Multiple comparisons tests (MCTs) are performed several times on the mean of experimental conditions. When the null hypothesis is rejected in a validation, MCTs are performed when certain experimental conditions have a statistically significant mean difference or there is a specific aspect between the group means. A problem occurs if the error rate increases while multiple hypothesis tests are performed simultaneously. Consequently, in an MCT, it is necessary to control the error rate to an appropriate level. In this paper, we discuss how to test multiple hypotheses simultaneously while limiting type I error rate, which is caused by α inflation. To choose the appropriate test, we must maintain the balance between statistical power and type I error rate. If the test is too conservative, a type I error is not likely to occur. However, concurrently, the test may have insufficient power resulted in increased probability of type II error occurrence. Most researchers may hope to find the best way of adjusting the type I error rate to discriminate the real differences between observed data without wasting too much statistical power. It is expected that this paper will help researchers understand the differences between MCTs and apply them appropriately.
Triboelectric
nanogenerators (TENGs) have emerged as a next-generation
sustainable power source for Internet of Things technology. Polyvinylidene
fluoride (PVDF) nanofibers (NFs) have been investigated widely to
enhance the TENG performance by controlling their polarity; however,
controlling the surface morphology of the PVDF NFs has rarely been
studied. Here, surface-roughened, churros-like PVDF NFs were fabricated
by controlling the solvent evaporation kinetics. The solvent evaporation
rate was modulated by varying the relative humidity (RH) during the
electrospinning process. With increasing RH, the fraction of polar
β-phase in the PVDF NFs increased, the specific surface area
of the PVDF NFs increased gradually and the surface morphology changed
from smooth to rough, finally resulting in a churros-like structure.
Therefore, the output performance of the TENG devices was enhanced
with increasing RH, because of the combined effects of the enlarged
surface area and the increased fraction of the polar phase in the
PVDF NFs. The TENG device with the churros-like PVDF NFs showed an
output voltage of 234 V, current of 11 μA, and power density
up to 1738 μW/cm2, giving it the capability to turn
on 60 series-connected commercial light-emitting diodes without using
an external charge storage circuit.
Visible-blind
ultraviolet (UV) photodetectors have received a great
deal of attention for realizing Internet of Things technologies as
well as for monitoring the level of UV exposure to humans. Realizing
next-generation flexible and visible-blind UV photodetectors requires
development of new functional material systems with easy fabrication,
selectively strong UV light absorption, environmental friendliness,
and high stability regardless of ambient conditions. Herein, flexible
visible-blind UV photodetectors are successfully fabricated on the
basis of two-dimensional ZnAl-layered double hydroxide (LDH) nanosheets
with scroll structures grown on flexible substrates. The ZnAl-LDH
nanosheet scrolls exhibit highly resistive semiconducting properties
with a band gap of 3.2 eV and work function of 3.64 eV. The photodetector
based on the ZnAl-LDH shows photoresponse in the UV spectral range
below 420 nm, indicating visible-blind spectral response. In addition,
the UV photodetector shows a maximum responsivity of 17 mA/W under
illumination with 365 nm light. Moreover, the flexible photodetector
shows reproducible photoresponse even after 1000 bending cycles, which
indicates the acceptable stability of the ZnAl-LDH nanosheet scrolls.
Colloidal quantum dot white light-emitting diode has received much attention for ambient lighting, photonics and display. Efficient white colour toning is demonstrated by hybridising Perovskite and Chalcopyrite as a single electroluminescence layer.
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