The Effect of Aluminum Ions on the DC Etching of Aluminum Foil

A study has been made of the electrochemical etching of 99.99% aluminum foils at a current density of 50 mA cm^–2in AlCl₃–HCl solutions (1 m Cl^–) at 80 °C. The solutions were made by dissolving metallic aluminum into 1m HCl solution, to give a Cl^– concentration of 1 m. The number density of etch tunnels and the homogeneity of tunnel length decreased, and the mean pit size and its standard deviation increased with increasing Al³⁺ concentration. The results were discussed based on potential transients at a current density of 50 mA cm^–2, current–potential curves at a scan rate of 10 m Vs^–1 and electrochemical impedance spectra.     

Air conditioner operation behaviour based on students' skin temperature in a classroom

A total of 25 college students participated in a study to determine when they would use an air conditioner during a lecture in a university classroom. The ambient temperature and relative humidity were measured 75 cm above the floor every minute. Skin temperatures were measured every minute at seven points, according to the recommendation of Hardy and Dubois. The average clothing insulation value (CLO) of subjects was 0.53 ± 0.07 CLO. The mean air velocity in the classroom was 0.13 ± 0.028 m/s. When the subjects turned the air conditioner both on and off, the average ambient temperatures, relative humidity and mean skin temperatures were 27.4 and 23.7 °C (p = 0.000), 40.9 and 40.0% (p = 0.528) and 32.7 and 32.2 °C (p = 0.024), respectively. When the status of the air conditioner was changed, the differences of skin temperatures in core body parts (head, abdomen and thigh) were not statistically significant. However, in the extremities (mid-lower arm, hand, shin and instep), the differences were statistically significant. Subjects preferred a fluctuating environment to a constant temperature condition. We found that a changing environment does not affect classroom study.     

Self-discharge mechanism of vanadium-titanium metal hydride electrodesfor Ni-MH rechargeable battery

In order to investigate the effect of the equilibrium hydrogen pressure (plateau pressure) of metal hydride (MH) alloys on self-discharge behavior, V₀₉Ti₀₁ alloys having multi-plateau pressures (the low and high plateau pressure) have been used as working electrodes in a half cell. A thermal desorption experiment and open-circuit potential monitoring were conducted to observe the self-discharge behavior of the electrodes. From the thermal desorption spectra of fully charged and discharged V₀₉Ti₀₁ electrodes (to-0.7 V vs. Hg/ HgO), it was found that only the high plateau pressure region from V₀₉Ti₀₁ electrodes is electrochemically useful in battery application. However, the open-circuit potential change and thermal desorption spectra of V₀₉Ti₀₁ electrodes after various open-circuit storage periods prove that self-discharge behavior is caused by hydrogen desorption from the low plateau pressure region (10^-8 atm) as well as the high plateau pressure region (0.1 atm). Therefore, it is suggested that the self-discharge behavior of V₀₉Ti₀₁ electrodes cannot be suppressed effectively by reduction of the plateau pressure of alloys through alloy modification.In addition, the pressure-composition-isotherms (P-C-T) of the low pressure region can be estimated by using the open-circuit potential corresponding to this region in Nernst’s equation.     

Characteristics of pressure distribution and solution to the problems caused by stack effect in high-rise residential buildings

This paper shows the characteristics of pressure distribution caused by stack effect in high-rise residential buildings and proposes solutions for stack effect problems during the cold season. First, field measurements were conducted in two high-rise residential buildings in Korea to understand the characteristics of pressure difference and problems due to stack effect. Next, several high-rise residential buildings were simulated to confirm these characteristics and problems. From the field measurements and simulation results, the Thermal Draft Coefficients varied from 0.20 to 0.49. These values meant that most of the stack pressure difference in high-rise residential buildings acted on interior partitions rather than on exterior walls, so that serious problems due to large pressure differentials can occur on the inside of the building. The separation method which includes installing ‘air-lock doors’ between the elevator core area and residential area, is proposed to solve the pressure difference problems.     

Proportional Fair Scheduling with Capacity Estimation for Wireless Multihop Networks

In this paper, we investigate the scheduling problem to achieve the proportional fairness among the flows in wireless multihop networks with time-varying channel capacity. Using the signal to interference noise ratio and the outage probability, we present an estimate of time-varying capacity. Then, we achieve the proportional fairness in terms of maximizing the network utility function with consideration of fast fading without measurement of channel state information. Finally, we show that the proposed scheme results in better performance compared to the existing schemes through the simulation results.     

Creep-fatigue design studies for a sodium-cooled fast reactor with tube sheet-to-shell structure subjected to elevated temperature service

In this paper, creep-fatigue damage under elevated temperatures is investigated for a tube sheet-to-shell structure, which is one of the main structures under Gen-IV class 1 components. To do this, detailed step-by-step procedures, including the elastic structural analysis and the ASME-NH code application, are described for a defined representative load cycle. From the sensitivity studies for various design parameters, such as hold time duration, shell thickness, and operating temperature, it is found that a reduction of thickness can decrease the thermal bending stresses, but the negative effect is that it may increase the primary stress and enhance the creep damage. The normal operating temperature is the most significant parameter in the creep-fatigue design.     

Simple multiresidue extraction method for the determination of fungicides and plant growth regulator in bean sprouts using low temperature partitioning and tandem mass spectrometry

A simple multiresidue analytical method is developed for the simultaneous determination of carbendazim (CB), thiabendazole (TB), and 6-benzyl aminopurine (6-BA) in bean sprouts. The samples were extracted with acetonitrile followed by partitioning at ?80 °C for 5–10 min. A YMC C₈ column was used to separate the analytes before being qualitatively and quantitatively determined by liquid chromatography–electrospray ionization tandem mass spectrometry (LC–ESI-MS/MS) in positive ion mode using multiple reaction monitoring (MRM). The matrix-matched calibration curves showed good linearity in the range 0.01–1.0 mg/kg with correlation coefficients in excess of 0.998. The mean recoveries were in the range of 80.4–96.3% at 0.1 and 0.5 spiked levels, and the relative standard deviations (RSDs) were in the range of 0.5–7.6%. The limits of quantifications (LOQ) were in the range of 0.005–0.01 mg/kg. The method was successfully applied to 90 samples (among which 45 were organic) collected from a commercial bean sprout production house throughout the city. Except for 6-BA, the rest of the analytes had values lower than their LOQs. In sum, carbendazim, thiabendazole, and 6-BA were extracted in a single step, and no steps for clean-up or concentration of the extracts were needed. The current method can be used for sensitive and accurate determination and confirmation of residues in bean sprout samples.     

High temperature structural integrity evaluation method and application studies by ASME-NH for the next generation reactor design

The main purpose of this paper is to establish the high temperature structural integrity evaluating procedures for the next generation reactors, which are to be operated at over 500°C and for 60 years. To do this, comparison studies of the high temperature structural design codes and assessment procedures such as the ASME-NH (USA), RCC-MR (France), DDS (Japan), and R5 (UK) are carried out in view of the accumulated inelastic strain and the creep-fatigue damage evaluations. Also the application procedures of the ASME-NH rules with the actual thermal and structural analysis results are described in detail. To overcome the complexity and the engineering costs arising from a real application of the ASME-NH rules by hand, all the procedures established in this study such as the time-dependent primary stress limits, total accumulated creep ratcheting strain limits, and the creep-fatigue damage limits are computerized and implemented into the SIE ASME-NH program. Using this program, the selected high temperature structures subjected to two cycle types are evaluated and the parametric studies for the effects of the time step size, primary load, number of cycles, normal temperature for the creep damage evaluations and the effects of the load history on the creep ratcheting strain calculations are investigated.     

HELIOS: Solar rights analysis system for apartment buildings

In Korea, the development of high-rise apartment buildings has brought about residential environment problems such as violation of solar rights. The number of civil petitions and disputes over solar rights has increased recently. Solar rights are demanded when buildings are restricted to solar access by adjacent buildings. In other words, the geometrical characteristics of new buildings influence the solar access of adjacent buildings. This problem has negatively affected human health, work productivity, thermal comfort, and visual comfort-Comment. As a measure, the Korean building code on solar rights was enacted to protect the rights of residents to solar access. As a result, a solar rights analysis system was developed to evaluate the solar rights in apartment buildings, quantitatively. Therefore, the main objectives of this study are to standardize the solar rights analysis process and data structure, and develop a solar rights analysis system (HELIOS). To this end, the definition of ‘solar right’ is examined by studying the various relevant literatures, and solar rights assessment methods are investigated to apply to the solar rights analysis system. The geometrical characteristics of apartment buildings are observed, and the geometric elements are extracted to create the data structure. Then the hierarchy and the relationships between these geometric elements are systematically clarified. Data structure for solar rights analysis system using XML is designed, HELIOS is developed by system integration of data structure, and analysis algorithms are developed according to the assessment processes and verified by field measurements.