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51.
Helman N.C. Roth J.E. Bour D.P. Altug H. Miller D.A.B. 《IEEE journal of selected topics in quantum electronics》2005,11(2):338-342
We present a surface-normal modulator architecture for optical interconnects that offers misalignment tolerance as well as high contrast ratio over a wide wavelength range for a small drive voltage. A contrast ratio greater than 3 dB was achieved for only 0.8-V drive across a 16-nm wavelength range from 1498 to 1514 nm. The misalignment tolerance between this device, and the input optical beam was measured to be 30 /spl mu/m. 相似文献
52.
O'Neill R.P. Helman U. Baldick R. Stewart W.R. Jr. Rothkopf M.H. 《Power Systems, IEEE Transactions on》2003,18(4):1331-1337
We define transmission rights that are compatible with the Federal Energy Regulatory Commission's proposed standard market design (SMD) and that provide flexibility in the points of receipt or delivery of energy contracts. The contingent transmission rights introduced here provide a viable, flexible method for defining SMD-compatible rights for transmission customers having current (pre-SMD) transmission rights that cover multiple points. These contingent rights can be bought and sold in the transmission rights auctions under SMD. 相似文献
53.
L Zhang S Zhan F Navid Q Li YH Choi M Kim P Seth LJ Helman 《Canadian Metallurgical Quarterly》1998,17(10):1261-1270
Ours is the age of science and technology. The conclusions of modern medical science and theories are derived from experimental research developed since the last century by the life sciences, with the methods of the exact and physical sciences, and the invaluable aid of technology. This paper compares past systems of medicine with our own, and examines the role of science and theory in medical practice, in the remote and recent past and at present. Has medical science and theory in the past been of benefit to medical practice? Has it helped the physician to understand disease? To treat the sick? Finally, the paper looks at a number of uncomfortable questions raised by medical practice in our own time. The widespread rejection of today's medical practice with its flawed doctor-patient relationship, its super-specialization and mechanization, and its incessantly growing reliance on technology, is examined in the light of the prodigious advances of modern medical science and some of its abuses and exorbitant claims as well as its rejection of the value of past medical systems. Our need is for an integration of the old and the new, in a synthesis that will lead us back to a more human medicine. 相似文献
54.
Helman I. Stern Professor Shaul P. Ladany 《The International Journal of Advanced Manufacturing Technology》1994,9(6):398-407
A production system comprised of multiple stages in tandem is considered. Each stage may be in either of two states: desirable or undesirable. Each stage may be placed under control so that it remains in the desirable state and produces the maximum fraction of conforming production units. Stages remaining uncontrolled may change randomly from the desired state to the undesired state. The controls may be mechanical or manual but involves costs which may or may not be dependent on the stage being controlled. It is desirable to find the optimal number of controls and their allocation among the stages which will maximise the net profit of production. The problem is formulated as a nonlinear mathematical program with binary variables. For the identical control cost case (independent of the stage to which control is applied), an 0(n) linear runtime algorithm is provided, wheren is the number of stages. It is shown that a k or nothing (wherek is the total number of controls applied) control policy is optimal and depends on a critical cost computed from the given parameters of the problem. In addition, conditions are provided under which all or nothing control policies are optimal. This is based on the computation of a critical cost and is independent of the number of stages in the system. It is shown that when these conditions are met the profit function is pointwise convex ink. Optimal solution techniques are provided and analysed for special cases in terms of the relationships between control cost and production parameters. Sensitivity analysis is provided for each of the parameters of the problem. The solutions are in general robust, with respect to these parameter variations. Numerical examples are provided throughout the paper to illustrate the relevant theorems. The paper ends with a discussion on the general control cost case and some feasible bounds on the optimal solution are offered. 相似文献
55.
In this work, we consider the recognition of dynamic gestures based on representative sub-segments of a gesture, which are denoted as most discriminating segments (MDSs). The automatic extraction and recognition of such small representative segments, rather than extracting and recognizing the full gestures themselves, allows for a more discriminative classifier. A MDS is a sub-segment of a gesture that is most dissimilar to all other gesture sub-segments. Gestures are classified using a MDSLCS algorithm, which recognizes the MDSs using a modified longest common subsequence (LCS) measure. The extraction of MDSs from a data stream uses adaptive window parameters, which are driven by the successive results of multiple calls to the LCS classifier. In a preprocessing stage, gestures that have large motion variations are replaced by several forms of lesser variation. We learn these forms by adaptive clustering of a training set of gestures, where we reemploy the LCS to determine similarity between gesture trajectories. The MDSLCS classifier achieved a gesture recognition rate of 92.6% when tested using a set of pre-cut free hand digit (0–9) gestures, while hidden Markov models (HMMs) achieved an accuracy of 89.5%. When the MDSLCS was tested against a set of streamed digit gestures, an accuracy of 89.6% was obtained. At present the HMMs method is considered the state-of-the-art method for classifying motion trajectories. The MDSLCS algorithm had a higher accuracy rate for pre-cut gestures, and is also more suitable for streamed gestures. MDSLCS provides a significant advantage over HMMs by not requiring data re-sampling during run-time and performing well with small training sets. 相似文献
56.
D Helman NR Staten J Grosclaude N Daniel C Nespoulous J Djiane A Gertler 《Canadian Metallurgical Quarterly》1998,273(26):16067-16074
Two new analogues of bovine placental lactogen (bPL), bPL(G133K) and bPL(G133R), were expressed in Escherichia coli, refolded, and purified to a native form. Binding experiments, which are likely to represent the binding to site 1 only, to intact FDC-P1 cells transfected with rabbit (rb) growth hormone receptor (GHR) or with human (h) GHR, to Nb2 rat lymphoma cells, or to rabbit mammary gland membranes prolactin receptor (PRLR), revealed only small or no reduction in binding capacity. The complex formation between these analogues and receptor extracellular domains (R-ECD) of various hormones was determined by gel filtration. Wild type bPL yielded 1:2 complex with hGHR-ECD, rat PRLR-ECD, and rbPRLR-ECD, whereas both analogues formed only 1:1 complexes with all R-ECDs tested. Real time kinetics experiments demonstrated that the ability of the analogues to form homodimeric complexes was compromised in both PRLR- and GHR-ECDs. The biological activity transduced through lactogenic receptors in in vitro bioassays in rabbit mammary gland acini culture and in Nb2 cells was almost fully retained, whereas the activity transduced through somatogenic receptors in FDC-P1 cells transfected with rbGHRs or with hGHRs was abolished. Both analogues exhibited antagonistic activity in the latter cells. To explain the discrepancy between the effect of the mutation on the signal transduced by PLR versus GHRs we suggest that: 1) the mutation impairs the ability of site 2 of bPL to form a stable homodimeric complex with both lactogenic and somatogenic receptors by a drastic shortening of the half-life of 2:1 complex; 2) the transient existence of the homodimeric complex is still sufficient to initiate the signal transduced through lactogenic receptors but not through somatogenic receptors; and 3) one possible reason for this difference is that JAK2, which serves as a mediator of both receptors, is already associated with lactogenic receptors prior to hormone binding-induced receptor dimerization, whereas in somatogenic receptors the JAK2 receptor association occurs subsequently to receptor dimerization. 相似文献
57.
58.
Helman P. Bhangoo J. 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》1997,27(4):449-466
This paper examines the problem of prioritizing actions under uncertainty. Our motivating applications come from the domain of data mining. Data mining problems present the user with a huge collection of individual items (e.g., abstracts, medical histories, and computer users' command histories) and require that these items be prioritized according to which should be pursued thoroughly. More precisely, each data item is assumed to be generated by one of two processes: A large majority of the data comes from a common, mundane process and a very small fraction comes from a rare, phenomenon process. The problem is to rank the information so as to optimally direct the user in his or her pursuit of the data items that were generated by the phenomenon process. Our previous work has developed the theoretical foundations of the information prioritization problem. The current paper summarizes these foundations, derives new theoretical results, and details initial experimental results of a prioritization system based on the theory. We focus here on feature selection techniques and the method of model surrogates, each tailored to the classes of prioritization applications of greatest current interest. Our results demonstrate the effectiveness of the techniques and motivate further research to improve the existing system 相似文献
59.
B. C. Schreiber R. P. Philp S. Benali M. L. Helman J. A. de la Peña R. Marfil P. Landais A. D. Cohen C.G.St.C. Kendall 《Journal of Petroleum Geology》2001,24(3):309-338
Sediments deposited under hypersaline conditions, particularly those laid down in the transition zone between marine carbonates and evaporites, are increasingly recognised as a potential source for oil. Recent environments that lie in waters with elevated salinities are sites of very high biological productivity that can be used as models for evaporite-related sedimentation in the geological record. Of particular importance is the range of elevated salinities well above the range for normal marine biota, in which organic-rich cyanobacterial carbonates form and accumulate in large quantities. Such organic matter collected from a number of modern evaporative settings has been examined in terms of oil potential and for biomarkers characteristic of hypersaline environments. The regions studied include marine-fed salinas (Santa Pola, Spain); marine-fed sabkhas (Abu Dhabi, UAE); and continental ponds and lakes (La Mancha region, Spain). High values of H/C ratio and HI demonstrate the oil source potential of this organic matter. The hydrocarbons generated during artificial maturation of these immature sediments resemble those naturally occurring in ancient petroleum-generating evaporitic systems. Variations in the total 相似文献
60.