A Cloud-Based Wireless Radio Intensity Recording System

Wireless Personal Communications - In recent years, many wireless communication services have become indispensable for our daily life, such as voice telephoning and the internet surfing. However,...     

Simulation of solid thermal explosion and liquid thermal explosion of dicumyl peroxide using calorimetric technique

Dicumyl peroxide (DCPO), is produced by cumene hydroperoxide (CHP) process, is utilized as an initiator for polymerization, a prevailing source of free radicals, a hardener, and a linking agent. DCPO has caused several thermal explosion and runaway reaction accidents in reaction and storage zone in Taiwan because of its unstable reactive property. Differential scanning calorimetry (DSC) was used to determine thermokinetic parameters including 700 J g^–1 of heat of decomposition (ΔH_d), 110 °C of exothermic onset temperature (T₀), 130 kJ mol^–1 of activation energy (E_a), etc., and to analyze the runaway behavior of DCPO in a reaction and storage zone. To evaluate thermal explosion of DCPO with storage equipment, solid thermal explosion (STE) and liquid thermal explosion (LTE) of thermal safety software (TSS) were applied to simulate storage tank under various environmental temperatures (T_e). T_e exceeding the T₀ of DCPO can be discovered as a liquid thermal explosion situation. DCPO was stored under room temperature without sunshine and was prohibited exceeding 67 °C of self-accelerating decomposition temperature (SADT) for a tank (radius = 1 m and height = 2 m). SADT of DCPO in a box (width, length and height = 1 m, respectively) was determined to be 60 °C. The TSS was employed to simulate the fundamental thermal explosion behavior in a large tank or a drum. Results from curve fitting demonstrated that, even at the earlier stage of the reaction in the experiments, ambient temperature could elicit exothermic reactions of DCPO. To curtail the extent of the risk, relevant hazard information is quite significant and must be provided in the manufacturing process.     

Inhibitory effects of three chemical dust suppressants on nitrocellulose dust cloud explosion

Three types of self-prepared chemical dust suppressants (CDSs) were investigated for their inhibitory effects on nitrocellulose (NC) cloud dust explosion. The results revealed that NC is extremely sensitive to electric sparks and has a high explosion intensity. CaCl₂-CDS effectively increased the particle size to control fly dust substantially inhibiting dust cloud explosions. However, both Na₂SO₄-CDS and MgCl₂-CDS exhibited poor abilities and even promoted explosion. Therefore, neither Na₂SO₄-CDS nor MgCl₂-CDS is recommended as a CDS for NC. Inappropriately using CDSs may engender severe explosions. Furthermore, a mechanism underlying NC dust cloud combustion and explosion was proposed. NC has three stages of heat release: autoxidation, thermal decomposition, and combustion. Thermal decomposition, combustion, and explosion were triggered depending on the energy provided from autoxidation. CaCl₂-CDS inhibited only combustion. This study reveals the mechanism underlying NC dust cloud explosions and provides useful information for the development of more optimized CDSs.     

Compression Artifacts in Perceptual Audio Coding

Perceptual audio coding achieves a high compression ratio by exploiting the perceptual irrelevance and data redundancies. By using advanced and sophisticated signal processing methods, perceptual coding has generated artifacts that are quite different from the traditional distortions. A new audio technology becomes mature through the successful modeling, measuring, and control on the artifacts incurred from the technology. With the advance of new coding modules in advanced audio coding (AAC), spectral band replication (SBR), and parametric coding, the incurred artifacts are far more difficult to model, measure, and control than those caused by previous encoding systems like pulse code modulation. This paper models the audible artifacts through the time-frequency diagrams, considers the artifacts-susceptible music types, and analyzes the critical encoding technologies incurring these artifacts.     

Bondability Study of Chip-on-Film (COF) Inner Lead Bonding (ILB) Using Conventional Gang Bonder

Inner lead bonding (ILB) is used to thermomechanically join the Cu inner leads on a flexible film tape and Au bumps on a driver IC chip to form electrical paths. With the newly developed film carrier assembly technology, called chip on film (COF), the bumps are prepared separately on a film tape substrate and bonded on the finger lead ends beforehand; therefore, the assembly of IC chips can be made much simpler and cheaper. In this paper, three kinds of COF samples, namely forming, wrinkle, and flat samples, were prepared using conventional gang bonder. The peeling test was used to examine the bondability of ILB in terms of the adhesion strength between the inner leads and the bumps. According to the peeling test results, flat samples have competent strength, less variation, and better appearance than when using flip-chip bonder.     

Effects of oxygen concentration on the macroscopic characteristic indexes of high-temperature oxidation of coal

To explore the macroscopic characteristic indexes for oxidation of coal under high-temperature conditions, an XKGW-1-type high-temperature-programmed heating experimental system was constructed. Tests on high-temperature oxidation of coal under high-temperature conditions at five oxygen concentrations of 21, 17, 13, 8, and 3 vol% were independently conducted. Laws of variation in high-temperature oxidation of coal indices, such as the coal temperature, gas ratios, rate of oxygen consumption, and exothermic strength from indoor temperature to 500 °C, were investigated at those oxygen concentrations. The results showed that the variation tendencies of characteristic indices for high-temperature oxidation of coal at different oxygen concentrations were extremely intricate. At the five oxygen concentrations, the rate of oxygen consumption increased rapidly with an increase in coal temperature and eventually remained at a higher range. The rate of oxygen consumption increased with temperature with an approximate exponential trend at the five oxygen concentrations tested. For the same coal temperature, the rate of oxygen consumption decreased with the oxygen concentration. The variation tendencies of the CO and CO₂ production rates were similar, both increased rapidly with an increase in coal temperature in the early stages and reached a maximum at a coal temperature of 380 °C. They decreased slightly with an increase in coal temperature at first and increased promptly thereafter. The concentrations of CH₄, C₂H₄, and C₂H₆ first increased with an increase in the coal temperature and markedly decreased after the maximal value. The temperatures for the extreme points were 480, 410, and 420 °C for CH₄, C₂H₄, and C₂H₆, respectively. The trends of the macroscopic characteristic indexes throughout the process of high-temperature oxidation of coal in a certain temperature range at various oxygen concentrations can be used for temperature prediction and fire prevention during coal mining.     

Calorimetric studies on the thermal hazard of methyl ethyl ketone peroxide with incompatible substances

In Taiwan, Japan, and China, methyl ethyl ketone peroxide (MEKPO) has caused many severe thermal explosions owing to its thermal instability and reactivity originating from the complexity of its structure. This study focused on the incompatible features of MEKPO as detected by calorimetry. The thermal decomposition and runaway behaviors of MEKPO with about 10wt.% incompatibilities, such as H(2)SO(4), HCl, NaOH, KOH, FeCl(3), and FeSO(4), were analyzed by dynamic calorimeter, differential scanning calorimetry (DSC) and adiabatic calorimeter, vent sizing package 2 (VSP2). Thermokinetic data, such as onset temperature, heat of decomposition, adiabatic temperature rise, and self-heat rate, were obtained and assessed. Experimental data were used for determining the incompatibility rating on hazards. From the thermal curves of MEKPO with assumed incompatible substances detected by DSC, all the onset temperatures in the other tests occurring earlier advanced, especially with alkaline or ferric materials. In some tests, significant incompatible reactions were found. Adiabatic runaway behaviors for simulating the worst case scenario were performed by using VSP2. These calorimetric data led to the same results that the alkaline or ferric solution was the most incompatible with MEKPO.     

Study of thermal decomposition of methyl ethyl ketone peroxide using DSC and simulation

Methyl ethyl ketone peroxide (MEKPO) is a typical organic peroxide with thermally unstable nature that has been broadly employed in the manufacturing process of acrylic resins, as a hardening agent for fiberglass-reinforced plastics, and as a curing agent for unsaturated polyester resins. The aim of this study was to identify the characteristics of MEKPO 31 wt.% while mixing with contaminants, such as H(2)SO(4), HCl, and NaCl under runaway conditions. To acquire the thermal runaway data, DSC and a simulation were used for thermal analysis. The results showed that the thermal decomposition of MEKPO and MEKPO+H(2)SO(4) follows two stages. The first one can be modeled by using an empirical nth order rate equation. The second stage can be modeled as autocatalytic. MEKPO+HCl and MEKPO+NaCl included two independent autocatalytic reactions. The decomposition of MEKPO in the presence of Cl- ions (added in MEKPO either in the form of HCl or NaCl) follows a significantly different path, an earlier decomposition "onset" temperature, higher amount of generated thermal power and smaller temperature of no return (T(NR)) and time to maximum rate (TMR) values. Simulations based on experimental data indicated that the effect of H(2)SO(4) was the most dangerous contaminant on MEKPO 31 wt.%. However, the impact of Cl ions was also important. It is therefore recommended that the means of fire fighting employed for this substance to be free of Cl-.     

Constructing an anticipation formula for fire loss in factory-type

The before fire assessment data from the ARC fire risk assessment system and the financial loss from post-fire damage report for factory-type buildings located in Taiwan were collected. The correlation between assessment data and degree of fire loss (DFL) was calculated by three regression analyses – linear, power, and exponential equations – to produce an anticipation formula. The results revealed that there is more a believable prediction when the fire loss is bigger, regardless of the amount of fire loss or the DFL, while the latter is more related to the assessment grade. By providing proprietors and insurance companies detailed fire risk analysis showing predictable financial loss, it is advantageous for budget management and fire protection, enforcement and should result in the reduction of fire risk and subsequent damage to factory-type buildings.