• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.429-436
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• 2005

This paper presents a precise and stable time integration method for dynamic analysis of vibration or multibody systems. A total system is divided into several subsystems and their responses are calculated separately, while the coupling effect is treated equivalently as constant force during time steps. By using iterative procedure to improve equivalent coupling forces, a precise and stable solution is obtained. Some examples such as a seismic response and multibody analyses were carried out to demonstrate its usefulness.

• 대한안전경영과학회지
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• 제10권1호
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• pp.155-166
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• 2008

During last two decades the transportation system has developed into very intelligent system with GIS, GPS and ITS. The practical transportation management system provides real time response module to manage the customer's order. We have surveyed research papers on the real time vehicle routing problem in last two decades to figure out the dynamic vehicle routing problem. The papers are classified by basic routing algorithms and by managing the dynamic events which are the order management, the routing re-optimization, the routing post-optimization and the waiting strategy.

• International Journal of Reliability and Applications
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• 제7권2호
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• pp.127-140
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• 2006

AIn this paper we introduce and study a multivariate notions of mean inactivity time (MIT) functions. Basic properties of these functions are derived and their relationship to the multivariate conditional reversed hazard rate functions is studied. A partial ordering, called MIT ordering, of non-negative random vectors is introduced and its basic properties are presented. Its relationship to reversed hazard rate ordering is pointed out. Finally, using the MIT ordering, a bivariate and multivariate notions of IMIT (increasing mean inactivity time) class is introduced and studied.

• 한국연초학회지
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• 제6권1호
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• pp.13-18
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• 1984

To find out the effect of transplanting time on the autonomic characters, yield of cured leaves and content of polyphenols in burley tobacco, three transplanting time were evaluated. The results obtained are as follows. Low temperature which was caused damage earliest stage of tobacco in early transplanting could escape by vinyl mulching and other treatment. 2. The major polyphenols in leaves were chlorogenic acid and rutin, small amount of scopolin and quercetin were also detected. 3. Chlorogenic acid decreased during curing. 4. Polyphenols content was not influenced by transplanting time.

• Archives of Reconstructive Microsurgery
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• 제5권1호
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• pp.121-127
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• 1996

Peripheral nerve injury occurs mostly by trauma and is usually associated with fracture of bone and joint, muscular injury and tendon injury and it also evokes paralysis and anesthesia. When treatment of peripheral nerve injury is considered,, the modality of treatment is decided by the general condition of the patient, type of injury, associated injuries and the condition of wound. To get the maximum results, surgical treatment and reconstruction and rehabilitation should all go in hand-in-hand. From January 1985 to December 1994, we observed 61 patients that had operation without reconstruction due to peripheral nerve injury with a follow-up period of more than 1 year. Among the 61 patients, 44 were men(72%) and 17 were women(28%). Follow-up period was average 19 months. Age distribution was mostly in their twenties with a mean age of 28 years. Time interval of operation after injury was average 11 months. Trauma was the main cause of peripheral nerve injuries with a proportion of 87%. 31 patients had neurorrhaphy, in which case 14 patients had stay suture and 17 patients did not. 14 patients had nerve graft, and 16 patients had neurolysis. We used our scales to compare the results of surgery on the basis of British Research Council System. We gave scores to every sensory and motor scale to estimate functional improvement and emphasized on motor functional improvement. The total score = sensory score + ($2{\times}motor$ score). We considered 8-9 points as excellent, 6-7 points as good, 2-5 points as fair, 0-1 points as poor result. We considered excellent and good as much improved. Excellent and good results were obtained in 13 out of 14 neurorrhaphy with stay suture(93%), 12 out of 17 neurorrhaphy without stay suture(71%), 6 out of 14 nerve graft(43%), 12 out of 16 neurolysis(75%). Among the patients with neurorrhaphy done within 3 months, 11 out of 14(86%) showed improvement, but among the patients after 4 months 3 out of 17(76%) showed improvement. 84% of improvement was observed in the patients with time interval from injury to surgery within 3 months, and 64% in the patients with time interval after 4 months. In the aspect of age, 77% with the age below 20 years, 70% with the age between 21 and 30 years, 66% with the age above 31 years showed improvement. We conclude that considering degree of injury, time interval from injury and age with the adequate method of treatment, we can obtain good results from surgery.

• Composites Research
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• 제34권4호
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• pp.233-240
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• 2021

VaRI(Vacuum assisted Resin Infusion) 공정은 공정비용이 저렴하며, 크기가 큰 복합재 제작에 적합한 OoA(Out of Autoclave) 공정이다. VaRI 공정에서는 원할한 수지 주입을 위해 섬유 상단에 유로망을 적층한다. 수지는 이 유로망을 따라 섬유의 면 방향으로 빠르게 공급되고, 공급된 수지는 다시 섬유의 두께방향으로 함침된다. 면방향의 유동과 두께방향의 유동이 동시에 일어나기 때문에 수지의 유동을 예측하기 힘들며, 수지 주입과정을 예측하기 위해 3D 수치해석 프로그램이 사용되고 있다. 하지만, 3D로 해석하기 위해서 섬유와 유로망의 두께방향에 많은 Element가 필요하고, 이로 인해 제품의 크기가 클수록 해석시간이 오래 걸린다. 따라서 본 연구에서는 3D 유동해석을 2D 해석으로 간소화하여 유동해석에 소요되는 시간을 줄이는 방법을 제시하였다. 3D 유동해석과 간소화된 2D 유동해석을 동일조건에서 비교하여 효용성을 검증하였고, 충진시간 오차율은 약 7%, 유동해석시간 감소율은 약 95%로 나타났다. 또한 3D 해석에서 섬유 상, 중, 하단 간의 유동 전진 거리의 차이가 일정하다는 것을 활용하여 간소화된 2D 유동해석에서도 상, 중, 하단의 유동 전진 거리를 예측할 수 있었다.

• 대한기계학회논문집B
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• 제22권6호
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• pp.788-802
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• 1998

A numerical method using dual time stepping and preconditioning procedure for efficient computations of unsteady low speed compressible flow problems is developed. The time-derivative preconditioning method which is valid at low speed flow conditions cannot maintain temporal accuracy because of the modification of the time-derivative term in Navier-Stokes equations. The dual time stepping procedure is incorporated to enable the time accurate computations and this procedure introduces a pseudo-time derivative in addition to the physical time derivative. At a given physical time, an inner iteration can be carried out until a steady state in pseudo-time is achieved. This will effectively yield a time accurate solution. Computational capabilities of the above algorithm are demonstrated through computation of a variety of practical fluid flows and it is shown that the algorithms is efficient in the essentially incompressible flows and low Mach number compressible flows with heat source.

• 한국소음진동공학회논문집
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• 제15권3호
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• pp.266-271
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• 2005

Although time-frequency analysis is useful for dispersive wave analysis, conventional methods such as the short-time Fourier transform do not take the dispersion phenomenon into consideration in the tiling of the time-frequency domain. The objective of this paper is to develop an adaptive time-frequency analysis method whose time-frequency tiling is determined with the consideration of signal dispersion characteristics. To achieve the adaptive time-frequency tiling, each of time-frequency atoms is rotated in the time-frequency plane depending on the local wave dispersion. To carry out this adaptive time-frequency transform, dispersion characteristics hidden in a signal are first estimated by an iterative scheme. To examine the effectiveness of the present method, the flexural wave signals measured in a plate were analyzed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.606-610
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• 2004

Although time-frequency analysis is useful for dispersive wave analysis, conventional methods such as the short-time Fourier transform do not take the dispersion phenomenon into consideration in the tiling of the time-frequency domain. The objective of this paper is to develop an adaptive time-frequency analysis method whose time-frequency tiling is determined with the consideration of signal dispersion characteristics. To achieve the adaptive time-frequency tiling, each of time-frequency atoms is rotated in the time-frequency plane depending on the local wave dispersion. To carry out this adaptive time-frequency transform, dispersion characteristics hidden in a signal are first estimated by an iterative scheme. To examine the effectiveness of the proposed method, the flexural wave signals measured in a plate were analyzed.

• 한국경영과학회지
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• 제32권3호
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• pp.47-61
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• 2007

This paper presents two elimination methods of subtours, which is obtained by applying the Out-of-Kilter algorithm to the sequential ordering problem (SOP) to produce a feasible solution for the SOP. Since the SOP is a kind of asymmetric traveling salesman problem (ATSP) with precedence constraints, we can apply the Out-of-Kilter algorithm to the SOP by relaxing the precedence constraints. Instead of patching subtours, both of two elimination methods construct a feasible solution of the SOP by using arcs constructing the subtours, and they improve solution by running 3-opt and 4-opt at each iteration. We also use a perturbation method. cost relaxation to explore a global solution. Six cases from two elimination methods are presented and their experimental results are compared to each other. The proposed algorithm found 32 best known solutions out of the 34 instances from the TSPLIB in a reasonable time.