• Advances in nano research
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• v.2 no.1
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• pp.23-56
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• 2014

The significant growth of the Si photovoltaic industry has been so far limited due to the high cost of the Si photovoltaic system. In this regard, the most expensive factors are the intrinsic cost of silicon material and the Si solar cell fabrication processes. Conventional Si solar cells have p-n junctions inside for an efficient extraction of light-generated charge carriers. However, the p-n junction is normally formed through very expensive processes requiring very high temperature (${\sim}1000^{\circ}C$). Therefore, several systems are currently under study to form heterojunctions at low temperatures. Among them, carbon nanotube (CNT)/Si hybrid solar cells are very promising, with power conversion efficiency up to 15%. In these cells, the p-type Si layer is replaced by a semitransparent CNT film deposited at room temperature on the n-doped Si wafer, thus giving rise to an overall reduction of the total Si thickness and to the fabrication of a device with cheaper methods at low temperatures. In particular, the CNT film coating the Si wafer acts as a conductive electrode for charge carrier collection and establishes a built-in voltage for separating photocarriers. Moreover, due to the CNT film optical semitransparency, most of the incoming light is absorbed in Si; thus the efficiency of the CNT/Si device is in principle comparable to that of a conventional Si one. In this paper an overview of several factors at the basis of this device operation and of the suggested improvements to its architecture is given. In addition, still open physical/technological issues are also addressed.

• Journal of KIISE
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• v.42 no.6
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• pp.707-712
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• 2015

Mobile cloud computing is a technology that uses cloud services to overcome resource constrains of a mobile device, and it applies the computation offloading scheme to transfer a portion of a task which should be executed from a mobile device to the cloud. If the communication cost of the computation offloading is less than the computation cost of a mobile device, the mobile device commits a certain task to the cloud. The previous cost analysis models, which were used for separating functions running on a mobile device and functions transferring to the cloud, only considered the amount of data transfer and response time as the offloading cost. In this paper, we proposed a new task partitioning scheme that considers the frequency of function calls and data synchronization, during the cost estimation of the computation offloading. We also verified the energy efficiency of the proposed scheme by using experimental results.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.27-35
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• 2021

NAND flash memory-based SSD needs an internal software, Flash Translation Layer(FTL) to provide traditional block device interface to the host because of its physical constraints, such as erase-before-write and large erase block. However, because useful host-side information cannot be delivered to FTL through the narrow block device interface, SSDs suffer from a variety of problems such as increasing garbage collection overhead, large tail-latency, and unpredictable I/O latency. Otherwise, the new type of SSD, open-channel SSD exposes the internal structure of SSD to the host so that underlying NAND flash memory can be managed directly by the host-level FTL. Especially, I/O data classification by using host-side information can achieve the reduction of garbage collection overhead. In this paper, we propose a new scheme to reduce garbage collection overhead of open-channel SSD by separating the journal from other file data for the journaling filesystem. Because journal has different lifespan with other file data, the Write Amplification Factor (WAF) caused by garbage collection can be reduced. The proposed scheme is implemented by modifying the host-level FTL of Linux and evaluated with both Fio and Filebench. According to the experiment results, the proposed scheme improves I/O performance by 46%~50% while reducing the WAF of open-channel SSDs by more than 33% compared to the previous one.

• The KIPS Transactions:PartA
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• v.11A no.3
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• pp.139-148
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• 2004

The number of applications of small embedded systems such as PDAs, electronic note books, etc. based on Kinux, have increased. Due to the monolithic characteristic of Linux kernel, it is not suitable to satisfy the various kinds of embedded application requirement. To assist the shortcoming of monolithic kernel, we implement uJFFS 113th file system as an application program process which runs in user space. This solution consists of a file system and a flash device driver, and makes Linux kernel smaller by separating the file system from the kernel. uJFFS consists of ujffs_fs that plays a part of file system and ujffs_drv that controls a flash device. Which provides the same user interface as Linux does. A Device driver for the physical device is implemented in user pace, which prevents kernel failures from file system errors. So uJFFS can increase stability of the system.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.12
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• pp.891-898
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• 2009

This paper suggests producer/consumer-based Data Binder enabling applications and biomedical devices developed by mutually different vendors to transfer data dynamically. Data Binder is implemented as a bundle of OSGi platform providing component-based programming model and service-oriented operation architecture. Data Binder complements the disadvantage of OSGi WireAdmin service enabling static data delivery between a producer and a consumer of data. Data Binder normalizes an application requirement as an application descriptor and a device capability as a device descriptor so that it enables dynamic data delivery by making data producer/consumer pair in runtime. Therefore, Data Binder can be used as a connection management of a data link between a data producer and a data consumer in sensor-based application development. The object of this paper is to provide the facility of the healthcare service development by separating a data producer such as a biomedical device from a data consumer such as a healthcare application.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.2
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• pp.80-85
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• 2014

Side jet thruster using nozzle closure separation device provides a solid rocket with a trajectory shift function. Side jet thruster consists of low combustion temperature propellant, neutral type propellant grain and nozzle closure separation device. If a trajectory shift is required, side jet thrust is generated on the rocket by separating some nozzle closures located in the opposite direction to thrust. After completing trajectory shift, the other nozzle closures located in the thrust direction are separated to cease side jet thrust. The operation process is verified through ground static test. The result in this study can be applied to changing rocket trajectory by controlling side jet thrust through nozzle closure separation.

• Journal of Labour Economics
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• v.23 no.1
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• pp.103-135
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• 2000

After scrutinizing the actual conditions of labor participation in management decision makings through analysing the collective agreements and the regulations of labor-management committee at the affiliated companies of Korea's top-five Chaebols, we could get some conclusions as follows. First, because the labor participation in management decision makings is in very inactive situations at the long-term management strategy level and the workplace practice level of industrial relations, both parties of the industrial relations in those companies surveyed show the serious lack of abilities to tackle the new and rapidly changing business environments as nowadays actively and cooperatively. Second, we could find the fact that in the surveyed companies the device of collective bargaining was used more commonly at the collective bargaining level of industrial relations and the device of labor-management committee was often used relatively at the long-term management strategy level and the workplace practice level. Third, we could conclude that the separating type of the labor-management committee which was able to keep a safe distance from the more antagonistic device, the collective bargaining, was much more efficient device of the labor participation in management decision makings.

• Journal of the Korea Society of Computer and Information
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• v.27 no.11
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• pp.191-198
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• 2022

The most basic thing to measure the condition of a companion animal is to check the breathing and pulse. There are several methods to measure the breathing and pulse of a companion animal, and the PPG method is generally used to measure the oxygen saturation (SpO₂) in a companion animal. However, since the input PPG signal is inputted with various information as well as oxygen saturation, it is necessary to separate and extract oxygen saturation information from the PPG signal in order to measure the oxygen saturation. Therefore, in this paper, a wearable measuring device for companion animals that can be measured by applying the PPG method was designed and implemented, and an algorithm for separating oxygen saturation information from the PPG signal input through the wearable measuring device was proposed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.8
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• pp.638-644
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• 2010

We have carry out numerical simulation of the electric-optical characteristics of organic light emitting diodes with gradient-doped emitting layer which were reported to be effective in improving luminous efficiency and lifetime. In this paper, the basic structure is comprised of ITO/NPB/$Alq_3$:C545T[%]/$Alq_3$/LiF/Al, six devices by separating the emitting layer of $Alq_3$:C545T[%] were studied. As the result, the uniformly-doped devices exhibited superior luminous efficiency-current density characteristics over conventional undoped device. In the case of gradient-doped devices, electric-optical characteristics were improved similar to uniformed-doped devices, unusually the distribution of traped-charge density in the OLED devices was shown as the staircase.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.9-18
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• 1998

The vortex tube is a simple device for separating a compressed gaseous fluid stream into two flows of high and low temperature without any chemical reactions. Recently, vortex tube is widely used to local cooler of industrial equipments and air supply system. The phenomena of energy separation through the vortex tube was investigated experimentally. This study is focused on the effect of the diameter of cold end orifice diameter on the energy separation. The experiment was carried out with various cold end orifice diameter ratio from 0.22 to 0.78 for different input pressure and cold air flow ratio. The experimental results were indicated that there are an optimum diameter of cold end orifice for the best cooling performance. The maximum cold air temperature difference was appeared when the diameter ratio of the cold end orifice was 0.5. The maximum cooling capacity was obtained when the diameter ratio of the cold end orifice was 0.6 and cold air flow ratio was 0.7.