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811.
LIU Jian-feng YUAN Gan-nan ZHOU Wei-dong 《船舶与海洋工程学报》2005,4(4):12-17
Some construct characteristics and composing material of the new Gyro' s rotor are introduced. Some factors resulting in deformation of the rotor surface are analyzed. Under different loads such as the fo,'ce of deflecting center, the change of temperature, the fo,ce of pressure and couple factors, the deformation of rotor is analyzed with the wavelet finite element simulation software. The vector distributing map of rotor reformation is given. The deformation resulting from the pressure force of photon is studied. Finally, the influence on Gyro' s performance because of anomalous surface of rotor due to deformation of rotor is researched and the result is useful to forecast the performance of the drift of gyroscope. The disturbing moment resulting from the deformation of rotor can be compensated using the mathematic method, and provides an important reference for both design and optimization of the rotor. 相似文献
812.
HUANG Shao-bin WU Yan-xia PIAO Xiu-feng 《船舶与海洋工程学报》2005,4(4):47-52
The electronic system in a comprehensive shipboard has a extremely wide bandwidth. It supports synchronized and asynchronous data transmission, multimedia correspondence, and videophone conferencing. In order to guarantee the security and correspondent real time of the communication, choosing a multicast routing protocol based on different applications is a key problem in terms of the complexity of the system. A simulation model was first designed for existing multicast routing protocols in NS-2 and analysis was performed on their corresponding application environments. The experiments proved that PIM-DM based on the shortest-path tree protocol is suitable for communication in the field of comprehensive shipboard. Further work that is necessary is also discussed. 相似文献
813.
A 2D finite element model was established for inertia friction welding of GH4169 nickel-base superalloy based on the ABAQUS
environment. The remeshing and map solution techniques were adopted to solve the problem of element distortion. The effect
of rotation speed on the temperature field and axial shortening of joints was investigated. The results show that the interface
temperature increases rapidly to higher than 900°C within 1 s. And then, it increases slowly to a quasi-stable value. The
axial shortening begins to augment quickly when a uniform interface temperature field has formed and the plasticized material
is extruded from the interface to form an obvious flash. The rotation speed of the flywheel controls the welding process and
has a significant influence on the temperature evolution and axial shortening of joints. 相似文献
814.
Bayes risk (BR) decoding methods have been widely investigated in the speech recognition area due to its flexibility and complexity
compared with the maximum a posteriori (MAP) method regarding to minimum word error (MWE) optimization. This paper investigates
two improved approaches to the BR decoding, aiming at minimizing word error. The novelty of the proposed methods is shown
in the explicit optimization of the objective function, the value of which is calculated by an improved forward algorithm
on the lattice. However, the result of the first method is obtained by an expectation maximization (EM) like iteration, while
the result of the second one is achieved by traversing the confusion network (CN), both of which lead to an optimized objective
function value with distinct approaches. Experimental results indicate that the proposed methods result in an error reduction
for lattice rescoring, compared with the traditional CN method for lattice rescoring. 相似文献
815.
The presence of wrinkles in the membrane is the main factor to induce the reflector surface inaccuracy of the space inflatable
antenna. Based on the commercial finite element package ABAQUS, a numerical procedure for membrane wrinkle analysis was set
up and used to analyze a space inflatable antenna which was under inner pressure to evaluate its wrinkle characteristics.
First, the inner pressure effect on the reflector’s wrinkle pattern was studied thoroughly. As inner pressure increases, both
the number and the amplitude of the wrinkles decrease, but the total deformation of the whole reflector surface increases
much. Second, the influence of the interactions between antenna’s parts was investigated comprehensively. Any kind of unwanted
interaction deteriorates reflector’s wrinkle characteristics. The works are valuable to the development and research of the
space inflatable antenna. 相似文献
816.
Paul S. Szwed 《WMU Journal of Maritime Affairs》2011,10(2):183-208
Given the inherent complexity of the maritime transportation system, developing effective policy can be challenging. Using
risk factors identified by an elicitation and aggregation of expert judgment, a relative-risk rating scheme was developed
in the theory-building tradition of the social sciences. The model was empirically evaluated using 18 months of data from
the US small passenger vessel sector. The model identified that the top 10% of relatively highest risk vessels accounted for
50% of all marine casualties during the period of examination. A policy for deploying the model nationally is proposed. 相似文献
817.
A generalized collaborative optimization (CO) framework is proposed to the optimization design of the lines of an underwater vehicle. The resistance and maneuvering performances are concerned about and taken as the optimization objectives in the optimization framework. The resistance, lateral force and yaw moment are calculated by RANS method. To improve the optimization efficiency, an automatic integration optimization platform is constructed in which a surrogate model is adopted. A SUBOFF model is taken as the verification model. The optimal results demonstrate the validity of the optimization strategy proposed. 相似文献
818.
It is widely recognized that individual decision-making is subject to the evaluation of gains and losses around a reference
point. The estimation of discrete choice models increasingly use data from stated choice experiments which are pivoted around
a reference alternative. However, to date, the specification of a reference alternative in transport studies has been fixed,
whereas it is common to observe individuals adjusting their preferences according to a change in their reference point. This
paper focuses on individual reactions, in a freight choice context, to a negative change in the reference alternative values,
identifying the behavioural implications in terms of loss aversion and diminishing sensitivity. The results show a significant
adjustment in the valuation of gains and losses around a shifted reference alternative. In particular, we find an average
increase in loss aversion for cost and time attributes, and a substantial decrease for punctuality. These findings are translated
to significant differences in the willingness to pay and willingness to accept measures, providing supporting evidence of
respondents’ behavioural reaction. 相似文献
819.
Seven adjustments of convergent-type Vortex Tube (VT) with different throttle angles were applied. The adjustments were made to analyze the influences of such angles on cold and hot temperature drops as well as flow structures inside the VTs. An experimental setup was designed, and tests were performed on different convergent VT configurations at injection pressures ranging from 0.45 to 0.65 MPa. The angles of the throttle valve were arranged between 30° to 90°, and the numbers of injection nozzles ranged between 2 and 6. Laboratory results indicated that the maximum hot and cold temperature drops ranged from 23.24 to 35 K and from 22.87 to 32.88 K, respectively, at four injection nozzles. Results also showed that temperature drop is a function of hot throttle valve angle with the maximum hot and cold temperature drops depending on the angle applied. We used graphs to demonstrate the changes in the cold and hot temperature drops with respect to hot throttle angle values. These values were interpreted and evaluated to determine the optimum angle, which was 60°. The CFD outputs agreed very well with the laboratory results. The proposed CFD results can help future researchers gain good insights into the complicated separation process taking place inside the VTs. 相似文献
820.
Small sample size problem is one of the main problems that heavy numerical control (NC) machine tools encounter in their reliability assessment. In order to deal with the small sample size problem, many indirect reliability data such as reliability data of similar products, expert opinion, and engineers’ experience are used in reliability assessment. However, the existing mathematical theories cannot simultaneously process the above reliability data of multiple types, and thus imprecise probability theory is introduced. Imprecise probability theory can simultaneously process multiple reliability data by quantifying multiple uncertainties (stochastic uncertainty, fuzzy uncertainty, epistemic uncertainty, etc.) together. Although imprecise probability theory has so many advantages, the existing natural extension models are complex and the computation result is imprecise. Therefore, they need some improvement for the better application of reliability engineering. This paper proposes an improved imprecise reliability assessment method by introducing empirical probability distributions to natural extension model, and the improved natural extension model is applied to the reliability assessment of heavy NC machine tool spindle to illustrate its effectiveness. 相似文献