle in physics and the linear system theory in engineering. This space-time duality concept leads to the conclusion that fundamental properties of matter are imbedded in all physically realizable systems. This conclusion has far reaching implications in many detection, instrumentation, and measurement systems—for example, the uncertainty principle can be applied to analyse the stability of atomic clocks and trap ion frequency standards. The medium's response to an applied field is dependent upon whether the observed field is due to a space-time point source, a space-time plane wave, or something in-between. The space-time system field theory has numerous applications in system engineering, e.g. communications, radar, sonar, optics, and various imaging systems.     

Relating the Global Vegetation Index to net primary productivity and actual evapotranspiration over Africa

Nel Primary Productivity (NPP) and Actual Evapotranspiration (AET) are key processes characterizing the vegetation activity. At a continental scale, Annual Net Primary Productivity (ANPP) and annual AET are related to the integrated Normalized Difference Vegetation Index (NDVI). When applied to the African continent, the ANPP/ZNDVI relation gives an estimation of the productivity with a precision comparable to those given by climate models. The estimation of annual AET is possible within climatic zones defined here by their Rain-Use Efficiencies (RUE). On the other hand, on a monthly basis, the AET/ SNDVI relations are less clear and are strongly dependent on the physiognomy of the vegetation community considered. These results show the limits of using ENDVI for estimating the elementary processes of terrestrial vegetation at a continental scale.     

A newly recognized entity: intraductal "oncocytic" papillary neoplasm of the pancreas

Intraductal papillary-mucinous tumors of the pancreas are increasingly recognized, and their characteristic endoscopic and radiological features are well reported in the literature in recent years. Oncocytic features in these tumors are uncommon and unrecognized. Intraductal oncocytic papillary neoplasm is a distinct pancreatic tumor and is a recently recognized entity. We report a case of a 69-yr-old patient who presented with symptoms mimicking pancreatitis, resulting in delay in the diagnosis of her pancreatic tumor. She underwent a successful Whipple's procedure and subsequently has remained well. The resected specimen showed an intraductal oncocytic papillary-mucinous neoplasm. The entity is new and the literature information is inadequate at present to judge the biological behavior of this tumor. We discuss this recently recognized entity.     

Boundary conditions for the diffusion equation in radiative transfer

Using the method of images, we examine the three boundary conditions commonly applied to the surface of a semi-infinite turbid medium. We find that the image-charge configurations of the partial-current and extrapolated-boundary conditions have the same dipole and quadrupole moments and that the two corresponding solutions to the diffusion equation are approximately equal. In the application of diffusion theory to frequency-domain photon-migration (FDPM) data, these two approaches yield values for the scattering and absorption coefficients that are equal to within 3%. Moreover, the two boundary conditions can be combined to yield a remarkably simple, accurate, and computationally fast method for extracting values for optical parameters from FDPM data. FDPM data were taken both at the surface and deep inside tissue phantoms, and the difference in data between the two geometries is striking. If one analyzes the surface data without accounting for the boundary, values deduced for the optical coefficients are in error by 50% or more. As expected, when aluminum foil was placed on the surface of a tissue phantom, phase and modulation data were closer to the results for an infinite-medium geometry. Raising the reflectivity of a tissue surface can, in principle, eliminate the effect of the boundary. However, we find that phase and modulation data are highly sensitive to the reflectivity in the range of 80-100%, and a minimum value of 98% is needed to mimic an infinite-medium geometry reliably. We conclude that noninvasive measurements of optically thick tissue require a rigorous treatment of the tissue boundary, and we suggest a unified partial-current--extrapolated boundary approach.     

The human type 1 inositol 1,4,5-trisphosphate receptor from T lymphocytes. Structure, localization, and tyrosine phosphorylation

Inositol 1,4,5-trisphosphate receptors (IP3R) are intracellular calcium release channels involved in diverse signaling pathways. An IP3R is thought to play a role in mobilizing calcium required for activation of T lymphocytes. The IP3R is a tetrameric structure comprised of four approximately 300-kDa subunits encoded by a approximately 10-kilobase mRNA. In the present study we determined the structure of the human type 1 IP3R expressed in T lymphocytes (Jurkats). The IP3R in human T cells had a predicted molecular mass of 308 kDa and was most similar to the non-neuronal form of the rodent type 1 IP3R. Two putative tyrosine phosphorylation sites were identified, one near the amino terminus and one near the putative channel pore at the carboxyl terminus. During T cell activation the IP3R was tyrosine phosphorylated. A site-specific anti-IP3R antibody was used to localize the carboxyl terminus of the IP3R to the cytoplasm in T cells.     

The effect of hydrophobic character of drugs and helix-coil transition of kappa-carrageenan on the polyelectrolyte-drug interaction

OBJECTIVE: Study of the value of a single positive prostatic biopsy in the staging of prostatic carcinoma and the significance of the tumour volume. METHOD: The clinical, laboratory and pathological parameters were studied in 27 prostatectomized patients with a single positive prostatic biopsy. RESULTS: The length of tumour invasion on the biopsy was 2.6 mm (evaluation on 25 biopsies). Six patients (23%) had an extracapsular tumour and 21 (78%) had a significant tumour volume. Among the 16 patients with a length of tumour invasion < or = 3 mm, 13 (81%) had a significant tumour volume. 25% of patients with less than 3 mm of invasion on the biopsy and a Gleason score < or = 6 and 12% of patients with less than 3 mm of invasion and a PSA < or = 10 ng/ml had a non-significant tumour volume. CONCLUSION: The presence of a single positive prostatic biopsy is not sufficient to determine the pathological stage of a prostatic carcinoma. In this retrospective study, the majority of patients with a single positive biopsy had a significant tumour volume > 0.5 cc. No preoperative predictive factor of tumour volume was demonstrated.