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Problem solving is one of the higher thinking skills required and must be built by students. This study aims to examine the ability of students to solve problems through the implementation of the STEM approach integrating PjBL model on the Immune system. This study was carried out at senior high school in Banda Aceh and Aceh Besar district. This study was an experimental pretest design with a non-randomized control group. The population was all 11th-grade students from both schools. Thus, the Science Class 1 and 3 (of SMAN 5 Banda Aceh) and the science class 1 and 4 (of SMAN 1 Darul Imarah) were selected as the sample. The test attached in the student working sheets, which was constructed using an Engineering Design loop, is the instrument used to assess the problem-solving capacity. The data from the study have been processed and descriptively analyzed. The results showed that the STEM approach integrating PjBL model could improve the abilities of students to solve problems. Therefore, the implementation of STEM approach combined with PjBL can be used as a strategy for teachers to carry out learning activities to enhance the meaningful learning and student’s capability in solving problem of biology content.

The IC engine converts the chemical energy of the fuels into the mechanic energy with the efficiency is around 35-40% depends on the type and operation condition of the engines. It means around 60-65% of the energy is wasted mostly in the form of heat (dissipated through the cooling process and exhaust gas) and friction. A thermoelectric exhaust heat recovery system can be used to harvest the waste heat which potentially could increase the efficiency of the IC engine indirectly. In this experimental study, the heat recovery system consists of a rectangular duct in which sixteen thermoelectric modules are attached to its sides (each side consist of four thermoelectric modules). The aluminium fins are mounted at the cold sides of thermoelectric modules (at the outer sides of the rectangular duct) and cooled by air supplied by computer fan coolers. To harvest the exhaust heat of the IC engine, the heat recovery system is connected to the exhaust pipe. The effect of aluminium fin arrangements, mounted on the inner surfaces of the rectangular duct of the heat recovery device, is investigated. The arrangements include mounting of the fins at the lateral sides, top and down sides, and the whole sides of the heat recovery device. Besides, the effect of the absence of the fins at the exhaust gas passage of the heat recovery device is examined. The performance of the heat recovery system is studied when the engine operates under the no-load condition at rotational speeds of 1300, 1600, 1900 and 2200 RPM. The experimental result reveals that the voltage and current generated by the thermoelectric exhaust gas recovery system increase in line with the increase of engine speed. In addition, it is found that the highest voltage and current are generated by the whole side fin arrangement, namely 12,52V and 122 mA respectively, at an engine speed of 2200 RPM. It is observed that the finless arrangement generates the lowest voltage and current among others, namely 5.36 V and 20.43 mA.

Pyrolyzed waste plastic-based green fuel has been reported to be used as an alternate fuel for diesel engines. Some of the main challenges for implementing this in current automotive technology include evaluating engine performance, emission, noise vibration harshness (NVH), and knock characteristics of this fuel. This study focuses on the engine performance of poly-ethylene terephthalate (PET)-based waste plastic oil (WPO) at varying engine speed conditions. The pyrolysis of mixed-waste plastic was carried out at 300 °C in a fixed-bed reactor. Physicochemical properties such as viscosity, density, calorific value, sulfur, and research octane number (RON) of the plastic fuel and its blends with gasoline were analyzed using ASTM standard test methods. The WPO was blended with two different types of gasoline (RON88 and RON90) at 10, 20, and 30%, and was tested in a spark-ignition (SI) engine. The experimental results showed that different WPO–gasoline blends can be used in an SI engine without any engine modifications, and the performance indicators for different blends were found to be close to that of pure gasoline. The brake power and brake specific fuel consumption (BSFC) were found to be 4.1 kW and 0.309 kg/kW h, respectively. The 10% WPO and 90% RON90 blend produced optimal engine performance at 3500 rpm.

IntoroductionPulverized coal injection (PCI) technology in blast furnaces has been applied since 1981 in Japan. Recently, the number of blast furnaces applying the PCI technology attains about 30 since this technology contributes to decreasing coke consumption. In order to accelerate reducing the coke consumption, it is necessary to increase coal injection rate. 1)A number of reviews relating to the PCI technology have already been reported. For instance, Inaba 2) presented performance of the blast furnace under the condition of highrate pulverized coal injection. Shibata et al., 3) Iwanaga et al. 4) and so forth showed distributions of both gas composition and temperature and the effect of oxygen enrichment on the combustion efficiency in the raceway. In order to improve the combustibility, Shen et al. 5) proposed the addition of KMnO 4 to the coal. Kugizaki et al. 6) suggested that the char structure affected reactivity of pulverized coal. Some researchers [7][8][9][10][11][12] have also proposed a mathematical model of combustion behaviors of pulverized coal in blowpipe and raceway in the blast furnace.For coke behaviors in the raceway of blast furnace applying the PCI technology, on the other hand, some researchers [13][14][15][16][17] have reported that the coke degradation in the raceway might occur due to the mechanical abrasion, thermal stress, chemical reactions and so on. Yamaguchi et al. 16) proposed that the degradation of coke in the raceway was mainly caused by the mechanical abrasion rather than by thermal stress or thermal shock.As found from those reviews above-mentioned, the effect of molten coal ash on the reaction and/or degradation behaviors of coke lump has not been precisely discussed yet. In this study, therefore, the reaction and/or degradation behaviors of coke lump due to ash particles of coal were elucidated experimentally by using a horizontal pulverized coal reactor with a pre-combustor to produce a high-temperature vitiated air. In the experiment, a coke lump was inserted into the furnace which coal particles were burning. In order to distinguish the effect of coal ash from the effect of other reactions such as combustion and gasification of coke, LPG was also injected into the furnace instead of the pulverized coal. Figure 1 shows a schematic diagram of the horizontal pulverized coal reactor with a pre-combustor employed in this study. The dimensions of the reactor are 2.1 m long and 0.12 m in inner diameter. In the pre-combustor a high-temperature vitiated air is produced by the combustion of town gas with an oxygen-enriched ambient air. The main reactor consists of two parts: the front two sections are watercooled since the particle temperature exceeds about 2 000 K, and the rear three sections are insulated by refractory to reduce the heat loss. ExperimentalThe coke lump is inserted at the position of 0.9 m apart from the coal injection point, at which the coal almost ISIJ International, Vol. 40 (2000), No. 8, © Reaction behaviors of a coke lump in raceway of blast fur...