• Journal of Korean Vacuum Science & Technology
• /
• v.4 no.1
• /
• pp.18-22
• /
• 2000

For the enhancement of the nucleation density of the diamond film, we introduced the cyclic process. The cyclic process was carried out by the on/off control of CH$_4$ flow rate for a relatively short time (10 min), compared with the total reaction time (6 h). Prior to depositing the diamond film, we made the pretreated glass substrate via the unidirectional scratch using ∼l $\mu\textrm{m}$ size diamond powders. Diamond films were deposited on the pretreated glass substrate in a microwave plasma enhanced chemical vapor deposition (MPECVD) system. We observed the enhancement of the nucleation density of the diamond films caused by the cyclic process. Detailed surface morphologies of the substrate were investigated after the cyclic process. Based on these results, we discussed the cause for the enhancement of the nucleation density on the pretreated glass substrate by the cyclic process.

• Journal of the Korean Society of Industry Convergence
• /
• v.26 no.6_3
• /
• pp.1333-1339
• /
• 2023

To produce activated carbon fibers, the process is carried out through either physical activation method or chemical activation method. In this study, we present the results regarding the characteristics of activated carbon fibers manufactured under various conditions through the quantitative control of steam. The yield after activation indicates a decreasing trend with the increase in steam quantity and activation time. Additionally, specific surface area characteristics exhibit variations based on activation time and steam flow rate. The SEM analysis results reveal that higher steam flow rates lead to the presence of both mesopores and macropores on the surface of activated carbon fibers (ACF).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.393-394
• /
• 2008

Carbon nanotubes are attractive nano-structured materials because of their remarkable electronic, physical, chemical properties. Due to these reasons, application researches of CNTs are actively processed on the display, the electronic element, the nano-diode fields and the semiconductor element. Today, The major issue of semiconductor technique are via and interconnects. CNTs are used to make via and interconnects because of high electric currents density and high heat transfer. Control of the orientation of grown CNTs is very important thing for making via and interconnects. Via are horizontal growth of CNTs and interconnects are vertical growth of CNTs. This research is based on the experiment using control of gas flow directions and DC bias. Scanning Electron Microscope (SEM) was used to check this experiment.

• Journal of Institute of Control, Robotics and Systems
• /
• v.3 no.5
• /
• pp.532-541
• /
• 1997

This article derives an analytic solution to determine the optimal size of multiple noncontinuous process and storage units. The total cost to be minimized consists of the setup cost of noncontinuous processing units and the inventory holding cost of feedstock/product storages. A novel approach, which is called PSW(Periodic Square Wave) model, is applied to represent the material flow among non-continuous units and storages. PSW model presumes that the material flow between unit and storage is periodic square wave shaped. The resulting optimal unit size has similar characteristics with the classical economic lot sizing model such as EOQ(Economic Order Quantity) or EPQ(Economic Production Quantity) model in a sense that the unit size is determined as the balance between setup and inventory holding cost. However, the influence of inventory holding cost of PSW model is different from that of EOQ/EPQ model. EOQ/EPQ model includes only the product inventory holding cost but PSW model includes all inventory holding costs around the non-continuous unit with proportional contribution. PSW model is suitable for analyzing interlinked process-storage system. The optimal lot size of PSW model is smaller than that of EOQ/EPQ model. This is quitea remarkable result considering that the EOQ/EPQ model has been is widely used since last half century.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.7
• /
• pp.2274-2278
• /
• 2011

Verapamil is a calcium channel blocker and is classified as a class IV anti-arrhythmic agent. It is used in the control of supra ventricular tachyarrhythmias, and in the management of classical and variant angina pectoris. It is also used in the treatment of hypertension and used as an important therapeutic agent for angina pectoris, ischemic heart disease, hypertension and hypertrophic cardiomyopathy. Verapamil commonly co-administered with NSAIDs (non-steroidal anti-inflammatory drugs) i.e. diclofenac sodium, flurbiprofen, Ibuprofen, mefanamic acid and meloxicam. A simple and rapid RP-HPLC method for simultaneous determination and quantification of verapamil and NSAIDs was developed and validated. The mobile phase constituted of acetonitrile: water (55:45) whose pH was adjusted at 2.7 and pumped at a flow rate of 2.0 mL $min^{-1}$ at 230 nm. The proposed method is simple, precise, accurate, low cost and least time consuming for the simultaneous determination of verapamil and NSAIDs which can be effectively applied for the analysis of human serum.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.5
• /
• pp.371-377
• /
• 1998

The plasma chemical vapor deposition is one of the most utilized techniques for the diamond growth. As the applications of diamond thin films prepared by plasma chemical vapor deposition(CVD) techniques become more demanding, improved fine-tuning and control of the process are required. The important parameters in diamond film deposition include the substrate temperature, $CO/H_2$gas flow ratio, total gas pressure, and gas excitation power. With the spectroscopic ellipsometry, the substrate temperature as well as the various parameters of the film can be determined without the physical contact and the destructiveness under the extreme environment associated with the diamond film deposition. Through this paper, the important parameters during the diamond film growth using $CO+H_2$are determined and it is shown that $sp^2$ C in the diamond film is greatly reduced.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.11
• /
• pp.3371-3381
• /
• 2010

In this study, quantitative and pattern recognition analysis for the quality evaluation of Magnoliae Flos using HPLC/UV was developed. For quantitative analysis, eleven major bioactive lignan compounds were determined. The separation conditions employed for HPLC/UV were optimized using ODS $C_{18}$ column ($250{\times}4.6\;mm$, $5\;{\mu}m$) with isocratic elution of acetonitrile and water with 1% acetic acid as the mobile phase at a flow rate of 1.0 mL/min and a detection wavelength of 278 nm. These methods were fully validated with respect to the linearity, accuracy, precision, recovery, and robustness. The HPLC/UV method was applied successfully to the quantification of eleven major compounds in the extract of Magnoliae Flos. The HPLC analytical method for pattern recognition analysis was validated by repeated analysis of twenty one reference samples corresponding to seven different species of Magnoliae Flos and nine samples purchased from market. The results indicate that the established HPLC/UV method is suitable for the quantitative analysis and quality control of multi-components in Magnoliae Flos.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.1
• /
• pp.239-246
• /
• 2011

In this study, quantitative and pattern recognition analysis for the quality evaluation of Cimicifugae Rhizoma using HPLC/UV was developed. For quantitative analysis, three major bioactive phenolic compounds were determined. The separation conditions employed for HPLC/UV were optimized using ODS $C_{18}$ column ($250{\times}4.6mm$, $5{\mu}M$) with isocratic elution of acetonitrile and water with 0.1% phosphoric acid as the mobile phase at a flow rate of 1.0 mL/min and a detection wavelength of 323 nm. These methods were fully validated with respect to the linearity, accuracy, precision, recovery, and robustness. The HPLC/UV method was applied successfully to the quantification of three major compounds in the extract of Cimicifugae Rhizoma. The HPLC analytical method for pattern recognition analysis was validated by repeated analysis of twelve reference samples corresponding to five different species of Cimicifugae Rhizoma and seventeen samples purchased from markets. The results indicate that the established HPLC/UV method is suitable for the quantitative analysis and quality control of multi-components in Cimicifugae Rhizoma.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.38-38
• /
• 2010

Ever since the experimental discovery of graphene exfoiliated from the graphite flakes by Geim et at., this area has drawn a lot of attention for its possible application in IT industry. For the growth of graphene, chemical vapor deposition (CVD) has been widely used to fabricate the large area graphene. The lateral size of this graphene can be easily controlled by the size of the metal substrate though the chemical etching to remove this substrate is somewhat troublesome. Another problem which is hard to avoid is the folding at the grain boundary. We will discuss the origin of the folding first and introduce the way to avoid this folding. To solve this problem, we have used the various types of micro-thin metal foils. The precise control of hydro-carbon and the carrier gas results in the formation of the graphene on top of substrate. The thickness of graphene layers can be controlled with the control of gas flow on top of Cu substrate in contrast to the previously reported self-limiting growth $behavior^1$. Uniformity of this graphene layer has been checked by micro-raman spectroscopy and SEM. The size of grain can be enhanced by thermal treatment or use of other metal substrate. The dependence of grain size on the lattice size of the substrate will be discussed. By selecting the shape of substrate, we can grow various types of graphene. We will introduce the micron size graphene tube and its application.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.9 no.3
• /
• pp.170-178
• /
• 2007

Rapid increases in the concentrations of greenhouse gases and many other chemically important trace gases have occurred over the last several centuries. For understanding the roles of these important gases in global change, it is essential to identify their sources and sinks, to characterize biogenic gas fluxes between the biosphere and atmosphere, and to understand the processes that control them. In this paper, enclosure-based measurements are described in a practical manner for field experiments. Theoretical reviews of mass balance equation in the enclosure and sensitivity of the flow-through dynamic flux chamber technique are presented; specifically for the case of NO flux measurements from soil surface. The physical system and theory behind the flow-through dynamic flux chamber method are examined. New calculation flux formula was introduced by considering NO chemical loss on chamber wall and uncertainties of the NO flux calculation were discussed.