• Journal of the Korea Society of Computer and Information
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• v.21 no.4
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• pp.1-8
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• 2016

In small embedded systems including IoT devices, memory size is very small and it is important to reduce memory amount for execution of application programs. For multi-threaded applications, stack may consume a large amount of memory because each thread has its own stack of sufficiently large size for worst case. This paper presents an implementation of single stack multi-threading, called SSThread (Single Stack Thread), by sharing a stack for all threads to reduce stack memory size. By using SSThread, multi-threaded applications can be programmed based on normal C language environment and there is no requirement of transporting multi-threading operating systems. It consists of several library functions and various C macro definitions. Even though some functional restrictions in comparison to operating systems supporting complete multi-thread functionalities, it is very useful for small embedded systems with tiny memory size and it is simple to setup programming environment for multi-thread applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.1
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• pp.77-82
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• 2003

The ac loss is an important issue in the design of high-Tc superconducting power devices such as transformers and cables. In these devices many Bi-2223 tapes are closely stacked together and exposed to alternating magnetic fields that can have different orientations with respect to a tape. In such arrangement the magnetization loss is influenced by the screening current induced in adjacent tapes and thus different from that in a single tape. This stacking effect was experimentally investigated by measuring the magnetization loss in a stack, which consists of a number of tapes. First the magnetization loss in the single tape was measured in order to confirm the reliability of the loss data measured in the stack. The results for the single tape coincide well will the loss characteristics described in other previous works. For the stack In parallel and longitudinal magnetic fields the measured loss is Independent of both the number of tapes and stacking type. The longitudinal magnetization loss Is well explained rather by the slab model for decoupled filaments. For the tall stack in perpendicular field the measured loss at low fields is greatly decreased, compared to the loss of the single tape. However the loss at high fields is unaffected. These loss behaviors in the tall stack are well described by the slab model for full coupling.

• Journal of the Korean Ceramic Society
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• v.44 no.12
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• pp.720-726
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• 2007

Current collectors of SOFC play a significant role on the performance of power generation. In this study a single cell stacked SOFC was assembled using Ag-mesh as a cathode current collector, and evaluated its performance. No gas leakages of the single cell stack occurred in the tests of gas detection and OCV measurement. The OCV and initial power of the stack were 1.09V and $0.45W/cm^2$, respectively, under the flow rates of air at 2,500 cc/min and $H_2$ at 1,000 cc/min at the test temperature of $750^{\circ}C$. A degradation rate of 44.0% was measured during the prolonged time of 307 h. The relatively low durability of the tested single cell stack was found to be the evaporation of Ag-mesh at the current corrector.

• Journal of Sensor Science and Technology
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• v.30 no.3
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• pp.148-153
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• 2021

During the manufacture of a ZnS lens with excellent transmittance in the mid-infrared region (3-5 ㎛) by the hot-press process, a single-layer sintering method is used in which one lens is manufactured in one process. Additional research is required to improve this single-layer sintering method because of its low manufacturing efficiency. To solve this problem, the variation in optical properties of ZnS lenses with change in sintering temperature was investigated by introducing a Stack sintering method that can sinter multiple lenses simultaneously. A carbon paper was placed between the molded lenses and sintered into five layers. The average permeability of 67% at medium infrared wavelengths of 3-5 ㎛ was excellent under the following sintering conditions: pressure of 50 MPa and temperature of 850℃. This value is 1% less than the average permeability in the case of single-layer sintering of the ZnS lens. It was confirmed that the stack sintering method developed in this study can be used to manufacture a large number of lenses with excellent characteristics in a single process.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.5
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• pp.47-53
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• 2013

The wide application of disc springs to the designing of mechanical products with space limit is mainly attributable to their property of sustaining large axial load with small displacement. Due to the impediments in expecting the final results caused by the significant differences existing between a single unit and a stacked form, the force-displacement characteristics of a single disc spring and stacked disc springs are mainly examined in this study. In particular, the hysteresis of the series stack and the parallel stack will be investigated through the FE analysis and the analytical results will finally be compared with the acquired experimental data. In the final result, the analytical results were in accordance with the experimental data.

• Fire Science and Engineering
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• v.23 no.5
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• pp.143-152
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• 2009

The numerical analyses for each single simplified shaft with three type openings were carried out by using computational fluid dynamics model for the calculation of the pressure difference and the location of the neutral plane and the visualization of stack effect. As the height of shaft heighten, the pressure difference of stack effect is much deviated against the theoretical value. For the Type A models shorter than 30 m height of shaft and the Type B models longer than 30m, the simulation results for the location of the neutral plane are well agreed to the theoretical values with 5% less deviations just after the beginning of simulation (t = 10s). For the Type B models longer than 30m with multiple openings, therefore, it is possible to calculate the location of the neutral plane by using a CFD model. The phenomenon of the air flow of stack effect can be easily understood with the visualization of stack effect.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.1
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• pp.53-59
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• 2008

In spite of increasing complexity of wireless sensor network applications, most of the sensor node platforms still have severe resource constraints. Especially a small amount of memory and absence of a memory management unit (MMU) cause many problems in managing application thread stacks. Hence, a shared-stack was proposed, which allows several threads to share one single stack for minimizing the amount of memory wasted by fixed-size stacks. In this paper, we present the memory usage models for thread stacks by deriving the overflow probability of the fixed-size stack and the shared-stack and also show that the shared-stack is more reliable than the fixed-size stack.

• Archives of Metallurgy and Materials
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• v.64 no.2
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• pp.513-518
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• 2019

Recently, attempts have been made to use porous metal as catalysts in a reactor for the hydrogen manufacturing process using steam methane reforming (SMR). This study manufactured Ni-Cr-Al based powder porous metal, stacked cubic form porous blocks, and investigated high temperature random stack creep property. To establish an environment similar to the actual situation, a random stack jig with a 1-inch diameter and height of 75 mm was used. The porous metal used for this study had an average pore size of ~1161 ㎛ by rolling direction. The relative density of the powder porous metal was measured as 6.72%. A compression test performed at 1073K identified that the powder porous metal had high temperature (800℃) compressive strength of 0.76 MPa. A 800℃ random stack creep test at 0.38 MPa measured a steady-state creep rate of 8.58×10^-10 s^-1, confirming outstanding high temperature creep properties. Compared to a single cubic powder porous metal with an identical stress ratio, this is a 1,000-times lower (better) steady-state creep rate. Based on the findings above, the reason of difference in creep properties between a single creep test and random stack creep test was discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.5
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• pp.396-401
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• 2000

In order to accurately measure the high voltage of 22.9[kV] power distribution lines we investigated the temperature dependence of measuring voltage on the number of stack layers in the voltage measurement system made from single and stack voltage divider capacitors (22, 44, 66 layers, respectively). Temperature coefficient of dielectric constant(TC$\varepsilon_{{\gamma}}$/)of voltage divider capacitors which were fabricated by BaTi $O_3$system ceramics showed the variations from -2.28% to +1.69% in the range of -25[$^{\circ}C$] ~50[$^{\circ}C$]) was decreased with increasing of stack number and the stack element of 66 layers showed the least error of $\pm$0.87%or of $\pm$0.87%.

• Journal of Hydrogen and New Energy
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• v.14 no.3
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• pp.229-235
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• 2003

A 50W class MCFC stack was operated in order to test a new design of the circular shaped separator. in the new design, the anode gas was supplied into the stack and was exhausted out of the stack after the anode reaction. The exhausted gas was reacted with the cathode gas supplied with excess oxygen in the vessel in which the stack was placed. Then the reacted gas flowed into the cathode side of the stack and was exhausted through the outlet located in the center of the stack. The average voltage of the single cells in the stack was 0.835V under the current density of $150mA/cm^2$, initially, and the degradation rate of the stack voltage was 1.7%/1,000h. High stack voltage with good stability of the present stack was due to the small temperature gradient in the stack. The small temperature gradient as well as the easiness of temperature control was the result of the new configuration of the separator which utilized the heat of the combustion reaction between anode outlet gas and the cathode inlet gas for heating the stack.