首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   25篇
  免费   0篇
化学工业   1篇
无线电   3篇
一般工业技术   6篇
冶金工业   8篇
自动化技术   7篇
  2022年   1篇
  2013年   4篇
  2009年   1篇
  2007年   2篇
  2004年   2篇
  2002年   1篇
  1998年   4篇
  1997年   3篇
  1996年   1篇
  1995年   1篇
  1993年   2篇
  1990年   1篇
  1989年   1篇
  1978年   1篇
排序方式: 共有25条查询结果,搜索用时 343 毫秒
1.
The crystal structure of the peptide Boc-Phe-Val-OMe determined by X-ray diffraction methods is reported in this paper. The crystals grown from aqueous methanol are orthorhombic, space group P2(1)2(1)2(1),a = 11.843(2), b = 21.493(4), c = 26.676(4) A3 and V = 6790 A3. Data were collected on a CAD4 diffractometer using MoK alpha radiation (lambda = 0.7107 A) up to Bragg angle theta = 26 degrees. The structure was solved by direct methods and refined by a least-squares procedure to an R value of 6.8% for 3288 observed reflections. There are three crystal-lographically independent peptide molecules in the asymmetric unit. All the three molecules exhibit extended conformation. The sidechain of the Val2 residue shows two different conformations. The conformation of the peptide Boc-Phe-Val-OMe is compared with the conformation of Ac-delta Phe-Val-OH. It is observed that while Boc-Phe-Val-OMe exhibits an extended conformation, Ac-delta Phe-Val-OH shows a folded conformation. The results of this comparison highlight the conformation constraining property of the delta Phe residue. Interestingly, even though Boc-Phe-Val-OMe and Ac-delta Phe-Val-OH are conformationally different, they exhibit similar packing patterns in the solid state.  相似文献   
2.
In the global market place, many companies have had to adapt their strategies to meet significant challenges. A strategy adopted by some companies has been international expansion via acquisitions. The need for expert knowledge to determine an appropriate company to acquire has been complicated by the sheer size of the global market place. The costs associated with this in relation to time and personnel have created the need for a computerised expert system to be developed. This paper endeavours to show how a proposed fuzzy based system can assist in the identification of a company for acquisition. The authors discuss the manipulation of the magnitude of fuzzy membership functions to communicate priorities within the system. The fuzzy system is designed to assist financial experts in identifying a suitable company for acquisition in the corporate acquisition process. This includes the deliberate weighting of certain inputs and results above others in the decision-making process. The system attempts to learn and simulate the human precedence given to particular financial statistics in company analysis. The system uses the magnitude of the fuzzy membership functions to reflect the human precedence given to each financial ratio. This enables a particular company's strengths and weakness to be considered while concurrently considering their significance and relevance to the acquiring organisation. The system will enable a larger number of companies to be analysed in a more time and cost-effective manner. The development of this system is intended to illustrate that a fuzzy system can aid the financial experts of an acquiring organisation in the global acquisition process.  相似文献   
3.
High-speed and low area hardware architectures of the Whirlpool hash function are presented in this paper. A full Look-up Table (LUT) based design is shown to be the fastest method by which to implement the non-linear layer of the algorithm in terms of logic. An unrolled Whirlpool architecture implemented on the Virtex XC4VLX100 device achieves a throughput of 4.9 Gbps. This is faster than a SHA-512 design implemented on the same device and other previously reported hash function architectures. A low area iterative architecture, which utilises 64-bit operations as opposed to full 512-bit operations, is also described. It runs at 430 Mbps and occupies 709 slices on a Virtex X4VLX15. This proves to be one of the smallest 512-bit hash function architectures currently available.  相似文献   
4.
5.
The effect of thyrotrophin suppression on bone mineral density (BMD) and serum cholesterol concentration was assessed in 31 treated hypothyroid women. Measurements of the BMD of the lumbar spine and femoral neck were repeated in seven of those with the lowest value after an average period of 22.7 months. Final cholesterol concentrations were compared with values before thyroxine was started. The dose of thyroxine was based on clinical assessment, serum triiodothyronine concentrations kept within the normal range, and thyrotrophin values within the normal range or suppressed. The patients had taken thyroxine replacement for a mean of 12.7 years. Two-thirds (21 subjects) had suppressed thyrotrophin concentrations, and it was normal in one-third (10). Fifteen subjects had a past history of thyrotoxicosis. BMD and cholesterol concentrations were compared between those with suppressed and normal thyrotrophin concentrations and between those with and without a past history of thyrotoxicosis. No patient had a pathological fracture. One had a Z value for the femoral neck of -1.6, denoting early but definite osteoporosis, and five had borderline osteoporosis with Z values for one or other site between -1.1 and -1.5. None of the seven with the lowest BMDs had any significant change when measurements were repeated. The difference in Z values between subjects with suppressed and normal thyrotrophin concentrations was not significant for either the lumbar spine (p = 0.68) or the femoral neck (p = 0.28). A past history of thyrotoxicosis had a greater effect on BMD for both sites than thyrotrophin suppression, but again the difference between those with and without a past history of thyrotoxicosis was significant neither for the lumbar spine (p = 0.18) nor for the femoral neck (p = 0.34). The combination of thyrotrophin suppression and a past history of thyrotoxicosis also failed significantly to reduce the BMD of the lumbar spine (p = 0.38) or femoral neck (p = 0.30) in comparison with those who had neither thyrotrophin suppression nor a past history of thyrotoxicosis. The mean fall in serum cholesterol concentration was 2.1 mmol/l (SD 1.78) (p = 0.001) in those with a suppressed thyrotrophin concentration taking a mean daily dose of thyroxine of 171 micrograms (SD: 34.7), compared with a fall of 0.89 mmol/l (SD: 1.04) (p = 0.065) in those whose thyrotrophin concentration was not suppressed on a mean daily thyroxine dose of 140 micrograms (SD: 50). No patient had atrial fibrillation or cardiographic evidence of coronary artery disease (CAD). The serum cholesterol concentration should play at least as important a part in influencing the dose of thyroxine as a fear of osteoporosis. Fractures are not a feature in the natural history of treated hypothyroidism, whereas CAD is a common cause of death in these patients.  相似文献   
6.
7.
8.
The aim of this paper is to show how a knowledge-based systems technology can assist in the area of strategic purchasing. The authors discuss a knowledge-based system (KBS) designed to help companies in the make or buy decision, which is arguably the most fundamental component of manufacturing strategy. A model of the make or buy decision was developed conceptually from a thorough review of the literature and was supported by a series of interviews with procurement managers. The model consists of five main stages: identifying and weighting performance categories; analyzing technical capabilities; comparing internal and external capabilities; analyzing supplier organizational capabilities; total acquisition cost analysis. A KBS was developed which incorporates these five phases into the outsourcing decision. Preliminary evaluation indicates that the KBS can assist the purchasing team by providing feedback to suppliers, monitoring suppliers against performance benchmarks, improving cooperation between the multifunctional purchasing team members and reduces the time involved in conducting the make or buy evaluation. Ultimately, the KBS tool developed can assist an organization in enhancing its competitive position.  相似文献   
9.
Thermal conductivity experiments are reported on unidirectional composites over the temperature range –150 to 130 ° C. Results for R-glass/Fibredux 914 specimens, and for carbon fibre GY-80/Code 69 resin specimens, in directions parallel and perpendicular to the fibre directions have been interpreted using standard theories. Experiments were also made on specimens in which the carbon fibres made angles of 30 °, 45 ° and 60 ° to the temperature gradient. An attempt was made to understand these data using a finite difference model.  相似文献   
10.
This paper considers the detrimental effect of promotions on the supply chain (SC), one of the main causes of the bullwhip effect. A genetic algorithm (GA) is proposed to reduce these negative effects. In order to validate the GA, it is used to determine the optimal ordering policy in an online version of the MIT beer distribution game. Subsequently, the GA is applied in a number of experiments involving deterministic and random demand and lead times combined with sales promotions. It is shown how GAs can be used to dampen the impact of the bullwhip effect and can be used to assist supply managers in predicting reorder quantities along the supply chain.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号