2,297 research outputs found
New Constructions of Zero-Correlation Zone Sequences
In this paper, we propose three classes of systematic approaches for
constructing zero correlation zone (ZCZ) sequence families. In most cases,
these approaches are capable of generating sequence families that achieve the
upper bounds on the family size () and the ZCZ width () for a given
sequence period ().
Our approaches can produce various binary and polyphase ZCZ families with
desired parameters and alphabet size. They also provide additional
tradeoffs amongst the above four system parameters and are less constrained by
the alphabet size. Furthermore, the constructed families have nested-like
property that can be either decomposed or combined to constitute smaller or
larger ZCZ sequence sets. We make detailed comparisons with related works and
present some extended properties. For each approach, we provide examples to
numerically illustrate the proposed construction procedure.Comment: 37 pages, submitted to IEEE Transactions on Information Theor
Rashba Spin Interferometer
A spin interferometer utilizing the Rashba effect is proposed. The novel
design is composed of a one-dimensional (1D) straight wire and a 1D half-ring.
By calculating the norm of the superposed wave function, we derive analytical
expressions to describe the spin interference spectrum as a function of the
Rashba coupling strength. Presented spin interference results are identified to
include (i) the quantum-mechanical 4pi rotation effect, (ii) geometric effect,
and (iii) Shubnikov-de Haas-like beating effect.Comment: 3 pages, 3 figures, appears in the proceedings of the 10th Joint
MMM/Intermag Conferenc
Quantum World-line Monte Carlo Method with Non-binary Loops and Its Application
A quantum world-line Monte Carlo method for high-symmetrical quantum models
is proposed. Firstly, based on a representation of a partition function using
the Matsubara formula, the principle of quantum world-line Monte Carlo methods
is briefly outlined and a new algorithm using non-binary loops is given for
quantum models with high symmetry as SU(N). The algorithm is called non-binary
loop algorithm because of non-binary loop updatings. Secondary, one example of
our numerical studies using the non-binary loop updating is shown. It is the
problem of the ground state of two-dimensional SU(N) anti-ferromagnets. Our
numerical study confirms that the ground state in the small N <= 4 case is a
magnetic ordered Neel state, but the one in the large N >= 5 case has no
magnetic order, and it becomes a dimer state.Comment: 14 pages, 5 figures, Invited talk at the 18th Annual Workshop on
Recent Developments of Computer Simulation Studies in Condensed Matter
Physics, Athens, 7-11 March, 200
Broken spin-Hall accumulation symmetry by magnetic field and coexisted Rashba and Dresselhaus interactions
The spin-Hall effect in the two-dimensional electron gas (2DEG) generates
symmetric out-of-plane spin Sz accumulation about the current axis in the
absence of external magnetic field. Here we employ the real space
Landauer-Keldysh formalism [B. K. Nikolic et al., Phys. Rev. Lett. 95, 046601
(2005); Phys. Rev. B 73, 075303 (2006)] by considering a four-terminal setup to
investigate the circumstances in which this symmetry is broken. For the absence
of Dresselhaus interaction, starting from the applied out-of-plane B
corresponding to Zeeman splitting energy 0 - 0.5 times the Rashba hopping
energy tR, the breaking process is clearly seen. The influence of the Rashba
interaction on the magnetization of the 2DEG is studied herein. For coexisted
Rashba tR and Dresselhaus tD spin-orbit couplings in the absence of B,
interchanging tR and tD reverses the entire accumulation pattern.Comment: 3 pages, 2 figures, appears in the proceedings of 10th MMM/INTERMAG
conferenc
A new modified Newton iteration for computing nonnegative Z-eigenpairs of nonnegative tensors
We propose a new modification of Newton iteration for finding some
nonnegative Z-eigenpairs of a nonnegative tensor. The method has local
quadratic convergence to a nonnegative eigenpair of a nonnegative tensor, under
the usual assumption guaranteeing the local quadratic convergence of the
original Newton iteration
Privacy Perils of Open Data and Data Sharing: A Case Study of Taiwan\u27s Open Data Policy and Practices
Governments and private sector players have hopped on the open data train in the past few years. Both the governments and civil society in Taiwan are exploring the opportunities provided by the data stored in public and private sectors. While they have been enjoying the benefits of the sharing and flowing of data among various databases, the government and some players in the private sectors have also posed tremendous privacy challenges by inappropriately gathering and processing personal data. The amended Personal Data Protection Act was originally enacted as a regulatory mechanism to protect personal data and create economic benefits via enhancing the uses of public and private sector data. In reality, the Act has instead resulted in harm to Taiwan’s data privacy situation in this big data era. This article begins with an overview of the Taiwan’s open data policy history and its current practices. Next, the article analyzes cases in which the data sharing practices between different sectors have given rise to privacy controversies, with a particular focus on 2020, when Taiwan used data surveillance in response to the COVID-19 pandemic. Finally, this article flags problems related to an open data system, including the protection of sensitive data, de-identification, the right to consent and opt-out, and the ambiguity of “public interest,” and concludes by proposing a feasible architecture for the implementation of a more sensible open data system with privacy-enhancing characteristics
Comparison of secondary signs as shown by unenhanced helical computed tomography in patients with uric acid or calcium ureteral stones
AbstractUnenhanced helical computed tomography (UHCT) has evolved into a well-accepted diagnostic method in patients with suspected ureterolithiasis. UHCT not only shows stones within the lumen of the ureter, it also permits evaluation of the secondary signs associated with ureteral obstruction from stones. However, there we could find no data on how secondary signs might differ in relation to different compositions of ureteral stones. In this study, we compared the degree of secondary signs revealed by UHCT in uric acid stone formers and in patients forming calcium stones. We enrolled 117 patients with ureteral stones who underwent UHCT examination and Fourier transform infra-red analysis of stone samples. Clinical data were collected as follows: age, sex, estimated glomerular filtration rate (eGFR), urine pH, and radiological data on secondary signs apparent on UHCT. The uric acid stone formers had significantly lower urine pH and eGFR in comparison to calcium stone formers, and on UHCT they also had a higher percentage of the secondary signs, including rim sign (78.9% vs. 60.2%), hydroureter (94.7% vs. 89.8%), perirenal stranding (84.2% vs. 59.2%) and kidney density difference (73.7% vs. 50.0%). The radiological difference was statistically significant for perirenal stranding (p=0.041). In conclusion, we found that UHCT scanning reveals secondary signs to be more frequent in patients with uric acid ureteral stones than in patients with calcium stones, a tendency that might result from an acidic urine environment
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