229 research outputs found
PID control system analysis and design
With its three-term functionality offering treatment of both transient and steady-state responses,
proportional-integral-derivative (PID) control provides a generic and efficient solution to realworld
control problems. The wide application of PID control has stimulated and sustained
research and development to "get the best out of PID", and "the search is on to find
the next key technology or methodology for PID tuning".
This article presents remedies for problems involving the integral and derivative terms. PID design objectives,
methods, and future directions are discussed. Subsequently, a computerized, simulation-based approach
is presented, together with illustrative design results for first-order, higher order, and nonlinear plants. Finally,
we discuss differences between academic research and industrial practice, so as to motivate new research
directions in PID control
PID control system analysis, design, and technology
Designing and tuning a proportional-integral-derivative
(PID) controller appears to be conceptually intuitive, but can
be hard in practice, if multiple (and often conflicting) objectives
such as short transient and high stability are to be achieved.
Usually, initial designs obtained by all means need to be adjusted
repeatedly through computer simulations until the closed-loop
system performs or compromises as desired. This stimulates
the development of "intelligent" tools that can assist engineers
to achieve the best overall PID control for the entire operating
envelope. This development has further led to the incorporation
of some advanced tuning algorithms into PID hardware modules.
Corresponding to these developments, this paper presents a
modern overview of functionalities and tuning methods in patents,
software packages and commercial hardware modules. It is seen
that many PID variants have been developed in order to improve
transient performance, but standardising and modularising PID
control are desired, although challenging. The inclusion of system
identification and "intelligent" techniques in software based PID
systems helps automate the entire design and tuning process to
a useful degree. This should also assist future development of
"plug-and-play" PID controllers that are widely applicable and
can be set up easily and operate optimally for enhanced productivity,
improved quality and reduced maintenance requirements
FSI simulations for explosions very near reinforced concrete structures
The analysis of explosives in contact or very near to reinforced concrete (RC)
structures is an important aspect in the design of protective structures and vulnerability
assessments. Although this remains a topic of high importance for defence, a more
widespread interest has developed as civilian structures become the targets of terrorism. This
type of assessment requires a robust simulation method for coupled fluid-structural
interactions (FSI) which can handle the explosive detonation, air blast propagation, structural
deformation, and damage evolution. This paper describes the application of a loose-coupling
method which combines the FEFLO CFD code and SAIC’s CSD code for 3D numerical
simulations of unconfined and semi-confined explosions near RC structures. This approach
takes advantage of the unstructured tetrahedral mesh for the CFD and an embedded method
for CSD structures inside the fluid domain. Comparisons of simulations with experiment
provide validation, but also reveal some weaknesses of the method. A good agreement
between simulation and experiment is found with moderate explosive loading. However, a
severe explosive loading with confinement results in extensive damage to the structure which
is difficult to reproduce in simulations
J Interpers Violence
Homicide-suicide incidents involving child victims can have a detrimental impact on survivors of the violence, family members and friends of the decedents, and other community members, but the rare occurrence of these acts makes using quantitative data to examine their associated antecedents challenging. Therefore, using qualitative data from the 2003-2011 National Violent Death Reporting System, we examined 175 cases of homicide-suicide involving child victims in an effort to better understand the complex situational factors of these events. Our findings indicate that 98% of homicide-suicides with child victims are perpetrated by adults (mostly parents) and propelled by the perpetrators' intimate partner problems, mental health problems, and criminal/legal problems. These events are often premeditated, and plans for the violence are sometimes disclosed prior to its occurrence. Findings provide support for several theoretical perspectives, and implications for prevention are discussed.CC999999/Intramural CDC HHS/United States2019-02-01T00:00:00Z26385898PMC4795978vault:1634
An Empirical Investigation into the Antecedents and Consequences of Customer Engagement in Omnichannel Retailing
Engaging customers across channels has become one of the biggest challenges for retailers adopting an omnichannel strategy. In this study, we examine how channel integration quality influences customer engagement in the context of omnichannel retailing. Drawing on the conceptual model of customer engagement, we proposed a research model to explain the effects of breadth of channel choice, transparency of channel-service configuration, content consistency, and process consistency on customer engagement, as well as the positive outcomes associated with the engagement. The research model will be tested with a sample of 500 omnichannel customers using a structural equation modeling approach. This study is expected to contribute to the research on, and practice of, the omnichannel customer engagement by validating the antecedents and consequences of such engagement as well as providing practitioners with insights into devising a successful omnichannel retailing strategy
Health-related quality of life in pediatric patients with leukemia in Singapore: a cross-sectional pilot study
There has been a paradigm shift in health service delivery to a more holistic approach, which
considers Quality of Life (QoL) and overall functioning. Health-Related Quality of Life (HRQoL)
is a multidimensional construct that encompasses physical functioning as well as psychosocial
aspects of emotional and social functioning. This study explored factors related to HRQoL in Asian
pediatric patients with leukemia in Singapore. The available variables included: age, treatment
duration, household income, gender, ethnicity, religion, diagnosis, and phase of treatment. It is
hypothesized that the relationships will be significant. In the current study, there were 60 patients
(60% males) with leukemia; their ages ranged from 1 to 21 years (Mean = 8.03, Standard Deviation
= 4.55). The hypothesis was partially supported. Age had a significant positive relationship with
physical functioning, r(60) = 0.28, p < 0.05, physical health, r(60) = 0.28, p < 0.05, and the total HRQoL
score, r(60) = 0.29, p < 0.05. Treatment duration had a positive relationship with school functioning,
r(60) = 0.28, p < 0.05. All other correlations were statistically non-significant. The effects of the
available psychosocial variables of gender, ethnicity, and religion were examined on scores from the
Pediatric Quality of Life Inventory (PedsQL). Ethnicity had a significant effect on social functioning,
U = 292.00, p < 0.05, r = 0.3 (medium effect size). Specifically, Chinese (Median = 85.00, n = 33) had
significantly higher scores on social functioning than others (Median = 70.00, n = 27). The remaining
comparisons were statistically non-significant. The current findings added to QoL research, and
provided an impetus for more research in the area of HRQoL for children with leukemia in Singapore
Conceptual design of a novel power-augmented hydrokinetic run-of- river turbine
Other than the water stream from ocean, river stream is also being considered as a viable source of renewable energy. Many researchers has approached and started the studies of river stream in order to harness the maximum power from the rivers. River stream offers promising energy especially to the rural areas which are surrounded by rivers. From previous studies, it shows that majority of the hydrokinetic run-of-river turbine systems are designed in vertical and horizontal axis. Besides, some of the vertical and horizontal axis turbines are also enclosed by the duct or diffuser in order to guide the river stream and increase the flow velocity. However, the design of the shape of diffuser faced the challenges during fabrication phase and additional supporting structures are needed during installation, causing the increases in the overall cost. In this paper, the authors would like to propose a conceptual design of a novel power-augmented hydrokinetic run-of-river turbine which utilizes the concept of cross-axis wind turbine and simple augmented guide vane. This conceptual design of hydrokinetic turbine able to capture the advantages of both the horizontal and vertical axis turbines. Helical blade design was chosen for this conceptual design due to its ability to capture the skewed flow created by the difference in velocity of upper and lower faces of turbine. When the vertical-axis turbine rotates, the angle of attack of each blade varies cyclically. The cyclical variation of the angle of attack creates cyclical blade loading, which increases the fatigue experienced by blades. Most of the cyclical loading can be alleviated by using helical instead of straight blades. The conceptual design of this cross-axis turbine with helical blade is similar to the Gorlov helical turbine but there are some differences in the radial blades which are designed as 8 degrees upper and lower respectively to the horizontal axis of the connector hub. The two layers radial blade-rotors are offset by 60 degrees. The turbine
system is designed by intercepting the two guide vanes in between three individual turbines and also two diffuservanes
as the outer part of the system. The NACA 0015 airfoil profile is used as turbine blade in this design. The
construction costs of cross-axis concept turbine and the helical blades are relatively low (about 30%) compared
with the huge ducted and diffuser turbine. A 3D model was constructed and simulated by using the computational
fluid dynamics software, ANSYS-Fluent. In the simulation, the velocity of water flow and the rotational speed of
turbine were increased with the integration of the guide-vane and diffuser features. It is estimated that this
conceptual design turbine will achieve 60% increase in energy gain
Weibull Strength Analysis of Pineapple Leaf Fiber
Pineapple leave fiber (PALF) can be considered as one of the green materials to the
industries, which is the potential to replace the non-renewable synthetic fiber. However, the high
disparity in the mechanical properties of PALF becomes an issue in structural composite design.
Hence, improved Weibull distribution is utilised to quantify the tensile strength variation of PALF
in various gauge lengths. The single fiber tensile test was performed after the fiber surface treatment
and fiber diameter scanning. The predicted PALF strength by applying the improved Weibull
distribution incorporating with conical frustum model is well compromised with experimental data
compared to the traditional Weibull model
- …