• Journal of Electrical Engineering and Technology
• /
• v.11 no.1
• /
• pp.65-75
• /
• 2016

Aiming at analyzing the power flow of the distribution systems with distribution transformer (DT) branches and PV nodes, a hybrid three-phase power flow methodology is presented in this paper. The incidence formulas among node voltages, loop currents and node current injections have been developed based on node-branch incidence matrix of the distribution network. The method can solve the power flow directly and has higher efficiency. Moreover, the paper provides a modified method to model DT branches by considering winding connections, phase shifting and off-nominal tap ratio, and then DT branches could be seen like one transmission line with the proposed power flow method. To deal with the PV nodes, an improved approach to calculate reactive power increment at each PV node was deduced based on the assumption that the positive-sequence voltage magnitude of PV node is fixed at a given value. Then during calculating the power flow at each iteration, it only needs to update current injection at each PV node with the proposed algorithm. The process is very simple and clear. The results of IEEE 4 nodes and the modified IEEE 34 nodes test feeders verified the correctness and efficiency of the proposed hybrid power flow algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.7B
• /
• pp.668-676
• /
• 2009

Hierarchical Mobile 1Pv6(HM1Pv6) have been proposed by IETF(Internet Engineering Task Force) beginning from Mobile 1Pv6 for mobility support in IP networks, however these researches relying on client based mobility support have not been drawn attention due to excessive consumption of wireless resources and long handover delay. In this paper, we propose the Router-based Binding Update(RBU) scheme to solve problems in existing client-based mobility support schemes. The router registers location information of mobile nodes through Neighbor Discovery protocol without additional codes for the RBU scheme to a terminal operated by existing HMlPv6. By using this the RBU scheme is designed so that it can support partial nupport based mobility and reduce handover latency rather than using HMIPv6. It is analysed and compared with existing HMIPv6 to verify efficiency of the RBU scheme. As a result, the RBU scheme has outperformed existing HMIPv6 by 15% in terms of macro handover delay especially when long delay on wireless links exists.

• ETRI Journal
• /
• v.45 no.3
• /
• pp.519-533
• /
• 2023

This paper implements a simultaneous solar and thermal energy harvesting system, as a hybrid energy harvesting (HEH) system, to convert ambient light into electrical energy through photovoltaic (PV) cells and heat absorbed in the body of PV cells. Indeed, a solar panel equipped with serially connected thermoelectric generators not only converts the incoming light into electricity but also takes advantage of heat emanating from the light. In a conventional HEH system, the diode block is used to provide the path for the input source with the highest value. In this scheme, at each time, only one source can be handled to generate its output, while other sources are blocked. To handle this challenge of combining resources in HEH systems, this paper proposes a method for collecting all incoming energies and conveying its summation to the load via the current mirror cells in an approach similar to the maximum power point tracking. This technique is implemented using off-the-shelf components. The measurement results show that the proposed method is a realistic approach for supplying electrical energy to wireless sensor nodes and low-power electronics.

• Proceedings of the KIEE Conference
• /
• 2000.07a
• /
• pp.147-149
• /
• 2000

This paper describes a power flow method for distribution systems, applying the method of symmetrical component to back/forward sweep method. The proposed algorithm is effective for unbalanced radial distribution system, with process of distributed resource(PQ & PV node), AVR(Auto Voltage Regulator), shunt capacitor. This proposed method compared conventional back/forward sweep method with the using three phase unbalanced distribution systems with 34 nodes.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• v.9 no.2
• /
• pp.82-85
• /
• 2005

In the MIPv6 network, when mobile nodes move into new newtwork, they need to find the new access router and points(AR/AP) for the newtwork. Unless they are not connected to authorized AR/APs, they can be exposed to a lot of attacks. In this paper we propose a protocol to authenticate AR/AR and MN each other. This protocol is based on the public key scheme which is used in the SEcure Neighbor Discovery(SEND) protocol.

• Proceedings of the Korean Information Science Society Conference
• /
• 2000.10c
• /
• pp.532-534
• /
• 2000

IPv4(Internet Protocol version 4)의 차세대 버전인 IPv6는 기존 IPv4의 문제점인 주소부족 및 새로운 부가기능 등의 필요성 때문에 IETF(Internet Engineering Task Force)에서 IPv4를 대체하기 위해 개발한 프로토콜이다. 하지만 IPv4를 어느 한순간에 IPv6로 대체하는 것은 불가능하기 때문에 기존 IPv4와의 호환 및 연동을 위한 터널링 및 기타 여러 가지 transition mechanism들이 고려되고 있다. 이러한 mechanism들 중에서 최근 표준으로 발표된 NAT-PT(Network Address Translation $\square$ Protocol Translation)는 DNS-ALG (Domain Name System $\square$ Application Level Gateway)라는 개념을 도입하여 IPv4와 IPv6간의 양방향 주소변환 및 프로토콜 변환기능을 수행한다. 각각의 기능에서 주소 변환은 주소크기와 형식이 다른 IPv4와 Pv6간의 서로 상대 노드를 엑세스할 수 있도록 하고 프로토콜 변환은 다른 버전의 프로토콜을 사용하는 노드들이 상대노드가 보낸 패킷의 헤더정보를 이해할 수 있도록 한다. 그리고 이러한 기본적인 변환 외에 헤더정보의 정확한 전달을 위해서는 기존의 path MTU(Maximum Transgfer Unit) discovery 그리고 pseudo header checksum 등도 고려되어야 한다.

• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.22
• /
• pp.10039-10043
• /
• 2014

Background: In Pakistan thyroid cancer is responsible for 1.2% cases of all malignant tumors. Ultrasonography (US) is helpful in detecting cancerous thyroid nodules on basis of different features like echogenicity, margins, microcalcifications, size, shape and abnormal neck lymph nodes. We therefore aimed to calculate diagnostic accuracy of ultrasound in detection of carcinoma in thyroid nodules taking fine needle aspiration cytology as the reference standard. Materials and Methods: A cross-sectional analytical study was designed to prospectively collect data from December 2010 till December 2012 from the Department of Radiology in Aga Khan University Hospital, Karachi, Pakistan. A total of 100 patients of both genders were enrolled after informed consent via applying non-probability consecutive sampling technique. Patients referred to Radiology department of Aga Khan University to perform thyroid ultrasound followed by fine-needle aspiration cytology of thyroid nodules were included. They were excluded if proven for thyroid malignancy or if their US or FNAC was conducted outside our institution. Results: The subjects comprised 76 (76%) females and 24 males. Mean age was $41.8{\pm}SD$ 12.3 years. Sensitivity and specificity with 95%CI of ultrasound in differentiating malignant thyroid nodule from benign thyroid nodule calculated to be 91.7% (95%CI, 0.72-0.98) and 78.94% (0.68-0.87) respectively. Reported positive predictive value and negative PV were 57.9% (0.41-0.73) and 96.8% (0.88-0.99) and overall accuracy was 82%. Likelihood ratio (LR) positive was computed to be 4.3 and LR negative was 0.1. Conclusions: Ultrasonography has a high diagnostic accuracy in detecting malignancy in thyroid nodules on the basis of features like echogenicity, margins, micro calcifications and shape.