• Computers and Concrete
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• v.19 no.5
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• pp.509-514
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• 2017

Concrete retaining walls are the most common types of geotechnical structures for controlling instable slopes resulting from lateral pressure. In analytical stability, calculation of the concrete retaining walls is regarded as a rigid mass when its safety is required. When cracks in these structures are created, the stability may be enforced and causes to defeat. Therefore, identification, creation and propagation of cracks are among the important steps in control of lacks and stabilization. Using the numerical methods for simulation of crack propagation in concrete retaining walls bodies are among the new aspects of geotechnical analysis. Among the considered analytical methods in geotechnical appraisal, the boundary element method (BEM) for simulation of crack propagation in concrete retaining walls is very convenient. Considered concrete retaining wall of this paper is Pars Power Plant structured in south side in Assalouyeh, SW of Iran. This wall's type is RW6 with 11 m height and 440 m length and endurance of refinery construction lateral forces. To evaluate displacement and stress distributions (${\sigma}_{1,max}/{\sigma}_{3,min}$), the surrounding, especially in tip and its opening crack BEM, is considered an appropriate method. By considering the result of this study, with accurate simulation of crack propagation, it is possible to determine the final status of progressive failure in concrete retaining walls and anticipate the suitable stabilization method.

• Journal of KIISE:Software and Applications
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• v.33 no.11
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• pp.923-935
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• 2006

As the knowledge-based society has been constructed, the size of work process that has to be done grows bigger and the amount of the information that has to be analyzed increases. So each company is trying to construct more conformable process models in business model. In order to support the process construction of companies practically, in this paper tools of Six Sigma is applied to process definition and tools of PSP is applied schedule management. And to use the proposed tools efficiently, the procedure of process definition and schedule management are suggested. The goal of the proposed method is to achieve the process aim within the Time-To-Market by applying the process management of organizations and persons. And the goal of individuals is to improve personal process with the collected data.

• Journal of the Korean Chemical Society
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• v.31 no.3
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• pp.258-270
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• 1987

A series of new thorium nitrate complexes with crown ethers have been synthesized from the reaction of the hydrated thorium nitrate, with the appropriate crown ethers of different cavity sizes in various solvents such as methanol, ethanol, butanol, methylacetate, acetone, tetrahydrofuran and acetylacetone. CHN elemental analysis, ICPAS, thermal analysis and Karl-Fischer method have been used to characterize their compositions, and the spectroscopic methods of IR, UV, $^1H-NMR$, and X-ray diffraction have been employed to determine the structures and solvolysis phenomena of these complexes. and the electrical conductances were measured in DMSO, and water solvent. The solvolysis have been observed only in the complexes synthesized in acetylacetone solvent. In the solvated complexes of 15-crown-5 and 18-crown-6, the mole ratio of $Th^{4+}$: ligand : acetylacetone is found to be 1:1:1, but in the non-solvated complexes of 12-crown-4 and 15-crown-5, the mole ratios of Th:L are 1:2 and 2:3, respectively, and that in the complexes of both 18-crown-6 and dicyclohexano-18-crown-6 is 1:1. All complexes which were not solvated have shown $n{\to}{\sigma}^{\ast}$ electronic transitions of crown ether whereas complexes solvated have exhibited both $n{\to}{\sigma}^{\ast}$ of crown ether and $n{\to}{\pi}^{\ast}$ transitions of acac. The dissociation mole ratio of $Th^{4+}$ and nitrate ion is found to be 1:1 in aprotic solvent, and 1:4 in protic solvent like water.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.6
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• pp.39-47
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• 1998

A fourth-order $\Sigma$-$\Delta$ modulator is designed and implemented in 0.6 $\mu\textrm{m}$ CMOS technology. The modulator is verified by introducing nonlinear factors such as DC gain and slew rate in system model that determines the transfer function in S-domain and in time-domain. Dynamic range is more than 110 dB and the peak SM is 102.6 dB at a clock rate of 2.8224 MHz for voiceband signal. The structure of a ∑-$\Delta$ modulator is a modified fourth-order ∑-$\Delta$ modulator using direct feedback loop method, which improves performance and consumes less power. The transmission zero for noise is located in the first-second integrator loop, which reduces entire size of capacitors, reduces the active area of the chip, improves the performance, and reduces power dissipation. The system is stable because the output variation with respect to unit time is small compared with that of the third integrator. It is easy to implement because the size of the capacitor in the first integrator, and the size of the third integrator is small because we use the noise reduction technique. This paper represents a new design method by modeling that conceptually decides transfer function in S-domain and in Z-domain, determines the cutoff frequency of signal, maximizes signal power in each integrator, and decides optimal transmission-zero frequency for noise. The active area of the prototype chip is 5.25$\textrm{mm}^2$, and it dissipates 10 mW of power from a 5V supply.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.11a
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• pp.89-98
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• 2001

Pb-free wave soldering process of AC Adapter was implemented by six sigma method using Sn-Cu-Ni type solder. The solder joint appearance, microstructural change, a lift-off phenomenon and reliability were evaluated through thermal shock teal. $(Cu,Ni)_6Sn_5$-type intermetallic compound of which thickness is about 5 micron was found at solder joint between Sn-Cu-Ni solder and copper land. After applying the thermal shock test of as-soldered product up to 750 cycles, no crack was found at the solder joint and the newly developed product was superior to conventions; one in terms of productivity and reliability.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.5
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• pp.808-815
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• 1990

This paper treats with the design method for the single loop oversampled Sigma-Delta A/D converter with one delay and the digital integrator. Such an integrator was kgenerated by means of the bilinear transform of the analog integrator. The frequency spectrums of the quantizer and the decimator output signal are evaluated by FFT respectively. With the performance evaluation system, the values of SNR are obtained versus the input sinusoidal signal amplitude, frequency, the oversampling ratio, the DC-input level, the loop gain and the limitting value of the integrator. As compared with existing results, values of SNR versus the input signal amplitude and the oversampling ratio for the suggested system are about 6dB higher then previously reported results respectively. Furthermore, this approach achieves an about 60dB input dynamic range.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.513-519
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• 1988

Constant load creep tests have been carried out over a range of stresses at high temperatures. The experimental equations of the steady-state creep rate and creep-rupture life were respectively found to be related to the normalized applied-stress and temperature as ln.epsilon.$_{s}$ =6.10 on.sigma./ $E_{T}$-12.81*10$^{3}$ 1/T+15.98 (h $r^{-1}$) ln $t_{R}$=-6.24ln.sigma./ $E_{T}$+15.08*10$^{3}$1/T-23.66 (hr) and the equation of creep-rupture life had a good agreement with the expression of the Minimum-Commitment Method (MCM). However, the relationship between the steady-state creep rate and the creep-rupture life, noted by Monkman and Grant, lnt/snb R/ = mln.epsilon.$_{S}$+b made a considerable deviation against the present creep-rupture data. It is believed that this problem is to be discussed and investigated continually.lly.lly..

• Geomechanics and Engineering
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• v.11 no.6
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• pp.739-756
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• 2016

The shear strength reduction finite element method (SSRFEM) is a powerful tool for slope stability analysis. The factor of safety (FOS) of the slope can be easily calculated only through reducing effective cohesion (c′) and tangent of effective friction angle ($tan{\varphi}^{\prime}$) in equal proportion. However, this method may not be applicable to soil slope under wetting-drying cycles (WDCs), because the influence of WDCs on c′ and $tan{\varphi}^{\prime}$ may be different. To research the method of estimating FOS of soil slopes under WDCs, this paper presents an experimental study firstly to investigate the effects of WDCs on the parameters of shear strength and stiffness. Twelve silty clay samples were subjected to different number of WDCs and then tested with triaxial test equipment. The test results show that WDCs have a degradation effect on shear strength (${\sigma}_1-{\sigma}_3)_f$, secant modulus of elasticity ($E_s$) and c′ while little influence on ${\varphi}^{\prime}$. Hence, conventional SSRFEM which reduces c′ and $tan{\varphi}^{\prime}$ in equal proportion cannot be adopted to compute the FOS of slope under conditions of WDCs. The SSRFEM should be modified. In detail, c′ is merely reduced among shear strength parameters, and elasticity modulus is reduced correspondingly. Besides, a new approach based on sudden substantial changes in the displacement of marked nodes is proposed to identify the slope failure in SSRFEM. Finally, the modified SSRFEM is applied to compute the FOS of a slope example.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.4
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• pp.425-435
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• 2016

This paper describes a spread-spectrum clock generation method by utilizing a ${\Delta}{\Sigma}$ digital PLL (DPLL) which is solely based on binary phase detection and does not require a linear time-to-digital converter (TDC) or other linear digital-to-time converter (DTC) circuitry. A 1-bit high-order ${\Delta}{\Sigma}$ modulator and a hybrid finite-impulse response (FIR) filter are employed to mitigate the phase-folding problem caused by the nonlinearity of the bang-bang phase detector (BBPD). The ${\Delta}{\Sigma}$ DPLL employs a two-point modulation technique to further enhance linearity at the turning point of a triangular modulation profile. We also show that the two-point modulation is useful for the BBPLL to improve the spread-spectrum performance by suppressing the frequency deviation at the input of the BBPD, thus reducing the peak phase deviation. Based on the proposed architecture, a 3.2 GHz spread-spectrum clock generator (SSCG) is implemented in 65 nm CMOS. Experimental results show that the proposed SSCG achieves peak power reductions of 18.5 dB and 11 dB with 10 kHz and 100 kHz resolution bandwidths respectively, consuming 6.34 mW from a 1 V supply.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.169-176
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• 2009

This paper introduces 60 apply method at a railroad vehicle including basic technique of the 60. Basically rolling stock maintenance cost is high and life cycle is long. Therefore, the maintenance efficiency is the most important. Usually the length of the rolling stock life cycle is over 20years, the method of maintenance technique must be reformed periodically. So the key point of a inspection efficiency is to update the maintenance method regularly. The early days 60 method began from the thing to reduce a productions era. But after the year 2000, it took the place to the management reform technique of all business field. Finally optimal rolling stock maintenance method is introduced through the example.