Liquid Nitrogen Gas Research Articles

Crack opening behavior of penetrated crack under fatigue load

The leak-before-break (LBB) behaviors of a structural component under high and low fatigue loads are an important problem in nuclear power plants, liquid nitrogen gas tankers and chemical plants. This paper is an experimental study to evaluate the crack opening behavior after penetration for plate and pipe specimens. Crack opening displacement after penetration under low fatigue load could be satisfactorily determined at the center of the plate thickness regardless of the specimen size. In the case of high fatigue load, it is shown that the crack opening displacement at the center of a penetrated crack can be derived using the gross stress,σ C , and the front surface crack length, a s , together with the back surface crack length, a b .

Experimental Evaluation on the Thermal Stress Due to Ice Plugging of Tubes in Nuclear Power Plant

Ice-plugging of tube in nuclear power plant has been widely used for the purpose of preventing flow of the tube temporarily like a valve. Most common plugging method employs Liquid Nitrogen Gas of . According to the change of tube materials and its dimension, the thermal stress caused from the application of the frozen gas can be varied. In this research, a series of experiments have been carried out to inspect the effect of tube geometry on thermal stresses induced due to ice-plugging. Two typical dimension of stainless and mild steels of 3 and 6 inch diameters were used for the experiments. Each critical spots were checked using strain rosette gages. Another inspection was made on the pressure and temperature of the fluid. It is shown that significant thermal stress level which can cause plastic deformation of failure has not been noticed in this series of experiments.

A Comparative Laboratory Study of Liquid Nitrogen and Argon Gas Cryosurgery Systems

Cryotherapy can now be applied using a variety of delivery systems and cryogens. We compared the Cryotech LCS 3000 liquid nitrogen system (Spembly, Andover, UK) with the CRYOcare argon gas-based system (Irvine, CA, U.S.A.) using three different 3-mm cryoprobes: anoldliquid nitrogen probe (N-probe), anewN-probe featuring gas bypass and an argon gas probe. Each probe was tested in two models: (i) fresh sheep liver at 20°C—the probe was inserted to a depth of 1.5 cm; the rate of ice ball formation was monitored by recording radial temperatures every 15 s at 5, 10, 15, and 20 mm from the cryoprobe, and the ice-ball diameter was measured every 2.5 min. After 10 min, the probe was warmed and the time taken until it could be extracted from the liver was recorded. (ii) Warm water bath—the probe was immersed in warm water (42°C) for 15 min and the ice-ball diameter was measured at 5-min intervals. Radial temperatures in liver declined more rapidly (P< 0.001) and time to probe extraction was less (P< 0.01) when the argon gas system was used. ThenewN-probe performed better than its older counterpart, but was still slower than the argon gas system. In liver (20°C), ice-ball diameters were similar after 10 min, but in warm water, they were larger when thenewN-probe was used (P< 0.02). It would appear that the argon gas system is initially faster, but it does not achieve as large an ice ball in a warm environment as the liquid nitrogen system.

Clathrate phase behavior of the phenolmethane, phenolcarbon dioxide and phenolnitrogen systems

Three-phase, solid clathratephenol-rich liquid-vapor, equilibrium lines for the two binary phenolmethane and phenolcarbon dioxide systems were measured using a newly-designed equilibrium apparatus. The measured clathrate dissociation pressure and corresponding temperature ranges are 88.8–326.8 bar and 312.4–325.4 K for the phenolmethane system and 21.0–99.2 bar and 314.2–319.3 K for the phenolcarbon dioxide system. An abrupt increase of dissociation pressures appeared near 319 K for the phenolcarbon dioxide system, while the phenolmethane system shows a continuous increase of dissociation pressures with no abrupt change over the whole range. In addition, three-phase, solid phenolphenol-rich liquid-nitrogen gas, equilibrium line for the phenolnitrogen system was also determined at the temperature range of 313.4–314.0 K and pressure range of 1.0–180.4 bar and showed a temperature minimum at 313.4 K. No clathrate phase was found in this system.

Energy dissipation in oscillating flow through straight and coiled pipes

The energy dissipation is reported for oscillating flow in U-shaped pipes with 180°, 540°, and 900° curves at the base of the U. Analysis permits separation of the dissipation in the straight and curved portions of the pipe. Using water, water/glycerine mixtures, liquid nitrogen, and helium gas, the dissipation was measured for fluid flow regimes (Reynolds number, quality factor, and pipe curvature) which have not previously been reported. Measured loss in the straight portion is compared to numerical solutions using a turbulent quasisteady representation of the wall shear stress. Measured loss in the curved portion is compared to simple theory. The results are applicable to thermoacoustic devices.

Accuracy of endodontic microleakage results: Autoradiographic vs. volumetric measurements

The correlation between autoradiographic and volumetric leakage measurements was evaluated. Seventy-two anterior teeth with a single canal were selected and divided into three groups of 24. Group 1 served as control (no obturation), group 2 was obturated with gutta-percha only, and group 3 was obturated with gutta-percha and endodontic sealer. Samples were placed in a vertical position in 48-well cell culture plates and immersed in 1 ml of [14C]urea for 14 days. One-mm-thick horizontal serial sections were cut with a diamond disk cooled with liquid-nitrogen gas. Linear penetration was recorded by five independent evaluators from autoradiographs. Volumetric results were based on counts per minute registered in a liquid scintillation spectrometer. Pearson's correlation coefficient test was used to determine the lineal correlation between both methods of evaluation. No acceptable correlation values were found in any of the three groups (group 1, r = 0.34; group 2, r = 0.23; group 3, r = 0.20). Our results indicate that there is no correlation between linear and volumetric measurements of leakage.

A conduction-cooled stage for high-resolution Cryo-SEM

The goal is to examine with high resolution cryo-SEM aqueous particulate suspensions used in coatings for printable paper. A metal-coating chamber for cryo-preparation of such suspensions was described previously. Here, a new conduction-cooling system for the stage and cold-trap in an SEM specimen chamber is described. Its advantages and disadvantages are compared to a convection-cooling system made by Hexland (model CT1000A) and its mechanical stability is demonstrated by examining a sample of styrene-butadiene latex.In recent high resolution cryo-SEM, some stages are cooled by conduction, others by convection. In the latter, heat is convected from the specimen stage by cold nitrogen gas from a liquid-nitrogen cooled evaporative heat exchanger. The advantage is the fast cooling: the Hexland CT1000A cools the stage from ambient temperature to 88 K in about 20 min. However it consumes huge amounts of liquid-nitrogen and nitrogen gas: about 1 ℓ/h of liquid-nitrogen and 400 gm/h of nitrogen gas. Its liquid-nitrogen vessel must be re-filled at least every 40 min.

LEAK‐BEFORE‐BREAK CONDITIONS OF PLATES AND PIPES UNDER HIGH FATIGUE STRESSES

AbstractThe leak‐before‐break(LBB) behaviour of a structural component under high fatigue stress, low‐cycle fatigue conditions is an important problem in nuclear power plants, liquid nitrogen gas tankers and chemical plants. This paper is an experimental study to clarify the crack shape at penetration, crack opening behaviour after penetration and the LBB condition for plate specimens and pipe specimens. The fatigue load which realizes the LBB condition, PFLBB' is based on a net‐stress criterion. It is found that PFLBB is dependent only on the initial crack length a0. Furthermore, it is shown that the crack opening displacement V at the centre of a penetrated crack can be derived using the gross stress, σG' and the front surface crack length, as' together with the back surface crack length, ab.

マウス精子の凍結保存

The spermatozoa of cauda epididymis of mature mice were suspended in 3% skim milk in distilled water supplemented with 12, 15, 18 or 21% (W/V) raffinose. The suspension of spermatozoa were frozen in liquid nitrogen gas for 10 min, then stored in liquid nitrogen (-196 degrees C). The frozen suspensions of spermatozoa were thawed by rapid warming in water bath at room temperature. For removing the cryopreservative solution, a pair of syringes connected with a three stop cock and a filter unit (pore size 0.45 mu) were used. Highest sperm motility was obtained after 1 hr of thawing from the cryopreservative solution containing 18% raffinose and 3% skim milk. These cryopreserved spermatozoa were used for fertilization in vitro. The proportion of pronuclear oocytes was 35.9% (74/206) 6 hr after insemination, and the proportion of 2-cell embryos was 33.6% (42/125) 28 hr after insemination. All 2-cell embryos were transferred to the oviducts of pseudopregnant recipients and 45.2% (19/42) developed to normal young.

New applications of the automatic thermal analysis system

The Automatic Thermal Analysis System has been developed because of the recent demand for improved efficiency of thermal analysis. The system is able to automate heating and cooling measurements for differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and TMA/SS (stress, strain control TMA) over a wide temperature range. A program-controlled liquid nitrogen gas cooling system is used with the same capabilities (reproducibility, noise level, etc.) for cooling and heating measurements. As a result of this automation, not only has the efficiency of thermal analysis work improved, but the following new applications have been made possible: (1) specific heat capacity measurement for DSC in cooling mode; and (2) characterization of plastic samples during cycle heating and cooling for TMA and DSC.

Heat dissipation from silicon chips in a vertical plate, elevated pressure cold wall system

The heat dissipation effects of elevated pressure and cold gas temperature on vertically configured module mounted and free hanging chips were examined. It was found that with both types of chips, the thermal resistance (temperature rise x area/power) varies linearly with pressure in a log-log plot. A free hanging chip exhibits a (-1/3) power dependency on pressure while the module mounted chip exhibits a (-1/5) power dependency on pressure. The thermal resistance of the module mounted chip also appears to exhibit a dependency on gas temperature, but not on the difference in temperature between the chip and cold gas. The thermal resistance of the module mounted chip is some 5x lower than that of the free hanging chip, demonstrating that the module acts to a degree as a thermal expander. The efficiency is less than 20% based on the fact that the module area is some 30x greater than the chip area. For the module mounted chip, and a combination of a liquid nitrogen gas temperature and 1500 psi ambient atmosphere pressure, > 30 W/chip (0.180 in. × 0.180 in.) (0.46 cm × 0.46 cm), can be dissipated with a temperature rise to 85°C. This translates to a heat dissipation capability of more than 900 W/in2.

Cryosurgery for benign disease of the cervix.

SummaryThree hundred and two patients with benign disease of the uterine cervix were treated by cryosurgery. Liquid nitrogen, liquid Freon or carbon dioxide gas delivered through special cervical probes were used as refrigerants. Treatment was performed in the out‐patient clinic without anaesthesia or analgesia. Little discomfort was noted by the patients and there were no serious complications. A single treatment was effective in eradicating the disease in 85 per cent of the patients. The results show that cryosurgery is more effective than hot cauterization with fewer complications. With the advent of this technique conization of the cervix should seldom be necessary for benign disease of the cervix.