• 제목/요약/키워드: ship wireless communication

검색결과 103건 처리시간 0.021초

선박-육지간 통신을 위한 실시간 H.264 to MPEG-2 트랜스코딩 (A Real-time H.264 to MPEG-2 Transcoding for Ship to Shore Communication)

  • 손남례;정민아;이성로
    • 대한전자공학회논문지SP
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    • 제48권1호
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    • pp.90-102
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    • 2011
  • 현재 위성방송을 통해 신호를 전송 또는 재전송하는 무선통신서비스를 이용하는 시청자 층은 다양하다. 하지만 방송국은 H.264표준으로 압축된 동영상들을 위성통신을 통하여 전송하기 때문에 H.264표준 디바이스를 갖추지 않는 선박은 실시간으로 데이터를 전송받지 못하는 단점을 가지고 있다. 따라서 본 논문에서는 기존 MPEG-2 표준 디바이스를 사용하고 있는 선박을 위하여 H.264 to MPEG-2 트랜스코딩 방법을 제안한다. 제안한 방법은 H.264 표준의 매크로블록모드의 특성을 분석하여 H.264 to MPEG-2 transcoding의 계산시간 및 화질을 개선한다. 첫째 H.264와 MPEG-2표준의 INTRA 모드 방법이 상이하므로 새로운 방법을 제안한다. 둘째 매크로블록모드가 INTER 모드인 경우에는 H.264표준의 가변블록 안에 존재하는 움직임 벡터의 방향성을 고려하여 새로운 예측움직임벡터 (PMV: predictor motion vector)를 제안한다. 이때 최종움직임벡터는 예측움직임벡터를 그대로 사용하거나, H.264표준의 매크로블록내에 존재하는 가변블록들의 움직임벡터들과 MPEG-2부호기(baseline)의 움직임벡터의 일치율을 비교하여 최종적으로 움직임벡터를 예측할 범위(window size)를 결정한다. 실험결과, 제안한 트랜스코딩방법의 PSNR은 MPEG-2 FSBMA와 거의 일치하고, 트랜스코딩에 필요한 계산시간은 평균적으로 각각 70% 또는 67% 감소하였다.

가속도 센서기반의 인체활동 및 낙상 분류를 위한 알고리즘 구현 (Implementation of Acceleration Sensor-based Human activity and Fall Classification Algorithm)

  • 박현;박준모;하연철
    • 융합신호처리학회논문지
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    • 제23권2호
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    • pp.76-83
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    • 2022
  • 최근 IT기술이 발달함에 따라 다양한 생체신호 측정 기기에 대한 연구 및 관심이 높아지고 있는 이유 중 하나로 고령사회가 본격화됨에 따라 IT 관련 기술을 이용한 고령 인구에 대한 연구가 지속해서 발전되고 있다. 본 논문은 초고령사회에 접어들면서 빠르게 발전하고 있는 노인층을 대상으로 한 의료서비스 영역 중 하나인 생활 패턴 감지와 낙상 감지 알고리즘 개발에 관한 것이다. 3축 가속도 센서와 심전도 센서를 이용한 시스템을 구성하여 데이터를 수집한 뒤 데이터를 분석하는 과정으로 진행하였고 실제 연구 결과로부터 행동 패턴의 분류가 가능함을 제안한다. 본 논문에 의해 구현된 인체 활동 모니터링 시스템의 유용성을 평가하기 위하여 자세 변화, 보행속도의 변화 등 다양한 조건에서 실험을 수행하여 인체의 중력 가속도와 인체 활동 정도를 반영하는 신호크기 범위 및 신호 벡터크기 파라미터를 추출하였다. 그리고 이들 파라미터값에 의해 피검자의 상태에 따라 판별이 가능하였다.

"무역상무(貿易商務)에의 역사적(歷史的) 어프로치와 무역취인(貿易取引)의 전자화(電子化)" (E-Commerce in the Historical Approach to Usage and Practice of International Trade)

  • 춘홍차
    • 무역상무연구
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    • 제19권
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    • pp.224-242
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    • 2003
  • The author believes that the main task of study in international trade usage and practice is the management of transactional risks involved in international sale of goods. They are foreign exchange risks, transportation risks, credit risk, risk of miscommunication, etc. In most cases, these risks are more serious and enormous than those involved in domestic sales. Historically, the merchant adventurers organized the voyage abroad, secured trade finance, and went around the ocean with their own or consigned cargo until around the $mid-19^{th}$ century. They did business faceto-face at the trade fair or the open port where they maintained the local offices, so-called "Trading House"(商館). Thererfore, the transactional risks might have been one-sided either with the seller or the buyer. The bottomry seemed a typical arrangement for risk sharing among the interested parties to the adventure. In this way, such organizational arrangements coped with or bore the transactional risks. With the advent of ocean liner services and wireless communication across the national border in the $19^{th}$ century, the business of merchant adventurers developed toward the clear division of labor; sales by mercantile agents, and ocean transportation by the steam ship companies. The international banking helped the process to be accelerated. Then, bills of lading backed up by the statute made it possible to conduct documentary sales with a foreign partner in different country. Thus, FOB terms including ocean freight and CIF terms emerged gradually as standard trade terms in which transactional risks were allocated through negotiation between the seller and the buyer located in different countries. Both of them did not have to go abroad with their cargo. Instead, documentation in compliance with the terms of the contract(plus an L/C in some cases) must by 'strictly' fulfilled. In other words, the set of contractual documents must be tendered in advance of the arrival of the goods at port of discharge. Trust or reliance is placed on such contractual paper documents. However, the container transport services introduced as international intermodal transport since the late 1960s frequently caused the earlier arrival of the goods at the destination before the presentation of the set of paper documents, which may take 5 to 10% of the amount of transaction. In addition, the size of the container vessel required the speedy transport documentation before sailing from the port of loading. In these circumstances, computerized processing of transport related documents became essential for inexpensive transaction cost and uninterrupted distribution of the goods. Such computerization does not stop at the phase of transportation but extends to cover the whole process of international trade, transforming the documentary sales into less-paper trade and further into paperless trade, i.e., EDI or E-Commerce. Now we face the other side of the coin, which is data security and paperless transfer of legal rights and obligations. Unfortunately, these issues are not effectively covered by a set of contracts only. Obviously, EDI or E-Commerce is based on the common business process and harmonized system of various data codes as well as the standard message formats. This essential feature of E-Commerce needs effective coordination of different divisions of business and tight control over credit arrangements in addition to the standard contract of sales. In a few word, information does not alway invite "trust". Credit flows from people, or close organizational tie-ups. It is our common understanding that, without well-orchestrated organizational arrangements made by leading companies, E-Commerce does not work well for paperless trade. With such arrangements well in place, participating E-business members do not need to seriously care for credit risk. Finally, it is also clear that E-International Commerce must be linked up with a set of government EDIs such as NACCS, Port EDI, JETRAS, etc, in Japan. Therefore, there is still a long way before us to go for E-Commerce in practice, not on the top of information manager's desk.

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