• International Journal of Naval Architecture and Ocean Engineering
• /
• 제6권4호
• /
• pp.1182-1196
• /
• 2014

In problems of global hydroelastic ship response in severe seas including the whipping problem, we need to know the hydrodynamic forces acting on the ship hull during almost arbitrary ship motions. In terms of ship sections, some of them can enter water but others exit from water. Computations of nonlinear free surface flows, pressure distributions and hydrodynamic forces in parallel with the computations of the ship motions including elastic vibrations of the ship hull are time consuming and are suitable only for research purposes but not for practical calculations. In this paper, it is shown that the slamming forces can be decomposed in two components within three semi-analytical models of water entry. Only heave motion is considered. The first component is proportional to the entry speed squared and the second one to the body acceleration. The coefficients in these two components are functions of the penetration depth only and can be precomputed for given shape of the body. During the exit stage the hydrodynamic force is proportional to the acceleration of the body and independent of the body shape for bodies with small deadrise angles.

• 한국정보시스템학회지:정보시스템연구
• /
• 제7권1호
• /
• pp.55-76
• /
• 1998

Various trials to overcome the limitation of current accounting which fails in synchronizing business activities and their information have failed to make satisfactory result merely showing a little saving of processing time. This is because such trials have been done within the boundary of double-entry bookkeeping system. Without consolidating business activities and their information, reformation efforts such as BPR(business process re-engineering), ABC(activity-based costing), CALS(commerce at light speed) etc to fit the business organization to the changing business environment could not be achieved. Overcoming the limitation of accounting takes precedence of any other attempt to construct the management information systems. Activity Information Accounting System(AIAS) proposes the way of overcoming the limitation of current accounting by using the new accounting methodology and unique solution to real time accounting information. AIAS produces accounting and management information directly of activity information without bookkeeping process of activity information. AIAS adopts method of transforming the details of corporation activities directly into accounting information rather than method of double-entry bookkeeping system. The purpose of this paper is to prove AIAS to be very flexible system by using flexibility concepts. Flexibilities are defined as three aspects, namely ① timeliness (rapid accounting information generations and presentations) ② easy systems modificabilities according to environment changes ③ adaptabilities to all industries.

• East Asian Economic Review
• /
• 제26권2호
• /
• pp.119-142
• /
• 2022

This paper uses social network theory and the internationalization process model (IPM) to determine how external network linkages influence the location choices of multinational enterprise from emerging economies (EMNEs); specifically, whether past alliance experience influences location choices and its impact on the subsequent entry of MNEs from emerging economies. This paper applies survival analysis using initial and secondary investments from 2,000 Chinese A-share listed companies that entered 90 countries between 1997 and 2018 to analyze both the initial and subsequent entries of Chinese outward foreign direct investments (OFDIs) in major host countries. The findings indicate that an MNE's previous experience with a company from a particular country will increase the likelihood of an initial investment in that country. Previous alliance experience may accelerate the foreign investment process of EMNE and stimulate firms making a commitment to a position in a foreign network, regardless of cultural distance and stage of internationalization. Alliance before initial investment may increase the likelihood and speed of entering a host country as wholly owned subsidiaries and that network linkages not only significantly influence the internationalization process of small and medium-sized enterprises, as indicated by the IPM, but also that of large listed firms.

• 한국안전학회지
• /
• 제14권4호
• /
• pp.204-210
• /
• 1999

본 논문에서는 정합필터의 데이터 베이스로 체적 홀로그램을 사용한 광 지문 인식 시스템을 제안하였다. VanderLugt 상관기에 사용되는 정합필터는 방대한 저장 능력과 실시간 랜덤 엑세스의 장점을 갖는 체적 홀로그램에 기록된다 데이터 베이스로 사용되는 지문 영상들은 각각 공간광변조기에 디스플레이 되어 퓨리에 변환 렌즈를 통과한 후 퓨리에 변환된 공간정합필터의 형태로 광굴절매질에 기록된다. 대용량의 데이터 베이스를 구성하기 위한 다중화 방법으로 스텝 모터를 이용하여 기준파의 각도를 회전하는 각다중화 기술을 사용하였다. 실험을 통해 본 시스템이 제한된 영역의 접근을 통제하기 위한 개인 인증용 안전 출입 시스템 및 크레디트카드, 여권, ID등의 위조방지에 이용이 가능함을 제시하였다

• 소음진동
• /
• 제7권6호
• /
• pp.959-966
• /
• 1997

In general, the booming noise intensity at tunnel exit is strongly related to the gradient of the compression wave front created by high speed train entering the tunnel. This paper presents some results in relation with the compression wave front produced when the high speed train enters a tunnel. Four kinds of tunnel entrance shape with real dimensions were studied to investigate the formation of compression wave front inside tunnel by train entering tunnel. Computations were carried out using three-dimensional compressible Euler equation with vanishing viscosity and conductivity of fluid. According to the results, the flow disturbances occured at tunnel entrance were eliminated by tunnel hood with same cross sectional area. The compression wave front is formed completely at 30-40m from tunnel entrance. The maximum pressure gradient of compression wave front is reduced by 29.8% for the inclined tunnel hood and reduced by 21.5% for the tunnel hood with holes at the top face with tunnel without hood. The length of the inclined hood is 15m and the length of the hood with holes is 20m.

• 한국분무공학회지
• /
• 제5권1호
• /
• pp.49-57
• /
• 2000

This study presents the flow visualization results, velocity and turbulence intensity measurements made within an air filter cover and entry region of a mass air flow sensor (MAFS) which is used in an induction system of 3.8L engine. Flow structure in two air filter cover assemblies were examined. The first was a clear plastic replica of the production cover while the second was a modified clear plastic cover with a geometry configured to reduce fluctuations. High speed flow visualization and laser doppler velocimetry (LDV) systems were used to reveal and analyze the flow field characteristics encountered in the sensor design process under steady flow conditions. A 40-watt copper vapor laser was used as a light source. Its beam is focused down to a sheet of light approximately 1.5mm thick. The light scattered off the particles was recorded by a 16mm high speed rotating prism camera at 5000 frames per second. A comparison of the flow patterns and LDV measurements in the original and modified air filter covers is presented to illustrate the controlling effect of the cover design on the turbulence structure formation near the bypass and on the sensor output signal. In both axial and radial planes of the main passage it was found that the turbulence flow pattern is remarkably influenced by the air filter cover and main passage configuration.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
• /
• pp.627-635
• /
• 1997

In general, the booming noise intensity at tunnel exit is strongly related to the gradient of the compression wave front created by high speed train entering the tunnel. This paper presents some results in relation with the compression wave front produced when the high speed train enters a tunnel. Four kinds of tunnel entrance shape with real dimensions were studied to investigate the formation of compression wave front inside tunnel by train entering tunnel. Computations were carried out using three-dimensional compressible Euler equation with vanishing viscosity and conductivity of fluid. According to the reslts, the flow disturbance occured at tunnel entrance were eliminated by tunnel hood with same cross sectional area. The compression wave front is formed completely at 30-40m from tunnel entrance. The maximum pressure gradient of compression wave front is reduced by 29.8% for the inclined tunnel hood and reduced by 21.5% for the tunnel hood with holes at the top face with tunnel without hood. The length of the inclined hood is 15m and the length of the hood with holes is 20m.

• 치위생과학회지
• /
• 제2권1호
• /
• pp.47-51
• /
• 2002

Sprague-Dawley계 흰쥐의 악하선에서 선세포를 분리하여 fura-2/AM(fura-2)으로 염색한 후 spectrofluorometer로 세포내 $Ca^{2+}$농도를 측정하였다. 악하선 세포를 관류장치(perfusion chamber)에 넣고 표준용액을 관류시키면서 isoproterenol($1{\mu}M$)과 octanol(1mM)을 투여한 후 $Ca^{2+}$농도 변화를 측정하였는데 단독 투여시 $Ca^{2+}$농도는 거의 변화하지 않았으나 함께 투여한 경우 세포 내 $Ca^{2+}$농도가 증가함을 확인할 수 있었다. Adenylate-cyclase를 활성화 시키는 forskolin($10{\mu}M$)과 octanol을 함께 투여하였을 때도 isoproterenol의 경우와 유사한 증가 현상을 보이는 것으로 볼 때 octanol과 isoproterenol 또는 forskolin이 함께 작용할 때 세포 내 $Ca^{2+}$가 증가하는 것을 확인할 수 있었다. $Ca^{2+}$의 증가기전을 확인하고자 표준용액의 $Ca^{2+}$를 제거함은 물론 EGTA를 처리하여 세포외부의 $Ca^{2+}$를 제거한 후 상기한 바와 동일한 실험을 반복한 결과 $Ca^{2+}$농도의 증가를 보이지 않았다. 따라서 세포 내 $Ca^{2+}$의 증가는 세포 외부로부터의 $Ca^{2+}$유입 때문인 것으로 확인할 수 있었다. 이러한 $Ca^{2+}$의 유입 capacitative entry pathway를 이용하는지 확인코자 gadolinium($10{\mu}M$)을 처리하였을 때 $Ca^{2+}$농도의 증가가 완전히 억제되지는 않았지만 $Ca^{2+}$의 증가속도와 증가량이 감소되어 있음을 확인할 수 있었다. 이상의 실험결과들을 정리하면 세포 내 $Ca^{2+}$농도의 증가와 관련 ${\beta}$-아드레날린계 관련 약물과 옥탄올(octanol)을 함께 처리할 경우 세포 내 $Ca^{2+}$는 세포 외부에서 유입되어 증가되고 그 경로는 일부 capacitative entry pathway를 통함을 확인할 수 있었다.

• 한국콘텐츠학회논문지
• /
• 제5권3호
• /
• pp.93-101
• /
• 2005

오늘날 현대사회는 산업사회에서 지식정보사회로의 '페러다임의 전환기'에 직면하고 있다. 이는 지식중심의 초고속 네트워크 사회로의 진입을 의미하는 것이며, 특히 우리나라는 일찍이 IT 관련 산업에 막대한 투자를 한 끝에 몇 몇 분야에서는 이제 세계 강대국들이 우리의 기술을 벤치마킹해 가는 현실이다. 하지만 이러한 성장 일변도의 정책적 대응은 정보화의 역기능에 대한 대비가 미흡하게 되었으며, 그 대표적인 것이 사이버 테러리즘이다. 익명성을 떤 행위자가 불특정 다수에게 행하는 사이버 테러리즘은 오늘날 뉴 테러리즘의 가장 대표적인 유형의 하나이다. 본 연구는 사이버테러리즘에 대한 정책적, 법적 쟁점을 중심으로 살펴보고 그 대응방안을 강구한다.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 1998년도 창립기념 춘계학술대회 논문집
• /
• pp.604-611
• /
• 1998

High-speed railway trains entering and leaving tunnels generate finite amplitude pressure wave which propagate back and forth along the tunnels, reflecting at the open ends of the tunnels and at other discontinuities such as ventilation shafts and the train themselves. In present day railways, the magnitudes of the pressure waves are much too small to cause structual damage, but they are a serious potential source of aural discomport for passengers on unsealed trains. Almost always do the pressure waves propagating along the tunnels lead to a hazardous impulse noise near the exit portal of the tunnel. In order to alleviate such undesirable phenomena, some control strategies have been applied to the compression wave propagating inside the tunnel. The objective of the current work is to investigate the effect of tunnel entrance hoods on the entry compression wave at the vicinity of the tunnel entrance. Three types of entrance hoods were tested by the numerical method using the characteristics of method for a wide range of train speeds. The results show that the maximum pressure gradient of compression wave can be considerably reduced by the tunnel entrance hood. Desirable hood shape for reduction of the pressure transients and impulse noise was found to be of abrupt type hood with its cross-sectional area 2.5times the tunnel area.