OBJECTIVES: The objectives were to measure the impact of specific features of imaging devices on tasks relevant to minimally invasive surgery (MIS) and to investigate cognitive and perceptual factors in such tasks. BACKGROUND: Although image-guided interventions used in MIS provide benefits for patients, they pose drawbacks for surgeons, including degraded depth perception and reduced field of view (FOV). It is important to identify design factors that affect performance. METHOD: In two navigation experiments, observers fed a borescope through an object until it reached a target. Task completion time and object shape judgments were measured. In a motion perception experiment, observers reported the direction of a line that moved behind an aperture. A motion illusion associated with reduced FOV was measured. RESULTS: Navigation through an object was faster when a preview of the object's exterior was provided. Judgments about the object's shape were more accurate with a preview (compared with none) and with active viewing (compared with passive viewing). The motion illusion decreased with a rectangular or rotating octagonal viewing aperture (compared with circular). CONCLUSIONS: Navigation performance may be enhanced when surgeons develop a mental model of the surgical environment, when surgeons (rather than assistants) control the camera, and when the shape of the image is designed to reduce visual illusions. APPLICATION: Unintentional contact between surgical tools and healthy tissues may be reduced during MIS when (a) visual aids permit surgeons to maintain a mental model of the surgical environment, (b) images are bound by noncircular apertures, and (c) surgeons manually control the camera. 相似文献
Cross Virtual Concatenation is the new technique proposed for bandwidth efficient transmission of data over SDH networks.
SDH networks came into existence for reliable voice transmission. As the demand of data traffic grew in wide area networks,
new technologies were developed and standardized for data transmission over SDH networks. The technologies used namely, GFP
(generic framing procedure), VCAT (virtual concatenation) and LCAS (link capacity adjustment scheme) enable network operator
to provide integrated voice and data services over their legacy SDH infrastructure. Data packets are encapsulated using framing
protocols GFP. VCAT is a process of distributing the GFP framed data payload in number of virtual channels of same capacity
forming a Virtually Concatenated Group (VCG). LCAS is used for dynamic bandwidth allocation. LCAS enhances the VCAT scheme
with hitless in service addition and removal of VC’s to/from the VCG.VCAT combines homogeneous virtual channels together which
in some cases limits the performance of VCAT. This paper describes the implementation of new concatenation technology named
cross virtual concatenation (CVC), which combines heterogeneous VC’s together to utilize the SDH bandwidth more efficiently.
CVC implementation requires only end node equipments to be upgraded as VCG members travel through the link similar to the
conventional VCAT. This paper proposes FPGA implementation of transmitter and receiver circuits for 100 Mbps Ethernet data
transmission over next Generation SDH systems using CVC, where two types of VC’s namely VC-3 and VC-12 are used for data transmission.
Total Transmission delay is calculated as 125 μs. There is no complexity added at the receiver side due to this delay. The
receiver is designed for 32 ms differential delay compensation which can be increased up to maximum 256 ms by increasing the
buffer size at the receiver. 相似文献
This paper analyzes the influence of electric poling on structure, magnetism, and ferroelectricity by temperature-dependent Raman scattering (180 K–500 K), magnetic susceptibility, and ferroelectric measurements on Pb0.9Bi0.1Fe0.55Nb0.45O3 (PBFNO) multiferroic. X-ray diffraction (XRD) has confirmed the monoclinic structure for PBFNO sample before and after poling. Rietveld refined XRD for poled and unpoled sample shows the influence of electric poling on Fe-O1, Fe-O2, Nb–O, and Bi-O modes with small variation in the lattice parameters. The unpoled PBFNO exhibits broad and overlapping 10 active modes at room temperature (100 to 1300 cm?1) at 147, 212, 255, 431, 479, 561, 700, 795, 835, and 1112 cm?1. In case of a poled sample, Pb–O and Nb–O-Nb modes become more active compared to the unpoled sample. Changes observed in the temperature-dependent magnetic measurements, i.e., ZFC/FC and M-H loop, evidence the poling effects on Fe–O and Nb–O active modes. By poling the improvement in ferroelectric domain, ordering occurs, and it is confirmed by P-E loops. The consequences of numerous investigations on electric poling of PBFNO will provide the foundation for future device development and design.
Oxidation resistance and water wettability of graphite flakes have been improved by a thin sol–gel film of magnesium aluminate spinel (MgAl2O4) over its surface. The hydrosol has been synthesized by less expensive precursors and the spinel formation has been studied by scanning electron microscopy (SEM), supplemented with energy dispersive spectral analysis. After an easy-to-use mixing procedure, drying (110°C), and subsequent calcination (550°C), coated graphites were sieved to below 75 μm. The coating over the powder contained 1.5 wt% MgAl2O4, which enormously increased the oxidation resistance (performed at 600°, 900°, and 1200°C) and water wettability, as revealed by hydrophilic functional groups from infrared spectra. Defective, intermediate spinel structure of fine, lamellar Mg-doped γ-Al2O3 has been considered to be significant for this improvement. An approximate (1:2) stoichiometry of (Mg:Al) in the coating composition was confirmed by an X-ray photoelectron spectroscopy test. Castables prepared by this graphite remarkably improved their bulk density and apparent porosity compared with those prepared by the as-received graphite. Casting water was reduced along with the amount of antioxidants. This also enhanced the resistance toward the basic slag by retaining the graphite in the refractory. 相似文献
When chlorobenzene was reacted with ethyl alcohol and carbon monoxide under pressure, the conversions of chlorobenzene to ethyl benzoate and benzoic acid under optimum reaction conditions were 31.3% and 30.1% respectively, with nickel naphthenate supported on silica gel (Ni:SiO2 = 50:50) as the best catalyst. When bromobenzene was used instead of chlorobenzene, the best catalyst was found to be nickel iodide supported on silica gel (Ni:SiO2 = 50:50), and the above conversions were 74.7% and 25.1% respectively under optimum reaction conditions. 相似文献
Wireless Personal Communications - With the advent of sensor technologies, cloud applications are able to acquire sensed data from remotely located sensors which are geographically distributed.... 相似文献
A site-directed mutation, F235C, was created at the penultimateresidue of the -repressor. Measurement of dimermonomerdissociation constant suggested that dimermonomer dissociationof the mutant repressor is similar to that of the wild-type.Affinity towards a single operator OR1 is also similar to thatof the wild-type repressor. The mutant repressor gene in a multi-copyplasmid confers immunity towards infection by a cI- lambda phage,suggesting preservation of functional integrity. Far-UV circulardichroism spectra show no major change in the secondary structure.Fluorescence quenching experiments, however, suggest increasedexposure of some tryptophan residues. The urea denaturationprofile indicates decreased stability of a part of the C-terminaldomain. Under non-denaturing conditions, cysteine-235 showshalf-of-the-sites reactivity, i.e. on average only one out oftwo cysteine-235 residues in the dimer shows reactivity towardssulfhydryl reagents. Fluorescence energy transfer between randomlylabeled donor and acceptor fluorescent probes indicates thatonly one sulfhydryl per dimer is reactive, suggesting true half-of-the-sitesreactivity. The structural role of the C-terminal tail in thewhole repressor dimer is discussed. 相似文献