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291.
Yoo-Chul Kim Youn-Mo Lee Myeong-jo Son Tae-wan Kim Jung-Chun Suh 《Journal of Marine Science and Technology》2009,14(3):275-284
We generate cutter paths free of interference and gouging for manufacturing model propellers using a five-axis numerical control
(NC) machine. Our approach is faster than using a general-purpose computer-aided design (CAD)/computer-aided manufacturing
(CAM) system. A roughing cut is made using only three axes for efficiency, and the finishing cut is made using all five axes
to avoid collisions. Elements of the cutter path that might produce gouging are eliminated and the pose of the cutter is adjusted
to eliminate interference. A number of models, including surface-piercing propellers, have been manufactured. 相似文献
292.
A steel impeller placed in a water pump has been studied with the aim of understanding the surface erosion-corrosion phenomena
responsible for reducing the pumping efficiency of water inside the cooling system. This experiment includes long-term (over
about half a year) observations with a powered microscope and precise weight measurements. The experiments were carried out
under different conditions of water using several mixtures of water and coolants with water contents of 25%, 50%, 75%, and
100% (i.e., pure tap water). The visual microscopy results reveal that most of the steel surface is pitted and clearly rusty, such that
corrosion phenomena are noticeable as time passes. In addition, the amount of weight lost from the sample specimens submerged
in static water increased linearly, whereas those placed in mixtures of water and coolant initially gained weight before reaching
an almost constant weight. In order to see the dynamic effect of the impeller on the erosion-corrosion phenomena, surface
observations of the steel impeller were also made at each time after suitable running conditions in water and water-coolant
mixtures, namely around 3∼4 hours of operation per day under changing rotation speeds. The results show that the rate of weight
loss was linear and 2∼3 times higher than the impeller in water under both static and dynamic conditions. However, when the
impeller was submerged in the mixtures, the weight loss was initially insignificant due to the corrosion-proof ingredients
of the coolant, but after around 2 months the weight loss substantially increased and gradually approached a linear curve. 相似文献
293.
Recent improvements in the quality of life have led to a consumer need for emotional quality. This need is regarded as extremely
important, particularly for products that require a close interaction between products and users and thus that directly lead
to product purchase. As a result, research on how to design user-friendly products has become an important task for corporations.
Discomfort evaluation in product use has been extensively researched for this purpose. Most of the research concludes that
the joint angles of the human body are the main cause of discomfort and propose a discomfort evaluation method based on joint
angles. In general, when a person uses great force, they feel discomfort, and the level of discomfort varies depending on
the size of the force. Accordingly, it can be inferred that the force acting on the muscle is one of the important causes
of discomfort, and research on the correlation between discomfort and muscle forces is needed. In this study, the authors
developed a method to evaluate discomfort during ingress into a vehicle to design a side panel for comfortable ingress into
a vehicle. The correlation between the muscle forces and discomfort was investigated, and a discomfort evaluation method based
on muscle forces was developed. To calculate the muscle forces during the ingress motion, an experimental mock-up of a vehicle
was made, and a motion capture experiment during the ingress motion was conducted with various side panel design parameters.
The biomechanical simulation tool was used to perform motion simulation based on the motion data obtained. The mathematical
correlation between the calculated muscle forces and discomfort was obtained by means of fuzzy logic, and the discomfort evaluation
method developed in this study was used to propose a method for designing a comfortable side panel for a vehicle. 相似文献
294.
N. G. Park J. H. Ryu H. W. Lee Y. H. Jeon N. Zhang 《International Journal of Automotive Technology》2009,10(3):341-346
An Inner Spherical CVT (ISCVT) transfers engine power by utilizing the traction force of the lubricant fluid film on the contact
point between concave and convex spherical rolling bodies. Since the concave and the convex contact surfaces of the ISCVT
are exactly spherical parts, they have a large circular (not elliptic) contact area, and the ISCVT mechanism has a larger
torque capacity, less spin loss, and better stability than other traction drive mechanisms. The IVT (Infinitely Variable Transmission)
performances also can easily be embodied in the ISCVT. In this work, we developed a prototype of the ISCVT for a motorcycle
with a 125cc single cylinder engine having a maximum torque of 13.73 Nm at 8,000 rpm. The design parameters were determined,
and the transmission performances were evaluated by optimal design procedure. The transmission efficiency, the life time,
the maximum severe stresses on each part of the ISCVT, and the work needed for varying speed ratio were theoretically investigated,
and the efficiency performances were experimentally measured. The manufactured prototype was installed in an actual motorcycle,
which was fixed on the test-bench equipped with a dynamometer. The parasitic loss of the prototype and the cross-sectional
road load performance were tested. The power efficiency of the simulated prototype was between 87∼92%, and the life span was
more than 50,000 hours. The tested overall power efficiency was around 70∼92% under frequent driving conditions, which is
an impressive performance in a motorcycle transmission despite the small difference from the simulation. 相似文献
295.
H. J. Kim C. H. Bae S. H. Kim H. Y. Lee K. J. Park M. W. Suh 《International Journal of Automotive Technology》2009,10(1):123-129
Urban transit is a complex system that contains both electrical and mechanical entities; therefore, it is necessary to construct
a maintenance system for ensuring safety during high-speed driving. Expert systems are computer programs that use numerical
or non-numerical domain-specific knowledge to solve problems. This research aims to develop an expert system that diagnoses
the causes of failures quickly and displays measures to correct them. For the development of this expert system, the standardization
of a failure code classification and the creation of a Bill of Materials (BOM) were first performed. Through the analysis
of both failure history and maintenance manuals, a knowledge base has been constructed. Also, for retrieving the procedure
of failure diagnosis and repair linking with the knowledge base, we have built a Rule-Based Reasoning (RRB) engine with a
pattern matching technique and a Case-Based Reasoning (CBR) engine with a similar search method. Finally, this system has
been developed as web based in order to maximize accessibility. 相似文献
296.
A heuristic for the train pathing and timetabling problem 总被引:5,自引:0,他引:5
In a railroad system, train pathing is concerned with the assignment of trains to links and tracks, and train timetabling allocates time slots to trains. These important tasks were traditionally done manually, but there is an increasing move toward automated software based on mathematical models and algorithms. Most published models in the literature either focus on train timetabling only, or are too complicated to solve when facing large instances. In this paper, we present an optimization heuristic that includes both train pathing and train timetabling, and has the ability to solve real-sized instances. This heuristic allows the operation time of trains to depend on the assigned track, and also lets the minimum headway between the trains to depend on the trains’ relative status. It generates an initial solution with a simple rule, and then uses a four-step process to derive the solution iteratively. Each iteration starts by altering the order the trains travel between stations, then it assigns the services to the tracks in the stations with a binary integer program, determines the order they pass through the stations with a linear program, and uses another linear program to produce a timetable. After these four steps, the heuristic accepts or rejects the new solution according to a Threshold Accepting rule. By decomposing the original complex problem into four parts, and by attacking each part with simpler neighborhood-search processes or mathematical programs, the heuristic is able to solve realistic instances. When tested with two real-world examples, one from a 159.3 km, 29-station railroad that offers 44 daily services, and another from a 345 km, eight-station high-speed rail with 128 services, the heuristic obtained timetables that are at least as good as real schedules. 相似文献
297.
T. Fang R. E. Coverdill C. -F. F. Lee R. A. White 《International Journal of Automotive Technology》2008,9(5):551-561
An optically accessible single-cylinder high speed direct-injection (HSDI) Diesel engine equipped with a Bosch common rail
injection system was used to study low temperature Modulated Kinetics (MK) combustion with a retarded single main injection.
High-speed liquid fuel Mie-scattering was employed to investigate the liquid distribution and evolution. By carefully setting
up the optics, three-dimensional images of fuel spray were obtained from both the bottom of the piston and the side window.
The NOx emissions were measured in the exhaust pipe. The influence of injection pressure and injection timing on liquid fuel
evolution and combustion characteristics was studied under similar fuel quantities. Interesting spray development was seen
from the side window images. Liquid impingement was found for all of the cases due to the small diameter of the piston bowl.
The liquid fuel tip hits the bowl wall obliquely and spreads as a wall jet in the radial direction of the spray. Due to the
bowl geometry, the fuel film moves back into the central part of the bowl, which enhances the air-fuel mixing process and
prepares a more homogeneous air-fuel mixture. Stronger impingement was seen for high injection pressures. Injection timing
had little effect on fuel impingement. No liquid fuel was seen before ignition, indicating premixed combustion for all the
cases. High-speed combustion video was taken using the same frame rate. Ignition was seen to occur on or near the bowl wall
in the vicinity of the spray tip, with the ignition delay being noticeably longer for lower injection pressure and later injection
timing. The majority of the flame was confined to the bowl region throughout the combustion event. A more homogeneous and
weaker flame was observed for higher injection pressures and later injection timing. The combustion structure also proves
the mixing enhancement effect of the liquid fuel impingement. The results show that ultra-low sooting combustion is feasible
in an HSDI diesel engine with a higher injection pressure, a higher EGR rate, or later injection timing, with little penalty
on power output. It was also found that injection timing has more influence on HCCI-like combustion using a single main injection
than the other two factors studied. Compared with the base cases, simultaneous reductions of soot and NOx were obtained by
increasing EGR rate and retarding injection timing. By increasing injection pressure, NOx emissions were increased due to
leaner and faster combustion with better air-fuel mixing. However, smoke emissions were significantly reduced with increased
injection pressure. 相似文献
298.
C. -J. Kim Y. J. Kang B. -H. Lee H. -J. Ahn 《International Journal of Automotive Technology》2012,13(3):451-458
Critical responses are frequently detected at the coupled torsional beam axle (CTBA) of a lightweight vehicle. However, the
freedom to modify the design of the axle shaft is limited because the suspension system must satisfy other vehicle requirements
such as steering performance. Conventional sensitivity analysis cannot provide practical information about the resonant behavior
because the analysis only identifies the contribution of the axle shaft to the behavior. This paper presents a novel sensitivity
analysis based on transmissibility ratios (TRs). The vehicle components other than the axle shaft that can be modified to
control the critical spectra are identified using acceleration responses. A multi-body vehicle model is constructed to simulate
the proposed design modifications, and the simulation results show that the vibration of the axle shaft is considerably reduced
by the modifications. Because the TRs on the CTBA are effectively minimized through the modified design strategy, the resonant
response from the axle shaft can be controlled efficiently. 相似文献
299.
S.?Lee Y.?Cho M.?Song H.?Kim J.?Park D.?BaikEmail author 《International Journal of Automotive Technology》2012,13(3):355-363
Particulate matter in diesel engine exhaust, particularly nano-particles, can cause serious human health problems including
diseases such as lung cancer. Because diesel nano-particle issues are of global concern, regulations on particulate matter
emissions specify that not only the weight of particulate matter emitted but also the concentration of nanoparticles must
be controlled. This study aimed to determine the effects on nano-particle and PM emissions from a diesel engine when applying
a urea-SCR system for NOx reduction. We found that PM weight increases by approximately 90% when urea is injected in ND-13 mode over the emission without
urea injection. Additionally, PM weight increases as the NH3/NOx mole ratio is increased at 250 °C. In SEM scans of the collected PM, spherical particles were observed during urea injection,
with sizes of approximately 200 nm to 1 μm. This study was designed to determine the conditions under which nano-particles
and PM are formed in a urea-SCR system and to relate these conditions to particle size and shape via a quantitative analysis
in ND-13 mode. 相似文献
300.
Virtualization is attracting significant interest in the automotive industry because it enables a highly secure and reliable
computing environment. More importantly, virtualization maintains the same operating environment for legacy automotive software
while exploiting the benefits of widely adopted multicore platforms. To exploit the virtualization technology in an automotive
system, it is important to predict the WCET of an automotive application running on a virtual machine monitor (VMM). Unfortunately,
the task is challenging because of difficulties in analyzing complicated interactions between a VMM and a guest OS. There
are no known attempts to predict the WCET of an application in such an environment. In this paper, we propose a hierarchical
and parametric WCET prediction framework. We divide the problem into two subproblems. First, we model the WCET of an application
as a function of WCETs of system calls provided by a guest OS. Second, we model WCETs of a system call as a function of WCETs
of VMM services. To establish this framework, we clearly identify the places and times of VMM services invoked during the
execution of an application. At the time of deployment, the WCET of an application is instantiated by composing the WCET models
altogether. We have performed experiments with the proposed framework by predicting the WCETs of sample programs on various
virtual and real machine platforms. These experimental results effectively demonstrate the viability of the proposed framework. 相似文献