• IEMEK Journal of Embedded Systems and Applications
• /
• v.1 no.2
• /
• pp.64-72
• /
• 2006

The long propagation delay over satellite internet causes degradation of TCP performance in slow start phase. Especially, web traffic performance is greatly reduced by low throughput in slow start phase. To improve web traffic performance, we propose the Dynamic ACK Generation Scheme which generates ACKs and considers sender RTO in PEP (Performance Enhancing Proxy). The Normal ACK generation mechanism improves TCP throughput, and also decreases sender RTO. if PEP stops generating ACKs, TCP performance will be reduced by frequent RTO expiration. To solve this problem, our scheme adjusts RTO using ACK generation interval. And it supports retransmission mechanism for loss recovery in PEP. The results of the performance analysis provide a good evidence to demonstrate the efficiency of our mechanisms over satellite internet.

• Journal of Pharmaceutical Investigation
• /
• v.5 no.1
• /
• pp.28-40
• /
• 1975

Polyporus would used as diuretics. Then, for the purpose of experimentally certifying the above mention, the effect on the renal function of dog was investigated, utilizing clearance technique. Water and alcohol extracts, when injected intravenously, produced significant increases of urinary sodium and potassium, osmolar and free water clearances, and urine flow, while glomerular filtration rate and renal plasma flow remained unchanged. During diuresis produced by furosemide, addition of water extract reduced the action of furosemide and markedly renal plasma flow. It would appear that these compounds are capable of action by a different mechanism or a different site. water extract, when infused directly into a renal artery, reduced the urine flow of experimental kidney as well as renal plasma flow, and the contralateral kidney exhibited diuresis, whereas amounts of sodium and potassium excreted in urine increased on both kidney. It is surmised from those observations that Polyporus induces diuresis by inhibition the reabsorptive mechanism of renal tubules through some endogeneous humoral substances, in addition, directly reduces the renal plasma flow.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.4 s.181
• /
• pp.132-138
• /
• 2006

A tape feeder is an important part to supply a micro chip such as 1005 and 0603 components in SMT process. Traditional sprocket wheel type feeder has several problems such as backlash and indexing errors, low compatibility and confidence. However, it is very difficult to solve such problems due to the inevitable fraction defectives of sprocket wheel. Thus, the object of this works is to develop a linear type high precision tape feeding system using cam-slider mechanism. The proposed cam-slider mechanism is composed of several links and a plate, pneumatic actuator is used to generate linear motion. The proposed mechanism has distinct advantages over the conventional mechanism. It has reduced feeding errors, long lift-cycle, and slim width. As a result, the developed tape feeder using cam-slider mechanism shows special characteristics far high precision feeding for chip-mounters.

• Journal of the Korean Geosynthetics Society
• /
• v.4 no.2
• /
• pp.19-28
• /
• 2005

This paper presents a laboratory investigation on the failure mechanism of geosynthetic reinforced slopes using 1/5-scale reduced model. The components of the model were selected with due consideration of the similitude law and the step-by-step actual wall construction procedure was closely simulated. The model tests successfully replicated the failure mechanism with relative density, slope and vertical spacing.

• Tribology and Lubricants
• /
• v.17 no.3
• /
• pp.171-178
• /
• 2001

In order to elucidate the lubricating mechanism of polyolester base oils [POEs], the wear characteristics of 27 kinds of polyolester base oils including mixed POEs were investigated. Their wear results were discussed in terms of the effect of molecular structure on wear performance and compared with those of mineral oil. In addition, the adsorption ability of POEs to reduced iron and their hydrolysis rates were measured and the effect of their molecular structures on the adsorptivity and hydrolysis rate of POEs was discussed, respectively. Finally, the lubricating mechanism anlyzed from these results of wear characteristics, adsorptivity and hydrolysis rate was proposed. That is to say, POEs are firstly adsorbed to friction surface and decomposed by hydrolysis or thermal degradation. Fatty acids obtained by degradation of POEs form adsorption film on friction surface. The larger become cohesive ability among fatty acid molecules in the adsorption film, the better gets the wear performance of POEs.

• Journal of Industrial Technology
• /
• v.19
• /
• pp.321-329
• /
• 1999

An automated manufacturing process mechanism for string musical instruments has been designed in this study. In contrast to other manufacturing products, classical string instruments try to preserve their traditional design shapes even in these days and involve variety of wood working(carpentry) characteristics including highly skilled curved surfaces treatments. Great efforts have been put to develop an integrated and automated system for improved product quality and process control, reduced physical labors, better safety etc. They, however, have been limited to devise jigs and tools with regard to selected processes due to lack of technology and research man-powers. We carefully examined the products and process characteristics, and an automated mechanism which overcome prevailing drawbacks has been derived.

• Journal of Microbiology
• /
• v.35 no.1
• /
• pp.15-20
• /
• 1997

Kinetic studies were done to elucidate the reaction mechanism of purine nucleoside phosphorylase (PNP) in Micrococcus Luteus. PNP catalyzes the reversible phosphorolysis of ribonucleosides to their respective base. The effect of alternative competing substrates suggested that a single enzyme was involved in binding to the active site for all purine nucleosides, inosine, deoxyiosine, guanosine, deoxyguanosine, adenosine and deoxyadenosine. Affinity studies showed that pentose moiety reduced the binding capacity and methylation of ring N-1 of inosine and guanosine had little effect on binding to bacterial enzyme, whereas these compounds did not bind to the mammalian enzymes. The initial velocity and product inhibition studies demonstrated that the predominant mechanism of reaction was an ordered bi, bi reaction. The nucleoside bound to the enzyme first, followed by phosphate. Ribose 1-phosphate was the first product to leave, followed by base.

• Structural Engineering and Mechanics
• /
• v.44 no.4
• /
• pp.501-519
• /
• 2012

Truss weight is one of the most important factors in the cost of construction that should be reduced. Different methods have been proposed to optimize the weight of trusses. The artificial bee colony algorithm has been proposed recently. This algorithm selects the lightest section from a list of available profiles that satisfy the existing provisions in the design codes and specifications. An important issue in optimization algorithms is how to impose constraints. In this paper, the artificial bee colony algorithm is used for the discrete optimization of trusses. The fly-back mechanism is chosen to impose constraints. Finally, with some basic examples that have been introduced in similar articles, the performance of this algorithm is tested using the fly-back mechanism. The results indicate that the rate of convergence and the accuracy are optimized in comparison with other methods.

• 한국정보통신설비학회:학술대회논문집
• /
• 2005.08a
• /
• pp.67-73
• /
• 2005

For power constrained applications, IEEE 802.15.4 networks may be operated in beacon enabled mode with inactive period. In this paper, we propose the Virtual Arrival Mechanism (VAM) to avoid the congestion at the beginning of each contention access period (CAP). Virtual Arrival Mechanism (VAM) is a kind of traffic shaping that spread the traffics congested at the beginning of CAP into the whole CAP. By using VAM, collisions and energy consumption can be reduced. Finally, we evaluate the performance enhancement of VAM using NS-2 simulator.

• Journal of Korean Institute of Industrial Engineers
• /
• v.25 no.2
• /
• pp.192-203
• /
• 1999

This paper deals with the order release problem for minimizing weighted earliness and tardiness as well as Work In Process (WIP) in dynamic job shop environments. A newly designed hierarchical order release mechanism is developed for efficient real-time control of the earliness/tardiness and WIP. The hierarchical order release mechanism consists of the order release plan and the order release control which is composed of two procedures. The experimental results show that the proposed order release mechanism is superior to other four order release mechanisms under overall simulation conditions of utilization rate, due-date allowances, and earliness/tardiness cost structures. In addition, the difference of total cost among the four dispatching rules is much more reduced in the proposed order release mechanism than in other release mechanisms.