• Journal of the Korean Ceramic Society
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• v.30 no.2
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• pp.148-156
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• 1993

TiN films were deposited onto high speed steel (SKH9) by plasma assisted chemical vapor deposition (PACVD) using a TiCl4/N2/H2/Ar gas mixture at around 50$0^{\circ}C$. The effects of the deposition temperature, R.F. power and TiCl4 concentration on the deposition of TiN and the microhardness of TiN film were investigated. The crystallinity and the microhardness of TiN films were improved with increase of the deposition temperature. Optimum deposition temperature in this study was 50$0^{\circ}C$, because a softening or phase transformation of the substrate occurred over 50$0^{\circ}C$. A large increase of the film growth rate with a strong(200) preferred orientation was obtained by increasing R.F. power. Much chlorine content of about 10at.% was found in the deposited films and resulted in relatively low average microhardness of about 1, 500Kgf/$\textrm{mm}^2$ compared with the theoretical value(~2, 000Kgf/$\textrm{mm}^2$).

• Carbon letters
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• v.1 no.3_4
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• pp.129-132
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• 2001

Carbonaceous thin films were prepared from acetylene and argon gases by plasma assisted chemical vapor deposition (Plasma CVD) at 873 K. The carbonaceous thin films were characterized by mainly Raman spectroscopy, and their electrochemical properties were studied by cyclic voltammetry and charge-discharge measurements in propylene carbonate (PC) solution. Raman spectra showed that crystallinity of carbonaceous thin films is correlated by the applied RF power. The difference of the applied RF power also affected on the results of cyclic voltammetry and charge-discharge measurements. In PC solution, intercalation and de-intercalation of lithium ion can occur as well as in the mixed solution of EC and DEC.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1039-1046
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• 2001

Among the automotive steering systems, an Electric Power Assisted steering (EPAS) system utilizes an electronically controlled electric motor to provide steering assistance to the driver. The key components of the EPAS system are torque sensor, ECU (Electronic Control Unit), and DC Motor. The most important component of the EPAS is the torque sensor. The conventional torque sensor has complicated mechanical mechanism of torque detection. However, we suggest a non-contact torque sensor for EPAS using Maluss polarization law. It was found that the sensor exhibited not only excellent linearity but also superior characteristics of hysteresis, temperature and vibration.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1195-1202
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• 2017

This paper presents a novel topology named a modified capacitor-assisted Z-source inverter (MCA-ZSI) based on the traditional ZSI. The impedance network of the proposed MCA-ZSI consists of two symmetrical cells coupled with two capacitors with an X-shape structure, and each cell has two inductors, two capacitors, and one diode. Compared with other topologies based on switched ZSI with the same number of components used at impedance network, the proposed topology provides higher boost ability, lower voltage stress across inverter switching devices, and lower capacitor voltage stress. The improved performances of the proposed topology are demonstrated in the simulation and experimental results.

• Journal of Surface Science and Engineering
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• v.37 no.3
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• pp.164-168
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• 2004

Polycrystalline silicon thin films were deposited by inductively coupled plasma (ICP) assisted magnetron sputtering using a gas mixture of Ar and $H_2$ on a glass substrate at $250^{\circ}C$. At constant Ar mass flow rate of 10 sccm, the working pressure was changed between 10mTorr and 70mTorr with changing $H_2$ flow rate. The effects of RF power applied to ICP coil and $Ar/H_2$ gas mixing ratio on the properties of the deposited Si films were investigated. The crystallinity was evaluated by both X-ray diffraction and Raman spectroscopy. From the results of Raman spectroscopy, the crystallinity was improved as hydrogen mixing ratio was increased up to$ Ar/H_2$=10/16 sccm; the maximum crystalline fraction was 74% at this condition. When RF power applied to ICP coil was increased, the crystallinity was also increased around 78%. In order to investigate the surface roughness of the deposited films, Atomic Force Microscopy was used.

• ETRI Journal
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• v.19 no.3
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• pp.98-115
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• 1997

The architecture of the CDMA mobile system (CMS) is developed based on three function groups - service resource, service control, and service management groups. In this paper, the CMS architecture is discussed from the point of view of implementing these functions. The variable length packets are used for transmission. The synchronization clock signals are derived form the GPS receiver. The open loop and closed loop techniques are used for the power control. The internationally accepted signaling and network protocols are employed. The call control for the primary services in designed to provide efficient mobile telecommunication services. The softer handoff is implemented in one card. The mobile assisted handoff and the network assisted handoff are employed in the soft and hard handoffs. The authentication is based on the secret data which includes random numbers. The management functions, which include the location management, resource management, cell boundary management and OAM management, are implemented to warrant the system efficiency, maximum capacity and high reliability. The architecture ensures that the CMS is flexible and expandable to provide subscribers with economic and efficient system configuration. The dynamic power control, adaptive channel allocation. and dynamic cell boundary management are recommended for future work.

• Applied Science and Convergence Technology
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• v.23 no.3
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• pp.145-150
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• 2014

MgO thin films were deposited by internal ICP-assisted reactive-magnetron sputtering with bipolar pulse bias on a substrate to suppress random arcs. Mg is reactively sputtered by a bipolar pulsed DC power of 100 kHz into ICP generated by a dielectrically shielded internal antenna. At a mass flow ratio of $Ar/O_2$ = 10 : 2 and an ICP/sputter power ratio of 1 : 1, optimal film properties were obtained (a powder-like crystal orientation distribution and a RMS surface roughness of approximately 0.42 nm). A bipolar pulse substrate bias at a proper frequency (~a few kHz) prevented random arc events. The crystalline preferred orientations varied between the (111), (200) and (220) orientations. By optimizing the plasma conditions, films having similar bulk crystallinity characteristics (JCPDS data) were successfully obtained.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.2
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• pp.23-29
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• 2022

To improve spectrum and energy efficiency in the fifth generation (5G) wireless channels, intelligent reflecting surface (IRS) transmissions have been envisioned, possibly towards the sixth generation (6G) networks. In this paper, we analyze the bit-error rate (BER) performance of intelligent reflecting surface (IRS) assisted non-orthogonal multiple access (NOMA) systems. First, we derive a closed-form expression of the BER in terms of Q functions. Then we analyze the BER improvement of the IRS NOMA system over the conventional NOMA system with respect to the power allocation. Furthermore, we also demonstrate numerically the BER improvement of the IRS NOMA network over the conventional NOMA network in respect of the number of reflecting devices.

• Nuclear Engineering and Technology
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• v.40 no.3
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• pp.225-232
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• 2008

To understand the effect of the cyclic strain rate on the environmentally assisted cracking behaviors of SA508 Gr.1a low alloy steel in deoxygenated water at $310^{\circ}C$, the fatigue surface and a sectioned area of specimens were observed after low cycle fatigue tests. On the fatigue surface of the specimen tested at a strain rate of 0.008 %/s, unclear ductile striations and a blunt crack tip were observed. Therefore, metal dissolution could be the main cracking mechanism of the material at this strain rate. On the other hand, on the fatigue surfaces of the specimens tested at strain rates of 0.04 and 0.4 %/s, brittle cracks and flat facets, which are evidences of the hydrogen induced cracking, were observed. In addition, a tendency of linkage between the main crack and the micro-cracks was observed on the sectioned area. Therefore, at higher strain rates, the main cracking mechanism could be hydrogen induced cracking. Additionally, evidence of the dissolved MnS inclusions was observed on the fatigue surface from energy dispersive x-ray spectrometer analyses. Thus, despite the low sulfur content of the test material, the sulfides seem to contribute to environmentally assisted cracking of SA508 Gr.1a low alloy steel in deoxygenated water at $310^{\circ}C$.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.4
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• pp.295-302
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• 2008

This paper examines the design and the performance of a PMA-RSM(permanent-magnet assisted reluctance synchronous motor) for washing machine. A FEM(finite element method) is used to analyze performance and maximum torque characteristic of the proposed PMA-RSM. The designed motor is a combination of salient poles, which is making reluctance torque, and permanent magnet which are located on the air-gap of rotor to get a enough torque during low speed resign. Typical flux barrier type reluctance synchronous motor and the effects of adding magnet into the flux barrier of the rotor of a PMA-RSM are compared and examined. Also the maximum torque point of the reluctance torque by reluctance and reaction torque by magnetic alignment torque, which is in barrier, of the proposed PMS-RSM are derived through simulation. Using this results, the characteristics analysis of a performance, an average torque and a torque ripple of flux barrier RSM and the proposed PMA-RSM are performed through FEM under the saturation effect respectively.