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Cu(In,Ga)Se2 (CIGSe) solar cells with absorber thicknesses of

Cu(In1-x,Gax)Se2 (CIGSe)-based solar cells have a high absorption coefficient (∼105), by which they can be used as thin-film solar cells that have the potential to be applied in various fields. To employ such a CIGSe-based solar cell as a transparent type, the conventional Mo substrate should be replaced with a transparent conductive oxide (TCO) substrate as the back electrode, and indium tin oxide (ITO) is one of the candidate TCO materials. However, various problems need to be addressed because the utilization of ITO may hinder solar cell performance, one of which is the contact occurring at the interface between CIGSe and ITO. This can be solved by adding an appropriate material at the interface while preserving the inherent purpose fulfilled by using the ITO electrode. In this study, we attempted to improve the contact properties using semi-metallic WTe2 flakes dispersed on the surface of the ITO substrate to form an electrical path between the CIGSe and the ITO substrate, which exhibit outstanding electrical conductivity among two-dimensional transition metal dichalcogenide materials. Accordingly, the effect of applying WTe2 flakes at the ITO and CIGSe interfaces on the performance of semi-transparent ultra-thin (STUT) CIGSe solar cells is discussed.

Along with highly efficient Cu(In1-x,Gax)Se2 (CIGSe)-based thin-film solar cells, versatile solar cells are urgently required to meet a variety of functional needs, such as photovoltaic (PV) power conversion, transparency, ultrathinness, and light weight. To meet these needs, a semitransparent ultrathin (STUT) CIGSe solar cell with two-dimensional (2D) transition metal dichalcogenide (TMD) as the buffer layer is proposed as a prospective next-generation solar cell structure that exhibits advantages based on both the distinguishable optical properties of 2D TMDs and the high efficiency of CIGSe-based solar cells. However, the application of 2D TMDs on top of CIGSe is challenging because the surface of 2D TMDs is nominally and supposedly flat and smooth, while that of CIGSe absorbers is typically rough, and their combination is prone to defect formation at the interface. To overcome degradation due to interfacial defects, a 2D-MoS2/ZnS/CIGSe semitransparent ultrathin solar cell was designed by inserting a ZnS nanolayer for heterojunction interface passivation, and the photovoltaic properties of the device were found to be improved. Furthermore, based on the binding energies of each layer, the energy band structures of n-MoS2/p-CIGSe with and without a ZnS passivation layer are suggested, and the related implications for device performance are discussed.

A Software Defined Network (SDN) separates an existing network structure into a control plane and a data plane and centrally manages the network at the control plane. SDN is able to control the network in detail and operate efficiently by managing the traffic by flow unit. However, if the performance of the switches comprising the SDN varies greatly from one to another, it has a problem of delayed handling of traffic due to the bottleneck caused by an overhead concentration at the controller when the message exchanges between the low performance switch and the controller for flow table replacement increase in number. This research paper suggests a flow table management scheme, called Proactive-LRU, to alleviate this problem and compares its performance to that of the existing replacement algorithms such as LRU, LFU, and FIFO. Proactive-LRU scheme is a flow table management scheme that deletes the flow from all switches available within the forwarding path when a flow is deleted and reduces the number of message exchanges and the controller overhead. In order to compare the performance of the suggested scheme against that of the existing algorithms (FIFO, LRU, LFU), video traffic and web browsing traffic have been mixed in certain ratios in an SDN environment for the experiment. The analysis of the results showed that the number of message exchanges as well as the overhead and table overflow of switches in the suggested scheme were significantly reduced.

As essential infrastructure networks become more common in diverse areas, a wide range of services have appeared related to increasing traffic and high-capacity content, though network-management problems have also increased. Because these problems cannot be easily solved within existing networks, new software defined networks (SDNs) technology has appeared. However, when the network becomes too large, the control plane's overhead may increase due to differing device performance within the data plane. This leads to network performance problems because of the characteristics of SDNs, in which the control plane controls management of the entire network. In this paper, problems that occur because of performance differences among the devices that constitute the data plane are explained, and a flow table management scheme able to reduce network overhead, occurring when the controller manages the flow table, is proposed.

The increase in services that utilize ultra-high-speed networks have caused an increase in network traffic problems. Existing networks require new technologies because the management of these networks is difficult and the traffic problems cannot be easily solved. These challenges have prompted the development of software-defined networks (SDNs). SDNs divide existing network structures into data planes, which manage data transmission, and control planes, which manage network controls. These planes enable easy, flexible network management or expansion through centralized structures. Specifically, SDNs efficiently control networks by monitoring network traffic or utilizing the state information of the connected switches. However, due to the characteristics of SDNs that centralize network management, specifically switch performance, controller overhead may increase, which may lead to problems throughout the entire network. This paper discusses these problems and proposes an algorithm that promotes efficient network management when the flows are replaced at the flow tables.

In the edge contraction algorithm for surface simplification, two major steps are (i) ordering of the edges to be collapsed, and (ii) positioning of the new vertex to replace the collapsed edge. The accuracy of the simplified result greatly depends on which procedures are taken in the above steps. During the simplification process, degenerate cases can occur in which the optimization problem for the new vertex position produces multiple solutions. In the previous algorithms, such redundancy was utilized to achieve other desirable effects (e.g, increasing the regularness of the triangles). In this paper we give a complete characterization of the geometric situation for the degenerate cases, and show that performing edge contraction procedure in those cases can produce unexpected damage to the original shape. To cope with the problem, we propose a new procedure, called edge elimination, which eliminates the degenerate edge and all the adjacent ones, and then retriangulates the hole in a way the geometrical ...

We derive absorbing boundary conditions for viscoelastic waves. Error estimates are given for such absorbing boundary conditions. We treat the problem in the space-frequency domain formulation after taking the Fourier transformation in time. Well-posedness is shown for the elliptic problems thus created, and Fourier invertibility is also proved. We also present some results of numerical simulations.

The technique of RSA private computation speedup by using Chinese Remainder Theorem (CRT) is well known and has already been widely employed in almost all RSA implementations. A recent CRT-based factorization attack exploiting hardware fault has received growing attention because of its potential vulnerability on most existing implementations. In this attack any single erroneous computation will make the RSA system be vulnerable to factorizing the public modulus. Recently, two hardware fault immune protocols for CRT speedup on RSA private computation were reported based on the concept of fault infective computation. A special property of these two protocols is that they do not assume the existence of totally fault free and tamper free comparison operation within the machine in order to enhance the reliability. However, it will be shown in this paper that these two protocols are still vulnerable to a potential computational fault attack on an auxiliary process that was not considered in the usual CRT-based factorization attack.

For Discrete Logarithm Problem(DLP) based public key cryptography, the most time consuming task is the mathematical operations in the underlying finite field. For computational efficiency, a predeterminate form of prime p has been proposed to be used in Diffie-Hellman Groups for Internet Key Exchange(IKE). In this paper, we analyze the effect of pre-fixed bits of the prime numbers related to the security and efficiency and we suggest some alternative choices for prime p’s for More Modular Exponential (MODP) Diffie-Hellman groups as a substitute for Internet Key Exchange(IKE) which has been published as RFC of IETF recently.