Search Results (9)

When water is spilled over dams, atmospheric gases can become entrained, resulting in supersaturated water. Total dissolved gas (TDG) > 110% saturation can cause gas bubble trauma (GBT) in fish. The negative effects of GBT include increased buoyancy, decreased swimming performance, and possible mortality. The lower Clark Fork River (LCFR) in Idaho frequently has TDG > 110% saturation due to the spill at Cabinet Gorge Dam as well as from upstream facilities. Spillway crests on Cabinet Gorge Dam were modified to reduce TDG production and the potential harm from GBT. To evaluate the effectiveness of spillway crest modifications, relationships between river discharge and measured TDG were developed pre- and post-modification and used to calculate the predicted TDG in the LCFR pre- and post-modification under two spill season discharge scenarios. The predicted TDG for the scenarios was used with an established TDG-GBT relationship for the LCFR to estimate the expected GBT incidence. Generally, TDG was lower post-modification, and the discharge at which 110% and 120% saturation were exceeded increased by about 198 m³/s. Modification also reduced the number of days with elevated TDG. The lower TDG post-modification resulted in significant (p < 0.05) reductions in the probability of observing GBT. The modification of Cabinet Gorge Dam spillway crests reduced TDG production over a range of discharges and has resulted in improved conditions for fish downstream of the dam. Full article

In this study, a superabsorbent polymer dryer (Polydryer) used to obtain dried medicinal plant materials (Simplicia) was incorporated with a heater to enhance the drying rate. In general, the Polydryer was constructed using a cabinet containing polymer hydrogel (polygel), a gas-fueled heater, and a drying cabinet. A polygel synthesized from acrylic acid and cassava starch was utilized to reduce the moisture content in the drying air prior to entering the heater. The drying performance of the Polydryer with and without heater operation was investigated. The results showed that the drying in the Polydryer with heater operation required 18–26 h to attain a final moisture content of 8.8–10%, significantly faster than the Polydryer without heater employment (95–119 h). In addition, the drying of medicinal plants in the modified Polydryer followed the Page thin-drying model. The Simplicia products also showed a slightly lighter color, with no significant structural differences than those obtained without heat implementation. Overall, this drying machine is a time-effective and energy-efficient system that can be applied in pharmaceutical and agricultural industries on a large scale. Full article

Marine microalgae, diatoms, are considered a source of a wide range of high-value compounds, and numerous studies indicate their biotechnological potential in the food and feed industry, cosmetic industry, nanotechnology, pharmaceutical industry, biodiesel production, fertilizers, and wastewater treatment. The aim of this study was to compare the growth, chemical profiles, and antioxidant activity of the diatom Skeletonema grevillei cultivated in a bioreactor and an incubation-shaking cabinet at different growth phases (after 192 and 312 h). Growth was monitored by evaluating cell density with the Sedgewick Rafter chamber, and the collected biomass was extracted with 70% ethanol assisted by ultrasound. Extracts were evaporated to dryness and compounds were identified in derivatized form by gas chromatography and mass spectrometry (GC-MS) analysis, while antioxidant capacity was evaluated by DPPH and ORAC. Significantly faster growth was observed in the bioreactor than in the incubation-shaking cabinet. Oleamide, palmitelaidic acid, glycerol monostearate, myristic acid, cholesterol, eicosapentaenoic acid, 1-monopalmitin, and 24-methylene cholesterol were identified as the major compounds in both systems. Among them, oleamide was the dominant compound in both systems. It is also shown that prolonging the cultivation period had a direct effect on increasing the extract yield. The highest DPPH inhibition (11.4 ± 1%) and ORAC values (93.3 ± 8.4 mM TE) were obtained for the S. grevillei extract recovered from the bioreactor after 312 h. The obtained results contribute to the possibility of using S. grevillei for various biotechnological applications in the future. Full article

Semiconductor manufacturing is performed through unit processes that use various chemicals and facilities. In particular, flammable gases, such as H₂, NH₃, and CH₄, are used, and there is a risk of explosion when such gases leak. In this study, computational fluid dynamics (CFD) simulation and a “tracer gas test” according to the SEMI (Semiconductor Equipment and Materials International) S6 Environmental, Health, and Safety Guideline for Exhaust Ventilation of Semiconductor Manufacturing Equipment specification were performed during the leakage of hydrogen, a highly flammable gas used in the etching process of a gas box in the semiconductor industry. The CFD simulation was conducted to investigate the safety of semiconductor production facilities in relation to the explosion risk. Flow analysis was performed for the interior of a gas box used in the etching process. A steady-state analysis was performed to predict the concentration range of the explosion limit in the case of continuous hydrogen gas leakage. The interior of the gas box used in the simulation was modeled, and the ventilation flow rate, which has a significant impact on the leakage gas concentration distribution, obtained from experiments was used. The lower flammability limit (LFL) value of the leaked gas was 4% based on H₂, and LFL/4 (25% of the LFL) was analyzed as the explosion limit concentration according to the acceptance criteria of the SEMI S6 tracer gas test. To validate the CFD simulation, a tracer gas test was performed according to SEMI S6. A mixture of hydrogen (5%) and nitrogen (95%) was used as the tracer gas. The flow rate was controlled by a gas regulator valve and measured using an Aalborg mass flow meter. The measured concentration of the tracer gas was calculated using the equivalent release concentration, which was calculated when 100% of the hydrogen was released, and the risk was assessed by comparing it with the LFL/4 of H₂. Full article

In the semiconductor industry, hydrogen is used with many other hazardous and dangerous substances with flammable, toxic, and corrosive properties. In order to safely handle them, convenient-to-use gas cabinets are often required. As known well, hydrogen is highly flammable and explosive, and risk analysis needs to safely use the gas in the cabinets. In this study, overpressure and impact according to various gas cabinet conditions were measured when hydrogen leaks in the gas cabinet, and the effect of overpressure on the protective wall was simulated. For the research, a demonstration experiment was conducted by custom manufacturing a gas cylinder cabinet identical to the standard used in the field, and the protection performance analysis was performed by reverse-engineering it through 3D scanning. As a result of the demonstration experiment, the maximum pressure at the time of hydrogen gas explosion in the gas cylinder cabinet was measured at 0.3 bar. After calculating the detonation pressure propagation profile using the TNT equivalence method, the protective performance of the protective wall was confirmed using AUTODYN. The maximum stress of the concrete and the maximum stress of the reinforcing bar due to the explosion in the gas cylinder cabinet were calculated to be 30.211 MPa and 112.88 MPa, respectively, which do not exceed the tensile strength of concrete and the yield strength of the reinforcing bar. This result is expected to be of great help to the development of the semiconductor industry by suggesting the rationale for mitigating the firewall when changing the semiconductor layout. Full article

An odor sensing system with chemosensitive resistors was used to identify the gases generated from overheated cables to prevent fire. Three different electric cables for a distribution cabinet were used. The cables had an insulation layer made of polyvinyl chloride (PVC) or cross-linked polyethylene (XLPE). The heat resistance of the cables was tested by differential thermal and thermogravimetric analyses. The thermal decomposition products of the cables were investigated by gas chromatography-mass spectrometry (GC-MS). For the odor sensing system, two types of 16-channel array were used to detect the generated gases. One contains high-polarity GC stationary phase materials and the other contains GC stationary phase materials of high to low polarity. The system could distinguish among three cable samples at 270 °C with an accuracy of about 75% through both arrays trained with machine learning. Furthermore, the system could achieve a recall rate of 90% and a precision rate of 70% when the abnormal temperature was set above the cables’ allowable conductor temperature at 130 °C. The odor sensing system could effectively detect the abnormal heating of the cables before the occurrence of fire. Therefore, it is helpful for fire prediction and detection systems in factories and substations. Full article

During an air separation unit shut-down in a methanol production plant, a stop signal was sent to the control cabinet of a synchronous motor for a booster compressor. The control cabinet stopped magnetizing the rotor, while the system logic ensured that the power circuit breakers for the start reactor coils were opened, in order to be ready for the next start-up. Unintentionally, the circuit breaker was still connected (i.e., power was let through the reactors for a prolonged time period), which led to extensive overheating. Subsequently, the central control room received an unaddressed sub-station smoke alarm, and plant operators were sent out to locate the possible source of smoke. The accessible rooms were searched, and traces of smoke were confirmed. The Emergency Response Organization (ERO) was mustered and, through inspection, the Emergency Response Team (ERT) realized that the smoke originated from a ground floor high-voltage room. Fire hoses were arranged for fire extinguishing, and the ERT withdrew to wait for the room to be electrically isolated. About one minute after briefly opening the only set of doors to the high-voltage room, flames were observed, and a quasi-smoke gas explosion violently forced both door blades open and released a substantial fire ball. Personnel had been in the risk zone shortly before the explosion, but luckily no personnel were hit by the slamming door blades or the emerging flames. The incident revealed several learning points related to improper maintenance, ambiguous smoke alarm, lack of flame detectors in the high-voltage room, insufficient risk understanding and training regarding electrically related fire incidents, and the absence of an automatic fire suppression system. In plants processing hydrocarbons, the safety focus regarding hydrocarbon fire and explosion risk is paramount. However, risks related to electrical accidents and compartment fire dynamics (e.g., backdraft and smoke gas explosion) should also be given proper attention. Full article

Structural fumigations using sulfuryl fluoride for the extermination of dry-wood termites are conducted by the thousands in California and other warm-weather states. Sulfuryl fluoride is an odorless gas that targets the nervous system and can cause respiratory irritation, pulmonary edema, nausea, vomiting, seizures, and death. Structural voids or compartments such as wall sockets, crawl spaces, cabinets, or cells in air mattresses may create ongoing exposure after a structure has been certified as safe. The authors describe a case of potential sulfuryl fluoride exposure to a family following home fumigation. Despite regulation, sulfuryl fluoride poisonings from structural fumigations continue to occur. This article examines the physical characteristics of sulfuryl fluoride and the regulatory oversight of its application, in an effort to understand how and why these poisonings happen. Increasing aeration times of fumigated structures, overseeing monitoring efficacy, and using technology to capture clearance data could reduce sulfuryl fluoride exposure and illness. Full article

Recent interest in greenhouse gas emissions from ruminants, such as cattle, has spawned a need for affordable, precise, and accurate methods for the measurement of gaseous emissions arising from enteric fermentation. A new head hood system for cattle designed to capture and quantify emissions was recently developed at the University of California, Davis. The system consists of two head hoods, two vacuum pumps, and an instrumentation cabinet housing the required data collection equipment. This system has the capability of measuring carbon dioxide, methane, ethanol, methanol, water vapor, nitrous oxide, acetic acid emissions and oxygen consumption in real-time. A unique aspect of the hoods is the front, back, and sides are made of clear polycarbonate sheeting allowing the cattle a full range of vision during gas sampling. Recovery rates for these slightly negative pressure chambers were measured ranging from 97.6 to 99.3 percent. This system can capture high quality data for use in improving emission inventories and evaluating gaseous emission mitigation strategies. Full article