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Since the aperture obstruction contributes to an energy leak from the core to the sidelobe of the far field spot, the Gaussian mode of the single-mode fiber (SMF) will receive less energy leading to the coupling efficiency (CE) degradation. A method based on diffraction optical element (DOE) and wavefront corrector is introduced to reshape the plane wave with hollow uniform intensity into the plane wave with uniform intensity to improve the core energy of spot. The SMF CE with and without DOE for different central obscuration ratio is studied by numerical simulation. The DOE is effective to improve the SMF CE. Without the DOE, the CE decreases from 81% to 54% when the central obscuration ratio increases from 0 to 0.4. Compared with 54% CE at the of 0.4, the CE can increase to 72%, 78% and 80% with 4 level, 8 level and 16 level quantized DOE, respectively. It is not necessary to use the DOE beam shaper when the central obscuration ratio is small. The 4 level, 8 level and 16 level quantized DOE can obtain benefits of the CE when the central obscuration ratio is above 21.6%, 11.5% and 7%, respectively.

Focusing on the phenomenon that many office buildings and student apartments in northern China with vertical single tube series heating systems are of high energy consumption and waste lots of thermal energy because of lacking heating regulation, this paper proposed a system of on-off regulation to optimize the regulation, where on-off values are installed in each vertical riser, indoor temperature controllers are installed in the room with lower temperature, and the on-off values control circulating water automatically according to the difference between the real temperature and the set temperature and finally the indoor temperatures are controlled. The temperature control effect and energy saving effect of this system were discussed in both simulation and measurement. The conclusion shows that: 1) the proposed system can optimize heating regulation and reduce the loss cause of heating non-uniformity.2) the on-off control on the flow of single vertical tube makes temperature of all rooms stringed in the riser meet the requirements.3) the indoor temperature differences in the same riser are controlled in 2 °C.4) in practical, users on-time is only 50% of total time through on-off regulation, the effect of energy saving is significant.

According to the internal mechanism of the formation of heat load, the formation of heat load consists of two parts, the systemic heat load, which is determined by the building envelope and outdoor environmental parameters and random load caused by the users randomness of events and solar radiation etc. Toward systemic heat load, this paper considered the influence of environmental parameters before the prediction time and used the method of stepwise trials and MSE to obtain the optimal solution. Toward random load, it is considered that the day of the same type have the same variation pattern. On this basis, this paper introduced a correction coefficient to obtain random load eventually. This paper selected DeST, the widely used energy simulation software in China, to analysis the case. The result shows that the prediction method is feasible and 50% of the predicted loads have the relative error of less than 5%.

It is a question if large scale heating/cooling network could be applied in China economically, environmental protection and energy saving. Toward this question, this paper studied the optimization of large scale heating and cooling network. The components of the system are analyzed and modeled in detail including heating/cooling source, heating/cooling users and transmit system. And the system can be optimized through the way of Life Cycle Cost, which compared the cost of large scale heating and cooling system with conventional system. The optimization also takes efficiency and economy in to consideration.

This paper discussed the optimization of two cases of large scale heating and cooling system. One is the heating/cooling system with heating/cooling source with distance from load center, the other is the heating/cooling system with heating/cooling source located in the load center. The affect of the temperature difference between supply and return water, load density and the price of energy towards optimized radius and max radius was discussed using the existed model. The optimized radius and appropriate system parameters are got. It is a reference to the designers and operators related.

As an advanced heat metering method, on-off valve regulation method has good temperature-control and energy-saving effects. But its hydraulic regime is different from other existing systems, the conditions are more complicated and researches are not enough. There is an opinion that differential pressure valve should be used in the buildings consumer heat inlet. For all the questions and uncertainties, this article conducted researches by field test and program simulation analysis. The field test was conducted in a housing estate in Beijing, one buildings flow regulations influence on other buildings hydraulic regime was tested. The simulation was done in HACNet hydraulic simulation software. A pipe net model was built to simulate different working conditions. Both results indicate that systems hydraulic regime is stable and differential pressure valve is not necessary.

Seismic analysis of the primary system in nuclear plant design is very important. The change of reactor coolant pump has some impact on the support seismic loads of primary equipment. Using the numerical calculation method, preliminary analysis was completed and some valuable results are obtained. The results show the natural frequency of system should be far away from the spectral peak with optimizing the reactor coolant pump configuration to raise the safety and economy of the plant.

The 946nm diode-pump microchip self-Q-switched laser of a chromium and neodymium codoped yttrium aluminum garnet crystal material (Cr4+Nd3+:YAG) is studied, especially about its physical mechanism of operation. The 4F3/2 → 4I9/2 transition of Nd3+ ion is beneficial to achieving laser oscillation in a quasi-three-level system based on coating the cavity mirrors of the microchip with films that suppress the 1064nm operation and enhance the 946nm laser. The Cr4+ ion is a saturable absorber. The initial loss Nt1 is high, which acts as the threshold for laser oscillation. The stable loss Nt2 is low because the Cr4+ ion is acceleratively bleached by the fast enhancement of the oscillating laser. The high Nt1, small Nt2 and fast progresses permit the oscillating laser of the Cr4+Nd3+:YAG to have a good self-Q-switched property whose full width at half maximum is about 4.2ns. Its highest laser power is about 5.7mW. Its peak power is about 150W. Its good fundamental transverse TEM00 mode results from the absorption bleaching established by both the pump and oscillating lasers, which suppress other transverse mode and allow the oscillation only in the fundamental transverse TEM00 mode.

High power fiber lasers and amplifiers are widely used in the scientific and industrial field. In order to meet the requirements for high output powers the effective area of fibers becomes larger and larger to reduce optical nonlinearities. With the increase of effective area, the number of high-order modes will increase. In the case of high output power, the spectral shift and broadening of the optical fiber will also affect the modal number and content. The number and content of fiber modes affect the pointing stablity and quality of the laser beam. The M2-parameter is commonly used to define the quality of the laser beam, but a small M2 number is not guaranteed for single mode operation. Therefore, the relationship between wavelength and transmission mode in fiber transmission is studied in this paper. We use the spatial and spectral Fourier transform (F2) method to establish a theoretical-experimental method of describing the relationship between wavelength and mode. This method can directly give out the modal content of optical fibers without any priori parameter such as the properties of fiber and requirement for setup accuracy. On the one hand, the theoretical modeling of wavelength affects modal content. In the simulation, the sources with the same wavelength bandwidth and different central wavelengths are used to test the fiber. The results show that the modal content and number of the fiber change with the wavelength bandwidth and center wavelength. The mode components of the corresponding optical fiber will change after changing the central wavelength. As the spectral width of the light source increases, the number of high-order modes increases. On the other hand, in order to further verify the relationship between wavelength and mode of fiber, the F2 method is used to measure the optical fiber modal content with different wavelengths. The final experimental results are in agreement with the theoretical results. The experimental and simulation results show that the mode field distribution of each mode varies with wavelength:the longer the wavelength, the larger the mode field is. The beam quality has little change with the wavelength except for those positions with frequency near the cutoff frequency, and the power ratio of each mode relates to the wavelength.

Large scale fire tests of building external wall insulation system were conducted. In the experiment, thermal-couples were mounted to measure the insulation system surface temperature and the gas temperature inside rooms at the second and third floors. Photos were also taken during the fire tests. The measurement provides information of the ignition and fire spread of the external insulation system which consists of surface protection layer, glass fibre net, bonding thin layer, anchor and the load bearing wall. Comprehensive simulations of the fire tests were carried out using an advanced CFD fire simulation software Simtec (Simulation of Thermal Engineering Complex) (1, 2), which is now released by Simtec Soft Sweden, with the turbulent flow, turbulent combustion, thermal radiation, soot formation, convective heat transfer, the fully coupled three dimensional heat transfer inside solid materials, the 'burn-out' of the surface protection layer and the pyrolysis of the insulation layer, etc, all computed. The simulation is compared with experimental measurement for validation. The simulation well captured the burning and fire spread of the external insulation wall. With strategic implementation of building energy conservation, external wall insulation system has been widely used in China. Thin plaster external thermal insulation systems (TPETIS), with advantages such as light weight, low thermal conductivity, wall structure protective, simplicity in construction and etc., have become the most widely used type of wall insulation system. Typical insulating materials used in TPETIS are EPS (Expanded Polystyrene), XPS, (Extruded Polystyrene) PUR (Polyurethane) and PIR (Polyisocyanurate). In recent years, however, a number of serious fire accidents of high-rise building are related to TPETIS. This has drawn people's high attention to the fire safety of TPETIS. The fire performance of TPETIS is mainly affected by factors such as ignition source, system structure and combustion property of the insulation materials. For ignition source factor, Lee (3-5) has analyzed of the spreading mechanism of window fires (the external wall insulation system fire is usually started by window fires) and proposed a new length scale for correlating window fire's flame height, plume temperature and heat flux. Himoto (6) considered pressure gradient effect of window fire plume, and proposed a model for predicting the trajectory of window flame ejected from a fire compartment. For system structure factor, Oleszkiewicz (7) pointed out that laterally projecting structure of building facade can reduce radiant heat flow by 90%, and the vertical extending structure can increase radiation heat flux by 50%. For TPETIS, he also proposed fire-barrier belts to be used between every one or two floors. In recent years, a number of scientists (8-10) have carried out a number of window and corner fire experimental studies and indicated that the systems with improved structure (such as additional This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

We investigate the relationship between the beam intensity and the four-wave mixing diffraction efficiency of the longitudinal-field multiple-quantum-well (LMQW) photorefractive device grown at low temperature. A optimum beam intensity is found. We also explain the different mechanisms of the beam intensity effect on the diffraction efficiency of the LMQW device and the transverse-field MQW device. Some advice on how to improve the diffraction efficiency is given.

A stable low-threshold self-Q-switched diode-pumped 946-nm Nd(3+), Cr(4+):YAG microchip laser operating in single frequency and fundamental transverse mode is reported. The output characteristics of the microchip laser were investigated under cw and pulsed pumping. By combination of the infrared microchip and an external frequency doubler, 473-nm pulses with a conversion efficiency of 18% were achieved.

AIM: To evaluate total embolization of the main splenic artery in patients with splenic artery aneurysms (SAAs) and normal spleen. METHODS: Thirty-five consecutive patients with SAAs were referred for treatment with coil embolization. Patients were classified into two groups: coil embolization of the main splenic artery with complete occlusion of the artery and aneurysms (group A, n = 16), and coil embolization of the aneurysmal sac with patency of the splenic artery (group B, n = 19). Data on white blood cell (WBC) and platelet counts, liver function, and complications were collected on days 7 and 30, and subsequently at a 6-mo interval postoperatively. Abdominal computed tomography was routinely performed to calculate the splenic volume before and 1 mo after the procedure, and subsequently every 6 mo during follow-up. RESULTS: Coil embolization of the SAAs was technically successful in all 35 patients, with no procedure-related complications. The post-embolization syndrome, including abdominal pain, fever and vomiting, occurred in six patients (37.5%) in group A and three patients in group B (15.8%). There were no significant differences in WBC and platelet counts between preoperatively and at each follow-up point after the procedures. There were also no significant differences in average WBC and platelet counts between the two groups at each follow-up point. There were significant differences in splenic volume in group A between preoperatively and at each follow-up point, and there were also significant differences in splenic volume between the two groups at each follow-up point. CONCLUSION: Total embolization of the main splenic artery was a safe and feasible procedure for patients with SAAs and normal spleen.

A diode-laser pumped blue intracavity frequency-doubled self-Q-switched microchip laser of a chromium Cr4+ Neodymium Nd3+ codoped yttrium aluminum garnet crystal (Cr4+Nd3+:YAG) combined with a potassium niobate (KNbO3) crystal is developed. By coating the cavity mirrors with the films that suppress the 1064-nm operation and enhance the 946-nm laser, the 4F3/24I9/2 transition of the Nd3+ ion is facilitated to achieve the 946-nm laser oscillation. The 946-nm laser of the Cr4+Nd3+:YAG is self-Q-switched due to the saturable absorption of the Cr4+ ion. The full width at half maximum (FWHM) of the laser pulse at a 964-nm wavelength is about 5.07 ns. A self-Q-switched 473-nm laser pulse is sequentially obtained through intracavity frequency doubling of the 946-nm laser by the KNbO3 crystal, whose FWHM is about 4.30 ns. The 473-nm intracavity doubled laser has a good fundamental transverse TEM00 mode, because the self-Q-switched 946-nm laser has a good TEM00 mode that results from the absorption bleaching established by both the 808-nm pump laser and 946-nm oscillating laser. The constant FWHM results from both the response time of the self-Q-switching and the establishing time of the oscillating laser being much faster than the accumulated time of the pump laser energy. The constant peak power of the 946-nm self-Q-switched laser mainly depends on the modulation ability of the self-Q-switching.