619 research outputs found
QCD critical end point from a realistic PNJL model
With parameters fixed by critical temperature and equation of state at zero
baryon chemical potential, a realistic Polyakov--Nambu--Jona-Lasinio (rPNJL)
model predicts a critical end point of chiral phase transition at . The extracted freeze-out line from heavy ion
collisions is close to the chiral phase transition boundary in the rPNJL model,
and the kurtosis of baryon number fluctuations from the rPNJL
model along the experimental freeze-out line agrees well with the BES-I
measurement. Our analysis shows that the dip structure of measured
is determined by the relationship between the freeze-out line
and chiral phase transition line at low baryon density region, and the peak
structure can be regarded as a clean signature for the existence of CEP.Comment: 8 papges, proceedings of QCD@Work 201
Clamping Force Distribution within Press Pack IGBTs
Press pack insulated gated bipolar transistors (PP IGBTs) have been gradually used in the high-voltage and high-power-density applications, such as the power system and electric locomotive, with its advantages of double-sided cooling, higher power density, and easy to connect in series compared with traditional wire-bonded power IGBT modules. However, the clamping force is quite important for PP IGBTs because too much clamping fore will cause mechanical damage to the silicon chips and too little clamping force will increase the junction temperature of the silicon chips due to the increased thermal contact resistance. And eventually it leads to thermal damage. Furthermore, the clamping force distribution within PP IGBTs is affected by many factors, and they can be divided into the internal and external factors. The finite element analysis model of the PP IGBTs is established based on the theory of elastic mechanics to obtain the influence of the affect factors, including the external clamping modes, spring design, thermal stress, the machining accuracy, and so on. The contribution of those affect factors to the clamping force distribution is ranked, and this can be a guideline not only for users but also for the manufacturers
Efficient, robust surface functionalization and stabilization of gold nanorods with quaternary ammonium-containing ionomers as multidentate macromolecular ligands
Surface functionalization of gold nanorods (GNRs) is critical to their applications in various
fields. While there are several existing strategies, we report in this article a new general strategy
for the surface functionalization of GNRs with quaternary ammonium-containing ionomers as a
novel class of multidentate macromolecular surface ligands. A range of tetralkylammoniumcontaining
hyperbranched polyethylene- and linear poly(n-butyl acrylate)-based ionomers has
been specifically designed and employed in the strategy. Acting as multidentate macromolecular
analogues of cetyltrimethylammonium bromide (CTAB), the ionomers have been demonstrated
to bind onto the GNR surface by displacing the surface-bound CTAB species via ligand
exchange to render CTAB-free ionomer-modified GNRs. By properly designing the enabling
ionomers, we have shown that the modified GNRs can be endowed with some desired properties,
such as excellent dispersibility in various organic solvents, robust stability under multiple rounds
(up to 12 investigated) of high-speed centrifugation in organic solvents, amphiphilicity with
dispersibility in both aqueous and organic media, fluorescence, and capability in carrying
hydrophobic guest species. This strategy thus provides potential new ways for the construction of
novel multifunctional GNR nanocomposites
The kurtosis of net baryon number fluctuations from a realistic Polyakov--Nambu--Jona-Lasinio model along the experimental freeze-out line
Firstly we qualitatively analyze the formation of the dip and peak structures
of the kurtosis of net baryon number fluctuation along
imagined freeze-out lines and discuss the signature of the existence of the QCD
critical end point (CEP) in the Nambu--Jona-Lasinio (NJL) model, Polyakov-NJL
(PNJL) model as well as -dependent PNJL( PNJL) model with different
parameter sets, and then we apply a realistic PNJL model with parameters fixed
by lattice data at zero chemical potential, and quantitatively investigate its
along the real freeze-out line extracted from experiments.
The important contribution from gluodynamics to the baryon number fluctuations
is discussed. The peak structure of along the freeze-out line
is solely determined by the existence of the CEP mountain and can be used as a
clean signature for the existence of CEP. The formation of the dip structure is
sensitive to the relation between the freeze-out line and the phase boundary,
and the freeze-out line starts from the back-ridge of the phase boundary is
required. To our surprise, the kurtosis produced from the
realistic PNJL model along the experimental freeze-out line agrees with BES-I
data well, which indicates that equilibrium result can explain the experimental
data. It is worth to point out that the extracted freeze-out temperatures from
beam energy scan measurement are indeed higher than the critical temperatures
at small chemical potentials, which supports our qualitative analysis.Comment: 15 pages, 10 figure
PolyBuilding: Polygon Transformer for End-to-End Building Extraction
We present PolyBuilding, a fully end-to-end polygon Transformer for building
extraction. PolyBuilding direct predicts vector representation of buildings
from remote sensing images. It builds upon an encoder-decoder transformer
architecture and simultaneously outputs building bounding boxes and polygons.
Given a set of polygon queries, the model learns the relations among them and
encodes context information from the image to predict the final set of building
polygons with fixed vertex numbers. Corner classification is performed to
distinguish the building corners from the sampled points, which can be used to
remove redundant vertices along the building walls during inference. A 1-d
non-maximum suppression (NMS) is further applied to reduce vertex redundancy
near the building corners. With the refinement operations, polygons with
regular shapes and low complexity can be effectively obtained. Comprehensive
experiments are conducted on the CrowdAI dataset. Quantitative and qualitative
results show that our approach outperforms prior polygonal building extraction
methods by a large margin. It also achieves a new state-of-the-art in terms of
pixel-level coverage, instance-level precision and recall, and geometry-level
properties (including contour regularity and polygon complexity)
Optimal Multicast Group Communication
Many IP multicast based applications, such as Pay-TV, Multiplayer games, require controlling the group
memberships of senders and receivers. One common solution is to encrypt the data with a session key shared
with all authorized senders/receivers. To efficiently update the session key in the event of member removal,
many rooted-tree based group key distribution schemes have been proposed. However, most of the existing
rooted-tree based schemes are not optimal. In other words, given the O(log N) storage overhead, the
communication overhead is not minimized. On the other hand, although Flat Table scheme
achieves optimality , it is rather dismissed due to the vulnerability to collusion
attacks.
In this paper, we propose a key distribution scheme -- EGK that attains the same optimality as Flat Table
without collusion vulnerability. EGK also support dynamic subgroup communication initialized by each group
members (imagine a virtual chat room in the multicast group). Additionally, EGK provides constant message
size and requires O(log N) storage overhead at the group controller, which makes EGK suitable for
applications containing a large number of multicasting group members. Moreover, adding members in EGK
requires just one multicasting message. EGK is the first work with such features and out-performs all
existing schemes
On efficient ciphertext-policy attribute based encryption and broadcast encryption
Abstract. Ciphertext Policy Attribute Based Encryption (CP-ABE) enforces an expressive data access policy, which consists of a number of attributes connected by logical gates. Only those decryptors whose attributes satisfy the data access policy can decrypt the ciphertext. CP-ABE is very appealing since the ciphertext and data access policies are integrated together in a natural and effective way. However, all existing CP-ABE schemes incur very large ciphertext size, which increases linearly with respect to the number of attributes in the access policy. Large ciphertext prevents CP-ABE from being adopted in the communication constrained environments. In this paper, we proposed a new construction of CP-ABE, named Constant-size CP-ABE (denoted as CCP-ABE) that significantly reduces the ciphertext to a constant size for an AND gate access policy with any given number of attributes. Each ciphertext in CCP-ABE requires only 2 elements on a bilinear group. Based on CCP-ABE, we further proposed an Attribute Based Broadcast Encryption (ABBE) scheme. Compared to existing Broadcast Encryption (BE) schemes, ABBE is more flexible because a broadcasted message can be encrypted by an expressive access policy, either with or without explicit specifying the receivers. Moreover, ABBE significantly reduces the storage and communication overhead to the order of O(log N), where N is the system size. Also, we proved, using information theoretical approaches, ABBE attains minimal bound on storage overhead for each user to construct all possible subgroups in the communication system.
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