Publish in OALib Journal
APC: Only $99
Power conditioner, that is responsible for electric power conversion, is
a critical component used in many renewable energy power generation systems.
Most of the electric power produced by distributed energy resources cannot
directly import to utility network without power conversion. Meanwhile, power
conversion may includes several different types, for example AC/DC, and DC/AC,
which is realized by a variety types of power conditioners in the electric
power system. Currently, many concerns are focused on the operation of these
power conditioners used in distributed energy resources due to the worse
designing may cause the terrible influence on safety and performance
characteristic of distributed energy resources. The power quality and
reliability of interconnected electric power network may be affected as well.
In the view of this, IEEE standards board provides a uniform standard for
interconnection of distributed resources with electric power systems. It
provides requirements relevant to the performance, operation, testing, safety
considerations, and maintenance of the interconnection. Based on the IEEE 1547
standard, this paper presents a test system for power conditioners that are used
in distributed energy resources or other renewable energy applications. Some of
the test items that described in IEEE 1547.1 relevant to interconnection issues
can be realized by proposed test system.
In this paper, three-dimensional finite element analysis using the
commercial ANSYS software is performed to study the thermal performance of a
thermally enhanced FC-PBGA (flip-chip plastic ball grid array) assembly in both
natural and forced convection environments. The thermally enhanced FC-PBGA
assembly is a basic FC-PBGA assembly
with a lid attached on top, after which an extruded-fin heatsink
is attached on the top of the lid. The finite element model is complete enough
to include key elements such as bumps, solder balls, substrate, printed circuit board, extruded-fin
heatsink, lid, vias, TIM1 (thermal interface material 1), TIM2 (thermal
interface material 2), lid-substrate adhesive and ground planes for both signal
and power. Temperature fields are simulated and presented for several package configurations. Thermal resistance is calculated to
characterize and compare the thermal performance by considering alternative
design parameters of the polymer-based materials and the thermal enhancement
components. The polymer-based materials include underfill, TIM1, TIM2,
lid-substrate adhesive and substrate core material. The specific thermal enhancement
components are the extruded-fin heatsink
and the lid.
Background: Obesity has been described among survivors of pediatric Acute Lymphoblastic Leukemia (ALL), especially those who have received cranial radiation. This study aims to evaluate the prevalence of overweight or obesity in pediatric ALL survivors who were not exposed to radiation, identify the time frame in which the rate of obesity rise is the greatest, and identify contributing clinical and treatment variables. Methods: In this retrospective, single institution study, the charts of 132 ALL survivors were reviewed. Odds Ratios (OR) and 95% Confidence Intervals (CI) were calculated for being overweight or obese at their 2 year follow-up for the following clinical variables: ethnicity, age at diagnosis, and weight at diagnosis. Changes in BMI percentiles between 4 different time points were assessed using t-test comparison and p values. Results: Survivors of ALL were more likely to be overweight or obese than the general population at the 2 and 5 year follow-up. White and Hispanic ethnicity and being overweight or obese at diagnosis were also risk factors for being overweight or obese 2 years after the end of treatment. When looking at the time frame of weight gain, survivors had a significant increase in BMI percentile between diagnosis and end of therapy, and between diagnosis and 2 year follow-up, but did not have a significant increase between end of therapy and 2 year follow-up. Conclusion: Patients with ALL have an increased risk of being obese at follow-up. They show early weight gain, between diagnosis and end of treatment, and remain overweight/obese long term. Ethnicity and BMI weight category at diagnosis were significant influences. A strategic plan to prevent this weight gain should be implemented early during therapy.