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31.
M Kubota A Izumida H Takuma K Kodama N Sasaki 《Nippon juigaku zasshi. The Japanese journal of veterinary science》1990,52(6):1229-1235
Colostrum-deprived, neonatal, 2 days old pigs were inoculated with the attenuated HT-/SK or the virulent 90HS strain of porcine parvovirus (PPV) by the oral or subcutaneous route and sacrificed 2, 4 or 6 days after inoculation. Then, comparison was made on viral multiplication in pigs between the two strains. Pigs inoculated with the HT-/SK strain showed no detectable viremia or HI antibody responses against PPV within 6 days after inoculation. Only in pigs inoculated by the subcutaneous route, a small amount of virus was recovered from the spleen, liver, or mesenteric lymph nodes. These viruses were distinguished from the parental virulent 90HS strain, as examined for rct maker in vitro. When pigs were inoculated with the virulent 90HS strain, viremia appeared in all of them 1 day after inoculation and continued for up to the sacrificed day. Moreover, a considerable amount of virus was also detected from all tissues, including brain, lung, liver, spleen, pancreas, small intestine, and lymph node tissues, in all pigs tested. HI antibodies were first detected 6 days after inoculation. 相似文献
32.
33.
This paper presents research on plywood frame corners jointed to glulam beams and columns by means of glued-in hardwood dowels. The frame corner was made of a solid block of ordinary plywood of the same width as the glulam beams and with plies parallel to the plane of the frame to avoid splitting due to stress perpendicular to the grain. Hardwood dowels with a diameter of 12mm and a maximum glued-in length of 120mm were glued into drilled holes in the plywood corner and glulam beam ends parallel to the grain direction of the beams to form a momentresisting joint. Static bending tests were conducted of frame corners with 100 X 200mm2 and 120 X 420mm2 beam cross sections. Bending capacities of the joints corresponding to a modulus of rupture of the jointed glulam beams of about 30MPa were obtained for both closing and opening moments for the small cross sections, and about 22MPa was obtained for the large cross sections. Simple design models for calculation of joint strength and rotational stiffness are also presented. 相似文献
34.
Summary For the preparation of specimens for testing the stress distribution with the photoelastic method, various techniques are applicable. In this paper the so-called glass-transition temperature method is tested on a specimen imitating the layered structure of wood. The observations made on this specimen are compared with those obtained from a specimen with isotropic properties.
Zusammenfassung Für die Herstellung von Modellen zur Untersuchung der Spannungsverteilung mit spannungsoptischen Verfahren gibt es verschiedene Techniken. In dieser Mitteilung wird das sogenannte Glas-Übergangstemperatur-Verfahren an einem Modell, das den Schichtaufbau des Holzes nachahmt, geprüft. Die Beobachtungen, die an diesem Modell gemacht wurden, werden mit jenen verglichen, die sich an einem Modell mit isotropen Eigenschaften ergaben.相似文献
35.
36.
Protoplasts were isolated from the leaves of sterile plants ofPopulus euphratica Oliv. by using 1% Cellulase “Onozuka” RS and 0.25% Pectolyase Y-23 in 0.6m of mannitol solution. Protoplasts were cultured in modified Murashige and Skoog's (MS) medium which contained no ammonium
ions but was supplemented with BAP (6-benzylaminopurine), 2,4-D (2,4- dichlorophenoxy-acetic acid), and 1% sucrose at the
cell density of 9×104/ml. Cell divisions occurred in every culture medium, especially in the medium containing 0.5 mg/l of BAP and 0.1 mg/l of
2,4-D, in which callus was successfully induced by successive culture through cell cluster formation. Shoots were regenerated
from the callus, and their growth was enhanced on 1/2 MS medium containing 0.8 mg/l of BAP. Finally, shoots were rooted and
plantlets were regenerated on 1/2 MS medium without a hormone.
A part of this paper was presented at the 106th Annual Meeting of the Jpn. For. Soc. (1995). 相似文献
37.
38.
Wood-based panels are subjected to cyclic panel shear load caused by wind and seismic forces in such an application as the sheathing of bearing walls. The fatigue behavior of structural plywood under panel shear load with two different loading frequencies was examined. Pulsating panel shear load with a triangular waveform and loading frequency of 0.5 or 5 Hz was applied to the plywood specimens. Stress−strain hysteresis loops were measured throughout the fatigue tests. Fatigue life was highly dependent on loading frequency at more than 0.5 stress level. The deterioration of mechanical property and damage accumulation in plywood specimen was observed to be slower at higher loading frequency at more than 0.5 stress level. Analyses based on energy loss suggest that panel shear load with higher loading frequency causes less damage to the plywood specimen during one loading cycle at higher stress level, and that the fatigue damage accumulation causing failure might be dependent on stress level although it seems to be unaffected by loading frequency. Based on these results, a new fatigue failure model for plywood specimen was qualitatively developed by combining Weibull’s weakest link model and Daniels’ fiber bundle model. 相似文献
39.
Toshihiro Hata Kenji Umemura Hidefumi Yamauchi Akihiro Nakayama Shuichi Kawai Hikaru Sasaki 《Journal of Wood Science》2001,47(2):115-123
A new spiral-winder was developed for continuous manufacturing of cylindrical laminated veneer lumber (LVL), and a suitable resin adhesive for this cylindrical LVL manufacturing system was investigated. This phase was followed by trial manufacturing and evaluation of cylindrical LVL with the optimum resin adhesive identified. The results are summarized as follows. (1) The shortest gelation time was recorded with a mixture of two commercial resorcinol based resins (DF-1000 and D-33) at a weight ratio of 2575. (2) Bath temperature had a remarkable effect on the gelation time of the adhesive mix. (3) High bonding strength was recorded by 2575 DF-1000/D-33 adhesive mix at a high press temperature despite a short pressing duration. Based on the results of items (1) to (3), 2575 DF-1000/ D-33 is recommended for use in the new spiral-winder. (4) The mechanical properties of cylindrical LVL could be improved by using 2575 DF-1000/D-33 with wider veneer width and longer pressing time. (5) The mechanical properties, especially the modulus of rupture, of the cylindrical LVL manufactured require further improvement for practical structural application. 相似文献
40.
The fatigue behavior of plywood specimens under shear through thickness was examined on the basis of strain energy to obtain
common empirical equations for the fatigue process and failure criterion under various loading conditions. Specimens were
cut from commercial plywood panels of 9-mm thickness. Loading conditions were set as follows: a square waveform at a loading
frequency of 0.5 Hz, a triangular waveform at 0.5 Hz, and a triangular waveform at 5.0 Hz. Peak stress applied was determined
to be 0.5, 0.7, and 0.9 of static strength, that is, stress levels of 0.5, 0.7, and 0.9. The stress-strain relationships were
measured throughout the fatigue test, and the strain energy was obtained at each loading cycle. Loading conditions apparently
affected the relationship between stress level and fatigue life. On the other hand, the relationship between mean strain energy
per cycle and fatigue life was found to be independent of loading conditions. Mean strain energy per cycle obtained as the
fatigue limit was 5.85 kJ/m3 per cycle. Assuming that the accumulation of strain energy is a fatigue indicator, the fatigue process and failure criterion
for the plywood specimens under the three loading conditions were commonly expressed by the relationship between cumulative
strain energy and loading cycles. 相似文献