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231.
The intake or exhaust noise of an internal combustion engine is usually predicted by the linear, time-invariant source model in frequency domain with reasonable precision. However, the actual finite amplitude pulsation involves the nonlinear, time-varying characteristics that are prominent in time-domain. To overcome the discrepancy between two source models, an approximate nonlinear and time-varying frequency domain source model can be employed by appending the nonlinear or time-varying terms to the linear, time-invariant source model. Proper selection of the nonlinear describing terms varying with time is important for the realistic and precise prediction of the radiated sound. For the selection of such terms, flow and motional characteristics in the valve and orifice of a simplified fluid machine comprised of very large reservoir, valve, and duct is considered. Effects of each describing term and the combined terms are investigated by comparing the sound spectrum predicted from nonlinear source model to that from linear source model. In the comparison, the sound spectrum calculated by the method of characteristics is used as a reference. It is found that the source model using only the velocityrelated terms yields the best result among all the models using various combinations of the terms with different characteristics. The best model yields a difference from the linear source model within ±5 dB in overall sound level. Change of acoustic loads results in a difference of 20–27 dB in linear source model from the reference data; however, maximum 10–22 dB deviations are observed in using the various nonlinear source models. It is concluded that more than 4 describing terms should be employed in the nonlinear model to obtain a realistic result of the radiated sound from the intake or exhaust system. 相似文献
232.
This paper presents a new active steering control system based on driving phase diagram (β fr ?δ f diagram). In order to make state variables to follow those of nominal vehicle model that was developed under no consideration of disturbance, Quadratic Programming Problem (QPP) is formulated, where time varying objective function minimizes the differences between nominal and actual parameters. The steering characteristic in active steering control system changes when the vehicle faces disturbance such as crosswind and flat tire, and driver tries to counteract it after recognizing the change. The proposed method defines a stability region on β fr ?δ f diagram. In order to make β fr and δ f remain in the stability region, a new model predictive controller is proposed. While conventional controllers are restrictive to satisfy the β fr ?δ f diagram based stability condition, the proposed controller ensures solution space and also plays a direct role to minimize the evaluation function in the constrained optimal control problem. 相似文献
233.
This study proposed a behavioral theory‐based approach to better assess pedestrian levels of service for sidewalks, using the concepts of personal space and pedestrian evasive movements. Data from pedestrian interviews and video recordings at 28 commercial, residential, and leisure locations were used to analyze the effects of pedestrian movements on pedestrian perceived levels of service. With these results, a new measure of pedestrian level of service was developed. With the use of a separate validation sample, the revised levels of service obtained were found to be more consistent with the pedestrian perceived levels than the levels prescribed by the Korean Highway Capacity Manual. Hence, this research recommended the use of the revised measures for pedestrian level of service in the design and evaluation of pedestrian facilities. We also found that pedestrian evasive movements on sidewalks could better explain pedestrians' perception of the levels of service for a given facility. Moreover, pedestrian evasive movements were found to be sensitive to the width of the sidewalk and pedestrian volume. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
234.
DongYoung Lee GyungNam Jo YunHo Kim Hang S. Choi Odd M. Faltinsen 《Journal of Marine Science and Technology》2011,16(3):323-330
In this paper, we investigated the effect of sloshing on the sway motions of two-dimensional rectangular cylinders in regular
waves, bearing in mind possible applications for LNG-FPSO and LNG-FSRU. First, we carried out experiments for two models with
different drafts, or the same draft but different filling ratios, in which the models were firmly connected to each other.
The sway motion was measured with a noncontact video camera. This is an extension of Rognebakke and Faltinsen’s work for a
single model (J Ship Res 47(3):208–221, 2003). It was found that the sway motion became small when the incident wave frequency was close to the lowest natural frequency
of each model. The sway motion greatly increased when the wave frequency was higher than this frequency. The measured data
were compared with numerical results obtained by a single-dominant multi-modal method; relatively good agreement was noted.
However, the numerical results deviated from the experimental results near the lowest natural frequency of the smaller model,
which was believed to be due to overturning waves, as observed during the experiment. Since this is out of the valid range
for the single-dominant multi-modal method, other, more appropriate, methods such as the multi-dominant modal method must
be applied instead. 相似文献
235.
Myeong-jo Son Sang Chul Lee Ki-chang Kwon Tae-wan Kim Rajiv Sharma 《Journal of Marine Science and Technology》2011,16(4):367-378
Ships are complex engineering structures that are designed and built on the basis of technical experience. A shipowner will
often be required to estimate the price of a new ship on the basis of the value of comparable ships identified in trade journals.
Similarly, shipbuilders are often interested in estimating approximate costs during the tendering phase in order to determine
whether a ship is likely to be competitive for a particular order. Thus, when designing a ship prior to having obtained a
contract, one of the most important processes is the estimation of approximate costs, including materials, associated labor,
and overhead. During this preliminary design phase, the design is temporary and subject to change based on variations in the
shipowner’s requirements. Hence, quick and flexible responses are key during this period and an integral aspect of the competitive
powers of the shipbuilder. Given this environment, we propose a “configuration estimation method.” Our method is based on
the configuration design method that is widely used in three-dimensional (3D) computer aided design (CAD) systems. We assume
that a product lifecycle management system is furnished and that the cost is then estimated via the configuration of the ship,
using an engineering bill of materials (E-BOM). In referring to the E-BOM, we utilize technical parametric costs derived from
similar ships built previously. Using the proposed method, it is possible to obtain an accurate list of materials from the
quotation, as well as a detailed work assessment for labor costs and overhead rates, so that reliable cost estimates can be
generated quickly and flexibly. To demonstrate the practical applicability and effectiveness of the proposed method, we implement
the prototype of a shipbuilding configuration estimation system by using a Microsoft Structured Query Language database and
an E-BOM from AVEVA Marine version 12.01, which is a representative CAD system for shipbuilding. 相似文献
236.
B. C. Choi S. K. Choi S. H. Chung J. S. Kim J. H. Choi 《International Journal of Automotive Technology》2011,12(2):183-191
Experimental and numerical analyses of laminar diffusion flames were performed to identify the effect of fuel mixing on soot
formation in a counterflow burner. In this experiment, the volume fraction, number density, and particle size of soot were
investigated using light extinction/scattering systems. The experimental results showed that the synergistic effect of an
ethylene-propane flame is appreciable. Numerical simulations showed that the benzene (C6H6) concentration in mixture flames was higher than in ethylene-base flames because of the increase in the concentration of
propargyl radicals. Methyl radicals were found to play an important role in the formation of propargyl, and the recombination
of propargyl with benzene was found to lead to an increase in the number density for cases exhibiting synergistic effects.
These results imply that methyl radicals play an important role in soot formation, particularly with regard to the number
density. 相似文献
237.
We analyzed the lubrication characteristics of a design-selected spiral groove liquid seal for the critical component, the
carrier, of a rotary vane-type fuel pump developed for external installation on fuel tanks for liquid phase LPG (liquefied
petroleum gas) injection (LPLi) vehicles, with the aim of fundamentally improving lubrication performance and so protecting
the carrier from early frictional wear damage at its suction face. The main reason for selecting a spiral groove pattern was
because the viscosity of liquid LPG is very low, comparable to that of air, and current commercial dry gas seals adopting
spiral grooves have been successfully employed in completely noncontacting applications. Utilizing the Galerkin finite element
lubrication analysis method, a detailed lubrication characteristic analysis of the seal was performed, and lubrication performance
optimization was performed by systematic parameter analyses of the design variables. Compared to the initial reference design,
the final optimized spiral groove seal design had a groove depth increased by 66.7% and an equilibrium seal clearance increased
by 65.3%. Our model also predicted that under a condition of equilibrium between the closing force of the pumping pressure
and the seal opening force, the optimally designed carrier spiral groove liquid seal was capable of maintaining a stable lubricating
film with sufficient axial stiffness and thereby demonstrated successful noncontact operation; in addition, leakage through
the seal was minimal. 相似文献
238.
D. -H. Shin B. -H. Lee J. -B. Jeong H. -S. Song H. -J. Kim 《International Journal of Automotive Technology》2011,12(1):125-130
Hybrid electric vehicles (HEV) utilize electric power and a mechanical engine for propulsion; therefore, the performance of
HEVs is directly influenced by the characteristics of the energy storage system (ESS). The ESS for an HEV generally requires
high power performance, long cycle life, reliability and cost effectiveness; thus, a hybrid energy storage system (HESS) that
combines different types of storage devices has been considered to fulfill both performance and cost requirements. To improve
the operating efficiency and cycle life of a HESS, an advanced dynamic control regime in which pertinent storage devices in
the HESS can be selectively operated based on their status is presented. Verification tests were performed to confirm the
degree of improvement in energy efficiency. In this paper, an advanced HESS with a battery management system (BMS) that includes
an optimal switching control function based on the estimated state of charge (SOC) is presented and verified. 相似文献
239.
There has been recent interest in intelligent vehicle technologies, such as advanced driver assistance systems (ADASs) or
in-vehicle information systems (IVISs), that offer a significant enhancement of safety and convenience to drivers and passengers.
However, the use of ADAS- and IVIS-based information devices may increase driver distraction and workload, which in turn can
increase the chance of traffic accidents. The number of traffic accidents involving older drivers that are due to distraction,
misjudgment, and delayed detection of danger, all of which are related to the drivers’ declining physical and cognitive capabilities,
has increased. Because the death rate in traffic accidents is higher when older drivers are involved, finding ways to reduce
the distraction and workload of older drivers is important. This paper generalizes driver information device operations and
assesses the workload while driving by means of experiments involving 40 drivers in real cars under actual road conditions.
Five driving tasks (manual only, manual primarily, visual only, visual primarily, and visual-manual) and three age groups
(younger (20–29 years of age), middle-aged (40–49 years of age), and older (60–69 years of age)) were considered in investigating
the effect of age-related workload difference. Data were collected from 40 drivers who drove in a real car under actual road
conditions. The experimental results showed that age influences driver workload while performing in-vehicle tasks. 相似文献
240.
C. -H. Lee J. -M. Lee M. -S. Choi C. -K. Kim E. -B. Koh 《International Journal of Automotive Technology》2011,12(2):193-198
Since the invention of automobiles, the need to know the braking performance of vehicles has been acknowledged. However, because
there are numerous design variables as well as nonlinearities in the braking system, it is difficult to predict the performance
accurately. In this paper, a computational program is developed to estimate the braking performance numerically. This synthetic
braking performance program accounts for pedal force, pedal travel and deceleration of braking parts, such as master cylinder,
booster, valve, brake pad, rotor, and hoses. To improve the accuracy of program, a semi-empirical model of a braking system
is introduced by using the empirical test data of pad compression, hose expansion and the friction coefficient between the
pad and rotor. The accuracy of the estimation is evaluated by comparing it to the actual vehicle test results. The developed
program is easy for the brake system engineers to manipulate and it can be used in the development of new vehicles by incorporating
the graphical presentations. 相似文献