• 센서학회지
• /
• 제31권5호
• /
• pp.293-300
• /
• 2022

Flexible, wearable, and implantable electronic sensors have started to gain popularity in improving the quality of life of sick and healthy people, shifting the future paradigm with high sensitivity. However, conventional technologies with a limited lifespan occasionally limit their continued usage, resulting in a high cost. In addition, traditional battery technologies with a short lifespan frequently limit operation, resulting in a substantial challenge to their growth. Subsequently, utilizing human biomechanical energy is extensively preferred motion for biologically integrated, self-powered, functioning devices. Ideally suited for this purpose are piezoelectric energy harvesters. To convert mechanical energy into electrical energy, devices must be mechanically flexible and stretchable to implant or attach to the highly deformable tissues of the body. A systematic analysis of piezoelectric nanogenerators (PENGs) for personalized healthcare is provided in this article. This article briefly overviews PENGs as self-powered sensor devices for energy harvesting, sensing, physiological motion, and healthcare.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.200-203
• /
• 2007

Carbon nanotubes (CNTs) have attracted an increasing attention due to their superior mechanical properties and potential application in industries. The strength of CNT has been predicted or calculated through several simulation techniques but actual experiments on stress-strain behavior are rare due to its dimensional limit, nanoscale positioning/manipulation, and instrumental resolution. We have attempted to observe straining responses of a multi-walled carbon nanotube (MWNT) with different growth methods by performing an in-situ tensile testing in a scanning electron microscope. Linear deformation and fracture behaviors of MWNT were successfully observed and its force-displacement curve was also measured from the bending stiffness and displacement of the force sensor and manipulator. We also obtained different tensile load of carbon nanotube with different growth methods.

• 대한기계학회논문집A
• /
• 제29권8호
• /
• pp.1139-1145
• /
• 2005

Most failures of ductile materials in metal forming processes occurred due to material damage evolution - void nucleation, growth and coalescence. In this paper, the modified yield function of Liao et al in conjunction with the Hosford's yield criterion is studied to clarify the plastic deformation characteristic of voided anisotropic sheet metals. The void growth of an anisotropic sheet under biaxial tensile loading and damage effect of void growth on forming limits of sheet metals are investigated. Also the characteristic length defining the neck geometry is introduced in M-K model to incorporate the effect of triaxial stress in necked region on forming limits. The forming limits theoretically predicted are compared with experimental data. Satisfactory agreement was obtained between the predictions and experimental data.

• 디지털산업정보학회논문지
• /
• 제11권4호
• /
• pp.1-12
• /
• 2015

This research analyzes the current state of the semiconductor industry delivering the prediction for the future development of the semiconductor industry along with some semiconductor memory's responsive strategies. In the 2014, top 10 semiconductor companies were targeted and studied its growth based on its profitability and growth indications in perspective during three years. The system semiconductor industry with the increase in Hyper-scale customers, proactive actions in the technology consortium, is polarizing caused by increased R&D expense to ensure process scaling limits and high performance, and some results have shown: PC and Mobile slowdown and growth recession phenomenon due to IoT's unclear direction. The leading company is to secure new growth engines through 'Acquiring'. While as the subordinated companies following this consecutive survival through the 'Acquired', the future of system semiconductor industry is to strengthen the market dominance and its techniques by concentrating on the reorganization of the market by few large companies. Accordingly, the semiconductor memory industry is expected to reach the limit of its expansion to domain of system semiconductor, and it is highly suggesting the need of the 'Memory Life Extension' growth strategy.

• 한국연소학회지
• /
• 제18권2호
• /
• pp.42-50
• /
• 2013

Linear stability analysis of radiating counterflow diffusion flames is numerically conducted to examine the instability characteristics of cellular patterns. Lewis number is assumed to be 0.5 to consider diffusional-thermal instability. Near kinetic limit extinction regime, growth rates of disturbances always have real eigen-values and neutral stability condition of planar disturbances perfectly falls into quasi-steady extinction. Cellular instability of disturbance with transverse direction occurs just before steady extinction. However, near radiative limit extinction regime, the eigenvalues are complex and pulsating instability of planar disturbances appears prior to steady extinction. Cellular instability occurs before the onset of planar pulsating instability, which means the extension of flammability.

• 환경영향평가
• /
• 제15권1호
• /
• pp.67-78
• /
• 2006

Global warming brings about changes of diverse environmental, especially changes of plant distribution. The purpose of this paper is to examine the relationship between temperature rise and changes of northern limit of vegetation growth in Korea. Bamboos (Phyllostachys) and boundary between the northern type and southern type of garlic (Allium sativum L.) were selected. The data of the distributions of bamboos and garlic are collected by field survey and interviews. Temperature is analyzed from 1904 to 2000. The northern limit of Phyllostachys moves 60-100 km northward, for about 100 years, the period of 1907-2003 and mean temperature of Korea increases about $2^{\circ}C$ during the same period. It means that the northern limit moves 30-50 km northward, for each $1^{\circ}C$ rising of January mean temperature. The boundary between the northern type and southern types of garlic moves northward 40-140 km from 1980s to 2000. The moving width is broad in the west coastal region while the width is narrow in the inland and mountain regions. The mean moving width is about 100 km.

• Journal of Forest and Environmental Science
• /
• 제24권3호
• /
• pp.119-126
• /
• 2008

Growth and yield prediction methods, ranging from whole-stand models to individual-tree models, have been developed for forest types managed for wood production. The resultant models are used for a host of purposes including inventory updating, management planning, evaluation of silvicultural alternatives, and harvest scheduling. Because of the large investment in developing growth and yield models for improved genotypes and silvicultural practices for loblolly pine (Pinus taeda) in the Southern United States, this region serves to illustrate approaches for modelling intensively managed forests. Analytical methods and computing power generally do not restrict development of reliable growth and yield models. However, long-term empirical observations on stand development, which are time consuming and expensive to obtain, often limit modelling efforts. Given that growth and yield models are used to project present volumes and to evaluate alternative treatment effects, data of both the inventory type and the experimental type are needed. Data for developing stand simulators for loblolly pine plantations have been obtained from a combination of permanent plots in operational forest stands and silvicultural experiments; these data collection efforts are described and summarized. Modelling is essential for integrating and synthesizing diverse information, identifying knowledge gaps, and making informed decisions. The questions being posed today are more complex than in the past, thus further accentuating the need for comprehensive models for stand development.

• 한국항해항만학회지
• /
• 제34권6호
• /
• pp.487-492
• /
• 2010

울산항은 국내 최대의 액체화물 거점항만으로 지속적인 물동량 증가에 대비하여 울산 신항 및 동북아오일허브 개발 등을 본격적으로 추진하고 있다. 그러나 국내 다른 무역항에 비해 항계 및 정박지가 협소하고, 해상교통 흐름이 복잡하여 해양사고의 발생 개연성이 매우 높은 실정이다. 본 연구에서는 울산항의 지형학적인 특성과 선박 교통량을 고려하여 울산항 정박지 확충을 위해 불가피하게 요구되는 항계 확장 방안을 모색하여 제시하고자 한다. 정박지 확충을 위한 항계 확장은 국내 다른 무역항의 정박지 및 항계 면적을 선석 및 통항 교통량 등과 상호 비교하여 확장 범위를 정량화한 후 울산 신항 개발에 필요한 정박지 확대 면적을 산출하였다. 또한 해당 정박지 면적을 수용할 수 있는 항계 범위를 확정한 후 전문가 그룹에 의한 설문조사를 기초로 적정한 항계 확장 형태를 결정하였다.

• 대한기계학회논문집
• /
• 제2권3호
• /
• pp.53-61
• /
• 1978

This study has been concentrated on the relations between the crack growth rate and the stress intensity factor, the fatigue limit and finally on the condition of the crack propagation along the laminated cross section of the laminated steel under the repeated plane bending through tests. The following results are obtained. 1. The fatigue limit of the laminated steel is higher than the single steel 2. The realtion between the fatigue crack growth rate, dL/dN and Stress intensity factor are ; dL/dN = 2.14 * 10$^{-11}$ $K^{2.95}$ for SUP 9 dL/dN = 1.70 * 10$^{-11}$ $K^{2.95}$ for SMS dL/dN = 9.77 * 10$^{-11}$ $K^{2.95}$ for SPMS dL/dN = 3.57 * 10$^{-8}$ $K^{1.53}$ for SPMM dL/dN = 5.5O * 10$^{-8}$ $K^{1.53}$ for MLD 3. The crack propagation of the laminated steel also tends to be completed through 3 steps; The first step proceeds swiftly, in a second slowly for a long time and last very rapidly for a short moments.

• 한국정보시스템학회지:정보시스템연구
• /
• 제18권1호
• /
• pp.47-76
• /
• 2009

The economic growth that depended on IT industry is reaching to a limit. In order to overcome the limit, the convergence industry that makes new market and products is essential. However, companies preparing a jump into the convergence industry must understand the exact visions and characteristics of convergence. Therefore, we investigated the structural changes of industries caused by convergence and importance characteristics of convergence. Also, we demonstrated the current status of the convergence industry and analyzed economical, social/cultural, and technological environments that the companies are facing, and elaborated the opportunities of convergence. At last, we suggested basic requirements and strategies for companies starting a convergence business and IT utilization methods to accelerate the convergence business activation.