• Journal of the Korean Society for Precision Engineering
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• v.19 no.12
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• pp.120-126
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• 2002

The needs of ultra-precisely machined parts are increasing more and more. But the experimental data required to ultra precision machining of nonferrous metal is insufficient. The behavior of cutting in micro cutting area is different from that of traditional cutting because of the size effect. Copper is widely used as optical parts such as LASER reflector's mirror and multimedia instrument. In experimental, after oxygen-free copper is machined by ultra precision machine with natural mono crystal diamond tool (NCD) and synthetic poly crystal diamond tool (PCD), we compared chip formation and tool's wear according to used tool. Also, we researched optimized cutting condition with the results measured according to cutting condition such as spindle speed, feed rate and depth of cut. As a result, the optimal working condition that makes good surface roughness is obtained. The surface roughness is good when spindle speed is above 80 m/min, and feed rate is small and depth of cut is above 0.5 ${\mu}{\textrm}{m}$. In cutting of klystron anode and cavity 3.2 nmRa of surface roughness is obtained.

• ETRI Journal
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• v.39 no.3
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• pp.406-416
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• 2017

Malware propagated via the World Wide Web is one of the most dangerous tools in the realm of cyber-attacks. Its methodologies are effective, relatively easy to use, and are developing constantly in an unexpected manner. As a result, rapidly detecting malware propagation websites from a myriad of webpages is a difficult task. In this paper, we present LoGos, an automated high-interaction dynamic analyzer optimized for a browser-based Windows virtual machine environment. LoGos utilizes Internet Explorer injection and API hooks, and scrutinizes malicious behaviors such as new network connections, unused open ports, registry modifications, and file creation. Based on the obtained results, LoGos can determine the maliciousness level. This model forms a very lightweight system. Thus, it is approximately 10 to 18 times faster than systems proposed in previous work. In addition, it provides high detection rates that are equal to those of state-of-the-art tools. LoGos is a closed tool that can detect an extensive array of malicious webpages. We prove the efficiency and effectiveness of the tool by analyzing almost 0.36 M domains and 3.2 M webpages on a daily basis.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.2
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• pp.69-74
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• 2004

In general the surge pressure generated in hydraulic systems causes noise, vibration and odd effect to the system. To reduce the surge pressure, high frequency PWM control of 20KHz was attempted. To estimate the braking noise caused by surge, a vehicle equipped with on-board ABS hydraulic modulator has been experimented with respect to the various breaking condition. Thorough this experiments, it was found that breaking noise has been reduced using high frequency PWM control method compare with low frequency method. To evaluate high frequency control m practice, including verification of general functionality, EMI tests was experimented. Its was found that it is necessary to have the solution to electromagnetic interference(EMI) generated by switching elements.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.3 no.2
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• pp.134-146
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• 2009

Traffic classification seeks to assign packet flows to an appropriate quality of service(QoS) class based on flow statistics without the need to examine packet payloads. Classification proceeds in two steps. Classification rules are first built by analyzing traffic traces, and then the classification rules are evaluated using test data. In this paper, we use self-organizing map and K-means clustering as unsupervised machine learning methods to identify the inherent classes in traffic traces. Three clusters were discovered, corresponding to transactional, bulk data transfer, and interactive applications. The K-nearest neighbor classifier was found to be highly accurate for the traffic data and significantly better compared to a minimum mean distance classifier.

• Korean Journal of Organic Agriculture
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• v.19 no.spc
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• pp.157-160
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• 2011

This study was conducted to find a method using the application of rice bran and mixed expeller cake at machine transplanting rice paddy field. Different ratios of rice bran and mixed expeller cake were sprayed as substitute of chemical fertilizer (nitrogen 90kg $ha^{-1}$) before transplanting. Nitrogen content was highest in 30th day after transplantation, and in relation to treatments the order was the following: Rice bran 1,000kg $ha^{-1}$ + Mixed expeller cake 1,374kg $ha^{-1}$ > rice bran 2,000kg $ha^{-1}$ + Mixed expeller cake 948kg $ha^{-1}$ > rice bran 3,000kg $ha^{-1}$ + Mixed expeller cake 522kg $ha^{-1}$. Number of panicle and spikelets per $m^{-2}$ was higher in rice bran 1,000kg $ha^{-1}$ + Mixed expeller cake 1,374kg $ha^{-1}$ and rice bran 2,000kg $ha^{-1}$ + Mixed expeller cake 948kg $ha^{-1}$ than in rice bran 3,000kg $ha^{-1}$ + Mixed expeller cake 522kg $ha^{-1}$ and the yields was the highest in rice bran 1,000kg $ha^{-1}$ + Mixed expeller cake 1,374kg $ha^{-1}$.

• Journal of Electrical Engineering and information Science
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• v.3 no.2
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• pp.193-201
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• 1998

In this paper, the standard Dole, Glover, Khargoneker, and Francis (abbr. : DGKF 1989) H\ulcorner controller (H\ulcornerC) is extended to the nonlinear feedback linearization-H\ulcorner/sliding mode controller (NFL-H\ulcorner/SMC), to tackle the problem of the unmeasurable state variables as in the conventional SMC, to obtain smooth control as the linearized controller in a linear system, and to improve the time-domain performance under a worst scenario. The proposed controller is obtained by combining the H\ulcorner estimator with the nonlinear feedback linearization-sliding mode controller (NFL-SMC) and it does not need to measure all the state variables as in the traditional SMC. The proposed controller is applied as a nonlinear power system stabilizer (PSS) for the improvement of the power system damping characteristics of an single machine infinite bus system (SMIBS) connected through a double circuit line. The effectiveness of the proposed controller is verified by nonlinear time-domain simulation in case of a 3-cycle line-to-ground fault and in case of the parameter variations for the AVR gain K\ulcorner and for the inertia moment M.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.523-527
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• 2011

Polycarbonate (PC) polymer is an engineering plastic which has large tensile strength and impact resistance and is wildly used as functional parts like micro mold. Direct machining of PC materials produces lots of burrs and rough surface due to large ductility and weak heat resistance and hence it is very difficult to machine PC materials using cutting tool to make micro-parts. In this study, elliptical vibration cutting (EVC) or 2-dimensional vibration cutting was performed to minimize the size of micro V-grooves on PC material. From the experimental results, it was observed that as the cutting depth and pattern size become smaller, the better machining quality was obtained, which is attributed to the positive effect of EVC that is dependent on the ratio of vibration amplitude to cutting depth. As the height of V-groove becomes less than $1.8{\mu}m$, however, the machining quality becomes lower as the pattern size decreases.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.3
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• pp.127-131
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• 2006

Existing orthopedic implants such as pedicle screw and spinal cage were designed to fix the spinal structure. But, nowadays, physicians want to rehabilitate there original functions. To achieve this request, we studied micro-movable structure for interspinous. As a first step, we designed interspinous structure by 3D CAD to join each spinous processes. Next, we simulate it with various factors such as the thickness of micro-movement structure and the design of clip. At last, we performed static compressive test to satisfy the failure load of 339N and dynamic endurance test of 1.2M cycle. As a result, we developed interspinous implant and did several surgery to evaluated its satisfaction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.441-444
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• 2004

In the sound insulation measurements, the influence of background (extraneous) noise is often serious problem and how to reduce its effect and to improve the signal-to-noise(S/N) ratio is an important theme. As the background noise, such extraneous noises as road traffic noise and machine noise often disturb the measurement. In laboratory measurements on specimens with high sound insulation performances, even the internal noise of the measurement system can become a problem. To improve the signal-to-noise ratio and to improve the measurement accuracy, various kinds of digital signal processing techniques can be applied. In this paper, four kinds of digital signal processing techniques are applied and their effectiveness is examined through field measurements.

• Journal of Chest Surgery
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• v.23 no.5
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• pp.854-863
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• 1990

Since the open heart surgery was performed, various kinds of problem concerning the extracorporeal circulation[EGG] have been known. The author investigated the changes of serum potassium ion before and after ECC among the 102 patients including 63 adults and 39 children who underwent open heart surgery from April 19S6 to February 1990 in Chung-Ang University Hospital. The mean values of potassium ion before and after ECC were analyzed according to the influencing factors such as priming solution, aortic cross clamping time, the underlying disease, the type of oxygenator and the amount of cardioplegic solution. The results were as follows: l. In the aspect of congenital and acquired heart disease groups, the mean values of serum potassium ion[Mean\ulcornerS.D.] before and after ECC revealed a significant change only in the acquired heart disease group[congenital; 3.87$\pm$0.48mEq /L vs. 4.05$\pm$0.73mEq /L, P>0.05, acquired: 4.40 $\pm$0.98mEq /L vs. 4.11$\pm$0.52mEq /L, P<0.05]. Between the two groups, the changes of the mean values of serum potassium ion before and after ECC were significant[P<0.05]. But all values were within normal limits. 2. In the aspect of the aortic cross clamping time[ACCT], in the groups of less or more than 120 minutes, the mean values of serum potassium ion before and after ECC revealed no significant change[less than 120 min; 3.97+-0.64mEq /L vs. 3.99+0.67mEq /L, P>0.05, more than 120 min; 4.34+0.82mEq /L vs. 4.27+0.62mEq /L, P>0.05], and The changes of mean values of serum potassium ion between the two groups were not significant[P>0.05]. 3. In both membrane and bubble oxygenator groups, the mean values of serum potassium ion before and after ECC did not reveal a significant difference respectively [membrane; 4.74 +1.40mEq /L vs. 4.28+0.3lmEq /L, P>0.05, bubble; 4.02 +0.60mEq /L vs. 4.05 L0.68mEq/L, P>0.05], and no differences between the membrane and bubble oxygenator groups[P >0.05]. 4. In the groups of membrane and bubble oxygenator in the cases of ACCT more than 120 minutes, the mean values of serum potassium ion before and after ECC did not reveal a significant difference respectively[membrane; 4.36$\pm$0.85mEq /L vs. 4.37$\pm$0.26mEq /L, P>0.05, bubble; 4.30 $\pm$0.80mEq/L vs. 4.23$\pm$0.67mEq/L, P>0.05], and no differences between the two groups[P>0.05]. 5. In spite of increased amount of cold potassium cardioplegic solution, the mean values of serum potassium ion before ECC were similar to those of serum potassium ion after ECC[less than 20ml /kg